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9,408,161 | https://en.wikipedia.org/wiki/Frame-bursting | Frame-bursting is a communication protocol feature used at the link layer in communication networks to alter the transmission characteristics in order to benefit from higher throughput. It is a technique sometimes used in communication protocols for shared mediums to achieve higher throughput by allowing the transmitter to send a series of frames in succession without relinquishing control of the transmission medium. Related techniques used to achieve the same goal include fast frames wherein the inter-frame wait interval is reduced, and jumbo frames wherein the size of the frame is increased. Frame bursting may also benefit from packet aggregation. Communication protocols for shared mediums are designed to relinquish the medium and wait for a while after the transmission of a MAC layer frame in order to facilitate the fair use of the medium by multiple users. Frame bursting may be permissible in certain scenarios such as when the link is point-to-point or when the signal from other users is indistinguishable from noise. Frame bursting allows for more data packets per time interval at the cost of wait time for other users.
In the case of wireless technology, the draft 802.11e quality of service specification allows frame bursting under some situations. Frame bursting may increase the throughput of any (point-to-point) 802.11a, b, g or n link connection under certain conditions. This is done by reducing the overhead associated with the wireless session in either of the following two modes:
Access point to client and vice versa
Client to client in ad hoc mode
Frame bursting and fast framing allow a wireless client to upload data at higher throughputs by using the inter-frame wait intervals to "burst" a sequence of up to three packets before waiting the required period. This allows more data to be sent with less waiting. However, their use can also result in unbalanced allocation of airtime where there are a mix of clients with and without Frame-Bursting. In such cases, the inter-frame wait periods cause unsupported stations to wait longer for service availability, and to receive less data transfer throughput. Therefore, it is not recommended for more than 2-3 wireless clients to use frame-bursting as the negative effects can adversely affect the throughput for all clients.
Proprietary extensions that have added frame bursting to the wireless standards include Nitro from Intersil, Super G from Atheros, Xpress from Broadcom and Xtreme G from D-Link.
References
Wireless networking | Frame-bursting | [
"Technology",
"Engineering"
] | 497 | [
"Wireless networking",
"Computer networks engineering"
] |
9,408,163 | https://en.wikipedia.org/wiki/Clean%20process%20oven | A clean process oven is a type of industrial batch oven that is ideal for high-temperature applications, such as curing polyimide, and annealing thin and film waters. Clean process ovens may be for air atmospheres, or inert atmospheres for oxidation-sensitive materials. Temperatures can be over 525 degrees Celsius.
In regards to new tier 4 restrictions, oven cleanings can continue as an essential service for customers. All precautions must be put into place to ensure 2m rules and correct PPE is used.
Other types of industrial batch ovens include laboratory, burn-in, reach-in, and walk-in/drive-in.
References
Industrial ovens | Clean process oven | [
"Engineering"
] | 140 | [
"Industrial ovens",
"Industrial machinery"
] |
9,408,192 | https://en.wikipedia.org/wiki/Symbols%20of%20Ontario | Ontario is a province of Canada that has established several official emblems and symbols to reflect the province's history, natural resources, and its people. In addition to official symbols, several other emblems and symbols exist that are commonly associated with the province.
Official symbols
Several emblems and symbols are used to officially represent the province, established through royal warrant or through the Legislative Assembly of Ontario. They include:
Other symbols
Several emblems and symbols exist that are commonly associated with province. They include:
Symbols of the lieutenant governor of Ontario
There exists several official emblems and symbols to represent the lieutenant governor of Ontario.
References
Ontario
Symbols
Canadian provincial and territorial symbols | Symbols of Ontario | [
"Mathematics"
] | 132 | [
"Symbols",
"Lists of symbols"
] |
9,408,226 | https://en.wikipedia.org/wiki/Symbols%20of%20Quebec | The people and province of Quebec have created and established several symbols throughout Quebec's history to represent the collective identity of its residents. Many of Quebec's symbols are related to its history, to Catholicism, to Quebec's winters and/or the fauna and flora of Quebec. The motif most commonly seen in Quebec's various symbols is the fleur de lys, which is associated with the French language and New France.
Symbols
The fleur-de-lis, one of Quebec's most common symbols, is an ancient symbol of the French monarchy and was first shown in Quebec on the shores of Gaspésie in 1534 when Jacques Cartier arrived in Quebec for the first time. Saint-Jean-Baptiste, the patron saint of Canadiens, is honoured every 24 June during Saint-Jean-Baptiste Day. The expression La belle province is still used as a nickname for the province. Finally, the Great Seal of Quebec is used to authenticate documents issued by the government of Quebec.
Coat of arms
The coat of arms of Quebec dates back to 1868, shortly after the creation of Quebec as a province of Canada. The arms were granted by a royal warrant issued by Queen Victoria.
The arms were adopted in their current form by the government of Quebec in 1939 to reflect Quebec's political history: the French regime is symbolised by the gold fleur-de-lis on a blue background; the British regime is symbolised by a gold lion on a red background; the pre-Confederation period is symbolised by three green maple leaves on a gold background.
Flag
The government of Quebec adopted the Fleurdelisé flag in 1948. The cross represents the faith of the province's founders, while the fleur-de-lys and blue colour recall Quebec's French origins.
When Samuel de Champlain founded Québec City in 1608, his ship hoisted the French merchant flag, which consisted of a white cross on a blue background. Later on, at the Battle of Carillon, in 1758, the Flag of Carillon was flown. This flag inspired the first members of the Saint-Jean-Baptiste Society to create the Carillon Sacré-Coeur flag, which consisted of a white cross on an azur background with white fleur-de-lis in each corner and a Sacred Heart surrounded by maple leaves in the centre. The Carillon Sacré-Coeur and French merchant flag went on to be the major inspirations for Québécois when creating Quebec's current flag in 1903, called the Fleurdelisé. The Fleurdelisé replaced the Union Jack on Quebec's Parliament Building on January 21, 1948, and it has flown there ever since.
Motto
The motto, Je me souviens ("I remember"), was devised by the architect of Quebec's Parliament Building, Eugène-Étienne Taché, in 1883. He carved it into the Parliament building in various locations. Je me souviens is an official part of the coat of arms and has been the official licence plate motto since 1978, replacing the previous one: La belle province ("the beautiful province").
Other symbols
Three new official symbols were adopted in the late 1900s:
Blue flag iris, the floral emblem of Quebec since 1999. It was chosen because it blooms around the time of Quebec's Fête nationale.
The snowy owl, the avian emblem of Quebec since 1987. It was selected by the Québécois government to symbolize Quebec's winters and northern climate.
The yellow birch, the tree emblem of Quebec since 1993. It was picked to emphasize the importance Québécois give to the forests. The tree is admired for its diverse uses, its commercial value and its autumn colours.
List
Here is a non-exhaustive list of Quebec's symbols:
References
Quebec
Symbols
Canadian provincial and territorial symbols | Symbols of Quebec | [
"Mathematics"
] | 778 | [
"Symbols",
"Lists of symbols"
] |
9,408,252 | https://en.wikipedia.org/wiki/Symbols%20of%20Prince%20Edward%20Island | Prince Edward Island is one of Canada's provinces, and has established several provincial symbols.
Symbols
References
Prince Edward Island
Symbols
Canadian provincial and territorial symbols | Symbols of Prince Edward Island | [
"Mathematics"
] | 31 | [
"Symbols",
"Lists of symbols"
] |
9,408,273 | https://en.wikipedia.org/wiki/Symbols%20of%20Saskatchewan | Saskatchewan is one of Canada's provinces, and has established several provincial symbols.
Symbols
References
Saskatchewan
Symbols
Canadian provincial and territorial symbols
Provincial symbols of Saskatchewan | Symbols of Saskatchewan | [
"Mathematics"
] | 31 | [
"Symbols",
"Lists of symbols"
] |
9,408,301 | https://en.wikipedia.org/wiki/Symbols%20of%20the%20Northwest%20Territories | The Northwest Territories, one of Canada's territories, has established several territorial symbols.
Symbols
References
Northwest Territories
Symbols
Canadian provincial and territorial symbols | Symbols of the Northwest Territories | [
"Mathematics"
] | 29 | [
"Symbols",
"Lists of symbols"
] |
9,408,332 | https://en.wikipedia.org/wiki/Symbols%20of%20Nunavut | Nunavut is one of Canada's territories, and has established several territorial symbols.
Symbols of Nunavut
Great Seal
Like Yukon, Nunavut does not have an official Great Seal.
Notes
References
Nunavut symbols
Nunavut
Indigenous peoples in Canada-related lists
Nunavut
Symbols | Symbols of Nunavut | [
"Mathematics"
] | 61 | [
"Symbols",
"Lists of symbols"
] |
9,408,345 | https://en.wikipedia.org/wiki/Symbols%20of%20Yukon | Yukon is one of Canada's territories, and has established several territorial symbols.
Official symbols
Great Seal
Like Nunavut, Yukon does not have an official Great Seal.
References
Territorial symbols of Yukon
Yukon
Symbols
Canadian provincial and territorial symbols | Symbols of Yukon | [
"Mathematics"
] | 48 | [
"Symbols",
"Lists of symbols"
] |
9,409,080 | https://en.wikipedia.org/wiki/G%20protein-coupled%20receptor%20kinase%202 | G-protein-coupled receptor kinase 2 (GRK2) is an enzyme that in humans is encoded by the ADRBK1 gene. GRK2 was initially called Beta-adrenergic receptor kinase (βARK or βARK1), and is a member of the G protein-coupled receptor kinase subfamily of the Ser/Thr protein kinases that is most highly similar to GRK3(βARK2).
Functions
G protein-coupled receptor kinases phosphorylate activated G protein-coupled receptors, which promotes the binding of an arrestin protein to the receptor. Arrestin binding to phosphorylated, active receptor prevents receptor stimulation of heterotrimeric G protein transducer proteins, blocking their cellular signaling and resulting in receptor desensitization. Arrestin binding also directs receptors to specific cellular internalization pathways, removing the receptors from the cell surface and also preventing additional activation. Arrestin binding to phosphorylated, active receptor also enables receptor signaling through arrestin partner proteins. Thus the GRK/arrestin system serves as a complex signaling switch for G protein-coupled receptors.
GRK2 and the closely related GRK3 phosphorylate receptors at sites that encourage arrestin-mediated receptor desensitization, internalization and trafficking rather than arrestin-mediated signaling (in contrast to GRK5 and GRK6, which have the opposite effect). This difference is one basis for pharmacological biased agonism (also called functional selectivity), where a drug binding to a receptor may bias that receptor’s signaling toward a particular subset of the actions stimulated by that receptor.
GRK2 is expressed broadly in tissues, but generally at higher levels than the related GRK3. GRK2 was originally identified as a protein kinase that phosphorylated the β2-adrenergic receptor, and has been most extensively studied as a regulator of adrenergic receptors (and other GPCRs) in the heart, where it has been proposed as a drug target to treat heart failure. Strategies to inhibit GRK2 include using small molecules (including Paroxetine and Compound-101) and using gene therapy approaches utilizing regulatory domains of GRK2 (particularly overexpressing the carboxy terminal pleckstrin-homology (PH) domain that binds the G protein βγ-subunit complex and inhibits GRK2 activation (often called the “βARKct”), or just a peptide from this PH domain).
GRK2 and the related GRK3 can interact with heterotrimeric G protein subunits resulting from GPCR activation, both to be activated and to regulate G protein signaling pathways. GRK2 and GRK3 share a carboxyl terminal pleckstrin homology (PH) domain that binds to G protein βγ subunits, and GPCR activation of heterotrimeric G proteins releases this free βγ complex that binds to GRK2/3 to recruit these kinases to the cell membrane precisely at the location of the activated receptor, augmenting GRK activity to regulate the activated receptor. The amino terminal RGS-homology (RH) domain of GRK2 and GRK3 binds to heterotrimeric G protein subunits of the Gq family to reduce Gq signaling by sequestering active G proteins away from their effector proteins such as phospholipase C-beta; but the GRK2 and GRK3 RH domains are unable to function as GTPase-activating proteins (as do traditional RGS proteins) to turn off G protein signaling.
Interactions
GRK2 has been shown to interact with numerous protein partners, including:
G protein βγ complex
G protein GNAQ family members
GIT1 and GIT2
PDE6G
PRKCB1
Src
See also
G protein-coupled receptor kinases
G protein
desensitization (medicine)
arrestin
Kinase
References
External links
Proteins
EC 2.7.11
Transferases
Protein kinases | G protein-coupled receptor kinase 2 | [
"Chemistry"
] | 832 | [
"Biomolecules by chemical classification",
"Proteins",
"Molecular biology"
] |
9,409,111 | https://en.wikipedia.org/wiki/Domus%20%28magazine%29 | Domus is an architecture and design magazine founded in 1928 by architect Gio Ponti and Barnabite father Giovanni Semeria. Published by Editoriale Domus, the magazine is issued 11 times a year on a monthly basis and has its headquarters in Rozzano, Milan.
History
Foundation – WWII
The first issue of Domus, subtitled "Architecture and decor of the modern home in the city and in the country," was published on 15 January 1928. Its mission was to renew architecture, interiors and Italian decorative arts without overlooking topics of interest to women, like the art of homemaking, gardening and cooking. Gio Ponti was the founder of the magazine and delineated the magazine's goals in his editorials, insisting on the importance of aesthetics and style in the field of industrial production.
Gianni Mazzocchi, a, 23-year-old publisher who had moved to Milan from the Marche region, purchased Domus on 11 July 1929 and founded Editoriale Domus, which today publishes numerous magazines (Quattroruote, Meridiani, Tuttotrasporti, Il cucchiaio d'argento, etc.).
Gio Ponti left the magazine after twelve years as editor; starting in July 1941, Domus came under the direction of Massimo Bontempelli, Giuseppe Pagano and Melchiorre Bega. In October 1942, Guglielmo Ulrich took over Giuseppe Pagano's role (who, because of his involvement in antifascist politics, died on 22 April 1945 at the Mauthausen concentration camp). Melchiorre Bega became editor in October 1943. The war years required continuous changes in the magazine's direction and its printing operations were forced to move to Bergamo. Domus was published monthly throughout 1944, but was suspended in 1945.
The postwar period
Publication resumed in January 1946 with issue 205. Domus was now directed by Ernesto Nathan Rogers (from the firm, BBPR) with a new look, but affirming a line of cultural continuity with Ponti's period as editor. These were years of innovation when the magazine embraced new cultural trends and sought out the collaboration of intellectuals like Elio Vittorini and Alberto Moravia. During that same year, Editoriale Domus bought Casabella, entrusting its direction first to Franco Albini and Giancarlo Palanti and then to Ernesto Nathan Rogers (from December 1953); Casabella was sold in 1964.
In 1948, Gio Ponti returned as editor of Domus which had become a bi-monthly; in 1951, the magazine resumed publication on a monthly basis.
The 1950s and '60s were marked by great vitality in architecture, the arts and design. Domus promoted everything that was new on the scene and its authors, becoming a key reference for the international debate among various artistic trends. In 1968, the magazine celebrated its 40th anniversary with issue 459 and in July 1971, the magazine published its 500th issue.
Gio Ponti was joined by Cesare Casati as managing editor in July 1976. The era was characterized by such features as Ettore Sottsass' travel diary, "Memoires di panna montata (Whipped Cream Memoires)" and Pierre Restany's "Letters" to the art world. The magazine went international with its translation into English and French until defining its current bilingual (Italian/English) format. In December 1978, Domus celebrated its 50th anniversary with an exhibition at Palazzo delle Stelline in Milan.
1980s postmodernism
Alessandro Mendini became editor in July 1979 (Gio Ponti died in October 1979). A leading figure in post-modern design, Mendini opened Domus to the neo avant-garde. Beginning in January 1980, Ettore Sottsass took over the magazine's graphic design. In 1982, Maria Grazia Mazzocchi, Valerio Castelli, Alessandro Guerriero and Editoriale Domus founded Domus Academy, a school for designers and product design managers directed by Andrea Branzi.
Publisher Gianni Mazzocchi died on 24 October 1984, and his daughter, Giovanna Mazzocchi Bordone, took over the direction of Editoriale Domus.
In 1985, Lisa Licitra Ponti became editor pro-tempore and, with the March 1986 issue, Mario Bellini became editor, engaging Italo Lupi for the new graphic design project. Domus accentuated its international calling: from 1988 to 1990, six issues included a Russian language version; a Chinese language version has been published since 1989. Bellini's term as editor ended in 1991.
From the 1990s to the present
Vittorio Magnago Lampugnani became editor in January 1992, flanked by graphic designer Alan Fletcher beginning in January 1994. Released in more than 100 countries across the globe, the magazine was now entirely bilingual.
From February 1996 to July 2000, Domus was directed by François Burkhardt, a Swiss citizen at the helm of an international editorial team for the first time in Domus''' history. The magazine expanded its interests beyond the traditional disciplines of architecture, industrial design and art to the field of communications.
To celebrate its 70th anniversary in 1998, Robert Wilson created the play 70 Angels on the Façade performed at the Nuovo Piccolo Teatro in Milan.
Deyan Sudjic took over as editor from François Burkhardt in August 2000 publishing his first issue in September of the same year. Simon Esterson's graphic design responded to strict requirements of linearity, simplicity and ease of reading. The editorial structure was organized into three main sections, giving more space to opinions and analysis supporting the features, with the intention of broadening the magazine's horizons to new fields of interest like car design and fashion.
Stefano Boeri was editor from January 2004 to April 2007 when Domus was characterized by interest in large architectural projects and new design frontiers, but also by its focus on some important geopolitical issues, among which the recent geo-design: the geopolitical aspects of design – how, where and why complex objects are designed today.
In 2006, the publisher decided to entrust an annual special, "Domus copyright," to a renowned international architect: Dutch architect Rem Koolhaas opened the initiative.
That same year, the German house, Taschen, published Domus 1928–1999, a monumental historical anthology of the magazine in 12 volumes.
Flavio Albanese became editor in May 2007. With his new direction, Domus reinforced the presence of built architecture and city design, focusing on the discovery of new and young international talents, continuing its investigation into the relationship between multiple art forms.
In 2008, the magazine celebrated 80 years of uninterrupted publication with a special issue revisiting Gio Ponti's work through original works produced by internationally renowned artists, shown at an exhibition during the Salone del Mobile in Milan.
In April 2010, Alessandro Mendini returned as editor of Domus whose subtitle, "The new utopia," was a response to the current crisis: "The history of grand transformations in architecture and design is marked by the new utopias, and it is our intention to pursue this opening line. To scour the world in search of projects that demonstrate scenarios and attitudes of living that represent a positive way of looking to the future. Not so much new utopias of a technical nature, but rather humanistic and psychological: the ecology of exterior environments is preceded by that of interiors. In this sense the new Domus re-establishes its links with its origins as a 'Magazine for the home', offering examples of the dignity of living the city, objects and the home. The new design of the magazine will also evoke memories of the Domus of the past through the classic, radiant sequencing of its articles and images." The issues published under Mendini's direction were distinguished by cover portraits drawn by Lorenzo Mattotti.
At the same time, Joseph Grima began his role as the magazine's new editor. He was mandated with two tasks: to create Domus Web whose graphic design was entrusted to Dan Hill, which went online on 9 December 2010 and to edit the paper version with graphics by Salottobuono (by Marco Ferrari from January 2013). The April 2011 (issue 946) was the first issue published under Grima's direction. His co-editors were Marcello Minerbi and Roberto Zancan.
According to publisher Giovanna Mazzocchi Bordone, Joseph Grima had the task of transforming Domus [10 ] : [...] "The magazine must delve more deeply, provide interpretive readings. The rest – trends, news, experiments – should showcase on all the platforms that today's technology allows us to use."
The semi-native iPad edition was launched in September 2012 (issues 961 – 974). Under Manuel Erhenfeld and Marco Ferrari's artistic direction, the app was Merit Winner at the 48th SPD Annual Awards in the App of the Year and Best News App categories. In September 2013, Joseph Grima handed the editorship over to Nicola Di Battista, deputy editor of the magazine in the 1990s, supported by a College of Masters (David Chipperfield, Kenneth Frampton, Hans Kollhoff, Werner Oechslin and Eduardo Souto de Moura) and a Study Center, comprising a team of young professionals. Di Battista's goal is to place people at the center of contemporary architecture.
Contents
Founded to circulate ideas regarding style in homemaking and furnishing, over the years Domus—through its various editors—has explored a wide range of nuances in the fields of architecture, the applied arts, industrial design, art, urban planning, editorial and advertising graphics, digital communications, always with an international perspective.
Editors
15 January 1928: Gio Ponti
July 1941: Massimo Bontempelli, Giuseppe Pagano and Melchiorre Bega
October 1942: Massimo Bontempelli, Guglielmo Ulrich and Melchiorre Bega
October 1943 – December 1944: Melchiorre Bega
1945: publication ceased due to the war
January 1946 (issue 205): Ernesto Nathan Rogers
January 1948: Gio Ponti
July 1976: Gio Ponti and Cesare Casati
July 1979: Alessandro Mendini
January 1985: Lisa Licitra Ponti
March 1986: Mario Bellini
January 1992: Vittorio Magnago Lampugnani
February 1996: François Burkhardt
September 2000: Deyan Sudjic
January 2004 (issue 866): Stefano Boeri
May 2007 (issue 903): Flavio Albanese
April 2010 (issue 935): Alessandro Mendini
April 2011 (issue 946): Joseph Grima
September 2013 (issue 972): Nicola Di Battista
January 2018 (issue 1020): Michele De Lucchi
Local versions
China (2006)
Israel (2009)
India (2011)
Mexico (2011)
América Central y el Caribe (2011)
German version for Germany, Austria and Switzerland (8 May 2013)
S. Korea (2018)
Website history
www.domusweb.it in Italian and English went on line in September 2000 with graphic design by Deepend. At the same, Domusxchange, designed as a B2B trading partner of the main site and as a content vehicle, was presented. From the late spring of the following year, graphic design was moved in-house to the editorial offices in order to develop a simpler and friendlier interface suitable for an information site. That same year, former editor Deyan Sudjic took over website direction. Since then, graphic design has been produced in-house, varying at each change of editorship (with the exception of Mendini). Albanese and Grima were the only editors to entrust the website to outside designers: Dan Hill. All editors have shared the intent of promoting autonomous content with respect to the paper version, but at the same time hosting a certain amount of magazine content. Since 2007, the website has been enriched with a video section with special videos produced by both Domus and other subjects during special events like the Salone del Mobile.
Archives
The cataloguing of over 180,000 photographic documents was completed in 2013. The Domus archives consist of published and unpublished documents ranging from correspondence between important figures to entire photographic reports, organized in different sections according to the nature and origin of the archival materials.
See also
List of magazines in Italy
References
Bibliography
Juliette Caputo, "Domus: 45 ans d'architecture, design, art", Domus, Milan, 1973.
Giancarlo De Carlo, "Scritti per Domus", Domus, Rozzano, 2005.
Charlotte & Peter Fiell (ed) Domus 1928 – 1999'', Taschen, Koln 2006, 12 volumi + 1 CD–Rom.
External links
Official magazine website
Magazine archives
1928 establishments in Italy
Architecture magazines
Design magazines
Italian-language magazines
Magazines established in 1928
Magazines published in Milan
Monthly magazines published in Italy
Compasso d'Oro Award recipients | Domus (magazine) | [
"Engineering"
] | 2,662 | [
"Design magazines",
"Design"
] |
9,409,170 | https://en.wikipedia.org/wiki/Command%20Data%20Buffer | Command Data Buffer (CDB) was a system used by the United States Air Force's Minuteman ICBM force. CDB was a method to transfer targeting information from a Minuteman Launch Control Center to an individual missile by communications lines. Prior to CDB, new missile guidance would have to be physically loaded at the launch facility; the process usually took hours.
History
The surviving remnant of the Minuteman Command Control System (MICCS), CDB permitted the rapid, remote, retargeting of the Minuteman III fleet. CDB was operational at all Minuteman III wings by 15 Aug 1977. Minuteman II wings had a similar install, designated Improved Launch Control System, providing the older system the potential for remote retargeting.
Phaseout
CDB was replaced in the late 1990s by the Rapid Execution and Combat Targeting system, currently in use by United States ICBM forces.
See also
LGM-30 Minuteman
Launch control center (ICBM)
Improved Launch Control System - Minuteman II upgrade similar to CDB
Rapid Execution and Combat Targeting System (REACT)
References
United States nuclear command and control
Cold War weapons of the United States
Nuclear weapons of the United States
Computer memory
Synchronization | Command Data Buffer | [
"Engineering"
] | 246 | [
"Telecommunications engineering",
"Synchronization"
] |
9,409,435 | https://en.wikipedia.org/wiki/16-cell%20honeycomb | In four-dimensional Euclidean geometry, the 16-cell honeycomb is one of the three regular space-filling tessellations (or honeycombs), represented by Schläfli symbol {3,3,4,3}, and constructed by a 4-dimensional packing of 16-cell facets, three around every face.
Its dual is the 24-cell honeycomb. Its vertex figure is a 24-cell. The vertex arrangement is called the B4, D4, or F4 lattice.
Alternate names
Hexadecachoric tetracomb/honeycomb
Demitesseractic tetracomb/honeycomb
Coordinates
Vertices can be placed at all integer coordinates (i,j,k,l), such that the sum of the coordinates is even.
D4 lattice
The vertex arrangement of the 16-cell honeycomb is called the D4 lattice or F4 lattice. The vertices of this lattice are the centers of the 3-spheres in the densest known packing of equal spheres in 4-space; its kissing number is 24, which is also the same as the kissing number in R4, as proved by Oleg Musin in 2003.
The related D lattice (also called D) can be constructed by the union of two D4 lattices, and is identical to the C4 lattice:
∪ = =
The kissing number for D is 23 = 8, (2n – 1 for n < 8, 240 for n = 8, and 2n(n – 1) for n > 8).
The related D lattice (also called D and C) can be constructed by the union of all four D4 lattices, but it is identical to the D4 lattice: It is also the 4-dimensional body centered cubic, the union of two 4-cube honeycombs in dual positions.
∪ ∪ ∪ = = ∪ .
The kissing number of the D lattice (and D4 lattice) is 24 and its Voronoi tessellation is a 24-cell honeycomb, , containing all rectified 16-cells (24-cell) Voronoi cells, or .
Symmetry constructions
There are three different symmetry constructions of this tessellation. Each symmetry can be represented by different arrangements of colored 16-cell facets.
Related honeycombs
It is related to the regular hyperbolic 5-space 5-orthoplex honeycomb, {3,3,3,4,3}, with 5-orthoplex facets, the regular 4-polytope 24-cell, {3,4,3} with octahedral (3-orthoplex) cell, and cube {4,3}, with (2-orthoplex) square faces.
It has a 2-dimensional analogue, {3,6}, and as an alternated form (the demitesseractic honeycomb, h{4,3,3,4}) it is related to the alternated cubic honeycomb.
See also
Regular and uniform honeycombs in 4-space:
Tesseractic honeycomb
24-cell honeycomb
Truncated 24-cell honeycomb
Snub 24-cell honeycomb
5-cell honeycomb
Truncated 5-cell honeycomb
Omnitruncated 5-cell honeycomb
Notes
References
Coxeter, H.S.M. Regular Polytopes, (3rd edition, 1973), Dover edition,
pp. 154–156: Partial truncation or alternation, represented by h prefix: h{4,4} = {4,4}; h{4,3,4} = {31,1,4}, h{4,3,3,4} = {3,3,4,3}, ...
Kaleidoscopes: Selected Writings of H.S.M. Coxeter, edited by F. Arthur Sherk, Peter McMullen, Anthony C. Thompson, Asia Ivic Weiss, Wiley-Interscience Publication, 1995,
(Paper 24) H.S.M. Coxeter, Regular and Semi-Regular Polytopes III, [Math. Zeit. 200 (1988) 3-45]
George Olshevsky, Uniform Panoploid Tetracombs, Manuscript (2006) (Complete list of 11 convex uniform tilings, 28 convex uniform honeycombs, and 143 convex uniform tetracombs)
x3o3o4o3o - hext - O104
Honeycombs (geometry)
5-polytopes
Regular tessellations | 16-cell honeycomb | [
"Physics",
"Chemistry",
"Materials_science"
] | 931 | [
"Regular tessellations",
"Honeycombs (geometry)",
"Tessellation",
"Crystallography",
"Symmetry"
] |
9,409,943 | https://en.wikipedia.org/wiki/String%20duality | String duality is a class of symmetries in physics that link different string theories, theories which assume that the fundamental building blocks of the universe are strings instead of point particles.
Overview
Before the so-called "duality revolution" there were believed to be five distinct versions of string theory, plus the (unstable) bosonic and gluonic theories.
Note that in the type IIA and type IIB string theories closed strings are allowed to move everywhere throughout the ten-dimensional space-time (called the bulk), while open strings have their ends attached to D-branes, which are membranes of lower dimensionality (their dimension is odd - 1,3,5,7 or 9 - in type IIA and even - 0,2,4,6 or 8 - in type IIB, including the time direction).
Before the 1990s, string theorists believed there were five distinct superstring theories: type I, types IIA and IIB, and the two heterotic string theories (SO(32) and E8×E8). The thinking was that out of these five candidate theories, only one was the actual theory of everything, and that theory was the theory whose low energy limit, with ten dimensions spacetime compactified down to four, matched the physics observed in our world today. It is now known that the five superstring theories are not fundamental, but are instead different limits of a more fundamental theory, dubbed M-theory. These theories are related by transformations called dualities. If two theories are related by a duality transformation, each observable of the first theory can be mapped in some way to the second theory to yield equivalent predictions. The two theories are then said to be dual to one another under that transformation. Put differently, the two theories are two mathematically different descriptions of the same phenomena. A simple example of a duality is the equivalence of particle physics upon replacing matter with antimatter; describing our universe in terms of anti-particles would yield identical predictions for any possible experiment.
String dualities often link quantities that appear to be separate: Large and small distance scales, strong and weak coupling strengths. These quantities have always marked very distinct limits of behavior of a physical system, in both classical field theory and quantum particle physics. But strings can obscure the difference between large and small, strong and weak, and this is how these five very different theories end up being related.
T-duality
Suppose we are in ten spacetime dimensions, which means we have nine space dimensions and one time. Take one of those nine space dimensions and make it a circle of radius R, so that traveling in that direction for a distance L = 2πR takes you around the circle and brings you back to where you started. A particle traveling around this circle will have a quantized momentum around the circle, because its momentum is linked to its wavelength (see wave–particle duality), and 2πR must be a multiple of that. In fact, the particle momentum around the circle - and the contribution to its energy - is of the form n/R (in standard units, for an integer n), so that at large R there will be many more states compared to small R (for a given maximum energy). A string, in addition to traveling around the circle, may also wrap around it. The number of times the string winds around the circle is called the winding number, and that is also quantized (as it must be an integer). Winding around the circle requires energy, because the string must be stretched against its tension, so it contributes an amount of energy of the form , where is a constant called the string length and w is the winding number (an integer). Now (for a given maximum energy) there will be many different states (with different momenta) at large R, but there will also be many different states (with different windings) at small R. In fact, a theory with large R and a theory with small R are equivalent, where the role of momentum in the first is played by the winding in the second, and vice versa. Mathematically, taking R to and switching n and w will yield the same equations. So exchanging momentum and winding modes of the string exchanges a large distance scale with a small distance scale.
This type of duality is called T-duality. T-duality relates type IIA superstring theory to type IIB superstring theory. That means if we take type IIA and Type IIB theory and compactify them both on a circle (one with a large radius and the other with a small radius) then switching the momentum and winding modes, and switching the distance scale, changes one theory into the other. The same is also true for the two heterotic theories. T-duality also relates type I superstring theory to both type IIA and type IIB superstring theories with certain boundary conditions (termed orientifold).
Formally, the location of the string on the circle is described by two fields living on it, one which is left-moving and another which is right-moving. The movement of the string center (and hence its momentum) is related to the sum of the fields, while the string stretch (and hence its winding number) is related to their difference. T-duality can be formally described by taking the left-moving field to minus itself, so that the sum and the difference are interchanged, leading to switching of momentum and winding.
S-duality
Every force has a coupling constant, which is a measure of its strength, and determines the chances of one particle to emit or absorb another particle. For electromagnetism, the coupling constant is proportional to the square of the electric charge. When physicists study the quantum behavior of electromagnetism, they can't solve the whole theory exactly, because every particle may emit and absorb many other particles, which may also do the same, endlessly. So events of emission and absorption are considered as perturbations and are dealt with by a series of approximations, first assuming there is only one such event, then correcting the result for allowing two such events, etc. (this method is called Perturbation theory). This is a reasonable approximation only if the coupling constant is small, which is the case for electromagnetism. But if the coupling constant gets large, that method of calculation breaks down, and the little pieces become worthless as an approximation to the real physics.
This also can happen in string theory. String theories have a coupling constant. But unlike in particle theories, the string coupling constant is not just a number, but depends on one of the oscillation modes of the string, called the dilaton. Exchanging the dilaton field with minus itself exchanges a very large coupling constant with a very small one. This symmetry is called S-duality. If two string theories are related by S-duality, then one theory with a strong coupling constant is the same as the other theory with weak coupling constant. The theory with strong coupling cannot be understood by means of perturbation theory, but the theory with weak coupling can. So if the two theories are related by S-duality, then we just need to understand the weak theory, and that is equivalent to understanding the strong theory.
Superstring theories related by S-duality are: type I superstring theory with heterotic SO(32) superstring theory, and type IIB theory with itself.
Furthermore, type IIA theory in strong coupling behaves like an 11-dimensional theory, with the dilaton field playing the role of an eleventh dimension. This 11-dimensional theory is known as M-theory.
Unlike the T-duality, however, S-duality has not been proven to even a physics level of rigor for any of the aforementioned cases. It remains, strictly speaking, a conjecture, although most string theorists believe in its validity.
See also
Mirror symmetry
U-duality
String theory
References | String duality | [
"Astronomy"
] | 1,642 | [
"String theory",
"Astronomical hypotheses"
] |
9,410,260 | https://en.wikipedia.org/wiki/Silicon%20Prairie | The Silicon Prairie, a take on the Silicon Valley, can refer to one of several places in the United States including: the Dallas–Fort Worth area in Texas, the Chicago and Champaign-Urbana areas in Illinois, and Madison, Wisconsin. Silicon Prairie is also a reference to a multi-state region loosely comprising parts of Minnesota, Wisconsin, Iowa, Missouri, Nebraska, Oklahoma and Kansas.
Dallas–Fort Worth Silicon Prairie
North Texas's Silicon Prairie refers to north Dallas and Dallas and Fort Worth's northern suburbs, all part of the Dallas–Fort Worth metroplex. It is named for the high concentration of semiconductor manufacturing, telecommunications, and other information technology related companies in the area.
Dallas–Fort Worth area business in these industry sectors include:
The Telecom Corridor in Richardson is usually considered the birthplace of the North Texas Silicon Prairie, with Texas Instruments and University of Texas at Dallas dating back to the 1960s. There are also a large number of recognized video and computer game developers in the area, known as the Dallas Gaming Mafia, including Gearbox Software, id Software, 3D Realms, Nerve Software, Bonfire Studios/Zynga Dallas, and Ensemble Studios. These videogame studios, especially Gearbox Software, helped get public interest and municipal funding for the National Videogame Museum to make its home in Frisco.
Illinois Silicon Prairie
The Illinois Silicon Prairie typically refers to the Chicago and Champaign/Urbana areas.
The Chicago Metropolitan Area is home to several companies in the industrial automation, consumer electronics, telecommunications, and online services industries. The Illinois Technology and Research Corridor along Interstate 88 and the Golden Corridor along Interstate 90 have particularly high concentrations of such businesses.
Among the Chicago area companies and organizations that comprise the Illinois Silicon Prairie are:
1871 (River North, Chicago)
Alcatel-Lucent (Naperville)
Amada America (Schaumburg)
Anixter (Glenview)
CDW (Lincolnshire)
Cisco (Chicago)
Classified Ventures (Chicago)
CommScope (Joliet, Illinois)
Continental Automotive Systems (Deer Park)
Enova International (Chicago)
FANUC Robotics America Corporation (Hoffman Estates)
Groupon (Chicago)
GrubHub (Chicago)
Guaranteed Rate (Chicago)
HighGround (Chicago)
Hostway (Chicago)
LiveText (LaGrange)
Molex (Lisle)
Mori Seiki USA/DMG (Hoffman Estates)
Motorola Mobility (Chicago)
Motorola Solutions (Schaumburg)
Northrop Grumman Electronic Systems (Rolling Meadows)
Omron (Schaumburg)
Orbitz (Chicago)
Panasonic Corporation (Buffalo Grove)
Rand McNally (Skokie)
Schneider Electric (Palatine)
Shure (Niles)
Tellabs (Naperville)
Trunk Club (River North, Chicago)
Underwriters Laboratories (Northbrook)
USRobotics (Schaumburg)
Westell (Aurora)
WMS Gaming (Waukegan)
Zebra Technologies (Lincolnshire)
Much of the high technology industry base in the Champaign–Urbana metropolitan area consists of research and small start-up companies working with the University of Illinois at Urbana–Champaign. Seven Fortune 500 companies have research entities at the university's research park located in Champaign. The National Center for Supercomputing Applications is in Urbana.
Midwest Silicon Prairie
An area of the Midwestern United States is often referred to as the Silicon Prairie. This region can loosely be defined as the states bordering along Interstate 29 in the Upper Midwest; mainly Missouri, Indiana, Iowa, Kansas, South Dakota, and Nebraska.
Gateway
Computer company Gateway 2000 and several other companies began using the moniker in the mid-1990s in advertisements and promotional materials.
Paycom
Founded in Oklahoma City in 1998, Paycom is one of the first online payroll and HR technology providers, recognized by Fortune magazine in 2020 as one of the fastest-growing publicly traded companies in the world. They also operate a secondary facility in Dallas, and broke ground on a new operations center in Grapevine in 2019.
Silicon Prairie Communications (prairie.net) - ISP and regional BBS
Founded in 1992, Silicon Prairie Communications started as a regional BBS and UUCP gateway, expanding to a boutique ISP that still serves as the delegated admin for a large group of .us domain localities, both regionally in Iowa and several large metro cities.
Silicon Prairie News
In 2008, the online technology and entrepreneurial news publication Silicon Prairie News was founded to highlight achievements of companies in the region's principal cities such as Des Moines, Kansas City, St. Louis, Omaha, Sioux Falls and any adjacent cities.
Silicon Prairie Portal & Exchange d/b/a Silicon Prairie Online
In 2016, the MNvest portal operator Silicon Prairie Online received registration approval from the Minnesota Department of Commerce to commence operations as a JOBS Act approved crowdfunding portal operator.
Iowa Governor Culver
In 2009, Governor Chet Culver (D-Iowa) used the term to describe his desired future reputation for his state after their investment in wind and other renewable energy industries.
ISU Research Park
Ames, Iowa
Workiva - An Ames, Iowa-based business enterprise software company. In 2016 Workiva received the Technology Association of Iowa's Prometheus Award for Top Growth Company of the Year.
Des Moines
Dwolla - A mobile payment company, whose business model includes speeding up business to business and business to consumer transactions and payments.
Nebraska Angels
An Omaha-based group of approximately 60 investors who fund local start-ups.
South Dakota
Property Meld is a Rapid City-based SaaS startup that streamlines maintenance coordination for property management companies across the US and Canada.
References
Economy of Dallas
Economy of Illinois
Economy of Texas
Economy of Chicago
High-technology business districts in the United States
Information technology places
Economy of Nebraska | Silicon Prairie | [
"Technology"
] | 1,157 | [
"Information technology",
"Information technology places"
] |
9,410,951 | https://en.wikipedia.org/wiki/Cayley%20plane | In mathematics, the Cayley plane (or octonionic projective plane) P2(O) is a projective plane over the octonions.
The Cayley plane was discovered in 1933 by Ruth Moufang, and is named after Arthur Cayley for his 1845 paper describing the octonions.
Properties
In the Cayley plane, lines and points may be defined in a natural way so that it becomes a 2-dimensional projective space, that is, a projective plane. It is a non-Desarguesian plane, where Desargues' theorem does not hold.
More precisely, as of 2005, there are two objects called Cayley planes, namely the real and the complex Cayley plane.
The real Cayley plane is the symmetric space F4/Spin(9), where F4 is a compact form of an exceptional Lie group and Spin(9) is the spin group of nine-dimensional Euclidean space (realized in F4). It admits a cell decomposition into three cells, of dimensions 0, 8 and 16.
The complex Cayley plane is a homogeneous space under the complexification of the group E6 by a parabolic subgroup P1. It is the closed orbit in the projectivization of the minimal complex representation of E6. The complex Cayley plane consists of two complex F4-orbits: the closed orbit is a quotient of the complexified F4 by a parabolic subgroup, the open orbit is the complexification of the real Cayley plane, retracting to it.
See also
Rosenfeld projective plane
Notes
References
Helmut Salzmann et al. "Compact projective planes. With an introduction to octonion geometry"; de Gruyter Expositions in Mathematics, 21. Walter de Gruyter & Co., Berlin, 1995. xiv+688 pp.
Projective geometry | Cayley plane | [
"Mathematics"
] | 384 | [
"Algebra stubs",
"Geometry",
"Algebra",
"Geometry stubs"
] |
9,411,116 | https://en.wikipedia.org/wiki/Complement%20control%20protein | Complement control proteins are proteins that interact with components of the complement system.
The complement system is tightly regulated by a network of proteins known as "regulators of complement activation (RCA)" that help distinguish target cells as "self" or "non-self." A subset of this family of proteins, complement control proteins (CCP), are characterized by domains of conserved repeats that direct interaction with components of the complement system. These "Sushi" domains have been used to identify other putative members of the CCP family. There are many other RCA proteins that do not fall into this family.
Most CCPs prevent activation of the complement system on the surface of host cells and protect host tissues against damage caused by autoimmunity. Because of this, these proteins play important roles in autoimmune disorders and cancers.
Members
Most of the well-studied proteins within this family can be categorized in two classes:
Membrane-bound complement regulators
Membrane Cofactor Protein, MCP (CD46)
Decay Accelerating Factor, DAF (CD55)
Protectin (CD59)
Complement C3b/C4b Receptor 1, CR1 (CD35)
Complement Regulator of the Immunoglobulin Superfamily, CRIg
Soluble complement regulators
Factor H
C4-Binding Protein (C4bp)
Other proteins with characteristic CCP domains have been identified including members of the sushi domain containing (SUSD) protein family and Human CUB and sushi multiple domains family (CSMD).
Mechanisms of protection
Every cell in the human body is protected by one or more of the membrane-associated RCA proteins, CR1, DAF or MCP. Factor H and C4BP circulate in the plasma and are recruited to self-surfaces through binding to host-specific polysaccharides such as the glycosaminoglycans.
Most CCPs function by preventing convertase activity. Convertases, specifically the C3 convertases C3b.Bb and C4b.2a, are the enzymes that drive complement activation by activating C3b, a central component of the complement system. Some CCPs, such as CD46, recruit other RCAs to proteolytically inactivate developing convertases. CD55 and other CCPs promote the rapid dissociation of active enzymes. Other CCPs prevent the activity of terminal effectors of the complement system, CD59 for example blocks oligomerization of the complement peptide C9 stalling the formation of the Membrane Attack Complex (MAC).
For example, C3b.Bb is an important convertase that is part of the alternative pathway, and it is formed when factor B binds C3b and is subsequently cleaved. To prevent this from happening, factor H competes with factor B to bind C3b; if it manages to bind, then the convertase is not formed. Factor H can bind C3b much more easily in the presence of sialic acid, which is a component of most cells in the human body; conversely, in the absence of sialic acid, factor B can bind C3b more easily. This means that if C3b is bound to a "self" cell, the presence of sialic acid and the binding of factor H will prevent the complement cascade from activating; if C3b is bound to a bacterium, factor B will bind and the cascade will be set off as normal. This mechanism of immune regulation using Factor H has been exploited by several bacterial pathogens.
Structure
RCA proteins typically possess CCP domains, also termed Sushi domains or Short Consensus Repeats (SCR). Such beta-sandwich domains contain about 60 amino acid residues, each with 4 conserved cysteines arranged in two conserved disulfide bonds (oxidized in 'abab' manner), and a conserved tryptophan, but otherwise can vary greatly in sequence. Recently, it has been demonstrated that the order, spatial relationship, and structure of these domains is essential for determining function.
The first CCP structure determined was a solution structure of the 16th module of factor H (pdb:1hcc). Since then, other CCP domains have been solved either by NMR-spectroscopy (also relaxation studies, e.g. module 2 and 3 from CD55 (pdb:1nwv)) or by X-ray diffraction (also with co-crystallized partner, e.g. CR2 CCP modules complexed with C3d (pdb:1ghq)).
Clinical significance
Complement has been implicated in many diseases associated with inflammation and autoimmunity. Efforts to develop therapeutics that target the interactions between the RCA network, CCPs, and components of the complement system have led to the development of successful drugs including Eculizumab.
There are two primary mechanisms by which dysfunction of complement can contribute to tissue damage:
Decreased protection of host tissues from complement activation due to the absence or lack of function of CCPs
Exhaustion of CRAs due to exposure of host cells that activate complement (either through direct damage or dysfunction) or prolonged attack by a potential pathogen such as during sepsis
The importance of complement regulation for good health is highlighted by recent work that seems to imply that individuals carrying point mutations or single nucleotide polymorphisms in their genes for factor H may be more susceptible to diseases including atypical hemolytic uremic syndrome, dense deposit diseases (or membranoproliferative glomerulonephritis type 2) and - most notably because of its prevalence in the elderly - age-related macular degeneration. Transgenic pigs that express human complement regulation factors were some of the first transgenic pigs used for xenotransplantation.
Complement control proteins also play a role in malignancy. Complement proteins protect against malignant cells- both by direct complement attack and through initiation of Complement-dependent cytotoxicity, which synergises with specific monoclonal antibody therapies. However, some malignant cells have been shown to have increased expression of membrane-bound complement control proteins, especially CD46, DAF and CD59. This mechanism allows some tumours to evade complement action.
CCPs have been exploited extensively by pathogenic microbes. Neisseria gonorhoeae and Neisseria meningitidis, the bacteria responsible for gonorrhea and meningitis have many well-studied evasion strategies involving CCPs, including binding soluble regulators like Factor H and C4bp. Many viruses, such as Vaccinia incorporate mimics of CCPs into their envelope for the purposes of evading the complement system. Still other microbes such as the measles virus use CCPs as receptors to gain entry to cells during infection. Each of these strategies may provide targets for the development of vaccines, as with the case of N. meningitidis.
Certain forms of schizophrenia are characterised by an underlying biological mechanism of excessive synaptic pruning, mediated by a dysregulated complement system in the brain. Accordingly, genetic variants of a brain-specific complement inhibitor, CSMD1, are associated with the risk of developing schizophrenia.
Sources
Further reading
External links
Complement system
Proteins | Complement control protein | [
"Chemistry"
] | 1,481 | [
"Biomolecules by chemical classification",
"Proteins",
"Molecular biology"
] |
9,411,318 | https://en.wikipedia.org/wiki/British%20Salt | British Salt Limited is a United Kingdom-based chemical company that produces pure white salt. The company is owned by Tata Chemicals Europe after a buy out from private equity company LDC in April 2010. It is based in Middlewich, Cheshire, employs 125 people, and produces approximately of pure white salt every year.
LDC bought British Salt from its previous owners, US Salt Holdings LLC in 2007, investing £35m in the company. A management team has taken a minority stake. US Salt had bought British Salt from its previous owners, Staveley Industries plc in 2000 for £80m. In 2005, British Salt acquired New Cheshire Salt Works Limited, known as NCSW Limited. This acquisition was referred to the Competition Commission who approved the purchase. Since the purchase the NCSW site in Wincham has been closed and the site sold to Chantry Developments.
The salt is extracted from strata that lie approximately below ground. Bore holes are drilled into the strata and water is forced down to dissolve the salt. The resulting brine solution is pumped along of pipes back to the surface and direct into the Middlewich factory for purification and water evaporation to produce the pure salt. It is estimated that there are salt reserves sufficient for 200 years.
Applications
The main uses for the salt products include:
Water softeners
Chemical industry
Food processing
Animal feeds
Textiles and tanning
During the severe weather experienced in the UK in February 2009, British Salt also started to supply low-grade salt for de-icing of roads, after local authorities announced they were running very low on salt used for gritting due to the unexpected weather.
See also
History of salt in Middlewich
Winter storms of 2009–2010
References
External links
Official Website
Chemical companies of the United Kingdom
Companies based in Cheshire
Middlewich
Snow removal
Salt production
Tata Chemicals | British Salt | [
"Chemistry"
] | 363 | [
"Salt production",
"Salts"
] |
9,412,160 | https://en.wikipedia.org/wiki/Lapel%20pin | A lapel pin, also known as an enamel pin, is a small pin worn on clothing, often on the lapel of a jacket, attached to a bag, or displayed on a piece of fabric. Lapel pins can be ornamental or can indicate the wearer's affiliation with a cause or an organization, such as a fraternal order or religious order; in the case of a chivalric order, the lapel pin is in the form of a rosette. Before the popularity of wearing lapel pins, boutonnières were worn.
Popular usage
Lapel pins are frequently used as symbols of achievement and belonging in different organizations. Lapel pins from the organization are often collected by members and non-members alike.
Businesses, corporates, & political parties also use lapel pins to designate achievement and membership. Lapel pins are a common element of employee recognition programs, and they are presented to individuals as a symbol of an accomplishment. Like fraternity and sorority pins, these lapel pins instill a sense of belonging to an elite group of performers at the organization. Businesses also award lapel pins to employees more frequently to boost employee morale, productivity, and employee engagement.
The Soviet Union had great production of these. Besides pins showing political figures and as souvenirs for tourist spots, there were pins for various sports, cultural, and political gatherings and for technical achievements of the Soviet Union.
In recent years, pin collecting and trading has also become a popular hobby. Demand for pin designs based on popular cartoon characters and themes such as Disney, Betty Boop, and Hard Rock Cafe has surged and led to the creation of pin trading events and other social activities. Disney pin trading is a prime example of this.
Cultural significance
In the USSR and the People's Republic of China, the prominent lapel pins with portraits of Lenin and Mao Zedong, respectively, were worn by youth as well as by Communist party members or people who felt like showing their official political credo. In Czechoslovakia, the Mao badges/pins were worn in the late 1960s and early 1970s by non-conformist youth as a prank and a way to provoke the "normalisationist" reactionaries of the purged post-1968 Communist Party of Czechoslovakia.
In the 1970s, initiates of Guru Maharaj Ji extensively used buttons, sometimes quite large, with images of the guru's face on them.
Politicians in the United States often wear American flag lapel pins, especially after the attacks of September 11, 2001. By 2008, the flag pin had become "the quickest sartorial method for a politician to telegraph his or her patriotism." The practice declined somewhat in the following decade.
Modern manufacturing process
Almost all manufacturing is currently done in China, specifically in and around Kunshan, a satellite city in the greater Suzhou region that is administratively at the county-level in southeast Jiangsu, China, just outside Shanghai. Inexpensive labor in China has made non-Chinese production of lapel pins few and far between. There are still multiple online shops run by people outside of China who make and sell lapel pins.
In the die struck manufacturing process, there are five basic types of pins: Cloisonné, soft enamel, photo etched, screen printed and 4-color printed. In all processes, the outer shape of the pin is stamped out from a sheet of steel, aluminum, copper, brass, or iron. In the case of cloisonne and soft enamel, the shape and the design are stamped out. Nowadays, due to the low melting point and low price of zinc alloy, a large number of lapel pins are made of die-cast zinc alloy.
Cloisonné Sometimes called epola (imitation cloisonné) or hard enamel, cloisonné is stamped out from a sheet of copper. The stamping leaves recessed areas, or pools, which are filled with enamel powder and high fired at 800° to 900°. After cooling, the surface of the pin is ground down to a smooth finish and then the copper is plated.
Soft enamel This process is like epola and cloisonné in that strips of metal separate areas of color. Unlike Cloisonné, the areas of color rest below the metal strip surface, which can be felt when you run your finger over the surface. Like the photo etched process, the top can be covered with protective epoxy so that the piece appears smooth.
Photo etched In the photo etch process, only the shape of the piece is stamped out. The design on the face of the pin is chemically etched into the base metal, then color-filled by hand and baked before being polished. In the final step, a thin coat of clear epoxy can be applied to the surface.
Photo dome The photo dome process begins by printing the art or design on vinyl or paper and then applying it to a metal pin base. The vinyl is then coated with an epoxy dome that protects the art from wear and the elements. This process is gaining in popularity because of advances in printing resolutions and the ability to complete these pins quickly in the United States.
Screen printed Screen printing, a.k.a. silk screening, is produced by applying each color to the metal base using a "silk screen" process. These are blocks of solid color. A very thin epoxy coat protects the color material from scratching.
4-color process 4-color process, a.k.a. offset printing, allows for bleeds and blends of colors, as is used in magazines. The colors are printed in the traditional CMYK process. This style is can be used for complex art and photo reproduction. An unlimited number of colors can be used.
Backside
The backside of a lapel pin holds the pin in place, and attachment pieces come in a variety of styles.
Butterfly clutch – One of the most popular modern methods of attaching pins is the butterfly clutch, sometimes called a military clutch. The back of the pin has a small prong attached and when the butterfly clutch is squeezed and pulled up from the prong the pin is released from the clutch. Butterfly clutches may be made out of metal, plastic, or rubber. Also known as a dammit.
Jewelry clutch – The jewelry clutch, or tie tack, is a simple but elegant design. The clutch locks into place when it covers the prong.
Safety clasp – A safety clasp is similar to a safety pin in design. A long pin prong tucks under a small hook or clasp to hold the pin in place.
Magnetic clasp – Magnetic clasps are composed of a small disc magnet that is attracted to another magnet that is attached to the back of the pin. Although this method is generally less secure, it is designed to prevent hole punctures in garments. Bar magnet clasps help disperse the tension with two sets of magnets.
Screw and nut – A screw and nut clasp is one of the most secure. The prong is threaded so that the nut screws into place to hold the pin firmly.
Stick pin – A stick pin has a thin needle with a collar that slides up and down the needle to secure or release the pin.
See also
Award pin
Boutonnière
Brooch
Collar pin
Campaign button
Disney pin trading
Kim Il-sung and Kim Jong-il badges
Pin
Pin-back button
Pin trading
Remembrance poppy
References
External links
Award items
Badges
Fashion accessories | Lapel pin | [
"Mathematics"
] | 1,492 | [
"Symbols",
"Badges"
] |
9,412,979 | https://en.wikipedia.org/wiki/Pushforward%20measure | In measure theory, a pushforward measure (also known as push forward, push-forward or image measure) is obtained by transferring ("pushing forward") a measure from one measurable space to another using a measurable function.
Definition
Given measurable spaces and , a measurable mapping and a measure , the pushforward of by is defined to be the measure given by
for
This definition applies mutatis mutandis for a signed or complex measure.
The pushforward measure is also denoted as , , , or .
Properties
Change of variable formula
Theorem: A measurable function g on X2 is integrable with respect to the pushforward measure f∗(μ) if and only if the composition is integrable with respect to the measure μ. In that case, the integrals coincide, i.e.,
Note that in the previous formula .
Functoriality
Pushforwards of measures allow to induce, from a function between measurable spaces , a function between the spaces of measures .
As with many induced mappings, this construction has the structure of a functor, on the category of measurable spaces.
For the special case of probability measures, this property amounts to functoriality of the Giry monad.
Examples and applications
If is a probability space, is a measurable space, and is a -valued random variable, then the probability distribution of is the pushforward measure of by onto .
A natural "Lebesgue measure" on the unit circle S1 (here thought of as a subset of the complex plane C) may be defined using a push-forward construction and Lebesgue measure λ on the real line R. Let λ also denote the restriction of Lebesgue measure to the interval [0, 2π) and let f : [0, 2π) → S1 be the natural bijection defined by f(t) = exp(i t). The natural "Lebesgue measure" on S1 is then the push-forward measure f∗(λ). The measure f∗(λ) might also be called "arc length measure" or "angle measure", since the f∗(λ)-measure of an arc in S1 is precisely its arc length (or, equivalently, the angle that it subtends at the centre of the circle.)
The previous example extends nicely to give a natural "Lebesgue measure" on the n-dimensional torus Tn. The previous example is a special case, since S1 = T1. This Lebesgue measure on Tn is, up to normalization, the Haar measure for the compact, connected Lie group Tn.
Gaussian measures on infinite-dimensional vector spaces are defined using the push-forward and the standard Gaussian measure on the real line: a Borel measure γ on a separable Banach space X is called Gaussian if the push-forward of γ by any non-zero linear functional in the continuous dual space to X is a Gaussian measure on R.
Consider a measurable function f : X → X and the composition of f with itself n times:
This iterated function forms a dynamical system. It is often of interest in the study of such systems to find a measure μ on X that the map f leaves unchanged, a so-called invariant measure, i.e one for which f∗(μ) = μ.
One can also consider quasi-invariant measures for such a dynamical system: a measure on is called quasi-invariant under if the push-forward of by is merely equivalent to the original measure μ, not necessarily equal to it. A pair of measures on the same space are equivalent if and only if , so is quasi-invariant under if
Many natural probability distributions, such as the chi distribution, can be obtained via this construction.
Random variables induce pushforward measures. They map a probability space into a codomain space and endow that space with a probability measure defined by the pushforward. Furthermore, because random variables are functions (and hence total functions), the inverse image of the whole codomain is the whole domain, and the measure of the whole domain is 1, so the measure of the whole codomain is 1. This means that random variables can be composed ad infinitum and they will always remain random variables and endow the codomain spaces with probability measures.
A generalization
In general, any measurable function can be pushed forward. The push-forward then becomes a linear operator, known as the transfer operator or Frobenius–Perron operator. In finite spaces this operator typically satisfies the requirements of the Frobenius–Perron theorem, and the maximal eigenvalue of the operator corresponds to the invariant measure.
The adjoint to the push-forward is the pullback; as an operator on spaces of functions on measurable spaces, it is the composition operator or Koopman operator.
See also
Measure-preserving dynamical system
Normalizing flow
Optimal transport
Notes
References
Measures (measure theory) | Pushforward measure | [
"Physics",
"Mathematics"
] | 1,039 | [
"Measures (measure theory)",
"Quantity",
"Physical quantities",
"Size"
] |
9,413,032 | https://en.wikipedia.org/wiki/Natural%20exponential%20family | In probability and statistics, a natural exponential family (NEF) is a class of probability distributions that is a special case of an exponential family (EF).
Definition
Univariate case
The natural exponential families (NEF) are a subset of the exponential families. A NEF is an exponential family in which the natural parameter η and the natural statistic T(x) are both the identity. A distribution in an exponential family with parameter θ can be written with probability density function (PDF)
where and are known functions.
A distribution in a natural exponential family with parameter θ can thus be written with PDF
[Note that slightly different notation is used by the originator of the NEF, Carl Morris. Morris uses ω instead of η and ψ instead of A.]
General multivariate case
Suppose that , then a natural exponential family of order p has density or mass function of the form:
where in this case the parameter
Moment and cumulant generating functions
A member of a natural exponential family has moment generating function (MGF) of the form
The cumulant generating function is by definition the logarithm of the MGF, so it is
Examples
The five most important univariate cases are:
normal distribution with known variance
Poisson distribution
gamma distribution with known shape parameter α (or k depending on notation set used)
binomial distribution with known number of trials, n
negative binomial distribution with known
These five examples – Poisson, binomial, negative binomial, normal, and gamma – are a special subset of NEF, called NEF with quadratic variance function (NEF-QVF) because the variance can be written as a quadratic function of the mean. NEF-QVF are discussed below.
Distributions such as the exponential, Bernoulli, and geometric distributions are special cases of the above five distributions. For example, the Bernoulli distribution is a binomial distribution with n = 1 trial, the exponential distribution is a gamma distribution with shape parameter α = 1 (or k = 1 ), and the geometric distribution is a special case of the negative binomial distribution.
Some exponential family distributions are not NEF. The lognormal and Beta distribution are in the exponential family, but not the natural exponential family.
The gamma distribution with two parameters is an exponential family but not a NEF and the chi-squared distribution is a special case of the gamma distribution with fixed scale
parameter, and thus is also an exponential family but not a NEF (note that only a gamma distribution with fixed shape
parameter is a NEF).
The inverse Gaussian distribution is a NEF with a cubic variance function.
The parameterization of most of the above distributions has been written differently from the parameterization commonly used in textbooks and the above linked pages. For example, the above parameterization differs from the parameterization in the linked article in the Poisson case. The two parameterizations are related by , where λ is the mean parameter, and so that the density may be written as
for , so
This alternative parameterization can greatly simplify calculations in mathematical statistics. For example, in Bayesian inference, a posterior probability distribution is calculated as the product of two distributions. Normally this calculation requires writing out the probability distribution functions (PDF) and integrating; with the above parameterization, however, that calculation can be avoided. Instead, relationships between distributions can be abstracted due to the properties of the NEF described below.
An example of the multivariate case is the multinomial distribution with known number of trials.
Properties
The properties of the natural exponential family can be used to simplify calculations involving these distributions.
Univariate case
Multivariate case
In the multivariate case, the mean vector and covariance matrix are
where is the gradient and is the Hessian matrix.
Natural exponential families with quadratic variance functions (NEF-QVF)
A special case of the natural exponential families are those with quadratic variance functions.
Six NEFs have quadratic variance functions (QVF) in which the variance of the distribution can be written as a quadratic function of the mean. These are called NEF-QVF. The properties of these distributions were first described by Carl Morris.
The six NEF-QVFs
The six NEF-QVF are written here in increasing complexity of the relationship between variance and mean.
The normal distribution with fixed variance is NEF-QVF because the variance is constant. The variance can be written , so variance is a degree 0 function of the mean.
The Poisson distribution is NEF-QVF because all Poisson distributions have variance equal to the mean , so variance is a linear function of the mean.
The Gamma distribution is NEF-QVF because the mean of the Gamma distribution is and the variance of the Gamma distribution is , so the variance is a quadratic function of the mean.
The binomial distribution is NEF-QVF because the mean is and the variance is which can be written in terms of the mean as
The negative binomial distribution is NEF-QVF because the mean is and the variance is
The (not very famous) distribution generated by the generalized hyperbolic secant distribution (NEF-GHS) has and
Properties of NEF-QVF
The properties of NEF-QVF can simplify calculations that use these distributions.
See also
Generalized linear model
Pearson distribution
Sheffer sequence
Orthogonal polynomials
References
Morris C. (1982) Natural exponential families with quadratic variance functions: statistical theory. Dept of mathematics, Institute of Statistics, University of Texas, Austin.
Exponentials
Types of probability distributions | Natural exponential family | [
"Mathematics"
] | 1,156 | [
"E (mathematical constant)",
"Exponentials"
] |
4,153,106 | https://en.wikipedia.org/wiki/T%20arm | The T-arm or T-loop is a specialized region on the tRNA molecule which acts as a special recognition site for the ribosome to form a tRNA-ribosome complex during protein biosynthesis or translation (biology).
The T-arm has two components to it; the T-stem and the T-loop.
The T-stem consists of a series of paired nucleotides, typically 5 pairs, but sometimes as few as 1 or as many as 6.
The T-loop is also often known as the TΨC arm due to the presence of ribothymidine (T/m5U), pseudouridine and cytidine residues. It folds into a unique structural element consisting of stacked bases in a U-turn, now termed the "T-loop motif".
In archaea, the m5U is replaced with N1-methylpseudouridine (m1Ψ). The m5U/m1Ψ modification at position 54 is thought to increase structural stability.
Organisms with T-loop lacking tRNA exhibit a much lower level of aminoacylation and EF-Tu-binding than in organisms which have the native tRNA.
The T-loop motif has been identified as a ubiquitous structural element in a number of noncoding RNAs. At least one other instance of the T-loop, found in rRNA, also carries the m5U modification.
References
RNA
Protein biosynthesis | T arm | [
"Chemistry"
] | 303 | [
"Protein biosynthesis",
"Gene expression",
"Biosynthesis"
] |
4,153,112 | https://en.wikipedia.org/wiki/Micromagnetics | Micromagnetics is a field of physics dealing with the prediction of magnetic behaviors at sub-micrometer length scales. The length scales considered are large enough for the atomic structure of the material to be ignored (the continuum approximation), yet small enough to resolve magnetic structures such as domain walls or vortices.
Micromagnetics can deal with static equilibria, by minimizing the magnetic energy, and with dynamic behavior, by solving the time-dependent dynamical equation.
History
Micromagnetics originated from a 1935 paper
by Lev Landau and Evgeny Lifshitz on antidomain walls.
Micromagnetics was then expanded upon by William Fuller Brown Jr. in several works in 1940-1941 using energy expressions taken from a 1938 paper by William Cronk Elmore.
According to D. Wei, Brown introduced the name "micromagnetics" in 1958.
The field prior to 1960 was summarised in Brown's book Micromagnetics.
In the 1970's computational methods were developed for the analysis of recording media due to the introduction of personal computers.
Static micromagnetics
The purpose of static micromagnetics is to solve for the spatial distribution of the magnetization at equilibrium. In most cases, as the temperature is much lower than the Curie temperature of the material considered, the modulus of the magnetization is assumed to be everywhere equal to the saturation magnetization . The problem then consists in finding the spatial orientation of the magnetization, which is given by the magnetization direction vector , also called reduced magnetization.
The static equilibria are found by minimizing the magnetic energy,
subject to the constraint or .
The contributions to this energy are the following:
Exchange energy
The exchange energy is a phenomenological continuum description of the quantum-mechanical exchange interaction. It is written as:
where is the exchange constant; , and are the components of ;
and the integral is performed over the volume of the sample.
The exchange energy tends to favor configurations where the magnetization varies slowly across the sample. This energy is minimized when the magnetization is perfectly uniform.
The exchange term is isotropic,
so any direction is equally acceptable.
Anisotropy energy
Magnetic anisotropy arises due to a combination of crystal structure and spin-orbit interaction. It can be generally written as:
where , the anisotropy energy density, is a function of the orientation of the magnetization. Minimum-energy directions for are called easy axes.
Time-reversal symmetry ensures that is an even function of . The simplest such function is
where K1 is called the anisotropy constant. In this approximation, called uniaxial anisotropy, the easy axis is the axis.
The anisotropy energy favors magnetic configurations where the magnetization is everywhere aligned along an easy axis.
Zeeman energy
The Zeeman energy is the interaction energy between the magnetization and any externally applied field. It is written as:
where is the applied field and is the vacuum permeability.
The Zeeman energy favors alignment of the magnetization parallel to the applied field.
Energy of the demagnetizing field
The demagnetizing field is the magnetic field created by the magnetic sample upon itself. The associated energy is:
where is the demagnetizing field. The field satisfies
and hence can be written as the gradient of a potential . This field depends on the magnetic configuration itself, and it can be found by solving
inside of the body and
outside of the body.
These are supplemented with the boundary conditions on the surface of the body
where is the unit normal to the surface. Furthermore, the potential satisfies the condition that and remain bounded as . The solution of these equations (c.f. magnetostatics) is:
The quantity is often called the volume charge density, and is called the surface charge density.
The energy of the demagnetizing field favors magnetic configurations that minimize magnetic charges. In particular, on the edges of the sample, the magnetization tends to run parallel to the surface. In most cases it is not possible to minimize this energy term at the same time as the others. The static equilibrium then is a compromise that minimizes the total magnetic energy, although it may not minimize individually any particular term.
Dzyaloshinskii–Moriya Interaction Energy
This interaction arises when a crystal lacks inversion symmetry, encouraging the magnetization to be perpendicular to its neighbours. It directly competes with the exchange energy. It is modelled with the energy contribution
where is the spiralization tensor,
that depends upon the crystal class. For bulk DMI,
and for a thin film in the plane
interfacial DMI takes the form
and for materials with symmetry class the energy contribution is
This term is important for the formation of magnetic skyrmions.
Magnetoelastic Energy
The magnetoelastic energy describes the energy storage due to elastic lattice distortions. It may be neglected if magnetoelastic coupled effects are neglected.
There exists a preferred local distortion of the crystalline solid associated with the magnetization director .
For a simple small-strain model, one can assume this strain to be isochoric and fully
isotropic in the lateral direction, yielding the deviatoric ansatz
where the material parameter is the isotropic magnetostrictive
constant. The elastic
energy density is assumed to be a function of the elastic, stress-producing
strains . A quadratic form for the magnetoelastic energy is
where
is the fourth-order elasticity tensor. Here the elastic response is assumed to be isotropic (based on
the two Lamé constants and ).
Taking into account the constant length of , we obtain the invariant-based representation
This energy term contributes to magnetostriction.
Dynamic micromagnetics
The purpose of dynamic micromagnetics is to predict the time evolution of the magnetic configuration. This is especially important if the sample is subject to some non-steady conditions such as the application of a field pulse or an AC field. This is done by solving the Landau-Lifshitz-Gilbert equation, which is a partial differential equation describing the evolution of the magnetization in terms of the local effective field acting on it.
Effective field
The effective field is the local field felt by the magnetization. The only real fields however are the magnetostatic field and the applied field. It can be described informally as the derivative of the magnetic energy density with respect to the orientation of the magnetization, as in:
where dE/dV is the energy density. In variational terms, a change dm of the magnetization and the associated change dE of the magnetic energy are related by:
Since m is a unit vector, dm is always perpendicular to m. Then the above definition leaves unspecified the component of Heff that is parallel to m. This is usually not a problem, as this component has no effect on the magnetization dynamics.
From the expression of the different contributions to the magnetic energy, the effective field can be found to be (excluding the DMI and magnetoelastic contributions):
Landau-Lifshitz-Gilbert equation
This is the equation of motion of the magnetization. It describes a Larmor precession of the magnetization around the effective field, with an additional damping term arising from the coupling of the magnetic system to the environment. The equation can be written in the so-called Gilbert form (or implicit form) as:
where is the electron gyromagnetic ratio and the Gilbert damping constant.
It can be shown that this is mathematically equivalent to the following Landau-Lifshitz (or explicit) form:
where is the Gilbert Damping constant, characterizing how quickly the damping term takes away energy from the system ( = 0, no damping, permanent precession).
These equations preserve the constraint , as
Applications
The interaction of micromagnetics with mechanics is also of interest in the context of industrial applications that deal with magneto-acoustic resonance such as in hypersound speakers, high frequency magnetostrictive transducers etc.
FEM simulations taking into account the effect of magnetostriction into micromagnetics are of importance. Such simulations use models described above within a finite element framework.
Apart from conventional magnetic domains and domain-walls, the theory also treats the statics and dynamics of topological line and point configurations, e.g. magnetic vortex and antivortex states; or even 3d-Bloch points, where, for example, the magnetization leads radially into all directions from the origin, or into topologically equivalent configurations. Thus in space, and also in time, nano- (and even pico-)scales are used.
The corresponding topological quantum numbers are thought to be used as information carriers, to apply the most recent, and already studied, propositions in information technology.
Another application that has emerged in the last decade is the application of micromagnetics towards neuronal stimulation. In this discipline, numerical methods such as finite-element analysis are used to analyze the electric/magnetic fields generated by the stimulation apparatus; then the results are validated or explored further using in-vivo or in-vitro neuronal stimulation. Several distinct set of neurons have been studied using this methodology including retinal neurons, cochlear neurons, vestibular neurons, and cortical neurons of embryonic rats.
See also
Magnetism
Magnetic nanoparticles
Footnotes and references
Further reading
External links
μMAG -- Micromagnetic Modeling Activity Group.
OOMMF -- Micromagnetic Modeling Tool.
MuMax -- GPU-accelerated Micromagnetic Modeling Tool.
Dynamical systems
Magnetic ordering
Magnetostatics | Micromagnetics | [
"Physics",
"Chemistry",
"Materials_science",
"Mathematics",
"Engineering"
] | 1,977 | [
"Electric and magnetic fields in matter",
"Materials science",
"Magnetic ordering",
"Mechanics",
"Condensed matter physics",
"Dynamical systems"
] |
4,153,139 | https://en.wikipedia.org/wiki/Cryptoregiochemistry | Cryptoregiochemistry refers to the site of initial oxidative attack in double bond formation by enzymes such as fatty acid desaturases. This is a mechanistic parameter that is usually determined through the use of kinetic isotope effect experiments, based on the premise that the initial C-H bond cleavage step should be energetically more difficult and therefore more sensitive to isotopic substitution than the second C-H bond breaking step.
References
Chemical kinetics
Stereochemistry | Cryptoregiochemistry | [
"Physics",
"Chemistry"
] | 97 | [
"Chemical reaction engineering",
"Stereochemistry",
"Space",
"Stereochemistry stubs",
"nan",
"Spacetime",
"Chemical kinetics"
] |
4,153,219 | https://en.wikipedia.org/wiki/Homeoviscous%20adaptation | Homeoviscous adaptation is the adaptation of the cell membrane lipid composition to keep the adequate membrane fluidity.
The maintenance of proper cell membrane fluidity is of critical importance for the function and integrity of the cell, essential for the mobility and function of embedded proteins and lipids, diffusion of proteins and other molecules laterally across the membrane for signaling reactions, and proper separation of membranes during cell division.
A fundamental biophysical determinant of membrane fluidity is the balance between saturated and unsaturated fatty acids. Regulating membrane fluidity is especially important in poikilothermic organisms such as bacteria, fungi, protists, plants, fish and other ectothermic animals. The general trend is an increase in unsaturated fatty acids at lower growth temperatures and an increase in saturated fatty acids at higher temperatures.
A recent work has explored the importance of the homeoviscous adaptation of the cell membrane for a psychrotolerant bacteria living in the cold biosphere of earth.
References
Membrane biology | Homeoviscous adaptation | [
"Chemistry"
] | 208 | [
"Membrane biology",
"Molecular biology"
] |
4,153,538 | https://en.wikipedia.org/wiki/Canton%20Tower | The Canton Tower (), formally Guangzhou TV Astronomical and Sightseeing Tower (), is a -tall multipurpose observation tower in the Haizhu District of Guangzhou (alternatively romanized as Canton). The tower was topped out in 2009 and it became operational on 29 September 2010 in time for the 2010 Asian Games. The tower briefly held the title of tallest tower in the world, replacing the CN Tower, before being surpassed by the Tokyo Skytree. It was the tallest structure in China prior to the topping out of the Shanghai Tower on 3 August 2013, and is now the second-tallest tower and the fifth-tallest freestanding structure in the world.
Naming and etymology
There had been a long discussion about the naming of the Canton Tower since the commencement of its construction in 2005 after the groundbreaking ceremony. In September 2020, at the request of the tower's investor, Guangzhou Daily launched a contest for naming proposals. The contest attracted over valid entries, among which "Haixin Tower" () was awarded the first prize. The name alluded to the city's historical setting as the start of the Maritime Silk Road and the tower's geographical proximity to Haixinsha Island. However, this name was considered obscure to people unfamiliar with the history of the city. Local residents continued to refer to the tower by various nicknames including "Slim Waist" (), "Twisted Firewood" (; a metaphor for "stubborn" in Cantonese) and "Yangdianfeng" (; homophone of "epilepsy" in colloquial Chinese).
The Naming was reconsidered in 2010. After surveying a broad range of public opinions, "Canton Tower" was decided as the official English name and announced at the end of September 2010. The new English name, which alludes to the city's prosperous past, was considered the most identifying and least ambiguous among the multitude of proposals.
History
Canton Tower was constructed by Guangzhou New Television Tower Group. It was designed by the Dutch architects Mark Hemel and Barbara Kuit of Information Based Architecture, together with Arup, the international design, engineering and business consulting firm headquartered in London, United Kingdom. In 2004, Information Based Architecture and Arup won the international competition, in which many internationally large architectural offices participated. In the same year, the IBA – Arup team in Amsterdam developed the tower's concept design. In later stages, IBA cooperated mainly with the local Chinese office of Arup and a Local Design Institute. Subsequently, in 2005, the groundbreaking of the Canton Tower took place.
The tower, although not fully completed, opened to the public on 1 October 2010 in time for the 16th Asian Games, hosted by Guangzhou in November 2010. The rooftop observatory finally received its official opening in December 2011.
Structure and construction
The Canton Tower's twisted shape or hyperboloid structure corresponds to the Russian Empire patent No. 1896, dated 12 March 1899 received by Vladimir Shukhov, the Russian engineer and architect. The structure is similar to the Adziogol Lighthouse (designed by Vladimir Shukhov in 1910) in Ukraine's Dnepr delta.
Structural concept
The tower was designed by Information Based Architecture and Arup. The Arup team led by structural engineer Prof. Dr. Joop Paul introduced near mass customization to the joint design, in combination with parametric design methods, and applied a simple structural concept of three elements: columns, rings and braces, to this more complex geometry.
The waist of the tower contains a open-air skywalk where visitors can physically climb the tower. There are outdoor gardens set within the structure, and at the top, just above , a large open-air observation deck.
The interior of the tower is subdivided into programmatic zones with various functions, including TV and radio transmission facilities, observatory decks, revolving restaurants, computer gaming, restaurants, exhibition spaces, conference rooms, shops, and 4D cinemas.
A deck at the base of the tower hides the tower's functional workings. All infrastructural connections – metro and bus stations – are situated underground. This level also includes exhibition spaces, a food court, a commercial space, a parking area for cars and coaches. There are two types of elevators: slow-speed panoramic and high-speed double-decker.
The zone from consists of a 4D cinema, a play-hall area, restaurants, coffee shops and outdoor gardens with teahouses. The highest and longest open-air staircase in the world, the Skywalk, starts at the height of and spirals almost higher, all the way through the waist. Parts of the skywalk's floors are laid with transparent glass.
The top zone of the tower begins above the stairway, housing various technical functions as well as a two-story rotating restaurant, a tuned mass damper and the upper observation levels. From the upper observation levels it is possible to ascend even higher, via a further set of the stairs, to a terraced observation square rising above the tower's top ring.
The twist
The form, volume and structure of the towers is generated by two ellipses, one at foundation level and the other at a horizontal plane at . These two ellipses are rotated relative to another. The tightening caused by the rotation between the two ellipses forms a "waist" and a densification of material halfway up the tower. This means that the lattice structure, which at the bottom of the tower is porous and spacious, becomes denser at waist level. The waist itself becomes tight, like a twisted rope; transparency is reduced and views to the outside are limited. Further up the tower the lattice opens again, accentuated here by the tapering of the structural column-tubes.
Rooftop observatory
The indoor public observatory is 449 m above the ground, which takes the form of a terraced elliptical space, roughly half the size of a standard football field. Opened in December 2011, the rooftop at 488 m was the highest and largest outdoor observation deck in the world, taking over the title from the observation deck of Burj Khalifa at 452m. This remained the case until 14 October 2014, when the record of highest outdoor observatory was retaken by Burj Khalifa when it opened its new observatory called at the Top – Sky, at a height of 555m.
Sixteen transparent "crystal" passenger cars, each with a diameter of and able to carry four to six people, travel on a track round the edge of the tower's roof, taking between 20 and 40 minutes to circumnavigate the rooftop. The installation is described by the media as a Ferris wheel; however, its passenger cars are not suspended from the rim of a wheel and remain horizontal without being fully rotated, and the track, which follows the incline of the roof, is closer to the horizontal than the vertical.
Architectural lighting design
At night, the tower glows and emits light, rather than being uplit. Lighting designer Rogier van der Heide is known for this concept, which he also applied at the Marunouchi Building in Tokyo. Each node in the lighting design is individually controllable to allow for animations and color changes across the entire height of the tower. As all lighting is based on LED technology, and all fixtures are located on the structure itself, the lighting scheme consumes only 15% of the allowed maximum for façade lighting.
At the time of the design of Canton Tower, lighting designer Rogier van der Heide was Global Leader of Arup Lighting.
Measurements
The Canton Tower's main body stands at . Combined with the tower's antenna, the Canton Tower has a total height of , making it the second tallest tower in the world, second tallest in Asia, and the tallest in the People's Republic of China. The tower has a total of 112 floors.
The Canton Tower weighs a total of , including the tower's antenna which weighs and the main body, which includes all the features of the tower, which weighs a total of .
The Canton Tower occupies a total floor area of . In addition, the tower's net usable area measures .
Events
In lieu of a traditional stadium setting, the opening ceremonies of the 2010 Asian Games in Guangzhou were held on Haixinsha Island. The Canton Tower and Pearl River were used as a focal point of the event.
The Canton Tower hosted an annual Christmas Concert on Christmas Eve inside the tower's ground floor, making it the first concert to be held in the Canton Tower. Celebrated on Christmas Eve, the concert was held on 24 December 2012.
Geography
The Canton Tower is situated alongside the Yiyuan Road (Yuejiang Road West), in the Haizhu District of Guangzhou, and is situated south of the Zhujiang New Town. Additionally, several famous landmarks surround the tower, including pagodas, a park towards the south, and several high-rise apartments, buildings, and skyscrapers, both commercial and residential.
Gallery
Construction history
Diagrams
See also
2010 Asian Games
2010 Asian Para Games
Cantonese architecture
Guangzhou Broadcasting Network
Guangzhou TV Tower
List of hyperboloid structures
List of tallest freestanding structures in the world
List of tallest towers in the world
References
External links
Canton Tower official website :: GzTvTower.info
2010 establishments in China
Buildings and structures in Guangzhou
Communication towers in China
Haizhu District
High-tech architecture
Hyperboloid structures
Observation towers in China
Restaurant towers
Tourist attractions in Guangzhou
Towers completed in 2010 | Canton Tower | [
"Technology"
] | 1,912 | [
"Structural system",
"Hyperboloid structures"
] |
4,153,740 | https://en.wikipedia.org/wiki/Inositol%20pentakisphosphate | Inositol pentakisphosphate (abbreviated IP5) is a molecule derived from inositol tetrakisphosphate by adding a phosphate group with the help of Inositol-polyphosphate multikinase (IPMK). It is believed to be one of the many second messengers in the inositol phosphate family. It "is implicated in a wide array of biological and pathophysiological responses, including tumorigenesis, invasion and metastasis, therefore specific inhibitors of the kinase may prove useful in cancer therapy."
IP5 also plays a role in defense signaling in plants. It potentiates the interaction of the plant hormone JA-Ile by its receptor.
References
Organophosphates
Inositol
Phosphate esters | Inositol pentakisphosphate | [
"Chemistry",
"Biology"
] | 164 | [
"Inositol",
"Biotechnology stubs",
"Signal transduction",
"Biochemistry stubs",
"Biochemistry"
] |
4,153,924 | https://en.wikipedia.org/wiki/Andromeda%20X | Andromeda X (And 10) is a dwarf spheroidal galaxy about 2.9 million light-years away from the Sun in the constellation Andromeda. Discovered in 2005 by Zucker et al., And X is a satellite galaxy of the Andromeda Galaxy (M31). Aided by the application of stellar photometry to data from the Sloan Digital Sky Survey similar to the Andromeda IX discovery, the new finding indicates that this type of extremely faint satellite might be common in the Local Group, potentially providing further support for hierarchical cold dark matter models.
See also
List of Andromeda's satellite galaxies
References
External links
SEDS webpage for Andromeda X
Andromeda X: Andromeda's Newest Satellite Galaxy
Dwarf spheroidal galaxies
5056921
Local Group
Andromeda Subgroup
Andromeda (constellation) | Andromeda X | [
"Astronomy"
] | 177 | [
"Andromeda (constellation)",
"Constellations"
] |
4,154,187 | https://en.wikipedia.org/wiki/Cosmogenic%20nuclide | Cosmogenic nuclides (or cosmogenic isotopes) are rare nuclides (isotopes) created when a high-energy cosmic ray interacts with the nucleus of an in situ Solar System atom, causing nucleons (protons and neutrons) to be expelled from the atom (see cosmic ray spallation). These nuclides are produced within Earth materials such as rocks or soil, in Earth's atmosphere, and in extraterrestrial items such as meteoroids. By measuring cosmogenic nuclides, scientists are able to gain insight into a range of geological and astronomical processes. There are both radioactive and stable cosmogenic nuclides. Some of these radionuclides are tritium, carbon-14 and phosphorus-32.
Certain light (low atomic number) primordial nuclides (isotopes of lithium, beryllium and boron) are thought to have been created not only during the Big Bang, but also (and perhaps primarily) to have been made after the Big Bang, but before the condensation of the Solar System, by the process of cosmic ray spallation on interstellar gas and dust. This explains their higher abundance in cosmic dust as compared with their abundances on Earth. This also explains the overabundance of the early transition metals just before iron in the periodic table – the cosmic-ray spallation of iron produces scandium through chromium on the one hand and helium through boron on the other. However, the arbitrary defining qualification for cosmogenic nuclides of being formed "in situ in the Solar System" (meaning inside an already aggregated piece of the Solar System) prevents primordial nuclides formed by cosmic ray spallation before the formation of the Solar System from being termed "cosmogenic nuclides"—even though the mechanism for their formation is exactly the same. These same nuclides still arrive on Earth in small amounts in cosmic rays, and are formed in meteoroids, in the atmosphere, on Earth, "cosmogenically". However, beryllium (all of it stable beryllium-9) is present primordially in the Solar System in much larger amounts, having existed prior to the condensation of the Solar System, and thus present in the materials from which the Solar System formed.
To make the distinction in another fashion, the timing of their formation determines which subset of cosmic ray spallation-produced nuclides are termed primordial or cosmogenic (a nuclide cannot belong to both classes). By convention, certain stable nuclides of lithium, beryllium, and boron are thought to have been produced by cosmic ray spallation in the period of time between the Big Bang and the Solar System's formation (thus making these primordial nuclides, by definition) are not termed "cosmogenic", even though they were formed by the same process as the cosmogenic nuclides (although at an earlier time). The primordial nuclide beryllium-9, the only stable beryllium isotope, is an example of this type of nuclide.
In contrast, even though the radioactive isotopes beryllium-7 and beryllium-10 fall into this series of three light elements (lithium, beryllium, boron) formed mostly by cosmic ray spallation nucleosynthesis, both of these nuclides have half lives too short (53 days and ca. 1.4 million years, resp.) for them to have been formed before the formation of the Solar System, and thus they cannot be primordial nuclides. Since the cosmic ray spallation route is the only possible source of beryllium-7 and beryllium-10 occurrence naturally in the environment, they are therefore cosmogenic.
Cosmogenic nuclides
Here is a list of radioisotopes formed by the action of cosmic rays; the list also contains the production mode of the isotope. Most cosmogenic nuclides are formed in the atmosphere, but some are formed in situ in soil and rock exposed to cosmic rays, notably calcium-41 in the table below.
Applications in geology listed by isotope
Use in geochronology
As seen in the table above, there are a wide variety of useful cosmogenic nuclides which can be measured in soil, rocks, groundwater, and the atmosphere. These nuclides all share the common feature of being absent in the host material at the time of formation. These nuclides are chemically distinct and fall into two categories. The nuclides of interest are either noble gases which due to their inert behavior are inherently not trapped in a crystallized mineral or has a short enough half-life such that it has decayed since nucleosynthesis, but a long enough half-life such that it has built up measurable concentrations. The former includes measuring abundances of 81Kr and 39Ar whereas the latter includes measuring abundances of 10Be, 14C, and 26Al.
Three types of cosmic-ray reactions can occur once a cosmic ray strikes matter which in turn produce the measured cosmogenic nuclides.
cosmic ray spallation, which is the most common reaction on the near-surface (typically 0 to 60 cm below) the Earth and can create secondary particles which can cause additional reaction upon interaction with another nuclei called a collision cascade.
muon capture, which pervades at depths a few meters below the subsurface because muons are inherently less reactive; in some cases, high-energy muons can reach greater depths
neutron capture, which due to the neutron's low energy are captured into a nucleus, most commonly by water, but this process is highly dependent on snow, soil moisture and trace element concentrations.
Corrections for cosmic-ray fluxes
Since the Earth bulges at the equator and mountains and deep oceanic trenches allow for deviations of several kilometers relative to a uniformly smooth spheroid, cosmic rays bombard the Earth's surface unevenly based on the latitude and altitude. Thus, many geographic and geologic considerations must be understood in order for cosmic-ray flux to be accurately determined. Atmospheric pressure, for example, which varies with altitude, can change the production rate of nuclides within minerals by a factor of 30 between sea level and the top of a 5 km high mountain. Even variations in the slope of the ground can affect how far high-energy muons can penetrate the subsurface. Geomagnetic field strength which varies over time affects the production rate of cosmogenic nuclides though some models assume variations of the field strength are averaged out over geologic time and are not always considered.
See also
Environmental radioactivity
References
Concepts in astrophysics
Environmental isotopes
Geochemistry
Nuclear technology
Nuclear chemistry
Nuclear physics
Radioactivity
Radiometric dating | Cosmogenic nuclide | [
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4,154,507 | https://en.wikipedia.org/wiki/Polymer%20brush | In materials science, a polymer brush is the name given to a surface coating consisting of polymers tethered to a surface. The brush may be either in a solvated state, where the tethered polymer layer consists of polymer and solvent, or in a melt state, where the tethered chains completely fill up the space available. These polymer layers can be tethered to flat substrates such as silicon wafers, or highly curved substrates such as nanoparticles. Also, polymers can be tethered in high density to another single polymer chain, although this arrangement is normally named a bottle brush. Additionally, there is a separate class of polyelectrolyte brushes, when the polymer chains themselves carry an electrostatic charge.
The brushes are often characterized by the high density of grafted chains. The limited space then leads to a strong extension of the chains. Brushes can be used to stabilize colloids, reduce friction between surfaces, and to provide lubrication in artificial joints.
Polymer brushes have been modeled with molecular dynamics, Monte Carlo methods, Brownian dynamics simulations, and molecular theories.
Structure
Polymer molecules within a brush are stretched away from the attachment surface as a result of the fact that they repel each other (steric repulsion or osmotic pressure). More precisely, they are more elongated near the attachment point and unstretched at the free end, as depicted on the drawing.
More precisely, within the approximation derived by Milner, Witten, Cates, the average density of all monomers in a given chain is always the same up to a prefactor:
where is the altitude of the end monomer and the number of monomers per chain.
The averaged density profile of the end monomers of all attached chains, convoluted with the above density profile for one chain, determines the density profile of the brush as a whole:
A dry brush has a uniform monomer density up to some altitude . One can show that the corresponding end monomer density profile is given by:
where is the monomer size.
The above monomer density profile for one single chain minimizes the total elastic energy of the brush,
regardless of the end monomer density profile , as shown in.
From a dry brush to any brush
As a consequence, the structure of any brush can be derived from the brush density profile . Indeed, the free end distribution is simply a convolution of the density profile with the free end distribution of a dry brush:
.
Correspondingly, the brush elastic free energy is given by:
.
This method has been used to derive wetting properties of polymer melts on polymer brushes of the same species and to understand fine interpenetration asymmetries between copolymer lamellae that may yield very unusual non-centrosymmetric lamellar structures.
Applications
Polymer brushes can be used in Area-selective deposition. Area-selective deposition is a promising technique for positional self-alignment of materials at a prepatterned surface.
See also
Dendronized polymer
References
Surface science
Soft matter
Polymer chemistry | Polymer brush | [
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"Chemistry",
"Materials_science",
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4,155,247 | https://en.wikipedia.org/wiki/Mental%20rotation | Mental rotation is the ability to rotate mental representations of two-dimensional and three-dimensional objects as it is related to the visual representation of such rotation within the human mind. There is a relationship between areas of the brain associated with perception and mental rotation. There could also be a relationship between the cognitive rate of spatial processing, general intelligence and mental rotation.
Mental rotation can be described as the brain moving objects in order to help understand what they are and where they belong. Mental rotation has been studied to try to figure out how the mind recognizes objects in their environment. Researchers generally call such objects stimuli. Mental rotation is one cognitive function for the person to figure out what the altered object is.
Mental rotation can be separated into the following cognitive stages:
Create a mental image of an object from all directions (imagining where it continues straight vs. turns).
Rotate the object mentally until a comparison can be made (orientating the stimulus to other figure).
Make the comparison.
Decide if the objects are the same or not.
Report the decision (reaction time is recorded when a lever is pulled or a button is pressed).
Assessment
Originally developed in 1978 by Vandenberg and Kuse based on the research by Shepard and Metzler (1971), a Mental Rotation Test (MRT) consists of a participant comparing two 3D objects (or letters), often rotated in some axis, and states if they are the same image or if they are mirror images (enantiomorphs). Commonly, the test will have pairs of images each rotated a specific number of degrees (e.g. 0°, 60°, 120° or 180°). A set number of pairs will be split between being the same image rotated, while others are mirrored. The researcher judges the participant on how accurately and rapidly they can distinguish between the mirrored and non-mirrored pairs.
Notable research
Shepard and Metzler (1971)
Roger Shepard and Jacqueline Metzler (1971) were some of the first to research the phenomenon. Their experiment specifically tested mental rotation on three-dimensional objects. Each subject was presented with multiple pairs of three-dimensional, asymmetrical lined or cubed objects. The experiment was designed to measure how long it would take each subject to determine whether the pair of objects were indeed the same object or two different objects. Their research showed that the reaction time for participants to decide if the pair of items matched or not was linearly proportional to the angle of rotation from the original position. That is, the more an object has been rotated from the original, the longer it takes an individual to determine if the two images are of the same object or enantiomorphs.
Vandenberg and Kuse (1978)
In 1978, Steven G. Vandenberg and Allan R. Kuse developed the Mental Rotations Test (MRT) to assess mental rotation abilities that was based on Shepard and Metzler's (1971) original study. The Mental Rotations Test was constructed using India ink drawings. Each stimulus was a two-dimensional image of a three-dimensional object drawn by a computer. The image was then displayed on an oscilloscope. Each image was then shown at different orientations rotated around the vertical axis. The original test contained 20 items, demanding the comparison of four figures with a criterion figure, with two of them being correct. Following the basic ideas of Shepard and Metzler's experiment, this study found a significant difference in the mental rotation scores between men and women, with men performing better. Correlations with other measures showed strong association with tests of spatial visualization and no association with verbal ability.
Neuropsychology
In 2000, a study was conducted to find out which part of the brain is activated during mental rotation. Seven volunteers (four males and three females) between the ages of twenty-nine to sixty-six participated in this experiment. For the study, the subjects were shown eight characters 4 times each (twice in normal orientation and twice reversed) and the subjects had to decide if the character was in its normal configuration or if it was the mirror image. During this task, a PET scan was performed and revealed activation in the right posterior parietal lobe.
Functional magnetic resonance imaging (fMRI) studies of brain activation during mental rotation reveal consistent increased activation of the parietal lobe, specifically the inter-parietal sulcus, that is dependent on the difficulty of the task. In general, the larger the angle of rotation, the more brain activity associated with the task. This increased brain activation is accompanied by longer times to complete the rotation task and higher error rates. Researchers have argued that the increased brain activation, increased time, and increased error rates indicate that task difficulty is proportional to the angle of rotation.
A 2006 study observed the following brain areas to be activated during mental rotation as compared to baseline: bilateral medial temporal gyrus, left medial occipital gyrus, bilateral superior occipital gyrus, bilateral superior parietal lobe, and left inferior occipital gyrus during the rotation task.
Development
A study from 2008 suggested that differences may occur early during development. The experiment was done on 3- to 4-month-old infants using a 2D mental rotation task. They used a preference apparatus that consists of observing during how much time the infant is looking at the stimulus. They started by familiarizing the participants with the number "1" and its rotations. Then they showed them a picture of a "1" rotated and its mirror image. It appears that gendered differences may appear early in development, as the study showed that males are more responsive to the mirror image. According to the study, this may mean that males and females process mental rotation differently even as infants. Supporting the presence of such differences early in development, other studies have found that gendered differences in mental rotation tests were visible in all age groups, including young children. Interestingly, these differences emerged much later for other categories of spatial tests.
In 2020, Advances in Child Development and Behavior published a review that examined mental rotation abilities during very early development. The authors concluded that an ability to mentally rotate objects can be detected in infants as young as 3 months of age. Also, MR processes in infancy likely remain stable over time into adulthood. Additional variables that appeared to influence infants' MR performance include motor activity, stimulus complexity, hormone levels, and parental attitudes
Factors that affect performance
Color
Physical objects that people imagine rotating in everyday life have many properties, such as textures, shapes, and colors. A study at the University of California Santa Barbara was conducted to specifically test the extent to which visual information, such as color, is represented during mental rotation. This study used several methods such as reaction time studies, verbal protocol analysis, and eye tracking. In the initial reaction time experiments, those with poor rotational ability were affected by the colors of the image, whereas those with good rotational ability were not. Overall, those with poor ability were faster and more accurate identifying images that were consistently colored. The verbal protocol analysis showed that the subjects with low spatial ability mentioned color in their mental rotation tasks more often than participants with high spatial ability. One thing that can be shown through this experiment is that those with higher rotational ability will be less likely to represent color in their mental rotation. Poor rotators will be more likely to represent color in their mental rotation using piecemeal strategies (Khooshabeh & Hegarty, 2008).
Athletic, musical, and artistic skills
Research on how athleticism and artistic ability affect mental rotation has been conducted. Pietsch, S., & Jansen, P. (2012) showed that people who were athletes or musicians had faster reaction times than people who were not. They tested this by splitting people from the age of 18 and higher into three groups. The groups consisted of music students, sports students, and education students. It was found that students who were focused on sports or music did much better than those who were education majors. Also, it was found that the male athletes and education majors in the experiment were faster than the respective females, but male and female musicians showed no significant difference in reaction time.
A 2007 study supported the results that musicians perform better on mental rotation tasks than non-musicians. In particular, orchestral musicians' MRT task performance exhibited aptitude levels significantly higher than the population baseline.
Moreau, D., Clerc, et al. (2012) also investigated if athletes were more spatially aware than non-athletes. This experiment took undergraduate college students and tested them with the mental rotation test before any sport training, and then again afterward. The participants were trained in two different sports to see if this would help their spatial awareness. It was found that the participants did better on the mental rotation test after they had trained in the sports, than they did before the training. This experiment brought to the research that if people could find ways to train their mental rotation skills they could perform better in high context activities with greater ease.
Researchers studied the difference in mental rotation ability between gymnasts, handball, and soccer players with both in-depth and in-plane rotations. Results suggested that athletes were better at performing mental rotation tasks that were more closely related to their sport of expertise.
There is a correlation in mental rotation and motor ability in children, and this connection is especially strong in boys ages 7–8. The study showed that there is considerable overlap between spatial reasoning and athletic ability, even among young children.
A mental rotation test (MRT) was carried out on gymnasts, orienteers, runners, and non athletes. Results showed that non athletes were greatly outperformed by gymnasts and orienteers, but not runners. Gymnasts (egocentric athletes) did not outperform orienteers (allocentric athletes). Egocentric indicates understanding the position of your body as it relates to objects in space, and allocentric indicates understanding the relation of multiple objects in space independently of the self-perspective.
A study investigated the effect of mental rotation on postural stability. Participants performed a MR (mental rotation) task involving either foot stimuli, hand stimuli, or non-body stimuli (a car) and then had to balance on one foot. The results suggested that MR tasks involving foot stimuli were more effective at improving balance than hand or car stimuli, even after 60 minutes.
Contrary to what one might expect, previous studies examining whether artists are superior at mental rotation have been mixed, and a recent study substantiates the null findings. It has been theorized that artists are adept at recognizing, creating, and activating visual stimuli, but not necessarily at manipulating them.
A 2018 study examined the effect of studying various subjects within higher education on mental rotation ability. The researchers found that architecture students performed significantly better than art students, who performed significantly better than both psychology and business majors, with gender and other demographic differences accounted for. These findings make sense intuitively, given that architecture students are highly acquainted with manipulating the orientation of structures in space.
Sex
Following the Vandenberg and Kuse study, subsequent research attempted to assess the presence of gendered differences in mental rotation ability. For the first couple of decades immediately following the research, the topic was addressed in different meta-analyses with inconclusive results. However, Voyer et al. conducted a comprehensive review in 1995, which showed that gender differences were reliable and more pronounced in specific tasks, indicating that sex affects the processes underlying performance in spatial memory tests. Analogous to other types of spatial reasoning tasks, men tended to outperform women by a statistically significant margin among the MR literature.
As mentioned above, many studies have shown that there is a difference between male and female performance in mental rotation tasks. To learn more about this difference, brain activation during a mental rotation task was studied. In 2012, a study was done in which males and females were asked to execute a mental rotation task, and their brain activity was recorded with an fMRI. The researchers found a difference of brain activation: males presented a stronger activity in the area of the brain used in a mental rotation task.
Furthermore, sex-related differences in mental rotation abilities may reflect evolutionary differences. Men assumed the role of hunting and foraging, which necessitates a greater degree of visual-spatial processing than the child-rearing and domestic tasks which women performed. Biologically, males receive higher fetal exposure to androgens than females, and retain these relatively higher levels for life. This difference plays a significant role in human sexual dimorphism, and may be a causal factor in the differences observed regarding mental rotation. Interestingly, women with congenital adrenal hyperplasia (CAH), who are exposed to higher levels of fetal androgen than control women, tend to perform better on the MRT than women with normal amounts of fetal androgen exposure. Additionally, the significant role of hormonal variation between the sexes was supported by a 2004 study, which revealed that testosterone (a principal androgen) level in young men was negatively correlated with the number of errors and response time in the MRT. Therefore, higher levels of testosterone probably contribute to better performance.
Another study from 2015 was focused on women and their abilities in a mental rotation task and an emotion recognition task. In this experiment they induced a feeling or a situation in which women feel more powerful or less powerful. They were able to conclude that women in a situation of power are better in a mental rotation task (but less performant in an emotion recognition task) than other women. Interestingly, the types of cognitive strategies that men and women typically employ may be a contributing factor. The literature has established that men generally prefer holistic strategies, whereas women prefer analytic-verbal strategies and focus on specific parts of the whole puzzle. Women tended to act more conservatively as well, sacrificing time to double-check the incorrect items more often than men. Consequently, women require more time to execute their technique when completing tasks like the MRT. In order to determine the extent of this variable's significance, Hirnstein et al. (2009) created a modified MRT in which the number of matching figures could vary between zero and four, which, compared to the original MRT, favored the strategy most often employed by women. The research found that gender differences declined somewhat, but men still outperformed women.
Along the same lines, a 2021 study found intriguing results in an attempt to discern the mechanisms behind the established gender disparity. The researchers hypothesized that task characteristics, not only anatomical or social differences, could explain men's advantage in mental rotation. In particular, the objects to be rotated were changed from the typical geometric or spherical shapes to male or female stereotyped objects, such as a tractor and a stroller, respectively. The results revealed significant gender differences only when male-stereotyped objects were used as rotational material. When female-stereotyped rotational material was used, men and women performed equally. This finding may explain underlying causes behind the usual disparate outcomes, in that the male ability to do somewhat better on MRT tests probably stems from the evolutionary applicability of spatial reasoning. Objects that aren't relevant to historical male gender roles, and are consequently generally unfamiliar to men, are much more difficult for men to conceptualize spatially than more familiar shapes. Likewise, other recent studies suggest that difference between Mental rotation cognition task are a consequence of procedure and artificiality of the stimuli. A 2017 study leveraged photographs and three-dimensional models, evaluating multiple approaches and stimuli. Results show that changing the stimuli can eliminate any male advantages found from the Vandenberg and Kuse test (1978).
Studying differences between male and female brains can have interesting applications. For example, it could help in the understanding of the autism spectrum disorders. One of the theories concerning autism is the EMB (extreme male brain). This theory considers autistic people to have an "extreme male brain". In a study from 2015, researchers confirmed that there is a difference between male and female in mental rotation task (by studying people without autism): males are more successful. Then they highlighted the fact that autistic people do not have this "male performance" in a mental rotation task. They conclude their study by "autistic people do not have an extreme version of a male cognitive profile as proposed by the EMB theory".
Current and future research directions
Much of the current and future research directions pertain to expanding on what has been established by the literature and investigating underlying causes behind previous results. Future studies will consider additional factors that could influence MR ability, including demographics, various aptitudes, personality, rare/deviant psychological profiles, among others. Many current and future studies are and will be examining the ways that certain brain abnormalities, including many of those caused by traumatic injuries, affect one's ability to perform mental rotation. There is some evidence that what appears to be mental rotation in depth is actually a response to the properties of flat pictures.
There may be relationships between competent bodily movement and the speed with which individuals can perform mental rotation. Researchers found children who trained with mental rotation tasks had improved strategy skills after practicing. People use many different strategies to complete tasks; psychologists will study participants who use specific cognitive skills to compare competency and reaction times. Others will continue to examine the differences in competency of mental rotation based on the objects being rotated. Participants' identification with the object could hinder or help their mental rotation abilities across gender and ages to support the earlier claim that males have faster reaction times. Psychologists will continue to test similarities between mental rotation and physical rotation, examining the difference in reaction times and relevance to environmental implications.
See also
Mental event
Space mapping
Notes
References
Campos-Juanatey, D., Pérez-Fabello, M. J., & Campos, A. (2018). Differences in image rotation between undergraduates from different university degrees. Imagination, Cognition and Personality, 38(2), 173–185.
Cimadevilla, J. M., Piccardi, L., Kranz, G. S. Savic, I. (2020). Spatial Skills. Handbook of Clinical Psychology, 175, 65–79. Retrieved 2022, https://doi.org/10.1016/B978-0-444-64123-6.00006-0.
Drake, J. E., Simmons, S., Rouser, S., Poloes, I., & Winner, E. (2021). Artists excel on image activation but not image manipulation tasks. Empirical Studies of the Arts, 39(1), 3–16.
Halari, R., Sharma, T., Hines, M., Andrew, C., Simmons, A., & Kumari, V. (2006). Comparable fMRI activity with differential behavioural performance on mental rotation and overt verbal fluency tasks in healthy men and women. Experimental Brain Research, 169(1), 1–14.
Hirnstein, M., Bayer, U., & Hausmann, M. (2009). Sex-specific response strategies in mental rotation. Learning and Individual Differences, 19(2), 225-228.
Hooven, C. K., Chabris, C. F., Ellison, P. T., & Kosslyn, S. M. (2004). The relationship of male testosterone to components of mental rotation. Neuropsychologia, 42(6), 782-790.
Moore, D. S., & Johnson, S. P. (2020). The development of mental rotation ability across the first year after birth. In Advances in Child Development and Behavior (Vol. 58, pp. 1–33. doi=10.1016/bs.acdb.2020.01.001). essay, Science Direct.
Plant, Tony M.; Zeleznik, Anthony J.; Forger, Nancy G.; de Vries, Geert J.; Breedlove, S. Marc (2015). "47". Knobil and Neill's Physiology of Reproduction (Fourth Edition). United States: Academic Press. pp. 2109–2155.
Rahe, M., Ruthsatz, V., & Quaiser-Pohl, C. (2021). Influence of the stimulus material on gender differences in a mental-rotation test. Psychological Research, 85(8), 2892-2899.
In Body, Language and Mind, vol. 2. Zlatev, Jordan; Ziemke, Tom; Frank, Roz; Dirven, René (eds.). Berlin: Mouton de Gruyter, forthcoming 2006.
Shepard, R and Cooper, L. "Mental images and their transformations." Cambridge, MA: MIT Press, 1982. .
Sluming, V., Brooks, J., Howard, M., Downes, J. J., & Roberts, N. (2007). Broca's area supports enhanced visuospatial cognition in orchestral musicians. The Journal of Neuroscience, 27(14), 3799–3806.
Vandenberg, S., & Kuse, A. (1978). Mental Rotation, a Group Test of Three-Dimensional Spatial Visualization. Perceptual and Motor Skills, 47, 599-604.
Voyer, D., Voyer, S., & Bryden, M. P. (1995). Magnitude of Sex Differences in Spatial Abilities: A Meta-Analysis and Consideration of Critical Variables. Psychological Bulletin, 117, 250-270.
External links
Mental rotation lesson using PsyToolkit
"Shepard-Metzler resource pack". An open source collection of items for use in the creation of mental rotation tasks.
Cognitive science
Cognitive tests
Visual thinking
Vision
Spatial cognition | Mental rotation | [
"Physics"
] | 4,476 | [
"Spacetime",
"Space",
"Spatial cognition"
] |
4,155,456 | https://en.wikipedia.org/wiki/Effects%20of%20the%20Chernobyl%20disaster | The Chernobyl disaster of 26 April 1986 triggered the release of radioactive contamination into the atmosphere in the form of both particulate and gaseous radioisotopes. , it remains the world's largest known release of radioactivity into the natural environment.
The work of the Scientific Committee on Problems of the Environment (SCOPE) suggests that the Chernobyl disaster cannot be directly compared to atmospheric tests of nuclear weapons by simply saying that it is better or worse. This is partly because the isotopes released at the Chernobyl Nuclear Power Plant tended to be longer-lived than those released by the detonation of atomic bombs.
It is estimated that the Chernobyl disaster caused US$235 billion in economic damages.
Radiation effects on humans
In a 2009 United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) study, the Chernobyl accident had by 2005 caused 61,200 man-Sv of radiation exposure to recovery workers and evacuees, 125,000 man-Sv to the populace of Ukraine, Belarus, and Russia, and a dose to most other European countries amounting to 115,000 man-Sv. The report estimated a further 25% more exposure would be received from residual radioisotopes after 2005. The global collective dose from Chernobyl was earlier estimated by UNSCEAR in 1988 to be "600,000 man Sv, equivalent on average to 21 additional days of world exposure to natural background radiation."
Dose to the general public within 30 km of the plant
The inhalation dose (internal dose) for the public during the time of the accident and their evacuation from the area in what is now the 30 km evacuation zone around the plant has been estimated, based on ground deposition of caesium-137, to be between 3 and 150 mSv.
Thyroid doses for adults around the Chernobyl area were estimated to be between 20 and 1000 mSv, while for one-year-old infants, these estimates were higher, at 20 to 6000 mSv. For those who left the area soon after the accident, the internal dose due to inhalation was 8 to 13 times higher than the external dose due to gamma/beta emitters. For those who remained until later (day 10 or later), the inhalation dose was 50 to 70% higher than the dose due to external exposure. The majority of the dose was due to iodine-131 (about 40%) and tellurium and rubidium isotopes (about 20 to 30% for Rb and Te).
The ingestion doses in this same group of people have also been estimated using the cesium activity per unit of area, isotope ratios, an average day of evacuation, intake rate of milk and green vegetables, and what is known about the transfer of radioactivity via plants and animals to humans. For adults, the dose has been estimated to be between 3 and 180 mSv, while for one-year-old infants, a dose of between 20 and 1300 mSv has been estimated. Again, the majority of the dose was thought to be due to iodine-131.
Childhood exposure
Ukraine, Belarus and parts of Russia were exposed to radiation after the Chernobyl disaster in 1986, but prior to the disaster the number of children affected by thyroid cancer was relatively low globally. Every year about, "0.1–2.2 individuals per million of all aged under 15 years old world wide" were affected by thyroid cancer. Research has shown after the Chernobyl disaster the level of thyroid cancer, particularly in children near the radiation exposure, increased. Although iodine-131 has a short half-life compared to other radioactive isotopes, iodine-131 made its way through the food chain through a milk-to-consumer pathway. 95% of iodine-131 was ingested through milk after the disaster. Communities were unaware of the contamination deposited in soil and the transforming capabilities of radiation into other food sources. Children also absorbed radiation after drinking milk.
The absorption rate discovered in children has also shown to be inversely proportional to age.
There is a high rate of thyroid cancer among children less than 15 years old who were exposed to the radiation after the disaster and an increasing level of dosage as age decreases. This inverse proportion could be explained by the way in which children absorb iodine-131. Children have smaller thyroid glands compared to adults and have a different dosage response after the ingestion of iodine-131. A cohort study conducted in 2013 discovered a similar trend between age and dosage response. The cohort was composed of 12,000 participants, all of which were exposed to the radiation in Belarus and reported to be under the age of 18 at the time of the exposure.
Future study
Studying the populations that were exposed to radiation after the Chernobyl accident has provided data linking exposure to radiation and the future development of cancer.
Cases of pediatric thyroid cancer, likely caused by absorption of Iodine-131 into the thyroid gland, increased in Ukraine and Belarus 3 to 4 years after the accident. Children were most at risk, and cases did not seem to increase in adults. The greatest increase was seen in children who were the youngest at the time of exposure, and most of the pediatric thyroid cases were reported in Gomel, Belarus, where the population was exposed to the highest levels of contamination. The majority of the cases that appeared in the exposed population were papillary thyroid cancer.
Before the accident, the rate of thyroid cancer in children in Belarus was less than 1 per million. By 1995, nine years after the disaster, the number of cases of pediatric thyroid cancer in Gomel Oblast rose to 100 per million per year. Even as adults those who were exposed to the radiation as children may still be at risk of developing thyroid cancer decades after the exposure. It is important to study the at risk population throughout their lives, and observe if different patterns arise in tumors that develop with longer latency.
A group of experts who are part of the Agenda for Research on Chernobyl Health (ARCH) have proposed a series of potential studies that would examine the continued effects from the Chernobyl accident, and provide more information on the full extent of related health consequences. Results from lifelong observation of the exposed population could provide more information on risks as well as future protection against radiation exposure.
Short-term health effects and immediate results
The explosion at the power station and subsequent fires inside the remains of the reactor resulted in the development and dispersal of a radioactive cloud which drifted not only over Russia, Belarus, and Ukraine, but also over most of Europe and as far as Canada.
The initial evidence that a release of radioactive material had occurred came not from Soviet sources, but from Sweden, where on 28 April, two days after the disaster itself, workers at the Forsmark Nuclear Power Plant, approximately 1100 km from the Chernobyl site were found to have radioactive particles on their clothing.
It was Sweden's search for the source of the radioactivity, after they had determined there was no leak at the Swedish plant, that led to the first hint of a critical incident in the Western Soviet Union.
Contamination from the Chernobyl disaster was not evenly spread across the surrounding countryside but scattered irregularly depending on weather conditions. Reports from Soviet and Western scientists indicate that Belarus received about 60% of the contamination that fell on the former Soviet Union. A large area in Russia south of Bryansk was also contaminated, as were parts of northwestern Ukraine.
203 people were hospitalized, of whom 31 died. 28 of them died from acute radiation exposure. Most of these were fire and rescue workers trying to bring the disaster under control, who were not aware of how dangerous the radiation exposure from the smoke was. (For a discussion of the more important isotopes in fallout see fission products). 135,000 people were evacuated from the area, including 50,000 from the nearby town of Pripyat, Ukraine. Health officials have predicted that over the next 70 years there will be a 28% increase in cancer rates in much of the population which was exposed to the 5–12 EBq (depending on source) of radioactive contamination released from the reactor.
Soviet scientists reported that the Chernobyl Unit 4 reactor contained about 180–190 metric tons of uranium dioxide fuel and fission products. Estimates of the amount of this material that escaped range from 5 to 30%. Because of the heat of the fire, and with no containment building to stop it, part of the ejected fuel was vaporized or particularized and rose into the atmosphere, where it spread.
Workers and "liquidators"
The workers involved in the recovery and clean up after the disaster, called "liquidators", received high doses of radiation. In most cases, these workers were not equipped with individual dosimeters to measure the amount of radiation received, so experts could only estimate their doses. Even where dosimeters were used, dosimetric procedures varied — some workers are thought to have been given more accurate estimated doses than others. According to Soviet estimates, between 300,000 and 600,000 people were involved in the cleanup of the 30 km evacuation zone around the reactor, but many of them entered the zone two years after the disaster.
Estimates of the number of "liquidators" vary; the World Health Organization, for example, puts the figure at about 600,000; Russia lists as liquidators some people who did not work in contaminated areas. In the first year after the disaster, the number of cleanup workers in the zone was estimated to be 2,000. These workers received an estimated average dose of 165 millisieverts (16.5 REM).
Studies of the increase in DNA mutations in the children of liquidators vary in their conclusions. One study identified a sevenfold increase in DNA mutations in children of liquidators conceived after the accident, when compared to their siblings that were conceived before, but another claimed to find no increase in developmental anomalies or a statistically significant increase in the frequencies of germline mutations in their progeny.
Evacuation
Soviet Military authorities started evacuating people from the area around Chernobyl on the second day after the disaster (after about 36 hours). By May 1986, about a month later, all those living within a radius of the plant (about 116,000 people) had been relocated. This area is often referred to as the zone of alienation. However, radiation affected the environment over a much wider scale than this 30 km radius encloses.
According to reports from Soviet scientists, 28,000 square kilometers (km2, or 10,800 square miles, mi2) were contaminated by caesium-137 to levels greater than 185 kBq per square meter. 830,000 people lived in this area. About 10,500 km2 (4,000 mi2) were contaminated by caesium-137 to levels greater than 555 kBq/m2. Of this total, roughly 7,000 km2 (2,700 mi2) lie in Belarus, 2,000 km2 (800 mi2) in the Russian Federation and 1,500 km2 (580 mi2) in Ukraine. About 250,000 people lived in this area. These reported data were corroborated by the International Chernobyl Project.
Civilians
Some children in the contaminated areas were exposed to high thyroid doses of up to 50 gray (Gy), mostly due to an intake of radioactive iodine-131 (a relatively short-lived isotope with a half-life of 8 days) from contaminated milk produced locally. Several studies have found that the incidence of thyroid cancer among children in Belarus, Ukraine, and Russia has risen since the Chernobyl disaster. The International Atomic Energy Agency (IAEA) notes "1800 documented cases of thyroid cancer in children who were between 0 and 14 years of age when the disaster occurred, which is far higher than normal", although this source fails to note the expected rate. The childhood thyroid cancers that have appeared are of an aggressive type but, if detected early, can be treated. Treatment entails surgery followed by iodine-131 therapy for any metastases. To date, such treatment appears to have been successful in the vast majority of cases.
Late in 1995, the World Health Organization (WHO) linked nearly 700 cases of thyroid cancer among children and adolescents to the Chernobyl disaster, and among these, some 10 deaths are attributed to radiation. However, the rapid increase in thyroid cancers detected suggests some of this increase may be an artifact of the screening process. Typical latency time of radiation-induced thyroid cancer is about 10 years, but the increase in childhood thyroid cancers in some regions was observed as early as 1987.
Plant and animal health
A swath of pine forest killed by acute radiation was named the Red Forest. The dead pines were bulldozed and buried. Livestock were removed during the human evacuations. Elsewhere in Europe, levels of radioactivity were examined in various natural food stocks. In both Sweden and Finland, fish in deep freshwater lakes were banned for resale and landowners were advised not to consume certain types.
Animals living in contaminated areas in and around Chernobyl developed side effects caused by the initial levels of radiation. When the disaster first occurred, the health and reproductive ability of animals and plants were negatively affected for the first six months.
Invertebrate populations (including bumblebees, butterflies, grasshoppers, dragonflies, and spiders) decreased. As of 2009, most radioactivity around Chernobyl was located in the top layer of soil, where many invertebrates live or lay their eggs.
Radionuclides migrate through either soil diffusion or transportation within the soil solution. The effects of ionizing radiation on plants and trees in particular depends on factors that include climatic conditions, the mechanism of radiation deposition, and the soil type. Altitude, soil disturbance, and biological activity are also factors that influence the amount of radioisotopes in soil. Radiated vegetation affects organisms further up the food chain. Upper-level trophic organisms may have received less contamination, due to their ability to be more mobile and feed from multiple areas.
The amount of radioactive nuclides found to have been deposited into surrounding lakes has increased the normal baseline radioactive amounts by 100 percent. Most of the radionuclides in surrounding water areas were found in the sediments at the bottom of the lakes. There has been a high incidence of chromosomal changes in plant and animal aquatic organisms, and this generally has correlated with the contamination and resulting genetic instability. Most of the lakes and rivers surrounding the Chernobyl exclusion zone are still contaminated with radionuclides (and will be for many years to come) as the natural decontamination processes of nuclides with longer half-lives can take years.
One of the mechanisms by which radionuclides were passed to humans was through the ingestion of milk from contaminated cows. Most of the rough grazing that the cows took part in contained plant species such as coarse grasses, sedges, rushes, and plants such as heather (also known as Calluna vulgaris). These plant species grow in soils that are high in organic matter, low in pH, and are often well hydrated, thus making the storage and intake of these radionuclides more feasible and efficient.
Shortly after the Chernobyl accident, high levels of radionuclides were found in the milk and were a direct result of contaminated feeding. Within two months of banning most of the milk that was being produced in the affected areas, officials had phased out the majority of the contaminated feed that was available to the cows and much of the contamination was isolated. In humans, ingestion of milk containing abnormally high levels of iodine radionuclides was the precursor for thyroid disease, especially in children and in the immunocompromised.
Due to the bioaccumulation of caesium-137, some mushrooms as well as wild animals which eat them, e.g. wild boars hunted in Germany and deer in Austria, may have levels which are not considered safe for human consumption. Mandatory radioactivity testing of sheep in parts of the UK that graze on lands with contaminated peat was lifted in 2012.
While effects on the immediate physical health of individual animals within the affected area tended to be negative, population levels of animals in the affected areas began to increase following the evacuation of humans.
In the 1996 BBC Horizon documentary 'Inside Chernobyl's Sarcophagus', birds are seen flying in and out of large holes in the structure itself. Other casual observations also reported an increase in biodiversity due to the reduced human presence.
Human pregnancy
Despite spurious studies from Germany and Turkey, the only robust evidence of negative pregnancy outcomes that transpired after the accident was the increase in elective abortions, these "indirect effects", in Greece, Denmark, Italy etc., have been attributed to "anxieties created" by the media.
Researchers at the time knew that high doses of radiation increase the rate of physiological pregnancy and fetal abnormalities, but select researchers who were familiar with both the prior human exposure data and animal testing knew that, unlike the dominant linear no-threshold model of radiation and cancer rate increases, the "Malformation of organs appears to be a deterministic effect (an effect not caused by chance) with a threshold dose" below which no rate increase is observed. Frank Castronovo of the Harvard Medical School discussed this teratology (birth defects) issue in 1999, publishing a review of dose reconstructions and the available pregnancy data following the Chernobyl accident, which included data from Kyiv's two largest obstetrics hospitals.
Castronovo concludes that "the lay press with newspaper reporters playing up anecdotal stories of children with birth defects" and dubious studies flawed by "selection bias", are the two primary factors causing the persistent belief that Chernobyl increased the background rate of birth defects. However, the data does not support this perception because, since no pregnant individuals took part in the most radioactive liquidator operations, no pregnant individuals were exposed to the threshold dose.
Despite Castronovo's statements, Karl Sperling, Heidemarie Neitzel and Hagen Scherb reported that the prevalence of Down syndrome (trisomy 21) in West Berlin, Germany, peaked 9 months following the main fallout [11, 12]. From 1980 to 1986 the birth prevalence of Down syndrome was quite stable (i.e., 1.35–1.59 per 1,000 live births [27–31 cases]). In 1987, 46 cases were diagnosed (prevalence = 2.11 per 1,000 live births) and most of the increase resulted from a cluster of 12 children born in January 1987. The prevalence of Down Syndrome in 1988 was 1.77, and in 1989, it reached pre-Chernobyl values. The authors noted that the cluster of children would have been conceived when radioactive clouds containing radionucleotides with short half-lives, like iodine, would have been covering the region and also that the isolated geographical position of West Berlin prior to reunification, the free genetic counseling, and complete coverage of the population through one central cytogenetic laboratory supported completeness of case ascertainment; in addition, constant culture preparation and analysis protocols ensure a high quality of data.
Long-term health effects
Science and politics: the problem of epidemiological studies
The issue of long-term effects of the Chernobyl disaster on civilians is controversial. Over 300,000 people were resettled because of the disaster. Millions lived and continue to live in the contaminated area. On the other hand, most of those affected received relatively low doses of radiation; there is little evidence of increased mortality, cancers or birth defects among them; and when such evidence is present, existence of a causal link to radioactive contamination is uncertain.
An increased incidence of thyroid cancer among children in areas of Belarus, Ukraine and Russia affected by the Chernobyl disaster has been established as a result of screening programs and, in the case of Belarus, an established cancer registry. The findings of most epidemiological studies must be considered interim, say experts, as analysis of the health effects of the disaster is an ongoing process. Multilevel modelling indicates that long-term psychological distress among Belarusians affected by the Chernobyl disaster is better predicted by stress-moderating psychosocial factors present in one's daily life than by level of residential radiation contamination.
Epidemiological studies have been hampered in Ukraine, Russian Federation and Belarus by a lack of funds, an infrastructure with little experience in chronic disease epidemiology, poor communication facilities, public health issues and a political culture of secrecy and deception. Emphasis has been placed on screening rather than on well-designed epidemiological studies. International efforts to organize such studies have been slowed in particular by the lack of a suitable scientific infrastructure.
The political nature of nuclear energy has affected scientific studies. In Belarus, Yury Bandazhevsky, a scientist who questioned the official estimates of Chernobyl's consequences and the relevancy of the official maximum limit of 1,000 Bq/kg, was imprisoned from 2001 to 2005. Bandazhevsky and some human rights groups allege his imprisonment was a reprisal for his publication of reports critical of the official research being conducted into the Chernobyl incident.
The activities undertaken by Belarus and Ukraine in response to the disaster — remediation of the environment, evacuation and resettlement, development of uncontaminated food sources and food distribution channels, and public health measures — have overburdened the governments of those countries. International agencies and foreign governments have provided logistic and humanitarian assistance. In addition, the work of the European Commission and World Health Organization in strengthening the epidemiological research infrastructure in Russia, Ukraine and Belarus is laying the basis for advances in these countries' general ability to conduct epidemiological studies.
Caesium radioisotopes
The main health concern initially involved radioactive iodine, with a half-life of eight days. Today, there is concern about contamination of the soil with strontium-90 and caesium-137, which have half-lives of about 30 years. The highest levels of caesium-137 are found in the surface layers of the soil where they are absorbed by plants, insects and mushrooms, which then enter the local food supply). Some scientists fear that radioactivity will affect the local population for the next several generations. Note that caesium is not mobile in most soils because it binds to the clay minerals.
Tests () showed that caesium-137 levels in trees were continuing to rise. It is unknown if this is still the case. There is evidence that contamination is migrating into underground aquifers and closed bodies of water such as lakes and ponds (2001, Germenchuk). The main source of elimination is predicted to be natural decay of caesium-137 to stable barium-137, since runoff by rain and groundwater has been demonstrated to be negligible. In 2021, Italian researcher Venturi reported the first correlations between caesium-137, pancreas and pancreatic cancer with the role of non-radioactive caesium in biology and of caesium-137 in chronic pancreatitis and in diabetes of pancreatic origin (Type 3c).
Thyroid cancer
An increased incidence of thyroid cancer was observed for about 4 years after the accident and slowed in 2005. The increase in incidence of thyroid cancer happened amongst individuals who were adolescents and young children living during the time of the accident, and residing in the most contaminated areas. High levels of radioactive iodine were released in the environment from the Chernobyl reactor after the accident, and accumulated in pastures which were eaten by cows. The milk was later consumed by children who already had an iodine deficient diet, therefore causing more of the radioactive iodine to be accumulated. Radioactive iodine has a short half-life of 8.02 days; if the contaminated milk had been avoided or stopped, it is likely that most of the rise in radiation-induced thyroid cancer wouldn't have happened.
Within the highly contaminated areas – Belarus, the Russian Federation and Ukraine, there were around 5000 cases of thyroid cancer that have been diagnosed since the accident. These cases were found in individuals who were aged 18 and younger during the time of the accident.
Supported by the Russian Federation and Ukraine, The European Commission, the National Cancer Institute of the US, and the Sasakawa Memorial Health Foundation, The Chernobyl Tissue Bank (CTB) was created in 1998, 6 years after published research showed a rise in childhood thyroid cancer. The project is the first international co-operation that collects biological samples from patients exposed to radioiodine during childhood. It started collecting a variety of biological samples from patients on 1 October 1998 and since July 2001 has been a source for ethically available tissue samples - specifically extracted nucleic acids and tissue sections - for 21 research projects in Japan, Europe and the USA. The CTB serves as a model for tissue banking for cancer research in the molecular age.
Contamination in the food supply
Twenty-five years after the incident, restriction orders had remained in place in the production, transportation and consumption of food contaminated by Chernobyl fallout. In the UK, only in 2012 was the mandatory radioactivity testing of sheep in contaminated parts of the UK that graze on lands was lifted. They covered 369 farms on 750 km2 and 200,000 sheep. In parts of Sweden and Finland, restrictions are in place on stock animals, including reindeer, in natural and near-natural environments.
"In certain regions of Germany, Austria, Italy, Sweden, Finland, Lithuania and Poland, wild game (including boar and deer), wild mushrooms, berries and carnivorous fish from lakes reach levels of several thousand Bq per kg of caesium-137", while "in Germany, caesium-137 levels in wild boar muscle reached 40,000 Bq/kg. The average level is 6,800 Bq/kg, more than ten times the EU limit of 600 Bq/kg", according to the TORCH 2006 report. The European Commission has stated that "The restrictions on certain foodstuffs from certain Member States must therefore continue to be maintained for years to come".
As of 2009, sheep farmed in some areas of the UK are still subject to inspection which may lead to them being prohibited from entering the human food chain because of contamination arising from the accident:
369 farms and 190,000 sheep are still affected, a reduction of 95% since 1986, when 9,700 farms and 4,225,000 sheep were under restriction across the United Kingdom.
Restrictions were finally lifted in 2012.
In Norway, the Sami people were affected by contaminated food (the reindeer had been contaminated by eating lichen, which accumulates some types of radioactivity emitters).
Data from a long-term monitoring program from 1998 to 2015 (The Korma Report II) shows a significant decrease in internal radiation exposure of the inhabitants of small villages in Belarus 80 km north of Gomel. Resettlement may even be possible in parts of the prohibited areas provided that people comply with appropriate dietary rules.
A 2021 study based on whole-genome sequencing of children of parents employed as liquidators in Chernobyl indicated no trans-generational genetic effects of exposure of parents to ionizing radiation.
Long-term effects on plant and animal health
Over time there have been many reports documenting and discussing the prevalence and health of plants and animals within the Chernobyl Exclusion Zone.
The absence of humans from the Exclusion Zone has made it attractive to wildlife, which now inhabit the area in larger numbers. This has led some scientists and reporters to describe the area as a natural wildlife sanctuary, and to enthuse about the ability of wildlife in the area to recover.
However, the mere presence of wildlife does not present a complete picture: the ongoing health of individuals and the health of the ecosystems in which they live are also of concern. These issues are difficult to study because many factors interact. Radiologic tolerance and the effects of fallout contamination vary with different species. In addition to ongoing low-dose radiation and quality of local habitat, it has been suggested that fauna in the area may inherit a higher likelihood for genetic damage from ancestors affected by the initial high doses of radiation.
Radiation levels
According to reports from Soviet scientists at the First International Conference on the Biological and Radiological Aspects of the Chernobyl Accident (September 1990), fallout levels in the 10 km zone around the plant were as high as 4.81 GBq/m2. The so-called "Red Forest" (or "Rusted Forest") is the swath of pine trees, located immediately behind the reactor complex within the 10 km zone, which were killed off by heavy radioactive fallout. The forest is so named because in the days following the disaster the trees appeared to have a deep red hue as they died because of extremely heavy radioactive fallout. In the post-disaster cleanup operations, a majority of the 10 km2 forest was bulldozed and buried. The site of the Red Forest remains one of the most contaminated areas in the world.
Population density
In the decades following the evacuation of its human population due to the disaster, the 30 km (19-mile) "exclusion zone" surrounding the Chernobyl disaster has become a de facto wildlife sanctuary. Animals have reclaimed the land including species such as the Przewalski's horse, Eurasian lynx, wild boar, grey wolf, elk, red deer, moose, brown bear, turtle, voles, mice, shrews, European badger, Eurasian beaver, raccoon dog, red fox, roe deer, European bison, black stork, golden eagle, white-tailed eagle and eagle owl.
A 2015 study found similar numbers of mammals in the zone compared to nearby similar nature reserves.
Long-term empirical data showed no evidence of a negative influence of radiation on mammal abundance.
In 2007, the Ukrainian government designated the Exclusion Zone as a wildlife sanctuary, and at 488.7 km2 it is one of the largest wildlife sanctuaries in Europe.
In 2016, the Ukrainian government designated its part of the area as a radiological and environmental biosphere reserve as part of a six-year project funded by the Global Environment Facility (GEF).
Health impacts
According to a 2005 U.N. report, wildlife has returned despite radiation levels that are presently 10 to 100 times higher than normal background radiation. Radiation levels were significantly higher soon after the accident, but have fallen since then because of radioactive decay.
While there are demonstrably populations of a wide variety of species within the zone, there are still concerns about the ongoing health of individuals within those populations and their ability to reproduce.
Møller and Mousseau have published the results of the largest census of animal life in the Chernobyl Exclusion Zone. It said, contrary to the Chernobyl Forum's 2005 report, that the biodiversity of insects, birds and mammals in the exclusion zone is declining.
Møller et al. (2005) suggested that the reproductive success and annual survival rates of barn swallows are lower in the exclusion zone; 28% of barn swallows inhabiting Chernobyl return each year, while at a control area at Kanev, 250 km to the southeast, the return rate is around 40%.
Barn swallows (Hirundo rustica) sampled between 1991 and 2006 in the Chernobyl exclusion zone are also claimed to display an increased rate of physical abnormalities compared to swallows from uncontaminated areas. Møller et al. (2007) reported an elevated frequency of eleven categories of physical abnormalities including
such as partially albinistic plumage, deformed toes, tumors, deformed tail feathers, deformed beaks, and deformed air sacks. Abnormal barn swallows mated with lower frequency, and had a reduced viability in the wild and a decrease in fitness. Effects were attributed to radiation exposure and elevated teratogenic effects of radioactive isotopes in the environment.
Smith et al. (2008) have disputed Møller's findings and instead proposed that a lack of human influence in the exclusion zone locally reduced the swallows' insect prey and that radiation levels across the vast majority of the exclusion zone are now too low to have an observable negative effect. The criticisms were responded to in the same issue by Møller et al. (2008). It is possible that barn swallows are vulnerable to elevated levels of ionizing radiation because they are migratory; they arrive in the exclusion area exhausted and with depleted reserves of radio-protective antioxidants after their journey.
Oxidative stress and low levels of antioxidants can affect the development of the nervous system, including reduced brain size and impaired cognitive abilities. It has been reported that birds living in contaminated areas have smaller brains, which has shown to be a deficit to viability in the wild.
Possible adaptation
It has been suggested that some plants and animals are able to adapt to the increased radiation levels present in and around Chernobyl.
Further research is needed to assess the long-term health effects of elevated ionizing radiation from Chernobyl on flora and fauna.
Several research groups have suggested that plants in the area have adapted to cope with the high radiation levels, for example by increasing the activity of DNA cellular repair machinery and by hypermethylation.
Arabidopsis, a plant native to Chernobyl, was able to resist high concentrations of ionizing radiation and resist forming mutations. This species of plant has been able to develop mechanisms to tolerate chronic radiation that would otherwise be harmful or lethal to other species.
Various birds in the area may have adapted to lower levels of radiation by producing more antioxidants, such as glutathione, to help mitigate oxidative stress.
Using robots, researchers have retrieved samples of highly melanized black fungus from the walls of the reactor core itself. It has been shown that certain species of fungus, such as Cryptococcus neoformans and Cladosporium, can actually thrive in a radioactive environment, growing better than non-melanized variants, implying that they use melanin to harness the energy of ionizing radiation from the reactor.
Chernobyl Forum report and criticisms
In September 2005, a comprehensive report was published by the Chernobyl Forum, composed of agencies that included the International Atomic Energy Agency (IAEA), the World Health Organization (WHO), United Nations bodies and the Governments of Belarus, the Russian Federation and Ukraine. This report titled: "Chernobyl's legacy: Health, Environmental and Socio-Economic Impacts", authored by about 100 recognized experts, put the total predicted number of deaths due to the disaster around 4,000, of which 2,200 deaths are expected to be in the ranks of 200,000 liquidators. This predicted death toll includes the 47 workers who died of acute radiation syndrome as a direct result of radiation from the disaster, nine children who died from thyroid cancer and an estimated 4000 people who could die from cancer as a result of exposure to radiation. This number was updated to 9,000 excess cancer deaths.
An IAEA press officer admitted that the 4,000 figure was given prominence in the report "...to counter the much higher estimates which had previously been seen. ... "It was a bold action to put out a new figure that was much less than conventional wisdom.""
The report stated that, apart from a 30 kilometer area around the site and a few restricted lakes and forests, radiation levels had returned to acceptable levels.
The methodology of the Chernobyl Forum report, supported by Elisabeth Cardis of the International Agency for Research on Cancer, has been disputed by some advocacy organizations opposed to nuclear energy, such as Greenpeace and the International Physicians for Prevention of Nuclear Warfare (IPPNW), as well as some individuals such as Michel Fernex, retired medical doctor from the WHO, and campaigner Dr. Christopher Busby (Green Audit, LLRC). They criticized the restriction of the Forum's study to Belarus, Ukraine and Russia. Furthermore, it only studied the case of 200,000 people involved in the cleanup, and the 400,000 most directly affected by the released radioactivity. German Green Party Member of the European Parliament Rebecca Harms, commissioned a report on Chernobyl in 2006 (TORCH, The Other Report on Chernobyl). The 2006 TORCH report claimed that:
While the IAEA/WHO and UNSCEAR considered areas with exposure greater than 40,000 Bq/m2, the TORCH report also included areas contaminated with more than 4,000 Bq/m2 of Cs-137.
The TORCH 2006 report "estimated that more than half the iodine-131 from Chernobyl [which increases the risk of thyroid cancer] was deposited outside the former Soviet Union. Possible increases in thyroid cancer have been reported in the Czech Republic and the UK, but more research is needed to evaluate thyroid cancer incidences in Western Europe". It predicted about 30,000 to 60,000 excess cancer deaths, 7 to 15 times greater than the figure of 4,000 in the IAEA press release; warned that predictions of excess cancer deaths strongly depend on the risk factor used; and predicted excess cases of thyroid cancer range between 18,000 and 66,000 in Belarus alone depending on the risk projection model. Elevated incidence in thyroid cancer is still seen among Ukrainians who were exposed to radioactivity due to the Chernobyl accident during their childhood, but who were diagnosed with the malignancy as adults.
Another study claims possible heightened mortality in Sweden.
Greenpeace quoted a 1998 WHO study, which counted 212 deaths from only 72,000 liquidators. The environmental NGO estimated a total death toll of 93,000 but cite in their report that "The most recently published figures indicate that in Belarus, Russia and Ukraine alone the disaster could have resulted in an estimated 200,000 additional deaths in the period between 1990 and 2004." In its report, Greenpeace suggested there will be 270,000 cases of cancer alone attributable to Chernobyl fallout, and that 93,000 of these will probably be fatal compared with the IAEA 2005 report which claimed that "99% of thyroid cancers wouldn't be lethal".
In 2006, the Union Chernobyl, the main organization of liquidators, stated that 10% of the 600,000 liquidators were dead, and 165,000 disabled.
An April 2006 report by the International Physicians for Prevention of Nuclear Warfare (IPPNW), entitled "Health Effects of Chernobyl - 20 years after the reactor catastrophe", stated that more than 10,000 people are today affected by thyroid cancer and 50,000 cases are expected. In Europe, the IPPNW claims that 10,000 deformities have been observed in newborns because of Chernobyl's radioactive discharge, with 5,000 deaths among newborn children. They also state that several hundreds of thousands of the people who worked on the site after the disaster are now sick because of radiation, and tens of thousands are dead.
Revisiting the issue for the 25th anniversary of the Chernobyl disaster, the Union of Concerned Scientists described the Forum's estimate of four thousand as pertaining only to "a much smaller subgroup of people who experienced the greatest exposure to released radiation". Their estimates for the broader population are 50,000 excess cancer cases resulting in 25,000 excess cancer deaths.
Human health effects Studies
The majority of premature deaths caused by Chernobyl are expected to be the result of cancers and other diseases induced by radiation in the decades after the event. This will be the result of a large population exposed to relatively low doses of radiation increasing the risk of cancer across that population. Some studies have considered the entire population of Europe. Interpretations of the current health state of exposed populations vary. Therefore, estimates of the ultimate human impact of the disaster have relied on numerical models of the effects of radiation on health. The effects of low-level radiation on human health are not well understood, and so the models used, notably the linear no threshold model, are open to question.
Given these factors, studies of Chernobyl's health effects have come up with different conclusions and are sometimes the subject of scientific and political controversy. The following section presents some of the major studies on this topic.
Official studies
Chernobyl Forum report
In September 2005, a draft summary report by the Chernobyl Forum, comprising a number of UN agencies including the International Atomic Energy Agency (IAEA), the World Health Organization (WHO), the United Nations Development Programme (UNDP), other UN bodies and the Governments of Belarus, the Russian Federation and Ukraine, set the number of deaths due to the accident at about 50 (47 workers who died of acute radiation syndrome and 9 children who died from thyroid cancer), and added that a "total of up to 4000 people could eventually die of radiation exposure from the Chernobyl nuclear power plant accident" (excess cancer deaths which might eventually happen among the 600,000 with the highest levels of exposure).
The full version of the WHO health effects report adopted by the UN, published in April 2006, included an added 5000 eventually possible fatalities from contaminated areas in Belarus, Russia and Ukraine and predicted that, in total, an upper limit of 9000 might eventually die from cancer among the 6.9 million most-exposed Soviet citizens. Some newspapers and antinuclear organizations claimed the paper was minimizing the consequences of the accident.
2008 UNSCEAR report
The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) produced a detailed report on the effects of Chernobyl for the General Assembly of the UN in 2011. This report concluded that 134 staff and emergency workers developed acute radiation syndrome and of those 28 died of radiation exposure within three months. Many of the survivors developed skin conditions and radiation induced cataracts, and 19 had since died, but from conditions not necessarily associated with radiation exposure. Of the several hundred thousand liquidators, apart from some emerging indications of increased leukaemia, there was no other evidence of health effects.
In the general public in the affected areas, the only effect with 'persuasive evidence' was the fraction of the 6,000 cases of thyroid cancer in adolescents of whom by 2005 15 cases had proved fatal. There was no evidence of increased rates of solid cancers or leukaemia among the general population. However, there was psychological worry about the effects of radiation.
The total deaths reliably attributable by UNSCEAR to the radiation produced by the accident therefore was 62.
The report concluded that 'the vast majority of the population need not live in fear of serious health consequences from the Chernobyl accident'.
Unofficial studies
TORCH report
In 2006, German Green Party Member of the European Parliament Rebecca Harms commissioned UK scientists Ian Fairlie and David Sumner for an alternate report (TORCH, The Other Report on CHernobyl) in response to the UN report. The report included areas not covered by the Chernobyl forum report, and also lower radiation doses. It predicted about 30,000 to 60,000 excess cancer deaths and warned that predictions of excess cancer deaths strongly depend on the risk factor used, and urged more research stating that large uncertainties made it difficult to properly assess the full scale of the disaster.
In 2016, an updated TORCH report was written by Ian Fairlie with support of Friends of the Earth Austria.
Greenpeace
Greenpeace claimed contradictions in the Chernobyl Forum reports, quoting a 1998 WHO study referenced in the 2005 report, which projected 212 dead from 72,000 liquidators. In its report, Greenpeace suggested there will be 270,000 cases of cancer attributable to Chernobyl fallout, and that 93,000 of these will probably be fatal, but state in their report that "The most recently published figures indicate that in Belarus, Russia and Ukraine alone the accident could have resulted in an estimated 200,000 additional deaths in the period between 1990 and 2004."
Blake Lee-Harwood, campaigns director at Greenpeace, believes that cancer was likely to be the cause of less than half of the final fatalities and that "intestinal problems, heart and circulation problems, respiratory problems, endocrine problems, and particularly effects on the immune system," will also cause fatalities. However, concern has been expressed about the methods used in compiling the Greenpeace report. It is not peer reviewed nor does it rely on peer review science as the Chernobyl Forum report did.
April 2006 IPPNW report
According to an April 2006 report by the German affiliate of the International Physicians for Prevention of Nuclear Warfare (IPPNW), entitled "Health Effects of Chernobyl", more than 10,000 people are today affected by thyroid cancer and 50,000 cases are expected. The report projected tens of thousands dead among the liquidators. In Europe, it alleges that 10,000 deformities have been observed in newborns because of Chernobyl's radioactive discharge, with 5000 deaths among newborn children. They also claimed that several hundreds of thousands of the people who worked on the site after the accident are now sick because of radiation, and tens of thousands are dead.
Yablokov/Nesterenko publication
Chernobyl: Consequences of the Catastrophe for People and the Environment is an English translation of the 2007 Russian publication Chernobyl by Alexey Yablokov, Vassily Nesterenko and Alexey Nesterenko. It was published online in 2009 by the New York Academy of Sciences in their Annals of the New York Academy of Sciences. The New York Academy of Sciences included a disclaimer to inform readers it did not commission, endorse or peer review the work.
"In no sense did Annals of the New York Academy of Sciences or the New York Academy of Sciences commission this work; nor by its publication does the Academy validate the claims made in the original Slavic language publications cited in the translated papers. Importantly, the translated volume has not been formally peer‐reviewed by the New York Academy of Sciences or by anyone else."
The report presents an analysis of scientific literature and concludes that medical records between 1986, the year of the accident, and 2004 reflect 985,000 deaths as a result of the radioactivity released. The authors suggest that most of the deaths were in Russia, Belarus and Ukraine, but others were spread through the many other countries the radiation from Chernobyl struck. The literature analysis draws on over 1,000 published titles and over 5,000 internet and printed publications discussing the consequences of the Chernobyl disaster. The authors contend that those publications and papers were written by Eastern European authorities and have been downplayed or ignored by the IAEA and UNSCEAR. Author Alexy V. Yablokov was also one of the general editors on the Greenpeace commissioned report also criticizing the Chernobyl Forum findings published one year prior to the Russian-language version of this report.
A critical review by Dr. Monty Charles in the journal Radiation Protection Dosimetry states that Consequences is a direct extension of the 2005 Greenpeace report, updated with data of unknown quality. The New York Academy of Sciences also published a severely critical review by M. I. Balonov from the Institute of Radiation Hygiene (St. Petersburg, Russia) which stated that "The value of [Consequences] is not zero, but negative, as its bias is obvious only to specialists, while inexperienced readers may well be put into deep error." Several other critical responses have also been published.
In 2016, 187 local Ukrainians had returned and were living permanently in the zone.
Higher than statistically normal appearances of defects
The American Academy of Pediatrics published a study state that the overall rate of neural tube defects in the Rivne region of Ukraine is one of the highest in Europe (22 per 10,000 live births). The rate in Polissia (Ukraine) is 27.0 per 10,000. The study suggested that rates of microcephaly and microphthalmia may also be higher than normal.
Other studies and claims
The claim is made, by Collette Thomas, writing on 24 April 2006, that someone in the Ukrainian Health Ministry claimed in 2006 that more than 2.4 million Ukrainians, including 428,000 children, have health problems related to the catastrophe. The claim appears to have been invented by her through interpretation of a webpage of the Kyiv Regional Administration. Psychological after-effects, as the 2006 UN report pointed out, have also had adverse effects on internally displaced persons.
In a recently published study scientists from Forschungszentrum Jülich, Germany, published the "Korma-Report" with data of radiological long-term measurements that were performed between 1998 and 2007 in a region in Belarus that was affected by the Chernobyl accident. The internal radiation exposure of the inhabitants in a village in Korma County/Belarus caused by the existing radioactive contamination has experienced a decrease from a very high level. The external exposure, however, reveals a different picture. Although an overall decrease was observed, the organic constituents of the soil show an increase in contamination, not observed in soils from cultivated land or gardens. According to the Korma Report the internal dose will decrease to less than 0.2 mSv/a in 2011 and to below 0.1 mSv/a in 2020. Despite this, the cumulative dose will remain higher than "normal" due to external exposure. Resettlement may even be possible in former prohibited areas provided that people comply with appropriate dietary rules.
Study of heightened mortality in Sweden. But it must be pointed out that this study, and in particular the conclusions drawn has been very criticized.
One study reports increased levels of birth defects in Germany and Finland in the wake of the accident.
A change in the human sex ratio at birth from 1987 onward in several European countries has been linked to Chernobyl fallout.
In the Czech Republic, thyroid cancer has increased significantly after Chernobyl.
The Abstract of the April 2006 International Agency for Research on Cancer report Estimates of the cancer burden in Europe from radioactive fallout from the Chernobyl accident stated "It is unlikely that the cancer burden from the largest radiological accident to date could be detected by monitoring national cancer statistics. Indeed, results of analyses of time trends in cancer incidence and mortality in Europe do not, at present, indicate any increase in cancer rates – other than of thyroid cancer in the most contaminated regions – that can be clearly attributed to radiation from the Chernobyl accident." They estimate, based on the linear no threshold model of cancer effects, that 16,000 excess cancer deaths could be expected from the effects of the Chernobyl accident up to 2065. Their estimates have very wide 95% confidence intervals from 6,700 deaths to 38,000.
The application of the linear no threshold model to predict deaths from low levels of exposure to radiation was disputed in a BBC (British Broadcasting Corporation) Horizon documentary, broadcast on 13 July 2006. It offered statistical evidence to suggest that there is an exposure threshold of about 200 millisieverts, below which there is no increase in radiation-induced disease. Indeed, it went further, reporting research from Professor Ron Chesser of Texas Tech University, which suggests that low exposures to radiation can have a protective effect. The program interviewed scientists who believe that the increase in thyroid cancer in the immediate area of the explosion had been over-recorded, and predicted that the estimates for widespread deaths in the long term would be proved wrong. It noted the view of the World Health Organization scientist Dr Mike Rapacholi that, while most cancers can take decades to manifest, leukemia manifests within a decade or so: none of the previously expected peak of leukemia deaths has been found, and none is now expected. Identifying the need to balance the "fear response" in the public's reaction to radiation, the program quoted Dr Peter Boyle, director of the IARC: "Tobacco smoking will cause several thousand times more cancers in the [European] population."
An article in Der Spiegel in April 2016 also cast doubt on the use of the linear no threshold model to predict cancer rates from Chernobyl. The article claimed that the threshold for radiation damage was over 100 millisieverts and reported initial results of large-scale trials in Germany by the GSI Helmholtz Centre for Heavy Ion Research and three other German institutes in 2016 showing beneficial results of decreasing inflammation and strengthening bones from lower radiation doses.
Professor Wade Allison of Oxford University (a lecturer in medical physics and particle physics) gave a talk on ionising radiation 24 November 2006 in which he gave an approximate figure of 81 cancer deaths from Chernobyl (excluding 28 cases from acute radiation exposure and the thyroid cancer deaths which he regards as "avoidable"). In a closely reasoned argument using statistics from therapeutic radiation, exposure to elevated natural radiation (the presence of radon gas in homes) and the diseases of Hiroshima and Nagasaki survivors he demonstrated that the linear no-threshold model should not be applied to low-level exposure in humans, as it ignores the well-known natural repair mechanisms of the body.
A photographic essay by photojournalist Paul Fusco documents problems in the children in the Chernobyl region. No evidence is offered to suggest these problems are in any way related to the nuclear incident
The work of photojournalist Michael Forster Rothbart documents the human impact of the disaster on residents who stayed in the affected area.
Bandashevsky measured levels of radioisotopes in children who had died in the Minsk area that had received Chernobyl fallout, and the cardiac findings were the same as those seen in test animals that had been administered Cs-137.
French legal action
Since March 2001, 400 lawsuits have been filed in France against "X" (the French equivalent of John Doe, an unknown person or company) by the French Association of Thyroid-affected People, including 200 in April 2006. These persons are affected by thyroid cancer or goitres, and have filed lawsuits alleging that the French government, at the time led by Prime Minister Jacques Chirac, had not adequately informed the population of the risks linked to the Chernobyl radioactive fallout. The complaint contrasts the health protection measures put in place in nearby countries, warning against consumption of green vegetables or milk by children and pregnant women, with the relatively high contamination suffered by the east of France and Corsica. Although the 2006 study by the French Institute of Radioprotection and Nuclear Safety said that no clear link could be found between Chernobyl and the increase of thyroid cancers in France, it also stated that papillary thyroid cancer had tripled in the following years.
International response
After the Chernobyl Disaster, a number of countries were reluctant to expand their nuclear programs. Italy and Switzerland tried to ban nuclear power altogether. Other countries, such as the Netherlands and Finland postponed the addition of nuclear power plants. The disaster reaffirmed policy made by Austria and Sweden to terminate use of all nuclear energy. Germany set up regulatory organizations and new policy including the Federal Ministry of Environment and Reactor Safety and a new act for precaution protection against nuclear radiation.
Policy levers were not only implemented on a national level, but on an international level as well. In June 1986, the European Community implemented new standards for cesium. They attempted to do the same for iodine, but could not reach an agreement. Several international programs were formed, including the World Association of Nuclear Operators. This association essentially linked 130 operators in 30 countries. Nuclear engineers would visit nuclear plants worldwide to learn and work towards better safety precautions.
The International Atomic Energy Agency (IAEA), established in 1957, created the Nuclear Safety Assistance Coordination Centre, which serves as an example of the international, multilateral cooperation resulting from the disaster (World Nuclear, 2016). They created the Convention on Early Notification of a Nuclear Accident and Convention on Assistance in the Case of a Nuclear Accident or Radiological Emergency. Nations called for a more comprehensive set of obligatory regulations for nuclear power plants from safe management of installation to safe management of radioactive waste. They created the Joint Convention of Safety of Spent Fuel Management in which obliged nations to create proper policy to control nuclear power plant management.
A number of charitable organizations were also created across various countries to support those affected by the disaster. In the United Kingdom, Chernobyl Children's Project (UK), Friends of Chernobyl's Children, Aid Convoy, Chernobyl 2000, and Chernobyl Children Life Line were set up to assist people affected by the meltdown, radiation, and evacuation. Organizations were also created in Ireland, with The Greater Chernobyl Cause, the Chernobyl Children's Trust, and the Chernobyl Children International. In the United States, the Chernobyl Children International was established to help those economically affected by the disaster.
See also
References
External links
Animated map of radioactive cloud, French IRSN (official Institut de Radioprotection et de Sûreté Nucléaire — Institute of Radioprotection and Nuclear Safety)
Chernobyl animals worse affected than thought: study
25 years of satellite imagery over Chernobyl
Radiation health effects
Environment of Ukraine
Health in the Soviet Union
Environment of the Soviet Union | Effects of the Chernobyl disaster | [
"Chemistry",
"Materials_science",
"Technology"
] | 11,679 | [
"Radiation health effects",
"Aftermath of the Chernobyl disaster",
"Environmental impact of nuclear power",
"Radiation effects",
"Radioactivity"
] |
4,155,495 | https://en.wikipedia.org/wiki/Community-led%20total%20sanitation | Community-led total sanitation (CLTS) is used mainly in developing countries to improve sanitation and hygiene practices in a community. It focuses on spontaneous and long-lasting behavioral change of an entire community. The aim of CLTS is to achieve behavior change with a "trigger" that is meant to lead to spontaneous and long-term abandonment of open defecation practices, thereby improving community sanitation and overall health. The term "triggering" is central to the CLTS process. It refers to ways of igniting community interest in ending open defecation, usually by building simple toilets, such as pit latrines. CLTS effect is two-fold: it involves actions leading to increased self-respect and pride in one's community, and it also involves shame and disgust about one's own open defecation behaviors. CLTS takes an approach to rural sanitation that works without hardware subsidies and that facilitates communities to recognize the problem of open defecation and take collective action to become "open defecation free" and clean up.
The concept was developed around the year 2000 by Kamal Kar for rural areas in Bangladesh. CLTS became an established approach around 2011. Non-governmental organizations were often in the lead when CLTS was first introduced in a country. Local governments may reward communities by certifying them with "open defecation free" (ODF) status. The original concept of CLTS purposefully did not include subsidies for toilets as they might hinder the process.
CLTS is practiced in at least 53 countries and has been adapted to the urban context. Along with this, it has also been applied to post-emergency and fragile states settings.
Challenges associated with CLTS include the risk of human rights infringements within communities, low standards for toilets, and concerns about usage rates in the long term. CLTS is in principle compatible with a human rights based approach to sanitation but there are bad practice examples in the name of CLTS. More rigorous coaching of CLTS practitioners, government public health staff and local leaders on issues such as stigma, awareness of social norms and pre-existing inequalities are important. People who are disadvantaged should benefit from CLTS programs as effectively as those who are not disadvantaged.
Definitions
Open defecation is the practice of defecating out in the open, rather than using a toilet.
"Open defecation free" (ODF) is a central term for community-led total sanitation (CLTS) programs. It primarily means the eradication of open defecation in the entire community. However, ODF can also include additional criteria, such as:
Household latrines or toilets are hygienic, provide the safe containment of feces, offer privacy and a roof to protect the user, have a lid to cover the hole, or a water seal for toilets.
All household members and all members of the community use these latrines or toilets.
A handwashing facility with water, soap or ash is nearby and used regularly.
Even more stringent criteria which may be required before a community is awarded "ODF status" might include:
Safe drinking water and storage.
Food hygiene.
Greywater disposal.
Solid waste management.
Provision of toilets for schools, markets, clinic or visitors to the community.
Aims and rationale
CLTS focuses on community-wide behavioral change, rather than merely toilet construction. The process raises the awareness that as long as even a minority continues to defecate in the open, everyone is at risk of disease. CLTS uses community-led methods, such as participatory mapping and analyzing pathways between feces and the mouth (fecal–oral transmission of disease), as a means of teaching the risks associated with OD.
The concept originally focused mainly on provoking shame and disgust about open defecation. It also involved actions leading to increased self-respect and pride in one's community. With time, CLTS evolved away from provoking negative emotions to educating people about how open defecation increases the risk of disease. Currently, CLTS triggering events focus more on promoting self-respect and pride.
CLTS shifted the focus on personal responsibility and low-cost solutions. CLTS aims to totally stop open defecation within a community rather than facilitating improved sanitation only to selected households. Combined with hygiene education, the approach aims to make the entire community realize the severe health impacts of open defecation. Since individual carelessness may affect the entire community, pressure on each person becomes stronger to follow sanitation principles such as using sanitary toilets, washing hands, and practicing good hygiene. To introduce sanitation even in the poorest households, low-cost toilets are promoted, constructed with local materials. The purchase of the facility is not subsidized, so that every household must finance its own toilets.
Use or non-use of subsidies
Prior to CLTS, most traditional sanitation programs relied on the provision of subsidies for the construction of latrines and hygiene education. Under this framework, the subsidized facilities were expensive and often did not reach all members of a community. In addition, the subsidies may have reduced the feeling of personal responsibility for the toilets.
The original concept of CLTS did not include subsidies for toilets. CLTS proponents at that time believed that provoking behavior change in the people alone would be sufficient to lead them to take ownership of their own sanitation situation, including paying for and constructing their own toilets. This was not always the case.
Kamal Kar and Robert Chambers stated in their 2008 CLTS Handbook:
In time, NGOs and governments began to see the value of the approach and ran their own schemes in various countries, some with less aversion to subsidies than Kamal Kar.
Phases
Pre-triggering
Pre-triggering is the process by which communities are assessed to be suitable for CLTS intervention. This involves visits and criteria to identify communities likely to respond well to triggering. During pre-triggering, facilitators introduce themselves to community members and begin to build a relationship.
Triggering
A tool called "triggering" is used to propel people into taking action. This takes place over a day with a team of facilitators. The team visits a community which is identified as practicing open defecation and encourages villagers to become aware of their own sanitation situation. This aims to cause disgust in participants, and the facilitators help participants to plan appropriate sanitation facilities.
Using the term "shit" (or other locally used crude words) during triggering events or presentations – rather than feces or excreta – is a deliberate aspect of the CLTS approach, as it is meant to be a practical, straightforward approach rather than a theoretical, academic conversation.
The "CLTS Handbook" from 2008 states that there is no "one way" of doing triggering in CLTS. A rough sequence of steps is given in this handbook which could be followed. Facilitators are encouraged to modify and change activities depending on the local situation.
The UNICEF manual approved for use of CLTS in Sierra Leone suggests the following steps for the triggering process:
Visit the community, emphasizing the purpose of learning about their sanitation situation
Facilitate "Kaka Mapping" – drawing a map of important locations in the village, then adding common sites for defecation
Pretend to leave the community
Facilitate a "Walk of Shame" to sites with frequent Open Defecation
Collect a piece of feces in a bag
Put feces on the ground where all present can see it, and discuss how flies move between food and feces
Wait for the shocked realization that the community is indirectly eating each other's feces
Put some feces into a water bottle and ask if anyone would drink it
Calculate how much feces is produced each day and ask where it goes
Ignition (see below)
Wait for the emergence of "natural" leaders to work with in order to develop a plan of action.
The "ignition" phase occurs when the community becomes convinced that there is a real sanitation problem, and motivated to do something about it. Natural leaders are members of the community who are engaged by the process, and able to drive change.
The goal of the triggering process is to let people see the problem first-hand, thereby evoking disgust. However, it has been reported that communities which respond favorably tend to be motivated more by improved health, dignity, and pride than by shame or disgust.
Post-triggering
After a positive response to the ignition phase, NGO facilitators work with communities to deliver sanitation services by providing information and guidance relevant to the local situation.
There are many challenges that occur in the post-triggering phase. These are mainly related to the supply of durable and affordable latrine hardware and technical support on latrine construction. Toilet owners may need advice how to upgrade and improve sanitation and handwashing facilities using local materials.
Applications and scale
Millions of people worldwide have benefited from CLTS which has reduced open defecation and increased latrine coverage in many rural communities. Practitioners have declared many villages as "ODF villages", where ODF stands for "open defecation free".
CLTS is practiced in at least 53 countries. CLTS has spread throughout Bangladesh and to many other Asian and African countries with financial support from the Water and Sanitation Program of the World Bank, DFID, Plan International, WaterAid, CARE, UNICEF and SNV. Large INGOs and many national NGOs have also been involved. Many governments have in the meantime initiated CLTS processes or made it a matter of national policy.
CLTS as an idea had grown beyond its founder and is now often being run in slightly different ways, e.g. in India, Pakistan, Philippines, Nepal, Sierra Leone and Zambia. Non-governmental organizations (NGOs) were often in the lead when CLTS was first introduced in a country. India was an exception – here the government led the somewhat similar "Total Sanitation Campaign" which has been turned into the "Clean India Mission" or Swachh Bharat Abhiyan in 2014.
CLTS as an idea now has many supporters around the world, with Robert Chambers, co-writer of the CLTS Foundation Handbook, describing it this way:
The Institute of Development Studies (IDS) coordinated research programmed on CLTS since about 2007 and regards it as a "radically different approach to rural sanitation in developing countries which has shown promising successes where traditional rural sanitation programmers have failed".
Today there are many NGOs and research institutes with an interest in CLTS, including for example the CLTS Knowledge Hub of the Institute of Development Studies, the CLTS Foundation led by Kamal Kar, The World Bank, WaterAid, Plan USA and the Water Institute at UNC, SNV from the Netherlands and UNICEF.
Applications to urban situations, schools and other settings
Since about 2016, CLTS has been adapted to the urban context. For example, in Kenya the NGOs Plan and Practical Action have implemented a form of urban CLTS. CLTS has also been used in schools and the surrounding communities, which is referred to as "school-led total sanitation". The school children act as messengers of change to households.
CLTS has also been applied to post-emergency and fragile states settings. There has been some experience with this in Haiti, Afghanistan, Pakistan, Philippines and Indonesia. In 2014, UNICEF reported positive outcomes with CLTS in fragile and insecure contexts, namely in Somalia and South Sudan.
People who are disadvantaged should benefit from CLTS programmers as effectively as those who are not disadvantaged. This is referred to as equality and nondiscrimination (EQND).
Effectiveness
To be successful in the longer term, CLTS should be treated as part of a larger WASH (water, sanitation and hygiene) strategy rather than as a singular solution to changing behavior.
A systematic review of 200 studies concluded in 2018 that the evidence base on CLTS effectiveness is still weak. This means that practitioners, policy makers, and program managers have little available evidence to reason their actions.
There is currently a lack of scientific review about the effectiveness of CLTS, although this has been changing since 2015. A study in 2012 reviewed reports by NGOs and practitioners and found that there was little review of the impact of local "natural" leaders, that anecdotes were used without assessing impacts, and that claims were made without supporting evidence. It concluded that these kinds of reports focus on the 'triggering' stage of CTLS instead of the measurable outcomes. A peer-reviewed article considered the sustainability of CLTS in the longer term: It found that there was little monitoring or evaluation of the impacts of CLTS, even though large international organizations were involved in funding the process.
Reviews about the effectiveness of CLTS to eliminate open defecation, reduce diarrhea and other gastrointestinal diseases, and decrease stunting in children are currently underway. In some cases, CLTS has been compared with India's Total Sanitation Campaign (TSC) when assessing the effectiveness of the approach. However, this comparison may be invalid, as the presence of subsidies in the TSC process may fundamentally change the effectiveness of the CLTS process.
One small study compared different CLTS programmes. Participants from NGOs involved in delivering CLTS reported that although they included some of the activities described in the guidance materials, they often omitted some and included others depending on the local situation. Some reported that subsidies were included, and some offered specific design and construction options.
A cluster-randomized controlled trial in rural Mali conducted during 2011 to 2013 found that CLTS with no monetary subsidies did not affect diarrhea incidence, but substantially increased child growth (thereby reducing stunting), particularly in children under two years of age.
Challenges and difficulties
Human rights
The CLTS behavioral change process is based on the use of shame. This is meant to promote collective consciousness-raising of the severe impacts of open defecation and trigger shock and self-awareness when participants realize the implications of their actions. The triggering process can however infringe the human rights of recipients, even if this was not intended by those promoting CLTS. There have been cases of fines (monetary and non-monetary), withholding of entitlements, public taunting, posting of humiliating pictures and even violence. In some cases CLTS successes might be based on coercion only. On the other hand, CLTS is in principle compatible with a human rights based approach to sanitation but there are bad practice examples in the name of CLTS. More rigorous coaching of CLTS practitioners, government public health officials and local leaders on issues such as stigma, awareness of social norms and pre-existing inequalities are important.
Catarina de Alburquerque, the former United Nations Special Rapporteur on the Right to Water and Sanitation, is quoted as saying that "Observers have also recognized that incentives for encouraging behavior change and the construction of latrines are sometimes unacceptable, and include public shaming, including photographing, of those who still practice open defecation."
More debate is still needed regarding human's rights consequences of post-triggering punitive measures.
Toilet standards and toilet types
CLTS does not specify technical standards for toilets. This is a benefit in terms of keeping the costs of constructing toilets very low and allowing villagers to start building their own toilets immediately. However, it can produce two problems: first in flood plains or areas near water tables, poorly constructed latrines are likely to contaminate the water table and thus represent little improvement. Second, long-term use of sanitation facilities is related to the pleasantness of the facilities, but dirty overflowing pits are unlikely to be utilised in the longer term. A related issue here is that CLTS does not address the issue of latrine emptying services or where they exist, how they dispose of waste. This has led some researchers to say that the success of CLTS is largely down to the cultural suitability of the way it is delivered and the degree to which supply-side constraints are addressed.
If villagers do not know about alternative toilet options (like urine-diverting dry toilets or composting toilets), and are not told about these options by the facilitators of the CLTS process, they may opt for pour flush pit latrines even in situations where groundwater pollution is a significant problem.
Reuse of treated excreta as fertiliser
Feces are given a strong negative connotation in the CLTS approach. This can cause confusion for villagers who are already using treated human excreta as a fertiliser in agriculture and can, in fact, discourage the reuse of human excreta.
Long-term usage rates (sustainability)
There is also concern about the number of people who go back to open defecation some months after having been through the CLTS process. A Plan Australia study from 2013 investigated that 116 villages were considered Open Defecation Free (ODF) following CLTS across several countries in Africa. After two years, 87% of the 4960 households had fully functioning latrines – but these were considered the most basic and none of the communities had moved up the sanitation ladder. 89% of households had no visible excreta in the vicinity, but only 37% had handwashing facilities present. When broader criteria for declaring communities ODF was used, an overall "slippage rate" of 92% was found. Some researchers suggest that this means support is needed for communities to upgrade facilities in ODF villages which have been triggered by CLTS.
A study in 2018 has found little evidence for sustained sanitation behavior change as a result of CLTS.
History
In 1999 and 2000, Kamal Kar was working in a village called Mosmoil in Rajshahi, Bangladesh, and decided that a system of attitudinal changes by villagers might have a longer-lasting effect than the existing top-down approach involving subsidies from NGOs and government. The Bangladeshi government began a programme of installing expensive latrines in the 1970s, but the government decided this was too costly, and many of the original latrines were abandoned. In the 1990s, a social mobilisation plan was put in place to encourage people to demand and install better sanitation systems, but early success did not last, according to Kar. At that point Kar, a participatory development expert from India, was brought in by Wateraid and he concluded that the problem with previous approaches was that local people had not "internalised" the demand for sanitation. He suggested a new approach: abandoning subsidies and appealing to the better nature of villagers and their sense of self-disgust to bring about change. The CLTS Foundation is the organisation set up by Kar to promote these ideas.
It eventually became standard practice for NGOs to leave the community quite soon after "triggering" activities. When communities took the lead, change in sanitation practices were more long term and sustainable.
See also
Ecopsychology
Orangi Pilot Project
Self-supply of water and sanitation
Swachh Bharat Abhiyan (Clean India Mission)
WASH (Water, sanitation and hygiene)
References
External links
CLTS Knowledge Hub at Institute for Development Studies (IDS) in the UK
CLTS Foundation by Kamal Kar
Publications on CTLS in the library of the Sustainable Sanitation Alliance (SuSanA)
Testing CLTS Approaches for Scalability
Rural community development
Sewerage
Sanitation | Community-led total sanitation | [
"Chemistry",
"Engineering",
"Environmental_science"
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"Sewerage",
"Water pollution",
"Environmental engineering"
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4,155,566 | https://en.wikipedia.org/wiki/List%20of%20defunct%20network%20processor%20companies | During the dot-com/internet bubble of the late 1990s and early 2000, the proliferation of many dot-com start-up companies created a secondary bubble in the telecommunications/computer networking infrastructure and telecommunications service provider markets. Venture capital and high tech companies rushed to build next generation infrastructure equipment for the expected explosion of internet traffic. As part of that investment fever, network processors were seen as a method of dealing with the desire for more network services and the ever-increasing data-rates of communication networks.
It has been estimated that dozens of start-up companies were created in the race to build the processors that would be a component of the next generation telecommunications equipment. Once the internet investment bubble burst, the telecom network upgrade cycle was deferred for years (perhaps for a decade). As a result, the majority of these new companies went bankrupt.
As of 2007, the only companies that are shipping network processors in sizeable volumes are Cisco Systems, Marvell, Freescale, Cavium Networks and AMCC.
OC-768/40Gb routing
ClearSpeed left network processor market, reverted to supercomputing applications
Propulsion Networks defunct
BOPS left network processor market, reverted to DSP applications
OC-192/10Gb routing
Terago defunct
Clearwater Networks originally named Xstream Logic, defunct
Silicon Access defunct
Solidum Systems acquired by Integrated Device Technology
Lexra defunct
Fast-Chip defunct
Cognigine Corp. defunct
Internet Machines morphed into IMC Semiconductors, a PCI-Express chip vendor
Acorn Networks defunct
XaQti acquired by Vitesse Semiconductor, product line discontinued
OC-48/2.5Gb routing
IP Semiconductors defunct
Entridia defunct
Stargate Solutions defunct
Gigabit Ethernet routing
Sibyte acquired by Broadcom, product line discontinued
PMC-Sierra product line discontinued
OC-12 routing
C-port acquired by Motorola (now Freescale), product line discontinued
IBM PowerNP product line discontinued
Sitera acquired by Vitesse, product line discontinued
Access products
Netargy defunct
Ishoni Networks defunct
HyWire defunct
VOIP products
Silicon Spice acquired by Broadcom, product line discontinued
Malleable Technologies acquired by PMC-Sierra, product line discontinued
Traffic managers
Extreme Packet Devices acquired by PMC-Sierra, product line discontinued
Azanda Network Devices acquired by Cortina, product line being sold as CS53xx family
Teradiant defunct
Orologic acquired by Vitesse, product line discontinued
Maker Communications acquired by Conexant, product line discontinued
Packet classifiers
SwitchOn acquired by PMC-Sierra, product line discontinued
FastChip defunct
Switch fabrics
Abrizio acquired by PMC-Sierra, product line discontinued
Stargen left networking market for computer server market
Security products
Chrysalis-ITS defunct
Defunct network processor companies
Network processor companies | List of defunct network processor companies | [
"Technology"
] | 569 | [
"Computing-related lists"
] |
4,155,979 | https://en.wikipedia.org/wiki/Orangi%20Pilot%20Project | The Orangi Pilot Project (; abbreviated OPP) collectively designates three Pakistani non-governmental organisations working together, having emerged from a socially innovative project carried out in 1980s in the squatter areas of Orangi, Karachi, Pakistan. It was initiated by Akhtar Hameed Khan and implemented by Perween Rahman. Innovative methods were used to provide adequate low cost sanitation, health, housing and microfinance facilities.
Currently OPP designates three organisations, born out of the original OPP in 1989 OPP-RTI (Research and Training Institute), OPP-OCT (Orangi Charitable Trust, involved in microfinance) and OPP-KHASDA (Karachi Health and Social Development Association, involved in health activities). A fourth organisation, OPP-RDT (Rural Development Trust) was merged with OPP-RTI in 2012.
The project also comprised a number of programmes, including a people's financed and managed low-cost sanitation programme; a housing programme; a basic health and family planning programme; a programme of supervised credit for small family enterprise units; an education programme; and a rural development programme in the nearby villages.
Today, the project encompasses much more than the neighbourhood level problems. The research and development programmes under the institutions developed by the project now cover wider issues related to the areas all over Karachi.
Its director until 2013 was Perween Rahman, who was murdered on 13 March 2013.
Organization's success
Orangi was a squatter community, and did not qualify for government aid due to their "unofficial" status. With endogenous research, the community was able to make an affordable sanitation system for the treatment of sewage, which helped to reduce the spread of disease. The system was created and paid for by the local community, who would not have had access to a sewer system otherwise.
The programme proved so successful that it was adopted by communities across developing countries. After the success of the initial phase, the programme was expanded into four autonomous groups.
The Orangi Pilot Project Society, to control funding for the other three groups.
The Orangi Research and Training Institute, to manage the programme and provide training for onward dissemination.
The Orangi Charitable Trust, to manage microcredit programmes.
The Karachi Health and Social Development Association, to manage a health programme.
Foundation of Orangi Pilot Project (OPP)
Dr Akhtar Hameed Khan (1914–1999) was the founder and first director of the project, and through his dynamic and innovative skills managed to bring modern sanitation to the squatter community of 1 million people. He had previously organised farmers' cooperatives and rural training centres and had served as an adviser to various development projects in Pakistan.
He was also a research fellow and visiting professor at Michigan State University (US), Director of the Pakistan Academy of Rural Development and Principal of Victoria College (Bangladesh).
Comparing the OPP with his earlier Comilla project, Akhtar Hameed Khan commented:
"The Orangi Pilot Project was very different from the Comilla Academy. OPP was a private body, dependent for its small fixed budget on another NGO. The vast resources and support of the government, Harvard advisers, MSU, and Ford Foundation was missing. OPP possessed no authority, no sanctions. It may observe and investigate but it could only advise, not enforce.".
However, both projects followed the same research and extension methods.
Orangi Pilot Project – Orangi Charitable Trust (OPP – OCT) now OPRCT
"OPRCT formerly (OPP-OCT) discovered that this growing settlement of Orangi was full of the enterprising spirit. The most impressive demonstration of the spirit of enterprises is the creation of employment everywhere in the lanes; inside the homes there are around twenty thousand family units, shops workshops, peddlers and vendors. In response to the dual challenge of inflation and recession, the residents have invented working family, modifying homes into workshops, promoting the women from mere dependents to economic partners and wage earners, abandoning the dominant patriarchal pattern with surprising speed.
OPP's research revealed two significant factors; first, there was unlimited demand for products and services of these family units. Second, the family units were extremely competitive (on account of very low over heads and very cheap and docile labour). The working family units of Orangi were completely integrated with the main Karachi markets. In fact many units are supplying goods to famous firms, who just put their labels and make big profits. What is required is to support their initiatives.
Research further revealed that the production and employment in urban as well as rural areas could easily be increased provided the credit is accessible, as there was no shortage of market demand or productive labour. But they would not get credit at reasonable rate, because banks were inaccessible to them. The lack of bank credit forced them to buy raw materials at exorbitant prices while they had to sell their products at depressed prices and forego expansion.
On the basis of the research findings, Orangi Pilot Project (OPP) decided to arrange access to credit to these micro enterprises. For this Orangi Pilot Project – Orangi Charitable Trust (OPP – OCT) was established in 1989 as an independent and autonomous institution in Orangi, a low income settlement of over one million people. The main objective is to support people effort in their economic development by providing credit in urban and rural areas."
Publications
Perween Rahman, 2004, Katchi Abadis of Karachi: A survey of 334 katchi abadis – Existing situation, problems and solutions related to sewage disposal, water supply, health and education. Orangi Pilot Project-Research and Training Institute. Sama Publishing.
Arif Hasan, 2000, Scaling Up of the Orangi Pilot Project Programs: successes, failures and potentials, City Press, Karachi.
Arif Hasan, 1999, Akhtar Hameed Khan and the Orangi Pilot Project, City Press, Karachi.
Akhtar Hameed Khan, 1996, Orangi Pilot Project: Reminiscences and Reflection, Oxford University Press, Karachi
Arif Hasan, 1993, Scaling Up of the OPP's Low Cost Sanitation Program, Research Training Institute, Karachi.
See also
Microfinance
Social innovation
References
External links
Orangi Pilot Project (OPP)
OPP Research and Training Institute
OPP's Microcredit Program
Orangi (self-help) Pilot Project
UNESCAP Good Practices Suite Example
Orangi Welfare Project (Trust) – A grassroots NGO inspired by the OPP
A WaterAid report describing a mapping project associated with the Orangi Pilot Project
Development in Asia
Sewerage
Appropriate technology
Orangi Town
Economy of Karachi
Rural development in Pakistan
Squatting in Pakistan | Orangi Pilot Project | [
"Chemistry",
"Engineering",
"Environmental_science"
] | 1,383 | [
"Sewerage",
"Water pollution",
"Environmental engineering"
] |
4,155,988 | https://en.wikipedia.org/wiki/Annubar | The Annubar primary element is an averaging Pitot tube manufactured by Rosemount Inc. used to measure the flow of fluid in a pipe.
A Pitot tube measures the difference between the static pressure and the flowing pressure of the media in the pipe. The volumetric flow is calculated from that difference using Bernoulli's principle, taking into account the pipe's inside diameter. An Annubar, as an averaging Pitot tube, takes multiple samples across a section of a pipe or duct, averaging the differential pressures encountered accounting for variations in flow across the section.
References
Measuring instruments | Annubar | [
"Technology",
"Engineering"
] | 121 | [
"Measuring instruments"
] |
4,156,092 | https://en.wikipedia.org/wiki/Alglucerase | Alglucerase was a biopharmaceutical drug for the treatment of Gaucher's disease. It was a modified form of human β-glucocerebrosidase enzyme, where the non-reducing ends of the oligosaccharide chains have been terminated with mannose residues.
Ceredase is the trade name of a citrate buffered solution of alglucerase that was manufactured by Genzyme Corporation from human placental tissue. It is given intravenously in the treatment of Type 1 Gaucher's disease. This was the first drug approved as an enzyme replacement therapy.
It was approved by the FDA in 1991. It has been withdrawn from the market due to the approval of similar drugs made with recombinant DNA technology instead of being harvested from tissue; drugs made recombinantly, since there is no concern about diseases being transmitted from the tissue used in harvesting, and are less expensive to manufacture (see imiglucerase).
References
External links
Ceredase page at Harvard's Gaucher Treatment Program
Hydrolases
Sanofi
Withdrawn drugs | Alglucerase | [
"Chemistry"
] | 230 | [
"Drug safety",
"Withdrawn drugs"
] |
4,156,419 | https://en.wikipedia.org/wiki/Imiglucerase | Imiglucerase is a medication used in the treatment of Gaucher's disease.
It is a recombinant DNA-produced analogue of the human enzyme β-glucocerebrosidase.
Cerezyme is a freeze-dried medicine containing imiglucerase, manufactured by Genzyme Corporation. It is given intravenously after reconstitution as a treatment for Type 1 and Type 3 Gaucher's disease. It is available in formulations containing 200 or 400 units per vial. The specific activity of highly purified human enzyme is 890,000 units/mg, meanwhile the enzyme activity produced by recombinant DNA technology is approximately 40 units/mg. A typical dose is 2.5U/kg every two weeks, up to a maximum of 60 U/kg once every two weeks, and safety has been established from ages 2 and up. It is one of more expensive medications, with an annual cost of $200,000 per person in the United States. Imiglucerase has been granted orphan drug status in the United States, Australia, and Japan.
Cerezyme was one of the drugs manufactured at Genzyme's Allston, Massachusetts plant, for which production was disrupted in 2009 after contamination with Vesivirus 2017.
Side effects
The most common side effect is hypersensitivity, which occurs in about 3% of patients. It is associated with symptoms such as cough, shortness of breath, rashes, itching, and angiooedema. Less common side effects include dizziness, headache, nausea, diarrhea, and reactions at the injection site; they are found in less than 1% of patients.
Interactions
No clinical interaction studies have been conducted. Miglustat appears to increase the clearance of imiglucerase by 70%, resulting in decreased enzyme activity.
See also
Other drugs for the treatment of Gaucher's disease
Afegostat (development terminated)
Eliglustat
Miglustat
Velaglucerase alfa
taliglucerase alfa
References
Drugs acting on the gastrointestinal system and metabolism
Orphan drugs
Recombinant proteins
Sanofi | Imiglucerase | [
"Biology"
] | 447 | [
"Recombinant proteins",
"Biotechnology products"
] |
4,156,794 | https://en.wikipedia.org/wiki/Soil%20compaction | In geotechnical engineering, soil compaction is the process in which stress applied to a soil causes densification as air is displaced from the pores between the soil grains. When stress is applied that causes densification due to water (or other liquid) being displaced from between the soil grains, then consolidation, not compaction, has occurred. Normally, compaction is the result of heavy machinery compressing the soil, but it can also occur due to the passage of, for example, animal feet.
In soil science and agronomy, soil compaction is usually a combination of both engineering compaction and consolidation, so may occur due to a lack of water in the soil, the applied stress being internal suction due to water evaporation as well as due to passage of animal feet. Affected soils become less able to absorb rainfall, thus increasing runoff and erosion. Plants have difficulty in compacted soil because the mineral grains are pressed together, leaving little space for air and water, which are essential for root growth. Burrowing animals also find it a hostile environment, because the denser soil is more difficult to penetrate. The ability of a soil to recover from this type of compaction depends on climate, mineralogy and fauna. Soils with high shrink–swell capacity, such as vertisols, recover quickly from compaction where moisture conditions are variable (dry spells shrink the soil, causing it to crack). But clays such as kaolinite, which do not crack as they dry, cannot recover from compaction on their own unless they host ground-dwelling animals such as earthworms—the Cecil soil series is an example.
Before soils can be compacted in the field, some laboratory tests are required to determine their engineering properties. Among various properties, the maximum dry density and the optimum moisture content are vital and specify the required density to be compacted in the field.
In construction
Soil compaction is a vital part of the construction process. It is used for support of structural entities such as building foundations, roadways, walkways, and earth retaining structures to name a few. For a given soil type certain properties may deem it more or less desirable to perform adequately for a particular circumstance. In general, the preselected soil should have adequate strength, be relatively incompressible so that future settlement is not significant, be stable against volume change as water content or other factors vary, be durable and safe against deterioration, and possess proper permeability.
When an area is to be filled or backfilled the soil is placed in layers called lifts. The ability of the first fill layers to be properly compacted will depend on the condition of the natural material being covered. If unsuitable material is left in place and backfilled, it may compress over a long period under the weight of the earth fill, causing settlement cracks in the fill or in any structure supported by the fill. In order to determine if the natural soil will support the first fill layers, an area can be proofrolled. Proofrolling consists of utilizing a piece of heavy construction equipment to roll across the fill site and watching for deflections to be revealed. These areas will be indicated by the development of rutting, pumping, or ground weaving.
To ensure adequate soil compaction is achieved, project specifications will indicate the required soil density or degree of compaction that must be achieved. These specifications are generally recommended by a geotechnical engineer in a geotechnical engineering report.
The soil type—that is, grain-size distributions, shape of the soil grains, specific gravity of soil solids, and amount and type of clay minerals, present—has a great influence on the maximum dry unit weight and optimum moisture content. It also has a great influence on how the materials should be compacted in given situations. Compaction is accomplished by use of heavy equipment. In sands and gravels, the equipment usually vibrates, to cause re-orientation of the soil particles into a denser configuration. In silts and clays, a sheepsfoot roller is frequently used, to create small zones of intense shearing, which drives air out of the soil.
Determination of adequate compaction is done by determining the in-situ density of the soil and comparing it to the maximum density determined by a laboratory test. The most commonly used laboratory test is called the Proctor compaction test and there are two different methods in obtaining the maximum density. They are the standard Proctor and modified Proctor tests; the modified Proctor is more commonly used. For small dams, the standard Proctor may still be the reference.
While soil under structures and pavements needs to be compacted, it is important after construction to decompact areas to be landscaped so that vegetation can grow.
Compaction methods
There are several means of achieving compaction of a material. Some are more appropriate for soil compaction than others, while some techniques are only suitable for particular soils or soils in particular conditions. Some are more suited to compaction of non-soil materials such as asphalt. Generally, those that can apply significant amounts of shear as well as compressive stress, are most effective.
The available techniques can be classified as:
Static – a large stress is slowly applied to the soil and then released.
Impact – the stress is applied by dropping a large mass onto the surface of the soil.
Vibrating – a stress is applied repeatedly and rapidly via a mechanically driven plate or hammer. Often combined with rolling compaction (see below).
Gyrating – a static stress is applied and maintained in one direction while the soil is a subjected to a gyratory motion about the axis of static loading. Limited to laboratory applications.
Rolling – a heavy cylinder is rolled over the surface of the soil. Commonly used on sports pitches. Roller-compactors are often fitted with vibratory devices to enhance their effectiveness.
Kneading – shear is applied by alternating movement in adjacent positions. An example, combined with rolling compaction, is the 'sheepsfoot' roller used in waste compaction at landfills.
The construction plant available to achieve compaction is extremely varied and is described elsewhere.
Test methods in laboratory
Soil compactors are used to perform test methods which cover laboratory compaction methods used to determine the relationship between molding water content and dry unit weight of soils. Soil placed as engineering fill is compacted to a dense state to obtain satisfactory engineering properties such as, shear strength, compressibility, or permeability. In addition, foundation soils are often compacted to improve their engineering properties. Laboratory compaction tests provide the basis for determining the percent compaction and molding water content needed to achieve the required engineering properties, and for controlling construction to assure that the required compaction and water contents are achieved. Test methods such as EN 13286-2, EN 13286-47, ASTM D698, ASTM D1557, AASHTO T99, AASHTO T180, AASHTO T193, BS 1377:4 provide soil compaction testing procedures.
See also
Soil compaction (agriculture)
Soil degradation
Compactor
Earthwork
Soil structure
Aeration
Shear strength (soil)
References
Soil science
Earthworks (engineering)
Soil degradation | Soil compaction | [
"Environmental_science"
] | 1,464 | [
"Soil degradation",
"Environmental soil science"
] |
4,156,844 | https://en.wikipedia.org/wiki/Cardiovascular%20physiology | Cardiovascular physiology is the study of the cardiovascular system, specifically addressing the physiology of the heart ("cardio") and blood vessels ("vascular").
These subjects are sometimes addressed separately, under the names cardiac physiology and circulatory physiology.
Although the different aspects of cardiovascular physiology are closely interrelated, the subject is still usually divided into several subtopics.
Heart
Cardiac output (= heart rate * stroke volume. Can also be calculated with Fick principle, palpating method.)
Stroke volume (= end-diastolic volume − end-systolic volume)
Ejection fraction (= stroke volume / end-diastolic volume)
Cardiac output is mathematically ` to systole
Inotropic, chronotropic, and dromotropic states
Cardiac input (= heart rate * suction volume Can be calculated by inverting terms in Fick principle)
Suction volume (= end-systolic volume + end-diastolic volume)
Injection fraction (=suction volume / end-systolic volume)
Cardiac input is mathematically ` to diastole
Electrical conduction system of the heart
Electrocardiogram
Cardiac marker
Cardiac action potential
Frank–Starling law of the heart
Wiggers diagram
Pressure volume diagram
Regulation of blood pressure
Baroreceptor
Baroreflex
Renin–angiotensin system
Renin
Angiotensin
Juxtaglomerular apparatus
Aortic body and carotid body
Autoregulation
Cerebral Autoregulation
Hemodynamics
Under most circumstances, the body attempts to maintain a steady mean arterial pressure.
When there is a major and immediate decrease (such as that due to hemorrhage or standing up), the body can increase the following:
Heart rate
Total peripheral resistance (primarily due to vasoconstriction of arteries)
Inotropic state
In turn, this can have a significant impact upon several other variables:
Stroke volume
Cardiac output
Pressure
Pulse pressure (systolic pressure - diastolic pressure)
Mean arterial pressure (usually approximated with diastolic pressure + 1/3 pulse pressure)
Central venous pressure
Regional circulation
See also
Cardiovascular System Dynamics Society
References
External links
Cardiovascular Physiology Concepts - Comprehensive explanation of basic cardiovascular concepts, based on a textbook of the same name.
The Gross Physiology of the Cardiovascular System - Mechanical overview of cardiovascular function. Free eBook and video resources.
Clinical Sciences - Cardiovascular An iPhone app covering detailed cardiovascular physiology and anatomy
Quantitative Cardiovascular Physiology and Clinical Applications for Engineers
Cardiology
Circulatory system
Heart
Cardiac anatomy | Cardiovascular physiology | [
"Biology"
] | 523 | [
"Organ systems",
"Circulatory system"
] |
4,156,879 | https://en.wikipedia.org/wiki/Cubohemioctahedron | In geometry, the cubohemioctahedron is a nonconvex uniform polyhedron, indexed as U15. It has 10 faces (6 squares and 4 regular hexagons), 24 edges and 12 vertices. Its vertex figure is a crossed quadrilateral.
It is given Wythoff symbol 4 | 3, although that is a double-covering of this figure.
A nonconvex polyhedron has intersecting faces which do not represent new edges or faces. In the picture vertices are marked by golden spheres, and edges by silver cylinders.
It is a hemipolyhedron with 4 hexagonal faces passing through the model center. The hexagons intersect each other and so only triangular portions of each are visible.
Related polyhedra
It shares the vertex arrangement and edge arrangement with the cuboctahedron (having the square faces in common), and with the octahemioctahedron (having the hexagonal faces in common).
Tetrahexagonal tiling
The cubohemioctahedron can be seen as a net on the hyperbolic tetrahexagonal tiling with vertex figure 4.6.4.6.
Hexahemioctacron
The hexahemioctacron is the dual of the cubohemioctahedron, and is one of nine dual hemipolyhedra. It appears visually indistinct from the octahemioctacron.
Since the cubohemioctahedron has four hexagonal faces passing through the model center, thus it is degenerate, and can be seen as having four vertices at infinity.
In Magnus Wenninger's Dual Models, they are represented with intersecting infinite prisms passing through the model center, cut off at a certain point that is convenient for the maker.
See also
Hemi-cube - The four vertices at infinity correspond directionally to the four vertices of this abstract polyhedron.
References
(Page 101, Duals of the (nine) hemipolyhedra)
External links
Uniform polyhedra and duals
Uniform polyhedra | Cubohemioctahedron | [
"Physics"
] | 433 | [
"Uniform polytopes",
"Uniform polyhedra",
"Symmetry"
] |
4,156,959 | https://en.wikipedia.org/wiki/Great%20ditrigonal%20icosidodecahedron | In geometry, the great ditrigonal icosidodecahedron (or great ditrigonary icosidodecahedron) is a nonconvex uniform polyhedron, indexed as U47. It has 32 faces (20 triangles and 12 pentagons), 60 edges, and 20 vertices. It has 4 Schwarz triangle equivalent constructions, for example Wythoff symbol 3 | 3 gives Coxeter diagram = . It has extended Schläfli symbol a{,3} or c{3,}, as an altered great stellated dodecahedron or converted great icosahedron.
Its circumradius is times the length of its edge, a value it shares with the cube.
Related polyhedra
Its convex hull is a regular dodecahedron. It additionally shares its edge arrangement with the small ditrigonal icosidodecahedron (having the triangular faces in common), the ditrigonal dodecadodecahedron (having the pentagonal faces in common), and the regular compound of five cubes.
References
External links
VRML model:
MathWorld
Uniform polyhedra | Great ditrigonal icosidodecahedron | [
"Physics"
] | 229 | [
"Uniform polytopes",
"Uniform polyhedra",
"Symmetry"
] |
4,157,031 | https://en.wikipedia.org/wiki/Small%20cubicuboctahedron | In geometry, the small cubicuboctahedron is a uniform star polyhedron, indexed as U13. It has 20 faces (8 triangles, 6 squares, and 6 octagons), 48 edges, and 24 vertices. Its vertex figure is a crossed quadrilateral.
The small cubicuboctahedron is a faceting of the rhombicuboctahedron. Its square faces and its octagonal faces are parallel to those of a cube, while its triangular faces are parallel to those of an octahedron: hence the name cubicuboctahedron. The small suffix serves to distinguish it from the great cubicuboctahedron, which also has faces in the aforementioned directions.
Related polyhedra
It shares its vertex arrangement with the stellated truncated hexahedron. It additionally shares its edge arrangement with the rhombicuboctahedron (having the triangular faces and 6 square faces in common), and with the small rhombihexahedron (having the octagonal faces in common).
Related tilings
As the Euler characteristic suggests, the small cubicuboctahedron is a toroidal polyhedron of genus 3 (topologically it is a surface of genus 3), and thus can be interpreted as a (polyhedral) immersion of a genus 3 polyhedral surface, in the complement of its 24 vertices, into 3-space. (A neighborhood of any vertex is topologically a cone on a figure-8, which cannot occur in an immersion. Note that the Richter reference overlooks this fact.) The underlying polyhedron (ignoring self-intersections) defines a uniform tiling of this surface, and so the small cubicuboctahedron is a uniform polyhedron. In the language of abstract polytopes, the small cubicuboctahedron is a faithful realization of this abstract toroidal polyhedron, meaning that it is a nondegenerate polyhedron and that they have the same symmetry group. In fact, every automorphism of the abstract genus 3 surface with this tiling is realized by an isometry of Euclidean space.
Higher genus surfaces (genus 2 or greater) admit a metric of negative constant curvature (by the uniformization theorem), and the universal cover of the resulting Riemann surface is the hyperbolic plane. The corresponding tiling of the hyperbolic plane has vertex figure 3.8.4.8 (triangle, octagon, square, octagon). If the surface is given the appropriate metric of curvature = −1, the covering map is a local isometry and thus the abstract vertex figure is the same. This tiling may be denoted by the Wythoff symbol 3 4 | 4, and is depicted on the right.
Alternatively and more subtly, by chopping up each square face into 2 triangles and each octagonal face into 6 triangles, the small cubicuboctahedron can be interpreted as a non-regular coloring of the combinatorially regular (not just uniform) tiling of the genus 3 surface by 56 equilateral triangles, meeting at 24 vertices, each with degree 7. This regular tiling is significant as it is a tiling of the Klein quartic, the genus 3 surface with the most symmetric metric (automorphisms of this tiling equal isometries of the surface), and the orientation-preseserving automorphism group of this surface is isomorphic to the projective special linear group PSL(2,7), equivalently GL(3,2) (the order 168 group of all orientation-preserving isometries). Note that the small cubicuboctahedron is not a realization of this abstract polyhedron, as it only has 24 orientation-preserving symmetries (not every abstract automorphism is realized by a Euclidean isometry) – the isometries of the small cubicuboctahedron preserve not only the triangular tiling, but also the coloring, and hence are a proper subgroup of the full isometry group.
The corresponding tiling of the hyperbolic plane (the universal covering) is the order-7 triangular tiling. The automorphism group of the Klein quartic can be augmented (by a symmetry which is not realized by a symmetry of the polyhedron, namely "exchanging the two endpoints of the edges that bisect the squares and octahedra) to yield the Mathieu group M24.
See also
Compound of five small cubicuboctahedra
List of uniform polyhedra
References
External links
Toroidal polyhedra | Small cubicuboctahedron | [
"Mathematics"
] | 919 | [
"Toroidal polyhedra",
"Topology"
] |
4,157,120 | https://en.wikipedia.org/wiki/Nonconvex%20great%20rhombicuboctahedron | In geometry, the nonconvex great rhombicuboctahedron is a nonconvex uniform polyhedron, indexed as U17. It has 26 faces (8 triangles and 18 squares), 48 edges, and 24 vertices. It is represented by the Schläfli symbol rr{4,} and Coxeter-Dynkin diagram of . Its vertex figure is a crossed quadrilateral.
This model shares the name with the convex great rhombicuboctahedron, also called the truncated cuboctahedron.
An alternative name for this figure is quasirhombicuboctahedron. From that derives its Bowers acronym: querco.
Orthographic projections
Cartesian coordinates
Cartesian coordinates for the vertices of a nonconvex great rhombicuboctahedron centered at the origin with edge length 1 are all the permutations of
Related polyhedra
It shares the vertex arrangement with the convex truncated cube. It additionally shares its edge arrangement with the great cubicuboctahedron (having the triangular faces and 6 square faces in common), and with the great rhombihexahedron (having 12 square faces in common). It has the same vertex figure as the pseudo great rhombicuboctahedron, which is not a uniform polyhedron.
Great deltoidal icositetrahedron
The great deltoidal icositetrahedron is the dual of the nonconvex great rhombicuboctahedron.
References
External links
Great Rhombicuboctahedron Paper model
Uniform polyhedra | Nonconvex great rhombicuboctahedron | [
"Physics"
] | 326 | [
"Uniform polytopes",
"Uniform polyhedra",
"Symmetry"
] |
4,157,127 | https://en.wikipedia.org/wiki/Small%20dodecahemidodecahedron | In geometry, the small dodecahemidodecahedron is a nonconvex uniform polyhedron, indexed as . It has 18 faces (12 pentagons and 6 decagons), 60 edges, and 30 vertices. Its vertex figure alternates two regular pentagons and decagons as a crossed quadrilateral.
It is a hemipolyhedron with six decagonal faces passing through the model center.
Related polyhedra
It shares its edge arrangement with the icosidodecahedron (its convex hull, having the pentagonal faces in common), and with the small icosihemidodecahedron (having the decagonal faces in common).
References
External links
Uniform polyhedra and duals
Uniform polyhedra | Small dodecahemidodecahedron | [
"Physics"
] | 157 | [
"Uniform polytopes",
"Uniform polyhedra",
"Symmetry"
] |
4,157,154 | https://en.wikipedia.org/wiki/Small%20dodecicosahedron | In geometry, the small dodecicosahedron (or small dodekicosahedron) is a nonconvex uniform polyhedron, indexed as U50. It has 32 faces (20 hexagons and 12 decagons), 120 edges, and 60 vertices. Its vertex figure is a crossed quadrilateral.
Related polyhedra
It shares its vertex arrangement with the great stellated truncated dodecahedron. It additionally shares its edges with the small icosicosidodecahedron (having the hexagonal faces in common) and the small ditrigonal dodecicosidodecahedron (having the decagonal faces in common).
References
External links
Uniform polyhedra | Small dodecicosahedron | [
"Physics"
] | 148 | [
"Uniform polytopes",
"Uniform polyhedra",
"Symmetry"
] |
4,157,168 | https://en.wikipedia.org/wiki/Octahemioctahedron | In geometry, the octahemioctahedron or allelotetratetrahedron is a nonconvex uniform polyhedron, indexed as . It has 12 faces (8 triangles and 4 hexagons), 24 edges and 12 vertices. Its vertex figure is a crossed quadrilateral.
It is one of nine hemipolyhedra, with 4 hexagonal faces passing through the model center.
Orientability
It is the only hemipolyhedron that is orientable, and the only uniform polyhedron with an Euler characteristic of zero (a topological torus).
Related polyhedra
It shares the vertex arrangement and edge arrangement with the cuboctahedron (having the triangular faces in common), and with the cubohemioctahedron (having the hexagonal faces in common).
By Wythoff construction it has tetrahedral symmetry (Td), like the rhombitetratetrahedron construction for the cuboctahedron, with alternate triangles with inverted orientations. Without alternating triangles, it has octahedral symmetry (Oh). In this respect it is akin to the Morin surface, which has fourfold symmetry if orientation is ignored and twofold symmetry otherwise. However the octahemioctahedron has a higher degree of symmetry and is genus 1 rather than 0.
Octahemioctacron
The octahemioctacron is the dual of the octahemioctahedron, and is one of nine dual hemipolyhedra. It appears visually indistinct from the hexahemioctacron.
Since the hemipolyhedra have faces passing through the center, the dual figures have corresponding vertices at infinity; properly, on the real projective plane at infinity. In Magnus Wenninger's Dual Models, they are represented with intersecting prisms, each extending in both directions to the same vertex at infinity, in order to maintain symmetry. In practice the model prisms are cut off at a certain point that is convenient for the maker. Wenninger suggested these figures are members of a new class of stellation figures, called stellation to infinity. However, he also suggested that strictly speaking they are not polyhedra because their construction does not conform to the usual definitions.
The octahemioctacron has four vertices at infinity.
See also
Compound of five octahemioctahedra
Hemi-cube - The four vertices at infinity correspond directionally to the four vertices of this abstract polyhedron.
References
(Page 101, Duals of the (nine) hemipolyhedra)
External links
Uniform polyhedra and duals
Toroidal polyhedra | Octahemioctahedron | [
"Mathematics"
] | 552 | [
"Toroidal polyhedra",
"Topology"
] |
4,157,181 | https://en.wikipedia.org/wiki/Small%20dodecicosidodecahedron | In geometry, the small dodecicosidodecahedron (or small dodekicosidodecahedron) is a nonconvex uniform polyhedron, indexed as U33. It has 44 faces (20 triangles, 12 pentagons, and 12 decagons), 120 edges, and 60 vertices. Its vertex figure is a crossed quadrilateral.
Related polyhedra
It shares its vertex arrangement with the small stellated truncated dodecahedron and the uniform compounds of 6 or 12 pentagrammic prisms. It additionally shares its edge arrangement with the rhombicosidodecahedron (having the triangular and pentagonal faces in common), and with the small rhombidodecahedron (having the decagonal faces in common).
Dual
The dual polyhedron to the small dodecicosidodecahedron is the small dodecacronic hexecontahedron (or small sagittal ditriacontahedron). It is visually identical to the small rhombidodecacron. Its faces are darts. A part of each dart lies inside the solid, hence is invisible in solid models.
Proportions
Faces have two angles of , one of and one of . Its dihedral angles equal . The ratio between the lengths of the long and short edges is .
References
External links
Uniform polyhedra | Small dodecicosidodecahedron | [
"Physics"
] | 278 | [
"Uniform polytopes",
"Uniform polyhedra",
"Symmetry"
] |
4,157,189 | https://en.wikipedia.org/wiki/Rhombicosahedron | In geometry, the rhombicosahedron is a nonconvex uniform polyhedron, indexed as U56. It has 50 faces (30 squares and 20 hexagons), 120 edges and 60 vertices. Its vertex figure is an antiparallelogram.
Related polyhedra
A rhombicosahedron shares its vertex arrangement with the uniform compounds of 10 or 20 triangular prisms. It additionally shares its edges with the rhombidodecadodecahedron (having the square faces in common) and the icosidodecadodecahedron (having the hexagonal faces in common).
Rhombicosacron
The rhombicosacron is a nonconvex isohedral polyhedron. It is the dual of the uniform rhombicosahedron, U56. It has 50 vertices, 120 edges, and 60 crossed-quadrilateral faces.
References
External links
Uniform polyhedra and duals
Uniform polyhedra | Rhombicosahedron | [
"Physics"
] | 201 | [
"Uniform polytopes",
"Uniform polyhedra",
"Symmetry"
] |
4,157,192 | https://en.wikipedia.org/wiki/Great%20icosicosidodecahedron | In geometry, the great icosicosidodecahedron (or great icosified icosidodecahedron) is a nonconvex uniform polyhedron, indexed as U48. It has 52 faces (20 triangles, 12 pentagons, and 20 hexagons), 120 edges, and 60 vertices. Its vertex figure is a crossed quadrilateral.
Related polyhedra
It shares its vertex arrangement with the truncated dodecahedron. It additionally shares its edge arrangement with the great ditrigonal dodecicosidodecahedron (having the triangular and pentagonal faces in common) and the great dodecicosahedron (having the hexagonal faces in common).
References
External links
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4,157,204 | https://en.wikipedia.org/wiki/Small%20rhombidodecahedron | In geometry, the small rhombidodecahedron is a nonconvex uniform polyhedron, indexed as U39. It has 42 faces (30 squares and 12 decagons), 120 edges, and 60 vertices. Its vertex figure is a crossed quadrilateral.
Related polyhedra
It shares its vertex arrangement with the small stellated truncated dodecahedron and the uniform compounds of 6 or 12 pentagrammic prisms. It additionally shares its edge arrangement with the rhombicosidodecahedron (having the square faces in common), and with the small dodecicosidodecahedron (having the decagonal faces in common).
Small rhombidodecacron
The small rhombidodecacron (or small dipteral ditriacontahedron) is a nonconvex isohedral polyhedron. It is the dual of the small rhombidodecahedron. It is visually identical to the Small dodecacronic hexecontahedron. It has 60 intersecting antiparallelogram faces.
References
External links
Uniform polyhedra and duals
Uniform polyhedra | Small rhombidodecahedron | [
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4,157,248 | https://en.wikipedia.org/wiki/Succinyl%20coenzyme%20A%20synthetase | Succinyl coenzyme A synthetase (SCS, also known as succinyl-CoA synthetase or succinate thiokinase or succinate-CoA ligase) is an enzyme that catalyzes the reversible reaction of succinyl-CoA to succinate. The enzyme facilitates the coupling of this reaction to the formation of a nucleoside triphosphate molecule (either GTP or ATP) from an inorganic phosphate molecule and a nucleoside diphosphate molecule (either GDP or ADP). It plays a key role as one of the catalysts involved in the citric acid cycle, a central pathway in cellular metabolism, and it is located within the mitochondrial matrix of a cell.
Chemical reaction and enzyme mechanism
Succinyl CoA synthetase catalyzes the following reversible reaction:
Succinyl CoA + Pi + NDP ↔ Succinate + CoA + NTP
where Pi denotes inorganic phosphate, NDP denotes nucleotide diphosphate (either GDP or ADP), and NTP denotes nucleotide triphosphate (either GTP or ATP). As mentioned, the enzyme facilitates coupling of the conversion of succinyl CoA to succinate with the formation of NTP from NDP and Pi. The reaction has a biochemical standard state free energy change of -3.4 kJ/mol. The reaction takes place by a three-step mechanism which is depicted in the image below. The first step involves displacement of CoA from succinyl CoA by a nucleophilic inorganic phosphate molecule to form succinyl phosphate. The enzyme then utilizes a histidine residue to remove the phosphate group from succinyl phosphate and generate succinate. Finally, the phosphorylated histidine transfers the phosphate group to a nucleoside diphosphate, which generates the high-energy carrying nucleoside triphosphate.
Structure
Subunits
Bacterial and mammalian SCSs are made up of α and β subunits. In E. coli two αβ heterodimers link together to form an α2β2 heterotetrameric structure. However, mammalian mitochondrial SCSs are active as αβ dimers and do not form a heterotetramer.
The E. coli SCS heterotetramer has been crystallized and characterized in great detail. As can be seen in Image 2, the two α subunits (pink and green) reside on opposite sides of the structure and the two β subunits (yellow and blue) interact in the middle region of the protein. The two α subunits only interact with a single β unit, whereas the β units interact with a single α unit (to form the αβ dimer) and the β subunit of the other αβ dimer. A short amino acid chain links the two β subunits which gives rise to the tetrameric structure.
The crystal structure of Succinyl-CoA synthetase alpha subunit (succinyl-CoA-binding isoform) was determined by Joyce et al. to a resolution of 2.10 A, with PDB code 1CQJ. .
Catalytic residues
Crystal structures for the E. coli SCS provide evidence that the coenzyme A binds within each α-subunit (within a Rossmann fold) in close proximity to a histidine residue (His246α). This histidine residue becomes phosphorylated during the succinate forming step in the reaction mechanism. The exact binding location of succinate is not well-defined. The formation of the nucleotide triphosphate occurs in an ATP grasp domain, which is located near the N-terminus of the each β subunit. However, this grasp domain is located about 35 Å away from the phosphorylated histidine residue. This leads researchers to believe that the enzyme must undergo a major change in conformation to bring the histidine to the grasp domain and facilitate the formation of the nucleoside triphosphate. Mutagenesis experiments have determined that two glutamate residues (one near the catalytic histidine, Glu208α and one near the ATP grasp domain, Glu197β) play a role in the phosphorylation and dephosphorylation of the histidine, but the exact mechanism by which the enzyme changes conformation is not fully understood.
Isoforms
Johnson et al. describe two isoforms of succinyl-CoA synthetase in amniotes, one that specifies synthesis of ATP, and one that synthesises GTP.
- ATP-forming - SUCLA2
- GTP-forming - SUCLG2
In amniotes, the enzyme is a heterodimer of an α- and a β-subunit. The specificity for either adenosine or guanosine phosphates is defined by the β-subunit, which is encoded by 2 genes. SUCLG2 is GTP-specific and SUCLA2 is ATP-specific, while SUCLG1 encodes the common α-subunit. β variants are produced at different amounts in different tissues, causing GTP or ATP substrate requirements.
Mostly consuming tissues such as heart and brain have more ATP-specific succinyl-CoA synthetase (ATPSCS), while synthetic tissues such as kidney and liver have the more GTP-specific form (GTPSCS). Kinetics analysis of ATPSCS from the breast muscle of pigeons and GTPSCS from pigeon liver showed that their apparent Michaelis constants were similar for CoA, but different for the nucleotides, phosphate, and succinate. The largest difference was for succinate: Kmapp of ATPSCS = 5mM versus that of GTPSCS = 0.5mM.
Function
Generation of nucleotide triphosphates
SCS is the only enzyme in the citric acid cycle that catalyzes a reaction in which a nucleotide triphosphate (GTP or ATP) is formed by substrate-level phosphorylation. Research studies have shown that E. coli SCSs can catalyze either GTP or ATP formation. However, mammals possess different types of SCSs that are specific for either GTP (G-SCS) or ATP (A-SCS) and are native to different types of tissue within the organism. An interesting study using pigeon cells showed that GTP specific SCSs were located in pigeon liver cells, and ATP specific SCSs were located in the pigeon breast muscle cells. Further research revealed a similar phenomenon of GTP and ATP specific SCSs in rat, mouse, and human tissue. It appears that tissue typically involved in anabolic metabolism (like the liver and kidneys) express G-SCS, whereas tissue involved in catabolic metabolism (like the brain, the heart, and muscular tissue) express A-SCS.
Formation of metabolic intermediates
SCS facilitates the flux of molecules into other metabolic pathways by controlling the interconversion between succinyl CoA and succinate. This is important because succinyl CoA is an intermediate necessary for porphyrin, heme, and ketone body biosynthesis.
Regulation and inhibition
In some bacteria, the enzyme is regulated at the transcriptional level. It has been demonstrated that the gene for SCS (sucCD) is transcribed along with the gene for α-ketoglutarate dehydrogenase (sucAB) under the control of a promoter called sdhC, which is part of the succinate dehydrogenase operon. This operon is up-regulated by the presence of oxygen and responds to a variety of carbon sources. Antibacterial drugs that prevent phosphorylation of histidine, like the molecule LY26650, are potent inhibitors of bacterial SCSs.
Optimal activity
Measurements (performed using a soy bean SCS) indicate an optimal temperature of 37 °C and an optimal pH of 7.0-8.0.
Role in disease
Fatal infantile lactic acidosis: Defective SCS has been implicated as a cause of fatal infantile lactic acidosis, which is a disease in infants that is characterized by the build-up of toxic levels of lactic acid. The condition (when it is most severe) results in death usually within 2–4 days after birth. It has been determined that patients with the condition display a two base pair deletion within the gene known as SUCLG1 that encodes the α subunit of SCS. As a result, functional SCS is absent in metabolism causing a major imbalance in flux between glycolysis and the citric acid cycle. Since the cells do not have a functional citric acid cycle, acidosis results because cells are forced to choose lactic acid production as the primary means of producing ATP.
See also
Citric acid cycle
Succinate dehydrogenase
Succinate—CoA ligase (ADP-forming)
Succinate—CoA ligase (GDP-forming)
References
External links
Metabolism
EC 6.2.1 | Succinyl coenzyme A synthetase | [
"Chemistry",
"Biology"
] | 1,888 | [
"Biochemistry",
"Metabolism",
"Cellular processes"
] |
4,157,350 | https://en.wikipedia.org/wiki/Small%20ditrigonal%20icosidodecahedron | In geometry, the small ditrigonal icosidodecahedron (or small ditrigonary icosidodecahedron) is a nonconvex uniform polyhedron, indexed as U30. It has 32 faces (20 triangles and 12 pentagrams), 60 edges, and 20 vertices. It has extended Schläfli symbol a{5,3}, as an altered dodecahedron, and Coxeter diagram or .
It is constructed from Schwarz triangle (3 3 ) with Wythoff symbol 3 | 3. Its hexagonal vertex figure alternates equilateral triangle and pentagram faces.
Related polyhedra
Its convex hull is a regular dodecahedron. It additionally shares its edge arrangement with the great ditrigonal icosidodecahedron (having the triangular faces in common), the ditrigonal dodecadodecahedron (having the pentagrammic faces in common), and the regular compound of five cubes. As a simple polyhedron, it is also a hexakis truncated icosahedron where the triangles touching the pentagons are made coplanar, making the others concave.
See also
List of uniform polyhedra
References
External links
Uniform polyhedra | Small ditrigonal icosidodecahedron | [
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4,157,363 | https://en.wikipedia.org/wiki/Stellated%20truncated%20hexahedron | In geometry, the stellated truncated hexahedron (or quasitruncated hexahedron, and stellatruncated cube) is a uniform star polyhedron, indexed as U19. It has 14 faces (8 triangles and 6 octagrams), 36 edges, and 24 vertices. It is represented by Schläfli symbol t'{4,3} or t{4/3,3}, and Coxeter-Dynkin diagram, . It is sometimes called quasitruncated hexahedron because it is related to the truncated cube, , except that the square faces become inverted into {8/3} octagrams.
Even though the stellated truncated hexahedron is a stellation of the truncated hexahedron, its core is a regular octahedron.
Orthographic projections
Related polyhedra
It shares the vertex arrangement with three other uniform polyhedra: the convex rhombicuboctahedron, the small rhombihexahedron, and the small cubicuboctahedron.
See also
List of uniform polyhedra
References
External links
Uniform polyhedra | Stellated truncated hexahedron | [
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4,157,379 | https://en.wikipedia.org/wiki/Dodecadodecahedron | In geometry, the dodecadodecahedron is a nonconvex uniform polyhedron, indexed as U36. It is the rectification of the great dodecahedron (and that of its dual, the small stellated dodecahedron). It was discovered independently by , and .
The edges of this model form 10 central hexagons, and these, projected onto a sphere, become 10 great circles. These 10, along with the great circles from projections of two other polyhedra, form the 31 great circles of the spherical icosahedron used in construction of geodesic domes.
Wythoff constructions
It has four Wythoff constructions between four Schwarz triangle families: 2 | 5 5/2, 2 | 5 5/3, 2 | 5/2 5/4, 2 | 5/3 5/4, but represent identical results. Similarly it can be given four extended Schläfli symbols: r{5/2,5}, r{5/3,5}, r{5/2,5/4}, and r{5/3,5/4} or as Coxeter-Dynkin diagrams: , , , and .
Net
A shape with the same exterior appearance as the dodecadodecahedron can be constructed by folding up these nets:
12 pentagrams and 20 rhombic clusters are necessary. However, this construction replaces the crossing pentagonal faces of the dodecadodecahedron with non-crossing sets of rhombi, so it does not produce the same internal structure.
Related polyhedra
Its convex hull is the icosidodecahedron. It also shares its edge arrangement with the small dodecahemicosahedron (having the pentagrammic faces in common), and with the great dodecahemicosahedron (having the pentagonal faces in common).
This polyhedron can be considered a rectified great dodecahedron. It is center of a truncation sequence between a small stellated dodecahedron and great dodecahedron:
The truncated small stellated dodecahedron looks like a dodecahedron on the surface, but it has 24 faces: 12 pentagons from the truncated vertices and 12 overlapping as (truncated pentagrams). The truncation of the dodecadodecahedron itself is not uniform and attempting to make it uniform results in a degenerate polyhedron (that looks like a small rhombidodecahedron with {10/2} polygons filling up the dodecahedral set of holes), but it has a uniform quasitruncation, the truncated dodecadodecahedron.
It is topologically equivalent to a quotient space of the hyperbolic order-4 pentagonal tiling, by distorting the pentagrams back into regular pentagons. As such, it is topologically a regular polyhedron of index two:
Medial rhombic triacontahedron
The medial rhombic triacontahedron is the dual of the dodecadodecahedron. It has 30 intersecting rhombic faces.
Related hyperbolic tiling
It is topologically equivalent to a quotient space of the hyperbolic order-5 square tiling, by distorting the rhombi into squares. As such, it is topologically a regular polyhedron of index two:
Note that the order-5 square tiling is dual to the order-4 pentagonal tiling, and a quotient space of the order-4 pentagonal tiling is topologically equivalent to the dual of the medial rhombic triacontahedron, the dodecadodecahedron.
See also
List of uniform polyhedra
References
External links
Uniform polyhedra and duals
Uniform polyhedra | Dodecadodecahedron | [
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4,157,391 | https://en.wikipedia.org/wiki/Great%20icosidodecahedron | In geometry, the great icosidodecahedron is a nonconvex uniform polyhedron, indexed as U54. It has 32 faces (20 triangles and 12 pentagrams), 60 edges, and 30 vertices. It is given a Schläfli symbol r{3,}. It is the rectification of the great stellated dodecahedron and the great icosahedron. It was discovered independently by , and .
Related polyhedra
The figure is a rectification of the great icosahedron or the great stellated dodecahedron, much as the (small) icosidodecahedron is related to the (small) icosahedron and (small) dodecahedron, and the cuboctahedron to the cube and octahedron.
It shares its vertex arrangement with the icosidodecahedron, which is its convex hull. Unlike the great icosahedron and great dodecahedron, the great icosidodecahedron is not a stellation of the icosidodecahedron, but a faceting of it instead.
It also shares its edge arrangement with the great icosihemidodecahedron (having the triangle faces in common), and with the great dodecahemidodecahedron (having the pentagram faces in common).
The truncated great stellated dodecahedron is a degenerate polyhedron, with 20 triangular faces from the truncated vertices, and 12 (hidden) pentagonal faces as truncations of the original pentagram faces, the latter forming a great dodecahedron inscribed within and sharing the edges of the icosahedron.
Great rhombic triacontahedron
The dual of the great icosidodecahedron is the great rhombic triacontahedron; it is nonconvex, isohedral and isotoxal. It has 30 intersecting rhombic faces. It can also be called the great stellated triacontahedron.
The great rhombic triacontahedron can be constructed by expanding the size of the faces of a rhombic triacontahedron by a factor of τ3 = 1+2τ = 2+√5, where τ is the golden ratio.
See also
List of uniform polyhedra
Rhombic hexecontahedron
Notes
References
External links
Uniform polyhedra and duals
Uniform polyhedra | Great icosidodecahedron | [
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4,157,399 | https://en.wikipedia.org/wiki/Cubitruncated%20cuboctahedron | In geometry, the cubitruncated cuboctahedron or cuboctatruncated cuboctahedron is a nonconvex uniform polyhedron, indexed as U16. It has 20 faces (8 hexagons, 6 octagons, and 6 octagrams), 72 edges, and 48 vertices, and has a shäfli symbol of tr{4,3/2}
Convex hull
Its convex hull is a nonuniform truncated cuboctahedron.
Orthogonal projection
Cartesian coordinates
Cartesian coordinates for the vertices of a cubitruncated cuboctahedron are all the permutations of
(±(−1), ±1, ±(+1))
Related polyhedra
Tetradyakis hexahedron
The tetradyakis hexahedron (or great disdyakis dodecahedron) is a nonconvex isohedral polyhedron. It has 48 intersecting scalene triangle faces, 72 edges, and 20 vertices.
Proportions
The triangles have one angle of , one of and one of . The dihedral angle equals . Part of each triangle lies within the solid, hence is invisible in solid models.
It is the dual of the uniform cubitruncated cuboctahedron.
See also
List of uniform polyhedra
References
p. 92
External links
http://gratrix.net Uniform polyhedra and duals
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4,157,407 | https://en.wikipedia.org/wiki/Great%20truncated%20cuboctahedron | In geometry, the great truncated cuboctahedron (or quasitruncated cuboctahedron or stellatruncated cuboctahedron) is a nonconvex uniform polyhedron, indexed as U20. It has 26 faces (12 squares, 8 hexagons and 6 octagrams), 72 edges, and 48 vertices. It is represented by the Schläfli symbol tr{4/3,3}, and Coxeter-Dynkin diagram . It is sometimes called the quasitruncated cuboctahedron because it is related to the truncated cuboctahedron, , except that the octagonal faces are replaced by {8/3} octagrams.
Convex hull
Its convex hull is a nonuniform truncated cuboctahedron. The truncated cuboctahedron and the great truncated cuboctahedron form isomorphic graphs despite their different geometric structure.
Orthographic projections
Cartesian coordinates
Cartesian coordinates for the vertices of a great truncated cuboctahedron centered at the origin are all permutations of
See also
List of uniform polyhedra
References
External links
Uniform polyhedra | Great truncated cuboctahedron | [
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4,157,430 | https://en.wikipedia.org/wiki/Truncated%20great%20dodecahedron | In geometry, the truncated great dodecahedron is a nonconvex uniform polyhedron, indexed as U37. It has 24 faces (12 pentagrams and 12 decagons), 90 edges, and 60 vertices. It is given a Schläfli symbol t{5,5/2}.
Related polyhedra
It shares its vertex arrangement with three other uniform polyhedra: the nonconvex great rhombicosidodecahedron, the great dodecicosidodecahedron, and the great rhombidodecahedron; and with the uniform compounds of 6 or 12 pentagonal prisms.
This polyhedron is the truncation of the great dodecahedron:
The truncated small stellated dodecahedron looks like a dodecahedron on the surface, but it has 24 faces, 12 pentagons from the truncated vertices and 12 overlapping as (truncated pentagrams).
Small stellapentakis dodecahedron
The small stellapentakis dodecahedron (or small astropentakis dodecahedron) is a nonconvex isohedral polyhedron. It is the dual of the truncated great dodecahedron. It has 60 intersecting triangular faces.
See also
List of uniform polyhedra
References
External links
Uniform polyhedra and duals
Nonconvex polyhedra
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4,157,444 | https://en.wikipedia.org/wiki/Small%20stellated%20truncated%20dodecahedron | In geometry, the small stellated truncated dodecahedron (or quasitruncated small stellated dodecahedron or small stellatruncated dodecahedron) is a nonconvex uniform polyhedron, indexed as U58. It has 24 faces (12 pentagons and 12 decagrams), 90 edges, and 60 vertices. It is given a Schläfli symbol t{,5}, and Coxeter diagram .
Related polyhedra
It shares its vertex arrangement with three other uniform polyhedra: the convex rhombicosidodecahedron, the small dodecicosidodecahedron and the small rhombidodecahedron.
It also has the same vertex arrangement as the uniform compounds of 6 or 12 pentagrammic prisms.
See also
List of uniform polyhedra
References
External links
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4,157,457 | https://en.wikipedia.org/wiki/Great%20stellated%20truncated%20dodecahedron | In geometry, the great stellated truncated dodecahedron (or quasitruncated great stellated dodecahedron or great stellatruncated dodecahedron) is a nonconvex uniform polyhedron, indexed as U66. It has 32 faces (20 triangles and 12 decagrams), 90 edges, and 60 vertices. It is given a Schläfli symbol
Related polyhedra
It shares its vertex arrangement with three other uniform polyhedra: the small icosicosidodecahedron, the small ditrigonal dodecicosidodecahedron, and the small dodecicosahedron:
Cartesian coordinates
Cartesian coordinates for the vertices of a great stellated truncated dodecahedron are all the even permutations of
where is the golden ratio.
See also
List of uniform polyhedra
References
External links
Uniform polyhedra | Great stellated truncated dodecahedron | [
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4,157,466 | https://en.wikipedia.org/wiki/Truncated%20great%20icosahedron | In geometry, the truncated great icosahedron (or great truncated icosahedron) is a nonconvex uniform polyhedron, indexed as U55. It has 32 faces (12 pentagrams and 20 hexagons), 90 edges, and 60 vertices. It is given a Schläfli symbol or as a truncated great icosahedron.
Cartesian coordinates
Cartesian coordinates for the vertices of a truncated great icosahedron centered at the origin are all the even permutations of
where is the golden ratio. Using one verifies that all vertices are on a sphere, centered at the origin, with the radius squared equal to The edges have length 2.
Related polyhedra
This polyhedron is the truncation of the great icosahedron:
The truncated great stellated dodecahedron is a degenerate polyhedron, with 20 triangular faces from the truncated vertices, and 12 (hidden) pentagonal faces as truncations of the original pentagram faces, the latter forming a great dodecahedron inscribed within and sharing the edges of the icosahedron.
Great stellapentakis dodecahedron
The great stellapentakis dodecahedron is a nonconvex isohedral polyhedron. It is the dual of the truncated great icosahedron. It has 60 intersecting triangular faces.
See also
List of uniform polyhedra
References
External links
Uniform polyhedra and duals
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4,157,474 | https://en.wikipedia.org/wiki/Great%20ditrigonal%20dodecicosidodecahedron | In geometry, the great ditrigonal dodecicosidodecahedron (or great dodekified icosidodecahedron) is a nonconvex uniform polyhedron, indexed as U42. It has 44 faces (20 triangles, 12 pentagons, and 12 decagrams), 120 edges, and 60 vertices. Its vertex figure is an isosceles trapezoid.
Related polyhedra
It shares its vertex arrangement with the truncated dodecahedron. It additionally shares its edge arrangement with the great icosicosidodecahedron (having the triangular and pentagonal faces in common) and the great dodecicosahedron (having the decagrammic faces in common).
See also
List of uniform polyhedra
References
External links
Uniform polyhedra | Great ditrigonal dodecicosidodecahedron | [
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4,157,482 | https://en.wikipedia.org/wiki/Great%20dodecicosidodecahedron | In geometry, the great dodecicosidodecahedron (or great dodekicosidodecahedron) is a nonconvex uniform polyhedron, indexed as U61. It has 44 faces (20 triangles, 12 pentagrams and 12 decagrams), 120 edges and 60 vertices.
Related polyhedra
It shares its vertex arrangement with the truncated great dodecahedron and the uniform compounds of 6 or 12 pentagonal prisms. It additionally shares its edge arrangement with the nonconvex great rhombicosidodecahedron (having the triangular and pentagrammic faces in common), and with the great rhombidodecahedron (having the decagrammic faces in common).
See also
List of uniform polyhedra
References
External links
Uniform polyhedra | Great dodecicosidodecahedron | [
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4,157,496 | https://en.wikipedia.org/wiki/Small%20icosicosidodecahedron | In geometry, the small icosicosidodecahedron (or small icosified icosidodecahedron) is a nonconvex uniform polyhedron, indexed as U31. It has 52 faces (20 triangles, 12 pentagrams, and 20 hexagons), 120 edges, and 60 vertices.
Related polyhedra
It shares its vertex arrangement with the great stellated truncated dodecahedron. It additionally shares its edges with the small ditrigonal dodecicosidodecahedron (having the triangular and pentagrammic faces in common) and the small dodecicosahedron (having the hexagonal faces in common).
See also
List of uniform polyhedra
References
External links
Uniform polyhedra | Small icosicosidodecahedron | [
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4,157,502 | https://en.wikipedia.org/wiki/Rhombidodecadodecahedron | In geometry, the rhombidodecadodecahedron is a nonconvex uniform polyhedron, indexed as U38. It has 54 faces (30 squares, 12 pentagons and 12 pentagrams), 120 edges and 60 vertices. It is given a Schläfli symbol t0,2, and by the Wythoff construction this polyhedron can also be named a cantellated great dodecahedron.
Cartesian coordinates
Cartesian coordinates for the vertices of a uniform great rhombicosidodecahedron are all the even permutations of
(±1/τ2, 0, ±τ2)
(±1, ±1, ±)
(±2, ±1/τ, ±τ)
where τ = (1+)/2 is the golden ratio (sometimes written φ).
Related polyhedra
It shares its vertex arrangement with the uniform compounds of 10 or 20 triangular prisms. It additionally shares its edges with the icosidodecadodecahedron (having the pentagonal and pentagrammic faces in common) and the rhombicosahedron (having the square faces in common).
Medial deltoidal hexecontahedron
The medial deltoidal hexecontahedron (or midly lanceal ditriacontahedron) is a nonconvex isohedral polyhedron. It is the dual of the rhombidodecadodecahedron. It has 60 intersecting quadrilateral faces.
See also
List of uniform polyhedra
References
External links
Uniform polyhedra and duals
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4,157,510 | https://en.wikipedia.org/wiki/Icositruncated%20dodecadodecahedron | In geometry, the icositruncated dodecadodecahedron or icosidodecatruncated icosidodecahedron is a nonconvex uniform polyhedron, indexed as U45.
Convex hull
Its convex hull is a nonuniform truncated icosidodecahedron.
Cartesian coordinates
Cartesian coordinates for the vertices of an icositruncated dodecadodecahedron are all the even permutations of
where is the golden ratio.
Related polyhedra
Tridyakis icosahedron
The tridyakis icosahedron is the dual polyhedron of the icositruncated dodecadodecahedron. It has 44 vertices, 180 edges, and 120 scalene triangular faces.
See also
Catalan solid Duals to convex uniform polyhedra
Uniform polyhedra
List of uniform polyhedra
References
Photo on page 96, Dorman Luke construction and stellation pattern on page 97.
External links
Uniform polyhedra | Icositruncated dodecadodecahedron | [
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4,157,518 | https://en.wikipedia.org/wiki/Truncated%20dodecadodecahedron | In geometry, the truncated dodecadodecahedron (or stellatruncated dodecadodecahedron) is a nonconvex uniform polyhedron, indexed as U59. It is given a Schläfli symbol It has 54 faces (30 squares, 12 decagons, and 12 decagrams), 180 edges, and 120 vertices. The central region of the polyhedron is connected to the exterior via 20 small triangular holes.
The name truncated dodecadodecahedron is somewhat misleading: truncation of the dodecadodecahedron would produce rectangular faces rather than squares, and the pentagram faces of the dodecadodecahedron would turn into truncated pentagrams rather than decagrams. However, it is the quasitruncation of the dodecadodecahedron, as defined by . For this reason, it is also known as the quasitruncated dodecadodecahedron. Coxeter et al. credit its discovery to a paper published in 1881 by Austrian mathematician Johann Pitsch.
Cartesian coordinates
Cartesian coordinates for the vertices of a truncated dodecadodecahedron are all the triples of numbers obtained by circular shifts and sign changes from the following points (where is the golden ratio):
Each of these five points has eight possible sign patterns and three possible circular shifts, giving a total of 120 different points.
As a Cayley graph
The truncated dodecadodecahedron forms a Cayley graph for the symmetric group on five elements, as generated by two group members: one that swaps the first two elements of a five-tuple, and one that performs a circular shift operation on the last four elements. That is, the 120 vertices of the polyhedron may be placed in one-to-one correspondence with the 5! permutations on five elements, in such a way that the three neighbors of each vertex are the three permutations formed from it by swapping the first two elements or circularly shifting (in either direction) the last four elements.
Related polyhedra
Medial disdyakis triacontahedron
The medial disdyakis triacontahedron is a nonconvex isohedral polyhedron. It is the dual of the uniform truncated dodecadodecahedron.
See also
List of uniform polyhedra
References
External links
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4,157,522 | https://en.wikipedia.org/wiki/Great%20truncated%20icosidodecahedron | In geometry, the great truncated icosidodecahedron (or great quasitruncated icosidodecahedron or stellatruncated icosidodecahedron) is a nonconvex uniform polyhedron, indexed as U68. It has 62 faces (30 squares, 20 hexagons, and 12 decagrams), 180 edges, and 120 vertices. It is given a Schläfli symbol and Coxeter-Dynkin diagram, .
Cartesian coordinates
Cartesian coordinates for the vertices of a great truncated icosidodecahedron centered at the origin are all the even permutations of
where is the golden ratio.
Related polyhedra
Great disdyakis triacontahedron
The great disdyakis triacontahedron (or trisdyakis icosahedron) is a nonconvex isohedral polyhedron. It is the dual of the great truncated icosidodecahedron. Its faces are triangles.
Proportions
The triangles have one angle of , one of and one of The dihedral angle equals Part of each triangle lies within the solid, hence is invisible in solid models.
See also
List of uniform polyhedra
References
p. 96
External links
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4,157,558 | https://en.wikipedia.org/wiki/Great%20snub%20icosidodecahedron | In geometry, the great snub icosidodecahedron is a nonconvex uniform polyhedron, indexed as U57. It has 92 faces (80 triangles and 12 pentagrams), 150 edges, and 60 vertices. It can be represented by a Schläfli symbol sr{,3}, and Coxeter-Dynkin diagram .
This polyhedron is the snub member of a family that includes the great icosahedron, the great stellated dodecahedron and the great icosidodecahedron.
In the book Polyhedron Models by Magnus Wenninger, the polyhedron is misnamed great inverted snub icosidodecahedron, and vice versa.
Cartesian coordinates
Let be the positive zero of the polynomial , where is the golden ratio. Let the point be given by
.
Let the matrix be given by
.
is the rotation around the axis by an angle of , counterclockwise. Let the linear transformations
be the transformations which send a point to the even permutations of with an even number of minus signs.
The transformations constitute the group of rotational symmetries of a regular tetrahedron.
The transformations , constitute the group of rotational symmetries of a regular icosahedron.
Then the 60 points are the vertices of a great snub icosahedron. The edge length equals , the circumradius equals , and the midradius equals .
For a great snub icosidodecahedron whose edge length is 1,
the circumradius is
Its midradius is
The four positive real roots of the sextic in ,
are, in order, the circumradii of the great retrosnub icosidodecahedron (U74), great snub icosidodecahedron (U57), great inverted snub icosidodecahedron (U69) and snub dodecahedron (U29).
Related polyhedra
Great pentagonal hexecontahedron
The great pentagonal hexecontahedron (or great petaloid ditriacontahedron) is a nonconvex isohedral polyhedron and dual to the uniform great snub icosidodecahedron. It has 60 intersecting irregular pentagonal faces, 120 edges, and 92 vertices.
Proportions
Denote the golden ratio by . Let be the negative zero of the polynomial . Then each pentagonal face has four equal angles of and one angle of . Each face has three long and two short edges. The ratio between the lengths of the long and the short edges is given by
.
The dihedral angle equals . Part of each face lies inside the solid, hence is invisible in solid models. The other two zeroes of the polynomial play a similar role in the description of the great inverted pentagonal hexecontahedron and the great pentagrammic hexecontahedron.
See also
List of uniform polyhedra
Great inverted snub icosidodecahedron
Great retrosnub icosidodecahedron
References
External links
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4,157,567 | https://en.wikipedia.org/wiki/Small%20snub%20icosicosidodecahedron | In geometry, the small snub icosicosidodecahedron or snub disicosidodecahedron is a uniform star polyhedron, indexed as U32. It has 112 faces (100 triangles and 12 pentagrams), 180 edges, and 60 vertices. Its stellation core is a truncated pentakis dodecahedron. It also called a holosnub icosahedron,
The 40 non-snub triangular faces form 20 coplanar pairs, forming star hexagons that are not quite regular. Unlike most snub polyhedra, it has reflection symmetries.
Convex hull
Its convex hull is a nonuniform truncated icosahedron.
Cartesian coordinates
Let be largest (least negative) zero of the polynomial , where is the golden ratio. Let the point be given by
.
Let the matrix be given by
.
is the rotation around the axis by an angle of , counterclockwise. Let the linear transformations
be the transformations which send a point to the even permutations of with an even number of minus signs.
The transformations constitute the group of rotational symmetries of a regular tetrahedron.
The transformations , constitute the group of rotational symmetries of a regular icosahedron.
Then the 60 points are the vertices of a small snub icosicosidodecahedron. The edge length equals , the circumradius equals , and the midradius equals .
For a small snub icosicosidodecahedron whose edge length is 1,
the circumradius is
Its midradius is
The other zero of plays a similar role in the description of the small retrosnub icosicosidodecahedron.
See also
List of uniform polyhedra
Small retrosnub icosicosidodecahedron
External links
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4,157,575 | https://en.wikipedia.org/wiki/Snub%20dodecadodecahedron | In geometry, the snub dodecadodecahedron is a nonconvex uniform polyhedron, indexed as . It has 84 faces (60 triangles, 12 pentagons, and 12 pentagrams), 150 edges, and 60 vertices. It is given a Schläfli symbol as a snub great dodecahedron.
Cartesian coordinates
Let be the smallest real zero of the polynomial . Denote by the golden ratio. Let the point be given by
.
Let the matrix be given by
.
is the rotation around the axis by an angle of , counterclockwise. Let the linear transformations
be the transformations which send a point to the even permutations of with an even number of minus signs.
The transformations constitute the group of rotational symmetries of a regular tetrahedron.
The transformations , constitute the group of rotational symmetries of a regular icosahedron.
Then the 60 points are the vertices of a snub dodecadodecahedron. The edge length equals , the circumradius equals , and the midradius equals .
For a great snub icosidodecahedron whose edge length is 1,
the circumradius is
Its midradius is
The other real root of P plays a similar role in the description of the Inverted snub dodecadodecahedron
Related polyhedra
Medial pentagonal hexecontahedron
The medial pentagonal hexecontahedron is a nonconvex isohedral polyhedron. It is the dual of the snub dodecadodecahedron. It has 60 intersecting irregular pentagonal faces.
See also
List of uniform polyhedra
Inverted snub dodecadodecahedron
References
External links
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4,157,586 | https://en.wikipedia.org/wiki/Ditrigonal%20dodecadodecahedron | In geometry, the ditrigonal dodecadodecahedron (or ditrigonary dodecadodecahedron) is a nonconvex uniform polyhedron, indexed as U41. It has 24 faces (12 pentagons and 12 pentagrams), 60 edges, and 20 vertices. It has extended Schläfli symbol b{5,}, as a blended great dodecahedron, and Coxeter diagram . It has 4 Schwarz triangle equivalent constructions, for example Wythoff symbol 3 | 5, and Coxeter diagram .
Related polyhedra
Its convex hull is a regular dodecahedron. It additionally shares its edge arrangement with the small ditrigonal icosidodecahedron (having the pentagrammic faces in common), the great ditrigonal icosidodecahedron (having the pentagonal faces in common), and the regular compound of five cubes.
Furthermore, it may be viewed as a facetted dodecahedron: the pentagrammic faces are inscribed in the dodecahedron's pentagons. Its dual, the medial triambic icosahedron, is a stellation of the icosahedron.
It is topologically equivalent to a quotient space of the hyperbolic order-6 pentagonal tiling, by distorting the pentagrams back into regular pentagons. As such, it is a regular polyhedron of index two:
See also
List of uniform polyhedra
References
External links
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4,157,594 | https://en.wikipedia.org/wiki/Great%20dodecahemidodecahedron | In geometry, the great dodecahemidodecahedron is a nonconvex uniform polyhedron, indexed as U70. It has 18 faces (12 pentagrams and 6 decagrams), 60 edges, and 30 vertices. Its vertex figure is a crossed quadrilateral.
Aside from the regular small stellated dodecahedron {5/2,5} and great stellated dodecahedron {5/2,3}, it is the only nonconvex uniform polyhedron whose faces are all non-convex regular polygons (star polygons), namely the star polygons {5/2} and {10/3}.
It is a hemipolyhedron with 6 decagrammic faces passing through the model center.
Related polyhedra
Its convex hull is the icosidodecahedron. It also shares its edge arrangement with the great icosidodecahedron (having the pentagrammic faces in common) and the great icosihemidodecahedron (having the decagrammic faces in common).
Gallery
See also
List of uniform polyhedra
References
External links
Uniform polyhedra and duals
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4,157,599 | https://en.wikipedia.org/wiki/Small%20dodecahemicosahedron | In geometry, the small dodecahemicosahedron (or great dodecahemiicosahedron) is a nonconvex uniform polyhedron, indexed as U62. It has 22 faces (12 pentagrams and 10 hexagons), 60 edges, and 30 vertices. Its vertex figure is a crossed quadrilateral.
It is a hemipolyhedron with ten hexagonal faces passing through the model center.
Related polyhedra
Its convex hull is the icosidodecahedron. It also shares its edge arrangement with the dodecadodecahedron (having the pentagrammic faces in common), and with the great dodecahemicosahedron (having the hexagonal faces in common).
Gallery
See also
List of uniform polyhedra
References
External links
Uniform polyhedra and duals
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4,157,609 | https://en.wikipedia.org/wiki/Great%20dodecahemicosahedron | In geometry, the great dodecahemicosahedron (or great dodecahemiicosahedron) is a nonconvex uniform polyhedron, indexed as U65. It has 22 faces (12 pentagons and 10 hexagons), 60 edges, and 30 vertices. Its vertex figure is a crossed quadrilateral.
It is a hemipolyhedron with ten hexagonal faces passing through the model center.
Related polyhedra
Its convex hull is the icosidodecahedron. It also shares its edge arrangement with the dodecadodecahedron (having the pentagonal faces in common), and with the small dodecahemicosahedron (having the hexagonal faces in common).
Great dodecahemicosacron
The great dodecahemicosacron is the dual of the great dodecahemicosahedron, and is one of nine dual hemipolyhedra. It appears visually indistinct from the small dodecahemicosacron.
Since the hemipolyhedra have faces passing through the center, the dual figures have corresponding vertices at infinity; properly, on the real projective plane at infinity. In Magnus Wenninger's Dual Models, they are represented with intersecting prisms, each extending in both directions to the same vertex at infinity, in order to maintain symmetry. In practice, the model prisms are cut off at a certain point that is convenient for the maker. Wenninger suggested these figures are members of a new class of stellation figures, called stellation to infinity. However, he also suggested that strictly speaking, they are not polyhedra because their construction does not conform to the usual definitions.
The great dodecahemicosahedron can be seen as having ten vertices at infinity.
See also
List of uniform polyhedra
Hemi-icosahedron - The ten vertices at infinity correspond directionally to the 10 vertices of this abstract polyhedron.
References
(Page 101, Duals of the (nine) hemipolyhedra)
External links
Uniform polyhedra and duals
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4,157,613 | https://en.wikipedia.org/wiki/Great%20icosihemidodecahedron | In geometry, the great icosihemidodecahedron (or great icosahemidodecahedron) is a nonconvex uniform polyhedron, indexed as U71. It has 26 faces (20 triangles and 6 decagrams), 60 edges, and 30 vertices. Its vertex figure is a crossed quadrilateral.
It is a hemipolyhedron with 6 decagrammic faces passing through the model center.
Related polyhedra
Its convex hull is the icosidodecahedron. It also shares its edge arrangement with the great icosidodecahedron (having the triangular faces in common), and with the great dodecahemidodecahedron (having the decagrammic faces in common).
Gallery
See also
List of uniform polyhedra
References
External links
Uniform polyhedra and duals
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4,157,622 | https://en.wikipedia.org/wiki/Icosidodecadodecahedron | In geometry, the icosidodecadodecahedron (or icosified dodecadodecahedron) is a nonconvex uniform polyhedron, indexed as U44. It has 44 faces (12 pentagons, 12 pentagrams and 20 hexagons), 120 edges and 60 vertices. Its vertex figure is a crossed quadrilateral.
Related polyhedra
It shares its vertex arrangement with the uniform compounds of 10 or 20 triangular prisms. It additionally shares its edges with the rhombidodecadodecahedron (having the pentagonal and pentagrammic faces in common) and the rhombicosahedron (having the hexagonal faces in common).
See also
List of uniform polyhedra
Snub icosidodecadodecahedron
References
External links
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4,157,630 | https://en.wikipedia.org/wiki/Small%20ditrigonal%20dodecicosidodecahedron | In geometry, the small ditrigonal dodecicosidodecahedron (or small dodekified icosidodecahedron) is a nonconvex uniform polyhedron, indexed as U43. It has 44 faces (20 triangles, 12 pentagrams and 12 decagons), 120 edges, and 60 vertices. Its vertex figure is a crossed quadrilateral.
Related polyhedra
It shares its vertex arrangement with the great stellated truncated dodecahedron. It additionally shares its edges with the small icosicosidodecahedron (having the triangular and pentagrammic faces in common) and the small dodecicosahedron (having the decagonal faces in common).
See also
List of uniform polyhedra
References
External links
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4,157,637 | https://en.wikipedia.org/wiki/Henry%20F.%20Schaefer%20III | Henry Frederick "Fritz" Schaefer III (born June 8, 1944) is an American computational, physical, and theoretical chemist.
Schaefer is the Graham Perdue Professor of Chemistry at the University of Georgia, where he is also the director of its Center for Computational Chemistry. He was previously a professor at the University of California, Berkeley, and the Wilfred T. Doherty Professor of Chemistry at the University of Texas at Austin, where he had been the inaugural director of the Institute for Theoretical Chemistry. He is one of the most highly cited chemists in the world, with a Thomson Reuters h-index of 121 as of 2020.
Schaefer is a fellow of the American Academy of Arts and Sciences, the American Physical Society, the American Association for the Advancement of Science, the Royal Society of Chemistry, the American Chemical Society, and an honorary fellow of the Chemical Research Society of India. He is the author of more than 1,600 scientific papers and was nominated for the Nobel Prize on five occasions.
Early life and education
Schaefer was born in Grand Rapids, Michigan, and was raised in Syracuse, New York; Menlo Park, California; and East Grand Rapids, Michigan. He was one of three children of Henry F. Schaefer Jr. and Janice Christine Trost, both graduates of the University of Michigan. As a high school student at local Rapids High School, Schaefer met his wife, Karen Rasmussen, and worked as a factory worker for a steel company.
Schaefer was educated at the Massachusetts Institute of Technology (MIT), where he initially intended to specialize in chemical engineering. After deciding to switch to chemical physics, he received a Bachelor of Science (B.S.) in the field in 1966. He had the opportunity to work with scientists George Whitesides, John C. Slater, F. Albert Cotton, and Richard C. Lord. Walter Thorson, Schaefer's academic advisor at MIT, recommended that he study quantum chemistry with Thorson's own guidance, under which Schaefer produced his senior thesis on the electronic structure of the compound cubane.
After graduating from MIT, Schaefer was awarded a fellowship from the National Defense Education Act Fellowship to study chemical physics at Stanford University and received his Ph.D. in 1969. At Stanford, he worked with chemist Frank E. Harris on ab initio electronic structure theory and quantum chemistry. For his Ph.D. thesis, he examined the electronic structure of first-row atoms and the oxygen molecule. He published 12 articles in journals including Physical Review and Physical Review Letters prior to defending his dissertation.
Career
Schaefer became an assistant professor of chemistry at the University of California, Berkeley in 1969, with access to Berkeley's Control Data Corporation (CDC) 6600 mainframe computer. Through collaborations with other researchers, he also gained access to resources at the University Computing Company (UCC) in Palo Alto, which had a UNIVAC 1108. He worked at Berkeley from 1969 to 1987, with one exception. Schaefer spent 1979-1980 as the Wilfred T. Doherty Professor of Chemistry and inaugural Director of the Institute for Theoretical Chemistry at the University of Texas, Austin, before deciding to return to Berkeley. During his time at Berkeley, Schaefer published 375 papers and several books, including The Electronic Structure of Atoms and Molecules: A Survey of Rigorous Quantum Mechanical Results (1972) and Quantum Chemistry: The Development of Ab Initio Methods in Molecular Electronic Structure Theory (1984), a survey of research with commentary.
In August 1987, Schaefer moved to the University of Georgia as Graham Perdue Professor of Chemistry and director of the newly formed Center for Computational Chemistry. With the help of an IBM 3090-200E mainframe (as well as later models) he and his research group developed various computer-based methods for advanced quantum chemistry.
Other academic appointments include Professeur d'Echange at the University of Paris (1977), Gastprofessur at the Eidgenossische Technische Hochshule (ETH), Zurich (1994, 1995, 1997, 2000, 2002, 2004, 2006, 2008, 2010), and David P. Craig Visiting professor at the Australian National University (1999). In 2004, he became Professor of Chemistry Emeritus, at UC Berkeley.
Schaefer became a member of the International Academy of Quantum Molecular Science (IAQMS) in 1984.
He was elected president of WATOC (World Association of Theoretical and Computational Chemists) in 1996, and held the position until 2005. He is also a Fellow of the American Physical Society as of 1977, of the American Association for the Advancement of Science as of 2002,
and of the American Academy of Arts and Sciences as of 2004.
As of January 2020, Schaefer was the author of more than 1,600 peer-reviewed publications. A majority of these appeared in the Journal of Chemical Physics, the Journal of the American Chemical Society, and the Journal of Physical Chemistry. He was the editor of Molecular Physics for 11 years. He has directed 123 Ph.D. students, as well as many postdoctoral associates and visiting professors, now working at 42 academic institutions around the world.
In 2023, Schaefer was the eighth highest paid faculty member at the University of Georgia, with a salary of $430,140.
Research
Research within the Schaefer group involves the use of computational hardware and theoretical methods to solve problems in molecular quantum mechanics. His contributions to the field of quantum chemistry include a paper challenging, on theoretical grounds, the geometry of triplet methylene as assigned by Nobel Prize-winning experimentalist Gerhard Herzberg; the development of the Z-vector method simplifying certain calculations of correlated systems; and a wide body of work undertaken in his research group on the geometries, properties, and reactions of chemical systems using highly accurate ab initio quantum chemical techniques. Many of these papers have predicted, or forced a reinterpretation of, experimental results.
Awards and honors
Schaefer was awarded the American Chemical Society's ACS Award in Pure Chemistry in 1979 "for the development of computational quantum chemistry into a reliable quantitative field of chemistry and for prolific exemplary calculations of broad chemical interest". The Pure Chemistry Award is given to the outstanding chemist in America under the age of 35. In 1983, he received the Leo Hendrik Baekeland award for the most distinguished North American chemist under the age of 40. In 1992, he was awarded the Centenary Prize of the Royal Society of Chemistry, London, for being "the first theoretical chemist successfully to challenge the accepted conclusion of a distinguished experimental group for a polyatomic molecule, namely methylene."
In 2003, Schaefer received the American Chemical Society Award in Theoretical Chemistry and the Ira Remsen Award of Johns Hopkins University. In 2004, a six-day conference was convened in Gyeongju, Korea on the “Theory and Applications of Computational Chemistry: A Celebration of 1000 Papers of Professor Henry F. Schaefer III.” Schaefer was honored with the $10,000 Joseph O. Hirschfelder Prize in 2005 by the University of Wisconsin's Theoretical Chemistry Institute.
In 2011, Schaefer received the Ide P. Trotter Prize from Texas A&M University.
In 2012, he received a Humboldt Research Award from the Alexander von Humboldt Foundation in Germany, and on March 29, 2012, he received the $20,000 SURA Distinguished Scientist Award from the Southeastern Universities Research Association for fulfilling SURA's mission of fostering excellence in scientific research.
In 2013, Schaefer received the Chemical Pioneer Award of the American Institute of Chemists. On March 18, 2014, Schaefer received the American Chemical Society Peter Debye Award in Physical Chemistry. In March 2015, Schaefer was elected as an Honorary Fellow of the Chemical Research Society of India. He returned to India to give his CRSI Honorary Fellow award lecture on February 6, 2016, at Panjab University in Chandigarh. Schaefer received the American Institute of Chemists Gold Medal on May 8, 2019.
Personal life
Schaefer married Karen Rasmussen, a graduate of Wells College and Stanford University, on September 2, 1966. He is an outspoken Christian, and has described himself as sympathetic to teleological arguments, but is primarily a "proponent of Jesus."
Religion and science
Schaefer is an active Protestant Christian educator who regularly speaks to university audiences, Christian groups and the public on science/faith issues. In 2003, he published Science and Christianity: Conflict or Coherence?, a collection of essays and talks on the subject. A second edition appeared in 2016. He is a member of the Christian Faculty Forum at the University of Georgia. Schaefer wrote the forward to William A. Dembski's 1998 book Mere Creation: Science, Faith and Intelligent Design. He is a creationist.
Schaefer is a proponent of intelligent design]] and a fellow of the Discovery Institute.
Published books
References
External links
The Center for Computational Quantum Chemistry Group Page
Henry F. Schaefer, PhD: UGA
HENRY F. SCHAEFER III: IAQMS
Henry Schaefer, Fellow-CSC: Discovery Institute
Dr. Henry F. "Fritz" Schaefer III: Leadership U
Public Lectures by Henry F. Schaefer III
Public Lectures by Henry F. Schaefer III Doc/PDF
Henry F. Schaefer III: Google Scholar
1944 births
Living people
Fellows of the American Academy of Arts and Sciences
21st-century American chemists
American Protestants
Christian scholars
Theoretical chemists
Discovery Institute fellows and advisors
Massachusetts Institute of Technology School of Science alumni
Stanford University alumni
University of Georgia faculty
Academic staff of ETH Zurich
Intelligent design advocates
Fellows of the International Society for Complexity, Information, and Design
Members of the International Academy of Quantum Molecular Science
Schrödinger Medal recipients
Computational chemists
People from Grand Rapids, Michigan
Fellows of the American Association for the Advancement of Science
Fellows of the American Physical Society
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4,157,639 | https://en.wikipedia.org/wiki/Nonconvex%20great%20rhombicosidodecahedron | In geometry, the nonconvex great rhombicosidodecahedron is a nonconvex uniform polyhedron, indexed as U67. It has 62 faces (20 triangles, 30 squares and 12 pentagrams), 120 edges, and 60 vertices. It is also called the quasirhombicosidodecahedron. It is given a Schläfli symbol Its vertex figure is a crossed quadrilateral.
This model shares the name with the convex great rhombicosidodecahedron, also known as the truncated icosidodecahedron.
Cartesian coordinates
Cartesian coordinates for the vertices of a nonconvex great rhombicosidodecahedron are all the even permutations of
where is the golden ratio.
Related polyhedra
It shares its vertex arrangement with the truncated great dodecahedron, and with the uniform compounds of 6 or 12 pentagonal prisms. It additionally shares its edge arrangement with the great dodecicosidodecahedron (having the triangular and pentagrammic faces in common), and the great rhombidodecahedron (having the square faces in common).
Great deltoidal hexecontahedron
The great deltoidal hexecontahedron is a nonconvex isohedral polyhedron. It is the dual of the nonconvex great rhombicosidodecahedron. It is visually identical to the great rhombidodecacron. It has 60 intersecting cross quadrilateral faces, 120 edges, and 62 vertices.
It is also called a great strombic hexecontahedron.
See also
List of uniform polyhedra
References
External links
Uniform polyhedra and duals
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4,157,645 | https://en.wikipedia.org/wiki/Great%20rhombihexahedron | In geometry, the great rhombihexahedron (or great rhombicube) is a nonconvex uniform polyhedron, indexed as U21. It has 18 faces (12 squares and 6 octagrams), 48 edges, and 24 vertices. Its dual is the great rhombihexacron. Its vertex figure is a crossed quadrilateral.
Orthogonal projections
Gallery
Related polyhedra
It shares the vertex arrangement with the convex truncated cube. It additionally shares its edge arrangement with the nonconvex great rhombicuboctahedron (having 12 square faces in common), and with the great cubicuboctahedron (having the octagrammic faces in common).
It may be constructed as the exclusive or (blend) of three octagrammic prisms. Similarly, the small rhombihexahedron may be constructed as the exclusive or of three octagonal prisms.
Great rhombihexacron
The great rhombihexacron is a nonconvex isohedral polyhedron. It is the dual of the uniform great rhombihexahedron (U21). It has 24 identical bow-tie-shaped faces, 18 vertices, and 48 edges.
It has 12 outer vertices which have the same vertex arrangement as the cuboctahedron, and 6 inner vertices with the vertex arrangement of an octahedron.
As a surface geometry, it can be seen as visually similar to a Catalan solid, the disdyakis dodecahedron, with much taller rhombus-based pyramids joined to each face of a rhombic dodecahedron.
See also
List of uniform polyhedra
References
uniform polyhedra and duals
External links
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4,157,654 | https://en.wikipedia.org/wiki/Great%20dodecicosahedron | In geometry, the great dodecicosahedron (or great dodekicosahedron) is a nonconvex uniform polyhedron, indexed as U63. It has 32 faces (20 hexagons and 12 decagrams), 120 edges, and 60 vertices. Its vertex figure is a crossed quadrilateral.
It has a composite Wythoff symbol, 3 ( ) |, requiring two different Schwarz triangles to generate it: (3 ) and (3 ). (3 | represents the great dodecicosahedron with an extra 12 pentagons, and 3 | represents it with an extra 20 triangles.)
Its vertex figure 6... is also ambiguous, having two clockwise and two counterclockwise faces around each vertex.
Related polyhedra
It shares its vertex arrangement with the truncated dodecahedron. It additionally shares its edge arrangement with the great icosicosidodecahedron (having the hexagonal faces in common) and the great ditrigonal dodecicosidodecahedron (having the decagrammic faces in common).
Gallery
See also
List of uniform polyhedra
References
External links
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4,157,661 | https://en.wikipedia.org/wiki/Great%20rhombidodecahedron | In geometry, the great rhombidodecahedron is a nonconvex uniform polyhedron, indexed as U73. It has 42 faces (30 squares, 12 decagrams), 120 edges and 60 vertices. Its vertex figure is a crossed quadrilateral.
Related polyhedra
It shares its vertex arrangement with the truncated great dodecahedron and the uniform compounds of 6 or 12 pentagonal prisms. It additionally shares its edge arrangement with the nonconvex great rhombicosidodecahedron (having the square faces in common), and with the great dodecicosidodecahedron (having the decagrammic faces in common).
Gallery
See also
List of uniform polyhedra
References
External links
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4,157,669 | https://en.wikipedia.org/wiki/Inverted%20snub%20dodecadodecahedron | In geometry, the inverted snub dodecadodecahedron (or vertisnub dodecadodecahedron) is a nonconvex uniform polyhedron, indexed as U60. It is given a Schläfli symbol
Cartesian coordinates
Let be the largest real zero of the polynomial . Denote by the golden ratio. Let the point be given by
.
Let the matrix be given by
.
is the rotation around the axis by an angle of , counterclockwise. Let the linear transformations
be the transformations which send a point to the even permutations of with an even number of minus signs.
The transformations constitute the group of rotational symmetries of a regular tetrahedron.
The transformations , constitute the group of rotational symmetries of a regular icosahedron.
Then the 60 points are the vertices of a snub dodecadodecahedron. The edge length equals , the circumradius equals , and the midradius equals .
For a great snub icosidodecahedron whose edge length is 1,
the circumradius is
Its midradius is
The other real root of P plays a similar role in the description of the Snub dodecadodecahedron
Related polyhedra
Medial inverted pentagonal hexecontahedron
The medial inverted pentagonal hexecontahedron (or midly petaloid ditriacontahedron) is a nonconvex isohedral polyhedron. It is the dual of the uniform inverted snub dodecadodecahedron. Its faces are irregular nonconvex pentagons, with one very acute angle.
Proportions
Denote the golden ratio by , and let be the largest (least negative) real zero of the polynomial . Then each face has three equal angles of , one of and one of . Each face has one medium length edge, two short and two long ones. If the medium length is , then the short edges have length
and the long edges have length
The dihedral angle equals . The other real zero of the polynomial plays a similar role for the medial pentagonal hexecontahedron.
See also
List of uniform polyhedra
Snub dodecadodecahedron
References
p. 124
External links
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4,157,674 | https://en.wikipedia.org/wiki/Great%20snub%20dodecicosidodecahedron | In geometry, the great snub dodecicosidodecahedron (or great snub dodekicosidodecahedron) is a nonconvex uniform polyhedron, indexed as U64. It has 104 faces (80 triangles and 24 pentagrams), 180 edges, and 60 vertices. It has Coxeter diagram . It has the unusual feature that its 24 pentagram faces occur in 12 coplanar pairs.
Cartesian coordinates
Let the point be given by
,
where is the golden ratio.
Let the matrix be given by
.
is the rotation around the axis by an angle of , counterclockwise. Let the linear transformations
be the transformations which send a point to the even permutations of with an even number of minus signs.
The transformations constitute the group of rotational symmetries of a regular tetrahedron.
The transformations , constitute the group of rotational symmetries of a regular icosahedron.
Then the 60 points are the vertices of a great snub dodecicosidodecahedron. The edge length equals , the circumradius equals , and the midradius equals .
For a great snub dodecicosidodecahedron whose edge length is 1,
the circumradius is
.
Its midradius is
.
Related polyhedra
It shares its vertices and edges, as well as 20 of its triangular faces and all its pentagrammic faces, with the great dirhombicosidodecahedron, (although the latter has 60 edges not contained in the great snub dodecicosidodecahedron). It shares its other 60 triangular faces (and its pentagrammic faces again) with the great disnub dirhombidodecahedron.
The edges and triangular faces also occur in the compound of twenty octahedra. In addition, 20 of the triangular faces occur in one enantiomer of the compound of twenty tetrahemihexahedra, and the other 60 triangular faces occur in the other enantiomer.
Gallery
See also
List of uniform polyhedra
References
External links
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4,157,679 | https://en.wikipedia.org/wiki/Great%20inverted%20snub%20icosidodecahedron | In geometry, the great inverted snub icosidodecahedron (or great vertisnub icosidodecahedron) is a uniform star polyhedron, indexed as U69. It is given a Schläfli symbol and Coxeter-Dynkin diagram . In the book Polyhedron Models by Magnus Wenninger, the polyhedron is misnamed great snub icosidodecahedron, and vice versa.
Cartesian coordinates
Let be the largest (least negative) negative zero of the polynomial , where is the golden ratio. Let the point be given by
.
Let the matrix be given by
.
is the rotation around the axis by an angle of , counterclockwise. Let the linear transformations
be the transformations which send a point to the even permutations of with an even number of minus signs.
The transformations constitute the group of rotational symmetries of a regular tetrahedron.
The transformations , constitute the group of rotational symmetries of a regular icosahedron.
Then the 60 points are the vertices of a great snub icosahedron. The edge length equals , the circumradius equals , and the midradius equals .
For a great snub icosidodecahedron whose edge length is 1,
the circumradius is
Its midradius is
The four positive real roots of the sextic in ,
are the circumradii of the snub dodecahedron (U29), great snub icosidodecahedron (U57), great inverted snub icosidodecahedron (U69), and great retrosnub icosidodecahedron (U74).
Related polyhedra
Great inverted pentagonal hexecontahedron
The great inverted pentagonal hexecontahedron (or petaloidal trisicosahedron) is a nonconvex isohedral polyhedron. It is composed of 60 concave pentagonal faces, 150 edges and 92 vertices.
It is the dual of the uniform great inverted snub icosidodecahedron.
Proportions
Denote the golden ratio by . Let be the smallest positive zero of the polynomial . Then each pentagonal face has four equal angles of and one angle of . Each face has three long and two short edges. The ratio between the lengths of the long and the short edges is given by
.
The dihedral angle equals . Part of each face lies inside the solid, hence is invisible in solid models. The other two zeroes of the polynomial play a similar role in the description of the great pentagonal hexecontahedron and the great pentagrammic hexecontahedron.
See also
List of uniform polyhedra
Great snub icosidodecahedron
Great retrosnub icosidodecahedron
References
p. 126
External links
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4,157,687 | https://en.wikipedia.org/wiki/Snub%20icosidodecadodecahedron | In geometry, the snub icosidodecadodecahedron is a nonconvex uniform polyhedron, indexed as U46. It has 104 faces (80 triangles, 12 pentagons, and 12 pentagrams), 180 edges, and 60 vertices. As the name indicates, it belongs to the family of snub polyhedra.
Cartesian coordinates
Let be the real zero of the polynomial . The number is known as the plastic ratio. Denote by the golden ratio. Let the point be given by
.
Let the matrix be given by
.
is the rotation around the axis by an angle of , counterclockwise. Let the linear transformations
be the transformations which send a point to the even permutations of with an even number of minus signs.
The transformations constitute the group of rotational symmetries of a regular tetrahedron.
The transformations , constitute the group of rotational symmetries of a regular icosahedron.
Then the 60 points are the vertices of a snub icosidodecadodecahedron. The edge length equals , the circumradius equals , and the midradius equals .
For a snub icosidodecadodecahedron whose edge length is 1,
the circumradius is
Its midradius is
Related polyhedra
Medial hexagonal hexecontahedron
The medial hexagonal hexecontahedron is a nonconvex isohedral polyhedron. It is the dual of the uniform snub icosidodecadodecahedron.
See also
List of uniform polyhedra
References
External links
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4,157,694 | https://en.wikipedia.org/wiki/Small%20retrosnub%20icosicosidodecahedron | In geometry, the small retrosnub icosicosidodecahedron (also known as a retrosnub disicosidodecahedron, small inverted retrosnub icosicosidodecahedron, or retroholosnub icosahedron) is a nonconvex uniform polyhedron, indexed as . It has 112 faces (100 triangles and 12 pentagrams), 180 edges, and 60 vertices. It is given a Schläfli symbol sr{⁵/₃,³/₂}.
The 40 non-snub triangular faces form 20 coplanar pairs, forming star hexagons that are not quite regular. Unlike most snub polyhedra, it has reflection symmetries.
George Olshevsky nicknamed it the yog-sothoth (after the Cthulhu Mythos deity).
Convex hull
Its convex hull is a nonuniform truncated dodecahedron.
Cartesian coordinates
Let be the smallest (most negative) zero of the polynomial , where is the golden ratio. Let the point be given by
.
Let the matrix be given by
.
is the rotation around the axis by an angle of , counterclockwise. Let the linear transformations
be the transformations which send a point to the even permutations of with an even number of minus signs.
The transformations constitute the group of rotational symmetries of a regular tetrahedron.
The transformations , constitute the group of rotational symmetries of a regular icosahedron.
Then the 60 points are the vertices of a small snub icosicosidodecahedron. The edge length equals , the circumradius equals , and the midradius equals .
For a small snub icosicosidodecahedron whose edge length is 1,
the circumradius is
Its midradius is
The other zero of plays a similar role in the description of the small snub icosicosidodecahedron.
See also
List of uniform polyhedra
Small snub icosicosidodecahedron
References
External links
Uniform polyhedra | Small retrosnub icosicosidodecahedron | [
"Physics"
] | 432 | [
"Uniform polytopes",
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] |
4,157,697 | https://en.wikipedia.org/wiki/Great%20retrosnub%20icosidodecahedron | In geometry, the great retrosnub icosidodecahedron or great inverted retrosnub icosidodecahedron is a nonconvex uniform polyhedron, indexed as . It has 92 faces (80 triangles and 12 pentagrams), 150 edges, and 60 vertices. It is given a Schläfli symbol
Cartesian coordinates
Let be the smallest (most negative) zero of the polynomial , where is the golden ratio. Let the point be given by
.
Let the matrix be given by
.
is the rotation around the axis by an angle of , counterclockwise. Let the linear transformations
be the transformations which send a point to the even permutations of with an even number of minus signs.
The transformations constitute the group of rotational symmetries of a regular tetrahedron.
The transformations , constitute the group of rotational symmetries of a regular icosahedron.
Then the 60 points are the vertices of a great snub icosahedron. The edge length equals , the circumradius equals , and the midradius equals .
For a great snub icosidodecahedron whose edge length is 1,
the circumradius is
Its midradius is
The four positive real roots of the sextic in ,
are the circumradii of the snub dodecahedron (U29), great snub icosidodecahedron (U57), great inverted snub icosidodecahedron (U69), and great retrosnub icosidodecahedron (U74).
See also
List of uniform polyhedra
Great snub icosidodecahedron
Great inverted snub icosidodecahedron
References
External links
Uniform polyhedra | Great retrosnub icosidodecahedron | [
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] | 370 | [
"Uniform polytopes",
"Uniform polyhedra",
"Symmetry"
] |
4,157,820 | https://en.wikipedia.org/wiki/California%20State%20Water%20Project | The California State Water Project, commonly known as the SWP, is a state water management project in the U.S. state of California under the supervision of the California Department of Water Resources. The SWP is one of the largest public water and power utilities in the world, providing drinking water for more than 27 million people and generating an average of 6,500 GWh of hydroelectricity annually. However, as it is the largest single consumer of power in the state itself, it has a net usage of 5,100 GWh.
The SWP collects water from rivers in Northern California and redistributes it to the water-scarce but populous cities through a network of aqueducts, pumping stations and power plants. About 70% of the water provided by the project is used for urban areas and industry in Southern California and the San Francisco Bay Area, and 30% is used for irrigation in the Central Valley. To reach Southern California, the water must be pumped over the Tehachapi Mountains, with at the Edmonston Pumping Plant alone, the highest single water lift in the world. The SWP shares many facilities with the federal Central Valley Project (CVP), which primarily serves agricultural users. Water can be interchanged between SWP and CVP canals as needed to meet peak requirements for project constituents. The SWP provides estimated annual benefits of $400 billion to California's economy.
Since its inception in 1960, the SWP has required the construction of 21 dams and more than of canals, pipelines and tunnels, although these constitute only a fraction of the facilities originally proposed. As a result, the project has only delivered an average of annually, as compared to total entitlements of . Environmental concerns caused by the dry-season removal of water from the Sacramento–San Joaquin River Delta, a sensitive estuary region, have often led to further reductions in water delivery. Work continues today to expand the SWP's water delivery capacity while finding solutions for the environmental impacts of water diversion.
History
The original purpose of the project was to provide water for arid Southern California, whose local water resources and share of the Colorado River were insufficient to sustain the region's growth. The SWP was rooted in two proposals. The United Western Investigation of 1951, a study by the U.S. Bureau of Reclamation, assessed the feasibility of interbasin water transfers in the Western United States. In California, this plan contemplated the construction of dams on rivers draining to California's North Coast – the wild and undammed Klamath, Eel, Mad and Smith River systems – and tunnels to carry the impounded water to the Sacramento River system, where it could be diverted southwards. In the same year, State Engineer A.D. Edmonston proposed the Feather River Project, which proposed the damming of the Feather River, a tributary of the Sacramento River, for the same purpose. The Feather River was much more accessible than the North Coast rivers, but did not have nearly as much water. Under both of the plans, a series of canals and pumps would carry the water south through the Central Valley to the foot of the Tehachapi Mountains, where it would pass through the Tehachapi Tunnel to reach Southern California.
Calls for a comprehensive statewide water management system (complementing the extensive, but primarily irrigation-based Central Valley Project) led to the creation of the California Department of Water Resources in 1956. The following year, the preliminary studies were compiled into the extensive California Water Plan, or Bulletin No. 3. The project was intended for "the control, protection, conservation, distribution, and utilization of the waters of California, to meet present and future needs for all beneficial uses and purposes in all areas of the state to the maximum feasible extent." California governor Pat Brown would later say it was to "correct an accident of people and geography".
The diversion of the North Coast rivers was abandoned in the plan's early stages after strong opposition from locals and concerns about the potential impact on the salmon in North Coast rivers. The California Water Plan would have to go ahead with the development of the Feather River alone, as proposed by Edmonston. The Burns-Porter Act of 1959 provided $1.75 billion of initial funding through a bond measure. Construction on Stage I of the project, which would deliver the first of water, began in 1960. Northern Californians opposed the measure as a boondoggle and an attempt to steal their water resources. In fact, the city of Los Angeles – which was to be one of the principal beneficiaries – also opposed the project; locals saw it as a ploy by politicians in the other Colorado River basin states to get Los Angeles to relinquish its share of the Colorado River. Historians largely attribute the success of the Burns-Porter Act and the State Water Project to major agribusiness lobbying, particularly by J.G. Boswell II of the J.G. Boswell cotton company. The bond was passed on an extremely narrow margin of 174,000 out of 5.8 million ballots cast. In 1966, the Metropolitan Water District passed Proposition W, a Southern California property tax bond to connect its regional water system to the new state project.
In 1961, ground was broken on Oroville Dam, and in 1963, work began on the California Aqueduct and San Luis Reservoir. The first deliveries to the Bay Area were made in 1962, and water reached the San Joaquin Valley by 1968. Due to concerns over the fault-ridden geography of the Tehachapi Mountains, the tunnel plan was scrapped; the water would have to be pumped over the mountains' crest. In 1973, the pumps and the East and West branches of the aqueduct were completed, and the first water was delivered to Southern California. A Peripheral Canal, which would have carried SWP water around the vulnerable and ecologically sensitive Sacramento–San Joaquin River Delta, was rejected in 1982 due to environmental concerns. The Coastal Branch, which delivers water to coastal central California, was completed in 1997.
Project description
Feather River facilities
The Feather River, a tributary of the Sacramento River, provides the primary watershed for the State Water Project. Runoff from the Feather River headwaters is captured in Antelope, Frenchman, and Davis reservoirs, which impound tributaries of the North and Middle forks of the Feather River. Collectively referred to as the Upper Feather River Lakes, these three reservoirs provide a combined storage capacity of about .
Water released from the Upper Feather River system flows into Lake Oroville, which is formed by the Oroville Dam several miles above the city of Oroville. At , Oroville is the tallest dam in the United States; by volume it is the largest dam in California. Authorized by an emergency flood control measure in 1957, Oroville Dam was built between 1961 and 1967 with the reservoir filling for the first time in 1968.
Lake Oroville has a capacity to store approximately of water which accounts for 61 percent of the SWP's total system storage capacity, and is the single most important reservoir of the project.
Water stored in Lake Oroville is released through the 819 MW Edward Hyatt pumped-storage powerplant and two other hydroelectric plants downstream of Oroville Dam, which together make up the Oroville-Thermalito Complex. The Thermalito Forebay and Afterbay support the 120 MW Thermalito Pumping-Generating Plant, and the Thermalito Diversion Dam supports a smaller 3.3 MW powerplant. The entire system generates approximately 2.2 billion kilowatt hours per year, making up about a third of the total power generated by SWP facilities.
Delta facilities
From Oroville, a regulated water flow travels down the Feather and Sacramento Rivers to the Sacramento–San Joaquin River Delta. North of Rio Vista, about per year is pumped into the North Bay Aqueduct, completed in 1988. The aqueduct delivers water to clients in Napa and Solano counties.
The vast majority of the SWP water is drawn through the Delta's complex estuary system into the Clifton Court Forebay, located northwest of Tracy on the southern end of the Delta. Here, the Harvey O. Banks Pumping Plant lifts water into the California Aqueduct. Completed in 1963, the eleven pump units can lift up to of water – upgraded in 1986 from its original capacity of across seven units.
From here the water flows briefly south along the California Aqueduct to the Bethany Reservoir. The South Bay Pumping Plant supplies the South Bay Aqueduct, which has delivered water west to Alameda County since 1962 and Santa Clara County since 1965. The aqueduct carries a maximum of per year. Up to of this water can be stored in Lake Del Valle, an offstream reservoir located near Livermore.
California Aqueduct
South of the Bay Area diversions, the bulk of the SWP water – ranging from per year – travels south along the western flank of the San Joaquin Valley through the California Aqueduct. The main section of the aqueduct stretches for ; it is composed mainly of concrete-lined canals but also includes of tunnels, of pipelines and of siphons. The aqueduct reaches a maximum width of and a maximum depth of ; some parts of the channel are capable of delivering more than . The section of the aqueduct that runs through the San Joaquin Valley includes multiple turnouts where water is released to irrigate roughly of land on the west side of the valley.
The aqueduct enters the O'Neill Forebay reservoir west of Volta, where water can be pumped into a giant offstream storage facility, San Luis Reservoir, formed by the nearby B.F. Sisk Dam. San Luis Reservoir is shared by the SWP and the federal Central Valley Project; here water can be switched between the California Aqueduct and Delta-Mendota Canal to cope with fluctuating demands. The SWP has a 50 percent share of the of storage available in San Luis Reservoir.
South of the San Luis Reservoir complex, the aqueduct steadily gains elevation through a series of massive pumping plants. Dos Amigos Pumping Plant is located shortly south of San Luis, lifting the water . Near Kettleman City, the Coastal Branch splits off from the main California Aqueduct. Buena Vista, Teerink and Chrisman Pumping Plants are located on the main aqueduct near the southern end of the San Joaquin Valley near Bakersfield. The aqueduct then reaches A.D. Edmonston Pumping Plant, which lifts the water over the Tehachapi Mountains that separate the San Joaquin Valley from Southern California. It is the highest pump-lift in the SWP, with a capacity of across fourteen units. Initial construction of Edmonston was completed in 1974, with the last three units installed in the 1980s.
Once reaching the crest of the Tehachapis, the aqueduct runs through a series of tunnels to the Tehachapi Afterbay, where its flow is partitioned between West and East Branches.
Coastal Branch
The Coastal Branch diverts about per year from the California Aqueduct to parts of San Luis Obispo and Santa Barbara counties. The aqueduct stretches for , and is mostly made up of buried pipeline. Pumping plants at Las Perillas, Badger Hill, Devil's Den, Bluestone, and Polonio Pass serve to lift the water over the California Coast Ranges. Once over the crest of the mountains, the water is reregulated in a series of small reservoirs numbered Tanks 1 through 5. The Coastal Branch was completed in 1994 following a severe drought that led to calls for importation of SWP water.
Through a pipeline known as the Central Coast Water Authority extension, completed in 1997, the Coastal Branch supplies water to Lake Cachuma, a reservoir on the Santa Ynez River.
West Branch
From the terminus of the main California Aqueduct at Tehachapi Afterbay, the West Branch carries water to a second reservoir, Quail Lake, via the Oso Pumping Plant. The water then runs south by gravity to the 78 MW William E. Warne Powerplant, located on the Pyramid Lake reservoir. The West Branch delivered about per year for the period 1995–2010.
From Pyramid Lake, water is released through the Angeles Tunnel to the Castaic Power Plant on Elderberry Forebay and the Castaic Lake reservoir located north of Santa Clarita. Castaic Power Plant is a pumped-storage hydroelectric plant capable of producing 1,247 MW on peak demand. Together, Pyramid and Castaic Lakes form the primary storage for West Branch water delivered to Southern California. Water is supplied to municipalities in Los Angeles and Ventura counties.
East Branch
The East Branch takes water from Tehachapi Afterbay along the north side of the San Gabriel Mountains and San Bernardino Mountains to the Silverwood Lake reservoir, which can hold . From here it passes through a tunnel under the San Bernardino Mountains to the Devil Canyon Powerplant, the largest "recovery plant", or aqueduct power plant, of the SWP system. The water then flows through the Santa Ana Tunnel to Lake Perris, which can store up to .
Water deliveries through the East Branch averaged per year from 1995 through 2012. The East Branch principally provides water for cities and farms in the Inland Empire, Orange County, and other areas south of Los Angeles. Through Lake Perris, the Metropolitan Water District of Southern California receives a large portion of its water from the SWP. Water is also supplied to the San Diego Aqueduct through a connection from Perris to Lake Skinner, further south.
Proposed and unbuilt features
North Coast diversions
The original 1957 California Water Plan included provisions for dams on the Klamath, Eel, Mad and Smith Rivers of California's North Coast. Fed by prolific rainfall in the western Coast Ranges and Klamath Mountains, these rivers discharge more than to the Pacific each year, more than that of the entire Sacramento River system. The plan was basically a variation of a contemporary Bureau of Reclamation project, the Klamath Diversion.
A series of dams in these watersheds would shunt water through interbasin transfers into the Klamath River system. The centerpiece of the project would be a reservoir on the Klamath River – the largest man-made lake in California – from where the water would flow through the Trinity Tunnel into the Sacramento River, and thence to the canals and pump systems of the SWP. This would have provided between of water each year for the SWP. The diversion of the North Coast rivers, however were dropped from the initial SWP program.
In the mid-1960s, devastating flooding brought renewed interest in damming the North Coast rivers. The Department of Water Resources formed the State-Federal Interagency Task Force with the Bureau of Reclamation and the Army Corps of Engineers to develop plans for developing the rivers in the name of flood control – which would, incidentally, provide a way to divert some of their water into the SWP system. Although most of the proposed projects met their demise over political squabbles, one that persisted was the Dos Rios Project on the Eel River system, which would have involved constructing a gigantic dam on the Middle Fork of the Eel River, diverting water through the Grindstone Tunnel into the Sacramento Valley. Supporters of this project cited the disastrous Christmas flood of 1964 and the flood control benefits Dos Rios would provide to the Eel River basin.
The Klamath and Dos Rios diversions were heavily opposed by local towns and Native American tribes, whose land would have been flooded under the reservoirs. Fishermen expressed concerns over the impact of the dams on the salmon runs of North Coast rivers, especially the Klamath – the largest Pacific coast salmon river south of the Columbia River. The project would have eliminated 98 percent of the salmon spawning grounds on the Klamath. California Governor Ronald Reagan refused to approve the Dos Rios project, citing economic insensibility and fraudulent claims made by project proponents. The flood control benefits, for example, were largely exaggerated; the Dos Rios dam would have reduced the record Eel River flood crest of 1964 by only had it been in place.
In 1980, the North Coast rivers were incorporated into the National Wild and Scenic Rivers system, effectively eliminating the possibility of any projects to divert them.
Peripheral Canal/California WaterFix
California WaterFix, is a planned twin tunnel project that would extend through the center of the Delta, below ground. Earlier designs called for a Peripheral Canal to skirt the Delta to the east. The tunnels would draw water from the Sacramento River to bypass the Sacramento–San Joaquin River Delta, a vast estuary and agricultural region consisting of over of tidal waterways. Supporters of the canal and tunnel have included the Central Valley farmers and the Metropolitan Water District and urban developers in Los Angeles. They claim it would eliminate the need to pull water directly through this sensitive region, reducing salinity intrusion and water quality problems during the dry season. The canal was included in the initial SWP planning, and the lack of the canal is among the principal reasons the SWP has never been able to deliver its full entitlement.
Tunnel opponents believe the construction project would do extensive damage to the sensitive Delta ecosystem, farms and communities. Opponents also believe there will be long-term damage to the Delta ecosystem from fresh water being removed prior to flushing through the Delta and flowing more naturally to the San Francisco Bay.
Governor Jerry Brown had supported a ballot initiative approving the canal in the early 1980s, and stated his intention to finish the project in its tunnel form during his second governorship (2011–2019). His successor, Gavin Newsom, has also supported the project. Supporters of the tunnel argue that water being drawn from the southern intakes creates problems for wildlife and changes the natural flow in these areas, which would be corrected by drawing water from farther north. Supporters also claim that the California levees are also vulnerable to earthquakes and directing water away from them protects the supply of water. Delta farmers, communities, and commercial salmon and bass fishermen are especially concerned about the tunnel. However, some Delta scientists disagree. The new proposed canal would transport of water to Silicon Valley, southern California and the majority of it would be directed to the Central Valley, a location with political influence and interest in the canal being built.
Sites Reservoir
Since the 1980s, there has been interest in creating a large off-stream reservoir in the Sacramento Valley. Water "skimmed" off high winter flows in the Sacramento River would be pumped into a storage basin in the western side of the valley known as Sites Reservoir. The reservoir would hold about of water to be released into the Sacramento River during low-flow periods, boosting the water supply available for SWP entitlement holders and improving water quality in the Sacramento–San Joaquin Delta. This project has previously arisen in several forms, including proposals for a Glenn Reservoir or the Glenn-Colusa Complex on nearby streams, which would also have been receiving reservoirs for water sent east through the Dos Rios Project's Grindstone Tunnel or other transfers from North Coast rivers.
With its large storage capacity, Sites Reservoir would increase the production and flexibility of California's water management system, yielding of new water per year. This project is being seriously considered by the Department of Water Resources, as California's water system is expected to face serious shortfalls of per year by 2020. However, the project has been criticized for its high cost, and potential disruption of fish migration when large amounts of water are drawn from the Sacramento River during the wet season.
Los Banos Grandes
The Los Banos Grandes reservoir was first proposed in 1983 and would have served a similar purpose to Sites. The reservoir would have been located along the California Aqueduct several miles south of San Luis Reservoir, and would have allowed for the storage of water during wet years when extra water could be pumped from the Sacramento–San Joaquin Delta. Pumped-storage hydroelectric plants would have been built between Los Banos Grandes and the existing Los Banos flood control reservoir, and between that reservoir and the aqueduct. The current status of Los Banos Grandes remains uncertain, as the DWR has been unable to appropriate funding since the 1990s.
Modern issues
The existing SWP facilities are collectively known as Stage I. Stage II, which includes such works as the Peripheral Canal and Sites Reservoir, was to have been built beginning in the late 1970s and 1980s – but due to concerted opposition from Northern Californians, environmentalist groups and some economic interests, as well as the state's increasing debt, attempts to begin construction have all met with failure. Parties currently receiving SWP water are also opposed to its expansion, because water rates could be raised up to 300 percent to help pay for the cost. As a result, SWP capacity falls short by an average of each year; contractors only occasionally receive their full shares of water.
The disparity of costs to the project's various constituents has been a frequent source of controversy. Although the overall average cost of SWP water is $147 per acre-foot ($119 per 1,000 m3), agricultural users pay far less than their urban counterparts for SWP water. The Kern County Water Agency (the second largest SWP entitlement holder) pays around $45–50 per acre-foot ($36–41 per 1,000 m3) of SWP water, which is mostly used for irrigation. The Metropolitan Water District of Southern California (the largest entitlement holder) pays $298 per acre-foot ($241 per 1,000 m3). This basically means that cities are subsidizing the cost of farm water, even though the cities also provided primary funding for the construction of the SWP.
In the early 1970s, the SWP system still had a lot of "surplus" – water supply developed through the construction of Oroville Dam, which was running unused to the Pacific Ocean because the water delivery infrastructure for Southern California had not yet been completed (and when it was, southern California was slow to use the water). The surplus water was given for irrigation in the San Joaquin Valley instead. Because the water would only be a temporary supply, farmers were advised to use it for seasonal crops (such as alfalfa or hay) rather than permanent crops such as orchards. Nevertheless, many farmers used the water to develop new permanent crops, creating a dependency on SWP water that is technically part of Southern California's entitlement, This is now causing tensions as Southern California continues to increase its use of SWP water, decreasing the amount of surplus available to the system, especially in years of drought.
In dry years, water pumped from the Delta creates a hazard to spring-run salmon. As the Banks Pumping Plant pulls water from the Sacramento River southward across the Delta, it disrupts the normal flow direction of east to west that salmon smolt follow to the Pacific Ocean. Populations of salmon and steelhead trout have reached critically low levels in the decades after SWP water withdrawals began. The fish migration issue has become hotly contested in recent years, with rising support for the construction of the Peripheral Canal, which would divert water around the Delta, restoring the natural flow direction.
Water use and environmental problems associated with the SWP led to the creation of the CALFED Bay-Delta Program (CALFED) in 1994. The primary goals are to improve quality of SWP water while preventing further ecological damage in the Sacramento–San Joaquin Delta.
In January 2014, after the moderately dry year of 2012 and the record California drought of 2013, the Department of Water Resources announced that the SWP would be making zero deliveries that year, the first time in the project's history, due to dangerously low snowpack and reservoir levels. On April 18, 2014, the Department of Water Resources increased the SWP allocation back to five percent and that level remained until the initial allocation for 2015 was give on December 1, 2014.
Project data
Contracting water agencies
Dams and reservoirs
Background color denotes facility shared with Central Valley Project.
*This is the portion of total capacity of San Luis Reservoir allocated to SWP; the total capacity is
Aqueducts
Pump plants
Powerplants
See also
Central Valley Project
Patrick D. McGee (1916–70), California State Assembly member who fought for the State Water Project
Peripheral Canal
Water in California
South–North Water Transfer Project, a project with similar goals in China
References
Works cited
Further reading
External links
State Water Project - page at Maven's Notebook
California Department of Water Resources State Water Project overview
CALFED
State Water Project - Santa Clara Valley
Image of three California State Water Project employees picketing Castaic Reservoir, California, 1972. Los Angeles Times Photographic Archive (Collection 1429). UCLA Library Special Collections, Charles E. Young Research Library, University of California, Los Angeles.
Water management authorities in California
Water in California
Interbasin transfer
1960 establishments in California
Government agencies established in 1960
Public utilities established in 1960
Hydroelectric power plants in California | California State Water Project | [
"Environmental_science"
] | 4,994 | [
"Hydrology",
"Interbasin transfer"
] |
4,157,871 | https://en.wikipedia.org/wiki/Word%20superiority%20effect | In cognitive psychology, the word superiority effect (WSE) refers to the phenomenon that people have better recognition of letters presented within words as compared to isolated letters and to letters presented within nonword (orthographically illegal, unpronounceable letter array) strings. Studies have also found a WSE when letter identification within words is compared to letter identification within pseudowords (e.g. "WOSK") and pseudohomophones (e.g. "WERK").
The effect was first described by Cattell (1886), and important contributions came from Reicher (1969) and Wheeler (1970). Cattell first wrote, "I find it takes about twice as long to read...words which have no connexion as words which make sentences, and letters which have no connexions as letters which make words. When the words make sentences and the letters words, not only do the processes of seeing and naming overlap, but by one mental effort the subject can recognize a whole group of words or letters".
G. Reicher and D. Wheeler developed the basic experimental paradigm to study the WSE, referred to as the Reicher-Wheeler paradigm. In this paradigm, an observer is presented with a word or nonword string that is followed by a mask (brief stimulus to measure effects on behavior). The observer is then asked to name one of the letters from the cued position in that word or string making the test a two-alternative forced choice (2-AFC). For example, for the letter R in the word "card", an observer might be asked to choose between the letter R and T, and will usually be more efficient in doing so than if they are asked to make the same choice with the string of letters such as "cqrd". Each possible completion with the two possible letters in the word condition produce a word.
The WSE has since been exhaustively studied in the context of cognitive processes involved during reading. Large amounts of research have also been done to try to model the effect using connectionist networks.
Experimental task
The WSE has traditionally been tested using a tachistoscope, as the durations of the letter string presentations need to be carefully controlled. Recently, stimulus presentation software has allowed much simpler manipulation of presentation durations using computers. The WSE has also been described without a tachistoscope.
A string of letters, usually four or five, is flashed for several milliseconds onto a screen. Readers are then asked to choose which of two letters had been in the flashed string. For example, if "WOSK" had been flashed, a reader might have to decide whether "K" or "H" had been in "WOSK". A WSE arises when subjects choose the correct letter more consistently when letter strings are real words rather than nonwords (e.g. "WKRG") or single letters.
Hypotheses
The existence of a WSE generally implies that there is some type of access or encoding advantage that words have in the mind that pseudowords or single letters do not have. Various studies have proposed that the distinction is a result of pronounceability differences (nonwords are not pronounceable and therefore are not as easily remembered), frequency (real words are more frequently encountered and used), meaningfulness (real words have semantic value and therefore are better retained in memory), orthographic regularity (real words follow familiar spelling conventions and are therefore better retained in memory), or neighborhood density (real words tend to share more letters with other words than nonwords and therefore have more activation in the mind).
Other studies have proposed that the WSE is heavily affected or even induced by experimental factors, such as the type of masking used after the presentation of the word, or the duration of the masks.
Models
The two popular models claiming to explain the WSE are the interactive activation model (IAM) and the dual-route coding model (DRC) Neither of these models takes attention into account; This is a relationship looked into through research on the WSE. Evidence shows that the WSE persists without an observer's conscious awareness of the word presented, which implies that attention is neither necessary for WSE nor involved in this phenomenon. However, attentional focus has been demonstrated to modulate the WSE which agrees with recent neurophysiological data explaining that attention, in fact, modulates early stages of word processing.
The activation-verification model (AVM) is another model that was developed to account for reaction time data from lexical decision and naming tasks. The basic operations explored in the AVM that are involved in word and letter recognition are encoding, verification, and decision. Both the IAM and the AVM share many basic assumptions such as the fact that stimulus input activates spatially-specific letter units, that activated letter units, modulate the activity of word units, and that letter and word recognition are frequently affected by top-down processes (e.g. Reading the phrase "A cow says..." a person would guess "moo" and in checking that the word begins with 'm' ignores the rest of the letters).
The WSE and an interactive-activation model
The WSE has proven to be an important finding for word recognition models, and specifically is supported by Rumelhart and McClelland's interactive-activation model of word recognition. According to this model, when a reader is presented with a word, each letter in parallel will either stimulate or inhibit different feature detectors (e.g. a curved shape for "C", horizontal and vertical bars for "H", etc.). Those feature detectors will then stimulate or inhibit different letter detectors, which will finally stimulate or inhibit different word detectors. Some words can be activated through these stimulations. However, the fact that there is no meaning to the combination of letters can inhibit these words which were previously activated. Each activated connection would carry a different weight, and thus the word "WORK" in the example would be activated more than any other word (and therefore recognized by a reader).
According to this interactive-activation model, the WSE is explained as such: When the target letter is presented within a word, the feature detectors, letter detectors and word detectors will all be activated, adding weight to the final recognition of the stimulus. However, when only the letter is presented, only the letter detector level will be activated. Therefore, we may remember the presented stimulus word more clearly, and thereby be more accurate in identifying its component letters, as observed in the WSE.
Activation-verification model
The AVM deals with encoding, verification, and decision operations. Encoding is used to describe the early operations that lead to the unconscious activation of learned units in memory. After encoding, verification occurs. Verification often leads to the conscious recognition of a single lexical entry from the respondents. Verification is to be viewed as an independent, top-down analysis of stimulus that is guided by the stored, or previously learned, representation of a word. Real-time processing in verification can be mimicked by a computer simulation. Lastly, the factors affecting speed and accuracy of performance in a particular paradigm depend on whether decisions are based primarily on information from encoding or verification.
Adverse word superiority effect
One of the findings of the Johnston and McClelland report was that the WSE does not occur inevitably whenever we compare a word and a nonword. Rather, it depends somewhat upon the strategies that readers use during a task. If readers paid more attention to the letter in a particular position, they would experience the adverse word superiority effect. This is because the reader would no longer have the benefit of having the word detector level activated with as much weight if they neglected to focus on the full word.
See also
Tachistoscope
Missing letter effect
References
Further reading
Sternberg, Robert J. (2006). Cognitive Psychology; fourth edition.
Crowder, Robert G. and Wagner, Richard K. (1992). The Psychology of Reading, second edition. p. 79.
Harris, Margaret and Coltheart, Max. (1986) Language Processing in Children and Adults. p. 155.
Francis, Greg, Neath, Ian, Mackewn, Angie, and Goldthwaite, Danalee. (2004). Belmont: Wadsworth, p. 73–74.
External links
"The Science of Word Recognition" by Kevin Larson, 2004
Cognitive psychology
Reading (process) | Word superiority effect | [
"Biology"
] | 1,731 | [
"Behavioural sciences",
"Behavior",
"Cognitive psychology"
] |
4,158,051 | https://en.wikipedia.org/wiki/Paul%20Offit | Paul Allan Offit (born March 27, 1951) is an American pediatrician specializing in infectious diseases, vaccines, immunology, and virology. He is the co-inventor of a rotavirus vaccine. Offit is the Maurice R. Hilleman Professor of Vaccinology, professor of pediatrics at the Perelman School of Medicine at the University of Pennsylvania, former chief of the Division of Infectious Diseases (1992–2014), and the director of the Vaccine Education Center at the Children's Hospital of Philadelphia.
Offit is a member of the Food and Drug Administration (FDA) Vaccines and Related Biological Products Advisory Committee; a board member of Every Child By Two; a founding board member of the Autism Science Foundation (ASF); and a former member of the Centers for Disease Control (CDC) Advisory Committee on Immunization Practices.
Offit has published more than 130 papers in medical and scientific journals in the areas of rotavirus-specific immune responses and vaccine safety, and is the author or co-author of books on vaccines, vaccination, the rejection of medicine by some religious groups, and antibiotics. He is one of the most public faces of the scientific consensus that vaccines have no association with autism. As a result, he has been the frequent target of hate mail and death threats.
In 2023, he was elected to the American Philosophical Society.
Life
Offit grew up in Baltimore, the son of a shirtmaker. He went to his father's sales meetings and reacted negatively to the tall tales told by salespeople, instead preferring the clean and straightforward practice of science. When he was five years old, he was sent to a polio ward to recover from clubfoot surgery; this experience caused him to see children as vulnerable and helpless, and motivated him through the 25 years of the development of the rotavirus vaccine.
Offit decided to become a doctor, the first in his family. Offit earned his bachelor's degree from Tufts University and his M.D. from the University of Maryland, Baltimore. In 1980, he completed his residency training in Pediatrics at Children's Hospital of Pittsburgh. That year, he began a fellowship in infectious diseases at Children's Hospital of Philadelphia. One of his mentors was Maurice Hilleman, who developed many of the major vaccines in use today.
In 1990, Offit married Bonnie Fass-Offit, who is also a pediatrician. They had two children.
By 2008 Offit had become a leading advocate of childhood immunizations. He was opposed by vaccine critics, many of whom believe vaccines cause autism, a belief that has been rejected by major medical journals and professional societies. He received a death threat and received protection by an armed guard during meetings at the CDC. His 2008 book Autism's False Prophets catalyzed a backlash against the antivaccine movement in the U.S. He donated the royalties from the book to the Center for Autism Research at Children's Hospital of Philadelphia. Offit served on the board of the American Council on Science and Health until 2015 when he resigned from the group, accusing them of crossing the line for their promotion of e-cigarettes. In 2015, Offit appeared in a vaccine awareness video created by Robert Till in which he advocated teenage vaccinations.
Rotavirus vaccine
Offit worked for 25 years on the development of a safe and effective vaccine against rotavirus, which is a cause of diarrhea, and which kills almost 600,000 children a year worldwide, about half as many as malaria kills; most deaths are outside the West. His interest in the disease stemmed from the death of a 9-month-old infant from rotavirus-caused dehydration while under his care as a pediatric resident in 1979.
Along with his colleagues Fred Clark and Stanley Plotkin, Offit invented RotaTeq, a pentavalent rotavirus vaccine manufactured by Merck & Co. Since 2006, RotaTeq has been one of two vaccines currently used against rotavirus.
In February 2006, RotaTeq was approved for inclusion in the recommended U.S. vaccination schedule, following its approval by the FDA. Premarketing studies found that RotaTeq was effective and safe, with an incidence of adverse events comparable to placebo. RotaTeq has been credited (by Peter Hotez) with saving hundreds of lives a day. Offit received an unspecified sum of money for his interest in RotaTeq. Offit was elected a fellow of the Committee for Skeptical Inquiry, in 2015.
Smallpox vaccine
In 2002, during a period of fears about bioterrorism, Offit was the only member of the CDC's advisory panel to vote against a program to give smallpox vaccine to tens of thousands of Americans. He later argued on 60 Minutes II and The NewsHour with Jim Lehrer that the risk of harm for people getting the vaccine outweighed the risk of getting smallpox in the U.S. at the time.
Action against dietary supplements and alternative medicine
In December 2013, Sarah Erush and Offit declared the Children's Hospital of Philadelphia has a moratorium on the use of dietary supplements without certain manufacturers' guarantee for quality.
Our hospital has acted to protect the safety of our patients. No longer will we administer dietary supplements unless the manufacturer provides a third-party written guarantee that the product is made under the F.D.A.’s “good manufacturing practice” (G.M.P.) conditions, as well as a Certificate of Analysis (C.O.A.) assuring that what is written on the label is what’s in the bottle.
Offit defines alternative medicine as quackery when it involves unappreciated harm and replacement of conventional therapies that work, with alternative therapies that do not. His books and articles warn against the expense and risk to health for recipients of alternative therapies. In 2013 he wrote the book Do you believe in Magic? – The Sense and Nonsense of Alternative Medicine. Offit states that the purpose of the book "is to take a critical look at the field of Alternative Medicine – to separate fact from myth" and that "There's only medicine that works and medicine that doesn't."(p. 6) One of Offit's concerns is the scare tactics he says proponents of alternative medicine will often use, in a 2010 podcast with the Point of Inquiry Offit stated "it is very difficult to unscare people when you scare them."
Offit has said that the Dietary Supplement Health and Education Act of 1994 should be overturned to provide proper oversight and action against supplement providers.
Reception
Offit is a recipient of numerous awards, including the J. Edmund Bradley Prize for Excellence in Pediatrics from the University of Maryland Medical School, the Young Investigator Award in Vaccine Development from the Infectious Diseases Society of America, the 2013 Maxwell Finland Award for Scientific Achievement and a Research Career Development Award from the National Institutes of Health. In 2018, Offit was awarded the Albert B. Sabin Gold Medal from the Sabin Vaccine Institute in Washington, DC for his work on the oral rotavirus vaccine and his leadership in promoting immunization.
In 2011 Offit was honored by the Biotechnology Industry Organization with the 2011 Biotech Humanitarian Award. Offit donated the award's $10,000 prize to the Vaccine Education Center at The Children's Hospital of Philadelphia. Also in 2011, Offit was elected to the Institute of Medicine at the group's annual meeting. In 2013 Offit was presented with the Robert B. Balles Prize in Critical Thinking by the Committee for Skeptical Inquiry (CSI) for Do You Believe in Magic? The Sense and Nonsense of Alternative Medicine. "Offit is a literal lifesaver... educates the public about the dangers of alternative medicine, may save many, many more."
Michael Specter wrote that Offit "has become a figure of hatred to the many vaccine denialists and conspiracy theorists." Specter reported that Offit had often been threatened with violence by anti-vaccine advocates, necessitating precautions such as screening Offit's packages for mail bombs and providing guards when Offit attends federal health advisory committee meetings. At a 2008 vaccine activism rally in Washington, D.C., environmental lawyer Robert F. Kennedy, Jr. criticized Offit's ties to drug companies, calling him a "poster child for the term 'biostitute'." Curt Linderman Sr., the editor of the Autism File blog, wrote online that it would "be nice" if Offit "was dead".
Such criticism has provoked statements in Offit's defense. Peter Hotez, a professor and vaccine researcher at George Washington University, has been quoted in a Newsweek article:
Peter Hotez ... says government health officials should take a bolder stand in reassuring the public. Hotez feels as strongly as Offit does about the science (saying vaccines cause autism, he says, "is like saying the world is flat"), but, like other busy scientists, he's less willing to enter the fray. "Here's someone who has created an invention that saves hundreds of lives every day," says Hotez, whose daughter, 15, has autism, "and he's vilified as someone who hates children. It's just so unfair."
Publications
Offit has written or co-written several books on vaccines, vaccination and the public, and antibiotics, as well as dozens of scholarly articles on the topic. Isabelle Rapin, a neurology professor at the Albert Einstein College of Medicine, wrote in Neurology Today about Autism's False Prophets:
This book explores why parents, seeking in vain for a cure and for an explanation of their child's problem, are so vulnerable to false hopes and to the nasty predators who have from time immemorial always taken advantage of the desperate in our society. ... [Offit] became outraged by Dr. Andrew Wakefield's 1998 study in the Lancet that blamed the measles-mumps-rubella (MMR) vaccine for causing autism. Dr. Offit predicted the paper would precipitate a resurgence of measles and its serious complications, and even deaths – a prophecy soon realized.
In "The Cutter Incident" (see Cutter Laboratories incident), Offit describes fallout relating to an early poliovirus vaccine tragedy that had the effect of deterring production of already licensed vaccines and discouraging the development of new ones. Offit advocates for the repeal of religious exemptions to vaccine requirements, saying that such exemptions amount to medical neglect.
He has also written books on the instances where science generated harmful ideas (Pandora's Lab) and the history of religious opposition (in some groups) to modern medicine (Bad Faith).
In 2021 Offit released You Bet Your Life, which is a history of medical innovations with a particular focus on how some degree of risk is always present in medical innovation.
Books
E-book version:
UK title: Killing Us Softly: The Sense and Nonsense of Alternative Medicine
References
External links
Paul Offit's scientific publications at PubMed
Children's Hospital of Philadelphia: Vaccine Education Center
American immunologists
American pediatricians
Living people
Physicians from Philadelphia
Vaccinologists
Tufts University alumni
University of Maryland School of Medicine alumni
University of Pennsylvania faculty
American medical writers
American male non-fiction writers
American critics of alternative medicine
1951 births
Members of the National Academy of Medicine
Perelman School of Medicine at the University of Pennsylvania faculty
Vaccination advocates
Members of the American Philosophical Society | Paul Offit | [
"Biology"
] | 2,364 | [
"Vaccination",
"Vaccination advocates"
] |
4,159,149 | https://en.wikipedia.org/wiki/Hostapd | hostapd (host access point daemon) is a user space daemon software enabling a network interface card to act as an access point and authentication server. There are three implementations: Jouni Malinen's hostapd, OpenBSD's hostapd and Devicescape's hostapd.
Jouni Malinen's hostapd
Jouni Malinen's hostapd is a user space daemon for access point and authentication servers. It can be used to create a wireless hotspot using a Linux computer. It implements IEEE 802.11 access point management, IEEE 802.1X/WPA/WPA2/EAP Authenticators, RADIUS client, EAP server, and RADIUS authentication server. The current version supports Linux (Host AP, MadWifi, Prism54 and some of the drivers which use the kernel's mac80211 subsystem), QNX, FreeBSD (net80211), and DragonFlyBSD.
OpenBSD's hostapd
OpenBSD's hostapd is a user space daemon that helps to improve roaming and monitoring of OpenBSD-based wireless networks. It implements Inter Access Point Protocol (IAPP) for exchanging station association information between access points. It can trigger a set of actions like frame injection or logging when receiving specified IEEE 802.11 frames.
Devicescape's hostapd
The Open Wireless Linux version of hostapd. It is kept as close as possible to the original open source release, but with OWL specific packaging and defaults.
The website appears to be dead (April 2013), probably as the project itself.
See also
HostAP
References
External links
DragonFlyBSD commit
Undeadly Article
Wi-Fi
OpenBSD | Hostapd | [
"Technology"
] | 360 | [
"Wireless networking",
"Wi-Fi"
] |
4,159,307 | https://en.wikipedia.org/wiki/Data%20access%20layer | A data access layer (DAL) in computer software is a layer of a computer program which provides simplified access to data stored in persistent storage of some kind, such as an entity-relational database. This acronym is prevalently used in Microsoft environments.
For example, the DAL might return a reference to an object (in terms of object-oriented programming) complete with its attributes instead of a row of fields from a database table. This allows the client (or user) modules to be created with a higher level of abstraction. This kind of model could be implemented by creating a class of data access methods that directly reference a corresponding set of database stored procedures. Another implementation could potentially retrieve or write records to or from a file system. The DAL hides this complexity of the underlying data store from the external world.
For example, instead of using commands such as insert, delete, and update to access a specific table in a database, a class and a few stored procedures could be created in the database. The procedures would be called from a method inside the class, which would return an object containing the requested values. Or, the insert, delete and update commands could be executed within simple functions like registeruser or loginuser stored within the data access layer.
Also, business logic methods from an application can be mapped to the data access layer. So, for example, instead of making a query into a database to fetch all users from several tables, the application can call a single method from a DAL which abstracts those database calls.
Applications using a data access layer can be either database server dependent or independent. If the data access layer supports multiple database types, the application becomes able to use whatever databases the DAL can talk to. In either circumstance, having a data access layer provides a centralized location for all calls into the database, and thus makes it easier to port the application to other database systems (assuming that 100% of the database interaction is done in the DAL for a given application).
Object-Relational Mapping tools provide data layers in this fashion, following the Active Record or Data Mapper patterns. The ORM/active-record model is popular with web frameworks.
See also
Data access object
Database abstraction layer
References
External links
Microsoft Application Architecture Guide
ASP.NET DAL tutorial
Object-oriented programming
Data mapping
Databases | Data access layer | [
"Engineering"
] | 465 | [
"Data engineering",
"Data mapping"
] |
4,159,362 | https://en.wikipedia.org/wiki/UK%20Centre%20for%20Ecology%20%26%20Hydrology | The UK Centre for Ecology & Hydrology (UKCEH) is a centre for excellence in environmental science across water, land and air.
The organisation has a long history of investigating, monitoring and modelling environmental change. It operates from four sites in the UK and one in Ghana. Research topics include: air pollution, biodiversity, chemical risks in the environment, extreme weather events, droughts, floods, greenhouse gas emissions, soil health, sustainable agriculture, sustainable ecosystems, water quality, and water resources management.
UKCEH coordinates a number of long-term environmental science monitoring sites and programmes, including the Predatory Bird Monitoring Scheme, the Isle of May Long-Term Study, the UK National River Flow Archive, the Plynlimon catchment study, lakes monitoring at Loch Leven and in the English Lake District, the UK Cosmic-ray soil moisture monitoring network (COSMOS-UK), the UK Upland Waters Monitoring Network, the Biological Records Centre, and the UKCEH Countryside Survey. The centre manages an urban atmospheric pollution observatory at the top of BT Tower in London. Its international work includes collaboration with the World Meteorological Organization on a global hydrological monitoring initiative and working with European partners to set up butterfly and wider pollinator monitoring schemes.
UKCEH is a strategic delivery partner for the Natural Environment Research Council (NERC), part of UK Research and Innovation (UKRI).
The institute has four locations: Wallingford (its headquarters), Edinburgh, Lancaster and Bangor.
UKCEH is a member of the Partnership for European Environmental Research (PEER).
History
The Centre for Ecology & Hydrology (CEH) was formally established in March 1994 by John Krebs, the then chief executive of NERC. It was formed by the drawing together of four research institutes: the Institute of Hydrology, the Institute of Terrestrial Ecology, the Institute of Freshwater Ecology and the Institute of Virology and Environmental Microbiology (IVEM).
In 1994, Brian Wilkinson, a professor of civil engineering at Cranfield University, director of the Institute of Hydrology, was appointed as the first CEH director. In 1994 CEH had 15 laboratories and field stations across the UK. From 1996 onwards the number of sites was reduced and the centre now operates from 4 locations across the UK.
In the early years there was a need to integrate environmental science across the institutes: joint science programs were established together with an inter-disciplinary science fund. CEH expanded and by 1999 there were some 600 staff and about 300 students linked to the universities, with most registered for post-graduate qualification. CEH had global outreach with around 60 worldwide research projects. A new headquarters was constructed on the Wallingford site.
In 1999 Wilkinson retired and Mike Roberts was appointed as CEH director. He was succeeded by Professor Nuttall in 2001. In 2012 Mark Bailey was appointed to the position of executive director.
In December 2019, following UK Government approval, the Centre for Ecology & Hydrology became autonomous from UK Research and Innovation (UKRI) and the Natural Environment Research Council (NERC), launching as a not-for-profit company limited by guarantee with charitable status on 1 December that year. At the same time, it also changed its name to the UK Centre for Ecology & Hydrology (UKCEH).
Dr Stuart Wainwright OBE became chief executive in June 2023.
Notable research and outputs
In 2008 the centre published a hydrological appraisal of the notable flooding in England and Wales in summer 2007.
In 2010 the centre led research that showed the seasonal timings of biological events in springs and summers were shifting forward in the UK, and that the trend was accelerating.
In 2017 the centre published research on the impact on honeybees of two commercial neonicotinoid-based seed treatments in commercially grown crops of oilseed rape.
The centre hosts the UK National River Flow Archive, which publishes monthly UK hydrological summaries and hydrological outlooks.
The centre is a pioneer in citizen science and hosts the Biological Records Centre in the UK and the iRecord biological records website. It has created numerous biological recording phone apps such as iRecord Butterflies, Asian Hornet Watch and Bloomin' Algae. In 2020 the Biological Records Centre received 1.77 million records from more than 20,000 contributors, covering over 24,000 species.
It organises and funds the UK Butterfly Monitoring Scheme (UKBMS), along with Butterfly Conservation, the British Trust for Ornithology and the Joint Nature Conservation Committee. UKBMS is one of the longest running insect monitoring schemes in the world.
It creates and licenses satellite-derived annual UK land cover maps and crop maps.
UKCEH coordinates development of the Joint UK Land Environment Simulator (JULES) land surface model with the UK Met Office. JULES is used both as a standalone model and as the land surface component in the Met Office Unified Model, used for weather forecasting in the UK.
The centre is part of a major research consortium announced by the UK Government in August 2021 to help the UK adapt and become more resilient to the impacts of climate change.
It coordinates international science efforts to encourage sustainable nitrogen management.
UKCEH is one of the partners in the UK National Climate Science Partnership, announced at COP26 in 2021.
Notable people
Ewen Cameron, Baron Cameron of Dillington, Chair of UKCEH Board of Trustees
Mark J. Bailey, executive director until June 2023
Mark O. Hill, mathematical ecologist and botanist known for developing Hill numbers, a type of diversity index used in ecology, as well as detrended correspondence analysis (DCA), two-way indicator species analysis (TWINSPAN), and the frequency scaling using local occupancy ("FreScaLo") technique used for adjusting for variable sampling effort in species' distribution time trends
Pat Nuttall, director between 2001 and 2011
Christopher D. Preston, botanist and historian, known for editing various vascular plant and bryophyte species distribution atlases for Britain and Ireland
Mike Roberts, director between 1999 and 2001
Helen Roy, principal scientist-ecologist at UKCEH and president of the Royal Entomological Society
Mark Sutton, nitrogen scientist and chair of the International Nitrogen Initiative
Sarah Wanless, ornithologist and seabird ecologist
Brian Wilkinson, director between 1994 and 1999
See also
OpenMI Standard · UKCEH is the lead organisation for the Open Modelling Interface standard.
References
External links
UK Centre for Ecology & Hydrology homepage
Environmental Information Data Centre, hosted by UKCEH
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South Oxfordshire District | UK Centre for Ecology & Hydrology | [
"Environmental_science"
] | 1,340 | [
"Hydrology",
"Hydrology organizations",
"Environmental research institutes",
"Environmental research"
] |
4,159,367 | https://en.wikipedia.org/wiki/Briggs%E2%80%93Rauscher%20reaction | The Briggs–Rauscher oscillating reaction is one of a small number of known oscillating chemical reactions. It is especially well suited for demonstration purposes because of its visually striking colour changes: the freshly prepared colourless solution slowly turns an amber colour, then suddenly changes to a very dark blue. This slowly fades to colourless and the process repeats, about ten times in the most popular formulation, before ending as a dark blue liquid smelling strongly of iodine.
History
The first known homogeneous oscillating chemical reaction, reported by W. C. Bray in 1921, was between hydrogen peroxide (H2O2) and iodate () in acidic solution. Because of experimental difficulty, it attracted little attention and was unsuitable as a demonstration. In 1958 Boris Pavlovich Belousov discovered the Belousov–Zhabotinsky reaction (BZ reaction). The BZ reaction is suitable as a demonstration, but it too met with skepticism, largely because such oscillatory behaviour was unheard of up to that time, until Anatol Zhabotinsky learned of it and in 1964 published his research. In May 1972 a pair of articles in the Journal of Chemical Education brought it to the attention of Thomas Briggs and Warren Rauscher, two science instructors at Galileo High School in San Francisco. They discovered the Briggs–Rauscher oscillating reaction by replacing bromate () in the BZ reaction with iodate and adding hydrogen peroxide. They produced the strikingly colorful demonstration by adding starch indicator. Since then, many other investigators have added to the knowledge and uses of this very unusual reaction.
Description
Initial conditions
The initial aqueous solution contains hydrogen peroxide, an iodate, divalent manganese (Mn2+) as catalyst, a strong chemically unreactive acid (sulphuric acid (H2SO4) or perchloric acid (HClO4) are good), and an organic compound with an active ("enolic") hydrogen atom attached to carbon which will slowly reduce free iodine (I2) to iodide (I−). (Malonic acid (CH2(COOH)2) is excellent for that purpose.) Starch is optionally added as an indicator to show the abrupt increase in iodide ion concentration as a sudden change from amber (free iodine) to dark blue (the "iodine-starch complex", which requires both iodine and iodide.)
Recently it has been shown, however, that the starch is not only an indicator for iodine in the reaction. In the presence of starch the number of oscillations is higher and the period times are longer compared to the starch-free mixtures. It was also found that the iodine consumption segment within one period of oscillation is also significantly longer in the starch-containing mixtures. This suggests that the starch probably acts as a reservoir for the iodine and iodide because of the starch-triiodide equilibrium, thereby modifying the kinetics of the steps in which iodine and iodide are involved.
The reaction is "poisoned" by chloride (Cl−) ion, which must therefore be avoided, and will oscillate under a fairly wide range of initial concentrations. For recipes suitable for demonstration purposes, see Shakhashiri or Preparations in the external links.
Terminal conditions
The residual mixture contains iodinated malonic acid, inorganic acid, manganous catalysts, unreacted iodate and hydrogen peroxide. After the oscillations cease, the iodomalonic acid decomposes and iodine is produced. The rate of decomposition depends on the conditions. All of the components present in the residual mixture are of environmental concern: Iodate, iodine and hydrogen peroxide are strong oxidants, the acid is corrosive and manganese has been suggested to cause neurological disorders. A simple method has been developed employing thiosulfate and carbonate – two inexpensive salts – to remove all oxidants, neutralize the acidity and recover the manganous ion in the form of manganese dioxide.
Behaviour in time
The reaction shows recurring periodic changes, both gradual and sudden, which are visible: slow changes in the intensity of colour, interrupted by abrupt changes in hue. This demonstrates that a complex combination of slow and fast reactions are taking place simultaneously. For example, following the iodide ion concentration with a silver/silver iodide electrode (see ]) shows sudden dramatic swings of several orders of magnitude separated by slower variations. This is shown by the oscillogram above.
Oscillations persist over a wide range of temperatures. Higher temperatures make everything happen faster, with some qualitative change observable (see ).
Stirring the solution throughout the reaction is helpful for sharp colour changes; otherwise spatial variations may develop (see ).
Bubbles of free oxygen are evolved throughout, and in most cases, the final state is rich in free iodine.
Variants
Changing the initial concentrations
As noted above, the reaction will oscillate in a fairly wide range of initial concentrations of the reactants. For oscillometric demonstrations, more cycles are obtained in dilute solutions, which produce weaker colour changes. See for example the graph, which shows more than 40 cycles in 8 minutes.
Changing the organic substrate
Malonic acid has been replaced by other suitable organic molecules, such as acetone (CH3COCH3) or acetylacetone (CH3COCH2COCH3, pentane-2,4-dione). More exotic substrates have been used. The resulting oscillographic records often show distinctive features, for example as reported by Szalai.
Continuous flow reactors
The reaction may be made to oscillate indefinitely by using a continuous flow stirred tank reactor (CSTR), in which the starting reagents are continuously introduced and excess fluid is drawn.
Two dimensional phase space plots
By omitting the starch and monitoring the concentration of I2 photometrically, (i.e., measuring the absorption of a suitable light beam through the solution) while simultaneously monitoring the concentration of iodide ion with an iodide-selective electrode, a distorted spiral XY-plot will result. In a continuous-flow reactor, this becomes a closed loop (limit cycle).
Fluorescent demonstration
By replacing the starch with a fluorescent dye, Weinberg and Muyskens (2007) produced a demonstration visible in darkness under UV illumination.
Use as a biological assay
The reaction has been proposed as an assay procedure for antioxidants in foodstuffs. The sample to be tested is added at the onset of oscillations, stopping the action for a period proportional to its antioxidant activity. Compared to existing assay methods, this procedure is quick and easy and operates at the pH of the human stomach. For a detailed description suitable for high school chemistry, see Preparations.
In contrast to the findings referring predominantly to polyphenolic compounds reported in the above cited literature, it was found that the salicylic acid – a simple monophenolic compound – did not stop the oscillations immediately after it was added into the active Briggs-Rauscher mixture. In the low concentration interval the salicyclic acid only damped the oscillations, while in higher concentrations the damping effect was much stronger and complete inhibition was also observed. Sulfosalicylic acid, a derivative of salicyclic acid, practically did not affect the oscillations.
Chemical mechanism
The detailed mechanism of this reaction is quite complex. Nevertheless, a good general explanation can be given.
For best results, and to prevent side reactions that may interfere with the main reaction, the solutions are best prepared a short time before the reaction. If left undisturbed, or exposed to ultra-violet radiation the reactants can decompose or react with themselves, interfering with the process.
The essential features of the system depend on two key processes (These processes each involve many reactions working together):
A ("non-radical process"): The slow consumption of free iodine by the malonic acid substrate in the presence of iodate. This process involves the intermediate production of iodide ion.
B ("radical process"): A fast auto-catalytic process involving manganese and free radical intermediates, which converts hydrogen peroxide and iodate to free iodine and oxygen. This process also can consume iodide up to a limiting rate.
But process B can operate only at low concentrations of iodide, creating a feedback loop as follows:
Initially, iodide is low and process B generates free iodine, which gradually accumulates. Meanwhile, process A slowly generates the intermediate iodide ion out of the free iodine at an increasing rate proportional to its (i.e. I2) concentration. At a certain point, this overwhelms process B, stopping the production of more free iodine, which is still being consumed by process A. Thus, eventually the concentration of free iodine (and thus iodide) falls low enough for process B to start up again and the cycle repeats as long as the original reactants hold out.
The overall result of both processes is (again, approximately):
+ 2 H2O2 + CH2(COOH)2 + H+ → ICH(COOH)2 + 2 O2 + 3 H2O
The colour changes seen during the reaction correspond to the actions of the two processes: the slowly increasing amber colour is due to the production of free iodine by process B. When process B stops, the resulting increase in iodide ion enables the sudden blue starch colour. But since process A is still acting, this slowly fades back to clear. The eventual resumption of process B is invisible, but can be revealed by the use of a suitable electrode.
A negative feedback loop which includes a delay (mediated here by process A) is a general mechanism for producing oscillations in many physical systems, but is very rare in nonbiological homogeneous chemical systems. (The BZ oscillating reaction has a somewhat similar feedback loop.)
External links
Videos
Continuously stirred demo showing rapid and uniform colour changes
Continuously stirred demo showing 16 colourful oscillations gradually increasing in intensity
Unstirred demo showing minor spatial variations
Unstirred demo showing extreme spatial variations
This demo runs to completion in 19 cycles. Here the blue starch complex appears late, so the variations in free iodine are plainly visible
This demo completes in 13 cycles. An iodide-selective electrode is used to produce a graph of I− in real time
This demo is continuously stirred and has notably distinct transitions
Effect of temperature
This series of four videos vividly shows the effect of temperature on the oscillations: 10 °C 22 °C 40 °C 60 °C
Preparations
from NCSU (PDF)
from about.com, with a brief description of the chemical mechanism
from John A. Pojman (uses readily available 3% H2O2)
complete description of use as an antioxidant assay suitable for use in high school chemistry class
References
Name reactions
Non-equilibrium thermodynamics
Articles containing video clips
Clock reactions | Briggs–Rauscher reaction | [
"Chemistry",
"Mathematics"
] | 2,319 | [
"Clock reactions",
"Non-equilibrium thermodynamics",
"Name reactions",
"Chemical kinetics",
"Dynamical systems"
] |
4,159,522 | https://en.wikipedia.org/wiki/Nokia%206170 | The Nokia 6170 was one of the clamshell phone series from Nokia.
Description
It comes with a VGA camera (640x480) with 2x and 4x electronic zoom, push to talk and speakerphone.
It has a built-in WAP web browser, and supports Java ME. It has 2.3 MBs integrated memory that can't be extended (and some elements that ship inside the phone's file system are impossible to delete).
The phone supports IRDA but not Bluetooth, and can send and receive multimedia messages of up to 100 KBs in size.
The phone has a metallic look and spots a small colour screen on the outside of the clamshell.
The European version 6170 RM-47 supports 900 MHz, 1800 MHz and 1900 MHz radios, while the U.S. version 6170b RM-48 supports 850 MHz, 1800 MHz and 1900 MHz radios.
It was the successor of Nokia 6102i and succeeded by the Nokia N71 which was released in June 2006.
References
6170 | Nokia 6170 | [
"Technology"
] | 216 | [
"Mobile technology stubs",
"Mobile phone stubs"
] |
4,160,051 | https://en.wikipedia.org/wiki/Tamil%20units%20of%20measurement | The Tamil units of measurement is a system of measurements that was traditionally used in ancient Tamil-speaking parts of South India.
These ancient measurement systems spanned systems of counting, distances, volumes, time, weight as well as tools used to do so. While modern India uses the metric system International System of Units (Tamil Nadu state included), some of these older day measurement systems, especially those of counting, are still used today.
Other units that have persisted are those of area – the 'ma' (not to be confused with the dollar-cent) and the ‘ground’, both used to measure land and the ‘molam’ which has been relegated to measuring the length of a sandanam garland sold on streets.
There are several similarities between the measurement system used in Tamil Nadu and that used by the Indus Valley civilisation. Recent excavation studies from Keeḻadi reveal existence of an older non-vedic civilisation in Tamil Nadu. New discovery suggest possibilities of source of ancient Indian mathematicians in Tamil Nadu.
Units of time in ancient Tamil history
10 (kuḻigaḷ) = 1 (miy) = 66.6666 millisecond-the time taken by the young human eyes to flap once.
2 (kaṇṇimaigaḷ) = 1 (kainoḍi) = 0.125 second
2 (kainoḍi) = 1 (māttirai) = 0.25 second
6 (miygaḷ) = 1 (ciṟṟuḻi (noḍi)) = 0.40 second-the time taken for a bubble (created by blowing air through a bamboo tube into a vessel 1 (cāṇ) high, full of water) to travel a distance of one (cāṇ).
2 (māttiraigaḷ) = 1 (kuṟu) = 0.50 second
2 (noḍigaḷ) = 1 (viṉāḍi) = 0.80 second-the time for the adult human heart to beat once
2 (noḍigaḷ) = 2 (kuṟu) = 1 (uyir) = 1 second
5 (noḍigaḷ) = 2 (uyir) = 1 (cāṇigam) = 1/2 (aṇu) = 2 seconds
10 (noḍigaḷ) = 1 (aṇu) = 4 seconds
6 (aṇukkaḷ) = 12 (cāṇigam) = 1 (tuḷi) = 1 (nāḻigai-viṉāḍi) = 24 seconds
10 (tuḷigaḷ) = 1 (kaṇam) = 4 minutes
6 (kaṇangaḷ) = 1 (nāḻigai) = 24 minutes
10 (nāḻigaikaḷ) = 4 (cāmam) = 1 (ciṟupoḻutu) = 240 minutes = 4 hours
6 (ciṟu-poḻutugaḷ) = 1 (nāḷ) = 1 day = 24 hours
7 (nāṭkaḷ) = 1 (vāram) = 1 week
15 (nāṭkaḷ) = 1 (aḻuvaluvamam) = 1 fortnight
29 (nāṭkaḷ) = 1 (tingaḷ) = 1 lunar month
2 (tingaḷ) = 1 (perum-poḻutu) = 1 season
6 (perum-poḻutu) = 1 (āṇdu) = 1 year
64 (āṇdukaḷ) = 1 (vaṭṭam) = 1 cycle
64 வட்டம்/cycles = 4096 (āṇdukaḷ) = 1 ōḻi = 1 epoch
Area Measurement
1 (marakkaḷ vitaippatu, seeds required for planting rice) = 8 cents
12 (marakkaḷ vitaippatu) = 100 cents
1 (kuṟuṇi) = 8 cents
1 (patakku) = 16 cents
1 (mukkuṟuṇi) = 24 cents
1 sq (kajam) = cents
1 (vīsam) = 36 sq ft
303 (kuḻi) = 100 cents
1 (kuḻi) = 144 சதுர அடி (144 sq ft = 12 ft x 12 ft)
1 (mā) = 100 (kuḻi)
1 (kāṇi) = 4 (mā)
1 (vēļi) = 5 (kāṇi)
1 தாக்கு (thakku) = 7.56 சதுர அடி (Sq. ft)
In Jaffna, Sri Lanka For House property
1 Parappu = 1 Lacham = 10 Perches
16 Parappu = 1 Acre
Varaku Culture (V.C.)
18 kulies = 1 lacham
16 lachams = 1 acre
Paddy Culture (P.C.)
12 kulies = 1 lacham
24 lachams = 1 acre
Units of ancient trade
Balance weights
Thanga edaihal
4 nel eḍai (நல் எடை) = 1 kuṉṟimaṇi (குன்றிமணி)
2 kuṉṟimaṇi (குன்றிமணி) = 1 māñcāḍi (மஞ்சாடி)
1 māñcāḍi (மஞ்சாடி) = 1 paṇaveḍai (பணவெடை)
5 paṇaveḍai (பணவெடை) = 1 kaḻañcu (கழஞ்சு)
8 paṇaveḍai (பணவெடை) = 1 varāgaṉeḍai (வராகனெடை)
20 paṇaveḍai (பணவெடை) = 4 kaḻañcu (கழஞ்சு) = 1 kaqhsu (கஃசு)
80 paṇaveaḍai (பணவெடை)= 16 kaḻañcu (கழஞ்சு)= 4 kaqhsu (கஃசு)= 1 palam (பலம்)
1.5 Kaḻan
cu (கழஞ்சு) = 8 grams or one sovereign/pavun.
The above is not in line with South Indian Inscriptions.
2 kuṉṟima குன்றிமணி = 1 māñcāḍi மஞ்சாடி
20 māñcāḍi மஞ்சாடி = 1 kaḻañcu கழஞ்சு
Ceylon Currency and Coins by H W Codrington page 10 too agrees with 20 māñcāḍi = 1 kaḻañcu.
Porutkal yedaihal
32 kuṉṟimaṇi = 1 varāgaṉeḍai
10 varāgaṉeḍai = 1 palam
40 palam = 1 veesai
1000 palam = 1 kā
6 veesai = 1 tulām
8 veesai = 1 maṇangu
20 maṇangu = 1 pāram.
Grain volume
1 kuṇam = smallest unit of volume
9 kuṇam = 1 mummi
11 mummi = 1 aṇu
7 aṇu = 1 immi
7 immi = 1 uminel
1 sittigai = 7 uminel
360 nel = 1 sevidu
5 sevidu = 1 āḻākku
2 āḻākku = 1 uḻakku
2 uḻakku = 1 uri
2 uri = 1 padi
8 padi = 1 marakkaal (kuṟuṇi)
2 marakkāl (kuṟuṇi) = 1 padakku
2 padakku = 1 tōṇi
3 tōṇi = 1 kalam (= 96 padi)
5 marakkāl = 1 paṟai
80 paṟai = 1 karisai
96 padi = 1 pothi (mōdai)
21 marakkal = 1 Kottai
22 mākāni = 100 g
1 padi = 1800 avarai pods = 12,800 miḷagu seeds = 14,400 nel grains = 14,800 payaṟu grains = 38,000 arisi grains = 115,200 sesame ellu seeds
Fluid volume
5 sevidu = 1 āḻākku
2 mahani = 1 āḻākku (arai kal padi)
2 āḻākku = 1 uḻakku (Kal padi)
2 uḻakku = 1 uri (Arai padi)
2 uri = 1 padi
4 padi= 1 marakkaal
2 marakkāl (kuṟuṇi) = 1 padakku
2 padakku = 1 tōṇi
21 Marakkal = 1 Kottai
Length
1 Koan = (115.8953125 picometre)
10 Koan = 1 Nunnanu (0.1158953125 nanometre)
10 Nunnanu = 1 Aṇu (atom) (1.158953125 nanometre)
8 Aṇu = 1 Kadirtugal (9.271625 nanometre)
8 Kadirtugal = 1 Tusumbu (74.173 nanometre)
8 Tusumbu = 1 Mayirnuni (0.593384 micrometre)
8 Mayirnuni = 1 Nunnmanal (4.74707 micrometre)
8 Nunnmanal = 1 Siru-kadugu (37.976563 micrometre)
8 Siru-kadugu = 1 Yel (303.8125 micrometre or 0.3038125 millimetre)
8 Yel = 1 Nel (2.4305 millimetre)
8 nel = 1 viral = 8^8 aṇu (atom) = 1.9444 centimetre
12 viral = 1 sāṇ = 100 immi= 23.3333 centimetre = 9 inch
2 sāṇ = 1 muḻam = 46.6666 centimetre = 1.5 feet
2 sāṇ = 1 muḻam
2 muḻam = 1 yard = 3 feet = 1 yard
2 yard(yaar) = 1 pāgam
110 pāgam = 1 furlong
8 furlong = 1 mile
5 furlong = 1 kilometre or 1000 metre
625 pāgam = 1 kādam = 5000 sāṇ = 1166.66 metres = 1.167 kilometre
Likeness (Sārttal)
Likeness has attributes of tone, sound, colour and shape for comparison of a given substance with a known standard.
Whole numbers
The following are the traditional numbers of the Ancient Tamil Country, Tamilakam.
Tamil texts also elaborate the following sanskritized version :
1 ONDRU = One = 10 0
10 = PATU = Ten = 10 1
100 = NŌRU = Hundred = 10 2
1,000 = ĀYIRAM = One Thousand = 10 3
10,000 = PATĀYIRAM = Ten Thousand = 10 4
1,00,000 = LATCHAM = Hundred Thousand = 10 5
10,00,000 = PATHU LATCHAM = One Million = 10 6
1,00,00,000 = KODI = Ten Million = 10 7
10,00,00,000 = PATHU KODI = Hundred Million = 10 8
1,00,00,00,000 = ARPUTAM = One Billion = 10 9
10,00,00,00,000 = PATU ARPUTAM = Ten Billion = 10 10
1,00,00,00,00,000 = NIGARPUTAM = Hundred Billion = 10 11
10,00,00,00,00,000 = PATU NIGARPUTAM = One Trillion = 10 12
1,00,00,00,00,00,000 = KUMBAM = Ten Trillion = 10 13
10,00,00,00,00,00,000 = PATU KUMBAM = Hundred Trillion = 10 14
1,00,00,00,00,00,00,000 = GANAM = One Quadrillion = 10 15
10,00,00,00,00,00,00,000 = PATHU GANAM = Ten Quadrillion = 10 16
1,00,00,00,00,00,00,00,000 = KARPAM = Hundred Quadrillion = 10 17
10,00,00,00,00,00,00,00,000 = PATU KARPAM = One Quintillion = 10 18
1,00,00,00,00,00,00,00,00,000 = NIKARPAM = Ten Quintillion = 10 19
10,00,00,00,00,00,00,00,00,000 = PATU NIKARPAM = Hundred Quintillion = 10 20
1,00,00,00,00,00,00,00,00,00,000 = PATUMAM = One Sextillion = 10 21
10,00,00,00,00,00,00,00,00,00,000 = PATU PATUMAM = Ten Sextillion = 10 22
1,00,00,00,00,00,00,00,00,00,00,000 = SANGGAM = Hundred Sextillion = 10 23
10,00,00,00,00,00,00,00,00,00,00,000 = PATU SANGGAM = One Septillion = 10 24
1,00,00,00,00,00,00,00,00,00,00,00,000 = VELLAM = Ten Septillion = 10 25
10,00,00,00,00,00,00,00,00,00,00,00,000 = PATU VELLAM = Hundred Septillion = 10 26
1,00,00,00,00,00,00,00,00,00,00,00,00,000 = ANNIYAM = One Octillion = 10 27
10,00,00,00,00,00,00,00,00,00,00,00,00,000 = PATU ANNIYAM = Ten Octillion = 10 28
1,00,00,00,00,00,00,00,00,00,00,00,00,00,000 = ARTTAM = Hundred Octillion = 10 29
10,00,00,00,00,00,00,00,00,00,00,00,00,00,000 = PATHU ARTTAM = One Nonillion = 10 30
1,00,00,00,00,00,00,00,00,00,00,00,00,00,00,000 = PARARTTAM = Ten Nonillion = 10 31
10,00,00,00,00,00,00,00,00,00,00,00,00,00,00,000 = PATU PARARTTAM = Hundred Nonillion = 10 32
1,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,000 = PŌRIYAM = One Decillion = 10 33
10,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,000 = PATU PŌRIYAM = Ten Decillion = 10 34
1,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,000 = MUKKODI = Hundred Decillion = 10 35
10,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,000 = PATU MUKKODI = One Undecillion = 10 36
1,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,000 = MAHAYUGAM = Ten Undecillion = 10 37
Malaysian text elaborates the following version
1 ONDRU = One = 10 0
10 = PATU = Ten = 10 1
100 = NŌRU = Hundred = 10 2
1,000 = ĀYIRAM = One Thousand = 10 3
10,000 = PATĀYIRAM = Ten Thousand = 10 4
100,000 = LATCHAM = Hundred Thousand = 10 5
1,000,000 = PATU LATCHAM = One Million = 10 6
10,000,000 = KODI = Ten Million = 10 7
100,000,000 = PATU KODI = Hundred Million = 10 8
1,000,000,000 = NŌRU KODI = One Billion = 10 9
Fractions
1 – ஒன்று – onRu
3/4 = 0.75 – முக்கால் – mukkāl
1/2 = 0.5 – அரை – arai
1/4 = 0.25 – கால் – kāl
1/5 = 0.2 – நாலுமா – nālumā
3/16 = 0.1875 – மும்மாகாணி –mummākāṇi this is called as Mukkhani
3/20 = 0.15 – மும்மா – mummaa
1/8 = 0.125 – அரைக்கால் – araikkāl
1/10 = 0.1 – இருமா – irumā
1/16 = 0.0625 – மாகாணி (வீசம்) – mākāṇi (vīsam)
1/20 = 0.05 – ஒருமா – orumā
3/64 = 0.046875 – முக்கால்வீசம் – mukkāl vīsam
3/80 = 0.0375 – முக்காணி – mukkāṇi
1/32 = 0.03125 – அரைவீசம் – araivīsam
1/40 = 0.025 – அரைமா – araimā
1/64 = 0.015625 – கால் வீசம் – kaal vīsam
1/80 = 0.0125 – காணி – kāṇi
3/320 = 0.009375 – அரைக்காணி முந்திரி – araikkāṇi muntiri
1/160 = 0.00625 – அரைக்காணி – araikkāṇi
1/320 = 0.003125 – முந்திரி – muntiri
3/1280 = 0.00234375 – கீழ் முக்கால் – kīḻ mukkal
1/640 = 0.0015625 – கீழரை – kīḻarai
1/1280 = 7.8125e-04 – கீழ் கால் – kīḻ kāl
1/1600 = 0.000625 – கீழ் நாலுமா – kīḻ nalumā
3/5120 ≈ 5.85938e-04 – கீழ் மூன்று வீசம் – kīḻ mūndru vīsam
3/6400 = 4.6875e-04 – கீழ் மும்மா – kīḻ mummā
1/2500 = 0.0004 – கீழ் அரைக்கால் – kīḻ araikkāl
1/3200 = 3.12500e-04 – கீழ் இருமா – kīḻ irumā
1/5120 ≈ 1.95313e-04 – கீழ் வீசம் – kīḻ vīsam
1/6400 = 1.56250e-04 – கீழொருமா – kīḻ orumā
1/102400 ≈ 9.76563e-06 – கீழ்முந்திரி – kīḻ muntiri
1/2150400 ≈ 4.65030e-07 – இம்மி – immi
1/23654400 ≈ 4.22754e-08 – மும்மி – mummi
1/165580800 ≈ 6.03935e-09 – அணு – aṇu
1/1490227200 ≈ 6.71039e-10 – குணம் – kuṇam
1/7451136000 ≈ 1.34208e-10 – பந்தம் – pantam
1/44706816000 ≈ 2.23680e-11 – பாகம் – pāgam
1/312947712000 ≈ 3.19542e-12 – விந்தம் – vintam
1/5320111104000 ≈ 1.87966e-13 – நாகவிந்தம் – nāgavintam
1/74481555456000 ≈ 1.34261e-14 – சிந்தை – sintai
1/1489631109120000 ≈ 6.71307e-16 – கதிர்முனை –katirmunai
1/59585244364800000 ≈ 1.67827e-17 – குரல்வளைப்படி –kuralvaḷaippiḍi
1/3575114661888000000 ≈ 2.79711e-19 -வெள்ளம் – veḷḷam
1/357511466188800000000 ≈ 2.79711e-21 – நுண்மணல் –nuṇmaṇal
1/2323824530227200000000 ≈ 4.30325e-22 – தேர்த்துகள் –tērttugaḷ
Currency
1 pal (wooden discs/sea shellots) = (approximately) 0.9 grain
8 (or 10 base 8) paṟkaḷ = 1 senkāṇi (copper/bronze) = 7.2 grains(misinterpretted by Roman accounts as 10 base 10 paRkal = 9 grains)
1/4 senkāṇi = 1 kālkāṇi (copper) = 1.8 grains (misinterpretted by Roman accounts as 2.25 grains)
64 (or 100 base 8) paṟkaḷ = 1 KaaNap-pon aka. Kāsu panam(gold) = 57.6 grains
1 Roman dinarium was traded on par with 2 Kāṇappon plus 1 Senkāṇi(=124 grains).
18 Ana = 2.85 Rupee, 16 Ana = 1 Rupee, 1 Ana = 3 Tuṭu, 1/4 Ana = 3/4 (mukkal) tuṭu
Divisions of a Day
சிறுபொழுது (Daily)
1. மாலை (mālai): 6 pm-10 pm
2. இடையாமம் (iḍaiyāmam): 10 pm-2 am
3. வைகறை (vaikaṟai): 2 am-6 am
4. காலை (kālai): 6 am-10 am
5. நண்பகல் (naṇpagal): 10 am-2 pm
6. எற்பாடு (eṟpāḍu): 2 pm-6 pm
Divisions of the Year
பெரும்பொழுது (பெரும்பொழுது என்பது யாது எனில்
பன்னிரு மாதங்களை ஆறாய்ப் பகுத்தது)
1. கார்காலம் (Kārkālam): ஆடி, ஆவணி
2. குளிர்காலம் (Kuḷirkālam): புரட்டாசி, ஐப்பசி
3. முன்பனிக் காலம்(Muṉpaṉik kālam): கார்த்திகை, மார்கழி
4. பின்பனிக் காலம் (Piṉpaṉik kālam): தை, மாசி
5. இளவேனில் (Iḷavēṉil): பங்குனி, சித்திரை
6. முதுவேனில் (Mutuvēṉil) :வைகாசி, ஆனி
See also
Tamil Calendar
References
Sources
3. http://tvaraj.com/2012/03/06/fractions-used-by-ancient-tamils/
Tamil Measurements
Tamil
Obsolete units of measurement
Systems of units
Economic history of Tamil Nadu | Tamil units of measurement | [
"Mathematics"
] | 4,688 | [
"Obsolete units of measurement",
"Quantity",
"Systems of units",
"Units of measurement"
] |
4,160,163 | https://en.wikipedia.org/wiki/List%20of%20random%20number%20generators | Random number generators are important in many kinds of technical applications, including physics, engineering or mathematical computer studies (e.g., Monte Carlo simulations), cryptography and gambling (on game servers).
This list includes many common types, regardless of quality or applicability to a given use case.
Pseudorandom number generators (PRNGs)
The following algorithms are pseudorandom number generators.
Cryptographic algorithms
Cipher algorithms and cryptographic hashes can be used as very high-quality pseudorandom number generators. However, generally they are considerably slower (typically by a factor 2–10) than fast, non-cryptographic random number generators.
These include:
Stream ciphers. Popular choices are Salsa20 or ChaCha (often with the number of rounds reduced to 8 for speed), ISAAC, HC-128 and RC4.
Block ciphers in counter mode. Common choices are AES (which is very fast on systems supporting it in hardware), TwoFish, Serpent and Camellia.
Cryptographic hash functions
A few cryptographically secure pseudorandom number generators do not rely on cipher algorithms but try to link mathematically the difficulty of distinguishing their output from a `true' random stream to a computationally difficult problem. These approaches are theoretically important but are too slow to be practical in most applications. They include:
Blum–Micali algorithm (1984)
Blum Blum Shub (1986)
Naor–Reingold pseudorandom function (1997)
Random number generators that use external entropy
These approaches combine a pseudo-random number generator (often in the form of a block or stream cipher) with an external source of randomness (e.g., mouse movements, delay between keyboard presses etc.).
/dev/random – Unix-like systems
CryptGenRandom – Microsoft Windows
Fortuna
RDRAND instructions (called Intel Secure Key by Intel), available in Intel x86 CPUs since 2012. They use the AES generator built into the CPU, reseeding it periodically.
True Random Number Generator using Corona Discharge.
Yarrow
See also
Diceware
Diehard tests – statistical test suite for random number generators
Non-uniform random variate generation
Hardware random number generator
Random number generator attack
Randomness
TestU01 – statistical test suite for random number generators
References
External links
SP800-90 series on Random Number Generation, NIST
Random Number Generation in the GNU Scientific Library Reference Manual
Random Number Generation Routines in the NAG Numerical Library
Chris Lomont's overview of PRNGs, including a good implementation of the WELL512 algorithm
Source code to read data from a TrueRNG V2 hardware TRNG
Computing-related lists
Mathematics-related lists | List of random number generators | [
"Technology"
] | 543 | [
"Computing-related lists"
] |
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