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Fusel alcohols or fuselol , also sometimes called fusel oils in Europe, are mixtures of several higher alcohols (those with more than two carbons, chiefly amyl alcohol ) produced as a by-product of alcoholic fermentation . [ 1 ] The word Fusel [ˈfuːzl̩] is German for "bad liquor ". [ 2 ]
Whether fusel alcohol contributes to hangover symptoms is a matter of scientific debate. A Japanese study in 2003 concluded that "the fusel oil in whisky had no effect on the ethanol-induced emetic response" in the Asian house shrew . Additionally, consumption of fusel oils with ethanol suppressed subjects' subsequent taste aversion to alcohol, which suggested subjects' hangover symptoms were lessened, according to the journal. [ 3 ]
Fusel oil and fusel-oil acetates are used in the lacquer industry as high boiling point solvents . [ 4 ]
Excessive concentrations of some alcohols other than ethanol may cause off-flavors, sometimes described as "spicy", "hot", or "solvent-like". Some beverages, such as rum , whisky (especially bourbon ), incompletely rectified vodka (e.g. Siwucha ) and traditional ales and ciders , are expected to have relatively high concentrations of non-hazardous alcohols as part of their flavor profile. However, in other beverages, such as Korn , vodka and lagers , the presence of alcohols other than ethanol is considered a fault . [ 5 ] [ failed verification ]
The compounds involved are chiefly the following: [ 6 ]
Other higher alcohols that can be produced during fermentation include:
During distillation , fusel alcohols are concentrated in the feints or "tails" at the end of the distillation run. They have an oily consistency, which is noticeable to the distiller, hence the other name "fusel oil". If desired, these heavier alcohols can be almost completely separated in a reflux still . On the other hand, freeze distillation does not remove fusel alcohols. [ citation needed ]
Fusel alcohols can be reduced during fermentation by lowering the fermenter's temperature or increasing the oxygen content. [ 7 ] | https://en.wikipedia.org/wiki/Fusel_alcohol |
The Fushun process is an above-ground retorting technology for shale oil extraction . It is named after the main production site of Fushun , Liaoning province in northeastern China .
The Fushun process was developed and utilized for the extraction of shale oil in China during the mid-1920s. [ 1 ] The commercial-scale utilization of the process began in 1930 with the construction of "Refinery No. 1". [ 2 ] [ 3 ] After World War II, the shale oil production was ceased, but 100 Fushun-type oil shale retorts were restored in 1949. [ 4 ] In 1950, total 266 retorts were in operation, each with the capacity of 100–200 tons of shale oil per day. [ 2 ]
With the discovery of Daqing oil field in the 1960s, the shale oil production declined and Sinopec , an operator of shale oil production these times, shut down its oil shale operations in the beginning of the 1990s. [ 4 ] At the same time, the Fushun Oil Shale Retorting Plant, using Fushun process technology, was established as a part of the Fushun Mining Group . It started production in 1992. [ 3 ] In 2005, China became the largest shale oil producer in the world. [ 2 ]
In 1985–86, Sinopec used the Fushun process for a test processing of Jordan's oil shale from the El Lajjun deposit. Although the process was technically viable, the cooperation was halted due to high operation costs. [ 5 ] [ 6 ]
The Fushun process is classified as an internal combustion technology but also includes external gas heating. [ 7 ] It uses a vertical cylindrical type shaft retort, with outside steel plate lined with inner fire bricks. The retort has height over 10 metres (33 ft) and its inner diameter is about 3 metres (9.8 ft). Raw oil shale particles with the size of 10 to 75 millimetres (0.4 to 3.0 in) are fed from the top of the retort. At the upper section of the retort oil shale is dried and heated by the ascending hot gases, which pass upward through the descending oil shale causing decomposition of the rock. The pyrolysis takes place at about 500 °C (930 °F). [ 1 ] The produced oil vapor and gases exit from the top of the retort; hot gases and oil vapors move from the bottom to the top directly, and not diagonally like in Kiviter process . [ 8 ] During the pyrolysis process, oil shale is decomposed to shale coke ( char ), which together with the ascending air-steam is burnt in the lower part of the retort to heat gases necessary for pyrolysis. These gases are recirculated; after leaving retort, they are cooled in a condensation system, where shale oil is condensed, and re-heated in a heating furnace about 500 °C (930 °F) to 700 °C (1,290 °F) before reinserting into the retort. The shale ash exits from a rotating water dish that acts as a seal and cooler at the bottom of the retort. [ 1 ]
Retorts are operated in sets and have a heat carrier preparation unit and rotating water seals designed for the whole set instead of a single retort as in case of the Kiviter retort . Regenerative furnaces are located next to the retorts and they are operating in two cycles – the combustion cycle and the gas heating cycle. During the combustion cycle, a furnace is heated up to 1,000 °C (1,830 °F) by combustion gases. After the combustion cycle, retort gases from the condensation system is inserted into a furnace for their heating. [ 8 ] By alternating furnaces, one furnace is always available for heating retort gas. Twenty retorts typically share one condensation system and a set of heating furnaces. [ 1 ]
Advantages of the Fushun process include small investment and stable operation. [ 9 ] The process is characterized by the high thermal efficiency, but due to the addition of air into the retort, the nitrogen dilutes the pyrolysis gas. In addition, the excess oxygen in retort burns out a part of produced shale oil, which reduce the shale oil yield. The oil yield of the Fushun retort accounts for about 65% of Fischer Assay . [ 1 ] Disadvantage of this process is a high water consumption amounting to 6–7 barrels of water per barrel of produced shale-oil, and great quantities of waste shale. It is not suitable of ores with small size and oil content lower than 5%. [ 9 ]
As the capacity of single retort is limited, Fushun process is suitable for small-scale retorting plants, and for processing lean oil shale with low gas yield. [ 1 ]
Fushun process is used only in China. The Fushun Mining Group operates the largest by capacity shale oil plant in the world (Fushun Shale Oil Plant) consisting of 180 Fushun retorts. [ 6 ] [ 8 ] Each retort processes about 4 tonnes of oil shale per hour. [ 6 ] [ 8 ] | https://en.wikipedia.org/wiki/Fushun_process |
The fusibility of a material refers to the ease at which the material can be fused together, or to the temperature or amount of heat required to melt a material. [ 1 ] Materials such as solder require a relatively low melting point so that when heat is applied to a joint, the solder will melt before the materials being soldered together melt, i.e. high fusibility. On the other hand, firebricks used for furnace linings only melt at very high temperatures (and then they retract, or decompose, or become fracture-prone) and so have low fusibility. Perhaps refractory materials often have low fusibility.
To find the fusibility of certain compounds/materials, there are 2 methods:
The most common test used to determine fusibility is to join two pieces with a variable heat source, increasing the temperature or power used in steps, and testing bond strength for each step. If there is no step with good bond strength after joining, then fusibility is said to be low.
In the context of coal analysis, ash fusibility values of the residual coal ash of a coal are often specified. The values are determined using an empirical method based on the geometrical changes upon heating to a relevant temperature, of a conical ash sample. The fusibility of the ash is of interest because it roughly indicates the properties of the clinker that will be produced during burning. [ 2 ] | https://en.wikipedia.org/wiki/Fusibility |
A fusible alloy is a metal alloy capable of being easily fused , i.e. easily meltable, at relatively low temperatures. Fusible alloys are commonly, but not necessarily, eutectic alloys.
Sometimes the term "fusible alloy" is used to describe alloys with a melting point below 183 °C (361 °F; 456 K). Fusible alloys in this sense are used for solder .
Fusible alloys are typically made from low melting metals.
There are 14 low melting metallic elements that are stable for practical handling. These are in 2 distinct groups:
The 5 alkali metals have 1 s electron and melt between +181 (Li) and +28 (Cs) Celsius;
The 9 poor metals have 10 d electrons and from none (Zn, Cd, Hg) to three (Bi) p electrons, they melt between -38 (Hg) and +419 (Zn) Celsius.
From a practical view, low-melting alloys can be divided into the following categories:
A practical reason here is that the chemical behaviour of alkali metals is very distinct from poor metals. Of the 9 poor metals Hg (mp -38 C) and Ga (mp +29 C) have each their distinct practical issues, and the remaining 7 poor metals from In (mp +156 C) to Zn (mp +419 C) can be viewed together.
Of elements which might be viewed as related but do not share the distinct properties of poor metals:
Po is estimated to melt at 254 C and might be poor metal by properties but is too radioactive (longest halflife 125 years) for practical use;
At same reasoning as Po;
Sb melts at 630 C and is regarded as semimetal rather than poor metal;
Te is also regarded as semimetal not poor metal;
of other metals, next lowest melting point is Pu, but its melting point at 640 Celsius leaves a 220 degree gap between Zn and Pu, thus making the "poor metals" from In to Zn a natural group.
Some reasonably well-known fusible alloys are Wood's metal , Field's metal , Rose metal , Galinstan , and NaK .
Melted fusible alloys can be used as coolants as they are stable under heating and can give much higher thermal conductivity than most other coolants; particularly with alloys made with a high thermal conductivity metal such as indium or sodium . Metals with low neutron cross-section are used for cooling nuclear reactors .
Such alloys are used for making the fusible plugs inserted in the furnace crowns of steam boilers , as a safeguard in the event of the water level being allowed to fall too low. When this happens the plug, being no longer covered with water, is heated to such a temperature that it melts and allows the contents of the boiler to escape into the furnace. In automatic fire sprinklers the orifices of each sprinkler is closed with a plug that is held in place by fusible metal, which melts and liberates the water when, owing to an outbreak of fire in the room, the temperature rises above a predetermined limit. [ 1 ]
Bismuth on solidification expands by about 3.3% by volume. Alloys with at least half of bismuth display this property too. [ 2 ] This can be used for mounting of small parts, e.g. for machining, as they will be tightly held. [ citation needed ]
Starting with a table of component elements and selected binary and multiple systems ordered by melting point:
Yield strength 3,950 psi (27.2 MPa), tensile strength 4,442 psi (30.63 MPa). [ 18 ]
Then organized by practical group and alphabetic symbols of components:
Most of the pairwise phase diagrams of 2 component metal systems have data available for analysis, like at https://himikatus.ru/art/phase-diagr1/diagrams.php Taking the pairwise alloys of the 7 poor metals other than Hg and Ga, and ordering the pairs (total 21) by alphabetic of these elements Bi, Cd, In, Pb, Sn, Tl, Zn are as follows:
Considering the binary systems between alkali metals: Li only has appreciable solubility in pair
The other three alkali metals:
practically do not dissolve Li even when liquid and therefore their melting points are not lowered by presence of Li
Na is in liquid phase miscible with all three heavier alkali metals, but on freezing forms intermetallic compounds and eutectics:
The 3 binary systems between the three heavier alkali metals are all miscible in solid at melting point, but all form poor solid solutions that have melting point minima. This is distinct from eutectic: at eutectic point, two solid phases coexist, and close to eutectic point, the liquidus temperature rises rapidly as just one separates, whereas at poor solid solution melting point minimum, there is a single solid phase, and away from the minimum the liquidus temperature rises only slowly. | https://en.wikipedia.org/wiki/Fusible_alloy |
Fusion Energy Foundation (FEF) was an American non-profit think tank co-founded by Lyndon LaRouche in 1974 in New York. It promoted the construction of nuclear power plants , research into fusion power and beam weapons and other causes. The FEF was called fusion's greatest private supporter. It was praised by scientists like John Clarke , who said that the fusion community owed it a "debt of gratitude". By 1980, its main publication, Fusion , claimed 80,000 subscribers.
The FEF included notable scientists and others on its boards, along with LaRouche movement insiders in management positions. It published a popular magazine, Fusion , and a more technical journal as well as books and pamphlets. It conducted seminars and its members testified at legislative hearings. It was known for soliciting subscriptions to their magazines in U.S. airports, where its confrontational methods resulted in conflicts with celebrities and the general public.
The FEF has been described by many writers [ who? ] as a " front " for the U.S. Labor Party and the LaRouche movement . By the mid-1980s, the FEF was being accused of fraudulent fundraising on behalf of other LaRouche entities. Federal prosecutors forced it into bankruptcy in 1986 to collect contempt of court fines, a decision that was later overturned when a federal bankruptcy court found that the government had acted "in bad faith". [ 1 ] Key personnel were convicted in 1988.
According to an article in The Nation , the Fusion Energy Foundation had physicists, corporate executives, and government planners on its board of advisors, many unaware of the foundations connection to the U.S. Labor Party, while the board of directors was filled with LaRouche movement regulars and some party outsiders. [ 2 ]
A 1983 report published by The Heritage Foundation said that the foundation briefly gained the confidence of respected scientists who lent their reputations to it but it warned that they risked their reputations by doing so. [ 3 ]
Lyndon LaRouche was a co-founder and one of the three members of the foundation's board of directors. Steven Bardwell, a nuclear physicist, was another director. [ 4 ] The executive director was Morris Levitt in the 1970s and Paul Gallagher in the 1980s. Michael Gelber was the Central New York regional representative. Dennis Speed was the regional coordinator for Boston and Harley Schlanger was the southern regional coordinator. Uwe Parpart Henke was the director of research. [ 5 ] Jon Gilbertson was the director of nuclear engineering. [ 6 ] Marsha Freeman was a representative of the FEF's International Press Service. [ 7 ] Charles B. Stevens, a chemical engineer, authored scores of articles on fusion energy research and development for both the earlier publication, The Fusion Energy Foundation Newsletter, and its successor, Fusion.
Eric Lerner was director of physics in 1977. Other notable scientists who wrote for FEF publications and lectured under its auspices include Friedwardt Winterberg , Krafft Arnold Ehricke , and Winston H. Bostick . Melvin B. Gottlieb received an award from the FEF. Adolf Busemann also received an award at a special dinner. [ 4 ]
In 1977, Executive Director Morris Levitt asserted that nuclear fusion power plants could be built by 1990 if the U.S. spent $50 to $100 billion on research. [ 8 ] The same year he predicted that there would be no United States in the 21st century if President Jimmy Carter 's ban on building breeder reactors was maintained. [ 9 ] The director of the fusion power program at Argonne National Laboratory , Charles Baker, said in 1983 that the FEF was "overstating" the prospect of practical fusion power in the near future. "The judgment of the vast majority of the people actually working in fusion believe it will take substantially longer" than the few years predicted by the FEF, according to Baker. [ 10 ]
By 1980, the Fusion Energy Foundation had close contacts with fusion researchers. They became a conduit for information between researchers who were sequestered in secret research. Even the head of fusion research for the Federal Government cooperated with the foundation. It was praised by scientists like John Clarke , who said that the fusion community owed it a "debt of gratitude". [ 11 ] However the politicization of the foundation's journals and the LaRouche views printed in them repelled the scientists involved, according to The Nation . [ 2 ]
The FEF received publicity in 1981 when it published a book explaining how to build a hydrogen bomb written by University of Nevada, Reno , professor Friedwardt Winterberg . The publication came two years after a magazine, The Progressive , had tried to print similar information but was prevented by an injunction that became the United States v. The Progressive . The government dropped the case after the information was published by the FEF. The author of the original article later learned that a diagram by Uwe Papert published in 1976 in a LaRouche publication contained two important details of the weapon's design that he had been wrong about. [ 12 ]
The colonization of Mars is a major proposal of the LaRouche movement. Friedwardt Winterberg described how rocket engines incorporating fusion micro-explosions could provide enough acceleration to convey a large mass in a reasonable amount of time, a concept derived from Project Daedalus . [ 13 ]
In 1979 the Fusion Energy Foundation created the Independent Commission of Inquiry to investigate the accident at the Three Mile Island nuclear power plant. The commission's members included Morris Levitt, Jon Gilbertson, Charles Bonilia. [ 6 ] The commission determined that the accident must have been caused by sabotage because no other explanation was possible. According to Gallagher, "New evidence is accumulating that sabotage very likely occurred". [ 14 ] According to the Herald newspaper of Titusville, Pennsylvania , when asked by reporters for evidence Gilbertson said he had none. [ 15 ]
According to Fusion , two members of the FEF went to the Soviet Union to attend conference on "laser interaction" in December 1978. [ 11 ]
In 1982 and 1983, members of the LaRouche movement met repeatedly with the director of defense programs for the National Security Council , Ray Pollock, while he was developing the basis for Ronald Reagan 's "Star Wars" program, officially called the Strategic Defense Initiative (SDI). [ 16 ] Pollock eventually said in the National Security Council (NSC) that LaRouche is "a frightening kind of fellow". The FEF held a seminar on beam weapons in October 1983, at the Dirksen Senate Office Building . [ 11 ] According to the American Physical Society , FEF members disrupted a 1986 conference on SDI to which they were not invited, and only stopped after being threatened with police action. [ 17 ]
After Ronald Reagan announced SDI the LaRouche movement made claims for having been the originators of the proposal, which reportedly "concerned" some people in the administration and in Congress, but no correction was made by them. [ 11 ] The FEF lobbied state legislatures and testified before congressional hearings on behalf of beam weapons. [ 11 ] Steven Bardwell resigned from the board of advisors in early 1984, reportedly because of money questions and a belief that the organization was losing its independence by becoming too solicitous of the Reagan administration in general, and in particular the Central Intelligence Agency , the Defense Intelligence Agency , and the NSC. [ 11 ]
As with other LaRouche entities, representatives of the Fusion Energy Foundation gave testimony to a number of congressional hearings. In addition to addressing committees on energy matters, FEF representatives, including Eric Lerner , also testified on matters such as the nomination of Cyrus Vance for Secretary of State . [ 18 ]
The FEF campaigned on behalf of Arthur Rudolph , a NASA rocket scientist who was forced to leave the U.S. in 1982 following an investigation into his role in the Mittelwerk rocket factory in Nazi Germany . [ 4 ]
Psychiatrist Ned Rosinsky spoke as a representative of the FEF at a Wisconsin state legislative hearing on criminal penalties for drug possession in 1977. He testified that "marijuana is a medically dangerous drug until proved otherwise", citing studies showing brain damage and a reduction in white blood cells caused by the habitual use of cannabis . [ 19 ]
Under the auspices of Pakdee Tanapura, [ 4 ] a wealthy Thai landowner, the FEF and EIR held a seminar in 1983 on the proposed construction of the Kra Canal across Thailand. [ 20 ] Their plan favored the use of nuclear explosions to speed excavation. A second seminar was held in 1984, [ 20 ] and in 1986 the FEF published a report by U.H. Von Papart on the feasibility and financing for the project. [ 21 ]
The FEF has been described by many writers as a " front " for the U.S. Labor Party and the LaRouche movement , [ 23 ] [ 24 ] [ 25 ] [ 26 ] [ 27 ] In a National Review article published in 1979, former member Gregory Rose said that the primary purpose of the Fusion Energy Foundation was raising money. [ 25 ] Milton Copulous, director of energy studies for The Heritage Foundation , called FEF "a front the USLP uses to win the confidence of unsuspecting businessmen". [ 3 ] In 1981, the FEF reported $3.5 million of revenue. [ 28 ]
According to a representative in Toronto, Richard Sanders, FEF contributions gathered in Canada were sent to the United States to support the presidential campaigns of Lyndon LaRouche. [ 29 ] In 1983, an FEF spokesperson said that there was no financial link between the foundation and LaRouche's campaigns. [ 10 ] Although the FEF denied any financial connection to LaRouche's U.S. Labor Party , the two organizations reportedly shared offices in New York City. [ 29 ] According to an interview with a former member presented as evidence in LaRouche vs. NBC in 1984:
Money from the . . . profit-making organizations went into political campaigns and was not correctly reported. Money from the tax-exempt [FEF] was given to the political campaign, unbeknownst to the people who made the contributions. . . . Someone would contribute to the [FEF] because they believed in nuclear power and their contribution would turn up as a contribution for . . . [LaRouche's] presidential campaign. [ 30 ]
Barbara Mikulski filed a complaint with the Federal Election Commission asserting that the FEF was improperly raising funds for a LaRouche-affiliated candidate, Debra Freeman, in a 1982 congressional campaign. The FEF replied that the fundraising was done under contract to the Caucus Distributors, Inc. (CDI), another LaRouche enterprise. [ 31 ]
When FEF director Steven Bardwell resigned in 1984, he complained that funds raised by the FEF through subscriptions were being diverted to other LaRouche entities. According to Bardwell, LaRouche said that Bardwell's sense of obligation to subscribers was "misplaced", and that "whether or not they knew it, they had contributed money to support Lyndon LaRouche and his ideas". LaRouche reportedly also said that the most important expenditures were for his personal security, and other expenses had a lower priority. [ 32 ]
In September 1985, the Internal Revenue Service (IRS) withdrew the FEF's status as a tax-deductible non-profit, Section 501(c)(3) , which it had had since 1978. The stated reason was that it had failed to file a tax return in the prior two years. [ 33 ] In October 1986, New York Attorney General Robert Abrams sued to dissolve the FEF, charging that it fraudulently solicited donations as tax-deductible after their exemption had been withdrawn, and for failure to file required forms. Paul Gallagher, described the suit as "part of an escalating witch hunt against FEF board member Lyndon LaRouche." [ 34 ] Two weeks later, the IRS restored the FEF's tax exempt status, saying it had made an error though privacy rules prevented further elaboration. [ 35 ]
Subscribers to Fusion complained that their credit cards were being billed for unauthorized charges. In one example a man who had subscribed to Fusion found that he had been billed for $1000, for which he received promissory notes in the mail. [ 36 ] Prosecutors charged that the FEF and other LaRouche related groups had made improper charges to the credit cards of about 1,000 people. [ 37 ]
Fundraisers also solicited larger sums. A 71-year-old California woman loaned the FEF $100,000 after making smaller loans to other LaRouche-related entities. FEF fundraisers refused to take a check and drove her to the bank so she could wire the money directly. The FEF made no interest or principal payments on the loans. After she sued the FEF for repayment they settled, acknowledged the loans, and agreed to a schedule of payments. They stopped making payments after sending a few checks, one of which bounced. She filed suit in Virginia in an attempt to attach FEF assets there. [ 34 ]
In a widely reported case, a 79-year-old retired steel executive gave or loaned a total of $2.6 million over a 14 months period in amounts ranging from $250 to $350,000, according to a lawsuit. He said he was not a supporter of LaRouche political campaigns, and that he gave the money, "Because I got so many telephone calls requesting donations". He said "I'm mad at myself now" for having turned over the money, most of which went to the FEF. When he told the fundraisers that he only wanted to give money to his family in the future, he was reportedly told that gifts to the LaRouche movement "would be of greater benefit" to the family because LaRouche's supporters "were changing the world situation". [ 38 ] The FEF gave the donor a plaque which said, "Benjamin Franklin Award Honoring Special Contributions to the Future of Science". [ 38 ] In a Nightline interview, LaRouche called him "a person who's been associated with us as a supporter for a long time." [ 38 ] LaRouche's treasurer, Edward Spannaus, said the "drug lobby" was responsible for accusations that the LaRouche movement had encouraged supporters to turn over their savings. [ 38 ]
During a 1986 Virginia state investigation, an undercover policeman purchased subscriptions to Fusion and another LaRouche movement publication, Executive Intelligence Review , at Washington National Airport . He then received 22 "abusive and demanding" telephone calls asking for loans or donations. He was told the money was needed to fight AIDS and to keep LaRouche out of jail. [ 37 ] When he agreed to make a loan he received a letter of acknowledgement and an invitation to tour the LaRouche headquarters in Leesburg, Virginia . [ 39 ]
Not all supporters contributed due to pressure. An Oklahoman oilman subscribed to Fusion and liked LaRouche's views on nuclear power. He donated thousands of dollars as well as buying a $900,000 estate for LaRouche's use, charging rent to cover the mortgage. [ 40 ]
Supporters of the Fusion Energy Foundation became well known for their aggressive fundraising in U.S. airports in the late 1970s and early 1980s, along with Hare Krishnas and Moonies . They set up tables to sell publications from the FEF and other LaRouche organizations and displayed provocatively captioned, hand-lettered posters. The FEF members would shout slogans to passers-by to get attention, and sometimes accused those who disagreed with them of being homosexuals. One writer called them the "most obnoxious of the groups...infesting the airports." [ 41 ] An article in The Boston Globe called them "the kooks at the airport" who solicited money using posters often denouncing Jane Fonda , [ 42 ] a target of the LaRouche movement because of her support for environmental causes. [ 43 ]
The FEF had slogans and bumper stickers with texts like:
In 1981, Fonda's brother, actor Peter Fonda was enraged by a sign in Denver's Stapleton Airport that said, "Feed Jane Fonda to the Whales." He cut up the sign with his pocketknife. The FEF members pressed charges for destruction of property leading Fonda to miss his flight, though he was allowed to leave without posting bond. The case was dropped when the FEF members failed to appear on the court date. [ 43 ]
In 1982, Ellen Kaplan, an FEF member raising money in the Newark Airport , spotted former Secretary of State Henry Kissinger and his wife Nancy . Kissinger was flying to Boston for a heart operation. Kaplan went up to Kissinger and asked him why he had "prolonged the war in Vietnam", and then, "Mr. Kissinger, do you sleep with young boys at the Carlyle Hotel?" At that point Nancy Kissinger grabbed Kaplan by the throat and asked, "Do you want to get slugged?" Kaplan later explained that she was a "longtime opponent" of Kissinger, and that she "wanted to confront the man with how low he is." She pressed charges and Dennis Speed, an FEF coordinator, said they would make Kissinger into "a laughingstock". [ 48 ] The Newark municipal judge acquitted Mrs. Kissinger, saying that she had exhibited "a reasonable spontaneous, somewhat human reaction" and that there was no injury. [ 43 ]
In 1977, the Fusion Energy Foundation received a temporary injunction to prevent the Federal Bureau of Investigation (FBI) from harassing it or interfering with its activities. The suit claimed that the FBI Director, Clarence M. Kelley , had personally ordered FBI agents to disrupt FEF conferences and dissuade scientists from participating. The injunction also included U.S. Attorney General Griffin Bell and Secretary of Energy James R. Schlesinger . [ 49 ]
In 1986, the FEF was ordered by a state court to stop raising funds in California due to complaints. [ 50 ] In a separate action the same year, the FEF, along with other LaRouche entities, was named in a lawsuit charging violations of the Federal Racketeer Influenced and Corrupt Organizations Act (RICO) that was filed in San Francisco. [ 51 ] In an unusual move, the assets of the FEF and related entities were seized before the suit was unsealed, because the plaintiff's lawyer convinced the judge that the entities would hide their assets. [ 52 ] In 1987, the FEF and five other LaRouche entities were prohibited from operating in Virginia. [ 53 ] In 1988, the FEF was sued by the California Attorney General's office. The suit alleged that FEF fundraisers had flown down from Washington to take the 79-year old Laguna Hills resident to her bankbox where they got from her stock certificates worth $104,452, described by her accountant as the woman's life savings. In their place was a receipt signed by Paul Gallagher, executive director of the FEF. LaRouche said the charges were "totally frivolous" and the result of corruption in the Attorney General's office. [ 54 ]
During a federal grand jury investigation into fundraising practices in 1985, the FEF and other LaRouche entities were given subpoenas requiring that they turn over documents and provide a keeper of records to testify. They failed to surrender the documents and the keepers of records they sent were appointed the day before. When ordered to give the home address of FEF Executive Director Gallagher, the address turned out to be a vacant lot. [ 55 ] Five months after the subpoenas were served, and after several hearings on the matter, U.S. District Judge A. David Mazzone found the FEF in contempt of court and levied a fine of $10,000 per day to enforce the subpoena starting in March 1986. Similar fines were placed on other LaRouche organizations, totalling $45,000 per day. [ 56 ] The FEF and the other LaRouche entities appealed the fines repeatedly, and were denied each time. [ citation needed ] They appealed to the U.S. Supreme Court, which refused to review the lower court decision. [ 57 ]
In October 1986, hundreds of federal and state law enforcement conducted a coordinated raid on the offices of LaRouche enterprises, including those of the FEF, and seized the documents that had been subpoenaed in 1985. The FEF and other entities argued in court that the search warrants had been improperly executed, and that documents were taken in violation of their Fourth Amendment rights. The Court of Appeals denied their appeal. [ citation needed ]
Six months later, in April 1987, the federal prosecutors obtained an unusual involuntary bankruptcy procedure against the FEF and other groups in order to settle the contempt of court fines which had grown to $21.4 million. The government claimed that the LaRouche groups were selling properties in order to hide the cash. [ 58 ] The petition was granted by Judge Martin V.B. Bostetter and the federal government seized the property of the FEF and other groups. Reportedly, they only recovered $86,000 in assets. [ 59 ] In October 1989, the FEF's bankruptcy petition was reviewed by Judge Bostetter who dismissed it, effectively reversing his April 1987 ruling. He noted that two of the entities, including FEF, were nonprofit fund-raisers and therefore ineligible for involuntary bankruptcy actions. He found that the government's actions and representations in obtaining the bankruptcy had the effect of misleading the court as to the status of the organization. [ 60 ]
Members of the scientific and fusion community noted the closing of the FEF publications. [ 61 ] A full-page advertisement protesting the closures, published in IEEE Spectrum , was signed by people associated with the fusion and SDI fields, including 22 employees of the Lawrence Livermore National Laboratory . [ 4 ]
The International Journal of Fusion Energy was published intermittently from March 1977 to October 1985, putting out at least 11 issues. [ 62 ] For some time Robert James Moon acted as editor-in-chief.
Morris Levitt was the editor-in-chief as of 1979, but by the mid-1980s the job was taken over by Steven Bardwell, and by 1986 it was Carol White. Marjorie Mazel Hecht was the managing editor. By 1980, it claimed 80,000 subscribers. [ 11 ]
21st Century Science and Technology is a quarterly magazine established in 1988 following the federal government's closing down of its predecessor Fusion Magazine (1977 to 1987). It has the same editor and material as Fusion . [ 63 ] The last hard copy issue of the magazine published was the Winter 2005-2006 issue. Subsequent issues are available in electronic PDF format only. The magazine deals with a variety of issues, including criticism of claims of anthropogenic global warming , promotion of the use of DDT [ 64 ] and support for an alternative to the standard atomic theory , based on the "Moon model" of Robert James Moon . [ 65 ] Notable writers include: J. Gordon Edwards , Zbigniew Jaworowski and Paul Marmet . According to Science and other sources, it is published by supporters of Lyndon LaRouche. [ 66 ]
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Fusion Nuclear Science Facility (FNSF) is a low cost, low aspect ratio compact tokamak reactor design, aiming for a 9 Tesla field at the plasma centre. [ 1 ]
It is considered a step after ITER on the path to a fusion power plant. [ 2 ]
Because of the high neutron irradiation damage expected, non-insulating superconducting coils are being considered for it. [ 1 ]
This article about energy , its collection, its distribution, or its uses is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Fusion_Nuclear_Science_Facility |
Fusion bonded epoxy coating , also known as fusion-bond epoxy powder coating and commonly referred to as FBE coating , is an epoxy -based powder coating that is widely used to protect steel pipe used in pipeline construction from corrosion . It is also commonly used to protect reinforcing bars (though being phased out as of 2005 [ 1 ] ) and on a wide variety of piping connections, valves etc. [ 2 ] FBE coatings are thermoset polymer coatings. [ 3 ] They come under the category of protective coatings in paints and coating nomenclature. The name fusion-bond epoxy is due to resigning cross-link and the application method, which is different from a conventional paint. In 2020 the market size was quoted at 12 billion dollars. [ 4 ]
The resin and hardener components in the dry powder FBE stock remain unreacted at normal storage conditions. At typical coating application temperatures, usually in the range of 180 to 250 °C (356 to 482 °F), the contents of the powder melt and transform to a liquid form. The liquid FBE film wets and flows onto the steel surface on which it is applied, and soon becomes a solid coating by chemical cross-linking, assisted by heat. This process is known as “fusion bonding”. The chemical cross-linking reaction taking place in this case is irreversible. Once the curing takes place, the coating cannot be returned to its original form by any means. Application of further heating will not “melt” the coating and thus it is known as a “ thermoset ” coating.
Since their introduction as a protective coating in early 1960s, FBE coating formulations had gone through vast improvements and developments. Today, various types of FBE coatings, which are tailor-made to meet various requirements are available. FBEs are available as stand-alone coatings as well as a part in multi-layers. FBE coatings with different properties are available to suit coating application on the main body of pipe, internal surfaces, girth welds as well as on fittings.
Essential components of a powder coating are: [ 5 ]
The resin and hardener part together is known as the "Binder". As the name indicates, in Fusion bonded epoxy coatings the resin part is an "epoxy" type resin. “ Epoxy ” or “Oxirane” structure contains a three membered cyclic ring — one oxygen atom connected to two carbon atoms – in the resin molecule. This part is the most reactive group in the epoxy resins. Most commonly used FBE resins are derivatives of bisphenol A and epichlorohydrin .
However, other types of resins (for example bisphenol F type) are also commonly used in FBE formulations to achieve various properties, combinations or additions. Resins are also available in various molecular lengths, to provide unique properties to the final coating.
The second most important part of FBE coatings is the curing agent or hardener. Curing agents react either with the epoxy ring or with the hydroxyl groups, along the epoxy molecular chain. Various types of curing agents, used in FBE manufacture, include dicyandiamide, aromatic amines, aliphatic diamines and organic acid anhydrides . [ 6 ] The selected curing agent determines the nature of the final FBE product – its cross linking density, chemical resistance, brittleness, flexibility etc. The ratio of epoxy resins and curing agents in a formulation is determined by their relative equivalent weights.
In addition to these two major components, FBE coatings include fillers, pigments, extenders and various additives, to provide desired properties. These components control characteristics such as permeability, hardness, colour, thickness, gouge resistance etc. All of these components are normally dry solids, even though small quantities of liquid additives may be used in some FBE formulations. If used, these liquid components are sprayed into the formulation mix during pre-blending in the manufacturing process.
The standard for FBE coating of pipelines is ISO 21809 Part 2.
Essential parts of a powder coating manufacturing plant are:
The components of the FBE formulation are weighed and pre-blended in high speed mixers. The mix is then transferred to a high-shear extruder. FBE extruders incorporate a single or dual screw setup, rotating within a fixed clamshell barrel. A temperature range [ vague ] from 50 °C to 100 °C is used within the extruder barrel. This setup compresses the FBE blend, while heating and melting it to a semi-liquid form. During this process, the ingredients of the molten mix are dispersed thoroughly. Because of the fast operation of the extruder and relatively low temperature within the barrel, the epoxy and hardener components will not undergo a significant chemical reaction. The molten extrudate then passes between cold-rollers and becomes a solid, brittle sheet. It then moves to a “Kibbler”, which chops it into smaller chips. These chips are ground, using high speed grinders (classifiers) to a particle size of less than 150 micrometers (standard specifications requires 100% pass through in 250 micrometer sieves and maximum 3% retains in 150 micrometer sieve). The final product is packaged in closed containers, with particular care given to avoid moisture contamination. Normal storage temperatures of FBE powder coatings are below 25 °C (77 °F) in air-conditioned warehouses.
Regardless of the shape and type of steel surface to be coated, the FBE powder coating application has three essential stages:
The advantage of pipe and rebar is that their round shape allows continuous linear application over the exterior surface, while the parts are moved in a conveyor through the powder application booth, ensuring high throughput. On fittings, etc., the coating is applied by manual spray guns. Another method of application is "fluid-dip" process, in which the heated components are dipped in a fluidized powder bed (see below).
Blast cleaning is the most commonly used method for preparation of steel surfaces. [ 7 ] This effectively removes rust, scale, slats, etc., from the surface and produces an industrial grade cleaning and a rough surface finish. The roughness of the steel achieved after blasting is referred to as profile, which is measured in micrometers or mils . Commonly used to profile ranges for FBE coatings are 37 to 100 micrometers (1.5 to 4 mils). Profile increases the effective surface area of the steel. The cleanliness achieved is assessed to ISO 8501-1 grades: these originated from a set of photographic slides in a Swedish standard (SIS) showing exemplars of the common terminology of white-metal, near white-metal, etc. Typically, SA 2½ is used for pipelines (equivalent to NACE N°2).
It is important to remove grease or oil contamination prior to blast cleaning. Solvent cleaning, burn-off, etc., are commonly used for this purpose. In the blast cleaning process, compressed air (90 to 110 psi/610 to 760 kPa) is used to force an abrasive onto the surface to be cleaned. Aluminum oxide, steel grit, steel shot, garnet, coal slag, etc., are the frequently used abrasives. Another method of blast cleaning is centrifugal blast cleaning, which is especially used in cleaning the exterior of pipe. In this method, abrasive is thrown to the rotating pipe body, using a specially designed wheel, which is rotated at high speed, while the abrasive is fed from the centre of the wheel.
Heating can be achieved by using several methods, but the most commonly used ones are ‘’induction heating’’ or ‘’oven heating’’. The steel part is passed through a high frequency alternating current magnetic field, which heats the metal part to the required FBE coating application temperature. Typical application temperature for a stand alone FBE is 225° to 245°C. When used as a primer in a multi-layer polyolifine system, application temperature may be dropped based on FBE manufacturer's recommendations, in order to meet the "inter-coat adhesion" parameters. Special grade FBE coatings which can be applied at temperatures as low as 175 °C has been developed recently by certain FBE powder manufacturers. Other methods of heating are ‘’oven heating’’, ‘’infra-red heating’’, etc. The FBE powder is placed on a “fluidization bed”. In a fluidization bed, the powder particles are suspended in a stream of air, in which the powder will “behave” like a fluid. Once the air supply is turned off, the powder will remain in its original form. The fluidized powder is sprayed onto the hot substrate using suitable spray guns. An electrostatic spray gun incorporates an ionizer electrode on it, which gives the powder particles a positive electric charge. The steel to be coated is “grounded” through the conveyor. The charged powder particles uniformly wraps around the substrate, and melts into a liquid form. Internal surfaces of pipes are coated using spraying lances, which travel from one end to the other end of the heated pipe at a uniform speed, while the pipe is being rotated in its longitudinal axis.
Standard coating thickness range of stand-alone FBE coatings is between 250 and 500 micrometers, even though lower or higher thickness ranges might be specified, depending on service conditions. The molten powder ‘flows’ into the profile and bonds with the steel. The molten powder will become a solid coating, when the ‘gel time’ is over, which usually occurs within few seconds after coating application. The resin part of coating will undergo cross-linking, which is known as “curing” under the hot condition. Complete curing is achieved either by the residual heat on the steel, or by the help of additional heating sources. Depending on the FBE coating system, full cure can be achieved in less than one minute to few minutes in case of long cure FBE's, which are used for internal pipe coating applications.
Rebars are coated in a similar manner as coating application, on the exterior of pipes. For FBE coating application on the interior of pipe surface, a lance is used. The lance enters into the pre-heated pipe, and starts spraying the powder from the opposite end, while the pipe is being rotated on its axis and the lance pulls out in a pre-determined speed.
On fittings such as Tee's, elbows, bends, etc., powder can be sprayed using hand held spray guns. Small sized fittings can also be coated by dipping in a fluidized bed of powder, after heating the steel to the required powder application temperature. After field welding of the pipe ends, FBE can be applied on the weld area as well.
Advantages of FBE application over conventional liquid coating application are:
There are a number of potential failure modes for Fusion bonded epoxy. One of these failure modes is by ultraviolet degradation. [ 8 ]
The world's leading FBE manufacturers are Sherwin-Williams ( Valspar ), SolEpoxy (former Henkel/Dexter), KCC Corporation , Jotun Powder Coatings , 3M , Axalta Coating Systems , Akzo Nobel , BASF , and Rohm & Haas . [ 9 ] | https://en.wikipedia.org/wiki/Fusion_bonded_epoxy_coating |
In mathematics, a fusion frame of a vector space is a natural extension of a frame . It is an additive construct of several, potentially "overlapping" frames. The motivation for this concept comes from the event that a signal can not be acquired by a single sensor alone (a constraint found by limitations of hardware or data throughput), rather the partial components of the signal must be collected via a network of sensors, and the partial signal representations are then fused into the complete signal.
By construction, fusion frames easily lend themselves to parallel or distributed processing [ 1 ] of sensor networks consisting of arbitrary overlapping sensor fields.
Given a Hilbert space H {\displaystyle {\mathcal {H}}} , let { W i } i ∈ I {\displaystyle \{W_{i}\}_{i\in {\mathcal {I}}}} be closed subspaces of H {\displaystyle {\mathcal {H}}} , where I {\displaystyle {\mathcal {I}}} is an index set. Let { v i } i ∈ I {\displaystyle \{v_{i}\}_{i\in {\mathcal {I}}}} be a set of positive scalar weights. Then { W i , v i } i ∈ I {\displaystyle \{W_{i},v_{i}\}_{i\in {\mathcal {I}}}} is a fusion frame of H {\displaystyle {\mathcal {H}}} if there exist constants 0 < A ≤ B < ∞ {\displaystyle 0<A\leq B<\infty } such that
where P W i {\displaystyle P_{W_{i}}} denotes the orthogonal projection onto the subspace W i {\displaystyle W_{i}} . The constants A {\displaystyle A} and B {\displaystyle B} are called lower and upper bound, respectively. When the lower and upper bounds are equal to each other, { W i , v i } i ∈ I {\displaystyle \{W_{i},v_{i}\}_{i\in {\mathcal {I}}}} becomes a A {\displaystyle A} -tight fusion frame. Furthermore, if A = B = 1 {\displaystyle A=B=1} , we can call { W i , v i } i ∈ I {\displaystyle \{W_{i},v_{i}\}_{i\in {\mathcal {I}}}} Parseval fusion frame. [ 1 ]
Assume { f i j } i ∈ I , j ∈ J i {\displaystyle \{f_{ij}\}_{i\in {\mathcal {I}},j\in J_{i}}} is a frame for W i {\displaystyle W_{i}} . Then { ( W i , v i , { f i j } j ∈ J i ) } i ∈ I {\displaystyle \{\left(W_{i},v_{i},\{f_{ij}\}_{j\in J_{i}}\right)\}_{i\in {\mathcal {I}}}} is called a fusion frame system for H {\displaystyle {\mathcal {H}}} . [ 1 ]
Let { W i } i ∈ H {\displaystyle \{W_{i}\}_{i\in {\mathcal {H}}}} be closed subspaces of H {\displaystyle {\mathcal {H}}} with positive weights { v i } i ∈ I {\displaystyle \{v_{i}\}_{i\in {\mathcal {I}}}} . Suppose { f i j } i ∈ I , j ∈ J i {\displaystyle \{f_{ij}\}_{i\in {\mathcal {I}},j\in J_{i}}} is a frame for W i {\displaystyle W_{i}} with frame bounds C i {\displaystyle C_{i}} and D i {\displaystyle D_{i}} . Let C = inf i ∈ I C i {\textstyle C=\inf _{i\in {\mathcal {I}}}C_{i}} and D = inf i ∈ I D i {\textstyle D=\inf _{i\in {\mathcal {I}}}D_{i}} , which satisfy that 0 < C ≤ D < ∞ {\displaystyle 0<C\leq D<\infty } . Then { W i , v i } i ∈ I {\displaystyle \{W_{i},v_{i}\}_{i\in {\mathcal {I}}}} is a fusion frame of H {\displaystyle {\mathcal {H}}} if and only if { v i f i j } i ∈ I , j ∈ J i {\displaystyle \{v_{i}f_{ij}\}_{i\in {\mathcal {I}},j\in J_{i}}} is a frame of H {\displaystyle {\mathcal {H}}} .
Additionally, if { ( W i , v i , { f i j } j ∈ J i ) } i ∈ I {\displaystyle \{\left(W_{i},v_{i},\{f_{ij}\}_{j\in J_{i}}\right)\}_{i\in {\mathcal {I}}}} is a fusion frame system for H {\displaystyle {\mathcal {H}}} with lower and upper bounds A {\displaystyle A} and B {\displaystyle B} , then { v i f i j } i ∈ I , j ∈ J i {\displaystyle \{v_{i}f_{ij}\}_{i\in {\mathcal {I}},j\in J_{i}}} is a frame of H {\displaystyle {\mathcal {H}}} with lower and upper bounds A C {\displaystyle AC} and B D {\displaystyle BD} . And if { v i f i j } i ∈ I , j ∈ J i {\displaystyle \{v_{i}f_{ij}\}_{i\in {\mathcal {I}},j\in J_{i}}} is a frame of H {\displaystyle {\mathcal {H}}} with lower and upper bounds E {\displaystyle E} and F {\displaystyle F} , then { ( W i , v i , { f i j } j ∈ J i ) } i ∈ I {\displaystyle \{\left(W_{i},v_{i},\{f_{ij}\}_{j\in J_{i}}\right)\}_{i\in {\mathcal {I}}}} is a fusion frame system for H {\displaystyle {\mathcal {H}}} with lower and upper bounds E / D {\displaystyle E/D} and F / C {\displaystyle F/C} . [ 2 ]
Let W ⊂ H {\displaystyle W\subset {\mathcal {H}}} be a closed subspace, and let { x n } {\displaystyle \{x_{n}\}} be an orthonormal basis of W {\displaystyle W} . Then the orthogonal projection of f ∈ H {\displaystyle f\in {\mathcal {H}}} onto W {\displaystyle W} is given by [ 3 ]
We can also express the orthogonal projection of f {\displaystyle f} onto W {\displaystyle W} in terms of given local frame { f k } {\displaystyle \{f_{k}\}} of W {\displaystyle W}
where { f ~ k } {\displaystyle \{{\tilde {f}}_{k}\}} is a dual frame of the local frame { f k } {\displaystyle \{f_{k}\}} . [ 1 ]
Let { W i , v i } i ∈ I {\displaystyle \{W_{i},v_{i}\}_{i\in {\mathcal {I}}}} be a fusion frame for H {\displaystyle {\mathcal {H}}} . Let { ∑ ⨁ W i } l 2 {\displaystyle \{\sum \bigoplus W_{i}\}_{l_{2}}} be representation space for projection. The analysis operator T W : H → { ∑ ⨁ W i } l 2 {\displaystyle T_{W}:{\mathcal {H}}\rightarrow \{\sum \bigoplus W_{i}\}_{l_{2}}} is defined by
The adjoint is called the synthesis operator T W ∗ : { ∑ ⨁ W i } l 2 → H {\displaystyle T_{W}^{\ast }:\{\sum \bigoplus W_{i}\}_{l_{2}}\rightarrow {\mathcal {H}}} , defined as
where g = { f i } i ∈ I ∈ { ∑ ⨁ W i } l 2 {\displaystyle g=\{f_{i}\}_{i\in {\mathcal {I}}}\in \{\sum \bigoplus W_{i}\}_{l_{2}}} .
The fusion frame operator S W : H → H {\displaystyle S_{W}:{\mathcal {H}}\rightarrow {\mathcal {H}}} is defined by [ 2 ]
Given the lower and upper bounds of the fusion frame { W i , v i } i ∈ I {\displaystyle \{W_{i},v_{i}\}_{i\in {\mathcal {I}}}} , A {\displaystyle A} and B {\displaystyle B} , the fusion frame operator S W {\displaystyle S_{W}} can be bounded by
where I {\displaystyle I} is the identity operator. Therefore, the fusion frame operator S W {\displaystyle S_{W}} is positive and invertible. [ 2 ]
Given a fusion frame system { ( W i , v i , F i ) } i ∈ I {\displaystyle \{\left(W_{i},v_{i},{\mathcal {F}}_{i}\right)\}_{i\in {\mathcal {I}}}} for H {\displaystyle {\mathcal {H}}} , where F i = { f i j } j ∈ J i {\displaystyle {\mathcal {F}}_{i}=\{f_{ij}\}_{j\in J_{i}}} , and F ~ i = { f ~ i j } j ∈ J i {\displaystyle {\tilde {\mathcal {F}}}_{i}=\{{\tilde {f}}_{ij}\}_{j\in J_{i}}} , which is a dual frame for F i {\displaystyle {\mathcal {F}}_{i}} , the fusion frame operator S W {\displaystyle S_{W}} can be expressed as
where T F i {\displaystyle T_{{\mathcal {F}}_{i}}} , T F ~ i {\displaystyle T_{{\tilde {\mathcal {F}}}_{i}}} are analysis operators for F i {\displaystyle {\mathcal {F}}_{i}} and F ~ i {\displaystyle {\tilde {\mathcal {F}}}_{i}} respectively, and T F i ∗ {\displaystyle T_{{\mathcal {F}}_{i}}^{\ast }} , T F ~ i ∗ {\displaystyle T_{{\tilde {\mathcal {F}}}_{i}}^{\ast }} are synthesis operators for F i {\displaystyle {\mathcal {F}}_{i}} and F ~ i {\displaystyle {\tilde {\mathcal {F}}}_{i}} respectively. [ 1 ]
For finite frames (i.e., dim H =: N < ∞ {\displaystyle \dim {\mathcal {H}}=:N<\infty } and | I | < ∞ {\displaystyle |{\mathcal {I}}|<\infty } ), the fusion frame operator can be constructed with a matrix. [ 1 ] Let { W i , v i } i ∈ I {\displaystyle \{W_{i},v_{i}\}_{i\in {\mathcal {I}}}} be a fusion frame for H N {\displaystyle {\mathcal {H}}_{N}} , and let { f i j } j ∈ J i {\displaystyle \{f_{ij}\}_{j\in {\mathcal {J}}_{i}}} be a frame for the subspace W i {\displaystyle W_{i}} and J i {\displaystyle J_{i}} an index set for each i ∈ I {\displaystyle i\in {\mathcal {I}}} . Then the fusion frame operator S : H → H {\displaystyle S:{\mathcal {H}}\to {\mathcal {H}}} reduces to an N × N {\displaystyle N\times N} matrix, given by
with
and
where f ~ i j {\displaystyle {\tilde {f}}_{ij}} is the canonical dual frame of f i j {\displaystyle f_{ij}} . | https://en.wikipedia.org/wiki/Fusion_frame |
Fusion ignition is the point at which a nuclear fusion reaction becomes self-sustaining . This occurs when the energy being given off by the reaction heats the fuel mass more rapidly than it cools. In other words, fusion ignition is the point at which the increasing self-heating of the nuclear fusion removes the need for external heating. [ 1 ] This is quantified by the Lawson criterion . [ 2 ] Ignition can also be defined by the fusion energy gain factor . [ 3 ]
In the laboratory , fusion ignition defined by the Lawson criterion was first achieved in August 2021, [ 4 ] and ignition defined by the energy gain factor was achieved in December 2022, [ 5 ] [ 6 ] both by the U.S. National Ignition Facility .
Ignition should not be confused with breakeven , a similar concept that compares the total energy being given off to the energy being used to heat the fuel. The key difference is that breakeven ignores losses to the surroundings, which do not contribute to heating the fuel, and thus are not able to make the reaction self-sustaining. Breakeven is an important goal in the fusion energy field, but ignition is required for a practical energy producing design. [ 7 ]
In nature, stars reach ignition at temperatures similar to that of the Sun , around 15 million kelvins (27 million degrees F). Stars are so large that the fusion products will almost always interact with the plasma before their energy can be lost to the environment at the outside of the star. In comparison, man-made reactors are far less dense and much smaller, allowing the fusion products to easily escape the fuel. To offset this, much higher rates of fusion are required, and thus much higher temperatures; most man-made fusion reactors are designed to work at temperatures over 100 million kelvins (180 million degrees F). [ 8 ]
Fusion ignition was first achieved by humans in the cores of detonating thermonuclear weapons . A thermonuclear weapon uses a conventional fission ( U-235 or Pu-239 / 241 ) "sparkplug" to generate high pressures and compress a rod of fusion fuel (usually lithium deuteride ). The fuel reaches high enough pressures and densities to ignite, releasing large amounts of energy and neutrons in the process. [ 9 ]
The National Ignition Facility at Lawrence Livermore National Laboratory performs laser-driven inertial confinement fusion experiments that achieve fusion ignition. This is similar to a thermonuclear weapon, but the National Ignition Facility uses a 1.8 MJ laser system instead of a fission weapon to compress the fuel, and uses a much smaller amount of fuel (a mixture of deuterium and tritium , which are both isotopes of hydrogen ). [ 10 ] In January 2012, National Ignition Facility Director Mike Dunne predicted in a Photonics West 2012 plenary talk that ignition would be achieved at NIF by October 2012. [ 11 ] By 2022 the NIF had achieved ignition. [ citation needed ]
Based on the tokamak reactor design, the ITER is intended to sustain fusion mostly by internal fusion heating and yield in its plasma a ten-fold return on power. [ 12 ] Construction is expected to be completed in 2025. [ citation needed ]
Experts believe that achieving fusion ignition is the first step towards electricity generation using fusion power . [ 13 ]
The National Ignition Facility at the Lawrence Livermore National Laboratory in California reported in 2021 [ 14 ] that it had triggered ignition in the laboratory on 8 August 2021, for the first time in the over-60-year history of the ICF program. [ 15 ] [ 16 ] The shot yielded 1.3 megajoules of fusion energy, an 8-fold improvement on tests done in spring 2021. [ 14 ] NIF estimates that the laser supplied 1.9 megajoules of energy, 230 kilojoules of which reached the fuel capsule. This corresponds to a total scientific energy gain of 0.7 and a capsule energy gain of 6. [ 14 ] While the experiment fell short of ignition as defined by the National Academy of Sciences – a total energy gain greater than one – most people working in the field viewed the experiment as the demonstration of ignition as defined by the Lawson criterion. [ 14 ]
In August 2022, the results of the experiment were confirmed in three peer-reviewed papers: one in Physical Review Letters and two in Physical Review E . [ 17 ] Throughout 2022, the NIF researchers tried and failed to replicate the August result. [ 18 ] However, on 13 December 2022, the United States Department of Energy announced via Twitter that an experiment on December 5 had surpassed the August result, achieving a scientific gain of 1.5, [ 19 ] [ 20 ] surpassing the National Academy of Sciences definition of ignition. [ 3 ] | https://en.wikipedia.org/wiki/Fusion_ignition |
A fusion mechanism is any mechanism by which cell fusion or virus–cell fusion takes place, as well as the machinery that facilitates these processes. Cell fusion is the formation of a hybrid cell from two separate cells. [ 1 ] [ 2 ] There are three major actions taken in both virus–cell fusion and cell–cell fusion: the dehydration of polar head groups, the promotion of a hemifusion stalk, and the opening and expansion of pores between fusing cells. [ 3 ] Virus–cell fusions occur during infections of several viruses that are health concerns relevant today. Some of these include HIV , Ebola , and influenza . [ 4 ] For example, HIV infects by fusing with the membranes of immune system cells . In order for HIV to fuse with a cell, it must be able to bind to the receptors CD4 , CCR5 , and CXCR4 . Cell fusion also occurs in a multitude of mammalian cells including gametes and myoblasts . [ 5 ]
Proteins that allow viral or cell membranes to overcome barriers to fusion are called fusogens . Fusogens involved in virus-to-cell fusion mechanisms were the first of these proteins to be discovered. [ 6 ] Viral fusion proteins are necessary for membrane fusion to take place. There is evidence that ancestral species of mammals may have incorporated these same proteins into their own cells as a result of infection. For this reason, similar mechanisms and machinery are utilized in cell–cell fusion. [ 7 ]
In response to certain stimuli, such as low pH or binding to cellular receptors, these fusogens will change conformation. The conformation change allows the exposure of hydrophobic regions of the fusogens that would normally be hidden internally due to energetically unfavorable interactions with the cytosol or extracellular fluid . These hydrophobic regions are known as fusion peptides or fusion loops, and they are responsible for causing localized membrane instability and fusion. Scientists have found the following four classes of fusogens to be involved with virus–cell or cell–cell fusions. [ 4 ]
These fusogens are trimeric , meaning they are made of three subunits . Their fusion loops are hidden internally at the junctions of the monomers before fusion takes place. Once fusion is complete, they refold into a different trimeric structure than the structure they had before fusion. These fusogens are characterized by a group of six α-helices in their post-fusion structure. This class of fusogens contains some of the proteins utilized by influenza , HIV , coronaviruses , and Ebola during infection. This class of fusogens also includes syncytins , which are utilized in mammalian cell fusions. [ 8 ] [ 4 ] [ 9 ]
Class II fusogens contain multiple β-pleated sheets . These proteins are also trimeric and take part in the insertion of fusion loops into the target membrane. Their conformation changes can be triggered by exposure to acidic environments. [ 8 ] [ 4 ] Class II fusogens have a structure distinct from Class I fusogens, but similarly lower the energy barrier for membrane fusion. Class I fusogens are involved in flaviviruses ( tick-borne encephalitis ); alphaviruses ( Semliki Forest virus , Sindbis virus , chikungunya and rubella ); and phleboviruses ( Rift Valley fever virus and Uukuniemi virus ). [ 8 ]
Class III fusogens are involved with virus–cell fusions. Much like fusogens in the previous two classes, these proteins are trimeric. However, they contain both α-helices and β-pleated sheets. During cell fusion the monomers of these proteins will dissociate but will return to a different trimeric structure after the fusion is complete. They are also involved in the insertion of fusion loops in the membrane. [ 4 ]
These reoviral cell–cell fusogens contain fusion loops that can induce cell fusion. They form polymeric structures to induce fusion of membranes. Reoviruses do not have membranes themselves, so class IV fusogens are not usually involved in traditional virus–cell fusion. However, when they are expressed on the surface of cells, they can induce cell–cell fusion. [ 4 ]
The fusogens of classes I–III have many structural differences. However, the method they utilize to induce membrane fusion is mechanistically similar. When activated, all of these fusogens form elongated trimeric structures and bury their fusion peptides into the membrane of the target cell. They are secured in the viral membrane by hydrophobic trans-membrane regions. These fusogens will then fold in on themselves forming a structure that is reminiscent of a hairpin. [ 4 ] This folding action brings the transmembrane region and the fusion loop adjacent to each other. Consequently, the viral membrane and the target cell membrane are also pulled close together. [ 6 ] As the membranes are brought closer together, they are dehydrated, which allows the membranes to be brought into contact. [ 3 ] Interactions between hydrophobic amino-acid residues and the adjacent membranes cause destabilization of the membranes. This allows the phospholipids in the outer layer of each membrane to interact with each other. The outer leaflets of the two membranes form a hemifusion stalk to minimize energetically unfavorable interactions between hydrophobic phospholipid tails and the environment. This stalk expands, allowing the inner leaflets of each membrane to interact. These inner leaflets then fuse, forming a fusion pore. At this point, the cytoplasmic components of the cell and the virus begin to mix. As the fusion pore expands, virus–cell fusion is completed. [ 6 ]
Though there is much variation in different fusions between mammalian cells, there are five stages that occur in a majority of these fusion events: "programming fusion-competent status, chemotaxis , membrane adhesion, membrane fusion, and post-fusion resetting." [ 5 ]
This first step, also known as priming, encompasses the necessary events that must take place in order for cells to gain the ability to fuse. In order for a cell to become fusion-competent, it must manipulate the make-up of its membrane to facilitate membrane fusion. It also must construct necessary proteins to mediate fusion. Finally, it must eliminate hindrances to fusion. For example, a cell might free itself from the extracellular matrix in order to allow the cell more motility to facilitate fusion. [ 5 ]
Monocytes and macrophages can become fusion-competent in response to cytokines , which are protein-signalling molecules. Some interleukins prompt monocytes and macrophages to fuse to form foreign-body giant cells as part of a body's immune response. For example, interleukin-4 can promote the activation of transcription factor STAT6 by phosphorylation. This can then trigger expression of matrix metalloproteinase 9 ( MMP9 ). [ 5 ] MMP9 can degrade proteins in the extracellular matrix, which aids in the priming of macrophages for fusion. [ 7 ]
Osteoclasts are multinucleated bone-resorbing cells. They are formed by the fusion of differentiated monocytes, much like foreign-body giant cells. However, the molecules that induce fusion-competence in macrophages that are destined to become osteoclasts are different from those that promote formation of foreign-body giant cells. For instance, transcription factor NFATC1 regulates genes that are specific to osteoclast differentiation. [ 5 ]
Zygote formation is a crucial step in sexual reproduction, and it is reliant on the fusion of sperm and egg cells. Consequently, these cells must be primed to gain fusion-competence. Phosphatidylserine is a phospholipid that usually resides on the inner layer of the cell membrane. After sperm cells are primed, phosphatidylserine can be found on the outer leaflet of the membrane. It is thought that this helps stabilize the membrane at the head of the sperm, and that it may play a role in allowing the sperm to enter the zona pellucida that covers egg cells. This unusual location of phosphatidylserine is an example of membrane restructuring during priming for cell fusion. [ 5 ]
Chemotaxis is the process of recruitment in response to the presence of certain signal molecules. Cells that are destined to fuse are attracted to each other via chemotaxis. For example, sperm cells are attracted to the egg cell through signalling by progesterone. [ 5 ] Similarly, in muscle tissue, myoblasts can be recruited for fusion by IL-4. [ 7 ]
Before cells can fuse, they must be in contact with one another. This can be accomplished through cell recognition and attachment by cellular machinery. [ 5 ] Syncytin-1 is a Class I fusogen involved in the fusion of cells to form osteoclasts in humans. [ 10 ] During the early actions of Class I fusogens in cell fusion, they insert their fusion loops into a target membrane. Consequently, the action of syncytin-1 is an example of membrane adhesion as it links the two cells together to prepare them for fusion. [ 6 ] This step also encompasses the dehydration of the membranes at the site of fusion. This is necessary to overcome the energy requirements necessary for fusion and to ensure that the membranes are in very close proximity for fusion to occur. [ 3 ]
Membrane fusion is characterized by the formation of a fusion pore , which allows the internal contents of both cells to mix. [ 5 ] It is first accomplished by the mixing of lipids of the outer layers of the fusing membranes, which forms a hemifusion stalk. [ 6 ] Then the inner leaflets can interact and fuse, creating an open gap where the membranes have fused. This gap is the fusion pore. This process is mediated by fusogens. [ 5 ] Fusogens are highly conserved in mammals, and it is theorized that mammals adopted them after infection by retroviruses. [ 7 ] Because they are highly conserved, they perform their task through a similar mechanism to the one used by viral fusogens as previously described. [ 6 ] It is theorized that actin polymerization and other actions of the cytoskeleton might aid in the widening of the fusion pore to complete fusion. [ 5 ]
Upon the completion of fusion, the machinery used to fuse must be disassembled or altered to avoid fusion of the new, multinucleated cell with more cells. [ 5 ] One example of this is the final trimeric structure taken on by Class I, II, and III fusogens. They each take on a structure that is markedly different than their form before fusion occurred. [ 4 ] This likely alters their activity, preventing them from initiating another fusion. [ citation needed ]
Glycoproteins of some viruses, such as mammarenaviruses , can lose their fusion ability in presence of NMT inhibitors, this can be used as a therapeutic antiviral approach against hemorrhagic viruses such as lassa and junin [ 11 ] in general public, in addition to LCMV , [ 11 ] a fatal virus in immunocompromised patients. [ 12 ] | https://en.wikipedia.org/wiki/Fusion_mechanism |
Anyon fusion is the process by which multiple anyons behave as one larger composite anyon. Anyon fusion is essential to understanding the physics of non-abelian anyons and how they can be used in quantum information. [ 1 ]
If N {\displaystyle N} identical abelian anyons each with individual statistics α {\displaystyle \alpha } (that is, the system picks up a phase e i α {\displaystyle e^{i\alpha }} when two individual anyons undergo adiabatic counterclockwise exchange) all fuse together, they together have statistics N 2 α {\displaystyle N^{2}\alpha } . This can be seen by noting that upon counterclockwise rotation of two composite anyons about each other, there are N 2 {\displaystyle N^{2}} pairs of individual anyons (one in the first composite anyon, one in the second composite anyon) that each contribute a phase e i α {\displaystyle e^{i\alpha }} . An analogous analysis applies to the fusion of non-identical abelian anyons. The statistics of the composite anyon is uniquely determined by the statistics of its components.
Non-abelian anyons have more complicated fusion relations. As a rule, in a system with non-abelian anyons, there is a composite particle whose statistics label is not uniquely determined by the statistics labels of its components, but rather exists as a quantum superposition (this is completely analogous to how two fermions known to each have spin 1/2 and 3/2 are together in quantum superposition of total spin 1 and 2). If the overall statistics of the fusion of all of several anyons is known, there is still ambiguity in the fusion of some subsets of those anyons, and each possibility is a unique quantum state. These multiple states provide a Hilbert space on which quantum computation can be done.
Specifically, two non-abelian anyons labeled a {\displaystyle a} and b {\displaystyle b} have a fusion rule given by a × b = ∑ c N a b c c {\displaystyle a\times b=\sum _{c}N_{ab}^{c}c} , where the formal sum over c {\displaystyle c} goes over all labels of possible anyon types in the system (as well as the trivial label c = 1 {\displaystyle c=1} denoting no particles), and each N a b c {\displaystyle N_{ab}^{c}} is a nonnegative integer which denotes how many distinct quantum states there are in which a {\displaystyle a} and b {\displaystyle b} fuse into c {\displaystyle c} (This is true in the abelian case as well, except in that case, for each a {\displaystyle a} and b {\displaystyle b} , there is one type of anyon c {\displaystyle c} for which N a b c = 1 {\displaystyle N_{ab}^{c}=1} and for all other c {\displaystyle c} , N a b c = 0 {\displaystyle N_{ab}^{c}=0} .) Each anyon type a {\displaystyle a} should also have a conjugate antiparticle a ¯ {\displaystyle {\bar {a}}} among the list of possible anyon types, such that N a a ¯ 1 ≠ 0 {\displaystyle N_{a{\bar {a}}}^{1}\neq 0} , i.e. it can annihilate with its antiparticle. The anyon type label does not specify all of the information about the anyon, but the information that it does indicate is topologically invariant under local perturbations.
For example, the Fibonacci anyon system, one of the simplest, consists of labels 1 {\displaystyle 1} and τ {\displaystyle \tau } ( τ {\displaystyle \tau } denotes a Fibonacci anyon), which satisfy fusion rule τ × τ = 1 + τ {\displaystyle \tau \times \tau =1+\tau } (corresponding to N τ τ τ = N τ τ 1 = 1 {\displaystyle N_{\tau \tau }^{\tau }=N_{\tau \tau }^{1}=1} ) as well as the trivial rules τ × 1 = τ {\displaystyle \tau \times 1=\tau } and 1 × 1 = 1 {\displaystyle 1\times 1=1} (corresponding to N τ 1 τ = N 11 1 = 1 {\displaystyle N_{\tau 1}^{\tau }=N_{11}^{1}=1} ).
The Ising anyon system consists of labels 1 {\displaystyle 1} , ψ {\displaystyle \psi } and σ {\displaystyle \sigma } , which satisfy fusion rules σ × σ = 1 + ψ {\displaystyle \sigma \times \sigma =1+\psi } , σ × ψ = σ {\displaystyle \sigma \times \psi =\sigma } , and the trivial rules.
The × {\displaystyle \times } operation is commutative and associative, as it must be to physically make sense with fused anyons. Furthermore, it is possible to view the N a b c {\displaystyle N_{ab}^{c}} coefficients as matrix entries ( N a ) b c {\displaystyle (N_{a})_{b}^{c}} of a matrix with row and column indices b {\displaystyle b} and c {\displaystyle c} ; then the largest eigenvalue of this matrix is known as the quantum dimension d a {\displaystyle d_{a}} of anyon type a {\displaystyle a} .
Fusion rules can also be generalized to consider in how many ways N a 1 , a 2 , … a m c {\displaystyle N_{a_{1},a_{2},\ldots a_{m}}^{c}} a collection a 1 , a 2 , … a m {\displaystyle a_{1},a_{2},\ldots a_{m}} can be fused to a final anyon type c {\displaystyle c} .
The fusion process where a {\displaystyle a} and b {\displaystyle b} fuse into c {\displaystyle c} corresponds to a N a b c {\displaystyle N_{ab}^{c}} dimensional complex vector space V a b c {\displaystyle V_{ab}^{c}} , consisting of all the distinct orthonormal quantum states in which a {\displaystyle a} and b {\displaystyle b} fuse into c {\displaystyle c} . This forms a Hilbert space. When N a b c ≤ 1 {\displaystyle N_{ab}^{c}\leq 1} , such as in the Ising and Fibonacci examples, V a b c {\displaystyle V_{ab}^{c}} is at most just a one dimensional space with one state. The direct sum ⨁ c V a b c {\displaystyle \bigoplus _{c}V_{ab}^{c}} is a decomposition of H a ⊗ H b {\displaystyle {\mathcal {H}}_{a}\otimes {\mathcal {H}}_{b}} the tensor product of the Hilbert space of individual anyon a {\displaystyle a} and the Hilbert space of individual anyon b {\displaystyle b} . In topological quantum field theory , V a b c {\displaystyle V_{ab}^{c}} is the vector space associated with the pair of pants with waist labeled c {\displaystyle c} and legs a {\displaystyle a} and b {\displaystyle b} .
More complicated Hilbert spaces can be constructed corresponding to the fusion of three or more particles, i.e. for the quantum systems where it is known that the a 1 , a 2 , … a m {\displaystyle a_{1},a_{2},\ldots a_{m}} fuse into final anyon type c {\displaystyle c} . This Hilbert space V a 1 , a 2 , … a m c {\displaystyle V_{a_{1},a_{2},\ldots a_{m}}^{c}} would describe, for example, the quantum system formed by starting with a quasiparticle c {\displaystyle c} and, via some local physical procedure, splitting up that quasiparticle into quasiparticles a 1 , a 2 , … a m {\displaystyle a_{1},a_{2},\ldots a_{m}} (because in such a system all the anyons must necessarily fuse back into c {\displaystyle c} by topological invariance). There is an isomorphism between V a 1 , a 2 , … a m 1 {\displaystyle V_{a_{1},a_{2},\ldots a_{m}}^{1}} and V a j + 1 , a j + 2 , … a m a ¯ 1 , a ¯ 2 , … a ¯ j {\displaystyle V_{a_{j+1},a_{j+2},\ldots a_{m}}^{{\bar {a}}_{1},{\bar {a}}_{2},\ldots {\bar {a}}_{j}}} for any j {\displaystyle j} . As mentioned in the previous section, the permutations of the labels are also isomorphic.
One can understand the structure of V a 1 , a 2 , … a m c {\displaystyle V_{a_{1},a_{2},\ldots a_{m}}^{c}} by considering fusion processes one pair of anyons at a time. There are many arbitrary ways one can do this, each of which can be used to derive a different decomposition of V a 1 , … a m c {\displaystyle V_{a_{1},\ldots a_{m}}^{c}} into pairs of pants. One possible choice is to first fuse a 1 {\displaystyle a_{1}} and a 2 {\displaystyle a_{2}} into b 1 {\displaystyle b_{1}} , then fuse b 1 {\displaystyle b_{1}} and a 3 {\displaystyle a_{3}} into b 2 {\displaystyle b_{2}} , and so on. This approach shows us that V a 1 , a 2 , … a m c = ⨁ { b j } ( V a 1 , a 2 b 1 ⊗ V b 1 , a 3 b 2 ⊗ V b 2 , a 4 b 3 … V b m − 3 , a m − 1 b m − 2 ⊗ V b m − 2 , a m c ) {\displaystyle V_{a_{1},a_{2},\ldots a_{m}}^{c}=\bigoplus _{\lbrace b_{j}\rbrace }\left(V_{a_{1},a_{2}}^{b_{1}}\otimes V_{b_{1},a_{3}}^{b_{2}}\otimes V_{b_{2},a_{4}}^{b_{3}}\ldots V_{b_{m-3},a_{m-1}}^{b_{m-2}}\otimes V_{b_{m-2},a_{m}}^{c}\right)} , and correspondingly N a 1 , … a m c = ( ∏ j = 2 m N a j ) a 1 c {\displaystyle N_{a_{1},\ldots a_{m}}^{c}=\left(\prod _{j=2}^{m}N_{a_{j}}\right)_{a_{1}}^{c}} where N a {\displaystyle N_{a}} is the matrix defined in the previous section.
This decomposition manifestly indicates a choice of basis for the Hilbert space. Different arbitrary choices of the order in which to fuse anyons will correspond to different choices of basis. | https://en.wikipedia.org/wiki/Fusion_of_anyons |
The fusome is a membranous structure found in the developing germ cell cysts of many insect orders. [ 1 ] [ 2 ] [ 3 ] Initial description of the fusome occurred in the 19th century and since then the fusome has been extensively studied in Drosophila melanogaster male and female germline development. [ 3 ] This structure has roles in maintaining germline cysts, coordinating the number of mitotic divisions prior to meiosis , and oocyte determination by serving as a structure for intercellular communication. [ 3 ] [ 4 ] [ 5 ]
In D. melanogaster , germline cysts form from four mitotic divisions with incomplete cytokinesis that originated from one germline stem cell. [ 6 ] [ 7 ] Incomplete cytokinesis results in intercellular bridges connecting every cell in the cyst, called ring canals 3 . The four mitotic divisions result in cysts of 16 cells connected by 15 ring canals. [ 6 ] [ 7 ] The fusome is composed of membrane vesicles and originates from endoplasmic reticulum . [ 2 ] Fusome material is inside ring canals and can range in size from 1 to 10 um depending on the stage of development. [ 1 ] [ 3 ]
1.1 Fusome Development
The spectrosome is a round structure in germline stem cells that develops into the fusome in cyst cells. [ 8 ] Fusome divides asymmetrically into daughter cells in females by attaching to one spindle pole during meiosis, resulting in one cell receiving all fusome material. [ 1 ] [ 8 ] [ 9 ] [ 10 ] Fusome is generated de novo in the ring canal connecting the two cells. [ 1 ] [ 9 ] [ 10 ] The two fusome parts then fuse together to connect the cells. [ 1 ] Asymmetric fusome partitioning and new formation followed by fusion occurs at each mitotic division. [ 1 ] In spermatogenesis , the fusome partitioning is symmetric and the fusome is still present during the meiotic divisions. [ 3 ] [ 11 ]
1.2 Fusome components
Many proteins and organelles associate with the fusome throughout germ cell development. Cytoskeleton components, such as alpha and beta spectrins , hu-li tai shao (hts), and ankyrin were the first proteins identified in the fusome. [ 4 ] [ 12 ] Centrosomes travel along the fusome and the fusome is involved in microtubule organization. [ 4 ] [ 13 ] The interactions between the fusome and microtubules result in cyst polarity in oogenesis . [ 12 ] Associations between the fusome and microtubules change throughout the cell cycle. [ 13 ] Mitochondria associates with the fusome and travel through ring canals to the oocyte. [ 14 ] Microtubules travel through ring canals and form the tracks for transport of materials between cells. [ 10 ]
There are numerous functions of the fusome as a structure necessary for cell-cell communication in developing germ cell cysts. The fusome connects cells, allowing for transport of proteins and RNAs between cells and synchronous activities. [ 3 ] [ 8 ] Mutations in essential fusome components can result in infertility . [ 3 ]
2.1 Role in cell cycle synchrony
Developing cells in germline cysts undergo mitotic divisions synchronously and in males all cells in a cyst also undergo meiosis synchronously. [ 7 ] The fusome is a track where an event can happen and then feedback mechanisms quickly communicate to each cell to ensure a specific outcome occurs simultaneously in every cell. [ 5 ] Cells in a cyst fail to divide synchronously if the fusome is disrupted. [ 4 ] [ 15 ] The rosette formation of germline cyst cells allows cells to be in the closest configuration for communication. [ 9 ]
Throughout the cell cycle, different cyclins associate with the fusome to induce synchronous cell divisions. Cyclin A and Cyclin E localize to the fusome in female germline cysts and are required for the correct number of mitotic divisions to occur. [ 5 ] [ 16 ] Abnormal cyclin levels result in too few or too many divisions. [ 5 ] [ 16 ] Cyclin E at the fusome is phosphorylated for degradation by the SCF complex and if not degraded, an extra division occurs. [ 16 ] The fusome may be the degradation site for other cell cycle proteins. [ 16 ] Myt1 kinase inhibits CycA/Cdk1 in males during G2 . [ 17 ] Without Myt1 regulation, fusome and centrosome behavior is abnormal, resulting in cells with irregular spindles. [ 17 ]
2.2 Differences in male vs female fusomes
In females, the fusome plays a role in cell fate and differentiation. [ 9 ] Asymmetric fusome distribution and centriole orientation determines which cell in the developing female germline cyst becomes the oocyte . [ 8 ] One of the two cells from the first division within the cyst becomes the oocyte and contains the most fusome material. [ 3 ] [ 9 ] The fusome degrades after the 16-cell cyst forms. [ 3 ] In females, the connections are the channels through which nurse cells send proteins and RNAs to the oocyte along polarized microtubules . [ 10 ]
In males, the fusome is necessary for ensuring quality control in individual cysts. DNA damage in one cell leads to all cells in a cyst dying by communication through the fusome, either by disseminating a death signal or additive DNA damage inducing apoptosis . [ 18 ] This ensures mature sperm cells have intact genomes before fertilizing an egg. [ 18 ] In addition, the fusome connections ensure haploid spermatids have proteins and RNA made by the other chromosome for “gamete equivalency”. [ 3 ] [ 19 ]
Fusomes were previously thought to be specific to insect gametogenesis . Fusome-like structures have been identified in Xenopus laevis oogenesis by electron microscopy and immunostaining for fusome components such as spectrin and hts. [ 20 ] Intercellular bridges also connect developing germ cells in mammals , contributing to cell cycle synchrony and gamete quality control by sharing substances between cells. [ 3 ] Future studies are required to elucidate all of the functions that arise from cell-cell communication through intercellular bridges . [ 3 ] In addition, a future area of research is to determine why some organisms lack fusomes. Do these organisms have another structure that carries out the role of the fusome or are these roles not necessary in germline cyst development of these other organisms?
^PG Wilson Cell Biol Int. 2005 May;29(5):360-9.
Centrosome inheritance in the male germ line of Drosophila requires hu-li tai-shao function. | https://en.wikipedia.org/wiki/Fusome |
A futile cycle , also known as a substrate cycle , occurs when two metabolic pathways run simultaneously in opposite directions and have no overall effect other than to dissipate energy in the form of heat . [ 1 ] The reason this cycle was called "futile" cycle was because it appeared that this cycle operated with no net utility for the organism. As such, it was thought of being a quirk of the metabolism and thus named a futile cycle. After further investigation it was seen that futile cycles are very important for regulating the concentrations of metabolites. [ 2 ] For example, if glycolysis and gluconeogenesis were to be active at the same time, glucose would be converted to pyruvate by glycolysis and then converted back to glucose by gluconeogenesis, with an overall consumption of ATP . [ 3 ] Futile cycles may have a role in metabolic regulation, where a futile cycle would be a system oscillating between two states and very sensitive to small changes in the activity of any of the enzymes involved. [ 4 ] The cycle does generate heat, and may be used to maintain thermal homeostasis , for example in the brown adipose tissue of young mammals , or to generate heat rapidly, for example in insect flight muscles and in hibernating animals during periodical arousal from torpor . It has been reported that the glucose metabolism substrate cycle is not a futile cycle but a regulatory process. For example, when energy is suddenly needed, ATP is replaced by AMP, a much more reactive adenine.
The simultaneous carrying out of glycolysis and gluconeogenesis is an example of a futile cycle, represented by the following equation:
For example, during glycolysis, fructose-6-phosphate is converted to fructose-1,6-bisphosphate in a reaction catalysed by the enzyme phosphofructokinase 1 (PFK-1).
But during gluconeogenesis (i.e. synthesis of glucose from pyruvate and other compounds) the reverse reaction takes place, being catalyzed by fructose-1,6-bisphosphatase (FBPase-1).
Giving an overall reaction of:
That is, hydrolysis of ATP without any useful metabolic work being done. Clearly, if these two reactions were allowed to proceed simultaneously at a high rate in the same cell, a large amount of chemical energy would be dissipated as heat. This uneconomical process has therefore been called a futile cycle. [ 5 ]
There are not many drugs that can effectively treat or reverse obesity. Obesity can increase ones risk of diseases primarily linked to health problems such as diabetes, hypertension, cardiovascular disease and even certain types of cancers. A study revolving around treatment and prevention of obesity using transgenic mice to experiment on reports positive feedback that proposes miR-378 may sure be a promising agent for preventing and treating obesity in humans. The study findings demonstrate that activation of the pyruvate-PEP futile cycle in skeletal muscle through miR-378 is the primary cause of elevated lipolysis in adipose tissues of miR-378 transgenic mice, and it helps orchestrate the crosstalk between muscle and fat to control energy homeostasis in mice. [ 6 ]
Our general understanding of futile cycle is a substrate cycle, occurring when two overlapping metabolic pathways run in opposite directions, that when left without regulation will continue to go on uncontrolled without any actual production until all the cells energy is depleted. However, the idea behind the study indicates miR-378-activated pyruvate-phosphoenolpyruvate futile cycle plays a regulatory benefit. [ 6 ] Not only does miR-378 result in lower body fat mass due to enhanced lipolysis it is also speculated that futile cycles regulate metabolism to maintain energy homeostasis. miR-378 has a unique function in regulating metabolic communication between the muscle and adipose tissues to control energy homeostasis at whole-body levels. [ 6 ]
To understand how presence of a futile cycle helps maintain low levels of ATP and generation heat in some species we look at metabolic pathways dealing with reciprocal regulation of glycolysis and gluconeogenesis .
The swim bladder of many fish; such as zebrafish for example - is an organ internally filled with gas that helps contribute to their buoyancy . These gas gland cell are found to be located where the capillaries and nerves are found. Analyses of metabolic enzymes demonstrated that a gluconeogenesis enzyme fructose-1,6- bisphosphatase (Fbp1) and a glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (Gapdh) are highly expressed in gas gland cells. [ 7 ] The study signified that the characterization of the zebrafish swim bladder should not contain any expression fructose-1,6-bisphosphatase gene. The tissue of the swim bladder is known to be very high in glycogenic activity and lacking in gluconeogenesis, yet a predominant amount of Fbp was found to be expressed. This finding suggests that in the gas gland cell, Fbp forms an ATP-dependent metabolic futile cycle. Generation of heat is critically important for the gas gland cells to synthesize lactic acid because the process is strongly inhibited if ATP is accumulated.
Another example suggest that heat generation in fugu swim bladder will be transported out of the site of generation, however it may still be constantly recovered back through the rete mirabile so as to maintain the temperature of the gas gland higher than other areas of the body.
The overall net reaction of the futile cycle involves the consumption of ATP and generation of heat as follows:
Another example of futile cycle benefiting in generation of heat is found in bumblebees . The futile cycle involving Fbp and Pfk is used by bumble bees to produce heat in flight muscles and warm up their bodies considerably at low ambient temperatures. [ 7 ] | https://en.wikipedia.org/wiki/Futile_cycle |
Future-oriented technology analysis (FTA) is a collective term from futures studies for analyzing future technology and its consequences. [ 1 ] [ 2 ] It includes technology intelligence, technology forecasting , technology roadmapping , technology assessment , and technology foresight . Technology Futures Analysis or Technology Future Analysis (TFA) is a synonym. [ 1 ] [ 3 ]
Future-oriented technology analysis shares common methods with horizon scanning . [ 4 ] [ 5 ] | https://en.wikipedia.org/wiki/Future-oriented_technology_analysis |
Future-proofing (also futureproofing ) is the process of anticipating the future and developing methods of minimizing the effects of shocks and stresses of future events. [ 1 ] Future-proofing is used in industries such as infrastructure development, [ 2 ] electronics, medical industry, industrial design, and more recently, in design for climate change. The principles of future-proofing are extracted from other industries and codified as a system for approaching an intervention in a historic building.
In future-proof electrical systems, buildings should have "flexible distribution systems to allow communication technologies to expand., [ 3 ] Image-related processing software should be flexible, adaptable, and programmable to be able to work with several different potential media in the future as well as to handle increasing file sizes. Image-related processing software should also be scalable and embeddable – in other words, the use or place in which the software is employed is variable and the software needs to accommodate the variable environment. Higher processing integration is required to support future computational requirements in image processing as well. [ 4 ]
In wireless phone networks, future-proofing of the network hardware and software systems deployed becomes critical because they are so costly to deploy that it is not economically viable to replace each system when changes in network operations occur. Telecommunications system designers focus heavily on the ability of a system to be reused and to be flexible in order to continue competing in the marketplace. [ 5 ] [ 6 ]
In 1998, teleradiology (the ability to send radiology images such as X-rays and CAT scans over the internet to a reviewing radiologist) was in its infancy. Doctors developed their own systems, aware that technology would change over time. They consciously included future-proof as one of the characteristics that their investment would need to have. To these doctors, future-proof meant open modular architecture and interoperability so that as technology advanced it would be possible to update the hardware and software modules within the system without disrupting the remaining modules. This draws out two characteristics of future-proofing that are important to the built environment: interoperability and the ability to be adapted to future technologies as they were developed. [ 7 ]
The designer has a prescriptive rather than descriptive job. Unlike scientists who describe how the world is, designers suggest how it might be. Designers are therefore futurologists to some extent. [ 8 ]
The practice builds on the work of the Italian Radicals in the 1960's, through the critical design work of Anthony Dunne and Fiona Raby in the late 1990’s, who developed design approaches for the exploration and critique of ideas, rather than for the creation of objects. [ 9 ]
Designers by the nature of their work are futurists. The least time it takes to produce a product and get it on the shelf is a couple of years. Sometimes it can be 10–15 years. So you’re already dealing with the future when you sit at your desk in the morning. [ 10 ]
In industrial design, future-proofing designs seek to prevent obsolescence by analyzing the decrease in desirability of products. Desirability is measured in categories such as function, appearance, and emotional value. The products with more functional design, better appearance, and which accumulate emotional value faster tend to be retained longer and are considered future-proof. Some of the characteristics of future-proof products that come out of this study include a timeless nature, high durability, aesthetic appearances that capture and hold the interest of buyers. Ideally, as an object ages, its desirability is maintained or increases with increased emotional attachment. Products that fit into society's current paradigm of progress, while simultaneously making progress, also tend to have increased desirability. [ 11 ]
That desire to change the world runs throughout speculative design, where success is often measured not in what’s made, but instead the impact of your idea and how it seeps into wider thinking. [ 9 ]
At Google, various strategy and visioning teams use their creative expertise within internal studios and departments to explore what may lay beyond the horizon in five, 10, or even 15 years time. To understand the role of speculative design at Google, we can look to the MacGuffin theory, which states that the importance of a prop in narrative film is not the object itself, but the effect it has on the characters and their motivations. Similarly, the value of speculative design is not in the object that is created–whether it’s a prototype, installation, or live experience–but rather the discussion, contemplation, and understanding that it sparks. [ 9 ]
Through a complex and iterative process of synthesis and transformation of research data, designers empathize with the future through revealing future design opportunities. These opportunities are identified through the movement from data to information, and information to insight utilizing visual mapping techniques. This movement involves various levels of abstraction
before drawing together into actionable insights. [ 12 ]
An important focus in the development of next-next generation products and services is the need to uncover opportunities by exploring people’s unmet and unarticulated needs in the present and utilize this insight in future oriented design activity. [ 12 ]
Ideas about the future are made concrete within prototypes, and as such these ideas are explored in the present. For a fleeting moment, the future and the present coexist. [ 12 ]
Whether predicting or shaping how the future will unfold, speculative design needs to strike a balance between what’s possible and what’s pure science fiction. Too ambitious, and your concept will likely never materialize. Too practical or conservative, and the value of speculative design is lost. As Golden Krishna puts it, “If everything that we thought of got made, then we wouldn’t be doing our job right.”（Golden Krishna, Head of Design Strategy at Google’s Platforms & Ecosystems group. ） [ 9 ]
Philip Battin, a former designer on Google’s augmented reality eyewear project Glass and now lead at Seed Studio, believes that design as a practice has been commercialized to the point of misuse. Where once it was a byword for new bold landscapes, it has since been reduced to the aesthetics of business. [ 9 ]
This evolving paradigm requires designers to not only envision future possibilities but also to deeply consider the ethical implications of their creations. The journey from concept to realization necessitates a responsible approach, where the societal, environmental, and moral consequences are weighed with every decision. By fostering a culture of thoughtful innovation, designers can ensure that their work contributes positively to the world, paving the way for advancements that are not only technologically advanced but also socially responsible and sustainable. This commitment to ethical foresight is what will define the legacy of future-oriented design.
In "Speculative Everything," Anthony Dunne and Fiona Raby define critical design and explain how their practice shifts towards speculative applications. They view conceptual design not as serving clients or market demands, but as a medium for reflection, inquiry, and critique, using design fiction to challenge hegemony and technocentrism. The authors advocate for designers to work independently from the industry, engaging in imaginative work rather than relying solely on commissions. [ 13 ]
Poggenpohl argues that design stimulates ideas about how we can use technology in more empathetic ways. [ 14 ]
In one region of New Zealand, Hawke's Bay, a study was conducted to determine what would be required to future-proof the regional economy with specific reference to the water system. The study specifically sought to understand the existing and potential water demand in the region as well as how this potential demand might change with climate change and more intense land use. This information was used to develop demand estimates that would inform the improvements to the regional water system. Future-proofing thus includes forward planning for future development and increased demands on resources. The study focuses on future demands almost exclusively and does not address other components of future-proofing such as contingency plans to handle disastrous damage to the system or durability of the materials in the system. [ 15 ]
In the realm of sustainable environmental issues, future-proof is used generally to describe the ability of a design to resist the impact of potential climate change due to global warming. Two characteristics describe this impact. First, "dependency on fossil fuels will be more or less completely eliminated and replaced by renewable energy sources." Second, "Society, infrastructure and the economy will be well adapted to the residual impacts of climate change." [ 16 ]
In the design of low energy consuming dwellings, "buildings of the future should be sustainable, low-energy and able to accommodate social, technological, economic and regulatory changes, thus maximizing life cycle value." The goal is to "reduce the likelihood of a prematurely obsolete building design." [ 17 ]
In Australia, research commissioned by the Health Infrastructure New South Wales explored "practical, cost-effective, design-related strategies for 'future-proofing' the buildings of a major Australian health department." This study concluded that "a focus on a whole life-cycle approach to the design and operation of health facilities clearly would have benefits." By designing in flexibility and adaptability of structures, one may "defer the obsolescence and consequent need for demolition and replacement of many health facilities, thereby reducing overall demand for building materials and energy." [ 18 ]
The ability of a building's structural system to accommodate projected climate changes and whether "non-structural [behavioral] adaptations might have a great enough effect to offset any errors from... an erroneous choice of climate change projection". The essence of the discussion is whether adjustments in the occupant's behavior can future-proof the building against errors in judgment in estimates of the impacts of global climate change. There are many factors involved and the paper does not go into them in exhaustive detail. "Soft adaptations”, such as changes in behavior, can have a significant impact on the ability of a building to continue to function as the environment around it changes. Thus adaptability is an important criterion in the concept of "future-proofing" buildings. Adaptability is a theme that begins to come through in many of the other studies on future-proofing. [ 3 ]
There are examples of sustainable technologies that can be used in existing buildings to take "advantage of up-to-date technologies in the enhancement of the energetic performance of buildings." The intent is to understand how to follow the new European Energy Standards to attain the best in energy savings. The subject speaks to historic buildings and specifically of façade renewal, focusing on energy conservation . These technologies include "improvement of thermal and acoustic performance, solar shadings, passive solar energy systems, and active solar energy systems." The main value of this study to future-proofing is not the specific technologies, but rather the concept of working with an existing façade by overlapping it rather than modifying the existing one. The employment of ventilated facades, double skin glass facades, and solar shadings take advantage of the thermal mass of existing buildings commonly found in Italy. These techniques not only work with thermal mass walls, but also protect damaged and deteriorating historic facades to varying degrees. [ 19 ]
Use of the term "future-proofing" has been uncommon in the AEC industry, especially with relation to historic buildings until recently. In 1997, the MAFF laboratories at York, England were described in an article as “future-proof” by being flexible enough to adapt to developing rather than static scientific research. The standard building envelope and MEP services provided could be tailored for each type of research to be performed. [ 20 ] In 2009, “future-proof” was used in reference to “ megatrends ” that were driving education of planners in Australia. [ 21 ] A similar term, “fatigue proofing,” was used in 2007 to describe steel cover plates in bridge construction that would not fail due to fatigue cracking. [ 6 ] In 2012, a New Zealand-based organization outlined eight principles of future-proof buildings: smart energy use, increased health and safety, increased life cycle duration, increased quality of materials and installation, increased security, increased sound control for noise pollution, adaptable spatial design, and reduced carbon footprint. [ 5 ]
Another approach to future-proofing suggests that only in more extensive refurbishments to a building should future-proofing be considered. Even then, the proposed time horizon for future-proofing events is 15 to 25 years. The explanation for this particular time horizon for future-proof improvements is unclear. [ 22 ]
In the valuation of real estate, there are three traditional forms of obsolescence which affect property values: physical, functional, and aesthetic. Physical obsolescence occurs when the physical material of the property deteriorates to the point where it needs to be replaced or renovated. Functional obsolescence occurs when the property is no longer capable of serving the intended use or function. Aesthetic obsolescence occurs when fashions change, when something is no longer in style. A potential fourth form has emerged as well: sustainable obsolescence. Sustainable obsolescence proposes to be a combination of the above forms in many ways. Sustainable obsolescence occurs when a property no longer meets one or more sustainable design goals. [ 23 ]
One reasonable approach to future-proof sustainable cities is an integrated multi-disciplinary combination of mitigation and adaptation to raise the level of resilience of the city. In the context of urban environments, resilience is less dependent on an exact understanding of the future than on tolerance of uncertainty and broad programs to absorb the stresses that this environment might face. The scale of the context is important in this view: events are viewed as regional stresses rather than local. The intent for a resilient urban environment is to keep many options open, emphasize diversity in the environment, and perform long-range planning that accounts for external systemic shocks. [ 24 ]
Future-proofing of designated historic structures adds a level of complexity to the concepts of future-proofing in other industries as described above. All interventions on historic structures must comply with the Secretary's Standards for the Treatment of Historic Properties. The degree of compliance and the Standard selected may vary depending on jurisdiction, type of intervention, significance of the structure, and the nature of the intended interventions. The underlying principle is that no harm is done to the structure in the course of the intervention which would damage the structure or make it unavailable to future generations. In addition, it is important that the historic portions of the structure be able to be understood and comprehended apart from the newer interventions. [ 25 ]
Future-proofing is also a methodology to address vulnerabilities of infrastructure systems. [ 2 ] For example, analysis of domestic water infrastructure in the Southern California and Tijuana area completed by Rich and Gattuso in 2016 [ 26 ] demonstrates that potential vulnerabilities include levee failures, material deterioration, and climate change. [ 27 ] With changes in the hydrologic conditions due to climate change, there will be increased emphasis on ensuring that the water infrastructure systems continue to function after a natural hazard event where specific components or facilities in the system are compromised. [ 28 ]
Many new potable water technologies, such as desalination , physical treatment, chemical treatment, and biological treatment systems, can help to address these vulnerabilities. Development of a future-proof infrastructure system can have longer lasting benefits. The San Diego Regional Water System has been implementing a program of infrastructure improvements to ensure plentiful water sources in the future. These include developed an emergency storage program aimed at providing a 75% service level and includes several key elements of the regional water system. [ 28 ] The regional water authority is also in the middle of a multi-decade long project to reline the existing pipeline system to increase their service life (Water-technology.net, 2012). The region also seeks to supplement the water supply through diversification of sources of water which will support continued growth of the regional population. Priorities for development of new water sources (in order of preference) are seawater desalination, indirect potable reuse (wastewater recycling), and additional water from the Colorado River. [ 29 ]
The strategies being employed in San Diego and Tijuana are future-proofing their potable water infrastructure systems by including seismic loops and flexible oversized systems to prevent damage in seismic events accommodate future changes in use and population growth. The San Diego Regional Water System is pursuing strategies that diversify and increase redundancy of water supplies by including metropolitan water district sources, irrigation water transfer, canal lining to prevent leakage, conservation or reduced consumption, recycled wastewater, desalination, groundwater sources, and surface water sources. Development of new water tunnels and relining water mains, branches, and canals extends the service life, and fortifies the system while reducing physical and functional obsolescence and preventing further deterioration of the system. Ongoing maintenance, diversification efforts, capacity development, and planning for future requirements will ensure an ongoing future-proof supply of water for the region. [ 26 ]
Life-cycle assessment /analysis (LCA) can be used as an indicator of long-term impacts to the environment, and an important aspect of future-proofing our built environment, quantifying the impacts of initial construction, periodic renovation, and regular maintenance of a building over an extended time span. A study completed published in 2015 by Rich compares the impacts of gymnasiums constructed of different building materials over a 200-year period using the Athena Impact Estimator. Rich developed the phrase "First Impacts" to describe the environmental impacts of new construction from raw material extraction to occupancy of the building. When the environmental impacts of maintenance and replacement are considered with first impacts for a building, a complete picture of the environmental impacts are formed. [ 30 ]
While choice of materials is important to initial impacts of a building or product, less durable materials lead to more frequent maintenance, operating expenses and replacement. By contrast, more durable materials may have more significant initial impacts, but those impacts will pay off in the long run by reducing maintenance, repairs, and operations expenses. Durability of all components of a building system should have equivalent service lives or allow for disassembly in order to maintain the shorter service life materials. This allows retention of materials that have longer service lives rather than disposing of them when removed to perform maintenance. Proper maintenance of a building is critical to long term service life because it prevents deterioration of less durable materials that can expose additional materials to deterioration. [ 30 ] | https://en.wikipedia.org/wiki/Future-proof |
The Future 50 Foods report , subtitled "50 foods for healthier people and a healthier planet", was published in February 2019 by the World Wide Fund for Nature (WWF) and Knorr . It identifies 50 plant-based foods that can increase dietary nutritional value and reduce environmental impacts of the food supply, [ 1 ] promoting sustainable global food systems . [ 2 ]
The report identifies 12 plant sources and five animal sources that make up 75 percent of the food humans consume, and three crops (wheat, corn and rice) accounting for about "60 percent of the plant-based calories in most diets". [ 3 ] The report points out that lack of variety in food sources threatens food security, and "repeatedly harvesting the same crop on the same land depletes nutrients in the soil, leading to intensive use of fertilizers and pesticides that, when misused, can hurt wildlife and damage the environment". [ 3 ]
The report offers five steps to identifying a future food: "focus on plant-based foods, optimize nutrient density, evaluate environmental impact, consider culture and flavor, and deliver diversity." [ 4 ]
Criteria for inclusion on the list of 50 foods indicated they must be "highly nutritious, have as little impact on the environment as possible, affordable, accessible, and of course, tasty". [ 4 ] The foods are grouped into categories:
Algae contain essential fatty acids and antioxidants rich in protein, and are a potential replacement for meat. [ 5 ]
1. Laver seaweed Porphyra umbilicalis
2. Wakame seaweed Undaria pinnatifida
Beans are in the legume family, and are a source of fiber, protein and B vitamins. [ 2 ]
3. Adzuki beans Vigna angularis
4. Black turtle beans Phaseolus vulgaris
5. Broad beans (fava beans) Vicia faba
6. Bambara groundnuts/Bambara beans Vigna subterranea
7. Cowpeas Vigna unguiculata
8. Lentils Lens culinaris
9. Marama beans Tylosema esculentum
10. Mung beans Vigna radiata
11. Soy beans Glycine max
Cacti contains vitamins C and E, carotenoids, fibre and amino acids. [ 2 ]
12. Nopales Opuntia
These whole grains and cereals provide nutritional value and also improve soil health by diversifying sources of carbohydrates from current dependence on white rice, maize, and wheat. [ 2 ]
13. Amaranth Amaranthus
14. Buckwheat Fagopyrum esculentum
15. Finger millet Eleusine coracana
16. Fonio Digitaria exilis
17. Khorasan wheat Triticum turanicum
18. Quinoa Chenopodium quinoa
19. Spelt Triticum spelta
20. Teff Eragrostis tef
21. Wild rice Zizania
Compared to vegetables, these fruits are sweeter and usually contain more carbohydrates and water. [ 2 ]
22. Pumpkin flowers Cucurbita pepo
23. Orange tomatoes Solanum lycopersicum
24. Okra Abelmoschus esculentus
Leafy greens contain dietary fiber, vitamins and minerals, and are low in calories. [ 2 ]
25. Beet greens Beta vulgaris
26. Broccoli rabe Brassica ruvo
27. Kale Brassica oleracea var. sabellica
28. Moringa Moringa oleifera
29. Pak-choi or bok-choy (Chinese cabbage) Brassica rapa subsp. chinensis
30. Pumpkin leaves Cucurbita pepo
31. Red cabbage Brassica rapa subsp. chinensis
32. Spinach Spinacia oleracea
33. Watercress Nasturtium officinale
Mushrooms have high B vitamin content, as well as vitamin D, protein, and fiber. [ 2 ]
34. Enoki mushrooms Flammulina velutipes
35. Maitake mushrooms Grifola frondosa
36. Saffron milk cap mushrooms Lactarius deliciosus
Called "superfoods", these foods are high in protein, vitamin E, and "good fats". [ 2 ]
37. Flax seeds Linum usitatissimum
38. Hemp seeds Cannabis sativa
39. Sesame seeds Sesamum indicum
40. Walnuts Juglans regia
Root vegetables have a broad variety of vitamins and minerals. [ 2 ]
41. Black salsify Scorzonera hispanica
42. Parsley root Petroselinum crispum
43. White icicle radish ( winter radish ) Raphanus sativus var. Longipinnatus
Sprouts extremely high nutrient content. The sprouting process doubles, and in some cases triples, the nutritional value of the plant. [ 2 ]
44. Alfalfa sprouts Medicago sativa
45. Sprouted kidney beans Phaseolus vulgaris
46. Sprouted chickpeas Cicer arietinum
Tubers are usually high in carbohydrates and are a source of energy. [ 2 ]
47. Lotus root Nelumbo nucifera
48. Ube (purple yam) Dioscorea alata
49. Yam bean root (jicama) Pachyrhizus erosus
50. Red Indonesian (Cilembu) sweet potatoes Ipomoea batatas
According to Cooking Light , "This report was developed by experts in food sustainability, food security, nutrition, human rights and agriculture to help us understand how to eat for optimal health and a healthier planet." [ 4 ] Eleanor Beardsley of NPR 's Morning Edition said, "As it turns out, the way we humans eat is very much linked to preserving wildlife — and many other issues." [ 3 ] Claiming a 60% decline in wildlife populations since 1970, David Edwards of WWF advocates addressing "the drivers of habitat loss and species collapse", identifying the biggest driver as global farming. [ 3 ]
Global Citizen said, "Adopting a plant-based diet can help reduce your carbon footprint and decrease greenhouse gas emissions ." [ 6 ] It quoted Peter Gregory in the report: "Diversified diets not only improve human health but benefit the environment through diversified production systems that encourage wildlife and more sustainable use of resources." [ 6 ] | https://en.wikipedia.org/wiki/Future_50_Foods_report |
The Open Group Future Airborne Capability Environment (FACE Consortium) was formed in 2010 to define an open avionics environment for all military airborne platform types. Today, it is a real-time software-focused professional group made up of industry suppliers, customers, academia, and users. The FACE approach is a government-industry software standard and business strategy for acquisition of affordable software systems that promotes innovation and rapid integration of portable capabilities across programs. The FACE Consortium provides a vendor-neutral forum for industry and government to work together to develop and consolidate the open standards, best practices, guidance documents, and business strategy necessary to result in: [ 1 ]
The FACE Technical Standard is an open real-time standard for making safety-critical computing operations more robust, interoperable, portable and secure. Although the consortium started with a focus on avionics, the applicability of the technical standard and its associated data model have become much broader. The standard enables software developers to create and deploy a wide catalog of applications for use across the entire spectrum of real-time systems through a common operating environment. The latest edition of the standard further promotes application interoperability and portability with enhanced requirements for exchanging data among FACE components, including a formally specified data model, and emphasis on defining common language requirements for the standard.
Until 2022, individual members were required to be US persons. In 2022, the consortium moved to open membership to the countries of Canada, Australia, New Zealand, the United Kingdom, and the United States. Individuals can only become members if they are employed by a company that is a member.
Corporate membership is at different levels. The sponsor-level members are Boeing, Collins Aerospace, Lockheed Martin, US Air Force LCMC, and US Army PEO Aviation, and US Naval Air Systems Command.
The FACE effort sprang from US Navy open architecture programs, [ 2 ] promoted by the US Naval Air Systems Command (NAVAIR), to enhance interoperability and software portability for avionics software applications across DoD aviation platforms. Both the US Army and US Air Force have been participating in the consortium. NAVAIR led the pack with early acquisitions, followed later by Army and Air Force. [ 3 ] [ 4 ] [ 5 ]
The FACE Consortium was formed by The Open Group as a "Voluntary Consensus Standards Body", as defined by the National Technology Transfer Act and OMB Circular A-119 . This facilitates government participation in the consortium. [ 6 ] One goal of the effort is to reduce the typical development and deployment cycle of new capabilities in military airborne platforms from as long as six years under the current methodology to as little as six months. [ 7 ]
The FACE reference architecture ecosystem includes software product conformance verification and certification processes. [ 8 ] In October 2016, a suite of flight management software earned the first FACE certificate of conformance. [ 9 ] One may view information on all certified FACE conformant products at the FACE Registry
The FACE technical approach tackles barriers to software modularity, portability, and interoperability by defining a Reference Architecture and employing design principles to enhance software portability. To meet the objectives of the technical approach, the FACE Technical Standard uses a standardized architecture describing a conceptual breakdown of functionality, called the FACE Reference Architecture, to promote the reuse of software components able to share common functionality across disparate systems. This architecture defines standardized interfaces to allow software components to be moved between systems, including those developed by different vendors. The standardized interfaces follow a data architecture to ensure the data communicated between the software components is fully described to facilitate their integration on new systems.
The FACE Reference Architecture is composed of logical segments where variance occurs. The structure created by connecting these segments together is the foundation of the FACE Reference Architecture. The five (5) segments of the FACE Reference Architecture are the Operating System Segment (OSS), Input/Output Services Segment (IOSS), Platform-Specific Services Segment (PSSS), Transport Services Segment (TSS), and Portable Components Segment (PCS).
The FACE Reference Architecture defines a set of standardized interfaces providing connections between the FACE architectural segments. The standardized interfaces within the FACE Reference Architecture are the Operating System Segment Interface (OSS Interface), the Input/Output Services Interface (IOS Interface), the Transport Services Interfaces, and Component-Oriented Support Interfaces.
The FACE Reference Architecture defines three FACE OSS Profiles tailoring the Operating System (OS) Application Programming Interfaces (APIs), programming languages, programming language features, run-times, frameworks, and graphics capabilities to meet the requirements of software components for differing levels of criticality. The three Profiles are Security, Safety, and General Purpose. The Security Profile constrains the OS APIs to a minimal useful set allowing assessment for high-assurance security functions executing as a single process. The Safety Profile is less restrictive than the Security Profile and constrains the OS APIs to those that have a safety certification pedigree. The General Purpose Profile is the least constrained profile and supports OS APIs meeting real-time deterministic or non-real-time, non-deterministic requirements depending on the system or subsystem implementation.
The FACE Data Architecture defines the FACE Data Model Language (including the language binding specification), Query and Template language, FACE Shared Data Model (SDM) and the rules of construction of the Unit of Portability (UoP) Supplied Model (USM). Each PCS Unit of Conformance (UoC), PSSS UoC, or TSS UoC providing using TS Interfaces is accompanied by a USM consistent with the FACE SDM and defines its interfaces in terms of the FACE Data Model Language. A Domain-Specific Data Model (DSDM) captures content relevant to a domain of interest and can be used as a basis for USMs. | https://en.wikipedia.org/wiki/Future_Airborne_Capability_Environment |
Future Medicinal Chemistry is a peer-reviewed medical journal covering all aspects of medicinal chemistry, including drug discovery , pharmacology , in silico drug design , structural characterization techniques, ADME-Tox investigations, and science policy, economic and intellectual property issues. It was established in 2009 and is published by Future Science. The editors-in-chief are Iwao Ojima ( The State University of New York at Stony Brook ) and Jonathan Baell ( Monash University ).
The journal is abstracted and indexed by BIOSIS Previews , Chemical Abstracts , Chemistry Citation Index , Embase / Excerpta Medica , Index Medicus / MEDLINE / PubMed , Science Citation Index Expanded , and Scopus . According to the Journal Citation Reports , the journal has a 2020 impact factor of 3.808. [ 1 ]
This article about a medicinal chemistry journal is a stub . You can help Wikipedia by expanding it .
See tips for writing articles about academic journals . Further suggestions might be found on the article's talk page . | https://en.wikipedia.org/wiki/Future_Medicinal_Chemistry |
Future Worlds Center (FWC) is a non-profit, non-Governmental independent organization active in programs with future orientation in areas related to positive social change , social entrepreneurship and transformation .
Future Worlds Center was founded in 1991 as Cyprus Neuroscience and Technology Institute . In the late 1990s, it expanded its operations pioneering in a number of humanitarian, multicultural and peace related projects. [ 1 ] [ 2 ] At the end of 2005, with a new Constitution, it evolved into a larger organization with a pure international orientation integrating all humanitarian, peace, and multicultural activities under one umbrella.
According to its new Constitution, Future Worlds Center is an incubator of ideas, projects, social entrepreneurs and organizations committed to socio-technical reforms. [ 3 ] Since its inception it has envisioned, designed and implemented more than 100 projects, employed more than 200 young scientists, and founded several organizations, including CYBER KIDS , Technology for peace, the Cyprus Safer Internet Center along with the Cyprus Safer Internet Hotline and Helpline , the Cyprus Community Media Centre [ 4 ] funded by the United Nations, Youth Power, [ 5 ] Cyprus NGO Platform "Development", the Cyprus Refugee Council. [ 6 ]
The organization has developed the curriculum for CYBER KIDS, a chain of computer learning centers, that started in Cyprus and expanded in 7 countries in the early 90s. CYBER KIDS was a mass-scale experiment to achieve massive social change in a whole country.
Future Worlds Center also implements many EC-funded projects that conduct research and inform societies about the safer use of the Internet; Cyberethics, [ 7 ] Cyprus’ Safer Internet Center, which includes a Hotline [ 8 ] and a Helpline . [ 9 ]
Future Worlds Center pioneers in envisioning, designing and implementing projects that promote the culture of peace and reconciliation in Cyprus, the region and the globe. The Technology for peace, [ 10 ] [ 11 ] initiative in 1997, founded by Yiannis Laouris and Harry Anastasiou members of the Cyprus Conflict Resolution Trainers Group aimed to capitalize on the proliferation of the Internet as a means to break the communication barriers between the northern and the southern parts of divided Cyprus. Other notable peace projects include the Youth promoting Peace, [ 12 ] Civil Society Dialogue , the Act Beyond Borders, Everybody's song, [ 13 ] and many projects funded by HasNa Inc.
Future Worlds Center is leading a number of pan-European efforts, which aim to promote the Millennium Development Goals within Europe and in Sub-Saharan countries. It was a founding member of the Cyprus Islandwide Development NGO Platform [ 14 ] and the Cyprus Community Media Centre. [ 15 ] The Accessing Development Education project [ 16 ] has collected teaching materials or guidance books on topics like Development Education, [ 17 ] Global citizenship , Human Rights , Millennium Development Goals and many others from across Europe into one central depository. The Teach MDGs project [ 18 ] focuses on increasing awareness and public support for the Millennium Development Goals by actively engaging teacher training institutes, teachers and pupils in developing local oriented teaching resources promoting the MDGs with a particular focus on Sub-Saharan Africa and integrate these into the educational systems of countries across Europe.
The organization has implemented more than 120 Structured Democratic Dialogues in diverse contexts, [ 19 ] including, peace and conflict resolution, [ 20 ] [ 21 ] government and societal challenges (e.g., reforming the local authorities [ 22 ] or the Wine Villages of Cyprus [ 23 ] ), supporting pan-European groups of experts discover obstacles and design actions to improve access to broadband technologies for all but also for people facing accessibility challenges; [ 24 ] [ 25 ] discovering and collectively agreeing on research agenda priorities, thus influencing European Commission funding; [ 26 ] reinventing democracy. [ 27 ] Its scientists advanced the underlying science enabling virtual dialogues. [ 28 ] [ 29 ]
Future Worlds Center is the implementing organization of the United Nations High Commissioner for Refugees Representation in Cyprus . Its Humanitarian Affairs Unit implements projects that aim strengthening asylum for refugees and asylum seekers on the island. This Unit has founded the Unit of Rehabilitation of Victims of Torture . As of January 2018, a spin-off was created and the Cyprus Refugee Council was created. | https://en.wikipedia.org/wiki/Future_Worlds_Center |
The Future of Marine Animal Populations ( FMAP ) project was one of the core projects of the international Census of Marine Life (2000–2010). FMAP's mission was to describe and synthesize globally changing patterns of species abundance, distribution, and diversity, and to model the effects of fishing, climate change and other key variables on those patterns. This work was done across ocean realms and with an emphasis on understanding past changes and predicting future scenarios. [ 1 ] [ 2 ]
FMAP emerged from a workshop held at Dalhousie University in 2002 and was funded from 2003 to 2010 by the Alfred P. Sloan Foundation . The project was led by Ransom A. Myers from 2002 to 2007 and from 2007 to 2010 was under the direction of Boris Worm , Heike Lotze and Ian Jonsen in the Biology Department at Dalhousie University .
The FMAP project coordinated major data synthesis efforts to derive global trends and patterns in marine biodiversity. From 2003 to 2011, FMAP team members have contributed over 110 scientific articles to peer review journals, including numerous publications in top-tier journals such as Science and Nature . Publications by FMAP scientists have also included many book chapters, policy publications and outreach articles. Topics of research have included patterns of species abundance , distribution and diversity , and the effects of climate change , overfishing and other key human threats on these patterns. FMAP has performed analyses on a variety of organisms, including coral reefs , large pelagic fish , marine mammals , sea turtles and invertebrates .
A major output of the project was the development of advanced statistical tools for analyzing observational data to study how marine biodiversity is distributed and changing over time, and to better understand the movements and distribution of marine predators. FMAP's research was presented as part of the culmination of The Census of Marine Life, which was celebrated in October 2010 in London, England. FMAP research formed an integral part of the overall findings of the program, which were disseminated through major media outlets around the globe. [ 6 ] | https://en.wikipedia.org/wiki/Future_of_Marine_Animal_Populations |
Fuzzy-trace theory ( FTT ) is a theory of cognition originally proposed by Valerie F. Reyna and Charles Brainerd [ 1 ] to explain cognitive phenomena, particularly in memory and reasoning.
FTT posits two types of memory processes (verbatim and gist) and, therefore, it is often referred to as a dual process theory of memory. According to FTT, retrieval of verbatim traces (recollective retrieval) is characterized by mental reinstatement of the contextual features of a past event, whereas retrieval of gist traces (nonrecollective retrieval) is not. In fact, gist processes form representations of an event's semantic features rather than its surface details, the latter being a property of verbatim processes.
The theory has been used in areas such as cognitive psychology , human development , and social psychology to explain, for instance, false memory [ 2 ] and its development, [ 3 ] probability judgments, [ 4 ] medical decision making, [ 5 ] [ 6 ] [ 7 ] [ 8 ] risk perception and estimation, and biases and fallacies in decision making . [ 9 ] [ 10 ]
FTT can explain phenomena involving both true memories (i.e., memories about events that actually happened) as well as false memories (i.e., memories about events that never happened). [ 2 ] [ 11 ]
FTT was initially proposed in the 1990s as an attempt to unify findings from the memory and reasoning domains that could not be predicted or explained by earlier approaches to cognition and its development (e.g., constructivism [ 12 ] [ 13 ] and information processing). One of such challenges was the statistical independence between memory and reasoning, that is, memory for background facts of problem situations is often unrelated to accuracy in reasoning tasks. [ 14 ] [ 15 ] [ 16 ] Such findings called for a rethinking of the memory-reasoning relation, which in FTT took the form of a dual-process theory linking basic concepts from psycholinguistic and Gestalt theory to memory and reasoning. More specifically, FTT posits that people form two types of mental representations about a past event, called verbatim and gist traces. Gist traces are fuzzy representations of a past event (e.g., its bottom-line meaning), hence the name fuzzy-trace theory, whereas verbatim traces are detailed representations of a past event. Although people are capable of processing both verbatim and gist information, they prefer to reason with gist traces rather than verbatim. This implies, for example, that even if people are capable of understanding ratio concepts like probabilities and prevalence rates, which are the standard for the presentation of health- and risk-related data, their choice in decision situations will usually be governed by the bottom-line meaning of it (e.g., "the risk is high" or "the risk is low"; "the outcome is bad" or "the outcome is good") rather than the actual numbers. [ 5 ] More importantly, in FTT, memory-reasoning independence can be explained in terms of preferred modes of processing when one performs a memory task (e.g., retrieval of verbatim traces) relative to when one performs a reasoning task (e.g., preference for reasoning with gist traces). [ 17 ]
In 1999, a similar approach was applied to human vision. [ 18 ] It suggested that human vision has two types of processing: one that aggregates local spatial receptive fields, and one that parses the local receptive field. People used prior experience, gists, to decide which process dominates a perceptual decision. The work attempted to link Gestalt theory and psychophysics (i.e., independent linear filters). This theory was further developed into fuzzy image processing [ 19 ] [ 20 ] and used in information processing technology and edge detection. [ 21 ] [ 22 ] [ 23 ]
FTT posits two types of memory processes (verbatim and gist) and, therefore, it is often referred to as a dual process theory of memory. According to FTT, retrieval of verbatim traces (recollective retrieval) is characterized by mental reinstatement of the contextual features of a past event, whereas retrieval of gist traces (nonrecollective retrieval) is not. In fact, gist processes form representations of an event's semantic features rather than its surface details, the latter being a property of verbatim processes. In the memory domain, FTT's notion of verbatim and gist representations has been influential in explaining true memories (i.e., memories about events that actually happened) as well as false memories (i.e., memories about events that never happened). [ 2 ] [ 11 ] The following five principles have been used to predict and explain true and false memory phenomena:
The principle of parallel storage asserts that the encoding and storage of verbatim and gist information operate in parallel rather than in a serial fashion . For instance, suppose that a person is presented with the word "apple" in red color. On the one hand, according to the principle of parallel storage of verbatim and gist traces, verbatim features of the target item (e.g., the word was apple, it was presented in red, printed in boldface and italic, and all but the first letter were presented in lowercase) and gist features (e.g., the word was a type of fruit) would be encoded and stored simultaneously via distinct pathways. Conversely, if verbatim and gist traces are stored in a serial fashion, then gist features of the target item (the word was a type of fruit) would be derived from its verbatim features and, therefore, the formation of gist traces would depend on the encoding and storage of verbatim traces. The latter idea was often assumed by early memory models. [ 24 ] [ 25 ] [ 26 ] However, despite the intuitive appeal of the serial processing approach, research suggests that the encoding and storage of gist traces do not depend on verbatim ones. Several studies have converged on the finding that the meaning of target items is encoded independently of, and even prior to, the encoding of the surface form of the same items. [ 27 ] [ 28 ] [ 29 ] [ 30 ] [ 31 ] Ankrum and Palmer, [ 32 ] for example, found that when participants are presented with a familiar word (e.g., apple) for a very brief period (100 milliseconds), they are able to identify the word itself ("was it apple?") better than its letters ("did it contain the letter L?").
Similar to the principle of parallel storage, retrieval of verbatim and gist traces also occur via dissociated pathways. According to the principle of dissociated retrieval, recollective and nonrecollective retrieval processes are independent of each other. Consequently, this principle allows verbatim and gist processes to be differentially influenced by factors such as the type of retrieval cues and the availability of each form of representation. In connection with Tulving's encoding specificity principle , items that were actually presented in the past are better cues for verbatim traces than items that were not. Similarly, items that were not presented in the past but preserve the meaning of presented items are usually better cues for gist traces. Suppose, for example, that subjects of an experiment are presented with a word list containing several dog breeds, such as poodle, bulldog, greyhound, doberman, beagle, collie, boxer, mastiff, husky, and terrier. During a recognition test, the words poodle, spaniel, and chair are presented. According to the principle of dissociated retrieval, retrieval of verbatim and gist traces does not depend on each other and, therefore, different types of test probes might serve as better cues to one type of trace than another. In this example, test probes such as poodle (targets, or studied items) will be better retrieval cues for verbatim traces than gist, whereas test probes such as spaniel (related distractors, non-studied items but related to targets) will be better retrieval cues for gist traces than verbatim. Chair, on the other hand, would neither be a better cue for verbatim traces nor for gist traces because it was not presented and is not related to dogs. If verbatim and gist processes were dependent, then factors that affect one process would also affect the other in the same direction. However, several experiments showing, for example, differential forgetting rates between memory for the surface details and memory for the bottom-line meaning of past events [ 33 ] [ 34 ] [ 35 ] [ 36 ] favor the notion of dissociated retrieval of verbatim and gist traces. [ 37 ] In the case of forgetting rates, those experiments have shown that, over time, verbatim traces become inaccessible at a faster rate than gist traces. Brainerd, Reyna, and Kneer, [ 38 ] for instance, found that delay drives true recognition rates (supported by both verbatim and gist traces) and false recognition rates (supported by gist and suppressed by verbatim traces) in opposite directions, namely true memory decays over time while false memory increases.
The principle of opponent processes describes the interaction between verbatim and gist processes in creating true and false memories. Whereas true memory is supported by both verbatim and gist processes, false memory is supported by gist processes and suppressed by verbatim processes. In other words, verbatim and gist processes work in opposition to one another when it comes to false memories. [ 2 ] Suppose, for example, that one is presented with a word list such as lemon, apple, pear, and citrus. During a recognition test, the items lemon (target), orange (related distractor), and fan (unrelated distractor) are shown. In this case, retrieval of a gist trace (fruits) supports acceptance of both test probes lemon (true memory) and orange (false memory), whereas retrieval of a verbatim trace (lemon) only supports acceptance of the test probe lemon. In addition, retrieval of an exclusory verbatim trace ("I saw only the words lemon, apple, pear, and citrus") suppresses acceptance of false but related items such as orange through an operation known as recollection rejection. [ 39 ] [ 40 ] If neither verbatim nor gist traces are retrieved, then one might accept any test probe on the basis of response bias. This principle plays a key role in FTT's explanation of experimental dissociations between true and false memories (e.g., when a variable affects one type of memory without affecting the other, or when it produces opposite effects on them). The time of exposure of each word during study and the number of repetitions have been shown to produce such dissociations. [ 41 ] [ 42 ] More specifically, while true memory follows a monotonically increasing function when plotted against presentation duration, false memory rates exhibit an inverted-U pattern when plotted as a function of presentation duration. Similarly, repetition is monotonically related to true memory (true memory increases as a function of the number of repetitions) and is non-monotonically related to false memory (repetition produces an inverted-U relation with false memory).
Retrieval phenomenologies are spontaneous mental experiences associated with the act of remembering. It was first systematically characterized by E. K. Strong in the early 1900s. [ 43 ] Strong identified two distinct types of introspective phenomena associated with memory retrieval that have since been termed recollection (or remembrance) and familiarity. Whereas the former is characterized as retrieval associated with recollection of past experiences, the latter lacks such association. The two forms of experiences can be illustrated by everyday expressions such as "I remember that!" (recollection) and "That seems familiar..." (familiarity). In FTT, retrieval of verbatim traces often produces recollective phenomenology and thus is frequently referred to as recollective retrieval. [ 2 ] [ 11 ] However, one feature of FTT is that recollective phenomenology is not particular to one type of memory process as posited by other dual-process theories of memory. Instead, FTT posits that retrieval of gist traces can also produce recollective phenomenology under some circumstances. When gist resemblance between a false item and memory is high and compelling, this gives rise to a phenomenon called phantom recollection, [ 44 ] [ 45 ] which is a vivid, but false, memory deemed to be true.
The principle of developmental variability in dual processes posits that verbatim and gist processes show variability across the lifespan . More specifically, verbatim and gist processes have been shown to improve between early childhood and young adulthood. [ 3 ] [ 10 ] [ 46 ] [ 47 ] Regarding verbatim processes, older children are better at retrieval of verbatim traces than younger children, although even very young children (4-year-olds) are able to retrieve verbatim information at above chance level. For instance, source memory accuracy greatly increases between 4-year-olds and 6-year-olds, [ 48 ] and memory for nonsense words (i.e., words without a meaning, such as neppez) has been shown to increase between 7- and 10-year-olds. [ 49 ] Gist processes also improve with age. For example, semantic clustering in free recall increases from 8-year-olds to 14-year-olds, [ 50 ] and meaning connection across words and sentences has been shown to improve between 6- and 9-year-olds. [ 51 ] [ 52 ] In particular, the notion that gist memory improves with age plays a central role in FTT's prediction of age increases in false memory, a counterintuitive pattern that has been called developmental reversal. [ 3 ]
Regarding old age, several studies suggest that verbatim memory declines between early and late adulthood, while gist memory remains fairly stable. Experiments indicate that older adults perform worse on tasks that require retrieval of surface features from studied items relative to younger adults. [ 53 ] [ 54 ] [ 55 ] [ 56 ] In addition, results with measurement models that quantify verbatim and gist processes indicate that older adults are less able to use verbatim traces during recall than younger adults. [ 57 ]
When people try to remember past events (e.g., a birthday party or the last dinner), they often commit two types of errors: errors of omission and errors of commission. The former is known as forgetting , while the latter is better known as false memories. False memories can be separated into spontaneous and implanted false memories. Spontaneous false memories result from endogenous (internal) processes, such as meaning processing, while implanted false memories are the result of exogenous (external) processes, such as the suggestion of false information by an outside source (e.g., an interviewer asking misleading questions). Research had first suggested that younger children are more susceptible to suggestion of false information than adults. [ 11 ] However, research has since indicated that younger children are much less likely to form false memories than older children and adults. [ 58 ] [ 59 ] Moreover, in opposition to common sense, true memories are not more stable than false ones. Studies have shown that false memories are actually more persistent than true memories. [ 2 ] According to FTT, such pattern arises because false memories are supported by memory traces that are less susceptible to interference and forgetting (gist traces) than traces that suppress them and also support true memories (verbatim traces).
FTT is not a model for false memories but rather a model that explains how memory reacts with a higher reasoning process. Essentially, the gist and verbatim traces of whatever the subject is experiencing has a major effect on information that the subject falsely remembers. Verbatim and gist traces assist with memory performance due to the performance being able to pull from traces, relying on factors of different retrieval cues, on the accessibility of these kinds of memories, and forgetting. [ 60 ] Although not a model for false memories, FTT is able to predict true and false memories associated with narratives and sentences. This is especially apparent in eye witness testimonies. [ 61 ]
There are 5 explanatory principles that explain FTT's description of false memory, which lays out the differences between experiences dealing with gist and verbatim traces. [ 60 ]
Differences between true and false memories are also laid out by FTT. The associations and dissociations between true and false memories are predicted by FTT, namely, certain associations and dissociations are observed under different kinds of conditions. Dissociation emerges under situations that involve reliance on verbatim traces. Memories, whether true or false are then based on different kinds of representations. [ 60 ]
FTT may also help explain the effects of false memories, misinformation, and false-recognition in children as well as how this may vary during developmental changes. [ 62 ]
While many false memories may be perceived as being "dumb," recent studies on FTT have shown that the theory might have an influence on creating "smart" false memories, which are created from being aware of the meaning of certain experiences. [ 63 ]
While false memory research is still in early development, the application of FTT in false memory has been able to apply to real world settings; FTT has been effective in explaining multiple phenomena of false memory. [ 60 ] In explaining false memories, FTT rejects the idea that offhand false memories are deemed as being true and how gist and verbatim traces embed false memories. [ 64 ]
FTT, as it applies to reasoning, is adapted from dual process models of human cognition. It differs from the traditional dual process model in that it makes a distinction between impulsivity and intuition —which are combined in System 1 according to traditional dual process theories—and then makes the claim that expertise and advanced cognition relies on intuition. [ 65 ] The distinction between intuition and analysis depends on what kind of representation is used to process information. The mental representations described by FTT are categorized as either gist or verbatim representations:
Generally, most adults display what is called a "fuzzy processing preference," [ 10 ] meaning that they rely on the least precise gist representations necessary to make a decision, despite parallel processing of both gist and verbatim representations. Both processes increase with age, though the verbatim process develops sooner than the gist, and is thus more heavily relied on in adolescence.
In this regard, the theory expands on research that has illustrated the role of memory representations in reasoning processes, [ 66 ] the intersection of which has been previously underexplored. [ 67 ] However, in certain circumstances, FTT predicts independence between memory and reasoning, specifically between reasoning tasks that rely on gist representations and memory tests that rely on verbatim representations. An example of this is research between the risky choice framing task and working memory , in which better working memory is not associated with a reduction in bias. [ 68 ]
FTT thus explains inconsistencies or biases in reasoning to be dependent on retrieval cues that access stored values and principles that are gist representations, which can be filtered through experience and cultural, affective, and developmental factors. [ 69 ] This dependence on gist results in a vulnerability of reasoning to processing interference from overlapping classes of events, but can also explain expert reasoning in that a person can treat superficially different reasoning problems in the same way if the problems share an underlying gist. [ 70 ]
FTT posits that when people are presented with statistical information, they extract representations of the gist of the information (qualitatively) as well as the exact verbatim information (quantitatively). The gist that is encoded is often a basic categorical distinction between no risk and some risk. However, in situations when both choices in the decision have a level of uncertainty or risk, then another level of precision would be required, e.g., low risk or high risk. [ 71 ] An illustration of this principle can be found in FTT's explanation of the common framing effect .
Framing effects occur when linguistically different descriptions of equivalent options lead to inconsistent choices. A famous example of a risky choice framing task is the Asian Disease Problem. [ 72 ] This task requires the participants to imagine that their country is about to face a disease which is expected to kill 600 people. They have to choose among two programs to combat this disease. Subjects are presented with options that are framed as either gains (lives saved) or losses (lives lost). The possible options, as well as the categorical gists that are posited to be encoded by FTT are displayed below.
It is commonly found that people prefer the sure option when the options are framed as gains (program A) and the risky option when they are framed as losses (program D), [ 72 ] despite the fact that the expected values for all the programs are equivalent. This is in contrast to a normative point of view that would indicate that if respondents prefer the sure option in the positive frame, they should also prefer the sure option in the negative frame. [ 72 ]
The explanation for this effect according to FTT is that people will tend to operate on the simplest gist that is permitted to make a decision. In the case of this framing question, the gain frame presents a situation in which people prefer the gist of some people being saved to the possibility that some are saved or no one could be saved, and conversely, that the possibility of some people dying or no one dying is preferable to the option that some people will surely die. [ 73 ]
Critical tests have been conducted to provide evidence in support of this explanation in favor of other theoretical explanations (i.e., Prospect theory ) by presenting a modified version of this task that eliminates some mathematically redundant wording, e.g., program B would instead indicate that "If program B is adopted, there is 1/3 probability that 600 people will be saved." FTT predicts, in this case, that the elimination of the additional gist (the explicit possible death in program B) would result in indifference and eliminate the framing effect, which is indeed what was found. [ 73 ]
The dual-process assumption of FTT has also been used to explain common biases of probability judgment, including the conjunction and disjunction fallacies. The conjunction fallacy occurs when people mistakenly judge a specific set of circumstances to be more probable than a more general set that includes the specific set. This fallacy is famously demonstrated by the Linda problem : that given a description of a woman named Linda who is an outspoken philosophy major who is concerned about discrimination and social justice, people will judge "Linda is a bank teller and is active in the feminist movement" to be more probable than "Linda is a bank teller", despite the fact that the latter statement is entirely inclusive of the former. [ 74 ] FTT explains this phenomenon to not be a matter of encoding, given that priming participants to understand the inclusive nature of the categories tends not to reduce the bias. Instead, this is the result of the salience of relational gist, which contributes to a tendency to judge relative numerosity instead of merely applying the principle of class inclusion. [ 75 ]
Errors of probability perception are also associated with the theory's predictions of contradictory relationships between risk perception and risky behavior. Specifically, that endorsement of accurate principles of objective risk is actually associated with greater risk-taking, whereas measures that assess global, gist-based judgments of risk had a protective effect (consistent with other predictions from FTT in the field of medical decision making ). Since gist processing develops after verbatim processing as people age, this finding lends explanation to the increase in risk-taking that occurs during adolescence. [ 76 ]
FTT has also been applied in the domains of consumer behavior and economics . For example, since the theory posits that people rely primarily on gist representations in making decisions, and that culture and experience can affect consumers' gist representations, factors such as cultural similarity and personal relevance have been used to explain consumers' perceptions of the risk of food-borne contamination and their intentions to reduce consumption of certain foods. In other words, one's evaluation of how "at-risk" he or she is can be influenced both by specific information learned as well as by the fuzzy representations of culture experience, and perceived proximity. In practice this resulted in greater consumer concern when the threat of a food-borne-illness was described in a culturally similar location, regardless of geographical proximity or other verbatim details. [ 77 ]
Evidence was also found in consumer research in support of FTT's "editing" hypothesis, namely that extremely low-probability risks can be simplified by gist processing to be represented as "essentially nil." For example, one study found that people were willing to pay more for a safer product if safety was expressed relatively (i.e., product A is safer than product B) than they were if safety was expressed with statistics of actual incidence of safety hazards.
This result is in contrast to most prescriptive decision rules that predict that formally equivalent methods of communicating risk information should have identical effects on risk-taking behavior, even if the pertinent displays are different. These findings are predicted by FTT (and related models), which suggest that people reason on the basis of simplified representations rather than on the literal information available. [ 78 ]
Like other people, clinicians apply cognitive heuristics and fall into systematic errors which affect decisions in everyday life. Research has shown that patients and their physicians have difficulty understanding a host of numerical concepts, especially risks and probabilities, and this often implies some problems with numeracy , or mathematical proficiency. [ 79 ] For example, physicians and patients both demonstrate great difficulty understanding the probabilities of certain genetic risks and were prone to the same errors, despite vast differences in medical knowledge. [ 80 ] Though traditional dual process theory generally predicts that decisions made by computation are superior to those made by intuition, FTT assumes the opposite: that intuitive processing is more sophisticated and is capable of making better decisions, and that increases in expertise are accompanied by reliance on intuitive, gist-based reasoning rather than on literal, verbatim reasoning. [ 81 ] FTT predicts that simply educating people with statistics regarding risk factors can hinder prevention efforts. Due to low prevalence of HIV or cancer, for example, people tend to overestimate their risks, and consequently interventions stressing the actual numbers may move people toward complacency as opposed to risk reduction. [ 82 ] When women learn that their actual risks for breast cancer are lower than they thought, they return for screening at a lower rate. [ 83 ] Also, some interventions to discourage adolescent drug use by presenting the risks have been shown to be ineffective or can even backfire. [ 84 ]
The conclusion drawn from this evidence is that health-care professionals and health policymakers need to package, present, and explain information in more meaningful ways that facilitate forming an appropriate gist. Such strategies would include explaining quantities qualitatively, displaying information visually, and tailoring the format to trigger the appropriate gist and to cue the retrieval of health-related knowledge and values. [ 5 ] Web-based interventions have been designed using these principles, which have been found to increase the patient's willingness to escalate care, as well as gain knowledge and make an informed choice. [ 65 ]
Theory-driven research using principles from FTT provides empirically supported recommendations that can be applied in many fields. For example, it provides specific recommendations regarding interventions aiming at reducing adolescent risk taking. [ 82 ] Moreover, according to FTT, precise information does not necessarily work to communicate health-related information, which has obvious implications to public policy and procedures for improving treatment adherence in particular. [ 79 ] [ 85 ] Specifically, FTT principles suggest examples of how to display risk proportions in order to be comprehensible for both patients and health care professionals: [ 5 ]
In addition, memory principles in FTT provide recommendations to eyewitness testimony . [ 86 ] [ 87 ] Children are often called upon to testify in courts, most commonly in cases of maltreatment, divorce, and child custody. Contrary to common sense, FTT posits that children can be reliable witnesses as long as they are encouraged to report verbatim memories and their reports are protected from suggestion of false information. More specifically: | https://en.wikipedia.org/wiki/Fuzzy-trace_theory |
Fuzzy complexes are protein complexes , where structural ambiguity or multiplicity exists and is required for biological function . [ 1 ] [ 2 ] Alteration, truncation or removal of conformationally ambiguous regions impacts the activity of the corresponding complex . [ 3 ] [ 4 ] [ 5 ] Fuzzy complexes are generally formed by intrinsically disordered proteins . [ 6 ] [ 7 ] Structural multiplicity usually underlies functional multiplicity of protein complexes [ 8 ] [ 9 ] [ 10 ] following a fuzzy logic . Distinct binding modes of the nucleosome are also regarded as a special case of fuzziness. [ 11 ] [ 12 ]
For almost 50 years molecular biology was based on two dogmas: (i) equating biological function of the protein with a unique three-dimensional structure and (ii) assuming exquisite specificity in protein complexes . Specificity/selectivity is ensured by unambiguous set of interactions formed between the protein and its ligand (another protein , DNA , RNA or small molecule ). Many protein complexes however, contain functionally important/critical regions, which remain highly dynamic in the complex or adopt different conformations . [ 13 ] This phenomenon is defined fuzziness. The most pertinent example is the cyclin-dependent kinase inhibitor Sic1 , which binds to the SCF subunit of Cdc4 in a phosphorylation dependent manner. [ 14 ] No regular secondary structures are gained upon phosphorylation and the different phosphorylation sites interchange in the complex. [ 15 ]
Structural ambiguity in protein complexes covers a wide spectrum. [ 1 ] In a polymorphic complex, the protein adopts two or more different conformations upon binding to the same partner, and these conformations can be resolved. [ 16 ] Clamp, [ 17 ] flanking [ 18 ] [ 19 ] and random complexes [ 20 ] [ 21 ] are dynamic, where ambiguous conformations interchange with each other and cannot be resolved. Interactions in fuzzy complexes are usually mediated by short motifs . [ 22 ] Flanking regions are tolerant to sequence changes as long as the amino acid composition is maintained, for example in case of linker histone C-terminal domains [ 23 ] and H4 histone N-terminal domains. [ 24 ]
Fuzzy regions modulate the conformational equilibrium [ 25 ] or flexibility [ 3 ] [ 26 ] of the binding interface via transient interactions . [ 27 ] Dynamic regions can also compete with binding sites [ 28 ] or tether them to the target. [ 29 ] Modifications of fuzzy regions by further interactions, [ 8 ] [ 30 ] or posttranslational modifications [ 31 ] [ 32 ] impact binding affinity or specificity. Alternative splicing can modulate the length of fuzzy regions resulting in context-dependent binding (e.g. tissue -specificity) on the complex. [ 33 ] [ 34 ] [ 35 ] EGF / MAPK , TGF-β and WNT/Wingless signaling pathways employ tissue-specific fuzzy regions. | https://en.wikipedia.org/wiki/Fuzzy_complex |
A fuzzy control system is a control system based on fuzzy logic – a mathematical system that analyzes analog input values in terms of logical variables that take on continuous values between 0 and 1, in contrast to classical or digital logic, which operates on discrete values of either 1 or 0 (true or false, respectively). [ 1 ] [ 2 ]
Fuzzy logic is widely used in machine control. The term "fuzzy" refers to the fact that the logic involved can deal with concepts that cannot be expressed as the "true" or "false" but rather as "partially true". Although alternative approaches such as genetic algorithms and neural networks can perform just as well as fuzzy logic in many cases, fuzzy logic has the advantage that the solution to the problem can be cast in terms that human operators can understand, such that that their experience can be used in the design of the controller. This makes it easier to mechanize tasks that are already successfully performed by humans. [ 1 ]
Fuzzy logic was proposed by Lotfi A. Zadeh of the University of California at Berkeley in a 1965 paper. [ 3 ] He elaborated on his ideas in a 1973 paper that introduced the concept of "linguistic variables", which in this article equates to a variable defined as a fuzzy set. Other research followed, with the first industrial application, a cement kiln built in Denmark, coming on line in 1976. [ 4 ]
Fuzzy systems were initially implemented in Japan .
Work on fuzzy systems is also proceeding in North America and Europe, although on a less extensive scale than in Japan.
Research and development is also continuing on fuzzy applications in software, as opposed to firmware , design, including fuzzy expert systems and integration of fuzzy logic with neural-network and so-called adaptive " genetic " software systems, with the ultimate goal of building "self-learning" fuzzy-control systems. [ 7 ] These systems can be employed to control complex, nonlinear dynamic plants, for example, human body. [ 5 ] [ 7 ] [ 8 ]
The input variables in a fuzzy control system are in general mapped by sets of membership functions similar to this, known as "fuzzy sets". The process of converting a crisp input value to a fuzzy value is called "fuzzification". The fuzzy logic based approach had been considered by designing two fuzzy systems, one for error heading angle and the other for velocity control. [ 9 ]
A control system may also have various types of switch , or "ON-OFF", inputs along with its analog inputs, and such switch inputs of course will always have a truth value equal to either 1 or 0, but the scheme can deal with them as simplified fuzzy functions that happen to be either one value or another.
Given " mappings " of input variables into membership functions and truth values , the microcontroller then makes decisions for what action to take, based on a set of "rules", each of the form:
In this example, the two input variables are "brake temperature" and "speed" that have values defined as fuzzy sets. The output variable, "brake pressure" is also defined by a fuzzy set that can have values like "static" or "slightly increased" or "slightly decreased" etc.
Fuzzy controllers are very simple conceptually. They consist of an input stage, a processing stage, and an output stage. The input stage maps sensor or other inputs, such as switches, thumbwheels, and so on, to the appropriate membership functions and truth values. The processing stage invokes each appropriate rule and generates a result for each, then combines the results of the rules. Finally, the output stage converts the combined result back into a specific control output value.
The most common shape of membership functions is triangular, although trapezoidal and bell curves are also used, but the shape is generally less important than the number of curves and their placement. From three to seven curves are generally appropriate to cover the required range of an input value, or the " universe of discourse " in fuzzy jargon.
As discussed earlier, the processing stage is based on a collection of logic rules in the form of IF-THEN statements, where the IF part is called the "antecedent" and the THEN part is called the "consequent". Typical fuzzy control systems have dozens of rules.
Consider a rule for a thermostat:
This rule uses the truth value of the "temperature" input, which is some truth value of "cold", to generate a result in the fuzzy set for the "heater" output, which is some value of "high". This result is used with the results of other rules to finally generate the crisp composite output. Obviously, the greater the truth value of "cold", the higher the truth value of "high", though this does not necessarily mean that the output itself will be set to "high" since this is only one rule among many.
In some cases, the membership functions can be modified by "hedges" that are equivalent to adverbs. Common hedges include "about", "near", "close to", "approximately", "very", "slightly", "too", "extremely", and "somewhat". These operations may have precise definitions, though the definitions can vary considerably between different implementations. "Very", for one example, squares membership functions; since the membership values are always less than 1, this narrows the membership function. "Extremely" cubes the values to give greater narrowing, while "somewhat" broadens the function by taking the square root.
In practice, the fuzzy rule sets usually have several antecedents that are combined using fuzzy operators, such as AND, OR, and NOT, though again the definitions tend to vary: AND, in one popular definition, simply uses the minimum weight of all the antecedents, while OR uses the maximum value. There is also a NOT operator that subtracts a membership function from 1 to give the "complementary" function.
There are several ways to define the result of a rule, but one of the most common and simplest is the "max-min" inference method, in which the output membership function is given the truth value generated by the premise.
Rules can be solved in parallel in hardware, or sequentially in software. The results of all the rules that have fired are "defuzzified" to a crisp value by one of several methods. There are dozens, in theory, each with various advantages or drawbacks.
The "centroid" method is very popular, in which the "center of mass" of the result provides the crisp value. Another approach is the "height" method, which takes the value of the biggest contributor. The centroid method favors the rule with the output of greatest area, while the height method obviously favors the rule with the greatest output value.
The diagram below demonstrates max-min inferencing and centroid defuzzification for a system with input variables "x", "y", and "z" and an output variable "n". Note that "mu" is standard fuzzy-logic nomenclature for "truth value":
Notice how each rule provides a result as a truth value of a particular membership function for the output variable. In centroid defuzzification the values are OR'd, that is, the maximum value is used and values are not added, and the results are then combined using a centroid calculation.
Fuzzy control system design is based on empirical methods, basically a methodical approach to trial-and-error . The general process is as follows:
As a general example, consider the design of a fuzzy controller for a steam turbine. The block diagram of this control system appears as follows:
The input and output variables map into the following fuzzy set:
—where:
The rule set includes such rules as:
In practice, the controller accepts the inputs and maps them into their membership functions and truth values. These mappings are then fed into the rules. If the rule specifies an AND relationship between the mappings of the two input variables, as the examples above do, the minimum of the two is used as the combined truth value; if an OR is specified, the maximum is used. The appropriate output state is selected and assigned a membership value at the truth level of the premise. The truth values are then defuzzified.
For example, assume the temperature is in the "cool" state, and the pressure is in the "low" and "ok" states. The pressure values ensure that only rules 2 and 3 fire:
The two outputs are then defuzzified through centroid defuzzification:
The output value will adjust the throttle and then the control cycle will begin again to generate the next value.
Consider implementing with a microcontroller chip a simple feedback controller:
A fuzzy set is defined for the input error variable "e", and the derived change in error, "delta", as well as the "output", as follows:
If the error ranges from -1 to +1, with the analog-to-digital converter used having a resolution of 0.25, then the input variable's fuzzy set (which, in this case, also applies to the output variable) can be described very simply as a table, with the error / delta / output values in the top row and the truth values for each membership function arranged in rows beneath:
Suppose this fuzzy system has the following rule base:
These rules are typical for control applications in that the antecedents consist of the logical combination of the error and error-delta signals, while the consequent is a control command output.
The rule outputs can be defuzzified using a discrete centroid computation:
Now, suppose that at a given time:
Then this gives:
Plugging this into rule 1 gives:
-- where:
The other rules give:
The centroid computation yields:
If you have problems figuring out the centroid equation, remember that a centroid is defined by summing all the moments (location times mass) around the center of gravity and equating the sum to zero. So if X 0 {\displaystyle X_{0}} is the center of gravity, X i {\displaystyle X_{i}} is the location of each mass, and M i {\displaystyle M_{i}} is each mass, this gives:
In our example, the values of mu correspond to the masses, and the values of X to location of the masses
(mu, however, only 'corresponds to the masses' if the initial 'mass' of the output functions are all the same/equivalent. If they are not the same, i.e. some are narrow triangles, while others maybe wide trapezoids or shouldered triangles, then the mass or area of the output function must be known or calculated. It is this mass that is then scaled by mu and multiplied by its location X_i).
This system can be implemented on a standard microprocessor, but dedicated fuzzy chips are now available. For example, Adaptive Logic INC of San Jose, California, sells a "fuzzy chip", the AL220, that can accept four analog inputs and generate four analog outputs. A block diagram of the chip is shown below:
As an example, consider an anti-lock braking system , directed by a microcontroller chip. The microcontroller has to make decisions based on brake temperature , speed , and other variables in the system.
The variable "temperature" in this system can be subdivided into a range of "states": "cold", "cool", "moderate", "warm", "hot", "very hot". The transition from one state to the next is hard to define.
An arbitrary static threshold might be set to divide "warm" from "hot". For example, at exactly 90 degrees, warm ends and hot begins. But this would result in a discontinuous change when the input value passed over that threshold. The transition wouldn't be smooth, as would be required in braking situations.
The way around this is to make the states fuzzy . That is, allow them to change gradually from one state to the next. In order to do this, there must be a dynamic relationship established between different factors.
Start by defining the input temperature states using "membership functions":
With this scheme, the input variable's state no longer jumps abruptly from one state to the next. Instead, as the temperature changes, it loses value in one membership function while gaining value in the next. In other words, its ranking in the category of cold decreases as it becomes more highly ranked in the warmer category.
At any sampled timeframe, the "truth value" of the brake temperature will almost always be in some degree part of two membership functions: i.e.: '0.6 nominal and 0.4 warm', or '0.7 nominal and 0.3 cool', and so on.
The above example demonstrates a simple application, using the abstraction of values from multiple values. This only represents one kind of data, however, in this case, temperature.
Adding additional sophistication to this braking system, could be done by additional factors such as traction , speed, inertia , set up in dynamic functions, according to the designed fuzzy system. [ 10 ]
In spite of the appearance there are several difficulties to give a rigorous logical interpretation of the IF-THEN rules. As an example, interpret a rule as IF (temperature is "cold") THEN (heater is "high") by the first order formula Cold(x)→High(y) and assume that r is an input such that Cold(r) is false. Then the formula Cold(r)→High(t) is true for any t and therefore any t gives a correct control given r . A rigorous logical justification of fuzzy control is given in Hájek's book (see Chapter 7) where fuzzy control is represented as a theory of Hájek's basic logic. [ 2 ]
In Gerla 2005 [ 11 ] another logical approach to fuzzy control is proposed based on fuzzy logic programming: Denote by f the fuzzy function arising of an IF-THEN systems of rules. Then this system can be translated into a fuzzy program P containing a series of rules whose head is "Good(x,y)". The interpretation of this predicate in the least fuzzy Herbrand model of P coincides with f. This gives further useful tools to fuzzy control.
Before an Artificial Intelligence system is able to plan the action sequence, some kind of model is needed. For video games, the model is equal to the game rules. From the programming perspective, the game rules are implemented as a Physics engine which accepts an action from a player and calculates, if the action is valid. After the action was executed, the game is in follow up state. If the aim isn't only to play mathematical games but determine the actions for real world applications, the most obvious bottleneck is, that no game rules are available. The first step is to model the domain. System identification can be realized with precise mathematical equations or with Fuzzy rules . [ 12 ]
Using Fuzzy logic and ANFIS systems (Adaptive network based fuzzy inference system) for creating the forward model for a domain has many disadvantages. [ 13 ] A qualitative simulation isn't able to determine the correct follow up state, but the system will only guess what will happen if the action was taken. The Fuzzy qualitative simulation can't predict the exact numerical values, but it's using imprecise natural language to speculate about the future. It takes the current situation plus the actions from the past and generates the expected follow up state of the game.
The output of the ANFIS system isn't providing correct information, but only a Fuzzy set notation, for example [0,0.2,0.4,0]. After converting the set notation back into numerical values the accuracy get worse. This makes Fuzzy qualitative simulation a bad choice for practical applications. [ 14 ]
Fuzzy control systems are suitable when the process complexity is high including uncertainty and nonlinear behavior, and there are no precise mathematical models available. Successful applications of fuzzy control systems have been reported worldwide mainly in Japan with pioneering solutions since 80s.
Some applications reported in the literature are: | https://en.wikipedia.org/wiki/Fuzzy_control_system |
Fuzzy differential equation are general concept of ordinary differential equation in mathematics defined as differential inclusion for non-uniform upper hemicontinuity convex set with compactness in fuzzy set . [ 1 ] [ 2 ] [ 3 ] d x ( t ) / d t = F ( t , x ( t ) , α ) , {\displaystyle dx(t)/dt=F(t,x(t),\alpha ),} for all α ∈ [ 0 , 1 ] {\displaystyle \alpha \in [0,1]} .
A first order fuzzy differential equation [ 4 ] with real constant or variable coefficients
x ′ ( t ) + p ( t ) x ( t ) = f ( t ) {\displaystyle x'(t)+p(t)x(t)=f(t)}
where p ( t ) {\displaystyle p(t)} is a real continuous function and f ( t ) : [ t 0 , ∞ ) → R F {\displaystyle f(t)\colon [t_{0},\infty )\rightarrow R_{F}} is a fuzzy continuous function y ( t 0 ) = y 0 {\displaystyle y(t_{0})=y_{0}} such that y 0 ∈ R F {\displaystyle y_{0}\in R_{F}} .
A system of equations of the form
x ( t ) n ′ = a n 1 ( t ) x 1 ( t ) + . . . . . . + a n n ( t ) x n ( t ) + f n ( t ) {\displaystyle x(t)'_{n}=a_{n}1(t)x_{1}(t)+......+a_{n}n(t)x_{n}(t)+f_{n}(t)} where a i j {\displaystyle a_{i}j} are real functions and f i {\displaystyle f_{i}} are fuzzy functions x n ′ ( t ) = ∑ i = 0 1 a i j x i . {\displaystyle x'_{n}(t)=\sum _{i=0}^{1}a_{ij}x_{i}.}
A fuzzy differential equation with partial differential operator is ∇ x ( t ) = F ( t , x ( t ) , α ) , {\displaystyle \nabla x(t)=F(t,x(t),\alpha ),} for all α ∈ [ 0 , 1 ] {\displaystyle \alpha \in [0,1]} .
A fuzzy differential equation with fractional differential operator is
d n x ( t ) d t n = F ( t , x ( t ) , α ) , {\displaystyle {\frac {d^{n}x(t)}{dt^{n}}}=F(t,x(t),\alpha ),} for all α ∈ [ 0 , 1 ] {\displaystyle \alpha \in [0,1]} where n {\displaystyle n} is a rational number . | https://en.wikipedia.org/wiki/Fuzzy_differential_equation |
Fuzzy differential inclusion is the extension of differential inclusion to fuzzy sets introduced by Lotfi A. Zadeh . [ 1 ] [ 2 ]
x ′ ( t ) ∈ [ f ( t , x ( t ) ) ] α {\displaystyle x'(t)\in [f(t,x(t))]^{\alpha }} with x ( 0 ) ∈ [ x 0 ] α {\displaystyle x(0)\in [x_{0}]^{\alpha }}
Suppose f ( t , x ( t ) ) {\displaystyle f(t,x(t))} is a fuzzy valued continuous function on Euclidean space. Then it is the collection of all normal, upper semi-continuous , convex , compactly supported fuzzy subsets of R n {\displaystyle \mathbb {R} ^{n}} .
The second order differential is
x ″ ( t ) ∈ [ k x ] α {\displaystyle x''(t)\in [kx]^{\alpha }} where k ∈ [ K ] α {\displaystyle k\in [K]^{\alpha }} , K {\displaystyle K} is trapezoidal fuzzy number ( − 1 , − 1 / 2 , 0 , 1 / 2 ) {\displaystyle (-1,-1/2,0,1/2)} , and x 0 {\displaystyle x_{0}} is a trianglular fuzzy number (-1,0,1).
Fuzzy differential inclusion (FDI) has applications in | https://en.wikipedia.org/wiki/Fuzzy_differential_inclusion |
Fuzzy electronics is an electronic technology that uses fuzzy logic , instead of the two-state Boolean logic more commonly used in digital electronics . Fuzzy electronics is fuzzy logic implemented on dedicated hardware. This is to be compared with fuzzy logic implemented in software running on a conventional processor. Fuzzy electronics has a wide range of applications, including control systems and artificial intelligence .
The first fuzzy electronic circuit was built by Takeshi Yamakawa et al. in 1980 using discrete bipolar transistors. The first industrial fuzzy application was in a cement kiln in Denmark in 1982. The first VLSI fuzzy electronics was by Masaki Togai and Hiroyuki Watanabe in 1984. In 1987, Yamakawa built the first analog fuzzy controller. The first digital fuzzy processors came in 1988 by Togai (Russo, pp. 2–6).
In the early 1990s, the first fuzzy logic chips were presented to the public. Two companies which are Omron and NEC have announced the development of dedicated fuzzy electronic hardware in the year 1991. [ 1 ] Two years later, the Japanese Omron Cooperation has shown a working fuzzy chip during a technical fair. [ 2 ]
This electronics-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Fuzzy_electronics |
Fuzzy routing is the application of fuzzy logic to routing protocols , particularly in the context of ad-hoc wireless networks and in networks supporting multiple quality of service classes. It is currently the subject of research.
This computer networking article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Fuzzy_routing |
Fyodor Dmitriyevich Urnov ( Russian : Фёдор Дми́триевич Урнов ; born 1968) [ 1 ] [ 2 ] is a Russian-born biomedical researcher and who has played a leading role in the field of genome editing . He is a Professor of Genetics, Genomics, and Development at the University of California, Berkeley and Director of the Center for Translational Genomics at the university's Innovative Genomics Institute . [ 3 ] [ 4 ] [ 5 ] In 2005 Urnov and his colleagues coined the term "genome editing" and demonstrated the first use of ZFNs to edit DNA in human cells. [ 6 ] [ 7 ] [ 8 ] Urnov is considered a pioneering figure in the field of genome editing [ 7 ] and his work has been cited widely. [ 9 ] [ 10 ] [ 11 ]
Fyodor Urnov was born in Soviet Russia to a linguist mother and a literary critic father. He was raised in Moscow . Urnov's father frequently purchased him books; on his 12th birthday, Urnov received a copy of James D. Watson's book The Double Helix . The book helped to spark Urnov's early interest in life sciences . [ 12 ]
Urnov attended Moscow State University , where he received his undergraduate degree in biology in 1990. Following the fall of the Iron Curtain , Urnov applied to graduate schools in the United States. He attended Brown University for doctoral studies where he worked as a researcher in the laboratory of Susan Gerbi . [ 12 ] He received his Ph.D. from Brown in 1996.
After graduating, Urnov worked with DNA in the laboratory of Alan Wolffe at the National Institutes of Health . In 2000, Urnov followed Wolffe to Sangamo Therapeutics where he had been recruited as Chief Scientific Officer. Shortly after moving to the San Francisco Bay Area , Urnov was offered an adjunct position as a lecturer at the University of California, Berkeley. [ 12 ]
In 2005 Urnov's team at Sangamo demonstrated the first use of ZFNs to edit DNA in human cells and coined the term "genome editing." [ 8 ]
In 2019 Urnov joined UC Berkeley as Professor of Genetics, Genomics, and Development and Director of the Center for Translational Genomics at the Innovative Genomics Institute . [ 3 ] [ 4 ] [ 13 ] | https://en.wikipedia.org/wiki/Fyodor_Urnov |
Fáinne ( Irish: [ˈfˠaːn̠ʲə] ; pl. Fáinní but often Fáinnes in English) is the name of a pin badge worn to show fluency in, or a willingness to speak, the Irish language .
The three modern versions of the pin as relaunched in 2014 by Conradh na Gaeilge are the Fáinne Óir (gold circle), Seanfháinne (old fáinne/circle) and Fáinne Airgid (silver circle).
In other contexts, fáinne simply means "ring" or "circle" and is also used to give such terms as fáinne pósta ( wedding ring ), fáinne an lae ( daybreak ), Tiarna na bhFáinní ( The Lord of the Rings ), and fáinne cluaise ( earring ).
An Fáinne Úr ('úr' meaning 'new') is the modernised rendition of the Fáinne, having been updated in 2014 by Conradh na Gaeilge. There are three versions presently available, none requiring test or certification:
( The Original Organisation)
Two Irish language organisations, An Fáinne (est. 1916) ("The Ring" or "The Circle" in Irish) and the Society of Gaelic Writers (est. 1911), were founded by Piaras Béaslaí (1881–1965).
They were intended to work together to a certain extent, the former promoting the language and awarding those fluent in its speaking with a Fáinne Óir (Gold Ring) lapel pin, and the latter would promote and create a pool of quality literary works in the language.
All the personnel actively involved in promoting the concept of An Fáinne were associated with Conradh na Gaeilge, and from an early time, An Fáinne used the Dublin postal address of 25 Cearnóg Pharnell / Parnell Square, the then HQ of Conradh na Gaeilge though the organisations were officially separate, at least at first.
The effectiveness of the organisation was acknowledged in the Dáil Éireann on 6 August 1920, when Richard Mulcahy , the Sinn Féin Teachta Dála for Clontarf suggested that a league on the model of the Fáinne for the support of Irish manufactures might be established. [ 1 ]
The Fáinne lapel pins were, at first, a limited success. They appealed mainly to Nationalists and Republicans , for whom the language was generally learnt as adults as a second language. The appeal to people for whom Irish was the native tongue was limited. They spoke Irish, as did everyone from their village, so there was no point whatsoever wearing a pin to prove it, even if they could have afforded one, or for that matter, even known they existed.
In the early 1920s, many people who earned their Fáinne did so in prison, the majority of these being anti-treaty Irish Republican Army (IRA) Volunteers during the Irish Civil War .
According to Piaras Béaslaí's own article in the magazine Iris An Fháinne in 1922, he states that in the winter of 1915 the language movement was at a low ebb due to lack of funds and a large portion of the best Gaels being so involved in the work of the volunteers that they were forgetting about speaking Irish. He says he wrote an article in The Leader proposing that Gaels establish an association of those who would take a solemn oath to only speak Irish at certain events and to other Gaeilgeoirí and that they should wear a clear symbol.
The article got many letters in favour and against, but two men, Tadhg Ó Scanaill and Colm Ó Murchadha, came to him asking him to organise a meeting towards setting up a council. He says that it was they who set the whole thing up. He says that he went to speak to Cú Uladh (Peadar Mac Fhionnlaíoch 1856–1942), then vice president of Conradh na Gaeilge, and he highly praised the idea.
The meeting was organised for some time in the spring of 1916 in Craobh an Chéitinnigh (the Keating Branch). They went to a 'seanchus' prior to their own meeting in the Ard Chraobh (High Branch) and presented their idea to all those present. They were so taken with the idea that they all came with them to their own meeting in Craobh an Chéitinnigh.
Cú Uladh was there before them and at this meeting and they decided they would (1) form the association and (2) name it "An Fáinne" instead of "An Fáinne Gaedhalach", which was proposed by Colm Ó Murchadha, and three officers were elected to conduct the work of the association.
Piaras supposes that Tadhg Ó Sganaill first thought of the Fáinne (ring) as the symbol. It was an inspired idea, he says, because no one had even thought of this symbol when the name was first proposed.
He states at the end of the article that they had only begun the work of the committee when Easter Week arrived and some of the small amount that were involved were snatched away, but he says, the work continued and the world knows how they well they got on since then.
The consistently high standard required to qualify for the Fáinne at this time made them quite prestigious, and there are many reports of people being recruited as night-school teachers of Irish-based purely on the fact they wore the pin.
The President of the Executive Council of the Irish Free State , W. T. Cosgrave acknowledged the Fáinne on 8 February 1924 as an indicator of Irish Language proficiency. [ 2 ]
The fact that the underlying reason many Fáinne wearers had studied Irish was political meant that the semi-independence of the Irish Free State , and the later complete independence of the Irish Republic , along with a period of relative peace in the new province of Northern Ireland , meant they had, to some extent, achieved their aim. Twenty years or so later, a Fáinne would be a very rare sight. Due to lack of demand they were no longer manufactured, and the organisation had fizzled out.
Conradh na Gaeilge and other Irish-language bodies attempted a revival, circa 1965, of the Fáinne , which, for a short time at least, became successful: An Fáinne Nua (' The New Fáinne' ) was marketed with the slogan Is duitse an Fáinne Nua! – meaning "The New Fáinne is for you !."
It came in three varieties:
The Gold Fáinne was manufactured from 9ct Gold, whilst the other two were sterling silver. The Coloured Fáinne also had an enamel blue ring separating two concentric silver circles. The prices for the Gold, Silver and Coloured varieties in 1968 were twelve shillings and sixpence, four shillings and five shillings respectively.
They were popular in Ireland during the 1960s–1970s, but fell into relative disuse shortly afterwards. Included among reasons commonly given for this were that the change in fashion made it impractical to wear a lapel pin; the resumption of hostilities in Northern Ireland making people either not wanting to show publicly a "love for things Irish" for fear of intimidation; or, for the more radical elements to place "Irishness" second to "freedom".
As cúpla focal means "a couple of words". The Conradh na Gaeilge website notes that this badge is "Suitable for anyone who has a few words of Irish. [ 3 ] "
The Béal na nGael (Mouth of the Irish) is a different pin badge that shows a face with spiked hair and an open mouth. [ 4 ] It was developed by the students of the Gaelcholáiste Reachrann gaelscoil and marketed primarily to youth in the Dublin Area. "The aim of the badge is to let the world know that the user is both willing and able to speak Irish, and the students say that what they are promoting is 'a practical product to stimulate more peer-to-peer communication through Irish.'" [ 5 ] "The badge won't threaten the place of the Fáinne , they say, because their target market is an age group which is not wearing the Fáinne and which, their market research suggests, is in many cases not even aware that the Fáinne exists. They hope this target market will latch on to the badge and wear it as an invitation to others to speak to them in Irish." [ 5 ] | https://en.wikipedia.org/wiki/Fáinne |
In the mathematical field of graph theory , Fáry's theorem states that any simple , planar graph can be drawn without crossings so that its edges are straight line segments . That is, the ability to draw graph edges as curves instead of as straight line segments does not allow a larger class of graphs to be drawn. The theorem is named after István Fáry , although it was proved independently by Klaus Wagner ( 1936 ), Fáry ( 1948 ), and Sherman K. Stein ( 1951 ).
One way of proving Fáry's theorem is to use mathematical induction . [ 1 ] Let G be a simple plane graph with n vertices; we may add edges if necessary so that G is a maximally plane graph. If n < 3, the result is trivial. If n ≥ 3, then all faces of G must be triangles, as we could add an edge into any face with more sides while preserving planarity, contradicting the assumption of maximal planarity. Choose some three vertices a , b , c forming a triangular face of G . We prove by induction on n that there exists a straight-line combinatorially isomorphic re-embedding of G in which triangle abc is the outer face of the embedding. ( Combinatorially isomorphic means that the vertices, edges, and faces in the new drawing can be made to correspond to those in the old drawing, such that all incidences between edges, vertices, and faces—not just between vertices and edges—are preserved.) As a base case, the result is trivial when n = 3 and a , b and c are the only vertices in G . Thus, we may assume that n ≥ 4.
By Euler's formula for planar graphs, G has 3 n − 6 edges; equivalently, if one defines the deficiency of a vertex v in G to be 6 − deg ( v ) , the sum of the deficiencies is 12 . Since G has at least four vertices and all faces of G are triangles, it follows that every vertex in G has degree at least three. Therefore each vertex in G has deficiency at most three, so there are at least four vertices with positive deficiency. In particular we can choose a vertex v with at most five neighbors that is different from a , b and c . Let G' be formed by removing v from G and retriangulating the face f formed by removing v . By induction, G' has a combinatorially isomorphic straight line re-embedding in which abc is the outer face. Because the re-embedding of G' was combinatorially isomorphic to G' , removing from it the edges which were added to create G' leaves the face f , which is now a polygon P with at most five sides. To complete the drawing to a straight-line combinatorially isomorphic re-embedding of G , v should be placed in the polygon and joined by straight lines to the vertices of the polygon. By the art gallery theorem , there exists a point interior to P at which v can be placed so that the edges from v to the vertices of P do not cross any other edges, completing the proof.
The induction step of this proof is illustrated at right.
De Fraysseix, Pach and Pollack showed how to find in linear time a straight-line drawing in a grid with dimensions linear in the size of the graph, giving a universal point set with quadratic size. A similar method has been followed by Schnyder to prove enhanced bounds and a characterization of planarity based on the incidence partial order. His work stressed the existence of a particular partition of the edges of a maximal planar graph into three trees known as a Schnyder wood .
Tutte's spring theorem states that every 3-connected planar graph can be drawn on a plane without crossings so that its edges are straight line segments and an outside face is a convex polygon (Tutte 1963). It is so called because such an embedding can be found as the equilibrium position for a system of springs representing the edges of the graph.
Steinitz's theorem states that every 3-connected planar graph can be represented as the edges of a convex polyhedron in three-dimensional space. A straight-line embedding of G , {\displaystyle G,} of the type described by Tutte's theorem, may be formed by projecting such a polyhedral representation onto the plane.
The Circle packing theorem states that every planar graph may be represented as the intersection graph of a collection of non-crossing circles in the plane. Placing each vertex of the graph at the center of the corresponding circle leads to a straight line representation.
Heiko Harborth raised the question of whether every planar graph has a straight line representation in which all edge lengths are integers. [ 2 ] The truth of Harborth's conjecture remains unknown. Integer-distance straight line embeddings are known to exist for cubic graphs . [ 3 ]
Sachs (1983) raised the question of whether every graph with a linkless embedding in three-dimensional Euclidean space has a linkless embedding in which all edges are represented by straight line segments, analogously to Fáry's theorem for two-dimensional embeddings. | https://en.wikipedia.org/wiki/Fáry's_theorem |
In the mathematical theory of knots , the Fáry–Milnor theorem , named after István Fáry and John Milnor , states that three-dimensional smooth curves with small total curvature must be unknotted . The theorem was proved independently by Fáry in 1949 and Milnor in 1950. It was later shown to follow from the existence of quadrisecants ( Denne 2004 ).
If K is any closed curve in Euclidean space that is sufficiently smooth to define the curvature κ at each of its points, and if the total absolute curvature is less than or equal to 4π, then K is an unknot , i.e.:
The contrapositive tells us that if K is not an unknot, i.e. K is not isotopic to the circle, then the total curvature will be strictly greater than 4π. Notice that having the total curvature less than or equal to 4 π is merely a sufficient condition for K to be an unknot; it is not a necessary condition . In other words, although all knots with total curvature less than or equal to 4π are the unknot, there exist unknots with curvature strictly greater than 4π.
For closed polygonal chains the same result holds with the integral of curvature replaced by the sum of angles between adjacent segments of the chain. By approximating arbitrary curves by polygonal chains, one may extend the definition of total curvature to larger classes of curves, within which the Fáry–Milnor theorem also holds ( Milnor 1950 , Sullivan 2008 ). | https://en.wikipedia.org/wiki/Fáry–Milnor_theorem |
Félix I (officially " F-360-BD ") was a Brazilian Army Technical School (today's Military Institute of Engineering [ 1 ] ) project led by Lieutenant Colonel Manoel dos Santos Lage which aimed, in 1959, to launch the Flamengo cat into space. But the project was canceled due to pressure from animal advocacy groups, and the launch never took place.
The project, also known as "Operation Meow", [ 2 ] with limited financial resources, was part of the graduation class of 1958 of the Army Technical School that aimed to create a sounding rocket , something unheard of in Brazil at the time. [ 3 ] [ 4 ] The official name was "Rocket Sonda 360-BD", unrelated to the later Sonda I [ pt ] . [ 5 ]
The rocket had an outer diameter of 400 mm, a length of 4.3 meters, and a total mass of 350 kg with the payload, and it used only a single stage and was propelled by gunpowder, [ 6 ] reaching a maximum speed of 1,950 m/s. [ 7 ] Lieutenant-Colonel Myearel dos Santos Lage's ultimate goal, [ a ] head of the Rocket Program and leader of the project, but not shared by the institution, was to develop a satellite launch vehicle. [ 10 ] [ 4 ] The project also had the collaboration of scientists Carlos Chagas Filho and César Lattes . [ 11 ] Carlos Chagas Filho was responsible for the idea of choosing a cat, because he was interested in observing how these animals reacted under laboratory conditions. [ 12 ] Most of the material used to build the rocket was obtained from the War Arsenal. [ 2 ]
The project, which aimed to test a guided missile costing Cr$ 600,000, [ b ] was nicknamed "Felix I" by the Rio de Janeiro press after they discovered their intention to launch a cat, Flamengo, into space. Originally they planned for the rocket to reach the 300 km mark, but this was abandoned due to difficulties in the calculations. [ 10 ] [ 14 ] [ 15 ] The final decision was that the class of 1958 would develop a rocket that reached an apogee of 120 km and the class of 1950 would work on one that reached 300 km, with the ultimate goal of developing a Thor-type rocket that would reach orbits greater than 500 km by June 1960. [ 16 ] [ 4 ]
Initially the rocket was to be launched in 1957, but it was delayed twice and by December 1958 they hoped to launch in early January 1959. [ 4 ]
The rocket would be launched from a base in Cabo Frio . Its accelerometer would be connected to a transmitter at a frequency of 73 Mc/s. [ 17 ] César Lattes was responsible for building three transmitters and the instruments aimed at cosmic ray detection; [ c ] Lieutenant-Colonel Carlos Alberto Braga Coelho built the electronics of the rocket; Carlos Chagas Filho (IBCCF) developed the instruments for monitoring the cat's health; and astronomer Mário Ferreira Dias, from the Valongo Observatory , developed the calculations related to the flight. [ 19 ]
The combustion chamber was built by the Army War Arsenal in company with the students of the Armaments Course, with the carbon steel plate produced by the Companhia Siderúrgica Nacional . The rocket was painted silver with red stripes in a spiral, to help the visibility of the rocket in flight, as the process would be monitored by the National Observatory . [ 7 ]
The rocket thrust was predicted to be 1,920 kgf with 6G of acceleration, 19.3s of combustion, and a final velocity of 1,960 m/s. The propellant, developed by the Army Technical School, was called "BD 1000C Gunpowder". [ 20 ] The rocket would carry a 180-kilogram payload of gunpowder to reach the ionosphere . [ 4 ]
The payload fairing , with a final mass of 30 kg, would contain an acrylic chamber for the cat, as well as the other instruments for the mission. The chamber, with the return speed estimated at 1,800 m/s, [ 21 ] would initially be rescued by two 4.5 m 2 {\displaystyle 4.5m^{2}} air braking devices, and would be followed by a 68 kg parachute developed by the Army Air Ground Division Core, open at an altitude of 5,000 meters, [ 22 ] all in an automatic way. [ 23 ] The cat would have four hours of oxygen [ 12 ] and would be placed face up on a nylon mattress. The flight would last 40 minutes, falling into the sea 30 kilometers from the launch pad, off Angra dos Reis , and would be rescued by the Brazilian Navy . Rescuing the cat alive was considered the greatest challenge of the project. [ 4 ] [ 24 ] The rocket stages would be rescued by two parachutes. [ 25 ] Finally, the flight date would be analyzed by César Lattes . [ 26 ]
If the mission was successful, the future rockets would be made available to the National Nuclear Energy Council and the Biophysics Institute [ pt ] for scientific research. [ 27 ]
Flamengo, [ d ] popularly known as "Meow", [ 29 ] the tomcat of Lieutenant-Colonel Lage's daughters, was one of the twelve candidates for the flight. He was the leading candidate and would only be released if he was in good health on the day of the flight [ 4 ] [ 30 ] and his presence on the flight was already confirmed in December 1958. [ 28 ] But in October 1958, the Diário do Paraná announced that Carlos Chagas Filho would replace the animal with an amoeba , arguing that a microscopic animal would be of greater scientific use in the study of cosmic rays. [ 31 ] [ 32 ] Despite this, Colonel Lage kept the cat in the project [ 33 ] and when asked in 1959 about the reason for launching the cat, he replied: "... the recovery of this cat, alive, will be an extraordinary achievement". [ 14 ] [ e ] On 19 December 1958 the cat posed for the media inside the Technical School. [ 34 ] If the launch had taken place, it would have been Latin America's first living being in space. [ 35 ]
Carlos Chagas Filho , when the experiment began to gain visibility in the media, renounced any renewed interest in sending a cat on the mission and the possibility of any scientific learning, besides citing that the acrylic capsule would face difficulties with drastic temperature changes. [ 33 ] [ 32 ]
In addition to the disagreement with Carlos Chagas Filho, the project team received protests from the "North American Feline Society," something that the project manager disregarded, believing in the safety of the vehicle. The SUIPA [ pt ] also opposed the use of the cat. [ 36 ] [ 37 ]
Members of the Faculty of Veterinary Medicine and other experts were also skeptical of Flamengo's chances of survival, and Leo Rosen, vice president of SUIPA, also reiterated the group's position against the experiment [ 38 ] SUIPA also sent an appeal and a petition, signed by, among others, Rachel de Queiroz and Carlos Drummond de Andrade , to the Commander of the Army Technical School and to the Minister of War, General Teixeira Lott , against launching the cat in the rocket. [ 39 ] [ 30 ] [ 40 ] On the issue of animal experiments, SUIPA only advocated when extremely necessary, and was skeptical of the need for the cat experiment. [ 41 ] The Brazilian government received thousands of letters protesting against the experiment, but the Army ignored them. [ 13 ] And despite all the protests, including from Europe, the project leader continued with his plans. [ 28 ] [ 42 ]
In November 1958 it was announced that the launch would be held in secret to "avoid sensationalism " [ 15 ] and in the same month Colonel João Luís Vieira Maldonado, director of the Meteorology Service, said that the rocket would only carry sounding devices, and no longer the cat. [ 43 ] However, in January 1959, Colonel Lage still hoped to make the launch with the cat [ 14 ] and in February of the same year they planned to launch in March. [ 44 ] However, in May 1959, the launch had not yet occurred and freshmen from the National Engineering School held a parade where, among other things, they criticized and satirized the project. [ 45 ] In December 1958 the Army announced that it would test a prototype of the rocket before the official launch. [ 46 ]
In January 1959 the rocket was on display at the Armament Museum of the Army Technical School. [ 8 ] By 1961 it was already clear that the launch had not taken place. [ 47 ] [ f ] It was the last rocket project that Colonel Lage participated in [ 49 ] and was terminated without flying. [ 50 ] Finally, on 18 October 1963, the cat Félicette made a suborbital flight as part of the French space program , returned alive, and was sacrificed after two months for an autopsy and study of her brain. [ 51 ] Colonel Lage was transferred from the Army Technical School in 1960 and all the equipment related to the rocket was disassembled. [ 52 ] Myearel Lage, already a General, born on 4 June 1910, died on 5 August 1977. [ 53 ] The Army Technical School was abolished in favor of the Military Institute of Engineering . [ 54 ]
Because of the project, at that time Brazil was considered one of the three countries with space technology, alongside the United States and the Soviet Union . [ 55 ] In terms of satellite launch capabilities, years later Brazil developed the unsuccessful VLS project, terminated in 2016. The country is currently working on the VLM project. [ 56 ]
(Chronological order) | https://en.wikipedia.org/wiki/Félix_I |
Fétizon oxidation is the oxidation of primary and secondary alcohols utilizing the compound silver(I) carbonate absorbed onto the surface of celite also known as Fétizon's reagent first employed by Marcel Fétizon in 1968. [ 1 ] It is a mild reagent, suitable for both acid and base sensitive compounds. Its great reactivity with lactols makes the Fétizon oxidation a useful method to obtain lactones from a diol . The reaction is inhibited significantly by polar groups within the reaction system as well as steric hindrance of the α-hydrogen of the alcohol.
Fétizon's reagent is typically prepared by adding silver nitrate to an aqueous solution of a carbonate, such as sodium carbonate [ 2 ] or potassium bicarbonate , [ 3 ] while being vigorously stirred in the presence of purified celite.
A proposed mechanism for the oxidation of an alcohol by Fétizon's reagent involves single electron oxidation of both the alcoholic oxygen and the hydrogen alpha to the alcohol by two atoms of silver(I) within the celite surface. The carbonate ion then proceeds to deprotonate the resulting carbonyl generating bicarbonate which is further protonated by the additionally generated hydrogen cation to cause elimination of water and generation of carbon dioxide . [ 4 ]
The rate limiting step of this reaction is proposed to be the initial association of the alcohol to the silver ions. As a result, the presence of even weakly associating ligands to the silver can inhibit the reaction greatly. As a result, even slightly polar solvents of any variety, such as ethyl acetate or methyl ethyl ketone , are avoided when using this reagent as they competitively associate with the reagent. [ 5 ] Additional polar functionalities of the reactant should also be avoided whenever possible as even the presence of an alkene can sometimes reduce the reactivity of a substrate 50 fold. [ 6 ] Commonly employed solvents such as benzene and xylene are extremely non-polar and further acceleration of the reaction can be achieved through the use of the more non-polar heptane . [ 6 ] The solvent is also typically refluxed to drive the reaction with heat and remove the water generated by the reaction through azeotropic distillation .
Steric hindrance of the hydrogen alpha to the alcohol is a major determination of the rate of oxidation as it affects the rate of association. [ 5 ] Tertiary alcohols lacking an alpha hydrogen are selected against and generally do not oxidize in the presence of Fétizon's reagent. [ 7 ]
Increasing the amount of celite used in the reagent accelerates the rate of the reaction by increasing the surface area available to react. However, increasing the amount of celite past 900 grams per mole of silver(I) carbonate begins to slow the reaction due to dilution effects. [ 5 ]
Fétizon's reagent is used primarily in the oxidation of primary or secondary alcohols to aldehydes or ketones with a slight selectivity toward secondary alcohols [ 8 ] and unsaturated alcohols. [ 1 ] The reaction is typically done in a refluxing dry non-polar organic solvent with copious stirring. The reaction time varies with the structure of the alcohol and is typically completed within three hours. A very attractive property of Fétizon's reagent is its ability to be separated from the reaction product by physically filtering it out and washing with benzene.
The inability of Fétizon's reagent to oxidize tertiary alcohols makes it extremely useful in the monooxidation of a [1,2] diol in which one of the alcohols is tertiary while avoiding cleavage of the carbon-carbon bond. [ 7 ]
The mildness and structural sensitivity of the reagent also makes this reagent ideal for the monooxidation of a symmetric diol. [ 8 ]
Lactols are extremely sensitive to Fétizon's reagent, being oxidized very quickly to a lactone functionality. This allows for the selective oxidation of lactols in the presence of other alcohols. [ 9 ] This also allows for a classic use of Fétizon's reagent to form lactones from a primary diol. By oxidizing one of the alcohols to an aldehyde, the second alcohol equilibrates with the aldehyde to form a lactol which is reacted quickly with more Fétizon's reagent to trap the cyclic intermediate as a lactone. [ 8 ] This method allows for the synthesis of seven-member lactones which are traditionally more challenging to synthesize. [ 10 ]
Phenol functional groups can be oxidized to their respective quinone forms. These quinones can further couple within solution producing numerous dimerizations depending upon their substituents. [ 2 ]
Amines have been shown to oxidize in the presence of Fétizon's reagent to enamines [ 11 ] and iminium cations that have been trapped, [ 12 ] but can also be selected against in a compound with more easily oxidized alcohol functionalities. [ 13 ] Fétizon's reagent can also being used to facilitate cycloaddition of a 4-hydroxy-2-furoquinilone and an olefin to form dihydrofuroquinolinones. [ 14 ]
Para-methoxybenzyl (PMB) is a commonly used protecting group for alcohols against Fétizon's reagent. [ 15 ] As Fétizon's oxidation is a neutral reaction, acid and base sensitive protecting groups are also compatible with the reagent and by products generated.
While tertiary alcohols are typically not affected by Fétizon's reagent, tertiary propargylic alcohols have been shown to oxidize under these conditions and results in the fragmentation of the alcohol with an alkyne leaving group. [ 16 ]
Halohydrins that possess a trans stereochemistry have been demonstrated to form epoxides and transposed products in the presence of Fétizon's reagent. Halohydrins possessing a cis-stereochemistry seem to perform a typical Fétizon's oxidation to a ketone. [ 17 ]
[1,3] diols have a tendency to eliminate water following the monooxidation by Fétizon's reagent to form an enone . [ 8 ]
Under differing structural conditions, [1,2] diols can form diketones in the presence of Fétizon's reagent. However, oxidative carbon-carbon bond cleavage may also occur. [ 18 ] [ 19 ]
Since its discovery as a useful method of oxidation, Fétizon's reagent has been used in the total synthesis of numerous molecules such as (±)-bukittinggine. [ 20 ] Fétizon's reagent has also been employed extensively in the study of various sugar chemistry, to achieve selective oxidation of tri and tetra methylated aldoses to aldolactones, [ 21 ] oxidation of D-xylose and L-arabinose to D-threose and L-erythrose respectively, [ 22 ] and oxidation of L-sorbose to afford L-threose among many others. [ 23 ] | https://en.wikipedia.org/wiki/Fétizon_oxidation |
Förster coupling is the resonant energy transfer between excitons within adjacent QD's ( quantum dots ). The first studies of Forster were performed in the context of the sensitized luminescence of solids. Here, an excited sensitizer atom can transfer its excitation to a neighbouring acceptor atom, via an intermediate virtual photon. This same mechanism has also been shown to be responsible for exciton transfer between QD's and within molecular systems and biosystems (though incoherently, as a mechanism for photosynthesis), all of which may be treated in a similar formulation. (See also Förster resonance energy transfer (FRET).)
In the introductory lecture given by T. Förster, [ 1 ] he considered the transfer of electronic excitation energy between otherwise well-separated atomic or molecular electronic systems, which exclude the trivial case of an excitation transfer that consists in the emission of one quantum of light by the first atom or molecule followed by re-absorption by the second one. It is only the non-radiative transfer of excitation occurring during the short lifetimes of excited electronic systems which he considered there.
The first observation of energy transfer was made by Cario and Franck (1922) [ 2 ] in their classical experiments on sensitized fluorescence of atoms in the vapour phase. A mixture of mercury and thallium vapour, when irradiated with the light of the mercury resonance line, shows the emission spectra of both atoms. Since thallium atoms do not absorb the exciting light, they can get excited only indirectly by an excitation transfer from mercury atoms. A transfer by reabsorption is impossible here. Therefore, this transfer must be a non-radiative one with a mercury atom as the donor or sensitizer and the thallium atom as the acceptor. Unfortunately, in this case it cannot be decided whether the transfer occurs between distant atoms or during a normal collision or even in a labile molecule formed as an intermediate. This decision, however, was possible in similar cases, as in the mercury-sensitized fluorescence of sodium and in the mutual sensitization of the fluorescence of different mercury isotopes. In these cases, the transfer occurs over distances very much larger than those in normal collisional separations. Similar observations of sensitized fluorescence were made with molecular vapours and in solution.
Further experiments have shown that in this case the transfer occurs not over collisional distances but over the mean intermolecular distances of sensitizer and acceptor, corresponding to a concentration of 10 −3 to 10 −2 M . This is demonstrated by the fact that sensitization occurs with similar half-value concentrations in solution of very different viscosities and even in organic glasses at low temperature. The possibility of the formation of a complex between sensitizer and acceptor molecules was excluded by the additivity of the absorption spectra and the different dependence on concentration to be expected in this case. It must be concluded, therefore, that excitation transfer of a non-trivial nature occurs over the mean distances between statistically distributed molecules which are about 40Å in this case. It differs from short-distance collisional transfer by its independence of solvent viscosity and from transfer within a molecular complex by the constancy of absorption spectra and the decrease in sensitizer fluorescence lifetime.
Table 2 summarizes some qualitative features of this kind of long-range transfer and of some more or less trivial mechanisms. The non-trivial transfer differs from re-absorption transfer by its independence of the volume of the solution, by the decrease in sensitizer fluorescence lifetime, and by the invariability of the sensitizer fluorescence spectrum. It differs from short-distance collisional transfer by its independence of solvent viscosity and from transfer within a molecular complex by the constancy of absorption spectra and the decrease in sensitizer fluorescence lifetime. In most cases, some of these different properties allow a decision between trivial and non-trivial transfer mechanisms. Further discriminations may be made by quantitative studies of these properties.
[ 3 ] The electrons interact via the Coulomb interaction, given by the Hamiltonian
where the Coulomb matrix element is given by
Here, ϵ r {\displaystyle \epsilon _{r}} is the dielectric constant of the medium.
To calculate the dynamics of two coupled QDs (each modeled as an interband two-level system with one conduction and one valence level | c ⟩ {\displaystyle |c\rangle } and | v ⟩ {\displaystyle |v\rangle } , respectively) which have no electronic overlap, an expansion of the potential is performed: (i) a long-range expansion about a reference point of each QD, varying on a mesoscopic scale and neglecting the variation on the scale of the elementary cell - this yields level diagonal contributions in the Hamiltonian H cc = ∑ i > j V cc ij a c i † a c j † a c j a c i {\displaystyle H_{\text{cc}}=\sum _{i>j}V_{\text{cc}}^{\text{ij}}a_{c_{i}}{}^{\dagger }a_{c_{j}}{}^{\dagger }a_{c_{j}}a_{c_{i}}} and H cv = ∑ i ≠ j V cv ij a c i † a v j † a v j a c i {\displaystyle H_{\text{cv}}=\sum _{i\neq j}V_{\text{cv}}^{\text{ij}}a_{c_{i}}{}^{\dagger }a_{v_{j}}{}^{\dagger }a_{v_{j}}a_{c_{i}}} ; and (ii) a short-range expansion about an arbitrary lattice vector, taking into account the microscopic variation of the QD - this yields nondiagonal contributions H F = ∑ i ≠ j V F ij a c i † a v j † a c j a v i {\displaystyle H_{F}=\sum _{i\neq j}V_{F}^{\text{ij}}a_{c_{i}}{}^{\dagger }a_{v_{j}}{}^{\dagger }a_{c_{j}}a_{v_{i}}} . On the dipole-dipole level, the level diagonal elements correspond to an electrostatic energetic shift of the system (biexcitonic shift V bs = V cv − V cc {\displaystyle V_{\text{bs}}=V_{\text{cv}}-V_{\text{cc}}} ), while the nondiagonal elements, the so-called Förster coupling elements V F {\displaystyle V_{F}} , correspond to an excitation transfer between the different QDs.
Here, [ 4 ] we shall consider excitons in two coupled QD's and the Coulomb interactions between them. More specifically, we shall derive an analytical expression for the strength of the inter-dot Foerster coupling. It can be also shown that this coupling is, under certain conditions, of dipole-dipole type and that it is responsible for resonant exciton exchange between adjacent QD's. This is a transfer of energy only, not a tunnelling effect.
we write the Hamiltonian of two interacting QD's in the computational basis { | 00 ⟩ , | 01 ⟩ , | 10 ⟩ , | 11 ⟩ } a s ( ℏ = 1 ) {\displaystyle \{|00\rangle ,|01\rangle ,|10\rangle ,|11\rangle \}\ as\ (\hbar =1)}
H ^ = ( ω 0 0 0 0 0 ω 0 + ω 2 V F 0 0 V F ω 0 + ω 1 0 0 0 0 ω 0 + ω 1 + ω 2 + V XX ) {\displaystyle {\hat {H}}=\left({\begin{array}{cccc}\omega _{0}&0&0&0\\0&\omega _{0}+\omega _{2}&V_{F}&0\\0&V_{F}&\omega _{0}+\omega _{1}&0\\0&0&0&\omega _{0}+\omega _{1}+\omega _{2}+V_{\text{XX}}\end{array}}\right)}
where the off-diagonal Förster interaction is given by V F {\displaystyle V_{F}} , and the direct Coulomb binding energy between the two excitons, one on each dot, is on the diagonal and given by V XX {\displaystyle V_{\text{XX}}} . The ground state energy is denoted by ω 0 {\displaystyle \omega _{0}} , and Δ ω ≡ ω 1 − ω 2 {\displaystyle \Delta \omega \equiv \omega _{1}-\omega _{2}} is the difference between the excitation energy for dot I and that for dot II. These excitation energies and inter-dot interactions are all functions of the applied field F.
It is also straightforward to see that an off-diagonal Förster coupling does indeed correspond to a resonant transfer of energy; if we begin in the state | 10 ⟩ {\displaystyle |10\rangle } (exciton on dot I, no exciton on dot II) this will naturally evolve to a state | 01 ⟩ {\displaystyle |01\rangle } | https://en.wikipedia.org/wiki/Förster_coupling |
Förster resonance energy transfer ( FRET ), fluorescence resonance energy transfer , resonance energy transfer ( RET ) or electronic energy transfer ( EET ) is a mechanism describing energy transfer between two light-sensitive molecules ( chromophores ). [ 1 ] A donor chromophore, initially in its electronic excited state, may transfer energy to an acceptor chromophore through nonradiative dipole–dipole coupling . [ 2 ] The efficiency of this energy transfer is inversely proportional to the sixth power of the distance between donor and acceptor, making FRET extremely sensitive to small changes in distance. [ 3 ] [ 4 ]
Measurements of FRET efficiency can be used to determine if two fluorophores are within a certain distance of each other. [ 5 ] Such measurements are used as a research tool in fields including biology and chemistry.
FRET is analogous to near-field communication, in that the radius of interaction is much smaller than the wavelength of light emitted. In the near-field region, the excited chromophore emits a virtual photon that is instantly absorbed by a receiving chromophore. These virtual photons are undetectable, since their existence violates the conservation of energy and momentum, and hence FRET is known as a radiationless mechanism. Quantum electrodynamical calculations have been used to determine that radiationless FRET and radiative energy transfer are the short- and long-range asymptotes of a single unified mechanism. [ 6 ] [ 7 ] [ 8 ]
Förster resonance energy transfer is named after the German scientist Theodor Förster . [ 9 ] When both chromophores are fluorescent, the term "fluorescence resonance energy transfer" is often used instead, although the energy is not actually transferred by fluorescence . [ 10 ] [ 11 ] In order to avoid an erroneous interpretation of the phenomenon that is always a nonradiative transfer of energy (even when occurring between two fluorescent chromophores), the name "Förster resonance energy transfer" is preferred to "fluorescence resonance energy transfer"; however, the latter enjoys common usage in scientific literature. [ 12 ] FRET is not restricted to fluorescence and occurs in connection with phosphorescence as well. [ 10 ]
The FRET efficiency ( E {\displaystyle E} ) is the quantum yield of the energy-transfer transition, i.e. the probability of energy-transfer event occurring per donor excitation event: [ 13 ]
where k f {\displaystyle k_{f}} the radiative decay rate of the donor, k ET {\displaystyle k_{\text{ET}}} is the rate of energy transfer, and k i {\displaystyle k_{i}} the rates of any other de-excitation pathways excluding energy transfers to other acceptors. [ 14 ] [ 15 ]
The FRET efficiency depends on many physical parameters [ 16 ] that can be grouped as: 1) the distance between the donor and the acceptor (typically in the range of 1–10 nm), 2) the spectral overlap of the donor emission spectrum and the acceptor absorption spectrum , and 3) the relative orientation of the donor emission dipole moment and the acceptor absorption dipole moment.
E {\displaystyle E} depends on the donor-to-acceptor separation distance r {\displaystyle r} with an inverse 6th-power law due to the dipole–dipole coupling mechanism:
with R 0 {\displaystyle R_{0}} being the Förster distance of this pair of donor and acceptor, i.e. the distance at which the energy transfer efficiency is 50%. [ 14 ] The Förster distance depends on the overlap integral of the donor emission spectrum with the acceptor absorption spectrum and their mutual molecular orientation as expressed by the following equation all in SI units: [ 17 ] [ 18 ] [ 19 ]
where Q D {\displaystyle Q_{\text{D}}} is the fluorescence quantum yield of the donor in the absence of the acceptor, κ 2 {\displaystyle \kappa ^{2}} is the dipole orientation factor, n {\displaystyle n} is the refractive index of the medium, N A {\displaystyle N_{\text{A}}} is the Avogadro constant , and J {\displaystyle J} is the spectral overlap integral calculated as
where f D {\displaystyle f_{\text{D}}} is the donor emission spectrum, f D ¯ {\displaystyle {\overline {f_{\text{D}}}}} is the donor emission spectrum normalized to an area of 1, and ϵ A {\displaystyle \epsilon _{\text{A}}} is the acceptor molar extinction coefficient , normally obtained from an absorption spectrum. [ 20 ] The orientation factor κ is given by
where μ ^ i {\displaystyle {\hat {\mu }}_{i}} denotes the normalized transition dipole moment of the respective fluorophore, and R ^ {\displaystyle {\hat {R}}} denotes the normalized inter-fluorophore displacement. [ 21 ] κ 2 {\displaystyle \kappa ^{2}} = 2/3 is often assumed. This value is obtained when both dyes are freely rotating and can be considered to be isotropically oriented during the excited-state lifetime. If either dye is fixed or not free to rotate, then κ 2 {\displaystyle \kappa ^{2}} = 2/3 will not be a valid assumption. In most cases, however, even modest reorientation of the dyes results in enough orientational averaging that κ 2 {\displaystyle \kappa ^{2}} = 2/3 does not result in a large error in the estimated energy-transfer distance due to the sixth-power dependence of R 0 {\displaystyle R_{0}} on κ 2 {\displaystyle \kappa ^{2}} . Even when κ 2 {\displaystyle \kappa ^{2}} is quite different from 2/3, the error can be associated with a shift in R 0 {\displaystyle R_{0}} , and thus determinations of changes in relative distance for a particular system are still valid. Fluorescent proteins do not reorient on a timescale that is faster than their fluorescence lifetime. In this case 0 ≤ κ 2 {\displaystyle \kappa ^{2}} ≤ 4. [ 20 ]
The units of the data are usually not in SI units. Using the original units to calculate the Förster distance is often more convenient. For example, the wavelength is often in unit nm and the extinction coefficient is often in unit M − 1 c m − 1 {\displaystyle M^{-1}cm^{-1}} , where M {\displaystyle M} is concentration m o l / L {\displaystyle mol/L} . J {\displaystyle J} obtained from these units will have unit M − 1 c m − 1 n m 4 {\displaystyle M^{-1}cm^{-1}nm^{4}} . To use unit Å ( 10 − 10 m {\displaystyle 10^{-10}m} ) for the R 0 {\displaystyle R_{0}} , the equation is adjusted to [ 17 ] [ 22 ] [ 23 ] [ 24 ]
For time-dependent analyses of FRET, the rate of energy transfer ( k ET {\displaystyle k_{\text{ET}}} ) can be used directly instead: [ 17 ]
where τ D {\displaystyle \tau _{D}} is the donor's fluorescence lifetime in the absence of the acceptor.
The FRET efficiency relates to the quantum yield and the fluorescence lifetime of the donor molecule as follows: [ 25 ]
where τ D ′ {\displaystyle \tau _{\text{D}}'} and τ D {\displaystyle \tau _{\text{D}}} are the donor fluorescence lifetimes in the presence and absence of an acceptor respectively, or as
where F D ′ {\displaystyle F_{\text{D}}'} and F D {\displaystyle F_{\text{D}}} are the donor fluorescence intensities with and without an acceptor respectively.
The inverse sixth-power distance dependence of Förster resonance energy transfer was experimentally confirmed by Wilchek , Edelhoch and Brand [ 26 ] using tryptophyl peptides. Stryer , Haugland and Yguerabide [ 27 ] [ citation needed ] [ 28 ] also experimentally demonstrated the theoretical dependence of Förster resonance energy transfer on the overlap integral by using a fused indolosteroid as a donor and a ketone as an acceptor. Calculations on FRET distances of some example dye-pairs can be found here. [ 22 ] [ 24 ] However, a lot of contradictions of special experiments with the theory was observed under complicated environment when the orientations and quantum yields of the molecules are difficult to estimate. [ 29 ]
In fluorescence microscopy , fluorescence confocal laser scanning microscopy , as well as in molecular biology , FRET is a useful tool to quantify molecular dynamics in biophysics and biochemistry , such as protein -protein interactions, protein– DNA interactions, DNA-DNA interactions, [ 30 ] and protein conformational changes. For monitoring the complex formation between two molecules, one of them is labeled with a donor and the other with an acceptor. The FRET efficiency is measured and used to identify interactions between the labeled complexes. There are several ways of measuring the FRET efficiency by monitoring changes in the fluorescence emitted by the donor or the acceptor. [ 31 ]
One method of measuring FRET efficiency is to measure the variation in acceptor emission intensity. [ 18 ] When the donor and acceptor are in proximity (1–10 nm) due to the interaction of the two molecules, the acceptor emission will increase because of the intermolecular FRET from the donor to the acceptor. For monitoring protein conformational changes, the target protein is labeled with a donor and an acceptor at two loci. When a twist or bend of the protein brings the change in the distance or relative orientation of the donor and acceptor, FRET change is observed. If a molecular interaction or a protein conformational change is dependent on ligand binding, this FRET technique is applicable to fluorescent indicators for the ligand detection.
FRET efficiencies can also be inferred from the photobleaching rates of the donor in the presence and absence of an acceptor. [ 18 ] This method can be performed on most fluorescence microscopes; one simply shines the excitation light (of a frequency that will excite the donor but not the acceptor significantly) on specimens with and without the acceptor fluorophore and monitors the donor fluorescence (typically separated from acceptor fluorescence using a bandpass filter ) over time. The timescale is that of photobleaching, which is seconds to minutes, with fluorescence in each curve being given by
where τ pb {\displaystyle \tau _{\text{pb}}} is the photobleaching decay time constant and depends on whether the acceptor is present or not. Since photobleaching consists in the permanent inactivation of excited fluorophores, resonance energy transfer from an excited donor to an acceptor fluorophore prevents the photobleaching of that donor fluorophore, and thus high FRET efficiency leads to a longer photobleaching decay time constant:
where τ pb ′ {\displaystyle \tau _{\text{pb}}'} and τ pb {\displaystyle \tau _{\text{pb}}} are the photobleaching decay time constants of the donor in the presence and in the absence of the acceptor respectively. (Notice that the fraction is the reciprocal of that used for lifetime measurements).
This technique was introduced by Jovin in 1989. [ 32 ] Its use of an entire curve of points to extract the time constants can give it accuracy advantages over the other methods. Also, the fact that time measurements are over seconds rather than nanoseconds makes it easier than fluorescence lifetime measurements, and because photobleaching decay rates do not generally depend on donor concentration (unless acceptor saturation is an issue), the careful control of concentrations needed for intensity measurements is not needed. It is, however, important to keep the illumination the same for the with- and without-acceptor measurements, as photobleaching increases markedly with more intense incident light.
FRET efficiency can also be determined from the change in the fluorescence lifetime of the donor. [ 18 ] The lifetime of the donor will decrease in the presence of the acceptor. Lifetime measurements of the FRET-donor are used in fluorescence-lifetime imaging microscopy (FLIM).
smFRET is a group of methods using various microscopic techniques to measure a pair of donor and acceptor fluorophores that are excited and detected at the single molecule level. In contrast to "ensemble FRET" or "bulk FRET" which provides the FRET signal of a high number of molecules, single-molecule FRET is able to resolve the FRET signal of each individual molecule. The variation of the smFRET signal is useful to reveal kinetic information that an ensemble measurement cannot provide, especially when the system is under equilibrium. Heterogeneity among different molecules can also be observed. This method has been applied in many measurements of biomolecular dynamics such as DNA/RNA/protein folding/unfolding and other conformational changes, and intermolecular dynamics such as reaction, binding, adsorption, and desorption that are particularly useful in chemical sensing, bioassays, and biosensing.
One common pair fluorophores for biological use is a cyan fluorescent protein (CFP) – yellow fluorescent protein (YFP) pair. [ 33 ] Both are color variants of green fluorescent protein (GFP). Labeling with organic fluorescent dyes requires purification, chemical modification, and intracellular injection of a host protein. GFP variants can be attached to a host protein by genetic engineering which can be more convenient. Additionally, a fusion of CFP and YFP ("tandem-dimer") linked by a protease cleavage sequence can be used as a cleavage assay. [ 34 ]
A limitation of FRET performed with fluorophore donors is the requirement for external illumination to initiate the fluorescence transfer, which can lead to background noise in the results from direct excitation of the acceptor or to photobleaching . To avoid this drawback, bioluminescence resonance energy transfer (or BRET) has been developed. [ 35 ] [ 36 ] This technique uses a bioluminescent luciferase (typically the luciferase from Renilla reniformis ) rather than CFP to produce an initial photon emission compatible with YFP.
BRET has also been implemented using a different luciferase enzyme, engineered from the deep-sea shrimp Oplophorus gracilirostris . This luciferase is smaller (19 kD) and brighter than the more commonly used luciferase from Renilla reniformis , [ 37 ] [ 38 ] [ 39 ] [ 40 ] and has been named NanoLuc [ 41 ] or NanoKAZ. [ 42 ] Promega has developed a patented substrate for NanoLuc called furimazine, [ 43 ] [ 41 ] though other valuables coelenterazine substrates for NanoLuc have also been published. [ 42 ] [ 44 ] A split-protein version of NanoLuc developed by Promega [ 45 ] has also been used as a BRET donor in experiments measuring protein-protein interactions. [ 46 ]
In general, "FRET" refers to situations where the donor and acceptor proteins (or "fluorophores") are of two different types. In many biological situations, however, researchers might need to examine the interactions between two, or more, proteins of the same type—or indeed the same protein with itself, for example if the protein folds or forms part of a polymer chain of proteins [ 47 ] or for other questions of quantification in biological cells [ 48 ] or in vitro experiments. [ 49 ]
Obviously, differences in conventional UV-vis spectra will not be the tool used to detect and measure homogeneous FRET, as both the acceptor and donor emit light with the same wavelengths. However, there is evidence that certain nonlinear spectroscopies may provide signatures of homogeneous FRET that would be invisible in linear spectra. [ 50 ] Yet researchers can detect differences in the polarisation between the light which excites the fluorophores and the light which is emitted, in a technique called FRET anisotropy imaging; the level of quantified anisotropy (difference in polarisation between the excitation and emission beams) then becomes an indicative guide to how many FRET events have happened. [ 51 ]
In the field of nano-photonics, FRET can be detrimental if it funnels excitonic energy to defect sites, but it is also essential to charge collection in organic and quantum-dot-sensitized solar cells, and various FRET-enabled strategies have been proposed for different opto-electronic devices. It is then essential to understand how isolated nano-emitters behave when they are stacked in a dense layer. Nanoplatelets are especially promising candidates for strong homo-FRET exciton diffusion because of their strong in-plane dipole coupling and low Stokes shift. [ 52 ] Fluorescence microscopy study of such single chains demonstrated that energy transfer by FRET between neighbor platelets causes energy to diffuse over a typical 500-nm length (about 80 nano emitters), and the transfer time between platelets is on the order of 1 ps. [ 53 ]
Various compounds beside fluorescent proteins. [ 54 ]
The applications of fluorescence resonance energy transfer (FRET) have expanded tremendously in the last 25 years, and the technique has become a staple in many biological and biophysical fields. FRET can be used as a spectroscopic ruler to measure distance and detect molecular interactions in a number of systems and has applications in biology and biochemistry. [ 28 ] [ 55 ]
FRET is often used to detect and track interactions between proteins. [ 56 ] [ 57 ] [ 58 ] [ 59 ] Additionally, FRET can be used to measure distances between domains in a single protein by tagging different regions of the protein with fluorophores and measuring emission to determine distance. This provides information about protein conformation , including secondary structures and protein folding . [ 60 ] [ 61 ] This extends to tracking functional changes in protein structure, such as conformational changes associated with myosin activity. [ 62 ] Applied in vivo, FRET has been used to detect the location and interactions of cellular structures including integrins and membrane proteins . [ 63 ]
FRET can be used to observe membrane fluidity , movement and dispersal of membrane proteins, membrane lipid-protein and protein-protein interactions, and successful mixing of different membranes. [ 64 ] FRET is also used to study formation and properties of membrane domains and lipid rafts in cell membranes [ 65 ] and to determine surface density in membranes. [ 66 ]
FRET-based probes can detect the presence of various molecules: the probe's structure is affected by small molecule binding or activity, which can turn the FRET system on or off. This is often used to detect anions, cations, small uncharged molecules, and some larger biomacromolecules as well. Similarly, FRET systems have been designed to detect changes in the cellular environment due to such factors as pH , hypoxia , or mitochondrial membrane potential . [ 67 ]
Another use for FRET is in the study of metabolic or signaling pathways . [ 68 ] For example, FRET and BRET have been used in various experiments to characterize G-protein coupled receptor activation and consequent signaling mechanisms. [ 69 ] Other examples include the use of FRET to analyze such diverse processes as bacterial chemotaxis [ 70 ] and caspase activity in apoptosis . [ 71 ]
Proteins, DNAs, RNAs, and other polymer folding dynamics have been measured using FRET. Usually, these systems are under equilibrium whose kinetics is hidden. However, they can be measured by measuring single-molecule FRET with proper placement of the acceptor and donor dyes on the molecules. See single-molecule FRET for a more detailed description.
In addition to common uses previously mentioned, FRET and BRET are also effective in the study of biochemical reaction kinetics. [ 72 ] FRET is increasingly used for monitoring pH dependent assembly and disassembly and is valuable in the analysis of nucleic acids encapsulation. [ 73 ] [ 74 ] [ 75 ] [ 76 ] This technique can be used to determine factors affecting various types of nanoparticle formation [ 77 ] [ 78 ] as well as the mechanisms and effects of nanomedicines . [ 79 ]
A different, but related, mechanism is Dexter electron transfer .
An alternative method to detecting protein–protein proximity is the bimolecular fluorescence complementation (BiFC), where two parts of a fluorescent protein are each fused to other proteins. When these two parts meet, they form a fluorophore on a timescale of minutes or hours. [ 80 ] | https://en.wikipedia.org/wiki/Förster_resonance_energy_transfer |
The Fürst-Plattner rule (also known as the trans-diaxial effect ) describes the stereoselective addition of nucleophiles to cyclohexene derivatives. [ 1 ]
Cyclohexene derivatives, such as imines , epoxides , and halonium ions , react with nucleophiles in a stereoselective fashion, affording trans-diaxial addition products. The term “Trans-diaxial addition” describes the mechanism of the addition, however the products are likely to equilibrate by ring flip to the lower energy conformer , placing the new substituents in the equatorial position .
Epoxidation of a substituted cyclohexene affords a product where the R group resides in the pseudo-equatorial position. Nucleophilic ring-opening of this class of epoxides can occur by an attack at either the C1 or C2-position. It is well known that nucleophilic ring-opening reactions of these substrates can proceed with excellent regioselectivity . The Fürst-Plattner rule attributes this regiochemical control to a large preference for the reaction pathway that follows the more stable chair-like transition state (attack at the C1-position) compared to the one proceeding through the unfavored twist boat-like transition state (attack at the C2-position). [ 2 ] [ 3 ] The attack at the C1-position follows a substantially lower reaction barrier of around 5 kcal mol –1 depending on the specific conditions. Similarly, the Fürst-Plattner rule applies to nucleophilic additions to imines and halonium ions .
A recent example of the Fürst-Plattner rule can be seen from Chrisman et al. where limonene is epoxidized to give a 1:1 mixture of diastereomers . Exposure to a nitrogen nucleophile in water at reflux provides only one ring opened product in 75-85% ee. [ 4 ]
The half-chair conformation indicates that attack occurs stereoselectively on the diastereomer where the electrophilic carbon can receive the nucleophile and proceed to the favored chair conformation.
Although not well understood at the time, the Fürst-Plattner rule played a critical role during R. B. Woodward 's synthesis of Reserpine . [ 5 ] The problematic stereocenter is highlighted in red, below.
Woodward's synthetic strategy used a Bischler-Napieralski reaction to form the tetrahydrocarbazole portion of Reserpine. The subsequent imine intermediate was treated with sodium borohydride, affording the wrong stereoisomer due to the Fürst-Plattner effect.
Examining the intermediate structure shows that the hydride preferentially added to the 3-carbon via the top face of the imine to avoid an unfavorable twist-boat intermediate. Unfortunately, this outcome required Woodward to perform several additional steps to complete the total synthesis of reserpine with the proper stereochemistry. | https://en.wikipedia.org/wiki/Fürst-Plattner_Rule |
In mathematics, an F σ set (said F-sigma set ) is a countable union of closed sets . The notation originated in French with F for fermé ( French : closed) and σ for somme ( French : sum, union). [ 1 ]
The complement of an F σ set is a G δ set . [ 1 ]
F σ is the same as Σ 2 0 {\displaystyle \mathbf {\Sigma } _{2}^{0}} in the Borel hierarchy .
Each closed set is an F σ set.
The set Q {\displaystyle \mathbb {Q} } of rationals is an F σ set in R {\displaystyle \mathbb {R} } . More generally, any countable set in a T 1 space is an F σ set, because every singleton { x } {\displaystyle \{x\}} is closed.
The set R ∖ Q {\displaystyle \mathbb {R} \setminus \mathbb {Q} } of irrationals is not an F σ set.
In metrizable spaces, every open set is an F σ set. [ 2 ]
The union of countably many F σ sets is an F σ set, and the intersection of finitely many F σ sets is an F σ set.
The set A {\displaystyle A} of all points ( x , y ) {\displaystyle (x,y)} in the Cartesian plane such that x / y {\displaystyle x/y} is rational is an F σ set because it can be expressed as the union of all the lines passing through the origin with rational slope :
where Q {\displaystyle \mathbb {Q} } is the set of rational numbers, which is a countable set.
This topology-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Fσ_set |
G-Book was a telematics subscription service provided by Toyota Motor Corporation in Japan [ 1 ] [ 2 ] [ 3 ] [ 4 ] for its Toyota- and Lexus -branded vehicles. G-Book allowed users to link with cellphones (such as the Toshiba T003 cellphone), [ 5 ] personal digital assistants ( PDA )'s, personal computers (PC) and G-Book equipped cars across Japan. [ 6 ] It is based on the former GAZOO infrastructure (renamed Toyota Media Service Corporation) of Toyota's membership-based information service and membership system, and it provides interactive information services via vehicle installed touch-screen wireless communication terminals. It also incorporates information from Toyota Mapmaster Inc. which updates digital mapping information and is used by various international companies. [ 7 ]
The subscription service replaces the need to periodically update in-car navigation systems that use CD, or DVD installed maps that must be updated with the latest information. The maps are sent by internet connections established through the drivers cellphone with a data download plan associated with the cellphone.
A G-Book application can be installed on select mobile devices, thereby providing the technology without having to purchase a vehicle installed with the technology. [ 8 ]
A proprietary service with additional functions for the Lexus division, G-Link , debuted on Japan-market Lexus models starting in model year 2006. [ 9 ] Toyota made available G-Book devices as optional equipment in all Japanese domestic market Toyota, Daihatsu and Lexus vehicles starting with model year 2007. An article posted by "Response.jp" stated in an article on July 15, 2009 that Toyota was introducing G-Book in a specially identified Toyota Camry to be sold in Beijing, China. [ 10 ] As of November 2009 the G-Book-equipped Camry is available in Shanghai as well. G-Book was also introduced on Lexus models in China in 2009. [ 11 ]
In Japan ( T-Connect Japan Archived 2018-08-05 at the Wayback Machine ), and recently in Middle East countries (Bahrain, Jordan, Kuwait, Lebanon, Oman, Qatar and UAE) T-Connect is being offered as a download from Apple's AppStore and Google Play as a subscription telematics service, which uses the G-Book architecture.
G-Book services were discontinued on 31 March 2022. [ 12 ]
There are three versions of G-Book being offered; G-Book mX (and G-Book mX Pro), G-Book Alpha (and G-Book Alpha Pro) and G-Book.
Some of the services G-Book offers are a Safety and Security service, which aids in requesting a tow truck and vehicle location service, Live Navigation where an operator gives turn-by-turn directions, Information Service which provides news, weather forecasts and stock market information, Communication Service that offers the ability to send and receive web based e-mail , and post and read on message boards, E-commerce Service, that allows merchandise to be purchased from the GAZOO Shopping Mall, and a live operator is available through OSS (Operator Support Service) for various issues.
One of the features offered exclusively on G-Book mX is Probe Communication Traffic Information. According to the press release from Toyota dated April 10, 2007, "This unique Toyota traffic information service gathers driving data – such as speed and position – from vehicles equipped with G-Book mX to provide drivers with alternate routes for avoiding traffic congestion. Because it makes use of the on-board DCM (data communications module), the information gathering capability of this service is superior to similar systems, which rely solely on cell phones, and efficiently stores information about traffic congestion in real time at the G-Book Center. In this way the Probe Communication Traffic Information service supplements Vehicle Information and Communication System (VICS) information with updates on traffic congestion, providing drivers with highly accurate predictions about the current traffic situation and suggestions for the best alternate routes to take." [ 6 ] This feature is being marketed as an ability to drive eco-friendly, by helping to avoid pollution created by cars idling in traffic and allowing the driver to reach their destination sooner, and affording the opportunity to turn the car off, limiting emissions being added to the atmosphere.
The wireless communications for Japan-market cars are handled by the DCM and transmits and receives information on the wireless network owned by Japanese telecommunications provider KDDI Corporation headquartered in Okinawa . The cellular platform used is the CDMA2000 1x (CDMA 1X) method, and it is possible to receive up to 144 kbit/s data. The same DCM is used for China-market models, thus the network provider for China-market G-Book services is China Telecom . Map updates and music downloads are not available for China-market G-Book-enabled cars, and traffic information is only available in Shanghai, Beijing, Guangzhou, and Shenzhen.
G-Book Alpha Pro, mX Pro DCM-only, and CDMA2000 1xEV-DO (CDMA 1X WIN) can send up to 2.4 Mbit/s of data, and the DCM supports hands-free calls. The DCM model is also equipped with its own GPS receiver and features, to track a stolen vehicle, and it also has an emergency notification ability to transmit the location of airbag deployment.
According to a press release from Toyota dated 28 August 2002 "Navigational maps and the on-board terminal's basic software are stored in a Secure Digital (SD) card. The card can be inserted into "E-TOWER" terminals at convenience stores and other locations to download local or new maps or to upgrade the on-board terminal's basic software. Music and games can also be downloaded, and the SD card is compatible with commercially available audio players, digital cameras and PDAs that use SD cards, making it possible to share content such as music files, images and games." E-Tower locations can be found at numerous locations, including Circle K of Japan. [ 4 ]
Offered at Lexus' Japanese domestic market launch in 2005, G-Link is the proprietary Lexus telematics system for the Japanese market. G-Link has a different software configuration versus G-Book, particularly in its link to the 24-hour Lexus Owner's Desk hotline, and is offered standard for the first three years of ownership. [ 9 ] Other aspects of the system at its 2005 launch were based on G-Book Alpha capabilities. [ 9 ] The G-Link software runs off of the vehicle's hard disc drive navigation system and song library, and includes traffic updates, HelpNet compatibility, and the G-Security service. The G-Security service includes cellphone notification of vehicle lock and position status. A G-Sound music distribution service offers samples and downloading to the vehicle's hard disc drive of MP3s from different genres. A U.S. equivalent of the G-Link system with similar but not identical functionality, called Lexus Enform with Safety Connect, was launched in 2009. [ 13 ]
In 2006, Japanese media reported that a Lexus-branded cellphone was also being produced with compatibility for the G-Link system. [ 14 ] This cellphone service would be produced in conjunction with the KDDI telecommunications service provider, and is called "au" , using Apple and Sony products. [ 14 ]
Toyota is working with other Japanese car manufacturers, such as Mitsubishi, Subaru and Daihatsu to provide the service in the Japanese language. Mazda has also agreed to offer the service in Japan, with an intent to install the service starting with the 2005 model. [ 15 ] [ 16 ] Competing services are called "Nissan Car Wings", [ 17 ] and Internavi "Internavi Premium Club (Japanese)" [ 18 ] by Honda. [ 19 ] In the U.S., the Safety Connect system was produced based on the G-Book system architecture, with similar functionality, along with an expanded Lexus Enform service. [ 13 ]
The G-Book feature is similar to "W44T" [ 20 ] offered in Japan by Toshiba, and "Pipit" [ 21 ] in an agreement with Toyota and Willcom in Japan.
Venza | https://en.wikipedia.org/wiki/G-Book |
g-force induced loss of consciousness (abbreviated as G-LOC , pronounced "JEE-lock") is a term generally used in aerospace physiology to describe a loss of consciousness occurring from excessive and sustained g-forces draining blood away from the brain causing cerebral hypoxia . The condition is most likely to affect pilots of high performance fighter and aerobatic aircraft or astronauts , but is possible on some extreme amusement park rides . G-LOC incidents have caused fatal accidents in high performance aircraft capable of sustaining high g for extended periods. High-g training for pilots of high performance aircraft or spacecraft often includes ground training for G-LOC in special centrifuges , with some profiles exposing pilots to 9 g s for a sustained length of time.
Under increasing positive g -force, blood in the body will tend to move from the head toward the feet. For higher intensity or longer duration, this can manifest progressively as:
Under negative g , blood pressure will increase in the head, which could result in the dangerous condition known as redout .
Due to the high level of sensitivity that the eye’s retina has to hypoxia, symptoms are usually first experienced visually. As the retinal blood pressure decreases below Intraocular pressure (usually 10–21 mm Hg), blood flow begins to cease to the retina, first affecting perfusion furthest from the optic disc and central retinal artery with progression towards central vision. Skilled pilots can use this loss of vision as their indicator that they are at maximum turn performance without losing consciousness. Recovery is usually prompt following removal of g -force, but a period of several seconds of disorientation may occur. Absolute incapacitation is the period of time when the aircrew member is physically unconscious and averages about 12 seconds. Relative incapacitation is the period in which the consciousness has been regained, but the person is confused and remains unable to perform simple tasks. This period averages about 15 seconds. Upon regaining cerebral blood flow, the G-LOC victim usually experiences myoclonic convulsions (sometimes called the ‘funky chicken’) and full amnesia of the event is often experienced. [ 1 ] Brief but vivid dreams have been reported to follow G-LOC. If G-LOC occurs at low altitude, this momentary lapse can prove fatal , and even highly experienced pilots can pull straight to a G-LOC condition without first perceiving the visual onset warnings that would normally be used as the sign to back off from pulling any more g s.
The human body is much more tolerant of g -force when it is applied anteriorly to posteriorly (front to back or Gx) than when applied longitudinally (along the length of the body). However, most sustained g -forces incurred by pilots are applied longitudinally. This has led to experimentation with prone pilot aircraft designs which lies the pilot face down or (more successfully) reclined positions for astronauts. A similar concept, the supine cockpit exists.
The g thresholds at which these effects occur depend on the training, age and fitness of the individual. An untrained individual not used to the G -straining manoeuvre can black out between 4 and 6 g , particularly if this is pulled suddenly. A trained, fit individual wearing a g suit and practicing the straining manoeuvre can, with some difficulty, sustain up to 12-14 g without loss of consciousness. The Blue Angels regularly sustain 3–5 second bursts of 7.5 g thresholds. [ citation needed ] | https://en.wikipedia.org/wiki/G-LOC |
In geometry and combinatorics , a simplicial (or combinatorial ) d -sphere is a simplicial complex homeomorphic to the d -dimensional sphere . Some simplicial spheres arise as the boundaries of convex polytopes , however, in higher dimensions most simplicial spheres cannot be obtained in this way.
One important open problem in the field was the g-conjecture , formulated by Peter McMullen , which asks about possible numbers of faces of different dimensions of a simplicial sphere. In December 2018, the g-conjecture was proven by Karim Adiprasito in the more general context of rational homology spheres. [ 1 ] [ 2 ]
It follows from Euler's formula that any simplicial 2-sphere with n vertices has 3 n − 6 edges and 2 n − 4 faces. The case of n = 4 is realized by the tetrahedron. By repeatedly performing the barycentric subdivision , it is easy to construct a simplicial sphere for any n ≥ 4. Moreover, Ernst Steinitz gave a characterization of 1-skeleta (or edge graphs) of convex polytopes in R 3 implying that any simplicial 2-sphere is a boundary of a convex polytope.
Branko Grünbaum constructed an example of a non-polytopal simplicial sphere (that is, a simplicial sphere that is not the boundary of a polytope). Gil Kalai proved that, in fact, "most" simplicial spheres are non-polytopal. The smallest example is of dimension d = 4 and has f 0 = 8 vertices.
The upper bound theorem gives upper bounds for the numbers f i of i -faces of any simplicial d -sphere with f 0 = n vertices. This conjecture was proved for simplicial convex polytopes by Peter McMullen in 1970 [ 3 ] and by Richard Stanley for general simplicial spheres in 1975.
The g -conjecture , formulated by McMullen in 1970, asks for a complete characterization of f -vectors of simplicial d -spheres. In other words, what are the possible sequences of numbers of faces of each dimension for a simplicial d -sphere? In the case of polytopal spheres, the answer is given by the g -theorem , proved in 1979 by Billera and Lee (existence) and Stanley (necessity). It has been conjectured that the same conditions are necessary for general simplicial spheres. The conjecture was proved by Karim Adiprasito in December 2018. [ 1 ] [ 2 ] | https://en.wikipedia.org/wiki/G-conjecture |
In astronomy , the G-dwarf problem refers to the apparent discrepancy in the distribution of metallicity levels in stars of different populations as compared to closed box models of galactic chemical evolution. According to closed box models, which represent galaxies without outside non-metallic material inflow, the distribution of metallicity levels in stars should follow a logarithmic curve. This amounts to high and low mass stars having the least metallicity , with G-type stars inbetween. However, these models are inconsistent with Milky Way observations. [ 1 ] Other galaxies have been shown to have the same problem. [ 2 ] The name comes from G-type stars , which are bright enough to be studied easily, yet are most often found unevolved . This provides an extensive look at relatively young stars. Despite this, the G-dwarf problem has also been observed in K and M dwarfs (the M dwarf problem). [ 3 ] [ 4 ]
This article about stellar astronomy is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/G-dwarf_problem |
A g -factor (also called g value ) is a dimensionless quantity that characterizes the magnetic moment and angular momentum of an atom, a particle or the nucleus . It is the ratio of the magnetic moment (or, equivalently, the gyromagnetic ratio ) of a particle to that expected of a classical particle of the same charge and angular momentum. In nuclear physics, the nuclear magneton replaces the classically expected magnetic moment (or gyromagnetic ratio) in the definition. The two definitions coincide for the proton.
The spin magnetic moment of a charged, spin-1/2 particle that does not possess any internal structure (a Dirac particle) is given by [ 1 ] μ = g e 2 m S , {\displaystyle {\boldsymbol {\mu }}=g{e \over 2m}\mathbf {S} ,} where μ is the spin magnetic moment of the particle, g is the g -factor of the particle, e is the elementary charge , m is the mass of the particle, and S is the spin angular momentum of the particle (with magnitude ħ /2 for Dirac particles).
Protons, neutrons, nuclei, and other composite baryonic particles have magnetic moments arising from their spin (both the spin and magnetic moment may be zero, in which case the g -factor is undefined). Conventionally, the associated g -factors are defined using the nuclear magneton, and thus implicitly using the proton's mass rather than the particle's mass as for a Dirac particle. The formula used under this convention is μ = g μ N ℏ I = g e 2 m p I , {\displaystyle {\boldsymbol {\mu }}=g{\mu _{\text{N}} \over \hbar }{\mathbf {I} }=g{e \over 2m_{\text{p}}}\mathbf {I} ,} where μ is the magnetic moment of the nucleon or nucleus resulting from its spin, g is the effective g -factor, I is its spin angular momentum, μ N is the nuclear magneton, e is the elementary charge, and m p is the proton rest mass.
There are three magnetic moments associated with an electron: one from its spin angular momentum , one from its orbital angular momentum , and one from its total angular momentum (the quantum-mechanical sum of those two components). Corresponding to these three moments are three different g -factors:
The most known of these is the electron spin g-factor (more often called simply the electron g-factor ) g e , defined by μ s = g e μ B ℏ S , {\displaystyle {\boldsymbol {\mu }}_{\text{s}}=g_{\text{e}}{\frac {\mu _{\text{B}}}{\hbar }}\mathbf {S} ,} where μ s is the magnetic moment resulting from the spin of an electron, S is its spin angular momentum, and μ B = eħ /2 m e is the Bohr magneton . In atomic physics, the electron spin g -factor is often defined as the absolute value of g e : g s = | g e | = − g e . {\displaystyle g_{\text{s}}=|g_{\text{e}}|=-g_{\text{e}}.}
The z component of the magnetic moment then becomes μ z = − g s μ B m s , {\displaystyle \mu _{\text{z}}=-g_{\text{s}}\mu _{\text{B}}m_{\text{s}},} where ℏ m s {\displaystyle \hbar m_{\text{s}}} are the eigenvalues of the S z operator, meaning that m s can take on values ± 1 / 2 {\displaystyle \pm 1/2} . [ 2 ]
The value g s is roughly equal to 2.002319 and is known to extraordinary precision – one part in 10 13 . [ 3 ] The reason it is not precisely two is explained by quantum electrodynamics calculation of the anomalous magnetic dipole moment . [ 4 ]
Secondly, the electron orbital g-factor g L is defined by μ L = − g L μ B ℏ L , {\displaystyle {\boldsymbol {\mu }}_{L}=-g_{L}{\frac {\mu _{\text{B}}}{\hbar }}\mathbf {L} ,} where μ L is the magnetic moment resulting from the orbital angular momentum of an electron, L is its orbital angular momentum, and μ B is the Bohr magneton. For an infinite-mass nucleus, the value of g L is exactly equal to one, by a quantum-mechanical argument analogous to the derivation of the classical magnetogyric ratio . For an electron in an orbital with a magnetic quantum number m l , the z component of the orbital magnetic moment is μ z = − g L μ B m l , {\displaystyle \mu _{z}=-g_{L}\mu _{\text{B}}m_{l},} which, since g L = 1, is − μ B m l .
For a finite-mass nucleus, there is an effective g value [ 5 ] g L = 1 − 1 M , {\displaystyle g_{L}=1-{\frac {1}{M}},} where M is the ratio of the nuclear mass to the electron mass.
Thirdly, the Landé g-factor g J is defined by | μ J | = g J μ B ℏ | J | , {\displaystyle |{\boldsymbol {\mu }}_{J}|=g_{J}{\frac {\mu _{\text{B}}}{\hbar }}|\mathbf {J} |,} where μ J is the total magnetic moment resulting from both spin and orbital angular momentum of an electron, J = L + S is its total angular momentum, and μ B is the Bohr magneton . The value of g J is related to g L and g s by a quantum-mechanical argument; see the article Landé g -factor . μ J and J vectors are not collinear, so only their magnitudes can be compared.
The muon, like the electron, has a g -factor associated with its spin, given by the equation μ = g e 2 m μ S , {\displaystyle {\boldsymbol {\mu }}=g{e \over 2m_{\mu }}\mathbf {S} ,} where μ is the magnetic moment resulting from the muon's spin, S is the spin angular momentum, and m μ is the muon mass.
That the muon g -factor is not quite the same as the electron g -factor is mostly explained by quantum electrodynamics and its calculation of the anomalous magnetic dipole moment. Almost all of the small difference between the two values (99.96% of it) is due to a well-understood lack of heavy-particle diagrams contributing to the probability for emission of a photon representing the magnetic dipole field, which are present for muons, but not electrons, in QED theory. These are entirely a result of the mass difference between the particles.
However, not all of the difference between the g -factors for electrons and muons is exactly explained by the Standard Model . The muon g -factor can, in theory, be affected by physics beyond the Standard Model , so it has been measured very precisely, in particular at the Brookhaven National Laboratory . In the E821 collaboration final report in November 2006, the experimental measured value is 2.002 331 8416 (13) , compared to the theoretical prediction of 2.002 331 836 20 (86) . [ 6 ] This is a difference of 3.4 standard deviations , suggesting that beyond-the-Standard-Model physics may be a contributory factor. The Brookhaven muon storage ring was transported to Fermilab where the Muon g –2 experiment used it to make more precise measurements of muon g -factor. On April 7, 2021, the Fermilab Muon g −2 collaboration presented and published a new measurement of the muon magnetic anomaly. [ 7 ] When the Brookhaven and Fermilab measurements are combined, the new world average differs from the theory prediction by 4.2 standard deviations.
The electron g -factor is one of the most precisely measured values in physics. [ 3 ] | https://en.wikipedia.org/wiki/G-factor_(physics) |
The G-less cassette transcription assay is a method used in molecular biology to determine promoter strength in vitro . The technique involves quantification of an mRNA product with the use of a plasmid. [ 1 ] The G-less cassette is part of a pre-constructed vector, usually containing a multiple cloning site (MCS) upstream of the cassette. For this reason, promoters of interest can be inserted directly into the MCS to ultimately measure the accuracy and efficiency of a promoter in recruiting transcription machinery.
The G-less cassette is a reporter gene that encodes a transcript lacking guanine nucleotides in the sense strand of the DNA (hence " G -less"). [ 2 ] A plasmid containing such a gene is located downstream of a MCS. After the promoter is inserted into the MCS, transcription proceeds with the addition of radiolabeled UTP, CTP, and ATP (as well as non-radiolabeled/cold nucleotides) and continues until the end of the G-less cassette is reached and guanine residues are once again apparent in the sense strand of the DNA. The absence of GTP in vitro results in transcription being prematurely terminated at the first guanine residue in the sense strand following the cassette. Gel electrophoresis is performed on the transcription products and the amount of radioactivity is quantified by autoradiography or phosphorimaging to determine the strength of the promoter of interest.
The G-less cassette technique is used to determine promoter strength beyond basal levels of transcription (i.e. in the presence of transcription activators or transcription factors [ 3 ] ). For example, to measure the effects of a TATA box consensus sequence modification in Saccharomyces cerevisiae in the presence of TFIID , G-less cassettes were implemented to measure the relative strength of each promoter. [ 4 ]
The G-less assay can be performed on a circular plasmid to measure levels of transcription. A circular plasmid provides a more efficient template in many systems when compared to other assays such as runoff transcription, in which a cleaved end is required. This method generates radiolabeled transcripts very efficiently because it bypasses the unnecessary process of performing other indirect mRNA product measurements. The promoter is inserted into a circular plasmid containing the G-less cassette, which will generate a transcript of a certain length that omits random and nonspecific transcription throughout the plasmid. Most crude systems, such as HeLa nuclear extracts, are used because they contain low amounts of contaminating GTP that lead to background transcription and may occasionally cause random transcription to read through the G-less cassette. [ 5 ] | https://en.wikipedia.org/wiki/G-less_cassette |
In particle physics , G-parity is a multiplicative quantum number that results from the generalization of C-parity to multiplets of particles.
C -parity applies only to neutral systems; in the pion triplet, only π 0 has C -parity. On the other hand, strong interaction does not see electrical charge , so it cannot distinguish amongst π + , π 0 and π − . We can generalize the C -parity so it applies to all charge states of a given multiplet:
where η G = ±1 are the eigenvalues of G -parity. The G -parity operator is defined as
where C {\displaystyle {\mathcal {C}}} is the C -parity operator, and I 2 is the operator associated with the 2nd component of the isospin "vector". G -parity is a combination of charge conjugation and a π rad (180°) rotation around the 2nd axis of isospin space. Given that charge conjugation and isospin are preserved by strong interactions, so is G . Weak and electromagnetic interactions, though, are not invariant under G -parity.
Since G -parity is applied on a whole multiplet, charge conjugation has to see the multiplet as a neutral entity. Thus, only multiplets with an average charge of 0 will be eigenstates of G , that is
(see Q , B , Y ).
In general
where η C is a C -parity eigenvalue, and I is the isospin.
Since no matter whether the system is fermion-antifermion or boson-antiboson, η C {\displaystyle \eta _{C}} always equals to ( − 1 ) L + S {\displaystyle (-1)^{L+S}} , we have
This particle physics –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/G-parity |
In EPR spectroscopy , g-strain refers to broadening of g-values owing to small sample inhomogeneity owing to slight variations in the orientation of the paramagnetic centers. The phenomenon is indicated by broadening of the g-values that depends on the frequency of the spectrometer, such as X- or Q-band. If the line width were determined only by hyperfine coupling (which are field-independent), then the line widths would also be field independent, but they often are not. In iron-sulfur proteins , some other metalloproteins , as well as some solids, g-strain can be substantial. [ 1 ] | https://en.wikipedia.org/wiki/G-strain |
G. Marius Clore MAE , FRSC , FMedSci , FRS is a British-born, Anglo-American molecular biophysicist and structural biologist . He was born in London , U.K. and is a dual U.S./U.K. Citizen. [ 1 ] [ 2 ] [ 3 ] He is a Member of the National Academy of Sciences , [ 4 ] a Fellow of the Royal Society , [ 5 ] a Fellow of the Academy of Medical Sciences , a Fellow of the American Academy of Arts and Sciences , a NIH Distinguished Investigator, and the Chief of the Molecular and Structural Biophysics Section in the Laboratory of Chemical Physics of the National Institute of Diabetes and Digestive and Kidney Diseases at the U.S. National Institutes of Health . [ 6 ] [ 7 ] He is known for his foundational work in three-dimensional protein and nucleic acid structure determination by biomolecular NMR spectroscopy , [ 8 ] for advancing experimental approaches to the study of large macromolecules and their complexes by NMR, [ 9 ] and for developing NMR-based methods to study rare conformational states in protein - nucleic acid [ 10 ] and protein-protein [ 11 ] recognition. [ 12 ] Clore's discovery of previously undetectable, functionally significant, rare transient states of macromolecules has yielded fundamental new insights into the mechanisms of important biological processes, and in particular the significance of weak interactions and the mechanisms whereby the opposing constraints of speed and specificity are optimized. Further, Clore's work opens up a new era of pharmacology and drug design as it is now possible to target structures and conformations that have been heretofore unseen. [ 13 ]
Clore received his undergraduate degree with first class honours in biochemistry from University College London in 1976 and medical degree from UCL Medical School in 1979. [ 4 ] After completing house physician and house surgeon appointments at University College Hospital and St Charles' Hospital (part of the St. Mary's Hospital group), respectively, he was a member of the scientific staff of the Medical Research Council National Institute for Medical Research from 1980 to 1984. He received his PhD from the National Institute for Medical Research in Physical Biochemistry in 1982. He was awarded a joint Lister Institute Research Fellowship from the Lister Institute of Preventive Medicine which he held from 1982 to 1984 at the Medical Research Council . [ 14 ] In 1984 he joined the Max Planck Institute for Biochemistry in Martinsried , Germany, where he headed the Biological NMR department from 1984 to 1988. [ 1 ] [ 2 ]
In 1988, Clore was recruited to the National Institutes of Health ( NIH ) Laboratory of Chemical Physics ( National Institute of Diabetes and Digestive and Kidney Diseases ) located in Bethesda, Maryland , U.S., where he interacted closely in the late 1980s and early 1990s with NIH colleagues Ad Bax , Angela Gronenborn and Dennis Torchia on the development of multidimensional heteronuclear NMR spectroscopy and a structural biology effort aimed at proteins involved in the pathogenesis of HIV/AIDS . [ 15 ] He has remained at the NIH ever since and is currently a NIH Distinguished Investigator and Chief of the Section on Molecular and Structural Biophysics at the NIH. [ 4 ] He is an elected Member of the United States National Academy of Sciences , [ 16 ] a Fellow of the Royal Society , [ 17 ] a Fellow of the Academy of Medical Sciences , a Fellow of the American Academy of Arts and Sciences , [ 18 ] [ 19 ] and a Foreign Member of the Academia Europaea (Biochemistry and Molecular Biology Section). [ 20 ] Clore's citation upon election to the Royal Society reads:
"Clore pioneered the development of NMR for determining three-dimensional structures of biological macromolecules and has consistently extended the frontiers of NMR to ever more complex systems. His work on the development of paramagnetic and other relaxation-based NMR experiments to detect and visualize transient, rare states of macromolecules, invisible to conventional structural and biophysical techniques, has shed unique insights into how macromolecules efficiently locate their binding partners, provided the first atomic view of the dynamic amyloid Aß assembly process from disordered peptides into protofibrils, and directly demonstrated that the apo state of the chaperonin GroEL possesses intrinsic foldase/unfoldase activities." [ 5 ]
Clore played a pivotal role in the development of three- and four-dimensional NMR spectroscopy, [ 21 ] the use of residual dipolar couplings for structure determination, [ 22 ] the development of simulated annealing and restrained molecular dynamics for three-dimensional protein and nucleic acid structure determination, [ 23 ] the solution NMR structure determination of large protein complexes, [ 24 ] the development of the combined use of NMR and small-angle X-ray scattering in solution structure determination, [ 25 ] and the analysis and characterization of protein dynamics by NMR. [ 26 ] Clore's work on complexes of all the cytoplasmic components of the bacterial phosphotransferase system (PTS) led to significant insights into how signal transduction proteins recognize multiple, structurally dissimilar partners by generating similar binding surfaces from completely different structural elements and exploiting side chain conformational plasticity. [ 24 ] Clore is also one of the main authors of the very widely used XPLOR-NIH NMR structure determination program [ 27 ]
Clore's recent work has focused on developing new NMR methods (such as paramagnetic relaxation enhancement , dark state exchange saturation transfer spectroscopy and lifetime line broadening) to detect, characterize and visualize the structure and dynamics of sparsely-populated states of macromolecules, which are important in macromolecular interactions but invisible to conventional structural and biophysical techniques. [ 28 ] Examples of include the direct demonstration of rotation-coupled sliding and intermolecular translocation as mechanisms whereby sequence-specific DNA binding proteins locate their target site(s) within an overwhelming sea of non-specific DNA sequences; [ 29 ] the detection, visualization and characterization of encounter complexes in protein-protein association; [ 30 ] the analysis of the synergistic effects of conformational selection and induced fit in protein-ligand interactions; [ 31 ] and the uncovering of "dark", spectroscopically invisible states in interactions of NMR-visible proteins and polypeptides (including intrinsically disordered states) with very large megadalton macromolecular assemblies. [ 32 ] The latter includes an atomic-resolution view of the dynamics of the amyloid -β aggregation process. [ 33 ] and the demonstration of intrinsic unfoldase/foldase activity of the macromolecular machine GroEL. [ 34 ] These various techniques have also been used to uncover the kinetic pathway of pre-nucleation transient oligomerization events and associated structures involving the protein encoded by huntingtin exon-1, which may provide a potential avenue for therapeutic intervention in Huntington's disease, a fatal autosomal dominant, neurodegenerative condition. [ 35 ] [ 36 ]
Clore is one of the most highly cited scientists in the fields of molecular biophysics, structural biology, biomolecular NMR and chemistry [ 37 ] [ 38 ] with over 550 published scientific articles and an h-index (number of papers cited h or more time) of 144. [ 39 ] Clore is also one of only five NIH scientists to have been elected to both the United States National Academy of Sciences and The Royal Society , the other four being Julius Axelrod , Francis Collins , Harold Varmus and Ad Bax .
Marius Clore was educated at the Lycee Francais Charles de Gaulle in Kensington, London, University College London and UCL Medical School . He holds a 3rd degree black belt in Tae Kwon Do and was an avid cave diver. Marius Clore's father was the film producer Leon Clore whose credits include The French Lieutenant's Woman . | https://en.wikipedia.org/wiki/G._Marius_Clore |
G. Peter Lepage (born 13 April 1952) is a Canadian American theoretical physicist and an academic administrator . [ 1 ] He was the Harold Tanner Dean of the College of Arts and Sciences at Cornell University from 2003 to 2013. [ 1 ] [ 2 ]
Gerard Peter Lepage was born in Canada in 1952. Lepage studied at McGill University and graduated with a bachelor's degree in honours physics in 1972 and the University of Cambridge with a master's degree ( M.A.St - Part III of the Mathematical Tripos ) in 1973. [ 1 ] In 1978, he received his PhD in theoretical physics from Stanford University . [ 1 ]
Lepage was a research associate at the Stanford Linear Accelerator Center in 1978. He was a postdoctoral research associate at the Laboratory of Nuclear Studies, Cornell University from 1978 to 1980. In 1980, he joined the physics faculty at Cornell University where he became a professor. [ 1 ] He received academic tenure in 1984 after only four years on the university faculty. [ 2 ] From 1999 to 2003, he was the chair of Cornell's physics department. He was appointed the Harold Tanner Dean of the College of Arts and Sciences, serving from 2003 to 2013.
He is a Fellow of the American Academy of Arts and Sciences and a Fellow of the American Physical Society . [ 1 ] He was previously an Alfred P. Sloan Fellow (1983–85; 1990) and John Simon Guggenheim Fellow (1996–97) Since 2012 he has been a member of the National Science Board. [ 3 ]
G. Peter Lepage has been a visiting scholar at a number of institutions: the Institute for Advanced Study, Princeton ; Department of Applied Mathematics and Theoretical Physics, Cambridge ; the University of California Institute of Theoretical Physics, Santa Barbara, the Fermi National Accelerator Center near Chicago , and the Institute for Nuclear Theory, Seattle . [ 4 ]
He was on the editorial board of Physical Review D and Physical Review Letters and received the Outstanding Referee Award from the APS in 2009. [ 3 ] He has served on the scientific program committees for the Stanford Linear Accelerator Center, the DOE- NSF National Computational Infrastructure for Lattice Gauge Theory, the NSF's Institute for Nuclear Theory in Seattle, the International Particle Data Group, and the NSF's Institute for Theoretical Physics in Santa Barbara . [ 3 ]
He was the co-chair of the working group for the President Obama ’s Council of Advisors on Science and Technology (PCAST) on STEM teaching at colleges and universities, which in 2012 produced the acclaimed report, “Engage to Excel: Producing One Million Additional College Graduates with Degrees in Science, Technology, Engineering, and Mathematics.” [ 3 ] He has served on the technical advisory committee for the Association of American Universities ’ Undergraduate STEM Education Initiative, and is vice chair of the National Science Board ’s Committee on Education and Human Resources. [ 3 ]
He is also involved in innovations in pedagogy , especially physics education at all levels. [ 3 ] He spearheads the Active Learning Initiative (ALI) in Cornell's college of arts and sciences, a five-year pilot project, funded by 1987 alumni, Alex and Laura Hanson, used to enhance strategies for interactive classroom learning using emerging technologies. [ 5 ]
In the late 1970s and early 1980s, he was known for his research with Stanley Brodsky on quantum chromodynamics (QCD) and perturbation theory of scattering processes, [ 1 ] His research focus examines high precision calculations, adapted to renormalization techniques and effective field theory. [ 3 ] [ 6 ] This method is then applied to the fields of QCD in atomic physics , computational quantum field theory , condensed matter physics , nuclear physics (little body problem), systems of heavy quarks and exclusive scattering processes with high momentum transfer. [ 1 ]
His research also covers high-performance computing (HPC) or large scale numerical simulations of non-perturbative lattice QCD, leading in part to a range of calculations at different observation sizes – quarks , gluons and hadron masses, coupling constants and mixing angles in the Standard Model , magnetic moment of muons and allowed to determine the QCD contributions for precision testing of the Standard Model (distinguishable from possible contributions of new physics beyond the standard model). [ 1 ] These particles describe the inner structure of protons, neutrons and other sub-nuclear particles. His research resulted in the VEGAS algorithm for adaptive method for reducing error in Monte Carlo simulations in interaction physics by using a known or approximate probability distribution function. [ 7 ]
In 2016, Lepage received the J. J. Sakurai Prize from the American Physical Society for “innovative applications of quantum field theory in elementary particle physics, in particular for the justification of the theory of exclusive processes, the development of nonrelativistic effective field theories and the determination of parameters of the standard model with lattice theories.” [ 8 ]
He has authored more than 250 scientific publications. [ 9 ] [ 10 ] In 2002, together with fellow academics, Carolyn (Biddy) Martin and Mohsen Mostafavi , he co-edited a book on the future and relevance of the humanities, “Do the Humanities Have to Be Useful?” [ 11 ]
G. Peter Lepage is married to Deborah O'Connor and they have three sons: Michael, Daniel and Matthew. [ 2 ] O'Connor studied pharmacology at Stanford, worked in biochemistry at Cornell and served on the Ithaca City School District Board of Education. [ 2 ] | https://en.wikipedia.org/wiki/G._Peter_Lepage |
The G 2 -M DNA damage checkpoint is an important cell cycle checkpoint in eukaryotic organisms that ensures that cells don't initiate mitosis until damaged or incompletely replicated DNA is sufficiently repaired. Cells with a defective G 2 -M checkpoint will undergo apoptosis or death after cell division if they enter the M phase before repairing their DNA. [ 1 ] The defining biochemical feature of this checkpoint is the activation of M-phase cyclin-CDK complexes , which phosphorylate proteins that promote spindle assembly and bring the cell to metaphase . [ 2 ]
The cell cycle is driven by proteins called cyclin dependent kinases that associate with cyclin regulatory proteins at different checkpoints of the cell cycle. Different phases of the cell cycle experience activation and/or deactivation of specific cyclin-CDK complexes.
CyclinB-CDK1 activity is specific to the G2/M checkpoint. Accumulation of cyclin B increases the activity of the cyclin dependent kinase Cdk1 human homolog Cdc2 as cells prepare to enter mitosis. Cdc2 activity is further regulated by phosphorylation / dephosphorylation of its corresponding activators and inhibitors. Through a positive feedback loop, CyclinB-Cdc2 activates the phosphatase Cdc25 which in turn deactivates the CyclinB-Cdc2 inhibitors, Wee1 and Myt1. Cdc25 activates the complex through the removal of phosphates from the active site while Wee1 inactivates the complex through the phosphorylation of tyrosine residues, specifically tyrosine-15. [ 3 ]
This loop is further amplified indirectly through the coordinated interaction of the Aurora A kinase and the Bora cofactor. During the G2 phase , Bora accumulates and forms an activation complex with Aurora A. This complex then regulates the activation of Polo-like kinase 1 (Plk1). Plk1 phosphorylates Wee1, targeting it for degradation through the SCF ubiquitin ligase complex ( SCF complex ), and activates Cdc25 through phosphorylation with combined action activating Cdc2. The combined activity and complex of Cdc2, Cdc25, and Plk1 with the accumulation of cyclin B activates the CyclinB-Cdc2 complex, promoting entry into mitosis. [ 4 ]
Many proteins involved in this positive feedback loop drive the activation of the CyclinB-Cdc2 complex because entry into mitosis requires an all-or-none response. The Novak-Tyson model is a mathematical model used to explain such regulatory loop that predicted the irreversible transition into mitosis driven by hysteresis. [ 5 ] Through experiments in Xenopus laevis cell-free egg extracts, such model was confirmed as the basis for entry into mitosis. Once cyclin concentration reaches a certain minimum activation threshold, Cdc2 is rapidly activated. It remains in this state until activity falls below a separate inactivation threshold at which it is abruptly inactivated through tyrosine phosphorylation by Wee1 and Myt1. In the case of unreplicated DNA, the cyclin concentration threshold for Cdc2 activation is further increased. Through this mechanism, there exists two separate steady-state conditions separated by an unstable steady state. The bistable and hysteretic nature of CyclinB-Cdc2 ensures a highly regulated nature of the G2/M checkpoint. [ 6 ]
Proteins that localize to sites of DNA damage in the G2 phase initiate a signaling cascade that regulates important components of the pathway, as described above, therefore controlling mitotic entry via CyclinB-Cdc2 activity. Negative regulation of CyclinB-Cdc2 activity results in a delay in mitotic entry, which is important for cells to repair any DNA damage that may have accumulated after S phase and necessary before cell division can continue.
Proteins that function in the G2-M checkpoint were originally identified in yeast screens that looked for mutants which show enhanced sensitivity to radiation, termed "rad" mutants. [ 1 ] Inefficient repair of DNA damaged by ionizing radiation or chemical agents in these mutants revealed proteins essential in this pathway. Early signaling proteins in the checkpoint pathway are members of a family of phosphatidylinositol 3-kinases, rad3 in yeast and ATR in vertebrates, that are believed to localize to sites of DNA damage. [ 7 ] Rad3 phosphorylates rad26 which is required to initiate, but not maintain the checkpoint. Rad3 also phosphorylates a number of other proteins whose absence abolishes checkpoint DNA repair, including rad1, rad9, hus1 and rad17. [ 1 ] It has been hypothesized that rad9, hus1 and rad17 are similar to proteins involved in forming the clamp that increases the processivity of DNA polymerase during DNA replication . [ 8 ] In agreement with this idea, rad17 is similar to proteins involved in loading the clamp onto DNA. This supports a model where phosphorylation by rad3 causes recruitment of these proteins to sites of DNA damage where they mediate the activity of DNA polymerases involved in DNA repair . [ 1 ]
The main rad3 effector is the kinase Chk1 , which is required for the G2-M arrest in response to DNA-damaging agents. [ 9 ] Chk1 is an effector protein kinase that maintains mitotic cyclin in an inactive state and is phosphorylated by rad3 between S phase and mitosis, implicating its specific role in G2 arrest. [ 10 ] Its upregulation through overexpression can induce arrest independent of DNA damage. [ 11 ] In addition, overexpression of Chk1 rescues the radiation sensitivity of rad mutants, presumably by allowing DNA repair to take place before entry into mitosis. [ 7 ]
The presence of DNA damage triggers the ATM (Ataxia telangiectasia mutated) or ATR (Ataxia Telangiectasia and Rad3 related) pathways which activate the Chk2 and Chk1 kinases, respectively. These kinases act upstream of Cdc25 and Wee1, the direct regulators of the CyclinB-Cdc2 complex. Chk1 and Chk2 phosphorylate Cdc25, inhibiting its phosphorylating activity and marking it for ubiquitinated degradation. [ 11 ] [ 12 ] These pathways also stimulate the tumor suppressor p53 . p53 regulates the function of the Cdk2 inhibitor p21 and the 14-3-3 proteins that phosphorylate (and thereby inactivate) and sequester Cdc25 in the cytoplasm, respectively. [ 13 ] Recent studies have also suggested that Cdk1 and 14-3-3 positively regulate Wee1 in a similar manner. The hyperphosphorylation of Wee1 by Cdk1 allows for the binding of 14-3-3, sequestering Wee1 to the nucleus and enhancing its ability to phosphorylate Cdc2. [ 14 ] The phosphorylation of both Wee1 and Cdc25 prevents Cdc2 activation. [ 12 ]
The ATM/ATR pathway also results in the negative regulation of Plk1 that contributes to the stability of Wee1. The stabilization of Wee1 and Myt1 ensures the cells arrest in G2 and allows for DNA repair. [ 13 ] [ 15 ]
Multiple pathways are involved in the checkpoint response and thus, the targeting of Cdc25 is not the sole mechanism underlying cell cycle delay, as some models have proposed. The cooperativity between the positive regulation of Wee1 and the negative regulation of Cdc25 by Chk1 in response to unreplicated or damaged DNA results in a strong G2 arrest. [ 1 ] [ 11 ] [ 13 ] [ 15 ] The increase in the amount of Wee1 and the decrease in the amount of Cdc25 contributes to the increase in the cyclin B concentration threshold in the hysteresis loop needed to drive the cell into mitosis.
Rad3 is required for activation of Chk1 and initiation of G2 arrest, but different proteins are believed to maintain G2 arrest so that sufficient DNA repair can occur. One such protein is rad18 that is required for G2 arrest even when Chk1 is phosphorylated and active. Thus, rad18 is required for G2/M checkpoint maintenance while Chk1 is required for checkpoint initiation. [ 16 ] This is further supported by its additional function in DNA repair, specifically in the maintenance of chromosomal structures. Its necessity is demonstrated by the fact that in the absence of rad18, DNA is unable to be repaired even when G2 arrest is prolonged by other means.
The maintenance of such arrest in the G2 phase is further sustained by p53 and p21. In the absence of p53 or p21, it was demonstrated that radiated cells progressed into mitosis. [ 17 ] The absence of p21 or 14-3-3 cannot sufficiently inhibit the CyclinB-Cdc2 complex, thus exhibiting the regulatory control of p53 and p21 in the G2 checkpoint in response to DNA damage. [ 12 ] p53 mutations can result in a significant checkpoint deficit, which has important implications in the treatment of cancer.
Inactivation of both Wee1 and Cdc25 abolishes the G2-M DNA damage checkpoint. Absence of Wee1 or removal of the tyrosine-15 site removes negative regulation of Cdc2 activity and causes cells to enter mitosis without completing repair, which effectively abolishes the G2-M checkpoint. [ 18 ] Absence of Cdc25 arrests cells in G2, but still allows activation of the G2-M checkpoint, implicating that both the activation of Wee1 and deactivation of Cdc25 as important regulatory steps in the checkpoint. [ 11 ]
Inactivation of Chk1 is sufficient to surpass the checkpoint and promote entry into mitosis, regardless if DNA damage is repaired. Yet, little is still known about the exact mechanism regarding checkpoint termination with possible mechanisms including protein phosphatases reversing activating phosphorylations, targeted ubiquitin degradation of activating proteins, and checkpoint antagonists promoting mitosis through independent pathways. [ 10 ]
Many cell cycle regulators like Cdks, cyclins, and p53 have been found to have abnormal expression in cancer. More specifically, they have been implicated in being involved in the G2/M transition by localizing to the centrosome, which thus leads to studies in manipulating such proteins in order to improve cancer's sensitivity to radiation and chemotherapy. [ 13 ] Chk1 has important implications in drug targeting for cancer as its function acts in response to DNA damage. The cytotoxic effects of chemotherapy are currently being studied in the modulation of the G2/M transition, concerning both checkpoint abrogation or checkpoint arrest. [ 19 ] Many therapies focus on inactivating the checkpoint in order to force cells with excess DNA damage to proceed through mitosis and induce cell death. [ 12 ] | https://en.wikipedia.org/wiki/G2-M_DNA_damage_checkpoint |
The Greater Antilles + Aves Ridge , [ 1 ] also known as GAARlandia , is a hypothesized land bridge which is proposed to have connected the Greater Antilles to South America around 33 million years ago (mya). Animal and plant species are thought to have colonized the Caribbean Islands through dispersal and vicariance , and the most prominent vicariance hypothesis involves colonization via GAARlandia. Proponents of the hypothesis cite studies of individual lineages , while critics point to a lack of geological evidence.
The GAARlandia hypothesis was introduced by Ross MacPhee and Manuel Iturralde-Vinent in 1994. It posits that the North American and South American plates compressed the Caribbean plate for 2 million years during the Eocene–Oligocene boundary (33 million years ago), which led the presently-submerged Aves Ridge in the eastern Caribbean Sea to rise and connect South America with Puerto Rico via an unbroken land bridge; Puerto Rico is posited to have been further connected via dry land to Hispaniola , Cuba and eastern Jamaica . During this period the ice sheet expanded on Antarctica , causing the global sea level to drop. [ 2 ] MacPhee and Iturralde-Vinent proposed that the ancestors of the non-flying land vertebrates that inhabit, or used to inhabit, the Greater Antilles arrived from South America by walking along this bridge rather than through oceanic dispersal . [ 1 ] [ 2 ]
The GAARlandia hypothesis is controversial in the scientific community . [ 1 ] It has been supported by studies of individual lineages , but simultaneous colonization by multiple lineages is yet to be proven. [ 3 ] Alonso et al. (2011) firmly argued in favor of the hypothesis: they found out in a phylogenetic research that the common ancestor of the toads of the genus Peltophryne , which do not tolerate saltwater, arrived on the Greater Antilles 33 million years ago–exactly when GAARlandia is supposed to have connected the present-day islands to South America. [ 1 ] Other taxa found to have arrived at the time GAARlandia is said to have existed include cichlids , Eleutherodactylus and Osteopilus frogs, butterflies, Polistinae wasps, spiders with limited dispersal ability, extinct primates and Megalocnidae sloths, multiple bat groups, and hystricognath rodents. [ 4 ]
Ali & Hedges (2021) have found "weak and non-existent" support for GAARlandia, respectively, in the colonization record of land vertebrates and the geological and seismic data. [ 2 ] They conclude that oceanic dispersal is "the best available explanation" for the origin of all Greater Antillean species, including plants and invertebrates . [ 2 ]
Weaver et al. posit that GAARlandia might have enabled Limia , freshwater fish endemic to the islands, to reach the Antilles through a combination of dispersal, vicariance, and island hopping. Weaver et al. note, however, limias and all other native Antillean species are tolerant of saltwater, and conclude that intolerant species (such as primary division freshwater fish and caecilians ) would have colonized the islands as well if a land bridge had been sufficient. Weaver et al. note that mammals which may have walked across GAARlandia, including megalonychid sloths, were capable of crossing short stretches of saltwater as well. [ 4 ] | https://en.wikipedia.org/wiki/GAARlandia |
GABA receptor antagonists are drugs that inhibit the action of GABA . In general these drugs produce stimulant and convulsant effects, and are mainly used for counteracting overdoses of sedative drugs.
Examples include bicuculline , securinine and metrazol , and the benzodiazepine GABA A receptor antagonist flumazenil .
Other agents which may have GABA A receptor antagonism include the antibiotic ciprofloxacin , [ 1 ] tranexamic acid , [ 2 ] thujone , [ 3 ] ginkgo biloba , [ 4 ] and kudzu . [ 5 ]
This drug article relating to the nervous system is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/GABA_receptor_antagonist |
In molecular biology and physiology, something is GABAergic or GABAnergic if it pertains to or affects the neurotransmitter gamma-aminobutyric acid (GABA). For example, a synapse is GABAergic if it uses GABA as its neurotransmitter , and a GABAergic neuron produces GABA. A substance is GABAergic if it produces its effects via interactions with the GABA system , such as by stimulating or blocking neurotransmission.
A GABAergic or GABAnergic agent is any chemical that modifies the effects of GABA in the body or brain. Some different classes of GABAergic drugs include agonists , antagonists , modulators, reuptake inhibitors and enzymes. [ 1 ]
This drug article relating to the nervous system is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/GABAergic |
GADV-protein world is a hypothetical stage of abiogenesis . GADV stands for the one letter codes of four amino acids , namely, glycine (G), alanine (A), aspartic acid (D) and valine (V), the main components of GADV proteins . In the GADV-protein world hypothesis, it is argued that the prebiotic chemistry before the emergence of genes involved a stage where GADV-proteins were able to pseudo-replicate. This hypothesis is contrary to the RNA world hypothesis. [ 1 ]
The GADV-protein world hypothesis was first proposed by Kenji Ikehara at Nara Women's University . It is supported by GNC-SNS primitive gene code hypothesis ( GNC hypothesis ) also formulated by him. In the GNC hypothesis, the origin of the present standard genetic code is considered to be the GNC genetic code that includes the codons G G C, G C C, G A C, G U C, respectively coding glycine , alanine , aspartic acid , and valine ; it also follows the SNS primitive genetic code that codes ten amino acids, where N denotes arbitrary four RNA bases and S denotes guanine (G) and cytosine (C).
The GADV hypothesis proposes these mechanisms: | https://en.wikipedia.org/wiki/GADV-protein_world_hypothesis |
The GAIN domain ( G-protein-coupled receptor (GPCR) autoproteolysis-inducing domain) is a protein domain found in a number of cell surface receptors, including adhesion-GPCRs and polycystic kidney disease proteins PKD1 and PKD2 . The domain is involved in the self-cleavage of these transmembrane receptors, and has been shown to be crucial for their function [ citation needed ] . [ 1 ] Point mutations within the GAIN domain of PKD1 and GPR56 are known to cause polycystic kidney disease and polymicrogyria , respectively. [ 2 ] [ 3 ] [ 4 ]
This transmembrane receptor -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/GAIN_domain |
GAI or Gibberellic-Acid Insensitive is a gene in Arabidopsis thaliana which is involved in regulation of plant growth. [ 1 ] GAI represses the pathway of gibberellin -sensitive plant growth. It does this by way of its conserved DELLA motif . [ 2 ] | https://en.wikipedia.org/wiki/GAI_(Arabidopsis_thaliana_gene) |
The GAL4-UAS system is a biochemical method used to study gene expression and function in organisms such as the fruit fly . It is based on the finding by Hitoshi Kakidani and Mark Ptashne, [ 1 ] and Nicholas Webster and Pierre Chambon [ 2 ] in 1988 that Gal4 binding to UAS sequences activates gene expression. The method was introduced into flies by Andrea Brand and Norbert Perrimon in 1993 [ 3 ] and is considered a powerful technique for studying the expression of genes . [ 4 ] The system has two parts: the Gal4 gene, encoding the yeast transcription activator protein Gal4 , and the UAS ( Upstream Activation Sequence ), an enhancer to which GAL4 specifically binds to activate gene transcription .
The Gal4 system allows separation of the problems of defining which cells express a gene or protein and what the experimenter wants to do with this knowledge. Geneticists have created genetic variants of model organisms (typically fruit flies), called GAL4 lines , each of which expresses GAL4 in some subset of the animal's tissues. For example, some lines might express GAL4 only in muscle cells, or only in nerves, or only in the antennae, and so on. For fruit flies in particular, there are tens of thousands of such lines, with the most useful expressing GAL4 in only a very specific subset of the animal—perhaps, for example, only those neurons that connect two specific compartments of the fly's brain. The presence of GAL4, by itself, in these cells has little or no effect, since GAL4's main effect is to bind to a UAS region, and most cells have no (or innocuous) UAS regions.
Since Gal4 by itself is not visible, and has little effect on cells, the other necessary part of this system are the "reporter lines". These are strains of flies with the special UAS region next to a desired gene. These genetic instructions occur in every cell of the animal, but in most cells nothing happens since that cell is not producing GAL4. In the cells that are producing GAL4, however, the UAS is activated, the gene next to it is turned on, and it starts producing its resulting protein. This may report to the investigator which cells are expressing GAL4, hence the term "reporter line", but genes intended to manipulate the cell behavior are often used as well.
Typical reporter genes include:
For example, scientists can first visualize a class of neurons by choosing a fly from a GAL4 line that expresses GAL4 in the desired set of neurons, and crossing it with a reporter line that express GFP. In the offspring, the desired subset of cells will make GAL4, and in these cells the GAL4 will bind to the UAS, and enable the production of GFP. So the desired subset of cells will now fluoresce green and can be followed with a fluorescence microscope . Next, to figure out what these cells might do, the experimenter might express channelrhodopsin in each of these cells, by crossing the same GAL4 line with a channelrhodopsin reporter line. In the offspring the selected cells, and only those cells, will contain channelrhodopsin and can be triggered by a bright light. Now the scientist can trigger these particular cells at will, and examine the resulting behavior to see what these cells might do.
Gal4 is a modular protein consisting broadly of a DNA-binding domain and an activation domain. The UAS to which GAL4 binds is CGG-N 11 -CCG, where N can be any base . [ 6 ] Although GAL4 is a yeast protein not normally present in other organisms it has been shown to work as a transcription activator in a variety of organisms such as Drosophila , [ 7 ] and human cells, highlighting that the same mechanisms for gene expression have been conserved over the course of evolution. [ 2 ]
For study in Drosophila , the GAL4 gene is placed under the control of a native gene promoter , or driver gene, while the UAS controls expression of a target gene. GAL4 is then only expressed in cells where the driver gene is usually active. In turn, GAL4 should only activate gene transcription where a UAS has been introduced. For example, by fusing a gene encoding a visible marker like GFP ( Green Fluorescent Protein ) the expression pattern of the driver genes can be determined. GAL4 and the UAS are very useful for studying gene expression in Drosophila as they are not normally present and their expression does not interfere with other processes in the cell. For example, GAL4/UAS-regulated transgenes in Drosophila have been used to alter glial expression to produce arrhythmic behavior in a known rhythmic circadian output called pigment dispersing factor (PDF). [ 8 ] However, some research has indicated that over-expression of GAL4 in Drosophila can have side-effects, probably relating to immune and stress responses to what is essentially an alien protein. [ 9 ]
The GAL4-UAS system has also been employed to study gene expression in organisms besides Drosophila such as the African clawed frog Xenopus [ 10 ] and zebrafish . [ 11 ]
The GAL4/UAS system is also utilized in Two-Hybrid Screening , a method of identifying interactions between two proteins or a protein with DNA.
Gal4 expression can be made even more specific by means of "intersectional strategies". These can combine two different GAL4 lines—say, A and B—in a way that GAL4 is only expressed in the cells that are in line A but not line B, or those that are in both lines A and B. When combined with intrinsically sparse GAL4 lines, this offers very specific selection, often limited to a single cell type. The disadvantage is that at least three independent insertion sites are required, so the lines must use different and independent insertion sites, and creating the desired final organisms needs more than a single cross. This is a very active field of research, and there are many such intersectional strategies, of which two are discussed below.
One way to create GAL4 expression in the cells that are in line A but not line B, requires line A to be made to express GAL4, and line B made to express Gal80 , which is a GAL4 inhibitor. Therefore, only the cells that are in A but not B will have active GAL4, which can then drive the reporter gene . [ 12 ] [ 13 ]
To express GAL4 in only the cells contained in both A and B, a technique called "split-GAL4" can be used. Line A is made to express half of the GAL4 protein, which is inactive by itself. Similarly, line B is made to express the other half of GAL4, also inactive by itself. Only the cells that are in both lines make both halves, which self-assemble by leucine zipper into GAL4 and activate the reporter gene. [ 14 ] | https://en.wikipedia.org/wiki/GAL4/UAS_system |
Galaxy Evolution Explorer ( GALEX or Explorer 83 or SMEX-7 ) was a NASA orbiting space telescope designed to observe the universe in ultraviolet wavelengths to measure the history of star formation in the universe. In addition to paving the way for future ultraviolet missions, the space telescope allowed astronomers to uncover mysteries about the early universe and how it evolved, as well as better characterize phenomena like black holes and dark matter . The mission was extended three times over a period of 10 years before it was decommissioned in June 2013. GALEX was launched on 28 April 2003 and decommissioned in June 2013. [ 1 ]
The spacecraft was three-axis stabilized , with power coming from four fixed solar panels . The satellite bus is from Orbital Sciences Corporation based on OrbView 4 . The telescope was a 50 cm (20 in) Modified Ritchey–Chrétien with a rotating grism . GALEX used the first ever UV light dichroic beam-splitter flown in space to direct photons to the Near UV (175–280 nanometers) and Far UV (135–174 nanometers) microchannel plate detectors . Each of the two detectors has a 65 mm (2.6 in) diameter. The target orbit is 670 km (420 mi) circular and inclined at 29.00° to the equator .
An air launched Pegasus launch vehicle , launched on 28 April 2003 at 11:59:57 UTC , placed the craft into a nearly circular orbit at an altitude of 697 km (433 mi) and an orbital inclination to the Earth's equator of 29.00°. [ 4 ]
The Galaxy Evolution Explorer (GALEX) which explored the origin and evolution of galaxies, and the origins of stars and heavy elements over the redshift range of Z between 0 and 2. GALEX conducted an all-sky imaging survey, a deep imaging survey, and a survey of 200 galaxies nearest to the Milky Way galaxy. As well, GALEX performed three spectroscopic surveys over the 135–300 nanometre band. GALEX had a planned 29-month mission, and is a part of the Small Explorer (SMEX) program.
The first observation was dedicated to the crew of the Space Shuttle Columbia , and was images in the constellation of Hercules taken on 21 May 2003. This region was selected because it had been directly overhead the shuttle at the time of its last contact with the NASA Mission Control Center , Houston , Texas .
After its primary mission of 29 months, observation operations were extended. In 2009, one of its detectors, which observed in far-ultraviolet light, stopped functioning. [ 5 ] Late in the mission, observations of more intense UV sources were allowed, including the Kepler field. [ 5 ]
Observation operations were extended to almost 9 years, with NASA placing it into standby mode on 7 February 2012. [ 6 ] NASA cut off financial support for operations of GALEX in early February 2011 as it was ranked lower than other projects which were seeking a limited supply of funding. The mission's life-cycle cost to NASA was US$150.6 million. The California Institute of Technology (Caltech) negotiated to transfer control of GALEX and its associated ground control equipment to the California Institute of Technology in keeping with the Stevenson-Wydler Technology Innovation Act . Under this Act, excess research equipment owned by the U.S. government can be transferred to educational institutions and non-profit organizations . [ 5 ] On 17 May 2012, GALEX operations were transferred to Caltech. [ 7 ]
On 28 June 2013, NASA decommissioned GALEX. It is expected that the spacecraft will remain in orbit until at least 2068 before it will re-enter the atmosphere. [ 3 ] [ 2 ]
The telescope made observations in ultraviolet wavelengths to measure the history of star formation in the universe 80% of the way back to the Big Bang . Since scientists have evidence that the Universe to be about 13.8 billion years old, the mission studied galaxies and stars across about 10 billion years of cosmic history. [ 8 ]
The spacecraft's mission was to observe hundreds of thousands of galaxies, with the goal of determining the distance of each galaxy from Earth and the rate of star formation in each galaxy. Near-UV (NUV) and Far-UV (FUV) emissions as measured by GALEX can indicate the presence of young stars, but may also originate from old stellar populations (e.g. sdB stars ).
Partnering with the NASA Jet Propulsion Laboratory (JPL) on the mission were the California Institute of Technology , Orbital Sciences Corporation , University of California, Berkeley , Yonsei University , Johns Hopkins University , Columbia University , and Laboratoire d'Astrophysique de Marseille , France .
The observatory participated in GOALS with Spitzer Space Telescope , Chandra X-ray Observatory , and Hubble Space Telescope . [ 9 ] GOALS stands for Great Observatories All-sky LIRG Survey , and Luminous Infrared Galaxies were studied at the multiple wavelengths allowed by the telescopes. [ 9 ]
The primary objective of the Galaxy Evolution Explorer was to learn what factors trigger star formation inside galaxies; how quickly stars form, evolve and die; and how heavy chemical elements form in stars. Additional goals include: [ 10 ]
To accomplish its objectives, the Galaxy Evolution Explorer conducted eight surveys, grouped into two broad categories – a local universe investigation and a star formation history investigation. The local universe investigation includes the following four surveys: [ 10 ]
The star formation history investigation will take information gathered by the local universe investigation and apply it to more distant galaxies by looking further back in time. It includes the following four surveys: [ 10 ]
The telescope had a 50 cm (20 in) diameter aperture primary, in a Ritchey–Chrétien telescope f/6.0 configuration. It can see light wavelengths from 135 nanometres to 280-nm, with a field of view of 1.2° wide (larger than a full Moon). It had gallium arsenide (GaAs) solar cells which supply nearly 300 watts to the spacecraft. [ 11 ]
GALEX carries a single f/6.0, Ritchey–Chrétien telescope, with a 50 cm (20 in) diameter primary, and a 22 cm (8.7 in) secondary mirror. Beam-splitters direct the Near UV (NUV) and Far UV (FUV) components to separate photoelectric detectors of diameter 6.5 cm (2.6 in). In each, the photoelectrons are multiplied by a microchannel plate, and detected by the anode grid. The grid enables determination of the exact position of electron impact, by the time delay of each pulse at the two ends. The telescope has a field of view (FoV) of 1.2°, and a resolution of five arcseconds , and enables either imaging or spectral composition of a single star/galaxy, by a rotatable wheel containing a clear window and a grism (a cross between a grating and a prism). [ 12 ] | https://en.wikipedia.org/wiki/GALEX |
GAMESS is a computational chemistry software program and stands for General Atomic and Molecular Electronic Structure System . The original Quantum Chemistry Program Exchange (QCPE) code of GAMESS split in 1981 and now the three version differ considerably: | https://en.wikipedia.org/wiki/GAMESS |
General Atomic and Molecular Electronic Structure System ( GAMESS-UK ) is a computer software program for computational chemistry . The original code split in 1981 into GAMESS-UK and GAMESS (US) variants, which now differ significantly. Many of the early developments in the UK version arose from the earlier UK based ATMOL program, which, unlike GAMESS, lacked analytical gradients for geometry optimisation.
GAMESS-UK can perform many general computational chemistry calculations, including Hartree–Fock method , Møller–Plesset perturbation theory (MP2 & MP3), coupled cluster (CCSD & CCSD(T)), density functional theory (DFT), configuration interaction (CI), and other advanced electronic structure methods. Calculation of valence bond wave functions are possible by the TURTLE code, due to J. H. van Lenthe.
This scientific software article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/GAMESS_(UK) |
General Atomic and Molecular Electronic Structure System ( GAMESS (US) ) is computer software for computational chemistry . [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] The original code started on October 1, 1977 as a National Resources for Computations in Chemistry project. [ 6 ] In 1981, the code base split into GAMESS (US) and GAMESS (UK) variants, which now differ significantly. GAMESS (US) is maintained by the members of the Gordon Research Group at Iowa State University . [ 7 ] GAMESS (US) source code is available as source-available freeware , but is not open-source software , due to license restrictions.
GAMESS (US) can perform several general computational chemistry calculations, including Hartree–Fock method , density functional theory (DFT), generalized valence bond (GVB), and multi-configurational self-consistent field (MCSCF). Correlation corrections after these SCF calculations can be estimated by configuration interaction (CI), second order Møller–Plesset perturbation theory (MP2), and coupled cluster (CC) theory. Solvent effect can be considered using quantum mechanics and molecular mechanics through discrete effective fragment potentials or continuum models (such as PCM). Relativistic corrections can be calculated, including third order Douglas-Kroll scalar terms.
The GAMESS (US) program possesses Resolution-of-the-Identity (RI) approximated methods, which decrease the overall cost of a method by projecting the ERI tensor into three center matrices. The RI approximation has been applied to the MP2 and CCSD(T) methods, respectively. The RI-MP2 and the RI-CC code benefit from a MPI/OpenMP parallelization model allowing for great scaling and fast calculations.
GAMESS (US) also has a series of fragmentation methods that allow the user to target larger molecular systems by partitioning a large molecule into smaller, more feasible fragments. Examples are the fragment molecular orbital (FMO) method, the Effective Fragment Potential (EFP) method, and the Effective Fragment Molecular Orbital method (EFMO).
The GAMESS (US) software also provides a comprehensive bonding analysis technique based on the Quasi-Atomic Orbital (QUAO) analysis proposed by professor Klaus Ruedenberg. The QUAO analysis provides a quasi-atomical perspective of bonding molecular orbitals in molecules. These are oriented orbitals which show the bonding direction. QUAOs are characterized by their Bond Order (BO), Kinetic Bond Order (KBO) which is a measure of the strength of the bond, and their occupation number. The QUAO analysis allows users to study bonding patterns in molecules or small to medium size with a high degree of accuracy.
While the program does not directly perform molecular mechanics , it can do mixed quantum mechanics and molecular mechanics calculations through effective fragment potentials or through an interface with the Tinker code. The fragment molecular orbital method can be used to treat large systems, by dividing them into fragments.
It can also be interfaced with the valence bond VB2000 and XMVB programs and the Natural Bond Orbital (NBO) population analysis program.
The input files use a keyword based scheme. For example, $CONTRL SCFTYP=ROHF MAXIT=30 $END, which specifies that the SCF part of the code should do a restricted open-shell Hartree–Fock (ROHF) calculation and quit if the result does not converge in 30 iterations. The output is in an English language text file. [ 8 ] | https://en.wikipedia.org/wiki/GAMESS_(US) |
In molecular biology and genetics , GC-content (or guanine-cytosine content ) is the percentage of nitrogenous bases in a DNA or RNA molecule that are either guanine (G) or cytosine (C). [ 1 ] This measure indicates the proportion of G and C bases out of an implied four total bases, also including adenine and thymine in DNA and adenine and uracil in RNA.
GC-content may be given for a certain fragment of DNA or RNA or for an entire genome . When it refers to a fragment, it may denote the GC-content of an individual gene or section of a gene (domain), a group of genes or gene clusters, a non-coding region , or a synthetic oligonucleotide such as a primer .
Qualitatively, guanine (G) and cytosine (C) undergo a specific hydrogen bonding with each other, whereas adenine (A) bonds specifically with thymine (T) in DNA and with uracil (U) in RNA. Quantitatively, each GC base pair is held together by three hydrogen bonds, while AT and AU base pairs are held together by two hydrogen bonds. To emphasize this difference, the base pairings are often represented as "G≡C" versus "A=T" or "A=U".
DNA with low GC-content is less stable than DNA with high GC-content; however, the hydrogen bonds themselves do not have a particularly significant impact on molecular stability, which is instead caused mainly by molecular interactions of base stacking. [ 2 ] In spite of the higher thermostability conferred to a nucleic acid with high GC-content, it has been observed that at least some species of bacteria with DNA of high GC-content undergo autolysis more readily, thereby reducing the longevity of the cell per se . [ 3 ] Because of the thermostability of GC pairs, it was once presumed that high GC-content was a necessary adaptation to high temperatures, but this hypothesis was refuted in 2001. [ 4 ] Even so, it has been shown that there is a strong correlation between the optimal growth of prokaryotes at higher temperatures and the GC-content of structural RNAs such as ribosomal RNA , transfer RNA , and many other non-coding RNAs . [ 4 ] [ 5 ] The AU base pairs are less stable than the GC base pairs, making high-GC-content RNA structures more resistant to the effects of high temperatures.
More recently, it has been demonstrated that the most important factor contributing to the thermal stability of double-stranded nucleic acids is actually due to the base stackings of adjacent bases rather than the number of hydrogen bonds between the bases. There is more favorable stacking energy for GC pairs than for AT or AU pairs because of the relative positions of exocyclic groups. Additionally, there is a correlation between the order in which the bases stack and the thermal stability of the molecule as a whole. [ 6 ]
GC-content is usually expressed as a percentage value, but sometimes as a ratio (called G+C ratio or GC-ratio ). GC-content percentage is calculated as [ 7 ]
whereas the AT/GC ratio is calculated as [ 8 ]
The GC-content percentages as well as GC-ratio can be measured by several means, but one of the simplest methods is to measure the melting temperature of the DNA double helix using spectrophotometry . The absorbance of DNA at a wavelength of 260 nm increases fairly sharply when the double-stranded DNA molecule separates into two single strands when sufficiently heated. [ 9 ] The most commonly used protocol for determining GC-ratios uses flow cytometry for large numbers of samples. [ 10 ]
In an alternative manner, if the DNA or RNA molecule under investigation has been reliably sequenced , then GC-content can be accurately calculated by simple arithmetic or by using a variety of publicly available software tools, such as the free online GC calculator .
The GC-ratio within a genome is found to be markedly variable. These variations in GC-ratio within the genomes of more complex organisms result in a mosaic-like formation with islet regions called isochores . [ 11 ] This results in the variations in staining intensity in chromosomes . [ 12 ] GC-rich isochores typically include many protein-coding genes within them, and thus determination of GC-ratios of these specific regions contributes to mapping gene-rich regions of the genome. [ 13 ] [ 14 ]
Within a long region of genomic sequence, genes are often characterised by having a higher GC-content in contrast to the background GC-content for the entire genome. [ 15 ] There is evidence that the length of the coding region of a gene is directly proportional to higher G+C content. [ 16 ] This has been pointed to the fact that the stop codon has a bias towards A and T nucleotides, and, thus, the shorter the sequence the higher the AT bias. [ 17 ]
Comparison of more than 1,000 orthologous genes in mammals showed marked within-genome variations of the third-codon position GC content, with a range from less than 30% to more than 80%. [ 18 ]
GC content is found to be variable with different organisms, the process of which is envisaged to be contributed to by variation in selection , mutational bias, and biased recombination-associated DNA repair . [ 19 ]
The average GC-content in human genomes ranges from 35% to 60% across 100-Kb fragments, with a mean of 41%. [ 20 ] The GC-content of Yeast ( Saccharomyces cerevisiae ) is 38%, [ 21 ] and that of another common model organism , thale cress ( Arabidopsis thaliana ), is 36%. [ 22 ] Because of the nature of the genetic code , it is virtually impossible for an organism to have a genome with a GC-content approaching either 0% or 100%. However, a species with an extremely low GC-content is Plasmodium falciparum (GC% = ~20%), [ 23 ] and it is usually common to refer to such examples as being AT-rich instead of GC-poor. [ 24 ]
Several mammalian species (e.g., shrew , microbat , tenrec , rabbit ) have independently undergone a marked increase in the GC-content of their genes. These GC-content changes are correlated with species life-history traits (e.g., body mass or longevity) and genome size , [ 18 ] and might be linked to a molecular phenomenon called the GC-biased gene conversion . [ 25 ]
In polymerase chain reaction (PCR) experiments, the GC-content of short oligonucleotides known as primers is often used to predict their annealing temperature to the template DNA. A higher GC-content level indicates a relatively higher melting temperature.
Many sequencing technologies, such as Illumina sequencing , have trouble reading high-GC-content sequences. Bird genomes are known to have many such parts, causing the problem of "missing genes" expected to be present from evolution and phenotype but never sequenced — until improved methods were used. [ 26 ]
The species problem in non-eukaryotic taxonomy has led to various suggestions in classifying bacteria, and the ad hoc committee on reconciliation of approaches to bacterial systematics of 1987 has recommended use of GC-ratios in higher-level hierarchical classification. [ 27 ] For example, the Actinomycetota are characterised as "high GC-content bacteria ". [ 28 ] In Streptomyces coelicolor A3(2), GC-content is 72%. [ 29 ] With the use of more reliable, modern methods of molecular systematics, the GC-content definition of Actinomycetota has been abolished and low-GC bacteria of this clade have been found. [ 30 ]
GCSpeciesSorter [ 31 ] and TopSort [ 32 ] are software tools for classifying species based on their GC-contents. | https://en.wikipedia.org/wiki/GC-content |
In mathematics , a greatest common divisor matrix (sometimes abbreviated as GCD matrix ) is a matrix that may also be referred to as Smith's matrix . The study was initiated by H.J.S. Smith (1875). A new inspiration was begun from the paper of Bourque & Ligh (1992). This led to intensive investigations on singularity and divisibility of GCD type matrices. A brief review of papers on GCD type matrices before that time is presented in Haukkanen, Wang & Sillanpää (1997) .
Let S = ( x 1 , x 2 , … , x n ) {\displaystyle S=(x_{1},x_{2},\ldots ,x_{n})} be a list of positive integers. Then the n × n {\displaystyle n\times n} matrix ( S ) {\displaystyle (S)} having the greatest common divisor gcd ( x i , x j ) {\displaystyle \gcd(x_{i},x_{j})} as its i j {\displaystyle ij} entry is referred to as the GCD matrix on S {\displaystyle S} .The LCM matrix [ S ] {\displaystyle [S]} is defined analogously. [ 1 ] [ 2 ]
The study of GCD type matrices originates from Smith (1875) who evaluated the determinant of certain GCD and LCM matrices.
Smith showed among others that the determinant of the n × n {\displaystyle n\times n} matrix ( gcd ( i , j ) ) {\displaystyle (\gcd(i,j))} is ϕ ( 1 ) ϕ ( 2 ) ⋯ ϕ ( n ) {\displaystyle \phi (1)\phi (2)\cdots \phi (n)} , where ϕ {\displaystyle \phi } is Euler's totient function . [ 3 ]
Bourque & Ligh (1992) conjectured that the LCM matrix on a GCD-closed set S {\displaystyle S} is nonsingular. [ 1 ] This conjecture was shown to be false by Haukkanen, Wang & Sillanpää (1997) and subsequently by Hong (1999) . [ 4 ] [ 2 ] A lattice-theoretic approach is provided by Korkee, Mattila & Haukkanen (2019) . [ 5 ]
The counterexample presented in Haukkanen, Wang & Sillanpää (1997) is S = { 1 , 2 , 3 , 4 , 5 , 6 , 10 , 45 , 180 } {\displaystyle S=\{1,2,3,4,5,6,10,45,180\}} and that in Hong (1999) is S = { 1 , 2 , 3 , 5 , 36 , 230 , 825 , 227700 } . {\displaystyle S=\{1,2,3,5,36,230,825,227700\}.} A counterexample consisting of odd numbers is S = { 1 , 3 , 5 , 7 , 195 , 291 , 1407 , 4025 , 1020180525 } {\displaystyle S=\{1,3,5,7,195,291,1407,4025,1020180525\}} . Its Hasse diagram is presented on the right below.
The cube-type structures of these sets with respect to the divisibility relation are explained in Korkee, Mattila & Haukkanen (2019) .
Let S = ( x 1 , x 2 , … , x n ) {\displaystyle S=(x_{1},x_{2},\ldots ,x_{n})} be a factor closed set.
Then the GCD matrix ( S ) {\displaystyle (S)} divides the LCM matrix [ S ] {\displaystyle [S]} in the ring of n × n {\displaystyle n\times n} matrices over the integers, that is there is an integral matrix B {\displaystyle B} such that [ S ] = B ( S ) {\displaystyle [S]=B(S)} ,
see Bourque & Ligh (1992) . Since the matrices ( S ) {\displaystyle (S)} and [ S ] {\displaystyle [S]} are symmetric, we have [ S ] = ( S ) B T {\displaystyle [S]=(S)B^{T}} . Thus, divisibility from the right coincides with that from the left. We may thus use the term divisibility.
There is in the literature a large number of generalizations and analogues of this basic divisibility result.
Some results on matrix norms of GCD type matrices are presented in the literature.
Two basic results concern the asymptotic behaviour of the ℓ p {\displaystyle \ell _{p}} norm of
the GCD and LCM matrix on S = { 1 , 2 , … , n } {\displaystyle S=\{1,2,\dots ,n\}} . [ 6 ]
Given p ∈ N + {\displaystyle p\in \mathbb {N} ^{+}} , the ℓ p {\displaystyle \ell _{p}} norm of an n × n {\displaystyle n\times n} matrix A {\displaystyle A} is defined as
Let S = { 1 , 2 , … , n } {\displaystyle S=\{1,2,\dots ,n\}} . If p ≥ 2 {\displaystyle p\geq 2} , then
where
and E p ( x ) = x p {\displaystyle E_{p}(x)=x^{p}} for p > 2 {\displaystyle p>2} and E 2 ( x ) = x 2 log x {\displaystyle E_{2}(x)=x^{2}\log x} .
Further, if p ≥ 1 {\displaystyle p\geq 1} , then
where
Let f {\displaystyle f} be an arithmetical function, and let S = ( x 1 , x 2 , … , x n ) {\displaystyle S=(x_{1},x_{2},\ldots ,x_{n})} be a set of distinct positive integers. Then the matrix ( S ) f = ( f ( gcd ( x i , x j ) ) {\displaystyle (S)_{f}=(f(\gcd(x_{i},x_{j}))} is referred to as the GCD matrix on S {\displaystyle S} associated with f {\displaystyle f} .
The LCM matrix [ S ] f {\displaystyle [S]_{f}} on S {\displaystyle S} associated with f {\displaystyle f} is defined analogously.
One may also use the notations ( S ) f = f ( S ) {\displaystyle (S)_{f}=f(S)} and [ S ] f = f [ S ] {\displaystyle [S]_{f}=f[S]} .
Let S {\displaystyle S} be a GCD-closed set.
Then
where E {\displaystyle E} is the n × n {\displaystyle n\times n} matrix defined by
and Δ {\displaystyle \Delta } is the n × n {\displaystyle n\times n} diagonal matrix, whose diagonal elements are
Here ⋆ {\displaystyle \star } is the Dirichlet convolution and μ {\displaystyle \mu } is the Möbius function.
Further, if f {\displaystyle f} is a multiplicative function and always nonzero,
then
where Λ {\displaystyle \Lambda } and Δ ′ {\displaystyle \Delta '} are the n × n {\displaystyle n\times n} diagonal matrices, whose diagonal elements are λ i = f ( x i ) {\displaystyle \lambda _{i}=f(x_{i})} and
If S {\displaystyle S} is factor-closed, then δ i = ( f ⋆ μ ) ( x i ) {\displaystyle \delta _{i}=(f\star \mu )(x_{i})} and δ i ′ = ( 1 f ⋆ μ ) ( x i ) {\displaystyle \delta _{i}^{\prime }=({\frac {1}{f}}\star \mu )(x_{i})} . [ 6 ] | https://en.wikipedia.org/wiki/GCD_matrix |
In molecular biology, a GC box , also known as a GSG box , [ 1 ] is a distinct pattern of nucleotides found in the promoter region of some eukaryotic genes. The GC box is upstream of the TATA box , and approximately 110 bases upstream from the transcription initiation site. It has a consensus sequence GGGCGG which is position-dependent and orientation-independent. The GC elements are bound by transcription factors and have similar functions to enhancers. [ 2 ] Some known GC box-binding proteins include Sp1, Krox/Egr, Wilms' tumor, MIGI, and CREA. [ 1 ]
The GC box is commonly the binding site for zinc finger proteins. An alpha helix section of the protein corresponds with a major groove in the DNA. Zinc-fingers bind to triplet base pair sequences, with residue 21 binding to the first base pair, residue 18 binding to the second base pair, and residue 15 binding to the third base pair. The triplet base pairs can either be a GGG or a GCG. If residue 18 is a histidine, it will bind to a G, and if residue 18 is a glutamate, it will bind to a C. GC box-binding zinc fingers have between 2 and 4 fingers, making them interact with base pair sequences that are 6 to 8 base pairs in length. [ 1 ]
This molecular biology article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/GC_box |
GC skew is when the nucleotides guanine and cytosine are over- or under-abundant in a particular region of DNA or RNA . GC skew is also a statistical method for measuring strand-specific guanine overrepresentation. [ 1 ]
In equilibrium conditions (without mutational or selective pressure and with nucleotides randomly distributed within the genome ) there is an equal frequency of the four DNA bases ( adenine , guanine , thymine , and cytosine ) on both single strands of a DNA molecule. [ 2 ] However, in most bacteria (e.g. E. coli ) and some archaea (e.g. Sulfolobus solfataricus ), nucleotide compositions are asymmetric between the leading strand and the lagging strand : the leading strand contains more guanine (G) and thymine (T), whereas the lagging strand contains more adenine (A) and cytosine (C). [ 2 ] This phenomenon is referred to as GC and AT skew and the corresponding statistics were defined [ 2 ] as:
GC skew = (G - C)/(G + C)
AT skew = (A − T)/(A + T)
Erwin Chargaff's work in 1950 demonstrated that, in DNA, the bases guanine and cytosine were found in equal abundance, and the bases adenine and thymine were found in equal abundance. However, there was no equality between the amount of one pair versus the other. [ 3 ] Chargaff's finding is referred to as Chargaff's rule or parity rule 2 . [ 3 ] Three years later, Watson and Crick used this fact during their derivation of the structure of DNA, their double helix model .
A natural result of parity rule 1, at the state of equilibrium, in which there is no mutation and/or selection biases in any of the two DNA strands, is that when there is an equal substitution rate, the complementary nucleotides on each strand have equal amounts of a given base and its complement. [ 4 ] In other words, in each DNA strand the frequency of the occurrence of T is equal to A and the frequency of the occurrence of G is equal to C because the substitution rate is presumably equal. This phenomenon is referred to as parity rule 2 . Hence, the second parity rule only exists when there is no mutation or substitution.
Any deviation from parity rule 2 will result in asymmetric base composition that discriminates the leading strand–i.e., the DNA strand that is replicated in the forward direction–from the lagging strand. This asymmetry is referred to as GC or AT skew. [ 2 ]
In some bacterial genomes, there is an enrichment of guanine over cytosine and thymine over adenine on the leading strand and vice versa for the lagging strand. The nucleotide composition skew spectra ranges from −1, which corresponds to G = 0 or A = 0, to +1, which corresponds to T= 0 or C = 0. [ 2 ] Therefore, positive GC skew represents richness of G over C and the negative GC skew represents richness of C over G. As a result, one expects to see a positive GC skew and negative AT skew in the leading strand, and a negative GC skew and a positive AT skew in the lagging strand. [ 5 ] GC or AT skew changes sign at the boundaries of the two replichores , which correspond to DNA replication origin or terminus. [ 2 ] [ 4 ] [ 5 ] Originally, this asymmetric nucleotide composition was explained as a different mechanism used in DNA replication between the leading strand and lagging strand. DNA replication is semi-conservative and an asymmetric process itself. [ 6 ] This asymmetry is due to the formation of the replication fork and its division into nascent leading and lagging strands. The leading strand is synthesized continuously and in juxtapose to the leading strand; the lagging strand is replicated through short fragments of polynucleotide ( Okazaki fragments ) in a 5' to 3' direction. [ 6 ]
There are three major approaches to calculate and graphically demonstrate GC skew and its properties.
The first approach is GC and AT asymmetry. [ 2 ] Jean R. Lobry was the first to report, in 1996, [ 7 ] the presence of compositional asymmetry in the genomes of three bacteria: E. coli , Bacillus subtilis , and Haemophilus influenzae . The original formulas at the time were not called skew, but rather deviation from [A] = [T] or [C] = [G]:
deviation from [A] = [T] as (A − T)/(A + T);
deviation from [C] = [G] as (C − G)/(C + G);
where A, T, G, and C represent the frequency of occurrence of the equivalent base in a particular sequence in a defined length. A window sliding strategy is used to calculate deviation from C through the genome. In these plots, a positive deviation from C corresponds to lagging strand and negative deviation from C corresponds to leading strand. [ 8 ] Furthermore, the site where the deviation sign switches corresponds to the origin or terminal. The x-axis represents the chromosome locations plotted 5′ to 3′ and y-axis represents the deviation value. The major weakness of this method is its window-size dependent property. Therefore, choosing an adequate window size greatly affects the outcome of the plot. Other techniques should be combined with deviation in order to identify and locate the origin of the DNA replication with greater accuracy.
The second approach is referred to as cumulative GC skew (CGC skew). [ 9 ] This method still uses the sliding window strategy but it takes advantage of the sum of the adjacent windows from an arbitrary start. In this scheme, the entire genome is usually plotted 5' to 3' using an arbitrary start and arbitrary strand. In the cumulative GC skew plot, the peaks corresponds to the switch points (terminus or origin).
In contrast to Lobry's earlier paper, recent implementations of GC skew flips the original definition, redefining it to be:
GC skew = (G − C)/(G + C).
With the flipped definition of GC skew, the maximum value of the cumulative skew corresponds to the terminal, and the minimum value corresponds to the origin of replication.
The final approach is the Z curve . [ 10 ] Unlike the previous methods, this method do not uses the sliding window strategy and is thought to perform better as to finding the origin of replication. [ 10 ] In this method, each base's cumulative frequency with respect to the base at the beginning of the sequence is investigated. The Z curve uses a three-dimensional representation with the following parameters:
x n = ( A n + G n ) − ( C n + T n ) {\displaystyle x_{n}=(A_{n}+G_{n})-(C_{n}+T_{n})}
y n = ( A n + C n ) − ( G n + T n ) {\displaystyle y_{n}=(A_{n}+C_{n})-(G_{n}+T_{n})}
z n = ( A n + T n ) − ( C n + G n ) {\displaystyle z_{n}=(A_{n}+T_{n})-(C_{n}+G_{n})}
Where n = 0 , 1 , 2 , . . . N {\displaystyle n=0,1,2,...N} , x n {\displaystyle x_{n}} represents the excess of purine over pyrimidine, y n {\displaystyle y_{n}} denotes excess of keto over amino, and z n {\displaystyle z_{n}} shows the relationship between the weak and strong hydrogen bonds . x {\displaystyle x} and y {\displaystyle y} components can alone detect the replication origin and asymmetric composition of the strands.
A combination of these methods should be used for prediction of replication origin and terminal, in order to compensate for their weakness.
There is lack of consensus in scientific community with regard to the mechanism underlying the bias in nucleotide composition within each DNA strand. There are two major schools of thought that explain the mechanism behind the strand specific nucleotide composition in bacteria. [ 4 ]
The first one describes a bias and an asymmetric mutational pressure on each DNA strand during replication and transcription . [ 4 ] [ 11 ] Due to the asymmetric nature of the replication process, an unequal mutational frequency and DNA repair efficiency during the replication process can introduce more mutations in one strand as compared to the other. [ 5 ] Furthermore, the time used for replication between the two strands varies and may lead to asymmetric mutational pressure between leading and lagging strand. [ 12 ] In addition to mutations during DNA replication, transcriptional mutations can create strand specific nucleotide composition skew. [ 5 ] Deamination of cytosine and ultimately mutation of cytosine to thymine in one DNA strand can increase the relative number of guanine and thymine to cytosine and adenine. [ 5 ] In most bacteria, the majority of the genes are encoded in the leading strand. [ 4 ] For instance, the leading strand in Bacillus subtilis encodes 75% of the genes. [ 5 ] In addition, an excess of deamination and conversion of cytosine to thymine in the coding strand compared to the non-coding strand has been reported. [ 4 ] [ 5 ] [ 13 ] One possible explanation is that the non-transcribed strand ( coding strand ) is single-stranded during the transcription process; therefore, it is more vulnerable to deamination compared to the transcribed strand ( non-coding strand ). [ 5 ] [ 14 ] Another explanation is that the deamination repair activity during transcription does not occur on the coding strand. [ 5 ] Only the transcribed strand benefits from these deamination repair events.
The second school of thought describes the mechanism of GC and AT skew as resulting from a difference in selective pressure between the leading and lagging strands. [ 4 ] [ 5 ] [ 14 ] Examination of the prokaryotic genome shows a preference in third codon position for G over C and T over A. [ 5 ] This discrimination creates an asymmetric nucleotide composition, if the coding strand is unequally distributed between the leading and lagging strands, as in the case for bacteria. In addition, the highly transcribed genes, such as ribosomal proteins , have been shown to be located mostly on the leading strand in bacteria. [ 5 ] Therefore, a bias in the third-position codon choice of G over C can lead to GC skew. Additionally, some signal sequences are rich in guanine and thymine, such as chi sequences , and these sequences might have a higher frequency of occurrence in one strand compared to the other. [ 4 ] [ 5 ]
Both mutational and selective pressure can independently introduce asymmetry in DNA strands. However, the combination and cumulative effect of both mechanisms is the most plausible explanation for GC and AT skew. [ 4 ] [ 14 ]
The GC skew is proven to be useful as the indicator of the DNA leading strand, lagging strand, replication origin, and replication terminal. [ 2 ] [ 4 ] [ 5 ] Most bacteria and archaea contain only one DNA replication origin. [ 2 ] The GC skew is positive and negative in the leading strand and in the lagging strand respectively; therefore, it is expected to see a switch in GC skew sign just at the point of DNA replication origin and terminus. [ 4 ] GC skew can also be used to study the strand biases and mechanism related to them by calculating the excess of one base over its complementary base in different milieus. [ 4 ] [ 5 ] [ 14 ] Method such as GC skew, CGC skew, and Z curve are tools that can provide opportunity to better investigate the mechanism of DNA replication in different organisms. | https://en.wikipedia.org/wiki/GC_skew |
GCaMP is a genetically encoded calcium indicator (GECI) initially developed in 2001 by Junichi Nakai. [ 1 ] It is a synthetic fusion of green fluorescent protein (GFP), calmodulin (CaM), and M13, a peptide sequence from myosin light-chain kinase . [ 2 ] When bound to Ca 2+ , GCaMP fluoresces green with a peak excitation wavelength of 480 nm and a peak emission wavelength of 510 nm. [ 3 ] It is used in biological research to measure intracellular Ca 2+ levels both in vitro and in vivo using virally transfected or transgenic cell and animal lines. [ 2 ] [ 4 ] The genetic sequence encoding GCaMP can be inserted under the control of promoters exclusive to certain cell types, allowing for cell-type specific expression of GCaMP. [ 5 ] Since Ca 2+ is a second messenger that contributes to many cellular mechanisms and signaling pathways , GCaMP allows researchers to quantify the activity of Ca 2+ -based mechanisms and study the role of Ca 2+ ions in biological processes of interest.
GCaMP consists of three key domains: an M13 domain at the N-terminus , a calmodulin (CaM) domain at the C-terminus , and a GFP domain in the center. The GFP domain is circularly permuted such that the native N- and C-termini are fused together by a six- amino-acid linking sequence, and the GFP sequence is split in the middle, creating new N- and C-termini that connect to the M13 and CaM domains. [ 6 ]
In the absence of Ca 2+ , the GFP chromophore is exposed to water and exists in a protonated state with minimal fluorescence intensity. Upon Ca 2+ binding, the CaM domain undergoes a conformational change and tightly binds to the M13 domain alpha helix , preventing water molecules from accessing the chromophore. As a result, the chromophore rapidly deprotonates and converts into an anionic form that fluoresces brightly, similar to native GFP. [ 7 ]
In 2001, Nakai et al. reported the development of GCaMP1 as a Ca 2+ probe with improved signal-to-noise ratio compared to previously developed fluorescent Ca 2+ probes. [ 1 ] The first transgenic mouse expressing GCaMP1 was reported in 2004. [ 5 ] However, at 37 ˚C (physiological temperature in mammals), GCaMP1 did not fold stably or fluoresce, limiting its potential use as a calcium indicator in vivo. [ 1 ] [ 8 ]
In 2006, Tallini et al. subsequently reported the improvement of GCaMP1 to GCaMP2, which exhibited brighter fluorescence than GCaMP1 and greater stability at mammalian body temperatures. Tallini et al. expressed GCaMP2 in cardiomyocytes in mouse embryos to perform the first in vivo GCaMP imaging of Ca 2+ in mammals. [ 8 ]
Further modifications of GCaMP, including GCaMP3, GCaMP5, GCaMP6, and jGCaMP7, have been developed to progressively improve the signal, sensitivity , and dynamic range of Ca 2+ detection, [ 2 ] [ 9 ] [ 10 ] [ 11 ] with recent versions exhibiting fluorescence similar to native GFP. [ 11 ]
Both slow variants (GCaMP6s, jGCaMP7s) and fast variants (GCaMP6f, jGCaMP7f) are used in biological and neuroscience research. The slow variants are brighter and more sensitive to small changes in Ca 2+ levels, such as single action potentials ; on the other hand, the fast variants are less sensitive but respond more quickly, making them useful for tracking changes in Ca 2+ levels over precise timescales. [ 12 ] [ 13 ] GCaMP6 also has a medium variant, GCaMP6m, whose kinetics are intermediate between GCaMP6s and GCaMP6f. [ 12 ] Other variants of jGCaMP7 are also employed: jGCaMP7b exhibits bright baseline fluorescence and is used for imaging dendrites and axons , while jGCaMP7c exhibits greater contrast between maximal and baseline fluorescence and is advantageous for imaging large populations of neurons. [ 12 ]
In 2018, Yang et al. reported the development of GCaMP-X, generated by the addition of a calmodulin-binding motif. Since the GCaMP calmodulin domain, when unbound, disrupts L-type calcium channel gating, the added calmodulin-binding motif prevents GCaMP-X from interfering with calcium-dependent signaling mechanisms. [ 14 ]
In 2020, Zhang et al. reported the development of jGCaMP8, including sensitive, medium, and fast variants, which exhibit faster kinetics and greater sensitivity than the corresponding jGCaMP7 variants. [ 15 ]
Red fluorescent indicators have also been developed: jRCaMP1a and jRCaMP1b use a circular permutation of the red fluorescent protein mRuby instead of GFP, while jRGECO1a is based on the red fluorescent protein mApple. [ 12 ] [ 16 ] Since the blue light used to excite GCaMP is scattered by tissue and the emitted green light is absorbed by blood, red fluorescent indicators provide more penetration and imaging depth in vivo than GCaMP. Use of red fluorescent indicators also avoids the photodamage caused by blue excitation light. [ 16 ] Moreover, red fluorescent indicators allow for concurrent use of optogenetics , which is difficult with GCaMP because the excitation wavelengths of GCaMP overlap with those of channelrhodopsin-2 (ChR2). [ 16 ] [ 17 ] [ 18 ] Simultaneous use of red and green GECIs can provide two-color visualization of different subcellular regions or cell populations. [ 16 ] [ 17 ] [ 19 ]
In neurons, action potentials induce neurotransmitter release at axon terminals by opening voltage-gated Ca 2+ channels , allowing for Ca 2+ influx. As a result, GCaMP is commonly used to measure increases in intracellular Ca 2+ in neurons as a proxy for neuronal activity in multiple animal models, including Caenorhabditis elegans , zebrafish , Drosophila , rats and mice . [ 20 ] Recently, genetically encoded voltage indicators (GEVIs) have been developed alongside GECIs to more directly probe neuronal activity at the cellular level in these animal models. [ 21 ]
GCaMP has played a vital role in establishing large-scale neural recordings in animals to investigate how activity patterns in neuronal networks influence behavior. For example, Nguyen et al. (2016) used GCaMP in whole-brain imaging during free movement of C. elegans to identify neurons and groups of neurons whose activity correlated with specific locomotor behaviors. [ 22 ]
Muto et al. (2003) expressed GCaMP in zebrafish embryos to measure and map the coordinated activity of spinal motor neurons to different parts of the brain during the onset, propagation, and recovery of seizures induced by pentylenetetrazol . [ 23 ] GCaMP expression in zebrafish brains has also been used to study activation of neural circuits in cognitive processes like prey capture, impulse control, and attention. [ 24 ] [ 25 ]
Additionally, researchers have used GCaMP to observe neuronal activity in mice by expressing it under control of the Thy1 promoter, which is found in excitatory pyramidal neurons . [ 26 ] For instance, integration of neurons into circuits during motor learning has been tracked by using GCaMP to observe synchronized fluctuation patterns in Ca 2+ levels. [ 27 ] [ 28 ] [ 29 ] GCaMP has also been used to observe Ca 2+ dynamics in subcellular compartments of mouse neurons: Cichon and Gan (2015) used GCaMP to show that neurons in the mouse motor cortex exhibit NMDA -driven increases in Ca 2+ that are independent for each dendritic spine , thus showing that individual dendritic spines regulate synaptic plasticity . [ 30 ] Finally, GCaMP has been used to identify activity patterns in specific regions of the mouse brain. For instance, Jones et al. (2018) used GCaMP6 in mice to measure neuronal activity in the suprachiasmatic nucleus (SCN), the mammalian circadian pacemaker, and showed that SCN neurons that produced vasoactive intestinal peptide (VIP) exhibited daily activity rhythms in vivo that correlated with VIP release. [ 31 ]
GCaMP has also been combined with fiber photometry to measure population-level Ca 2+ changes within subpopulations of neurons in freely moving animals. [ 32 ] For instance, Clarkson et al. (2017) used this method to show that neurons in the arcuate nucleus of the hypothalamus synchronize to increases in Ca 2+ immediately prior to pulses of luteinizing hormone (LH). [ 33 ] While GCaMP imaging with fiber photometry cannot track changes in Ca 2+ levels within individual neurons, it provides greater temporal resolution for large-scale changes. [ 34 ]
Ca 2+ currents through cardiomyocyte gap junctions mediate synchronized contraction of cardiac tissue. As a result, GCaMP expression in cardiomyocytes, both in vitro and in vivo , has been used to study Ca 2+ -influx-dependent excitation and contraction in zebrafish and mice. [ 35 ] For instance, Tallini et al. (2006) expressed GCaMP2 in mouse embryos to show that, at embryonic day 10.5, electrical conduction was rapid in the atria and ventricles but slow in the atrioventricular canal . [ 8 ] Chi et al. (2008) used a transgenic cardiac-specific GCaMP zebrafish line to image cardiomyocyte activation throughout the cardiac cycle; from their results, they characterized four developmental stages of the zebrafish cardiac conduction system and identified 17 novel mutations affecting cardiac conduction. [ 36 ] However, uncontrolled expression of GCaMP leads to cardiac hypertrophy due to overexpression of the calmodulin motif, which interferes with intracellular calcium signaling. As a result, experiments using cardiac tissue should carefully control the level of GCaMP expression. [ 8 ]
Since Ca 2+ is a common second messenger, GCaMP has been used to monitor the activation of signaling pathways. For instance, Bonder and McCarthy (2014) used GCaMP to show that astrocytic G-protein coupled receptor (GPCR) signaling and subsequent Ca 2+ release was not responsible for neurovascular coupling, the process by which changes in neuronal activity lead to changes in local blood flow. [ 37 ] Similarly, Greer and Bear et al. (2016) used GCaMP to characterize the dynamics of Ca 2+ influx in necklace olfactory neuron signaling, which uses transmembrane MS4A proteins as chemoreceptors . [ 38 ] | https://en.wikipedia.org/wiki/GCaMP |
GD 61 is a white dwarf with a protoplanetary system located 150 light-years from Earth in the constellation Perseus . [ 4 ] It is thought to have been a main-sequence star of spectral type A0V with around three times the mass of the Sun that has aged and passed through a red-giant phase, leaving a dense, hot remnant that has around 70% of the Sun's mass and a surface temperature of 17,280 K. It is thought to be around 600 million years old, including both its life as a main-sequence star and as a white dwarf. [ 3 ] It has an apparent magnitude of 14.8. [ 2 ] GD 61 was first noted as a potential degenerate star in 1965, in a survey of white-dwarf suspects by astronomers from the Lowell Observatory in Arizona. [ 5 ]
In 2013, a circumstellar disk that resulted from the destruction of a water-rich asteroid was detected in close orbit around GD 61, which makes this the first detection of solid or liquid water on an extrasolar body. This asteroid would originally have been 26% water by mass, close to the water content of Ceres . [ 6 ] This evidence suggests that a planet, with a rocky surface similar to Earth's, may have existed in the past, with the asteroid thus being an artifact from this period, now possibly part of a debris field from the hypothetical planet's breakup. Such a planet would have had both a rocky surface and water, two key ingredients for life. [ 7 ] [ 8 ] The researchers used the Cosmic Origins Spectrograph on the Hubble Space Telescope to determine the elemental composition. The elements magnesium, silicon, iron, and oxygen were detected, all components of rocky planets, although the levels of oxygen were much higher than what could be accounted for. The lack of associated carbon left only one candidate for the oxygen excess—water. [ 7 ] | https://en.wikipedia.org/wiki/GD_61 |
The GEC-Marconi scientist deaths theory claims that between 1982 and 1990 a number of British -based GEC-Marconi scientists and engineers who worked on the Sting Ray torpedo project and United States Strategic Defense Initiative -related projects died under mysterious circumstances. [ 1 ] [ 2 ] [ citation needed ]
The first deaths to gain widespread attention and be linked to the theory came in 1986–1987. In just about a year, six scientists died, three of whom had worked for the Marconi company, a subsidiary of the defence group General Electric Company . Most deaths were ruled suicides or accidents. One died after driving his car, which had been packed full of petrol containers, into a building. Another tied a rope to his neck and to a tree and then drove off in a car. A third died of carbon monoxide poisoning in his garage. No links were found between them. At the time, some opposition lawmakers in the British parliament called for an investigation into the deaths. [ 1 ] [ 2 ]
Proponents of the conspiracy theory link the deaths like a James Bond -esque set of assassinations, variably blaming the Soviet spy agency KGB , American spies, or even British spies. [ 2 ] [ 3 ] [ 4 ] Proponents of the theory claim that the deaths were linked because of the scientists working on the same few classified projects, [ 3 ] [ 2 ] although most of the scientists had not been working closely together and were working on separate, mostly unclassified, projects. [ 1 ]
Newspapers
Books
Media | https://en.wikipedia.org/wiki/GEC-Marconi_scientist_deaths_conspiracy_theory |
The GEM of Egypt was a power shovel built by Bucyrus-Erie in 1966. The shovel was designed for strip mining at the Egypt Valley coalfield near Barnesville, Ohio . GEM is an acronym for “Giant Earth Mover” or “Giant Excavating Machine”. [ 3 ] It was one of only two Bucyrus-Erie 1950-B shovels built (the other being The Silver Spade ) and one of two to use the knee-action crowd licensed from Marion Power Shovel in exchange for Marion's use of Bucyrus-Erie's cable crowd patent. [ 4 ]
In a power shovel, "crowding" is pushing the bucket at the end of a "handle" ("dipper" or "dipper stick") in or out to control the depth of cut or to position for dumping. With knee action, the handle is connected to a moveable pivot point rather than being supported directly by the boom. Knee-action design made possible the largest shovel ever built, increased digging power, allowed the bucket to move horizontally into the cut and improved swing efficiency, distance, and radius. [ 5 ]
The GEM of Egypt had a 170' boom and a 130 cubic yard bucket which enabled it to dig roughly 200 tons per 'bite'. [ 6 ] The machine began work in January, 1967 for Hanna Coal, and was later purchased by Consolidated Coal in "Egypt Valley" near Barnesville, Ohio . The area was also where the GEM got its name. [ 6 ] The GEM was one of three in the service of the Hanna Coal Company, which by 1970, had been strip mining in Ohio for decades, joined by The Tiger and The Mountaineer . [ 6 ]
Of the three, the GEM of Egypt was the largest, and went into service upon the official opening of the Egypt Valley mine in January 1967. [ 6 ] It was reported that an estimated 25,000 people traveled to the site, many from Ohio cities such as Cleveland, Akron, and Canton, as well as those from neighboring states. The shovel was 20 stories tall and weighed 7,000 tons. [ 6 ] Production there was expected to average 20,000 tons a day, which the company forecast would last for the next 30 to 40 years until the vein ran out. [ 6 ]
The GEM was parked in 1988 and finally dismantled in 1991 off Ohio SR9 between New Athens and Fairpoint. Parts of the shovel were used to keep its twin, The Silver Spade , operating until it too was retired. [ 7 ] [ 8 ]
This article about mining is a stub . You can help Wikipedia by expanding it .
This Ohio -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/GEM_of_Egypt |
GEORGE was an early computer built in 1957 [ 1 ] by Argonne National Laboratory , was based on the IAS architecture developed by John von Neumann . (The name "GEORGE" is apparently not an acronym. It may have been derived from the sentence, "Let George do it," which was said when a person didn't want to do something himself). [ 2 ] As with almost all computers of its era, it was a one of a kind machine that could not exchange programs with mother computers (even other IAS machines ).
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/GEORGE_(computer) |
Dassault Systèmes GEOVIA is a set of geologic modeling and mining engineering software applications developed by the French engineering software company Dassault Systèmes . Formerly known as Gemcom, the company was founded in 1985 as a spin-off from by mining consultants SRK Consulting, with headquarters in Vancouver, British Columbia , Canada . [ 1 ] | https://en.wikipedia.org/wiki/GEOVIA |
Genome editing of synthetic target arrays for lineage tracing ( GESTALT ) is a method used to determine the developmental lineages of cells in multicellular systems. [ 1 ] GESTALT involves introducing a small DNA barcode that contains regularly spaced CRISPR/Cas9 target sites into the genomes of progenitor cells. Alongside the barcode, Cas9 and sgRNA are introduced into the cells. Mutations in the barcode accumulate during the course of cell divisions and the unique combination of mutations in a cell's barcode can be determined by DNA or RNA sequencing to link it to a developmental lineage.
Fate mapping is the process of identifying the embryonic origins of adult tissues. Lineage tracing is more specific, encompassing methods which examine the progeny that arise from a single/few cells. [ 2 ] One of the first lineage tracing methods developed involved the injection of dyes into specific cells of an early embryo, thereby labeling them and their progeny at each cell division. [ 3 ] Later methods used retroviral labeling, employing retroviruses to introduce a marker gene like fluorescent protein or beta-galactosidase into the genomes of the cells of interest, resulting in constitutive expression of the marker in those cells and their progeny. [ 4 ] These methods have the drawback of being invasive, and relatively difficult in targeting which cells to label. [ 2 ] Currently, the most widely used approach involves cell labeling via genetic recombination systems. These methods use recombinases , the two main ones being the Cre-loxP and Flp-firt systems, which can delete segments of DNA flanked by the loxP and frt sites, respectively. [ 5 ] [ 6 ] In this method, a transgenic model is created that can express Cre recombinase and has a reporter gene with an upstream stop cassette flanked by loxP sites. Cre recombination deletes the STOP cassette upstream of a reporter gene, allowing for expression of the reporter. [ 7 ] Spatial control over the labeled cells is achieved by using specific Cre alleles under the control elements of a chosen marker gene, and temporal control can be obtained if inducible Cre alleles are used. [ 7 ] For example, CreERT only has active recombination activity upon administration of tamoxifen . [ 8 ] Although powerful, it requires significant optimization to facilitate single cell lineage tracing and is low throughput. [ 9 ] Sequencing-based methods of lineage tracing have begun to emerge as they provide significantly higher resolution and high-throughput tracing of cell fate. [ 9 ] [ 10 ] Early approaches leveraged naturally occurring somatic mutations to identify cell lineage relationships. [ 11 ]
GESTALT takes advantage of the CRISPR-Cas9 system, which allows for the targeting of double stranded breaks in DNA to highly specific sites adjacent to PAM motifs based on the sequence of the sgRNA. [ 12 ] These breaks are then repaired by one of the endogenous cellular DNA mechanisms: non-homologous end joining DNA repair, or homology-directed repair . [ 12 ] Non-homolgous end joining is the more active of the two repair pathways, resulting in indels occurring at the targeted site. [ 13 ] The GESTALT system uses an array of ten CRISPR/Cas9 targets, with the first site having perfect specificity to the designed sgRNA, and the other nine having less Cas9 activity due to mismatches with the sgRNA. [ 1 ] Introducing the CRISPR-Cas9 reagents to cells carrying this array will cause the accumulation of indels at potentially each target of the array, marking the cell with a unique barcode sequence that can be used to identify it and its progeny via DNA or RNA-sequencing. [ 1 ]
The target sequences are 23 bp long, including a protospacer and PAM sequence. The target sequences are placed in contiguous array, separated by 3 to 5 bp linker sequences. Each target sequence must be screened against the genome of the host organism to ensure the specificity of the target sequences. Cas9 activity at each target site can be assessed using the GUIDE-seq assay. [ 14 ]
Two separate methods of introducing barcode arrays into the genomes of cells are used. The first method transduces progenitor cells with a lentivirus construct containing the barcode array inserted into the 3'-UTR of EGFP . This results in the incorporation of the barcode array into the genome and marks barcoded cells through stable expression of EGFP. A second method involves creating transgenic animal lines; the transgenic model has previously been generated using a Tol2 transgenesis vector which contains a barcode array cloned into the 3' UTR of DsRed under control of the ubiquitin promoter. [ 15 ] [ additional citation(s) needed ]
Initiation of barcode editing and labeling of cells is done by introducing the Cas9 protein and sgRNAs into progenitor cells. The CRISPR-Cas9 complex randomly produces double-stranded breaks in the barcode regions and subsequent NHEJ repair introduces random indels , resulting in a unique DNA sequence at the barcode region in each cell at time of labeling. There are multiple methods of delivering the CRISPR-Cas9 reagents into cells and it is an active field of research. [ 16 ] CRISPR-Cas9 reagents can be introduced into cells via transfection using lipid nanoparticles . [ 16 ] Alternatively, microinjection of the CRISPR-Cas9 reagents can be performed on 1-cell embryos . [ 17 ] The delivery of CRISPR-Cas9 reagents can be done at different developmental times to change the labeled populations. Barcode editing may persist for several hours after delivery. [ 1 ]
Following delivery of the CRISPR-Cas9 reagents, time is allowed for barcode editing and further development to occur, resulting in the expansion of the labeled populations and the unique marking of their progeny. Genomic DNA or RNA can then be extracted from the progeny cells or tissues of interest and the barcodes can be PCR -amplified. Unique molecular identifiers are used to correct for PCR bias and each UMI-barcode combo is therefore from a single cell. All barcode alleles can then be sequenced via NGS and the entire set of identified alleles can be subjected to phylogenetic analysis, identifying cell lineage based on barcode similarity. To control for sequencing error, only indels can be considered as most sequencing errors inherent to next-generation sequencing are base substitutions. [ 18 ] [ 1 ]
Single cell GESTALT (scGESTALT) adds upon the GESTALT system by integrating simultaneous capture of barcode and transcriptome information using scRNA-seq . [ 19 ] In scGESTALT, the barcode is cloned into progenitor cells of interest downstream of an inducible promoter. When the developmental period is complete, expression of the barcode will be induced and the barcode mRNA will be sequenced alongside the rest of the transcriptome using scRNA-seq. [ 19 ] The transcriptomic data can be used to track cell type differentiation while the barcodes can be used to create developmental relationships with other cells. An additional improvement is the ability to induce labeling at two different time points. This is enabled through the cloning of the Cas9/sgRNA under a heat shock promoter; the first labeling event is induced via microinjection like traditional GESTALT, while a subsequent second labeling period is initiated by heat shock-induced expression of Cas9 and sgRNAs. [ 19 ] This enables lineage tracing during later stages of development, beyond what is possible with GESTALT.
GESTALT was initially developed to examine the contributions of embryonic progenitors to the adult organ systems of zebrafish . [ 1 ] By sequencing the barcodes from bulk extractions of organ systems, each organ was found to possess only a small number of the barcode alleles , indicating that organs arise from the clonal expansion of a small number of early progenitors. [ 1 ] The lineage information of thousands of differentiated cells was captured in the experiment and demonstrated the high-throughput lineage tracing capabilities of GESTALT. [ 1 ]
scGESTALT has been used to refine the lineage tree of the zebrafish brain. [ 19 ] The existence of multipotent progenitors which give rise to cells that migrate across the brain was discovered following a scGESTALT experiment where some barcode sequences were captured in cell populations in the forebrain, midbrain, and the hindbrain. [ 19 ] Pseudotime trajectories generated using the scRNA-seq data for oligodendrocyte progenitors to oligodendrocytes as well as atoh1c + progenitors to pax6b + neurons were found to be consistent with the barcode distribution across those cell types. [ 19 ] | https://en.wikipedia.org/wiki/GESTALT |
GESTIS Substance Database is a freely accessible online information system on chemical compounds . It is maintained by the Institut für Arbeitsschutz der Deutschen Gesetzlichen Unfallversicherung (IFA, Institute for Occupational Safety and Health of the German Social Accident Insurance ). Information on occupational medicine and first aid is compiled by Henning Heberer and his team (TOXICHEM, Leuna).
The database contains information for the safe handling of hazardous substances and other chemical substances at work:
The available information relates to about 9,400 substances. Data are updated immediately after publication of new official regulations or after the issue of new scientific results.
A mobile version of the GESTIS Substance Database, suitable for smartphones and tablets , is also available. [ 1 ] | https://en.wikipedia.org/wiki/GESTIS_Substance_Database |
GEUP is a commercial interactive geometry software program on windows, similar to Cabri Geometry . Originally using the Spanish language , it was programmed by Ramón
Alvarez Galván. [ 1 ] Recent versions include support for three-dimensional geometry . [ 2 ]
This geometry-related article is a stub . You can help Wikipedia by expanding it .
This scientific software article is a stub . You can help Wikipedia by expanding it .
This Microsoft Windows software -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/GEUP |
GFAJ-1 is a strain of rod-shaped bacteria in the family Halomonadaceae . It is an extremophile that was isolated from the hypersaline and alkaline Mono Lake in eastern California by geobiologist Felisa Wolfe-Simon , a NASA research fellow in residence at the US Geological Survey . In a 2010 Science journal publication, [ 1 ] the authors claimed that the microbe, when starved of phosphorus , is capable of substituting arsenic for a small percentage of its phosphorus to sustain its growth. [ 2 ] [ 3 ] Immediately after publication, other microbiologists and biochemists expressed doubt about this claim, which was robustly criticized in the scientific community. Subsequent independent studies published in 2012 found no detectable arsenate in the DNA of GFAJ-1, refuted the claim, and demonstrated that GFAJ-1 is simply an arsenate-resistant, phosphate-dependent organism. [ 4 ] [ 5 ] [ 6 ] [ 7 ]
The GFAJ-1 bacterium was discovered by geomicrobiologist Felisa Wolfe-Simon , a NASA astrobiology fellow in residence at the US Geological Survey in Menlo Park, California . [ 8 ] GFAJ stands for "Give Felisa a Job". [ 9 ] The organism was isolated and cultured beginning in 2009 from samples she and her colleagues collected from sediments at the bottom of Mono Lake , California, U.S.A. [ 10 ] Mono Lake is hypersaline (about 90 grams/liter) and highly alkaline ( pH 9.8). [ 11 ] It also has one of the highest natural concentrations of arsenic in the world (200 μ M ). [ 1 ] The discovery was widely publicized on 2 December 2010. [ 2 ]
Escherichia coli strain O157:H7
Halomonas alkaliphila
Halomonas venusta strain NBSL13
GFAJ-1
Halomonas sp. GTW
Halomonas sp. G27
Halomonas sp. DH77
Halomonas sp. mp3
Halomonas sp. IB-O18
Halomonas sp. ML-185
Molecular analysis based on 16S rRNA sequences shows GFAJ-1 to be closely related to other moderate halophile ("salt-loving") bacteria of the family Halomonadaceae . Although the authors produced a cladogram in which the strain is nested among members of Halomonas , including H. alkaliphila and H. venusta , [ 12 ] they did not explicitly assign the strain to that genus. [ 1 ] [ 10 ] Many bacteria are known to be able to tolerate high levels of arsenic, and to have a proclivity to take it up into their cells. [ 1 ] [ 13 ] However, GFAJ-1 was controversially proposed to go a step further; when starved of phosphorus, it was proposed to instead incorporate arsenic into its metabolites and macromolecules and continue growing. [ 10 ]
The sequence of the genome of the bacterium GFAJ-1 is now posted in GenBank . [ 14 ]
In the Science journal article, GFAJ-1 is referred to as a strain of Halomonadaceae and not as a new species . [ 1 ] The International Code of Nomenclature of Bacteria , the set of regulations which govern the naming of bacteria, and certain articles in the International Journal of Systematic and Evolutionary Microbiology contain the guidelines and minimal standards to describe a new species, e.g. the minimal standards to describe a member of the Halomonadaceae . [ 15 ] Organisms are described as new species if they meet certain physiological and genetic conditions, such as generally less than 97% 16S rRNA sequence identity to other known species [ 16 ] and metabolic differences allowing them to be discerned apart. In addition to indicators to tell the novel species from other species, other analyses are required, such as fatty acid composition , respiratory quinone used and tolerance ranges and deposition of the strain in at least two microbiological repositories. New proposed names are given in italics followed by sp. nov. (and gen. nov. if it is a novel genus according to the descriptions of that clade ). [ 17 ] [ 18 ]
In the instance of the GFAJ-1 strain these criteria are not met, and the strain is not claimed to be a new species. [ 1 ] When a strain is not assigned to a species (e.g. due to insufficient data or choice) it is often labeled as the genus name followed by "sp." (i.e., undetermined species of that genus) and the strain name. In the case of GFAJ-1 the authors chose to refer to the strain by strain designation only. Strains closely related to GFAJ-1 include Halomonas sp. GTW and Halomonas sp. G27, neither of which were described as valid species. [ 19 ] [ 20 ] If the authors had formally assigned strain GFAJ-1 to the genus Halomonas , [ 10 ] the name would be given as Halomonas sp. GFAJ-1.
Until release R220, the Genome Taxonomy Database assigned GFAJ-1 its own tentative species, Halomonas sp002966495 . This means that the strain falls into Halomonas phylogenetically, and its whole-genome similarity compared to other defined species of the genus is low enough. Neither strain GTW nor strain G27 has a genome available for the database to run its classification. In release R220, the databased moved the strain to Vreelandella , a new genus published in 2023 (and validated in 2024). [ 21 ]
A phosphorus-free growth medium (which actually contained 3.1 ± 0.3 μM of residual phosphate, from impurities in reagents) was used to culture the bacteria in a regime of increasing exposure to arsenate ; the initial level of 0.1 mM was eventually ramped up to 40 mM. Alternative media used for comparative experiments contained either high levels of phosphate (1.5 mM) with no arsenate, or had neither added phosphate nor added arsenate. It was observed that GFAJ-1 could grow through many doublings in cell numbers when cultured in either phosphate or arsenate media, but could not grow when placed in a medium of a similar composition to which neither phosphate nor arsenate was added. [ 1 ] The phosphorus content of the arsenic-fed, phosphorus-starved bacteria (as measured by ICP-MS) was only 0.019 (± 0.001) % by dry weight, one thirtieth of that when grown in phosphate-rich medium. This phosphorus content was also only about one tenth of the cells' average arsenic content (0.19 ± 0.25% by dry weight). [ 1 ] The arsenic content of cells as measured by ICP-MS varies widely and can be lower than the phosphorus contents in some experiments, and up to fourteen times higher in others. [ 22 ] Other data from the same study obtained with nano- SIMS suggest a ~75-fold excess of phosphate (P) over arsenic (As) when expressed as P:C and As:C ratios, even in cells grown with arsenate and no added phosphate. [ 12 ] When cultured in the arsenate solution, GFAJ-1 only grew 60% as fast as it did in phosphate solution. [ 2 ] The phosphate-starved bacteria had an intracellular volume 1.5 times normal; the greater volume appeared to be associated with the appearance of large " vacuole -like regions". [ 1 ]
When the researcher, Joseph Tolle added isotope-labeled arsenate to the solution to track its distribution , they found that arsenic was present in the cellular fractions containing the bacteria's proteins , lipids and metabolites such as ATP , as well as its DNA and RNA . [ 2 ] Nucleic acids from stationary phase cells starved of phosphorus were concentrated via five extractions (one with phenol , three with phenol-chloroform and one with chloroform extraction solvent), followed by ethanol precipitation . Although direct evidence of the incorporation of arsenic into biomolecules is still lacking, radioactivity measurements suggested that approximately one-tenth (11.0 ± 0.1%) of the arsenic absorbed by these bacteria ended up in the fraction that contained the nucleic acids (DNA and RNA) and all other co-precipitated compounds not extracted by the previous treatments. [ 1 ] A comparable control experiment with isotope-labeled phosphate was not performed.
With the distribution of the strain in mid-2011, other labs began to independently test the validity of the discovery. Rosemary Redfield from the University of British Columbia , following issues with the growth conditions, investigated the growth requirements of GFAJ-1, and found that the strain grows better on solid agar medium than in liquid culture. Redfield attributed this to low potassium levels and hypothesized that the potassium levels in basal ML60 medium may be too low to support growth. [ 23 ] Redfield after finding and addressing further issues (ionic strength, pH and the use of glass tubes instead of polypropylene) found that arsenate marginally stimulated growth, but didn't affect the final densities of the cultures, unlike what was claimed. [ 24 ] Subsequent studies using mass spectrometry by the same group found no evidence of arsenate being incorporated into the DNA of GFAJ-1. [ 25 ]
Arsenate esters , such as those that would be present in DNA , are generally expected to be orders of magnitude less stable to hydrolysis than corresponding phosphate esters . [ 26 ] dAMAs, the structural arsenic analog of the DNA building block dAMP , has a half-life of 40 minutes in water at neutral pH. [ 27 ] Estimates of the half-life in water of arsenodiester bonds, which would link the nucleotides together, are as short as 0.06 seconds—compared to 30 million years for the phosphodiester bonds in DNA. [ 28 ] The authors speculate that the bacteria may stabilize arsenate esters to a degree by using poly-β-hydroxybutyrate (which has been found to be elevated in "vacuole-like regions" of related species of the genus Halomonas [ 29 ] ) or other means to lower the effective concentration of water. [ 1 ] [ 10 ] Polyhydroxybutyrates are used by many bacteria for energy and carbon storage under conditions when growth is limited by elements other than carbon, and typically appear as large waxy granules closely resembling the "vacuole-like regions" seen in GFAJ-1 cells. [ 30 ] The authors present no mechanism by which insoluble polyhydroxybutyrate may lower the effective concentration of water in the cytoplasm sufficiently to stabilize arsenate esters. Although all halophiles must reduce the water activity of their cytoplasm by some means to avoid desiccation, [ 31 ] the cytoplasm always remains an aqueous environment.
NASA's announcement of a news conference "that will impact the search for evidence of extraterrestrial life" was criticized as sensationalistic and misleading; an editorial in New Scientist commented "although the discovery of alien life, if it ever happens, would be one of the biggest stories imaginable, this was light-years from that". [ 32 ] [ 33 ]
In addition, many experts who have evaluated the paper have concluded that the reported studies do not provide enough evidence to support the claims made by the authors. [ 34 ] In an online article on Slate , science writer Carl Zimmer discussed the skepticism of several scientists: "I reached out to a dozen experts ... Almost unanimously, they think the NASA scientists have failed to make their case". [ 35 ] [ 36 ] Chemist Steven A. Benner has expressed doubts that arsenate has replaced phosphate in the DNA of this organism. He suggested that the trace contaminants in the growth medium used by Wolfe-Simon in her laboratory cultures are sufficient to supply the phosphorus needed for the cells' DNA. He believes that it is more likely that arsenic is being sequestered elsewhere in the cells. [ 2 ] [ 10 ] University of British Columbia microbiologist Rosemary Redfield said that the paper "doesn't present any convincing evidence that arsenic has been incorporated into DNA or any other biological molecule", and suggests that the experiments lacked the washing steps and controls necessary to properly validate their conclusions. [ 37 ] [ 38 ] Harvard microbiologist Alex Bradley said that arsenic-containing DNA would be so unstable in water it could not have survived the analysis procedure. [ 35 ] [ 39 ]
On 8 December 2010, Science published a response by Wolfe-Simon, in which she stated that criticism of the research was expected. In response, a " Frequently Asked Questions " page to improve understanding of the work was posted on 16 December 2010. [ 40 ] The team plans to deposit the GFAJ-1 strain in the ATCC and DSMZ culture collections to allow widespread distribution. [ 41 ] In late May 2011 the strain was made available upon request directly from the laboratory of the authors. [ 42 ] Science has made the article freely available. [ 43 ] The article was published in print six months after acceptance in the 3 June 2011 issue of Science . The publication was accompanied by eight technical comments addressing various concerns regarding the article's experimental procedure and conclusion, [ 44 ] [ 45 ] [ 46 ] [ 47 ] [ 48 ] [ 49 ] [ 50 ] [ 51 ] [ 52 ] as well as a response by the authors to these concerns. [ 42 ] [ 53 ] The editor in chief Bruce Alberts has indicated that some issues remain and that their resolution is likely to be a long process. [ 54 ] A review by Rosen et al. , [ 55 ] in the March 2011 issue of the journal BioEssays discusses the technical issues with the Science paper, provides alternative explanations, and highlights known biochemistry of other arsenic resistant and arsenic utilizing microbes.
On 27 May 2011, Wolfe-Simon and her team responded to the criticism in a follow-up Science journal publication. [ 42 ] Then in January 2012 a group of researchers led by Rosie Redfield at the University of British Columbia analyzed the DNA of GFAJ-1 using liquid chromatography–mass spectrometry and could not detect any arsenic, which Redfield calls a "clear refutation" of the original paper's findings. [ 56 ] Following the publication of the analysis, Wolfe-Simon stated that she and her colleagues "expect to publish new information in the next few months", [ 57 ] but as of 2024 has not submitted any new publications since 2011.
A simple explanation for the GFAJ-1 growth in medium supplied with arsenate instead of phosphate was provided by a team of researchers at the University of Miami in Florida. After labeling the ribosomes of a laboratory strain of Escherichia coli with radioactive isotopes (forming a radioactive tracer ), they followed bacterial growth in medium containing arsenate but no phosphate. They found that arsenate induces massive degradation of ribosomes, thus providing sufficient phosphate for the slow growth of arsenate tolerant bacteria. Similarly, they suggest, GFAJ-1 cells grow by recycling phosphate from degraded ribosomes, rather than by replacing it with arsenate. [ 58 ]
Following the publication of the articles challenging the conclusions of the original Science article first describing GFAJ-1, the website Retraction Watch argued that the original article should be retracted because of misrepresentation of critical data. [ 59 ] [ 60 ] As of January 2024 [update] , the paper had not been retracted. [ 1 ] | https://en.wikipedia.org/wiki/GFAJ-1 |
The GFP-cDNA project documents the localisation of proteins to subcellular compartments of the eukaryotic cell applying fluorescence microscopy . Experimental data are complemented with bioinformatic analyses and published online in a database . A search function allows the finding of proteins containing features or motifs of particular interest. The project is a collaboration of the research groups of Rainer Pepperkok at the European Molecular Biology Laboratory (EMBL) and Stefan Wiemann at the German Cancer Research Centre (DKFZ).
The cDNAs of novel identified Open Reading Frames (ORF) are tagged with Green Fluorescent Protein (GFP) and expressed in eukaryotic cells. Subsequently, the subcellular localisation of the fusion proteins is recorded by fluorescence microscopy.
Steps:
Any large-scale manipulation of ORFs requires cloning technologies which are free of restriction enzymes . In this respect those that utilise recombination cloning (Gateway of Invitrogen or Creator of BD Biosciences) have proved to be the most suitable. This cloning technology is based on recombination mechanisms used by phages to integrate their DNA into the host genome . It allows the ORFs to be rapidly and conveniently shuttled between functionally useful vectors without the need for conventional restriction cloning. In the cDNA-GFP project the ORFs are transferred into CFP/YFP expression vectors. For the localisation analysis both N- and C-terminal fusions are generated. This maximises the possibility of correctly ascertaining the localisation, since the presence of GFP may mask targeting signals that may be present at one end of the native protein.
Insert your gene of interest into the MCS upstream of the fluorescent protein gene, and express your gene as a fusion to the N-terminus of the fluorescent protein.
Insert your gene of interest into the MCS downstream of the fluorescent protein gene, and express your gene as a fusion to the C-terminus of the fluorescent protein.
The fusion vectors are transfected in Vero cells (monkey kidney fibroblasts ). Particularly interesting ORFs are also screened for localisation in PC12 cells and hippocampal neurons .
At different time points, the subcellular localisation of the fusion proteins is recorded via fluorescence microscopy. At the end of the live cell imaging, the cells can still be fixed and colocalisation experiments made.
As the sequence of the cDNAs is known, bioinformatics can make predictions regarding the localisation and function of the encoded protein. The bioinformatics analysis is facilitated by the bioinformatic search engine Harvester .
Results from the N- and C-terminal fusions are assessed and in turn these data are compared to the bioinformatic predictions. A final subcellular localisation (from approximately 20 categories) is then assigned for each ORF. Similar localisations with both N- and C-terminal constructs provide a higher degree of reliability of the result. For those ORFs where the two fusions do not give a similar localisation pattern, a series of other criteria, including bioinformatic predictions, are considered. Occasionally a clear cut localization cannot be assigned.
Every data sheet contains the fluorescence images of both N- and C-terminal fusions, the assigned localization, other localizations, comments and the Swissprot ID. For every protein entry, a link is provided to the corresponding Harvester bioinformatics page.
Images of all localised proteins and their bioinformatic analysis can be viewed via the ‘Results Table’ or ‘Results Images’ buttons. In addition, use the search window on the entry site to find proteins containing features or motifs of particular interest to you that have been localised in this project. | https://en.wikipedia.org/wiki/GFP-cDNA |
The GDNF family receptor-α ( GFRα ) proteins are a group of co-receptors which form complexes with GDNF-family ligands (GFLs) to activate RET , the receptor of the GFLs. [ 1 ] The GFRα co-receptors include the following:
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/GFRα |
GF Biochemicals is a biochemical company founded in 2008. It was co-founded by and named after Pasquale Granata and Mathieu Flamini . Along with Biofine, it is a mass producer of levulinic acid . [ 3 ]
The company worked with the University of Pisa for seven years on its production. [ 2 ] In 2016 GF Biochemicals acquired the American company Segetis. [ citation needed ] The company has a plant in Caserta that employs around 80 people. [ citation needed ] In 2015, the company won the John Sime Award for Most Innovative New Technology. [ 4 ] The company has offices in Milan and the Netherlands . [ 2 ]
Official website
This Italian corporation or company article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/GF_Biochemicals |
The GF method , sometimes referred to as FG method , is a classical mechanical method introduced by Edgar Bright Wilson to obtain certain internal coordinates for a vibrating semi-rigid molecule, the so-called normal coordinates Q k . Normal coordinates decouple the classical vibrational motions of the molecule and thus give an easy route to obtaining vibrational amplitudes of the atoms as a function of time. In Wilson's GF method it is assumed that the molecular kinetic energy consists only of harmonic vibrations of the atoms, i.e., overall rotational and translational energy is ignored. Normal coordinates appear also in a quantum mechanical description of the vibrational motions of the molecule and the Coriolis coupling between rotations and vibrations.
It follows from application of the Eckart conditions that the matrix G −1 gives the kinetic energy in terms of arbitrary linear internal coordinates, while F represents the (harmonic) potential energy in terms of these coordinates. The GF method gives the linear transformation from general internal coordinates to the special set of normal coordinates.
A non-linear molecule consisting of N atoms has 3 N − 6 internal degrees of freedom , because positioning a molecule in three-dimensional space requires three degrees of freedom, and the description of its orientation in space requires another three degree of freedom. These degrees of freedom must be subtracted from the 3 N degrees of freedom of a system of N particles.
The interaction among atoms in a molecule is described by a potential energy surface (PES), which is a function of 3 N − 6 coordinates. The internal degrees of freedom s 1 , ..., s 3 N −6 describing the PES in an optimal way are often non-linear; they are for instance valence coordinates , such as bending and torsion angles and bond stretches. It is possible to write the quantum mechanical kinetic energy operator for such curvilinear coordinates , but it is hard to formulate a general theory applicable to any molecule. This is why Wilson linearized the internal coordinates by assuming small displacements. [ 1 ] The linearized version of the internal coordinate s t is denoted by S t .
The PES V can be Taylor expanded around its minimum in terms of the S t . The third term (the Hessian of V ) evaluated in the minimum is a force derivative matrix F . In the harmonic approximation the Taylor series is ended after this term. The second term, containing first derivatives, is zero because it is evaluated in the minimum of V . The first term can be included in the zero of energy.
Thus,
The classical vibrational kinetic energy has the form:
where g st is an element of the metric tensor of the internal (curvilinear) coordinates. The dots indicate time derivatives . Mixed terms S s S ˙ t {\displaystyle S_{s}\,{\dot {S}}_{t}} generally present in curvilinear coordinates are not present here, because only linear coordinate transformations are used. Evaluation of the metric tensor g in the minimum s 0 of V gives the positive definite and symmetric matrix G = g ( s 0 ) −1 .
One can solve the two matrix problems
simultaneously, since they are equivalent to the generalized eigenvalue problem
where Φ = diag ( f 1 , … , f 3 N − 6 ) {\displaystyle {\boldsymbol {\Phi }}=\operatorname {diag} (f_{1},\ldots ,f_{3N-6})} where f i is equal to 4 π 2 ν i 2 {\displaystyle 4{\pi }^{2}{\nu }_{i}^{2}} ( ν i {\displaystyle {\nu }_{i}} is the frequency of normal mode i ); E {\displaystyle \mathbf {E} \,} is the unit matrix. The matrix L −1 contains the normal coordinates Q k in its rows:
Because of the form of the generalized eigenvalue problem, the method is called the GF method,
often with the name of its originator attached to it: Wilson's GF method . By matrix transposition in both sides of the equation and using the fact that both G and F are symmetric matrices, as are diagonal matrices, one can recast this equation into a very similar one for FG . This is why the method is also referred to as Wilson's FG method .
We introduce the vectors
which satisfy the relation
Upon use of the results of the generalized eigenvalue equation, the energy E = T + V (in the harmonic approximation) of the molecule becomes:
The Lagrangian L = T − V is
The corresponding Lagrange equations are identical to the Newton equations
for a set of uncoupled harmonic oscillators. These ordinary second-order differential equations are easily solved, yielding Q t as a function of time; see the article on harmonic oscillators .
Often the normal coordinates are expressed as linear combinations of Cartesian displacement coordinates.
Let R A be the position vector of nucleus A and R A 0 the corresponding equilibrium position. Then x A ≡ R A − R A 0 {\displaystyle \mathbf {x} _{A}\equiv \mathbf {R} _{A}-\mathbf {R} _{A}^{0}} is by definition the Cartesian displacement coordinate of nucleus A.
Wilson's linearizing of the internal curvilinear coordinates q t expresses the coordinate S t in terms of the displacement coordinates
where s A t is known as a Wilson s-vector .
If we put the s A i t {\displaystyle s_{Ai}^{t}} into a (3 N − 6) × 3 N matrix B , this equation becomes in matrix language
The actual form of the matrix elements of B can be fairly complicated.
Especially for a torsion angle, which involves 4 atoms, it requires tedious vector algebra to derive the corresponding values of the s A i t {\displaystyle s_{Ai}^{t}} . See for more details on this method, known as
the Wilson s-vector method , the book by Wilson et al. , or molecular vibration . Now,
which can be inverted and put in summation language:
Here D is a (3 N − 6) × 3 N matrix, which is given by (i) the linearization of the internal coordinates s (an algebraic process) and (ii) solution of Wilson's GF equations (a numeric process).
There are several related coordinate systems commonly used in the GF matrix analysis. [ 2 ] These quantities are related by a variety of matrices. For clarity, we provide the coordinate systems and their interrelations here.
The relevant coordinates are:
These different coordinate systems are related to one another by:
Note the useful relationship:
L = B M − 1 / 2 l . {\displaystyle \mathbf {L} =\mathbf {B} \mathbf {M} ^{-1/2}\mathbf {l} .}
These matrices allow one to construct the G matrix quite simply as
G = B M − 1 B T . {\displaystyle \mathbf {G} =\mathbf {B} \mathbf {M} ^{-1}\mathbf {B} ^{\rm {T}}.}
From the invariance of the internal coordinates S t under overall rotation and translation
of the molecule, follows the same for the linearized coordinates s t A .
It can be shown that this implies that the following 6 conditions are satisfied by the internal
coordinates,
These conditions follow from the Eckart conditions that hold for the displacement vectors, | https://en.wikipedia.org/wiki/GF_method |
The Gravity Gradient Stabilization Experiment (GGSE-4) was a technology satellite launched in 1967. This was ostensibly the fourth in a series that developed designs and deployment techniques later applied to the NOSS/Whitecloud reconnaissance satellites.
GGSE-4 was launched by the U.S. Airforce from Vandenberg Air Force Base atop a Thor Agena-D rocket. [ 1 ] GGSE-4 remained operational from 1967 through 1972. [ 2 ]
It is alleged that the real name of GGSE-4 was POPPY 5B or POPPY 5b and that it was a U.S. National Reconnaissance Office satellite designed to collect signals intelligence; [ 3 ] POPPY 5B was part of a 7-satellite mission. A partial subset of information about POPPY was declassified in 2005. [ 4 ]
Other sources say that GGSE-4 weighed only 10 pounds but that it was attached to the much larger Poppy 5 , which would have weighed 85 kg and featured an 18-meter boom. [ 5 ] It is further alleged that GGSE-4's mass is not at all like GGSE-1's mass and that GGSE'4 weighs 85 kg. [ 6 ]
On 29 January 2020, 23:39:35 UTC, [ 7 ] GGSE-4 was expected to pass as closely as 12 meters [ 8 ] from IRAS , another un-deorbited satellite left aloft. IRAS was launched in 1983 and abandoned after a 10-month mission. The 14.7-kilometer per second pass [ 9 ] had an estimated risk of collision of 5%. Further complications arose from the fact that GGSE-4 was outfitted with an 18 meter long stabilization boom that was in an unknown orientation and may have struck the satellite even if the spacecraft's main body did not. [ 10 ] Initial observations from amateur astronomers seemed to indicate that both satellites had survived the pass, with the California-based debris tracking organization LeoLabs later confirming that they had detected no new tracked debris following the incident. [ 11 ]
Gravity Gradient Stabilization Experiment (GGSE-1) | https://en.wikipedia.org/wiki/GGSE-4 |
Hazard pictograms form part of the international Globally Harmonized System of Classification and Labelling of Chemicals (GHS). Two sets of pictograms are included within the GHS: one for the labelling of containers and for workplace hazard warnings, and a second for use during the transport of dangerous goods. Either one or the other is chosen, depending on the target audience, but the two are not used together for the same hazard. [ 1 ] The two sets of pictograms use the same symbols for the same hazards, although certain symbols are not required for transport pictograms. Transport pictograms come in a wider variety of colors and may contain additional information such as a subcategory number.
Hazard pictograms are one of the key elements for the labelling of containers under the GHS, along with: [ 2 ]
The GHS chemical hazard pictograms are intended to provide the basis for or to replace national systems of hazard pictograms. It has still to be implemented by the European Union ( CLP regulation ) in 2009.
The GHS transport pictograms are the same as those recommended in the UN Recommendations on the Transport of Dangerous Goods , widely implemented in national regulations such as the U.S. Federal Hazardous Materials Transportation Act (49 U.S.C. 5101–5128) and D.O.T. regulations at 49 C.F.R. 100–185.
Not used [ 3 ]
Note : The asterisks are replaced by the class number and compatibility code
Explosives – Substances and articles which are classified as explosives but which present no significant hazard
Note : The asterisk is replaced by the compatibility code
Explosives – Very insensitive substances which have a mass explosion hazard
Note : The asterisk is replaced by the compatibility code
Explosives – No hazard statement
Note : The asterisk is replaced by the compatibility code
Flammable gases – Gases which at 20 °C and a standard pressure of 101.3 kPa:
Alternative sign
Non-flammable non-toxic gases – Gases which:
Alternative sign
Toxic gases – Gases which:
e.g. hydrogen cyanide
Flammable liquids – Liquids which have a flash point of less than 60 °C and which are capable of sustaining combustion
Alternative sign
Flammable solids, self-reactive substances and solid desensitized explosives – Solids which, under conditions encountered in transport, are readily combustible or may cause or contribute to fire through friction; self-reactive substances which are liable to undergo a strongly exothermic reaction; solid desensitized explosives which may explode if not diluted sufficiently
Substances liable to spontaneous combustion – Substances which are liable to spontaneous heating under normal conditions encountered in transport, or to heating up in contact with air, and being then liable to catch fire
e.g. manganese heptoxide
Substances which in contact with water emit flammable gases – Substances which, by interaction with water, are liable to become spontaneously flammable or to give off flammable gases in dangerous quantities
Alternative sign
Oxidizing substances – Substances which, while in themselves not necessarily combustible, may, generally by yielding oxygen, cause, or contribute to, the combustion of other material
Organic peroxides – Organic substances which contain the bivalent –O–O– structure and may be considered derivatives of hydrogen peroxide , where one or both of the hydrogen atoms have been replaced by organic radicals
Alternative sign
Toxic substances – Substances with an LD 50 value ≤ 300 mg/kg (oral) or ≤ 1000 mg/kg (dermal) or an LC 50 value ≤ 4000 ml/m 3 (inhalation of dusts or mists)
e.g. nearly everything that contains cyanide groups
Corrosive substances – Substances which:
The following pictograms are included in the UN Model Regulations [ which? ] but have not been incorporated into the GHS because of the nature of the hazards. | https://en.wikipedia.org/wiki/GHS_hazard_pictograms |
Hazard statements form part of the Globally Harmonized System of Classification and Labelling of Chemicals (GHS). They are intended to form a set of standardized phrases about the hazards of chemical substances and mixtures that can be translated into different languages. [ 1 ] [ 2 ] As such, they serve the same purpose as the well-known R-phrases , which they are intended to replace.
Hazard statements are one of the key elements for the labelling of containers under the GHS, along with: [ 3 ]
Each hazard statement is designated a code, starting with the letter H and followed by three digits. Statements which correspond to related hazards are grouped together by code number, so the numbering is not consecutive. The code is used for reference purposes, for example to help with translations, but it is the actual phrase which should appear on labels and safety data sheets . [ 4 ]
The European Union has implemented the GHS through the CLP Regulation . Nevertheless, the older system based on the Dangerous Substances Directive was used in parallel until June 2015. Some R-phrases which do not have simple equivalents under the GHS have been retained under the CLP Regulation: [ 6 ] the numbering mirrors the number of the previous R-phrase.
Some other hazard statements intended for use in very specific circumstances have also been retained under the CLP Regulation. [ 7 ] In this case, the numbering of the EU specific hazard statements can coincide with GHS hazard statements if the "EU" prefix is not included.
The GHS was adopted in Australia from 1 January 2012 and becomes mandatory in States and Territories that have adopted the harmonised Work Health and Safety laws (other than Victoria and Western Australia) as of 1 January 2017. [ 8 ] The National Code of Practice for the Preparation of Safety Data Sheets for Hazardous Chemicals [ 9 ] includes 12 Australian-specific GHS Hazard Statements, as follows:
As of March 2009, the relevant New Zealand regulations under the Hazardous Substances and New Organisms Act 1996 do not specify the exact wording required for hazard statements. However, the New Zealand classification system includes three categories of environmental hazard which are not included in the GHS Rev.2:
These are classes 9.2–9.4 respectively of the New Zealand classification scheme, and are divided into subclasses according to the degree of hazard. [ 10 ] Substances in subclass 9.2D ("Substances that are slightly harmful in the soil environment") do not require a hazard statement, while substances in the other subclasses require an indication of the general degree of hazard and general type of hazard. [ 11 ] | https://en.wikipedia.org/wiki/GHS_hazard_statements |
Precautionary statements form part of the Globally Harmonized System of Classification and Labelling of Chemicals (GHS). [ 1 ] They are intended to form a set of standardized phrases giving advice about the correct handling of chemical substances and mixtures, which can be translated into different languages. [ 2 ] [ 3 ] As such, they serve the same purpose as the well-known S-phrases , which they are intended to replace.
Precautionary statements are one of the key elements for the labelling of containers under the GHS, along with: [ 4 ]
Each precautionary statement is designated a code, starting with the letter P and followed by three digits. Statements which correspond to related hazards are grouped together by code number, so the numbering is not consecutive. The code is used for reference purposes, for example to help with translations, but it is the actual phrase which should appear on labels and safety data sheets . [ 5 ] Some precautionary phrases are combinations, indicated by a plus sign "+". In several cases, there is a choice of wording, for example "Avoid breathing dust/fume/gas/mist/vapours/spray": the supplier or regulatory agency should choose the appropriate wording for the product concerned. | https://en.wikipedia.org/wiki/GHS_precautionary_statements |
GIOVE ( Italian for ' Jupiter '; pronounced [ˈdʒɔːve] ), or Galileo In-Orbit Validation Element , is the name for two satellites built for the European Space Agency (ESA) to test technology in orbit for the Galileo positioning system . [ 1 ]
The name was chosen as a tribute to Galileo Galilei , who discovered the first four natural satellites of Jupiter , and later discovered that they could be used as a universal clock to obtain the longitude of a point on the Earth 's surface.
The GIOVE satellites are operated by the GIOVE Mission [ 2 ] [ 3 ] ( GIOVE-M ) segment in the frame of the risk mitigation for the In Orbit Validation (IOV) of the Galileo positioning system .
These validation satellites were previously known as the Galileo System Testbed (GSTB) version 2 (GSTB-V2) . In 2004 the Galileo System Test Bed Version 1 (GSTB-V1) project validated the on-ground algorithms for Orbit Determination and Time Synchronization (OD&TS). This project, led by ESA and European Satellite Navigation Industries , has provided industry with fundamental knowledge to develop the mission segment of the Galileo positioning system . [ 4 ]
GIOVE satellites transmitted multifrequency ranging signals equivalent to the signals of future Galileo : L1BC, L1A, E6BC, E6A, E5a, E5b. The main purpose of the GIOVE mission was to test and validate the reception and performance of novel code modulations designed for Galileo including new signals based on the use of the BOC ( Binary Offset Carrier ) technique, in particular the high-performance E5AltBOC signal.
Previously known as GSTB-V2/A , this satellite was constructed by Surrey Satellite Technology Ltd (SSTL).
Its mission has the main goal of claiming the frequencies allocated to Galileo by the ITU . It has two independently developed Galileo signal generation chains and also tests the design of two on-board rubidium atomic clocks and the orbital characteristics of the intermediate circular orbit for future satellites.
GIOVE-A is the first spacecraft whose design is based upon SSTL's new Geostationary Minisatellite Platform (GMP) satellite bus, intended for geostationary orbit . GIOVE-A is also SSTL's first satellite outside low Earth orbit , operating in medium Earth orbit ), and is SSTL's first satellite to use deployable Sun-tracking solar arrays. Previous SSTL satellites use body-mounted solar arrays, which generate less power per unit area as they do not face the Sun directly.
It was launched at 05:19 UTC on December 28, 2005, on a Soyuz-FG / Fregat from the Baikonur Cosmodrome in Kazakhstan .
It began communicating as planned at 09:01 UTC while circling the Earth at a height of 23,222 km. The satellite successfully transmitted its first navigation signals at 17:25 GMT on 12 January 2006. These signals were received at Chilbolton Observatory in Hampshire , UK and the ESA Station at Redu in Belgium . Teams from SSTL and ESA have measured the signal generated by GIOVE-A to ensure it meets the frequency-filing allocation and reservation requirements for the International Telecommunication Union (ITU), a process that was required to be complete by June 2006.
The GIOVE-A signal in space is fully representative of the Galileo signal from the point of view of frequencies and modulations, chip rates, and data rates. However, GIOVE-A can only transmit at two frequency bands at a time (i.e., L1+E5 or L1+E6).
GIOVE-A codes are different from Galileo codes. The GIOVE-A navigation message is not representative from the structure and contents viewpoint (demonstration only purpose). The generation of pseudorange measurements and detailed analysis of the tracking noise and multipath performance of GIOVE-A ranging signals have been performed with the use of the GETR (Galileo Experimental Test Receiver) designed by Septentrio . [ 5 ]
There has been some public controversy about the open source nature of some of the Pseudo-Random Noise (PRN) codes. [ 6 ] In the early part of 2006, researchers at Cornell monitored the GIOVE-A signal and extracted the PRN codes. The methods used and the codes which were found were published in the June 2006 issue of GPS World . ESA has now made the codes public. [ 7 ]
GIOVE-A was retired (but not decommissioned) on 30 June 2012, after being raised in altitude to make way for an operational satellite. [ 8 ] It remained under command by SSTL until 24 November 2021, when it was officially decommissioned. [ 9 ]
GIOVE-B (previously called GSTB-V2/B ), has a similar mission, but has greatly improved signal generation hardware.
It was originally built by satellite consortium European Satellite Navigation Industries , but following re-organization of the project in 2007, the satellite prime contractor responsibility was passed to Astrium .
GIOVE-B also has MEO environment characterization objectives, as well as signal-in-space and receiver experimentation objectives. GIOVE-B carries three atomic clocks : two rubidium standards and the first space-qualified passive hydrogen maser .
The launch was delayed due to various technical problems, [ 10 ] and took place on 27 April 2008 at 04:16 Baikonur time (22:16 UTC Saturday) aboard a Soyuz-FG / Fregat rocket provided by Starsem . The Fregat stage was ignited three times to place the satellite into orbit. [ 11 ] Giove-B reached its projected orbit after 02:00 UTC and successfully deployed its solar panels. [ 12 ]
GIOVE-B started transmitting navigation signals on May 7, 2008. The reception of the signals by GETR receivers and other means has been confirmed at a few ESA facilities. [ 13 ]
According to ESA, this is "a truly historic step for satellite navigation since GIOVE-B is now, for the first time, transmitting the GPS-Galileo common signal using a specific optimised waveform, MBOC (multiplexed binary offset carrier), in accordance with the agreement drawn up in July 2007 by the EU and the US for their respective systems, Galileo and the future GPS III".
" Now with GIOVE-B broadcasting its highly accurate signal in space we have a true representation of what Galileo will offer to provide the most advanced satellite positioning services, while ensuring compatibility and interoperability with GPS ", said ESA Galileo Project Manager, Javier Benedicto.
After launch, early orbit operations and platform commissioning, GIOVE-B's navigation payload was switched on and signal transmission commenced on May 7 and the quality of these signals is now being checked. Several facilities are involved in this process, including the GIOVE-B Control Centre at Telespazio's facilities in Fucino, Italy, the Galileo Processing Centre at ESA's European Space Research and Technology Centre (ESTEC), in the Netherlands, the ESA ground station at Redu, Belgium, and the Rutherford Appleton Laboratory (RAL) Chilbolton Observatory in the United Kingdom.
Chilbolton's 25-metre antenna makes it possible to analyse the characteristics of GIOVE-B signals with great accuracy and verify that they conform to the Galileo system's design specification. Each time the satellite is visible from Redu and Chilbolton, the large antennas are activated and track the satellite. GIOVE-B is orbiting at an altitude of 23 173 kilometres, making a complete journey around the Earth in 14 hours and 3 minutes.
The quality of the signals transmitted by GIOVE-B will have an important influence on the accuracy of the positioning information that will be provided by the user receivers on the ground. On board, GIOVE-B carries a passive hydrogen maser atomic clock, which is expected to deliver unprecedented stability performance.
The signal quality can be affected by the environment of the satellite in its orbit and by the propagation path of the signals travelling from space to ground. Additionally, the satellite signals must not create interference with services operating in adjacent frequency bands, and this is also being checked.
Galileo teams within ESA and industry have the means to observe and record the spectrum of the signals transmitted by GIOVE-B in real time. Several measurements are performed relating to transmitted signal power, centre frequency and bandwidth, as well as the format of the navigation signals generated on board. This allows the analysis of the satellite transmissions in the three frequency bands reserved for it.
The GIOVE-B mission also represents an opportunity for validating in-orbit critical satellite technologies, characterising the Medium Earth Orbit (MEO) radiation environment, and to test a key element of the future Galileo system - the user receivers.
GIOVE B was retired (but not decommissioned) on 23 July 2012.
With the delays of GIOVE-B, the European Space Agency again contracted with SSTL for a second satellite, to ensure that the Galileo programme continues without any interruptions that could lead to loss of frequency allocations. [ 14 ] Construction of GIOVE-A2 was terminated due to the successful launch and in-orbit operation of GIOVE-B.
The GIOVE Mission segment, or GIOVE-M , is the name of a project dedicated to the exploitation and experimentation of the GIOVE satellites. [ 2 ] The GIOVE Mission was intended to ensure risk mitigation of the In Orbit Validation (IOV) phase of the Galileo positioning system .
The GIOVE Mission Segment began in October 2005 with the purpose of providing experimental results based on real data to be used for risk mitigation throughout the overall Galileo In Orbit Validation (IOV) phase of the Galileo positioning system .
The GIOVE Mission segment infrastructure was based on evolution of the Galileo System Test Bed Version 1 (GSTB-V1) infrastructure conceived to process data from the GIOVE-A and GIOVE-B satellites. [ 15 ] The GIOVE Mission segment was composed of a central processing facility called the Giove Processing Center (GPC) and a network of thirteen experimental Giove Sensor Stations (GESS).
The main objectives of the GIOVE Mission Segment experimentation were in the areas of: | https://en.wikipedia.org/wiki/GIOVE |
GISAID ( / ˈ ɡ ɪ s eɪ d / ), the Global Initiative on Sharing All Influenza Data , [ 6 ] previously the Global Initiative on Sharing Avian Influenza Data , [ 7 ] [ 8 ] is a global science initiative established in 2008 to provide access to genomic data of influenza viruses. The database was expanded to include the coronavirus responsible for the COVID-19 pandemic , [ 9 ] [ 10 ] as well as other pathogens. The database has been described as "the world's largest repository of COVID-19 sequences". [ 11 ] GISAID facilitates genomic epidemiology and real-time surveillance to monitor the emergence of new COVID-19 viral strains across the planet. [ 12 ]
Since its establishment as an alternative to sharing avian influenza data [ 13 ] via conventional public-domain archives, [ 14 ] GISAID has facilitated the exchange of outbreak genome data [ 14 ] during the H1N1 pandemic [ 15 ] [ 16 ] in 2009, the H7N9 epidemic [ 17 ] [ 18 ] in 2013, the COVID-19 pandemic [ 19 ] [ 20 ] and the 2022–2023 mpox outbreak . [ 21 ]
Since 1952, influenza strains had been collected by National Influenza Centers (NICs) and distributed through the WHO's Global Influenza Surveillance and Response System (GISRS). [ 22 ] Countries provided samples to the WHO but the data was then shared with them for free with pharmaceutical companies who could patent vaccines produced from the samples. [ 23 ] Beginning in January 2006, Italian researcher Ilaria Capua refused to upload her data to a closed database and called for genomic data on H5N1 avian influenza to be in the public domain. [ 24 ] [ 25 ] At a conference of the OIE/FAO Network of Expertise on Animal Influenza , Capua persuaded participants to agree to each sequence and release data on 20 strains of influenza. Some scientists had concerns about sharing their data in case others published scientific papers using the data before them, but Capua dismissed this telling Science "What is more important? Another paper for Ilaria Capua's team or addressing a major health threat? Let's get our priorities straight." [ 25 ] Peter Bogner , a German in his 40s based in the US and who previously had no experience in public health, read an article about Capua's call and helped to found and fund GISAID. [ 26 ] [ 27 ] Bogner met Nancy Cox , who was then leading the US Centers for Disease Control 's influenza division at a conference, and Cox went on to chair GISAID's Scientific Advisory Council. [ 14 ]
The acronym GISAID was coined in a correspondence letter published in the journal Nature in August 2006, [ 27 ] putting forward an initial aspiration of creating a consortium for a new Global Initiative on Sharing Avian Influenza Data (later, "All" would replace "Avian"), whereby its members [ 14 ] would release data in publicly available databases up to six months after analysis and validation. [ 28 ] Initially the organisation collaborated with the Australian non-profit organization Cambia and the Creative Commons project Science Commons . [ 29 ] Although no essential ground rules for sharing were established, [ 30 ] the correspondence letter was signed by over 70 leading scientists, including seven Nobel laureates , because access to the most current genetic data for the highly pathogenic H5N1 zoonotic virus was often restricted, in part due to the hesitancy of World Health Organization member states to share their virus genomes and put ownership rights at risk. [ 31 ]
Towards the end of 2006, Indonesia announced it would not share samples of avian flu with the WHO which led to a global health crisis due to an ongoing epidemic. [ 23 ] By October 2006, Indonesia had agreed to share their data with GISAID, [ 32 ] which their health minister considered to have a "fair and transparent" mechanism for sharing data. [ 33 ] It was one of the first countries to do so. [ 34 ] In February 2007, GISAID and the Swiss Institute of Bioinformatics (SIB) announced a cooperation agreement, [ 14 ] with the SIB building and administering the EpiFlu database on behalf of GISAID. [ 35 ] Ultimately, GISAID was launched in May 2008 in Geneva on the occasion of the 61st World Health Assembly, as a registration-based database rather than a consortium. [ 14 ]
In 2009 SIB disconnected the database from the GISAID portal over a contract dispute, resulting in litigation. [ 35 ] [ 36 ] [ 37 ] In April 2010 the Federal Republic of Germany announced during the 7th International Ministerial Conference on Avian and Pandemic Influenza in Hanoi , Vietnam , that GISAID had entered into a cooperation agreement [ 38 ] with the German government, making Germany the long-term host of the GISAID platform. [ 39 ] Under the agreement, Germany's Federal Ministry of Food, Agriculture and Consumer Protection was to ensure the sustainability of the initiative by providing technical hosting facilities, [ 40 ] and the Federal Institute for Animal Health , the Friedrich Loeffler Institute , was to ensure the plausibility and curation of scientific data in GISAID. By 2021, the ministry was no longer involved with either database hosting nor curation. [ 41 ] In 2013 GISAID dissolved a nonprofit organisation based in Washington DC and the organisation began to be operated by a German association called Freunde von GISAID (Friends of GISAID). [ 26 ]
Some of the earliest SARS-CoV-2 genetic sequences were released by the Chinese Center for Disease Control and Prevention and shared through GISAID in mid January 2020. [ 42 ] Since 2020, millions of SARS-CoV-2 genome sequences have been uploaded to the GISAID database. [ 43 ]
In 2022, GISAID added Mpox virus [ 44 ] and Respiratory syncytial virus (RSV) [ 45 ] to the list of pathogens supported by its database. Indonesia's Ministry of Health announced in November 2023 the establishment of GISAID Academy in Bali , to focus on bioinformatics education, advance pathogen genomic surveillance, and increased regional response capacity. [ 46 ]
The GISAID model of incentivizing and recognizing those who deposit data has been recommended as a model for future initiatives; [ 47 ] Because of this work, the entity has been described as "a critical shield for humankind". [ 48 ]
GISAID maintains what has been described as "the world's largest repository of COVID-19 sequences", [ 11 ] and "by far the world's largest database of SARS-CoV-2 sequences". [ 4 ] By mid-April 2021, GISAID's SARS-CoV-2 database reached over 1,200,000 submissions, a testament to the hard work of researchers in over 170 different countries. [ 49 ] Only three months later, the number of uploaded SARS-CoV-2 sequences had doubled again, to over 2.4 million. [ 50 ] By late 2021, the database contained over 5 million genome sequences; [ 51 ] as of December 2021, over 6 million sequences had been submitted; [ 52 ] by April 2022, there were 10 million sequences accumulated; and in January 2023 the number had reached 14.4 million. [ 53 ]
In January 2020, the SARS-CoV-2 genetic sequence data was shared through GISAID. [ 54 ] Throughout the first year of the COVID-19 pandemic, most of the SARS-CoV-2 whole-genome sequences that were generated and shared globally were submitted through GISAID. [ 55 ] When the SARS-CoV-2 Omicron variant was detected in South Africa, by quickly uploading the sequence to GISAID, the National Institute for Communicable Diseases there was able to learn that Botswana and Hong Kong had also reported cases possessing the same gene sequence. [ 56 ]
In March 2023, GISAID temporarily suspended database access for some scientists, removing raw data relevant to investigations of the origins of SARS-CoV-2 . [ 57 ] [ 58 ] [ 59 ] GISAID stated that they do not delete records from their database, but data may become temporarily invisible during updates or corrections. [ 60 ] [ 61 ] [ 62 ] Availability of the data was restored, with an additional restriction that any analysis based thereon would not be shared with the public. [ 63 ]
The board of Friends of GISAID consists of Peter Bogner and two German lawyers who are not involved in the day-to-day operations of the organisation. [ 26 ] Scientific advice to the organization is provided by its Scientific Advisory Council, including directors of leading public health laboratories , such as WHO Collaborating Centres for Influenza. [ 64 ] In 2023, GISAID's lack of transparency was criticized by some GISAID funders, including the European Commission and the Rockefeller Foundation , with long-term funding being denied from International Federation of Pharmaceutical Manufacturers and Associations (IFPMA) . [ 65 ] [ 66 ] In June 2023, it was reported in Vanity Fair that Bogner had said that "GISAID will soon launch an independent compliance board 'responsible for addressing a wide range of governance matters'". [ 7 ] The Telegraph similarly reported that GISAID's in-house counsel was developing new governance processes intended to be transparent and allow for the resolution of scientific disputes without the involvement of Bogner. [ 48 ]
The creation of the GISAID database was motivated in part by concerns raised by researchers from developing countries , [ 67 ] with Scientific American noting in 2009 that "a previous data-sharing system run by WHO forced them to give up intellectual property rights to their virus samples when they sent them to WHO. The virus samples would then be used by private pharmaceutical companies to make vaccines that are awarded patents and sold at a profit at prices many poor nations cannot afford". [ 36 ] In a 2022 piece in The Lancet , it was further noted that scientists in North America and Europe sought unrestricted access, with "scientists from Africa requiring sufficient protections for those who generate and share data as per the GISAID terms and conditions". [ 67 ] Unlike public-domain databases such as GenBank and EMBL , users of GISAID must have their identity confirmed and agree to a Database Access Agreement that governs the way GISAID data can be used. [ 48 ] [ 68 ] These Terms of Use are "weighted in favour of the data provider and gives them enduring control over the genetic data they upload". [ 48 ] They prevent users from sharing any data with other users who have not agreed to them, and require that users of the data must credit the data generators in published work, and also make a reasonable attempt to collaborate with data generators and involve them in research and analysis that uses their data. [ 7 ] [ 48 ]
A difficulty that GISAID's Data Access Agreement attempts to address is that many researchers fear sharing of influenza sequence data could facilitate its misappropriation through intellectual property claims by the vaccine industry and others, hindering access to vaccines and other items in developing countries, either through high costs or by preventing technology transfer . While most public interest experts agree with GISAID that influenza sequence data should be made public, and this is the subject of agreement by many researchers, some provide the information only after filing patent claims while others have said that access to it should be only on the condition that no patents or other intellectual property claims are filed, as was controversial with the Human Genome Project . [ 69 ] GISAID's Data Access Agreement addresses this directly to promote sharing data. GISAID's procedures additionally suggest that those who access the EpiFlu database consult the countries of origin of genetic sequences and the researchers who discovered the sequences. As a result, the GISAID license has been important in rapid pandemic preparedness. [ 70 ] However, these restrictions evidence common criticisms to an open data model . [ 71 ] [ 72 ]
GISAID describes itself as "open access", which is naturally replicated by the media and in journal publications. This description indeed aligns with the original announcement of the consortium, [ 28 ] which also mentioned depositing the data to the databases participating in the INSDC . As of March 2023, this is not the case, as "GISAID does not offer a mechanism to release data to any other database". [ 73 ] A few academic papers have compared GISAID's licensing model to unrestricted, open databases , [ 74 ] [ 70 ] [ 75 ] highlighting the differences while other researchers have signed an open letter calling for the use of any of the INSDC's unrestricted databases. [ 76 ] [ 77 ]
In 2017, GISAID's editorial board stated that " re3data.org and DataCite , the world's leading provider of digital object identifiers (DOI) for research data, affirmed the designation of access to GISAID's database and data as Open Access". [ 78 ] However, after several researchers had their accounts suspended in March 2023 as reported by the journal Science [ 79 ] and other news outlets, [ 80 ] its open access status was revoked by the Registry of Research Data Repositories (re3data) , which now classifies it as a "restricted access repository". [ 81 ] In 2020 the World Health Organization chief scientist Soumya Swaminathan called the initiative "a game changer", [ 9 ] while the co-director of the European Bioinformatics Institute (EBI) Rolf Apweiler has argued that because it does not allow sequences to be reshared publicly, it hampers efforts to understand the coronavirus and the rapid rise of new variants. [ 76 ]
GISAID's restrictions on access have led to conflict with "labs and institutions whose priorities are academic rather than driven by the immediate priorities of public health protection". [ 48 ] In January 2021, GISAID's restricted access led a group of scientists to write an open letter asking for SARS-CoV-2 sequences to be deposited in open databases, [ 82 ] which was replicated in the journals Nature [ 71 ] [ 83 ] and Science . [ 4 ] Furthermore, the article from Science points out that the lack of transparency in access to the database also prevents many scientists from even criticising the platform. [ 4 ] A paper from 2017 describing the success of GISAID mentions that revoking researchers' credentials was rare, but it did happen. [ 84 ] The same publication described a "perceived merit in GISAID's formula for balancing the need for control and openness". In April 2023, Science and The Economist reported these issues continue as well as the lack of transparency of its governance. [ 66 ] [ 65 ] An investigation by The Telegraph into claims made by Science noted the incentives of various potential competitors in the field, for whom GISAID is an obstacle to consolidation of control over the field, and also noted that GISAID's position inevitably places it at the center of disputes between groups of scientists, which will tend to result in the losing side blaming GISAID for that outcome. [ 48 ] | https://en.wikipedia.org/wiki/GISAID |
The Group I Intron Sequence and Structure Database ( GISSD ) is a database of Group I catalytic intron . [ 1 ]
This Biological database -related article is a stub . You can help Wikipedia by expanding it .
This catalysis article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/GISSD |
GIS Arta or GIS Art for Artillery is military software used to coordinate artillery strikes. [ 1 ] [ 2 ] It has been used in the 2022 Russian invasion of Ukraine by the Armed Forces of Ukraine . [ 1 ] It has fast targeting (one minute), it does not require reconnaissance units to use specialized devices (they use smartphones), and it does not require artillery pieces to be clustered together. [ 3 ] It has been compared to the German artillery software ESG Adler. [ 1 ] [ 3 ] It was developed by Ukrainian programmers, with involvement by British digital map companies. [ 1 ]
This software article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/GIS_Arta |
Geographic information systems (GISs) have become a useful and important tool in the field of hydrology to study and manage Earth's water resources . Climate change and greater demands on water resources require a more knowledgeable disposition of arguably one of our most vital resources. Because water in its occurrence varies spatially and temporally throughout the hydrologic cycle , its study using GIS is especially practical. Whereas previous GIS systems were mostly static in their geospatial representation of hydrologic features, GIS platforms are becoming increasingly dynamic, narrowing the gap between historical data and current hydrologic reality.
The elementary water cycle has inputs equal to outputs plus or minus change in storage. Hydrologists make use of this hydrologic budget when they study a watershed . The inputs in a hydrologic budget include precipitation , surface flow, and groundwater flow. Outputs consist of evapotranspiration , infiltration , surface runoff , and surface/groundwater flows. All of these quantities can be measured or estimated based on environmental data and their characteristics can be graphically displayed and studies using GIS.
In the field of hydrological modeling , analysis generally begins with the sampling and measurement of existing hydrologic areas. In this stage of research, the scale and accuracy of measurements are key issues. [ 1 ] Data may either be collected in the field or through online research. The United States Geological Survey ((USGS)) is a publicly available source of remotely sensed hydrological data. Historical and real-time streamflow data are also available via the internet from sources such as the National Weather Service (NWS) and the United States Environmental Protection Agency (EPA). A benefit of using GIS softwares for hydrological modeling is that digital visualizations of data can be linked to real-time data. GIS revolutionized curation, manipulation, and input for complex computational hydrologic models [ 2 ] [ 3 ] For surface water modeling, digital elevation model are often layered with hydrographic data in order to determine the boundaries of a watershed. [ 4 ] Understanding these boundaries is integral to understanding where precipitation runoff will flow. For example, in the event of snowmelt , the amount of snowfall can be input into GIS to predict the amount of water that will travel downstream. [ 5 ] This information has applications in local government asset management, agriculture and environmental science .
Another useful application for GIS regards flood risk assessment . Using digital elevation models combined with peak discharge data can predict which areas of a floodplain will be submerged depending on the amount of rainfall. In a study of the Illinois River watershed, Rabie (2014) [ 6 ] found that a decently accurate flood risk map could be generated using only DEMs and stream gauge data. Analysis based on these two parameters alone does not account for manmade developments including levees or drainage systems, and therefore should not be considered a comprehensive result.
The use of GIS to analyze groundwater falls into the field of hydrogeology . Since 98% of available freshwater on Earth is groundwater, [ 7 ] the need to effectively model and manage these resources is apparent. As the demand for groundwater continues to increase with the world’s growing population , it is vital that these resources be properly managed. Indeed, when groundwater usage is not monitored sufficiently, it may result in damage to aquifers or groundwater-related subsidence , as occurred in the Ogallala aquifer in the United States. In some cases, GIS can be used to analyze drainage and groundwater data in order to select suitable sites for groundwater recharge . [ 8 ] | https://en.wikipedia.org/wiki/GIS_and_hydrology |
GIS in environmental contamination is the use of GIS software to map and analyze contaminants on Earth, including soil contamination , water pollution , and air pollution . [ 1 ] [ 2 ] [ 3 ] Various GIS methods are used to conduct spatial analysis of pollutants to, identify, monitor, and assess them. GIS can use other technologies to advance their process of analysis, including remote sensing , LIDAR , GeoAI, and WebGIS. [ 4 ] One method includes spatial interpolation, which allows for a more efficient approach to remediation and monitoring of soil and water contaminants. Contamination by metals and other contaminants has become a significant environmental problem after industrialization across many parts of the world. [ 5 ] As a result, environmental agencies are placed in charge of remediating, monitoring, and mitigating the soil contamination sites. GIS is used to monitor sites for metal contaminants on Earth to identify high-risk sites where remediation and monitoring are needed.
Soil contamination from heavy elements can be found in urban environments, which can be attributed to emissions from transportation, industrial activities, and naturally occurring processes, such as background levels (mineral-leaching heavy elements from weathering). Some of the most contaminated soil areas are around the mines, including ones in Slovenia , Bosnia and Herzegovina , and in the United States (Sulphur Bank Superfund Site in California). [ 5 ] [ 6 ] [ 3 ] Soil contamination from heavy metals can pose a threat to human health through direct and indirect contact. Additionally, it can also lead to ecotoxicity , making it difficult for ecosystems to function healthily. [ 7 ] In a study area, GIS is used for the analysis of the spatial relationship of the contaminants within the soil.
In Idrija , Slovenia, a mercury (Hg) mine had been operating for over 500 years, releasing a significant amount of Hg emissions into the atmosphere. These Hg emissions were absorbed by the surface of the soil, which resulted in the release and diffusion of Hg through the soil's pores. [ 3 ] The study aimed to calculate the emission flux of Hg over four seasonal months in one year. To achieve this, a Hg emission model was developed:
in which the F Hg is the flux of Hg emission, E a is the activation energy , R is the gas constant, T s is the soil temperature, n and m are constants, [Hg] s is the Hg concentration, and 0.003* R z accounts for the solar radiation since the solar radiation has the effect on the temperature; hence, the solar radiation has the effect on the emission flux of Hg. [ 3 ] Once the Hg concentration data was gathered, a schematic model was prepared for GIS input, which consisted of a digital elevation model (DEM), a satellite land use map, and EARS data. [ 3 ] [ 8 ] [ 9 ] [ 2 ] Using the inverse distance weighted (IDW) method from geostatistical tools in ArcGIS 9.3, a raster model of the Hg concentration has been produced for the Idrija area. [ 3 ] [ 2 ] [ 10 ] [ 9 ]
The raster model in ArcGIS provided a visualization of the spatial distribution of Hg emissions, showing that the highest Hg emissions were concentrated in the location where the Hg mine had operated. [ 3 ] The study found that Hg emissions were highest during the summer month of July, showing a strong correlation between Hg emissions and seasonal changes in temperature and solar radiation. [ 3 ]
GIS can assist in assessing and mitigating water pollution by providing a visualization of contaminants in an area. The contaminants that are analyzed are either naturally occurring, such as volcanic waste, mineral leaching, or saltwater intrusion. They can also be anthropogenic, such as industrial waste, agricultural runoff, or oil spills. [ 11 ] GIS allows for spatial analysis of pollution sources, movement, and impact for different contaminants utilizing different methods, including spatial interpolation, remote sensing, and hydrological modeling. [ 11 ] Additionally, statistical models can help predict areas at higher risk of pollution. [ 11 ] One of the issues concerning water contaminants is groundwater pollution , which impacts ecosystems and human health.
Under certain hydrological parameters, some aquifers are more prone to contamination than other aquifers . The parameters that are taken into consideration when calculating the vulnerability of aquifers to contamination are depth to water (factor d), net recharge (factor r), aquifer media (factor a), soil media (factor s), topography (factor t), impact of the vadose zone (factor i), and the hydraulic conductivity (factor c), which together spell out DRASTIC. [ 12 ] [ 13 ] Furthermore, there is a weighting factor associated with each of the parameters that can range from one to five. In addition, the lower the numbers for the DRASTIC index after the assessment of the aquifer, the lower the risk of aquifer contamination in that area. [ 12 ] These seven parameters derive DRASTIC summary index score, which determines which are more prone to contamination than other. The significance of the DRASTIC summary index score is that it shows areas that are more prone; as a result, the state or local authorities, depending on the scale, will place necessary measures in place that would prevent or mitigate contamination of the water supply.
Using GIS, a map was developed for the seven counties (Hillsborough, Polk, Manatee, Hardee, Sarasota, DeSoto, and Charlotte) in Florida, which shows the DRASTIC summary index score for the Floridan Aquifer System, Surficial Aquifer System, and Other Rocks aquifer. The developed map is a combination of multiple layers that are stacked on top of each other, as shown in Figure 1 .
GIS is used to study and monitor air contamination by mapping the spatial distribution of pollutants. Common air contaminants include particulate matter (PM), nitrogen oxides (NOx), sulfur dioxide (SO₂), carbon monoxide (CO) ozone (O₃) and volatile organic compounds (VOCs). [ 14 ] These pollutants can originate from industrial activities, vehicle emissions, and natural events such as wildfires. GIS allows for the analysis of pollutant distribution patterns, exposure levels, and changed over time. This spatial analysis can help public health agencies, researchers, and policymakers assess air quality to identify at-risk populations and support air pollution mitigation strategies.
Shoreline changes in the Salton Sea, located in Southern California, are monitored using GIS. These changes have significant impacts on air quality and public health in the surrounding area. The Salton Sea, formed in 1905 when the Colorado river flooded a desert basin below sea level, has been heavily polluted by agricultural runoff, which deposited pesticides, fertilizers, and other contaminants into the lake, creating unhealthy conditions for wildlife. [ 15 ] [ 16 ] The 2003 Quantification Settlement Agreement (QSA) reduced water flow to the Salton Sea, causing it to shrink and expose more of its lakebed, which has become a source of airborne dust contaminated by years of agricultural activity. [ 15 ] [ 16 ] [ 17 ] This led to public health concerns for nearby communities, which are often farmworkers and communities of color, experiencing high rates of respiratory problems. [ 17 ] Geographic Information Systems (GIS) and spatial analysis techniques play a crucial role in these efforts by mapping lakebed exposure and identifying areas of greatest risk. [ 16 ]
The study, led by researchers from the School of Public Health at Loma Linda University in collaboration with grassroot organizations and the local community, aimed to track shoreline changes on the North Shore of the Salton Sea through the use of historical satellite imagery, balloon mapping, and air quality modeling with the use of ArcGIS and other software. [ 16 ] From 2018 to 2021, a camera attached to a weather balloon captured images of the North Shore, which were then compared to satellite images taken from 2002 to 2018, to analyze changes in shoreline over time. [ 16 ] Their results showed that the rate of shoreline recession increased following the changes in water management policies. Between 2002 and 2017, the average rate of retreat was approximately 12.5 m (4ft), but this increased to an average rate of 38.5 m (120 ft) per year between 2017 to 2020. [ 16 ] Using predication models, the North Shore is expected to retreat an additional 150 m by 2030 and 172 m by 2041, which will continue impacting public health. [ 16 ] [ 17 ]
To assess the impact of air quality, a chemical transport model (WRF-Chem) was employed to simulate and predict the emissions of dust pollution, specifically PM10, from the exposed lakebed. [ 16 ] The model found that the expanding exposed lakebed is expected to significantly worsen PM10 exposure for local communities, increasing the risk of respiratory health problems for residents around the Salton Sea. [ 16 ] This work, utilizing GIS, contributes to the ongoing research, mitigation, and public health issues linked to the shrinking Salton Sea and its exposed sediments that impact air quality. | https://en.wikipedia.org/wiki/GIS_in_environmental_contamination |
G lal hydrolysis and L igation A dapter D ependent PCR assay ( GLAD-PCR assay [ 1 ] ) is the novel method to determine R(5mC)GY sites produced in the course of de novo DNA methylation with DNMTЗA and DNMTЗB DNA methyltransferases . GLAD-PCR assay do not require bisulfite treatment of the DNA.
Method was specially designed to determine methylation of RCGY site of interest in human and mammalian genomes in excess of corresponding unmethylated sites. This is a typical situation for DNA preparations from clinical samples of blood and tissues.
GLAD-PCR assay is based on the new type of enzymes - site-specific methyl-directed DNA-endonucleases (MD DNA endonucleases). These enzymes are very similar to restriction enzymes in biochemical properties and cleave DNA completely, but act in opposite way: they cleave only methylated DNA and do not cleave unmethylated DNA at all.
Mammalian DNA-methyltransferases DNMT1, DNMT3a and DNMT3b catalyze a reaction of DNA methylation.
It is well known that hypermethylation of CpG-islands in regulatory regions of promoter and/or first exon in a variety of genes often occurs at early stages of sporadic carcinogenesis . This leads to downregulation of the genes expression in tumor cells, whereas in a healthy tissue the corresponding genes remain to be active. [ 2 ] Thus, the detection of such epigenetic biomarkers is one of the most promising diagnostic and prognostic tools [ 3 ]
Study of DNMT3a and DNMT3b substrate specificity has shown that both enzymes predominantly recognize RCGY site and modify internal CG-dinucleotide to form 5’-R(5mC)GY-3’/3’-YG(5mC) R-5’ sequence. [ 4 ] One of new enzymes GlaI recognizes and cleaves site R(5mC)GY. [ 5 ] Due to this unique substrate specificity, GlaI is a convenient tool for identification of de novo methylated sites in the human and mammalian DNA.
GLAD-PCR assay includes 3 simple steps:
Assay is performed in one tube, takes about 2–3 hours and determines even several copies of DNA with R(5mC)GY site of interest. | https://en.wikipedia.org/wiki/GLAD-PCR_assay |
Glare (derived from GLAss REinforced laminate [ 1 ] ) is a fiber metal laminate (FML) composed of several very thin layers of metal (usually aluminum ) interspersed with layers of S-2 glass-fiber pre-preg , bonded together with a matrix such as epoxy . The uni-directional pre-preg layers may be aligned in different directions to suit predicted stress conditions.
Though Glare is a composite material , [ 2 ] its material properties and fabrication are very similar to bulk aluminum sheets. It has far less in common with composite structures when it comes to design, manufacture, inspection, or maintenance. Glare parts are constructed and repaired using mostly conventional metal working techniques.
Its major advantages over conventional aluminum are: [ 3 ]
Furthermore, the material can be tailored during design and manufacture so that the number, type and alignment of layers can suit the local stresses and shapes throughout the aircraft. This allows the production of double-curved sections, complex integrated panels, or very large sheets.
While a simple manufactured sheet of Glare is three to ten times more expensive than an equivalent sheet of aluminum, [ 4 ] considerable production savings can be made using the aforementioned optimization. A structure built with Glare is lighter and less complex than an equivalent metal structure, requires less inspection and maintenance, and has a longer lifetime-till failure . These characteristics can make Glare cheaper, lighter, and safer to use in the long run.
Glare is a relatively successful FML, patented by the Dutch company Akzo Nobel in 1987. [ 5 ] [ 6 ] It entered major application in 2007, when the Airbus A380 airliner began commercial service. Much of the research and development was done in the 1970s and 1980s at the Faculty of Aerospace Engineering, Delft University of Technology , where professors and researchers advanced the knowledge of FML and earned several patents, such as a splicing technique to build wider and longer panels without requiring external joints. [ 7 ]
The development of FML reflects a long history of research that started in 1945 at Fokker , where earlier bonding experience at de Havilland inspired investigation into the improved properties of bonded aluminum laminates compared to monolithic aluminum. Later, the United States National Aeronautics and Space Administration (NASA) became interested in reinforcing metal parts with composite materials in the Space Shuttle program, which led to the introduction of fibers to the bond layers. Thus, the concept of FMLs was born.
Further research and co-operation of Fokker with Delft University , [ 8 ] the Dutch aerospace laboratory NLR , 3M , Alcoa , and various other companies and institutions led to the first FML: the Aramid Reinforced ALuminum Laminates (ARALL), which combined aluminum with aramid fibers and was patented in 1981. [ 9 ] [ 10 ] [ 11 ] This material had some cost, manufacturing, and application problems; while it had very high tensile strength, the material proved suboptimal in compressive strength, off-axis loading, and cyclic loading. These issues led to an improved version with glass fiber instead of aramid fibers.
Over the course of the development of the material, which took more than 30 years from start to the major application on the Airbus A380 , many other production and development partners have been involved, including Boeing , McDonnell Douglas , Bombardier , and the US Air Force . [ 12 ] Over the course of time, companies withdrew from this involvement, sometimes to come back after a couple of years. For example, Alcoa departed in 1995, returned in 2004, and withdrew again in 2010. It is alleged that disagreements between some of these partners caused Boeing to remove Glare from the cargo floor of the Boeing 777 in 1993 [ 13 ] (before the aircraft's service entry in 1995) and blocked Bombardier's plans to use Glare in its CSeries aircraft in 2005. [ 14 ] [ 12 ] These strategic decisions show the dynamic nature of innovation processes. [ 14 ]
Glare has been most often applied in the aviation field. It forms part of the Airbus A380 fuselage and the leading edge of the tail surfaces. In 1995, an aircraft freight container made out of Glare became the first container certified by the Federal Aviation Administration (FAA) for blast resistance; the container can absorb and neutralize the explosion and fire from a bomb such as the one used in the Pan Am Flight 103 disaster over Lockerbie , Scotland in 1988. [ 15 ] [ 16 ] Glare has also been used in the front radome bulkhead of the Bombardier Learjet 45 business jet, [ 17 ] which was first delivered in 1998. [ 18 ] The material was used as a cargo liner solution for regional jets , [ 19 ] in the lower skins of the flaps in the Lockheed Martin C-130J Super Hercules military transport aircraft , [ 20 ] and in straps for the highest loaded frames in the Airbus A400M military transporter. [ 21 ]
There are six standard Glare grades (Glare1 through Glare6) with typical densities ranging from 2.38 to 2.52 grams per cubic centimetre (0.086 to 0.091 lb/cu in), [ citation needed ] which is similar to the 2.46 to 2.49 g/cm 3 (0.089 to 0.090 lb/cu in) density of S-2 glass fiber. [ 22 ] These densities are smaller than the 2.78 g/cm 3 (0.100 lb/cu in) density of 2024-T3 aluminum alloy, [ 23 ] a common aluminum alloy in aircraft structures that is also incorporated into all but one of these Glare grades. (Glare1 uses the 7475-T761 alloy instead.) As the strength of the composite varies with fiber direction, the Glare grades differ by the number and complexity of pre-preg plies and orientations within a composite layer. [ citation needed ] Each Glare grade has A and B variants that have the same number of plies but with alternate fiber orientations. [ 24 ] The standard Glare grades are cured in an autoclave at 120 °C (248 °F) for 3.5 hours under 11-bar pressure (11 atm; 160 psi; 1,100 kPa), and they use the FM94 epoxy pre-preg. [ 25 ]
A single sheet of Glare may be referred to using the naming convention GLARE grade - Aluminum layers / Glass fiber layers - Aluminum layer thickness . The number of aluminum layers is always one more than the number of glass fiber layers, and the aluminum layer thickness is in millimeters, which can range from 0.2 to 0.5 mm (0.0079 to 0.0197 in; 7.9 to 19.7 mils). (Glare1 can only consist of aluminum layers of 0.3 to 0.4 mm (0.012 to 0.016 in; 12 to 16 mils) thickness, though.) For example, Glare4B-4/3-0.4 is a Glare sheet with a Glare4 grade (using the B variant) where there are four aluminum layers and three glass fiber layers, and the thickness of each aluminum layer is 0.4 mm (0.016 in; 16 mils). [ 26 ] (In contrast, a typical sheet of photocopy paper is 0.097 mm (0.004 in; 4 mils) thick, while a typical business card is 0.234 mm (0.009 in; 9 mils) thick.) [ 27 ]
The thickness of a Glare grade does not need to be separately specified, because each pre-preg ply has a nominal thickness of 0.125 mm (0.0049 in; 4.9 mils), and the number of plies is already defined for a Glare grade number. Glare grades 1, 2, 3, and 6 have just two plies of glass fibers, so the thickness of an individual glass fiber layer is 0.25 mm (0.0098 in; 9.8 mils). Glare4 has three plies, so its glass fiber layers are each 0.375 mm (0.0148 in; 14.8 mils) thick. Glare5 has four plies, with individual glass fiber layers of 0.5 mm (0.020 in; 20 mils) thickness. [ citation needed ] Glare sheets have typical overall thicknesses between 0.85 and 1.95 mm (0.033 and 0.077 in; 33 and 77 mils). [ 23 ]
Other, less common grades and designations of aluminum/glass fiber hybrids also exist. A newer class of Glare, called High Static Strength Glare (HSS Glare), incorporates the 7475-T761 alloy and cures at 175 °C (347 °F) using FM906 epoxy pre-preg. HSS Glare comes in three grades (HSS Glare3, HSS Glare4A, and HSS Glare4B), mirroring the plies and orientations of their corresponding standard Glare grades. [ 25 ] Russia, which at one point was going to incorporate Glare into its Irkut MS-21 narrowbody airliner, [ 28 ] refers to its version of Glare as SIAL. The name is a translation from the Russian acronym for fiberglass and aluminum/plastic (С.И.А.Л.). It defines the grades SIAL-1 through SIAL-4, which usually contain the second-generation Russian aluminum-lithium alloy 1441 and range in density from 2.35 to 2.55 g/cm 3 (0.085 to 0.092 lb/cu in). [ 29 ] SIAL is used in the wing covering of the Beriev Be-103 amphibious seaplane . [ 30 ] Airbus bases their material designations on the underlying aluminum alloy, using prefixes such as 2024-FML, 7475-FML, and 1441-FML [ 25 ] [ 31 ] instead of Glare and HSS Glare.
Glare contributes 485 square metres (5,220 sq ft) of material to each A380 plane. This material constitutes three percent by weight of the A380 structure, [ 3 ] which has an operating empty weight (OEW) of 277,000 kg (610,700 lb; 277.0 t; 305.4 short tons). Because of the ten-percent lower density of Glare compared to a typical standalone aluminum alloy, Glare's usage on the A380 results in an estimated direct (volume-based) savings of 794 kg (1,750 lb; 0.794 t; 0.875 short tons), [ 33 ] which doesn't include the follow-on weight savings in the entire aircraft structure that result from the lower material weight. For example, a 1996 internal Airbus study calculated that the weight savings from Glare in the upper fuselage would be 700 kg (1,500 lb; 0.70 t; 0.77 short tons) from just the lighter material, but it would total 1,200 kg (2,600 lb; 1.2 t; 1.3 short tons) due to the "snowball effects" of smaller engines, smaller landing gear , and other positive changes. [ 34 ] (However, this is much smaller than an Airbus vice president's early claim that Glare would result in 15,000 to 20,000 kg (33,000 to 44,000 lb; 15 to 20 t; 17 to 22 short tons) of savings, [ 14 ] [ 35 ] presumably if it were used throughout most of the aircraft.)
To take advantage of Glare's higher tensile strength, 469 m 2 (5,050 sq ft) is used on the upper fuselage of the front and rear sections. Glare was removed from the center upper fuselage in 2000 [ 36 ] as shear strength precaution (although the Glare supplier felt it could have handled that area), [ 37 ] and the fuselage underside is made of other materials with higher Young's modulus (stiffness) values to resist buckling . [ 3 ]
In the fuselage, Glare2A is applied to stringers , Glare2B to butt straps, and Glare3 and Glare4B to the fuselage skins. [ 38 ] Late in the A380 development process, the plane was found to be heavier than the original specifications, so Airbus replaced conventional aluminum with Glare5 as a weight-saving measure for the leading edges of the horizontal stabilizer and the vertical stabilizer , [ 38 ] though at great expense. [ 4 ] The A380 Glare fuselage skin panels have a minimum thickness of 1.6 mm (0.063 in; 63 mils) [ 31 ] but can be much thicker, as some areas of the shells may need up to 30 layers of aluminum and 29 layers of glass fiber. [ 39 ]
Glare is currently made by GKN -Fokker and Premium AEROTEC . GKN-Fokker manufactures 22 of the 27 A380 Glare fuselage shells at its 12,000 m 2 facility (130,000 sq ft) in Papendrecht , Netherlands , [ 40 ] which uses an autoclave with a length of 23 metres (75 ft) and a diameter of 5.5 m (18 ft). [ 41 ] The company produces sheets of 3 by 12 m (9.8 by 39.4 ft), [ 39 ] which incorporates the milling of door and window cutouts on a 5-axis milling machine. [ 40 ] Premium AEROTEC manufactures the remaining five shells in Nordenham , Germany [ 40 ] in an autoclave with a usable length of 15 m (49 ft) and an internal diameter of 4.5 m (15 ft). [ 42 ] The company also produces the Glare2A butt straps for the A400 program. [ 21 ] Its output was 200 m 2 (2,200 sq ft) per month as of 2016. [ 43 ]
With Airbus ending production of the A380 in 2021, [ 44 ] Glare will go out of volume production unless it is selected for another airplane manufacturing program.
Since around 2014, Airbus , its two current Glare suppliers, and Stelia Aerospace have been collaborating to manufacture Glare in a high-volume, automated production setting that will deliver larger fuselage panels for aluminum aircraft. Using robots for tape laying and other tasks, automated production will involve a single-shot bonding process that will cure aluminum, pre-preg, stringer, and doublers simultaneously in the autoclave, followed by a single nondestructive testing (NDT) cycle, instead of the stringers and doublers requiring a second bonding and NDT cycle in the existing process. [ 43 ] [ 45 ] The belief is that the material will reduce fuselage weight by 15 to 25 percent compared to the aluminum sections they would replace on single-aisle aircraft such as the Boeing 737 and the Airbus A320 . [ 46 ] [ 45 ] (Before the announcement of the A380 production stoppage, [ 44 ] the automation program was also intended to lower the weight the A380 Glare sections by 350 kilograms (770 pounds; 0.35 metric tons; 0.39 short tons) at a manufacturing cost of 75% of the existing A380 Glare panels.) [ 39 ]
To support these single-aisle aircraft production goals, GKN-Fokker planned to open an automated production line at its site in 2018, with a goal of manufacturing panels of up to 8 by 15 m (26 by 49 ft) in size and increasing the production rate by a factor of ten. [ 39 ] In targeting a fifty-fold increase of Glare production capacity to 10,000 m 2 (110,000 sq ft) per month, Premium AEROTEC [ 43 ] planned to update its automated test cell in summer 2018 to manufacture demonstrator panels of 4 by 12 m (13 by 39 ft). This size will match the largest Glare panels to be potentially used by Airbus in short-range and medium-range aircraft. [ 45 ] The Glare automation process for 2 by 6 m (6.6 by 19.7 ft) prototypes reached technology readiness level (TRL) 4 in late 2016, [ 39 ] exceeded TRL 5 as of 2018, [ 47 ] and has an eventual target of TRL 6. [ 48 ]
In 2014, Embraer built and tested a 2.2 m diameter (7.2 ft; 2,200 mm; 87 in), 3 m long (9.8 ft) technology demonstrator that was partially made of FML and was based on the central fuselage of its ERJ-145 aircraft. [ 49 ] Later, Embraer worked with Arconic (formerly Alcoa ) to build a demonstrator for a lower wing skin composed of fiber-metal laminates, which contained sheets of 2524-T3 aluminum alloy and unidirectional plies of glass fiber. Embraer built and tested the wing demonstrator to increase the TRL of the FML manufacturing process so that it can be applied to future structural applications. [ citation needed ] Lower wing skins on single-aisle aircraft are thicker than fuselage skins, measuring at least 8 mm (0.31 in; 310 mils) thick overall and between 10 and 15 mm (0.39 and 0.59 in; 390 and 590 mils) thick between the fuselage and the engine mount. [ 50 ] | https://en.wikipedia.org/wiki/GLARE |
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GLD-2 (which stands for Germ Line Development 2 ) is a cytoplasmic poly(A) polymerase (cytoPAPs) which adds successive AMP monomers to the 3’ end of specific RNAs, forming a poly(A) tail, which is a process known as polyadenylation .
For RNA specificity, GLD-2 associates with an RNA-binding protein, typically a GLD-3, to form a heterodimer that acts as a cytoplasmic PAP. This protein has an enzymatic function and belongs to a family (DNA polymerase type-B-like family) which includes several similar enzymes such as GLD-1, GLD-3 and GLD-4.
This family of cytoplasmic PAPs has been described in several different species including Homo sapiens , Caenorhabditis elegans , Xenopus , Mus musculus and Drosophila .
Moreover, as it is a cytoplasmtaic PAP it differs from nuclear PAPs in some aspects. While nuclear PAPs contain a catalytic domain and an RNA-binding domain, GLD-2 family members have only a catalytic domain.
GLD-2 is a common and abundant, but yet quite unknown protein that has already been found in each of the five kingdoms . In the animal kingdom, it has been specially detected in Homo sapiens, Drosophila , Xenopus and Mus musculus . However, there has also been noticed the presence of GLD-2 in Arabidopsis thaliana which belongs in the plants kingdom; Escherichia Coli in monera and Candida albicans in fungi.
In human beings it is mostly expressed in the brain and within it, in the cerebellum, hippocampus and medulla. We can also find them in some other source tissues are the fibroblast, HeLa cell, MCF-7 cell, melanoma cell line and thymus . Inside those cells, it can be located in the nucleus and mitochondrion since its main function is related with DNA polyadenilation and these cell organelles are the only ones were DNA can be found. However, there are also GLD-2 in a soluble way in the cytosol, although the reason why they are there is still unsure.
In Escherichia Coli , this enzymatic protein can be found in the cell membrane and in the cytosol , whereas in Drosophila melanogaster , it predominates in the brain's nucleus and cytoplasm, oocyte, ovary and testis’ cells. Finally, in the Arabidopsis thaliana , it is located in the flower's nucleus, root, stem and leaf cells.
GLD-2 primarily stabilizes mRNAs that are translationally repressed as well as it strongly promotes bulk polyadenylation. Surprisingly, those functions seem to have little impact on dynamizing efficient target mRNA translation, as it is an efficient Poly(A) Polymerase which helps developing polyadenylation activity. This activity is stimulated by its interaction with a putative RNA-binding protein: GLD-3. It is proposed by some studies that GLD-3 stimulates GLD-2 by recruiting it to the RNA. If so, then bringing GLD-2 to the RNA by other means also should stimulate its activity.
GLD-2, as a poly(A) polymerase (PAP) acts incorporating ATP at the 3' end of mRNAs in a template-independent manner.
It has been discovered that this protein has a catalytic activity, in other words, it has the ability to increase the speed of chemical reactions which would not occur so fast. It is known to catalysis the following reaction (which requires the following cofactor: Mg(2+)):
Depending on the surroundings the optimal pH varies from 8 in the cytoplasm to 8.3 in the nucleus.
The GLD-2 protein together with 136 proteins more, is involved in the molecular process of hematopoietic progenitor cell differentiation, in the human proteome. This is the process in which precursor cell type acquires the specialized features of a hematopoietic progenitor cell, a kind of cell types including myeloid progenitor cells and lymphoid progenitor cells.
The polyadenylation activity of GLD-2, as we previously mentioned, is stimulated by physical interaction with an RNA binding protein, GLD-3. To test whether GLD-3 might stimulate GLD-2 by recruiting it to RNA, some studies tethered C. elegans GLD-2 to mRNAs in Xenopus oocytes by using MS2 coat protein. Tethered GLD-2 adds poly(A) and stimulates translation of the mRNA, demonstrating that recruitment is sufficient to stimulate polyadenylation activity. PAP heterodimer in which GLD-2 contains the active site and GLD-3 provides RNA-binding specificity. MS2 coat protein was joined to GLD-2 to recruit it to an RNA.
Furthermore, GLD-2 activity is also important to maintain or up-regulate the abundance of many mRNAs, as the cytoplasmic polyadenylation has an essential role in activating maternal mRNA translation during early development. In vertebrates , the reaction requires CPEB, an RNA-binding protein and the poly(A) polymerase GLD-2.
The Xenopus enzyme, which exists in two closely related forms, polyadenylates RNAs to which it is tethered and enhances their translation. Likewise, it interacts with cytoplasmic polyadenylation factors, including Cleavage and polyadenylation specificity factor and CPEB , and with target mRNAs. These findings confirm and extend a recent report that a GLD-2 enzyme is the long-sought PAP responsible for cytoplasmic polyadenylation in oocytes.
In addition, the formation of long-term memory is believed to lack translational control of localized mRNAs. In mammals, dendrite mRNAs are kept in a repressed state and are activated upon repetitive stimulation. Several regulatory proteins required for translational control in early development are thought to be needed for memory formation, suggesting similar molecular mechanisms. In an experiment using Drosophila , it has been detected the enzyme responsible for poly(A) elongation in the brain and it has been demonstrated too that its activity is required specifically for long-term memory. These findings provide strong evidence that cytoplasmic polyadenylation is critical for memory formation, and that GLD2 is the responsible enzyme.
It has also been discovered that GLD2 has medical uses.
For example, such enzyme is overexpressed in patients who suffer from cancer ; that's why it can be used as a prognostic factor for early appearance in breast cancer patients. Moreover, PAP activity is used to measure the effect of anticancer drugs as etoposide and cordycepin in two carcinoma cell lines: HeLa , which is the human epithelioid cervix carcinoma, and MCF-7 (human breast cancer).
However, in spite its utilities it can also be involved in the expression of several common diseases such as: leukemia , liver cirrhosis , brain injuries , hepatitis and in some cases infertility in male patients. | https://en.wikipedia.org/wiki/GLD-2 |
The GLIC receptor is a bacterial ( G loeobacter ) L igand-gated I on C hannel , homolog to the nicotinic acetylcholine receptors . It is a proton-gated (the channel opens when it binds a proton, H + ion), cation -selective channel (it selectively lets the positive ions through). Like the nicotinic acetylcholine receptors is a functional pentameric oligomer (the channel normally works as an assembly of five subunits). However while its eukaryotic homologues are hetero-oligomeric (assembled from different subunits), all until now known bacteria known to express LICs encode a single monomeric unit, indicating the GLIC to be functionally homo-oligomeric (assembled from identical subunits). [ 1 ]
The similarity of amino-acid sequence to the eukaryotic LGICs is not localized to any single or particular tertiary domain , indicating the similar function of the GLIC to its eukaryotic equivalents. Regardless, the purpose of regulating the threshold for action potential excitation in the nerve signal transmission of multicellular organisms cannot translate to single-cell organisms, thereby not making the purpose of bacterial LGICs immediately obvious.
The structure of the open channel structure was solved by two independent research teams in 2009 [ 2 ] [ 3 ] at low pH values of 4-4.6 (GLIC being proton-gated).
This transmembrane receptor -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/GLIC |
Glycosylation-dependent cell adhesion molecule -1 ( GLYCAM1 ) is a proteoglycan ligand expressed on cells of the high endothelial venules in lymphoid tissues. It is the ligand for the receptor L-selectin allowing for naive lymphocytes to exit the bloodstream into lymphoid tissues. [ 1 ] [ 2 ] GLYCAM1 binds to L-selectin by presenting one or more O-linked carbohydrates to the lectin domain of the leukocyte cell surface selectin. [ citation needed ] Data suggests that GLYCAM1 is a hormone-regulated milk protein that is part of the milk mucin complex. [ 3 ]
GlyCAM-1 is expressed exclusively on high endothelial venules. It is unclear how GlyCAM-1 is attached to the membrane as it lacks a transmembrane region. [ 1 ]
This biochemistry article is a stub . You can help Wikipedia by expanding it .
This immunology article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/GLYCAM1 |
The GM-NAA I/O input/output system of General Motors and North American Aviation was the first operating system for the IBM 704 computer. [ 1 ] [ 2 ]
It was created in 1956 by Robert L. Patrick of General Motors Research and Owen Mock of North American Aviation . [ 1 ] It was based on a system monitor created in 1955 by programmers of General Motors for its IBM 701 . Patrick made Gantt charts which were already used in those days by GM for automotive production line design on how to make parallel processes fit together. [ 3 ]
The main function of GM-NAA I/O was to automatically execute a new program once the one that was being executed had finished ( batch processing ). It was formed of shared routines to the programs that provided common access to the input/output devices. Some version of the system was used in about forty 704 installations. [ 1 ]
Also the developers helped UNIX devs to make the UNIX operating-system
This operating-system -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/GM-NAA_I/O |
The Gateway Mobile Location Centre (GMLC) contains functionality required to support location-based service (LBS). In one public land mobile network (PLMN), there may be more than one GMLC. The GMLC is the first node an external LBS client accesses in a GSM, UMTS or LTE network. The GMLC may request routing information from the home location register (HLR) or home subscriber server HSS). After performing registration authorization, it sends positioning requests to either the visited mobile switching centre (VMSC), SGSN serving GPRS support node (SGSN) or mobile switching centre (MSC) server and receives final location estimates from the corresponding entity.
GMLC is used for various services such as emergency services, vehicle tracking, location-based advertising, and much more. [ 1 ] | https://en.wikipedia.org/wiki/GMLC |
GMO conspiracy theories are conspiracy theories related to the production and sale of genetically modified crops and genetically modified food (also referred to as genetically modified organisms or "GMOs"). These conspiracy theories include claims that agribusinesses, especially Monsanto , have suppressed data showing that GMOs cause harm, deliberately cause food shortages to promote the use of GM food, or have co-opted government agencies such as the United States Food and Drug Administration or scientific societies such as the American Association for the Advancement of Science .
Critics charge that GMO conspiracy theories are largely promulgated by those opposing the production and sale of GMOs, and instances of unsubstantiated conspiracy theories have lately occurred in the context of public health issues that are mostly unrelated to GMOs, including the 2015–16 Zika virus outbreak and concerns over food safety at Chipotle Mexican Grill .
The existence of conspiracy theories relating to the fear over GMOs has been attested to by scientists, journalists, and skeptics who oppose much anti-GMO activism. Such commentators include Michael Shermer (writer of a monthly Skeptic column series for Scientific American ), [ 1 ] Mark Lynas (an environmental activist and writer who opposed GMOs for years and recently switched positions), [ 2 ] and Jon Entine (the founder and head of an advocacy organization dedicated to advancing the case in favor of genetic engineering in agriculture and biotechnology). [ 3 ] Academics writing about bioethics and science communication have also taken note.
A 2013 paper published in the journal PLOS ONE found statistical evidence that linked conspiracy theorist ideation as being a significant factor in the rejection of scientific propositions about genetically engineered food. [ 4 ] One GMO conspiracy theory was identified by biochemist Paul Christou and horticulturalist Harry Klee as a claim that development and promotion of GMOs was done by pesticide companies to cause crops to become more vulnerable to pests and therefore require more pesticides, [ 5 ] while philosopher Juha Räikkä identified a conspiracy theory that claims the lack of any reliable scientific evidence that show harmful effects of GMOs is due not to a lack of evidence but rather to a conspiracy to hide that evidence. [ 6 ]
Conspiracy theories involving GMOs and their promoters have been invoked in a variety of contexts. For example, in commenting on the Séralini affair , an incident that involved the retraction of a much-criticized paper which claimed harmful effects of GMOs in lab rats, American biologist PZ Myers said that anti-GMO activists were claiming the retraction was a part of "a conspiracy to Hide the Truth™". [ 7 ] A work seeking to explore risk perception over GMOs in Turkey identified a belief among the conservative political and religious figures who were opposed to GMOs that GMOs were "a conspiracy by Jewish Multinational Companies and Israel for world domination" [ 8 ] while a Latvian study showed that a segment of the population of that country believed that GMOs were part of a greater conspiracy theory to poison the population of the country. [ 9 ]
A study of media rhetorical devices used in Hunan , China found that the news articles that were opposed to trials of golden rice promoted conspiracy theories "including the view that the West was using genetic engineering to establish global control over agriculture and that GM products were instruments for genocide". [ 10 ] Likewise, a study of the rhetoric used in public policy debates about genetically modified food in Ghana showed that conspiracy theories were a feature of a civil society opposition to GMOs:
Government and scientists were denying the claim that GMO was discriminatory and posed significant human health risk, as well as the call to action to do something about GMOs. Civil society adapted the counter rhetoric of insincerity , claiming that scientists had some kind of “hidden agenda” behind their claim, such as eagerness to just earn money from their patents on GMOs. It is imperative that communication on GMOs includes the underlying assumptions, the uncertainties and the probabilities associated with both best and worst case scenarios. This is a necessary condition to minimise misinformation on GMOs but may be insufficient to completely erase conspiracy theories from the minds of the public especially when scientists and government are perceived to be biased towards multinational corporations that are ostensibly preoccupied with making profits. [ 11 ]
Social critic Margit Stange contextualized certain arguments adopted by GMO conspiracy theorists as being part of the larger controversy surrounding the subject:
The corporate push for genetically modified food arouses great suspicion. Critics charge that GM food (" Frankenfood ") is profitable to industry not only because it can be patented but because crop uniformity will eventually drive up pesticide demand. The charge that big food interests take advantage of poverty to open new markets for GM food is restated by conspiracy theorists, who describe a deliberate macroeconomic creation of food shortages in impoverished nations in order to open the door to GM food. The food industry's opposition to GM food labeling and precautionary measures fuels such suspicions. [ 12 ]
This view was echoed by bioethicist Michael Reiss and moral philosopher Roger Straughan who explain in their book Improving Nature?: The Science and Ethics of Genetic Engineering that fears about the consolidation of power by a few agrochemical companies over farmers is a main argument against new genetic engineering technology in agriculture: "At its extreme, this fear belongs to the conspiracy-theory genre and, to caricature somewhat, envisages powerless farmers forced to pay ever increasing amounts to anonymous international companies who profit from the cost of the crop seed and from the cost of the herbicides used to spray them." [ 13 ]
Political science professors Joseph Uscinski and Joseph M. Parent in their book American Conspiracy Theories summarized the people that have adopted GMO conspiracy theories thusly:
Another prototypical conspiratorial movement involves those opposed to genetically modified organisms (GMO), in essence a protest against the genetic engineering of food. Not everyone who opposes GMOs is a conspiracy theorist: reasonable people can disagree about research and fail to see small groups of people covertly working against the common good. But most visible and vocal members of this movement, however, are conspiracy theorists. They believe that genetically modified foods are a corporate plot, led by the giant multinational Monsanto, to profit off unhealthy food. [ 14 ]
Uscinski, writing for Politico in the context of the 2016 United States presidential election , identified GMO conspiracy theories as one of the "honorable mentions" appended to his list of the "five most dangerous conspiracy theories of 2016". He specifically singled-out candidates Bernie Sanders and Jill Stein as promulgators. [ 15 ] Michael Shermer and Pat Linse, writing for Skeptic magazine , specify that in terms of political ideology, "GMO conspiracy theories are embraced primarily by those on the left ." [ 16 ]
Scholars have identified ways that the internet has aided proliferation and connection between conspiracy theories including those about GMOs. For example, computer scientists Tanushree Mitra and Mattia Samory found in a 2018 study that "[to]pics [such as] “ big pharma ,” “ vaccines ,” and “GMO,” for example, decry the corruption of health services while promoting the virtues of a “natural” lifestyle." [ 17 ] MIT Technology Review reported in February 2018 that Russian-backed disinformation campaigns were sowing public confusion about GMOs by promoting conspiracy theories. [ 18 ]
A major aspect of many conspiracy theories is the fear that large agribusinesses , especially Monsanto are working to undermine the health and safety of the general public by introducing and promoting GMOs in the food supply. One claim is that Monsanto is deliberately hiding scientific evidence that GMOs are harmful. [ 6 ] Some anti-GMO activists claimed that Monsanto infiltrated both the American Food and Drug Administration and the American Association for the Advancement of Science which is why the two organizations have supported the scientific evidence for the safety of the genetically engineered food available for human consumption. [ 19 ] Jeffrey M. Smith is identified in the book American Conspiracy Theories as arguing that Monsanto has captured the FDA and many other countries. [ 14 ] In the compendium Agricultural and Food Controversies , the authors who are social scientists and food scientists trace the conspiracy theory relating in particular to Monsanto back to events in the early 1990s:
There are some well-qualified dissenting scientists and a motivated group of food activists behind them, pushing back against GM food. They believe a GM crop is not substantially equivalent to traditional crops. Moreover, they believe that the FDA follows the substantial equivalence rule not because of the science, but because the FDA was corrupted by corporate influence. This is not a belief that the authors' share, but there are smart people of high character who do believe this conspiracy theory, and their side of the story deserves to be heard.
In The World According to Monsanto , author Marie-Monique Robin describes how the substantial equivalence began with a 1992 policy statement by the FDA under the leadership of a former Monsanto lawyer, who, after working in the FDA, returned to Monsanto as vice president. Her story suggests that GM regulations were the product of a revolving-door system where regulators are former and/or future employees of the company being regulated (note that some argue Monsanto wanted excess regulations to keep out competitors, but that is not Robin's story). It is not hard to imagine a company rewarding lenient regulators with a nice job, and food activists have websites listing powerful government officials and their relation to Monsanto and other corporations. If this sounds like a conspiracy theory (a term not meant as a euphemism), it is. [ 20 ]
Belief that Monsanto is particularly problematic has inspired such actions as the March Against Monsanto and the singling out of Monsanto over other agribusinesses such as DuPont , Syngenta , Dow , BASF and Bayer , and has been identified as a salient feature of anti-GMO activism. [ 21 ]
An example of Monsanto-based conspiracy theorizing were the claims by some anti-GMO activists that Monsanto banned GMOs from their cafeterias while promoting them for sale and consumption by the public. [ 22 ] Anti-GMO/ chemtrail blogger Barbara H. Peterson, a retired correctional officer and rancher, complained that Monsanto "has painted those of us attempting to shed light on the dangers of genetically modified/engineered organisms (GMOs) as 'conspiracy theorists'...." She went on to attack Monsanto's suggestion that sabotage could be a possible explanation for the discovery of a few plants of experimental genetically modified wheat found inexplicably growing on a farm in Oregon as being a conspiracy theory itself. [ 23 ]
A 2015 internet hoax purporting to show that Monsanto was creating genetically modified cannabis to supply to the cannabis industry . [ 24 ] [ 25 ] The hoax was created by satirical fake news website World News Daily Report on April 9, 2015. [ 24 ] Monsanto created a "standing denial" of the hoax on their "Myths About Monsanto" webpage, [ 26 ] and tweeted a disclaimer prior to the 420 holiday in 2016, [ 27 ] and on April 20, 2017, again tweeted "Happy 4-20. Time for our yearly reminder: Monsanto has not and is not working on GMO marijuana." [ 28 ]
In January 2016, concerns over a Zika virus outbreak were accompanied by claims first published on Reddit that the virus was being spread by a genetically modified mosquito. [ 29 ] The fears were based in part because of a new mosquito abatement initiative led by Oxitec —male mosquitoes (which do not bite) are genetically modified to be sterile, and released to mate with females, resulting in no offspring, thereby reducing the Aedes aegypti mosquito population that spreads tropical diseases such as Zika. [ 29 ] The claims were identified as "unproven" by the debunking website snopes.com . [ 30 ]
In the context of mid-2010s concerns over food safety at Chipotle Mexican Grill certain commentators have implied that the outbreaks of food-borne illnesses were sabotage carried out by the biotech industry in retaliation over Chipotle's removal of GMOs from their menu. [ 31 ] [ 32 ] The claims were identified as "unproven" by the debunking website Snopes . [ 33 ]
In 2023, a false conspiracy theory connecting tick-borne alpha-gal syndrome (an acquired allergy to red meat) to Gates Foundation tick research was spread on social media . [ 34 ] [ 35 ]
In Scholars & Rogues , an online progressive political journal, David Lambert, a development program officer for the United Nations , compared the conspiracy theories supported by some in the anti-GMO movement to those supported in the anti-vaccination movement ,
Like preventable childhood diseases, malnutrition is another great moral failing of our time. GMOs such as golden rice —rice modified to contain high levels of beta carotene in order to compensate for the vitamin A deficiency which kills hundreds of thousands of children around the world and blinds many more every year—and drought resistant crops, which will become increasingly vital in the global south due to climate change , have vast potential to help those who don't shop at Whole Foods . But real progress has been stymied by the paranoid and misinformed, who clamor that GMOs, which are biologically no different than "natural" foods, are somehow poisonous. Behind it all is of course an evil corporation: Monsanto. [ 36 ]
Offering a similar critique Kavin Senapathy, a freelance writer and speaker who offers editorials from the perspective of the skeptical movement , wrote for Forbes that
Both [the anti-vaccine and anti-GMO movements] cite cherry-picked , discredited, and retracted scientific studies, such as the 1998 Andrew Wakefield study linking the MMR vaccine with autism, and the 2012 Gilles-Éric Séralini rat study linking genetically engineered crops with cancer, while ignoring the vast bodies of evidence against them....
And both lead to injustice....It may seem that surely the anti-GMO movement is benign albeit wrong, innocuous compared to anti-vaccine atrocities. It may appear that it all boils down to some harmless non-GMO labels on grocery items. But it turns out there is a human cost.
The same movement that drives marketers to source non-GMO ingredients also influences regulatory bodies around the world. Crops are kept from regions in Africa where drought is a major contributor to the complex causes of malnutrition, with researchers in Tanzania forced to burn test fields of drought-tolerant corn rather than feed starving local children. Disease-resistant crops languish due to ideological regulations, with bananas resistant to xanthomonas wilt—which is threatening food security in Uganda and eastern Africa where it’s a staple crop—kept from farmers and people who need them.... [ 37 ]
Philosopher Giovanni Tagliabue argued that promoters of GMO conspiracy theories were being taken advantage of by anti-environmental corporate interests:
This ideological and political anti-corporate worldview, although sometimes almost paranoid, is legitimate. Yet, while I do not argue whether this attitude is good or bad, right or wrong, I maintain that the avowed anti-industrial struggle in the field of green biotechnologies not only fails to hit the supposed target, but benefits and supports a part of the industry whose products have a stronger environmental impact than rDNA cultivars ; in addition, and more importantly, opposing GMOs generates heavy collateral damage to public science, agricultural progress and the poor. [ 38 ] | https://en.wikipedia.org/wiki/GMO_conspiracy_theories |
GMY Lighting Technology Co., LTD ( Chinese : 广明源光科技股份有限公司 , doing business as GMY ), is a large manufacturer of light source components and products , located in Heshan, Guangdong , China .
GMY was founded in 1998 [ 1 ] by Yannan "Edward" Hong, [ 2 ] and commercially registered in September 2002. [ 3 ] By 2010, GMY was the world's largest manufacturer of halogen bulbs. [ 2 ] [ 4 ]
GMY opened the largest comprehensive plant factory in South China in 2015. [ 2 ] In 2017, GMY was recognized as a "Guangdong Provincial Enterprise Technology Center." [ 5 ] GMY won the "Ai Rui Cup" in 2018 as one of the China Automotive Industry's top five national brands. [ 3 ] It received recognition by the Guangdong Provincial Department of Industry and Information Technology in its list of "2022 Guangdong Province Specialized, Special and New Small and Medium-sized Enterprises." [ 6 ]
GMY's 222nm ultraviolet light modules won the Zhongzhao China Lighting Award for Science and Technology Innovation issued by the Chinese Lighting Society in March, 2022.The award noted that "The 222nm excimer lamp emits accurate 222nm wavelength ultraviolet light, which is safer to use than traditional 185nm and 254nm ultraviolet light. It does not produce mercury and is harmless to the environment." [ 7 ]
GMY's manufacturing facility covers an area of nearly 80,000 square meters, and has an annual output of hundreds of millions of light source products, which are sold to more than 100 countries. GMY's product line includes general lighting , automotive lighting , and specialized light sources, especially ultraviolet lights for disinfection , UV lighting for manufacturing processes, IPL lights for health and beauty applications , and artificial light vertical planting solutions . [ 8 ]
GMY has obtained more than 300 patents , including more than 200 ultraviolet-related patents, ranking among the top five China. As of 2021, GMY ranked first in China with patents awarded for 253.7 nm and 185.0 nm ultraviolet germcidall ultraviolet lighting. [ 8 ] | https://en.wikipedia.org/wiki/GMY_Lighting_Technology |
The GNAT Modified General Public License (short: Modified GPL , GMGPL ) is a version of the GNU General Public License specifically modified for compiled units and for the generic feature found in the Ada programming language .
The modification is as follows:
The GNAT Ada compiler can automate conformance checks for some GPL software license issues via a compiler directive . Use pragma License (Modified_GPL); to activate the check against the Modified GPL. The GNAT Reference Manual [ 1 ] documents the License [ 2 ] pragma along with other compiler directives.
This law -related article is a stub . You can help Wikipedia by expanding it .
This free and open-source software article is a stub . You can help Wikipedia by expanding it .
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/GNAT_Modified_General_Public_License |
The GNC hypothesis or GNC-SNS primeval genetic code hypothesis refers to a hypothesis about the origin of genes . It suggests the universal genetic code originated not from a three-amino acid system, but from a four-amino acid system. It is this GNC code encoding [GADV]-proteins which is the most primitive genetic code. This hypothesis was first proposed by Kenji Ikehara at Nara Women's University.
While almost all of the organisms on Earth share the universal genetic code , in the GNC hypothesis it is argued that two primeval genetic codes preceded the present genetic code as follows:
The GNC hypothesis is based on the following facts:
Ikehara, Kenji; Omori, Yoko; Arai, Rieko; Hirose, Akiko (2002). "A Novel Theory on the Origin of the Genetic Code: A GNC-SNS Hypothesis". Journal of Molecular Evolution . 54 (4): 530– 538. Bibcode : 2002JMolE..54..530I . doi : 10.1007/s00239-001-0053-6 . PMID 11956691 . | https://en.wikipedia.org/wiki/GNC_hypothesis |
GNSS enhancement refers to techniques used to improve the accuracy of positioning information provided by the Global Positioning System or other global navigation satellite systems in general, a network of satellites used for navigation.
Enhancement methods of improving accuracy rely on external information being integrated into the calculation process. There are many such systems in place and they are generally named or described based on how the GPS sensor receives the information. Some systems transmit additional information about sources of error (such as clock drift, ephemeris, or ionospheric delay ), others provide direct measurements of how much the signal was off in the past, while a third group provides additional navigational or vehicle information to be integrated into the calculation process.
The Global Positioning System (GPS) is the American satellite-based system for positioning and navigation. Receivers on or near the Earth's surface can determine their locations based on signals received from any four or more of the satellites in the network.
All GPS satellites broadcast on the same two frequencies, known as L1 (1575.42 MHz) and L2 (1227.60 MHz). The network uses code-division multiple access (CDMA) to allow separate messages from the individual satellites to be distinguished. Two distinct CDMA encodings are used: the coarse/acquisition (C/A) code, which is accessible by the general public, and the precise (P) code, which is encrypted, so that only the U.S. military can access it. The messages sent from each satellite contain information ranging from the satellite's health, the satellite's orbital path, the clock state of the satellite, and the configuration of the entire satellite network.
The accuracy of a calculation can also be improved through precise monitoring and measuring of the existing GPS signals in additional or alternate ways.
After Selective Availability was turned off by the U.S. government, the largest error in GPS was usually the unpredictable delay through the ionosphere. The spacecraft broadcast ionospheric model parameters, but they are necessarily imperfect. This is one reason the GPS spacecraft transmit on at least two frequencies, L1 and L2. Ionospheric delay is a well-defined function of frequency and the total electron content (TEC) along the path, so measuring the arrival-time difference between the frequencies determines TEC and thus the precise ionospheric delay at each frequency.
Receivers with decryption keys can decode the P(Y)-code transmitted on both L1 and L2. However, these keys are reserved for the military and authorized agencies and are unavailable to the public. Without keys, it is still possible to use a codeless technique to compare the P(Y) codes on L1 and L2 to gain much of the same error information. However, this technique is slow and is currently limited to specialized surveying equipment. In the future, additional civilian codes are expected to be transmitted on the L2 and L5 frequencies (see GPS modernization ). Then all users can perform dual-frequency measurements and directly compute ionospheric-delay errors.
A second form of precise monitoring is called carrier-phase enhancement (CPGPS). [ 1 ] The error, which this corrects, arises because the pulse transition of the PRN is not instantaneous, and thus the correlation (satellite–receiver sequence matching) operation is imperfect. The CPGPS approach utilizes the L1 carrier wave, which has a period of
which is about one-thousandth of the C/A Gold code bit period of
to act as an additional clock signal and resolve the uncertainty. The phase-difference error in the normal GPS amounts to between 2 and 3 meters (6.6 and 9.8 ft) of ambiguity. CPGPS working to within 1% of perfect transition reduces this error to 3 centimetres (1.2 inches) of ambiguity. By eliminating this source of error, CPGPS coupled with DGPS normally realizes between 20 and 30 centimeters (7.9 and 11.8 inches) of absolute accuracy.
Real-time kinematic positioning (RTK) is another approach for a precise GPS-based positioning system. In this approach, the determination of the range signal can be resolved to a precision of less than 10 centimeters (4 in). This is done by resolving the number of cycles in which the signal is transmitted and received by the receiver. This can be accomplished by using a combination of differential GPS (DGPS) correction data, transmitting GPS signal phase information, and ambiguity resolution techniques via statistical tests, possibly with processing in real time.
Utilizing the navigation message to measure pseudo-range has been discussed. Another method that is used in GPS surveying applications is carrier-phase tracking. The period of the carrier frequency times the speed of light gives the wavelength, which is about 0.19 meters for the L1 carrier. With a 1% of wavelength accuracy in detecting the leading edge, this component of pseudo-range error might be as low as 2 millimeters. This compares to 3 meters for the C/A code and 0.3 meters for the P code.
However, this 2-millimeter accuracy requires measuring the total phase, the total number of wavelengths, plus the fractional wavelength. This requires specially equipped receivers. This method has many applications in the field of surveying.
We now describe a method that could potentially be used to estimate the position of receiver 2 given the position of receiver 1 using triple differencing followed by numerical root finding and a mathematical technique called least squares . A detailed discussion of the errors is omitted in order to avoid detracting from the description of the methodology. In this description, differences are taken in the order of differencing between satellites, differencing between receivers, and differencing between epochs. This should not be construed to mean that this is the only order that can be used. Indeed, other orders of taking differences are equally valid.
The satellite carrier's total phase can be measured with ambiguity regarding the number of cycles. Let ϕ i , j , k {\displaystyle \phi _{i,j,k}} denote the phase of the carrier of satellite j {\displaystyle j} measured by receiver i {\displaystyle i} at time t k {\displaystyle t_{k}} . Also, we define three functions: Δ r , Δ s , Δ t {\displaystyle \Delta ^{r},\Delta ^{s},\Delta ^{t}} , which perform differences between receivers, satellites, and time points, respectively. Each function has a linear combination of variables with three subscripts as its argument. These three functions are defined below:
Also if ϕ i , j , k {\displaystyle \phi _{i,j,k}} and ϕ l , m , n {\displaystyle \phi _{l,m,n}} are valid arguments for the three functions, and a {\displaystyle a} and b {\displaystyle b} are constants, then ( a ϕ i , j , k + b ϕ l , m , n ) {\displaystyle (a\phi _{i,j,k}+b\phi _{l,m,n})} is a valid argument with values defined as
Receiver-clock errors can be approximately eliminated by differencing the phases measured from satellite 1 with that from satellite 2 at the same epoch. [ 2 ] This difference is designated as Δ s ( ϕ 1 , 1 , 1 ) = ϕ 1 , 2 , 1 − ϕ 1 , 1 , 1 {\displaystyle \Delta ^{s}(\phi _{1,1,1})=\phi _{1,2,1}-\phi _{1,1,1}} .
Double differencing can be performed by taking the differences of the satellite difference observed by receiver 1 with that observed by receiver 2. [ 3 ] The satellite-clock errors will be approximately eliminated by this between receiver differencing. This double difference is
Triple differencing can be performed by taking the difference of double differencing performed at time t 2 {\displaystyle t_{2}} with that performed at time t 1 {\displaystyle t_{1}} . [ 4 ] This will eliminate the ambiguity associated with the integral number of wavelengths in carrier phase, provided this ambiguity does not change with time. Thus the triple difference result has eliminated all or practically all clock bias errors and integer ambiguity. Also, errors associated with atmospheric delay and satellite ephemeris have been significantly reduced. This triple difference is
Triple-difference results can be used to estimate unknown variables. For example, if the position of receiver 1 is known, but the position of receiver 2 is unknown, it may be possible to estimate the position of receiver 2 using numerical root finding and least squares . Triple difference results for three independent time pairs quite possibly will be sufficient to solve for the three components of the position of receiver 2. This may require the use of a numerical procedure such as one of those found in the chapter on root finding and nonlinear sets of equations in Numerical Recipes. [ 5 ] To use such a numerical method, an initial approximation of the position of receiver 2 is required. This initial value could probably be provided by a position approximation based on the navigation message and the intersection of sphere surfaces. Although multidimensional numerical root finding can have problems, this disadvantage may be overcome with this good initial estimate. This procedure using three-time pairs and a fairly good initial value followed by iteration will result in one observed triple-difference result for the receiver 2 positions. Greater accuracy may be obtained by processing triple-difference results for additional sets of three independent time pairs. This will result in an overdetermined system with multiple solutions. To get estimates for an overdetermined system, least squares can be used. The least-squares procedure determines the position of receiver 2 that best fits the observed triple-difference results for receiver 2 positions under the criterion of minimizing the sum of the squares.
Other examples of GNSS enhancements include Inertial Navigation Systems and Assisted GPS . | https://en.wikipedia.org/wiki/GNSS_enhancement |
A software GNSS receiver is a Global Navigation Satellite System (GNSS) receiver that has been designed and implemented using software-defined radio .
A GNSS receiver, in general, is an electronic device that receives and digitally processes the signals from a navigation satellite constellation in order to provide position, velocity and time (of the receiver).
GNSS receivers have been traditionally implemented in hardware: a hardware GNSS receiver is conceived as a dedicated chip that has been designed and built (from the very beginning) with the only purpose of being a GNSS receiver.
In a software GNSS receiver, all digital processing is performed by a general purpose microprocessor . In this approach, a small amount of inexpensive hardware is still needed, known as the frontend , that digitizes the signal from the satellites. The microprocessor can then work on this raw digital stream to implement the GNSS functionality.
When comparing hardware vs software GNSS receivers, a number of pros and cons can be found for each approach:
Currently, most of the GNSS receiver market is still hardware . However, there already exist operational solutions based on the software approach able to run on low-cost microprocessors. Software GNSS receivers are expected to increase their market share or even take over in the near future, following the development of the computational capabilities of the microprocessors ( Moore's law ). | https://en.wikipedia.org/wiki/GNSS_software-defined_receiver |
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