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983,281 | https://en.wikipedia.org/wiki/Water%20miscible%20oil%20paint | Water-miscible oil paint (also called water-soluble oil paint or water-mixable oil paint) is oil paint either engineered or to which an emulsifier has been added, allowing it to be thinned and cleaned up with water. These paints make it possible to avoid using, or at least reduce volatile organic compounds such as turpentine that may be harmful if inhaled. Water-miscible oil paint can be mixed and applied using the same techniques as traditional oil-based paint, but while still wet it can be removed from brushes, palettes, and rags with ordinary soap and water. One of the ways its water solubility comes from is the use of an oil medium in which one end of the molecule has been engineered to be hydrophilic and thus bind loosely to water molecules, as in a solution. This type of paint is different to those that are engineered to enable cleaning of brushes and application equipment in water but are not in themselves water reducible.
History
A precursor to water-miscible oil paint is "tempera grassa", an egg tempera method where oil paint is mixed with the tempera and the egg acts an emulsifier to be used for glazing underpaintings and providing added luminosity to paintings.
Handling in comparison with other media
The traditional rule of gradation of layers — "fat over lean," or flexible over less flexible — applies to water miscible oil paint as it does to traditional oil, and in this respect the two kinds of paint behave in the same way. However, their handling is slightly different: when thinned with water to a considerably liquid phase, water miscible oil paint tends to feel and behave like watercolor (although, unlike watercolor, and to a greater extent than traditional oil, it may lose adhesion to the ground or support if over-thinned); by contrast, when used as a short paste without water for heavy impasto work, it tends to drag, developing a consistency somewhat "gummier" or tackier than the more buttery one characteristic of oils. At midrange (between short paste and long paste) water miscible oil paint is gouache-like, sharing the properties of both transparent watercolor and opaque oil (in the manner of watercolor, for example, some colors will darken upon drying, the more so as more water is mixed into the paint, and in the manner of oil, the paint film will have some thickness to it). Also gouache-like is the overall effect, which tends to be matte as compared to the glossier oil, but this too is a property that will vary, depending on the pigment used and on any mediums (or diluents) mixed into it, as well as on the pastiness of the paint (as a general rule, the pastier, the glossier). The handling of water miscible oil paint, in summary, changes considerably as it passes from one phase to another. This makes it a versatile medium but, by the same token, it also requires the artist to develop by experience specific skills with which to successfully manipulate it and exploit its range to achieve the desired effect.
Although the practice of mixing water-mixable oils with acrylics is possible (as some brands claim), it is not recommended if the painting's longevity is a concern. The reason is that once the acrylic dries, its impermeability isolates the oil from oxygen, preventing it from oxidizing properly.
Since each manufacture of these paints has its own formula for creating the water-mixable capacity, the following should be checked with each manufacturer’s paint. As the artist writing this paragraph uses Lukas Berlin water-mixable oils, the following applies to Lukas Berlin. They are quite stable on acrylic gesso primed surfaces. Therefore, after all polymerization has occurred, when subjected to a damaging force can with stand quite some force without suffering damage to the paint film. The same is not true when they are applied to oil primed, or oil ground surfaces, i.e., canvas, canvas board, or paper. When fully dried the paint is not fully attached to the oil primed surface. It is easily damaged by any force acted upon it. Subsequent testing has established that Royal Talents’ - Cobra, Holbein Works’ - Duo and Daniel Smith’s - Water Soluble Oil Colors also exhibit the same problem with oil primed surfaces.
Brands
There are several manufacturers producing water miscible oil paint, including: Daler-Rowney (Georgian Water Mixable Oil);Mont Marte (H2O Water Mixable Oil); Daniel Smith (Water Soluble Oil Colors); Grumbacher (Max Water Mixable Oil); Holbein Works (DUO); Lukas (BERLIN); Martin F. Weber Co. (wOil); Reeves (tube sets and complete painting set); Royal Talens (Cobra Artist and Cobra Study); Schmincke (Norma Blue Water Mixable Oil); and Winsor & Newton (Artisan Water Mixable Oil Color).
Mediums
Although this type of paint may be thinned with water, artists may prefer to use specially prepared mediums for improved texture and control. These mediums improve flow (i.e., make the thinned paint less runny and more easily controlled) and can slow or speed up drying time. Mediums are offered by many of the paint manufacturers.
Royal Talens also has produced a water mixable painting paste that acts as a thickener as well as transparetizer which will not change the consistency of the paint. There are many documented issues with accelerator products in this category causing cracking and damaging the archivability of the medium.
Winsor and Newton has created a special line of oils, mediums, varnishes, and thinners to complement their “Artisan” brand of water mixable oil colors. This line includes thinner, linseed oil, safflower oil, stand oil, painting medium, fast drying medium, and impasto medium, as well as gloss varnish, matt varnish, satin varnish, and varnish remover.
Daniel Smith also offers a range of suitable mediums.
See also
Waterborne resins
References
Paints
Oil paints | Water miscible oil paint | [
"Chemistry"
] | 1,302 | [
"Paints",
"Coatings"
] |
983,400 | https://en.wikipedia.org/wiki/L%20ring | The L-ring of the bacterial flagellum is the ring in the lipid outer cell membrane through which the axial filament (rod, hook, and flagellum) passes. that l ring stands for lipopolysaccharide.
References
Bacteria | L ring | [
"Biology"
] | 56 | [
"Bacteria stubs",
"Prokaryotes",
"Microorganisms",
"Bacteria"
] |
983,401 | https://en.wikipedia.org/wiki/NGC%201 | NGC 1 is an intermediate spiral galaxy of the morphological type Sbc, located in the constellation of Pegasus. It was discovered on 30 September 1861 by Heinrich d'Arrest.
Observation history
Heinrich d'Arrest discovered NGC 1 on 30 Sep 1861 while testing the 11-inch f/17.5 Merz refractor of the Copenhagen Observatory. He missed nearby NGC 2. This was d'Arrest's first deep sky discovery, though he was uncertain if his object was identical to h4 or h5 (both of which refer to NGC 16). His descriptions (combination of 4 observations) read "faint, small, round, 20", no concentration. In a straight line connecting two stars 11 and 14 mag." Herman Schultz observed NGC 1 three times in 1866 and 1868 with a 9.6-inch refractor at Uppsala and he also missed fainter NGC 2. The NGC 1 and 2 pair are not physically related. NGC 1 lies at a distance of ~200 million l.y. with NGC 2 at roughly 320 million l.y.
The initial observers missed NGC 2, which is much fainter. NGC 1 appears to be quite close to NGC 2, in reality however, the two objects are far apart and unrelated. NGC 2 was first observed as a "companion" of NGC 1 by Lawrence Parsons.
Properties
At an estimated 140,000 light-years in diameter, NGC 1 is roughly the same size as our galaxy, the Milky Way, which is believed to be approximately 160,000 light-years across. Although its apparent magnitude of 13.65 makes the galaxy appear too faint to see with the naked eye, its absolute magnitude of -22.08 makes NGC 1 two to three times more luminous than our home galaxy. The galaxy is 4.0 Mly away from the 80,000 light-years wide galaxy UGC 69, its nearest major neighbor.
NGC 1 has a visual size of 1.6' × 1.2'. Being classified as a SABbc class galaxy using the Hubble sequence and the De Vaucouleurs system as an extension, NGC 1 is a spiral galaxy with the presence of a weak nuclear bar and loosely wound arms. Although the central galaxy is only about 90,000 light-years across, a large, diffuse arm extends eastwards from it, possibly from a past merger.
Based on its redshift of approximately 0.015177 and thus recessional velocity of 4450 km/s, the distance of the galaxy from the Solar System can be calculated using Hubble's law. Using current observation data, this places the galaxy at approximately 210 to 215 million light-years from Earth, which is in good agreement with redshift-independent distance estimates of 175 to 245 million light years. An opposing measurement of the galaxy's recessional velocity of 2215 km/s would place the galaxy only about 100 million light-years away. However, this is regarded unlikely by most astronomers and believed to be a misattributed value for a different galaxy.
Listing in astronomical catalogues
After being logged as the first object in the General Catalogue, the galaxy is also the first object to be listed in the catalogue's successor, the New General Catalogue. With an original right ascension of at the time of the catalog's compilation (epoch 1860), this object had the lowest right ascension of all the objects in the catalog, making it the first listing in the New General Catalogue as the objects were arranged by right ascension. Since then, the coordinates have shifted, and this object no longer has the lowest right ascension of all the NGC objects.
NGC 1 is also listed in the Uppsala General Catalogue (UGC 57) and in the Principal Galaxies Catalogue (PGC 564).
See also
Pegasus (constellation)
List of NGC objects (1–1000)
Spiral galaxy
References
External links
SEDS
Galaxies discovered in 1861
Intermediate spiral galaxies
Pegasus (constellation)
0001
00057
00564
18610930
Discoveries by Heinrich Louis d'Arrest | NGC 1 | [
"Astronomy"
] | 816 | [
"Pegasus (constellation)",
"Constellations"
] |
983,405 | https://en.wikipedia.org/wiki/NGC%202 | NGC 2 is an intermediate spiral galaxy with the morphological type of Sab, located in the constellation of Pegasus. NGC 2 was discovered by Lawrence Parsons, 4th Earl of Rosse on 20 August 1873."
Observational History
NGC 2 was first observed by Lawrence Parsons, 4th Earl of Rosse on 24 August 1873, and was described as "very faint, small, south of GC 1."
Properties
NGC 2 is located about 345 million light-years from the Solar System, with a magnitude of +14.2, while the distance to NGC 1 is 210 million light-years. Although visually close in the sky, NGC 1 and NGC 2 are at very different distances; were they stars, they would be referred to as an "optical double" as seen from Earth.
AGC 102559, a spiral galaxy 60,000 light-years in diameter, is the closest galaxy to NGC 2, only 1.8 million light-years from it. Although it is quite close to NGC 1, the latter is closer and unrelated to NGC 2.
NGC 2 is a spiral galaxy with a diameter of about 60 thousand light-years, smaller than the size of the Milky Way.
Listing in astronomical catalogues
NGC 2 is first cataloged as GC 6246, an addendum to Dreyer's 1877 Supplement to the General Catalogue of Nebulae And Clusters of Stars. The object is cataloged as UGC 59, PGC 567, CGCG 478–027, and MCG +04-01-026.
Gallery
References
External links
Source: NGC/IC Project
Galaxies discovered in 1873
NGC 0002
NGC 0002
0002
00059
00567
18730820
Discoveries by Lawrence Parsons | NGC 2 | [
"Astronomy"
] | 350 | [
"Pegasus (constellation)",
"Constellations"
] |
983,406 | https://en.wikipedia.org/wiki/NGC%203 | NGC 3 is a lenticular galaxy with the morphological type of S0, located in the constellation of Pisces. Other sources classify NGC 3 as a barred spiral galaxy as a type of SBa. It was discovered on November 29, 1864, by Albert Marth.
Observational History
NGC 3 was discovered by Albert Marth on 29 November 1864 and was described as "faint, very small, round, almost stellar".
Properties
NGC 3 is a lenticular galaxy, while other sources tagged NGC 3 as a barred spiral galaxy. NGC 3 is located at a distance of about 172 million light-years from Earth. NGC 3 has a magnitude of 14.2.
NGC 3 appears to have a faint spiral arm structure, along with a weak bar.
Listing in Astronomical Catalogues
NGC 3 is first cataloged as GC 5080, an addendum to Dreyer's 1877 Supplement to the General Catalogue of Nebulae And Clusters of Stars. The object is cataloged as UGC 58, PGC 565, Ark 1, MCG+01-01-037, and CGCG 408–35.
Gallery
References
External links
Galaxies discovered in 1864
Lenticular galaxies
Pisces (constellation)
0003
00565
00058
18641129 | NGC 3 | [
"Astronomy"
] | 257 | [
"Pisces (constellation)",
"Constellations"
] |
983,423 | https://en.wikipedia.org/wiki/47%20Tucanae | 47 Tucanae or 47 Tuc (also designated as NGC 104 and Caldwell 106) is a globular cluster located in the constellation Tucana. It is about from Earth, and 120 light years in diameter. 47 Tuc can be seen with the naked eye, with an apparent magnitude of 4.1. It appears about 44 arcminutes across including its far outreaches. Due to its far southern location, 18° from the south celestial pole, it was not catalogued by European astronomers until the 1750s, when the cluster was first identified by Nicolas-Louis de Lacaille from South Africa.
47 Tucanae is the second brightest globular cluster after Omega Centauri, and telescopically reveals about ten thousand stars, many appearing within a small dense central core. The cluster may contain an intermediate-mass black hole.
Early history
The cluster was recorded in 1751-2 by Nicolas-Louis de Lacaille, who initially thought it was the nucleus of a bright comet. Lacaille then listed it as "Lac I-1", the first object listed in his deep-sky catalogue. The number "47" was assigned in Allgemeine Beschreibung und Nachweisung der Gestirne nebst Verzeichniss ("General description and verification of the stars and indexes"), compiled by Johann Elert Bode and published in Berlin in 1801. Bode did not observe this cluster himself, but had reordered Lacaille's catalogued stars by constellation in order of right ascension.
In the 19th century, Benjamin Apthorp Gould assigned the Greek letter ξ (Xi) to the cluster to designate it ξ Tucanae, but this was not widely adopted and it is almost universally referred to as 47 Tucanae.
Characteristics
47 Tucanae is the second brightest globular cluster in the sky (after Omega Centauri), and is noted for having a small very bright and dense core. It is one of the most massive globular clusters in the Galaxy, containing millions of stars. The cluster appears roughly the size of the full moon in the sky under ideal conditions. Though it appears adjacent to the Small Magellanic Cloud, the latter is some distant, being over fifteen times farther than 47 Tuc.
A blue giant star with a spectral class of B8III is the brightest star in visible and ultraviolet light, with a luminosity of about 1,100 times that of the Sun, and is aptly known as the "Bright Star". It is a post-AGB star, having passed the asymptotic giant branch phase of its life, and is currently fusing helium. It has an effective temperature of about 10,850 K, and is about 54% the mass of the Sun.
The core of 47 Tuc was the subject of a major survey for planets, using the Hubble Space Telescope to look for partial eclipses of stars by their planets. No planets were found, though ten to fifteen were expected based on the rate of planet discoveries around stars near the Sun. This indicates that planets are relatively rare in globular clusters. A later ground-based survey in the uncrowded outer regions of the cluster also failed to detect planets when several were expected. This strongly indicates that the low metallicity of the environment, rather than the crowding, is responsible.
47 Tucanae contains at least two stellar populations of stars, of different ages or metallicities. The dense core contains a number of exotic stars of scientific interest, including at least 21 blue stragglers. Globular clusters efficiently sort stars by mass, with the most massive stars falling to the center.
47 Tucanae contains hundreds of X-ray sources, including stars with enhanced chromospheric activity due to their presence in binary star systems, cataclysmic variable stars containing white dwarfs accreting from companion stars and low-mass X-ray binaries containing neutron stars that are not currently accreting, but can be observed by the X-rays emitted from the hot surface of the neutron star.
47 Tucanae has 35 known millisecond pulsars, the second largest population of pulsars in any globular cluster, after Terzan 5.
These pulsars are thought to be spun up by the accretion of material from binary companion stars, in a previous X-ray binary phase. The companion of one pulsar in 47 Tucanae, 47 Tuc W, seems to still be transferring mass towards its companion, indicating that this system is completing a transition from being an accreting low-mass X-ray binary to a millisecond pulsar. X-ray emission has been individually detected from most millisecond pulsars in 47 Tucanae with the Chandra X-ray Observatory, likely emission from the neutron star surface, and gamma-ray emission has been detected with the Fermi Gamma-ray Space Telescope from its millisecond pulsar population (making 47 Tucanae the first globular cluster to be detected in gamma-rays).
Possible central black hole
It is not yet clear whether 47 Tucanae hosts a central black hole. Hubble Space Telescope data constrain the mass of any possible black hole at the cluster's center to be less than approximately 1,500 solar masses. However, in February, 2017, astronomers announced that a black hole of some 2,200 solar masses may be located in the cluster; the researchers detected the black hole's signature from the motions and distributions of pulsars in the cluster. Despite this, a recent analysis of an updated and more extensive timing data set on these pulsars provides no solid evidence in favor of the existence of a black hole.
Modern discoveries
In December 2008, Ragbir Bhathal of the University of Western Sydney claimed the detection of a strong laser-like signal from the direction of 47 Tucanae.
In May 2015, the first evidence of the process of mass segregation in this globular cluster was announced. The cluster's Hertzsprung–Russell diagram suggests stars approximately 13 billion years old, which is unusually old.
References
External links
47 Tucanae at the ESA-Hubble website
47 Tucanae, Galactic Globular Clusters Database page
47 Tucanae at the Chandra X-ray Observatory website
NGC 104
The Toucan's Diamond ESO
Globular clusters
Tucana
Tucanae, Xi
Xi Tucanae
106b
17510914
Articles containing video clips
0095
002051
Intermediate-mass black holes | 47 Tucanae | [
"Physics",
"Astronomy"
] | 1,360 | [
"Black holes",
"Unsolved problems in physics",
"Intermediate-mass black holes",
"Constellations",
"Tucana"
] |
983,438 | https://en.wikipedia.org/wiki/NGC%20457 | NGC 457 (also designated Caldwell 13, and known as the Dragonfly Cluster, E.T. Cluster, Owl Cluster, Kachina Doll Cluster or Phi Cassiopeiae Cluster) is an open star cluster in the constellation Cassiopeia.
Discovery
It was discovered by William Herschel on August 18, 1780, with a 6.2 inch reflector telescope, and catalogued as VII 42.
Visibility
It is an easy target for amateur astronomers, and can be seen even with small telescopes in light-polluted skies.
Characteristics
It lies over 7,900 light years away from the Sun. It has an estimated age of 21 million years. The cluster is sometimes referred by amateur astronomers as the Owl Cluster or the E.T. Cluster (due to its resemblance to the movie character).
Two bright stars Phi Cassiopeiae (magnitude 5 and spectral type F0) and HD 7902 (magnitude 7) can be imagined as eyes. It is not yet clear if Phi Cassiopeiae is a member of the cluster, and if it is, then it would be one of the brightest stars known, surpassing Rigel in luminosity. For comparison, the Sun at the same distance as Phi Cassiopeiae would shine at just 17.3 magnitude. The next brightest star is the red supergiant variable star V466 Cassiopeiae. The cluster features a rich field of about 150 stars of magnitude 9-13. About 60 stars have been identified as true members of the cluster.
Gallery
References
External links
NGC 0457
NGC 0457
0457
013b
17871018 | NGC 457 | [
"Astronomy"
] | 329 | [
"Cassiopeia (constellation)",
"Constellations"
] |
983,444 | https://en.wikipedia.org/wiki/NGC%20752 | NGC 752 (also known as Caldwell 28) is an open cluster in the constellation Andromeda. The cluster was discovered by Caroline Herschel in 1783 and cataloged by her brother William Herschel in 1786, although an object that may have been NGC 752 was described by Giovanni Batista Hodierna before 1654.
The large cluster lies 1,400 light-years away from the Earth and is easily seen through binoculars, although it may approach naked eye visibility under good observing conditions. A telescope reveals about 60 stars no brighter than 9th magnitude within NGC 752.
Components
The most up-to-date research lists 302 stars as members of NGC 752. Since the age of the cluster is , they are mainly low mass stars on the main sequence or red giants, with a main sequence turnoff at about F0. A blue straggler star is also present, along with some spectroscopic binaries and variable stars. The detached eclipsing binary DS Andromedae is a member of this cluster.
Images
Notable stars
References
External links
SEDS – NGC 752
perseus.gr – NGC 752 in a hires LRGB CCD image
Open clusters
Andromeda (constellation)
0752
028
Discoveries by Caroline Herschel | NGC 752 | [
"Astronomy"
] | 255 | [
"Andromeda (constellation)",
"Constellations"
] |
983,463 | https://en.wikipedia.org/wiki/NGC%205078 | NGC 5078 is a spiral galaxy in the Hydra constellation, approximately 94 million light-years away from Earth. It has a diameter of 127,000 light-years and is probably a member of the NGC 5061 group. The dust lane of NGC 5078 is warped, probably by interaction with the nearby galaxy IC 879, which is itself distorted into an 'S' shape by the interaction. At the presumed distance the two galaxies would have a minimal separation of about 61,000 light-years. For comparison, the Large Magellanic Cloud is about 160,000 light-years from the Milky Way.
NGC 5078 is also only separated in the sky from the spiral galaxy NGC 5101 by about 0.5 degrees, and both are believed to be at the same distance from the Earth. This would mean they are approximately 800,000 light-years apart.
One supernova has been observed in NGC 5078: SN 1999cz (type Ic, mag. 16).
References
External links
Unbarred spiral galaxies
Hydra (constellation)
5078
46490 | NGC 5078 | [
"Astronomy"
] | 224 | [
"Hydra (constellation)",
"Constellations"
] |
983,476 | https://en.wikipedia.org/wiki/NGC%205189 | NGC 5189 (Gum 47, IC 4274, nicknamed Spiral Planetary Nebula) is a planetary nebula in the constellation Musca. It was discovered by James Dunlop on 1 July 1826, who catalogued it as Δ252. For many years, well into the 1960s, it was thought to be a bright emission nebula. It was Karl Gordon Henize in 1967 who first described NGC 5189 as quasi-planetary based on its spectral emissions.
Seen through the telescope it seems to have an S shape, reminiscent of a barred spiral galaxy. The S shape, together with point-symmetric knots in the nebula, have for a long time hinted to astronomers that a binary central star is present.
The Hubble Space Telescope imaging analysis showed that this S shape structure is indeed two dense low-ionization regions: one moving toward the north-east and another one moving toward the south-west of the nebula, which could be a result of a recent outburst from the central star. Observations with the Southern African Large Telescope have finally found a white dwarf companion in a 4.04 day orbit around the rare low-mass Wolf-Rayet type central star of NGC 5189. NGC 5189 is estimated to be 546 parsecs or 1,780 light years away from Earth. Other measurements have yielded results up to 900 parsecs (~3000 light-years).
References
External links
A Cosmic Holiday Ornament, Hubble-Style
Southern African Large Telescope: Elusive Binary System
Musca
5189
Planetary nebulae
18260701
IC objects
Discoveries by James Dunlop | NGC 5189 | [
"Astronomy"
] | 322 | [
"Musca",
"Constellations"
] |
983,493 | https://en.wikipedia.org/wiki/NGC%205195 | NGC 5195 (also known as Messier 51b or M51b) is a dwarf galaxy that is interacting with the Whirlpool Galaxy (also known as M51a or NGC 5194). Both galaxies are located approximately 25 million light-years away in the constellation Canes Venatici. Together, the two galaxies are one of the most famous interacting galaxy pairs.
History
NGC 5195 was discovered by Pierre Méchain on March 20, 1781.
Interaction with the Whirlpool Galaxy
NGC 5195 and the Whirlpool Galaxy compose one of the most noted interacting galaxy pairs in astronomy. The two galaxies are listed in the Atlas of Peculiar Galaxies as one of several prominent examples of a spiral galaxy with a companion galaxy. The system was also the subject of very early theoretical investigations into galaxy interactions. The two galaxies are connected by a dust-rich tidal bridge. The dust in this tidal bridge can be seen silhouetted against the center of NGC 5195. This demonstrates that NGC 5195 appears to lie behind the Whirlpool Galaxy. The encounter has significantly enhanced the spiral structure of M51.
A three-pronged structure extends from NGC 5195. The middle prong seems to be bluer than the other prongs, suggesting that this feature is an extension of the Whirlpool Galaxy’s tidal tails. The structure leads to several massive plumes and streams of stars produced by the interaction with the aforementioned grand-design spiral galaxy. One massive plume is called the "Northwest Plume". However, diffuse high-speed gas within the plume suggests an origin within the Whirlpool Galaxy and not NGC 5195. The Northwest plume partially overlaps and blends it with two stellar streams extending from NGC 5195. Unlike the northwest plume, the stellar streams are bifurcated and similar in color to NGC 5195. A 2015 study observing the Whirlpool galaxy and its companion found two new and very faint tidal structures. One of them is called the "South Plume" while the other one is called the "Northeast Plume".
In January 2016, BBC science reporter Jonathan Webb said, "Astronomers have spotted two huge waves of gas being 'burped' by the black hole at the heart of a nearby galaxy. The swathes of hot gas, detected in X-ray images from NASA's Chandra space telescope, appear to be sweeping cooler hydrogen gas ahead of them. This vast, rippling belch is taking place in NGC 5195 – a small, neglected sibling of the 'Whirlpool Galaxy', 26 million light years away. That makes it one of the closest black holes blasting gas in this way". He added, "The findings, presented at the 227th meeting of the American Astronomical Society (AAS) in Florida, are a dramatic example of 'feedback' between a supermassive black hole and its host galaxy". Webb's report cited Marie Machacek, co-author of the study from the Harvard–Smithsonian Center for Astrophysics (CFA), as saying, "We think that feedback keeps galaxies from becoming too large ... But at the same time, it can be responsible for how some stars form. This shows that black holes can create, not just destroy."
Morphology
As a consequence of the gravitational interaction with the Whirlpool Galaxy, NGC 5195 is highly distorted. Classification of its morphology is difficult, as it is sometimes identified as a lenticular galaxy or as an amorphous or irregular galaxy. It has been described as falling outside the standard morphological classification system.
Supernova
SN 1945A is the only supernova that has been detected within NGC 5195. It was found 10″ northwest of the nucleus on April 6, 1945, by Milton L. Humason using the telescope at Mount Wilson Observatory. The supernova, classified as a Type I supernova, reached a peak apparent magnitude of 14.0.
See also
NGC 1097
NGC 1167
Dwingeloo 1
List of NGC objects (5001–6000)
References
External links
SEDS: Irregular Galaxy M51B (NGC 5195)
Irregular galaxies
Interacting galaxies
Peculiar galaxies
LINER galaxies
M51 Group
Canes Venatici
Messier objects
5195
08494
47413
085
17810320
Discoveries by Pierre Méchain
+08-25-014
13278+4731 | NGC 5195 | [
"Astronomy"
] | 907 | [
"Canes Venatici",
"Constellations"
] |
983,601 | https://en.wikipedia.org/wiki/Comparative%20genomic%20hybridization | Comparative genomic hybridization (CGH) is a molecular cytogenetic method for analysing copy number variations (CNVs) relative to ploidy level in the DNA of a test sample compared to a reference sample, without the need for culturing cells. The aim of this technique is to quickly and efficiently compare two genomic DNA samples arising from two sources, which are most often closely related, because it is suspected that they contain differences in terms of either gains or losses of either whole chromosomes or subchromosomal regions (a portion of a whole chromosome). This technique was originally developed for the evaluation of the differences between the chromosomal complements of solid tumor and normal tissue, and has an improved resolution of 5–10 megabases compared to the more traditional cytogenetic analysis techniques of giemsa banding and fluorescence in situ hybridization (FISH) which are limited by the resolution of the microscope utilized.
This is achieved through the use of competitive fluorescence in situ hybridization. In short, this involves the isolation of DNA from the two sources to be compared, most commonly a test and reference source, independent labelling of each DNA sample with fluorophores (fluorescent molecules) of different colours (usually red and green), denaturation of the DNA so that it is single stranded, and the hybridization of the two resultant samples in a 1:1 ratio to a normal metaphase spread of chromosomes, to which the labelled DNA samples will bind at their locus of origin. Using a fluorescence microscope and computer software, the differentially coloured fluorescent signals are then compared along the length of each chromosome for identification of chromosomal differences between the two sources. A higher intensity of the test sample colour in a specific region of a chromosome indicates the gain of material of that region in the corresponding source sample, while a higher intensity of the reference sample colour indicates the loss of material in the test sample in that specific region. A neutral colour (yellow when the fluorophore labels are red and green) indicates no difference between the two samples in that location.
CGH is only able to detect unbalanced chromosomal abnormalities. This is because balanced chromosomal abnormalities such as reciprocal translocations, inversions or ring chromosomes do not affect copy number, which is what is detected by CGH technologies. CGH does, however, allow for the exploration of all 46 human chromosomes in single test and the discovery of deletions and duplications, even on the microscopic scale which may lead to the identification of candidate genes to be further explored by other cytological techniques.
Through the use of DNA microarrays in conjunction with CGH techniques, the more specific form of array CGH (aCGH) has been developed, allowing for a locus-by-locus measure of CNV with increased resolution as low as 100 kilobases. This improved technique allows for the aetiology of known and unknown conditions to be discovered.
History
The motivation underlying the development of CGH stemmed from the fact that the available forms of cytogenetic analysis at the time (giemsa banding and FISH) were limited in their potential resolution by the microscopes necessary for interpretation of the results they provided. Furthermore, giemsa banding interpretation has the potential to be ambiguous and therefore has lowered reliability, and both techniques require high labour inputs which limits the loci which may be examined.
The first report of CGH analysis was by Kallioniemi and colleagues in 1992 at the University of California, San Francisco, who utilised CGH in the analysis of solid tumors. They achieved this by the direct application of the technique to both breast cancer cell lines and primary bladder tumors in order to establish complete copy number karyotypes for the cells. They were able to identify 16 different regions of amplification, many of which were novel discoveries.
Soon after in 1993, du Manoir et al. reported virtually the same methodology. The authors painted a series of individual human chromosomes from a DNA library with two different fluorophores in different proportions to test the technique, and also applied CGH to genomic DNA from patients affected with either Downs syndrome or T-cell prolymphocytic leukemia as well as cells of a renal papillary carcinoma cell line. It was concluded that the fluorescence ratios obtained were accurate and that differences between genomic DNA from different cell types were detectable, and therefore that CGH was a highly useful cytogenetic analysis tool.
Initially, the widespread use of CGH technology was difficult, as protocols were not uniform and therefore inconsistencies arose, especially due to uncertainties in the interpretation of data. However, in 1994 a review was published which described an easily understood protocol in detail and the image analysis software was made available commercially, which allowed CGH to be utilised all around the world.
As new techniques such as microdissection and degenerate oligonucleotide primed polymerase chain reaction (DOP-PCR) became available for the generation of DNA products, it was possible to apply the concept of CGH to smaller chromosomal abnormalities, and thus the resolution of CGH was improved.
The implementation of array CGH, whereby DNA microarrays are used instead of the traditional metaphase chromosome preparation, was pioneered by Solinas-Tolodo et al. in 1997 using tumor cells and Pinkel et al. in 1998 by use of breast cancer cells. This was made possible by the Human Genome Project which generated a library of cloned DNA fragments with known locations throughout the human genome, with these fragments being used as probes on the DNA microarray. Now probes of various origins such as cDNA, genomic PCR products and bacterial artificial chromosomes (BACs) can be used on DNA microarrays which may contain up to 2 million probes. Array CGH is automated, allows greater resolution (down to 100 kb) than traditional CGH as the probes are far smaller than metaphase preparations, requires smaller amounts of DNA, can be targeted to specific chromosomal regions if required and is ordered and therefore faster to analyse, making it far more adaptable to diagnostic uses.
Basic methods
Metaphase slide preparation
The DNA on the slide is a reference sample, and is thus obtained from a karyotypically normal man or woman, though it is preferential to use female DNA as they possess two X chromosomes which contain far more genetic information than the male Y chromosome. Phytohaemagglutinin stimulated peripheral blood lymphocytes are used. 1mL of heparinised blood is added to 10ml of culture medium and incubated for 72 hours at 37 °C in an atmosphere of 5% CO2. Colchicine is added to arrest the cells in mitosis, the cells are then harvested and treated with hypotonic potassium chloride and fixed in 3:1 methanol/acetic acid.
One drop of the cell suspension should then be dropped onto an ethanol cleaned slide from a distance of about 30 cm, optimally this should be carried out at room temperature at humidity levels of 60–70%. Slides should be evaluated by visualisation using a phase contrast microscope, minimal cytoplasm should be observed and chromosomes should not be overlapping and be 400–550 bands long with no separated chromatids and finally should appear dark rather than shiny. Slides then need to be air dried overnight at room temperature, and any further storage should be in groups of four at −20 °C with either silica beads or nitrogen present to maintain dryness. Different donors should be tested as hybridization may be variable. Commercially available slides may be used, but should always be tested first.
Isolation of DNA from test tissue and reference tissue
Standard phenol extraction is used to obtain DNA from test or reference (karyotypically normal individual) tissue, which involves the combination of Tris-Ethylenediaminetetraacetic acid and phenol with aqueous DNA in equal amounts. This is followed by separation by agitation and centrifugation, after which the aqueous layer is removed and further treated using ether and finally ethanol precipitation is used to concentrate the DNA.
May be completed using DNA isolation kits available commercially which are based on affinity columns.
Preferentially, DNA should be extracted from fresh or frozen tissue as this will be of the highest quality, though it is now possible to use archival material which is formalin fixed or paraffin wax embedded, provided the appropriate procedures are followed. 0.5-1 μg of DNA is sufficient for the CGH experiment, though if the desired amount is not obtained DOP-PCR may be applied to amplify the DNA, however it in this case it is important to apply DOP-PCR to both the test and reference DNA samples to improve reliability.
DNA labelling
Nick translation is used to label the DNA and involves cutting DNA and substituting nucleotides labelled with fluorophores (direct labelling) or biotin or oxigenin to have fluophore conjugated antibodies added later (indirect labelling). It is then important to check fragment lengths of both test and reference DNA by gel electrophoresis, as they should be within the range of 500kb-1500kb for optimum hybridization.
Blocking
Unlabelled Life Technologies Corporation's Cot-1 DNA (placental DNA enriched with repetitive sequences of length 50bp-100bp)is added to block normal repetitive DNA sequences, particularly at centromeres and telomeres, as these sequences, if detected, may reduce the fluorescence ratio and cause gains or losses to escape detection.
Hybridization
8–12μl of each of labelled test and labelled reference DNA are mixed and 40 μg Cot-1 DNA is added, then precipitated and subsequently dissolved in 6μl of hybridization mix, which contains 50% formamide to decrease DNA melting temperature and 10% dextran sulphate to increase the effective probe concentration in a saline sodium citrate (SSC) solution at a pH of 7.0.
Denaturation of the slide and probes are carried out separately. The slide is submerged in 70% formamide/2xSSC for 5–10 minutes at 72 °C, while the probes are denatured by immersion in a water bath of 80 °C for 10 minutes and are immediately added to the metaphase slide preparation. This reaction is then covered with a coverslip and left for two to four days in a humid chamber at 40 °C.
The coverslip is then removed and 5 minute washes are applied, three using 2xSSC at room temperature, one at 45 °C with 0.1xSSC and one using TNT at room temperature. The reaction is then preincubated for 10 minutes then followed by a 60-minute, 37 °C incubation, three more 5 minute washes with TNT then one with 2xSSC at room temperature. The slide is then dried using an ethanol series of 70%/96%/100% before counterstaining with DAPI (0.35 μg/ml), for chromosome identification, and sealing with a coverslip.
Fluorescence visualisation and imaging
A fluorescence microscope with the appropriate filters for the DAPI stain as well as the two fluorophores utilised is required for visualisation, and these filters should also minimise the crosstalk between the fluorophores, such as narrow band pass filters. The microscope must provide uniform illumination without chromatic variation, be appropriately aligned and have a "plan" type of objective which is apochromatic and give a magnification of x63 or x100.
The image should be recorded using a camera with spatial resolution at least 0.1 μm at the specimen level and give an image of at least 600x600 pixels. The camera must also be able to integrate the image for at least 5 to 10 seconds, with a minimum photometric resolution of 8 bit.
Dedicated CGH software is commercially available for the image processing step, and is required to subtract background noise, remove and segment materials not of chromosomal origin, normalize the fluorescence ratio, carry out interactive karyotyping and chromosome scaling to standard length. A "relative copy number karyotype" which presents chromosomal areas of deletions or amplifications is generated by averaging the ratios of a number of high quality metaphases and plotting them along an ideogram, a diagram identifying chromosomes based on banding patterns. Interpretation of the ratio profiles is conducted either using fixed or statistical thresholds (confidence intervals). When using confidence intervals, gains or losses are identified when 95% of the fluorescence ratio does not contain 1.0.
Extra notes
Extreme care must be taken to avoid contamination of any step involving DNA, especially with the test DNA as contamination of the sample with normal DNA will skew results closer to 1.0, thus abnormalities may go undetected. FISH, PCR and flow cytometry experiments may be employed to confirm results.
Array comparative genomic hybridization
Array comparative genomic hybridization (also microarray-based comparative genomic hybridization, matrix CGH, array CGH, aCGH) is a molecular cytogenetic technique for the detection of chromosomal copy number changes on a genome wide and high-resolution scale. Array CGH compares the patient's genome against a reference genome and identifies differences between the two genomes, and hence locates regions of genomic imbalances in the patient, utilizing the same principles of competitive fluorescence in situ hybridization as traditional CGH.
With the introduction of array CGH, the main limitation of conventional CGH, a low resolution, is overcome. In array CGH, the metaphase chromosomes are replaced by cloned DNA fragments (+100–200 kb) of which the exact chromosomal location is known. This allows the detection of aberrations in more detail and, moreover, makes it possible to map the changes directly onto the genomic sequence.
Array CGH has proven to be a specific, sensitive, fast and high-throughput technique, with considerable advantages compared to other methods used for the analysis of DNA copy number changes making it more amenable to diagnostic applications. Using this method, copy number changes at a level of 5–10 kilobases of DNA sequences can be detected. , even high-resolution CGH (HR-CGH) arrays are accurate to detect structural variations (SV) at resolution of 200 bp. This method allows one to identify new recurrent chromosome changes such as microdeletions and duplications in human conditions such as cancer and birth defects due to chromosome aberrations.
Methodology
Array CGH is based on the same principle as conventional CGH. In both techniques, DNA from a reference (or control) sample and DNA from a test (or patient) sample are differentially labelled with two different fluorophores and used as probes that are cohybridized competitively onto nucleic acid targets. In conventional CGH, the target is a reference metaphase spread. In array CGH, these targets can be genomic fragments cloned in a variety of vectors (such as BACs or plasmids), cDNAs, or oligonucleotides.
Figure 2. is a schematic overview of the array CGH technique. DNA from the sample to be tested is labeled with a red fluorophore (Cyanine 5) and a reference DNA sample is labeled with green fluorophore (Cyanine 3). Equal quantities of the two DNA samples are mixed and cohybridized to a DNA microarray of several thousand evenly spaced cloned DNA fragments or oligonucleotides, which have been spotted in triplicate on the array. After hybridization, digital imaging systems are used to capture and quantify the relative fluorescence intensities of each of the hybridized fluorophores. The resulting ratio of the fluorescence intensities is proportional to the ratio of the copy numbers of DNA sequences in the test and reference genomes. If the intensities of the flurochromes are equal on one probe, this region of the patient's genome is interpreted as having equal quantity of DNA in the test and reference samples; if there is an altered Cy3:Cy5 ratio this indicates a loss or a gain of the patient DNA at that specific genomic region.
Technological approaches to array CGH
Array CGH has been implemented using a wide variety of techniques. Therefore, some of the advantages and limitations of array CGH are dependent on the technique chosen.
The initial approaches used arrays produced from large insert genomic DNA clones, such as BACs. The use of BACs provides sufficient intense signals to detect single-copy changes and to locate aberration boundaries accurately. However, initial DNA yields of isolated BAC clones are low and DNA amplification techniques are necessary. These techniques include ligation-mediated polymerase chain reaction (PCR), degenerate primer PCR using one or several sets of primers, and rolling circle amplification. Arrays can also be constructed using cDNA. These arrays currently yield a high spatial resolution, but the number of cDNAs is limited by the genes that are encoded on the chromosomes, and their sensitivity is low due to cross-hybridization. This results in the inability to detect single copy changes on a genome wide scale. The latest approach is spotting the arrays with short oligonucleotides. The amount of oligos is almost infinite, and the processing is rapid, cost-effective, and easy. Although oligonucleotides do not have the sensitivity to detect single copy changes, averaging of ratios from oligos that map next to each other on the chromosome can compensate for the reduced sensitivity. It is also possible to use arrays which have overlapping probes so that specific breakpoints may be uncovered.
Design approaches
There are two approaches to the design of microarrays for CGH applications: whole genome and targeted.
Whole genome arrays are designed to cover the entire human genome. They often include clones that provide an extensive coverage across the genome; and arrays that have contiguous coverage, within the limits of the genome. Whole-genome arrays have been constructed mostly for research applications and have proven their outstanding worth in gene discovery. They are also very valuable in screening the genome for DNA gains and losses at an unprecedented resolution.
Targeted arrays are designed for a specific region(s) of the genome for the purpose of evaluating that targeted segment. It may be designed to study a specific chromosome or chromosomal segment or to identify and evaluate specific DNA dosage abnormalities in individuals with suspected microdeletion syndromes or subtelomeric rearrangements. The crucial goal of a targeted microarray in medical practice is to provide clinically useful results for diagnosis, genetic counseling, prognosis, and clinical management of unbalanced cytogenetic abnormalities.
Applications
Conventional
Conventional CGH has been used mainly for the identification of chromosomal regions that are recurrently lost or gained in tumors, as well as for the diagnosis and prognosis of cancer. This approach can also be used to study chromosomal aberrations in fetal and neonatal genomes. Furthermore, conventional CGH can be used in detecting chromosomal abnormalities and have been shown to be efficient in diagnosing complex abnormalities associated with human genetic disorders.
In cancer research
CGH data from several studies of the same tumor type show consistent patterns of non-random genetic aberrations. Some of these changes appear to be common to various kinds of malignant tumors, while others are more tumor specific. For example, gains of chromosomal regions lq, 3q and 8q, as well as losses of 8p, 13q, 16q and 17p, are common to a number of tumor types, such as breast, ovarian, prostate, renal and bladder cancer (Figure. 3). Other alterations, such as 12p and Xp gains in testicular cancer, 13q gain 9q loss in bladder cancer, 14q loss in renal cancer and Xp loss in ovarian cancer are more specific, and might reflect the unique selection forces operating during cancer development in different organs. Array CGH is also frequently used in research and diagnostics of B cell malignancies, such as chronic lymphocytic leukemia.
Chromosomal aberrations
Cri du Chat (CdC) is a syndrome caused by a partial deletion of the short arm of chromosome 5. Several studies have shown that conventional CGH is suitable to detect the deletion, as well as more complex chromosomal alterations. For example, Levy et al. (2002) reported an infant with a cat-like cry, the hallmark of CdC, but having an indistinct karyotype. CGH analysis revealed a loss of chromosomal material from 5p15.3 confirming the diagnosis clinically. These results demonstrate that conventional CGH is a reliable technique in detecting structural aberrations and, in specific cases, may be more efficient in diagnosing complex abnormalities.
Array CGH
Array CGH applications are mainly directed at detecting genomic abnormalities in cancer. However, array CGH is also suitable for the analysis of DNA copy number aberrations that cause human genetic disorders. That is, array CGH is employed to uncover deletions, amplifications, breakpoints and ploidy abnormalities. Earlier diagnosis is of benefit to the patient as they may undergo appropriate treatments and counseling to improve their prognosis.
Genomic abnormalities in cancer
Genetic alterations and rearrangements occur frequently in cancer and contribute to its pathogenesis. Detecting these aberrations by array CGH provides information on the locations of important cancer genes and can have clinical use in diagnosis, cancer classification and prognostification. However, not all of the losses of genetic material are pathogenetic, since some DNA material is physiologically lost during the rearrangement of immunoglobulin subgenes. In a recent study, array CGH has been implemented to identify regions of chromosomal aberration (copy-number variation) in several mouse models of breast cancer, leading to identification of cooperating genes during myc-induced oncogenesis.
Array CGH may also be applied not only to the discovery of chromosomal abnormalities in cancer, but also to the monitoring of the progression of tumors. Differentiation between metastatic and mild lesions is also possible using FISH once the abnormalities have been identified by array CGH.
Submicroscopic aberrations
Prader–Willi syndrome (PWS) is a paternal structural abnormality involving 15q11-13, while a maternal aberration in the same region causes Angelman syndrome (AS). In both syndromes, the majority of cases (75%) are the result of a 3–5 Mb deletion of the PWS/AS critical region. These small aberrations cannot be detected using cytogenetics or conventional CGH, but can be readily detected using array CGH. As a proof of principle Vissers et al. (2003) constructed a genome wide array with a 1 Mb resolution to screen three patients with known, FISH-confirmed microdeletion syndromes, including one with PWS. In all three cases, the abnormalities, ranging from 1.5 to 2.9Mb, were readily identified. Thus, array CGH was demonstrated to be a specific and sensitive approach in detecting submicroscopic aberrations.
When using overlapping microarrays, it is also possible to uncover breakpoints involved in chromosomal aberrations.
Prenatal genetic diagnosis
Though not yet a widely employed technique, the use of array CGH as a tool for preimplantation genetic screening is becoming an increasingly popular concept. It has the potential to detect CNVs and aneuploidy in eggs, sperm or embryos which may contribute to failure of the embryo to successfully implant, miscarriage or conditions such as Down syndrome (trisomy 21). This makes array CGH a promising tool to reduce the incidence of life altering conditions and improve success rates of IVF attempts. The technique involves whole genome amplification from a single cell which is then used in the array CGH method. It may also be used in couples carrying chromosomal translocations such as balanced reciprocal translocations or Robertsonian translocations, which have the potential to cause chromosomal imbalances in their offspring.
Limitations of CGH and array CGH
A main disadvantage of conventional CGH is its inability to detect structural chromosomal aberrations without copy number changes, such as mosaicism, balanced chromosomal translocations, and inversions. CGH can also only detect gains and losses relative to the ploidy level. In addition, chromosomal regions with short repetitive DNA sequences are highly variable between individuals and can interfere with CGH analysis. Therefore, repetitive DNA regions like centromeres and telomeres need to be blocked with unlabeled repetitive DNA (e.g. Cot1 DNA) and/or can be omitted from screening. Furthermore, the resolution of conventional CGH is a major practical problem that limits its clinical applications. Although CGH has proven to be a useful and reliable technique in the research and diagnostics of both cancer and human genetic disorders, the applications involve only gross abnormalities. Because of the limited resolution of metaphase chromosomes, aberrations smaller than 5–10 Mb cannot be detected using conventional CGH.
For the detection of such abnormalities, a high-resolution technique is required.
Array CGH overcomes many of these limitations. Array CGH is characterized by a high resolution, its major advantage with respect to conventional CGH. The standard resolution varies between 1 and 5 Mb, but can be increased up to approximately 40 kb by supplementing the array with extra clones. However, as in conventional CGH, the main disadvantage of array CGH is its inability to detect aberrations that do not result in copy number changes and is limited in its ability to detect mosaicism. The level of mosaicism that can be detected is dependent on the sensitivity and spatial resolution of the clones. At present, rearrangements present in approximately 50% of the cells is the detection limit. For the detection of such abnormalities, other techniques, such as SKY (Spectral karyotyping) or FISH have to still be used.
See also
Cytogenetics
Virtual karyotype
References
External links
Virtual Grand Rounds: "Differentiating Microarray Technologies and Related Clinical Implications" by Arthur Beaudet, MD
arrayMap repository: Continuously expanded collection cancer genome array datasets, with per-array and aggregated data visualisation (ca. 64'000 arrays, September 2014).
The former NCBI's Cancer Chromosomes resource has been discontinued.
Molecular genetics
Gene tests
Cytogenetics
Comparisons | Comparative genomic hybridization | [
"Chemistry",
"Biology"
] | 5,571 | [
"Genetics techniques",
"Molecular genetics",
"Gene tests",
"Molecular biology"
] |
983,754 | https://en.wikipedia.org/wiki/MIFARE | MIFARE is a series of integrated circuit (IC) chips used in contactless smart cards and proximity cards.
The brand includes proprietary solutions based on various levels of the ISO/IEC 14443 Type-A 13.56 MHz contactless smart card standard. It uses AES and DES/Triple-DES encryption standards, as well as an older proprietary encryption algorithm, Crypto-1. According to NXP, 10 billion of their smart card chips and over 150 million reader modules have been sold.
The MIFARE trademark is owned by NXP Semiconductors, which was spun off from Philips Electronics in 2006.
Variants
MIFARE products are embedded in contactless and contact smart cards, smart paper tickets, wearables and phones.
The MIFARE brand name (derived from the term MIKRON FARE collection and created by the company Mikron) covers four families of contactless cards:
MIFARE Classic Employs a proprietary protocol compliant with parts 1–3 of ISO/IEC 14443 Type A, with an NXP proprietary security protocol for authentication and ciphering.
Subtypes: MIFARE Classic EV1 (other subtypes are no longer in use).
MIFARE Plus Drop-in replacement for MIFARE Classic with certified security level (AES-128 based) and is fully backwards compatible with MIFARE Classic.
Subtypes: MIFARE Plus S, MIFARE Plus X, MIFARE Plus SE and MIFARE Plus EV2.
MIFARE Ultralight Low-cost ICs that are useful for high volume applications such as public transport, loyalty cards and event ticketing.
Subtypes: MIFARE Ultralight C, MIFARE Ultralight EV1, MIFARE Ultralight Nano and MIFARE Ultralight AES.
MIFARE DESFire Contactless ICs that comply with parts 3 and 4 of ISO/IEC 14443-4 Type A with a mask-ROM operating system from NXP. The DES in the name refers to the use of a DES, two-key 3DES, three-key 3DES and AES encryption; while Fire is an acronym for Fast, innovative, reliable, and enhanced.
Subtypes: MIFARE DESFire EV1, MIFARE DESFire EV2, MIFARE DESFire EV3 and MIFARE DESFire Light.
There is also the MIFARE SAM AV2 contact smart card. This can be used to handle the encryption in communicating with the contactless cards. The SAM (Secure Access Module) provides the secure storage of cryptographic keys and cryptographic functions.
MIFARE Classic family
The MIFARE Classic IC is a basic memory storage device, where the memory is divided into segments and blocks with simple security mechanisms for access control. They are ASIC-based and have limited computational power. Due to their reliability and low cost, those cards are widely used for electronic wallets, access control, corporate ID cards, transportation or stadium ticketing. It uses an NXP proprietary security protocol (Crypto-1) for authentication and ciphering.
MIFARE Classic encryption has been compromised; see below for details.
The MIFARE Classic with 1K memory offers 1,024 bytes of data storage, split into 16 sectors; each sector is protected by two different keys, called A and B. Each key can be programmed to allow operations such as reading, writing, increasing value blocks, etc. MIFARE Classic with 4K memory offers 4,096 bytes split into forty sectors, of which 32 are the same size as in the 1K with eight more that are quadruple size sectors. MIFARE Classic Mini offers 320 bytes split into five sectors. For each of these IC types, 16 bytes per sector are reserved for the keys and access conditions and can not normally be used for user data. Also, the very first 16 bytes contain the serial number of the card and certain other manufacturer data and are read-only. That brings the net storage capacity of these cards down to 752 bytes for MIFARE Classic with 1K memory, 3,440 bytes for MIFARE Classic with 4K memory, and 224 bytes for MIFARE Mini.
The Samsung TecTile NFC tag stickers use MIFARE Classic chips. This means only devices with an NXP NFC controller chip can read or write these tags. At the moment BlackBerry phones, the Nokia Lumia 610 (August 2012), the Google Nexus 4, Google Nexus 7 LTE and Nexus 10 (October 2013) can't read/write TecTile stickers.
MIFARE Plus family
MIFARE Plus
MIFARE Plus is a replacement IC solution for the MIFARE Classic.
It is less flexible than a MIFARE DESFire EV1 contactless IC.
MIFARE Plus was publicly announced in March 2008 with first samples in Q1 2009.
MIFARE Plus, when used in older transportation systems that do not yet support AES on the reader side, still leaves an open door to attacks. Though it helps to mitigate threats from attacks that broke the Crypto-1 cipher through the weak random number generator, it does not help against brute force attacks and crypto analytic attacks.
During the transition period from MIFARE Classic to MIFARE Plus where only a few readers might support AES in the first place, it offers an optional AES authentication in Security Level 1 (which is in fact MIFARE Classic operation). This does not prevent the attacks mentioned above but enables a secure mutual authentication between the reader and the card to prove that the card belongs to the system and is not fake.
In its highest security level SL3, using 128-bit AES encryption, MIFARE Plus is secured from attacks.
MIFARE Plus EV1
MIFARE Plus EV1 was announced in April 2016.
New features compared to MIFARE Plus X include:
Sector-wise security-level switching The choice of crypto algorithm used in the authentication protocol can be set separately for each sector. This makes it possible to use the same card with both readers that can read MIFARE Classic products (with sectors protected by 48-bit CRYPTO1 keys, "Security Level 1") and readers that can read MIFARE Plus products (with sectors protected by 128-bit AES keys, "Security Level 3"). This feature is intended to make it easier to gradually migrate existing MIFARE Classic product-based installations to MIFARE Plus, without having to replace all readers at the same time.
ISO 7816-4 wrapping The card can now be accessed in either the protocol for MIFARE (which is not compliant with the ISO 7816-4 APDU format), or using a new protocol variant that runs on top of ISO 7816-4. This way the cards become compatible with NFC reader APIs that can only exchange messages in ISO 7816-4 APDU format, with a maximum transfer data buffer size of 256 bytes.
Proximity check While the protocol for MIFARE Classic tolerated message delays of several seconds, and was therefore vulnerable to relay attacks, MIFARE Plus EV1 now implements a basic "ISO compliant" distance-bounding protocol. This puts tighter timing constraints on the permitted round-trip delay during authentication, to make it harder to forward messages to far-away cards or readers via computer networks.
Secure end-2-end channel Permits AES-protected over-the-air updates even to Crypto1 application sectors (SL1SL3 mix mode).
Transaction MAC The card can produce an additional message-authentication code over a transaction that can be verified by a remote clearing service, independent of the keys used by the local reader during the transaction.
MIFARE Plus EV2
The MIFARE Plus EV2 was introduced to the market on 23 June 2020. It comes with an enhanced read performance and transaction speed compared to MIFARE Plus EV1.
New features compared to MIFARE Plus EV1 include:
Transaction Timer To help mitigate man-in-the-middle attacks, the Transaction Timer feature, which is also available on NXP's MIFARE DESFire EV3 IC, makes it possible to set a maximum time per transaction, so it's harder for an attacker to interfere with the transaction.
MIFARE Ultralight family
MIFARE Ultralight
The MIFARE Ultralight has only 512 bits of memory (i.e. 64 bytes), without cryptographic security. The memory is provided in 16 pages of 4 bytes. Cards based on these chips are so inexpensive that they are often used for disposable tickets for events such as the 2006 FIFA World Cup.
It provides only basic security features such as one-time-programmable (OTP) bits and a write-lock feature to prevent re-writing of memory pages but does not include cryptography as applied in other MIFARE product-based cards.
MIFARE Ultralight EV1
MIFARE Ultralight EV1 introduced in November 2012 the next generation of paper ticketing smart card ICs for limited-use applications for ticketing schemes and additional security options. It comes with several enhancements above the original MIFARE Ultralight:
384 and 1024 bits user memory product variants
OTP, lock bits, configurable counters for improved security
Three independent 24-bit one-way counters to stop reloading
Protected data access through 32-bit password
NXP Semiconductors originality signature function, this is an integrated originality checker and is effective cloning protection that helps to prevent counterfeit of tickets. However, this protection is applicable only to "mass penetration of non NXP originated chips and does not prevent hardware copy or emulation of a single existing valid chip"
MIFARE Ultralight C
Introduced at the Cartes industry trade show in 2008, the MIFARE Ultralight C IC is part of NXP's low-cost MIFARE product offering (disposable ticket). With Triple DES, MIFARE Ultralight C uses a widely adopted standard, enabling easy integration in existing infrastructures. The integrated Triple DES authentication provides an effective countermeasure against cloning.
Key applications for MIFARE Ultralight C are public transportation, event ticketing, loyalty and NFC Forum tag type 2.
MIFARE Ultralight AES
It was introduced in 2022.
MIFARE DESFire family
MIFARE DESFire
The MIFARE DESFire (MF3ICD40) was introduced in 2002 and is based on a core similar to SmartMX, with more hardware and software security features than MIFARE Classic. It comes pre-programmed with the general-purpose MIFARE DESFire operating system which offers a simple directory structure and files. They are sold in four variants: One with Triple-DES only and 4 KiB of storage, and three with AES (2, 4, or 8 kiB; see MIFARE DESFire EV1). The AES variants have additional security features; e.g., CMAC. MIFARE DESFire uses a protocol compliant with ISO/IEC 14443-4. The contactless IC is based on an 8051 processor with 3DES/AES cryptographic accelerator, making very fast transactions possible.
The maximal read/write distance between card and reader is , but the actual distance depends on the field power generated by the reader and its antenna size.
In 2010, NXP announced the discontinuation of the MIFARE DESFire (MF3ICD40) after it had introduced its successor MIFARE DESFire EV1 (MF3ICD41) in late 2008. In October 2011 researchers of Ruhr University Bochum announced that they had broken the security of MIFARE DESFire (MF3ICD40), which was acknowledged by NXP (see MIFARE DESFire security).
MIFARE DESFire EV1
First evolution of MIFARE DESFire contactless IC, broadly backwards compatible. Available with 2 KiB, 4 KiB, and 8 KiB non-volatile memory. Other features include:
Support for random ID
Support for 128-bit AES
Hardware and operating system are Common Criteria certified at level EAL 4+
MIFARE DESFire EV1 was publicly announced in November 2006.
MIFARE DESFire EV2
The second evolution of the MIFARE DESFire contactless IC family, broadly backwards compatible.
New features include:
MI smart App enabling to offer or sell memory space for additional applications of 3rd parties without the need to share secret keys
Transaction MAC to authenticate transactions by 3rd parties
Virtual Card Architecture for privacy protection
Proximity check against relay attacks
MIFARE DESFire EV2 was publicly announced in March 2016 at the IT-TRANS event in Karlsruhe, Germany
MIFARE DESFire EV3
The latest evolution of the MIFARE DESFire contactless IC family, broadly backward compatible. New features include:
ISO/IEC 14443 A 1–4 and ISO/IEC 7816-4 compliant
Common Criteria EAL5+ certified for IC hardware and software
NFC Forum Tag Type 4 compliant
SUN message authentication for advanced data protection within standard NDEF read operation
Choice of open DES/2K3DES/3K3DES/AES crypto algorithms
Flexible file structure: hosts as many applications as the memory size supports
Proof of transaction with card generated MAC
Transaction Timer mitigates risk of man-in-the-middle attacks
MIFARE DESFire EV3 was publicly announced on 2 June 2020.
MIFARE SAM AV2
MIFARE SAMs are not contactless smart cards. They are secure access modules designed to provide the secure storage of cryptographic keys and cryptographic functions for terminals to access the MIFARE products securely and to enable secure communication between terminals and host (backend). MIFARE SAMs are available from NXP in the contact-only module (PCM 1.1) as defined in ISO/IEC 7816-2 and the HVQFN32 format.
Integrating a MIFARE SAM AV2 in a contactless smart card reader enables a design that integrates high-end cryptography features and the support of cryptographic authentication and data encryption/decryption. Like any SAM, it offers functionality to store keys securely and perform authentication and encryption of data between the contactless card and the SAM and the SAM towards the backend. Next to a classical SAM architecture, the MIFARE SAM AV2 supports the X-mode which allows a fast and convenient contactless terminal development by connecting the SAM to the microcontroller and reader IC simultaneously.
MIFARE SAM AV2 offers AV1 mode and AV2 mode where in comparison to the SAM AV1 the AV2 version includes public key infrastructure (PKI), hash functions like SHA-1, SHA-224, and SHA-256. It supports MIFARE Plus and secure host communication. Both modes provide the same communication interfaces, cryptographic algorithms (Triple-DES 112-bit and 168-bit key, MIFARE products using Crypto1, AES-128 and AES-192, RSA with up to 2048-bit keys), and X-mode functionalities. The MIFARE SAM AV3 is the third generation of NXP's Secure Access Module, and it supports MIFARE ICs as well as NXP's UCODE DNA, ICODE DNA and NTAG DNA ICs.
MIFARE 2GO
A cloud-based platform that digitizes MIFARE product-based smart cards and makes them available on NFC-enabled smartphones and wearables. With this, new Smart City use cases such as mobile transit ticketing, mobile access and mobile micropayments are being enabled.
Byte layout
History
1994 – MIFARE Classic IC with 1K user memory introduced.
1996 – First transport scheme in Seoul using MIFARE Classic with 1K memory.
1997 – MIFARE PRO with Triple DES coprocessor introduced.
1997 – MIFARE LIGHT with 384Bit user memory introduced.
1999 – MIFARE PROX with PKI coprocessor introduced.
2001 – MIFARE Ultralight introduced.
2002 – MIFARE DESFire introduced, microprocessor based product.
2004 – MIFARE SAM introduced, secure infrastructure counterpart of MIFARE DESFire.
2006 – MIFARE DESFire EV1 is announced as the first product to support 128-bit AES.
2008 – MIFARE4Mobile industry Group is created, consisting of leading players in the Near Field Communication (NFC) ecosystem.
2008 – MIFARE Plus is announced as a drop-in replacement for MIFARE Classic based on 128-bit AES.
2008 – MIFARE Ultralight C is introduced as a smart paper ticketing IC featuring Triple DES Authentication.
2010 – MIFARE SAM AV2 is introduced as secure key storage for readers AES, Triple DES, PKI Authentication.
2012 – MIFARE Ultralight EV1 introduced, backward compatible to MIFARE Ultralight but with extra security.
2014 – MIFARE SDK was introduced, allowing developers to create and develop their own NFC Android applications.
2014 – NXP Smart MX2 the world's first secure smart card platform supporting MIFARE Plus and MIFARE DESFire EV1 with EAL 50 was released.
2015 – MIFARE Plus SE, the entry-level version of NXP's proven and reliable MIFARE Plus product family, was introduced.
2016 – MIFARE Plus EV1 was introduced, the proven mainstream smart card product compatible with MIFARE Classic in its backward compatible security level.
2016 – MIFARE DESFire EV2 is announced with improved performance, security, privacy and multi-application support.
2016 – MIFARE SDK is rebranded to TapLinx, with additional supported products.
2018 – MIFARE 2GO cloud service was introduced, allows to manage MIFARE DESFire and MIFARE Plus (in SL3) product-based credentials onto NFC-enabled mobile and wearable devices.
2020 – MIFARE DESFire EV3 is announced
2020 – MIFARE Plus EV2 was introduced, adding SL3 to support MIFARE 2GO, EAL5+ certification & Transaction Timer to help mitigate man-in-the-middle attacks.
2022 – MIFARE Ultralight AES was introduced.
The MIFARE product portfolio was originally developed by Mikron in Gratkorn, Austria. Mikron was acquired by Philips in 1995. Mikron sourced silicon from Atmel in the US, Philips in the Netherlands, and Siemens in Germany.
Infineon Technologies (then Siemens) licensed MIFARE Classic from Mikron in 1994 and developed both stand alone and integrated designs with MIFARE product functions. Infineon currently produces various derivatives based on MIFARE Classic including 1K memory (SLE66R35) and various microcontrollers (8 bit (SLE66 series), 16 bit (SLE7x series), and 32 bit (SLE97 series) with MIFARE implementations, including devices for use in USIM with Near Field Communication.
Motorola tried to develop MIFARE product-like chips for the wired-logic version but finally gave up. The project expected one million cards per month for start, but that fell to 100,000 per month just before they gave up the project.
In 1998 Philips licensed MIFARE Classic to Hitachi Hitachi licensed MIFARE products for the development of the contactless smart card solution for NTT's IC telephone card which started in 1999 and finished in 2006. In the NTT contactless IC telephone card project, three parties joined: Tokin-Tamura-Siemens, Hitachi (Philips-contract for technical support), and Denso (Motorola-only production). NTT asked for two versions of chip, i.e. wired-logic chip (like MIFARE Classic) with small memory and big memory capacity. Hitachi developed only big memory version and cut part of the memory to fit for the small memory version.
The deal with Hitachi was upgraded in 2008 by NXP (by then no longer part of Philips) to include MIFARE Plus and MIFARE DESFire to the renamed semiconductor division of Hitachi Renesas Technology.
In 2010 NXP licensed MIFARE products to Gemalto. In 2011 NXP licensed Oberthur to use MIFARE products on SIM cards. In 2012 NXP signed an agreement with Giesecke & Devrient to integrate MIFARE product-based applications on their secure SIM products. These licensees are developing Near Field Communication products
Security
MIFARE Classic
The encryption used by the MIFARE Classic IC uses a 48-bit key.
A presentation by Henryk Plötz and Karsten Nohl at the Chaos Communication Congress in December 2007 described a partial reverse-engineering of the algorithm used in the MIFARE Classic chip. Abstract and slides are available online. A paper that describes the process of reverse engineering this chip was published at the August 2008 USENIX security conference.
In March 2008 the Digital Security research group of the Radboud University Nijmegen made public that they performed a complete reverse-engineering and were able to clone and manipulate the contents of an OV-Chipkaart which is using MIFARE Classic chip. For demonstration they used the Proxmark3 device, a 125 kHz / 13.56 MHz research instrument. The schematics and software are released under the free GNU General Public License by Jonathan Westhues in 2007. They demonstrate it is even possible to perform card-only attacks using just an ordinary stock-commercial NFC reader in combination with the libnfc library.
The Radboud University published four scientific papers concerning the security of the MIFARE Classic:
A Practical Attack on the MIFARE Classic
Dismantling MIFARE Classic
Wirelessly Pickpocketing a MIFARE Classic Card
Ciphertext-only Cryptanalysis on Hardened MIFARE Classic Cards
In response to these attacks, the Dutch Minister of the Interior and Kingdom Relations stated that they would investigate whether the introduction of the Dutch Rijkspas could be brought forward from Q4 of 2008.
NXP tried to stop the publication of the second article by requesting a preliminary injunction. However, the injunction was denied, with the court noting that, "It should be considered that the publication of scientific studies carries a lot of weight in a democratic society, as does inform society about serious issues in the chip because it allows for mitigating of the risks."
Both independent research results are confirmed by the manufacturer NXP. These attacks on the cards didn't stop the further introduction of the card as the only accepted card for all Dutch public transport the OV-chipkaart continued as nothing happened but in October 2011 the company TLS, responsible for the OV-Chipkaart announced that the new version of the card will be better protected against fraud.
The MIFARE Classic encryption Crypto-1 can be broken in about 200 seconds on a laptop from 2008, if approx. 50 bits of known (or chosen) keystream are available. This attack reveals the key from sniffed transactions under certain (common) circumstances and/or allows an attacker to learn the key by challenging the reader device.
Another attack recovers the secret key in about 40 ms on a laptop. This attack requires just one (partial) authentication attempt with a legitimate reader.
Additionally, there are a number of attacks that work directly on a card and without the help of a valid reader device. These attacks have been acknowledged by NXP.
In April 2009 new and better card-only attack on MIFARE Classic has been found. It was first announced at the rump session of Eurocrypt 2009.
This attack was presented at SECRYPT 2009.
The full description of this latest and fastest attack to date can also be found in the IACR preprint archive.
The new attack improves by a factor of more than 10 all previous card-only attacks on MIFARE Classic, has instant running time, and does not require a costly precomputation. The new attack allows recovering the secret key of any sector of the MIFARE Classic card via wireless interaction, within about 300 queries to the card. It can then be combined with the nested authentication attack in the Nijmegen Oakland paper to recover subsequent keys almost instantly. Both attacks combined and with the right hardware equipment such as Proxmark3, one should be able to clone any MIFARE Classic card in 10 seconds or less. This is much faster than previously thought.
In an attempt to counter these card-only attacks, new "hardened" cards have been released in and around 2011, such as the MIFARE Classic EV1. These variants are insusceptible for all card-only attacks publicly known until then, while remaining backward compatible with the original MIFARE Classic. In 2015, a new card-only attack was discovered that is also able to recover the secret keys from such hardened variants.
Since the discovery of this attack, NXP is officially recommending to migrate from MIFARE Classic product-based systems to higher security products.
MIFARE DESFire
In November 2010, security researchers from the Ruhr University released a paper detailing a side-channel attack against MIFARE product-based cards. The paper demonstrated that MIFARE DESFire product-based cards could be easily emulated at a cost of approximately $25 in "off the shelf" hardware. The authors asserted that this side-channel attack allowed cards to be cloned in approximately 100 ms. Furthermore, the paper's authors included hardware schematics for their original cloning device, and have since made corresponding software, firmware and improved hardware schematics publicly available on GitHub.
In October 2011 David Oswald and Christof Paar of Ruhr-University in Bochum, Germany, detailed how they were able to conduct a successful "side-channel" attack against the card using equipment that can be built for nearly $3,000. Called "Breaking MIFARE DESFire MF3ICD40: Power Analysis and Templates in the Real World", they stated that system integrators should be aware of the new security risks that arise from the presented attacks and can no longer rely on the mathematical security of the used 3DES cipher. Hence, to avoid, e.g. manipulation or cloning of smart cards used in payment or access control solutions, proper actions have to be taken: on the one hand, multi-level countermeasures in the back end allow to minimize the threat even if the underlying RFID platform is insecure," In a statement NXP said that the attack would be difficult to replicate and that they had already planned to discontinue the product at the end of 2011. NXP also stated "Also, the impact of a successful attack depends on the end-to-end system security design of each individual infrastructure and whether diversified keys – recommended by NXP – are being used. If this is the case, a stolen or lost card can be disabled simply by the operator detecting the fraud and blacklisting the card, however, this operation assumes that the operator has those mechanisms implemented. This will make it even harder to replicate the attack with a commercial purpose."
MIFARE Ultralight
In September 2012 a security consultancy Intrepidus demonstrated at the EU SecWest event in Amsterdam, that MIFARE Ultralight product-based fare cards in the New Jersey and San Francisco transit systems can be manipulated using an Android application, enabling travelers to reset their card balance and travel for free in a talk entitled "NFC For Free Rides and Rooms (on your phone)". Although not a direct attack on the chip but rather the reloading of an unprotected register on the device, it allows hackers to replace value and show that the card is valid for use. This can be overcome by having a copy of the register online so that values can be analyzed and suspect cards hot-listed. NXP has responded by pointing out that they had introduced the MIFARE Ultralight C in 2008 with 3DES protection and in November 2012 introduced the MIFARE Ultralight EV1 with three decrement only counters to foil such reloading attacks.
Considerations for systems integration
For systems based on contactless smartcards (e.g. public transportation), security against fraud relies on many components, of which the card is just one. Typically, to minimize costs, systems integrators will choose a relatively cheap card such as a MIFARE Classic and concentrate security efforts in the back office. Additional encryption on the card, transaction counters, and other methods known in cryptography are then employed to make cloned cards useless, or at least to enable the back office to detect a fraudulent card, and put it on a blacklist. Systems that work with online readers only (i.e., readers with a permanent link to the back office) are easier to protect than systems that have offline readers as well, for which real-time checks are not possible and blacklists cannot be updated as frequently.
Certification
Another aspect of fraud prevention and compatibility guarantee is to obtain certification called to live in 1998 ensuring the compatibility of several certified MIFARE product-based cards with multiple readers. With this certification, the main focus was placed on the contactless communication of the wireless interface, as well as to ensure proper implementation of all the commands of MIFARE product-based cards. The certification process was developed and carried out by the Austrian laboratory called Arsenal Research. Today, independent test houses such as Arsenal Testhouse, UL and LSI-TEC, perform the certification tests and provide the certified products in an online database.
Places that use MIFARE products
Transportation
Application references
Institutions
Northwest University, South Africa – Student/staff ID, access control, library, student meals, sport applications, payments
Cambridge University – Student/Staff ID and access card, library card, canteen payments in some colleges
The University of Queensland – Staff and student ID, access control, library, copy/print, building access (MIFARE DESFire EV1)
See also
RFID
Campus card
Physical security
NFC
Smart card
References
Further reading
Dayal, Geeta, "How they hacked it: The MiFare RFID crack explained; A look at the research behind the chip compromise, Computerworld, 19 March 2008.
External links
Comparison Table MIFARE DESFire EV1 / EV2 / EV3
NXP in eGovernment
24C3 Talk about MIFARE Classic Video of the 24C3 Talk presenting the results of reverse engineering the MIFARE Classic family, raising serious security concerns
Presentation of 24th Chaos Computer Congress in Berlin Claiming that the MIFARE classic chip is possibly not safe
Demonstration of an actual attack on MIFARE Classic (a building access control system) by the Radboud University Nijmegen.https://www.mersinliakaryakit.com/
Contactless smart cards
Near-field communication
NXP Semiconductors | MIFARE | [
"Technology"
] | 6,219 | [
"Near-field communication",
"Mobile telecommunications"
] |
983,787 | https://en.wikipedia.org/wiki/Foreword | A foreword is a (usually short) piece of writing, sometimes placed at the beginning of a book or other piece of literature. Typically written by someone other than the primary author of the work, it often tells of some interaction between the writer of the foreword and the book's primary author or the story the book tells. Later editions of a book sometimes have a new foreword prepended (appearing before an older foreword if there was one), which might explain in what respects that edition differs from previous ones.
When written by the author, the foreword may cover the story of how the book came into being or how the idea for the book was developed, and may include thanks and acknowledgments to people who were helpful to the author during the time of writing. Unlike a preface, a foreword is always signed.
Information essential to the main text is generally placed in a set of explanatory notes, or perhaps in an introduction, rather than in the foreword or like preface.
The pages containing the foreword and preface (and other front matter) are typically not numbered as part of the main work, which usually uses Arabic numerals. If the front matter is paginated, it uses lowercase Roman numerals. If there is both a foreword and a preface, the foreword appears first; both appear before the introduction, which may be paginated either with the front matter or the main text.
The word foreword was first used around the mid-17th century, originally as a term in philology. It was possibly a calque of German Vorwort, itself a calque of Latin praefatio.
See also
Afterword
Epigraph
Introduction
Preface
Prologue
References
External links
The difference between a preface, foreword, and introduction – PatMcNees.com
Book design
Book terminology
Literature | Foreword | [
"Engineering"
] | 368 | [
"Book design",
"Design"
] |
983,873 | https://en.wikipedia.org/wiki/NGC%203184 | NGC 3184, the Little Pinwheel Galaxy, is an unbarred spiral galaxy approximately 40 million light-years away in the constellation Ursa Major. Its name comes from its resemblance to the Pinwheel Galaxy. It was discovered on 18 March 1787 by German-British astronomer William Herschel. It has two HII regions named NGC 3180 and NGC 3181.
NGC 3184 houses a high abundance of heavy elements. The blue color of its spiral arms comes mostly from relatively few bright young blue stars. The bright stars that highlight the arms were created in huge density waves that circle the center.
Structure
NGC 3184 has two prominent spiral arms. They have constant pitch angles, which makes them both symmetrical.
Supernovae and Astronomical Transients
Seven supernovae and astronomical transients have been observed in NGC 3184:
SN 1921B (type unknown, mag. 13.5) was discovered by Fritz Zwicky on 6 April 1921.
SN 1921C (type unknown, mag. 11) was discovered on 5 December 1921.
SN 1937F (type unknown, mag. 13.5) was discovered by Fritz Zwicky on 9 December 1937.
SN 1999gi (type II, mag. 14) was discovered by Reiki Kushida on 9 December 1999.
SN 2010dn (type ILRT, mag. 17) was discovered by Kōichi Itagaki on 31 May 2010.
SN 2016bkv (type II, mag. 17.2), was discovered by Kōichi Itagaki on 21 March 2016.
AT 2019sfe (type unknown, mag. 20.6) was discovered on 8 October 2019.
SN 2010dn
On May 31, 2010, Kōichi Itagaki detected a magnitude 17 optical transient 33" east and 61" north of the center of NGC 3184 at coordinates 10 18 19.89 +41 26 28.8. Designated SN 2010dn, this event was initially thought to be an outbursting luminous blue variable (LBV) star, but later analysis categorized it as an intermediate-luminosity red transient (ILRT), also known as a luminous red nova. Archival Hubble and Spitzer images of NGC 3184 seem to show no progenitor for optical transient SN 2010dn. SN 2010dn is just like SN 2008S and NGC 300-OT. On day 2, SN 2010dn had an unfiltered magnitude of 17.1, corresponding to a peak absolute magnitude of roughly -13.3.
See also
Pinwheel Galaxy
Bode's galaxy
Cigar galaxy
NGC 2787
Messier 83
References
External links
Spiral Galaxy NGC 3184 & Supernova 1999gi (20-inch F/8.1 Ritchey Chretien Cassegrain)
Supernova 1999gi in NGC 3184 (supernovae.net)
Discovery image of SN2010dn (2010-05-31 mag 17.5) / Wikisky DSS2 and SDSS zoom-in of the same region
Galaxies discovered in 1787
3184
05557
Unbarred spiral galaxies
Ursa Major
17870318
19991209
030087
Discoveries by William Herschel | NGC 3184 | [
"Astronomy"
] | 658 | [
"Ursa Major",
"Constellations"
] |
983,904 | https://en.wikipedia.org/wiki/NGC%206946 | NGC 6946, sometimes referred to as the Fireworks Galaxy, is a face-on intermediate spiral galaxy with a small bright nucleus, whose location in the sky straddles the boundary between the northern constellations of Cepheus and Cygnus. Its distance from Earth is about 25.2 million light-years or 7.72 megaparsecs, similar to the distance of M101 (NGC 5457) in the constellation Ursa Major. Both were once considered to be part of the Local Group, but are now known to be among the dozen bright spiral galaxies near the Milky Way but beyond the confines of the Local Group. NGC 6946 lies within the Virgo Supercluster.
The galaxy was discovered by William Herschel on 9 September 1798. Based on an estimation by the Third Reference Catalogue of Bright Galaxies (RC3) in 1991, the galaxy has a D25 B-band isophotal diameter of . It is heavily obscured by interstellar matter due to its location close to the galactic plane of the Milky Way. Due to its prodigious star formation it has been classified as an active starburst galaxy. NGC 6946 has also been classified as a double-barred spiral galaxy, with the inner, smaller bar presumably responsible for funneling gas into its center.
Various unusual celestial objects have been observed within NGC 6946. This includes the so-called 'Red Ellipse' along one of the northern arms that looks like a super-bubble or very large supernova remnant, and which may have been formed by an open cluster containing massive stars. There are also two regions of unusual dark lanes of nebulosity, while within the spiral arms several regions appear devoid of stars and gaseous hydrogen, some spanning up to two kiloparsecs across. A third peculiar object, discovered in 1967, is now known as "Hodge's Complex". This was once thought to be a young supergiant cluster, but in 2017 it was conjectured to be an interacting dwarf galaxy superimposed on NGC 6946.
Supernovae
Ten supernovae have been observed in NGC 6946 in the 20th and early 21st century: SN 1917A, SN 1939C, SN 1948B, SN 1968D, SN 1969P, SN 1980K, SN 2002hh, SN 2004et, SN 2008S, and SN 2017eaw. For this reason, NGC 6946 has sometimes been referred to as the "Fireworks Galaxy". This is about ten times the rate observed in our Milky Way galaxy, even though the Milky Way has twice as many stars as NGC 6946.
On 27 September 2004, the Type II supernova SN 2004et was observed at magnitude 15.2 and rose to a maximum visual magnitude of 12.7. Images taken during the preceding days revealed that the supernova explosion occurred on 22 September. The progenitor of the supernova was identified on earlier images –– only the seventh time that such an event was directly identified with its host star. The red supergiant progenitor had an initial mass of about 15 in an interacting binary system shared with a blue supergiant.
During 2009, a bright star within NGC 6946 flared up over several months to become over one million times as bright as the Sun. Shortly thereafter it faded rapidly. Observations with the Hubble Space Telescope suggest that the star did not survive, although there remains some infrared emission from its position. This is thought to come from debris falling onto a black hole that formed when the star died. This potential black hole-forming star is designated N6946-BH1. The progenitor is believed to have been a yellow hypergiant star.
In May 2017, supernova SN 2017eaw was detected in the northwest region of the galaxy, and light curves obtained over the next 600 days showed that it was a Type II-P. The progenitor was determined to have been a red supergiant, with a mass of around 15.
As of 2017, more supernovae had been seen in NGC 6946 than in any other galaxy, a record that has since been surpassed by NGC 3690.
Gallery
See also
IC 342 – similar galaxy heavily obscured by Milky Way stars and dust.
List of galaxies
References
External links
SEDS: Spiral Galaxy NGC 6946
Atlas of the Universe
N6946-BH1 Giant Star Becomes A Black Hole Right Before Our Eyes!
List of observations and images of supernova SN 2017eaw
Cepheus (constellation)
Cygnus (constellation)
Intermediate spiral galaxies
6946
11597
65001
029
012b
17980909
Virgo Supercluster | NGC 6946 | [
"Astronomy"
] | 960 | [
"Cygnus (constellation)",
"Constellations",
"Cepheus (constellation)"
] |
984,020 | https://en.wikipedia.org/wiki/What%20the%20Bleep%20Do%20We%20Know%21%3F | What the Bleep Do We Know!? (stylized as What tнē #$*! D̄ө ωΣ (k)πow!? and What the #$*! Do We Know!?) is a 2004 American pseudo-scientific film that posits a spiritual connection between quantum physics and consciousness (as part of a belief system known as quantum mysticism). The plot follows the fictional story of a photographer, using documentary-style interviews and computer-animated graphics, as she encounters emotional and existential obstacles in her life and begins to consider the idea that individual and group consciousness can influence the material world. Her experiences are offered by the creators to illustrate the film's scientifically unsupported ideas.
Bleep was conceived and its production funded by William Arntz, who serves as co-director along with Betsy Chasse and Mark Vicente; all three were students of Ramtha's School of Enlightenment. A moderately low-budget independent film, it was promoted using viral marketing methods and opened in art-house theaters in the western United States, winning several independent film awards before being picked up by a major distributor and eventually grossing over $10 million. The 2004 theatrical release was succeeded by a substantially changed, extended home media version in 2006.
The film has been described as an example of quantum mysticism, and has been criticized for both misrepresenting science and containing pseudoscience. While many of its interviewees and subjects are professional scientists in the fields of physics, chemistry, and biology, one of them has noted that the film quotes him out of context.
Synopsis
Filmed in Portland, Oregon, What the Bleep Do We Know!? presents a viewpoint of the physical universe and human life within it, with connections to neuroscience and quantum physics. Some ideas discussed in the film are:
That the universe is best seen as constructed from thoughts and ideas rather than from matter.
That "empty space" is not empty.
That matter is not solid, and electrons are able to pop in and out of existence without it being known where they disappear to.
That beliefs about who one is and what is real are a direct cause of oneself and of one's own realities.
That peptides produced by the brain can cause a bodily reaction to emotion.
In the narrative segments of the film, Marlee Matlin portrays Amanda, a photographer who plays the role of everywoman as she experiences her life from startlingly new and different perspectives.
In the documentary segments of the film, interviewees discuss the roots and meaning of Amanda's experiences. The comments focus primarily on a single theme: "We create our own reality." The director, William Arntz, has described What the Bleep as a film for the "metaphysical left".
Cast
Marlee Matlin as Amanda
Elaine Hendrix as Jennifer
Barry Newman as Frank
Robert Bailey Jr. as Reggie
John Ross Bowie as Elliot
Armin Shimerman as Man
Robert Blanche as Bob
Larry Brandenburg as Bruno
Patti B. Collins as Mother of the Bride
Production
Work was split between Toronto-based Mr. X Inc., Lost Boys Studios in Vancouver, and Atomic Visual Effects in Cape Town, South Africa. The visual-effects team, led by Evan Jacobs, worked closely with the other film-makers to create visual metaphors that would capture the essence of the film's technical subjects with attention to aesthetic detail.
Release
Promotion
Lacking the funding and resources of the typical Hollywood film, the filmmakers relied on "guerrilla marketing" first to get the film into theaters, and then to attract audiences. This has led to accusations, both formal and informal, directed towards the film's proponents, of spamming online message boards and forums with many thinly veiled promotional posts. Initially, the film was released in only two theaters: one in Yelm, Washington (the home of the producers, which is also the home of Ramtha), and the other the Bagdad Theater in Portland, Oregon, where it was filmed. Within several weeks, the film had appeared in a dozen or more theaters (mostly in the western United States), and within six months it had made its way into 200 theaters across the US.
Box office
According to Publishers Weekly, the film was one of the sleeper hits of 2004, as "word-of-mouth and strategic marketing kept it in theaters for an entire year." The article states that the domestic gross exceeded $10 million, described as not bad for a low-budget documentary, and that the DVD release attained even more significant success with over a million units shipped in the first six months following its release in March 2005. Foreign gross added another $5 million for a worldwide gross of just over $21 million.
Critical response
In the Publishers Weekly article, publicist Linda Rienecker of New Page Books says that she sees the success as part of a wider phenomenon, stating "A large part of the population is seeking spiritual connections, and they have the whole world to choose from now". Author Barrie Dolnick adds that "people don't want to learn how to do one thing. They'll take a little bit of Buddhism, a little bit of veganism, a little bit of astrology... They're coming into the marketplace hungry for direction, but they don't want some person who claims to have all the answers. They want suggestions, not formulas." The same article quotes Bill Pfau, Advertising Manager of Inner Traditions, as saying "More and more ideas from the New Age community have become accepted into the mainstream."
Critics offered mixed reviews as seen on the film review website Rotten Tomatoes, where it scored a "Rotten" 34% score with an average score of 4.6/10, based on 77 reviews. In his review, Dave Kehr of The New York Times described the "transition from quantum mechanics to cognitive therapy" as "plausible", but stated also that "the subsequent leap—from cognitive therapy into large, hazy spiritual beliefs—isn't as effectively executed. Suddenly people who were talking about subatomic particles are alluding to alternate universes and cosmic forces, all of which can be harnessed in the interest of making Ms. Matlin's character feel better about her thighs."
What the Bleep Do We Know!? has been described as "a kind of New Age answer to The Passion of the Christ and other films that adhere to traditional religious teachings." It offers alternative spirituality views characteristic of New Age philosophy, including critiques of the competing claims of stewardship among traditional religions [viz., institutional Judaism, Christianity, and Islam] of universally recognized and accepted moral values.
Academic reaction
Scientists who have reviewed What the Bleep Do We Know!? have described distinct assertions made as pseudoscience. Lisa Randall refers to the film as "the bane of scientists". Amongst the assertions in the film that have been challenged are that water molecules can be influenced by thought (as popularized by Masaru Emoto), that meditation can reduce violent crime rates of a city, and that quantum physics implies that "consciousness is the ground of all being." The film was also discussed in a letter published in Physics Today that challenges how physics is taught, saying teaching fails to "expose the mysteries physics has encountered [and] reveal the limits of our understanding". In the letter, the authors write: "the movie illustrates the uncertainty principle with a bouncing basketball being in several places at once. There's nothing wrong with that. It's recognized as pedagogical exaggeration. But the movie gradually moves to quantum 'insights' that lead a woman to toss away her antidepressant medication, to the quantum channeling of Ramtha, the 35,000-year-old Lemurian warrior, and on to even greater nonsense." It went on to say that "Most laypeople cannot tell where the quantum physics ends and the quantum nonsense begins, and many are susceptible to being misguided," and that "a physics student may be unable to convincingly confront unjustified extrapolations of quantum mechanics," a shortcoming which the authors attribute to the current teaching of quantum mechanics, in which "we tacitly deny the mysteries physics has encountered".
Richard Dawkins stated that "the authors seem undecided whether their theme is quantum theory or consciousness. Both are indeed mysterious, and their genuine mystery needs none of the hype with which this film relentlessly and noisily belabours us", concluding that the film is "tosh". Professor Clive Greated wrote that "thinking on neurology and addiction are covered in some detail but, unfortunately, early references in the film to quantum physics are not followed through, leading to a confused message". Despite his caveats, he recommends that people see the film, stating: "I hope it develops into a cult movie in the UK as it has in the US. Science and engineering are important for our future, and anything that engages the public can only be a good thing." Simon Singh called it pseudoscience and said the suggestion "that if observing water changes its molecular structure, and if we are 90% water, then by observing ourselves we can change at a fundamental level via the laws of quantum physics" was "ridiculous balderdash". According to João Magueijo, professor in theoretical physics at Imperial College, the film deliberately misquotes science. The American Chemical Society's review criticizes the film as a "pseudoscientific docudrama", saying "Among the more outlandish assertions are that people can travel backward in time, and that matter is actually thought."
Bernie Hobbs, a science writer with ABC Science Online, explains why the film is incorrect about quantum physics and reality: "The observer effect of quantum physics isn't about people or reality. It comes from the Heisenberg Uncertainty Principle, and it's about the limitations of trying to measure the position and momentum of subatomic particles... this only applies to sub-atomic particles—a rock doesn't need you to bump into it to exist. It's there. The sub-atomic particles that make up the atoms that make up the rock are there too." Hobbs also discusses Hagelin's experiment with Transcendental Meditation and the Washington DC rate of violent crime, saying that "the number of murders actually went up". Hobbs further disputed the film's use of the ten percent of the brain myth.
David Albert, a philosopher of physics who appears in the film, has accused the filmmakers of selectively editing his interview to make it appear that he endorses the film's thesis that quantum mechanics is linked with consciousness. He says he is "profoundly unsympathetic to attempts at linking quantum mechanics with consciousness".
In the film, during a discussion of the influence of experience on perception, Candace Pert gives an apocryphal version of the invisible ships myth whereby Native Americans were unable to see Columbus's ships because they were outside the natives' experience. According to an article in Fortean Times by David Hambling, the origins of this story likely involved the voyages of Captain James Cook, not Columbus, and an account related by Robert Hughes which said Cook's ships were "...complex and unfamiliar as to defy the natives' understanding". Hambling says it is likely that both the Hughes account and the story told by Pert were exaggerations of the records left by Captain Cook and the botanist Joseph Banks.
Skeptic James Randi described the film as "a fantasy docudrama" and "[a] rampant example of abuse by charlatans and cults". Eric Scerri in a review for Committee for Skeptical Inquiry dismisses it as "a hodgepodge of all kinds of crackpot nonsense," where "science [is] distorted and sensationalized". A BBC reviewer described it as "a documentary aimed at the totally gullible".
According to Margaret Wertheim, "History abounds with religious enthusiasts who have read spiritual portent into the arrangement of the planets, the vacuum of space, electromagnetic waves and the big bang. But no scientific discovery has proved so ripe for spiritual projection as the theories of quantum physics, replete with their quixotic qualities of uncertainty, simultaneity and parallelism." Wertheim continues that the film "abandons itself entirely to the ecstasies of quantum mysticism, finding in this aleatory description of nature the key to spiritual transformation. As one of the film's characters gushes early in the proceedings, 'The moment we acknowledge the quantum self, we say that somebody has become enlightened'. A moment in which 'the mathematical formalisms of quantum mechanics [...] are stripped of all empirical content and reduced to a set of syrupy nostrums'."
Journalist John Gorenfeld, writing in Salon, notes that the film's three directors, William Arntz, Betsy Chasse, and Mark Vicente, were at the time students of Ramtha's School of Enlightenment, which he says has been described as a cult. Mark Vicente later became involved with another prominent cult: NXIVM, the human-potential-development and sex-trafficking pyramid scheme founded by convicted con artist Keith Raniere. After leaving NXIVM, Vicente participated in the exposé documentary series The Vow, revealing many of the cult's damaging tactics; however, nowhere in The Vow does Vicente admit that NXIVM was not his first time adhering to a cult-like group.
Accolades
Ashland Independent Film Festival – Best Documentary
DCIFF – DC Independent Film Festival – Grand Jury Documentary Award
Maui Film Festival – Audience Choice Award – Best Hybrid Documentary
Sedona International Film Festival – Audience Choice Award, Most Thought-Provoking Film
Pigasus Award – an annual tongue-in-cheek award, this particular award's category was #3: "to the media outlet that reported as factual the most outrageous supernatural, paranormal or occult claims".
Legacy
In mid-2005, the filmmakers worked with HCI Books to expand on the themes in a book titled What the Bleep Do We Know!?—Discovering the Endless Possibilities of Your Everyday Reality. HCI president Peter Vegso stated that in regard to this book, "What the Bleep is the quantum leap in the New Age world," and "by marrying science and spirituality, it is the foundation of future thought."
On August 1, 2006, What the Bleep! Down the Rabbit Hole - Quantum Edition multi-disc DVD set was released, containing two extended versions of What the Bleep Do We Know!?, with over 15 hours of material on three double-sided DVDs.
Featured individuals
The film features interview segments with:
Dean Radin, Senior Scientist at the Institute of Noetic Sciences (IONS) in Petaluma, California and proponent of paranormal phenomena.
John Hagelin of Maharishi University of Management, director of MUM's Institute for Science, Technology, and Public Policy, and three-time presidential candidate of the Transcendental Meditation-linked Natural Law Party.
Stuart Hameroff, anesthesiologist, author, and associate director of the Center for Consciousness Studies at the University of Arizona, who developed with Roger Penrose a quantum hypothesis of consciousness in the books The Emperor's New Mind, and Shadows of the Mind.
JZ Knight, a spiritual teacher who is identified in interview segments as the spirit "Ramtha" that Knight claims to channel.
Andrew B. Newberg, assistant professor of radiology at the University of Pennsylvania Hospital, and physician in nuclear medicine, who coauthored the book Why God Won't Go Away: Brain Science & the Biology of Belief ()
Candace Pert, a neuroscientist, who discovered the cellular bonding site for endorphins in the brain, and in 1997 wrote the book Molecules of Emotion ()
Fred Alan Wolf, independent physicist, author of Taking the Quantum Leap, winner of the 1982 National Book Award in science, and featured in the documentary film Spirit Space. Wolf has taught at San Diego State University, the University of Paris, the Hebrew University of Jerusalem, the University of London, and Birkbeck College, London.
David Albert, philosopher of physics and professor at Columbia University, author of Quantum Mechanics and Experience, who according to a Popular Science article was "outraged at the final product" of his interview which he felt misrepresented his views about quantum mechanics and consciousness.
Micheál Ledwith, author and former professor of theology at St. Patrick's College, Maynooth;
Daniel Monti, physician and director of the Mind-Body Medicine Program at Thomas Jefferson University;
Jeffrey Satinover, psychiatrist, author and professor;
William Tiller, Professor Emeritus of Material Science and Engineering at Stanford University;
Joe Dispenza, former Ramtha School of Enlightenment teacher, chiropractor.
See also
Mind-body problem
Hard problem of consciousness
Law of attraction
List of films featuring the deaf and hard of hearing
References
Further reading
External links
2004 films
2004 comedy-drama films
2000s American films
2000s English-language films
2000s German-language films
2000s Spanish-language films
American comedy-drama films
English-language comedy-drama films
Films about quantum mechanics
Films about spirituality
Films set in Oregon
Films scored by Christopher Franke
Films shot in Portland, Oregon
Quantum mysticism
New Age media
Pseudoscience documentary films
Roadside Attractions films | What the Bleep Do We Know!? | [
"Physics"
] | 3,580 | [
"Quantum mechanics",
"Quantum mysticism"
] |
984,038 | https://en.wikipedia.org/wiki/Video%20server | A video server is a computer-based device that is dedicated to delivering video. Video servers are used in a number of applications, and often have additional functions and capabilities that address the needs of particular applications. For example, video servers used in security, surveillance and inspection applications typically are designed to capture video from one or more cameras and deliver the video via a computer network. In video production and broadcast applications, a video server may have the ability to record and play recorded video, and to deliver many video streams simultaneously.
Video broadcast and production
In TV broadcast industries, a server is a device used to store broadcast quality images and allows several users to edit stories using the images they contain simultaneously.
The video server can be used in a number of contexts, some of which include:
News: providing short news video clips as part of a news broadcast as seen on networks such as CNN, Fox News and the BBC.
Production: enhance live events with instant replays and slow motion and highlights (sport production) (see OB Vans)
Instruction: delivering course material in video format.
Public Access: delivering city specific information to residents over a cable system.
Surveillance: deliver real-time video images of protected site.
Entertainment: deliver anything used for entertainment. It can be gaming, news, movie trailers, or movies.
A professional-grade video server performs recording, storage, and playout of multiple video streams without any degradation of the video signal. Broadcast quality video servers often store hundreds of hours of compressed audio and video (in different codecs), play out multiple and synchronised simultaneous streams of video by, and offer quality interfaces such as SDI for digital video and XLR for balanced analog audio, AES/EBU digital audio and also Time Code. A genlock input is usually provided to provide a means of synchronizing with the house reference clock, thereby avoiding the need for timebase correction or frame synchronizers.
Video servers usually offer some type of control interface allowing them to be driven by broadcast automation systems that incorporate sophisticated broadcast programming applications. Popular protocols include VDCP and the 9-Pin Protocol.
They can optionally allow direct to disk recording using the same codec that is used in various post-production video editing software packages to prevent any wasted time in transcoding.
Features
Typically, a video server can do the following:
Ingest of different sources : video cameras (multiple angles), satellite data feeds, disk drives and other video servers. This can be done in different codecs.
Temporary or definitive storage of these video feeds.
Maintain a clear structure of all stored media with appropriate metadata to allow fast search : name, remarks, rating, date, time code, etc.
video editing of the different clips
Transfer those clips to other video servers or playout directly (via IP interface or SDI)
Generally, they have several bi directional channels (record and ingest) for video and audio. A perfect synchronisation is necessary between those channels to manage the feeds.
Video surveillance and inspection
In some surveillance and inspection applications, IP video servers are employed which convert analog video signals into IP video streams. These IP video servers can stream digitized video over IP networks in the same way that an IP camera can. Because an IP Video server uses IP protocols, it can stream video over any IP-compatible network, including via a modem for access over a phone or ISDN connection. With the use of a video server attached to an analog camera, the video from an existing surveillance system can be converted and networked into a new IP surveillance system.
In the video security industry a video server is a device to which one or more video sources can be attached. Video servers are used to give existing analog systems network connectivity. Video servers are essentially transmission/ telemetry / monitoring devices. Viewing is done using a web browser or in some cases supplied software. These products also allow the upload of images to the internet or direct viewing from the internet. In order to upload to the internet an account with an ISP (internet service provider) may be required.
Phone apps that send direct security video feed to smartphones from security video servers are another recent security video server application innovation. This allows smartphone users to view security video server feed from anywhere they can use their smartphone.
See also
Broadcast automation and playout
Centralcasting
Media server (Consumer)
References
Broadcast engineering
Television terminology
server
server | Video server | [
"Engineering"
] | 891 | [
"Broadcast engineering",
"Electronic engineering"
] |
2,990,227 | https://en.wikipedia.org/wiki/Nested%20Context%20Language | In the field of digital and interactive television, Nested Context Language (NCL) is a declarative authoring language for hypermedia documents. NCL documents do not contain multimedia elements such as audio or video content; rather they function as a "glue" language that specifies how multimedia components are related. In particular, NCL documents specify how these components are synchronized relative to each other and how the components are composed together into a unified document. Among its main facilities, it treats hypermedia relations as first-class entities through the definition of hypermedia connectors, and it can specify arbitrary semantics for a hypermedia composition using the concept of composite templates.
NCL is an XML application language that is an extension of XHTML, with XML elements and attributes specified by a modular approach. NCL modules can be added to standard web languages, such as XLink and SMIL.
NCL was initially designed for the Web environment, but a major application of NCL is use as the declarative language of the Japanese-Brazilian ISDB-Tb (International Standard for Digital Broadcasting) terrestrial DTV digital television middleware (named Ginga). It is also the first standardized technology of the ITU-T multimedia application framework series of specifications for IPTV (internet protocol television) services. In both cases it is used to develop interactive applications to digital television.
Structure of an NCL document
NCL was designed to be modular to allow for use of subsets of modules according to the needs of the particular application. The 3.1 version of the standard is split into 14 areas with each module assigned to an area. Each module in turn defines one or more XML elements. The areas and associated modules are
Structure
Structure Module
Components
Media Module
Context Module
Interfaces
MediaContentAnchor Module
CompositeNodeInterface Module
PropertyAnchor Module
SwitchInterface Module
Layout
Layout Module
Presentation Specification
Descriptor Module
Timing
Timing Module
Transition Effects
TransitionBase Module
Transition Module
Navigational Key
KeyNavigation Module
Presentation Control
TestRule Module
TestRuleUse Module
ContentControl Module
DescriptorControl Module
Linking
Linking Module
Connectors
ConnectorCommonPart Module
ConnectorAssessmentExpression Module
ConnectorCausalExpression Module
CausalConnector Module
CausalConnectorFunctionality Module
ConnectorBase Module
Animation
Animation Module
Reuse
Import Module
EntityReuse Module
ExtendedEntityReuse Module
Meta-Information
Metainformation Module
NCL profiles
Profiles are standard subsets of modules. Profiles defined by the standard include
Full profile – includes all NCL Modules
Enhanced Digital TV profile (EDTV) – includes the Structure, Layout, Media, Context, MediaContentAnchor, CompositeNodeInterface, PropertyAnchor, SwitchInterface, Descriptor, Linking, CausalConnectorFunctionality, ConnectorBase, TestRule, TestRuleUse, ContentControl, DescriptorControl, Timing, Import, EntityReuse, ExtendedEntityReuse, KeyNavigation, Animation, TransitionBase, Transition and Metainformation modules
NCL Basic Digital TV profile (BDTV) – includes the Enhanced Digital TV profiles except for the Animation, TransitionBase and Transition modules
Authoring tools
Tools for creating interactive DTV application in NCL include:
NCL Eclipse
NCL Composer.
See also
SMIL
eXtensible Markup Language (XML)
References
Further reading
External links
NCL Official Web Site
NCL Handbook
Telemidia Lab
NCL Resources: a number of resources supporting NCL.
NCL players
GINGA-NCL Reference Implementation, available under GPLv2 (in Portuguese).
GHTV GINGA-NCL player for Windows and Linux under Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License (in Portuguese).
WebNCL Player Web-based, available under GPL.
Markup languages
XML-based standards
Technical communication
Computer file formats
Broadcast engineering
Digital television
ISDB | Nested Context Language | [
"Technology",
"Engineering"
] | 817 | [
"Broadcast engineering",
"Computer standards",
"Electronic engineering",
"XML-based standards"
] |
2,990,507 | https://en.wikipedia.org/wiki/Telent | Telent Technology Services Limited is a British radio, telecommunications, and digital infrastructure systems installation and services provision company. The name is used from 2006 for those parts of the United Kingdom and German services businesses of Marconi Corporation (formerly General Electric Company, GEC) which had not been acquired by Ericsson. Companies with Marconi in their name can trace their ultimate origins, through mergers and takeovers, to The Marconi Company Ltd., founded by Guglielmo Marconi in 1897 as The Wireless Telegraph & Signal Company.
History
The company's predecessor was formed in September 1961 as GEC Telecommunications Limited, a division of the GEC conglomerate. In 1988 the division became part of the GEC Plessey Telecommunications joint venture, and following the breakup of GPT during the 1990s it was renamed Marconi Communications Limited in 1998, when GEC decided to switch to use the better known Marconi brand name which it had owned for some time.
In January 2006, following Ericsson's acquisition of most Marconi assets, including the rights to the Marconi name, the remaining UK and German services business of Marconi Corporation which was not acquired and no longer had the rights to use the Marconi name was renamed Telent. In May 2007, Telent announced its move from Coventry to Warwick's Opus 40 business park.
In November 2007 Telent, which had inherited GEC's £2.5 billion pension scheme with several tens of thousands of members, was purchased by Pension Corporation for £400 million; the following month its shares were delisted and Telent became a private company.
In 2008 Telent made various acquisitions, including intelligent traffic systems group TSEU in March, leading communications infrastructure provider, the Alan Campbell Group, in July and telecoms service provider Premises Networks in September.
In September 2019 the pension scheme, described by Telent as a "disproportionately large liability", was bought out by Rothesay Life.
In September 2020, it was announced that Telent were awarded a contract with Openreach to support a £12 billion project for the UK's largest ultrafast broadband build, which would bring 'Full Fibre' broadband to thousands of homes and businesses.
Operations
The company provides a range of network and communications services to industries including Rail, Traffic, Public Safety, Defence, Service Providers, Enterprise and Public Sector. Products include enterprise software systems, emergency services communications and logistics, integrated warehouse logistics systems and rail and metro systems. Customers include BAE Systems, BT, National Highways, HM Coastguard, Interoute, London Ambulance Service, Merseyside Fire & Rescue, Metropolitan Police, Network Rail, RNLI, Sky, Transport for London, Virgin Media and Vodafone.
The company has many operational sites within the UK and Ireland, including at Chorley in Lancashire, Warwick, Camberley in Surrey, Harbour Exchange in London, and Dublin. A team of telecommunications technicians and engineers provide support and new features development for the TDM System X network used by BT, Virgin Media, Kingston Communications, Vodafone, and Gibtelecom.
People
From its formation in 2006, Telent's CEO was Mark Plato. He died in a motorcycle accident in September 2019. Non-executive director Frank McKay, former CEO of Travis Perkins and Brakes Group, was appointed as his temporary replacement and was succeeded in July 2020 by Jo Gretton, a Telent executive since 2006.
See also
Marconi Electronic Systems
References
Engineering companies of the United Kingdom
Computer companies of the United Kingdom
Computer hardware companies
Telecommunications companies of the United Kingdom
Guglielmo Marconi
Companies formerly listed on the London Stock Exchange
Telecommunications companies established in 2006 | Telent | [
"Technology"
] | 743 | [
"Computer hardware companies",
"Computers"
] |
2,990,560 | https://en.wikipedia.org/wiki/Waistline%20%28clothing%29 | The waistline is the line of demarcation between the upper and lower portions of a garment, which notionally corresponds to the natural waist but may vary with fashion from just below the bust to below the hips. The waistline of a garment is often used to accentuate different features. The waistline is also important as a boundary at which shaping darts (such as those over the bust and in the back) can be ended.
Types of waistlines
Similar to necklines, waistlines may be grouped by their shape, depth, and location of the body.
None: The princess seams style of dress needs no waistline at all, since it does its shaping without darts, by joining edges of different curvature. The resulting "princess seams" typically run vertically from the shoulder (or under the arm) over the bust point and down to the lower hem. This creates a long, slimming look, often seen in dresses with an "A-line" silhouette.
Diagonal: An asymmetrical waistline that runs across the body diagonally. Usually the highest point is below the natural waistline.
Drop waist: A low, horizontal waistline that usually falls near the level of the upper hips. Balances the upper and lower bodies, and adds to the visual impression of height by lengthening the torso. Common in 1920s silhouettes.
Empire: A high waistline that cuts horizontally across the body, just below the bust. This waistline gives a long, slender look and excellent fabric drape in the skirt and allows for short, inconspicuous shaping darts. This waistline was popular in Jane Austen's time; see Empire silhouette.
Raised: A horizontal waistline that falls significantly above (>1 in.) the natural waist.
Natural: A horizontal waistline that falls at the natural waist and tends to make the wearer seem shorter by visually dividing the figure in half.
V-shaped: A generally flattering waistline, especially for figures with notable curvature. Also known as the Basque waistline or the Antebellum waistline.
U-shaped: A softer, less pronounced version of the Basque waistline.
Inverted V-shaped: Starts high in the center and drops at the sides and can fall as high as the bustline (e.g., paired with a low V neckline to give a "bowtie" look), but usually found near the hips (e.g., extending Bolero curves in the bodice).
Inverted U-shaped: A softer, less pronounced version of the inverted-V waistline, usually a gentle downwards curve.
Secure mechanisms
Waistlines can be secured with a variety of methods:
Button
Clasp
Drawstring
Elastic
Knot
Zipper
See also
Hemline
Low-rise (fashion)
Midriff
Navel in popular culture
Neckline
References
Fashion design
Parts of clothing
Waist | Waistline (clothing) | [
"Technology",
"Engineering"
] | 579 | [
"Design",
"Fashion design",
"Components",
"Parts of clothing"
] |
2,990,689 | https://en.wikipedia.org/wiki/Modeling%20perspective | A modeling perspective in information systems is a particular way to represent pre-selected aspects of a system. Any perspective has a different focus, conceptualization, dedication and visualization of what the model is representing.
The traditional way to distinguish between modeling perspectives is structural, functional and behavioral/processual perspectives. This together with rule, object, communication and actor and role perspectives is one way of classifying modeling approaches.
Types of perspectives
Structural modeling perspective
This approach concentrates on describing the static structure. The main concept in this modeling perspective is the entity, this could be an object, phenomena, concept, thing etc.
The data modeling languages have traditionally handled this perspective, examples of such being:
The ER-language (Entity-Relationship)
Generic Semantic Modeling language (GSM)
Other approaches including:
The NIAM language (Binary relationship language)
Conceptual graphs (Sowa)
Looking at the ER-language we have the basic components:
Entities: Distinctively identifiable phenomenon.
Relationships: An association among the entities.
Attributes: Used to give value to a property of an entity/relationship.
Looking at the generic semantic modeling language we have the basic components:
Constructed types built by abstraction: Aggregation, generalization, and association.
Attributes.
Primitive types: Data types in GSM are classified into printable and abstract types.
Printable: Used to specify visible values.
Abstract: Representing entities.
Functional modeling perspective
The functional modeling approach concentrates on describing the dynamic process. The main concept in this modeling perspective is the process, this could be a function, transformation, activity, action, task etc. A well-known example of a modeling language employing this perspective is data flow diagrams.
The perspective uses four symbols to describe a process, these being:
Process: Illustrates transformation from input to output.
Store: Data-collection or some sort of material.
Flow: Movement of data or material in the process.
External Entity: External to the modeled system, but interacts with it.
Now, with these symbols, a process can be represented as a network of these symbols.
This decomposed process is a DFD, data flow diagram.
Behavioral perspective
Behavioral perspective gives a description of system dynamics. The main concepts in behavioral perspective are states and transitions between states. State transitions are triggered by events. State Transition Diagrams (STD/STM), State charts and Petri-nets are some examples of well-known behaviorally oriented modeling languages. Different types of State Transition Diagrams are used particularly within real-time systems and telecommunications systems.
Rule perspective
Rule perspective gives a description of goals/means connections. The main concepts in rule perspective are rule, goal and constraint. A rule is something that influences the actions of a set of actors. The standard form of rule is “IF condition THEN action/expression”. Rule hierarchies (goal-oriented modeling), Tempora and Expert systems are some examples of rule oriented modeling.
Object perspective
The object-oriented perspective describes the world as autonomous, communicating objects. An object is an “entity” which has a unique and unchangeable identifier and a local state consisting of a collection of attributes with assignable values. The state can only be manipulated with a set of methods defined on the object. The value of the state can only be accessed by sending a message to the object to call on one of its methods. An event is when an operation is being triggered by receiving a message, and the trace of the events during the existence of the object is called the object’s life cycle or the process of an object. Several objects that share the same definitions of attributes and operations can be parts of an object class. The perspective is originally based on design and programming of object oriented systems. Unified Modelling Language (UML) is a well known language for modeling with an object perspective.
Communication perspective
This perspective is based on language/action theory from philosophical linguistics. The basic assumption in this perspective is that person/objects cooperate on a process/action through communication within them.
An illocutionary act consists of five elements: Speaker, hearer, time, location and circumstances. It is a reason and goal for the communication, where the participations in a communication act is oriented towards mutual agreement. In a communication act, the speaker generally can raise three claims: truth (referring an object), justice (referring a social world of the participations) and claim to sincerity (referring the subjective world of the speaker).
Actor and role perspective
Actor and role perspective is a description of organisational and system structure. An actor can be defined as a phenomenon that influences the history of another actor, whereas a role can be defined as the behaviour which is expected by an actor, amongst other actors, when filling the role. Modeling within these perspectives is based both on work with object-oriented programming languages and work with intelligent agents in artificial intelligence. I* is an example of an actor oriented language.
See also
Domain-Specific Modeling (DSM)
Glossary of Unified Modeling Language terms
General-purpose modeling
Model Driven Engineering (MDE)
Modeling language
Three schema approach for data modeling
View model
References
Further reading
Ingeman Arbnor and Björn Bjerke (1997). Methodology for Creating Business Knowledge. California : Sage Publications. (Third Edition 2009).
Information systems
Scientific modelling
Systems engineering | Modeling perspective | [
"Technology",
"Engineering"
] | 1,071 | [
"Information systems",
"Systems engineering",
"Information technology"
] |
2,990,869 | https://en.wikipedia.org/wiki/Ectopic%20expression | Ectopic is a word used with a prefix ecto-, meaning “out of”, and the suffix -topic, meaning "place." Ectopic expression is an abnormal gene expression in a cell type, tissue type, or developmental stage in which the gene is not usually expressed. The term ectopic expression is predominantly used in studies using metazoans, especially in Drosophila melanogaster for research purposes.
How is it used
Although ectopic expression can be caused by a natural condition, it is uncommonly seen in nature because it is a product of defects in gene regulation. In fact, ectopic expression is more commonly used for research purposes. Artificially induced gene expression helps to determine the function of a gene of interest. Common techniques such as overexpressing or misexpressing the genes by UAS-Gal4 system in D. melanogaster are used. In model organisms, such techniques are used to perform genetic screens to identify a function of the gene involved in specific cellular or developmental processes.
Ectopic expression using these techniques is a useful tool because phenotypes induced in a tissue or cell type where are not normally expressed are easily distinguishable compared to a tissue or cell type where the gene is normally expressed. By the comparison with its basal expression, the function of a gene of interest can be identified.
Although the understanding of ectopic expressions deals with endogenous genes in an organism, it can be expended to a similar concept like transgenesis, which an exogenous gene is introduced to a cell or tissue type in which the gene is not usually expressed. Practices of ectopic expression in biological science is not only limited to identifying a function of the gene in a known cell or tissue type but also implemented to discover unknown or additional functions of the gene by ectopic expression.
Research examples
Paired box protein
Paired box protein Pax-6 in humans is a transcription factor, which is a main regulatory gene of eye and brain development. Ectopic expression of Drosophila homolog eyeless (ey) has been used to identify roles of Pax-6 in humans. Using tissue specific UAS-Gal4 system, ey can be induced on the legs, wings, halters and antennae of the transgenic flies to demonstrate that functions of ey.
Olfactory receptor genes
Olfactory receptor gene (OR) is normally expressed in human and mouse olfactory tissue with a main function as odorant receptor for the detection of odorants. Individuals with a defect in this gene have disorders of taste and smell. It has been reported that ORs is also expressed on sperms and testis with special emphasis in a manner of ectopic expression. In a study, researchers identified ectopic expression of OR genes in non-olfactory tissues in the mouse model by measuring transcript levels. Here they found relatively low OR gene expression compared to the olfactory tissue, which result indicates that the OR gene in other tissue have no extra function, but they suggest that there is a possibility that small OR subsets can have functional roles in different tissue.
Synovial Sarcoma X chromosome breakpoint-2
Synovial Sarcoma X chromosome breakpoint-2 (SSX2) proteins are known to localize in nucleus and work as a transcriptional repressor. In addition, expression of SSX2 is frequently observed in melanoma, but the role of the gene has not been evaluated. Thus, researchers have used the principle of ectopic expression to express SSX2 to different cell lines including cancer model cells. They found important phenotypes of ectopic SSX2 expression that is involved in tumorigenesis: 1) immediate induction of genomic instability, 2) long-term support of tumor cell growth.
References
Gene expression | Ectopic expression | [
"Chemistry",
"Biology"
] | 781 | [
"Gene expression",
"Molecular genetics",
"Cellular processes",
"Molecular biology",
"Biochemistry"
] |
2,990,996 | https://en.wikipedia.org/wiki/Klamath%20Project | The Klamath Project is a water-management project developed by the United States Bureau of Reclamation to supply farmers with irrigation water and farmland in the Klamath Basin. The project also supplies water to the Tule Lake National Wildlife Refuge, and the Lower Klamath National Wildlife Refuge. The project was one of the first to be developed by the Reclamation Service, which later became the Bureau of Reclamation.
The two main water supply sources for the project are Upper Klamath Lake and the Klamath River. The main bodies of water in the Klamath Project are Clear Lake Reservoir, Klamath River, Link River, Lost River, Lower Klamath Lake, Tule Lake, and Upper Klamath Lake. The project fills these reservoirs from the spring runoff, peaking generally in March and April, and keeps the runoff from flooding the historical marshes that are a large portion of the present farmland. There are also many minor streams in the area. Lost River historically drained into Tule Lake, an endorheic lake. The project now diverts excess Lost River water to the Klamath River, allowing portions of Tule Lake to be reclaimed.
Some of rangeland have been transformed into active farmland through the Klamath Project. Of that total, were recovered by draining a portion of Lower Klamath Lake, a shallow marsh straddling the Oregon-California border between the California towns of Dorris and Tulelake. Tule Lake was also reduced in size by diverting water from Lost River to the Klamath River.
Farmers in the project raise barley, alfalfa hay, and other hay, oats, potatoes, and wheat. The Klamath Basin is on the Pacific Flyway and the Klamath Basin National Wildlife Refuges Complex is visited by migratory game birds every year.
The project can be distinguished the Klamath River Hydroelectric Project, which is a set of hydro dams on the mainstem of the Klamath operated by for-profit energy company PacifiCorp. The Link River Dam belongs to both.
History
Construction began on the project in 1906 with the building of the main "A" Canal. Water was first made available May 22, 1907. The Clear Lake Dam was completed in 1910, the Lost River Diversion Dam and many of the distribution structures in 1912, and the Anderson-Rose Diversion Dam (formally Lower Lost River Diversion Dam) in 1921. The Malone Diversion Dam on Lost River was built in 1923 to divert water to Langell Valley.
A contract executed February 24, 1917, between the California-Oregon Power Company (now Pacific Power) and the United States authorized the company to construct the Link River Dam for the benefit of the project and for the company's use, and in particular extended to the water users of the Klamath Project certain preferential power rates. The dam was completed in 1921.
In more recent times, the Klamath Project has been the focus of nationwide controversy. The Lost River and Shortnose suckers were listed as endangered in 1988. This, as well as concerns for salmon runs, led to a cutoff of irrigation water to local farmers on April 6, 2001. After many protests by farmers and concerned citizens alike, the decision was reversed the next year. The impact of the salmon kill was detailed in the book Salmon is Everything. A 2002 report by the National Research Council however, determined that the decision to stop delivery of irrigation water in 2001 was not scientifically justified and that the 2002 fish kill was caused by a combination of natural factors.
A massive die off of salmon occurred in 2002 due to low water and high temperatures in the lower reaches of the river during the salmon migration. Studies showed that drought conditions and low flow from the entire drainage were among the factors that caused a unique mix of conditions to allow a gill rot disease to attack the salmon population.
The conflict in balancing the economic and ecological concerns of the region was the focus of the 2006 book River of Renewal: Myth and History in the Klamath Basin. Today, there is still much antagonism between opposing sides on this issue.
Engineering
Dams
The Klamath Project contains seven dams, all of them on tributaries of the Klamath River itself. In chronological order of completion, they are:
the Clear Lake Dam, completed in 1910, replaced 2002, for flood control and water storage. It impounds Lost River to form Clear Lake Reservoir
the Lost River Diversion Dam, completed in 1912, diverts the waters of the Lost River into the Klamath, thereby controlling flow into the adjacent Tule Lake National Wildlife Refuge and reclaimed parts of the Tule Lake bed
the Link River Dam, completed in 1921 for flood control, water storage, and hydro power. It impounds Link River to form Upper Klamath Lake
the Anderson-Rose Diversion Dam, completed in 1921 as a diversion dam, on the Lost River close to Merrill, Oregon
the Malone Diversion Dam, finished in 1923, on the upper Lost River
the Miller Diversion Dam, completed in 1924, on Miller Creek, below Gerber Dam
the Gerber Dam, completed in 1925 for water storage, impounding Miller Creek to form Gerber Reservoir
Canals
There are over of canals, laterals and diversion channels in the Klamath Project. The canals transport irrigation water from Klamath Lake and the Klamath River, Clear Lake and the Lost River, and Tule Lake. There are two tunnels: the "A" Canal (the main canal that starts just above the Link River Dam) has an underground section as it flows through Klamath Falls, and the Tule Lake Tunnel.
There are almost of drainage canals in the Klamath Project which allow land that would otherwise be wetlands to be farmed. The Lower Klamath Lake was before it was drained and would naturally evaporate about each summer. This is roughly equivalent to the annual delivery of the A canal.
Pumps
There are 28 pumping stations in the Klamath Project. These pumps have a total output of over 1937 ft³/s (55 m³/s).
Water management
The Bureau must consider water needs for threatened coho salmon in the river, and two species of endangered sucker fish in Upper Klamath Lake. In 2001, a court order withheld irrigation water from Klamath Project farmers, to comply with mandated river levels for the threatened Coho salmon and the endangered Lost River Sucker. Downstream populations of Coho salmon are within the Southern Oregon/Northern California Evolutionary Significant Unit and are listed as threatened (2011).
The 2010 Klamath Basin Restoration Agreement (KBRA) is a multi-party legal agreement determining river usage and water rights involving the Klamath River, the Klamath Project, and the Klamath Basin, within the states of California and Oregon. Among the more notable signatories to the agreement were the Governors of California and Oregon, and the Chairman of the Klamath Tribes.
As opposed to the government-owned irrigation dams of the Klamath Project on upper tributaries, the seven dams of the Klamath River Hydroelectric Project are operated by for-profit energy company PacifiCorp. The systems share one facility, the Link River Dam, which is owned by the United States Bureau of Reclamation but operated by PacifiCorp primarily to regulate its own downstream water supply, and secondarily for power generation.
References
External links
United States Bureau of Reclamation
Klamath Waters Digital Library
Historic American Engineering Record (HAER) documentation, filed under Klamath Falls, Klamath County, OR:
Klamath River
Interbasin transfer
United States Bureau of Reclamation
Water in Oregon
Water in California
Klamath County, Oregon
Historic American Engineering Record in Oregon
History of Modoc County, California
History of Siskiyou County, California
Hydroelectric power plants in Oregon
Klamath Mountains
Geography of Klamath County, Oregon
Geography of Modoc County, California
Geography of Siskiyou County, California | Klamath Project | [
"Environmental_science"
] | 1,608 | [
"Hydrology",
"Interbasin transfer"
] |
2,991,011 | https://en.wikipedia.org/wiki/EL34 | The EL34 is a thermionic vacuum tube of the power pentode type. The EL34 was introduced in 1955 by Mullard, who were owned by Philips. The EL34 has an octal base (indicated by the '3' in the part number) and is found mainly in the final output stages of audio amplification circuits; it was also designed to be suitable as a series regulator by virtue of its high permissible voltage between heater and cathode and other parameters. The American RETMA tube designation number for this tube is 6CA7. The USSR analog was 6P27S (Cyrillic: 6П27C).
Specifications
In common with all 'E' prefix tubes, using the Mullard–Philips tube designation, the EL34 has a heater voltage of 6.3 V. According to the data sheets found in old vacuum tube reference manuals, a pair of EL34s with 800 V plate voltage can produce 90 watts output in class AB1 in push–pull configuration. However, this configuration is rarely found. One application of this type was in "Australian Sound" public address amplifiers commonly used in government schools in Australia in the 1950s, using four EL34s for ≈200 watts. More commonly found is a pair of EL34s running class AB1 in push–pull around 375–450 V plate voltage and producing 50 watts output (if fixed bias is used), while a quad of EL34s running class AB1 in push–pull typically run anywhere from 425 to 500 V plate voltage and produces 100 watts output. This configuration is typically found in guitar amplifiers.
The EL34 is a pentode, while the 6L6, which delivers a similar range of power output, is a beam tetrode which RCA referred to as a beam power tube. Although power pentodes and beam tetrodes have some differences in their principles of operation (the beam forming plates of the beam tetrode or fifth electrode (3rd grid) of the pentode, both serving to hinder the return of unabsorbed electrons from the anode (or plate) to the 4th electrode (2nd grid)) and have some internal construction differences, they are functionally closely equivalent. Unlike the 6L6, (EIA base 7AC) the EL34 has its grid 3 connection brought out to a separate Pin (Pin 1) (EIA base 8ET) and its heater draws 1.5 Amps compared to the 0.9 Amp heater in the 6L6. However, Sylvania (and possibly GE) marketed a tube as 6CA7 which was not only in a markedly different 'fat boy' envelope, but used a beam forming plate much like a 6L6. Examining the mica spacer on the top of the tube will confirm the lack of a suppressor grid. Although these tubes have similar (but not identical) characteristics, they are made very differently.
While the EL34 is no longer made by Philips, it is currently manufactured by EkspoPUL in Saratov, Russia (Electro-Harmonix, Tung-Sol, Mullard and Genalex Gold Lion brands), JJ Electronic in Čadca, Slovakia and by Hengyang Electronics at former Foshan Nanhai Guiguang Electron Tube Factory in southern China, (Psvane and TAD brands).
Some firms make a related tube called an E34L which is rated to require a higher grid bias voltage, but which may be interchangeable in some equipment.
Application
The EL34 was widely used in higher-powered audio amplifiers of the 1960s and 1970s, such as the popular Dynaco Stereo 70 and the Leak TL25 (mono) and Stereo 60, and is also widely used in high-end guitar amplifiers because it is characterized by greater distortion (considered desirable in this application) at lower power than other octal tubes such as 6L6, KT88, or 6550. The EL34 is found in many British guitar amps and is associated with the "British tone" (Vox, Marshall, Hiwatt, Orange) as compared to the 6L6 which is generally associated with the "American tone" (Fender/Mesa Boogie; the earlier classic Marshall "Plexi" amps used the KT66, a beam tetrode similar to the 6L6, as well).
Replacement
6CA7
Similar tubes
KT77
6P27S (6П27С)
See also
EL84
6V6
6L6
5881
KT66
KT88
6550
List of vacuum tubes
References
Technical specifications
EL34 Philips Metal Base
Valvo Gmbh, Valvo Taschenbuch, 1958.
RCA, RCA Receiving Tube Manual RC26, 1968.
JJ Electronics EL34 and E34L data sheet (PDF)
EL34 EI Yugoslavia
External links
Duncan's Amps TDSL
Reviews of EL34 tubes
Tube Data Archive, thousands of tube data sheets
Vacuum tubes
Guitar amplification tubes | EL34 | [
"Physics"
] | 1,025 | [
"Vacuum tubes",
"Vacuum",
"Matter"
] |
2,991,090 | https://en.wikipedia.org/wiki/Hodgkin%E2%80%93Huxley%20model | The Hodgkin–Huxley model, or conductance-based model, is a mathematical model that describes how action potentials in neurons are initiated and propagated. It is a set of nonlinear differential equations that approximates the electrical engineering characteristics of excitable cells such as neurons and muscle cells. It is a continuous-time dynamical system.
Alan Hodgkin and Andrew Huxley described the model in 1952 to explain the ionic mechanisms underlying the initiation and propagation of action potentials in the squid giant axon. They received the 1963 Nobel Prize in Physiology or Medicine for this work.
Basic components
The typical Hodgkin–Huxley model treats each component of an excitable cell as an electrical element (as shown in the figure). The lipid bilayer is represented as a capacitance (Cm). Voltage-gated ion channels are represented by electrical conductances (gn, where n is the specific ion channel) that depend on both voltage and time. Leak channels are represented by linear conductances (gL). The electrochemical gradients driving the flow of ions are represented by voltage sources (En) whose voltages are determined by the ratio of the intra- and extracellular concentrations of the ionic species of interest. Finally, ion pumps are represented by current sources (Ip). The membrane potential is denoted by Vm.
Mathematically, the current flowing through the lipid bilayer is written as
and the current through a given ion channel is the product of that channel's conductance and the driving potential for the specific ion
where is the reversal potential of the specific ion channel.
Thus, for a cell with sodium and potassium channels, the total current through the membrane is given by:
where I is the total membrane current per unit area, Cm is the membrane capacitance per unit area, gK and gNa are the potassium and sodium conductances per unit area, respectively, VK and VNa are the potassium and sodium reversal potentials, respectively, and gl and Vl are the leak conductance per unit area and leak reversal potential, respectively. The time dependent elements of this equation are Vm, gNa, and gK, where the last two conductances depend explicitly on the membrane voltage (Vm) as well.
Ionic current characterization
In voltage-gated ion channels, the channel conductance is a function of both time and voltage ( in the figure), while in leak channels, , it is a constant ( in the figure). The current generated by ion pumps is dependent on the ionic species specific to that pump. The following sections will describe these formulations in more detail.
Voltage-gated ion channels
Using a series of voltage clamp experiments and by varying extracellular sodium and potassium concentrations, Hodgkin and Huxley developed a model in which the properties of an excitable cell are described by a set of four ordinary differential equations. Together with the equation for the total current mentioned above, these are:
where I is the current per unit area and and are rate constants for the i-th ion channel, which depend on voltage but not time. is the maximal value of the conductance. n, m, and h are dimensionless probabilities between 0 and 1 that are associated with potassium channel subunit activation, sodium channel subunit activation, and sodium channel subunit inactivation, respectively. For instance, given that potassium channels in squid giant axon are made up of four subunits which all need to be in the open state for the channel to allow the passage of potassium ions, the n needs to be raised to the fourth power. For , and take the form
and are the steady state values for activation and inactivation, respectively, and are usually represented by Boltzmann equations as functions of . In the original paper by Hodgkin and Huxley, the functions and are given by
where denotes the negative depolarization in mV.
In many current software programs
Hodgkin–Huxley type models generalize and to
In order to characterize voltage-gated channels, the equations can be fitted to voltage clamp data. For a derivation of the Hodgkin–Huxley equations under voltage-clamp, see. Briefly, when the membrane potential is held at a constant value (i.e., with a voltage clamp), for each value of the membrane potential the nonlinear gating equations reduce to equations of the form:
Thus, for every value of membrane potential the sodium and potassium currents can be described by
In order to arrive at the complete solution for a propagated action potential, one must write the current term I on the left-hand side of the first differential equation in terms of V, so that the equation becomes an equation for voltage alone. The relation between I and V can be derived from cable theory and is given by
where a is the radius of the axon, R is the specific resistance of the axoplasm, and x is the position along the nerve fiber. Substitution of this expression for I transforms the original set of equations into a set of partial differential equations, because the voltage becomes a function of both x and t.
The Levenberg–Marquardt algorithm is often used to fit these equations to voltage-clamp data.
While the original experiments involved only sodium and potassium channels, the Hodgkin–Huxley model can also be extended to account for other species of ion channels.
Leak channels
Leak channels account for the natural permeability of the membrane to ions and take the form of the equation for voltage-gated channels, where the conductance is a constant. Thus, the leak current due to passive leak ion channels in the Hodgkin-Huxley formalism is .
Pumps and exchangers
The membrane potential depends upon the maintenance of ionic concentration gradients across it. The maintenance of these concentration gradients requires active transport of ionic species. The sodium-potassium and sodium-calcium exchangers are the best known of these. Some of the basic properties of the Na/Ca exchanger have already been well-established: the stoichiometry of exchange is 3 Na+: 1 Ca2+ and the exchanger is electrogenic and voltage-sensitive. The Na/K exchanger has also been described in detail, with a 3 Na+: 2 K+ stoichiometry.
Mathematical properties
The Hodgkin–Huxley model can be thought of as a differential equation system with four state variables, , and , that change with respect to time . The system is difficult to study because it is a nonlinear system, cannot be solved analytically, and therefore has no closed-form solution. However, there are many numerical methods available to analyze the system. Certain properties and general behaviors, such as limit cycles, can be proven to exist.
Center manifold
Because there are four state variables, visualizing the path in phase space can be difficult. Usually two variables are chosen, voltage and the potassium gating variable , allowing one to visualize the limit cycle. However, one must be careful because this is an ad-hoc method of visualizing the 4-dimensional system. This does not prove the existence of the limit cycle.
A better projection can be constructed from a careful analysis of the Jacobian of the system, evaluated at the equilibrium point. Specifically, the eigenvalues of the Jacobian are indicative of the center manifold's existence. Likewise, the eigenvectors of the Jacobian reveal the center manifold's orientation. The Hodgkin–Huxley model has two negative eigenvalues and two complex eigenvalues with slightly positive real parts. The eigenvectors associated with the two negative eigenvalues will reduce to zero as time t increases. The remaining two complex eigenvectors define the center manifold. In other words, the 4-dimensional system collapses onto a 2-dimensional plane. Any solution starting off the center manifold will decay towards the center manifold. Furthermore, the limit cycle is contained on the center manifold.
Bifurcations
If the injected current were used as a bifurcation parameter, then the Hodgkin–Huxley model undergoes a Hopf bifurcation. As with most neuronal models, increasing the injected current will increase the firing rate of the neuron. One consequence of the Hopf bifurcation is that there is a minimum firing rate. This means that either the neuron is not firing at all (corresponding to zero frequency), or firing at the minimum firing rate. Because of the all-or-none principle, there is no smooth increase in action potential amplitude, but rather there is a sudden "jump" in amplitude. The resulting transition is known as a canard.
Improvements and alternative models
The Hodgkin–Huxley model is regarded as one of the great achievements of 20th-century biophysics. Nevertheless, modern Hodgkin–Huxley-type models have been extended in several important ways:
Additional ion channel populations have been incorporated based on experimental data.
The Hodgkin–Huxley model has been modified to incorporate transition state theory and produce thermodynamic Hodgkin–Huxley models.
Models often incorporate highly complex geometries of dendrites and axons, often based on microscopy data.
Conductance-based models similar to Hodgkin–Huxley model incorporate the knowledge about cell types defined by single cell transcriptomics.
Stochastic models of ion-channel behavior, leading to stochastic hybrid systems.
The Poisson–Nernst–Planck (PNP) model is based on a mean-field approximation of ion interactions and continuum descriptions of concentration and electrostatic potential.
Several simplified neuronal models have also been developed (such as the FitzHugh–Nagumo model), facilitating efficient large-scale simulation of groups of neurons, as well as mathematical insight into dynamics of action potential generation.
See also
Anode break excitation
Autowave
Neural circuit
GHK flux equation
Goldman equation
Memristor
Neural accommodation
Reaction–diffusion
Theta model
Rulkov map
Chialvo map
References
Further reading
External links
Interactive Javascript simulation of the HH model Runs in any HTML5 – capable browser. Allows for changing the parameters of the model and current injection.
Interactive Java applet of the HH model Parameters of the model can be changed as well as excitation parameters and phase space plottings of all the variables is possible.
Direct link to Hodgkin–Huxley model and a Description in BioModels Database
Neural Impulses: The Action Potential In Action by Garrett Neske, The Wolfram Demonstrations Project
Interactive Hodgkin–Huxley model by Shimon Marom, The Wolfram Demonstrations Project
ModelDB A computational neuroscience source code database containing 4 versions (in different simulators) of the original Hodgkin–Huxley model and hundreds of models that apply the Hodgkin–Huxley model to other channels in many electrically excitable cell types.
Several articles about the stochastic version of the model and its link with the original one.
Nonlinear systems
Electrophysiology
Ion channels
Computational neuroscience | Hodgkin–Huxley model | [
"Chemistry",
"Mathematics"
] | 2,283 | [
"Nonlinear systems",
"Neurochemistry",
"Ion channels",
"Dynamical systems"
] |
2,991,258 | https://en.wikipedia.org/wiki/Lead%20oxide | Lead oxides are a group of inorganic compounds with formulas including lead (Pb) and oxygen (O).
Common lead oxides include:
Lead(II) oxide, PbO, litharge (red), massicot (yellow)
Lead tetroxide or red lead, , minium, which is a lead (II,IV) oxide and may be thought of as lead(II) orthoplumbate(IV) , vivid orange crystals
Lead dioxide (lead(IV) oxide), , dark-brown or black powder
Less common lead oxides are:
Lead sesquioxide, , which is a lead (II,IV) oxide as well (lead(II) metaplumbate(IV) ), reddish yellow
, monoclinic, dark-brown or black crystals
The so-called black lead oxide, which is a mixture of PbO and fine-powdered Pb metal and used in the production of lead–acid batteries.
Lead compounds
Oxides | Lead oxide | [
"Chemistry"
] | 206 | [
"Oxides",
"Salts"
] |
2,991,382 | https://en.wikipedia.org/wiki/Parenthesome | Within the cells of some members of basidiomycetes fungi are found microscopic structures called parenthesomes or septal pore caps. They are shaped like parentheses and found on either side of pores in the dolipore septum which separates cells within a hypha. Their function has not been established, and their composition has not been fully elucidated. The variations in their appearance are useful in distinguishing individual species.
Generally, they are barrel shaped, with an endoplasmic reticulum covering.
See also
Pit connection
References
Organelles
Mycology
Fungal morphology and anatomy | Parenthesome | [
"Biology"
] | 122 | [
"Mycology"
] |
2,991,457 | https://en.wikipedia.org/wiki/Synapsis | Synapsis or Syzygy is the pairing of two chromosomes that occurs during meiosis. It allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them. Synapsis takes place during prophase I of meiosis. When homologous chromosomes synapse, their ends are first attached to the nuclear envelope. These end-membrane complexes then migrate, assisted by the extranuclear cytoskeleton, until matching ends have been paired. Then the intervening regions of the chromosome are brought together, and may be connected by a protein-DNA complex called the synaptonemal complex (SC). The SC protein scaffold stabilizes the physical pairing of homologous chromosomes by polymerizing between them during meiotic prophase. During synapsis, autosomes are held together by the synaptonemal complex along their whole length, whereas for sex chromosomes, this only takes place at one end of each chromosome.
This is not to be confused with mitosis. Mitosis also has prophase, but does not ordinarily do pairing of two homologous chromosomes. In contrast to the mitosis cycle, during meiosis, the number of chromosomes is reduced by half to create haploid gametes; this reduction is called Haploidization; after fertilization, diploidy is restored. Homologous chromosomes – two copies inherited from each parent – recognize one another and pair before reductional segregation, which is essential for crossover recombination and forms chiasmata, a stable physical connection that hold homologous chromosomes together until metaphase. In most species, every homologous chromosome experiences at least one meiotic crossover referred to as the obligate crossover.
When the non-sister chromatids intertwine, segments of chromatids with similar sequence may break apart and be exchanged in a process known as genetic recombination or "crossing-over". This exchange produces a chiasma, a region that is shaped like an X, where the two chromosomes are physically joined. At least one chiasma per chromosome often appears to be necessary to stabilise bivalents along the metaphase plate during separation. The crossover of genetic material also provides a possible defences against 'chromosome killer' mechanisms, by removing the distinction between 'self' and 'non-self' through which such a mechanism could operate. A further consequence of recombinant synapsis is to increase genetic variability within the offspring. Repeated recombination also has the general effect of allowing genes to move independently of each other through the generations, allowing for the independent concentration of beneficial genes and the purging of the detrimental.
Following synapsis, a type of recombination referred to as synthesis dependent strand annealing (SDSA) occurs frequently. SDSA recombination involves information exchange between paired non-sister homologous chromatids, but not physical exchange. SDSA recombination does not cause crossing-over. Both the non-crossover and crossover types of recombination function as processes for repairing DNA damage, particularly double-strand breaks (see Genetic recombination).
The central function of synapsis is therefore the identification of homologues by pairing, an essential step for a successful meiosis. The processes of DNA repair and chiasma formation that take place following synapsis have consequences at many levels, from cellular survival through to impacts upon evolution itself.
Mechanisms of homologous chromosome cohesion
Homologous chromosomes are held together by several mechanisms during meiosis, ensuring their proper pairing, alignment, and recombination. These mechanisms include:
The synaptonemal complex (SC) is a key protein structure that physically holds homologous chromosomes together during prophase I of meiosis I, facilitating their alignment and the pairing of homologs, named synapsis. The SC is composed of proteins like SYCP1, SYCP2, and SYCP3, which work together to stabilize the homologs and promote homologous or meiotic recombination, where homologous chromosomes exchange genetic material. Any flaws in its formation lead to failures in meiotic recombination, chromosome segregation, and the completion of meiosis. Furthermore, incorrect segregation of homologous chromosomes during meiosis I leads to the formation of aneuploid gametes, which are a primary cause of miscarriage, infertility, and birth defects.
Centromere pairing and Cohesin Complex: The formation of connections between homologous chromosomes, called crossovers, create links that enable homologous chromosomes to attach properly to the meiosis I spindle and ensure correct chromosome segregation. Through tension-sensing biorientation mechanisms centromere pairing establishes connections between chromosomes allowing their interdependent attachment to the meiotic spindle. The SC complex interacts with the chromosome axis, directly interacting with the chromatin and the regulation of meiotic recombination. Cohesin-related proteins are a key component of the chromosome axis and are particularly abundant at the centromeres of meiotic chromosomes. Cohesin primarily holds sister chromatids together after DNA replication, which plays a critical role in stabilizing homologous chromosome pairing during meiosis. Once homologs pair, cohesins at the centromere regions help maintain their cohesion in the early stages of meiosis, ensuring the chromosomes remain together until the proper time for segregation. The assembly of the SC complex relies on two cohesin complexes: one essential for interhomolog interactions and another necessary for sister chromatid interactions.
Chromosome silencing
In mammals, surveillance mechanisms remove meiotic cells in which synapsis is defective. One such surveillance mechanism is meiotic silencing that involves the transcriptional silencing of genes on asynapsed chromosomes. Any chromosome region, either in males or females, that is asynapsed is subject to meiotic silencing. ATR, BRCA1 and gammaH2AX localize to unsynapsed chromosomes at the pachytene stage of meiosis in human oocytes and this may lead to chromosome silencing. The DNA damage response protein TOPBP1 has also been identified as a crucial factor in meiotic sex chromosome silencing. DNA double-strand breaks appear to be initiation sites for meiotic silencing.
Recombination
In female Drosophila melanogaster fruit flies, meiotic chromosome synapsis occurs in the absence of recombination. Thus synapsis in Drosophila is independent of meiotic recombination, consistent with the view that synapsis is a precondition required for the initiation of meiotic recombination. Meiotic recombination is also unnecessary for homologous chromosome synapsis in the nematode Caenorhabditis elegans.
References
External links
UC Berkeley video of chromosome end migration and match assessment during prophase
Cell biology
Cytogenetics | Synapsis | [
"Biology"
] | 1,458 | [
"Cell biology"
] |
2,991,563 | https://en.wikipedia.org/wiki/Neutrodyne | The Neutrodyne radio receiver, invented in 1922 by Louis Hazeltine, was a particular type of tuned radio frequency (TRF) receiver, in which the instability-causing inter-electrode capacitance of the triode RF tubes is cancelled out or "neutralized" to prevent parasitic oscillations which caused "squealing" or "howling" noises in the speakers of early radio sets. In most designs, a small extra winding on each of the RF amplifiers' tuned anode coils was used to generate a small antiphase signal, which could be adjusted by special variable trim capacitors to cancel out the stray signal coupled to the grid via plate-to-grid capacitance. The Neutrodyne circuit was popular in radio receivers until the 1930s, when it was superseded by the superheterodyne receiver.
History
The circuit was developed about 1922 by Harold Wheeler who worked in Louis Hazeltine's laboratory at Stevens Institute of Technology, so Hazeltine is usually given the credit. The tuned radio frequency (TRF) receiver, one of the most popular radio receiver designs of the time, consisted of several tuned radio frequency (RF) amplifier stages, followed by a detector and several audio amplifier stages. A major defect of the TRF receiver was that, due to the high interelectrode capacitance of early triode vacuum tubes, feedback within the RF amplifier stages gave them a tendency to oscillate, creating unwanted radio frequency alternating currents. These parasitic oscillations mixed with the carrier wave in the detector, creating heterodynes (beat notes) in the audio frequency range, which were heard as annoying whistles and howls from the speaker.
Hazeltine's innovation was to add a circuit to each radio frequency amplifier stage which fed back a small amount of energy from the plate (output) circuit to the grid (input) circuit with opposite phase to cancel ("neutralize") the feedback which was causing the oscillation. This effectively prevented the high-pitched squeals that had plagued early radio sets. A group of more than 20 companies known as the Independent Radio Manufacturers Association licensed the circuit from Hazeltine and manufactured "Neutrodyne" receivers throughout the 1920s. At the time, RCA held a virtual monopoly over commercial radio receiver production due to its ownership of the rights to the Armstrong regenerative and superheterodyne circuits. The Neutrodyne ended this control, allowing competition. Compared to the technically superior superheterodyne the Neutrodyne was cheaper to build. As basically a TRF receiver, it was also considered easier for non-technical owners to use than the early superhets. After manufacture each tuned amplifier stage had to be neutralized, adjusted to cancel feedback; after this the set would not produce the parasitic oscillations which caused the objectionable noises. By 1927 some ten million of these receivers had been sold to consumers in North America.
By the 1930s, advances in vacuum tube manufacturing had yielded the tetrode, which had reduced control grid to plate (Miller) capacitance. These advances made it possible to build TRF receivers that did not need neutralization, but also made Edwin Armstrong's superheterodyne design practical for domestic receivers. So the TRF circuit, including the Neutrodyne, became obsolete in radio receivers and was superseded by the superheterodyne design.
The Neutrodyne neutralization technique continues to be used in other applications to suppress parasitic oscillation, such as in RF power amplifiers in radio transmitters.
See also
Crystal radio receiver
Low IF receiver
Regenerative radio receiver
Superheterodyne receiver
Tuned radio frequency receiver
References
External links
Louis Alan Hazeltine "Scanning the Past" the Proceedings of the IEEE Vol. 81, No. 4, April 1993
Neutralisation of Philco Neutrodyne-Plus Receivers
The Neutrodyne circuit
Radio electronics
History of radio
Receiver (radio) | Neutrodyne | [
"Engineering"
] | 814 | [
"Radio electronics",
"Receiver (radio)"
] |
2,991,580 | https://en.wikipedia.org/wiki/%CE%93-convergence | In the field of mathematical analysis for the calculus of variations, Γ-convergence (Gamma-convergence) is a notion of convergence for functionals. It was introduced by Ennio De Giorgi.
Definition
Let be a topological space and denote the set of all neighbourhoods of the point . Let further be a sequence of functionals on . The Γ-lower limit and the Γ-upper limit are defined as follows:
.
are said to -converge to , if there exist a functional such that .
Definition in first-countable spaces
In first-countable spaces, the above definition can be characterized in terms of sequential -convergence in the following way.
Let be a first-countable space and a sequence of functionals on . Then are said to -converge to the -limit if the following two conditions hold:
Lower bound inequality: For every sequence such that as ,
Upper bound inequality: For every , there is a sequence converging to such that
The first condition means that provides an asymptotic common lower bound for the . The second condition means that this lower bound is optimal.
Relation to Kuratowski convergence
-convergence is connected to the notion of Kuratowski-convergence of sets. Let denote the epigraph of a function and let be a sequence of functionals on . Then
where denotes the Kuratowski limes inferior and the Kuratowski limes superior in the product topology of . In particular, -converges to in if and only if -converges to in . This is the reason why -convergence is sometimes called epi-convergence.
Properties
Minimizers converge to minimizers: If -converge to , and is a minimizer for , then every cluster point of the sequence is a minimizer of .
-limits are always lower semicontinuous.
-convergence is stable under continuous perturbations: If -converges to and is continuous, then will -converge to .
A constant sequence of functionals does not necessarily -converge to , but to the relaxation of , the largest lower semicontinuous functional below .
Applications
An important use for -convergence is in homogenization theory. It can also be used to rigorously justify the passage from discrete to continuum theories for materials, for example, in elasticity theory.
See also
Mosco convergence
Kuratowski convergence
Epi-convergence
References
A. Braides: Γ-convergence for beginners. Oxford University Press, 2002.
G. Dal Maso: An introduction to Γ-convergence. Birkhäuser, Basel 1993.
Calculus of variations
Variational analysis
Convergence (mathematics) | Γ-convergence | [
"Mathematics"
] | 521 | [
"Sequences and series",
"Functions and mappings",
"Convergence (mathematics)",
"Mathematical structures",
"Mathematical objects",
"Mathematical relations"
] |
2,991,899 | https://en.wikipedia.org/wiki/Lao-Lao | Lao-Lao () is a Laotian rice whisky produced in Laos. Along with Beerlao, lao-Lao is a staple drink in Laos.
Etymology
The name lao-Lao is not the same word repeated twice, but two different words pronounced with different tones: the first, ເຫລົ້າ, means "alcohol" and is pronounced with a low-falling tone in the standard dialect, while the second, ລາວ, means Laotian ("Lao") and is pronounced with a high(-rising) tone.
Taste
Quality, taste and alcohol concentration vary by source of the drink. However, all variations are strong. Lao satoe, the white liquid by-product from lao-Lao production, is also drunk and it has a very yeasty and sweet taste.
Production and consumption
Although lao-Lao is traditionally drunk neat, a cocktail that is rising in popularity is the "Pygmy Slow Lorange", named after the pygmy slow loris, a species endemic to Laos. Various flavoured lao-Laos are made by macerating such additives as honey or scorpions. It is women who often distill lao-Lao and sell it as a source of income locally, often being their second major income. Lao-Lao sold on retail is usually clear, but amber colored varieties exist too.
It is traditional to serve two glasses of lao-Lao on ceremonies, feasts and other comparable situations. The drink is customarily expected to be drunk with a single gulp.
A less powerful version of lao-Lao, called lao-hai, , and is drunk from large communal earthenware pots (hai) through long bamboo straws.
See also
Sra peang, a similar form of wine drunk in Cambodia
Rượu cần, a similar form of wine drunk in Vietnam
Rice wine
Rice baijiu
Sato (rice wine) – Isan version
References
External links
Lao-Lao Rice Whisky
Recipe for Lao-Lao
Description of meal with Lao-Lao
Lao cuisine
Laotian drinks
Distilled drinks
Rice drinks | Lao-Lao | [
"Chemistry"
] | 413 | [
"Distillation",
"Distilled drinks"
] |
2,991,908 | https://en.wikipedia.org/wiki/Area%20compatibility%20factor | In survival analysis, the area compatibility factor, F, is used in indirect standardisation of population mortality rates.
where:
is the standardised central exposed-to risk from age x to x + t for the standard population,
is the central exposed-to risk from age x to x + t for the population under study and
is the mortality rate in the standard population for ages x to x + t.
The expression can be thought of as the crude mortality rate for the standard population divided by what the crude mortality rate is for the region being studied, assuming the mortality rates are the same as for the standard population.
F is then multiplied by the crude mortality rate to arrive at the indirectly standardised mortality rate.
References
Actuarial science
Demography
Epidemiology | Area compatibility factor | [
"Mathematics",
"Environmental_science"
] | 155 | [
"Epidemiology",
"Applied mathematics",
"Actuarial science",
"Demography",
"Environmental social science"
] |
2,991,971 | https://en.wikipedia.org/wiki/263%20%28number%29 | 263 (two hundred [and] sixty-three) is the natural number between 262 and 264. It is also a prime number.
In mathematics
263 is
a balanced prime,
an irregular prime,
a Ramanujan prime, a Chen prime, and
a safe prime.
It is also a strictly non-palindromic number and a happy number.
References
Integers | 263 (number) | [
"Mathematics"
] | 75 | [
"Mathematical objects",
"Number stubs",
"Elementary mathematics",
"Integers",
"Numbers"
] |
2,992,000 | https://en.wikipedia.org/wiki/269%20%28number%29 | 269 (two hundred [and] sixty-nine) is the natural number between 268 and 270. It is also a prime number.
In mathematics
269 is a twin prime,
and a Ramanujan prime.
It is the largest prime factor of 9! + 1 = 362881,
and the smallest natural number that cannot be represented as the determinant of a 10 × 10 (0,1)-matrix.
In other fields
Calf 269 was a calf that rose to fame after being rescued by Israeli activists in 2012. As a result, numerous people branded the number "269" into their bodies over 2012 and 2013.
References
See also
269 AD
269 BC
Integers | 269 (number) | [
"Mathematics"
] | 137 | [
"Mathematical objects",
"Number stubs",
"Elementary mathematics",
"Integers",
"Numbers"
] |
2,992,104 | https://en.wikipedia.org/wiki/Brawling%20%28legal%20definition%29 | Brawling (probably connected with German language brüllen, to roar, shout), in law, was the offence of quarrelling, or creating a disturbance in a church or churchyard. Brawling was covered in ecclesiastic courts until 1860. It has rarely been prosecuted since then.
History
During the early stages of the Reformation in England, religious controversy too often became converted into actual disturbance, and the ritual lawlessness of the parochial clergy very frequently provoked popular violence. To repress these disturbances, the Brawling Act 1551
(5 & 6 Edw. 6. c. 4) was passed, by which it was enacted: "that if any person shall, by words only, quarrel, chide or brawl in any church or churchyard, it shall be lawful for the ordinary of the place where the same shall be done and proved by two lawful witnesses, to suspend any person so offending, if he be a layman, from the entrance of the church, and if he be a clerk, from the ministration of his office, for so long as the said ordinary shall think meet, according to the fault."
The Brawling Act 1553 (1 Mar. Sess. 2. c. 3) added the punishment of imprisonment until the party should repent. The Brawling Act 1551 was partly repealed in 1828 and wholly repealed as regards laymen by the Ecclesiastical Courts Jurisdiction Act 1860. Under that Act, which applies to Ireland as well as to England, persons guilty of riotous, violent or indecent behaviour, in churches and chapels of the Church of England or Ireland, or in any chapel of any religious denomination, or in England in any place of religious worship duly certified, or in churchyards or burial-grounds, were liable on conviction before two justices to a penalty of not more than £5, or imprisonment for any term not exceeding two months. This enactment applied to clergy as well as to laity, and a clergyman of the Church of England convicted under it could also be dealt with under the Clergy Discipline Act 1892 (Girt v. Fillingham, 1901, L.R. Prob. 176).
When Mr J. Kensit during an ordination service in St Paul's Cathedral "objected" to one of the candidates for ordination, on grounds which did not constitute an impediment or notable crime within the meaning of the ordination service, he was held to have unlawfully disturbed the Bishop of London in the conduct of the service, and to be liable to conviction under the Ecclesiastical Courts Jurisdiction Act 1860 (Kensit v. Dean and Chapter of St Paul's, 1905, L.R. 2 K.B. 249). The public worship of Protestant Dissenters, Roman Catholics and Jews in England had before 1860 been protected by a series of statutes beginning with the Toleration Act 1688, and ending with the Liberty of Religious Worship Act 1855. These enactments, though not repealed, were for practical purposes superseded by the summary remedy given by the Act of 1860. In Scotland disturbance of public worship is punishable as a breach of the peace (Dougall v. Dykes, 1861, 4 Irvine 101).
In the British Empire
In British possessions, interference with religious worship was usually dealt with by legislation, and not as a common-law offence. In India it was an offence voluntarily to cause disturbance to any assembly lawfully engaged in the performance of religious worship or religious ceremonies (Penal Code, s. 296). Under the Queensland Criminal Code of 1899 (s. 207) penalties were imposed on persons who wilfully and without lawful justification or excuse (the proof of which lies on them) disquiet or disturb any meeting of persons lawfully assembled for religious worship, or assault any forces lawfully officiating at such meeting, or any of the persons there assembled.
In the United States
In the United States disturbance of religious worship is treated as an offense under the common law, which is in many states supplemented by legislation (see Bishop, Amer. Crim. Law, 8th ed. 1892, vol. i. s. 542, vol. ii. ss. 303-305; California Penal Code, s. 302; Revised Laws of Massachusetts, 1902, chap. 212, s. 30.).
--
(Dissenting correction to the above)
Modern case
In 1998, Peter Tatchell of OutRage! was prosecuted for interrupting the Archbishop of Canterbury's Easter sermon with a short gay rights speech. The 1860 legislation (which transferred jurisdiction away from the ecclesiastic courts) was used to try him; his defense focused on the Human Rights Act 1998. He was convicted and fined £18.60 (referring to the 1860 legislation) plus court costs.
See also
Brawling Act 1551
Brawling Act 1553
References
Crimes in religion
Violence
Christianity and law in the 19th century | Brawling (legal definition) | [
"Biology"
] | 989 | [
"Behavior",
"Aggression",
"Human behavior",
"Violence"
] |
2,992,310 | https://en.wikipedia.org/wiki/Difference%20set | In combinatorics, a difference set is a subset of size of a group of order such that every non-identity element of can be expressed as a product of elements of in exactly ways. A difference set is said to be cyclic, abelian, non-abelian, etc., if the group has the corresponding property. A difference set with is sometimes called planar or simple. If is an abelian group written in additive notation, the defining condition is that every non-zero element of can be written as a difference of elements of in exactly ways. The term "difference set" arises in this way.
Basic facts
A simple counting argument shows that there are exactly pairs of elements from that will yield nonidentity elements, so every difference set must satisfy the equation
If is a difference set and then is also a difference set, and is called a translate of ( in additive notation).
The complement of a -difference set is a -difference set.
The set of all translates of a difference set forms a symmetric block design, called the development of and denoted by In such a design there are elements (usually called points) and blocks (subsets). Each block of the design consists of points, each point is contained in blocks. Any two blocks have exactly elements in common and any two points are simultaneously contained in exactly blocks. The group acts as an automorphism group of the design. It is sharply transitive on both points and blocks.
In particular, if , then the difference set gives rise to a projective plane. An example of a (7,3,1) difference set in the group is the subset . The translates of this difference set form the Fano plane.
Since every difference set gives a symmetric design, the parameter set must satisfy the Bruck–Ryser–Chowla theorem.
Not every symmetric design gives a difference set.
Equivalent and isomorphic difference sets
Two difference sets in group and in group are equivalent if there is a group isomorphism between and such that for some The two difference sets are isomorphic if the designs and are isomorphic as block designs.
Equivalent difference sets are isomorphic, but there exist examples of isomorphic difference sets which are not equivalent. In the cyclic difference set case, all known isomorphic difference sets are equivalent.
Multipliers
A multiplier of a difference set in group is a group automorphism of such that for some If is abelian and is the automorphism that maps , then is called a numerical or Hall multiplier.
It has been conjectured that if p is a prime dividing and not dividing v, then the group automorphism defined by fixes some translate of D (this is equivalent to being a multiplier). It is known to be true for when is an abelian group, and this is known as the First Multiplier Theorem. A more general known result, the Second Multiplier Theorem, says that if is a -difference set in an abelian group of exponent (the least common multiple of the orders of every element), let be an integer coprime to . If there exists a divisor of such that for every prime p dividing m, there exists an integer i with , then t is a numerical divisor.
For example, 2 is a multiplier of the (7,3,1)-difference set mentioned above.
It has been mentioned that a numerical multiplier of a difference set in an abelian group fixes a translate of , but it can also be shown that there is a translate of which is fixed by all numerical multipliers of
Parameters
The known difference sets or their complements have one of the following parameter sets:
-difference set for some prime power and some positive integer . These are known as the classical parameters and there are many constructions of difference sets having these parameters.
-difference set for some positive integer Difference sets with are called Paley-type difference sets.
-difference set for some positive integer A difference set with these parameters is a Hadamard difference set.
-difference set for some prime power and some positive integer Known as the McFarland parameters.
-difference set for some positive integer Known as the Spence parameters.
-difference set for some prime power and some positive integer Difference sets with these parameters are called Davis-Jedwab-Chen difference sets.
Known difference sets
In many constructions of difference sets, the groups that are used are related to the additive and multiplicative groups of finite fields. The notation used to denote these fields differs according to discipline. In this section, is the Galois field of order where is a prime or prime power. The group under addition is denoted by , while is the multiplicative group of non-zero elements.
Paley -difference set:
Let be a prime power. In the group , let be the set of all non-zero squares.
Singer -difference set:
Let . Then the set is a -difference set, where is the trace function
Twin prime power -difference set when and are both prime powers:
In the group , let
History
The systematic use of cyclic difference sets and methods for the construction of symmetric block designs dates back to R. C. Bose and a seminal paper of his in 1939. However, various examples appeared earlier than this, such as the "Paley Difference Sets" which date back to 1933. The generalization of the cyclic difference set concept to more general groups is due to R.H. Bruck in 1955. Multipliers were introduced by Marshall Hall Jr. in 1947.
Application
It is found by Xia, Zhou and Giannakis that difference sets can be used to construct a complex vector codebook that achieves the difficult Welch bound on maximum cross correlation amplitude. The so-constructed codebook also forms the so-called Grassmannian manifold.
Generalisations
A difference family is a set of subsets of a group such that the order of is , the size of is for all , and every non-identity element of can be expressed as a product of elements of for some (i.e. both come from the same ) in exactly ways.
A difference set is a difference family with The parameter equation above generalises to
The development of a difference family is a 2-design.
Every 2-design with a regular automorphism group is for some difference family
See also
Combinatorial design
Notes
References
Further reading
.
Combinatorics | Difference set | [
"Mathematics"
] | 1,296 | [
"Discrete mathematics",
"Combinatorics"
] |
2,992,378 | https://en.wikipedia.org/wiki/Jena%20Observatory | Astrophysikalisches Institut und Universitäts-Sternwarte Jena (AIU Jena, Astrophysical Institute and University Observatory Jena, or simply Jena Observatory) is an astronomical observatory owned and operated by Friedrich Schiller University of Jena. It has two main locations in Jena, Germany
and the neighbouring village of Großschwabhausen.
History
The first observatory was built in 1813, and replaced by a bigger one in 1889. It was funded by local regent Karl August von Sachsen-Weimar-Eisenach and planned by Johann Wolfgang Goethe. Its most famous director in the later decades was Ernst Abbe.
The new observatory in Großschwabhausen was built in 1962, in order to avoid the light pollution from the city of Jena. The old main observatory in the city centre is the home of "Volkssternwarte Urania", a society of hobbyist astronomers. They offer public access and courses for children and adults, and host events like watching comets or lunar eclipses.
WASP-3c & TTV
Transit Timing Variation (TTV), a variation on the transit method, was used to discover an exoplanet WASP-3c by Rozhen Observatory, Jena Observatory, and Toruń Centre for Astronomy.
See also
List of astronomical observatories
References
External links
Jena Observatory
Universitäts-Sternwarte Jena
Astronomical observatories in Germany
Buildings and structures in Jena
Glass engineering and science | Jena Observatory | [
"Materials_science",
"Engineering"
] | 303 | [
"Glass engineering and science",
"Materials science"
] |
2,992,440 | https://en.wikipedia.org/wiki/Antibody%20opsonization | Antibody opsonization is a process by which a pathogen is marked for phagocytosis through coating of a target cell with antibodies. Immunoglobulins participate in molecular tagging of pathogens which display antigens recognised by their specific paratope. The binding of antibodies enhances pathogen identification and recruitment of immune effector cells, ultimately accelerating microbial clearance through phagocytic destruction or antibody-dependent cellular cytotoxicity.
Principles
Antibody-mediated opsonisation (marking) of pathogens depends on high affinity paratope-epitope interactions. Immunoglobulins are highly effective opsonins, with the IgG subclasses IgG1 and IgG3 being recognised as the most efficacious opsonins in humans.
Antibodies structurally contain two important domains
Fab domain - the region of the antibody which displays the paratope capable of binding to antigenic epitopes
Fc fragment - the 'tail' region of the Y-shaped immunoglobulin which provides a binding site for endogenous Fc receptors (FcRs) displayed on immune cell surfaces
This Fc domain allows antibodies to engage with various effector leukocytes, enhancing the detection and elimination of encountered pathogens. The interaction with leukocytes is largely driven by the predominant antibody isotype as well as the presence and concentration of immune cells recruited to the local environment. The resulting immune cell recruitment may result in phagocytosis if monocytes, macrophages, or neutrophils are the primary cells recruited, release of granzymes and other killing factors if NK cells or neutrophils are recruited, and release of pro-inflammatory cytokines in nearly all cases.
Recruitment and Clearance
Antibody-stimulated Phagocytosis
Mononuclear phagocytes and neutrophils express FcRs that bind strongly to the Fc regions of particular antibody isotypes.
During a normal inflammatory response, microbial pathogen-associated molecular patterns (PAMPs) bind with phagocytic pattern recognition receptors (PRRs), triggering sequential intracellular signalling cascades culminating in phagocytotic clearance. Co-expression of opsonin receptors such as FcRs enhances their ability to detect microbes which have been tagged by as pathogenic.
These interactions result in envelopment of the particle by the cytoplasmic membrane of the phagocytic cell, until the particle is contained in a membrane-bound vacuole (phagosome) within the cell. The pathogen is subsequently destroyed following intracellular vesicle fusion with lytic vessels.
Antibody-dependent Cell-mediated Cytotoxicity
In antibody-dependent cell-mediated cytotoxicity, the pathogen does not need to be internalised to be destroyed. ADCC requires an effector cell with the ability to eliminate pathogens through release of cytotoxic agents, most notably natural killer cells. However, macrophages, neutrophils and eosinophils are sometimes implicated.
During this process, the pathogen is opsonized and bound with the antibody IgG via its Fab domain. Cells with cyotoxic function (e.g. NK cells) expresses Fcγ receptors which recognize and bind to the reciprocal Fc portion of an antibody. This receptor conjugation triggers degranulation and release of cytotoxic granules containing perforin and granzymes to kill antibody-sensitized target cells.
References
Immune system | Antibody opsonization | [
"Biology"
] | 718 | [
"Immune system",
"Organ systems"
] |
2,992,856 | https://en.wikipedia.org/wiki/Rhodamine%20B | Rhodamine B is a chemical compound and a dye. It is often used as a tracer dye within water to determine the rate and direction of flow and transport. Rhodamine dyes fluoresce and can thus be detected easily and inexpensively with fluorometers.
Rhodamine B is used in biology as a staining fluorescent dye, sometimes in combination with auramine O, as the auramine-rhodamine stain to demonstrate acid-fast organisms, notably Mycobacterium. Rhodamine dyes are also used extensively in biotechnology applications such as fluorescence microscopy, flow cytometry, fluorescence correlation spectroscopy and ELISA.
Other uses
Rhodamine B is often mixed with herbicides to show where they have been used.
It is also being tested for use as a biomarker in oral rabies vaccines for wildlife, such as raccoons, to identify animals that have eaten a vaccine bait. The rhodamine is incorporated into the animal's whiskers and teeth. Rhodamine B is an important hydrophilic xanthene dye well known for its stability and is widely used in the textile industry, leather, paper printing, paint, coloured glass and plastic industries.
Rhodamine B (BV10) is mixed with quinacridone magenta (PR122) to make the bright pink watercolor known as Opera Rose.
Properties
Rhodamine B can exist in equilibrium between two forms: an "open"/fluorescent form and a "closed"/nonfluorescent spirolactone form. The "open" form dominates in acidic condition while the "closed" form is colorless in basic condition.
The fluorescence intensity of rhodamine B will decrease as temperature increases.
The solubility of rhodamine B in water varies by manufacturer, and has been reported as 8 g/L and ~15 g/L, while solubility in alcohol (presumably ethanol) has been reported as 15 g/L. Chlorinated tap water decomposes rhodamine B. Rhodamine B solutions adsorb to plastics and should be kept in glass.
Rhodamine B is tunable around 610 nm when used as a laser dye. Its luminescence quantum yield is 0.65 in basic ethanol, 0.49 in ethanol, 1.0, and 0.68 in 94% ethanol. The fluorescence yield is temperature dependent; the compound is fluxional in that its excitability is in thermal equilibrium at room temperature.
Safety and health
In California, rhodamine B is suspected to be carcinogenic and thus products containing it must contain a warning on its label. Cases of economically motivated adulteration, where it has been illegally used to impart a red color to chili powder, have come to the attention of food safety regulators.
See also
Dye laser
Laser dyes
Rhodamine
Rhodamine 6G
References
Notes
Microscopy
Microbiology techniques
Laboratory techniques
Histopathology
Histotechnology
Staining dyes
Staining
Laser gain media
Benzoic acids
Aromatic amines
Chlorides
Quaternary ammonium compounds
Triarylmethane dyes
Xanthenes
Diethylamino compounds
Fluorescent dyes | Rhodamine B | [
"Chemistry",
"Biology"
] | 673 | [
"Chlorides",
"Inorganic compounds",
"Staining",
"Salts",
"Microbiology techniques",
"nan",
"Microscopy",
"Cell imaging",
"Histopathology"
] |
2,992,945 | https://en.wikipedia.org/wiki/Auroral%20kilometric%20radiation | Auroral kilometric radiation (AKR) is the intense radio radiation emitted in the acceleration zone (at a height of three times the radius of the Earth) of the polar lights. The radiation mainly comes from cyclotron radiation from electrons orbiting around the magnetic field lines of the Earth. The radiation has a frequency of between 50 and 500 kHz and a total power of between about 1 million and 10 million watts. The radiation is absorbed by the ionosphere and therefore can only be measured by satellites positioned at vast heights, such as the Fast Auroral Snapshot Explorer (FAST). According to the data of the Cluster mission, it is beamed out in the cosmos in a narrow plane tangent to the magnetic field at the source. The sound produced by playing AKR over an audio device has been described as "whistles", "chirps", and even "screams".
As some other planets emit cyclotron radiation too, AKR could be used to learn more about Jupiter, Saturn, Uranus and Neptune, and to detect extrasolar planets.
References
Radio astronomy
Planetary science | Auroral kilometric radiation | [
"Astronomy"
] | 226 | [
"Astronomical sub-disciplines",
"Astronomy stubs",
"Radio astronomy",
"Planetary science",
"Planetary science stubs"
] |
2,992,989 | https://en.wikipedia.org/wiki/Petroleum%20seep | A petroleum seep is a place where natural liquid or gaseous hydrocarbons escape to the Earth's atmosphere and surface, normally under low pressure or flow. Seeps generally occur above either natural terrestrial or underwater petroleum accumulation structures (e.g., sandstones, siltstones, limestones, dolomites). The hydrocarbons may escape along geological layers, or across them through fractures and fissures in the rock, or directly from an outcrop of oil-bearing rock.
Petroleum seeps are quite common in many areas of the world, and have been exploited by mankind since paleolithic times. A comprehensive compendium of seeps around the world was published in 2022. Natural products associated with seeps include bitumen, pitch, asphalt and tar. In locations where seeps of natural gas are sufficiently large, natural "eternal flames" often persist. The occurrence of surface petroleum was often included in location names that developed; these locations are also associated with early oil and gas exploitation as well as scientific and technological developments, which have grown into the petroleum industry.
History of petroleum seep exploitation
Prehistory
The exploitation of bituminous rocks and natural seep deposits dates back to paleolithic times. The earliest known use of bitumen (natural asphalt) was by Neanderthals some 70,000 years ago, with bitumen adhered to ancient tools found at Neanderthal sites in Syria.
Ancient civilizations
After the arrival of Homo sapiens, humans used bitumen for construction of buildings and waterproofing of reed boats, among other uses. The use of bitumen for waterproofing and as an adhesive dates at least to the fifth millennium BCE in the early Indus community of Mehrgarh where it was used to line the baskets in which they gathered crops. The material was also used as early as the third millennium BCE in statuary, mortaring brick walls, waterproofing baths and drains, in stair treads, and for shipbuilding. According to Herodotus, and confirmed by Diodorus Siculus, more than four thousand years ago natural asphalt was employed in the construction of the walls and towers of Babylon; there were oil pits near Ardericca (near Babylon), as well as a pitch spring on Zacynthus (Ionian islands, Greece). Great quantities of it were found on the banks of the river Issus, one of the tributaries of the Euphrates.
In ancient times, bitumen was primarily a Mesopotamian commodity used by the Sumerians and Babylonians, although it was also found in the Levant and Persia. Along the Tigris and Euphrates rivers, the area was littered with hundreds of pure bitumen seepages. The Mesopotamians used the bitumen for waterproofing boats and buildings. Ancient Persian tablets indicate the medicinal and lighting uses of petroleum in the upper levels of their society. In ancient Egypt, the use of bitumen was important in creating Egyptian mummies—in fact, the word mummy is derived from the Arab word mūmiyyah, which means bitumen. Oil from seeps was exploited in the Roman province of Dacia, now in Romania, where it was called picula.
In East Asia these locations were known in China, where the earliest known drilled oil wells date to 347 CE or earlier. The ancient records of China and Japan are said to contain many allusions to the use of natural gas for lighting and heating. Petroleum was known as burning water in Japan in the 7th century. In his book Dream Pool Essays written in 1088, the polymathic scientist and statesman Shen Kuo of the Song dynasty coined the word 石油 (Shíyóu, literally "rock oil") for petroleum, which remains the term used in contemporary Chinese.
In southwest Asia the first streets of 8th century Baghdad were paved with tar, derived from natural seep fields in the region. In the 9th century, oil fields were exploited in the area around modern Baku, Azerbaijan. These fields were described by the Arab geographer Abu al-Hasan 'Alī al-Mas'ūdī in the 10th century, and by Marco Polo in the 13th century, who described the output of those wells as hundreds of shiploads. Distillation of petroleum was described by the Persian alchemist, Muhammad ibn Zakarīya Rāzi (Rhazes). There was production of chemicals such as kerosene in the alembic (al-ambiq), which was mainly used for kerosene lamps. Arab and Persian chemists also distilled crude oil in order to produce flammable products for military purposes. Through Islamic Spain, distillation became available in Western Europe by the 12th century. It has also been present in Romania since the 13th century, being recorded as păcură.
Eighteenth century Europe
In Europe, petroleum seeps were extensively mined near the Alsace city of Pechelbronn, where the vapor separation process was in use in 1742. In Switzerland c. 1710, the Russian-born Swiss physician and Greek teacher Eyrini d'Eyrinis discovered asphaltum at Val-de-Travers, (Neuchâtel). He established a bitumen mine de la Presta there in 1719 that operated until 1986. Oil sands here were mined from 1745 under the direction of Louis Pierre Ancillon de la Sablonnière, by special appointment of Louis XV. The Pechelbronn oil field was active until 1970, and was the birthplace of companies like Antar and Schlumberger. In 1745 under the Empress Elisabeth of Russia the first oil well and refinery were built in Ukhta by Fiodor Priadunov. Through the process of distillation of the "rock oil" (petroleum) he received a kerosene-like substance, which was used in oil lamps by Russian churches and monasteries (though households still relied on candles).
Colonial Americas
The earliest mention of petroleum seeps in the Americas occurs in Sir Walter Raleigh's account of the Pitch Lake on Trinidad in 1595. Thirty-seven years later, the account of a visit of a Franciscan, Joseph de la Roche d'Allion, to the oil springs of New York was published in Sagard's Histoire du Canada. In North America, the early European fur traders found Canadian First Nations using bitumen from the vast Athabasca oil sands to waterproof their birch bark canoes. A Swedish scientist, Peter Kalm, in his 1753 work Travels into North America, showed on a map the oil springs of Pennsylvania.
In 1769 the Portolà expedition, a group of Spanish explorers led by Gaspar de Portolà, made the first written record of the tar pits in California. Father Juan Crespí wrote, "While crossing the basin the scouts reported having seen some geysers of tar issuing from the ground like springs; it boils up molten, and the water runs to one side and the tar to the other. The scouts reported that they had come across many of these springs and had seen large swamps of them, enough, they said, to caulk many vessels. We were not so lucky ourselves as to see these tar geysers, much though we wished it; as it was some distance out of the way we were to take, the Governor [Portola] did not want us to go past them. We christened them Los Volcanes de Brea [the Tar Volcanoes]."
Modern extraction and industry
During the nineteenth and the beginning of the twentieth century, oil seepages in Europe were exploited everywhere with the digging, and later drilling, of wells near to their occurrences and the discovery of numerous small oil fields such as in Italy.
The modern history of petroleum exploitation, in relation to extraction from seeps, began in the 19th century with the refining of kerosene from crude oil as early as 1823, and the process of refining kerosene from coal by Nova Scotian Abraham Pineo Gesner in 1846. It was only after Ignacy Łukasiewicz had improved Gesner's method to develop a means of refining kerosene from the more readily available "rock oil" ("petr-oleum") seeps in 1852 that the first rock oil mine was built near Krosno in central European Galicia (Poland/Ukraine) in 1853. In 1854, Benjamin Silliman, a science professor at Yale University, was the first American to fractionate petroleum by distillation. These discoveries rapidly spread around the world.
The world's first commercial oil well was drilled in Poland in 1853, and the second in nearby Romania in 1857. At around the same time the world's first, but small, oil refineries were opened at Jasło in Poland, with a larger one being opened at Ploiești in Romania shortly after. Romania is the first country in the world to have its crude oil output officially recorded in international statistics, namely 275 tonnes. By the end of the 19th century the Russian Empire, particularly in Azerbaijan, had taken the lead in production.
The first oil "well" in North America was in Oil Springs, Ontario, Canada in 1858, dug by James Miller Williams. The US petroleum industry began with Edwin Drake's drilling of a oil well in 1859 on Oil Creek near Titusville, Pennsylvania, both named for their petroleum seeps.
Other sources of oil initially associated with petroleum seeps were discovered in Peru's Zorritos District in 1863, in the Dutch East Indies on Sumatra in 1885, in Persia at Masjed Soleiman in 1908, as well as in Venezuela, Mexico, and the province of Alberta, Canada.
By 1910, these too were being developed at an industrial level. Initially these petroleum sources and products were for use in fueling lamps, but with the development of the internal combustion engine, their supply could not meet the increased demand; many of these early traditional sources and "local finds" were soon outpaced by technology and demand.
Petroleum seep formation
A petroleum seep occurs as a result of the seal above the reservoir being breached, causing tertiary migration of hydrocarbons towards the surface under the influence of the associated buoyancy force. The seal is breached due to the effects of overpressure adding to the buoyancy force, overcoming the capillary resistance that initially kept the hydrocarbons sealed.
Causes of overpressure
The most common cause of overpressure is the rapid loading of fine-grained sediments preventing water from escaping fast enough to equalise the pressure of the overburden. If burial stops or slows, then excess pressure can equalize at a rate that is dependent on the permeability of the overlying and adjacent rocks. A secondary cause of overpressure is fluid expansion, due to changes in the volume of solid and/or fluid phases. Some examples include: aquathermal pressuring (thermal expansion), clay dehydration reactions (such as anhydrite) and mineral transformation (such as kerogen to oil/gas and excess kerogen).
Types of seeps
There are two types of seep that can occur, depending on the degree of overpressure. Capillary failure can occur in moderate overpressure conditions, resulting in widespread but low intensity seepage until the overpressure equalizes and resealing occurs. In some cases, the moderate overpressure cannot be equalized because the pores in the rock are small so the displacement pressure, the pressure required to break the seal, is very high. If the overpressure continues to increase to the point that it overcomes the rock's minimum stress and its tensile strength before overcoming the displacement pressure, then the rock will fracture, causing local and high intensity seepage until the pressure equalizes and the fractures close.
California seeps
California has several hundred naturally occurring seeps, found in 28 counties across the state. Much of the petroleum discovered in California during the 19th century was from observations of seeps. The world's largest natural oil seepage is Coal Oil Point in the Santa Barbara Channel, California. Three of the better known tar seep locations in California are McKittrick Tar Pits, Carpinteria Tar Pits and the La Brea Tar Pits.
At Kern River Oil Field, there are no currently active seeps. However, oil-stained formations in the outcrops remain from previously active seeps.
Seeps known as the McKittrick Tar Pits occur in the McKittrick Oil Field in western Kern County. Some of the seeps occur in watersheds that drain toward the San Joaquin Valley floor. These seeps were originally mined for asphalt by Native Americans, and in the 1870s larger scale mining was undertaken by means of both open pits and shafts. In 1893, Southern Pacific Railroad constructed a line to Asphalto, two miles from present day McKittrick. Fuel oil for the railroad was highly desired, especially since there are very few coal-bearing formations in California. The field is produced now by conventional oil wells, as well as by steam fracturing.
The oil seeps at McKittrick are located in diatomite formation that has been thrust faulted over the younger sandstone formations. Similarly, in the Upper Ojai Valley in Ventura County, tar seeps are aligned with east–west faulting. In the same area, Sulphur Mountain is named for the hydrogen sulfide-laden springs. The oil fields in the Sulphur Mountain area date from the 1870s. Production was from tunnels dug into the face of a cliff, and produced by gravity drainage.
The petroleum fly (Helaeomyia petrolei) is a species of fly that was first described from the La Brea Tar Pits and is found at other California seeps as well. It is highly unusual among insects for its tolerance of crude oil; larvae of this fly live within petroleum seeps where they feed on insects and other arthropods that die after becoming trapped in the oil.
Offshore seeps
In the Gulf of Mexico, there are more than 600 natural oil seeps that leak between one and five million barrels of oil per year, equivalent to roughly 80,000 to 200,000 tonnes. When a petroleum seep forms underwater it may form a peculiar type of volcano known as an asphalt volcano.
The California Division of Oil, Gas and Geothermal Resources published a map of offshore oil seeps from Point Aguello (north of Santa Barbara) to Mexico. In addition, they published a brochure describing the seeps. The brochure also discusses the underground blowout at Platform A which caused the 1969 Santa Barbara oil spill. It also describes accounts from divers, who describe seepage changes after the 1971 San Fernando earthquake.
In Utah, there are natural oil seeps at Rozel Point on the Great Salt Lake. The oil seeps at Rozel Point can be seen when the lake level drops below an elevation of approximately ; if the lake level is higher, the seeps are underwater. The seeps can be found by going to the Golden Spike historical site, and from there, following signs for the Spiral Jetty. Both fresh tar seeps and re-worked tar (tar caught by the waves and thrown up on the rocks) are visible at the site.
The petroleum seeping at Rozel Point is high in sulfur, but has no hydrogen sulfide. This may be related to deposition in a hypersaline lacustrine environment.
See also
Asphalt volcano
Cold seep
Mud volcano
Tar pit
References
External links
Oil Seeps Articles
Asphalt lakes
Petroleum geology
Economic geology | Petroleum seep | [
"Chemistry"
] | 3,169 | [
"Petroleum",
"Asphalt",
"Petroleum geology",
"Asphalt lakes"
] |
2,993,016 | https://en.wikipedia.org/wiki/Lexxe | Lexxe is an internet search engine that applies Natural Language Processing
in its semantic search technology. Founded in 2005 by Dr. Hong Liang Qiao,
Lexxe is based in Sydney, Australia. Today, Lexxe's key focus is on sentiment search with the launch of a news sentiment search site at News & Moods (www.newsandmoods.com).
Lexxe has experienced several stages of change of focus in search technology:
Lexxe launched its Alpha version in 2005, featuring Natural Language question
answering (i.e. users could ask questions in English to the search engine apart from keyword searches — this feature has been suspended for redevelopment since 2010). It used only algorithms to extract answers from web pages, with no question-answer pair databases prepared in advance.
In 2011, Lexxe launched a beta version with a new search technology called Semantic Key. Semantic Keys enable users to query with a conceptual keyword
(or a keyword with a special meaning, hence the term Semantic Key) in order
to find instances under the concept, e.g. price → $5.95 or €200, color →
red, yellow, white. For example, “price: a pound of apples”, “color:
ferrari”. With initial 500 Semantic Keys at the Beta launch, Lexxe
became the first search engine in the world to offer this unique and useful
search technology to the users. The cost of building Semantic Keys was too heavy though.
In 2017, Lexxe launched News & Moods (www.newsandmoods.com), an open platform for news sentiment search, a first step towards sentiment search feature for the entire Internet search in Lexxe search engine. News & Moods also comes with smartphone apps in Android and iOS.
References
External links
Lexxe main web site
News & Moods web site
Internet search engines
Natural language processing | Lexxe | [
"Technology"
] | 383 | [
"Natural language processing",
"Natural language and computing"
] |
2,993,391 | https://en.wikipedia.org/wiki/Globar | A Globar is used as a thermal light source for infrared spectroscopy. The preferred material for making Globar is silicon carbide that is shaped as rods or arches of various sizes. When inserted into a circuit that provides it with electric current, it emits radiation from ~ 2 to 50 micrometres wavelength via the Joule heating phenomenon. Globars are used as infrared sources for spectroscopy because their spectral behavior corresponds approximately to that of a Planck radiator (i.e. a black body). Alternative infrared sources are Nernst lamps, coils of chrome–nickel alloy or high-pressure mercury lamps.
The technical term Globar is an English portmanteau word consisting of glow and bar. The term glowbar is sometimes used synonymously in English (which is an incorrect spelling in the strict sense).
The American Resistor Company in Milwaukee, Wisconsin, had word and lettering Globar registered as a trademark (in a special decorative script font) with the United States Patent and Trademark Office on June 30, 1925 (registration number 0200201) and on October 18, 1927 (registration number 0234147). This registration had been renewed for the third time in 1987 (by various companies throughout 60 years).
See also
Nernst lamp
List of light sources
References
External links
Viewgraphs about infrared beamlines and IR spectroscopy Advanced Light Source, Berkeley, CA, USA
Introduction to the optical principles of IR spectroscopy, light sources Ralf Arnold (in German)
Lighting
Spectroscopy | Globar | [
"Physics",
"Chemistry"
] | 310 | [
"Instrumental analysis",
"Molecular physics",
"Spectroscopy",
"Spectrum (physical sciences)"
] |
2,993,422 | https://en.wikipedia.org/wiki/Immunostimulant | Immunostimulants, also known as immunostimulators, are substances (drugs and nutrients) that stimulate the immune system usually in a non-specific manner by inducing activation or increasing activity of any of its components. One notable example is the granulocyte macrophage colony-stimulating factor. The goal of this stimulated immune response is usually to help the body have a stronger immune system response in order to improve outcomes in the case of an infection or cancer malignancy. There is also some evidence that immunostimulants may be useful to help decrease severe acute illness related to chronic obstructive pulmonary disease or acute infections in the lungs.
Classification
There are two main categories of immunostimulants:
Specific immunostimulants provide antigenic specificity in immune response, such as vaccines or any antigen.
Non-specific immunostimulants act irrespective of antigenic specificity to augment immune response of other antigen or stimulate components of the immune system without antigenic specificity, such as adjuvants and non-specific immunostimulators.
Non-specific
Many endogenous substances are non-specific immunostimulators. For example, female sex hormones are known to stimulate both adaptive and innate immune responses. Some autoimmune diseases such as lupus erythematosus strike women preferentially, and their onset often coincides with puberty. Other hormones appear to regulate the immune system as well, most notably prolactin, growth hormone and vitamin D.
Some publications point towards the effect of deoxycholic acid (DCA) as an immunostimulant of the non-specific immune system, activating its main actors, the macrophages. According to these publications, a sufficient amount of DCA in the human body corresponds to a good immune reaction of the non-specific immune system.
Claims made by marketers of various products and alternative health providers, such as chiropractors, homeopaths, and acupuncturists to be able to stimulate or "boost" the immune system generally lack meaningful explanation and evidence of effectiveness.
Uses
Immunostimulants have been recommended to help prevent acute illness related to chronic obstructive pulmonary disease and they are sometimes used to treat chronic bronchitis. The evidence in the form of high quality clinical trials to support their use is weak, however, there is some evidence of benefit and they appear to be safe. The most commonly used immunostimulant type for this purpose are bacterial-derived immunostimulants. The goal is to stimulate the person's immune system in order to prevent future infections that may result in an acute episode or exacerbation of COPD.
See also
General
Antigen
Co-stimulation
Immunogenicity
Immunologic adjuvant
Immunomodulator
Immunotherapy
Endogenous immunostimulants
Deoxycholic acid, a stimulator of macrophages
Synthetic immunostimulants
Imiquimod and resiquimod, activate immune cells through the toll-like receptor 7
References
External links
Veterinary Immunology and Immunopathology journal
Deoxycholic acid as immunostimulant
Immunology
Immune system | Immunostimulant | [
"Biology"
] | 687 | [
"Organ systems",
"Immunology",
"Immune system"
] |
2,993,470 | https://en.wikipedia.org/wiki/Thyrse | A thyrse is a type of inflorescence in which the main axis grows indeterminately, and the subaxes (branches) have determinate growth.
Gallery
References
Plant morphology | Thyrse | [
"Biology"
] | 40 | [
"Plant morphology",
"Plants"
] |
2,993,504 | https://en.wikipedia.org/wiki/Kloosterman%20sum | In mathematics, a Kloosterman sum is a particular kind of exponential sum. They are named for the Dutch mathematician Hendrik Kloosterman, who introduced them in 1926 when he adapted the Hardy–Littlewood circle method to tackle a problem involving positive definite diagonal quadratic forms in four variables, strengthening his 1924 dissertation research on five or more variables.
Let be natural numbers. Then
Here x* is the inverse of modulo .
Context
The Kloosterman sums are a finite ring analogue of Bessel functions. They occur (for example) in the Fourier expansion of modular forms.
There are applications to mean values involving the Riemann zeta function, primes in short intervals, primes in arithmetic progressions, the spectral theory of automorphic functions and related topics.
Properties of the Kloosterman sums
If or then the Kloosterman sum reduces to the Ramanujan sum.
depends only on the residue class of and modulo . Furthermore and if .
Let with and coprime. Choose and such that and . Then
This reduces the evaluation of Kloosterman sums to the case where for a prime number and an integer .
The value of is always an algebraic real number. In fact is an element of the subfield which is the compositum of the fields
where ranges over all odd primes such that and
for with .
The Selberg identity:
was stated by Atle Selberg and first proved by Kuznetsov using the spectral theory of modular forms. Nowadays elementary proofs of this identity are known.
For an odd prime, there are no known simple formula for , and the Sato–Tate conjecture suggests that none exist. The lifting formulas below, however, are often as good as an explicit evaluation. If one also has the important transformation:
where denotes the Jacobi symbol.
Let with prime and assume . Then:
where is chosen so that and is defined as follows (note that is odd):
This formula was first found by Hans Salie and there are many simple proofs in the literature.
Estimates
Because Kloosterman sums occur in the Fourier expansion of modular forms, estimates for Kloosterman sums yield estimates for Fourier coefficients of modular forms as well. The most famous estimate is due to André Weil and states:
Here is the number of positive divisors of . Because of the multiplicative properties of Kloosterman sums these estimates may be reduced to the case where is a prime number . A fundamental technique of Weil reduces the estimate
when ab ≠ 0 to his results on local zeta-functions. Geometrically the sum is taken along a 'hyperbola' XY = ab and we consider this as defining an algebraic curve over the finite field with elements. This curve has a ramified Artin–Schreier covering , and Weil showed that the local zeta-function of has a factorization; this is the Artin L-function theory for the case of global fields that are function fields, for which Weil gives a 1938 paper of J. Weissinger as reference (the next year he gave a 1935 paper of Hasse as earlier reference for the idea; given Weil's rather denigratory remark on the abilities of analytic number theorists to work out this example themselves, in his Collected Papers, these ideas were presumably 'folklore' of quite long standing). The non-polar factors are of type , where is a Kloosterman sum. The estimate then follows from Weil's basic work of 1940.
This technique in fact shows much more generally that complete exponential sums 'along' algebraic varieties have good estimates, depending on the Weil conjectures in dimension > 1. It has been pushed much further by Pierre Deligne, Gérard Laumon, and Nicholas Katz.
Short Kloosterman sums
Short Kloosterman sums are defined as trigonometric sums of the form
where runs through a set of numbers, coprime to , the number of elements in which is essentially smaller than , and the symbol denotes the congruence class, inverse to modulo :
Up to the early 1990s, estimates for sums of this type were known mainly in the case where the number of summands was greater than . Such estimates were due to H. D. Kloosterman, I. M. Vinogradov, H. Salie,
L. Carlitz, S. Uchiyama and A. Weil. The only exceptions were the special modules of the form , where is a fixed prime and the exponent increases to infinity (this case was studied by A.G. Postnikov by means of the method of Ivan Matveyevich Vinogradov).
In the 1990s Anatolii Alexeevitch Karatsuba developed a new method of estimating short Kloosterman sums. Karatsuba's method makes it possible to estimate Kloosterman's sums, the number of summands in which does not exceed , and in some cases even , where is an arbitrarily small fixed number. The last paper of A.A. Karatsuba on this subject was published after his death.
Various aspects of the method of Karatsuba found applications in solving the following problems of analytic number theory:
finding asymptotics of the sums of fractional parts of the form:
where runs, one after another, through the integers satisfying the condition , and runs through the primes that do not divide the module (A.A.Karatsuba);
finding the lower bound for the number of solutions of the inequalities of the form:
in the integers , coprime to , (A.A. Karatsuba);
the precision of approximation of an arbitrary real number in the segment by fractional parts of the form:
where (A.A. Karatsuba);
a more precise constant in the Brun–Titchmarsh theorem :
where is the number of primes , not exceeding and belonging to the arithmetic progression (J. Friedlander, H. Iwaniec);
a lower bound for the greatest prime divisor of the product of numbers of the form: .(D. R. Heath-Brown);
proving that there are infinitely many primes of the form: .(J. Friedlander, H. Iwaniec);
combinatorial properties of the set of numbers (A.A.Glibichuk):
Lifting of Kloosterman sums
Although the Kloosterman sums may not be calculated in general they may be "lifted" to algebraic number fields, which often yields more convenient formulas. Let be a squarefree integer with Assume that for any prime factor of we have
Then for all integers a, b coprime to we have
Here is the number of prime factors of counting multiplicity. The sum on the right can be reinterpreted as a sum over algebraic integers in the field This formula is due to Yangbo Ye, inspired by Don Zagier and extending the work of Hervé Jacquet and Ye on the relative trace formula for . Indeed, much more general exponential sums can be lifted.
Kuznetsov trace formula
The Kuznetsov or relative trace formula connects Kloosterman sums at a deep level with the spectral theory of automorphic forms. Originally this could have been stated as follows. Let be a sufficiently "well behaved" function. Then one calls identities of the following type Kuznetsov trace formula:
The integral transform part is some integral transform of g and the spectral part is a sum of Fourier coefficients, taken over spaces of holomorphic and non-holomorphic modular forms twisted with some integral transform of g. The Kuznetsov trace formula was found by Kuznetsov while studying the growth of weight zero automorphic functions. Using estimates on Kloosterman sums he was able to derive estimates for Fourier coefficients of modular forms in cases where Pierre Deligne's proof of the Weil conjectures was not applicable.
It was later translated by Jacquet to a representation theoretic framework. Let be a reductive group over a number field F and be a subgroup. While the usual trace formula studies the harmonic analysis on G, the relative trace formula is a tool for studying the harmonic analysis on the symmetric space . For an overview and numerous applications see the references.
History
Weil's estimate can now be studied in W. M. Schmidt, Equations over finite fields: an elementary approach, 2nd ed. (Kendrick Press, 2004). The underlying ideas here are due to S. Stepanov and draw inspiration from Axel Thue's work in Diophantine approximation.
There are many connections between Kloosterman sums and modular forms. In fact the sums first appeared (minus the name) in a 1912 paper of Henri Poincaré on modular forms. Hans Salié introduced a form of Kloosterman sum that is twisted by a Dirichlet character: Such Salié sums have an elementary evaluation.
After the discovery of important formulae connecting Kloosterman sums with non-holomorphic modular forms by Kuznetsov in 1979, which contained some 'savings on average' over the square root estimate, there were further developments by Iwaniec and Deshouillers in a seminal paper in Inventiones Mathematicae (1982). Subsequent applications to analytic number theory were worked out by a number of authors, particularly Bombieri, Fouvry, Friedlander and Iwaniec.
The field remains somewhat inaccessible. A detailed introduction to the spectral theory needed to understand the Kuznetsov formulae is given in R. C. Baker, Kloosterman Sums and Maass Forms, vol. I (Kendrick press, 2003). Also relevant for students and researchers interested in the field is .
Yitang Zhang used Kloosterman sums in his proof of bounded gaps between primes.
See also
Hasse's bound
Notes
References
External links
Analytic number theory | Kloosterman sum | [
"Mathematics"
] | 2,037 | [
"Analytic number theory",
"Number theory"
] |
2,993,692 | https://en.wikipedia.org/wiki/Kuiper%27s%20theorem | In mathematics, Kuiper's theorem (after Nicolaas Kuiper) is a result on the topology of operators on an infinite-dimensional, complex Hilbert space H. It states that the space GL(H) of invertible bounded endomorphisms of H is such that all maps from any finite complex Y to GL(H) are homotopic to a constant, for the norm topology on operators.
A significant corollary, also referred to as Kuiper's theorem, is that this group is weakly contractible, ie. all its homotopy groups are trivial. This result has important uses in topological K-theory.
General topology of the general linear group
For finite dimensional H, this group would be a complex general linear group and not at all contractible. In fact it is homotopy equivalent to its maximal compact subgroup, the unitary group U of H. The proof that the complex general linear group and unitary group have the same homotopy type is by the Gram-Schmidt process, or through the matrix polar decomposition, and carries over to the infinite-dimensional case of separable Hilbert space, basically because the space of upper triangular matrices is contractible as can be seen quite explicitly. The underlying phenomenon is that passing to infinitely many dimensions causes much of the topological complexity of the unitary groups to vanish; but see the section on Bott's unitary group, where the passage to infinity is more constrained, and the resulting group has non-trivial homotopy groups.
Historical context and topology of spheres
It is a surprising fact that the unit sphere, sometimes denoted S∞, in infinite-dimensional Hilbert space H is a contractible space, while no finite-dimensional spheres are contractible. This result, certainly known decades before Kuiper's, may have the status of mathematical folklore, but it is quite often cited. In fact more is true: S∞ is diffeomorphic to H, which is certainly contractible by its convexity. One consequence is that there are smooth counterexamples to an extension of the Brouwer fixed-point theorem to the unit ball in H. The existence of such counter-examples that are homeomorphisms was shown in 1943 by Shizuo Kakutani, who may have first written down a proof of the contractibility of the unit sphere. But the result was anyway essentially known (in 1935 Andrey Nikolayevich Tychonoff showed that the unit sphere was a retract of the unit ball).
The result on the group of bounded operators was proved by the Dutch mathematician Nicolaas Kuiper, for the case of a separable Hilbert space; the restriction of separability was later lifted. The same result, but for the strong operator topology rather than the norm topology, was published in 1963 by Jacques Dixmier and Adrien Douady. The geometric relationship of the sphere and group of operators is that the unit sphere is a homogeneous space for the unitary group U. The stabiliser of a single vector v of the unit sphere is the unitary group of the orthogonal complement of v; therefore the homotopy long exact sequence predicts that all the homotopy groups of the unit sphere will be trivial. This shows the close topological relationship, but is not in itself quite enough, since the inclusion of a point will be a weak homotopy equivalence only, and that implies contractibility directly only for a CW complex. In a paper published two years after Kuiper's,
Bott's unitary group
There is another infinite-dimensional unitary group, of major significance in homotopy theory, that to which the Bott periodicity theorem applies. It is certainly not contractible. The difference from Kuiper's group can be explained: Bott's group is the subgroup in which a given operator acts non-trivially only on a subspace spanned by the first N of a fixed orthonormal basis {ei}, for some N, being the identity on the remaining basis vectors.
Applications
An immediate consequence, given the general theory of fibre bundles, is that every Hilbert bundle is a trivial bundle.
The result on the contractibility of S∞ gives a geometric construction of classifying spaces for certain groups that act freely on it, such as the cyclic group with two elements and the circle group. The unitary group U in Bott's sense has a classifying space BU for complex vector bundles (see Classifying space for U(n)). A deeper application coming from Kuiper's theorem is the proof of the Atiyah–Jänich theorem (after Klaus Jänich and Michael Atiyah), stating that the space of Fredholm operators on H, with the norm topology, represents the functor K(.) of topological (complex) K-theory, in the sense of homotopy theory. This is given by Atiyah.
Case of Banach spaces
The same question may be posed about invertible operators on any Banach space of infinite dimension. Here there are only partial results. Some classical sequence spaces have the same property, namely that the group of invertible operators is contractible. On the other hand, there are examples known where it fails to be a connected space. Where all homotopy groups are known to be trivial, the contractibility in some cases may remain unknown.
References
K-theory
Operator theory
Hilbert spaces
Theorems in topology
Topology of Lie groups | Kuiper's theorem | [
"Physics",
"Mathematics"
] | 1,115 | [
"Quantum mechanics",
"Theorems in topology",
"Topology",
"Mathematical problems",
"Hilbert spaces",
"Mathematical theorems"
] |
2,993,703 | https://en.wikipedia.org/wiki/Data%20position%20measurement | Data position measurement (DPM) is a CD and DVD copy protection mechanism that operates by measuring the physical location of data on an optical disc. Stamped CDs are perfect clones and always have the data at the expected location, while a burned copy would exhibit physical differences. DPM detects these differences to identify user-made copies. DPM was first used publicly in 1996 by Link Data Security's CD-Cops. It was used in volume on Lademans Leksikon published by Egmont in November 1996.
RMPS
DPM can be observed and subsequently encoded into a recordable media physical signature (RMPS). In concert with emulation software RMPS can reproduce the effects of DPM thereby appearing as an original disc and fooling the protection mechanism. This technique was pioneered by the software Alcohol 120%, for which it created the .mds file format.
References
"Microsoft buy Danish copy-protection, 1997 (Danish)"
Compact Disc and DVD copy protection
Optical computer storage | Data position measurement | [
"Technology"
] | 203 | [
"Computing stubs"
] |
2,993,817 | https://en.wikipedia.org/wiki/Bugonia | In the ancient Mediterranean region, bugonia or bougonia was a ritual based on the belief that bees were spontaneously (equivocally) generated from a cow's carcass, although it is possible that the ritual had more currency as a poetic and learned trope than as an actual practice.
Description
A detailed description of the bugonia process can be found in Byzantine Geoponica:
Build a house, ten cubits high, with all the sides of equal dimensions, with one door, and four windows, one on each side; put an ox into it, thirty months old, very fat and fleshy; let a number of young men kill him by beating him violently with clubs, so as to mangle both flesh and bones, but taking care not to shed any blood; let all the orifices, mouth, eyes, nose etc. be stopped up with clean and fine linen, impregnated with pitch; let a quantity of thyme be strewed under the reclining animal, and then let windows and doors be closed and covered with a thick coating of clay, to prevent the access of air or wind. After three weeks have passed, let the house be opened, and let light and fresh air get access to it, except from the side from which the wind blows strongest. Eleven days afterwards, you will find the house full of bees, hanging together in clusters, and nothing left of the ox but horns, bones and hair.
The story of Aristaeus was an archetype of this ritual, serving to instruct bee keepers on how to recover from the loss of their bees. By extension, it was thought that fumigation with cow dung was beneficial to the health of the hive.
Variations
The idea that wasps are born of the corpses of horses was often described alongside bugonia. And given that European wasps bear a passing resemblance to European bees, it may be possible that the myth arose out of a mis-reported or misunderstood observation of a natural event.
Different variations are attested, such as simply burying the cow, or covering the corpse with mud or dung. Another variation states that use of the rumen alone is sufficient.
In Ancient Egypt the ox would be buried with its horns projecting above the surface of the ground. When severed, bees would emerge from the base of the horns.
Bugonia is described twice in the second half of Virgil's Georgics and frames the Aristaeus epyllion in the second half. The first description, opening the second half of the fourth book, describes a 'traditional' form of the ritual, followed by the tale of Aristaeus, who after losing his bees, descends to the home of his mother, the nymph Cyrene, where he is given instructions on how to restore his colonies. He must capture the seer, Proteus, and force him to reveal which divine spirit he angered. Proteus changes into many forms but is bound at last and recounts how he caused the death of Eurydice, thus angering the nymphs. The ritual demanded of Aristaeus by Cyrene upon his return is markedly different. He is to sacrifice four bulls, four heifers, a black sheep and a calf in an open glen. This second version served as the climax of a large work so may be based more on the traditional Roman sacrificial ritual than bugonia itself in order to close the Georgics in a more symbolically appropriate way. Thus the first version can reflect man's relation to the gods in the Golden Age and the later the current relation.
Etymology
Bougonia comes from the Greek "βοῦς", meaning "ox" and "γονή" meaning "progeny". Furthermore, the expressions "bugenès melissae" and "taurigenae apes" meant "oxen-born bees" and the ancient Greeks would sometimes simply call honey bees "bugenès" or "taurigenae".
Ancient attestation
Perhaps the earliest mention is by Nicander of Colophon.
The process is described by Virgil in the fourth book of the Georgics. Many other writers mention the practice.
In the Hermetic Cyranides it is reported that worms are born after one week and bees after three weeks.
Quoting Ovid's Metamorphoses (XV.361–68), Florentinus of the Geoponica reports the process as a proven and obvious fact:
If any further evidence is necessary to enhance the faith in things already proved, you may behold that carcases, decaying from the effect of time and tepid moisture, change into small animals. Go, and bury slaughtered oxen -- the fact is known from experience -- the rotten entrails produce flower-sucking bees, who, like their parents, roam over pastures, bent upon work, and hopeful of the future. A buried war-horse produces the hornet.
Scepticism
Pre-dating Nicander by a century, Aristotle never mentions bugonia and dismisses generation of bees from other animals. Furthermore, he is able to distinguish the castes of drone, worker, and "king" so he would certainly have been able to distinguish bees from their mimics. Later authors mention bugonia in commentaries on Aristotle's Physics. Archelaus calls bees the "factitious progeny of a decaying ox". Celsus and Columella are recorded as having opposed the practice.
Later sources
Pietro de' Crescenzi refers to Bugonia circa 1304. In 1475, Konrad of Megenberg, in the first German book of natural history, cites Michel von Schottenlant and Virgil, claiming that the bees are born from the skin and the stomach of an ox. Michael Herren gives a detailed description of bugonia drawn from Geoponica. Johannes Colerus whose book constituted the book of reference for many generations of apiarists expresses the same belief in bugonia. The method appears even in European apiculture books of the 1700s.
In Abrahamic religions
A similar story of the creation of bees is seen in the Book of Judges, where Samson puts forward the riddle of "out of the strong came forth sweetness," referring to a swarm of bees found inside a dead lion.
The bugonia belief is also reported in the Jerusalem Talmud and the Babylonian Talmud.
Philo offers this origin of bees as a possible reason why honey is forbidden as a sacrifice to Yahweh.
Origin of the belief
One explanation claims that any of the numerous Batesian mimics of bees with scavenger larvae were mistaken for bees ("footless at first, anon with feet and wings"). More specifically, the hoverfly Eristalis tenax has received particular attention. While not providing honey, these flies would have been productive pollinators.
Others argue that beekeepers would have understood that flies do not produce honey and give the explanation that Apis mellifera (western honey bee) resorts to any cavity, and in particular cavities of trees and rocks, but also in skulls and in thoracic cavities of large animal carcasses in which to construct a nest. There is one, possibly apocryphal, attestation of actual usage of a man's skull by wasps.
In popular culture
The story of Samson and the bees is celebrated on tins of Tate & Lyle golden syrup.
William Shakespeare knew of bugonia as he says in Henry IV: "Tis seldom when the bee doth leave her comb, in the dead carrion".
See also
Aristaeus
Bee (mythology)
Bull (mythology)
Bucranium
Georgics
References
Further reading
Luciano Landolfi, Ovidio, Aristeo e i "ritocchi" della bugonia
Origin of life | Bugonia | [
"Biology"
] | 1,595 | [
"Biological hypotheses",
"Origin of life"
] |
2,993,836 | https://en.wikipedia.org/wiki/Tensor%20product%20of%20modules | In mathematics, the tensor product of modules is a construction that allows arguments about bilinear maps (e.g. multiplication) to be carried out in terms of linear maps. The module construction is analogous to the construction of the tensor product of vector spaces, but can be carried out for a pair of modules over a commutative ring resulting in a third module, and also for a pair of a right-module and a left-module over any ring, with result an abelian group. Tensor products are important in areas of abstract algebra, homological algebra, algebraic topology, algebraic geometry, operator algebras and noncommutative geometry. The universal property of the tensor product of vector spaces extends to more general situations in abstract algebra. The tensor product of an algebra and a module can be used for extension of scalars. For a commutative ring, the tensor product of modules can be iterated to form the tensor algebra of a module, allowing one to define multiplication in the module in a universal way.
Balanced product
For a ring R, a right R-module M, a left R-module N, and an abelian group G, a map is said to be R-balanced, R-middle-linear or an R-balanced product if for all m, m′ in M, n, n′ in N, and r in R the following hold:
The set of all such balanced products over R from to G is denoted by .
If , are balanced products, then each of the operations and −φ defined pointwise is a balanced product. This turns the set into an abelian group.
For M and N fixed, the map is a functor from the category of abelian groups to itself. The morphism part is given by mapping a group homomorphism to the function , which goes from to .
Remarks
Properties (Dl) and (Dr) express biadditivity of φ, which may be regarded as distributivity of φ over addition.
Property (A) resembles some associative property of φ.
Every ring R is an R-bimodule. So the ring multiplication in R is an R-balanced product .
Definition
For a ring R, a right R-module M, a left R-module N, the tensor product over R
is an abelian group together with a balanced product (as defined above)
which is universal in the following sense:
For every abelian group G and every balanced product there is a unique group homomorphism such that
As with all universal properties, the above property defines the tensor product uniquely up to a unique isomorphism: any other abelian group and balanced product with the same properties will be isomorphic to and ⊗. Indeed, the mapping ⊗ is called canonical, or more explicitly: the canonical mapping (or balanced product) of the tensor product.
The definition does not prove the existence of ; see below for a construction.
The tensor product can also be defined as a representing object for the functor ; explicitly, this means there is a natural isomorphism:
This is a succinct way of stating the universal mapping property given above. (If a priori one is given this natural isomorphism, then can be recovered by taking and then mapping the identity map.)
Similarly, given the natural identification , one can also define by the formula
This is known as the tensor-hom adjunction; see also .
For each x in M, y in N, one writes
for the image of (x, y) under the canonical map . It is often called a pure tensor. Strictly speaking, the correct notation would be x ⊗R y but it is conventional to drop R here. Then, immediately from the definition, there are relations:
The universal property of a tensor product has the following important consequence:
Proof: For the first statement, let L be the subgroup of generated by elements of the form in question, and q the quotient map to Q. We have: as well as . Hence, by the uniqueness part of the universal property, q = 0. The second statement is because to define a module homomorphism, it is enough to define it on the generating set of the module.
Application of the universal property of tensor products
Determining whether a tensor product of modules is zero
In practice, it is sometimes more difficult to show that a tensor product of R-modules is nonzero than it is to show that it is 0. The universal property gives a convenient way for checking this.
To check that a tensor product is nonzero, one can construct an R-bilinear map to an abelian group such that . This works because if , then .
For example, to see that , is nonzero, take to be and . This says that the pure tensors as long as is nonzero in .
For equivalent modules
The proposition says that one can work with explicit elements of the tensor products instead of invoking the universal property directly each time. This is very convenient in practice. For example, if R is commutative and the left and right actions by R on modules are considered to be equivalent, then can naturally be furnished with the R-scalar multiplication by extending
to the whole by the previous proposition (strictly speaking, what is needed is a bimodule structure not commutativity; see a paragraph below). Equipped with this R-module structure, satisfies a universal property similar to the above: for any R-module G, there is a natural isomorphism:
If R is not necessarily commutative but if M has a left action by a ring S (for example, R), then can be given the left S-module structure, like above, by the formula
Analogously, if N has a right action by a ring S, then becomes a right S-module.
Tensor product of linear maps and a change of base ring
Given linear maps of right modules over a ring R and of left modules, there is a unique group homomorphism
The construction has a consequence that tensoring is a functor: each right R-module M determines the functor
from the category of left modules to the category of abelian groups that sends N to and a module homomorphism f to the group homomorphism .
If is a ring homomorphism and if M is a right S-module and N a left S-module, then there is the canonical surjective homomorphism:
induced by
The resulting map is surjective since pure tensors generate the whole module. In particular, taking R to be this shows every tensor product of modules is a quotient of a tensor product of abelian groups.
Several modules
(This section need to be updated. For now, see for the more general discussion.)
It is possible to extend the definition to a tensor product of any number of modules over the same commutative ring. For example, the universal property of
is that each trilinear map on
corresponds to a unique linear map
The binary tensor product is associative: (M1 ⊗ M2) ⊗ M3 is naturally isomorphic to M1 ⊗ (M2 ⊗ M3). The tensor product of three modules defined by the universal property of trilinear maps is isomorphic to both of these iterated tensor products.
Properties
Modules over general rings
Let R1, R2, R3, R be rings, not necessarily commutative.
For an R1-R2-bimodule M12 and a left R2-module M20, is a left R1-module.
For a right R2-module M02 and an R2-R3-bimodule M23, is a right R3-module.
(associativity) For a right R1-module M01, an R1-R2-bimodule M12, and a left R2-module M20 we have:
Since R is an R-R-bimodule, we have with the ring multiplication as its canonical balanced product.
Modules over commutative rings
Let R be a commutative ring, and M, N and P be R-modules. Then
Identity
Associativity The first three properties (plus identities on morphisms) say that the category of R-modules, with R commutative, forms a symmetric monoidal category. Thus is well-defined.
Symmetry In fact, for any permutation σ of the set {1, ..., n}, there is a unique isomorphism:
Distribution over direct sums In fact, for an index set I of arbitrary cardinality. Since finite products coincide with finite direct sums, this imples:
Distribution over finite products For any finitely many ,
Base extension If S is an R-algebra, writing , cf. . A corollary is:
Distribution over localization For any multiplicatively closed subset S of R, as an -module. Since is an R-algebra and , this is a special case of:
Commutation with direct limits For any direct system of R-modules Mi,
Adjunction A corollary is:
Right-exaction If is an exact sequence of R-modules, then is an exact sequence of R-modules, where
Tensor-hom relation There is a canonical R-linear map: which is an isomorphism if either M or P is a finitely generated projective module (see for the non-commutative case); more generally, there is a canonical R-linear map: which is an isomorphism if either or is a pair of finitely generated projective modules.
To give a practical example, suppose M, N are free modules with bases and . Then M is the direct sum
and the same for N. By the distributive property, one has:
i.e., are the R-basis of . Even if M is not free, a free presentation of M can be used to compute tensor products.
The tensor product, in general, does not commute with inverse limit: on the one hand,
(cf. "examples"). On the other hand,
where are the ring of p-adic integers and the field of p-adic numbers. See also "profinite integer" for an example in the similar spirit.
If R is not commutative, the order of tensor products could matter in the following way: we "use up" the right action of M and the left action of N to form the tensor product ; in particular, would not even be defined. If M, N are bi-modules, then has the left action coming from the left action of M and the right action coming from the right action of N; those actions need not be the same as the left and right actions of .
The associativity holds more generally for non-commutative rings: if M is a right R-module, N a (R, S)-module and P a left S-module, then
as abelian group.
The general form of adjoint relation of tensor products says: if R is not necessarily commutative, M is a right R-module, N is a (R, S)-module, P is a right S-module, then as abelian group
where is given by .
Tensor product of an R-module with the fraction field
Let R be an integral domain with fraction field K.
For any R-module M, as R-modules, where is the torsion submodule of M.
If M is a torsion R-module then and if M is not a torsion module then .
If N is a submodule of M such that is a torsion module then as R-modules by .
In , if and only if or . In particular, where .
where is the localization of the module at the prime ideal (i.e., the localization with respect to the nonzero elements).
Extension of scalars
The adjoint relation in the general form has an important special case: for any R-algebra S, M a right R-module, P a right S-module, using , we have the natural isomorphism:
This says that the functor is a left adjoint to the forgetful functor , which restricts an S-action to an R-action. Because of this, is often called the extension of scalars from R to S. In the representation theory, when R, S are group algebras, the above relation becomes the Frobenius reciprocity.
Examples
, for any R-algebra S (i.e., a free module remains free after extending scalars.)
For a commutative ring and a commutative R-algebra S, we have: in fact, more generally, where is an ideal.
Using , the previous example and the Chinese remainder theorem, we have as rings This gives an example when a tensor product is a direct product.
.
Examples
The structure of a tensor product of quite ordinary modules may be unpredictable.
Let G be an abelian group in which every element has finite order (that is G is a torsion abelian group; for example G can be a finite abelian group or ). Then:
Indeed, any is of the form
If is the order of , then we compute:
Similarly, one sees
Here are some identities useful for calculation: Let R be a commutative ring, I, J ideals, M, N R-modules. Then
. If M is flat, .
(because tensoring commutes with base extensions)
.
Example: If G is an abelian group, ; this follows from 1.
Example: ; this follows from 3. In particular, for distinct prime numbers p, q,
Tensor products can be applied to control the order of elements of groups. Let G be an abelian group. Then the multiples of 2 in
are zero.
Example: Let be the group of n-th roots of unity. It is a cyclic group and cyclic groups are classified by orders. Thus, non-canonically, and thus, when g is the gcd of n and m,
Example: Consider . Since is obtained from by imposing -linearity on the middle, we have the surjection
whose kernel is generated by elements of the form
where r, s, x, u are integers and s is nonzero. Since
the kernel actually vanishes; hence, .
However, consider and . As -vector space, has dimension 4, but has dimension 2.
Thus, and are not isomorphic.
Example: We propose to compare and . Like in the previous example, we have: as abelian group and thus as -vector space (any -linear map between -vector spaces is -linear). As -vector space, has dimension (cardinality of a basis) of continuum. Hence, has a -basis indexed by a product of continuums; thus its -dimension is continuum. Hence, for dimension reason, there is a non-canonical isomorphism of -vector spaces:
Consider the modules for irreducible polynomials such that . Then,
Another useful family of examples comes from changing the scalars. Notice that
Good examples of this phenomenon to look at are when .
Construction
The construction of takes a quotient of a free abelian group with basis the symbols , used here to denote the ordered pair , for m in M and n in N by the subgroup generated by all elements of the form
−m ∗ (n + n′) + m ∗ n + m ∗ n′
−(m + m′) ∗ n + m ∗ n + m′ ∗ n
(m · r) ∗ n − m ∗ (r · n)
where m, m′ in M, n, n′ in N, and r in R. The quotient map which takes to the coset containing ; that is,
is balanced, and the subgroup has been chosen minimally so that this map is balanced. The universal property of ⊗ follows from the universal properties of a free abelian group and a quotient.
If S is a subring of a ring R, then is the quotient group of by the subgroup generated by , where is the image of under . In particular, any tensor product of R-modules can be constructed, if so desired, as a quotient of a tensor product of abelian groups by imposing the R-balanced product property.
More category-theoretically, let σ be the given right action of R on M; i.e., σ(m, r) = m · r and τ the left action of R of N. Then, provided the tensor product of abelian groups is already defined, the tensor product of M and N over R can be defined as the coequalizer:
where without a subscript refers to the tensor product of abelian groups.
In the construction of the tensor product over a commutative ring R, the R-module structure can be built in from the start by forming the quotient of a free R-module by the submodule generated by the elements given above for the general construction, augmented by the elements . Alternately, the general construction can be given a Z(R)-module structure by defining the scalar action by when this is well-defined, which is precisely when r ∈ Z(R), the centre of R.
The direct product of M and N is rarely isomorphic to the tensor product of M and N. When R is not commutative, then the tensor product requires that M and N be modules on opposite sides, while the direct product requires they be modules on the same side. In all cases the only function from to G that is both linear and bilinear is the zero map.
As linear maps
In the general case, not all the properties of a tensor product of vector spaces extend to modules. Yet, some useful properties of the tensor product, considered as module homomorphisms, remain.
Dual module
The dual module of a right R-module E, is defined as with the canonical left R-module structure, and is denoted E∗. The canonical structure is the pointwise operations of addition and scalar multiplication. Thus, E∗ is the set of all R-linear maps (also called linear forms), with operations
The dual of a left R-module is defined analogously, with the same notation.
There is always a canonical homomorphism from E to its second dual. It is an isomorphism if E is a free module of finite rank. In general, E is called a reflexive module if the canonical homomorphism is an isomorphism.
Duality pairing
We denote the natural pairing of its dual E∗ and a right R-module E, or of a left R-module F and its dual F∗ as
The pairing is left R-linear in its left argument, and right R-linear in its right argument:
An element as a (bi)linear map
In the general case, each element of the tensor product of modules gives rise to a left R-linear map, to a right R-linear map, and to an R-bilinear form. Unlike the commutative case, in the general case the tensor product is not an R-module, and thus does not support scalar multiplication.
Given right R-module E and right R-module F, there is a canonical homomorphism such that is the map .
Given left R-module E and right R-module F, there is a canonical homomorphism such that is the map .
Both cases hold for general modules, and become isomorphisms if the modules E and F are restricted to being finitely generated projective modules (in particular free modules of finite ranks). Thus, an element of a tensor product of modules over a ring R maps canonically onto an R-linear map, though as with vector spaces, constraints apply to the modules for this to be equivalent to the full space of such linear maps.
Given right R-module E and left R-module F, there is a canonical homomorphism such that is the map . Thus, an element of a tensor product ξ ∈ F∗ ⊗R E∗ may be thought of giving rise to or acting as an R-bilinear map .
Trace
Let R be a commutative ring and E an R-module. Then there is a canonical R-linear map:
induced through linearity by ; it is the unique R-linear map corresponding to the natural pairing.
If E is a finitely generated projective R-module, then one can identify through the canonical homomorphism mentioned above and then the above is the trace map:
When R is a field, this is the usual trace of a linear transformation.
Example from differential geometry: tensor field
The most prominent example of a tensor product of modules in differential geometry is the tensor product of the spaces of vector fields and differential forms. More precisely, if R is the (commutative) ring of smooth functions on a smooth manifold M, then one puts
where Γ means the space of sections and the superscript means tensoring p times over R. By definition, an element of is a tensor field of type (p, q).
As R-modules, is the dual module of .
To lighten the notation, put and so . When p, q ≥ 1, for each (k, l) with 1 ≤ k ≤ p, 1 ≤ l ≤ q, there is an R-multilinear map:
where means and the hat means a term is omitted. By the universal property, it corresponds to a unique R-linear map:
It is called the contraction of tensors in the index (k, l). Unwinding what the universal property says one sees:
Remark: The preceding discussion is standard in textbooks on differential geometry (e.g., Helgason). In a way, the sheaf-theoretic construction (i.e., the language of sheaf of modules) is more natural and increasingly more common; for that, see the section .
Relationship to flat modules
In general,
is a bifunctor which accepts a right and a left R module pair as input, and assigns them to the tensor product in the category of abelian groups.
By fixing a right R module M, a functor
arises, and symmetrically a left R module N could be fixed to create a functor
Unlike the Hom bifunctor the tensor functor is covariant in both inputs.
It can be shown that and are always right exact functors, but not necessarily left exact (, where the first map is multiplication by , is exact but not after taking the tensor with ). By definition, a module T is a flat module if is an exact functor.
If and are generating sets for M and N, respectively, then will be a generating set for Because the tensor functor sometimes fails to be left exact, this may not be a minimal generating set, even if the original generating sets are minimal. If M is a flat module, the functor is exact by the very definition of a flat module. If the tensor products are taken over a field F, we are in the case of vector spaces as above. Since all F modules are flat, the bifunctor is exact in both positions, and the two given generating sets are bases, then indeed forms a basis for .
Additional structure
If S and T are commutative R-algebras, then, similar to #For equivalent modules, will be a commutative R-algebra as well, with the multiplication map defined by and extended by linearity. In this setting, the tensor product become a fibered coproduct in the category of commutative R-algebras. (But it is not a coproduct in the category of R-algebras.)
If M and N are both R-modules over a commutative ring, then their tensor product is again an R-module. If R is a ring, RM is a left R-module, and the commutator
of any two elements r and s of R is in the annihilator of M, then we can make M into a right R module by setting
The action of R on M factors through an action of a quotient commutative ring. In this case the tensor product of M with itself over R is again an R-module. This is a very common technique in commutative algebra.
Generalization
Tensor product of complexes of modules
If X, Y are complexes of R-modules (R a commutative ring), then their tensor product is the complex given by
with the differential given by: for x in Xi and y in Yj,
For example, if C is a chain complex of flat abelian groups and if G is an abelian group, then the homology group of is the homology group of C with coefficients in G (see also: universal coefficient theorem.)
Tensor product of sheaves of modules
The tensor product of sheaves of modules is the sheaf associated to the pre-sheaf of the tensor products of the modules of sections over open subsets.
In this setup, for example, one can define a tensor field on a smooth manifold M as a (global or local) section of the tensor product (called tensor bundle)
where O is the sheaf of rings of smooth functions on M and the bundles are viewed as locally free sheaves on M.
The exterior bundle on M is the subbundle of the tensor bundle consisting of all antisymmetric covariant tensors. Sections of the exterior bundle are differential forms on M.
One important case when one forms a tensor product over a sheaf of non-commutative rings appears in theory of D-modules; that is, tensor products over the sheaf of differential operators.
See also
Tor functor
Tensor product of algebras
Tensor product of fields
Derived tensor product
Eilenberg–Watts theorem
Notes
References
.
.
Module theory
Multilinear algebra
Homological algebra
Operations on structures | Tensor product of modules | [
"Mathematics"
] | 5,323 | [
"Mathematical structures",
"Fields of abstract algebra",
"Category theory",
"Module theory",
"Homological algebra"
] |
2,993,946 | https://en.wikipedia.org/wiki/IEEE%201541 | IEEE 1541-2002 is a standard issued in 2002 by the Institute of Electrical and Electronics Engineers (IEEE) concerning the use of prefixes for binary multiples of units of measurement related to digital electronics and computing. IEEE 1541-2021 revises and supersedes IEEE 1541–2002, which is 'inactive'.
While the International System of Units (SI) defines multiples based on powers of ten (like k = 103, M = 106, etc.), a different definition is sometimes used in computing, based on powers of two (like k = 210, M = 220, etc.). This is due to binary nature of current computing systems, making powers of two the simplest to calculate.
In the early years of computing, there was no significant error in using the same prefix for either quantity (210 = 1,024 and 103 = 1000 are equal, to two significant figures). Thus, the SI prefixes were borrowed to indicate nearby binary multiples for these computer-related quantities.
Meanwhile, manufacturers of storage devices, such as hard disks, traditionally used the standard decimal meanings of the prefixes, and decimal multiples are used for transmission rates and processor clock speeds as well. As technology improved, all of these measurements and capacities increased. As the binary meaning was extended to higher prefixes, the absolute error between the two meanings increased. This has even resulted in litigation against hard drive manufacturers, because some operating systems report the size using the larger binary interpretation.
Moreover, there is not a consistent use of the symbols to indicate quantities of bits and bytes – the unit symbol "Mb", for instance, has been widely used for both megabytes and megabits. IEEE 1541 sets new recommendations to represent these quantities and unit symbols unambiguously.
After a trial period of two years, in 2005, IEEE 1541-2002 was elevated to a full-use standard by the IEEE Standards Association, and was reaffirmed on 27 March 2008.
IEEE 1541 is closely related to Amendment 2 of the international standard IEC 60027-2. Later, the IEC standard was harmonized into the common ISO/IEC 80000-13:2008 – Quantities and units – Part 13: Information science and technology. IEC 80000-13 uses 'bit' as the symbol for bit, as opposed to 'b'.
Recommendations
IEEE 1541 recommends:
a set of units to refer to quantities used in digital electronics and computing:
bit (symbol 'b'), a binary digit;
byte (symbol 'B'), a set of adjacent bits (usually, but not necessarily, eight) operated on as a group;
octet (symbol 'o'), a group of eight bits;
a set of prefixes to indicate binary multiples of the aforesaid units:
kibi (symbol 'Ki'), 210 = ;
mebi (symbol 'Mi'), 220 = ;
gibi (symbol 'Gi'), 230 = ;
tebi (symbol 'Ti'), 240 = ;
pebi (symbol 'Pi'), 250 = ;
exbi (symbol 'Ei'), 260 = ;
zebi (symbol 'Zi'), 270 = ;
yobi (symbol 'Yi'), 280 = ;
that the first part of the binary prefix is pronounced as the analogous SI prefix, and the second part is pronounced as bee;
that SI prefixes are not used to indicate binary multiples.
The bi part of the prefix comes from the word binary, so for example, kibibyte means a kilobinary byte, that is 1024 bytes.
Acceptance
In 1998, the International Bureau of Weights and Measures (BIPM), one of the organizations that maintain SI, published a brochure stating, among other things, that SI prefixes strictly refer to powers of ten and should not be used to indicate binary multiples, using as an example that 1 kilobit is 1000 bits and not 1024 bits.
The binary prefixes have been adopted by the European Committee for Electrotechnical Standardization (CENELEC) as the harmonization document HD 60027-2:2003-03. Adherence to this standard implies that binary prefixes would be used for powers of two and SI prefixes for powers of ten. This document has been adopted as a European standard.
The IEC binary prefixes (kibi, mebi, ...) are gaining acceptance in open source software and in scientific literature. Elsewhere adoption has been slow, with some operating systems, most notably Windows, continuing to use SI prefixes (kilo, mega, ...) for binary multiples.
Supporters of IEEE 1541 emphasize that the standard solves the confusion of units in the market place. Some software (most notably free and open source) uses the decimal SI prefixes and binary prefixes according to the standard.
See also
Powers of 1024
Binary prefixes
Timeline of binary prefixes
TU (time unit), defined as 1024 μs in IEEE 802.11
References
External links
IEEE 1541-2002 - IEEE Standard for Prefixes for Binary Multiples (original document)
SI Brochure: The International System of Units (SI)
Electronics standards
Prefixes
Measurement
Naming conventions
Units of information
IEEE standards | IEEE 1541 | [
"Physics",
"Mathematics",
"Technology"
] | 1,072 | [
"Physical quantities",
"Computer standards",
"Quantity",
"Measurement",
"Size",
"Units of information",
"IEEE standards",
"Units of measurement"
] |
2,994,042 | https://en.wikipedia.org/wiki/Marek%20Karpinski | Marek Karpinski is a computer scientist and mathematician known for his research in the theory of algorithms and their applications, combinatorial optimization, computational complexity, and mathematical foundations. He is a recipient of several research prizes in the above areas.
He is currently a Professor of Computer Science, and the Head of the Algorithms Group at the University of Bonn. He is also a member of Bonn International Graduate School in Mathematics BIGS and the Hausdorff Center for Mathematics.
See also
List of computer scientists
List of mathematicians
References
American theoretical computer scientists
Mathematical logicians
Graph theorists
Academic staff of the University of Bonn
American computer scientists
20th-century Polish mathematicians
21st-century Polish mathematicians
Members of Academia Europaea
Polish computer scientists
Living people
Year of birth missing (living people) | Marek Karpinski | [
"Mathematics"
] | 152 | [
"Mathematical logicians",
"Mathematical logic",
"Graph theory",
"Mathematical relations",
"Graph theorists"
] |
2,994,276 | https://en.wikipedia.org/wiki/Thue%27s%20lemma | In modular arithmetic, Thue's lemma roughly states that every modular integer may be represented by a "modular fraction" such that the numerator and the denominator have absolute values not greater than the square root of the modulus.
More precisely, for every pair of integers with , given two positive integers and such that , there are two integers and such that
and
Usually, one takes and equal to the smallest integer greater than the square root of , but the general form is sometimes useful, and makes the uniqueness theorem (below) easier to state.
The first known proof is attributed to who used a pigeonhole argument. It can be used to prove Fermat's theorem on sums of two squares by taking m to be a prime p that is congruent to 1 modulo 4 and taking a to satisfy a2 + 1 ≡ 0 mod p. (Such an "a" is guaranteed for "p" by Wilson's theorem.)
Uniqueness
In general, the solution whose existence is asserted by Thue's lemma is not unique. For example, when there are usually several solutions , provided that and are not too small. Therefore, one may only hope for uniqueness for the rational number , to which is congruent modulo if y and m are coprime. Nevertheless, this rational number need not be unique; for example, if , and , one has the two solutions
.
However, for and small enough, if a solution exists, it is unique. More precisely, with above notation, if
and
,
with
and
then
This result is the basis for rational reconstruction, which allows using modular arithmetic for computing rational numbers for which one knows bounds for numerators and denominators.
The proof is rather easy: by multiplying each congruence by the other and subtracting, one gets
The hypotheses imply that each term has an absolute value lower than , and thus that the absolute value of their difference is lower than . This implies that , hence the result.
Computing solutions
The original proof of Thue's lemma is not efficient, in the sense that it does not provide any fast method for computing the solution.
The extended Euclidean algorithm, allows us to provide a proof that leads to an efficient algorithm that has the same computational complexity of the Euclidean algorithm.
More precisely, given the two integers and appearing in Thue's lemma, the extended Euclidean algorithm computes three sequences of integers , and such that
where the are non-negative and strictly decreasing. The desired solution is, up to the sign, the first pair such that .
See also
Padé approximant, a similar theory, for approximating Taylor series by rational functions
References
Lemmas in number theory
Modular arithmetic | Thue's lemma | [
"Mathematics"
] | 560 | [
"Theorems in number theory",
"Arithmetic",
"Lemmas in number theory",
"Lemmas",
"Modular arithmetic",
"Number theory"
] |
2,994,278 | https://en.wikipedia.org/wiki/Egress%20filtering | In computer networking, egress filtering is the practice of monitoring and potentially restricting the flow of information outbound from one network to another. Typically, it is information from a private TCP/IP computer network to the Internet that is controlled.
TCP/IP packets that are being sent out of the internal network are examined via a router, firewall, or similar edge device. Packets that do not meet security policies are not allowed to leave – they are denied "egress".
Egress filtering helps ensure that unauthorized or malicious traffic never leaves the internal network.
In a corporate network, typical recommendations are that all traffic except that emerging from a select set of servers would be denied egress. Restrictions can further be made such that only select protocols such as HTTP, email, and DNS are allowed. User workstations would then need to be configured either manually or via proxy auto-config to use one of the allowed servers as a proxy.
Corporate networks also typically have a limited number of internal address blocks in use. An edge device at the boundary between the internal corporate network and external networks (such as the Internet) is used to perform egress checks against packets leaving the internal network, verifying that the source IP address in all outbound packets is within the range of allocated internal address blocks.
Egress filtering may require policy changes and administrative work whenever a new application requires external network access. For this reason, egress filtering is an uncommon feature on consumer and very small business networks. PCI DSS requires outbound filtering to be in place on any server in the cardholder's environment. This is described in PCI-DSS v3.0, requirement 1.3.3.
See also
Content-control software
Ingress filtering
Web Proxy Autodiscovery Protocol
References
External links
RFC 3013
Pcisecuritystandards.org
Pcisecuritystandards.org
Sans.org
Computer network security | Egress filtering | [
"Technology",
"Engineering"
] | 399 | [
"Cybersecurity engineering",
"Computer network stubs",
"Computer networks engineering",
"Computer network security",
"Computing stubs"
] |
2,994,458 | https://en.wikipedia.org/wiki/Blade%20pitch | Blade pitch or simply pitch refers to the angle of a blade in a fluid. The term has applications in aeronautics, shipping, and other fields.
Aeronautics
In aeronautics, blade pitch refers to the angle of the blades of an aircraft propeller or helicopter rotor. Blade pitch is measured relative to the aircraft body. It is usually described as "fine" or "low" for a more vertical blade angle, and "coarse" or "high" for a more horizontal blade angle.
Blade pitch is normally described as a ratio of forward distance per rotation assuming no slip.
Blade pitch acts much like the gearing of the final drive of a car. Low pitch yields good low speed acceleration (and climb rate in an aircraft) while high pitch optimizes high speed performance and fuel economy.
It is quite common for an aircraft to be designed with a variable-pitch propeller, to give maximum thrust over a larger speed range. A fine pitch would be used during take-off and landing, whereas a coarser pitch is used for high-speed cruise flight. This is because the effective angle of attack of the propeller blade decreases as airspeed increases. To maintain the optimum effective angle of attack, the pitch must be increased. Blade pitch angle is not the same as blade angle of attack. As speed increases, blade pitch is increased to keep blade angle of attack constant.
A propeller blade's "lift", or its thrust, depends on the angle of attack combined with its speed. Because the velocity of a propeller blade varies from the hub to the tip, it is of twisted form in order for the thrust to remain approximately constant along the length of the blade; this is called "blade twist". This is typical of all but the crudest propellers.
Helicopters
In helicopters, pitch control changes the angle of incidence of the rotor blades, which in turn affects the blades' angle of attack. Main rotor pitch is controlled by both collective and cyclic, whereas tail rotor pitch is altered using pedals.
Feathering
Feathering the blades of a propeller means to increase their angle of pitch by turning the blades to be parallel to the airflow. This minimizes drag from a stopped propeller following an engine failure in flight.
Reverse thrust
Some propeller-driven aircraft permit the pitch to be decreased beyond the fine position until the propeller generates thrust in the reverse direction. This is called thrust reversal, and the propeller position is called the beta position.
Wind turbines
Blade pitch control is a feature of nearly all large modern horizontal-axis wind turbines. It is used to adjust the rotation speed and the generated power. While operating, a wind turbine's control system adjusts the blade pitch to keep the rotor speed within operating limits as the wind speed changes. Feathering the blades stops the rotor during emergency shutdowns, or whenever the wind speed exceeds the maximum rated speed. During construction and maintenance of wind turbines, the blades are usually feathered to reduce unwanted rotational torque in the event of wind gusts.
Blade pitch control is preferred over rotor brakes, as brakes are subject to failure or overload by the wind force on the turbine. This can lead to runaway turbines. By contrast, pitch control allows the blades to be feathered, so that wind speed does not affect the stress on the control mechanism.
Pitch control can be implemented via hydraulic or electric mechanisms. Hydraulic mechanisms have longer life, faster response time due to higher driving force, and a lower maintenance backup spring. However, hydraulics tend to require more power to keep the system at a high pressure, and can leak. Electric systems consume and waste less power, and do not leak. However, they require costly fail safe batteries and capacitors in the event of power failure.
Pitch control does not need to be active (reliant on actuators). Passive (stall-controlled) wind turbines rely on the fact that angle of attack increases with wind speed. Blades can be designed to stop functioning past a certain speed. This is another use for twisted blades: the twist allows for a gradual stall as each portion of the blade has a different angle of attack and will stop at a different time.
Blade pitch control typically accounts for less than 3% of a wind turbine's expense while blade pitch malfunctions account for 23% of all wind turbine production downtime, and account for 21% of all component failures.
Shipping
In shipping, blade pitch is measured in the number of inches of forward propulsion through the water for one complete revolution of the propeller. For example, a propeller with a 12" pitch will propel the vessel 12" ahead when rotated once. Note that this is the theoretical maximum distance; in reality, due to "slip" between the propeller and the water, the actual distance propelled will invariably be less.
Some composite propellers have interchangeable blades, which enables the blade pitch to be changed when the propeller is stopped. A lower pitch would be used for transporting heavy loads at low speed, whereas a higher pitch would be used for high-speed travel.
Rowing (sport)
In rowing, blade pitch is the inclination of the blade towards the stern of the boat during the drive phase of the rowing stroke. Without correct blade pitch, a blade would have a tendency to dive too deep, or pop out of the water and/or cause difficulties with balancing on the recovery phase of the stroke.
References
External links
Aerodynamics | Blade pitch | [
"Chemistry",
"Engineering"
] | 1,081 | [
"Aerospace engineering",
"Aerodynamics",
"Fluid dynamics"
] |
2,994,661 | https://en.wikipedia.org/wiki/Lewis%20number | In fluid dynamics and thermodynamics, the Lewis number (denoted ) is a dimensionless number defined as the ratio of thermal diffusivity to mass diffusivity. It is used to characterize fluid flows where there is simultaneous heat and mass transfer. The Lewis number puts the thickness of the thermal boundary layer in relation to the concentration boundary layer. The Lewis number is defined as
.
where:
is the thermal diffusivity,
is the mass diffusivity,
is the thermal conductivity,
is the density,
is the mixture-averaged diffusion coefficient,
is the specific heat capacity at constant pressure.
In the field of fluid mechanics, many sources define the Lewis number to be the inverse of the above definition.
The Lewis number can also be expressed in terms of the Prandtl number () and the Schmidt number ():
It is named after Warren K. Lewis (1882–1975), who was the first head of the Chemical Engineering Department at MIT. Some workers in the field of combustion assume (incorrectly) that the Lewis number was named for Bernard Lewis (1899–1993), who for many years was a major figure in the field of combustion research.
References
Further reading
Fluid dynamics
Dimensionless numbers of fluid mechanics
Combustion | Lewis number | [
"Chemistry",
"Engineering"
] | 254 | [
"Piping",
"Chemical engineering",
"Combustion",
"Fluid dynamics"
] |
2,994,664 | https://en.wikipedia.org/wiki/Schmidt%20number | In fluid dynamics, the Schmidt number (denoted ) of a fluid is a dimensionless number defined as the ratio of momentum diffusivity (kinematic viscosity) and mass diffusivity, and it is used to characterize fluid flows in which there are simultaneous momentum and mass diffusion convection processes. It was named after German engineer Ernst Heinrich Wilhelm Schmidt (1892–1975).
The Schmidt number is the ratio of the shear component for diffusivity (viscosity divided by density) to the diffusivity for mass transfer . It physically relates the relative thickness of the hydrodynamic layer and mass-transfer boundary layer.
It is defined as:
where (in SI units):
is the kinematic viscosity (m2/s)
is the mass diffusivity (m2/s).
is the dynamic viscosity of the fluid (Pa·s = N·s/m2 = kg/m·s)
is the density of the fluid (kg/m3)
is the Peclet Number
is the Reynolds Number.
The heat transfer analog of the Schmidt number is the Prandtl number (). The ratio of thermal diffusivity to mass diffusivity is the Lewis number ().
Turbulent Schmidt Number
The turbulent Schmidt number is commonly used in turbulence research and is defined as:
where:
is the eddy viscosity in units of (m2/s)
is the eddy diffusivity (m2/s).
The turbulent Schmidt number describes the ratio between the rates of turbulent transport of momentum and the turbulent transport of mass (or any passive scalar). It is related to the turbulent Prandtl number, which is concerned with turbulent heat transfer rather than turbulent mass transfer. It is useful for solving the mass transfer problem of turbulent boundary layer flows. The simplest model for Sct is the Reynolds analogy, which yields a turbulent Schmidt number of 1. From experimental data and CFD simulations, Sct ranges from 0.2 to 6.
Stirling engines
For Stirling engines, the Schmidt number is related to the specific power.
Gustav Schmidt of the German Polytechnic Institute of Prague published an analysis in 1871 for the now-famous closed-form solution for an idealized isothermal Stirling engine model.
where:
is the Schmidt number
is the heat transferred into the working fluid
is the mean pressure of the working fluid
is the volume swept by the piston.
References
Dimensionless numbers of fluid mechanics
Dimensionless numbers of thermodynamics
Fluid dynamics | Schmidt number | [
"Physics",
"Chemistry",
"Engineering"
] | 509 | [
"Thermodynamic properties",
"Physical quantities",
"Dimensionless numbers of thermodynamics",
"Chemical engineering",
"Piping",
"Fluid dynamics"
] |
2,994,800 | https://en.wikipedia.org/wiki/Transfer%20factor | Transfer factors (which come from White cells called ‘T cells’) are essentially small immune messenger molecules that are produced by all higher organisms. Transfer factors were originally described as immune molecules that are derived from blood or spleen cells that cause antigen-specific cell-mediated immunity, primarily delayed hypersensitivity and the production of lymphokines, as well as binding to the antigens themselves. They have a molecular weight of approximately 5000 daltons and are composed entirely of amino acids. Transfer factors were discovered by Henry Sherwood Lawrence in 1954.
A second use of the term transfer factor applies to a likely different entity derived from cow colostrum or chicken egg yolk which is marketed as an oral dietary supplement under the same name citing claims of benefit to the immune system.
History
In 1942, Merrill Chase discovered that cells taken from the peritoneum of Guinea pigs that had been immunized against an antigen could transfer immunity when injected into Guinea pigs that had never been exposed to the antigen; this phenomenon was the discovery of cell-mediated immunity. Subsequent research attempted to uncover how the cells imparted their effects. Henry Sherwood Lawrence, in 1955, discovered that partial immunity could be transferred even when the immune cells had undergone lysis - indicating that cells did not need to be fully intact in order to produce immune effects. Lawrence went on to discover that only the factors less than 8000 daltons were required to transfer this immunity; he termed these to be "transfer factors".
The history of cellular derived transfer factor as a treatment effectively ended in the early 1980s. While the research world was initially excited by the discovery of Dr. Lawrence and the possibility that a small molecule could affect the immune system, the concept of small molecules having such profound biologic effect had not been proven. Despite several successes in using transfer factor to treat human disease and uncover immune effects, one then-prominent researcher was exposed for falsifying data related to his work on transfer factor and guinea pigs; effectively casting all of transfer factor science in a negative light. This scandal was followed shortly thereafter by the discovery of the Interleukin-1 alpha molecule and thus attention further shifted towards research on interleukins. By 1973, it was discovered that blood products could harbor viruses such as hepatitis A, indicating that transfer factor treatments derived from human or cow blood cells had the potential to transmit these diseases. With the eventual discovery of HIV/AIDS as an additional blood-borne disease most researchers viewed a product derived from blood as an unsafe treatment since screening for hepatitis B and HIV/AIDS would not be developed until after 1985. Some studies using transfer factor have been conducted after the discovery of HIV/AIDS, but almost all have been outside of the United States.
Most recently, transfer factor has been harvested from sources other than blood, and administered orally, as opposed to intravenously. This use of transfer factors from sources other than blood has not been accompanied by the same concerns associated with blood-borne diseases, since no blood is involved. Transfer factor based nutritional supplements have become extremely popular throughout the world. However the way transfer factor works is still not clear.
Scientific claims
To communicate between cells, the immune system employs hormone-like signal substances; transfer factors are one class of such immune system communication substances. Transfer factors include both inducer/helper functions (Inducer Factors) and regulator functions (Regulator Factors)—historically called "suppressor functions". The Inducer Factors translate an apparently mature immune response from the donor to the recipient. Regulator Factors help control overreactions and limit allergies and autoimmune conditions. Transfer factors have been shown to induce an immune response in less than 24 hours. Transfer factors are not species-specific, thus transfer factors produced by a cow's immune system are just as effective in humans as they are in the cow.
Henry Sherwood Lawrence discovered that blood cells could 'transfer' antigen-specific cell-mediated immunity even after the cells had undergone lysis. This lymphocyte product is sometimes referred to as "dialyzable leukocyte extract" in the scientific literature due to being an extract from white blood cells undergoing dialysis to remove all molecules larger than ~5000 daltons. Studies on cellular transfer factor have involved mostly animal models and small human clinical trials. These studies have demonstrated preliminary evidence of immune modulation as well as some clinical benefits in a handful of diseases, but the studies not been assessed beyond primary sources and the trials should only be considered pre-clinical.
The exact identity (protein primary structure) of the transfer factor is unknown. HPLC studies suggest that a common part in them is the fragment LLYAQD[LV]EDN, a sequence not found in any mammalian genomes.
Uses
Despite a small modicum of successes, transfer factor generated from human blood (human-derived), cow spleen (bovine-derived), or mouse spleen (murine derived) is not in routine clinical use today. A trial investigating its ability to immunize children with leukemia against shingles showed promise in a small number of patients, but represents only one of two placebo-controlled studies.
Instead, transfer factors derived from cow colostrum and/or chicken eggs yolks are used predominantly today.
Side effects
Colostrum-derived transfer factors
Long-term oral administration of colostrum-derived transfer factors has been shown to be safe.
Blood-derived transfer factors
Human-derived transfer factor appears to be safe for use for up to two years and bovine-derived cellular (from blood sources) transfer factor for up to three months. Side effects include fever and swelling and pain at the injection site. Concern has been raised over the possibility of catching Bovine spongiform encephalopathy (Mad Cow Disease) or other diseases from animal blood-derived products. Transfer factors are contraindicated for women who are pregnant or breastfeeding. When human- and bovine-derived transfer factor are generated from blood cells they carry the potential for blood-borne disease such as HIV/AIDS and Hepatitis C.
Transfer factor (dietary supplement) history, claims, and side effects
Colostrum is a form of milk produced by the mammary glands of mammals (including humans) in late pregnancy. Colostrum also contains multiple immune modulating molecules, including high antibody levels. Based on studies noting an overlap in the observed in vitro effects between a molecule contained in colostrum called colostrinin and the dialyzable leukocyte extract mentioned above, a hypothesis formed that the two were the same. There has been no recent research investigations comparing the two entities and thus there is no verifiable evidence that either colostrum or egg whites do or do not contain the cellular product that shares the name transfer factor. The orally available transfer factor is not obtained from humans nor from blood products of any mammal or animal and thus does not carry the presumed risks of contracting blood-borne or animal tissue derived diseases. Retailers of dietary supplement transfer factors advice against use by those with an organ transplant or women that are pregnant.
Colostrum/egg derived transfer factors have been promoted as a treatment for a large number of diseases and health concerns but have not been proven effective in the treatment of any of these conditions. The United States Food and Drug Administration regulates transfer factors as a dietary supplement and has issued a warning notice to a website selling transfer factors that they have not been proven to be effective or safe in the treatment of any condition, nor have there been any biological licenses or New Drug Applications produced for the substance.
See also
Lymphokine
References
External links
Immune system | Transfer factor | [
"Biology"
] | 1,549 | [
"Immune system",
"Organ systems"
] |
2,994,894 | https://en.wikipedia.org/wiki/Semantic%20translation | Semantic translation is the process of using semantic information to aid in the translation of data in one representation or data model to another representation or data model. Semantic translation takes advantage of semantics that associate meaning with individual data elements in one dictionary to create an equivalent meaning in a second system.
An example of semantic translation is the conversion of XML data from one data model to a second data model using formal ontologies for each system such as the Web Ontology Language (OWL). This is frequently required by intelligent agents that wish to perform searches on remote computer systems that use different data models to store their data elements. The process of allowing a single user to search multiple systems with a single search request is also known as federated search.
Semantic translation should be differentiated from data mapping tools that do simple one-to-one translation of data from one system to another without actually associating meaning with each data element.
Semantic translation requires that data elements in the source and destination systems have "semantic mappings" to a central registry or registries of data elements. The simplest mapping is of course where there is equivalence.
There are three types of Semantic equivalence:
Class Equivalence - indicating that class or "concepts" are equivalent. For example: "Person" is the same as "Individual"
Property Equivalence - indicating that two properties are equivalent. For example: "PersonGivenName" is the same as "FirstName"
Instance Equivalence - indicating that two individual instances of objects are equivalent. For example: "Dan Smith" is the same person as "Daniel Smith"
Semantic translation is very difficult if the terms in a particular data model do not have direct one-to-one mappings to data elements in a foreign data model. In that situation, an alternative approach must be used to find mappings from the original data to the foreign data elements. This problem can be alleviated by centralized metadata registries that use the ISO-11179 standards such as the National Information Exchange Model (NIEM).
See also
Data mapping
Federated search
Intelligent agents
ISO/IEC 11179
National Information Exchange Model
Semantic heterogeneity
Semantic mapper
Semantic Web
Vocabulary-based transformation
Web Ontology Language
References
Data management
Enterprise application integration
Semantics | Semantic translation | [
"Technology"
] | 446 | [
"Data management",
"Data"
] |
2,995,108 | https://en.wikipedia.org/wiki/Throughput%20%28business%29 | Throughput is rate at which a product is moved through a production process and is consumed by the end-user, usually measured in the form of sales or use statistics. The goal of most organizations is to minimize the investment in inputs as well as operating expenses while increasing throughput of its production systems. Successful organizations which seek to gain market share strive to match throughput to the rate of market demand of its products.
Overview
In the business management theory of constraints, throughput is the rate at which a system achieves its goal. Oftentimes, this is monetary revenue and is in contrast to output, which is inventory that may be sold or stored in a warehouse. In this case, throughput is measured by revenue received (or not) at the point of sale—exactly the right time. Output that becomes part of the inventory in a warehouse may mislead investors or others about the organizations condition by inflating the apparent value of its assets. The theory of constraints and throughput accounting explicitly avoid that trap.
Throughput can be best described as the rate at which a system generates its products or services per unit of time. Businesses often measure their throughput using a mathematical equation known as Little's law, which is related to inventories and process time: time to fully process a single product.
Basic formula
Using Little's Law, one can calculate throughput with the equation:
where:
I is the number of units contained within the system, inventory;
T is the time it takes for all the inventory to go through the process, flow time;
R is the rate at which the process is delivering throughput, flow rate or throughput.
If you solve for R, you will get:
References
Further reading
Goldratt, Eliyahu and Jeff Cox. The Goal. Croton-on-Hudson: North River Press, 2004.
Business terms
Manufacturing
Production economics | Throughput (business) | [
"Engineering"
] | 380 | [
"Manufacturing",
"Mechanical engineering"
] |
2,995,116 | https://en.wikipedia.org/wiki/Vanlalzawma | Vanlalzawma a politician from Mizoram who was a Member of the Mizoram (Lok Sabha constituency) in the 13th Lok Sabha and 14th Lok Sabha.
Before he became a politician, he was the president of Central Young Mizo Association (CYMA) in 1993 at the age of 37 and served two terms. During this period CYMA had wildlife conservation as its yearly goal ("nungcha humhalh kum" in Mizo) and Vanlalzawma received an award for CYMA from the President of India, for successful wildlife conservation in Mizoram.
At the age of 43, he was elected to be the MP of Mizoram in 1999 (He was a history lecturer prior to this and he has deep interest in education). Immediately after he became the MP in 2000, he successfully pursued the overdue Mizoram University Bill in the Parliament. Which as a result, Mizoram University (MZU) was established on 2 July 2001, by the Mizoram University Act (2000) of the Parliament of India.
He is a good mathematician and besides his career he loves playing Chess. He was the highest rated chess player in Mizoram for several years. He is also very good at running and has won several medals at Mizoram games in 100 meters sprint.
In the confidence voting on 22 July 2008 that the United Progressive Alliance (UPA) won with a 275-256 margin. Among these ten, two MPs toed their party line of equidistance from the Indian National Congress and Bharatiya Janata Party (BJP). Those two are:
Trinamool Congress: Mamata Banerjee and
Mizo National Front: Vanlalzawma
Education
He was educated in Pachhunga University College and North-Eastern Hill University (NEHU)and has completed his Education in MA History.
Career
He served as lecturer in Hrangbana College and was elected as President of Young Mizo Association (YMA), the largest NGO in Mizoram.
Politics
He is a member of the Mizo National Front and has represented the Mizoram constituency in the Lok Sabha since 1999. He was a member of the following committees.
Member of Committee on Petroleum & Natural Gas
Member of Consultative Committee, Department of Youth Affairs and Sports.
Member of Committee on Human Resource Development.
Member of Committee on Ministry of Communications and Information Technology
References
Lok Sabha Member's homepage.
1956 births
Living people
Wildlife conservation
Mizo people
India MPs 2004–2009
People from Lunglei
India MPs 1999–2004
North-Eastern Hill University alumni
Lok Sabha members from Mizoram
Mizoram MLAs 2013–2018
Leaders of the Opposition in Mizoram | Vanlalzawma | [
"Biology"
] | 547 | [
"Wildlife conservation",
"Biodiversity"
] |
2,995,237 | https://en.wikipedia.org/wiki/Glucocorticoid%20receptor | The glucocorticoid receptor (GR or GCR) also known as NR3C1 (nuclear receptor subfamily 3, group C, member 1) is the receptor to which cortisol and other glucocorticoids bind.
The GR is expressed in almost every cell in the body and regulates genes controlling the development, metabolism, and immune response. Because the receptor gene is expressed in several forms, it has many different (pleiotropic) effects in different parts of the body.
When glucocorticoids bind to GR, its primary mechanism of action is the regulation of gene transcription. The unbound receptor resides in the cytosol of the cell. After the receptor is bound to glucocorticoid, the receptor-glucocorticoid complex can take either of two paths. The activated GR complex up-regulates the expression of anti-inflammatory proteins in the nucleus or represses the expression of pro-inflammatory proteins in the cytosol (by preventing the translocation of other transcription factors from the cytosol into the nucleus).
In humans, the GR protein is encoded by gene which is located on chromosome 5 (5q31).
Structure
Like the other steroid receptors, the glucocorticoid receptor is modular in structure and contains the following domains (labeled A - F):
A/B - N-terminal regulatory domain
C - DNA-binding domain (DBD)
D - hinge region
E - ligand-binding domain (LBD)
F - C-terminal domain
Ligand binding and response
In the absence of hormone, the glucocorticoid receptor (GR) resides in the cytosol complexed with a variety of proteins including heat shock protein 90 (hsp90), the heat shock protein 70 (hsp70) and the protein FKBP4 (FK506-binding protein 4). The endogenous glucocorticoid hormone cortisol diffuses through the cell membrane into the cytoplasm and binds to the glucocorticoid receptor (GR) resulting in release of the heat shock proteins. The resulting activated form GR has two principal mechanisms of action, transactivation and transrepression, described below.
Transactivation
A direct mechanism of action involves homodimerization of the receptor, translocation via active transport into the nucleus, and binding to specific DNA response elements activating gene transcription. This mechanism of action is referred to as transactivation. The biological response depends on the cell type.
Transrepression
In the absence of activated GR, other transcription factors such as NF-κB or AP-1 themselves are able to transactivate target genes. However activated GR can complex with these other transcription factors and prevent them from binding their target genes and hence repress the expression of genes that are normally upregulated by NF-κB or AP-1. This indirect mechanism of action is referred to as transrepression. GR transrepression via NF-κB and AP-1 is restricted only to certain cell types, and is not considered the universal mechanism for IκBα repression.
Clinical significance
The GR is abnormal in familial glucocorticoid resistance.
In central nervous system structures, the glucocorticoid receptor is gaining interest as a novel representative of neuroendocrine integration, functioning as a major component of endocrine influence - specifically the stress response - upon the brain. The receptor is now implicated in both short and long-term adaptations seen in response to stressors and may be critical to the understanding of psychological disorders, including some or all subtypes of depression and post-traumatic stress disorder (PTSD). Indeed, long-standing observations such as the mood dysregulations typical of Cushing's disease demonstrate the role of corticosteroids in regulating psychologic state; recent advances have demonstrated interactions with norepinephrine and serotonin at the neural level.
In preeclampsia (a hypertensive disorder commonly occurring in pregnant women), the level of a miRNA sequence possibly targeting this protein is elevated in the blood of the mother. Rather, the placenta elevates the level of exosomes containing this miRNA, which can result in inhibition of translation of molecule. Clinical significance of this information is not yet clarified.
Agonists and antagonists
Dexamethasone and other corticosteroids are agonists, while mifepristone and ketoconazole are antagonists of the GR. Anabolic steroids also prevent cortisol from binding to the glucocorticoid receptor.
Interactions
Glucocorticoid receptor has been shown to interact with:
BAG1,
CEBPB,
CREBBP,
DAP3,
DAXX,
HSP90AA1,
HNRPU,
MED1,
MED14,
Mineralocorticoid receptor,
NRIP1,
NCOR1,
NCOA1,
NCOA2,
NCOA3,
POU2F1,
RANBP9,
RELA,
SMAD3,
SMARCD1,
SMARCA4
STAT3,
STAT5B,
Thioredoxin,
TRIM28, and
YWHAH.
See also
Membrane glucocorticoid receptor
Selective glucocorticoid receptor agonist (SEGRA)
References
Further reading
External links
Human Protein Reference Database
Genome projects
3 | Glucocorticoid receptor | [
"Biology"
] | 1,133 | [
"Genome projects"
] |
2,995,449 | https://en.wikipedia.org/wiki/Bell%20jar | A bell jar is a glass jar, similar in shape to a bell (i.e. in its best-known form it is open at the bottom, while its top and sides together are a single piece), and can be manufactured from a variety of materials (ranging from glass to different types of metals). Bell jars are often used in laboratories to form and contain a vacuum. It is a common science apparatus used in experiments. Bell jars have a limited ability to create strong vacuums; vacuum chambers are available when higher performance is needed. They have been used to demonstrate the effect of vacuum on sound propagation.
In addition to their scientific applications, bell jars may also serve as display cases or transparent dust covers. In these situations, the bell jar is not usually placed under vacuum.
Vacuum
A vacuum bell jar is placed on a base which is vented to a hose fitting, that can be connected via a hose to a vacuum pump. A vacuum is formed by pumping the air out of the bell jar.
The lower edge of a vacuum bell jar forms a flange of heavy glass, ground smooth on the bottom for better contact. The base of the jar is equally heavy and flattened. A smear of vacuum grease is usually applied between them. As the vacuum forms inside, it creates a considerable compression force, so there is no need to clamp the seal. For this reason, a bell jar cannot be used to contain pressures above atmospheric, only below.
Bell jars are generally used for classroom demonstrations or by hobbyists, when only a relatively low-quality vacuum is required. Cutting-edge research done at ultra-high vacuum requires a more sophisticated vacuum chamber. However, several tests may be completed in a bell jar chamber having an effective pump and low leak rate.
Some of the first scientific experiments using a bell jar to provide a vacuum were reported by Robert Boyle. In his book, New Experiments Physico-Mechanicall, Touching the Spring of the Air, and its Effects, (Made, for the Most Part, in a New Pneumatical Engine), he described 43 separate experiments, some of which were carried out with Robert Hooke, investigating the effect of reducing the air pressure within the bell jar on the objects contained within.
Sound propagation experiments
One of the best known of these experiments involved placing a ringing bell inside the jar, and observing that upon pumping out the air, the ringing disappeared. This experiment demonstrated that the propagation of sound is mediated by the air, and that in the absence of the air medium, the sound waves cannot travel. This experiment is often used as a classroom science experiment, where the experiment is repeated with an item such as an alarm clock placed under a bell jar, and the noise of the alarm clock fading as the air is pumped out being used to demonstrate the effect. By additionally placing a microphone inside the bell jar and observing that the sound detected by the microphone reduces as the air is pumped out, the effect of absorbance of the sound by the glass of the jar itself can be excluded.
Candle in a bell jar experiments
Another common experiment using a bell jar involves placing a jar over a lit candle, and observing that the flame goes out, demonstrating that oxygen is required for combustion. A common variation of this experiment is to place the candle and bell jar over water, and to observe that when the candle extinguishes, the water level will rise inside the bell jar. The explanation for this observation is that the heating of the air inside the jar by the candles causes it to expand, and when the candle has exhausted the oxygen supply and extinguishes, the air will cool and contract, leading to the water being drawn up to fill the space. A common misconception is that the water level rises to replace the consumed oxygen, but since the combustion reaction produces carbon dioxide gas as a product, this explanation is not correct.
Joseph Priestley also used a candle and a mint plant placed beneath a bell jar in an experiment reported in Experiments and Observations on Different Kinds of Air to demonstrate the effect of photosynthesis. The candle was initially lit, and then the bell jar placed over the two items, and once the oxygen had been consumed by the candle, the flame extinguished. However, the candle was able to be reignited a number of days later, demonstrating that the plant had produced the oxygen required.
Physiological experiments
Priestley also carried out experiments using plants and mice beneath a bell jar. He found that whilst a mouse kept alone inside a bell jar eventually died, when a plant was also placed inside the jar the mouse would survive.
Boyle also studied the effect of removing the air from bell jars containing a number of different animals including insects, mice, birds and fish and observed how they reacted when the air was removed. In "Experiment 40", from New Experiments Physico-Mechanicall, Touching the Spring of the Air, and its Effects, (Made, for the Most Part, in a New Pneumatical Engine) he tested the ability of insects to fly under reduced air pressure, whilst in "Experiment 41," he demonstrated the reliance of living creatures on air for their survival.
The oil painting An Experiment on a Bird in the Air Pump depicts a natural philosopher repeating a similar experiment to that of Boyle with a bird inside a bell jar.
Risks
A vacuum produces a pressure difference of one atmosphere, approximately 14 psi, over the surface of the glass. The energy contained within an implosion is defined by the pressure difference and the volume evacuated. Flask volumes can change by orders of magnitude between experiments. Whenever working with liter sized or larger flasks, chemists should consider using a safety screen or the sash of a flow hood to protect them from shards of glass, should an implosion occur. Glassware can also be wrapped with spirals of tape to catch shards, or wrapped with webbed mesh more commonly seen on scuba cylinders.
Glass under vacuum becomes more sensitive to chips and scratches in its surface, as these form stress risers, so older glass is best avoided if possible. Impacts to the glass and thermally induced stresses are also concerns under vacuum. Round bottom flasks more effectively spread the stress across their surfaces, and are therefore safer when working under vacuum.
Decorative or preservative
Purely decorative bell jars were commonly used in the Victorian period to display and serve as transparent dust covers and display cases for a wide variety of items, including clocks, taxidermy, shells, and wax flowers and fruit. Decorative bell jars were made of thin glass, with more care being taken regarding their optical clarity, and they did not have a thickened base flange. For this reason, they are not suitable for vacuum use and would usually fail if pumped down.
Similar glass domes were used as cheese domes or cakebells.
In popular culture
"The Jar" (November 1944) is a short story by Ray Bradbury, published in Weird Fiction
Under a Glass Bell (1944) is a short story collection by Anaïs Nin
The Bell Jar (1963) is a roman à clef by Sylvia Plath, originally published under the pen name "Victoria Lucas"
See also
References
Vacuum systems
Laboratory equipment | Bell jar | [
"Physics",
"Engineering"
] | 1,450 | [
"Vacuum systems",
"Vacuum",
"Matter"
] |
2,995,450 | https://en.wikipedia.org/wiki/Seeligerite | Seeligerite is a rare complex lead chloride iodate mineral with formula: Pb3Cl3(IO3)O. It is a yellow mineral crystallizing in the orthorhombic system. It has perfect to good cleavage in two directions and a quite high specific gravity of 6.83 due to the lead content. It is translucent to transparent with refractive indices of nα=2.120 nβ=2.320 nγ=2.320.
It was first reported in 1971 from the Casucha Mine, Sierra Gorda, Antofagasta Region, Chile.
References
Lead minerals
Oxide minerals
Iodates
Orthorhombic minerals
Minerals in space group 20
Oxychlorides | Seeligerite | [
"Chemistry"
] | 145 | [
"Iodates",
"Oxidizing agents"
] |
2,995,499 | https://en.wikipedia.org/wiki/Crosstalk | In electronics, crosstalk is a phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. Crosstalk is usually caused by undesired capacitive, inductive, or conductive coupling from one circuit or channel to another.
Where the electric, magnetic, or traveling fields of two electric signals overlap, the electromagnetic interference created causes crosstalk. For example, crosstalk can comprise magnetic fields that induce a smaller signal in neighboring wires.
In electrical circuits sharing a common signal return path, electrical impedance in the return path creates between the signals, resulting in crosstalk.
Crosstalk is a significant issue in structured cabling, audio electronics, integrated circuit design, wireless communication and other communications systems.
In cabling
In structured cabling, crosstalk refers to electromagnetic interference from one unshielded twisted pair to another twisted pair, normally running in parallel. Signals traveling through adjacent pairs of wire create magnetic fields that interact with each other, inducing interference in the neighboring pair. The pair causing the interference is called the disturbing pair, while the pair experiencing the interference is the disturbed pair.
(NEXT) NEXT is a measure of the ability of a cable to reject crosstalk, so the higher the NEXT value, the greater the rejection of crosstalk at the local connection. It is referred to as near end because the interference between the two signals in the cable is measured at the same end of the cable as the interfering transmitter. The NEXT value for a given cable type is generally expressed in decibels per feet or decibels per 1000 feet and varies with the frequency of transmission. General specifications for cabling (such as CAT 5) usually include the minimum NEXT values.
Power sum near-end crosstalk (PSNEXT) PSNEXT is a NEXT measurement which includes the sum of crosstalk contributions from all adjacent pairs as an algebraic sum of the NEXT of the three wire pairs as they affect the fourth pair in a four-pair cable (e.g., Category 6 cable). The Superior Modular Products White paper states that the testing process for PSNEXT consists of measuring all pair-to-pair crosstalk combinations and then summing all of the values for each pair. The specification was developed to directly address the effect of transmissions on multiple adjacent pairs on the pair being tested and is relevant to all connecting hardware and associated communications cables. Cabling bandwidth in excess of 100 MHz (Category 5 cable bandwidth) make consideration of PSNEXT more important as Gigabit Ethernet through Cat 6 uses all four wire pairs simultaneously and bidirectionally. The additional wire pair usage and growing bandwidth increases the need to keep NEXT in check.
(FEXT) FEXT measures the interference between two pairs of a cable measured at the far end of the cable with respect to the interfering transmitter.
Equal level far end crosstalk (ELFEXT) ELFEXT measures the FEXT with attenuation compensation.
(AXT) AXT is interference caused by other cables routed close to the cable of interest as opposed to signals contained in the same cable.
In audio
In stereo audio reproduction, crosstalk can refer to signal leakage across from one program channel to another, reducing channel separation and stereo imaging. Crosstalk between channels in mixing consoles, and between studio feeds is a much more noticeable problem, as these are likely to be carrying very different programs or material.
Crosstalk is an electrical effect and can be quantified with a crosstalk measurement. Crosstalk measurements are made on audio systems to determine the amount of signal leaking from one channel to another. The Independent Broadcasting Authority published a weighting curve for use in crosstalk measurement that gives due emphasis to the subjective audibility of different frequencies. In the absence of any international standards, this is still in use despite the demise of the IBA.
Good crosstalk performance for a stereo system is not difficult to achieve in today's digital audio systems, though it is difficult to keep below the desired figure of −30 dB or so on vinyl recordings and FM radio.
Other examples
In telecommunication or telephony, crosstalk is often distinguishable as pieces of speech or in-band signaling tones leaking from other people's connections. If the connection is analog, twisted pair cabling can often be used to reduce crosstalk. Alternatively, the signals can be converted to digital form, which is typically less susceptible to crosstalk.
In wireless communication, crosstalk is often denoted co-channel interference, and is related to adjacent-channel interference.
In integrated circuit design, crosstalk normally refers to a signal affecting another nearby signal. Usually, the coupling is capacitive, and to the nearest neighbor, but other forms of coupling and effects on signal further away are sometimes important, especially in analog designs. See signal integrity for tools used to measure and prevent this problem, and substrate coupling for a discussion of crosstalk conveyed through the integrated circuit substrate. There are a wide variety of repair solutions, with increased spacing, wire re-ordering, and shielding being the most common.
In full-field optical coherence tomography, "crosstalk" refers to the phenomenon that due to highly scattering objects, multiple scattered photons reach the image plane and generate a coherent signal after travelling a path length that matches that of the sample depth within a coherence length.
In stereoscopic 3D displays, crosstalk refers to the incomplete isolation of the left and right image channels so that one bleeds into the other – like a double exposure, which produces a ghosting effect.
See also
Attenuation-to-crosstalk ratio
Audio system measurements
Print-through
Signal integrity
Signal-to-interference ratio (SIR or S/I), also known as carrier-to-interference ratio (CIR or C/I)
Substrate coupling
Unger model
References
External links
Minimizing Crosstalk in Wiring and Cabling
Electrical phenomena
Electrical parameters
Electromagnetic compatibility
Audio amplifier specifications
Telecommunication theory
Audio engineering
Broadcast engineering
Sound measurements | Crosstalk | [
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"Electromagnetic compatibility",
"Physical quantities",
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"Electronic engineering",
"Electrical phenomena",
"Electrical engineering",
"Audio engineering",
"Audio amplifier specifications",
"El... |
2,995,501 | https://en.wikipedia.org/wiki/Crosstalk%20%28biology%29 | Biological crosstalk refers to instances in which one or more components of one signal transduction pathway affects another. This can be achieved through a number of ways with the most common form being crosstalk between proteins of signaling cascades. In these signal transduction pathways, there are often shared components that can interact with either pathway. A more complex instance of crosstalk can be observed with transmembrane crosstalk between the extracellular matrix (ECM) and the cytoskeleton.
Crosstalk between signalling pathways
One example of crosstalk between proteins in a signalling pathway can be seen with cyclic adenosine monophosphate's (cAMP) role in regulating cell proliferation by interacting with the mitogen-activated protein (MAP) kinase pathway. cAMP is a compound synthesized in cells by adenylate cyclase in response to a variety of extracellular signals. cAMP primarily acts as an intracellular second messenger whose major intracellular receptor is the cAMP-dependent protein kinase (PKA) that acts through the phosphorylation of target proteins. The signal transduction pathway begins with ligand-receptor interactions extracellularly. This signal is then transduced through the membrane, stimulating adenylyl cyclase on the inner membrane surface to catalyze the conversion of ATP to cAMP.
ERK, a participating protein in the MAPK signaling pathway, can be activated or inhibited by cAMP. cAMP can inhibit ERKs in a variety of ways, most of which involve the cAMP-dependent protein kinase (PKA) and the inhibition of Ras-dependent signals to Raf-1. However, cAMP can also stimulate cell proliferation by stimulating ERKs. This occurs through the induction of specific genes via phosphorylation of the transcription factor CREB by PKA. Though ERKs do not appear to be a requirement for this phosphorylation of CREB, the MAPK pathway does play into crosstalk again, as ERKs are required to phosphorylate proteins downstream of CREB. Other known examples of the requirement of ERKs for cAMP-induced transcriptional effects include induction of the prolactin gene in pituitary cells, and of the dopamine beta-hydroxylate gene in pheochromocytomal cells (PC12). A number of diverse mechanisms exist by which cAMP can influence ERK signaling. Most mechanisms involving cAMP inhibition of ERKs uncouple Raf-1 from Ras activation through direct interaction of PKA with Raf-1 or indirectly through PKA interaction with the GTPase Rap1 (see figure 1). PKA may also negatively regulate ERKs by the activation of PTPases. Mechanisms for the activation of ERKs by cAMP are even more varied, usually including Rap1 or Ras, and even cAMP directly.
Transmembrane crosstalk
Crosstalk can even be observed across membranes. Membrane interactions with the extracellular matrix (ECM) and with neighboring cells can trigger a variety of responses within the cell. However, the topography and mechanical properties of the ECM also come to play an important role in powerful, complex crosstalk with the cells growing on or inside the matrix. For example, integrin-mediated cytoskeleton assembly and even cell motility are affected by the physical state of the ECM. Binding of the α5β1 integrin to its ligand (fibronectin) activates the formation of fibrillar adhesions and actin filaments. Yet, if the ECM is immobilized, matrix reorganization of this kind and formation of fibrillar adhesions is inhibited. In turn, binding of the same integrin (α5β1) to an immobilized fibronectin ligand is seen to form highly phosphorylated focal contacts/focal adhesion (cells involved in matrix adhesion) within the membrane and reduces cell migration rates In another example of crosstalk, this change in the composition of focal contacts in the cytoskeleton can be inhibited by members of yet another pathway: inhibitors of myosin light-chain kinases or Rho kinases, H-7 or ML-7, which reduce cell contractility and consequently motility. (see figure 2).
Crosstalk in lymphocyte activation
A more complex, specific example of crosstalk between two major signaling pathways can be observed with the interaction of the cAMP and MAPK signaling pathways in the activation of lymphocytes. In this case, components of the cAMP pathway directly and indirectly affect MAPK signaling pathway meant to activate genes involving immunity and lymphocytes.
Newly formed cAMP is released from the membrane and diffuses across the intracellular space where it serves to activate PKA. The catalytic subunit of PKA must bind four molecules of cAMP to be activated, whereupon activation consists of cleavage between the regulatory and catalytic subunits. This cleavage in turn activates PKA by exposing the catalytic sites of the C subunits, which can then phosphorylate an array of proteins in the cell.
In lymphocytes, the intracellular levels of cAMP increase upon antigen-receptor stimulation and even more so in response to prostaglandin E and other immunosuppression agents. In this case, cAMP serves to inhibit immunity players. PKA type I colocalizes with the T-cell and B-cell antigen receptors and causes inhibition of T- and B-cell activation. PKA has even been highlighted as a direct inducer of genes contributing to immunosuppression.
Additionally, the cAMP pathway also interacts with the MAPK pathway in a more indirect manner through its interaction with hematopoietic PTPase (HePTP). HePTP is expressed in all leukocytes. When overexpressed in T-cells, HePTP reduces the transcriptional activation of the interleukin-2 promoter typically induced by the activated T-cell receptor through a MAPK signaling cascade. The way that HePTP effectively inhibits the MAPK signaling is by interacting with the MAP kinases Erk1, Erk2, and p38 through a short sequence in HePTP's non-catalytic N terminus termed the kinase interaction motif (KIM)., The highly-specific binding of Erk and p38 to this subunit of HePTP results in rapid inactivation of the signaling cascade (see figure 3).
Yet, since both HePTP and Erk are cytosolic enzymes, it is reasonable to conclude that there exists a mechanism for the inhibition of Erk by HePTP to cease in order to allow for the translocation of activated Erk to the nucleus. Indeed, like in many other cases of protein-protein interaction, HePTP appears to be phosphorylated by Erk and p38 at the sites Thr45 and Ser72. Importantly though, a third phosphorylation site in the non-catalytic N terminus (the KIM region) of HePTP has been found—one that is phosphorylated to a much higher stoichiometry by the cAMP pathway, in yet another instance of crosstalk between the cAMP and MAPK pathways.
Phosphorylation of this third site by PKAs from the cAMP pathway inhibits binding of MAP kinases to HePTP and thereby upregulates the MAPK/ERK signaling cascade. The MAPK pathway, through Ras, Raf, Mek, and Erk, shows low activity in the presence of unphosphorylated (active) HePTP. However, activation the cAMP pathway stimulates the activation of PKA, which in turn phosphorylates HePTP at Ser23. This prevents HePTP from binding to Erk and frees the MAPK pathway from inhibition, allowing downstream signaling to continue (see figure 4).
Moreover, studies involving smooth muscle cells from the atrium of the heart have shown that PKA can reduce the activation of MAP kinases in response to platelet-derived growth factor (PDGF) by phosphorylating the kinase c-Raf. Thus, it seems plausible that PKA in the cAMP pathway could even be further involved in the regulation of lymphocyte activation not only by inhibiting the antigen-receptor MAPK signal pathway at its final stage, but even further upstream.
Notes and references
Signal transduction | Crosstalk (biology) | [
"Chemistry",
"Biology"
] | 1,732 | [
"Biochemistry",
"Neurochemistry",
"Signal transduction"
] |
2,995,508 | https://en.wikipedia.org/wiki/Sony%20HDVS | Sony HDVS (High-Definition Video System) is a range of high-definition video equipment developed in the 1980s to support the Japanese Hi-Vision standard which was an early analog high-definition television system (used in multiple sub-Nyquist sampling encoding (MUSE) broadcasts) thought to be the broadcast television systems that would be in use today. The line included professional video cameras, video monitors and linear video editing systems.
History
Sony first demonstrated a wideband analog video HDTV capable video camera, monitor and video tape recorder (VTR) in April 1981 at an international meeting of television engineers in Algiers, Algeria.
The HDVS range was launched in April 1984, with the HDC-100 camera, which was the world's first commercially available HDTV camera and HDV-1000 video recorder, with its companion HDT-1000 processor/TBC, and HDS-1000 video switcher all working in the 1125-line component video format with interlaced video and a 5:3 aspect ratio. The first system consisting of a monitor, camera and VTR was sold by Sony in 1985 for $1.5 million, and the first HDTV production studio, Captain Video, was opened in Paris.
The helical scan VTR (the HDV-100) used magnetic tape similar to 1" type C videotape for analog recording. Sony in 1988 unveiled a new HDVS digital line, including a reel-to-reel digital recording VTR (the HDD-1000) that used digital signals between the machines for dubbing but the primary I/O remained analog signals. The Sony HDVS HDC-300 camera was also introduced. The large HDD-1000 unit was housed in a 1-inch reel-to-reel transport, and because of the high tape speed needed, had a limit of 1-hour per reel. By this time, the aspect ratio of the system had been changed to 16:9. Sony, owner of Columbia Pictures/Tri-Star, would start to archive feature films on this format, requiring an average of two reels per movie. There was also a portable videocassette recorder (the HDV-10) for the HDVS system, using the "UniHi" format of videocassette using 1/2" wide tape. The tape housing is similar in appearance to Sony's D1/D2 Standard Definition Digital VTRs, but recorded analog HD. The small cassette size limited recording time to about 63 min.
The price of the HDD-1000 and its required companion HDDP-1000 video processor in 1988 was US$600,000. The metal evaporate tape (tape whose magnetic material was evaporated and deposited onto the tape in a vacuum chamber using physical vapor deposition) cost US$2500.00 per hour of tape and each reel weighed nearly 10 pounds. The high price of the system limited its adoption severely, selling just several dozen systems and making its adoption largely limited to medical, aerospace engineering, and animation applications. In 1986, HDVS systems cost $1.5 million, and 30-40 were sold until then. Sony HDVS systems made video with a total of 1125 (horizontal) lines, and 1035 active lines of resolution.
The Sony HDL-5800 had a price of over 56,000 US dollars
Uses
The Sony HDVS system was used in the production of a 5-min feature film about Halley's Comet in 1986, titled "Arrival", and shown in US theatres later that year after being transferred to 35mm film.
The first drama film shot using the HDVS professional video camera was RAI's Julia and Julia (Italian: ) in 1987, and the first HDTV television show was CBC's Chasing Rainbows, shot using the HDVS system in 1988. For the Genesis Invisible Touch Tour shows at Wembley Stadium in July 1987, the Sony HDVS system was used to film these shows, which were later released on VHS and LaserDisc in 1988 and DVD in 2003.
Montreux Jazz Festival in 1991 was recorded using the Sony HDVS video system. Four HDC-300 cameras in 1125-line format (1035i visible, close to 1080i today), 60 fps, and one Sony HDC-500 3 CCD prototype HDVS camera were used. The five cameras were connected to a 7-input HDS-1000T switcher and the live mix was recorded to an HDD-1000 Digital 1" VTR.
World War II: When Lions Roared (also known as Then There Were Giants) is a 1994 TV movie, directed by Joseph Sargent, that stars John Lithgow, Michael Caine and Bob Hoskins as the three major Allied leaders. It was the first video production to be produced in the 1125-line high-definition television (HDTV) format. It was converted to NTSC for broadcast in the United States.
The HDVS brand and logo was still used by Sony since 1997 as "Digital HDVS" on their digital high-definition HDCAM-format cameras such as the HDW-750, HDW-F900, HDC-1550, "Power HAD" camera Sony HSC-300 Series, and XDCAM camera PDW-850, PXW-X500. By 2022, HDVS branded cameras have been discontinued and new camera models released don't have the HDVS logo.
Equipment
Camera system
HDC-100 High Definition Color Camera (3 tube Saticon)
HDC-300 High Definition Color Camera (3 tube Saticon) (Sony HDVS cameras weigh on average.)
HDC-500 High Definition Color Camera (3 CCD, world's first CCD-based HD video camera)
HDCA-350 Camera Adapter
HDCA-50 Camera Adapter
HDCO-300 Camera Operation Control Unit (CCU)
HDCO-350 Camera Operation Control Unit (CCU)
HDCS-300 Camera Signal Processor
HDCS-350 Camera Signal Processor
Camera system/Optional accessories
HDCC-2/5/50/100 Multicore Cable (2m, 5m 50m, 100m)
HDCD-50 Signal Distributor
HDCR-350 Remote Control Panel
HDM-140 14 inch Monochrome monitor
HDM-145 14 inch Monochrome monitor
HDM-90 9-inch Monochrome monitor
HDVF-150 1.5-inch Viewfinder
HDVF-30 3-inch viewfinder
HDVF-500 5-inch viewfinder
HDVF-700 7-inch viewfinder
HDVF-75 7-inch viewfinder
HKCF-750 Pan Tilt Table
HKCF-90 Rack Mount Plate Kit
HKCH-500 Shoulder Pad
VTR system
HDD-1000 Digital 1" Type C VTR (Wide band (30 MHz) Y, PB, PR) with BVH-3000 like operation and appearance. It used two sets of separate flying erase, record and video heads with a higher linear tape speed than Type C videotape, of 80.5 cm/sec and a writing speed at the heads of 51.5m/sec, 30 MHz luma and 15 MHz chroma bandwidth, uses HD-1D series tape
HDDP-1000 VTR Signal Processor (8-bit digital, required by the HDD-1000 for operation)
HDV-1000 Analog VTR (based on Sony's BVH-2000 1" Type C standard-definition VTR, unlike most Type C VTRs it used separate video and video record heads.) It had a linear tape speed of 48.31 cm/sec and a writing speed at the heads, of 25.9m/sec, 20 MHz luma and 10 MHz chroma bandwidth and a 63-min recording time with 11.75 inch tape reels, could use the same conventional tape as the BVH-2000 type C VTR.
HDT-1000 TBC/Signal Processor (required by the HDV-1000 for operation)
HDDF-500 Digital Frame Recorder (G, B, R)
HDDR-1000 VTR Control Unit
HDDR-A1000 Audio Remote Control Unit
HDDR-V1000 Video Remote Control Unit
HDL-2000 Videodisc Player, 20 MHz luma and 6 MHz chroma bandwidth
HDL-5800 Video Disc Recorder, same bandwidths as the HDL-2000, 3 min record time per side of disc in CAV mode, 10 mins per side in CLV mode, and for read only (pre recorded/pressed/replicated) discs, 8 min playback time per side in CAV mode, and 15 mins per side in CLV mode. 20 MHz luma and 6 MHz chroma bandwidth. Had a price of over 50,000 US dollars and requires optical discs to be placed in a cartridge.
HDN-22000 NTSC Down-Converter
HDV-10 Videocassette Recorder (UNIHI), with a tape speed of 119.7mm/sec and a writing speed at the heads of 21.4m/sec with HCT-63 cassette, 20 MHz bandwidth for Y component video signal/luma, 7 MHz bandwidth for YB and YR component video signals/chroma
Optional accessories
HCT-63 UNIHI videocassette, with 465m of 1/2 inch magnetic tape and a recording time of 63 minutes with HDV-10 recorder
HD-1D Series High Quality Video Tape (1-inch) for use with the HDD- 1000, similar to type C videotape, has a 63 minute record time with 11.75 inch reels holding 3,080 meters of tape
HDIE-100 HD camera image enhancer
HDIP-100 HD camera image enhancer power unit
HDKF-508 Frame Memory Board (8 frames)
HDSC-1000 Sync Converter
HKDF-504 Frame Memory Board (4 frames)
LBX-1000 Lightbox for use with the HDST-100T Telop Camera
VF-503 Monitor Hood
Post-production equipment
EBR System, Digital Electron Beam Recording (EBR) System (Video Tape to Film, Film recorder)
HDS-1000 Switcher
HDST-1000T Telop Camera (Saticon)
Optical Fiber Transmission System
(G/B/R analog component video (signals for Green, Blue and Red portions of images with Green for sync,
a kind of RGB (component) video Analog audio x2; AES/EBU x6)
HDFR-300 Optical Fiber Receiver
HDFT-300 Optical Fiber Transmitter
Projection system
HDI-120 Concave Screen-Type Projector System
HDIH-1200/1200M High Definition Projector
HDIH-2000/2000M High Definition Projector
HDIH-3000/3000M High Definition Projector
HDIR-550 High Definition Rear Projector
HDIS-1200RK Rear Projection
Color monitors
HDM-1220/1220E 12" Color monitor
HDM-1230/1230E 12" Color monitor
HDM-1730/1730E 17" Color monitor
HDM-1820/1820E 18" Color monitor
HDM-2820/2820E 28" Color monitor
HDM-2830/2830E 28" Color monitor
HDM-3720/3720E 37" Color monitor
HDM-3830/3830E 38" Color monitor
References
External links
Sony corp history page
Sony corp history page 2
Sony copy history page 3
Television technology
High-definition television
Japanese inventions
Audiovisual introductions in 1984
Sony products | Sony HDVS | [
"Technology"
] | 2,379 | [
"Information and communications technology",
"Television technology"
] |
2,995,566 | https://en.wikipedia.org/wiki/Zolotarev%27s%20lemma | In number theory, Zolotarev's lemma states that the Legendre symbol
for an integer a modulo an odd prime number p, where p does not divide a, can be computed as the sign of a permutation:
where ε denotes the signature of a permutation and πa is the permutation of the nonzero residue classes mod p induced by multiplication by a.
For example, take a = 2 and p = 7. The nonzero squares mod 7 are 1, 2, and 4, so (2|7) = 1 and (6|7) = −1. Multiplication by 2 on the nonzero numbers mod 7 has the cycle decomposition (1,2,4)(3,6,5), so the sign of this permutation is 1, which is (2|7). Multiplication by 6 on the nonzero numbers mod 7 has cycle decomposition (1,6)(2,5)(3,4), whose sign is −1, which is (6|7).
Proof
In general, for any finite group G of order n, it is straightforward to determine the signature of the permutation πg made by left-multiplication by the element g of G. The permutation πg will be even, unless there are an odd number of orbits of even size. Assuming n even, therefore, the condition for πg to be an odd permutation, when g has order k, is that n/k should be odd, or that the subgroup <g> generated by g should have odd index.
We will apply this to the group of nonzero numbers mod p, which is a cyclic group of order p − 1. The jth power of a primitive root modulo p will have index the greatest common divisor
i = (j, p − 1).
The condition for a nonzero number mod p to be a quadratic non-residue is to be an odd power of a primitive root.
The lemma therefore comes down to saying that i is odd when j is odd, which is true a fortiori, and j is odd when i is odd, which is true because p − 1 is even (p is odd).
Another proof
Zolotarev's lemma can be deduced easily from Gauss's lemma and vice versa. The example
,
i.e. the Legendre symbol (a/p) with a = 3 and p = 11, will illustrate how the proof goes. Start with the set {1, 2, . . . , p − 1} arranged as a matrix of two rows such that the sum of the two elements in any column is zero mod p, say:
Apply the permutation :
The columns still have the property that the sum of two elements in one column is zero mod p. Now apply a permutation V which swaps any pairs in which the upper member was originally a lower member:
Finally, apply a permutation W which gets back the original matrix:
We have W−1 = VU. Zolotarev's lemma says (a/p) = 1 if and only if the permutation U is even. Gauss's lemma says (a/p) = 1 iff V is even. But W is even, so the two lemmas are equivalent for the given (but arbitrary) a and p.
Jacobi symbol
This interpretation of the Legendre symbol as the sign of a permutation can be extended to the Jacobi symbol
where a and n are relatively prime integers with odd n > 0: a is invertible mod n, so multiplication by a on Z/nZ is a permutation and a generalization of Zolotarev's lemma is that the Jacobi symbol above is the sign of this permutation.
For example, multiplication by 2 on Z/21Z has cycle decomposition (0)(1,2,4,8,16,11)(3,6,12)(5,10,20,19,17,13)(7,14)(9,18,15), so the sign of this permutation is (1)(−1)(1)(−1)(−1)(1) = −1 and the Jacobi symbol (2|21) is −1. (Note that multiplication by 2 on the units mod 21 is a product of two 6-cycles, so its sign is 1. Thus it's important to use all integers mod n and not just the units mod n to define the right permutation.)
When n = p is an odd prime and a is not divisible by p, multiplication by a fixes 0 mod p, so the sign of multiplication by a on all numbers mod p and on the units mod p have the same sign. But for composite n that is not the case, as we see in the example above.
History
This lemma was introduced by Yegor Ivanovich Zolotarev in an 1872 proof of quadratic reciprocity.
References
External links
PlanetMath article on Zolotarev's lemma; includes his proof of quadratic reciprocity
Articles containing proofs
Lemmas in number theory
Permutations
Quadratic residue
Squares in number theory | Zolotarev's lemma | [
"Mathematics"
] | 1,102 | [
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"Permutations",
"Mathematical objects",
"Combinatorics",
"Theorems in number theory",
"Mathematical relations",
"Articles containing proofs",
"Lemmas in number theory",
"Lemmas",
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"Number theory"
] |
2,995,611 | https://en.wikipedia.org/wiki/Theta%20correspondence | In mathematics, the theta correspondence or Howe correspondence is a mathematical relation between representations of two groups of a reductive dual pair. The local theta correspondence relates irreducible admissible representations over a local field, while the global theta correspondence relates irreducible automorphic representations over a global field.
The theta correspondence was introduced by Roger Howe in . Its name arose due to its origin in André Weil's representation theoretical formulation of the theory of theta series in . The Shimura correspondence as constructed by Jean-Loup Waldspurger in and may be viewed as an instance of the theta correspondence.
Statement
Setup
Let be a local or a global field, not of characteristic . Let be a symplectic vector space over , and the symplectic group.
Fix a reductive dual pair in . There is a classification of reductive dual pairs.
Local theta correspondence
is now a local field. Fix a non-trivial additive character of . There exists a Weil representation of the metaplectic group associated to , which we write as .
Given the reductive dual pair in , one obtains a pair of commuting subgroups in by pulling back the projection map from to .
The local theta correspondence is a 1-1 correspondence between certain irreducible admissible representations of and certain irreducible admissible representations of , obtained by restricting the Weil representation of to the subgroup . The correspondence was defined by Roger Howe in . The assertion that this is a 1-1 correspondence is called the Howe duality conjecture.
Key properties of local theta correspondence include its compatibility with Bernstein-Zelevinsky induction and conservation relations concerning the first occurrence indices along Witt towers .
Global theta correspondence
Stephen Rallis showed a version of the global Howe duality conjecture for cuspidal automorphic representations over a global field, assuming the validity of the Howe duality conjecture for all local places.
Howe duality conjecture
Define the set of irreducible admissible representations of , which can be realized as quotients of
. Define and , likewise.
The Howe duality conjecture asserts that is the graph of a bijection between and .
The Howe duality conjecture for archimedean local fields was proved by Roger Howe. For -adic local fields with odd it was proved by Jean-Loup Waldspurger. Alberto Mínguez later gave a proof for dual pairs of general linear groups, that works for arbitrary residue characteristic. For orthogonal-symplectic or unitary dual pairs, it was proved by Wee Teck Gan and Shuichiro Takeda. The final case of quaternionic dual pairs was completed by Wee Teck Gan and Binyong Sun.
See also
Reductive dual pair
Metaplectic group
References
Bibliography
Langlands program
Representation theory | Theta correspondence | [
"Mathematics"
] | 559 | [
"Representation theory",
"Fields of abstract algebra",
"Langlands program",
"Number theory"
] |
2,995,702 | https://en.wikipedia.org/wiki/Multimedia%20Broadcast%20Multicast%20Service | Multimedia Broadcast Multicast Services (MBMS) is a point-to-multipoint interface specification for existing 3GPP cellular networks, which is designed to provide efficient delivery of broadcast and multicast services, both within a cell as well as within the core network. For broadcast transmission across multiple cells, it defines transmission via single-frequency network configurations. The specification is referred to as Evolved Multimedia Broadcast Multicast Services (eMBMS) when transmissions are delivered through an LTE (Long Term Evolution) network. eMBMS is also known as LTE Broadcast.
Target applications include mobile TV and radio broadcasting, live streaming video services, as well as file delivery and emergency alerts.
Questions remain whether the technology is an optimization tool for the operator or if an operator can generate new revenues with it. Several studies have been published on the domain identifying both cost savings and new revenues.
Deployments
In 2013, Verizon announced that it would launch eMBMS services in 2014, over its nationwide (United States) LTE networks. AT&T subsequently announced plans to use the 700 MHz Lower D and E Block licenses it acquired in 2011 from Qualcomm for an LTE Broadcast service.
Several major operators worldwide have been lining-up to deploy and test the technology. The frontrunners being Verizon in the United States, Kt and Reliance in Asia, and recently EE and Vodafone in Europe.
In January 2014, Korea’s Kt launched the first commercial LTE Broadcast service. The solution includes Kt’s internally developed eMBMS Bearer Service, and Samsung mobile devices fitted with the ENENSYS Expway Middleware as the eMBMS User Service.
In February 2014, Verizon demonstrated the potential of LTE Broadcast during Super Bowl XLVIII, using Samsung Galaxy Note 3s, fitted with ENENSYS Expway's eMBMS User Service.
In July 2014, Nokia demonstrated the use of LTE Broadcast to replace Traditional Digital TV. This use case remains controversial as some study are doubting about the capability of LTE Broadcast to address this use case efficiently in its current version.
Also in July 2014, BBC Research & Development and EE demonstrated LTE Broadcast during the XX Commonwealth Games in Glasgow, Scotland using equipment from Huawei and Qualcomm.
In August 2014, Ericsson and Polkomtel successfully tested LTE Broadcast technology by streaming the opening game of the 2014 World Volleyball Championship to hundreds of guests at Warsaw’s National Stadium in Poland on August 30.
In June 2015, BBC Research & Development and EE demonstrated LTE Broadcast during the FA Cup final in the U.K.
In September 2015, Verizon demonstrated eMBMS by broadcasting INDYCAR races.
In October 2015, Verizon commercially launched their Go90 eMBMS service. Go90 offers both On-Demand and LiveTV, in both Unicast and Broadcast, and supports more than 10 different LTE Broadcast mobile devices.
Verizon ceased operating the go90 service on July 31, 2018.
In February 2016, Akamai demonstrated with ENENSYS Expway, delivery of video streams across LTE networks with live on the fly switching from unicast to broadcast, at Mobile World Congress 2016.
In April 2016, Verizon, Telstra, KT and EE launched the LTE Broadcast Alliance.
As of January 2019, the Global Mobile Suppliers Association had identified 41 operators that have invested in eMBMS (including those considering/testing/trialling, deploying or piloting and those that have deployed or launched eMBMS). Five operators state they have now deployed eMBMS or launched some sort of commercial service using eMBMS.
The range of chipsets available that can support eMBMS has been steadily growing, with three mobile processors/platforms released since March 2018. GSA has identified 69 chipsets supporting eMBMS, and there are at least 59 devices that support eMBMS (in some instances after operator-specific upgrades).
Competing technologies
Main competing technologies of MBMS include DVB-H/DVB-T, DVB-SH, DMB, ESM-DAB, and MediaFLO. However, due to spectrum scarcity and the cost of building new broadcast infrastructure some of these technologies may not be viable. MediaFLO has been deployed commercially in the US by Verizon Wireless through their relationship with MediaFLO USA, Inc. (a subsidiary of Qualcomm) however the service was shut down in early 2011. DMB and DVB-H trials have been ongoing for more than a year now, like those during the football 2006 championships in Germany.
Huawei's proprietary CMB is a precursor to the Multimedia Broadcast Multicast Service. It was specified in 3GPP R6 and is using existing UMTS infrastructure. Huawei says that CMB is based on existing UMTS infrastructure and real time streaming application protocol.
The most significant competition is from services that stream individual video feeds to users over uni-cast data connections. While less efficient in certain situations, particularly the traditional case where everyone watches the same stream simultaneously, the user convenience of individual streaming has taken over the vast majority of the mobile media streaming market.
Technical description
The MBMS feature is split into the MBMS Bearer Service and the MBMS User Service and has been defined to be offered over both UTRAN (i.e. WCDMA, TD-CDMA and TD-SCDMA) and LTE (where it is often referred to as eMBMS). The MBMS Bearer Service includes a Unicast and a Broadcast Mode. MBMS Operation On-Demand (MOOD) allows dynamic switching between Unicast and Broadcast over LTE, based on configured triggers. The MBMS Bearer Service uses IP multicast addresses for the IP flows. The advantage of the MBMS Bearer Service compared to unicast bearer services (interactive, streaming, etc.) is that the transmission resources in the core and radio networks are shared. One MBMS packet flow is replicated by GGSN, SGSN and RNCs. MBMS may use an advanced counting scheme to decide, whether or not zero, one or more dedicated (i.e. unicast) radio channels lead to a more efficient system usage than one common (i.e. broadcast) radio channel.
UTRAN MBMS offers up to 256 kbit/s per MBMS Bearer Service and between 800 kbit/s and 1.7 Mbit/s per cell/band. The actual cell capacity depends on the UE capabilities.
GERAN MBMS offers between 32 kbit/s and 128 kbit/s. Up to 4 GSM timeslots may be used for one MBMS bearer in the downlink direction. The actual data rate per Traffic Slot depends on network dimensioning.
The MBMS User Service is basically the MBMS Service Layer and offers two different data Delivery Methods:
The Streaming Delivery Method can be used for continuous transmissions like mobile television services. An application layer FEC code may be used to increase the transmission reliability.
The Download Delivery Method is intended for “download and play” services. A File Repair service may be offered to compensate for unreliable delivery.
MBMS has been standardized in various groups of 3GPP (Third Generation Partnership Project), and the first phase standards are found in UMTS release 6. As Release 6 was functionally frozen by the 3rd quarter of 2004, practical network implementations may be expected by the end of 2007, and the first functional mobile terminals supporting MBMS are estimated to be available by also end of 2007.
eMBMS has been standardized in various groups of 3GPP as part of LTE release 9. The LTE version of MBMS, referred to as Multicast-broadcast single-frequency network (MBSFN), supports broadcast only services and is based on a Single Frequency Network (SFN) based OFDM waveform and so is functional similar to other broadcast solutions such as DVB-H, -SH and -NGH. In Release 14, the 3GPP enhanced the specifications for eMBMS with a view to making the technology more attractive for deployment by operators and broadcasters. The 3GPP’s work on the next generation of technology in Release 16 includes a study on LTE-based broadcast on 5G networks, MBMS APIs for mission-critical services and MBMS user services for IoT.
3GPP technical specifications
MBMS Bearer Service (Distribution Layer):
3GPP TS 22.146 Multimedia Broadcast/Multicast Service (MBMS); Stage 1
3GPP TS 23.246 Multimedia Broadcast/Multicast Service (MBMS); Architecture and functional description
3GPP TS 25.346 Introduction of the Multimedia Broadcast/Multicast Service (MBMS) in the Radio Access Network (RAN); Stage 2
3GPP TS 25.992 Multimedia Broadcast Multicast Service (MBMS); UTRAN/GERAN Requirements
3GPP TS 36.300 Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 (see chapter 15 for eMBMS)
3GPP TS 36.440 General aspects and principles for interfaces supporting Multimedia Broadcast Multicast Service (MBMS) within E-UTRAN
3GPP TS 43.246 Multimedia Broadcast/Multicast Service (MBMS) in the GERAN; Stage 2
3GPP TR 25.803 S-CCPCH performance for Multimedia Broadcast/Multicast Service (MBMS)
MBMS User Service (Service Layer):
3GPP TS 22.246 Multimedia Broadcast/Multicast Service (MBMS) user services; Stage 1
3GPP TS 26.346 Multimedia Broadcast/Multicast Service (MBMS); Protocols and codecs
3GPP TR 26.946 Multimedia Broadcast/Multicast Service (MBMS) user service guidelines
3GPP TS 33.246 3G Security; Security of Multimedia Broadcast/Multicast Service (MBMS)
3GPP TS 32.273 Telecommunication management; Charging management; Multimedia Broadcast and Multicast Service (MBMS) charging
See also
LTE
Mobile television
TDtv
Broadcast and Multicast Service (BCMCS), a point-to-multipoint service defined for 3GPP2 systems
References
Broadcast engineering
LTE (telecommunication)
Mobile technology
Mobile telephone broadcasting | Multimedia Broadcast Multicast Service | [
"Technology",
"Engineering"
] | 2,128 | [
"Broadcast engineering",
"Mobile telephone broadcasting",
"Mobile telecommunications",
"Electronic engineering",
"nan"
] |
2,995,826 | https://en.wikipedia.org/wiki/Meteor%20burst%20communications | Meteor burst communications (MBC), also referred to as meteor scatter communications, is a radio propagation mode that exploits the ionized trails of meteors during atmospheric entry to establish brief communications paths between radio stations up to apart. There can be forward-scatter or back-scatter of the radio waves.
How it works
As the Earth moves along its orbital path, millions of particles known as meteoroids enter the Earth's atmosphere every day, a small fraction of which have properties useful for point-to-point communication. When these meteoroids begin to burn up, they create a glowing trail of ionized particles (called a meteor) in the E layer of the atmosphere that can persist for up to several seconds. The ionization trails can be very dense and thus used to reflect radio waves. The frequencies that can be reflected by any particular ion trail are determined by the intensity of the ionization created by the meteor, often a function of the initial size of the particle, and are generally between 30 MHz and 50 MHz.
The distance over which communications can be established is determined by the altitude at which the ionization is created, the location over the surface of the Earth where the meteoroid is falling, the angle of entry into the atmosphere, and the relative locations of the stations attempting to establish communications. Because these ionization trails only exist for fractions of a second to as long as a few seconds, they create only brief windows of opportunity for communications.
Development
The earliest direct observation of interaction between meteors and radio propagation was reported in 1929 by Hantaro Nagaoka of Japan. In 1931, Greenleaf Pickard noticed that bursts of long-distance propagation occurred at times of major meteor showers. At the same time, Bell Labs researcher A. M. Skellett was studying ways to improve night-time radio propagation, and suggested that the oddities that many researchers were seeing were due to meteors. The next year Schafer and Goodall noted that the atmosphere was disturbed during that year's Leonid meteor shower, prompting Skellett to postulate that the mechanism was reflection or scattering from electrons in meteor trails. In 1944, while researching a radar system that was "pointed up" to detect the V-2 missiles falling on London, James Stanley Hey confirmed that the meteor trails were in fact reflecting radio signals.
In 1946 the US Federal Communications Commission (FCC) found a direct correlation between enhancements in VHF radio signals and individual meteors. Studies conducted in the early 1950s by the National Bureau of Standards and the Stanford Research Institute had limited success at actually using this as a medium.
The first serious effort to utilize this technique was carried out by the Canadian Defence Research Board in the early 1950s. Their project, "JANET" (named for Janus, who looked both ways), sent bursts of data pre-recorded on magnetic tape from their radar research station in Prince Albert, Saskatchewan to Toronto, a distance exceeding 2,000 km. A 90 MHz "carrier" signal was monitored for sudden increases in signal strength, signalling a meteor, which triggered a burst of data. The system was used operationally starting in 1952, and provided useful communications until the radar project was shut down around 1960.
Military use
One of the first major deployments was "COMET" (COmmunication by MEteor Trails), used for long-range communications with NATO's Supreme Headquarters Allied Powers Europe headquarters. COMET became operational in 1965, with stations located in the Netherlands, France, Italy, West Germany, the United Kingdom, and Norway. COMET maintained an average throughput between 115 and 310 bits per second, depending on the time of year.
Meteor burst communications faded from interest with the increasing use of satellite communications systems starting in the late 1960s. In the late 1970s it became clear that the satellites were not as universally useful as originally thought, notably at high latitudes or where signal security was an issue. For these reasons, the U.S. Air Force installed the Alaska Air Command MBC system in the 1970s, although it is not publicly known whether this system is still operational.
A more recent study is the Advanced Meteor Burst Communications System (AMBCS), a testbed set up by SAIC under DARPA funding. Using phase-steerable antennas directed at the proper area of the sky for any given time of day, in the direction where the Earth is moving "forward", AMBCS was able to greatly improve the data rates, averaging 4 kilobits per second (kbit/s). While satellites may have a nominal throughput about 14 times as great, they are vastly more expensive to operate.
Additional gains in throughput are theoretically possible through the use of real-time steering. The basic concept is to use backscattered signals to pinpoint the exact location of the ion trail and direct the antenna to that spot, or in some cases, several trails simultaneously. This improves the gain, allowing much improved data rates. To date, this approach has not been tried experimentally, so far as is known.
Scientific use
The United States Department of Agriculture (USDA) used meteor scatter extensively in its SNOTEL system for over 40 years, but discontinued this use in 2023. Over 900 snow water content gauging stations in the Western United States were equipped with radio transmitters that relied upon meteor-scatter communications to send measurements to a data center.
Amateur radio use
Most meteor-scatter communication is conducted between radio stations that are engaged in a precise schedule of transmission and reception periods. Because the presence of a meteor trail at a suitable location between two stations cannot be predicted, stations attempting meteor-scatter communications must transmit the same information repeatedly until an acknowledgement of reception from the other station is received. Established protocols are employed to regulate the progress of information flow between stations. While a single meteor may create an ion trail that supports several steps of the communication protocol, often a complete exchange of information requires several meteors and a long period of time to complete.
Any form of communications mode can be used for meteor-scatter communications. Single sideband audio transmission has been popular among amateur radio operators in North America attempting to establish contact with other stations during meteor showers without planning a schedule in advance with the other station. The use of Morse code has been more popular in Europe, where amateur radio operators used modified tape recorders, and later computer programs, to send messages at transmission speeds as high as 800 words per minute. Stations receiving these bursts of information record the signal and play it back at a slower speed to copy the content of the transmission. Since 2000, several digital modes implemented by computer programs have replaced voice and Morse code communications in popularity. The most popular mode for amateur radio operations is MSK144, which is implemented in the WSJT-X software.
References
Further reading
External links
Meteor Burst Communications: An Additional Means of Long-Haul Communications
MeteorComm Meteor Burst Technology
Meteor burst communications tutorial
Listen to live meteor echoes at Livemeteors.com
Meteor scatter Databases
Meteor scatter Homemade
Radio detection of meteors, updated every minute, at the Lockyer Observatory and Planetarium.
Radio frequency propagation
Meteoroids | Meteor burst communications | [
"Physics"
] | 1,443 | [
"Physical phenomena",
"Spectrum (physical sciences)",
"Radio frequency propagation",
"Electromagnetic spectrum",
"Waves"
] |
2,995,864 | https://en.wikipedia.org/wiki/Interstitium | In anatomy, the interstitium is a contiguous fluid-filled space existing between a structural barrier, such as a cell membrane or the skin, and internal structures, such as organs, including muscles and the circulatory system. The fluid in this space is called interstitial fluid, comprises water and solutes, and drains into the lymph system. The interstitial compartment is composed of connective and supporting tissues within the body – called the extracellular matrix – that are situated outside the blood and lymphatic vessels and the parenchyma of organs. The role of the interstitium in solute concentration, protein transport and hydrostatic pressure impacts human pathology and physiological responses such as edema, inflammation and shock.
Structure
The non-fluid parts of the interstitium are predominantly collagen types I, III, and V; elastin; and glycosaminoglycans, such as hyaluronan and proteoglycans, that are cross-linked to form a honeycomb-like reticulum. Collagen bundles of the extracellular matrix form scaffolding with a high tensile strength. Interstitial cells (e.g., fibroblasts, dendritic cells, adipocytes, interstitial cells of Cajal and inflammatory cells, such as macrophages and mast cells), serve a variety of structural and immune functions. Fibroblasts synthesize the production of structural molecules as well as enzymes that break down polymeric molecules. Such structural components exist both for the general interstitium of the body, and within individual organs, such as the myocardial interstitium of the heart, the renal interstitium of the kidney, and the pulmonary interstitium of the lung.
The interstitium in the submucosae of visceral organs, the dermis, superficial fascia, and perivascular adventitia are fluid-filled spaces supported by a collagen bundle lattice. Blind end, highly permeable, lymphatic capillaries extend into the interstitium. The fluid spaces communicate with draining lymph nodes, although they do not have lining cells or structures of lymphatic channels. Interstitial fluid entering the lymphatic system becomes lymph, which is transported through lymphatic vessels until it empties into the microcirculation and the venous system.
Functions
The interstitial fluid is a reservoir and transportation system for nutrients and solutes distributing among organs, cells, and capillaries, for signaling molecules communicating between cells, and for antigens and cytokines participating in immune regulation. The structure of the gel reticulum plays a role in the distribution of solutes across the interstitium, as the microstructure of the extracellular matrix in some parts excludes larger molecules (exclusion volume). The density of the collagen matrix fluctuates with the fluid volume of the interstitium. Increasing fluid volume is associated with a decrease in matrix fiber density, and a lower exclusion volume.
The total fluid volume of the interstitium during health is about 20% of body weight(volume is not weight), but this space is dynamic and may change in volume and composition during immune responses and in conditions such as cancer, and specifically within the interstitium of tumors. The amount of interstitial fluid varies from about 50% of the tissue weight in skin to about 10% in skeletal muscle. Interstitial fluid pressure is variable, ranging from -1 to -4 mmHg in tissues like the skin, intestine and lungs to 21 to 24 mmHg in the liver, kidney and myocardium. Generally, increasing interstitial volume is associated with increased interstitial pressure and microvascular filtration.
The renal interstitium facilitates solute and water transport between blood and urine in the vascular and tubular elements of the kidneys, and water reabsorption through changes in solute concentrations and hydrostatic gradients. The myocardial interstitium participates in ionic exchanges associated with the spread of electrical events. The pulmonary interstitium allows for fluctuations in lung volume between inspiration and expiration.
The composition and chemical properties of the interstitial fluid vary among organs and undergo changes in chemical composition during normal function, as well as during body growth, conditions of inflammation, and development of diseases, as in heart failure and chronic kidney disease.
Disease
In people with lung diseases, heart disease, cancer, kidney disease, immune disorders, and periodontal disease, the interstitial fluid and lymph system are sites where disease mechanisms may develop. Interstitial fluid flow is associated with the migration of cancer cells to metastatic sites. The enhanced permeability and retention effects refers to increased interstitial flow causing a neutral or reversed pressure differential between blood vessels and healthy tissue, limiting the distribution of intravenous drugs to tumors, which under other circumstances display a high-pressure gradient at their periphery.
Changes in interstitial volume and pressure play critical roles in the onset of conditions like shock and inflammation. During hypovolemic shock, digestive enzymes and inflammatory agents diffuse to the interstitial space, then drain into the mesenteric lymphatic system and enter into circulation, contributing to systemic inflammation. Accumulating fluid in the interstitial space (interstitial edema) is caused by increased microvascular pressure and permeability, a positive feedback loop mechanism resulting in an associated in increasing the rate of microvascular filtration into the interstitial space. Decreased lymphatic drainage due to blockage can compound these effects. Interstitial edema can prevent oxygen diffusion across tissue and in the brain, kidney and intestines lead to the onset of compartment syndrome.
See also
Extracellular matrix
Extracellular fluid
References
Anatomy
Extracellular matrix
Matrices (biology)
Tissues (biology) | Interstitium | [
"Biology"
] | 1,224 | [
"Anatomy"
] |
2,995,958 | https://en.wikipedia.org/wiki/Potential%20isomorphism | In mathematical logic and in particular in model theory, a potential isomorphism is a collection of finite partial isomorphisms between two models which satisfies certain closure conditions. Existence of a partial isomorphism entails elementary equivalence, however the converse is not generally true, but it holds for ω-saturated models.
Definition
A potential isomorphism between two models M and N is a non-empty collection F of finite partial isomorphisms between M and N which satisfy the following two properties:
for all finite partial isomorphisms Z ∈ F and for all x ∈ M there is a y ∈ N such that Z ∪ {(x,y)} ∈ F
for all finite partial isomorphisms Z ∈ F and for all y ∈ N there is a x ∈ M such that Z ∪ {(x,y)} ∈ F
A notion of Ehrenfeucht-Fraïssé game is an exact characterisation of elementary equivalence and potential isomorphism can be seen as an approximation of it. Another notion that is similar to potential isomorphism is that of local isomorphism.
References
Model theory | Potential isomorphism | [
"Mathematics"
] | 221 | [
"Mathematical logic",
"Model theory"
] |
2,995,992 | https://en.wikipedia.org/wiki/Duoplasmatron | The Duoplasmatron is an ion source in which a cathode filament emits electrons into a vacuum chamber. A gas such as argon is introduced in very small quantities into the chamber, where it becomes charged or ionized through interactions with the free electrons from the cathode, forming a plasma. The plasma is then accelerated through a series of at least two highly charged grids, and becomes an ion beam, moving at a fairly high speed from the aperture of the device.
History
The duoplasmatron was first developed in 1956 by Manfred von Ardenne to provide a powerful source of gas ions. Other contributors such as Demirkanov, Frohlich and Kistemaker continued development between 1959 and 1965. Throughout the 1960s, many continued to investigate, discovering negative ion extraction and multiply charged ion production. There are two types of plasmatrons, the uniplasmatron and the duoplasmatron. The prefix refers to the constriction of discharge.
Operation
The standard duoplasmatron consists of three main components that are responsible for its operation. These include the hot cathode, the intermediate electrode, and the anode. The intermediate electrode's main job is to produce discharge. This discharge is confined to a small portion near the anode and a short magnetic field between the intermediate electrode and the anode. The duoplasmatron has two different types of plasma: the cathode plasma which is close to the cathode and the anode plasma which is close to the anode. The cathode works by injecting a beam of electrons with a suitable amount of energy. This injection ionizes the gas molecules, typically Argon gas, in the anode and increases the potential near the anode. The ions that are repulsed, however, combine with the ions that contain enough energy to pass the deceleration region and this combination of ions fills the expansion cup with directed ions and electrons. The best operational mode for the duoplasmatron is considered to be when the cathode is adjusted to an emission where the intermediate electrode and the cathode potential are approximately equal.
Applications
The duoplasmatron is a type of ion source. Ion sources are necessary to form ions for mass spectrometers and other types of instruments. In comparison to Penning ionization sources, the duoplasmatron features advantages such as less expenditure, easier handling, and a longer lifetime. However, the duoplasmatron does have lower beam intensity, which can be a large disadvantage.
References
Further reading
Brown, I.G., "The Physics and Technology of Ion Sources", Wiley-VCH (2004), p. 110
Dass, Chhabil (24 August 2006). Fundamentals of Contemporary Mass Spectrometry. John Wiley & Sons, Inc. .
External links
Duoplasmatron-Animation
Ion source
Plasma technology and applications | Duoplasmatron | [
"Physics"
] | 604 | [
"Spectrum (physical sciences)",
"Plasma physics",
"Plasma technology and applications",
"Ion source",
"Mass spectrometry"
] |
2,996,022 | https://en.wikipedia.org/wiki/Cerebral%20perfusion%20pressure | Cerebral perfusion pressure, or CPP, is the net pressure gradient causing cerebral blood flow to the brain (brain perfusion). It must be maintained within narrow limits because too little pressure could cause brain tissue to become ischemic (having inadequate blood flow), and too much could raise intracranial pressure (ICP).
Definitions
The cranium encloses a fixed-volume space that holds three components: blood, cerebrospinal fluid (CSF), and very soft tissue (the brain). While both the blood and CSF have poor compression capacity, the brain is easily compressible.
Every increase of ICP can cause a change in tissue perfusion and an increase in stroke events.
From resistance
CPP can be defined as the pressure gradient causing cerebral blood flow (CBF) such that
where:
CVR is cerebrovascular resistance
By intracranial pressure
An alternative definition of CPP is:
where:
MAP is mean arterial pressure
ICP is intracranial pressure
JVP is jugular venous pressure
This definition may be more appropriate if considering the circulatory system in the brain as a Starling resistor, where an external pressure (in this case, the intracranial pressure) causes decreased blood flow through the vessels. In this sense, more specifically, the cerebral perfusion pressure can be defined as either:
(if ICP is higher than JVP)
or
(if JVP is higher than ICP).
Physiologically, increased intracranial pressure (ICP) causes decreased blood perfusion of brain cells by mainly two mechanisms:
Increased ICP constitutes an increased interstitial hydrostatic pressure that, in turn, causes a decreased driving force for capillary filtration from intracerebral blood vessels.
Increased ICP compresses cerebral arteries, causing increased cerebrovascular resistance (CVR).
FLOW
Ranging from in white matter to in grey matter.
Autoregulation
Under normal circumstances a MAP between 60 and 160 mmHg and ICP about 10 mmHg (CPP of 50-150 mmHg) sufficient blood flow can be maintained with autoregulation. Although the classic 'autoregulation curve' suggests that CBF is fully stable between these blood pressure values (known also as the limits of autoregulation), in practice spontaneous fluctuations can occur.
Outside of the limits of autoregulation, raising MAP raises CBF and raising ICP lowers it (this is one reason that increasing ICP in traumatic brain injury is potentially deadly). In trauma some recommend CPP not go below 70 mmHg. Recommendations in children is at least 60 mmHg.
Within the autoregulatory range, as CPP falls there is, within seconds, vasodilation of the cerebral resistance vessels, a fall in cerebrovascular resistance and a rise in cerebral-blood volume (CBV), and therefore CBF will return to baseline value within seconds (see as ref. Aaslid, Lindegaard, Sorteberg, and Nornes 1989: http://stroke.ahajournals.org/cgi/reprint/20/1/45.pdf). These adaptations to rapid changes in blood pressure (in contrast with changes that occur over periods of hours or days) are known as dynamic cerebral autoregulation.
Footnotes
References
Medical terminology
Neurology
Neurotrauma
Physiology | Cerebral perfusion pressure | [
"Biology"
] | 706 | [
"Physiology"
] |
2,996,055 | https://en.wikipedia.org/wiki/Anti-nuclear%20movement | The anti-nuclear movement is a social movement that opposes various nuclear technologies. Some direct action groups, environmental movements, and professional organisations have identified themselves with the movement at the local, national, or international level. Major anti-nuclear groups include Campaign for Nuclear Disarmament, Friends of the Earth, Greenpeace, International Physicians for the Prevention of Nuclear War, Peace Action, Seneca Women's Encampment for a Future of Peace and Justice and the Nuclear Information and Resource Service. The initial objective of the movement was nuclear disarmament, though since the late 1960s opposition has included the use of nuclear power. Many anti-nuclear groups oppose both nuclear power and nuclear weapons. The formation of green parties in the 1970s and 1980s was often a direct result of anti-nuclear politics.
Scientists and diplomats have debated nuclear weapons policy since before the atomic bombings of Hiroshima and Nagasaki in 1945. The public became concerned about nuclear weapons testing from about 1954, following extensive nuclear testing. In 1963, many countries ratified the Partial Test Ban Treaty which prohibited atmospheric nuclear testing.
Some local opposition to nuclear power emerged in the early 1960s, and in the late 1960s some members of the scientific community began to express their concerns. In the early 1970s, there were large protests about a proposed nuclear power plant in Wyhl, West Germany. The project was cancelled in 1975 and anti-nuclear success at Wyhl inspired opposition to nuclear power in other parts of Europe and North America. Nuclear power became an issue of major public protest in the 1970s and while opposition to nuclear power continues, increasing public support for nuclear power has re-emerged over the last decade in light of growing awareness of global warming and renewed interest in all types of clean energy (see the Pro-nuclear movement).
A protest against nuclear power occurred in July 1977 in Bilbao, Spain, with up to 200,000 people in attendance. Following the Three Mile Island accident in 1979, an anti-nuclear protest was held in New York City, involving 200,000 people. In 1981, Germany's largest anti-nuclear power demonstration took place to protest against the Brokdorf Nuclear Power Plant west of Hamburg; some 100,000 people came face to face with 10,000 police officers. The largest protest was held on 12 June 1982, when one million people demonstrated in New York City against nuclear weapons. A 1983 nuclear weapons protest in West Berlin had about 600,000 participants. In May 1986, following the Chernobyl disaster, an estimated 150,000 to 200,000 people marched in Rome to protest against the Italian nuclear program. In Australia unions, peace activists and environmentalists opposed uranium mining from the 1970s onwards and rallies bringing together hundreds of thousands of people to oppose nuclear weapons peaked in the mid- 1980s. In the US, public opposition preceded the shutdown of the Shoreham, Yankee Rowe, Millstone 1, Rancho Seco, Maine Yankee, and many other nuclear power plants.
For many years after the 1986 Chernobyl disaster, nuclear power was off the policy agenda in most countries, and the anti-nuclear power movement seemed to have won its case, so some anti-nuclear groups disbanded. In the 2000s, however, following public relations activities by the nuclear industry, advances in nuclear reactor designs, and concerns about climate change, nuclear power issues came back into energy policy discussions in some countries. The 2011 Fukushima nuclear accident subsequently undermined the nuclear power industry's proposed renaissance and revived nuclear opposition worldwide, putting governments on the defensive. As of 2016, countries such as Australia, Austria, Denmark, Greece, Malaysia, New Zealand, and Norway have no nuclear power stations and remain opposed to nuclear power. Germany, Italy, Spain, and Switzerland are phasing-out nuclear power. Sweden formerly had a nuclear phase-out policy, aiming to end nuclear power generation in Sweden by 2010. On 5 February 2009, the Government of Sweden announced an agreement allowing for the replacement of existing reactors, effectively ending the phase-out policy.
Globally, the number of operable reactors remains nearly the same over the last 30 years, and nuclear electricity production is steadily growing after the Fukushima disaster.
History and issues
Roots of the movement
The application of nuclear technology, as a source of energy and as an instrument of war, has been controversial. These issues are discussed in nuclear weapons debate, nuclear power debate, and uranium mining debate.
Scientists and diplomats have debated nuclear weapons policy since before the Atomic bombings of Hiroshima and Nagasaki in 1945. The public became concerned about nuclear weapons testing from about 1954, following extensive nuclear testing in the Pacific, with some calling it nuclear imperialism and colonialism. In 1961, at the height of the Cold War, about 50,000 women brought together by Women Strike for Peace marched in 60 cities in the United States to demonstrate against nuclear weapons. In 1963, many countries ratified the Partial Test Ban Treaty which prohibited atmospheric nuclear testing.
Some local opposition to nuclear power emerged in the early 1960s, and in the late 1960s some members of the scientific community began to express their concerns. In the early 1970s, there were large protests about a proposed nuclear power plant in Wyhl, Germany. The project was cancelled in 1975 and anti-nuclear success at Wyhl inspired opposition to nuclear power in other parts of Europe and North America. Nuclear power became an issue of major public protest in the 1970s.
Fossil fuels industry
The fossil fuel industry starting from the 1950s was engaging in campaigns against the nuclear industry which it perceived as a threat to their commercial interests. Organizations such as the American Petroleum Institute, the Pennsylvania Independent Oil and Gas Association and Marcellus Shale Coalition were engaged in anti-nuclear lobbying in the late 2010s and from 2019, large fossil fuel suppliers started advertising campaigns portraying fossil gas as a "perfect partner for renewables" (wording from Shell and Statoil advertisements). Groups like the Sierra Club, Environmental Defense Fund and Natural Resources Defense Council are receiving grants from other fossil fuel companies. As of 2011, a strategy paper released by Greenpeace titled "Battle of Grids" proposed gradual replacement of nuclear power by fossil gas plants which would provide "flexible backup for wind and solar power". However, Greenpeace has since distanced itself from advocating for fossil gas, instead proposing grid energy storage as a solution to issues caused by intermittent renewable energy. In Germany the Energiewende, which was advertised as a shift to renewable energy but included a gradual phaseout of nuclear power from 2000 to end 2022, caused among other things a rise in fossil gas power production from 49.2 TWh in 2000 to 94.7 TWh in 2020. In the same interval total electricity generation barely changed (576.6 TWh in 2000 vs 574.2 TWh in 2020) while it did rise and fall in the meantime, reaching a peak of 652.9 TWh in 2017. As much of that fossil gas was and is imported from Russia, controversial pipeline projects like Nord Stream 1 were built to satisfy increasing German gas demand. After the 2022 Russian invasion of Ukraine it came to light that significant amounts of Russian lobbying was involved in both the continued anti-nuclear movement in Germany and the anti-fracking movement.
Anti-nuclear perspectives
Concerns about nuclear weapons
From an anti-nuclear point of view, there is a threat to modern civilization from global nuclear war by accidental or deliberate nuclear strike. Some climate scientists estimate that a war between two countries that resulted in 100 Hiroshima-size atomic explosions would cause significant loss of life, in the tens of millions from climatic effects alone as well as disabled future generations. Soot thrown up into the atmosphere could blanket the earth, causing food chain disruption in what is termed a nuclear winter.
Many anti-nuclear weapons groups cite the 1996 Advisory Opinion of the International Court of Justice, Legality of the Threat or Use of Nuclear Weapons, in which it found that 'the threat or use of nuclear weapons would generally be contrary to the rules of international law applicable in armed conflict'.
Ridding the world of nuclear weapons has been a cause for pacifists for decades. But more recently mainstream politicians and retired military leaders have advocated nuclear disarmament. In January 2007 an article in The Wall Street Journal, authored by Henry Kissinger, Bill Perry, George Shultz and Sam Nunn. These men were veterans of the cold-war who believed in using nuclear weapons for deterrence. But they now reversed their previous position and asserted that instead of making the world safer, nuclear weapons had become a source of extreme concern.
Since the 1970s, some countries have built their own second-strike capability of massive deterrence in the event of a military attack with weapons of mass destruction.
Two examples of this second-strike capability are the Samson Option strategy of Israel, and the Dead Hand system of Russia.
During the era of nuclear weapons testing many local communities were affected, and some are still affected by uranium mining, and radioactive waste disposal.
It should however be noted, that countries can possess nuclear weapons without possessing nuclear power plants (as is almost certainly the case with Israel) or indeed the reverse, as is the case with most users of nuclear power past and present.
Concerns about nuclear power
There are large variations in peoples' beliefs regarding the issues surrounding nuclear power, including the technology itself, its deployment, climate change, and energy security. There is a wide spectrum of views and concerns over nuclear power and it remains a controversial area of public policy. When compared to other energy sources, nuclear power has one of the lowest death rates per unit of energy produced – 0.07 per TWh, as compared to over 32 per TWh in case of brown coal. This figure is driven by a 2005 WHO projection of up to 4000 stochastic cancer deaths that could result from the Chernobyl disaster. The UNSCEAR reports in its 2008 summary on Chernobyl that no increases in cancer incidence (other than thyroid cancer) have been observed to date that can be attributed to radiation from the accident.
Many studies have shown that the public "perceives nuclear power as a very risky technology" and, around the world, nuclear energy declined in popularity in the aftermath of the Fukushima Daiichi nuclear disaster, but it has recently rebounded in response to the climate crisis. Anti-nuclear critics see nuclear power as a dangerous, expensive way to boil water to generate electricity. Opponents of nuclear power have raised a number of related concerns:
Nuclear accidents: a safety concern that the core of a nuclear power plant could overheat and melt down, releasing radioactivity.
Nuclear Fuel Mining: mining waste of nuclear fuels like uranium and thorium, results in its radioactive decay. That causes radium pollution and radon pollution in environment and ultimately affects public health.
Radioactive waste disposal: a concern that nuclear power results in large amounts of radioactive waste, some of which remains dangerous for very long periods.
Nuclear proliferation: a concern that some types of nuclear reactor designs use and/or produce fissile material which could be used in nuclear weapons.
High cost: a concern that nuclear power plants are very expensive to build, and that clean up from nuclear accidents are highly expensive and can take decades.
Attacks on nuclear plants: a concern that nuclear facilities could be targeted by terrorists or criminals.
Curtailed civil liberties: a concern that the risk of nuclear accidents, proliferation and terrorism may be used to justify restraints on citizen rights.
Of these concerns, nuclear accidents and disposal of long-lived radioactive waste have probably had the greatest public impact worldwide. Anti-nuclear campaigners point to the 2011 Fukushima nuclear emergency as proof that nuclear power can never be 100% safe. Costs resulting from the Fukushima Daiichi nuclear disaster are likely to exceed 12 trillion yen ($100 billion) and the clean up effort to decontaminate affected areas and decommission the plant is estimated to take 30 to 40 years. Excluding accidents, the standard amount of high-level radioactive waste is claimed to be manageable (UK has produced just 2150 m3 during its 60 years nuclear program), with the Geological Society of London alleging that it can be effectively recycled and stored safely.
In his book Global Fission: The Battle Over Nuclear Power, Jim Falk explores connections between technological concerns and political concerns. Falk suggests that concerns of citizen groups or individuals who oppose nuclear power have often focused initially on the "range of physical hazards which accompany the technology" and leads to a "concern over the political relations of the nuclear industry". Baruch Fischhoff, a social scientist, said that many people really do not trust the nuclear industry. Wade Allison, a physicist, said "radiation is safe & all nations should embrace nuclear technology"
M.V. Ramana says that "distrust of the social institutions that manage nuclear energy is widespread", and a 2001 survey by the European Commission found that "only 10.1 percent of Europeans trusted the nuclear industry". This public distrust is periodically reinforced by nuclear safety violations, or through ineffectiveness or corruption of the nuclear regulatory authorities. Once lost, says Ramana, trust is extremely difficult to regain.
Faced with public antipathy, the nuclear industry has "tried a variety of strategies to persuade the public to accept nuclear power", including the publication of numerous "fact sheets" that discuss issues of public concern. M.V. Ramana says that none of these strategies have been very successful. Nuclear proponents have tried to regain public support by offering newer, purportedly safer, reactor designs. These designs include those that incorporate passive safety and Small Modular Reactors. While these reactor designs "are intended to inspire trust, they may have an unintended effect: creating distrust of older reactors that lack the touted safety features".
Since 2000 the nuclear power was promoted as potential solution to the greenhouse effect and climate change as nuclear power emits no or negligible amounts of carbon dioxide during operations. Anti-nuclear groups highlighted the fact that other stages of the nuclear fuel chain – mining, milling, transport, fuel fabrication, enrichment, reactor construction, decommissioning and waste management – use fossil fuels and hence emit carbon dioxide. As this is the case with any energy sources, including renewable energy, IPCC analyzed total life-cycle greenhouse-gas emissions, which account for all emissions during manufacturing, installation, operations and decommissioning. With 12 gCO2eq/kWh nuclear power still remains one of the lowest emitting energy sources available.
In 2011, a French court fined Électricité de France (EDF) €1.5m and jailed two senior employees for spying on Greenpeace, including hacking into Greenpeace's computer systems. Greenpeace was awarded €500,000 in damages.
There are some energy-related studies which conclude that energy efficiency programs and renewable power technologies are a better energy option than nuclear power plants.
Other technologies
The international nuclear fusion project International Thermonuclear Experimental Reactor (ITER) is constructing the world's largest and most advanced experimental tokamak nuclear fusion reactor in the south of France. A collaboration between the European Union (EU), India, Japan, China, Russia, South Korea and the United States, the project aims to make a transition from experimental studies of plasma physics to electricity-producing fusion power plants. In 2005, Greenpeace International issued a press statement criticizing government funding of the ITER, believing the money should have been diverted to renewable energy sources and claiming that fusion energy would result in nuclear waste and nuclear weapons proliferation issues. A French association including about 700 anti-nuclear groups, Sortir du nucléaire (Get Out of Nuclear Energy), claimed that ITER was a hazard because scientists did not yet know how to manipulate the high-energy deuterium and tritium hydrogen isotopes used in the fusion process. According to most anti-nuclear groups, nuclear fusion power "remains a distant dream". The World Nuclear Association have said that fusion "presents so far insurmountable scientific and engineering challenges". Construction of the ITER facility began in 2007, but the project has run into many delays and budget overruns. Several milestones of the project has already been finished, but the finishing date for First Plasma has been discussed and postponed many times with various conclusions. In late 2016, the ITER council agreed on an updated project schedule, with a planned First Plasma opening by 2025, nine years after the originally anticipated opening.
Some anti-nuclear groups advocate reduced reliance on reactor-produced medical radioisotopes, through the use of alternative radioisotope production and alternative clinical technologies. Cyclotrons are being increasingly used to produce medical radioisotopes to the point where nuclear reactors are no longer needed to make the most common medical isotopes. However, the development of newer, more reliable and efficient particle accelerators also fuels the proposals for subcritical reactors with a spallation neutron source being used for nuclear transmutation of "legacy" waste and/or power generation. Such reactors could also be used to produce medical isotopes. Some isotopes, like Cobalt-60 are currently mostly produced in reactors like the Canadian CANDU.Plutonium-238, the preferred material for radioisotope thermal generators for use in spacecraft, faced a significant shortage after a single reactor producing it shut down, before the U.S. established a capacity to produce it from Neptunium-237 at one of their laboratories.
Nuclear-free alternatives
Anti-nuclear groups say that reliance on nuclear energy can be reduced by adopting energy conservation and energy efficiency measures. Energy efficiency can reduce energy consumption while providing the same level of energy "services".
Renewable energy flows involve natural phenomena such as sunlight, wind, tides, plant growth, and geothermal heat, as the International Energy Agency explains:
Anti-nuclear groups also favour the use of renewable energy, such as hydro, wind power, solar power, geothermal energy and biofuel. According to the International Energy Agency renewable energy technologies are essential contributors to the energy supply portfolio, as they contribute to world energy security and provide opportunities for mitigating greenhouse gases. Fossil fuels are being replaced by clean, climate-stabilizing, non-depletable sources of energy. According to Lester R. Brown:
...the transition from coal, oil, and gas to wind, solar, and geothermal energy is well under way. In the old economy, energy was produced by burning something – oil, coal, or natural gas – leading to the carbon emissions that have come to define our economy. The new energy economy harnesses the energy in wind, the energy coming from the sun, and heat from within the earth itself.
In 2014 global wind power capacity expanded 16% to 369,553 MW. Yearly wind energy production is also growing rapidly and has reached around 4% of worldwide electricity usage, 11.4% in the EU, and it is widely used in Asia, and the United States. In 2014, worldwide installed photovoltaics capacity increased to 177 gigawatts (GW), sufficient to supply 1 per cent of global electricity demands. As of 2020 wind power expansion slowed down due to protests of residents and environmentalists.
Solar thermal energy stations operate in the United States and Spain, and as of 2016, the largest of these is the 392 MW Ivanpah Solar Electric Generating System in California. The world's largest geothermal power installation is The Geysers in California, with a rated capacity of 750 MW. Brazil has one of the largest renewable energy programs in the world, involving production of ethanol fuel from sugar cane, and ethanol now provides 18% of the country's automotive fuel. Ethanol fuel is also widely available in the United States. As of 2020 expansion of biomass as fuel, which was previously praised by environmental organizations such as Greenpeace, has been criticized for environmental damage.
Greenpeace advocates a reduction of fossil fuels by 50% by 2050 as well as phasing out nuclear power, contending that innovative technologies can increase energy efficiency, and suggests that by 2050 most electricity will come from renewable sources. The International Energy Agency estimates that nearly 50% of global electricity supplies will need to come from renewable energy sources in order to halve carbon dioxide emissions by 2050 and minimise climate change impacts.
Mark Z. Jacobson says producing all new energy with wind power, solar power, and hydropower by 2030 is feasible and existing energy supply arrangements could be replaced by 2050. Barriers to implementing the renewable energy plan are seen to be "primarily social and political, not technological or economic". Jacobson says that energy costs with a wind, solar, water system should be similar to today's energy costs. Many have since referred to Jacobson's work to justify advocating for all 100% renewables, however, in February, 2017, a group of twenty-one scientists published a critique of Jacobson's work and found that his analysis involves "errors, inappropriate methods and implausible assumptions" and failed to provide "credible evidence for rejecting the conclusions of previous analyses that point to the benefits of considering a broad portfolio of energy system options."
Critics state that the anti-nuclear arguments overestimate the benefits of renewable energy and fail to consider land per unit of energy inefficiencies and data that claims to forecast, "...biomass, wind, and solar power are set to occupy an area equivalent of the size of the European Union by 2050."
Anti-nuclear organizations
The anti-nuclear movement is a social movement which operates at the local, national, and international level. Various types of groups have identified themselves with the movement:
direct action groups, such as the Clamshell Alliance and Shad Alliance
environmental groups, such as Friends of the Earth and Greenpeace
consumer protection groups, such as Ralph Nader's Critical Mass
professional organisations, such as International Physicians for the Prevention of Nuclear War
political parties such as European Free Alliance
Anti-nuclear groups have undertaken public protests and acts of civil disobedience which have included occupations of nuclear plant sites. Other salient strategies have included lobbying, petitioning government authorities, influencing public policy through referendum campaigns and involvement in elections. Anti-nuclear groups have also tried to influence policy implementation through litigation and by participating in licensing proceedings.
Anti-nuclear power organisations have emerged in every country that has had a nuclear power programme. Protest movements against nuclear power first emerged in the United States, at the local level, and spread quickly to Europe and the rest of the world. National nuclear campaigns emerged in the late 1970s. Fuelled by the Three Mile Island accident and the Chernobyl disaster, the anti-nuclear power movement mobilised political and economic forces which for some years "made nuclear energy untenable in many countries". In the 1970s and 1980s, the formation of green parties was often a direct result of anti-nuclear politics (e.g., in Germany and Sweden).
Some of these anti-nuclear power organisations are reported to have developed considerable expertise on nuclear power and energy issues. In 1992, the chairman of the Nuclear Regulatory Commission said that "his agency had been pushed in the right direction on safety issues because of the pleas and protests of nuclear watchdog groups".
International organizations
European Nuclear Disarmament, which held annual conventions in the 1980s involving thousands of anti-nuclear weapons activists mostly from Western Europe but also from Eastern Europe, the United States, and Australia.
Friends of the Earth International, a network of environmental organizations in 77 countries. Since 2014, however, Friends of the Earth (UK) has softened its stance; the fierce opposition against nuclear reactors has shifted into a more pragmatic opposition, which still opposes the construction of new nuclear (fission) reactors, but doesn't campaign against closing down the existing ones any more.
Global Zero, an international non-partisan group of 300 world leaders dedicated to achieving the elimination of nuclear weapons.
Global Initiative to Combat Nuclear Terrorism, an international partnership of 83 nations.
Greenpeace International, a non-governmental environmental organization with offices in over 41 countries and headquarters in Amsterdam, Netherlands.
International Campaign to Abolish Nuclear Weapons
International Network of Engineers and Scientists for Global Responsibility
International Physicians for the Prevention of Nuclear War, which had affiliates in 41 nations in 1985, representing 135,000 physicians; IPPNW was awarded the UNESCO Peace Education Prize in 1984 and the Nobel Peace Prize in 1985.
Nuclear Information and Resource Service
OPANAL
Parliamentarians for Nuclear Non-Proliferation and Disarmament, a global network of over 700 parliamentarians from more than 75 countries working to prevent nuclear proliferation
Pax Christi International, a Catholic group which took a "sharply anti-nuclear stand"
Ploughshares Fund
Pugwash Conferences on Science and World Affairs
Socialist International, the world body of social democratic parties
Sōka Gakkai, a peace-orientated Buddhist organisation, which held anti-nuclear exhibitions in Japanese cities during the late 1970s, and gathered 10 million signatures on petitions calling for the abolition of nuclear weapons
United Nations Office for Disarmament Affairs
World Disarmament Campaign
World Information Service on Energy, based in Amsterdam, the Netherlands
World Union for Protection of Life
Other groups
National and local anti-nuclear groups are listed at Anti-nuclear groups in the United States and List of anti-nuclear groups.
Symbols
Activities
Large protests
In 1971, the town of Wyhl, in Germany, was a proposed site for a nuclear power station. In the years that followed, public opposition steadily mounted, and there were large protests. Television coverage of police dragging away farmers and their wives helped to turn nuclear power into a major issue. In 1975, an administrative court withdrew the construction licence for the plant. The Wyhl experience encouraged the formation of citizen action groups near other planned nuclear sites.
In 1972, the nuclear disarmament movement maintained a presence in the Pacific, largely in response to French nuclear testing there. New Zealand activists sailed boats into the test zone, interrupting the testing program. In Australia, thousands of people joined protest marches in Adelaide, Melbourne, Brisbane, and Sydney. Scientists issued statements demanding an end to the nuclear tests. In Fiji, anti-nuclear activists formed an Against Testing on Mururoa organization.
In the Basque Country (Spain and France), a strong anti-nuclear movement emerged in 1973, which ultimately led to the abandonment of most of the planned nuclear power projects. On 14 July 1977, in Bilbao, between 150,000 and 200,000 people protested against the Lemoniz Nuclear Power Plant. This has been called the "biggest ever anti-nuclear demonstration".
In France, there were mass protests in the early 1970s, organized at nearly every planned nuclear site in France. Between 1975 and 1977, some 175,000 people protested against nuclear power in ten demonstrations. In 1977 there was a massive demonstration at the Superphénix breeder reactor in Creys-Malvillein which culminated in violence.
In West Germany, between February 1975 and April 1979, some 280,000 people were involved in seven demonstrations at nuclear sites. Several site occupations were also attempted. Following the Three Mile Island accident in 1979, some 120,000 people attended a demonstration against nuclear power in Bonn.
In the Philippines, there were many protests in the late 1970s and 1980s against the proposed Bataan Nuclear Power Plant, which was built but never operated due to safety concerns and issues regarding corruption.
In 1981, Germany's largest anti-nuclear power demonstration protested against the construction of the Brokdorf Nuclear Power Plant west of Hamburg. Some 100,000 people came face to face with 10,000 police officers.
In the late 1970s and early 1980s, the revival of the nuclear arms race, triggered a new wave of protests about nuclear weapons. Older organizations such as the Federation of Atomic Scientists revived, and newer organizations appeared, including the Nuclear Weapons Freeze Campaign and Physicians for Social Responsibility. In the UK, on 1 April 1983, about 70,000 people linked arms to form a 14-mile-long human chain between three nuclear weapons centres in Berkshire.
On Palm Sunday 1982, 100,000 Australians participated in anti-nuclear rallies in the nation's largest cities. Growing year by year, the rallies drew 350,000 participants in 1985. On 29 October 1983, the organised a demonstration in The Hague, Netherlands which was attended by 550,000 people, and was the largest demonstration in the history of the Netherlands.
In May 1986, following the Chernobyl disaster, clashes between anti-nuclear protesters and West German police were common. More than 400 people were injured in mid-May at a nuclear-waste reprocessing plant being built near Wackersdorf. Also in May 1986, an estimated 150,000 to 200,000 people marched in Rome to protest against the Italian nuclear program, and 50,000 marched in Milan. Hundreds of people walked from Los Angeles to Washington, D.C., in 1986 in what is referred to as the Great Peace March for Global Nuclear Disarmament. The march took nine months to traverse , advancing approximately fifteen miles per day.
The anti-nuclear organisation "Nevada Semipalatinsk" was formed in 1989 and was one of the first major anti-nuclear groups in the former Soviet Union. It attracted thousands of people to its protests and campaigns which eventually led to the closure of the nuclear test site in north-east Kazakhstan, in 1991.
The World Uranium Hearing was held in Salzburg, Austria in September 1992. Anti-nuclear speakers from all continents, including indigenous speakers and scientists, testified to the health and environmental problems of uranium mining and processing, nuclear power, nuclear weapons, nuclear tests, and radioactive waste disposal. People who spoke at the 1992 Hearing included Thomas Banyacya, Katsumi Furitsu, Manuel Pino and Floyd Red Crow Westerman.
Protests in the United States
There were many anti-nuclear protests in the United States which captured national public attention during the 1970s and 1980s. These included the well-known Clamshell Alliance protests at Seabrook Station Nuclear Power Plant and the Abalone Alliance protests at Diablo Canyon Nuclear Power Plant, where thousands of protesters were arrested. Other large protests followed the 1979 Three Mile Island accident.
A large anti-nuclear demonstration was held in May 1979 in Washington, D.C., when 65,000 people including the Governor of California, attended a march and rally against nuclear power. In New York City on 23 September 1979, almost 200,000 people attended a protest against nuclear power. Anti-nuclear power protests preceded the shutdown of the Shoreham, Yankee Rowe, Millstone I, Rancho Seco, Maine Yankee, and about a dozen other nuclear power plants.
On 12 June 1982, one million people demonstrated in New York City's Central Park against nuclear weapons and for an end to the cold war arms race. It was the largest anti-nuclear protest and the largest political demonstration in American history. International Day of Nuclear Disarmament protests were held on 20 June 1983 at 50 sites across the United States.
In 1986, hundreds of people walked from Los Angeles to Washington, D.C., in the Great Peace March for Global Nuclear Disarmament. There were many Nevada Desert Experience protests and peace camps at the Nevada Test Site during the 1980s and 1990s.
On 1 May 2005, 40,000 anti-nuclear/anti-war protesters marched past the United Nations in New York, 60 years after the atomic bombings of Hiroshima and Nagasaki. This was the largest anti-nuclear rally in the U.S. for several decades. In the 2000s there were protests about, and campaigns against, several new nuclear reactor proposals in the United States. In 2013, four aging, uncompetitive, reactors were permanently closed: San Onofre 2 and 3 in California, Crystal River 3 in Florida, and Kewaunee in Wisconsin. Vermont Yankee, in Vernon, is scheduled to close in 2014, following many protests. Protesters in New York State are seeking to close Indian Point Energy Center, in Buchanan, 30 miles from New York City.
Recent developments
For many years after the 1986 Chernobyl disaster nuclear power was off the policy agenda in most countries, and the anti-nuclear power movement seemed to have won its case. Some anti-nuclear groups disbanded. In the 2000s (decade), however, following public relations activities by the nuclear industry, advances in nuclear reactor designs, and concerns about climate change, nuclear power issues came back into energy policy discussions in some countries. The Fukushima Daiichi nuclear disaster subsequently undermined the nuclear power industry's proposed come back.
2004–2006
In January 2004, up to 15,000 anti-nuclear protesters marched in Paris against a new generation of nuclear reactors, the European Pressurised Water Reactor (EPWR).
On 1 May 2005, 40,000 anti-nuclear/anti-war protesters marched past the United Nations in New York, 60 years after the atomic bombings of Hiroshima and Nagasaki. This was the largest anti-nuclear rally in the U.S. for several decades. In Britain, there were many protests about the government's proposal to replace the aging Trident weapons system with a newer model. The largest protest had 100,000 participants and, according to polls, 59 per cent of the public opposed the move.
2007–2009
On 17 March 2007 simultaneous protests, organised by Sortir du nucléaire, were staged in five French towns to protest construction of EPR plants; Rennes, Lyon, Toulouse, Lille, and Strasbourg.
In June 2007, 4,000 local residents, students and anti-nuclear activists took to the streets in the city of Kudzus in Indonesia's Central Java, calling on the Government to abandon plans to build a nuclear power plant there.
In February 2008, a group of concerned scientists and engineers called for the closure of the Kazantzakis-Kariwa Nuclear Power Plant in Japan.
The International Conference on Nuclear Disarmament took place in Oslo in February 2008, and was organized by The Government of Norway, the Nuclear Threat Initiative and the Hoover Institute. The Conference was entitled Achieving the Vision of a World Free of Nuclear Weapons and had the purpose of building consensus between nuclear weapon states and non-nuclear weapon states in relation to the Nuclear Non-proliferation Treaty.
During a weekend in October 2008, some 15,000 people disrupted the transport of radioactive nuclear waste from France to a dump in Germany. This was one of the largest such protests in many years and, according to Der Spiel, it signals a revival of the anti-nuclear movement in Germany. In 2009, the coalition of green parties in the European parliament, who are unanimous in their anti-nuclear position, increased their presence in the parliament from 5.5% to 7.1% (52 seats).
In October 2008 in the United Kingdom, more than 30 people were arrested during one of the largest anti-nuclear protests at the Atomic Weapons Establishment at Aldermaston for 10 years. The demonstration marked the start of the UN World Disarmament Week and involved about 400 people.
In 2008 and 2009, there have been protests about, and criticism of, several new nuclear reactor proposals in the United States. There have also been some objections to license renewals for existing nuclear plants.
A convoy of 350 farm tractors and 50,000 protesters took part in an anti-nuclear rally in Berlin on 5 September 2009. The marchers demanded that Germany close all nuclear plants by 2020 and close the Gorleben radioactive dump. Gorleben is the focus of the anti-nuclear movement in Germany, which has tried to derail train transports of waste and to destroy or block the approach roads to the site. Two above-ground storage units house 3,500 containers of radioactive sludge and thousands of tonnes of spent fuel rods.
2010
On 21 April 2010, a dozen environmental organizations called on the United States Nuclear Regulatory Commission to investigate possible limitations in the AP1000 reactor design. These groups appealed to three federal agencies to suspend the licensing process because they believed containment in the new design is weaker than existing reactors.
On 24 April 2010, about 120,000 people built a human chain (KETTENreAKTION!) between the nuclear plants at Krümmel and Brunsbüttel. In this way they were demonstrating against the plans of the German government to extend the life of nuclear power reactors.
In May 2010, some 25,000 people, including members of peace organizations and 1945 atomic bomb survivors, marched for about two kilometers from downtown New York to the United Nations headquarters, calling for the elimination of nuclear weapons. In September 2010, German government policy shifted back toward nuclear energy, and this generated some new anti-nuclear sentiment in Berlin and beyond. On 18 September 2010, tens of thousands of Germans surrounded Chancellor Angela Merkel's office in an anti-nuclear demonstration that organisers said was the biggest of its kind since the 1986 Chernobyl disaster. In October 2010, tens of thousands of people protested in Munich against the nuclear power policy of Angela Merkel's coalition government. The action was the largest anti-nuclear event in Bavaria for more than two decades. In November 2010, there were violent protests against a train carrying reprocessed nuclear waste in Germany. Tens of thousands of protesters gathered in Dannenberg to signal their opposition to the cargo. Around 16,000 police were mobilised to deal with the protests.
In December 2010, some 10,000 people (mainly fishermen, farmers and their families) turned out to oppose the Jaitapur Nuclear Power Project in the Maharashtra state of India, amid a heavy police presence.
In December 2010, five anti-nuclear weapons activists, including octogenarians and Jesuit priests, were convicted of conspiracy and trespass in Tacoma, US. They cut fences at Naval Base Kitsap-Bangor in 2009 to protest submarine nuclear weapons, and reached an area near where Trident nuclear warheads are stored in bunkers. Members of the group could face up to 10 years in prison.
2011
In January 2011, five Japanese young people held a hunger strike for more than a week, outside the Prefectural Government offices in Yamaguchi City, to protest against the planned Kaminoseki Nuclear Power Plant near the environmentally sensitive Seto Inland Sea.
Following the Fukushima Daiichi nuclear disaster, anti-nuclear opposition intensified in Germany. On 12 March 2011, 60,000 Germans formed a 45-km human chain from Stuttgart to the Neckarwestheim power plant. On 14 March 110,000 people protested in 450 other German towns, with opinion polls indicating 80% of Germans opposed the government's extension of nuclear power. On 15 March 2011, Angela Merkel said that seven nuclear power plants which went online before 1980 would be closed and the time would be used to study speedier renewable energy commercialization.
In March 2011, around 2,000 anti-nuclear protesters demonstrated in Taiwan for an immediate halt to the construction of the island's fourth nuclear power plant. The protesters were also opposed to plans to extend the lifespan of three existing nuclear plants.
In March 2011, more than 200,000 people took part in anti-nuclear protests in four large German cities, on the eve of state elections. Organisers called it the largest anti-nuclear demonstration the country has seen. Thousands of Germans demanding an end to the use of nuclear power took part in nationwide demonstrations on 2 April 2011. About 7,000 people took part in anti-nuclear protests in Bremen. About 3,000 people protested outside RWE's headquarters in Essen.
Citing the Fukushima nuclear disaster, environmental activists at a U.N. meeting in April 2011 "urged bolder steps to tap renewable energy so the world doesn't have to choose between the dangers of nuclear power and the ravages of climate change".
In mid-April, 17,000 people protested at two demonstrations in Tokyo against nuclear power.
In India, environmentalists, local farmers and fishermen have been protesting for months over the planned Jaitapur Nuclear Power Project six-reactor complex, 420 km south of Mumbai. If built, it would be one of the world's largest nuclear power complexes. Protests have escalated following Japan's Fukushima nuclear disaster and during two days of violent rallies in April 2011, a local man was killed and dozens were injured.
In May 2011, some 20,000 people turned out for Switzerland's largest anti-nuclear power demonstration in 25 years. Demonstrators marched peacefully near the Beznau Nuclear Power Plant, the oldest in Switzerland, which started operating 40 years ago. Days after the anti-nuclear rally, Cabinet decided to ban the building of new nuclear power reactors. The country's five existing reactors would be allowed to continue operating, but "would not be replaced at the end of their life span".
In May 2011, 5,000 people joined a carnival-like anti-nuclear protest in Taipei City. This was part of a nationwide "No Nuke Action" protest, urging the government to stop construction of a Fourth Nuclear Plant and pursue a more sustainable energy policy.
On World Environment Day in June 2011, environmental groups demonstrated against Taiwan's nuclear power policy. The Taiwan Environmental Protection Union, together with 13 environmental groups and legislators, gathered in Taipei and protested against the nation's three operating nuclear power plants and the construction of a fourth plant.
Three months after the Fukushima nuclear disaster, thousands of anti-nuclear protesters marched in Japan. Company workers, students, and parents with children rallied across Japan, "venting their anger at the government's handling of the crisis, carrying flags bearing the words 'No Nukes!' and 'No More Fukushima'."
In August 2011, about 2,500 people including farmers and fishermen marched in Tokyo. They are suffering heavy losses following the Fukushima nuclear disaster, and called for prompt compensation from plant operator TEPCO and the government.
In September 2011, anti-nuclear protesters, marching to the beat of drums, "took to the streets of Tokyo and other cities to mark six months since the March earthquake and tsunami and vent their anger at the government's handling of the nuclear crisis set off by meltdowns at the Fukushima power plant". Protesters called for a complete shutdown of Japanese nuclear power plants and demanded a shift in government policy toward alternative sources of energy. Among the protestors were four young men who started a 10-day hunger strike to bring about change in Japan's nuclear policy.
Tens of thousands of people marched in central Tokyo in September 2011, chanting "Sayonara nuclear power" and waving banners, to call on Japan's government to abandon atomic energy in the wake of the Fukushima nuclear disaster. Author Kenzaburō Ōe and musician Ryuichi Sakamoto were among the event's supporters.
Since the March 2011 Japanese Fukushima nuclear disaster, "populations around proposed Indian NPP sites have launched protests that are now finding resonance around the country, raising questions about atomic energy as a clean and safe alternative to fossil fuels". Assurances by Prime Minister Manmohan Singh that all safety measures will be implemented, have not been heeded, and there have thus been mass protests against the French-backed 9900 MW Jaitapur Nuclear Power Project in Maharashtra and the 2000 MW Koodankulam Nuclear Power Plant in Tamil Nadu. The state government of West Bengal state has also refused permission to a proposed 6000 MW facility where six Russian reactors were to be built. A Public Interest Litigation (PIL) has also been filed against the government's civil nuclear program at the apex Supreme Court. The PIL specifically asks for the "staying of all proposed nuclear power plants till satisfactory safety measures and cost-benefit analyses are completed by independent agencies".
Michael Banach, the current Vatican representative to the International Atomic Energy Agency, told a conference in Vienna in September 2011 that the Japanese nuclear disaster created new concerns about the safety of nuclear plants globally. Auxiliary bishop of Osaka Michael Goro Matsuura said this serious nuclear power incident should be a lesson for Japan and other countries to abandon nuclear projects. He called on the worldwide Christian solidarity to provide wide support for this anti-nuclear campaign. Statements from bishops' conferences in Korea and the Philippines called on their governments to abandon atomic power. Nobel laureate Kenzaburō Ōe has said Japan should decide quickly to abandon its nuclear reactors.
In the UK, in October 2011, more than 200 protesters blockaded the Hinkley Point C nuclear power station site. Members of the Stop New Nuclear alliance barred access to the site in protest at EDF Energy's plans to build two new reactors on the site.
2012
In January 2012, 22 South Korean women's groups appealed for a nuclear free future, saying they believe nuclear weapons and power reactors "threaten our lives, the lives of our families and all living creatures". The women said they feel an enormous sense of crisis after the Fukushima nuclear disaster in March 2011, which demonstrated the destructive power of radiation in the disruption of human lives, environmental pollution, and food contamination.
Thousands of demonstrators took to the streets of Yokohama, Japan, on 14–15 January 2012, to show their support for a nuclear power-free world. The demonstration showed that organized opposition to nuclear power has gained momentum following the Fukushima nuclear disaster. The most immediate demand of the demonstrators was for the protection of rights, including basic human rights such as health care, for those affected by the Fukushima accident.
In January 2012, three hundred anti-nuclear protestors marched against plans to build a new nuclear power station at Wylfa in the UK. The march was organised by Pobl Atal Wylfa B, Greenpeace and Cymdeithas yr Iaith, which are supporting a farmer who is in dispute with Horizon.
On the anniversary of the 11 March earthquake and tsunami, protesters across Japan called for the abolishment of nuclear power and nuclear reactors. In Koriyama, Fukushima, 16,000 people called for the end of nuclear power. In Shizuoka Prefecture, 1,100 people appealed for the scrapping of the Hamaoka Nuclear Power Plant. In Tsuruga, Fukui, 1,200 people marched in the streets of the city of Tsuruga, the home of the Monju fast-breeder reactor prototype and other nuclear reactors. In Nagasaki and Hiroshima, anti-nuclear protesters and atomic-bomb survivors marched together and demanded that Japan should end its nuclear dependency.
Austrian Chancellor Werner Faymann expects anti-nuclear petition drives to start in at least six European Union countries in 2012 in an effort to have the EU abandon nuclear power. Under the EU's Lisbon Treaty, petitions that attract at least one million signatures can seek legislative proposals from the European Commission, which would pave the way for anti-nuclear activists to garner support.
In March 2012, about 2,000 people staged an anti-nuclear protest in Taiwan's capital following the massive tsunami that hit Japan one year ago. The protesters rallied in Taipei to renew calls for a nuclear-free island. They "want the government to scrap a plan to operate a newly constructed nuclear power plant – the fourth in densely populated Taiwan". Scores of aboriginal protesters "demanded the removal of 100,000 barrels of nuclear waste stored on their Orchid Island".
In March 2012, hundreds of anti-nuclear demonstrators converged on the Australian headquarters of global mining giants BHP Billiton and Rio Tinto. The 500-strong march through southern Melbourne called for an end to uranium mining in Australia, and included speeches and performances by representatives of the expatriate Japanese community as well as Australia's Indigenous communities, who are concerned about the effects of uranium mining near tribal lands. There were also events in Sydney.
In March 2012, South Korean environmental groups held a rally in Seoul to oppose nuclear power. Over 5,000 people attended, and the turnout was one of the largest in recent memory for an anti-nuclear rally. The demonstration demanded that President Lee Myung Bak abandon his policy of promoting nuclear power.
In March 2012, police said they had arrested nearly 200 anti-nuclear activists who were protesting the restart of work at the long-stalled Indian Kudankulam nuclear power plant.
In June 2012, tens of thousands of Japanese protesters participated in anti-nuclear power rallies in Tokyo and Osaka, over the government's decision to restart the first idled reactors since the Fukushima disaster, at Oi Nuclear Power Plant in Fukui Prefecture.
2013
Thousands of protesters marched in Tokyo on 11 March 2013 calling on the government to reject nuclear power.
In March 2013, 68,000 Taiwanese protested across major cities against nuclear power and the island's fourth nuclear plant, which is under construction. Taiwan's three existing nuclear plants are near the ocean, and prone to geological fractures, under the island.
In April 2013, thousands of Scottish campaigners, MSPs, and union leaders, rallied against nuclear weapons. The Scrap Trident Coalition wants to see an end to nuclear weapons, and says saved monies should be used for health, education and welfare initiatives. There was also a blockade of the Faslane Naval Base, where Trident missiles are stored.
2014
In March 2014, around 130,000 Taiwanese marched for an anti-nuclear protest around Taiwan. They demanded that the government remove nuclear power plants in Taiwan. The march came ahead of the 3rd anniversary of Fukushima disaster. Around 50,000 people marched in Taipei while another three separate events were held around other Taiwanese cities attended by around 30,000 people. Among the participants are the organizations from Green Citizen Action's Alliance, Homemakers United Foundation, Taiwan Association for Human Rights and Taiwan Environmental Protection Union. Facing on-going opposition and a host of delays, construction of the Lungmen Nuclear Power Plant was halted in April 2014.
Casualties
Casualties during anti-nuclear protests include:
On 9 December 1982, Norman Mayer, an American anti–nuclear weapons activist, was shot and killed by the United States Park Police after threatening to blow up the Washington Monument, Washington, D.C., unless a national dialogue on the threat of nuclear weapons was seriously undertaken.
On 10 July 1985, the flagship of Greenpeace, Rainbow Warrior, was sunk by France in New Zealand waters, and a Greenpeace photographer was killed. The ship was involved in protests against nuclear weapons testing at Mururoa Atoll. The French Government initially denied any involvement with the sinking but eventually admitted its guilt in October 1985. Two French agents pleaded guilty to charges of manslaughter, and the French Government paid $7 million in damages.
In 1990, two pylons holding high-voltage power lines connecting the French and Italian grid were blown up by Italian eco-terrorists, and the attack is believed to have been directly in opposition against the Superphénix.
In 2004, activist Sébastien Briat, who had tied himself to train tracks in front of a shipment of reprocessed nuclear waste, was run over by the wheels of the train. The event happened in Avricourt, France, and the fuel (totaling 12 containers) was from a German plant, on its way to be reprocessed.
Impact
Impact on popular culture
Beginning in the 1950s, anti-nuclear ideas received coverage in the popular media with novels such as Fail-Safe and feature films such as Godzilla (1954),Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb (1964), The China Syndrome (1979), Silkwood (1983), and The Rainbow Warrior (1992).
Dr. Strangelove explored "what might happen within the Pentagon ... if some maniac Air Force general should suddenly order a nuclear attack on the Soviet Union". One reviewer called the movie "one of the cleverest and most incisive satiric thrusts at the awkwardness and folly of the military that has ever been on the screen".
The China Syndrome has been described as a "gripping 1979 drama about the dangers of nuclear power" which had an extra impact when the real-life accident at the Three Mile Island nuclear plant occurred several weeks after the film opened. Jane Fonda plays a TV reporter who witnesses a near-meltdown (the "China syndrome" of the title) at a local nuclear plant, which was averted by a quick-thinking engineer, played by Jack Lemmon. The plot suggests that corporate greed and cost-cutting "have led to potentially deadly faults in the plant's construction".
Silkwood was inspired by the true-life story of Karen Silkwood, who died in a suspicious car accident while investigating alleged wrongdoing at the Kerr-McGee plutonium plant where she worked.
Dark Circle is a 1982 American documentary film that focuses on the connections between the nuclear weapons and the nuclear power industries, with a strong emphasis on the individual human and protracted U.S. environmental costs involved. A clear point made by the film is that while only two bombs were dropped on Japan, many hundreds were exploded in the United States. The film won the Grand Prize for documentary at the Sundance Film Festival and received a national Emmy Award for "Outstanding individual achievement in news and documentary." For the opening scenes and about half of its length, the film focuses on the Rocky Flats Plant and its plutonium contamination of the area's environment.
, (literally "Humming of Bees and Rotation of the Earth") is a Japanese documentary directed by Hitomi Kamanaka and released in 2010. It is the third in Kamanaka's trilogy of films on the problems of nuclear power and radiation, preceded by Hibakusha at the End of the World (also known as Radiation: A Slow Death) and Rokkasho Rhapsody.
Nuclear Tipping Point is a 2010 documentary film produced by the Nuclear Threat Initiative. It features interviews with four American government officials who were in office during the Cold War period, but are now advocating for the elimination of nuclear weapons. They are: Henry Kissinger, George Shultz, Sam Nunn, and William Perry.
Musicians United for Safe Energy (MUSE) was a musical group founded in 1979 by Jackson Browne, Graham Nash, Bonnie Raitt, and John Hall, following the Three Mile Island nuclear accident. The group organized a series of five No Nukes concerts held at Madison Square Garden in New York City in September 1979. On 23 September 1979, almost 200,000 people attended a large anti-nuclear rally staged by MUSE on the then-empty north end of the Battery Park City landfill in New York. The album No Nukes, and a film, also titled No Nukes, were both released in 1980 to document the performances.
In 2007, Bonnie Raitt, Graham Nash, and Jackson Browne, as part of the No Nukes group, recorded a music video of the Buffalo Springfield song "For What It's Worth".
Filmmakers Taylor Dunne and Eric Stewart are working on a documentary called "Off country" that looks at the devastating effects of atomic bomb testing on the communities around the White Sands missile range in New Mexico, the Nevada Test Site and the Rocky Flats Plant in Colorado. They were interviewed by Screen Comment's Sam Weisberg in 2017.
Impact on policy
The Bulletin of the Atomic Scientists is a nontechnical online magazine that has been published continuously since 1945, when it was founded by former Manhattan Project physicists after the atomic bombings of Hiroshima and Nagasaki. The Bulletins primary aim is to inform the public about nuclear policy debates while advocating for the international control of nuclear weapons. One of the driving forces behind the creation of the Bulletin was the amount of public interest surrounding atomic energy at the dawn of the atomic age. In 1945 the public interest in atomic warfare and weaponry inspired contributors to the Bulletin to attempt to inform those interested about the dangers and destruction that atomic war could bring about. In the 1950s, the Bulletin was involved in the formation of the Pugwash Conferences on Science and World Affairs, annual conferences of scientists concerned about nuclear proliferation.
Historian Lawrence S. Wittner has argued that anti-nuclear sentiment and activism led directly to government policy shifts about nuclear weapons. Public opinion influenced policymakers by limiting their options and also by forcing them to follow certain policies over others. Wittner credits public pressure and anti-nuclear activism with "Truman's decision to explore the Baruch Plan, Eisenhower's efforts towards a nuclear test ban and the 1958 testing moratorium, and Kennedy's signing of the Partial Test Ban Treaty".
In terms of nuclear power, Forbes magazine, in the September 1975 issue, reported that "the anti-nuclear coalition has been remarkably successful ... [and] has certainly slowed the expansion of nuclear power." California has banned the approval of new nuclear reactors since the late 1970s because of concerns over waste disposal, and some other U.S. states have a moratorium on construction of nuclear power plants. Between 1975 and 1980, a total of 63 nuclear units were canceled in the United States. Anti-nuclear activities were among the reasons, but the primary motivations were the overestimation of future demand for electricity and steadily increasing capital costs, which made the economics of new plants unfavorable.
The proliferation of nuclear weapons became a presidential priority issue for the Carter Administration in the late 1970s. To deal with proliferation problems, President Carter promoted stronger international control over nuclear technology, including nuclear reactor technology. Although a strong supporter of nuclear power generally, Carter turned against the breeder reactor because the plutonium it produced could be diverted into nuclear weapons.
For many years after the 1986 Chernobyl disaster nuclear power was off the policy agenda in most countries. In recent years, intense public relations activities by the nuclear industry, increasing evidence of climate change and failures to address it, have brought nuclear power issues back to the forefront of policy discussion in the nuclear renaissance countries. But some countries are not prepared to expand nuclear power and are still divesting themselves of their nuclear legacy, through nuclear power phase-out legislation.
Under the New Zealand Nuclear Free Zone, Disarmament, and Arms Control Act 1987, all territorial sea and land of New Zealand is declared a nuclear free zone. Nuclear-powered and nuclear-armed ships are prohibited from entering the country's territorial waters. Dumping of foreign radioactive waste and development of nuclear weapons in the country are outlawed. This followed a decades long campaign by peace activists which included the disruption of US warship visits. Despite common misconception, this act does not make nuclear power plants illegal, nor does it make radioactive medical treatments produced in overseas reactors illegal. A 2008 survey shows that 19% of New Zealanders favour nuclear power as the best energy source, while 77% prefer wind power as the best energy source.
On 26 February 1990, FW de Klerk issued orders to terminate the country's nuclear weapons programme, which until then had been a state secret. South Africa becomes the first country in the world to voluntary give-up its nuclear weapons programme.
Ireland, in 1999, had no plans to change its non-nuclear stance and pursue nuclear power in the future.
In the United States, the Navajo Nation forbids uranium mining and processing in its land.
In the United States, a 2007 University of Maryland survey showed that 73 per cent of the public surveyed favours the elimination of all nuclear weapons, 64 per cent support removing all nuclear weapons from high alert, and 59 per cent support reducing U.S. and Russian nuclear stockpiles to 400 weapons each. Given the unpopularity of nuclear weapons, U.S. politicians have been wary of supporting new nuclear programs. Republican-dominated congresses "have defeated the Bush administration's plan to build so-called 'bunker-busters' and 'mini-nukes'."
The Megatons to Megawatts Program converts weapons-grade material from nuclear warheads into fuel for nuclear power plants.
Thirty-one countries operate nuclear power plants. Nine nations possess nuclear weapons:
Today, some 26,000 nuclear weapons remain in the arsenals of the nine nuclear powers, with thousands on hair-trigger alert. Although U.S., Russian, and British nuclear arsenals are shrinking in size, those in the four Asian nuclear nations—China, India, Pakistan, and North Korea—are growing, in large part because of tensions among them. This Asian arms race also has possibilities of bringing Japan into the nuclear club.
During Barack Obama's successful U.S. presidential election campaign, he advocated the abolition of nuclear weapons. Since his election he has reiterated this goal in several major policy addresses. In 2010, the Obama administration negotiated a new weapons accord with Russia for a reduction of the maximum number of deployed nuclear weapons on each side from 2,200 to between 1,500 and 1,675—a reduction of some 30 per cent. In addition, President Obama has committed $15 billion over the next five years to improving the safety of the nuclear weapons stockpile.
Following the Fukushima Daiichi nuclear disaster, the Italian government put a one-year moratorium on plans to revive nuclear power. On 11–12 June 2011, Italian voters passed a referendum to cancel plans for new reactors. Over 94% of the electorate voted in favor of the construction ban, with 55% of the eligible voters participating, making the vote binding.
German Chancellor Angela Merkel's coalition announced on 30 May 2011, that Germany's 17 nuclear power stations will be shut down by 2022, in a policy reversal following Japan's Fukushima I nuclear accidents and anti-nuclear protests within Germany. Seven of the German power stations were closed temporarily in March, and they will remain off-line and be permanently decommissioned. An eighth was already off line, and will stay so.
As of 2011, countries such as Australia, Austria, Denmark, Greece, Ireland, Italy, Latvia, Liechtenstein, Luxembourg, Malta, Portugal, Israel, Malaysia, New Zealand, and Norway remain opposed to nuclear power. Germany, Switzerland and Belgium are phasing-out nuclear power.
Public opinion surveys on nuclear issues
In 2005, the International Atomic Energy Agency presented the results of a series of public opinion surveys in the Global Public Opinion on Nuclear Issues report. Majorities of respondents in 14 of the 18 countries surveyed believed that the risk of terrorist acts involving radioactive materials at nuclear facilities is high, because of insufficient protection. While majorities of citizens generally supported the continued use of existing nuclear power reactors, most people did not favor the building of new nuclear plants, and 25% of respondents felt that all nuclear power plants should be closed down. Stressing the climate change benefits of nuclear energy positively influences 10% of people to be more supportive of expanding the role of nuclear power in the world, but there is still a general reluctance to support the building of more nuclear power plants.
There was little support across the world for building new nuclear reactors, a 2011 poll for the BBC indicated. The global research agency GlobeScan, commissioned by BBC News, polled 23,231 people in 23 countries from July to September 2011, several months after the Fukushima nuclear disaster. In countries with existing nuclear programmes, people are significantly more opposed than they were in 2005, with only the UK and US bucking the trend. Most believed that boosting energy efficiency and renewable energy can meet their needs.
Eurobarometer 2008 poll indicated 44% supporting and 45% opposing nuclear energy in the European Union. Majority (over 62%) also appreciated nuclear power as means to prevent climate change. Both Eurobarometer and subsequent OECD poll (2010) indicated a "clear correlation between knowledge and support", so respondents who were more aware of the greenhouse gas emissions from energy sector were more likely to support low-emission nuclear power. A 2012 meta-analysis also confirmed positive correlation between support for nuclear power and understanding of nuclear power operations, with a significant effect where people living closer to nuclear power plant showed higher levels of support in general. In the United States, support and opposition to nuclear power plants is split almost equally.
Criticism
Attempts to reach political agreement on effective policies for climate change continue, and pro-nuclear environmentalists seek to reverse the traditionally anti-nuclear attitudes of environmentalists. Filmmaker Rob Stone's Pandora's Promise (2013) is a good example of this trend.
Some environmentalists criticise the anti-nuclear movement for under-stating the environmental costs of fossil fuels and non-nuclear alternatives, and overstating the environmental costs of nuclear energy.
Anti-nuclear activists are accused of encouraging radiophobic emotions among the public. In The War Against the Atom (Basic Books, 1982) Samuel MacCracken of Boston University argued that in 1982, 50,000 deaths per year could be attributed directly to non-nuclear power plants, if fuel production and transportation, as well as pollution, were taken into account. He argued that if non-nuclear plants were judged by the same standards as nuclear ones, each US non-nuclear power plant could be held responsible for about 100 deaths per year.
The Nuclear Energy Institute (NEI) is the main lobby group for companies doing nuclear work in the United States, while most countries that employ nuclear energy have a national industry group. The World Nuclear Association is the only global trade body. In seeking to counteract the arguments of nuclear opponents, it points to independent studies that quantify the costs and benefits of nuclear energy and compares them to the costs and benefits of alternatives. NEI sponsors studies of its own, but it also references studies performed for the World Health Organization, for the International Energy Agency, and by university researchers.
Critics of the anti-nuclear movement point to independent studies that show that the capital resources required for renewable energy sources are often prohibitively higher than those required for nuclear power.
Some people, including former opponents of nuclear energy, criticize the movement on the basis of the claim that nuclear power is necessary for reducing carbon dioxide emissions. These individuals include James Lovelock, originator of the Gaia hypothesis, Patrick Moore, an early member of Greenpeace and former director of Greenpeace International, George Monbiot and Stewart Brand, creator of the Whole Earth Catalog. Lovelock goes further to refute claims about the danger of nuclear energy and its waste products. In a January 2008 interview, Moore said that "It wasn't until after I'd left Greenpeace and the climate change issue started coming to the forefront that I started rethinking energy policy in general and realised that I had been incorrect in my analysis of nuclear as being some kind of evil plot." Stewart Brand has apologized for his past anti-nuclear stance in the 2010 book Whole Earth Discipline, saying that "Greens caused gigatons of carbon dioxide to enter the atmosphere from the coal and gas burning that went ahead instead of nuclear".
Some anti-nuclear organisations have acknowledged that their positions are subject to review.
In April 2007, Dan Becker, Director of Global Warming for the Sierra Club, declared, "Switching from dirty coal plants to dangerous nuclear power is like giving up smoking cigarettes and taking up crack." James Lovelock criticizes holders of such a view: "Opposition to nuclear energy is based on irrational fear fed by Hollywood-style fiction, the Green lobbies and the media." ". . .I am a Green and I entreat my friends in the movement to drop their wrongheaded objection to nuclear energy."
George Monbiot, an English writer known for his environmental and political activism, once expressed deep antipathy to the nuclear industry. He finally rejected his later neutral position regarding nuclear power in March 2011. Monbiot now advocates its use, having been convinced of its relative safety by what he considers the limited effects of the 2011 Japan tsunami on nuclear reactors in the region. Subsequently, he has harshly condemned the anti-nuclear movement, writing that it "has misled the world about the impacts of radiation on human health ... made [claims] ungrounded in science, unsupportable when challenged and wildly wrong." He singled out Helen Caldicott for, he wrote, making unsourced and inaccurate claims, dismissing contrary evidence as part of a cover-up, and overstating the death toll from the Chernobyl disaster by a factor of more than 140.
An evaluation of sequential games of the door-in-the-face technique concluded that spreading fears of nuclear warfare enables Russia to strengthen its bargaining position in the Russo-Ukrainian War while the real possibility of the nuclear holocaust is unacceptable for Russia.
See also
The Bomb
Doomsday Clock
Environmental movement
John Gofman
Green politics
International Day against Nuclear Tests
List of Chernobyl-related articles
List of nuclear whistleblowers
List of peace activists
List of states with nuclear weapons
Lists of nuclear disasters and radioactive incidents
Mainau Declaration
Mayors for Peace
Gregory Minor
Nuclear-Free Future Award
Nuclear-free zone
Nuclear organizations (Wikipedia category)
Nuclear power phase-out
Nuclear safety and security
Nuclear weapons convention
Nuclear weapons in popular culture
Otto Hahn Peace Medal
Pandora's Promise
Plowshares movement
The Ribbon International
Uranium
Vulnerability of nuclear plants to attack
World Association of Nuclear Operators
Notes and references
1
Bibliography
Brown, Jerry and Rinaldo Brutoco (1997). Profiles in Power: The Anti-nuclear Movement and the Dawn of the Solar Age, Twayne Publishers.
Byrne, John and Steven M. Hoffman (1996). Governing the Atom: The Politics of Risk, Transaction Publishers.
Clarfield, Gerald H. and William M. Wiecek (1984). Nuclear America: Military and Civilian Nuclear Power in the United States 1940–1980, Harper & Row.
Cooke, Stephanie (2009). In Mortal Hands: A Cautionary History of the Nuclear Age, Black Inc.
Cragin, Susan (2007). Nuclear Nebraska: The Remarkable Story of the Little County That Couldn't Be Bought, AMACOM.
Dickerson, Carrie B. and Patricia Lemon (1995). Black Fox: Aunt Carrie's War Against the Black Fox Nuclear Power Plant, Council Oak Publishing Company,
Diesendorf, Mark (2009). Climate Action: A Campaign Manual for Greenhouse Solutions, University of New South Wales Press.
Diesendorf, Mark (2007). Greenhouse Solutions with Sustainable Energy, University of New South Wales Press.
Elliott, David (2007). Nuclear or Not? Does Nuclear Power Have a Place in a Sustainable Energy Future?, Palgrave.
Falk, Jim (1982). Global Fission: The Battle Over Nuclear Power, Oxford University Press.
Fradkin, Philip L. (2004). Fallout: An American Nuclear Tragedy, University of Arizona Press.
Freeman, Stephanie L. (2023) Dreams for a Decade: International Nuclear Abolitionism and the End of the Cold War (University of Pennsylvania Press, 2023).
Giugni, Marco (2004). Social Protest and Policy Change: Ecology, Antinuclear, and Peace Movements in Comparative Perspective, Rowman and Littlefield.
Lovins, Amory B. (1977). Soft Energy Paths: Towards a Durable Peace, Friends of the Earth International,
Lovins, Amory B. and John H. Price (1975). Non-Nuclear Futures: The Case for an Ethical Energy Strategy, Ballinger Publishing Company, 1975,
Lowe, Ian (2007). Reaction Time: Climate Change and the Nuclear Option, Quarterly Essay.
McCafferty, David P. (1991). The Politics of Nuclear Power: A History of the Shoreham Power Plant, Kluwer.
McKay, George (2019) '"They've got a bomb": sounding anti-nuclearism in the anarcho-punk movement in Britain, 1978-84.' Rock Music Studies 6(2): 1-20.
McKay, George (2021) 'Rethinking the cultural politics of punk: anti-nuclear and anti-war (post-)punk popular music in 1980s Britain.' In George McKay and Gina Arnold, eds. The Oxford Handbook of Punk Rock. New York: Oxford University Press.
Natti, Susanna and Bonnie Acker (1979). No Nukes: Everyone's Guide to Nuclear Power, South End Press.
Newtan, Samuel Upton (2007). Nuclear War 1 and Other Major Nuclear Disasters of the 20th Century, AuthorHouse.
Ondaatje, Elizabeth H. (c1988). Trends in Antinuclear Protests in the United States, 1984–1987, Rand Corporation.
Parkinson, Alan (2007). Maralinga: Australia's Nuclear Waste Cover-up, ABC Books.
Pernick, Ron and Clint Wilder (2012). Clean Tech Nation: How the U.S. Can Lead in the New Global Economy.
Peterson, Christian (2003). Ronald Reagan and Antinuclear Movements in the United States and Western Europe, 1981–1987, Edwin Mellen Press.
Price, Jerome (1982). The Antinuclear Movement, Twayne Publishers.
Rudig, Wolfgang (1990). Anti-nuclear Movements: A World Survey of Opposition to Nuclear Energy, Longman.
Schneider, Mycle, Steve Thomas, Antony Froggatt, Doug Koplow (August 2009). The World Nuclear Industry Status Report, German Federal Ministry of Environment, Nature Conservation and Reactor Safety.
Smith, Jennifer (Editor), (2002). The Antinuclear Movement, Cengage Gale.
Sovacool, Benjamin K. (2011). Contesting the Future of Nuclear Power: A Critical Global Assessment of Atomic Energy, World Scientific.
Surbrug, Robert (2009). Beyond Vietnam: The Politics of Protest in Massachusetts, 1974–1990, University of Massachusetts Press.
Walker, J. Samuel (2004). Three Mile Island: A Nuclear Crisis in Historical Perspective, University of California Press.
Wellock, Thomas R. (1998). Critical Masses: Opposition to Nuclear Power in California, 1958–1978, The University of Wisconsin Press,
Wills, John (2006). Conservation Fallout: Nuclear Protest at Diablo Canyon, University of Nevada Press.
Wittner, Lawrence S. (2009). Confronting the Bomb: A Short History of the World Nuclear Disarmament Movement, Stanford University Press.
External links
The M and S Collection at the Library of Congress contains anti-nuclear movement materials.
Jennifer Fay Gow photographs of Brisbane anti-nuclear and civil liberties demonstrations October 1977, State Library of Queensland
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Nuclear history
Nuclear weapons policy
Social movements
Ethics of science and technology | Anti-nuclear movement | [
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2,996,193 | https://en.wikipedia.org/wiki/Weierstrass%E2%80%93Enneper%20parameterization | In mathematics, the Weierstrass–Enneper parameterization of minimal surfaces is a classical piece of differential geometry.
Alfred Enneper and Karl Weierstrass studied minimal surfaces as far back as 1863.
Let and be functions on either the entire complex plane or the unit disk, where is meromorphic and is analytic, such that wherever has a pole of order , has a zero of order (or equivalently, such that the product is holomorphic), and let be constants. Then the surface with coordinates is minimal, where the are defined using the real part of a complex integral, as follows:
The converse is also true: every nonplanar minimal surface defined over a simply connected domain can be given a parametrization of this type.
For example, Enneper's surface has , .
Parametric surface of complex variables
The Weierstrass-Enneper model defines a minimal surface () on a complex plane (). Let (the complex plane as the space), the Jacobian matrix of the surface can be written as a column of complex entries:
where and are holomorphic functions of .
The Jacobian represents the two orthogonal tangent vectors of the surface:
The surface normal is given by
The Jacobian leads to a number of important properties: , , , . The proofs can be found in Sharma's essay: The Weierstrass representation always gives a minimal surface. The derivatives can be used to construct the first fundamental form matrix:
and the second fundamental form matrix
Finally, a point on the complex plane maps to a point on the minimal surface in by
where for all minimal surfaces throughout this paper except for Costa's minimal surface where .
Embedded minimal surfaces and examples
The classical examples of embedded complete minimal surfaces in with finite topology include the plane, the catenoid, the helicoid, and the Costa's minimal surface. Costa's surface involves Weierstrass's elliptic function :
where is a constant.
Helicatenoid
Choosing the functions and , a one parameter family of minimal surfaces is obtained.
Choosing the parameters of the surface as :
At the extremes, the surface is a catenoid or a helicoid . Otherwise, represents a mixing angle. The resulting surface, with domain chosen to prevent self-intersection, is a catenary rotated around the axis in a helical fashion.
Lines of curvature
One can rewrite each element of second fundamental matrix as a function of and , for example
And consequently the second fundamental form matrix can be simplified as
One of its eigenvectors is which represents the principal direction in the complex domain. Therefore, the two principal directions in the space turn out to be
See also
Associate family
Bryant surface, found by an analogous parameterization in hyperbolic space
References
Differential geometry
Surfaces
Minimal surfaces | Weierstrass–Enneper parameterization | [
"Chemistry"
] | 572 | [
"Foams",
"Minimal surfaces"
] |
2,996,487 | https://en.wikipedia.org/wiki/Dutch%20Waterline | The Dutch Waterline (, modern spelling: Hollandse Waterlinie) was a series of water-based defences conceived by Maurice of Nassau in the early 17th century, and realised by his half brother Frederick Henry. Combined with natural bodies of water, the Waterline could be used to transform Holland, the westernmost region of the Netherlands and adjacent to the North Sea, almost into an island. In the 19th century, the Line was extended to include Utrecht.
On July 26, 2021, the line was added to the Defence Line of Amsterdam to become the Dutch Water Defence Lines UNESCO World Heritage Site.
History
Early in the Eighty Years' War of Independence against Spain, the Dutch realized that flooding low-lying areas formed an excellent defence against enemy troops. This was demonstrated, for example, during the Siege of Leiden in 1574. In the latter half of the war, when the province of Holland had been freed of Spanish troops, Maurice of Nassau planned to defend it with a line of flooded land protected by fortresses that ran from the Zuiderzee (present IJsselmeer) down to the river Waal.
Old Dutch Waterline
In 1629, Prince Frederick Henry started the execution of the plan. Sluices were constructed in dikes and forts and fortified towns were created at strategic points along the line with guns covering the dikes that traversed the water line. The water level in the flooded areas was carefully maintained at a level deep enough to make an advance on foot precarious and shallow enough to rule out effective use of boats (other than the flat bottomed gun barges used by the Dutch defenders). Under the water level additional obstacles like ditches and trous de loup (and much later, barbed wire and land mines) were hidden. The trees lining the dikes that formed the only roads through the line could be turned into abatis in time of war. In wintertime the water level could be manipulated to weaken ice covering, while the ice itself could be used when broken up to form further obstacles that would expose advancing troops to fire from the defenders for longer.
The Dutch Water Line proved its value less than forty years after its construction during the Franco-Dutch War (or Third Anglo-Dutch War) (1672), when it stopped the armies of Louis XIV from conquering Holland, although the freezing over of the line came close to rendering it useless. In 1794 and 1795, the revolutionary French armies overcame the obstacle posed by the Dutch Water Line only by the heavy frost that had frozen the flooded areas solid.
New Dutch Waterline
After the final defeat of Napoleon in 1815 at the Battle of Waterloo, the United Kingdom of the Netherlands was formed. Soon after King William I decided to modernise the Water Line. The Water Line was partly shifted east of Utrecht.
In the next 100 years the main Dutch defence line would be the new Water Line. It was further extended and modernised in the 19th century, with forts containing round gun towers reminiscent of Martello towers. The line was mobilised but never attacked during the Franco-Prussian war in 1870 and World War I.
At the advent of World War II, most of the earth and brick fortifications in the Water Line were too vulnerable to modern artillery and bombs to withstand a protracted siege. To remedy this a large number of pillboxes were added. However, the Dutch had decided to use a more eastern main defence line, the Grebbe Line, and reserved a secondary role for the Water Line.
When the Grebbe Line was broken on May 13, the field army was withdrawn to the Water Line. However, modern tactics could circumvent fixed defense lines, as happened during the French Maginot Line. While the Dutch army was fighting a fixed battle at the Grebbe Line, German airborne troops captured the southern approaches into the heart of "Fortress Holland" by surprise, the key points being the bridges at Moerdijk, Dordrecht and Rotterdam. When resistance did not cease, the Germans forced the Dutch into surrender by aerial bombing of Rotterdam and threatening the same for Utrecht and Amsterdam.
From its conception in 1815, until the last modernisation in 1940, the equivalent of around 50 billion euro was spent on the New Dutch Water Line.
After World War II, the Dutch government redesigned the idea of a waterline to counter a possible Soviet invasion. This third version of the Water Line was erected more to the east at the IJssel (the IJssel Line) and in Gelderland. In case of an invasion, the water of the Rhine and the Waal were set to divert into the IJssel, flooding the river and bordering lands. The plan was never tested, and it was dismantled by the Dutch government in 1964.
Dimensions and units
At present
Today many of the forts are still more or less intact. There is renewed interest in the waterline for its natural beauty. Bike tours and hiking paths are organised with the line as a theme. Some of the forts are open for bikers/hikers to stay the night. Others have a variety of uses, for example Utrecht University houses its botanical garden in Fort Hoofddijk.
Due to the unique nature of the line, the Dutch government considered whether to nominate the whole defensive line as a UNESCO World Heritage Site, as they did with the ring of fortresses around Amsterdam. On July 26, 2021, the line was added as a UNESCO World Heritage Site.
A 25-year plan has been developed by the artist, Agnes Denes.
In 2010, one of the forts on the Line Bunker 599, was opened as a publicly accessible work of art that was created through a cooperation between RAAAF and Atelier de Lyon. The bunker was sliced open, with a walkway placed through it forming an installation allowing a view to look into and through the bunker.
Constructions
Forts
To protect weaknesses in the waterline a series of forts and fortified towns have been constructed.
Order of forts following the line from north to south.
Forts explicitly built to defend a town are mentioned with the relevant town in parentheses
Permanent battery De Westbatterij (Muiden)
Castle Muiderslot (Muiden)
Fortified town of Muiden
Fortified town of Weesp
Fort aan de Ossenmarkt (Weesp)
Fort Uitermeer
Fort Hinderdam
Fort Ronduit (Naarden)
Fortified town of Naarden
Permanent batteries at the Karnemelksloot (Naarden)
Fort Uitermeer
Fort Kijkuit
Fort Spion
Fort Nieuwersluis
Fort bij Tienhoven
Fort aan de Klop (Utrecht)
Fort de Gagel (Utrecht)
Fort op de Ruigenhoeksedijk (Utrecht)
Fort Blauwkapel (Utrecht)
Fort op de Voordorpsdijk (Utrecht)
Fort aan de Biltstraat (Utrecht)
Minor fort Werk aan de Hoofddijk (Utrecht)
Fort bij Rhijnauwen (Utrecht)
Lunetten, a series of small crescent-shaped forts:
Lunet I (Utrecht)
Lunet II (Utrecht)
Lunet III (Utrecht)
Lunet IV (Utrecht)
Fort bij Vechten (Utrecht)
Fort bij 't Hemeltje
Fort bij Jutphaas (Nieuwegein)
Minor fort Werk aan de Waalse Wetering
Minor fort Werk aan de Korte Uitweg
Lunet aan de Snel
Fort Honswijk
Minor fort Werk aan de Groeneweg
Fort Everdingen
Minor fort Werk aan het Spoel
Fort Pannerden
Fort Boven Lent
Minor fort Werk op de spoorweg bij de Diefdijk
Fort bij Asperen
Fort bij de Nieuwe Steeg
Fort bij Vuren
Fortified town of Gorinchem
Fortified town of Woudrichem
Castle Loevestein
Minor fort Werk aan de Bakkerskil
Fort Steurgat
Fort aan de Uppelse Dijk (Fort Altena)
Fort Giessen
Locks
Plofsluis
See also
Dutch waterlines
Defence Line of Amsterdam
Frisian waterline
Grebbe line
IJssel Line
Maas Line
Peel-Raam Line
West Brabant waterline
Other
Defence lines of the Netherlands
Crossing the Lines
List of fortifications
Notes
References
Wandelplatform-LAW. Waterliniepad (in Dutch) 1st edition, 2004.
Klinkert, W., Het Vaderland Verdedigt (in Dutch) 1st edition, 1992,
External links
New Dutch Waterline - official site (in English; Dutch, German, French also available)
Dutch Water Defence Lines UNESCO collection on Google Arts and Culture
Nieuwe Hollandse Waterlinie - Knowledge database for the Dutch Waterline (in Dutch)
Installations of the Dutch States Army
Fortifications in the Netherlands
Military history of the Netherlands
Fortification lines
World War II sites in the Netherlands
History of North Brabant
History of North Holland
History of South Holland
History of Utrecht (province)
Buildings and structures in Utrecht (city)
Dutch Water Defence Lines | Dutch Waterline | [
"Engineering"
] | 1,852 | [
"Fortification lines"
] |
2,996,488 | https://en.wikipedia.org/wiki/Choked%20flow | Choked flow is a compressible flow effect. The parameter that becomes "choked" or "limited" is the fluid velocity.
Choked flow is a fluid dynamic condition associated with the Venturi effect. When a flowing fluid at a given pressure and temperature passes through a constriction (such as the throat of a convergent-divergent nozzle or a valve in a pipe) into a lower pressure environment the fluid velocity increases. At initially subsonic upstream conditions, the conservation of energy principle requires the fluid velocity to increase as it flows through the smaller cross-sectional area of the constriction. At the same time, the venturi effect causes the static pressure, and therefore the density, to decrease at the constriction. Choked flow is a limiting condition where the mass flow cannot increase with a further decrease in the downstream pressure environment for a fixed upstream pressure and temperature.
For homogeneous fluids, the physical point at which the choking occurs for adiabatic conditions is when the exit plane velocity is at sonic conditions; i.e., at a Mach number of 1. At choked flow, the mass flow rate can be increased only by increasing the upstream density of the substance.
The choked flow of gases is useful in many engineering applications because the mass flow rate is independent of the downstream pressure, and depends only on the temperature and pressure and hence the density of the gas on the upstream side of the restriction. Under choked conditions, valves and calibrated orifice plates can be used to produce a desired mass flow rate.
Choked flow in liquids
If the fluid is a liquid, a different type of limiting condition (also known as choked flow) occurs when the venturi effect acting on the liquid flow through the restriction causes a decrease of the liquid pressure beyond the restriction to below that of the liquid's vapor pressure at the prevailing liquid temperature. At that point, the liquid partially flashes into bubbles of vapor and the subsequent collapse of the bubbles causes cavitation. Cavitation is quite noisy and can be sufficiently violent to physically damage valves, pipes and associated equipment. In effect, the vapor bubble formation in the restriction prevents the flow from increasing any further.
Mass flow rate of a gas at choked conditions
All gases flow from higher pressure to lower pressure. Choked flow can occur at the change of the cross section in a de Laval nozzle or through an orifice plate. The choked velocity is observed upstream of an orifice or nozzle. The upstream volumetric flow rate is lower than the downstream condition because of the higher upstream density. The choked velocity is a function of the upstream pressure but not the downstream. Although the velocity is constant, the mass flow rate is dependent on the density of the upstream gas, which is a function of the upstream pressure. Flow velocity reaches the speed of sound in the orifice, and it may be termed a .
Choking in change of cross section flow
Assuming ideal gas behavior, steady-state choked flow occurs when the downstream pressure falls below a critical value . That critical value can be calculated from the dimensionless critical pressure ratio equation
,
where is the heat capacity ratio of the gas and where is the total (stagnation) upstream pressure.
For air with a heat capacity ratio , then ; other gases have in the range 1.09 (e.g. butane) to 1.67 (monatomic gases), so the critical pressure ratio varies in the range , which means that, depending on the gas, choked flow usually occurs when the downstream static pressure drops to below 0.487 to 0.587 times the absolute pressure in stagnant upstream source vessel.
When the gas velocity is choked, one can obtain the mass flowrate as a function of the upstream pressure. For isentropic flow Bernoulli's equation should hold:
,
where - is the enthalpy of gas, - molar specific heat at constant pressure, with being the universal gas constant, - absolute temperature. If we neglect the initial gas velocity upstream, we can obtain the ultimate gas velocity as follows:
In a choked flow this velocity happens to coincide exactly with the sonic velocity at the critical cross-section:
,
where is the density at the critical cross-section. We can now obtain the pressure as:
,
taking in account that . Now remember that we have neglected gas velocity upstream, that is pressure at the critical section must be essentially the same or close to the stagnation pressure upstream , and . Finally we obtain:
as an approximate equation for the mass flowrate.
The more precise equation for the choked mass flow rate is:
The mass flow rate is primarily dependent on the cross-sectional area of the nozzle throat and the upstream pressure , and only weakly dependent on the temperature . The rate does not depend on the downstream pressure at all. All other terms are constants that depend only on the composition of the material in the flow. Although the gas velocity reaches a maximum and becomes choked, the mass flow rate is not choked. The mass flow rate can still be increased if the upstream pressure is increased as this increases the density of the gas entering the orifice.
The value of can be calculated using the below expression:
The above equations calculate the steady state mass flow rate for the pressure and temperature existing in the upstream pressure source.
If the gas is being released from a closed high-pressure vessel, the above steady state equations may be used to approximate the initial mass flow rate. Subsequently, the mass flow rate decreases during the discharge as the source vessel empties and the pressure in the vessel decreases. Calculating the flow rate versus time since the initiation of the discharge is much more complicated, but more accurate.
The technical literature can be confusing because many authors fail to explain whether they are using the universal gas law constant R, which applies to any ideal gas or whether they are using the gas law constant Rs, which only applies to a specific individual gas. The relationship between the two constants is Rs = R / M where M is the molecular weight of the gas.
Real gas effects
If the upstream conditions are such that the gas cannot be treated as ideal, there is no closed form equation for evaluating the choked mass flow. Instead, the gas expansion should be calculated by reference to real gas property tables, where the expansion takes place at constant enthalpy.
Minimum pressure ratio required for choked flow to occur
The minimum pressure ratios required for choked conditions to occur (when some typical industrial gases are flowing) are presented in Table 1. The ratios were obtained using the criterion that choked flow occurs when the ratio of the absolute upstream pressure to the absolute downstream pressure is equal to or greater than , where is the specific heat ratio of the gas. The minimum pressure ratio may be understood as the ratio between the upstream pressure and the pressure at the nozzle throat when the gas is traveling at Mach 1; if the upstream pressure is too low compared to the downstream pressure, sonic flow cannot occur at the throat.
Notes:
Pu, absolute upstream gas pressure
Pd, absolute downstream gas pressure
Venturi nozzles with pressure recovery
The flow through a venturi nozzle achieves a much lower nozzle pressure than downstream pressure. Therefore, the pressure ratio is the comparison between the upstream and nozzle pressure. Therefore, flow through a venturi can reach Mach 1 with a much lower upstream to downstream ratio.
Thin-plate orifices
The flow of real gases through thin-plate orifices never becomes fully choked. The mass flow rate through the orifice continues to increase as the downstream pressure is lowered to a perfect vacuum, though the mass flow rate increases slowly as the downstream pressure is reduced below the critical pressure. Cunningham (1951) first drew attention to the fact that choked flow does not occur across a standard, thin, square-edged orifice.
Vacuum conditions
In the case of upstream air pressure at atmospheric pressure and vacuum conditions downstream of an orifice, both the air velocity and the mass flow rate become choked or limited when sonic velocity is reached through the orifice.
The flow pattern
Figure 1a shows the flow through the nozzle when it is completely subsonic (i.e. the nozzle is not choked). The flow in the chamber accelerates as it converges toward the throat, where it reaches its maximum (subsonic) speed at the throat. The flow then decelerates through the diverging section and exhausts into the ambient as a subsonic jet. In this state, lowering the back pressure increases the flow speed everywhere in the nozzle.
When the back pressure, pb, is lowered enough, the flow speed is Mach 1 at the throat, as in figure 1b. The flow pattern is exactly the same as in subsonic flow, except that the flow speed at the throat has just reached Mach 1. Flow through the nozzle is now choked since further reductions in the back pressure can't move the point of M=1 away from the throat. However, the flow pattern in the diverging section does change as you lower the back pressure further.
As pb is lowered below that needed to just choke the flow, a region of supersonic flow forms just downstream of the throat. Unlike in subsonic flow, the supersonic flow accelerates as it moves away from the throat. This region of supersonic acceleration is terminated by a normal shock wave. The shock wave produces a near-instantaneous deceleration of the flow to subsonic speed. This subsonic flow then decelerates through the remainder of the diverging section and exhausts as a subsonic jet. In this regime if you lower or raise the back pressure you move the shock wave away from (increase the length of supersonic flow in the diverging section before the shock wave) the throat.
If the pb is lowered enough, the shock wave sits at the nozzle exit (figure 1d). Due to the long region of acceleration (the entire nozzle length) the flow speed reaches its maximum just before the shock front. However, after the shock the flow in the jet is subsonic.
Lowering the back pressure further causes the shock to bend out into the jet (figure 1e), and a complex pattern of shocks and reflections is set up in the jet that create a mixture of subsonic and supersonic flow, or (if the back pressure is low enough) just supersonic flow. Because the shock is no longer perpendicular to the flow near the nozzle walls, it deflects the flow inward as it leaves the exit producing an initially contracting jet. This is referred as overexpanded flow because in this case the pressure at the nozzle exit is lower than that in the ambient (the back pressure)- i.e. the flow has been expanded by the nozzle too much.
A further lowering of the back pressure changes and weakens the wave pattern in the jet. Eventually the back pressure becomes low enough so that it is now equal to the pressure at the nozzle exit. In this case, the waves in the jet disappear altogether (figure 1f), and the jet becomes uniformly supersonic. This situation, since it is often desirable, is referred to as the 'design condition'.
Finally, lowering the back-pressure even further creates a new imbalance between the exit and back pressures (exit pressure greater than back pressure), figure 1g. In this situation (called 'underexpanded') expansion waves (that produce gradual turning perpendicular to the axial flow and acceleration in the jet) form at the nozzle exit, initially turning the flow at the jet edges outward in a plume and setting up a different type of complex wave pattern.
See also
Accidental release source terms includes mass flow rate equations for non-choked gas flows as well.
Orifice plate includes derivation of non-choked gas flow equation.
de Laval nozzles are venturi tubes that produce supersonic gas velocities as the tube and the gas are first constricted and then the tube and gas are expanded beyond the choke plane.
Rocket engine nozzles discusses how to calculate the exit velocity from nozzles used in rocket engines.
Hydraulic jump
High pressure jet
References
External links
Choked flow of gases
Development of source emission models
Restriction orifice sizing control Perform orifice plate, restriction orifice sizing calculation for a single phase flow.
Flow regimes
Aerodynamics
Gas technologies | Choked flow | [
"Chemistry",
"Engineering"
] | 2,490 | [
"Aerospace engineering",
"Aerodynamics",
"Flow regimes",
"Fluid dynamics"
] |
2,996,528 | https://en.wikipedia.org/wiki/Metered-dose%20inhaler | A metered-dose inhaler (MDI) is a device that delivers a specific amount of medication to the lungs in the form of a short burst of aerosolized medicine that is usually self-administered by the patient via inhalation. It is the most commonly used delivery system for treating asthma, chronic obstructive pulmonary disease (COPD) and other respiratory diseases. The medication in a metered dose inhaler is most commonly a bronchodilator, corticosteroid or a combination of both for treating asthma and COPD. Other medications less commonly used but also administered by MDI are mast cell stabilizers, such as cromoglicate or nedocromil.
Description
A metered-dose inhaler consists of three major components: the canister, which is produced in aluminum or stainless steel by means of deep drawing, where the formulation resides; the metering valve, which allows a metered quantity of the formulation to be dispensed with each actuation; and an actuator (or mouthpiece) which enables the patient to operate the device and directs the aerosol into the patient's lungs. The formulation comprises the drug, a liquefied gas propellant and, in many cases, stabilizing excipients. The actuator contains the mating discharge nozzle and generally includes a dust cap to prevent contamination.
To use the inhaler, the patient presses down on the top of the canister, with their thumb supporting the lower portion of the actuator. Actuation of the device releases a single metered dose of the formulation, which contains the medication either dissolved or suspended in the propellant. Breakup of the volatile propellant into droplets, followed by rapid evaporation of these droplets, results in the generation of an aerosol consisting of micrometer-sized medication particles that are then inhaled.
Uses
Metered-dose inhalers are only one type of inhaler, but they are the most commonly used type. The replacement of chlorofluorocarbons propellants with hydrofluoroalkanes (HFA) resulted in the redesign of metered-dose inhalers in the 1990s. For one variety of beclomethasone inhalers, this redesign resulted in considerably smaller aerosol particles being produced and increased in potency by a factor of 2.6.
Asthma inhalers contain a medication that treats the symptoms of asthma.
Nicotine inhalers allow cigarette smokers to get nicotine without using tobacco, much like nicotine gum or a nicotine patch. The US Food and Drug Administration (FDA) has approved some nicotine inhaler products for smoking cessation. Nicotine inhalers that are marketed as nicotine replacement therapy should not be confused with electronic cigarettes, which produce an aerosol, usually from a tobacco extract, using a heating coil, while nicotine inhalers produce a noncombusted nicotine aerosol. A study found that "levels of carcinogens and toxins in e-cigarettes typically exceeded those measured in an FDA-approved nicotine inhaler." Nicotine inhalers are also known by their nickname of "the puffer." These devices are made of thin plastic, sometimes resembling a cigarette or a cylinder shape. They contain a porous nicotine-filled plug located at the base of the product. When you puff on the inhaler, nicotine aerosol is inhaled and absorbed in the mouth's lining. Every inhaler delivers almost four hundred puffs of this nicotine vapor. The nicotine inhaler is also temperature-sensitive. In cooler weather, less nicotine is delivered. The nicotine inhaler is considered more straightforward to use than the electronic cigarette as it is usually disposable and contains fewer parts than the electronic cigarette.
Nicotine inhalers also exist as non-MDIs; for example, the format for the Nicorette Inhalator is an "inhalation vapour solution."
Dry powder inhalers involve micronized powder, often packaged in single-dose quantities in blisters or gel capsules containing the powdered medication to be drawn into the lungs by the user's breath. These systems tend to be more expensive than the MDI, and patients with severely compromised lung function, such as those that occur during an asthma attack, may find it difficult to generate enough airflow to get good function from them.
Metered-dose inhalers can be used to treat COPD, both in a stable state and during lung attacks.
History
Before the invention of the MDI, asthma medication was delivered using a fragile and unreliable squeeze bulb nebulizer. The relatively crude nature of these devices also meant that the particles that they generated were relatively large, too large for effective drug delivery to the lungs. Nonetheless, these nebulizers paved the way for inhalation drug delivery, inspiring the MDI.
MDIs were first developed in 1955 by Riker Laboratories, now a subsidiary of 3M Healthcare. At that time, MDIs represented a convergence of two relatively new technologies, the CFC propellant and the Meshburg metering valve, originally designed for dispensing perfume. The initial design by Riker used a glass canister coated with vinyl plastic to improve its resilience. By 1956, Riker had developed two MDI-based products, the Medihaler-Ept containing epinephrine and the Medihaler-Iso containing Isoprenaline. Both products are agonists that provide short-term relief from asthma symptoms and have now largely been replaced in asthma treatment by salbutamol, which is more selective.
Spacers
Metered-dose inhalers are sometimes used with add-on devices referred to as holding chambers or spacers, tubes attached to the inhaler that act as a reservoir or holding chamber and reduce the speed at which the aerosol enters the mouth. They serve to hold the medication that is sprayed by the inhaler. This makes it easier to use the inhaler and helps ensure that more of the medication gets into the lungs instead of just into the mouth or the air. Proper use of a spacer can make an inhaler more effective in delivering medicine.
Spacers can be especially helpful to adults and children who find a regular metered dose inhaler hard to use. People who use corticosteroid inhalers should use a spacer to prevent getting the medicine in their mouth, where oral yeast infections and dysphonia can occur.
Lifespan and replacement
The deposition of the content of drug formulation on the canister surface can result in a shorter shelf life of an MDI inhaler. Applying a suitable surface coating to the components helps to extend this shelf life. Over the years, various coating processes have been developed that can be applied to both the canister and valve to protect the contents from deposition and degradation.
Gas plasma processing is an industrial technique carried out in a vacuum to coat the entire MDI inhaler. It involves constant or pulsed gas excitation by radio frequency (RF) or the microwave field to produce an energetic plasma. This coating ensures that the drug formulation does not stick to the interior wall of the MD inhaler and results in the patient receiving the prescribed dose of medication, extending the product's shelf-life.
A metered dose inhaler contains enough medication for a certain number of actuations (or "puffs") printed on the canister. Even though the inhaler may continue to work beyond that number of uses, the amount of medication delivered may not be correct. It is important to keep track of the number of times an inhaler is used so that it can be replaced after its recommended number of uses. For this reason, several regulatory authorities have requested that manufacturers add a dose counter or dose indicator to the actuator. Several inhalation products are now sold with a dose counter-actuator. Depending on the manufacturer and the product, inhalers are sold as a complete unit or the individual canister as a refill prescription.
Inhaler technique and use
While MDIs are commonly used in the treatment of lung-based disorders, their use requires dexterity to complete the required sequential steps to achieve the application of these devices. Incorrect completion of one or more steps in using an MDI can substantially reduce the delivery of the administered medication and, consequently, its effectiveness and safety. Numerous studies have demonstrated that between 50-100% of patients do not use their inhaler devices correctly, with patients often unaware that they are using their inhaled medication incorrectly. Incorrect inhaler technique has been associated with poorer outcomes. Incorrect maintenance and cleaning of metered dose inhalers is also an issue identified by many users, highlighting the need for clear guidance for patients prescribed MDIs.
Propellants
One of the most crucial components of an MDI is its propellant. The propellant provides the force to generate the aerosol cloud and is also the medium where the active component must be suspended or dissolved. Propellants in MDIs typically make up more than 99% of the delivered dose, so the properties of the propellant dominate more than any other individual factor. This is often overlooked in literature and in industry because so few propellants are used, and their contribution is often taken for granted. Suitable propellants must pass a stringent set of criteria, and they must:
have a boiling point in the range of -100 to +30 °C
have a density of approximately 1.2 to 1.5 g cm−3 (approximately that of the drug to be suspended or dissolved)
have a vapour pressure of 40 to 80 psig
have no toxicity to the patient
be non-flammable
be able to dissolve common additives (active ingredients should be either fully soluble or fully insoluble)
Chlorofluorocarbons (CFCs)
In the early days of MDIs, the most commonly used propellants were the chlorofluorocarbons CFC-11, CFC-12 and CFC-114.
In 2008, the Food and Drug Administration announced that inhalers using chlorofluorocarbons as a propellant, such as Primatene Mist, could no longer be manufactured or sold as of 2012. This followed from U.S. decision to agree to the 1987 Montreal Protocol on Substances that deplete the ozone layer.
Hydrofluorocarbons
Hydrofluorocarbon propellants have replaced CFC propellants. Concerns about the use of hydrofluorocarbon propellants have, however, since arisen since these compounds are potent greenhouse gases; propellants released during the use of a single inhaler result in a greenhouse footprint equivalent to greenhouse gases released during a 180-mile car journey.
Surfactant lipids
Phospholipids are important natural surfactant lipids. used to enhance penetration and bioavailability. Phospholipids reduce the high surface tension forces at the air-water interface within the alveoli, thereby reducing the pressure needed to expand the lungs. Thus, commercially available formulations of phospholipids have been designed to spread rapidly over an air-aqueous interface, thereby reducing what is otherwise a very high surface tension of water.
Colours
For ease of identification, many MDI's are colour-coded
See also
Inhaler
Dry powder inhaler
Asthma
Spray bottle
References
External links
UpToDate Patient Information: Metered dose inhaler techniques in adults
Using a metered-dose inhaler with a spacer: techniques for children, illustrated
Using a metered-dose inhaler without a spacer: techniques for children, illustrated
Asthma
Drug delivery devices
Smoking cessation
Dosage forms | Metered-dose inhaler | [
"Chemistry"
] | 2,433 | [
"Pharmacology",
"Drug delivery devices"
] |
2,996,632 | https://en.wikipedia.org/wiki/Disemvoweling | Disemvoweling, disemvowelling (British and Commonwealth English), or disemvowelment is writing a piece of text with all the vowel letters removed. Disemvoweling is often used in band and company names. It used to be a common feature of SMS language where space was costly.
Etymology
The word disemvowel is a pun and portmanteau combining vowel and disembowel. One of the earliest attestations of the word dates back to the 1860s. The 1939 novel Finnegans Wake by James Joyce also uses it: "Secret speech Hazelton and obviously disemvowelled".
Use as a moderation tool
A technique dubbed splat out was used by Usenet moderators to prevent flamewars, by substituting a "splat" (i.e., asterisk) for some letters, often the vowels, of highly charged words in postings. Examples include Nazi→N*z*, evolution→*v*l*t**n, gun control→g*n c*ntr*l. According to the Jargon File, "the purpose is not to make the word unrecognizable but to make it a mention rather than a use." The term "disemvoweling"—attested from 1990—was occasionally used for the splat-out of vowels.
Teresa Nielsen Hayden used the vowel-deletion technique in 2002 for internet forum moderation on her blog Making Light. This was termed disemvoweling by Arthur D. Hlavaty later in the same thread.
Nielsen Hayden joined the group blog Boing Boing as community manager in August 2007, when it re-enabled comments on its posts, and implemented disemvoweling. Gawker Media sites adopted disemvoweling as a moderation tool in August 2008. On 30 October 2008, Time magazine listed disemvoweling as #42 of their "Top 50 Inventions of 2008".
Xeni Jardin, co-editor of Boing Boing, said of the practice, "the dialogue stays, but the misanthrope looks ridiculous, and the emotional sting is neutralized." Also, Boing Boing producers claim that disemvoweling sends a clear message to internet forums as to types of behavior that are unacceptable.
After Jeff Bezos acquired The Washington Post in 2013, one of his ideas was to install a feature that allowed a reader to "disemvowel" an article they didn't enjoy, the idea being that another reader would have to pay to reinstate the vowels. Shailesh Prakash, the newspaper's chief product and technology officer, said "the idea didn't go far".
Criticism
In July 2008, New York Times reporter Noam Cohen criticized disemvoweling as a moderation tool, citing a June 2008 dispute about the deletion of all posts on Boing Boing that mentioned sex columnist Violet Blue. In the Boing Boing comment threads resulting from this controversy, Nielsen Hayden used the disemvoweling technique. Cohen noted that disemvoweling was "Not quite censorship, but not quite unfettered commentary either." A subsequent unsigned case study on online crisis communication asserted that "removing the vowels from participants' comments only increased the gulf between the editors and the community" during the controversy.
Matt Baumgartner, a blogger at the Albany Times Union, reported in August 2009 that the newspaper's lawyers had told him to stop disemvoweling comments.
Implementation
Nielsen Hayden originally disemvoweled postings manually, using Microsoft Word. Because the letter Y is sometimes a vowel and sometimes a consonant, there are a variety of ways to treat it. Nielsen Hayden's policy was never to remove Y, in order to maintain legibility.
The technique has been facilitated by plug-in filters to automate the process. The first, for MovableType, was written in 2002; others are available for WordPress and other content management systems.
Use in company and band names
Since the 2000s, various company and band names have been making use of full or partial disemvowelling, such as twttr (original name of Twitter), abrdn, BHLDN, Tumblr, Flickr, or Scribd. Artists and band names without vowels include Mstrkrft, MGMT, MSCHF, MNDR, Blk Jks, Sbtrkt, WSTRN, HMGNC, Strfkr, Kshmr, LNDN DRGS, LNZNDRF, PVT, RDGLDGRN, Dvsn, SWMRS, and Dwntwn. Disemvoweling can be used due to copyright or search engine optimization reasons. For voice user interfaces, band and song names without vowels can be difficult to process.
See also
English words without vowels
Vanity plate
Abjad, a writing system similar to an alphabet that removes most or all vowels
References
External links
Internet terminology
Internet forum terminology
Censorship
Vowel letters
Nonstandard spelling | Disemvoweling | [
"Technology"
] | 1,075 | [
"Computing terminology",
"Internet terminology"
] |
7,143,248 | https://en.wikipedia.org/wiki/External%20intercostal%20membrane | Unlike the other two intercostal muscles, the external intercostal muscle does not retain its muscular character all the way to the sternum, and so the tissue in this location is called the external intercostal membrane.
The fibers of the external intercostal muscles run downward and forward between adjacent ribs. Each muscle begins posteriorly at the tubercles of the ribs and extends anteriorly to the costochondral junction, the junction between the costal cartilage and the sternal end of the rib. The muscle between the costal cartilages is replaced by a membranous layer called the external intercostal membrane.
Links and References:
Grant's: 1.15, 1.20
Netter: 176
Rohen/Yokochi: 193, 194
See also
Aponeuroses
External links
- "Thoracic Wall: The External Intercostal Muscle"
Musculoskeletal system | External intercostal membrane | [
"Biology"
] | 190 | [
"Organ systems",
"Musculoskeletal system"
] |
7,143,378 | https://en.wikipedia.org/wiki/Motion%20field | In computer vision, the motion field is an ideal representation of motion in three-dimensional space (3D) as it is projected onto a camera image. Given a simplified camera model, each point in the image is the projection of some point in the 3D scene but the position of the projection of a fixed point in space can vary with time. The motion field can formally be defined as the time derivative of the image position of all image points given that they correspond to fixed 3D points. This means that the motion field can be represented as a function which maps image coordinates to a 2-dimensional vector. The motion field is an ideal description of the projected 3D motion in the sense that it can be formally defined but in practice it is normally only possible to determine an approximation of the motion field from the image data.
Introduction
A camera model maps each point in 3D space to a 2D image point according to some mapping functions :
Assuming that the scene depicted by the camera is dynamic; it consists of objects moving relative each other, objects which deform, and possibly also the camera is moving relative to the scene, a fixed point in 3D space is mapped to varying points in the image. Differentiating the previous expression with respect to time gives
Here
is the motion field and the vector u is dependent both on the image position as well as on the time t. Similarly,
is the motion of the corresponding 3D point and its relation to the motion field is given by
where is the image position dependent matrix
This relation implies that the motion field, at a specific image point, is invariant to 3D motions which lies in the null space of . For example, in the case of a pinhole camera all 3D motion components which are directed to or from the camera focal point cannot be detected in the motion field.
Special cases
The motion field is defined as:
where
.
where
is a point in the scene where Z is the distance to that scene point.
is the relative motion between the camera and the scene,
is the translational component of the motion, and
is the angular velocity of the motion.
Relation to optical flow
The motion field is an ideal construction, based on the idea that it is possible to determine the motion of each image point, and above it is described how this 2D motion is related to 3D motion. In practice, however, the true motion field can only be approximated based on measurements on image data. The problem is that in most cases each image point has an individual motion which therefore has to be locally measured by means of a neighborhood operation on the image data. As consequence, the correct motion field cannot be determined for certain types of neighborhood and instead an approximation, often referred to as the optical flow, has to be used. For example, a neighborhood which has a constant intensity may correspond to a non-zero motion field, but the optical flow is zero since no local image motion can be measured. Similarly, a neighborhood which is intrinsic 1-dimensional (for example, an edge or line) can correspond to an arbitrary motion field, but the optical flow can only capture the normal component of the motion field. There are also other effects, such as image noise, 3D occlusion, temporal aliasing, which are inherent to any method for measuring optical flow and causes the resulting optical flow to deviate from the true motion field.
In short, the motion field cannot be correctly measured for all image points, and the optical flow is an approximation of the motion field. There are several different ways to compute the optical flow based on different criteria of how an optical estimation should be made.
References
Motion in computer vision | Motion field | [
"Physics"
] | 722 | [
"Physical phenomena",
"Motion (physics)",
"Motion in computer vision"
] |
7,143,470 | https://en.wikipedia.org/wiki/Generic%20Eclipse%20Modeling%20System | Generic Eclipse Modeling System (GEMS) is a configurable toolkit for creating domain-specific modeling and program synthesis environments for Eclipse. The project aims to bridge the gap between the communities experienced with visual metamodeling tools like those built around the Eclipse modeling technologies, such as the Eclipse Modeling Framework (EMF) and Graphical Modeling Framework (GMF). GEMS helps developers rapidly create a graphical modeling tool from a visual language description or metamodel without any coding in third-generation languages. Graphical modeling tools created with GEMS automatically support complex capabilities, such as remote updating and querying, template creation, styling with Cascading Style Sheets (CSS), and model linking.
The configuration is accomplished through metamodels specifying the modeling paradigm of the application domain, i.e. a domain-specific modeling language (DSML). The modeling paradigm contains all the syntactic, semantic, and presentation information regarding the domain; which concepts will be used to construct models, what relationships may exist among those concepts, how the concepts may be organized and viewed by the modeler, and rules governing the construction of models. The modeling paradigm defines the family of models that can be created using the resultant modeling environment.
The built-in metamodeling language is based on the UML class diagram notation. Metamodels in other eCore readable formats can be used as well. Metamodel constraints can be specified in declarative languages (e.g. OCL, Prolog) or, alternatively, in Java. Once a metamodel has been created, GEMS plug-in generator can be invoked to create the modeling tool. The generated plug-in uses Eclipse's Graphical Editing Framework (GEF) and Draw2D plug-in to visualize the DSML as a diagram. GEMS extension points can be used to create an interpreter which traverses the domain-specific model and generates code. Interpreters can also interpret the model to provide executable semantics and perform complex analyses.
References
Related tools
GEMS EMF Intelligence Framework
External links
GEMS Homepage
Programming language topics
Simulation programming languages
Eclipse (software) | Generic Eclipse Modeling System | [
"Engineering"
] | 436 | [
"Software engineering",
"Programming language topics"
] |
7,143,530 | https://en.wikipedia.org/wiki/PowerVu | PowerVu is a conditional access system for digital television developed by Scientific Atlanta. It is used for professional broadcasting, notably by Retevision, Bloomberg Television, Discovery Channel, AFRTS, ABS-CBN, GMA Network, and American Forces Network. It is also used by cable companies to prevent viewing by unauthorized viewers and non-cable subscribers.
PowerVu has decoders that decode signals from certain satellites for cable distribution services. These decoders can also be used just like the FTA (Free-To-Air) satellite receivers if properly configured.
See also
Basic Interoperable Scrambling System
References
Broadcast engineering
Digital television
Conditional-access television broadcasting | PowerVu | [
"Engineering"
] | 130 | [
"Broadcast engineering",
"Electronic engineering"
] |
7,143,554 | https://en.wikipedia.org/wiki/Scorpius%E2%80%93Centaurus%20association | The Scorpius–Centaurus association (sometimes called Sco–Cen or Sco OB2) is the nearest OB association to the Sun. This stellar association is composed of three subgroups (Upper Scorpius, Upper Centaurus–Lupus, and Lower Centaurus–Crux) and its distance is about 130 parsecs or 420 light-years. Analysis using improved Hipparcos data has brought the number of known members to 436. The cluster shows a continuous spread of stars with no apparent need for subclassification.
The Sco–Cen subgroups range in age from 11 million years (Upper Scorpius) to roughly 15 million years (Upper Centaurus–Lupus and Lower Centaurus–Crux). Many of the bright stars in the constellations Scorpius, Lupus, Centaurus, and Crux are members of the Sco–Cen association, including Antares (the most massive member of Upper Scorpius), and most of the stars in the Southern Cross. Hundreds of stars have been identified as members of Sco-Cen, with masses ranging from roughly 15 solar masses (Antares) down to below the hydrogen-burning limit (i.e. brown dwarfs), and the total stellar population in each of the three subgroups is probably of the order 1000–2000.
The Sco–Cen OB association appears to be the most pronounced part of a large complex of recent (<20 million years) and ongoing star-formation. The complex contains several star-forming molecular clouds in Sco–Cen's immediate vicinity—the Rho Oph, Pipe Nebula, Barnard 68, Chamaeleon, Lupus, Corona Australis, and Coalsack cloud complexes (all at distances of ~120-200 parsecs), and several less populous, young stellar groups on the periphery of Sco–Cen, including the ~3–5 million-year-old Epsilon Chamaeleontis group, ~7 million-year-old Eta Chamaeleontis moving group, ~8 million-year-old TW Hydrae association, ~12 million-year-old Beta Pictoris moving group, and possibly the ~30–50 million-year-old IC 2602 open cluster.
The stellar members of the Sco–Cen association have convergent proper motions of approximately 0.02–0.04 arcseconds per year, indicative that the stars have nearly parallel velocity vectors, moving at about 20 km/s with respect to the Sun. The dispersion of the velocities within the subgroups are only of order 1–2 km/s, and the group is most likely gravitationally unbound. Several supernovae have exploded in Sco–Cen over the past 15 million years, leaving a network of expanding gas superbubbles around the group, including the Loop I Bubble.
To explain the presence of radioactive 60Fe in deep ocean ferromanganese crusts and in biogenic magnetite crystals within Pacific Ocean sediments it has been hypothesized that a nearby supernova, possibly a member of Sco–Cen, exploded in the Sun's vicinity roughly 3 million years ago, causing the Pliocene–Pleistocene boundary marine extinction. However, other findings cite the distance at which this supernova occurred at more than 100 parsec, maintaining that it is not likely not to have contributed to this extinction through the mechanism of what is known as the ultra-violet B (UV-B) catastrophe.
In 2019, researchers found interstellar iron in Antarctica which they relate to the Local Interstellar Cloud, which might have been formed near the Sco-Cen association.
In December 2021, around 70 new rogue planets were discovered in the Upper Scorpius association.
The subgroups of the Scorpius-Centaurus association contains the youngest transiting exoplanets: K2-33 b (11 Myrs), TOI-1227 b (11 Myrs) and HIP 67522 b (17 Myrs). It also contains directly imaged exoplanets such as UScoCTIO 108 b and the PDS 70 system.
Notable stars
Antares
Acrux
Mimosa
Beta Centauri
Zeta Ophiuchi is a runaway star that likely originated in the association.
See also
List of nearby stellar associations and moving groups
β Pictoris moving group
Ursa Major Moving Group
References
Stellar associations
Scorpius
Centaurus
Lupus (constellation)
Crux | Scorpius–Centaurus association | [
"Astronomy"
] | 940 | [
"Centaurus",
"Constellations",
"Crux",
"Scorpius",
"Lupus (constellation)"
] |
7,143,953 | https://en.wikipedia.org/wiki/Antiparasitic | Antiparasitics are a class of medications which are indicated for the treatment of parasitic diseases, such as those caused by helminths, amoeba, ectoparasites, parasitic fungi, and protozoa, among others. Antiparasitics target the parasitic agents of the infections by destroying them or inhibiting their growth; they are usually effective against a limited number of parasites within a particular class. Antiparasitics are one of the antimicrobial drugs which include antibiotics that target bacteria, and antifungals that target fungi. They may be administered orally, intravenously or topically. Overuse or misuse of antiparasitics can lead to the development of antimicrobial resistance.
Broad-spectrum antiparasitics, analogous to broad-spectrum antibiotics for bacteria, are antiparasitic drugs with efficacy in treating a wide range of parasitic infections caused by parasites from different classes.
Types
Broad-spectrum
Nitazoxanide
Antiprotozoals
Melarsoprol (for treatment of sleeping sickness caused by Trypanosoma brucei)
Eflornithine (for sleeping sickness)
Metronidazole (for vaginitis caused by Trichomonas)
Tinidazole (for intestinal infections caused by Giardia lamblia)
Miltefosine (for the treatment of visceral and cutaneous leishmaniasis, currently undergoing investigation for Chagas disease)
Antihelminthic
Antinematodes
Mebendazole (for most nematode infections)
Pyrantel pamoate (for most nematode infections)
Thiabendazole (for roundworm infections)
Diethylcarbamazine (for treatment of Lymphatic filariasis)
Ivermectin (for prevention of river blindness)
Fenbendazole
Anticestodes
Niclosamide (for tapeworm infections)
Praziquantel (for tapeworm infections)
Albendazole (broad spectrum)
Antitrematodes
[Praziquantel]
Antiamoebics
Rifampin
Amphotericin B
Antifungals
Fumagillin (for microsporidiosis)
Medical uses
Antiparasitics treat parasitic diseases, which impact an estimated 2 billion people.
Administration
Antiparastics may be given via a variety of routes depending on the specific medication, including oral, topical, and intravenous.
Resistance to antiparasitics has been a growing concern, especially in veterinary medicine. The Egg hatch assay can be used to determine whether a parasite causing an infection has become resistant to standard drug treatments.
Drug development history
Early antiparasitics were ineffective, frequently toxic to patients, and difficult to administer due to the difficulty in distinguishing between the host and the parasite.
Between 1975 and 1999 only 13 of 1,300 new drugs were antiparasitics, which raised concerns that insufficient incentives existed to drive development of new treatments for diseases that disproportionately target low-income countries. This led to new public sector and public-private partnerships (PPPs), including investment by the Bill and Melinda Gates Foundation. Between 2000 and 2005, twenty new antiparasitic agents were developed or in development. Metal-containing compounds are the subject of another avenue of approach.
Research
In the last decades, triazolopyrimidines and their metal complexes have been looked at as an alternative drug to the existing commercial antimonials, searching for a decrease in side effects and the development of parasite drug resistance.
See also
Balsam of Peru, which has antiparasitic attributes
Naegleria fowleri
Balamuthia mandrillaris
References
Biocides | Antiparasitic | [
"Biology",
"Environmental_science"
] | 759 | [
"Biocides",
"Antiparasitic agents",
"Toxicology"
] |
7,144,771 | https://en.wikipedia.org/wiki/Stepped%20nozzle | A stepped nozzle (or dual-bell nozzle) is a de Laval rocket nozzle which has altitude compensating properties.
The characteristic of this kind of nozzle is that part of the way along the inside of the nozzle there is a straightening of the curve of the nozzle contour, followed by a sharp step outwards.
At low altitude, this causes the jet to separate at the step and ambient pressure maintains the jet at this place, avoiding jet instabilities and avoiding massive overexpansion.
As the altitude rises, the jet becomes progressively under-expanded and grows until it fills the nozzle, at which point the gas provides more pressure against the rest of the nozzle and thrust and specific impulse increases.
See also
Nozzle extension
Bell nozzle
References
Rocket propulsion
Nozzles | Stepped nozzle | [
"Engineering"
] | 166 | [
"Mechanical engineering stubs",
"Mechanical engineering"
] |
7,145,373 | https://en.wikipedia.org/wiki/Glaze%20defects | Glaze defects are any flaws in the surface quality of a ceramic glaze, its physical structure or its interaction with the body.
Glaze and body mismatch
Certain glaze defects are a result of differences in the thermal expansion coefficient of the glaze and the clay body.
Crazing
Crazing is a spider web pattern of cracks penetrating the glaze. It is caused by tensile stresses greater than the glaze is able to withstand. Common reasons for such stresses are: a mismatch between the thermal expansions of glaze and body; from moisture expansion of the body; and in the case of glazed tiles fixed to a wall, movement of the wall or of the bonding material used to fix the tile to the wall.
The cracks can allow the ingress of water into the cracks. Once fired, ware tends to be more resistant to crazing due to better development of the glaze/body interfacial layer, which reduces stress gradients between the glaze and body.
In pottery a distinction is often made between crazing, as an accidental defect, and "crackle", which is when the same phenomenon, often strongly accentuated, is produced deliberately. The Chinese in particular enjoyed the random effects of crackle, though it spans a spectrum: in Ru ware it is a tolerated feature of most pieces, but not sought, while in Guan ware a strong crackle is a desired effect.
The causes of crazing include:
Thermal expansion mis-match. Poor fit between the glaze and the body's thermal expansion is the main cause of crazing and can be due to:
Under-firing resulting in failure to develop sufficient body thermal expansion.
Firing too quickly, resulting in failure to achieve sufficient heatwork.
Low thermal expansion body.
High thermal expansion glaze.
Over-firing of vitreous ware.
Moisture expansion of the body. Porous bodies swell slightly due to absorption of moisture. Where glazes are in only slight compression this can be sufficient to bring them into tension. The problem results in delayed or secondary crazing, which occurs over a period of time after the ware has been produced.
Glazing too thickly. This is a common cause of crazing. Glazes, which should be craze resistant, can craze if applied too thickly. This is because the further the glaze surface is away from the body, the lower the compression acting on it.
Thermal shock. Opening the kiln too soon above 100 °C can cause crazing and dunting. Above 200 °C catastrophic failure can occur due to the volume changes at the cristobalite inversion (around 225 °C)
Steger's Crazing Test is a method for the assessment of the glaze fit. It is undertaken by measuring any deformation on cooling of a thin bar that was glazed only on one side. A common method of testing glazed ceramic ware for crazing resistance is to expose pieces of ware to the steam in an autoclave at a minimum of 50 psi.
Seger's Rules are a series of empirical rules put forward by Hermann Seger for the prevention of crazing and peeling. To prevent crazing, the body should be adjusted as follows: decrease the clay, increase the free silica; replace some of the ball clay by kaolin; decrease the feldspar; grind the silica more finely; biscuit fire at higher temperature. Alternatively, the glaze can be adjusted: increase silica and/or decrease fluxes; replace some SiO2 by B2O3; replace fluxes of high equivalent weight by fluxes of lower equivalent weight. To prevent peeling, the body or glaze should be adjusted in the reverse direction.
Shivering
Shivering describes the breaking away of glaze from ceramic ware as a result of greater compression in the glaze layer than the body caused by the glaze having an expansion coefficient below the clay body's.
It is the opposite of crazing, as are the preventative steps: see Seger's Rule above. Shivering is also known as peeling.
Metal release
Regulations have existed since the late 1960s to protect consumers from the potential risk of toxic materials, mainly metals, being released from glazes into drink and foodstuffs. Lead and cadmium are the metals of greatest concern, although testing can be extended to include others. The propensity for any glaze to release metal may depend on complex interactions between the formulation used, any applied decoration and the kiln atmosphere.
Monitoring the level of metal release from glazed ware forms part of the quality control procedures of all reputable producers. Test methods are specified according to national and international standards, although testing usually involves: the ware being immersed or filled with a 4% acetic acid solution; covered and left for 24 hours at room temperature, although if cooking ware is being tested higher temperatures are needed; the acetic acid solution decanted from the ware and the concentration of leached metal measured by Atomic absorption spectroscopy. Acceptance limits are enforced by legislation, and whilst varying between countries all are within the ppm range. Some of the most well recognised legislation are: across Europe 'EC Directive 84/500/EEC 1984'; for the UK 'GB Ceramic Ware (Safety) Regulations SI 1647, 1988'; and for the USA 'FDA Compliance Policy Guide 7117.06 and 7117.07 for cadmium and lead.'
Glaze surface defects
Blisters
A large bubble sometimes present as a fault in ceramic ware. Blisters appear as large bubbles either just below or penetrating the surface, leaving sharp, rough edges that collect dirt. The surface of the glaze is very unpleasant and looks like a boiled mass of bubbles, craters and pinholes.
Crawling
A defect that appears as irregular, bare patches of fired body showing through the glaze where it has failed to adhere to or wet the body on firing. The cause is a weak bond between glaze and body; this may result from greasy patches or dust on the surface of the biscuit ware or from shrinkage of the applied glaze slip during drying. The fault is more likely to occur with once-fired ware such as sanitaryware.
Metal marking
Metal marks are dark lines, often accompanied by damage in the glaze, caused by the deposition of metal during the use of metal utensils. The cutlery, or other relatively soft metal, will leave a very thin smear of metal on pottery ware if the glaze is minutely pitted. A glaze may have this defective surface as it leaves the glost kiln, or it may subsequently develop such a surface as a result of inadequate chemical durability. The fault is also known as cutlery marking.
Pin-hole
A fault that is commonly the result of a bubble in the glaze when it was molten that burst but was only partially healed. The bubbles are most often from gas that originates from air trapped between the particles of powdered glaze as the glaze begins to mature, or from gases evolved from carbonate compounds.
A specific example of pin-holes is Spit-out. These are pin-holes or craters sometimes occurring in glazed non-vitreous ceramics while they are in the decorating kiln. The cause of this defect is the evolution of water vapour, adsorbed by the porous body, during the period between the glost firing and the decorating firing, via minute cracks in the glaze.
References
External links
A study of Glaze expansion
Pottery
Ceramic art
Ceramic engineering
Ceramic glazes | Glaze defects | [
"Chemistry",
"Engineering"
] | 1,540 | [
"Ceramic engineering",
"Ceramic glazes",
"Coatings"
] |
7,146,057 | https://en.wikipedia.org/wiki/Edict%20of%20Roussillon | The Edict of Roussillon () was a 1564 edict decreeing that in France the year would begin on 1 January.
During a trip to various parts of his kingdom, the King of France, Charles IX, found that depending on the diocese, the year began either at Christmas (at Lyon, for instance) or on 25 March (as at Vienne), on 1 March, or at Easter.
In order to standardise the date for the new year in the entire kingdom, he added an article to an edict given at Paris in January 1563 which he promulgated at Roussillon on 9 August 1564. It started being applied on 1 January 1567.
The 42 articles that comprised this edict concerned justice, except the last four, added during the king's stay at Roussillon. Article 39 ruled that henceforth every year would start on 1 January.
List of regions
References
Dictionnaire Historique de la France, by Ludovic Lalanne, p. 84, vol. 1, 1877, Reprinted by Burt Franklin, New York, 1968.
The New American Cyclopaedia: A Popular Dictionary of General Knowledge, p. 493, ed. George Ripley, Charles A. Dana. D. Appleton and Company, 1858.
Le calendrier grégorien en France by Rodolphe Audette
1564 in France
Roussillon
Charles IX of France
Calendars
New Year celebrations
1564 in law | Edict of Roussillon | [
"Physics"
] | 297 | [
"Spacetime",
"Calendars",
"Physical quantities",
"Time"
] |
7,146,399 | https://en.wikipedia.org/wiki/Rietdijk%E2%80%93Putnam%20argument | In philosophy, the Rietdijk–Putnam argument, named after and Hilary Putnam, uses 20th-century findings in physicsspecifically in special relativityto support the philosophical position known as four-dimensionalism.
If special relativity is true, then each observer will have their own plane of simultaneity, which contains a unique set of events that constitutes the observer's present moment. Observers moving at different relative velocities have different planes of simultaneity, and hence different sets of events that are present. Each observer considers their set of present events to be a three-dimensional universe, but even the slightest movement of the head or offset in distance between observers can cause the three-dimensional universes to have differing content. If each three-dimensional universe exists, then the existence of multiple three-dimensional universes suggests that the universe is four-dimensional. The argument is named after the discussions by Rietdijk (1966) and Putnam (1967). It is sometimes called the Rietdijk–Putnam–Penrose argument.
Andromeda paradox
Roger Penrose advanced a form of this argument that has been called the Andromeda paradox in which he points out that two people walking past each other on the street could have very different present moments. If one of the people were walking towards the Andromeda Galaxy, then events in this galaxy might be hours or even days advanced of the events on Andromeda for the person walking in the other direction. If this occurs, it would have dramatic effects on our understanding of time. Penrose highlighted the consequences by discussing a potential invasion of Earth by aliens living in the Andromeda Galaxy. As Penrose put it:
The "paradox" consists of two observers who are, from their conscious perspective, in the same place and at the same instant having different sets of events in their "present moment". Notice that neither observer can actually "see" what is happening in Andromeda, because light from Andromeda (and the hypothetical alien fleet) will take 2.5 million years to reach Earth. The argument is not about what can be "seen"; it is purely about what events different observers consider to occur in the present moment.
Criticisms
The interpretations of relativity used in the Rietdijk–Putnam argument and the Andromeda paradox are not universally accepted. Howard Stein and Steven F. Savitt note that in relativity the present is a local concept that cannot be extended to global hyperplanes. Furthermore, N. David Mermin states:
So stressing that the "present moment" cannot be applied to very distant events with any accuracy.
References
Further reading
Vesselin Petkov (2005) "Is There an Alternative to the Block Universe View?" in Dennis Dieks (ed.), The Ontology of Spacetime, Elsevier, Amsterdam, 2006; "Philosophy and Foundations of Physics" Series, pp. 207–228
Wikibook:The relativity of simultaneity and the Andromeda paradox
"Being and Becoming in Modern Physics", Stanford Encyclopedia of Philosophy
Relativistic paradoxes
Special relativity | Rietdijk–Putnam argument | [
"Physics"
] | 631 | [
"Special relativity",
"Theory of relativity"
] |
7,146,636 | https://en.wikipedia.org/wiki/Hexabromocyclododecane | Hexabromocyclododecane (HBCD or HBCDD) is a brominated flame retardant. It consists of twelve carbon, eighteen hydrogen, and six bromine atoms tied to the ring. Its primary application is in extruded (XPS) and expanded (EPS) polystyrene foam used as thermal insulation in construction. Other uses are upholstered furniture, automobile interior textiles, car cushions and insulation blocks in trucks, packaging material, video cassette recorder housing, and electric and electronic equipment. According to UNEP, "HBCD is produced in China, Europe, Japan, and the USA. The last known current annual production is approximately 28,000 tonnes per year. The main share of the market volume is used in Europe and China" (figures from 2009 to 2010). Due to its persistence, toxicity, and ecotoxicity, the Stockholm Convention on Persistent Organic Pollutants decided in May 2013 to list hexabromocyclododecane in Annex A to the convention with specific exemptions for production and use in expanded polystyrene and extruded polystyrene in buildings. Because HBCD has 16 possible stereo-isomers with different biological activities, the substance poses a difficult problem for manufacture and regulation.
Toxicity
HBCD's toxicity and its harm to the environment are current sources of concern. HBCD can be found in environmental samples such as birds, mammals, fish, and other aquatic organisms as well as soil and sediment.
On this basis, on 28 October 2008, the European Chemicals Agency decided to include HBCD in the SVHC list, Substances of Very High Concern, within the Registration, Evaluation, Authorisation and Restriction of Chemicals framework. On 18 February 2011, HBCD was listed in Annex XIV of REACH and hence is subject to Authorisation. HBCD can be used until the so-called “sunset date” (21 August 2015). After that date, only authorized applications will be allowed in the EU.
HBCD has been found widely present in biological samples from remote areas and supporting pieces of evidence for its classification as Persistent, Bioaccumulative, and Toxic (PBT) and undergoes long-range environmental transportation.
In July 2012, an EU-harmonized classification and labeling for HBCD entered into force. HBCD has been classified as a category 2 for reproductive toxicity. Since August 2010 hexabromocyclododecanes are included in the EPA's List of Chemicals of Concern.
In May 2013 the Stockholm Convention on Persistent Organic Pollutants (POPs) decided to include HBCD in the convention's Annex A for elimination, with specific exemptions for expanded and extruded polystyrene in buildings needed to give countries time to phase-in safer substitutes. HBCD is listed for elimination, but with a specific exemption for expanded polystyrene (EPS) and extruded polystyrene (XPS) in buildings. Countries may choose to use this exemption for up to five years after the request for exemption is submitted. Japan was the first country to implement a ban on the import and production of HBCD effective in May 2014.
Because HBCD has 16 possible stereo-isomers with different biological activities, the substance poses a difficult problem for manufacture and regulation.
The HBCD commercial mixture is composed of three main diastereomers denoted as alpha (α-HBCD), beta (β-HBCD), and gamma (γ-HBCD) with traces of others. A series of four published in vivo mice studies were conducted between several federal and academic institutions to characterize the toxicokinetic profiles of individual HBCD stereoisomers. The predominant diastereomer in the HBCD mixture, γ-HBCD, undergoes rapid hepatic metabolism, fecal and urinary elimination, and biological conversion to other diastereomers with a short biological half-life of 1–4 days. After oral exposure to the γ-HBCD diastereomer, β-HBCD was detected in the liver and brain, and α-HBCD and β-HBCD was detected in the fat and feces with multiple novel metabolites identified - monohydroxy-pentabromocyclododecane, monohydroxy-pentabromocyclododecene, dihydroxy-pentabromocyclododecene, and dihydroxy-pentabromocyclododecadiene. In contrast, α-HBCD is more biologically persistent, resistant to metabolism, bioaccumulates in lipid-rich tissues after a 10-day repeated exposure study, and has a longer biological half-life of up to 21 days; only α-HBCD was detected in the liver, brain, fat and feces with no stereoisomerization to γ-HBCD or β-HBCD and low trace levels of four different hydroxylated metabolites were identified. Developing mice had higher HBCD tissue levels than adult mice after exposure to either α-HBCD or γ-HBCD indicating the potential for increased susceptibility of the developing young to HBCD effects. The reported toxicokinetic differences of individual HBCD diastereoisomers have important implications for the extrapolation of toxicological studies of the commercial HBCD mixture to the assessment of human risk.
Environmental Concerns
Due to its persistence, toxicity, and ecotoxicity, the Stockholm Convention on Persistent Organic Pollutants decided in May 2013 to list hexabromocyclododecane in Annex A to the convention with specific exemptions for production and use in expanded polystyrene and extruded polystyrene in buildings. Countries may choose to use this exemption for up to five years after the request for exemption is submitted.
There is a large and still increasing stock of HBCD in the anthroposphere, mainly in EPS and XPS insulation boards.
A long-term environmental monitoring program run by the Fraunhofer Institute for Molecular Biology and Applied Ecology demonstrates a general trend that HBCD concentrations are decreasing over time. HBCD emissions into the environment are controlled under the voluntary industry emission management program: the Voluntary Emissions Control Action Programme (VECAP). The VECAP annual report demonstrates a continuous decrease of potential emissions of HBCD to the environment.
References
External links
MPI Milebrome B-972, FR 50 & GC SAM: The low-cost alternatives to Hexabromocyclododecane (HBCD) in EPS and XPS applications , Stockholm Convention on Persistent Organic Pollutants 2012
An Overview of Alternatives to Tetrabromobisphenol A (TBBPA) and Hexabromocyclododecane (HBCD) , University of Massachusetts Lowell, March 2006
ECHA: MEMBER STATE COMMITTEE SUPPORT DOCUMENT FOR IDENTIFICATION OF HEXABROMOCYCLODODECANE AND ALL MAJOR DIASTEREOISOMERS IDENTIFIED AS A SUBSTANCE OF VERY HIGH CONCERN, 8 October 2008
Factsheet BSEF
BSEF – the bromine industry website’s page on HBCD
Flame retardants
Organobromides
PBT substances
Persistent organic pollutants under the Stockholm Convention | Hexabromocyclododecane | [
"Chemistry"
] | 1,524 | [
"Persistent organic pollutants under the Stockholm Convention"
] |
7,147,157 | https://en.wikipedia.org/wiki/Absolutely%20integrable%20function | In mathematics, an absolutely integrable function is a function whose absolute value is integrable, meaning that the integral of the absolute value over the whole domain is finite.
For a real-valued function, since
where
both and must be finite. In Lebesgue integration, this is exactly the requirement for any measurable function f to be considered integrable, with the integral then equaling , so that in fact "absolutely integrable" means the same thing as "Lebesgue integrable" for measurable functions.
The same thing goes for a complex-valued function. Let us define
where and are the real and imaginary parts of . Then
so
This shows that the sum of the four integrals (in the middle) is finite if and only if the integral of the absolute value is finite, and the function is Lebesgue integrable only if all the four integrals are finite. So having a finite integral of the absolute value is equivalent to the conditions for the function to be "Lebesgue integrable".
External links
Integral calculus
References
Tao, Terence, Analysis 2, 3rd ed., Texts and Readings in Mathematics, Hindustan Book Agency, New Delhi. | Absolutely integrable function | [
"Mathematics"
] | 245 | [
"Integral calculus",
"Calculus"
] |
7,147,287 | https://en.wikipedia.org/wiki/Aspherical%20space | In topology, a branch of mathematics, an aspherical space is a topological space with all homotopy groups equal to 0 when .
If one works with CW complexes, one can reformulate this condition: an aspherical CW complex is a CW complex whose universal cover is contractible. Indeed, contractibility of a universal cover is the same, by Whitehead's theorem, as asphericality of it. And it is an application of the exact sequence of a fibration that higher homotopy groups of a space and its universal cover are same. (By the same argument, if E is a path-connected space and is any covering map, then E is aspherical if and only if B is aspherical.)
Each aspherical space X is, by definition, an Eilenberg–MacLane space of type , where is the fundamental group of X. Also directly from the definition, an aspherical space is a classifying space for its fundamental group (considered to be a topological group when endowed with the discrete topology).
Examples
Using the second of above definitions we easily see that all orientable compact surfaces of genus greater than 0 are aspherical (as they have either the Euclidean plane or the hyperbolic plane as a universal cover).
It follows that all non-orientable surfaces, except the real projective plane, are aspherical as well, as they can be covered by an orientable surface of genus 1 or higher.
Similarly, a product of any number of circles is aspherical. As is any complete, Riemannian flat manifold.
Any hyperbolic 3-manifold is, by definition, covered by the hyperbolic 3-space H3, hence aspherical. As is any n-manifold whose universal covering space is hyperbolic n-space Hn.
Let X = G/K be a Riemannian symmetric space of negative type, and Γ be a lattice in G that acts freely on X. Then the locally symmetric space is aspherical.
The Bruhat–Tits building of a simple algebraic group over a field with a discrete valuation is aspherical.
The complement of a knot in S3 is aspherical, by the sphere theorem
Metric spaces with nonpositive curvature in the sense of Aleksandr D. Aleksandrov (locally CAT(0) spaces) are aspherical. In the case of Riemannian manifolds, this follows from the Cartan–Hadamard theorem, which has been generalized to geodesic metric spaces by Mikhail Gromov and Hans Werner Ballmann. This class of aspherical spaces subsumes all the previously given examples.
Any nilmanifold is aspherical.
Symplectically aspherical manifolds
In the context of symplectic manifolds, the meaning of "aspherical" is a little bit different. Specifically, we say that a symplectic manifold (M,ω) is symplectically aspherical if and only if
for every continuous mapping
where denotes the first Chern class of an almost complex structure which is compatible with ω.
By Stokes' theorem, we see that symplectic manifolds which are aspherical are also symplectically aspherical manifolds. However, there do exist symplectically aspherical manifolds which are not aspherical spaces.
Some references drop the requirement on c1 in their definition of "symplectically aspherical." However, it is more common for symplectic manifolds satisfying only this weaker condition to be called "weakly exact."
See also
Acyclic space
Essential manifold
Whitehead conjecture
Notes
References
External links
Aspherical manifolds on the Manifold Atlas.
Algebraic topology
Homology theory
Homotopy theory | Aspherical space | [
"Mathematics"
] | 767 | [
"Fields of abstract algebra",
"Topology",
"Algebraic topology"
] |
7,147,380 | https://en.wikipedia.org/wiki/S%C3%ADragon | Síragon, C.A. is a Venezuelan manufacturer and assembler of computer hardware and other electronic products such as digital cameras, tablet, computers and LCD televisions. Siragon also designs and manufactures its own RAM and flash memory and printed circuit boards. The company was created in an alliance between Venezuela and Japanese investors. Its plant is located in the North Industrial Zone of Valencia, Carabobo, in Venezuela.
In November 2009, Síragon started to distribute its product line in Argentina, Allied with the Argentinian computer wholesale vendor Greentech. Síragon manufactures its own designs and also builds under license, all-in-one computers from Brazilian Itautec.
Siragon products are all manufactured in Venezuela. At the 2012 international consumer electronics show Siragon formally announced its intent to enter the US market by the end of 2012. Siragon is engaged in a design partnership with BMW for which it both manufactures electronics for and collaborates on electronic designs with.
Siragon currently holds the third largest share of the electronics market in Venezuela.
See also
Products
Digital cameras
Video cameras
Desktop computers
Laptop computers
Netbooks
Computer servers
LCD televisions and monitors
LED television
Plasma TV screens
Sound systems
Peripherals
Tablet computers
References
External links
Síragon Webpage
Electronics companies of Venezuela
Venezuelan brands
Computer hardware companies
Computer memory companies
Computer systems companies
Display technology companies
Netbook manufacturers
Home appliance manufacturers of Venezuela
Electronics companies established in 2004
2004 establishments in Venezuela | Síragon | [
"Technology"
] | 292 | [
"Computer hardware companies",
"Computer systems companies",
"Computers",
"Computer systems"
] |
7,147,618 | https://en.wikipedia.org/wiki/CALS%20Table%20Model | The CALS Table Model is a standard for representing tables in SGML/XML. It was developed as part of the Continuous Acquisition and Life-cycle Support (CALS) initiative by the United States Department of Defense.
History and rationale
The CALS Table Model was developed by the Continuous Acquisition and Life-cycle Support (CALS) Industry Steering Group Electronic Publishing Committee (EPC).
The EPC subcommittee, of which Harvey Bingham was co-chair and a major contributor, designed the CALS Table Model in 1989–1990. The EPC was made up of industry and military service representatives. Some represented traditional military document printing agencies. Others represented electronic publishing organizations. SGML itself was new. At that time, the CALS intent for all their technical manuals was to use that document type definition (DTD) to achieve system-neutral interchange of content and structure.
Its basis was a minimal description and example of a table from the prior Mil-M-38784B specification for producing technical manuals. The incomplete specification of the semantics associated with the table model allowed too much freedom for vendor interpretation, and resulted in problems with interchange. SGML-Open, the former name of the Organization for the Advancement of Structured Information Standards (OASIS), surveyed the implementing vendors to identify differences as the initial step toward reaching a common interpretation. The next step was an updated CALS Table Model DTD and semantics. Both are now available from OASIS.
As implementations of the CALS Table Model were developed, a number of ambiguities and omissions were detected and reported to the EPC. The differences in interpretation had led to serious interoperability problems. To resolve these differences, OASIS identified a subset of the full CALS table model that had a high probability of successful interoperability among the OASIS vendor products. This subset is the Exchange Table Model DTD.
Example
<table frame="none">
<tgroup cols="2" colsep="0">
<colspec colnum="1" colname="col1" colwidth="32mm"/>
<colspec colnum="2" colname="col2" colwidth="132mm"/>
<thead>
<row>
<entry valign="top"/>
<entry valign="top">(IUPAC) name</entry>
</row>
</thead>
<tbody>
<row rowsep="0">
<entry>pyro-EGTA</entry>
<entry>2,2',2'',2'''-(2,2'-(1,2-phenylene bis(oxy))bis(ethane-2,1-diyl))
bis(azanetriyl)tetraacetic acid</entry>
</row>
<row rowsep="0">
<entry>EGTA</entry>
<entry>ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid</entry>
</row>
<row rowsep="0">
<entry>EDTA</entry>
<entry>2,2',2'',2'''-(ethane-1,2-diyldinitrilo)tetraacetic acid (ethylenediamine
tetraacetic acid)</entry>
</row>
<row rowsep="0">
<entry>AATA</entry>
<entry>2,2'-(2-(2-(2-(bis(carboxymethyl)amino)ethoxy)ethoxy)
phenylazanediyl)diacetic acid</entry>
</row>
<row rowsep="0">
<entry>APTRA</entry>
<entry>2-carboxymethoxy-aniline-N,N-diacetic acid</entry>
</row>
<row rowsep="0">
<entry>BAPTA</entry>
<entry>1,2-bis(-2-aminophenoxy)ethane- N,N,N',N'-tetraacetic acid</entry>
</row>
<row rowsep="0">
<entry>HIDA</entry>
<entry>N-(2-hydroxyethyl)iminodiacetic acid</entry>
</row>
<row rowsep="0">
<entry>Carboxyglutamate</entry>
<entry>3-Aminopropane-1,1,3-tricarboxylic acid</entry>
</row>
</tbody>
</tgroup>
</table>
See also
OASIS, a global consortium that develops data representation standards for use in computer software
Footnotes
External links
OASIS table models
CALS Table Model History by Harvey Bingham
OASIS official website
Computer-related introductions in 1990
Technical communication
United States Department of Defense standards
XML-based standards
XML markup languages | CALS Table Model | [
"Technology"
] | 1,098 | [
"Computer standards",
"XML-based standards"
] |
7,147,956 | https://en.wikipedia.org/wiki/Differential%20calculus%20over%20commutative%20algebras | In mathematics the differential calculus over commutative algebras is a part of commutative algebra based on the observation that most concepts known from classical differential calculus can be formulated in purely algebraic terms. Instances of this are:
The whole topological information of a smooth manifold is encoded in the algebraic properties of its -algebra of smooth functions as in the Banach–Stone theorem.
Vector bundles over correspond to projective finitely generated modules over via the functor which associates to a vector bundle its module of sections.
Vector fields on are naturally identified with derivations of the algebra .
More generally, a linear differential operator of order k, sending sections of a vector bundle to sections of another bundle is seen to be an -linear map between the associated modules, such that for any elements :
where the bracket is defined as the commutator
Denoting the set of th order linear differential operators from an -module to an -module with we obtain a bi-functor with values in the category of -modules. Other natural concepts of calculus such as jet spaces, differential forms are then obtained as representing objects of the functors and related functors.
Seen from this point of view calculus may in fact be understood as the theory of these functors and their representing objects.
Replacing the real numbers with any commutative ring, and the algebra with any commutative algebra the above said remains meaningful, hence differential calculus can be developed for arbitrary commutative algebras. Many of these concepts are widely used in algebraic geometry, differential geometry and secondary calculus. Moreover, the theory generalizes naturally to the setting of graded commutative algebra, allowing for a natural foundation of calculus on supermanifolds, graded manifolds and associated concepts like the Berezin integral.
See also
References
J. Nestruev, Smooth Manifolds and Observables, Graduate Texts in Mathematics 220, Springer, 2002.
I. S. Krasil'shchik, "Lectures on Linear Differential Operators over Commutative Algebras". Eprint DIPS-01/99.
I. S. Krasil'shchik, A. M. Vinogradov (eds) "Algebraic Aspects of Differential Calculus", Acta Appl. Math. 49 (1997), Eprints: DIPS-01/96, DIPS-02/96, DIPS-03/96, DIPS-04/96, DIPS-05/96, DIPS-06/96, DIPS-07/96, DIPS-08/96.
I. S. Krasil'shchik, A. M. Verbovetsky, "Homological Methods in Equations of Mathematical Physics", Open Ed. and Sciences, Opava (Czech Rep.), 1998; Eprint arXiv:math/9808130v2.
G. Sardanashvily, Lectures on Differential Geometry of Modules and Rings, Lambert Academic Publishing, 2012; Eprint arXiv:0910.1515 [math-ph] 137 pages.
A. M. Vinogradov, "The Logic Algebra for the Theory of Linear Differential Operators", Dokl. Akad. Nauk SSSR, 295(5) (1972) 1025-1028; English transl. in Soviet Math. Dokl. 13(4) (1972), 1058-1062.
A. M. Vinogradov, "Some new homological systems associated with differential calculus over commutative algebras" (Russian), Uspechi Mat.Nauk, 1979, 34 (6), 145-150;English transl. in Russian Math. Surveys, 34(6) (1979), 250-255.
Commutative algebra
Differential calculus | Differential calculus over commutative algebras | [
"Mathematics"
] | 775 | [
"Fields of abstract algebra",
"Commutative algebra",
"Differential calculus",
"Calculus"
] |
7,148,261 | https://en.wikipedia.org/wiki/Ultra%20Electronics | Ultra Electronics Holdings is a British defence and security company. It was listed on the London Stock Exchange and was a constituent of the FTSE 250 Index until it was acquired by Cobham, which is itself owned by Advent International.
The company was originally founded as Edward E. Rosen & Co., a manufacturer of headphones and loudspeakers, in 1920. In 1925, a new company, known as Ultra Electric Ltd., was established. During 1930, the firm launched its first all-electric radio receiver; it produced numerous domestic radio receivers around this time. Ultra diversified into aviation during the Second World War, building fuselage elements and engine components. Relaunching itself into the civilian markets following the conflict, Ultra started producing television sets in 1953. In 1961, Ultra's consumer electronics interests became part of Thorn Electrical Industries.
During 1977, Ultra Electronics was bought by the Dowty Group and regained its independence via a management buyout in 1993. Into the twenty-first century, it has continued to be an active supplier to the aerospace sector; various companies, including Bombardier Aerospace and Airbus, have chosen to incorporate Ultra Electronics' noise reduction and vibration dampening products onto their aircraft. By 2005, Ultra Electronics was ranked as the 66th biggest aerospace company in the world. In August 2021, the British aerospace and defence company, Cobham, agreed to acquire Ultra Electronics in exchange for £2.6 billion.
History
Early activities
The company that would eventually become Ultra Electronics was started by wireless specialist Teddy Rosen as Edward E. Rosen & Co. during 1920. The firm was initially focused upon the manufacture of high quality headphones and loudspeakers. During 1923, the company relocated to new premises at Harrow Road, London. In 1925, a new company, known as Ultra Electric Ltd., was formed; the Ultra name had been previously used for one of its products, the first commercial moving iron loudspeaker.
During 1930, Ultra launched its first all-electric radio receiver. During 1931, the firm introduced its first mains-powered wireless set, known as the Ultra Twin Cub. That same year, Ultra received its first order from the aviation industry, having been placed by the Japanese Kawasaki Company. As a result of further expansion, the company moved to larger premises at Erskine Road, Chalk Farm, NW3 in 1932; three years later, a new factory at Western Avenue, Acton.
During the 1930s, Ultra manufactured a wide range of domestic radio receivers including the Blue Fox, Lynx, Panther and Tiger models. In 1939, the company presented a television receiver to the market for the BBC High Definition Television Service which was transmitted on 405 lines from the studios at Alexandra Palace, north London.
During the Second World War, Ultra diversified into aviation; the Short Stirling was the first aircraft to incorporate their products, the company acting as a subcontractor to produce tails and bomb doors for the bomber. Ultra would produce a wide range of aerostructures for numerous aircraft throughout the conflict. The firm solely focused on wartime demands, only relaunching itself into the civilian market during 1947, although it would continue to have an interest in the military sector during the post-war period.
Post-war
Ultra continued to manufacture products for the aviation industry after the conflict. Various engines, including the Armstrong Siddeley Mamba and the Rolls-Royce Avon, incorporated components such as temperature regulators, fuel flow valves, and throttle controls produced by Ultra. Electronic control systems would become a key part of the company's product range.
In 1953, Ultra started manufacturing television sets. During 1956, the firm opened a new factory at Gosport for the production of both televisions and radio sets; Ultra acquired rival company Pilot Radio & Television in 1959. During the following year, Ultra reorganised itself, splitting into two divisions, one specialising in domestic radio and television and the other focused on all other electronic products. In 1961, Ultra's consumer electronics interests became part of Thorn Electrical Industries, who continued to manufacture products using the Ultra brandname until 1974.
As a result of the acquisition, the remainder of the company became Ultra Electronics Ltd. Amongst its varied product range at this time, it produced the "Jezebel" and "Mini-Jezebel" sonobuoys. In 1962, Ultra developed their Search and Rescue and Homing (SARAH) radio beacon, this would be widely used throughout the world. Various subsystems of Concorde, include the droop nose controls and the full authority engine controls, incorporated Ultra technologies.
During 1977, Ultra Electronics was bought by the Dowty Group.
Reemergence
In 1993, Ultra was the subject of a management buyout, led by Julian Blogh, of seven Dowty Group plc companies which formed the Dowty Group Electronic Systems Divisions, which had been previously acquired by TI Group during 1992. In September 1995, Ultra Electronics received its first major export order from the American government, to supply support equipment for its McDonnell Douglas AV-8B Harrier II fleet. It was floated on the London Stock Exchange in 1996.
During the late 1990s, Ultra Electronics began to vigorously promote its active noise control systems, marketed as UltraQuiet: the firm argued that aircraft manufacturers can deploy it to decrease cabin noise, which has been a traditionally prevalent drawback of turboprop-powered aircraft, such as regional airliners, in comparison to their jet-powered counterparts. It also developed further noise reduction technologies during this period. Various companies, including Bombardier Aerospace and Airbus, have chosen to incorporate Ultra Electronics' noise reduction and vibration dampening products onto their aircraft.
According to Flight International, since regaining its independence in the 1990s, the corporate strategy of Ultra Electronics appears to have been slanted towards maintaining a diverse product range, avoiding any large exposures to a single market, as well as being intentionally widely dispersed geographically. In 2000, Ultra Electronics acquired Datel Ferranti Group. It also acquired American voice communications provider Audiopack Technologies in 2004. By 2005, Ultra Electronics was ranked as the 66th biggest aerospace company in the world: at this point in time, the American market accounted for around one-third of the business's turnover.
In August 2021, the British aerospace and defence company, Cobham, agreed to acquire Ultra Electronics in exchange for £2.6 billion. A merger enquiry into the anticipated acquisition (Ultra Electronics is a key national security and the defence contractor, Cobham, is American owned) was completed in January 2022, with a report being passed to the Secretary of State for Business, Energy and Industrial Strategy, Kwasi Kwarteng. In July 2022, Kwarteng announced that the acquisition was cleared to proceed.
Operations
The company operates under five strategic business units; Maritime, Intelligence & Communications, Precision Control Systems, Energy and Forensic Technology. It has facilities in the UK, North America and Australia. In January 2020, Ultra launched new branding.
See also
Aerospace industry in the United Kingdom
References
1920 establishments in England
Aircraft component manufacturers of the United Kingdom
Companies listed on the London Stock Exchange
Defence companies of the United Kingdom
Electronics companies established in 1920
Electronics companies of the United Kingdom
Electronics industry in London
Manufacturing companies based in London
Sonar manufacturers
Radio manufacturers | Ultra Electronics | [
"Engineering"
] | 1,457 | [
"Radio electronics",
"Radio manufacturers"
] |
7,148,302 | https://en.wikipedia.org/wiki/Ptolemy%27s%20inequality | In Euclidean geometry, Ptolemy's inequality relates the six distances determined by four points in the plane or in a higher-dimensional space. It states that, for any four points , , , and , the following inequality holds:
It is named after the Greek astronomer and mathematician Ptolemy.
The four points can be ordered in any of three distinct ways (counting reversals as not distinct) to form three different quadrilaterals, for each of which the sum of the products of opposite sides is at least as large as the product of the diagonals. Thus, the three product terms in the inequality can be additively permuted to put any one of them on the right side of the inequality, so the three products of opposite sides or of diagonals of any one of the quadrilaterals must obey the triangle inequality.
As a special case, Ptolemy's theorem states that the inequality becomes an equality when the four points lie in cyclic order on a circle.
The other case of equality occurs when the four points are collinear in order. The inequality does not generalize from Euclidean spaces to arbitrary metric spaces. The spaces where it remains valid are called the Ptolemaic spaces; they include the inner product spaces, Hadamard spaces, and shortest path distances on Ptolemaic graphs.
Assumptions and derivation
Ptolemy's inequality is often stated for a special case, in which the four points are the vertices of a convex quadrilateral, given in cyclic order. However, the theorem applies more generally to any four points; it is not required that the quadrilateral they form be convex, simple, or even planar.
For points in the plane, Ptolemy's inequality can be derived from the triangle inequality by an inversion centered at one of the four points. Alternatively, it can be derived by interpreting the four points as complex numbers, using the complex number identity:
to construct a triangle whose side lengths are the products of sides of the given quadrilateral, and applying the triangle inequality to this triangle. One can also view the points as belonging to the complex projective line, express the inequality in the form that the absolute values of two cross-ratios of the points sum to at least one, and deduce this from the fact that the cross-ratios themselves add to exactly one.
A proof of the inequality for points in three-dimensional space can be reduced to the planar case, by observing that for any non-planar quadrilateral, it is possible to rotate one of the points around the diagonal until the quadrilateral becomes planar, increasing the other diagonal's length and keeping the other five distances constant. In spaces of higher dimension than three, any four points lie in a three-dimensional subspace, and the same three-dimensional proof can be used.
Four concyclic points
For four points in order around a circle, Ptolemy's inequality becomes an equality, known as Ptolemy's theorem:
In the inversion-based proof of Ptolemy's inequality, transforming four co-circular points by an inversion centered at one of them causes the other three to become collinear, so the triangle equality for these three points (from which Ptolemy's inequality may be derived) also becomes an equality. For any other four points, Ptolemy's inequality is strict.
In three dimensions
Four non-coplanar points , , , and in 3D form a tetrahedron. In this case, the strict inequality holds:
.
In general metric spaces
Ptolemy's inequality holds more generally in any inner product space, and whenever it is true for a real normed vector space, that space must be an inner product space.
For other types of metric space, the inequality may or may not be valid. A space in which it holds is called Ptolemaic. For instance, consider the four-vertex cycle graph, shown in the figure, with all edge lengths equal to 1. The sum of the products of opposite sides is 2. However, diagonally opposite vertices are at distance 2 from each other, so the product of the diagonals is 4, bigger than the sum of products of sides. Therefore, the shortest path distances in this graph are not Ptolemaic. The graphs in which the distances obey Ptolemy's inequality are called the Ptolemaic graphs and have a restricted structure compared to arbitrary graphs; in particular, they disallow induced cycles of length greater than three, such as the one shown.
The Ptolemaic spaces include all CAT(0) spaces and in particular all Hadamard spaces. If a complete Riemannian manifold is Ptolemaic, it is necessarily a Hadamard space.
Inner product spaces
Suppose that is a norm on a vector space Then this norm satisfies Ptolemy's inequality:
if and only if there exists an inner product on such that for all vectors Another necessary and sufficient condition for there to exist such an inner product is for the norm to satisfy the parallelogram law:
If this is the case then this inner product will be unique and it can be defined in terms of the norm by using the polarization identity.
See also
References
Geometric inequalities
Ptolemy | Ptolemy's inequality | [
"Mathematics"
] | 1,053 | [
"Geometric inequalities",
"Inequalities (mathematics)",
"Theorems in geometry"
] |
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