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565,218 | https://en.wikipedia.org/wiki/8000%20%28number%29 | 8000 (eight thousand) is the natural number following 7999 and preceding 8001.
8000 is the cube of 20, as well as the sum of four consecutive integers cubed, 113 + 123 + 133 + 143.
The fourteen tallest mountains on Earth, which exceed 8000 meters in height, are sometimes referred to as eight-thousanders.
Selected numbers in the range 8001–8999
8001 to 8099
8001 – triangular number
8002 – Mertens function zero
8011 – Mertens function zero, super-prime
8012 – Mertens function zero
8017 – Mertens function zero
8021 – Mertens function zero
8039 – safe prime
8059 – super-prime
8069 – Sophie Germain prime
8093 – Sophie Germain prime
8100 to 8199
8100 = 902
8101 – super-prime
8111 – Sophie Germain prime
8117 – super-prime, balanced prime
8119 – octahedral number; 8119/5741 ≈ √2
8125 – pentagonal pyramidal number
8128 – perfect number, harmonic divisor number, 127th triangular number, 64th hexagonal number, eighth 292-gonal number, fourth 1356-gonal number
8147 – safe prime
8189 – highly cototient number
8190 – harmonic divisor number
8191 – Mersenne prime
8192 = 213
8200 to 8299
8208 – base 10 narcissistic number as 84 + 24 + 04 + 84 = 8208
8219 – twin prime with 8221
8221 – super-prime, twin prime with 8219
8233 – super-prime, centered heptagonal number
8243 – Sophie Germain prime
8256 – triangular number
8257 – sum of the squares of the first fourteen primes
8269 – cuban prime of the form x = y + 1
8273 – Sophie Germain prime
8281 = 912, sum of the cubes of the first thirteen integers, nonagonal number, centered octagonal number
8287 – super-prime
8300 to 8399
8321 – super-Poulet number
8326 – decagonal number
8345 - smallest pandigital number in base 6
8361 – Leyland number
8363 – prime number, number of prime numbers having five digits
8377 – super-prime
8385 – triangular number
8389 – super-prime, twin prime
8400 to 8499
8423 – safe prime
8436 – tetrahedral number
8437 - star number
8464 = 922
8500 to 8599
8513 – Sophie Germain prime, super-prime
8515 – triangular number
8521 – sexy prime with 8527
8527 – super-prime, sexy prime with 8521
8543 – safe prime
8555 – square pyramidal number
8558 – Large Schröder number
8576 – centered heptagonal number
8581 – super-prime
8600 to 8699
8625 – nonagonal number
8646 – triangular number
8649 = 932, centered octagonal number
8658 - sum of the first four perfect numbers (6, 28, 496, 8128) and the product of the culturally significant 666 and 13
8663 – Sophie Germain prime
8693 – Sophie Germain prime
8695 – decagonal number
8699 – safe prime
8700 to 8799
8712 – smallest number that is divisible by its reverse: 8712 = 4 × 2178 (excluding palindromes and numbers with trailing zeros)
8713 – balanced prime
8719 – super-prime
8741 – Sophie Germain prime
8747 – safe prime, balanced prime, super-prime
8748 – 3-smooth number (22×37)
8751 – perfect totient number
8760 - the number of hours in a non-leap year; 365 × 24
8761 – super-prime
8778 – triangular number
8783 – safe prime
8784 - the number of hours in a leap year; 366 × 24
8800 to 8899
8801 – magic constant of n × n normal magic square and n-Queens Problem for n = 26.
8807 – super-prime, sum of eleven consecutive primes (761 + 769 + 773 + 787 + 797 + 809 + 811 + 821 + 823 + 827 + 829)
8819 – safe prime
8833 = 882 + 332
8836 = 942
8839 – sum of twenty-three consecutive primes (313 + 317 + 331 + 337 + 347 + 349 + 353 + 359 + 367 + 373 + 379 + 383 + 389 + 397 + 401 + 409 + 419 + 421 + 431 + 433 + 439 + 443 + 449)
8849 – super-prime
8855 – member of a Ruth-Aaron pair (first definition) with 8856
8856 – member of a Ruth-Aaron pair (first definition) with 8855
8888 - repdigit
8893 - star prime
8900 to 8999
8911 – Carmichael number, triangular number
8923 – super-prime
8926 – centered heptagonal number
8933 – the 1,111th prime number
8944 – sum of the cubes of the first seven primes
8951 – Sophie Germain prime
8963 – safe prime
8964 – number referring to the 1989 Tiananmen Square Protests
8969 – Sophie Germain prime
8976 – enneagonal number
8999 – super-prime
Prime numbers
There are 110 prime numbers between 8000 and 9000:
8009, 8011, 8017, 8039, 8053, 8059, 8069, 8081, 8087, 8089, 8093, 8101, 8111, 8117, 8123, 8147, 8161, 8167, 8171, 8179, 8191, 8209, 8219, 8221, 8231, 8233, 8237, 8243, 8263, 8269, 8273, 8287, 8291, 8293, 8297, 8311, 8317, 8329, 8353, 8363, 8369, 8377, 8387, 8389, 8419, 8423, 8429, 8431, 8443, 8447, 8461, 8467, 8501, 8513, 8521, 8527, 8537, 8539, 8543, 8563, 8573, 8581, 8597, 8599, 8609, 8623, 8627, 8629, 8641, 8647, 8663, 8669, 8677, 8681, 8689, 8693, 8699, 8707, 8713, 8719, 8731, 8737, 8741, 8747, 8753, 8761, 8779, 8783, 8803, 8807, 8819, 8821, 8831, 8837, 8839, 8849, 8861, 8863, 8867, 8887, 8893, 8923, 8929, 8933, 8941, 8951, 8963, 8969, 8971, 8999
References
Integers | 8000 (number) | [
"Mathematics"
] | 1,551 | [
"Elementary mathematics",
"Integers",
"Mathematical objects",
"Numbers"
] |
565,250 | https://en.wikipedia.org/wiki/Paternoster%20lift | A paternoster (, , or ) or paternoster lift is a passenger elevator which consists of a chain of open compartments (each usually designed for two people) that move slowly in a loop up and down inside a building without stopping. Passengers can step on or off at any floor they like. The same technique is also used for filing cabinets to store large amounts of (paper) documents or for small spare parts. The much smaller belt manlift, which consists of an endless belt with steps and rungs but no compartments, is also sometimes called a paternoster.
The name paternoster ("Our Father", the first two words of the Lord's Prayer in Latin) was originally applied to the device because the elevator is in the form of a loop and is thus similar to rosary beads used as an aid in reciting prayers.
The construction of new paternosters was stopped in the mid-1970s out of concern for safety, but public sentiment has kept many of the remaining examples open. By far, most remaining paternosters are in Europe, with 230 examples in Germany and 68 in the Czech Republic. Only three have been identified outside Europe; one each in Malaysia, Sri Lanka, and Peru.
History
British architect Peter Ellis obtained a patent in July 1866 for "an improved lift, hoist, or mechanical elevator" with two shafts and subsequently installed the first elevators that could be described as paternoster lifts in Oriel Chambers in Liverpool in 1868. This patent lapsed in July 1873. Another was used in 1876 to transport parcels at the General Post Office in London. In 1878, British engineer Frederick Hart obtained a patent on the paternoster. In 1884, the engineering firm of J & E Hall of Dartford, Kent, installed its first "Cyclic Elevator", using Hart's patent, in a London office block, and the firm is generally considered the company first involved in regular construction of the lifts.
The newly built Dovenhof in Hamburg was inaugurated in 1886. The prototype of the Hamburg office buildings equipped with the latest technology also had a paternoster. This first system outside of Great Britain already had the technology that would later become common, but was still driven by steam power like the British systems.
The highest paternoster lift in the world was located in Stuttgart in the 16-floor Tagblatt tower, which was completed in 1927. This was replaced with conventional elevators in 1959.
Paternosters were popular throughout the first half of the 20th century because they could carry more passengers than ordinary elevators. They were more common in continental Europe, especially in public buildings, than in the United Kingdom. They are relatively slow elevators, typically travelling at about to facilitate passengers embarking and disembarking.
Safety
Paternoster elevators are intended only for transporting people. Accidents have occurred when they have been misused for transporting large items such as ladders or library trolleys. Their overall rate of accidents is estimated as 30 times higher than conventional elevators. A representative of the Union of Technical Inspection Associations stated that Germany saw an average of one death per year due to paternosters prior to 2002, at which point many of them were made inaccessible to the general public.
Because the accident risk is much greater than for conventional elevators, the construction of new paternosters is no longer allowed in many countries. In 2012, an 81-year-old man was killed when he fell into the shaft of a paternoster in the Dutch city of The Hague. Elderly people, disabled people and children are most vulnerable.
In September 1975, the paternoster in Newcastle University's Claremont Tower was temporarily taken out of service after a passenger was killed when a car left its guide rail at the top of its journey and forced the two cars ascending behind it into the winding room above. In October 1988 a second, non-fatal accident occurred in the same lift. A conventional lift replaced it in 1989–1990.
In West Germany, new paternoster installations were banned in 1974, and in 1994 there was an attempt to shut down all existing installations. However, there was a wave of popular resistance to the ban, and to a similar attempt in 2015, and as a result many are still in operation. , Germany had 231 paternosters.
In April 2006, Hitachi announced plans for a modern paternoster-style elevator with computer-controlled cars and standard elevator doors to alleviate safety concerns. A prototype was revealed . In 2009, Solon received special permission to build a brand new paternoster in its Berlin headquarters.
Surviving examples
Austria
In Vienna, the Vienna City Hall, the Ringturm (headquarters of the Vienna Insurance Group), an office building at Trattnerhof 2 near Stephansplatz and Haus der Industrie on Schwartzenbergplatz have the last four running and frequently used paternosters in the city. The university also had one or more.
In Klagenfurt, the Headquarters of the energy company Kelag still have one paternoster active for daily use.
Belgium
A paternoster lift dating from 1958 survives in Avenue Fonsny 47, Brussels, a currently disused office building forming part of Midi/Zuid railway station.
At the Huis van de Vlaamse Volksvertegenwoordigers (House of Flemish Representatives), previously the Postcheque Building, at Leuvenseweg/Rue de Louvain 86, the paternoster is operational but not used.
Czech Republic
In Prague, New City Hall – an early 20th century paternoster renovated in 2017. The lift was temporarily closed in April 2023 due to misuse by tourists.
In Prague, Czech Technical University – Faculty of Electrotechnical Engineering at Technická 2, Dejvice
In Prague, Czech Technical University – Faculty of Mechanical Engineering at Technická 4, Dejvice
In Prague, Charles University – Faculty of Law
In Prague, Ministry of Transport (Czech Republic) head office
In Prague, Ministry of Agriculture (Czech Republic)
In Prague, Lucerna Palace (near the southeast entrance)
In Prague, Czech Radio building (oldest paternoster lift in the Czech Republic, not publicly accessible)
In Prague, YMCA building
In Plzeň, municipal office – Škroupova 1900/5
In Brno, Brno Technical University – Faculty of Mechanical Engineering at Technická 2896/2
In Brno, municipal office – Malinovského Square 624/3
In Most, Business centrum, tř. Budovatelů 2957
In the offices of Czech Post at Brno railway station, (returned to use in 2013, after being out of service for six years)
In Jablonec nad Nisou, city hall built in 1933
In Ostrava, New City Hall built in 1930
In Liberec, Liberec Regional Office building build in 1971, highest paternoster in the country (56.8 m high and has 35 wooden cabins)
In Zlín, Baťa's Skyscraper or Building No. 21 built in 1938
Denmark
In the Christiansborg Palace where the Danish parliament resides
At Vognmagergade 8. Today the building is used by KVUC – Københavns VUC (Copenhagen's adult-education center)
In the corporate office building Axelborg, located in central Copenhagen
In Frederiksberg Town Hall
In the 11-story main administrative building at Danfoss headquarters on the island of Als
In the hospital in Vejle
In Sydvestjysk Hospital in Esbjerg
In Regionshospitalet Randers
Finland
The following locations have paternosters:
In Turku, Town hall in Yliopistonkatu 27
In Helsinki, in the office building at Hämeentie 19
In Helsinki, at Eduskunta, the parliament of Finland at Mannerheimintie 30, accessible to staff only
In Helsinki, in Stockmann, Helsinki centre at Aleksanterinkatu 52, accessible to staff only
Germany
In Kiel, the State Parliament building for the state of Schleswig-Holstein has had a working paternoster since 1950.
In Kiel, the city hall has had a paternoster in use for over 100 years.
In Berlin, the offices of the alt-left newspaper Neues Deutschland contain a working paternoster (), while those of the conservative tabloid Bild contain a 19-storey paternoster that is still in use but not open to the public. The Rathaus Schöneberg, including scenes with its paternoster elevator, were used to film the TV series Babylon Berlin.
In Berlin, the building at Kleiststr. 23–26 that houses Argentina's embassy contains an 8-story paternoster.
In the in Berlin paternosters are in use.
In the German Academy of Sciences in Berlin another paternoster is in use.
In the Siemens building in Berlin at Nonnendammallee 101 a paternoster is in use.
Berlin's Flughafen Tempelhof through at least 1967 (when it shared an identity as Tempelhof Air Base) had at least 1 fully-functional paternoster in the tower on the left end (as seen from the Luftbrückeplatz) of the quarter-circular pre-WW2 building.
Bremen has a paternoster in the Bremen Cotton Exchange, at Wachtstraße 17-24, just off the market square.
In Hamburg, the building at 25 Deichstraße, Speicherstadt, has an operating paternoster, the Bezirksamt at Grindelberg 62–66 in Eimsbüttel and Hapag Lloyd buildings in Balindamm street also have a working Paternoster. As well as the building at Stadthausebrücke 8. The Laeiszhof Building in Trostbrücke 1 also has a working Paternoster.
In Cologne, the building at Hansaring 97 has a working and in-use paternoster.
In Frankfurt, the former IG Farben Building has running and frequently used paternosters as seen in the movies "Berlin Express" (1948) and "Night People" (1954).
In Frankfurt the hotel Fleming's has an operational paternoster.
In Jena, a paternoster is in use at the headquarters of Jenapharm.
In Kassel, a paternoster is still in use at the headquarters of Wintershall Dea
In Lippstadt, a paternoster is still in use at the headquarter of Hella/Forvia.
In Wiesbaden, a paternoster is still in use at the Federal Statistical Office of Germany.
In Wetzlar, a paternoster is in use at the headquarters of Leica Microsystems
In Stuttgart, a paternoster is still in use at city hall (Stuttgart Rathaus).
In Leipzig, a paternoster is still in use at city hall (Leipzig Neues Rathaus)
Hungary
In Jahn Ferenc hospital in Budapest.
In Miskolc, the University of Miskolc, has a working and in-use paternoster.
In the central office of National Tax and Duty Administration Budapest.
In the MVM building in Budapest.
In the headquarters of BKV Budapesti Közlekedési Zrt. in Budapest. (operating in 2020)
In the Ministry of Education in Budapest (operating and in daily use in March 2022).
In Kiskun County Hospital, Kecskemét
ELMŰ-székház (HQ) (Váci út – Dráva u. sarok, Budapest)
Pesti Központi Kerületi Bíróság (Pest District Court)(Budapest, Markó utca 25.)
Tőzsdepalota (volt MTV-székház / HQ) (Budapest, Szabadság tér 17.)
Italy
In Fiat's Head Office Building, Mirafiori, Turin (Torino) [as of 1985].
Netherlands
In the Netherlands, seven paternoster lifts could be found in 2012, some of which were still operational:
In the former Ziggo building at Spaarneplein 2, The Hague: no longer in use. (Stork Hijsch 1922, conversion 1976 Starlift, damage repair 1999 Schindler.) On 13 April 2012, a fatal accident occurred when an 81-year-old man was trapped between the lift and the wall.
At the Dudokhuis, Tata Steel Europe in IJmuiden: shut down in 1999. (Eggers Kehrhan, 1957):
In the HaKa building (the old head office of the Coöperatieve Groothandelsvereniging 'de Handelskamer' ) on the Vierhavenstraat in Rotterdam. This 1936 Hensen-Schindler lift has been operational again since the end of 2011, although the building is empty. For safety reasons, the lift can only be visited with the building manager. The lift can be put into operation for interested parties on request.
In the former tax office on Puntegaalstraat in Rotterdam; it is put into operation during Heritage Days, but may not be used. To enforce this, gates have been built across the entrances. (Backer and Rueb Breda, 1948, conversion December 1975 by De Reus BV.)
In the former post office on the Coolsingel 42 in Rotterdam: disused.
Two examples in the Scheepvaarthuis (now Grand Hotel Amrâth Amsterdam) in Amsterdam: working, can be used on request. (Roux Combaluzier, 1928.)
In the old school building on the Mauritskade in Amsterdam: whether the elevator is still working is unknown.
Norway
In Oslo, Landbrukets hus, on Schweigaards Gate. The building was built in 1965 as the headquarters for Norges Bondelag, who vacated it in 2016.
Poland
Building of Silesian Parliament in Katowice.
In Wrocław, Poland, Santander Bank building, Main Square. Available for employees only.
In Opole, Poland, Urząd Wojewódzki building, Ostrówek.
Russia
In the building of the Ministry of Agriculture in Moscow
Serbia
In Belgrade in the headquarters building of Serbian Railways there is one operating paternoster lift and another one which is not in service.
Slovakia
In Bratislava there are at least 5 operating paternosters: Ministry of Transport and Construction, Ministry of Interior, Ministry of Finance, Ministry of Agriculture and Rural Development and the headquarters of Railways of the Slovak Republic.
In Košice, the Technical University of Košice operates a paternoster in the main building called L9 since 1972. There's another paternoster in an administrative building of U.S.Steel Košice, steel manufacturing company in Košice.
Sri Lanka
Ceylon Electricity Board Headquarters building in Colombo
Sweden
In Sweden there is at least one functional Paternoster lift at HSB-huset, Kungsholmen, Stockholm
Mäster Samuelsgatan 56, in central Stockholm, houses a multi-floor Paternoster lift.
Ukraine
One functional paternoster in the building of Zakarpattia Oblast Administration in Uzhhorod.
United Kingdom
Current
The Arts Tower at the University of Sheffield has a paternoster, which is said to be the largest in Europe. It has 38 two-person cars and serves 22 storeys. A journey between two floors takes 13 seconds.
The Albert Sloman Library at the University of Essex on the Colchester campus has a working paternoster which began operating in 1967. The lift was temporarily out of service for refurbishment between December 2019 and June 2021.
Northwick Park Hospital in Harrow, North West London (part of the London North West University Healthcare NHS Trust) has the last working paternoster in London. It had been out of commission for many years until July 2020, when it was reopened for staff use.
Former
Aston University in Birmingham were operating paternoster lifts in the main building. These are no longer in use, but one is remaining and is visible on the 4th floor of the south wing. The lift cars are covered with a perspex wall, and some visual displays explain the story and operation of the lift.
On 8 December 2017 it was announced that the paternoster in the Attenborough tower at the University of Leicester which was constructed in 1968–70 would be taken out of service as maintenance had become too expensive. This was undertaken shortly afterwards.
At the University of Birmingham, both the main library and the Muirhead Tower had paternosters. The library was demolished in 2017, and replaced with a new library. The paternoster in the Muirhead Tower was closed for many years before a major refurbishment added two new lifts.
Birmingham Polytechnic (now Birmingham City University) had a paternoster in the 1970s in the Baker building on its City North Campus at Perry Barr. The building closed in 2018.
Birmingham College of Food, Tourism & Creative Studies, Summer Row, Birmingham. (now University College Birmingham)
Birmingham Dental School. The building was demolished during 2020–21
London School of Economics. The Clare Market Building had a paternoster until 1991
There was a paternoster in the Co-op's six-storey Fairfax House department store, in Bristol's Broadmead shopping centre. The store opened in March 1962 and was demolished in 1988.
Leeds University in the Roger Stevens building.
Newcastle University's Claremont Tower paternoster had a fatal accident in September 1975 after a car left its guide rail at the top of its journey and forced the two cars ascending behind it into the winding room above. Another accident in 1988 led to its subsequent closure and removal.
University of Glasgow. The Pontecorvo Building which housed The Institute of Genetics had a paternoster lift.
Oxford University Department of Engineering Science. The Thom Building had a paternoster lift through into the 1980s, now replaced by a pair of conventional lifts.
University of Salford Chemistry Tower had a paternoster lift. The building has been demolished.
Risley, Cheshire – Former United Kingdom Atomic Energy Authority (UKAEA) site, now Birchwood Park Business Park. The original management block 'A Block', and the later engineering building 'E Block' had paternoster lifts. Those in the former E Block (Chadwick House) survived into the 21st century (sealed off), and still exist in place. The adjacent ‘Y Block’ also had two sets, these are also sealed off.
UKAEA Winfrith Heath Dorset 4 floor Administration Building
BNFL Sellafield had a paternoster in its administration building B403. Demolished in 2002.
Viscount House, a British Airways office building at Hatton Cross. Now demolished.
Unipart House, Oxford had two of them. They were at each end of the building but were taken out due to the cost of maintenance. Bob Geldof and The Boomtown Rats filmed their video of Love or Something in them.
Schofields Department Store, Leeds had one in their Lands Lane building giving staff only access to the staff restaurant. Operational late 1970's. From personal memory.
Gallery
See also
Belt manlift
Escalator
List of elevator manufacturers
Shabbat elevator
Revolving door
References
External links
A look at the last remaining paternoster lifts | Associated Press, 2017 (YouTube)
Information and photos regarding the GEC Marconi paternoster featured in "The Prisoner" TV series
Elevators
Vertical transport devices
English inventions
1884 introductions
Articles containing video clips | Paternoster lift | [
"Technology",
"Engineering"
] | 4,051 | [
"Building engineering",
"Vertical transport devices",
"Transport systems",
"Elevators"
] |
565,501 | https://en.wikipedia.org/wiki/Status%20symbol | A status symbol is a visible, external symbol of one's social position, an indicator of economic or social status. Many luxury goods are often considered status symbols. Status symbol is also a sociological term – as part of social and sociological symbolic interactionism – relating to how individuals and groups interact and interpret various cultural symbols.
Etymology
The term "status symbol" was first written in English in 1955, but from 1959 with the publication of the bestseller "The Status Seekers" greater distribution. There, journalist Vance Packard describes the social strategy and behavior in the USA.
By region and time
As people aspire to high status, they often seek also its symbols. As with other symbols, status symbols may change in value or meaning over time, and will differ among countries and cultural regions, based on their economy and technology.
For example, before the invention of the printing press, possession of a large collection of laboriously hand-copied books was a symbol of wealth and scholarship. In later centuries, books (and literacy) became more common, so a private library became less-rarefied as a status symbol, though a sizable collection still commands respect.
In some past cultures of East Asia, pearls and jade were major status symbols, reserved exclusively for royalty. Similar legal exclusions applied to the toga and its variants in ancient Rome, and to cotton in the Aztec Empire. Special colors, such as imperial yellow (in China) or royal purple (in ancient Rome) were reserved for royalty, with severe penalties for unauthorized display. Another common status symbol of the European medieval past was heraldry, a display of one's family name and history.
Societal recognition
Status symbols also indicate the cultural values of a society or a subculture. For example, in a commercial society, having money or wealth and things that can be bought by wealth, such as cars, houses, or fine clothing, are considered status symbols. Where warriors are respected, a scar can represent honor or courage. Among intellectuals being able to think in an intelligent and educated way is an important status symbol regardless of material possessions. In academic circles, a long list of publications and a securely tenured position at a prestigious university or research institute are a mark of high status. It has been speculated that the earliest foods to be domesticated were luxury feast foods used to cement one's place as a "rich person".
A uniform symbolizes membership in an organization, and may display additional insignia of rank, specialty, tenure and other details of the wearer's status within the organization. A state may confer decorations, medals or badges that can show that the wearer has heroic or official status. Elaborate color-coded academic regalia is often worn during commencement ceremonies, indicating academic rank and specialty.
In many cultures around the world, diverse visual markers of marital status are widely used. Coming of age rituals and other rites of passage may involve granting and display of symbols of a new status. Dress codes may specify who ought to wear particular kinds or styles of clothing, and when and where specific items of clothing are displayed.
Body modifications
The condition and appearance of one's body can be a status symbol. In times past, when most workers did physical labor outdoors under the sun and often had little food, being pale and fat was a status symbol, indicating wealth and prosperity (through having more than enough food and not having to do manual labor). Now that workers usually do less-physical work indoors and find little time for exercise, being tanned and thin is often a status symbol in modern cultures.
Dieting to reduce excess body fat is widely practiced in Western society, while some traditional societies still value obesity as a sign of prosperity. Development of muscles through exercise, previously disdained as a stigma of doing heavy manual labor, is now valued as a sign of personal achievement. Some groups, such as extreme bodybuilders and sumo wrestlers use special exercise and diet to "bulk up" into an impressive appearance.
Ancient Central American Maya cultures artificially induced crosseyedness and flattened the foreheads of high-born infants as a permanent, lifetime sign of noble status. The Mayans also filed their teeth to sharp points to look fierce, or inset precious stones into their teeth as decoration.
Material possessions
Luxury goods are often perceived as status symbols. Examples may include a mansion or penthouse apartment, a trophy wife, haute couture fashionable clothes, jewellery, or a luxury vehicle. A sizeable collection of high-priced artworks or antiques may be displayed, sometimes in multiple seasonally occupied residences located around the world. Privately owned aircraft and luxury yachts are movable status symbols that can be taken from one glamorous location to another; the "jet set" refers to wealthy individuals who travel by private jet and who frequent fashionable resorts.
Status symbols are also used by persons of much more modest means. In the Soviet Union before the fall of the Berlin Wall, possession of American-style blue jeans or rock music recordings (even pirated or bootlegged copies) was an important status symbol among rebellious teenagers. In the 1990s, foreign cigarettes in China, where a pack of Marlboro could cost one day's salary for some workers, were seen as a status symbol. Mobile phone usage had been considered a status symbol (for example in Turkey in the early 1990s), but is less distinctive today, because of the spread of inexpensive mobile phones. Nonetheless Apple products such as iPhone are common status symbols among modern teenagers.
A common type of modern status symbol is a prestigious luxury branded item, whether apparel or other type of a good. The brand name or logo is often prominently displayed, or featured as a graphic design element of decoration. Certain brands are so highly valued that cheap counterfeit goods or knock-off copies are purchased and displayed by those who do not want to, or are unable to, pay for the genuine item.
See also
Badge of shame
Belongingness
Conspicuous consumption
Fashion accessory
Identity performance
Narcissistic supply
Occupational prestige
Positional good
Relative deprivation
Social stratification
Veblen good
References
Further reading
Vance Oakley Packard: The status seekers: an exploration of class behaviour in Amerika. Harmondsworth, Pelican books, 1963.
Samuel I. Hayakawa: Symbol, status, and personality. New York, Harcourt, Brace & World, 1963. ISBN 9780156876117
Pierre Bourdieu: Distinction: a social critique of the judgement of taste. London/New York, Routledge, 1984. ISBN 9780674212800
Social status
Narcissism | Status symbol | [
"Biology"
] | 1,324 | [
"Behavior",
"Narcissism",
"Human behavior"
] |
565,530 | https://en.wikipedia.org/wiki/Mesopelagic%20zone | The mesopelagic zone (Greek μέσον, middle), also known as the middle pelagic or twilight zone, is the part of the pelagic zone that lies between the photic epipelagic and the aphotic bathypelagic zones. It is defined by light, and begins at the depth where only 1% of incident light reaches and ends where there is no light; the depths of this zone are between approximately 200 to 1,000 meters (~656 to 3,280 feet) below the ocean surface.
The mesopelagic zone occupies about 60% of the planet's surface and about 20% of the ocean's volume, amounting to a large part of the total biosphere. It hosts a diverse biological community that includes bristlemouths, blobfish, bioluminescent jellyfish, giant squid, and a myriad of other unique organisms adapted to live in a low-light environment. It has long captivated the imagination of scientists, artists and writers; deep sea creatures are prominent in popular culture.
Physical conditions
The mesopelagic zone includes the region of sharp changes in temperature, salinity and density called the thermocline, halocline, and pycnocline respectively. The temperature variations are large; from over 20 °C (68 °F) at the upper layers to around 4 °C (39 °F) at the boundary with the bathyal zone. The variation in salinity is smaller, typically between 34.5 and 35 psu. The density ranges from 1023 to 1027 g/L of seawater. These changes in temperature, salinity, and density induce stratification which create ocean layers. These different water masses affect gradients and mixing of nutrients and dissolved gasses. This makes this a dynamic zone.
The mesopelagic zone has some unique acoustic features. The Sound Fixing and Ranging (SOFAR) channel, where sound travels the slowest due to salinity and temperature variations, is located at the base of the mesopelagic zone at about 600–1,200m. It is a wave-guided zone where sound waves refract within the layer and propagate long distances. The channel got its name during World War II when the US Navy proposed using it as a life saving tool. Shipwreck survivors could drop a small explosive timed to explode in the SOFAR channel and then listening stations could determine the position of the life raft. During the 1950s, the US Navy tried to use this zone to detect Soviet submarines by creating an array of hydrophones called the Sound Surveillance System (SOSUS.) Oceanographers later used this underwater surveillance system to figure out the speed and direction of deep ocean currents by dropping SOFAR floats that could be detected with the SOSUS array.
The mesopelagic zone is important for water mass formation, such as mode water. Mode water is a water mass that is typically defined by its vertically mixed properties. It often forms as deep mixed layers at the depth of the thermocline. The mode water in the mesopelagic has residency times on decadal or century scales. The longer overturning times contrast with the daily and shorter scales that a variety of animals move vertically through the zone and sinking of various debris.
Biogeochemistry
Carbon
The mesopelagic zone plays a key role in the ocean's biological pump, which contributes to the oceanic carbon cycle. In the biological pump, organic carbon is produced in the surface euphotic zone where light promotes photosynthesis. A fraction of this production is exported out of the surface mixed layer and into the mesopelagic zone. One pathway for carbon export from the euphotic layer is through sinking of particles, which can be accelerated through repackaging of organic matter in zooplankton fecal pellets, ballasted particles, and aggregates.
In the mesopelagic zone, the biological pump is key to carbon cycling, as this zone is largely dominated by remineralization of particulate organic carbon (POC). When a fraction of POC is exported from the euphotic zone, an estimated 90% of that POC is respired in the mesopelagic zone. This is due to the microbial organisms that respire organic matter and remineralize the nutrients, while mesopelagic fish also package organic matter into quick-sinking parcels for deeper export.
Another key process occurring in this zone is the diel vertical migration of certain species, which move between the euphotic zone and mesopelagic zone and actively transport particulate organic matter to the deep. In one study in the Equatorial Pacific, myctophids in the mesopelagic zone were estimated to actively transport 15–28% of the passive POC sinking to the deep, while a study near the Canary Islands estimated 53% of vertical carbon flux was due to active transport from a combination of zooplankton and micronekton. When primary productivity is high, the contribution of active transport by vertical migration has been estimated to be comparable to sinking particle export.
Particle Packaging and sinking
Mean particle sinking rates are 10 to 100 m/day. Sinking rates have been measured in the project VERTIGO (Vertical Transport in the Global Ocean) using settling velocity sediment traps. The variability in sinking rates is due to differences in ballast, water temperature, food web structure and the types of phyto and zooplankton in different areas of the ocean. If the material sinks faster, then it gets respired less by bacteria, transporting more carbon from the surface layer to the deep ocean. Larger fecal pellets sink faster due to lower friction-surface/mass ratio. More viscous waters could slow the sinking rate of particles.
Oxygen
Dissolved oxygen is a requirement for aerobic respiration, and while the surface ocean is usually oxygen-rich due to atmospheric gas exchange and photosynthesis, the mesopelagic zone is not in direct contact with the atmosphere, due to stratification at the base of the surface mixed layer. Organic matter is exported to the mesopelagic zone from the overlying euphotic layer, while the minimal light in the mesopelagic zone limits photosynthesis. The oxygen consumption due to respiration of most of the sinking organic matter and lack of gas exchange, often creates an oxygen minimum zone (OMZ) in the mesopelagic. The mesopelagic OMZ is particularly severe in the eastern tropical Pacific Ocean and tropical Indian Ocean due to poor ventilation and high rates of organic carbon export to the mesopelagic. Oxygen concentrations in the mesopelagic are occasionally result in suboxic concentrations, making aerobic respiration difficult for organisms. In these anoxic regions, chemosynthesis may occur in which CO2 and reduced compounds such as sulfide or ammonia are taken up to form organic carbon, contributing to the organic carbon reservoir in the mesopelagic. This pathway of carbon fixation has been estimated to be comparable in rate to the contribution by heterotrophic production in this ocean realm.
Nitrogen
The mesopelagic zone, an area of significant respiration and remineralization of organic particles, is generally nutrient-rich. This is in contrast to the overlying euphotic zone, which is often nutrient-limited. Areas of low oxygen such as OMZ's are a key area of denitrification by prokaryotes, a heterotrophic pathways in which nitrate is converted into nitrogen gas, resulting in a loss to the ocean reservoir of reactive nitrogen. At the suboxic interface that occurs at the edge of the OMZ, nitrite and ammonium can be coupled to produce nitrogen gas through anammox, also removing nitrogen from the biologically available pool.
Biology
Although some light penetrates the mesopelagic zone, it is insufficient for photosynthesis. The biological community of the mesopelagic zone has adapted to a low-light environment. This is a very efficient ecosystem with many organisms recycling the organic matter sinking from the epipelagic zone resulting in very little organic carbon making it to deeper ocean waters. The general types of life forms found are daytime-visiting herbivores, detritivores feeding on dead organisms and fecal pellets, and carnivores feeding on those detritivores.
Many organisms in the mesopelagic zone move up into the epipelagic zone at night, and retreat to the mesopelagic zone during the day, which is known as diel vertical migration. These migrators can therefore avoid visual predators during the day and feed at night, while some of their predators also migrate up at night to follow the prey. There is so much biomass in this migration that sonar operators in World War II would regularly misinterpret the signal returned by this thick layer of plankton as a false sea floor.
Estimates of the global biomass of mesopelagic fishes range from 1 gigatonne (Gt) based on net tows to 7–10 Gt based on measurements using active acoustics.
Virus and microbial ecology
Very little is known about the microbial community of the mesopelagic zone because it is a difficult part of the ocean to study. Recent work using DNA from seawater samples emphasized the importance of viruses and microbes role in recycling organic matter from the surface ocean, known as the microbial loop. These many microbes can get their energy from different metabolic pathways. Some are autotrophs, heterotrophs, and a 2006 study even discovered chemoautotrophs. This chemoautotrophic Archaea crenarchaeon Candidatus can oxidize ammonium as their energy source without oxygen, which could significantly impact the nitrogen and carbon cycles. One study estimates these ammonium-oxidizing bacteria, which are only 5% of the microbial population, can annually capture 1.1 Gt of organic carbon.
Microbial biomass and diversity typically decline exponentially with depth in the mesopelagic zone, tracking the general decline of food from above. The community composition varies with depths in the mesopelagic as different organisms are evolved for varying light conditions. Microbial biomass in the mesopelagic is greater at higher latitudes and decreases towards the tropics, which is likely linked to the differing productivity levels in the surface waters. Viruses however are very abundant in the mesopelagic, with around 1010 - 1012 every cubic meter, which is fairly uniform throughout the mesopelagic zone.
Zooplankton ecology
The mesopelagic zone hosts a diverse zooplankton community. Common zooplankton include copepods, krill, jellyfish, siphonophores, larvaceans, cephalopods, and pteropods. Food is generally scarce in the mesopelagic, so predators have to be efficient in capturing food. Gelatinous organisms are thought to play an important role in the ecology of the mesopelagic and are common predators. Though previously thought to be passive predators just drifting through the water column, jellyfish could be more active predators. One study found that the helmet jellyfish Periphylla periphylla exhibit social behavior and can find each other at depth and form groups. Such behavior was previously attributed to mating, but scientists speculate this could be a feeding strategy to allow a group of jellyfish to hunt together. Mesopelagic zooplankton have unique adaptations for the low light. Bioluminescence is a very common strategy in many zooplankton. This light production is thought to function as a form of communication between conspecifics, prey attraction, prey deterrence, and/or reproduction strategy. Another common adaption are enhanced light organs, or eyes, which is common in krill and shrimp, so they can take advantage of the limited light. Some octopus and krill even have tubular eyes that look upwards in the water column.
Most life processes, like growth rates and reproductive rates, are slower in the mesopelagic. Metabolic activity has been shown to decrease with increasing depth and decreasing temperature in colder-water environments. For example, the mesopelagic shrimp-like mysid, Gnathophausia ingens, lives for 6.4 to 8 years, while similar benthic shrimp only live for 2 years.
Fish ecology
The mesopelagic is home to a significant portion of the world's total fish biomass. Mesopelagic fish are found globally, with exceptions in the Arctic Ocean. A 1980 study puts the mesopelagic fish biomass at about one billion tons. Then a 2008 study estimated the world marine fish biomass at between 0.8 and 2 billion tons. A more recent study concluded mesopelagic fish could have a biomass amounting to 10 billion tons, equivalent to about 100 times the annual catch of traditional fisheries of about 100 million metric tons. However, there is a lot of uncertainty in this biomass estimate. This ocean realm could contain the largest fishery in the world and there is active development for this zone to become a commercial fishery.
There are currently thirty families of known mesopelagic fish. One dominant fish in the mesopelagic zone are lanternfish (Myctophidae), which include 245 species distributed among 33 different genera. They have prominent photophores along their ventral side. The Gonostomatidae, or bristlemouth, are also common mesopelagic fish. The bristlemouth could be the Earth's most abundant vertebrate, with numbers in the hundreds of trillions to quadrillions.
Mesopelagic fish are difficult to study due to their unique anatomy. Many of these fish have swim bladders to help them control their buoyancy, which makes them hard to sample because those gas-filled chambers typically burst as the fish come up in nets and the fish die. Scientists in California have made progress on mesopelagic fish sampling by developing a submersible chamber that can keep fish alive on the way up to the surface under a controlled atmosphere and pressure. A passive method to estimate mesopelagic fish abundance is by echosounding to locate the 'deep scattering layer' through the backscatter received from these acoustic sounders. A 2015 study suggested that some areas have had a decline in abundance of mesopelagic fish, including off the coast of Southern California, using a long-term study dating back to the 1970s. Cold water species were especially vulnerable to decline.
Mesopelagic fish are adapted to a low-light environment. Many fish are black or red, because these colors appear dark due to the limited light penetration at depth. Some fish have rows of photophores, small light-producing organs, on their underside to mimic the surrounding environment. Other fish have mirrored bodies which are angled to reflect the surrounding ocean low-light colors and protect the fish from being seen, while another adaptation is countershading where fish have light colors on the ventral side and dark colors on the dorsal side.
Food is often limited and patchy in the mesopelagic, leading to dietary adaptations. Common adaptations fish may have include sensitive eyes and huge jaws for enhanced and opportunistic feeding. Fish are also generally small to reduce the energy requirement for growth and muscle formation. Other feeding adaptations include jaws that can unhinge, elastic throats, and massive, long teeth. Some predators develop bioluminescent lures, like the tasselled anglerfish, which can attract prey, while others respond to pressure or chemical cues instead of relying on vision.
Human impacts
Pollution
Marine debris
Marine debris, specifically in the plastic form, have been found in every ocean basin and have a wide range of impacts on the marine world.
One of the most critical issues is ingestion of plastic debris, specifically microplastics. Many mesopelagic fish species migrate to the surface waters to feast on their main prey species, zooplankton and phytoplankton, which are mixed with microplastics in the surface waters. Additionally, research has shown that even zooplankton are consuming the microplastics themselves. Mesopelagic fish play a key role in energy dynamics, meaning they provide food to a number of predators including birds, larger fish and marine mammals. The concentration of these plastics has the potential to increase, so more economically important species could become contaminated as well. Concentration of plastic debris in mesopelagic populations can vary depending on geographic location and the concentration of marine debris located there. In 2018, approximately 73% of approximately 200 fish sampled in the North Atlantic had consumed plastic.
Bioaccumulation
Bioaccumulation (a buildup of a certain substance in the adipose tissue) and biomagnification (the process in which the concentration of the substance grows higher as you rise through the food chain) are growing issues in the mesopelagic zone. Mercury in fish can be traced back to a combination of anthropological factors (such as coal mining) in addition to natural factors. Mercury is a particularly important bioaccumulation contaminant because its concentration in the mesopelagic zone is increasing faster than in surface waters. Inorganic mercury occurs in anthropogenic atmospheric emissions in its gaseous elemental form, which then oxidizes and can be deposited in the ocean. Once there, the oxidized form can be converted to methylmercury, which is its organic form. Research suggests that current levels anthropogenic emissions will not equilibrate between the atmosphere and ocean for a period of decades to centuries, which means we can expect current mercury concentrations in the ocean to keep rising. Mercury is a potent neurotoxin, and poses health risks to the whole food web, beyond the mesopelagic species that consume it. Many of the mesopelagic species, such as myctophids, that make their diel vertical migration to the surface waters, can transfer the neurotoxin when they are consumed by pelagic fish, birds and mammals.
Fishing
Historically, there have been few examples of efforts to commercialize the mesopelagic zone due to low economic value, technical feasibility and environmental impacts. While the biomass may be abundant, fish species at depth are generally smaller in size and slower to reproduce. Fishing with large trawl nets poses threats to a high percentage of bycatch as well as potential impacts to the carbon cycling processes. Additionally, ships trying to reach productive mesopelagic regions requires fairly long journeys offshore. In 1977, a Soviet fishery opened but closed less than 20 years later due to low commercial profits, while a South African purse seine fishery closed in the mid-1980s due to processing difficulties from the high oil content of fish.
As the biomass in the mesopelagic is so abundant, there has been an increased interest to determine whether these populations could be of economic use in sectors other than direct human consumption. For example, it has been suggested that the high abundance of fish in this zone could potentially satisfy a demand for fishmeal and nutraceuticals. With a growing global population, the demand for fishmeal in support of a growing aquaculture industry is high. There is potential for an economically viable harvest. For example, 5 billion tons of mesopelagic biomass could result in the production of circa 1.25 billion tons of food for human consumption. Additionally, the demand for nutraceuticals is also rapidly growing, stemming from the popular human consumption of Omega-3 Fatty Acids in addition to the aquaculture industry that requires a specific marine oil for feed material. Lanternfish are of much interest to the aquaculture market, as they are especially high in fatty acids.
Climate Change
The mesopelagic region plays an important role in the global carbon cycle, as it is the area where most of the surface organic matter is respired. Mesopelagic species also acquire carbon during their diel vertical migration to feed in surface waters, and they transport that carbon to the deep sea when they die. It is estimated that the mesopelagic cycles between 5 and 12 billion tons of carbon dioxide from the atmosphere per year, and until recently, this estimate was not included in many climate models. It is difficult to quantify the effects of climate change on the mesopelagic zone as a whole, as climate change does not have uniform impacts geographically. Research suggests that in warming waters, as long as there are adequate nutrients and food for fish, then mesopelagic biomass could actually increase due to higher trophic efficiency and increased temperature-driven metabolism. However, because ocean warming will not be uniform throughout the global mesopelagic zone, it is predicted that some areas may actually decrease in fish biomass, while others increase.
Water column stratification will also likely increase with ocean warming and climate change. Increased ocean stratification reduces the introduction of nutrients from the deep ocean into the euphotic zone resulting in decreases in both net primary production and sinking particulate matter. Additional research suggests shifts in the geographical range of many species could also occur with warming, with many of them shifting poleward. The combination of these factors could potentially mean that as global ocean basins continue to warm, there could be areas in the mesopelagic that increase in biodiversity and species richness, while declines in other areas, especially moving farther from the equator.
Research and Exploration
There is a dearth of knowledge about the mesopelagic zone so researchers have begun to develop new technology to explore and sample this area. The Woods Hole Oceanographic Institution (WHOI), NASA, and the Norwegian Institute of Marine Research are all working on projects to gain a better understanding of this zone in the ocean and its influence on the global carbon cycle. Traditional sampling methods like nets have proved to be inadequate because they scare off creatures due to the pressure wave formed by the towed net and the light produced by the bioluminescent species caught in the net.
Mesopelagic activity was first investigated by use of sonar because the return bounces off of plankton and fish in the water. However, there are many challenges with acoustic survey methods and previous research has estimated errors in measured amounts of biomass of up to three orders of magnitude. This is due to inaccurate incorporation of depth, species size distribution, and acoustic properties of the species. Norway's Institute of Marine Research has launched a research vessel named Dr. Fridtjof Nansen to investigate mesopelagic activity using sonar with their focus being on the sustainability of fishing operations. To overcome the challenges faced with acoustic sampling, WHOI is developing remote operated vehicles (ROVs) and robots (Deep-See, Mesobot, and Snowclops) that are capable of studying this zone more precisely in a dedicated effort called the Ocean Twilight Zone project that launched in August 2018.
Discovery and Detection
The deep scattering layer often characterizes the mesopelagic due to the high amount of biomass that exists in the region. Acoustic sound sent into the ocean bounces off particles and organisms in the water column and return a strong signal. The region was initially discovered by American researchers during World War II in 1942 during anti-submarine research with sonar. Sonar at the time could not penetrate below this depth due to the large number of creatures obstructing sound waves. It is uncommon to detect deep scattering layers below 1000m. Until recently, sonar has been the predominant method for studying the mesopelagic.
The Malaspina Circumnavigation Expedition was a Spanish-led scientific quest in 2011 to gain a better understanding of the state of the ocean and the diversity in the deep oceans. The data collected, particularly through sonar observations showed that the biomass estimation in the mesopelagic was lower than previously thought.
Deep-See
WHOI is currently working on a project to characterize and document the pelagic ecosystem. They have developed a device named Deep-See weighing approximately 700 kg, which is designed to be towed behind a research vessel. The Deep-See is capable of reaching depths up to 2000 m and can estimate the amount of biomass and biodiversity in this mesopelagic ecosystem. Deep-See is equipped with cameras, sonars, sensors, water sample collection devices, and a real-time data transmission system.
Mesobot
WHOI is collaborating with the Monterey Bay Aquarium Research Institute (MBARI), Stanford University, and the University of Texas Rio Grande Valley to develop a small autonomous robot, Mesobot, weighing approximately 75 kg. Mesobot is equipped with high-definition cameras to track and record mesopelagic species on their daily migration over extended periods of time. The robot's thrusters were designed so that they do not disturb the life in the mesopelagic that it is observing. Traditional sample collection devices fail to preserve organisms captured in the mesopelagic due to the large pressure change associated with surfacing. The Mesobot also has a unique sampling mechanism that is capable of keeping the organisms alive during their ascent. The first sea trial of this device is expected to be in 2019.
MINIONS
Another mesopelagic robot developed by WHOI are the MINIONS. This device descends down the water column and takes images of the amount and size distribution of marine snow at various depths. These tiny particles are a food source for other organisms so it is important to monitor the different levels of marine snow to characterize the carbon cycling processes between the surface ocean and the mesopelagic.
SPLAT cam
The Harbor Branch Oceanographic Institute has developed the Spatial PLankton Analysis Technique (SPLAT) to identify and map distribution patterns of bioluminescent plankton. The various bioluminescent species produce a unique flash that allows the SPLAT to distinguish each specie's flash characteristic and then map their 3-dimensional distribution patterns. Its intended use was not for investigating the mesopelagic zone, although it is capable of tracking movement patterns of bioluminescent species during their vertical migrations. It would be interesting to apply this mapping technique in the mesopelagic to obtain more information about the diurnal vertical migrations that occur in this zone of the ocean.
See also
Ocean Twilight Zone project at Woods Hole Oceanographic Institution
Ocean Twilight Zone creature features
Value of the ocean twilight zone to humans
Climate and the ocean twilight zone
Mesopelagic fish
References
External links
Aquatic biomes
Oceanography | Mesopelagic zone | [
"Physics",
"Environmental_science"
] | 5,422 | [
"Oceanography",
"Hydrology",
"Applied and interdisciplinary physics"
] |
565,536 | https://en.wikipedia.org/wiki/Bathypelagic%20zone | The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of below the ocean surface. It lies between the mesopelagic above and the abyssopelagic below. The bathypelagic is also known as the midnight zone because of the lack of sunlight; this feature does not allow for photosynthesis-driven primary production, preventing growth of phytoplankton or aquatic plants. Although larger by volume than the photic zone, human knowledge of the bathypelagic zone remains limited by ability to explore the deep ocean.
Physical characteristics
The bathypelagic zone is characterized by a nearly constant temperature of approximately and a salinity range of 33-35 g/kg. This region has little to no light because sunlight does not reach this deep in the ocean and bioluminescence is limited. The hydrostatic pressure in this zone ranges from 100-400 atmospheres (atm) due to the increase of 1 atm for every 10 m depth. It is believed that these conditions have been consistent for the past 8000 years.
This ocean depth spans from the edge of the continental shelf down to the top of the abyssal zone, and along continental slope depths. The bathymetry of the bathypelagic zone consists of limited areas where the seafloor is in this depth range along the deepest parts of the continental margins, as well as seamounts and mid-ocean ridges. The continental slopes are mostly made up of accumulated sediment, while seamounts and mid-ocean ridges contain large areas of hard substrate that provide habitats for bathypelagic fishes and benthic invertebrates. Although currents at these depths are very slow, the topography of seamounts interrupts the currents and creates eddies that retain plankton in the seamount region, thus increasing fauna nearby as well
Hydrothermal vents are also a common feature in some areas of the bathypelagic zone and are primarily formed from the spreading of Earth's tectonic plates at mid-ocean ridges. As the bathypelagic region lacks light, these vents play an important role in global ocean chemical processes, thus supporting unique ecosystems that have adapted to utilize chemicals as energy, via chemoautotrophy, instead of sunlight, to sustain themselves. In addition, hydrothermal vents facilitate precipitation of minerals on the seafloor, making them regions of interest for deep-sea mining.
Biogeochemistry
Many of the biogeochemical processes in the bathypelagic region are dependent upon the input of organic matter from the overlying epipelagic and mesopelagic zones. This organic material, sometimes called marine snow, sinks in the water column or is transported within downward convected water masses such as the Thermohaline Circulation. Hydrothermal vents also deliver heat and chemicals such as sulfide and methane. These chemicals can be utilized to sustain metabolism by organisms in the region. Our understanding of these biogeochemical processes has historically been limited due to the difficulty and cost of collecting samples from these ocean depths. Other technological challenges, such as measuring microbial activity under the pressure conditions experienced in the bathypelagic zone, have also restricted our knowledge of the region. Although scientific advancements have increased our understanding over the past several decades, many aspects remain a mystery. One of the major areas of current research is focused on understanding carbon remineralization rates in the region. Prior studies have struggled to quantify the rates at which prokaryotes in this region remineralize carbon because previously developed techniques may not be adequate for this region, and indicate remineralization rates much higher than expected. Further work is needed to explore this question, and may require revisions to our understanding of the global carbon cycle.
Particulate organic matter
Organic material from primary production in the epipelagic zone, and to a far lesser extent, organic inputs from terrestrial sources, make up a majority of the Particulate Organic Matter (POM) in the ocean. POM is delivered to the bathypelagic zone via sinking copepod fecal pellets and dead organisms; these parcels of organic matter fall through the water column and deliver organic carbon, nitrogen, and phosphorus, to organisms that live below the photic zone. These parcels are sometimes referred to as marine snow or ocean dandruff. This is also the dominant delivery mechanism of food to organisms in the bathypelagic zone because there is no sunlight for photosynthesis, with chemoautotrophy playing a more minor role as far as we know.
As POM sinks through the water column, it is consumed by organisms which deplete it of nutrients. The size and density of these particles affect their likelihood of reaching organisms in the bathypelagic zone. Smaller parcels of POM often become aggregated together as they fall, which quickens their descent and prohibits their consumption by other organisms, increasing their likelihood of reaching lower depths. The density of these particles may be increased in some regions where minerals associated with some forms of phytoplankton, such as biogenic silica and calcium carbonate "ballast" resulting in more rapid transport to deeper depth.
Carbon
A majority of organic carbon is produced in the epipelagic zone, with a small portion transported deeper into the ocean interior. This process, known as the biological pump, plays a large role in the sequestration of carbon from the atmosphere into the ocean. Organic carbon is primarily exported to the bathypelagic zone in the form of particulate organic carbon (POC) and dissolved organic carbon (DOC).
POC is the largest component of organic carbon delivered to the bathypelagic zone; it primarily takes the form of fecal pellets and dead organisms that sink out of the surface waters and fall toward the ocean floor. Regions with higher primary productivity where particles are able to sink quickly, such as equatorial upwelling zones and the Arabian Sea, have the greatest amount of POC delivery to the bathypelagic zone.
The vertical mixing of DOC-rich surface waters is also a process that delivers carbon to the bathypelagic zone, however, it constitutes a substantially smaller portion of overall transport than POC delivery. DOC transport occurs most readily in regions with high rates of ventilation or ocean turnover, such as the interior of gyres or deep water formation sites along the thermohaline circulation.
Calcium carbonate dissolution
The region in the water column at which calcite dissolution begins to occur rapidly, known as the lysocline, is typically located near the base bathypelagic zone at approximately 3,500 m depth, but varies among ocean basins. The lysocline lies below the saturation depth (the transition to undersaturated conditions with respect to calcium carbonate) and above the carbonate compensation depth (below which there is no calcium carbonate preservation). In a supersaturated environment, the tests of calcite-forming organisms are preserved as they sink toward the sea floor, resulting in sediments with relatively high amounts of CaCO3. However, as depth and pressure increase and temperature decreases, the solubility of calcium carbonate also increases, which results in more dissolution and less net transport to the deeper, underlying seafloor. As a result of this rapid change in dissolution rates, sediments in the bathypelagic region vary widely in CaCO3 content and burial.
Ecology
The ecology of the bathypelagic ecosystem is constrained by its lack of sunlight and primary producers, with limited production of microbial biomass via autotrophy. The trophic networks in this region rely on particulate organic matter (POM) that sinks from the epipelagic and mesopelagic water, and oxygen inputs from the thermohaline circulation. Despite these limitations, this open-ocean ecosystem is home to microbial organisms, fish, and nekton.
Microbial ecology
A comprehensive understanding of the inputs driving the microbial ecology in the bathypelagic zone is lacking due to limited observational data, but has been improving with advancements in deep-sea technology. A majority of our knowledge of ocean microbial activity comes from studies of the shallower regions of the ocean because it is easier to access, and it was previously assumed that deeper water did not have suitable physical conditions for diverse microbial communities. The bathypelagic zone receives inputs of organic material and POM from the surface ocean on the order of 1-3.6 Pg C/year.
Prokaryote biomass in the bathypelagic is dependent and thus correlated with the amount of sinking POM and organic carbon availability. These essential organic carbon inputs for microbes typically decrease with depth as they are utilized while sinking to the bathypelagic. Microbial production varies over six orders of magnitude based on resource availability in a given area. Prokaryote abundance can range from 0.03-2.3x105 cells ml−1, and have population turnover times that can range from 0.1–30 years. Archaea make up a larger portion of the total prokaryote cell abundance, and different groups have different growth needs, with some archaea groups for example utilizing amino acid groups more readily than others. Some archaea like Crenarchaeota have Crenarchaeota 16S rRNA and archaeal amoA gene abundances correlated to dissolved inorganic carbon (DIC) fixation. The utilization of DIC is thought to be fueled by the oxidation of ammonium and is one form of chemoautotrophy. Based on regional variation and differences in prokaryote abundance, heterotrophic prokaryote production, and particulate organic carbon (POC) inputs to the bathypelagic zone.
Research to quantify bacterial-consuming grazers, like heterotrophic eukaryotes, has been limited by difficulties in sampling. Oftentimes organisms do not survive being brought to the surface due to experiencing drastic pressure changes in a short amount of time. Work is underway to quantify cell abundance and biomass, but due to poor survival, it is difficult to get accurate counts. In more recent years there has been an effort to categorize the diversity of the eukaryotic assemblages in the bathypelagic zone using methods to assess the genetic compositions of microbial communities based on supergroups, which is a way to classify organisms that have common ancestry. Some important groups of bacterial grazers include Rhizaria, Alveolata, Fungi, Stramenopiles, Amoebozoa, and Excavata (listed from most to least abundant), with the remaining composition classified as uncertain or other.
Viruses influence biogeochemical cycling through the role they play in marine food webs. Their overall abundance can be up to two orders of magnitude lower than the mesopelagic zone, however, there is often high viral abundance found around deep-sea hydrothermal vents. The magnitude of their impacts on biological systems is demonstrated by the varying range of viral-to-prokaryote abundance ratios ranging from 1-223, this indicates that there are the same amount or more viruses than prokaryotes.
Fauna
Fish ecology
Despite the lack of light, vision plays a role in life within the bathypelagic with bioluminescence a trait among both nektonic and planktonic organisms. In contrast to organisms in the water column, benthic organisms in this region tend to have limited to no bioluminescence. The bathypelagic zone contains sharks, squid, octopuses, and many species of fish, including deep-water anglerfish, gulper eel, amphipods, and dragonfish. The fish are characterized by weak muscles, soft skin, and slimy bodies. The adaptations of some of the fish that live there include small eyes and transparent skin. However, this zone is difficult for fish to live in since food is scarce; resulting in species evolving slow metabolic rates in order to conserve energy. Occasionally, large sources of organic matter from decaying organisms, such as whale falls, create a brief burst of activity by attracting organisms from different bathypelagic communities.
Diel vertical migration
Some bathypelagic species undergo vertical migration, which differs from the diel vertical migration of mesopelagic species in that it is not driven by sunlight. Instead, the migration of bathypelagic organisms is driven by other factors, most of which remain unknown. Some research suggests the movement of species within the overlying pelagic region could prompt individual bathypelagic species to migrate, such as Sthenoteuthis sp., a species of squid. In this particular example, Sthenoteuthis sp. appears to migrate individually over the course of ~4–5 hours towards the surface and then form into groups. While in most regions migration patterns can be driven by predation, in this particular region, the migration patterns are not believed to result solely from predator-prey relations. Instead, these relations are commensalistic, with the species who remain in the bathypelagic benefitting from the POM mixing caused by the upward movement of another species. In addition, the vertical migrating species' timing bathypelagic appears linked to the lunar cycle. However, the exact indicators causing this timing are still unknown.
Research and exploration
This region is understudied due to a lack of data/observations and difficulty of access (i.e. cost, remote locations, extreme pressure). Historically in oceanography, continental margins were the most sampled and researched due to their relatively easy access. However, more recently locations further offshore and at greater depths, such as ocean ridges and seamounts, are being increasingly studied due to advances in technology and laboratory methods, as well as collaboration with industry. The first discovery of communities subsisting off of the chemical energy in hydrothermal vents was aboard an expedition in 1977 led by Jack Corliss, an oceanographer from Oregon State University. More recent advancements include remotely operated vehicles (ROVs), autonomous underwater vehicles (AUVs), and independent gliders and floats.
Specific technologies and research projects
SERPENT Project
Ocean Twilight Zone (OTZ) Project
DEEP SEARCH Project
DEEPEND Project
AUV Sentry
ROV Jason
Hybrid ROV Nereus
AUV Autosub Long Range
Climate change
The oceans act as a buffer for anthropogenic climate change due to their ability to take up atmospheric CO2 and absorb heat from the atmosphere. However, the ocean's ability to do so will be negatively affected as atmospheric CO2 concentrations continue to rise and global temperatures continue to warm. This will lead to changes such as deoxygenation, ocean acidification, temperature increase, and carbon sequestration decrease, among other physical and chemical alterations. These perturbations may have significant impacts on the organisms that dwell in the bathypelagic region and the properties that deliver organic carbon to the deep sea.
Carbon storage
The bathypelagic zone currently acts as a significant reservoir for carbon because of its sheer volume and the century to millennial timescales these waters are isolated from the atmosphere, this ocean zone plays an important role in moderating the effects of anthropogenic climate change. The burial of particulate organic carbon (POC) in the underlying sediments via the biological carbon pump, and the solubility pump of dissolved inorganic carbon (DIC) into the ocean interior via the thermohaline conveyor are key processes for removing excess atmospheric carbon. However, as atmospheric CO2 concentrations and global temperatures continue to rise, the efficiency at which the bathypelagic will store and bury the influx of carbon will most likely decrease. While some regions may experience an increase in POC input, such as Arctic regions where increased periods of minimal sea ice coverage will increase the downward flux of carbon from the surface oceans, overall, there will likely be less carbon sequestered to the bathypelagic region.
References
External links
Woods Hole Oceanographic Institution - Midnight Zone
Oregon Coast Aquarium OceanScape - Midnight Zone
Oceanography | Bathypelagic zone | [
"Physics",
"Environmental_science"
] | 3,302 | [
"Oceanography",
"Hydrology",
"Applied and interdisciplinary physics"
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565,694 | https://en.wikipedia.org/wiki/John%20N.%20Little | John N. "Jack" Little is an American electrical engineer and the CEO and co-founder of MathWorks and a co-author of early versions of the company's MATLAB product.
He is a Fellow of the IEEE and a Trustee of the Massachusetts Technology Leadership Council. He holds a Bachelor's degree in Electrical Engineering from the Massachusetts Institute of Technology (1978), and a Master's degree from Stanford University (1980). He is the son of the academic John D. C. Little.
External links
His biography on mathworks.com.
References
Fellows of the IEEE
MIT School of Engineering alumni
Stanford University School of Engineering alumni
Living people
Year of birth missing (living people) | John N. Little | [
"Technology"
] | 141 | [
"Computing stubs",
"Computer specialist stubs"
] |
565,742 | https://en.wikipedia.org/wiki/Symbolic%20method | In mathematics, the symbolic method in invariant theory is an algorithm developed by Arthur Cayley, Siegfried Heinrich Aronhold, Alfred Clebsch, and Paul Gordan in the 19th century for computing invariants of algebraic forms. It is based on treating the form as if it were a power of a degree one form, which corresponds to embedding a symmetric power of a vector space into the symmetric elements of a tensor product of copies of it.
Symbolic notation
The symbolic method uses a compact, but rather confusing and mysterious notation for invariants, depending on the introduction of new symbols a, b, c, ... (from which the symbolic method gets its name) with apparently contradictory properties.
Example: the discriminant of a binary quadratic form
These symbols can be explained by the following example from Gordan. Suppose that
is a binary quadratic form with an invariant given by the discriminant
The symbolic representation of the discriminant is
where a and b are the symbols. The meaning of the expression (ab)2 is as follows. First of all, (ab) is a shorthand form for the determinant of a matrix whose rows are a1, a2 and b1, b2, so
Squaring this we get
Next we pretend that
so that
and we ignore the fact that this does not seem to make sense if f is not a power of a linear form.
Substituting these values gives
Higher degrees
More generally if
is a binary form of higher degree, then one introduces new variables a1, a2, b1, b2, c1, c2, with the properties
What this means is that the following two vector spaces are naturally isomorphic:
The vector space of homogeneous polynomials in A0,...An of degree m
The vector space of polynomials in 2m variables a1, a2, b1, b2, c1, c2, ... that have degree n in each of the m pairs of variables (a1, a2), (b1, b2), (c1, c2), ... and are symmetric under permutations of the m symbols a, b, ....,
The isomorphism is given by mapping aa, bb, .... to Aj. This mapping does not preserve products of polynomials.
More variables
The extension to a form f in more than two variables x1, x2, x3,... is similar: one introduces symbols a1, a2, a3 and so on with the properties
Symmetric products
The rather mysterious formalism of the symbolic method corresponds to embedding a symmetric product Sn(V) of a vector space V into a tensor product of n copies of V, as the elements preserved by the action of the symmetric group. In fact this is done twice, because the invariants of degree n of a quantic of degree m are the invariant elements of SnSm(V), which gets embedded into a tensor product of mn copies of V, as the elements invariant under a wreath product of the two symmetric groups. The brackets of the symbolic method are really invariant linear forms on this tensor product, which give invariants of SnSm(V) by restriction.
See also
Umbral calculus
References
Footnotes
Further reading
pp. 32–7, "Invariants of n-ary forms: the symbolic method. Reprinted as
Algebra
Invariant theory | Symbolic method | [
"Physics",
"Mathematics"
] | 684 | [
"Algebra",
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"Group actions",
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565,743 | https://en.wikipedia.org/wiki/Economic%20materialism | Economic materialism can be described as either a personal attitude that attaches importance to acquiring (and often consuming) material goods, or as a logistical analysis of how physical resources are shaped into consumable products.
The use of the term "materialistic" to describe a person's personality or a society tends to have a negative or critical connotation. Also called acquisitiveness, it is often associated with a value system that regards social status as being determined by affluence (see conspicuous consumption), as well as the belief that possessions can provide happiness, which has been critiqued as a lie brought about by capitalism. Environmentalism can be considered a competing orientation to materialism.
The definition of materialism coincides with how and why resources to extract and create the material object are logistically formed. "Success materialism" can be considered a pragmatic form of enlightened self-interest based on a prudent understanding of the character of market-oriented economy and society.
Definition
Consumer research typically looks at materialism in two ways: one as a collection of personality traits; and the other as an enduring belief or value.
Materialism as a personality trait
Russell W. Belk conceptualizes materialism to include three original personality traits:
Nongenerosity – an unwillingness to give or share possessions with others.
Envy – desire for other people's possessions.
Possessiveness – concern about loss of possessions and a desire for the greater control of ownership.
Materialism as a value
Acquisition centrality is when acquiring material possession functions as a central life goal with the belief that possessions are the key to happiness and that success can be judged by a person's material wealth and the quality and price of material goods she or he can buy.
Growing materialism in the Western world
In the Western world, there is a growing trend of increasing materialism in reaction to discontent. Research conducted in the United States shows that recent generations are focusing more on money, image, and fame than ever before, especially since the generations of Baby Boomers and Generation X.
In one survey of Americans, over 7% said they would seriously consider murdering someone for $3 million and 65% of respondents said they would spend a year on a deserted island to earn $1 million.
A survey conducted by the University of California and the American Council on Education on 250,000 new college students found that their main reason for attending college was to gain material wealth. From the 1970s to the late 1990s, the percentage of students who stated that their main reason for going to college was to develop a meaningful life philosophy dropped from 73% to 44%, while the purpose of obtaining financial gain rose from about 44% to 75%.
Materialism and happiness
A series of studies have observed a correlation between materialism and unhappiness. Studies in the United States have found that an increase in material wealth and goods in the country has had little to no effect on the well-being and happiness of its citizens. Tibor Scitovsky called this a "joyless economy" in which people endlessly pursue comforts to the detriments of pleasures.
Using two measures of subjective well-being, one study found that materialism was negatively related to happiness, meaning that people who tended to be more materialistic were also less happy with themselves and their lives. When people derive a lot of pleasure from buying things and believe that acquiring material possessions are important life goals, they tend to have lower life satisfaction scores. Materialism also positively correlates with more serious psychological issues like depression, narcissism and paranoia.
However, the relationship between materialism and happiness is more complex. The direction of the relationship can go both ways. Individual materialism can cause diminished well-being or lower levels of well-being can cause people to be more materialistic in an effort to get external gratification.
In many East Asian cultures, the relationship between materialism, happiness, and well-being are associated with neutral or positive feelings. In China, materialism is often motivated by and through social relations, like families or villages, rather than an individualist pursuit of wealth. This suggests that materialism in interdependent, community-oriented cultures, like in China and Japan, may improve well-being and happiness rather harm them. However, even in independent cultures, people with social motives to acquire wealth may view materialism positively, indicating that the relationship between materialism and happiness is more complex than cultural differences.
Instead, research shows that purchases made with the intention of acquiring life experiences, such as going on a family vacation, make people happier than purchases made to acquire material possessions such as an expensive car. Even just thinking about experiential purchases makes people happier than thinking about material ones. A survey conducted by researchers at the Binghamton University School of Management found differences between what is called “success materialism” and “happiness materialism.” People who see materialism as a source of success tend to be more motivated to work hard and drive to succeed in order to make their lives better as opposed to people who see materialism as a source of happiness. However neither mindset accounts for other factors, such as income or status, that can affect happiness.
See also
References
Consumerism
Consumer behaviour
Materialism | Economic materialism | [
"Physics",
"Biology"
] | 1,067 | [
"Behavior",
"Consumer behaviour",
"Materialism",
"Human behavior",
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565,896 | https://en.wikipedia.org/wiki/Exploding%20head%20syndrome | Exploding head syndrome (EHS) is an abnormal sensory perception during sleep in which a person experiences auditory hallucinations that are loud and of short duration when falling asleep or waking up. The noise may be frightening, typically occurs only occasionally, and is not a serious health concern. People may also experience a flash of light. Pain is typically absent.
The cause is unknown. Potential organic explanations that have been investigated but ruled out include ear problems, temporal lobe seizure, nerve dysfunction, or specific genetic changes. Potential risk factors include psychological stress. It is classified as a sleep disorder or headache disorder. People often go undiagnosed.
There is no high-quality evidence to support treatment. Reassurance may be sufficient. Clomipramine and calcium channel blockers have been tried. While the frequency of the condition is not well studied, some have estimated that it occurs in about 10% of people. Women are reportedly more commonly affected. The condition was initially described at least as early as 1876. The current name came into use in 1988.
Signs and symptoms
Individuals with exploding head syndrome hear or experience loud imagined noises as they are falling asleep or are waking up, have a strong, often frightened emotional reaction to the sound, and do not report significant pain; around 10% of people also experience visual disturbances like perceiving visual static, lightning, or flashes of light. Some people may also experience heat, strange feelings in their torso, or a feeling of electrical tingling that ascends to the head before the auditory hallucinations occur. With the heightened arousal, people experience distress, confusion, myoclonic jerks, tachycardia, sweating, and a feeling that they have stopped breathing and need to make a conscious effort to breathe again.
The pattern of the auditory hallucinations is variable. Some people report having a total of two or four attacks followed by a prolonged or total remission, having attacks over the course of a few weeks or months before the attacks spontaneously disappear, or the attacks may even recur irregularly every few days, weeks, or months for much of a lifetime.
Causes
The cause of EHS is unknown. A number of hypotheses have been put forth with the most common being dysfunction of the reticular formation in the brainstem responsible for transition between waking and sleeping.
Other theories into causes of EHS include:
Minor seizures affecting the temporal lobe
Ear dysfunctions, including sudden shifts in middle ear components or the Eustachian tube, or a rupture of the membranous labyrinth or labyrinthine fistula
Stress and anxiety
Variable and broken sleep, associated with a decline in delta sleep
Antidepressant discontinuation syndrome
Temporary calcium channel dysfunction
PTSD
Exploding head syndrome was first described in the 19th century, and may have first been mentioned in the 17th century.
Diagnosis
Exploding head syndrome is classified under other parasomnias by the 2014 International Classification of Sleep Disorders (ICSD, 3rd.Ed.) and is an unusual type of auditory hallucination in that it occurs in people who are not fully awake.
According to ICD-10 and DSM-5 EHS is classified as either other specified sleep-wake disorder (codes:780.59 or G47.8) or unspecified sleep-wake disorder (codes: 780.59 or G47.9).
Treatment
, no clinical trials had been conducted to determine what treatments are safe and effective; a few case reports had been published describing treatment of small numbers of people (two to twelve per report) with clomipramine, flunarizine, nifedipine, topiramate, carbamazepine. Studies suggest that education and reassurance can reduce the frequency of EHS episodes. There is some evidence that individuals with EHS rarely report episodes to medical professionals.
Epidemiology
There have not been sufficient studies to make conclusive statements about how common or who is most often affected. One study found that 14% of a sample of undergrads reported at least one episode over the course of their lives, with higher rates in those who also have sleep paralysis.
History
Case reports of EHS have been published since at least 1876, which Silas Weir Mitchell described as "sensory discharges" in a patient. However, it has been suggested that the earliest written account of EHS was described in the biography of the French philosopher René Descartes in 1691. The phrase "snapping of the brain" was coined in 1920 by the British physician and psychiatrist Robert Armstrong-Jones. A detailed description of the syndrome and the name "exploding head syndrome" was given by British neurologist John M. S. Pearce in 1989. More recently, Peter Goadsby and Brian Sharpless have proposed renaming EHS "episodic cranial sensory shock" as it describes the symptoms more accurately and better attributes to Mitchell.
See also
References
Further reading
External links
Sleep disorders
Sleep physiology
Lucid dreams
Neurological disorders
Hallucinations
Syndromes of unknown causes
Parasomnias
Syndromes affecting the nervous system
Wikipedia medicine articles ready to translate | Exploding head syndrome | [
"Biology"
] | 1,028 | [
"Behavior",
"Sleep physiology",
"Sleep",
"Sleep disorders"
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565,905 | https://en.wikipedia.org/wiki/Disassortative%20mating | Disassortative mating (also known as negative assortative mating or heterogamy) is a mating pattern in which individuals with dissimilar phenotypes mate with one another more frequently than would be expected under random mating. Disassortative mating reduces the mean genetic similarities within the population and produces a greater number of heterozygotes. The pattern is character specific, but does not affect allele frequencies. This nonrandom mating pattern will result in deviation from the Hardy-Weinberg principle (which states that genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences, such as "mate choice" in this case).
Disassortative mating is different from outbreeding, which refers to mating patterns in relation to genotypes rather than phenotypes.
Due to homotypic preference (bias toward the same type), assortative mating occurs more frequently than disassortative mating. This is because homotypic preferences increase relatedness between mates and between parents and offspring that would promote cooperation and increases inclusive fitness. With disassortative mating, heterotypic preference (bias towards different types) in many cases has been shown to increase overall fitness. When this preference is favored, it allows a population to generate and/or maintain polymorphism (genetic variation within a population).
The fitness advantage aspect of disassortative mating seems straightforward, but the evolution of selective forces involved in disassortative mating are still largely unknown in natural populations.
Types of disassortative mating
Imprinting is one example of disassortative mating. A model shows that individuals imprint on a genetically transmitted trait during early ontogeny and choosy females later use those parental images as a basis of mate choice. A viability-reducing trait may be maintained even without the fertility cost of same-type matings. With imprinting, preference can be established even if it is initially rare, when there is a fertility cost of same-type matings.
One uncommon type of disassortative mating is the female preference on rare (or novel) male phenotypes. A study on guppies, Poecilia reticulata, revealed that the female preference was sufficient to tightly maintain polymorphism in male traits. This type of mate choice shows that costly preferences can persist at higher frequencies if mate choice is hindered, which would allow the alleles to approach fixation.
Effects
Disassortative mating may result in balancing selection and the maintenance of high genetic variation in the population. This is due to the excess heterozygotes that are produced from disassortative mating relative to a randomly mating population.
In humans
The best-known example of disassortative mating in humans is preference for genes in the major histocompatibility complex (MHC) region on chromosome 6. Individuals feel more attracted to odors of individuals who are genetically different in this region. This promotes MHC heterozygosity in the children, making them less vulnerable to pathogens.
In non-human species
Evidence from research regarding coloration in Heliconius butterflies suggests that disassortative mating is more likely to emerge when phenotypic variation is based on self-referencing (mate preference depends on phenotype of the choosing individual, therefore dominance in relationships influence the evolution of disassortative mating).
Disassortative mating has been found with traits such as body symmetry in Amphridromus inversus snails. Normally in snails, rarely are individuals of the opposite coil able to mate with individuals of a normal coil pattern. However, it has been discovered that this species of snail frequents mating between individuals of opposing coils. It is said that the chirality of the spermatophore and the females reproductive tract have a greater chance of producing offspring. This example of disassortative mating promotes polymorphism within the population.
In the scale eating predator fish, Perissodus microlepis, disassortative mating allows the individuals with the rare phenotype of mouth-opening direction to have better success as predators.
House mice conduct disassortative mating as they prefer mates genetically dissimilar to themselves. Specifically, odor profiles in mice are strongly linked to genotypes at the MHC loci controlling changes in the immune response. When MHC-heterozygous offspring are produced, it enhances their immunocompetence because of their ability to recognize a large range of pathogens. Thus, the mice tend to prefer providing "good genes" to their offspring so they will mate with individuals with differences at the MHC loci.
In the seaweed fly, Coelopa frigida, heterozygotes at the locus alcohol dehydrogenase (Adh) have been shown to express better fitness by having higher larval density and relative viability. Females displayed disassortative mating in respect to the Adh locus because they would only mate with males of the opposite Adh genotype. It is suspected that they do this to maintain genetic variation in the population.
White-throated sparrows, Zonotrichia albicollis, prefer strong disassortative mating behaviors regarding the color of their head stripe. The single locus that controls this expression is only observed in heterozygotes. Additionally, the heterozygote arrangement of chromosome 2 from disassortative mating produced offspring of high aggression which is shown to be a social behavior that allows them to dominate their opponents.
References
Mating
Mating systems
Population genetics
Ecology | Disassortative mating | [
"Biology"
] | 1,141 | [
"Behavior",
"Ecology",
"Ethology",
"Mating systems",
"Mating"
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566,014 | https://en.wikipedia.org/wiki/Tint%20control | Because the NTSC color television standard relies on the absolute phase of the color information, color errors occur when the phase of the video signal is altered between source and receiver, or due to non linearities in electronics. To correct for phase errors, a tint control is provided on NTSC television sets, which allows the user to manually adjust the phase relationship between the color information in the video and the reference for decoding the color information, known as the "color burst", so that correct colors may be displayed.
The tint control is normally set by sight to create satisfactory skin tones in a picture. The range of adjustment typically allows these colors to be adjusted from a green to a magenta tint. Television sets produced in recent decades typically include a (sometimes non-defeatable) distortion of the color decoding spectrum, to minimize the visual effects of phase error and lessen the need to adjust the tint control.
On broadcast equipment, such as timebase correctors and studio monitors, this control is typically marked "phase," as it adjusts the phase of the color signal with respect to the color burst signal.
Since the problem of phase errors in the real world became well known after the introduction of NTSC, the later PAL and SECAM color television standards attempted to correct for them. PAL uses the same color modulation scheme as NTSC but averages the received color information over adjacent scan lines, resulting in reduced color detail but canceling out small to moderate phase errors. (Severe phase errors result in picture grain and loss of color saturation in the PAL scheme.) SECAM uses a different modulation scheme that does not rely on the phase of the color signal. Because of this the amplitude of the color signal (color saturation) is unaffected as well. Because SECAM only broadcasts half the color information on each line, the color resolution is halved just like in the PAL system. Most TV sets designed for these later standards lack tint controls, as PAL and SECAM are not supposed to experience the problems a tint control would correct. (This leaves the viewer unable to correct for color errors originating at the transmission site, however.) Multistandard sets have tint controls for NTSC viewing, but the controls are inoperative when watching PAL or SECAM signals.
References
Television technology | Tint control | [
"Technology"
] | 468 | [
"Information and communications technology",
"Television technology"
] |
14,350,137 | https://en.wikipedia.org/wiki/Through-silicon%20via | In electronic engineering, a through-silicon via (TSV) or through-chip via is a vertical electrical connection (via) that passes completely through a silicon wafer or die. TSVs are high-performance interconnect techniques used as an alternative to wire-bond and flip chips to create 3D packages and 3D integrated circuits. Compared to alternatives such as package-on-package, the interconnect and device density is substantially higher, and the length of the connections becomes shorter.
Classification
Dictated by the manufacturing process, there exist three different types of TSVs: via-first TSVs are fabricated before the individual component (transistors, capacitors, resistors, etc.) are patterned (front end of line, FEOL), via-middle TSVs are fabricated after the individual component are patterned but before the metal layers (back-end-of-line, BEOL), and via-last TSVs are fabricated after (or during) the BEOL process. Via-middle TSVs are currently a popular option for advanced 3D ICs as well as for interposer stacks.
TSVs through the front end of line (FEOL) have to be carefully accounted for during the EDA and manufacturing phases. That is because TSVs induce thermo-mechanical stress in the FEOL layer, thereby impacting the transistor behaviour.
Applications
Image sensors
CMOS image sensors (CIS) were among the first applications to adopt TSV(s) in volume manufacturing. In initial CIS applications, TSVs were formed on the backside of the image sensor wafer to form interconnects, eliminate wire bonds, and allow for reduced form factor and higher-density interconnects. Die stacking came about only with the advent of backside illuminated (BSI) CIS, and involved reversing the order of the lens, circuitry, and photodiode from traditional front-side illumination so that the light coming through the lens first hits the photodiode and then the circuitry. This was accomplished by flipping the photodiode wafer, thinning the backside, and then bonding it on top of the readout layer using a direct oxide bond, with TSVs as interconnects around the perimeter.
3D packages
A 3D package (System in Package, Chip Stack MCM, etc.) contains two or more dies stacked vertically so that they occupy less space and/or have greater connectivity. An alternate type of 3D package can be found in IBM's Silicon Carrier Packaging Technology, where ICs are not stacked but a carrier substrate containing TSVs is used to connect multiple ICs together in a package. In most 3D packages, the stacked chips are wired together along their edges; this edge wiring slightly increases the length and width of the package and usually requires an extra "interposer" layer between the dies. In some new 3D packages, TSVs replace edge wiring by creating vertical connections through the body of the dies. The resulting package has no added length or width. Because no interposer is required, a TSV 3D package can also be flatter than an edge-wired 3D package. This TSV technique is sometimes also referred to as TSS (Through-Silicon Stacking or Thru-Silicon Stacking).
3D integrated circuits
A 3D integrated circuit (3D IC) is a single integrated circuit built by stacking silicon wafers and/or dies and interconnecting them vertically so that they behave as a single device. By using TSV technology, 3D ICs can pack a great deal of functionality into a small "footprint". The different devices in the stack may be heterogeneous, e.g. combining CMOS logic, DRAM and III-V materials into a single IC. In addition, critical electrical paths through the device can be drastically shortened, leading to faster operation. The Wide I/O 3D DRAM memory standard (JEDEC JESD229) includes TSVs in the design.
History
The origins of the TSV concept can be traced back to William Shockley's patent "Semiconductive Wafer and Method of Making the Same" filed in 1958 and granted in 1962, which was further developed by IBM researchers Merlin Smith and Emanuel Stern with their patent "Methods of Making Thru-Connections in Semiconductor Wafers" filed in 1964 and granted in 1967, the latter describing a method for etching a hole through silicon. TSV was not originally designed for 3D integration, but the first 3D chips based on TSV were invented later in the 1980s.
The first three-dimensional integrated circuit (3D IC) stacked dies fabricated with a TSV process were invented in 1980s Japan. Hitachi filed a Japanese patent in 1983, followed by Fujitsu in 1984. In 1986, Fujitsu filed a Japanese patent describing a stacked chip structure using TSV. In 1989, Mitsumasa Koyonagi of Tohoku University pioneered the technique of wafer-to-wafer bonding with TSV, which he used to fabricate a 3D LSI chip in 1989. In 1999, the Association of Super-Advanced Electronics Technologies (ASET) in Japan began funding the development of 3D IC chips using TSV technology, called the "R&D on High Density Electronic System Integration Technology" project. The Koyanagi Group at Tohoku University used TSV technology to fabricate a three-layer stacked image sensor chip in 1999, a three-layer memory module in 2000, a three-layer artificial retina chip in 2001, a three-layer microprocessor in 2002, and a ten-layer memory chip in 2005.
The inter-chip via (ICV) method was developed in 1997 by a FraunhoferSiemens research team including Peter Ramm, D. Bollmann, R. Braun, R. Buchner, U. Cao-Minh, Manfred Engelhardt and Armin Klumpp. It was a variation of the TSV process, and was later called SLID (solid liquid inter-diffusion) technology.
The term "through-silicon via" (TSV) was coined by Tru-Si Technologies researchers Sergey Savastiouk, O. Siniaguine, and E. Korczynski, who proposed a TSV method for a 3D wafer-level packaging (WLP) solution in 2000.
CMOS image sensors utilising TSV were commercialized by companies including Toshiba, Aptina and STMicroelectronics during 20072008, with Toshiba naming their technology "Through Chip Via" (TCV). 3D-stacked random-access memory (RAM) was commercialized by Elpida Memory, which developed the first 8GB DRAM module (stacked with four DDR3 SDRAM dies) in September 2009, and released it in June 2011. TSMC announced plans for 3D IC production with TSV technology in January 2010. In 2011, SK Hynix introduced 16GB DDR3 SDRAM (40nm class) using TSV technology, Samsung introduced 3D-stacked 32GB DDR3 (30nm class) based on TSV in September, and then Samsung and Micron Technology announced TSV-based Hybrid Memory Cube (HMC) technology in October. In 2013, SK Hynix manufactured the first High Bandwidth Memory (HBM) module based on TSV technology. The via middle technology was developed by imec under the vision of Eric Beyne. The via middle provided the best trade off in terms of cost and interconnect density. The work was supported by Qualcomm, and then later Nvidia, Xilinx and Altera, who were looking for ways to beat Intel at its game - increasing on-die memory, but then by stacking, rather than scaling.
References
External links
Integrated circuits
Semiconductor device fabrication | Through-silicon via | [
"Materials_science",
"Technology",
"Engineering"
] | 1,601 | [
"Semiconductor device fabrication",
"Integrated circuits",
"Computer engineering",
"Microtechnology"
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14,350,461 | https://en.wikipedia.org/wiki/IdMOC | Integrated discrete Multiple Organ Culture (IdMOC) is an in vitro, cell culture based experimental model for the study of intercellular communication. In conventional in vitro systems, each cell type is studied in isolation ignoring critical interactions between organs or cell types. IdMOC technology is based on the concept that multiple organs signal or communicate via the systemic circulation (i.e., blood).
The IdMOC plate consists of multiple inner wells within a large interconnecting chamber. Multiple cell types are first individually seeded in the inner wells and, when required, are flooded with an overlying medium to facilitate well-to-well communication. Test material can be added to the overlying medium and both media and cells can be analyzed individually. Plating of hepatocytes with other organ-specific cells allows evaluation of drug metabolism and organotoxicity.
The IdMOC system has numerous applications in drug development, such as the evaluation of drug metabolism and toxicity. It can simultaneously evaluate the toxic potential of a drug on cells from multiple organs and evaluate drug stability, distribution, metabolite formation, and efficacy. By modeling multiple-organ interactions, IdMOC can examine the pharmacological effects of a drug and its metabolites on target and off-target organs as well as evaluate drug-drug interactions by measuring cytochrome P450 (CYP) induction or inhibition in hepatocytes.
IdMOC can also be used for routine and high throughput screening of drugs with desirable ADME or ADME-Tox properties. In vitro toxicity screening using hepatocytes in conjunction with other primary cells such as cardiomyocytes (cardiotoxicity model), kidney proximal tubule epithelial cells (nephrotoxicity model), astrocytes (neurotoxicity model), endothelial cells (vascular toxicity model), and airway epithelial cells (pulmonary toxicity model) is invaluable to the drug design and discovery process.
The IdMOC was patented by Dr. Albert P. Li in 2004.
See also
Cytochrome P450
Drug metabolism
Pharmacology
Toxicology
References
External links
http://www.apsciences.com
http://www.invitroadmet.com
"Scientist shows the way to take guinea pigs off lab," Karthika Gopalakrishnan. The Times of India. 17 February 2011. Retrieved 19 August 2015.
Drug development
Pharmacokinetics
Pharmacodynamics
Pharmaceutics
Metabolism
Biochemistry
Cell communication | IdMOC | [
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"Pharmacodynamics",
"Cellular processes",
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"Biochemistry",
"Metabolism"
] |
14,350,687 | https://en.wikipedia.org/wiki/Halogen%20bond | In chemistry, a halogen bond (XB or HaB) occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. Like a hydrogen bond, the result is not a formal chemical bond, but rather a strong electrostatic attraction. Mathematically, the interaction can be decomposed in two terms: one describing an electrostatic, orbital-mixing charge-transfer and another describing electron-cloud dispersion. Halogen bonds find application in supramolecular chemistry; drug design and biochemistry; crystal engineering and liquid crystals; and organic catalysis.
Definition
Halogen bonds occur when a halogen atom is electrostatically attracted to a partial negative charge. Necessarily, the atom must be covalently bonded in an antipodal σ-bond; the electron concentration associated with that bond leaves a positively charged "hole" on the other side. Although all halogens can theoretically participate in halogen bonds, the σ-hole shrinks if the electron cloud in question polarizes poorly or the halogen is so electronegative as to polarize the associated σ-bond. Consequently halogen-bond propensity follows the trend F < Cl < Br < I.
There is no clear distinction between halogen bonds and expanded octet partial bonds; what is superficially a halogen bond may well turn out to be a full bond in an unexpectedly relevant resonance structure.
Donor characteristics
A halogen bond is almost collinear with the halogen atom's other, conventional bond, but the geometry of the electron-charge donor may be much more complex.
Multi-electron donors such as ethers and amines prefer halogen bonds collinear with the lone pair and donor nucleus.
Pyridine derivatives tend to donate halogen bonds approximately coplanar with the ring, and the two C–N–X angles are about 120°.
Carbonyl, thiocarbonyl-, and selenocarbonyl groups, with a trigonal planar geometry around the Lewis donor atom, can accept one or two halogen bonds.
Anions are usually better halogen-bond acceptors than neutral species: the more dissociated an ion pair is, the stronger the halogen bond formed with the anion.
Comparison to other bond-like forces
A parallel relationship can easily be drawn between halogen bonding and hydrogen bonding. Both interactions revolve around an electron donor/electron acceptor relationship, between a halogen-like atom and an electron-dense one. But halogen bonding is both much stronger and more sensitive to direction than hydrogen bonding. A typical hydrogen bond has energy of formation ; known halogen bond energies range from 10–200 kJ/mol.
The σ-hole concept readily extends to pnictogen, chalcogen and aerogen bonds, corresponding to atoms of Groups 15, 16 and 18 (respectively).
History
In 1814, Jean-Jacques Colin discovered (to his surprise) that a mixture of dry gaseous ammonia and iodine formed a shiny, metallic-appearing liquid. Frederick Guthrie established the precise composition of the resulting I2···NH3 complex fifty years later, but the physical processes underlying the molecular interaction remained mysterious until the development of Robert S. Mulliken's theory of inner-sphere and outer-sphere interactions. In Mulliken's categorization, the intermolecular interactions associated with small partial charges affect only the "inner sphere" of an atom's electron distribution; the electron redistribution associated with Lewis adducts affects the "outer sphere" instead.
Then, in 1954, Odd Hassel fruitfully applied the distinction to rationalize the X-ray diffraction patterns associated with a mixture of 1,4-dioxane and bromine. The patterns suggested that only 2.71 Å separated the dioxane oxygen atoms and bromine atoms, much closer than the sum (3.35 Å) of the atoms' van der Waals radii; and that the angle between the O−Br and Br−Br bond was about 180°. From these facts, Hassel concluded that halogen atoms are directly linked to electron pair donors in a direction with a bond direction that coincides with the axes of the orbitals of the lone pairs in the electron pair donor molecule. For this work, Hassel was awarded the 1969 Nobel Prize in Chemistry.
Dumas and coworkers first coined the term "halogen bond" in 1978, during their investigations into complexes of CCl4, CBr4, SiCl4, and SiBr4 with tetrahydrofuran, tetrahydropyran, pyridine, anisole, and di-n-butyl ether in organic solvents.
However, it was not until the mid-1990s, that the nature and applications of the halogen bond began to be intensively studied. Through systematic and extensive microwave spectroscopy of gas-phase halogen bond adducts, Legon and coworkers drew attention to the similarities between halogen-bonding and better-known hydrogen-bonding interactions.
In 2007, computational calculations by Politzer and Murray showed that an anisotropic electron density distribution around the halogen nucleus — the "σ-hole" — underlay the high directionality of the halogen bond. This hole was then experimentally observed using Kelvin probe force microscopy.
In 2020, Kellett et al. showed that halogen bonds also have a π-covalent character similar to metal coordination bonds. In August 2023 the "π-hole" was too experimentally observed
Applications
Crystal engineering
The strength and directionality of halogen bonds are a key tool in the discipline of crystal engineering, which attempts to shape crystal structures through close control of intermolecular interactions. Halogen bonds can stabilize copolymers or induce mesomorphism in otherwise isotropic liquids. Indeed, halogen bond-induced liquid crystalline phases are known in both alkoxystilbazoles and silsesquioxanes (pictured). Alternatively, the steric sensitivity of halogen bonds can cause bulky molecules to crystallize into porous structures; in one notable case, halogen bonds between iodine and aromatic π-orbitals caused molecules to crystallize into a pattern that was nearly 40% void.
Controlled polymerization
Conjugated polymers offer the tantalizing possibility of organic molecules with a manipulable electronic band structure, but current methods for production have an uncontrolled topology. Sun, Lauher, and Goroff discovered that certain amides ensure a linear polymerization of poly(diiododiacetylene). The underlying mechanism is a self-organization of the amides via hydrogen bonds that then transfers to the diiododiacetylene monomers via halogen bonds. Although pure diiododiacetylene crystals do not polymerize spontaneously, the halogen-bond induced organization is sufficiently strong that the cocrystals do spontaneously polymerize.
Biological macromolecules
Most biological macromolecules contain few or no halogen atoms. But when molecules do contain halogens, halogen bonds are often essential to understanding molecular conformation. Computational studies suggest that known halogenated nucleobases form halogen bonds with oxygen, nitrogen, or sulfur in vitro. Interestingly, oxygen atoms typically do not attract halogens with their lone pairs, but rather the π electrons in the carbonyl or amide group.
Halogen bonding can be significant in drug design as well. For example, inhibitor IDD 594 binds to human aldose reductase through a bromine halogen bond, as shown in the figure. The molecules fail to bind to each other if similar aldehyde reductase replaces the enzyme, or chlorine replaces the drug halogen, because the variant geometries inhibit the halogen bond.
Notes
References
Further reading
An early review:
Chemical bonding
Intermolecular forces | Halogen bond | [
"Physics",
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"Materials_science",
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14,350,837 | https://en.wikipedia.org/wiki/Tobacco%20and%20other%20drugs | An association between tobacco and other drug use has been well established. The nature of this association remains unclear. The two main theories, which are not mutually exclusive, are the phenotypic causation (gateway) model and the correlated liabilities model. The causation model argues that smoking is a primary influence on future drug use, while the correlated liabilities model argues that smoking and other drug use are predicated on genetic or environmental factors.
Causation model
A 1994 report from the Center on Addiction and Substance Abuse at Columbia University, found a correlation between the use of cigarettes and alcohol and the subsequent use of cannabis. The report asserted a link between alcohol and cannabis use and the subsequent use of illicit drugs like cocaine. It found that when younger children used, the more often they use them, the more likely they were to use cocaine, heroin, hallucinogens and other illicit drugs. The report concludes that the data is already robust enough to make a strong case to step up efforts to prevent childhood use of cigarettes and to take firm steps to reduce children’s access to these "gateway drugs".
Researchers have found that craving nicotine also increases craving for illicit drugs among drug abusers who smoke tobacco, and this suggests that smokers in drug rehabilitation programs may be less successful than nonsmokers in staying off drugs.
In mice, nicotine increased the probability of later consumption of cocaine. the experiments permitted concrete conclusions on the underlying molecular biological alteration in the brain. The biological changes in mice correspond to the epidemiological observations in humans that nicotine consumption is coupled to an increased probability of later use of cocaine.
Correlative model
Smoking may have a genetic predisposing factor; one 1990 study posited that 52% of the variance in smoking behaviour is attributable to heritable factors. The concept received support from a large-scale genetic analysis of 2016 that showed a genetic basis for the connection of the prevalence of cigarette smoking and cannabis use during the life of a person.
See also
Gateway drug theory
References
Habits
Tobacco smoking
Tobacco
Health effects of tobacco | Tobacco and other drugs | [
"Biology"
] | 422 | [
"Behavior",
"Human behavior",
"Habits"
] |
14,350,883 | https://en.wikipedia.org/wiki/Brown%20Dog%20affair | The Brown Dog affair was a political controversy about vivisection that raged in Britain from 1903 until 1910. It involved the infiltration of University of London medical lectures by Swedish feminists, battles between medical students and the police, police protection for the statue of a dog, a libel trial at the Royal Courts of Justice, and the establishment of a Royal Commission to investigate the use of animals in experiments. The affair became a that divided the country.
The controversy was triggered by allegations that, in February 1903, William Bayliss of the Department of Physiology at University College London performed an illegal vivisection, before an audience of 60 medical students, on a brown terrier dog—adequately anaesthetised, according to Bayliss and his team; conscious and struggling, according to the Swedish activists. The procedure was condemned as cruel and unlawful by the National Anti-Vivisection Society. Outraged by the assault on his reputation, Bayliss, whose research on dogs led to the discovery of hormones, sued for libel and won.
Anti-vivisectionists commissioned a bronze statue of the dog as a memorial, unveiled on the Latchmere Recreation Ground in Battersea in 1906, but medical students were angered by its provocative plaque—"Men and women of England, how long shall these Things be?"—leading to frequent vandalism of the memorial and the need for a 24-hour police guard against the so-called anti-doggers. On 10 December 1907, hundreds of medical students marched through central London waving effigies of the brown dog on sticks, clashing with suffragettes, trade unionists and 300 police officers, one of a series of battles known as the Brown Dog riots.
In March 1910, tired of the controversy, Battersea Council sent four workers accompanied by 120 police officers to remove the statue under cover of darkness, after which it was reportedly melted down by the council's blacksmith, despite a 20,000-strong petition in its favour. A new statue of the brown dog, commissioned by anti-vivisection groups, was erected in Battersea Park in 1985. On 6 September 2021, the 115th anniversary of when the original statue was unveiled, a new campaign was launched by the author Paula S. Owen to recast the original statue.
Background
Cruelty to Animals Act 1876
There was significant opposition to vivisection in England, in both houses of Parliament, during the reign of Queen Victoria (1837–1901); the Queen herself strongly opposed it. The term vivisection referred to the dissection of living animals, with and without anaesthesia, often in front of audiences of medical students. In 1878 there were under 300 experiments on animals in the UK, a figure that had risen to 19,084 in 1903 when the brown dog was vivisected (according to the inscription on the second Brown Dog statue), and to five million by 1970.
Physiologists in the 19th century were frequently criticised for their work. The prominent French physiologist Claude Bernard appears to have shared the distaste of his critics, who included his wife, referring to "the science of life" as a "superb and dazzlingly lighted hall which may be reached only by passing through a long and ghastly kitchen". In 1875, Irish feminist Frances Power Cobbe founded the National Anti-Vivisection Society (NAVS) in London and in 1898 the British Union for the Abolition of Vivisection (BUAV). The former sought to restrict vivisection and the latter to abolish it.
The opposition led the British government, in July 1875, to set up the first Royal Commission on the "Practice of Subjecting Live Animals to Experiments for Scientific Purposes". After hearing that researchers did not use anaesthesia regularly—one scientist, Emmanuel Klein told the commission he had "no regard at all" for the suffering of the animals—the commission recommended a series of measures, including a ban on experiments on dogs, cats, horses, donkeys and mules. The General Medical Council and British Medical Journal objected, so additional protection was introduced instead. The result was the Cruelty to Animals Act 1876, criticised by NAVS as "infamous but well-named".
The act stipulated that researchers could not be prosecuted for cruelty, but that the animal must be anaesthetised, unless the anaesthesia would interfere with the point of the experiment. Each animal could be used only once, although several procedures regarded as part of the same experiment were permitted. The animal had to be killed when the study was over, unless doing so would frustrate the object of the experiment. Prosecutions could take place only with the approval of the home secretary. At the time of the Brown Dog affair, this was Aretas Akers-Douglas, who was unsympathetic to the anti-vivisectionist cause.
Ernest Starling and William Bayliss
In the early 20th century, Ernest Starling, professor of physiology at University College London, and his brother-in-law William Bayliss, were using vivisection on dogs to determine whether the nervous system controls pancreatic secretions, as postulated by Ivan Pavlov. Bayliss had held a licence to practice vivisection since 1890 and had taught physiology since 1900. According to Starling's biographer John Henderson, Starling and Bayliss were "compulsive experimenters", and Starling's lab was the busiest in London.
The men knew that the pancreas produces digestive juices in response to increased acidity in the duodenum and jejunum, because of the arrival of chyme there. By severing the duodenal and jejunal nerves in anaesthetised dogs, while leaving the blood vessels intact, then introducing acid into the duodenum and jejunum, they discovered that the process is not mediated by a nervous response, but by a new type of chemical reflex. They named the chemical messenger secretin, because it is secreted by the intestinal lining into the bloodstream, stimulating the pancreas on circulation. In 1905 Starling coined the term hormone—from the Greek hormao meaning "I arouse" or "I excite"—to describe chemicals such as secretin that are capable, in extremely small quantities, of stimulating organs from a distance.
Bayliss and Starling had also used vivisection on anaesthetised dogs to discover peristalsis in 1899. They went on to discover a variety of other important physiological phenomena and principles, many of which were based on their experimental work involving animal vivisection.
Lizzy Lind af Hageby and Leisa Schartau
Starling and Bayliss's lectures had been infiltrated by two Swedish feminists and anti-vivisection activists, Lizzy Lind af Hageby and Leisa Schartau. The women had known each other since childhood and came from distinguished families; Lind af Hageby, who had attended Cheltenham Ladies College, was the granddaughter of a chamberlain to the king of Sweden.
In 1900, the women visited the Pasteur Institute in Paris, a centre of animal experimentation, and were shocked by the rooms full of caged animals given diseases by the researchers. When they returned home, they founded the Anti-Vivisection Society of Sweden, and to gain medical training to help their campaigning, they enrolled in 1902 at the London School of Medicine for Women, a vivisection-free college that had visiting arrangements with other colleges. They attended 100 lectures and demonstrations at King's and University College, including 50 experiments on live animals, of which 20 were what Mason called "full-scale vivisection". Their diary, at first called Eye-Witnesses, was later published as The Shambles of Science: Extracts from the Diary of Two Students of Physiology (1903); shambles was a name for a slaughterhouse. The women were present when the brown dog was vivisected, and wrote a chapter about it entitled "Fun", referring to the laughter they said they heard in the lecture room during the procedure.
The following year, a revised edition was published without that chapter; the authors wrote: "The story of the thrice vivisected brown dog as told by its vivisectors to the Lord Chief Justice and a special jury, and as it is found in the verbatim report of the trial, proved the true nature of vivisection far better than the chapter 'Fun' which can now be dispensed with."
The brown dog
Vivisection of the dog
According to Starling, the brown dog was "a small brown mongrel allied to a terrier with short roughish hair, about 14–15 lb [c. 6 kg] in weight". He was first used in a vivisection in December 1902 by Starling, who cut open his abdomen and ligated the pancreatic duct. For the next two months he lived in a cage, until Starling and Bayliss used him again for two procedures on 2 February 1903, the day the Swedish women were present.
Outside the lecture room before the students arrived, according to testimony Starling and others gave in court, Starling cut the dog open again to inspect the results of the previous surgery, which took about 45 minutes, after which he clamped the wound with forceps and handed the dog over to Bayliss. Bayliss cut a new opening in the dog's neck to expose the lingual nerves of the salivary glands, to which he attached electrodes. The aim was to stimulate the nerves with electricity to demonstrate that salivary pressure was independent of blood pressure. The dog was then carried to the lecture theatre, stretched on his back on an operating board, with his legs tied to the board, his head clamped and his mouth muzzled.
According to Bayliss, the dog had been given a morphine injection earlier in the day, then was anaesthetised during the procedure with six fluid ounces of alcohol, chloroform and ether (ACE), delivered from an ante-room to a tube in his trachea, via a pipe hidden behind the bench on which the men were working. The Swedish students disputed that the dog had been adequately anaesthetised. They said the dog had appeared conscious during the procedure, had tried to lift himself off the board, and that there was no smell of anaesthesia or the usual hissing sound of the apparatus. Other students said the dog had not struggled, but had merely twitched.
In front of around 60 students, Bayliss stimulated the nerves with electricity for half an hour, but was unable to demonstrate his point. The dog was then handed to a student, Henry Dale, a future Nobel laureate, who removed the dog's pancreas, then killed him with a knife through the heart. This became a point of embarrassment during the libel trial, when Bayliss's laboratory assistant, Charles Scuttle, testified that the dog had been killed with chloroform or the ACE mixture. After Scuttle's testimony, Dale told the court that he had, in fact, used a knife.
Women's diary
On 14 April 1903, Lind af Hageby and Schartau showed their unpublished 200-page diary, published later that year as The Shambles of Science, to the barrister Stephen Coleridge, secretary of the National Anti-Vivisection Society. Coleridge was the son of John Duke Coleridge, former Lord Chief Justice of England, and great-grandson of the poet Samuel Taylor Coleridge. His attention was drawn to the account of the brown dog. The 1876 Cruelty to Animals Act forbade the use of an animal in more than one experiment, yet it appeared that the brown dog had been used by Starling to perform surgery on the pancreas, used again by him when he opened the dog to inspect the results of the previous surgery, and used for a third time by Bayliss to study the salivary glands. The diary said of the procedures on the brown dog:
Today's lecture will include a repetition of a demonstration which failed last time. A large dog, stretched on its back on an operation board, is carried into the lecture-room by the demonstrator and the laboratory attendant. Its legs are fixed to the board, its head is firmly held in the usual manner, and it is tightly muzzled.
There is a large incision in the side of the neck, exposing the gland. The animal exhibits all signs of intense suffering; in his struggles, he again and again lifts his body from the board, and makes powerful attempts to get free.
The allegations of repeated use and inadequate anaesthesia represented prima facie violations of the Cruelty to Animals Act. In addition the diary said the dog had been killed by Henry Dale, an unlicensed research student, and that the students had laughed during the procedure; there were "jokes and laughter everywhere" in the lecture hall, it said.
Coleridge's speech
According to Mason, Coleridge decided there was no point in relying on a prosecution under the act, which he regarded as deliberately obstructive. Instead he gave an angry speech about the dog on 1 May 1903 to the annual meeting of the National Anti-Vivisection Society at St James's Hall in Piccadilly, attended by 2,000–3,000 people. Mason writes that support and apologies for absence were sent by Jerome K. Jerome, Thomas Hardy and Rudyard Kipling. Coleridge accused the scientists of torture: "If this is not torture, let Mr. Bayliss and his friends ... tell us in Heaven's name what torture is."
Details of the speech were published the next day by the radical Daily News (founded in 1846 by Charles Dickens), and questions were raised in the House of Commons, particularly by Sir Frederick Banbury, a Conservative MP and sponsor of a bill aimed at ending vivisection demonstrations. Banbury asked the Home Secretary to state "under what certificate the operation on a brown dog was performed at University College Hospital on Feb. 2 last; and, whether, seeing that a second operation was performed upon this animal before the wounds caused by the first operation had healed, he proposes to take any action in the matter."
Bayliss demanded a public apology from Coleridge, and, when it had failed to materialise by 12 May, he issued a writ for libel. Ernest Starling decided not to sue; The Lancet, no friend of Coleridge, wrote that "it may be contended that Dr. Starling and Mr. Bayliss committed a technical infringement of the Act under which they performed their experiments." Coleridge tried to persuade the women not to publish their diary before the trial began, but they went ahead anyway, and it was published by Ernest Bell of Covent Garden in July 1903.
Bayliss v. Coleridge
Trial
The trial opened at the Old Bailey on 11 November 1903 before Lord Alverstone, the Lord Chief Justice, and lasted four days, closing on 18 November. There were queues 30 yards long outside the courthouse. Bayliss's barrister, Rufus Isaacs, called Starling as his first witness. Starling admitted that he had broken the law by using the dog twice, but said that he had done so to avoid sacrificing two dogs. Bayliss testified that the dog had been given one-and-a-half grains of morphia earlier in the day, then six ounces of alcohol, chloroform and ether, delivered from an ante room to a tube connected to the dog's trachea. The tubes were fragile, he said, and had the dog been struggling they would have broken.
A veterinarian, Alfred Sewell, said the system Bayliss was using was unlikely to be adequate, but other witnesses, including Frederick Hobday of the Royal Veterinary College, disagreed; there was even a claim that Bayliss had used too much anaesthesia, which is why the dog had failed to respond to the electrical stimulation. According to Bayliss, the dog had been suffering from chorea, a disease that causes involuntary spasm, and that any movement reported by Lind af Hageby and Schartau had not been purposive. Four students, three women and a man, testified that the dog had seemed unconscious.
Coleridge's barrister, John Lawson Walton, called Lind af Hageby and Schartau. They repeated they had been the first students to arrive and had been left alone with the dog for about two minutes. They had observed scars from the previous operations and an incision in the neck where two tubes had been placed. They had not smelled the anaesthetic and had not seen any apparatus delivering it. They said, Mason wrote, that the dog had arched his back and jerked his legs in what they regarded as an effort to escape. When the experiment began the dog continued to "upheave its abdomen" and tremble, they said, movements they regarded as "violent and purposeful".
Bayliss's lawyer criticised Coleridge for having accepted the women's statements without seeking corroboration, and for speaking about the issue publicly without first approaching Bayliss, despite knowing that doing so could lead to litigation. Coleridge replied that he had not sought verification because he knew the claims would be denied, and that he continued to regard the women's statement as true. The Times wrote of his testimony: "The Defendant, when placed in the witness box, did as much damage to his own case as the time at his disposal for the purpose would allow."
Verdict
Lord Alverstone told the jury that the case was an important one of national interest. He called The Shambles of Science "hysterical" and advised the jury not to be swayed by arguments about the validity of vivisection. After retiring for 25 minutes on 18 November 1903, the jury unanimously found that Bayliss had been defamed, to the applause of physicians in the public gallery. Bayliss was awarded £2,000 with £3,000 costs; Coleridge gave him a cheque the next day. The Daily News asked for donations to cover Coleridge's costs and raised £5,700 within four months. Bayliss donated his damages to UCL for use in research; according to Mason, Bayliss ignored the Daily Mails suggestion that he call it the "Stephen Coleridge Vivisection Fund". Gratzer wrote in 2004 that the fund may still have been in use then to buy animals.
The Times declared itself satisfied with the verdict, although it criticised the rowdy behaviour of medical students during the trial, accusing them of "medical hooliganism". The Sun, Star and Daily News backed Coleridge, calling the decision a miscarriage of justice. Ernest Bell, publisher of The Shambles of Science, apologised to Bayliss on 25 November, and pledged to withdraw the diary and pass its remaining copies to Bayliss's solicitors.
The Animal Defence and Anti-Vivisection Society, founded by Lind af Hageby in 1903, republished the book, printing a fifth edition by 1913. The chapter "Fun" was replaced by one called "The Vivisections of the Brown Dog", describing the experiment and the trial. The novelist Thomas Hardy kept a copy of the book on a table for visitors; he told a correspondent that he had "not really read [it], but everybody who comes into this room, where it lies on my table, dips into it, etc, and, I hope, profits something". According to historian Hilda Kean, the Research Defence Society, a lobby group founded in 1908 to counteract the antivivisectionist campaign, discussed how to have the revised editions withdrawn because of the book's impact.
In December 1903, Mark Twain, who opposed vivisection, published a short story, A Dog's Tale, in Harper's, written from the point of view of a dog whose puppy is experimented on and killed. Given the timing and Twain's views, the story may have been inspired by the libel trial, according to Mark Twain scholar Shelley Fisher Fishkin. Coleridge ordered 3,000 copies of A Dog's Tale, which were specially printed for him by Harper's.
Second Royal Commission on Vivisection
On 17 September 1906, the government appointed the Second Royal Commission on Vivisection, which heard evidence from scientists and anti-vivisection groups; Ernest Starling addressed the commission for three days in December 1906. After much delay (two of its ten members died and several fell ill), the commission reported its findings in March 1912. Its 139-page report recommended an increase in the number of full-time inspectors from two to four, and restrictions on the use of curare, a poison used to immobilise animals during experiments. The Commission decided that animals should be adequately anaesthetised, and euthanised if the pain was likely to continue, and experiments should not be performed "as an illustration of lectures" in medical schools and similar. All the restrictions could be lifted if they would "frustrate the object of the experiment". There was also a tightening of the definition and practice of pithing. The Commission recommended the maintenance of more detailed records and the establishment of a committee to advise the Secretary of State on matters related to the Cruelty to Animals Act. The latter became the Animal Procedures Committee under the Animals (Scientific Procedures) Act 1986.
Brown Dog memorial
Original memorial
After the trial Anna Louisa Woodward, founder of the World League Against Vivisection, raised £120 for a public memorial and commissioned a bronze statue of the dog from sculptor Joseph Whitehead. The statue sat on top of a granite memorial stone, 7 ft 6 in (2.29 m) tall, that housed a drinking fountain for human beings and a lower trough for dogs and horses. It also carried an inscription (right), described by The New York Times in 1910 as the "hysterical language customary of anti-vivisectionists" and "a slander on the whole medical profession".
The group turned to the borough of Battersea for a location for the memorial. Lansbury wrote that the area was a hotbed of radicalism—proletarian, socialist, full of belching smoke and slums, and closely associated with the anti-vivisection movement. The National Anti-Vivisection and Battersea General Hospital—opened in 1896, on the corner of Albert Bridge Road and Prince of Wales Drive, and closed in 1972—refused until 1935 to perform vivisection or employ doctors who engaged in it, and was known locally as the "antiviv" or the "old anti". The chairman of the Battersea Dogs Home, William Cavendish-Bentinck, 6th Duke of Portland, rejected a request in 1907 that its lost dogs be sold to vivisectors as "not only horrible, but absurd".
Battersea council agreed to provide space for the statue on its Latchmere Recreation Ground, part of the council's new Latchmere Estate, which offered terraced homes to rent for seven and sixpence a week. The statue was unveiled on 15 September 1906 in front of a large crowd, with speakers that included George Bernard Shaw, the Irish feminist Charlotte Despard, the mayor of Battersea, James H. Brown (secretary of the Battersea Trades and Labour Council), and the Reverend Charles Noel.
Riots
November–December 1907
Medical students at London's teaching hospitals were enraged by the plaque. The first year of the statue's existence was a quiet one, while University College explored whether they could take legal action over it, but from November 1907 the students turned Battersea into the scene of frequent disruption.
The first action was on 20 November, when undergraduate William Howard Lister led a group of medical students across the Thames to Battersea to attack the statue with a crowbar and sledgehammer. One of them, Duncan Jones, hit the statue with a hammer, denting it, at which point all ten were arrested by just two police officers. According to Mason, a local doctor told the South Western Star that this signalled the "utter degeneration" of junior doctors: "I can remember the time when it was more than 10 policemen could do to take one student. The Anglo-Saxon race is played out."
The students were fined £5 by the magistrate, Paul Taylor, at South-West London Police Court in Battersea and warned they would be jailed next time. This triggered another protest two days later, when medical students from UCL, King's, Guy's, and the West Middlesex hospitals marched along the Strand toward King's College, waving miniature brown dogs on sticks and a life-sized effigy of the magistrate, and singing, "Let's hang Paul Taylor on a sour apple tree / As we go marching on." The Times reported that they tried to burn the effigy but, unable to light it, threw it in the Thames instead.
Women's suffrage meetings were invaded, although the students knew that not all suffragettes were anti-vivisectionists. A meeting organised by Millicent Fawcett on 5 December 1907 at the Paddington Baths Hall in Bayswater was left with chairs and tables smashed and one steward with a torn ear. Two fireworks were let off, and Fawcett's speech was drowned out by students singing "John Brown's Body", after which they marched down Queen's Road led by someone with bagpipes. The Daily Express reported the meeting as "Medical Students' Gallant Fight with Women".
10 December 1907
The rioting reached its height five days later, on Tuesday, 10 December, when 100 medical students tried to pull the memorial down. The previous protests had been spontaneous, but this one was organised to coincide with the annual Oxford–Cambridge rugby match at Queen's Club, West Kensington. The protesters hoped (in vain, as it turned out) that some of the thousands of Oxbridge students would swell their numbers. The intention was that, after toppling the statue and throwing it in the Thames, 2,000–3,000 students would meet at 11:30 pm in Trafalgar Square. Street vendors sold handkerchiefs stamped with the date of the protest and the words, "Brown Dog's inscription is a lie, and the statuette an insult to the London University."
In the afternoon, protesters headed for the statue, but were driven off by locals. The students proceeded down Battersea Park Road instead, intending to attack the Anti-Vivisection Hospital, but were again forced back. When one student fell from the top of a tram, the workers shouted that it was "the brown dog's revenge" and refused to take him to hospital. The British Medical Journal responded that, given that it was the Anti-Vivisection Hospital, the crowd's actions may have been "prompted by benevolence".
A second group of students headed for central London, waving effigies of the brown dog, joined by a police escort and, briefly, a busker with bagpipes. As the marchers reached Trafalgar Square, they were 400 strong, facing 200–300 police officers, 15 of them on horseback. The students gathered around Nelson's Column, where the ringleaders climbed onto its base to make speeches. While students fought with police on the ground, mounted police charged the crowd, scattering them into smaller groups and arresting the stragglers, including one undergraduate, Alexander Bowley, who was arrested for "barking like a dog". The fighting continued for hours before the police gained control. At Bow Street magistrate's court the next day, ten students were bound over to keep the peace; several were fined 40 shillings, or £3 if they had fought with police.
Strange relationships
Rioting broke out elsewhere over the following days and months, as medical and veterinary students united. Whenever Lizzy Lind af Hageby spoke, students would shout her down. When she arranged a meeting of the Ealing and Acton Anti-Vivisection Society at Acton Central Hall on 11 December 1906, over 100 students disrupted it, throwing chairs and stink bombs, particularly when she objected to a student blowing her a kiss. The Daily Chronicle reported: "The rest of Miss Lind-af-Hageby's indignation was lost in a beautiful 'eggy' atmosphere that was now rolling heavily across the hall. 'Change your socks!' shouted one of the students." Furniture was smashed and clothing torn.
For Susan McHugh of the University of New England, the political coalition of trade unionists, socialists, Marxists, liberals and suffragettes that rallied to the statue's defence reflected the brown dog's mongrel status. The riots saw them descend on Battersea to fight the medical students, even though, she writes, the suffragettes were not a group toward whom male workers felt any warmth. But the "Brown Terrier Dog Done to Death" by the male scientific establishment united them all.
Lizzy Lind af-Hageby and Charlotte Despard saw the affair as a battle between feminism and machismo. According to Coral Lansbury, the fight for women's suffrage became closely linked with the anti-vivisection movement, and the iconography of vivisection struck a chord with women. Three of the four vice-presidents of the National Anti-Vivisection Hospital were women. Lansbury argues that the Brown Dog affair became a matter of opposing symbols: the vivisected dog on the operating board blurred into images of suffragettes force-fed in Brixton Prison, or women strapped down for childbirth or forced to have their ovaries and uteruses removed as a cure for mania. The "vivisected animal stood for vivisected woman".
Both sides saw themselves as heirs to the future. Hilda Kean writes that the Swedish activists were young and female, anti-establishment and progressive, and viewed the scientists as remnants of a previous age. Their access to higher education had made the case possible, creating what feminist scholar Susan Hamilton called a "new form of witnessing". Against this, Lansbury writes, the students saw themselves and their teachers as the "New Priesthood" and the women and trade unionists as representatives of superstition and sentimentality.
"Exit the 'Brown Dog'"
Questions were asked in the House of Commons about the cost of policing the statue, which required six constables a day at a cost of £700 a year. In February 1908 Sir Philip Magnus, MP for the London University constituency, asked the Home Secretary, Herbert Gladstone, "whether his attention has been called to the special expense of police protection of a public monument at Battersea that bears a controversial inscription". Gladstone replied that six constables were needed daily to protect the statue, and that the overall cost of extra policing had been equivalent to employing 27 inspectors, 55 sergeants, and 1,083 constables for a day.
London's police commissioner wrote to Battersea Council to ask that they contribute to the cost. Councillor John Archer, later Mayor of Battersea and the first black mayor in London, told the Daily Mail that he was amazed by the request, considering Battersea was already paying £22,000 a year in police rates. The Canine Defence League wondered whether, if Battersea were to organise raids on laboratories, the laboratories would be asked to pay the policing costs themselves.
Other councillors suggested the statue be encased in a steel cage and surrounded by a barbed wire fence. Suggestions were made through the letters pages of the Times and elsewhere that it be moved, perhaps to the grounds of the Anti-Vivisection Hospital. The British Medical Journal wrote in March 1910:
May we suggest that the most appropriate resting place for the rejected work of art is the Home for Lost Dogs at Battersea, where it could be "done to death", as the inscription says, with a hammer in the presence of Miss Woodword, the Rev. Lionel S. Lewis, and other friends; if their feelings were too much for them, doubtless an anaesthetic could be administered.
Battersea Council grew tired of the controversy. A new Conservative council was elected in November 1909 amid talk of removing the statue. There were protests in support of it, and the 500-strong Brown Dog memorial defence committee was established. Twenty thousand people signed a petition, and 1,500 attended a rally in February 1910 addressed by Lind af Hageby, Charlotte Despard and Liberal MP George Greenwood. There were more demonstrations in central London and speeches in Hyde Park, with supporters wearing masks of dogs.
The protests were to no avail. The statue was quietly removed before dawn on 10 March 1910 by four council workmen, accompanied by 120 police officers. Nine days later, 3,000 anti-vivisectionists gathered in Trafalgar Square to demand its return, but it was clear by then that Battersea Council had turned its back on the affair. The statue was at first hidden in the borough surveyor's bicycle shed, according to a letter his daughter wrote in 1956 to the British Medical Journal, then reportedly destroyed by a council blacksmith, who melted it down. Anti-vivisectionists filed a High Court petition demanding its return, but the case was dismissed in January 1911.
New memorial
On 12 December 1985, over 75 years after the statue's removal, a new memorial to the brown dog was unveiled by actress Geraldine James in Battersea Park behind the Pump House. Created by sculptor Nicola Hicks, the new bronze dog is mounted on a rectangular plinth of Portland stone and based on Hicks's own terrier, Brock. Three of the four plaques affixed to the column of the current Brown Dog statue bear the original inscriptions.
The British Medical Journal (Clinical Research Edition) published an editorial in March 1986,
"A new antivivisectionist libellous statue at Battersea", criticising Battersea Council and the Greater London Council for allowing it.
Echoing the fate of the previous memorial, the new dog was moved into storage in 1992 by Battersea Park's owners, the Conservative Borough of Wandsworth, they said as part of a park renovation scheme. Anti-vivisectionists campaigned for its return, suspicious of the explanation. It was reinstated in the park's Woodland Walk in 1994, near the Old English Garden, a more secluded spot than before.
The new statue was criticised in 2003 by historian Hilda Kean. She saw the old Brown Dog as a radical statement, upright and defiant: "The dog has changed from a public image of defiance to a pet". For Kean, the new Brown Dog, located near the Old English Garden as "heritage", is too safe; unlike its controversial ancestor, she argues, it makes no one uncomfortable.
On 6 September 2021, the 115th anniversary of when the original statue was unveiled, a new campaign was launched by author Paula S. Owen to recast the original statue. Owen is author of Little Brown Dog, a novel that is based on the true story.
See also
Animal welfare in the United Kingdom
List of public art in Wandsworth
Cruel Treatment of Cattle Act 1822
Cruelty to Animals Act 1835
Cruelty to Animals Act 1849
Cruelty to Animals Act 1876
Wild Animals in Captivity Protection Act 1900
Protection of Animals Act 1911
Protection of Animals Act 1934
Abandonment of Animals Act 1960
Animals (Scientific Procedures) Act 1986
Animal Welfare Act 2006
Animal Health and Welfare (Scotland) Act 2006
RSPCA
List of individual dogs
Sources
Notes
References
Works cited
Books
Journal articles
Royal Commissions
Further reading
Bayliss, Leonard (Spring 1957). "The 'Brown Dog' Affair". Potential (UCL magazine). 11–22.
Coult, Tony (1988). "The Strange Affair of the Brown Dog" (radio play based on Peter Mason's The Brown Dog Affair).
Coleridge, Stephen (1916). Vivisection, a heartless science. London: John Lane.
Elston, Mary Ann (1987). "Women and Anti-vivisection in Victorian England, 1870–1900", in Nicolaas Rupke (ed.). Vivisection in Historical Perspective. London: Routledge.
Gålmark, Lisa (1996). Shambles of Science: Lizzy Lind af Hageby and Leisa Schartau, Anti-vivisektionister 1903–1913/14. Stockholm: Stockholm University.
Harte, Negley; North, John (1991). The World of UCL, 1828–1990. London: Routledge (image of the restaged experiment on the brown dog, 127).
Le Fanu, James (23 November 2003). "In Sickness and in Health: Vivisection's Undoing". The Daily Telegraph.
McIntosh, Anthony (1 April 2021). "The Great British Art Tour: The Little Dog that Caused Violent Riots". The Guardian.
Statue locations
Location of the new Brown Dog, Old English Garden, Battersea Park on Wikimapia ()
Location of the old Brown Dog (now empty), Latchmere Recreation Ground on Wikimapia ()
1900s in England
1903 in British law
1903 in case law
1903 in England
1903 in London
1907 in London
1907 riots
Animal cruelty incidents
Animal rights
Animals in politics
Animal testing in the United Kingdom
Animal welfare and rights in the United Kingdom
Anti-vivisection movement
Buildings and structures in Battersea
Dogs in the United Kingdom
Dog monuments
English defamation case law
History of animal testing
Individual dogs
Outdoor sculptures in London
Political controversies in the United Kingdom
Political history of England
Public art in London
20th-century riots in London
1903 animal deaths | Brown Dog affair | [
"Chemistry"
] | 7,750 | [
"Animal testing",
"Anti-vivisection movement",
"Vivisection",
"History of animal testing"
] |
14,351,101 | https://en.wikipedia.org/wiki/Giovanni%20Battista%20Belluzzi | Giovanni Battista Belluzzi (1506–1554), also known as Giovanni Battista di Bartolomeo Bellucci and as Il Sanmarino, was a Sammarinese architect and military engineer. He was born in San Marino on September 27, 1506, and at 18 years of age was sent by his father to Bologna, to learn commerce under Bastiano di Ronco, a merchant of the Guild of Wool.
After two years, he returned to San Marino, where he set up a wool business of his own. His first wife, Cagli, died shortly after they were married. His second wife was the daughter of Girolamo Genga (1467–1551). The couple lived with Girolamo Genga, from whom Giovanni learned architecture. In 1541, his second wife died, leaving Giovanni to raise two sons. In 1543, Giovanni entered into the service of Cosimo I de' Medici, Grand Duke of Tuscany, as an engineer. He designed fortifications for Florence, Pistoia, Pisa and San Miniato and also wrote a book on military architecture. He was wounded in the siege of Montalcino and was killed by enemy fire in a fortress of Aiuola.
Works
References
Istituto della enciclopedia italiana, Dizionario biografico degli Italiani, Rome, Istituto della enciclopedia italiana, 1966.
Thieme, Ulrich and Felix Becker, Allgemeines Lexikon der bildenden Künstler von der Antike bis zur Gegenwart, Reprint of 1907 edition, Leipzig, Veb E.A. Seemann Verlag, 1980–1986.
{{cite book | first= Stefano| last= Ticozzi| year=1830| title= Dizionario degli architetti, scultori, pittori, intagliatori in rame ed in pietra, coniatori di medaglie, musaicisti, niellatori, intarsiatori d'ogni etá e d'ogni nazione''' (Volume 1)| pages= 138 | publisher=Gaetano Schiepatti |location=Milan | url= https://books.google.com/books?id=0ownAAAAMAAJ }}
Vasari, Giorgio, Le Vite delle più eccellenti pittori, scultori, ed architettori'', many editions and translations.
1506 births
1554 deaths
16th-century Italian architects
Italian Renaissance architects
Architects from Tuscany
Sammarinese artists
Renaissance architects
Military engineers | Giovanni Battista Belluzzi | [
"Engineering"
] | 537 | [
"Military engineers",
"Military engineering"
] |
14,352,042 | https://en.wikipedia.org/wiki/FENE%20model | In polymer physics, the finite extensible nonlinear elastic (FENE) model, also called the FENE dumbbell model, represents the dynamics of a long-chained polymer. It simplifies the chain of monomers by connecting a sequence of beads with nonlinear springs.
Its direct extension the FENE-P model, is more commonly used in computational fluid dynamics to simulate turbulent flow. The P stands for the last name of physicist Anton Peterlin, who developed an important approximation of the model in 1966. The FENE-P model was introduced by Robert Byron Bird et al. in the 1980s.
In 1991 the FENE-MP model (PM for modified Peterlin) was introduced and in 1988 the FENE-CR was introduced by M.D. Chilcott and J.M. Rallison.
Formulation
The spring force in the FENE model is given Warner's spring force, as
,
where , k is the spring constant and Lmax the upper limit for the length extension. Total stretching force on i-th bead can be written as .
The Werner's spring force approximate the inverse Langevin function found in other models.
FENE-P model
The FENE-P model takes the FENE model and assumes the Peterlin statistical average for the restoring force as
,
where the indicates the statistical average.
Advantages and disanvatages
FENE-P is one of few polymer models that can be used in computational fluid dynamics simulations since it removes the need of statistical averaging at each grid point at any instant in time. It is demonstrated to be able to capture some of the most important polymeric flow behaviors such as polymer turbulence drag reduction and shear thinning. It is the most commonly used polymer model that can be used in a turbulence simulation since direct numerical simulation of turbulence is already extremely expensive.
Due to its simplifications FENE-P is not able to show the hysteresis effects that polymers have, while the FENE model can.
References
Dynamics of dissolved polymer chains in isotropic turbulence
External links
QPolymer: an open source (for Mac OS X) FENE model Brownian dynamics simulation software
Stretching of Polymers in Isotropic Turbulence: A Statistical Closure
Polymers | FENE model | [
"Chemistry",
"Materials_science"
] | 450 | [
"Polymers",
"Polymer chemistry"
] |
14,352,573 | https://en.wikipedia.org/wiki/Smokestack%20industry | A smokestack industry is a basic, usually cyclical, heavy industry. The factories stereo-typically used in such industries have smoke stacks, hence the name, and produce a high volume of pollution.
Example industries include:
Iron and steelworks
Automotive
Chemical
Power generation
History
Smokestacks were first used during Industrial Revolution between the 18th and 19th centuries and were known to foul the airs in most larger cities but were most noted in large industrial centers like Manchester England or Pittsburgh Pennsylvania. During the dramatic growth and evolution of systems used to produce electricity coal burning central electric stations that relied on direct current were found throughout cities that released noxious fumes and soot into the city air. Taller smokestacks helped to reduce this environmental issue.
External links
European Union: Global sources of air pollution by country
References
Manufacturing | Smokestack industry | [
"Engineering"
] | 162 | [
"Manufacturing",
"Mechanical engineering"
] |
14,352,658 | https://en.wikipedia.org/wiki/EMIEW | EMIEW is a robot developed by Hitachi. Another version has also been made called EMIEW 2. EMIEW stands for Excellent Mobility and Interactive Existence as Workmate. Two EMIEWs have been made, called Pal and Chum. Hitachi stated that Pal and Chum, have a vocabulary of about 100 words, and Pal exhibited these skills by telling reporters: "I want to be able to walk about in places like Shinjuku and Shibuya in the future without bumping into people and cars". Both EMIEWs have a top speed of 6 km/h (matching Honda's ASIMO) and can avoid obstacles.
Specifications
See also
Humanoid robot
References
External links
Social robots
Bipedal humanoid robots
2005 robots
Robots of Japan
Hitachi products | EMIEW | [
"Technology"
] | 156 | [
"Social robots",
"Computing and society"
] |
14,352,711 | https://en.wikipedia.org/wiki/Lateral%20flow%20test | A lateral flow test (LFT), is an assay also known as a lateral flow immunochromatographic test (ICT), or rapid test. It is a simple device intended to detect the presence of a target substance in a liquid sample without the need for specialized and costly equipment. LFTs are widely used in medical diagnostics in the home, at the point of care, and in the laboratory. For instance, the home pregnancy test is an LFT that detects a specific hormone. These tests are simple and economical and generally show results in around five to thirty minutes. Many lab-based applications increase the sensitivity of simple LFTs by employing additional dedicated equipment. Because the target substance is often a biological antigen, many lateral flow tests are rapid antigen tests (RAT or ART).
LFTs operate on the same principles of affinity chromatography as the enzyme-linked immunosorbent assays (ELISA). In essence, these tests run the liquid sample along the surface of a pad with reactive molecules that show a visual positive or negative result. The pads are based on a series of capillary beds, such as pieces of porous paper, microstructured polymer, or sintered polymer. Each of these pads has the capacity to transport fluid (e.g., urine, blood, saliva) spontaneously.
The sample pad acts as a sponge and holds an excess of sample fluid. Once soaked, the fluid flows to the second conjugate pad in which the manufacturer has stored freeze dried bio-active particles called conjugates (see below) in a salt–sugar matrix. The conjugate pad contains all the reagents required for an optimized chemical reaction between the target molecule (e.g., an antigen) and its chemical partner (e.g., antibody) that has been immobilized on the particle's surface. This marks target particles as they pass through the pad and continue across to the test and control lines. The test line shows a signal, often a color as in pregnancy tests. The control line contains affinity ligands which show whether the sample has flowed through and the bio-molecules in the conjugate pad are active. After passing these reaction zones, the fluid enters the final porous material, the wick, that simply acts as a waste container.
LFTs can operate as either competitive or sandwich assays.
History
LFTs derive from paper chromatography, which was developed in 1943 by Martin and Synge, and elaborated in 1944 by Consden, Gordon and Martin. There was an explosion of activity in this field after 1945. The ELISA technology was developed in 1971. A set of LFT patents, including the litigated US 6,485,982 described below, were filed by Armkel LLC starting in 1988.
Synopsis
Colored particles
In principle, any colored particle can be used, but latex (blue color) or nanometer-sized particles of gold (red color) are most commonly used. The gold particles are red in color due to localized surface plasmon resonance. Fluorescent or magnetic labelled particles can also be used, but these require the use of an electronic reader to assess the test result.
Sandwich assays
Sandwich assays are generally used for larger analytes because they tend to have multiple binding sites. As the sample migrates through the assay it first encounters a conjugate, which is an antibody specific to the target analyte labelled with a visual tag, usually colloidal gold. The antibodies bind to the target analyte within the sample and migrate together until they reach the test line. The test line also contains immobilized antibodies specific to the target analyte, which bind to the migrated analyte bound conjugate molecules. The test line then presents a visual change due to the concentrated visual tag, hence confirming the presence of the target molecules. The majority of sandwich assays also have a control line which will appear whether or not the target analyte is present to ensure proper function of the lateral flow pad.
The rapid, low-cost sandwich-based assay is commonly used for home pregnancy tests which detect human chorionic gonadotropin, hCG, in the urine of pregnant women.
Competitive assays
Competitive assays are generally used for smaller analytes since smaller analytes have fewer binding sites. The sample first encounters antibodies to the target analyte labelled with a visual tag (colored particles). The test line contains the target analyte fixed to the surface. When the target analyte is absent from the sample, unbound antibody will bind to these fixed analyte molecules, meaning that a visual marker will show. Conversely, when the target analyte is present in the sample, it binds to the antibodies to prevent them binding to the fixed analyte in the test line, and thus no visual marker shows. This differs from sandwich assays in that no band means the analyte is present.
Quantitative tests
Most LFTs are intended to operate on a purely qualitative basis. However, it is possible to measure the intensity of the test line to determine the quantity of analyte in the sample. Handheld diagnostic devices known as lateral flow readers are used by several companies to provide a fully quantitative assay result. By utilizing unique wavelengths of light for illumination in conjunction with either CMOS or CCD detection technology, a signal rich image can be produced of the actual test lines. Using image processing algorithms specifically designed for a particular test type and medium, line intensities can then be correlated with analyte concentrations. One such handheld lateral flow device platform is made by Detekt Biomedical L.L.C. Alternative non-optical techniques are also able to report quantitative assays results. One such example is a magnetic immunoassay (MIA) in the LFT form also allows for getting a quantified result. Reducing variations in the capillary pumping of the sample fluid is another approach to move from qualitative to quantitative results. Recent work has, for example, demonstrated capillary pumping with a constant flow rate independent from the liquid viscosity and surface energy.
Control line
Most tests will incorporate a second line which contains a further antibody (one which is not specific to the analyte) that binds some of the remaining colored particles which did not bind to the test line. This confirms that fluid has passed successfully from the sample-application pad, past the test line. By giving confirmation that the sample has had a chance to interact with the test line, this increases confidence that a visibly-unchanged test line can be interpreted as a negative result (or that a changed test line can be interpreted as a negative result in a competitive assay).
Blood plasma extraction
Because the intense red color of hemoglobin interferes with the readout of colorimetric or optical detection-based diagnostic tests, blood plasma separation is a common first step to increase diagnostic test accuracy. Plasma can be extracted from whole blood via integrated filters or via agglutination.
Speed and simplicity
Time to obtain the test result is a key driver for these products. Tests results can be available in as little as a few minutes. Generally there is a trade off between time and sensitivity: more sensitive tests may take longer to develop. The other key advantage of this format of test compared to other immunoassays is the simplicity of the test, by typically requiring little or no sample or reagent preparation.
Patents
This is a highly competitive area and a number of people claim patents in the field, most notably Alere (formerly Inverness Medical Innovations, now owned by Abbott) who own patents originally filed by Unipath. The US 6,485,982 patent, that has been litigated, expired in 2019. A number of other companies also hold patents in this arena. A group of competitors are challenging the validity of the patents. The original patent is apparently from 1988.
Applications
Lateral flow assays have a wide array of applications and can test a variety of samples including urine, blood, saliva, sweat, serum, and other fluids. They are currently used by clinical laboratories, hospitals, physicians and veterinary clinics, food analysis labs and environmental testing facilities.
Immediacy in obtaining results is normally the key factor in choosing this technique, although simplicity and lack of a need for formal equipment are also important factors. These features allow ICTs to be used a at-home test or in pharmacies. Because of their exceptional quality, rapid test are also used routinely in well-equippped laboratories when the demand for test is low.
The broad applications of rapid test can be realized because of their simplicity accompanied by high quality analytical production. The sensitivity and specificity of these techniques tend to be comparable to those of other more complex methods, and on occasion significantly better.
Other uses for lateral flow assays are food and environmental safety and veterinary medicine for chemicals such as diseases and toxins. LFTs are also commonly used for disease identification such as ebola, but the most common LFT are the home pregnancy and SARS-CoV-2 tests.
COVID-19 testing
Lateral flow assays have played a critical role in COVID-19 testing as they have the benefit of delivering a result in 15–30 minutes. The systematic evaluation of lateral flow assays during the COVID-19 pandemic was initiated at Oxford University as part of a UK collaboration with Public Health England. A study that started in June 2020 in the United Kingdom, FALCON-C19, confirmed the sensitivity of some lateral flow devices (LFDs) in this setting. Four out of 64 LFDs tested had desirable performance characteristics according to these early tests; the Innova SARS-CoV-2 Antigen Rapid Qualitative Test performed moderately in viral antigen detection/sensitivity with excellent specificity, although kit failure rates and the impact of training were potential issues. The Innova test's specificity is more widely publicised, but sensitivity in phase 4 trials was 50.1%. This describes a device for which one out of every two patients infected with COVID-19 and tested in real-world conditions would receive a false-negative result. After closure of schools in January 2021, biweekly LFTs were introduced in England for teachers, pupils, and households of pupils when schools re-opened on March 8, 2021 for asymptomatic testing. Biweekly LFT were made universally available to everyone in England on April 9, 2021. LFTs have been used for mass testing for COVID-19 globally and complement other public health measures for COVID-19.
Some scientists outside government expressed serious misgivings in late 2020 about the use of Innova LFDs for screening for Covid. According to Jon Deeks, a professor of biostatistics at the University of Birmingham, England, the Innova test is "entirely unsuitable" for community testing: "as the test may miss up to half of cases, a negative test result indicates a reduced risk of Covid, but does not exclude Covid".
Sensitivity of tests used in 2022 was around 70%.
See also
: LFT test for ovulation
References
Further reading
Porex Clinical Sciences (manufacturer)
Medical terminology
Molecular biology
Biotechnology
Molecular biology techniques
Chromatography
Immunologic tests | Lateral flow test | [
"Chemistry",
"Biology"
] | 2,313 | [
"Chromatography",
"Separation processes",
"Immunologic tests",
"Biotechnology",
"Molecular biology techniques",
"nan",
"Molecular biology",
"Biochemistry"
] |
14,352,975 | https://en.wikipedia.org/wiki/Jugate | A jugate consists of two portraits side by side to suggest, to the viewer, the closeness of each to the other. The word comes from the Latin, jugatus, meaning joined or overlapping.
On coins, it is commonly used for married couples, brothers, a father and son, or ruler and divinity.
In political contexts, it refers to the pairing of candidates with an emphasis on their joint candidacy and collaboration on campaign ideas. Often this would be a presidential and vice presidential candidates although sometimes a state or local candidate is included with a presidential candidate.Voters may be better able to connect with and see the candidates as a coherent team thanks to these pictures. Campaign posters, banners, and other promotional items featuring candidates collectively was a method of reinforcing the notion of a cohesive leadership.
Jugates may be seen on medals, pinbacks, buttons, posters or other campaign items. If a third figure appears on the item, it is called a trigate.
Gallery
References
Hake, Ted: Guide to Presidential Campaign Collectibles, Krause Publications, 1991, p. 175
Wert, H. E.:Hanging Around Us in Plain Sight: The Great American Political Campaign Poster, 1844–2012, 2016
Posters
Memorabilia
Badges | Jugate | [
"Mathematics"
] | 251 | [
"Symbols",
"Badges"
] |
14,353,229 | https://en.wikipedia.org/wiki/Viral%20shedding | Viral shedding is the expulsion and release of virus progeny following successful reproduction during a host cell infection. Once replication has been completed and the host cell is exhausted of all resources in making viral progeny, the viruses may begin to leave the cell by several methods.
The term is variously used to refer to viral particles shedding from a single cell, from one part of the body into another, and from a body into the environment, where the virus may infect another.
Vaccine shedding is a form of viral shedding which can occur in instances of infection caused by some attenuated (or "live virus") vaccines.
Means
Shedding from a cell into extracellular space
Budding (through cell envelope)
"Budding" through the cell envelope—in effect, borrowing from the cell membrane to create the virus' own viral envelope— into extracellular space is most effective for viruses that require their own envelope. These include such viruses as HIV, HSV, SARS or smallpox. When beginning the budding process, the viral nucleocapsid cooperates with a certain region of the host cell membrane. During this interaction, the glycosylated viral envelope protein inserts itself into the cell membrane. In order to successfully bud from the host cell, the nucleocapsid of the virus must form a connection with the cytoplasmic tails of envelope proteins. Though budding does not immediately destroy the host cell, this process will slowly use up the cell membrane and eventually lead to the cell's demise. This is also how antiviral responses are able to detect virus-infected cells. Budding has been most extensively studied for viruses of eukaryotes. However, it has been demonstrated that viruses infecting prokaryotes of the domain Archaea also employ this mechanism of virion release.
Apoptosis (cell destruction)
Animal cells are programmed to self-destruct when they are under viral attack or damaged in some other way. By forcing the cell to undergo apoptosis or cell suicide, release of progeny into the extracellular space is possible. However, apoptosis does not necessarily result in the cell simply popping open and spilling its contents into the extracellular space. Rather, apoptosis is usually controlled and results in the cell's genome being chopped up, before apoptotic bodies of dead cell material clump off the cell to be absorbed by macrophages. This is a good way for a virus to get into macrophages either to infect them or simply travel to other tissues in the body.
Although this process is primarily used by non-enveloped viruses, enveloped viruses may also use this. HIV is an example of an enveloped virus that exploits this process for the infection of macrophages.
Exocytosis (cell release)
Viruses that have envelopes that come from nuclear or endosomal membranes can leave the cell via exocytosis, in which the host cell is not destroyed. Viral progeny are synthesized within the cell, and the host cell's transport system is used to enclose them in vesicles; the vesicles of virus progeny are carried to the cell membrane and then released into the extracellular space. This is used primarily by non-enveloped viruses, although enveloped viruses display this too. An example is the use of recycling viral particle receptors in the enveloped varicella-zoster virus.
Shedding from one part of the body to another
Shedding from a body into the environment
Contagiousness
A human with a viral disease can be contagious if they are shedding virus particles, even if they are unaware of doing so. Some viruses such as HSV-2 (which produces genital herpes) can cause asymptomatic shedding and therefore spread undetected from person to person, as no fever or other hints reveal the contagious nature of the host.
See also
Vaccine shedding - a form of viral shedding following administration of an attenuated (or "live virus") vaccine
References
Virology
Viral life cycle | Viral shedding | [
"Biology"
] | 831 | [
"Viral life cycle"
] |
14,353,361 | https://en.wikipedia.org/wiki/Wiring%20closet | A wiring cupboard is a small room commonly found in institutional buildings, such as schools and offices, where electrical connections are made. While they are used for many purposes, their most common use is for computer networking where it may be called a premises wire distribution room (PWD room). Many types of network connections place limits on the distance between end user equipment, such as personal computers, and network access devices, such as routers. These restrictions might require multiple wiring cupboards on each floor of a large building.
Equipments
Equipment that may be found in a wiring closet includes:
Patch panels
Alarm systems
Circuit breaker panels
Video systems, such as cable TV and closed-circuit television systems
Ethernet routers, Network switches, Firewalls
Fiber optic terminations
Telephone punch blocks
Wireless access points
See also
Equipment room
Server room
On-premises wiring
External links
Conduit Wire Fill Chart
Rooms
Electrical wiring
Networking hardware | Wiring closet | [
"Physics",
"Engineering"
] | 181 | [
"Electrical systems",
"Building engineering",
"Computer networks engineering",
"Rooms",
"Physical systems",
"Networking hardware",
"Electrical engineering",
"Electrical wiring",
"Architecture"
] |
14,353,870 | https://en.wikipedia.org/wiki/Toms%20effect | In fluid dynamics, the Toms effect is a reduction of the drag of a turbulent flow thought a pipeline when polymer solutions are added.
In 1948, B. A. Toms discovered by experiments that the addition of a small amount of polymer into a Newtonian solvent (parts per million by weight), which results in a non-Newtonian fluid solution, can reduce the skin frictional drag on a stationary surface by up to 80% when turbulence is present.
This technology has been successfully implemented to reduce pumping cost for oil pipelines, to increase the flow rate in fire fighting equipment and to help irrigation and drainage. It also has potential applications in the design of ship and submarine hulls to achieve an increased speed and reduced energy cost.
See also
Drag reducing agent
FENE model
Non-Newtonian fluid
Direct numerical simulation
References
External links
Alyeska Pipe Line
EFFECTS OF FRICTION AND POLYMERS ON 2D TURBULENCE
Polymers | Toms effect | [
"Chemistry",
"Materials_science"
] | 183 | [
"Polymers",
"Polymer chemistry"
] |
14,354,472 | https://en.wikipedia.org/wiki/Surface%20Air%20Lifted | Surface Air Lifted (SAL) is a postal service used to send international mail items. Thirty-nine postal authorities provide this service. It is a cost-effective international mail. At first SAL mail is processed and transported by surface in the origin country. Then it is transported by air to the destination country and finally processed and delivered as standard-type mail by the destination postal administration. The service is faster than surface mail while the cost is lower than air mail.
SAL is more economical for sending heavy items; with light items, it sometimes costs more than air mail.
History
Prior to World War II a number of European countries adopted the practice of forwarding letters to distant destinations at no extra cost to the sender (such as British mail sent to most parts of the British Empire). The consistently high costs of air mail curtailed this trend after the war. During the mid-1960s in response to the continuing increase of aircraft capacity, the UPU adopted the policy of maximizing air conveyance of mail and in the mid-1970s the concept of “surface air lifted” mail was developed in conjunction with the International Air Transport Association (IATA).
This arrangement allows some mail to receive, for little or no surcharge, speedier transmission than by surface but without the priority of fully surcharged mail.
See also
Express Mail Service (EMS)
References
Postal systems
Philatelic terminology | Surface Air Lifted | [
"Technology"
] | 279 | [
"Transport systems",
"Postal systems"
] |
14,354,550 | https://en.wikipedia.org/wiki/Fencing%20%28computing%29 | Fencing is the process of isolating a node of a computer cluster or protecting shared resources when a node appears to be malfunctioning.
As the number of nodes in a cluster increases, so does the likelihood that one of them may fail at some point. The failed node may have control over shared resources that need to be reclaimed and if the node is acting erratically, the rest of the system needs to be protected. Fencing may thus either disable the node, or disallow shared storage access, thus ensuring data integrity.
Basic concepts
A node fence (or I/O fence) is a virtual "fence" that separates nodes which must not have access to a shared resource from that resource. It may separate an active node from its backup. If the backup crosses the fence and, for example, tries to control the same disk array as the primary, a data hazard may occur. Mechanisms such as STONITH are designed to prevent this condition.
Isolating a node means ensuring that I/O can no longer be done from it. Fencing is typically done automatically, by cluster infrastructure such as shared disk file systems, in order to protect processes from other active nodes modifying the resources during node failures. Mechanisms to support fencing, such as the reserve/release mechanism of SCSI, have existed since at least 1985.
Fencing is required because it is impossible to distinguish between a real failure and a temporary hang. If the malfunctioning node is really down, then it cannot do any damage, so theoretically no action would be required (it could simply be brought back into the cluster with the usual join process). However, because there is a possibility that a malfunctioning node could itself consider the rest of the cluster to be the one that is malfunctioning, a split brain condition could ensue, and cause data corruption. Instead, the system has to assume the worst scenario and always fence in case of problems.
Approaches to fencing
There are two classes of fencing methods, one which disables a node itself, the other disallows access to resources such as shared disks. In some cases, it is assumed that if a node does not respond after a given time-threshold it may be assumed as non-operational, although there are counterexamples, e.g. a long paging rampage.
The STONITH method stands for "Shoot The Other Node In The Head", meaning that the suspected node is disabled or powered off. For instance, power fencing uses a power controller to turn off an inoperable node. The node may then restart itself and join the cluster later. However, there are approaches in which an operator is informed of the need for a manual restart for the node.
The resources fencing approach disallows access to resources without powering off the node. This may include:
Persistent reservation fencing uses the SCSI3 persistent reservations to block access to shared storage.
Fibre Channel fencing disables the fibre channel port
Global network block device (GNBD) fencing which disables access to the GNBD server
When the cluster has only two nodes, the reserve/release method may be used as a two node STONITH whereby upon detecting that node B has 'failed', node A will issue the reserve and obtain all resources (e.g. shared disk) for itself. Node B will be disabled if it tries to do I/O (in case it was temporarily hung). On node B the I/O failure triggers some code to kill the node.
Persistent reservation is essentially a match on a key, so the node which has the right key can do I/O, otherwise its I/O fails. Therefore, it is sufficient to change the key on a failure to ensure the right behavior during failure. However, it may not always be possible to change the key on the failed node.
STONITH is an easier and simpler method to implement on multiple clusters, while the various approaches to resources fencing require specific implementation approaches for each cluster implementation.
See also
Fault tolerance
Failover
References
External links
Red Hat GFS 6.0: Administrator's Guide - Using the Fencing System
OCFS2 FAQ - Quorum and fencing
Fault-tolerant computer systems | Fencing (computing) | [
"Technology",
"Engineering"
] | 857 | [
"Fault-tolerant computer systems",
"Reliability engineering",
"Computer systems"
] |
14,355,155 | https://en.wikipedia.org/wiki/List%20of%20rodents | Rodents are animals that gnaw with two continuously growing incisors. Forty percent of mammal species are rodents, and they inhabit every continent except Antarctica.
This list contains circa 2,700 species in 518 genera in the order Rodentia.
Suborder Hystricomorpha
Family Ctenodactylidae
Genus Ctenodactylus
Ctenodactylus gundi - North African gundi
Ctenodactylus vali - Val's gundi
Genus Felovia
Felovia vae - Felou gundi
Genus Massoutiera
Massoutiera mzabi - Mazab gundi
Genus Pectinator
Pectinator spekei - Speke's pectinator
Family Diatomyidae
Genus Laonastes
Laonastes aenigmamus - Laotian rock rat
Family Bathyergidae
Genus Bathyergus
Bathyergus janetta - Namaqua dune mole rat
Bathyergus suillus - Cape dune mole rat
Genus Cryptomys
Cryptomys hottentotus - African mole rat
Cryptomys mahali - Mahali mole-rat
Cryptomys natalensis - Mahali mole-rat
Cryptomys nimrodi - Matabeleland mole-rat
Cryptomys pretoriae - Highveld mole-rat
Genus Fukomys
Fukomys amatus - Zambian mole-rat
Fukomys anselli - Ansell's mole-rat
Fukomys bocagei - Bocage's mole-rat
Fukomys damarensis - Damaraland mole-rat
Fukomys darlingi - Mashona mole-rat
Fukomys foxi - Nigerian mole-rat
Fukomys hanangensis - Hanang mole-rat
Fukomys ilariae - Somali striped mole rat
Fukomys kafuensis - Kafue mole-rat
Fukomys livingstoni - Livingstone's mole-rat
Fukomys mechowii - Mechow's mole-rat
Fukomys micklemi - Micklem's mole-rat
Fukomys ochraceocinereus - Ochre mole-rat
Fukomys vandewoestijneae - Caroline's mole rat
Fukomys whytei - Whyte's mole-rat
Fukomys zechi - Ghana mole-rat
Genus Georychus
Georychus capensis - Cape mole rat
Genus Heliophobius
Heliophobius argenteocinereus - southern silvery mole rat
Heliophobius kapiti - northern silvery mole rat
Family Heterocephalidae
Genus Heterocephalus
Heterocephalus glaber - naked mole-rat
Family Hystricidae
Genus Atherurus
Atherurus africanus - African brush-tailed porcupine
Atherurus macrourus - Asiatic brush-tailed porcupine
Genus Hystrix
Subgenus Acanthion
Hystrix brachyura - Malayan porcupine
Hystrix javanica - Sunda porcupine
Subgenus Hystrix
Hystrix africaeaustralis - Cape porcupine
Hystrix cristata - Crested porcupine
Hystrix indica - Indian porcupine
Subgenus Thecurus
Hystrix crassispinis - Thick-spined porcupine
Hystrix pumila - Philippine porcupine
Hystrix sumatrae - Sumatran porcupine
Genus Trichys
Trichys fasciculata - Long-tailed porcupine
Family Petromuridae
Genus Petromus
Petromus antiquus (extinct)
Petromus minor (extinct)
Petromus typicus - Dassie rat
Family Thryonomyidae
Genus Thryonomys
Thryonomys asakomae (extinct)
Thryonomys gregorianus - Lesser cane rat
Thryonomys swinderianus - Greater cane rat
Family Erethizontidae
Subfamily Chaetomyinae
Genus Chaetomys
Chaetomys subspinosus - Bristle-spined rat
Subfamily Erethizontinae
Genus Coendou
Coendou baturitensis - Baturite porcupine
Coendou bicolor - Bicolored-spined porcupine
Coendou ichillus - Streaked dwarf porcupine
Coendou insidiosus - Bahia porcupine
Coendou longicaudatus - Amazonian long-tailed porcupine
Coendou melanurus - Black-tailed hairy dwarf porcupine
Coendou mexicanus - Mexican hairy dwarf porcupine
Coendou nycthemera - Black dwarf porcupine
Coendou prehensilis - Brazilian porcupine
Coendou pruinosus - Frosted hairy dwarf porcupine
Coendou quichua - Andean porcupine
Coendou roosmalenorum - Roosmalen's dwarf porcupine
Coendou rothschildi? - Rothschild's porcupine
Coendou rufescens - Stump-tailed porcupine
Coendou sanctamartae - Santa Marta porcupine
Coendou speratus - Pernambuco dwarf porcupine
Coendou spinosus - Paraguaian hairy dwarf porcupine
Coendou vestitus - Brown hairy dwarf porcupine
Genus Erethizon
Erethizon bathygnathum (extinct)
Erethizon cascoensis (extinct)
Erethizon dorsatum - North American porcupine
Erethizon kleini (extinct)
Erethizon poyeri (extinct)
Family Chinchillidae
Genus Chinchilla
Chinchilla chinchilla - Short-tailed chinchilla
Chinchilla lanigera - Long-tailed chinchilla
Genus Lagidium
Lagidium ahuacaense - Ecuadorean mountain viscacha
Lagidium peruanum - Northern viscacha
Lagidium viscacia - Southern viscacha
Lagidium wolffsohni - Wolffsohn's viscacha
Genus Lagostomus
Lagostomus crassus? (extinct)
Lagostomus maximus - Plains viscacha
Lagostomus telenkechanum (extinct)
Family Dinomyidae
Genus Dinomys
Dinomys branickii - Pacarana
Family Caviidae
Subfamily Caviinae
Genus Cavia
Cavia anolaimae?
Cavia aperea - Brazilian guinea pig
Cavia fulgida - Shiny guinea pig
Cavia guianae?
Cavia intermedia - Santa Catarina's guinea pig
Cavia magna - Greater guinea pig
Cavia patzelti? - Sacha guinea pig
Cavia porcellus - Domestic guinea pig
Cavia tschudii - Montane guinea pig
Genus Galea
Galea comes - Southern highland yellow-toothed cavy
Galea flavidens - Brandt's yellow-toothed cavy
Galea leucoblephara - Lowland yellow-toothed cavy
Galea monasteriensis? - Muenster yellow-toothed cavy
Galea musteloides - Common yellow-toothed cavy
Galea spixii - Spix's yellow-toothed cavy
Genus Microcavia
Microcavia australis - Southern mountain cavy
Microcavia jayat - Jayat's mountain cavy
Microcavia maenas - Thomas's mountain cavy
Microcavia niata - Andean mountain cavy
Microcavia shiptoni - Shipton's mountain cavy
Microcavia sorojchi - Sorojchi mountain cavy
Subfamily Dolichotinae
Genus Dolichotis
Dolichotis patagonum - Patagonian mara
Genus Pediolagus
Pediolagus salinicola - Chacoan mara
Subfamily Hydrochoerinae
Genus Hydrochoerus
Hydrochoerus ballesterensis (extinct)
Hydrochoerus gaylordi (extinct)
Hydrochoerus hesperotiganites (extinct)
Hydrochoerus hydrochaeris - Capybara
Hydrochoerus isthmius - Lesser capybara
Genus Kerodon
Kerodon acrobata - Acrobatic cavy
Kerodon rupestris - Rock cavy
Family Dasyproctidae
Genus Dasyprocta
Dasyprocta azarae - Azara's agouti
Dasyprocta coibae - Coiban agouti
Dasyprocta cristata - Crested agouti
Dasyprocta fuliginosa - Black agouti
Dasyprocta guamara - Orinoco agouti
Dasyprocta kalinowskii - Kalinowski agouti
Dasyprocta leporina - Red-rumped agouti
Dasyprocta mexicana - Mexican agouti
Dasyprocta prymnolopha - Black-rumped agouti
Dasyprocta punctata - Central American agouti
Dasyprocta ruatanica - Ruatan Island agouti
Genus Myoprocta
Myoprocta acouchy - Red acouchi
Myoprocta pratti - Green acouchi
Family Cuniculidae
Genus Cuniculus
Cuniculus hernandezi?
Cuniculus paca - Lowland paca
Cuniculus taczanowskii - Mountain paca
Family Ctenomyidae
Genus Ctenomys
Ctenomys andersoni - Anderson's cujuchi
Ctenomys argentinus - Argentine tuco-tuco
Ctenomys australis - Southern tuco-tuco
Ctenomys azarae? - Azara's tuco-tuco
Ctenomys bergi - Berg's tuco-tuco
Ctenomys bidaui - Bidau's tuco-tuco
Ctenomys boliviensis - Bolivian tuco-tuco
Ctenomys bonettoi - Bonetto's tuco-tuco
Ctenomys brasiliensis - Brazilian tuco-tuco
Ctenomys budini? - Budin's tuco-tuco
Ctenomys colburni - Colburn's tuco-tuco
Ctenomys coludo - Puntilla tuco-tuco
Ctenomys conoveri - Conover's tuco-tuco
Ctenomys contrerasi - Contreras's tuco-tuco
Ctenomys coyhaiquensis - Coyhaique tuco-tuco
Ctenomys dorbignyi - D'Orbigny's tuco-tuco
Ctenomys dorsalis - Chacoan tuco-tuco
Ctenomys erikacuellarae - Erika's tuco-tuco
Ctenomys emilianus - Emily's tuco-tuco
Ctenomys famosus - Famatina tuco-tuco
Ctenomys flamarioni - Flamarion's tuco-tuco
Ctenomys fochi - Foch's tuco-tuco
Ctenomys fodax - Lago Blanco tuco-tuco
Ctenomys frater - Reddish tuco-tuco
Ctenomys fulvus - Tawny tuco-tuco
Ctenomys goodfellowi - Goodfellow's tuco-tuco
Ctenomys haigi - Haig's tuco-tuco
Ctenomys ibicuiensis - Ibicui tuco-tuco
Ctenomys johannis - San Juan tuco-tuco
Ctenomys juris - Jujuy tuco-tuco
Ctenomys knighti - Catamarca tuco-tuco
Ctenomys lami - Lami tuco-tuco
Ctenomys latro - Mottled tuco-tuco
Ctenomys lessai - Lessa's tuco-tuco
Ctenomys leucodon - White-toothed tuco-tuco
Ctenomys lewisi - Lewis' tuco-tuco
Ctenomys magellanicus - Magellanic tuco-tuco
Ctenomys maulinus - Maule tuco-tuco
Ctenomys mendocinus - Mendoza tuco-tuco
Ctenomys minutus - Tiny tuco-tuco
Ctenomys nattereri - Natterer's tuco-tuco
Ctenomys occultus - Furtive tuco-tuco
Ctenomys opimus - Highland tuco-tuco
Ctenomys osvaldoreigi - Reig's tuco-tuco
Ctenomys pearsoni - Pearson's tuco-tuco
Ctenomys perrensi - Goya tuco-tuco
Ctenomys peruanus - Peruvian tuco-tuco
Ctenomys pilarensis - Pilar tuco-tuco
Ctenomys pontifex - San Luis tuco-tuco
Ctenomys porteousi? - Porteous' tuco-tuco
Ctenomys pundti - Pundt's tuco-tuco
Ctenomys rionegrensis - Rio Negro tuco-tuco
Ctenomys roigi - Roig's tuco-tuco
Ctenomys saltarius - Salta tuco-tuco
Ctenomys scagliai - Scaglia's tuco-tuco
Ctenomys sericeus - Silky tuco-tuco
Ctenomys sociabilis - Social tuco-tuco
Ctenomys steinbachi - Steinbach's tuco-tuco
Ctenomys sylvanus - Forest tuco-tuco
Ctenomys talarum - Talas tuco-tuco
Ctenomys thalesi - Thales's tuco-tuco
Ctenomys torquatus - Collared tuco-tuco
Ctenomys tuconax - Robust tuco-tuco
Ctenomys tucumanus - Tucuman tuco-tuco
Ctenomys tulduco - Sierra Tontal tuco-tuco
Ctenomys validus - Strong tuco-tuco
Ctenomys viarapaensis (extinct)
Ctenomys viperinus - Vipos tuco-tuco
Ctenomys yatesi - Yates's tuco-tuco
Ctenomys yolandae - Yolanda's tuco-tuco
Family Octodontidae
Genus Aconaemys
Aconaemys fuscus - Chilean rock rat
Aconaemys porteri - Porter's rock rat
Aconaemys sagei - Sage's rock rat
Genus Octodon
Octodon bridgesi - Bridge's degu
Octodon degus - Common degu
Octodon lunatus - Moon-toothed degu
Octodon pacificus - Isla Mocha degu
Octodon ricardojeda - Ricardo Ojeda's degu
Genus Octodontomys
Octodontomys gliroides - Mountain degu
Genus Octomys
Octomys mimax - Mountain viscacha-rat
Genus Pipanacoctomys
Pipanacoctomys aureus - Golden viscacha-rat
Genus Spalacopus
Spalacopus cyanus - Coruro
Genus Tympanoctomys
Tympanoctomys barrerae - Plains viscacha-rat
Tympanoctomys cordubensis (extinct)
Tympanoctomys kirchnerorum - Kirchner's viscacha rat
Tympanoctomys loschalchalerosorum - Los Chalchaleros' viscacha-rat
Family Abrocomidae
Genus Abrocoma
Abrocoma bennettii - Bennett's chinchilla rat
Abrocoma boliviensis - Bolivian chinchilla rat
Abrocoma budini - Budin's chinchilla rat
Abrocoma cinerea - Ashy chinchilla rat
Abrocoma famatina - Famatina chinchilla rat
Abrocoma schistacea - Sierra del Tontal chinchilla rat
Abrocoma uspallata - Uspallata chinchilla rat
Abrocoma vaccarum - Punta de Vacas chinchilla rat
Genus Cuscomys
Cuscomys ashanika - Asháninka arboreal chinchilla rat
Cuscomys oblativus - Machu Picchu arboreal chinchilla rat
Family Echimyidae
Subfamily Dactylomyinae
Genus Dactylomys
Dactylomys boliviensis - Bolivian bamboo rat
Dactylomys dactylinus - Amazon bamboo rat
Dactylomys peruanus - Peruvian bamboo rat
Genus Kannabateomys
Kannabateomys amblyonyx - southern bamboo rat
Genus Olallamys
Olallamys albicauda - white-tailed olalla rat
Olallamys edax - greedy olalla rat
Subfamily Echimyinae
Genus Callistomys
Callistomys pictus - painted tree rat
Genus Diplomys
Diplomys caniceps - Colombian soft-furred spiny rat
Diplomys labilis - rufous soft-furred spiny-rat
Genus Echimys
Echimys chrysurus - white-faced tree rat
Echimys saturnus - dark tree rat
Echimys vieirai - Vieira's spiny tree-rat
Genus Hoplomys
Hoplomys gymnurus - Armored rat
Genus Isothrix
Isothrix barbarabrownae - Barbara Brown's brush-tailed rat
Isothrix bistriata - yellow-crowned brush-tailed rat
Isothrix negrensis - Rio Negro brush-tailed rat
Isothrix pagurus - plain brush-tailed rat
Isothrix sinnamariensis - Sinnamary brush-tailed rat
Genus Makalata
Makalata didelphoides - armored spiny rat
Makalata macrura - Long-tailed armored tree-rat
Makalata obscura - Dusky spiny tree-rat
Makalata rhipidura - Peruvian armored tree-rat
Genus Pattonomys
Pattonomys occasius - Bare-tailed armored tree-rat
Pattonomys semivillosus - speckled tree rat
Genus Phyllomys
Phyllomys blainvilii - Golden Atlantic tree-rat
Phyllomys brasiliensis- Orange-brown Atlantic tree-rat
Phyllomys dasythrix - Drab Atlantic tree-rat
Phyllomys kerri - Kerr's Atlantic tree-rat
Phyllomys lamarum - Pallid Atlantic tree-rat
Phyllomys lundi - Lund's Atlantic tree-rat
Phyllomys mantiqueirensis - Mantiqueira Atlantic tree-rat
Phyllomys medius - Long-furred Atlantic tree-rat
Phyllomys nigrispinus - black-spined Atlantic tree rat
Phyllomys pattoni - Rusty-sided Atlantic tree-rat
Phyllomys sulinus - Southern Atlantic tree-rat
Phyllomys thomasi - Giant Atlantic tree-rat
Phyllomys unicolor - Short-furred Atlantic tree-rat
Genus Santamartamys
Santamartamys rufodorsalis - Red-crested tree-rat
Genus Toromys
Toromys grandis - Giant tree-rat
Subfamily Eumysopinae
Genus Carterodon
Carterodon sulcidens - Owl's spiny rat
Genus Clyomys
Clyomys bishopi? - Bishop's fossorial spiny rat
Clyomys laticeps - Broad-headed spiny rat
Genus Euryzygomatomys
Euryzygomatomys guiara - Brandt's guiara
Euryzygomatomys spinosus - Fischer's guiara
Genus Lonchothrix
Lonchothrix emiliae - tuft-tailed spiny tree rat
Genus Mesomys
Mesomys hispidus - spiny tree rat
Mesomys leniceps - woolly-headed spiny tree rat
Mesomys occultus - Tufted-tailed spiny tree-rat
Mesomys stimulax - Surinam spiny tree rat
Genus Proechimys
Proechimys canicollis group
Proechimys canicollis - Colombian spiny rat
Proechimys decumanus group
Proechimys decumanus - Pacific spiny rat
Proechimys echinothrix group
Proechimys echinothrix - Stiff-spine spiny rat
Proechimys gardneri group
Proechimys gardneri - Gardner's spiny rat
Proechimys kulinae - Kulina spiny rat
Proechimys pattoni - Patton's spiny rat
Proechimys goeldii group
Proechimys goeldii - Goeldi's spiny rat
Proechimys quadruplicatus - Napo spiny rat
Proechimys steerei - Steere's spiny rat
Proechimys guyannensis group
Proechimys guyannensis - Guyenne spiny rat
Proechimys roberti - Roberto's spiny rat
Proechimys longicaudatus group
Proechimys brevicauda - Huallaga spiny rat
Proechimys cuvieri - Cuvier's spiny rat
Proechimys longicaudatus - long-tailed spiny rat
Proechimys semispinosus group
Proechimys oconnelli - O'Connell's spiny rat
Proechimys semispinosus - Tome's spiny rat
Proechimys simonsi group
Proechimys simonsi - Simon's spiny rat
Proechimys trinitatus group
Proechimys trinitatus - Trinidad spiny rat
Proechimys chrysaeolus - Boyaca spiny rat
Proechimys guairae - Guaira spiny rat
Proechimys hoplomyoides - Guyanan spiny rat
Proechimys magdalenae - Magdelena spiny rat
Proechimys mincae - minca spiny rat
Proechimys poliopus - gray-footed spiny rat
Proechimys urichi - Sucre spiny rat
Proechimys (Others)
Proechimys amphichoricus? - white-spined spiny rat
Proechimys cayennensis? - Cayenne spiny rat
Proechimys oris? - Para spiny rat
Genus Thrichomys
Thrichomys apereoides - Common punaré
Thrichomys fosteri - Foster's punaré
Thrichomys inermis - Highlands punaré
Thrichomys laurentius - Sao Lourenço punaré
Thrichomys pachyurus - Paraguayan punaré
Genus Trinomys
Trinomys albispinus - White-spined Atlantic spiny rat
Trinomys dimidiatus - Atlantic spiny rat
Trinomys eliasi - Elias's Atlantic spiny rat
Trinomys gratiosus - Gracile Atlantic spiny rat
Trinomys iheringi - Ihering's Atlantic spiny rat
Trinomys mirapitanga - Dark-caped Atlantic spiny rat
Trinomys moojeni - Moojen's Atlantic spiny rat
Trinomys myosuros - Mouse-tailed Atlantic spiny rat
Trinomys paratus - Spiked Atlantic spiny rat
Trinomys setosus - Hairy Atlantic spiny rat
Trinomys yonenagae - Yonenaga's Atlantic spiny rat
Subfamily Heteropsomyinae
Genus Puertoricomys
Puertoricomys corozalus - Corozal rat
Genus Heteropsomys
Heteropsomys antillensis - Antillean cave rat
Heteropsomys insulans - insular cave rat
Genus Brotomys
Brotomys voratus - Hispaniolan edible rat (extinct)
Genus Boromys
Boromys offella - Oriente cave rat (extinct)
Boromys torrei - Torre's cave rat (extinct)
Subfamily Capromyinae (hutias)
Tribe Capromyini
Genus Capromys
Capromys garridoi - Garrido's hutia
Capromys pilorides - Desmarest's hutia
C. p. gundlachianus - Archipélago de Sabana hutia
Genus Mesocapromys
Mesocapromys angelcabrerai - Cabrera's hutia
Mesocapromys auritus - eared hutia
Mesocapromys melanurus - black-tailed hutia
Mesocapromys nanus - dwarf hutia (possibly extinct)
Mesocapromys sanfelipensis - San Felipe hutia (possibly extinct)
Genus Mysateles
Mysateles prehensilis - prehensile-tailed hutia
M. p. gundlachi - Gundlach's hutia
M. p. meridionalis - Isla De La Juventud tree hutia
Genus Geocapromys
Geocapromys brownii - Jamaican hutia
Geocapromys caymanensis - Cayman hutia (extinct)
Geocapromys columbianus - Cuban hutia (extinct)
Geocapromys ingrahami - Bahamian hutia
Geocapromys megas (extinct)
Geocapromys pleistocenicus (extinct)
Geocapromys thoracatus - Swan Island hutia (extinct)
Tribe Plagiodontini
Genus Hyperplagiodontia
Hyperplagiodontia araeum - wide-toothed hutia (extinct)
Genus Plagiodontia
Plagiodontia aedium - Hispaniolan hutia
Plagiodontia ipnaeum - Samana hutia (extinct)
Plagiodonta spelaeum - Small Haitian hutia (extinct)
Genus Rhizoplagiodontia
Rhizoplagiodontia lemkei - Lemke's hutia (extinct)
Tribe Isolobodontini
Genus Isolobodon
Isolobodon montanus - montane hutia (extinct)
Isolobodon portoricensis - Puerto Rican hutia (extinct)
Tribe Hexolobodontini
Genus Hexolobodon
Hexolobodon phenax - imposter hutia (extinct)
Family Heptaxodontidae
Subfamily Clidomyinae
Genus Clidomys
Clidomys osborni - Osborn's key mouse (extinct)
Subfamily Heptaxodontinae
Genus Elasmodontomys
Elasmodontomys obliquus - plate-toothed mouse (extinct)
Genus Quemisia
Quemisia gravis - Hispaniolan giant hutia (extinct)
Genus Amblyrhiza
Amblyrhiza inundata - blunt-toothed mouse (extinct)
Family Myocastoridae
Genus Myocastor
Myocastor coypus - coypu or nutria
Suborder Anomaluromorpha
Family Anomaluridae
Subfamily Anomalurinae
Genus Anomalurus
Anomalurus beecrofti - Beecroft's flying squirrel
Anomalurus derbianus - Lord Derby's scaly-tailed squirrel
Anomalurus peli - Pel's scaly-tailed squirrel
Anomalurus pusillus - dwarf scaly-tailed squirrel
Subfamily Zenkerellinae
Genus Idiurus
Idiurus zenkeri - pygmy scaly-tailed squirrel
Idiurus macrotis - long-eared scaly-tailed squirrel
Genus Zenkerella
Zenkerella insignis - Cameroon scaly-tailed squirrel
Family Pedetidae
Genus Pedetes
Pedetes capensis - South African springhare
Pedetes surdaster - East African springhare
Suborder Sciuromorpha
Family Aplodontidae
Genus Aplodontia
Aplodontia rufa - mountain beaver
Family Sciuridae
Subfamily Ratufinae
Genus Ratufa
Ratufa affinis - pale giant squirrel
Ratufa bicolor - black giant squirrel
Ratufa indica - Indian giant squirrel
Ratufa macroura - grizzled giant squirrel
Subfamily Sciurillinae
Genus Sciurillus
Sciurillus pusillus - Neotropical pygmy squirrel
Subfamily Sciurinae
Tribe Sciurini
Genus Microsciurus
Microsciurus alfari - Central American dwarf squirrel
Microsciurus flaviventer - Amazon dwarf squirrel or Guianan squirrel
Microsciurus mimulus - western dwarf squirrel
Microsciurus santanderensis - Santander dwarf squirrel
Genus Rheithrosciurus
Rheithrosciurus macrotis - tufted ground squirrel
Genus Sciurus
Subgenus Guerlinguetus
Sciurus aestuans - Brazilian squirrel or Guianan squirrel
Sciurus argentinius - South Yungas red squirrel
Sciurus gilvigularis - yellow-throated squirrel
Sciurus granatensis - red-tailed squirrel
Sciurus ignitus - Bolivian squirrel
Sciurus ingrami - Ingram's squirrel
Sciurus pucheranii - Andean squirrel
Sciurus richmondi - Richmond's squirrel
Sciurus sanborni - Sanborn's squirrel
Sciurus stramineus - Guayaquil squirrel
Subgenus Hadrosciurus
Sciurus flammifer - fiery squirrel
Sciurus pyrrhinus - Junín red squirrel
Subgenus Hesperosciurus
Sciurus griseus - western gray squirrel
Subgenus Otosciurus
Sciurus aberti - Abert's squirrel
Subgenus Sciurus
Sciurus alleni - Allen's squirrel
Sciurus arizonensis - Arizona gray squirrel
Sciurus aureogaster - Mexican gray squirrel
Sciurus carolinensis - eastern gray squirrel
Sciurus colliaei - Collie's squirrel
Sciurus deppei - Deppe's squirrel
Sciurus lis - Japanese squirrel
Sciurus meridionalis - Calabrian black squirrel
Sciurus nayaritensis - Mexican fox squirrel
Sciurus niger - eastern fox squirrel
Sciurus oculatus - Peters's squirrel
Sciurus variegatoides - variegated squirrel
Sciurus vulgaris - Eurasian red squirrel
Sciurus yucatanensis - Yucatán squirrel
Subgenus Tenes
Sciurus anomalus - Persian squirrel
Subgenus Urosciurus
Sciurus igniventris - northern Amazon red squirrel
Sciurus spadiceus - southern Amazon red squirrel
Genus Syntheosciurus
Syntheosciurus brochus - Bangs's mountain squirrel
Genus Tamiasciurus
Tamiasciurus douglasii - Douglas's squirrel
Tamiasciurus douglasii mearnsi - Mearns's squirrel
Tamiasciurus fremonti - Southwestern red squirrel
Tamiasciurus fremonti grahamensis - Mount Graham red squirrel
Tamiasciurus hudsonicus - American red squirrel
Tribe Pteromyini
Genus Aeretes
Aeretes melanopterus - North Chinese flying squirrel
Genus Aeromys
Aeromys tephromelas - black flying squirrel
Aeromys thomasi - Thomas' flying squirrel
Genus Belomys
Belomys pearsonii - hairy-footed flying squirrel
Genus Biswamoyopterus
Biswamoyopterus biswasi - Namdapha flying squirrel
Biswamoyopterus gaoligongensis - Mount Gaoligong flying squirrel
Biswamoyopterus laoensis - Laotian giant flying squirrel
Genus Eoglaucomys
Eoglaucomys fimbriatus - Kashmir flying squirrel
Eoglaucomys fimbriatus baberi - Afghan flying squirrel
Genus Eupetaurus
Eupetaurus cinereus - Western woolly flying squirrel
Eupetaurus nivamons - Yunnan woolly flying squirrel
Eupetaurus tibetensis - Tibetan woolly flying squirrel
Genus Glaucomys
Glaucomys oregonensis - Humboldt's flying squirrel
Glaucomys sabrinus - northern flying squirrel
Glaucomys volans - southern flying squirrel
Genus Hylopetes
Hylopetes alboniger - particolored flying squirrel
Hylopetes bartelsi - Bartel's flying squirrel
Hylopetes electilis - Hainan flying squirrel
Hylopetes lepidus? - gray-cheeked flying squirrel
Hylopetes nigripes - Palawan flying squirrel
Hylopetes phayrei - Indochinese flying squirrel
Hylopetes platyurus - gray-cheeked flying squirrel
Hylopetes sagitta - Arrow flying squirrel
Hylopetes sipora - Sipora flying squirrel
Hylopetes spadiceus - red-cheeked flying squirrel
Hylopetes winstoni - Sumatran flying squirrel
Genus Iomys
Iomys horsfieldii - Javanese flying squirrel
Iomys sipora - Mentawi flying squirrel
Genus Petaurillus
Petaurillus emiliae - lesser pygmy flying squirrel
Petaurillus hosei - Hose's pygmy flying squirrel
Petaurillus kinlochii - Selangor pygmy flying squirrel
Genus Petaurista
Petaurista alborufus - red and white giant flying squirrel
Petaurista elegans - spotted giant flying squirrel
Petaurista leucogenys - Japanese giant flying squirrel
Petaurista magnificus - Hodgson's giant flying squirrel
Petaurista mechukaensis - Mechuka giant flying squirrel
Petaurista mishmiensis - Mishmi giant flying squirrel
Petaurista nobilis - Bhutan giant flying squirrel
Petaurista petaurista - red giant flying squirrel
Petaurista philippensis - Indian giant flying squirrel
Petaurista siangensis - Hodgson's giant flying squirrel
Petaurista xanthotis - Mebo giant flying squirrel
Genus Petinomys
Petinomys crinitus - Mindanao flying squirrel
Petinomys fuscocapillus - Travancore flying squirrel
Petinomys genibarbis - whiskered flying squirrel
Petinomys hageni - Hagen's flying squirrel
Petinomys lugens - Siberut flying squirrel
Petinomys mindanensis - Mindanao flying squirrel
Petinomys sagitta - arrow flying squirrel
Petinomys setosus - Temminck's flying squirrel
Petinomys vordermanni - Vordermann's flying squirrel
Genus Pteromys
Pteromys momonga - Japanese flying squirrel
Pteromys volans - Siberian flying squirrel
Genus Pteromyscus
Pteromyscus pulverulentus - smoky flying squirrel
Genus Trogopterus
Trogopterus xanthipes - complex-toothed flying squirrel
Subfamily Callosciurinae
Genus Callosciurus
Callosciurus adamsi - ear-spot squirrel
Callosciurus albescens - Kloss's squirrel
Callosciurus baluensis - Kinabalu squirrel
Callosciurus caniceps - gray-bellied squirrel
Callosciurus erythraeus - Pallas's squirrel
Callosciurus finlaysonii - Finlayson's squirrel
Callosciurus flavimanus?
Callosciurus honkhoaiensis - Hon Khoai squirrel
Callosciurus inornatus - inornate squirrel
Callosciurus melanogaster - Mentawai squirrel
Callosciurus nigrovittatus - black-striped squirrel
Callosciurus notatus - plantain squirrel
Callosciurus orestes - Borneo black-banded squirrel
Callosciurus phayrei - Phayre's squirrel
Callosciurus prevostii - Prevost's squirrel
Callosciurus pygerythrus - Irrawaddy squirrel
Callosciurus quinquestriatus - Anderson's squirrel
Genus Dremomys
Dremomys everetti - Bornean mountain ground squirrel
Dremomys gularis - red-throated squirrel
Dremomys lokriah - orange-bellied Himalayan squirrel
Dremomys pernyi - Perny's long-nosed squirrel
Dremomys pyrrhomerus - red-hipped squirrel
Dremomys rufigenis - Asian red-cheeked squirrel
Genus Exilisciurus
Exilisciurus concinnus - Philippine pygmy squirrel
Exilisciurus exilis - least pygmy squirrel
Exilisciurus whiteheadi - tufted pygmy squirrel
Genus Funambulus
Subgenus Funambulus
Funambulus layardi - Layard's palm squirrel
Funambulus obscurus - Dusky palm squirrel
Funambulus palmarum - Indian palm squirrel
Funambulus sublineatus - dusky palm squirrel
Funambulus tristriatus - jungle palm squirrel
Subgenus Prasadsciurus
Funambulus pennantii - northern palm squirrel
Genus Glyphotes
Glyphotes simus - sculptor squirrel
Genus Hyosciurus
Hyosciurus heinrichi - montane long-nosed squirrel
Hyosciurus ileile - lowland long-nosed squirrel
Genus Lariscus
Lariscus hosei - four-striped ground squirrel
Lariscus insignis - three-striped ground squirrel
Lariscus niobe - Niobe ground squirrel
Lariscus obscurus - Mentawai three-striped squirrel
Genus Menetes
Menetes berdmorei - Berdmore's ground squirrel
Genus Nannosciurus
Nannosciurus melanotis - black-eared squirrel
Genus Prosciurillus
Prosciurillus abstrusus - secretive dwarf squirrel
Prosciurillus alstoni - Alston's Sulawesi dwarf squirrel
Prosciurillus leucomus - whitish dwarf squirrel
Prosciurillus murinus - Celebes dwarf squirrel
Prosciurillus rosenbergii - Sanghir squirrel
Prosciurillus topapuensis - Roux's Sulawesi dwarf squirrel
Prosciurillus weberi - Weber's dwarf squirrel
Genus Rhinosciurus
Rhinosciurus laticaudatus - shrew-faced squirrel
Genus Rubrisciurus
Rubrisciurus rubriventer - red-bellied squirrel
Genus Sundasciurus
Sundasciurus altitudinis - Sumatran mountain squirrel
Sundasciurus brookei - Brooke's squirrel
Sundasciurus davensis - Davao squirrel
Sundasciurus everetti - Bornean mountain ground squirrel
Sundasciurus fraterculus - fraternal squirrel
Sundasciurus hippurus - horse-tailed squirrel
Sundasciurus hoogstraali - Busuanga squirrel
Sundasciurus jentinki - Jentink's squirrel
Sundasciurus juvencus - northern Palawan tree squirrel
Sundasciurus lowii - Low's squirrel
Sundasciurus mindanensis - Mindanao squirrel
Sundasciurus moellendorffi - Culion tree squirrel
Sundasciurus natunensis - Natuna squirrel
Sundasciurus philippinensis - Philippine tree squirrel
Sundasciurus rabori - Palawan montane squirrel
Sundasciurus robinsoni - Robinson's squirrel
Sundasciurus samarensis - Samar squirrel
Sundasciurus steerii - southern Palawan tree squirrel
Sundasciurus tahan - Upland squirrel
Sundasciurus tenuis - slender squirrel
Genus Tamiops
Tamiops mcclellandii - Himalayan striped squirrel
Tamiops maritimus - maritime striped squirrel
Tamiops rodolphii - Cambodian striped squirrel
Tamiops swinhoei - Swinhoe's striped squirrel
Subfamily Xerinae
Tribe Xerini
Genus Atlantoxerus
Atlantoxerus getulus - Barbary ground squirrel
Genus Spermophilopsis
Spermophilopsis leptodactylus - long-clawed ground squirrel
Genus Euxerus
Euxerus erythropus - striped ground squirrel
Genus Geosciurus
Geosciurus inauris - Cape ground squirrel or South African ground squirrel
Geosciurus princeps - Damara ground squirrel
Genus Xerus
Xerus rutilus - unstriped ground squirrel
Tribe Protoxerini
Genus Epixerus
Epixerus ebii - Ebian's palm squirrel, Temminck's giant squirrel, western palm squirrel
Epixerus ebii wilsoni - Biafran palm squirrel
Genus Funisciurus
Funisciurus anerythrus - Thomas's rope squirrel
Funisciurus bayonii - Lunda rope squirrel
Funisciurus carruthersi - Carruther's mountain squirrel
Funisciurus congicus - Congo rope squirrel
Funisciurus isabella - Lady Burton's rope squirrel
Funisciurus lemniscatus - ribboned rope squirrel
Funisciurus leucogenys - red-cheeked rope squirrel
Funisciurus pyrropus - fire-footed rope squirrel
Funisciurus substriatus - Kintampo rope squirrel
Genus Heliosciurus
Heliosciurus gambianus - Gambian sun squirrel
Heliosciurus mutabilis - mutable sun squirrel
Heliosciurus punctatus - Small sun squirrel
Heliosciurus rufobrachium - red-legged sun squirrel
Heliosciurus ruwenzorii - Ruwenzori sun squirrel
Heliosciurus undulatus - Zanj sun squirrel
Genus Myosciurus
Myosciurus pumilio - African pygmy squirrel
Genus Paraxerus
Paraxerus alexandri - Alexander's bush squirrel
Paraxerus boehmi - Boehm's bush squirrel
Paraxerus cepapi - Smith's bush squirrel
Paraxerus cooperi - Cooper's green squirrel
Paraxerus flavovittis - striped bush squirrel
Paraxerus lucifer - African red bush squirrel
Paraxerus ochraceus - Huet's bush squirrel
Paraxerus palliatus - red bush squirrel
Paraxerus poensis - Fernando Po squirrel
Paraxerus vexillarius - Swynnerton's bush squirrel
Paraxerus vincenti - Vincent's bush squirrel
Genus Protoxerus
Protoxerus aubinnii - slender-tailed squirrel
Protoxerus stangeri - forest giant squirrel or Stanger's squirrel
Tribe Marmotini
Genus Ammospermophilus
Ammospermophilus harrisii - Harris's antelope squirrel
Ammospermophilus insularis - Espirito Santo Island squirrel
Ammospermophilus interpres - Texas antelope squirrel
Ammospermophilus leucurus - white-tailed antelope squirrel
Ammospermophilus nelsoni - Nelson's antelope squirrel
Genus Callospermophilus
Callospermophilus lateralis - golden-mantled ground squirrel
Callospermophilus madrensis - Sierra Madre ground squirrel
Callospermophilus saturatus - Cascade golden-mantled ground squirrel
Genus Cynomys
Cynomys gunnisoni - Gunnison's prairie dog
Cynomys leucurus - white-tailed prairie dog
Cynomys ludovicianus - black-tailed prairie dog
Cynomys mexicanus - Mexican prairie dog
Cynomys parvidens - Utah prairie dog
Genus Eutamias
Eutamias sibiricus - Siberian chipmunk
Genus Ictidomys
Ictidomys mexicanus - Mexican ground squirrel
Ictidomys parvidens - Rio Grande ground squirrel
Ictidomys tridecemlineatus - thirteen-lined ground squirrel
Genus Marmota
Subgenus Marmota
Marmota baibacina - gray marmot
Marmota bobak - Bobak marmot
Marmota broweri - Alaska marmot
Marmota camtschatica - black-capped marmot
Marmota caudata - long-tailed marmot
Marmota himalayana - Himalayan marmot
Marmota marmota - alpine marmot
Marmota marmota latirostris - tatra marmot
Marmota menzbieri - Menzbier's marmot
Marmota monax - woodchuck
Marmota sibirica - Tarbagan marmot
Subgenus Petromarmota
Marmota caligata - hoary marmot
Marmota flaviventris - yellow-bellied marmot
Marmota olympus - Olympic marmot
Marmota vancouverensis - Vancouver marmot
Genus Neotamias
Neotamias alpinus - alpine chipmunk
Neotamias amoenus - yellow-pine chipmunk
Neotamias bulleri - Buller's chipmunk
Neotamias canipes - gray-footed chipmunk
Neotamias cinereicollis - gray-collared chipmunk
Neotamias dorsalis - cliff chipmunk
Neotamias durangae - Durango chipmunk
Neotamias merriami - Merriam's chipmunk
Neotamias minimus - least chipmunk
Neotamias obscurus - California chipmunk
Neotamias ochrogenys - yellow-cheeked chipmunk
Neotamias palmeri - Palmer's chipmunk
Neotamias panamintinus - Panamint chipmunk
Neotamias quadrimaculatus - long-eared chipmunk
Neotamias quadrivittatus - Colorado chipmunk
Neotamias ruficaudus - red-tailed chipmunk
Neotamias rufus - Hopi chipmunk
Neotamias senex - Allen's chipmunk
Neotamias siskiyou - Siskiyou chipmunk
Neotamias sonomae - Sonoma chipmunk
Neotamias speciosus - lodgepole chipmunk
Neotamias townsendii - Townsend's chipmunk
Neotamias umbrinus - Uinta chipmunk
Genus Notocitellus
Notocitellus adocetus - tropical ground squirrel
Notocitellus annulatus - ring-tailed ground squirrel
Genus Otospermophilus
Otospermophilus atricapillus - Baja California rock squirrel
Otospermophilus beecheyi - California ground squirrel
Otospermophilus variegatus - rock squirrel
Genus Poliocitellus
Poliocitellus franklinii - Franklin's ground squirrel
Genus Sciurotamias
Sciurotamias davidianus - Père David's rock squirrel
Sciurotamias forresti - Forrest's rock squirrel
Genus Spermophilus
Spermophilus alashanicus - Alashan ground squirrel
Spermophilus brevicauda - Brandt's ground squirrel
Spermophilus citellus - European ground squirrel
Spermophilus dauricus - Daurian ground squirrel
Spermophilus erythrogenys - red-cheeked ground squirrel
Spermophilus fulvus - yellow ground squirrel
Spermophilus major - russet ground squirrel
Spermophilus musicus - Caucasian mountain ground squirrel
Spermophilus nilkaensis - Tian Shan ground squirrel
Spermophilus pallidicauda - Pallid ground squirrel
Spermophilus pygmaeus - little ground squirrel
Spermophilus relictus - Relict ground squirrel
Spermophilus suslicus - Speckled ground squirrel
Spermophilus taurensis - Taurus ground squirrel
Spermophilus xanthoprymnus - Asia Minor ground squirrel
Genus Tamias
Tamias striatus - eastern chipmunk
Genus Urocitellus
Urocitellus armatus - Uinta ground squirrel
Urocitellus beldingi - Belding's ground squirrel
Urocitellus brunneus - Northern Idaho ground squirrel
Urocitellus canus - Merriam's ground squirrel
Urocitellus columbianus - Columbian ground squirrel
Urocitellus elegans - Wyoming ground squirrel
Urocitellus endemicus - Southern Idaho ground squirrel
Urocitellus mollis - Piute ground squirrel
Urocitellus parryii - Arctic ground squirrel
Urocitellus richardsonii - Richardson's ground squirrel
Urocitellus townsendii - Townsend's ground squirrel
Urocitellus undulatus - long-tailed ground squirrel
Urocitellus washingtoni - Washington ground squirrel
Genus Xerospermophilus
Xerospermophilus mohavensis - Mohave ground squirrel
Xerospermophilus perotensis - Perote ground squirrel
Xerospermophilus spilosoma - spotted ground squirrel
Xerospermophilus tereticaudus - round-tailed ground squirrel
Family Gliridae
Subfamily Graphiurinae
Genus Graphiurus
Graphiurus angolensis - Angolan African dormouse
Graphiurus christyi - Christy's dormouse
Graphiurus crassicaudatus - Jentink's dormouse
Graphiurus johnstoni - Johnston's African dormouse
Graphiurus kelleni - Kellen's dormouse
Graphiurus lorraineus - Lorrain dormouse
Graphiurus microtis - small-eared dormouse
Graphiurus monardi - Monard's dormouse
Graphiurus murinus - woodland dormouse
Graphiurus nagtglasii - Nagtglas's African dormouse
Graphiurus ocularis - spectacled dormouse
Graphiurus platyops - rock dormouse
Graphiurus rupicola - stone dormouse
Graphiurus surdus - silent dormouse
Graphiurus walterverheyeni - Walter Verheyen's African dormouse
Subfamily Leithiinae
Genus Chaetocauda
Chaetocauda sichuanensis - Chinese dormouse
Genus Dryomys
Dryomys laniger - woolly dormouse
Dryomys niethammeri - Niethammer's forest dormouse
Dryomys nitedula - forest dormouse
Genus Eliomys
Eliomys melanurus - Asian garden dormouse
Eliomys munbyanus - Maghreb garden dormouse
Eliomys quercinus - garden dormouse
Genus Muscardinus
Muscardinus avellanarius - hazel dormouse
Genus Myomimus
Myomimus personatus - masked mouse-tailed dormouse
Myomimus roachi - Roach's mouse-tailed dormouse
Myomimus setzeri - Setzer's mouse-tailed dormouse
Genus Selevinia
Selevinia betpakdalaensis - desert dormouse
Subfamily Glirinae
Genus Glirulus
Glirulus japonicus - Japanese dormouse
Genus Glis
Glis glis - edible dormouse
Glis persicus - Iranian edible dormouse
Suborder Castorimorpha
Family Castoridae
Genus Castor
Castor canadensis - Canadian beaver
Castor fiber - Eurasian beaver
Family Geomyidae
Genus Cratogeomys
Cratogeomys castanops - Yellow-faced pocket gopher
Cratogeomys fulvescens - Oriental Basin pocket gopher
Cratogeomys fumosus - Smoky pocket gopher
Cratogeomys goldmani - Goldman's pocket gopher
Cratogeomys merriami - Merriam's pocket gopher
Cratogeomys perotensis - Perote pocket gopher
Cratogeomys planiceps - Flat-headed pocket gopher
Genus Geomys
Geomys arenarius - desert pocket gopher
Geomys attwateri - Attwater's pocket gopher
Geomys breviceps - Baird's pocket gopher
Geomys bursarius - plains pocket gopher
Geomys jugossicularis - Hall's pocket gopher
Geomys knoxjonesi - Knox Jones's pocket gopher
Geomys lutescens - Sand Hills pocket gopher
Geomys personatus - Texas pocket gopher
Geomys pinetis - southeastern pocket gopher
Geomys streckeri - Strecker's pocket gopher
Geomys texensis - Llano pocket gopher
Geomys tropicalis - tropical pocket gopher
Genus Heterogeomys
Heterogeomys cavator - Chiriqui pocket gopher
Heterogeomys cherriei - Cherrie's pocket gopher
Heterogeomys dariensis - Darien pocket gopher
Heterogeomys heterodus - variable pocket gopher
Heterogeomys hispidus - hispid pocket gopher
Heterogeomys lanius - big pocket gopher
Heterogeomys underwoodi - Underwood's pocket gopher
Genus Orthogeomys
Orthogeomys cuniculus? - Oaxacan pocket gopher
Orthogeomys grandis - giant pocket gopher
Orthogeomys matagalpae? - Nicaraguan pocket gopher
Orthogeomys thaeleri? - Thaeler's pocket gopher
Genus Pappogeomys
Pappogeomys bulleri - Buller's pocket gopher
Pappogeomys bulleri alcorni - Alcorn's pocket gopher
Genus Thomomys
Subgenus Megascapheus
Thomomys atrovarius - Black-and-Brown pocket gopher
Thomomys bottae - Botta's pocket gopher
Thomomys bulbivorus - Camas pocket gopher
Thomomys nayarensis - Nayar pocket gopher
Thomomys sheldoni - Sierra Madre Occidental pocket gopher
Thomomys townsendii - Townsend's pocket gopher
Thomomys umbrinus - southern pocket gopher
Subgenus Thomomys
Thomomys clusius - Wyoming pocket gopher
Thomomys idahoensis - Idaho pocket gopher
Thomomys mazama - western pocket gopher
Thomomys mazama tacomensis - Tacoma pocket gopher
Thomomys monticola - mountain pocket gopher
Thomomys talpoides - northern pocket gopher
Genus Zygogeomys
Zygogeomys trichopus - Michoacan pocket gopher
Family Heteromyidae
Subfamily Dipodomyinae
Genus Dipodomys
Dipodomys agilis - agile kangaroo rat
Dipodomys californicus - California kangaroo rat
Dipodomys compactus - Gulf Coast kangaroo rat
Dipodomys deserti - desert kangaroo rat
Dipodomys elator - Texas kangaroo rat
Dipodomys elephantinus - big-eared kangaroo rat
Dipodomys gravipes - San Quintin kangaroo rat
Dipodomys heermanni - Heerman's kangaroo rat
Dipodomys ingens - giant kangaroo rat
Dipodomys insularis - San Jose Island kangaroo rat
Dipodomys merriami margaritae - Margarita Island kangaroo rat
Dipodomys merriami - Merriam's kangaroo rat
Dipodomys microps - chisel-toothed kangaroo rat
Dipodomys nelsoni - Nelson's kangaroo rat
Dipodomys nitratoides - Fresno kangaroo rat
Dipodomys ordii - Ord's kangaroo rat
Dipodomys panamintinus - Panamint kangaroo rat
Dipodomys phillipsii - Phillip's kangaroo rat
Dipodomys simulans - Dulzura kangaroo rat
Dipodomys spectabilis - bannertail kangaroo rat
Dipodomys stephensi - Stephen's kangaroo rat
Dipodomys venustus - narrow-faced kangaroo rat
Genus Microdipodops
Microdipodops megacephalus - dark kangaroo mouse
Microdipodops pallidus - pale kangaroo mouse
Subfamily Heteromyinae
Genus Heteromys
Heteromys adspersus - Panamanian spiny pocket mouse
Heteromys anomalus - Trinidad spiny pocket mouse
Heteromys australis - southern spiny pocket mouse
Heteromys catopterius - Overlook spiny pocket mouse
Heteromys desmarestianus - Desmarest's spiny pocket mouse
Heteromys gaumeri - Gaumer's spiny pocket mouse
Heteromys goldmani - Goldman's spiny pocket mouse
Heteromys irroratus - Mexican spiny pocket mouse
Heteromys nelsoni - Nelson's spiny pocket mouse
Heteromys nubicolens - Cloud-dwelling spiny pocket mouse
Heteromys oasicus - Paraguaná spiny pocket mouse
Heteromys oresterus - mountain spiny pocket mouse
Heteromys pictus - painted spiny pocket mouse
Heteromys salvini - Salvin's spiny pocket mouse
Heteromys spectabilis - Jaliscan spiny pocket mouse
Heteromys teleus - Ecuadoran spiny pocket mouse
Subfamily Perognathinae
Genus Chaetodipus
Chaetodipus arenarius - little desert pocket mouse
Chaetodipus artus - narrow-skulled pocket mouse
Chaetodipus baileyi - Bailey's pocket mouse
Chaetodipus californicus - California pocket mouse
Chaetodipus dalquesti - Dalquest's pocket mouse
Chaetodipus eremicus - Chihuahuan pocket mouse
Chaetodipus fallax - San Diego pocket mouse
Chaetodipus formosus - long-tailed pocket mouse
Chaetodipus goldmani - Goldman's pocket mouse
Chaetodipus hispidus - hispid pocket mouse
Chaetodipus intermedius - rock pocket mouse
Chaetodipus lineatus - lined pocket mouse
Chaetodipus nelsoni - Nelson's pocket mouse
Chaetodipus penicillatus - desert pocket mouse
Chaetodipus pernix - Sinaloan pocket mouse
Chaetodipus rudinoris - Baja California pocket mouse
Chaetodipus spinatus - spiny pocket mouse
Genus Perognathus
Perognathus alticola - white-eared pocket mouse
Perognathus amplus - Arizona pocket mouse
Perognathus fasciatus - olive-backed pocket mouse
Perognathus flavescens - plains pocket mouse
Perognathus flavus - silky pocket mouse
Perognathus inornatus - San Joaquin pocket mouse
Perognathus longimembris - little pocket mouse
Perognathus longimembris pacificus - Pacific pocket mouse
Perognathus merriami - Merriam's pocket mouse
Perognathus parvus - Great Basin pocket mouse
Suborder Myomorpha
Family Dipodidae
Subfamily Allactaginae
Genus Allactaga
Subgenus Allactaga
Allactaga firouzi - Iranian jerboa
Allactaga hotsoni - Hotson's jerboa
Allactaga major - great jerboa
Allactaga severtzovi - Severtzov's jerboa
Subgenus Orientallactaga
Allactaga balikunica - Balikun jerboa
Allactaga bullata - Gobi jerboa
Allactaga sibirica - Mongolian five-toed jerboa
Genus Allactodipus
Allactodipus bobrinskii - Bobrinski's jerboa
Genus Pygeretmus
Pygeretmus platyurus - lesser fat-tailed jerboa
Pygeretmus pumilio - dwarf fat-tailed jerboa
Pygeretmus shitkovi - greater fat-tailed jerboa
Genus Scarturus
Scarturus elater - small five-toed jerboa
Scarturus euphratica - Euphrates jerboa
Scarturus tetradactyla - four-toed jerboa
Scarturus vinogradovi - Vinogradov's jerboa
Scarturus williamsi - Williams's jerboa
Subfamily Cardiocraniinae
Genus Cardiocranius
Cardiocranius paradoxus - five-toed pygmy jerboa
Genus Salpingotulus
Salpingotulus michaelis - Baluchistan pygmy jerboa
Genus Salpingotus
Subgenus Anguistodontus
Salpingotus crassicauda - thick-tailed pygmy jerboa
Subgenus Prosalpingotus
Salpingotus heptneri - Heptner's pygmy jerboa
Salpingotus pallidus - pallid pygmy jerboa
Salpingotus thomasi - Thomas' pygmy jerboa
Subgenus Salpingotus
Salpingotus kozlovi - Koslov's pygmy jerboa
Subfamily Dipodinae
Genus Dipus
Dipus sagitta - northern three-toed jerboa
Genus Eremodipus
Eremodipus lichtensteini - Lichtenstein's jerboa
Genus Jaculus
Jaculus blanfordi - Blanford's jerboa
Jaculus hirtipes - African hammada jerboa
Jaculus jaculus - lesser Egyptian jerboa
Jaculus orientalis - greater Egyptian jerboa
Jaculus thaleri - Thaler's jerboa
Jaculus turcmenicus? - Turkmen jerboa
Genus Paradipus
Paradipus ctenodactylus - comb-toed jerboa
Genus Stylodipus
Stylodipus andrewsi - Andrew's three-toed jerboa
Stylodipus sungorus - Mongolian three-toed jerboa
Stylodipus telum - thick-tailed three-toed jerboa
Subfamily Euchoreutinae
Genus Euchoreutes
Euchoreutes naso - long-eared jerboa
Subfamily Sicistinae
Genus Sicista
Sicista armenica - Armenian birch mouse
Sicista betulina - northern birch mouse
Sicista caucasica - Caucasian birch mouse
Sicista caudata - long-tailed birch mouse
Sicista cimlanica - Tsimlyansk birch mouse
Sicista concolor - Chinese birch mouse
Sicista kazbegica - Kazbeg birch mouse
Sicista kluchorica - Kluchor birch mouse
Sicista loriger - Nordmann's birch mouse
Sicista napaea - Altai birch mouse
Sicista pseudonapaea - gray birch mouse
Sicista severtzovi - Severtzov's birch mouse
Sicista strandi - Strand's birch mouse
Sicista subtilis - southern birch mouse
Sicista talgarica - Talgar birch mouse
Sicista terskeica - Terskey birch mouse
Sicista tianshanica - Tien Shan birch mouse
Sicista trizona - Hungarian birch mouse
Sicista zhetysuica - Zhetysu birch mouse
Subfamily Zapodinae
Genus Eozapus
Eozapus setchuanus - Chinese jumping mouse
Genus Napaeozapus
Napaeozapus insignis - woodland jumping mouse
Genus Zapus
Zapus hudsonius - Northern meadow jumping mouse
Zapus hudsonius preblei - Preble's meadow jumping mouse
Zapus luteus - Southern meadow jumping mouse
Zapus montanus - Central Pacific jumping mouse
Zapus oregonus - Oregon jumping mouse
Zapus pacificus - South Pacific jumping mouse
Zapus princeps - Southwestern jumping mouse
Zapus saltator - Northwestern jumping mouse
Zapus trinotatus - North Pacific jumping mouse
Family Platacanthomyidae
Genus Platacanthomys
Platacanthomys lasiurus - Malabar spiny dormouse
Genus Typhlomys
Typhlomys cinereus - Chapa pygmy dormouse
Family Spalacidae
Subfamily Myospalacinae
Genus Eospalax
Eospalax fontanierii - Chinese zokor
Eospalax rothschildi - Rothschild's zokor
Eospalax smithii - Smith's zokor
Genus Myospalax
Myospalax aspalax - false zokor
Myospalax epsilanus? - Manchurian zokor
Myospalax myospalax - Siberian zokor
Myospalax psilurus - Transbaikal zokor
Subfamily Rhizomyinae
Genus Cannomys
Cannomys badius - lesser bamboo rat
Genus Rhizomys
Rhizomys pruinosus - hoary bamboo rat
Rhizomys sinensis - Chinese bamboo rat
Rhizomys sumatrensis - large bamboo rat
Subfamily Tachyoryctinae
Genus Tachyoryctes
Tachyoryctes ankoliae - Ankole mole rat
Tachyoryctes annectens - Mianzini mole rat
Tachyoryctes audax - audacious mole rat
Tachyoryctes daemon - demon mole rat
Tachyoryctes ibeanus - Kenyan African mole rat
Tachyoryctes macrocephalus - big-headed mole rat
Tachyoryctes naivashae - Naivasha mole rat
Tachyoryctes rex - king mole rat
Tachyoryctes ruandae - Ruanda mole rat
Tachyoryctes ruddi - Rudd's mole rat
Tachyoryctes spalacinus - Embi mole rat
Tachyoryctes splendens - East African mole rat
Tachyoryctes storeyi - Storey's African mole rat
Subfamily Spalacinae
Genus Nannospalax
Nannospalax carmeli? - Mt. Carmel blind mole rat
Nannospalax ehrenbergi? - Middle East blind mole rat
Nannospalax galili? - Upper Galilee Mountains blind mole rat
Nannospalax golani? - Golan Heights blind mole rat
Nannospalax leucodon - lesser blind mole rat
Nannospalax judaei? - Judean Mountains blind mole rat
Nannospalax nehringi? - Nehring's blind mole rat
Nannospalax xanthodon - Anatolian blind mole-rat
Genus Spalax
Spalax antiquus - Mehely's blind mole-rat
Spalax arenarius - sandy mole rat
Spalax giganteus - giant mole rat
Spalax graecus - Bukovin mole rat
Spalax istricus - Oltenia blind mole-rat
Spalax microphthalmus - greater mole rat
Spalax munzuri? - Munzur mole-rat
Spalax uralensis - Kazakhstan blind mole rat
Spalax zemni - Podolsk mole rat
Family Calomyscidae
Genus Calomyscus
Calomyscus bailwardi - Zagros mouse-like hamster
Calomyscus baluchi - Balochistan mouse-like hamster
Calomyscus elburzensis - Elburz mouse-like hamster
Calomyscus grandis - Noble mouse-like hamster
Calomyscus hotsoni - Makran mouse-like hamster
Calomyscus mystax - Turkmen mouse-like hamster
Calomyscus tsolovi - Syrian mouse-like hamster from
Calomyscus urartensis - Azerbaijani mouse-like hamster
Family Nesomyidae
Subfamily Petromyscinae
Genus Petromyscus
Petromyscus barbouri - Barbour's rock mouse
Petromyscus collinus - pygmy rock mouse
Petromyscus monticularis - Brukkaros pygmy rock mouse
Petromyscus shortridgei - Shortridge's rock mouse
Subfamily Delanymyinae
Genus Delanymys
Delanymys brooksi - Delany's swamp mouse
Subfamily Dendromurinae
Genus Dendromus
Dendromus insignis - remarkable climbing mouse
Dendromus kahuziensis - Mount Kahuzi climbing mouse
Dendromus kivu? - Kivu climbing mouse
Dendromus lachaisei - Lachaise's climbing mouse
Dendromus leucostomus - Monard's African climbing mouse
Dendromus lovati - Lovat's climbing mouse
Dendromus melanotis - gray climbing mouse
Dendromus mesomelas - Brant's climbing mouse
Dendromus messorius - banana climbing mouse
Dendromus mystacalis - chestnut climbing mouse
Dendromus nyasae - Kivu climbing mouse
Dendromus nyikae - Nyika climbing mouse
Dendromus oreas - Cameroon climbing mouse
Dendromus ruppi - Rupp's African climbing mouse
Dendromus vernayi - Vernay's climbing mouse
Genus Dendroprionomys
Dendroprionomys rousseloti - velvet climbing mouse
Genus Malacothrix
Malacothrix typica - gerbil mouse
Genus Megadendromus
Megadendromus nikolausi - Nikolaus's mouse
Genus Prionomys
Prionomys batesi - Dollman's tree mouse
Genus Steatomys
Steatomys bocagei - Bocage's African fat mouse
Steatomys caurinus - northwestern fat mouse
Steatomys cuppedius - dainty fat mouse
Steatomys jacksoni - Jackson's fat mouse
Steatomys krebsii - Kreb's fat mouse
Steatomys opimus - Pousargue's African fat mouse
Steatomys parvus - tiny fat mouse
Steatomys pratensis - fat mouse
Subfamily Mystromyinae
Genus Mystromys
Mystromys albicaudatus - white-tailed rat or white-tailed mouse
Subfamily Cricetomyinae
Genus Beamys
Beamys hindei - long-tailed pouched rat
Beamys major - greater long-tailed pouched rat
Genus Cricetomys
Cricetomys ansorgei - Southern giant pouched rat
Cricetomys emini - Emin's giant pouched rat
Cricetomys gambianus - Gambian giant pouched rat
Cricetomys kivuensis - Kivu giant pouched rat
Genus Saccostomus
Saccostomus campestris - South African pouched mouse
Saccostomus mearnsi - Mearns's pouched mouse
Subfamily Nesomyinae
Genus Brachytarsomys
Brachytarsomys albicauda - white-tailed rat
Brachytarsomys mahajambaensis - (extinct)
Brachytarsomys villosa - hairy-tailed antsangy
Genus Brachyuromys
Brachyuromys betsileoensis - Betsileo short-tailed rat
Brachyuromys ramirohitra - gregarious short-tailed rat
Genus Eliurus
Eliurus antsingy - Tsingy tufted-tailed rat
Eliurus carletoni - Ankarana Special Reserve tufted-tailed rat
Eliurus danieli - Daniel's tufted-tailed rat
Eliurus ellermani - Ellerman's tufted-tailed rat
Eliurus grandidieri - Grandidier's tufted-tailed rat
Eliurus majori - Major's tufted-tailed rat
Eliurus minor - lesser tufted-tailed rat
Eliurus myoxinus - dormouse tufted-tailed rat
Eliurus penicillatus - white-tipped tufted-tailed rat
Eliurus petteri - Petter's tufted-tailed rat
Eliurus tanala - Tanala tufted-tailed rat
Eliurus webbi - Webb's tufted-tailed rat
Genus Gymnuromys
Gymnuromys roberti - voalavoanala
Genus Hypogeomys
Hypogeomys antimena - Malagasy giant rat
Hypogeomys australis - (extinct)
Genus Macrotarsomys
Macrotarsomys bastardi - bastard big-footed mouse
Macrotarsomys ingens - greater big-footed mouse
Macrotarsomys petteri - Petter's big-footed mouse
Genus Monticolomys
Monticolomys koopmani - Koopman's montane voalavo
Genus Nesomys
Nesomys audeberti - white-bellied nesomys
Nesomys lambertoni - western nesomys
Nesomys narindaensis - (extinct)
Nesomys rufus - island mouse
Genus Voalavo
Voalavo antsahabensis - Eastern voalavo
Voalavo gymnocaudus - Northern voalavo
Family Cricetidae
Subfamily Lophiomyinae
Genus Lophiomys
Lophiomys imhausi - maned rat or crested rat
Subfamily Cricetinae
Genus Allocricetulus
Allocricetulus curtatus - Mongolian hamster
Allocricetulus eversmanni - Eversmann's hamster
Genus Cansumys
Cansumys canus - Gansu hamster
Genus Cricetulus
Cricetulus barabensis - Chinese striped hamster
Cricetulus griseus - Chinese hamster
Cricetulus lama - Lama dwarf hamster
Cricetulus longicaudatus - long-tailed ratlike hamster
Cricetulus sokolovi - Sokolov's ratlike hamster
Genus Cricetus
Cricetus cricetus - European hamster or black-bellied hamster
Genus Mesocricetus
Mesocricetus auratus - golden hamster
Mesocricetus brandti - Turkish hamster
Mesocricetus newtoni - Romanian hamster
Mesocricetus raddei - Ciscaucasian hamster
Genus Nothocricetulus
Nothocricetulus migratorius - grey ratlike hamster
Genus Phodopus
Phodopus campbelli - Campbell's dwarf hamster
Phodopus roborovski - Roborovski's (desert) dwarf hamster
Phodopus sungorus - winter white (Dzhungarian) dwarf hamster
Genus Tscherskia
Tscherskia triton - greater long-tailed hamster
Genus Urocricetus
Urocricetus alticola - Tibetan ratlike hamster
Cricetulus kamensis - Kam ratlike hamster
Subfamily Arvicolinae
Genus Alticola
Alticola albicaudus - white-tailed mountain vole
Alticola argentatus - silver mountain vole
Alticola barakshin - Gobi Altai mountain vole
Alticola lemminus - lemming vole
Alticola macrotis - large-eared vole
Alticola montosa - Central Kashmir vole
Alticola olchonensis - Lake Baikal mountain vole
Alticola roylei - Royle's mountain vole
Alticola semicanus - Mongolian silver vole
Alticola stoliczkanus - Stoliczka's mountain vole
Alticola strelzowi - flat-headed vole
Alticola tuvinicus - Tuva silver vole
Genus Arborimus
Arborimus albipes - white-footed vole
Arborimus longicaudus - red tree vole
Arborimus pomo - Sonoma tree vole
Genus Arvicola
Arvicola amphibius - European (or northern) water vole
Arvicola sapidus - southwestern (or southern) water vole
Arvicola scherman - montane water vole
Genus Blanfordimys
Blanfordimys afghanus - Afghan vole
Blanfordimys bucharicus - Bucharian vole
Blanfordimys juldaschi - juniper vole
Genus Caryomys
Caryomys eva - Eva's red-backed vole
Caryomys inez - Inez's red-backed vole
Genus Chionomys
Chionomys gud - Caucasian snow vole
Chionomys nivalis - European snow vole
Chionomys roberti - Robert's snow vole
Genus Dicrostonyx
Dicrostonyx exsul? - St Lawrence Island collared lemming
Dicrostonyx groenlandicus - northern collared lemming
Dicrostonyx hudsonius - Ungava collared lemming
Dicrostonyx kilangmiutak? - Victoria collared lemming
Dicrostonyx nelsoni - Nelson's collared lemming
Dicrostonyx nunatakensis - Ogilvie Mountain collared lemming
Dicrostonyx richardsoni - Richardson's collared lemming
Dicrostonyx rubricatus? - Bering collared lemming
Dicrostonyx torquatus - Arctic lemming
Dicrostonyx unalascensis - Unalaska collared lemming
Dicrostonyx vinogradovi? - Wrangel lemming
Genus Dinaromys
Dinaromys bogdanovi - Balkan snow vole or Martino's snow vole
Genus Ellobius
Ellobius alaicus - Alai mole vole
Ellobius fuscocapillus - southern mole vole
Ellobius lutescens - Transcaucasian mole vole
Ellobius talpinus - northern mole vole
Ellobius tancrei - Zaisan mole vole
Genus Eolagurus
Eolagurus luteus - yellow steppe lemming
Eolagurus przewalskii - Przewalski's steppe lemming
Genus Eothenomys
Eothenomys cachinus - Kachin red-backed vole
Eothenomys chinensis - Pratt's vole
Eothenomys custos - southwest China vole
Eothenomys melanogaster - Pere David's vole
Eothenomys miletus - Yunnan red-backed vole
Eothenomys olitor - Chaotung vole
Eothenomys proditor - Yulungshan vole
Eothenomys wardi - Ward's red-backed vole
Genus Hyperacrius
Hyperacrius fertilis - True's vole
Hyperacrius wynnei - Murree vole
Genus Lagurus
Lagurus lagurus - steppe lemming
Genus Lasiopodomys
Lasiopodomys brandtii - Brandt's vole
Lasiopodomys fuscus - plateau vole
Lasiopodomys mandarinus - Mandarin vole
Genus Lemmiscus
Lemmiscus curtatus - sagebrush vole
Genus Lemmus
Lemmus amurensis - Amur lemming
Lemmus lemmus - Norway lemming
Lemmus nigripes - Beringian lemming
Lemmus paulus - Wrangel Island lemming
Lemmus sibiricus - Siberian brown lemming
Lemmus trimucronatus - North American brown lemming
Genus Microtus
Subgenus Microtus
Microtus agrestis - field vole
Microtus anatolicus - Anatolian vole
Microtus arvalis - common vole
Microtus cabrerae - Cabrera's vole
Microtus dogramacii - Doğramaci's vole
Microtus elbeyli - Elbeyli vole
Microtus guentheri - Günther's vole
Microtus hartingii? - Harting's vole?
Microtus ilaeus - Tien Shan vole
Microtus irani - Persian vole
Microtus kermanensis? - Baluchistan vole
Microtus lavernedii - Mediterranean field vole
Microtus levis - Southern vole
Microtus lydius - Turkish vole
Microtus mystacinus - East European vole
Microtus obscurus? - Altai vole
Microtus paradoxus - Paradox vole
Microtus qazvinensis - Qazvin vole
Microtus rosianus? - Portuguese field vole?
Microtus schidlovskii - Schidlovsky's vole
Microtus socialis - social vole
Microtus transcaspicus - Transcaspian vole
Subgenus Alexandromys
Microtus clarkei - Clarke's vole
Microtus evoronensis - evorsk vole
Microtus fortis - reed vole
Microtus gerbii - Gerbe's vole
Microtus kikuchii - Taiwan vole
Microtus limnophilus - lacustrine vole
Microtus maximowiczii - Maximowicz's vole
Microtus middendorffi - Middendorf's vole
Microtus mongolicus - Mongolian vole
Microtus montebelli - Japanese grass vole
Microtus mujanensis - muisk vole
Microtus oeconomus - tundra vole
Microtus sachalinensis - Sakhalin vole
Subgenus Hyrcanicola
Microtus schelkovnikovi - Schelkovnikov's pine vole
Subgenus Mynomes
Microtus breweri - beach vole
Microtus canicaudus - gray-tailed vole
Microtus drummondi - Western meadow vole
Microtus dukecampbelli - Florida salt marsh vole
Microtus montanus - montane vole
Microtus oregoni - creeping vole
Microtus pennsylvanicus - meadow vole
Microtus townsendii - Townsend's vole
Subgenus Pedomys
Microtus ochrogaster - prairie vole
Subgenus Pitymys
Microtus guatemalensis - Guatemalan vole
Microtus oaxacensis - Tarabundi vole
Microtus pinetorum - woodland vole
Microtus quasiater - Jalapan pine vole
Subgenus Stenocranius
Microtus gregalis - narrow-headed vole
Subgenus Terricola
Microtus bavaricus - Bavarian pine vole
Microtus brachycercus - Calabria pine vole
Microtus daghestanicus - Daghestan pine vole
Microtus duodecimcostatus - Mediterranean pine vole
Microtus felteni - Felten's vole
Microtus liechtensteini - Lichtenstein's pine vole
Microtus lusitanicus - Lusitanian pine vole
Microtus majori - Major's pine vole
Microtus multiplex - alpine pine vole
Microtus nebrodensis? - Sicilian pine vole?
Microtus savii - Savi's pine vole
Microtus subterraneus - European pine vole
Microtus tatricus - Tatra pine vole
Microtus thomasi - Thomas's pine vole
Subgenus incertae sedis
Microtus abbreviatus - insular vole
Microtus californicus - California vole
Microtus chrotorrhinus - rock vole
Microtus longicaudus - long-tailed vole
Microtus mexicanus - Mexican vole
Microtus miurus - singing vole
Microtus mogollonensis? - Mogollon vole?
Microtus richardsoni - water vole
Microtus umbrosus - Zempoaltepec vole
Microtus xanthognathus - taiga vole
Others Microtus "Species"
Microtus hyperboreus? - North Siberian vole
Microtus kirgisorum? - Tien Shan vole
Microtus nasarovi? - Nasarov's vole
Microtus rossiaemeridionalis? - southern vole
Genus Myodes
Myodes andersoni - Japanese red-backed vole
Myodes californicus - western red-backed vole
Myodes centralis - Tien Shan red-backed vole
Myodes gapperi - southern red-backed vole
Myodes glareolus - bank vole
Myodes imaizumii - Imaizumi's red-backed vole
Myodes regulus - Royal vole
Myodes rex - Hokkaido red-backed vole
Myodes rufocanus - grey red-backed vole
Myodes rutilus - northern red-backed vole
Myodes shanseius - Shansei vole
Myodes smithii - Smith's vole
Myodes sikotanensis? - Shikotan vole
Genus Myopus
Myopus schisticolor - wood lemming
Genus Neodon
Neodon forresti - Forrest's mountain vole
Neodon irene - Irene's mountain vole
Neodon linzhiensis - Linzhi mountain vole
Neodon sikimensis - Sikkim mountain vole
Genus Neofiber
Neofiber alleni - round-tailed muskrat
Genus Ondatra
Ondatra zibethicus - muskrat or musquash
Genus Phaiomys
Phaiomys leucurus - Blyth's mountain vole
Genus Phenacomys
Phenacomys intermedius - western heather vole
Phenacomys ungava - eastern heather vole
Genus Proedromys
Proedromys bedfordi - Duke Of Bedford's vole
Proedromys liangshanensis - Liangshan vole
Genus Prometheomys
Prometheomys schaposchnikowi - long-clawed mole vole
Genus Synaptomys
Synaptomys borealis - northern bog lemming
Synaptomys cooperi - southern bog lemming
Genus Volemys
Volemys millicens - Szechuan vole
Volemys musseri - Marie's vole
Subfamily Tylomyinae
Tribe Nyctomyini
Genus Nyctomys
Nyctomys sumichrasti - Sumichrast's vesper rat
Genus Otonyctomys
Otonyctomys hatti - Hatt's vesper rat
Tribe Tylomyini
Genus Ototylomys
Ototylomys chiapensis - La Pera big-eared climbing rat
Ototylomys phyllotis - big-eared climbing rat
Genus Tylomys
Tylomys bullaris - Chiapan climbing rat
Tylomys fulviventer - fulvous-bellied climbing rat
Tylomys mirae - Mira climbing rat
Tylomys nudicaudus - Peters's climbing rat
Tylomys panamensis - Panamanian climbing rat
Tylomys tumbalensis - Tumbala climbing rat
Tylomys watsoni - Watson's climbing rat
Subfamily Neotominae
Genus Baiomys
Baiomys brunneus - southern pygmy mouse
Baiomys musculus - Mexican pygmy mouse
Baiomys taylori - northern pygmy mouse or ratón-pigmeo norteño
Genus Habromys
Habromys chinanteco - Chinanteco deer mouse
Habromys delicatulus - delicate deermouse
Habromys ixtlani - Ixtlán deermouse
Habromys lepturus - slender-tailed deer mouse
Habromys lophurus - crested-tailed deer mouse
Habromys schmidlyi - Schmidly's deer mouse
Habromys simulatus - Jico deer mouse
Genus Hodomys
Hodomys alleni - Allen's woodrat
Genus Isthmomys
Isthmomys flavidus - yellow isthmus rat
Isthmomys pirrensis - Mt. Pirri isthmus rat
Genus Megadontomys
Megadontomys cryophilus - Oaxaca giant deer mouse
Megadontomys nelsoni - Nelson's giant deer mouse
Megadontomys thomasi - Thomas's giant deer mouse
Genus Nelsonia
Nelsonia goldmani - Nelson and Goldman's woodrat
Nelsonia neotomodon - diminutive woodrat
Genus Neotoma
Subgenus (Neotoma)
Neotoma albigula - white-throated woodrat
Neotoma albigula varia - Turner Island woodrat
Neotoma angustapalata - Tamaulipan woodrat
Neotoma bryanti - Bryant's woodrat
Neotoma bryanti anthonyi - Anthony's woodrat
Neotoma bryanti bunkeri - Bunker's woodrat
Neotoma bryanti martinensis - San Martin Island woodrat
Neotoma chrysomelas - Nicaraguan woodrat
Neotoma devia - Arizona woodrat
Neotoma findleyi - Findley's woodrat (extinct)
Neotoma floridana - Florida woodrat or eastern woodrat
Neotoma floridana smalli - Key Largo woodrat
Neotoma goldmani - Goldman's woodrat
Neotoma insularis - Angel de la Guarda woodrat
Neotoma lepida - desert woodrat
Neotoma leucodon - White-toothed woodrat
Neotoma macrotis - big-eared woodrat
Neotoma magister - Allegheny woodrat
Neotoma mexicana - Mexican woodrat
Neotoma micropus - southern plains woodrat
Neotoma nelsoni - Nelson's woodrat
Neotoma palatina - Bolaos woodrat
Neotoma stephensi - Stephens's woodrat
Subgenus (Teanopus)
Neotoma phenax - Sonoran woodrat
Subgenus (Teonoma)
Neotoma cinerea - bushy-tailed woodrat
Neotoma fuscipes - dusky-footed woodrat
Genus Neotomodon
Neotomodon alstoni - Mexican volcano mouse
Genus Ochrotomys
Ochrotomys nuttalli - golden mouse
Genus Onychomys
Onychomys arenicola - Mearns's grasshopper mouse
Onychomys leucogaster - northern grasshopper mouse
Onychomys torridus - southern grasshopper mouse
Genus Osgoodomys
Osgoodomys banderanus - Michoacan deer mouse
Genus Peromyscus
californicus group
Peromyscus californicus - California deermouse
eremicus group
Peromyscus caniceps - Burt's deer mouse
Peromyscus dickeyi - Dickey's deer mouse
Peromyscus eremicus - cactus mouse
Peromyscus eva - Eva's desert mouse
Peromyscus fraterculus - Northern Baja deer mouse
Peromyscus guardia - Angel Island mouse [possibly extinct]
Peromyscus interparietalis - San Lorenzo mouse
Peromyscus merriami - mesquite mouse
Peromyscus pembertoni - Pemberton's deer mouse [extinct]
Peromyscus pseudocrinitus - false canyon mouse
hooperi group
Peromyscus hooperi - Hooper's mouse
crinitus group
Peromyscus crinitus - canyon mouse
maniculatus group
Peromyscus arcticus - Yukon deer mouse
Peromyscus gambellii - Gambel's deer mouse
Peromyscus keeni - Northwestern deer mouse
Peromyscus labecula - Southern deer mouse
Peromyscus maniculatus - Eastern deer mouse
Peromyscus melanotis - black-eared mouse
Peromyscus nesodytes - (Extinct)
Peromyscus oreas? - Columbian mouse
Peromyscus polionotus - oldfield mouse
Peromyscus polionotus decoloratus - Pallid beach mouse (extinct)
Peromyscus polionotus phasma - Anastasia Island beach mouse
Peromyscus sejugis - Santa Cruz mouse
Peromyscus sitkensis? - Sitka mouse
Peromyscus slevini - Slevin's mouse
Peromyscus sonoriensis - Western deer mouse
leucopus group
Peromyscus gossypinus - cotton mouse
Peromyscus gossypinus allapaticola - Key Largo cotton mouse
Peromyscus gossypinus restrictus - Chadwick Beach cotton mouse (extinct)
Peromyscus leucopus - white-footed mouse
aztecus group
Peromyscus aztecus - Aztec mouse
Peromyscus hylocetes - Transvolcanic deer mouse
Peromyscus oaxacensis - Oaxacan deer mouse
Peromyscus spicilegus - gleaning mouse
Peromyscus winkelmanni - Winkelmann's mouse
boylii group
Peromyscus beatae - Orizaba deer mouse
Peromyscus boylii - brush mouse
Peromyscus carletoni - Carleton's deer mouse
Peromyscus kilpatricki - Kilpatrick's deer mouse
Peromyscus levipes - nimble-footed mouse
Peromyscus madrensis - Tres Marias Island mouse
Peromyscus polius - Chihuahuan mouse
Peromyscus sagax - La Palma deer mouse
Peromyscus schmidlyi - Schmidly's deer mouse
Peromyscus simulus - Nayarit mouse
Peromyscus stephani - San Eseban Island mouse
truei group
Peromyscus attwateri - Texas mouse
Peromyscus bullatus - Perote mouse
Peromyscus difficilis - Zacatecan deer mouse
Peromyscus gratus - Osgood's mouse
Peromyscus laceianus - Northern white-ankled mouse
Peromyscus nasutus - northern rock mouse
Peromyscus ochraventer - El Carrizo deer mouse
Peromyscus pectoralis - Southern white-ankled mouse
Peromyscus truei - pinyon mouse
melanophrys group
Peromyscus melanophrys - plateau mouse
Peromyscus mekisturus - Puebla deer mouse
Peromyscus perfulvus - marsh mouse
furvus group
Peromyscus furvus - blackish deer mouse
Peromyscus latirostris - Wide-rostrum deer mouse
megalops group
Peromyscus megalops - brown deer mouse
Peromyscus melanocarpus - Zempoaltepec
Peromyscus melanurus - black-tailed mouse
mexicanus group
Peromyscus bakeri - Baker's deer mouse
Peromyscus carolpattonae - Carol Patton's deer-mouse
Peromyscus gardneri - Gardner's deer-mouse
Peromyscus grandis - big deer mouse
Peromyscus guatemalensis - Guatemalan deer mouse
Peromyscus gymnotis - naked-eared deer mouse
Peromyscus mayensis - Maya mouse
Peromyscus mexicanus - Mexican deer mouse
Peromyscus nicaraguae - Nicaraguan deer mouse
Peromyscus nudipes - Talamancan deer mouse
Peromyscus salvadorensis - Salvadoran deer mouse
Peromyscus stirtoni - Stirton's deer mouse
Peromyscus tropicalis - Chimoxan deer mouse
Peromyscus yucatanicus - Yucatán deer mouse
Peromyscus zarhynchus - Chiapan deer mouse
Genus Podomys
Podomys floridanus - Florida mouse
Genus Reithrodontomys
Reithrodontomys bakeri - Guerrero harvest mouse
Reithrodontomys brevirostris - short-nosed harvest mouse
Reithrodontomys burti - Sonoran harvest mouse
Reithrodontomys chrysopsis - volcano harvest mouse
Reithrodontomys creper - Chiriqui harvest mouse
Reithrodontomys darienensis - Darien harvest mouse
Reithrodontomys fulvescens - fulvous harvest mouse
Reithrodontomys gracilis - slender harvest mouse
Reithrodontomys hirsutus - hairy harvest mouse
Reithrodontomys humulis - eastern harvest mouse
Reithrodontomys megalotis - western harvest mouse
Reithrodontomys mexicanus - Mexican harvest mouse
Reithrodontomys microdon - small-toothed harvest mouse
Reithrodontomys montanus - plains harvest mouse
Reithrodontomys musseri - Small harvest mouse
Reithrodontomys paradoxus - Nicaraguan harvest mouse
Reithrodontomys raviventris - saltmarsh harvest mouse
Reithrodontomys rodriguezi - Rodriguez's harvest mouse
Reithrodontomys spectabilis - Cozumel harvest mouse
Reithrodontomys sumichrasti - Sumichrast's harvest mouse
Reithrodontomys tenuirostris - narrow-nosed harvest mouse
Reithrodontomys zacatecae - Zacatecas harvest mouse
Genus Scotinomys
Scotinomys teguina - Alston's brown mouse
Scotinomys xerampelinus - Chiriqui brown mouse
Genus Xenomys
Xenomys nelsoni - Magdalena rat
Subfamily Sigmodontinae
Genus Delomys
Delomys collinus - montane delomys
Delomys dorsalis - striped Atlantic forest rat
Delomys sublineatus - pallid Atlantic forest rat
Genus Irenomys
Irenomys tarsalis - Chilean climbing mouse
Genus Juliomys
Juliomys anoblepas (extinct)
Juliomys ossitenuis - Delicate red-nosed tree mouse
Juliomys pictipes - Contreras' juliomys
Juliomys rimofrons - cleft-headed juliomys
Juliomys ximenezi - Aracuaria Forest tree mouse
Genus Phaenomys
Phaenomys ferrugineus - Rio de Janeiro arboreal rat
Genus Punomys
Punomys kofordi - eastern puna mouse
Punomys lemminus - puna mouse
Genus Wiedomys
Wiedomys cerradensis - Cerrado red-nosed mouse
Wiedomys pyrrhorhinos - red-nosed mouse
Genus Wilfredomys
Wilfredomys oenax - greater Wilfred's mouse
Tribe Abrotrichini
Genus Abrothrix
Abrothrix andinus - Andean akodont
Abrothrix hershkovitzi - Hershkovitz's akodont
Abrothrix hirta - Hairy soft-haired mouse
Abrothrix illuteus - gray akodont
Abrothrix jelskii - ornate akodont
Abrothrix lanosus - woolly akodont
Abrothrix longipilis - long-haired akodont
Abrothrix manni - Mann's soft-haired mouse
Abrothrix olivaceus - Manso grass mouse
Abrothrix olivaceus markhami - Wellington akodont
Abrothrix sanborni - Sanborn's akodont
Abrothrix xanthorhina
Genus Chelemys
Chelemys delfini - Magellanic long-clawed akodont
Chelemys macronyx - Andean long-clawed mouse
Chelemys megalonyx - large long-clawed mouse
Genus Geoxus
Geoxus annectens - Pearson's long-clawed akodont
Geoxus valdivianus - long-clawed mole mouse
Genus Notiomys
Notiomys edwardsii - Edward's long-clawed mouse
Tribe Akodontini
Genus Akodon
Akodon aerosus - Yungas akodont
Akodon affinis - Cordillera Occidental akodont
Akodon albiventer - white-bellied akodont
Akodon azarae - Azara's akodont
Akodon boliviensis - Bolivian akodont
Akodon budini - Budin's akodont
Akodon caenosus- unicolored grass mouse
Akodon cursor - cursorial akodont
Akodon dayi - dusky akodont
Akodon dolores - Córdoba akodont
Akodon fumeus - smoky akodont
Akodon glaucinus
Akodon iniscatus - Patagonian akodont
Akodon juninensis - Junín akodont
Akodon kofordi - Koford's akodont
Akodon lindberghi - Lindbergh's akodont
Akodon lutescens - Altiplano akodont
Akodon mimus - hocicudo-like akodont
Akodon molinae - Molina's grass mouse
Akodon mollis - soft-furred akodont
Akodon montensis - montane akodont
Akodon mystax - Caparaó akodont
Akodon neocenus - Neuquén akodont
Akodon orophilus - Utcubamba akodont
Akodon paranaensis - Paraná akodont
Akodon pervalens - Tarija akodont
Akodon philipmyersi - Philip Myers' akodont
Akodon polopi - Polop's grass mouse
Akodon reigi - Reig's akodont
Akodon sanctipaulensis - São Paulo akodont
Akodon serrensis - Serra do Mar akodont
Akodon siberiae - Cochabamba akodont
Akodon simulator - white-throated akodont
Akodon spegazzinii - Spegazzini's akodont
Akodon subfuscus - Puno akodont
Akodon surdus - slate-bellied akodont
Akodon sylvanus - woodland akodont
Akodon tartareus
Akodon toba - Toba akodont
Akodon torques - cloud forest grass akodont
Akodon varius - variable akodont
Genus Bibimys
Bibimys chacoensis - Chaco crimson-nosed rat
Bibimys labiosus - large-lipped crimson-nosed rat
Bibimys torresi - Torres' crimson-nosed rat
Genus Blarinomys
Blarinomys breviceps - Brazilian shrew-mouse
Genus Brucepattersonius
Brucepattersonius albinasus? - white-nosed brucie
Brucepattersonius griserufescens - gray-bellied brucie
Brucepattersonius guarani - Guaraní brucie
Brucepattersonius igniventris - red-bellied brucie
Brucepattersonius iheringi - Ihering's hocicudo
Brucepattersonius misionensis - Misiones brucie
Brucepattersonius paradisus - Arroyo of Paradise brucie
Brucepattersonius soricinus - Soricine brucie
Genus Deltamys
Deltamys kempi - Kemp's akodont
Genus Gyldenstolpia
Gyldenstolpia fronto - fossorial giant rat
Gyldenstolpia planaltensis - Cerrado giant rat
Genus Juscelinomys
Juscelinomys candango - Brasilia burrowing mouse or candango mouse (extinct)
Juscelinomys guaporensis - Rio Guapore burrowing mouse
Juscelinomys huanchacae - Huanchaca akodont
Juscelinomys talpinus - molelike mouse
Genus Kunsia
Kunsia tomentosus - woolly giant rat
Genus Lenoxus
Lenoxus apicalis - Andean rat
Genus Necromys
Necromys amoenus - pleasant bolo mouse
Necromys benefactus - Argentine bolo mouse
Necromys lactens - rufous-bellied bolo mouse
Necromys lasiurus - hairy-tailed bolo mouse
Necromys lenguarum - Paraguayan bolo mouse
Necromys obscurus - dark bolo mouse
Necromys punctulatus - spotted bolo mouse
Necromys temchuki - Temchuk's bolo mouse
Necromys urichi - northern grass mouse
Genus Neomicroxus
Neomicroxus bogotensis - Bogotá akodont
Neomicroxus latebricola - Ecuadorian akodont
Genus Oxymycterus
Oxymycterus akodontius - Argentine hocicudo
Oxymycterus amazonicus - Amazon hocicudo
Oxymycterus angularis - angular hocicudo
Oxymycterus caparaoe - Caparao hocicudo
Oxymycterus dasytrichus - Atlantic Forest hocicudo
Oxymycterus delator - spy hocicudo
Oxymycterus hiska - small hocicudo
Oxymycterus hispidus - hispid hocicudo
Oxymycterus hucucha - Quechuan hocicudo
Oxymycterus inca - Incan hocicudo
Oxymycterus itapeby - Itapevi hocicudo rat
Oxymycterus josei - Jose's hocicudo
Oxymycterus nasutus - long-nosed hocicudo
Oxymycterus paramensis - paramo hocicudo
Oxymycterus quaestor - Quaestor hocicudo
Oxymycterus roberti - Robert's hocicudo
Oxymycterus rufus - red hocicudo
Oxymycterus wayku - Ravine hocicudo
Genus Podoxymys
Podoxymys roraimae - Roraima mouse
Genus Scapteromys
Scapteromys aquaticus - Argentine swamp rat
Scapteromys meridionalis - Plateau swamp rat
Scapteromys tumidus - swamp rat
Genus Thalpomys
Thalpomys cerradensis - cerrado mouse
Thalpomys lasiotis - hairy-eared cerrado mouse
Genus Thaptomys
Thaptomys nigrita - blackish grass mouse
Tribe Ichthyomyini
Genus Anotomys
Anotomys leander - Ecuador fish-eating rat
Genus Chibchanomys
Chibchanomys orcesi - Las Cajas ichthyomyine
Chibchanomys trichotis - Chibchan water mouse
Genus Ichthyomys
Ichthyomys hydrobates - crab-eating rat
Ichthyomys pittieri - Pittier's crab-eating rat
Ichthyomys stolzmanni - Stolzmann's crab-eating rat
Ichthyomys tweedii - Tweedy's crab-eating rat
Genus Neusticomys
Neusticomys ferreirai - Ferreira's fish-eating rat
Neusticomys monticolus - montane fish-eating rat
Neusticomys mussoi - Musso's fish-eating rat
Neusticomys oyapocki - Oyapock's fish-eating rat
Neusticomys peruviensis - Peruvian fish-eating rat
Neusticomys venezuelae - Venezuelan fish-eating rat
Neusticomys vossi - Voss's fish-eating rat
Genus Rheomys
Rheomys mexicanus - Mexican water mouse
Rheomys raptor - Goldman's water mouse
Rheomys thomasi - Thomas's water mouse
Rheomys underwoodi - Underwood's water mouse
Tribe Oryzomyini
Genus Aegialomys
Aegialomys galapagoensis - Galápagos rice rat
Aegialomys xanthaeolus - Yellowish rice rat
Genus Amphinectomys
Amphinectomys savamis - Ucayali water rat
Genus Cerradomys
Cerradomys akroai - Akroa rice rat
Cerradomys goytaca - Goytaca rice rat
Cerradomys langguthi - Langguth's rice rat
Cerradomys maracajuensis - Maracaju oryzomys
Cerradomys marinhus - Marinho's rice rat
Cerradomys scotti - Lindbergh's oryzomys
Cerradomys subflavus - Flavescent oryzomys
Cerradomys vivoi - Vivo's rice rat
Genus Drymoreomys
Drymoreomys albimaculatus - White-throated montane forest rat
Genus Eremoryzomys
Eremoryzomys polius - gray rice rat
Genus Euryoryzomys
Euryoryzomys emmonsae - Emmons' rice rat
Euryoryzomys lamia - monster rice rat
Euryoryzomys legatus - big-headed rice rat
Euryoryzomys macconnelli - MacConnell's rice rat
Euryoryzomys nitidus - elegant rice rat
Euryoryzomys russatus - russet rice rat
Genus Handleyomys
Handleyomys alfaroi - Alfaro's rice rat
Handleyomys chapmani - Chapman's rice rat
Handleyomys fuscatus - dusky-footed montane mouse
Handleyomys intectus - Colombian rice rat
Handleyomys melanotis - black-eared rice rat
Handleyomys rhabdops - striped rice rat
Handleyomys rostratus - long-nosed rice rat
Handleyomys saturatior - cloud forest rice rat
Genus Holochilus
Holochilus brasiliensis - Brazilian marsh rat
Holochilus chacarius - Chacoan marsh rat
Holochilus nanus - Amazonian marsh rat
Holochilus oxe - Brazilian North-eastern marsh rat
Holochilus sciureus - Cerrado marsh rat
Genus Hylaeamys
Hylaeamys acritus - Bolivian rice rat
Hylaeamys laticeps - Atlantic Forest oryzomys
Hylaeamys megacephalus - Azara's broad-headed oryzomys
Hylaeamys oniscus - sowbug rice rat
Hylaeamys perenensis - western Amazonian oryzomys
Hylaeamys tatei - Tate's oryzomys
Hylaeamys yunganus - Yungas rice rat
Genus Lundomys
Lundomys molitor - Lund's amphibious rat
Genus Megalomys
Megalomys audreyae - Barbuda giant rice-rat (Extinct)
Megalomys curazensis - (Extinct)
Megalomys desmarestii - Desmarest's pilorie (extinct)
Megalomys georginae - Barbados giant rice rat (extinct)
Megalomys luciae - Saint Lucia pilorie (extinct)
Genus Melanomys
Melanomys caliginosus - dusky melanomys
Melanomys robustulus - robust melanomys
Melanomys zunigae - Zuniga's melanomys
Genus Microakodontomys
Microakodontomys transitorius - Transitional colilargo
Genus Microryzomys
Microryzomys altissimus - Páramo colilargo
Microryzomys minutus - montane colilargo
Genus Mindomys
Mindomys hammondi - Hammond's rice rat
Mindomys kutuku - Kutukú rat
Genus Neacomys
Neacomys aletheia - Upper Juruá bristly mouse
Neacomys amoenus - pleasant bristly mouse
Neacomys dubosti - Dubost's bristly mouse
Neacomys elieceri - Eliecer's bristly mouse
Neacomys guianae - Guiana bristly mouse
Neacomys jau - Jaú bristly mouse
Neacomys macedoruizi - Macedo Ruiz's bristly mouse
Neacomys marajoara - Marajó bristly mouse
Neacomys minutus - small bristly mouse
Neacomys musseri - Musser's bristly mouse
Neacomys paracou - Paracou bristly mouse
Neacomys pictus - painted bristly mouse
Neacomys rosalindae - Rosalind's bristly mouse
Neacomys serranensis - Serrano bristly mouse
Neacomys spinosus - large bristly mouse
Neacomys tenuipes - narrow-footed bristly mouse
Neacomys vargasllosai - Vargas Llosa's bristly mouse
Neacomys vossi - Voss's bristly mouse
Neacomys xingu - Xingu bristly mouse
Genus Nectomys
Nectomys apicalis - western Amazonian nectomys
Nectomys magdalenae - Magdalena-Cauca water rat
Nectomys palmipes - Trinidad nectomys
Nectomys rattus - small-footed bristly mouse
Nectomys squamipes - Atlantic Forest nectomys
Genus Nephelomys
Nephelomys albigularis - white-throated oryzomys
Nephelomys auriventer - golden-bellied oryzomys
Nephelomys caracolus - Costa Central oryzomys
Nephelomys childi - Child's rice rat
Nephelomys devius - Talamancan oryzomys
Nephelomys keaysi - Keays's oryzomys
Nephelomys levipes - nimble-footed oryzomys
Nephelomys maculiventer - Santa Marta rice rat
Nephelomys meridensis - Mérida oryzomys
Nephelomys moerex - gray-bellied rice rat
Nephelomys nimbosus - lesser golden-bellied rice rat
Nephelomys pectoralis - Western Colombian rice rat
Nephelomys pirrensis - Mount Pirre rice rat
Nephelomys ricardopalmai - Ricardo Palma's rice rat
Genus Nesoryzomys
Nesoryzomys darwini - Darwin's nesoryzomys (extinct
Nesoryzomys fernandinae - Fernandina nesoryzomys
Nesoryzomys indefessus - Indefatigable Galápagos mouse (extinct)
Nesoryzomys narboroughi - large Fernandina Galapagos mouse
Nesoryzomys swarthi - Santiago nesoryzomys
Genus Noronhomys
Noronhomys vespuccii - Vespucci's rodent (extinct)
Genus Oecomys
Oecomys auyantepui - north Amazonian arboreal rice rat
Oecomys bicolor - bicolored arboreal rice rat
Oecomys catherinae - Atlantic Forest oecomys
Oecomys cleberi - Cleber's oecomys
Oecomys concolor - unicolored arboreal rice rat
Oecomys flavicans - yellow arboreal rice rat
Oecomys mamorae - Mamore arboreal rice rat
Oecomys paricola - Brazilian arboreal rice rat
Oecomys phaeotis - dusky arboreal rice rat
Oecomys rex - king arboreal rice rat
Oecomys roberti - Robert's arboreal rice rat
Oecomys rutilus - red arboreal rice rat
Oecomys speciosus - Venezuelan arboreal rice rat
Oecomys superans - foothill arboreal rice rat
Oecomys sydandersoni - Anderson's arboreal rice rat
Oecomys trinitatis - Trinidad arboreal rice rat
Genus Oligoryzomys
Oligoryzomys andinus - Andean colilargo
Oligoryzomys arenalis - sandy colilargo
Oligoryzomys brendae - Brenda's colilargo
Oligoryzomys chacoensis - Chacoan colilargo
Oligoryzomys destructor - destructive pygmy rice rat
Oligoryzomys flavescens - flavescent colilargo
Oligoryzomys fornesi - Fornes' colilargo
Oligoryzomys fulvescens - fulvous colilargo
Oligoryzomys griseolus - grizzled colilargo
Oligoryzomys longicaudatus - long-tailed colilargo
Oligoryzomys magellanicus - Magellanic pygmy rice rat
Oligoryzomys microtis - small-eared pygmy rice rat
Oligoryzomys moojeni - Moojen's pygmy rice rat
Oligoryzomys nigripes - black-footed colilargo
Oligoryzomys rupestris - Highlands pygmy rice rat
Oligoryzomys stramineus - straw-colored pygmy rice rat
Oligoryzomys transitorius - Synonym of Microakodontomys transitorius ?
Oligoryzomys vegetus - sprightly colilargo
Oligoryzomys victus - St. Vincent pygmy rice rat (extinct)
Genus Oreoryzomys
Oreoryzomys balneator - Peruvian rice rat
Genus Oryzomys
Oryzomys albiventer - white-bellied marsh rice rat
Oryzomys antillarum - Jamaican rice rat (extinct)
Oryzomys couesi - Coues's rice rat
Oryzomys dimidiatus - Thomas's rice rat
Oryzomys gorgasi - Gorgas's rice rat
Oryzomys nelsoni - Tres Marias rice rat (extinct)
Oryzomys palustris - marsh rice rat
Oryzomys peninsulae? - Lower California rice rat (extinct)
Genus Pseudoryzomys
Pseudoryzomys simplex - false oryzomys
Genus Scolomys
Scolomys melanops - short-nosed scolomys
Scolomys ucayalensis - Ucayali spiny mouse
Genus Sigmodontomys
Sigmodontomys alfari - Alfaro's rice water rat
Genus Sooretamys
Sooretamys angouya - Paraguayan rice rat
Genus Tanyuromys
Tanyuromys aphrastus - Harris's rice water rat
Tanyuromys thomasleei - Lee's long-tailed montane rat
Genus Transandinomys
Transandinomys bolivaris - long-whiskered rice rat
Transandinomys talamancae - Talamancan rice rat
Genus Zygodontomys
Zygodontomys brevicauda - short-tailed zygodont
Zygodontomys brunneus - brown zygodont
Tribe Phyllotini
Genus Andalgalomys
Andalgalomys olrogi - Olrog's chaco mouse
Andalgalomys pearsoni - Pearson's chaco mouse
Andalgalomys roigi - Roig's pericote
Genus Andinomys
Andinomys edax - Andean mouse
Genus Auliscomys
Auliscomys boliviensis - Bolivian big-eared mouse
Auliscomys pictus - painted big-eared mouse
Auliscomys sublimis - Andean big-eared mouse
Genus Calomys
Calomys boliviae - Bolivian vesper mouse
Calomys callidus - crafty vesper mouse
Calomys callosus - large vesper mouse
Calomys cerqueirai - Cerqueira's vesper mouse
Calomys expulsus - Caatinga vesper mouse
Calomys fecundus - fecund vesper mouse
Calomys hummelincki - Hummelinck's vesper mouse
Calomys laucha - small vesper mouse
Calomys lepidus - Andean vesper mouse
Calomys musculinus - drylands vesper mouse
Calomys sorellus - Peruvian vesper mouse
Calomys tener - delicate vesper mouse
Calomys tocantinsi - Tocantins vesper mouse
Calomys venustus - Córdoba vesper mouse
Genus Chinchillula
Chinchillula sahamae - altiplano chinchilla mouse
Genus Eligmodontia
Eligmodontia hirtipes - hairy-footed gerbil mouse
Eligmodontia moreni - Monte laucha
Eligmodontia morgani - western Patagonian laucha
Eligmodontia puerulus - Altiplano laucha
Eligmodontia typus - eastern Patagonian laucha
Genus Galenomys
Galenomys garleppi - Garlepp's mouse
Genus Graomys
Graomys centralis - central pericote
Graomys domorum - pale leaf-eared mouse
Graomys edithae - Edith's leaf-eared mouse
Graomys griseoflavus - gray leaf-eared mouse
Genus Loxodontomys
Loxodontomys micropus - Southern big-eared mouse
Loxodontomys pikumche - Pikumche pericote
Genus Phyllotis
Phyllotis alisosiensis - Los Alisos leaf-eared mouse
Phyllotis amicus - friendly leaf-eared mouse
Phyllotis andium - Andean leaf-eared mouse
Phyllotis anitae - Anita's leaf-eared mouse
Phyllotis bonariensis - Bonaerense pericote
Phyllotis caprinus - capricorn leaf-eared mouse
Phyllotis darwini - Darwin's leaf-eared mouse
Phyllotis definitus - definitive leaf-eared mouse
Phyllotis gerbillus - gerbilline pericote
Phyllotis haggardi - Haggard's leaf-eared mouse
Phyllotis limatus - Lima pericote
Phyllotis magister - master leaf-eared mouse
Phyllotis osgoodi - Osgood's leaf-eared mouse
Phyllotis osilae - bunchgrass leaf-eared mouse
Phyllotis pearsoni - Pearson's leaf-eared mouse
Phyllotis pehuenche - Pehuenche leaf-eared mouse
Phyllotis wolffsohni - Wolffsohn's leaf-eared mouse
Phyllotis xanthopygus - yellow-rumped leaf-eared mouse
Genus Salinomys
Salinomys delicatus - delicate salt flat mouse
Genus Tapecomys
Tapecomys primus - primordial tapecua
Tribe Reithrodontini
Genus Euneomys
Euneomys chinchilloides - Patagonian chinchilla mouse
Euneomys fossor - burrowing chinchilla mouse
Euneomys mordax - biting chinchilla mouse
Euneomys petersoni - Peterson's chinchilla mouse
Genus Neotomys
Neotomys ebriosus - Andean swamp rat
Genus Reithrodon
Reithrodon auritus - bunny rat
Reithrodon typicus - naked-soled conyrat
Tribe Sigmodontini
Genus Sigmodon
Subgenus Sigmodon
Sigmodon hispidus species group
Sigmodon alleni - Allen's cotton rat
Sigmodon arizonae - Arizona cotton rat
Sigmodon hirsutus - southern cotton rat
Sigmodon hispidus - hispid cotton rat
Sigmodon mascotensis - West Mexican cotton rat
Sigmodon ochrognathus - yellow-nosed cotton rat
Sigmodon planifrons - Miahuatlán cotton rat
Sigmodon toltecus - Toltec cotton rat
Sigmodon zanjonensis - montane cotton rat
Sigmodon fulviventer species group
Sigmodon fulviventer - tawny-bellied cotton rat
Sigmodon inopinatus - Ecuadorian cotton rat
Sigmodon leucotis - white-eared cotton rat
Sigmodon peruanus - Peruvian cotton rat
Subgenus Sigmomys
Sigmodon alstoni - Alston's cotton rat
Tribe Thomasomyini
Genus Abrawayaomys
Abrawayaomys ruschii - Ruschi's rat
Genus Aepeomys
Aepeomys lugens - olive montane mouse
Aepeomys reigi - Reig's aepeomys
Genus Chilomys
Chilomys instans - Colombian forest mouse
Genus Rhagomys
Rhagomys longilingua - long-tongued rhagomys
Rhagomys rufescens - Brazilian arboreal mouse
Genus Rhipidomys
Rhipidomys albujai - Albuja's climbing rat
Rhipidomys austrinus - Southern climbing mouse
Rhipidomys cariri - Cairi climbing mouse
Rhipidomys caucensis - Cauca climbing mouse
Rhipidomys couesi - Coues's climbing mouse
Rhipidomys emiliae - Eastern Amazon climbing mouse
Rhipidomys fulviventer - Buff-bellied climbing mouse
Rhipidomys gardneri - Gardner's climbing mouse
Rhipidomys ipukensis - Ipuca climbing rat
Rhipidomys itoan - Sky climbing rat
Rhipidomys latimanus - Broad-footed climbing mouse
Rhipidomys leucodactylus - White-footed climbing mouse
Rhipidomys macconnelli - MacConnell's climbing mouse
Rhipidomys macrurus - Cerrado climbing mouse
Rhipidomys mastacalis - Atlantic Forest climbing mouse
Rhipidomys modicus - Peruvian climbing mouse
Rhipidomys nitela - Splendid climbing mouse
Rhipidomys ochrogaster - Yellow-bellied climbing mouse
Rhipidomys similis - Greater Colombian climbing rat
Rhipidomys tenuicauda - Turimiquire climbing rat
Rhipidomys tribei - Tribe's climbing rat
Rhipidomys venezuelae - Venezuelan climbing mouse
Rhipidomys venustus - Charming climbing mouse
Rhipidomys wetzeli - Wetzel's climbing mouse
Genus Thomasomys
Thomasomys andersoni - Anderson's Oldfield mouse
Thomasomys antoniobracki - Antonio Brack's Oldfield mouse
Thomasomys apeco - Apeco Oldfield mouse
Thomasomys aureus - golden Oldfield mouse
Thomasomys baeops - beady-eyed mouse
Thomasomys bombycinus - silky Oldfield mouse
Thomasomys burneoi - Burneo's Oldfield mouse
Thomasomys caudivarius - white-tipped Oldfield mouse
Thomasomys cinereiventer - ashy-bellied Oldfield mouse
Thomasomys cinereus - ash-colored Oldfield mouse
Thomasomys cinnameus - cinnamon-colored Oldfield mouse
Thomasomys daphne - Daphne's Oldfield mouse
Thomasomys eleusis - Peruvian Oldfield mouse
Thomasomys erro - wandering Oldfield mouse
Thomasomys gracilis - slender Oldfield mouse
Thomasomys hudsoni - Hudson's Oldfield mouse
Thomasomys hylophilus - woodland Oldfield mouse
Thomasomys incanus - Inca Oldfield mouse
Thomasomys ischyrus - long-tailed Oldfield mouse
Thomasomys kalinowskii - Kalinowski's Oldfield mouse
Thomasomys ladewi - Ladew's Oldfield mouse
Thomasomys laniger - soft-furred Oldfield mouse
Thomasomys macrotis - large-eared Oldfield mouse
Thomasomys monochromos - unicolored Oldfield mouse
Thomasomys niveipes - snow-footed Oldfield mouse
Thomasomys notatus - distinguished Oldfield mouse
Thomasomys onkiro - Ashaninka Oldfield mouse
Thomasomys oreas - montane Oldfield mouse
Thomasomys paramorum - paramo Oldfield mouse
Thomasomys pardignasi - Pardiñas's Oldfield mouse
Thomasomys popayanus - Popayán Oldfield mouse
Thomasomys praetor - Cajamarca Oldfield mouse
Thomasomys pyrrhonotus - Thomas's Oldfield mouse
Thomasomys rhoadsi - Rhoads's Oldfield mouse
Thomasomys rosalinda - Rosalinda's Oldfield mouse
Thomasomys silvestris - forest Oldfield mouse
Thomasomys taczanowskii - Taczanowski's Oldfield mouse
Thomasomys ucucha - ucucha thomasomys
Thomasomys vestitus - dressy Oldfield mouse
Thomasomys vulcani - Pichincha thomasomys
Family Muridae
Subfamily Leimacomyinae
Genus Leimacomys
Leimacomys buettneri - Togo mouse, Büttner's African forest mouse, groove-toothed forest mouse
Subfamily Deomyinae
Genus Acomys
Acomys airensis - western Saharan spiny mouse
Acomys cahirinus - Cairo spiny mouse
Acomys chudeaui - Chudeau's spiny mouse
Acomys cilicicus - Asia Minor spiny mouse
Acomys cineraceus - grey spiny mouse
Acomys dimidiatus - Eastern spiny mouse
Acomys ignitus - fiery spiny mouse
Acomys johannis - Johan's spiny mouse
Acomys kempi - Kemp's spiny mouse
Acomys louisae - Louise's spiny mouse
Acomys minous - Crete spiny mouse
Acomys mullah - mullah spiny mouse
Acomys muzei - Muze spiny mouse
Acomys nesiotes - Cyprus spiny mouse
Acomys ngurui - Nguru spiny mouse
Acomys percivali - Percival's spiny mouse
Acomys russatus - golden spiny mouse
Acomys seurati - Seurat's spiny mouse
Acomys spinosissimus - spiny mouse
Acomys subspinosus - Cape spiny mouse
Acomys wilsoni - Wilson's spiny mouse
Genus Deomys
Deomys ferugineus - link rat
Genus Lophuromys
Lophuromys angolensis - Angolan brush-furred rat
Lophuromys ansorgei - Ansorge's brush-furred mouse
Lophuromys aquilus - Gray brush-furred rat
Lophuromys brevicaudus - Short-tailed brush-furred rat
Lophuromys brunneus - Thomas's Ethiopian brush-furred rat
Lophuromys chercherensis - Mount Chercher brush-furred rat
Lophuromys chrysopus - Ethiopian forest brush-furred rat
Lophuromys cinereus?
Lophuromys dieterleni - Dieterlen's brush-furred mouse
Lophuromys dudui - Dudu's brush-furred rat
Lophuromys eisentrauti - Mount Lefo brush-furred mouse
Lophuromys flavopunctatus - Yellow-spotted brush-furred rat
Lophuromys huttereri - Hutterer's brush-furred mouse
Lophuromys kilonzoi - Kilonzo's brush-furred rat
Lophuromys laticeps - Albertine Rift brush-furred rat
Lophuromys luteogaster - Yellow-bellied brush-furred rat
Lophuromys machangui - Machandu's brush-furred rat
Lophuromys makundii - Makundi's brush-furred rat
Lophuromys margarettae - Margaret's brush-furred rat
Lophuromys medicaudatus - Medium-tailed brush-furred rat
Lophuromys melanonyx - Black-clawed brush-furred rat
Lophuromys menageshae - North Western Rift brush-furred rat
Lophuromys nudicaudus - Fire-bellied brush-furred rat
Lophuromys pseudosikapusi - Sheko Forest brush-furred rat
Lophuromys rahmi - Rahm's brush-furred rat
Lophuromys rita - Congolese brush-furred rat
Lophuromys roseveari - Mount Cameroon brush-furred rat
Lophuromys sabunii - Sabuni's brush-furred rat
Lophuromys sikapusi - Rusty-bellied brush-furred rat
Lophuromys simensis - Simien brush-furred rat
Lophuromys stanleyi - Stanley's brush-furred rat
Lophuromys verhageni - Verhagen's brush-furred rat
Lophuromys woosnami - Woosnam's brush-furred rat
Lophuromys zena - Zena's brush-furred rat
Genus Uranomys
Uranomys ruddi - Rudd's mouse or the white-bellied brush-furred rat
Subfamily Otomyinae
Genus Myotomys
Myotomys sloggetti - rock karroo rat
Myotomys unisulcatus - bush karroo rat
Genus Otomys
Otomys anchietae - Angolan vlei rat
Otomys angoniensis - Angoni vlei rat
Otomys barbouri - Barbour's vlei rat
Otomys burtoni - Burton's vlei rat
Otomys cheesmani - Cheesman's vlei rat
Otomys cuanzensis - Cuanza vlei rat
Otomys dartmouthi - Ruwenzori vlei rat
Otomys denti - Dent's vlei rat
Otomys dollmani - Dollman's vlei rat
Otomys fortior - Charada vlei rat
Otomys helleri - Heller's vlei rat
Otomys irroratus - vlei rat
Otomys jacksoni - Mount Elgon vlei rat
Otomys lacustris - Tanzanian vlei rat
Otomys laminatus - laminate vlei rat
Otomys maximus - large vlei rat
Otomys occidentalis - western vlei rat
Otomys orestes - Afroalpine vlei rat
Otomys saundersiae - Saunders's vlei rat
Otomys simiensis - Simien vlei rat
Otomys thomasi - Thomas's vlei rat
Otomys tropicalis - tropical vlei rat
Otomys typus - typical vlei rat
Otomys uzungwensis - Uzungwe vlei rat
Otomys yaldeni - Yalden's vlei rat
Otomys zinki - Mount Kilimanjaro vlei rat
Genus Parotomys
Parotomys brantsii - Brants's whistling rat
Parotomys littledalei - Littledale's whistling rat
Subfamily Gerbillinae
Genus Ammodillus
Ammodillus imbellis - ammodile
Genus Brachiones
Brachiones przewalskii - Przewalski's gerbil
Genus Desmodilliscus
Desmodilliscus braueri - pouched gerbil
Genus Desmodillus
Desmodillus auricularis - Cape short-eared gerbil
Genus Dipodillus
Dipodillus bottai - Botta's dipodil
Dipodillus campestris - North African dipodil
Dipodillus dasyurus - Wagner's dipodil
Dipodillus harwoodi - Harwood's dipodil
Dipodillus jamesi - James's dipodil
Dipodillus lowei - Lowe's dipodil
Dipodillus mackilligini - Mackilligin's dipodil
Dipodillus maghrebi - Maghreb dipodil
Dipodillus rupicola - rupicolous dipodil
Dipodillus simoni - Simon's dipodil
Dipodillus somalicus - Somalian dipodil
Dipodillus stigmonyx - Khartoum dipodil
Dipodillus zakariai - Kerkennah Islands dipodil
Genus Gerbilliscus
Gerbilliscus afra - Cape gerbil
Gerbilliscus boehmi - Boehm's gerbil
Gerbilliscus brantsii - highveld gerbil
Gerbilliscus guineae - Guinean gerbil
Gerbilliscus inclusus - Gorongoza gerbil
Gerbilliscus kempi - northern savanna gerbil
Gerbilliscus leucogaster - bushveld gerbil
Gerbilliscus nigricaudus - black-tailed gerbil
Gerbilliscus phillipsi - Phillips's gerbil
Gerbilliscus robustus - fringe-tailed gerbil
Gerbilliscus validus - southern savanna gerbil
Genus Gerbillurus
Gerbillurus paeba - hairy-footed gerbil
Gerbillurus setzeri - Setzer's hairy-footed gerbil
Gerbillurus tytonis - dune hairy-footed gerbil
Gerbillurus vallinus - bushy-tailed hairy-footed gerbil
Genus Gerbillus
Subgenus Handecapleura
Gerbillus amoenus - Pleasant gerbil
Gerbillus brockmani - Brockman's gerbil
Gerbillus diminutus?
Gerbillus famulus - Black-tufted gerbil
Gerbillus garamantis - Algerian gerbil
Gerbillus grobbeni - Grobben's gerbil
Gerbillus henleyi - Pygmy gerbil
Gerbillus juliani?
Gerbillus mauritaniae - Mauritanian gerbil
Gerbillus mesopotamiae - Harrison's gerbil
Gerbillus muriculus - Darfur gerbil
Gerbillus nanus - Balochistan gerbil
Gerbillus percivali?
Gerbillus poecillops - Large Aden gerbil
Gerbillus principulus - Principal gerbil
Gerbillus pusillus - Least gerbil
Gerbillus quadrimaculatus?
Gerbillus ruberrimus?
Gerbillus syrticus - Sand gerbil
Gerbillus watersi - Waters's gerbil
Subgenus Gerbillus
Gerbillus acticola - Berbera gerbil
Gerbillus agag - Agag gerbil
Gerbillus allenbyi?
Gerbillus andersoni - Anderson's gerbil
Gerbillus aquilus - Swarthy gerbil
Gerbillus bilensis?
Gerbillus bonhotei?
Gerbillus burtoni - Burton's gerbil
Gerbillus cheesmani - Cheesman's gerbil
Gerbillus cosensi?
Gerbillus dalloni?
Gerbillus dongolanus - Dongola gerbil
Gerbillus dunni - Dunn's gerbil
Gerbillus floweri - Flower's gerbil
Gerbillus gerbillus - Lesser Egyptian gerbil
Gerbillus gleadowi - Indian hairy-footed gerbil
Gerbillus hesperinus - Western gerbil
Gerbillus hoogstraali - Hoogstraal's gerbil
Gerbillus latastei - Lataste's gerbil
Gerbillus nancillus - Sudan gerbil
Gerbillus nigeriae - Nigerian gerbil
Gerbillus occiduus - Occidental gerbil
Gerbillus perpallidus - Pale gerbil
Gerbillus pulvinatus - Cushioned gerbil
Gerbillus pyramidum - Greater Egyptian gerbil
Gerbillus riggenbachi?
Gerbillus rosalinda - Rosalinda gerbil
Gerbillus tarabuli - Tarabul's gerbil
Genus Meriones
Subgenus Meriones
Meriones tamariscinus - Tamarisk jird
Subgenus Parameriones
Meriones persicus - Persian jird
Meriones rex - king jird
Subgenus Pallasiomys
Meriones arimalius - Arabian jird
Meriones chengi - Cheng's jird
Meriones crassus - Sundevall's jird
Meriones dahli - Dahl's jird
Meriones grandis - Moroccan jird
Meriones libycus - Libyan jird
Meriones meridianus - midday jird
Meriones sacramenti - Buxton's jird
Meriones shawi - Shaw's jird
Meriones tristrami - Tristram's jird
Meriones unguiculatus - Mongolian jird
Meriones vinogradovi - Vinogradov's jird
Meriones zarudnyi - Zarudny's jird
Subgenus Cheliones
Meriones hurrianae - Indian desert jird
Genus Microdillus
Microdillus peeli - Somali pygmy gerbil
Genus Pachyuromys
Pachyuromys duprasi - fat-tailed gerbil or duprasi gerbil
Genus Psammomys
Psammomys obesus - fat sand rat
Psammomys vexillaris - thin sand rat
Genus Rhombomys
Rhombomys opimus - great gerbil
Genus Sekeetamys
Sekeetamys calurus - bushy-tailed jird
Genus Tatera
Tatera indica - Indian gerbil
Genus Taterillus
Taterillus arenarius - Sahel gerbil
Taterillus congicus - Congo gerbil
Taterillus emini - Emin's gerbil
Taterillus gracilis - slender gerbil
Taterillus harringtoni - Harrington's gerbil
Taterillus lacustris - Lake Chad gerbil
Taterillus petteri - Petter's gerbil
Taterillus pygargus - Senegal gerbil
Taterillus tranieri - Tranieri's tateril
Subfamily Murinae
Genus Abditomys
Abditomys latidens - Luzon broad-toothed rat
Genus Abeomelomys
Abeomelomys sevia - Papuan abeomelomys
Genus Aethomys
Aethomys bocagei - Bocage's rock rat
Aethomys chrysophilus - red rock rat
Aethomys granti - Grant's rock rat
Aethomys hindei - Hinde's rock rat
Aethomys ineptus - Tete veld aethomys
Aethomys kaiseri - Kaiser's rock rat
Aethomys namaquensis - Namaqua rock rat
Aethomys nyikae - Nyika rock rat
Aethomys silindensis - Silinda rock rat
Aethomys stannarius - Tinfield's rock rat
Aethomys thomasi - Thomas's rock rat
Genus Anisomys
Anisomys imitator - squirrel-toothed rat
Genus Anonymomys
Anonymomys mindorensis - Mindoro rat
Genus Apodemus
Apodemus agrarius - striped field mouse
Apodemus alpicola - alpine field mouse
Apodemus argenteus - small Japanese field mouse
Apodemus arianus? - Persian field mouse
Apodemus avicennicus - Persian wood mouse
Apodemus chevrieri - Chevrier's field mouse
Apodemus draco - South China field mouse
Apodemus epimelas - Western broad-toothed field mouse
Apodemus flavicollis - yellow-necked mouse
Apodemus fulvipectus? - yellow-breasted mouse
Apodemus gurkha - Himalayan field mouse
Apodemus hermonensis? - Mount Hermon field mouse
Apodemus hyrcanicus - Caucasus field mouse
Apodemus latronum - Sichuan field mouse
Apodemus mystacinus - broad-toothed field mouse
Apodemus pallipes - Ward's field mouse
Apodemus peninsulae - Korean field mouse
Apodemus ponticus - Black Sea field mouse
Apodemus rusiges - Kashmir field mouse
Apodemus semotus - Taiwan field mouse
Apodemus speciosus - large Japanese field mouse
Apodemus sylvaticus - wood mouse
Apodemus uralensis - Ural field mouse
Apodemus witherbyi - Steppe field mouse
Genus Apomys
Apomys abrae - Luzon Cordillera forest mouse
Apomys aurorae - Luzon Aurora forest mouse
Apomys banahao - Mount Banahaw forest mouse
Apomys brownorum - Mount Tapulao forest mouse
Apomys camiguinensis - Camiguin forest mouse
Apomys datae - Luzon montane forest mouse
Apomys gracilirostris - Large Mindoro forest mouse
Apomys hylocoetes - Mount Apo forest mouse
Apomys insignis - Mindanao montane forest mouse
Apomys iridensis - Mount Irid forest mouse
Apomys littoralis - Mindanao lowland forest mouse
Apomys lubangensis - Lubang forest mouse
Apomys magnus - Luzon giant forest mouse
Apomys microdon - Small Luzon forest mouse
Apomys minganensis - Mount Mingan forest mouse
Apomys musculus - Least forest mouse
Apomys sacobianus - Long-nosed Luzon forest mouse
Apomys sierrae - Sierra Madre forest mouse
Apomys zambalensis - Luzon Zambales forest mouse
Genus Archboldomys
Archboldomys luzonensis - Mt. Isarog shrew-mouse
Archboldomys maximus - Large Cordillera shrew-mouse
Genus Arvicanthis
Arvicanthis abyssinicus - Abyssinian grass rat
Arvicanthis ansorgei - Sudanian grass rat
Arvicanthis blicki - Blick's grass rat
Arvicanthis nairobae - Nairobi grass rat
Arvicanthis neumanni - Neumann's grass rat
Arvicanthis niloticus - African grass rat
Arvicanthis rufinus - Guinean grass rat
Genus Baiyankamys
Baiyankamys habbema - mountain water rat
Baiyankamys shawmayeri - Shaw Mayer's water rat
Genus Bandicota
Bandicota bengalensis - Lesser bandicoot rat
Bandicota indica - Greater bandicoot rat
Bandicota savilei - Savile's bandicoot rat
Genus Batomys
Batomys cagayanensis (extinct)
Batomys dentatus - Large-toothed hairy-tailed rat
Batomys granti - Luzon hairy-tailed rat
Batomys hamiguitan - Luzon hairy-tailed rat
Batomys russatus - Hamiguitan hairy-tailed rat
Batomys salomonseni - Mindanao hairy-tailed rat
Batomys uragon - Mount Isarog hairy-tailed rat
Genus Berylmys
Berylmys berdmorei - Small white-toothed rat
Berylmys bowersi - Bower's white-toothed rat
Berylmys mackenziei - Kenneth's white-toothed rat
Berylmys manipulus - Manipur white-toothed rat
Genus Brassomys
Brassomys albidens - White-toothed brush mouse
Genus Bullimus
Bullimus bagobus - Bagobo rat
Bullimus carletoni - Carleton's forest rat
Bullimus gamay - Camiguin forest rat
Bullimus luzonicus - Large Luzon forest rat
Genus Bunomys
Bunomys andrewsi - Andrew's hill rat
Bunomys chrysocomus - Yellow-haired hill rat
Bunomys coelestis - Heavenly hill rat
Bunomys fratrorum - Fraternal hill rat
Bunomys heinrichi?
Bunomys karokophilus - Karoko hill rat
Bunomys penitus - Inland hill rat
Bunomys prolatus - Long-headed hill rat
Bunomys torajae - Tana Toraja hill rat
Genus Carpomys
Carpomys dakai (extinct)
Carpomys melanurus - short-footed Luzon tree rat
Carpomys phaeurus - white-bellied Luzon tree rat
Genus Chiromyscus
Chiromyscus chiropus - Fea's tree rat
Genus Chiropodomys
Chiropodomys calamianensis - Palawan pencil-tailed tree mouse
Chiropodomys gliroides - Indomalayan pencil-tailed tree mouse
Chiropodomys karlkoopmani - Koopman's pencil-tailed tree mouse
Chiropodomys major - Large pencil-tailed tree mouse
Chiropodomys muroides - Gray-bellied pencil-tailed tree mouse
Chiropodomys pusillus - Small pencil-tailed tree mouse
Chiropodomys maximus (Extinct)
Chiropodomys primitivus (Extinct)
Genus Chiruromys
Chiruromys forbesi - Greater tree mouse
Chiruromys lamia - lamia
Chiruromys vates - Lesser tree mouse
Genus Chrotomys
Chrotomys gonzalesi - Isarog shrew-rat
Chrotomys mindorensis - lowland striped shrew-rat
Chrotomys sibuyanensis - Sibuyan striped shrew-rat
Chrotomys silaceus - silver earth rat
Chrotomys whiteheadi - Luzon montane shrew rat
Genus Coccymys
Coccymys kirrhos - Tawny brush mouse
Coccymys ruemmleri - Ruemmler's brush mouse
Coccymys shawmayeri - Central Cordillera brush mouse
Genus Colomys
Colomys goslingi - African water rat
Genus Congomys
Congomys lukolelae - Lukolela swamp rat
Congomys verschureni - Verschuren's swamp rat
Genus Conilurus
Conilurus albipes - white-footed rabbit rat (extinct)
Conilurus capricornensis - Capricorn rabbit rat (extinct)
Conilurus penicillatus - brush-tailed rabbit rat
Genus Coryphomys
Coryphomys buehleri - Buehler's rat (extinct)
Coryphomys musseri - Timor giant rat (extinct)
Genus Crateromys
Crateromys australis - Dinagat bushy-tailed cloud rat
Crateromys ballik (extinct)
Crateromys heaneyi - Panay crateromys
Crateromys paulus - Ilin bushy-tailed cloud rat
Crateromys schadenbergi - Luzon bushy-tailed cloud rat
Genus Cremnomys
Cremnomys cutchicus - Cutch rat
Cremnomys elvira - Elvira rat
Genus Crossomys
Crossomys moncktoni - earless water rat
Genus Crunomys
Crunomys celebensis - Celebes shrew rat
Crunomys fallax - northern Luzon shrew rat
Crunomys melanius - Leyte shrew rat
Crunomys suncoides - Katanglad shrew mouse
Genus Dacnomys
Dacnomys millardi - Millard's rat
Genus Dasymys
Dasymys alleni - Glover Allen's dasymys
Dasymys cabrali - Crawford-Cabral's dasymys
Dasymys foxi - Fox's shaggy rat
Dasymys incomtus - African marsh rat
Dasymys montanus - montane shaggy rat
Dasymys nudipes - Angolan marsh rat
Dasymys robertsii - Robert's shaggy rat
Dasymys rufulus - West African shaggy rat
Dasymys rwandae - Rwandan dasymys
Dasymys shortridgei
Dasymys sua - Tanzanian dasymys
Genus Dephomys
Dephomys defua - defua rat
Dephomys eburneae - Ivory Coast dephomys
Genus Desmomys
Desmomys harringtoni - Harrington's rat
Desmomys yaldeni - Yalden's desmomys
Genus Diomys
Diomys crumpi - Crump's mouse
Genus Diplothrix
Diplothrix legata - Ryukyu Islands tree rat
Diplothrix yangziensis (extinct)
Genus Echiothrix
Echiothrix centrosa - Central Sulawesi echiothrix
Echiothrix leucura - Sulawesi spiny rat
Genus Eropeplus
Eropeplus canus - Sulawesi soft-furred rat
Genus Golunda
Golunda aouraghei (extinct)
Golunda dulamensis (extinct)
Golunda ellioti - Indian bush rat
Golunda gurai (extinct)
Golunda jaegeri (extinct)
Golunda kelleri (extinct)
Golunda tatroticus (extinct)
Genus Grammomys
Grammomys aridulus - arid thicket rat
Grammomys brevirostris - short-snouted thicket rat
Grammomys buntingi - Bunting's thicket rat
Grammomys caniceps - gray-headed thicket rat
Grammomys cometes - Mozambique thicket rat
Grammomys dolichurus - woodland thicket rat
Grammomys dryas - forest thicket rat
Grammomys gigas - giant thicket rat
Grammomys ibeanus - Ruwenzori thicket rat
Grammomys kuru - eastern rainforest grammomys
Grammomys macmillani - Macmillan's thicket rat
Grammomys minnae - Ethiopian thicket rat
Grammomys poensis - western rainforest grammomys
Grammomys selousi - Selous thicket rat
Grammomys surdaster? - African woodland thicket rat
Genus Hadromys
Hadromys humei - Manipur bush rat
Hadromys loujacobsi (extinct)
Hadromys yunnanensis - Yunnan hadromys
Genus Haeromys
Haeromys margarettae - ranee mouse
Haeromys minahassae - Minahassa ranee mouse
Haeromys pusillus - lesser ranee mouse
Genus Hapalomys
Hapalomys delacouri - Delacour's marmoset rat
Hapalomys gracilis (extinct)
Hapalomys longicaudatus - marmoset rat
Hapalomys suntsovi - Suntsov's marmoset rat
Genus Heimyscus
Heimyscus fumosus - African smoky mouse
Genus Hybomys
Hybomys badius - Cameroon highland hybomys
Hybomys basilii - Father Basilio's striped mouse
Hybomys lunaris - moon striped mouse
Hybomys planifrons - Miller's striped mouse
Hybomys trivirgatus - Temminck's striped mouse
Hybomys univittatus - Peter's striped mouse
Genus Hydromys
Hydromys chrysogaster - water rat or rakali
Hydromys hussoni - Western water rat
Hydromys neobrittanicus - New Britain water rat
Hydromys ziegleri - Ziegler's water rat
Genus Hylomyscus
Hylomyscus aeta - beaded wood mouse
Hylomyscus alleni - Allen's wood mouse
Hylomyscus anselli - Ansell's wood mouse
Hylomyscus arcimontensis - Arc Mountain wood mouse
Hylomyscus baeri - Baer's wood mouse
Hylomyscus carillus - Angolan wood mouse
Hylomyscus denniae - montane wood mouse
Hylomyscus endorobae - Mount Kenya wood mouse
Hylomyscus grandis - Mount Oku hylomyscus
Hylomyscus heinrichorum - Heinrich's wood mouse
Hylomyscus kerbispeterhansi - Kerbis Peterhans's wood mouse
Hylomyscus mpungamachagorum - Mahale wood mouse
Hylomyscus pamfi - Dahomey Gap wood mouse
Hylomyscus parvus - little wood mouse
Hylomyscus pygmaeus - Pygmy wood mouse
Hylomyscus simus - Flat-nosed wood mouse
Hylomyscus stanleyi - Stanley's wood mouse
Hylomyscus stella - Stella wood mouse
Hylomyscus thornesmithae - Mother Ellen's wood mouse
Hylomyscus vulcanorum - Albertine Rift wood mouse
Hylomyscus walterverheyeni - Walter Verheyeni's mouse
Genus Hyomys
Hyomys dammermani - Western white-eared giant rat
Hyomys goliath - Eastern white-eared giant rat
Genus Kadarsanomys
Kadarsanomys sodyi - Sody's tree rat
Genus Komodomys
Komodomys rintjanus - Komodo rat
Genus Lamottemys
Lamottemys okuensis - Mt. Oku rat
Genus Leggadina
Leggadina forresti - Forrest's mouse
Leggadina lakedownensis - Lakeland Downs mouse
Genus Lemniscomys
Lemniscomys barbarus - Barbary striped grass mouse
Lemniscomys bellieri - Bellier's striped grass mouse
Lemniscomys griselda - Griselda's striped grass mouse
Lemniscomys hoogstraali - Hoogstral's striped grass mouse
Lemniscomys linulus - Senegal one-striped grass mouse
Lemniscomys macculus - buffoon striped grass mouse
Lemniscomys mittendorfi - Mittendorf's striped grass mouse
Lemniscomys rosalia - single-striped grass mouse
Lemniscomys roseveari - Rosevear's striped grass mouse
Lemniscomys striatus - typical striped grass mouse
Lemniscomys zebra - Heuglin's lemniscomys
Genus Lenomys
Lenomys grovesi - Groves's giant rat (extinct)
Lenomys meyeri - trefoil-toothed giant rat
Genus Lenothrix
Lenothrix canus - gray tree rat
Genus Leopoldamys
Leopoldamys ciliatus - Sundaic mountain leopoldamys
Leopoldamys diwangkarai - Diwangkara's long-tailed giant rat
Leopoldamys edwardsi - Edwards's long-tailed giant rat
Leopoldamys milleti - Millet's leopoldamys
Leopoldamys neilli - Neill's long-tailed giant rat
Leopoldamys sabanus - long-tailed giant rat
Leopoldamys siporanus - Mentawai long-tailed giant rat
Genus Leporillus
Leporillus apicalis - lesser stick-nest rat
Leporillus conditor - greater stick-nest rat
Genus Leptomys
Leptomys arfakensis - Arfak water rat
Leptomys elegans - Long-footed water rat
Leptomys ernstmayri - Ernst Mayr's water rat
Leptomys paulus - Small water rat
Leptomys signatus - Fly River water rat
Genus Limnomys
Limnomys bryophilus - gray-bellied limnomys
Limnomys sibuanus - Mindanao mountain rat
Genus Lorentzimys
Lorentzimys nouhuysi - New Guinean jumping mouse
Genus Macruromys
Macruromys elegans - western small-toothed rat
Macruromys major - eastern small-toothed rat
Genus Madromys
Madromys blanfordi - Blanford's madromys
Genus Malacomys
Malacomys cansdalei - Cansdale's swamp rat
Malacomys edwardsi - Edward's swamp rat
Malacomys longipes - big-eared swamp rat
Genus Mallomys
Mallomys aroaensis - De Vis's woolly rat
Mallomys gunung - alpine woolly rat
Mallomys istapantap - subalpine woolly rat
Mallomys rothschildi - Rothschild's woolly rat
Mallomys sp. nov - Bosavi woolly rat
Mallomys sp. nov - Arfak woolly rat
Mallomys sp. nov - Foja woolly rat
Genus Mammelomys
Mammelomys lanosus - highland mammelomys
Mammelomys rattoides - lowland mammelomys
Genus Margaretamys
Margaretamys beccarii - Beccari's margareta rat
Margaretamys christinae - Christine's margareta rat
Margaretamys elegans - elegant margareta rat
Margaretamys parvus - little margareta rat
Genus Mastacomys
Mastacomys fuscus - Broad-toothed mouse
Genus Mastomys
Mastomys angolensis - Angolan multimammate mouse
Mastomys awashensis - Awash mastomys
Mastomys coucha - southern multimammate mouse
Mastomys erythroleucus - Guinea multimammate mouse
Mastomys huberti - Hubert's mastomys
Mastomys kollmannspergeri - Kollmannsperger's mastomys
Mastomys natalensis - Hildebrandt's multimammate mouse
Mastomys shortridgei - Shortridge's multimammate mouse
Genus Maxomys
Maxomys alticola - Mountain spiny rat
Maxomys baeodon - small Bornean maxomys
Maxomys bartelsii - Bartels's spiny rat
Maxomys dollmani - Dollman's spiny rat
Maxomys hellwaldii - Hellwald's spiny rat
Maxomys hylomyoides - Sumatran spiny rat
Maxomys inas - Malayan mountain spiny rat
Maxomys inflatus - Fat-nosed spiny rat
Maxomys moi - Mo's spiny rat
Maxomys musschenbroekii - Musschenbroek's spiny rat
Maxomys ochraceiventer - Chestnut-bellied spiny rat
Maxomys pagensis - Pagai spiny rat
Maxomys panglima - Palawan spiny rat
Maxomys rajah - Rajah spiny rat
Maxomys surifer - Red spiny rat
Maxomys tajuddinii - Tajuddin's spiny rat
Maxomys wattsi - Watts's spiny rat
Maxomys whiteheadi - Whitehead's spiny rat
Genus Melasmothrix
Melasmothrix naso - Sulawesian shrew rat
Genus Melomys
Melomys aerosus - dusky mosaic-tailed rat
Melomys arcium - Rossel Island melomys
Melomys bannisteri - Great Key Island melomys
Melomys bougainville - Bougainville mosaic-tailed rat
Melomys burtoni - grassland mosaic-tailed rat
Melomys capensis - Cape York mosaic-tailed rat
Melomys caurinus - short-tailed Talaud melomys
Melomys cervinipes - fawn-footed mosaic-tailed rat
Melomys cooperae - Yamdena Island melomys
Melomys dollmani - Dollman's melomys
Melomys fraterculus - Manusela mosaic-tailed rat
Melomys frigicola - Snow Mountains grassland melomys
Melomys fulgens - Seram long-tailed melomys
Melomys howi - Riama Island melomys
Melomys leucogaster - white-bellied mosaic-tailed rat
Melomys lutillus - Papua grassland melomys
Melomys matambuai - Manus Island melomys
Melomys obiensis - Obi mosaic-tailed rat
Melomys paveli - Pavel's Seram melomys
Melomys rubicola - Bramble Cay mosaic-tailed rat
Melomys rufescens - black-tailed mosaic-tailed rat
Melomys spechti - Specht's mosaic-tailed rat
Melomys talaudium - long-tailed Talaud melomys
Genus Mesembriomys [incomplete species listing?]
Mesembriomys gouldii - black-footed tree-rat
Mesembriomys macrurus - Golden-backed tree-rat
Genus Microhydromys
Microhydromys musseri - Musser's shrew mouse
Microhydromys richardsoni - groove-toothed shrew mouse
Genus Micromys
Micromys bendai (extinct)
Micromys caesaris (extinct)
Micromys chalceus (extinct)
Micromys cingulatus (extinct)
Micromys coronensis (extinct)
Micromys erythrotis - Indochinese harvest mouse
Micromys kozaniensis (extinct)
Micromys liui (extinct)
Micromys minutus - Eurasian harvest mouse
Micromys paricioi (extinct)
Micromys praeminutus (extinct)
Micromys steffensi (extinct)
Genus Millardia
Millardia gleadowi - sand-colored soft-furred rat
Millardia kathleenae - Miss Ryley's soft-furred rat
Millardia kondana - Kondana soft-furred rat
Millardia meltada - soft-furred rat
Genus Mirzamys
Mirzamys louiseae - Mirza's western moss rat
Mirzamys norahae - Mirza's eastern moss rat
Genus Montemys
Montemys delectorum - delectable soft-furred mouse
Genus Muriculus
Muriculus imberbis - striped-back mouse
Genus Mus
Mus baoulei - Baoule's mouse
Mus booduga - Little Indian field mouse
Mus bufo - Toad mouse
Mus callewaerti - Callewaert's mouse
Mus caroli - Ryukyu mouse
Mus cervicolor - Fawn-coloured mouse
Mus cookii - Cook's mouse
Mus crociduroides - Sumatran shrewlike mouse
Mus cypriacus - Cypriot mouse
Mus famulus - Servant mouse
Mus fernandoni - Ceylon spiny mouse
Mus fragilicauda - Sheath-tailed mouse
Mus goundae - Gounda mouse
Mus haussa - Hausa mouse
Mus indutus - desert pygmy mouse
Mus lepidoides - Little Burmese field mouse
Mus macedonicus - Macedonian mouse
Mus mahomet - Mahomet mouse
Mus mattheyi - Matthey's mouse
Mus mayori - Mayor's mouse
Mus minutoides - African pygmy mouse
Mus musculoides - Temminck's mouse
Mus musculus - House mouse
Mus musculus domesticus - Western European house mouse
Mus musculus molossinus - Japanese house mouse
Mus neavei - Neave's mouse
Mus nitidulus - Blyth's mouse
Mus orangiae - Free State pygmy mouse/orange mouse
Mus oubanguii - Oubangui mouse
Mus pahari - Gairdner's shrewmouse
Mus phillipsi - Phillips's mouse
Mus platythrix - Flat-haired mouse
Mus saxicola - Rock-loving mouse
Mus setulosus - Peters's mouse
Mus setzeri - Setzer's pygmy mouse
Mus shortridgei - Shortridge's mouse
Mus sorella - Thomas's pygmy mouse
Mus spicilegus - Mound-building mouse/steppe mouse
Mus spretus - Algerian mouse
Mus tenellus - Delicate mouse
Mus terricolor - Earth-coloured mouse
Mus triton - Gray-bellied pygmy mouse
Mus vulcani - Volcano mouse
Genus Musseromys
Musseromys anacuao - Sierra Madre tree-mouse
Musseromys beneficus - Mount Pulag tree-mouse
Musseromys gulantang - Banahaw tree mouse
Musseromys inopinatus - Amuyao tree-mouse
Genus Mylomys
Mylomys dybowskii - African groove-toothed rat
Mylomys rex - Ethiopian mylomys
Genus Myomyscus
Myomyscus verreauxii - Verreaux's white-footed rat
Genus Nesokia
Nesokia bunnii - Bunn's short-tailed bandicoot rat
Nesokia indica - short-tailed bandicoot rat
Genus Nesoromys
Nesoromys ceramicus - Seram Island mountain rat
Genus Nilopegamys
Nilopegamys plumbeus - Ethiopian amphibious rat
Genus Niviventer
Niviventer andersoni - Anderson's white-bellied rat
Niviventer brahma - Brahma white-bellied rat
Niviventer bukit - Bukit white-bellied rat
Niviventer cameroni - Cameron highlands niviventer
Niviventer confucianus - Chinese white-bellied rat
Niviventer coninga - spiny Taiwan niviventer
Niviventer cremoriventer - dark-tailed tree rat
Niviventer culturatus - Oldfield white-bellied rat
Niviventer eha - smoke-bellied rat
Niviventer excelsior - large white-bellied rat
Niviventer fengi - Tibetan white-bellied rat
Niviventer fraternus - montane Sumatran niviventer
Niviventer fulvescens - chestnut white-bellied rat
Niviventer hinpoon - limestone rat
Niviventer huang - South China white-bellied rat
Niviventer langbianis - Lang Bian white-bellied rat
Niviventer lepturus - narrow-tailed white-bellied rat
Niviventer lotipes - Hainan white-bellied rat
Niviventer mekongis - Mekong white-bellied rat
Niviventer niviventer - white-bellied rat
Niviventer rapit - long-tailed mountain rat
Niviventer tenaster - Tenasserim white-bellied rat
Genus Notomys
Notomys alexis - Spinifex hopping mouse
Notomys amplus - Short-tailed hopping mouse (extinct)
Notomys aquilo - Northern hopping mouse
Notomys cervinus - Fawn hopping mouse
Notomys fuscus - Dusky hopping mouse
Notomys longicaudatus - Long-tailed hopping mouse (extinct)
Notomys mitchellii - Mitchell's hopping mouse
Notomys macrotis - Big-eared hopping mouse (extinct)
Notomys mordax - Darling Downs hopping mouse (extinct)
Notomys robustus - Great hopping mouse (extinct)
Genus Ochromyscus
Ochromyscus brockmani - Brockman's rock mouse
Ochromyscus yemeni - Yemeni mouse
Genus Oenomys
Oenomys hypoxanthus - rufous-nosed rat
Oenomys hypoxanthus albiventris
Oenomys ornatus - Ghana rufous-nosed rat
Oenomys tiercelini
Genus Palawanomys
Palawanomys furvus - Palawan soft-furred mountain rat
Genus Papagomys
Papagomys armandvillei - Flores giant rat
Papagomys theodorverhoeveni - Verhoeven's giant tree rat (extinct)
Genus Parahydromys
Parahydromys asper - New Guinea waterside rat
Genus Paraleptomys
Paraleptomys rufilatus - northern water rat
Paraleptomys wilhelmina - short-haired water rat
Genus Paramelomys
Paramelomys gressitti - Gressitt's paramelomys
Paramelomys levipes - Papuan lowland paramelomys
Paramelomys lorentzii - Lorentz's paramelomys
Paramelomys mollis - montane soft-furred paramelomys
Paramelomys moncktoni - Monckton's paramelomys
Paramelomys naso - long-nosed paramelomys
Paramelomys platyops - common lowland paramelomys
Paramelomys rubex - mountain paramelomys
Paramelomys steini - Stein's paramelomys
Genus Paruromys
Paruromys dominator - Sulawesi bear rat
Genus Paulamys
Paulamys naso - Flores long-nosed rat
Genus Pelomys
Pelomys campanae - bell groove-toothed swamp rat
Pelomys fallax - creek groove-toothed swamp rat
Pelomys hopkinsi - Hopkins's groove-toothed swamp rat
Pelomys isseli - Issel's groove-toothed swamp rat
Pelomys minor - least groove-toothed swamp rat
Genus Phloeomys
Phloeomys cumingi - southern Luzon giant cloud rat
Phloeomys pallidus - northern Luzon giant cloud rat
Genus Pithecheir
Pithecheir melanurus - red tree rat
Pithecheir parvus - Malayan tree rat
Genus Pithecheirops
Pithecheirops otion - Bornean pithecheirops
Genus Pogonomelomys
Pogonomelomys brassi - Grey pogonomelomys
Pogonomelomys bruijni - lowland brush mouse
Pogonomelomys mayeri - Shaw Mayer's brush mouse
Genus Pogonomys
Pogonomys championi - Champion's tree mouse
Pogonomys fergussoniensis - D'Entrecasteaux Archipelago pogonomys
Pogonomys loriae - large tree mouse
Pogonomys macrourus - chestnut tree mouse
Pogonomys mollipilosus - Prehensile-tailed rat
Pogonomys sylvestris - gray-bellied tree mouse
Genus Praomys
Praomys coetzeei - Coetzee's soft-furred mouse
Praomys daltoni - Dalton's praomys
Praomys degraaffi - De Graaff's praomys
Praomys derooi - Deroo's praomys
Praomys hartwigi - Hartweg's soft-furred mouse
Praomys jacksoni - Jackson's soft-furred mouse
Praomys minor - least soft-furred mouse
Praomys misonnei - Misonne's soft-furred mouse
Praomys morio - Cameroon soft-furred mouse
Praomys mutoni - Muton's soft-furred mouse
Praomys obscurus - Gotel Mountain praomys
Praomys petteri - Petter's praomys
Praomys rostratus - forest soft-furred mouse
Praomys tullbergi - Tullberg's soft-furred mouse
Genus Protochromys
Protochromys fellowsi - Papuan protochromys
Genus Pseudohydromys
Pseudohydromys berniceae - Bishop's moss mouse
Pseudohydromys carlae - Huon small-toothed moss mouse
Pseudohydromys eleanorae - Laurie's moss mouse
Pseudohydromys ellermani - Shaw Mayer's shrew mouse
Pseudohydromys fuscus - mottled-tailed shrew mouse
Pseudohydromys germani - German's one-toothed moss mouse
Pseudohydromys murinus - eastern shrew mouse
Pseudohydromys musseri - Musser's shrew mouse
Pseudohydromys occidentalis - western shrew mouse
Pseudohydromys patriciae - Woolley's moss mouse
Pseudohydromys pumehanae - Southern small-toothed moss mouse
Pseudohydromys sandrae - White-bellied moss mouse
Genus Pseudomys
Pseudomys albocinereus - Ash-grey mouse
Pseudomys apodemoides - Silky mouse
Pseudomys australis - Plains rat
Pseudomys bolami - Bolam's mouse
Pseudomys calabyi - Kakadu pebble-mound mouse
Pseudomys chapmani - Western pebble-mound mouse
Pseudomys delicatulus - Little native mouse
Pseudomys desertor - Desert mouse
Pseudomys fieldi?
Pseudomys fumeus - Smoky mouse
Pseudomys glaucus - Blue-gray mouse (possibly extinct)
Pseudomys gouldii - Gould's mouse
Pseudomys gracilicaudatus - Eastern chestnut mouse
Pseudomys hermannsburgensis - Sandy inland mouse
Pseudomys higginsi - Long-tailed mouse
Pseudomys johnsoni - Central pebble-mound mouse
Pseudomys laborifex?
Pseudomys nanus - Western chestnut mouse
Pseudomys novaehollandiae - New Holland mouse
Pseudomys occidentalis - Western mouse
Pseudomys oralis - Hastings River mouse
Pseudomys patrius - Country mouse
Pseudomys pilligaensis - Pilliga mouse
Pseudomys praeconis?
Pseudomys shortridgei - Heath mouse
Pseudomys vandycki (extinct)
Genus Rattus
Rattus adustus - Sunburned rat
Rattus andamanensis - Sikkim rat
Rattus arfakiensis - Vogelkop mountain rat
Rattus argentiventer - Ricefield rat
Rattus arrogans - Western New Guinea mountain rat
Rattus baluensis - Summit rat
Rattus blangorum - Aceh rat
Rattus bontanus - Bonthain rat
Rattus burrus - Nonsense rat
Rattus colletti - Dusky rat
Rattus detentus - Manus Island spiny rat
Rattus elaphinus - Sula rat
Rattus enganus - Enggano rat
Rattus everetti - Philippine forest rat
Rattus exulans - Polynesian rat
Rattus facetus - Lore Lindu xanthurus rat
Rattus feliceus - Spiny Ceram rat
Rattus foramineus?
Rattus fuscipes - bush rat
Rattus giluwensis - Giluwe rat
Rattus hainaldi - Hainald's rat
Rattus hoffmanni - Hoffmann's rat
Rattus hoogerwerfi - Hoogerwerf's rat
Rattus jobiensis - Japen rat
Rattus koopmani - Koopman's rat
Rattus korinchi - Korinch's rat
Rattus leucopus - Cape York rat
Rattus losea - Lesser ricefield rat
Rattus lugens - Mentawai rat
Rattus lutreolus - Australian swamp rat
Rattus macleari - Maclear's rat
Rattus marmosurus - Opossum rat
Rattus mindorensis - Mindoro black rat
Rattus mollicomulus - Little soft-furred rat
Rattus montanus - Nillu rat
Rattus mordax - Eastern rat
Rattus morotaiensis - Molaccan prehensile-tailed rat
Rattus nativitatis - bulldog rat, extinct (1903)
Rattus nikenii - Gag Island rat
Rattus niobe - Moss-forest rat
Rattus nitidus - Himalayan field rat
Rattus norvegicus - Brown rat
Rattus novaeguineae - New Guinean rat
Rattus omichlodes - Arianus's rat
Rattus osgoodi - Osgood's rat
Rattus palmarum - Palm rat
Rattus pelurus - Peleng rat
Rattus pococki - Pocock's highland rat
Rattus praetor - Large New Guinea spiny rat
Rattus pyctoris - Turkestan rat
Rattus ranjiniae - Kerala rat
Rattus rattus - Black rat
Rattus richardsoni - Glacier rat
Rattus sakeratensis - little Indochinese field rat
Rattus salocco - Southeastern xanthurus rat
Rattus sanila - New Ireland forest rat
Rattus satarae - Sahyadris forest rat
Rattus sikkimensis?
Rattus simalurensis - Simalur rat
Rattus sordidus - Dusky field rat
Rattus steini - Stein's rat
Rattus stoicus - Andaman rat
Rattus tanezumi - Tanezumi rat
Rattus tawitawiensis - Tawitawi forest rat
Rattus timorensis - Timor rat
Rattus tiomanicus - Malayan field rat
Rattus tunneyi - Pale field rat
Rattus turkestanicus?
Rattus vandeuseni - Van Deusen's rat
Rattus verecundus - Slender rat
Rattus villosissimus - Long-haired rat
Rattus xanthurus - Yellow-tailed rat
Genus Serengetimys
Serengetimys pernanus - dwarf multimammate mouse
Genus Rhabdomys
Rhabdomys dilectus - mesic four-striped grass rat
Rhabdomys pumilio - Four-striped grass mouse
Genus Rhynchomys
Rhynchomys banahao - Banahao shrew-rat
Rhynchomys isarogensis - Isarog shrew-rat
Rhynchomys labo - Labo shrew rat
Rhynchomys mingan - Mingan shrew-rat
Rhynchomys soricoides - Mt. Data shrew-rat
Rhynchomys tapulao - Tapulao shrew-rat
Genus Saxatilomys
Saxatilomys paulinae - Paulina's limestone rat
Genus Solomys
Solomys ponceleti - Poncelet's naked-tailed rat
Solomys salamonis - Florida naked-tailed rat
Solomys salebrosus - Bougainville naked-tailed rat
Solomys sapientis - Isabel naked-tailed rat
Solomys spriggsarum - Buka naked-tailed rat (extinct)
Genus Soricomys
Soricomys kalinga - Kalinga shrew mouse
Soricomys leonardocoi - Leonardo shrew mouse
Soricomys montanus - Southern Cordillera shrew-mouse
Soricomys musseri - Sierra Madre shrew-mouse
Genus Sommeromys
Sommeromys macrorhinos - Sommer's Sulawesi rat
Genus Spelaeomys
Spelaeomys florensis - Flores cave rat
Genus Srilankamys
Srilankamys ohiensis - Ohiya rat
Genus Stenocephalemys
Stenocephalemys albipes - white-footed stenocephalemys
Stenocephalemys albocaudata - Ethiopian narrow-headed rat
Stenocephalemys griseicauda - gray-tailed narrow-headed rat
Stenocephalemys ruppi - Rupp's stenocephalemys
Stenocephalemys sokolovi - Sokolov's Ethiopian rat
Stenocephalemys zimai - Zima's Ethiopian rat
Genus Stochomys
Stochomys longicaudatus - target rat
Genus Sundamys
Sundamys annandalei - Annandale's rat
Sundamys infraluteus - mountain giant rat
Sundamys maxi - Bartels's rat
Sundamys muelleri - Mueller's giant Sunda rat
Genus Taeromys
Taeromys arcuatus - Salokko rat
Taeromys callitrichus - lovely-haired rat
Taeromys celebensis - Celebes rat
Taeromys hamatus - Sulawesi montane rat
Taeromys microbullatus - small-eared taeromys
Taeromys punicans - Sulawesi forest rat
Taeromys taerae - Tondano rat
Genus Tarsomys
Tarsomys apoensis - long-footed rat
Tarsomys echinatus - spiny long-footed rat
Genus Tateomys
Tateomys macrocercus - Long-tailed shrew rat
Tateomys rhinogradoides - Tate's shrew rat
Genus Thallomys
Thallomys loringi - Loring's rat
Thallomys nigricauda - Black-tailed tree rat
Thallomys paedulcus - Acacia rat
Thallomys shortridgei - Shortridge's rat
Genus Thamnomys
Thamnomys kempi - Kemp's thicket rat
Thamnomys major - Hatt's thicket rat
Thamnomys rutilans?
Thamnomys venustus - Charming thicket rat
Genus Tokudaia
Tokudaia muenninki - Muennink's spiny rat
Tokudaia osimensis - Ryukyu spiny rat
Tokudaia tokunoshimensis - Tokunoshima spiny rat
Genus Tonkinomys
Tonkinomys daovantieni - Daovantien's limestone rat
Genus Tryphomys
Tryphomys adustus - Luzon short-nosed rat
Genus Uromys
Uromys anak - Giant naked-tailed rat
Uromys boeadii - Biak giant rat
Uromys caudimaculatus - giant white-tailed rat
Uromys emmae - Emma's giant rat
Uromys hadrourus - Masked white-tailed rat
Uromys imperator - Emperor rat
Uromys neobritanicus - Bismarck giant rat
Uromys porculus - Guadalcanal rat
Uromys rex - King rat
Uromys siebersi - Great Key Island giant rat
Uromys vika - Vangunu giant rat
Genus Vandeleuria
Vandeleuria nilagirica - Nilgiri long-tailed tree mouse
Vandeleuria nolthenii - Nolthenius's long-tailed climbing mouse
Vandeleuria oleracea - Asiatic long-tailed climbing mouse
Genus Vernaya
Vernaya foramena
Vernaya fulva - red climbing mouse
Vernaya meiguites
Vernaya nushanensis
Vernaya prefulva (extinct)
Vernaya pristina (extinct)
Vernaya giganta (extinct)
Vernaya wushanica (extinct)
Genus Xenuromys
Xenuromys barbatus - Mimic tree rat
Genus Xeromys
Xeromys myoides - false water rat
Genus Zelotomys
Zelotomys hildegardeae - Hildegarde's broad-headed mouse
Zelotomys woosnami - Woosnam's broad-headed mouse
Genus Zyzomys
Zyzomys argurus - common rock rat
Zyzomys maini - Arnhem Land rock rat
Zyzomys palatilis - Carpentarian rock rat
Zyzomys pedunculatus - central rock rat
Zyzomys woodwardi - Kimberley rock rat
See also
Mammal classification
References
Rodentia
Rodents
Rodents | List of rodents | [
"Biology"
] | 38,891 | [
"Lists of biota",
"Lists of animals",
"Animals"
] |
14,355,284 | https://en.wikipedia.org/wiki/Smallest-circle%20problem | The smallest-circle problem (also known as minimum covering circle problem, bounding circle problem, least bounding circle problem, smallest enclosing circle problem) is a computational geometry problem of computing the smallest circle that contains all of a given set of points in the Euclidean plane. The corresponding problem in n-dimensional space, the smallest bounding sphere problem, is to compute the smallest n-sphere that contains all of a given set of points. The smallest-circle problem was initially proposed by the English mathematician James Joseph Sylvester in 1857.
The smallest-circle problem in the plane is an example of a facility location problem (the 1-center problem) in which the location of a new facility must be chosen to provide service to a number of customers, minimizing the farthest distance that any customer must travel to reach the new facility. Both the smallest circle problem in the plane, and the smallest bounding sphere problem in any higher-dimensional space of bounded dimension are solvable in worst-case linear time.
Characterization
Most of the geometric approaches for the problem look for points that lie on the boundary of the minimum circle and are based on the following simple facts:
The minimum covering circle is unique.
The minimum covering circle of a set S can be determined by at most three points in S which lie on the boundary of the circle. If it is determined by only two points, then the line segment joining those two points must be a diameter of the minimum circle. If it is determined by three points, then the triangle consisting of those three points is not obtuse.
Let be any set of points in the plane, and suppose that there are two smallest enclosing disks of , with centers at and . Let be their shared radius, and let be the distance between their centers. Since is a subset of both disks it is a subset of their intersection. However, their intersection is contained within the disk with center and radius , as shown in the following image:
Since is minimal, we must have , meaning , so the disks are identical.
Linear-time solutions
As Nimrod Megiddo showed, the minimum enclosing circle can be found in linear time, and the same linear time bound also applies to the smallest enclosing sphere in Euclidean spaces of any constant dimension. His article also gives a brief overview of earlier and algorithms; in doing so, Megiddo demonstrated that Shamos and Hoey's conjecture – that a solution to the smallest-circle problem was computable in at best – was false.
Emo Welzl proposed a simple randomized algorithm for the
minimum covering circle problem that runs in expected time , based on a linear programming algorithm of Raimund Seidel.
Subsequently, the smallest-circle problem was included in a general class of LP-type problems that can be solved by algorithms like Welzl's based on linear programming. As a consequence of membership in this class, it was shown that the dependence on the dimension of the constant factor in the time bound, which was factorial for Seidel's method, could be reduced to subexponential.
Welzl's minidisk algorithm has been extended to handle Bregman divergences which include the squared Euclidean distance.
Megiddo's algorithm
Megiddo's algorithm is based on the technique called prune and search, reducing the size of the problem by removing unnecessary points.
That leads to the recurrence giving .
The algorithm is rather complicated and it is reflected by its big multiplicative constant.
The reduction needs to solve twice the similar problem where the center of the sought-after enclosing circle is constrained to lie on a given line.
The solution of the subproblem is either the solution of the unconstrained problem or it is used to determine the half-plane where the unconstrained solution center is located.
The points to be discarded are found as follows:
The points are arranged into pairs which defines lines as their bisectors.
The median average of bisectors in order by their directions (oriented to the same half-plane determined by bisector ) is found and pairs of bisectors are made, such that in each pair one bisector has direction at most and the other at least
(direction could be considered as − or + according our needs.) Let be the intersection of the bisectors in the -th pair.
The line q in the direction is placed to go through an intersection such that there are intersections in each half-plane defined by the line (median position).
The constrained version of the enclosing problem is run on the line q' which determines half-plane where the center is located.
The line q′ in the direction is placed to go through an intersection such that there are intersections in each half of the half-plane not containing the solution.
The constrained version of the enclosing problem is run on line q′ which together with q determines the quadrant where the center is located.
We consider the points in the quadrant not contained in a half-plane containing the solution.
One of the bisectors of the pair defining has the direction ensuring which of points defining the bisector is closer to each point in the quadrant containing the center of the enclosing circle. This point could be discarded.
The constrained version of the algorithm is also solved by the prune and search technique, but reducing the problem size by removal of points leading to recurrence
giving .
The points to be discarded are found as follows:
Points are arranged into pairs.
For each pair, the intersection of its bisector with the constraining line is found (If this intersection does not exist we could remove one point from the pair immediately).
The median of points on the line is found and in O(n) time is determined which halfline of starting in
contains the solution of the constrained problem.
We consider points from the other half.
We know which of the points defining is closer to the each point of the halfline containing center of the enclosing circle of the constrained problem solution. This point could be discarded.
The half-plane where the unconstrained solution lies could be determined by the points on the boundary of the constrained circle solution. (The first and last point on the circle in each half-plane suffice. If the center belongs to their convex hull, it is unconstrained solution, otherwise the direction to the nearest edge determines the half-plane of the unconstrained solution.)
Welzl's algorithm
The algorithm is recursive.
The initial input is a set P of points. The algorithm selects one point p randomly and uniformly from P, and recursively finds the minimal circle containing P – {p}, i.e. all of the other points in P except p. If the returned circle also encloses p, it is the minimal circle for the whole of P and is returned.
Otherwise, point p must lie on the boundary of the result circle. It recurses, but with the set R of points known to be on the boundary as an additional parameter.
The recursion terminates when P is empty, and a solution can be found from the points in R: for 0 or 1 points the solution is trivial, for 2 points the minimal circle has its center at the midpoint between the two points, and for 3 points the circle is the circumcircle of the triangle described by the points. (In three dimensions, 4 points require the calculation of the circumsphere of a tetrahedron.)
Recursion can also terminate when R has size 3 (in 2D, or 4 in 3D) because the remaining points in P must lie within the circle described by R.
algorithm welzl is
input: Finite sets P and R of points in the plane |R| ≤ 3.
output: Minimal disk enclosing P with R on the boundary.
if P is empty or |R| = 3 then
return trivial(R)
choose p in P (randomly and uniformly)
D := welzl(P − {p}, R)
if p is in D then
return D
return welzl( − {p}, R ∪ {p})
Welzl's paper states that it is sufficient to randomly permute the input at the start, rather than performing independently random choices of p on each recursion.
It also states that performance is improved by dynamically re-ordering the points so that those that are found to be outside a circle are subsequently considered earlier, but this requires a change in the structure of the algorithm to store P as a "global".
Other algorithms
Prior to Megiddo's result showing that the smallest-circle problem may be solved in linear time, several algorithms of higher complexity appeared in the literature. A naive algorithm solves the problem in time O(n4) by testing the circles determined by all pairs and triples of points.
An algorithm of Chrystal and Peirce applies a local optimization strategy that maintains two points on the boundary of an enclosing circle and repeatedly shrinks the circle, replacing the pair of boundary points, until an optimal circle is found. Chakraborty and Chaudhuri propose a linear-time method for selecting a suitable initial circle and a pair of boundary points on that circle. Each step of the algorithm includes as one of the two boundary points a new vertex of the convex hull, so if the hull has h vertices this method can be implemented to run in time O(nh).
Elzinga and Hearn described an algorithm which maintains a covering circle for a subset of the points. At each step, a point not covered by the current sphere is used to find a larger sphere that covers a new subset of points, including the point found. Although its worst case running time is O(h3n), the authors report that it ran in linear time in their experiments. The complexity of the method has been analyzed by Drezner and Shelah. Both Fortran and C codes are available from .
The smallest sphere problem can be formulated as a quadratic program defined by a system of linear constraints with a convex quadratic objective function. Therefore, any feasible direction algorithm can give the solution of the problem. Hearn and Vijay proved that the feasible direction approach chosen by Jacobsen is equivalent to the Chrystal–Peirce algorithm.
The dual to this quadratic program may also be formulated explicitly; an algorithm of Lawson can be described in this way as a primal dual algorithm.
Shamos and Hoey proposed an O(n log n) time algorithm for the problem based on the observation that the center of the smallest enclosing circle must be a vertex of the farthest-point Voronoi diagram of the input point set.
Weighted variants of the problem
The weighted version of the minimum covering circle problem takes as input a set of points in a Euclidean space, each with weights; the goal is to find a single point that minimizes the maximum weighted distance (i.e., distance multiplied by the corresponding weight) to any point. The original (unweighted) minimum covering circle problem corresponds to the case when all weights are equal to 1. As with the unweighted problem, the weighted problem may be solved in linear time in any space of bounded dimension, using approaches closely related to bounded dimension linear programming algorithms, although slower algorithms are again frequent in the literature.
Smallest enclosing balls in non-Euclidean geometry
The smallest enclosing ball of a finite point set has been studied in Riemannian geometry including Cartan-Hadamard manifolds.
See also
Bounding sphere
1-center problem
Circumscribed circle
Closest string
Jung's Theorem
Minimum-diameter spanning tree
References
External links
Bernd Gärtner's smallest enclosing ball code
CGAL the Min_sphere_of_spheres package of the Computational Geometry Algorithms Library (CGAL)
Miniball an open-source implementation of an algorithm for the smallest enclosing ball problem for low and moderately high dimensions
Computational geometry
Combinatorial optimization
Circles | Smallest-circle problem | [
"Mathematics"
] | 2,469 | [
"Circles",
"Computational mathematics",
"Pi",
"Computational geometry"
] |
14,355,539 | https://en.wikipedia.org/wiki/Nucleotide%20sugars%20metabolism | In nucleotide sugar metabolism a group of biochemicals known as nucleotide sugars act as donors for sugar residues in the glycosylation reactions that produce polysaccharides. They are substrates for glycosyltransferases. The nucleotide sugars are also intermediates in nucleotide sugar interconversions that produce some of the activated sugars needed for glycosylation reactions. Since most glycosylation takes place in the endoplasmic reticulum and golgi apparatus, there are a large family of nucleotide sugar transporters that allow nucleotide sugars to move from the cytoplasm, where they are produced, into the organelles where they are consumed.
Nucleotide sugar metabolism is particularly well-studied in yeast, fungal pathogens, and bacterial pathogens, such as E. coli and Mycobacterium tuberculosis, since these molecules are required for the synthesis of glycoconjugates on the surfaces of these organisms. These glycoconjugates are virulence factors and components of the fungal and bacterial cell wall. These pathways are also studied in plants, but here the enzymes involved are less well understood.
References
Metabolism | Nucleotide sugars metabolism | [
"Chemistry",
"Biology"
] | 259 | [
"Biotechnology stubs",
"Biochemistry stubs",
"Cellular processes",
"Biochemistry",
"Metabolism"
] |
14,356,754 | https://en.wikipedia.org/wiki/Hatta%20number | The Hatta number (Ha) was developed by Shirôji Hatta (1895-1973 ) in 1932, who taught at Tohoku University from 1925 to 1958. It is a dimensionless parameter that compares the rate of reaction in a liquid film to the rate of diffusion through the film. For a second order reaction (), the maximum rate of reaction assumes that the liquid film is saturated with gas at the interfacial concentration ; thus, the maximum rate of reaction is .
For a reaction order in and order in :
For gas-liquid absorption with chemical reactions, a high Hatta number indicates the reaction is much faster than diffusion. In this case, the reaction occurs within a thin film, and the surface area limits the overall rate. Conversely, a Hatta number smaller than unity suggests the reaction is the limiting factor, and the reaction takes place in the bulk fluid, requiring larger volumes.
References
See also
Dimensionless quantity
Dimensional analysis
Catalysis
Dimensionless numbers of chemistry
Transport phenomena | Hatta number | [
"Physics",
"Chemistry",
"Engineering"
] | 202 | [
"Transport phenomena",
"Catalysis",
"Physical phenomena",
"Chemical engineering",
"Chemical reaction stubs",
"Chemical kinetics",
"Dimensionless numbers of chemistry",
"Chemical process stubs"
] |
14,356,889 | https://en.wikipedia.org/wiki/Gamow%20factor | The Gamow factor, Sommerfeld factor or Gamow–Sommerfeld factor, named after its discoverer George Gamow or after Arnold Sommerfeld, is a probability factor for two nuclear particles' chance of overcoming the Coulomb barrier in order to undergo nuclear reactions, for example in nuclear fusion. By classical physics, there is almost no possibility for protons to fuse by crossing each other's Coulomb barrier at temperatures commonly observed to cause fusion, such as those found in the Sun. When George Gamow instead applied quantum mechanics to the problem, he found that there was a significant chance for the fusion due to tunneling.
The probability of two nuclear particles overcoming their electrostatic barriers is given by the following equation:
where is the Gamow energy,
Here, is the reduced mass of the two particles. The constant is the fine-structure constant, is the speed of light, and and are the respective atomic numbers of each particle.
While the probability of overcoming the Coulomb barrier increases rapidly with increasing particle energy, for a given temperature, the probability of a particle having such an energy falls off very fast, as described by the Maxwell–Boltzmann distribution. Gamow found that, taken together, these effects mean that for any given temperature, the particles that fuse are mostly in a temperature-dependent narrow range of energies known as the Gamow window.
Derivation
Gamow first solved the one-dimensional case of quantum tunneling using the WKB approximation. Considering a wave function of a particle of mass m, we take area 1 to be where a wave is emitted, area 2 the potential barrier which has height V and width l (at ), and area 3 its other side, where the wave is arriving, partly transmitted and partly reflected. For a wave number k and energy E we get:
where and .
This is solved for given A and α by taking the boundary conditions at the both barrier edges, at and , where both and its derivative must be equal on both sides.
For , this is easily solved by ignoring the time exponential and considering the real part alone (the imaginary part has the same behavior). We get, up to factors depending on the phases which are typically of order 1, and up to factors of the order of (assumed not very large, since V is greater than E not marginally):
Next Gamow modeled the alpha decay as a symmetric one-dimensional problem, with a standing wave between two symmetric potential barriers at and , and emitting waves at both outer sides of the barriers.
Solving this can in principle be done by taking the solution of the first problem, translating it by and gluing it to an identical solution reflected around .
Due to the symmetry of the problem, the emitting waves on both sides must have equal amplitudes (A), but their phases (α) may be different. This gives a single extra parameter; however, gluing the two solutions at requires two boundary conditions (for both the wave function and its derivative), so in general there is no solution. In particular, re-writing (after translation by ) as a sum of a cosine and a sine of , each having a different factor that depends on k and α, the factor of the sine must vanish, so that the solution can be glued symmetrically to its reflection. Since the factor is in general complex (hence its vanishing imposes two constraints, representing the two boundary conditions), this can in general be solved by adding an imaginary part of k, which gives the extra parameter needed. Thus E will have an imaginary part as well.
The physical meaning of this is that the standing wave in the middle decays; the emitted waves newly emitted have therefore smaller amplitudes, so that their amplitude decays in time but grows with distance. The decay constant, denoted λ, is assumed small compared to .
λ can be estimated without solving explicitly, by noting its effect on the probability current conservation law. Since the probability flows from the middle to the sides, we have:
Note the factor of 2 is due to having two emitted waves.
Taking , this gives:
Since the quadratic dependence in is negligible relative to its exponential dependence, we may write:
Remembering the imaginary part added to k is much smaller than the real part, we may now neglect it and get:
Note that is the particle velocity, so the first factor is the classical rate by which the particle trapped between the barriers hits them.
Finally, moving to the three-dimensional problem, the spherically symmetric Schrödinger equation reads (expanding the wave function in spherical harmonics and looking at the n-th term):
Since amounts to enlarging the potential, and therefore substantially reducing the decay rate (given its exponential dependence on ), we focus on , and get a very similar problem to the previous one with , except that now the potential as a function of r is not a step function.
The main effect of this on the amplitudes is that we must replace the argument in the exponent, taking an integral of over the distance where rather than multiplying by l. We take the Coulomb potential:
where is the vacuum electric permittivity, e the electron charge, z = 2 is the charge number of the alpha particle and Z the charge number of the nucleus (Z-z after emitting the particle). The integration limits are then , where we assume the nuclear potential energy is still relatively small, and , which is where the nuclear negative potential energy is large enough so that the overall potential is smaller than E. Thus, the argument of the exponent in λ is:
This can be solved by substituting and then and solving for θ, giving:
where .
Since x is small, the x-dependent factor is of order 1.
Gamow assumed , thus replacing the x-dependent factor by , giving:
with:
which is the same as the formula given in the beginning of the article with ,
and the fine-structure constant .
For a radium alpha decay, Z = 88, z = 2 and m = 4mp, EG is approximately 50 GeV. Gamow calculated the slope of with respect to E at an energy of 5 MeV to be ~ 1014 J−1, compared to the experimental value of .
References
External links
Modeling Alpha Half-life (Georgia State University)
Nuclear physics
George Gamow | Gamow factor | [
"Physics"
] | 1,306 | [
"Nuclear physics"
] |
14,357,195 | https://en.wikipedia.org/wiki/Fides%20%28reliability%29 | Fides (Latin: trust) is a guide allowing estimated reliability calculation for electronic components and systems. The reliability prediction is generally expressed in FIT (number of failures for 109 hours) or MTBF (Mean Time Between Failures). This guide provides reliability data for RAMS (Reliability, Availability, Maintainability, Safety) studies.
Purpose
Fides is a DGA (French armament industry supervision agency) study conducted by a European consortium formed by eight industrialists from the fields of aeronautics and Defence:
Airbus France
Eurocopter
Nexter Electronics
MBDA Missiles Systems
Thales Services
Thales Airborne Systems
Thales Avionics
Thales Underwater Systems
The first aim of the Fides project was to develop a new reliability assessment method for electronic components which takes into consideration COTS (commercial off-the-shelf) and specific parts and the new technologies. The global aim is to find a replacement to the worldwide reference MIL-HDBK-217F, which is old and has not been revised since 1995 (issue F notice 2). Moreover, the MIL HDBK 217F is very pessimistic for COTS components which are more and more widely used in military and aerospace systems.
The second aim was to write a reliability engineering guide in order to provide engineering process and tools to improve reliability in the development of new electronic systems.
Method content
The Fides guide is made of two distinct parts. The first is a reliability prediction calculation method concerning main electronic component families and complete subassemblies like hard disks or LCD displays. The second part is a process control and audit guide which is a tool to assess the reliability quality and technical know-how in the operating time of the studied product, operational specification and maintenance.
Availability
The Fides guide is freely available on the Fides reliability website.
Standardization
The French standardisation organisation UTE (Union Technique de l'Electricité) has accepted the Fides publication, with the reference UTE C 80 811 (available in both French and English). An international normative reference extension (International Electrotechnical Commission) is planned for the future.
Future
Fides has met great interest and success since the end of the study in 2004. The method has been quickly declared a standard that can be applied to French military programs. For two years, the French military experts of DGA have already used FIDES method in different major programs for Defence, in missiles or tactical telecommunications fields for example.
American companies like Boeing, Japanese organisations like JAXA (Japan Aerospace Exploration Agency) as well as French companies or organisations like EDF (Electricité de France, French electricity provider) or CNES (Centre National d’Etudes Spatiales, the French space agency) showed an interest in FIDES methodology, but none of them are using FIDES at this time.
Further developments of the Fides guide (such as the improvement of existing models and the widening of the spectrum covered by component families) resulted in a new version of the Fides guide being published in the middle of year 2009.
See also
Reliability
Reliability theory
MTBF
Failure rate
References
Sources
(Software information sheet)
Further reading
External links
Fides guide website (Requires free registration to obtain the Fides guide in both English and French)
Survival analysis
Reliability engineering
Engineering statistics | Fides (reliability) | [
"Engineering"
] | 654 | [
"Systems engineering",
"Engineering statistics",
"Reliability engineering"
] |
14,357,725 | https://en.wikipedia.org/wiki/In%20vivo%20magnetic%20resonance%20spectroscopy | In vivo magnetic resonance spectroscopy (MRS) is a specialized technique associated with magnetic resonance imaging (MRI).
Magnetic resonance spectroscopy (MRS), also known as nuclear magnetic resonance (NMR) spectroscopy, is a non-invasive, ionizing-radiation-free analytical technique that has been used to study metabolic changes in brain tumors, strokes, seizure disorders, Alzheimer's disease, depression, and other diseases affecting the brain. It has also been used to study the metabolism of other organs such as muscles. In the case of muscles, NMR is used to measure the intramyocellular lipids content (IMCL).
Magnetic resonance spectroscopy is an analytical technique that can be used to complement the more common magnetic resonance imaging (MRI) in the characterization of tissue. Both techniques typically acquire signal from hydrogen protons (other endogenous nuclei such as those of Carbon, Nitrogen, and Phosphorus are also used), but MRI acquires signal primarily from protons which reside within water and fat, which are approximately a thousand times more abundant than the molecules detected with MRS. As a result, MRI often uses the larger available signal to produce very clean 2D images, whereas MRS very frequently only acquires signal from a single localized region, referred to as a "voxel". MRS can be used to determine the relative concentrations and physical properties of a variety of biochemicals frequently referred to as "metabolites" due to their role in metabolism.
Data Acquisition
Acquiring an MRS scan is very similar to that of MRI with a few additional steps preceding data acquisition. These steps include:
Shimming the magnetic field: this step is taken to correct for the inhomogeneity of the magnetic field by tuning different pulses in the x, y, and z directions. This step is usually automated but can be performed manually.
Suppressing the water signal: because water molecules contain hydrogen, and the relative concentration of water to metabolite is about 10,000:1, the water signal is often suppressed or the metabolite peaks will not be discernible in the spectra. This is achieved by adding water suppression pulses. Recent advances allow proton MRS without water suppression.
Choosing a spectroscopic technique: careful planning of measurements is important in the context of a specific experiment.
Single Voxel Spectroscopy (SVS): has a minimum spatial resolution of approximately 1 cm3, and has the cleanest spectrum free from unwanted artifacts due to the small acquired volume leading to easy shim and less unwanted signals from outside the voxel.
Magnetic Resonance Spectroscopic Imaging (MRSI): a 2-dimensional (or 3-dimensional) MRS technique which uses two/three phase-encoding directions to create a two/three-dimensional map of spectra. The drawbacks of this technique is that having two/three phase encoding directions requires lengthy scan time, and the larger volume of acquisition is more likely to introduce artefacts due to poorer shimming, unsuppressed water, as well as the inherent sinc point-spread-function due to the finite sampling of k-space which results in the signal from one voxel bleeding into all others.
Data Quantification
During data acquisition, the scan acquires raw data in the form of spectra. This raw data must be quantified to achieve a meaningful understanding of the spectrum. This quantification is achieved via linear combination. Linear combination requires knowledge of the underlying spectral shapes, referred to as basis sets. Basis sets are acquired either via numerical simulation or experimentally measured in phantoms. There are numerous packages available to numerically simulate basis sets, including MARSS, FID-A, among others such as GAMMA, VESPA and Spinach. With the basis sets, the raw data can now be quantified as measured concentrations of different chemical species. Software is used to complete this. LCModel, a commercial software, has been for most of the field's history the standard software quantification package. However, now there are many freeware packages for quantification: AMARES, AQSES, Gannet, INSPECTOR, jMRUI, TARQUIN, and more.
Before linear combination, peak extraction used to be used for data quantification. However, this is no longer popular nor recommended. Peak extraction is a technique which integrates the area underneath a signal. Despite its seemingly straightforwardness, there are several confounds with this technique. Chiefly, the individual Lorentzian shapes employed do not scale up to match the complexity of the spectral shapes of J-coupled metabolites and is too simple to discern between overlapping peaks.
Pulse Sequences
Similar to MRI, MRS uses pulse sequences to acquire signal from several different molecules to generate a spectra instead of an image. In MRS, STEAM (Stimulated Echo Acquisition Method) and PRESS (Point Resolved Spectroscopy) are the two primary pulse sequence techniques used. In terms of advantages, STEAM is best for imaging metabolites with shorter T2 and has lower SAR, while PRESS has higher SNR than STEAM. STEAM and PRESS are most widely used due to their implementation on the major vendors of MR scanners. Beyond STEAM and PRES there are sequences which utilize adiabatic pulses. Adiabatic pulses produce uniform flip angles even when there is extreme B1 inhomogeneity. Thus, these sequences allow us to achieve excitation that achieves the sought-for B1 insensitivity and off-resonance in the RF coil and sampled object. Specifically, adiabatic pulses solve the problem of signal dropout that comes from the different B1 flux patterns that result from the surface transmit coils used and the usage of normal pulses. Adiabatic pulses are also useful for constraints on RF peak power for excitation and lowering tissue heating. Additionally, adiabatic pulses have substantially higher bandwidth, which reduces chemical shift displacement artefact, which is particularly important at high field strengths and when a large range of frequencies are desired to be measured (i.e., measuring both the signals upfield and downfield of water in proton MRS).
Spatial Localization Sequences
In PRESS, the two chief drawbacks are lengthy echo time (TE) and chemical shift displacement (CSD) artifacts. Lengthy echo time arises from the fact that PRESS uses two 180° pulses, unlike STEAM which uses exclusively 90° pulses. The duration of 180° pulses are generally longer than 90° pulses because it takes more energy to flip a net magnetization vector completely as opposed to only 90°. Chemical shift displacement artifacts arises partly because of less optimal slice selection profiles. Multiple 180° pulses does not allow a very short TE, resulting in less optimal slice selection profile. Additionally, multiple 180° pulses means smaller bandwidth and thus larger chemical shift displacement. Specifically, the chemical shift displacement artifacts occur because signals with different chemical shifts experience different frequency-encoded slice selections and thus do not originate from same volume. Additionally, this effect becomes greater at higher magnetic field strengths.
SPECIAL consists of a spatially selective pre-excitation inversion pulse (typically AFP) followed by spatially selective excitation and refocusing pulses, both of which are usually SLR or truncated sinc pulses.
SPECIAL is a hybrid of PRESS and Image-Selected In Vivo Spectroscopy (ISIS). ISIS achieves spatial localization in the three spatial dimensions through a series of eight slice-selective preinversion pulses that can be appropriately positioned so that the sum of the eight cycles removes all signal outside the desired 3D region. SPECIAL obtains spatial localization from only a single dimension with pre-excitation inversion pulses (cycled on and off every other repetition time [TR]), making it a two-cycle sequence.
The use of the preinversion pulse to remove one refocusing pulse (as compared with PRESS) is what allows SPECIAL to achieve a short TE, reaching a minimum of 2.2 msec on a preclinical scanner in rat brain while being able to recover the full signal and as low as 6 msec on a clinical 3T scanner.
The largest drawback of SPECIAL and SPECIAL-sLASER is that they are two-cycle schemes, and systematic variations between cycles will manifest in their difference spectrum. Lipid contamination is a particularly large problem with SPECIAL and similar sequences.
The state-of-the-art localization sequence is sLASER, which utilizes two pairs of adiabatic refocusing pulses. This has recently been recommended by consensus.
The first is through OVS, which will reduce the contamination of lipid signals that originate from outside the voxel, although this comes at the cost of an increase in SAR. The second is not to set the amplitude of the pre-excitation inversion pulse to zero every other TR, but instead to shift the location of this ISIS plane such that the excited volume for the off condition is outside the object. This has been shown to greatly reduce lipid contamination, speculated to have arisen from the interaction between the RF pulse and lipid compartments due to incomplete relaxation, magnetization transfer, or the homonuclear Overhauser effect, although the exact mechanism remains unknown. The third is to use an echo-planar readout that dephases magnetization from outside the voxel, also shown to substantially reduce lipid artifacts. All three methods could be combined to overcome lipid contamination.
One of the dimensions to understand about a pulse sequence is its coherence pathway. The coherence pathway is the sequence of quantum coherence number(s) the signal takes prior to its acquisition. All coherence pathways end in -1, as this is the only coherence pathway detected by quadrature coils. The spin echo-type sequences (PRESS, sLASER, LASER) simply alternate between +1 and -1. For example, the coherence pathway for PRESS (expressed as a vector) is [-1, 1, -1]. This indicates that after the initial RF pulse (excitation pulse) the spins have a -1 quantum coherence. The refocusing pulses then swap the -1 to +1, then back from +1 to -1 (where it is then detected). Similarly for sLASER the coherence pathway is [-1, 1, -1, 1, -1]. The coherence pathway for LASER is [-1, 1, -1, 1, -1, 1, -1]. The coherence pathway for sPECIAL is [0, 1, -1]. This indicates that after the first RF pulse the signal resides as a population, due to its 0 quantum coherence number. Coherence pathways are critical as the explain how the sequences are affected by crushers and phase cycling. As such, coherence pathway analysis has been used to develop optimized crusher schemes and phase cycling schemes for an arbitrary MRS experiment.
Uses
MRS allows doctors and researchers to obtain biochemical information about the tissues of the human body in a non-invasive way (without the need for a biopsy), whereas MRI only gives them information about the structure of the body (the distribution of water and fat).
For example, whereas MRI can be used to assist in the diagnosis of cancer, MRS could potentially be used to assist in information regarding to the aggressiveness of the tumor. Furthermore, because many pathologies appear similar in diagnostic imaging (such as radiation-induced necrosis and recurring tumor following radiotherapy), MRS may in the future be used to assist in distinguishing between similarly appearing prognoses.
MRS equipment can be tuned (just like a radio receiver) to pick up signals from different chemical nuclei within the body. The most common nuclei to be studied are protons (hydrogen), phosphorus, carbon, sodium and fluorine.
The types of biochemicals (metabolites) which can be studied include choline-containing compounds (which are used to make cell membranes), creatine (a chemical involved in energy metabolism), inositol and glucose (both sugars), N-acetylaspartate, and alanine and lactate which are elevated in some tumors.
At present MRS is mainly used as a tool by scientists (e.g. medical physicists and biochemists) for medical research projects, but it is becoming clear that it also has the ability to give doctors useful clinical information, especially with the discovery that it can be used to probe the concentration of alpha-Hydroxyglutaric acid, which is only present in IDH1 and IDH2 mutated gliomas, which alters the prescribed treatment regimen.
MRS is currently used to investigate a number of diseases in the human body, most notably cancer (in brain, breast and prostate), epilepsy, Alzheimer's disease, Parkinson's disease, and Huntington's chorea. MRS has been used to diagnose pituitary tuberculosis.
Prostate cancer: Combined with a magnetic resonance imaging (MRI) and given equal results, then the three-dimensional MRS can predict the prevalence of a malignant degeneration of prostate tissue by approximately 90%. The combination of both methods may be helpful in the planning of biopsies and therapies of the prostate, as well as to monitor the success of a therapy.
Example
Shown below is an MRI brain scan (in the axial plane, that is slicing from front-to-back and side-to-side through the head) showing a brain tumor (meningioma) at the bottom right. The red box shows the volume of interest from which chemical information was obtained by MRS (a cube with 2 cm sides which produces a square when intersecting the 5 mm thick slice of the MRI scan).
Each biochemical, or metabolite, has a different peak in the spectrum which appears at a known frequency. The peaks corresponding to the amino acid alanine, are highlighted in red (at 1.4 ppm). This is an example of the kind of biochemical information which can help doctors to make their diagnosis. Other metabolites of note are choline (3.2 ppm) and creatine (3.0 ppm).
Applications of MRS
In 1H Magnetic Resonance Spectroscopy each proton can be visualized at a specific chemical shift (peak position along x-axis) depending on its chemical environment. This chemical shift is dictated by neighboring protons within the molecule. Therefore, metabolites can be characterized by their unique set of 1H chemical shifts. The metabolites that MRS probes for have known (1H) chemical shifts that have previously been identified in NMR spectra. These metabolites include:
N-acetyl Aspartate (NAA): with its major resonance peak at 2.02 ppm, decrease in levels of NAA indicate loss or damage to neuronal tissue, which results from many types of insults to the brain. Its presence in normal conditions indicates neuronal and axonal integrity.
Choline: with its major peak at 3.2 ppm, choline is known to be associated with membrane turnover, or increase in cell division. Increased choline indicates increase in cell production or membrane breakdown, which can suggest demyelination or presence of malignant tumors.
Creatine and phosphocreatine: with its major peak at 3.0 ppm, creatine marks metabolism of brain energy. Gradual loss of creatine in conjunction with other major metabolites indicates tissue death or major cell death resulting from disease, injury or lack of blood supply. Increase in creatine concentration could be a response to cranialcerebral trauma. Absence of creatine may be indicative of a rare congenital disease.
Lipids: with their major aliphatic peaks located in the 0.9–1.5 ppm range, increase in lipids is seen is also indicative of necrosis. These spectra are easily contaminated, as lipids are not only present in the brain, but also in other biological tissue such as the fat in the scalp and area between the scalp and skull.
Lactate: Is an AX3 system which results in a doublet (two symmetric peaks) centered about 1.31 ppm, and a quartet (four peaks with relative peak heights of 1:2:2:1) centered about 4.10 ppm. The doublet at 1.31 ppm is typically quantified as the quartet may be suppressed through water saturation or obscured by residual water. In healthy subjects lactate is not visible, for its concentration is lower than the detection limit of MRS; however, presence of this peak indicates glycolysis has been initiated in an oxygen-deficient environment. Several causes of this include ischemia, hypoxia, mitochondrial disorders, and some types of tumors.
Myo-inositol: with its major peak at 3.56 ppm, an increase in Myo-inositol has been seen to be disrupted in patients with Alzheimer's, dementia, and HIV patients.
Glutamate and glutamine: these amino acids are marked by a series of resonance peaks between 2.2 and 2.4 ppm. Hyperammonemia, hepatic encephalopathy are two major conditions that result in elevated levels of glutamine and glutamate. MRS, used in conjunction with MRI or some other imaging technique, can be used to detect changes in the concentrations of these metabolites, or significantly abnormal concentrations of these metabolites.
GABA can be detected primarily from its peaks at approximately 3.0 ppm, however because creatine has a strong singlet at 3.0 ppm with approximately 20x the amplitude a technique which exploits J-coupling must be used to accurately quantify GABA. The most common techniques for this are J-difference editing (MEGA), or J-resolved (as used in JPRESS)
Glutathione can also be detected from its peak at peak at 3.0 ppm, however similar to GABA it also must use a method which exploits J-coupling to remove the overlaying creatine signal.
Limitations of MRS
The major limitation to MRS is its low available signal due to the low concentration of metabolites as compared to water. As such, it has inherently poor temporal and spatial resolution. Nevertheless, no alternate technique is able to quantify metabolism in vivo non-invasively and thus MRS remains a valuable tool for research and clinical scientists.
In addition, despite recent efforts toward international expert consensus on methodological details like shimming, motion correction, spectral editing, spectroscopic neuroimaging, other advanced acquisition methods, data processing and quantification, application to brain, proton spectroscopy application to skeletal muscle, phosphorus application to skeletal muscle, methods description, results reporting, and other considerations, currently published implementations of in vivo magnetic resonance spectroscopy cluster into literatures exhibiting a broad variety of individualized acquisition, processing, quantification, and reporting techniques. This situation may contribute to a low sensitivity and specificity of, for example, in vivo proton magnetic resonance spectroscopy to disorders such as multiple sclerosis, that continue to fall below clinically beneficial thresholds for, e.g., diagnosis.
Non-Proton (1H) MRS
31Phosphorus Magnetic Resonance Spectroscopy
1H MRS's clinical success is only rivaled by 31P MRS. This is in large part because of the relatively high sensitivity of phosphorus NMR (7% of protons) combined with a 100% natural abundance.
Consequently, high-quality spectra are acquired within minutes. Even at low field strengths, great spectra resolution is obtained because of the relatively large (~30 ppm) chemical shift dispersion for in vivo phosphates. Clinically, phosphorus NMR excels because it detects all metabolites playing key roles in tissue energy metabolism and can indirectly deduce intracellular pH. However, phosphorus NMR is chiefly challenged by the limited number of metabolites it can detect.
13Carbon Magnetic Resonance Spectroscopy
In contrast to phosphorus NMR, carbon NMR is an insensitive technique. This arises from the fact that 13C NMR has a low abundance (1.1%) and carbon's low gyromagnetic ratio. This low abundance is because 12C does not have a magnetic moment, making it not NMR active, leading to 13C's use for spectroscopy purposes. However, this low sensitivity can be improved via decoupling, averaging, polarization transfer, and larger volumes. Despite the low natural abundance and sensitivity of 13C, 13C MRS has been used to study several metabolites, especially glycogen and triglycerides. It has proven especially useful at providing insight on the metabolic fluxes from 13C-labeled precursors. There is great overlap in what 1H MRS and 13C MRS can obtain spectra-wise and large reason, combined with 1H MRS's high sensitivity, why 13C MRS has never seen wide application like 1H MRS. See also Hyperpolarized carbon-13 MRI.
23Sodium Magnetic Resonance Spectroscopy
Sodium NMR is infamous for its low sensitivity (9.2% relative to proton sensitivity) and low SNR because of its low sodium concentration (30 - 100 mM), especially compared to protons (40 - 50 M). However, interest in sodium NMR has been reinspired by recent significant gains in SNR at high magnetic fields, along with improved coil designs and optimized pulse sequences. There is much hope for sodium NMR's clinical potential because the detection of abnormal intracellular sodium in vivo may have significant diagnostic potential and reveal new insights into tissue electrolysis homeostasis.
19Fluorine Magnetic Resonance Spectroscopy
Fluorine NMR has high sensitivity (82% relative to proton sensitivity) and 100% natural abundance. However, it is important to note that no endogenous 19F containing compounds are found in biological tissues and thus the fluorine signal comes from an external reference compound. Because19F is not found in biological tissues, 19F does not have to deal with interference from background signals like in vivo 1H MRS does with water, making it especially powerful for pharmacokinetic studies. 1H MRI provides the anatomical landmarks, while 19F MRI/MRS allows us to follow and map the specific interactions of specific compounds. in vivo 19F MRS can be used to monitor the uptake and metabolism of drugs, study the metabolism of anesthetic, determine cerebral blood flow, and measure, via fluorinated compounds ("probes"), various parameters like pH, oxygen levels, and metal concentration.
See also
Functional magnetic resonance spectroscopy of the brain
Magnetic resonance imaging
Magnetization transfer
NMR
NMR spectroscopy
References
External links
Online Physics Tutorial for MRI and MRS
https://aclarion.com/
NOCISCAN (aclarion) – The first, evidence-supported, SaaS platform to leverage MR Spectroscopy to noninvasively help physicians distinguish between painful and nonpainful discs in the spine.
In vivo
Nuclear magnetic resonance spectroscopy | In vivo magnetic resonance spectroscopy | [
"Physics",
"Chemistry"
] | 4,724 | [
"Nuclear magnetic resonance",
"Spectrum (physical sciences)",
"Magnetic resonance imaging",
"Nuclear magnetic resonance spectroscopy",
"Spectroscopy"
] |
14,357,843 | https://en.wikipedia.org/wiki/System%20requirements%20%28spacecraft%20system%29 | System requirements in spacecraft systems are the specific system requirements needed to design and operate a spacecraft or a spacecraft subsystem.
Overview
Spacecraft systems are normally developed under the responsibility of space agencies as NASA, ESA etc. In the space area standardized terms and processes have been introduced to allow for unambiguous communication between all partners and efficient usage of all documents. For instance the life cycle of space systems is divided in phases:
Phase A: Feasibility Study
Phase B: Requirements Definition
Phase C/D: Design / Manufacturing / Verification
Phase E: Operational usage.
At the end of phase B the system requirements together with a statement of work are sent out requesting proposals from industry.
Technical systems requirement
Both technical and nontechnical system requirements are contained in the statement of work.
The technical system requirements documented in the System Specification stay on mission level: System functions and performances, Orbit, Launch vehicle, etc.
Non-technical system (task) requirements: Cost and progress reporting, Documentation maintenance, etc.
The customer (requirements) specification is answered by the contractor by a design-to specification.
For example, the requirement "Columbus shall be launched by the Space Shuttle." is detailed in the contractor system specification "Columbus shall be a cylindrical pressurized module with max. length of 6.9 meters and 4.5 meters diameter as agreed in the Shuttle/Columbus ICD."
Operations environment
The spacecraft's systems specification, according to David Michael Harland (2005), usually also defines the operation environment of the spacecraft. It mostly is defined "as a model - often provide by the scientific community from available data - in the form of a set of curves, numerical tables, or software, usually with a nominal expectation and the minimal and maximum profiles which the environment is not expected to exceed".
System specification structure
A typical industry generated system specification for a spacecraft has the following structure (e.g. Columbus Design Spec (COL-RIBRE-SPE-0028, iss.10/F, 06.25.2004):
Document change record
1. Scope
1.1 Purpose
1.2 Summary description
1.3 Classification
1.4 Applicability
2. Related documents
2.1 Applicable documents (incl. order of precedence)
2.2 Reference documents
3. Functional /Performance Requirements
4. Support requirements
4.1 Product assurance
4.2 Electro-magnetic compatibility
4.3 Contamination
4.4 etc.
5. Interface requirements
5.1 System interfaces
5.1.1 Launcher
5.1.2 Ground stations
5.1.3 etc.
5.2 Subsystem interfaces
5.2.1 Electrical power
5.2.2 Data
5.2.3 etc.
6. Implementation requirements
6.1 Configuration
6.2 Budget Allocations
6.2.1 Mass
6.2.2 Electrical power
6.2.3 etc.
7. Preparation for delivery
Attachments (Abbreviation list etc.)
Each requirement paragraph consists of the requirement to be fulfilled by the product to be delivered and the verification requirement (Review of design, analysis, test, inspection).
Specification tree
The spacecraft system specification defines also the subsystems of the spacecraft e.g.: Structure, Data management subsystem incl. software, Electrical Power, Mechanical, etc.
For each subsystem a subsystem specification is prepared by the Prime Contractor with the same specification structure shown above including references to the parent paragraph in the system specification. In the same way the subsystem contractor prepares an assembly or unit specification. All these specifications are listed in a so-called specification tree showing all specifications and their linkage as well as the issue / date of each specification.
Literature
2005, David Michael Harland, Ralph Lorenz, Space Systems Failures: Disasters and Rescues of Satellites, Rockets, Springer, p. 178.
2003, Peter W. Fortescue, Graham Swinerd, Spacecraft Systems Engineering, John Wiley and Sons, 704 pp.
2001, DoD - Systems Management College, Systems Engineering Fundamentals. Defense Acquisition University Press, January 2001.
See also
Requirements
Requirements analysis
Requirements engineering
Requirements management
Verification of system requirements
Verification (spaceflight)
References
External links
NASA Completes Milestone Review Of Next Human Spacecraft System Nasa article 1999.
Example of a SYSTEM REQUIREMENTS sheet for a spacecraft
Columbus System Specification COL-RIBRE-SPE-0028 for phase C/D
Spaceflight concepts
Systems engineering | System requirements (spacecraft system) | [
"Engineering"
] | 889 | [
"Systems engineering"
] |
14,357,922 | https://en.wikipedia.org/wiki/Sleeper%20wall | A sleeper wall may refer to the following types of walls:
sleeper wall is a short wall used to support floor joists, beam and block or hollowcore slabs at ground floor. It is constructed in this fashion when a suspended floor(Also called suspended slab) is required due to bearing conditions or ground water presence. Essentially it is a wall in the way that it is constructed but a sleeper in the way that it functions. Stretcher bond or header-stretcher bond can be used in these walls.
sleeper wall can also refer to a retaining wall made from railroad ties. It is used to prevent erosion. It can be made from bricks or concrete blocks. The wall is often used in landscaping.
References
Structural system
Types of wall | Sleeper wall | [
"Technology",
"Engineering"
] | 148 | [
"Structural system",
"Types of wall",
"Structural engineering",
"Building engineering"
] |
14,359,155 | https://en.wikipedia.org/wiki/Carcinoembryonic%20antigen%20peptide-1 | Carcinoembryonic antigen peptide-1 is a nine amino acid peptide fragment of carcinoembryonic antigen (CEA), a protein that is overexpressed in several cancer cell types, including gastrointestinal, breast, and non-small-cell lung.
Synonyms:
CAP-1
Carcinoembryonic Antigen Peptide-1
Carcinoembryonic Peptide-1
CEA Peptide 1
CEA Peptide 9-mer
External links
National Cancer Institute Definition of carcinoembryonic antigen peptide 1
Tumor markers
Peptides | Carcinoembryonic antigen peptide-1 | [
"Chemistry",
"Biology"
] | 111 | [
"Biomolecules by chemical classification",
"Biomarkers",
"Biotechnology stubs",
"Tumor markers",
"Biochemistry stubs",
"Molecular biology",
"Biochemistry",
"Chemical pathology",
"Peptides"
] |
14,360,086 | https://en.wikipedia.org/wiki/Nucleotide%20sugar | Nucleotide sugars are the activated forms of monosaccharides. Nucleotide sugars act as glycosyl donors in glycosylation reactions. Those reactions are catalyzed by a group of enzymes called glycosyltransferases.
History
The anabolism of oligosaccharides - and, hence, the role of nucleotide sugars - was not clear until the 1950s when Leloir and his coworkers found that the key enzymes in this process are the glycosyltransferases. These enzymes transfer a glycosyl group from a sugar nucleotide to an acceptor.
Biological importance and energetics
To act as glycosyl donors, those monosaccharides should exist in a highly energetic form. This occurs as a result of a reaction between nucleoside triphosphate (NTP) and glycosyl monophosphate (phosphate at anomeric carbon). The recent discovery of the reversibility of many glycosyltransferase-catalyzed reactions calls into question the designation of sugar nucleotides as 'activated' donors.
Types
There are nine sugar nucleotides in humans which act as glycosyl donors and they can be classified depending on the type of the nucleoside forming them:
Uridine Diphosphate: UDP-α-D-Glc, UDP-α-D-Gal, UDP-α-D-GalNAc, UDP-α-D-GlcNAc, UDP-α-D-GlcA, UDP-α-D-Xyl
Guanosine Diphosphate: GDP-α-D-Man, GDP-β-L-Fuc.
Cytidine Monophosphate: CMP-β-D-Neu5Ac; in humans, it is the only nucleotide sugar in the form of nucleotide monophosphate.
Cytidine Diphosphate: CDP-D-Ribitol (i.e. CMP-[ribitol phosphate]); though not a sugar, the phosphorylated sugar alcohol ribitol phosphate is incorporated into matriglycan as if it were a monosaccharide.
In other forms of life many other sugars are used and various donors are utilized for them. All five of the common nucleosides are used as a base for a nucleotide sugar donor somewhere in nature. As examples, CDP-glucose and TDP-glucose give rise to various other forms of CDP and TDP-sugar donor nucleotides.
Structures
Listed below are the structures of some nucleotide sugars (one example from each type).
Relationship to disease
Normal metabolism of nucleotide sugars is very important. Any malfunction in any contributing enzyme will lead to a certain disease for example:
Inclusion body myopathy: is a congenital disease resulted from altered function of UDP-GlcNAc epimerase .
Macular corneal dystrophy: is a congenital disease resulted from malfunction of GlcNAc-6-sulfotransferase.
Congenital disorder in α-1,3 mannosyl transferase will result in a variety of clinical symptoms, e.g. hypotonia, psychomotor retardation, liver fibrosis and various feeding problems.
Relationship to drug discovery
The development of chemoenzymatic strategies to generate large libraries of non-native sugar nucleotides has enabled a process referred to as glycorandomization where these sugar nucleotide libraries serve as donors for permissive glycosyltransferases to afford differential glycosylation of a wide range of pharmaceuticals and complex natural product-based leads.
See also
Carbohydrate chemistry
EamA
Glycorandomization
Glycosyltransferase
Nucleotide sugars metabolism
References
External links
Metabolism
Coenzymes
Carbohydrate chemistry
Carbohydrates
Nucleotides | Nucleotide sugar | [
"Chemistry",
"Biology"
] | 848 | [
"Biomolecules by chemical classification",
"Carbohydrates",
"Coenzymes",
"Organic compounds",
"Carbohydrate chemistry",
"nan",
"Chemical synthesis",
"Biochemistry",
"Glycobiology",
"Cellular processes",
"Metabolism"
] |
14,360,306 | https://en.wikipedia.org/wiki/Guanosine%20diphosphate%20mannose | Guanosine diphosphate mannose or GDP-mannose is a nucleotide sugar that is a substrate for glycosyltransferase reactions in metabolism. This compound is a substrate for enzymes called mannosyltransferases.
Known as donor of activated mannose in all glycolytic reactions, GDP-mannose is essential in eukaryotes.
Biosynthesis
GDP-mannose is produced from GTP and mannose-6-phosphate by the enzyme mannose-1-phosphate guanylyltransferase (GDP-mannose pyrophosphorylase, GDP-MP). This enzyme belongs to a family of nucleotidyl-transferases and is a pervasive enzyme found in bacteria, fungi, plants, and animals.
References
See also
Nucleoside
Nucleotide
Guanosine
Guanosine diphosphate
Nucleotides
Coenzymes | Guanosine diphosphate mannose | [
"Chemistry"
] | 200 | [
"Organic compounds",
"Coenzymes"
] |
14,360,772 | https://en.wikipedia.org/wiki/Microbarom | In acoustics, microbaroms, also known as the "voice of the sea", are a class of atmospheric infrasonic waves generated in marine storms by a non-linear interaction of ocean surface waves with the atmosphere. They typically have narrow-band, nearly sinusoidal waveforms with amplitudes up to a few microbars, and wave periods near 5 seconds (0.2 hertz). Due to low atmospheric absorption at these low frequencies, microbaroms can propagate thousands of kilometers in the atmosphere, and can be readily detected by widely separated instruments on the Earth's surface.
History
The reason for the discovery of this phenomenon was an accident: the aerologists working at the marine Hydrometeorology stations and watercraft drew attention to the strange pain that a person experiences when approaching the surface of a standard meteorological probe (a balloon filled with hydrogen). During one of the expeditions, this effect was demonstrated to the Soviet academician V. V. Shuleikin by the chief meteorologist V. A. Berezkin. This phenomenon drew genuine interest among scientists; in order to study it, special equipment was designed to record powerful but low-frequency vibrations that are not audible to human ears.
As a result of several series of experiments, the physical essence of this phenomenon was clarified and in 1935 when V.V. Shuleikin published his first work entirely devoted to the infrasonic nature of the “voice of the sea”. Microbaroms were first described in United States in 1939 by American seismologists Hugo Benioff and Beno Gutenberg at the California Institute of Technology at Pasadena, based on observations from an electromagnetic microbarograph, consisting of a wooden box with a low-frequency loudspeaker mounted on top.
They noted their similarity to microseisms observed on seismographs, and correctly hypothesized that these signals were the result of low pressure systems in the Northeast Pacific Ocean. In 1945, Swiss geoscientist L. Saxer showed the first relationship of microbaroms with wave height in ocean storms and microbarom amplitudes.
Following up on the theory of microseisms by M. S. Longuet-Higgins, Eric S. Posmentier proposed that the oscillations of the center of gravity of the air above the Ocean surface on which the standing waves appear were the source of microbaroms, explaining the doubling of the ocean wave frequency in the observed microbarom frequency.
Microbaroms are now understood to be generated by the same mechanism that makes secondary microseisms. The first quantitatively correct theory of microbarom generation is due to L. M. Brekhovskikh who showed that it is the source of microseisms in the ocean that couples to the atmosphere. This explains that most of the acoustic energy propagates near the horizontal direction at the sea level.
Theory
Isolated traveling ocean surface gravity waves radiate only evanescent acoustic waves,
and don't generate microbaroms.
The interaction of two trains of surface waves of different frequencies and directions generates wave groups. For waves propagating almost in the same direction, this gives the usual sets of waves that travel at the group speed, which is slower than phase speed of water waves. For typical ocean waves with a period around 10 seconds, this group speed is close to 10 m/s.
In the case of opposite propagation direction the groups travel at a much larger speed, which is now 2π(f1 + f2)/(k1 − k2) with k1 and k2 the wave numbers of the interacting water waves. For wave trains with a very small difference in frequency (and thus wave numbers), this pattern of wave groups may have the same horizontal velocity as acoustic waves, more than 300 m/s, and will excite microbaroms.
As far as seismic and acoustic waves are concerned, the motion of ocean waves in deep water is, to the leading order, equivalent to a pressure applied at the sea surface. This pressure is nearly equal to the water density times the wave orbital velocity squared. Because of this square, it is not the amplitude of the individual wave trains that matter (red and black lines in the figures) but the amplitude of the sum, the wave groups (blue line in figures). The ocean motion generated by this "equivalent pressure" is then transmitted to the atmosphere.
If the wave groups travel faster than the sound speed, microbaroms are generated, with propagation directions closer to the vertical for the faster wave groups.
Real ocean waves are composed of an infinite number of wave trains of all directions and frequencies, giving a broad range of acoustic waves. In practice, the transmission from the ocean to the atmosphere is strongest for angles around 0.5 degrees from the horizontal. For near-vertical propagation, the water depth may play an amplifying role as it does for microseisms.
The water depth is only important for those acoustic waves that have a propagation direction within 12° of the vertical at the sea surface
There is always some energy propagating in the opposite direction. However, their energy may be extremely low. Significant microbarom generation only occurs when there is significant energy at the same frequency and in opposing directions. This is strongest when waves from different storms interact or in the lee of a storm
which produce the required standing wave conditions, also known as the clapotis. When the ocean storm is a tropical cyclone, the microbaroms are not produced near the eye wall where wind speeds are greatest, but originate from the trailing edge of the storm where the storm generated waves interact with the ambient ocean swells.
Microbaroms may also be produced by standing waves created between two storms, or when an ocean swell is reflected at the shore. Waves with approximately 10-second periods are abundant in the open oceans, and correspond to the observed 0.2 Hz infrasonic spectral peak of microbaroms, because microbaroms exhibit frequencies twice that of the individual ocean waves. Studies have shown that the coupling produces propagating atmospheric waves only when non-linear terms are considered.
Microbaroms are a form of persistent low-level atmospheric infrasound, generally between 0.1 and 0.5 Hz, that may be detected as coherent energy bursts or as a continuous oscillation. When the plane wave arrivals from a microbarom source are analyzed from a phased array of closely spaced microbarographs, the source azimuth is found to point toward the low-pressure center of the originating storm. When the waves are received at multiple distant sites from the same source, triangulation can confirm the source is near the center of an ocean storm.
Microbaroms that propagate up to the lower thermosphere may be carried in an atmospheric waveguide, refracted back toward the surface from below 120 km and above 150 km altitudes,
or dissipated at altitudes between 110 and 140 km.
They may also be trapped near the surface in the lower troposphere by planetary boundary layer effects and surface winds, or they may be ducted in the stratosphere by upper-level winds and returned to the surface through refraction, diffraction or scattering.
These tropospheric and stratospheric ducts are only generated along the dominant wind directions,
may vary by time of day and season,
and will not return the sound rays to the ground when the upper winds are light.
The angle of incidence of the microbarom ray determines which of these propagation modes it experiences. Rays directed vertically toward the zenith are dissipated in the thermosphere, and are a significant source of heating in that layer of the upper atmosphere. At mid latitudes in typical summer conditions, rays between approximately 30 and 60 degrees from the vertical are reflected from altitudes above 125 km where the return signals are strongly attenuated first.
Rays launched at shallower angles may be reflected from the upper stratosphere at approximately 45 km above the surface in mid-latitudes,
or from 60 to 70 km in low latitudes.
Microbaroms and upper atmosphere
Atmospheric scientists have used these effects for inverse remote sensing of the upper atmosphere using microbaroms.
Measuring the trace velocity of the reflected microbarom signal at the surface gives the propagation velocity at the reflection height, as long as the assumption that the speed of sound only varies along the vertical, and not over the horizontal, is valid. If the temperature at the reflection height can be estimated with sufficient precision, the speed of sound can be determined and subtracted from the trace velocity, giving the upper-level wind speed. One advantage of this method is the ability to measure continuously – other methods that can only take instantaneous measurements may have their results distorted by short-term effects.
Additional atmospheric information can be deduced from microbarom amplitude if the source intensity is known. Microbaroms are produced by upward directed energy transmitted from the ocean surface through the atmosphere. The downward directed energy is transmitted through the ocean to the sea floor, where it is coupled to the Earth's crust and transmitted as microseisms with the same frequency spectrum. However, unlike microbaroms, where the near vertical rays are not returned to the surface, only the near vertical rays in the ocean are coupled to the sea floor. By monitoring the amplitude of received microseisms from the same source using seismographs, information on the source amplitude can be derived. Because the solid earth provides a fixed reference frame,
the transit time of the microseisms from the source is constant, and this provides a control for the variable transit time of the microbaroms through the moving atmosphere.
Microbaroms and Nuclear Explosions
Microbaroms are a significant noise source that can potentially interfere with the detection of infrasound from nuclear explosions. Accurate detection of explosions is a goal of the International Monitoring System organized under the Comprehensive Nuclear-Test-Ban Treaty (which has not entered into force). It is a particular problem for detecting low-yield tests in the one-kiloton range because the frequency spectra overlap.
See also
Microseism
Further reading
References
Acoustics
Satellite meteorology | Microbarom | [
"Physics"
] | 2,067 | [
"Classical mechanics",
"Acoustics"
] |
14,360,911 | https://en.wikipedia.org/wiki/Visual%20control | Visual control is a business management technique employed in many places where information is communicated by using visual signals instead of texts or other written instructions. The design is deliberate in allowing quick recognition of the information being communicated, in order to increase efficiency and clarity. These signals can be of many forms, from different coloured clothing for different teams, to focusing measures upon the size of the problem and not the size of the activity, to kanban, obeya and heijunka boxes and many other diverse examples. In The Toyota Way, it is also known as mieruka.
Purpose
Visual control methods aim to increase the efficiency and effectiveness of a process by making the steps in that process more visible. The theory behind visual control is that if something is clearly visible or in plain sight, it is easy to remember and keep at the forefront of the mind. Another aspect of visual control is that everyone is given the same visual cues and so are likely to have the same vantage point.
There are many different techniques that are used to apply visual control in the workplace. Some companies use visual control as an organizational tool for materials. A clearly labeled storage board lets the employee know exactly where a tool belongs and what tools are missing from the display board. Another simple example of a common visual control is to have reminders posted on cubicle walls so that they remain in plain sight. Visual signs and signals communicate information that is needed to make effective decisions. These decisions may be safety oriented or they may give reminders as to what steps should be taken to resolve a problem. Most companies use visual controls in one degree or another, many of them not even realizing that the visual controls that they are making have a name and a function in the workplace. Whether it is recognized by the name of "visual control" or not, the fact is that replacing text or number with graphics makes a set of information easier to understand with only a glance, making it a more efficient way of communicating a message. It is also commonly used for internal team communication.
Visual controls are designed to make the control and management of a company as simple as possible. This entails making problems, abnormalities, or deviations from standards visible to everyone. When these deviations are visible and apparent to all, corrective action can be taken to immediately correct these problems.
Visual controls are meant to display the operating or progress status of a given operation in an easy to see format and also to provide instruction and to convey information. A visual control system must have an action component associated with it in the event that the visually represented procedures are not being followed in the real production process. Therefore, visual controls must also have a component where immediate feedback is provided to workers.
Types
There are two groups and seven types of application in visual controls. Displays group and controls group.
A visual display group relates information and data to employees in the area. For example, charts showing the monthly revenues of the company or a graphic depicting a certain type of quality issue that group members should be aware of. Large scale, (typically 2x4m) examples of this are known as communications boards. Communication boards are large enough to contain several displays and allow teams of people to view at once. This supports team decision making and promotes a "shared vision".
A visual control group is intended to actually control or guide the action of the group members. Examples of controls are readily apparent in society: stop signs, handicap parking signs, no smoking signs, etc.
References
Further reading
Lean manufacturing | Visual control | [
"Engineering"
] | 701 | [
"Lean manufacturing"
] |
15,882,146 | https://en.wikipedia.org/wiki/Bomb%2C%20ground%2C%206%20lb | Bomb, Ground, 6 lb was a British World War II grenade containing about 2 pints (1.1 L) of mustard gas. It was intended to be used to contaminate trenches, dug-outs, rooms, observation posts and small enclosures, and on cross-roads, narrow defiles, obstacles and debris of demolition.
Design
As described in the training instructions: "The bomb consists of a cylindrical steel container... 3-3/4 in. in diameter, 9 in. high, weighing 6 lb. [...] It holds 3½ lb. (about 2 pints) of mustard gas... The bomb is fitted with a metal lid 2in. deep which is a good push fit on the body. This lid is fastened to the body by adhesive tape. In the centre of the underside of the lid is a striker for use on the match composition head of the ejection charge. [...] At one end of the bomb is a screwed plug. This is the filling plug. In order that any leakage may be readily detected the plug is coated with detector paint. [...] the ejection charge... consists of about 1/7 oz. of gunpowder connected by 32 in. of safety fuze to the match composition head. This length of fuze gives a delay of two minutes. The safety fuze is coiled in concentric circles in a shallow metal saucer and is set in bakelite cement. [...] The ejection charge has therefore the appearance of a circular plate 3½ in. in diameter. On the lower side is a threaded boss closed by a tin plate disc. This boss screwes into the bomb, the gunpowder charge being just above the tin plate disc. On the upper side of the ejection charge in the centre there is a flatened projection used for screwing the ejection charge into the bomb. The charge is also housed in the projection. On the rim there is another smaller projection holding the match composition head. The ejection charge is designed to blow out the end of the bomb fitted with the filling plug."
Notes
References
The Tactical and Technical Employment of Chemical Weapons Military Training Pamphlet No. 32. Part VI – Bombs, Ground, 6-Lb (1940) The War Office.
World War II grenades of the United Kingdom
Chemical weapon delivery systems | Bomb, ground, 6 lb | [
"Chemistry"
] | 490 | [
"Chemical weapon delivery systems",
"Chemical weapons"
] |
15,882,149 | https://en.wikipedia.org/wiki/Tensairity | Tensairity is a trademarked term for a light weight structural concept that uses low pressure air to stabilize compression elements against buckling. It employs an ancient foundational splinting structure using inflated airbeams and attached stiffeners or cables that gains mechanical advantages for low mass. The structure modality has been particularly developed by Mauro Pedretti.
Known applications
Bridges, band stand shells,, geodesic domes, aircraft wing construction, temporary shop and hospitality.
Related technology
A related structure modality is tensegrity. Conceivably, an ultralightweight structure evacuated of air would float in the atmosphere, much as a buoy floats in water A crushing load is present destabilizing such structures. However, enclosed-air structures perhaps made of tensairity beams in a tensegrity format holding an enveloping skin could be heated by solar energy and interior activity and then become lighter than air, like hot-air balloons. A torus of 72 inch major diameter and 27 inch minor diameter displaces about 5 pounds of atmosphere, so if the torus weighed less than 5 pounds, and was evacuated, it would be buoyant. Buckminster Fuller designed floating cities (air-filled) so lightweight that they would be buoyant only by the effect of solar heat warming the air within to slightly less density than the surrounding air. As domes, they were about 1/2 mile diameter. As floating spheres, the cities would not experience earthquakes.
References
Tensile architecture | Tensairity | [
"Technology"
] | 307 | [
"Structural system",
"Tensile architecture"
] |
15,882,673 | https://en.wikipedia.org/wiki/Plate%20notation | In Bayesian inference, plate notation is a method of representing variables that repeat in a graphical model. Instead of drawing each repeated variable individually, a plate or rectangle is used to group variables into a subgraph that repeat together, and a number is drawn on the plate to represent the number of repetitions of the subgraph in the plate. The assumptions are that the subgraph is duplicated that many times, the variables in the subgraph are indexed by the repetition number, and any links that cross a plate boundary are replicated once for each subgraph repetition.
Example
In this example, we consider Latent Dirichlet allocation, a Bayesian network that models how documents in a corpus are topically related. There are two variables not in any plate; α is the parameter of the uniform Dirichlet prior on the per-document topic distributions, and β is the parameter of the uniform Dirichlet prior on the per-topic word distribution.
The outermost plate represents all the variables related to a specific document, including , the topic distribution for document i. The M in the corner of the plate indicates that the variables inside are repeated M times, once for each document. The inner plate represents the variables associated with each of the words in document i: is the topic distribution for the jth word in document i, and is the actual word used.
The N in the corner represents the repetition of the variables in the inner plate times, once for each word in document i. The circle representing the individual words is shaded, indicating that each is observable, and the other circles are empty, indicating that the other variables are latent variables. The directed edges between variables indicate dependencies between the variables: for example, each depends on and β.
Extensions
A number of extensions have been created by various authors to express more information than simply the conditional relationships. However, few of these have become standard. Perhaps the most commonly used extension is to use rectangles in place of circles to indicate non-random variables—either parameters to be computed, hyperparameters given a fixed value (or computed through empirical Bayes), or variables whose values are computed deterministically from a random variable.
The diagram on the right shows a few more non-standard conventions used in some articles in Wikipedia (e.g. variational Bayes):
Variables that are actually random vectors are indicated by putting the vector size in brackets in the middle of the node.
Variables that are actually random matrices are similarly indicated by putting the matrix size in brackets in the middle of the node, with commas separating row size from column size.
Categorical variables are indicated by placing their size (without a bracket) in the middle of the node.
Categorical variables that act as "switches", and which pick one or more other random variables to condition on from a large set of such variables (e.g. mixture components), are indicated with a special type of arrow containing a squiggly line and ending in a T junction.
Boldface is consistently used for vector or matrix nodes (but not categorical nodes).
Software implementation
Plate notation has been implemented in various TeX/LaTeX drawing packages, but also as part of graphical user interfaces to Bayesian statistics programs such as BUGS and BayesiaLab and PyMC.
References
Graphical models
Bayesian networks
Mathematical notation | Plate notation | [
"Mathematics"
] | 681 | [
"nan"
] |
15,882,907 | https://en.wikipedia.org/wiki/PrairieTek | PrairieTek was a hard drive manufacturer located in Longmont, Colorado in the late 1980s and early 1990s. It was founded by Terry Johnson in 1985. It manufactured 5 and 10 megabyte "ruggedized" miniature hard drives for the laptop computer market.
Its PrairieTek 220 was the first hard drive, a potentially profitable move, but by the time the drive entered into mass production, its storage capacity was already low for the market. "PrairieTek's single disk 40MB model, potentially a
cost-effective competitive product, was...late to market."
Unlike many manufacturers of the time, PrairieTek did not rest the drive heads on the disks, but instead used reverse EMF (ElectroMagnetic Force) to park the drives on a spreader bar. At the time all manufacturers parked heads on the platters in an out of the way place. When the platters spun up, with the increasingly smooth surface of the platter, the heads had a tendency to stick to the surface (sticktion) which resulted in ripping them off the arms. This dynamic loading of the heads avoided the problem and was a carry over from a previous design used in 8 inch removable drives.
The company first went into the black in September 1990, at which point co-founder Steve Volk and the core group of engineers resigned to found Intégral Peripherals, to develop 1.8" drives.
The company failed within a year of Volk leaving. The first round of layoffs started in February 1991, all production activity ceased at the end of June - and the company filed for Chapter 11 bankruptcy in September 1991.
The bidding war for PrairieTek's patent portfolio in 1992 rose to the then astounding price of $18M, paid by Conner Peripherals and Alps Electric - PrairieTek's patent #4,933,785 in particular was sought after.
References
1985 establishments in Colorado
1991 disestablishments in Colorado
American companies established in 1985
American companies disestablished in 1991
Companies that filed for Chapter 11 bankruptcy in 1991
Computer companies established in 1985
Computer companies disestablished in 1991
Computer storage companies
Defunct companies based in Colorado
Defunct computer companies of the United States
Defunct computer hardware companies
Electronics companies established in 1985
Electronics companies disestablished in 1991
Technology companies established in 1985
Technology companies disestablished in 1991 | PrairieTek | [
"Technology"
] | 469 | [
"Computing stubs",
"Computer company stubs"
] |
15,883,470 | https://en.wikipedia.org/wiki/Online%20identity%20management | Online identity management (OIM), also known as online image management, online personal branding, or personal reputation management (PRM), is a set of methods for generating a distinguished web presence of a person on the Internet. Online identity management also refers to identity exposure and identity disclosure, and has particularly developed in the management on online identity in social network services or online dating services.
Identity management is also an important building block of cybersecurity. It forms the basis for most access control types and establishing accountability online.
Aspects
One aspect of the online identity management process has to do with improving the quantity and quality of traffic to sites that have content related to a person. In that aspect, OIM is a part of another discipline called search engine optimization with the difference that the only keyword is the person's name, and the optimization object is not necessary a single web site; it can consider a set of completely different sites that contain positive online references. The objective in this case is to get high rankings for as many sites as possible when someone search for a person's name. If the search engine used is Google, this action is called "to google someone".
Another aspect has to do with impression management, i.e. "the process through which people try to control the impressions other people form of them". One of the objectives, in particular, is to increase the online reputation of the person.
Pseudonyms are sometimes used to protect the true online identity of individuals from harm. This can be the case when presenting unpopular views or dissenting opinion online in a way that will not affect the true identity of the author. Facebook estimates that up to 11.2% of accounts are fake. Many of these profiles are used as logins to protect the true identity of online authors.
An individual's presence could be reflected in any kind of content that refers to that person, including news, participation in blogs and forums, personal web sites, social media presence, pictures, video, etc. Because of that, online identity management often involves participation in social media sites like Facebook, Google+, LinkedIn, Flickr, YouTube, Twitter, Last.fm, Myspace, Quora, Tumblr, Pinterest and other online communities and community websites, and is related to blogging, blog social networks like MyBlogLog and blog search engines like Technorati.
OIM can serve specific purposes such as a professional networking platform. OSN platforms represent who the user is and what attributes they bring to the world. The information a user can plug into their profile is usually not verified, which can lead to specifics forms of false identity. OIM can also consist in more questionable practices such as the case of buying "likes", "friends", or "subscribers".
Objective
The Objective of Online Identity Management is to:
Maximize the appearances of positive online references about a specific person, targeting not only to users that actively search for that person on any search engine, but also to those that eventually can reach a person's reference while browsing the web.
Build an online identity in case the person's web presence is minimal or nonexistent.
Solve online reputation problems. In this case, the process can also be named online reputation management.
To express opinions that may be unheard, if the person's reputation was not previously favored.
Online Identity management can be utilized on a personal and professional level. Online identity management utilizes web presence to gain attention from potential huge clients to followers. A person managing online identity will use social media sites like Twitter, Facebook, Instagram Youtube, Snapchat, and networking sites to increase their online activity. They also use other tools like search engine optimization and advertisements to boost their audience and gain insights on their audience. Online Identity Management is most effective with the use of all social networking sites and posting frequently. This technique is used to target their audience and to make sure their audience does not miss any content. Additionally, Online Identity Management can be used to manipulate followers, viewers, and clients by using misleading or over-exaggerated information.
Motivation
The reason why someone would be interested in doing online identity management is closely related to the increasing number of constituencies that use the internet as a tool to find information about people. A survey by CareerBuilder.com found that one in four hiring managers used search engines to screen candidates. One in 10 also checked candidates' profiles on social networking sites such as Facebook, Instagram, Twitter, Youtube and other communicative networks. According to a December 2007 survey by the Ponemon Institute, a privacy research organization, roughly half of U.S. hiring officials use the Internet in vetting job applications. Online identity management may also be used to increase an individual's professional online presence. When practicing online identity management, employers receive a satisfied notion regarding their candidate's professional attitudes and personality. This may result in a candidate receiving the job based on their professional online presence. Online Identity management is key to having a successful business and relationship with the public. An online presence is vital to the digital world we live in today. Many employers check the social network account of their candidate to grasp the kind of person they are. Even after being hired companies will continuously check account to ensure professionalism and company privacy is being maintained.
The concept of manipulating search results to show positive results is intriguing for both individuals and businesses. Individuals that want to hide from their past can use OIM to repair their online image and suppress content that damages their credibility, employability and reputation. By changing what people see when searching for an individual, they are able to create a completely new and positive identity in its place. In 2014, the EU ruled that people have "The right to be forgotten", and that in some circumstances content can be removed from Google's search index.
In 1988, the European Union passed the Safe Harbor Act which prohibited the sharing unauthorized personal information. Many companies to this day voluntarily comply to this law; however, it is the job of the user to fully ensure the safety of their online identity. The European Union later passed the a landmark ruling back in 2014, that stated that all individuals have the "right to be forgotten". This granted user's the removal of all irrelevant data that could harm one's online identity
Online identity management is also a factor and important when a person is seeking a need or good. Depending on companies online viewers and content can encourage or discourage a sale. Online identity management is important because decisions can be made depending on online activity. Depending on the motives of the goods, company, and person their online identity should serve the purpose of heightening their likeness, attractiveness, and exposure.
See also
Digital identity
Identity management
Customer Identity Access Management
Impression management
Information privacy
Internet activism
Online identity
Online participation
Online reputation management (ORM)
Persona (user experience)
Personal branding
Personalized marketing
Reputation capital
Reputation system
Search engine optimization
Signalling theory
Social profiling
Social media optimization
Social network service
References
Internet terminology
Online advertising
Identity management | Online identity management | [
"Technology"
] | 1,418 | [
"Computing terminology",
"Internet terminology"
] |
15,883,635 | https://en.wikipedia.org/wiki/Sense%20switch | A sense switch, or program switch, is a switch on the front panel of a computer whose state can be tested by conditional branch instructions in software. Most early computers had several sense switches. They were typically used by the operator to set program options.
IBM's first commercial computer, the IBM 701 Defense Calculator, announced on May 21, 1952, had four lights and six switches on the upper right of its front panel marked Sense (see photo). The switches could be tested and the lights turned on or off under program control. The same number of sense switches and lights were on the front panels of all first and second generation machines in the IBM scientific computer line, the IBM 701, IBM 704, IBM 709, IBM 7090 and the IBM 7094. IBM's Fortran language, first released for the 704, included statements to test the switches and set or reset the lights.
IF (SENSE SWITCH i) n1, n2
SENSE LIGHT i
IF (SENSE LIGHT i) n1, n2
where n1 and n2 are statement numbers. SENSE LIGHT 0 reset all four lights.
On the IBM 1620 there are four switches, and their state can be tested via special forms of the IF-statement offered by the FORTRAN compiler for the IBM 1620. For the IBM 1130 there are sixteen switches matching the sixteen-bit word size of the computer, plus a toggle switch adjacent to the power on/off switch. These bit-switches are more normally used with the computer stopped to specify some memory address to be viewed (via the indicator lights on the front panel), or set. The state of these switches can be determined by a program, and so a running program might modify its behavior depending on the switches, such as change the amount of progress information printed, alter the tactics of a multi-variable optimization attempt, and so on. The IBM 1130 also has an "Interrupt Request" key associated with the console printer, whose pressing might cause a suitably programmed long-running program to type a progress report on the console printer. In the more usual batch job environment, it was pressed by the computer operator to signal the operating system to terminate a running program that had perhaps overrun its allowed time, or commenced misbehavior such as repeatedly printing blank lines.
The front panel of the Data General Eclipse computer has 5 sense switches, 16 address switches, and 5 control switches, as shown (left to right) in the figure at right.
Personal computers replace the function of fixed sense switches with the keyboard and screen user interface.
A typical running application has two modes: either it has nothing to do and awaits some user action, or, some action is in progress that will take a long time to complete. If a program does not regularly test the state of sense switches during a long calculation, they are ineffective at changing the program's operation.
References
Sense switch | Sense switch | [
"Technology"
] | 593 | [
"Computing stubs",
"Computer hardware stubs"
] |
15,883,912 | https://en.wikipedia.org/wiki/Wurster%27s%20blue | Wurster's blue is the radical cation of the colorless chemical N,N,N′,N′-tetramethyl-p-phenylenediamine, also known as TMPD. This is an easily oxidized phenylenediamine, which loses two electrons in one-electron oxidation steps; the radical cation is a characteristic blue-violet color, which gives the compound part of its name. The remaining part of its name comes from its discoverer, the German chemist Casimir Wurster (7 August 1854 – 29 November 1913).
The hydrochloride salt of TMPD finds use as a redox indicator in the oxidase test and is also used in electron transport chain analysis as it is capable of donating electrons to cytochrome c. The midpoint potential for titration of the first electron is given as 0.276 V vs Standard hydrogen electrode, and this transition is useful in potentiometric titrations as both a redox mediator and indicator. The two electron-oxidized colorless p-quinone-diiminium cation is unstable in aqueous solutions; therefore, highly oxidizing conditions should be avoided in titrations relying on TMPD, or reached only during the final stage of the titration. The second oxidation step is not well separated from the first on the redox scale, so some instability will be encountered on the oxidizing side of 0.276, and it is impossible to prepare pure aqueous solutions of Wurster's blue due to its dismutation to the unstable di-iminium ion and TMPD.
References
Anilines
Diamines
Redox indicators | Wurster's blue | [
"Chemistry"
] | 359 | [
"Redox indicators",
"Electrochemistry"
] |
15,884,738 | https://en.wikipedia.org/wiki/Monocarboxylate%20transporter%201 | Monocarboxylate transporter 1 is a ubiquitous protein that in humans is encoded by the SLC16A1 gene (also known as MCT1). It is a proton coupled monocarboxylate transporter.
Biochemistry
Detailed kinetic analysis of monocarboxylate transport in erythrocytes revealed that MCT1 operates through an ordered mechanism. MCT1 has a substrate binding site open to the extracellular matrix which binds a proton first followed by the lactate anion. The protein then undergoes a conformational change to a new 'closed'' conformation that exposes both the proton and lactate to the opposite surface of the membrane where they are released, lactate first and then the proton. For net transport of lactic acid, the rate-limiting step is the return of MCT1 without bound substrate to the open conformation. For this reason, exchange of one monocarboxylate inside the cell with another outside is considerably faster than net transport of a monocarboxylate across the membrane.
MCT1 can be upregulated by PPAR-α, Nrf2, and AMPK.
Animal studies
Overexpression of MCT1 has been shown to increase the efficacy of an anti-cancer drug currently undergoing clinical trials called 3-bromopyruvate in breast cancer cells.
Clinical significance
Most cases of alveolar soft part sarcoma show PAS(+), diastase-resistant (PAS-D (+)) intracytoplasmic crystals which contain CD147 and monocarboxylate transporter 1 (MCT1). Overexpression of MCT1 in pancreatic beta cells leads to hyperinsulinism during exercise.
Hyperinsulinemic hypoglycemia, familial, 7 (HHF7) is an autosomal dominant disease on the SLC16A1/MCT gene on chromosome 1p13.2. It causes hyperinsulinemic hypoglycemia, where hyperinsulinism is exercise-induced.
Monocarboxylate transporter 1 deficiency (MCTD1) is an autosomal dominant and recessive disease on the SLC16A1/MCT1 gene on chromosome 1p13.2. It causes poor feeding and vomiting, intellectual disability, ketotic hypoglycemia, ketoacidosis, ketonuria, with episodes brought on by fasting or infection.
Erythrocyte lactate transporter defect (formerly, myopathy due to lactate transport defect) is an autosomal dominant disease on the SLC16A1/MCT gene on chromosome 1p.13.2. It causes exercise-induced muscle cramping, stiffness, and fatigue (exercise intolerance); symptoms may also be induced by heat. Although symptoms present in the muscles, muscle biopsy and EMG are normal. Decreased erythrocyte (red blood cell) lactate clearance, decreased lactate clearance from muscle after exercise, and elevated serum creatine kinase.
References
Further reading
Solute carrier family
Inborn errors of carbohydrate metabolism | Monocarboxylate transporter 1 | [
"Chemistry"
] | 658 | [
"Inborn errors of carbohydrate metabolism",
"Carbohydrate metabolism"
] |
15,885,588 | https://en.wikipedia.org/wiki/8-Oxoguanine | 8-Oxoguanine (8-hydroxyguanine, 8-oxo-Gua, or OH8Gua) is one of the most common DNA lesions resulting from reactive oxygen species modifying guanine, and can result in a mismatched pairing with adenine resulting in G to T and C to A substitutions in the genome. In humans, it is primarily repaired by DNA glycosylase OGG1. It can be caused by ionizing radiation, in connection with oxidative metabolism.
In body fluids
Increased concentrations of 8-oxoguanine in body fluids have been found to be associated with increased risk of mutagenesis and carcinogenesis.
Care must be taken in the assay of 8-oxoguanine due to the ease with which it can be oxidised during extraction and the assay procedure.
Cancer, aging, infertility
The role of the deoxyriboside form of 8-oxoguanine, 8-oxo-2'-deoxyguanosine (abbreviated 8-oxo-dG or 8-OHdG) in cancer and aging also applies to 8-oxoguanine. Oxoguanine glycosylase is employed in the removal of 8-oxoguanine from DNA by the process of base excision repair. As described in oxoguanine glycosylase, deficient expression of this enzyme causes 8-oxoguanine to accumulate in DNA. This accumulation may then lead upon replication of DNA to mutations including some that contribute to carcinogenesis. 8-oxoguanine is usually formed by the interaction of reactive oxygen species (ROS) with the guanine base in DNA under conditions of oxidative stress; as noted in the article about them, such species may have a role in aging and male infertility, and 8-oxoguanine can be used to measure such stress.
References
DNA repair
Purines | 8-Oxoguanine | [
"Biology"
] | 410 | [
"Molecular genetics",
"DNA repair",
"Cellular processes"
] |
15,885,724 | https://en.wikipedia.org/wiki/Prime%20mover%20%28locomotive%29 | In engineering, a prime mover is an engine that converts chemical energy of a fuel into useful work. In a locomotive, the prime mover is thus the source of power for its propulsion. In an engine-generator set, the engine is the prime mover, as distinct from the generator.
Definition
In a diesel-mechanical locomotive, the prime mover is the diesel engine that is mechanically coupled to the driving wheels (drivers). In a diesel-hydraulic locomotive, the prime mover is the diesel engine that powers the pumps of one or more torque converters mechanically coupled to the drivers. In a diesel-electric locomotive, the prime mover is the diesel engine that rotates the main generator responsible for producing electricity to power the traction motors that are geared to the drivers. The prime mover can also be a gas turbine instead of a diesel engine. In either case, the generator, traction motors and interconnecting apparatus are considered to be the power transmission system and not part of the prime mover. A wired-electric or battery-electric locomotive has no on-board prime mover, instead relying on an external power station.
Weight distribution
The power unit represents the main weight in a locomotive design, other than the chassis or body. Its position back and forth is at the designer's choice and may be used to control overall weight distribution. In most locomotives designs, the power unit is placed centrally. In some locomotives, it is offset to one end, or the heavier engine is outboard of the generator. In extreme cases, such as C-B wheel arrangements, the weight on each bogie may differ so much that the engine-end bogie is given an extra carrying axle, to keep individual axle loads more consistent.
See also
Engine
Powerpack (drivetrain)
References
Locomotive engines | Prime mover (locomotive) | [
"Technology"
] | 366 | [
"Locomotive engines",
"Engines"
] |
15,887,272 | https://en.wikipedia.org/wiki/Hiatus%20%28anatomy%29 | In anatomy, a hiatus is a natural fissure in a structure. Examples include:
Adductor hiatus
Aortic hiatus
Esophageal hiatus, the opening in the diaphragm through which the esophagus passes from the thorax into the abdomen
Greater petrosal nerve hiatus
Maxillary hiatus
Sacral hiatus
Semilunar hiatus
Urogenital hiatus
Anatomy | Hiatus (anatomy) | [
"Biology"
] | 78 | [
"Anatomy"
] |
13,200,604 | https://en.wikipedia.org/wiki/Derivator | In mathematics, derivators are a proposed frameworkpg 190-195 for homological algebra giving a foundation for both abelian and non-abelian homological algebra and various generalizations of it. They were introduced to address the deficiencies of derived categories (such as the non-functoriality of the cone construction) and provide at the same time a language for homotopical algebra.
Derivators were first introduced by Alexander Grothendieck in his long unpublished 1983 manuscript Pursuing Stacks. They were then further developed by him in the huge unpublished 1991 manuscript Les Dérivateurs of almost 2000 pages. Essentially the same concept was introduced (apparently independently) by Alex Heller.
The manuscript has been edited for on-line publication by Georges Maltsiniotis. The theory has been further developed by several other people, including Heller, Franke, Keller and Groth.
Motivations
One of the motivating reasons for considering derivators is the lack of functoriality with the cone construction with triangulated categories. Derivators are able to solve this problem, and solve the inclusion of general homotopy colimits, by keeping track of all possible diagrams in a category with weak equivalences and their relations between each other. Heuristically, given the diagramwhich is a category with two objects and one non-identity arrow, and a functorto a category with a class of weak-equivalences (and satisfying the right hypotheses), we should have an associated functorwhere the target object is unique up to weak equivalence in . Derivators are able to encode this kind of information and provide a diagram calculus to use in derived categories and homotopy theory.
Definition
Prederivators
Formally, a prederivator is a 2-functorfrom a suitable 2-category of indices to the category of categories. Typically such 2-functors come from considering the categories where is called the category of coefficients. For example, could be the category of small categories which are filtered, whose objects can be thought of as the indexing sets for a filtered colimit. Then, given a morphism of diagramsdenote byThis is called the inverse image functor. In the motivating example, this is just precompositition, so given a functor there is an associated functor . Note these 2-functors could be taken to bewhere is a suitable class of weak equivalences in a category .
Indexing categories
There are a number of examples of indexing categories which can be used in this construction
The 2-category of finite categories, so the objects are categories whose collection of objects are finite sets.
The ordinal category can be categorified into a two category, where the objects are categories with one object, and the functors come from the arrows in the ordinal category.
Another option is to just use the category of small categories.
In addition, associated to any topological space is a category which could be used as the indexing category.
Moreover, the sites underlying the Zariski, Etale, etc., topoi of for some scheme or algebraic space along with their morphisms can be used for the indexing category
This can be generalized to any topos , so the indexing category is the underlying site.
Derivators
Derivators are then the axiomatization of prederivators which come equipped with adjoint functors
where is left adjoint to and so on. Heuristically, should correspond to inverse limits, to colimits.
References
Bibliography
External links
derivator in nLab
Subtopoi, open subtopos and closed subtopos
https://golem.ph.utexas.edu/category/2018/03/stabilization_of_derivators.html
Homotopical algebra
Homological algebra | Derivator | [
"Mathematics"
] | 800 | [
"Fields of abstract algebra",
"Mathematical structures",
"Category theory",
"Homological algebra"
] |
13,200,698 | https://en.wikipedia.org/wiki/List%20of%20historical%20Gnutella%20clients | Many projects have attempted to use the Gnutella network, since its introduction in early 2000. This list enumerates abandoned or discontinued projects.
List of discontinued clients
List of former gnutella clients
Software that still work but dropped the GNUtella protocol.
Additional information
Mutella
Developers - Max Zaitsev, Gregory Block
Operating system - UNIX
Latest release version - 0.4.5
Genre - peer-to-peer
License - GPL
Website - Mutella development site
Mutella was a Gnutella client developed by Max Zaitsev and Gregory Block. It had two user interfaces, one for textmode use and another called remote control, which ran on an integrated web server and was used by a web browser. The first public version of Mutella was published on October 6, 2001.
The Mutella logo was changed into a squid somewhere around version 4.1. Before this change the logo used to be an Ouroboros. There was a blue and a black version of the ouroboros logo.
SwapNut
Slashdot reports that LimeWire and SwapNut used the same code. The website was www.swapnut.com.
XoloX
XoloX was a Gnutella-based peer-to-peer file sharing application for Windows. It advertised having no spyware, adware, or hijackware. However, upon installation, it prompted the user to install programs suspected to be of that kind. Also, Microsoft Anti-Spyware detected adware programs when you started to install the program.
XoloX links
www.xolox.nl was the Official Website. Dead since June 2007.
Review: Xolox
See also
Abandonware
Comparison of Gnutella software
References
Discontinued Gnutella Clients
Gnutella clients
Gnutella clients, historical | List of historical Gnutella clients | [
"Technology"
] | 364 | [
"Computing-related lists",
"Lists of software"
] |
13,200,967 | https://en.wikipedia.org/wiki/Entegris | Entegris, Inc. is a supplier of materials for the semiconductor and other high-tech industries. Entegris has approximately 8,000 employees throughout its global operations. It has manufacturing, customer service and/or research facilities in the United States, Canada, China, Germany, Israel, Japan, Malaysia, Singapore, South Korea, and Taiwan. The company’s corporate headquarters are in Billerica, Massachusetts.
The company seeks to help manufacturers increase their yields by improving contamination control in several key processes, including photolithography, wet etch and clean, chemical-mechanical planarization, thin-film deposition, bulk chemical processing, wafer and reticle handling and shipping, and testing, assembly and packaging. Approximately 80% of the company's products are used in the semiconductor industry.
Products
Entegris products include: filtration products that purify process gases and fluids, as well as the ambient environment; liquid systems and components that dispense, control, or transport process fluids; high-performance materials and specialty gas management solutions; wafer carriers and shippers that protect the semiconductor wafer from contamination and breakage; and specialized graphite, silicon carbide, and coatings.
History
The company was incorporated in 1999 as the combined entity of Fluoroware, Inc., which began operating in 1966, and EMPAK, Inc. The company went public in 2000.
In August 2005, Entegris merged with Mykrolis Corporation, a publicly held supplier of filtration products to the semiconductor industry. Mykrolis was spun-out of Millipore Corporation in 2000.
In August 2008, Entegris acquired Poco Graphite, Inc., a Decatur, Texas supplier of specialized graphite and silicon carbide products for use in semiconductor, EDM, glass bottling, biomedical, aerospace, and alternative energy applications.
On April 30, 2014, Entegris acquired Danbury, Connecticut-based ATMI, a publicly held company providing critical materials and materials-handling solutions to the semiconductor industry, in a $1.1 billion transaction.
In Dec 2020, Entegris announced an investment of US$500 million, building a state-of-the-art facility in Taiwan. The project is expected to complete in three years in Kaohsiung Science Park.
In July 2022, Entegris acquired another US semiconductor chemicals company, CMC Materials Inc, for $5.7 billion. The acquisition, previously known as Cabot Microelectronics Corp, had 2,200 employees.
References
Li1, S., Shih, S., Yen, S., Yang, J.: "Case Study of Microcontamination Control." Aerosol and Air Quality Research, Vol. 7, No. 3, pp. 432–442, 2007
Manufacturing companies based in Massachusetts
Manufacturing companies established in 1966
Equipment semiconductor companies
1966 establishments in Massachusetts
Companies listed on the Nasdaq
2000 initial public offerings
2005 mergers and acquisitions
1999 mergers and acquisitions | Entegris | [
"Engineering"
] | 626 | [
"Equipment semiconductor companies",
"Semiconductor fabrication equipment"
] |
13,201,898 | https://en.wikipedia.org/wiki/Nokia%201610 | Nokia 1610 is a mid-range mobile phone model manufactured by Nokia. It complemented the Nokia 2110 business model, but had significantly fewer features. It was introduced in April 1996 and released in May and became popular at the time.
Description
The Nokia 1610 had a monochromatic display which could show two rows of text at a time. The operating manual did not mention a possibility to send text messages, but at least units sold from 1996 and onwards included the function. The SMS capable version was called 1610 Plus. The phone used an external rigid antenna, but had a groove on the inside of the battery to accommodate a pull-out type antenna. The 1610 used a credit card size SIM-card, and was powered by a NiMH type battery with a capacity of 600 mAh. The phone was stated to have up to 7 hours of call time and up to 200 hours of standby time. There was a dedicated voicemail button.
Chargers compatible: ACH-6, ACH-8
Reception
Contemporary French magazine Mobiles gave an overall positive review of the phone, noting the long battery life, accessible software and font size, and affordable price. It was noted that the large size of the phone made it seem outdated. The book Mobile Usability praised the user interface, stating it "supported the necessary features of its time quite well."
References
1610
Mobile phones introduced in 1996 | Nokia 1610 | [
"Technology"
] | 281 | [
"Mobile technology stubs",
"Mobile phone stubs"
] |
13,202,316 | https://en.wikipedia.org/wiki/Near-semiring | In mathematics, a near-semiring, also called a seminearring, is an algebraic structure more general than a near-ring or a semiring. Near-semirings arise naturally from functions on monoids.
Definition
A near-semiring is a set S with two binary operations "+" and "·", and a constant 0 such that (S, +, 0) is a monoid (not necessarily commutative), (S, ·) is a semigroup, these structures are related by a single (right or left) distributive law, and accordingly 0 is a one-sided (right or left, respectively) absorbing element.
Formally, an algebraic structure (S, +, ·, 0) is said to be a near-semiring if it satisfies the following axioms:
(S, +, 0) is a monoid,
(S, ·) is a semigroup,
(a + b) · c = a · c + b · c, for all a, b, c in S, and
0 · a = 0 for all a in S.
Near-semirings are a common abstraction of semirings and near-rings [Golan, 1999; Pilz, 1983]. The standard examples of near-semirings are typically of the form M(Г), the set of all mappings on a monoid (Г; +, 0), equipped with composition of mappings, pointwise addition of mappings, and the zero function. Subsets of M(Г) closed under the operations provide further examples of near-semirings. Another example is the ordinals under the usual operations of ordinal arithmetic (here Clause 3 should be replaced with its symmetric form c · (a + b) = c · a + c · b. Strictly speaking, the class of all ordinals is not a set, so the above example should be more appropriately called a class near-semiring. We get a near-semiring in the standard sense if we restrict to those ordinals strictly less than some multiplicatively indecomposable ordinal.
Bibliography
Golan, Jonathan S., Semirings and their applications. Updated and expanded version of The theory of semirings, with applications to mathematics and theoretical computer science (Longman Sci. Tech., Harlow, 1992, . Kluwer Academic Publishers, Dordrecht, 1999. xii+381 pp.
Krishna, K. V., Near-semirings: Theory and application, Ph.D. thesis, IIT Delhi, New Delhi, India, 2005.
Pilz, G., Near-Rings: The Theory and Its Applications, Vol. 23 of North-Holland Mathematics Studies, North-Holland Publishing Company, 1983.
The Near Ring Main Page at the Johannes Kepler Universität Linz
Willy G. van Hoorn and B. van Rootselaar, Fundamental notions in the theory of seminearrings, Compositio Mathematica v. 18, (1967), pp. 65–78.
Algebraic structures | Near-semiring | [
"Mathematics"
] | 646 | [
"Mathematical structures",
"Mathematical objects",
"Algebraic structures"
] |
13,203,670 | https://en.wikipedia.org/wiki/Shell%20Rotella | Shell Rotella is a line of heavy-duty engine lubrication products produced by Shell plc. The line includes engine oils, gear oils and coolants. The oil carries both the American Petroleum Institute (API) diesel "C" rating as well as the API gasoline engine "S" rating. Ratings differ based on the oil. Rotella oils, like the T3 15W-40, meet both the API CJ-4 and SM specifications, and may be used in both gasoline and diesel engines. However, it is formulated specifically for vehicles without catalytic converters, containing phosphorus levels beyond the 600–800 ppm range. Therefore, Rotella is not recommended for gasoline vehicles with catalytic converters due to the higher risk of damaging these emission controls. Newer formulations of Rotella T6 however are API SM rated as safe for pre-2011 gasoline vehicles.
Product lineup
The Rotella product family is categorized by Shell into the following product families:
Engine oils
Coolants
Tractor fluid (a universal transmission, gear, hydraulic, and wet brake fluid)
Gear oil
In the engine oil family, there are four basic oil sub-families:
Multigrade conventional oil—in SAE 10W-30 and 15W-40 viscosity ranges
Multigrade synthetic oil—in SAE 5W-40 and 15w-40 viscosity ranges
Single grade conventional oil—in SAE 20, 30, 40 and 50
Synthetic blend oil
Shell is marketing their new CJ-4/SM oil as "Triple Protection," meaning it provides enhanced qualities for engine wear, soot control and engine cleanliness. Shell's Rotella website indicates that on-road testing confirms the new Triple Protection technology produces better anti-wear characteristics than their existing CI-4+ rated Rotella oil. This is achieved despite a lower zinc and phosphorus additive level as called for by the API CJ-4 specification. (The 15W-40 Rotella T with Triple Protection oil has approximately 1200 ppm of zinc and 1100 ppm phosphorus at the time of manufacture.)
The Shell Rimula brand is multi-national and comparable in all aspects, including the classification names. (i.e. T-5, T-6, Etc.)
Competitors
Rotella competes with similar lubrication products from other oil manufacturers. Some notable competitive products are:
ConocoPhillips 76 Lubricants Guardol ECT with Liquid Titanium
Mobil Delvac
Chevron Delo
Petro-Canada Duron
CITGO Citgard
Petrol Ofisi Maximus
Royal Purple
Valvoline Premium Blue
Castrol Tection
Motorcycle usage
Though marketed as an engine oil for diesel trucks, Rotella oil has found popularity with motorcyclists as well. The lack of "friction modifiers" in Rotella means they do not interfere with wet clutch operations. This is called a "shared sump" design, which is unlike automobiles which maintain separate oil reservoirs – one for the engine and one for the transmission. Used oil analysis reports on BobIsTheOilGuy.com have shown wear metals levels comparable to oils marketed as motorcycle-specific.
Older cars
Rotella oil is ideal for older cars without catalytic converters and for which zinc was a requirement at the time for engine oil. It eliminates the need for adding a zinc additive to modern oils.
JASO-MA
Both Rotella T4 15W-40 conventional and, Rotella T6 5W-40 and 15w-40 Synthetic both list the JASO MA/MA 2 standard; this information can be found on the bottle adjacent to the SAE/API rating stamp. JASO is an acronym that stands for Japanese Automotive Standards Organization. Note that the 10W-30 conventional oil does not list JASO-MA.
Use in Passenger and turbocharged cars
Likewise with motorcycles, though marketed as an engine oil for diesel trucks, Rotella T6 5W-40 synthetic oil has also found popularity with drivers and tuners of gasoline powered vehicles that utilize turbocharging or other forms of forced induction. Several owners of high performance model cars have adopted its use due to its high heat tolerance and its resistance to shearing. Rotella T6 is a Non Energy Conserving Oil, and does not meet GF-5 Oil specifications. When Rotella T6 was revised for the API specification (for use in spark ignition engines), its zinc levels were effectively reduced. Higher (content) zinc additives (ZDDP) are required for flat tappet engines and cartridge bearings, which in previous formulations Rotella T6 had desirable levels of zinc (ZDDP).
CK-4 Update
In December 2016 Shell Rotella Oils were updated to the newer API CK-4 Oil specification (Previously CJ-4).
″The new API CK-4 and FA-4 categories are driven by changes in engine technology to meet emissions, renewable fuel and fuel economy standards for reduced CO2 and other greenhouse gas emissions″
CK-4 Update Controversy
Upon Release of CK-4 API Licensing (Dec/2016) FORD issued a statement stating ″Ford testing has shown some CK-4 type formulations have shown inadequate wear protection compared to CJ-4 formulations developed and licensed before 2016″ Similarly, Stellantis also issued a TSB citing Oil requirements that eliminated CK-4 Rotella from being an approved option in the 6.7L Diesel engines. .And RAM's 3rd Gen ECO-Diesel equipped trucks no longer recommend CK-4 in their Diesel engines.
Rotella has since gained Fords updated oil specification by raising the phosphorus level of Rotella products. Rotella does not meet Stellantis' new oil specification as of Jan/2024.
With Rotella's CK-4 offerings under a new light, their robustness for use in Gasoline engines has come into question. Many users that once relied on Rotella in their gasoline engines have moved onto Motor oils that meet more stringent Gasoline Motor oil tests such as Porsche A40, BMW LL01, and MB229.5. Another Shell product that meets these specifications would be Pennzoil Platinum® Euro.
References
External links
Petroleum products
Lubricants
Motor oils
Shell plc brands
Dutch brands | Shell Rotella | [
"Chemistry"
] | 1,259 | [
"Petroleum",
"Petroleum products"
] |
13,203,980 | https://en.wikipedia.org/wiki/Hull%20classification%20symbol%20%28Canada%29 | The Royal Canadian Navy uses hull classification symbols to identify the types of its ships, which are similar to the United States Navy's hull classification symbol system. The Royal Navy and some European and Commonwealth navies (19 in total) use a somewhat analogous system of pennant numbers.
In a ship name such as the ship prefix HMCS for Her or His Majesty's Canadian Ship indicates the vessel is a warship in service to the Monarch of Canada, while the proper name Algonquin may follow a naming convention for the class of vessel. The hull classification symbol in the example is the parenthetical suffix (DDG 283), where the hull classification type DDG indicates that the Algonquin is a guided-missile destroyer and the hull classification number 283 is unique within that type. Listed below are various hull classification types with some currently in use and others that are retired and no longer in use.
Auxiliary ships
AGOR: Auxiliary General Oceanographic Research (retired),
AGSC: surveying vessel (retired) Example included:
AOR: Auxiliary Oiler Replenishment,
ARE: Auxiliary Replenishment Escort (retired). Examples
ASL: diving support vessel (retired from the Royal Canadian Navy) Included:
F: escort armed ships (retired pre World War II passenger ships that were converted to military roles during the war)
FHE: Fast Hydrofoil Escort (retired, prototype tested 1968–1971),
K: sloop and submarine tender (also used for frigates and corvettes). Example included:
KC: sail training. Example includes:
PCT: Patrol Craft Training (supersedes YAG) Examples include: s
T: armed trawler (retired). Example included: ,
YAG: Yard Auxiliary General (retired training vessels, superseded by PCT) YAG training vessels CFAV Grizzly (YAG 306), CFAV Cougar (YAG 308)
YTB: Yard Tug. Examples include:
YTL: Yard Tug. Examples include: s Lawrenceville (YTL 590), CFAV Parksville (YTL 591)
YTM: Yard Tug. Example includes:
YTR: Yard Tractor tug fireboats. Examples include: s
Aircraft carriers
CVL: light carrier (retired) Examples included: , , and
D: World War II escort carrier (retired) Examples included and s:
R: carrier World War II (retired, was also used for destroyers)
Corvettes
K: corvette (retired, was also used for frigates and a sloop-of-war). Examples included: s
Cruisers
C: light cruiser (retired) Examples included
Destroyers
D: destroyer - World War II era (retired) eg
DD: destroyer - World War II era (retired, DD was used by the United States Navy, I was used by the Royal Canadian Navy for US built DD destroyers)
DDE: escort destroyer (retired)
DDH: air defence destroyer - helicopter, eg
DDG: area air defence - guided missile
G: destroyer - World War II era (retired, included and es)
H: escort destroyer - World War II era (retired, included and es)
I: destroyer - World War II era (retired)< Examples included: , ,
R: destroyer (post World War II retired, was also used for a carrier) World War II destroyer examples included: - V class and -
Frigates
F: frigate
FFE: escort frigate (post World War II; used for , retired)
FFH: multi-role patrol frigate - helicopter eg
Minesweepers
J: minesweeper (retired, used for World War II era , , and s)
MCB: post World War II minesweeper (retired) used for
MSA: Mine Sweeper Auxiliary: (in use 1989–2000, retired)
MM: Mechanical Minesweeper - more recently known as coastal defence vessels such as
Submarines
CC: World War I era gas powered submarines
CH: World War I era diesel-electric submarines
S: Submarine (retired Cold War era diesel electric: last used by s)
SS: Submarine (retired, used for US built (1961–1969) and (1968–1974)-class vessels)
SSK: Hunter-Killer Submarine or long range submarines. Eg Victoria-class submarines
Patrol
AOPV: Arctic and Offshore Patrol Vessel
Notes
References
Royal Canadian Navy
Naval ships of Canada
Ship identification numbers | Hull classification symbol (Canada) | [
"Mathematics"
] | 881 | [
"Ship identification numbers",
"Mathematical objects",
"Numbers"
] |
13,204,455 | https://en.wikipedia.org/wiki/Kowalski%20ester%20homologation | The Kowalski ester homologation is a chemical reaction for the homologation of esters.
This reaction was designed as a safer alternative to the Arndt–Eistert synthesis, avoiding the need for diazomethane. The Kowalski reaction is named after its inventor, Conrad J. Kowalski.
Reaction mechanism
The mechanism is disputed.
Variations
By changing the reagent in the second step of the reaction, the Kowalski ester homologation can also be used for the preparation of silyl ynol ethers.
See also
Curtius rearrangement
References
Rearrangement reactions
Homologation reactions
Carbon-carbon bond forming reactions
Name reactions | Kowalski ester homologation | [
"Chemistry"
] | 133 | [
"Name reactions",
"Carbon-carbon bond forming reactions",
"Rearrangement reactions",
"Organic reactions"
] |
13,205,367 | https://en.wikipedia.org/wiki/Separable%20algebra | In mathematics, a separable algebra is a kind of semisimple algebra. It is a generalization to associative algebras of the notion of a separable field extension.
Definition and first properties
A homomorphism of (unital, but not necessarily commutative) rings
is called separable if the multiplication map
admits a section
that is a homomorphism of A-A-bimodules.
If the ring is commutative and maps into the center of , we call a separable algebra over .
It is useful to describe separability in terms of the element
The reason is that a section σ is determined by this element. The condition that σ is a section of μ is equivalent to
and the condition that σ is a homomorphism of A-A-bimodules is equivalent to the following requirement for any a in A:
Such an element p is called a separability idempotent, since regarded as an element of the algebra it satisfies .
Examples
For any commutative ring R, the (non-commutative) ring of n-by-n matrices is a separable R-algebra. For any , a separability idempotent is given by , where denotes the elementary matrix which is 0 except for the entry in the entry, which is 1. In particular, this shows that separability idempotents need not be unique.
Separable algebras over a field
A field extension L/K of finite degree is a separable extension if and only if L is separable as an associative K-algebra. If L/K has a primitive element with irreducible polynomial , then a separability idempotent is given by . The tensorands are dual bases for the trace map: if are the distinct K-monomorphisms of L into an algebraic closure of K, the trace mapping Tr of L into K is defined by . The trace map and its dual bases make explicit L as a Frobenius algebra over K.
More generally, separable algebras over a field K can be classified as follows: they are the same as finite products of matrix algebras over finite-dimensional division algebras whose centers are finite-dimensional separable field extensions of the field K. In particular: Every separable algebra is itself finite-dimensional. If K is a perfect field – for example a field of characteristic zero, or a finite field, or an algebraically closed field – then every extension of K is separable, so that separable K-algebras are finite products of matrix algebras over finite-dimensional division algebras over field K. In other words, if K is a perfect field, there is no difference between a separable algebra over K and a finite-dimensional semisimple algebra over K.
It can be shown by a generalized theorem of Maschke that an associative K-algebra A is separable if for every field extension the algebra is semisimple.
Group rings
If K is commutative ring and G is a finite group such that the order of G is invertible in K, then the group algebra K[G] is a separable K-algebra. A separability idempotent is given by .
Equivalent characterizations of separability
There are several equivalent definitions of separable algebras. A K-algebra A is separable if and only if it is projective when considered as a left module of in the usual way. Moreover, an algebra A is separable if and only if it is flat when considered as a right module of in the usual way.
Separable algebras can also be characterized by means of split extensions: A is separable over K if and only if all short exact sequences of A-A-bimodules that are split as A-K-bimodules also split as A-A-bimodules. Indeed, this condition is necessary since the multiplication mapping arising in the definition above is a A-A-bimodule epimorphism, which is split as an A-K-bimodule map by the right inverse mapping given by . The converse can be proven by a judicious use of the separability idempotent (similarly to the proof of Maschke's theorem, applying its components within and without the splitting maps).
Equivalently, the relative Hochschild cohomology groups of in any coefficient bimodule M is zero for . Examples of separable extensions are many including first separable algebras where R is a separable algebra and S = 1 times the ground field. Any ring R with elements a and b satisfying , but ba different from 1, is a separable extension over the subring S generated by 1 and bRa.
Relation to Frobenius algebras
A separable algebra is said to be strongly separable if there exists a separability idempotent that is symmetric, meaning
An algebra is strongly separable if and only if its trace form is nondegenerate, thus making the algebra into a particular kind of Frobenius algebra called a symmetric algebra (not to be confused with the symmetric algebra arising as the quotient of the tensor algebra).
If K is commutative, A is a finitely generated projective separable K-module, then A is a symmetric Frobenius algebra.
Relation to formally unramified and formally étale extensions
Any separable extension of commutative rings is formally unramified. The converse holds if A is a finitely generated K-algebra. A separable flat (commutative) K-algebra A is formally étale.
Further results
A theorem in the area is that of J. Cuadra that a separable Hopf–Galois extension has finitely generated natural R. A fundamental fact about a separable extension is that it is left or right semisimple extension: a short exact sequence of left or right that is split as , is split as . In terms of G. Hochschild's relative homological algebra, one says that all are relative -projective. Usually relative properties of subrings or ring extensions, such as the notion of separable extension, serve to promote theorems that say that the over-ring shares a property of the subring. For example, a separable extension R of a semisimple algebra S has R semisimple, which follows from the preceding discussion.
There is the celebrated Jans theorem that a finite group algebra A over a field of characteristic p is of finite representation type if and only if its Sylow p-subgroup is cyclic: the clearest proof is to note this fact for p-groups, then note that the group algebra is a separable extension of its Sylow p-subgroup algebra B as the index is coprime to the characteristic. The separability condition above will imply every finitely generated M is isomorphic to a direct summand in its restricted, induced module. But if B has finite representation type, the restricted module is uniquely a direct sum of multiples of finitely many indecomposables, which induce to a finite number of constituent indecomposable modules of which M is a direct sum. Hence A is of finite representation type if B is. The converse is proven by a similar argument noting that every subgroup algebra B is a direct summand of a group algebra A.
Citations
References
Samuel Eilenberg and Tadasi Nakayama, On the dimension of modules and algebras. II. Frobenius algebras and quasi-Frobenius rings, Nagoya Math. J. Volume 9 (1955), 1–16.
Algebras | Separable algebra | [
"Mathematics"
] | 1,576 | [
"Algebras",
"Mathematical structures",
"Algebraic structures"
] |
13,205,440 | https://en.wikipedia.org/wiki/Kavli%20Prize | The Kavli Prize was established in 2005 as a joint venture of the Norwegian Academy of Science and Letters, the Norwegian Ministry of Education and Research, and the Kavli Foundation. It honors, supports, and recognizes scientists for outstanding work in the fields of astrophysics, nanoscience and neuroscience. Three prizes are awarded every second year. Each of the three Kavli Prizes consists of a gold medal, a scroll, and a cash award of US$1,000,000. The medal has a diameter of , a thickness of , and weighs .
The first Kavli Prizes were awarded on 9 September 2008 in Oslo, presented by Haakon, Crown Prince of Norway.
Selection committees
The Norwegian Academy of Science and Letters appoints three prize committees consisting of leading international scientists after receiving recommendations made from the following organisations:
Chinese Academy of Sciences
French Academy of Sciences
Max Planck Society
United States National Academy of Sciences
Norwegian Academy of Science and Letters
Royal Society
Laureates
Astrophysics
Nanoscience
Neuroscience
See also
List of general science and technology awards
List of astronomy awards
List of neuroscience awards
The Brain Prize
Golden Brain Award
Gruber Prize in Neuroscience
W. Alden Spencer Award
Karl Spencer Lashley Award
Mind & Brain Prize
Ralph W. Gerard Prize in Neuroscience
References
External links
The Kavli Prize, official site
The Kavli Prize on The Kavli Foundation site
The Norwegian Ministry of Education and Research
Science and technology awards
Awards established in 2005
Astrophysics
Neuroscience awards
Norwegian science and technology awards
Astronomy prizes
2005 establishments in Norway | Kavli Prize | [
"Physics",
"Astronomy",
"Technology"
] | 305 | [
"Astronomy prizes",
"Astrophysics",
"Neuroscience awards",
"Science and technology awards",
"Astronomical sub-disciplines"
] |
13,205,506 | https://en.wikipedia.org/wiki/Grease%20ice | Grease ice is a very thin, soupy layer of frazil crystals clumped together, and only formed in large, open bodies of water most notably the ocean. Grease ice makes the water resemble an oil slick, the small crystals of ice held closely together reflect and refract light similarly to how oil will on water. Grease ice is the second stage in the formation of ice floes being the stage immediately following the frazil ice stage. Outside the ocean and seas, the Laurentian Great Lakes and Lake Baikal also form grease ice.
New sea ice formation takes place throughout the winter in the Arctic, and Antarctic where frazil forms and coalesces in polynyas or in cold-exposed regions of the open-ocean. Similarly, in seas and lakes, where latent energy is sufficient (waves, swells, fetch, tides, seiche, etc), turbulence mixes the frazil ice down into the upper layer and forms a surface layer of grease ice.
The term ‘grease ice’ follows World Meteorological Organization nomenclature. Grease ice differs from ‘slush’, where slush is similarly created by snow falling into the top layer of an ocean basin, river, or lake. The two terms are related due to the process of ice crystals being blown into a polynya, lake, ocean, or sea which can be the initiation of the grease ice layer, given a minimum level of mixing and cooling on the ocean surface.
Formation
When the water surface begins to lose heat rapidly, the water becomes supercooled. Turbulence, caused by strong winds or flow from a river, will mix the supercooled water throughout its entire depth. The supercooled water will already be encouraging the formation of small ice crystals (frazil ice) and the crystals will be mixed into the upper layer and form a surface layer.
Sea ice growth in turbulent water differs from sea ice growth in calm water. In turbulent water, the ice crystals accumulate at the surface, forming a grease-ice layer composed of individual ice crystals and small irregular clumps of ice crystals. In calm water conditions, nilas, a thin, almost invisible elastic crust, forms at the surface as water molecules freeze to the ice-water interface.
References
Sea ice
Snow or ice weather phenomena | Grease ice | [
"Physics"
] | 466 | [
"Physical phenomena",
"Earth phenomena",
"Sea ice"
] |
13,205,517 | https://en.wikipedia.org/wiki/Krapcho%20decarboxylation | Krapcho decarboxylation is a chemical reaction used to manipulate certain organic esters. This reaction applies to esters with a beta electron-withdrawing group (EWG).
The reaction proceeds by nucleophilic dealkylation of the ester by the halide followed by decarboxylation, followed by hydrolysis of the resulting stabilized carbanion.
Reaction conditions
The reaction is carried in dipolar aprotic solvents such as dimethyl sulfoxide (DMSO) at high temperatures, often around 150 °C.
A variety of salts assist in the reaction including NaCl, LiCl, KCN, and NaCN. It is suggested that the salts were not necessary for reaction, but greatly accelerates the reaction when compared to the reaction with water alone.
The ester must contain an EWG in the beta position . The reaction works best with a methyl esters. which are more susceptible to SN2 reactions.
Mechanisms
The mechanisms are still not fully uncovered. However, the following are suggested mechanisms for two different substituents:
α,α-Disubstituted Ester
For an α,α-disubstituted ester, it is suggested that the anion in the salt attacks the R3 in an SN2 fashion, kicking off R3 and leaving a negative charge on the oxygen. Then, decarboxylation occurs to produce a carbanion intermediate. The intermediate picks up a hydrogen from water to form the products.
The byproducts of the reaction (X-R3 and CO2) are often lost as gases, which helps drive the reaction; entropy increases and Le Chatelier's principle takes place.
α-Monosubstituted Ester
For an α-monosubstituted ester, it is speculated that the anion in the salt attacks the carbonyl group to form a negative charge on the oxygen, which then cleaves off the cyanoester. With the addition of water, the cyanoester is then hydrolyzed to form CO2 and alcohol, and the carbanion intermediate is protonated.
The byproduct of this reaction (CO2) is also lost as gas, which helps drive the reaction; entropy increases and Le Chatelier's principle takes place.
Advantages
The Krapcho decarboxylation is a comparatively simpler method to manipulate malonic esters because it cleaves only one ester group, without affecting the other ester group. The conventional method involves saponification to form carboxylic acids, followed by decarboxylation to cleave the carboxylic acids, and an esterification step to regenerate the esters. Additionally, Krapcho decarboxylation avoids harsh alkaline or acidic conditions.
References
Elimination reactions
Substitution reactions
Name reactions | Krapcho decarboxylation | [
"Chemistry"
] | 589 | [
"Name reactions"
] |
13,206,338 | https://en.wikipedia.org/wiki/Protein%20subfamily | Protein subfamily is a level of protein classification, based on their close evolutionary relationship. It is below the larger levels of protein superfamily and protein family.
Proteins typically share greater sequence and function similarities with other subfamily members than they do with members of their wider family. For example, in the Structural Classification of Proteins database classification system, members of a subfamily share the same interaction interfaces and interaction partners. These are stricter criteria than for a family, where members have similar structures, but may be more distantly related and so have different interfaces. Subfamilies are assigned by a variety of methods, including sequence similarity, motifs linked to function, or phylogenetic clade. There is no exact and consistent distinction between a subfamily and a family. The same group of proteins may sometimes be described as a family or a subfamily, depending on the context.
References
External links
SCOP DB at Cambridge UK
CATH protein structure DB
Protein classification | Protein subfamily | [
"Chemistry",
"Biology"
] | 184 | [
"Biochemistry stubs",
"Protein stubs",
"Protein classification"
] |
13,207,749 | https://en.wikipedia.org/wiki/Snow%20pillow | A snow pillow is a device for measuring snowpack, especially for automated reporting stations such as SNOTEL.
The snow pillow measures the water equivalent of the snow pack based on hydrostatic pressure created by overlying snow. Any discrepancy due to bridging is minimized by the large dimension of the pillow, typically .
Another application for snow pillows is to estimate the snow weight on a roof to warn of potential for roof collapse.
Snow pillows were developed in the early 1960s.
Set-up
Large dimensions (e.g. 3 m × 3 m) of the pillow prevent any bridging that might occur from having an effect on the measurement readings. For snow pressure measurement on roofs using a smaller snow pillow (e.g. 1 m × 1 m) is the better choice, because of the weight of the filling of the snow pillow.
See also
Snowboard
Snow gauge
References
Snow
Telemetry
Meteorological instrumentation and equipment | Snow pillow | [
"Technology",
"Engineering"
] | 190 | [
"Meteorological instrumentation and equipment",
"Measuring instruments"
] |
13,207,925 | https://en.wikipedia.org/wiki/Event-related%20functional%20magnetic%20resonance%20imaging | Event-related functional magnetic resonance imaging (efMRI) is a technique used in magnetic resonance imaging of medical patients.
EfMRI is used to detect changes in the BOLD (blood oxygen level dependent) hemodynamic response to neural activity in response to certain events.
Description
Within fMRI methodology, there are two different ways that are typically employed to present stimuli. One method is a block related design, in which two or more different conditions are alternated in order to determine the differences between the two conditions, or a control may be included in the presentation occurring between the two conditions. By contrast, event related designs are not presented in a set sequence; the presentation is randomized and the time in between stimuli can vary.
efMRI attempts to model the change in fMRI signal in response to neural events associated with behavioral trials. According to D'Esposito, "event-related fMRI has the potential to address a number of cognitive psychology questions with a degree of inferential and statistical power not previously available."
Each trial can be composed of one experimentally controlled (such as the presentation of a word or picture) or a participant mediated "event" (such as a motor response). Within each trial, there are a number of events such as the presentation of a stimulus, delay period, and response. If the experiment is properly set up and the different events are timed correctly, efMRI allows a person to observe the differences in neural activity associated with each event.
History
Positron emission tomography (PET), was the most frequently used brain mapping technique before the development of fMRI. There are a number of advantages that are presented in comparison to PET. According to D'Esposito, they include that fMRI "does not require an injection of radioisotope into participants and is otherwise noninvasive, has better spatial resolution, and has better temporal resolution."
The first MRI studies employed the use of "exogenous paramagnetic tracers to map changes in cerebral blood volume", which allowed for the assessment of brain activity over several minutes. This changed with two advancements to MRI, the rapidness of MRI techniques were increased to 1.5 Tesla by the end of the 1980s, which provided a 2-d image. Next, endogenous contrast mechanisms were discovered by Detre, Koretsky, and colleagues was based on the net longitudinal magnetization within an organ, and a "second based on changes in the magnetic susceptibility induced by changing net tissue deoxyhemoglobin content", which has been labeled BOLD contrast by Siege Ogawa.
These discoveries served as inspiration for future brain mapping advancements. This allowed researchers to develop more complex types of experiments, going beyond observing the effects of single types of trials. When fMRI was developed one of its major limitations was the inability to randomize trials, but the event related fMRI fixed this problem. Cognitive subtraction was also an issue, which tried to correlate cognitive-behavioral differences between tasks with brain activity by pairing two tasks that are assumed to be matched perfectly for every sensory, motor, and cognitive process except the one of interest.
Next, a push for the improvement of temporal resolution of fMRI studies led to the development of event-related designs, which according to Peterson, was inherited from ERP research in electrophysiology, but it was discovered that this averaging did not apply very well to the hemodynamic response because the response from trials could overlap. As a result, random jittering of the events was applied, which meant that the time repetition was varied and randomized for the trials in order to ensure that the activation signals did not overlap.
Hemodynamic response
In order to function, neurons require energy which is supplied by blood flow. Although it is not completely understood, the hemodynamic response has been correlated with neuronal activity, that is, as the activity level increases, the amount of blood used by neurons increases. This response takes several seconds to completely develop. Accordingly, fMRI has limited temporal resolution.
The hemodynamic response is the basis for the BOLD (blood oxygen level dependent) contrast in fMRI. The hemodynamic response occurs within seconds of the presented stimuli, but it is essential to space out the events in order to ensure that the response being measured is from the event that was presented and not from a prior event. Presenting stimuli in a more rapid sequence allows experimenters to run more trials and gather more data, but this is limited by the slow course of hemodynamic response, which generally must be allowed to return baseline before the presentation of another stimulus.
According to Burock "as the presentation rate increases in the random event related design, the variance in the signal increases thereby increasing the transient information and ability to estimate the underlying hemodynamic response".
Rapid event-related efMRI
In a typical efMRI, after every trial the hemodynamic response is allowed to return to baseline. In rapid event-related fMRI, trials are randomized and the HRF is deconvolved afterwards. In order for this to be possible, every possible combination of trial sequences must be used and the inter-trial intervals jittered so that the time in between trials is not always the same.
Advantages
Ability to randomize and mix different types of events, which ensures that one event is not influenced by others and not affected by the cognitive state of an individual, does not allow for predictability of events.
Events can be organized into categories after the experiment based on the subjects behavior
The occurrence of events can be defined by the subject
Sometimes the blocked event design cannot be applied to an event.
Treating stimuli, even when blocked, as separate events can potentially result in a more accurate model.
Rare events can be measured.
Chee argues that event related designs provide a number of advantages in language-related tasks, including the ability to separate correct and incorrect responses, and show task dependent variations in temporal response profiles.
Disadvantages
More complex design and analysis.
Need to increase the number of trials because the MR signal is small.
Some events are better blocked.
Timing issues: sampling (fix: random jitter, varying the timing of the presentation of the stimuli, allows for a mean hemodynamic response to be calculated at the end).
Blocked designs have higher statistical power.
Easier to identify artifacts arising from non-physiologic signal fluctuations.
Statistical analysis
In fMRI data, it is assumed that there is a linear relationship between neural stimulation and the BOLD response. The use of GLMs allows for the development of a mean to represent the mean hemodynamic response within the participants.
Statistical parametric mapping is used to produce a design matrix, which includes all of the different response shapes produced during the event. For more information on this, see Friston (1997).
Applications
Visual priming and object recognition
Examining differences between parts of a task
Changes over time
Memory research – working memory using cognitive subtraction
Deception – truth from lies
Face perception
Imitation learning
Inhibition
Stimulus specific responses
References
Sources
Buckner, M., Burock, M., Dale, A., Rosen, B., Woldorff, M. Randomized event-related experimental designs allow for extremely rapid presentation rates using functional MRI. (1998) NeuroReport. 19. 3735–3739.
Buckner, R. Event-Related fMRI and the Hemodynamic Response. (1998). Human Brain Mapping. 6. 373–377.
Buckner, R., Dale, A., Rosen, B. Event-Related functional MRI:Past, Present and Future. (1998). Proc. Natl. Acad. Sci. USA. 95. 773–780.
Chee, M. Siong, S., Venkatraman, V., Westphal, C. Comparison of Block and Event-Related fMRI Designs in Evaluating the Word-Frequency Effect. (2003). Human Brain Mapping. 18. 186–193.
Dale, A., Friston, K., Henson, R., Josephs, O., Zarahn, E. Stochastic Designs in Event-Related fMRI. (1999). NeuroImage. 10. 607-6-19.
D'Esposito, M., Zarahn, E., & Aguirre, G. K. (1999). Event-related functional MRI: Implications for cognitive psychology. Psychological Bulletin, 125(1). 155–164.
Dubis, J. Petersen, S. The Mized block/event-related design. (2011). NeuroImage. doi 10.1016/j.neuroimage.2011.09.084.
Friston, K., Josephs, O., Turner, R. Event-Related fMRI. (1997). Human Brain Mapping. 5. 243–248.
Henson, R. Event-related fMRI: Introduction, Statistical Modelling, Design Optimization and Examples. University College London. Paper to be presented at the 5th Congress of the Cognitive Neuroscience Society of Japan.
Magnetic resonance imaging | Event-related functional magnetic resonance imaging | [
"Chemistry"
] | 1,888 | [
"Nuclear magnetic resonance",
"Magnetic resonance imaging"
] |
13,207,951 | https://en.wikipedia.org/wiki/Bridgeport%20Covered%20Bridge | The Bridgeport Covered Bridge is located in Bridgeport, Nevada County, California, southwest of French Corral and north of Lake Wildwood. It is used as a pedestrian crossing over the South Yuba River. The bridge was built in 1862 by David John Wood. Its lumber came from Plum Valley in Sierra County, California. The bridge was closed to vehicular traffic in 1972 and pedestrian traffic in 2011 due to deferred maintenance and "structural problems".
On June 20, 2014, California Gov. Jerry Brown signed budget legislation that included $1.3 million for the bridge's restoration. The work was slated to be done in two phases—near-term stabilization followed by restoration. The bridge reopened to pedestrians in November 2021 following completion of the restoration work.
The Bridgeport Covered Bridge has the longest clear single span of any surviving wooden covered bridge in the world.
Historic landmark
The bridge is California Registered Historical Landmark No. 390, was designated as a National Historic Civil Engineering Landmark in 1970, and was listed in the National Register of Historic Places in 1971. There are four plaques at the site.
The State Historical Landmark plaque was placed in 1964. The landmark was rededicated in 2014. The inscription on the current plaque reads:
"Built in 1862 by David J. Wood with lumber from his mill in Sierra County. The covered bridge was part of the Virginia Turnpike Company toll road that served the northern mines and the Nevada Comstock Lode. The associated ranch and resources for rest and repair provided a necessary lifeline across the Sierra Nevada. Utilizing a unique combination truss and arch construction, Bridgeport Covered Bridge is one of the oldest housed spans in the western United States and the longest single span wooden covered bridge in the world."
The bridge was an important link in a freight-hauling route that stretched from the San Francisco Bay to Virginia City, Nevada and points beyond after the discovery of the Comstock Lode in 1859 sparked a mining boom in Nevada. Steamboats carried freight from the San Francisco Bay up the Sacramento River to Marysville, where it was loaded onto wagons for the trip across the Sierra Nevada via the Virginia Turnpike, and Henness Pass Road. The route across the bridge was ultimately eclipsed by the completion of the First transcontinental railroad as far as Reno in 1868 via Donner Pass, but it continued to serve nearby communities in the foothills until improved roads and bridges on other routes drew away most of the traffic.
Longest span
A report by the U.S. Department of the Interior states that the Bridgeport Covered Bridge ( No. CA-41) has clear spans of on one side and on the other, while Old Blenheim Bridge ( No. NY-331) had a documented clear span of in the middle (1936 drawings).
With the 2011 destruction of the Old Blenheim Bridge, the Bridgeport Covered Bridge is the undisputed longest-span wooden covered bridge still surviving. Historically, the longest single-span covered bridge on record was Pennsylvania's McCall's Ferry Bridge with a claimed clear span of (built 1814–15, destroyed by ice jam 1817).
See also
California Historical Landmarks in Nevada County
List of bridges documented by the Historic American Engineering Record in California
List of covered bridges in California
National Register of Historic Places listings in Nevada County, California
External links
Bridgeport Covered Bridge, at Nevada County, California website
Pictures of the Bridgeport Covered Bridge, at California Dept. of Transportation
South Yuba River State Park
Bridgeport Covered Bridge at the Covered Spans of Yesteryear website
South Yuba River Park Adventures, pictures, events, maps, wildflowers
References
Wooden bridges in California
Pedestrian bridges in California
Bridges in Nevada County, California
Bridges completed in 1862
California Historical Landmarks
Historic Civil Engineering Landmarks
Covered bridges on the National Register of Historic Places in California
National Register of Historic Places in Nevada County, California
Former road bridges in the United States
Historic American Buildings Survey in California
Historic American Engineering Record in California
Tourist attractions in Nevada County, California
1862 establishments in California
Road bridges on the National Register of Historic Places in California
Burr Truss bridges in the United States | Bridgeport Covered Bridge | [
"Engineering"
] | 815 | [
"Civil engineering",
"Historic Civil Engineering Landmarks"
] |
13,209,748 | https://en.wikipedia.org/wiki/Adder%20Technology | Adder Technology is a manufacturer of information technology hardware based in Cambridge, England, UK. It is the largest producer of keyboard, video, mouse (KVM) controllers in Europe.
History
The company began in 1984 as Adder Publishing and was rebranded as Adder Technology in 1986. It relocated to Bar Hill in 2012.
Overview
Adder develops hardware-based, remote-management devices sold under the brand 'Adder'. Products include KVM switches (analog and Cat5), KVM over IP, digital signage products, remote office/branch office solutions, and out-of-band management solutions.
Adder Technology has won Deloitte Touche Tohmatsu's "Fast 50" designation in the Deloitte Fast 500 awards for 8 consecutive years. The company has received a Queen's Award for Enterprise.
The company has US, UK, Germany, Netherlands, and Singapore offices and a global distribution network. Some 60% of its production is exported to Europe and the United States. It was founded in 1984 by Adrian Dickens.
References
Computer companies of the United Kingdom
Computer hardware companies
Computer peripheral companies
Companies based in Cambridge
Computer companies established in 1984 | Adder Technology | [
"Technology"
] | 236 | [
"Computer hardware companies",
"Computers"
] |
13,210,015 | https://en.wikipedia.org/wiki/Reflections%20on%20the%20Motive%20Power%20of%20Fire | Reflections on the Motive Power of Fire and on Machines Fitted to Develop that Power is a scientific treatise written by the French military engineer Sadi Carnot. Published in 1824 in French as Réflexions sur la puissance motrice du feu et sur les machines propres à développer cette puissance, the short book (118 pages in the original) sought to advance a rational theory of heat engines. At the time, heat engines had acquired great technological and economic importance, but very little was understood about them from the point of view of physics.
Carnot's Reflections is now widely regarded as a key document in the development of modern thermodynamics, and Carnot himself (who published nothing else during his lifetime) has often been identified as the "father of thermodynamics". The book introduced such concepts as thermodynamic efficiency, reversible processes, the thermodynamic cycle, and Carnot's theorem.
Overview
The book is considered the founding work of thermodynamics. It contains the preliminary outline of the second law of thermodynamics. Carnot stated that motive power is due to the fall of caloric (chute de calorique) from a hot to a cold body, which he analogized to the work done by a water wheel due to a waterfall (chute d'eau).
Despite the fact that the caloric theory of heat was incorrect, Carnot's work brought together three insights that remain relevant and were used by his successors to develop the concept of entropy:
The "fall of heat" from a high temperature to a lower temperature is where the work comes from.
Analyzing a cycle, rather than an open system, is the correct way to analyze a heat engine.
The concept of a reversible process.
Similar to how the Reflections was the precursor to the second law, English physicist James Joule's 1843 paper Mechanical equivalent of heat was the precursor to the first law of thermodynamics. In his essay, Carnot also derived the result that later came to be known as the Clausius-Clapeyron relation.
Influence
Carnot's essay received very little attention during Carnot's lifetime. Carnot published nothing else and died in 1832, at the age of 36. However, in 1834 a French mining engineer, Émile Clapeyron, published a Memoir on the Motive Power of Heat that presented Carnot's analysis graphically.
The German physicist Rudolf Clausius learned of Carnot's work through Clapeyron's memoir. Clausius corrected Carnot's theory by replacing the conservation of caloric with the work-heat equivalence (i.e., energy conservation). Clausius also put the second law of thermodynamics into mathematical form by defining the concept of entropy. That work appeared in 1850 in Clausius's Mechanical Theory of Heat.
Another highly influential commentary on Carnot's essay (also through Clapeyron's memoir) was published in 1849 by William Thomson (the future Lord Kelvin), in a paper titled An Account of Carnot's Theory of the Motive Power of Heat. In that paper, Kelvin said of Carnot's derivation of what would later be called the "Clausius-Clapeyron equation" that "nothing in the whole range of Natural Philosophy is more remarkable than the establishment of general laws by such a process of reasoning."
Because of their respective commentary's on Carnot's essay, modern textbooks on thermodynamics usually introduce a "Clausius statement" and a "Kelvin statement" of the second law of thermodynamics. These statements appear to be different, but they can be shown to be logically equivalent, by an argument based on the Carnot cycle.
See also
Timeline of thermodynamics
References
External links
Reflections on the Motive Power of Fire (1824), analysed on BibNum (click "À télécharger" for English analysis)
American Institute of Physics, 2011. . Abstract at: . Full article (24 pages ), also at .
Thermodynamics literature
Physics books | Reflections on the Motive Power of Fire | [
"Physics",
"Chemistry"
] | 853 | [
"Thermodynamics literature",
"Thermodynamics"
] |
13,210,188 | https://en.wikipedia.org/wiki/Volume%20units%20used%20in%20petroleum%20engineering | Several units of volume are used in petroleum engineering.
Units
Due to the risk of confusion with the SI convention where the "M" prefix stands for "mega" representing million, the Society of Petroleum Engineers recommends in their style guide that abbreviations or prefixes M or MM are not used for barrels of oil or barrel of oil equivalent, but rather that thousands, millions or billions are spelled out.
Conversion factors
Oil conversion factor from m³ to bbl (or stb) is 6.28981100
Gas conversion factor from standard m³ to scf is 35.314666721
Note that the m³ gas conversion factor takes into account a difference in the standard temperature base for measurement of gas volumes in metric and imperial units. The standard temperature for metric measurement is 15 degrees Celsius (i.e. 59 degrees Fahrenheit) while for English measurement the standard temperature is 60 °F. Gas undergoes a slight expansion when the temperature is raised from 15 °C (59 °F) to 60 °F and this expansion is built into the above factor for gas.
The standard temperature and pressure (STP) for gas varies depending on the particular code being used. It is just as important to know the standard pressure as the temperature. Formerly, OPEC used 101.325 kPa (14.696 psia) but now the standard is 101.560 kPa (14.73 psia).
References
Petroleum engineering | Volume units used in petroleum engineering | [
"Engineering"
] | 288 | [
"Petroleum engineering",
"Energy engineering"
] |
13,210,272 | https://en.wikipedia.org/wiki/Royal%20Maintenance%20Corps%20%28Jordan%29 | The Royal Maintenance Corps "silah al siyana al-malaki" (سلاح الصيانة الملكي) is a branch of the Jordanian Armed Forces. It must furnish continuous operation to the field and is responsible for flow of parts, and for every vehicle being operational and ready for battle. The corps' engineers are also responsible for upgrading the tanks in use.
Role in improving the Jordanian military
The maintenance corps role in improving Jordanian ground units, is to apply enhanced targeting systems on the M60 Patton, the full reconstruction of several other vehicles such as the Centurion tank and to upgrade the 274 Chieftain tank in a redesign called Khalid ibn al-Walid.
The Jordanian engineers were able to revolutionise the Challenger 1 turret system with an auto loader and a 120 mm smooth-bore gun. Maintenance specialists were sent to the United States and Britain for advanced training.
History
In 1972, the Chieftain Tank needed enhancement in order to meet changing military needs. The Corps Commander, Major General Kharabsheh, installed the new laser targeting system on several tanks including the M60. This move was revolutionary for the Jordanian military. It made it possible for the cavalry to balance power with its neighbors.
Commanders
The king of Jordan selected the commanders of the corps. A list follows:
Brigadier General Engineer Nael AL-Ragad 2009–present
Major General Abdilwahab Kharabsheh ? - 1992
Major General Mosleh AlMuthanna AlYamani 1988-1992
Brigadier General Waleed a. Samkari 1992 - ?
Major General Engineer Fadel Mohammed Ali 2000 - 2001
References
External links
Royal Jordanian maintenance corp
Jordanian armed forces
Maintenance Corps
Military administrative corps
Military units and formations established in 1920 | Royal Maintenance Corps (Jordan) | [
"Engineering"
] | 353 | [
"Engineering units and formations",
"Military engineer corps"
] |
13,212,005 | https://en.wikipedia.org/wiki/List%20of%20countries%20by%20proven%20oil%20reserves | Proven oil reserves are those quantities of petroleum which, by analysis of geological and engineering data, can be estimated, with a high degree of confidence, to be commercially recoverable from a given date forward from known reservoirs and under current economic conditions.
Some statistics on this page are disputed and controversial—different sources (OPEC, CIA World Factbook, oil companies) give different figures. Some of the differences reflect different types of oil included. Different estimates may or may not include oil shale, mined oil sands or natural gas liquids.
Because proven reserves include oil recoverable under current economic conditions, nations may see large increases in proven reserves when known, but previously uneconomic deposits become economic to develop. In this way, Canada's proven reserves increased suddenly in 2003 when the oil sands of Alberta were seen to be economically viable. Similarly, Venezuela's proven reserves jumped in the late 2000s when the heavy oil of the Orinoco Belt was judged economic.
Sources
Sources sometimes differ on the volume of proven oil reserves. The differences sometimes result from different classes of oil included, and sometimes result from different definitions of proven. (The data below does not seem to include shale oil and other unconventional sources of oil such as tar sands. For instance, North America has over 3 trillion barrels of shale oil reserves, and the majority of oil produced in the US is from shale, leading to the paradoxical data below that the US will finish all its oil at 2024 production levels in 10 years.)
Countries
Reserve amounts are listed in millions of barrels.
indicates links to "Oil reserves in Country or Territory" or "Energy in Country or Territory" pages.
See also
List of countries by oil production
List of countries by oil consumption
List of countries by natural gas proven reserves
References
Oil, proven
Reserves
List of countries by proven oil reserves
Lists of countries | List of countries by proven oil reserves | [
"Chemistry"
] | 368 | [
"Petroleum",
"Petroleum by country"
] |
9,211,532 | https://en.wikipedia.org/wiki/Gyula%20O.%20H.%20Katona | Gyula O. H. Katona (born 16 March 1941 in Budapest) is a Hungarian mathematician known for his work in combinatorial set theory, and especially for the Kruskal–Katona theorem and his beautiful and elegant proof of the Erdős–Ko–Rado theorem in which he discovered a new method, now called Katona's cycle method. Since then, this method has become a powerful tool in proving many interesting results in extremal set theory. He is affiliated with the Alfréd Rényi Institute of Mathematics of the Hungarian Academy of Sciences.
Katona was secretary-general of the János Bolyai Mathematical Society from 1990 to 1996. In 1966 and 1968 he won the Grünwald Prize, awarded by the Bolyai Society to outstanding young mathematicians, he was awarded the Alfréd Rényi Prize of the Hungarian Academy of Sciences in 1975, and the same academy awarded him the Prize of the Academy in 1989. In 2011 the Alfréd Rényi Institute, the János Bolyai Society and the Hungarian Academy of Sciences organized a conference in honor of Katona's 70th birthday.
Gyula O.H. Katona is the father of Gyula Y. Katona, another Hungarian mathematician with similar research interests to those of his father.
References
External links
Katona's web site
Katona on IMDB, appearing as himself in N is a Number
2024 Interview with Gyula O. H. Katona
Members of the Hungarian Academy of Sciences
20th-century Hungarian mathematicians
Combinatorialists
1941 births
Living people | Gyula O. H. Katona | [
"Mathematics"
] | 317 | [
"Combinatorialists",
"Combinatorics"
] |
9,211,582 | https://en.wikipedia.org/wiki/Cochliobolus%20miyabeanus | Cochliobolus miyabeanus (teleomorph, formerly known as Helminthosporium oryzae, anamorph Bipolaris oryzae) is a fungus that causes brown spot disease in rice.
It was considered for use by the US as a biological weapon against Japan during World War II.
Hosts and symptoms
Brown spot of rice is a plant fungal disease that usually occurs on the host leaves and glume, as well as seedlings, sheaths, stems and grains of adult host plants. Hosts include Oryza (Asian rice), Leersia (Cutgrass), Zizania (Wild rice), and other species as well such as Echinochloa colona (junglerice) and Zea mays (maize).
Cochliobolus miyabeanus may cause a wide range of symptoms. General symptoms occurring on the hosts can be observed on many parts of the plant, including leaves, seeds, stems and inflorescences, along with the presence of brown spot. Discoloration of stems is another symptom develops from brown spot of rice disease. Oval-shaped brown spots are the fungal growth sign, which have grey colored center developed on host leaves. The fungus produces a toxin known as ophiobolin which inhibits the growth of roots, coleoptiles, and leaves. This pathogen has also been known to produce non-host specific toxins which suppress plant defenses, causing the characteristic brown spots on rice leaves.
Dark coffee-coloured spots appear in the panicle and severe attacks cause spots in the grain and loss of yield and milling quality.
Also, lesions on glumes and seeds occur if the pathogen associates with other fungi and insects. Such lesions may develop when favorable condition for sporulation is present.
Importance
Cochliobolus miyabeanus is an important plant pathogen because it causes a common and widespread rice disease that causes high level of crop yield losses. It was a major cause of the Bengal famine of 1943, where the crop yield was dropped by 40% to 90% and the death of 2 million people was recorded. It is a possible agroterrorism weapon. Other known severe crop loss cases caused by Cochliobolus miyabeanus are globally distributed. In the Philippines, rice seedling mortality rate has been recorded up to 60%. In India and Nigeria, it can reduce total crop yield by up to 40%. Similar losses are observed in Suriname and Sumatra.
Environment
There are several factors influencing the disease cycle and epidemics of brown spot of rice disease.
Rainfall and drought – The first factor affecting Cochliobolus miyabeanus life cycle is rainfall and drought. It tends to proliferate when there is reduced rainfall and in dewy conditions. In addition to a low level of precipitation, severe epidemics of rice brown spot occur during drought season. Compared to well-flooded or irrigated areas, disease occurrence is favored in drier environments where a reduced amount of water is present.
Temperature and humidity – Another factor affecting disease development for Cochliobolus miyabeanus is temperature and humidity. Infection efficiency is influenced by the humidity level of the leaves, and lowered minimum temperature for crop cultivation favors epidemics of this disease. Infection by this pathogen is favored by long durations of leaf wetness; however, this disease has even been reported without free water when humidity levels are above 89%. Cochliobolus miyabeanus grows well at lower temperatures during its developmental stages compared to the developed stage, so if high temperatures are maintained in the area it is likely that farmers can restrict the growth of this pathogen. The optimal temperature for the pathogen is between 20 and 30 °C, however the pathogen can occur anywhere between 16 and 36 °C.
Nutrition level – Nutrition of the host plant may also influence the level of disease development. For example, low soil nutrient content is associated with epidemics of rice brown spot. If soil minerals such as nitrogen, potassium, phosphorus, silicon and manganese are deficient, this will likely favor disease development. In specific, in areas where silicon is present in a high amount in the soil, the host becomes less susceptible to this disease because silicon not only alleviates physiological stresses of the host, but also promotes disease resistance ability in the host. Furthermore, soil moisture level contributes to disease occurrence. Brown spot of rice is favored in areas where water content is low in soil.
Management
Prevention
The spread of the fungus can be prevented by using certified disease-free seed and using available resistant varieties such as MAC 18.
Avoiding dense sowing will can also help prevent the spread of the fungus as it reduces humidity.
Maintaining control of weeds and removal of volunteer crops in the field can also prevent fungal spread, as well as burning the stubble of infected plants.
Seed treatments can also be used as a preventative measure. Seeds can be treated with fungicides or alternatively soaking seeds in cold water for 8 hours before treating with hot water (53–54 °C) for 10–12 minutes prior to planting.
Soil treatments can also be used to prevent the spread of C. miyabeanus. The addition of potassium and calcium if the soil is deficient can help boost disease resistance. However, excessive application of nitrogen fertilisers should be avoided.
Control
Once symptoms are observed the disease may be controlled by burning removal and burning of any plants and maintaining water levels up to 3 inches at grain formation. below grain formation.
See also
list of rice diseases
References
World Food Crisis: Meeting the demands of a growing population by Jeff Batten, APS/CPS Annual Meeting, Monday, August 9, 1999
Sources
Fungal plant pathogens and diseases
Rice diseases
Cochliobolus
Fungus species | Cochliobolus miyabeanus | [
"Biology"
] | 1,173 | [
"Fungi",
"Fungus species"
] |
9,211,703 | https://en.wikipedia.org/wiki/Leptosphaeria%20maculans | Leptosphaeria maculans (anamorph Phoma lingam) is a fungal pathogen of the phylum Ascomycota that is the causal agent of blackleg disease on Brassica crops. Its genome has been sequenced, and L. maculans is a well-studied model phytopathogenic fungus. Symptoms of blackleg generally include basal stem cankers, small grey lesions on leaves, and root rot. The major yield loss is due to stem canker. The fungus is dispersed by the wind as ascospores or rain splash in the case of the conidia. L. maculans grows best in wet conditions and a temperature range of 5–20 degrees Celsius. Rotation of crops, removal of stubble, application of fungicide, and crop resistance are all used to manage blackleg. The fungus is an important pathogen of Brassica napus (canola) crops.
Host and symptoms
Leptosphaeria maculans causes phoma stem canker or blackleg. Symptoms generally include basal stem cankers, small grey oval lesions on the leaf tissue and root rot (as the fungus can directly penetrate roots). L. maculans infects a wide variety of Brassica crops including cabbage (Brassica oleracea) and oilseed rape (Brassica napus). L. maculans is especially virulent on Brassica napus. The first dramatic epidemic of L. maculans occurred in Wisconsin on cabbage. The disease is diagnosed by the presence of small black pycnidia which occur on the edge of the leaf lesions. The presence of these pycnidia allow for this disease to be distinguished from Alternaria brassicae, another foliar pathogen with similar lesions, but no pycnidia.
Disease cycle
Leptosphaeria maculans has a complicated life cycle. The pathogen begins as a saprophyte on stem residue and survives in the stubble. It then begins a hemibiotrophic stage that results in the production of leaf spots. Colonizing the plant tissue systemically, it begins its endophytic stage within the stem. (Due to its systemic parasitism, quantitative assessment of L. maculanss impact cannot include lesion size or number.) When the growing season ends, the fungus causes cankers at the base of the plant thereby beginning another necrotrophic stage.
Leptosphaeria maculans has both a teleomorph phase (sexual reproduction to generate pseudothecia that release ascospores) and an anamorph phase (asexual reproduction to produce pycnidia that release pycnidiospores). The disease spreads by wind born dispersal of ascospores and rain splash of conidia. In addition, phoma stem canker can also be spread by infected seeds when the fungus infects the seed pods of Brassica napus during the growing season, but this is far less frequent. The disease is polycyclic in nature even though the conidia are not as virulent as the ascospores. The disease cycle starts with airborne ascospores which are released from the pseudothecia in the spring. The ascospores enter through the stomata to infect the plant. Soon after the infection, gray lesions and black pycnidia form on the leaves.
During the growing season, these pycnidia produce conidia that are dispersed by rain splash. These spores cause a secondary infection which is usually less severe than primary infection with ascospores. Stem cankers form from the disease moving systemically through the plant. Following the colonization of the intercellular spaces, the fungus will reach a vascular strand and spread down the stalk between the leaf and the stem. The disease will spread into as well as between the cells of the xylem. This colonization leads to the invasion and destruction of the stem cortex, which leads to the formation of stem canker.
Stubble forms after the growing season due to residual plant material left in the field after harvest. The disease overwinters as pseudothecia and mycelium in the stubble. In spring the pseudothecia release their ascospores and the cycle repeats itself.
Virulence genetics
is a gene which produces an effector which is recognized by Rlm3, in which case it is an avirulence gene, see .
Environment
Temperature and moisture are the two most important environmental conditions for the development of L. maculans spores. A temperature of 5-20 degrees Celsius is the optimal temperature range for pseudothecia to mature. A wet humid environment increases the severity of the disease due to the dispersal of conidia by rain splash. As well as rain, hail storms also increase the severity of the disease.
Management
Cultural methods such as removing stubble and crop rotation can be very effective. By removing the stubble, overwintering pseudothecia and mycelium are less prevalent, reducing the risk of infection. In Canada, crop rotation decreases blackleg dramatically in canola crops. It is suggested to have a 3-year crop rotation of canola and to plant non-host plants such as cereals in between these periods. Chemical methods, such as the application of fungicides, can decrease instances of disease. EBI and MBC fungicides are typically used. EBI fungicides inhibit Ergosterol biosynthesis whereas MBC fungicides disrupt beta tubuline assembly in mitosis. EBIs are the best option for control of L. maculans as they inhibit the growth of conidia. Although fungicides such as EBIs are effective on conidia, they have no effect on ascospores which will grow regardless of the fungicide concentration. Resistance methods can also be used to great effect. Typically race specific Rlm genes are used for resistance (Rlm1-Rlm9) in Brassica napus crops.
Plant disease resistance
Leptosphaeria maculans is controlled by both race-specific gene-for-gene resistance via so-called resistance (R) genes detecting corresponding avirulence (Avr) genes and quantitative, broad, resistance traits. Since L. maculans is sequenced and due to the importance of this pathogen, many different Avr genes have been identified and cloned.
Arabidopsis thaliana model system
Arabidopsis thaliana is a commonly used model organism in plant sciences which is closely related to Brassica. Interestingly, this model organism shows a very high degree of resistance to L. maculans in all accessions tested (except An-1, which provided the source for the rlm3 allele, see below) with no known virulent races known to date, which makes this pathosystem close to a non-host interaction. Interestingly, this high level of resistance can be broken by mutation and some resistance can be transferred from A. thaliana to Brassica napus - for example is a B. napus chromosome addition line with A. thaliana chromosome 3 more resistant to L. maculans.
RLM1 and RLM2
Despite all A. thaliana accessions being resistant to L. maculans, it was discovered that this resistance could be regulated by different loci. In crosses between different accessions, two loci were discovered: RLM1 on chromosome 1 and RLM2 on chromosome 4. The R gene responsible for RLM1 resistance was identified as an R gene of the TIR-NB-LRR family, but the T-DNA insertion mutants were less susceptible than the natural rlm1 allele, indicating that multiple genes at the locus could contribute to resistance.
RLM3
In contrast to RLM1 and RLM2 , RLM3 is not specific to L. maculans and mutant alleles in this gene cause broad susceptibility to multiple fungi.
Camalexin
Camalexin is a phytoalexin which is induced independently of RLM1-mediated resistance and mutants disrupted in camalexin biosynthesis show susceptibility to L. maculans, indicating that this is a critical resistance mechanism.
Phytohormones
Mutants in signaling and biosynthesis of the traditional plant disease resistance hormones salicylic acid (SA), jasmonic acid (JA) and ethylene (ET) do not disrupt A. thaliana resistance to L. maculans. On the other hand, are mutants disrupted in abscisic acid (ABA) biosynthesis or signaling susceptible to L. maculans. Interestingly, however, is SA and JA contributing to tolerance in a compatible interaction where RLM1 and camalexin-mediated resistances have been mutated, and a quadruple mutant (where RLM1, camalexin, JA and SA-dependent responses are blocked) is hyper-susceptible. In contrast, ET appears to be detrimental for disease resistance.
Brassica crops
The Brassica crops consists of combinations of 3 major ancestral genomes (A, B and C) where the most important canola crop is Brassica napus with an AACC genome. Most resistance traits have been introgressed into B. napus from wild Brassica rapa (AA genome) relatives. In contrast, none or very few L. maculans resistance traits can be found in the Brassica oleracea (CC genome) parental species. Additionally, some resistance traits have been introgressed from the "B" genomes from Brassica nigra (BB genome), Brassica juncea (AABB genome) or Brassica carinata (BBCC genome) into B. napus. In the Brassica-L. maculans interactions, there are many race-specific resistance genes known, and some of the corresponding fungal avirulence genes have also been identified.
Rlm1
Rlm1 has been mapped to Brassica chromosome A07. Rlm1 will induce a resistance response against an L. maculans strain harboring the AvrLm1 avirulence gene.
Rlm2
Rlm2 will induce a resistance response against an L. maculans strain harboring the AvrLm2 avirulence gene. Rlm2 s located on chromosome A10 at the same locus as LepR3 as and has been cloned. The Rlm2 gene encodes for a receptor-like protein with a transmembrane domain and extracellular leucine rich repeats.
Rlm3
Rlm3 has been mapped to Brassica chromosome A07. Rlm3 will induce a resistance response against an L. maculans strain harboring AvrLm3, see .
Rlm4Rlm4 has been mapped to Brassica chromosome A07. Rlm4 will induce a resistance response against an L. maculans strain harboring the AvrLm4-7 avirulence gene.
Rlm5Rlm5 and RlmJ1 have been found in Brassica juncea but it is still uncertain whether they reside on the A or B genomes.
Rlm6Rlm6 is normally found in the B genome in Brassica juncea or Brassica nigra. This resistance gene was introgressed into Brassica napus from the mustard Brassica juncea.
Rlm7Rlm7 has been mapped to Brassica chromosome A07.
Rlm8Rlm8 resides on the A genome in Brassica rapa and Brassica napus, but it has not yet been mapped further.
Rlm9
The Rlm9 gene (mapped to chromosome A07) has been cloned and it encodes a Wall-associated-kinase-like (WAKL) protein. Rlm9 responds to the AvrLm5-9 avirulence gene.
Rlm10
Like with Rlm6, Rlm10 is present in the B genome of Brassica juncea or Brassica nigra, but it has not yet been introgressed into Brassica napus.
Rlm11Rlm11 resides on the A genome in Brassica rapa and Brassica napus, but it has not yet been mapped further.
LepR3LepR3 was introduced into the Australian B. napus cultivar Surpass 400 from a wild B. rapa var. sylvestris. This resistance became ineffective within three years of commercial cultivation. LepR3 will induce a resistance response against an L. maculans strain harboring the AvrLm1 avirulence gene. LepR3 is located at the same locus as Rlm2 and also this gene has been cloned. Like the Rlm2 allele, the encoded LepR3 protein is a receptor-like protein with a transmembrane domain and extracellular leucine rich repeats. The predicted protein structure indicates that the LepR3 and Rlm2 R genes (in contrast to the intracellular Arabidopsis RLM1 R gene) senses L. maculans in the extracellular space (apoplast).
Importance Leptosphaeria maculans is the most damaging pathogen of Brassica napus, which is used as a feed source for livestock and for its rapeseed oil. L. maculans destroys around 5–20% of canola yields in France. The disease is very important in England as well: from 2000 to 2002, the disease resulted in approximately £56 million worth of damage per season. Rapeseed oil is the preferred European oil source for biofuel due to its high yield. B. napus produces more oil per land area than other sources like soybeans. Major losses to oilseed crops have also occurred in Australia. The most recent significant losses were in 2003, to the widely planted B. napus cultivars containing a resistance gene from B. rapa.L. maculans metabolizes brassinin, an important phytoalexin produced by Brassica species, into indole-3-carboxaldehyde and indole-3-carboxylic acid. Virulent isolates proceed through the (3-indolylmethyl)dithiocarbamate S-oxide intermediate, while avirulent isolates first convert brassinin to N-acetyl-3-indolylmethylamine and 3-indolylmethylamine. Research has shown that brassinin could be important as a chemo-preventative agent in the treatment of cancer.
As a bioengineering innovation, in 2010 it was shown that a light-driven protein from L. maculans'' could be used to mediate, alongside earlier reagents, multi-color silencing of neurons in the mammalian nervous system.
References
Further reading
Pleosporales
Fungal plant pathogens and diseases
Canola diseases
Fungi described in 1803
Taxa named by James Sowerby
Fungus species | Leptosphaeria maculans | [
"Biology"
] | 3,097 | [
"Fungi",
"Fungus species"
] |
9,211,715 | https://en.wikipedia.org/wiki/Aronszajn%20line | In mathematical set theory, an Aronszajn line (named after Nachman Aronszajn) is a linear ordering of cardinality
which contains no subset order-isomorphic to
with the usual ordering
the reverse of
an uncountable subset of the Real numbers with the usual ordering.
Unlike Suslin lines, the existence of Aronszajn lines is provable using the standard axioms of set theory. A linear ordering is an Aronszajn line if and only if it is the lexicographical ordering of some Aronszajn tree.
References
Order theory | Aronszajn line | [
"Mathematics"
] | 119 | [
"Order theory"
] |
9,211,759 | https://en.wikipedia.org/wiki/10th%20FAI%20World%20Rally%20Flying%20Championship | 10th FAI World Rally Flying Championship took place between September 14–21, 1997 in Antalya, Turkey, as a part of the 1st World Air Games.
Competitors
There were 82 crews from Poland (5), South Africa (5), Germany (5), Austria (5), Chile (5), Greece (5), Czech Republic (4), Slovakia (4), Hungary (4), Turkey (4), United States (3), France (3), Croatia (3), Italy (3), Russia (3), United Kingdom (2), Spain (2), Republic of Macedonia (2), Cyprus (2), Brazil (2), Switzerland (1), Lithuania (1), New Zealand (1), Slovenia (1), Denmark (1), the Netherlands (1), Luxembourg (1), Mozambique (1), Indonesia (1) (there are no details given as for two crews).
Contest
First navigation competition results:
Krzysztof Wieczorek / Wacław Wieczorek - 54 points (penal)
Janusz Darocha / Zbigniew Chrząszcz - 64 pts
Jiři Jakes / Lubomir Šťovíček - 80 pts
Włodzimierz Skalik / Ryszard Michalski - 84 pts
Marek Kachaniak / Sławomir Własiuk - 160 pts
Second navigation competition results:
Marek Kachaniak / Sławomir Własiuk - 62 pts
Jiři Jakes / Lubomir Šťovíček - 88 pts
Kazda / Stastny - 115 pts
Dariusz Zawłocki / Jerzy Markiewicz - 133 pts
Włodzimierz Skalik / Ryszard Michalski - 180 pts
Third navigation competition results:
Krzysztof Wieczorek / Wacław Wieczorek - 84 pts
František Cihlář / Petr Toužimský - 168 pts
Włodzimierz Skalik / Ryszard Michalski - 180 pts
Philippe Odeon / Girault - 245 pts
Marek Kachaniak / Sławomir Własiuk - 247 pts
Results
Individual (10 best)
Note: crews from the 1st, 2nd and 7th places apparently were taken into account with a result of only one (worst) competition.
Team
Two best crews were counted
- 634 pkt
- 1159
- 2341
- 2366
- 2661
- 2898
- 3808
- 4099
- 4286
- 4369
- 5948
- 6048
- 6843
- 7364
- 9057
- 9135
- 9978
- 11474
- 13035
- 14628
External links
10th FAI World Rally Flying Championship (source for the page)
See also
9th FAI World Rally Flying Championship
11th FAI World Rally Flying Championship
Rally Flying 10
1997 FAI World Flying Championship
Rally Flying
1997 in Turkish sport
Fédération Aéronautique Internationale
September 1997 sports events in Turkey
Aviation history of Turkey | 10th FAI World Rally Flying Championship | [
"Engineering"
] | 628 | [
"Fédération Aéronautique Internationale",
"Aeronautics organizations"
] |
9,212,193 | https://en.wikipedia.org/wiki/Bow%20shock%20%28aerodynamics%29 | A bow shock, also called a detached shock or bowed normal shock, is a curved propagating disturbance wave characterized by an abrupt, nearly discontinuous, change in pressure, temperature, and density. It occurs when a supersonic flow encounters a body, around which the necessary deviation angle of the flow is higher than the maximum achievable deviation angle for an attached oblique shock (see detachment criterion). Then, the oblique shock transforms in a curved detached shock wave. As bow shocks occur for high flow deflection angles, they are often seen forming around blunt bodies, because of the high deflection angle that the body impose to the flow around it.
The thermodynamic transformation across a bow shock is non-isentropic and the shock decreases the flow velocity from supersonic velocity upstream to subsonic velocity downstream.
Applications
The bow shock significantly increases the drag in a vehicle traveling at a supersonic speed. This property was utilized in the design of the return capsules during space missions such as the Apollo program, which need a high amount of drag in order to slow down during atmospheric reentry.
Shock relations
As in normal shock and oblique shock,
The upstream static pressures is lower than the downstream static pressure.
The upstream static density is lower than the downstream static density.
The upstream static temperature is lower than the downstream static temperature.
The upstream total pressure is greater than the downstream total pressure.
The upstream total density is lower than the downstream total density.
The upstream total temperature is equal to the downstream total temperature, as the shock wave is supposed isenthalpic.
For a curved shock, the shock angle varies and thus has variable strength across the entire shock front. The post-shock flow velocity and vorticity can therefore be computed via the Crocco's theorem, which is independent of any EOS (equation of state) assuming inviscid flow.
See also
Bow shock
Gas dynamics
Moving shock
Prandtl–Meyer expansion fan
References
Aerodynamics
Shock waves | Bow shock (aerodynamics) | [
"Physics",
"Chemistry",
"Engineering"
] | 406 | [
"Physical phenomena",
"Shock waves",
"Aerodynamics",
"Waves",
"Aerospace engineering",
"Fluid dynamics"
] |
9,212,913 | https://en.wikipedia.org/wiki/List%20of%20impossible%20puzzles | This is a list of puzzles that cannot be solved. An impossible puzzle is a puzzle that cannot be resolved, either due to lack of sufficient information, or any number of logical impossibilities.
Kookrooster maken 23
15 Puzzle – Slide fifteen numbered tiles into numerical order. It is impossible to solve in half of the starting positions.
Five room puzzle – Cross each wall of a diagram exactly once with a continuous line.
MU puzzle – Transform the string to according to a set of rules.
Mutilated chessboard problem – Place 31 dominoes of size 2×1 on a chessboard with two opposite corners removed.
Coloring the edges of the Petersen graph with three colors.
Seven Bridges of Königsberg – Walk through a city while crossing each of seven bridges exactly once.
Squaring the circle, the impossible problem of constructing a square with the same area as a given circle, using only a compass and straightedge.
Three cups problem – Turn three cups right-side up after starting with one wrong and turning two at a time.
Three utilities problem – Connect three cottages to gas, water, and electricity without crossing lines.
Thirty-six officers problem – Arrange six regiments consisting of six officers each of different ranks in a 6 × 6 square so that no rank or regiment is repeated in any row or column.
See also
Impossible Puzzle, or "Sum and Product Puzzle", which is not impossible
-gry, a word puzzle
List of undecidable problems, no algorithm can exist to answer a yes–no question about the input
Puzzles
Mathematics-related lists
References | List of impossible puzzles | [
"Mathematics"
] | 322 | [
"Mathematical problems",
"Unsolvable puzzles"
] |
9,213,667 | https://en.wikipedia.org/wiki/Field%20of%20definition | In mathematics, the field of definition of an algebraic variety V is essentially the smallest field to which the coefficients of the polynomials defining V can belong. Given polynomials, with coefficients in a field K, it may not be obvious whether there is a smaller field k, and other polynomials defined over k, which still define V.
The issue of field of definition is of concern in diophantine geometry.
Notation
Throughout this article, k denotes a field. The algebraic closure of a field is denoted by adding a superscript of "alg", e.g. the algebraic closure of k is kalg. The symbols Q, R, C, and Fp represent, respectively, the field of rational numbers, the field of real numbers, the field of complex numbers, and the finite field containing p elements. Affine n-space over a field F is denoted by An(F).
Definitions for affine and projective varieties
Results and definitions stated below, for affine varieties, can be translated to projective varieties, by replacing An(kalg) with projective space of dimension n − 1 over kalg, and by insisting that all polynomials be homogeneous.
A k-algebraic set is the zero-locus in An(kalg) of a subset of the polynomial ring k[x1, ..., xn]. A k-variety is a k-algebraic set that is irreducible, i.e. is not the union of two strictly smaller k-algebraic sets. A k-morphism is a regular function between k-algebraic sets whose defining polynomials' coefficients belong to k.
One reason for considering the zero-locus in An(kalg) and not An(k) is that, for two distinct k-algebraic sets X1 and X2, the intersections X1∩An(k) and X2∩An(k) can be identical; in fact, the zero-locus in An(k) of any subset of k[x1, ..., xn] is the zero-locus of a single element of k[x1, ..., xn] if k is not algebraically closed.
A k-variety is called a variety if it is absolutely irreducible, i.e. is not the union of two strictly smaller kalg-algebraic sets. A variety V is defined over k if every polynomial in kalg[x1, ..., xn] that vanishes on V is the linear combination (over kalg) of polynomials in k[x1, ..., xn] that vanish on V. A k-algebraic set is also an L-algebraic set for infinitely many subfields L of kalg. A field of definition of a variety V is a subfield L of kalg such that V is an L-variety defined over L.
Equivalently, a k-variety V is a variety defined over k if and only if the function field k(V) of V is a regular extension of k, in the sense of Weil. That means every subset of k(V) that is linearly independent over k is also linearly independent over kalg. In other words those extensions of k are linearly disjoint.
André Weil proved that the intersection of all fields of definition of a variety V is itself a field of definition. This justifies saying that any variety possesses a unique, minimal field of definition.
Examples
The zero-locus of x12+ x22 is both a Q-variety and a Qalg-algebraic set but neither a variety nor a Qalg-variety, since it is the union of the Qalg-varieties defined by the polynomials x1 + ix2 and x1 - ix2.
With Fp(t) a transcendental extension of Fp, the polynomial x1p- t equals (x1 - t1/p) p in the polynomial ring (Fp(t))alg[x1]. The Fp(t)-algebraic set V defined by x1p- t is a variety; it is absolutely irreducible because it consists of a single point. But V is not defined over Fp(t), since V is also the zero-locus of x1 - t1/p.
The complex projective line is a projective R-variety. (In fact, it is a variety with Q as its minimal field of definition.) Viewing the real projective line as being the equator on the Riemann sphere, the coordinate-wise action of complex conjugation on the complex projective line swaps points with the same longitude but opposite latitudes.
The projective R-variety W defined by the homogeneous polynomial x12+ x22+ x32 is also a variety with minimal field of definition Q. The following map defines a C-isomorphism from the complex projective line to W: (a,b) → (2ab, a2-b2, -i(a2+b2)). Identifying W with the Riemann sphere using this map, the coordinate-wise action of complex conjugation on W interchanges opposite points of the sphere. The complex projective line cannot be R-isomorphic to W because the former has real points, points fixed by complex conjugation, while the latter does not.
Scheme-theoretic definitions
One advantage of defining varieties over arbitrary fields through the theory of schemes is that such definitions are intrinsic and free of embeddings into ambient affine n-space.
A k-algebraic set is a separated and reduced scheme of finite type over Spec(k). A k-variety is an irreducible k-algebraic set. A k-morphism is a morphism between k-algebraic sets regarded as schemes over Spec(k).
To every algebraic extension L of k, the L-algebraic set associated to a given k-algebraic set V is the fiber product of schemes V ×Spec(k) Spec(L). A k-variety is absolutely irreducible if the associated kalg-algebraic set is an irreducible scheme; in this case, the k-variety is called a variety. An absolutely irreducible k-variety is defined over k if the associated kalg-algebraic set is a reduced scheme. A field of definition of a variety V is a subfield L of kalg such that there exists a k∩L-variety W such that W ×Spec(k∩L) Spec(k) is isomorphic to V and the final object in the category of reduced schemes over W ×Spec(k∩L) Spec(L) is an L-variety defined over L.
Analogously to the definitions for affine and projective varieties, a k-variety is a variety defined over k if the stalk of the structure sheaf at the generic point is a regular extension of k; furthermore, every variety has a minimal field of definition.
One disadvantage of the scheme-theoretic definition is that a scheme over k cannot have an L-valued point if L is not an extension of k. For example, the rational point (1,1,1) is a solution to the equation x1 + ix2 - (1+i)x3 but the corresponding Q[i]-variety V has no Spec(Q)-valued point. The two definitions of field of definition are also discrepant, e.g. the (scheme-theoretic) minimal field of definition of V is Q, while in the first definition it would have been Q[i]. The reason for this discrepancy is that the scheme-theoretic definitions only keep track of the polynomial set up to change of basis. In this example, one way to avoid these problems is to use the Q-variety Spec(Q[x1,x2,x3]/(x12+ x22+ 2x32- 2x1x3 - 2x2x3)),
whose associated Q[i]-algebraic set is the union of the Q[i]-variety Spec(Q[i][x1,x2,x3]/(x1 + ix2 - (1+i)x3)) and its complex conjugate.
Action of the absolute Galois group
The absolute Galois group Gal(kalg/k) of k naturally acts on the zero-locus in An(kalg) of a subset of the polynomial ring k[x1, ..., xn]. In general, if V is a scheme over k (e.g. a k-algebraic set), Gal(kalg/k) naturally acts on V ×Spec(k) Spec(kalg) via its action on Spec(kalg).
When V is a variety defined over a perfect field k, the scheme V can be recovered from the scheme V ×Spec(k) Spec(kalg) together with the action of Gal(kalg/k) on the latter scheme: the sections of the structure sheaf of V on an open subset U are exactly the sections of the structure sheaf of V ×Spec(k) Spec(kalg) on U ×Spec(k) Spec(kalg) whose residues are constant on each Gal(kalg/k)-orbit in U ×Spec(k) Spec(kalg). In the affine case, this means the action of the absolute Galois group on the zero-locus is sufficient to recover the subset of k[x1, ..., xn] consisting of vanishing polynomials.
In general, this information is not sufficient to recover V. In the example of the zero-locus of x1p- t in (Fp(t))alg, the variety consists of a single point and so the action of the absolute Galois group cannot distinguish whether the ideal of vanishing polynomials was generated by x1 - t1/p, by x1p- t, or, indeed, by x1 - t1/p raised to some other power of p.
For any subfield L of kalg and any L-variety V, an automorphism σ of kalg will map V isomorphically onto a σ(L)-variety.
Further reading
The terminology in this article matches the terminology in the text of Fried and Jarden, who adopt Weil's nomenclature for varieties. The second edition reference here also contains a subsection providing a dictionary between this nomenclature and the more modern one of schemes.
Kunz deals strictly with affine and projective varieties and schemes but to some extent covers the relationship between Weil's definitions for varieties and Grothendieck's definitions for schemes.
Mumford only spends one section of the book on arithmetic concerns like the field of definition, but in it covers in full generality many scheme-theoretic results stated in this article.
Diophantine geometry
Algebraic geometry | Field of definition | [
"Mathematics"
] | 2,286 | [
"Fields of abstract algebra",
"Algebraic geometry"
] |
9,214,056 | https://en.wikipedia.org/wiki/Gyula%20Y.%20Katona | Gyula Y. Katona (born 4 December 1965) is a Hungarian mathematician, the son of mathematician Gyula O. H. Katona. He received his Ph.D. in 1997 from Hungarian Academy of Sciences, with a dissertation titled Paths and Cycles in Graphs and Hypergraphs under the advisement of László Lovász and András Recski, and is on the faculty of the Budapest University of Technology and Economics.
Katona is the coauthor of three textbooks, Introduction to Computer Science (Typotex, Budapest, 2002), Introduction to Finite Mathematics, (Eötvös L. University, Budapest, 1993), and Combinatorics, Graph Theory and Algorithms (Technical University of Budapest, 1993). In addition his research publications include several works on Hamiltonian cycles and related properties of graphs.
External links
Katona's web site
Katona at the Mathematics Genealogy Project
20th-century Hungarian mathematicians
Combinatorialists
Living people
1965 births | Gyula Y. Katona | [
"Mathematics"
] | 197 | [
"Combinatorialists",
"Combinatorics"
] |
9,214,162 | https://en.wikipedia.org/wiki/Turritopsis%20dohrnii | Turritopsis dohrnii, also known as the immortal jellyfish, is a species of small, biologically immortal jellyfish found worldwide in temperate to tropic waters. It is one of the few known cases of animals capable of reverting completely to a sexually immature, colonial stage after having reached sexual maturity as a solitary individual.
Like most other hydrozoans, T. dohrnii begin their lives as tiny, free-swimming larvae known as planulae. As a planula settles down, it gives rise to a colony of polyps that are attached to the sea floor. All the polyps and jellyfish arising from a single planula are genetically identical clones. The polyps form into an extensively branched form, which is not commonly seen in most jellyfish. Jellyfish, also known as medusae, then bud off these polyps and continue their life in a free-swimming form, eventually becoming sexually mature. When sexually mature, they have been known to prey on other jellyfish species at a rapid pace. If the T. dohrnii jellyfish is exposed to environmental stress, physical assault, or is sick or old, it can revert to the polyp stage, forming a new polyp colony. It does this through the cell development process of transdifferentiation, which alters the differentiated state of the cells and transforms them into new types of cells.
Theoretically, this process can go on indefinitely, effectively rendering the jellyfish biologically immortal, although in practice individuals can still die. In nature, most Turritopsis dohrnii are likely to succumb to predation or disease in the medusa stage without reverting to the polyp form.
The capability of biological immortality with no maximum lifespan makes T. dohrnii an important target of basic biological aging and pharmaceutical research.
Taxonomy
The species was formerly considered conspecific with T. nutricula before being reclassified as a separate species. It was named in 1883 in honour of Anton Dohrn, the founder of the Stazione Zoologica Anton Dohrn in Naples, Italy.
Until a 2006 study, it was thought that Turritopsis rubra and Turritopsis nutricula were the same species as Turritopsis dohrnii. It is not known whether or not T. rubra medusae can also transform back into polyps, however further research is still to be done.
Description
The medusa of Turritopsis dohrnii is bell-shaped, with a maximum diameter of about and is about as tall as it is wide. The mesoglea in the walls of the bell is uniformly thin, except for some thickening at the apex. The relatively large stomach is bright red and has a cruciform shape in cross section. Young specimens 1 mm in diameter have only eight tentacles evenly spaced out along the edge, whereas adult specimens have 80–90 tentacles. The medusa (jellyfish) is free-living in the plankton. Dense nerve net cells are also present in the epidermis in the cap. They form a large ring-like structure above the radial canal commonly presented in cnidarians.
Turritopsis dohrnii also has a bottom-living polyp form, or hydroid, which consists of stolons that run along the substrate and upright branches with feeding polyps that can produce medusa buds. These polyps develop over a few days into tiny 1 mm medusae, which are liberated and swim free from the parent hydroid colony.
Distribution and invasion
Turritopsis is believed to have originated in the Pacific, but has spread all over the world through trans-Arctic migrations, and has speciated into several populations that are easy to distinguish morphologically, but whose species distinctions have recently been verified by a study and comparison of mitochondrial ribosomal gene sequences. Turritopsis are found in temperate to tropical regions in all of the world's oceans. Turritopsis is believed to be spreading across the world through ballast water discharge. Unlike other species invasions which caused serious economic and ecological consequences, T. dohrnii's invasion around the world was unnoticed due to their tiny size and innocuity. "We are looking at a worldwide silent invasion", said Smithsonian Tropical Marine Institute scientist Maria Miglietta.
Life cycle
The eggs develop in gonads of female medusae, which are located in the walls of the manubrium (stomach). Mature eggs are presumably spawned and fertilized in the sea by sperm produced and released by male medusae, as is the case for most hydromedusae. However, the related species Turritopsis rubra seems to retain fertilized eggs until the planula stage. Fertilized eggs develop into planula larvae, which settle onto the sea floor (or even the rich marine communities that live on floating docks), and develop into polyp colonies (hydroids). The hydroids bud new jellyfishes, which are released at about one millimetre in size and then grow and feed in the plankton, becoming sexually mature after a few weeks (the exact duration depends on the ocean temperature; at it is 25 to 30 days and at it is 18 to 22 days). Medusae of T. dohrnii are able to survive between 14 °C and 25 °C.
Biological immortality
Most jellyfish species have a relatively fixed lifespan, which varies by species from hours to many months (long-lived mature jellyfish spawn every day or night; the time is also fairly fixed and species-specific). The medusa of Turritopsis dohrnii is the only form known to have the ability to return to a polyp state, by a specific transformation process that requires the presence of certain cell types (tissue from both the jellyfish bell surface and the circulatory canal system).
Experiments have revealed that all stages of the medusae, from newly released to fully mature individuals, can transform back into polyps under the conditions of starvation, sudden temperature change, reduction of salinity, and artificial damage of the bell with forceps or scissors. The transforming medusa is characterized first by deterioration of the bell, mesoglea, and tentacles. All immature medusa (with 12 tentacles at most) then turned into a cyst-like stage and then transformed into stolons and polyps. However, about 20%-40% of mature medusa went into the stolons and polyps stage without passing the cyst-like stage. Polyps were formed after 2 days since stolons had developed and fed on food. Polyps further multiply by growing additional stolons, branches, and then polyps to form colonial hydroids. In the experiment, they would eventually transform into stolons and polyps and begin their lives once again, even without environmental changes or injury.
This ability to reverse the biotic cycle (in response to adverse conditions) is unique in the animal kingdom. It allows the jellyfish to bypass death, rendering Turritopsis dohrnii potentially biologically immortal. The process has not been observed in their natural habitat, in part because the process is quite rapid and because field observations at the right moment are unlikely. Regardless, most individual medusae are likely to fall victim to the general hazards of life as mesoplankton, including being eaten by predators or succumbing to disease.
The species possesses unique mechanisms related to telomere maintenance, which play a significant role in its regenerative abilities. T. dohrnii maintains telomere length through specific cellular processes during its life cycle reversal, effectively resetting cellular aging.
The species' cell development method of transdifferentiation has inspired scientists to find a way to make stem cells using this process for renewing damaged or dead tissue in humans.
Ecology
Diet
Turritopsis dohrnii are a carnivorous species that commonly feed on zooplankton. Their diet mainly consists of plankton, fish eggs and small mollusks. T. dohrnii ingests food and excretes waste through the mouth. T. dohrnii hunts by using its tentacles as it drifts through the water. Its tentacles, which contain stinging cells called nematocysts, spread and sting its prey. The tentacles can then flex to direct its prey to the mouth. T. dohrnii, like other jellyfish, may use its bell to catch its prey. T. dohrnii's bell will expand, sucking in water, as it propels itself to swim. This expansion of the bell brings potential prey in closer reach of the tentacles.
Predation
Turritopsis dohrnii, like other jellyfish, are preyed on most commonly by other jellyfish. Other predators of T. dohrnii include sea anemones, tuna, sharks, swordfish, sea turtles, and penguins. Many species prey on T. dohrnii and other jellyfish due to their simple composition. They are only approximately 5% non-aqueous matter, and the remaining part is composed of water. They are composed of three layers. An outer layer (the epidermis), a middle layer (mesoglea; a thick, jelly-like substance), and an inner layer (gastrodermis).
Habitat
Turritopsis dohrnii was first discovered in the Mediterranean Sea, but has since been found worldwide. T. dohrnii is generally found living in temperate to tropical waters. They can be found in marinas or docks, on vessel hulls, and on the ocean floor. They typically live in a salinity range of polyhaline (18–30 PSU) and euhaline (30-40 PSU).
Genomic analysis
Genomic analyses such as sequence analysis on mRNA or mitochondria DNA have been employed to investigate its lifecycle. mRNA analysis of each life stage showed that a stage-specific gene in the medusae stage is expressed tenfold more than in other stages. This gene is relative to a Wnt signal that can induce a regeneration process upon injury.
Analysis of nucleotide sequence homologs and protein homologs identified Nemopsis bachei as the species' closest relative. None of the closely related species display biological immortality.
In 2022, a study reported the key molecular mechanisms of rejuvenation they found in a comparison of the newly presented genomes of this biologically immortal jellyfish and a similar but non-rejuvenating jellyfish, involving e.g. DNA replication and repair, and stem cell renewal.
Culturing
Keeping T. dohrnii in captivity is quite difficult. Currently, only one scientist, Shin Kubota from Kyoto University, has managed to sustain a group of these jellyfish for a prolonged period of time. The plankton must be inspected daily to ensure that they have properly digested the Artemia cysts they are being fed.
Kubota reported that during a two-year period, his colony rebirthed itself 11 times. Kubota regularly appears on Japanese television to talk about his immortal jellyfish and has recorded several songs about them, often singing them at the end of his conference presentations.
See also
Hydra – another kind of cnidarian that is claimed to be immortal
List of longest-living organisms
References
Further reading
.
.
External links
Cheating Death: The Immortal Life Cycle of Turritopsis
Telomerase activity is not related to life-history stage in the jellyfish Cassiopea sp.
Scientists are Close to Finding a Way to be Immortal
Oceaniidae
Immortality
Negligibly senescent organisms
Animals described in 1883 | Turritopsis dohrnii | [
"Biology"
] | 2,418 | [
"Senescence",
"Negligibly senescent organisms",
"Organisms by adaptation"
] |
9,214,986 | https://en.wikipedia.org/wiki/Slamannan%20Railway | The Slamannan Railway was an early mineral railway between the north-eastern margin of Airdrie and Causewayend on the Union Canal, near Linlithgow, Scotland.
The Slamannan Railway was built to give access for minerals from pits in the Slamannan area to market in Glasgow (over connecting railways) and Edinburgh (over the Union Canal), and it also briefly provided an early passenger connection between Glasgow and Edinburgh in association with other railways and the canal. It had a rope-worked incline at Causewayend.
The line opened on 31 August 1840. It crossed very thinly populated moorland, and it was dependent on promised mineral extraction on its own route, but this proved disappointing, and traffic was limited by the extended route over other railways westward, and transshipment to the canal eastward. It was never successful commercially, and in 1848 it combined with other companies, forming the Monkland Railways.
None of the route is still in use, and much of it near Airdrie has been obliterated by modern open-cast mineral extraction.
Origins
In the first decades of the nineteenth century, there was a considerable increase in coal and iron ore extraction, and of iron smelting, in the general area of Coatbridge and Airdrie, and improvements in the efficiency of the process of iron manufacture led to accelerating demand for coal and iron ore, which in turn emphasised the weakness of the means of transport of the heavy materials. In 1771 the Monkland Canal had opened between the Airdrie pits and Glasgow, and it was followed by the Forth and Clyde Canal in 1790. In 1826 the Monkland and Kirkintilloch Railway (M&KR) was opened, conveying the minerals to the canal at Kirkintilloch for onward transport to Glasgow and Edinburgh.
In 1828 the Ballochney Railway gave access from pits north and east of Airdrie to the M&KR and thence onward to the canal; and in 1831 the Garnkirk and Glasgow Railway was opened, giving a more direct rail connection to Glasgow, but terminating at Townhead canal wharf there. In 1831–2 the Edinburgh and Dalkeith Railway opened, giving access from pits in the Eskbank and Dalhousie areas to Edinburgh and Leith.
Coal and iron deposits were being worked on a small scale in the Slamannan area, about halfway between Airdrie and Linlithgow; it was then in Stirlingshire, now in Falkirk District. Seeing the success of the other railways, businessmen interested in the pits promoted a railway to open up their own district, and they formed the Slamannan Railway Company. It was to run from a junction with the Ballochney Railway near Arbuckle, north-east of Airdrie, to a wharf on the Union Canal at Causeway End (nowadays spelt Causewayend), 23 miles (38 km) from Edinburgh. Thus it would give transport access for pits on the line to Glasgow (over the Ballochney and Monkland and Kirkintilloch lines) and to Edinburgh, by transshipping to the Union Canal at Causewayend.
The promoters anticipated a relatively frequent horse-drawn one-coach passenger service between Airdrie and Causewayend. The undulations on the route would allow the horse to ride on the downhill sections:
The drawing horse [would be] carried behind the coach in a covered stable waggon. In this way a single Horse would be enabled to perform the journey from Airdrie to Causewayend with a Passenger Carriage once a day, and allowing for spare Horses, five opportunities per day could be given at the expense of maintaining six Horses, with the means of conveying from 130 to 140 Passengers each way daily.
The company is authorised
The company was incorporated by the (5 & 6 Will. 4. c. lv) on 3 July 1835 with a share capital of £86,000 and loan capital of £20,000. The proprietors had presented the bill to Parliament with the minimum of publicity, and no subscription list had been prepared. Thomas Grahame had said that "The scheme is so obviously advantageous that the subscriptions would be easily filled up."
The act of Parliament specified that work on construction could not start until the estimated cost of construction was fully subscribed, and this forced a delay until mid-1836, and first contracts were not let until October. John Benjamin Macneill (later to be called "the Father of the Irish railway system") was appointed principal engineer and Thomas Telford Mitchell was Resident Engineer.
At the annual general meeting in February 1838 it was reported that one of the two construction contractors had failed to achieve the required output, and part of his contract was taken over by the company directly; however a year later it was stated that both contractors had failed to achieve the required progress, and moreover that almost the whole of the subscribed capital had been expended. A further act of Parliament, the (2 & 3 Vict. c. lvii), was obtained in July 1839, authorising total share capital of £140,000 and the usual additional one-third of the value in borrowings.
The construction process had been painful, the company "suffered during construction from 'considerable difficulty' in obtaining land, procrastinating contractors, high material costs, and problems of money raising in the deepening depression of the late 1830s"
The engineer Macneill reported to the committee of management that the nearby Wishaw and Coltness Railway had experienced difficulties with horse haulage by independent operators, referring to "the great confusion which always takes place on railways where a great number of horses are employed by persons of different interests". Prompted by Macneill, the thoughts of the Committee turned to locomotive haulage, and to the possibility of a through passenger service between Glasgow and Edinburgh. This would require the co-operation of three other railways—the Garnkirk and Glasgow Railway (G&GR), the M&KR and the Ballochney Railway (BRly)—as well as the Union Canal Company. The M&KR was not encouraging.
Opening at last
Eventually the contractors' difficulties were overcome, and on 30 July 1840 the directors, some shareholders, the directors of the Union Canal, and some engineers made a special journey throughout from the Garnkirk and Glasgow Railway's Townhead depot to Edinburgh over the G&GR, M&KR, BRly, the Slamannan line itself, and after transferring to a boat, the Union Canal. The railway part of this journey took 95 minutes to "Causeyend" (Causeway End) and
The directors of the Union Canal had subscribed some of the Slamannan capital and its parliamentary costs, and evidently saw collaboration with the Slamannan as being the future. They were evidently persuaded by this demonstration run, for on 4 August they ordered a larger passenger boat for the new intercity trade. The arrival in "Edinburgh" was of course at the canal's basin at Port Hopetoun, some distance from the city centre.
On 5 August 1840 the line opened, with a daily passenger train each way.
Operation
Passenger
At first, the passenger trade seemed to boom, with the daily train leaving Townhead at 10:15 a.m. and the westbound journey starting by boat at 7:00 a.m. An omnibus ran from the centre of Edinburgh to connect, departing at 6:45 a.m. Fares were 7s 6d (first class and cabin on the boat), and 5s (second class and steerage). The journey took something over four hours, comparable with the stagecoach transit; a throughout boat trip over the Union Canal and the Forth and Clyde Canal continued in operation for the time being, taking 7½ hours. By October the Union Canal had procured a second boat and there were now two railway-and-canal journeys each way daily.
This was now the principal means of travel between the two great cities, involving a canal boat trip, the transit of three rope-worked inclines over four railway companies, and a railway running on stone block sleepers and, west of Arbuckle, finding a path among horse-drawn coal trains.
It was not long before a businessman started to operate a coach direct from Princes Street in Edinburgh to Causewayend, cutting 45 minutes off the journey (at a premium price) and of course by-passing the canal transit altogether. This proved popular, and the G&GR (apparently the driving force in this joint operation) encouraged the development of the stagecoach connection: the stagecoach operator would offer a fare reduction in return for being the favoured connection at the Edinburgh end. The Union Canal had provided considerable financial support to the Slamannan company in its early days and it was now being squeezed out. Reliability of the westbound canal trip seems to have been poor, and on 5 November 1841, the Slamannan board decided that the westbound train would leave at the advertised time whether or not the connecting boat had arrived. As this made the boat-and-railway journey practically impossible, the G&GR stopped selling through tickets for that journey, and the poor Union Canal had to try to reinvigorate its intercity business over the Forth and Clyde Canal instead.
Nonetheless the railway transit was also under threat, and a fare reduction in December 1841 did little to stave off the approaching doom: on 21 February 1842 the Edinburgh and Glasgow Railway opened its railway (to Haymarket). As a relatively modern, fast and direct line, it put an end to the Slamannan's through passenger service.
Mineral and goods
By contrast the mineral traffic was disappointing at the beginning; of course it relied on as-yet unproven pits in the area being developed. Moreover, all the trade to Edinburgh involved a transshipment to the canal at Causewayend. There was practically no goods (non-mineral) traffic. Thus in 1841 mineral receipts were £1,271 (from 26,776 tons) compared with £6,174 from passengers. The mineral tonnage climbed steadily, rising to 74,130 tons in 1845, still woefully weak.
Locomotives
At first the Company operated two locomotives on passenger duties; it seems that until March 1842 one of them worked exclusively below the Ballochney's inclines, to and from Townhead. In this period there was one goods engine operating, although the sparse traffic levels led to only one engine at a time being required for duty from 1842.
The locomotive stock included Borealis from the Rowan Company and two Fairbairn locomotives, Thistle and Rose.
After the opening of the Edinburgh and Glasgow Railway
The Slamannan Railway had been built with high hopes of revolutionising transport between Glasgow and Edinburgh, as well as gaining access to rich new mineral fields. It was disappointed in both respects, and the opening of the Edinburgh and Glasgow Railway (E&GR) in 1842 seemed to be a hammer blow to the Slamannan company, with their primitive sleeper block railway and a suddenly out-of-date track gauge. Although the line gave access for the first time to isolated moorland communities, the traffic brought little money in.
In the best ways of management, the directors saw this as an opportunity: if they could connect to the E&GR with its more efficient connections to Edinburgh and elsewhere, they could enhance the traffic they carried. At Causewayend they were close to the E&GR and a connecting line there was the solution.
Slamannan Junction Railway
The E&GR was persuaded to subscribe half the cost of the connecting link, and a nominally independent company, the Slamannan Junction Railway was promoted in Parliament, getting its act of Parliament on 4 July 1844. It was to run from Bo'ness Junction (later renamed Manuel High Level, near Myrehead) on the E&GR main line, to Causewayend, forming an east-to-south connection.
Its application to Parliament had been supported jointly by the E&GR and the Slamannan Company, and shortly after obtaining its act, the shareholders sold the company to the E&GR. So the E&GR built the line, on the standard gauge; the work was finished by January 1847, but it did not come into operation until August 1847 when the Slamannan had converted its gauge.
Attempted take over and change of gauge
The Edinburgh and Glasgow Railway started negotiations in 1844 to take over the various Monkland coal railways; and at the same time they applied for permission to change to the gauge of the track to standard. However, in May 1846, the Edinburgh and Glasgow Railway was refused permission to amalgamate and it decide to withdraw on 31 December 1846. The Caledonian Railway had by that time taken over the Wishaw and Coltness Railway and the Garnkirk and Glasgow Railway, as part of its plan to get access to Glasgow over those lines.
The Slamannan Railway, together with the Ballochney Railway and the Monkland and Kirkintilloch Railway obtained authorisation to change to standard gauge and completed the process on 26 July and 27 July 1847.
In 1847 a branch was opened to a pit at Jawcraig.
Amalgamation to form the Monkland Railways and after
On 14 August 1848 the Slamannan Railway merged with the Monkland and Kirkintilloch Railway and the Ballochney Railway to become the Monkland Railways.
A 4.5-mile (7 km) extension—the Slamannan and Borrowstounness Railway—was built to Bo'ness, opening on 17 March 1851. The 26 June 1846 act of Parliament authorising this extension, also allowed the railway to lease the harbour at Bo'ness but this lease was not followed through.
Under the Monkland Railways the connections to the E&GR improved the Slamannan main line's value, and some of the mineral deposits became commercially viable at last. A number of branch lines were opened to serve those remote from the Slamannan main line, and numerous tramways and private mineral lines extended the reach of the branches further. In 1855 a more ambitious branch, to Bathgate, was opened, from Blackston Junction (often also spelt Blackstone Junction). This was no passenger branch: it turned south away from the passenger station, and led to the important chemical works on the south of the town.
The terrain crossed by the railway never encouraged significant local passenger traffic, and in this period the passenger train service continued at a moderate level.
The commercial performance of the Monkland Railways improved a little, but they were unable to compete against the more modern railways, and a sale to the E&GR became the best way forward. The Monkland Railways were absorbed by the Edinburgh and Glasgow Railway, ratified by act of Parliament dated 5 July 1865, and the sale was effective from 31 July 1865. A day later (on 1 August 1865) the Edinburgh and Glasgow Railway was absorbed into the North British Railway.
Engineering
The track gauge originally adopted was 4 ft 6 in, to conform to the gauge of the adjoining railways. A single line was laid with space for subsequent doubling. Rails of 50 lb per yard with a parallel single-headed profile were used. Stone blocks were used for sleepers although some timber sleepers were used also. There was an area of very poor ground at Arden Moss, where longitudinal timber bearers on cross-timbers were used in effect forming floating rafts:
The line at the western end passes over a flow-moss from 30 to 40 feet deep, for a distance of 2 miles. Here the rails had to be literally floated on rafts of timber, and continued floating for some time after the trade had commenced, until at length, by continued pouring in of hard material—such as gravel, stones, &c.—this part of the road is now comparatively firm and solid. It had, however, for some months after the trains commenced to run, a very singular, and to many, an alarming appearance,—the engines and carriages, as they went along, causing a deflection of the platforms or rafts, of from 2 to 3 feet, which gradually rose to their proper level behind the train, exactly like a sluggish wave, as soon as the whole had passed over.
The inclined plane at Causewayend was 800 yards (732 m) long. Murdoch, Aitken & Co supplied a 50-horsepower (37 kW) stationary engine, and Thomas Nicholson of Dundee provided the rope and "a cask of patent oil".
A canal basin and wharves were provided at Causewayend, paid for jointly by the Slamannan company and the Union Canal.
The route
The line ran from the northern branch of the Ballochney Railway at Arbuckle to Causewayend, a distance of 12.5 miles (20 km).
Whishaw lists the "inclinations" on the route; only one is steeper than 1 in 100, at Causewayend where the line descends to the level of the canal at a gradient of 1 in 22. The length of this incline is 800 yards and it is "to be worked by a fixed engine of 50-horse power". This was a rope-worked inclined plane, where groups of wagons were hauled up or let down under the control of the rope.
Whishaw states that the rest of the line is "to be worked by locomotive engines".
"The level road-crossings are fifteen in number."
Land was acquired for a double track line, although only single track was laid. The rails "are of the single parallel form [i.e. not fish-bellied] ... weighing 50 lbs to the yard lineal, and are fixed with 3-feet bearings in cast-iron chairs, the sockets of which are made to correspond exactly with the cross-section of the rails, so that keys are entirely dispensed with."
"Both stone blocks and wooden sleepers are used for the permanent-way".
"In passing over Arden Moss, for a length of 1½ miles, the rails are entirely laid on longitudinal timbers of red pine, having a scantling of 10 inches by 4 inches. These timbers rest on cross sleepers of beech, larch, or Scotch fir, which are 9 feet in length, and have a cross section of 12 inches by 6 inches, being placed at intervals of 3 feet."
"The ballasting consists of broken freestone, 10 inches below [the level of the underside of] the blocks or sleepers."
In 1844 a two-mile extension at Causeway End, to link it to the Edinburgh and Glasgow Railway was authorised.
It was built to the track gauge of , then commonly used among similar railways in Scotland.
The North British Railway and later
The attraction to the North British Railway of purchasing the Monkland lines was access to pits and iron works on the network, and in effect the Slamannan became a mineral branch line. The passenger service continued, no longer aspiring to be other than purely local, with (in 1895) an unbalanced service of three and four trains between Coatbridge and Manuel, taking about an hour for the journey. In 1922 the service was pretty well the same.
The coal extraction on the Slamannan's line declined in the twentieth century, and in 1930 the passenger service was discontinued, and the route was severed in the centre, becoming a branch from Manuel to Avonbridge at the east end, and from Airdrie to Slamannan at the west end. These lines too closed down and by 1964 everything had closed.
Paradoxically open cast mining has become widespread in the area around Arbuckle and the western extremity of the line, obliterating its course. The remainder of the route is relatively intact, crossing unpromising moorland which has seen little development.
Topography
The western extremity of the Slamannan Railway was Whiterigg. Taking that as a starting point, locations on the route are located as follows:
Whiterigg station; opened 3 October 1862; closed 1 May 1930:
Arden station; opened 31 December 1840; closed 1 May 1930;
Longriggend (earlier the location was spelt Langrigend); passenger station opened November 1862; closed 1 May 1930;
Limerigg Junction: Limerigg Branch diverged to the south; coal pits;
North Monkland Junction: North Monkland Railway converges from the north; opened 1878;
Slamannan station; opened 5 August 1840; closed 1 May 1930; numerous pits served by tramways on south side of the line
Strathavon Junction; branch to Jawcraig pit opened 1847, converged on north side; later much extended when the pits multiplied; also known as the Strathavon Valley Branch;
Glenellrig station; opened in the late 1840s and closed 1 January 1850;
Avonbridge station; opened 5 August 1840; closed 1 May 1930; apparently on the east side of the level crossing at first, moved later to the west side
Blackstone station; opened January 1863; later Blackstone Junction, then Blackston Junction; closed 1 May 1930; branch opened 1855, diverging to the south to Bathgate;
Bowhouse station; opened late 1840s; closed 1 May 1930; Bowhouse Branch from Roughrigg Colliery opened 1868 converged from west; several mineral branches later extended the line;
Causewayend incline;
Causewayend Junction; the Slamannan and Borrowstounness Railway diverged to the south, and the Slamannan Junction Railway diverged to the north. The Almond Iron Works was also located at this point later, with extensive sidings on the north side of the line;
Causewayend Wharf on the Union Canal; Causewayend passenger station opened 5 August 1840; closed 1 May 1930;
The Causewayend passenger station was later built on the east side of the canal, on the Slamannan and Borrowstounness Railway route to Bo'ness.
Notes
References
Sources
Further reading
North British Railway
Closed railway lines in Scotland
Early Scottish railway companies
Mining railways
Pre-grouping British railway companies
Railway companies established in 1835
Railway lines opened in 1840
Railway companies disestablished in 1848
Standard gauge railways in Scotland
4 ft 6 in gauge railways in Scotland
1835 establishments in Scotland
1848 disestablishments in Scotland
Railway inclines in the United Kingdom | Slamannan Railway | [
"Engineering"
] | 4,532 | [
"Mining equipment",
"Mining railways"
] |
9,215,935 | https://en.wikipedia.org/wiki/Traymore%20Hotel | The Traymore Hotel was a resort in Atlantic City, New Jersey. Begun as a small boarding house in 1879, the hotel expanded and became one of the city's premier resorts. As Atlantic City began to decline in its popularity as a resort town, during the 1950s and 1960s, the Traymore diminished in popularity. By the early 1970s the hotel was abandoned and severely run down. It was imploded and demolished between April and May 1972, a full four years before the New Jersey Legislature passed the referendum that legalized gambling in Atlantic City.
Beginnings
Like most of the pre-casino Atlantic City resorts, the Traymore went through several incarnations. It started off as a modest ten-room wooden cottage boarding house located at Illinois Avenue and the Boardwalk. The name "Traymore" came from the hotel's steadiest customer, "Uncle Al Harvey", a rich Marylander who had named his estate "Traymore" after his home town in Ireland.
The first hotel was rather flimsy, as it was destroyed by a severe winter storm on January 10, 1884. It was quickly rebuilt and enlarged. When rebuilt, the owners made the hotel stronger and more modern, adding indoor plumbing and bathrooms. They also added a spacious lawn between the hotel and the Boardwalk that proved to be valuable when a September 1889 storm struck the city. The lawn protected the hotel from any serious damage. The hotel's modern appointments led to it becoming very popular. It stayed open year-round, and by 1898 it grew into the city's largest hotel with over 450 rooms. By 1906 the Traymore's owner, Daniel White, hired the firm of Price and McLanahan to construct a new tower which brought the hotel right up to the boardwalk.
Expansion
By 1914, the Traymore, which had been the city's most popular hotel, now had stiff competition from the Marlborough-Blenheim Hotel, located across from the Traymore on Ohio Avenue and the Boardwalk. Owner Josiah White III, Daniel White's half brother, had contracted the services of Price and McLanahan to build an extension to his Marlborough House which had opened in 1902. The result was the modern Blenheim hotel which was one of the first hotels constructed using reinforced concrete.
Built during the autumn and winter of 1914–15, White contracted with Price and McLanahan to replace the existing wooden-frame Traymore with a massive concrete structure that would rival the Marlborough-Blenheim. Price's Traymore was built directly behind the 1906 tower, and was designed to take advantage of its ocean views: hotel wings jutted out further from the central tower toward Pacific Avenue, thus affording more guests ocean views. The new Traymore opened in time for the 1915 season, and was a success. Built with tan brick and capped by yellow-tiled domes, the Traymore instantly became the city's architectural showpiece when it opened in June 1915. The hotel was such a success that White commissioned a 25-story additional tower to be built, but was unable to secure funding for the project due to World War I.
The Traymore catered to an upscale clientele, and was described in 1924 as "the Taj Mahal of Atlantic City," decades before Donald Trump opened a casino resort with that name.
The Traymore featured four faucets in every bathtub: hot and cold city water, hot and cold ocean water. There was a fifth faucet in the sink for ice water.
The Traymore was leased by the US Military during World War II, as part of Army Air Force Basic Training Center No. 7. The forty-seven Atlantic City resort hotels taken over by the United States Military were collectively dubbed "Camp Boardwalk". The Traymore was operated jointly with the adjacent Chalfonte-Haddon Hall Hotel as the England General Hospital, which opened on April 28, 1944. The hospital was named for Lt. Col. Thomas Marcus England, who had worked with Walter Reed researching yellow fever in Cuba in 1900. The Traymore served as the convalescent reconditioning section of the hospital. The last patients left the hospital in June 1946 and the Traymore was returned to its owners and reopened soon after.
The Traymore Hotel Outdoor and Indoor Swimming Pools were built 1954 to designs by architect Samuel Juster of New York City.
Demise and present status
The hotel remained popular well into the 1950s, but as Atlantic City declined in the 1960s, the Traymore did as well. The availability of home air conditioning and swimming pools, coupled with inexpensive and frequent airline services to destinations in Florida and the Caribbean, led to the decline of Atlantic City as the premier ocean resort. By the early 1970s, the hotel was defunct and was causing its owners large financial deficits. It was decided to demolish the hotel, despite a campaign to save the architectural landmark.
On April 27, 1972 the hotel experienced the first of four planned controlled implosions implemented by Jack Loizeaux. By May 1972 the hotel was completely demolished. For a time, the once-famous hotel held the Guinness World Record for largest controlled demolition—with a capacity of nearly , the Traymore was the largest (though not highest) structure yet demolished. The spectacle is captured in the 1980 film Atlantic City.
As well as the 1974 Walt Disney Film Herbie Rides Again in the beginning of the film where Alonzo Hawk demolishes numerous buildings.
Caesars Atlantic City purchased the land in the late 1970s and utilized it as a parking lot. The casino intended to develop a hotel there, however, the plan did not materialize. In 2006, Pinnacle Entertainment announced that it purchased the Traymore site and the adjacent Sands Atlantic City casino hotel. Pinnacle demolished the Sands and planned to develop a new casino on the combined parcels. Harsh economic times later caused Pinnacle to delay construction of the new resort. In February 2010, the company announced that it had canceled its construction plans and would instead seek to sell the land. Most of the Traymore site remains a parking lot.
Popular culture
Traymore Hotel is one of the locations featured in Grace Livingston Hill's 1911 novel Aunt Crete's Emancipation.
It can be seen in several exterior scenes of the 1972 Bob Rafelson film The King of Marvin Gardens, which was shot in Atlantic City only a few months before the building was demolished.
Footage of the Traymore's demolition features in the opening of Louis Malle's 1980 film Atlantic City. Nevertheless, the Traymore was demolished in 1972 for financial reasons and not in anticipation of legalized gambling (a 1974 referendum to allow casinos throughout the state was not approved by New Jersey voters). Gambling was legalized four years after the demolition in 1976 with Resorts International being the first legal casino to open in 1978.
The HBO drama Boardwalk Empire used the Atlantic City skyline, circa 1920, as the back drop for the series opening titles, including both the Traymore and the famed Marlborough-Blenheim Hotel.
See also
List of tallest buildings in Atlantic City
References
Further reading
Includes numerous reproductions of architectural renderings and construction photographs.
Hotel buildings completed in 1915
Skyscraper hotels in Atlantic City, New Jersey
Demolished hotels in New Jersey
Hotels established in 1879
Buildings and structures demolished by controlled implosion
Buildings and structures demolished in 1972
1972 disestablishments in New Jersey
Former skyscraper hotels
Former National Register of Historic Places in New Jersey | Traymore Hotel | [
"Engineering"
] | 1,489 | [
"Buildings and structures demolished by controlled implosion",
"Architecture"
] |
9,216,410 | https://en.wikipedia.org/wiki/BBCH-scale%20%28coffee%29 | In biology, the BBCH-scale for coffee describes the phenological development of bean plants using the BBCH-scale.
The phenological growth stages and BBCH-identification keys of coffee plants are:
References
BBCH-scale
Coffee chemistry | BBCH-scale (coffee) | [
"Chemistry"
] | 52 | [
"Coffee chemistry",
"Food chemistry"
] |
9,217,017 | https://en.wikipedia.org/wiki/Transition%20state%20theory | In chemistry, transition state theory (TST) explains the reaction rates of elementary chemical reactions. The theory assumes a special type of chemical equilibrium (quasi-equilibrium) between reactants and activated transition state complexes.
TST is used primarily to understand qualitatively how chemical reactions take place. TST has been less successful in its original goal of calculating absolute reaction rate constants because the calculation of absolute reaction rates requires precise knowledge of potential energy surfaces, but it has been successful in calculating the standard enthalpy of activation (ΔH‡, also written Δ‡Hɵ), the standard entropy of activation (ΔS‡ or Δ‡Sɵ), and the standard Gibbs energy of activation (ΔG‡ or Δ‡Gɵ) for a particular reaction if its rate constant has been experimentally determined (the ‡ notation refers to the value of interest at the transition state; ΔH‡ is the difference between the enthalpy of the transition state and that of the reactants).
This theory was developed simultaneously in 1935 by Henry Eyring, then at Princeton University, and by Meredith Gwynne Evans and Michael Polanyi of the University of Manchester. TST is also referred to as "activated-complex theory", "absolute-rate theory", and "theory of absolute reaction rates".
Before the development of TST, the Arrhenius rate law was widely used to determine energies for the reaction barrier. The Arrhenius equation derives from empirical observations and ignores any mechanistic considerations, such as whether one or more reactive intermediates are involved in the conversion of a reactant to a product. Therefore, further development was necessary to understand the two parameters associated with this law, the pre-exponential factor (A) and the activation energy (Ea). TST, which led to the Eyring equation, successfully addresses these two issues; however, 46 years elapsed between the publication of the Arrhenius rate law, in 1889, and the Eyring equation derived from TST, in 1935. During that period, many scientists and researchers contributed significantly to the development of the theory.
Theory
The basic ideas behind transition state theory are as follows:
Rates of reaction can be studied by examining activated complexes near the saddle point of a potential energy surface. The details of how these complexes are formed are not important. The saddle point itself is called the transition state.
The activated complexes are in a special equilibrium (quasi-equilibrium) with the reactant molecules.
The activated complexes can convert into products, and kinetic theory can be used to calculate the rate of this conversion.
Development
In the development of TST, three approaches were taken as summarized below.
Thermodynamic treatment
In 1884, Jacobus van 't Hoff proposed the Van 't Hoff equation describing the temperature dependence of the equilibrium constant for a reversible reaction:
{A} <=> {B}
where ΔU is the change in internal energy, K is the equilibrium constant of the reaction, R is the universal gas constant, and T is thermodynamic temperature. Based on experimental work, in 1889, Svante Arrhenius proposed a similar expression for the rate constant of a reaction, given as follows:
Integration of this expression leads to the Arrhenius equation
where k is the rate constant. A was referred to as the frequency factor (now called the pre-exponential coefficient), and Ea is regarded as the activation energy. By the early 20th century many had accepted the Arrhenius equation, but the physical interpretation of A and Ea remained vague. This led many researchers in chemical kinetics to offer different theories of how chemical reactions occurred in an attempt to relate A and Ea to the molecular dynamics directly responsible for chemical reactions.
In 1910, French chemist René Marcelin introduced the concept of standard Gibbs energy of activation. His relation can be written as
At about the same time as Marcelin was working on his formulation, Dutch chemists Philip Abraham Kohnstamm, Frans Eppo Cornelis Scheffer, and Wiedold Frans Brandsma introduced standard entropy of activation and the standard enthalpy of activation. They proposed the following rate constant equation
However, the nature of the constant was still unclear.
Kinetic-theory treatment
In early 1900, Max Trautz and William Lewis studied the rate of the reaction using collision theory, based on the kinetic theory of gases. Collision theory treats reacting molecules as hard spheres colliding with one another; this theory neglects entropy changes, since it assumes that the collision between molecules are completely elastic.
Lewis applied his treatment to the following reaction and obtained good agreement with experimental result.
2 HI → H2 + I2
However, later when the same treatment was applied to other reactions, there were large discrepancies between theoretical and experimental results.
Statistical-mechanical treatment
Statistical mechanics played a significant role in the development of TST. However, the application of statistical mechanics to TST was developed very slowly given the fact that in mid-19th century, James Clerk Maxwell, Ludwig Boltzmann, and Leopold Pfaundler published several papers discussing reaction equilibrium and rates in terms of molecular motions and the statistical distribution of molecular speeds.
It was not until 1912 when the French chemist A. Berthoud used the Maxwell–Boltzmann distribution law to obtain an expression for the rate constant.
where a and b are constants related to energy terms.
Two years later, René Marcelin made an essential contribution by treating the progress of a chemical reaction as a motion of a point in phase space. He then applied Gibbs' statistical-mechanical procedures and obtained an expression similar to the one he had obtained earlier from thermodynamic consideration.
In 1915, another important contribution came from British physicist James Rice. Based on his statistical analysis, he concluded that the rate constant is proportional to the "critical increment". His ideas were further developed by Richard Chace Tolman. In 1919, Austrian physicist Karl Ferdinand Herzfeld applied statistical mechanics to the equilibrium constant and kinetic theory to the rate constant of the reverse reaction, k−1, for the reversible dissociation of a diatomic molecule.
AB <=>[k_1][k_{-1}] {A} + {B}
He obtained the following equation for the rate constant of the forward reaction
where is the dissociation energy at absolute zero, kB is the Boltzmann constant, h is the Planck constant, T is thermodynamic temperature, is vibrational frequency of the bond.
This expression is very important since it is the first time that the factor kBT/h, which is a critical component of TST, has appeared in a rate equation.
In 1920, the American chemist Richard Chace Tolman further developed Rice's idea of the critical increment. He concluded that critical increment (now referred to as activation energy) of a reaction is equal to the average energy of all molecules undergoing reaction minus the average energy of all reactant molecules.
Potential energy surfaces
The concept of potential energy surface was very important in the development of TST. The foundation of this concept was laid by René Marcelin in 1913. He theorized that the progress of a chemical reaction could be described as a point in a potential energy surface with coordinates in atomic momenta and distances.
In 1931, Henry Eyring and Michael Polanyi constructed a potential energy surface for the reaction below. This surface is a three-dimensional diagram based on quantum-mechanical principles as well as experimental data on vibrational frequencies and energies of dissociation.
H + H2 → H2 + H
A year after the Eyring and Polanyi construction, Hans Pelzer and Eugene Wigner made an important contribution by following the progress of a reaction on a potential energy surface. The importance of this work was that it was the first time that the concept of col or saddle point in the potential energy surface was discussed. They concluded that the rate of a reaction is determined by the motion of the system through that col.
Kramers theory of reaction rates
By modeling reactions as Langevin motion along a one dimensional reaction coordinate, Hendrik Kramers was able to derive a relationship between the shape of the potential energy surface along the reaction coordinate and the transition rates of the system. The formulation relies on approximating the potential energy landscape as a series of harmonic wells. In a two state system, there will be three wells; a well for state A, an upside-down well representing the potential energy barrier, and a well for state B.
In the overdamped (or "diffusive") regime, the transition rate from state A to B is related to the resonant frequency of the wells via
where is the frequency of the well for state A, is the frequency of the barrier well, is the viscous damping, is the energy of the top of the barrier, is the energy of bottom of the well for state A, and is the temperature of the system times the Boltzmann constant.
For general damping (overdamped or underdamped), there is a similar formula.
Justification for the Eyring equation
One of the most important features introduced by Eyring, Polanyi and Evans was the notion that activated complexes are in quasi-equilibrium with the reactants. The rate is then directly proportional to the concentration of these complexes multiplied by the frequency (kBT/h) with which they are converted into products. Below, a non-rigorous plausibility argument is given for the functional form of the Eyring equation. However, the key statistical mechanical factor kBT/h will not be justified, and the argument presented below does not constitute a true "derivation" of the Eyring equation.
Quasi-equilibrium assumption
Quasi-equilibrium is different from classical chemical equilibrium, but can be described using a similar thermodynamic treatment. Consider the reaction below
{A} + {B} <=> {[AB]^\ddagger} -> {P}
where complete equilibrium is achieved between all the species in the system including activated complexes, [AB]‡ . Using statistical mechanics, concentration of [AB]‡ can be calculated in terms of the concentration of A and B.
TST assumes that even when the reactants and products are not in equilibrium with each other, the activated complexes are in quasi-equilibrium with the reactants. As illustrated in Figure 2, at any instant of time, there are a few activated complexes, and some were reactant molecules in the immediate past, which are designated [ABl]‡ (since they are moving from left to right). The remainder of them were product molecules in the immediate past ([ABr]‡).
In TST, it is assumed that the flux of activated complexes in the two directions are independent of each other. That is, if all the product molecules were suddenly removed from the reaction system, the flow of [ABr]‡ stops, but there is still a flow from left to right. Hence, to be technically correct, the reactants are in equilibrium only with [ABl]‡, the activated complexes that were reactants in the immediate past.
Plausibility argument
The activated complexes do not follow a Boltzmann distribution of energies, but an "equilibrium constant" can still be derived from the distribution they do follow. The equilibrium constant K‡ for the quasi-equilibrium can be written as
.
So, the chemical activity of the transition state AB‡ is
.
Therefore, the rate equation for the production of product is
,
where the rate constant k is given by
.
Here, k‡ is directly proportional to the frequency of the vibrational mode responsible for converting the activated complex to the product; the frequency of this vibrational mode is . Every vibration does not necessarily lead to the formation of product, so a proportionality constant , referred to as the transmission coefficient, is introduced to account for this effect. So k‡ can be rewritten as
.
For the equilibrium constant K‡ , statistical mechanics leads to a temperature dependent expression given as
().
Combining the new expressions for k‡ and K‡, a new rate constant expression can be written, which is given as
.
Since, by definition, ΔG‡ = ΔH‡ –TΔS‡, the rate constant expression can be expanded, to give an alternative form of the Eyring equation:
.
For correct dimensionality, the equation needs to have an extra factor of (c⊖)1–m for reactions that are not unimolecular:
,
where c⊖ is the standard concentration 1 mol⋅L−1 and m is the molecularity.
Inferences from TST and relationship with Arrhenius theory
The rate constant expression from transition state theory can be used to calculate the ΔG‡, ΔH‡, ΔS‡, and even ΔV‡ (the volume of activation) using experimental rate data. These so-called activation parameters give insight into the nature of a transition state, including energy content and degree of order, compared to the starting materials and has become a standard tool for elucidation of reaction mechanisms in physical organic chemistry. The free energy of activation, ΔG‡, is defined in transition state theory to be the energy such that holds. The parameters ΔH‡ and ΔS‡ can then be inferred by determining ΔG‡ = ΔH‡ – TΔS‡ at different temperatures.
Because the functional form of the Eyring and Arrhenius equations are similar, it is tempting to relate the activation parameters with the activation energy and pre-exponential factors of the Arrhenius treatment. However, the Arrhenius equation was derived from experimental data and models the macroscopic rate using only two parameters, irrespective of the number of transition states in a mechanism. In contrast, activation parameters can be found for every transition state of a multistep mechanism, at least in principle. Thus, although the enthalpy of activation, ΔH‡, is often equated with Arrhenius's activation energy Ea, they are not equivalent. For a condensed-phase (e.g., solution-phase) or unimolecular gas-phase reaction step, Ea = ΔH‡ + RT. For other gas-phase reactions, Ea = ΔH‡ + (1 − Δn‡)RT, where Δn‡ is the change in the number of molecules on forming the transition state. (Thus, for a bimolecular gas-phase process, Ea = ΔH‡ + 2RT.)
The entropy of activation, ΔS‡, gives the extent to which transition state (including any solvent molecules involved in or perturbed by the reaction) is more disordered compared to the starting materials. It offers a concrete interpretation of the pre-exponential factor A in the Arrhenius equation; for a unimolecular, single-step process, the rough equivalence A = (kBT/h) exp(1 + ΔS‡/R) (or A = (kBT/h) exp(2 + ΔS‡/R) for bimolecular gas-phase reactions) holds. For a unimolecular process, a negative value indicates a more ordered, rigid transition state than the ground state, while a positive value reflects a transition state with looser bonds and/or greater conformational freedom. It is important to note that, for reasons of dimensionality, reactions that are bimolecular or higher have ΔS‡ values that depend on the standard state chosen (standard concentration, in particular). For most recent publications, 1 mol L−1 or 1 molar is chosen. Since this choice is a human construct, based on our definitions of units for molar quantity and volume, the magnitude and sign of ΔS‡ for a single reaction is meaningless by itself; only comparisons of the value with that of a reference reaction of "known" (or assumed) mechanism, made at the same standard state, is valid.
The volume of activation is found by taking the partial derivative of ΔG‡ with respect to pressure (holding temperature constant): . It gives information regarding the size, and hence, degree of bonding at the transition state. An associative mechanism will likely have a negative volume of activation, while a dissociative mechanism will likely have a positive value.
Given the relationship between equilibrium constant and the forward and reverse rate constants, , the Eyring equation implies that
.
Another implication of TST is the Curtin–Hammett principle: the product ratio of a kinetically-controlled reaction from R to two products A and B will reflect the difference in the energies of the respective transition states leading to product, assuming there is a single transition state to each one:
().
(In the expression for ΔΔG‡ above, there is an extra term if A and B are formed from two different species SA and SB in equilibrium.)
For a thermodynamically-controlled reaction, every difference of RT ln 10 ≈ (1.987 × 10−3 kcal/mol K)(298 K)(2.303) ≈ 1.36 kcal/mol in the free energies of products A and B results in a factor of 10 in selectivity at room temperature (298 K), a principle known as the "1.36 rule":
().
Analogously, every 1.36 kcal/mol difference in the free energy of activation results in a factor of 10 in selectivity for a kinetically-controlled process at room temperature:
().
Using the Eyring equation, there is a straightforward relationship between ΔG‡, first-order rate constants, and reaction half-life at a given temperature. At 298 K, a reaction with ΔG‡ = 23 kcal/mol has a rate constant of k ≈ 8.4 × 10−5 s−1 and a half life of t1/2 ≈ 2.3 hours, figures that are often rounded to k ~ 10−4 s−1 and t1/2 ~ 2 h. Thus, a free energy of activation of this magnitude corresponds to a typical reaction that proceeds to completion overnight at room temperature. For comparison, the cyclohexane chair flip has a ΔG‡ of about 11 kcal/mol with k ~ 105 s−1, making it a dynamic process that takes place rapidly (faster than the NMR timescale) at room temperature. At the other end of the scale, the cis/trans isomerization of 2-butene has a ΔG‡ of about 60 kcal/mol, corresponding to k ~ 10−31 s−1 at 298 K. This is a negligible rate: the half-life is 12 orders of magnitude longer than the age of the universe.
Limitations
In general, TST has provided researchers with a conceptual foundation for understanding how chemical reactions take place. Even though the theory is widely applicable, it does have limitations. For example, when applied to each elementary step of a multi-step reaction, the theory assumes that each intermediate is long-lived enough to reach a Boltzmann distribution of energies before continuing to the next step. When the intermediates are very short-lived, TST fails. In such cases, the momentum of the reaction trajectory from the reactants to the intermediate can carry forward to affect product selectivity. An example of such a reaction is the ring closure of cyclopentane biradicals generated from the gas-phase thermal decomposition of 2,3-diazabicyclo[2.2.1]hept-2-ene.
Transition state theory is also based on the assumption that atomic nuclei behave according to classical mechanics. It is assumed that unless atoms or molecules collide with enough energy to form the transition structure, then the reaction does not occur. However, according to quantum mechanics, for any barrier with a finite amount of energy, there is a possibility that particles can still tunnel across the barrier. With respect to chemical reactions this means that there is a chance that molecules will react, even if they do not collide with enough energy to overcome the energy barrier. While this effect is negligible for reactions with large activation energies, it becomes an important phenomenon for reactions with relatively low energy barriers, since the tunneling probability increases with decreasing barrier height.
Transition state theory fails for some reactions at high temperature. The theory assumes the reaction system will pass over the lowest energy saddle point on the potential energy surface. While this description is consistent for reactions occurring at relatively low temperatures, at high temperatures, molecules populate higher energy vibrational modes; their motion becomes more complex and collisions may lead to transition states far away from the lowest energy saddle point. This deviation from transition state theory is observed even in the simple exchange reaction between diatomic hydrogen and a hydrogen radical.
Given these limitations, several alternatives to transition state theory have been proposed. A brief discussion of these theories follows.
Generalized transition state theory
Any form of TST, such as microcanonical variational TST, canonical variational TST, and improved canonical variational TST, in which the transition state is not necessarily located at the saddle point, is referred to as generalized transition state theory.
Microcanonical variational TST
A fundamental flaw of transition state theory is that it counts any crossing of the transition state as a reaction from reactants to products or vice versa. In reality, a molecule may cross this "dividing surface" and turn around, or cross multiple times and only truly react once. As such, unadjusted TST is said to provide an upper bound for the rate coefficients. To correct for this, variational transition state theory varies the location of the dividing surface that defines a successful reaction in order to minimize the rate for each fixed energy. The rate expressions obtained in this microcanonical treatment can be integrated over the energy, taking into account the statistical distribution over energy states, so as to give the canonical, or thermal rates.
Canonical variational TST
A development of transition state theory in which the position of the dividing surface is varied so as to minimize the rate constant at a given temperature.
Improved canonical variational TST
A modification of canonical variational transition state theory in which, for energies below the threshold energy, the position of the dividing surface is taken to be that of the microcanonical threshold energy. This forces the contributions to rate constants to be zero if they are below the threshold energy. A compromise dividing surface is then chosen so as to minimize the contributions to the rate constant made by reactants having higher energies.
Nonadiabatic TST
An expansion of TST to the reactions when two spin-states are involved simultaneously is called nonadiabatic transition state theory (NA-TST).
Semiclassical TST
Using vibrational perturbation theory, effects such as tunnelling and variational effects can be accounted for within the SCTST formalism.
Applications
Enzymatic reactions
Enzymes catalyze chemical reactions at rates that are astounding relative to uncatalyzed chemistry at the same reaction conditions. Each catalytic event requires a minimum of three or often more steps, all of which occur within the few milliseconds that characterize typical enzymatic reactions. According to transition state theory, the smallest fraction of the catalytic cycle is spent in the most important step, that of the transition state. The original proposals of absolute reaction rate theory for chemical reactions defined the transition state as a distinct species in the reaction coordinate that determined the absolute reaction rate. Soon thereafter, Linus Pauling proposed that the powerful catalytic action of enzymes could be explained by specific tight binding to the transition state species Because reaction rate is proportional to the fraction of the reactant in the transition state complex, the enzyme was proposed to increase the concentration of the reactive species.
This proposal was formalized by Wolfenden and coworkers at University of North Carolina at Chapel Hill, who hypothesized that the rate increase imposed by enzymes is proportional to the affinity of the enzyme for the transition state structure relative to the Michaelis complex. Because enzymes typically increase the non-catalyzed reaction rate by factors of 106-1026, and Michaelis complexes often have dissociation constants in the range of 10−3-10−6 M, it is proposed that transition state complexes are bound with dissociation constants in the range of 10−14 -10−23 M. As substrate progresses from the Michaelis complex to product, chemistry occurs by enzyme-induced changes in electron distribution in the substrate. Enzymes alter the electronic structure by protonation, proton abstraction, electron transfer, geometric distortion, hydrophobic partitioning, and interaction with Lewis acids and bases. Analogs that resemble the transition state structures should therefore provide the most powerful noncovalent inhibitors known.
All chemical transformations pass through an unstable structure called the transition state, which is poised between the chemical structures of the substrates and products. The transition states for chemical reactions are proposed to have lifetimes near 10−13 seconds, on the order of the time of a single bond vibration. No physical or spectroscopic method is available to directly observe the structure of the transition state for enzymatic reactions, yet transition state structure is central to understanding enzyme catalysis since enzymes work by lowering the activation energy of a chemical transformation.
It is now accepted that enzymes function to stabilize transition states lying between reactants and products, and that they would therefore be expected to bind strongly any inhibitor that closely resembles such a transition state. Substrates and products often participate in several enzyme catalyzed reactions, whereas the transition state tends to be characteristic of one particular enzyme, so that such an inhibitor tends to be specific for that particular enzyme. The identification of numerous transition state inhibitors supports the transition state stabilization hypothesis for enzymatic catalysis.
Currently there is a large number of enzymes known to interact with transition state analogs, most of which have been designed with the intention of inhibiting the target enzyme. Examples include HIV-1 protease, racemases, β-lactamases, metalloproteinases, cyclooxygenases and many others.
Adsorption on surfaces and reactions on surfaces
Desorption as well as reactions on surfaces are straightforward to describe with transition state theory. Analysis of adsorption to a surface from a liquid phase can present a challenge due to lack of ability to assess the concentration of the solute near the surface. When full details are not available, it has been proposed that reacting species' concentrations should be normalized to the concentration of active surface sites, an approximation called the surface reactant equi-density approximation (SREA).
See also
Curtin–Hammett principle
Electron transfer
Marcus theory
Notes
References
Anslyn, Eric V.; Doughtery, Dennis A., Transition State Theory and Related Topics. In Modern Physical Organic Chemistry University Science Books: 2006; pp 365–373
Cleland, W.W., Isotope Effects: Determination of Enzyme Transition State Structure. Methods in Enzymology 1995, 249, 341–373
Laidler, K.; King, C., Development of transition-state theory. The Journal of Physical Chemistry 1983, 87, (15), 2657
Laidler, K., A lifetime of transition-state theory. The Chemical Intelligencer 1998, 4, (3), 39
Radzicka, A.; Woldenden, R., Transition State and Multisubstrate Analog Inhibitors. Methods in Enzymology 1995, 249, 284–312
Schramm, VL., Enzymatic Transition States and Transition State Analog Design. Annual Review of Biochemistry 1998, 67, 693–720
Schramm, V.L., Enzymatic Transition State Theory and Transition State Analogue Design. Journal of Biological Chemistry 2007, 282, (39), 28297–28300
External links
Simple application of TST
Chemical kinetics
Chemistry theories | Transition state theory | [
"Chemistry"
] | 5,728 | [
"Chemical reaction engineering",
"nan",
"Chemical kinetics"
] |
9,220,301 | https://en.wikipedia.org/wiki/Belt%20course | A belt course, also called a string course or sill course, is a continuous row or layer of stones or brick set in a wall. Set in line with window sills, it helps to make the horizontal line of the sills visually more prominent. Set between the floors of a house, it helps to make the separate floors distinguishable from the exterior of the building.
The belt course often projects from the side of the building. Georgian architecture is notable for the use of belt courses.
Although the belt course has its origins as a structural component of a building, by the 18th century it was almost purely a decorative element and had no functional purpose. In brick or stone buildings taller than three stories, however, a shelf angle is usually used to transfer the load of the wall to a hidden, interior steel wall. Flashing is used to cover the space exposed by the shelf angle to help limit the intrusion of water. Where flashing is considered aesthetically unpleasing, a belt course is often used.
In Jamaican building construction, "belt course" or "belting" refers to a continuous concrete beam or slab that is boxed and cast across the top of the wall spanning the concrete blocks and tying in all columns to provide structural support and to carry the weight of the roof or another story. The slabs or beams across windows and doors are called "lintel" and are there for structural support.
See also
Course (architecture)
References
Types of wall
Architectural elements | Belt course | [
"Technology",
"Engineering"
] | 295 | [
"Structural engineering",
"Building engineering",
"Types of wall",
"Architectural elements",
"Components",
"Architecture"
] |
9,220,925 | https://en.wikipedia.org/wiki/Worley%20%28company%29 | Worley Limited is an Australian engineering and professional services company which provides consulting and project delivery expertise to the resources and energy sectors, and complex process industries.
History
Early history
John Grill (chief executive officer 1975–2012), joined Smith, de Kantzow & Wholohan, which led to the 1976 establishment Wholohan Grill and Partners, a small Australian engineering consultancy. Wholohan Grill and Partners grew steadily throughout the 1970s and 80s.
In 1987, Wholohan Grill and Partners acquired the Australian interests of Worley, an American-based engineering firm founded by Steve Worley. The company changed its name to Worley and from this point began expanding steadily, securing long-term contracts in Brunei, Malaysia, Thailand and Singapore, and creating local joint ventures, most of which are still active today.
In the 1990s, Worley expanded both its industry sector and geographical footprint. A policy of diversification saw Worley grow from its roots in the hydrocarbons sector into the power, infrastructure and environment, and minerals and metals sectors. At the start of the new millennium, Worley was well poised to continue its industry sector and geographic expansion with 30 offices and 3,000 personnel globally. This success enabled Worley to diversify further through additional partnerships and acquisitions.
2000s
In 2002 Worley became a publicly listed company on the Australian Stock Exchange, leading to a period of increased global acquisitions, including companies in Canada, Oman, and China. In 2004, Worley acquired Parsons E&C. Parsons E&C had its own history stemming back to 1944, when Ralph M. Parsons started what is now the Parsons Corporation in Los Angeles. In 2002, Parsons Corporation separated Parsons E&C from its other business units. Worley merged operations with Parsons E&C and commenced trading as WorleyParsons.
Further acquisitions included Astron in 2004, and Komex, which was involved in environmental services, in 2005, DRPL in the power sector, TMG and Watkins & Godwin in the infrastructure sector, HG Engineering, Gas Cleaning Technologies, and Jones & Jones in the mineral and metals sector, continued to deepen and broaden WorleyParsons' capability and geographic presence.
In 2006, WorleyParsons entered the South American market through a joint venture with Santiago-based ARA, a leading base metals and infrastructure engineering firm, and Colt Companies, Canada's largest engineering and project services firm, became part of the WorleyParsons family in 2007. Later that year, the companies Patterson Britton and Partners, and John Wilson and Partners, were acquired, both consultants in the water and environmental services market in Australia, with specific capabilities in the coastal and marine, water resources and waste water, environmental, civil and structural and power markets. That provided a significant expansion of the organisation's ability to support its customers in the areas of water and environmental services. In November 2007, WorleyParsons' capability in the nuclear consulting and analysis segment of the international nuclear industry was complemented with the acquisition of Polestar and UniField Engineering, with the aim of further expanding its presence in the U.S. electrical power business.
WorleyParsons also developed its business in Africa, with the establishment of offices in Egypt and Libya, joint venture in Nigeria as DeltaAfrik with Delta Tek Engineering and by the 2008 acquisition of a 50% share in Pangaea – a Pretoria-based project services company, which was renamed PangaeaWorleyParsons.
The acquisitions of SEA Engineering in 2007, and INTEC (now known as INTECSEA) in April 2008, both international offshore deep-water hydrocarbons engineering and project services companies, strategically positioned the company to provide large-scale integrated deep-water facilities, subsea and marine systems projects.
The acquisition of Westmar in 2008, a Canadian-based marine and port facility, resource and mining infrastructure, bulk material handling and transportation specialist, extended the Infrastructure and Minerals & Metals capabilities in both Canada and international markets.
In 2009, WorleyParsons acquired the United Kingdom assets of Day & Zimmermann to form the hub of WorleyParsons' UK Improve business. The same year saw the acquisition of Brazilian based on CNEC. The capability of CNEC complements the existing capabilities of WorleyParsons' resource and energy businesses.
2010s
In 2010, WorleyParsons acquired the business advisory services company, Evans & Peck. Operating in Australia and China, Evans & Peck provide services across the transport, power and energy, resources, water and social infrastructure sectors.
More recently, the acquisition of Kwezi V3 Engineers, (KV3) a leading South African engineering firm in 2011 and TWP Holdings (Proprietary) Limited ("TWP") in 2013 gives WorleyParsons' customers access to the specialized underground mine planning and engineering capabilities, mineral processing and project management of TWP.
In 2012, WorleyParsons purchased a 50% share in a joint venture company with Cergetec in Canada.
In 2013, WorleyParsons acquired Bergen Group Rosenberg AS ("Rosenberg"). Worley Rosenberg is a wholly owned subsidiary of Bergen Group ASA, a listed Norwegian company.
In 2014, WorleyParsons acquired MTG, Ltd., an American management consulting firm in the oil and gas, petrochemicals and chemicals industries with operations in North America, the United Kingdom and Australia.
In October 2018, WorleyParsons reached an agreement with Jacobs to take over its ECR business line for $3.3 billion. The transaction was completed in April 2019. The total number of employees of the combined organisation now employs 57,600 people in 51 countries.
In April 2019, it was announced that the company would re-brand to Worley, subject to approval at its October 2019 Annual General Meeting. Chris Ashton was named as the new CEO, to replace Andrew Wood, effective from 24 February 2020.
In November 2023, Worley launched a refreshed brand direction, which included a new logo and a consolidation of its portfolio of subsidiaries. Advisian, Chemetics, Comprimo, Cord, Intecsea, and Rosenberg were all combined under the single Worley brand. New portfolio subsidiaries now include Industries, Services and Technology, and Worley Consulting.
References
See also
List of oilfield service companies
Energy engineering and contractor companies
Engineering companies of Australia
Companies based in Sydney
Design companies established in 1971
Business services companies established in 1971
Australian companies established in 1971
Companies listed on the Australian Securities Exchange
2002 initial public offerings
Mining services companies of Australia | Worley (company) | [
"Engineering"
] | 1,325 | [
"Energy engineering and contractor companies",
"Engineering companies"
] |
9,221,221 | https://en.wikipedia.org/wiki/Ceramic%20capacitor | A ceramic capacitor is a fixed-value capacitor where the ceramic material acts as the dielectric. It is constructed of two or more alternating layers of ceramic and a metal layer acting as the electrodes. The composition of the ceramic material defines the electrical behavior and therefore applications. Ceramic capacitors are divided into two application classes:
Class 1 ceramic capacitors offer high stability and low losses for resonant circuit applications.
Class 2 ceramic capacitors offer high volumetric efficiency for buffer, by-pass, and coupling applications.
Ceramic capacitors, especially multilayer ceramic capacitors (MLCCs), are the most produced and used capacitors in electronic equipment that incorporate approximately one trillion (1012) pieces per year.
Ceramic capacitors of special shapes and styles are used as capacitors for RFI/EMI suppression, as feed-through capacitors and in larger dimensions as power capacitors for transmitters.
History
Since the beginning of the study of electricity non-conductive materials such as glass, porcelain, paper and mica have been used as insulators. These materials some decades later were also well-suited for further use as the dielectric for the first capacitors.
Even in the early years of Marconi's wireless transmitting apparatus, porcelain capacitors were used for high voltage and high frequency application in the transmitters. On the receiver side, the smaller mica capacitors were used for resonant circuits. Mica dielectric capacitors were invented in 1909 by William Dubilier. Prior to World War II, mica was the most common dielectric for capacitors in the United States.
Mica is a natural material and not available in unlimited quantities. So in the mid-1920s the deficiency of mica in Germany and the experience in porcelain—a special class of ceramic—led in Germany to the first capacitors using ceramic as dielectric, founding a new family of ceramic capacitors. Paraelectric titanium dioxide (rutile) was used as the first ceramic dielectric because it had a linear temperature dependence of capacitance for temperature compensation of resonant circuits and can replace mica capacitors. In 1926 these ceramic capacitors were produced in small quantities with increasing quantities in the 1940s. The style of these early ceramics was a disc with metallization on both sides contacted with tinned wires. This style predates the transistor and was used extensively in vacuum-tube equipment (e.g., radio receivers) from about 1930 through the 1950s.
But this paraelectric dielectric had relatively low permittivity so that only small capacitance values could be realized. The expanding market of radios in the 1930s and 1940s create a demand for higher capacitance values but below electrolytic capacitors for HF decoupling applications. Discovered in 1921, the ferroelectric ceramic material barium titanate with a permittivity in the range of 1,000, about ten times greater than titanium dioxide or mica, began to play a much larger role in electronic applications.
The higher permittivity resulted in much higher capacitance values, but this was coupled with relatively unstable electrical parameters. Therefore, these ceramic capacitors only could replace the commonly used mica capacitors for applications where stability was less important. Smaller dimensions, as compared to the mica capacitors, lower production costs and independence from mica availability accelerated their acceptance.
The fast-growing broadcasting industry after the Second World War drove deeper understanding of the crystallography, phase transitions and the chemical and mechanical optimization of the ceramic materials. Through the complex mixture of different basic materials, the electrical properties of ceramic capacitors can be precisely adjusted. To distinguish the electrical properties of ceramic capacitors, standardization defined several different application classes (Class 1, Class 2, Class 3). It is remarkable that the separate development during the War and the time afterwards in the US and the European market had led to different definitions of these classes (EIA vs IEC), and only recently (since 2010) has a worldwide harmonization to the IEC standardization taken place.
The typical style for ceramic capacitors beneath the disc (at that time called condensers) in radio applications at the time after the War from the 1950s through the 1970s was a ceramic tube covered with tin or silver on both the inside and outside surface. It included relatively long terminals forming, together with resistors and other components, a tangle of open circuit wiring.
The easy-to-mold ceramic material facilitated the development of special and large styles of ceramic capacitors for high-voltage, high-frequency (RF) and power applications.
With the development of semiconductor technology in the 1950s, barrier layer capacitors, or IEC class 3/EIA class IV capacitors, were developed using doped ferroelectric ceramics. Because this doped material was not suitable to produce multilayers, they were replaced decades later by Y5V class 2 capacitors.
The early style of the ceramic disc capacitor could be more cheaply produced than the common ceramic tube capacitors in the 1950s and 1970s. An American company in the midst of the Apollo program, launched in 1961, pioneered the stacking of multiple discs to create a monolithic block. This "multi-layer ceramic capacitor" (MLCC) was compact and offered high-capacitance capacitors. The production of these capacitors using the tape casting and ceramic-electrode cofiring processes was a great manufacturing challenge. MLCCs expanded the range of applications to those requiring larger capacitance values in smaller cases. These ceramic chip capacitors were the driving force behind the conversion of electronic devices from through-hole mounting to surface-mount technology in the 1980s. Polarized electrolytic capacitors could be replaced by non-polarized ceramic capacitors, simplifying the mounting.
In 1993, TDK Corporation succeeded in displacing palladium bearing electrodes with much cheaper nickel electrodes, significantly reducing production costs and enabling mass production of MLCCs.
, more than 1012 MLCCs are manufactured each year. Along with the style of ceramic chip capacitors, ceramic disc capacitors are often used as safety capacitors in electromagnetic interference suppression applications. Besides these, large ceramic power capacitors for high voltage or high frequency transmitter applications are also to be found.
New developments in ceramic materials have been made with anti-ferroelectric ceramics. This material has a nonlinear antiferroelectric/ferroelectric phase change that allows increased energy storage with higher volumetric efficiency. They are used for energy storage (for example, in detonators).
Application classes, definitions
The different ceramic materials used for ceramic capacitors, paraelectric or ferroelectric ceramics, influences the electrical characteristics of the capacitors. Using mixtures of paraelectric substances based on titanium dioxide results in very stable and linear behavior of the capacitance value within a specified temperature range and low losses at high frequencies. But these mixtures have a relatively low permittivity so that the capacitance values of these capacitors are relatively small.
Higher capacitance values for ceramic capacitors can be attained by using mixtures of ferroelectric materials like barium titanate together with specific oxides. These dielectric materials have much higher permittivities, but at the same time their capacitance value are more or less nonlinear over the temperature range, and losses at high frequencies are much higher. These different electrical characteristics of ceramic capacitors requires to group them into "application classes". The definition of the application classes comes from the standardization. As of 2013, two sets of standards were in use, one from International Electrotechnical Commission (IEC) and the other from the now-defunct Electronic Industries Alliance (EIA).
The definitions of the application classes given in the two standards are different. The following table shows the different definitions of the application classes for ceramic capacitors:
Manufacturers, especially in the US, preferred Electronic Industries Alliance (EIA) standards. In many parts very similar to the IEC standard, the EIA RS-198 defines four application classes for ceramic capacitors.
The different class numbers within both standards are the reason for a lot of misunderstandings interpreting the class descriptions in the datasheets of many manufacturers. The EIA ceased operations on February 11, 2011, but the former sectors continue to serve international standardization organizations.
In the following, the definitions of the IEC standard will be preferred and in important cases compared with the definitions of the EIA standard.
Class 1 ceramic capacitors
Class 1 ceramic capacitors are accurate, temperature-compensating capacitors. They offer the most stable voltage, temperature, and to some extent, frequency. They have the lowest losses and therefore are especially suited for resonant circuit applications where stability is essential or where a precisely defined temperature coefficient is required, for example in compensating temperature effects for a circuit. The basic materials of class 1 ceramic capacitors are composed of a mixture of finely ground granules of paraelectric materials such as titanium dioxide (), modified by additives of zinc, zirconium, niobium, magnesium, tantalum, cobalt and strontium, which are necessary to achieve the capacitor's desired linear characteristics.
The general capacitance temperature behavior of class 1 capacitors depends on the basic paraelectric material, for example . The additives of the chemical composition are used to adjust precisely the desired temperature characteristic.
Class 1 ceramic capacitors have the lowest volumetric efficiency among ceramic capacitors. This is the result of the relatively low permittivity (6 to 200) of paraelectric materials. Therefore, class 1 capacitors have capacitance values in the lower range.
Class 1 capacitors have a temperature coefficient that is typically fairly linear with temperature. These capacitors have very low electrical losses with a dissipation factor of approximately 0.15%. They undergo no significant aging processes and the capacitance value is nearly independent of the applied voltage. These characteristics allow applications for high Q filters, in resonant circuits and oscillators (for example, in phase-locked loop circuits).
The EIA RS-198 standard codes ceramic class 1 capacitors with a three character code that indicates temperature coefficient. The first letter gives the significant figure of the change in capacitance over temperature (temperature coefficient α) in ppm/K. The second character gives the multiplier of the temperature coefficient. The third letter gives the maximum tolerance from that in ppm/K. All ratings are from 25 to 85 °C:
In addition to the EIA code, the temperature coefficient of the capacitance dependence of class 1 ceramic capacitors is commonly expressed in ceramic names like "NP0", "N220" etc. These names include the temperature coefficient (α). In the IEC/EN 60384-8/21 standard, the temperature coefficient and tolerance are replaced by a two digit letter code (see table) in which the corresponding EIA code is added.
For instance, an "NP0" capacitor with EIA code "C0G" will have 0 drift, with a tolerance of ±30 ppm/K, while an "N1500" with the code "P3K" will have −1500 ppm/K drift, with a maximum tolerance of ±250 ppm/K. Note that the IEC and EIA capacitor codes are industry capacitor codes and not the same as military capacitor codes.
Class 1 capacitors include capacitors with different temperature coefficients α. Especially, NP0/CG/C0G capacitors with an α ±0•10−6 /K and an α tolerance of 30 ppm are technically of great interest. These capacitors have a capacitance variation dC/C of ±0.54% within the temperature range −55 to +125 °C. This enables accurate frequency response over a wide temperature range (in, for example, resonant circuits). The other materials with their special temperature behavior are used to compensate a counter temperature run of parallel connected components like coils in oscillator circuits. Class 1 capacitors exhibit very small tolerances of the rated capacitance.
Class 2 ceramic capacitors
Class 2 ceramic capacitors have a dielectric with a high permittivity and therefore a better volumetric efficiency than class 1 capacitors, but lower accuracy and stability. The ceramic dielectric is characterized by a nonlinear change of capacitance over the temperature range. The capacitance value also depends on the applied voltage. They are suitable for bypass, coupling and decoupling applications or for frequency discriminating circuits where low losses and high stability of capacitance are less important. They typically exhibit microphony.
Class 2 capacitors are made of ferroelectric materials such as barium titanate () and suitable additives such as aluminium silicate, magnesium silicate and aluminium oxide. These ceramics have very high permittivity (200 to 14,000), allowing an extreme electric field and therefore capacitance within relatively small packages — class 2 capacitors are significantly smaller than comparable class 1 capacitors. However, the permittivity is nonlinear with respect to field strength, meaning the capacitance varies significantly as the voltage across the terminals increases. Class 2 capacitors also exhibit poor temperature stability and age over time.
Due to these traits, class 2 capacitors are typically used in applications where only a minimum value of capacitance (as opposed to an accurate value) is required, such as the buffering/filtering of inputs and outputs of power supplies, and the coupling of electric signals.
Class 2 capacitors are labeled according to the change in capacitance over the temperature range. The most widely used classification is based on the EIA RS-198 standard and uses a three-digit code. The first character, a letter, denotes the coldest operating temperature; the second character, a numeral, denotes the hottest temperature; and the third character, another letter, denotes the maximum allowed capacitance change over the capacitor's entire specified temperature range:
For instance, a Z5U capacitor will operate from +10 °C to +85 °C with a capacitance change of at most +22% to −56%. An X7R capacitor will operate from −55 °C to +125 °C with a capacitance change of at most ±15%.
Some commonly used class 2 ceramic capacitor materials are listed below:
X8R (−55/+150, ΔC/C0 = ±15%),
X7R (−55/+125 °C, ΔC/C0 = ±15%),
X6R (−55/+105 °C, ΔC/C0 = ±15%),
X5R (−55/+85 °C, ΔC/C0 = ±15%),
X7S (−55/+125, ΔC/C0 = ±22%),
Z5U (+10/+85 °C, ΔC/C0 = +22/−56%),
Y5V (−30/+85 °C, ΔC/C0 = +22/−82%),
The IEC/EN 60384 -9/22 standard uses another two-digit-code.
In most cases it is possible to translate the EIA code into the IEC/EN code. Slight translation errors occur, but normally are tolerable.
X7R correlates with 2X1
Z5U correlates with 2E6
Y5V similar to 2F4, aberration: ΔC/C0 = +30/−80% instead of +30/−82%
X7S similar to 2C1, aberration: ΔC/C0 = ±20% instead of ±22%
X8R no IEC/EN code available
Because class 2 ceramic capacitors have lower capacitance accuracy and stability, they require higher tolerance.
For military types the class 2 dielectrics specify temperature characteristic (TC) but not temperature-voltage characteristic (TVC). Similar to X7R, military type BX cannot vary more than 15% over temperature, and in addition, must remain within +15%/-25 % at maximum rated voltage. Type BR has a TVC limit of +15%/-40%.
Class 3 ceramic capacitors
Class 3 barrier layer or semiconductive ceramic capacitors have very high permittivity, up to 50,000 and therefore a better volumetric efficiency than class 2 capacitors. However, these capacitors have worse electrical characteristics, including lower accuracy and stability. The dielectric is characterized by very high nonlinear change of capacitance over the temperature range. The capacitance value additionally depends on the voltage applied. As well, they have very high losses and age over time.
Barrier layer ceramic capacitors are made of doped ferroelectric materials such as barium titanate (). As this ceramic technology improved in the mid-1980s, barrier layer capacitors became available in values of up to 100 μF, and at that time it seemed that they could substitute for smaller electrolytic capacitors.
Because it is not possible to build multilayer capacitors with this material, only leaded single layer types are offered in the market.
Due to advancements in multilayer ceramic capacitors enabling superior performance in a smaller package, barrier layer capacitors as a technology are now considered obsolete and no longer standardized by the IEC.
Construction and styles
Ceramic capacitors are composed of a mixture of finely ground granules of paraelectric or ferroelectric materials, appropriately mixed with other materials to achieve the desired characteristics. From these powder mixtures, the ceramic is sintered at high temperatures. The ceramic forms the dielectric and serves as a carrier for the metallic electrodes. The minimum thickness of the dielectric layer, which today (2013) for low voltage capacitors is in the size range of 0.5 micrometers is limited downwards by the grain size of the ceramic powder. The thickness of the dielectric for capacitors with higher voltages is determined by the dielectric strength of the desired capacitor.
The electrodes of the capacitor are deposited on the ceramic layer by metallization. For MLCCs alternating metallized ceramic layers are stacked one above the other. The outstanding metallization of the electrodes at both sides of the body are connected with the contacting terminal. A lacquer or ceramic coating protects the capacitor against moisture and other ambient influences.
Ceramic capacitors come in various shapes and styles. Some of the most common are:
Multilayer ceramic chip capacitor (MLCC), rectangular block, for surface mounting
Ceramic disc capacitor, single layer disc, resin coated, with through-hole leads
Feedthrough ceramic capacitor, used for bypass purposes in high-frequency circuits. Tube shape, inner metallization contacted with a lead, outer metallization for soldering
Ceramic power capacitors, larger ceramic bodies in different shapes for high voltage applications
Multi-layer ceramic capacitors (MLCC)
Manufacturing
An MLCC can be thought of as consisting of many single-layer capacitors stacked together into a single package. The starting material for all MLCC chips is a mixture of finely ground granules of paraelectric or ferroelectric raw materials, modified by accurately determined additives. The composition of the mixture and the size of the powder particles, as small as 10 nm, reflect the manufacturer's expertise.
A thin ceramic foil is cast from a suspension of the powder with a suitable binder. Rolls of foil are cut into equal-sized sheets, which are screen printed with a metal paste layer, which will become the electrodes. In an automated process, these sheets are stacked in the required number of layers and solidified by pressure. Besides the relative permittivity, the size and number of layers determines the later capacitance value. The electrodes are stacked in an alternating arrangement slightly offset from the adjoining layers so that they each can later be connected on the offset side, one left, one right. The layered stack is pressed and then cut into individual components. High mechanical precision is required, for example, to produce a 500 or more layer stack of size "0201" (0.5 mm × 0.3 mm).
After cutting, the binder is burnt out of the stack. This is followed by sintering at temperatures between , producing the final, mainly crystalline, structure. This burning process creates the desired dielectric properties. Burning is followed by cleaning and then metallization of both end surfaces. Through the metallization, the ends and the inner electrodes are connected in parallel and the capacitor gets its terminals. Finally, each capacitor is electrically tested to ensure functionality and adequate performance, and packaged in a tape reel.
Miniaturizing
The capacitance formula (C) of a MLCC capacitor is based on the formula for a plate capacitor enhanced with the number of layers:
where ε stands for dielectric permittivity; A for electrode surface area; n for the number of layers; and d for the distance between the electrodes.
A thinner dielectric or a larger electrode area each increase the capacitance value, as will a dielectric material of higher permittivity.
With the progressive miniaturization of digital electronics in recent decades, the components on the periphery of the integrated logic circuits have been scaled down as well. Shrinking an MLCC involves reducing the dielectric thickness and increasing the number of layers. Both options require huge efforts and are connected with a lot of expertise.
In 1995 the minimum thickness of the dielectric was 4 μm. By 2005 some manufacturers produced MLCC chips with layer thicknesses of 1 μm. , the minimum thickness is about 0.5 μm. The field strength in the dielectric increased to 35 V/μm.
The size reduction of these capacitors is achieved reducing powder grain size, the assumption to make the ceramic layers thinner. In addition, the manufacturing process became more precisely controlled, so that more and more layers can be stacked.
Between 1995 and 2005, the capacitance of a Y5V MLCC capacitor of size 1206 was increased from 4.7 μF to 100 μF. Meanwhile, (2013) a lot of producers can deliver class 2 MLCC capacitors with a capacitance value of 100 μF in the chip-size 0805.
MLCC case sizes
MLCCs don't have leads, and as a result they are usually smaller than their counterparts with leads. They don't require through-hole access in a PCB to mount and are designed to be handled by machines rather than by humans. As a result, surface-mount components like MLCCs are typically cheaper.
MLCCs are manufactured in standardized shapes and sizes for comparable handling. Because the early standardization was dominated by American EIA standards the dimensions of the MLCC chips were standardized by EIA in units of inches. A rectangular chip with the dimensions of 0.06-inch length and 0.03-inch width is coded as "0603". This code is international and in common use. JEDEC (IEC/EN), devised a second, metric code. The EIA code and the metric equivalent of the common sizes of multilayer ceramic chip capacitors, and the dimensions in mm are shown in the following table. Missing from the table is the measure of the height "H". This is generally not listed, because the height of MLCC chips depends on the number of layers and thus on the capacitance. Normally, however, the height H does not exceed the width W.
NME and BME metallization
Originally, MLCC electrodes were constructed out of noble metals such as silver and palladium which can withstand high sintering temperatures of without readily oxidizing. These noble metal electrode (NME) capacitors offered very good electrical properties.
However, a surge in prices of noble metals in the late 1990s greatly increased manufacturing costs; these pressures resulted in the development of capacitors that used cheaper metals like copper and nickel. These base metal electrode (BME) capacitors possessed poorer electrical characteristics; exhibiting greater shrinkage of capacitance at higher voltages and increased loss factor.
The disadvantages of BME were deemed acceptable for class 2 capacitors, which are primarily used in accuracy-insensitive, low-cost applications such as power supplies. NME still sees use in class 1 capacitors where conformance to specifications are critical and cost is less of a concern.
MLCC capacitance ranges
Capacitance of MLCC chips depends on the dielectric, the size and the required voltage (rated voltage). Capacitance values start at about 1pF. The maximum capacitance value is determined by the production technique. For X7R that is 47 μF, for Y5V: 100 μF.
The picture right shows the maximum capacitance for class 1 and class 2 multilayer ceramic chip capacitors. The following two tables, for ceramics NP0/C0G and X7R each, list for each common case size the maximum available capacitance value and rated voltage of the leading manufacturers Murata, TDK, KEMET, AVX. (Status April 2017)
Low-ESL styles
In the region of its resonance frequency, a capacitor has the best decoupling properties for noise or electromagnetic interference. The resonance frequency of a capacitor is determined by the inductance of the component. The inductive parts of a capacitor are summarized in the equivalent series inductance, or ESL. (Note that L is the electrical symbol for inductance.) The smaller the inductance, the higher the resonance frequency.
Because, especially in digital signal processing, switching frequencies have continued to rise, the demand for high frequency decoupling or filter capacitors increases. With a simple design change the ESL of an MLCC chip can be reduced. Therefore, the stacked electrodes are connected on the longitudinal side with the connecting terminations. This reduces the distance that the charge carriers flow over the electrodes, which reduces inductance of the component.
For example, an 0.1 μF X7R MLCC in a 0805 package resonates at 16 MHz. The same capacitor with leads on its long sides (i.e. an 0508) has a resonance frequency of 22 MHz.
Another possibility is to form the device as an array of capacitors. Here, several individual capacitors are built in a common housing. Connecting them in parallel, the resulting ESL as well as ESR values of the components are reduced.
X2Y decoupling capacitor
A standard multi-layer ceramic capacitor has many opposing electrode layers stacked inside connected with two outer terminations. The X2Y ceramic chip capacitor however is a 4 terminal chip device. It is constructed like a standard two-terminal MLCC out of the stacked ceramic layers with an additional third set of shield electrodes incorporated in the chip. These shield electrodes surround each existing electrode within the stack of the capacitor plates and are low ohmic contacted with two additional side terminations across to the capacitor terminations. The X2Y construction results in a three-node capacitive circuit that provides simultaneous line-to-line and line-to-ground filtering.
Capable of replacing 2 or more conventional devices, the X2Y ceramic capacitors are ideal for high frequency filtering or noise suppression of supply voltages in digital circuits, and can prove invaluable in meeting stringent EMC demands in dc motors, in automotive, audio, sensor and other applications.
The X2Y footprint results in lower mounted inductance. This is particularly of interest for use in high-speed digital circuits with clock rates of several 100 MHz and upwards. There the decoupling of the individual supply voltages on the circuit board is difficult to realize due to parasitic inductances of the supply lines. A standard solution with conventional ceramic capacitors requires the parallel use of many conventional MLCC chips with different capacitance values. Here X2Y capacitors are able to replace up to five equal-sized ceramic capacitors on the PCB. However, this particular type of ceramic capacitor is patented, so these components are still comparatively expensive.
An alternative to X2Y capacitors may be a three-terminal capacitor.
Mechanical susceptibility
Ceramics are brittle, and MLCC chips surface-mount soldered to a circuit board are often vulnerable to cracking from thermal expansion or mechanical stresses like depanelization, more so than leaded through-hole components.
The cracks can come from automated machine assembly line, or from high current in the circuit.
Vibration and shock forces on the circuit board are more or less transmitted undampened to the MLCC and its solder joints; excessive force may cause the capacitor to crack (flex crack). Excess solder in the joints are undesirable as they may magnify the forces that the capacitor is subject to.
The capability of MLCC chips to withstand mechanical stress is tested by a so-called substrate bending test, where a PCB with a soldered MLCC is bent by a punch by 1 to 3 mm. Failure occurs if the MLCC becomes a short-circuit or significantly changes in capacitance.
Bending strengths of MLCC chips differ by the ceramic material, the size of the chip, and the physical construction of the capacitors. Without special mitigation, NP0/C0G class 1 ceramic MLCC chips reach a typical bending strength of 2 mm while larger types of X7R, Y5V class 2 ceramic chips achieved only a bending strength of approximately 1 mm. Smaller chips, such as the size of 0402, reached in all types of ceramics larger bending strength values.
With special design features, particularly at the electrodes and terminations, the bending strength can be improved. For example, an internal short circuit arises by the contact of two electrodes with opposite polarity, which will be produced at the break of the ceramic in the region of the terminations. This can be prevented when the overlap surfaces of the electrodes are reduced. This is achieved e.g. by an "Open Mode Design" (OMD). Here a break in the region of the terminations only reduce the capacitance value a little bit (AVX, KEMET).
With a similar construction called "Floating Electrode Design" (FED) or "Multi-layer Serial Capacitors" (MLSC), also, only capacitance reduction results if parts of the capacitor body break. This construction works with floating electrodes without any conductive connection to the termination. A break doesn't lead to a short, only to capacitance reduction.
However, both structures lead to larger designs with respect to a standard MLCC version with the same capacitance value.
The same volume with respect to standard MLCCs is achieved by the introduction of a flexible intermediate layer of a conductive polymer between the electrodes and the termination called "Flexible Terminations" (FT-Cap) or "Soft Terminations". In this construction, the rigid metallic soldering connection can move against the flexible polymer layer, and thus can absorb the bending forces, without resulting in a break in the ceramic.
Some automotive capacitors are specified to adhere to AEC-Q200 and/or VW 80808.
RFI/EMI suppression with X- and Y capacitors
Suppression capacitors are effective interference reduction components because their electrical impedance decreases with increasing frequency, such that at higher frequencies they appear as short circuits to high-frequency electrical noise and transients between the lines, or to ground. They therefore prevent equipment and machinery (including motors, inverters, and electronic ballasts, as well as solid-state relay snubbers and spark quenchers) from sending and receiving electromagnetic and radio frequency interference as well as transients in across-the-line (X capacitors) and line-to-ground (Y capacitors) connections. X capacitors effectively absorb symmetrical, balanced, or differential interference. Y capacitors are connected in a line bypass between a line phase and a point of zero potential, to absorb asymmetrical, unbalanced, or common-mode interference.
EMI/RFI suppression capacitors are designed so that any remaining interference or electrical noise does not exceed the limits of EMC directive EN 50081. Suppression components are connected directly to mains voltage for 10 to 20 years or more and are therefore exposed to potentially damaging overvoltages and transients. For this reason, suppression capacitors must comply with the safety and non-flammability requirements of international safety standards such as
Europe: EN 60384-14,
USA: UL 1414, UL 1283
Canada: CSA C22.2, No.1, CSA C22.2, No.8
China: CQC (GB/T 14472-1998)
RFI capacitors that fulfill all specified requirements are imprinted with the certification mark of various national safety standards agencies. For power line applications, special requirements are placed on the non-flammability of the coating and the epoxy resin impregnating or coating the capacitor body. To receive safety approvals, X and Y powerline-rated capacitors are destructively tested to the point of failure. Even when exposed to large overvoltage surges, these safety-rated capacitors must fail in a fail-safe manner that does not endanger personnel or property.
most ceramic capacitors used for EMI/RFI suppression were leaded ones for through-hole mounting on a PCB, the surface-mount technique is becoming more and more important. For this reason, in recent years a lot of MLCC chips for EMI/RFI suppression from different manufacturers have received approvals and fulfill all requirements given in the applicable standards.
Ceramic power capacitors
Although the materials used for large power ceramic capacitors mostly are very similar to those used for smaller ones, ceramic capacitors with high to very high power or voltage ratings for applications in power systems, transmitters and electrical installations are often classified separately, for historical reasons. The standardization of ceramic capacitors for lower power is oriented toward electrical and mechanical parameters as components for use in electronic equipment. The standardization of power capacitors, contrary to that, is strongly focused on protecting personnel and equipment, given by the local regulating authority.
As modern electronic equipment gained the ability to handle power levels that were previously the exclusive domain of "electrical power" components, the distinction between the "electronic" and "electrical" power ratings has become less distinct. In the past, the boundary between these two families was approximately at a reactive power of 200 volt-amps, but modern power electronics can handle increasing amounts of power.
Power ceramic capacitors are mostly specified for much higher than 200 volt-amps. The great plasticity of ceramic raw material and the high dielectric strength of ceramics deliver solutions for many applications and are the reasons for the enormous diversity of styles within the family of power ceramic capacitors. These power capacitors have been on the market for decades. They are produced according to the requirements as class 1 power ceramic capacitors with high stability and low losses or class 2 power ceramic capacitors with high volumetric efficiency.
Class 1 power ceramic capacitors are used for resonant circuit application in transmitter stations. Class 2 power ceramic capacitors are used for circuit breakers, for power distribution lines, for high voltage power supplies in laser-applications, for induction furnaces and in voltage-doubling circuits. Power ceramic capacitors can be supplied with high rated voltages in the range of 2 kV up to 100 kV.
The dimensions of these power ceramic capacitors can be very large. At high power applications the losses of these capacitors can generate a lot of heat. For this reason some special styles of power ceramic capacitors have pipes for water-cooling.
Electrical characteristics
Series-equivalent circuit
All electrical characteristics of ceramic capacitors can be defined and specified by a series equivalent circuit composed out of an idealized capacitance and additional electrical components, which model all losses and inductive parameters of a capacitor. In this series-equivalent circuit the electrical characteristics of a capacitors is defined by
C, the capacitance of the capacitor,
Rinsul, the insulation resistance of the dielectric, not to be confused with the insulation of the housing
RESR, the equivalent series resistance, which summarizes all ohmic losses of the capacitor, usually abbreviated as "ESR".
LESL, the equivalent series inductance, which is the effective self-inductance of the capacitor, usually abbreviated as "ESL".
The use of a series equivalent circuit instead of a parallel equivalent circuit is defined in IEC/EN 60384-1.
Capacitance standard values and tolerances
The "rated capacitance" CR or "nominal capacitance" CN is the value for which the capacitor has been designed. The actual capacitance depends on the measuring frequency and the ambient temperature. Standardized conditions for capacitors are a low-voltage AC measuring method at a temperature of 20 °C with frequencies of
Class 1 ceramic capacitors
CR ≤ 100 pF at 1 MHz, measuring voltage 5 V
CR > 100 pF at 1 kHz, measuring voltage 5 V
Class 2 ceramic capacitors
CR ≤ 100 pF at 1 MHz, measuring voltage 1 V
100 pF < CR ≤ 10 μF at 1 kHz, measuring voltage 1 V
CR > 10 μF at 100/120 Hz, measuring voltage 0.5 V
Capacitors are available in different, geometrically increasing preferred values as specified in the E series standards specified in IEC/EN 60063. According to the number of values per decade, these were called the E3, E6, E12, E24, etc. series. The units used to specify capacitor values includes everything from picofarad (pF), nanofarad (nF), microfarad (μF) and farad (F).
The percentage of allowed deviation of the capacitance from the rated value is called capacitance tolerance. The actual capacitance value must be within the tolerance limits, or the capacitor is out of specification. For abbreviated marking in tight spaces, a letter code for each tolerance is specified in IEC/EN 60062.
The required capacitance tolerance is determined by the particular application. The narrow tolerances of E24 to E96 will be used for high-quality class 1 capacitors in circuits such as precision oscillators and timers. For applications such as non-critical filtering or coupling circuits, for class 2 capacitors the tolerance series E12 down to E3 are sufficient.
Temperature dependence of capacitance
Capacitance of ceramic capacitors varies with temperature. The different dielectrics of the many capacitor types show great differences in temperature dependence. The temperature coefficient is expressed in parts per million (ppm) per degree Celsius for class 1 ceramic capacitors or in percent (%) over the total temperature range for class 2 capacitors.
Frequency dependence of capacitance
Most discrete capacitor types have greater or smaller capacitance changes with increasing frequencies. The dielectric strength of class 2 ceramic and plastic film diminishes with rising frequency. Therefore, their capacitance value decreases with increasing frequency. This phenomenon is related to the dielectric relaxation in which the time constant of the electrical dipoles is the reason for the frequency dependence of permittivity. The graph on the right hand side shows typical frequency behavior for class 2 vs class 1 capacitors.
Voltage dependence of capacitance
Capacitance of ceramic capacitors may also change with applied voltage. This effect is more prevalent in class 2 ceramic capacitors. The ferroelectric material depends on the applied voltage. The higher the applied voltage, the lower the permittivity. Capacitance measured or applied with higher voltage can drop to values of −80% of the value measured with the standardized measuring voltage of 0.5 or 1.0 V. This behavior is a small source of nonlinearity in low-distortion filters and other analog applications. In audio applications this can be the reason for harmonic distortions.
The voltage dependence of capacitance in the two diagrams above shows curves from ceramic capacitors with NME metallization. For capacitors with BME metallization the voltage dependence of capacitance increased significantly.
Voltage proof
For most capacitors, a physically conditioned dielectric strength or a breakdown voltage usually could be specified for each dielectric material and thickness. This is not possible with ceramic capacitors. The breakdown voltage of a ceramic dielectric layer may vary depending on the electrode material and the sintering conditions of the ceramic up to a factor of 10. A high degree of precision and control of process parameters is necessary to keep the scattering of electrical properties for today's very thin ceramic layers within specified limits.
The voltage proof of ceramic capacitors is specified as rated voltage (UR). This is the maximum DC voltage that may be continuously applied to the capacitor up to the upper temperature limit. This guaranteed voltage proof is tested according to the voltages shown in the adjacent table.
Furthermore, in periodic life time tests (endurance tests) the voltage proof of ceramic capacitors is tested with increased test voltage (120 to 150% of UR) to ensure safe construction.
Impedance
The frequency dependent AC resistance of a capacitor is called impedance and is a complex ratio of voltage to current in an AC circuit. Impedance extends the concept of Ohm's law to AC circuits, and possesses both magnitude and phase at a particular frequency, unlike resistance, which has only magnitude.
Impedance is a measure of the ability of the capacitor to pass alternating currents. In this sense impedance can be used like Ohms law
to calculate either the peak or the effective value of the current or the voltage.
As shown in the series-equivalent circuit of a capacitor, the real-world component includes an ideal capacitor , an inductance and a resistor .
To calculate the impedance the resistance and then both reactances have to be added geometrically
wherein the capacitive reactance (Capacitance) is
and an inductive reactance (Inductance) is
.
In the special case of resonance, in which both reactive resistances have the same value (), then the impedance will only be determined by .
Data sheets of ceramic capacitors only specify the impedance magnitude . The typical impedance curve shows that with increasing frequency, impedance decreases, down to a minimum. The lower the impedance, the more easily alternating currents can pass through the capacitor. At the minimum point of the curve, the point of resonance, where XC has the same value as XL, the capacitor exhibits its lowest impedance value. Here only the ohmic ESR determines the impedance. With frequencies above the resonance, impedance increases again due to the ESL.
ESR, dissipation factor, and quality factor
The summarized losses in ceramic capacitors are ohmic AC losses. DC losses are specified as "leakage current" or "insulating resistance" and are negligible for an AC specification. These AC losses are nonlinear and may depend on frequency, temperature, age, and for some special types, on humidity. The losses result from two physical conditions,
line losses with internal supply line resistances, the contact resistance of the electrode contact, the line resistance of the electrodes
the dielectric losses out of the dielectric polarization
The largest share of these losses in larger capacitors is usually the frequency dependent ohmic dielectric losses. Regarding the IEC 60384-1 standard, the ohmic losses of capacitors are measured at the same frequency used to measure capacitance. These are:
100 kHz, 1 MHz (preferred) or 10 MHz for ceramic capacitors with CR ≤ 1 nF:
1 kHz or 10 kHz for ceramic capacitors with 1 nF < CR ≤ 10 μF
50/60 Hz or 100/120 Hz for ceramic capacitors with CR > 10 μF
Results of the summarized resistive losses of a capacitor may be specified either as equivalent series resistance (ESR), as dissipation factor (DF, tan δ), or as quality factor (Q), depending on the application requirements.
Class 2 capacitors are mostly specified with the dissipation factor, tan δ. The dissipation factor is determined as the tangent of the reactance – and the ESR, and can be shown as the angle δ between the imaginary and impedance axes in the above vector diagram, see paragraph "Impedance".
If the inductance is small, the dissipation factor can be approximated as:
Class 1 capacitors with very low losses are specified with a dissipation factor and often with a quality factor (Q). The quality factor is defined as the reciprocal of the dissipation factor.
The Q factor represents the effect of electrical resistance, and characterizes a resonator's bandwidth relative to its center or resonant frequency . A high Q value is a mark of the quality of the resonance for resonant circuits.
In accordance with IEC 60384-8/-21/-9/-22 ceramic capacitors may not exceed the following dissipation factors:
The ohmic losses of ceramic capacitors are frequency, temperature and voltage dependent. Additionally, class 2 capacitor measurements change because of aging. Different ceramic materials have differing losses over the temperature range and the operating frequency. The changes in class 1 capacitors are in the single-digit range while class 2 capacitors have much higher changes.
HF use, inductance (ESL) and self-resonant frequency
Electrical resonance occurs in a ceramic capacitor at a particular resonance frequency where the imaginary parts of the capacitor impedance and admittances cancel each other.
This frequency where XC is as high as XL is called the self-resonant frequency and can be calculated with:
where ω = 2πf, in which f is the resonance frequency in Hertz, L is the inductance in henries, and C is the capacitance in farads.
The smaller the capacitance C and the inductance L the higher is the resonance frequency.
The self-resonant frequency is the lowest frequency at which impedance passes through a minimum. For any AC application the self-resonant frequency is the highest frequency at which a capacitor can be used as a capacitive component. At frequencies above the resonance, the impedance increases again due to ESL: the capacitor becomes an inductor with inductance equal to capacitor's ESL, and resistance equal to ESR at the given frequency.
ESL in industrial capacitors is mainly caused by the leads and internal connections used to connect the plates to the outside world. Larger capacitors tend to higher ESL than small ones, because the distances to the plate are longer and every millimeter increases inductance.
Ceramic capacitors, which are available in the range of very small capacitance values (pF and higher) are already out of their smaller capacitance values suitable for higher frequencies up to several 100 MHz (see formula above).
Due to the absence of leads and proximity to the electrodes, MLCC chips have significantly lower parasitic inductance than f. e. leaded types, which makes them suitable for higher frequency applications. A further reduction of parasitic inductance is achieved by contacting the electrodes on the longitudinal side of the chip instead of the lateral side.
Sample self-resonant frequencies for one set of NP0/C0G and one set of X7R ceramic capacitors are:
Note that X7Rs have better frequency response than C0Gs. It makes sense, however, since class 2 capacitors are much smaller than class 1, so they ought to have lower parasitic inductance.
Aging
In ferroelectric class 2 ceramic capacitors capacitance decreases over time. This behavior is called "aging". Aging occurs in ferroelectric dielectrics, where domains of polarization in the dielectric contribute to total polarization. Degradation of the polarized domains in the dielectric decreases permittivity over time so that the capacitance of class 2 ceramic capacitors decreases as the component ages.
The aging follows a logarithmic law. This law defines the decrease of capacitance as a percentage for a time decade after the soldering recovery time at a defined temperature, for example, in the period from 1 to 10 hours at 20 °C. As the law is logarithmic, the percentage loss of capacitance will twice between 1 h and 100 h and 3 times between 1 h and 1000 h and so on. So aging is fastest near the beginning, and the capacitance value effectively stabilizes over time.
The rate of aging of class 2 capacitors mainly depends on the materials used. A rule of thumb is, the higher the temperature dependence of the ceramic, the higher the aging percentage. The typical aging of X7R ceramic capacitors is about 2.5% per decade The aging rate of Z5U ceramic capacitors is significantly higher and can be up to 7% per decade.
The aging process of class 2 capacitors may be reversed by heating the component above the Curie point.
Class 1 capacitors do not experience ferroelectric aging like Class 2's. But environmental influences such as higher temperature, high humidity and mechanical stress can, over a longer period of time, lead to a small irreversible decline in capacitance, sometimes also called aging. The change of capacitance for P 100 and N 470 Class 1's is lower than 1%, for capacitors with N 750 to N 1500 ceramics it is ≤ 2%.
Insulation resistance and self-discharge constant
The resistance of the dielectric is never infinite, leading to some level of DC "leakage current", which contributes to self-discharge. For ceramic capacitors this resistance, placed in parallel with the capacitor in the series-equivalent circuit of capacitors, is called "insulation resistance Rins". The insulation resistance must not be confused with the outer isolation with respect to the environment.
The rate of self-discharge with decreasing capacitor voltage follows the formula
With the stored DC voltage and the self-discharge constant
That means, after capacitor voltage dropped to 37% of the initial value.
The insulation resistance given in the unit MΩ (106 Ohm) as well as the self-discharge constant in seconds is an important parameter for the quality of the dielectric insulation. These time values are important, for example, when a capacitor is used as timing component for relays or for storing a voltage value as in a sample and hold circuits or operational amplifiers.
In accordance with the applicable standards, Class 1 ceramic capacitors have an Rins ≥ 10,000 MΩ for capacitors with CR ≤ 10 nF or τs ≥ 100 s for capacitors with CR > 10 nF. Class 2 ceramic capacitors have an Rins ≥ 4,000 MΩ for capacitors with CR ≤ 25 nF or τs ≥ 100 s for capacitors with CR > 25 nF.
Insulation resistance and thus the self-discharge time rate are temperature dependent and decrease with increasing temperature at about 1 MΩ per 60 °C.
Dielectric absorption (soakage)
Dielectric absorption is the name given to the effect by which a capacitor, which has been charged for a long time, discharges only incompletely. Although an ideal capacitor remains at zero volts after discharge, real capacitors will develop a small voltage coming from time-delayed dipole discharging, a phenomenon that is also called dielectric relaxation, "soakage" or "battery action".
In many applications of capacitors dielectric absorption is not a problem but in some applications, such as long-time-constant integrators, sample-and-hold circuits, switched-capacitor analog-to-digital converters and very low-distortion filters, it is important that the capacitor does not recover a residual charge after full discharge, and capacitors with low absorption are specified. The voltage at the terminals generated by dielectric absorption may in some cases possibly cause problems in the function of an electronic circuit or can be a safety risk to personnel. To prevent shocks, most very large capacitors like power capacitors are shipped with shorting wires that are removed before use.
Microphony
All class 2 ceramic capacitors using ferroelectric ceramics exhibit piezoelectricity, and have a piezoelectric effect called microphonics, microphony or in audio applications squealing. Microphony describes the phenomenon wherein electronic components transform mechanical vibrations into an electrical signal which in many cases is undesired noise. Sensitive electronic preamplifiers generally use class 1 ceramic and film capacitors to avoid this effect.
In the reverse microphonic effect, the varying electric field between the capacitor plates exerts a physical force, moving them as a speaker. High current impulse loads or high ripple currents can generate audible acoustic sound coming from the capacitor, but discharges the capacitor and stresses the dielectric.
Soldering
Ceramic capacitors may experience changes to their electrical parameters due to soldering stress. The heat of the solder bath, especially for SMD styles, can cause changes of contact resistance between terminals and electrodes. For ferroelectric class 2 ceramic capacitors, the soldering temperature is above the Curie point. The polarized domains in the dielectric are going back and the aging process of class 2 ceramic capacitors is starting again.
Hence after soldering a recovery time of approximately 24 hours is necessary. After recovery some electrical parameters like capacitance value, ESR, leakage currents are changed irreversibly. The changes are in the lower percentage range depending on the style of capacitor.
Additional information
Standardization
The standardization for all electrical, electronic components and related technologies follows the rules given by the International Electrotechnical Commission (IEC), a non-profit, non-governmental international standards organization.
The definition of the characteristics and the procedure of the test methods for capacitors for use in electronic equipment are set out in the generic specification:
IEC 60384-1, Fixed capacitors for use in electronic equipment – Part 1: Generic specification
The tests and requirements to be met by ceramic capacitors for use in electronic equipment for approval as standardized types are set out in the following sectional specifications:
IEC 60384-8, Fixed capacitors of ceramic dielectric, Class 1
IEC 60384-9, Fixed capacitors of ceramic dielectric, Class 2
IEC 60384-21, Fixed surface mount multilayer capacitors of ceramic dielectric, Class 1
IEC 60384-22, Fixed surface mount multilayer capacitors of ceramic dielectric, Class 2
Tantalum capacitor replacement
Multilayer ceramic capacitors are increasingly used to replace tantalum and low capacitance aluminium electrolytic capacitors in applications such as bypass or high frequency switched-mode power supplies as their cost, reliability and size becomes competitive. In many applications, their low ESR allows the use of a lower nominal capacitance value.
Features and disadvantages of ceramic capacitors
For features and disadvantages of ceramic capacitors see main article Capacitor types#Comparison of types
Marking
Imprinted markings
If space permits ceramic capacitors, like most other electronic components, have imprinted markings to indicate the manufacturer, the type, their electrical and thermal characteristics and their date of manufacture. In the ideal case, if they are large enough, the capacitor will be marked with:
manufacturer's name or trademark;
manufacturer's type designation;
rated capacitance;
tolerance on rated capacitance
rated voltage and nature of supply (AC or DC)
climatic category or rated temperature;
year and month (or week) of manufacture;
certification marks of safety standards (for safety EMI/RFI suppression capacitors)
Smaller capacitors use a shorthand notation, to display all the relevant information in the limited space. The most commonly used format is: XYZ J/K/M VOLTS V, where XYZ represents the capacitance (calculated as XY × 10Z pF), the letters J, K or M indicate the tolerance (±5%, ±10% and ±20% respectively) and VOLTS V represents the working voltage.
Examples
A capacitor with the following text on its body: 105K 330V has a capacitance of 10 × 105 pF = 1 μF (K = ±10%) with a working voltage of 330 V.
A capacitor with the following text: 473M 100V has a capacitance of 47 × 103 pF = 47 nF (M = ±20%) with a working voltage of 100 V.
Capacitance, tolerance and date of manufacture can be identified with a short code according to IEC/EN 60062. Examples of short-marking of the rated capacitance (microfarads):
μ47 = 0.47 μF
4μ7 = 4.7 μF
47μ = 47 μF
The date of manufacture is often printed in accordance with international standards.
Version 1: coding with year/week numeral code, "1208" is "2012, week number 8".
Version 2: coding with year code/month code,
Year code: "R" = 2003, "S"= 2004, "T" = 2005, "U" = 2006, "V" = 2007, "W" = 2008, "X" = 2009, "A" = 2010, "B" = 2011, "C" = 2012, "D" = 2013 etc.
Month code: "1" to "9" = Jan. to Sept., "O" = October, "N" = November, "D" = December
"X5" is then "2009, May"
For very small capacitors like MLCC chips no marking is possible. Here only the traceability of the manufacturers can ensure the identification of a type.
Colour coding
The identification of modern capacitors has no detailed color coding.
See also
Decoupling capacitor
List of capacitor manufacturers
Tape casting
Types of capacitor
References
External links
Capacitors | Ceramic capacitor | [
"Physics"
] | 12,452 | [
"Capacitance",
"Capacitors",
"Physical quantities"
] |
9,221,578 | https://en.wikipedia.org/wiki/Threatened%20arthropods | Threatened arthropods are defined here as any of a number of species within the phylum Arthropoda, whose extinction is likely in the foreseeable future. Estimating the number of threatened arthropod species is extremely difficult, primarily because a vast number of the species themselves are not yet named or described. Furthermore, according to Deyrup and Eisner, "The rate of destruction and degradation of natural habitats is currently so great that there are not nearly enough biologists to even catalog the arthropod species that are suddenly on the edge of extinction." In any case, independent estimates indicate that there are millions of undocumented arthropods on Earth.
Arthropods as a group have been very successful organisms on this planet, comprising over half of all the higher life forms. However the expansion of human activities has led to demise of many arthropod species through the mechanisms of deforestation, conventional farming, slash-and-burn methods in the tropics, habitat fragmentation via urban development, excessive use of pesticides and even the success of forest fire suppression.
The social/political practice whereby a species is given a formal designation as "Endangered" or "Protected" is a different matter, called "Conservation status", and discussed elsewhere; see Endangered Species List for the United States, and IUCN Red List for international purposes. Only a tiny fraction of the planet's endangered arthropods are formally recognized as such, as no one has ever evaluated the conservation status of the vast majority of arthropod species.
Difficulty of estimating numbers of species
It is difficult to estimate the total number of endangered arthropod species, since many of the taxa themselves have not been recorded. For example, in North America the estimated number of insect species exceeds 163,000, of which only about two thirds are taxonomically known. An even greater discovery awaiting, over 72 percent of North American arachnids are yet to be named and described.
The total number of living arthropod species is probably in the tens of millions. One conservative estimate puts the number of arthropod species in tropical forests alone at six to nine million species. As a consequence of all of the above, most published estimates of the total number of endangered insects and arachnids are probably low by at least an order of magnitude. Conservatively at least eighty percent of all living animal species are arthropods.
Ecological risks
Since arthropods constitute the majority of the faunal biomass on Earth, their role is vital to the survival of large numbers of insectivores and other animals that prey upon arthropods. This includes enormous numbers of mammals, avafauna, fishes, reptiles and amphibians; in addition, arthropods constitute the bulk of faunal pollinators, so that the survival of crops as well as millions of natural flora species depend on robust and biologically diverse arthropod populations.
The survival of diverse arthropods is essential to propagation of higher animals on the food chain, e.g. those species who prey upon the insectivores and other taxa that consume arthropods. Even if constant arthropod total biomass results after certain arthropod extinctions, the ecosystem stability is compromised by reduction in species numbers. Thus extinction of arthropods species threaten to make extinct hundreds of thousands, if not millions, of higher order birds, amphibians, reptiles and mammals.
Mechanisms of arthropod endangerment
Most endangerment of arthropod populations is from habitat destruction by growing human populations and related human activities such as agriculture, construction and transportation.
Agriculture, in particular has a number of direct effects: a monocultures from intensive practices cannot support the biodiversity nurtured by the predecessor natural environment. Normally arthropods represent the largest number of species that are displaced by such farming. In tropical regions the major threat is slash-and-burn agricultural techniques pursued by indigenous peoples in their sometimes only available method of subsistence. Pesticide use is also a major threat to arthropod species survival. Pesticides may have an intended effect of killing specified insects in a farming environment; however, considerable pesticide applications kill unintended species by the lack of specificity of most chemical formulations; moreover, much of the insect mortality arises from pesticide runoff entering surface waters or from transporting toxic chemicals to downgradient environments.
Habitat fragmentation has special methods of endangerment beyond the amount of land consumed by the fragmenting agent. As an example, consider the construction of a highway, whose width is an effective barrier to arthropod migration. Many arthropods never migrate more than about 200 feet from their place of birth, so a freeway or dual carriageway effectively fragments many arthropod colonies such that they cannot interact. Studies have shown the greater vulnerability to extinction where habitats are fragmented.
Example endangered arthropods
The following is a very small fraction of the potentially hundreds of thousands of endangered arthropods, limited to species which have been formally recognized as to their special conservation status:
Alabama cave shrimp (Palaemonias alabamae)
California freshwater shrimp (Syncaris pacifica)
Delhi Sands flower-loving fly (Rhaphiomidas terminatus abdominalis), due to severely limited range of habitat and development
South African black millipedes (Doratogonus spp.), due to habitat destruction
Kentucky cave shrimp (Palaemonias ganteri)
Salt Creek tiger beetle (Cicindela nevadica lincolniana)
San Bruno elfin butterfly (Incisalia mossii bayensis), due to limited range of habitat and development encroachment
Smith's blue butterfly (Euphilotes enoptes smithidue), to human overpopulation of coastal dunes areas and associated highway and land development
Spruce-fir moss spider (Microhexura montivaga)
Tasmanian giant freshwater crayfish (Astacopsis gouldi)
Tooth cave spider (Neoleptoneta myopica)
Poecilotheria Parachute Tarantula (Poecilotheria spp)
White-clawed crayfish (Austropotamobius pallipes)
See also
List of critically endangered arthropods
List of endangered arthropods
List of vulnerable arthropods
List of near threatened arthropods
Habitat fragmentation
Minimum viable population
United States Fish and Wildlife Service list of threatened and endangered arthropods
Short-range endemic invertebrates
References
External links
The Xerces Society for Invertebrate Conservation
Endangered Insect List at Earth's Endangered Creatures
Arthropod conservation
Endangered species | Threatened arthropods | [
"Biology"
] | 1,361 | [
"Biota by conservation status",
"Endangered species"
] |
9,221,649 | https://en.wikipedia.org/wiki/Joanna%20Fowler | Joanna Sigfred Fowler (born August 9, 1942) is a scientist emeritus at the U.S. Department of Energy's Brookhaven National Laboratory in New York. She served as professor of psychiatry at Mount Sinai School of Medicine and director of Brookhaven's Radiotracer Chemistry, Instrumentation and Biological Imaging Program. Fowler studied the effect of disease, drugs, and aging on the human brain and radiotracers in brain chemistry. She has received many awards for her pioneering work, including the National Medal of Science.
Life and education
Fowler was born in Miami, Florida, and attended the University of South Florida, where she received her bachelor's degree in chemistry in 1964. There, she worked in the laboratories of Jack Fernandez. Fowler received her Ph.D. in chemistry from the University of Colorado in 1967 and did her postdoctoral work at the University of East Anglia in England and at Brookhaven National Laboratory. Fowler worked at Brookhaven National Laboratory from 1969 until her retirement in January 2014. She is an emeritus professor in the chemistry department at Stony Brook University.
She is married to Frank Fowler, an emeritus professor of organic chemistry at Stony Brook University.
Research and achievements
Fowler's research has led to new fundamental knowledge, development of important scientific tools, and has broad impacts in the application of nuclear medicine to diagnostics and health. She has worked for much of her career developing radiotracers for brain imaging to understand the mechanisms underlying drug addiction. Most recently, she has been engaged in developing methods to understand the relationship between genes, brain chemistry, and behavior.
In 1976, Fowler and her colleagues designed and synthesized a radioactively "tagged" form of sugar that is now used widely to study brain function and also to diagnose and plan treatment for cancer. She also developed another radiotracer, as these "tagged" molecules are called, that first showed that cocaine's distribution in the human brain parallels its effects on behavior.
Fowler played a central role in the development of a fluorine-18-labeled glucose molecule (FDG) enabling human brain glucose metabolism to be measured noninvasively. This positron-emitting molecule, together with positron emission tomography (PET) imaging, has become a mainstay for brain-imaging studies in schizophrenia, aging and cancer.
Another of her major accomplishments was the development of the first radiotracers to map monoamine oxidase (MAO), a brain enzyme that regulates the levels of other nerve-cell communication chemicals and one of the two major enzymes involved in neurotransmitter regulation in the brain and peripheral organs. Using these radiotracers, she discovered that smokers have reduced levels of MAO in their brains and lungs. This may account for some of the behavioral and epidemiological features of smoking, such as the high rate of smoking in individuals with depression and drug addiction, two conditions involving poor nerve-cell communication, and has led to many studies on reduced MAO and smoking.
Fowler holds eight patents for radiolabeling procedures.
Major publications
Fowler has published approximately 530 papers. The following are a few of the most cited:
Inhibition of monoamine oxidase B in the brains of smokers. Fowler, J.S., Volkow, N.D., Wang, G.-J., et al. Nature. Volume 379, Issue 6567, 22 February 1996, Pages 733-736
Distribution volume ratios without blood sampling from graphical analysis of PET data. Logan, J., Fowler, J.S., Volkow, N.D., et al. Journal of Cerebral Blood Flow and Metabolism. Volume 16, Issue 5, 1996, Pages 834-840
Decreased dopamine D2 receptor availability is associated with reduced frontal metabolism in cocaine abusers. Volkow, N.D., Fowler, J.S., Wang, G.-J., et al. Synapse. Volume 14, Issue 2, 1993, Pages 169-177
Brain dopamine and obesity. Wang, G.-J., Volkow, N., Fowler, J., et al. The Lancet. Volume 327, Issue 9253, 2001, Pages 354–357.
Cocaine cues and dopamine in dorsal striatum: mechanism of craving in cocaine addiction. Volkow, N., Wang, G.-J., Fowler, J., et al. Journal of Neuroscience. Volume 26, Issue 24, 2006, Pages 6583-6588
Awards and honors
Fowler's scientific excellence and achievements have been recognized by prestigious awards, including the National Medal of Science, awarded in 2009 by President Obama. In 2003, Fowler was elected to the National Academy of Sciences.
Her numerous other honors include:
1997 – Society of Nuclear Medicine's Paul C. Aebersold Award for outstanding achievement in basic science
1998 – American Chemical Society's Francis P. Garvan-John M. Olin Medal
1998 – E.O. Lawrence Award, awarded by the Department of Energy
2000 – Society of Nuclear Imaging in Drug Development's Alfred P. Wolf Award
2002 – American Chemical Society's Glen T. Seaborg Award for Nuclear Chemistry
2005 – Distinguished Basic Scientist of the Year Award from the Academy of Molecular Imaging (AMI)
2008 – National Medal of Science, administered by the National Science Foundation and bestowed by the president of the United States
2009 – National Academy of Science Award in Chemical Sciences, awarded by the National Academy of Sciences
2011 – Distinguished Women in Chemistry/Chemical Engineering Award, sponsored by the American Chemical Society
Distinguished Scientist Fellowship, sponsored by the Department of Energy's Office of Biological and Environmental Research
References
External links
Video of Fowler discussing her work, from the National Science & Technology Medals Foundation
Joanna Fowler's lab page at BNL
Joanna Fowler's page at Stony Brook University
1942 births
Living people
Nuclear chemists
American women chemists
People associated with the University of East Anglia
Recipients of the Garvan–Olin Medal
Brookhaven National Laboratory staff
Members of the United States National Academy of Sciences
National Medal of Science laureates
20th-century American chemists
American organic chemists
21st-century American scientists
University of South Florida alumni
20th-century American women scientists
21st-century American women scientists
Chemists from Florida | Joanna Fowler | [
"Chemistry"
] | 1,279 | [
"Nuclear chemists",
"Organic chemists",
"American organic chemists"
] |
9,223,199 | https://en.wikipedia.org/wiki/Pressure%20ridge%20%28ice%29 | A pressure ridge, when consisting of ice in an oceanic or coastal environment, is a linear pile-up of sea ice fragments formed in pack ice by accumulation in the convergence between floes.
Such a pressure ridge develops in an ice cover as a result of a stress regime established within the plane of the ice. Within sea ice expanses, pressure ridges originate from the interaction between floes, as they collide with each other. Currents and winds are the main driving forces, but the latter is particularly effective when they have a predominant direction. Pressure ridges are made up of angular ice blocks of various sizes that pile up on the floes. The part of the ridge that is above the water surface is known as the sail; that below it as the keel. Pressure ridges are the thickest sea ice features and account for up to 30–40% of the total sea ice area and about one-half of the total sea ice volume. Stamukhi are pressure ridges that are grounded and that result from the interaction between fast ice and the drifting pack ice. Similar to undeformed ice, pressure ridges can be first-, second-, and multiyear depending on how many melt seasons they managed to survive. Ridges can be formed from ice of different ages, but mostly consist of 20–40 cm thick blocks of thin and young ice.
Internal structure
The blocks making up pressure ridges are mostly from the thinner ice floe involved in the interaction, but they can also include pieces from the other floe if it is not too thick. In the summer, the ridge can undergo a significant amount of weathering, which turns it into a smooth hill. During this process, the ice loses its salinity (as a result of brine drainage and meltwater flushing). This is known as an aged ridge. A fully consolidated ridge is one whose base has undergone complete freezing. The term consolidated layer is used to designate the freezing up of the rubble just below the water line. The existence of a consolidated layer depends on air temperature — in this layer, the water between individual blocks is frozen, with a resulting reduction in porosity and an increase in mechanical strength. A keel's depth of an ice ridge is much higher than its sail's height — typically about 3–5 times. The keel is also 2–3 times wider than the sail. Ridges are usually melting faster than level ice, both at the surface and at the bottom. While first-year ridges melt approximately 4 times faster than surrounding level ice, second-year ridges melt only 1.6 times faster than surrounding level ice. Sea-ice ridges also play an important role in confining meltwater within under-ice meltwater layers, which may lead to the formation of false bottoms. Ridges also play an important role in controlling the values of atmospheric drag coefficients.
Thickness and consolidation
One of the largest pressure ridges on record had a sail extending 12 m above the water surface, and a keel depth of 45 m. The total thickness for a multiyear ridge was reported to be 40 m. On average, total thickness ranges between 5 m and 30 m, with a mean sail height that remains below 2 m. The average keel depth of Arctic ridges is 4.5 m. The sail height is usually proportional to the square root of the ridge block thickness. Ice ridges in Fram Strait usually have a trapezoidal shape with a bottom horizontal section covering around 17% of the total ridge width and with a mean draft of 7 m, while ice ridges in the Chukchi and Beaufort Seas have a concave close to triangular shape.
The average consolidated layer thickness of Arctic ridges is 1.6 m. Usually, ridges consolidate faster than level ice because of their initial macroporosity. Ridge rubble porosity (or water-filled void fraction of ridge unconsolidated part) is in the wide range of 10–40%. During winter, ice ridges consolidate up to two times faster than level ice, with the ratio of level ice and consolidated layer thickness proportional to the square root of ridge rubble porosity. This results in 1.6–1.8 ratio of consolidated layer and level ice thickness by the end of winter season. Meanwhile, snow is usually about three times thicker above ridges than above level ice. Sometimes ridges can be found fully consolidated with the total thickness up to 8 m. Ridges may also contain from 6% to 11% of snow mass fraction, which can be potentially linked to the mechanisms of ridge consolidation. Fram Strait ridge observations suggest, that the largest part of ridge consolidation happens during the spring season when during warm air intrusions or dynamic events snow can enter ridge keels via open leads and increase the speed of ridge consolidation. These observations are supported by high snow mass fraction in refrozen leads, observed during the spring season.
The ridge consolidation potentially reduces light levels and the habitable space available for organisms, which may have negative ecological impacts as ridges have been identified as ecological hotspots.
Characterization methods
The physical characterization of pressure ridges can be done using the following methods:
Mechanical drilling of the ice with non-coring or coring augers (when the ice core is retrieved for analysis).
Surveying, whereby a level, theodolite or a differential GPS system is used to determine sail geometry.
Thermal drilling — drilling involving melting of the ice.
Observation of the ice canopy by scuba divers.
Upward looking sonars and multibeam sonars fixed on seabed or mounted on a submarine or remotely operated underwater vehicle.
A series of thermistors (ice mass balance buoy), to monitor temperature changes.
Electromagnetic induction, from the ice surface or from an aircraft.
Satellite (ICESat‐2) and airborne laser altimeters to measure surface topography and ridge spacing.
Interest for pressure ridges
From an offshore engineering and naval perspective, there are three reasons why pressure ridges are a subject of investigation. Firstly, the highest loads applied on offshore structures operating in cold oceans by drift ice are associated with these features. Secondly, when pressure ridges drift into shallower areas, their keel may come into contact with the seabed, thereby representing a risk for subsea pipelines (see Seabed gouging by ice) and other seabed installations. Thirdly, they have a significant impact on navigation. In the Arctic, ridged ice makes up about 40% of the overall mass of sea ice. First-year ridges with large macroporosity are important for the ice-associated sympagic communities and identified as potential ecological hotspots and proposed to serve as refugia of ice-associated organisms.
See also
Finger rafting
Iceberg
Ice volcano
Offshore geotechnical engineering
Notes
References
Geomorphology
Landforms
Glaciology
Sea ice
Snow or ice weather phenomena | Pressure ridge (ice) | [
"Physics"
] | 1,370 | [
"Physical phenomena",
"Earth phenomena",
"Sea ice"
] |
9,223,226 | https://en.wikipedia.org/wiki/Gullstrand%E2%80%93Painlev%C3%A9%20coordinates | Gullstrand–Painlevé coordinates are a particular set of coordinates for the Schwarzschild metric – a solution to the Einstein field equations which describes a black hole. The ingoing coordinates are such that the time coordinate follows the proper time of a free-falling observer who starts from far away at zero velocity, and the spatial slices are flat. There is no coordinate singularity at the Schwarzschild radius (event horizon). The outgoing ones are simply the time reverse of ingoing coordinates (the time is the proper time along outgoing particles that reach infinity with zero velocity).
The solution was proposed independently by Paul Painlevé in 1921 and Allvar Gullstrand in 1922. It was not explicitly shown that these solutions were simply coordinate transformations of the usual Schwarzschild solution until 1933 in Lemaître's paper, although Einstein immediately believed that to be true.
Derivation
The derivation of GP coordinates requires defining the following coordinate systems and understanding how data measured for events in one coordinate system is interpreted in another coordinate system.
Convention: The units for the variables are all geometrized. Time and mass have units in meters. The speed of light in flat spacetime has a value of 1. The gravitational constant has a value of 1.
The metric is expressed in the +−−− sign convention.
Schwarzschild coordinates
A Schwarzschild observer is a far observer or a bookkeeper. He does not directly make measurements of events that occur in different places. Instead, he is far away from the black hole and the events. Observers local to the events are enlisted to make measurements and send the results to him. The bookkeeper gathers and combines the reports from various places. The numbers in the reports are translated into data in Schwarzschild coordinates, which provide a systematic means of evaluating and describing the events globally. Thus, the physicist can compare and interpret the data intelligently. He can find meaningful information from these data. The Schwarzschild form of the Schwarzschild metric using Schwarzschild coordinates is given by
where
G=1=c
t, r, θ, φ are the Schwarzschild coordinates,
M is the mass of the black hole.
GP coordinates
Define a new time coordinate by
for some arbitrary function . Substituting in the Schwarzschild metric one gets
where .
If we now choose such that the term multiplying is unity, we get
and the metric becomes
The spatial metric (i.e. the restriction of the metric on the surface where is constant) is simply the flat metric expressed in spherical polar coordinates. This metric is regular along the horizon where r=2M, since, although the temporal term goes to zero, the off-diagonal term in the metric is still non-zero and ensures that the metric is still invertible (the determinant of the metric is ).
The function is given by
where .
The function is clearly singular at r=2M as it must be to remove that singularity in the Schwarzschild metric.
Other choices for lead to other coordinate charts for the Schwarzschild vacuum; a general treatment is given in Francis & Kosowsky.
Motion of raindrop
Define a raindrop as an object which plunges radially toward a black hole from rest at infinity.
In Schwarzschild coordinates, the velocity of a raindrop is given by
The speed tends to 0 as r approaches the event horizon. The raindrop appears to have slowed as it gets nearer the event horizon and halted at the event horizon as measured by the bookkeeper. Indeed, an observer outside the event horizon would see the raindrop plunge slower and slower. Its image infinitely redshifts and never makes it through the event horizon. However, the bookkeeper does not physically measure the speed directly. He translates data relayed by the shell observer into Schwarzschild values and computes the speed. The result is only an accounting entry.
In GP coordinates, the velocity is given by
The speed of the raindrop is inversely proportional to the square root of the radius and equals the negative newtonian escape velocity. At points very far away from the black hole, the speed is extremely small. As the raindrop plunges toward the black hole, the speed increases. At the event horizon, the speed has the value 1. There is no discontinuity or singularity at the event horizon.
Inside the event horizon, the speed increases as the raindrop gets closer to the singularity. Eventually, the speed becomes infinite at the singularity. As shown below the speed is always less than the speed of light. The results may not be correctly predicted by the equation at and very near the singularity since the true solution may be quite different when quantum mechanics is incorporated.
Despite the problem with the singularity, it's still possible to compute the travel time for the raindrop from the horizon to the center of black hole mathematically.
Integrate the equation of motion:
The result is
Using this result for the speed of the raindrop we can find the proper time along the trajectory of the raindrop in terms of the time . We have
I.e. along the rain drops trajectory, the elapse of time is exactly the proper time along the trajectory. One could have defined the GP coordinates by this requirement, rather than by demanding that the spatial surfaces be flat.
A closely related set of coordinates is the Lemaître coordinates, in which the "radial" coordinate is chosen to be constant along the paths of the raindrops. Since r changes as the raindrops fall, this metric is time dependent while the GP metric is time independent.
The metric obtained if, in the above, we take the function f(r) to be the negative of what we choose above is also called the GP coordinate system. The only change in the metric is that cross term changes sign. This metric is regular for outgoing raindrops—i.e. particles which leave the black hole travelling outward with just escape velocity so that their speed at infinity is zero. In the usual GP coordinates, such particles cannot be described for r<2M. They have a zero value for at r=2M. This is an indication that the Schwarzschild black hole has two horizons, a past horizon, and a future horizon. The Original form of the GP coordinates is regular across the future horizon (where particles fall into when they fall into a black hole) while the alternative negative version is regular across the past horizon (from which particles come out of the black hole if they do so).
The Kruskal–Szekeres coordinates are regular across both horizons at the expense of making the metric strongly dependent on the time coordinate.
Speeds of light
Assume radial motion. For light, Therefore,
At places very far away from the black hole, The speed of light is 1, the same as in special relativity.
At the event horizon, the speed of light shining outward away from the center of black hole is It can not escape from the event horizon. Instead, it gets stuck at the event horizon. Since light moves faster than all others, matter can only move inward at the event horizon. Everything inside the event horizon is hidden from the outside world.
Inside the event horizon, the rain observer measures that the light moves toward the center with speed greater than 2. This is plausible. Even in special relativity, the proper speed of a moving object is
There are two important points to consider:
No object should have speed greater than the speed of light as measured in the same reference frame. Thus, the principle of causality is preserved. Indeed, the speed of raindrop is less than that of light:
The time of travel for light shining inward from event horizon to the center of black hole can be obtained by integrating the equation for the velocity of light,
The result is
The light travel time for a stellar black hole with a typical size of 3 solar masses is about 11 microseconds.
Ignoring effects of rotation, for Sagittarius A*, the supermassive black hole residing at the center of the Milky Way, with mass of 3.7 million solar masses, the light travel time is about 14 seconds.
The supermassive black hole at the center of Messier 87, a giant elliptical galaxy in the Virgo Cluster, is one of the largest known supermassive black holes. With a mass of 3 billion solar masses, it takes about 3 hours for light to travel to the central singularity and 5 hours for a raindrop.
A rain observer's view of the universe
How does the universe look like as seen by a rain observer plunging into the black hole? The view can be described by the following equations:
where
are the rain observer's and shell observer's viewing angles with respect to the radially outward direction.
is the angle between the distant star and the radially outward direction.
is the impact parameter. Each incoming light ray can be backtraced to a corresponding ray at infinity. The Impact parameter for the incoming light ray is the distance between the corresponding ray at infinity and a ray parallel to it that plunges directly into the black hole.
Because of spherical symmetry, the trajectory of light always lies in a plane passing through the center of sphere. It's possible to simplify the metric by assuming .
The impact parameter can be computed knowing the rain observer's r-coordinate and viewing angle . Then, the actual angle of the distant star, is determined by numerically integrating from to infinity. A chart of the sample results is shown at right.
At r/M = 500, the black hole is still very far away. It subtends a diametrical angle of ~ 1 degree in the sky. The stars are not distorted much by the presence of the black hole, except for the stars directly behind it. Due to gravitational lensing, these obstructed stars are now deflected 5 degrees away from the back. In between these stars and the black hole is a circular band of secondary images of the stars. The duplicate images are instrumental in the identification of the black hole.
At r/M = 30, the black hole has become much bigger, spanning a diametrical angle of ~15 degrees in the sky. The band of secondary images has also grown to 10 degrees. It's now possible to find faint tertiary images in the band, which are produced by the light rays that have looped around the black hole once already. The primary images are distributed more tightly in the rest of the sky. The pattern of distribution is similar to that previously exhibited.
At r/M = 2, the event horizon, the black hole now occupies a substantial portion of the sky. The rain observer would see an area up to 42 degrees from the radially inward direction that is pitch dark. The band of secondary and tertiary images, rather than increasing, has decreased in size to 5 degrees. The aberration effect is now quite dominant. The speed of plunging has reached the light speed. The distribution pattern of primary images is changing drastically. The primary images are shifting toward the boundary of the band. The edge near the band is now crowded with stars. Due to Doppler effect, the primary image of the stars which were originally located behind the rain observer have their images appreciably red-shifted, while those that were in front are blue-shifted and appear very bright.
At r/M=0.001, the curve of distant star angle versus view angle appears to form a right angle at the 90 degrees view angle. Almost all of the star images are congregated in a narrow ring 90 degrees from the radially inward direction. Between the ring and the radially inward direction is the enormous black hole. On the opposite side, only a few stars shine faintly.
As the rain observer approaches the singularity, , and . Most of the stars and their images caused by multiple orbits of the light around the black hole are squeezed to a narrow band at the 90° viewing angle. The observer sees a magnificent bright ring of stars bisecting the dark sky.
History
Although the publication of Gullstrand's paper came after Painlevé's, Gullstrand's paper was dated 25 May 1921, whereas Painlevé's publication was a writeup of his presentation before the Academie des Sciences in Paris on 24 October 1921. In this way, Gullstrand's work appears to have priority.
Both Painlevé and Gullstrand used this solution to argue that Einstein's theory was incomplete in that it gave multiple solutions for the gravitational field of a spherical body, and moreover gave different physics (they argued that the lengths of rods could sometimes be longer and sometimes shorter in the radial than the tangential directions). The "trick" of the Painlevé proposal was that he no longer stuck to a full quadratic (static) form but instead, allowed a cross time-space product making the metric form no longer static but stationary and no longer direction symmetric but preferentially oriented.
In a second, longer paper (November 14, 1921), Painlevé explains how he derived his solution by directly solving Einstein's equations for a generic spherically symmetric form of the metric.
The result, equation (4) of his paper, depended on two arbitrary functions of the r coordinate yielding a double infinity of solutions. We now know that these simply represent a variety of choices of both the time and radial coordinates.
Painlevé wrote to Einstein to introduce his solution and invited Einstein to Paris for a debate. In Einstein's reply letter (December 7),
he apologized for not being in a position to visit soon and explained why he was not pleased with Painlevé's arguments, emphasising that the coordinates themselves have no meaning. Finally, Einstein came to Paris in early April. On the 5th of April 1922, in a debate at the "Collège de France" with Painlevé, Becquerel, Brillouin, Cartan, De Donder, Hadamard, Langevin and Nordmann on "the infinite potentials", Einstein, baffled by the non quadratic cross term in the line element, rejected the Painlevé solution.
See also
Isotropic coordinates
Eddington–Finkelstein coordinates
Kruskal–Szekeres coordinates
Lemaître coordinates
References
External links
The River Model of Black Holes
Dr. Andrew J S Hamilton's video "Inside Black Holes"
Black hole orbit simulation in GP coordinates.
Coordinate charts in general relativity
Lorentzian manifolds
Black holes | Gullstrand–Painlevé coordinates | [
"Physics",
"Astronomy",
"Mathematics"
] | 2,964 | [
"Black holes",
"Physical phenomena",
"Physical quantities",
"Unsolved problems in physics",
"Astrophysics",
"Density",
"Coordinate systems",
"Stellar phenomena",
"Astronomical objects",
"Coordinate charts in general relativity"
] |
9,223,854 | https://en.wikipedia.org/wiki/Greenhouse%20debt | Greenhouse debt is the measure to which an individual person, incorporated association, business enterprise, government instrumentality or / [and] (per Neb., USA) geographic community exceeds its permitted greenhouse footprint and emits greenhouse gases that contribute to global warming and climate change.
Friends of the Earth and similar organisations put forward the concept to define specifically the environmental harm caused by developed countries' past and present policies. Some governments, at least the Australian Labor leadership, have a tendency to accept such a line of reasoning. The concept, however, makes no sense without a clear numerical value for the permitted greenhouse footprint, which is not easily defined or estimated.
The greenhouse debt assessment thus forms an ecological footprint analysis, but can be used separately. Taken conjointly with a 'water debt' analysis and an ecological impact assessment, greenhouse debt analysis is basic to giving individuals, organisations, governments and communities an understanding of the effects they are having on Gaia, life, and global warming.
Ensuring that the greenhouse debt is zero is essential towards achieving ecologically sustainable development or a sustainable retreat. Any greenhouse debt incurred will contribute to making life harder for future generations of humans and non-human lifeforms.
There are three possible consequences that occur as a result of a greenhouse debt.
Mitigation: finding compensatory ways of reducing the greenhouse debt so its effects are neutralised
Adaptation: finding ways of adjusting to the resulting global warming or climate change
Suffering: having one's quality of life reduced as a result of the consequences
See also
Ecological debt
Ecological deficit
Ecological footprint
References
Climate change assessment and attribution
Greenhouse gas emissions
Sustainable development | Greenhouse debt | [
"Chemistry"
] | 327 | [
"Greenhouse gases",
"Greenhouse gas emissions"
] |
9,224,555 | https://en.wikipedia.org/wiki/IEC%2060929 | IEC 60929 is an international standard created by the International Electrotechnical Commission and covers electronic ballasts used in AC supplies with voltages up to 1000 V and with operating frequencies at 50 Hz or 60 Hz. The actual operating frequency may deviate from the specified supply frequency.
The standard essentially covers the same material as IEC 60921, but it is considerably more complex due to the high frequency aspect of electronic ballasts. Appendix E of the standard defines the DALI, which specifies how ballasts are controlled.
References
External links
60929 | IEC 60929 | [
"Technology"
] | 111 | [
"Computer standards",
"IEC standards"
] |
9,224,636 | https://en.wikipedia.org/wiki/Certified%20reference%20materials | Certified reference materials (CRMs) are 'controls' or standards used to check the quality and metrological traceability of products, to validate analytical measurement methods, or for the calibration of instruments. A certified reference material is a particular form of measurement standard.
Reference materials are particularly important for analytical chemistry and clinical analysis. Since most analytical instrumentation is comparative, it requires a sample of known composition (reference material) for accurate calibration. These reference materials are produced under stringent manufacturing procedures and differ from laboratory reagents in their certification and the traceability of the data provided.
Quality management systems involving laboratory accreditation under national and international accreditation/certification standards such as ISO/IEC 17025 require metrological traceability to Certified Reference Materials (where possible) when using reference materials for calibration.
Whilst Certified Reference Materials are preferred where available, their availability is limited. Reference Materials that do not meet all the criteria for certified reference materials are more widely available: the principal difference is the additional evidence of metrological traceability and statement of measurement uncertainty provided on the certificate for certified reference materials.
Terminology
ISO REMCO definitions
ISO REMCO, the ISO committee responsible for guidance on reference materials within ISO, defines the following classes of reference material:
Reference Material Material, sufficiently homogeneous and stable with respect to one or more specified properties, which has been established to be fit for its intended use in a measurement process.
Certified Reference Material Reference material characterized by a metrologically valid procedure for one or more specified properties, accompanied by a certificate that provides the value of the specified property, its associated uncertainty, and a statement of metrological traceability.
Alternative terminology
Other bodies may define classes of reference material differently. WHO guidelines for biological reference materials provide the terms:
Reference standards: materials that are used as calibrators in assays
International biological measurement standard: a biological substance provided to enable the results of biological assay or immunological assay procedures to be expressed in the same way throughout the world
Secondary reference standards: Reference standards calibrated against and traceable to primary WHO materials and intended for use in routine tests
Reference reagent: a WHO reference standard, the activity of which is defined by WHO in terms of a unit
For chemical substances some pharmacopoeias use the WHO terms
Primary chemical reference substance: a chemical reference substance ... whose value is accepted without requiring comparison to another chemical substance.
Secondary chemical reference substance: substance whose characteristics are assigned and/or calibrated by comparison with a primary chemical reference substance.
The United States National Institute of Standards and Technology (NIST) uses the trade marked term Standard Reference Material (SRM) to denote a certified reference material that satisfies additional NIST-specific criteria. In addition, commercial producers adhering to criteria and protocols defined by NIST may use the trademark "NIST traceable reference material" to designate certified reference materials with a well-defined traceability linkage to existing NIST standards for chemical measurements.
Types of reference material
ILAC describes the following five types of reference material:
Pure substances; essentially pure chemicals, characterised for chemical purity and/or trace impurities.
Standard solutions and gas mixtures, often prepared gravimetrically from pure substances.
Matrix reference materials, characterised for the composition of specified major, minor or trace chemical constituents. Such materials may be prepared from matrices containing the components of interest, or by preparing synthetic mixtures.
Physico-chemical reference materials, characterised for properties such as melting point, viscosity, or optical density.
Reference objects or artifacts, characterised for functional properties such as taste, odour, octane number, flash point and hardness. This type also includes microscopy specimens characterised for properties ranging from fibre type to microbiological specimens.
Production
Principal steps in producing certified reference materials
The preparation of certified reference materials is described in general in ISO Guide 17034 and in more detail in ISO Guide 35. Preparation of biological reference standards is described in WHO Guidance. General steps required in production of a certified reference material typically include:
Collection or synthesis of material
Sample preparation (including homogenization, stabilization, bottling etc.)
Homogeneity testing
Stability assessment
Value assignment ("characterization" in ISO REMCO terms).
In addition it may be important to assess the commutability of a reference material; this is especially important for biological materials.
Sample preparation
Detailed sample preparation depends on the type of material. Pure standards are most likely to be prepared by chemical synthesis and purification and characterized by determination of remaining impurities. This is often done by commercial producers. Natural matrix CRMs (often shortened to 'matrix CRMs') contain an analyte or analytes in a natural sample (for, example, lead in fish tissue). These are typically produced by homogenization of a naturally occurring material followed by measurement of each analyte. Due to the difficulty in production and value assignment, these are usually produced by national or transnational metrology institutes like NIST (USA), BAM (Germany), KRISS (Korea) and EC JRC ( European Commission Joint Research Centre).
For natural materials, homogenization is often critical; natural materials are rarely homogeneous on the scale of grams so production of a solid natural matrix reference material typically involves processing to a fine powder or paste. Homogenization can have adverse effects, for example on proteins, so producers must take care not to over-process materials. Stability of a certified reference material is also important, so a range of strategies may be used to prepare a reference material that is more stable than the natural material it is prepared from. For example, stabilizing agents such as antioxidants or antimicrobial agents may be added to prevent degradation, liquids containing certified concentrations of trace metals may have pH adjusted to keep metals in solution, and clinical reference materials may be freeze-dried for long term storage if they can be reconstituted successfully.
Homogeneity testing
Homogeneity testing for a candidate reference material typically involves replicated measurements on multiple units or subsamples of the material.
Homogeneity tests for CRMs follow planned experimental designs. Because the experiment is intended to test for (or estimate the size of) variation in value between different CRM units, the designs are chosen to allow separation of variation in results due to random measurement error and variation due to differences between units of the CRM. Among the simplest designs recommended for this purpose is a simple balanced nested design (see schematic). Typically 10-30 CRM units are taken from the batch at random; stratified random sampling is recommended so that the selected units are spread across the batch. An equal number of subsamples (usually two or three) is then taken from each CRM unit and measured. Subsamples are measured in random order. Other designs, such as randomized block designs, have also been used for CRM certification.
Data processing for homogeneity tests usually involves a statistical significance test for evidence of differences between units of the candidate CRM. For the simple balanced design above, this typically uses an F test following ANOVA. A check for trends with production order is also recommended.
This approach is not taken in ISO Guide 35:2017; rather, emphasis is placed on deciding whether the between-unit standard deviation is sufficiently small for the intended end use. If statistical tests are used, however, the homogeneity experiment should be capable of detecting important heterogeneity, ISO Guide 35:2017 in turn requiring a sufficient combination of precision of the measurement procedure, number of RM units and number of replicates per unit. Statistical power calculations can assist in ensuring a sufficiently effective test .
In extreme cases, such as microanalysis, materials must be checked for homogeneity on sub-micron scales; this may involve much larger numbers of observations and adjustments to statistical analysis.
Stability assessment
Stability assessment and testing strategies
Stability is among the essential properties of a CRM (see definitions above), and stability assessment is accordingly required for certified reference materials. Stability under long term storage and also under conditions of transport are both expected to be assessed. "Assessment" is not synonymous with "testing"; some materials - for example, many minerals and metal alloys - may be so stable that experimental tests are not considered necessary. Other reference materials will usually undergo experimental tests of stability at some point prior to the material being distributed for sale.
Where reference materials are certified for more than one property, stability is expected to be demonstrated for every certified property.
There are two important strategies for CRM stability testing; simple real-time studies and accelerated testing. Real-time studies simply keep units of the material at their planned storage temperature for a suitable period of time and observe the material at intervals. Accelerated studies use a range of more stringent conditions, most commonly increased temperature, to test whether the material is likely to be stable over longer time scales.
Real-time stability studies
Real-time stability studies simply hold a set of RM units at a proposed storage temperature and test a proportion of them at regular intervals. The results are usually assessed by inspection and by linear regression to determine whether there is a significant change in measured value over time.
Accelerated stability studies
Accelerated studies have been in use since at least the mid-1950s, at least for biological reference materials. CRMs are typically monitored at a range of temperatures and the results are used to predict the rate of change at a proposed, usually low, storage temperature. Often, the prediction uses a well known degradation model such as an Arrhenius model. The advantage over real-time studies is that results are available sooner and predictions of stability over a much longer period than the stability study can be defended. For some applications, accelerated studies have been described as the only practical approach:
The principal disadvantage of accelerated studies is that reference materials, like any other material, can degrade for unexpected reasons over time, or can degrade following different kinetic models; predictions can then become unreliable.
Isochronous studies
In most stability studies, real-time or accelerated, a few units of the reference material are tested at intervals. If the measurement system used for testing the materials is not perfectly stable, this can generate imprecise data or can be mistaken for instability of the material. To overcome these difficulties, it is often possible to move RM units, at intervals, to some reference temperature where they remain stable, and then test all the accumulated units - which have undergone different exposure times - at the same time. This is referred to as an isochronous study. This strategy has the advantage of improving the precision of data used in assessing stability at the cost of delaying results until the end of the stability study period.
See also
Canadian Reference Materials
Geological and Environmental Reference Materials (GeoReM) Database
National Institute of Standards and Technology (NIST)
National Institute of Advanced Industrial Science and Technology (AIST)
Notes
References
External links
ISO Committee on Reference Materials (ISO/REMCO)
ISO Guide 33:2015 Reference materials—Good practice in using reference materials
Geological and Environmental Reference Materials (GeoReM) Database
Certified Reference Materials from the European Commission
Measurement
Analytical chemistry | Certified reference materials | [
"Physics",
"Chemistry",
"Mathematics"
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"Physical quantities",
"Quantity",
"Measurement",
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9,225,209 | https://en.wikipedia.org/wiki/Belterra%2C%20Par%C3%A1 | Belterra is a municipal seat and rubber plantation site some south of the Brazilian city of Santarém in the Northern federal state of Pará, at the edge of the Planalto at above sea level.
Location
Amongst soil scientists, Belterra is famous for the underlying fertile, anthropogenic soil of 'Terra preta', which might have been amongst the criteria for the selection of this site for the plantation. While Terra Preta soil patterns occur all over the Brazilian lowland, this site is extremely well developed and also scientifically surveyed and documented
The tertiary highland is composed of some clay layers (Belterra clay) of kaolinitic sediments of a Pliocene lake, with a distinct escarpment to the North and West of the plain, which leads down to the Várzea forest lowland at the river bank of the Tapajós river.
The municipality holds part of the Tapajós National Forest, a sustainable use conservation unit created in 1974.
History
14C analyses based on Terra Preta ceramic artefacts found in Belterra showed, that this area was populated and cultivated by the indigenous population in an intensive way at least since 500 B.C.
Belterra was founded as a rubber plantation, after the economic failure of Fordlândia, which had been founded in 1928 by Henry Ford. The intention of the US-Department of Commerce in the 1920s was to produce rubber in Brazil and to import it to USA. The advantage of the Belterra plantation over the plantation of Fordlândia to the south is the flat topography, which enables the use of machinery. In its peak time in the late 1930s some were cultivated with Hevea brasiliensis (rubber tree).
In Belterra, new breeding methods with local varieties were applied, which prevented the leaf disease, a result of the monoculture in Fordlândia. This was very labour-intensive and therefore expensive. Together with the worldwide decline on demand on natural rubber, the plantation was not cost-effective anymore. Ford sold it to the Brazilian government, which is still running the plantation under EMBRAPA.
Today, the area of the plantation is some covered extensively with mainly old rubber trees. It still gives the impression of a plantation with some 1000 - 2000 inhabitants (mainly plantation workers and their families). At the peak time, it had a population of some 8 - 10,000 people. According to a 2010 census, the entire district population, including surrounding villages, is reported as 16,324.
Climate
Belterra has a tropical monsoon climate (Köppen: Am) characterized by high temperatures and humidity throughout the year. The city experiences a distinct wet season from January to June, while the rest of the year is drier.
See also
List of municipalities in Pará
References
External links
Description of Belterra
Google-based map of Terra Preta sites in Amazonia/Belterra (with further refs)
Municipalities in Pará
Environmental soil science
Amazon basin | Belterra, Pará | [
"Environmental_science"
] | 595 | [
"Environmental soil science"
] |
6,928,058 | https://en.wikipedia.org/wiki/S.%20Donald%20Stookey | Stanley Donald Stookey (May 23, 1915 – November 4, 2014) was an American inventor. He had 60 patents in his name related to glass and ceramics, some patents solely his and others shared as joint patents with other inventors. His discoveries and inventions have contributed to the development of ceramics, eyeglasses, sunglasses, cookware, defense systems, and electronics.
He was a research director at Corning Glass Works for 47 years doing R&D in glass and ceramic development. His inventions include Fotoform, CorningWare, Cercor, Pyroceram and Photochromic Ophthalmic glass eyewear.
Early life
Stookey was born on May 23, 1915, in Hay Springs, Nebraska, the eldest of four children born to Stanley and Hermie Stookey. Both of his parents were teachers, and his father also worked at some point in time as a bank clerk. When Stookey was about 6 years old, the family moved to Cedar Rapids, Iowa.
Career
Stookey went to Coe College from 1934 to 1936, where he graduated with his first degree, a liberal arts degree in chemistry and mathematics. Stookey’s grandfather (Stephen Stookey) was once a professor of botany and geology at that same college. After graduation from Coe College, Stookey went to Lafayette College in Easton, Pennsylvania, in 1937. He received a $1000 fellowship to cover living expenses and as a teaching laboratory assistant in the chemistry lab. In 1938, he earned his Master of Science degree in chemistry from Lafayette College. Stookey then went to Massachusetts Institute of Technology in Cambridge where he received a doctorate in chemistry in 1940. The same year, he married his wife Ruth. He received an honorary degree from Alfred University in 1984.
Stookey took his career job at Corning Glass Works in 1940. He carried out research on glass and ceramics, which led to several inventions. Stookey studied and experimented with opal glass and glass ceramics.
FotoForm glass
One of Stookey's earliest innovations was FotoForm glass. The scientific community recognized its value around 1948. FotoForm glass is used in computer manufacturing and communications technology. A serendipitous invention made by Stookey in 1953 was when he took a piece of FotoForm glass and mistakenly heated it to 900 °C when he meant to heat it to 600 °C. When an oven thermometer was stuck on the higher temperature, Stookey had accidentally created the first glass-ceramic, Fotoceram. It was later known also as Pyroceram. This was the first glass-ceramic and eventually led to the development of CorningWare in 1957. CorningWare went to the consumer marketplace the next year in 1958 for cookware by Corning Glass Works and became just one of Stookey's multimillion-dollar inventions. It influenced the development of VisionWare, which is transparent cookware. VisionWare was patented by Corning Glass Works in 1966.
Pyroceramic glass has the necessary properties to be used by the military for the nose cones of supersonic radar domes in guided missiles applied in defense. It has the special properties of extreme hardness, super strength, resistance to high heat and transparency to radar waves. It is the basis for Gorilla Glass, used in iPhones and other LCD screens.
Stookey also developed photochromic glass. Photochromic glass is a glass that is used to make ophthalmic lenses that darken in bright light. These lenses were first available to consumers in the 1960s as sunglasses made by Corning Glass Works. It was a joint discovery and development of Stookey with William Armistead. Stookey also invented photosensitive glass using gold in which permanent colored photographs can be produced.
Timeline
1936 magna cum laude, Coe College
1937 Master of Science in chemistry, Lafayette College
1940 Ph.D., physical chemistry, Massachusetts Institute of Technology
1950 First of 60 U.S. Patents Awarded, No. 2.515.937 for photosensitive glass.
1953 John Price Wetherill Medal, Franklin Institute
1955 Alumni Award of Merit, Coe College
1960 Ross Coffin Purdy Award, American Ceramic Society
1962 John Price Wetherill Medal, Franklin Institute (2nd time)
1963 Honorary doctor of science degree in 1963, Coe College.
1964 Toledo Glass and Ceramic Award
1970 Inventor of the Year, George Washington University
1971 Award for Creative Invention, American Chemical Society
1971 E.C. Sullivan Award, Corning Section, American Ceramic Society
1973 Beverly Myers Achievement Award, Educational Foundation in Ophthalmic Optics
1975 American Phoenix Award of the Glass Industry
1979 IRI Achievement Award, Industrial Research Institute
1982 Samuel Giejsbeek Award, Pacific Coast Sections, ACerS
1984 Distinguished Inventor Award, Central New York Patent Law Association
1984 Honorary doctor of science degree, Alfred University
1985 Published "Journey to the Center of the Crystal Ball", an autobiography
1986 United States Medal of Technology presented by President Ronald Reagan
1989 Distinguished Life Member, American Ceramic Society
1993 Wilhelm Eitel Medallion for Excellence in Silicate Science
1994 National Medal of Technology, White House Council
2010 Inducted into National Inventors Hall of Fame
Later life
Stookey retired from Corning Glass Works in 1987 after a career of 47 years.
Together he and his wife raised three children named Robert, Margaret and Donald Bruce. They had six grandchildren and eight great-grandchildren. He died at the age of 99 in 2014.
Organization membership
Stookey held membership in many professional organizations and societies, including:
Sigma Xi
National Academy of Engineering
British Society of Glass Technology
American Institute of Chemical Engineers (Fellow)
The American Ceramic Society (Distinguished Life and Fellow)
A section on the innovations of glass and glass-ceramics at the Corning Museum of Glass with a Stookey video describing his glass-ceramics inventions.
Bibliography
References
American chemists
Glass makers
Glass-ceramics
American inorganic chemists
1915 births
2014 deaths
Corning Inc.
People from Cedar Rapids, Iowa
People from Sheridan County, Nebraska
Coe College alumni
Lafayette College alumni
Massachusetts Institute of Technology School of Science alumni
Writers from Iowa
Writers from Nebraska
Fellows of the American Ceramic Society | S. Donald Stookey | [
"Chemistry"
] | 1,253 | [
"American inorganic chemists",
"Inorganic chemists"
] |
6,928,255 | https://en.wikipedia.org/wiki/Raksi | Raksi (Devanagari:रक्सी) (Bantawa language: Hengmawa/Hengma, Limbu language: Sijongwaa aara, Nepal Bhasa: aila) is the Nepali term for a traditional distilled alcoholic beverage in Nepal, India (Darjeeling, Sikkim) and Tibet. It is often made at home.
Raksi is a strong drink, clear like vodka or gin, tasting somewhat like Japanese sake. It is usually made from kodo millet (kodo) or rice; different grains produce different flavors. It is made by distilling a chhaang, a brewed alcoholic drink.
The Limbus and Kirati people, for whom it is a traditional beverage, drink tongba and raksi served with pieces of pork, water buffalo or goat meat sekuwa. For the Newars, aila is indispensable during festivals and various religious rituals as libation, prasad or sagan.
In CNN's list of the world's 50 most delicious drinks, raksi was ranked 41st and was described as follows: "made from millet or rice, raksi is strong on the nose and sends a burning sensation straight down your throat that resolves itself into a surprisingly smooth, velvety sensation. Nepalese drink this home brew to celebrate festivals, though some think that the prized drink itself is the reason to celebrate."
Because of its popularity, various temperance movements exist in Nepal, including various women's groups. Raksi, however, remains an important requirement of various religious rituals and social events, due in part perhaps to its antiseptic properties.
GC-MS based metabolomics revealed medicinal compounds present in raksi collected from high altitudes of Singalila Ridge of the Himalayas. Study claims raksi contains compounds which are useful as a remedy of high altitudes sickness.
Serving
Raksi is often served in a bhatti glass and during special occasions, the drink is poured from a great height via a pitcher with a small spout, making an entertaining spectacle.
Production
Raksi is produced, sold and mostly consumed at rustic distilleries scattered around the countryside. Usually it is not aged before consumption. A large amount of wood is used in the distillation process.
See also
Alcohol in Nepal
Ara, a Bhutanese drink
Chhaang, a Tibetan and Nepalese drink
List of Tibetan dishes
References
External links
Traditional way of making rice wine in Nepal
Alcohol in Nepal
Indian drinks
Nepalese drinks
Tibetan cuisine
Distilled drinks
Rice wine
Traditional Indian alcoholic beverages | Raksi | [
"Chemistry"
] | 534 | [
"Distillation",
"Distilled drinks"
] |
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