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Patina ( / p ə ˈ t iː n ə / pə- TEE -nə or / ˈ p æ t ɪ n ə / PAT -ih-nə ) is a thin layer that variously forms on the surface of copper , brass , bronze , and similar metals and metal alloys ( tarnish produced by oxidation or other chemical processes), or certain stones [ 1 ] and wooden furniture (sheen produced by age, wear, and polishing), or any similar acquired change of a surface through age and exposure.
Additionally, the term is used to describe the aging of high-quality leather . The patinas on leather goods are unique to the type of leather, frequency of use, and exposure.
Patinas can provide a protective covering to materials that would otherwise be damaged by corrosion or weathering. They may also be aesthetically appealing.
On metal, patina is a coating of various chemical compounds such as oxides , carbonates , sulfides , or sulfates formed on the surface during exposure to atmospheric elements ( oxygen , rain , acid rain , carbon dioxide , sulfur -bearing compounds). [ 2 ] Patina also refers to accumulated changes in surface texture and color that result from normal use of an object such as a coin or a piece of furniture over time. [ 3 ]
Archaeologists also use the term patina to refer to a corticated layer that develops over time that is due to a range of complex factors on flint tools and ancient stone monuments. [ 1 ] This has led stone tool analysts in recent times to generally prefer the term cortification as a better term to describe the process than patination . [ 4 ]
In geology and geomorphology , the term patina is used to refer to discolored film or thin outer layer produced either on or within the surface of a rock or other material by either the development of a weathering rind within the surface of a rock, the formation of desert varnish on the surface of a rock, or combination of both. It also refers to development as the result of weathering of a case-hardened layer, called cortex by geologists, within the surface of either a flint or chert nodule . [ 5 ] [ 6 ]
The word patina comes from the Italian patina (shallow layer of deposit on a surface), derived from the Latin patĭna (pan, shallow dish). Figuratively, patina can refer to any fading, darkening, or other signs of age, which are felt to be natural or unavoidable (or both).
The chemical process by which a patina forms or is deliberately induced is called patination , and a work of art coated by a patina is said to be patinated .
The green patina that forms naturally on copper and bronze, sometimes called verdigris , usually consists of varying mixtures of copper chlorides , sulfides , sulfates , and carbonates , depending upon environmental conditions such as sulfur-containing acid rain . [ 7 ] [ 8 ] [ 9 ] [ 10 ] In clean air rural environments, the patina is created by the slow chemical reaction of copper with carbon dioxide and water, producing a basic copper carbonate . In industrial and urban air environments containing sulfurous acid rain from coal-fired power plants or industrial processes, the final patina is primarily composed of sulphide or sulphate compounds. [ 11 ] [ 12 ] [ 13 ]
A patina layer takes many years to develop under natural weathering. Buildings in damp coastal or marine environments will develop patina layers faster than ones in dry inland areas.
Façade cladding ( copper cladding ; copper wall cladding ) with alloys of copper, like brass or bronze, will weather differently from "pure" copper cladding. Even a lasting gold colour is possible with copper-alloy cladding, for example Bristol Beacon in Bristol, or the Novotel at Paddington Central, London.
Antique and well-used firearms will often develop a layer of rust on the action, barrel, or other steel parts after the original finish has worn. On this subject gunsmith Mark Novak says "... This is what everybody calls patina, I call it a nice thick coat of rust..." [ 15 ] The removal of such rust is often necessary for a firearm conservation to prevent further decay of the firearm.
Artists and metalworkers often deliberately add patinas as a part of the original design and decoration of art and furniture, or to simulate antiquity in newly made objects. The process is often called distressing .
A wide range of chemicals, both household and commercial, can give a variety of patinas. They are often used by artists as surface embellishments either for color, texture, or both. Patination composition varies with the reacted elements and these will determine the color of the patina. For copper alloys, such as bronze, exposure to chlorides leads to green, while sulfur compounds (such as " liver of sulfur ") tend to brown. The basic palette for patinas on copper alloys includes chemicals like ammonium sulfide (blue-black), liver of sulfur (brown-black), cupric nitrate (blue-green), and ferric nitrate (yellow-brown). For artworks, patination is often deliberately accelerated by applying chemicals with heat. Colors range from matte sandstone yellow to deep blues, greens, whites, reds, and various blacks. Some patina colors are achieved by the mixing of colors from the reaction with the metal surface with pigments added to the chemicals. Sometimes the surface is enhanced by waxing, oiling, or other types of lacquers or clear-coats. More simply, the French sculptor Auguste Rodin used to instruct assistants at his studio to urinate over bronzes stored in the outside yard [ citation needed ] . A patina can be produced on copper by the application of vinegar ( acetic acid ). This patina is water-soluble and will not last on the outside of a building like a "true" patina. It is usually used as pigment.
Patina is also found on slip rings and commutators . This type of patina is formed by corrosion, what elements the air might hold, residue from the wear of the carbon brush, and moisture; thus, the patina needs special conditions to work as intended.
Patinas can also be found in woks or other metal baking dishes. The process of applying patinas to cookware is known as seasoning . The patina on a wok is a dark coating of oils that have been polymerized onto it to prevent food from sticking. Scrubbing or using soap on a wok or other dishware could damage the patina and possibly allow rust.
Knife collectors that own carbon steel blades sometimes force a patina onto the blade to help protect it and give it a more personalized look. This can be done using various chemicals and substances such as muriatic acid, apple cider vinegar, or mustard. It can also be done by sticking the blade into any acidic vegetable or fruit such as an orange or an apple.
In the case of antiques, a range of views are held on the value of patination and its replacement if damaged, known as repatination.
Preserving a piece's look and character is important and removal or reduction may dramatically reduce its value. If patination has flaked off, repatination may be recommended. [ 16 ] Appraiser Reyne Haines notes that a repatinated metal piece will be worth more than one with major imperfections in the patina, but less than a piece still with its original finish. [ 16 ] | https://en.wikipedia.org/wiki/Patina |
Patinho Feio (Portuguese for "Ugly Duckling", in reference to the fairy tale ) was the first minicomputer designed and manufactured entirely in Brazil. [ 1 ] It was made between 1971 and 1972 in the Polytechnic School of the University of São Paulo by the Digital Systems Laboratory (currently called Department of Computer Engineering and Digital Systems). [ 2 ] [ 3 ] [ 4 ]
Patinho Feio was an 8-bit minicomputer with a memory of 8 kB and an instruction cycle of 2 microseconds. It was programmed in assembly language .
This computing article is a stub . You can help Wikipedia by expanding it .
This computer hardware article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Patinho_Feio |
The patio process is a process for extracting silver from ore . Smelting , or refining , is most often necessary because silver is only infrequently found as a native element like some metals nobler than the redox couple 2 H + + 2 e − ⇌ H 2 ( gold , mercury , ...). Instead, it is made up of a larger ore body. Thus, smelting, or refining, is necessary to reduce the compound containing the Ag + cation into metallic Ag and to remove other byproducts to get at pure silver. [ 1 ] The process, which uses mercury amalgamation to recover silver from ore, was first used at scale by Bartolomé de Medina in Pachuca , Mexico , in 1554. [ 2 ] It replaced smelting as the primary method of extracting silver from ore at Spanish colonies in the Americas. Although some knowledge of amalgamation techniques were likely known since the classical era, it was in the New World that it was first used on a large industrial scale. [ 3 ] Other amalgamation processes were later developed, importantly the pan amalgamation process, and its variant, the Washoe process . The silver separation process generally differed from gold parting and gold extraction , although amalgamation with mercury is also sometimes used to extract gold. While gold was often found in the Americas as a native metal or alloy , silver was often found as a compound such as silver chloride and silver sulfide , and therefore required mercury amalgamation for refinement. [ 4 ]
Bartolomé de Medina was a successful Spanish merchant who became fascinated with the problem of decreasing silver yields from ores mined in Spanish America. By the mid-sixteenth century, it was well known in Spain that American silver production was in decline due to the depletion of high-grade ores and increasing production costs. The New Laws , prohibiting the enslavement of Indians, had resulted in higher labor costs as miners turned to wage labor and expensive African slaves. These higher production costs made mining and smelting anything but the highest grade silver ores prohibitively expensive, just as the availability of high grade ores was in decline. [ 5 ] Bartolomé de Medina initially focused his attentions on learning about new smelting methods from smelters in Spain. He was approached during his research by an unknown German man, known only as "Maestro Lorenzo," who told him that silver could be extracted from ground ores using mercury and a salt-water brine. [ 6 ] With this knowledge, Medina left Spain for New Spain ( Mexico ) in 1554 and established a model patio refinery in order to prove the effectiveness of the new technology. Medina is generally credited with adding "magistral" (a type of copper sulfate CuSO 4 derived from pyrites ) to the mercury and salt-water (H 2 O · NaCl) solution in order to catalyze the amalgamation reaction. [ 7 ] Some historians assert that there were already sufficient copper sulfates in the local ores and that no additional magistral was needed, though others argue that while naturally occurring copper sulfates allowed for potential amalgamation sans magistral, the erratic results of this method made magistral a key component of the effective refinement of ore on a large scale. [ 8 ] [ 9 ] Regardless of whether or not Medina's contribution was entirely original, he promoted his process to local miners and was able to obtain a patent from the Viceroy of New Spain. As a result, he is generally credited with the invention of silver amalgamation in the form of the patio process. [ 10 ]
The effectiveness of this method was such that when German experts arrived in America in the late 1700s to teach the newest amalgamation technology, they admitted they did not believe they could improve upon the American method in its context. Friedrich Sonneschmidt, a German refiner, stated: "It is not to be expected that there will ever be found a method by which all varieties of ore can be refined, having expenses lower than or even equal to those required by the patio beneficiation ." [ 11 ] The amalgamation was so efficient that a refiner could turn a profit even if the ores were poor enough to yield only 1.5 oz of silver per 100 lbs of original material. [ 12 ]
Before being taken to the ingenio (amalgamation refinery), excess material would be broken off of the silver ore. At the refiner, it was ground to a fine sand (harina) by an arrastra or stamp mill , which consisted of a rotating shaft fitted with heavy iron stamps that crushed the ore against a mortar block. [ 13 ] The harina was then placed in heaps of 2,000 lbs or more, to which was added salt , water, magistral (essentially an impure form of copper sulfate , CuSO 4 ), and mercury. This was then mixed by bare-legged Indian laborers or by horses or mules and spread in a 1-to-2-foot-thick (0.30 to 0.61 m) layer in a patio (a shallow-walled, open enclosure). After six to eight weeks of mixing and soaking in the sun, a complex reaction converted the silver to native metal, which formed an amalgam with the mercury. The mixture was then washed and strained through a canvas bag before being placed into a hooded oven. [ 14 ] Heating this amalgam vaporized the mercury, leaving the silver. [ 15 ] The mercury vapor would then condense on the cooled hood, where it could be collected and reused. [ 16 ] The amount of salt and copper sulfate varied from one-quarter to ten pounds of one or the other, or both, per ton of ore treated. The decision of how much of each ingredient to add, how much mixing was needed, and when to halt the process depended on the skill of an azoguero (English: quicksilver man). The loss of mercury in amalgamation processes is generally one to two times the weight of silver recovered. [ 17 ]
The patio process was the first form of amalgamation. However, it is unclear whether this process or a similar process—in which amalgamation occurred in heated vats rather than open patios—was the predominant form of amalgamation in New Spain, as the earliest known illustration of the patio process dates from 1761. There is substantial evidence that both processes were used from an early date in New Spain, while open patios were never adopted in Peru . [ 18 ] Instead, Andean refiners placed milled ore in stone tanks vaulted over a fire, which helped accelerate amalgamation by mitigating the bitterly cold temperatures at the high elevation of the Andean mines. [ 19 ] Both processes required that ore be crushed and refiners quickly established mills to process ore once amalgamation was introduced. Water mills were common in the Andes, powered by man-made dams, while in New Spain, where water was relatively scarce, mills were often powered by horses or other draft animals. [ 20 ] [ 21 ]
Due to amalgamation's reliance upon mercury, an expansion of mercury production was central to the expansion of silver production. A key source of mercury was at Huancavelica , Peru, where vast deposits were discovered in 1563. [ 22 ] Additional mercury was sourced from Almadén , Spain, and Idrija in present-day Slovenia. [ 23 ] [ 24 ] From shortly after the invention of mercury amalgamation to the end of the colonial period, the Spanish crown maintained a monopoly on mercury production and distribution, ensuring a steady supply of royal income. Fluctuations in mercury prices generally resulted in corresponding increases and decreases in silver production. [ 25 ] Crown control over these prices could be used to intentionally depress or stimulate silver production in Spanish colonies. [ 26 ]
The introduction of amalgamation to silver refining in the Americas not only ended the mid-sixteenth century crisis in silver production, it also inaugurated a rapid expansion of silver production in New Spain and Peru as miners could now profitably mine lower-grade ores. In addition, places that were rich in ore but too isolated from indigenous populations or forests for the labor- and fuel-intensive smelting method to be profitable, as was the case with Potosí in modern-day Bolivia , were now viable. [ 27 ] As a result of this expansion, the Americas became the primary producer of the world's silver, with Spanish America producing three-fifths of the world's silver supply prior to 1900. [ 28 ]
Increased silver production due to the introduction of mercury amalgamation resulted in an increased demand for labor. In New Spain , mining labor was initially supplied by the encomienda system or by enslaved Indians before transitioning to a repartimiento rotating labor system, but by the early 1600s, the majority of workers were Indian free wage or debt peonage workers. [ 29 ] These naboríos were free, unattached Indians who contracted themselves out for sustenance and payment. Spaniards tended to distrust naboríos and accused them of profiteering by stealing ore, taking advances and fleeing, or contracting themselves out to multiple employers at a time. [ 30 ] Regardless, the mines in New Spain increasingly relied on naboríos, who constituted over two thirds of mine workers in the region. Repartimiento Indian workers made up roughly seventeen percent of laborers, with another fourteen percent composed of Black slaves. [ 31 ] [ 32 ] Throughout the Spanish colonies, white men typically took positions as supervisors or mine owners. [ 33 ]
The introduction of silver amalgamation allowed for an expansion of silver production in Peru that had profound consequences for Peru's native population. From 1571, the year the amalgamation process was introduced to the Andes, to 1575, Peru's silver production quintupled. [ 34 ] In 1572, in order to provide sufficient labor to accommodate the expansion of silver mining to lower-grade ores, Viceroy Francisco Toledo organized an Indian draft labor system, the mita . [ 35 ] This system of forced labor was based on the mit'a, a rotating, reciprocal labor obligation instituted in pre-Hispanic Andean society. Under this system, thousands of natives were forced to work in silver and mercury mines for less than subsistence-level wages. Thirteen thousand draft laborers per year worked at the largest mine in the Americas, located at Potosí in modern Bolivia. Native attempts to avoid the mita led to the abandonment of many Indian villages throughout Peru as thousands of Indians either moved permanently to Potosí or fled their traditional ayllus in order to escape the labor draft. [ 36 ] Spanish monopolization of refining through amalgamation cut natives out of what had earlier been a native-dominated enterprise. Refining represented the most profitable segment of silver production. In conjunction with the mita, the exclusion of natives from owning refineries contributed to the transformation of Peruvian natives into a poorly paid labor force. [ 37 ]
The rapid expansion of silver production and coinage—made possible due to the invention of amalgamation—has often been identified as the primary driver of the price revolution , a period of high inflation lasting from the sixteenth to early seventeenth-century in Europe. Proponents of this theory argue that Spain's reliance on silver coins from the Americas to finance its large balance of payments deficits resulted in a general expansion of the European money supply and corresponding inflation. Critics of the theory, however, argue that inflation was really a result of European government policies and population growth . [ 38 ]
While the role of the expansion in silver production in the price revolution may be disputed, this expansion is often acknowledged as a key ingredient in the formation of early-modern world trade. In the 1530s, China decreed that all internal taxation must be paid in silver, driving demand for Spanish American silver and facilitating the development of extensive trade networks linking Europe, Africa, Asia, and the Americas as Europeans sought to gain access to Chinese wares. [ 39 ] [ 40 ] | https://en.wikipedia.org/wiki/Patio_process |
Patoka Oil Terminal is a pipeline hub located near the towns of Patoka and Vernon . It services five major pipelines in the second district of the Petroleum Administration for Defense Districts including Dakota Access and the Keystone Pipeline .
The Patoka Oil Terminal Hub is located near the towns of Patoka and Vernon, Illinois. [ 1 ] The Patoka Terminal is the second-largest pipeline terminal in the Midwest next to the Cushing-Drumright Oil Field . It has 82 storage tanks and stores up to 19 million barrels of crude oil, servicing five major incoming as well as five major outgoing pipelines. [ 1 ] It has more than 50 storage tanks [ 2 ] and facilitates the transport of oil through pipelines to refineries in various parts of the United States. [ 1 ]
Patoka Oil Terminal is part of District Two of the Petroleum Administration for Defense Districts . It was responsible for three-quarters of pipeline movements in that district in 2010 and processes approximately 2.2 million barrels of oil per day. [ 3 ] [ 4 ]
Patoka is the main oil terminal in the region where oil was first discovered in 1938. [ 5 ] Tax revenue from operations are collected and distributed by Marion County, Illinois . It was reported by the Chicago Tribune that Dakota Access paid approximately $750,000 in tax revenue for its operations in Illinois. [ 1 ]
The following pipelines are part of the Patoka Energy Terminal: | https://en.wikipedia.org/wiki/Patoka_Oil_Terminal |
E. O. Paton Electric Welding Institute ( Ukrainian : Інститут електрозварювання ім. Є. О. Патона , romanized : Insytut elektrozvariuvannia im. Ye. O. Patona ) is a welding research institution situated in Kyiv , Ukraine . It is named after its founder, Professor Evgeny Paton .
The institute was established in 1934 following the decree of the Ukrainian Academy of Sciences. The institute was formed from the Laboratories of the State Electric Welding Committee and Electric Welding Department of Kyiv Polytechnic Institute in 1934. Until 1991 it was known as the Ukrainian SSR Academy of Sciences Electric Welding Institute . The first leader of the institute was Evgeny Paton.
For many years the institute was directed by Evgeny Paton's son, Borys Paton . Since 2020 following Borys Paton's death the institute is led by Ihor Krivtsun [ 1 ]
Currently the institute research staff includes 70 Doctor of Science , 250 Kandidats of Science . The institute is the main Ukrainian research facility dealing with electric welding and electrical discharge machining . | https://en.wikipedia.org/wiki/Paton_Institute_of_Electric_Welding |
The patriarch hypothesis is a hypothesis that explains the occurrence of menopause in human females and how a long post-fertile period (up to one third of a female's life-span) [ 1 ] could confer an evolutionary advantage. It is an alternative theory to the grandmother hypothesis which tends to ignore male benefits of continued spermatogenesis and their roles in assistance.
The patriarch hypothesis incorporates these neglected areas. It suggests selection pressure on male longevity extended the female lifespan; whose adjustment of life history has been constrained by the size of the ovaries – resulting in human females surviving beyond the age at which they can reproduce. With an extension of the post-reproductive female life stage, they could enhance their inclusive fitness by giving kin assistance . This way, with no choice in the timing of fertility termination, females are optimising an essentially bad situation. [ citation needed ]
Frank Marlowe first put forward the patriarch hypothesis. [ 2 ] He postulates that if women survive beyond an age at which they can reproduce and men continue spermatogenesis , then old males can benefit greatly if they can copulate with younger females. It is theorised that increased use of tools and weapons compensates for the decline in natural fighting ability with age. [ 3 ] This serves to produce a more stable male hierarchy, where attainment of high social status and reproductive access is less reliant on physical strength. [ citation needed ]
With such a scenario older males are able to retain a competitive ability with younger males, thereby asserting a selection pressure on extending longevity in males that could retain social status. Higher ranking males may also be a more attractive mate choice . One mechanism that could extend the lifespan is delaying the age at maturity. Offspring with a slower life history would exhibit a protracted period of dependence. If depletion of oocytes occurs at age 50, females should selectively counter this as it reduces their fecundity .
Recruitment of help from kin and husbands may compensate by enabling females to reduce birth intervals by weaning offspring at an earlier age. In addition, by passing on longevity to her sons, a female would stand to gain inclusive fitness . [ 2 ]
Some of the criticisms include the fact that actually most fathers, especially first time fathers, are predominantly under 40, and only one percent of 1st time fathers are above 50. [ 4 ] Even in today's hunter-gather societies, younger males are preferred by women and their parents as husbands, as hunting and rearing children require extensive strength that tools can't compensate for in elderly males. [ 5 ] And because demographic data has shown that historically rising numbers in older people among the population correlated with lower numbers of younger people, this means that more elderly men do not result in more children, quite the opposite. [ 6 ] Frank Marlowe also fails to explain the pressure on men to reproduce in later life, especially with the fact that the genetic quality and the survival of a fetus of an elderly male is lower than that with a young father, making having a child with an elderly man risky for a woman. [ 7 ] It also fails to consider the fact that reproducing sperm is much less costly than reproducing eggs, bearing the young and feeding them, which means there is no need for the elderly man to stop his spermatogenesis even if it's almost useless. Furthermore, men are much more likely to die earlier than women and have more cancers than them, [ 8 ] sex hormones play a significant role in this.
The patriarch hypothesis rests on three assumptions:
Longevity is a central determinant of the grandmother hypothesis ; selection for greater longevity in males, as suggested by the patriarch hypothesis, could extend female lifespan, provided such a gene is not on the Y chromosome. Males have much to gain from late reproduction, even if they die shortly after conception. [ 14 ] Females that found their longevity extended, were constrained by the difficulties of increasing their follicular reserves and thus could enhance their inclusive fitness by giving kin assistance.
However, the hypothesis is committing a fallacy in which it starts with the conclusion that it's supposed to prove. The author starts with the fact that women go through menopause to reach a conclusion of male longevity instead of trying to prove it. [ citation needed ] | https://en.wikipedia.org/wiki/Patriarch_hypothesis |
Patricia Molina is the Richard Ashman, PhD Professor and Department Head of Physiology and Director of the Alcohol and Drug Abuse Center of Excellence (ADACE) at Louisiana State University Health Sciences Center New Orleans . [ 1 ] In 2015, she was the 88th President of the American Physiological Society , and is the author of the Lange monographic series Endocrine Physiology . [ 2 ] [ 3 ]
Molina graduated from the Universidad Francisco Marroquín , and from Louisiana State University Health Sciences Center New Orleans with a PhD in physiology.
She was assistant professor of surgery and physiology at the Stony Brook University , director of surgical research at North Shore University Hospital , and guest scientist at Brookhaven National Laboratory prior to joining the Department of Physiology at Louisiana State University Health Sciences Center New Orleans as an associate professor in 1999.
In 2008, she was named the Richard Ashman, PhD Professor (endowed chair) and Department Head of Physiology and was appointed as director of the Alcohol and Drug Abuse Center of Excellence.
Molina is principal investigator and director of the National Institutes of Health -funded Comprehensive Alcohol-HIV/AIDS Research Center, [ 4 ] Biomedical Research Training Program, [ 5 ] and Medical Student Alcohol Research Internship Program. [ 6 ]
In addition to being the first Hispanic woman to be chair of a department of physiology, Molina has served in a number of leadership roles in her discipline. In 2015, she was the first Hispanic woman president of the American Physiological Society . [ 7 ] [ 8 ] In 2019, she was president of the Association of Chairs of Department of Physiology, [ 9 ] and in 2020-2021 served as president of the Research Society on Alcoholism . [ 10 ]
Molina's research focuses on the impact of unhealthy alcohol use on risk of behavioral and metabolic comorbidities associated with HIV/AIDS. Her research is currently funded by the National Institute on Alcohol Abuse and Alcoholism of the National Institutes of Health . [ 11 ] [ 12 ] | https://en.wikipedia.org/wiki/Patricia_E._Molina |
Patricia Ana Matrai is a marine scientist known for her work on the cycling of sulfur. She is a senior research scientist at Bigelow Laboratory for Ocean Sciences .
Matrai is originally from Chile. [ 1 ] Matria has a B.A. from the Universidad de Concepción (1981), an M.S. (1984) and a Ph.D. (1988) from Scripps Institution of Oceanography and the University of California San Diego . Following her Ph.D. she moved to the University of Miami . She became a senior research scientist at Bigelow Laboratory for Ocean Sciences in 1995. [ 2 ]
Matrai is known for her work on marine aerosols , especially those that contain sulfur. She has examined the production of sulfur compounds by coccolithophores , [ 3 ] a type of phytoplankton. [ 4 ] She has also examined the amount of organic sulfur inside phytoplankton cells [ 5 ] and during phytoplankton blooms. [ 6 ] Matrai has worked on the impact of declines in sea ice [ 7 ] and how primary production is measured in the Arctic. [ 8 ] [ 9 ] In 2001 she went to the North Pole on an icebreaker where she studied aerosols produced by phytoplankton. [ 10 ] She also does work on outreach and mentoring children to introduce them to science [ 11 ]
In 2017 Matrai was named a fellow of the Association for the Sciences of Limnology and Oceanography . [ 12 ] | https://en.wikipedia.org/wiki/Patricia_Matrai |
Patricia C. Zambryski is a plant and microbial scientist known for her work on Type IV secretion and cell-to-cell transport in plants. She is also professor emeritus at the University of California, Berkeley . [ 1 ]
She was an elected member of the National Academy of Sciences , the American Association for the Advancement of Science , and the American Society for Microbiology .
Zambryski received her B.S. from McGill University in 1969, and earned a Ph.D. from the University of Colorado in 1974. [ 2 ] [ 3 ]
Zambryski is known for her work in the field of genetic engineering, specifically for her work with Agrobacterium tumefaciens , a bacterium she uses to track the molecular mechanisms that change plants and how plant cells communicate with each other. [ 3 ] She has examined the structure of plant cells that have been altered by Agrobacterium tumefaciens. [ 4 ] While working in Marc Van Montagu 's lab, Zambryski determined how the Ti plasmid is identified by the bacterium, and she developed a vector that allowed the transfer of genetic material into a plant without altering the plant tissue. [ 5 ] [ 6 ] This advance was used to inject novel genes into plants. [ 7 ] She has also examined plasmodesmata , which are the channels that reach across the spaces in plant cells. [ 8 ] [ 9 ]
In 2001 she was elected a member of the National Academy of Sciences [ 10 ] and a fellow of the American Society for Microbiology. [ 2 ] In 2010 she was elected a fellow of the American Association for the Advancement of Science. [ 2 ] | https://en.wikipedia.org/wiki/Patricia_Zambryski |
Patrick H. [ 1 ] Scully was a Catholic priest and astronomer who served as a missionary in Cape Town and built the first Catholic parish church in South Africa .
After the Anglo-Dutch Treaty of 1814 , the Colonial Office gave permission for a Catholic priest to be stationed in Cape Town. [ 2 ] Irish priest Patrick H. Scully arrived in Cape Town on 1 January 1820, in the company of the bishop Edward Bede Slater [ de ] . [ 3 ] [ 4 ] [ 5 ] [ 6 ] On 13 February 1820, Scully opened a church in a repurposed store on Buitekant street, donated by a local Catholic, Philip Albertus. There he said Mass on Sundays and holy days at 11 AM. [ 5 ] [ 7 ] He initially ministered mainly to local Irish soldiers. [ 5 ] [ 8 ]
Rufane Shaw Donkin , the acting governor of Cape Town, approved a salary of £75 for Scully on 17 January 1821. [ 2 ] [ 5 ] [ 9 ] In April 1821, Scully petitioned the burgher senate for land to build a proper church. The senate agreed, and Scully announced the planned construction in September. [ 7 ] [ 9 ] In November, the Cape Gazette announced that the plans for the church were available to view. [ 7 ]
In 1821, the churchwardens of Cape Town wrote to Slater with a number of complaints about Scully. Scully, they said, only offered Mass on Sundays, gave infrequent and inaudible sermons, failed to follow up on home visits to parishioners, and was irregular in recording baptisms. They also claimed that Scully was breaking the law by baptizing slaves. In response, Slater told the churchwardens not to interfere in Scully's pastoral decisions. [ 7 ]
Low donations from parishioners were a recurring problem. In 1821, the churchwardens attempted to raise funding for the parish by charging a fee for access to the sacraments. Scully continued to perform sacraments without their permission, and fired the sacristan when he attempted to interfere. [ 7 ]
Lord Charles Somerset , the governor of Cape Town, returned from leave in December 1821 and stopped Scully's salary. Scully therefore looked for work elsewhere, and that same year, Fearon Fallows , head of the Royal Observatory, Cape of Good Hope , wrote to John Barrow asking for approval to hire Scully as an assistant. Scully began work on 18 January 1822, and on 4 April 1822 the Board of Longitude sent their official approval for the decision to hire Scully at a salary of £100. [ 5 ] [ 9 ]
In a letter to Barrow, Fallows wrote of Scully: [ 9 ]
He is a person of gentlemanly manners, having received a good classical education & as much mathematical knowledge as is usually taught in Catholic Colleges ... he is of a tractable, mild and amiable disposition, never giving me a cross word, and withal desirous of improving himself in the knowledge of the various parts of Practical Astronomy.
Fallows also praised Scully in a letter to John Herschel , writing: [ 9 ]
Scully ... is a quiet, gentle, good natured man and does his best (which is saying a great deal) and can really now observe very well with the Transit Instrument. My friends in England will no doubt marvel in finding me speak well of a Catholic, and a priest too. Though I am as high church as any man and a sincere believer in the articles &c, our most excellent establishment, I cannot bring myself (with all the causistry I am master of) to think that a person may not be a good Catholic & astronomer at the same time. You need be under no alarm of conversion, for we have no opportunity of talking about the question being sufficiently employed in the day with reducing the observations & at night we are not likely to trouble ourselves about the matter.
Construction began on Scully's church on 28 October 1822. Due to continuing funding issues, Scully took out a number of loans in 1823 to fund the ongoing construction of the church. He never paid interest on these loans, and they were the subject of extensive litigation after his departure. In March 1824, he began to say Mass in the unfinished chapel. [ 7 ]
In July 1824, Fallows found Scully in bed with Fallows's 17-year-old maid. Due to the "improprieties" committed and the "violence of [Scully's] manner" when discovered, Fallows promptly dismissed Scully, who was also defrocked over the incident. [ 9 ] Scully left the colony for London on 11 July 1824, aboard the Venus . Upon his departure, he entrusted the church he had built to two curators. [ 5 ] He was succeeded as chaplain by Theodore Wagner. [ 6 ] Fallows asked the Admiralty to continue Scully's salary for six months after his dismissal, but the request was declined, and Scully was formally dismissed on 5 October 1824. [ 5 ] | https://en.wikipedia.org/wiki/Patrick_H._Scully |
Patrick Michael Grundy (16 November 1917, Yarmouth, Isle of Wight – 4 November 1959) was an English mathematician and statistician . He was one of the eponymous co-discoverers of the Sprague–Grundy function and its application to the analysis of a wide class of combinatorial games . [ 1 ]
Grundy received his secondary education from Malvern College , to which he had obtained a Major Scholarship in 1931, and from which he graduated in 1935. While there, he demonstrated his aptitude for mathematics by winning three prizes in that subject. After leaving school he entered Clare College, Cambridge , on a Foundation Scholarship, where he read for the Mathematical Tripos from 1936 to 1939, earning first class honours in Part II and a distinction in Part III .
The work for which he is best known appeared in his first paper, Mathematics and Games , first published in the Cambridge University Mathematical Society's magazine, Eureka in 1939, [ 2 ] and reprinted by the same magazine in 1964. [ 3 ] The main results of this paper were discovered independently by Grundy and by Roland Sprague , and had already been published by the latter in 1935. [ 4 ] The key idea is that of a function that assigns a non-negative integer to each position of a class of combinatorial games, now called impartial games , and which greatly assists in the identification of winning and losing positions, and of the winning moves from the former. The number assigned to a position by this function is called its Grundy value (or Grundy number), and the function itself is called the Sprague–Grundy function, in honour of its co-discoverers. [ 5 ] The procedures developed by Sprague and Grundy for using their function to analyse impartial games are collectively called Sprague–Grundy theory, and at least two different theorems concerning these procedures have been called Sprague–Grundy theorems. [ 6 ] The maximum number of colors used by a greedy coloring algorithm is called the Grundy number , also after this work on games, as its definition has some formal similarities with the Sprague–Grundy theory. [ 7 ]
In 1939 Grundy began research in algebraic geometry as a research student at the University of Cambridge , eventually specialising in the theory of ideals . In 1941 he won a Smith's Prize for an essay entitled On the theory of R-modules , and his first research paper in the area, A generalisation of additive ideal theory , was published in the following year. [ 8 ] In 1943 he was appointed to an assistant lectureship at the University College of Hull , which he left in 1944. He was awarded a Ph.D. from the University of Cambridge in 1945.
Shortly after the end of World War II, Grundy moved away from the field of algebra to take up work in statistics . In 1947 he began formal training in the latter discipline at the Rothamsted Experimental Station under a Ministry of Agriculture scholarship, graduating in 1949, when he then joined the permanent staff of the former organisation as an Experimental Officer. In 1951 he was promoted to Senior Experimental Officer. During his time at Rothamsted he performed most of his published statistical research, which included investigations of problems in the design and analysis of experiments , sampling , composition of animal populations, and fitting truncated distributions .
From 1954 to 1958 Grundy worked as a statistician at the National Institute for Educational Research. During this period, he collaborated with Michael Healy and D.H. Rees to extend Frank Yates 's work on cost–benefit analysis of experimentation. The results of this collaboration were reported in an influential paper, Economic choice of the amount of experimentation , published in series B of the Journal of the Royal Statistical Society in 1956. [ 9 ] In 1958 Grundy moved to a position in the Biometry Unit at Oxford. However, he retired from this position after only one term, due to ill health.
Early in 1959 Grundy married Hilary Taylor, a former colleague from the National Institute of Educational Research. Although his health then greatly improved throughout 1959, he was unfortunately killed in an accident in November of that year.
With the exception of the final item, this list is taken from Smith's obituary ( 1960 ). The first item is missing from Goddard's ( 1960 ) list, which is otherwise the same as Smith's. | https://en.wikipedia.org/wiki/Patrick_Michael_Grundy |
Patritumab deruxtecan ( U3-1402/ MK-1022 ) is an experimental antibody–drug conjugate developed by Merck and Daiichi Sankyo to treat non-small-cell lung cancer . [ 1 ] [ 2 ] [ 3 ] | https://en.wikipedia.org/wiki/Patritumab_deruxtecan |
Patrizia M. Gianni (born 1952) [ 1 ] is an Italian mathematician specializing in computer algebra . She is known for her early research on Gröbner bases including her discovery of the FGLM algorithm for changing monomial orderings in Gröbner bases, [ 2 ] and for her development of the components of the Axiom computer algebra system concerning polynomials and rational functions . [ 3 ]
Gianni is a professor of algebra in the mathematics department of the University of Pisa . [ 4 ] She earned a laurea from the University of Pisa, [ 3 ] and has worked for IBM Research as well as for the University of Pisa. [ 5 ]
This article about an Italian mathematician is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Patrizia_Gianni |
A patrocladogram is a cladistic branching pattern that has been precisely modified by use of patristic distances (i.e., divergences between lineages); a type of phylogram . [ 1 ] The patristic distance is defined as, "the number of apomorphic step changes separating two taxa on a cladogram," [ 2 ] and is used exclusively to determine the amount of divergence of a characteristic from a common ancestor. This means that cladistic and patristic distances are combined to construct a new tree using various phenetic algorithms . [ 3 ] The purpose of the patrocladogram in biological classification is to form a hypothesis about which evolutionary processes are actually involved before making a taxonomic decision. [ 4 ] Patrocladograms are based on biostatistics that include but are not limited to: parsimony , distance matrix , likelihood methods , and Bayesian probability . Some examples of genomically related data that can be used as inputs for these methods are: molecular sequences , whole genome sequences, gene frequencies, restriction sites , distance matrices, unique characters, mutations such as SNPs , and mitochondrial genome data.
Patrocladograms are graphs that assert hypotheses of similarity whereas phylogenetic trees are graphs that assert hypotheses of common ancestry . When a patrocladogram does not logically match with a comparable phylogenetic tree hypothesis it should not be used to define monophyletic groups. The usage of patrocladograms can skew interpretations of novel evolution or depict homologous traits as homoplastic . [ 5 ]
Most phylograms are saved in some variant of the Newick format such as: PAUP* , MEGA, Molecular Evolutionary Genetics Analysis , Clustal , PHYLIP , or Nexus file . These various versions of the Newick format can then be used as an input for patristic distances in patrocladogram formation. There are two widely used pieces of software ; one is used for analyzing patristic distance, and the other for creating a viewable patrocladogram.
See both programs below:
Patristic is a Java program that uses different tree files as input and computes their patristic distances. Patristic allows saving and editing those distances. Patristic provides different graphic views of the results as well as the possibility to save them in the CSV format for building graphics using Excel. [ 6 ]
RAMI uses branch lengths to create clusters which can then be visualized as a patrocladogram. [ 7 ]
This bioinformatics-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Patrocladogram |
Patronage in astronomy is an approach which one can use to examine the history of astronomy from a cultural standpoint. Rather than simply focusing on the findings and discoveries of individual astronomers, this approach emphasizes the importance of patronage in shaping the field of astronomy. [ 1 ]
An often overlooked dimension in the history of science , the patronage system and the realities that existed within such a system played an important role in the lives of many of science's icons and heroes. The history of astronomy in particular is filled with examples demonstrating the relationship between patron and client, including that of Galileo Galilei and his ties to the Medici family. Many historians have begun to examine the importance of examining scientific history through this relatively forgotten lens. Dr. Robert Smith, in an article examining patronage in the early history of NASA , begins with the assertion that “the history of space astronomy is usually written from the perspective of the remarkable scientific findings garnered by space astronomers and the ways these findings have enriched and guided new views of the universe.” [ 2 ] But, as Barker and Goldstein ensure, “following the groundbreaking work of Robert Westman and Richard S. Westfall , historians of astronomy and historians of science in general have come to appreciate the importance of patronage in understanding the development of science during the sixteenth and seventeenth centuries.” [ 3 ] As crucial as the many developments and findings of science's heroes are to the historiography of science, many historians, like Nicholas Jardine, Mario Biagioli, Richard Westfall and others, have sought to bring to light the issues of patronage within this discourse, and their works have looked to enrich the understandings of many of science's heroes, including Galileo Galilei, Johannes Kepler , and Tycho Brahe amongst others. Patronage cannot provide the lone solution to understanding the social history of the Scientific Revolution , as some figures in the movement “were not sustained by patronage, and it is not yet clear how many were so supported.” [ 4 ] Despite this, patronage “was perhaps the most pervasive institution of preindustrial society.” [ 5 ] Richard Westfall concludes:
Only now are scholars beginning to chart its course in the science of the age, and we have every reason to expect that it will prove to be very important there as well. I would like to suggest, that patronage, together with other practices that the age itself reveals to us, may be the avenue most likely to lead us into a fruitful social history of the Scientific Revolution, a movement to which the present generation of scholars has devoted itself extensively. In our investigations, it appears to me, we have allowed ourselves to be dominated excessively by concepts derived in the nineteenth century which are more applicable to that century and our own than to [the] [seventeenth] [century]... Efforts to impose them on the 17th century have appeared forced and largely barren, and I want to propose, not as a new dogmatism, but as a topic for discussion, the possibility that we need to come at the problem from a different angle, using seventeenth-century categories instead of nineteenth-century ones. Patronage was certainly a seventeenth-century category. [ 6 ]
The system of patronage in 16th- and early 17th-century astronomy was different from the modern definition of patronage. The system of patronage, in the context of Astronomers such as Galileo, Kepler, and Copernicus , was a complex system of relations held between such astronomers and other individuals of high social standing.
These relations allowed for the likes of Galileo to hold positions under such powerful people as the Medici family, granting him not only increased social status due to his relations with such high social ranks, but entry into these positions also allowed for the time and monies to work on scientific endeavors. As important as these relationships were for patrons such as Galileo, for reasons of gaining monies and higher social status, clients also found importance in patronage from the reciprocal nature of the relationship. Gifts to be bestowed upon clients, such as the Medici Stars given to the Medici family by Galileo (he named Jupiter's moons after the family upon his discovery of them) gave increased social splendor and honor to the recipients of such extravagance and rarity.
The courts where these patronage relationships played out would also contribute to the “cognitive legitimation of the new science by providing venues for the social legitimation of its practitioners, and this, in turn, boosted the epistemological status of their discipline.” [ 7 ] Although Patronage can be explained as a system of social connections and relationships amongst social elite and practitioners of what we now umbrella under the term science, it was actually a “set of dyadic relations between patrons and clients, each of them unique… [having] no institutions and little if any formal structure. [ 8 ] Patronage embodied no guarantees, and the “relation between patron and client was voluntary on both sides and subject always to disintegration” where past “performance counted only to the extent that it promised more in the future.” Westfall notes a “client's only claim on a patron was his capacity to illuminate further the magnificence of the man who recognized his value and encouraged him.” [ 9 ]
In his article titled The Places of Astronomy in Early-Modern Culture, Nicholas Jardine looks to examine how the system of patronage and the codes of courtly conduct shaped a new agenda for astronomy: the quest for the true world system. [ 10 ] Jardine begins his article by noting that astronomy “did not then make up a specialty or discipline in anything like the modern sense… rather, it comprised a whole series of practices widely diffused through the various social sites and strata.” [ 11 ] The focus of University teachings on astronomy was “predominantly practical and utilitarian, directed towards the calendrical, navigational, agricultural, and above all, medical applications of the subject… [p]lanetary models were on the whole considered as fictions devised for predictive purposes.” [ 12 ] But, during the course of the sixteenth century “there arose an entirely new kind of princely and aristocratic involvement in astronomy, an involvement in which astronomical observations, instruments, models, and ultimately world systems themselves became objects of courtly production, exchange, and competition.” Some notable places of this “new courtly culture of astronomy were the court of Landgraf Wilhelm IV of Hesse-Kassel , Tycho Brahe’s island of Hven (held in fief from Frederick II of Denmark ) and, some decades later, Rudo III’s imperial court at Prague, the Medici court and the papal court .” [ 13 ] By the later decades of the sixteenth century, in these places, as a consequence of astronomers utilizing the patronage system, a fair number of astronomers found themselves dining at princely tables “rather than seated below the salt at university feasts.” [ 14 ] Jardine divides the main sites of astronomy into university, court and city, and notes aspects of University such as appointments and curricula as “very often under direct or indirect court control: Wilhelm IV of Hesse-Kassel, for example, closely supervised appointments and the curriculum at his father’s new university of Marburg … [a]nd conversely, court mathematical appointments were often held concurrently with university posts or filled on university nomination.” [ 15 ] Further, Jardine argues that at “least in the court context, the model of stable, salary-based patron-client relationships is inappropriate… [r]ather, power and dependence arose out of mechanism of mutual recognition of status and honour, regulated by exchange of gifts, tokens, and services.” [ 16 ] He notes that in “such an ‘economy of honour’, princes often competed to secure the service of notable astronomers; and they, in turn, played patrons off against each other as they shifted and multiplied their allegiances... [in] [other] [words] patrons and clients collected and displayed each other. [ 17 ] Jardine observes how recent authors have noted ways in which the new cosmologies of the sixteenth century embodied courtly ideals. For example, “in his De rebus coelestibus of 1512 Giovanni Gioviano Pontano, secretary and ambrassador of the Aragonese rulers of Naples, projected into the heavens a court society, in which the planets dance to the tunes of their master, the Sun; much like how that at the Neapolitan court , as at many other European courts, the courtiers danced before their ruler on ceremonial occasions.” [ 18 ] Not merely the “forms of the new cosmologies , but the very quest for a true world system was”, Jardine believes, “a product of courtly ethos.” [ 19 ] He recalls that many recent historians “have emphasized the constitutive roles of gift exchange in the sixteenth-century court… [where] [g]ifts were displayed as symbolic representations of power and as object of erudite, often playful conversation- that is, in a somewhat later idiom, as ‘ conversation pieces ’.” [ 20 ] Often it was through the presentation of instruments, gift-books, and “discoveries in the case of astronomy- that positions of service at court were solicited and secured.” [ 21 ] Patronage relationships often helped both parties achieve social distinction, maintaining honor and mutual distinction, even after death; for example:
in 1592 Hieronymus Treutler, Professor of Law at the University of Marburg, delivered a funeral oration for Wilhelm IV of Hesse-Kassel. At the end of the oration Treutler turn[ed] to the Landgraf’s astronomical activities… prais[ing] him as a skilled practitioner and celebrat[ing] him as a patron who ha[d] emulated those great examples Julius Ceaser, patron of Sosigene’s reform of the calendar, and Alfonso the Wise. He [told] how the Landgraf’s clockmaker, Jost Bürgi , made a wonderful gilded globe , “which in accordance with the most exact observations exactly represented the motions not only of the planets, but of the entire firmament”. The Emperor Rudolf heard of the globe and requested that it and its maker be sent to him. “It is wonderful to relate”, declare[d] Treutler, “what pleasure this gave our Prince.” In return, the Emperor sent a personal thank-you letter, received just before the Landgraf’s death. [ 22 ]
Jardine notes that this “honourable exchange of tokens figures in the oration as the culmination of the Landgraf’s life. [ 23 ] Jardine also highlights a dispute between Tycho Brahe and Ursus where Ursus was accused of stealing a diagram of Tycho’s planetary ordering while at Hven. Tycho eventually brought in the help of Kepler, who wrote a detailed defence of Tycho’s claims to priority [ 24 ] Jardine contends that “in the course of these challenges and counter challenges Tycho and Kepler had redefined the object of the dispute in Tycho’s favour… [t]he claim to priority in the construction of a world system was not the starting point of this courtly duel, but its end-product… [being] so to speak, the final challenge.” [ 25 ] Upon recognition of these events, and looking through this interpretation, it seems “the very setting of the world system- a complete physically grounded model of the cosmos—as the goal of astronomy was a product of the competitive practices of courtly exchange of gifts and novelties.” [ 26 ] In conclusion, Jardine points that early modern astronomy was formed by its cultural settings, settings in which patronage played a significant part. Further, he suggests that the “courtly patronage of astronomy generated a new agenda for astronomy—specifically, the quest for the true and complete world system .” [ 27 ]
In his book, Galileo Courtier: The Practice of Science in the Culture of Absolutism, Mario Biagioli looks to shed light on the ways in which a society characterized by patronage relationships affected one of astronomy's, and modern science's, greatest heroes: Galileo Galilei. Biagioli looks to uncover aspects of Galileo's life by “vividly [presenting] the pioneer physicist to us through the active social relations he experienced with persons in the different courts with which he was connected.” [ 28 ]
The book reveals how Galileo “used patronage to obtain his teaching position in Pisa … [and] maneuvered his transfer from Padua to the “home court” of the Medicis... used contacts with Prince Cesi and other well-placed persons in Roman circles to become an Academian, and a person of influence, and how all of this turned to dust for Galileo, when he lost the patronage of Urban VIII , one of his two most special patrons”. [ 29 ] In a review of Biagioli's work, Larry Wolff noted Biagioli as demonstrating Galileo's legitimacy as a direct consequence of “his ‘career strategies’” and not just “his ‘cognitive attitudes’” and that Galileo is shown to be a master of attaining power and a seventeenth-century career in science [ 30 ] The book acknowledges that “gifts within the logic of patronage [explain] the role of spectacular scientific production in Galileo’s career… [in that he] needed to produce or discover things that could be used as gifts for his patrons” [ 31 ] Jardine adds, as Biagioli has shown, Galileo's gift to Cosimo II of his discovery of the satellites of Jupiter, transformed into emblems of Medici dynastic power, was a spectacularly successful instance. Through exchange of gifts, highly ritualized and often highly competitive, princes and nobles achieved social distinction, maintaining their honour and mutual recognition. [ 32 ]
Westman has observed “how in the preface to his De revolutionibus Copernicus appealed to Pope Paul III in a courtly, or rather curial, humanist language of clerical reform- promoting his new ordering of the planets as a restoration of lost order and harmony, and as a basis for the repair of the derelict calendar.” [ 33 ] Westman's “reading is strongly confirmed by the dedication to Paul III of another new ordering of the planetary motions, Fracastoro’s Homocentrica , in which the strategies of appeal to the humanist Pope are closely similar.” [ 34 ]
Westfall notes that, in the early modern period, the “word 'friend' carries special connotations within a context of patronage; authorities on patronage distinguish what they call instrumental friendship from emotional friendship… [for] [example] Galileo's "friends" in Venice appear to have understood that the "friendship" entailed the use of their connections and influence on his behalf. [ 35 ] In all of Galileo's attempts to rise up the ladder of Patronage, one of his connections, Sagredo , would write him words that Westfall considers “[o]ne would be hard pressed to find a better example of the language of patronage.” Westfall writes, “Sagredo, who was clearly tiring of the exercise, wanted to be sure that Galileo understood he had fulfilled his duty as a patron [in] [writing] ‘Since I have already satisfied abundantly enough the friendship I hold for you, the obligations to you which I acknowledge, and the favor and help that true gentlemen try to extend to the qualified who deserve it,’ he thought he might now honorably desist.” [ 36 ] Westfall also provides fantastic evidence directly from the mouth of Galileo as to the importance of Patronage to himself
and his scientific endeavors:
"Having labored now twenty years, the best ones of my life, in dispensing at retail, as the saying goes, at the demand of everyone, that little talent in my profession that God and my own efforts have given me, my desires would truly be to obtain enough leisure and quiet as would enable me before I die to complete three great works that I have in hand in order to be able to publish them, perhaps with some praise for me and for whoever has helped me in the business. ... It is not possible to receive a salary from a Republic , however splendid and generous, without serving the public, because to get something from the public one must satisfy it and not just one particular person; and while I remain able to teach and to serve, no one can exempt me from the burden while leaving me the income; and in sum I cannot hope for such a benefit from anyone but an absolute prince." [ 37 ]
Westfall describes that Galileo, upon discovering Jupiter’s moons, made sure to tantalize the Grand Duke of Tuscany, the position now held by Cosimo of the Medici family, with the honour of being attributed the award of such a discovery by means of them being named after him. As Westfall describes, “Galileo was sure he had found what he wanted, a ticket to Florence .” [ 38 ] Westfall describes that “[i]n a word, Galileo had raised himself with one inspired blow from the level of an obscure professor of mathematics at the University of Padua to the status of the most desirable client in Italy .” [ 39 ] Following the discovery of the Jupiter's moons, Galileo would then look to discover their periods ; due to ensuing competition and even some minimizing the importance of only discovering the moons without knowledge of their period, Galileo's “acknowledged position as the messenger from the heavens was threatened”. [ 40 ] Westfall also contends that evidence of Galileo's patterns of observing the sky suggest that “at the time Galileo began his celestial observations , he had not formulated a program of systematic observations designed to settle the Copernican issue .” [ 41 ] Rather, Westfall asserts:
[H]e saw the telescope more as an instrument of patronage than as an instrument of astronomy. When Galileo, having seized what the moon and stars could quickly offer, had turned his telescope on the next brightest object in the evening sky, Jupiter , early in January, Venus was visible in the predawn sky. For a Copernican, Venus was in a critical part of its orbit, past maximum elongation, approaching superior conjunction, and thus exhibiting a shape incompatible with the Ptolemaic system . As we have seen, however, Jupiter had offered something quite different, an incomparable present to the grand duke, and Galileo had not paused to look further. [ 42 ]
Westfall questions Galileo's commitment to Copernicanism , and instead views Galileo as being more concerned with finding discoveries that could help further his patronage relationship, and that Galileo was prepared to try to monopolize the telescope in order to do so. [ 43 ] | https://en.wikipedia.org/wiki/Patronage_in_astronomy |
A pattern is a regularity in the world, in human-made design, [ 1 ] or in abstract ideas. As such, the elements of a pattern repeat in a predictable manner. A geometric pattern is a kind of pattern formed of geometric shapes and typically repeated like a wallpaper design.
Any of the senses may directly observe patterns. Conversely, abstract patterns in science , mathematics , or language may be observable only by analysis. Direct observation in practice means seeing visual patterns, which are widespread in nature and in art. Visual patterns in nature are often chaotic , rarely exactly repeating, and often involve fractals . Natural patterns include spirals , meanders , waves , foams , tilings , cracks , and those created by symmetries of rotation and reflection . Patterns have an underlying mathematical structure; [ 2 ] : 6 indeed, mathematics can be seen as the search for regularities, and the output of any function is a mathematical pattern. Similarly in the sciences, theories explain and predict regularities in the world.
In many areas of the decorative arts , from ceramics and textiles to wallpaper , "pattern" is used for an ornamental design that is manufactured, perhaps for many different shapes of object. In art and architecture, decorations or visual motifs may be combined and repeated to form patterns designed to have a chosen effect on the viewer.
Nature provides examples of many kinds of pattern, including symmetries , trees and other structures with a fractal dimension, spirals , meanders , waves , foams , tilings , cracks and stripes. [ 3 ]
Symmetry is widespread in living things. Animals that move usually have bilateral or mirror symmetry as this favours movement. [ 2 ] : 48–49 Plants often have radial or rotational symmetry , as do many flowers, as well as animals which are largely static as adults, such as sea anemones . Fivefold symmetry is found in the echinoderms , including starfish , sea urchins , and sea lilies . [ 2 ] : 64–65
Among non-living things, snowflakes have striking sixfold symmetry : each flake is unique, its structure recording the varying conditions during its crystallisation similarly on each of its six arms. [ 2 ] : 52 Crystals have a highly specific set of possible crystal symmetries ; they can be cubic or octahedral , but cannot have fivefold symmetry (unlike quasicrystals ). [ 2 ] : 82–84
Spiral patterns are found in the body plans of animals including molluscs such as the nautilus , and in the phyllotaxis of many plants, both of leaves spiralling around stems, and in the multiple spirals found in flowerheads such as the sunflower and fruit structures like the pineapple . [ 4 ]
Chaos theory predicts that while the laws of physics are deterministic , there are events and patterns in nature that never exactly repeat because extremely small differences in starting conditions can lead to widely differing outcomes. [ 5 ] The patterns in nature tend to be static due to dissipation on the emergence process, but when there is interplay between injection of energy and dissipation there can arise a complex dynamic. [ 6 ] Many natural patterns are shaped by this complexity, including vortex streets , [ 7 ] other effects of turbulent flow such as meanders in rivers. [ 8 ] or nonlinear interaction of the system [ 9 ]
Waves are disturbances that carry energy as they move. Mechanical waves propagate through a medium – air or water, making it oscillate as they pass by. [ 10 ] Wind waves are surface waves that create the chaotic patterns of the sea. As they pass over sand, such waves create patterns of ripples; similarly, as the wind passes over sand, it creates patterns of dunes . [ 11 ]
Foams obey Plateau's laws , which require films to be smooth and continuous, and to have a constant average curvature . Foam and bubble patterns occur widely in nature, for example in radiolarians , sponge spicules , and the skeletons of silicoflagellates and sea urchins . [ 12 ] [ 13 ]
Cracks form in materials to relieve stress: with 120 degree joints in elastic materials, but at 90 degrees in inelastic materials. Thus the pattern of cracks indicates whether the material is elastic or not. Cracking patterns are widespread in nature, for example in rocks, mud, tree bark and the glazes of old paintings and ceramics. [ 14 ]
Alan Turing , [ 15 ] and later the mathematical biologist James D. Murray [ 16 ] and other scientists, described a mechanism that spontaneously creates spotted or striped patterns, for example in the skin of mammals or the plumage of birds: a reaction–diffusion system involving two counter-acting chemical mechanisms, one that activates and one that inhibits a development, such as of dark pigment in the skin. [ 17 ] These spatiotemporal patterns slowly drift, the animals' appearance changing imperceptibly as Turing predicted.
In visual art, pattern consists in regularity which in some way "organizes surfaces or structures in a consistent, regular manner." At its simplest, a pattern in art may be a geometric or other repeating shape in a painting , drawing , tapestry , ceramic tiling or carpet , but a pattern need not necessarily repeat exactly as long as it provides some form or organizing "skeleton" in the artwork. [ 18 ] In mathematics, a tessellation is the tiling of a plane using one or more geometric shapes (which mathematicians call tiles), with no overlaps and no gaps. [ 19 ]
In architecture, motifs are repeated in various ways to form patterns. Most simply, structures such as windows can be repeated horizontally and vertically (see leading picture). Architects can use and repeat decorative and structural elements such as columns , pediments , and lintels . [ 20 ] Repetitions need not be identical; for example, temples in South India have a roughly pyramidal form, where elements of the pattern repeat in a fractal -like way at different sizes. [ 21 ]
Language provides researchers in linguistics with a wealth of patterns to investigate, [ 22 ] and literary studies can investigate patterns in areas such as sound, grammar, motifs, metaphor, imagery, and narrative plot. [ 23 ]
Mathematics is sometimes called the "Science of Pattern", in the sense of rules that can be applied wherever needed. [ 24 ] For example, any sequence of numbers that may be modeled by a mathematical function can be considered a pattern. Mathematics can be taught as a collection of patterns. [ 25 ]
Gravity is a source of ubiquitous scientific patterns or patterns of observation. The rising and falling pattern of the sun each day results from the rotation of the earth while in orbit around the sun. Likewise, the moon's path through the sky is due to its orbit of the earth. These examples, while perhaps trivial, are examples of the "unreasonable effectiveness of mathematics" which obtain due to the differential equations whose application within physics function to describe the most general empirical patterns of the universe . [ 26 ]
Daniel Dennett 's notion of real patterns , discussed in his 1991 paper of the same name, [ 27 ] provides an ontological framework aiming to discern the reality of patterns beyond mere human interpretation, by examining their predictive utility and the efficiency they provide in compressing information. For example, centre of gravity is a real pattern because it allows the prediction of the movements of a bodies such as the earth around the sun, and it compresses all the information about all the particles in the sun and the earth that allows scientists to make those predictions.
Some mathematical rule-patterns can be visualised, and among these are those that explain patterns in nature including the mathematics of symmetry, waves, meanders, and fractals. Fractals are mathematical patterns that are scale-invariant. This means that the shape of the pattern does not depend on how closely you look at it. Self-similarity is found in fractals. Examples of natural fractals are coastlines and tree-shapes, which repeat their shape regardless of the magnification used by the viewer. While self-similar patterns can appear indefinitely complex, the rules needed to describe or produce their formation can be simple (e.g. Lindenmayer systems describing tree -shapes). [ 28 ]
In pattern theory , devised by Ulf Grenander , mathematicians attempt to describe the world in terms of patterns. The goal is to lay out the world in a more computationally-friendly manner. [ 29 ]
In the broadest sense, any regularity that can be explained by a scientific theory is a pattern. As in mathematics, science can be taught as a set of patterns. [ 30 ]
A 2021 study, "Aesthetics and Psychological Effects of Fractal Based Design", [ 31 ] suggested that
fractal patterns possess self-similar components that repeat at varying size scales. The perceptual experience of human-made environments can be impacted with inclusion of these natural patterns. Previous work has demonstrated consistent trends in preference for and complexity estimates of fractal patterns. However, limited information has been gathered on the impact of other visual judgments. Here we examine the aesthetic and perceptual experience of fractal 'global-forest' designs already installed in humanmade spaces and demonstrate how fractal pattern components are associated with positive psychological experiences that can be utilized to promote occupant wellbeing. These designs are composite fractal patterns consisting of individual fractal 'tree-seeds' which combine to create a 'global fractal forest.' The local 'tree-seed' patterns, global configuration of tree-seed locations, and overall resulting 'global-forest' patterns have fractal qualities. These designs span multiple mediums yet are all intended to lower occupant stress without detracting from the function and overall design of the space. In this series of studies, we first establish divergent relationships between various visual attributes, with pattern complexity, preference, and engagement ratings increasing with fractal complexity compared to ratings of refreshment and relaxation which stay the same or decrease with complexity. Subsequently, we determine that the local constituent fractal ('tree-seed') patterns contribute to the perception of the overall fractal design, and address how to balance aesthetic and psychological effects (such as individual experiences of perceived engagement and relaxation) in fractal design installations. This set of studies demonstrates that fractal preference is driven by a balance between increased arousal (desire for engagement and complexity) and decreased tension (desire for relaxation or refreshment). Installations of these composite mid-high complexity 'global-forest' patterns consisting of 'tree-seed' components balance these contrasting needs, and can serve as a practical implementation of biophilic patterns in human-made environments to promote occupant wellbeing.
Hazem's Pattern | https://en.wikipedia.org/wiki/Pattern |
Pattern-Oriented Software Architecture is a series of software engineering books describing software design patterns .
David E. DeLano of C++ Report praised the first volume, writing, "Overall this text is good and I recommend it as an addition to any collection of books on patterns." He said "some of the language and grammar usage feels awkward to the reader" and some of the book has "stiffness and flow problems". [ 1 ] Ian Graham reviewed the first volume in the Journal of Object-Oriented Programming . [ 2 ] DBMS columnist David S. Linthicum found the first volume to be "the best book on patterns for application architects", while Bin Yang of JavaWorld thought it had "many interesting architecture and design patterns". [ 3 ] [ 4 ]
ACCU writer Ian Glassborow reviewed the second volume, writing, "This book is one of the more important contributions to the literature on 'patterns' and deserves to become a standard text on its specified area of interest." [ 5 ] The Software Engineering Institute author Paul Clemente found the first two volumes to be "the best-known catalog of architectural patterns". [ 6 ] Regarding the third volume, D. Murali recommended that software engineers should follow the "eager acquisition" pattern. [ 7 ]
Architectural patterns
Design patterns
Service access and configuration patterns
Event handling patterns
Synchronization patterns
Concurrency patterns
Resource acquisition
Resource lifecycle
Resource release
Software architecture
Distribution Infrastructure
Adaptation and execution
Resource management
Database access
Patterns referenced in volume 5:
This article about a software book or series of books is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Pattern-Oriented_Software_Architecture |
Collective intelligence Collective action Self-organized criticality Herd mentality Phase transition Agent-based modelling Synchronization Ant colony optimization Particle swarm optimization Swarm behaviour
Social network analysis Small-world networks Centrality Motifs Graph theory Scaling Robustness Systems biology Dynamic networks
Evolutionary computation Genetic algorithms Genetic programming Artificial life Machine learning Evolutionary developmental biology Artificial intelligence Evolutionary robotics
Reaction–diffusion systems Partial differential equations Dissipative structures Percolation Cellular automata Spatial ecology Self-replication
Conversation theory Entropy Feedback Goal-oriented Homeostasis Information theory Operationalization Second-order cybernetics Self-reference System dynamics Systems science Systems thinking Sensemaking Variety
Ordinary differential equations Phase space Attractors Population dynamics Chaos Multistability Bifurcation
Rational choice theory Bounded rationality
The science of pattern formation deals with the visible, ( statistically ) orderly outcomes of self-organization and the common principles behind similar patterns in nature .
In developmental biology , pattern formation refers to the generation of complex organizations of cell fates in space and time. The role of genes in pattern formation is an aspect of morphogenesis , the creation of diverse anatomies from similar genes, now being explored in the science of evolutionary developmental biology or evo-devo. The mechanisms involved are well seen in the anterior-posterior patterning of embryos from the model organism Drosophila melanogaster (a fruit fly), one of the first organisms to have its morphogenesis studied, and in the eyespots of butterflies, whose development is a variant of the standard (fruit fly) mechanism.
Examples of pattern formation can be found in biology, physics, and science, [ 1 ] and can readily be simulated with computer graphics, as described in turn below.
Biological patterns such as animal markings , the segmentation of animals, and phyllotaxis are formed in different ways. [ 2 ]
In developmental biology , pattern formation describes the mechanism by which initially equivalent cells in a developing tissue in an embryo assume complex forms and functions. [ 3 ] Embryogenesis , such as of the fruit fly Drosophila , involves coordinated control of cell fates . [ 4 ] [ 5 ] [ 6 ] Pattern formation is genetically controlled, and often involves each cell in a field sensing and responding to its position along a morphogen gradient, followed by short distance cell-to-cell communication through cell signaling pathways to refine the initial pattern. In this context, a field of cells is the group of cells whose fates are affected by responding to the same set positional information cues. This conceptual model was first described as the French flag model in the 1960s. [ 7 ] [ 8 ] More generally, the morphology of organisms is patterned by the mechanisms of evolutionary developmental biology , such as changing the timing and positioning of specific developmental events in the embryo. [ 9 ]
Possible mechanisms of pattern formation in biological systems include the classical reaction–diffusion model proposed by Alan Turing [ 10 ] and the more recently found elastic instability mechanism which is thought to be responsible for the fold patterns on the cerebral cortex of higher animals, among other things. [ 11 ] [ 12 ]
Bacterial colonies show a large variety of patterns formed during colony growth. The resulting shapes depend on the growth conditions. In particular, stresses (hardness of the culture medium, lack of nutrients, etc.) enhance the complexity of the resulting patterns. [ 13 ] Other organisms such as slime moulds display remarkable patterns caused by the dynamics of chemical signaling. [ 14 ] Cellular embodiment (elongation and adhesion) can also have an impact on the developing patterns. [ 15 ]
Vegetation patterns such as tiger bush [ 16 ] and fir waves [ 17 ] form for different reasons. Tiger bush consists of stripes of bushes on arid slopes in countries such as Niger where plant growth is limited by rainfall. Each roughly horizontal stripe of vegetation absorbs rainwater from the bare zone immediately above it. [ 16 ] In contrast, fir waves occur in forests on mountain slopes after wind disturbance, during regeneration. When trees fall, the trees that they had sheltered become exposed and are in turn more likely to be damaged, so gaps tend to expand downwind. Meanwhile, on the windward side, young trees grow, protected by the wind shadow of the remaining tall trees. [ 17 ] In flat terrains additional pattern morphologies appear besides stripes - hexagonal gap patterns and hexagonal spot patterns. Pattern formation in this case is driven by positive feedback loops between local vegetation growth and water transport towards the growth location. [ 18 ] [ 19 ]
Pattern formation has been well studied in chemistry and chemical engineering, including both temperature and concentration patterns. [ 20 ] The Brusselator model developed by Ilya Prigogine and collaborators is one such example that exhibits Turing instability . [ 21 ] Pattern formation in chemical systems often involve oscillatory chemical kinetics or autocatalytic reactions [ 22 ] such as Belousov–Zhabotinsky reaction or Briggs–Rauscher reaction . In industrial applications such as chemical reactors, pattern formation can lead to temperature hot spots which can reduce the yield or create hazardous safety problems such as a thermal runaway . [ 23 ] [ 20 ] The emergence of pattern formation can be studied by mathematical modeling and simulation of the underlying reaction-diffusion system . [ 20 ] [ 22 ]
Similarly as in chemical systems, patterns can develop in a weakly ionized plasma of a positive column of a glow discharge. In such cases creation and annihilation of charged particles due to collisions of atoms corresponds to reactions in chemical systems. Corresponding processes are essentially non-linear and lead in a discharge tube to formation of striations with regular or random character. [ 24 ] [ 25 ]
When a planar body of fluid under the influence of gravity is heated from below, Rayleigh-Bénard convection can form organized cells in hexagons or other shapes. These patterns form on the surface of the Sun and in the mantle of the Earth as well as during more pedestrian processes. The interaction between rotation, gravity, and convection can cause planetary atmospheres to form patterns, as is seen in Saturn's hexagon and the Great Red Spot and stripes of Jupiter . The same processes cause ordered cloud formations on Earth, such as stripes and rolls .
In the 1980s Lugiato and Lefever developed a model of light propagation in an optical cavity that results in pattern formation by the exploitation of nonlinear effects.
Precipitating and solidifying materials can crystallize into intricate patterns, such as those seen in snowflakes and dendritic crystals .
Sphere packings and coverings. Mathematics underlies the other pattern formation mechanisms listed.
Some types of automata have been used to generate organic-looking textures for more realistic shading of 3d objects . [ 26 ] [ 27 ]
A popular Photoshop plugin, KPT 6 , included a filter called 'KPT reaction'. Reaction produced reaction–diffusion style patterns based on the supplied seed image.
A similar effect to the 'KPT reaction' can be achieved with convolution functions in digital image processing , with a little patience, by repeatedly sharpening and blurring an image in a graphics editor. If other filters are used, such as emboss or edge detection , different types of effects can be achieved.
Computers are often used to simulate the biological, physical or chemical processes that lead to pattern formation, and they can display the results in a realistic way. Calculations using models like reaction–diffusion or MClone are based on the actual mathematical equations designed by the scientists to model the studied phenomena. | https://en.wikipedia.org/wiki/Pattern_formation |
Pattern gardening is a method of designing gardens influenced by the concepts of design pattern and pattern language originated by Christopher Alexander . It reflects the archetypal patterns of garden making, based on proportions and how the senses react. Patterns give coherence to garden design and communicate creativity and aesthetics.
Specific elements are instinctively looked for in a garden. Working with these elements is the basis for all good garden design. Each such element, or pattern, is archetypal, and therefore any pattern can be easily adapted to any garden situation. The fourteen pattern elements are: | https://en.wikipedia.org/wiki/Pattern_gardening |
A pattern language is an organized and coherent set of patterns , each of which describes a problem and the core of a solution that can be used in many ways within a specific field of expertise. The term was coined by architect Christopher Alexander and popularized by his 1977 book A Pattern Language .
A pattern language can also be an attempt to express the deeper wisdom of what brings aliveness within a particular field of human endeavor, through a set of interconnected patterns. Aliveness is one placeholder term for "the quality that has no name": a sense of wholeness, spirit, or grace, that while of varying form, is precise and empirically verifiable. [ 1 ] Alexander claims that ordinary people can use this design approach to successfully solve very large, complex design problems.
When a designer designs something – whether a house, computer program, or lamp – they must make many decisions about how to solve problems. A single problem is documented with its typical place (the syntax ), and use (the grammar ) with the most common and recognized good solution seen in the wild, like the examples seen in dictionaries . Each such entry is a single design pattern . Each pattern has a name, a descriptive entry, and some cross-references, much like a dictionary entry. A documented pattern should explain why that solution is good in the pattern's contexts.
Elemental or universal patterns such as "door" or "partnership" are versatile ideals of design, either as found in experience or for use as components in practice, explicitly described as holistic resolutions of the forces in recurrent contexts and circumstances, whether in architecture, medicine, software development or governance, etc. Patterns might be invented or found and studied, such as the naturally occurring patterns of design that characterize human environments. [ 2 ]
Like all languages, a pattern language has vocabulary , syntax , and grammar – but a pattern language applies to some complex activity other than communication. In pattern languages for design, the parts break down in this way:
This simplifies the design work because designers can start the process from any part of the problem they understand and work toward the unknown parts. At the same time, if the pattern language has worked well for many projects, there is reason to believe that even a designer who does not completely understand the design problem at first will complete the design process, and the result will be usable. For example, skiers coming inside must shed snow and store equipment. The messy snow and boot cleaners should stay outside. The equipment needs care, so the racks should be inside.
Just as words must have grammatical and semantic relationships to each other in order to make a spoken language useful, design patterns must be related to each other in position and utility order to form a pattern language. Christopher Alexander's work describes a process of decomposition, in which the designer has a problem (perhaps a commercial assignment), selects a solution, then discovers new, smaller problems resulting from the larger solution. Occasionally, the smaller problems have no solution, and a different larger solution must be selected. Eventually all of the remaining design problems are small enough or routine enough to be solved by improvisation by the builders, and the "design" is done.
The actual organizational structure ( hierarchical , iterative , etc.) is left to the discretion of the designer, depending on the problem. This explicitly lets a designer explore a design, starting from some small part. When this happens, it's common for a designer to realize that the problem is actually part of a larger solution. At this point, the design almost always becomes a better design.
In the language, therefore, each pattern has to indicate its relationships to other patterns and to the language as a whole. This gives the designer using the language a great deal of guidance about the related problems that must be solved.
The most difficult part of having an outside expert apply a pattern language is in fact to get a reliable, complete list of the problems to be solved. Of course, the people most familiar with the problems are the people that need a design. So, Alexander famously advocated on-site improvisation by concerned, empowered users, [ 3 ] [ 4 ] as a powerful way to form very workable large-scale initial solutions, maximizing the utility of a design, and minimizing the design rework. The desire to empower users of architecture was, in fact, what led Alexander to undertake a pattern language project for architecture in the first place.
An important aspect of design patterns is to identify and document the key ideas that make a good system different from a poor system (that may be a house, a computer program or an object of daily use), and to assist in the design of future systems. The idea expressed in a pattern should be general enough to be applied in very different systems within its context, but still specific enough to give constructive guidance.
The range of situations in which the problems and solutions addressed in a pattern apply is called its context. An important part in each pattern is to describe this context. Examples can further illustrate how the pattern applies to very different situation.
For instance, Alexander's pattern "A PLACE TO WAIT" addresses bus stops in the same way as waiting rooms in a surgery, while still proposing helpful and constructive solutions. The "Gang-of-Four" book Design Patterns by Gamma et al. proposes solutions that are independent of the programming language, and the program's application domain.
Still, the problems and solutions described in a pattern can vary in their level of abstraction and generality on the one side, and specificity on the other side. In the end this depends on the author's preferences. However, even a very abstract pattern will usually contain examples that are, by nature, absolutely concrete and specific.
Patterns can also vary in how far they are proven in the real world. Alexander gives each pattern a rating by zero, one or two stars, indicating how well they are proven in real-world examples. It is generally claimed that all patterns need at least some existing real-world examples. It is, however, conceivable to document yet unimplemented ideas in a pattern-like format.
The patterns in Alexander's book also vary in their level of scale – some describing how to build a town or neighbourhood, others dealing with individual buildings and the interior of rooms. Alexander sees the low-scale artifacts as constructive elements of the large-scale world, so they can be connected to a hierarchic network .
A pattern must characterize the problems that it is meant to solve, the context or situation where these problems arise, and the conditions under which the proposed solutions can be recommended.
Often these problems arise from a conflict of different interests or "forces". A pattern emerges as a dialogue that will then help to balance the forces and finally make a decision.
For instance, there could be a pattern suggesting a wireless telephone. The forces would be the need to communicate, and the need to get other things done at the same time (cooking, inspecting the bookshelf). A very specific pattern would be just "WIRELESS TELEPHONE". More general patterns would be "WIRELESS DEVICE" or "SECONDARY ACTIVITY", suggesting that a secondary activity (such as talking on the phone, or inspecting the pockets of your jeans) should not interfere with other activities.
Though quite unspecific in its context, the forces in the "SECONDARY ACTIVITY" pattern are very similar to those in "WIRELESS TELEPHONE". Thus, the competing forces can be seen as part of the essence of a design concept expressed in a pattern.
Usually a pattern contains a rationale referring to some given values. For Christopher Alexander, it is most important to think about the people who will come in contact with a piece of architecture. One of his key values is making these people feel more alive. He talks about the "quality without a name" (QWAN).
More generally, we could say that a good system should be accepted, welcomed and happily embraced as an enrichment of daily life by those who are meant to use it, or – even better – by all people it affects. For instance, when discussing a street café, Alexander discusses the possible desires of a guest, but also mentions people who just walk by.
The same thinking can be applied to technical devices such as telephones and cars, to social structures like a team working on a project, or to the user interface of a computer program. The qualities of a software system, for instance, could be rated by observing whether users spend their time enjoying or struggling with the system.
By focusing on the impacts on human life, we can identify patterns that are independent from changing technology, and thus find "timeless quality" (Alexander).
Usually the author of a pattern language or collection chooses a generic structure for all the patterns it contains, breaking each into generic sections like context, problem statement, solution etc.
Christopher Alexander's patterns, for instance, each consist of a short name, a rating (up to two '*' symbols), a sensitizing picture, the context description, the problem statement, a longer part of text with examples and explanations, a solution statement, a sketch and further references. This structure and layout is sometimes referred to as the "Alexandrian form".
Alexander uses a special text layout to mark the different sections of his patterns. For instance, the problem statement and the solution statement are printed in bold font, the latter is always preceded by the "Therefore:" keyword. Some authors instead use explicit labels, which creates some degree of redundancy.
When design is done by a team, pattern names will form a vocabulary they can share. This makes it necessary for pattern names to be easy to remember and highly descriptive. Some examples from Alexander's works are WINDOW PLACE (helps define where windows should go in a room) and A PLACE TO WAIT (helps define the characteristics of bus stops and hospital waiting rooms, for example).
A pattern language, as conceived by Alexander, contains links from one pattern to another, so when trying to apply one pattern in a project, a designer is pushed to other patterns that are considered helpful in its context.
In Alexander's book, such links are collected in the "references" part, and echoed in the linked pattern's "context" part – thus the overall structure is a directed graph . A pattern that is linked to in the "references" usually addresses a problem of lower scale, that is suggested as a part of the higher-scale problem. For instance, the "PUBLIC OUTDOOR ROOM" pattern has a reference to "STAIR SEATS".
Even without the pattern description, these links, along with meaningful names, carry a message: When building a place outside where people can spend time ("PUBLIC OUTDOOR ROOM"), consider to surround it by stairs where people can sit ("STAIR SEATS"). If you are planning an office ("WORKSHOPS AND OFFICES"), consider to arrange workspaces in small groups ("SMALL WORKING GROUPS"). Alexander argues that the connections in the network can be considered even more meaningful than the text of the patterns themselves.
The links in Alexander's book clearly result in a hierarchic network. Alexander draws a parallel to the hierarchy of a grammar – that is one argument for him to speak of a pattern language .
The idea of linking is generally accepted among pattern authors, though the semantic rationale behind the links may vary. Some authors, however, like Gamma et al. in Design Patterns , make only little use of pattern linking – possibly because it did not make that much sense for their collection of patterns. In such a case we would speak of a pattern catalogue rather than a pattern language . [ 5 ]
Alexander encouraged people who used his system to expand his language with patterns of their own. In order to enable this, his books do not focus strictly on architecture or civil engineering; he also explains the general method of pattern languages. The original concept for the book A Pattern Language was that it would be published in the form of a 3-ring binder, so that pages could easily be added later; this proved impractical in publishing. [ 6 ] The pattern language approach has been used to document expertise in diverse fields. Some examples are architectural patterns , computer science patterns , interaction design patterns , pedagogical patterns , pattern gardening , social action patterns, and group facilitation patterns. The pattern language approach has also been recommended as a way to promote civic intelligence by helping to coordinate actions for diverse people and communities who are working together on significant shared problems. [ 7 ] Alexander's specifications for using pattern languages as well as creating new ones remain influential, and his books are referenced for style by experts in unrelated fields.
It is important to note that notations such as UML or the flowchart symbol collection are not pattern languages. They could more closely be compared to an alphabet: their symbols could be used to document a pattern language, but they are not a language by themselves. A recipe or other sequential set of steps to be followed, with only one correct path from start to finish, is also not a pattern language. However, the process of designing a new recipe might benefit from the use of a pattern language.
Christopher Alexander , an architect and author, coined the term pattern language. [ 3 ] He used it to refer to common problems of the design and construction of buildings and towns and how they should be solved. The solutions proposed in the book include suggestions ranging from how cities and towns should be structured to where windows should be placed in a room.
The framework and philosophy of the "pattern language" approach was initially popularized in the book A Pattern Language that was written by Christopher Alexander and five colleagues at the Center for Environmental Structure in Berkeley, California in the late 1970s. While A Pattern Language contains 253 "patterns" from the first pattern, "Independent Regions" (the most general) to the last, "Things from Your Life", Alexander's book The Timeless Way of Building goes into more depth about the motivation and purpose of the work. The following definitions of "pattern" and "pattern language" are paraphrased from A Pattern Language : [ 3 ]
"A pattern is a careful description of a perennial solution to a recurring problem within a building context, describing one of the configurations that brings life to a building. Each pattern describes a problem that occurs over and over again in our environment, and then describes the core solution to that problem, in such a way that you can use the solution a million times over, without ever doing it the same way twice." [ 3 ]
A pattern language is a network of patterns that call upon one another. Patterns help us remember insights and knowledge about design and can be used in combination to create solutions.
Christopher Alexander's idea has been adopted in other disciplines, often much more heavily than the original application of patterns to architecture as depicted in the book A Pattern Language . [ 3 ] Examples since the 1990s include software design patterns in software engineering and, more generally, architectural patterns in computer science , as well as interaction design patterns . Since the late 1990s, pedagogical patterns have been used to document good practices in teaching. [ 8 ] Since at least the mid-2000s, the idea of pattern language was introduced into systems architecture design [ 9 ] [ 10 ] and Design science (methodology) patterns in a book authored by Vijay Vaishnavi and William Kuechler with 66 patterns; [ 11 ] the second revised and expanded edition of this book has been published in 2015 with 84 patterns. [ 12 ] The book Liberating Voices: A Pattern Language for Communication Revolution , containing 136 patterns for using information and communication to promote sustainability, democracy and positive social change, was published in 2008 along with a website containing even more patterns. [ 13 ] The deck "Group Works: A Pattern Language for Bringing Life to Meetings and Other Gatherings" was published in 2011. [ 14 ] The idea of a pattern language has also been applied in permaculture design. [ 15 ]
Ward Cunningham , the inventor of wiki , coauthored a paper with Michael Mehaffy arguing that there are deep relationships between wikis and pattern languages, and that wikis "were in fact developed as tools to facilitate efficient sharing and modifying of patterns". [ 16 ] | https://en.wikipedia.org/wiki/Pattern_language |
Patterned vegetation is a vegetation community that exhibits distinctive and repetitive patterns. Examples of patterned vegetation include fir waves , tiger bush , and string bog . The patterns typically arise from an interplay of phenomena that differentially encourage plant growth or mortality. A coherent pattern arises because there is a strong directional component to these phenomena, such as wind in the case of fir waves, or surface runoff in the case of tiger bush. Patterns can include relatively evenly spaced patches, parallel bands, or some intermediate between those two. These patterns in the vegetation can appear without any underlying pattern in soil types, and are thus said to "self-organize" rather than be determined by the environment.
Several of the mechanisms underlying patterning of vegetation have been known and studied since at least the middle of the 20th century, [ 1 ] however, mathematical models replicating them have only been produced much more recently. Self-organization in spatial patterns is often a result of spatially uniform states becoming unstable through the monotonic growth and amplification of nonuniform perturbations. [ 2 ] A well-known instability of this kind leads to so-called Turing patterns . These patterns occur at many scales of life, from cellular development (where they were first proposed) to pattern formation on animal pelts to sand dunes and patterned landscapes (see also pattern formation ). In their simplest form models that capture Turing instabilities require two interactions at differing scales: local facilitation and more distant competition. For example, when Sato and Iwasa [ 3 ] produced a simple model of fir waves in the Japanese Alps, they assumed that trees exposed to cold winds would suffer mortality from frost damage, but upwind trees would protect nearby downwind trees from wind. Banding appears because the protective boundary layer created by the wind-most trees is eventually disrupted by turbulence, exposing more distant downwind trees to freezing damage once again.
When there is no directional resource flow across the landscape, spatial patterns may still appear in various regular and irregular forms along the rainfall gradient, including, in particular, hexagonal gap patterns at relatively high rainfall rates, stripe patterns at intermediate rates, and hexagonal spot patterns at low rates. [ 4 ] The presence of a clear directionality to some important factor (such as a freezing wind or surface flow down a slope) favors the formation of stripes (bands), oriented perpendicular to the flow direction, in wider ranges of rainfall rates.
Several mathematical models have been published that reproduce a wide variety of patterned landscapes, including semi-arid "tiger bush", [ 5 ] [ 6 ] hexagonal "fairy-circle" gap-patterns, [ 7 ] woody-herbaceous landscapes, [ 8 ] salt marshes, [ 9 ] fog-dependent desert vegetation, [ 10 ] and mires and fens. [ 11 ]
Although not strictly vegetation, sessile marine invertebrates such as mussels and oysters, have also been shown to form banding patterns. [ 12 ] | https://en.wikipedia.org/wiki/Patterned_vegetation |
A patternmaker is a skilled worker who produces patterns on paper or fabric for use in the clothing industry.
Apparel patternmakers draft patterns based on a designer's sketch of a style. The designer gives the sketch to the patternmaker, who can ask questions to determine details the designer is looking for. [ 1 ]
Patterns may be drafted on paper or in a computer program designed for patternmaking. Most of the time, in modern American samplerooms, the patternmaker pulls an existing pattern (or block) and makes a modified copy of it to match the new style, either on paper or on computer. If the style is completely new, the patternmaker will usually drape a rough draft in muslin fabric on a dress form, then show it to the designer to discuss any changes before transferring the markings to paper to create the pattern for cutting. Patterns may also be drafted from measurements, this method can also produce well fitting garments as long as the patternmaker has a good handle on shapes and balance. Patternmakers are also asked to copy existing garments without damaging them. This is a common practice in American samplerooms.
Patternmakers have a combination of engineering and design skill. They need to be able to understand what the designer wants, and translate that into the lines of a pattern that will cause the garment to fit correctly. Ideally, the pattern captures not only the fit, but also the flair intended by the designer.
Patternmaking is taught in conjunction with fashion design education, as it is vital for designers to understand the apparel development process. It is also taught as a major at certain trade schools. There are many books on the subject, but it is rare for a patternmaker to become a professional through teaching oneself. Apprenticeships are almost unheard of in modern America, but would serve well to improve the transition from student to professional status. Because this occupation is relatively unknown outside of the apparel industry, there is a serious lack of patternmakers who can accurately interpret designs in Los Angeles , and possibly other fashion capitals. | https://en.wikipedia.org/wiki/Patternmaker_(clothing) |
Ants are simple animals and their behavioural repertory is limited to somewhere between ten and forty elementary behaviours. This is an attempt to explain the different patterns of self-organization in ants . [ 1 ]
Ant colonies are self-organized systems: complex collective behaviors arise as the product of interactions between many individuals each following a simple set of rules, not via top-down instruction from elite individuals or the queen. No one worker has universal knowledge of the colony's needs; individual workers react only to their local environment. Because of this, ants are a popular source of inspiration for design in software engineering, robotics, industrial design, and other fields involving many simple parts working together to perform complex tasks. [ 2 ]
The most popular current model of self-organization in ants and other social insects is the response threshold model. A threshold for a particular task is the amount of stimulus, such as a pheromone or interactions with other workers, necessary to cause the worker to perform the associated task. A higher threshold requires a stronger stimulus, and thus translates into less preference for performing a specific task. Different workers have different thresholds for different tasks, allowing certain workers to function as specialists that preferentially perform one or more tasks. Threshold levels can be affected by several factors: worker age, since workers frequently switch from within-nest work to outside-nest work with age; [ 3 ] size, since larger workers often perform different tasks, such as defense or seed processing; caste; health, since injuries can encourage young workers to switch to outside-nest work earlier; [ 3 ] or be randomly distributed. As demand for a task increases, so does the proportion of workers whose thresholds are met; as demand decreases, fewer workers' thresholds are met and fewer workers are allocated to that task. In this way, simple individual rules allow for the regulation of work on a large scale in diverse settings. This system can also evolve in response to different environments and life history strategies, leading to the immense variation observed in ants.
This is an instant transition of the whole system to a new stable pattern when a threshold is reached. Bifurcation is also known as multi-stability in which many stable states are possible. [ 4 ]
Examples of pattern types:
Oscillating patterns of activity in which individuals at different activity levels stimulate one another emerging from mutual activation. [ 4 ]
Examples of pattern types:
Traveling waves of chemical concentration or mechanical deformation. [ 4 ]
Examples of pattern types:
Self-organized criticality is an abrupt disturbance in a system resulting from a buildup of events without external stimuli. [ 4 ]
Examples of pattern types: | https://en.wikipedia.org/wiki/Patterns_of_self-organization_in_ants |
The Patterson function is used to solve the phase problem in X-ray crystallography . It was introduced in 1935 by Arthur Lindo Patterson while he was a visiting researcher in the laboratory of Bertram Eugene Warren at MIT . [ 1 ] [ 2 ]
The Patterson function is defined as
P ( u , v , w ) = ∑ h , k , ℓ ∈ Z | F h , k , ℓ | 2 e − 2 π i ( h u + k v + ℓ w ) . {\displaystyle P(u,v,w)=\sum _{h,k,\ell \in \mathbb {Z} }\left|F_{h,k,\ell }\right|^{2}\;e^{-2\pi i(hu+kv+\ell w)}.}
It is essentially the Fourier transform of the intensities rather than the structure factors . The Patterson function is also equivalent to the electron density convolved with its inverse:
Furthermore, a Patterson map of N points will have N ( N − 1) peaks, excluding the central (origin) peak and any overlap.
The peaks' positions in the Patterson function are the interatomic distance vectors and the peak heights are proportional to the product of the number of electrons in the atoms concerned.
Because for each vector between atoms i and j there is an oppositely oriented vector of the same length (between atoms j and i ), the Patterson function always has centrosymmetry .
Consider the series of delta functions given by
The Patterson function is given by the following series of delta functions and unit step functions | https://en.wikipedia.org/wiki/Patterson_function |
The Patterson power cell is a cold fusion device invented by chemist James A. Patterson, [ 1 ] which he claimed created 200 times more energy than it used. [ 2 ] Patterson claimed the device neutralized radioactivity without emitting any harmful radiation. [ 1 ] Cold fusion was the subject of an intense scientific controversy in 1989, before being discredited in the eyes of mainstream science. [ 3 ] [ 4 ] Physicist Robert L. Park describes the device as fringe science in his book Voodoo Science . [ 1 ]
In 1995, Clean Energy Technologies Inc. was formed to produce and promote the power cell. [ 6 ]
Patterson variously said it produced a hundred or two hundred times more power than it used. [ 2 ] [ 7 ] Representatives promoting the device at the Power-Gen '95 Conference said that an input of 1 watt would generate more than 1,000 watts of excess heat ( waste heat ). [ 8 ] This supposedly happened as hydrogen or deuterium nuclei fuse together to produce heat through a form of low energy nuclear reaction . [ 1 ] The by-products of nuclear fusion, e.g. a tritium nucleus and a proton or an 3 He nucleus and a neutron , were not detected in any reliable way, leading experts to think that no such fusion was taking place. [ 3 ]
It was further claimed that if radioactive isotopes such as uranium were present, the cell enables the hydrogen nuclei to fuse with these isotopes, transforming them into stable elements and thus neutralizing the radioactivity. It was claimed that the transformation would be achieved without releasing any radiation to the environment and without expending any energy. [ 1 ] A televised demonstration on June 11, 1997, on Good Morning America provided no proof for the claims. [ 1 ] As at 2002, the neutralization of radioactive isotopes has only been achieved through intense neutron bombardment in a nuclear reactor or large scale high energy particle accelerator , and at a large expense of energy. [ 1 ]
Patterson has carefully distanced himself from the work of Fleischmann and Pons and from the label of "cold fusion", due to the negative connotations associated to them since 1989. [ 3 ] [ 9 ] Ultimately, this effort was unsuccessful, and not only did it inherit the label of pathological science , but it managed to make cold fusion look a little more pathological in the public eye. [ 10 ] Some cold fusion proponents view the cell as a confirmation of their work, while critics see it as "the fringe of the fringe of cold fusion research", since it attempts to commercialize cold fusion on top of making bad science. [ 11 ]
In 2002, John R. Huizenga , professor of nuclear chemistry at the University of Rochester, who was head of a government panel convened in 1989 to investigate the cold fusion claims of Fleischmann and Pons, and who wrote a book about the controversy, said "I would be willing to bet there's nothing to it", when asked about the Patterson Power Cell. [ 1 ]
George H. Miley is a professor of nuclear engineering and a cold fusion researcher who claims to have replicated the Patterson power cell. During the 2011 World Green Energy Symposium, Miley stated that his device continuously produces several hundred watts of power. [ 12 ] Earlier results by Miley have not convinced researchers. [ 3 ]
On Good Morning America , Quintin Bowles, professor of mechanical engineering at the University of Missouri–Kansas City , claimed in 1996 to have successfully replicated the Patterson power cell. [ 13 ] In the book Voodoo Science , Bowles is quoted as having stated: "It works, we just don't know how it works." [ 1 ]
A replication has been attempted at Earthtech, using a CETI supplied kit. They were not able to replicate the excess heat . [ 14 ] | https://en.wikipedia.org/wiki/Patterson_power_cell |
Pattinson's process or pattinsonisation is a method for removing silver from lead , discovered by Hugh Lee Pattinson in 1829 [ 1 ] and patented in 1833.
The process is dependent on the fact that lead which has least silver in it solidifies first on liquefaction , leaving the remaining liquid richer in silver.
In practice several crystallisations were required, so Pattinson's equipment consisted basically of nothing more complex than a row of up to 13 iron pots, which were heated from below. Some lead, naturally containing a small percentage of silver, was loaded into the central pot and melted. This was then allowed to cool. As the lead solidified it was removed using large perforated iron ladles and moved to the next pot in one direction, and the remaining metal which was now richer in silver was then transferred to the next pot in the opposite direction. The process was repeated from one pot to the next, the lead accumulating in the pot at one end and metal enriched in silver in the pot at the other. [ 2 ] [ 3 ]
The level of enrichment possible is limited by the lead-silver eutectic and typically the silver content of the silver-rich melt could not be raised above 2% (around 600 to 700 ounces per ton), so further separation is carried out by cupellation . [ 4 ]
The process was economic for lead containing at least 250 grams of silver per ton. [ 5 ] Being the first process applicable to low-grade lead, [ 1 ] it supplemented earlier patio process and pan amalgamation .
It was replaced by the Parkes process in the mid-19th century. | https://en.wikipedia.org/wiki/Pattinson's_process |
In biochemistry , paucimannosylation is an enzymatic post-translational modification involving the attachment of relatively simple mannose (Man) and N-Acetylglucosamine (GlcNAc) containing carbohydrates ( glycans ) to proteins . [ 1 ] The paucimannosidic glycans may also be modified with other types of monosaccharides including fucose (Fuc) and xylose (Xyl) depending on the species, tissue and cell origin. [ 2 ]
Paucimannosylation forms a separate sub-type in the asparagine N-linked glycosylation system. The short paucimannosidic glycans neither structurally nor functionally fit into the three well-established N-glycan classes i.e. oligomannosidic-, hybrid- and complex-type N-glycans.
Paucimannosylation has traditionally been referred to as a N-glycosylation type of "lower organisms", [ 3 ] mostly documented in insects, worms and plants. Recent findings have, however, added nuances to this view, by showing their presence and roles in mammals in the areas of immunity, cellular development, pathogen infection and cancer. [ 4 ] [ 5 ] To this end, paucimannosylation is therefore now considered to be a distinct type of N-glycosylation that adds diversity to the highly heterogeneous glycoproteome across the eukaryotic domain. [ 4 ] [ 6 ]
The term "paucimannose" (occasionally spelled as "pauci-mannose") was coined in the early 1990s glycobiology literature. [ 4 ] Paucimannose utilises the prefix "pauci" meaning few or small in Latin and the suffix "mannose" indicating glycans involving mannose-terminating glycans.
The phrases protein paucimannosylation and paucimannosidic proteins are commonly used in the literature to describe paucimannose-modified glycoproteins displaying intact structural and functional integrity. In contrast, the oligosaccharides themselves are often referred to as paucimannosidic, low mannose, and truncated glycans or other less conventional nomenclature. [ 4 ]
A simple shorthand nomenclature has been proposed as a convenient way to name the individual paucimannosidic glycan structures, e.g. M3F denotes Man 3 GlcNAc 2 Fuc 1 . [ 6 ] [ 7 ] [ 8 ] [ 9 ]
Paucimannosidic glycans span the base composition Man 1-3 GlcNAc 2 . [ 5 ] [ 10 ] Additional modifications with Fuc, Xyl and/or Galactose (Gal) are common in mammals ref, plants [ 4 ] [ 11 ] and invertebrates, respectively. [ 10 ] [ 12 ] Paucimannosidic glycans expressed by insects and nematodes are particularly rich in structural diversity. [ 4 ]
Paucimannosylation has been extensively studied and documented in insects, nematodes and plants over the past decades. The paucimannosidic proteins are constitutively and broadly expressed across tissues in these organisms under normal physiology. [ 13 ] It is widely recognised that paucimannosylation is a central component of the glycoproteome in these "lower" organisms. [ 12 ] Recently, paucimannosylation was reported to form an unconventional type of protein N-glycosylation in vertebrates. [ 3 ] It has been proposed that "higher" species including humans, rodents and other mammals use paucimannosylation in a more tissue- and context-restricted manner in pathophysiological conditions including cancer, [ 14 ] pathogen infection, inflammation and stemness. [ 15 ]
Paucimannosidic glycans form the main component of the N-glycome of insects such as Drosophila melanogaster . [ 16 ] Glycoprofiling of the venom component of the western honeybee, Apis mellifera , identified that paucimannosylation is a common modification of key proteins including hyaluronidase and phospholipase . [ 17 ] [ 18 ]
Insect cells lines are frequently utilised for recombinant expression of mammalian glycoproteins, which therefore are decorated with paucimannosidic glycans e.g. mouse interferon-β, [ 19 ] human IgG 1 [ 20 ] and calf alkaline phosphatase . [ 21 ]
The model organism Caenorhabditis elegans classified under the phylum Nematoda is amongst the most studied invertebrate species in glycobiology. The literature clearly documents a repertoire of nematodal paucimannosidic glycans. [ 22 ] Another model nematode, Pristionchus pacificus , was also documented to express common nematodal paucimannosidic glycans. [ 10 ]
Parasitic nematodes such as Haemonchus contortus have been reported to carry paucimannosidic glycans conjugated to an intestinal microsomal aminopeptidase. [ 23 ] In addition, there have been reports documenting the expression of paucimannosidic glycans by others parasitic nematodes such as Ascaris suum, [ 24 ] Heligmosomoides polygyrus [ 25 ] and Trichuris suis. [ 26 ]
Most plant species studied to date are recognised to constitutively express paucimannosidic N-glycoproteins. The paucimannosidic N-glycoproteins are abundantly expressed in the vacuoles of plants such as the legume seeds of Lotus japonicus , [ 27 ] the rice seeds and leaves of Oryza sativa. [ 28 ] Literature has provided evidence for plant-specific paucimannosidic glycan structures modified with Xyl and Fuc. Such structures are found across the broad Streptophyta (land plants) and Chlorophyta (green algae) clade and in diatoms such as Phaeodactylum tricornutum . [ 4 ] Less reported bixylosylated paucimannosidic glycans have also been documented. [ 29 ]
Paucimannosidic proteins have been reported in vertebrates such as quail, [ 30 ] chicken [ 31 ] and in mammals, [ 6 ] encompassing a limited diversity of paucimannosidic glycan structures. [ 4 ] Early findings reported on paucimannosidic glycans on lysosomal glycoproteins in domestic animals. [ 32 ] and human tissues, [ 33 ] but have subsequently been found also to decorate non-lysosomal glycoproteins. [ 34 ] [ 35 ] Particularly, the granules of human neutrophils are a principal source of paucimannosidic proteins. [ 6 ] [ 7 ] [ 36 ] [ 37 ] [ 38 ] Paucimannosidic proteins were also observed in human monocytes and macrophages [ 39 ] and paucimannosidic immunoglycopeptides were found to be presented by SARS-CoV-2 challenged dendritic cells. [ 40 ] Species within other classes under Animalia related to vertebrates were also documented to express paucimannosidic proteins. [ 41 ] with some observations of unusual plant- and invertebrate-like paucimannosidic glycan structures [ 5 ]
Despite receiving considerable focus, the glycobiological literature do not contain evidence for the presence of paucimannosidic proteins within Fungi. Fungal species within this kingdom are therefore considered devoid of protein paucimannosylation [ 11 ] and instead carry high mannosylated N-glycoproteins comprising extended and branched mannose-decorated antennae. [ 42 ] [ 43 ]
Similar to other N -linked glycan types, the biosynthesis of paucimannosidic proteins across most species has been documented to be facilitated by the actions of a limited set of glyco-enzymes including beta-N-acetyl hexosaminidases (Hex) and alpha-mannosidases , through GnT-I-dependent and -independent truncation pathways. [ 4 ]
Studies on insect cell lines and in vivo experiments on D. melanogaster have revealed active expression of Hexo1 and Hexo2, and, most importantly, the fused lobe (fdl) gene encoding fused ß-lobe (FDL), also known as GNase, an orthologue of A. thaliana and human Hex. FDL is expressed in high abundance in vesicles and the plasma membrane and has, unlike Hexo1 and Hexo2, been linked to fruit fly paucimannosidic protein production. [ 44 ] [ 45 ] [ 46 ] [ 47 ] However, except for the well-studied D. melanogaster and other common insect model organisms, solid evidence for active involvement of Hex and/or the possible concerted usage of the GnT-I-independent pathway or alternative truncation pathways for paucimannosidic protein production remains unavailable across the diverse class of insects.
The model organism C. elegans is well studied; solid glycobiological literature have provided insights on the nematodal N -glycosylation machinery which shares many traits with other eukaryotic species. [ 48 ] [ 49 ] C. elegans is known to produce paucimannosidic proteins via a GnT-I-dependent route in which GnT-I firstly produces GlcNAc-capped glycoprotein intermediates. Further processing by two Hex isoenzymes (HEX-2 and HEX-3) encoded by two C. elegans genes (hex-2, hex-3) generate the unsubstituted C. elegans paucimannosidic glycans.
Other glycoenzymes catalise further processing and structural diversity including α-Man II and α1,6- and α1,3-fucosyltransferases. Albeit less active, a GnT-I-independent α1,6-fucosyltransferase has also been observed for C. elegans , [ 50 ] [ 51 ] indicating that both the GnT-I-dependent and -independent pathways may contribute to the formation of paucimannosidic N -glycoproteins in worms. However, the biosynthetic processes underpinning the unusual non-sugar and core-modified paucimannosidic N -glycans in C. elegans remain to be elucidated.
Hexosaminidases (Hex) are important glycoside hydrolases for the generation of plant-specific paucimannosidic proteins across Plantae. HEXO1-HEXO3 have been reported to be key mediators of paucimannose expression in various plant species including Nicotiana benthamiana, [ 52 ] A.thaliana [ 53 ] and L. japonicus . [ 54 ] Moreover, α1,3-fucosyltransferase (FUT11/12) [ 55 ] and β1,2-xylosyltransferase [ 56 ] as well as α-mannosidase II [ 57 ] were also reported to play critical roles in the generation of the paucimannosidic proteins expressed by plants. [ 54 ]
In humans, the Hex-mediated GnT-I-dependent truncation pathway is known to facilitate, at least in some tissues including neutrophils, the production of paucimannosidic proteins. [ 9 ] Human Hex isoenzymes are assembled with alpha and beta subunits encoded by the HEXA and HEXB genes, respectively. [ 58 ] From these two subunits, isoenzymes such as Hex A (one alpha and one beta subunit), Hex B (two beta subunits) and Hex S (two alpha subunits) are generated. Both Hex A and Hex B are reported to play important functional roles in human, [ 58 ] particularly in the lysosomal degradation of gangliosides. Recently, both HEXA and HEXB were documented to mediate protein paucimannosylation in human neutrophils [ 9 ] and may therefore also be the main driver for the elevated production of paucimannosidic proteins during cancer development. [ 14 ] Recent in vitro observations have suggested other noncanonical truncation pathways with direct core fucosylation of paucimannosidic proteins in vertebrates, but this remains to be validated [ 4 ] Hex A and Hex B isoenzymes are mainly present in the azurophilic granules of human neutrophils as a result of a proposed targeting-by-timing mechanism that supposedly directs these enzymes to this compartment during neutrophil development. [ 59 ] Recently, granule-specific glycosylation was shown in neutrophils featuring prominent paucimannosylation in the azurophilic granules an observation that was suggested to arise from a "glycosylation-by-timing" mechanism yet to be documented. [ 60 ] More widely across vertebrate species, the biosynthesis of paucimannosidic proteins remains largely unstudied.
The function of protein paucimannosylation remains largely unexplored in vertebrates. Recent literature however has emerged demonstrating that paucimannosylation play roles in mediating pathophysiological processes such as in inflammation, pathogen infection, cancer and in the development of stem cells and in normal homeostasis. For example, elevated expression of paucimannosidic proteins was shown in Mycobacterium tuberculosis infected macrophages, [ 61 ] during preclampsia [ 62 ] and on Tamm-Horsfall proteins secreted by human urothelial cells during urinary tract infections suggesting the involvement of paucimannosylation in those conditions. [ 63 ] Additionally, sputum from individuals suffering from cystic fibrosis and airway infections were also observed to be rich in paucimannosidic proteins. [ 64 ] [ 65 ] Furthermore, paucimannosylation was reported to be prominent features of human neutrophils [ 8 ] [ 38 ] [ 66 ] [ 7 ] and in monocytes [ 39 ] and macrophages. [ 61 ] Recent literature have also demonstrated elevated signatures of paucimannosidic proteins associated with a range of human cancers [ 14 ] including brain, [ 67 ] breast, [ 68 ] blood, [ 61 ] melanoma, [ 69 ] non-melanoma, [ 70 ] liver, [ 71 ] ovarian [ 72 ] and prostate cancers. [ 73 ] Enriched paucimannosidic glycoepitopes were found in the tumours when compared to the adjacent non-tumour tissues. Literature have also reported the presence of paucimannosylation in embryonic stem cells [ 74 ] and neuronal stem cells, [ 75 ] suggesting potential functional role(s) in these cells. Notably, deficiency of hexosaminidases results in clinically significant Tay-Sachs and Sandhoff diseases, which also implicates Hex and paucimannosidic proteins in those conditions.
Endogenous and exogenous binding partners of mammalian paucimannosidic glycans have been suggested, [ 3 ] including the macrophage mannose receptor (CD206) and dectin-2. Other putative endogenous paucimannosidic protein receptors such as dectin-1, DC-SIGN and DC-SIGNR have been proposed, but experimental support is still lacking. Exogeneous binders of paucimannosidic glycans such as the Escherichia coli FimH [ 76 ] and P. aeruginosa PA-IIL [ 77 ] were also reported to play important roles in the adhesion and pathophysiology of these opportunistic pathogens.
In D. melanogaster, FDL-deficient mutants showed paucimannose-deficiency and, notably, caused locomotion defects in fruit flies, indicating that Hex and/or paucimannosidic proteins are involved, via elusive pathways, in essential fruit fly processes. [ 78 ] As expected, the less-consequential monoallelic fdl mutation was shown to result in reduced paucimannosidic protein formation and caused a non-lethal, but still severe phenotype, by halting the generation of peripheral long-term memory neurons. Impaired generation of peripheral long-term memory neurons [ 12 ] was also observed for fruit fly fdl and MgatI null mutations, which, in turn, resulted in infertility and locomotion defects. The lack of fucosylated paucimannosidic glycans was proposed to contribute to neuronal impairment in both fdl and Mgat1 mutants. The importance of fucosylated paucimannosidic glycans was supported by a study reporting that mutations in the FucT6 gene encoding the D. melanogaster α1,6-fucosyltransferase resulted in an impaired fruit fly immune response towards parasitic infections. [ 79 ] Taken together, these phenotypic observations suggest that the fruit fly paucimannosidic glycans, some of which overlap with the human repertoire, are pivotal in the development, immune function and survival processes of D. melanogaster. It was reported that T. castaneum abundantly expresses paucimannosidic proteins during its post-larval stages, [ 80 ] recapitulating findings from other studies proposing that paucimannosidic proteins are strongly regulated during early development. [ 15 ] Thus, it is likely that paucimannosidic glycans conjugated to still unknown flour beetle carrier proteins, similar to those in nematodes and fruit flies, are vital for growth and survival processes of the flour beetle.
Expression of phosphocholine-modified and unsubstituted C. elegans paucimannosidic glycans is reportedly development stage-specific, implying important roles in nematodal development. [ 81 ] In support, C. elegans hex-2 gene knock-out mutants displayed reduced paucimannosidic protein levels and altered sensitivity towards nematotoxic lectins relative to wild-type worms, a correlation suggesting involvement of paucimannosidic proteins in key C. elegans survival processes. [ 82 ] Functionally, phosphocholine-containing paucimannosidic glycans were demonstrated to display immune-modulating roles in parasitic nematodes. [ 83 ] Paucimannosidic glycans were suggested to play roles in the nematodal innate immune system by impacting the nematode's ability to fight and survive pathogenic bacteria [ 84 ] | https://en.wikipedia.org/wiki/Paucimannosylation |
Paul-Peter Tak is a Dutch immunologist and academic specialising in the fields of internal medicine , rheumatology and immunology . Tak has been the President & CEO of Candel Therapeutics since September 2020.
Tak graduated with a medical degree cum laude from the Amsterdam University Medical Centers and began his medical career as a practitioner in the Bronovo Hospital, The Hague . He joined Leiden University Medical Centre as a Fellow in Internal Medicine in 1990 and was awarded a Fellowship in Rheumatology in 1995. Tak received his PhD from Leiden University in 1996 for his thesis Immunohistologic studies of rheumatoid synovial tissue . He worked as a Clinical Associate Professor of Medicine at the University of California, San Diego , and next served as Professor of Medicine and Chair of the Department of Clinical Immunology & Rheumatology at Amsterdam UMC . [ 1 ]
Tak has studied the role of the vagus nerve in chronic inflammation, work which provided the basis for clinical trials exploring bioelectronics as a novel therapeutic approach in rheumatoid arthritis patients. He is also known for his studies on synovial biopsy and synovial tissue analysis. In his academic life, Tak has been Visiting Professor, William Harvey Research Institute (London), Honorary Senior Visiting Fellow (University of Cambridge), Honorary Professor of Rheumatology (Ghent University) and was elected a Fellow of the Academy of Medical Sciences (U.K.) in 2016. [ 2 ] [ 3 ] [ 4 ]
He was elected by peers as "Best Rheumatologist" in the Netherlands in 2011, and received the Medal of Honour of the Netherlands Society for Rheumatology the same year. He was rated as one of the world’s top 3 doctors in the field of rheumatoid arthritis by Expertscape in 2014. [ 5 ] [ 6 ] [ 7 ]
From 2011 to 2018, Tak worked at GlaxoSmithKline as Senior Vice President, Chief Immunology Officer and Global Development Leader. He was also the Chair of the Scientific Review Board. In 2018, Tak cofounded Sitryx Therapeutics with researchers Houman Ashrafian, Luke O'Neill, Jonathan Powell, Jeff Rathmell, Michael Rosenblum. Tak was appointed as Board Director of Levicept in July 2018. Tak was chief executive at Tempero Pharmaceutical, which was acquired by GlaxoSmithKline , then served as Chief Executive Officer at Kintai Therapeutics in 2018. He was also a venture partner at Flagship Pioneering . In September 2020, Tak became president and CEO of Candel Therapeutics and, in July of the following year, led the company to an Initial Public Offering (IPO) on the Nasdaq . In 2021, Tak was named as one of the most inspiring people in life sciences on the PharmaVOICE100 list. Tak was included in The Medicine Maker Power List 2023 as one of the top ten leaders in the Biopharmaceuticals category. In March 2023, Tak was appointed Chair of the Board of Directors at Citryll. [ 8 ] [ 9 ] [ 10 ] [ 11 ]
Tak has an h-index of 144 according to Google Scholar . [ 12 ] His publications include: | https://en.wikipedia.org/wiki/Paul-Peter_Tak |
Armand Paul Alivisatos (born November 12, 1959) is a Greek and American chemist and academic administrator who is the 14th president of the University of Chicago since September 2021. He is a pioneer in nanomaterials development [ 1 ] [ 2 ] and an authority on the fabrication of nanocrystals and their use in biomedical and renewable energy applications. [ 3 ] He was ranked fifth among the world's top 100 chemists for the period 2000–2010 in the list released by Thomson Reuters. [ 4 ] [ 5 ]
On September 1, 2021, Alivisatos became the 14th president of the University of Chicago , where he also holds a faculty appointment as the John D. MacArthur Distinguished Service Professor in the Department of Chemistry, the Pritzker School of Molecular Engineering , and the College; and serves as the chair of the board of governors of Argonne National Laboratory and chair of the board of directors of Fermi Forward Discovery Group LLC, the operator of Fermi National Accelerator Laboratory . [ 6 ]
Prior to joining the University of Chicago, Alivisatos was the executive vice chancellor and provost (2017–2021) of the University of California, Berkeley , where he had taught since 1988. [ 7 ] [ 8 ] He previously served as the director of the Lawrence Berkeley National Laboratory (2009–2016), and as Berkeley’s interim vice chancellor for research (2016–2017). He held a number of faculty appointments at Berkeley, including the Samsung Distinguished Professor in Nanoscience and Nanotechnology Research [ 9 ] and professor of chemistry and materials science and engineering. Alivisatos was also the founding director of the Kavli Energy Nanosciences Institute (ENSI), an institute on the Berkeley campus launched by the Kavli Foundation to explore the application of nanoscience to sustainable energy technologies. [ 10 ] [ 11 ]
Paul Alivisatos was born in Chicago , Illinois, to a Greek family, [ 1 ] where he lived until the age of 10, when his family moved to Athens , Greece . Alivisatos has said of his years in Greece that it was a great experience for him because he had to learn the Greek language and culture then catch up with the more advanced students. "When I found something very interesting it was sometimes a struggle for me to understand it the very best that I could," he has said of that experience. "That need to work harder became an important motivator for me." Alivisatos returned to the United States to attend the University of Chicago in the late 1970s. [ 12 ]
In 1981, Alivisatos earned a B.A. with honors in chemistry from the University of Chicago . In 1986, he received a Ph.D. in physical chemistry from the University of California, Berkeley , where he worked under Charles Harris . [ 13 ] His Ph.D. thesis concerned the photophysics of electronically excited molecules near metal and semiconductor surfaces. He then joined AT&T Bell Labs working with Louis E. Brus , and began research in the field of nanotechnology .
Alivisatos returned to Berkeley in 1988 as an assistant professor of chemistry, becoming associate professor in 1993 and professor in 1995. He served as Chancellor's Professor from 1998 to 2001, and added an appointment as a professor of materials science and engineering in 1999.
Alivisatos' affiliation with Lawrence Berkeley National Lab (or Berkeley Lab) began in 1991 when he joined the staff of the Materials Sciences Division. [ 14 ] From 2005 to 2007 Alivisatos served as Berkeley Lab's Associate Laboratory Director for the Physical Sciences area. In 2008, he served as Deputy Lab Director under Berkeley Lab Director Steven Chu, and then as interim director when Chu stepped down to become the Secretary of Energy. He was named the seventh Director of Berkeley Lab on November 19, 2009, by the University of California Board of Regents on the recommendation of UC President Mark Yudof and with the concurrence of the U.S. Department of Energy. [ 15 ] He played a critical role in the establishment of the Molecular Foundry, a U.S. Department of Energy's Nanoscale Science Research Center; and was the facility's founding director.
Energy Secretary , Nobel laureate, and fellow Berkeley alumnus Steven Chu noted that Alivisatos is "an incredible scientist with incredible judgment on a variety of issues. He's level-headed and calm, and he has an ability to inspire people…[and he can] take projects from material science to real-world applications." [ 16 ]
Alivisatos is an internationally recognized authority on nano chemistry in the synthesis of semiconductor quantum dots and multi-shaped artificial nanostructures. [ 17 ] Further, he is a world expert on the chemistry of nanoscale crystals; one of his papers (Science, 271: 933–937, 1996) has been cited over 13,800 times. [ 18 ] He is also an expert on how these can be applied, for example as biological markers (e.g., Science, 281: 2013–16, 1998; a paper cited over 10,900 times [ 19 ] ). In addition, his use of DNA in this area ( DNA nanotechnology ) has shown the surprising versatility of this molecule. He has used it to direct crystal growth and create new materials, as in Nature, 382: 609–11, 1996, and even to measure nanoscale distances (see Nature Nanotechnology, 1: 47–52, 2006). [ 20 ]
He is widely recognized as being the first to demonstrate that semiconductor nanocrystals can be grown into complex two-dimensional shapes, as opposed to simple one-dimensional spheres. [ 20 ] [ 21 ] Alivisatos proved that controlling the growth of nanocrystals is the key to controlling both their size and shape. This achievement altered the nanoscience landscape and paved the way for a slew of new potential applications, including biomedical diagnostics, revolutionary photovoltaic cells, and LED materials. [ 22 ]
Nanocrystals are aggregates of anywhere from a few hundred to tens of thousands of atoms that combine into a crystalline form of matter known as a "cluster." Typically a few nanometers in diameter, nanocrystals are larger than molecules but smaller than bulk solids and therefore often exhibit physical and chemical properties somewhere in between. Given that a nanocrystal is virtually all surface and no interior, its properties can vary considerably as the crystal grows in size.
Prior to Alivisatos' research, all non-metal nanocrystals were dot-shaped, meaning they were essentially one-dimensional. No techniques had been reported for making two-dimensional or rod-shaped semiconductor nanocrystals that would also be of uniform size. However, in a landmark paper that appeared in the March 2, 2000 issue of the journal Nature , [ 23 ] Alivisatos reported on techniques used to select the size but vary the shapes of the nanocrystals produced. This was hailed as a major breakthrough in nanocrystal fabrication because rod-shaped semiconductor nanocrystals can be stacked to create nano-sized electronic devices.
The rod-shaped nanocrystal research, coupled with earlier work led by Alivisatos in which it was shown that quantum dots or "qdots"–nanometer-sized crystal dots (spheres a few billionths of a meter in size)– made from semiconductors such as cadmium selenide can emit multiple colors of light depending upon the size of the crystal, opened the door to using nanocrystals as fluorescent probes for the study of biological materials, biomedical research tools and aids to diagnosis, [ 24 ] and as light-emitting diodes (LEDs). Alivisatos went on to use his techniques to create an entirely new generation of hybrid solar cells that combined nanotechnology with plastic electronics. [ 17 ]
Alivisatos is the founding scientist of Quantum Dot Corporation, [ 25 ] a company that makes crystalline nanoscale tags that are used in the study of cell behavior. [ 26 ] (Quantum Dot is now part of Life Technologies.) He also founded the nanotechnology company Nanosys, [ 27 ] and Solexant, a photovoltaic start-up that has since restarted as Siva Power . [ 28 ] His research has led to the development of applications in range of industries, including bioimaging (for example, the use of quantum dots for luminescent labeling of biological tissue); display technologies (his quantum dot emissive film is found in the Kindle Fire HDX tablet); [ 29 ] and renewable energy (solar applications of quantum dots).
Alivisatos became president of the University of Chicago on September 1, 2021. He is the 14th president of the University of Chicago, succeeding Robert J. Zimmer who was president from 2006 to 2021. [ 30 ] Alivisatos also serves as a John D. MacArthur Distinguished Service Professor in the Department of Chemistry, Pritzker School of Molecular Engineering , and the College .
Under Alivisatos’ leadership, the Lawrence Berkeley National Lab shifted its priorities to the more interdisciplinary areas of renewable energy and climate-change research. [ 1 ] [ 2 ] During his tenure, the Lab began construction on new buildings for computational research, building efficiencies, solar energy research, and biological science. [ 31 ]
Alivisatos focused on integrating the Lab into the nation's innovation ecosystem, especially in the areas of energy and the environment. While some of the groundwork for this integration was laid by former Director Steve Chu, Alivisatos led efforts to leverage the wide range of scientific capabilities at Berkeley Lab with a variety of industry partners and entrepreneurs. These public/private sector collaborations resulted in technology transfer for industries as diverse as automobiles and medicine, and contributed to an increased speed of development in manufacturing and renewable energy. [ 32 ] On March 23, 2015 Alvisatos announced that he would step down as Director when a replacement was identified. [ 33 ]
Alivisatos has also been outspoken on the issue of basic science funding at the federal level and America's ability to stay competitive in the areas global scientific research and development. [ 34 ] [ 35 ]
Alivisatos is married to Nicole Alivisatos, a retired chemist, former editor of the journal Nano Letters , and daughter of the noted chemist, Gábor A. Somorjai . They have two daughters.
In addition to those listed above, Alivisatos has held fellowships with the American Association for the Advancement of Science , [ 64 ] the American Physical Society (1996), [ 65 ] and the American Chemical Society . [ 66 ] He is a member of the National Academy of Sciences [ 67 ] and the American Academy of Arts and Sciences . [ 68 ]
For a full list of publications, see http://www.cchem.berkeley.edu/pagrp/publications.html
Alivisatos is the founding editor of Nano Letters , a publication of the American Chemical Society. [ 69 ] He formerly served on the Senior Editorial Board of Science . He has also served on the editorial advisory boards of ACS Nano , the Journal of Physical Chemistry , Chemical Physics , the Journal of Chemical Physics , and Advanced Materials . | https://en.wikipedia.org/wiki/Paul_Alivisatos |
Paul Gardner Allen (January 21, 1953 – October 15, 2018) was an American businessman, computer programmer, researcher, film producer, explorer, sports executive, investor, author, and philanthropist. He co-founded Microsoft Corporation with his childhood friend Bill Gates in 1975, which was followed by the microcomputer revolution of the 1970s and 1980s. Allen was ranked as the 44th-wealthiest person in the world by Forbes with an estimated net worth of $20.3 billion at the time of his death in October 2018. [ 2 ] [ 3 ]
Allen quit from day-to-day work at Microsoft in early 1983 after a Hodgkin lymphoma diagnosis, remaining on its board as vice-chairman. He and his sister, Jody Allen , founded Vulcan Inc. in 1986, [ 4 ] a privately held company that managed his business and philanthropic efforts. At the time of his death, he had a multi-billion dollar investment portfolio, including technology and media companies, scientific research, real estate holdings, private space flight ventures, and stakes in other sectors. He owned the Seattle Seahawks of the National Football League [ 5 ] and the Portland Trail Blazers of the National Basketball Association , [ 6 ] and was part-owner of the Seattle Sounders FC of Major League Soccer . [ 7 ] Under Allen's helm, the Seahawks won Super Bowl XLVIII and made it to two other Super Bowls ( XL and XLIX ). In 2000 he resigned from his position on Microsoft's board and assumed the post of senior strategy advisor to the company's management team.
Allen founded the Allen Institutes for Brain Science , [ 8 ] Artificial Intelligence , [ 9 ] and Cell Science , [ 10 ] as well as companies like Stratolaunch Systems [ 11 ] and Apex Learning . [ 12 ] He gave more than $2 billion to causes such as education, wildlife and environmental conservation, the arts, healthcare, and community services. [ 13 ] In 2004, he funded the first crewed private spaceplane with SpaceShipOne . [ 14 ] [ 15 ] He received numerous awards and honors, and was listed among the Time 100 Most Influential People in the World in 2007 and 2008. [ 16 ]
Allen was diagnosed with non-Hodgkin lymphoma in 2009. He died of septic shock related to cancer on October 15, 2018, at the age of 65. [ 17 ] Shortly after his death, in April 2019, the Allen-funded Stratolaunch first flew and became the largest aircraft in history by wingspan . [ 18 ]
Allen was born on January 21, 1953, in Seattle , Washington, to Kenneth Sam Allen (a librarian) [ 19 ] and Edna Faye (née Gardner) Allen [ 20 ] (a fourth-grade teacher). [ 21 ] From 1965 to 1971 he attended Lakeside School , [ 22 ] a private school in Seattle where he befriended Bill Gates , with whom he shared an enthusiasm for computers. [ 22 ] They used Lakeside's Teletype terminals to develop their programming skills on several time-sharing computer systems. [ 23 ] They also used the laboratory of the Computer Science Department of the University of Washington for personal research and computer programming until they were banned in 1971 for abusing their privileges. [ 24 ]
Gates and Allen joined with Ric Weiland and Gates' childhood best friend and first collaborator, Kent Evans, to form the Lakeside Programming Club and find bugs in Computer Center Corporation 's software, in exchange for extra computer time. [ 25 ] In 1972, after Evans' sudden death due to a mountain climbing accident, Gates turned to Allen for help finishing an automated class scheduling system for Lakeside. [ 26 ] They then formed Traf-O-Data to make traffic counters based on the Intel 8008 processor. According to Allen, he and Gates would go dumpster diving during their teenage years for computer program code. [ 27 ]
Allen achieved a perfect SAT score of 1600 [ 28 ] and went to Washington State University , where he joined the Phi Kappa Theta fraternity. [ 29 ] [ 30 ] [ 31 ] He dropped out of college after two years to work as a programmer for Honeywell in Boston near Harvard University where Gates was enrolled. [ 23 ] Allen convinced Gates to drop out of Harvard in order to found Microsoft . [ 32 ]
Allen and Gates formed Microsoft in 1975 in Albuquerque, New Mexico , and began marketing a BASIC programming language interpreter, with their first employee being high school friend and collaborator Ric Weiland . [ 33 ] [ 23 ] Allen came up with the name of "Micro-Soft", a combination of "microcomputer" and "software". [ 34 ]
Microsoft committed to delivering a disk operating system ( DOS ) to IBM for the original IBM PC in 1980, although they had not yet developed one, and Allen spearheaded a deal for Microsoft to purchase QDOS (Quick and Dirty Operating System) written by Tim Paterson who was employed at Seattle Computer Products . [ 35 ] [ 36 ] As a result of this transaction, Microsoft secured a contract to supply the DOS that ran on IBM's PC line, which opened the door to Allen's and Gates' wealth and success. [ 23 ]
The company restructured on June 25, 1981, to become an incorporated business in its home state of Washington (with a further change of its name to "Microsoft Corporation, Inc."). As part of the restructuring, Gates became president of the company and chairman of the board, and Allen became executive vice president and vice chairman. [ 23 ] [ 37 ] The relationship between Allen and Gates became strained as they argued even over small things. [ 26 ] Allen effectively left Microsoft in 1982 after being diagnosed with Hodgkin's lymphoma , though he remained on the board of directors as vice chairman. [ 23 ] [ 38 ] Gates reportedly asked Allen to give him some of his shares to compensate for the higher amount of work that Gates was doing. [ 39 ] [ 40 ] According to Allen, Gates said that he "did almost everything on BASIC " and the company should be split 60–40 in his favor. Allen agreed to this arrangement, which Gates later renegotiated to 64–36. [ 41 ] In 1983, Gates tried to buy Allen out at $5 per share, but Allen refused and left the company with his shares intact; this made him a billionaire when Microsoft went public. [ 41 ] [ 42 ] Gates later repaired his relationship with Allen, and the two men donated $2.2 million to their childhood school Lakeside in 1986. [ 26 ] They remained friends for the rest of Allen's life. [ 43 ]
Allen resigned from his position on the Microsoft board of directors on November 9, 2000, but he remained as a senior strategy advisor to the company's executives. [ 1 ] [ 44 ] [ 45 ] In January 2014, he still held 100 million shares of Microsoft. [ 46 ]
Allen confirmed that he was the sole investor behind aerospace engineer and entrepreneur Burt Rutan 's SpaceShipOne suborbital commercial spacecraft on October 4, 2004. [ 62 ] The craft was developed and flown by Mojave Aerospace Ventures , which was a joint venture between Allen and Rutan's aviation company, Scaled Composites . SpaceShipOne climbed to an altitude of 367,442 feet (111,996 m) over the Mojave Air and Space Port and was the first privately funded effort to successfully put a civilian in suborbital space. It won the Ansari X Prize competition and received the $10 million prize. [ 63 ]
On December 13, 2011, Allen announced the creation of Stratolaunch Systems , based at the Mojave Air and Space Port . The Stratolaunch is a proposed orbital launch system consisting of a dual-bodied, 6-engine jet aircraft, capable of carrying a rocket to high altitude; the rocket would then separate from its carrier aircraft and fire its own engines to complete its climb into orbit. If successful, this project would be the first wholly privately funded space transport system. [ 64 ] Stratolaunch, which is partnering with Orbital ATK and Scaled Composites, is intended to launch in inclement weather, fly without worrying about the availability of launch pads and to operate from different locations. Stratolaunch plans to ultimately host six to ten missions per year. [ 65 ] On April 13, 2015, Vulcan Aerospace was announced. It is the company within Allen's Vulcan Inc. that plans and executes projects to shift how the world conceptualizes space travel through cost reduction and on-demand access. [ 66 ]
On April 13, 2019, the Stratolaunch aircraft made its maiden flight, reaching 15,000 ft (4,600 m) and 165 kn (306 km/h) in a 2 h 29 min flight. [ 67 ] [ 68 ] Stratolaunch CEO Jean Floyd offered this comment: "We dedicate this day to the man who inspired us all to strive for ways to empower the world's problem-solvers, Paul Allen. Without a doubt, he would have been exceptionally proud to see his aircraft take flight". Upon its flight, the airplane became the largest in history by wingspan . [ 18 ]
As of the end of May 2019, Stratolaunch Systems Corporation had ceased operations. [ 69 ]
Allen's Vulcan Real Estate [ 70 ] division offers development and portfolio management services, and was involved in the redevelopment of the South Lake Union neighborhood immediately north of downtown Seattle. [ 71 ] Vulcan has developed 6.3 million square feet (590,000 m 2 ) of new residential, office, retail and biotechnology research space, and has a total development capacity of 10,000,000 sq ft (930,000 m 2 ). Vulcan advocated for the Seattle Streetcar line known as South Lake Union Streetcar , which runs from Seattle's Westlake Center to the south end of Lake Union. [ 72 ] In 2012, The Wall Street Journal called Allen's South Lake Union investment "unexpectedly lucrative" and one that led to his firm selling a 1,800,000-square-foot (170,000 m 2 ) office complex to Amazon.com for US$1.16 billion, one of the most expensive office deals ever in Seattle. [ 73 ] "It's exceeded my expectations", Allen said of the South Lake Union development. [ 74 ]
Allen purchased the Portland Trail Blazers NBA team in 1988 from California real estate developer Larry Weinberg for $70 million. [ 6 ] He was instrumental in the development and funding of the Moda Center (previously known as the Rose Garden), the arena where the Blazers play. He purchased the arena on April 2, 2007, and stated that this was a major milestone and a positive step for the franchise. [ 23 ] [ 80 ] The Allen-owned Trail Blazers reached the playoffs 19 times including the NBA Finals in 1990 and 1992 . [ 81 ] According to Forbes , the Blazers were valued at $2.09 billion in 2021 and ranked No. 13 out of 30 NBA teams. [ 82 ]
Allen purchased the National Football League 's Seattle Seahawks in 1997 from owner Ken Behring , [ 83 ] [ 84 ] who had attempted to move the team to southern California the previous year . [ 5 ] [ 85 ] [ 86 ] Herman Sarkowsky, a former Seahawks minority owner, told The Seattle Times about Allen's decision to buy the team, "I'm not sure anybody else in this community would have done what [Allen] did." [ 87 ]
In 2002, the team moved into Seahawks Stadium (now known as Lumen Field ), after Allen invested into the upgrade of the stadium. [ 88 ] Acquired for US$200 million in 1997, [ 83 ] [ 84 ] the Seahawks were valued at $1.33 billion in August 2014 by Forbes , which says the team has "one of the most rabid fan bases in the NFL". [ 89 ] Under the helm of Allen, the Seahawks made the Super Bowl three times following NFC Championship victories ( 2005 , 2013 , 2014 ), and won Super Bowl XLVIII in February 2014. [ 90 ]
Allen's Vulcan Sports & Entertainment is part of the ownership team of Seattle Sounders FC, a Major League Soccer (MLS) franchise that began play in 2009 at CenturyLink Field , a stadium which was also controlled by Allen. [ 7 ] The ownership team also includes film producer Joe Roth , businessman Adrian Hanauer , and comedian Drew Carey . The Sounders sold out every home game during its first season, setting a new MLS record for average match attendance. [ 91 ]
Allen and his sister, Jody Allen , together were the owners and executive producers of Vulcan Productions , [ 92 ] a television and film production company headquartered in Seattle within the entertainment division of Vulcan Inc. Their films have received various recognition, ranging from a Peabody Award [ 93 ] to Independent Spirit Awards , [ 94 ] Grammys [ 95 ] and Emmys .
In 2014 alone, Allen's film, We The Economy, won 12 awards including a Webby award for best Online News & Politics Series. The films have also been nominated for Golden Globes [ 95 ] and Academy Awards [ 94 ] among many others. Vulcan Productions' films and documentary projects include Far from Heaven [ 94 ] (2002), Hard Candy [ 96 ] (2005), Rx for Survival: A Global Health Challenge [ 97 ] [ 98 ] (2005), Where God Left His Shoes [ 99 ] (2006), Judgment Day: Intelligent Design on Trial [ 100 ] [ 101 ] (2007), This Emotional Life [ 102 ] [ 103 ] (2010), We The Economy [ 104 ] (2014) Racing Extinction [ 105 ] (2015) and Oscar-nominated Body Team 12 [ 106 ] (2015).
In 2013, Vulcan Productions co-produced the Richard E. Robbins-directed film Girl Rising [ 107 ] which tells the stories of girls from different parts of the world who seek an education. Globally, over 205 million households watched Girl Rising during the CNN premier, [ 108 ] and over 4 million people have engaged with Girl Rising through websites and social media. Through the associated 10×10 program, over $2.1 million has been donated to help girls receive an education worldwide. [ 109 ]
Also in 2013, Vulcan Productions signed on as a producing partner of Pandora's Promise , [ 110 ] a documentary about nuclear power, directed by Oscar-nominated director Robert Stone . It was released on CNN in November 2013. A variety of college and private screenings as well as panel discussions have been hosted throughout the country. [ 111 ]
Allen gave more than $2 billion towards the advancement of science, technology, education, wildlife conservation, the arts, and community services in his lifetime. [ 13 ] The Paul G. Allen Family Foundation, which he founded with his sister Jody, was established to administer a portion of Allen's philanthropic contributions. Since its formation, the foundation has given more than $494 million to over 1,500 nonprofits; and, [ 112 ] in 2010, Allen became a signatory of The Giving Pledge , promising to give at least half of his fortune to philanthropic causes. [ 113 ] Allen received commendations for his philanthropic commitments including the Andrew Carnegie Medal of Philanthropy [ 114 ] and Inside Philanthropy ' s "Philanthropist of the Year". [ 115 ]
In September 2003, Allen launched the Allen Institute for Brain Science with a $100 million contribution dedicated to understanding how the human brain works. In total, Allen donated $500 million to the institute, making it his single largest philanthropic recipient. Since its launch, the Allen Institute for Brain Science has taken a Big Science and open science approach to tackle projects. The institute makes research tools available to the scientific community using an open data model. [ 116 ] Some of the institute's projects include the Allen Mouse Brain Atlas , Allen Human Brain Atlas and the Allen Mouse Brain Connectivity Atlas. The Allen Institute is also helping to advance and shape the White House 's BRAIN Initiative as well as the Human Brain Project . [ 117 ]
Founded in 2014, the Allen Institute for Artificial Intelligence (AI2)'s main focus is to research and engineer artificial intelligence . [ 118 ] The institute is modeled after the Allen Institute for Brain Science and led by researcher and professor, Dr. Oren Etzioni . AI2 has undertaken four main projects, Aristo, Semantic Scholar , Euclid, and Plato. As of 2015 [update] Project Aristo is working to build an AI system capable of passing an 8th-grade science exam. [ 119 ]
In December 2014, Allen committed $100 million to create the Allen Institute for Cell Science in Seattle. The institute is investigating and creating a virtual model of cells in the hope of bringing forth treatment of different diseases. [ 120 ] Like the institutes before it, all data generated and tools developed will be made publicly available online. [ 121 ]
Launched in 2016 with a $100 million commitment, The Paul G. Allen Frontiers Group aims to discover and support ideas at the frontier of bioscience in an effort to accelerate the pace of discovery. [ 122 ] The group will target scientists and research areas that "some might consider out-of-the-box at the very edges of knowledge". [ 123 ]
Allen launched the Allen Distinguished Investigators Awards (ADI) in 2010 to support scientists pursuing early-stage research projects who often have difficulty securing funding from traditional sources. [ 124 ] Allen donated the seed money to build SETI 's Allen Telescope Array , eventually contributing $30 million to the project. [ 125 ]
The Paul Allen's flower fly was named in recognition of his contributions to Dipterology . [ 126 ]
Allen provided more than $7 million to fund a census of elephant populations in Africa, the largest such endeavour since the 1970s. The Great Elephant Census team flew over 20 countries to survey African savannah elephants. The survey results were published in 2015 and showed rapid rates of decline which were accelerating. [ 127 ]
He began supporting the University of British Columbia 's Sea Around Us Project in 2014 to improve data on global fisheries as a way to fight illegal fishing . Part of his $2.6 million in funding went towards the creation of FishBase , [ 128 ] an online database about adult finfish. [ 129 ] Allen funded the Global FinPrint initiative, launched in July 2015, a three-year survey of sharks and rays in coral reef areas. The survey is the largest of its kind and designed to provide data to help conservation programs. [ 130 ] [ 131 ]
Allen backed Washington state initiative 1401 to prohibit the purchase, sale and distribution of products made from 10 endangered species including elephants, rhinos, lions, tigers, leopards, cheetahs, marine turtles, pangolins, sharks and rays. The initiative gained enough signatures to be on the state's ballot on November 3, 2015, and passed. [ 132 ]
Alongside the United States Department of Transportation (USDOT), Allen and Vulcan Inc. launched the Smart City Challenge, [ 133 ] a contest inviting American cities to transform their transportation systems. Created in 2015 with the USDOT's $40 million commitment as well as $10 million from Allen's Vulcan Inc., the challenge aims to create a first-of-its-kind modern city that will demonstrate how cities can improve quality of life while lowering greenhouse gas emissions. [ 134 ] The winning city was Columbus, Ohio . [ 135 ]
As a member of the International SeaKeepers Society , Allen hosted its proprietary SeaKeeper 1000TM oceanographic and atmospheric monitoring system on all three of his megayachts. [ 136 ]
Allen funded the building of microgrids , which are small-scale power grids that can operate independently, in Kenya, to help promote reusable energy and empower its businesses and residents. [ 137 ] He was an early investor in the Mawingu Networks, a wireless and solar-powered Internet provider which aims to connect rural Africa with the world, and Off Grid Electric, a company focused on providing solar energy to people in emerging nations. [ 138 ]
In 2014, Allen pledged at least $100 million toward the fight to end the Ebola virus epidemic in West Africa , [ 139 ] making him the largest private donor in the Ebola crisis. He also created a website called TackleEbola.org [ 140 ] as a way to spread awareness and serve as a vehicle for donors to fund projects in need. The site highlighted organizations working to stop Ebola that Allen supported, such as International Red Cross and Red Crescent Movement , Médecins Sans Frontières , Partners in Health , UNICEF and World Food Program USA . On April 21, 2015, Allen brought together key leaders in the Ebola fight at the Ebola Innovation Summit in San Francisco. The summit aimed to share key learnings and reinforce the need for continued action and support to reduce the number of Ebola cases to zero, which was achieved in January 2016. [ 141 ]
In October 2015, the Paul G. Allen Family Foundation announced it would award seven new grants totaling $11 million to prevent future widespread outbreaks of the virus. [ 142 ]
In 2012, along with his research team and the Royal Navy , Allen attempted to retrieve the ship's bell from HMS Hood , which sank in the Denmark Strait during World War II, but the attempt failed due to poor weather. On August 7, 2015, they tried again and recovered the bell in very good condition. [ 143 ] It was restored and put on display in May 2016 in the National Museum of the Royal Navy, Portsmouth , in remembrance of the 1,415 crewmen lost. [ 144 ]
Since 2015, Allen funded the research ship RV Petrel , which he purchased in 2016. The project team aboard Petrel was responsible for locating the Japanese battleship Musashi in 2015. [ 145 ] In 2017, at Allen's direction, Petrel found USS Indianapolis , USS Ward , the wrecks of the Battle of Surigao Strait and the Battle of Ormoc Bay . In 2018, Petrel found a lost US Navy C-2A Greyhound aircraft in the Philippine Sea, USS Lexington in the Coral Sea and the USS Juneau off the coast of the Solomon Islands . [ 146 ] [ 147 ] [ 148 ]
Allen established non-profit community institutions to display his collections of historic artifacts. These include:
An active art collector, Allen gifted more than $100 million to support the arts. [ 154 ] On October 15, 2012, the Americans for the Arts gave Allen the Eli and Edythe Broad Award for Philanthropy in the Arts. [ 155 ] Allen loaned out more than 300 pieces from his private art collection to 47 different venues. The original 541-page typescript of Bram Stoker 's novel Dracula was in his collection at one point. [ 156 ] In 2013, Allen sold Barnett Newman 's Onement VI (1953) at Sotheby's in New York for $43.8 million, then the record for a work by the abstract artist. [ 157 ] [ 158 ]
In 2015, Allen founded the Seattle Art Fair, a four-day event with 60-plus galleries from around the world including the participation of the Gagosian Gallery , David Zwirner . The event drew thousands and inspired other satellite fairs throughout the city. [ 159 ]
In August 2016, Allen announced the launch of Upstream Music Fest + Summit, [ 160 ] an annual festival fashioned after South by Southwest . [ 161 ] Held in Pioneer Square , the first festival took place in May 2017. [ 162 ] It was cancelled in 2019 following Allen's death in 2018. [ 163 ]
In November 2022, Allen's art collection was auctioned at Christie's New York . [ 164 ] It was the biggest sale in art auction history, surpassing $1.5 billion in sales. Six works sold for more than $100 million: Seurat 's Les Poseuses Ensemble (Petite version) , ($149 million, with fees); Paul Cézanne 's 1888-90 La Montagne Sainte-Victoire ($138 million); van Gogh's Verger avec cyprès ($117 million); and Gustav Klimt 's 1903 Birch Forest ($105 million). The auction also included paintings by Botticelli , David Hockney , Roy Lichtenstein , Edward Hopper , Andy Warhol , Jasper Johns and Jan Brueghel the Younger . Proceeds from the auction benefitted undisclosed philanthropies. [ 165 ] [ 166 ] [ 167 ]
In 1989, Allen donated $2 million to the University of Washington to construct the Allen Library, which was named after his father Kenneth S. Allen, a former associate director of the University of Washington library system. [ 168 ] In the same year, Allen donated an additional $8 million to establish the Kenneth S. Allen Library Endowment. [ 169 ] In 2012, the endowment was renamed the Kenneth S. and Faye G. Allen Library Endowment after Allen's mother (a noted bibliophile) died. [ 170 ]
In 2002, Allen donated $14 million to the University of Washington to construct the Paul G. Allen Center for Computer Science and Engineering. [ 171 ] The building was dedicated in October 2003. [ 172 ]
In 2010, Allen announced a gift of $26 million to build the Paul G. Allen School of Global Animal Health at Washington State University , his alma mater. The gift was the largest private donation in the university's history. [ 173 ]
In 2016, Allen pledged a $10 million donation over four years for the creation of the Allen Discovery Centers at Tufts University and Stanford University . The centers would fund research that would read and write the morphogenetic code. Over eight years the donation could be as much as $20 million. [ 174 ]
In 2017, Allen donated $40 million (with an additional $10 million from Microsoft) to reorganize the University of Washington's Computer Science and Engineering department into the Paul G. Allen School of Computer Science and Engineering. [ 175 ]
While Allen expressed interest in romantic love and one day having a family, [ 176 ] he never married and had no children. [ 177 ] His marriage plans with his first girlfriend were cancelled as he felt he "was not ready to marry at 23". [ 39 ] He was sometimes considered reclusive . [ 178 ] [ 179 ] In the 1990s, he purchased Rock Hudson 's Los Angeles estate from film director John Landis and added the Neptune Valley recording studio to the property. Allen's family put the home on the market for $56 million after his death. [ 180 ]
Allen received his first electric guitar at the age of sixteen, and was inspired to play it by listening to Jimi Hendrix . [ 181 ] In 2000, Allen played rhythm guitar on the independently produced album Grown Men . [ 182 ] In 2013, he had a major label release on Sony's Legacy Recordings: Everywhere at Once by Paul Allen and the Underthinkers. [ 183 ] PopMatters.com described Everywhere at Once as "a quality release of blues-rock that's enjoyable from start to finish". [ 184 ] [ 185 ]
On February 7, 2018, an interview by the magazine New York on their Vulture website, Quincy Jones expressed respect for Allen's talent, saying he "sings and plays just like Hendrix". [ 186 ]
Allen's 414-foot (126 m) yacht, Octopus , was launched in 2003. [ 187 ] As of 2019, it was 20th on the list of motor yachts by length . The yacht is equipped with two helicopters, a submarine, an ROV , a swimming pool, a music studio and a basketball court. [ 188 ] Octopus is a member of AMVER , a voluntary group ship reporting system used worldwide by authorities to arrange assistance for those in distress at sea. [ 189 ] The ship is also known for its annual celebrity-studded parties which Allen hosted at the Cannes film festival , [ 190 ] where Allen and his band played for guests. These performances included musicians such as Usher and Dave Stewart . [ 191 ] Octopus was also used in the search for a missing American pilot and two officers whose plane disappeared off Palau , [ 192 ] and the study of a rare fish called a coelacanth , among many others. [ 193 ] Following Allen's death in 2018, Octopus was refitted and put on the market for $325 million. [ 194 ]
Allen also owned Tatoosh , one of the world's 100 largest yachts. In January 2016, it was reported that Tatoosh severely damaged approximately 1300 square meters of coral reef in the West Bay replenishment zone, Cayman Islands . [ 195 ] In April 2016, the Department of Environment (DoE) and Allen's Vulcan Inc. successfully completed a restoration plan to help speed recovery and protect the future of coral in this area. [ 196 ]
In 2011, Allen's memoir, Idea Man: A Memoir by the Co-founder of Microsoft , was published by Portfolio, a Penguin Group imprint. The book recounts how Allen became enamored with computers and, at an early age, conceived the idea for Microsoft, recruited his friend Bill Gates to join him, and launched what would become the world's most successful software company. It also explores Allen's business and creative ventures following his 1983 departure from Microsoft, including his involvement in SpaceShipOne, his purchase of the Portland Trail Blazers and Seattle Seahawks, his passion for music, and his ongoing support for scientific research. The book made the New York Times Best Seller list . A paperback version, which included a new epilogue, was published on October 30, 2012. [ 197 ] [ 198 ]
Allen was diagnosed with Stage 1-A Hodgkin's lymphoma in 1982. [ 41 ] His cancer was successfully treated by several months of radiation therapy . [ 38 ] Allen was diagnosed with non-Hodgkin lymphoma in 2009. Likewise, the cancer was successfully treated until it returned in 2018. It ultimately caused his death by septic shock on October 15, 2018. [ 199 ] [ 17 ] He was 65 years old. [ 200 ] [ 201 ] Allen's sister, Jody Allen , was named executor and trustee of his estate. [ 194 ] [ 202 ]
Several Seattle-area landmarks, including the Space Needle , Columbia Center and Lumen Field , as well as various Microsoft offices throughout the United States, were illuminated in blue on November 3, 2018, as a tribute to Allen. [ 203 ] He was also honored by his early business partner and lifelong friend Bill Gates , who said in a statement:
Paul loved life and those around him, and we all cherished him in return. He deserved much more time, but his contributions to the world of technology and philanthropy will live on for generations to come. We will miss him tremendously. [ 43 ]
Allen received numerous awards in many different areas, including sports, technology, philanthropy, and the arts: | https://en.wikipedia.org/wiki/Paul_Allen |
John Paul Attfield (born 1962) [ 3 ] is a British chemist who is Professor of Materials science in the School of Chemistry at the University of Edinburgh and Director of the Centre for Science at Extreme Conditions (CSEC). [ 4 ] [ 5 ] [ 6 ]
Attfield was educated at Durham Johnston School [ 3 ] in Durham, England and the University of Oxford where he was a student at Magdalen College, Oxford . He was awarded a Bachelor of Arts degree in chemistry followed by a Doctor of Philosophy degree in 1987 for his work on chemical crystallography supervised by Anthony Cheetham and Peter Battle. [ 2 ]
Attfield was appointed a lecturer, [ when? ] and subsequently a Reader [ when? ] at the University of Cambridge from 1991 to 2003. [ 1 ] Attfield's research focuses on synthesis, structural studies, and property measurements for electronic materials such as transition metal oxides . His research has been funded by the Engineering and Physical Sciences Research Council (EPSRC). [ 7 ] Attfield has made significant contributions to the study of the Verwey transition in magnetite , solving its charge ordering properties.
Paul Attfield has made distinctive contributions to the experimental understanding of structure in the solid-state , in particular pioneering the use of resonant X-ray scattering to study cation and valence ordering effects and characterising charge-order in strongly correlated systems such as magnetite . [ 8 ] He introduced the cation-size variance as a concept to rationalise and predict disorder effects, with a substantial impact on the study and preparation of technologically important materials. [ 8 ] He has synthesised and characterised new materials with novel electronic properties, including high-Tc superconductivity , colossal magnetoresistance , and negative thermal expansion , including new developments in chemical synthesis . [ 8 ]
Attfield was awarded the Meldola Medal and Prize by the Royal Society of Chemistry (RSC) in 1991; the Corday-Morgan Medal of the RSC in 1998; and the Peter Day Award in 2013. He was elected a Fellow of the Royal Society (FRS) in 2014 for “substantial contribution to the improvement of natural knowledge”. [ 8 ] In 2016, Attield was awarded a Daiwa Adrian Prize , recognizing his work as part of a British-Japanese scientific collaboration, [ 9 ] and in 2022 he received the John B. Goodenough Award for materials chemistry from the Royal Chemistry Society, specifically "For transformative discoveries of new materials from high pressure synthesis and of novel electronic phenomena in solids." [ 10 ]
“All text published under the heading 'Biography' on Fellow profile pages is available under Creative Commons Attribution 4.0 International License .” -- Royal Society Terms, conditions and policies at the Wayback Machine (archived 2016-11-11)
This article incorporates text available under the CC BY 4.0 license. | https://en.wikipedia.org/wiki/Paul_Attfield |
Paul Benjamin Ferrara (November 2, 1942 – May 30, 2011) was a scientist and administrator who pioneered the use of DNA profiling in America.
Ferrara graduated from Syracuse University and State University of New York College of Environmental Science and Forestry with doctorate degree in organic chemistry. [ 1 ]
In 1987 the private New York laboratory, Lifecodes, began assisting Dr. Ferrara in his efforts to establish a DNA laboratory for the state of Virginia.
In 1988 Timothy Spencer, the "Southside Strangler", became first serial killer in the United States to be convicted on the basis of DNA evidence. Spencer committed three rapes and murders in Richmond Virginia, and one in Arlington, Virginia in the fall of 1987.
Ferrara recognized the potential utility of the precedent that had been set in Spencer case, and immediately focused his political savvy on convincing the Virginia General Assembly to fund the creation of the first State DNA Database in the country.
In 1989 under his leadership, Virginia became the first state laboratory capable of performing DNA fingerprinting. The FBI had started its limited DNA laboratory operations just four months earlier.
In addition to his directorship of the Virginia Department of Forensic Science (VA-DFS), Dr. Ferrara was an honorary professor at Virginia Commonwealth University. Through his passion for teaching and research, as well as his commitment to developing a nationally recognized Forensic Science educational program at VCU, the program officially became a department in 2005.
In the mid-2000s, Dr. Ferrara was diagnosed with early-stage lung cancer. Several years after the initial lung surgery, it was discovered that the cancer had spread.
Dr. Ferrara died on May 30, 2011, of brain cancer at the age of 68. [ 2 ] [ 3 ] [ 4 ]
Upon approval of Governor McDonnell, the DFS Central Laboratory building was renamed the Paul B. Ferrara Building, in honor of the late department director who died in May 2011. A ceremony and reception was held at the Central Laboratory on November 18, 2011, to unveil the signage displaying the new building name. | https://en.wikipedia.org/wiki/Paul_B._Ferrara |
Paul Anthony Benioff [ 1 ] (May 1, 1930 – March 29, 2022) was an American physicist who helped pioneer the field of quantum computing . Benioff was best known for his research in quantum information theory during the 1970s and 80s that demonstrated the theoretical possibility of quantum computers by describing the first quantum mechanical model of a computer. In this work, Benioff showed that a computer could operate under the laws of quantum mechanics by describing a Schrödinger equation description of Turing machines . Benioff's body of work in quantum information theory encompassed quantum computers, quantum robots, and the relationship between foundations in logic, math, and physics.
Benioff was born on May 1, 1930, in Pasadena, California. [ 2 ] His father, Hugo Benioff , was a professor of seismology at the California Institute of Technology , and his mother, Alice Pauline Silverman, received a master's degree in English from the University of California, Berkeley .
Benioff also attended Berkeley, where he earned an undergraduate degree in botany in 1951. After a two-year stint working in nuclear chemistry for Tracerlab, he returned to Berkeley. In 1959, he obtained his PhD in nuclear chemistry.
In 1960, Benioff spent a year at the Weizmann Institute of Science in Israel as a postdoctoral fellow. He then spent six months at the Niels Bohr Institute in Copenhagen as a Ford Fellow. In 1961, he began a long career at Argonne National Laboratory , first with its Chemistry Division and later in 1978 in the lab's Environmental Impact Division. Benioff remained at Argonne until he retired in 1995. He continued to conduct research at the laboratory as a post-retirement emeritus scientist for the Physics Division until his death in 2022, survived by his wife of 62 years, Hanna (née Hannelore Leshner) and their three children. Chicago Tribune, April 3, 2022 .
In addition, Benioff taught the foundations of quantum mechanics as a visiting professor at Tel Aviv University in 1979, and he worked as a visiting scientist at CNRS Marseilles in 1979 and 1982.
In the 1970s, Benioff began to research the theoretical feasibility of quantum computing. His early research culminated in a paper, [ 3 ] published in 1980, that described a quantum mechanical model of Turing machines . This work was based on a classical description in 1973 of reversible Turing machines by physicist Charles H. Bennett . [ 4 ]
Benioff's model of a quantum computer was reversible and did not dissipate energy. [ 5 ] At the time, there were several papers arguing that the creation of a reversible model of quantum computing was impossible. Benioff's paper was the first to show that reversible quantum computing was theoretically possible, which in turn showed the possibility of quantum computing in general. This work, along with later work by several other authors (including David Deutsch , Richard Feynman , and Peter Shor ), initiated the field of quantum computing.
In a paper published in 1982, [ 6 ] Benioff further developed his original model of quantum mechanical Turing machines. This work put quantum computers on a solid theoretical foundation. Richard Feynman then produced a universal quantum simulator . [ 7 ] Building on the work of Benioff and Feynman, Deutsch proposed that quantum mechanics can be used to solve computational problems faster than classical computers, and in 1994, Shor described a factoring algorithm that is considered to have an exponential speedup over classical computers. [ 8 ]
After Benioff and his peers in the field published several more papers on quantum computers, the idea began to gain traction with industry, banking, and government agencies. The field is now a fast-growing area of research that could have applications in cybersecurity , cryptography , quantum system modeling and more.
Throughout his career at Argonne, Benioff conducted research in many fields, including mathematics , physics and chemistry . While in the Chemistry Division, he conducted research on nuclear reaction theory, as well as the relationship between the foundations of physics and mathematics.
After joining Argonne's Environmental Impact Division in 1978, Benioff continued work on quantum computing and on foundational issues. This included descriptions of quantum robots, quantum mechanical models of different types of numbers, and other topics. Later in his career he studied the effects of number scaling and local mathematics on physics and geometry . As an emeritus, he continued to work on these and other foundational topics.
In 2000, Benioff received the Quantum Communication Award of the International Organization for Quantum Communication, Computing, and Measurement, as well as the Quantum Computing and Communication Prize from Tamagawa University in Japan. He became a fellow of the American Physical Society in 2001. [ 9 ] The following year, he was awarded the Special University of Chicago Medal for Distinguished Performance at Argonne National Laboratory . In 2016, Argonne held a conference in honor of his quantum computing work. | https://en.wikipedia.org/wiki/Paul_Benioff |
Paul Berg (June 30, 1926 – February 15, 2023) was an American biochemist and professor at Stanford University .
He was the recipient of the Nobel Prize in Chemistry in 1980, along with Walter Gilbert and Frederick Sanger . The award recognized their contributions to basic research involving nucleic acids , especially recombinant DNA .
Berg received his undergraduate education at Penn State University , where he majored in biochemistry . He received his PhD in biochemistry from Case Western Reserve University in 1952. Berg worked as a professor at Washington University School of Medicine and Stanford University School of Medicine , in addition to serving as the director of the Beckman Center for Molecular and Genetic Medicine .
In addition to the Nobel Prize, Berg was presented with the National Medal of Science in 1983 and the National Library of Medicine Medal in 1986. Berg was a member of the Board of Sponsors for the Bulletin of the Atomic Scientists . [ 4 ]
Berg was born in Brooklyn , New York City. He was the son of a Russian Jewish immigrant couple, [ 5 ] Sarah Brodsky, a homemaker, and Harry Berg, a clothing manufacturer. [ 6 ] Berg graduated from Abraham Lincoln High School in 1943, [ 7 ] received his Bachelor of Science degree in biochemistry from Penn State University in 1948 and PhD in biochemistry from Case Western Reserve University in 1952. He was a member of the Jewish fraternity , ΒΣΡ . [ 8 ]
After completing his graduate studies, Berg spent two years (1952–1954) as a postdoctoral fellow with the American Cancer Society , working at the Institute of Cytophysiology in Copenhagen , Denmark, and the Washington University School of Medicine , and spent additional time in 1954 as a scholar in cancer research with the department of microbiology at the Washington University School of Medicine. [ 9 ] He worked with Arthur Kornberg , while at Washington University. [ 6 ] Berg was also tenured as a research fellow at Clare Hall, Cambridge . [ 2 ] [ 10 ] He was a professor at Washington University School of Medicine from 1955 until 1959. After 1959, Berg moved to Stanford University , where he taught biochemistry from 1959 until 2000 and served as director of the Beckman Center for Molecular and Genetic Medicine from 1985 until 2000. [ 9 ] In 2000 he retired from his administrative and teaching posts, continuing to be active in research. [ 11 ]
Berg's postgraduate studies involved the use of radioisotope tracers to study intermediary metabolism . This resulted in the understanding of how foodstuffs are converted to cellular materials, through the use of isotopic carbons or heavy nitrogen atoms. Paul Berg's doctorate paper is now known as the conversion of formic acid , formaldehyde and methanol to fully reduced states of methyl groups in methionine . He was also one of the first to demonstrate that folic acid and B 12 cofactors had roles in the processes mentioned.
Berg is arguably most famous for his pioneering work involving gene splicing of recombinant DNA . [ 12 ] Berg was the first scientist to create a molecule containing DNA from two different species by inserting DNA from another species into a molecule. This gene-splicing technique was a fundamental step in the development of modern genetic engineering . After developing the technique, Berg used it for his studies of viral chromosomes. [ 13 ]
Berg was a professor emeritus at Stanford. [ 9 ] As of 2000, he stopped doing active research, to focus on other interests, including involvement in public policy for biomedical issues involving recombinant DNA and embryonic stem cells and publishing a book about geneticist George Beadle . [ 14 ]
Berg was a member of the Board of Sponsors of the Bulletin of the Atomic Scientists . [ 4 ] He was also an organizer of the Asilomar conference on recombinant DNA in 1975. The previous year, Berg and other scientists had called for a voluntary moratorium on certain recombinant DNA research until they could evaluate the risks. That influential conference did evaluate the potential hazards and set guidelines for biotechnology research. It can be seen as an early application of the precautionary principle .
Berg was awarded one-half of the 1980 Nobel Prize in Chemistry , with the other half being shared by Walter Gilbert and Frederick Sanger . [ 9 ] [ 15 ] [ 16 ] Berg was recognized for "his fundamental studies of the biochemistry of nucleic acids , with particular regard to recombinant DNA ", while Sanger and Gilbert were honored for "their contributions concerning the determination of base sequences in nucleic acids." [ 17 ]
He was elected a Fellow of the American Academy of Arts and Sciences and a member of the United States National Academy of Sciences in 1966. [ 18 ] [ 19 ] In 1983, Ronald Reagan presented Berg with the National Medal of Science . That same year, he was elected to the American Philosophical Society . [ 20 ] In 1989, he received the Golden Plate Award of the American Academy of Achievement . [ 21 ] He was elected a Foreign Member of the Royal Society (ForMemRS) in 1992 . [ 22 ] In 2005 he was awarded the Biotechnology Heritage Award by the Biotechnology Industry Organization (BIO) and the Chemical Heritage Foundation . [ 23 ] [ 24 ] In 2006 he received Wonderfest 's Carl Sagan Prize for Science Popularization. [ 25 ]
Berg died on February 15, 2023, at the age of 96. [ 5 ] [ 26 ] | https://en.wikipedia.org/wiki/Paul_Berg |
Paul Isaac Bernays ( / b ɜːr ˈ n eɪ z / bur- NAYZ ; Swiss Standard German: [bɛrˈnaɪs] ; 17 October 1888 – 18 September 1977) was a Swiss mathematician who made significant contributions to mathematical logic , axiomatic set theory , and the philosophy of mathematics . He was an assistant and close collaborator of David Hilbert .
Bernays was born into a distinguished German-Jewish family of scholars and businessmen. His great-grandfather, Isaac ben Jacob Bernays , served as chief rabbi of Hamburg from 1821 to 1849. [ 1 ]
Bernays spent his childhood in Berlin, and attended the Köllnische Gymnasium , 1895–1907. At the University of Berlin , he studied mathematics under Issai Schur , Edmund Landau , Ferdinand Georg Frobenius , and Friedrich Schottky ; philosophy under Alois Riehl , Carl Stumpf and Ernst Cassirer ; and physics under Max Planck . At the University of Göttingen , he studied mathematics under David Hilbert , Edmund Landau , Hermann Weyl , and Felix Klein ; physics under Voigt and Max Born ; and philosophy under Leonard Nelson .
In 1912, the University of Berlin awarded him a Ph.D. in mathematics for a thesis, supervised by Landau, on the analytic number theory of binary quadratic forms . That same year, the University of Zurich awarded him habilitation for a thesis on complex analysis and Picard's theorem . The examiner was Ernst Zermelo . Bernays was Privatdozent at the University of Zurich, 1912–1917, where he came to know George Pólya . His collected communications with Kurt Gödel span many decades.
Starting in 1917, David Hilbert employed Bernays to assist him with his investigations of the foundation of arithmetic. Bernays also lectured on other areas of mathematics at the University of Göttingen. In 1918, that university awarded him a second habilitation for a thesis on the axiomatics of the propositional calculus of Principia Mathematica . [ 2 ]
In 1922, Göttingen appointed Bernays extraordinary professor without tenure. His most successful student there was Gerhard Gentzen . After Nazi Germany enacted the Law for the Restoration of the Professional Civil Service in 1933, the university fired Bernays because of his Jewish ancestry.
After working privately for Hilbert for six months, Bernays and his family moved to Switzerland , whose nationality he had inherited from his father, and where the ETH Zurich employed him on occasion. He also visited the University of Pennsylvania and was a visiting scholar at the Institute for Advanced Study in 1935–36 and again in 1959–60. [ 3 ]
His habilitation thesis was written under the supervision of Hilbert himself, on the topic of the axiomatisation of propositional logic in Whitehead and Russell 's Principia Mathematica . It contains the first known proof of semantic completeness of propositional logic, which was reproved independently also by Emil Post later on.
Bernays's collaboration with Hilbert culminated in the two volume work, Grundlagen der Mathematik (English: Foundations of Mathematics ) published in 1934 and 1939, which is discussed in Sieg and Ravaglia (2005). A proof in this work that a sufficiently strong consistent theory cannot contain its own reference functor is known as the Hilbert–Bernays paradox .
In seven papers, published between 1937 and 1954 in the Journal of Symbolic Logic (republished in Müller 1976), Bernays set out an axiomatic set theory whose starting point was a related theory John von Neumann had set out in the 1920s. Von Neumann's theory took the notions of function and argument as primitive. Bernays recast von Neumann's theory so that classes and sets were primitive. Bernays's theory, with modifications by Kurt Gödel , is known as von Neumann–Bernays–Gödel set theory . | https://en.wikipedia.org/wiki/Paul_Bernays |
The Paul Bunge Prize is an international award for seminal and lasting contributions to the history of scientific instruments. Endowed in 1993 by the late Hans R. Jenemann (1920–1996), [ 1 ] glass chemist at Schott AG in Mainz, and collector and historian of antique chemical balances. The name of the prize commemorates the leading German maker of precision balances in the nineteenth century Paul Bunge (1839–1888). [ 2 ] The Prize is given by the Hans R. Jenemann Foundation and jointly administered by the German Chemical Society and the Deutsche Bunsen-Gesellschaft für Physikalische Chemie . | https://en.wikipedia.org/wiki/Paul_Bunge_Prize |
Paul Chaleff (born 1947) [ 1 ] is an American ceramist and professor emeritus of Fine Arts at Hofstra University . [ 2 ] He is considered a pioneer of the revival of wood-fired ceramics in the US and credited as one of the first to use wood-burning dragon kilns in the style of the anagama tradition. He is best known as an innovator of large-scale ceramic sculpture. His work can be found in the collections of the Museum of Modern Art Department of Architecture and Design, [ 1 ] and in the Metropolitan Museum of Art . [ 3 ] [ 4 ]
Paul Chaleff's work was strongly influenced by master potter Takeshi Nakazato . In 1989, Chaleff began collaborating with sculptor Sir Anthony Caro . Together they created nearly 50 works, both figurative and abstract. Caro's sculpture has had a direct influence on Chaleff's work as has the sculpture of Isamu Noguchi , and the ceramics of John Mason and Lucie Rie . [ 5 ] [ 6 ] Chaleff has also been recognized as an innovator of large-scale ceramic sculpture. [ 7 ] The strength of his works stems from their being rough, gestural, split, and impure while remaining elegant. [ 8 ]
Chaleff attended the Bronx High School of Science . In 1968, while studying biology at the City College of New York , Chaleff survived a drowning accident that took his friend's life. He graduated in 1969 with a degree in Fine Arts . In 1971, Chaleff received his Master of Fine Arts in Ceramic Design from City College of New York. [ 2 ] In 1975 he traveled to Japan to study Japanese pottery and wood-burning kiln design [ 9 ] and returned to New York in 1977 where he built a studio and kilns in Pine Plains .
Chaleff's anagama kiln was one of the first in the US. [ 10 ] In 1980, the Museum of Modern Art purchased and exhibited his work from that kiln. [ 11 ] In 1980, his wood-fired work was showcased at an official State dinner at the White House . Between 1989 and 2000, Chaleff collaborated on a series of clay sculptures with Sir Anthony Caro in his studio, first in Pine Plains and then Ancram . [ 12 ] In 1995, he participated in Fire and Clay, a symposium of international clay sculptors held in Iksan . [ 13 ] In 1997, Chaleff accepted a professorship from Hofstra University , where he directed the ceramics program until retirement in 2021. [ 14 ]
Chaleff's work is represented in the following museum collections. [ 15 ] | https://en.wikipedia.org/wiki/Paul_Chaleff |
Paul Moritz Cohn FRS [ 1 ] (8 January 1924 – 20 April 2006) was Astor Professor of Mathematics at University College London , 1986–1989, and author of many textbooks on algebra . [ 4 ] His work was mostly in the area of algebra , especially non-commutative rings . [ 3 ] [ 5 ]
Cohn was the only child of Jewish parents, James (or Jakob) Cohn, owner of an import business, and Julia ( née Cohen [ 6 ] ), a schoolteacher. [ 5 ] [ 7 ]
Both of his parents were born in Hamburg, as were three of his grandparents. His ancestors came from various parts of Germany. His father fought in the German army in World War I ; he was wounded several times and awarded the Iron Cross . [ 7 ] A street in Hamburg is named in memory of his mother. [ 8 ]
When he was born, his parents were living with his mother's mother in Isestraße. After her death in October 1925, the family moved to a rented flat in a new building in Lattenkamp, in the Winterhude quarter. He attended a kindergarten then, in April 1930, moved to Alsterdorfer Straße School. After a while, he had a new teacher, a National Socialist, who picked on him and punished him without cause. Thus in 1931, he moved to the Meerweinstraße School where his mother taught. [ 7 ]
Following the rise of the Nazis in 1933, his father's business was confiscated and his mother dismissed. He moved to the Talmud-Tora-Schule, a Jewish school. In mid-1937, the family moved to Klosterallee. This was nearer the school, the synagogue and other pupils, being in the Jewish area. His German teacher was Dr. Ernst Loewenberg, the son of the poet Jakob Loewenberg . [ 7 ]
On the night of 9/10 November 1938 ( Kristallnacht ), his father was arrested and sent to Sachsenhausen concentration camp . He was released after four months but told to emigrate. Cohn went to Britain in May 1939 on the Kindertransport to work on a chicken farm, and never saw his parents again. He corresponded regularly with them until late 1941. At the end of the War , he learned that they were deported to Riga on 6 December 1941 and never returned. At the end of 1941, the farm closed. He trained as a precision engineer , acquired a work permit and worked in a factory for 4½ years. He passed the Cambridge Scholarship Examination, and won an exhibition to Trinity College, Cambridge . [ 5 ] [ 7 ]
He received a B.A in mathematics from Cambridge University in 1948 and a Ph.D. (supervised by Philip Hall ) in 1951. He then spent a year as a Chargé de Recherches at the University of Nancy . On his return, he became a lecturer in mathematics at Manchester University . He was a visiting professor at Yale University in 1961–1962, and for part of 1962 was at the University of California at Berkeley . On his return, he became Reader at Queen Mary College . He was a visiting professor at the University of Chicago in 1964 and at the State University of New York at Stony Brook in 1967. [ 3 ] [ 5 ] By then, he was regarded as one of the world's leading algebraists. [ 8 ]
Also in 1967, he became head of the Department of Mathematics at Bedford College , London. He held several visiting professorships, in America, Paris, Delhi , Canada, Haifa and Bielefeld . [ 3 ] He was awarded the Lester R. Ford Award from the Mathematical Association of America in 1972 [ 9 ] and the Senior Berwick Prize of the London Mathematical Society in 1974. [ 4 ] [ 6 ]
In the early 1980s, funding cuts caused the closure of the small colleges of the University of London . Cohn moved to University College London in 1984, [ 10 ] together with the two other experts at Bedford on ring theory , Bill Stephenson and Warren Dicks. [ 11 ] He became Astor Professor of Mathematics there in 1986. He continued to be a visiting professor, for example to the University of Alberta in 1986 and to Bar Ilan University in 1987. He retired in 1989, but remained active as professor emeritus and honorary research fellow until his death. [ 3 ] [ 5 ]
He was president of the London Mathematical Society , 1982–1984, having been its secretary, 1965–1967 and a council member in 1968–1971, 1972–1975 and 1979–1982. He was editor of the society's monographs in 1968–1977 and 1980–1993. He was elected a Fellow of the Royal Society in 1980 and was on its council, 1985–1987. He was a member of the Mathematical Committee of the Science Research Council , 1977–1980. [ 3 ] He chaired the National Committee for Mathematics, 1988–1989. [ 4 ]
In all, Cohn wrote nearly 200 mathematical papers. [ 10 ] He worked in many areas of algebra, mainly in non-commutative ring theory. His first papers, covering many topics, were published in 1952. He generalised a theorem due to Wilhelm Magnus , and worked on the structure of tensor spaces. In 1953 he published a joint paper with Kurt Mahler on pseudo-valuations and in 1954 he published a work on Lie algebras . [ 3 ] Papers over the next few years covered areas such as group theory , field theory , Lie rings , semigroups , abelian groups and ring theory . After that, he moved into the areas of Jordan algebras , skew fields , and non-commutative unique factorisation domains .
In 1957 Cohn published his first book, Lie Groups , on groups that are analytic manifolds : Lie groups . His second book, Linear Equations , appeared in 1958 and his third, Solid geometry , in 1961. Universal algebra appeared in 1965 (second edition 1981). After that, he concentrated on non-commutative ring theory and the theory of algebras . [ 3 ] His monograph Free Rings and their Relations appeared in 1971. It covered the work of Cohn and others on free associative algebras and related classes of rings, especially free ideal rings . He included all of his own published results on the embedding of rings into skew fields. The second, enlarged edition appeared in 1985. [ 3 ]
Cohn also wrote undergraduate textbooks . Algebra I appeared in 1974 and Algebra II in 1977. The second edition, in three volumes, was published by Wiley between 1982 and 1991. [ 3 ] These volumes were in line with the British (rather than American) curricula at the time and include both linear algebra and abstract algebra . Cohn wrote a subsequent revised iteration of the first volume as Classical Algebra (Wiley, 2000) as a more "user friendly" version for undergraduates (according to its preface); this book also includes a few selected topics from volumes II and III of Algebra .
The final incarnation of Cohn's algebra textbooks appeared in 2003 as two Springer volumes Basic Algebra and Further Algebra and Applications . The material in Basic Algebra is (according to its preface) rather more concise and, while corresponding roughly with Algebra I , assumes knowledge of linear algebra. The material on basic theories (groups, rings, fields) is pursued in more depth in Basic Algebra compared to Algebra I . Further Algebra and Applications roughly corresponds to volumes II and III of Algebra , but reflects the shift of some material from these volumes to Basic Algebra .
His recreation was etymology and language in all its forms. He married Deirdre Sharon in 1958, and they had two daughters. [ 4 ] [ 6 ] | https://en.wikipedia.org/wiki/Paul_Cohn |
Paul S. Cremer (born 1967) is an American chemist in physical and analytical chemistry at biological interfaces.
Cremer graduated from University of Wisconsin-Madison with a BA in 1990, completed his PhD at University of California, Berkeley in 1996, and completed postdoctoral work at Stanford University (1996-1998). [ 1 ]
Cremer joined the faculty in the chemistry department, Texas A&M University in 1998.
He is known for his work in Hofmeister series and supported lipid bilayers . [ 1 ] [ 2 ] He is also interested in nanofabrication, sum-frequency generation and biosensing.
Cremer joined the faculty in the chemistry department, Penn State University, in 2013. He continues his research in the lipid bilayer and protein folding . | https://en.wikipedia.org/wiki/Paul_Cremer |
Paul E. Ceruzzi (born 1949) is curator emeritus at the Smithsonian's National Air and Space Museum in Washington, D.C. [ 2 ]
Ceruzzi received a BA from Yale University in 1970 and received a Ph.D. from the University of Kansas in 1981, both in American studies . [ 1 ] Before joining the National Air and Space Museum, he was a Fulbright scholar [ 3 ] in Hamburg , Germany, and taught History of Technology at Clemson University in Clemson, South Carolina . [ 4 ] Ceruzzi is the author and co-author of several books on the history of computing and aerospace technology. He has curated or assisted in the mounting of several exhibitions at NASM , including: Beyond the Limits - Flight Enters the Computer Age, The Global Positioning System - A New Constellation, Space Race, How Things Fly and the James McDonnell Space Hangar of the museum's Steven F. Udvar-Hazy Center , at Dulles Airport. | https://en.wikipedia.org/wiki/Paul_E._Ceruzzi |
Paul Ernest is a contributor to the social constructivist philosophy of mathematics.
Paul Ernest is currently emeritus professor of the philosophy of mathematics education at University of Exeter , UK. [ 1 ] He is best known for his work on philosophical aspects of mathematics education , which includes establishing the subfield entitled the philosophy of mathematics education, and for his contributions to developing a social constructivist philosophy of mathematics . He is currently working on questions about ethics in mathematics . | https://en.wikipedia.org/wiki/Paul_Ernest |
Paul Francis McMillan (3 June 1956 – 2 February 2022) was a British chemist who held the Sir William Ramsay Chair of Chemistry at University College London . [ 1 ] His research considered the study of matter under extreme conditions of temperature and pressure, with a focus on phase transitions, amorphisation, and the study of glassy states. He has also investigated the survival of bacteria and larger organisms ( tardigrades ) under extreme compression, studies of amyloid fibrils, [ 2 ] the synthesis and characterisation of carbonitride nanocrystals and the study of water motion in confined environments. He has made extensive use of Raman spectroscopy together with X-ray diffraction and neutron scattering techniques.
McMillan was born in Edinburgh , Midlothian , and brought up in Loanhead , a small mining and farming village at the base of the Pentland Hills . [ 3 ] He attended Lasswade High School , where he graduated with the Marshall Memorial medal. [ 3 ] He then studied for a bachelor's degree in chemistry at the University of Edinburgh . [ 3 ] After graduating, McMillan moved to Arizona State University , where he researched geochemistry with John Holloway and Alexandra Navrotsky . [ 3 ] His doctoral research was in using vibrational spectroscopy to investigate the structures of silicate glasses. [ 4 ]
McMillan worked as a postdoctoral fellow at Arizona State University , where he installed one of the first micro-beam Raman spectroscopy instruments in the US. He used Raman spectroscopy to study high pressure minerals and materials. He was hired to a teaching position at Arizona State University in 1983, and promoted to Professor in the Department of Chemistry and Biochemistry in 1993. [ 3 ] He was appointed Director of the Center for Solid State Science in 1997 and was named Presidential Professor of the Sciences. [ 3 ] In 2000 he was awarded the Brunauer Cement Award of American Ceramic Society. [ 5 ] In 2000, McMillan returned to the United Kingdom , where he was made Professor of Solid State Chemistry at University College London , an appointment jointly held with the Royal Institution . [ 3 ] McMillan has also held visiting positions at the Universités of Nantes and Rennes, the Ecole Normale Supérieure and Université Claude Bernard . [ citation needed ]
McMillan's research involved the exploration of solid state chemistry under extreme high pressure and high temperature conditions using diamond anvil cells . [ 6 ] New compounds and materials are prepared and studied at up to a million atmospheres and thousands of degrees Celsius using spectroscopy and synchrotron X-ray diffraction. [ 7 ] He studied the properties and structure of liquids, amorphous solids and biological molecules at high pressure. [ 6 ] McMillan has contributed across numerous fields and has published work relating to solid state inorganic/materials chemistry, high pressure-high temperature research, [ 8 ] amorphous solids and liquids, [ 9 ] vibrational spectroscopy, [ 10 ] synchrotron X-ray and neutron scattering, mineral physics, graphitic carbonitrides, [ 11 ] battery materials and the response of bacteria to high pressures. [ 12 ]
In 2015 McMillan was a panellist on Melvyn Bragg 's In Our Time on BBC Radio 4. [ 13 ]
McMillan died in London on 2 February 2022, at the age of 65. [ 14 ] [ 15 ] [ 16 ] | https://en.wikipedia.org/wiki/Paul_F._McMillan |
Paul G. Mezey is a Hungarian-Canadian mathematical chemist . He was the Canada Research Chair in Scientific Modeling and Simulation in the Department of Chemistry at the Memorial University of Newfoundland . [ 1 ] He retired from Memorial University in 2018.
Mezey earned a Master's degrees in chemistry, a Ph.D. in Chemistry, and a Master's degree in mathematics, all from Eötvös Loránd University in Budapest , in the years 1967, 1970, and 1972 respectively.
From 1982 to 2003, he was a professor of chemistry and mathematics at the University of Saskatchewan , where he earned a D. Sc. in 1985 in mathematical chemistry. He was a faculty member at Memorial University from 2003 to 2018.
Mezey is editor in chief of the Journal of Mathematical Chemistry . [ 2 ]
In 2003, Mezey received a Canada Research Chair; the chair was renewed for a second term 2010 and concluded in 2017. [ 3 ] [ 4 ] Mezey is a foreign member of the Hungarian Academy of Sciences . [ 5 ] | https://en.wikipedia.org/wiki/Paul_G._Mezey |
Paul Albert Gordan (27 April 1837 – 21 December 1912) was a German mathematician known for work in invariant theory and for the Clebsch–Gordan coefficients and Gordan's lemma . [ 1 ] He was called "the king of invariant theory". [ 2 ] [ 3 ] His most famous result is that the ring of invariants of binary forms of fixed degree is finitely generated. [ 3 ] Clebsch–Gordan coefficients are named after him and Alfred Clebsch . Gordan also served as the thesis advisor for Emmy Noether . [ 4 ] [ 5 ]
Gordan was born to Jewish parents in Breslau , Germany (now Wrocław , Poland), and died in Erlangen , Germany. [ 6 ]
He received his Dr. phil. at the University of Breslau with the thesis De Linea Geodetica , (On Geodesics of Spheroids ) under Carl Jacobi in 1862. He moved to Erlangen in 1874 to become professor of mathematics at the University of Erlangen-Nuremberg . [ 4 ]
A famous quote attributed to Gordan about David Hilbert 's proof of Hilbert's basis theorem , a result which vastly generalized his result on invariants, is "This is not mathematics; this is theology ." [ 2 ] [ 7 ] The proof in question was the (non-constructive) existence of a finite basis for invariants. It is not clear if Gordan really said this since the earliest reference to it is 25 years after the events and after his death. Nor is it clear whether the quote was intended as criticism, or praise, or a subtle joke. Gordan himself encouraged Hilbert and used Hilbert's results and methods, and the widespread story that he opposed Hilbert's work on invariant theory is a myth (though he did correctly point out in a referee's report that some of the reasoning in Hilbert's paper was incomplete). [ 8 ] [ 9 ]
He later said "I have convinced myself that even theology has its merits". He also published a simplified version of the proof. [ 10 ] [ 11 ] | https://en.wikipedia.org/wiki/Paul_Gordan |
Paul Hyman Silverman (October 8, 1924 – July 15, 2004) was an American medical researcher in the fields of immunology , epidemiology , and parasitology . [ 1 ] He was recognized for his research on stem cells and on the human genome . [ 2 ]
Silverman was born on October 8, 1924, in Minneapolis , Minnesota . [ 1 ] Growing up, he became fascinated with reading, and he won a local prize for his reading comprehension ability. He attended the University of Minnesota as a pre-medical student while also working three part-time jobs . He went on to serve in a MASH in the United States Army during World War II . [ 3 ] He received a bachelor's degree from Roosevelt University . [ 1 ] In 1951, Silverman received his M.S. from Northwestern University , after which he moved to Israel with his family. In Israel, he began research on malaria , which he continued to study for many years thereafter. In 1953, he and his family moved again, this time to England . There, he began studying at the Liverpool School of Tropical Medicine , from which he received his Ph.D. in parasitology and epidemiology in 1955. [ 3 ] [ 4 ]
Silverman returned to the United States when he was 39 years old. He then accepted a position at the University of Illinois at Urbana–Champaign before moving to the University of New Mexico in 1972. [ 3 ] [ 5 ] At the University of New Mexico, he and his team developed a killed malaria vaccine based on Jonas Salk 's polio vaccine . He became Vice President for Research and Graduate Studies at the University of New Mexico in 1975, and joined the State University of New York as their Provost for Research and Graduate Studies in 1978. In 1980, he became president of the University of Maine , a position he held until 1984. [ 3 ] At the University of Maine, he was credited with expanding the scope of research activities. [ 6 ] In 1984, he returned to research as a senior scientist at the Lawrence Berkeley National Laboratory . He also served at the University of California, Berkeley as Associate Laboratory Director for Life Sciences and Director of the Donner Lab. [ 3 ] In 1987, he helped organize a partnership between the University of California, Berkeley and Lawrence Livermore National Laboratory to establish the first research center dedicated to the study of the human genome. [ 4 ] He then worked at Beckman Instruments for several years before being appointed Associate Chancellor for Health Sciences at the University of California, Irvine in 1994, a position he held until his retirement in 1996. [ 3 ] [ 7 ] Also in 1994, he was elected to the World Academy of Art and Science . In the fall of 2003, he gave the commencement speech to the class of Roosevelt University, from which he received an honorary doctorate of human letters . [ 5 ]
Silverman was a member of the Human Genome Project 's advisory committee. [ 2 ] After its results showed that humans had about 30,000 genes, he noted that this suggested that genes were much less important causes of human diseases than previously thought. In an article published in The Scientist shortly before his death, he urged his fellow researchers to abandon genetic determinism , asking, "With only 30,000 genes, what is it that makes humans human?" [ 1 ] [ 2 ] [ 8 ]
Silverman met his wife, Nancy Josephs, [ 2 ] while he was serving in the Army during World War II. The two married on May 20, 1945, and their son, Daniel, was born in 1950; they also had a daughter, Claire. Paul Silverman died on July 16, 2004, of complications resulting from a bone marrow transplant he had received to treat his myelofibrosis . [ 3 ] [ 4 ] | https://en.wikipedia.org/wiki/Paul_H._Silverman |
Paul Hagenmuller (August 3, 1921 – January 7, 2017) was a French chemist. Hagenmuller founded the Laboratoire de Chimie du Solide (Solid-State Chemistry Laboratory) of the French National Centre for Scientific Research (CNRS) and he served as its Director until 1985. He is considered "one of the founders of solid-state chemistry ." [ 1 ]
Hagenmuller was born in 1921 in Alsace , France . [ 2 ] After studying in Strasbourg and Clermont-Ferrand , during WW2 , Hagenmuller was imprisoned in the Buchenwald and Mittelbau-Dora concentration camps. During those years, he was involved in sabotaging German missiles. [ 3 ] In 1950 he received his PhD from Sorbonne University . Subsequently, he spent two years teaching as a lecturer ( maître de conférences ) in Vietnam. He returned to France in 1956 and was appointed Professor of Inorganic Chemistry at the University of Rennes , working on "nonstoichiometry in vanadium and tungsten bronzes, two-dimensional oxyhalogenides, borides, and silicides, magnetic spinels". In 1961 he started working at the University of Bordeaux . [ 1 ]
Hagenmuller was noted for instigating cooperation between French researchers and researchers from the Soviet Union and Germany, his years in the concentration camps greatly affected his character. [ 3 ] He also collaborated with noted scientists such as John Goodenough , Jacques Friedel and Nevill Francis Mott on insulator-to-metal transitions of vanadium oxides . In the 1970s, he started working with Neil Bartlett on metal fluorides . His most noted research discovery was the synthesis of LaCuO 3 and LaSrCuO 4 , which would later become important superconductor materials. [ 1 ] His work on sodium-ion batteries received great interest years after it was published. [ 4 ]
In 2018 Hagenmuller remained the 4th most cited author from the Journal of Solid State Chemistry . [ 4 ] | https://en.wikipedia.org/wiki/Paul_Hagenmuller |
Paul Richard Halmos ( Hungarian : Halmos Pál ; 3 March 3 1916 – 2 October 2006) was a Hungarian -born American mathematician and probabilist who made fundamental advances in the areas of mathematical logic , probability theory , operator theory , ergodic theory , and functional analysis (in particular, Hilbert spaces ). He was also recognized as a great mathematical expositor. He has been described as one of The Martians . [ 1 ]
Born in the Kingdom of Hungary into a Jewish family, Halmos immigrated to the United States at age 13. He obtained his B.A. from the University of Illinois , majoring in mathematics while also fulfilling the requirements for a degree in philosophy. He obtained the degree after only three years, and was 19 years old when he graduated. He then began a Ph.D. in philosophy, still at the Champaign–Urbana campus. However, after failing his masters' oral exams, [ 2 ] he shifted to mathematics and graduated in 1938. Joseph L. Doob supervised his dissertation, titled Invariants of Certain Stochastic Transformations: The Mathematical Theory of Gambling Systems . [ 3 ]
Shortly after his graduation, Halmos left for the Institute for Advanced Study , lacking both job and grant money. Six months later, he was working under John von Neumann , which proved a decisive experience. While at the Institute, Halmos wrote his first book, Finite Dimensional Vector Spaces , which immediately established his reputation as a fine expositor of mathematics. [ 4 ]
From 1967 to 1968 he was the Donegall Lecturer in Mathematics at Trinity College Dublin .
Halmos taught at Syracuse University , the University of Chicago (1946–60), the University of Michigan (~1961–67), the University of Hawaii (1967–68), Indiana University (1969–85), and the University of California at Santa Barbara (1976–78). From his 1985 retirement from Indiana until his death, he was affiliated with the Mathematics department at Santa Clara University (1985–2006).
In a series of papers reprinted in his 1962 Algebraic Logic , Halmos devised polyadic algebras , an algebraic version of first-order logic differing from the better known cylindric algebras of Alfred Tarski and his students. An elementary version of polyadic algebra is described in monadic Boolean algebra .
In addition to his original contributions to mathematics, Halmos was an unusually clear and engaging expositor of university mathematics. He won the Lester R. Ford Award in 1971 [ 5 ] and again in 1977 (shared with W. P. Ziemer, W. H. Wheeler, S. H. Moolgavkar, J. H. Ewing and W. H. Gustafson). [ 6 ] Halmos chaired the American Mathematical Society committee that wrote the AMS style guide for academic mathematics, published in 1973. In 1983, he received the AMS's Leroy P. Steele Prize for exposition.
In the American Scientist 56(4): 375–389 (Winter 1968), Halmos argued that mathematics is a creative art, and that mathematicians should be seen as artists, not number crunchers. He discussed the division of the field into mathology and mathophysics, further arguing that mathematicians and painters think and work in related ways.
Halmos's 1985 "automathography" I Want to Be a Mathematician is an account of what it was like to be an academic mathematician in 20th century America. He called the book "automathography" rather than "autobiography", because its focus is almost entirely on his life as a mathematician, not his personal life. The book contains the following quote on Halmos' view of what doing mathematics means:
Don't just read it; fight it! Ask your own questions, look for your own examples, discover your own proofs. Is the hypothesis necessary? Is the converse true? What happens in the classical special case? What about the degenerate cases? Where does the proof use the hypothesis?
What does it take to be [a mathematician]? I think I know the answer: you have to be born right, you must continually strive to become perfect, you must love mathematics more than anything else, you must work at it hard and without stop, and you must never give up.
In these memoirs, Halmos claims to have invented the "iff" notation for the words " if and only if " and to have been the first to use the "tombstone" notation to signify the end of a proof , [ 7 ] and this is generally agreed to be the case. The tombstone symbol ∎ ( Unicode U+220E) is sometimes called a halmos . [ 8 ]
In 1994, Halmos received the Deborah and Franklin Haimo Award for Distinguished College or University Teaching of Mathematics . [ 9 ]
In 2005, Halmos and his wife Virginia Halmos funded the Euler Book Prize , an annual award given by the Mathematical Association of America for a book that is likely to improve the view of mathematics among the public. The first prize was given in 2007, the 300th anniversary of Leonhard Euler 's birth, to John Derbyshire for his book about Bernhard Riemann and the Riemann hypothesis : Prime Obsession . [ 10 ]
In 2009 George Csicsery featured Halmos in a documentary film also called I Want to Be a Mathematician . [ 11 ]
Books by Halmos have led to so many reviews that lists have been assembled. [ 12 ] [ 13 ] | https://en.wikipedia.org/wiki/Paul_Halmos |
Paul Lyon Houston (born January 27, 1947) is Professor Emeritus of Chemistry at Cornell University and Professor Emeritus of Chemistry and Biochemistry at the Georgia Institute of Technology .
Houston started his professorial career at Cornell University in 1975 following undergraduate study at Yale University , doctoral work at MIT , and postdoctoral research at the University of California at Berkeley . He became chair of Cornell's department of chemistry and chemical biology (1997–2001), senior associate dean of the college of arts and sciences (2002–2005), and the Peter J. W. Debye Professor of Chemistry. Most recently, he was dean of the college of sciences at Georgia Tech (from 2007-2013). [ 1 ]
Houston was a member of the Cornell Center for Materials Research, the Kavli Institute at Cornell for Nanoscale Science, and the Graduate Field of Applied Physics. Houston has held visiting positions at the Max Planck Institute for Quantum Optics (1982), Columbia University (1986, 1987), the Institute for Molecular Science, Okazaki , Japan (1989), the University of California at Berkeley (2003), and the University of Rome La Sapienza (2001, 2006). He has been an Alfred P. Sloan Research Fellow (1979–81), a Camille and Henry Dreyfus Teacher Scholar (1980), and a John Simon Guggenheim Fellow (1986–87). [ 1 ]
Houston served as a senior editor of the Journal of Physical Chemistry (1991–97), as chair of the American Physical Society Division of Laser Chemistry (1997–98), and as a member of the science and technology steering committee of Brookhaven National Laboratories (1998–2005). Houston has authored or co-authored over 160 publications in the field of physical chemistry and a textbook on chemical kinetics . [ 1 ]
Houston was elected a Fellow of the American Physical Society in 1989 for "important contributions toward understanding molecular photodissociation dynamics, energy transfer, and gas-solid interactions; in particular, for his imaginative use of photofragment imaging and his development of the field of vector correlations". [ 2 ]
In 2001, Housont shared with David W. Chandler the Herbert P. Broida Prize of the American Physical Society for work on product imaging in chemical dynamics . He was elected a fellow of the American Academy of Arts and Sciences in 2003. [ 3 ] | https://en.wikipedia.org/wiki/Paul_Houston_(chemist) |
Paul J. Gemperline (born 1955) is an American analytical chemist and chemometrician . He is a Distinguished Professor of Chemistry at East Carolina University (ECU) located in Greenville, North Carolina and has been the recipient of several scientific awards, including the 2003 Eastern Analytical Symposium Award in Chemometrics. He is author of more than 60 publications in the field of chemometrics. [ 1 ] Dr. Gemperline served as Dean of the Graduate School at ECU from 2008 to 2022. [ 1 ] He retired from ECU June 30, 2022 and is now professor emeritus. [ 1 ] [ 2 ] [ 3 ]
Gemperline completed both undergraduate and graduate studies at Cleveland State University (CSU), graduating with a Bachelor of Science in Chemistry in 1978 and a Ph.D. in Analytical Chemistry in 1982. [ 3 ] His dissertation was titled, "The Design of the Laboratory Network DISNET."
In 2014 CSU recognized Gemperline as a distinguished alumnus. [ 4 ] [ 5 ] [ 6 ]
Gemperline joined the chemistry faculty at East Carolina University (ECU) as an assistant professor in 1982. [ 1 ] [ 2 ] He was promoted to full professor in 1993. [ 1 ] According to The Daily Reflector he had a long and distinguished teaching and research career at ECU with "more than 30 years of research experience in chemometrics involving 38 undergraduate students, 20 master’s students, nine visiting doctoral students and six post-doctoral research assistants" and "more than 60 publications in the field and more than $1.8 million in external grant funds." [ 1 ] He also is one of three inventors listed on a licensed patent for designing optical filters for chemical calibration. [ 7 ] [ 8 ] He received the Helms Award for Outstanding Research from the East Carolina University Chapter of Sigma Xi in 1987, the East Carolina University Distinguished Research Professor of Chemistry (award for 5-year achievement and permanent title) in 1999, and in 2001 was made an East Carolina University College of Arts and Sciences Distinguished Professor of Chemistry, [ 9 ] [ 10 ] an award for lifetime achievement and permanent title, given in recognition of "outstanding teaching and advising, research and creative productivity, and professional service." [ 11 ]
In 2003 Gemperline joined the university administration as associate vice chancellor of research and graduate studies. [ 12 ] He became dean of the Graduate School in 2008 and remained in that position until his retirement in 2022. [ 1 ] [ 2 ] Gemperline served in the positions of president-elect (2009-2010), president (2010-2011), and immediate past president (2011-2012) of the North Carolina Council of Graduate Schools. [ 13 ]
Gemperline came to the notice of a larger scientific community in 1984 with the publication of a paper describing DISNET in the Journal of Automated Methods and Management in Chemistry . [ 14 ] (The journal title was changed to Journal of Analytical Methods in Chemistry in 2013.) Gemperline and his colleagues provided methodologies which underlay the improvements in calibration accuracy, computer-based data acquisition and mathematical analysis in chemometrics. The qualitative advances helped open new scientific fields such as molecular modeling and QSAR , cheminformatics , the ‘-omics’ fields of genomics , proteomics , metabonomics and metabolomics , process modeling and process analytical technology .
Gemperline is a self-taught chemometrician, [ 15 ] [ 16 ] and he has been most influential by dispersing knowledge of his chemometric methodologies through his publications. Perhaps the best example of this is his book, Practical Guide to Chemometrics , for which he served as both editor and as a contributor. [ 15 ] Better process methods can create inflection points that became the foundation for radical improvements and transitions in the scientific enterprise. It can be decades before the implications of particular advances are intuited, especially those related to the basic training of the next generations of chemists. His research in chemometrics has been "focused on development of new algorithms and software tools for analysis of multivariate spectroscopic measurements using pattern recognition methods, artificial neural networks, multivariate statistical methods, multivariate calibration, and non-linear model estimation." [ 17 ] Sandia National Laboratories researcher, David Haaland, called Gemperline a "chemometrician extraordinaire," with a "deep understanding of chemometrics" and "wide-ranging" contributions to the research literature, and said after his first meeting with Gemperline he "always read his publications and attended his talks at conferences knowing that I would learn something new every time." [ 16 ]
According to former graduate student, Patrick Cutler, another important aspect of Gemperline's research and teaching career has been his ability to collaborate with industry, which allowed "opportunities for students to gain invaluable experience." [ 15 ] Cutler mentions pharmaceutical company Burroughs Wellcome in particular which at one time operated a production plant in Greenville, North Carolina, in close proximity to East Carolina University. [ 18 ] Gemperline collaborated with Burroughs Wellcome in the 1980s to develop software for multivariate pattern recognition analysis of near-infrared reflectance spectra for rapid, non-destructive testing of pharmaceutical ingredients and products. His research and publications in this area furthered his international recognition. [ 17 ] Cutler notes that Gemperline, "built his career and has produced world-renowned chemometrics research with the limited resources of mostly undergraduates and master's level students." [ 15 ]
Gemperline also has had research collaborations with Pfizer, Inc . and GlaxoSmithKline and he has received "significant" funding for his research from the National Science Foundation (NSF) and the Measurement and Control Engineering Center (MCEC) at University of Tennessee, Knoxville , an NSF-sponsored Industry-University Cooperative Research Center (IUCRC). [ 17 ] He collaborated with David Haaland at Sandia National Laboratories to develop chemometric tools to study kinetics in cells using hyperspectral fluorescence imaging. Their efforts were judged successful, and led to the 2010 Meggers Award for them and coauthors Patrick Cutler and Erik Andres for their two 2009 publications in Applied Spectroscopy about their research. [ 16 ] [ 19 ]
Gemperline served as the editor-in-chief of Journal of Chemometrics for ten years, from 2007 to 2017, [ 20 ] [ 21 ] and before that as the North American editor for five years, from 1996 to 2001. [ 9 ] The journal honored him with a special issue in July 2020. [ 22 ] He joined the editorial advisory board of Spectroscopy Magazine in 2020. [ 7 ]
Outside of his scientific, teaching and administrative pursuits, Gemperline enjoys cycling, sailing, kayaking, photography [ 15 ] and watching Dancing with the Stars on TV . [ 16 ]
Gemperline is author of more than 60 peer-reviewed publications in the field of Chemometrics. [ 1 ]
His most-cited publication is his book, Practical Guide to Chemometrics ( CRC Press ), for which he served as both editor and as a contributor. The chapters he contributed were based on the teaching notes he had developed at East Carolina University for use with undergraduate and master's degree level students. [ 15 ] | https://en.wikipedia.org/wiki/Paul_J._Gemperline |
Paul Karrer (21 April 1889 – 18 June 1971) was a Swiss organic chemist best known for his research on vitamins . He and British chemist Norman Haworth won the Nobel Prize for Chemistry in 1937.
Karrer was born in Moscow , Russia to Paul Karrer and Julie Lerch, both Swiss nationals. In 1892 Karrer's family returned to Switzerland where he was educated at Wildegg and at the Old Cantonal School Aarau where he matriculated in 1908. He studied chemistry at the University of Zurich under Alfred Werner and after gaining his Ph.D. in 1911, he spent a further year as an assistant in the Chemical Institute. He then took a post as a chemist with Paul Ehrlich at the Georg Speyer Haus , Frankfurt-am-Main . In 1919 he became Professor of Chemistry and Director of the Chemical Institute.
Karrer's early research concerned complex metal compounds but his most important work has concerned plant pigments , particularly the yellow carotenoids . He elucidated their chemical structure and showed that some of these substances are transformed in the body into vitamin A . His work led to the establishment of the correct constitutional formula for beta-carotene , the chief precursor of vitamin A; the first time that the structure of a vitamin or provitamin had been established. George Wald worked briefly in Karrer's lab while studying the role of vitamin A in the retina . Later, Karrer confirmed the structure of ascorbic acid ( vitamin C ) and extended his researches into the vitamin B 2 and E. His important contributions to the chemistry of the flavins led to the identification of lactoflavin as part of the complex originally thought to be vitamin B 2 .
Karrer published many papers and received many honours and awards, including the Nobel Prize in 1937. His textbook Lehrbuch der Organischen Chemie (Textbook of Organic Chemistry) was published in 1927, went through thirteen editions, and was published in seven languages. [ citation needed ]
Karrer married Helena Froelich in 1914 and had three sons, one of whom died in infancy. [ 1 ] He died on 18 June 1971, at the age of 82 in Zürich . His wife died in 1972. [ citation needed ]
The prestigious Paul Karrer Gold Medal and lecture were established in his honour in 1959 by a group of leading companies such as CIBA AG, J.R. Geigy, F. Hoffmann-La Roche & Co. AG, Sandoz AG, Société des Produits Nestlé AG and Dr. A. Wander AG. It is awarded annually or biannually to an outstanding chemist who delivers a lecture at the University of Zurich . [ 2 ]
The Paul Karrer Lecture Foundation is based at the Chemistry Institute of the University of Zurich at Rämistrasse 71, in Zürich . [ 3 ] | https://en.wikipedia.org/wiki/Paul_Karrer |
Paul Kazuo Kuroda (1 April 1917 – 16 April 2001) was a Japanese-American chemist and nuclear scientist.
He was born on April 1, 1917, in Fukuoka Prefecture, Japan. [ 1 ] He had three children, including Mitzi Kuroda . [ 2 ] He died on April 16, 2001, at his home in Las Vegas, Nevada. [ 3 ]
He received bachelors and doctoral degrees from the Imperial University of Tokyo . He studied under Professor Kenjiro Kimura. [ 1 ]
His first paper was published in 1935. [ 1 ] He focused mostly on radio and cosmochemistry, and most of his 40 papers published prior to 1944 are about the chemistry of hot springs. In 1944, he became the youngest faculty member of the Imperial University of Tokyo, and after World War II, despite the ban on radiochemistry in Japan, he continued to study radiochemistry until 1949.
On arrival to the United States in 1949, he met with nuclear chemist, Glenn Seaborg . He became an assistant professor of chemistry at the University of Arkansas in 1952, becoming a US citizen in 1955. [ 1 ]
In 1956, Kuroda was the first to propose that natural self-sustaining nuclear chain reactions were possible. Such a reactor was discovered in September 1972 in the Oklo Mines of Gabon .
He became the first Edgar Wertheim Distinguished Professor of Chemistry in 1979, he officially retired from the University of Arkansas in 1987. [ 1 ]
He is the winner of the Pure Chemistry Prize. [ 1 ] | https://en.wikipedia.org/wiki/Paul_Kuroda |
Paul Christian Lauterbur (May 6, 1929 – March 27, 2007) was an American chemist who shared the Nobel Prize in Physiology or Medicine in 2003 with Peter Mansfield for his work which made the development of magnetic resonance imaging (MRI) possible. [ 1 ]
Lauterbur was a professor at Stony Brook University from 1963 until 1985, where he conducted his research for the development of the MRI . [ 2 ] In 1985 he became a professor along with his wife Joan at the University of Illinois at Urbana-Champaign for 22 years until his death in Urbana . He never stopped working with undergraduates on research, and he served as a professor of chemistry, with appointments in bioengineering, biophysics, the College of Medicine at Urbana-Champaign and computational biology at the Center for Advanced Study. [ 3 ]
Lauterbur was of Luxembourgish ancestry. Born and raised in Sidney, Ohio , Lauterbur graduated from Sidney High School , where a new Chemistry, Physics, and Biology wing was dedicated in his honor. As a teenager , he built his own laboratory in the basement of his parents' house. [ 4 ] His chemistry teacher at school understood that he enjoyed experimenting on his own, so the teacher allowed him to do his own experiments at the back of class. [ 4 ]
When he was drafted into the United States Army in the 1950s, his superiors allowed him to spend his time working on an early nuclear magnetic resonance (NMR) machine; he had published four scientific papers by the time he left the Army. [ 4 ] Paul became an atheist later on. [ 5 ]
Lauterbur received a BS in chemistry from the Case Institute of Technology, now part of Case Western Reserve University in Cleveland, Ohio where he became a Brother of the Alpha Delta chapter of Phi Kappa Tau fraternity. He then went to work at the Mellon Institute laboratories of the Dow Corning Corporation, with a 2-year break to serve at the Army Chemical Center in Edgewood, Maryland . While working at Mellon Institute he pursued graduate studies in chemistry at the University of Pittsburgh . Earning his PhD in 1962, the following year Lauterbur accepted a position as associate professor at Stony Brook University . As a visiting faculty in chemistry at Stanford University during the 1969–1970 academic year, he undertook NMR-related research with the help of local businesses Syntex and Varian Associates . Lauterbur returned to Stony Brook, continuing there until 1985 when he moved to the University of Illinois . [ 6 ]
Lauterbur credits the idea of the MRI to a brainstorm one day at a suburban Pittsburgh Eat'n Park Big Boy Restaurant , with the MRI's first model scribbled on a table napkin while he was a student and researcher at both the University of Pittsburgh and the Mellon Institute of Industrial Research . [ 4 ] [ 7 ] [ 8 ] The further research that led to the Nobel Prize was performed at Stony Brook University [ 9 ] in the 1970s.
The Nobel Prize in Physics in 1952, which went to Felix Bloch and Edward Purcell , was for the development of nuclear magnetic resonance (NMR), the scientific principle behind MRI. However, for decades magnetic resonance was used mainly for studying the chemical structure of substances. It wasn't until the 1970s with Lauterbur's and Mansfield's developments that NMR could be used to produce images of the body.
Lauterbur used the idea of Robert Gabillard (developed in his doctoral thesis, 1952) of introducing gradients in the magnetic field which allows for determining the origin of the radio waves emitted from the nuclei of the object of study. This spatial information allows two-dimensional pictures to be produced. [ 4 ]
While Lauterbur conducted his work at Stony Brook, the best NMR machine on campus belonged to the chemistry department; he had to visit it at night to use it for experimentation and would carefully change the settings so that they would return to those of the chemists' as he left. [ 10 ] The original MRI machine is located at the Chemistry building on the campus of Stony Brook University in Stony Brook, New York .
Some of the first images taken by Lauterbur included those of a 4-mm-diameter clam [ 11 ] his daughter had collected on the beach at the Long Island Sound , green peppers [ 4 ] and two test tubes of heavy water within a beaker of ordinary water; no other imaging technique in existence at that time could distinguish between two different kinds of water. This last achievement is particularly important as the human body consists mostly of water. [ 10 ]
When Lauterbur first submitted his paper with his discoveries to Nature , the paper was rejected by the editors of the journal. Lauterbur persisted and requested them to review it again, upon which time it was published and is now acknowledged as a classic Nature paper. [ 12 ] The Nature editors pointed out that the pictures accompanying the paper were too fuzzy, although they were the first images to show the difference between heavy water and ordinary water. [ 4 ] Lauterbur said of the initial rejection: "You could write the entire history of science in the last 50 years in terms of papers rejected by Science or Nature ." [ 10 ]
Peter Mansfield of the University of Nottingham in the United Kingdom took Lauterbur's initial work another step further, replacing the slow (and prone to artefacts) projection-reconstruction method used by Lautebur's original technique with a method that used frequency and phase encoding by spatial gradients of magnetic field. Owing to Larmor precession , a mathematical technique called a Fourier transformation could then be used to recover the desired image, greatly speeding up the imaging process. [ 10 ]
Lauterbur unsuccessfully attempted to file patents related to his work to commercialize the discovery. [ 13 ] The State University of New York chose not to pursue patents, with the rationale that the expense would not pay off in the end. "The company that was in charge of such applications decided that it would not repay the expense of getting a patent. That turned out not to be a spectacularly good decision," Lauterbur said in 2003. He attempted to get the federal government to pay for an early prototype of the MRI machine for years in the 1970s, and the process took a decade. [ 14 ] The University of Nottingham did file patents which later made Mansfield wealthy. [ 14 ]
Lauterbur was awarded the Nobel Prize along with Mansfield in the fall of 2003. Controversy occurred when Raymond Damadian took out full-page ads in The New York Times , The Washington Post and The Los Angeles Times headlined "The Shameful Wrong That Must Be Righted" saying that the Nobel committee had not included him as a Prize winner alongside Lauterbur and Mansfield for his early work on the MRI. Damadian claimed that he discovered MRI and the two Nobel-winning scientists refined his technology.
The New York Times published an editorial saying that while scientists credit Damadian for holding an early patent in MRI technology, Lauterbur and Mansfield expanded upon Herman Carr 's technique in order to produce first 2D and then 3D MR images. The editorial deems this to be worthy of a Nobel prize even though it states clearly in Alfred Nobel's will that prizes are not to be given out solely on the basis of improving an existing technology for commercial use. The newspaper then points out a few cases in which precursor discoveries had been awarded with a Nobel, along with a few deserving cases in which it had not, such as Rosalind Franklin , Oswald Avery , Robert Gabillard [ fr ] . [ 15 ] [ 16 ]
Lauterbur died aged 77 in March 2007 of kidney disease at his home in Urbana, Illinois . University of Illinois Chancellor Richard Herman said, "Paul's influence is felt around the world every day, every time an MRI saves the life of a daughter or a son, a mother or a father." [ 16 ] | https://en.wikipedia.org/wiki/Paul_Lauterbur |
Paul Malliavin ( French: [maljavɛ̃] ; September 10, 1925 – June 3, 2010) was a French mathematician who made important contributions to harmonic analysis and stochastic analysis .
He is known for the Malliavin calculus , an infinite dimensional calculus for functionals on the Wiener space and his probabilistic proof of Hörmander's theorem .
He was Professor at the Pierre and Marie Curie University and a member of the French Academy of Sciences from 1979 to 2010. [ 1 ]
Malliavin was the son of René Malliavin, also known as Michel Dacier , a political writer and journalist, and Madeleine Delavenne, a physician. On 27 April 1965 he married Marie-Paule Brameret , who was also a mathematician and with whom he published several mathematical papers. [ 2 ] [ 3 ] They had two children. [ 2 ]
Malliavin's early work was in harmonic analysis , where he derived important results on the spectral synthesis problem, providing definitive answers to fundamental questions in this field, including a complete characterization of 'band-limited' functions whose Fourier transform has compact support, known as the Beurling-Malliavin theorem . [ 4 ]
In stochastic analysis , Malliavin is known for his work on the stochastic calculus of variation, now known as the Malliavin calculus , a mathematical theory which has found many applications in Monte Carlo simulation and mathematical finance .
As stated by Stroock and Yor : "Like Norbert Wiener, Paul Malliavin came to probability theory from harmonic analysis, and, like Wiener, his analytic origins were apparent in everything he did there." [ 5 ] Malliavin introduced a differential operator on Wiener space , now called the Malliavin derivative , and derived an integration by parts formula for Wiener functionals. Using this integration by parts formula, Malliavin initiated a probabilistic approach to Hörmander's theorem for hypo-elliptic operators and gave a condition for the existence of smooth densities for Wiener functionals in terms of their Malliavin covariance matrix . | https://en.wikipedia.org/wiki/Paul_Malliavin |
The Paul Pellas-Graham Ryder Award is jointly sponsored by the Meteoritical Society and the Planetary Geology Division of the Geological Society of America . [ 1 ] It recognizes the best planetary science paper, published during the previous year in a peer-reviewed scientific journal, and written by an undergraduate or graduate student (as first author). The topics covered by the award are listed on the cover of Meteoritics and Planetary Science . It has been given since 2002, and honors the memories of the incomparable meteoriticist Paul Pellas [ 2 ] and lunar scientist Graham Ryder .
There have been 21 recipients of the award since its inception in 2002. The recipient's journal articles awarded have collectively been cited more than 2100 times as of December 31, 2019.
Sources: Meteoritical Society , GSA Planetary Geology Division
*Timing of award adjusted by presenting two in the same year.
**Jointly awarded to two recipients in the same year. | https://en.wikipedia.org/wiki/Paul_Pellas-Graham_Ryder_Award |
Paul Jules Portier ( French pronunciation: [pɔl ʒyl pɔʁtje] ; 22 May 1866 – 26 January 1962) was a French physiologist who made important contributions to the discovery of anaphylaxis and the development of symbiogenesis . [ 1 ] [ 2 ] On a scientific expedition organised by Albert I, Prince of Monaco , he and Charles Richet discovered that toxins produced by marine animals (cnidarians such as Portuguese man o' war and sea anemone ) could induce fatal shocks. They named the medical phenomenon "anaphylaxis," from which Richet went on to receive the 1913 Nobel Prize in Physiology or Medicine . [ 3 ] Portier was the first scientist to explain that the cell organelle, mitochondrion , arose by symbiosis according to his evolutionary theory in 1918. [ 4 ]
Portier was born in Bar-sur-Seine , France, to Ernest Paul and Julie Moreau Laure. He studied elementary education at the Lycée de Troyes from 1878 to 1885. After passing the final secondary examination (called bac ) from the Saint-Sigisbert in Nancy, he qualified for service in the Ministry of Finance in 1888. [ 5 ] However, he chose to study biology, following his childhood dream. [ 6 ] In 1889, he entered the University of Paris [ 7 ] from where he earned an M.D. in 1897 and Doctor of Science ( docteur ès sciences ) degree in 1912. [ 5 ] He continued to work in the university as an assistant physician. [ 8 ]
In 1906, Albert I, Prince of Monaco founded the Institute of Oceanography ( Institut océanographique de Paris ); Portier was appointed its professor. When the institute was inaugurated in 1911, Portier became its first director. [ 9 ] In 1920, he was appointed professor of professor of comparative physiology at the University of Paris. [ 7 ] In 1923, the University of Paris created a chair of physiology, which he held for the rest of his career. He retired in 1936, and the university awarded him the position of honorary professor. [ 5 ] He played active roles in the administrations of the French Academy of Sciences and the French Academy of Medicine . He published his last book The Biology of Butterflies in 1949. [ 1 ]
Portier married Françoise Noiret Claudine in 1911, and had three daughters, Andrée, Jeannine and Paulette. [ 5 ] He spent his last days at his home in Bourg-la-Reine . [ 1 ]
In 1901, Albert I, Prince of Monaco organised a scientific expedition around the French coast of the Atlantic Ocean. [ 8 ] He specifically invited Portier and Charles Richet, professor of physiology at the Collège de France , to join him for investigating the toxins produced by cnidarians (like jellyfish and sea anemones ). [ 10 ] Richet and Portier boarded Albert's ship Princesse Alice II from where they collected various marine animals. [ 11 ]
Richet and Portier extracted a toxin called hypnotoxin from their collection of jellyfish (but the real source was later identified as Portuguese man o' war ) [ 12 ] and sea anemone ( Actinia sulcata ) from Cape Verde Islands . [ 6 ] [ 13 ] In their first experiment on the ship, they injected a dog with the toxin in an attempt to immunise the dog, which instead developed a severe reaction ( hypersensitivity ). To confirm the findings, they knew that more experimental works were needed in the laboratory. [ 6 ] In 1902, they repeated the injections in their laboratory and found that dogs normally tolerated the toxin at first injection, but on re-exposure, three weeks later with the same dose, they always developed fatal shock. They also found that the effect was not related to the doses of toxin used, as even small amounts in secondary injections were lethal. [ 13 ] Thus, instead of inducing tolerance ( prophylaxis ) which they expected, they discovered effects of the toxin as deadly. [ 14 ]
In 1902, Richet introduced the term aphylaxis to describe the condition of lack of protection. He later changed the term to anaphylaxis on grounds of euphony . [ 15 ] The term is from the Greek ἀνά-, ana- , meaning "against", and φύλαξις, phylaxis , meaning "protection". [ 16 ] On 15 February 1902, Richet and Portier jointly presented their findings before the Société de biologie in Paris. [ 17 ] [ 18 ] The moment is regarded as the birth of allergy (the term invented by Clemens von Pirquet in 1906) study ( allergology ). [ 18 ] Richet continued to study on the phenomenon and was eventually awarded the Nobel Prize in Physiology or Medicine for his work on anaphylaxis in 1913. [ 3 ] [ 11 ] [ 19 ]
Portier never claimed the co-discovery of anaphylaxis, instead honoured Richet as a senior scientist. After the Nobel Prize, Richet praised him for "giving up all claim to the honor of the discovery." [ 8 ] Portier explained: "We discovered anaphylaxis without looking for it, and almost in spite of ourselves. But it was necessary to have the eyes and mind of a physiologist to understand the interest." [ 2 ]
Portier was the first to realise that condensation of water vapour was the cause of the spout of a blowing whale and other marine mammals. He showed that condensation occurred in the expelled air as water vapour was spread and cooled down. [ 6 ] His studies from 1909 established the principle of surface tension in insects that walked on water. [ 1 ] His studies in 1922 involved osmoregulation (salt-water balance) in fishes. In 1934, he showed that deaths of marine birds in oil spills were due to loss of body heat caused by oils infiltrating the feathers. [ 6 ]
Following his interest in entomology and physiology, Portier studied how insects such as termites digest cellulose . He found out that bacteria in termite's gut were essential for cellulose digestion. In addition, the bacteria provided essential vitamins to the termites and were involved during the developmental processes of the hosts. Thus, the bacteria were symbionts . [ 20 ] It was at the time a known fact that such bacteria were parasites. Portier began to realised that microbes could be necessary for the lives and formation of higher organisms. In 1917, he published the role of symbiosis in the lives of plants and animals, and by that time he started writing a book, he called Les Symbiotes. [ 21 ] He was able to link the similarities of bacteria and mitochondria, the energy-producing cell organelles, and claimed that mitochondria behaved just like bacteria in culture. [ 22 ] [ 23 ]
In 1918, Portier, summing up his observations on symbiosis in nature and his evolutionary idea (now known as symbiogenesis), published Les Symbiotes , dedicating it to Prince Albert. [ 24 ] According to Portier, symbiosis is a universal process by which all complex life forms (eukaryotes) arose from the fusion of independent unicellular organisms; mitochondria, for examples, are just a type of bacteria. [ 4 ] [ 22 ] He made a statement:
All living beings, all animals from Amoeba to Man, all plants from Cryptogams to Dicotyledons are constituted by an association, the emboîtement [embodiment] of two different beings. Each living cell contains in its protoplasm formations, which histologists designate by the name of mitochondria. These organelles are, for me, nothing other than symbiotic bacteria, which I call "symbiotes." [ 21 ]
As Portier himself remarked that his theory was "a veritable scientific heresy," [ 21 ] the book and the evolutionary idea were received with scepticism and ridicule. The Société de biologie created a committee to investigate the controversy. [ 23 ] Scientists at the Pasteur Institute openly argued that mitochondria could never be cultured and challenged Portier to demonstrate his experiments. As John Archibald described: " Les Symbiotes caused a brouhaha in France... Portier's reputation as a competent experimentalist was damaged and his grand hypothesis was ignored." [ 24 ] The next year, Auguste Lumière published a refutation Le Mythe des Symbiotes (" The Myth of Symbiotes "). [ 20 ] Portier had prepared a draft of the sequel to Les Symbiotes , but never published it or touched on the subject of evolution again. [ 24 ] (Symbiogenesis is now widely accepted, and mitochondria are evidently once free-living bacteria. [ 25 ] [ 26 ] )
Portier received the Montyon Prize in 1912, La Caze in 1934, and Jean Toy in 1951 from the French Academy of Sciences. He was given Chevalier ( Knight ) in 1923, Officier (Officer) in 1935, and Commandeur ( Commander ) in 1951 of the Legion of Honour . He was honoured Commander of the Order of Saint Charles (1951) and of the Order of Cultural Merit (1954) of Monaco. He was elected member of the French Academy of Medicine in 1929 and of the French Academy of Sciences in 1936. [ 5 ] | https://en.wikipedia.org/wiki/Paul_Portier_(physiologist) |
Paul Sabatier ( French: [sabatje] ; 5 November 1854 – 14 August 1941) was a French chemist , born in Carcassonne . In 1912, Sabatier was awarded the Nobel Prize in Chemistry along with Victor Grignard . Sabatier was honoured for his work improving the hydrogenation of organic species in the presence of metals.
Sabatier studied at the École Normale Supérieure , starting in 1874. Three years later, he graduated at the top of his class. [ 3 ] In 1880, he was awarded a Doctor of Science degree from the College de France . [ 3 ]
In 1883 Sabatier succeeded Édouard Filhol at the Faculty of Science, and began a long collaboration with Jean-Baptiste Senderens , so close that it was impossible to distinguish the work of either man.
They jointly published 34 notes in the Accounts of the Academy of Science , 11 memoirs in the Bulletin of the French Chemical Society and 2 joint memoirs to the Annals of Chemistry and Physics . [ 4 ]
After the discovery of nickel tetracarbonyl in 1890 they tried to synthesize similar compound with nitrogen oxides, but only discovered different types of oxidation. As late as 1912, Sabatier believed that it's possible to get "true nitro metals" with dinitrogen tetroxide , [ 5 ] but it was later proven that these were not real chemical compounds but just metal oxides with nitrogen dioxide physically absorbed on them. [ 6 ]
In 1896 Henri Moissan and Charles Moureu discovered that acetylene reacts with some transition metals . [ 7 ] Bearing in mind Prosper de Wilde (1835-1916) hydrogenated acetylene on platinum black in 1874, Sabatier and Senderens picked up the topic and continued investigations in the area.
The methanation reactions of COx were first discovered by Sabatier and Senderens in 1902. [ 8 ] Sabatier and Senderen shared the Academy of Science's Jecker Prize in 1905 for their discovery of the Sabatier–Senderens Process. [ 4 ]
After 1905–06 Senderens and Sabatier published few joint works, perhaps due to the classic problem of recognition of the merit of contributions to joint work. [ 4 ] Sabatier taught science classes most of his life before he became Dean of the Faculty of Science at the University of Toulouse in 1905.
Sabatier's earliest research concerned the thermochemistry of sulfur and metallic sulfates , the subject for the thesis leading to his doctorate. In Toulouse , he continued his physical and chemical investigations to sulfides , chlorides , chromates and copper compounds. He also studied the oxides of nitrogen and nitrosodisulfonic acid and its salts and carried out fundamental research on partition coefficients and absorption spectra . Sabatier greatly facilitated the industrial use of hydrogenation . In 1897, building on the recent biochemical work of the American chemist, James Boyce , he discovered that the introduction of a trace amount of nickel (as a catalyst) facilitated the addition of hydrogen to molecules of most carbon compounds.
Sabatier is best known for the Sabatier process and his works such as La Catalyse en Chimie Organique (Catalysis in organic chemistry) which was published in 1913. He won the Nobel Prize in Chemistry jointly with fellow Frenchman Victor Grignard in 1912. [ 3 ]
The reduction of carbon dioxide using hydrogen at high temperature and pressure is another use of nickel catalyst to produce methane .
He is also known for the Sabatier principle of catalysis.
Sabatier was married and had four daughters, one of whom wed the Italian chemist Emilio Pomilio. [ 3 ]
The Paul Sabatier University in Toulouse , France is named in honour of Paul Sabatier, as is one of Carcassonne 's high schools. Paul Sabatier was a co-founder of the Annales de la Faculté des Sciences de Toulouse , together with the mathematician Thomas Joannes Stieltjes .
Sabatier died on 14 August, 1941 in Toulouse at the age of 86. | https://en.wikipedia.org/wiki/Paul_Sabatier_(chemist) |
Paul A. Strassmann (January 24, 1929 – April 4, 2025) was a Slovak -born American information technology executive, author, and academic. He served as the first Director of Defense Information at the U.S. Department of Defense and as Chief Information Officer (CIO) at NASA. Strassmann was a pioneer in the field of information management, advocating for the measurement of information as a corporate asset and developing concepts such as "Return on Management" and "Information Productivity."
Strassmann was born in Trenčín , Czechoslovakia (now Slovakia), to a Jewish family. During World War II, he joined the partisan resistance against Nazi occupation. After the war, he emigrated to the United States in 1948. He earned a bachelor's degree in engineering from The Cooper Union and a master's degree in industrial management from the Massachusetts Institute of Technology (MIT). [ 1 ] [ 2 ]
While pursuing a master's degree in industrial management at the MIT, Strassmann learned to operate a mainframe computer as part of a project aimed at forecasting traffic and determining staffing requirements for toll collectors on the New Jersey Turnpike. This work generated sufficient data for a comprehensive 600-page thesis. The experience of applying computers to address complex business challenges and improve organizational efficiency would become a defining aspect of his subsequent career. [ 3 ]
Strassmann began his corporate career at General Foods in 1961 and later became Chief Information Systems Executive at Kraft Foods. In 1969, he joined Xerox Corporation as Director of Administration and Information Systems. He later served as Vice President of Strategic Planning for Xerox’s Information Products Group. He founded and managed Xerox's Information Services Division, overseeing computer centers, software development, and management consulting services. [ 4 ] [ 5 ]
In 1991, Strassmann was appointed the first Director of Defense Information at the U.S. Department of Defense, managing the Corporate Information Management program. He received the Defense Medal for Distinguished Public Service in 1993. [ 4 ]
In 2002, he became Acting Chief Information Officer at NASA, where he oversaw the agency’s information systems and telecommunications. He received the NASA Exceptional Service Medal in 2003. [ 4 ]
After his government service, Strassmann taught as a Distinguished Professor of Information Sciences at George Mason University and held visiting positions at the National Defense University and the United States Military Academy at West Point. [ 1 ] [ 5 ]
Strassmann wrote nine books and over 500 articles on information technology and management. Notable titles include:
Strassmann was married to Mona Frankel for 68 years. They had several children and grandchildren. He died on April 4, 2025, at his home in New Canaan, Connecticut , at the age of 96. [ 8 ]
Strassmann's contributions to the field of information economics and his influence on IT governance are widely recognized. His ideas on measuring the business value of IT have influenced industry leaders, including Steve Jobs. [ 8 ] | https://en.wikipedia.org/wiki/Paul_Strassman |
Paul Walden ( Latvian : Pauls Valdens ; Russian : Павел Иванович Вальден ; German : Paul von Walden ; 26 July 1863 – 22 January 1957) was a Russian , Latvian and German chemist known for his work in stereochemistry and history of chemistry. In particular, he discovered the Walden rule , [ 1 ] he invented the stereochemical reaction known as Walden inversion and synthesized the first room-temperature ionic liquid , ethylammonium nitrate . [ 2 ] [ 3 ]
Walden was born in Rozulas in the Russian Empire (now Stalbe parish, Pārgauja municipality , Latvia) in a large Latvian peasant family. At the age of four, he lost his father and later his mother. Thanks to financial support from his two older brothers who lived in Riga (one was a merchant and another served as a lieutenant in the military) Walden managed to complete his education – first graduated with honors from the district school in the town of Cēsis (1876), and then from the Riga Technical High School (1882).
In December 1882, he enrolled into the Riga Technical University and became seriously interested in chemistry. In 1886, he published his first scientific study on the color evaluation of the reactions of nitric and nitrous acid with various reagents and establishing the limits of sensitivity of the color method to detection of nitric acid.
In April 1887, Walden became an active member of the Russian Physico-chemical Society. During this time, Walden started his collaboration with Wilhelm Ostwald ( Nobel Prize in Chemistry 1909) which greatly influenced his development as a scientist. Their first work together was published in 1887 and was devoted to the dependence of the electrical conductivity of aqueous solutions of salts on their molecular weight. [ 4 ] [ 5 ] [ 6 ]
In 1888, Walden graduated from the university with a degree in chemical engineering and continued working at the Chemistry Department as an assistant to professor C. Bischof.
Under his guidance, Walden began compiling "Handbook of Stereochemistry" which was published in 1894. In preparation of this handbook, Walden had to perform numerous chemical syntheses and characterizations which resulted in 57 journal papers on stereochemistry alone, published between 1889 and 1900 in Russian and foreign journals 57 articles on the stereochemistry. He also continued his research in the field of physical chemistry, establishing in 1889 that the ionizing power of non-aqueous solvent is directly proportional to the dielectric constant.
During the summer vacations of 1890 and 1891, Walden was visiting Ostwald at the University of Leipzig and in September 1891 defended there a master thesis on the affinity values of certain organic acids. Ostwald suggested that he stay in Leipzig as a private lecturer, but Walden declined, hoping for a better career in Riga. [ 4 ] [ 6 ]
In the summer of 1892 he was appointed assistant professor of physical chemistry . A year later he defended his doctorate on osmotic phenomena in sedimentary layers and in September 1894 became professor of analytical and physical chemistry at the Riga Technical University. He worked there until 1911 and during 1902–1905 was rector of the university. In 1895, Walden made his most remarkable discovery which was later named Walden inversion , namely that various stereoisomers can be obtained from the same compound via certain exchange reactions involving hydrogen. [ 7 ] This topic became the basis for his habilitation thesis defended in March 1899 at St. Petersburg University . [ 4 ]
After that, Walden became interested in electrochemistry of nonaqueous solutions. In 1902, he proposed a theory of autodissociation of inorganic and organic solvents. In 1905, he found a relationship between the maximum molecular conductivity and viscosity of the medium and in 1906, coined the term " solvation ". Together with his work on stereochemistry, these results brought him to prominence; in particular, he was considered a candidate for the Nobel Prize in Chemistry in 1913 and 1914. [ 4 ] [ 6 ]
Walden was also credited as a talented chemistry lecturer. In his memoirs, he wrote: "My audience usually was crowded and the feedback of sympathetic listeners gave me strength ... my lectures I was giving spontaneously, to bring freshness to the subject ... I never considered teaching as a burden". [ 4 ] [ 6 ]
1896 brought reforms to the Riga Technical University. Whereas previously, all teaching was conducted in German and Walden was the only professor giving some courses in Russian, from then on, Russian became the official language. This change allowed receiving subsidies from the Russian government and helped the alumni in obtaining positions in Russia. These reforms resulted in another and rather unusual collaboration of Walden with Ostwald: Walden was rebuilding the Chemistry Department and Ostwald sent him the blueprints of the chemical laboratories in Leipzig as an example. In May 1910, Walden was elected a member of the St. Petersburg Academy of Sciences and in 1911 was invited to Saint Petersburg to lead the Chemical Laboratories of the academy founded in 1748, by Mikhail Lomonosov . He remained in that position till 1919. As an exception, he was allowed to stay in Riga where he had better research possibilities, but he was traveling, almost every week, by train, to St. Petersburg for the academy meetings and guidance of research. In the period 1911–1915, Walden published 14 articles in the "Proceedings of the Academy of Sciences" on electrochemistry of nonaqueous solutions. In particular, in 1914 he synthesized the first room-temperature ionic liquid , namely ethylammonium nitrate ( C 2 H 5 ) NH + 3 · NO − 3 with the melting point of 12 °C. [ 2 ] [ 4 ] [ 6 ] [ 8 ]
After 1915, due to the difficulties caused by the World War I, political unrest in Russia and then October Revolution, Walden had reduced his research activity and focused on teaching and administrative work, taking numerous leading positions in science. Due to the political unrest in Latvia, Walden had immigrated to Germany. He was appointed as professor of inorganic chemistry at the University of Rostock where he worked until retirement in 1934. In 1924 he was invited back to Riga, where he gave a series of lectures. He was offered leading positions in chemistry in Riga and in St. Petersburg, but declined. Despite his emigration, Walden retained his popularity in Russia, and in 1927 he was appointed as a foreign member of the Russian Academy of Sciences. Later, he also became a member of the Swedish (1928) and Finnish (1932) Academies. [ 4 ] [ 6 ]
Walden's daughter, Antonina Anna Walden (1899–1983), was a music teacher who married Finnish translator and essayist Juho August Hollo . Their son was the Finnish poet and translator Anselm Hollo .
In his last years, Walden focused on history of chemistry and collected a unique library of over 10,000 volumes. The library and his house were destroyed when the British bombed Rostock in 1942. Walden moved to Berlin and then to Frankfurt am Main , where he became a visiting professor of the history of chemistry at the local university. He met the end of World War II in the French Occupation Zone , cut off from Rostock University, located in the Soviet Zone , and thus left without any source of income.
Walden survived on a modest pension arranged by German chemists, giving occasional lectures in Tübingen and writing memoirs. [ 5 ] In 1949, he published his best-known book, History of Chemistry . He died in Gammertingen in 1957, at the age of 93. His memoirs were published only in 1974. [ 4 ] [ 6 ] | https://en.wikipedia.org/wiki/Paul_Walden |
Paula L. Diaconescu is a Romanian-American chemistry professor at the University of California, Los Angeles . She is known for her research on the synthesis of redox active transition metal complexes, the synthesis of lanthanide complexes, metal-induced small molecule activation, and polymerization reactions. She is a fellow of the American Association for the Advancement of Science .
Diaconescu was born in Romania and received a Bachelor of Science degree from the University of Bucharest in 1998 conducting research on transition metal complexes and f-block metals. [ 1 ] [ 2 ] In 2003, Diaconescu received a PhD in chemistry from the Massachusetts Institute of Technology working with Christopher C. Cummins on uranium chemistry. [ 3 ] Before joining the faculty at UCLA in 2005, she spent two years as a postdoctoral fellow at the California Institute of Technology with Robert Grubbs . [ 1 ] [ 2 ]
While Diaconescu is best known for her work on the reactivity of early transition metals, lanthanides, and actinides, she has also contributed to the field of redox active ligand systems for small molecule activation. Her group has exploited ferrocene's electronic and redox properties to enable catalytic transformations with electrophilic transition metal centers. [ 4 ] [ 5 ] Diaconescu's research on redox active systems is studying how ferrocene's electronic and redox properties when strategically incorporated into a ligand affect the reactivity of d-block metal complexes. [ 6 ] This extends to redox switchable catalysis and small molecule activation with applications in polyaniline nanofiber supporting metal catalysis and bioorganometallic polymers. [ 7 ] [ 8 ] She recognized that redox-switchable catalysis can generate multiple catalytically active species with varying reactivity. The idea is that a compound can have orthogonal reactivity between the oxidized and reduced forms of the catalyst. [ 9 ] The ring-opening polymerization of cyclic ethers and esters as well as the polymerization of alkenes has been exploited with catalysts containing ferrocene. [ 10 ]
Diaconescu received a Sloan Fellowship in 2009, [ 11 ] and received the Humboldt Foundation's Friedrich Wilhelm Bessel Research Award in 2014. [ 12 ] In 2015, she was named a Guggenheim Fellow , [ 13 ] and Diaconescu was named a fellow of the American Association for the Advancement of Science in 2019. [ 14 ] | https://en.wikipedia.org/wiki/Paula_Diaconescu |
The Pauli effect or Pauli's device corollary is the supposed tendency of technical equipment to encounter critical failure in the presence of certain people — originally, Austrian physicist Wolfgang Pauli . The Pauli effect is not related to the Pauli exclusion principle , which is a bona fide physical phenomenon named after Pauli. However the Pauli effect was humorously tagged as a second Pauli exclusion principle, according to which a functioning device and Wolfgang Pauli may not occupy the same room . [ 1 ]
Since the 20th century, the work in some subfields of physics research has been divided between theorists and experimentalists. Those theorists who lack an aptitude or interest in experimental work have on occasion earned a reputation for accidentally breaking experimental equipment.
An incident occurred in the physics laboratory at the University of Göttingen . An expensive measuring device, for no apparent reason, suddenly stopped working, although Pauli was in fact absent . James Franck , the director of the institute, reported the incident to his colleague Pauli in Zürich with the humorous remark that at least this time Pauli was innocent. However, it turned out that Pauli had been on a railway journey to Zürich and had switched trains in the Göttingen rail station at about the time of the failure. The incident is reported in George Gamow 's book Thirty Years That Shook Physics , [ 2 ] where it is also claimed the more talented the theoretical physicist, the stronger the effect.
R. Peierls describes a case when at one reception this effect was to be parodied by deliberately crashing a chandelier upon Pauli's entrance. The chandelier was suspended on a rope to be released, but it stuck instead, thus becoming a real example of the Pauli effect. [ 3 ]
In 1934, Pauli saw a failure of his car during a honeymoon tour with his second wife as proof of a real Pauli effect since it occurred without an obvious external cause. [ 4 ]
In February 1950, when he was at Princeton University , the cyclotron burnt, and he asked himself if this mischief belonged to such a Pauli effect, named after him. [ 5 ]
For fear of the Pauli effect, experimental physicist Otto Stern banned Pauli from his laboratory located in Hamburg despite their friendship. [ 6 ]
Pauli was convinced that the effect named after him was real. [ 7 ] He corresponded with Carl Jung and Marie-Louise von Franz about the concept of synchronicity . He also corresponded with Hans Bender , lecturer at Freiburg university Institut für Grenzgebiete der Psychologie und Psychohygiene and the only parapsychology chair in Germany. [ 8 ]
Jung and Pauli saw some parallels between physics and depth psychology . [ 9 ] Pauli was among the honored guests at the foundation festivities of the C.G. Jung Institute in Zürich in 1948. An example of the Pauli effect happened at the ceremony: As he entered, a china flower vase fell on the floor for no obvious reason. This incident caused Pauli to write his article "Background-Physics", in which he tries to find complementary relationships between physics and depth psychology. [ 10 ]
Philip K. Dick makes reference to "Pauli's synchronicity" in his 1963 science fiction novel The Game-Players of Titan , in reference to pre-cognitive psionic abilities being interfered with by other psionic abilities such as psychokinesis : "an acausal connective event." [ 11 ]
In the anime series Yu-Gi-Oh! Sevens , Tatsuhisa Kamijō is a self-proclaimed "demon-embodied" human who can randomly cause electronic devices such as phones and drones to malfunction or self destruct with his hands. The main character, Yuga Ohdo, attributes this to the Pauli Effect. [ 12 ]
The anime Amnesia: Fated Memories and the video game Signalis also reference the Pauli effect.
In the movie Babylon 5: The River of Souls , Captain Lochley describes this effect to Lieutenant Corwin, drawing a parallel to how crises seem to emerge only when President Sheridan or ex-security chief Garibaldi are at the station. | https://en.wikipedia.org/wiki/Pauli_effect |
In quantum mechanics , the Pauli equation or Schrödinger–Pauli equation is the formulation of the Schrödinger equation for spin-1/2 particles, which takes into account the interaction of the particle's spin with an external electromagnetic field . It is the non- relativistic limit of the Dirac equation and can be used where particles are moving at speeds much less than the speed of light , so that relativistic effects can be neglected. It was formulated by Wolfgang Pauli in 1927. [ 1 ] In its linearized form it is known as Lévy-Leblond equation .
For a particle of mass m {\displaystyle m} and electric charge q {\displaystyle q} , in an electromagnetic field described by the magnetic vector potential A {\displaystyle \mathbf {A} } and the electric scalar potential ϕ {\displaystyle \phi } , the Pauli equation reads:
[ 1 2 m ( σ ⋅ ( p ^ − q A ) ) 2 + q ϕ ] | ψ ⟩ = i ℏ ∂ ∂ t | ψ ⟩ {\displaystyle \left[{\frac {1}{2m}}({\boldsymbol {\sigma }}\cdot (\mathbf {\hat {p}} -q\mathbf {A} ))^{2}+q\phi \right]|\psi \rangle =i\hbar {\frac {\partial }{\partial t}}|\psi \rangle }
Here σ = ( σ x , σ y , σ z ) {\displaystyle {\boldsymbol {\sigma }}=(\sigma _{x},\sigma _{y},\sigma _{z})} are the Pauli operators collected into a vector for convenience, and p ^ = − i ℏ ∇ {\displaystyle \mathbf {\hat {p}} =-i\hbar \nabla } is the momentum operator in position representation. The state of the system, | ψ ⟩ {\displaystyle |\psi \rangle } (written in Dirac notation ), can be considered as a two-component spinor wavefunction , or a column vector (after choice of basis):
The Hamiltonian operator is a 2 × 2 matrix because of the Pauli operators .
Substitution into the Schrödinger equation gives the Pauli equation. This Hamiltonian is similar to the classical Hamiltonian for a charged particle interacting with an electromagnetic field. See Lorentz force for details of this classical case. The kinetic energy term for a free particle in the absence of an electromagnetic field is just p 2 2 m {\displaystyle {\frac {\mathbf {p} ^{2}}{2m}}} where p {\displaystyle \mathbf {p} } is the kinetic momentum , while in the presence of an electromagnetic field it involves the minimal coupling Π = p − q A {\displaystyle \mathbf {\Pi } =\mathbf {p} -q\mathbf {A} } , where now Π {\displaystyle \mathbf {\Pi } } is the kinetic momentum and p {\displaystyle \mathbf {p} } is the canonical momentum .
The Pauli operators can be removed from the kinetic energy term using the Pauli vector identity :
Note that unlike a vector, the differential operator p ^ − q A = − i ℏ ∇ − q A {\displaystyle \mathbf {\hat {p}} -q\mathbf {A} =-i\hbar \nabla -q\mathbf {A} } has non-zero cross product with itself. This can be seen by considering the cross product applied to a scalar function ψ {\displaystyle \psi } :
where B = ∇ × A {\displaystyle \mathbf {B} =\nabla \times \mathbf {A} } is the magnetic field.
For the full Pauli equation, one then obtains [ 2 ]
H ^ | ψ ⟩ = [ 1 2 m [ ( p ^ − q A ) 2 − q ℏ σ ⋅ B ] + q ϕ ] | ψ ⟩ = i ℏ ∂ ∂ t | ψ ⟩ {\displaystyle {\hat {H}}|\psi \rangle =\left[{\frac {1}{2m}}\left[\left(\mathbf {\hat {p}} -q\mathbf {A} \right)^{2}-q\hbar {\boldsymbol {\sigma }}\cdot \mathbf {B} \right]+q\phi \right]|\psi \rangle =i\hbar {\frac {\partial }{\partial t}}|\psi \rangle }
for which only a few analytic results are known, e.g., in the context of Landau quantization with homogenous magnetic fields or for an idealized, Coulomb-like, inhomogeneous magnetic field. [ 3 ]
For the case of where the magnetic field is constant and homogenous, one may expand ( p ^ − q A ) 2 {\textstyle (\mathbf {\hat {p}} -q\mathbf {A} )^{2}} using the symmetric gauge A ^ = 1 2 B × r ^ {\textstyle \mathbf {\hat {A}} ={\frac {1}{2}}\mathbf {B} \times \mathbf {\hat {r}} } , where r {\textstyle \mathbf {r} } is the position operator and A is now an operator. We obtain
where L ^ {\textstyle \mathbf {\hat {L}} } is the particle angular momentum operator and we neglected terms in the magnetic field squared B 2 {\textstyle B^{2}} . Therefore, we obtain
[ 1 2 m [ | p ^ | 2 − q ( L ^ + 2 S ^ ) ⋅ B ] + q ϕ ] | ψ ⟩ = i ℏ ∂ ∂ t | ψ ⟩ {\displaystyle \left[{\frac {1}{2m}}\left[|\mathbf {\hat {p}} |^{2}-q(\mathbf {\hat {L}} +2\mathbf {\hat {S}} )\cdot \mathbf {B} \right]+q\phi \right]|\psi \rangle =i\hbar {\frac {\partial }{\partial t}}|\psi \rangle }
where S = ℏ σ / 2 {\textstyle \mathbf {S} =\hbar {\boldsymbol {\sigma }}/2} is the spin of the particle. The factor 2 in front of the spin is known as the Dirac g -factor . The term in B {\textstyle \mathbf {B} } , is of the form − μ ⋅ B {\textstyle -{\boldsymbol {\mu }}\cdot \mathbf {B} } which is the usual interaction between a magnetic moment μ {\textstyle {\boldsymbol {\mu }}} and a magnetic field, like in the Zeeman effect .
For an electron of charge − e {\textstyle -e} in an isotropic constant magnetic field, one can further reduce the equation using the total angular momentum J = L + S {\textstyle \mathbf {J} =\mathbf {L} +\mathbf {S} } and Wigner-Eckart theorem . Thus we find
where μ B = e ℏ 2 m {\textstyle \mu _{\rm {B}}={\frac {e\hbar }{2m}}} is the Bohr magneton and m j {\textstyle m_{j}} is the magnetic quantum number related to J {\textstyle \mathbf {J} } . The term g J {\textstyle g_{J}} is known as the Landé g-factor , and is given here by
where ℓ {\displaystyle \ell } is the orbital quantum number related to L 2 {\displaystyle L^{2}} and j {\displaystyle j} is the total orbital quantum number related to J 2 {\displaystyle J^{2}} .
The Pauli equation can be inferred from the non-relativistic limit of the Dirac equation , which is the relativistic quantum equation of motion for spin-1/2 particles. [ 4 ]
The Dirac equation can be written as: i ℏ ∂ t ( ψ 1 ψ 2 ) = c ( σ ⋅ Π ψ 2 σ ⋅ Π ψ 1 ) + q ϕ ( ψ 1 ψ 2 ) + m c 2 ( ψ 1 − ψ 2 ) , {\displaystyle i\hbar \,\partial _{t}{\begin{pmatrix}\psi _{1}\\\psi _{2}\end{pmatrix}}=c\,{\begin{pmatrix}{\boldsymbol {\sigma }}\cdot {\boldsymbol {\Pi }}\,\psi _{2}\\{\boldsymbol {\sigma }}\cdot {\boldsymbol {\Pi }}\,\psi _{1}\end{pmatrix}}+q\,\phi \,{\begin{pmatrix}\psi _{1}\\\psi _{2}\end{pmatrix}}+mc^{2}\,{\begin{pmatrix}\psi _{1}\\-\psi _{2}\end{pmatrix}},}
where ∂ t = ∂ ∂ t {\textstyle \partial _{t}={\frac {\partial }{\partial t}}} and ψ 1 , ψ 2 {\displaystyle \psi _{1},\psi _{2}} are two-component spinor , forming a bispinor .
Using the following ansatz: ( ψ 1 ψ 2 ) = e − i m c 2 t ℏ ( ψ χ ) , {\displaystyle {\begin{pmatrix}\psi _{1}\\\psi _{2}\end{pmatrix}}=e^{-i{\tfrac {mc^{2}t}{\hbar }}}{\begin{pmatrix}\psi \\\chi \end{pmatrix}},} with two new spinors ψ , χ {\displaystyle \psi ,\chi } , the equation becomes i ℏ ∂ t ( ψ χ ) = c ( σ ⋅ Π χ σ ⋅ Π ψ ) + q ϕ ( ψ χ ) + ( 0 − 2 m c 2 χ ) . {\displaystyle i\hbar \partial _{t}{\begin{pmatrix}\psi \\\chi \end{pmatrix}}=c\,{\begin{pmatrix}{\boldsymbol {\sigma }}\cdot {\boldsymbol {\Pi }}\,\chi \\{\boldsymbol {\sigma }}\cdot {\boldsymbol {\Pi }}\,\psi \end{pmatrix}}+q\,\phi \,{\begin{pmatrix}\psi \\\chi \end{pmatrix}}+{\begin{pmatrix}0\\-2\,mc^{2}\,\chi \end{pmatrix}}.}
In the non-relativistic limit, ∂ t χ {\displaystyle \partial _{t}\chi } and the kinetic and electrostatic energies are small with respect to the rest energy m c 2 {\displaystyle mc^{2}} , leading to the Lévy-Leblond equation . [ 5 ] Thus χ ≈ σ ⋅ Π ψ 2 m c . {\displaystyle \chi \approx {\frac {{\boldsymbol {\sigma }}\cdot {\boldsymbol {\Pi }}\,\psi }{2\,mc}}\,.}
Inserted in the upper component of Dirac equation, we find Pauli equation (general form): i ℏ ∂ t ψ = [ ( σ ⋅ Π ) 2 2 m + q ϕ ] ψ . {\displaystyle i\hbar \,\partial _{t}\,\psi =\left[{\frac {({\boldsymbol {\sigma }}\cdot {\boldsymbol {\Pi }})^{2}}{2\,m}}+q\,\phi \right]\psi .}
The rigorous derivation of the Pauli equation follows from Dirac equation in an external field and performing a Foldy–Wouthuysen transformation [ 4 ] considering terms up to order O ( 1 / m c ) {\displaystyle {\mathcal {O}}(1/mc)} . Similarly, higher order corrections to the Pauli equation can be determined giving rise to spin-orbit and Darwin interaction terms, when expanding up to order O ( 1 / ( m c ) 2 ) {\displaystyle {\mathcal {O}}(1/(mc)^{2})} instead. [ 6 ]
Pauli's equation is derived by requiring minimal coupling , which provides a g -factor g =2. Most elementary particles have anomalous g -factors, different from 2. In the domain of relativistic quantum field theory , one defines a non-minimal coupling, sometimes called Pauli coupling, in order to add an anomalous factor
where p μ {\displaystyle p_{\mu }} is the four-momentum operator, A μ {\displaystyle A_{\mu }} is the electromagnetic four-potential , a {\displaystyle a} is proportional to the anomalous magnetic dipole moment , F μ ν = ∂ μ A ν − ∂ ν A μ {\displaystyle F^{\mu \nu }=\partial ^{\mu }A^{\nu }-\partial ^{\nu }A^{\mu }} is the electromagnetic tensor , and σ μ ν = i 2 [ γ μ , γ ν ] {\textstyle \sigma _{\mu \nu }={\frac {i}{2}}[\gamma _{\mu },\gamma _{\nu }]} are the Lorentzian spin matrices and the commutator of the gamma matrices γ μ {\displaystyle \gamma ^{\mu }} . [ 7 ] [ 8 ] In the context of non-relativistic quantum mechanics, instead of working with the Schrödinger equation, Pauli coupling is equivalent to using the Pauli equation (or postulating Zeeman energy ) for an arbitrary g -factor. | https://en.wikipedia.org/wiki/Pauli_equation |
In quantum mechanics , the Pauli exclusion principle (German: Pauli-Ausschlussprinzip ) states that two or more identical particles with half-integer spins (i.e. fermions ) cannot simultaneously occupy the same quantum state within a system that obeys the laws of quantum mechanics . This principle was formulated by Austrian physicist Wolfgang Pauli in 1925 for electrons , and later extended to all fermions with his spin–statistics theorem of 1940.
In the case of electrons in atoms, the exclusion principle can be stated as follows: in a poly-electron atom it is impossible for any two electrons to have the same two values of all four of their quantum numbers , which are: n , the principal quantum number ; ℓ , the azimuthal quantum number ; m ℓ , the magnetic quantum number ; and m s , the spin quantum number . For example, if two electrons reside in the same orbital , then their values of n , ℓ , and m ℓ are equal. In that case, the two values of m s (spin) pair must be different. Since the only two possible values for the spin projection m s are +1/2 and −1/2, it follows that one electron must have m s = +1/2 and one m s = −1/2.
Particles with an integer spin ( bosons ) are not subject to the Pauli exclusion principle. Any number of identical bosons can occupy the same quantum state, such as photons produced by a laser , or atoms found in a Bose–Einstein condensate .
A more rigorous statement is: under the exchange of two identical particles, the total (many-particle) wave function is antisymmetric for fermions and symmetric for bosons. This means that if the space and spin coordinates of two identical particles are interchanged, then the total wave function changes sign for fermions, but does not change sign for bosons.
So, if hypothetically two fermions were in the same state—for example, in the same atom in the same orbital with the same spin—then interchanging them would change nothing and the total wave function would be unchanged. However, the only way a total wave function can both change sign (required for fermions), and also remain unchanged is that such a function must be zero everywhere, which means such a state cannot exist. This reasoning does not apply to bosons because the sign does not change.
The Pauli exclusion principle describes the behavior of all fermions (particles with half-integer spin ), while bosons (particles with integer spin) are subject to other principles. Fermions include elementary particles such as quarks , electrons and neutrinos . Additionally, baryons such as protons and neutrons ( subatomic particles composed from three quarks) and some atoms (such as helium-3 ) are fermions, and are therefore described by the Pauli exclusion principle as well. Atoms can have different overall spin, which determines whether they are fermions or bosons: for example, helium-3 has spin 1/2 and is therefore a fermion, whereas helium-4 has spin 0 and is a boson. [ 2 ] : 123–125 The Pauli exclusion principle underpins many properties of everyday matter, from its large-scale stability to the chemical behavior of atoms .
Half-integer spin means that the intrinsic angular momentum value of fermions is ℏ = h / 2 π {\displaystyle \hbar =h/2\pi } ( reduced Planck constant ) times a half-integer (1/2, 3/2, 5/2, etc.). In the theory of quantum mechanics , fermions are described by antisymmetric states . In contrast, particles with integer spin (bosons) have symmetric wave functions and may share the same quantum states. Bosons include the photon , the Cooper pairs which are responsible for superconductivity , and the W and Z bosons . Fermions take their name from the Fermi–Dirac statistical distribution , which they obey, and bosons take theirs from the Bose–Einstein distribution .
In the early 20th century it became evident that atoms and molecules with even numbers of electrons are more chemically stable than those with odd numbers of electrons. In the 1916 article "The Atom and the Molecule" by Gilbert N. Lewis , for example, the third of his six postulates of chemical behavior states that the atom tends to hold an even number of electrons in any given shell, and especially to hold eight electrons, which he assumed to be typically arranged symmetrically at the eight corners of a cube . [ 3 ] In 1919 chemist Irving Langmuir suggested that the periodic table could be explained if the electrons in an atom were connected or clustered in some manner. Groups of electrons were thought to occupy a set of electron shells around the nucleus. [ 4 ] In 1922, Niels Bohr updated his model of the atom by assuming that certain numbers of electrons (for example 2, 8 and 18) corresponded to stable "closed shells". [ 5 ] : 203
Pauli looked for an explanation for these numbers, which were at first only empirical . At the same time he was trying to explain experimental results of the Zeeman effect in atomic spectroscopy and in ferromagnetism . He found an essential clue in a 1924 paper by Edmund C. Stoner , which pointed out that, for a given value of the principal quantum number ( n ), the number of energy levels of a single electron in the alkali metal spectra in an external magnetic field, where all degenerate energy levels are separated, is equal to the number of electrons in the closed shell of the noble gases for the same value of n . This led Pauli to realize that the complicated numbers of electrons in closed shells can be reduced to the simple rule of one electron per state if the electron states are defined using four quantum numbers. For this purpose he introduced a new two-valued quantum number, identified by Samuel Goudsmit and George Uhlenbeck as electron spin . [ 6 ] [ 7 ]
In his Nobel lecture, Pauli clarified the importance of quantum state symmetry to the exclusion principle: [ 8 ]
Among the different classes of symmetry, the most important ones (which moreover for two particles are the only ones) are the symmetrical class , in which the wave function does not change its value when the space and spin coordinates of two particles are permuted, and the antisymmetrical class , in which for such a permutation the wave function changes its sign...[The antisymmetrical class is] the correct and general wave mechanical formulation of the exclusion principle.
The Pauli exclusion principle with a single-valued many-particle wavefunction is equivalent to requiring the wavefunction to be antisymmetric with respect to exchange . If | x ⟩ {\displaystyle |x\rangle } and | y ⟩ {\displaystyle |y\rangle } range over the basis vectors of the Hilbert space describing a one-particle system, then the tensor product produces the basis vectors | x , y ⟩ = | x ⟩ ⊗ | y ⟩ {\displaystyle |x,y\rangle =|x\rangle \otimes |y\rangle } of the Hilbert space describing a system of two such particles. Any two-particle state can be represented as a superposition (i.e. sum) of these basis vectors:
where each A ( x , y ) is a (complex) scalar coefficient. Antisymmetry under exchange means that A ( x , y ) = − A ( y , x ) . This implies A ( x , y ) = 0 when x = y , which is Pauli exclusion. It is true in any basis since local changes of basis keep antisymmetric matrices antisymmetric.
Conversely, if the diagonal quantities A ( x , x ) are zero in every basis , then the wavefunction component
is necessarily antisymmetric. To prove it, consider the matrix element
This is zero, because the two particles have zero probability to both be in the superposition state | x ⟩ + | y ⟩ {\displaystyle |x\rangle +|y\rangle } . But this is equal to
The first and last terms are diagonal elements and are zero, and the whole sum is equal to zero. So the wavefunction matrix elements obey:
or
For a system with n > 2 particles, the multi-particle basis states become n -fold tensor products of one-particle basis states, and the coefficients of the wavefunction A ( x 1 , x 2 , … , x n ) {\displaystyle A(x_{1},x_{2},\ldots ,x_{n})} are identified by n one-particle states. The condition of antisymmetry states that the coefficients must flip sign whenever any two states are exchanged: A ( … , x i , … , x j , … ) = − A ( … , x j , … , x i , … ) {\displaystyle A(\ldots ,x_{i},\ldots ,x_{j},\ldots )=-A(\ldots ,x_{j},\ldots ,x_{i},\ldots )} for any i ≠ j {\displaystyle i\neq j} . The exclusion principle is the consequence that, if x i = x j {\displaystyle x_{i}=x_{j}} for any i ≠ j , {\displaystyle i\neq j,} then A ( … , x i , … , x j , … ) = 0. {\displaystyle A(\ldots ,x_{i},\ldots ,x_{j},\ldots )=0.} This shows that none of the n particles may be in the same state.
According to the spin–statistics theorem , particles with integer spin occupy symmetric quantum states, and particles with half-integer spin occupy antisymmetric states; furthermore, only integer or half-integer values of spin are allowed by the principles of quantum mechanics.
In relativistic quantum field theory , the Pauli principle follows from applying a rotation operator in imaginary time to particles of half-integer spin.
In one dimension, bosons, as well as fermions, can obey the exclusion principle. A one-dimensional Bose gas with delta-function repulsive interactions of infinite strength is equivalent to a gas of free fermions. The reason for this is that, in one dimension, the exchange of particles requires that they pass through each other; for infinitely strong repulsion this cannot happen. This model is described by a quantum nonlinear Schrödinger equation . In momentum space, the exclusion principle is valid also for finite repulsion in a Bose gas with delta-function interactions, [ 9 ] as well as for interacting spins and Hubbard model in one dimension, and for other models solvable by Bethe ansatz . The ground state in models solvable by Bethe ansatz is a Fermi sphere .
The Pauli exclusion principle helps explain a wide variety of physical phenomena. One particularly important consequence of the principle is the elaborate electron shell structure of atoms and the way atoms share electrons, explaining the variety of chemical elements and their chemical combinations. An electrically neutral atom contains bound electrons equal in number to the protons in the nucleus . Electrons, being fermions, cannot occupy the same quantum state as other electrons, so electrons have to "stack" within an atom, i.e. have different spins while at the same electron orbital as described below.
An example is the neutral helium atom (He), which has two bound electrons, both of which can occupy the lowest-energy ( 1s ) states by acquiring opposite spin; as spin is part of the quantum state of the electron, the two electrons are in different quantum states and do not violate the Pauli principle. However, the spin can take only two different values ( eigenvalues ). In a lithium atom (Li), with three bound electrons, the third electron cannot reside in a 1s state and must occupy a higher-energy state instead. The lowest available state is 2s, so that the ground state of Li is 1s 2 2s. Similarly, successively larger elements must have shells of successively higher energy. The chemical properties of an element largely depend on the number of electrons in the outermost shell; atoms with different numbers of occupied electron shells but the same number of electrons in the outermost shell have similar properties, which gives rise to the periodic table of the elements . [ 10 ] : 214–218
To test the Pauli exclusion principle for the helium atom, Gordon Drake [ 11 ] carried out very precise calculations for hypothetical states of the He atom that violate it, which are called paronic states . Later, K. Deilamian et al. [ 12 ] used an atomic beam spectrometer to search for the paronic state 1s2s 1 S 0 calculated by Drake. The search was unsuccessful and showed that the statistical weight of this paronic state has an upper limit of 5 × 10 −6 . (The exclusion principle implies a weight of zero.)
In conductors and semiconductors , there are very large numbers of molecular orbitals which effectively form a continuous band structure of energy levels . In strong conductors ( metals ) electrons are so degenerate that they cannot even contribute much to the thermal capacity of a metal. [ 13 ] : 133–147 Many mechanical, electrical, magnetic, optical and chemical properties of solids are the direct consequence of Pauli exclusion.
The stability of each electron state in an atom is described by the quantum theory of the atom, which shows that close approach of an electron to the nucleus necessarily increases the electron's kinetic energy, an application of the uncertainty principle of Heisenberg. [ 14 ] However, stability of large systems with many electrons and many nucleons is a different question, and requires the Pauli exclusion principle. [ 15 ]
It has been shown that the Pauli exclusion principle is responsible for the fact that ordinary bulk matter is stable and occupies volume. This suggestion was first made in 1931 by Paul Ehrenfest , who pointed out that the electrons of each atom cannot all fall into the lowest-energy orbital and must occupy successively larger shells. Atoms, therefore, occupy a volume and cannot be squeezed too closely together. [ 16 ]
The first rigorous proof was provided in 1967 by Freeman Dyson and Andrew Lenard ( de ), who considered the balance of attractive (electron–nuclear) and repulsive (electron–electron and nuclear–nuclear) forces and showed that ordinary matter would collapse and occupy a much smaller volume without the Pauli principle. [ 17 ] [ 18 ] A much simpler proof was found later by Elliott H. Lieb and Walter Thirring in 1975. They provided a lower bound on the quantum energy in terms of the Thomas-Fermi model , which is stable due to a theorem of Teller . The proof used a lower bound on the kinetic energy which is now called the Lieb–Thirring inequality .
The consequence of the Pauli principle here is that electrons of the same spin are kept apart by a repulsive exchange interaction , which is a short-range effect, acting simultaneously with the long-range electrostatic or Coulombic force . This effect is partly responsible for the everyday observation in the macroscopic world that two solid objects cannot be in the same place at the same time.
Dyson and Lenard did not consider the extreme magnetic or gravitational forces that occur in some astronomical objects. In 1995 Elliott Lieb and coworkers showed that the Pauli principle still leads to stability in intense magnetic fields such as in neutron stars , although at a much higher density than in ordinary matter. [ 19 ] It is a consequence of general relativity that, in sufficiently intense gravitational fields, matter collapses to form a black hole .
Astronomy provides a spectacular demonstration of the effect of the Pauli principle, in the form of white dwarf and neutron stars . In both bodies, the atomic structure is disrupted by extreme pressure, but the stars are held in hydrostatic equilibrium by degeneracy pressure , also known as Fermi pressure. This exotic form of matter is known as degenerate matter . The immense gravitational force of a star's mass is normally held in equilibrium by thermal pressure caused by heat produced in thermonuclear fusion in the star's core. In white dwarfs, which do not undergo nuclear fusion, an opposing force to gravity is provided by electron degeneracy pressure . In neutron stars , subject to even stronger gravitational forces, electrons have merged with protons to form neutrons. Neutrons are capable of producing an even higher degeneracy pressure, neutron degeneracy pressure , albeit over a shorter range. This can stabilize neutron stars from further collapse, but at a smaller size and higher density than a white dwarf. Neutron stars are the most "rigid" objects known; their Young modulus (or more accurately, bulk modulus ) is 20 orders of magnitude larger than that of diamond . However, even this enormous rigidity can be overcome by the gravitational field of a neutron star mass exceeding the Tolman–Oppenheimer–Volkoff limit , leading to the formation of a black hole . [ 20 ] : 286–287 | https://en.wikipedia.org/wiki/Pauli_exclusion_principle |
In mathematical physics and mathematics , the Pauli matrices are a set of three 2 × 2 complex matrices that are traceless , Hermitian , involutory and unitary . Usually indicated by the Greek letter sigma ( σ ), they are occasionally denoted by tau ( τ ) when used in connection with isospin symmetries. σ 1 = σ x = ( 0 1 1 0 ) , σ 2 = σ y = ( 0 − i i 0 ) , σ 3 = σ z = ( 1 0 0 − 1 ) . {\displaystyle {\begin{aligned}\sigma _{1}=\sigma _{x}&={\begin{pmatrix}0&1\\1&0\end{pmatrix}},\\\sigma _{2}=\sigma _{y}&={\begin{pmatrix}0&-i\\i&0\end{pmatrix}},\\\sigma _{3}=\sigma _{z}&={\begin{pmatrix}1&0\\0&-1\end{pmatrix}}.\\\end{aligned}}}
These matrices are named after the physicist Wolfgang Pauli . In quantum mechanics , they occur in the Pauli equation , which takes into account the interaction of the spin of a particle with an external electromagnetic field . They also represent the interaction states of two polarization filters for horizontal/vertical polarization, 45 degree polarization (right/left), and circular polarization (right/left).
Each Pauli matrix is Hermitian , and together with the identity matrix I (sometimes considered as the zeroth Pauli matrix σ 0 ), the Pauli matrices form a basis of the vector space of 2 × 2 Hermitian matrices over the real numbers , under addition. This means that any 2 × 2 Hermitian matrix can be written in a unique way as a linear combination of Pauli matrices, with all coefficients being real numbers.
The Pauli matrices satisfy the useful product relation: σ i σ j = δ i j + i ϵ i j k σ k . {\displaystyle {\begin{aligned}\sigma _{i}\sigma _{j}=\delta _{ij}+i\epsilon _{ijk}\sigma _{k}.\end{aligned}}}
Hermitian operators represent observables in quantum mechanics, so the Pauli matrices span the space of observables of the complex two-dimensional Hilbert space . In the context of Pauli's work, σ k represents the observable corresponding to spin along the k th coordinate axis in three-dimensional Euclidean space R 3 . {\displaystyle \mathbb {R} ^{3}.}
The Pauli matrices (after multiplication by i to make them anti-Hermitian ) also generate transformations in the sense of Lie algebras : the matrices iσ 1 , iσ 2 , iσ 3 form a basis for the real Lie algebra s u ( 2 ) {\displaystyle {\mathfrak {su}}(2)} , which exponentiates to the special unitary group SU(2) . [ a ] The algebra generated by the three matrices σ 1 , σ 2 , σ 3 is isomorphic to the Clifford algebra of R 3 , {\displaystyle \mathbb {R} ^{3},} [ 1 ] and the (unital) associative algebra generated by iσ 1 , iσ 2 , iσ 3 functions identically ( is isomorphic ) to that of quaternions ( H {\displaystyle \mathbb {H} } ).
All three of the Pauli matrices can be compacted into a single expression:
where δ jk is the Kronecker delta , which equals +1 if j = k and 0 otherwise. This expression is useful for "selecting" any one of the matrices numerically by substituting values of j = 1, 2, 3, in turn useful when any of the matrices (but no particular one) is to be used in algebraic manipulations.
The matrices are involutory :
where I is the identity matrix .
The determinants and traces of the Pauli matrices are
from which we can deduce that each matrix σ j has eigenvalues +1 and −1.
With the inclusion of the identity matrix I (sometimes denoted σ 0 ), the Pauli matrices form an orthogonal basis (in the sense of Hilbert–Schmidt ) of the Hilbert space H 2 {\displaystyle {\mathcal {H}}_{2}} of 2 × 2 Hermitian matrices over R {\displaystyle \mathbb {R} } , and the Hilbert space M 2 , 2 ( C ) {\displaystyle {\mathcal {M}}_{2,2}(\mathbb {C} )} of all complex 2 × 2 matrices over C {\displaystyle \mathbb {C} } .
The Pauli matrices obey the following commutation relations:
where the Levi-Civita symbol ε jkl is used.
These commutation relations make the Pauli matrices the generators of a representation of the Lie algebra ( R 3 , × ) ≅ s u ( 2 ) ≅ s o ( 3 ) . {\displaystyle (\mathbb {R} ^{3},\times )\cong {\mathfrak {su}}(2)\cong {\mathfrak {so}}(3).}
They also satisfy the anticommutation relations:
where { σ j , σ k } {\displaystyle \{\sigma _{j},\sigma _{k}\}} is defined as σ j σ k + σ k σ j , {\displaystyle \sigma _{j}\sigma _{k}+\sigma _{k}\sigma _{j},} and δ jk is the Kronecker delta . I denotes the 2 × 2 identity matrix.
These anti-commutation relations make the Pauli matrices the generators of a representation of the Clifford algebra for R 3 , {\displaystyle \mathbb {R} ^{3},} denoted C l 3 ( R ) . {\displaystyle \mathrm {Cl} _{3}(\mathbb {R} ).}
The usual construction of generators σ j k = 1 4 [ σ j , σ k ] {\displaystyle \sigma _{jk}={\tfrac {1}{4}}[\sigma _{j},\sigma _{k}]} of s o ( 3 ) {\displaystyle {\mathfrak {so}}(3)} using the Clifford algebra recovers the commutation relations above, up to unimportant numerical factors.
A few explicit commutators and anti-commutators are given below as examples:
Each of the ( Hermitian ) Pauli matrices has two eigenvalues : +1 and −1 . The corresponding normalized eigenvectors are
The Pauli vector is defined by [ b ] σ → = σ 1 x ^ 1 + σ 2 x ^ 2 + σ 3 x ^ 3 , {\displaystyle {\vec {\sigma }}=\sigma _{1}{\hat {x}}_{1}+\sigma _{2}{\hat {x}}_{2}+\sigma _{3}{\hat {x}}_{3},} where x ^ 1 {\displaystyle {\hat {x}}_{1}} , x ^ 2 {\displaystyle {\hat {x}}_{2}} , and x ^ 3 {\displaystyle {\hat {x}}_{3}} are an equivalent notation for the more familiar x ^ {\displaystyle {\hat {x}}} , y ^ {\displaystyle {\hat {y}}} , and z ^ {\displaystyle {\hat {z}}} .
The Pauli vector provides a mapping mechanism from a vector basis to a Pauli matrix basis [ 2 ] as follows: a → ⋅ σ → = ∑ k , l a k σ ℓ x ^ k ⋅ x ^ ℓ = ∑ k a k σ k = ( a 3 a 1 − i a 2 a 1 + i a 2 − a 3 ) . {\displaystyle {\begin{aligned}{\vec {a}}\cdot {\vec {\sigma }}&=\sum _{k,l}a_{k}\,\sigma _{\ell }\,{\hat {x}}_{k}\cdot {\hat {x}}_{\ell }\\&=\sum _{k}a_{k}\,\sigma _{k}\\&={\begin{pmatrix}a_{3}&a_{1}-ia_{2}\\a_{1}+ia_{2}&-a_{3}\end{pmatrix}}.\end{aligned}}}
More formally, this defines a map from R 3 {\displaystyle \mathbb {R} ^{3}} to the vector space of traceless Hermitian 2 × 2 {\displaystyle 2\times 2} matrices. This map encodes structures of R 3 {\displaystyle \mathbb {R} ^{3}} as a normed vector space and as a Lie algebra (with the cross-product as its Lie bracket) via functions of matrices, making the map an isomorphism of Lie algebras. This makes the Pauli matrices intertwiners from the point of view of representation theory.
Another way to view the Pauli vector is as a 2 × 2 {\displaystyle 2\times 2} Hermitian traceless matrix-valued dual vector, that is, an element of Mat 2 × 2 ( C ) ⊗ ( R 3 ) ∗ {\displaystyle {\text{Mat}}_{2\times 2}(\mathbb {C} )\otimes (\mathbb {R} ^{3})^{*}} that maps a → ↦ a → ⋅ σ → . {\displaystyle {\vec {a}}\mapsto {\vec {a}}\cdot {\vec {\sigma }}.}
Each component of a → {\displaystyle {\vec {a}}} can be recovered from the matrix (see completeness relation below) 1 2 tr ( ( a → ⋅ σ → ) σ → ) = a → . {\displaystyle {\frac {1}{2}}\operatorname {tr} {\Bigl (}{\bigl (}{\vec {a}}\cdot {\vec {\sigma }}{\bigr )}{\vec {\sigma }}{\Bigr )}={\vec {a}}.} This constitutes an inverse to the map a → ↦ a → ⋅ σ → {\displaystyle {\vec {a}}\mapsto {\vec {a}}\cdot {\vec {\sigma }}} , making it manifest that the map is a bijection.
The norm is given by the determinant (up to a minus sign) det ( a → ⋅ σ → ) = − a → ⋅ a → = − | a → | 2 . {\displaystyle \det {\bigl (}{\vec {a}}\cdot {\vec {\sigma }}{\bigr )}=-{\vec {a}}\cdot {\vec {a}}=-|{\vec {a}}|^{2}.} Then, considering the conjugation action of an SU ( 2 ) {\displaystyle {\text{SU}}(2)} matrix U {\displaystyle U} on this space of matrices,
we find det ( U ∗ a → ⋅ σ → ) = det ( a → ⋅ σ → ) , {\displaystyle \det(U*{\vec {a}}\cdot {\vec {\sigma }})=\det({\vec {a}}\cdot {\vec {\sigma }}),} and that U ∗ a → ⋅ σ → {\displaystyle U*{\vec {a}}\cdot {\vec {\sigma }}} is Hermitian and traceless. It then makes sense to define U ∗ a → ⋅ σ → = a → ′ ⋅ σ → , {\displaystyle U*{\vec {a}}\cdot {\vec {\sigma }}={\vec {a}}'\cdot {\vec {\sigma }},} where a → ′ {\displaystyle {\vec {a}}'} has the same norm as a → , {\displaystyle {\vec {a}},} and therefore interpret U {\displaystyle U} as a rotation of three-dimensional space. In fact, it turns out that the special restriction on U {\displaystyle U} implies that the rotation is orientation preserving. This allows the definition of a map R : S U ( 2 ) → S O ( 3 ) {\displaystyle R:\mathrm {SU} (2)\to \mathrm {SO} (3)} given by
where R ( U ) ∈ S O ( 3 ) . {\displaystyle R(U)\in \mathrm {SO} (3).} This map is the concrete realization of the double cover of S O ( 3 ) {\displaystyle \mathrm {SO} (3)} by S U ( 2 ) , {\displaystyle \mathrm {SU} (2),} and therefore shows that SU ( 2 ) ≅ S p i n ( 3 ) . {\displaystyle {\text{SU}}(2)\cong \mathrm {Spin} (3).} The components of R ( U ) {\displaystyle R(U)} can be recovered using the tracing process above:
The cross-product is given by the matrix commutator (up to a factor of 2 i {\displaystyle 2i} ) [ a → ⋅ σ → , b → ⋅ σ → ] = 2 i ( a → × b → ) ⋅ σ → . {\displaystyle [{\vec {a}}\cdot {\vec {\sigma }},{\vec {b}}\cdot {\vec {\sigma }}]=2i\,({\vec {a}}\times {\vec {b}})\cdot {\vec {\sigma }}.} In fact, the existence of a norm follows from the fact that R 3 {\displaystyle \mathbb {R} ^{3}} is a Lie algebra (see Killing form ).
This cross-product can be used to prove the orientation-preserving property of the map above.
The eigenvalues of a → ⋅ σ → {\displaystyle \ {\vec {a}}\cdot {\vec {\sigma }}\ } are ± | a → | . {\displaystyle \ \pm |{\vec {a}}|.} This follows immediately from tracelessness and explicitly computing the determinant.
More abstractly, without computing the determinant, which requires explicit properties of the Pauli matrices, this follows from ( a → ⋅ σ → ) 2 − | a → | 2 = 0 , {\displaystyle \ ({\vec {a}}\cdot {\vec {\sigma }})^{2}-|{\vec {a}}|^{2}=0\ ,} since this can be factorised into ( a → ⋅ σ → − | a → | ) ( a → ⋅ σ → + | a → | ) = 0. {\displaystyle \ ({\vec {a}}\cdot {\vec {\sigma }}-|{\vec {a}}|)({\vec {a}}\cdot {\vec {\sigma }}+|{\vec {a}}|)=0.} A standard result in linear algebra (a linear map that satisfies a polynomial equation written in distinct linear factors is diagonal) means this implies a → ⋅ σ → {\displaystyle \ {\vec {a}}\cdot {\vec {\sigma }}\ } is diagonal with possible eigenvalues ± | a → | . {\displaystyle \ \pm |{\vec {a}}|.} The tracelessness of a → ⋅ σ → {\displaystyle \ {\vec {a}}\cdot {\vec {\sigma }}\ } means it has exactly one of each eigenvalue.
Its normalized eigenvectors are ψ + = 1 2 | a → | ( a 3 + | a → | ) [ a 3 + | a → | a 1 + i a 2 ] ; ψ − = 1 2 | a → | ( a 3 + | a → | ) [ i a 2 − a 1 a 3 + | a → | ] . {\displaystyle \psi _{+}={\frac {1}{{\sqrt {2\left|{\vec {a}}\right|\ (a_{3}+\left|{\vec {a}}\right|)\ }}\ }}{\begin{bmatrix}a_{3}+\left|{\vec {a}}\right|\\a_{1}+ia_{2}\end{bmatrix}};\qquad \psi _{-}={\frac {1}{\sqrt {2|{\vec {a}}|(a_{3}+|{\vec {a}}|)}}}{\begin{bmatrix}ia_{2}-a_{1}\\a_{3}+|{\vec {a}}|\end{bmatrix}}~.} These expressions become singular for a 3 → − | a → | {\displaystyle a_{3}\to -\left|{\vec {a}}\right|} . They can be rescued by letting a → = | a → | ( ϵ , 0 , − ( 1 − ϵ 2 / 2 ) ) {\displaystyle {\vec {a}}=\left|{\vec {a}}\right|(\epsilon ,0,-(1-\epsilon ^{2}/2))} and taking the limit ϵ → 0 {\displaystyle \epsilon \to 0} , which yields the correct eigenvectors (0,1) and (1,0) of σ z {\displaystyle \sigma _{z}} .
Alternatively, one may use spherical coordinates a → = a ( sin ϑ cos φ , sin ϑ sin φ , cos ϑ ) {\displaystyle {\vec {a}}=a(\sin \vartheta \cos \varphi ,\sin \vartheta \sin \varphi ,\cos \vartheta )} to obtain the eigenvectors ψ + = ( cos ( ϑ / 2 ) , sin ( ϑ / 2 ) exp ( i φ ) ) {\displaystyle \psi _{+}=(\cos(\vartheta /2),\sin(\vartheta /2)\exp(i\varphi ))} and ψ − = ( − sin ( ϑ / 2 ) exp ( − i φ ) , cos ( ϑ / 2 ) ) {\displaystyle \psi _{-}=(-\sin(\vartheta /2)\exp(-i\varphi ),\cos(\vartheta /2))} .
The Pauli 4-vector, used in spinor theory, is written σ μ {\displaystyle \ \sigma ^{\mu }\ } with components
This defines a map from R 1 , 3 {\displaystyle \mathbb {R} ^{1,3}} to the vector space of Hermitian matrices,
which also encodes the Minkowski metric (with mostly minus convention) in its determinant:
This 4-vector also has a completeness relation. It is convenient to define a second Pauli 4-vector
and allow raising and lowering using the Minkowski metric tensor. The relation can then be written x ν = 1 2 tr ( σ ¯ ν ( x μ σ μ ) ) . {\displaystyle x_{\nu }={\tfrac {1}{2}}\operatorname {tr} {\Bigl (}{\bar {\sigma }}_{\nu }{\bigl (}x_{\mu }\sigma ^{\mu }{\bigr )}{\Bigr )}.}
Similarly to the Pauli 3-vector case, we can find a matrix group that acts as isometries on R 1 , 3 ; {\displaystyle \ \mathbb {R} ^{1,3}\ ;} in this case the matrix group is S L ( 2 , C ) , {\displaystyle \ \mathrm {SL} (2,\mathbb {C} )\ ,} and this shows S L ( 2 , C ) ≅ S p i n ( 1 , 3 ) . {\displaystyle \ \mathrm {SL} (2,\mathbb {C} )\cong \mathrm {Spin} (1,3).} Similarly to above, this can be explicitly realized for S ∈ S L ( 2 , C ) {\displaystyle \ S\in \mathrm {SL} (2,\mathbb {C} )\ } with components
In fact, the determinant property follows abstractly from trace properties of the σ μ . {\displaystyle \ \sigma ^{\mu }.} For 2 × 2 {\displaystyle \ 2\times 2\ } matrices, the following identity holds:
That is, the 'cross-terms' can be written as traces. When A , B {\displaystyle \ A,B\ } are chosen to be different σ μ , {\displaystyle \ \sigma ^{\mu }\ ,} the cross-terms vanish. It then follows, now showing summation explicitly, det ( ∑ μ x μ σ μ ) = ∑ μ det ( x μ σ μ ) . {\textstyle \det \left(\sum _{\mu }x_{\mu }\sigma ^{\mu }\right)=\sum _{\mu }\det \left(x_{\mu }\sigma ^{\mu }\right).} Since the matrices are 2 × 2 , {\displaystyle \ 2\times 2\ ,} this is equal to ∑ μ x μ 2 det ( σ μ ) = η ( x , x ) . {\textstyle \sum _{\mu }x_{\mu }^{2}\det(\sigma ^{\mu })=\eta (x,x).}
Pauli vectors elegantly map these commutation and anticommutation relations to corresponding vector products. Adding the commutator to the anticommutator gives
so that,
σ j σ k = δ j k I + i ε j k ℓ σ ℓ . {\displaystyle ~~\sigma _{j}\sigma _{k}=\delta _{jk}I+i\varepsilon _{jk\ell }\,\sigma _{\ell }~.~}
Contracting each side of the equation with components of two 3 -vectors a p and b q (which commute with the Pauli matrices, i.e., a p σ q = σ q a p ) for each matrix σ q and vector component a p (and likewise with b q ) yields
Finally, translating the index notation for the dot product and cross product results in
( a → ⋅ σ → ) ( b → ⋅ σ → ) = ( a → ⋅ b → ) I + i ( a → × b → ) ⋅ σ → {\displaystyle ~~{\Bigl (}{\vec {a}}\cdot {\vec {\sigma }}{\Bigr )}{\Bigl (}{\vec {b}}\cdot {\vec {\sigma }}{\Bigr )}={\Bigl (}{\vec {a}}\cdot {\vec {b}}{\Bigr )}\,I+i{\Bigl (}{\vec {a}}\times {\vec {b}}{\Bigr )}\cdot {\vec {\sigma }}~~}
If i is identified with the pseudoscalar σ x σ y σ z then the right hand side becomes a ⋅ b + a ∧ b {\displaystyle a\cdot b+a\wedge b} , which is also the definition for the product of two vectors in geometric algebra.
If we define the spin operator as J = ħ / 2 σ , then J satisfies the commutation relation: J × J = i ℏ J {\displaystyle \mathbf {J} \times \mathbf {J} =i\hbar \mathbf {J} } Or equivalently, the Pauli vector satisfies: σ → 2 × σ → 2 = i σ → 2 {\displaystyle {\frac {\vec {\sigma }}{2}}\times {\frac {\vec {\sigma }}{2}}=i{\frac {\vec {\sigma }}{2}}}
The following traces can be derived using the commutation and anticommutation relations.
If the matrix σ 0 = I is also considered, these relationships become
tr ( σ α ) = 2 δ 0 α tr ( σ α σ β ) = 2 δ α β tr ( σ α σ β σ γ ) = 2 ∑ ( α β γ ) δ α β δ 0 γ − 4 δ 0 α δ 0 β δ 0 γ + 2 i ε 0 α β γ tr ( σ α σ β σ γ σ μ ) = 2 ( δ α β δ γ μ − δ α γ δ β μ + δ α μ δ β γ ) + 4 ( δ α γ δ 0 β δ 0 μ + δ β μ δ 0 α δ 0 γ ) − 8 δ 0 α δ 0 β δ 0 γ δ 0 μ + 2 i ∑ ( α β γ μ ) ε 0 α β γ δ 0 μ {\displaystyle {\begin{aligned}\operatorname {tr} \left(\sigma _{\alpha }\right)&=2\delta _{0\alpha }\\\operatorname {tr} \left(\sigma _{\alpha }\sigma _{\beta }\right)&=2\delta _{\alpha \beta }\\\operatorname {tr} \left(\sigma _{\alpha }\sigma _{\beta }\sigma _{\gamma }\right)&=2\sum _{(\alpha \beta \gamma )}\delta _{\alpha \beta }\delta _{0\gamma }-4\delta _{0\alpha }\delta _{0\beta }\delta _{0\gamma }+2i\varepsilon _{0\alpha \beta \gamma }\\\operatorname {tr} \left(\sigma _{\alpha }\sigma _{\beta }\sigma _{\gamma }\sigma _{\mu }\right)&=2\left(\delta _{\alpha \beta }\delta _{\gamma \mu }-\delta _{\alpha \gamma }\delta _{\beta \mu }+\delta _{\alpha \mu }\delta _{\beta \gamma }\right)+4\left(\delta _{\alpha \gamma }\delta _{0\beta }\delta _{0\mu }+\delta _{\beta \mu }\delta _{0\alpha }\delta _{0\gamma }\right)-8\delta _{0\alpha }\delta _{0\beta }\delta _{0\gamma }\delta _{0\mu }+2i\sum _{(\alpha \beta \gamma \mu )}\varepsilon _{0\alpha \beta \gamma }\delta _{0\mu }\end{aligned}}}
where Greek indices α , β , γ and μ assume values from {0, x , y , z } and the notation ∑ ( α … ) {\textstyle \sum _{(\alpha \ldots )}} is used to denote the sum over the cyclic permutation of the included indices.
For
one has, for even powers, 2 p , p = 0, 1, 2, 3, ...
which can be shown first for the p = 1 case using the anticommutation relations. For convenience, the case p = 0 is taken to be I by convention.
For odd powers, 2 q + 1, q = 0, 1, 2, 3, ...
Matrix exponentiating , and using the Taylor series for sine and cosine ,
In the last line, the first sum is the cosine, while the second sum is the sine; so, finally,
e i a ( n ^ ⋅ σ → ) = I cos a + i ( n ^ ⋅ σ → ) sin a {\displaystyle ~~e^{ia\left({\hat {n}}\cdot {\vec {\sigma }}\right)}=I\cos {a}+i({\hat {n}}\cdot {\vec {\sigma }})\sin {a}~~}
which is analogous to Euler's formula , extended to quaternions . In particular,
e i a σ 1 = ( cos a i sin a i sin a cos a ) , e i a σ 2 = ( cos a sin a − sin a cos a ) , e i a σ 3 = ( e i a 0 0 e − i a ) . {\displaystyle e^{ia\sigma _{1}}={\begin{pmatrix}\cos a&i\sin a\\i\sin a&\cos a\end{pmatrix}},\quad e^{ia\sigma _{2}}={\begin{pmatrix}\cos a&\sin a\\-\sin a&\cos a\end{pmatrix}},\quad e^{ia\sigma _{3}}={\begin{pmatrix}e^{ia}&0\\0&e^{-ia}\end{pmatrix}}.}
Note that
while the determinant of the exponential itself is just 1 , which makes it the generic group element of SU(2) .
A more abstract version of formula (2) for a general 2 × 2 matrix can be found in the article on matrix exponentials . A general version of (2) for an analytic (at a and − a ) function is provided by application of Sylvester's formula , [ 3 ]
A straightforward application of formula (2) provides a parameterization of the composition law of the group SU(2) . [ c ] One may directly solve for c in e i a ( n ^ ⋅ σ → ) e i b ( m ^ ⋅ σ → ) = I ( cos a cos b − n ^ ⋅ m ^ sin a sin b ) + i ( n ^ sin a cos b + m ^ sin b cos a − n ^ × m ^ sin a sin b ) ⋅ σ → = I cos c + i ( k ^ ⋅ σ → ) sin c = e i c ( k ^ ⋅ σ → ) , {\displaystyle {\begin{aligned}e^{ia\left({\hat {n}}\cdot {\vec {\sigma }}\right)}e^{ib\left({\hat {m}}\cdot {\vec {\sigma }}\right)}&=I\left(\cos a\cos b-{\hat {n}}\cdot {\hat {m}}\sin a\sin b\right)+i\left({\hat {n}}\sin a\cos b+{\hat {m}}\sin b\cos a-{\hat {n}}\times {\hat {m}}~\sin a\sin b\right)\cdot {\vec {\sigma }}\\&=I\cos {c}+i\left({\hat {k}}\cdot {\vec {\sigma }}\right)\sin c\\&=e^{ic\left({\hat {k}}\cdot {\vec {\sigma }}\right)},\end{aligned}}}
which specifies the generic group multiplication, where, manifestly, cos c = cos a cos b − n ^ ⋅ m ^ sin a sin b , {\displaystyle \cos c=\cos a\cos b-{\hat {n}}\cdot {\hat {m}}\sin a\sin b~,} the spherical law of cosines . Given c , then, k ^ = 1 sin c ( n ^ sin a cos b + m ^ sin b cos a − n ^ × m ^ sin a sin b ) . {\displaystyle {\hat {k}}={\frac {1}{\sin c}}\left({\hat {n}}\sin a\cos b+{\hat {m}}\sin b\cos a-{\hat {n}}\times {\hat {m}}\sin a\sin b\right).}
Consequently, the composite rotation parameters in this group element (a closed form of the respective BCH expansion in this case) simply amount to [ 4 ]
e i c k ^ ⋅ σ → = exp ( i c sin c ( n ^ sin a cos b + m ^ sin b cos a − n ^ × m ^ sin a sin b ) ⋅ σ → ) . {\displaystyle e^{ic{\hat {k}}\cdot {\vec {\sigma }}}=\exp \left(i{\frac {c}{\sin c}}\left({\hat {n}}\sin a\cos b+{\hat {m}}\sin b\cos a-{\hat {n}}\times {\hat {m}}~\sin a\sin b\right)\cdot {\vec {\sigma }}\right).}
(Of course, when n ^ {\displaystyle {\hat {n}}} is parallel to m ^ {\displaystyle {\hat {m}}} , so is k ^ {\displaystyle {\hat {k}}} , and c = a + b .)
It is also straightforward to likewise work out the adjoint action on the Pauli vector, namely rotation of any angle a {\displaystyle a} along any axis n ^ {\displaystyle {\hat {n}}} : R n ( − a ) σ → R n ( a ) = e i a 2 ( n ^ ⋅ σ → ) σ → e − i a 2 ( n ^ ⋅ σ → ) = σ → cos ( a ) + n ^ × σ → sin ( a ) + n ^ n ^ ⋅ σ → ( 1 − cos ( a ) ) . {\displaystyle R_{n}(-a)~{\vec {\sigma }}~R_{n}(a)=e^{i{\frac {a}{2}}\left({\hat {n}}\cdot {\vec {\sigma }}\right)}~{\vec {\sigma }}~e^{-i{\frac {a}{2}}\left({\hat {n}}\cdot {\vec {\sigma }}\right)}={\vec {\sigma }}\cos(a)+{\hat {n}}\times {\vec {\sigma }}~\sin(a)+{\hat {n}}~{\hat {n}}\cdot {\vec {\sigma }}~(1-\cos(a))~.}
Taking the dot product of any unit vector with the above formula generates the expression of any single qubit operator under any rotation. For example, it can be shown that R y ( − π 2 ) σ x R y ( π 2 ) = x ^ ⋅ ( y ^ × σ → ) = σ z {\textstyle R_{y}{\mathord {\left(-{\frac {\pi }{2}}\right)}}\,\sigma _{x}\,R_{y}{\mathord {\left({\frac {\pi }{2}}\right)}}={\hat {x}}\cdot \left({\hat {y}}\times {\vec {\sigma }}\right)=\sigma _{z}} .
An alternative notation that is commonly used for the Pauli matrices is to write the vector index k in the superscript, and the matrix indices as subscripts, so that the element in row α and column β of the k -th Pauli matrix is σ k αβ .
In this notation, the completeness relation for the Pauli matrices can be written
The fact that the Pauli matrices, along with the identity matrix I , form an orthogonal basis for the Hilbert space of all 2 × 2 complex matrices M 2 , 2 ( C ) {\displaystyle {\mathcal {M}}_{2,2}(\mathbb {C} )} over C {\displaystyle \mathbb {C} } , means that we can express any 2 × 2 complex matrix M as M = c I + ∑ k a k σ k {\displaystyle M=c\,I+\sum _{k}a_{k}\,\sigma ^{k}} where c is a complex number, and a is a 3-component, complex vector. It is straightforward to show, using the properties listed above, that tr ( σ j σ k ) = 2 δ j k {\displaystyle \operatorname {tr} \left(\sigma ^{j}\,\sigma ^{k}\right)=2\,\delta _{jk}} where " tr " denotes the trace , and hence that c = 1 2 tr M , a k = 1 2 tr σ k M . ∴ 2 M = I tr M + ∑ k σ k tr σ k M , {\displaystyle {\begin{aligned}c&={}{\tfrac {1}{2}}\,\operatorname {tr} \,M\,,{\begin{aligned}&&a_{k}&={\tfrac {1}{2}}\,\operatorname {tr} \,\sigma ^{k}\,M.\end{aligned}}\\[3pt]\therefore ~~2\,M&=I\,\operatorname {tr} \,M+\sum _{k}\sigma ^{k}\,\operatorname {tr} \,\sigma ^{k}M~,\end{aligned}}} which can be rewritten in terms of matrix indices as 2 M α β = δ α β M γ γ + ∑ k σ α β k σ γ δ k M δ γ , {\displaystyle 2\,M_{\alpha \beta }=\delta _{\alpha \beta }\,M_{\gamma \gamma }+\sum _{k}\sigma _{\alpha \beta }^{k}\,\sigma _{\gamma \delta }^{k}\,M_{\delta \gamma }~,} where summation over the repeated indices is implied γ and δ . Since this is true for any choice of the matrix M , the completeness relation follows as stated above. Q.E.D.
As noted above, it is common to denote the 2 × 2 unit matrix by σ 0 , so σ 0 αβ = δ αβ . The completeness relation can alternatively be expressed as ∑ k = 0 3 σ α β k σ γ δ k = 2 δ α δ δ β γ . {\displaystyle \sum _{k=0}^{3}\sigma _{\alpha \beta }^{k}\,\sigma _{\gamma \delta }^{k}=2\,\delta _{\alpha \delta }\,\delta _{\beta \gamma }~.}
The fact that any Hermitian complex 2 × 2 matrices can be expressed in terms of the identity matrix and the Pauli matrices also leads to the Bloch sphere representation of 2 × 2 mixed states ’ density matrix, ( positive semidefinite 2 × 2 matrices with unit trace. This can be seen by first expressing an arbitrary Hermitian matrix as a real linear combination of { σ 0 , σ 1 , σ 2 , σ 3 } as above, and then imposing the positive-semidefinite and trace 1 conditions.
For a pure state, in polar coordinates, a → = ( sin θ cos ϕ sin θ sin ϕ cos θ ) , {\displaystyle {\vec {a}}={\begin{pmatrix}\sin \theta \cos \phi &\sin \theta \sin \phi &\cos \theta \end{pmatrix}},} the idempotent density matrix 1 2 ( 1 + a → ⋅ σ → ) = ( cos 2 ( θ 2 ) e − i ϕ sin ( θ 2 ) cos ( θ 2 ) e + i ϕ sin ( θ 2 ) cos ( θ 2 ) sin 2 ( θ 2 ) ) {\displaystyle {\tfrac {1}{2}}\left(\mathbf {1} +{\vec {a}}\cdot {\vec {\sigma }}\right)={\begin{pmatrix}\cos ^{2}\left({\frac {\,\theta \,}{2}}\right)&e^{-i\,\phi }\sin \left({\frac {\,\theta \,}{2}}\right)\cos \left({\frac {\,\theta \,}{2}}\right)\\e^{+i\,\phi }\sin \left({\frac {\,\theta \,}{2}}\right)\cos \left({\frac {\,\theta \,}{2}}\right)&\sin ^{2}\left({\frac {\,\theta \,}{2}}\right)\end{pmatrix}}}
acts on the state eigenvector ( cos ( θ 2 ) e + i ϕ sin ( θ 2 ) ) {\displaystyle {\begin{pmatrix}\cos \left({\frac {\,\theta \,}{2}}\right)&e^{+i\phi }\,\sin \left({\frac {\,\theta \,}{2}}\right)\end{pmatrix}}} with eigenvalue +1, hence it acts like a projection operator .
Let P jk be the transposition (also known as a permutation) between two spins σ j and σ k living in the tensor product space C 2 ⊗ C 2 {\displaystyle \mathbb {C} ^{2}\otimes \mathbb {C} ^{2}} ,
This operator can also be written more explicitly as Dirac's spin exchange operator ,
Its eigenvalues are therefore [ d ] 1 or −1. It may thus be utilized as an interaction term in a Hamiltonian, splitting the energy eigenvalues of its symmetric versus antisymmetric eigenstates.
The group SU(2) is the Lie group of unitary 2 × 2 matrices with unit determinant; its Lie algebra is the set of all 2 × 2 anti-Hermitian matrices with trace 0. Direct calculation, as above, shows that the Lie algebra s u 2 {\displaystyle {\mathfrak {su}}_{2}} is the three-dimensional real algebra spanned by the set { iσ k } . In compact notation,
As a result, each iσ j can be seen as an infinitesimal generator of SU(2). The elements of SU(2) are exponentials of linear combinations of these three generators, and multiply as indicated above in discussing the Pauli vector. Although this suffices to generate SU(2), it is not a proper representation of su(2) , as the Pauli eigenvalues are scaled unconventionally. The conventional normalization is λ = 1 / 2 , so that
As SU(2) is a compact group, its Cartan decomposition is trivial.
The Lie algebra s u ( 2 ) {\displaystyle {\mathfrak {su}}(2)} is isomorphic to the Lie algebra s o ( 3 ) {\displaystyle {\mathfrak {so}}(3)} , which corresponds to the Lie group SO(3) , the group of rotations in three-dimensional space. In other words, one can say that the iσ j are a realization (and, in fact, the lowest-dimensional realization) of infinitesimal rotations in three-dimensional space. However, even though s u ( 2 ) {\displaystyle {\mathfrak {su}}(2)} and s o ( 3 ) {\displaystyle {\mathfrak {so}}(3)} are isomorphic as Lie algebras, SU(2) and SO(3) are not isomorphic as Lie groups. SU(2) is actually a double cover of SO(3) , meaning that there is a two-to-one group homomorphism from SU(2) to SO(3) , see relationship between SO(3) and SU(2) .
The real linear span of { I , iσ 1 , iσ 2 , iσ 3 } is isomorphic to the real algebra of quaternions , H {\displaystyle \mathbb {H} } , represented by the span of the basis vectors { 1 , i , j , k } . {\displaystyle \left\{\;\mathbf {1} ,\,\mathbf {i} ,\,\mathbf {j} ,\,\mathbf {k} \;\right\}.} The isomorphism from H {\displaystyle \mathbb {H} } to this set is given by the following map (notice the reversed signs for the Pauli matrices): 1 ↦ I , i ↦ − σ 2 σ 3 = − i σ 1 , j ↦ − σ 3 σ 1 = − i σ 2 , k ↦ − σ 1 σ 2 = − i σ 3 . {\displaystyle \mathbf {1} \mapsto I,\quad \mathbf {i} \mapsto -\sigma _{2}\sigma _{3}=-i\,\sigma _{1},\quad \mathbf {j} \mapsto -\sigma _{3}\sigma _{1}=-i\,\sigma _{2},\quad \mathbf {k} \mapsto -\sigma _{1}\sigma _{2}=-i\,\sigma _{3}.}
Alternatively, the isomorphism can be achieved by a map using the Pauli matrices in reversed order, [ 5 ]
As the set of versors U ⊂ H {\displaystyle \mathbb {H} } forms a group isomorphic to SU(2) , U gives yet another way of describing SU(2) . The two-to-one homomorphism from SU(2) to SO(3) may be given in terms of the Pauli matrices in this formulation.
In classical mechanics , Pauli matrices are useful in the context of the Cayley-Klein parameters. [ 6 ] The matrix P corresponding to the position x → {\displaystyle {\vec {x}}} of a point in space is defined in terms of the above Pauli vector matrix,
Consequently, the transformation matrix Q θ for rotations about the x -axis through an angle θ may be written in terms of Pauli matrices and the unit matrix as [ 6 ]
Similar expressions follow for general Pauli vector rotations as detailed above.
In quantum mechanics , each Pauli matrix is related to an angular momentum operator that corresponds to an observable describing the spin of a spin 1 ⁄ 2 particle, in each of the three spatial directions. As an immediate consequence of the Cartan decomposition mentioned above, iσ j are the generators of a projective representation ( spin representation ) of the rotation group SO(3) acting on non-relativistic particles with spin 1 ⁄ 2 . The states of the particles are represented as two-component spinors . In the same way, the Pauli matrices are related to the isospin operator .
An interesting property of spin 1 ⁄ 2 particles is that they must be rotated by an angle of 4 π in order to return to their original configuration. This is due to the two-to-one correspondence between SU(2) and SO(3) mentioned above, and the fact that, although one visualizes spin up/down as the north–south pole on the 2-sphere S 2 , they are actually represented by orthogonal vectors in the two-dimensional complex Hilbert space .
For a spin 1 ⁄ 2 particle, the spin operator is given by J = ħ / 2 σ , the fundamental representation of SU(2) . By taking Kronecker products of this representation with itself repeatedly, one may construct all higher irreducible representations. That is, the resulting spin operators for higher spin systems in three spatial dimensions, for arbitrarily large j , can be calculated using this spin operator and ladder operators . They can be found in Rotation group SO(3) § A note on Lie algebras . The analog formula to the above generalization of Euler's formula for Pauli matrices, the group element in terms of spin matrices, is tractable, but less simple. [ 7 ]
Also useful in the quantum mechanics of multiparticle systems, the general Pauli group G n is defined to consist of all n -fold tensor products of Pauli matrices.
In relativistic quantum mechanics , the spinors in four dimensions are 4 × 1 (or 1 × 4) matrices. Hence the Pauli matrices or the Sigma matrices operating on these spinors have to be 4 × 4 matrices. They are defined in terms of 2 × 2 Pauli matrices as
It follows from this definition that the Σ k {\displaystyle \ {\mathsf {\Sigma }}_{k}\ } matrices have the same algebraic properties as the σ k matrices.
However, relativistic angular momentum is not a three-vector, but a second order four-tensor . Hence Σ k {\displaystyle \ {\mathsf {\Sigma }}_{k}\ } needs to be replaced by Σ μν , the generator of Lorentz transformations on spinors . By the antisymmetry of angular momentum, the Σ μν are also antisymmetric. Hence there are only six independent matrices.
The first three are the Σ k ℓ ≡ ϵ j k ℓ Σ j . {\displaystyle \ \Sigma _{k\ell }\equiv \epsilon _{jk\ell }{\mathsf {\Sigma }}_{j}.} The remaining three, − i Σ 0 k ≡ α k , {\displaystyle \ -i\ \Sigma _{0k}\equiv {\mathsf {\alpha }}_{k}\ ,} where the Dirac α k matrices are defined as
The relativistic spin matrices Σ μν are written in compact form in terms of commutator of gamma matrices as
In quantum information , single- qubit quantum gates are 2 × 2 unitary matrices . The Pauli matrices are some of the most important single-qubit operations. In that context, the Cartan decomposition given above is called the "Z–Y decomposition of a single-qubit gate". Choosing a different Cartan pair gives a similar "X–Y decomposition of a single-qubit gate ". | https://en.wikipedia.org/wiki/Pauli_matrices |
Pauline Rudd FRSM is a British biochemist and Professor at the Microbiome Institute, University College Cork . [ 2 ] She is a founder of Wessex Biochemicals, a Fellow of the Royal Society of Medicine and was awarded the James Gregory Medal in 2010. [ 3 ]
Rudd grew up in Bournemouth and attended Bournemouth School for Girls . As a child she wanted to be a physicist. Her uncle was a physicist, and Rudd joined the British Junior Astronomical Association. She was the only girl in a group of 48 boys, and said she was never allowed to look down the telescope. [ 4 ] The male dominated environment of physics made Rudd consider a career in chemistry instead. [ 4 ] When she was fourteen, she started to use washing machines and liquidisers to create rare sugars and sugar phosphates. She sold these chemicals through and co-founded Wessex Biochemicals. [ 4 ] [ 5 ] Rudd was an undergraduate chemistry student at Westfield College , then part of the University of London . [ 4 ] After earning her degree, she joined Wessex Biochemicals which employed thirty people before being acquired by Sigma-Aldrich . [ when? ] [ 4 ] She completed her PhD in 1995 which was awarded by the Open University . [ 1 ]
Rudd joined the glycobiology institute at the University of Oxford in 1985. At the time, it was difficult for women scientists to secure jobs as academic personnel , and Rudd joined as a glass washer. She learned how to work with glycoproteins and large sugars and eventually completed a doctorate on glycoforms at the Open University in 1995. [ 1 ] Rudd moved to the Scripps Research institute, and held a visiting position at the Ben-Gurion University of the Negev . She commercialised her work on liquid chromatography–mass spectrometry (LCMS) with Waters Corporation . [ citation needed ]
Rudd has worked to miniaturise technologies for glycol analysis. For example, she has used genome-wide association studies (GWAS) to link individual genomes to their serum glycome and individual proteins . [ 6 ] She moved to University College Dublin in 2006, where was made head of the Dublin - Oxford glycobiology laboratory research group. [ 7 ] [ 8 ] She opened the National Institute for Bioprocessing Research and Training (NIBRT), where she developed new processes for protein glycosylation in an attempt to characterise recombinant protein drugs. [ 9 ]
Rudd serves as an associate of the Anglican Church at the Community of St Mary the Virgin in Wantage , Oxfordshire . [ 14 ] She took a fifteen-year career break to raise her four children. [ 4 ] | https://en.wikipedia.org/wiki/Pauline_Rudd |
Pauling's principle of electroneutrality states that each atom in a stable substance has a charge close to zero. It was formulated by Linus Pauling in 1948 and later revised. [ 1 ] The principle has been used to predict which of a set of molecular resonance structures would be the most significant, to explain the stability of inorganic complexes and to explain the existence of π-bonding in compounds and polyatomic anions containing silicon, phosphorus or sulfur bonded to oxygen; it is still invoked in the context of coordination complexes. [ 2 ] [ 3 ] However, modern computational techniques indicate many stable compounds have a greater charge distribution than the principle predicts (they contain bonds with greater ionic character). [ 4 ]
Pauling first stated his "postulate of the essential electroneutrality of atoms" in his 1948 Liversidge lecture (in a broad-ranging paper that also included his ideas on the calculation of oxidation states in molecules):
A slightly revised version was published in 1970:
Pauling said in his Liversidge lecture in 1948 that he had been led to the principle by a consideration of ionic bonding. In the gas phase, molecular caesium fluoride has a polar covalent bond. The large difference in electronegativity gives a calculated covalent character of 9%. In the crystal (CsF has the NaCl structure with both ions being 6-coordinate) if each bond has 9% covalent character the total covalency of Cs and F would be 54%. This would be represented by one bond of around 50% covalent character resonating between the six positions and the overall effect would be to reduce the charge on Cs to about + 0.5 and fluoride to -0.5. It seemed reasonable to him that since CsF is the most ionic of ionic compounds, most, if not all substances will have atoms with even smaller charges. [ 5 ]
There are two possible structures for hydrogen cyanide, HCN and CNH, differing only as to the position of the hydrogen atom. The structure with hydrogen attached to nitrogen, CNH, leads to formal charges of -1 on carbon and +1 on nitrogen, which would be partially compensated for by the electronegativity of nitrogen and Pauling calculated the net charges on H, N and C as -0.79, +0.75 and +0.04 respectively. In contrast the structure with hydrogen bonded to carbon, HCN, has formal charges on carbon and nitrogen of 0, and the effect of the electronegativity of the nitrogen would make the charges on H, C and N +0.04, +0.17 and -0.21. [ 6 ] The triple bonded structure is therefore favored.
As an example the cyanate ion (OCN) − can be assigned three resonance structures:-
The rightmost structure in the diagram has a charge of -2 on the nitrogen atom. Applying the principle of electroneutrality this can be identified as only a minor contributor. Additionally as the most electronegative atom should carry the negative charge, then the triple bonded structure on the left is predicted to be the major contributor. [ 7 ]
The hexammine cobalt(III) complex [Co(NH 3 ) 6 ] 3+ would have all of charge on the central Co atom if the bonding to the ammonia molecules were electrostatic. On the other hand, a covalent linkage would lead to a charge of -3 on the metal and +1 on each of the nitrogen atoms in the ammonia molecules. Using the electroneutrality principle the assumption is made that the Co-N bond will have 50% ionic character thus resulting in a zero charge on the cobalt atom. Due to the difference in electronegativity the N-H bond would 17% ionic character and therefore a charge of 0.166 on each of the 18 hydrogen atoms. This essentially spreads the 3+ charge evenly onto the "surface" of the complex ion. [ 1 ]
Pauling invoked the principle of electroneutrality in a 1952 paper to suggest that pi bonding is present, for example, in molecules with 4 Si-O bonds. [ 8 ] The oxygen atoms in such molecules would form polar covalent bonds with the silicon atom because their electronegativity (electron withdrawing power) was higher than that of silicon. Pauling calculated the charge build up on the silicon atom due to the difference in electronegativity to be +2. The electroneutrality principle led Pauling to the conclusion that charge transfer from O to Si must occur using d orbitals forming a π-bond and he calculated that this π-bonding accounted for the shortening of the Si-O bond.
The "adjacent charge rule" was another principle of Pauling's for determining whether a resonance structure would make a significant contribution. [ 1 ] First published in 1932, it stated that structures that placed charges of the same sign on adjacent atoms would be unfavorable. [ 9 ] [ 10 ]
CONCLUSION;
If we have a stable substance than the all atoms present in it must have charge tends to equal to zero...
thankyou' | https://en.wikipedia.org/wiki/Pauling's_principle_of_electroneutrality |
Pauling's rules are five rules published by Linus Pauling in 1929 for predicting and rationalizing the crystal structures of ionic compounds . [ 1 ] [ 2 ]
For typical ionic solids, the cations are smaller than the anions , and each cation is surrounded by coordinated anions which form a polyhedron . The sum of the ionic radii determines the cation-anion distance, while the cation-anion radius ratio r + / r − {\displaystyle r_{+}/r_{-}} (or r c / r a {\displaystyle r_{c}/r_{a}} ) determines the coordination number (C.N.) of the cation, as well as the shape of the coordinated polyhedron of anions. [ 2 ] : 524 [ 3 ]
For the coordination numbers and corresponding polyhedra in the table below, Pauling mathematically derived the minimum radius ratio for which the cation is in contact with the given number of anions (considering the ions as rigid spheres). If the cation is smaller, it will not be in contact with the anions which results in instability leading to a lower coordination number.
The three diagrams at right correspond to octahedral coordination with a coordination number of six: four anions in the plane of the diagrams, and two (not shown) above and below this plane. The central diagram shows the minimal radius ratio. The cation and any two anions form a right triangle , with 2 r − = 2 ( r − + r + ) {\displaystyle 2r_{-}={\sqrt {2}}(r_{-}+r_{+})} , or 2 r − = r − + r + {\displaystyle {\sqrt {2}}r_{-}=r_{-}+r_{+}} . Then r + = ( 2 − 1 ) r − = 0.414 r − {\displaystyle r_{+}=({\sqrt {2}}-1)r_{-}=0.414r_{-}} . Similar geometrical proofs yield the minimum radius ratios for the highly symmetrical cases C.N. = 3, 4 and 8. [ 4 ]
For C.N. = 6 and a radius ratio greater than the minimum, the crystal is more stable since the cation is still in contact with six anions, but the anions are further from each other so that their mutual repulsion is reduced. An octahedron may then form with a radius ratio greater than or equal to 0.414, but as the ratio rises above 0.732, a cubic geometry becomes more stable. This explains why Na + in NaCl with a radius ratio of 0.55 has octahedral coordination, whereas Cs + in CsCl with a radius ratio of 0.93 has cubic coordination. [ 5 ]
If the radius ratio is less than the minimum, two anions will tend to depart and the remaining four will rearrange into a tetrahedral geometry where they are all in contact with the cation.
The radius ratio rules are a first approximation which have some success in predicting coordination numbers, but many exceptions do exist. [ 3 ] In a set of over 5000 oxides , only 66% of coordination environments agree with Pauling's first rule. Oxides formed with alkali or alkali-earth metal cations that contain multiple cation coordinations are common deviations from this rule. [ 6 ]
For a given cation, Pauling defined [ 2 ] the electrostatic bond strength to each coordinated anion as s = z ν {\displaystyle s={\frac {z}{\nu }}} , where z is the cation charge and ν is the cation coordination number. A stable ionic structure is arranged to preserve local electroneutrality , so that the sum of the strengths of the electrostatic bonds to an anion equals the charge on that anion.
where ξ {\displaystyle \xi } is the anion charge and the summation is over the adjacent cations. For simple solids, the s i {\displaystyle s_{i}} are equal for all cations coordinated to a given anion, so that the anion coordination number is the anion charge divided by each electrostatic bond strength. Some examples are given in the table.
Pauling showed that this rule is useful in limiting the possible structures to consider for more complex crystals such as the aluminosilicate mineral orthoclase , KAlSi 3 O 8 , with three different cations. [ 2 ] However, from data analysis of oxides from the Inorganic Crystal Structure Database (ICSD), the result showed that only 20% of all oxygen atoms matched with the prediction from second rule (using a cutoff of 0.01). [ 6 ]
The sharing of edges and particularly faces by two anion polyhedra decreases the stability of an ionic structure. Sharing of corners does not decrease stability as much, so (for example) octahedra may share corners with one another. [ 2 ] : 559
The decrease in stability is due to the fact that sharing edges and faces places cations in closer proximity to each other, so that cation-cation electrostatic repulsion is increased. The effect is largest for cations with high charge and low C.N. (especially when r+/r- approaches the lower limit of the polyhedral stability). Generally, smaller elements fulfill the rule better. [ 6 ]
As one example, Pauling considered the three mineral forms of titanium dioxide , each with a coordination number of 6 for the Ti 4+ cations. The most stable (and most abundant) form is rutile , in which the coordination octahedra are arranged so that each one shares only two edges (and no faces) with adjoining octahedra. The other two, less stable, forms are brookite and anatase , in which each octahedron shares three and four edges respectively with adjoining octahedra. [ 2 ] : 559
In a crystal containing different cations, those of high valency and small coordination number tend not to share polyhedron elements with one another. [ 2 ] : 561 This rule tends to increase the distance between highly charged cations, so as to reduce the electrostatic repulsion between them.
One of Pauling's examples is olivine , M 2 SiO 4 , where M is a mixture of Mg 2+ at some sites and Fe 2+ at others. The structure contains distinct SiO 4 tetrahedra which do not share any oxygens (at corners, edges or faces) with each other. The lower-valence Mg 2+ and Fe 2+ cations are surrounded by polyhedra which do share oxygens.
The number of essentially different kinds of constituents in a crystal tends to be small. [ 2 ] The repeating units will tend to be identical because each atom in the structure is most stable in a specific environment. There may be two or three types of polyhedra, such as tetrahedra or octahedra, but there will not be many different types.
In a study of 5000 oxides, only 13% of them satisfy all of the last 4 rules, indicating limited universality of Pauling's rules. [ 6 ] | https://en.wikipedia.org/wiki/Pauling's_rules |
Paulo Eduardo Artaxo Netto is a Brazilian atmospheric physicist . [ 1 ]
Born in São Paulo, Brazil, Artaxo pursued his undergraduate and graduate studies at the University of São Paulo, where he obtained both his MSc and PhD in Physics. [ 2 ]
Artaxo has held postdoctoral positions at several institutions, including the University of Antwerp in Belgium , Lund University in Sweden , and the NASA Goddard Space Flight Center in the United States . [ 3 ]
At USP, Artaxo leads a research group that has revealed how aerosol particles, emitted by both natural processes and human activities, are critical to cloud formation and, consequently, to the regional and global climate. His research on the Amazon has highlighted the region's vulnerability to climate change, especially regarding the potential feedback loops that could exacerbate global warming. [ 4 ]
He was awarded the TWAS Prize in Earth Sciences in 2007 and has been recognized as one of the most influential researchers in his field by Clarivate Analytics multiple times. [ 5 ] | https://en.wikipedia.org/wiki/Paulo_Artaxo |
The Pauly reaction is a chemical test used for detecting the presence of tyrosine or histidine in proteins. It is named after German chemist Hermann Pauly , who first described the reaction. [ 1 ] When proteins containing either tyrosine or histidine are reacted with diazotized sulfanilic acid under alkaline conditions, a red color is formed by a coupling reaction . [ 2 ] [ 3 ] [ 4 ] [ 5 ]
This article about analytical chemistry is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Pauly_reaction |
PauseAI is a global political movement founded in the Netherlands with the stated aim of achieving global coordination to stop the development of artificial intelligence systems more powerful than GPT-4 , at least until it is known how to build them safely, and keep them under democratic control. [ 1 ] The movement was established in Utrecht in May 2023 by software entrepreneur Joep Meindertsma. [ 2 ] [ 3 ] [ 4 ]
PauseAI's stated goal is to “implement a pause on the training of AI systems more powerful than GPT-4”. Their website lists some proposed steps to achieve this goal: [ 1 ]
During the late 2010s and early 2020s, a rapid improvement in the capabilities of artificial intelligence models known as the AI boom was underway, which included the release of large language model GPT-3 , its more powerful successor GPT-4 , and image generation models Midjourney and DALL-E . This led to an increased concern about the risks of advanced AI, causing the Future of Life Institute to release an open letter calling for "all AI labs to immediately pause for at least 6 months the training of AI systems more powerful than GPT-4". The letter was signed by thousands of AI researchers and industry CEOs such as Yoshua Bengio , Stuart Russell , and Elon Musk . [ 5 ] [ 6 ] [ 7 ]
Founder Joep Meindertsma first became worried about the existential risk from artificial general intelligence after reading philosopher Nick Bostrom 's 2014 book Superintelligence: Paths, Dangers, Strategies . He founded PauseAI in May 2023, putting his job as the CEO of a software firm on hold. Meindertsma claimed the rate of progress in AI alignment research is lagging behind the progress in AI capabilities, and said "there is a chance that we are facing extinction in a short frame of time". As such, he felt an urge to organise people to act. [ 3 ] [ 8 ] [ 4 ]
PauseAI's first public action was to protest in front of Microsoft's Brussels lobbying office in May 2023 during an event on artificial intelligence. [ 4 ] In November of the same year, they protested outside the inaugural AI Safety Summit at Bletchley Park . [ 9 ] The Bletchley Declaration that was signed at the summit, which acknowledged the potential for catastrophic risks stemming from AI, was perceived by Meindertsma to be a small first step. But, he argued "binding international treaties" are needed. He mentioned the Montreal Protocol and treaties banning blinding laser weapons as examples of previous successful global agreements. [ 3 ]
In February 2024, members of PauseAI gathered outside OpenAI's headquarters in San Francisco , in part due to OpenAI changing its usage policy that prohibited the use of its models for military purposes. [ 10 ]
On 13 May 2024, protests were held across thirteen different countries before the AI Seoul Summit , including the United States, the United Kingdom, Brazil, Germany, Australia, and Norway. Meindertserma said that those attending the summit "need to realize that they are the only ones who have the power to stop this race". Protesters in San Francisco held signs reading "When in doubt, pause", and "Quit your job at OpenAI. Trust your conscience". [ 11 ] [ 12 ] [ 3 ] [ 13 ] Jan Leike , head of the "superalignment" team at OpenAI, resigned 2 days later due to his belief that "safety culture and processes [had] taken a backseat to shiny products". [ 14 ] | https://en.wikipedia.org/wiki/PauseAI |
Pause Giant AI Experiments: An Open Letter is the title of a letter published by the Future of Life Institute in March 2023. The letter calls "all AI labs to immediately pause for at least 6 months the training of AI systems more powerful than GPT-4 ", citing risks such as AI-generated propaganda, extreme automation of jobs, human obsolescence, and a society-wide loss of control. [ 1 ] It received more than 30,000 signatures, including academic AI researchers and industry CEOs such as Yoshua Bengio , Stuart Russell , Elon Musk , Steve Wozniak and Yuval Noah Harari . [ 1 ] [ 2 ] [ 3 ]
The publication occurred a week after the release of OpenAI 's large language model GPT-4 . It asserts that current large language models are "becoming human-competitive at general tasks", referencing a paper about early experiments of GPT-4, described as having "Sparks of AGI ". [ 4 ] AGI is described as posing numerous important risks, especially in a context of race-to-the-bottom dynamics in which some AI labs may be incentivized to overlook security to deploy products more quickly. [ 5 ]
It asks to refocus AI research on making powerful AI systems "more accurate, safe, interpretable, transparent, robust, aligned, trustworthy, and loyal". The letter also recommends more governmental regulation, independent audits before training AI systems, as well as "tracking highly capable AI systems and large pools of computational capability" and "robust public funding for technical AI safety research". [ 1 ] FLI suggests using the "amount of computation that goes into a training run" as a proxy to for how powerful an AI is, and thus as a threshold. [ 6 ]
The letter received widespread coverage, with support coming from a range of high-profile figures. As of July 2024, a pause has not been realized - instead, as FLI pointed out on the letter's one-year anniversary, AI companies have directed "vast investments in infrastructure to train ever-more giant AI systems". [ 7 ] However, it was credited with generating a "renewed urgency within governments to work out what to do about the rapid progress of AI", and reflecting the public's increasing concern about risks presented by AI. [ 8 ]
Eliezer Yudkowsky wrote that the letter "doesn't go far enough" and argued that it should ask for an indefinite pause. He fears that finding a solution to the alignment problem might take several decades and that any misaligned AI sufficiently intelligent might cause human extinction . [ 9 ]
Some IEEE members have expressed various reasons for signing the letter, such as that "There are too many ways these systems could be abused. They are being freely distributed, and there is no review or regulation in place to prevent harm." [ 10 ] One AI ethicist argued that the letter provides awareness to multiple issues such as voice cloning, but argued the letter was unactionable and unenforceable. [ 11 ]
The letter has been criticized for diverting attention from more immediate societal risks such as algorithmic biases . [ 12 ] Timnit Gebru and others argued that the letter was sensationalist and amplified "some futuristic, dystopian sci-fi scenario" instead of current problems with AI today. [ 11 ]
Former Microsoft's CEO Bill Gates chose not to sign the letter, stating that he does not think "asking one particular group to pause solves the challenges". [ 13 ] Sam Altman , CEO of OpenAI , commented that the letter was "missing most technical nuance about where we need the pause" and stated that "An earlier version of the letter claimed OpenAI is training GPT-5 right now. We are not and won't for some time." [ 14 ] Reid Hoffman argued the letter was " virtue signalling ", with no real impact. [ 15 ]
Listed below are some notable signatories of the letter. [ 1 ] | https://en.wikipedia.org/wiki/Pause_Giant_AI_Experiments:_An_Open_Letter |
The Pauson–Khand (PK) reaction is a chemical reaction , described as a [2+2+1] cycloaddition . In it, an alkyne , an alkene , and carbon monoxide combine into a α,β- cyclopentenone in the presence of a metal-carbonyl catalyst [ 1 ] [ 2 ] Ihsan Ullah Khand (1935–1980) discovered the reaction around 1970, while working as a postdoctoral associate with Peter Ludwig Pauson (1925–2013) at the University of Strathclyde in Glasgow. [ 3 ] [ 4 ] [ 5 ] Pauson and Khand's initial findings were intermolecular in nature, but the reaction has poor selectivity. Some modern applications instead apply the reaction for intramolecular ends. [ 6 ]
The traditional reaction requires a stoichiometric amounts of dicobalt octacarbonyl , stabilized by a carbon monoxide atmosphere . [ 7 ] Catalytic metal quantities, enhanced reactivity and yield, or stereoinduction are all possible with the right chiral auxiliaries , choice of transition metal (Ti, Mo, W, Fe, Co, Ni, Ru, Rh, Ir and Pd), and additives. [ 8 ] [ 9 ] [ 10 ] [ 11 ]
While the mechanism has not yet been fully elucidated, Magnus' 1985 explanation [ 12 ] is widely accepted for both mono- and dinuclear catalysts, and was corroborated by computational studies published by Nakamura and Yamanaka in 2001. [ 13 ] The reaction starts with dicobalt hexacarbonyl acetylene complex . Binding of an alkene gives a metallacyclopentene complex. CO then migratorily inserts into an M-C bond. Reductive elimination delivers the cyclopentenone . Typically, the dissociation of carbon monoxide from the organometallic complex is rate limiting. [ 8 ]
The reaction works with both terminal and internal alkynes, although internal alkynes tend to give lower yields. The order of reactivity for the alkene is
(strained cyclic) > (terminal) > (disubstituted) > (trisubstituted).
Tetrasubstituted alkenes and alkenes with strongly electron-withdrawing groups are unsuitable.
With unsymmetrical alkenes or alkynes, the reaction is rarely regioselective , although some patterns can be observed.
For mono-substituted alkenes, alkyne substituents typically direct: larger groups prefer the C 2 position, and electron-withdrawing groups prefer the C 3 position.
But the alkene itself struggles to discriminate between the C 4 and C 5 position, unless the C 2 position is sterically congested or the alkene has a chelating heteroatom.
The reaction's poor selectivity is ameliorated in intramolecular reactions . For this reason, the intramolecular Pauson-Khand is common in total synthesis, particularly the formation of 5,5- and 6,5-membered fused bicycles .
Generally, the reaction is highly syn -selective about the bridgehead hydrogen and substituents on the cyclopentane.
Appropriate chiral ligands or auxiliaries can make the reaction enantioselective (see § Amine N-oxides ). BINAP is commonly employed.
Typical Pauson-Khand conditions are elevated temperatures and pressures in aromatic hydrocarbon (benzene, toluene) or ethereal ( tetrahydrofuran , 1,2-dichloroethane) solvents. These harsh conditions may be attenuated with the addition of various additives.
Adsorbing the metallic complex onto silica or alumina can enhance the rate of decarbonylative ligand exchange as exhibited in the image below. [ 15 ] [ 16 ] This is because the donor posits itself on a solid surface (i.e. silica). [ clarification needed ] Additionally using a solid support restricts conformational movement ( rotamer effect ). [ 17 ] [ 18 ] [ 19 ]
Traditional catalytic aids such as phosphine ligands make the cobalt complex too stable, but bulky phosphite ligands are operable.
Lewis basic additives, such as n -BuSMe , are also believed to accelerate the decarbonylative ligand exchange process. However, an alternative view holds that the additives make olefin insertion irreversible instead. [ 20 ] Sulfur compounds are typically hard to handle and smelly, but n-dodecyl methyl sulfide [ 21 ] and tetramethylthiourea [ 22 ] do not suffer from those problems and can improve reaction performance.
The two most common amine N -oxides are N -methylmorpholine N -oxide (NMO) and trimethylamine N -oxide (TMANO) . It is believed that these additives remove carbon monoxide ligands via nucleophilic attack of the N -oxide onto the CO carbonyl, oxidizing the CO into CO 2 , and generating an unsaturated organometallic complex. [ 23 ] [ 24 ] This renders the first step of the mechanism irreversible, and allows for more mild conditions. Hydrates of the aforementioned amine N -oxides have similar effect. [ 25 ] [ 26 ] [ 27 ]
N -oxide additives can also improve enantio- and diastereoselectivity, although the mechanism thereby is not clear. [ 28 ] [ 29 ] [ 30 ]
(Co) 4 (CO) 12 and Co 3 (CO) 9 (μ 3 -CH) also catalyze the PK reaction [ 31 ] [ 32 ] although Takayama et al detail a reaction catalyzed by dicobalt octacarbonyl . [ 33 ]
One stabilization method is to generate the catalyst in situ . Chung reports that Co(acac) 2 can serve as a precatalyst , activated by sodium borohydride . [ 35 ]
catalyst requires a silver triflate co-catalyst to effect the Pauson–Khand reaction: [ 36 ]
Molybdenum hexacarbonyl is a carbon monoxide donor in PK-type reactions between allenes and alkynes with dimethyl sulfoxide in toluene. [ 37 ] Titanium, nickel, [ 38 ] and zirconium [ 39 ] complexes admit the reaction. Other metals can also be employed in these transformations. [ 40 ] [ 9 ]
In general allenes, support the Pauson–Khand reaction; regioselectivity is determined by the choice of metal catalyst. Density functional investigations show the variation arises from different transition state metal geometries. [ 41 ]
Heteroatoms are also acceptable: Mukai et al 's total synthesis of physostigmine applied the Pauson–Khand reaction to a carbodiimide . [ 42 ]
Cyclobutadiene also lends itself to a [2+2+1] cycloaddition, although this reactant is too active to store in bulk. Instead, ceric ammonium nitrate cyclobutadiene is generated in situ from decomplexation of stable cyclobutadiene iron tricarbonyl with (CAN).
An example of a newer version is the use of the chlorodicarbonylrhodium(I) dimer , [(CO) 2 RhCl] 2 , in the synthesis of (+)-phorbol by Phil Baran . In addition to using a rhodium catalyst, this synthesis features an intramolecular cyclization that results in the normal 5-membered α,β- cyclopentenone as well as 7-membered ring. [ 43 ]
The cyclopentenone motif can be prepared from aldehydes, carboxylic acids, and formates. These examples typically employ rhodium as the catalyst, as it is commonly used in decarbonylation reactions. The decarbonylation and PK reaction occur in the same reaction vessel. [ 44 ] [ 45 ]
For Khand and Pauson's perspective on the reaction:
For a modern perspective: | https://en.wikipedia.org/wiki/Pauson–Khand_reaction |
The Pauthenier equation states [ 1 ] [ 2 ] that the maximum charge accumulated by a particle modelled by a small sphere passing through an electric field is given by:
Q m a x = 4 π R 2 ϵ 0 p E {\displaystyle Q_{\mathrm {max} }=4\pi R^{2}\epsilon _{0}pE}
where ϵ 0 {\displaystyle \epsilon _{0}} is the permittivity of free space , R {\displaystyle R} is the radius of the sphere, E {\displaystyle E} is the electric field strength, and p {\displaystyle p} is a material dependent constant.
For conductors, p = 3 {\displaystyle p=3} .
For dielectrics : p = 3 ϵ r / ( ϵ r + 2 ) {\displaystyle p=3\epsilon _{r}/(\epsilon _{r}+2)} where ϵ r {\displaystyle \epsilon _{r}} is the relative permittivity .
Low charges on nanoparticles and microparticles are stable over more than 10 3 second time scales.
This particle physics –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Pauthenier_equation |
Pavel Jungwirth (born 20 May 1966 in Prague , Czech Republic ) is a Czech physical chemist. Since 2004, he has been the head of the Senior Research Group at the Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences . He has also been a professor in the Faculty of Mathematics and Physics at Charles University since 2000. [ 1 ] [ 2 ] He has also been a senior editor of the Journal of Physical Chemistry since 2009. [ 2 ] He is popularly known for studying the explosive reaction between alkali metals, such as sodium and potassium, and water; his research on this subject indicates that these reactions result from a Coulomb explosion . [ 3 ] He and his colleagues have also discovered a way to slow down this reaction, which they used to determine the source of a blue flash that is briefly produced during the reaction. [ 4 ]
Pavel Jungwirth is a coordinator of an international science competition Dream Chemistry Award . The historian of philosophy explores the scientific tradition and its roots in an international context, examining the influence of scientific elites in European history. The laureate also appeared on the Academy of Sciences podcast. [ 5 ]
This article about a Czech scientist is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Pavel_Jungwirth |
Pavement milling ( cold planing , asphalt milling , or profiling ) is the process of removing at least part of the surface of a paved area such as a road , bridge , or parking lot .
Milling removes anywhere from just enough thickness to level and smooth the surface to a full depth removal.
There are a number of different reasons for milling a paved area instead of simply repaving over the existing surface.
Recycling of the road surface is one of the main reasons for milling a road surface.
Milling is widely used for pavement recycling today, where the pavement is removed and ground up to be used as the aggregate in new pavement. [ 2 ] For asphalt surfaces the product of milling is reclaimed asphalt pavement (RAP), which can be recycled in the asphalt hot mix asphalt (pavement) by combining with new aggregate and asphalt cement (binder) or a recycling agent. [ 2 ] This reduces the impact that resurfacing has on the environment.
Milling can also remove distresses from the surface, providing a better driving experience and/or longer roadway life.
Some of the issues that milling can remove include: [ 3 ]
It can also be used to control or change the height of part or all of the road.
This can be done to control heights and clearances of other road structures such as: curb reveals, manhole and catch basin heights, shoulder and guardrail heights, and overhead clearances. [ 3 ] It can also be done to change the slope or camber of the road or for grade adjustments which can help with drainage. [ 8 ]
Specialty milling can be used to form rumble strips which are often used along highways. [ 9 ] Using milling instead of other methods, such as rolling them in, means that the rumble strips can be added at any time after the road surface has hardened. [ 9 ]
Another example is to modify the roto-milling head to create slots in concrete slabs for the dowel bar retrofit process. The typical process is to saw cut and jackhammer out the slots for the dowels. Following dowel placement, the slots are then typically backfilled with a non-shrink concrete mixture, and the pavement is diamond-ground to restore smoothness. This special milling process shortens the time to create slots from the traditional method which is labor-intensive. [ 10 ]
In the USA, the Asphalt Recycling and Reclaiming Association has defined five classes of cold planing that the Federal Highway Administration has recognized.
The classes are:
Asphalt milling is performed by construction equipment named cold planers or commonly referred to as milling machines. [ 11 ] These machines use a large rotating drum to remove and grind the road surface.
The drum consists of scrolls of tool holders. [ 3 ] The scrolls are positioned around the drum such that the ground pavement is moved toward the center and can be loaded onto the machine's conveyor belt . [ 3 ] The tool holders can wear out over time and can be broken if highway structures like manholes are encountered while milling. [ 3 ]
The tool holders on the drum hold carbide cutters. [ 3 ] The cutters can be removed and replaced as they wear out.
The amount of wear (and therefore the interval between replacement) varies with the type and consistency of the material being milled; intervals can range from a few hours to several days. [ 3 ]
The drum is enclosed in a housing/scrapper that is used to contain the milled material to be collected and deposited on the conveyor. [ 3 ] The spacing of the tool spirals around the drum affect the end surface of the road, with micro-milling having the tightest spacing. [ 3 ]
The majority of milling machines use an up-cut setup which means that the drum rotates in the direction opposite that of the drive wheel or tracks, (i.e. work surface feeds into the cut). [ 12 ] The speed of the rotating drum should be slower than the forward speed of the machine for a suitable finished surface. [ 3 ]
Modern machines generally use a front-loading conveyor system that have the advantage of picking up any material that falls off the conveyor as milling progresses. [ 2 ] Water is generally applied to the drum as it spins, because of the heat generated during the milling process.
Additionally, water helps control the dust created. [ 3 ] In order to control the depth, slopes, and profile of the final milled surface many millers now have automatic depth control using lasers , string-lines, or other methods to maintain milled surfaces to ±5 mm (0.20 in) of the target height. [ 8 ]
Micro milling is also known as carbide grinding.
It is a lower cost alternative to diamond grinding of pavement . [ 3 ] Micro milling uses a specialty drum with three to four times as many cutting teeth than a standard milling drum. [ 13 ] Micro milling can be used either as the final surface [ 14 ] or as a treatment before applying a thin overlay. [ 13 ] Micro milling can be used to remove many of the same distresses that standard milling can remove, although usually to a shallower depth. [ 14 ] A micro milled surface has a uniform finish with reduced road noise compared to standard milling. [ 3 ]
Media related to Cold milling machines at Wikimedia Commons | https://en.wikipedia.org/wiki/Pavement_milling |
A paver ( road paver finisher , asphalt finisher , road paving machine ) is a piece of construction equipment used to lay asphalt concrete or Portland cement concrete on roads, bridges, parking lots and other such places. It lays the material flat and provides minor compaction. This is typically followed by final compaction by a road roller .
The asphalt paver was developed by Harry Barber of the Barber Greene Co., that originally manufactured material handling systems. In 1929 the Chicago Testing Laboratory approached them to use their material loaders to construct asphalt roads. [ 1 ] This did not result in a partnership but Barber did develop a machine based on the concrete pavers of the day that mixed and placed the concrete in a single process. This setup did not prove as effective as desired and the processes were separated and the modern paver was on its way. [ 2 ] In 1933 the independent float screed was invented and when combined with the tamper bar provided for uniform material density and thickness. [ 2 ] Barber filed for a patent a "Machine for and process of laying roads" on 10 April 1936 and received patent U.S. patent 2,138,828 on 6 December 1938. [ 3 ] The main features of the paver developed by the Barber-Greene have been incorporated into most pavers since, although improvements have been made to control of the machine. [ 1 ]
The asphalt is added from a dump truck or a material transfer unit into the paver's hopper. The conveyor then carries the asphalt from the hopper to the auger. The auger places a stockpile of material in front of the screed . The screed takes the stockpile of material and spreads it over the width of the road and provides initial compaction. [ 4 ]
The paver should provide a smooth uniform surface behind the screed. In order to provide a smooth surface a free floating screed is used. It is towed at the end of a long arm which reduces the base topology effect on the final surface. The height of the screed is controlled by a number of factors including the attack angle of the screed, weight and vibration of the screed, the material head and the towing force. [ 4 ]
To conform to the elevation changes for the final grade of the road modern pavers use automatic screed controls, which generally control the screed's angle of attack from information gathered from a grade sensor. Additional controls are used to correct the slope, crown or superelevation of the finished pavement. [ 5 ]
In order to provide a smooth surface the paver should proceed at a constant speed and have a consistent stockpile of material in front of the screed. [ 6 ] Increase in material stockpile or paver speed will cause the screed to rise resulting in more asphalt being placed therefore a thicker mat of asphalt and an uneven final surface. Alternatively a decrease in material or a drop in speed will cause the screed to fall and the mat to be thinner. [ 4 ]
The need for constant speed and material supply is one of the reasons for using a material transfer unit in combination with a paver. A material transfer unit allows for constant material feed to the paver without contact, providing a better end surface. [ 5 ] When a dump truck is used to fill the hopper of the paver, it can make contact with the paver or cause it to change speed and affect the screed height.
Large freeways are often paved with Portland cement concrete and this is done using a slipform paver. Trucks dump loads of readymix concrete in heaps along in front of this machine and then the slipform paver spreads the concrete out and levels it off using a screed . | https://en.wikipedia.org/wiki/Paver_(vehicle) |
A pawtograph is a print of an animal's paw, regarded in some contexts as equivalent to a human signature . This term is used in particular for the practice of collecting pawtographs of celebrity animals. [ 1 ] [ 2 ] The hobby of collecting pawtographs is known as pawtography. [ citation needed ]
A pawtograph is made by one of two methods: | https://en.wikipedia.org/wiki/Pawtograph |
In computing and telecommunications , the payload is the part of transmitted data that is the actual intended message. Headers and metadata are sent only to enable payload delivery [ 1 ] [ 2 ] and are considered overhead .
In the context of a computer virus or worm , the payload is the portion of the malware which performs malicious action.
The term is borrowed from transportation , where payload refers to the part of the load that pays for transportation.
In computer networking , the data to be transmitted is the payload. It is almost always encapsulated in some type of frame format, composed of framing bits and a frame check sequence . [ 3 ] [ 4 ] Examples are Ethernet frames , Point-to-Point Protocol (PPP) frames, Fibre Channel frames , and V.42 modem frames .
In computer programming , the most common usage of the term is in the context of message protocols, to differentiate the protocol overhead from the actual data. For example, a JSON web service response might be:
The string Hello, world! is the payload of JSON message, while the rest is protocol overhead.
In computer security , the payload is the part of the private user text which could also contain malware such as worms or viruses which performs the malicious action; deleting data, sending spam or encrypting data. [ 5 ] In addition to the payload, such malware also typically has overhead code aimed at simply spreading itself, or avoiding detection. | https://en.wikipedia.org/wiki/Payload_(computing) |
In aerospace engineering , payload fraction is a common term used to characterize the efficiency of a particular design. The payload fraction is the quotient of the payload mass and the total vehicle mass at the start of its journey. It is a function of specific impulse , propellant mass fraction and the structural coefficient . In aircraft, loading less than full fuel for shorter trips is standard practice to reduce weight and fuel consumption. For this reason, the useful load fraction calculates a similar number, but it is based on the combined weight of the payload and fuel together in relation to the total weight.
Propeller-driven airliners had useful load fractions on the order of 25–35%. Modern jet airliners have considerably higher useful load fractions, on the order of 45–55%.
For orbital rockets the payload fraction is between 1% and 5%, while the useful load fraction is perhaps 90%.
For payload fractions and fuel fractions in aviation, see Fuel Fraction . | https://en.wikipedia.org/wiki/Payload_fraction |
Payment and settlement systems are used for financial transactions in India . Covered by the Payment and Settlement Systems Act of 2007 (PSS Act), legislated in December 2007, they are regulated by the Reserve Bank of India (RBI) and the Board for Regulation and Supervision of Payment and Settlement Systems . [ 1 ]
India has multiple payments and settlement systems, both gross and net settlement systems. For gross settlement India has a real-time gross settlement (RTGS) system called by the same name. Its net settlement systems include the Electronic Clearing Services (ECS Credit), Electronic Clearing Services (ECS Debit), credit cards , debit cards , the National Electronic Fund Transfer (NEFT) system, Immediate Payment Service , and Unified Payments Interface (UPI).
According to a survey by Celent, the use of e-payments instead of paper-based transactions increased considerably between 2004 and 2008 due to technological developments and increasing consumer awareness and comfort with internet and mobile transactions. [ 2 ]
The RBI is encouraging alternative methods of payments to make the financial payment and settlement process in India more secure and efficient. It has made RTGS compulsory for high-value transactions. It introduced NEFT and NECS (National Electronic Clearing Services) to encourage individuals and businesses to switch from paper to electronic transactions.
Growing availability of Internet connected services and the issuance of 1.3 billion biometric ID numbers in the region has made it easier for Indian customers to open bank accounts and use electronic payment systems. As of 2023 there are 907.4 million internet users in India (64% of the population), a 35% increase since 2018. [ 3 ] 63% payments still being made in cash. E-payments have been heavily promoted in India showing consumers the various ways they can make these payments Including ATMs , the Internet, mobile phones and drop boxes.
Due to RBI efforts and the Board for Regulation and Supervision of Payment and Settlement Systems (BPSS), now over 75% of all transaction volume is electronic, including both large-value and retail payments. Out of this 75%, 98% come from the RTGS (large-value payments) whereas a meager 2% come from retail payments. This means consumers have not yet accepted this as a regular means of paying their bills and still prefer conventional methods. Retail payments if made via electronic modes are done by ECS (debit and credit), EFT and card payments. [ 2 ] The Reserve Bank on Monday asked banks to put in place additional arrangements for export and import transactions in Indian rupees in view of increasing interest of the global trading community in the domestic currency. Before putting in place this mechanism, banks will require prior approval from the Foreign Exchange Department of the Reserve Bank of India (RBI) , the central bank said in a circular. [ 4 ]
The acronym ' RTGS ' stands for Real-time gross settlement. The Reserve Bank of India (India's Central Bank) maintains this payment network. Real-time gross settlement is a funds transfer mechanism where transfer of money takes place from one bank to another on a 'real time' and on 'gross' basis. This is the fastest possible money transfer system through the banking channel. Settlement in 'real time' means payment transaction is not subjected to any waiting period. The transactions are settled as soon as they are processed. 'Gross settlement' means the transaction is settled on one to one basis without bunching with any other transaction. Considering that money transfer takes place in the books of the Reserve Bank of India, the payment is regarded as final and irrevocable.
Fees for RTGS vary from bank to bank. RBI has prescribed upper limit for the fees that can be charged by all banks both for NEFT and RTGS. Both the remitting and receiving parties must have core banking in place to engage into RTGS transactions. Core Banking enabled banks and branches are assigned an Indian Financial System Code (IFSC) for RTGS and NEFT purposes. This is an eleven digit alphanumeric code and unique to each bank branch. The first four letters indicate the identity of the bank and remaining seven numerals indicate a single branch. This code is provided on the cheque books, which is required for transactions along with recipient's account number.
RTGS is a large value funds transfer system (with a minimum transaction value of ₹ 200,000 (US$2,400)) where financial intermediaries can settle interbank transfers for their own account as well as for their customers. The system achieves final settlement of interbank funds transfers on a continuous, transaction-by-transaction basis throughout the processing day. Customers can access the RTGS facility between 09:00 to 16:30 (Interbank transactions up to 18:30) on weekdays and 09:00 to 14:00 (Interbank transactions up to 15:00) on Saturdays. However, the timings may vary depending on the bank branch. Time-varying charges were introduced by the RBI effective from 1 October 2011. The primary purpose of RTGS is to facilitate transactions that require immediate completion.
Banks could use balances maintained under the cash reserve ratio (CRR) and the intra-day liquidity (IDL) to be supplied by the central bank, for meeting any eventuality arising out of the real time gross settlement (RTGS). The RBI fixed the IDL limit for banks to three times their net owned fund (NOF).
The IDL will be charged at ₹ 25 per transaction entered into by the bank on the RTGS platform. The marketable securities and treasury bills will have to be placed as collateral with a margin of five per cent. However, the apex bank will also impose severe penalties if the IDL is not paid back at the end of the day.
Since 26 August 2019, the RTGS service window for customers' transactions is available from 07:00 to 18:00 from Monday to Saturday (except the second and fourth Saturday of each month). No transactions are settled on Sundays and bank holidays . [ 5 ] The service is scheduled to become available 24 hours a day starting in December 2020. [ 6 ]
The RBI announced on 11 June 2019 that 'all charges for payments via RTGS and National Electronic Funds Transfer (NEFT) collected from banks would be waived from 1 July 2019, and asked banks to pass on the benefits to customers.' [ 7 ]
Inward transactions: No charge to be levied.
Outward transactions:
No time varying charges are applicable for RTGS transactions settled up to 1300 hrs.
To push digital transactions RBI has removed charges for payments via NEFT and RTGS and asked banks to pass on the benefits to customers. This means that payments via NEFT and RTGS would become either free or charges would be drastically reduced. [ 9 ] [ 10 ]
24x7 Availability of Real Time Gross Settlement (RTGS) System
In a major development, Reserve Bank of India (RBI) Governor Shaktikanta Das has confirmed that RTGS facility is now operational 24×7. [ 11 ]
Started in November 2005, [ 1 ] the National Electronic Fund Transfer (NEFT) system is a nationwide system that facilitates individuals, firms and corporates to electronically transfer funds from any bank branch to any individual, firm or corporate having an account with any other bank branch in the country. It is done via electronic messages. Even though it is not on real time basis like RTGS (Real Time Gross Settlement), half hourly batches are run in order to speed up the transactions. [ 12 ] [ 13 ]
For being part of the NEFT funds transfer network, a bank branch has to be NEFT-enabled. NEFT has gained popularity due to it saving on time and the ease with which the transactions can be concluded. As at 31 January 2011, 74,680 branches or offices of 101 banks in the country (out of around 82,400 bank branches) were NEFT-enabled. Steps are being taken to further widen the coverage both in terms of banks and branches offices. As on 30 December 2017 total number of NEFT enabled branches was increased to 139682 of 188 banks. [ 14 ]
Indo-Nepal Remittance Facility is a cross-border remittance scheme to transfer funds from India to Nepal , enabled under the NEFT Scheme. The scheme was launched to provide a safe and cost-efficient avenue to migrant Nepalese workers in India to remit money back to their families in Nepal. A remitter can transfer funds up to ₹ 50,000 (maximum permissible amount) from any of the NEFT-enabled branches in India. The beneficiary would receive funds in Nepalese Rupees.
Immediate Payment Service (IMPS) is an initiative of National Payments Corporation of India (NPCI) . It is a service through which money can be transferred immediately from one account to the other account, within the same bank or accounts across other banks. Upon registration, both the individuals are issued an MMID (Mobile Money Identifier) Code from their respective banks. This is a 7-digit numeric code. To initiate the transaction, the sender in his mobile banking application need to enter the registered mobile number of the receiver, MMID of the receiver and amount to be transferred. Upon successful transaction, the money gets credited in the account of the receiver instantly. This facility is available 24/7 and can be used through mobile banking application. Some banks have also started providing this service through internet banking profile of their customers. Though most banks offer this facility free of cost to encourage paperless payment system, ICICI bank and Axis bank charge for it as per their respective NEFT charges.
Money through this service can be transferred directly also by using the receiver's bank account number and IFS code . In such case, neither the receiver of the money need to be registered for mobile banking service of his bank, nor does he need MMID code. IMPS facility differs from NEFT and RTGS as there is no time limit to carry out the transaction. This facility can be availed 24/7 and on all public and bank holidays including RBI holidays.
Unified Payments Interface (UPI) is an instant real-time payment system developed by National Payments Corporation of India facilitating inter-bank transactions. The interface is regulated by the Reserve Bank of India and works by instantly transferring funds between two bank accounts on a mobile platform .
The Unified Payment Interface (UPI) can be thought of like an email ID for your money. It will be a unique identifier that your bank uses to transfer money and make payments using the IMPS (Immediate Payments Service). IMPS is faster than NEFT and lets you transfer money immediately and unlike NEFT, it works 24/7. This means that the online payments will become much easier without requiring a digital wallet or credit or debit card.
Bharat Bill Payment System (BBPS) is an integrated bill payment system in India offering interoperable and accessible bill payment service to customers through a network of agents, enabling multiple payment modes, and providing instant confirmation of payment. [ 15 ] This is still [ when? ] in the implementation stage. Guidelines for implementation of this system were issued on 28 November 2014.
The key difference between RTGS and NEFT is that while RTGS is on gross settlement basis, NEFT is on net settlement basis. Besides, RTGS facilitates real-time (" push ") transfer, while NEFT involves regular settlements and is operating 24/7/365 since December 2019. Customers can access the RTGS facility between 09:00 to 16:30 on weekdays and 09:00 to 13:30 on Saturday. RTGS is available 24/7/365 from 00:30 on 14 December 2020. Round the clock availability of RTGS will provide extended flexibility to businesses for effecting payments.
RTGS facility is available in over 113,000 branches across India, while NEFT is available in little over 115,000 branches of a 100 banks. | https://en.wikipedia.org/wiki/Payment_and_settlement_systems_in_India |
The Payne rearrangement is the isomerization, under basic conditions , of 2,3-epoxy alcohols to isomeric 1,2-epoxy alcohols with inversion of configuration. Aza- and thia-Payne rearrangements of aziridines and thiiraniums, respectively, are also known. [ 1 ]
Under basic, protic conditions, 2,3-epoxy alcohols undergo a rearrangement in which the alcohol oxygen opens the epoxide with inversion of configuration, forming an isomeric 1,2-epoxy alcohol. Overall, the Payne rearrangement represents a migration of the epoxide. Although the migration itself is fully reversible, nucleophilic opening under Curtin–Hammett conditions provides good yields of functionalized diols derived from a single epoxy alcohol isomer. [ 2 ] Intramolecular electrophilic trapping of the new alkoxide generated upon rearrangement may also be used to drive the reaction to completion. In some cases, the thermodynamic difference between epoxide isomers is large enough to obtain a single isomer in synthetically useful yield without relying on kinetic differences associated with trapping.
(1)
Strongly basic conditions are required to induce equilibration, which limits the synthetic utility of the transformation to substrates lacking base-labile functionality. Many epoxy alcohol equilibria are very finely balanced; [ 3 ] however, taking advantage of the trapping strategies described above may lead to high yields of single isomers.
The basic mechanism of the Payne rearrangement involves deprotonation of the free hydroxyl group, invertive nucleophilic attack on the proximal epoxide carbon, and re-protonation of the newly freed alkoxide. Each step of the process is reversible. [ 4 ]
(2)
Several observations suggest that this mechanistic picture is oversimplified. Epoxide migration either does not occur or is very sluggish under aprotic conditions [ 3 ] —it has been suggested that nucleophilic attack is slowed by the coordination of metal ions to the nucleophilic oxygen under aprotic conditions. In addition, when an external nucleophile is added to equilibrating epoxide isomers, the ratio of opened products does not reflect the ratio of epoxide isomers in solution or their relative thermodynamic stability. [ 5 ] In situ nucleophilic opening of equilibrating epoxides is an example of Curtin-Hammett conditions —because the epoxides are equilibrating rapidly relative to the rate of epoxide opening, it is the kinetic barriers of ring opening that control the observed product ratio. In the example below, the product of opening of the terminal epoxide is the major product, even though the terminal epoxide itself is less thermodynamically stable than the internal isomer.
(3)
Halo diols may be used as precursors to 2,3-epoxy alcohols prior to rearrangement. Issues of site selectivity may arise if the two hydroxyl groups flanking the halide are not equivalent. In general, the formation of internal, substituted epoxides is more rapid than the formation of terminal epoxides. [ 6 ] This idea can be used to predict the course of migrations of in situ -generated epoxides.
(4)
The Payne rearrangement occurs with inversion of stereochemistry at C-2. Substrates containing multiple adjacent hydroxyl groups may undergo "cascade" epoxide migrations with inversion at each site of nucleophilic attack. In one example, inversion of three contiguous stereocenters results after two epoxide migrations, opening of the epoxide by carboxylate, and hydrolysis of the resulting lactone. [ 7 ]
(5)
The position of equilibrium in both cyclic and acyclic systems may be predicted from the structures of the two equilibrating epoxides. In acyclic systems, these rules have been established: [ 8 ]
Pyranosides are the most heavily studied cyclic systems. Studies of epoxide migration in pyranosides and other cyclic epoxy alcohols have revealed three generalizations:
Conformationally locked pyranosides reveal the thermodynamic preference of cyclic substrates for more pseudoequatorial groups. [ 9 ]
(6)
Under aprotic conditions, nucleophilic opening of epoxide isomers can be achieved with hydrides or organocuprates. Nucleophilic attack generally takes place at the least substituted carbon, yielding the more substituted diol product. [ 10 ]
(7)
Under protic conditions, opening at the least substituted position is also usually favored. Nucleophiles that may be used under protic conditions include phenols, secondary amines, azide anion, and sulfides. [ 11 ]
(8)
Intermolecular nucleophilic trapping of a single epoxide isomer is difficult, as reaction of the epoxy alcohol with the electrophile is typically faster than migration. However, intra molecular electrophies are often effective for trapping a single epoxide isomer. For instance, a second nearby epoxide in the starting material of equation (9) is trapped by a single epoxide isomer, leading to a tetrahydrofuran . [ 12 ]
(9)
The aza-Payne rearrangement may be effected in either the "forward" (epoxide to aziridine) or "reverse" (aziridine to epoxide) direction depending on the conditions employed. Electron-poor aziridines undergo the reverse rearrangement in the presence of hydride base, [ 13 ] while the corresponding epoxy amines undergo the forward rearrangement in the presence of boron trifluoride etherate. [ 14 ]
(10)
The thia-Payne rearrangement has only been observed in the forward direction (epoxide to thiiranium) with in situ opening of the thiiranium. Invertive nucleophilic opening at C-2 is possible through the use of trialkylaluminum reagents. [ 15 ]
(11)
The synthesis of borjatriol involved the rare isolation of a migrated epoxide. The diastereomeric mixture of rearrangement products was carried through the remainder of the synthesis. [ 16 ]
(12)
The final two steps in the total synthesis of spatol involved intramolecular electrophilic trapping of an alkoxide derived from a rearranged epoxide. Attack of the intermediate alkoxide on the adjacent mesylate afforded a bis(epoxide), and debenzylation provided the target compound. [ 17 ]
(13)
Other methods available for the preparation of 2,3-epoxy alcohols have the advantage that they do not begin with an existing 2,3-epoxy alcohol; however, they tend to involve more steps than epoxide migration. Asymmetric dihydroxylation may be used to synthesize epoxy alcohols with high stereoselectivity, and some of the methods relying on dihydroxylation avoid the use of strongly basic conditions. [ 18 ]
(14)
An alternative method that leads to retention of configuration at C-2 involves mesylation of an epoxy alcohol, epoxide opening, and re-closing by displacement of the mesylate. [ 11 ]
(15)
Opening of terminal epoxides by adventitious hydroxide may occur under the conditions of rearrangement; if this is not desired, anhydrous solvents, reagents, and glassware must be used. Freshly prepared sodium methoxide in methanol is commonly used to effect rearrangement without opening. Nucleophilic opening can be accomplished through the use of sodium azide , excess hydroxide, or cuprate reagents in the presence of lithium chloride . Electrophilic trapping is carried out under standard conditions in the presence of an electrophile such as benzyl bromide . Silyl halides have also been used as electrophilic trapping agents.
To prevent epoxide migration, weakly basic conditions may be employed. Neither aqueous potassium carbonate nor aqueous amine bases cause epoxide rearrangement. Low temperatures are also beneficial when epoxide migration is not desired.
(16)
A solution of methyl(cyano)cuprate (Solution A) was prepared as follows: to a suspension of 0.35 g (3.91 mmol) of copper(I) cyanide in 5 mL of tetrahydrofuran under argon at 0° was added dropwise over about 5 minutes 2.76 mL of a solution of methyllithium in ethyl ether (1.4 M, 3.86 mmol). The colorless solution was stirred for 10 minutes at 0°, warmed to 25° over 30 minutes, then cooled again to 0°. Separately, a solution of the lithium salt of (±)-cis-4-benzyloxy-2,3-epoxy-1-butanol (Solution B) was prepared as follows: to a solution of 0.5 g (2.58 mmol) of the epoxy alcohol and 0.90 g (21.4 mmol) of lithium chloride in 10 mL of tetrahydrofuran under argon at −78° was added dropwise 1.65 mL of a solution of n-butyllithium in hexane (1.56 M, 2.58 mmol). The solution was stirred for 5 minutes at −78°, allowed to warm to 0°, and then stirred at that temperature for 10 minutes. The reaction was effected by the addition of Solution A to Solution B via cannula at 0° followed by warming to room temperature over 2 hours. The reaction mixture was then stirred for a further 12 hours and then cautiously treated with 5 mL of saturated aqueous ammonium chloride . The mixture was stirred for 1–2 hours to aid removal of copper residues. Ethyl ether (20 mL) was then added, and the organic layer was separated. The aqueous phase was extracted twice with 20 mL of ethyl ether, and the combined organic phases were dried over magnesium sulfate , filtered, and concentrated to give 0.51 g of the product as a colorless oil (95%), IR (film) 3400, 3100, 3060, 3030, 2970, 2930, 2870, 1600, 1500, 1465, 1445, 1385, 1370, 1320, 1285, 1210, 1180, 1120, 1100, 1075, 1030, 1020, 980, 905, 830, 750, 730, 710, 695 cm–1; 1H NMR (CDCl 3 ) δ 0.90 (t, J = 6.0 Hz, 3 H), 1.37–1.53 (m, 2 H), 3.20 (br s, 2 H), 3.40–3.65 (m, 4 H), 4.48 (s, 2 H), 7.29 (s, 5 H). | https://en.wikipedia.org/wiki/Payne_rearrangement |
Payroll automation [ 1 ] refers to the use of computers to produce paychecks and manage benefit payments for a company or community. Often, payroll automation is integrated into the company's enterprise resource planning system that provides an overall view of the company's or community's finances; in addition to payroll, it can manage customer relationships, production , personnel resources, invoicing and accounting .
Payroll management consists of several stages and procedures that require expertise in financial administration, such as employment contract management.
Payroll management performs the following tasks:
The travel costs and travel invoices from the employees are usually processed together with payroll.
Payroll functions can be automated using software to facilitate the collection, organization and storage of all information required for payroll calculations and regulatory agency reportage requirements. If the payroll software is not purchased as part of a comprehensive business management system, it can usually be combined with the company's existing solutions for accounting, sales ledger, working hour management and recruiting. Information that has been captured in one part of the system can be used by other modules. Hours registered in the work management system, for example, are automatically transferred to the wage calculation system.
Effective payroll automation collects all relevant information in one place in electronic format, reducing mistakes by eliminating the need to synchronize and manage otherwise duplicate data sets. [ 3 ]
Well planned, modern payroll software provides the following benefits: | https://en.wikipedia.org/wiki/Payroll_automation |
Lead(II) acetate is a white crystalline chemical compound with a slightly sweet taste . Its chemical formula is usually expressed as Pb(CH 3 COO) 2 or Pb(OAc) 2 , where Ac represents the acetyl group . Like many other lead compounds, it causes lead poisoning . Lead acetate is soluble in water and glycerin . With water it forms the trihydrate, Pb(OAc) 2 ·3H 2 O , a colourless or white efflorescent monoclinic crystalline substance.
The substance is used as a reagent to make other lead compounds and as a fixative for some dyes. In low concentrations, it formerly served as the principal active ingredient in progressive types of hair colouring dyes. [ 6 ] Lead(II) acetate is also used as a mordant in textile printing and dyeing , and as a drier in paints and varnishes . It was historically used as a sweetener and preservative in wines and in other foods and for cosmetics .
Lead(II) acetate can be made by boiling elemental lead in acetic acid and hydrogen peroxide. This method will also work with lead(II) carbonate or lead(II) oxide .
Lead(II) acetate can also be made by dissolving lead(II) oxide in acetic acid: [ 7 ]
Lead(II) acetate can also be made via a single-displacement reaction between copper acetate and lead metal:
The crystal structure of anhydrous lead(II) acetate has been described as a 2D coordination polymer . In comparison, lead(II) acetate trihydrate 's structure is a 1D coordination polymer. [ 8 ] In the trihydrate, the Pb 2+ ion's coordination sphere consists of nine oxygen atoms belonging to three water molecules, two bidentate acetate groups and two bridging acetate groups. The coordination geometry at Pb is a monocapped square antiprism. [ 9 ] [ 10 ] The trihydrate thermally decomposes to a hemihydrate, Pb(OAc) 2 · 1 ⁄ 2 H 2 O, and to basic acetates such as Pb 4 O(OAc) 6 and Pb 2 O(OAc) 2 . [ 8 ]
Lead acetate is used as a precursor to other lead compounds such as the various carbonate.
Lead(II) acetate paper is used to detect the poisonous gas hydrogen sulfide . The gas reacts with lead(II) acetate on the moistened test paper to form a grey precipitate of lead(II) sulfide .
An aqueous solution of lead(II) acetate is a byproduct of the process used in the cleaning and maintenance of stainless steel firearm suppressors (silencers) and compensators when using a 1:1 ratio of hydrogen peroxide and white vinegar (acetic acid). The solution is agitated by the bubbling action of the hydrogen peroxide, with the main reaction being the oxidation of lead by hydrogen peroxide and subsequent dissolution of lead oxide by the acetic acid, which forms lead acetate. Because of its high toxicity, this chemical solution must be appropriately disposed by a chemical processing facility or hazardous materials centre. Alternatively, the solution may be reacted with sulfuric acid to precipitate nearly insoluble lead(II) sulfate . The solid may then be removed by mechanical filtration and is safer to dispose of than aqueous lead acetate.
Like other lead(II) salts, lead(II) acetate has a sweet taste, which led to its historical use as a sugar substitute in both wines and foods. [ 11 ] The ancient Romans , who had few sweeteners besides honey , would boil must (unfiltered grape juice) in lead pots to produce a reduced sugar syrup called defrutum , concentrated again into sapa . This syrup was used to sweeten wine and to sweeten and preserve fruit. It is possible that lead(II) acetate or other lead compounds leaching into the syrup might have caused lead poisoning in those who consumed it. [ 12 ] Lead acetate is no longer used in the production of sweeteners because of its recognized toxicity. Legislation prohibiting its use as a wine sweetener circa 1750 proved ineffective until decades later, when chemical methods of detecting its presence had been developed. [ 13 ]
The earliest confirmed poisoning by lead acetate was that of Pope Clement II , who died in October 1047. A toxicological examination of his remains conducted in the mid-20th century confirmed centuries-old rumors that he had been poisoned with lead sugar. [ 14 ] It is not clear whether he was assassinated.
In 1787 painter and biographer Albert Christoph Dies swallowed, by accident, approximately 3 / 4 ounce (20 g) of lead acetate. His recovery from this poison was slow and incomplete. He lived with illnesses until his death in 1822. [ 15 ] [ 16 ]
Although the use of lead(II) acetate as a sweetener was already illegal at that time, composer Ludwig van Beethoven may have died of lead poisoning caused by wines adulterated with lead acetate (see also Beethoven's liver ). [ 17 ] [ 18 ]
In 1887, 38 hunting horses belonging to Captain William Hollwey Steeds were poisoned in their stables at Clonsilla House, Dublin, Ireland. At least ten of the hunters died. Captain Steeds, an "extensive commission agent", had previously supplied the horses for the Bray and Greystones Coach. It transpired that they had been fed a bran mash that had been sweetened with a toxic lead acetate. [ 19 ]
Lead(II) acetate and white lead have been used in cosmetics throughout history. [ 20 ]
It was once used for men's hair colouring products [ 21 ] like Grecian Formula . The manufacturer did not remove lead acetate from its product until 2018. Lead acetate has been replaced by bismuth citrate as the progressive colorant. Its use in cosmetics has been banned in Canada by Health Canada since 2005 (effective at the end of 2006) based on tests showing possible carcinogenicity and reproductive toxicity, [ 22 ] and it is also banned in the European Union. [ 22 ]
Lead(II) acetate solution was a commonly used folk remedy for sore nipples. [ 23 ] In modern medicine, for a time, it was used as an astringent , in the form of Goulard's extract , and it has also been used to treat poison ivy . [ 24 ]
In the 1850s, Mary Seacole applied lead(II) acetate, among other remedies, against an epidemic of cholera in Panama. [ 25 ] [ 26 ]
It was also used in making of slow matches during the Middle Ages . It was made by mixing a natural form of lead(II) oxide called litharge and vinegar .
Sugar of lead was a recommended agent added to linseed oil during heating to produce "boiled" linseed oil , the lead and heat acting to cause the oil to cure faster than raw linseed oil. [ 27 ]
Lead(II) acetate ("salt of Saturn") was used to synthesise acetone which was then known as "spirit of Saturn" for being made with the salt of Saturn and thought to be a lead compound in the 17th century. [ 28 ] | https://en.wikipedia.org/wiki/Pb(C2H3O2)2 |
Tetraethyl lead
Tetraethyllead (commonly styled tetraethyl lead ), abbreviated TEL , is an organolead compound with the formula Pb ( C 2 H 5 ) 4 . It was widely used as a fuel additive for much of the 20th century, first being mixed with gasoline beginning in the 1920s. This "leaded gasoline" had an increased octane rating that allowed engine compression to be raised substantially and in turn increased vehicle performance and fuel economy. [ 3 ] [ 4 ] TEL was first synthesized by German chemist Carl Jacob Löwig in 1853. American chemical engineer Thomas Midgley Jr. , who was working for the U.S. corporation General Motors , was the first to discover its effectiveness as an antiknock agent on December 9th, 1921, after spending six years attempting to find an additive that was both highly effective and inexpensive. [ 5 ]
Of the some 33,000 substances in total screened, lead was found to be the most effective antiknock agent, [ 6 ] [ 7 ] in that it necessitated the smallest concentrations necessary; a treatment of 1 part TEL to 1300 parts gasoline by weight is sufficient to suppress detonation. [ 8 ] The four ethyl groups in the compound served to dissolve the active lead atom within the fuel. [ 9 ] When injected into the combustion chamber, tetraethyllead decomposed upon heating into ethyl radicals , lead, and lead oxide. The lead oxide scavenges radicals and therefore inhibits a flame from developing until full compression has been achieved, allowing the optimal timing of ignition , as well as the lowering of fuel consumption. [ 9 ] Throughout the sixty year period from 1926 to 1985, an estimated 20 trillion liters of leaded gasoline at an average lead concentration of 0.4 g/L were produced and sold in the United States alone, or an equivalent of 8 million tons of inorganic lead, [ 10 ] three quarters of which would have been emitted in the form of lead chloride and lead bromide . A similar amount of lead could have derived from other countries' emissions, possibly leading to a total injection of >15,000,000,000,000 grams of lead into the terrestrial atmosphere . [ 11 ]
In the mid-20th century, scientists discovered that TEL caused lead poisoning and was highly neurotoxic to the human brain, especially in children. [ 12 ] Approximately 90% of the total lead in a human is present in the bones, deposited in the form of insoluble Pb 3 (PO 4 ) 2 phosphate salt, and has a half life of more than twenty years. [ 13 ] [ 14 ] The United States and many other countries began phasing out the use of TEL in automotive fuel in the 1970s. With EPA guidance and oversight, the US achieved the total elimination of sales of leaded gasoline for on-road vehicles on January 1st, 1996. [ 15 ] By the early 2000s, most countries had banned the use of TEL in gasoline. In July 2021, the sale of leaded gasoline for cars was completely phased out worldwide following the termination of production by Algeria , prompting the United Nations Environment Program (UNEP) to declare an "official end" of its use in cars on August 30, 2021. [ 16 ]
In 2011, researchers retroactively estimated the annual impact of tetraethyl lead worldwide to be the following: 1,100,000 excess deaths, 322 million lost IQ points, 60+ million cases of crime, and a loss of 2.4 trillion United States dollars in worldwide GDP per year, equal to 4% of its value. [ 17 ]
TEL is produced on an industrial scale by reacting chloroethane (ethyl chloride) with a sodium – lead alloy . [ 18 ] [ 19 ]
The product is recovered by steam distillation, leaving a sludge of lead and sodium chloride . [ 20 ] TEL is a viscous colorless liquid with a sweet odor. [ 21 ] Because TEL is charge neutral and contains an exterior of alkyl groups, it is highly lipophilic and soluble in petrol (gasoline). This property, which allows it to dissolve so evenly and effectively in motor fuel, also allowed easy absorption by body fats and lipids and diffusion through the blood–brain barrier (BBB). The lead (II) ions (Pb 2+ ) would accumulate within the limbic forebrain, frontal cortex, and hippocampus . [ 22 ] Practically speaking, TEL is a "central nervous system toxin which produces an acute toxic psychosis." [ 23 ]
There is no cure for direct poisoning by TEL. Inorganic lead compounds, such as those present in engine exhausts , could be removed from the system through the administration of chelating agents , which bind to the inorganic lead and flush them out of the body. However, highly lipid-soluble TEL cannot be removed this way, and treatments are of a supportive nature. [ 24 ]
Despite decades of research, no reactions were found to improve upon this process; it is rather difficult, involves reactive metallic sodium, and converts only 25% of the lead to TEL. A related compound, tetramethyllead , was commercially produced by a different electrolytic reaction. However, tetramethyllead was even more difficult to make, and it did not find use beyond niche applications. [ 18 ] A highly efficient pathway utilizing ethyl chloride with a slight excess of lithium was developed, with a TEL yield over lead of over 90%. However, by then the fuel additive had started to fall out of favor and into disrepute, and the process was never put into practice. [ 25 ]
A noteworthy feature of TEL is the weakness of its four C–Pb bonds. At the temperatures found in internal combustion engines , TEL decomposes completely into lead as well as combustible, short-lived ethyl radicals . Lead and lead oxide scavenge radical intermediates in combustion reactions. Engine knock is caused by a cool flame , an oscillating low-temperature combustion reaction that occurs before the proper, hot ignition. Lead quenches the pyrolyzed radicals and thus kills the radical chain reaction that would sustain a cool flame, preventing it from disturbing the smooth ignition of the hot flame front. Lead itself is the reactive antiknock agent, and the ethyl groups serve as a gasoline-soluble carrier. [ 18 ]
When TEL burns, it produces not only carbon dioxide and water, but also lead and lead(II) oxide: [ 26 ]
Pb and PbO would quickly over-accumulate and foul an engine. For this reason, 1,2-dichloroethane and 1,2-dibromoethane were also added to gasoline as lead scavengers—these agents form volatile lead(II) chloride and lead(II) bromide , respectively, which flush the lead from the engine and into the air: [ 26 ]
TEL was extensively used as a gasoline additive beginning in the 1920s, [ 27 ] wherein it served as an effective antiknock agent and reduced exhaust valve and valve seat wear. Concerns were raised in reputable journals of likely health outcomes of fine particles of lead in the atmosphere as early as 1924. [ 28 ] [ 29 ] [ 30 ]
Tetraethyllead helps cool intake valves and is an excellent buffer against microwelds forming between exhaust valves and their seats . [ 31 ] Once these valves reopen, the microwelds pull apart and abrade the valves and seats, leading to valve recession. When TEL began to be phased out, the automotive industry began specifying hardened valve seats and upgraded materials which allow for high wear resistance without requiring lead. [ 32 ]
A gasoline-fueled reciprocating engine requires fuel of sufficient octane rating to prevent uncontrolled combustion (pre-ignition and detonation ). [ 18 ] Antiknock agents allow the use of higher compression ratios for greater efficiency [ 33 ] and peak power . [ 34 ] Adding varying amounts of additives to gasoline allowed easy, inexpensive control of octane ratings. TEL offered the business advantage of being commercially profitable because its use for this purpose could be patented. [ 27 ] Aviation fuels with TEL used in WWII reached octane ratings of 150 to enable turbocharged and supercharged engines such as the Rolls-Royce Merlin and Griffon to reach high horsepower ratings at altitude. [ 35 ] In military aviation, TEL manipulation allowed a range of different fuels to be tailored for particular flight conditions. [ citation needed ]
In 1935 a license to produce TEL was given to IG Farben , enabling the newly formed German Luftwaffe to use high-octane gasoline for high altitude flight. A company, Ethyl GmbH, was formed that produced TEL at two sites in Germany with a government contract from 10 June 1936. [ 36 ]
In 1938 the United Kingdom Air Ministry contracted with ICI for the construction and operation of a TEL plant. A site was chosen at Holford Moss, near Plumley in Cheshire. Construction started in April 1939 and TEL was being produced by September 1940. [ 37 ]
For mixing with raw gasoline, TEL was most commonly supplied in the form of "Ethyl Fluid", consisting of TEL blended with 1,2-dichloroethane and 1,2-dibromoethane, which prevent lead from building up in the engine. Ethyl Fluid also contained a reddish dye to distinguish treated from untreated gasoline and discourage the use of leaded gasoline for other purposes such as cleaning. [ 38 ]
In the 1920s, before safety procedures were strengthened, 17 workers for the Ethyl Corporation , DuPont , and Standard Oil died from the effects of exposure to lead. [ 27 ] The grim news was not well received by US legislators and a brief ban was put into place. However, it was lifted on recommendation of the United States Surgeon General and a panel of scientists in 1929, after extensive lobbying efforts by the aforementioned companies. [ 27 ] It would be another half a century, until the 1980s, that a similar effort was made to rein in the additive, this time spearheaded by the EPA. This was done not because of its being responsible for the worst environmental catastrophe in recorded history. Instead, the ban arose out of industry concerns over evidence that lead fouled up the newly invented catalytic converters. [ 25 ]
Ethyl Fluid's formulation consisted of: [ 18 ]
It was found that dichloroethane and dibromoethane act in a synergistic manner, in that approximately equal quantities of both provide the best scavenging ability, thus preventing engines from fouling up due to deposits of inorganic lead within the pistons and exhausts. [ 18 ]
In most industrialized countries, a phaseout of TEL from road vehicle fuels was completed by the early 2000s because of concerns over air and soil lead levels and the accumulative neurotoxicity of lead . In the European Union, tetraethyllead has been classified as a Substance of Very High Concern and placed on the Candidate List for Authorization under Registration, Evaluation, Authorization and Restriction of Chemicals (REACH). [ 39 ] Potential use of TEL would need to be authorized through the REACH authorization procedure . While not a complete ban, it introduces significant obligations such as a mandatory analysis of alternatives and socioeconomic analysis. [ citation needed ]
The use of catalytic converters , mandated in the United States for 1975 and later model-year cars to meet tighter emissions regulations, started a gradual phase-out of leaded gasoline in the U.S. [ 40 ] The need for TEL was lessened by several advances in automotive engineering and petroleum chemistry. Safer methods for making higher-octane blending stocks such as reformate and iso-octane reduced the need to rely on TEL, as did other antiknock additives of varying toxicity including metallic compounds such as methylcyclopentadienyl manganese tricarbonyl (MMT) as well as oxygenates including methyl tert -butyl ether (MTBE), tert -amyl methyl ether (TAME), and ethyl tert -butyl ether (ETBE). [ citation needed ]
The first country to completely ban leaded gasoline was Japan in 1986. [ 41 ]
Since January 1993, all gasoline powered cars sold in the European Union and the United Kingdom have been required to use unleaded fuel. This was to comply with the Euro 1 emission standards which mandated that all new cars to be fitted with a catalytic converter . [ 42 ] Unleaded fuel was first introduced in the United Kingdom in June 1986. [ 43 ]
Leaded gasoline was removed from the forecourts in the United Kingdom on January 1, 2000, and a Lead Replacement Petrol was introduced although this was largely withdrawn by 2003 due to dwindling sales. [ 44 ] [ 45 ] An exemption to the ban exists for owners of classic cars. [ citation needed ]
Vehicles designed and built to run on leaded fuel often require modification to run on unleaded gasoline. These modifications fall into two categories: those required for physical compatibility with unleaded fuel, and those performed to compensate for the relatively low octane of early unleaded fuels. Physical compatibility requires the installation of hardened exhaust valves and seats. Compatibility with reduced octane was addressed by reducing compression, generally by installing thicker cylinder head gaskets and/or rebuilding the engine with compression-reducing pistons, although modern high-octane unleaded gasoline has eliminated the need to decrease compression ratios. [ citation needed ]
Leaded gasoline remained legal as of late 2014 [ 46 ] in parts of Algeria , Iraq , Yemen , Myanmar , North Korea , and Afghanistan . [ 47 ] [ 48 ] [ needs update ] North Korea and Myanmar purchased their TEL from China, while Algeria, Iraq, and Yemen purchased it from the specialty chemical company Innospec , the world's sole remaining legal manufacturer of TEL. [ 49 ] In 2011 several Innospec executives were charged and imprisoned for bribing various government state-owned oil companies to approve the sale of their TEL products. [ 48 ] [ 50 ]
As of June 2016 [update] the UNEP -sponsored phase-out was nearly complete: only Algeria, Iraq, and Yemen continued widespread use of leaded gasoline, although not exclusively. [ 51 ] In July 2021, Algeria had halted its sale. [ 16 ]
Leaded-fuel bans for road vehicles came into effect as follows:
Leaded fuel was commonly used in professional motor racing , until its phase out beginning in the 1990s. Since 1992, Formula One racing cars have been required to use fuel containing no more than 5 mg/L of lead. [ 94 ] [ verification needed ]
NASCAR began experimentation in 1998 with an unleaded fuel, and in 2006 began switching the national series to unleaded fuel, completing the transition at the Fontana round in February 2007 when the premier class switched. This was influenced after blood tests of NASCAR teams revealed elevated blood lead levels. [ 95 ] [ 96 ]
TEL remains an ingredient of 100 octane avgas for piston-engine aircraft. The current formulation of 100LL (low lead, blue) aviation gasoline contains 2.12 grams per US gallon (0.56 g/L) of TEL, half the amount of the previous 100/130 (green) octane avgas (at 4.24 grams per gallon), [ 97 ] and twice as much as the 1 gram per gallon permitted in regular automotive leaded gasoline prior to 1988 and substantially greater than the allowed 0.001 grams per gallon in automotive unleaded gasoline sold in the United States today. [ 98 ] The United States Environmental Protection Agency, FAA , and others are working on economically feasible replacements for leaded avgas, which still releases 100 tons of lead every year. [ 99 ]
Antiknock agents are classed as high-percentage additives, such as alcohol, and low-percentage additives based on heavy elements . Since the main problem with TEL is its lead content, many alternative additives that contain less poisonous metals have been examined. A manganese-carrying additive, methylcyclopentadienyl manganese tricarbonyl (MMT or methylcymantrene), was used for a time as an antiknock agent, though its safety is controversial and it has been the subject of bans and lawsuits. Ferrocene , an organometallic compound of iron , is also used as an antiknock agent although with some significant drawbacks. [ 100 ]
High-percentage additives are organic compounds that do not contain metals, but require much higher blending ratios, such as 20–30% for benzene and ethanol . It had been established by 1921 that ethanol was an effective antiknock agent, but TEL was introduced instead mainly for commercial reasons. [ 40 ] Oxygenates such as TAME derived from natural gas, MTBE made from methanol, and ethanol-derived ETBE , have largely supplanted TEL. MTBE has environmental risks of its own and there are also bans on its use. [ citation needed ]
Improvements to gasoline itself decrease the need for antiknock additives. Synthetic iso-octane and alkylate are examples of such blending stocks. Benzene and other high-octane aromatics can be also blended to raise the octane number, but they are disfavored today because of toxicity and carcinogenicity . [ citation needed ]
6 mL of tetraethyllead is enough to induce severe lead poisoning . [ 101 ] The hazards of TEL content are heightened due to the compound's volatility and high lipophilicity , enabling it to easily cross the blood–brain barrier .
Early symptoms of acute exposure to tetraethyllead can manifest as irritation of the eyes and skin, sneezing, fever, vomiting, and a metallic taste in the mouth. Later symptoms of acute TEL poisoning include pulmonary edema , anemia , ataxia, convulsions, severe weight loss, delirium , irritability, hallucinations, nightmares, fever, muscle and joint pain, swelling of the brain , coma, and damage to cardiovascular and renal organs. [ 102 ] Chronic exposure to TEL can cause long-term negative effects such as memory loss , delayed reflexes, neurological problems, insomnia, tremors, psychosis, loss of attention, and an overall decrease in IQ and cognitive function. [ 103 ]
The carcinogenity of tetraethyllead is debatable. It is believed to harm the male reproductive system and cause birth defects. [ 104 ]
Concerns over the toxicity of lead [ 105 ] eventually led to the ban on TEL in automobile gasoline in many countries. Some neurologists have speculated that the lead phaseout may have caused average IQ levels to rise by several points in the US (by reducing cumulative brain damage throughout the population, especially in the young). For the entire US population, during and after the TEL phaseout, the mean blood lead level dropped from 16 μg/dL in 1976 to only 3 μg/dL in 1991. [ 106 ] The U.S. Centers of Disease control previously labelled children with 10 μg/dL or more as having a "blood lead level of concern". In 2021, the level was lowered in accordance with the average lead level in the U.S. decreasing to 3.5 μg/dL or more as having a "blood lead level of concern". [ 107 ] [ 108 ]
In 1853, German chemist Karl Jacob Löwig (1803–1890) first prepared what he claimed was Pb 2 (C 2 H 5 ) 3 from ethyl iodide and an alloy of lead and sodium. [ 109 ] In 1859, English chemist George Bowdler Buckton (1818–1905) reported what he claimed was Pb(C 2 H 5 ) 2 from zinc ethyl (Zn(C 2 H 5 ) 2 ) and lead(II) chloride . [ 110 ] Later authors credit both methods of preparation with producing tetraethyl lead. [ 111 ]
TEL remained unimportant commercially until the 1920s. [ 40 ] In 1921, at the direction of DuPont Corporation, which manufactured TEL, it was found to be an effective antiknock agent by Thomas Midgley , working under Charles Kettering at General Motors Corporation Research. [ 112 ] General Motors patented the use of TEL as an antiknock agent and used the name "Ethyl" that had been proposed by Kettering in its marketing materials, thereby avoiding the negative connotation of the word "lead". [ 40 ] Early research into " engine knocking " (also called "pinging" or "pinking") was also led by A.H. Gibson and Harry Ricardo in England and Thomas Boyd in the United States. The discovery that lead additives modified this behavior led to the widespread adoption of their use in the 1920s, and therefore more powerful, higher-compression engines. [ 27 ] In 1924, Standard Oil of New Jersey (ESSO/EXXON) and General Motors created the Ethyl Gasoline Corporation to produce and market TEL. Deepwater, New Jersey, across the river from Wilmington, was the site for production of some of DuPont's most important chemicals, particularly TEL. After TEL production at the Bayway Refinery was shut down, Deepwater was the only plant in the Western hemisphere producing TEL up to 1948, when it accounted for the bulk of the Dupont/Deepwater's production. [ 113 ]
The toxicity of concentrated TEL was recognized early on, as lead had been recognized since the 19th century as a dangerous substance that could cause lead poisoning . In 1924, a public controversy arose over the "loony gas", after five [ 114 ] workers died, and many others were severely injured, in Standard Oil refineries in New Jersey. [ 115 ] There had also been a private controversy for two years prior to this controversy; several public health experts, including Alice Hamilton and Yandell Henderson , engaged Midgley and Kettering with letters warning of the dangers to public health. [ 27 ] After the death of the workers, dozens of newspapers reported on the issue. [ 116 ] The New York Times editorialized in 1924 that the deaths should not interfere with the production of more powerful fuel. [ 27 ]
To settle the issue, the U.S. Public Health Service conducted a conference in 1925, and the sales of TEL were voluntarily suspended for one year to conduct a hazard assessment. [ 18 ] [ 40 ] [ 117 ] The conference was initially expected to last for several days, but reportedly the conference decided that evaluating presentations on alternative anti-knock agents was not "its province", so it lasted a single day. Kettering and Midgley stated that no alternatives for anti-knocking were available, although private memos showed discussion of such agents. One commonly discussed agent was ethanol. The Public Health Service created a committee that reviewed a government-sponsored study of workers and an Ethyl lab test, and concluded that while leaded gasoline should not be banned, it should continue to be investigated. [ 27 ] The low concentrations present in gasoline and exhaust were not perceived as immediately dangerous. A U.S. Surgeon General committee issued a report in 1926 that concluded there was no real evidence that the sale of TEL was hazardous to human health but urged further study. [ 40 ] In the years that followed, research was heavily funded by the lead industry; in 1943, Randolph Byers found children with lead poisoning had behavior problems, but the Lead Industries Association threatened him with a lawsuit and the research ended. [ 27 ] [ 118 ]
In the late 1920s, Robert A. Kehoe of the University of Cincinnati was the Ethyl Corporation's chief medical consultant and one of the lead industry's staunchest advocates, who would not be discredited until decades later by Dr. Clair Patterson 's work on human lead burdens (see below) and other studies. [ 40 ] In 1928, Dr. Kehoe expressed the opinion that there was no basis for concluding that leaded fuels posed any health threat. [ 40 ] He convinced the Surgeon General that the dose–response relationship of lead had "no effect" below a certain threshold. [ 119 ] As the head of Kettering Laboratories for many years, Kehoe would become a chief promoter of the safety of TEL, an influence that did not begin to wane until about the early 1960s. But by the 1970s, the general opinion of the safety of TEL would change, and by 1976 the U.S. government would begin to require the phaseout of this product. [ 120 ]
In the late 1940s and early 1950s, Clair Cameron Patterson accidentally discovered the pollution caused by TEL in the environment while determining the age of the Earth . As he attempted to measure lead content of very old rocks, and the time it took uranium to decay into lead, the readings were made inaccurate by lead in the environment that contaminated his samples. He was then forced to work in a cleanroom to keep his samples uncontaminated by environmental pollution of lead. After coming up with a fairly accurate estimate of the age of the Earth, he turned to investigating the lead contamination problem by examining ice cores from countries such as Greenland . He realized that the lead contamination in the environment dated from about the time that TEL became widely used as a fuel additive in gasoline. Being aware of the health dangers posed by lead and suspicious of the pollution caused by TEL, he became one of the earliest and most effective proponents of removing it from use. [ 121 ] [ 122 ]
In the 1960s, the first clinical works were published proving the toxicity of this compound in humans, e.g. by Mirosław Jan Stasik . [ 102 ]
In the 1970s, Herbert Needleman found that higher lead levels in children were correlated with decreased school performance. Needleman was repeatedly accused of scientific misconduct by individuals within the lead industry, but he was eventually cleared by a scientific advisory council. [ 27 ] Needleman also wrote the average US child's blood lead level was 13.7 μg/dL in 1976 and that Patterson believed that everyone was to some degree poisoned by TEL in gasoline. [ 123 ]
In the U.S. in 1973, the United States Environmental Protection Agency issued regulations to reduce the lead content of leaded gasoline over a series of annual phases, which therefore came to be known as the "lead phasedown" program. EPA's rules were issued under section 211 of the Clean Air Act , as amended 1970. The Ethyl Corp challenged the EPA regulations in Federal court. Although the EPA's regulation was initially invalidated, [ 27 ] the EPA won the case on appeal, so the TEL phasedown began to be implemented in 1976. Leaded gas was banned in vehicles with catalytic converters in 1975 due to damage of catalytic converters but it continued to be sold for vehicles without catalytic converters. [ 124 ] Additional regulatory changes were made by EPA over the next decade (including adoption of a trading market in "lead credits" in 1982 that became the precursor of the Acid Rain Allowance Market, adopted in 1990 for SO 2 ), but the decisive rule was issued in 1985. [ 125 ] The EPA mandated that lead additive be reduced by 91 percent by the end of 1986. A 1994 study had indicated that the concentration of lead in the blood of the U.S. population had dropped 78% from 1976 to 1991. [ 126 ] The U.S. phasedown regulations also were due in great part to studies conducted by Philip J. Landrigan . [ 127 ]
In Europe, Professor Derek Bryce-Smith was among the first to highlight the potential dangers of TEL and became a leading campaigner for removal of lead additives from petrol. [ 128 ]
From 1 January 1996, the U.S. Clean Air Act banned the sale of leaded fuel for use in on-road vehicles although that year the US EPA indicated that TEL could still be used in aircraft, racing cars, farm equipment, and marine engines. [ 129 ] Thus, what had begun in the U.S. as a phase down ultimately ended in a phase-out for on-road vehicle TEL. Similar bans in other countries have resulted in lowering levels of lead in people's bloodstreams . [ 130 ] [ 131 ]
Taking cue from the domestic programs, the U.S. Agency for International Development undertook an initiative to reduce tetraethyl lead use in other countries, notably its efforts in Egypt begun in 1995. In 1996, with the cooperation of the U.S. AID, Egypt took almost all of the lead out of its gasoline. The success in Egypt provided a model for AID efforts worldwide. [ 132 ]
By 2000, the TEL industry had moved the major portion of their sales to developing countries whose governments they lobbied against phasing out leaded gasoline. [ 40 ] Leaded gasoline was withdrawn entirely from the European Union market on 1 January 2000, although it had been banned earlier in most member states. Other countries also phased out TEL. [ 133 ] India banned leaded petrol in March 2000. [ 81 ]
By 2011, the United Nations announced that it had been successful in phasing out leaded gasoline worldwide. "Ridding the world of leaded petrol, with the United Nations leading the effort in developing countries, has resulted in $2.4 trillion in annual benefits, 1.2 million fewer premature deaths, higher overall intelligence and 58 million fewer crimes", the United Nations Environmental Program said. [ 134 ] [ 135 ] The announcement was slightly premature, as a few countries still had leaded gasoline for sale as of 2017. [ 51 ] On 30 August 2021 the United Nations Environment Program announced that leaded gasoline had been eliminated. The final stocks of the product were used up in Algeria, which had continued to produce leaded gasoline until July 2021. [ 136 ] [ 137 ]
Reduction in the average blood lead level is believed to have been a major cause for falling violent crime rates in the United States. [ 138 ] A statistically significant correlation has been found between the usage rate of leaded gasoline and violent crime: the violent crime curve virtually tracks the lead exposure curve with a 22-year time lag. [ 106 ] [ 139 ] After the ban on TEL, blood lead levels in U.S. children dramatically decreased. [ 106 ] Researchers including Amherst College economist Jessica Wolpaw Reyes, Department of Housing and Urban Development consultant Rick Nevin, and Howard Mielke of Tulane University say that declining exposure to lead is responsible for an up to 56% decline in crime from 1992 to 2002. [ 140 ] Taking into consideration other factors that are believed to have increased crime rates over that period, Reyes found that the reduced exposure to lead led to an actual decline of 34% over that period. [ 141 ] [ 142 ]
Although leaded gasoline has long since ended its history of regular use in U.S. transportation, it has left high concentrations of lead in the soil adjacent to roads that were heavily used prior to its phaseout. These contaminated materials present health dangers even when merely touched or when components of it get breathed in . Children, especially those in poverty inside of the U.S. , are particularly at risk. [ 143 ] | https://en.wikipedia.org/wiki/Pb(C2H5)4 |
Lead(II) acetate is a white crystalline chemical compound with a slightly sweet taste . Its chemical formula is usually expressed as Pb(CH 3 COO) 2 or Pb(OAc) 2 , where Ac represents the acetyl group . Like many other lead compounds, it causes lead poisoning . Lead acetate is soluble in water and glycerin . With water it forms the trihydrate, Pb(OAc) 2 ·3H 2 O , a colourless or white efflorescent monoclinic crystalline substance.
The substance is used as a reagent to make other lead compounds and as a fixative for some dyes. In low concentrations, it formerly served as the principal active ingredient in progressive types of hair colouring dyes. [ 6 ] Lead(II) acetate is also used as a mordant in textile printing and dyeing , and as a drier in paints and varnishes . It was historically used as a sweetener and preservative in wines and in other foods and for cosmetics .
Lead(II) acetate can be made by boiling elemental lead in acetic acid and hydrogen peroxide. This method will also work with lead(II) carbonate or lead(II) oxide .
Lead(II) acetate can also be made by dissolving lead(II) oxide in acetic acid: [ 7 ]
Lead(II) acetate can also be made via a single-displacement reaction between copper acetate and lead metal:
The crystal structure of anhydrous lead(II) acetate has been described as a 2D coordination polymer . In comparison, lead(II) acetate trihydrate 's structure is a 1D coordination polymer. [ 8 ] In the trihydrate, the Pb 2+ ion's coordination sphere consists of nine oxygen atoms belonging to three water molecules, two bidentate acetate groups and two bridging acetate groups. The coordination geometry at Pb is a monocapped square antiprism. [ 9 ] [ 10 ] The trihydrate thermally decomposes to a hemihydrate, Pb(OAc) 2 · 1 ⁄ 2 H 2 O, and to basic acetates such as Pb 4 O(OAc) 6 and Pb 2 O(OAc) 2 . [ 8 ]
Lead acetate is used as a precursor to other lead compounds such as the various carbonate.
Lead(II) acetate paper is used to detect the poisonous gas hydrogen sulfide . The gas reacts with lead(II) acetate on the moistened test paper to form a grey precipitate of lead(II) sulfide .
An aqueous solution of lead(II) acetate is a byproduct of the process used in the cleaning and maintenance of stainless steel firearm suppressors (silencers) and compensators when using a 1:1 ratio of hydrogen peroxide and white vinegar (acetic acid). The solution is agitated by the bubbling action of the hydrogen peroxide, with the main reaction being the oxidation of lead by hydrogen peroxide and subsequent dissolution of lead oxide by the acetic acid, which forms lead acetate. Because of its high toxicity, this chemical solution must be appropriately disposed by a chemical processing facility or hazardous materials centre. Alternatively, the solution may be reacted with sulfuric acid to precipitate nearly insoluble lead(II) sulfate . The solid may then be removed by mechanical filtration and is safer to dispose of than aqueous lead acetate.
Like other lead(II) salts, lead(II) acetate has a sweet taste, which led to its historical use as a sugar substitute in both wines and foods. [ 11 ] The ancient Romans , who had few sweeteners besides honey , would boil must (unfiltered grape juice) in lead pots to produce a reduced sugar syrup called defrutum , concentrated again into sapa . This syrup was used to sweeten wine and to sweeten and preserve fruit. It is possible that lead(II) acetate or other lead compounds leaching into the syrup might have caused lead poisoning in those who consumed it. [ 12 ] Lead acetate is no longer used in the production of sweeteners because of its recognized toxicity. Legislation prohibiting its use as a wine sweetener circa 1750 proved ineffective until decades later, when chemical methods of detecting its presence had been developed. [ 13 ]
The earliest confirmed poisoning by lead acetate was that of Pope Clement II , who died in October 1047. A toxicological examination of his remains conducted in the mid-20th century confirmed centuries-old rumors that he had been poisoned with lead sugar. [ 14 ] It is not clear whether he was assassinated.
In 1787 painter and biographer Albert Christoph Dies swallowed, by accident, approximately 3 / 4 ounce (20 g) of lead acetate. His recovery from this poison was slow and incomplete. He lived with illnesses until his death in 1822. [ 15 ] [ 16 ]
Although the use of lead(II) acetate as a sweetener was already illegal at that time, composer Ludwig van Beethoven may have died of lead poisoning caused by wines adulterated with lead acetate (see also Beethoven's liver ). [ 17 ] [ 18 ]
In 1887, 38 hunting horses belonging to Captain William Hollwey Steeds were poisoned in their stables at Clonsilla House, Dublin, Ireland. At least ten of the hunters died. Captain Steeds, an "extensive commission agent", had previously supplied the horses for the Bray and Greystones Coach. It transpired that they had been fed a bran mash that had been sweetened with a toxic lead acetate. [ 19 ]
Lead(II) acetate and white lead have been used in cosmetics throughout history. [ 20 ]
It was once used for men's hair colouring products [ 21 ] like Grecian Formula . The manufacturer did not remove lead acetate from its product until 2018. Lead acetate has been replaced by bismuth citrate as the progressive colorant. Its use in cosmetics has been banned in Canada by Health Canada since 2005 (effective at the end of 2006) based on tests showing possible carcinogenicity and reproductive toxicity, [ 22 ] and it is also banned in the European Union. [ 22 ]
Lead(II) acetate solution was a commonly used folk remedy for sore nipples. [ 23 ] In modern medicine, for a time, it was used as an astringent , in the form of Goulard's extract , and it has also been used to treat poison ivy . [ 24 ]
In the 1850s, Mary Seacole applied lead(II) acetate, among other remedies, against an epidemic of cholera in Panama. [ 25 ] [ 26 ]
It was also used in making of slow matches during the Middle Ages . It was made by mixing a natural form of lead(II) oxide called litharge and vinegar .
Sugar of lead was a recommended agent added to linseed oil during heating to produce "boiled" linseed oil , the lead and heat acting to cause the oil to cure faster than raw linseed oil. [ 27 ]
Lead(II) acetate ("salt of Saturn") was used to synthesise acetone which was then known as "spirit of Saturn" for being made with the salt of Saturn and thought to be a lead compound in the 17th century. [ 28 ] | https://en.wikipedia.org/wiki/Pb(CH3COO)2 |
Lead(II) carbonate is the chemical compound with the chemical formula PbCO 3 . It is a white, toxic solid. [ 2 ] It occurs naturally as the mineral cerussite . [ 3 ]
Like all metal carbonates, lead(II) carbonate adopts a dense, highly crosslinked structure consisting of intact CO 2− 3 and metal cation sites. As verified by X-ray crystallography , the Pb(II) centers are seven-coordinate, being surrounded by multiple carbonate ligands. The carbonate centers are bonded bidentate to a single Pb and bridge to five other Pb sites. [ 4 ]
Lead carbonate is manufactured by passing carbon dioxide into a cold dilute solution of lead(II) acetate , or by shaking a suspension of a lead salt more soluble than the carbonate with ammonium carbonate at a low temperature to avoid formation of basic lead carbonate. [ 2 ]
Lead carbonate is used as a catalyst to polymerize formaldehyde to poly(oxymethylene) . It improves the bonding of chloroprene to wire. [ 2 ]
The supply and use of this compound is restricted in Europe. [ 5 ]
A number of lead carbonates are known: | https://en.wikipedia.org/wiki/Pb(CO3) |
Lead(II) nitrate is an inorganic compound with the chemical formula Pb ( NO 3 ) 2 . It commonly occurs as a colourless crystal or white powder and, unlike most other lead(II) salts , is soluble in water .
Known since the Middle Ages by the name plumbum dulce , the production of lead(II) nitrate from either metallic lead or lead oxide in nitric acid was small-scale, for direct use in making other lead compounds . In the nineteenth century lead(II) nitrate began to be produced commercially in Europe and the United States. Historically, the main use was as a raw material in the production of pigments for lead paints , but such paints have been superseded by less toxic paints based on titanium dioxide . Other industrial uses included heat stabilization in nylon and polyesters , and in coatings of photothermographic paper. Since around the year 2000, lead(II) nitrate has begun to be used in gold cyanidation .
Lead(II) nitrate is toxic and must be handled with care to prevent inhalation, ingestion and skin contact. Due to its hazardous nature , the limited applications of lead(II) nitrate are under constant scrutiny.
Lead nitrate was first identified in 1597 by the alchemist Andreas Libavius , who called the substance plumbum dulce , meaning "sweet lead", because of its taste. [ 5 ] It is produced commercially by reaction of metallic lead with concentrated nitric acid in which it is sparingly soluble. [ 6 ] [ 7 ] It has been produced as a raw material for making pigments such as chrome yellow (lead(II) chromate, PbCrO 4 ) and chrome orange (basic lead(II) chromate, Pb 2 CrO 5 ) and Naples yellow . These pigments were used for dyeing and printing calico and other textiles. [ 8 ] It has been used as an oxidizer in black powder and together with lead azide in special explosives . [ 9 ]
Lead nitrate is produced by reaction of lead(II) oxide with concentrated nitric acid: [ 10 ]
It may also be obtained by evaporation of the solution obtained by reacting metallic lead with dilute nitric acid . [ 11 ]
Solutions and crystals of lead(II) nitrate are formed in the processing of lead– bismuth wastes from lead refineries. [ 12 ]
The crystal structure of solid lead(II) nitrate has been determined by neutron diffraction . [ 13 ] [ 14 ] The compound crystallizes in the cubic system with the lead atoms in a face-centred cubic system. Its space group is Pa3 Z=4 ( Bravais lattice notation), with each side of the cube with length 784 picometres .
The black dots represent the lead atoms, the white dots the nitrate groups 27 picometres above the plane of the lead atoms, and the blue dots the nitrate groups the same distance below this plane. In this configuration, every lead atom is bonded to twelve oxygen atoms ( bond length : 281 pm). All N–O bond lengths are identical, at 127 picometres. [ 15 ]
Research interest in the crystal structure of lead(II) nitrate was partly based on the possibility of free internal rotation of the nitrate groups within the crystal lattice at elevated temperatures, but this did not materialise. [ 14 ]
Lead nitrate is an oxidizer and has been used as such in pyrotechnics . [ 9 ] It is soluble in water and dilute nitric acid.
Basic nitrates are formed when alkali is added to a solution. Pb 2 (OH) 2 (NO 3 ) 2 is the predominant species formed at low pH . At higher pH Pb 6 (OH) 5 NO 3 is formed. [ 17 ] The cation Pb 6 O(OH) 6 4+ is unusual in having an oxide ion inside a cluster of 3 face-sharing PbO 4 tetrahedra. [ 18 ] There is no evidence for the formation of the hydroxide, Pb(OH) 2 , in aqueous solution below pH 12.
Solutions of lead nitrate can be used to form co-ordination complexes. Lead(II) is a hard acceptor ; it forms stronger complexes with nitrogen and oxygen electron-donating ligands. For example, combining lead nitrate and pentaethylene glycol (shortened to EO5 in the referenced paper) in a solution of acetonitrile and methanol followed by slow evaporation produced the compound [ Pb(NO 3 ) 2 EO5]. [ 19 ] In the crystal structure for this compound, the EO5 chain is wrapped around the lead ion in an equatorial plane similar to that of a crown ether . The two bidentate nitrate ligands are in trans configuration . The total coordination number is 10, with the lead ion in a bicapped square antiprism molecular geometry .
The complex formed by lead nitrate with a bithiazole bidentate N-donor ligand is binuclear. The crystal structure shows that the nitrate group forms a bridge between two lead atoms. [ 20 ] One aspect of this type of complexes is the presence of a physical gap in the coordination sphere ; i.e., the ligands are not placed symmetrically around the metal ion. This is potentially due to a lone pair of lead electrons, also found in lead complexes with an imidazole ligand. [ 21 ]
Lead nitrate has been used as a heat stabiliser in nylon and polyesters, as a coating for photothermographic paper, and in rodenticides . [ 10 ]
Heating lead nitrate is convenient means of making nitrogen dioxide :
In the gold cyanidation process, addition of lead(II) nitrate solution improves the leaching process. Only limited amounts (10 to 100 milligrams lead nitrate per kilogram gold) are required. [ 22 ] [ 23 ]
In organic chemistry, it may be used in the preparation of isothiocyanates from dithiocarbamates . [ 24 ] Its use as a bromide scavenger during S N 1 substitution has been reported. [ 25 ]
Lead(II) nitrate is toxic, and ingestion may lead to acute lead poisoning, as is applicable for all soluble lead compounds. [ 26 ] All inorganic lead compounds are classified by the International Agency for Research on Cancer (IARC) as probably carcinogenic to humans (Category 2A). [ 27 ] They have been linked to renal cancer and glioma in experimental animals and to renal cancer, brain cancer and lung cancer in humans, although studies of workers exposed to lead are often complicated by concurrent exposure to arsenic . [ 28 ] Lead is known to substitute for zinc in a number of enzymes , including δ-aminolevulinic acid dehydratase (porphobilinogen synthase) in the haem biosynthetic pathway and pyrimidine-5′-nucleotidase , important for the correct metabolism of DNA and can therefore cause fetal damage. [ 29 ] | https://en.wikipedia.org/wiki/Pb(NO3)2 |
soluble in ammonium acetate (≥ 6 mol/L)
soluble in ammonium tartrate in presence of ammonium chloride and ammonia
Lead(II) sulfate (PbSO 4 ) is a white solid, which appears white in microcrystalline form. It is also known as fast white , milk white , sulfuric acid lead salt or anglesite .
It is often seen in the plates/electrodes of car batteries , as it is formed when the battery is discharged (when the battery is recharged, then the lead sulfate is transformed back to metallic lead and sulfuric acid on the negative terminal or lead dioxide and sulfuric acid on the positive terminal). Lead sulfate is poorly soluble in water.
Anglesite (lead(II) sulfate, PbSO 4 ) adopts the same orthorhombic crystal structure as celestite ( strontium sulfate , SrSO 4 ) and barite ( barium sulfate , BaSO 4 ). All three minerals' structures are in the space group Pbnm (number 62) . [ 6 ] Each lead(II) ion is surrounded by 12 oxygen atoms from 7 sulfate ions, forming a PbO 12 polyhedron. [ 7 ] The lead–oxygen distances range from 2.612 Å to 3.267 Å and the average distance is 2.865 Å. [ 6 ]
Lead(II) sulfate is prepared by treating lead oxide, hydroxide or carbonate with warm sulfuric acid or by treating a soluble lead salt with sulfuric acid.
Alternatively, it can be made by the interaction of solutions of lead nitrate and sodium sulfate.
Lead sulfate is toxic by inhalation, ingestion and skin contact. It is a cumulative poison , and repeated exposure may lead to anemia, kidney damage, eyesight damage or damage to the central nervous system (especially in children). It is also corrosive - contact with the eyes can lead to severe irritation or burns. Typical threshold limit value is 0.15 mg/m 3 .
The naturally occurring mineral anglesite , PbSO 4 , occurs as an oxidation product of primary lead sulfide ore,
A number of lead basic sulfates are known: PbSO 4 ·PbO; PbSO 4 ·2PbO; PbSO 4 ·3PbO; PbSO 4 ·4PbO. They are used in manufacturing of active paste for lead–acid batteries. A related mineral is leadhillite , 2PbCO 3 ·PbSO 4 ·Pb(OH) 2 .
At high concentration of sulfuric acid (>80%), lead hydrogensulfate, Pb(HSO 4 ) 2 , forms. [ 8 ]
Lead(II) sulfate can be dissolved in concentrated HNO 3 , HCl, H 2 SO 4 producing acidic salts or complex compounds, and in concentrated alkali giving soluble tetrahydroxidoplumbate(II) [Pb(OH) 4 ] 2− complexes.
Lead(II) sulfate decomposes when heated above 1000 °C: | https://en.wikipedia.org/wiki/Pb(SO4) |
Plumbylenes (or plumbylidenes ) are divalent organolead(II) analogues of carbenes , with the general chemical formula, R 2 Pb , where R denotes a substituent. Plumbylenes possess 6 electrons in their valence shell , and are considered open shell species.
The first plumbylene reported was the dialkylplumbylene, [(Me 3 Si) 2 CH] 2 Pb, which was synthesized by Michael F. Lappert et al in 1973. [ 1 ]
Plumbylenes may be further classified into carbon-substituted plumbylenes, plumbylenes stabilized by a group 15 or 16 element, and monohalogenated plumbylenes (RPbX). [ 2 ]
Plumbylenes can generally be synthesized via the transmetallation of PbX 2 (where X denotes halogen) with an organolithium (RLi) or Grignard reagent (RMgX). [ 2 ] The first reported plumbylene, [((CH 3 ) 3 Si) 2 CH] 2 Pb, was synthesized by Michael F. Lappert et al by transmetallation of PbCl 2 with [((CH 3 ) 3 Si) 2 CH]Li. [ 1 ] The addition of equimolar RLi to PbX 2 produces the monohalogenated plumbylene (RPbX); addition of 2 equivalents leads to disubstituted plumbylene (R 2 Pb). [ 3 ] Adding an organolithium or Grignard reagent with a different organic substituent (i.e. R’Li/R’MgX) from RPbX leads to the synthesis of heteroleptic plumbylenes (RR’Pb). [ 3 ] Dialkyl-, [ 1 ] diaryl-, [ 4 ] diamido-, [ 5 ] dithioplumbylenes, [ 3 ] and monohalogenated plumbyelenes [ 3 ] have been successfully synthesized this way.
Transmetallation with [((CH 3 ) 3 Si) 2 N] 2 Pb as the Pb(II) precursor has also been used to synthesize diarylplumbylenes, [ 6 ] disilylplumbylenes, [ 7 ] and saturated N -heterocyclic plumbylenes. [ 8 ]
Alternatively, plumbylenes may be synthesized from the reductive dehalogenation of tetravalent organolead compounds (R 2 PbX 2 ). [ 6 ]
The bonding and reactivity in plumbylenes are dictated by the inert pair effect , whereby the combination of a widening s–p orbital energy gap as a trend down the group 14 elements and a strong relativistic contraction of the 6s orbital limits sp hybridization . The 6s orbital is deep in energy and inert. [ 9 ] Consequently, plumbylenes exclusively have a singlet spin state . They tend to exist in an equilibrium between monomeric and dimeric forms in solution. [ 9 ] In contrast carbenes sometimes have a triplet ground state and in all cases readily dimerize.
In dimethyllead, (CH 3 ) 2 Pb, the Pb–C bond length is 2.267 Å and the C–Pb–C bond angle is 93.02°; the singlet–triplet gap is 36.99 kcal mol −1 . [ 10 ] [ verification needed ]
The Pb–C bond distance was found to be 2.303 Å and the C–Pb–C angle 105.7°. Notwithstanding the different levels of theory, the larger bond angle for (C 6 H 5 ) 2 Pb compared to (CH 3 ) 2 Pb can be rationalized by steric effects.
Plumbylenes occur as reactive intermediates in the formation of tetravalent plumbanes (R 4 Pb). [ 11 ] Although the inert pair effect suggests the divalent state should be thermodynamically more stable than the tetravalent state, in the absence of stabilizing substituents, plumbylenes are sensitive to heat and light, [ 12 ] and tend to undergo polymerization and disproportionation , forming elemental lead in the process. [ 11 ] [ 12 ]
Plumbylenes can be stabilized as monomers by the use of sterically bulky ligands (kinetic stabilization) or heteroatom-containing substituents that can donate electron density into the vacant 6p orbital (thermodynamic stabilization). [ 2 ]
Organoplumbylenes tend to exist in an equilibrium between the monomeric and dimeric form in solution, and, due to the low dimerization energy, as either monomers or dimers in the solid state, depending on the steric bulk of substituents. [ 2 ] [ 9 ] [ 13 ] [ 14 ] Bulky substituents allow the plumbylene to exist exclusively as monomers. [ 15 ] [ 3 ] [ 14 ] In the dimerization, a Lewis acidic vacant 6p orbital interacts with a weakly Lewis basic 6s lone pair . [ 7 ] [ 16 ]
These diplumbenes possess a trans -bent structure similar to that in lighter, non-carbon congeners ( disilenes , digermylenes , distannylenes ). [ 9 ] The observed Pb–Pb bond lengths in diplumbenes (2.90 – 3.53 Å) have been found to typically be longer than those in tetravalent diplumbanes R 3 PbPbR 3 (2.84 – 2.97 Å). [ 14 ] This, together with the low computed dimerization energy (energy released from the formation of dimers from monomers) of 24 kJ mol −1 for Pb 2 H 4 , [ 17 ] indicates weak multiple bonding . This counterintuitive result is due to the pair of 6s-6p donor-acceptor interactions representing the Pb=Pb double bond in diplumbenes being less energetically favourable compared to the overlap of sp n orbitals (with a higher degree of hybridization than in diplumbenes) in the Pb–Pb single bond in diplumbanes. [ 14 ]
Monohalogenated plumbylenes dimerize by formation of bridging halide. The halogen donate a lone pair into the vacant 6p orbital of a second lead atom. Again, sufficiently bulky substituents on lead can sterically block this dimerization mode. [ 2 ]
Due to decreasing dimerization energy down Group 14, while monohalogenated stannylenes and plumbylenes dimerize via the halogen-bridging mode, monohalogenated silylenes and germylenes tend to dimerize via the abovementioned multiply-bonded mode instead. [ 2 ]
N -heterocyclic plumbylene also dimerize leading to C–H activation, existing in solution in an equilibrium between the monomer and a dimer resulting from cleavage of an aryl C–H bond and formation of Pb–C and N–H bonds. [ 18 ]
Plumbylenes may be stabilized by electron donation into the vacant orbital of the lead atom. The two common intramolecular modes are resonance from a lone pair on the atom directly attached to the lead or by coordination from a Lewis base elsewhere in the molecule. [ 19 ]
For example, Group 15 or 16 elements directly adjacent to Pb donate a lone pair in manner similar to their stabilizing effect on Fisher carbenes . [ 2 ] [ 4 ] [ 20 ] [ 21 ] Common examples of more remote electron-donors include nitrogen atoms that can lead to a six-memberd ring by bonding to the lead. [ 19 ] Even a fluorine atom on a remote trifluoromethyl group has been seen forming a coordination to lead in [2,4,6-(CF 3 ) 3 C 6 H 2 ] 2 Pb. [ 22 ]
Agostic interactions have also been shown to stabilize plumbylenes. DFT computations on the compounds [(R(CH 3 ) 2 Si){(CH 3 ) 2 P(BH 3 )}CH] 2 Pb (R = Me or Ph) found that agostic interactions between bonding B–H orbitals and the vacant 6p orbital lowered the energy of the molecule by ca. 38 kcal mol −1 ; this was supported by X-ray crystal structures showing the favourable positioning of said B–H bonds in proximity of Pb. [ 23 ]
As previously mentioned, unstabilized plumbylenes are prone to polymerization and disproportionation, and plumbylenes without bulky substituents tend to dimerize in one of two modes. Below, the reactions of stabilized plumbylenes (at least at the temperatures at which they were studied) are listed.
Plumbylenes are Lewis acidic via the vacant 6p orbital and tend to form adducts with Lewis bases, such as trimethylamine N -oxide (Me 3 NO), [ 24 ] 1-azidoadamantane (AdN 3 ), [ 25 ] and mesityl azide (MesN 3 ). [ 24 ] In contrast, the reaction between stannylenes and Me 3 NO produces the corresponding distannoxane (from oxidation of Sn(II) to Sn(IV)) instead of the Lewis adduct, which can be attributed to tin being a period above Pb, experiencing the inert pair effect to a lesser degree and hence having a higher susceptibility to oxidation. [ 26 ]
In reactions with azides, the precise nature of adducts depends on the moieties near the lead(II) center. A nearby phosphorus atom also acts as a Lewis base, and in the known instance forms a bridging ring; [ 25 ] absent such an atom, the azide evolves N 2 to form a nitrene, which then inserts into a C-H bond of an arene substituent and coordinates to Pb as an amine base. [ 24 ]
Similar to carbenes [ 27 ] and other Group 14 congeners, [ 2 ] plumbylenes have been shown to undergo insertion reactions, specifically into C–X (X = Br, I) and Group 16 E–E (E = S, Se) bonds. [ 6 ]
Insertions into lead-substituent bonds can also occur. 27 In the examples below, insertion is accompanied by intramolecular rearrangement to place more electron-donating heteroatoms next to the electron-deficient lead. 27
Plumbylenes are known to undergo nucleophilic substitution with organometallic reagents to form transmetallated products. 28 In an unusual example, the use of TlPF 6 , bearing the weakly coordinating anion PF 6 − , led to the formation of crystals of an oligonuclear lead compound with a chain structure upon work-up, highlighting the interesting reactivity of plumbylenes. 28
In addition, plumbylenes can also undergo metathesis with group 13 E(CH 3 ) 3 (E = Al, Ga ) compounds. [ 15 ]
Plumbylenes bearing different substituents can also undergo transmetallation and exchange substituents, with the driving force being the relief of steric strain and the low Pb-C bond dissociation energy . [ 28 ]
Plumbylenes can be used as concurrent σ-donor-σ-acceptor ligands to metal complexes , functioning as σ-donor via its filled 6s orbital and σ-acceptor via its empty 6p orbital. [ citation needed ]
Room temperature-stable plumbylenes have also been suggested as precursors in chemical vapour deposition (CVD) and atomic layer deposition (ALD) of lead-containing materials. [ 29 ] Dithioplumbylenes and dialkoxyplumbylenes may be useful as precursors for preparing the semiconductor material lead sulphide and piezoelectric PZT respectively. [ 30 ] | https://en.wikipedia.org/wiki/Pb2H4 |
Naples yellow , also called antimony yellow or lead antimonate yellow , is an inorganic pigment that largely replaced lead-tin-yellow and has been used in European paintings since the seventeenth century. [ 2 ] [ 3 ] : 219 While the mineral orpiment is considered to be the oldest yellow pigment, Naples yellow, like Egyptian blue , is one of the oldest known synthetic pigments. [ 4 ] [ 3 ] : 219 Naples yellow was used in ancient Egypt and Mesopotamia, finding widespread application during the Hellenistic and Roman periods. [ 3 ] : 221 Prior to its earliest occurrences in European paintings, the pigment was commonly employed in pottery, glazes, enamels, and glass. [ 3 ] : 225 The pigment ranged in hue from a muted, earthy, reddish yellow to a bright light yellow.
A Latin treatise from the late 17th century by Andrea Pozzo referred to the pigment as luteolum napolitanum, which is the first recorded use of the term "Naples yellow"; its English name first appeared in print in 1738. [ 5 ] : 76 [ 6 ] Naples yellow originally referred to the chemical compound lead antimonate (Pb 2 Sb 2 O 7 ), but by the middle of the nineteenth century, a majority of manufacturers had stopped producing pure lead antimonate. [ 3 ] : 219 Since then, writers and artists have incorrectly used Naples yellow to refer to other lead-based yellows. [ 7 ] The related mineral of lead antimonate is bindheimite . However, this natural version was rarely employed as a pigment. After 1800, Naples yellow was superseded by chrome yellow ( lead chromate ) cadmium sulfide , and cobalt yellow . [ 2 ]
Naples yellow is one of the earliest synthetic pigments, its earliest uses dating from the period between the sixteenth and fourteenth century BC in ancient Egypt and Mesopotamia . [ 3 ] : 219 Traces of Naples yellow have been discovered on glass fragments, glazed bricks, and glazed tiles from these ancient civilizations. [ 3 ] : 221 Since its basic components, such as lead oxide and antimony oxide , had to be chemically manufactured, its early production would have required a high level of knowledge and skill. [ 5 ] : 77 Early color theorists speculated that Naples yellow had originated from Naples or Italy's Mount Vesuvius . [ 6 ] It was not until the late eighteenth century that Naples yellow was generally recognized as a synthetic pigment of lead antimonate. [ 6 ]
The Italians first adopted Naples yellow as an enamel for tin-glazed pottery, or maiolica , from the beginning of the sixteenth century. [ 3 ] : 221 The pigment then started to appear in European paintings, and between 1750 and 1850, when it achieved greater popularity in the art world. [ 3 ] : 226 "Naples yellow" was a phrase that was first used in a treatise on frescos by Andrea Pozzo , published in Rome between 1693 and 1700. There, Pozzo refers to Naples yellow as luteolum napolitanum. [ 5 ] : 76 By 1850, Naples yellow was sold in a variety of shades, such as French Naples yellow. [ 3 ] : 223 Manufacturers like C. Roberson and Co. produced Naples yellow until 1885. [ 3 ] : 231 However, its popularity declined and it was progressively replaced by other yellow pigments like lead chromate and cadmium sulfide . [ 3 ] : 226 Manufacturers today typically produce Naples yellow in combination with other pigments, such as ochre , iron oxide , lead white , titanium white , or zinc white , rather than pure lead antimonate. [ 3 ] : 245
Naples yellow is a saturated yellow, occasionally with pink or off-white hues. [ 9 ] It has a strong hiding power and effectively covers other pigments. [ 9 ] Temperature during production affects its hue. A more vibrant lemon-yellow is produced at higher temperatures, whereas an orange-yellow is produced at lower temperatures. [ 3 ] : 227 Some manufacturers also note that there are six different shades of Naples yellow, ranging from a greenish yellow to a pinkish orange yellow. [ 3 ] : 227
Naples yellow is not a stable pigment. [ 5 ] : 76 It is susceptible to discoloration in humid air. George Field warned that Naples yellow can turn black. [ 5 ] : 77 Naples yellow can also discolor in the presence of iron. [ 3 ] : 227 Field therefore advised artists to use a palette knife made of ivory or horn, not metal. [ 5 ] : 77
Naples yellow was frequently used in ancient times to glaze pottery and glass. A piece of glass from the site of Amenhotep II 's palace at Thebes (now at the Victoria and Albert Museum) is one of the earliest known examples. [ 3 ] : 248 Naples yellow has frequently appeared on the palettes of European painters such as Anton Raphael Mengs , Francisco Goya , Jacques-Louis-David , Jean-Auguste-Dominique Ingres , Eugène Delacroix , and Paul Cézanne . [ 3 ] : 245 The earliest occurrence of Naples yellow in European art is Matthias Stom 's Arrest of Christ. [ 3 ] : 223 | https://en.wikipedia.org/wiki/Pb2Sb2O7 |
Berryite is a mineral with the formula Pb 3 (Ag,Cu) 5 Bi 7 S 16 . It occurs as gray to blue-gray monoclinic prisms. It is opaque and has a metallic luster . It has a Mohs hardness of 3.5 and a specific gravity of 6.7.
It was first identified in 1965 using X-ray diffraction by mineralogist Leonard Gascoigne Berry (1914–1982). It is found in Park and San Juan counties in Colorado . It occurs in sulfide bearing quartz veins in Colorado and with siderite -rich cryolite in Ivigtut, Greenland .
This article about a specific sulfide mineral is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Pb3(Ag,Cu)5Bi7S16 |
Lead(II) phosphate is an ionic compound with chemical formula Pb 3 ( P O 4 ) 2 . Lead(II) phosphate is a long-lived electronically neutral reagent chemical. [ 2 ] Despite limited tests on humans, it has been identified as a carcinogen based on tests on animals conducted by the EPA . [ 3 ] Lead(II) phosphate appears as hexagonal, colorless crystals or as a white powder. Lead(II) phosphate is insoluble in water and alcohol but soluble in nitric acid (HNO 3 ) and fused alkali metal hydroxides. When lead(II) phosphate is heated for decomposition it emits very toxic fumes containing Lead (Pb) and PO x . [ 4 ]
It is prepared by reacting lead(II) hydroxide with orthophosphoric acid .
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Pb3(PO4)2 |
Lead(II,IV) oxide , also called red lead or minium , is the inorganic compound with the formula Pb 3 O 4 . A bright red or orange solid, it is used as pigment , in the manufacture of batteries , and rustproof primer paints . It is an example of a mixed valence compound , being composed of both Pb(II) and Pb(IV) in the ratio of two to one. [ 2 ]
Lead(II,IV) oxide is lead(II) orthoplumbate(IV) [Pb 2+ ] 2 [PbO 4− 4 ] . [ 3 ] It has a tetragonal crystal structure at room temperature , which then transforms to an orthorhombic ( Pearson symbol oP 28, Space group Pbam, No. 55) form at temperature 170 K (−103 °C). This phase transition only changes the symmetry of the crystal and slightly modifies the interatomic distances and angles. [ 4 ]
Lead(II,IV) oxide is prepared by calcination of lead(II) oxide (PbO; also called litharge ) in air at about 450–480 °C: [ 5 ]
The resulting material is contaminated with PbO. If a pure compound is desired, PbO can be removed by a potassium hydroxide solution:
Another method of preparation relies on annealing of lead(II) carbonate ( cerussite ) in air:
Yet another method is oxidative annealing of white lead :
In solution, lead(II,IV) oxide can be prepared by reaction of potassium plumbate with lead(II) acetate , yielding yellow insoluble lead(II,IV) oxide monohydrate Pb 3 O 4 ·H 2 O , which can be turned into the anhydrous form by gentle heating:
Natural minium is uncommon, forming only in extreme oxidizing conditions of lead ore bodies. The best known natural specimens come from Broken Hill , New South Wales , Australia, where they formed as the result of a mine fire . [ 6 ]
Red lead is virtually insoluble in water and in ethanol . However, it is soluble in hydrochloric acid present in the stomach , and is therefore toxic when ingested. It also dissolves in glacial acetic acid and a diluted mixture of nitric acid and hydrogen peroxide .
When heated to 500 °C, it decomposes to lead(II) oxide and oxygen. At 580 °C, the reaction is complete.
Nitric acid dissolves the lead(II) oxide component, leaving behind the insoluble lead(IV) oxide :
With iron oxides and with elemental iron , lead(II,IV) oxide forms insoluble iron(II) and iron(III) plumbates , which is the basis of the anticorrosive properties of lead-based paints applied to iron objects.
Red lead has been used as a pigment for primer paints for iron objects. Due to its toxicity , its use is being limited. It finds limited use in some amateur pyrotechnics as a delay charge and was used in the past in the manufacture of dragon's egg pyrotechnic stars .
Red lead is used as a curing agent in some polychloroprene rubber compounds. It is used in place of magnesium oxide to provide better water resistance properties.
Red lead was used for engineer's scraping , before being supplanted by engineer's blue . Although red lead still offers more accurate markings since it doesn't flow as readily as engineer's blue under pressure.
It is also used as an adulterating agent in turmeric powder .
When inhaled, lead(II,IV) oxide irritates the lungs. In case of high dose, the victim experiences a metallic taste, chest pain, and abdominal pain. When ingested, it is dissolved in the gastric acid and absorbed, leading to lead poisoning . High concentrations can be absorbed through skin as well, and it is important to follow safety precautions when working with lead-based paint.
Long-term contact with lead(II,IV) oxide may lead to accumulation of lead compounds in organisms, with development of symptoms of acute lead poisoning. Chronic poisoning displays as agitation, irritability, vision disorders, hypertension , and a grayish facial hue.
Lead(II,IV) oxide was shown to be carcinogenic for laboratory animals . Its carcinogenicity for humans was not proven.
This compound's Latin name minium originates from the Minius , a river in northwest Iberia where it was first mined.
Lead(II,IV) oxide was used as a red pigment in ancient Rome , where it was prepared by calcination of white lead . In the ancient and medieval periods it was used as a pigment in the production of illuminated manuscripts , and gave its name to the minium or miniature , a style of picture painted with the colour.
Made into a paint with linseed oil , red lead was used as a durable paint to protect exterior ironwork. In 1504 the portcullis at Stirling Castle in Scotland was painted with red lead, as were cannons including Mons Meg . [ 7 ]
As a finely divided powder, it was also sprinkled on dielectric surfaces to study Lichtenberg figures .
In traditional Chinese medicine , red lead is used to treat ringworms and ulcerations , though the practice is limited due to its toxicity. Also, azarcón , a Mexican folk remedy for gastrointestinal disorders, contains up to 95% lead(II,IV) oxide. [ 8 ]
It was also used before the 18th century as medicine. [ 9 ] | https://en.wikipedia.org/wiki/Pb3O4 |
Lead(II) bromide is the inorganic compound with the formula PbBr 2 . It is a white powder. It is produced in the burning of typical leaded gasolines. [ 4 ]
It is typically prepared from treating solutions of lead salts (e.g., ( lead(II) nitrate ) with bromide salts. This process exploits its low solubility in water - only 0.455 g dissolves in 100 g of water at 0 °C. It is about ten times more soluble in boiling water. [ 5 ]
PbBr 2 has the same crystal structure as lead chloride ( cotunnite ) – they are isomorphous . In this structure, Pb 2+ is surrounded by nine Br − ions in a distorted tricapped trigonal prismatic geometry. Seven of the Pb-Br distances are shorter, in the range 2.9-3.3 Å, while two of them are longer at 3.9 Å. The coordination is therefore sometimes described as (7+2). [ 6 ] [ 3 ]
Lead bromide was prevalent in the environment as the result of the use of leaded gasoline. Tetraethyl lead was once widely used to improve the combustion properties of gasoline. To prevent the resulting lead oxides from fouling the engine, gasoline was treated with 1,2-Dibromoethane , which converted lead oxides into the more volatile lead bromide, which was then exhausted from the engine into the environment. [ 4 ]
Like other compounds containing lead, lead(II) bromide is categorized as probably carcinogenic to humans (Category 2A), by the International Agency for Research on Cancer (IARC). Its release into the environment as a product of leaded gasoline was highly controversial. | https://en.wikipedia.org/wiki/PbBr2 |
Soluble in hot water as well as in presence of alkali hydroxide
Soluble in concentrated HCl (>6M)
Lead(II) chloride (PbCl 2 ) is an inorganic compound which is a white solid under ambient conditions. It is poorly soluble in water. Lead(II) chloride is one of the most important lead -based reagents . It also occurs naturally in the form of the mineral cotunnite .
In solid PbCl 2 , each lead ion is coordinated by nine chloride ions in a tricapped triangular prism formation — six lie at the vertices of a triangular prism and three lie beyond the centers of each rectangular prism face. The 9 chloride ions are not equidistant from the central lead atom, 7 lie at 280–309 pm and 2 at 370 pm. [ 6 ] PbCl 2 forms white orthorhombic needles.
In the gas phase, PbCl 2 molecules have a bent structure with the Cl–Pb–Cl angle being 98° and each Pb–-Cl bond distance being 2.44 Å. [ 7 ] Such PbCl 2 is emitted from internal combustion engines that use ethylene chloride- tetraethyllead additives for antiknock purposes.
PbCl 2 is sparingly soluble in water, solubility product K sp = 1.7 × 10 −5 at 20 °C. It is one of only 5 commonly water-insoluble chlorides, the other 4 being thallium(I) chloride , silver chloride (AgCl) with K sp = 1.8 × 10 −10 , copper(I) chloride (CuCl) with K sp = 1.72 × 10 −7 and mercury(I) chloride (Hg 2 Cl 2 ) with K sp = 1.3 × 10 −18 . [ 8 ] [ 9 ]
Solid lead(II) chloride precipitates upon addition of aqueous chloride sources (HCl, NaCl, KCl) to aqueous solutions of lead (II) compounds, such as lead(II) nitrate and lead(II) acetate :
It also forms by treatment of basic lead(II) compounds such as Lead(II) oxide and lead(II) carbonate .
Lead dioxide is reduced by chloride as follows:
It also formed by the oxidation of lead metal by copper(II) chloride :
Or most straightforwardly by the action of chlorine gas on lead metal:
Addition of chloride ions to a suspension of PbCl 2 gives rise to soluble complex ions. In these reactions the additional chloride (or other ligands ) break up the chloride bridges that comprise the polymeric framework of solid PbCl 2(s) .
PbCl 2 reacts with molten NaNO 2 to give PbO :
PbCl 2 is used in synthesis of lead(IV) chloride (PbCl 4 ): Cl 2 is bubbled through a saturated solution of PbCl 2 in aqueous NH 4 Cl forming [NH 4 ] 2 [PbCl 6 ]. The latter is reacted with cold concentrated sulfuric acid (H 2 SO 4 ) forming PbCl 4 as an oil. [ 10 ]
Lead(II) chloride is the main precursor for organometallic derivatives of lead, such as plumbocenes . [ 11 ] The usual alkylating agents are employed, including Grignard reagents and organolithium compounds:
These reactions produce derivatives that are more similar to organosilicon compounds, i.e. that Pb(II) tends to disproportionate upon alkylation.
PbCl 2 can be used to produce PbO 2 by treating it with sodium hypochlorite (NaClO), forming a reddish-brown precipitate of PbO 2 .
Like other soluble lead compounds, exposure to PbCl 2 may cause lead poisoning . | https://en.wikipedia.org/wiki/PbCl2 |
Lead tetrachloride , also known as lead(IV) chloride , has the molecular formula PbCl 4 . It is a yellow, oily liquid which is stable below 0 °C, and decomposes at 50 °C. [ 2 ] It has a tetrahedral configuration , with lead as the central atom. The Pb– Cl covalent bonds have been measured to be 247 pm and the bond energy is 243 kJ⋅mol −1 . [ 4 ]
Lead tetrachloride can be made by reacting lead(II) chloride PbCl 2 , and hydrochloric acid HCl, in the presence of chlorine gas (Cl 2 ), [ 5 ] leading to the formation of chloroplumbic acid H 2 PbCl 6 . It is then converted to the ammonium salt (NH 4 ) 2 PbCl 6 by adding ammonium chloride (NH 4 Cl). Finally, the solution is treated with concentrated sulfuric acid H 2 SO 4 , to separate out lead tetrachloride. This series of reactions is conducted at 0 °C. The following equations illustrate the reaction:
Unlike carbon tetrachloride , another group IV (IUPAC: group 14) chloride, lead tetrachloride reacts with water . This is because the central atom is bigger (Pb is bigger than C ) so there is less cluttering and water can easily access it. [ 3 ] Also, because of the presence of empty d orbitals on the Pb atom, oxygen can bind to it before a Pb–Cl bond has to break, thus requiring less energy . The overall reaction is thus as follow:
Lead tetrachloride tends to decompose further into lead dichloride and chlorine gas: [ 3 ]
There are reports that this reaction can proceed explosively and that the compound is best stored under pure sulfuric acid at -80 °C in the dark. [ 6 ]
The stability of the +4 oxidation state decreases as we travel down this group of the periodic table. [ 3 ] Thus while carbon tetrachloride is a stable compound, with lead the oxidation state +2 is favored and PbCl 4 quickly becomes PbCl 2 . Indeed, the inert pair effect causes lead to favor its +2 oxidation state: Pb atom loses all its outermost p electrons and ends up with a stable, filled s subshell. [ 7 ]
Lead is a cumulative poison . [ 4 ] Only limited evidence have been shown of lead's carcinogenic effect, but lead tetrachloride, as well as all other lead compounds, is "reasonably anticipated to be human carcinogens" according to the Report on Carcinogens , Twelfth Edition (2011). [ 8 ] Lead can be absorbed by the body through several routes, primarily inhalation but also ingestion and dermal contact. Lead compounds are also teratogens . [ 9 ] | https://en.wikipedia.org/wiki/PbCl4 |
Lead(II) chromate is an inorganic compound with the chemical formula Pb Cr O 4 . It is a bright yellow salt that is very poorly soluble in water. It occurs also as the mineral crocoite . It is used as a pigment.
Two polymorphs of lead chromate are known, orthorhombic and the more stable monoclinic form. Monoclinic lead chromate is used in paints under the name chrome yellow , and many other names. [ 2 ] Lead chromate adopts the monazite structure, meaning that the connectivity of the atoms is very similar to other compounds of the type MM'O 4 . Pb(II) has a distorted coordination sphere being surrounded by eight oxides with Pb-O distances ranging from 2.53 to 2.80 Å. The chromate anion is tetrahedral, as usual. [ 3 ] Unstable polymorphs of lead chromate are the greenish yellow orthorhombic form and a red-orange tetragonal form. [ 2 ]
Approximately 37,000 tons were produced in 1996. The main applications are as a pigment in paints, under the name chrome yellow . [ 6 ]
Lead(II) chromate can be produced by treating sodium chromate with lead salts such as lead(II) nitrate or by combining lead(II) oxide with chromic acid .
Related lead sulfochromate pigments are produced by the replacement of some chromate by sulfate, resulting in a mixed lead-chromate-sulfate compositions Pb(CrO 4 ) 1− x (SO 4 ) x . This replacement is possible because sulfate and chromate are isostructural. Since sulfate is colorless, sulfochromates with high values of x are less intensely colored than lead chromate. [ 6 ] In some cases, chromate is replaced by molybdate . [ 2 ]
Heating in hydroxide solution produces chrome red , a red or orange powder made by PbO and CrO 3 . Also, in hydroxide solution lead chromate slowly dissolves forming plumbite complex.
Despite containing both lead and hexavalent chromium , lead chromate is not acutely lethal because of its very low solubility. The LD50 for rats is only 5,000 mg/kg. [ clarification needed ] Lead chromate must be treated with great care in its manufacture, the main concerns being dust of the chromate precursor. Lead chromate is highly regulated in advanced countries. As one of the greatest threats comes from inhalation of particles, so much effort has been devoted to production of low-dust forms of the pigment. [ 2 ]
In the 1800s, the product was used to impart a bright yellow color to some types of candy . [ 7 ] It is used (illegally) to enhance the color of certain spices, particularly turmeric , [ 8 ] [ 9 ] particularly in Bangladesh. [ 10 ] [ 11 ]
Unlike other lead-based paint pigments, lead chromate is still widely used, especially in road marking paint. [ 12 ]
In 2023 and 2024, consumption of adulterated cinnamon [ 13 ] led to at least 136 cases of lead toxicity in children in the United States as reported by the US Centers for Disease Control and Prevention . [ 14 ] The affected products were recalled. [ 13 ] The US Food and Drug Administration determined that the ratio of lead to chromium in the cinammon indicated that lead chromate had been added to the cinnamon. [ 13 ] | https://en.wikipedia.org/wiki/PbCrO4 |
Lead(II) fluoride is the inorganic compound with the formula Pb F 2 . It is a white solid. The compound is polymorphic , at ambient temperatures it exists in orthorhombic (PbCl 2 type) form, while at high temperatures it is cubic ( Fluorite type ). [ 2 ]
Lead(II) fluoride can be prepared by treating lead(II) hydroxide or lead(II) carbonate with hydrofluoric acid : [ 3 ]
Alternatively, it is precipitated by adding hydrofluoric acid to a lead(II) salt solution, or by adding a fluoride salt to a lead salt, such as potassium fluoride to a lead(II) nitrate solution, [ 4 ]
or sodium fluoride to a lead(II) acetate solution.
It appears as the very rare mineral fluorocronite . [ 5 ] [ 6 ]
Lead(II) fluoride is used in low melting glasses , in glass coatings to reflect infrared rays, in phosphors for television-tube screens, and as a catalyst for the manufacture of picoline . [ 3 ] The Muon g−2 experiment uses PbF 2 crystals in conjunction with silicon photomultipliers . High energy charged particles create Cerenkov light as they pass through the crystals, which is measured by the silicon photomultipliers. [ 7 ] [ 8 ]
It also serves as an oxygen scavenger in high-temperature fluorine chemistry , as plumbous oxide is relatively volatile . [ 9 ] | https://en.wikipedia.org/wiki/PbF2 |
Lead tetrafluoride is a compound of lead and fluorine . The yellow solid (melting point 600 °C) is the only room-temperature stable tetrahalide of lead. [ 3 ] Lead tetrafluoride is isostructural with tin(IV) fluoride and contains planar layers of octahedrally coordinated lead, where the octahedra share four corners and there are two terminal, unshared, fluorine atoms trans to one another. [ 4 ]
This inorganic compound –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/PbF4 |
Lead(II) iodide (or lead iodide ) is a chemical compound with the formula PbI 2 . At room temperature , it is a bright yellow odorless crystalline solid, that becomes orange and red when heated. [ 11 ] It was formerly called plumbous iodide .
The compound currently has a few specialized applications, such as the manufacture of solar cells , [ 12 ] X-rays and gamma-ray detectors. [ 13 ] Its preparation is an entertaining and popular demonstration in chemistry education, to teach topics such as precipitation reactions and stoichiometry . [ 14 ] It is decomposed by light at temperatures above 125 °C (257 °F), and this effect has been used in a patented photographic process. [ 4 ] [ 15 ]
Lead iodide was formerly employed as a yellow pigment in some paints, with the name iodide yellow . However, that use has been largely discontinued due to its toxicity and poor stability. [ 16 ]
PbI 2 is commonly synthesized via a precipitation reaction between potassium iodide KI and lead(II) nitrate Pb ( NO 3 ) 2 in water solution:
While the potassium nitrate KNO 3 is soluble, the lead iodide PbI 2 is nearly insoluble at room temperature , and thus precipitates out. [ 17 ]
Other soluble compounds containing lead(II) and iodide can be used instead, for example lead(II) acetate [ 12 ] and sodium iodide .
The compound can also be synthesized by reacting iodine vapor with molten lead between 500 and 700 °C. [ 18 ]
A thin film of PbI 2 can also be prepared by depositing a film of lead sulfide PbS and exposing it to iodine vapor, by the reaction
The sulfur is then washed with dimethyl sulfoxide . [ 19 ]
Lead iodide prepared from cold solutions usually consists of many small hexagonal platelets, giving the yellow precipitate a silky appearance. Larger crystals can be obtained by exploiting the fact that solubility of lead iodide in water (like those of lead chloride and lead bromide ) increases dramatically with temperature. The compound is colorless when dissolved in hot water, but crystallizes on cooling as thin but visibly larger bright yellow flakes, that settle slowly through the liquid — a visual effect often described as "golden rain". [ 20 ] Larger crystals can be obtained by autoclaving the PbI 2 with water under pressure at 200 °C. [ 21 ]
Even larger crystals can be obtained by slowing down the common reaction. A simple setup is to submerge two beakers containing the concentrated reactants in a larger container of water, taking care to avoid currents. As the two substances diffuse through the water and meet, they slowly react and deposit the iodide in the space between the beakers. [ 22 ]
Another similar method is to react the two substances in a gel medium, that slows down the diffusion and supports the growing crystal away from the container's walls. Patel and Rao have used this method to grow crystals up to 30 mm in diameter and 2 mm thick. [ 23 ]
The reaction can be slowed also by separating the two reagents with a permeable membrane. This approach, with a cellulose membrane, was used in September 1988 to study the growth of PbI 2 crystals in zero gravity, in an experiment flown on the Space Shuttle Discovery . [ 24 ]
PbI 2 can also be crystallized from powder by sublimation at 390 °C, in near vacuum [ 25 ] or in a current of argon with some hydrogen . [ 26 ]
Large high-purity crystals can be obtained by zone melting or by the Bridgman–Stockbarger technique . [ 18 ] [ 25 ] These processes can remove various impurities from commercial PbI 2 . [ 27 ]
Lead iodide is a precursor material in the fabrication of highly efficient Perovskite solar cell . Typically, a solution of PbI 2 in an organic solvent, such as dimethylformamide or dimethylsulfoxide, is applied over a titanium dioxide layer by spin coating . The layer is then treated with a solution of methylammonium iodide CH 3 NH 3 I and annealed , turning it into the double salt methylammonium lead iodide CH 3 NH 3 PbI 3 , with a perovskite structure. The reaction changes the film's color from yellow to light brown. [ 12 ]
PbI 2 is also used as a high-energy photon detector for gamma-rays and X-rays, due to its wide band gap which ensures low noise operation. [ 4 ] [ 13 ] [ 25 ]
Lead iodide was formerly used as a paint pigment under the name "iodine yellow". It was described by Prosper Mérimée (1830) as "not yet much known in commerce, is as bright as orpiment or chromate of lead . It is thought to be more permanent; but time only can prove its pretension to so essential a quality. It is prepared by precipitating a solution of acetate or nitrate of lead, with potassium iodide: the nitrate produces a more brilliant yellow color." [ 16 ] However, due to the toxicity and instability of the compound it is no longer used as such. [ 16 ] It may still be used in art for bronzing and in gold-like mosaic tiles. [ 4 ]
Common material characterization techniques such as electron microscopy can damage samples of lead(II) iodide. [ 28 ] Thin films of lead(II) iodide are unstable in ambient air. [ 29 ] Ambient air oxygen oxidizes iodide into elemental iodine :
Lead iodide is very toxic to human health. Ingestion will cause many acute and chronic consequences characteristic of lead poisoning . [ 30 ] Lead iodide has been found to be a carcinogen in animals suggesting the same may hold true in humans. [ 31 ] Lead iodide is an inhalation hazard, and appropriate respirators should be used when handling powders of lead iodide.
The structure of PbI 2 , as determined by X-ray powder diffraction , is primarily hexagonal close-packed system with alternating between layers of lead atoms and iodide atoms, with largely ionic bonding. Weak van der Waals interactions have been observed between lead–iodide layers. [ 13 ] The most common stacking forms are 2H and 4H. The 4H polymorph is most common in samples grown from the melt, by precipitation, or by sublimation, whereas the 2H polymorph is usually formed by sol-gel synthesis. [ 9 ] The solid can also take an R6 rhombohedral structure. [ 32 ] | https://en.wikipedia.org/wiki/PbI2 |
Lead(IV) oxide , commonly known as lead dioxide , is an inorganic compound with the chemical formula PbO 2 . It is an oxide where lead is in an oxidation state of +4. [ 1 ] It is a dark-brown solid which is insoluble in water. [ 2 ] It exists in two crystalline forms. It has several important applications in electrochemistry , in particular as the positive plate of lead acid batteries .
Lead dioxide has two major polymorphs, alpha and beta, which occur naturally as rare minerals scrutinyite and plattnerite , respectively. Whereas the beta form had been identified in 1845, [ 3 ] α- PbO 2 was first identified in 1946 and found as a naturally occurring mineral 1988. [ 4 ]
The alpha form has orthorhombic symmetry, space group Pbcn (No. 60), Pearson symbol oP 12, lattice constants a = 0.497 nm, b = 0.596 nm, c = 0.544 nm, Z = 4 (four formula units per unit cell). [ 4 ] The lead atoms are six-coordinate.
The symmetry of the beta form is tetragonal , space group P4 2 /mnm (No. 136), Pearson symbol tP 6, lattice constants a = 0.491 nm, c = 0.3385 nm, Z = 2 [ 5 ] and related to the rutile structure and can be envisaged as containing columns of octahedra sharing opposite edges and joined to other chains by corners. This contrasts with the alpha form where the octahedra are linked by adjacent edges to give zigzag chains. [ 4 ]
Lead dioxide decomposes upon heating in air as follows:
The stoichiometry of the end product can be controlled by changing the temperature – for example, in the above reaction, the first step occurs at 290 °C, second at 350 °C, third at 375 °C and fourth at 600 °C. In addition, Pb 2 O 3 can be obtained by decomposing PbO 2 at 580–620 °C under an oxygen pressure of 1,400 atm (140 MPa). Therefore, thermal decomposition of lead dioxide is a common way of producing various lead oxides. [ 6 ]
Lead dioxide is an amphoteric compound with prevalent acidic properties. It dissolves in strong bases to form the hydroxy plumbate ion, [Pb(OH) 6 ] 2− : [ 2 ]
It also reacts with basic oxides in the melt, yielding orthoplumbates M 4 [PbO 4 ] .
Because of the instability of its Pb 4+ cation, lead dioxide reacts with hot acids, converting to the more stable Pb 2+ state and liberating oxygen: [ 6 ]
However these reactions are slow.
Lead dioxide is well known for being a good oxidizing agent , with an example reactions listed below: [ 7 ]
Although the formula of lead dioxide is nominally given as PbO 2 , the actual oxygen to lead ratio varies between 1.90 and 1.98 depending on the preparation method. Deficiency of oxygen (or excess of lead) results in the characteristic metallic conductivity of lead dioxide, with a resistivity as low as 10 −4 Ω·cm and which is exploited in various electrochemical applications. Like metals, lead dioxide has a characteristic electrode potential , and in electrolytes it can be polarized both anodically and cathodically . Lead dioxide electrodes have a dual action, that is both the lead and oxygen ions take part in the electrochemical reactions. [ 8 ]
Lead dioxide is produced commercially by several methods, which include oxidation of red lead ( Pb 3 O 4 ) in alkaline slurry in a chlorine atmosphere, [ 6 ] reaction of lead(II) acetate with "chloride of lime" ( calcium hypochlorite ), [ 9 ] [ 10 ] The reaction of Pb 3 O 4 with nitric acid also affords the dioxide: [ 2 ] [ 11 ]
PbO 2 reacts with sodium hydroxide to form the hexahydroxoplumbate(IV) ion [Pb(OH) 6 ] 2− , soluble in water.
An alternative synthesis method is electrochemical : lead dioxide forms on pure lead, in dilute sulfuric acid , when polarized anodically at electrode potential about +1.5 V at room temperature. This procedure is used for large-scale industrial production of PbO 2 anodes. Lead and copper electrodes are immersed in sulfuric acid flowing at a rate of 5–10 L/min. The electrodeposition is carried out galvanostatically , by applying a current of about 100 A/m 2 for about 30 minutes.
The drawback of this method for the production of lead dioxide anodes is its softness, especially compared to the hard and brittle PbO 2 which has a Mohs hardness of 5.5. [ 12 ] This mismatch in mechanical properties results in peeling of the coating which is preferred for bulk PbO 2 production. Therefore, an alternative method is to use harder substrates, such as titanium , niobium , tantalum or graphite and deposit PbO 2 onto them from lead(II) nitrate in static or flowing nitric acid. The substrate is usually sand-blasted before the deposition to remove surface oxide and contamination and to increase the surface roughness and adhesion of the coating. [ 13 ]
Lead dioxide is used in the production of matches , pyrotechnics , dyes and the curing of sulfide polymers . It is also used in the construction of high-voltage lightning arresters . [ 6 ]
Lead dioxide is used as an anode material in electrochemistry. β- PbO 2 is more attractive for this purpose than the α form because it has relatively low resistivity , good corrosion resistance even in low- pH medium, and a high overvoltage for the evolution of oxygen in sulfuric- and nitric-acid-based electrolytes. Lead dioxide can also withstand chlorine evolution in hydrochloric acid . Lead dioxide anodes are inexpensive and were once used instead of conventional platinum and graphite electrodes for regenerating potassium dichromate . They were also applied as oxygen anodes for electroplating copper and zinc in sulfate baths. In organic synthesis, lead dioxide anodes were applied for the production of glyoxylic acid from oxalic acid in a sulfuric acid electrolyte. [ 13 ]
The most important use of lead dioxide is as the cathode of lead acid batteries . Its utility arises from the anomalous metallic conductivity of PbO 2 . The lead acid battery stores and releases energy by shifting the equilibrium (a comproportionation) between metallic lead, lead dioxide, and lead(II) salts in sulfuric acid .
Lead compounds are poisons . Chronic contact with the skin can potentially cause lead poisoning through absorption, or redness and irritation in the short term. [ 14 ]
PbO 2 is not combustible, but it enhances flammability of other substances and the intensity of the fire. In case of a fire it gives off irritating and toxic fumes. [ 15 ] [ better source needed ]
Lead dioxide is poisonous to aquatic life, but because of its insolubility it usually settles out of water. [ 16 ] [ 15 ] | https://en.wikipedia.org/wiki/PbO2 |
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