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Martinus Willem Beijerinck ( Dutch pronunciation: [mɑrˈtinʏs ˈʋɪləm ˈbɛiərɪŋk] , 16 March 1851 – 1 January 1931) was a Dutch microbiologist and botanist who was one of the founders of virology and environmental microbiology . He is credited with the co-discovery of viruses (1898), which he called " contagium vivum fluidum ".
Born in Amsterdam , Beijerinck studied at the Technical School of Delft, where he was awarded the degree of biology in 1872. He obtained his Doctor of Science degree from the University of Leiden in 1877. [ 1 ]
At the time, Delft, then a Polytechnic , did not have the right to confer doctorates, so Leiden did this for them. He became a teacher in microbiology at the Agricultural School in Wageningen (now Wageningen University ) and later at the Polytechnische Hogeschool Delft (Delft Polytechnic, currently Delft University of Technology ) (from 1895). He established the Delft School of Microbiology. His studies of agricultural and industrial microbiology yielded fundamental discoveries in the field of biology . His achievements have been perhaps unfairly overshadowed by those of his contemporaries, Robert Koch and Louis Pasteur , because unlike them, Beijerinck never actually studied human disease.
In 1877, he wrote his first notable research paper, discussing plant galls . The paper later became the basis for his doctoral dissertation. [ 2 ]
In 1885 he became a member of the Royal Netherlands Academy of Arts and Sciences . [ 3 ]
He is considered one of the founders of virology . [ 4 ] [ 5 ] [ 6 ] [ 7 ] In 1898, he published results on the filtration experiments demonstrating that tobacco mosaic disease is caused by an infectious agent smaller than a bacterium . [ 8 ]
His results were in accordance with the similar observation made by Dmitri Ivanovsky in 1892. [ 9 ] Like Ivanovsky before him and Adolf Mayer , predecessor at Wageningen, Beijerinck could not culture the filterable infectious agent; however, he concluded that the agent can replicate and multiply in living plants. He named the new pathogen virus to indicate its non-bacterial nature. Beijerinck asserted that the virus was somewhat liquid in nature, calling it " contagium vivum fluidum " (contagious living fluid). [ 10 ] It was not until the first crystals of the tobacco mosaic virus (TMV) obtained by Wendell Stanley in 1935, the first electron micrographs of TMV produced in 1939 and the first X-ray crystallographic analysis of TMV performed in 1941 proved that the virus was particulate.
Nitrogen fixation , [ 11 ] the process by which diatomic nitrogen gas is converted to ammonium ions and becomes available to plants, was also investigated by Beijerinck. Bacteria perform nitrogen fixation, dwelling inside root nodules of certain plants ( legumes ). In addition to having discovered a biochemical reaction vital to soil fertility and agriculture , Beijerinck revealed this archetypical example of symbiosis between plants and bacteria .
Beijerinck discovered the phenomenon of bacterial sulfate reduction , a form of anaerobic respiration . He learned bacteria could use sulfate as a terminal electron acceptor, instead of oxygen. This discovery has had an important impact on our current understanding of biogeochemical cycles . Spirillum desulfuricans , now known as Desulfovibrio desulfuricans , [ 12 ] the first known sulfate-reducing bacterium, was isolated and described by Beijerinck.
Beijerinck invented the enrichment culture , a fundamental method of studying microbes from the environment. He is often incorrectly credited with framing the microbial ecology idea that "everything is everywhere, but, the environment selects", which was stated by Lourens Baas Becking . [ 13 ] [ 14 ]
Beijerinck was a socially eccentric figure. He was verbally abusive to students, never married, and had few professional collaborations. He was also known for his ascetic lifestyle and his view of science and marriage being incompatible. His low popularity with his students and their parents periodically depressed him, as he very much loved spreading his enthusiasm for biology in the classroom. After his retirement at the Delft School of Microbiology in 1921, at age 70, he moved to Gorssel where he lived for the rest of his life, together with his two sisters. [ 15 ]
Beijerinckia (a genus of bacteria), [ 16 ] Beijerinckiaceae (a family of Hyphomicrobiales ), and Beijerinck crater are named after him.
The M.W. Beijerinck Virology Prize ( M.W. Beijerinck Virologie Prijs ) is awarded in his honor. | https://en.wikipedia.org/wiki/Martinus_Beijerinck |
Marwencol is a miniature town in Kingston, New York [ 1 ] created by the American artist Mark Hogancamp .
On April 8, 2000, Mark Hogancamp was attacked outside of a bar by five men who beat him nearly to death after he drunkenly told them he was a cross-dresser . [ 1 ] After nine days in a coma and 40 days in the hospital, Hogancamp was discharged with brain damage that left him little memory of his previous life. Unable to afford therapy, he created his own memory by building a 1 ⁄ 6 -scale World War II -era Belgian town in his yard and populating it with dolls representing himself, his friends, and even his attackers. [ 1 ] He called the town "Marwencol", blending his own name with that of a local bartender Wendy and his neighbor Colleen. [ 2 ]
Hogancamp was initially discovered by photographer David Naugle, who documented and shared his story with Esopus magazine, [ 3 ] whereby his work was shown in White Columns art gallery .
The film Marwencol (also known as Village of the Dolls in the UK) [ 4 ] [ 5 ] [ 6 ] is a 2010 American documentary film that explores Hogancamp's life and work. It is the debut feature of director-editor Jeff Malmberg. It was the inspiration for Welcome to Marwen , a 2018 drama directed by Robert Zemeckis and starring Steve Carell as Hogancamp. [ 7 ] [ 8 ]
Welcome to Marwencol is a 2015 art book by Hogancamp and Chris Shellen, published by Princeton Architectural Press , that documents Hogancamp's life and work. It was named one of the best books of 2015 by Amazon.com . [ 9 ] | https://en.wikipedia.org/wiki/Marwencol_(art_installation) |
Mary Everest Boole (11 March 1832 in Wickwar , Gloucestershire – 17 May 1916 in Middlesex , England) was a self-taught mathematician who is best known as an author of didactic works on mathematics, such as Philosophy and Fun of Algebra , and as the wife of fellow mathematician George Boole . Her progressive ideas on education, as expounded in The Preparation of the Child for Science , included encouraging children to explore mathematics through playful activities such as curve stitching . Her life is of interest to feminists as an example of how women made careers in an academic system that did not welcome them. [ 1 ]
Mary Everest was born in England, the daughter of Reverend Thomas Roupell Everest, Rector of Wickwar, and Mary nee Ryall. Her uncle was George Everest , the surveyor and geographer after whom Mount Everest was named. She spent the first part of her life in France where she received an education in mathematics from a private tutor . On returning to England at the age of 11, she continued to pursue her interest in mathematics through self-instruction . Self-taught mathematician George Boole tutored her, and she visited him in Ireland where he held the position of professor of mathematics at Queen's College Cork . Upon the death of her father in 1855, they married and she moved to Cork. Mary greatly contributed as an editor to Boole's The Laws of Thought , a work on algebraic logic . She had five daughters with him.
She was widowed in 1864, at the age of 32, and returned to England, where she was offered a post as a librarian at Queen's College on Harley Street , London. In August 1865, her address was listed as 68 Harley Street in a Deed of Assignment in which she disposed of her husband's former house in Ireland, acting as the Executrix of his will. [ 2 ] The deed was witnessed by "John Knights, Porter at Queens College, Harley Street, London and Jane White, Housekeeper at 68 Harley Street, London" . As well as working as a librarian, she also tutored privately in mathematics and developed a philosophy of teaching that involved the use of natural materials and physical activities to encourage an imaginative conception of the subject. Her interest extended beyond mathematics to Darwinian theory, philosophy and psychology and she organised discussion groups on these subjects among others. At Queen's College, against the approval of the authorities, she organised discussion groups of students with the unconventional James Hinton , a promulgator of polygamy. This in part led to her mental breakdown and the dispersal of her children. [ 3 ]
In later life, she belonged to the circle of the Tolstoyan pacifist publisher, C. W. Daniel; she chose the name The Crank for his magazine because, she said, 'a crank was a little thing that made revolutions'. [ 4 ]
Mary took an active interest in politics, introducing her daughter Ethel to the Russian anti-tsarist cause under Sergei Stepniak. After the Boer war 1899–1902 she became more outspoken in her writings against imperialism, organised religion, the financial world and the tokenism she felt that Parliament represented. She opposed women's suffrage and probably for this reason has not generally been regarded as a feminist. [ 3 ] She died in 1916, at the age of 84.
Boole was a practitioner of homeopathic medicine . [ 5 ]
Mary first became interested in mathematics and teaching through her tutor in France, Monsieur Deplace. He helped her understand mathematics through questioning and journal writing. After marrying George Boole she began contributing to the scientific world by advising her husband in his work while attending his lectures, both of which were unheard of for a woman to do in that time period. [ 6 ] During this time she also shared ideas with Victoria Welby , another female scholar and dear friend. They discussed everything from logic and mathematics, to pedagogy , theology, and science. [ 7 ]
Her teaching first began while working as a librarian. Mary would tutor students with new methods; using natural objects, such as sticks or stones. She theorized that using physical manipulations would strengthen the unconscious understanding of materials learned in a classroom setting. [ 6 ] One of her most notable contributions in the area of physical manipulations is curve stitching with the use of sewing cards, which she discovered as a form of amusement as a child. [ 8 ] This helped to encourage the connections of mathematical concepts to outside sources.
Her book Philosophy and Fun of Algebra explained algebra and logic to children in interesting ways, starting with a fable, and including bits of history throughout. [ 9 ] She references not only history, but also philosophy and literature, using a mystical tone to keep the attention of children. [ 10 ] Mary encouraged the use of mathematical imagination with critical thinking and creativity. This, along with reflective journal writing and creating one's own formulas, was essential in strengthening comprehension and understanding. Cooperative learning was also important because students could share discoveries with each other in an environment of peer tutoring and develop new ideas and methods. [ 6 ]
She worked on promoting her husband's works, with great attention to mathematical psychology . George Boole's main focus was on psychologism , and Mary provided a more ideological view of his work. She supported the idea that arithmetic was not purely abstract as many believed, but more anthropomorphic . Pulsation was also important in her works and could be described as a sequence of mental attitudes, with her attention being analysis and synthesis. [ 8 ] She believed that Indian logic played a role in the development of modern logic by her husband George Boole and others. [ 11 ]
Boole was interested in parapsychology and the occult, and was a convinced spiritualist . She was the first female member of the Society for Psychical Research which she joined in 1882. However, being the only female member at the time, she resigned after six months. [ 12 ]
Boole was the author of the book The Message of Psychic Science for Mothers and Nurses . She revealed the manuscript to Frederick Denison Maurice who objected to its controversial ideas and this resulted in her losing her job as librarian at Queens College. [ 13 ] The book was not published until 1883. [ 14 ] It was later republished as The Message of Psychic Science to the World (1908).
Her five daughters made their marks in a range of fields. Alicia Boole Stott (1860–1940) became an expert in four-dimensional geometry . Ethel Lilian (1864–1960) married the Polish revolutionary Wilfrid Michael Voynich and was the author of a number of works including The Gadfly . Mary Ellen (1856–1908) married mathematician Charles Hinton and Margaret (1858–1935) was the mother of mathematician G. I. Taylor . Lucy Everest (1862–1905) was a talented chemist and became the first woman Fellow of the Institute of Chemistry . [ 15 ] Geoffrey Hinton is a great-grandson of Boole, and is well known for research in Artificial Intelligence (AI). | https://en.wikipedia.org/wiki/Mary_Everest_Boole |
Mary Jean Garson AM FAA is a British-Australian organic chemist and academic. She is an Emerita Professor in the School of Chemistry and Molecular Biosciences at the University of Queensland .
Garson was born in Rugby , England, [ 1 ] the daughter of an engineer and botanist. [ 2 ] She took her B.A with Honours from the University of Cambridge , Newnham College in 1974. Garson's focus was the natural sciences, specializing in chemistry. She obtained an MA in Natural Sciences and she took her PhD in organic chemistry from Cambridge in 1977. [ 3 ] [ 1 ]
Garson won a Royal Society postdoctoral fellowship after her PhD, undertaking research in Rome, Italy from 1977 to 1978. [ 1 ] She continued her research at New Hall at Cambridge on a college research fellowship from 1978 to 1981. [ 1 ] [ 4 ] She worked as a medicinal chemist from 1981 to 1983 at Smith Kline and French Research Ltd in Welwyn , England,. [ 4 ]
Garson won a Queen Elizabeth II Research Fellowship from James Cook University (1983–1986), based in the Townsville region to research the bioactive organic chemicals in marine organisms. In Townsville, she undertook dive training to study on the Great Barrier Reef . [ 1 ] Garson then took a teaching/research position as the first female academic in chemistry at the University of Wollongong , before moving to the University of Queensland as a lecturer in 1990. She was promoted to Senior Lecturer in 1992 and Reader in 1998. [ 4 ] She researches and publishes on the structure, biosynthesis and function of natural products, especially those from marine invertebrates and other microorganisms. [ 5 ] [ 6 ] She also researches the chemistry of South East Asian medicinal plants. [ 5 ]
Garson was promoted to Professor in the School of Chemistry and Molecular Biosciences in 2006, and has served as Deputy Head of the School from 2005 to 2009. Since 2021, she is an Emeritus Professor of Chemistry at the university. [ citation needed ]
A species of marine flatworm, discovered at Heron Island , is named for her Maritigrella marygarsonae . [ 1 ] [ 11 ] | https://en.wikipedia.org/wiki/Mary_Garson |
Mary Jane Alvero-Al Mahdi (born April 29, 1970) is a CEO of Geoscience Testing Laboratory . She has performed many safety tests on construction materials, food, water, and air throughout the United Arab Emirates. [ 1 ] Some of her accomplished works are mega-projects like Downtown Burj Dubai .
Mary Jane Alvero-Al Mahdi was born in Makati , Philippines on April 29, 1970. She was born to Renato Alvero and Martha Alvero, along with four other children. [ 2 ] Her father supported the family as a successful businessman, until he began to develop emphysema. [ 2 ] Her father could no longer maintain the business and stayed confined to a bed, leaving her mother to take care of the children and at the same time worked hard to keep the family financially stable. Alvero-Al Mahdi took part and helped her mother by working part time jobs, and at the same time, studied chemical engineering at Adamson University . She graduated, and received her B.S. in chemical engineering in 1991. [ 3 ] After graduating, she took the Chemical Engineer Licensure Exam and passed. She worked under a company in Manila before she accepted the job offer in Dubai .
Alvero-Al Mahdi began her career at first in Manila as a trainee of the Department of Environment and Natural Resources . She helped in reviving a biologically dead river called Pasig . [ 2 ] After six months of finishing up her work on Pasig, she took on the job at Galadari Hoshiery Mills , a textile factory in the United Arabic Emirates as a quality control engineer in 1992. [ 2 ] Her employers soon saw that she was overly qualified for the job and soon she promoted from Galadari Hoshiery Mills to Al Futtaim Wimpey Laboratories. She worked her way up to higher positions such as, chemist to civil engineer to Chief Chemist. After working for Al Futtaim Wimpey Laboratories for six years, she was scouted by the Geoscience Testing Laboratories to become a Quality Assurance Officer. [ 2 ] Similar to her career in Al Futtaim Wimpey Laboratories, she rose to several promotions to finally the position of CEO of Geoscience Testing Laboratory in 2003. [ 2 ]
Throughout the years, Alvero-Al Mahdi has been recognized in various awards from both the Philippines; as well as, the UAE. | https://en.wikipedia.org/wiki/Mary_Jane_Alvero |
Mary Leng is a British philosopher specialising in the philosophy of mathematics and philosophy of science . She is a professor at the University of York .
Leng studied as an undergraduate at Balliol College , University of Oxford and as postgraduate student at the University of Toronto . [ 1 ] She worked at the University of Cambridge from 2002 to 2006, and then the University of Liverpool from 2006 to 2011. In 2007, she co-edited a collection called Mathematical Knowledge with Alexander Paseau and Michael Potter, which was published by Oxford University Press , [ 2 ] and, in 2010, she published a monograph called Mathematics and Reality , again with Oxford University Press. In Mathematics and Reality , Leng defends mathematical fictionalism . [ 3 ] Leng joined the University of York in 2012, where she is now a professor. [ 1 ]
This article about a philosopher is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mary_Leng |
Mary Stella Edwards (1898–1989) was an English painter, creator of dioramas and poet.
Mary Stella Edwards was born in Hampstead in 1898, the daughter of Robert Cromwell Edwards an architect. She grew up at 12 Fairfield Avenue, in Staines , Middlesex (now part of Surrey). [ 1 ]
Edwards studied art at the Royal College of Art and The Regent Street Polytechnic (now part of the University of Westminster ) where she met fellow student Judith Ackland . [ 1 ] [ 2 ] They became life partners and used a tiny cabin, a former fisherman's store, dating from the mid-19th century, at Bucks Mills as their studio from 1924 until Ackland's death in 1971. [ 3 ]
Together with Ackland, Edwards produced dioramas, Ackland made all the models (she invented a method called "Jackanda" to make the models), and Edwards painted their backdrops. [ 2 ] [ 3 ] The town of Windsor commissioned these dioramas to celebrate the town's history, and they are now at the Windsor & Royal Borough Museum . [ 4 ]
Edwards was also a poet and published several volumes throughout her life. [ 4 ] She published her first book of poetry Time and Chance in 1926 with the Hogarth Press of Leonard Woolf and Virginia Woolf ; Gilbert Murray , philologist, wrote the introduction. [ 5 ] The London antique dealer Maggs Bros Ltd has a copy Edwards dedicated to Irish publisher and book collector Alan Clodd , who in 1967 published her works with his Enitharmon Press . Individual poems subsequently appeared in Thomas Moult 's The Best Poems of 1930 , Art, Prose and Poetry , The Contemporary Review and The Living Age . She also published poetry between 1962 and 1964 in Literary Criticism Teaching edited by Margaret Willy for the Oxford University Press . In 1968 she published A Truce with Time and in 1978 Before and After , with poems in memory of her late partner, Judith Ackland: these poems, according to May Sarton , "express the long-standing affection and solidarity of these two remarkable women and give strength to make unbearable bearable". The volume was published by Enitharmon Press , as did Years Between (1982) and A Further Harvest (1985) with unpublished poems from the period between 1932 and 1984. [ 1 ]
Edwards also illustrated books, mostly children's books, painted or drew the frontispiece and designed dust covers. Examples include: The Normal Saturday Fairy Book (1924), The Grand Buffalo (1926), From Track to Highway. A Book of British Roads (1935), Worzel Gummidge Or the Scarecrow of Scatterbrook (1936), Miss Milligan Comes Out (1937), The Muddle-Headed Postman and Other Stories (1937), The Giant Who Made Mistakes (1938) and The Dogs at Abbey Lodge (1937). In addition, she designed - as well as Nina Hamnett , among others - an envelope for the literary journal Coterie , in which the Sitwells, Huxley, Eliot and others published texts; critics thought the cover was too reminiscent of Beardsley. [ 4 ] [ 1 ]
Edwards' book covers from 1922 to 1938 include illustrations for authors such as Douglas Jerrold , Countess Barcynska , Henryk Sienkiewicz , Anatole France , Rufus King , G.B. Stern , Peggy Wood . After Ackland's death, Edwards closed The Cabin at Bucks Mill and moved to live with her family in Staines. She died in 1989. [ 4 ]
Mary Stella Edwards donated a collection of her own and Ackland's work, dating from 1913 and 1965, to Burton Art Gallery and Museum in Bideford. [ 4 ] Other works by Ackland and Edwards are held by the Victoria and Albert Museum , the Museum of London , Amgueddfa Cymru – Museum Wales and Abbot Hall Art Gallery in Kendal, Westmorland. [ 4 ] [ 5 ]
Bucks Mills Cabin, originally managed by the Ackland-Edwards Charitable Trust, passed to The National Trust in 2004. It is a Grade II listed building under the Planning Act 1990 as amended for its special architectural or historic interest. [ 3 ] As agreed with the Ackland-Edwards Charitable Trust, it is an artist–in–residence summer home and occasionally open to public. [ 4 ] Listed in 2017, the Cabin was one of Historic England's properties to be given listed status as part of a "queer histories" project. [ 6 ] | https://en.wikipedia.org/wiki/Mary_Stella_Edwards |
Maryam Mirzakhani ( Persian : مریم میرزاخانی , pronounced [mæɾˈjæm miːɾzɑːxɑːˈniː] ; 12 May 1977 – 14 July 2017) was an Iranian [ 5 ] [ 4 ] mathematician and a professor of mathematics at Stanford University . [ 6 ] [ 7 ] Her research topics included Teichmüller theory , hyperbolic geometry , ergodic theory , and symplectic geometry . [ 5 ] On 13 August 2014, Mirzakhani was honored with the Fields Medal , the most prestigious award in mathematics, [ 8 ] [ 9 ] becoming the first woman to win the prize, as well as the first Iranian. [ 10 ] The award committee cited her work in "the dynamics and geometry of Riemann surfaces and their moduli spaces ". [ 11 ] Mirzakhani was considered a leading force in the fields of hyperbolic geometry, topology and dynamics. [ 12 ]
Throughout her career, she achieved milestones that cemented her reputation as one of the greatest mathematicians of her time, such as the "magic wand theorem", which tied together fields such as dynamical systems, geometry, and topology. [ 12 ] After completing her PhD at Harvard University in 2004, Mirzakhani became a research fellow at the Clay Mathematics Institute and later joined Princeton University as a professor. In 2009, she moved to Stanford University, where she continued her pioneering research until her death. Her work focused on the intricate and complex dynamics of geometric structures, with particular emphasis on moduli spaces and Riemann surfaces. Her approaches and profound insights significantly advanced the field, earning her widespread acclaim and recognition, leading her to win the Fields Medal , the highest honor in mathematics. [ 8 ]
Born and raised in Tehran , Mirzakhani's passion for mathematics began at a young age. She earned her undergraduate degree from Sharif University of Technology and went on to pursue her PhD at Harvard University under the mentorship of Fields Medalist Curtis T. McMullen. Her academic journey led her to positions at Princeton University and Stanford University , where she became a full professor in 2009. Despite her death at the age of 40 due to breast cancer , [ 13 ] her legacy endures through numerous accolades in her honor, including the Maryam Mirzakhani New Frontiers Prize and the 12 May Initiative, both dedicated to promoting women in mathematics.
Mirzakhani was born on 12 May 1977 [ 14 ] [ 3 ] in Tehran , Iran. [ 15 ] As a child, she attended Tehran Farzanegan School , part of the National Organization for Development of Exceptional Talents (NODET). In her junior and senior years of high school, she won the gold medal for mathematics in the Iranian National Olympiad, thus allowing her to bypass the national college entrance exam. [ 16 ] In 1994, Mirzakhani became the first Iranian woman to win a gold medal at the International Mathematical Olympiad in Hong Kong , scoring 41 out of 42 points. [ 17 ] The following year, in Toronto , she became the first Iranian to achieve the full score and to win two gold medals in the International Mathematical Olympiad. [ 18 ] [ 19 ] Later in her life, she collaborated with friend, colleague, and Olympiad silver medalist Roya Beheshti Zavareh ( Persian : رؤیا بهشتی زواره ) on their book Elementary Number Theory, Challenging Problems (in Persian ), which was published in 1999. [ 16 ] Mirzakhani and Zavareh together were the first women to compete in the Iranian National Mathematical Olympiad and won gold and silver medals in 1995, respectively.
On 17 March 1998, after attending a conference consisting of gifted individuals and former Olympiad competitors, Mirzakhani and Zavareh, along with other attendees, boarded a bus in Ahvaz en route to Tehran. The bus fell off a cliff, killing seven of the passengers, all Sharif University students, in what is remembered as a national tragedy in Iran. Mirzakhani and Zavareh were two of the few survivors. [ 20 ]
In 1999, she obtained a Bachelor of Science in mathematics from the Sharif University of Technology . During her time there, she developed a simpler proof of a theorem of Schur . [ 21 ] [ 22 ] She then went to the United States for graduate work, earning a PhD in 2004 from Harvard University , where she worked under the supervision of the Fields Medalist, Curtis T. McMullen . [ 23 ] At Harvard, she is said to have been "distinguished by determination and relentless questioning". She used to take her class notes in her native language Persian . [ 24 ] [ 25 ]
Mirzakhani was a 2004 research fellow of the Clay Mathematics Institute and a professor at Princeton University . [ 26 ] In 2009, she became a professor at Stanford University . [ 27 ] [ 11 ] [ 28 ]
Mirzakhani made several contributions to the theory of moduli spaces of Riemann surfaces . Mirzakhani's early work solved the problem of counting simple closed geodesics on hyperbolic Riemann surfaces by finding a relationship to volume calculations on moduli space. Geodesics are the natural generalization of the idea of a " straight line " to " curved spaces ". Slightly more formally, a curve is a geodesic if no slight deformation can make it shorter. Closed geodesics are geodesics which are also closed curves—that is, they are curves that close up into loops. A closed geodesic is simple if it does not cross itself. [ 29 ]
A previous result, known as the " prime number theorem for geodesics", established that the number of closed geodesics of length less than L {\displaystyle L} grows exponentially with L {\displaystyle L} – it is asymptotic to e L / L {\displaystyle e^{L}/L} . However, the analogous counting problem for simple closed geodesics remained open, despite being "the key object to unlocking the structure and geometry of the whole surface," according to University of Chicago topologist Benson Farb . [ 30 ] Mirzakhani's 2004 PhD thesis solved this problem, showing that the number of simple closed geodesics of length less than L {\displaystyle L} is polynomial in L {\displaystyle L} . Explicitly, it is asymptotic to c L 6 g − 6 {\displaystyle cL^{6g-6}} , where g {\displaystyle g} is the genus (roughly, the number of "holes") and c {\displaystyle c} is a constant depending on the hyperbolic structure. This result can be seen as a generalization of the theorem of the three geodesics for spherical surfaces . [ 31 ] [ 32 ]
Mirzakhani solved this counting problem by relating it to the problem of computing volumes in moduli space —a space whose points correspond to different complex structures on a surface genus g {\displaystyle g} . In her thesis, Mirzakhani found a volume formula for the moduli space of bordered Riemann surfaces of genus g {\displaystyle g} with n {\displaystyle n} geodesic boundary components. From this formula followed the counting for simple closed geodesics mentioned above, as well as a number of other results. This led her to obtain a new proof for the formula discovered by Edward Witten and Maxim Kontsevich on the intersection numbers of tautological classes on moduli space. [ 6 ] [ 33 ]
Her subsequent work focused on Teichmüller dynamics of moduli space. In particular, she was able to prove the long-standing conjecture that William Thurston 's earthquake flow on Teichmüller space is ergodic . [ 34 ] One can construct a simple earthquake map by cutting a surface along a finite number of disjoint simple closed geodesics, sliding the edges of each of these cut past each other by some amount, and closing the surface back up. One can imagine the surface being cut by strike-slip faults . An earthquake is a sort of limit of simple earthquakes, where one has an infinite number of geodesics, and instead of attaching a positive real number to each geodesic, one puts a measure on them.
In 2014, with Alex Eskin and with input from Amir Mohammadi, Mirzakhani proved that complex geodesics and their closures in moduli space are surprisingly regular, rather than irregular or fractal . [ 35 ] [ 36 ] The closures of complex geodesics are algebraic objects defined in terms of polynomials and therefore, they have certain rigidity properties, which is analogous to a celebrated result that Marina Ratner arrived at during the 1990s. [ 36 ] The International Mathematical Union said in its press release that "It is astounding to find that the rigidity in homogeneous spaces has an echo in the inhomogeneous world of moduli space." [ 36 ]
Mirzakhani was awarded the Fields Medal in 2014 for "her outstanding contributions to the dynamics and geometry of Riemann surfaces and their moduli spaces". [ 37 ] The award was made in Seoul at the International Congress of Mathematicians on 13 August. [ 38 ] At the time of the award, Jordan Ellenberg explained her research to a popular audience:
[Her] work expertly blends dynamics with geometry. Among other things, she studies billiards. But now, in a move very characteristic of modern mathematics, it gets kind of meta: She considers not just one billiard table, but the universe of all possible billiard tables. And the kind of dynamics she studies doesn't directly concern the motion of the billiards on the table, but instead a transformation of the billiard table itself, which is changing its shape in a rule-governed way; if you like, the table itself moves like a strange planet around the universe of all possible tables ... This isn't the kind of thing you do to win at pool, but it's the kind of thing you do to win a Fields Medal. And it's what you need to do in order to expose the dynamics at the heart of geometry; for there's no question that they're there. [ 39 ]
In 2014, President Hassan Rouhani of Iran congratulated her for winning the award. [ 40 ]
In 2008, Mirzakhani married Jan Vondrák , a Czech theoretical computer scientist and applied mathematician who currently is a professor at Stanford University . [ 41 ] [ 42 ] They had a daughter. [ 43 ] Mirzakhani lived in Palo Alto, California . [ 44 ] Mirzakhani described herself as a "slow" mathematician, saying that "you have to spend some energy and effort to see the beauty of math." To solve problems, Mirzakhani would draw doodles on sheets of paper and write mathematical formulas around the drawings. Her daughter described her mother's work as "painting". [ 24 ] [ 45 ]
She declared:
I don't have any particular recipe [for developing new proofs] ... It is like being lost in a jungle and trying to use all the knowledge that you can gather to come up with some new tricks, and with some luck, you might find a way out. [ 24 ]
Mirzakhani was diagnosed with breast cancer in 2013. [ 24 ] In 2016, the cancer spread to her bones and liver, [ 24 ] [ 46 ] and she died on 14 July 2017 at the age of 40 at Stanford Hospital in Stanford, California . [ 24 ] [ 47 ]
Iranian president Hassan Rouhani and other officials offered their condolences and praised Mirzakhani's scientific achievements. Rouhani said in his message that "the unprecedented brilliance of this creative scientist and modest human being, who made Iran's name resonate in the world's scientific forums, was a turning point in showing the great will of Iranian women and young people on the path towards reaching the peaks of glory and in various international arenas." [ 24 ]
Upon her death, several Iranian newspapers, along with President Hassan Rouhani, broke taboo and published photographs of Mirzakhani with her hair uncovered. Although most newspapers used photographs with a dark background, digital manipulation, and even paintings to "hide" her hair, [ 10 ] [ 48 ] this gesture was widely noted in the western press and on social media. [ 49 ] [ 50 ]
Mirzakhani's death has also renewed debates within Iran regarding matrilineal citizenship for children of mixed-nationality parentage; Fars News Agency reported that, subsequent to Mirzakhani's death, 60 Iranian MPs urged the speeding up of an amendment to a law that would allow children of Iranian mothers married to foreigners to be given Iranian nationality , in order to make it easier for Mirzakhani's daughter to visit Iran. [ 10 ] [ 49 ]
Numerous obituaries and tributes were published in the days following Mirzakhani's death. [ 51 ] [ 52 ] As a result of advocacy carried out by the Women's Committee within the Iranian Mathematical Society ( Persian : کمیته بانوان انجمن ریاضی ایران ), the International Council for Science agreed to declare Mirzakhani's birthday, 12 May, as International Women in Mathematics Day in respect of her memory. [ 53 ] [ 54 ]
Various establishments have also been named after Mirzakhani to honor her life and achievements. In 2017, Farzanegan High School – the high school Mirzakhani formerly attended – named their amphitheater and library after her. Additionally, Sharif University of Technology , the institute wherein Mirzakhani obtained her bachelor's, has since named their main library in the College of Mathematics after her. Further, the House of Mathematics in Isfahan , in collaboration with the mayor, named a conference hall in the city after her. [ 55 ]
In 2014, students at the University of Oxford founded the Mirzakhani Society, a society for women and non-binary students studying mathematics at the University of Oxford. Mirzakhani met the society in September 2015, when she visited Oxford. [ 56 ]
In 2016, Mirzakhani was made a member of the National Academy of Sciences (of the United States), making her the first Iranian woman to be officially accepted as a member of the academy. [ 57 ]
On 2 February 2018, Satellogic , a high-resolution Earth observation imaging and analytics company, launched a ÑuSat type micro-satellite named in honor of Mirzakhani. [ 58 ]
On 4 November 2019, The Breakthrough Prize Foundation announced that the Maryam Mirzakhani New Frontiers Prize has been created to be awarded to outstanding women in the field of mathematics each year. The $50,000 award will be presented to early-career mathematicians who have completed their PhDs within the past two years. [ 59 ] [ 60 ]
In February 2020, on International Day of Women and Girls in STEM , Mirzakhani was honored by UN Women as one of seven female scientists dead or alive who have shaped the world. [ 61 ]
In 2020, George Csicsery featured her in the documentary film Secrets of the Surface: The Mathematical Vision of Maryam Mirzakhani . [ 62 ] [ 63 ]
The 12 May Initiative was created in Mirzakhani's honor [ 14 ] to celebrate women in mathematics. The Initiative is coordinated by the European Women in Mathematics , Association for Women in Mathematics , African Women in Mathematics Association , Colectivo de Mujeres Matemáticas de Chile , and the Women's Committee of the Iranian Mathematical Society . In 2020, 152 events were held. [ 64 ]
In 2022, following a £2.48m donation from XTX Markets , the University of Oxford launched the Maryam Mirzakhani Scholarships, which provide support for female mathematicians pursuing doctoral studies at the university. [ 65 ]
On 8 March 2022, the Ecole Polytechnique Fédérale de Lausanne named one of its streets in honor of Mirzakhani. [ 66 ] | https://en.wikipedia.org/wiki/Maryam_Mirzakhani |
Maryna Sergiivna Viazovska ( Ukrainian : Марина Сергіївна Вязовська , [ 2 ] pronounced [mɐˈrɪnɐ wjɐˈzɔu̯sʲkɐ] ; born 2 December 1984) [ 3 ] is a Ukrainian mathematician known for her work in sphere packing . She is a full professor and Chair of Number Theory at the Institute of Mathematics of the École Polytechnique Fédérale de Lausanne in Switzerland. [ 4 ] She was awarded the Fields Medal in 2022. [ 5 ] [ 6 ]
Viazovska was born in Kyiv , the oldest of three sisters. Her father was a chemist who worked at the Antonov aircraft factory and her mother was an engineer. [ 6 ] She attended a specialized secondary school for high-achieving students in science and technology, Kyiv Natural Science Lyceum No. 145 . An influential teacher there, Andrii Knyazyuk, had previously worked as a professional research mathematician before becoming a secondary school teacher. [ 7 ] Viazovska competed in domestic mathematics Olympiads when she was at high school, placing 13th in a national competition where 12 students were selected to a training camp before a six-member team for the International Mathematical Olympiad was chosen. [ 6 ] As a student at Taras Shevchenko National University of Kyiv , she competed at the International Mathematics Competition for University Students in 2002, 2003, 2004, and 2005, and was one of the first-place winners in 2002 and 2005. [ 8 ] She co-authored her first research paper in 2005. [ 6 ]
Viazovska earned a master's from the University of Kaiserslautern in 2007, PhD from the Institute of Mathematics of the National Academy of Sciences of Ukraine in 2010, [ 2 ] and a doctorate ( Dr. rer. nat. ) from the University of Bonn in 2013. Her doctoral dissertation, Modular Functions and Special Cycles , concerns analytic number theory and was supervised by Don Zagier and Werner Müller . [ 9 ]
She was a postdoctoral researcher at the Berlin Mathematical School and the Humboldt University of Berlin [ 10 ] and a Minerva Distinguished Visitor [ 11 ] at Princeton University . Since January 2018 she has held the Chair of Number Theory as a full professor at the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland after a short stint as tenure-track assistant professor. [ 4 ]
In 2016, Viazovska solved the sphere-packing problem in dimension 8. [ 12 ] [ 13 ] [ 14 ] Her dimension 8 solution quickly led to collaboration with others, and a solution in dimension 24. [ 15 ] [ 10 ] Previously, the problem had been solved only for three or fewer dimensions, and the proof of the three-dimensional version (the Kepler conjecture ) involved long computer calculations. In contrast, Viazovska's proof for 8 and 24 dimensions is "stunningly simple". [ 10 ]
A few years later, in 2018, Viazovska and her collaborators significantly extended [ 16 ] their sphere packing results in dimensions 8 and 24 to address potential energy minimization. [ 17 ] In 2019, Vyazovska and her team solved a mathematical equation that determines how an infinite number of points repelling each other are placed in 8- and 24-dimensional spaces. [ 18 ] [ 19 ] [ 20 ]
As well as for her work on sphere packing, Viazovska is also known for her research on spherical designs with Bondarenko and Radchenko. With them she proved a conjecture of Korevaar and Meyers on the existence of small designs in arbitrary dimensions. This result was one of the contributions for which her co-author Andriy Bondarenko won the Vasil A. Popov Prize for approximation theory in 2013. [ 21 ]
In 2016, Viazovska received the Salem Prize [ 22 ] and, in 2017, the Clay Research Award and the SASTRA Ramanujan Prize for her work on sphere packing and modular forms . [ 23 ] [ 24 ] In December 2017, she was awarded a 2018 New Horizons Prize in Mathematics . [ 25 ] She was an invited speaker at the 2018 International Congress of Mathematicians . [ 26 ] For 2019 she was awarded the Ruth Lyttle Satter Prize in Mathematics [ 27 ] and the Fermat Prize . [ 28 ] She is one of the 2020 winners of the EMS Prize . [ 29 ] In 2020, she also received the National Latsis Prize awarded by the Latsis Foundation . [ 30 ] She was elected to the Academia Europaea in 2021. [ 31 ] She was appointed Senior Scholar at the Clay Mathematics Institute in July 2022. [ 32 ]
She was awarded the Fields Medal in July 2022, making her the second woman (after Maryam Mirzakhani ), the second person born in the Ukrainian SSR and the first with a degree from a Ukrainian university to ever receive it. [ 33 ] [ 34 ] [ 35 ] She was honored as one of the BBC 100 Women in December 2022. [ 36 ]
Viazovska met her husband, Daniil Evtushinsky, at an after-school physics group for schoolchildren. He is also a researcher at EPFL, in physics. They have two children, a son and a daughter. [ 6 ] [ 37 ] | https://en.wikipedia.org/wiki/Maryna_Viazovska |
María Gracia Manzano Arjona (born 1950) [ 2 ] is a Spanish philosopher specializing in mathematical logic and model theory .
Manzano earned her Ph.D. in 1977 from the University of Barcelona . Her dissertation, Sistemas generales de la lógica de segundo orden [General systems of second-order logic ], was supervised by Jesús Mosterín . [ 3 ] She is a professor of logic and the philosophy of science at the University of Salamanca . [ 1 ]
She is the author of several books on logic and model theory:
This article about a European mathematician is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/María_Manzano |
María Orosa y Ylagan [ 3 ] (November 29, 1892 – February 13, 1945) was a Filipina food technologist , pharmaceutical chemist , humanitarian, and war heroine. [ 4 ] She experimented with foods native to the Philippines , and during World War II developed Soyalac (a nutrient rich drink from soybeans) and Darak (rice cookies packed with vitamin B-1 , which prevents beriberi disease), which she also helped smuggle into Japanese-run internment camps that helped save the lives of thousands of Filipinos, Americans, and other nationals. [ 5 ] She invented banana ketchup . [ 6 ] [ 5 ]
Orosa completed her bachelor's and master's degrees in pharmaceutical chemistry, as well as an additional degree in food chemistry . She was then offered a position as an assistant chemist for the state of Washington before returning to the Philippines in 1922 to focus on addressing the problem of malnutrition in her homeland. She invented many types of food to minimize the need of imported products to feed Filipinos. She took advantage of the abundant natural resources of the Philippine islands such as native fruits, crops and vegetables to make the Philippines self-sufficient. [ 6 ]
During World War II, Orosa joined Marking's Guerrillas to fight for Philippines freedom. She invented over 700 recipes during her lifetime, including Soyalac and Darak, which saved thousands of lives during the war. She also invented a process for canning goods for the guerrilla warriors fighting for the liberation of the Philippines. Without her food inventions, thousands of people would have died in internment camps, hospitals, and on the streets. [ 7 ]
Orosa was born on November 29, 1892, in Taal, Batangas , [ 8 ] and was the fourth among the eight children of Simplicio A. Orosa and Juliana Ylagan-Orosa. Although her father died when she was still a child (and helped her mother in the family's general store), [ 9 ] many of her siblings also became distinguished in the Philippines. Her elder brother, Engr. Vicente Ylagan Orosa Sr. , became Secretary of Public Works and Communications, and, later, Chairman of the People’s Homesite and Housing Corporation (PHHC) during the administration of President Ramon Magsaysay . Her brother, Dr. Sixto Ylagan Orosa Sr. , became a pioneering doctor, and her nieces and nephews included banker Sixto L. Orosa, Jr., Philippine National Artist in Dance Leonor Orosa Goquiñgco, businessman José R. L. Orosa, award-winning cultural journalist Rosalinda L. Orosa , and her biographer Helen Orosa del Rosario.
After studying at the University of the Philippines , Orosa became a government-sponsored scholar who was sent to the United States in 1916. [ 7 ] [ 8 ] She enrolled at the University of Washington in Seattle , where she ((then continue and delete " from the University of Washington". Keep reference and add [ 7 ] )) earned a bachelor's and master's degrees in pharmaceutical chemistry, and an additional degree in food chemistry from the University of Washington . [ 5 ] She worked in fish canneries in Alaska during her summer breaks in college. [ 5 ] There she learned about factory canning. [ 7 ]
Although offered a job as an assistant chemist by the Washington state government, Orosa returned to the Philippines in 1922. [ 7 ] She initially taught home economics at the Centro Escolar University , and later transferred to the Philippine Bureau of Science's food preservation division. Beginning in 1926, Orosa visited China, Japan, Hawaii, Britain, the Netherlands, France, Germany, Italy and Spain to research food technology and preservation . She toured more than 50 canning factories. After she returned to the Philippines, she was appointed the head of the Food Preservation Division and, later, the Home Economics Division of the Bureau of Science. By 1934, Orosa was in charge of the Plant Utilization Division at the Bureau of Plant Industry. [ 7 ] [ 8 ]
Orosa wanted to help the Philippines become self-sufficient, as well as empower Filipino families. [ 7 ] She organized 4-H clubs in the islands [ 5 ] (which had more than 22,000 members by 1924), [ 7 ] and traveled into the barrios to teach women how to raise chickens, preserve local produce, and plan healthy meals. With the help of this organization, she and numerous protesters visited various communities throughout the Philippines to educate women on innovative methods of food preparation and preservation. [ 7 ] Orosa invented the palayók oven to enable families without access to electricity to bake, [ 5 ] and developed recipes for local produce, including cassava, bananas, and coconut. Imported tomato ketchup , introduced by the Americans, was popular but expensive. Orosa invented a ketchup made with bananas and other local ingredients, instead of tomatoes. [ 7 ] [ 5 ] Banana ketchup became a favorite condiment and cooking ingredient in the archipelago. [ 6 ] [ 8 ] She also developed wines and calamansi nip, a desiccated and powdered form of the citrus fruit used to make reconstituted calamansi juice, banana ketchup, and in other recipes. Using both her local and technical knowledge, Orosa made culinary contributions and taught proper preservation methods for native dishes such as adobo , dinuguan , kilawin and escabeche .
During World War II , Orosa used her food science background to invent Soyalac (a protein-rich powdered soybean product) and Darák (a rice bran powder rich in thiamine and other vitamins which could also treat beri-beri ). [ 5 ] She also became a captain in Marking's Guerrillas, [ 8 ] a Filipino guerrilla group organized by Marcos “Marking” V. Augustín. The guerrillas helped United States forces fight the occupying Imperial Japanese troops, and employed carpenters to insert Soyalac and Darák into hollow bamboo sticks, which were then smuggled to civilians imprisoned at the University of Santo Tomas and in Japanese-run prisoners of war camps in Capas, Tarlac and Corregidor . The powders saved the lives of many starving imprisoned guerrillas and U.S. soldiers. [ 5 ] [ 7 ] [ 8 ] Her "Tiki-Tiki" cookies (also made using Darák) saved many civilian lives during wartime food shortages.
Although her family and friends urged her to flee Manila for her hometown as American and Filipino forces fought Japanese troops in the Battle of Manila , Orosa refused and insisted that, as a soldier, she had to remain at her post. [ 7 ] On February 13, 1945, Orosa was injured by shrapnel wounds in her government office during an American bombing raid. The Remedios Hospital, to which she had been taken was later also bombed, causing a shrapnel shard to pierce her heart and kill her instantly. [ 5 ] [ 7 ] [ 8 ] The American Red Cross posthumously gave Orosa a humanitarian award for her food-smuggling efforts. [ 9 ] [ 7 ] Her niece Helen Orosa del Rosario in 1970 published Maria Orosa: Her Life and Work , which also included 700 of Orosa's recipes.
The Philippines has officially recognized Orosa's contributions. Her home province, Batangas, installed a bust and historical marker in her honor. [ 7 ] A street in Ermita, Manila (where the Court of Appeals of the Philippines is now located), is named after her, [ 8 ] as is a building in the Bureau of Plant Industry. During the 65th anniversary of the Institute of Science and Technology, she became one of 19 scientists who received special recognition. On November 29, 1983, the National Historical Institute installed a marker in her honor at the Bureau of Plant Industry in Malate, Manila . [ 8 ] For the centennial of her birth anniversary, the Philippine Postal Corporation issued a postage stamp in her honor. Her hometown of Taal, Batangas also celebrated the 125th anniversary of her birth on November 29, 2018. On 29 November 2019, Google celebrated her 126th birthday with a Google Doodle . [ 10 ]
On February 8, 2020, Orosa's tombstone was found at the Malate Catholic School , the site of the Remedios Hospital during the Second World War. [ 7 ] [ 11 ] [ 12 ] Her remains were reinterred in the crypt of San Agustín Church in Intramuros as part of commemorations for the 80th anniversary of the Battle of Manila on February 13, 2025. [ 13 ] | https://en.wikipedia.org/wiki/María_Orosa |
Maria Teresa González Garza y Barrón was a professor and researcher in biotechnology at Monterrey Institute of Technology and Higher Education , Monterrey Campus.
After completing a university degree in biology, from the National Autonomous University of Mexico (UNAM) in 1969, she spent 15 years at the university and within the Mexican Social Security Institute in a Department of Biomedical Research. In 1992, she received her doctorate in biology with a specialty in microbiology from the Autonomous University of Nuevo León.
Her specialties included cellular biology, molecular biology, cell therapy and ethnobiology . In particular, her research focused on cellular mechanisms in cancer lines, differences between normal and cancerous cells, and the use of cell therapies using stem cells to replace damaged tissue. She also investigated natural substances from traditional medicine for their potential anticancer and antiparasitic properties.
Throughout her career, she worked with el Centro de Investigación Biomédica del Noreste (IMSS) and el Instituto Tecnológico y de Estudios Superiores de Monterrey (ITESM) and the Centro de Innovación y Transferencia en Salud and the Cátedra de Terapia Celular. [ 1 ] [ 2 ] She was part of a team which has had success in combating amyotrophic lateral sclerosis with stem cell therapy . [ 3 ]
Her research work has been recognized by Mexico's Sistema Nacional de Investigadores with Level II membership. [ 4 ] She has received various awards including the Dr. Jorge Rosenkranz Medical Research Award (1988) and the Canifarma Award (1993). [ 1 ]
This article about a Mexican scientist is a stub . You can help Wikipedia by expanding it .
This article about a biologist is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/María_Teresa_González-Garza_y_Barron |
María Vallet-Regí (born 19 April 1946) is a Spanish inorganic chemist. As of 2012, she heads the Smart Biomaterials group at the Universidad Complutense de Madrid .
María Vallet-Regí was born in Las Palmas, Spain . [ 1 ] She studied chemistry at the Universidad Complutense de Madrid (Spain) and received her Ph.D. there in 1974.
As of 2012, she is a full professor of inorganic chemistry and head of the research group Smart Biomaterials in the Department of Inorganic and Bioinorganic Chemistry of the Faculty of Pharmacy at Universidad Complutense de Madrid.
Vallet-Regí has written more than 600 articles and several books. She was the most-cited Spanish scientist, according to ISI Web of Knowledge, in the field of Materials Science in these past decades. [ 1 ]
María Vallet-Reg is Fellow of Biomaterials Science and Engineering at the International College of Fellows of Biomaterials Science and Engineering (ICF-BSE), Numbered Fellow of the Spanish Royal Academy of Engineering and the Royal National Academy of Pharmacy.
She received the Prix Franco-Espagnol 2000 from Societé Française de Chimie, the Spanish Royal Society of Chemistry (RSEQ) award in Inorganic Chemistry 2008, the Spanish National Research Award in Engineering 2008, FEIQUE Research award 2011 and the RSEQ Research Award and Gold Medal 2011. | https://en.wikipedia.org/wiki/María_Vallet-Regí |
Masatoşi Gündüz İkeda (25 February 1926 – 9 February 2003), was a Japanese -born Turkish mathematician known for his contributions to the field of algebraic number theory . [ 2 ]
Ikeda was born on 25 February 1926 in Tokyo , Japan, to Junzo Ikeda, head of the statistics department of an insurance company, and his wife Yaeko Ikeda. He was the youngest child with a brother and two sisters. He grew up reading mathematics books belonging to his father. During his school years, he bought himself used books about mathematics and the life story of mathematicians. He was very impressed by the French mathematician Évariste Galois (1811–1832). [ 3 ]
Ikeda graduated from the mathematics department of Osaka University in 1948. He received a PhD degree with his thesis " On Absolutely Segregated Algebras ", written in 1953 under the direction of Kenjiro Shoda . [ 4 ] He was appointed associate professor in 1955. He pursued scientific research at the University of Hamburg in Germany, under the supervision of Helmut Hasse (1898–1979) between 1957 and 1959. On a suggestion from Hasse, he went to Turkey in 1960 and landed at Ege University in İzmir . In 1961, he was appointed a foreigner specialist in the Faculty of Science at the same university. [ 3 ] [ 5 ] [ 6 ]
In 1964, Ikeda married Turkish biochemist Emel Ardor, whom he met and followed to Turkey. He was naturalized, converted to Islam and adopted the Turkish name Gündüz . He became associate professor in 1965 and a full professor in 1966. In 1968, with permission of the university, he went to the Middle East Technical University (METU) in Ankara as a visiting professor for one year. However, following the end of his term, he was offered a permanent post as a full professor, which he accepted upon the proposal of the mathematician Cahit Arf , whom he had known since his early years in Turkey. [ 3 ] [ 6 ]
From time to time, Ikeda was invited as a visiting professor to various universities such as the University of Hamburg (1966), San Diego State University , California (1971), and Yarmouk University in Irbid , Jordan (1984, 1985–86). In 1976, Ikeda carried out research work at Princeton University . In 1976, Ikeda went to Hacettepe University in Ankara, where he chaired the mathematics department until 1978, before he returned to METU. He retired in 1992 at METU. His scientific devotion was in Galois theory . [ 3 ] [ 6 ]
Among the research institutions Ikeda served were TÜBİTAK Marmara Research Center and Turkish National Research Institute of Electronics and Cryptology . Finally, he worked at the Feza Gürsey Basic Sciences Research Center in Istanbul . [ 5 ]
Ikeda was a member of the Basic Sciences Board at the Scientific and Technological Research Council of Turkey (TÜBİTAK), and served as the head of the Mathematic Research Unit at the METU. [ citation needed ]
Ikeda died on 9 February 2003, in Ankara. Following a religious funeral service held on 12 February at Kocatepe Mosque , he was laid to rest at the Karşıyaka Cemetery . [ 5 ] He was the father of two sons, both born in Turkey . [ 3 ]
In 1979, Ikeda was honored with the TÜBİTAK Science Award. [ citation needed ]
The Mathematics Foundation of Turkey established the "Masatoshi Gündüz İkeda Research Award" in Ikeda's memory. [ 7 ] | https://en.wikipedia.org/wiki/Masatoshi_Gündüz_Ikeda |
Masayoshi Nagata ( Japanese : 永田 雅宜 Nagata Masayoshi ; February 9, 1927 – August 27, 2008) was a Japanese mathematician , known for his work in the field of commutative algebra .
Nagata's compactification theorem shows that algebraic varieties can be embedded in complete varieties . The Chevalley–Iwahori–Nagata theorem describes the quotient of a variety by a group .
In 1959, he introduced a counterexample to the general case of Hilbert's fourteenth problem on invariant theory . His 1962 book on local rings contains several other counterexamples he found, such as a commutative Noetherian ring that is not catenary , and a commutative Noetherian ring of infinite dimension .
Nagata's conjecture on curves concerns the minimum degree of a plane curve specified to have given multiplicities at given points; see also Seshadri constant . Nagata's conjecture on automorphisms concerns the existence of wild automorphisms of polynomial algebras in three variables. Recent work has solved this latter problem in the affirmative. [ 1 ] | https://en.wikipedia.org/wiki/Masayoshi_Nagata |
Mascot is a software search engine that uses mass spectrometry data to identify proteins from peptide sequence databases. [ 1 ] [ 2 ] Mascot is widely used by research facilities around the world. Mascot uses a probabilistic scoring algorithm for protein identification that was adapted from the MOWSE algorithm. Mascot is freely available to use on the website of Matrix Science. [ 3 ] A license is required for in-house use where more features can be incorporated.
MOWSE was one of the first algorithms developed for protein identification using peptide mass fingerprinting . [ 4 ] It was originally developed in 1993 as a collaboration between Darryl Pappin of the Imperial Cancer Research Fund (ICRF) and Alan Bleasby of the Science and Engineering Research Council (SERC). MOWSE stood apart from other protein identification algorithms in that it produced a probability-based score for identification. It was also the first to take into account the non-uniform distribution of peptide sizes, caused by the enzymatic digestion of a protein that is needed for mass spectrometry analysis. However, MOWSE was only applicable to peptide mass fingerprint searches and was dependent on pre-compiled databases which were inflexible with regard to post-translational modifications and enzymes other than trypsin. To overcome these limitations, to take advantage of multi-processor systems and to add non-enzymatic search functionality, development was begun again from scratch by David Perkins at the Imperial Cancer Research Fund. The first versions were developed for Silicon Graphics Irix and Digital Unix systems. Eventually this software was named Mascot and to reach a wider audience, an external bioinformatics company named Matrix Science was created by David Creasy and John Cottrell to develop and distribute Mascot. Legacy software versions exist for Tru64, Irix, AIX, Solaris, Microsoft Windows NT4 and Microsoft Windows 2000. Mascot has been available as a free service on the Matrix Science website since 1999 and has been cited in scientific literature over 5,000 times. Matrix Science still continues to work on improving Mascot’s functionality.
Mascot identifies proteins by interpreting mass spectrometry data. The prevailing experimental method for protein identification is a bottom-up approach , where a protein sample is typically digested with trypsin to form smaller peptides. While most proteins are too large, peptides usually fall within the limited mass range that a typical mass spectrometer can measure. Mass spectrometers measure the molecular weights of peptides in a sample. Mascot then compares these molecular weights against a database of known peptides. The program cleaves every protein in the specified search database in silico according to specific rules depending on the cleavage enzyme used for digestion and calculates the theoretical mass for each peptide. Mascot then computes a score based on the probability that the peptides from a sample match those in the selected protein database. The more peptides Mascot identifies from a particular protein, the higher the Mascot score for that protein.
The software processes data from mass spectrometers of the following companies:
Mascot’s fundamental approach to identifying peptides is to calculate the probability whether an observed match between experimental data and peptide sequences found in a reference database has occurred by chance. The match with the lowest probability of occurring by chance is returned as the most significant match. The significance of the match depends on the size of the database that is being queried. Mascot employs the widely used significance level of 0.05, meaning that in a single test the probability of observing an event at random is less than or equal to 1 in 20. In this light, a score of 10 −5 might seem very promising. However, if the database being searched contains 10 6 sequences several scores of this magnitude would be expected by chance alone because the algorithm carried out 10 6 individual comparisons. For a database of that size, by applying a Bonferroni correction to account for multiple comparisons , the significance threshold drops to 5*10 −8 . [ 1 ]
In addition to the calculated peptide scores, Mascot also estimates the False Discovery Rate (FDR) by searching against a decoy database. When performing a decoy search, Mascot generates a randomized sequence of the same length for every sequence in the target database. The decoy sequence is generated such that it has the same average amino acid composition as the target database. The FDR is estimated as the ratio of decoy database matches to target database matches. This relates to the standard formula FDR = FP / (FP + TP), where FP are false positives and TP are true positives. The decoy matches are certain to be spurious identifications, but we can't discriminate between true and false positives identified in the target database. FDR estimation was added in response to journals' guidelines on protein identification reports like the ones from Molecular and Cellular Proteomics. [ 5 ] Mascot's FDR calculation incorporates ideas from different publications. [ 6 ] [ 7 ]
The most common alternative database search programs are listed in the Mass spectrometry software article. The performance of a variety of mass spectrometry software, including Mascot, can be observed in the 2011 iPRG study . Genome-based peptide fingerprint scanning is another method that compares the peptide fingerprints to the entire genome instead of only annotated genes. | https://en.wikipedia.org/wiki/Mascot_(software) |
In Mathematics , the Mashreghi–Ransford inequality is a bound on the growth rate of certain sequences . It is named after J. Mashreghi and T. Ransford .
Let ( a n ) n ≥ 0 {\displaystyle (a_{n})_{n\geq 0}} be a sequence of complex numbers , and let
and
Here the binomial coefficients are defined by
Assume that, for some β > 1 {\displaystyle \beta >1} , we have b n = O ( β n ) {\displaystyle b_{n}=O(\beta ^{n})} and c n = O ( β n ) {\displaystyle c_{n}=O(\beta ^{n})} as n → ∞ {\displaystyle n\to \infty } . Then Mashreghi-Ransford showed that
where α = β 2 − 1 . {\displaystyle \alpha ={\sqrt {\beta ^{2}-1}}.} Moreover, there is a universal constant κ {\displaystyle \kappa } such that
The precise value of κ {\displaystyle \kappa } is still unknown. However, it is known that | https://en.wikipedia.org/wiki/Mashreghi–Ransford_inequality |
In computer science , a mask or bitmask is data that is used for bitwise operations , particularly in a bit field . Using a mask, multiple bits in a byte , nibble , word , etc. can be set either on or off, or inverted from on to off (or vice versa) in a single bitwise operation. An additional use of masking involves predication in vector processing , where the bitmask is used to select which element operations in the vector are to be executed (mask bit is enabled) and which are not (mask bit is clear).
To turn certain bits on, the bitwise OR operation can be used, following the principle that for an individual bit Y , Y OR 1 = 1 and Y OR 0 = Y . Therefore, to make sure a bit is on, OR can be used with a 1 . To leave a bit unchanged, OR is used with a 0 .
Example: Masking on the higher nibble (bits 4, 5, 6, 7) while leaving the lower nibble (bits 0, 1, 2, 3) unchanged.
More often in practice, bits are "masked off " (or masked to 0 ) than "masked on " (or masked to 1 ). When a bit is AND ed with a 0, the result is always 0, i.e. Y AND 0 = 0 . To leave the other bits as they were originally, they can be AND ed with 1 as Y AND 1 = Y
Example: Masking off the higher nibble (bits 4, 5, 6, 7) while leaving the lower nibble (bits 0, 1, 2, 3) unchanged.
It is possible to use bitmasks to easily check the state of individual bits regardless of the other bits. To do this, turning off all the other bits using the bitwise AND is done as discussed above and the value is compared with 0 . If it is equal to 0 , then the bit was off, but if the value is any other value, then the bit was on. What makes this convenient is that it is not necessary to figure out what the value actually is, just that it is not 0 .
Example: Querying the status of the 4th bit
So far the article has covered how to turn bits on and turn bits off, but not both at once. Sometimes it does not really matter what the value is, but it must be made the opposite of what it currently is. This can be achieved using the XOR (exclusive or) operation. XOR returns 1 if and only if an odd number of bits are 1 . Therefore, if two corresponding bits are 1 , the result will be a 0 , but if only one of them is 1 , the result will be 1 . Therefore inversion of the values of bits is done by XOR ing them with a 1 . If the original bit was 1 , it returns 1 XOR 1 = 0 . If the original bit was 0 it returns 0 XOR 1 = 1 . Also note that XOR masking is bit-safe, meaning that it will not affect unmasked bits because Y XOR 0 = Y , just like an OR .
Example: Toggling bit values
To write arbitrary 1s and 0s to a subset of bits, first write 0s to that subset, then set the high bits:
In programming languages such as C , bit fields are a useful way to pass a set of named Boolean arguments to a function. For example, in the graphics API OpenGL , there is a command, glClear() which clears the screen or other buffers. It can clear up to four buffers (the color, depth, accumulation, and stencil buffers ), so the API authors could have had it take four arguments. But then a call to it would look like
which is not very descriptive. Instead there are four defined field bits, GL_COLOR_BUFFER_BIT , GL_DEPTH_BUFFER_BIT , GL_ACCUM_BUFFER_BIT , and GL_STENCIL_BUFFER_BIT and glClear() is declared as
Then a call to the function looks like this
Internally, a function taking a bitfield like this can use binary and to extract the individual bits. For example, an implementation of glClear() might look like:
The advantage to this approach is that function argument overhead is decreased. Since the minimum datum size is one byte, separating the options into separate arguments would be wasting seven bits per argument and would occupy more stack space. Instead, functions typically accept one or more 32-bit integers, with up to 32 option bits in each. While elegant, in the simplest implementation this solution is not type-safe . A GLbitfield is simply defined to be an unsigned int , so the compiler would allow a meaningless call to glClear(42) or even glClear(GL_POINTS) . In C++ an alternative would be to create a class to encapsulate the set of arguments that glClear could accept and could be cleanly encapsulated in a library.
Masks are used with IP addresses in IP ACLs (Access Control Lists) to specify what should be permitted and denied. To configure IP addresses on interfaces, masks start with 255 and have the large values on the left side: for example, IP address 203.0.113.129 with a 255.255.255.224 mask. Masks for IP ACLs are the reverse: for example, mask 0.0.0.255 . This is sometimes called an inverse mask or a wildcard mask . When the value of the mask is broken down into binary (0s and 1s), the results determine which address bits are to be considered in processing the traffic. A 0 -bit indicates that the address bit must be considered (exact match); a 1 -bit in the mask is a "don't care". This table further explains the concept.
Mask example:
network address (traffic that is to be processed): 192.0.2.0
mask: 0.0.0.255
network address (binary): 11000000.00000000.00000010.00000000
mask (binary): 00000000.00000000.00000000.11111111
Based on the binary mask, it can be seen that the first three sets ( octets ) must match the given binary network address exactly (11000000.00000000.00000010). The last set of numbers is made of "don't cares" (.11111111). Therefore, all traffic that begins with " 192.0.2. " matches, since the last octet is "don't care". Therefore, with this mask, network addresses 192.0.2.1 through 192.0.2.255 ( 192.0.2.x ) are processed.
Subtract the normal mask from 255.255.255.255 in order to determine the ACL inverse mask. In this example, the inverse mask is determined for network address 198.51.100.0 with a normal mask of 255.255.255.0 .
255.255.255.255 − 255.255.255.0 (normal mask) = 0.0.0.255 (inverse mask)
ACL equivalents
The source/source-wildcard of 0.0.0.0 / 255.255.255.255 means "any".
The source/wildcard of 198.51.100.2 / 0.0.0.0 is the same as "host 198.51.100.2 "
In computer graphics , when a given image is intended to be placed over a background, the transparent areas can be specified through a binary mask. [ 1 ] This way, for each intended image there are actually two bitmaps : the actual image, in which the unused areas are given a pixel value with all bits set to 0s, and an additional mask , in which the correspondent image areas are given a pixel value of all bits set to 0s and the surrounding areas a value of all bits set to 1s. In the sample at right, black pixels have the all-zero bits and white pixels have the all-one bits.
At run time , to put the image on the screen over the background, the program first masks the screen pixel's bits with the image mask at the desired coordinates using the bitwise AND operation. This preserves the background pixels of the transparent areas while resets with zeros the bits of the pixels which will be obscured by the overlapped image.
Then, the program renders the image pixel's bits by combining them with the background pixel's bits using the bitwise OR operation. This way, the image pixels are appropriately placed while keeping the background surrounding pixels preserved. The result is a perfect compound of the image over the background.
This technique is used for painting pointing device cursors, in typical 2-D videogames for characters, bullets and so on (the sprites ), for GUI icons , and for video titling and other image mixing applications. A faster method is to simply overwrite the background pixels with the foreground pixels if their alpha=1
Although related (due to being used for the same purposes), transparent colors and alpha channels are techniques which do not involve the image pixel mixage by binary masking.
To create a hashing function for a hash table , often a function is used that has a large domain. To create an index from the output of the function, a modulo can be taken to reduce the size of the domain to match the size of the array; however, it is often faster on many processors to restrict the size of the hash table to powers of two sizes and use a bitmask instead.
An example of both modulo and masking in C: | https://en.wikipedia.org/wiki/Mask_(computing) |
In microtechnology , mask inspection or photomask inspection is an operation of checking the correctness of the fabricated photomasks , used, e.g., for semiconductor device fabrication . [ 1 ]
Modern technologies for locating defects in photomasks are automated systems that involve scanning electron microscopy and other advanced tools. [ 2 ]
The term "mask inspection" may also informally refer to mask data inspection step performed before actual writing the real mask. [ 3 ] Other methods of inspection use specially constructed light microscope systems such as are available from Probing Solutions Inc. These rely on white light, typically optimized at approximately 538 nM and use incident bright and dark field as well as transmitted bright and dark field illumination to see pin holes, edge defects and many forms of contamination and substrate defects.
This electronics-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mask_inspection |
A masking agent is a reagent used in chemical analysis which reacts with chemical species that may interfere in the analysis.
In sports a masking agent is used to hide or prevent detection of a banned substance or illegal drug like anabolic steroids or stimulants . Diuretics are the simplest form of masking agent and work by enhancing water loss via urine excretion and thus diluting the urine, which results in lower concentrations of the banned substance as more of it is being excreted from the body making it more difficult for laboratories to detect. [ 1 ]
This article about analytical chemistry is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Masking_agent |
In electronics , Mason's invariant , named after Samuel Jefferson Mason , is a measure of the quality of transistors .
"When trying to solve a seemingly difficult problem, Sam said to concentrate on the easier ones first; the rest, including the hardest ones, will follow," recalled Andrew Viterbi , co-founder and former vice-president of Qualcomm . He had been a thesis advisee under Samuel Mason at MIT , and this was one lesson he especially remembered from his professor. [ 1 ] A few years earlier, Mason had heeded his own advice when he defined a unilateral power gain for a linear two-port device, or U. After concentrating on easier problems with power gain in feedback amplifiers , a figure of merit for all three-terminal devices followed that is still used today as Mason's Invariant. [ 2 ]
In 1953, transistors were only five years old, and they were the only successful solid-state three-terminal active device . They were beginning to be used for RF applications, and they were limited to VHF frequencies and below. Mason wanted to find a figure of merit to compare transistors, and this led him to discover that the unilateral power gain of a linear two-port device was an invariant figure of merit. [ 2 ]
In his paper Power Gain in Feedback Amplifiers published in 1953, Mason stated in his introduction,
"A vacuum tube , very often represented as a simple transconductance driving a passive impedance, may lead to relatively simple amplifier designs in which the input impedance (and hence the power gain ) is effectively infinite, the voltage gain is the quantity of interest, and the input circuit is isolated from the load. The transistor, however, usually cannot be characterized so easily." [ 3 ]
He wanted to find a metric to characterize and measure the quality of transistors since up until then, no such measure existed. His discovery turned out to have applications beyond transistors.
Mason first defined the device being studied with the three constraints listed below. [ 2 ]
Then, according to Madhu Gupta in Power Gain in Feedback Amplifiers, a Classic Revisited , Mason defined the problem as "being the search for device properties that are invariant with respect to transformations as represented by an embedding network" that satisfy the four constraints listed below. [ 2 ]
He next showed that all transformations that satisfy the above constraints can be accomplished with just three simple transformations performed sequentially. Similarly, this is the same as representing an embedding network by a set of three embedding networks nested within one another. The three mathematical expressions can be seen below. [ 2 ]
1. Reactance padding: [ Z 11 ′ Z 12 ′ Z 21 ′ Z 22 ′ ] = [ Z 11 + j x 11 Z 12 + j x 12 Z 21 + j x 21 Z 22 + j x 22 ] {\displaystyle {\begin{bmatrix}Z'_{11}&Z'_{12}\\Z'_{21}&Z'_{22}\end{bmatrix}}={\begin{bmatrix}Z_{11}+jx_{11}&Z_{12}+jx_{12}\\Z_{21}+jx_{21}&Z_{22}+jx_{22}\end{bmatrix}}}
2. Real Transformations: [ Z 11 ′ Z 12 ′ Z 21 ′ Z 22 ′ ] = [ n 11 n 12 n 21 n 22 ] [ Z 11 Z 12 Z 21 Z 22 ] [ n 11 n 12 n 21 n 22 ] {\displaystyle {\begin{bmatrix}Z'_{11}&Z'_{12}\\Z'_{21}&Z'_{22}\end{bmatrix}}={\begin{bmatrix}n_{11}&n_{12}\\n_{21}&n_{22}\end{bmatrix}}{\begin{bmatrix}Z_{11}&Z_{12}\\Z_{21}&Z_{22}\end{bmatrix}}{\begin{bmatrix}n_{11}&n_{12}\\n_{21}&n_{22}\end{bmatrix}}}
3. Inversion: [ Z 11 ′ Z 12 ′ Z 21 ′ Z 22 ′ ] = [ Z 11 Z 12 Z 21 Z 22 ] − 1 {\displaystyle {\begin{bmatrix}Z'_{11}&Z'_{12}\\Z'_{21}&Z'_{22}\end{bmatrix}}={\begin{bmatrix}Z_{11}&Z_{12}\\Z_{21}&Z_{22}\end{bmatrix}}^{-1}}
Mason then considered which quantities remained invariant under each of these three transformations. His conclusions, listed respectively to the transformations above, are shown below. Each transformation left the values below unchanged. [ 2 ]
1. Reactance padding: [ Z − Z t ] {\displaystyle \left[Z-Z_{t}\right]} and [ Z + Z ∗ ] {\displaystyle \left[Z+Z^{*}\right]}
2. Real transformations: [ Z − Z t ] [ Z + Z ∗ ] {\displaystyle \left[Z-Z_{t}\right]\left[Z+Z^{*}\right]} and det [ Z − Z t ] det [ Z + Z ∗ ] {\displaystyle {\dfrac {\det {\left[Z-Z_{t}\right]}}{\det {\left[Z+Z^{*}\right]}}}}
3. Inversion:
The magnitudes of the two determinants and the sign of the denominator in the above fraction remain unchanged in the inversion transformation. Consequently, the quantity invariant under all three conditions is: [ 2 ]
Mason's Invariant, or U, is the only device characteristic that is invariant under lossless, reciprocal embeddings. In other words, U can be used as a figure of merit to compare any two-port active device (which includes three-terminal devices used as two-ports). For example, a factory producing BJTs can calculate U of the transistors it is producing and compare their quality to the other BJTs on the market. Furthermore, U can be used as an indicator of activity. If U is greater than one, the two-port device is active; otherwise, that device is passive. This is especially useful in the microwave engineering community. Though originally published in a circuit theory journal, Mason's paper becomes especially relevant to microwave engineers since U is usually slightly greater than or equal to one in the microwave frequency range. When U is smaller than or considerably larger than one, it becomes relatively useless. [ 2 ]
While Mason's Invariant can be used as a figure of merit across all operating frequencies, its value at ƒ max is especially useful. ƒ max is the maximum oscillation frequency of a device, and it is discovered when U ( f max ) = 1 {\displaystyle U(f_{\max })=1} . This frequency is also the frequency at which the maximum stable gain G ms and the maximum available gain G ma of the device become one. Consequently, ƒ max is a characteristic of the device, and it has the significance that it is the maximum frequency of oscillation in a circuit where only one active device is present, the device is embedded in a passive network, and only single sinusoidal signals are of interest. [ 2 ]
In his revisit of Mason's paper, Gupta states, "Perhaps the most convincing evidence of the utility of the concept of a unilateral power gain as a device figure of merit is the fact that for the last three decades, practically every new, active, two-port device developed for high frequency use has been carefully scrutinized for the achievable value of U..." [ 2 ] This assumption is appropriate because "U max " or "maximum unilateral gain" is still listed on transistor specification sheets, and Mason's Invariant is still taught in some undergraduate electrical engineering curricula. Though now it has been over five decades, Mason's finding of an invariant device characteristic still plays a significant role in transistor design. | https://en.wikipedia.org/wiki/Mason's_invariant |
A mason's mark is an engraved symbol often found on dressed stone in buildings and other public structures.
Regulations issued in Scotland in 1598 by James VI 's Master of Works, William Schaw , stated that on admission to the guild , every mason had to enter his name and his mark in a register. There are three types of marks used by stonemasons . [ 1 ]
Freemasonry , a fraternal order that uses an analogy to stonemasonry for much of its structure, also makes use of marks. A Freemason who takes the degree of Mark Master Mason will be asked to create his own Mark, as a type of unique signature or identifying badge. Some of these can be quite elaborate. | https://en.wikipedia.org/wiki/Mason's_mark |
The Mason equation is an approximate analytical expression for the growth (due to condensation ) or evaporation of a water droplet—it is due to the meteorologist B. J. Mason . [ 1 ] The expression is found by recognising that mass diffusion towards the water drop in a supersaturated environment transports energy as latent heat , and this has to be balanced by the diffusion of sensible heat back across the boundary layer , (and the energy of heatup of the drop, but for a cloud-sized drop this last term is usually small).
In Mason's formulation the changes in temperature across the boundary layer can be related to the changes in saturated vapour pressure by the Clausius–Clapeyron relation ; the two energy transport terms must be nearly equal but opposite in sign and so this sets the interface temperature of the drop. The resulting expression for the growth rate is significantly lower than that expected if the drop were not warmed by the latent heat.
Thus if the drop has a size r , the inward mass flow rate is given by [ 1 ]
and the sensible heat flux by [ 1 ]
and the final expression for the growth rate is [ 1 ]
where
This thermodynamics -related article is a stub . You can help Wikipedia by expanding it .
This meteorology –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mason_equation |
Masonry veneer walls consist of a single non-structural external layer of masonry , typically made of brick , stone or manufactured stone. [ 1 ] Masonry veneer can have an air space behind it and is technically called "anchored veneer". A masonry veneer attached directly to the backing is called "adhered veneer". The innermost element is structural, and may consist of masonry, concrete, timber or metal frame.
Because brick itself is not waterproof, the airspace also functions as a drainage plane, allowing any water that has penetrated the veneer to drain to the bottom of the air space, where it encounters flashing (weatherproofing) and is directed to the outside through weep holes, rather than entering the building.
Other advantages of a masonry veneer include:
Because the masonry veneer is non-structural, it must be tied back to the building structure to prevent movement under wind and earthquake loads. Brick ties are used for this purpose, and may take the form of corrugated metal straps nailed or screwed to the structural framing, or as wire extensions to horizontal joint reinforcement in a fully masonry veneer or cavity wall. Although the veneer is vertically self-supporting, shelf angles are often used in multi-story buildings, typically at floor edges, to provide a horizontal expansion joint that allows expansion of the brick and potential shrinkage of the frame. In multi-story buildings, such a system may be called a curtain wall . Adhered masonry veneer is bonded to the backing so it does not typically need a shelf angle.
Masonry veneers can be made of brick , concrete , natural stone or manufactured stone product. Typically, masonry refers to individual units that are placed in a mortar bed, making a distinction with panelized products.
A variant on masonry veneer is the rainscreen veneer. Rainscreens are ventilated at the top and bottom of the cavity to prevent wind-driven rain from being driven into the building by unbalanced pressure. Such systems are typically encountered in areas where blowing rain is a significant concern.
Masonry has high thermal mass , so masonry is slower to heat up, and can continue to release heat long into the night; without insulation half of that heat will be released into the building. Masonry with a dark external surface absorbs more heat than with a lighter external surface, especially if exposed to sunlight. Reverse masonry veneer walls have the brickwork inside and the lightweight frame and cladding outside; this has the advantage of providing the thermal mass on the inside of a building.
Masonry itself provides very little insulation, however:
Different configurations of such foil(s), air-space(s), and/or insulating material(s) can perform significantly better at excluding heat during summer and/or retaining heat during winter; these configurations often perform in counter-intuitive ways. Because of the enormous long-term potential for reducing energy requirements and improving occupant comfort, building designers should consult engineers or adopt configurations with known performances. | https://en.wikipedia.org/wiki/Masonry_veneer |
The Mason–Weaver equation (named after Max Mason and Warren Weaver ) describes the sedimentation and diffusion of solutes under a uniform force , usually a gravitational field. [ 1 ] Assuming that the gravitational field is aligned in the z direction (Fig. 1), the Mason–Weaver equation may be written
where t is the time, c is the solute concentration (moles per unit length in the z -direction), and the parameters D , s , and g represent the solute diffusion constant , sedimentation coefficient and the (presumed constant) acceleration of gravity , respectively.
The Mason–Weaver equation is complemented by the boundary conditions
at the top and bottom of the cell, denoted as z a {\displaystyle z_{a}} and z b {\displaystyle z_{b}} , respectively (Fig. 1). These boundary conditions correspond to the physical requirement that no solute pass through the top and bottom of the cell, i.e., that the flux there be zero. The cell is assumed to be rectangular and aligned with
the Cartesian axes (Fig. 1), so that the net flux through the side walls is likewise
zero. Hence, the total amount of solute in the cell
is conserved, i.e., d N tot / d t = 0 {\displaystyle dN_{\text{tot}}/dt=0} .
A typical particle of mass m moving with vertical velocity v is acted upon by three forces (Fig. 1): the drag force f v {\displaystyle fv} , the force of gravity m g {\displaystyle mg} and the buoyant force ρ V g {\displaystyle \rho Vg} , where g is the acceleration of gravity , V is the solute particle volume and ρ {\displaystyle \rho } is the solvent density . At equilibrium (typically reached in roughly 10 ns for molecular solutes ), the
particle attains a terminal velocity v term {\displaystyle v_{\text{term}}} where the three forces are balanced. Since V equals the particle mass m times its partial specific volume ν ¯ {\displaystyle {\bar {\nu }}} , the equilibrium condition may be written as
where m b {\displaystyle m_{b}} is the buoyant mass .
We define the Mason–Weaver sedimentation coefficient s = d e f m b / f = v term / g {\displaystyle s\ {\stackrel {\mathrm {def} }{=}}\ m_{b}/f=v_{\text{term}}/g} . Since the drag coefficient f is related to the diffusion constant D by the Einstein relation
the ratio of s and D equals
where k B {\displaystyle k_{B}} is the Boltzmann constant and T is the temperature in kelvins .
The flux J at any point is given by
The first term describes the flux due to diffusion down a concentration gradient, whereas the second term
describes the convective flux due to the average velocity v term {\displaystyle v_{\text{term}}} of the particles. A positive net flux out of a small volume produces a negative change in the local concentration within that volume
Substituting the equation for the flux J produces the Mason–Weaver equation
The parameters D , s and g determine a length scale z 0 {\displaystyle z_{0}}
and a time scale t 0 {\displaystyle t_{0}}
Defining the dimensionless variables ζ = d e f z / z 0 {\displaystyle \zeta \ {\stackrel {\mathrm {def} }{=}}\ z/z_{0}} and τ = d e f t / t 0 {\displaystyle \tau \ {\stackrel {\mathrm {def} }{=}}\ t/t_{0}} , the Mason–Weaver equation becomes
subject to the boundary conditions
at the top and bottom of the cell, ζ a {\displaystyle \zeta _{a}} and ζ b {\displaystyle \zeta _{b}} , respectively.
This partial differential equation may be solved by separation of variables . Defining c ( ζ , τ ) = d e f e − ζ / 2 T ( τ ) P ( ζ ) {\displaystyle c(\zeta ,\tau )\ {\stackrel {\mathrm {def} }{=}}\ e^{-\zeta /2}T(\tau )P(\zeta )} , we obtain two ordinary differential equations coupled by a constant β {\displaystyle \beta }
where acceptable values of β {\displaystyle \beta } are defined by the boundary conditions
at the upper and lower boundaries, ζ a {\displaystyle \zeta _{a}} and ζ b {\displaystyle \zeta _{b}} , respectively. Since the T equation has the solution T ( τ ) = T 0 e − β τ {\displaystyle T(\tau )=T_{0}e^{-\beta \tau }} , where T 0 {\displaystyle T_{0}} is a constant, the Mason–Weaver equation is reduced to solving for the function P ( ζ ) {\displaystyle P(\zeta )} .
The ordinary differential equation for P and its boundary conditions satisfy the criteria
for a Sturm–Liouville problem , from which several conclusions follow. First , there is a discrete set of orthonormal eigenfunctions P k ( ζ ) {\displaystyle P_{k}(\zeta )} that satisfy the ordinary differential equation and boundary conditions . Second , the corresponding eigenvalues β k {\displaystyle \beta _{k}} are real, bounded below by a lowest eigenvalue β 0 {\displaystyle \beta _{0}} and grow asymptotically like k 2 {\displaystyle k^{2}} where the nonnegative integer k is the rank of the eigenvalue . (In our case, the lowest eigenvalue is zero, corresponding to the equilibrium solution.) Third , the eigenfunctions form a complete set; any solution for c ( ζ , τ ) {\displaystyle c(\zeta ,\tau )} can be expressed as a weighted sum of the eigenfunctions
where c k {\displaystyle c_{k}} are constant coefficients determined from the initial distribution c ( ζ , τ = 0 ) {\displaystyle c(\zeta ,\tau =0)}
At equilibrium, β = 0 {\displaystyle \beta =0} (by definition) and the equilibrium concentration distribution is
which agrees with the Boltzmann distribution . The P 0 ( ζ ) {\displaystyle P_{0}(\zeta )} function satisfies the ordinary differential equation and boundary conditions at all values of ζ {\displaystyle \zeta } (as may be verified by substitution), and the constant B may be determined from the total amount of solute
To find the non-equilibrium values of the eigenvalues β k {\displaystyle \beta _{k}} , we proceed as follows. The P equation has the form of a simple harmonic oscillator with solutions P ( ζ ) = e i ω k ζ {\displaystyle P(\zeta )=e^{i\omega _{k}\zeta }} where
Depending on the value of β k {\displaystyle \beta _{k}} , ω k {\displaystyle \omega _{k}} is either purely real ( β k ≥ 1 4 {\displaystyle \beta _{k}\geq {\frac {1}{4}}} ) or purely imaginary ( β k < 1 4 {\displaystyle \beta _{k}<{\frac {1}{4}}} ). Only one purely imaginary solution can satisfy the boundary conditions , namely, the equilibrium solution. Hence, the non-equilibrium eigenfunctions can be written as
where A and B are constants and ω {\displaystyle \omega } is real and strictly positive.
By introducing the oscillator amplitude ρ {\displaystyle \rho } and phase φ {\displaystyle \varphi } as new variables,
the second-order equation for P is factored into two simple first-order equations
Remarkably, the transformed boundary conditions are independent of ρ {\displaystyle \rho } and the endpoints ζ a {\displaystyle \zeta _{a}} and ζ b {\displaystyle \zeta _{b}}
Therefore, we obtain an equation
giving an exact solution for the frequencies ω k {\displaystyle \omega _{k}}
The eigenfrequencies ω k {\displaystyle \omega _{k}} are positive as required, since ζ a > ζ b {\displaystyle \zeta _{a}>\zeta _{b}} , and comprise the set of harmonics of the fundamental frequency ω 1 = d e f π / ( ζ a − ζ b ) {\displaystyle \omega _{1}\ {\stackrel {\mathrm {def} }{=}}\ \pi /(\zeta _{a}-\zeta _{b})} . Finally, the eigenvalues β k {\displaystyle \beta _{k}} can be derived from ω k {\displaystyle \omega _{k}}
Taken together, the non-equilibrium components of the solution correspond to a Fourier series decomposition of the initial concentration distribution c ( ζ , τ = 0 ) {\displaystyle c(\zeta ,\tau =0)} multiplied by the weighting function e ζ / 2 {\displaystyle e^{\zeta /2}} . Each Fourier component decays independently as e − β k τ {\displaystyle e^{-\beta _{k}\tau }} , where β k {\displaystyle \beta _{k}} is given above in terms of the Fourier series frequencies ω k {\displaystyle \omega _{k}} . | https://en.wikipedia.org/wiki/Mason–Weaver_equation |
Masreliez theorem [ 1 ] describes a recursive algorithm within the technology of extended Kalman filter , named after the Swedish-American physicist John Masreliez , who is its author. The algorithm estimates the state of a dynamic system with the help of often incomplete measurements marred by distortion . [ 2 ]
Masreliez's theorem produces estimates that are quite good approximations to the exact conditional mean in non-Gaussian additive outlier (AO) situations. Some evidence for this can be had by Monte Carlo simulations . [ 3 ]
The key approximation property used to construct these filters is that the state prediction density is approximately Gaussian . Masreliez discovered in 1975 [ 1 ] that this approximation yields an intuitively appealing non-Gaussian filter recursions, with data dependent covariance (unlike the Gaussian case) this derivation also provides one of the nicest ways of establishing the standard Kalman filter recursions. Some theoretical justification for use of the Masreliez approximation is provided by the "continuity of state prediction densities" theorem in Martin (1979). [ 3 ] | https://en.wikipedia.org/wiki/Masreliez's_theorem |
Mass-analyzed ion kinetic-energy spectrometry ( MIKES ) is a mass spectrometry technique by which mass spectra are obtained from a sector instrument that incorporates at least one magnetic sector plus one electric sector in reverse geometry (the beam first enters the magnetic sector). [ 1 ] [ 2 ] [ 3 ] The accelerating voltage V , and the magnetic field B , are set to select the precursor ions of a particular m/z . The precursor ions then dissociate or react in an electric field -free region between the two sectors. The ratio of the kinetic energy to charge of the product ions are analyzed by scanning the electric sector field E . The width of the product ion spectrum peaks is related to the kinetic energy release distribution for the dissociation process. [ 4 ]
MIKES was developed at Purdue University in 1973 by Beynon , Cooks , J. W. Amy, W. E. Baitinger, and T. Y. Ridley. [ 5 ] MIKES was invented because researches at Purdue and Cornell thought that if the parent ion was mass-selected before the dissociation and mass analysis of the products by the electric sector it would be easier to study the metastable ions and the collision-induced dissociation (CID). [ 6 ] This was an achievement because it combined the utility of previous instruments such as the ion kinetic energy spectrometer with the ability to mass select precursor ions. That precursor ion is mass selected with the magnetic sector. The dissociation products are then mass analyzed using the electric sector. "The peak shapes revealed from the electric sector scan can provide information on the kinetic energy release from in the course of fragmentation and on the kinetic energy uptake in the course of ionic collision processes." [ citation needed ] The dispersion of velocities due to kinetic energy release leads to the characteristic wide metastable peaks observed using MIKES techniques. [ 5 ]
MIKES is a powerful technique used for structural studies of organic compounds, gaseous ions, and also for direct analysis of complex mixtures without separation of the components. [ 3 ] [ 7 ] In other words, it is used for molecular structure studies. [ 8 ] The reason why MIKES is good for molecular structure studies is due to the reverse-geometry of MIKES. The MIKES Schematic shows that the ion species in the source goes into the magnetic field. After which, the chemistry is later studied in the second field-free region (FFR) by scanning the electric sector which defines the nature of the fragments by measuring their kinetic energy. This causes competitive unimolecular fragmentations that can be observed in the MIKE spectra. Furthermore, if gas is brought into the second FFR, more dissociation will be induced by collision, that will later appear in the MIKE spectra. [ 3 ]
This scan uses reverse-geometry (BE-type) instruments. These instruments use a front-end magnetic sector that allows for exclusive mass selection of the precursor ion. The fragmentation region is in-between the two analyzers. The electric sector scan gives the product-ion spectrum. MIKES can also be used for direct measurement of kinetic-energy release values. [ 9 ]
MIKES, as the name implies, is used for kinetic energy spectrometery. This means that certain criteria are needed to accomplish this. One such feature of MIKES is that it has high kinetic energy resolution and good angular resolution . [ 7 ] This is due to the fact that MIKES has low accelerating voltage, around 3 kilo-volts. [ 3 ] Another feature is that it has good differential pumping between the various regions of the instrument. In addition, MIKES has multiple systems for bringing in and/or overseeing collision gases or vapors and the ability to vary slit height and width. This prevents favoritism when determining kinetic energy distributions. Although common now, back in the 1970s, MIKES had a great computer compatibility that allowed for readily obtainable molecular structures. [ 7 ]
A disadvantage to MIKES is that observations are made later in the ion flight path when compared to other methods. Also, a smaller number of ions will typically decompose . This will in turn cause the sensitivity to be lower than other kinetic energy spectroscopy methods. [ 10 ] | https://en.wikipedia.org/wiki/Mass-analyzed_ion-kinetic-energy_spectrometry |
The mass-flux fraction (or Hirschfelder-Curtiss variable or Kármán-Penner variable ) is the ratio of mass-flux of a particular chemical species to the total mass flux of a gaseous mixture. It includes both the convectional mass flux and the diffusional mass flux. It was introduced by Joseph O. Hirschfelder and Charles F. Curtiss in 1948 [ 1 ] and later by Theodore von Kármán and Sol Penner in 1954. [ 2 ] [ 3 ] The mass-flux fraction of a species i is defined as [ 4 ]
where
It satisfies the identity
similar to the mass fraction, but the mass-flux fraction can take both positive and negative values. This variable is used in steady, one-dimensional combustion problems in place of the mass fraction. [ 5 ] For one-dimensional ( x {\displaystyle x} direction) steady flows, the conservation equation for the mass-flux fraction reduces to
where w i {\displaystyle w_{i}} is the mass production rate of species i . | https://en.wikipedia.org/wiki/Mass-flux_fraction |
Mass-independent isotope fractionation or Non-mass-dependent fractionation (NMD), [ 1 ] refers to any chemical or physical process that acts to separate isotopes , where the amount of separation does not scale in proportion with the difference in the masses of the isotopes. Most isotopic fractionations (including typical kinetic fractionations and equilibrium fractionations ) are caused by the effects of the mass of an isotope on atomic or molecular velocities, diffusivities or bond strengths. Mass-independent fractionation processes are less common, occurring mainly in photochemical and spin-forbidden reactions . Observation of mass-independently fractionated materials can therefore be used to trace these types of reactions in nature and in laboratory experiments.
The most notable examples of mass-independent fractionation in nature are found in the isotopes of oxygen and sulfur . The first example was discovered by Robert N. Clayton , Toshiko Mayeda , and Lawrence Grossman in 1973, [ 2 ] in the oxygen isotopic composition of refractory calcium–aluminium-rich inclusions in the Allende meteorite . The inclusions, thought to be among the oldest solid materials in the Solar System , show a pattern of low 18 O/ 16 O and 17 O/ 16 O relative to samples from the Earth and Moon . Both ratios vary by the same amount in the inclusions, although the mass difference between 18 O and 16 O is almost twice as large as the difference between 17 O and 16 O. Originally this was interpreted as evidence of incomplete mixing of 16 O-rich material (created and distributed by a large star in a supernova ) into the Solar nebula . However, recent measurement of the oxygen-isotope composition of the Solar wind , using samples collected by the Genesis spacecraft , shows that the most 16 O-rich inclusions are close to the bulk composition of the solar system. This implies that Earth, the Moon, Mars, and asteroids all formed from 18 O- and 17 O-enriched material. Photodissociation of carbon monoxide in the Solar nebula has been proposed to explain this isotope fractionation.
Mass-independent fractionation also has been observed in ozone . Large, 1:1 enrichments of 18 O/ 16 O and 17 O/ 16 O in ozone were discovered in laboratory synthesis experiments by Mark Thiemens and John Heidenreich in 1983, [ 3 ] and later found in stratospheric air samples measured by Konrad Mauersberger. [ 4 ] These enrichments were eventually traced to the three-body ozone formation reaction. [ 5 ]
Theoretical calculations [ 6 ] by Rudolph Marcus and others suggest that the enrichments are the result of a combination of mass-dependent and mass-independent kinetic isotope effects (KIE) involving the excited state O 3 * intermediate related to some unusual symmetry properties. The mass-dependent isotope effect occurs in asymmetric species, and arises from the difference in zero-point energy of the two formation channels available (e.g., 18 O 16 O + 16 O vs 18 O + 16 O 16 O for formation of 18 O 16 O 16 O.) These mass-dependent zero-point energy effects cancel one another out and do not affect the enrichment in heavy isotopes observed in ozone. [ 7 ] The mass-independent enrichment in ozone is still not fully understood, but may be due to isotopically symmetric O 3 * having a shorter lifetime than asymmetric O 3 *, thus not allowing a statistical distribution of energy throughout all the degrees of freedom , resulting in a mass-independent distribution of isotopes.
The mass-independent distribution of isotopes in stratospheric ozone can be transferred to carbon dioxide (CO 2 ). [ 8 ] This anomalous isotopic composition in CO 2 can be used to quantify gross primary production , the uptake of CO 2 by vegetation through photosynthesis . This effect of terrestrial vegetation on the isotopic signature of atmospheric CO 2 was simulated with a global model [ 9 ] and confirmed experimentally. [ 10 ]
Mass-independent fractionation of sulfur can be observed in ancient sediments, [ 11 ] where it preserves a signal of the prevailing environmental conditions. The creation and transfer of the mass-independent signature into minerals would be unlikely in an atmosphere containing abundant oxygen, constraining the Great Oxygenation Event to some time after 2,450 million years ago . Prior to this time, the MIS record implies that sulfate-reducing bacteria did not play a significant role in the global sulfur cycle, and that the MIS signal is due primarily to changes in volcanic activity. [ 12 ] | https://en.wikipedia.org/wiki/Mass-independent_fractionation |
The mass-spring-damper model consists of discrete mass nodes distributed throughout an object and interconnected via a network of springs and dampers .
This form of model is also well-suited for modelling objects with complex material behavior such as those with nonlinearity or viscoelasticity .
As well as engineering simulation, these systems have applications in computer graphics and computer animation . [ 1 ]
Deriving the equations of motion for this model is usually done by summing the forces on the mass (including any applied external forces F external ) {\displaystyle F_{\text{external}})} :
By rearranging this equation, we can derive the standard form:
ω n {\displaystyle \omega _{n}} is the undamped natural frequency and ζ {\displaystyle \zeta } is the damping ratio . The homogeneous equation for the mass spring system is:
This has the solution:
If ζ < 1 {\displaystyle \zeta <1} then ζ 2 − 1 {\displaystyle \zeta ^{2}-1} is negative, meaning the square root will be imaginary and therefore the solution will have an oscillatory component. [ 2 ]
This engineering-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mass-spring-damper_model |
The mass-to-charge ratio ( m / Q ) is a physical quantity relating the mass (quantity of matter) and the electric charge of a given particle, expressed in units of kilograms per coulomb (kg/C). It is most widely used in the electrodynamics of charged particles , e.g. in electron optics and ion optics .
It appears in the scientific fields of electron microscopy , cathode ray tubes , accelerator physics , nuclear physics , Auger electron spectroscopy , cosmology and mass spectrometry . [ 1 ] The importance of the mass-to-charge ratio, according to classical electrodynamics, is that two particles with the same mass-to-charge ratio move in the same path in a vacuum, when subjected to the same electric and magnetic fields.
Some disciplines use the charge-to-mass ratio ( Q / m ) instead, which is the multiplicative inverse of the mass-to-charge ratio. The CODATA recommended value for an electron is Q / m = −1.758 820 008 38 (55) × 10 11 C⋅kg −1 . [ 2 ]
When charged particles move in electric and magnetic fields the following two laws apply:
where F is the force applied to the ion, m is the mass of the particle, a is the acceleration , Q is the electric charge , E is the electric field , and v × B is the cross product of the ion's velocity and the magnetic flux density .
This differential equation is the classic equation of motion for charged particles. Together with the particle's initial conditions, it completely determines the particle's motion in space and time in terms of m / Q . Thus mass spectrometers could be thought of as "mass-to-charge spectrometers". When presenting data in a mass spectrum , it is common to use the dimensionless m / z , which denotes the dimensionless quantity formed by dividing the mass number of the ion by its charge number. [ 1 ]
Combining the two previous equations yields: ( m Q ) a = E + v × B . {\displaystyle \left({\frac {m}{Q}}\right)\mathbf {a} =\mathbf {E} +\mathbf {v} \times \mathbf {B} .}
This differential equation is the classic equation of motion of a charged particle in a vacuum. Together with the particle's initial conditions, it determines the particle's motion in space and time. It immediately reveals that two particles with the same m / Q ratio behave in the same way. This is why the mass-to-charge ratio is an important physical quantity in those scientific fields where charged particles interact with magnetic or electric fields.
There are non-classical effects that derive from quantum mechanics , such as the Stern–Gerlach effect that can diverge the path of ions of identical m / Q .
The IUPAC-recommended symbols for mass and charge are m and Q , respectively, [ 3 ] however using a lowercase q for charge is also very common. Charge is a scalar property, meaning that it can be either positive (+) or negative (−). The Coulomb (C) is the SI unit of charge; however, other units can be used, such as expressing charge in terms of the elementary charge ( e ). The SI unit of the physical quantity m / Q is kilogram per coulomb.
The units and notation above are used when dealing with the physics of mass spectrometry; however, the m / z notation is used for the independent variable in a mass spectrum . [ 4 ] This notation eases data interpretation since it is numerically more related to the dalton . [ 1 ] For example, if an ion carries one charge the m / z is numerically equivalent to the molecular or atomic mass of the ion in daltons (Da), where the numerical value of m / Q is abstruse. The m refers to the molecular or atomic mass number (number of nucleons) and z to the charge number of the ion ; however, the quantity of m / z is dimensionless by definition. [ 4 ] An ion with a mass of 100 Da (daltons) ( m = 100 ) carrying two charges ( z = 2 ) will be observed at m / z 50 . However, the empirical observation m / z 50 is one equation with two unknowns and could have arisen from other ions, such as an ion of mass 50 Da carrying one charge. Thus, the m / z of an ion alone neither infers mass nor the number of charges. Additional information, such as the mass spacing between mass isotopomers or the relationship between multiple charge states, is required to assign the charge state and infer the mass of the ion from the m / z . This additional information is often but not always available. Thus, the m / z is primarily used to report an empirical observation in mass spectrometry. This observation may be used in conjunction with other lines of evidence to subsequently infer the physical attributes of the ion, such as mass and charge. On rare occasions, the thomson has been used as a unit of the x-axis of a mass spectrum.
In the 19th century, the mass-to-charge ratios of some ions were measured by electrochemical methods.
The first attempt to measure the mass-to-charge ratio of cathode ray particles, assuming them to be ions, was made in 1884-1890 by German-born British physicist Arthur Schuster . He put an upper limit of 10^10 coul/kg, [ 5 ] but even that resulted in much greater value than expected, so little credence was given to his calculations at the time.
In 1897, the mass-to-charge ratio of the electron was first measured by J. J. Thomson . [ 6 ] By doing this, he showed that the electron was in fact a particle with a mass and a charge, and that its mass-to-charge ratio was much smaller than that of the hydrogen ion H + . In 1898, Wilhelm Wien separated ions ( canal rays ) according to their mass-to-charge ratio with an ion optical device with superimposed electric and magnetic fields ( Wien filter ). In 1901 Walter Kaufman measured the increase of electromagnetic mass of fast electrons ( Kaufmann–Bucherer–Neumann experiments ), or relativistic mass increase in modern terms. In 1913, Thomson measured the mass-to-charge ratio of ions with an instrument he called a parabola spectrograph. [ 7 ] Today, an instrument that measures the mass-to-charge ratio of charged particles is called a mass spectrometer .
The charge-to-mass ratio ( Q / m ) of an object is, as its name implies, the charge of an object divided by the mass of the same object. This quantity is generally useful only for objects that may be treated as particles. For extended objects, total charge, charge density, total mass, and mass density are often more useful.
Derivation: q v B = m v v r {\displaystyle qvB=mv{\frac {v}{r}}} or
Since F electric = F magnetic {\displaystyle F_{\text{electric}}=F_{\text{magnetic}}} , E q = B q v {\displaystyle Eq=Bqv} or
Equations ( 1 ) and ( 2 ) yield q m = E B 2 r {\displaystyle {\frac {q}{m}}={\frac {E}{B^{2}r}}}
In some experiments, the charge-to-mass ratio is the only quantity that can be measured directly. Often, the charge can be inferred from theoretical considerations, so the charge-to-mass ratio provides a way to calculate the mass of a particle.
Often, the charge-to-mass ratio can be determined by observing the deflection of a charged particle in an external magnetic field. The cyclotron equation, combined with other information such as the kinetic energy of the particle, will give the charge-to-mass ratio. One application of this principle is the mass spectrometer. The same principle can be used to extract information in experiments involving the cloud chamber .
The ratio of electrostatic to gravitational forces between two particles will be proportional to the product of their charge-to-mass ratios. It turns out that gravitational forces are negligible on the subatomic level, due to the extremely small masses of subatomic particles.
The electron charge-to-mass quotient, − e / m e {\displaystyle -e/m_{e}} , is a quantity that may be measured in experimental physics. It bears significance because the electron mass m e is difficult to measure directly, and is instead derived from measurements of the elementary charge e and e / m e {\displaystyle e/m_{e}} . It also has historical significance; the Q / m ratio of the electron was successfully calculated by J. J. Thomson in 1897—and more successfully by Dunnington, which involves the angular momentum and deflection due to a perpendicular magnetic field . Thomson's measurement convinced him that cathode rays were particles, which were later identified as electrons , and he is generally credited with their discovery.
The CODATA recommended value is − e / m e = −1.758 820 008 38 (55) × 10 11 C⋅kg −1 . [ 2 ] CODATA refers to this as the electron charge-to-mass quotient , but ratio is still commonly used.
There are two other common ways of measuring the charge-to-mass ratio of an electron, apart from Thomson and Dunnington's methods.
The charge-to-mass ratio of an electron may also be measured with the Zeeman effect , which gives rise to energy splittings in the presence of a magnetic field B : Δ E = e ℏ B 2 m ( m j , f g J , f − m j , i g J , i ) {\displaystyle \Delta E={\frac {e\hbar B}{2m}}(m_{j,f}g_{J,f}-m_{j,i}g_{J,i})}
Here m j are quantum integer values ranging from − j to j , with j as the eigenvalue of the total angular momentum operator J , with [ 2 ]
where S is the spin operator with eigenvalue s and L is the angular momentum operator with eigenvalue l . g J is the Landé g-factor , calculated as g J = 1 + j ( j + 1 ) + s ( s + 1 ) − l ( l + 1 ) 2 j ( j + 1 ) {\displaystyle g_{J}=1+{\frac {j(j+1)+s(s+1)-l(l+1)}{2j(j+1)}}}
The shift in energy is also given in terms of frequency υ and wavelength λ as Δ E = h Δ ν = h c Δ ( 1 λ ) = h c Δ λ λ 2 {\displaystyle \Delta E=h\Delta \nu =hc\Delta \left({\frac {1}{\lambda }}\right)=hc{\frac {\Delta \lambda }{\lambda ^{2}}}}
Measurements of the Zeeman effect commonly involve the use of a Fabry–Pérot interferometer , with light from a source (placed in a magnetic field) being passed between two mirrors of the interferometer. If δD is the change in mirror separation required to bring the m th-order ring of wavelength λ + Δλ into coincidence with that of wavelength λ , and Δ D brings the ( m + 1)th ring of wavelength λ into coincidence with the m th-order ring, then Δ λ = λ 2 δ D 2 D Δ D . {\displaystyle \Delta \lambda =\lambda ^{2}{\frac {\delta D}{2D\Delta D}}.}
It follows then that h c Δ λ λ 2 = h c δ D 2 D Δ D = e ℏ B 2 m ( m j , f g J , f − m j , i g J , i ) . {\displaystyle hc{\frac {\Delta \lambda }{\lambda ^{2}}}=hc{\frac {\delta D}{2D\Delta D}}={\frac {e\hbar B}{2m}}(m_{j,f}g_{J,f}-m_{j,i}g_{J,i})\,.}
Rearranging, it is possible to solve for the charge-to-mass ratio of an electron as e m = 4 π c B ( m j , f g J , f − m j , i g J , i ) δ D D Δ D . {\displaystyle {\frac {e}{m}}={\frac {4\pi c}{B(m_{j,f}g_{J,f}-m_{j,i}g_{J,i})}}{\frac {\delta D}{D\Delta D}}\,.} | https://en.wikipedia.org/wiki/Mass-to-charge_ratio |
In astrophysics and physical cosmology the mass-to-light ratio , normally designated with the Greek letter upsilon , ϒ , [ 1 ] is the quotient between the total mass of a spatial volume (typically on the scales of a galaxy or a cluster ) and its luminosity .
These ratios are calculated relative to the Sun as a baseline ratio which is a constant ϒ ☉ = 5133 kg / W : equal to the solar mass M ☉ divided by the solar luminosity L ☉ , M ☉ / L ☉ . The mass-to-light ratios of galaxies and clusters are all much greater than ϒ ☉ due in part to the fact that most of the matter in these objects does not reside within stars and observations suggest that a large fraction is present in the form of dark matter . [ 2 ] : 368
Luminosities are obtained from photometric observations, correcting the observed brightness of the object for the distance dimming and extinction effects. In general, unless a complete spectrum of the radiation emitted by the object is obtained, a model must be extrapolated through either power law or blackbody fits. The luminosity thus obtained is known as the bolometric luminosity . [ citation needed ]
Masses are often calculated from the dynamics of the virialized system or from gravitational lensing . Masses can also be measured through CMB backlighting. [ 3 ] Typical mass-to-light ratios for galaxies range from 2 to 10 ϒ ☉ while on the largest scales, the mass to light ratio of the observable universe is approximately 100 ϒ ☉ , in concordance with the current best fit cosmological model . [ citation needed ]
Mass-to-light ratios in application can be used to gain insight into the dark matter content and dust extinction in a galaxy. [ 4 ] Historically, rotation curves for spiral galaxies have been used to study galaxies, but mass-to-light ratios prove more accurate as a method of measuring mass. [ 5 ] | https://en.wikipedia.org/wiki/Mass-to-light_ratio |
MassLynx is a software package to control analytical equipment produced by Waters Corporation including liquid chromatography systems such as the ACQUITY UPLC series of UHPLC systems and mass spectrometers such as the Xevo TQ-S.
MassLynx is used for hardware control, creating, editing and executing run sequences as well as configuration of acquisition methods. Data treatment is performed in other software such as TargetLynx or ChromaLynx .
This scientific software article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/MassLynx |
MassMatrix is a mass spectrometry data analysis software that uses a statistical model to achieve increased mass accuracy over other database search algorithms. [ 1 ] This search engine is set apart from others dues to its ability to provide extremely efficient judgement between true and false positives for high mass accuracy data that has been obtained from present day mass spectrometer instruments. It is useful for identifying disulphide bonds in tandem mass spectrometry data. [ 2 ] This search engine is set apart from others due to its ability to provide extremely efficient judgement between true and false positives for high mass accuracy data that has been obtained from present day mass spectrometer instruments. [ 3 ]
This article about chemistry software is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/MassMatrix |
MassTag PCR is a modification of PCR based on mass-spectrometric detection of an end product. This technology was developed by researchers from the Mailman School of Public Health at Columbia University and the Columbia Genome Center. [ 1 ] [ 2 ]
Like conventional PCR, MassTag-PCR uses primer pairs . The difference is primers used for MassTag PCR are tagged with molecules of known masses or MassCodes. Instead of single pair of primers this technology uses a number of primers, making it a multiplex system. Unlike, conventional Multiplex PCR system, in MassTag PCR more than 15 primer pairs could be used. If DNA from any of the agent of primer panel is present, it will be amplified. Each amplified product will carry its specific Masscodes.
The PCR product is then purified to remove unbound primers, dNTPs, enzyme and other impurities. Finally, the purified PCR products are subjected to UV light as the chemical bond between the nucleic acids and primers is photolabile . As the Masscodes are liberated from PCR products they are detected with a Mass Spectrometer. Presence of specific MassCode indicates the presence of specific pathogen. [ 1 ]
This technique has been found to detect a previously uncharacterized clade of rhinovirus . [ 3 ] MassTag PCR is a more comprehensive and sensitive diagnostic technique, CII was able to determine the cause of this illness for 26 out of 79 previously unknown cases. MassTag PCR demonstrated its tripartite value as a tool for surveillance, outbreak detection, and epidemiology . | https://en.wikipedia.org/wiki/MassTag-PCR |
Mass Effect 3 is an action role-playing video game and the third installment of the Mass Effect video game series, developed by BioWare and published by Electronic Arts (EA), the first in the series to not be published by Microsoft Game Studios (MGS). Upon its release March 6, 2012, for the PlayStation 3 , Xbox 360 , and Windows , Mass Effect 3 generated controversy when its ending was poorly received by players who felt that it did not meet their expectations. Criticisms included the ending rendering character choices inconsequential, a general lack of closure, plot holes , and narrative inconsistency.
On June 26, 2012, developers released an Extended Cut as downloadable content (DLC) intended to clarify the endings and remedy fan concerns. The initial announcement of the development of add-on content to amend the ending as well as the subsequent release of Extended Cut sparked debates over the treatment of video games as art and whether BioWare should have to alter their vision of the work in response to external pressure, regardless of its quality.
In the original Mass Effect trilogy, players assume the role of Commander Shepard , a customizable avatar who leads allies from across the Milky Way galaxy in a struggle against a collective of powerful synthetic lifeforms called the Reapers , who harvest the galaxy of sentient spacefaring life every 50,000 years. By the events of Mass Effect 3 , the Reapers have arrived in the galaxy and begin harvesting entire worlds. To stop them, Shepard must form an alliance between all of Mass Effect ' s alien races to build the Crucible, a megastructure built from blueprints designed by the civilizations from previous cycles, including the Protheans , which can theoretically destroy the Reapers.
As Shepard, players dispatch a final "Marauder" enemy, entering a Reaper teleportation beam on Earth to reach the Citadel alongside their close ally and mentor, David Anderson, and begin the game's ending sequence. This follows a long and grueling battle in London where Shepard is gravely wounded by Harbinger, the leader of the Reapers. [ 2 ] Once there, Shepard and Anderson engage in a dialog-based final showdown with the Illusive Man , the leader of Cerberus ; only Shepard survives the confrontation. Shepard then attempts to fire the Crucible, only to be transported to the Citadel's pinnacle. They encounter the Star Child, the Reaper gestalt intelligence as manifested by the Catalyst in the form of a child. The AI explains the Reapers' true motives - the repeated culling prevents organic life from inevitably being rendered extinct by their own less-advanced artificially intelligent creations.
Having conceded defeat to Shepard, it presents up to three options for activating the Crucible, which will break the Reapers' galactic cycle of extinction: [ 3 ]
By making any of the above choices, Shepard activates the Crucible, which emits a wave of energy that spreads throughout the galaxy via the mass relays, damaging them in the process in the case of the destroy option. As the Normandy is hit by the wave of energy, it crashes on a remote planet.
Chris Hepler, one of the game's writers and the project's de facto "loremaster", explained in a 2021 interview that the final ending decision was both easier and had "much more project momentum", and that it was embraced by the project leads almost immediately, including its use of "space magic". The controversial aspects about the endings, such as Destroy ignoring the AI problem the Reapers aimed to prevent, Control rewarding the Reapers, and Synthesis violating the galaxy's bodily autonomy, were intentional in order to not make any of the choices perfectly moral or "right" for everyone. However, he also agreed that the game hinted at alternate endings that could have been used, and that a more hard science-based ending had been considered. [ 4 ] Concept scenarios for alternate endings that were discarded included:
The developers attempted to write a viable ending around the concept of dark energy and had considered a number of hypothetical theories surrounding it as the reason behind the creation of the Reapers: examples that were proposed by team members included curbing the use of dark energy by organic civilizations due to its cumulative entropic effect that would hasten the end of the universe , or preventing the universe's inevitable descent into a Big Crunch by focusing on organic species with biotic potential. [ 5 ] The game was acknowledged to contain direct hints that the Citadel species and the Reapers would team up to stop a dark energy anomaly that threatened the universe with destruction, although this was not seriously discussed by the writers. [ 4 ]
This ending scenario, shared by series concept artist Matt Rhodes on his personal website, envisions a villainous Shepard being confronted by either Ashley Williams or Kaidan Alenko , the survivor of the Virmire incident from the first game, after being willingly modified by Reaper technology. This is intended to echo the character arc and downfall of Saren Arterius in the first Mass Effect as a "cyclical twist". [ 6 ]
An endgame scenario which never progressed past the concept art stage would have the Illusive Man transform into a Reaper creature, not unlike Saren at the end of the first game, for a final boss fight . [ 7 ]
Former Mass Effect lead writer Drew Karpyshyn revealed in a July 2022 interview that a proposed ending which was under serious consideration by the team would involve the Reapers being lured through the mass relays, and the entire network is then detonated to wipe them out. Since every galactic community is isolated from each other as a result of the damaged relays, it would serve as the premise for a direct sequel which would have been the fourth main series installment. [ 8 ]
Hepler's preferred ending eschewed "space magic" entirely and involved the Crucible being a weapon that annihilated objects with a high atomic number , including the Reapers, their creations, such as the Husks (which were implied to be created with niobium cybernetics) and Commander Shepard themselves, an idea inspired by Probability Moon by Nancy Kress . However, the final ending was approved too quickly for Hepler to pitch his idea, and he was afraid of being sued for copying the idea without permission. [ 4 ]
Shepard would discover a Reaper "Queen" that had been trapped somewhere within the Citadel and would then be prompted with three choices on how to deal with her. The choices offered by this discarded scenario ended up being similar in nature to the choices offered by the Catalyst in the final game's ending. [ 9 ]
Although Mass Effect 3 launched in early March 2012 to a predominantly positive critical reception, its endings received a very poor reception from players. By mid-March 2012, a contingent of displeased fans had organized an internet campaign called "Retake Mass Effect" to demand a better ending to the game, part of which included a charity drive for the organization Child's Play . [ 10 ] The drive raised $80,000 in less than two weeks before it was stopped. [ 11 ] One fan made a complaint to the Federal Trade Commission , arguing that BioWare did not deliver on the promise of its game. [ 12 ] Marjorie Stephens, Better Business Bureau director of marketplace services, alleged that the game falsely advertised the ability to completely shape the outcome. [ 13 ] However, in June 2012, the UK Advertising Standards Authority ruled that, while disappointing, the endings were different enough to not be misleading to an actionable extent. [ 14 ]
Opinions over the game's endings divided many critics. Among the criticisms include the ending rendering character choices inconsequential; a general lack of closure; lore contradictions and plot holes; character and narrative inconsistencies; the absence of a final boss battle; and inconsistencies between statements by BioWare staff during the game's development and the form the endings ultimately took. [ 15 ] [ 16 ] [ 17 ] [ 18 ] [ 19 ] Commentators took note of the magnitude and scale of the public reaction and highlighted how invested the series had made its players. A widely discussed fan theory proposed that the endings were a hallucinated consequence of Shepard's gradual, forcible Reaper indoctrination over the course of the trilogy, also positing that the "Destroy" ending was purposely colored red to dissuade Shepard from picking it, and thus, overcoming the mind control. [ 20 ] Dissatisfied fans also turned the final enemy unit encountered in combat into a sarcastic Internet meme called Marauder Shields . [ 21 ] [ 22 ]
A number of individuals associated with Mass Effect 3 , such as project director Casey Hudson and cast member Jessica Chobot , initially spoke out in support of the ending shortly after the game's launch. [ 24 ] [ 25 ] By March 16, 2012, Hudson and community coordinator Chris Priestly had acknowledged the growing controversy and provided assurances that the team were listening to feedback. [ 25 ] Hudson later went on record and conceded that players ought to have more closure and answers for the creative direction they had taken. [ 26 ] BioWare co-founder Ray Muzyka later announced that the company planned to address the criticism, with a further announcement to be made in April 2012. [ 26 ] [ 27 ] [ 28 ] Chobot issued a public apology on a blog post dated April 2, 2012 following backlash from some players in response to her choice of tone and words. [ 24 ]
BioWare announced a free downloadable content pack on April 5, 2012, that would expand upon the ending. [ 23 ] Some commentators expressed concerns that changing the endings by giving into fan demand would compromise the developers' creative vision as well as the artistic integrity of their work, and ultimately sets a bad precedent for the development of creative works in the video game industry. [ 29 ] [ 30 ] Video game developer Ken Levine remarked that he felt sad that players were fervently calling for a revised Mass Effect 3 ending as they would be left “disappointed”. [ 31 ] Others like Stephen Totilo from Kotaku welcomed BioWare's decision to be open towards revising the ending to their work. [ 32 ]
The expansion, Extended Cut , was released for most platforms on June 26, 2012. [ 33 ] While not drastically changing the existing endings, it retconned various plot holes noted by fans, such as the complete destruction of the Mass Relays, and more thoroughly explained the Star Child's logic. [ 34 ] Each ending was supplemented with additional cutscenes during the ending sequence, and a montage -based epilogue that depicts the aftermath of Shepard's actions, such as the fates of various supporting characters, alien species and entire worlds, all of which are variable based on prior narrative choices made by players along with their accumulated "Effective Military Strength" (EMS) score. [ 35 ] Extended Cut also provides an additional choice for players to refuse the offer and have Shepard attack the Catalyst, which results in the Crucible not being activated and an inevitable Reaper victory over the current cycle of organics. Following the release of the Extended Cut pack, Mike Fahey from Kotaku observed that fan reaction was generally mixed, [ 36 ] although certain individuals like the FTC complainant expressed satisfaction with the reworked ending sequences it introduced. [ 37 ] Video game publications were similarly divided, with some critics such as Joe Juba of Game Informer describing the new additions as a "substantial improvement" over the original ending, [ 38 ] while others such as Paul Tassi of Forbes felt it was "too little, far too late." [ 39 ]
A notable and widely circulated, though now allegedly discredited, fan theory about the ending was that Shepard had undergone gradual "indoctrination", or brainwashing , over the course of the series, and their mind had been fully infiltrated by the Reapers. The theory was created by dissatisfied fans by piecing together apparent evidence throughout the game, starting when Shepard touched the Prothean Beacon on Eden Prime, an event that caused them to have visions. After being hit by Harbinger's beam, Shepard hallucinates the ending, which metaphorically represents whether they can resist the brainwashing. In the theory, only "Destroy" would free Shepard from the mind control and allow them to awaken. [ 40 ]
Hepler clarified that the theory was based on a coincidence, saying "we didn't write that" and that it was never discussed in staff meetings as a plot point. While he agreed the ending was "trippy", it was entirely due to Shepard being on the verge of death. However, he expressed approval at the theory, calling it "interesting" and supporting the idea of mods or fanfiction based on the topic. [ 4 ]
"I remember about a week or so after we had launched [the game], we'd seen all these excellent critical reviews ... then all of a sudden people were saying, 'I felt the ending was weak.' And someone would say, 'Yeah, I thought it was actually pretty bad.' And someone else would say, 'I hated that ending.' It just snowballed like crazy, and pretty soon the whole issue was on fire."
Retrospective discussions of Mass Effect 3 inevitably involve attention towards its ending . James Davenport of PC Gamer opined that the game's ending received an "inordinate" amount of criticism, which distracts players from the other positive or exemplary aspects of Mass Effect 3 . [ 42 ] Forbes contributor Erik Kain took the view that the public outcry and the subsequent response from BioWare and EA "may end up being a healthy one for the industry, opening a new chapter in gamer/developer/publisher relations", and called the release Extended Edition as a complementary expansion to the original endings a "remarkable" choice that made gamers realize "that they are entitled, and that it isn't a bad thing, to quality games". [ 43 ] In 2018, Lucy O'Brien from IGN concurred and remarked that fan-driven internet campaigns like "Retake Mass Effect" have contributed to a paradigm shift in how consumers influence video game developers. [ 44 ] With the inclusion of Mass Effect 3 and its DLC content into the Mass Effect Legendary Edition compilation released in 2021, BioWare staff are hopeful that following the passage of time and the release of Legendary Edition , players would reassess their opinion about the ending as the culmination of the trilogy's overarching story arc. [ 45 ]
In the absence of significant official changes to the ending, fans released various mods to change the ending into a more satisfying one. One such mod, Priority: Earth Overhaul , makes wide-ranging changes to the main game and its final mission, such as adding new cutscenes and letting the player fight alongside the geth. [ 46 ] Another, the Happy Ending Mod by Audemus, removes controversial aspects of the ending such as the Star Child sequence and destruction of the Mass Relays, adding the Star Child's exposition to the Codex. "Destroy" is made the sole ending, but its drawbacks, such as all AI being destroyed and Shepard's possible death, are removed. Having been released for the original game, it was also released for Legendary Edition in 2022. [ 47 ] The mod also compatible with Citadel Epilogue Mod , which repurpose the Citadel DLC as an epilogue set a year after Mass Effect 3 .
The backlash to Mass Effect 3 's ending was suggested as having a significant impact on EA being named Consumerist 's 2012 and 2013 Worst Company in America. [ 48 ] [ 49 ] | https://en.wikipedia.org/wiki/Mass_Effect_3_ending_controversy |
In electronics and semiconductor physics, the law of mass action relates the concentrations of free electrons and electron holes under thermal equilibrium . It states that, under thermal equilibrium , the product of the free electron concentration n {\displaystyle n} and the free hole concentration p {\displaystyle p} is equal to a constant square of intrinsic carrier concentration n i {\displaystyle n_{\text{i}}} . The intrinsic carrier concentration is a function of temperature.
The equation for the mass action law for semiconductors is: [ 1 ] n p = n i 2 {\displaystyle np=n_{\text{i}}^{2}}
In semiconductors, free electrons and holes are the carriers that provide conduction . For cases where the number of carriers are much less than the number of band states, the carrier concentrations can be approximated by using Boltzmann statistics , giving the results below.
The free-electron concentration n can be approximated by n = N c exp [ − E c − E F k B T ] , {\displaystyle n=N_{\text{c}}\exp \left[-{\frac {E_{\text{c}}-E_{\text{F}}}{k_{\text{B}}T}}\right],} where
The free-hole concentration p is given by a similar formula p = N v exp [ − E F − E v k B T ] , {\displaystyle p=N_{\text{v}}\exp \left[-{\frac {E_{\text{F}}-E_{\text{v}}}{k_{\text{B}}T}}\right],} where
Using the carrier concentration equations given above, the mass action law can be stated as n p = N c N v exp ( − E g k B T ) = n i 2 , {\displaystyle np=N_{\text{c}}N_{\text{v}}\exp \left(-{\frac {E_{\text{g}}}{k_{\text{B}}T}}\right)=n_{i}^{2},} where E g is the band gap energy given by E g = E c − E v . The above equation holds true even for lightly doped extrinsic semiconductors as the product n p {\displaystyle np} is independent of doping concentration.
This electronics-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mass_action_law_(electronics) |
In neuroscience, the mass action principle suggests that the proportion of the brain that is injured is directly proportional to the decreased ability of memory functions. [ 1 ] In other words, memory cannot be localized to a single cortical area, but is instead distributed throughout the cortex. This theory is contrasted by functional specialization . This is one of two principles that Karl Lashley published in 1950, alongside the equipotentiality principle.
In the 19th century, animal researchers and scientists were divided into two main groups in terms of how they believe the brain compensated for induced brain damage. The redundancy theorists hypothesized that any lesioned section of cerebral mass had an almost duplicate section, usually on the opposing hemisphere. This "back-up" area was considered to be what takes over the functions of the lesioned area. On the other hand, vicariation theorists believed that different areas of the brain with different functions could assume responsibility for the affected area. Both ideas were highly debated and led to increased research on neuroplasticity and lesion research, eventually affecting the lesion research of Flourens and Lashley. [ citation needed ]
Localization theories can be dated as far back as Aristotle, but the man credited with the beginning concepts of field theory was Jean Pierre Flourens . [ citation needed ] Field theory is the concept that the brain acts as a single functional unit. He devised the first principle of mass action, stating,
"As long as not too much of the lobes is removed, they may in due time regain the exercise of their functions. Passing certain limits, however, the animal regains them only imperfectly, and passing these new limits it does not regain them at all. Finally, if one sensation comes back, all come back. If one faculty reappears, they all reappear.... This shows that each of these organs is only a single organ." [ citation needed ]
He also developed the theory of equipotentiality , stating, "All sensations, all perceptions, and all volition occupy concurrently the same seat in these organs. The faculty of sensation, perception, and volition is then essentially one faculty." [ 2 ]
Karl Lashley 's most famous research was an attempt to find the parts of the brain that were responsible for learning and memory traces, a hypothetical structure he called the engram . He trained rats to perform specific tasks (seeking a food reward), then lesioned varying portions of the rats' cortexes, either before or after the animals received the training depending upon the experiment. The amount of cortical tissue removed had specific effects on acquisition and retention of knowledge, but the location of the removed cortex had no effect on the rats' performance in the maze. This led Lashley to conclude that memories are not localized but widely distributed across the cortex. [ citation needed ]
There is evidence supporting both the mass action principle and functional specialization within the brain. Functional specialization is the idea that functions are localized within the brain and can only be carried out by particular area(s) of the brain. [ citation needed ] Some tasks appear to work on the mass action principle, with lesions causing less drastic effects than would be expected if the tasks were localized within the brain. [ citation needed ] This was shown in Lashley's rat maze experiments, in which the amount of tissue removed was more important to the rat's performance than where the tissue was removed from within the brain. [ citation needed ] There are, however, examples of highly specialized areas of the brain in which even small amounts of damage can cause dramatic effects on people's abilities to perform certain tasks. Two such areas effect the comprehension of speech and the ability to produce coherent speech, Wernicke's area and Broca's area, respectively. [ citation needed ]
It is now believed that Flourens may have removed more than just the parts of the hemispheres that he claimed because his experiments can be replicated without his same drastic results. [ citation needed ] At the time, extraction methods were very crude and little was understood about the stages of recovery. These things contributed to the increased likelihood of symptoms occurring right after extraction to be attributed directly to the site of the lesion. [ citation needed ] Flourens' doctrine was widely accepted even though there were anatomists and physiologists disproving his ideas:
Currently mass action principle is accepted as a mechanism for some functions within the brain. However, there have been some functions that are believed to be contained within specific areas of the brain (many related to speech, which was impossible to determine when the mass action principle was theorized, as experiments historically only used animals). It does not appear that this difference is determined by difficulty of the function, as some highly specialized tasks are localized. | https://en.wikipedia.org/wiki/Mass_action_principle_(neuroscience) |
The mass attenuation coefficient , or mass narrow beam attenuation coefficient of a material is the attenuation coefficient normalized by the density of the material; that is, the attenuation per unit mass (rather than per unit of distance). Thus, it characterizes how easily a mass of material can be penetrated by a beam of light , sound , particles , or other energy or matter . [ 1 ] In addition to visible light, mass attenuation coefficients can be defined for other electromagnetic radiation (such as X-rays ), sound , or any other beam that can be attenuated. The SI unit of mass attenuation coefficient is the square metre per kilogram ( m 2 /kg ). Other common units include cm 2 /g (the most common unit for X-ray mass attenuation coefficients) and L⋅g −1 ⋅cm −1 (sometimes used in solution chemistry). Mass extinction coefficient is an old term for this quantity. [ 1 ]
The mass attenuation coefficient can be thought of as a variant of absorption cross section where the effective area is defined per unit mass instead of per particle.
Mass attenuation coefficient is defined as
where
When using the mass attenuation coefficient, the Beer–Lambert law is written in alternative form as
where
When a narrow ( collimated ) beam passes through a volume, the beam will lose intensity to two processes: absorption and scattering .
Mass absorption coefficient , and mass scattering coefficient are defined as
where
In chemistry, mass attenuation coefficients are often used for a chemical species dissolved in a solution . In that case, the mass attenuation coefficient is defined by the same equation, except that the "density" is the density of only that one chemical species, and the "attenuation" is the attenuation due to only that one chemical species. The actual attenuation coefficient is computed by
where each term in the sum is the mass attenuation coefficient and density of a different component of the solution (the solvent must also be included). This is a convenient concept because the mass attenuation coefficient of a species is approximately independent of its concentration (as long as certain assumptions are fulfilled).
A closely related concept is molar absorptivity . They are quantitatively related by
Tables of photon mass attenuation coefficients are essential in radiological physics, radiography (for medical and security purposes), dosimetry , diffraction , interferometry , crystallography , and other branches of physics. The photons can be in form of X-rays , gamma rays , and bremsstrahlung .
The values of mass attenuation coefficients, based on proper values of photon cross section , are dependent upon the absorption and scattering of the incident radiation caused by several different mechanisms such as
The actual values have been thoroughly examined and are available to the general public through three databases run by National Institute of Standards and Technology (NIST):
If several known chemicals are dissolved in a single solution, the concentrations of each can be calculated using a light absorption analysis. First, the mass attenuation coefficients of each individual solute or solvent, ideally across a broad spectrum of wavelengths, must be measured or looked up. Second, the attenuation coefficient of the actual solution must be measured. Finally, using the formula
the spectrum can be fitted using ρ 1 , ρ 2 , … as adjustable parameters, since μ and each μ / ρ i are functions of wavelength. If there are N solutes or solvents, this procedure requires at least N measured wavelengths to create a solvable system of simultaneous equations , although using more wavelengths gives more reliable data. | https://en.wikipedia.org/wiki/Mass_attenuation_coefficient |
In physics , a mass balance , also called a material balance , is an application of conservation of mass [ 1 ] to the analysis of physical systems . By accounting for material entering and leaving a system, mass flows can be identified which might have been unknown, or difficult to measure without this technique. The exact conservation law used in the analysis of the system depends on the context of the problem, but all revolve around mass conservation, i.e., that matter cannot disappear or be created spontaneously. [ 2 ] : 59–62
Therefore, mass balances are used widely in engineering and environmental analyses . For example, mass balance theory is used to design chemical reactors , to analyse alternative processes to produce chemicals, as well as to model pollution dispersion and other processes of physical systems. Mass balances form the foundation of process engineering design. [ 3 ] Closely related and complementary analysis techniques include the population balance , energy balance and the somewhat more complex entropy balance. These techniques are required for thorough design and analysis of systems such as the refrigeration cycle .
In environmental monitoring , the term budget calculations is used to describe mass balance equations where they are used to evaluate the monitoring data (comparing input and output, etc.). In biology , the dynamic energy budget theory for metabolic organisation makes explicit use of mass and energy balance.
The general form quoted for a mass balance is The mass that enters a system must, by conservation of mass, either leave the system or accumulate within the system .
Mathematically the mass balance for a system without a chemical reaction is as follows: [ 2 ] : 59–62
Input = Output + Accumulation {\displaystyle {\text{Input}}={\text{Output}}+{\text{Accumulation}}}
Strictly speaking the above equation holds also for systems with chemical reactions if the terms in the balance equation are taken to refer to total mass, i.e. the sum of all the chemical species of the system. In the absence of a chemical reaction the amount of any chemical species flowing in and out will be the same; this gives rise to an equation for each species present in the system. However, if this is not the case then the mass balance equation must be amended to allow for the generation or depletion (consumption) of each chemical species. Some use one term in this equation to account for chemical reactions, which will be negative for depletion and positive for generation. However, the conventional form of this equation is written to account for both a positive generation term (i.e. product of reaction) and a negative consumption term (the reactants used to produce the products). Although overall one term will account for the total balance on the system, if this balance equation is to be applied to an individual species and then the entire process, both terms are necessary. This modified equation can be used not only for reactive systems, but for population balances such as arise in particle mechanics problems. The equation is given below; note that it simplifies to the earlier equation in the case that the generation term is zero. [ 2 ] : 59–62
Input + Generation = Output + Accumulation + Consumption {\displaystyle {\text{Input}}+{\text{Generation}}={\text{Output}}+{\text{Accumulation}}\ +{\text{Consumption}}}
A simple example can illustrate the concept. Consider the situation in which a slurry is flowing into a settling tank to remove the solids in the tank. Solids are collected at the bottom by means of a conveyor belt partially submerged in the tank, and water exits via an overflow outlet.
In this example, there are two substances: solids and water. The water overflow outlet carries an increased concentration of water relative to solids, as compared to the slurry inlet, and the exit of the conveyor belt carries an increased concentration of solids relative to water.
Assumptions
Analysis
Suppose that the slurry inlet composition (by mass) is 50% solid and 50% water, with a mass flow of 100 kg / min . The tank is assumed to be operating at steady state, and as such accumulation is zero, so input and output must be equal for both the solids and water. If we know that the removal efficiency for the slurry tank is 60%, then the water outlet will contain 20 kg / min of solids (40% times 100 kg / min times 50% solids). If we measure the flow rate of the combined solids and water, and the water outlet is shown to be 65 kg / min , then the amount of water exiting via the conveyor belt must be 5 kg / min . This allows us to completely determine how the mass has been distributed in the system with only limited information and using the mass balance relations across the system boundaries. The mass balance for this system can be described in a tabular form:
Mass balances can be performed across systems which have cyclic flows. In these systems output streams are fed back into the input of a unit, often for further reprocessing. [ 2 ] : 97–105
Such systems are common in grinding circuits, where grain is crushed then sieved to only allow fine particles out of the circuit and the larger particles are returned to the roller mill (grinder). However, recycle flows are by no means restricted to solid mechanics operations; they are used in liquid and gas flows, as well. One such example is in cooling towers , where water is pumped through a tower many times, with only a small quantity of water drawn off at each pass (to prevent solids build up) until it has either evaporated or exited with the drawn off water. The mass balance for water is M = D + W + E .
The use of the recycle aids in increasing overall conversion of input products, which is useful for low per-pass conversion processes (such as the Haber process ).
A mass balance can also be taken differentially . The concept is the same as for a large mass balance, but it is performed in the context of a limiting system (for example, one can consider the limiting case in time or, more commonly, volume). A differential mass balance is used to generate differential equations that can provide an effective tool for modelling and understanding the target system.
The differential mass balance is usually solved in two steps: first, a set of governing differential equations must be obtained, and then these equations must be solved, either analytically or, for less tractable problems, numerically.
The following systems are good examples of the applications of the differential mass balance:
The ideal completely mixed batch reactor is a closed system. Isothermal conditions are assumed, and mixing prevents concentration gradients as reactant concentrations decrease and product concentrations increase over time. [ 4 ] : 40–41 Many chemistry textbooks implicitly assume that the studied system can be described as a batch reactor when they write about reaction kinetics and chemical equilibrium .
The mass balance for a substance A becomes
IN + PROD = OUT + ACC 0 + r A V = 0 + d n A d t {\displaystyle {\begin{array}{ccccccc}{\text{IN}}&+&{\text{PROD}}&=&{\text{OUT}}&+&{\text{ACC}}\\0&+&r_{\rm {A}}V&=&0&+&\displaystyle {\frac {dn_{\rm {A}}}{dt}}\end{array}}}
where
In a fed-batch reactor some reactants/ingredients are added continuously or in pulses (compare making porridge by either first blending all ingredients and then letting it boil, which can be described as a batch reactor, or by first mixing only water and salt and making that boil before the other ingredients are added, which can be described as a fed-batch reactor). Mass balances for fed-batch reactors become a bit more complicated.
In the first example, we will show how to use a mass balance to derive a relationship between the percent excess air for the combustion of a hydrocarbon-base fuel oil and the percent oxygen in the combustion product gas. First, normal dry air contains 0.2095 mol of oxygen per mole of air, so there is one mole of O 2 in 4.773 mol of dry air. For stoichiometric combustion, the relationships between the mass of air and the mass of each combustible element in a fuel oil are:
Carbon: mass of air mass of C = 4.773 × 28.96 12.01 = 11.51 Hydrogen: mass of air mass of H = 1 4 ( 4.773 ) × 28.96 1.008 = 34.28 Sulfur: mass of air mass of S = 4.773 × 28.96 32.06 = 4.31 {\displaystyle {\begin{array}{rccc}{\text{Carbon:}}&{\frac {\text{mass of air}}{\text{mass of C}}}&=&{\frac {4.773\times 28.96}{12.01}}&=&11.51\\[2pt]{\text{Hydrogen:}}&{\frac {\text{mass of air}}{\text{mass of H}}}&=&{\frac {{\frac {1}{4}}(4.773)\times 28.96}{1.008}}&=&34.28\\[6pt]{\text{Sulfur:}}&{\frac {\text{mass of air}}{\text{mass of S}}}&=&{\frac {4.773\times 28.96}{32.06}}&=&4.31\end{array}}}
Considering the accuracy of typical analytical procedures, an equation for the mass of air per mass of fuel at stoichiometric combustion is:
mass of air mass of fuel = A F R mass = 11.5 w C + 34.3 w H + ( w S − w O ) {\displaystyle {\frac {\text{mass of air}}{\text{mass of fuel}}}=\mathrm {AFR} _{\text{mass}}=11.5\,w_{\rm {C}}+34.3\,w_{\rm {H}}+(w_{\rm {S}}-w_{\rm {O}})}
where w C , w H , w S , w O refer to the mass fraction of each element in the fuel oil, sulfur burning to SO 2 , and AFR mass refers to the air-fuel ratio in mass units.
For 1 kg of fuel oil containing 86.1% C, 13.6% H, 0.2% O, and 0.1% S the stoichiometric mass of air is 14.56 kg , so AFR = 14.56. The combustion product mass is then 15.56 kg . At exact stoichiometry, O 2 should be absent. At 15 percent excess air, the AFR = 16.75, and the mass of the combustion product gas is 17.75 kg , which contains 0.505 kg of excess oxygen. The combustion gas thus contains 2.84 percent O 2 by mass. The relationships between percent excess air and % O 2 in the combustion gas are accurately expressed by quadratic equations, valid over the range 0–30 percent excess air:
% excess air = 1.2804 × ( % O 2 in combustion gas ) 2 + 4.49 × ( % O 2 in combustion gas ) % O 2 in combustion gas = − 0.00138 × ( % excess air ) 2 + 0.210 × ( % excess air ) {\displaystyle {\begin{aligned}&\%{\text{ excess air}}=1.2804\times (\%{\ce {O2}}{\text{ in combustion gas}})^{2}+4.49\times (\%{\ce {O2}}{\text{ in combustion gas}})\\[4pt]&\%{\ce {O2}}{\text{ in combustion gas}}=-0.00138\times (\%{\text{ excess air}})^{2}+0.210\times (\%{\text{ excess air}})\end{aligned}}}
In the second example, we will use the law of mass action to derive the expression for a chemical equilibrium constant.
Assume we have a closed reactor in which the following liquid phase reversible reaction occurs:
a A + b B ↔ c C + d D {\displaystyle a\mathrm {A} +b\mathrm {B} \leftrightarrow c\mathrm {C} +d\mathrm {D} }
The mass balance for substance A becomes
IN + PROD = OUT + ACC 0 + r A V = 0 + d n A d t {\displaystyle {\begin{array}{ccccccc}{\text{IN}}&+&{\text{PROD}}&=&{\text{OUT}}&+&{\text{ACC}}\\0&+&r_{\rm {A}}V&=&0&+&\displaystyle {\frac {dn_{\mathrm {A} }}{dt}}\end{array}}}
As we have a liquid phase reaction we can (usually) assume a constant volume and since n A = V ∗ C A {\displaystyle n_{\rm {A}}=V*C_{\rm {A}}} we get
r A V = V d C A d t {\displaystyle r_{\rm {A}}V=V{\frac {dC_{\rm {A}}}{dt}}}
or
r A = d C A d t {\displaystyle r_{\rm {A}}={\frac {dC_{\rm {A}}}{dt}}}
In many textbooks this is given as the definition of reaction rate without specifying the implicit assumption that we are talking about reaction rate in a closed system with only one reaction. This is an unfortunate mistake that has confused many students over the years.
According to the law of mass action the forward reaction rate can be written as
r 1 = k 1 [ A ] a [ B ] b {\displaystyle r_{1}=k_{1}[\mathrm {A} ]^{a}[\mathrm {B} ]^{b}}
and the backward reaction rate as
r − 1 = k − 1 [ C ] c [ D ] d {\displaystyle r_{-1}=k_{-1}[\mathrm {C} ]^{c}[\mathrm {D} ]^{d}}
The rate at which substance A is produced is thus
r A = a ( r − 1 − r 1 ) {\displaystyle r_{\mathrm {A} }=a(r_{-1}-r_{1})}
and since, at equilibrium, the concentration of A is constant we get
r A = a ( r − 1 − r 1 ) = d C A d t = 0 {\displaystyle r_{\mathrm {A} }=a(r_{-1}-r_{1})={\frac {dC_{\mathrm {A} }}{dt}}=0}
or, rearranged
k 1 k − 1 = [ C ] c [ D ] d [ A ] a [ B ] b = K e q {\displaystyle {\frac {k_{1}}{k_{-1}}}={\frac {[\mathrm {C} ]^{c}[\mathrm {D} ]^{d}}{[\mathrm {A} ]^{a}[\mathrm {B} ]^{b}}}=K_{eq}}
The continuously mixed tank reactor is an open system with an influent stream of reactants and an effluent stream of products. [ 4 ] : 41 A lake can be regarded as a tank reactor, and lakes with long turnover times (e.g. with low flux-to-volume ratios) can for many purposes be regarded as continuously stirred (e.g. homogeneous in all respects). The mass balance then becomes
IN + PROD = OUT + ACC Q 0 ⋅ C A , 0 + r A ⋅ V = Q ⋅ C A + d n A d t {\displaystyle {\begin{array}{ccccccc}{\text{IN}}&+&{\text{PROD}}&=&{\text{OUT}}&+&{\text{ACC}}\\Q_{0}\cdot C_{\rm {A,0}}&+&r_{\rm {A}}\cdot V&=&Q\cdot C_{\rm {A}}&+&\displaystyle {\frac {dn_{\rm {A}}}{dt}}\end{array}}}
where
In an open system we can never reach a chemical equilibrium. We can, however, reach a steady state where all state variables (temperature, concentrations, etc.) remain constant ( ACC = 0 ).
Consider a bathtub in which there is some bathing salt dissolved. We now fill in more water, keeping the bottom plug in. What happens?
Since there is no reaction, PROD = 0 and since there is no outflow Q = 0 . The mass balance becomes
IN + PROD = OUT + ACC Q 0 ⋅ C A , 0 + 0 = 0 ⋅ C A + d n A d t {\displaystyle {\begin{array}{ccccccc}{\text{IN}}&+&{\text{PROD}}&=&{\text{OUT}}&+&{\text{ACC}}\\Q_{0}\cdot C_{\rm {A,0}}&+&0&=&0\cdot C_{\rm {A}}&+&\displaystyle {\frac {dn_{\rm {A}}}{dt}}\end{array}}}
or
Q 0 ⋅ C A , 0 = d C A V d t = V d C A d t + C A d V d t {\displaystyle Q_{0}\cdot C_{\rm {A,0}}={\frac {dC_{\rm {A}}V}{dt}}=V{\frac {dC_{\rm {A}}}{dt}}+C_{\rm {A}}{\frac {dV}{dt}}}
Using a mass balance for total volume, however, it is evident that d V d t = Q 0 {\displaystyle {\tfrac {dV}{dt}}=Q_{0}} and that V = V t = 0 + Q 0 t . {\displaystyle V=V_{t=0}+Q_{0}t.} Thus we get
d C A d t = Q 0 ( V t = 0 + Q 0 t ) ( C A , 0 − C A ) {\displaystyle {\frac {dC_{\rm {A}}}{dt}}={\frac {Q_{0}}{(V_{t=0}+Q_{0}t)}}\left(C_{\rm {A,0}}-C_{\rm {A}}\right)}
Note that there is no reaction and hence no reaction rate or rate law involved, and yet d C A d t ≠ 0 {\displaystyle {\tfrac {dC_{\rm {A}}}{dt}}\neq 0} . We can thus draw the conclusion that reaction rate can not be defined in a general manner using d C d t {\displaystyle {\tfrac {dC}{dt}}} . One must first write down a mass balance before a link between d C d t {\displaystyle {\tfrac {dC}{dt}}} and the reaction rate can be found. Many textbooks, however, define reaction rate as
r = d C A d t {\displaystyle r={\frac {dC_{\mathrm {A} }}{dt}}}
without mentioning that this definition implicitly assumes that the system is closed, has a constant volume and that there is only one reaction.
The idealized plug flow reactor is an open system resembling a tube with no mixing in the direction of flow but perfect mixing perpendicular to the direction of flow, often used for systems like rivers and water pipes if the flow is turbulent. When a mass balance is made for a tube, one first considers an infinitesimal part of the tube and make a mass balance over that using the ideal tank reactor model. [ 4 ] : 46–47 That mass balance is then integrated over the entire reactor volume to obtain:
d ( Q ⋅ C A ) d V = r A {\displaystyle {\frac {d(Q\cdot C_{\rm {A}})}{dV}}=r_{\rm {A}}}
In numeric solutions, e.g. when using computers, the ideal tube is often translated to a series of tank reactors, as it can be shown that a PFR is equivalent to an infinite number of stirred tanks in series, but the latter is often easier to analyze, especially at steady state.
In reality, reactors are often non-ideal, in which combinations of the reactor models above are used to describe the system. Not only chemical reaction rates, but also mass transfer rates may be important in the mathematical description of a system, especially in heterogeneous systems. [ 5 ]
As the chemical reaction rate depends on temperature it is often necessary to make both an energy balance (often a heat balance rather than a full-fledged energy balance) as well as mass balances to fully describe the system. A different reactor model might be needed for the energy balance: A system that is closed with respect to mass might be open with respect to energy e.g. since heat may enter the system through conduction .
In industrial process plants, using the fact that the mass entering and leaving any portion of a process plant must balance, data validation and reconciliation algorithms may be employed to correct measured flows, provided that enough redundancy of flow measurements exist to permit statistical reconciliation and exclusion of detectably erroneous measurements. Since all real world measured values contain inherent error, the reconciled measurements provide a better basis than the measured values do for financial reporting, optimization, and regulatory reporting. Software packages exist to make this commercially feasible on a daily basis. | https://en.wikipedia.org/wiki/Mass_balance |
A mass call event or mass calling event (also MCE in telephony usage) is a situation in which an extraordinarily high number of telephone calls are attempted into or out of an area, causing tremendous network congestion , and resulting in service that is significantly degraded or potentially unavailable. [ 1 ]
The term is typically used with mobile telephony systems, in which there are simply not enough radio channels available in a given cell or cells. This causes blocked calls or dropped calls . However, it can also apply to landline phones, in which not enough trunking telephone circuits are available into and out of any given telephone exchange or equivalent switching office at any level of the public switched telephone network (PSTN).
An MCE is typically caused by a sudden disaster of some sort, such as an earthquake or explosion . One of the earliest examples was the Iroquois Theatre Fire in Chicago in 1903. The 1963 Kennedy assassination represented a mass call event for Washington, DC . One of the most notable examples of a MCE was the 9/11 attacks . A more recent example was the 2013 Boston Marathon bombing , in which mobile network service was so degraded by people checking on the safety of friends and family (or reporting their own status to others) that journalists and the public both assumed that the networks had been shut down to prevent further remote detonations , although this was not the case with any mobile phone company .
Access-class barring is one solution in such a situation, allowing public safety (PS) personnel such as emergency responders to have priority on the network, as well as general emergency calls to public-safety answering points (PSAPs). This typically only affects voice calls, therefore text messaging is a very effective way of communication during an MCE, as it only needs a brief connection to the network to be sent or received, and uses almost nothing in terms of network resources like bandwidth .
Mass call events can also be caused by planned events. In 1982, Eddie Murphy's Larry the Lobster shtick on Saturday Night Live resulted in record call volume, as Murphy held a live lobster and declared that the show's audience would determine whether he lived or died via telephone calls. The gathering in Washington, D.C. for the 2009 U.S. Presidential Inauguration of Barack Obama also created a MCE. In this case, network overload was avoided by deploying multiple cell-on-wheels (CoW) units with their own wireless backhauls . This was a particularly major situation for cell carriers because many attendees wanted to be live on the phone (via voice call or video chat ) with others who could not attend the ceremony, further increasing network usage.
This article related to telecommunications is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mass_call_event |
In chemistry , the mass concentration ρ i (or γ i ) is defined as the mass of a constituent m i divided by the volume of the mixture V . [ 1 ]
For a pure chemical the mass concentration equals its density (mass divided by volume); thus the mass concentration of a component in a mixture can be called the density of a component in a mixture. This explains the usage of ρ (the lower case Greek letter rho ), the symbol most often used for density.
The volume V in the definition refers to the volume of the solution, not the volume of the solvent . One litre of a solution usually contains either slightly more or slightly less than 1 litre of solvent because the process of dissolution causes volume of liquid to increase or decrease. Sometimes the mass concentration is called titre .
The notation common with mass density underlines the connection between the two quantities (the mass concentration being the mass density of a component in the solution), but it can be a source of confusion especially when they appear in the same formula undifferentiated by an additional symbol (like a star superscript, a bolded symbol or varrho ).
Mass concentration depends on the variation of the volume of the solution due mainly to thermal expansion. On small intervals of temperature the dependence is:
where ρ i ( T 0 ) is the mass concentration at a reference temperature, α is the thermal expansion coefficient of the mixture.
The sum of the mass concentrations of all components (including the solvent) gives the density ρ of the solution:
Thus, for pure component the mass concentration equals the density of the pure component.
The SI-unit for mass concentration is kg/m 3 ( kilogram / cubic metre ). This is the same as mg / mL and g/L. Another commonly used unit is g/(100 mL), which is identical to g/dL ( gram / decilitre ).
In biology and medicine , the " % " symbol is widely used in a misnomer sense to denote mass concentration, also called "mass/volume percentage". A solution with 1 g of solute dissolved in a final volume of 100 mL of solution would be labeled as "1%" or "1% m/v" (mass/volume). The common names of intravenous sugar solutions, such as D5W and D50W , reflect this convention. The notation is mathematically flawed because the unit " % " can only be used for dimensionless quantities. "Percent solution" or "percentage solution" are thus terms best reserved for "mass percent solutions" (m/m = m% = mass solute/mass total solution after mixing), or "volume percent solutions" (v/v = v% = volume solute per volume of total solution after mixing). The very ambiguous terms "percent solution" and "percentage solutions" with no other qualifiers, continue to occasionally be encountered.
This common usage of % to mean m/v in biology is because of many biological solutions being dilute and water-based, an aqueous solution . Liquid water has a density of approximately 1 g/cm 3 (1 g/mL). Thus 100 mL of water is equal to approximately 100 g. Therefore, a solution with 1 g of solute dissolved in final volume of 100 mL aqueous solution may also be considered 1% m/m (1 g solute in 99 g water). This approximation breaks down as the solute concentration is increased (for example, in water–NaCl mixtures ). High solute concentrations are often not physiologically relevant, but are occasionally encountered in pharmacology, where the mass per volume notation is still sometimes encountered. An extreme example is saturated solution of potassium iodide (SSKI) which attains 100 "%" m/v potassium iodide mass concentration (1 gram KI per 1 mL solution) only because the solubility of the dense salt KI is extremely high in water, and the resulting solution is very dense (1.72 times as dense as water).
Although there are examples to the contrary, it should be stressed that the commonly used "units" of % w/v are grams per millilitre (g/mL). 1% m/v solutions are sometimes thought of as being gram/100 mL but this detracts from the fact that % m/v is g/mL; 1 g of water has a volume of approximately 1 mL (at standard temperature and pressure) and the mass concentration is said to be 100%. To make 10 mL of an aqueous 1% cholate solution, 0.1 grams of cholate are dissolved in 10 mL of water. Volumetric flasks are the most appropriate piece of glassware for this procedure as deviations from ideal solution behavior can occur with high solute concentrations.
In solutions, mass concentration is commonly encountered as the ratio of mass/[volume solution], or m/v. In water solutions containing relatively small quantities of dissolved solute (as in biology), such figures may be "percentivized" by multiplying by 100 a ratio of grams solute per mL solution. The result is given as "mass/volume percentage". Such a convention expresses mass concentration of 1 gram of solute in 100 mL of solution, as "1 m/v %".
The relation between mass concentration and density of a pure component (mass concentration of single component mixtures) is:
where ρ ∗ i is the density of the pure component, V i the volume of the pure component before mixing.
Specific volume is the inverse of mass concentration only in the case of pure substances, for which mass concentration is the same as the density of the pure-substance:
The conversion to molar concentration c i is given by:
where M i is the molar mass of constituent i .
The conversion to mass fraction w i is given by:
The conversion to mole fraction x i is given by:
where M is the average molar mass of the mixture.
For binary mixtures, the conversion to molality b i is given by:
The values of (mass and molar) concentration different in space triggers the phenomenon of diffusion . | https://en.wikipedia.org/wiki/Mass_concentration_(chemistry) |
Mass cytometry is a mass spectrometry technique based on inductively coupled plasma mass spectrometry and time of flight mass spectrometry used for the determination of the properties of cells ( cytometry ). [ 1 ] [ 2 ] In this approach, antibodies are conjugated with isotopically pure elements , and these antibodies are used to label cellular proteins. Cells are nebulized and sent through an argon plasma , which ionizes the metal-conjugated antibodies. The metal signals are then analyzed by a time-of-flight mass spectrometer. The approach overcomes limitations of spectral overlap in flow cytometry by utilizing discrete isotopes as a reporter system instead of traditional fluorophores which have broad emission spectra. [ 3 ]
Tagging technology and instrument development occurred at the University of Toronto and DVS Sciences , Inc. [ 1 ] [ 4 ] CyTOF (cytometry by time of flight) was initially commercialized by DVS Sciences in 2009. In 2014, Fluidigm acquired DVS Sciences [ 5 ] to become a reference company in single cell technology. [ 6 ] In 2022 Fluidigm received a capitol infusion and changed its name to Standard BioTools. [ 7 ] The CyTOF, CyTOF2, Helios (CyTOF3) and CyTOF XT [ 8 ] (4th generation) have been commercialized up to now. Fluidigm sells a variety of commonly used metal-antibody conjugates, and an antibody conjugation kit.
Imaging mass cytometry (IMC) is a relatively new imaging technique, emerged from previously available CyTOF technology (cytometry by time of flight), that combines mass spectrometry with UV laser ablation to generate pseudo images of tissue samples. [ 9 ] [ 10 ] This approach adds spatial resolution to the data, which enables simultaneous analysis of multiple cell markers at subcellular resolution and their spatial distribution in tissue sections. [ 9 ] [ 11 ] The IMC approach, in the same way as CyTOF , relies on detection of metal-tagged antibodies using time-of-flight mass spectrometry, allowing for quantification of up to 40 markers simultaneously. [ 12 ] [ 13 ]
CyTOF mass cytometry data is recorded in tables that list, for each cell, the signal detected per channel, which is proportional to the number of antibodies tagged with the corresponding channel's isotope bound to that cell. These data are formatted as FCS files, which are compatible with traditional flow cytometry software. Due to the high-dimensional nature of mass cytometry data, novel data analysis tools have been developed as well. [ 14 ]
Imaging Mass Cytometry data analysis has its specificity due to different nature of data obtained. In terms of data analysis, both IMC and CyTOF generate large datasets with high dimensionality that require specialized computational methods for analysis. However, data generated by IMC can be more challenging to analyze due to additional data complexity and need for specific tools and pipelines specific for digital image analysis, whereas the data generated by CyTOF is generally analyzed using conventional flow cytometry software. A comprehensive overview of IMC data analysis techniques has been given by Milosevic in. [ 15 ]
Advantages include minimal overlap in metal signals meaning the instrument is theoretically capable of detecting 100 parameters per cell, entire cell signaling networks can be inferred organically without reliance on prior knowledge, and one well-constructed experiment produces large amounts of data. [ 3 ]
Disadvantages, in the case of CyTOF , include the practical flow rate is around 500 cells per second versus several thousand in flow cytometry and current reagents available limit cytometer use to around 50 parameters per cell. Additionally, mass cytometry is a destructive method and cells cannot be sorted for further analysis. In the case of IMC, the resolution of the data is relatively low (1μm2/pixel), the technique is as well destructive, acquiring of the data is also very slow, and it requires specialized expensive equipment and expertise.
Mass cytometry has research applications in medical fields including immunology , hematology , and oncology . It has been used in studies of hematopoiesis , [ 16 ] cell cycle , [ 17 ] cytokine expression , and differential signaling responses.
MC has been used in various research fields, such as cancer biology , immunology , and neuroscience , to provide a more comprehensive understanding of tissue architecture and cellular interactions. [ 18 ] [ 19 ] [ 20 ] [ 21 ] [ 22 ] [ 23 ] | https://en.wikipedia.org/wiki/Mass_cytometry |
Mass deacidification is a term used in library and information science as one possible measure against the degradation of paper in old books , the so-called " slow fires ". The goal of the process is to increase the pH of acidic paper . Although acid-free paper has become more common, a large body of acidic paper still exists in books made after the 1850s; this is because of its cheaper and simpler production methods. Acidic paper, especially when exposed to light , air pollution , or high relative humidity , yellows and becomes brittle over time. [ 1 ] During mass deacidification an alkaline agent is deposited in the paper to neutralize existing acid and prevent further decay. [ 2 ] Mass deacidification is intended for objects on acidic paper that will be lost if no action is performed.
Mass deacidification—along with microfilm and lamination —was developed during the early and mid-20th century as a response to the chemical process of hydrolysis by which the fibers that constitute paper, providing its structure and strength, have their bonds broken, resulting in paper that becomes increasingly brittle over time. Environmental pollutants can react with paper to form acids that promote oxidation, creating more acid as a by-product, which results in a positive feedback loop of autocatalytic destruction. [ 3 ] Supported in part by grants from the Council on Library Resources, William J. Barrow conducted research into paper decay and found that no more than three percent of books published between 1900 and 1949 would survive more than fifty years. In response to this, a Standing Committee on the Preservation of Research Library Materials was formed by the Association of Research Libraries (ARL) in 1960. [ 4 ]
Barrow also invented an aqueous process to neutralize acid in paper while depositing an alkaline buffer that would slow the rate of decay. [ 5 ] In addition to Barrow's original method, both non-aqueous—employing organic solvents—and vaporous—the Library of Congress' DEZ (diethyl zinc) treatment—methods of achieving the same results have been researched in an attempt to reduce time, labor, and cost requirements. [ 6 ]
One technique proposed is to place books in an evacuated chamber, then introduce diethylzinc (DEZ). In theory, the diethylzinc would react with acidic residues in the paper, leaving an alkaline residue that would protect the paper against further degradation. [ 7 ] In practice, the heating required to remove trace water from the books before reaction (DEZ reacts violently with water) caused an accelerated degradation of the paper, a series of chemical reactions between DEZ and other components of the book (glues, bindings), caused further damage, and produced unpleasant aromas. In the 1980s, a pilot plant for mass deacidification, using this process, was constructed by NASA and was tested on books provided by the Library of Congress. [ 8 ] In 1986 it was discovered that the DEZ had not been removed in one of the deacidification runs and pooled in the bottom of the chamber, possibly remaining within the plumbing. DEZ is violently flammable when it comes in contact with either oxygen or water vapor, so the vacuum chamber could not be opened to remove the books within. Eventually, explosives were used to rupture the suspect plumbing; suspicions of the presence of residual DEZ were confirmed by the subsequent fire that destroyed the plant. In his book Double Fold , Nicholson Baker discusses the failure of the NASA program at great length.
The chemical company AkzoNobel made later attempts at refining the process. The risks of fire and explosions were reduced by a better process design, however, damage and odors remained a problem. In the end, AkzoNobel determined the process was not a viable commercial proposition and shut down their research at the end of 1994.
These are the results that the Library of Congress expected of an ideal mass deacidification treatment in 1994:
Faculty members of the Slovak University of Technology added these further requirements:
All of the processes imparted an adequately high pH in studies conducted by the European Commission on Preservation and Access, the Library of Congress, and a team of scientists from the Centre de Recherches sur la Conservation des Documents Graphiques in the early and mid-nineties. BookKeeper produced a pH of 9–10. [ 9 ] CSC Book Saver yielded a pH of 8.78–10.5. [ 11 ] Wei T'o gives 7.5 to 10.4, [ 12 ] and Papersave gives a pH of 7.5–9. [ 13 ]
The same studies also found that the processes had adverse cosmetic side effects. BookKeeper left "a palpable residue", clamp marks on the covers, and caused some of the colored inks to rub off. [ 9 ] CSC Book Saver left a "white powdery deposit" on books. [ 14 ] Papersave caused "discoloration, white deposit, Newton's rings , bleeding of inks and dyes, odor and different 'feel' of the paper." [ 15 ] Wei T'o caused "odor, white residues, rings, cockling, (yellow) discolorations and adhesive bleeding." [ 16 ]
Conservators from the British Library acknowledge that the existing mass deacidification processes are still being developed and further research needs to be conducted on their chemical and mechanical effects. [ 17 ]
Several commercial deacidification techniques are on the market as of 2008 [update] :
BookKeeper, CSC Booksaver, Papersave, and Wei T'o are also available as hand-held sprays.
While deacidification has been adopted by major research libraries such as the Library of Congress and the New York Public Library, it is not clear whether many archives, particularly those in the United States, have followed suit. Some European national archives have tested deacidification techniques. The United States' National Archives and Records Administration (NARA), which pioneered an aqueous technique that improved upon Barrow's, chose to invest its preservation dollars elsewhere. [ 5 ] In 2000, the Chief of the NARA Document Conservation Laboratory defended the lack of a mass deacidification program by pointing to differences between library and archival collections. For example, noting that many of the papers coming to NARA were of a higher quality than those in library collections; that the Archives does not receive records from federal government agencies until they are at least 30 years old, by which time acidic paper will have already been irrevocably weakened, and that limited resources might best be applied elsewhere, such as climate control. Under the Archives' Twenty-Year Preservation Plan, emphasis was placed on achieving the "maximum benefit for the greatest number of records." [ 25 ]
Though now dated, several sources estimate the costs and suitability of deacidification treatment. Studies conducted by the Harry Ransom Humanities Research Center and the General State Archive of the Netherlands found the DEZ method might be particularly applicable to archival materials. [ 26 ] It was estimated that deacidification costs, excluding transportation and handling, during the early 1990s was $5–10 per volume. [ 27 ] During 1995–1997, the Library of Congress received $2 million in appropriations to deacidify 72,000 books using the Bookkeeper commercial method and evaluate alternative methods. The actual cost per book was $11.70. [ 28 ] Finally, a 2003 cost comparison with reformatting options per volume yielded $125 for microfilming, $50 for scanning and minimal indexing and, based on a New York Public Library project, $16.20 for deacidification. [ 6 ] However, already in 2004 Google Books was able to scan for only $10-$20 per book. [ 29 ]
As of 2022, there were five mass deacidification plants in the world. [ 30 ] | https://en.wikipedia.org/wiki/Mass_deacidification |
In astronomy , mass deficit is the amount of mass (in stars) that has been removed from the center of a galaxy , presumably by the action of a binary , supermassive black hole .
The density of stars increases toward the center in most galaxies. In small galaxies, this increase continues into the very center. In large galaxies, there is usually a "core", a region near the center where the density is constant or slowly rising. The size of the core – the "core radius" – can be a few hundred parsecs in large elliptical galaxies . [ 1 ] [ 2 ] The greatest observed stellar cores reach 3.2 to 5.7 kiloparsecs in radius. [ 3 ] [ 4 ] [ 5 ]
It is believed that cores are produced by binary supermassive black holes (SMBHs). Binary SMBHs form during the merger of two galaxies . [ 6 ] If a star passes near the massive binary, it will be ejected, by a process called the gravitational slingshot . This ejection continues until most of the stars near the center of the galaxy have been removed. The result is a low-density core. Such cores are ubiquitous in giant elliptical galaxies.
The mass deficit is defined [ 7 ] as the amount of mass that was removed in creating the core. Mathematically, the mass deficit is defined as M d e f = 4 π ∫ 0 R c [ ρ i ( r ) − ρ ( r ) ] r 2 d r , {\displaystyle M_{\mathrm {def} }=4\pi \int _{0}^{R_{c}}\left[\rho _{i}(r)-\rho (r)\right]r^{2}dr,}
where ρ i is the original density, ρ is the observed density, and R c is the core radius. In practice, the core-Sersic model can be used to help quantify the deficits. [ 8 ]
Observed mass deficits are typically in the range of one to a few times the mass of the central SMBH, [ 9 ] and observed core radii are comparable to the influence radii of the central SMBH. These properties are consistent with what is predicted in theoretical models of core formation [ 10 ] and lend support to the hypothesis that all bright galaxies once contained binary SMBHs at their centers.
It is not known whether most galaxies still contain massive binaries, or whether the two black holes have coalesced. Both possibilities are consistent with the presence of mass deficits. | https://en.wikipedia.org/wiki/Mass_deficit |
Diffusivity , mass diffusivity or diffusion coefficient is usually written as the proportionality constant between the molar flux due to molecular diffusion and the negative value of the gradient in the concentration of the species. More accurately, the diffusion coefficient times the local concentration is the proportionality constant between the negative value of the mole fraction gradient and the molar flux. This distinction is especially significant in gaseous systems with strong temperature gradients. Diffusivity derives its definition from Fick's law and plays a role in numerous other equations of physical chemistry .
The diffusivity is generally prescribed for a given pair of species and pairwise for a multi-species system. The higher the diffusivity (of one substance with respect to another), the faster they diffuse into each other. Typically, a compound's diffusion coefficient is ~10,000× as great in air as in water. Carbon dioxide in air has a diffusion coefficient of 16 mm 2 /s, and in water its diffusion coefficient is 0.0016 mm 2 /s. [ 1 ] [ 2 ]
Diffusivity has dimensions of length 2 / time, or m 2 /s in SI units and cm 2 /s in CGS units .
The diffusion coefficient in solids at different temperatures is generally found to be well predicted by the Arrhenius equation :
D = D 0 exp ( − E A R T ) {\displaystyle D=D_{0}\exp \left(-{\frac {E_{\text{A}}}{RT}}\right)}
where
Diffusion in crystalline solids, termed lattice diffusion , is commonly regarded to occur by two distinct mechanisms, [ 3 ] interstitial and substitutional or vacancy diffusion . The former mechanism describes diffusion as the motion of the diffusing atoms between interstitial sites in the lattice of the solid it is diffusing into, the latter describes diffusion through a mechanism more analogue to that in liquids or gases: Any crystal at nonzero temperature will have a certain number of vacancy defects (i.e. empty sites on the lattice) due to the random vibrations of atoms on the lattice, an atom neighbouring a vacancy can spontaneously "jump" into the vacancy, such that the vacancy appears to move. By this process the atoms in the solid can move, and diffuse into each other. Of the two mechanisms, interstitial diffusion is typically more rapid. [ 3 ]
An approximate dependence of the diffusion coefficient on temperature in liquids can often be found using Stokes–Einstein equation , which predicts that
D T 1 D T 2 = T 1 T 2 μ T 2 μ T 1 , {\displaystyle {\frac {D_{T_{1}}}{D_{T_{2}}}}={\frac {T_{1}}{T_{2}}}{\frac {\mu _{T_{2}}}{\mu _{T_{1}}}},}
where
The description of diffusion coefficients in liquid mixtures is more difficult. They can be, for example, modeled using entropy scaling. [ 4 ]
The dependence of the diffusion coefficient on temperature for gases can be expressed using Chapman–Enskog theory (predictions accurate on average to about 8%): [ 5 ]
D = A T 3 2 p σ 12 2 Ω 1 M 1 + 1 M 2 , {\displaystyle D={\frac {AT^{\frac {3}{2}}}{p\sigma _{12}^{2}\Omega }}{\sqrt {{\frac {1}{M_{1}}}+{\frac {1}{M_{2}}}}},} A = 3 8 k b 3 2 N A 2 π {\displaystyle A={\frac {3}{8}}k_{b}^{\frac {3}{2}}{\sqrt {\frac {N_{A}}{2\pi }}}}
where
The relation
D ∼ T 3 / 2 p Ω ( T ) {\displaystyle D\sim {\frac {T^{3/2}}{p\Omega (T)}}}
is obtained when inserting the ideal gas law into the expression obtained directly from Chapman-Enskog theory , [ 9 ] which may be written as
D = D 0 T 1 / 2 n Ω ( T ) {\displaystyle D=D_{0}{\frac {T^{1/2}}{n\Omega (T)}}}
where n {\displaystyle n} is the molar density (mol / m 3 ) of the gas, and
D 0 = 3 8 σ 12 2 ( R 2 π ) ( 1 M 1 + 1 M 2 ) , {\displaystyle D_{0}={\frac {3}{8\sigma _{12}^{2}}}{\sqrt {\left({\frac {R}{2\pi }}\right)\left({\frac {1}{M_{1}}}+{\frac {1}{M_{2}}}\right)}},}
with R = k B N A {\displaystyle R=k_{B}N_{A}} the universal gas constant. At moderate densities (i.e. densities at which the gas has a non-negligible co-volume , but is still sufficiently dilute to be considered as gas-like rather than liquid-like) this simple relation no longer holds, and one must resort to Revised Enskog Theory . [ 10 ] Revised Enskog Theory predicts a diffusion coefficient that decreases somewhat more rapidly with density, and which to a first approximation may be written as
D = D 0 T 1 / 2 n g ( σ ) Ω ( T ) {\displaystyle D=D_{0}{\frac {T^{1/2}}{ng(\sigma )\Omega (T)}}}
where g ( σ ) {\displaystyle g(\sigma )} is the radial distribution function evaluated at the contact diameter of the particles. For molecules behaving like hard, elastic spheres , this value can be computed from the Carnahan-Starling Equation , while for more realistic intermolecular potentials such as the Mie potential or Lennard-Jones potential , its computation is more complex, and may involve invoking a thermodynamic perturbation theory , such as SAFT .
For self-diffusion in gases at two different pressures (but the same temperature), the following empirical equation has been suggested: [ 5 ] D P 1 D P 2 = ρ P 2 ρ P 1 , {\displaystyle {\frac {D_{P1}}{D_{P2}}}={\frac {\rho _{P2}}{\rho _{P1}}},} where
In population dynamics, kinesis is the change of the diffusion coefficient in response to the change of conditions. In models of purposeful kinesis, diffusion coefficient depends on fitness (or reproduction coefficient) r : D = D 0 e − α r , {\displaystyle D=D_{0}e^{-\alpha r},}
where D 0 {\displaystyle D_{0}} is constant and r depends on population densities and abiotic characteristics of the living conditions. This dependence is a formalisation of the simple rule: Animals stay longer in good conditions and leave quicker bad conditions (the "Let well enough alone" model).
The effective diffusion coefficient describes diffusion through the pore space of porous media . [ 11 ] It is macroscopic in nature, because it is not individual pores but the entire pore space that needs to be considered. The effective diffusion coefficient for transport through the pores, D e , is estimated as follows: D e = D ε t δ τ , {\displaystyle D_{\text{e}}={\frac {D\varepsilon _{t}\delta }{\tau }},} where
The transport-available porosity equals the total porosity less the pores which, due to their size, are not accessible to the diffusing particles, and less dead-end and blind pores (i.e., pores without being connected to the rest of the pore system). The constrictivity describes the slowing down of diffusion by increasing the viscosity in narrow pores as a result of greater proximity to the average pore wall. It is a function of pore diameter and the size of the diffusing particles.
Gases at 1 atm., solutes in liquid at infinite dilution. Legend: (s) – solid; (l) – liquid; (g) – gas; (dis) – dissolved. | https://en.wikipedia.org/wiki/Mass_diffusivity |
In physics and mechanics , mass distribution is the spatial distribution of mass within a solid body. In principle, it is relevant also for gases or liquids , but on Earth their mass distribution is almost homogeneous.
In astronomy mass distribution has decisive influence on the development e.g. of nebulae , stars and planets .
The mass distribution of a solid defines its center of gravity and influences its dynamical behaviour - e.g. the oscillations and eventual rotation .
A mass distribution can be modeled as a measure . This allows point masses, line masses, surface masses, as well as masses given by a volume density function. Alternatively the latter can be generalized to a distribution . For example, a point mass is represented by a delta function defined in 3-dimensional space . A surface mass on a surface given by the equation f ( x , y , z ) = 0 may be represented by a density distribution g ( x , y , z ) δ ( f ( x , y , z )) , where g / | ∇ f | {\textstyle g/\left|\nabla f\right|} is the mass per unit area.
The mathematical modelling can be done by potential theory , by numerical methods (e.g. a great number of mass points ), or by theoretical equilibrium figures.
In geology the aspects of rock density are involved.
Rotating solids are affected considerably by the mass distribution, either if they are homogeneous or inhomogeneous - see Torque , moment of inertia , wobble , imbalance and stability.
This geophysics -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mass_distribution |
The mass excess of a nuclide is the difference between its actual mass and its mass number in daltons . It is one of the predominant methods for tabulating nuclear mass. The mass of an atomic nucleus is well approximated (less than 0.1% difference for most nuclides) by its mass number, which indicates that most of the mass of a nucleus arises from mass of its constituent protons and neutrons . Thus, the mass excess is an expression of the nuclear binding energy , relative to the binding energy per nucleon of carbon-12 (which defines the dalton). If the mass excess is negative, the nucleus has more binding energy than 12 C, and vice versa. If a nucleus has a large excess of mass compared to a nearby nuclear species, it can radioactively decay , releasing energy.
The 12 C standard provides a convenient unit (the dalton) in which to express nuclear mass for defining the mass excess. However, its usefulness arises in the calculation of nuclear reaction kinematics or decay. Only a small fraction of the total energy that is associated with an atomic nucleus by mass–energy equivalence , on the order of 0.01% to 0.1% of the total mass, may be absorbed or liberated as radiation. By working in terms of the mass excess, much of the mass changes which arise from the transfer or release of nucleons is effectively removed, highlighting the net energy difference.
Nuclear reaction kinematics are customarily performed in units involving the electronvolt , which derives from accelerator technology. The combination of this practical point with the theoretical relation E = mc 2 makes the unit megaelectronvolt over the speed of light squared (MeV/ c 2 ) a convenient form in which to express nuclear mass. However, the numerical values of nuclear masses in MeV/ c 2 are quite large (even the proton mass is ~938.27 MeV/c 2 ), while mass excesses range in the tens of MeV/ c 2 . This makes tabulated mass excess less cumbersome for use in calculations. The 1/ c 2 factor is typically omitted when quoting mass excess values in MeV, since the interest is more often energy and not mass; if one wanted units of mass, one would simply change the units from MeV to MeV/ c 2 without altering the numerical value.
Consider the nuclear fission of 236 U into 92 Kr, 141 Ba, and three neutrons.
The mass number of the reactant, 236 U, is 236. Because the actual mass is 236.045 563 Da , its mass excess is + 0.045 563 Da . Calculated in the same manner, the respective mass excesses for the products, 92 Kr, 141 Ba, and three neutrons, are −0.073 843 Da , −0.085 588 Da and 3 × 0.008 665 Da = + 0.025 994 Da , respectively, for a total mass excess of −0.133 437 Da . The difference between the mass excess of the reactants and that of the products is 0.179 000 Da , which shows that the mass excess of the products is less than that of the reactants, and so the fission can occur – a calculation which could have also been done with only the masses of the reactants.
The mass excess can be converted into energy using 1 Da = 931.494 MeV/ c 2 , and E = mc 2 , yielding 166.737 MeV . | https://en.wikipedia.org/wiki/Mass_excess |
In the life sciences , mass flow , also known as mass transfer and bulk flow , is the movement of fluids down a pressure or temperature gradient. [ 1 ] As such, mass flow is a subject of study in both fluid dynamics and biology. Examples of mass flow include blood circulation and transport of water in vascular plant tissues. Mass flow is not to be confused with diffusion which depends on concentration gradients within a medium rather than pressure gradients of the medium itself.
In general, bulk flow in plant biology typically refers to the movement of water from the soil up through the plant to the leaf tissue through xylem , but can also be applied to the transport of larger solutes (e.g. sucrose) through the phloem .
According to cohesion-tension theory , water transport in xylem relies upon the cohesion of water molecules to each other and adhesion to the vessel's wall via hydrogen bonding combined with the high water pressure of the plant's substrate and low pressure of the extreme tissues (usually leaves). [ 2 ]
As in blood circulation in animals, (gas) embolisms may form within one or more xylem vessels of a plant. If an air bubble forms, the upward flow of xylem water will stop because the pressure difference in the vessel cannot be transmitted. Once these embolisms are nucleated [ definition needed ] , the remaining water in the capillaries begins to turn to water vapor. When these bubbles form rapidly by cavitation , the "snapping" sound can be used to measure the rate of cavitation within the plant . [ 3 ] Plants [ which? ] do, however, have physiological mechanisms to reestablish the capillary action within their cells [ clarification needed ] [ citation needed ] .
Solute flow is driven by a difference in hydraulic pressure created from the unloading of solutes in the sink tissues. [ 4 ] That is, as solutes are off-loaded into sink cells (by active or passive transport), the density of the phloem liquid decreases locally, creating a pressure gradient. | https://en.wikipedia.org/wiki/Mass_flow_(life_sciences) |
A mass flow controller ( MFC ) is a device used to measure and control the flow of liquids and gases . [ 1 ] A mass flow controller is designed and calibrated to control a specific type of liquid or gas at a particular range of flow rates. The MFC can be given a setpoint from 0 to 100% of its full scale range but is typically operated in the 10 to 90% of full scale where the best accuracy is achieved. The device will then control the rate of flow to the given setpoint. MFCs can be either analog or digital . A digital flow controller is usually able to control more than one type of fluid whereas an analog controller is limited to the fluid for which it was calibrated.
All mass flow controllers have an inlet port, an outlet port, a mass flow sensor and a proportional control valve. The MFC is fitted with a closed loop control system which is given an input signal by the operator (or an external circuit/computer) that it compares to the value from the mass flow sensor and adjusts the proportional valve accordingly to achieve the required flow. The flow rate is specified as a percentage of its calibrated full scale flow and is supplied to the MFC as a voltage signal.
Mass flow controllers require the supply gas or liquid to be within a specific pressure range. Low pressure will starve the MFC of fluid and cause it to fail to achieve its setpoint. High pressure may cause erratic flow rates. There are many different technologies which can help to measure the flow of the fluids and eventually help in controlling flow. Those technologies define the types of Mass Flow Controllers, and they include differential pressure (ΔP), differential temperature (ΔT), Coriolis , Ultrasonic, electromagnetic, turbine , etc. | https://en.wikipedia.org/wiki/Mass_flow_controller |
A mass flow meter , also known as an inertial flow meter , is a device that measures mass flow rate of a fluid traveling through a tube. The mass flow rate is the mass of the fluid traveling past a fixed point per unit time.
The mass flow meter does not measure the volume per unit time (e.g. cubic meters per second) passing through the device; it measures the mass per unit time (e.g. kilograms per second) flowing through the device. Volumetric flow rate is the mass flow rate divided by the fluid density . If the density is constant, then the relationship is simple. If the fluid has varying density, then the relationship is not simple. For example, the density of the fluid may change with temperature, pressure , or composition. The fluid may also be a combination of phases such as a fluid with entrained bubbles. Actual density can be determined due to dependency of sound velocity on the controlled liquid concentration. [ 1 ]
The Coriolis flow meter is based on the Coriolis force , which bends rotating objects depending on their velocity.
There are two basic configurations of Coriolis flow meter: the curved tube flow meter and the straight tube flow meter . This article discusses the curved tube design.
The animations on the right do not represent an actually existing Coriolis flow meter design. The purpose of the animations is to illustrate the operating principle, and to show the connection with rotation.
Fluid is being pumped through the mass flow meter. When there is mass flow, the tube twists slightly. The arm through which fluid flows away from the axis of rotation must exert a force on the fluid, to increase its angular momentum , so it bends backwards. The arm through which fluid is pushed back to the axis of rotation must exert a force on the fluid to decrease the fluid's angular momentum again, hence that arm will bend forward. In other words, the inlet arm (containing an outwards directed flow), is lagging behind the overall rotation, the part which in rest is parallel to the axis is now skewed, and the outlet arm (containing an inwards directed flow) leads the overall rotation.
The animation on the right represents how curved tube mass flow meters are designed. The fluid is led through two parallel tubes. An actuator (not shown) induces equal counter vibrations on the sections parallel to the axis, to make the measuring device less sensitive to outside vibrations. The actual frequency of the vibration depends on the size of the mass flow meter, and ranges from 80 to 1000 Hz. The amplitude of the vibration is too small to be seen, but it can be felt by touch.
When no fluid is flowing, the motion of the two tubes is symmetrical, as shown in the left animation. The animation on the right illustrates what happens during mass flow: some twisting of the tubes. The arm carrying the flow away from the axis of rotation must exert a force on the fluid to accelerate the flowing mass to the vibrating speed of the tubes at the outside (increase of absolute angular momentum), so it is lagging behind the overall vibration. The arm through which fluid is pushed back towards the axis of movement must exert a force on the fluid to decrease the fluid's absolute angular speed (angular momentum) again, hence that arm leads the overall vibration.
The inlet arm and the outlet arm vibrate with the same frequency as the overall vibration, but when there is mass flow the two vibrations are out of sync: the inlet arm is behind, the outlet arm is ahead. The two vibrations are shifted in phase with respect to each other, and the degree of phase-shift is a measure for the amount of mass that is flowing through the tubes and line.
The mass flow of a U-shaped Coriolis flow meter is given as:
Q m = K u − I u ω 2 2 K d 2 τ {\displaystyle Q_{m}={\frac {K_{u}-I_{u}\omega ^{2}}{2Kd^{2}}}\tau }
where K u is the temperature dependent stiffness of the tube, K is a shape-dependent factor, d is the width, τ is the time lag, ω is the vibration frequency, and I u is the inertia of the tube. As the inertia of the tube depend on its contents, knowledge of the fluid density is needed for the calculation of an accurate mass flow rate.
If the density changes too often for manual calibration to be sufficient, the Coriolis flow meter can be adapted to measure the density as well. The natural vibration frequency of the flow tubes depends on the combined mass of the tube and the fluid contained in it. By setting the tube in motion and measuring the natural frequency, the mass of the fluid contained in the tube can be deduced. Dividing the mass on the known volume of the tube gives us the density of the fluid.
An instantaneous density measurement allows the calculation of flow in volume per time by dividing mass flow with density.
Both mass flow and density measurements depend on the vibration of the tube. Calibration is affected by changes in the rigidity of the flow tubes.
Changes in temperature and pressure will cause the tube rigidity to change, but these can be compensated for through pressure and temperature zero and span compensation factors.
Additional effects on tube rigidity will cause shifts in the calibration factor over time due to degradation of the flow tubes. These effects include pitting, cracking, coating, erosion or corrosion. It is not possible to compensate for these changes dynamically, but efforts to monitor the effects may be made through regular meter calibration or verification checks. If a change is deemed to have occurred, but is considered to be acceptable, the offset may be added to the existing calibration factor to ensure continued accurate measurement. | https://en.wikipedia.org/wiki/Mass_flow_meter |
In physics and engineering , mass flow rate is the rate at which mass of a substance changes over time . Its unit is kilogram per second (kg/s) in SI units, and slug per second or pound per second in US customary units . The common symbol is m ˙ {\displaystyle {\dot {m}}} (pronounced "m-dot"), although sometimes μ {\displaystyle \mu } ( Greek lowercase mu ) is used.
Sometimes, mass flow rate as defined here is termed "mass flux" or "mass current". [ a ] Confusingly, "mass flow" is also a term for mass flux , the rate of mass flow per unit of area. [ 2 ]
Mass flow rate is defined by the limit [ 3 ] [ 4 ] m ˙ = lim Δ t → 0 Δ m Δ t = d m d t , {\displaystyle {\dot {m}}=\lim _{\Delta t\to 0}{\frac {\Delta m}{\Delta t}}={\frac {dm}{dt}},} i.e., the flow of mass Δ m {\displaystyle \Delta m} through a surface per time Δ t {\displaystyle \Delta t} .
The overdot on m ˙ {\displaystyle {\dot {m}}} is Newton's notation for a time derivative . Since mass is a scalar quantity, the mass flow rate (the time derivative of mass) is also a scalar quantity. The change in mass is the amount that flows after crossing the boundary for some time duration, not the initial amount of mass at the boundary minus the final amount at the boundary, since the change in mass flowing through the area would be zero for steady flow .
Mass flow rate can also be calculated by
m ˙ = ρ ⋅ V ˙ = ρ ⋅ v ⋅ A = j m ⋅ A , {\displaystyle {\dot {m}}=\rho \cdot {\dot {V}}=\rho \cdot \mathbf {v} \cdot \mathbf {A} =\mathbf {j} _{\text{m}}\cdot \mathbf {A} ,}
where
The above equation is only true for a flat, plane area. In general, including cases where the area is curved, the equation becomes a surface integral : m ˙ = ∬ A ρ v ⋅ d A = ∬ A j m ⋅ d A . {\displaystyle {\dot {m}}=\iint _{A}\rho \mathbf {v} \cdot d\mathbf {A} =\iint _{A}\mathbf {j} _{\text{m}}\cdot d\mathbf {A} .}
The area required to calculate the mass flow rate is real or imaginary, flat or curved, either as a cross-sectional area or a surface, e.g. for substances passing through a filter or a membrane , the real surface is the (generally curved) surface area of the filter, macroscopically - ignoring the area spanned by the holes in the filter/membrane. The spaces would be cross-sectional areas. For liquids passing through a pipe, the area is the cross-section of the pipe, at the section considered. The vector area is a combination of the magnitude of the area through which the mass passes through, A {\displaystyle A} , and a unit vector normal to the area, n ^ {\displaystyle \mathbf {\hat {n}} } . The relation is A = A n ^ {\displaystyle \mathbf {A} =A\mathbf {\hat {n}} } .
The reason for the dot product is as follows. The only mass flowing through the cross-section is the amount normal to the area, i.e. parallel to the unit normal. This amount is
where θ {\displaystyle \theta } is the angle between the unit normal n ^ {\displaystyle \mathbf {\hat {n}} } and the velocity of mass elements. The amount passing through the cross-section is reduced by the factor cos θ {\displaystyle \cos \theta } , as θ {\displaystyle \theta } increases less mass passes through. All mass which passes in tangential directions to the area, that is perpendicular to the unit normal, doesn't actually pass through the area, so the mass passing through the area is zero. This occurs when θ = π / 2 {\displaystyle \theta =\pi /2} : m ˙ = ρ v A cos ( π / 2 ) = 0. {\displaystyle {\dot {m}}=\rho vA\cos(\pi /2)=0.} These results are equivalent to the equation containing the dot product. Sometimes these equations are used to define the mass flow rate.
Considering flow through porous media, a special quantity, superficial mass flow rate, can be introduced. It is related with superficial velocity , v s {\displaystyle v_{s}} , with the following relationship: [ 5 ] m ˙ s = v s ⋅ ρ = m ˙ / A {\displaystyle {\dot {m}}_{s}=v_{s}\cdot \rho ={\dot {m}}/A} The quantity can be used in particle Reynolds number or mass transfer coefficient calculation for fixed and fluidized bed systems.
In the elementary form of the continuity equation for mass, in hydrodynamics : [ 6 ] ρ 1 v 1 ⋅ A 1 = ρ 2 v 2 ⋅ A 2 . {\displaystyle \rho _{1}\mathbf {v} _{1}\cdot \mathbf {A} _{1}=\rho _{2}\mathbf {v} _{2}\cdot \mathbf {A} _{2}.}
In elementary classical mechanics, mass flow rate is encountered when dealing with objects of variable mass , such as a rocket ejecting spent fuel. Often, descriptions of such objects erroneously [ 7 ] invoke Newton's second law F = d ( m v ) / d t {\displaystyle \mathbf {F} =d(m\mathbf {v} )/dt} by treating both the mass m {\displaystyle m} and the velocity v {\displaystyle \mathbf {v} } as time-dependent and then applying the derivative product rule. A correct description of such an object requires the application of Newton's second law to the entire, constant-mass system consisting of both the object and its ejected mass. [ 7 ]
Mass flow rate can be used to calculate the energy flow rate of a fluid: [ 8 ] E ˙ = m ˙ e , {\displaystyle {\dot {E}}={\dot {m}}e,} where e {\displaystyle e} is the unit mass energy of a system.
Energy flow rate has SI units of kilojoule per second or kilowatt . | https://en.wikipedia.org/wiki/Mass_flow_rate |
In physics and engineering , mass flux is the rate of mass flow per unit of area. Its SI units are kg ⋅ s −1 ⋅ m −2 . The common symbols are j , J , q , Q , φ , or Φ ( Greek lowercase or capital Phi ), sometimes with subscript m to indicate mass is the flowing quantity.
This flux quantity is also known simply as "mass flow". [ 1 ] "Mass flux" can also refer to an alternate form of flux in Fick's law that includes the molecular mass , or in Darcy's law that includes the mass density . [ 2 ] Less commonly the defining equation for mass flux in this article is used interchangeably with the defining equation in mass flow rate . [ a ]
Mathematically, mass flux is defined as the limit j m = lim A → 0 I m A , {\displaystyle j_{m}=\lim _{A\to 0}{\frac {I_{m}}{A}},} where I m = lim Δ t → 0 Δ m Δ t = d m d t {\displaystyle I_{m}=\lim _{\Delta t\to 0}{\frac {\Delta m}{\Delta t}}={\frac {dm}{dt}}} is the mass current (flow of mass m per unit time t ) and A is the area through which the mass flows.
For mass flux as a vector j m , the surface integral of it over a surface S , followed by an integral over the time duration t 1 to t 2 , gives the total amount of mass flowing through the surface in that time ( t 2 − t 1 ): Δ m = ∫ t 1 t 2 ∬ S j m ⋅ n ^ d A d t . {\displaystyle \Delta m=\int _{t_{1}}^{t_{2}}\iint _{S}\mathbf {j} _{m}\cdot \mathbf {\hat {n}} \,dA\,dt.}
The area required to calculate the flux is real or imaginary, flat or curved, either as a cross-sectional area or a surface.
For example, for substances passing through a filter or a membrane , the real surface is the (generally curved) surface area of the filter, macroscopically - ignoring the area spanned by the holes in the filter/membrane. The spaces would be cross-sectional areas. For liquids passing through a pipe, the area is the cross-section of the pipe, at the section considered.
The vector area is a combination of the magnitude of the area through which the mass passes through, A , and a unit vector normal to the area, n ^ {\displaystyle \mathbf {\hat {n}} } . The relation is A = A n ^ {\displaystyle \mathbf {A} =A\mathbf {\hat {n}} } .
If the mass flux j m passes through the area at an angle θ to the area normal n ^ {\displaystyle \mathbf {\hat {n}} } , then j m ⋅ n ^ = j m cos θ {\displaystyle \mathbf {j} _{m}\cdot \mathbf {\hat {n}} =j_{m}\cos \theta } where · is the dot product of the unit vectors. That is, the component of mass flux passing through the surface (i.e. normal to it) is j m cos θ . While the component of mass flux passing tangential to the area is given by j m sin θ , there is no mass flux actually passing through the area in the tangential direction. The only component of mass flux passing normal to the area is the cosine component.
Consider a pipe of flowing water . Suppose the pipe has a constant cross section and we consider a straight section of it (not at any bends/junctions), and the water is flowing steadily at a constant rate, under standard conditions . The area A is the cross-sectional area of the pipe. Suppose the pipe has radius r = 2 cm = 2 × 10 −2 m . The area is then A = π r 2 . {\displaystyle A=\pi r^{2}.} To calculate the mass flux j m (magnitude), we also need the amount of mass of water transferred through the area and the time taken. Suppose a volume V = 1.5 L = 1.5 × 10 −3 m 3 passes through in time t = 2 s. Assuming the density of water is ρ = 1000 kg m −3 , we have: Δ m = ρ Δ V m 2 − m 1 = ρ ( V 2 − V 1 ) m = ρ V {\displaystyle {\begin{aligned}\Delta m&=\rho \Delta V\\m_{2}-m_{1}&=\rho (V_{2}-V_{1})\\m&=\rho V\\\end{aligned}}} (since initial volume passing through the area was zero, final is V , so corresponding mass is m ), so the mass flux is j m = Δ m A Δ t = ρ V π r 2 t . {\displaystyle j_{m}={\frac {\Delta m}{A\Delta t}}={\frac {\rho V}{\pi r^{2}t}}.}
Substituting the numbers gives: j m = 1000 × ( 1.5 × 10 − 3 ) π × ( 2 × 10 − 2 ) 2 × 2 = 3 16 π × 10 4 , {\displaystyle j_{m}={\frac {1000\times \left(1.5\times 10^{-3}\right)}{\pi \times \left(2\times 10^{-2}\right)^{2}\times 2}}={\frac {3}{16\pi }}\times 10^{4},} which is approximately 596.8 kg s −1 m −2 .
Using the vector definition, mass flux is also equal to: [ 4 ] j m = ρ u {\displaystyle \mathbf {j} _{\rm {m}}=\rho \mathbf {u} }
where:
Sometimes this equation may be used to define j m as a vector.
In the case fluid is not pure, i.e. is a mixture of substances (technically contains a number of component substances), the mass fluxes must be considered separately for each component of the mixture.
When describing fluid flow (i.e. flow of matter), mass flux is appropriate. When describing particle transport (movement of a large number of particles), it is useful to use an analogous quantity, called the molar flux .
Using mass, the mass flux of component i is j m , i = ρ i u i . {\displaystyle \mathbf {j} _{{\rm {m}},\,i}=\rho _{i}\mathbf {u} _{i}.}
The barycentric mass flux of component i is j m , i = ρ ( u i − ⟨ u ⟩ ) , {\displaystyle \mathbf {j} _{{\rm {m}},\,i}=\rho \left(\mathbf {u} _{i}-\langle \mathbf {u} \rangle \right),} where ⟨ u ⟩ {\displaystyle \langle \mathbf {u} \rangle } is the average mass velocity of all the components in the mixture, given by ⟨ u ⟩ = 1 ρ ∑ i ρ i u i = 1 ρ ∑ i j m , i {\displaystyle \langle \mathbf {u} \rangle ={\frac {1}{\rho }}\sum _{i}\rho _{i}\mathbf {u} _{i}={\frac {1}{\rho }}\sum _{i}\mathbf {j} _{{\rm {m}},\,i}} where
The average is taken over the velocities of the components.
If we replace density ρ by the "molar density", concentration c , we have the molar flux analogues.
The molar flux is the number of moles per unit time per unit area, generally: j n = c u . {\displaystyle \mathbf {j} _{\rm {n}}=c\mathbf {u} .}
So the molar flux of component i is (number of moles per unit time per unit area): j n , i = c i u i {\displaystyle \mathbf {j} _{{\rm {n}},\,i}=c_{i}\mathbf {u} _{i}} and the barycentric molar flux of component i is j n , i = c ( u i − ⟨ u ⟩ ) , {\displaystyle \mathbf {j} _{{\rm {n}},\,i}=c\left(\mathbf {u} _{i}-\langle \mathbf {u} \rangle \right),} where ⟨ u ⟩ {\displaystyle \langle \mathbf {u} \rangle } this time is the average molar velocity of all the components in the mixture, given by: ⟨ u ⟩ = 1 n ∑ i c i u i = 1 c ∑ i j n , i . {\displaystyle \langle \mathbf {u} \rangle ={\frac {1}{n}}\sum _{i}c_{i}\mathbf {u} _{i}={\frac {1}{c}}\sum _{i}\mathbf {j} _{{\rm {n}},\,i}.}
Mass flux appears in some equations in hydrodynamics , in particular the continuity equation : ∇ ⋅ j m + ∂ ρ ∂ t = 0 , {\displaystyle \nabla \cdot \mathbf {j} _{\rm {m}}+{\frac {\partial \rho }{\partial t}}=0,} which is a statement of the mass conservation of fluid. In hydrodynamics, mass can only flow from one place to another.
Molar flux occurs in Fick's first law of diffusion : ∇ ⋅ j n = − ∇ ⋅ D ∇ n {\displaystyle \nabla \cdot \mathbf {j} _{\rm {n}}=-\nabla \cdot D\nabla n} where D is the diffusion coefficient . | https://en.wikipedia.org/wiki/Mass_flux |
In chemistry , the mass fraction of a substance within a mixture is the ratio w i {\displaystyle w_{i}} (alternatively denoted Y i {\displaystyle Y_{i}} ) of the mass m i {\displaystyle m_{i}} of that substance to the total mass m tot {\displaystyle m_{\text{tot}}} of the mixture. [ 1 ] Expressed as a formula, the mass fraction is:
Because the individual masses of the ingredients of a mixture sum to m tot {\displaystyle m_{\text{tot}}} , their mass fractions sum to unity:
Mass fraction can also be expressed, with a denominator of 100, as percentage by mass (in commercial contexts often called percentage by weight , abbreviated wt.% or % w/w ; see mass versus weight ). It is one way of expressing the composition of a mixture in a dimensionless size ; mole fraction (percentage by moles , mol%) and volume fraction ( percentage by volume , vol%) are others.
When the prevalences of interest are those of individual chemical elements , rather than of compounds or other substances, the term mass fraction can also refer to the ratio of the mass of an element to the total mass of a sample. In these contexts an alternative term is mass percent composition . The mass fraction of an element in a compound can be calculated from the compound's empirical formula [ 2 ] or its chemical formula . [ 3 ]
In thermal engineering , vapor quality is used for the mass fraction of vapor in the steam.
In alloys, especially those of noble metals, the term fineness is used for the mass fraction of the noble metal in the alloy.
The mass fraction is independent of temperature.
The mixing of two pure components can be expressed introducing the (mass) mixing ratio of them r m = m 2 m 1 {\displaystyle r_{m}={\frac {m_{2}}{m_{1}}}} . Then the mass fractions of the components will be
The mass ratio equals the ratio of mass fractions of components:
due to division of both numerator and denominator by the sum of masses of components.
The mass fraction of a component in a solution is the ratio of the mass concentration of that component ρ i (density of that component in the mixture) to the density of solution ρ {\displaystyle \rho } .
The relation to molar concentration is like that from above substituting the relation between mass and molar concentration:
where c i {\displaystyle c_{i}} is the molar concentration, and M i {\displaystyle M_{i}} is the molar mass of the component i {\displaystyle i} .
Mass percentage is defined as the mass fraction multiplied by 100.
The mole fraction x i {\displaystyle x_{i}} can be calculated using the formula
where M i {\displaystyle M_{i}} is the molar mass of the component i {\displaystyle i} , and M ¯ {\displaystyle {\bar {M}}} is the average molar mass of the mixture.
Replacing the expression of the molar-mass products,
In a spatially non-uniform mixture, the mass fraction gradient gives rise to the phenomenon of diffusion . | https://en.wikipedia.org/wiki/Mass_fraction_(chemistry) |
General relativity does not offer a single definition of the term mass , but offers several different definitions that are applicable under different circumstances. Under some circumstances, the mass of a system in general relativity may not even be defined. The subtlety of this definition stems from the fact that the energy and momentum in a gravitational field cannot be unambiguously localized. [ 1 ] : Ch. 20 As such, rigorous definitions of mass in general relativity cannot be not local as they are in classical mechanics or special relativity , but must make reference to the asymptotic nature of spacetime. A well-defined notion of mass exists for asymptotically flat spacetimes and for asymptotically anti-de Sitter space . However, these definitions must be used with care in other settings.
In special relativity, the rest mass of a particle can be defined unambiguously in terms of its energy and momentum (see Mass in special relativity ). Generalizing the notion of the energy and momentum to general relativity, however, is subtle. The main reason for this is that that the gravitational field itself contributes to the energy and momentum. However, the "gravitational field energy" is not a part of the energy–momentum tensor; instead, what might be identified as the contribution of the gravitational field to a total energy is part of the Einstein tensor on the other side of Einstein's equation (and, as such, a consequence of these equations' non-linearity). While in certain situations it is possible to rewrite the equations so that part of the "gravitational energy" now stands alongside the other source terms in the form of the stress–energy–momentum pseudotensor , this separation is not true for all observers, and there is no general definition for obtaining it. [ 2 ]
The total mass of a system – a concept easily defined in classical mechanics – may be defined for spacetimes which are asymptotically flat (roughly speaking, which represent some isolated gravitating system in otherwise empty and gravity-free infinite space) using the ADM 3+1 split. As in the usual Hamiltonian formalism , the time direction used in that split has an associated energy, which can be integrated up to yield a global quantity known as the ADM mass (or, equivalently, ADM energy). [ 3 ] Alternatively, there is a possibility to define mass for a spacetime that is stationary , in other words, one that has a time-like Killing vector field (which, as a generating field for time, is canonically conjugate to energy); the result is the so-called Komar mass [ 4 ] [ 5 ] Although defined in a different way, it can be shown to be equivalent to the ADM mass for stationary spacetimes. [ 6 ] The Komar integral definition can also be generalized to non-stationary fields for which there is at least an asymptotic time translation symmetry ; imposing a certain gauge condition, one can define the Bondi energy at null infinity. In a way, the ADM energy measures all of the energy contained in spacetime, while the Bondi energy excludes those parts carried off by gravitational waves to infinity. [ 5 ] Effort has been expended on proving positivity theorems for the masses just defined, not least because positivity, or at least the existence of a lower limit, has a bearing on the more fundamental question of boundedness from below: if there were no lower limit to the energy, then no isolated system would be absolutely stable; there would always be the possibility of a decay to a state of even lower total energy. Several kinds of proofs that both the ADM mass and the Bondi mass are indeed positive exist; in particular, this means that Minkowski space (for which both are zero) is indeed stable. [ 7 ] While the focus here has been on energy, analogue definitions for global momentum exist; given a field of angular Killing vectors and following the Komar technique, one can also define global angular momentum. [ 8 ]
The disadvantage of all the definitions mentioned so far is that they are defined only at (null or spatial) infinity; since the 1970s, physicists and mathematicians have worked on the more ambitious endeavor of defining suitable quasi-local quantities, such as the mass of an isolated system defined using only quantities defined within a finite region of space containing that system. However, while there is a variety of proposed definitions such as the Hawking energy , the Geroch energy or Penrose's quasi-local energy–momentum based on twistor methods, the field is still in flux. Eventually, the hope is to use a suitable defined quasi-local mass to give a more precise formulation of the hoop conjecture , prove the so-called Penrose inequality for black holes (relating the black hole's mass to the horizon area) and find a quasi-local version of the laws of black hole mechanics. [ 9 ]
A non-technical definition of a stationary spacetime is a spacetime where none of the metric coefficients g μ ν {\displaystyle g_{\mu \nu }\,} are functions of time. The Schwarzschild metric of a black hole and the Kerr metric of a rotating black hole are common examples of stationary spacetimes.
By definition, a stationary spacetime exhibits time translation symmetry . This is technically called a time-like Killing vector . Because the system has a time translation symmetry, Noether's theorem guarantees that it has a conserved energy. Because a stationary system also has a well defined rest frame in which its momentum can be considered to be zero, defining the energy of the system also defines its mass. In general relativity, this mass is called the Komar mass of the system. Komar mass can only be defined for stationary systems.
Komar mass can also be defined by a flux integral. This is similar to the way that Gauss's law defines the charge enclosed by a surface as the normal electric force multiplied by the area. The flux integral used to define Komar mass is slightly different from that used to define the electric field, however – the normal force is not the actual force, but the "force at infinity". See the main article for more detail.
Of the two definitions, the description of Komar mass in terms of a time translation symmetry provides the deepest insight.
If a system containing gravitational sources is surrounded by an infinite vacuum region, the geometry of the space-time will tend to approach the flat Minkowski geometry of special relativity at infinity. Such space-times are known as "asymptotically flat" space-times.
For systems in which space-time is asymptotically flat , the ADM and Bondi energy, momentum, and mass can be defined. In terms of Noether's theorem, the ADM energy, momentum, and mass are defined by the asymptotic symmetries at spatial infinity , and the Bondi energy, momentum, and mass are defined by the asymptotic symmetries at null infinity . Note that mass is computed as the length of the energy–momentum four-vector , which can be thought of as the energy and momentum of the system "at infinity".
The ADM energy is defined through the following flux integral at infinity. [ 1 ] If a spacetime is asymptotically flat this means that near "infinity" the metric tends to that of flat space. The asymptotic deviations of the metric away from flat space can be parametrized by
where η μ ν {\displaystyle \eta _{\mu \nu }} is the flat space metric.
The ADM energy is then given by an integral over a surface, S {\displaystyle S} at infinity
where S j {\displaystyle S_{j}} is the outward-pointing normal to S {\displaystyle S} . The Einstein summation convention is assumed for repeated indices but the sum over k and j only runs over the spatial directions. The use of ordinary derivatives instead of covariant derivatives in the formula above is justified because of the assumption that the asymptotic geometry is flat.
Some intuition for the formula above can be obtained as follows. Imagine that that we take the surface, S, to be a spherical surface so that the normal points radially outwards. At large distances from the source of the energy, r, the tensor h i j {\displaystyle h_{ij}} is expected to fall off as r − 1 {\displaystyle r^{-1}} and the derivative with respect to r converts this into r − 2 {\displaystyle r^{-2}} . The area of the sphere at large radius also grows precisely as r 2 {\displaystyle r^{2}} and therefore one obtains a finite value for the energy.
It is also possible to obtain expressions for the momentum in asymptotically flat spacetime. To obtain such an expression one defines
where
Then the momentum is obtained by a flux integral in the asymptotically flat region
Note that the expression for P 0 {\displaystyle P^{0}} obtained from the formula above coincides with the expression for the ADM energy given above as can easily be checked using the explicit expression for H.
In the Newtonian limit, for quasi-static systems in nearly flat space-times, one can approximate the total energy of the system by adding together the non-gravitational components of the energy of the system and then subtracting the Newtonian gravitational binding energy.
Translating the above statement into the language of general relativity, we say that a system in nearly flat space-time has a total non-gravitational energy E and momentum P given by:
When the components of the momentum vector of the system are zero, i.e. P i = 0, the approximate mass of the system is just (E+E binding )/c 2 , E binding being a negative number representing the Newtonian gravitational self-binding energy.
Hence when one assumes that the system is quasi-static, one assumes that there is no significant energy present in the form of "gravitational waves". When one assumes that the system is in "nearly-flat" space-time, one assumes that the metric coefficients are essentially Minkowskian within acceptable experimental error.
The formulas for the total energy and momentum can be seen to arise naturally in this limit as follows. [ 1 ] In the linearized limit, the equations of general relativity can be written in the form
In this limit, the total energy-momentum of the system is simply given by integrating the stress-tensor on a spacelike slice.
But using the equations of motion, one can also write this as
where the sum over j runs only over the spatial directions and the second equality uses the fact that H μ α ν β {\displaystyle H^{\mu \alpha \nu \beta }} is anti-symmetric in ν {\displaystyle \nu } and β {\displaystyle \beta } .
Finally, one uses the Gauss law to convert the integral of a divergence over the spatial slice into an integral over a Gaussian sphere
which coincides precisely with the formula for the total momentum given above.
In 1918, David Hilbert wrote about the difficulty in assigning an energy to a "field" and "the failure of the energy theorem" in a correspondence with Felix Klein . In this letter, Hilbert conjectured that this failure is a characteristic feature of the general theory, and that instead of "proper energy theorems" one had 'improper energy theorems'.
This conjecture was soon proved to be correct by one of Hilbert's close associates, Emmy Noether . Noether's theorem applies to any system which can be described by an action principle . Noether's theorem associates conserved energies with time-translation symmetries. When the time-translation symmetry is a finite parameter continuous group , such as the Poincaré group , Noether's theorem defines a scalar conserved energy for the system in question. However, when the symmetry is an infinite parameter continuous group, the existence of a conserved energy is not guaranteed. In a similar manner, Noether's theorem associates conserved momenta with space-translations, when the symmetry group of the translations is finite-dimensional. Because general relativity is a diffeomorphism invariant theory, it has an infinite continuous group of symmetries rather than a finite-parameter group of symmetries, and hence has the wrong group structure to guarantee a conserved energy. Noether's theorem has been influential in inspiring and unifying various ideas of mass, system energy, and system momentum in general relativity.
As an example of the application of Noether's theorem is the example of stationary space-times and their associated Komar mass.(Komar 1959). While general space-times lack a finite-parameter time-translation symmetry, stationary space-times have such a symmetry, known as a Killing vector . Noether's theorem proves that such stationary space-times must have an associated conserved energy. This conserved energy defines a conserved mass, the Komar mass.
ADM mass was introduced (Arnowitt et al., 1960) from an initial-value formulation of general relativity. It was later reformulated in terms of the group of asymptotic symmetries at spatial infinity, the SPI group, by various authors. (Held, 1980). This reformulation did much to clarify the theory, including explaining why ADM momentum and ADM energy transforms as a 4-vector (Held, 1980). Note that the SPI group is actually infinite-dimensional. The existence of conserved quantities is because the SPI group of "super-translations" has a preferred 4-parameter subgroup of "pure" translations, which, by Noether's theorem, generates a conserved 4-parameter energy–momentum. The norm of this 4-parameter energy–momentum is the ADM mass.
The Bondi mass was introduced (Bondi, 1962) in a paper that studied the loss of mass of physical systems via gravitational radiation. The Bondi mass is also associated with a group of asymptotic symmetries, the BMS group at null infinity. Like the SPI group at spatial infinity, the BMS group at null infinity is infinite-dimensional, and it also has a preferred 4-parameter subgroup of "pure" translations.
Another approach to the problem of energy in general relativity is the use of pseudotensors such as the Landau–Lifshitz pseudotensor .(Landau and Lifshitz, 1962). Pseudotensors are not gauge invariant – because of this, they only give consistent gauge-independent answers for the total energy when additional constraints (such as asymptotic flatness) are met. The gauge dependence of pseudotensors also prevents any gauge-independent definition of the local energy density, as every different gauge choice results in a different local energy density. | https://en.wikipedia.org/wiki/Mass_in_general_relativity |
Mass injection flow ( a.k.a. Limbach Flow) refers to inviscid , adiabatic flow through a constant area duct where the effect of mass addition is considered. For this model, the duct area remains constant, the flow is assumed to be steady and one-dimensional, and mass is added within the duct. Because the flow is adiabatic, unlike in Rayleigh flow , the stagnation temperature is a constant. [ 1 ] Compressibility effects often come into consideration, though this flow model also applies to incompressible flow .
For supersonic flow (an upstream Mach number greater than 1), deceleration occurs with mass addition to the duct and the flow can become choked . Conversely, for subsonic flow (an upstream Mach number less than 1), acceleration occurs and the flow can become choked given sufficient mass addition. Therefore, mass addition will cause both supersonic and subsonic Mach numbers to approach Mach 1, resulting in choked flow.
The 1D mass injection flow model begins with a mass-velocity relation derived for mass injection into a steady, adiabatic, frictionless, constant area flow of calorically perfect gas:
d m m = − d u u ( M 2 − 1 ) {\displaystyle \ {\frac {dm}{m}}=-{\frac {du}{u}}\left(M^{2}-1\right)}
where m {\displaystyle m} represents a mass flux , m = m ˙ / A {\displaystyle m={\dot {m}}/A} . This expression describes how velocity will change with a change in mass flux (i.e. how a change in mass flux d m {\displaystyle dm} drives a change in velocity d u {\displaystyle du} ). From this relation, two distinct modes of behavior are seen:
From the mass-velocity relation, an explicit mass-Mach relation may be derived:
d m m = 1 − M 2 M + 1 2 M 3 ( γ − 1 ) d M {\displaystyle {\frac {dm}{m}}={\frac {1-M^{2}}{M+{\frac {1}{2}}M^{3}(\gamma -1)}}dM}
Although Fanno flow and Rayleigh flow are covered in detail in many textbooks, mass injection flow is not. [ 1 ] [ 2 ] [ 3 ] [ 4 ] For this reason, derivations of fundamental mass flow properties are given here. In the following derivations, the constant R {\displaystyle R} is used to denote the specific gas constant (i.e. R = R ¯ / M {\displaystyle R={\bar {R}}/M} ).
We begin by establishing a relationship between the differential enthalpy, pressure, and density of a calorically perfect gas:
From the adiabatic energy equation ( d h 0 = 0 {\displaystyle dh_{0}=0} ) [ 1 ] we find:
Substituting the enthalpy-pressure-density relation ( 1 ) into the adiabatic energy relation ( 2 ) yields
Next, we find a relationship between differential density, mass flux ( m = m ˙ / A {\displaystyle m={\dot {m}}/A} ), and velocity:
Substituting the density-mass-velocity relation ( 4 ) into the modified energy relation ( 3 ) yields
Substituting the 1D steady flow momentum conservation equation (see also the Euler equations ) of the form d p = − ρ u d u {\displaystyle dp=-\rho udu} [ 5 ] into ( 5 ) yields
From the ideal gas law we find,
and from the definition of a calorically perfect gas [ 1 ] we find,
Substituting expressions ( 7 ) and ( 8 ) into the combined equation ( 6 ) yields
Using the speed of sound in an ideal gas ( a 2 = γ R T {\displaystyle a^{2}=\gamma RT} ) [ 1 ] and the definition of the Mach number ( M = u / a {\displaystyle M=u/a} ) [ 1 ] yields
d m m = − d u u [ M 2 − 1 ] {\displaystyle {\frac {dm}{m}}=-{\frac {du}{u}}[M^{2}-1]}
This is the mass-velocity relationship for mass injection into a steady, adiabatic, frictionless, constant area flow of calorically perfect gas.
To find a relationship between differential mass and Mach number, we will find an expression for d u / u {\displaystyle du/u} solely in terms of the Mach number, M {\displaystyle M} . We can then substitute this expression into the mass-velocity relation to yield a mass-Mach relation. We begin by relating differential velocity, mach number, and speed of sound:
We can now re-express d a {\displaystyle da} in terms of d T {\displaystyle dT} :
Substituting ( 12 ) into ( 11 ) yields,
We can now re-express d T {\displaystyle dT} in terms of d u {\displaystyle du} :
By substituting ( 14 ) into ( 13 ), we can create an expression completely in terms of d u {\displaystyle du} and d M {\displaystyle dM} . Performing this substitution and solving for d u / u {\displaystyle du/u} yields,
Finally, expression ( 15 ) for d u / u {\displaystyle du/u} in terms of d M {\displaystyle dM} may be substituted directly into the mass-velocity relation ( 10 ):
d m m = 1 − M 2 M + 1 2 M 3 ( γ − 1 ) d M {\displaystyle {\frac {dm}{m}}={\frac {1-M^{2}}{M+{\frac {1}{2}}M^{3}(\gamma -1)}}dM}
This is the mass-Mach relationship for mass injection into a steady, adiabatic, frictionless, constant area flow of calorically perfect gas. | https://en.wikipedia.org/wiki/Mass_injection_flow |
Mass interconnect systems act as the connector interface between test instruments ( PXI , VXI , LXI , GPIB, SCXI, & PCI) and devices/units under test (D/UUT) and are most often used in defense , aerospace , automotive, manufacturing , and other applications. By mating a receiver on the tester side with an interchangeable test adapter (ITA) on the UUT, a mass interconnect enables the entire system to mate together at one time. Mass interconnect systems are available in multiple sizes and configurations to accommodate virtually any testing requirement.
Companies that manufacture mass interconnects include VPC and MAC Panel Company . | https://en.wikipedia.org/wiki/Mass_interconnect |
The mass number (symbol A , from the German word: Atomgewicht , "atomic weight"), [ 1 ] also called atomic mass number or nucleon number , is the total number of protons and neutrons (together known as nucleons ) in an atomic nucleus . It is approximately equal to the atomic (also known as isotopic ) mass of the atom expressed in atomic mass units . Since protons and neutrons are both baryons , the mass number A is identical with the baryon number B of the nucleus (and also of the whole atom or ion ). The mass number is different for each isotope of a given chemical element , and the difference between the mass number and the atomic number Z gives the number of neutrons ( N ) in the nucleus: N = A − Z . [ 2 ]
The mass number is written either after the element name or as a superscript to the left of an element's symbol. For example, the most common isotope of carbon is carbon-12 , or 12 C , which has 6 protons and 6 neutrons. The full isotope symbol would also have the atomic number ( Z ) as a subscript to the left of the element symbol directly below the mass number: 12 6 C . [ 3 ]
Different types of radioactive decay are characterized by their changes in mass number as well as atomic number , according to the radioactive displacement law of Fajans and Soddy .
For example, uranium-238 usually decays by alpha decay , where the nucleus loses two neutrons and two protons in the form of an alpha particle . Thus the atomic number and the number of neutrons each decrease by 2 ( Z : 92 → 90, N : 146 → 144), so that the mass number decreases by 4 ( A = 238 → 234); the result is an atom of thorium-234 and an alpha particle ( 4 2 He 2+ ): [ 4 ]
On the other hand, carbon-14 decays by beta decay , whereby one neutron is transmuted into a proton with the emission of an electron and an antineutrino . Thus the atomic number increases by 1 ( Z : 6 → 7) and the mass number remains the same ( A = 14), while the number of neutrons decreases by 1 ( N : 8 → 7). [ 5 ] The resulting atom is nitrogen-14 , with seven protons and seven neutrons:
Beta decay is possible because different isobars [ 6 ] have mass differences on the order of a few electron masses . If possible, a nuclide will undergo beta decay to an adjacent isobar with lower mass. In the absence of other decay modes, a cascade of beta decays terminates at the isobar with the lowest atomic mass .
Another type of radioactive decay without change in mass number is emission of a gamma ray from a nuclear isomer or metastable excited state of an atomic nucleus. Since all the protons and neutrons remain in the nucleus unchanged in this process, the mass number is also unchanged.
The mass number gives an estimate of the isotopic mass measured in atomic mass units (u). For 12 C, the isotopic mass is exactly 12, since the atomic mass unit is defined as 1/12 of the mass of 12 C. For other isotopes, the isotopic mass is usually within 0.1 u of the mass number. For example, 35 Cl (17 protons and 18 neutrons) has a mass number of 35 and an isotopic mass of 34.96885. [ 7 ] The difference of the actual isotopic mass minus the mass number of an atom is known as the mass excess , [ 8 ] which for 35 Cl is –0.03115. Mass excess should not be confused with mass defect which is the difference between the mass of an atom and its constituent particles (namely protons , neutrons and electrons ).
There are two reasons for mass
excess:
The mass number should also not be confused with the standard atomic weight (also called atomic weight ) of an element, which is the ratio of the average atomic mass of the different isotopes of that element (weighted by abundance) to the atomic mass constant . [ 9 ] The atomic weight is a mass ratio, while the mass number is a counted number (and so an integer).
This weighted average can be quite different from the near-integer values for individual isotopic masses. For instance, there are two main isotopes of chlorine : chlorine-35 and chlorine-37. In any given sample of chlorine that has not been subjected to mass separation there will be roughly 75% of chlorine atoms which are chlorine-35 and only 25% of chlorine atoms which are chlorine-37. This gives chlorine a relative atomic mass of 35.5 (actually 35.4527 g/ mol ).
Moreover, the weighted average mass can be near-integer, but at the same time not corresponding to the mass of any natural isotope. For example, bromine has only two stable isotopes, 79 Br and 81 Br, naturally present in approximately equal fractions, which leads to the standard atomic mass of bromine close to 80 (79.904 g/mol), [ 10 ] even though the isotope 80 Br with such mass is unstable. | https://en.wikipedia.org/wiki/Mass_number |
In aerospace engineering , mass ratio is a measure of the efficiency of a rocket . It describes how much more massive the vehicle is with propellant than without; that is, the ratio of the rocket's wet mass (vehicle plus contents plus propellant) to its dry mass (vehicle plus contents). A more efficient rocket design requires less propellant to achieve a given goal, and would therefore have a lower mass ratio; however, for any given efficiency a higher mass ratio typically permits the vehicle to achieve higher delta-v .
The mass ratio is a useful quantity for back-of-the-envelope rocketry calculations: it is an easy number to derive from either Δ v {\displaystyle \Delta {v}} or from rocket and propellant mass, and therefore serves as a handy bridge between the two. It is also a useful for getting an impression of the size of a rocket: while two rockets with mass fractions of, say, 92% and 95% may appear similar, the corresponding mass ratios of 12.5 and 20 clearly indicate that the latter system requires much more propellant.
Typical multistage rockets have mass ratios in the range from 8 to 20. The Space Shuttle , for example, has a mass ratio around 16.
The definition arises naturally from Tsiolkovsky's rocket equation : Δ v = v e ln m 0 m 1 {\displaystyle \Delta v=v_{e}\ln {\frac {m_{0}}{m_{1}}}} where
This equation can be rewritten in the following equivalent form: m 0 m 1 = e Δ v / v e {\displaystyle {\frac {m_{0}}{m_{1}}}=e^{\Delta v/v_{e}}}
The fraction on the left-hand side of this equation is the rocket's mass ratio by definition.
This equation indicates that a Δv of n {\displaystyle n} times the exhaust velocity requires a mass ratio of e n {\displaystyle e^{n}} . For instance, for a vehicle to achieve a Δ v {\displaystyle \Delta v} of 2.5 times its exhaust velocity would require a mass ratio of e 2.5 {\displaystyle e^{2.5}} (approximately 12.2). One could say that a "velocity ratio" of n {\displaystyle n} requires a mass ratio of e n {\displaystyle e^{n}} .
Sutton defines the mass ratio inversely as: [ 1 ] M R = m 1 m 0 {\displaystyle M_{R}={\frac {m_{1}}{m_{0}}}}
In this case, the values for mass fraction are always less than 1.
Zubrin, Robert (1999). Entering Space: Creating a Spacefaring Civilization . Tarcher/Putnam. ISBN 0-87477-975-8 . | https://en.wikipedia.org/wiki/Mass_ratio |
In astronomy , dynamical mass segregation is the process by which heavier members of a gravitationally bound system, such as a star cluster , tend to move toward the center, while lighter members tend to move farther away from the center.
During a close encounter of two members of the cluster, the members exchange both energy and momentum . Although energy can be exchanged in either direction, there is a statistical tendency for the kinetic energy of the two members to equalize during an encounter; this statistical phenomenon is called equipartition , and is similar to the fact that the expected kinetic energy of the molecules of a gas are all the same at a given temperature.
Since kinetic energy is proportional to mass times the square of the speed, equipartition requires the less massive members of a cluster to be moving faster. The more massive members will thus tend to sink into lower orbits (that is, orbits closer to the center of the cluster), while the less massive members will tend to rise to higher orbits.
The time it takes for the kinetic energies of the cluster members to roughly equalize is called the relaxation time of the cluster. A relaxation time-scale assuming energy is exchanged through two-body interactions was approximated in the textbook by Binney & Tremaine [ 1 ] as
where N {\displaystyle N} is the number of stars in the cluster and t c r o s s {\displaystyle t_{\mathrm {cross} }} is the typical time it takes for a star to cross the cluster. This is on the order of 100 million years for a typical globular cluster with radius 10 parsecs consisting of 100 thousand stars. The most massive stars in a cluster can segregate more rapidly than the less massive stars. This time-scale can be approximated using a toy model developed by Lyman Spitzer of a cluster where stars only have two possible masses ( m 1 {\displaystyle m_{1}} and m 2 {\displaystyle m_{2}} ). In this case, the more massive stars (mass m 1 {\displaystyle m_{1}} ) will segregate in the time
Outward segregation of white dwarfs was observed in the globular cluster 47 Tucanae in a HST study of the region. [ 2 ]
Primordial mass segregation is non-uniform distribution of masses present at the formation of a cluster. The argument that a star cluster is primordially mass segregated is typically based on a comparison of virialization timescales and the cluster's age. However, several dynamical mechanisms to accelerate virialization compared to two-body interactions have been examined. [ 4 ] In star-forming regions, it is often observed that O-type stars are preferentially located in the center of a young cluster.
After relaxation, the speed of some low mass members can be greater than the escape velocity of the cluster, which results in these members being lost to the cluster. This process is called evaporation . (A similar phenomenon explains the loss of lighter gases from a planet, such as hydrogen and helium from the Earth—after equipartition, some molecules of sufficiently light gases at the top of the atmosphere will exceed the escape velocity of the planet and be lost.)
Through evaporation, most open clusters eventually dissipate, as indicated by the fact that most existing open clusters are quite young. Globular clusters , being more tightly bound, appear to be more durable.
The relaxation time of the Milky Way galaxy is approximately 10 trillion years, on the order of thousand times the age of the galaxy itself. Thus, any observed mass segregation in our galaxy must be almost entirely primordial. [ citation needed ] | https://en.wikipedia.org/wiki/Mass_segregation_(astronomy) |
Mass spectrometric immunoassay ( MSIA ) is a rapid method is used to detect and/ or quantify antigens and or antibody analytes. [ 1 ] This method uses an analyte affinity (either through antigens or antibodies) isolation to extract targeted molecules and internal standards from biological fluid in preparation for matrix assisted laser desorption ionization-time of flight mass spectrometry ( MALDI-TOF-MS ). [ 2 ] [ 3 ] [ 4 ] This method allows for "top down" and "bottom up" analysis. This sensitive method allows for a new and improved process for detecting multiple antigens and antibodies in a single assay. [ 1 ] This assay is also capable of distinguishing mass shifted forms of the same molecule via a panantibody, as well as distinguish point mutations in proteins. [ 4 ] [ 5 ] Each specific form is detected uniquely based on their characteristic molecular mass. MSIA has dual specificity because of the antibody-antigen reaction coupled with the power of a mass spectrometer.
There are various other immunoassy techniques that have been used previously such as radioimmunoassay (RIA) and enzyme immunoassay (EIA and ELISA). These techniques are extremely sensitive however, there are many limitations to these methods. For example, quantification for ELISA and EIA require several hours because the binding has to reach equilibrium. [ 1 ] RIA's disadvantage is that you need radioactive particles which are universally known to be carcinogens.
The creation of MSIA fulfilled the need to determine the presence of one or more antigens in a specimen as well as the quantification of those said species.
This assay was patented in 2006 by Randall Nelson, Peter Williams and Jennifer Reeve Krone. [ 1 ] The idea first came about with the development of ELISA and RIA. [ 6 ] An earlier patent method suggested tagging antigens or antibodies with stable isotopes or long-lived radioactive elements. [ 7 ] But limitations to both methods called for a better detection methods of a protein or proteins. The invention combines antigen-antibody binding with a mass spectrometer which aids in identifying qualitatively and quantifying analytes respectively.
An early MSIA experiment was done on a venom laced human blood sample for the Antigen myotoxin. The experiment was successful in that the mass spectrum resulting from the analysis showed a distinct response for myotoxin at the molecular weight corresponding to 4,822 Da (a). [ 1 ] The m/z ratio at 5,242 Da (b) is the molecular weight of the modified variant H-myotoxina, used as an internal reference species. The figure of the mass spectrum is shown below.
An illustration of the MSIA procedure is depicted in the figure to the right. Analytes in a biological liquid sample are collected from solution by using a MSIA tip (also known as MSIA microcolumns [ 8 ] ) that contains a derivatized affinity frit. Biological samples contain various proteins that span a wide dynamic range so purification is needed to minimize the complex matrix and maximize mass spectrometry sensitivity. [ 9 ] the MSIA tip serves as a place to purify these samples by immobilizing the analyte with high selectivity and specificity. Analytes are bound to the frit based on their affinities and all other nonspecific molecules are rinsed away. The specific targets are then eluted on to a mass spectrometer target plate with a MALDI matrix. However, proteins may be digested prior to ms analysis. A MALDI-TOF-MS later follows and targeted analytes are detected based on their m/z values. This method is qualitative, but the addition of mass shifted variants of the analyte for use as an internal standard makes this method useful for quantitative analysis. [ 5 ]
Pipetor tips, which have been termed MSIA tips or affinity pipette tips play a key role in the process of detecting analytes within biological samples. MSIA tips typically contain porous solid support which has derivatized antigens or antibodies covalently attached. Different analytes have different affinity for the tips so it is necessary to derivatize MSIA tips based on the analyte of interest. The main use of these tips are to flow samples through and the analytes affinity for the bound antigen/antibody allows for the capture of analyte. Non specifically bound compounds are rinsed out of the MSIA tips.
The process can be simplified into 6 simple steps which Thermo termed the "work flow".
Many "work flows" are commercially available for purchase.
MSIA is a method that can be used as an assay for a variety of different molecules such as proteins, hormones, drugs, toxins, and various pathogens found in biological fluids (Human and animal plasma, saliva, urine, tears etc.). [ 1 ] [ 10 ] MSIA has also been applied to clinical samples and have been proven to be a unique assay for clinically relevant proteins. [ 11 ] Successfully assaying toxins, drugs and other pathogens are important to the environment as well as the human body. MSIA can be used for a range of biomedical and environmental applications.
An important application of mass spectrometric immunoassy is that it can be used as a rapid, sensitive and accurate screening of apolipoproteins and mutations of them. Apolipoproteins represent a groups of proteins with many functions such as transport and clearance as well as enzyme activation. [ 4 ] Recent studies have claimed that mutations in apopliproteins result in, or assist in the progression of various associated diseases including amyloidosis, amyloid cardiomyopathy, Alzheimer's disease, hypertriglyceridemic, lowered cholesterol, hyperlipidemia and atherosclerosis to name a few. Nelson and colleagues did a study using MSIA to characterize and isolate apolipoproteins species. [ citation needed ]
There are many benefits to using a mass spectrometric immunoassay. Most importantly, the assay is extremely fast and the data are reproducible, and automated. They are sensitive, precise and allows for absolute quantification. Analytes can be detected to low detection limits (as low as picomolar) and the assay covers a wide dynamic range [ 9 ] . | https://en.wikipedia.org/wiki/Mass_spectrometric_immunoassay |
Mass spectrometry ( MS ) is an analytical technique that is used to measure the mass-to-charge ratio of ions . The results are presented as a mass spectrum , a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used in many different fields and is applied to pure samples as well as complex mixtures.
A mass spectrum is a type of plot of the ion signal as a function of the mass-to-charge ratio. These spectra are used to determine the elemental or isotopic signature of a sample, the masses of particles and of molecules , and to elucidate the chemical identity or structure of molecules and other chemical compounds .
In a typical MS procedure, a sample, which may be solid, liquid, or gaseous, is ionized , for example by bombarding it with a beam of electrons . This may cause some of the sample's molecules to break up into positively charged fragments or simply become positively charged without fragmenting. These ions (fragments) are then separated according to their mass-to-charge ratio, for example by accelerating them and subjecting them to an electric or magnetic field: ions of the same mass-to-charge ratio will undergo the same amount of deflection. [ 1 ] The ions are detected by a mechanism capable of detecting charged particles, such as an electron multiplier . Results are displayed as spectra of the signal intensity of detected ions as a function of the mass-to-charge ratio. The atoms or molecules in the sample can be identified by correlating known masses (e.g. an entire molecule) to the identified masses or through a characteristic fragmentation pattern.
In 1886, Eugen Goldstein observed rays in gas discharges under low pressure that traveled away from the anode and through channels in a perforated cathode , opposite to the direction of negatively charged cathode rays (which travel from cathode to anode). Goldstein called these positively charged anode rays "Kanalstrahlen"; the standard translation of this term into English is " canal rays ". Wilhelm Wien found that strong electric or magnetic fields deflected the canal rays and, in 1899, constructed a device with perpendicular electric and magnetic fields that separated the positive rays according to their charge-to-mass ratio ( Q/m ). Wien found that the charge-to-mass ratio depended on the nature of the gas in the discharge tube. English scientist J. J. Thomson later improved on the work of Wien by reducing the pressure to create the mass spectrograph.
The word spectrograph had become part of the international scientific vocabulary by 1884. [ 2 ] [ 3 ] Early spectrometry devices that measured the mass-to-charge ratio of ions were called mass spectrographs which consisted of instruments that recorded a spectrum of mass values on a photographic plate . [ 4 ] [ 5 ] A mass spectroscope is similar to a mass spectrograph except that the beam of ions is directed onto a phosphor screen. [ 6 ] A mass spectroscope configuration was used in early instruments when it was desired that the effects of adjustments be quickly observed. Once the instrument was properly adjusted, a photographic plate was inserted and exposed. The term mass spectroscope continued to be used even though the direct illumination of a phosphor screen was replaced by indirect measurements with an oscilloscope . [ 7 ] The use of the term mass spectroscopy is now discouraged due to the possibility of confusion with light spectroscopy . [ 1 ] [ 8 ] Mass spectrometry is often abbreviated as mass-spec or simply as MS . [ 1 ]
Modern techniques of mass spectrometry were devised by Arthur Jeffrey Dempster and F.W. Aston in 1918 and 1919 respectively.
Sector mass spectrometers known as calutrons were developed by Ernest O. Lawrence and used for separating the isotopes of uranium during the Manhattan Project . [ 9 ] Calutron mass spectrometers were used for uranium enrichment at the Oak Ridge, Tennessee Y-12 plant established during World War II.
In 1989, half of the Nobel Prize in Physics was awarded to Hans Dehmelt and Wolfgang Paul for the development of the ion trap technique in the 1950s and 1960s.
In 2002, the Nobel Prize in Chemistry was awarded to John Bennett Fenn for the development of electrospray ionization (ESI) and Koichi Tanaka for the development of soft laser desorption (SLD) and their application to the ionization of biological macromolecules , especially proteins . [ 10 ]
A mass spectrometer consists of three components: an ion source, a mass analyzer, and a detector. The ionizer converts a portion of the sample into ions. There is a wide variety of ionization techniques, depending on the phase (solid, liquid, gas) of the sample and the efficiency of various ionization mechanisms for the unknown species. An extraction system removes ions from the sample, which are then targeted through the mass analyzer and into the detector . The differences in masses of the fragments allows the mass analyzer to sort the ions by their mass-to-charge ratio. The detector measures the value of an indicator quantity and thus provides data for calculating the abundances of each ion present. Some detectors also give spatial information, e.g., a multichannel plate.
The following describes the operation of a spectrometer mass analyzer, which is of the sector type. (Other analyzer types are treated below.) Consider a sample of sodium chloride (table salt). In the ion source, the sample is vaporized (turned into gas ) and ionized (transformed into electrically charged particles) into sodium (Na + ) and chloride (Cl − ) ions. Sodium atoms and ions are monoisotopic , with a mass of about 23 daltons (symbol: Da or older symbol: u). Chloride atoms and ions come in two stable isotopes with masses of approximately 35 u (at a natural abundance of about 75 percent) and approximately 37 u (at a natural abundance of about 25 percent). The analyzer part of the spectrometer contains electric and magnetic fields, which exert forces on ions traveling through these fields. The speed of a charged particle may be increased or decreased while passing through the electric field, and its direction may be altered by the magnetic field. The magnitude of the deflection of the moving ion's trajectory depends on its mass-to-charge ratio. Lighter ions are deflected by the magnetic force to a greater degree than heavier ions (based on Newton's second law of motion , F = ma ). The streams of magnetically sorted ions pass from the analyzer to the detector, which records the relative abundance of each ion type. This information is used to determine the chemical element composition of the original sample (i.e. that both sodium and chlorine are present in the sample) and the isotopic composition of its constituents (the ratio of 35 Cl to 37 Cl).
The ion source is the part of the mass spectrometer that ionizes the material under analysis (the analyte). The ions are then transported by magnetic or electric fields to the mass analyzer.
Techniques for ionization have been key to determining what types of samples can be analyzed by mass spectrometry. Electron ionization and chemical ionization are used for gases and vapors . In chemical ionization sources, the analyte is ionized by chemical ion-molecule reactions during collisions in the source. Two techniques often used with liquid and solid biological samples include electrospray ionization (invented by John Fenn [ 11 ] ) and matrix-assisted laser desorption/ionization (MALDI, initially developed as a similar technique "Soft Laser Desorption (SLD)" by K. Tanaka [ 12 ] for which a Nobel Prize was awarded and as MALDI by M. Karas and F. Hillenkamp [ 13 ] ).
In mass spectrometry, ionization refers to the production of gas phase ions suitable for resolution in the mass analyser or mass filter. Ionization occurs in the ion source . There are several ion sources available; each has advantages and disadvantages for particular applications. For example, electron ionization (EI) gives a high degree of fragmentation, yielding highly detailed mass spectra which when skilfully analysed can provide important information for structural elucidation/characterisation and facilitate identification of unknown compounds by comparison to mass spectral libraries obtained under identical operating conditions. However, EI is not suitable for coupling to HPLC , i.e. LC-MS , since at atmospheric pressure, the filaments used to generate electrons burn out rapidly. Thus EI is coupled predominantly with GC , i.e. GC-MS , where the entire system is under high vacuum.
Hard ionization techniques are processes which impart high quantities of residual energy in the subject molecule invoking large degrees of fragmentation (i.e. the systematic rupturing of bonds acts to remove the excess energy, restoring stability to the resulting ion). Resultant ions tend to have m/z lower than the molecular ion (other than in the case of proton transfer and not including isotope peaks). The most common example of hard ionization is electron ionization (EI).
Soft ionization refers to the processes which impart little residual energy onto the subject molecule and as such result in little fragmentation. Examples include fast atom bombardment (FAB), chemical ionization (CI), atmospheric-pressure chemical ionization (APCI), atmospheric-pressure photoionization (APPI), electrospray ionization (ESI), desorption electrospray ionization (DESI), and matrix-assisted laser desorption/ionization (MALDI).
Inductively coupled plasma (ICP) sources are used primarily for cation analysis of a wide array of sample types. In this source, a plasma that is electrically neutral overall, but that has had a substantial fraction of its atoms ionized by high temperature, is used to atomize introduced sample molecules and to further strip the outer electrons from those atoms. The plasma is usually generated from argon gas, since the first ionization energy of argon atoms is higher than the first of any other elements except He, F and Ne, but lower than the second ionization energy of all except the most electropositive metals. The heating is achieved by a radio-frequency current passed through a coil surrounding the plasma.
Photoionization can be used in experiments which seek to use mass spectrometry as a means of resolving chemical kinetics mechanisms and isomeric product branching. [ 14 ] In such instances a high energy photon, either X-ray or uv, is used to dissociate stable gaseous molecules in a carrier gas of He or Ar. In instances where a synchrotron light source is utilized, a tuneable photon energy can be utilized to acquire a photoionization efficiency curve which can be used in conjunction with the charge ratio m/z to fingerprint molecular and ionic species. More recently atmospheric pressure photoionization (APPI) has been developed to ionize molecules mostly as effluents of LC-MS systems.
Some applications for ambient ionization include environmental applications as well as clinical applications. In these techniques, ions form in an ion source outside the mass spectrometer. Sampling becomes easy as the samples don't need previous separation nor preparation. Some examples of ambient ionization techniques are Direct Analysis in Real Time (DART), DESI , SESI , LAESI , desorption atmospheric-pressure chemical ionization (DAPCI), Soft Ionization by Chemical Reaction in Transfer (SICRT) and desorption atmospheric pressure photoionization DAPPI among others.
Others include glow discharge , field desorption (FD), fast atom bombardment (FAB), thermospray , desorption/ionization on silicon (DIOS), atmospheric pressure chemical ionization (APCI), secondary ion mass spectrometry (SIMS), spark ionization and thermal ionization (TIMS). [ 15 ]
Mass analyzers separate the ions according to their mass-to-charge ratio . The following two laws govern the dynamics of charged particles in electric and magnetic fields in vacuum:
Here F is the force applied to the ion, m is the mass of the ion, a is the acceleration, Q is the ion charge, E is the electric field, and v × B is the vector cross product of the ion velocity and the magnetic field
Equating the above expressions for the force applied to the ion yields:
This differential equation is the classic equation of motion for charged particles . Together with the particle's initial conditions, it completely determines the particle's motion in space and time in terms of m/Q . Thus mass spectrometers could be thought of as "mass-to-charge spectrometers". When presenting data, it is common to use the (officially) dimensionless m/z , where z is the number of elementary charges ( e ) on the ion (z=Q/e). This quantity, although it is informally called the mass-to-charge ratio, more accurately speaking represents the ratio of the mass number and the charge number, z .
There are many types of mass analyzers, using either static or dynamic fields, and magnetic or electric fields, but all operate according to the above differential equation. Each analyzer type has its strengths and weaknesses. Many mass spectrometers use two or more mass analyzers for tandem mass spectrometry (MS/MS) . In addition to the more common mass analyzers listed below, there are others designed for special situations.
There are several important analyzer characteristics. The mass resolving power is the measure of the ability to distinguish two peaks of slightly different m/z . The mass accuracy is the ratio of the m/z measurement error to the true m/z . Mass accuracy is usually measured in ppm or milli mass units . The mass range is the range of m/z amenable to analysis by a given analyzer. The linear dynamic range is the range over which ion signal is linear with analyte concentration. Speed refers to the time frame of the experiment and ultimately is used to determine the number of spectra per unit time that can be generated.
A sector field mass analyzer uses a static electric and/or magnetic field to affect the path and/or velocity of the charged particles in some way.
As shown above, sector instruments bend the trajectories of the ions as they pass through the mass analyzer, according to their mass-to-charge ratios, deflecting the more charged and faster-moving, lighter ions more. The analyzer can be used to select a narrow range of m/z or to scan through a range of m/z to catalog the ions present. [ 16 ]
The time-of-flight (TOF) analyzer uses an electric field to accelerate the ions through the same potential , and then measures the time they take to reach the detector. If the particles all have the same charge , their kinetic energies will be identical, and their velocities will depend only on their masses . For example, ions with a lower mass will travel faster, reaching the detector first. [ 17 ] Ions usually are moving prior to being accelerated by the electric field , this causes particles with the same m/z to arrive at different times at the detector. This difference in initial velocities is often not dependent on the mass of the ion, and will turn into a difference in the final velocity. This distribution in velocities broadens the peaks shown on the count vs m/z plot, but will generally not change the central location of the peaks, since the starting velocity of ions is generally centered at zero. To fix this problem, time-lag focusing/ delayed extraction has been coupled with TOF-MS. [ 18 ]
Quadrupole mass analyzers use oscillating electrical fields to selectively stabilize or destabilize the paths of ions passing through a radio frequency (RF) quadrupole field created between four parallel rods. Only the ions in a certain range of mass/charge ratio are passed through the system at any time, but changes to the potentials on the rods allow a wide range of m/z values to be swept rapidly, either continuously or in a succession of discrete hops. A quadrupole mass analyzer acts as a mass-selective filter and is closely related to the quadrupole ion trap , particularly the linear quadrupole ion trap except that it is designed to pass the untrapped ions rather than collect the trapped ones, and is for that reason referred to as a transmission quadrupole.
A magnetically enhanced quadrupole mass analyzer includes the addition of a magnetic field, either applied axially or transversely. This novel type of instrument leads to an additional performance enhancement in terms of resolution and/or sensitivity depending upon the magnitude and orientation of the applied magnetic field. [ 19 ] [ 20 ] A common variation of the transmission quadrupole is the triple quadrupole mass spectrometer. The "triple quad" has three consecutive quadrupole stages, the first acting as a mass filter to transmit a particular incoming ion to the second quadrupole, a collision chamber, wherein that ion can be broken into fragments. The third quadrupole also acts as a mass filter, to transmit a particular fragment ion to the detector. If a quadrupole is made to rapidly and repetitively cycle through a range of mass filter settings, full spectra can be reported. Likewise, a triple quad can be made to perform various scan types characteristic of tandem mass spectrometry .
The quadrupole ion trap works on the same physical principles as the quadrupole mass analyzer, but the ions are trapped and sequentially ejected. Ions are trapped in a mainly quadrupole RF field, in a space defined by a ring electrode (usually connected to the main RF potential) between two endcap electrodes (typically connected to DC or auxiliary AC potentials). The sample is ionized either internally (e.g. with an electron or laser beam), or externally, in which case the ions are often introduced through an aperture in an endcap electrode.
There are many mass/charge separation and isolation methods but the most commonly used is the mass instability mode in which the RF potential is ramped so that the orbit of ions with a mass a > b are stable while ions with mass b become unstable and are ejected on the z -axis onto a detector. There are also non-destructive analysis methods.
Ions may also be ejected by the resonance excitation method, whereby a supplemental oscillatory excitation voltage is applied to the endcap electrodes, and the trapping voltage amplitude and/or excitation voltage frequency is varied to bring ions into a resonance condition in order of their mass/charge ratio. [ 21 ] [ 22 ]
The cylindrical ion trap mass spectrometer (CIT) is a derivative of the quadrupole ion trap where the electrodes are formed from flat rings rather than hyperbolic shaped electrodes. The architecture lends itself well to miniaturization because as the size of a trap is reduced, the shape of the electric field near the center of the trap, the region where the ions are trapped, forms a shape similar to that of a hyperbolic trap.
A linear quadrupole ion trap is similar to a quadrupole ion trap, but it traps ions in a two dimensional quadrupole field, instead of a three-dimensional quadrupole field as in a 3D quadrupole ion trap. Thermo Fisher's LTQ ("linear trap quadrupole") is an example of the linear ion trap. [ 23 ]
A toroidal ion trap can be visualized as a linear quadrupole curved around and connected at the ends or as a cross-section of a 3D ion trap rotated on edge to form the toroid, donut-shaped trap. The trap can store large volumes of ions by distributing them throughout the ring-like trap structure. This toroidal shaped trap is a configuration that allows the increased miniaturization of an ion trap mass analyzer. Additionally, all ions are stored in the same trapping field and ejected together simplifying detection that can be complicated with array configurations due to variations in detector alignment and machining of the arrays. [ 24 ]
As with the toroidal trap, linear traps and 3D quadrupole ion traps are the most commonly miniaturized mass analyzers due to their high sensitivity, tolerance for mTorr pressure, and capabilities for single analyzer tandem mass spectrometry (e.g. product ion scans). [ 25 ]
Orbitrap instruments are similar to Fourier-transform ion cyclotron resonance mass spectrometers (see text below). Ions are electrostatically trapped in an orbit around a central, spindle shaped electrode. The electrode confines the ions so that they both orbit around the central electrode and oscillate back and forth along the central electrode's long axis. This oscillation generates an image current in the detector plates which is recorded by the instrument. The frequencies of these image currents depend on the mass-to-charge ratios of the ions. Mass spectra are obtained by Fourier transformation of the recorded image currents.
Orbitraps have a high mass accuracy, high sensitivity and a good dynamic range. [ 26 ]
Fourier-transform mass spectrometry (FTMS), or more precisely Fourier-transform ion cyclotron resonance MS, measures mass by detecting the image current produced by ions cyclotroning in the presence of a magnetic field. Instead of measuring the deflection of ions with a detector such as an electron multiplier , the ions are injected into a Penning trap (a static electric/magnetic ion trap ) where they effectively form part of a circuit. Detectors at fixed positions in space measure the electrical signal of ions which pass near them over time, producing a periodic signal. Since the frequency of an ion's cycling is determined by its mass-to-charge ratio, this can be deconvoluted by performing a Fourier transform on the signal. FTMS has the advantage of high sensitivity (since each ion is "counted" more than once) and much higher resolution and thus precision. [ 27 ] [ 28 ]
Ion cyclotron resonance (ICR) is an older mass analysis technique similar to FTMS except that ions are detected with a traditional detector. Ions trapped in a Penning trap are excited by an RF electric field until they impact the wall of the trap, where the detector is located. Ions of different mass are resolved according to impact time.
The final element of the mass spectrometer is the detector. The detector records either the charge induced or the current produced when an ion passes by or hits a surface. In a scanning instrument, the signal produced in the detector during the course of the scan versus where the instrument is in the scan (at what m/Q ) will produce a mass spectrum , a record of ions as a function of m/Q .
Typically, some type of electron multiplier is used, though other detectors including Faraday cups and ion-to-photon detectors are also used. Because the number of ions leaving the mass analyzer at a particular instant is typically quite small, considerable amplification is often necessary to get a signal. Microchannel plate detectors are commonly used in modern commercial instruments. [ 29 ] In FTMS and Orbitraps , the detector consists of a pair of metal surfaces within the mass analyzer/ion trap region which the ions only pass near as they oscillate. No direct current is produced, only a weak AC image current is produced in a circuit between the electrodes. Other inductive detectors have also been used. [ 30 ]
A tandem mass spectrometer is one capable of multiple rounds of mass spectrometry, usually separated by some form of molecule fragmentation. For example, one mass analyzer can isolate one peptide from many entering a mass spectrometer. A collision cell then stabilizes the peptide ions while they collide with a gas, causing them to fragment by collision-induced dissociation (CID). A further mass analyzer then sorts the fragments produced from the peptides. Tandem MS can also be done in a single mass analyzer over time, as in a quadrupole ion trap . There are various methods for fragmenting molecules for tandem MS, including collision-induced dissociation (CID), electron capture dissociation (ECD), electron transfer dissociation (ETD), infrared multiphoton dissociation (IRMPD), blackbody infrared radiative dissociation (BIRD), electron-detachment dissociation (EDD) and surface-induced dissociation (SID). An important application using tandem mass spectrometry is in protein identification. [ 31 ]
Tandem mass spectrometry enables a variety of experimental sequences. Many commercial mass spectrometers are designed to expedite the execution of such routine sequences as selected reaction monitoring (SRM), precursor ion scanning, product ion scanning, and neutral loss scanning. [ 32 ]
Another type of tandem mass spectrometry used for radiocarbon dating is accelerator mass spectrometry (AMS), which uses very high voltages, usually in the mega-volt range, to accelerate negative ions into a type of tandem mass spectrometer.
The METLIN Metabolite and Chemical Entity Database [ 33 ] [ 34 ] [ 35 ] [ 36 ] is the largest repository of experimental tandem mass spectrometry data acquired from standards. The tandem mass spectrometry data on over 930,000 molecular standards (as of January 2024) [ 33 ] [ 36 ] is provided to facilitate the identification of chemical entities from tandem mass spectrometry experiments. [ 37 ] In addition to the identification of known molecules it is also useful for identifying unknowns using its similarity searching/analysis. [ 38 ] All tandem mass spectrometry data comes from the experimental analysis of standards at multiple collision energies and in both positive and negative ionization modes. [ 33 ]
When a specific combination of source, analyzer, and detector becomes conventional in practice, a compound acronym may arise to designate it succinctly. One example is MALDI-TOF , which refers to a combination of a matrix-assisted laser desorption/ionization source with a time-of-flight mass analyzer. Other examples include inductively coupled plasma-mass spectrometry (ICP-MS) , accelerator mass spectrometry (AMS) , thermal ionization-mass spectrometry (TIMS) and spark source mass spectrometry (SSMS) .
Certain applications of mass spectrometry have developed monikers that although strictly speaking would seem to refer to a broad application, in practice have come instead to connote a specific or a limited number of instrument configurations. An example of this is isotope-ratio mass spectrometry (IRMS), which refers in practice to the use of a limited number of sector based mass analyzers; this name is used to refer to both the application and the instrument used for the application.
An important enhancement to the mass resolving and mass determining capabilities of mass spectrometry is using it in tandem with chromatographic and other separation techniques.
A common combination is gas chromatography-mass spectrometry (GC/MS or GC-MS). In this technique, a gas chromatograph is used to separate different compounds. This stream of separated compounds is fed online into the ion source, a metallic filament to which voltage is applied. This filament emits electrons which ionize the compounds. The ions can then further fragment, yielding predictable patterns. Intact ions and fragments pass into the mass spectrometer's analyzer and are eventually detected. [ 39 ] However, the high temperatures (300 °C) used in the GC-MS injection port (and oven) can result in thermal degradation of injected molecules, thus resulting in the measurement of degradation products instead of the actual molecule(s) of interest. [ 40 ]
Similarly to gas chromatography MS (GC-MS), liquid chromatography-mass spectrometry (LC/MS or LC-MS) separates compounds chromatographically before they are introduced to the ion source and mass spectrometer. It differs from GC-MS in that the mobile phase is liquid, usually a mixture of water and organic solvents , instead of gas. Most commonly, an electrospray ionization source is used in LC-MS. Other popular and commercially available LC-MS ion sources are atmospheric pressure chemical ionization and atmospheric pressure photoionization . There are also some newly developed ionization techniques like laser spray .
Capillary electrophoresis–mass spectrometry (CE-MS) is a technique that combines the liquid separation process of capillary electrophoresis with mass spectrometry. [ 41 ] CE-MS is typically coupled to electrospray ionization. [ 42 ]
Ion mobility spectrometry-mass spectrometry (IMS/MS or IMMS) is a technique where ions are first separated by drift time through some neutral gas under an applied electrical potential gradient before being introduced into a mass spectrometer. [ 43 ] Drift time is a measure of the collisional cross section relative to the charge of the ion. The duty cycle of IMS (the time over which the experiment takes place) is longer than most mass spectrometric techniques, such that the mass spectrometer can sample along the course of the IMS separation. This produces data about the IMS separation and the mass-to-charge ratio of the ions in a manner similar to LC-MS . [ 44 ]
The duty cycle of IMS is short relative to liquid chromatography or gas chromatography separations and can thus be coupled to such techniques, producing triple modalities such as LC/IMS/MS. [ 45 ]
Mass spectrometry produces various types of data. The most common data representation is the mass spectrum .
Certain types of mass spectrometry data are best represented as a mass chromatogram . Types of chromatograms include selected ion monitoring (SIM), total ion current (TIC), and selected reaction monitoring (SRM), among many others.
Other types of mass spectrometry data are well represented as a three-dimensional contour map . In this form, the mass-to-charge, m/z is on the x -axis, intensity the y -axis, and an additional experimental parameter, such as time, is recorded on the z -axis.
Mass spectrometry data analysis is specific to the type of experiment producing the data. General subdivisions of data are fundamental to understanding any data.
Many mass spectrometers work in either negative ion mode or positive ion mode . It is very important to know whether the observed ions are negatively or positively charged. This is often important in determining the neutral mass but it also indicates something about the nature of the molecules.
Different types of ion source result in different arrays of fragments produced from the original molecules. An electron ionization source produces many fragments and mostly single-charged (1-) radicals (odd number of electrons), whereas an electrospray source usually produces non-radical quasimolecular ions that are frequently multiply charged. Tandem mass spectrometry purposely produces fragment ions post-source and can drastically change the sort of data achieved by an experiment.
Knowledge of the origin of a sample can provide insight into the component molecules of the sample and their fragmentations. A sample from a synthesis/manufacturing process will probably contain impurities chemically related to the target component. A crudely prepared biological sample will probably contain a certain amount of salt, which may form adducts with the analyte molecules in certain analyses.
Results can also depend heavily on sample preparation and how it was run/introduced. An important example is the issue of which matrix is used for MALDI spotting, since much of the energetics of the desorption/ionization event is controlled by the matrix rather than the laser power. Sometimes samples are spiked with sodium or another ion-carrying species to produce adducts rather than a protonated species.
Mass spectrometry can measure molar mass, molecular structure, and sample purity. Each of these questions requires a different experimental procedure; therefore, adequate definition of the experimental goal is a prerequisite for collecting the proper data and successfully interpreting it.
Since the precise structure or peptide sequence of a molecule is deciphered through the set of fragment masses, the interpretation of mass spectra requires combined use of various techniques. Usually the first strategy for identifying an unknown compound is to compare its experimental mass spectrum against a library of mass spectra. If no matches result from the search, then manual interpretation [ 46 ] or software assisted interpretation of mass spectra must be performed. Computer simulation of ionization and fragmentation processes occurring in mass spectrometer is the primary tool for assigning structure or peptide sequence to a molecule. An a priori structural information is fragmented in silico and the resulting pattern is compared with observed spectrum. Such simulation is often supported by a fragmentation library [ 47 ] that contains published patterns of known decomposition reactions. Software taking advantage of this idea has been developed for both small molecules and proteins .
Analysis of mass spectra can also be spectra with accurate mass . A mass-to-charge ratio value ( m/z ) with only integer precision can represent an immense number of theoretically possible ion structures; however, more precise mass figures significantly reduce the number of candidate molecular formulas . A computer algorithm called formula generator calculates all molecular formulas that theoretically fit a given mass with specified tolerance.
A recent technique for structure elucidation in mass spectrometry, called precursor ion fingerprinting , identifies individual pieces of structural information by conducting a search of the tandem spectra of the molecule under investigation against a library of the product-ion spectra of structurally characterized precursor ions. [ 48 ]
Mass spectrometry has both qualitative and quantitative uses. These include identifying unknown compounds, determining the isotopic composition of elements in a molecule, and determining the structure of a compound by observing its fragmentation. Other uses include quantifying the amount of a compound in a sample or studying the fundamentals of gas phase ion chemistry (the chemistry of ions and neutrals in a vacuum). MS is now commonly used in analytical laboratories that study physical, chemical, or biological properties of a great variety of compounds. Quantification can be relative (analyzed relative to a reference sample) or absolute (analyzed using a standard curve method). [ 49 ]
As an analytical technique it possesses distinct advantages such as: Increased sensitivity over most other analytical techniques because the analyzer, as a mass-charge filter, reduces background interference, Excellent specificity from characteristic fragmentation patterns to identify unknowns or confirm the presence of suspected compounds, Information about molecular weight, Information about the isotopic abundance of elements, Temporally resolved chemical data.
A few of the disadvantages of the method is that it often fails to distinguish between optical and geometrical isomers and the positions of substituent in o-, m- and p- positions in an aromatic ring. Also, its scope is limited in identifying hydrocarbons that produce similar fragmented ions.
Mass spectrometry is also used to determine the isotopic composition of elements within a sample. Differences in mass among isotopes of an element are very small, and the less abundant isotopes of an element are typically very rare, so a very sensitive instrument is required. These instruments, sometimes referred to as isotope ratio mass spectrometers (IR-MS), usually use a single magnet to bend a beam of ionized particles towards a series of Faraday cups which convert particle impacts to electric current . A fast on-line analysis of deuterium content of water can be done using flowing afterglow mass spectrometry , FA-MS. Probably the most sensitive and accurate mass spectrometer for this purpose is the accelerator mass spectrometer (AMS). This is because it provides ultimate sensitivity, capable of measuring individual atoms and measuring nuclides with a dynamic range of ~10 15 relative to the major stable isotope. [ 50 ] Isotope ratios are important markers of a variety of processes. Some isotope ratios are used to determine the age of materials for example as in carbon dating . Labeling with stable isotopes is also used for protein quantification. (see protein characterization below)
Membrane-introduction mass spectrometry combines the isotope ratio MS with a reaction chamber/cell separated by a gas-permeable membrane. This method allows the study of gases as they evolve in solution. This method has been extensively used for the study of the production of oxygen by Photosystem II . [ 51 ]
Several techniques use ions created in a dedicated ion source injected into a flow tube or a drift tube: selected ion flow tube (SIFT-MS), and proton transfer reaction (PTR-MS), are variants of chemical ionization dedicated for trace gas analysis of air, breath or liquid headspace using well defined reaction time allowing calculations of analyte concentrations from the known reaction kinetics without the need for internal standard or calibration.
Another technique with applications in trace gas analysis field is secondary electrospray ionization (SESI-MS), which is a variant of electrospray ionization . SESI consist of an electrospray plume of pure acidified solvent that interacts with neutral vapors. Vapor molecules get ionized at atmospheric pressure when charge is transferred from the ions formed in the electrospray to the molecules. One advantage of this approach is that it is compatible with most ESI-MS systems. [ 52 ] [ 53 ]
A residual gas analyzer (RGA) is a small and usually rugged mass spectrometer , typically designed for process control and contamination monitoring in vacuum systems . When constructed as a quadrupole mass analyzer , there exist two implementations, utilizing either an open ion source (OIS) or a closed ion source (CIS). RGAs may be found in high vacuum applications such as research chambers, surface science setups, accelerators , scanning microscopes , etc. RGAs are used in most cases to monitor the quality of the vacuum and easily detect minute traces of impurities in the low-pressure gas environment. These impurities can be measured down to 10 − 14 {\displaystyle 10^{-14}} Torr levels, possessing sub- ppm detectability in the absence of background interferences.
An atom probe is an instrument that combines time-of-flight mass spectrometry and field-evaporation microscopy to map the location of individual atoms.
Pharmacokinetics is often studied using mass spectrometry because of the complex nature of the matrix (often blood or urine) and the need for high sensitivity to observe low dose and long time point data. The most common instrumentation used in this application is LC-MS with a triple quadrupole mass spectrometer . Tandem mass spectrometry is usually employed for added specificity. Standard curves and internal standards are used for quantitation of usually a single pharmaceutical in the samples. The samples represent different time points as a pharmaceutical is administered and then metabolized or cleared from the body. Blank or t=0 samples taken before administration are important in determining background and ensuring data integrity with such complex sample matrices. Much attention is paid to the linearity of the standard curve; however it is not uncommon to use curve fitting with more complex functions such as quadratics since the response of most mass spectrometers is less than linear across large concentration ranges. [ 54 ] [ 55 ] [ 56 ]
There is currently considerable interest in the use of very high sensitivity mass spectrometry for microdosing studies, which are seen as a promising alternative to animal experimentation .
Recent studies show that secondary electrospray ionization (SESI) is a powerful technique to monitor drug kinetics via breath analysis. [ 57 ] [ 58 ] Because breath is naturally produced, several datapoints can be readily collected. This allows for the number of collected data-points to be greatly increased. [ 59 ] In animal studies, this approach SESI can reduce animal sacrifice. [ 58 ] In humans, SESI-MS non-invasive analysis of breath can help study the kinetics of drugs at a personalized level. [ 57 ] [ 60 ] [ 61 ]
Mass spectrometry is an important method for the characterization and sequencing of proteins. The two primary methods for ionization of whole proteins are electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI). In keeping with the performance and mass range of available mass spectrometers, two approaches are used for characterizing proteins. In the first, intact proteins are ionized by either of the two techniques described above, and then introduced to a mass analyzer. This approach is referred to as " top-down " strategy of protein analysis. The top-down approach however is largely limited to low-throughput single-protein studies. In the second, proteins are enzymatically digested into smaller peptides using proteases such as trypsin or pepsin , either in solution or in gel after electrophoretic separation. Other proteolytic agents are also used. The collection of peptide products are often separated by chromatography prior to introduction to the mass analyzer. When the characteristic pattern of peptides is used for the identification of the protein the method is called peptide mass fingerprinting (PMF), if the identification is performed using the sequence data determined in tandem MS analysis it is called de novo peptide sequencing . These procedures of protein analysis are also referred to as the " bottom-up " approach, and have also been used to analyse the distribution and position of post-translational modifications such as phosphorylation on proteins. [ 62 ] A third approach is also beginning to be used, this intermediate "middle-down" approach involves analyzing proteolytic peptides that are larger than the typical tryptic peptide. [ 63 ]
As a standard method for analysis, mass spectrometers have reached other planets and moons. Two were taken to Mars by the Viking program . In early 2005 the Cassini–Huygens mission delivered a specialized GC-MS instrument aboard the Huygens probe through the atmosphere of Titan , the largest moon of the planet Saturn . This instrument analyzed atmospheric samples along its descent trajectory and was able to vaporize and analyze samples of Titan's frozen, hydrocarbon covered surface once the probe had landed. These measurements compare the abundance of isotope(s) of each particle comparatively to earth's natural abundance. [ 64 ] Also on board the Cassini–Huygens spacecraft was an ion and neutral mass spectrometer which had been taking measurements of Titan's atmospheric composition as well as the composition of Enceladus ' plumes. A Thermal and Evolved Gas Analyzer mass spectrometer was carried by the Mars Phoenix Lander launched in 2007. [ 65 ]
Mass spectrometers are also widely used in space missions to measure the composition of plasmas. For example, the Cassini spacecraft carried the Cassini Plasma Spectrometer (CAPS), [ 66 ] which measured the mass of ions in Saturn's magnetosphere .
Mass spectrometers were used in hospitals for respiratory gas analysis beginning around 1975 through the end of the century. Some are probably still in use but none are currently being manufactured. [ 67 ]
Found mostly in the operating room , they were a part of a complex system, in which respired gas samples from patients undergoing anesthesia were drawn into the instrument through a valve mechanism designed to sequentially connect up to 32 rooms to the mass spectrometer. A computer directed all operations of the system. The data collected from the mass spectrometer was delivered to the individual rooms for the anesthesiologist to use.
The uniqueness of this magnetic sector mass spectrometer may have been the fact that a plane of detectors, each purposely positioned to collect all of the ion species expected to be in the samples, allowed the instrument to simultaneously report all of the gases respired by the patient. Although the mass range was limited to slightly over 120 u , fragmentation of some of the heavier molecules negated the need for a higher detection limit. [ 68 ]
The primary function of mass spectrometry is as a tool for chemical analyses based on detection and quantification of ions according to their mass-to-charge ratio. However, mass spectrometry also shows promise for material synthesis. [ 50 ] Ion soft landing is characterized by deposition of intact species on surfaces at low kinetic energies which precludes the fragmentation of the incident species. [ 69 ] The soft landing technique was first reported in 1977 for the reaction of low energy sulfur containing ions on a lead surface. [ 70 ] | https://en.wikipedia.org/wiki/Mass_spectrometry |
Swansea University has had a long established history of development and innovation in mass spectrometry and chromatography .
In 1975, John H. Beynon was appointed the Royal Society Research Professor and established the Mass Spectrometry Research Unit at Swansea University (at that time known as the University College of Swansea). [ 1 ] In 1986, Dai Games moved from Cardiff University to become the Units new Director. [ 2 ]
In 1984, the first observation of He 2 2+ was made at the unit, its the same as molecular hydrogen (isolectronic molecules) except it has lots more energy 3310 kJ per mole. [ 3 ]
A grant of £670,000 was awarded in 1985 by the then Science and Engineering Research Council (SERC) to establish a national Mass Spectrometry Center at Swansea University to provide an analytical service to British Universities. It was officially opened in April 1987 by Lord Callaghan . In 2002, the center was enlarged and the new laboratories were opened by Lord Morgan . Following successful £3,000,000 contract renewal Edwina Hart , the Minister for Economy, Science and Transport, officially re-opened the EPSRC National Research Facility after refurbishment in 2015. [ 4 ] [ 5 ]
A Biomolecular Analysis Mass Spectrometry (BAMS) facility was officially opened in 2003, headed by Professor Newton and Dr Dudley. It was a collaborative entity between the Department of Biological Sciences and the Medical School. It focused on the study of nucleosides, nucleotides and cyclic nucleotides. [ 6 ]
Stable isotope mass spectrometry is conducted in the Department of Geography, and was recently used by the Landmark Trust to determine very precisely the age of the timber from Llwyn Celyn farmhouse to the year 1420. [ 7 ] | https://en.wikipedia.org/wiki/Mass_spectrometry_at_Swansea |
Mass spectrometry is a scientific technique for measuring the mass-to-charge ratio of ions. It is often coupled to chromatographic techniques such as gas- or liquid chromatography and has found widespread adoption in the fields of analytical chemistry and biochemistry where it can be used to identify and characterize small molecules and proteins ( proteomics ). The large volume of data produced in a typical mass spectrometry experiment requires that computers be used for data storage and processing. Over the years, different manufacturers of mass spectrometers have developed various proprietary data formats for handling such data which makes it difficult for academic scientists to directly manipulate their data. To address this limitation, several open , XML -based data formats have recently been developed by the Trans-Proteomic Pipeline at the Institute for Systems Biology to facilitate data manipulation and innovation in the public sector. [ 1 ] These data formats are described here.
This format was one of the earliest attempts to supply a standardized file format for data exchange in mass spectrometry. JCAMP-DX was initially developed for infrared spectrometry. JCAMP-DX is an ASCII based format and therefore not very compact even though it includes standards for file compression. JCAMP was officially released in 1988. [ 2 ] Together with the American Society for Mass Spectrometry a JCAMP-DX format for mass spectrometry was developed with aim to preserve legacy data. [ 3 ]
The Analytical Data Interchange Format for Mass Spectrometry is a format for exchanging data. Many mass spectrometry software packages can read or write ANDI files. ANDI is specified in the ASTM E1947 Standard. [ 4 ] ANDI is based on netCDF which is a software tool library for writing and reading data files. ANDI was initially developed for chromatography-MS data and therefore was not used in the proteomics gold rush where new formats based on XML were developed. [ 5 ]
AnIML is a joined effort of IUPAC and ASTM International to create an XML based standard that covers a wide variety of analytical techniques including mass spectrometry. [ 6 ]
mzData was the first attempt by the Proteomics Standards Initiative (PSI) from the Human Proteome Organization (HUPO) to create a standardized format for Mass Spectrometry data. [ 7 ] This format is now deprecated, and replaced by mzML. [ 8 ]
mzXML is a XML (eXtensible Markup Language) based common file format for proteomics mass spectrometric data. [ 9 ] [ 10 ] This format was developed at the Seattle Proteome Center/Institute for Systems Biology while the HUPO-PSI was trying to specify the standardized mzData format, and is still in use in the proteomics community.
Y et A nother F ormat for M ass S pectrometry (YAFMS) is a suggestion to save data in four table relational server-less database schema with data extraction and appending being exercised using SQL queries. [ 11 ]
As two formats (mzData and mzXML) for representing the same information is an undesirable state, a joint effort was set by HUPO-PSI, the SPC/ISB and instrument vendors to create a unified standard borrowing the best aspects of both mzData and mzXML, and intended to replace them. Originally called dataXML, it was officially announced as mzML. [ 12 ] The first specification was published in June 2008. [ 13 ] This format was officially released at the 2008 American Society for Mass Spectrometry Meeting, and is since then relatively stable with very few updates.
On 1 June 2009, mzML 1.1.0 was released. There are no planned further changes as of 2013.
Instead of defining new file formats and writing converters for proprietary vendor formats a group of scientists proposed to define a common application program interface to shift the burden of standards compliance to the instrument manufacturers' existing data access libraries. [ 14 ]
The mz5 format addresses the performance problems of the previous XML based formats. It uses the mzML ontology, but saves the data using the HDF5 backend for reduced storage space requirements and improved read/write speed. [ 15 ]
The imzML standard was proposed to exchange data from mass spectrometry imaging in a standardized XML file based on the mzML ontology. It splits experimental data into XML and spectral data in a binary file. Both files are linked by a universally unique identifier . [ 16 ]
mzDB saves data in an SQLite database to save on storage space and improve access times as the data points can be queried from a relational database . [ 17 ]
Toffee is an open lossless file format for data-independent acquisition mass spectrometry. It leverages HDF5 and aims to achieve file sizes similar to those from the proprietary and closed vendor formats. [ 18 ]
mzMLb is another take on using a HDF5 backend for performant raw data saving. It, however, preserves the mzML XML data structure and stays compliant to the existing standard. [ 19 ]
The Allotrope Foundation curates a HDF5 and Triplestore based file format named Allotrope Data Format (ADF) and a flat JSON representation ASM short for Allotrope Simple Model. Both are based on the Allotrope Foundation Ontologies (AFO) and contain schemas for mass spectrometry and chromatography coupled with MS detectors. [ 20 ]
Below is a table of different file format extensions.
(*) Note that the RAW formats of each vendor are not interchangeable; software from one cannot handle the RAW files from another. (**) Micromass was acquired by Waters in 1997 (***) Finnigan is a division of Thermo
There are several viewers for mzXML, mzML and mzData. These viewers are of two types: Free Open Source Software (FOSS) or proprietary.
In the FOSS viewer category, one can find MZmine, [ 22 ] mineXpert2 (mzXML, mzML, native timsTOF, xy, MGF, BafAscii) [ 23 ] MS-Spectre, [ 24 ] TOPPView (mzXML, mzML and mzData), [ 25 ] Spectra Viewer, [ 26 ] SeeMS, [ 27 ] msInspect, [ 28 ] jmzML. [ 29 ]
In the proprietary category, one can find PEAKS, [ 30 ] Insilicos , [ 31 ] Mascot Distiller, [ 32 ] Elsci Peaksel. [ 33 ]
There is a viewer for ITA images. [ 34 ] ITA and ITM images can be parsed with the pySPM python library. [ 35 ]
Known converters for mzData to mzXML:
Known converters for mzXML:
Known converters for mzML:
Converters for proprietary formats:
Currently available converters are : | https://en.wikipedia.org/wiki/Mass_spectrometry_data_format |
Mass transfer is the net movement of mass from one location (usually meaning stream, phase , fraction, or component) to another. Mass transfer occurs in many processes, such as absorption , evaporation , drying , precipitation , membrane filtration , and distillation . Mass transfer is used by different scientific disciplines for different processes and mechanisms. The phrase is commonly used in engineering for physical processes that involve diffusive and convective transport of chemical species within physical systems .
Some common examples of mass transfer processes are the evaporation of water from a pond to the atmosphere , the purification of blood in the kidneys and liver , and the distillation of alcohol. In industrial processes, mass transfer operations include separation of chemical components in distillation columns, absorbers such as scrubbers or stripping, adsorbers such as activated carbon beds, and liquid-liquid extraction . Mass transfer is often coupled to additional transport processes , for instance in industrial cooling towers . These towers couple heat transfer to mass transfer by allowing hot water to flow in contact with air. The water is cooled by expelling some of its content in the form of water vapour.
In astrophysics , mass transfer is the process by which matter gravitationally bound to a body, usually a star , fills its Roche lobe and becomes gravitationally bound to a second body, usually a compact object ( white dwarf , neutron star or black hole ), and is eventually accreted onto it. It is a common phenomenon in binary systems , and may play an important role in some types of supernovae and pulsars .
Mass transfer finds extensive application in chemical engineering problems. It is used in reaction engineering, separations engineering, heat transfer engineering, and many other sub-disciplines of chemical engineering like electrochemical engineering. [ 1 ]
The driving force for mass transfer is usually a difference in chemical potential , when it can be defined, though other thermodynamic gradients may couple to the flow of mass and drive it as well. A chemical species moves from areas of high chemical potential to areas of low chemical potential. Thus, the maximum theoretical extent of a given mass transfer is typically determined by the point at which the chemical potential is uniform. For single phase-systems, this usually translates to uniform concentration throughout the phase, while for multiphase systems chemical species will often prefer one phase over the others and reach a uniform chemical potential only when most of the chemical species has been absorbed into the preferred phase, as in liquid-liquid extraction .
While thermodynamic equilibrium determines the theoretical extent of a given mass transfer operation, the actual rate of mass transfer will depend on additional factors including the flow patterns within the system and the diffusivities of the species in each phase. This rate can be quantified through the calculation and application of mass transfer coefficients for an overall process. These mass transfer coefficients are typically published in terms of dimensionless numbers , often including Péclet numbers , Reynolds numbers , Sherwood numbers , and Schmidt numbers , among others. [ 2 ] [ 3 ] [ 4 ]
There are notable similarities in the commonly used approximate differential equations for momentum, heat, and mass transfer. [ 2 ] The molecular transfer equations of Newton's law for fluid momentum at low Reynolds number ( Stokes flow ), Fourier's law for heat, and Fick's law for mass are very similar, since they are all linear approximations to transport of conserved quantities in a flow field.
At higher Reynolds number, the analogy between mass and heat transfer and momentum transfer becomes less useful due to the nonlinearity of the Navier–Stokes equation (or more fundamentally, the general momentum conservation equation ), but the analogy between heat and mass transfer remains good. A great deal of effort has been devoted to developing analogies among these three transport processes so as to allow prediction of one from any of the others. | https://en.wikipedia.org/wiki/Mass_transfer |
In engineering , the mass transfer coefficient is a diffusion rate constant that relates the mass transfer rate, mass transfer area, and concentration change as driving force: [ 1 ]
k c = n ˙ A A Δ c A {\displaystyle k_{c}={\frac {{\dot {n}}_{A}}{A\Delta c_{A}}}}
Where:
This can be used to quantify the mass transfer between phases , immiscible and partially miscible fluid mixtures (or between a fluid and a porous solid [ 2 ] ). Quantifying mass transfer allows for design and manufacture of separation process equipment that can meet specified requirements, estimate what will happen in real life situations (chemical spill), etc.
Mass transfer coefficients can be estimated from many different theoretical equations , correlations , and analogies that are functions of material properties, intensive properties and flow regime ( laminar or turbulent flow). Selection of the most applicable model is dependent on the materials and the system, or environment, being studied.
Note, the units will vary based upon which units the driving force is expressed in. The driving force shown here as ' Δ c A {\displaystyle {\Delta c_{A}}} ' is expressed in units of moles per unit of volume, but in some cases the driving force is represented by other measures of concentration with different units. For example, the driving force may be partial pressures when dealing with mass transfer in a gas phase and thus use units of pressure.
This engineering-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mass_transfer_coefficient |
Mass vaccination is a public policy effort to vaccinate a large number of people, possibly the entire population of the world or of a country or region, within a short period of time. This policy may be directed during a pandemic , when there is a localized outbreak or scare of a disease for which a vaccine exists, or when a new vaccine is invented.
Under normal circumstances, vaccines are provided as part of an individual's medical care starting from birth and given as part of routine checkups. But there are times when there is a need to quickly vaccinate the population at large and provide easy access to the service. When this occurs, temporary clinics may be established around communities that can efficiently handle the many people within at once.
Challenges of a mass vaccination effort include vaccine supply , logistics , storage, finding vaccinators and other necessary staff, vaccine safety and public outreach. [ 1 ]
Measles is a viral infection known for its highly contagious properties. [ 2 ] Infection with measles is transmitted through the respiratory tract and can manifest as fevers, the "three C's of measles": cough, coryza (runny nose), conjunctivitis(red/watery eyes), and a maculopapular rash. [ 2 ] Prevention can be achieved with vaccination, as a single dose is 93% effective against measles and both doses of the two-shot series provides 97% effectiveness against measles. [ 3 ] Management of measles, not prevention of measles, can be accomplished with vitamin A supplementation. [ 2 ]
Measles was first described by physicians in the 9th century. [ 4 ] In the centuries after, as explorers traveled from their borders and encountered new populations, these previously unexposed groups were acutely effected by measles. [ 4 ] It wasn't until 1757 that Francis Home discovered the cause of measles to be as a result of infection from a pathogen. [ 4 ] Deaths from measles dropped by the 20th century due to advances in medicine and standards of living, though this improvement was largely seen in developed nations. [ 4 ] Globally, there is still a documented yearly occurrence of 2 million deaths from 30 million cases. [ 4 ]
John Franklin Enders developed a live measles vaccine which underwent testing from 1958-1960, followed by public licensing in 1963. [ 4 ] The vaccine used in the United States since 1968 was a vaccine developed by Maurice Hilleman, which is a weaker live vaccine and showed increased efficacy, leading to a more effective measles vaccine. [ 5 ] In 1971, the Measles vaccine began to be produced as a combined vaccine with two other newly developed vaccines: mumps and rubella (MMR Vaccine). [ 5 ] In 1989, the two-dose regimen of the MMR vaccine began due to improved immunity developed from two doses rather than one. [ 5 ]
Under the Vaccination Assistance Act of 1962, President John F. Kennedy directed federal money to states in an effort to provide affordable and effective vaccinations to children and the broader population. [ 4 ] By 1965, President Lyndon B. Johnson worked with Congress to extend the Vaccination Assistance Act to cover Measles. [ 4 ] In 1967, Johnson and the CDC set out to eradicate measles and saw a drop in weekly measles cases from 1,000 to 200. [ 4 ] Cases of measles dropped in 1968 with 22,000 cases compared to 450,000 cases per year prior to the advent of the vaccine. [ 4 ] Following an uptick in cases in the early 1970's President Jimmy Carter set a goal for 90% vaccination, achieved partly through school mandates. [ 4 ] This found success, with 96% of school children being vaccinated by the end of his term in 1981 and a record low number of cases: 2,600. [ 4 ] Through the 80's and early 90's, vaccination hesitancy picked up steam. [ 4 ] This was met by President Bill Clinton with the Comprehensive Child Immunization Act of 1993. [ 4 ] By 2000, the last full year of his second term, the United States officially declared measles had been eradicated. [ 5 ]
As with any mass vaccination effort, vaccine-hesitancy remains a major barrier to maintaining low levels of measles cases. [ 6 ] A key cause of this challenge was a research article written in 1998 in "The Lancet" claimed to show a link between autism and the MMR vaccine. [ 6 ] In the wake of the article, negative news coverage of the MMR vaccine increased along with vaccine skepticism. [ 7 ] "The Lancet" retraced the paper in 2010 for incorrect data resulting from the study and for unethical treatment of the children in the study. [ 8 ] Due to the high infectivity rate of measles, the vaccination level to reach 'herd immunity' is 95%. [ 6 ] However, anti-vaccination campaigns and misinformation has caused the vaccination level to dip below the threshold, leading to a rise in measles cases in the USA. [ 6 ] Despite previously declaring measles had been eliminated in the US, there is now a Measles resurgence in the United States . [ 4 ]
In 1947, after a man traveled from Mexico to New York City and developed smallpox , Dr. Israel Weinstein announced to the residents of New York the need to get vaccinated. Vaccine clinics were established throughout the city and within less than a month, 6,350,000 residents were vaccinated. [ 1 ] This was enabled by improvements in vaccine production and storage. Prior to new developments, transportation represented a major issue and hindered mass vaccinations. [ 9 ] Because smallpox vaccination requires a live virus, it originally required a sample to be transferred from person-to-person or animal-to-person directly. [ 9 ] The creation of a liquid vaccine stored in capillary tubes marked a major advancement for the smallpox vaccine. [ 10 ] This method involved the use of glycerol as a preservative and was significant for storage and transportation. [ 10 ] In addition to these benefits, it enabled mass production through the use of animals, and ensured long term viability at temperatures below freezing. [ 10 ] However, this method was insufficient to enable widespread vaccination in tropical regions of the world, and thus was largely restricted to temperate countries. [ 10 ] Compulsory vaccinations were used throughout the beginning of the 20th century in a most of these countries, which led to the decline of smallpox. [ 10 ] For countries such as the United States, Canada, the United Kingdom, and some other European countries, outbreaks were quickly shut down by strong public health policies. [ 10 ] Soon, the more deadly Variola Major smallpox variant steadily declined, and endemics were only brought on by travelers from countries that lacked control over smallpox outbreaks. [ 10 ] It's important to note that the milder Variola Minor smallpox variant remained prevalent until the mid-20th century, as it often didn't warrant hospital visits or was misdiagnosed. [ 10 ] The success of health policies in controlling and eliminating smallpox by 1950s in many countries led some to believe that the world eradication of smallpox would be possible. [ 10 ]
The creation of a heat stable, freeze-dried vaccine occurred in the 1950s. [ 9 ] Further improvements in freeze-drying technology allowed for the mass production of the vaccine at a commercial level. [ 10 ] The Health Assembly, a group within the World Health organization (WHO) , began discussing the possibility of eliminating smallpox between 1950 and 1955. [ 10 ] The idea was ultimately rejected, as many viewed it an impossible task to take on. In 1958, a professor from the USSR, acting as a Health Assembly delegate, once again pushed the idea of smallpox being an issue for all countries, whether or not endemics are still occurring. [ 10 ] He presented a report to the Eleventh World Health Assembly , which argued that world eradication of the disease is possible, as shown by the success of countries that managed to eliminate it through health policy. [ 10 ] This was particularly significant as the professor, Viktor Zhdanov , had come to the conclusion on his own, without knowledge of arguments from previous World Health Assemblies. In this Zhdanov Report, he used the USSR as an example, arguing that the success of mandatory vaccinations throughout his country proves that it's possible to eliminate it in any country. [ 10 ] Zhdanov offered the support of the USSR, and backed the legitimacy of the report through the donation of millions of vaccines and previous offers of support to central-Asian countries. [ 10 ] The method of eradication would that was proposed involved the use of the newly developed freeze-dried vaccinations and mandatory vaccination. [ 10 ] Surveillance containment programs was also mentioned, which actually came to dominate in the later years of the eradication campaign. [ 10 ] Over the course of the next year, resolutions coordinating the start of the program, as well as to ensure the success of it, were made. [ 10 ] During the Twelve World Health Assembly in 1959, the proposal of an eradication campaign for smallpox was voted for successfully. [ 10 ]
The eradication of smallpox seemed to be easier and less costly than other previously eradicated diseases. [ 10 ] Smallpox had no vectors , as humans were the only reservoirs carrying the disease. Furthermore, the elimination of the disease would be mostly on mass vaccination and did not require vector control. [ 10 ] Directed by Donald Henderson , this first effort involved the use of mass vaccinations with a goal to have 80% of every country's population immunized. [ 9 ] Although the program was brought forth by WHO, implementation would largely depend on individual governments. WHO would be responsible for supporting the programs through vaccine production, and training of staff. [ 10 ] Each country would be required to cover most of the costs and actual functions of the program. A lack of universal commitment from countries hindered this campaign allowing smallpox to remain prevalent almost a decade later. [ 11 ] This was particularly a problem in developing countries. [ 9 ] The WHO was not designed to provide considerable material support and close collaboration between countries on a wide scale. [ 10 ] Over the first few years of the program's initiation, a lack of donations of vaccines and money hindered the success of the program. [ 10 ] The WHO created the Expert Committee on Smallpox in 1964 due to the lack of progress. A report was released giving a more clear strategy to be implemented, in the form of different phases. [ 10 ] Based on outbreaks that occurred in India in regions that claimed to have more than 80% vaccination rates, the committee determined that 100% of the population would need to be vaccinated in the first mass vaccination phase. After this, they would focus on stopping subsequent cases and investigating them. [ 10 ] This was not well received during the Seventeenth World Health Assembly, in which many express doubts over the success especially with extreme vaccine shortages following a lack of donations. [ 10 ] It wasn't until 1965 that the USA increased commitment to the cause, yet not out of interest but because they were already starting a measles eradication campaign and felt this could be added on. [ 10 ] This along with continued support from the USSR led the WHO to develop an intensified program for smallpox eradication, however many members still lacked confidence in this new programs success. [ 10 ]
From 1967, the Intensified Smallpox Program now called for surveillance reporting and investigation in addition to mass vaccination. [ 10 ] Teams were directed to find alternative or unique solutions in their regions. [ 12 ] In the years following the initiation of this plan, the WHO saw an increase in qualified volunteers, contributions from countries and participation in their campaign. [ 10 ] They worked on increasing training of staff and publicizing the program worldwide. Improvements in procedures and technology had a significant effect on advancing the program. [ 10 ] Particularly, the invention of the bifurcated needle made administration of vaccines in the field more practical than the previously used jet-injectors . [ 10 ] The number of outbreaks, instead of the percent of population vaccinated, became the new focus. [ 10 ] By 1973, smallpox only remained a problem in five countries. Improved methods of surveillance and containment, as well as a large increase in support, was a critical part of finally eradicating smallpox. [ 10 ] The regions would contain the spread out smallpox through vaccinating anyone exposed to an infected person; this was the method of ring vaccination. [ 13 ] It would not be until May 8, 1980, during the World Health Assembly that smallpox was announced as officially eradicated. [ 14 ]
Vaccination policies were not met without resistance, as countries that had mandatory vaccination policies saw a rise in antivaccination movements. [ 10 ] In Brazil, compulsory vaccination was met with riots. [ 10 ] The lack of control led to large outbreaks and many deaths. [ 10 ] Other countries had more success in vaccination, which led to Variola Minor replacing Variola Major as the cause of smallpox outbreaks in these countries. [ 10 ] Antivaccinationists rejected vaccination policy more, as this more mild form was not seen as significant. [ 10 ] This was particularly an issue in the United States as only some states had compulsory vaccination, while others banned or lacked laws for it. [ 10 ]
Poliomyelitis is a disease which causes lower body paralysis through the damage of motor neurons caused by three strains of the poliovirus. [ 15 ] Only 1% of polio cases actually result in paralysis. [ 15 ] In 1916, the United States experienced a polio epidemic which paralyzed over 27,000 people and lead to 6,000 deaths. [ 15 ] These outbreaks gradually became worse and worse as it spread throughout the Americas and to Europe. [ 15 ] Jonas Salk developed the first inactivated polio vaccine (IPV) in 1953 which was tested in a clinical trial that enrolled 1.6 million children in Canada , Finland and the United States. [ 15 ] With the distribution of Salk's vaccine, cases decreased from 13.9 to 0.8 cases per 100,000 in a period of only 7 years from 1954 to 1961. [ 15 ] By 1956, Albert Sabin had created the live-attenuated vaccine also known as the oral polio vaccine (OPV) which contained three types of wild polio strains. [ 15 ] After almost two decades in 1972, Sabin decided to donate his vaccine strains to the World Health Organization (WHO) which greatly increased the distribution and accessibility of the vaccine across the world. [ 15 ]
In the years following the development of the vaccines from 1977 to 1995, children who had been fully vaccinated with all three doses of OPV had risen from 5% to 80%. [ 15 ] In 1988, the World Health Assembly decided to make efforts to completely eradicate polio by the year 2000 with a large amount of the progress occurring before the target date. [ 16 ] This effort was titled the Global Polio Eradication Initiative and has seen wild success with a decrease in 99% of cases worldwide by 2018. [ 17 ] When the global campaign began in 1988, there were over 125 polio-endemic countries compared to only 20 by the year 2000. [ 16 ] Wealthier countries with better infrastructure were able to use more resources and introduce better health strategies to achieve herd immunity early on. [ 16 ] The WHO Region of the Americas declared themselves to be polio free in 1994. [ 17 ] Following this enormous achievement, other WHO regions quickly followed with the Western Pacific Region declared polio free in 2000, the European Region in 2002 and South-East Asia Region in 2014. [ 17 ]
Mass vaccination strategies such as National Immunization Days were key to the success of the oral polio vaccine (OPV). [ 18 ] In South America, transmission rates severely declined in the mid-1980s following the invention and widespread use of the OPV. [ 18 ] With such an incredibly high amount of vaccinations within a short time frame, the overall incidence of Polio was decreased. [ 18 ] Other countries such as India , were able to vaccinate over 120 million children in large scale vaccination days which became a regular occurrence. [ 18 ]
Several famous Americans helped pave the way for the acceptance of the polio vaccine in the United States . Franklin D. Roosevelt , one of the most famous polio patients in the world, created the National Foundation for Infantile Paralysis in 1938 which eventually became known as March of Dimes . [ 19 ] The March of Dimes funded a large portion of the polio research all throughout the epidemic and eventually resulted in the development of the vaccine by Jonas Salk . [ 19 ] Following the years after its invention and distribution, polio cases decreased from tens of thousands to only a handful per year. [ 19 ] With the help of Elvis Presley , who took the vaccine publicly, the acceptance of the polio vaccine increased even further. [ 20 ] This act embodied three of the most important pillars of a behavioral change campaign: social influence, social norms and examples. [ 21 ] Elvis Presley used his social influence to normalize getting the polio vaccine, which increased vaccination rates among American youth to over 80% in just under 6 months. [ 21 ] These types campaigns were the heart of the mass vaccination efforts in America. [ 21 ]
Despite the global efforts to vaccinate and eradicate polio, the virus still causes outbreaks every year. [ 22 ] As of 2021, only wild polio virus type 1(WPV1) affects the world and are localized in Afghanistan and Pakistan . [ 22 ] The circulating vaccine-derived poliovirus (cVDPV) caused outbreaks in 32 countries in 2020. [ 22 ] The cVDPV is a result of live oral poliovirus vaccine becoming infectious after extended circulation. [ 22 ] This prompted an update to the Global Polio Eradication Initiative (GPEI) Strategy for the years 2022–2026. [ 22 ] With the most recent update in August 2020, the WHO African Region was declared polio free leaving only one of the six WHO regions with polio. [ 22 ] The GPEI's new initiatives focused on eradicating the WPV1 in both Afghanistan and Pakistan while also combating the new outbreaks of cVDPV. [ 22 ] The difficulty arises when the world must not only eliminate the wild type polio virus but also the vaccine-derived form, making eradication even more complex. [ 23 ] While both the live and inactivated polio vaccines were wildly successful in saving the world from the historic endemic, there still are drawbacks with each of the vaccines. [ 23 ] The OPV vaccine was reverted to an infectious strain which led to the rise of the cVDPV. [ 23 ] While the inactivated polio vaccine (IPV) protected the host, it was not strong enough to generate intestinal mucosa immunity and therefore did not prevent the transmission of the virus. [ 23 ] These weaknesses suggest that more innovative vaccines or a combination of the two is needed to completely eradicate polio. [ 23 ]
In 1918, the deadly H1N1 influenza virus which infected approximately 500 million people around the world and resulted in the deaths of 50 to 100 million people (3% to 5% of the world population). [ 24 ] New York City had created two major mass immunization programs, the first was the smallpox immunization program initiated in 1947 and the second was the swine flu influenza program in 1976. [ 18 ]
For the first mass immunization campaign in 1947, the New York City Department of Health maintained the outbreak within a period of 29 days and vaccinated 6.35 million people successfully. [ 18 ] Weinstein and colleagues established vaccination clinics at many locations such as at the Department of Health's 125 Worth Street headquarters, at the 21 district health centers, 60 child health clinics, and 13 municipal hospitals in order to accommodate for the high demand of people requesting for a vaccination. [ 18 ] The smallpox vaccination effort was announced to be officially terminated on May 3, 1947. [ 18 ] In which case, it was rather surprising to see that the second mass immunization campaign in 1976, which was a national immunization effort, was only able to accomplish vaccinating 639,000 against swine influenza over a period of 60 days. [ 18 ] It was also noted that in 1976, the mass swine flu vaccination programme was discontinued after 362 cases of Guillain–Barré syndrome were identified among 45 million vaccinated people. [ 18 ] The vast differences between the number of people vaccinated in 1947 versus 1976, despite the outbreaks, are reflected mainly by the public's skeptical perception of the minimal severity and low threat of swine flu. [ 18 ]
Swine flu, also known as H1N1 influenza A virus, is a type of infectious respiratory disease that has caused high economical and medical burden every year around the world. [ 25 ] There are important lessons to be learned from the recent 'Swine Flu' pandemic. Improving techniques are necessary in trying to decrease the spread of infection-both in the community and within our hospitals would mean improving infection control and hygiene, and the use of masks, alcohol hand rubs and so on. [ 26 ]
A worldwide study was conducted which comprehensively analyzed adamantanes resistance in H1N1 influenza viruses from 1918 to 2019 and showed 77.32% H1N1 influenza variants demonstrating resistance to adamantanes . [ 25 ] This study emphasizes the importance of global surveillance, especially in many third-world countries, as well as the evolution of drug-resistant H1N1 influenza variants in an effort to prevent another pandemic. [ 25 ]
The introduction of multiple COVID-19 vaccines throughout the pandemic such as Pfizer , Moderna , Johnson and Johnson , and the newly approved Novavax vaccine have helped allow large amounts of the population to get vaccinated. [ citation needed ]
When COVID-19 was identified in December 2019 there were no vaccines readily available to vaccinate mass populations. [ 27 ] By December 2020, the Pfizer vaccine was the first to receive emergency use approval by the Food and Drug Administration . [ 27 ] Vaccines under normal circumstances can take up to 10–15 years to be made and approved. [ 27 ] Without worldwide collaboration, funding for research, and rigorous guidelines for clinical trials there would not have been a quickly developed vaccine. [ 27 ]
The type of vaccines that are available are messenger RNA, vector, and protein subunit. Messenger RNA vaccines work by giving cells specific instructions to make the S protein found on the surface of the COVID-19 virus. [ 28 ] It does not infect recipients of the vaccine with the virus but allows for the body to detect and fight the COVID-19 virus. [ 28 ] Both Pfizer and Moderna COVID-19 vaccines fall in to the messenger RNA category. [ 28 ] Vector vaccines also deliver instructions on how to make the S protein found on the surface of the virus. [ 28 ] It also does not cause the recipient to become infected with the virus after vaccination. [ 28 ] The Johnson & Johnson vaccine falls into the vector category. [ 28 ] Lastly the subunit vaccine only contains a part of the virus needed to create an immune response. [ 28 ] The S protein is the harmless subunit that will allow for an immune response when the COVID-19 virus is detected. [ 28 ] The Novavax vaccine falls into the subunit protein category. [ 28 ]
When vaccinating large populations an action plan must be created to organize which groups will receive the vaccination first. [ 29 ] The California Department of Public Health created an action plan to vaccinate by population group. [ 29 ] First immunocompromised groups, second unvaccinated or not fully vaccinated, third under 12 populations, fourth boosters for those 65 and older, and lastly boosters for ages 12–64. [ 29 ]
As well as mass vaccination centers being established at many locations, such as stadiums led to many people getting vaccinated. [ 30 ]
In the United States, NFL commissioner Roger Goodell offered the league's 30 stadiums as mass vaccination sites. [ 31 ] As of April 2021, NFL stadiums have administered more than 2 million doses. [ 32 ] By December 2021, more than 100,000 people had received vaccinations at Indianapolis Motor Speedway . [ 33 ]
Pharmacist have also played an important role in getting mass populations vaccinated since they are a skilled and trained workforce able to help increase vaccination rates. [ 34 ] Many people can turn to drug or convivence stores to get vaccinated since it can be a quick and easy place to access. [ 35 ] Pharmacies have played a large roll in mass vaccination now more than ever due to the pandemic. [ 35 ] Some states prior to the pandemic did not allow pharmacist to vaccinate or administer flu vaccines. [ 35 ] Now, pharmacies are contracting with state and federal governments since they have become key players in vaccinations. [ 35 ] Without the involvement of pharmacies mass vaccination would be difficult to achieve. [ 35 ] in most communities 90% of people live within five miles of a pharmacy. [ 35 ] Pharmacist can oftentimes be the quickest access to a healthcare provider, making it a desirable option for the public to come and get vaccinated. [ 35 ]
Not only have pharmacist been involved in COVID-19 vaccinations but pharmacy technicians as well. [ 36 ] Pharmacy technicians have helped alleviate the workload on pharmacist with the large increase in demand for vaccinations. [ 36 ] They also can create more opportunities to interact with people who are hesitant in getting the COVID-19 vaccines. [ 36 ] Pharmacy technicians can support pharmacist which will allow more vaccination services to be accommodated efficiently and safety. [ 36 ] These efforts will allow for an increase in vaccinations and help vaccinate large groups at a time. [ 36 ]
During the pandemic pharmacist have had a fundamental roll in sharing information about COVID-19 vaccines. [ 37 ] Pharmacist are a quick resource for information and can help relieve some common concerns about reactions or misinformation to the vaccines. [ 37 ] They are also advocates for getting vaccinated since they are educators and vaccine administrators. [ 37 ] Sharing information to the public about COVID-19 vaccines can help increase vaccinations rates. [ 37 ] Since pharmacist are easily accessible in the community setting they can help motivate or encourage getting vaccinated helping decrease preventable infections or diseases such as COVID-19. [ 37 ]
Mass vaccination of COVID-19 vaccines is important to help stop the spread of the coronavirus and eventually end the pandemic. [ 38 ] Individual governments have been allocating billions of dollars to increase production of vaccines to help with the current global manufacturing need of vaccines. [ 38 ] Countries such as the United States , Canada , and Australia were able to receive many vaccines early on due to them being wealthier countries. [ 38 ] They were able to receive many doses enough to vaccinate their own countries but this left other lower-income countries with limited supply of the vaccines. [ 38 ] With some countries receiving more vaccines than others this leads to inequitable distribution and can increase the risk of new outbreaks. [ 38 ] Without proper global vaccine distribution it will make it more difficult to end the pandemic and allow for mass vaccination as a global effort. [ 38 ] Amid the new strains of the coronavirus such as the omicron variant , scientist and healthcare officials have raised concern about reduced effectiveness of available vaccines. [ 38 ] In response to a concern about vaccines having reduced effectiveness countries have encouraged booster shots for most of their population. [ 38 ] The World Health Organization would like to prioritize unvaccinated people over booster doses so more of the population will have received their initial dose. [ 38 ] | https://en.wikipedia.org/wiki/Mass_vaccination |
In common usage, the mass of an object is often referred to as its weight , though these are in fact different concepts and quantities. Nevertheless, one object will always weigh more than another with less mass if both are subject to the same gravity (i.e. the same gravitational field strength).
In scientific contexts, mass is the amount of " matter " in an object (though "matter" may be difficult to define), but weight is the force exerted on an object's matter by gravity . [ 1 ] At the Earth 's surface, an object whose mass is exactly one kilogram weighs approximately 9.81 newtons , the product of its mass and the gravitational field strength there. The object's weight is less on Mars , where gravity is weaker; more on Saturn , where gravity is stronger; and very small in space, far from significant sources of gravity, but it always has the same mass.
Material objects at the surface of the Earth have weight despite such sometimes being difficult to measure. An object floating freely on water, for example, does not appear to have weight since it is buoyed by the water. But its weight can be measured if it is added to water in a container which is entirely supported by and weighed on a scale. Thus, the "weightless object" floating in water actually transfers its weight to the bottom of the container (where the pressure increases). Similarly, a balloon has mass but may appear to have no weight or even negative weight, due to buoyancy in air. However the weight of the balloon and the gas inside it has merely been transferred to a large area of the Earth's surface, making the weight difficult to measure. The weight of a flying airplane is similarly distributed to the ground, but does not disappear. If the airplane is in level flight, the same weight-force is distributed to the surface of the Earth as when the plane was on the runway, but spread over a larger area.
A better scientific definition of mass is its description as being a measure of inertia , which is the tendency of an object to not change its current state of motion (to remain at constant velocity) unless acted on by an external unbalanced force. Gravitational "weight" is the force created when a mass is acted upon by a gravitational field and the object is not allowed to free-fall, but is supported or retarded by a mechanical force, such as the surface of a planet. Such a force constitutes weight. [ 2 ] This force can be added to by any other kind of force.
While the weight of an object varies in proportion to the strength of the gravitational field, its mass is constant, as long as no energy or matter is added to the object. [ 3 ] For example, although a satellite in orbit (essentially a free-fall) is "weightless", it still retains its mass and inertia. Accordingly, even in orbit, an astronaut trying to accelerate the satellite in any direction is still required to exert force, and needs to exert ten times as much force to accelerate a 10‑ton satellite at the same rate as one with a mass of only 1 ton.
Mass is (among other properties) an inertial property; that is, the tendency of an object to remain at constant velocity unless acted upon by an outside force . Under Sir Isaac Newton's 338-year-old laws of motion and an important formula that sprang from his work, F = ma , an object with a mass, m , of one kilogram accelerates , a , at one meter per second per second (about one-tenth the acceleration due to Earth's gravity ) [ 4 ] when acted upon by a force, F , of one newton .
Inertia is seen when a bowling ball is pushed horizontally on a level, smooth surface, and continues in horizontal motion. This is quite distinct from its weight, which is the downwards gravitational force of the bowling ball one must counter when holding it off the floor. The weight of the bowling ball on the Moon would be one-sixth of that on the Earth, although its mass remains unchanged. Consequently, whenever the physics of recoil kinetics (mass, velocity, inertia, inelastic and elastic collisions ) dominate and the influence of gravity is a negligible factor, the behavior of objects remains consistent even where gravity is relatively weak. For instance, billiard balls on a billiard table would scatter and recoil with the same speeds and energies after a break shot on the Moon as on Earth; they would, however, drop into the pockets much more slowly. [ citation needed ]
In the physical sciences, the terms "mass" and "weight" are rigidly defined as separate measures, as they are different physical properties. In everyday use, as all everyday objects have both mass and weight and one is almost exactly proportional to the other, "weight" often serves to describe both properties, its meaning being dependent upon context. For example, in retail commerce, the "net weight" of products actually refers to mass, and is expressed in mass units such as grams or ounces (see also Pound: Use in commerce ) . Conversely, the load index rating on automobile tires, which specifies the maximum structural load for a tire in kilograms, refers to weight; that is, the force due to gravity. Before the late 20th century, the distinction between the two was not strictly applied in technical writing, so that expressions such as "molecular weight" (for molecular mass ) are still seen. [ citation needed ]
Because mass and weight are separate quantities, they have different units of measure. In the International System of Units (SI), the kilogram is the basic unit of mass, and the newton is the basic unit of force. The non-SI kilogram-force is also a unit of force typically used in the measure of weight. Similarly, the avoirdupois pound , used in both the Imperial system and U.S. customary units , is a unit of mass, and its related unit of force is the pound-force . [ citation needed ]
When an object's weight (its gravitational force) is expressed in "kilograms", this actually refers to the kilogram-force (kgf or kg-f), also known as the kilopond (kp), which is a non-SI unit of force. All objects on the Earth's surface are subject to a gravitational acceleration of approximately 9.8 m/s 2 . The General Conference on Weights and Measures fixed the value of standard gravity at precisely 9.80665 m/s 2 so that disciplines such as metrology would have a standard value for converting units of defined mass into defined forces and pressures . Thus the kilogram-force is defined as precisely 9.80665 newtons. In reality, gravitational acceleration (symbol: g ) varies slightly with latitude , elevation and subsurface density; these variations are typically only a few tenths of a percent. See also Gravimetry . [ citation needed ]
Engineers and scientists understand the distinctions between mass, force, and weight. Engineers in disciplines involving weight loading (force on a structure due to gravity), such as structural engineering , convert the mass of objects like concrete and automobiles (expressed in kilograms) to a force in newtons (by multiplying by some factor around 9.8; 2 significant figures is usually sufficient for such calculations) to derive the load of the object. Material properties like elastic modulus are measured and published in terms of the newton and pascal (a unit of pressure related to the newton). [ citation needed ]
Usually, the relationship between mass and weight on Earth is highly proportional; objects that are a hundred times more massive than a one-liter bottle of soda almost always weigh a hundred times more—approximately 1,000 newtons, which is the weight one would expect on Earth from an object with a mass slightly greater than 100 kilograms. Yet, this is not always the case and there are familiar objects that violate this mass / weight proportionality. [ citation needed ]
A common helium-filled toy balloon is something familiar to many. When such a balloon is fully filled with helium, it has buoyancy —a force that opposes gravity. When a toy balloon becomes partially deflated, it often becomes neutrally buoyant and can float about the house a meter or two off the floor. In such a state, there are moments when the balloon is neither rising nor falling and—in the sense that a scale placed under it has no force applied to it—is, in a sense perfectly weightless (actually as noted below, weight has merely been redistributed along the Earth's surface so it cannot be measured). Though the rubber comprising the balloon has a mass of only a few grams, which might be almost unnoticeable, the rubber still retains all its mass when inflated. [ citation needed ]
Again, unlike the effect that low-gravity environments have on weight, buoyancy does not make a portion of an object's weight vanish; the missing weight is instead being borne by the ground, which leaves less force (weight) being applied to any scale theoretically placed underneath the object in question (though one may perhaps have some trouble with the practical aspects of accurately weighing something individually in that condition). If one were however to weigh a small wading pool that someone then entered and began floating in, they would find that the full weight of the person was being borne by the pool and, ultimately, the scale underneath the pool. Whereas a buoyant object (on a properly working scale for weighing buoyant objects) would weigh less, the object / fluid system becomes heavier by the value of object's full mass once the object is added. Since air is a fluid, this principle applies to object / air systems as well; large volumes of air—and ultimately the ground—supports the weight a body loses through mid-air buoyancy. [ citation needed ]
The effects of buoyancy do not just affect balloons; both liquids and gases are fluids in the physical sciences, and when all macro‑size objects larger than dust particles are immersed in fluids on Earth, they have some degree of buoyancy. [ 5 ] In the case of either a swimmer floating in a pool or a balloon floating in air, buoyancy can fully counter the gravitational weight of the object being weighed, for a weighing device in the pool. However, as noted, an object supported by a fluid is fundamentally no different from an object supported by a sling or cable—the weight has merely been transferred to another location, not made to disappear.
The mass of "weightless" (neutrally buoyant) balloons can be better appreciated with much larger hot air balloons. Although no effort is required to counter their weight when they are hovering over the ground (when they can often be within one hundred newtons of zero weight), the inertia associated with their appreciable mass of several hundred kilograms or more can knock fully grown men off their feet when the balloon's basket is moving horizontally over the ground. [ citation needed ]
Buoyancy and the resultant reduction in the downward force of objects being weighed underlies Archimedes' principle , which states that the buoyancy force is equal to the weight of the fluid that the object displaces. If this fluid is air, the force may be small. [ citation needed ]
Normally, the effect of air buoyancy on objects of normal density is too small to be of any consequence in day-to-day activities. For instance, buoyancy's diminishing effect upon one's body weight (a relatively low-density object) is 1 ⁄ 860 that of gravity (for pure water it is about 1 ⁄ 770 that of gravity). Furthermore, variations in barometric pressure rarely affect a person's weight more than ±1 part in 30,000. [ 6 ] However, in metrology (the science of measurement), the precision mass standards for calibrating laboratory scales and balances are manufactured with such accuracy that air density is accounted for to compensate for buoyancy effects. Given the extremely high cost of platinum-iridium mass standards like the international prototype of the kilogram ( the mass standard in France that defined the magnitude of the kilogram), high-quality "working" standards are made of special stainless steel alloys [ 7 ] with densities of about 8,000 kg/m 3 , which occupy greater volume than those made of platinum-iridium, which have a density of about 21,550 kg/m 3 . For convenience, a standard value of buoyancy relative to stainless steel was developed for metrology work and this results in the term "conventional mass". [ 8 ] Conventional mass is defined as follows: "For a mass at 20 °C, 'conventional mass' is the mass of a reference standard of density 8,000 kg/m 3 which it balances in air with a density of 1.2 kg/m 3 ." The effect is a small one, 150 ppm for stainless steel mass standards, but the appropriate corrections are made during the manufacture of all precision mass standards so they have the true labeled mass.
Whenever a high-precision scale (or balance) in routine laboratory use is calibrated using stainless steel standards, the scale is actually being calibrated to conventional mass; that is, true mass minus 150 ppm of buoyancy. Since objects with precisely the same mass but with different densities displace different volumes and therefore have different buoyancies and weights, any object measured on this scale (compared to a stainless steel mass standard) has its conventional mass measured; that is, its true mass minus an unknown degree of buoyancy. In high-accuracy work, the volume of the article can be measured to mathematically null the effect of buoyancy.
When one stands on a balance-beam -type scale at a doctor's office, they are having their mass measured directly. This is because balances ("dual-pan" mass comparators) compare the gravitational force exerted on the person on the platform with that on the sliding counterweights on the beams; gravity is the force-generating mechanism that allows the needle to diverge from the "balanced" (null) point. These balances could be moved from Earth's equator to the poles and give exactly the same measurement, i.e. they would not spuriously indicate that the doctor's patient became 0.3% heavier; they are immune to the gravity-countering centrifugal force due to Earth's rotation about its axis. But if one steps onto spring-based or digital load cell -based scales (single-pan devices), one is having one's weight (gravitational force) measured; and variations in the strength of the gravitational field affect the reading. In practice, when such scales are used in commerce or hospitals, they are often adjusted on-site and certified on that basis, so that the mass they measure, expressed in pounds or kilograms, is at the desired level of accuracy. [ 9 ]
In the United States of America the United States Department of Commerce , the Technology Administration , and the National Institute of Standards and Technology (NIST) have defined the use of mass and weight in the exchange of goods under the Uniform Laws and Regulations in the areas of legal metrology and engine fuel quality in NIST Handbook 130 :
K. "Mass" and "Weight" [See Section K. NOTE]
The mass of an object is a measure of the object's inertial property, or the amount of matter it contains. The weight of an object is a measure of the force exerted on the object by gravity, or the force needed to support it. The pull of gravity on the earth gives an object a downward acceleration of about 9.8 m/s 2 . In trade and commerce and everyday use, the term "weight" is often used as a synonym for "mass". The "net mass" or "net weight" declared on a label indicates that the package contains a specific amount of commodity exclusive of wrapping materials. The use of the term "mass" is predominant throughout the world, and is becoming increasingly common in the United States. (Added 1993)
Section K. NOTE: When used in this law (or regulation), the term "weight" means "mass". (see paragraphs K. "Mass" and "Weight" and L. Use of the Terms "Mass" and "Weight" in Section I. Introduction of NIST Handbook 130 for an explanation of these terms.) (Note Added 1993)
L. Use of the Terms "Mass" and "Weight" [See Section K. NOTE]
When used in this handbook, the term "weight" means "mass". The term "weight" appears when inch-pound units are cited, or when both inch-pound and SI units are included in a requirement. The terms "mass" or "masses" are used when only SI units are cited in a requirement. The following note appears where the term "weight" is first used in a law or regulation.
U.S. federal law, which supersedes this handbook, also defines weight, particularly Net Weight, in terms of the avoirdupois pound or mass pound. From 21 CFR § 101.105 – Declaration of net quantity of contents when exempt :
(a) The principal display panel of a food in package form shall bear a declaration of the net quantity of contents. This shall be expressed in the terms of weight, measure, numerical count, or a combination of numerical count and weight or measure. The statement shall be in terms of fluid measure if the food is liquid, or in terms of weight if the food is solid, semisolid, or viscous, or a mixture of solid and liquid; except that such statement may be in terms of dry measure if the food is a fresh fruit, fresh vegetable, or other dry commodity that is customarily sold by dry measure. If there is a firmly established general consumer usage and trade custom of declaring the contents of a liquid by weight, or a solid, semisolid, or viscous product by fluid measure, it may be used. Whenever the Commissioner determines that an existing practice of declaring net quantity of contents by weight, measure, numerical count, or a combination in the case of a specific packaged food does not facilitate value comparisons by consumers and offers opportunity for consumer confusion, he will by regulation designate the appropriate term or terms to be used for such commodity.
(b)(1) Statements of weight shall be in terms of avoirdupois pound and ounce.
See also 21 CFR § 201.51 – Declaration of net quantity of contents for general labeling and prescription labeling requirements. | https://en.wikipedia.org/wiki/Mass_versus_weight |
Mass wasting , also known as mass movement , [ 1 ] is a general term for the movement of rock or soil down slopes under the force of gravity . It differs from other processes of erosion in that the debris transported by mass wasting is not entrained in a moving medium, such as water, wind, or ice. Types of mass wasting include creep , solifluction , rockfalls , debris flows , and landslides , each with its own characteristic features, and taking place over timescales from seconds to hundreds of years. Mass wasting occurs on both terrestrial and submarine slopes, and has been observed on Earth , Mars , Venus , Jupiter's moon Io , and on many other bodies in the Solar System .
Subsidence is sometimes regarded as a form of mass wasting. A distinction is then made between mass wasting by subsidence, which involves little horizontal movement, and mass wasting by slope movement .
Rapid mass wasting events, such as landslides, can be deadly and destructive. More gradual mass wasting, such as soil creep, poses challenges to civil engineering , as creep can deform roadways and structures and break pipelines. Mitigation methods include slope stabilization , construction of walls, catchment dams, or other structures to contain rockfall or debris flows, afforestation , or improved drainage of source areas.
Mass wasting is a general term for any process of erosion that is driven by gravity and in which the transported soil and rock is not entrained in a moving medium, such as water, wind, or ice. [ 2 ] The presence of water usually aids mass wasting, but the water is not abundant enough to be regarded as a transporting medium. Thus, the distinction between mass wasting and stream erosion lies between a mudflow (mass wasting) and a very muddy stream (stream erosion), without a sharp dividing line. [ 3 ] Many forms of mass wasting are recognized, each with its own characteristic features, and taking place over timescales from seconds to hundreds of years. [ 2 ]
Based on how the soil, regolith or rock moves downslope as a whole, mass movements can be broadly classified as either creeps or landslides . [ 4 ] Subsidence is sometimes also regarded as a form of mass wasting. [ 5 ] A distinction is then made between mass wasting by subsidence, which involves little horizontal movement, [ 6 ] and mass wasting by slope movement. [ 7 ]
Soil creep is a slow and long term mass movement. The combination of small movements of soil or rock in different directions over time is directed by gravity gradually downslope. The steeper the slope, the faster the creep. The creep makes trees and shrubs curve to maintain their perpendicularity, and they can trigger landslides if they lose their root footing. The surface soil can migrate under the influence of cycles of freezing and thawing, or hot and cold temperatures, inching its way towards the bottom of the slope forming terracettes . Landslides are often preceded by soil creep accompanied with soil sloughing —loose soil that falls and accumulates at the base of the steepest creep sections. [ 8 ]
Solifluction is a form of creep characteristics of arctic or alpine climates. It takes place in soil saturated with moisture that thaws during the summer months to creep downhill. It takes place on moderate slopes, relatively free of vegetation, that are underlain by permafrost and receive a constant supply of new debris by weathering . Solifluction affects the entire slope rather than being confined to channels and can produce terrace-like landforms or stone rivers . [ 9 ]
A landslide, also called a landslip, [ 10 ] is a relatively rapid movement of a large mass of earth and rocks down a hill or a mountainside. Landslides can be further classified by the importance of water in the mass wasting process. In a narrow sense, landslides are rapid movement of large amounts of relatively dry debris down moderate to steep slopes. With increasing water content, the mass wasting takes the form of debris avalanches , then earthflows , then mudflows . Further increase in water content produces a sheetflood, which is a form of sheet erosion rather than mass wasting. [ 11 ]
On Earth , mass wasting occurs on both terrestrial and submarine slopes. [ 12 ] Submarine mass wasting is particularly common along glaciated coastlines where glaciers are retreating and great quantities of sediments are being released. Submarine slides can transport huge volumes of sediments for hundreds of kilometers in a few hours. [ 13 ]
Mass wasting is a common phenomenon throughout the Solar System, occurring where volatile materials are lost from a regolith . Such mass wasting has been observed on Mars , Io , Triton , and possibly Europa and Ganymede . [ 14 ] Mass wasting also occurs in the equatorial regions of Mars, where stopes of soft sulfate -rich sediments are steepened by wind erosion. [ 15 ] Mass wasting on Venus is associated with the rugged terrain of tesserae . [ 16 ] Io shows extensive mass wasting of its volcanic mountains. [ 17 ]
Mass wasting affects geomorphology , most often in subtle, small-scale ways, but occasionally more spectacularly. [ 18 ]
Soil creep is rarely apparent but can produce such subtle effects as curved forest growth and tilted fences and telephone poles. It occasionally produces low scarps and shallow depressions. [ 19 ] Solifluction produced lobed or sheetlike deposits, with fairly definite edges, in which clasts (rock fragments) are oriented perpendicular to the contours of the deposit. [ 20 ]
Rockfall can produce talus slopes at the feet of cliffs. A more dramatic manifestation of rockfall is rock glaciers , which form from rockfall from cliffs oversteepened by glaciers. [ 19 ]
Landslides can produce scarps and step-like small terraces. [ 21 ] Landslide deposits are poorly sorted . Those rich in clay may show stretched clay lumps (a phenomenon called boudinage ) and zones of concentrated shear. [ 20 ]
Debris flow deposits take the form of long, narrow tracks of very poorly sorted material. These may have natural levees at the sides of the tracks, and sometimes consist of lenses of rock fragments alternating with lenses of fine-grained earthy material. [ 20 ] Debris flows often form much of the upper slopes of alluvial fans . [ 22 ]
Triggers for mass wasting can be divided into passive and activating (initiating) causes. Passive causes include: [ 23 ]
Activating causes include: [ 23 ]
Mass wasting causes problems for civil engineering , particularly highway construction . It can displace roads, buildings, and other construction and can break pipelines. Historically, mitigation of landslide hazards on the Gaillard Cut of the Panama Canal accounted for 55,860,400 cubic meters (73,062,600 cu yd) of the 128,648,530 cubic meters (168,265,924 cu yd) of material removed while excavating the cut. [ 25 ]
Rockslides or landslides can have disastrous consequences, both immediate and delayed. The Oso disaster of March 2014 was a landslide that caused 43 fatalities in Oso, Washington , US. [ 26 ] Delayed consequences of landslides can arise from the formation of landslide dams , as at Thistle, Utah , in April 1983. [ 27 ] [ 28 ]
Volcano flanks can become over-steep resulting in instability and mass wasting. This is now a recognised part of the growth of all active volcanoes. [ 29 ] It is seen on submarine volcanoes as well as surface volcanoes: [ 30 ] Kamaʻehuakanaloa (formerly Loihi) in the Hawaiian–Emperor seamount chain [ 31 ] and Kick 'em Jenny in the Lesser Antilles Volcanic Arc [ 32 ] are two submarine volcanoes that are known to undergo mass wasting. The failure of the northern flank of Mount St. Helens in 1980 showed how rapidly volcanic flanks can deform and fail. [ 33 ]
Methods of mitigation of mass wasting hazards include: | https://en.wikipedia.org/wiki/Mass_wasting |
The Division of Ecological Restoration (DER) is a division of the Massachusetts Department of Fish and Game within the Executive Office of Energy and Environmental Affairs . DER was created in 2009 with the merger of the Riverways and Wetlands Restoration Programs (formally within the Massachusetts Office of Coastal Zone Management). DER coordinates ecological restoration to improve ecological condition and to restore important ecosystem services that improve the quality of life for all Massachusetts citizens.
The Riverways Program ( MGL Chapter 21A Section 8 ) has been maintained within DER and coordinates outreach and technical assistance to support watershed conservation and protection.
The Division and partners facilitate capital-based projects including (but not limited to) dam removal and culvert replacement with the goal of restoring aquatic habitats (e.g. salt marshes)
and ecosystems across the state. These projects support commercial and recreational fisheries and provide many other benefits such as reduced flooding, improved water quality, carbon sequestration and increased public safety.
Ecological restoration is a core component of the Commonwealth of Massachusetts efforts to build habitat resiliency to better allow fish and wildlife to adapt to climate change – including sea level rise , elevated water temperatures, and increased floods and periods of drought.
Beth Lambert currently serves as the director of the Division of Ecological Restoration. The founding director was Tim Purinton, who served in this role from 2009 to 2017. [ 1 ] | https://en.wikipedia.org/wiki/Massachusetts_Division_of_Ecological_Restoration |
Massicot is lead (II) oxide mineral with an orthorhombic lattice structure .
Lead(II) oxide (formula: PbO) can occur in one of two lattice formats, orthorhombic and tetragonal . The red tetragonal form is called litharge . PbO can be changed from massicot to litharge (or vice versa) by controlled heating and cooling. At room temperature massicot forms soft ( Mohs hardness of 2) yellow to reddish-yellow, earthy, scaley masses which are very dense, with a specific gravity of 9.64. Massicot can be found as a natural mineral, though it is only found in minor quantities. In bygone centuries it was mined. Nowadays massicot arises during industrial processing of lead and lead oxides, [ 6 ] especially in the glass industry, which is the biggest user of PbO.
The definition of massicot as orthorhombic PbO dates from the 1840s, [ 5 ] but the substance massicot and the name massicot has been in use since the late medieval era. [ 7 ] There is some evidence that the ancient Romans used the substance. [ 8 ]
It may occur as an oxidation product of other lead-bearing minerals such as galena , bournonite , boulangerite , either naturally or in industrial processing. When massicot is found in a natural environment, some other minerals that may be found with it may include cerussite , litharge, minium , wulfenite , valentinite and limonite . [ 3 ]
This article about a specific oxide mineral is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Massicot |
In thermodynamics , the Massieu function (sometimes called Massieu–Gibbs function , Massieu potential , or Gibbs function , or characteristic (state) function in its original terminology), symbol Ψ ( Psi ), is defined by the following relation:
where for every system with degree of freedom r one may choose r variables, e.g. ( X 1 , … , X i , Y i + 1 , … Y r ) , {\displaystyle {\big (}X_{1},\dots ,X_{i},Y_{i+1},\dots Y_{r}{\big )},} to define a coordinate system , where X and Y are extensive and intensive variables , respectively, and where at least one extensive variable must be within this set in order to define the size of the system. The ( r + 1) -th variable, Ψ , is then called the Massieu function. [ 1 ]
The Massieu function was introduced in the 1869 paper "On the Characteristic Functions of Various Fluids" by French engineer François Massieu (1832-1896). The name "Gibbs function" is the eponym of American physicist Willard Gibbs (1839-1903), who cited Massieu in his 1876 On the Equilibrium of Heterogeneous Substances . Massieu, as discussed in the first footnote to the abstract of Gibbs' Equilibrium , “appears to have been the first to solve the problem of representing all the properties of a body of invariable composition which are concerned in reversible processes by means of a single function.” Massieu's 1869 paper seems to be the source for the generalized mathematical conception of the energy of a system being equal to summations of the products of pairs of conjugate variables . | https://en.wikipedia.org/wiki/Massieu_function |
Massive online open research ( MOOR ) is an online research and development (R&D) open access platform or higher education study program aiming at unlimited participation via the internet.
It may be used to create, on a very large participative scale, a new discovery, development or creation which will be allegedly accompanied by a peer-review publication.
In September 2013, The University of California in San Diego bioinformatics department, proposed a massive online open course which would feature "an opportunity (for students) to work on specific research projects under the leadership of prominent bioinformatics scientists". [ 1 ]
Several internet platforms have shown their interest in bridging prominent science, technology, engineering and mathematics (i.e., STEM fields ) researchers with students, as means to accelerate STEM discoveries and education. The internet social network Research Gate has unveiled that multiple discoveries and advancements in science have been made collaboratively in an open access scheme since its creation, [ 2 ] essentially serving as a MOOR platform.
The University of Amsterdam has been developing an online tool for massive online open research since February 2014. This tool will primarily focus on collaborative (qualitative) data analysis. | https://en.wikipedia.org/wiki/Massive_online_open_research |
The physics technical term massive particle refers to a massful particle which has real non-zero rest mass (such as baryonic matter ), the counter-part to the term massless particle . According to special relativity , the velocity of a massive particle is always less than the speed of light . [ 1 ] When highlighting relativistic speeds, the synonyms bradyon (from Greek : βραδύς , bradys , “slow”), tardyon [ 2 ] or ittyon [ 3 ] are sometimes used to contrast with luxon (which moves at light speed) and hypothetical tachyon (which moves faster than light ).
This particle physics –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Massive_particle |
Massively Parallel Quantum Chemistry ( MPQC ) is an ab initio computational chemistry software program. [ 1 ] Three features distinguish it from other quantum chemistry programs such as Gaussian and GAMESS : it is open-source , has an object-oriented design, and is created from the beginning as a parallel processing program. [ 2 ] It is available in Ubuntu and Debian . [ 3 ] [ 4 ]
MPQC provides implementations for a number of important methods for calculating electronic structure, including Hartree–Fock , Møller–Plesset perturbation theory (including its explicitly correlated linear R12 versions), and density functional theory .
This scientific software article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Massively_parallel_quantum_chemistry |
Massive parallel signature sequencing ( MPSS ) is a procedure that is used to identify and quantify mRNA transcripts, resulting in data similar to serial analysis of gene expression (SAGE), although it employs a series of biochemical and sequencing steps that are substantially different.
MPSS is a method for determining expression levels of mRNA by counting the number of individual mRNA molecules produced by each gene. It is "open ended" in the sense that the identity of the RNAs to be measured are not pre-determined as they are with gene expression microarrays .
A sample of mRNA are first converted to complementary DNA ( cDNA ) using reverse transcriptase , which makes subsequent manipulations easier. These cDNA are fused to a small oligonucleotide "tag" which allows the cDNA to be PCR amplified and then coupled to microbeads. After several rounds of sequence determination, using hybridization of fluorescent labeled probes, a sequence signature of ~16–20 bp is determined from each bead. Fluorescent imaging captures the signal from all of the beads, while affixed to a 2-dimensional surface, so DNA sequences are determined from all the beads in parallel. There is some amplification of the starting material so, in the end, approximately 1,000,000 sequence reads are obtained per experiment. [ 1 ]
MPSS allows mRNA transcripts to be identified through the generation of a 17–20 bp ( base pair ) signature sequence adjacent to the 3'-end of the 3'-most site of the designated restriction enzyme (commonly Sau3A or DpnII ). Each signature sequence is cloned onto one of a million microbeads . The technique ensures that only one type of DNA sequence is on a microbead. So if there are 50 copies of a specific transcript in the biological sample, these transcripts will be captured onto 50 different microbeads, each bead holding roughly 100,000 amplified copies of the specific signature sequence. The microbeads are then arrayed in a flow cell for sequencing and quantification. The sequence signatures are deciphered by the parallel identification of four bases by hybridization to fluorescently labeled encoders (Figure 5). Each of the encoders has a unique label which is detected after hybridization by taking an image of the microbead array. The next step is to cleave and remove that set of four bases and reveal the next four bases for a new round of hybridization to encoders and image acquisition. The raw output is a list of 17–20 bp signature sequences, that can be annotated to the human genome for gene identification.
The longer tag sequence confers a higher specificity than the classical SAGE tag of 9–10 bp . The level of unique gene expression is represented by the count of transcripts present per million molecules, similar to SAGE output. A significant advantage is the larger library size compared with SAGE. An MPSS library typically holds 1 million signature tags, which is roughly 20 times the size of a SAGE library. Some of the disadvantages related to SAGE apply to MPSS as well, such as loss of certain transcripts due to lack of restriction enzyme recognition site and ambiguity in tag annotation. The high sensitivity and absolute gene expression certainly favors MPSS. However, the technology is only available through Lynxgen Therapeutics, Inc. (then Solexa Inc till 2006 and then Illumina ). | https://en.wikipedia.org/wiki/Massively_parallel_signature_sequencing |
In particle physics , a massless particle is an elementary particle whose invariant mass is zero. At present the only confirmed massless particle is the photon .
The photon (carrier of electromagnetism ) is one of two known gauge bosons thought to be massless. The photon is well-known from direct observation to exist and be massless.
The other massless gauge boson is the gluon (carrier of the strong force ) whose existence has been inferred from particle collision decay products; it is expected to be massless, but a zero mass has not been confirmed by experiment.
Although there are compelling theoretical reasons to believe that gluons are massless, they can never be observed as free particles due to being confined within hadrons , and hence their presumed lack of rest mass cannot be confirmed by any feasible experiment. [ 1 ] [ 2 ]
The only other observed gauge bosons are the W and Z bosons , which are known from experiments to be extremely massive, even heavier than iron nuclei.
The graviton is a hypothetical tensor boson proposed to be the carrier of gravitational force in some quantum theories of gravity , but no such theory has been successfully incorporated into the Standard Model , so the Standard Model neither predicts any such particle nor requires it, and no gravitational quantum particle has been indicated by experiment. Whether a graviton would be massless if it existed is likewise an open question.
The Weyl fermion discovered in 2015 is also expected to be massless, [ 3 ] [ 4 ] but these are not actual particles. At one time neutrinos were thought to perhaps be Weyl fermions, but when they were discovered to have mass, that left no fundamental particles of the Weyl type.
The Weyl fermions discovered in 2015 are merely quasiparticles – composite motions found in the structure of molecular latices that have particle-like behavior, but are not themselves real particles. Weyl fermions in matter are like phonons , which are also quasiparticles. No real particle that is a Weyl fermion has been found to exist, and there is no compelling theoretical reason that requires them to exist.
Neutrinos were originally thought to be massless. However, because neutrinos change flavour as they travel, at least two of the types of neutrinos must have mass (and cannot be Weyl fermions). [ 5 ] The discovery of this phenomenon, known as neutrino oscillation , led to Canadian scientist Arthur B. McDonald and Japanese scientist Takaaki Kajita sharing the 2015 Nobel Prize in Physics . [ 6 ] | https://en.wikipedia.org/wiki/Massless_particle |
The mass–action ratio , [ 1 ] [ 2 ] often denoted by Γ {\displaystyle \Gamma } , is the ratio of the product concentrations, p, to reactant concentrations, s. The concentrations may or may not be at equilibrium.
Γ = p 1 p 2 … s 1 s 2 … {\displaystyle \Gamma ={\frac {p_{1}p_{2}\ldots }{s_{1}s_{2}\ldots }}}
This assumes that the stoichiometric amounts are all unity. If not, then each concentration must be raised to the power of its corresponding stoichiometric amount. If the product and reactant concentrations are at equilibrium then the mass–action ratio will equal the equilibrium constant. At equilibrium:
Γ = K e q {\displaystyle \Gamma =K_{eq}}
The ratio of the mass–action ratio to the equilibrium constant is often called the disequilibrium ratio , denoted by the symbol ρ {\displaystyle \rho } .
ρ = Γ K e q {\displaystyle \rho ={\frac {\Gamma }{K_{eq}}}}
and is a useful measure for indicating how far from equilibrium a given reaction is. The ratio is always greater than zero, and at equilibrium, the ratio is one: ρ = 1 {\displaystyle \rho =1} . When the reaction is out of equilibrium, ρ ≠ 1 {\displaystyle \rho \neq 1} . When ρ < 1 {\displaystyle \rho <1} , the reaction is out of equilibrium with a forward rate higher than the reverse rate, and the reaction has a negative free energy (i.e., a spontaneous, exergonic reaction), as explained below.
For a uni-molecular reaction such as A ⇌ B {\displaystyle A\rightleftharpoons B} , where the net reaction rate is given by the reversible mass-action ratio:
v = k 1 A − k 2 B = v f − v r {\displaystyle v=k_{1}A-k_{2}B=v_{f}-v_{r}}
At thermodynamic equilibrium the rate equals zero, that is 0 = k 1 A e q − k 2 B e q {\textstyle 0=k_{1}A_{eq}-{k_{2}B_{eq}}} . Rearranging gives:
k 1 k 2 = B e q A e q = K e q {\displaystyle {\frac {k_{1}}{k_{2}}}={\frac {B_{eq}}{A_{eq}}}=K_{eq}}
but ρ = Γ K e q {\textstyle \rho ={\frac {\Gamma }{K_{eq}}}} , therefore ρ = Γ k 2 k 1 {\displaystyle \rho =\Gamma {\frac {k_{2}}{k_{1}}}} and therefore ρ = B A k 2 k 1 = v r v f {\displaystyle \rho ={\frac {B}{A}}{\frac {k_{2}}{k_{1}}}={\frac {v_{r}}{v_{f}}}}
In other words, the disequilibrium ratio is the ratio of the reverse to the forward rate. When the reverse rate, v r {\textstyle v_{r}} is less than the forward rate, the ratio is less than one, ρ < 1 {\textstyle \rho <1} , indicating that the net reaction is from left to right.
The thermodynamic equation of the chemical equilibrium states that
where R is the universal gas constant and T the temperature .
The standard Gibbs free energy, Δ r G ⊖ {\displaystyle \Delta _{\mathrm {r} }G^{\ominus }} , can also be expressed in function of the equilibrium constant:
Δ r G ⊖ = − R T ln K e q {\displaystyle \Delta _{\mathrm {r} }G^{\ominus }=-RT\ln K_{eq}}
Introducing this in the previous equation, one obtains:
Δ r G T , p = − R T ln K e q + R T ln Γ {\displaystyle \Delta _{\mathrm {r} }G_{T,p}=-RT\ln K_{eq}+RT\ln \Gamma }
Substituting the mass-action ratio by the disequilibrium ratio times the equilibrium constant, this leads to:
Δ r G T , p = − R T ln K e q + R T ln ( ρ K e q ) {\displaystyle \Delta _{\mathrm {r} }G_{T,p}=-RT\ln K_{eq}+RT\ln(\rho K_{eq})}
Therefore
Δ r G T , p = − R T ln K e q + R T ln ( ρ ) + R T ln ( K e q ) {\displaystyle \Delta _{\mathrm {r} }G_{T,p}=-RT\ln K_{eq}+RT\ln(\rho )+RT\ln(K_{eq})}
and
Δ r G T , p = R T ln ( ρ ) {\displaystyle \Delta _{\mathrm {r} }G_{T,p}=RT\ln(\rho )}
This shows that the disequilibrium ratio is just an alternative way of expressing the free energy of a reaction and as such gives a more intuitive interpretation of free energy. That is if the free energy for a reaction is less than zero then it indicates that ρ < 1 {\textstyle \rho <1} and hence v r < v f {\textstyle v_{r}<v_{f}} , i.e the net reaction rate is from left to right. | https://en.wikipedia.org/wiki/Mass–action_ratio |
In physics , mass–energy equivalence is the relationship between mass and energy in a system's rest frame . The two differ only by a multiplicative constant and the units of measurement. [ 1 ] [ 2 ] The principle is described by the physicist Albert Einstein 's formula: E = m c 2 {\displaystyle E=mc^{2}} . [ 3 ] In a reference frame where the system is moving, its relativistic energy and relativistic mass (instead of rest mass ) obey the same formula.
The formula defines the energy ( E ) of a particle in its rest frame as the product of mass ( m ) with the speed of light squared ( c 2 ). Because the speed of light is a large number in everyday units (approximately 300 000 km/s or 186 000 mi/s), the formula implies that a small amount of mass corresponds to an enormous amount of energy.
Rest mass, also called invariant mass , is a fundamental physical property of matter , independent of velocity . Massless particles such as photons have zero invariant mass, but massless free particles have both momentum and energy.
The equivalence principle implies that when mass is lost in chemical reactions or nuclear reactions , a corresponding amount of energy will be released. The energy can be released to the environment (outside of the system being considered) as radiant energy , such as light , or as thermal energy . The principle is fundamental to many fields of physics, including nuclear and particle physics .
Mass–energy equivalence arose from special relativity as a paradox described by the French polymath Henri Poincaré (1854–1912). [ 4 ] Einstein was the first to propose the equivalence of mass and energy as a general principle and a consequence of the symmetries of space and time . The principle first appeared in "Does the inertia of a body depend upon its energy-content?", one of his annus mirabilis papers , published on 21 November 1905. [ 5 ] [ 6 ] The formula and its relationship to momentum, as described by the energy–momentum relation , were later developed by other physicists.
Mass–energy equivalence states that all objects having mass , or massive objects , have a corresponding intrinsic energy, even when they are stationary. In the rest frame of an object, where by definition it is motionless and so has no momentum , the mass and energy are equal or they differ only by a constant factor, the speed of light squared ( c 2 ). [ 1 ] [ 2 ] In Newtonian mechanics , a motionless body has no kinetic energy , and it may or may not have other amounts of internal stored energy, like chemical energy or thermal energy , in addition to any potential energy it may have from its position in a field of force . These energies tend to be much smaller than the mass of the object multiplied by c 2 , which is on the order of 10 17 joules for a mass of one kilogram. Due to this principle, the mass of the atoms that come out of a nuclear reaction is less than the mass of the atoms that go in, and the difference in mass shows up as heat and light with the same equivalent energy as the difference. In analyzing these extreme events, Einstein's formula can be used with E as the energy released (removed), and m as the change in mass.
In relativity , all the energy that moves with an object (i.e., the energy as measured in the object's rest frame) contributes to the total mass of the body, which measures how much it resists acceleration . If an isolated box of ideal mirrors could contain light, the individually massless photons would contribute to the total mass of the box by the amount equal to their energy divided by c 2 . [ 7 ] For an observer in the rest frame, removing energy is the same as removing mass and the formula m = E / c 2 indicates how much mass is lost when energy is removed. [ 8 ] In the same way, when any energy is added to an isolated system, the increase in the mass is equal to the added energy divided by c 2 . [ 9 ]
An object moves at different speeds in different frames of reference , depending on the motion of the observer. This implies the kinetic energy , in both Newtonian mechanics and relativity, is 'frame dependent', so that the amount of relativistic energy that an object is measured to have depends on the observer. The relativistic mass of an object is given by the relativistic energy divided by c 2 . [ 10 ] Because the relativistic mass is exactly proportional to the relativistic energy, relativistic mass and relativistic energy are nearly synonymous ; the only difference between them is the units . The rest mass or invariant mass of an object is defined as the mass an object has in its rest frame, when it is not moving with respect to the observer. The rest mass is the same for all inertial frames , as it is independent of the motion of the observer, it is the smallest possible value of the relativistic mass of the object. Because of the attraction between components of a system, which results in potential energy, the rest mass is almost never additive ; in general, the mass of an object is not the sum of the masses of its parts. [ 9 ] The rest mass of an object is the total energy of all the parts, including kinetic energy, as observed from the center of momentum frame, and potential energy. The masses add up only if the constituents are at rest (as observed from the center of momentum frame) and do not attract or repel, so that they do not have any extra kinetic or potential energy. [ note 1 ] Massless particles are particles with no rest mass, and therefore have no intrinsic energy; their energy is due only to their momentum.
Relativistic mass depends on the motion of the object, so that different observers in relative motion see different values for it. The relativistic mass of a moving object is larger than the relativistic mass of an object at rest, because a moving object has kinetic energy. If the object moves slowly, the relativistic mass is nearly equal to the rest mass and both are nearly equal to the classical inertial mass (as it appears in Newton's laws of motion ). If the object moves quickly, the relativistic mass is greater than the rest mass by an amount equal to the mass associated with the kinetic energy of the object. Massless particles also have relativistic mass derived from their kinetic energy, equal to their relativistic energy divided by c 2 , or m rel = E / c 2 . [ 11 ] [ 12 ] The speed of light is one in a system where length and time are measured in natural units and the relativistic mass and energy would be equal in value and dimension. As it is just another name for the energy, the use of the term relativistic mass is redundant and physicists generally reserve mass to refer to rest mass, or invariant mass, as opposed to relativistic mass. [ 13 ] [ 14 ] A consequence of this terminology is that the mass is not conserved in special relativity, whereas the conservation of momentum and conservation of energy are both fundamental laws. [ 13 ]
Conservation of energy is a universal principle in physics and holds for any interaction, along with the conservation of momentum. [ 13 ] The classical conservation of mass, in contrast, is violated in certain relativistic settings. [ 14 ] [ 13 ] This concept has been experimentally proven in a number of ways, including the conversion of mass into kinetic energy in nuclear reactions and other interactions between elementary particles . [ 14 ] While modern physics has discarded the expression 'conservation of mass', in older terminology a relativistic mass can also be defined to be equivalent to the energy of a moving system, allowing for a conservation of relativistic mass . [ 13 ] Mass conservation breaks down when the energy associated with the mass of a particle is converted into other forms of energy, such as kinetic energy, thermal energy, or radiant energy . [ 13 ]
Massless particles have zero rest mass. The Planck–Einstein relation for the energy for photons is given by the equation E = hf , where h is the Planck constant and f is the photon frequency . This frequency and thus the relativistic energy are frame-dependent. If an observer runs away from a photon in the direction the photon travels from a source, and it catches up with the observer, the observer sees it as having less energy than it had at the source. The faster the observer is traveling with regard to the source when the photon catches up, the less energy the photon would be seen to have. As an observer approaches the speed of light with regard to the source, the redshift of the photon increases, according to the relativistic Doppler effect . The energy of the photon is reduced and as the wavelength becomes arbitrarily large, the photon's energy approaches zero, because of the massless nature of photons, which does not permit any intrinsic energy.
For closed systems made up of many parts, like an atomic nucleus , planet, or star, the relativistic energy is given by the sum of the relativistic energies of each of the parts, because energies are additive in these systems. If a system is bound by attractive forces, and the energy gained in excess of the work done is removed from the system, then mass is lost with this removed energy. The mass of an atomic nucleus is less than the total mass of the protons and neutrons that make it up. [ 15 ] This mass decrease is also equivalent to the energy required to break up the nucleus into individual protons and neutrons. This effect can be understood by looking at the potential energy of the individual components. The individual particles have a force attracting them together, and forcing them apart increases the potential energy of the particles in the same way that lifting an object up on earth does. This energy is equal to the work required to split the particles apart. The mass of the Solar System is slightly less than the sum of its individual masses.
For an isolated system of particles moving in different directions, the invariant mass of the system is the analog of the rest mass, and is the same for all observers, even those in relative motion. It is defined as the total energy (divided by c 2 ) in the center of momentum frame . The center of momentum frame is defined so that the system has zero total momentum; the term center of mass frame is also sometimes used, where the center of mass frame is a special case of the center of momentum frame where the center of mass is put at the origin. A simple example of an object with moving parts but zero total momentum is a container of gas. In this case, the mass of the container is given by its total energy (including the kinetic energy of the gas molecules), since the system's total energy and invariant mass are the same in any reference frame where the momentum is zero, and such a reference frame is also the only frame in which the object can be weighed. In a similar way, the theory of special relativity posits that the thermal energy in all objects, including solids, contributes to their total masses, even though this energy is present as the kinetic and potential energies of the atoms in the object, and it (in a similar way to the gas) is not seen in the rest masses of the atoms that make up the object. [ 9 ] Similarly, even photons, if trapped in an isolated container, would contribute their energy to the mass of the container. Such extra mass, in theory, could be weighed in the same way as any other type of rest mass, even though individually photons have no rest mass. The property that trapped energy in any form adds weighable mass to systems that have no net momentum is one of the consequences of relativity. It has no counterpart in classical Newtonian physics, where energy never exhibits weighable mass. [ 9 ]
Physics has two concepts of mass, the gravitational mass and the inertial mass. The gravitational mass is the quantity that determines the strength of the gravitational field generated by an object, as well as the gravitational force acting on the object when it is immersed in a gravitational field produced by other bodies. The inertial mass, on the other hand, quantifies how much an object accelerates if a given force is applied to it. The mass–energy equivalence in special relativity refers to the inertial mass. However, already in the context of Newtonian gravity, the weak equivalence principle is postulated: the gravitational and the inertial mass of every object are the same. Thus, the mass–energy equivalence, combined with the weak equivalence principle, results in the prediction that all forms of energy contribute to the gravitational field generated by an object. This observation is one of the pillars of the general theory of relativity .
The prediction that all forms of energy interact gravitationally has been subject to experimental tests. One of the first observations testing this prediction, called the Eddington experiment , was made during the solar eclipse of May 29, 1919 . [ 16 ] [ 17 ] During the eclipse, the English astronomer and physicist Arthur Eddington observed that the light from stars passing close to the Sun was bent. The effect is due to the gravitational attraction of light by the Sun. The observation confirmed that the energy carried by light indeed is equivalent to a gravitational mass. Another seminal experiment, the Pound–Rebka experiment , was performed in 1960. [ 18 ] In this test a beam of light was emitted from the top of a tower and detected at the bottom. The frequency of the light detected was higher than the light emitted. This result confirms that the energy of photons increases when they fall in the gravitational field of the Earth. The energy, and therefore the gravitational mass, of photons is proportional to their frequency as stated by the Planck's relation.
In some reactions, matter particles can be destroyed and their associated energy released to the environment as other forms of energy, such as light and heat. [ 1 ] One example of such a conversion takes place in elementary particle interactions, where the rest energy is transformed into kinetic energy. [ 1 ] Such conversions between types of energy happen in nuclear weapons, in which the protons and neutrons in atomic nuclei lose a small fraction of their original mass, though the mass lost is not due to the destruction of any smaller constituents. Nuclear fission allows a tiny fraction of the energy associated with the mass to be converted into usable energy such as radiation; in the decay of the uranium , for instance, about 0.1% of the mass of the original atom is lost. [ 19 ] In theory, it should be possible to destroy matter and convert all of the rest-energy associated with matter into heat and light, but none of the theoretically known methods are practical. One way to harness all the energy associated with mass is to annihilate matter with antimatter . Antimatter is rare in the universe , however, and the known mechanisms of production require more usable energy than would be released in annihilation. CERN estimated in 2011 that over a billion times more energy is required to make and store antimatter than could be released in its annihilation. [ 20 ]
As most of the mass which comprises ordinary objects resides in protons and neutrons, converting all the energy of ordinary matter into more useful forms requires that the protons and neutrons be converted to lighter particles, or particles with no mass at all. In the Standard Model of particle physics , the number of protons plus neutrons is nearly exactly conserved. Despite this, Gerard 't Hooft showed that there is a process that converts protons and neutrons to antielectrons and neutrinos . [ 21 ] This is the weak SU(2) instanton proposed by the physicists Alexander Belavin , Alexander Markovich Polyakov , Albert Schwarz , and Yu. S. Tyupkin. [ 22 ] This process, can in principle destroy matter and convert all the energy of matter into neutrinos and usable energy, but it is normally extraordinarily slow. It was later shown that the process occurs rapidly at extremely high temperatures that would only have been reached shortly after the Big Bang . [ 23 ]
Many extensions of the standard model contain magnetic monopoles , and in some models of grand unification , these monopoles catalyze proton decay , a process known as the Callan–Rubakov effect . [ 24 ] This process would be an efficient mass–energy conversion at ordinary temperatures, but it requires making monopoles and anti-monopoles, whose production is expected to be inefficient. Another method of completely annihilating matter uses the gravitational field of black holes. The British theoretical physicist Stephen Hawking theorized [ 25 ] it is possible to throw matter into a black hole and use the emitted heat to generate power. According to the theory of Hawking radiation , however, larger black holes radiate less than smaller ones, so that usable power can only be produced by small black holes.
Unlike a system's energy in an inertial frame, the relativistic energy ( E r e l {\displaystyle E_{\rm {rel}}} ) of a system depends on both the rest mass ( m 0 {\displaystyle m_{0}} ) and the total momentum of the system. The extension of Einstein's equation to these systems is given by: [ 26 ] [ 27 ] [ note 2 ]
E r e l 2 − | p | 2 c 2 = m 0 2 c 4 {\displaystyle {\begin{aligned}E_{\rm {rel}}^{2}-|\mathbf {p} |^{2}c^{2}&=m_{0}^{2}c^{4}\\\end{aligned}}}
or
E r e l 2 − ( p c ) 2 = ( m 0 c 2 ) 2 {\displaystyle {\begin{aligned}E_{\rm {rel}}^{2}-(pc)^{2}&=(m_{0}c^{2})^{2}\\\end{aligned}}}
or
E r e l = ( m 0 c 2 ) 2 + ( p c ) 2 {\displaystyle {\begin{aligned}E_{\rm {rel}}={\sqrt {(m_{0}c^{2})^{2}+(pc)^{2}}}\,\!\end{aligned}}}
where the ( p c ) 2 {\displaystyle (pc)^{2}} term represents the square of the Euclidean norm (total vector length) of the various momentum vectors in the system, which reduces to the square of the simple momentum magnitude, if only a single particle is considered. This equation is called the energy–momentum relation and reduces to E r e l = m c 2 {\displaystyle E_{\rm {rel}}=mc^{2}} when the momentum term is zero. For photons where m 0 = 0 {\displaystyle m_{0}=0} , the equation reduces to E r e l = p c {\displaystyle E_{\rm {rel}}=pc} .
Using the Lorentz factor , γ , the energy–momentum can be rewritten as E = γmc 2 and expanded as a power series :
For speeds much smaller than the speed of light, higher-order terms in this expression get smaller and smaller because v / c is small. For low speeds, all but the first two terms can be ignored:
In classical mechanics , both the m 0 c 2 term and the high-speed corrections are ignored. The initial value of the energy is arbitrary, as only the change in energy can be measured and so the m 0 c 2 term is ignored in classical physics. While the higher-order terms become important at higher speeds, the Newtonian equation is a highly accurate low-speed approximation; adding in the third term yields:
The difference between the two approximations is given by 3 v 2 4 c 2 {\displaystyle {\tfrac {3v^{2}}{4c^{2}}}} , a number very small for everyday objects. In 2018 NASA announced the Parker Solar Probe was the fastest ever, with a speed of 153,454 miles per hour (68,600 m/s). [ 28 ] The difference between the approximations for the Parker Solar Probe in 2018 is 3 v 2 4 c 2 ≈ 3.9 × 10 − 8 {\displaystyle {\tfrac {3v^{2}}{4c^{2}}}\approx 3.9\times 10^{-8}} , which accounts for an energy correction of four parts per hundred million. The gravitational constant , in contrast, has a standard relative uncertainty of about 2.2 × 10 − 5 {\displaystyle 2.2\times 10^{-5}} . [ 29 ]
The nuclear binding energy is the minimum energy that is required to disassemble the nucleus of an atom into its component parts. [ 30 ] The mass of an atom is less than the sum of the masses of its constituents due to the attraction of the strong nuclear force . [ 31 ] The difference between the two masses is called the mass defect and is related to the binding energy through Einstein's formula. [ 31 ] [ 32 ] [ 33 ] The principle is used in modeling nuclear fission reactions, and it implies that a great amount of energy can be released by the nuclear fission chain reactions used in both nuclear weapons and nuclear power .
A water molecule weighs a little less than two free hydrogen atoms and an oxygen atom. The minuscule mass difference is the energy needed to split the molecule into three individual atoms (divided by c 2 ), which was given off as heat when the molecule formed (this heat had mass). Similarly, a stick of dynamite in theory weighs a little bit more than the fragments after the explosion; in this case the mass difference is the energy and heat that is released when the dynamite explodes. Such a change in mass may only happen when the system is open, and the energy and mass are allowed to escape. Thus, if a stick of dynamite is detonated in a hermetically sealed chamber, the mass of the chamber and fragments, the heat, sound, and light would still be equal to the original mass of the chamber and dynamite. If sitting on a scale, the weight and mass would not change. This would in theory also happen even with a nuclear bomb, if it could be kept in an ideal box of infinite strength, which did not rupture or pass radiation . [ note 3 ] Thus, a 21.5 kiloton ( 9 × 10 13 joule ) nuclear bomb produces about one gram of heat and electromagnetic radiation, but the mass of this energy would not be detectable in an exploded bomb in an ideal box sitting on a scale; instead, the contents of the box would be heated to millions of degrees without changing total mass and weight. If a transparent window passing only electromagnetic radiation were opened in such an ideal box after the explosion, and a beam of X-rays and other lower-energy light allowed to escape the box, it would eventually be found to weigh one gram less than it had before the explosion. This weight loss and mass loss would happen as the box was cooled by this process, to room temperature. However, any surrounding mass that absorbed the X-rays (and other "heat") would gain this gram of mass from the resulting heating, thus, in this case, the mass "loss" would represent merely its relocation.
Einstein used the centimetre–gram–second system of units (cgs), but the formula is independent of the system of units. In natural units, the numerical value of the speed of light is set to equal 1, and the formula expresses an equality of numerical values: E = m . In the SI system (expressing the ratio E / m in joules per kilogram using the value of c in metres per second ): [ 35 ]
So the energy equivalent of one kilogram of mass is
Any time energy is released, the process can be evaluated from an E = mc 2 perspective. For instance, the "gadget"-style bomb used in the Trinity test and the bombing of Nagasaki had an explosive yield equivalent to 21 kt of TNT. [ 36 ] About 1 kg of the approximately 6.15 kg of plutonium in each of these bombs fissioned into lighter elements totaling almost exactly one gram less, after cooling. The electromagnetic radiation and kinetic energy (thermal and blast energy) released in this explosion carried the missing gram of mass.
Whenever energy is added to a system, the system gains mass, as shown when the equation is rearranged:
While Einstein was the first to have correctly deduced the mass–energy equivalence formula, he was not the first to have related energy with mass, though nearly all previous authors thought that the energy that contributes to mass comes only from electromagnetic fields. [ 38 ] [ 39 ] [ 40 ] Once discovered, Einstein's formula was initially written in many different notations, and its interpretation and justification was further developed in several steps. [ 41 ] [ 42 ]
Eighteenth century theories on the correlation of mass and energy included that devised by the English scientist Isaac Newton in 1717, who speculated that light particles and matter particles were interconvertible in "Query 30" of the Opticks , where he asks: "Are not the gross bodies and light convertible into one another, and may not bodies receive much of their activity from the particles of light which enter their composition?" [ 43 ] Swedish scientist and theologian Emanuel Swedenborg , in his Principia of 1734 theorized that all matter is ultimately composed of dimensionless points of "pure and total motion". He described this motion as being without force, direction or speed, but having the potential for force, direction and speed everywhere within it. [ 44 ] [ 45 ]
During the nineteenth century there were several speculative attempts to show that mass and energy were proportional in various ether theories . [ 46 ] In 1873 the Russian physicist and mathematician Nikolay Umov pointed out a relation between mass and energy for ether in the form of Е = kmc 2 , where 0.5 ≤ k ≤ 1 . [ 47 ] English engineer Samuel Tolver Preston in 1875 [ 48 ] and the Italian industrialist and geologist Olinto De Pretto in 1903, [ 49 ] [ 50 ] following physicist Georges-Louis Le Sage , imagined that the universe was filled with an ether of tiny particles that always move at speed c . Each of these particles has a kinetic energy of mc 2 up to a small numerical factor, giving a mass–energy relation.
In 1905, independently of Einstein, French polymath Gustave Le Bon speculated that atoms could release large amounts of latent energy, reasoning from an all-encompassing qualitative philosophy of physics . [ 51 ] [ 52 ]
There were many attempts in the 19th and the beginning of the 20th century—like those of British physicists J. J. Thomson in 1881 and Oliver Heaviside in 1889, and George Frederick Charles Searle in 1897, German physicists Wilhelm Wien in 1900 and Max Abraham in 1902, and the Dutch physicist Hendrik Antoon Lorentz in 1904—to understand how the mass of a charged object depends on the electrostatic field . [ 53 ] This concept was called electromagnetic mass , and was considered as being dependent on velocity and direction as well. Lorentz in 1904 gave the following expressions for longitudinal and transverse electromagnetic mass:
where
Another way of deriving a type of electromagnetic mass was based on the concept of radiation pressure . In 1900, French polymath Henri Poincaré associated electromagnetic radiation energy with a "fictitious fluid" having momentum and mass [ 4 ]
By that, Poincaré tried to save the center of mass theorem in Lorentz's theory, though his treatment led to radiation paradoxes. [ 40 ]
Austrian physicist Friedrich Hasenöhrl showed in 1904 that electromagnetic cavity radiation contributes the "apparent mass"
to the cavity's mass. He argued that this implies mass dependence on temperature as well. [ 54 ]
Einstein did not write the exact formula E = mc 2 in his 1905 Annus Mirabilis paper "Does the Inertia of an object Depend Upon Its Energy Content?"; [ 5 ] rather, the paper states that if a body gives off the energy L by emitting light, its mass diminishes by L / c 2 . This formulation relates only a change Δ m in mass to a change L in energy without requiring the absolute relationship. The relationship convinced him that mass and energy can be seen as two names for the same underlying, conserved physical quantity. [ 55 ] He has stated that the laws of conservation of energy and conservation of mass are "one and the same". [ 56 ] Einstein elaborated in a 1946 essay that "the principle of the conservation of mass… proved inadequate in the face of the special theory of relativity. It was therefore merged with the energy conservation principle—just as, about 60 years before, the principle of the conservation of mechanical energy had been combined with the principle of the conservation of heat [thermal energy]. We might say that the principle of the conservation of energy, having previously swallowed up that of the conservation of heat, now proceeded to swallow that of the conservation of mass—and holds the field alone." [ 57 ]
In developing special relativity , Einstein found that the kinetic energy of a moving body is
with v the velocity , m 0 the rest mass, and γ the Lorentz factor.
He included the second term on the right to make sure that for small velocities the energy would be the same as in classical mechanics, thus satisfying the correspondence principle :
Without this second term, there would be an additional contribution in the energy when the particle is not moving.
Einstein, following Lorentz and Abraham, used velocity- and direction-dependent mass concepts in his 1905 electrodynamics paper and in another paper in 1906. [ 58 ] [ 59 ] In Einstein's first 1905 paper on E = mc 2 , he treated m as what would now be called the rest mass , [ 5 ] and it has been noted that in his later years he did not like the idea of "relativistic mass". [ 60 ]
In modern physics terminology, relativistic energy is used in lieu of relativistic mass and the term "mass" is reserved for the rest mass. [ 13 ] Historically, there has been considerable debate over the use of the concept of "relativistic mass" and the connection of "mass" in relativity to "mass" in Newtonian dynamics. One view is that only rest mass is a viable concept and is a property of the particle; while relativistic mass is a conglomeration of particle properties and properties of spacetime. Another view, attributed to Norwegian physicist Kjell Vøyenli, is that the Newtonian concept of mass as a particle property and the relativistic concept of mass have to be viewed as embedded in their own theories and as having no precise connection. [ 61 ] [ 62 ]
Already in his relativity paper "On the electrodynamics of moving bodies", Einstein derived the correct expression for the kinetic energy of particles:
Now the question remained open as to which formulation applies to bodies at rest. This was tackled by Einstein in his paper "Does the inertia of a body depend upon its energy content?", one of his Annus Mirabilis papers . Here, Einstein used V to represent the speed of light in vacuum and L to represent the energy lost by a body in the form of radiation. [ 5 ] Consequently, the equation E = mc 2 was not originally written as a formula but as a sentence in German saying that "if a body gives off the energy L in the form of radiation, its mass diminishes by L / V 2 ." A remark placed above it informed that the equation was approximated by neglecting "magnitudes of fourth and higher orders" of a series expansion . [ note 6 ] Einstein used a body emitting two light pulses in opposite directions, having energies of E 0 before and E 1 after the emission as seen in its rest frame. As seen from a moving frame, E 0 becomes H 0 and E 1 becomes H 1 . Einstein obtained, in modern notation:
He then argued that H − E can only differ from the kinetic energy K by an additive constant, which gives
Neglecting effects higher than third order in v / c after a Taylor series expansion of the right side of this yields:
Einstein concluded that the emission reduces the body's mass by E / c 2 , and that the mass of a body is a measure of its energy content.
The correctness of Einstein's 1905 derivation of E = mc 2 was criticized by German theoretical physicist Max Planck in 1907, who argued that it is only valid to first approximation. Another criticism was formulated by American physicist Herbert Ives in 1952 and the Israeli physicist Max Jammer in 1961, asserting that Einstein's derivation is based on begging the question . [ 41 ] [ 63 ] Other scholars, such as American and Chilean philosophers John Stachel and Roberto Torretti , have argued that Ives' criticism was wrong, and that Einstein's derivation was correct. [ 64 ] American physics writer Hans Ohanian , in 2008, agreed with Stachel/Torretti's criticism of Ives, though he argued that Einstein's derivation was wrong for other reasons. [ 65 ]
Like Poincaré, Einstein concluded in 1906 that the inertia of electromagnetic energy is a necessary condition for the center-of-mass theorem to hold. On this occasion, Einstein referred to Poincaré's 1900 paper and wrote: "Although the merely formal considerations, which we will need for the proof, are already mostly contained in a work by H. Poincaré 2 , for the sake of clarity I will not rely on that work." [ 66 ] In Einstein's more physical, as opposed to formal or mathematical, point of view, there was no need for fictitious masses. He could avoid the perpetual motion problem because, on the basis of the mass–energy equivalence, he could show that the transport of inertia that accompanies the emission and absorption of radiation solves the problem. Poincaré's rejection of the principle of action–reaction can be avoided through Einstein's E = mc 2 , because mass conservation appears as a special case of the energy conservation law .
There were several further developments in the first decade of the twentieth century. In May 1907, Einstein explained that the expression for energy ε of a moving mass point assumes the simplest form when its expression for the state of rest is chosen to be ε 0 = μV 2 (where μ is the mass), which is in agreement with the "principle of the equivalence of mass and energy". In addition, Einstein used the formula μ = E 0 / V 2 , with E 0 being the energy of a system of mass points, to describe the energy and mass increase of that system when the velocity of the differently moving mass points is increased. [ 67 ] Max Planck rewrote Einstein's mass–energy relationship as M = E 0 + pV 0 / c 2 in June 1907, where p is the pressure and V 0 the volume to express the relation between mass, its latent energy, and thermodynamic energy within the body. [ 68 ] Subsequently, in October 1907, this was rewritten as M 0 = E 0 / c 2 and given a quantum interpretation by German physicist Johannes Stark , who assumed its validity and correctness. [ 69 ] In December 1907, Einstein expressed the equivalence in the form M = μ + E 0 / c 2 and concluded: "A mass μ is equivalent, as regards inertia, to a quantity of energy μc 2 . […] It appears far more natural to consider every inertial mass as a store of energy." [ 70 ] [ 71 ] American physical chemists Gilbert N. Lewis and Richard C. Tolman used two variations of the formula in 1909: m = E / c 2 and m 0 = E 0 / c 2 , with E being the relativistic energy (the energy of an object when the object is moving), E 0 is the rest energy (the energy when not moving), m is the relativistic mass (the rest mass and the extra mass gained when moving), and m 0 is the rest mass. [ 72 ] The same relations in different notation were used by Lorentz in 1913 and 1914, though he placed the energy on the left-hand side: ε = Mc 2 and ε 0 = mc 2 , with ε being the total energy (rest energy plus kinetic energy) of a moving material point, ε 0 its rest energy, M the relativistic mass, and m the invariant mass. [ 73 ]
In 1911, German physicist Max von Laue gave a more comprehensive proof of M 0 = E 0 / c 2 from the stress–energy tensor , [ 74 ] which was later generalized by German mathematician Felix Klein in 1918. [ 75 ]
Einstein returned to the topic once again after World War II and this time he wrote E = mc 2 in the title of his article [ 76 ] intended as an explanation for a general reader by analogy. [ 77 ]
An alternative version of Einstein's thought experiment was proposed by American theoretical physicist Fritz Rohrlich in 1990, who based his reasoning on the Doppler effect . [ 78 ] Like Einstein, he considered a body at rest with mass M . If the body is examined in a frame moving with nonrelativistic velocity v , it is no longer at rest and in the moving frame it has momentum P = Mv . Then he supposed the body emits two pulses of light to the left and to the right, each carrying an equal amount of energy E / 2 . In its rest frame, the object remains at rest after the emission since the two beams are equal in strength and carry opposite momentum. However, if the same process is considered in a frame that moves with velocity v to the left, the pulse moving to the left is redshifted , while the pulse moving to the right is blue shifted . The blue light carries more momentum than the red light, so that the momentum of the light in the moving frame is not balanced: the light is carrying some net momentum to the right. The object has not changed its velocity before or after the emission. Yet in this frame it has lost some right-momentum to the light. The only way it could have lost momentum is by losing mass. This also solves Poincaré's radiation paradox. The velocity is small, so the right-moving light is blueshifted by an amount equal to the nonrelativistic Doppler shift factor 1 − v / c . The momentum of the light is its energy divided by c , and it is increased by a factor of v / c . So the right-moving light is carrying an extra momentum Δ P given by:
The left-moving light carries a little less momentum, by the same amount Δ P . So the total right-momentum in both light pulses is twice Δ P . This is the right-momentum that the object lost.
The momentum of the object in the moving frame after the emission is reduced to this amount:
So the change in the object's mass is equal to the total energy lost divided by c 2 . Since any emission of energy can be carried out by a two-step process, where first the energy is emitted as light and then the light is converted to some other form of energy, any emission of energy is accompanied by a loss of mass. Similarly, by considering absorption, a gain in energy is accompanied by a gain in mass.
It was quickly noted after the discovery of radioactivity in 1897 that the total energy due to radioactive processes is about one million times greater than that involved in any known molecular change, raising the question of where the energy comes from. After eliminating the idea of absorption and emission of some sort of Lesagian ether particles, the existence of a huge amount of latent energy, stored within matter, was proposed by New Zealand physicist Ernest Rutherford and British radiochemist Frederick Soddy in 1903. Rutherford also suggested that this internal energy is stored within normal matter as well. He went on to speculate in 1904: "If it were ever found possible to control at will the rate of disintegration of the radio-elements, an enormous amount of energy could be obtained from a small quantity of matter." [ 79 ] [ 80 ] [ 81 ]
Einstein's equation does not explain the large energies released in radioactive decay, but can be used to quantify them. The theoretical explanation for radioactive decay is given by the nuclear forces responsible for holding atoms together, though these forces were still unknown in 1905. The enormous energy released from radioactive decay had previously been measured by Rutherford and was much more easily measured than the small change in the gross mass of materials as a result. Einstein's equation, by theory, can give these energies by measuring mass differences before and after reactions, but in practice, these mass differences in 1905 were still too small to be measured in bulk. Prior to this, the ease of measuring radioactive decay energies with a calorimeter was thought possibly likely to allow measurement of changes in mass difference, as a check on Einstein's equation itself. Einstein mentions in his 1905 paper that mass–energy equivalence might perhaps be tested with radioactive decay, which was known by then to release enough energy to possibly be "weighed," when missing from the system. However, radioactivity seemed to proceed at its own unalterable pace, and even when simple nuclear reactions became possible using proton bombardment, the idea that these great amounts of usable energy could be liberated at will with any practicality, proved difficult to substantiate. Rutherford was reported in 1933 to have declared that this energy could not be exploited efficiently: "Anyone who expects a source of power from the transformation of the atom is talking moonshine ." [ 82 ]
This outlook changed dramatically in 1932 with the discovery of the neutron and its mass, allowing mass differences for single nuclides and their reactions to be calculated directly, and compared with the sum of masses for the particles that made up their composition. In 1933, the energy released from the reaction of lithium-7 plus protons giving rise to two alpha particles , allowed Einstein's equation to be tested to an error of ±0.5%. [ 83 ] However, scientists still did not see such reactions as a practical source of power, due to the energy cost of accelerating reaction particles. After the very public demonstration of huge energies released from nuclear fission after the atomic bombings of Hiroshima and Nagasaki in 1945, the equation E = mc 2 became directly linked in the public eye with the power and peril of nuclear weapons. The equation was featured on page 2 of the Smyth Report , the official 1945 release by the US government on the development of the atomic bomb, and by 1946 the equation was linked closely enough with Einstein's work that the cover of Time magazine prominently featured a picture of Einstein next to an image of a mushroom cloud emblazoned with the equation. [ 84 ] Einstein himself had only a minor role in the Manhattan Project : he had cosigned a letter to the U.S. president in 1939 urging funding for research into atomic energy, warning that an atomic bomb was theoretically possible. The letter persuaded Roosevelt to devote a significant portion of the wartime budget to atomic research. Without a security clearance, Einstein's only scientific contribution was an analysis of an isotope separation method in theoretical terms. It was inconsequential, on account of Einstein not being given sufficient information to fully work on the problem. [ 85 ]
While E = mc 2 is useful for understanding the amount of energy potentially released in a fission reaction, it was not strictly necessary to develop the weapon, once the fission process was known, and its energy measured at 200 MeV (which was directly possible, using a quantitative Geiger counter , at that time). The physicist and Manhattan Project participant Robert Serber noted that somehow "the popular notion took hold long ago that Einstein's theory of relativity, in particular his equation E = mc 2 , plays some essential role in the theory of fission. Einstein had a part in alerting the United States government to the possibility of building an atomic bomb, but his theory of relativity is not required in discussing fission. The theory of fission is what physicists call a non-relativistic theory, meaning that relativistic effects are too small to affect the dynamics of the fission process significantly." [ note 7 ] There are other views on the equation's importance to nuclear reactions. In late 1938, the Austrian-Swedish and British physicists Lise Meitner and Otto Robert Frisch —while on a winter walk during which they solved the meaning of Hahn's experimental results and introduced the idea that would be called atomic fission—directly used Einstein's equation to help them understand the quantitative energetics of the reaction that overcame the "surface tension-like" forces that hold the nucleus together, and allowed the fission fragments to separate to a configuration from which their charges could force them into an energetic fission . To do this, they used packing fraction , or nuclear binding energy values for elements. These, together with use of E = mc 2 allowed them to realize on the spot that the basic fission process was energetically possible. [ 86 ]
According to the Einstein Papers Project at the California Institute of Technology and Hebrew University of Jerusalem , there remain only four known copies of this equation as written by Einstein. One of these is a letter written in German to Ludwik Silberstein , which was in Silberstein's archives, and sold at auction for $1.2 million, RR Auction of Boston, Massachusetts said on May 21, 2021. [ 87 ] | https://en.wikipedia.org/wiki/Mass–energy_equivalence |
A mast cell (also known as a mastocyte or a labrocyte [ 1 ] ) is a resident cell of connective tissue that contains many granules rich in histamine and heparin . Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a part of the immune and neuroimmune systems. Mast cells were discovered by Friedrich von Recklinghausen and later rediscovered by Paul Ehrlich in 1877. [ 2 ] Although best known for their role in allergy and anaphylaxis , mast cells play an important protective role as well, being intimately involved in wound healing, angiogenesis , immune tolerance , defense against pathogens , and vascular permeability in brain tumors. [ 3 ] [ 4 ]
The mast cell is very similar in both appearance and function to the basophil , another type of white blood cell . Although mast cells were once thought to be tissue-resident basophils, it has been shown that the two cells develop from different hematopoietic lineages and thus cannot be the same cells. [ 5 ]
Mast cells are very similar to basophil granulocytes (a class of white blood cells ) in blood , in the sense that both are granulated cells that contain histamine and heparin , an anticoagulant . Their nuclei differ in that the basophil nucleus is lobated while the mast cell nucleus is round. The Fc region of immunoglobulin E (IgE) becomes bound to mast cells and basophils, and when IgE's paratopes bind to an antigen, it causes the cells to release histamine and other inflammatory mediators. [ 6 ] These similarities have led many to speculate that mast cells are basophils that have "homed in" on tissues. Furthermore, they share a common precursor in bone marrow expressing the CD34 molecule. Basophils leave the bone marrow already mature, whereas the mast cell circulates in an immature form, only maturing once in a tissue site. The site an immature mast cell settles in probably determines its precise characteristics. [ 7 ] The first in vitro differentiation and growth of a pure population of mouse mast cells was carried out using conditioned medium derived from concanavalin A-stimulated splenocytes. [ 8 ] Later, it was discovered that T cell-derived interleukin 3 was the component present in the conditioned media that was required for mast cell differentiation and growth. [ 9 ]
Mast cells in rodents are classically divided into two subtypes: connective tissue -type mast cells and mucosal mast cells. The activities of the latter are dependent on T-cells . [ 10 ]
Mast cells are present in most tissues characteristically surrounding blood vessels, nerves and lymphatic vessels, [ 11 ] and are especially prominent near the boundaries between the outside world and the internal milieu, such as the skin , mucosa of the lungs , and digestive tract , as well as the mouth , conjunctiva , and nose . [ 7 ]
Mast cells play a key role in the inflammatory process. When activated, a mast cell can either selectively release ( piecemeal degranulation ) or rapidly release ( anaphylactic degranulation ) "mediators", or compounds that induce inflammation, from storage granules into the local microenvironment. [ 3 ] [ 12 ] Mast cells can be stimulated to degranulate by allergens through cross-linking with immunoglobulin E receptors (e.g., FcεRI ), physical injury through pattern recognition receptors for damage-associated molecular patterns (DAMPs), microbial pathogens through pattern recognition receptors for pathogen-associated molecular patterns (PAMPs), and various compounds through their associated G-protein coupled receptors (e.g., morphine through opioid receptors ) or ligand-gated ion channels . [ 3 ] [ 12 ] Complement proteins can activate membrane receptors on mast cells to exert various functions as well. [ 7 ]
Mast cells express a high-affinity receptor ( FcεRI ) for the Fc region of IgE, the least-abundant member of the antibodies. This receptor is of such high affinity that binding of IgE molecules is in essence irreversible. As a result, mast cells are coated with IgE, which is produced by plasma cells (the antibody-producing cells of the immune system). IgE antibodies are typically specific to one particular antigen .
In allergic reactions, mast cells remain inactive until an allergen binds to IgE already coated upon the cell. Other membrane activation events can either prime mast cells for subsequent degranulation or act in synergy with FcεRI signal transduction. [ 13 ] In general, allergens are proteins or polysaccharides . The allergen binds to the antigen-binding sites, which are situated on the variable regions of the IgE molecules bound to the mast cell surface. It appears that binding of two or more IgE molecules (cross-linking) is required to activate the mast cell. The clustering of the intracellular domains of the cell-bound Fc receptors, which are associated with the cross-linked IgE molecules, causes a complex sequence of reactions inside the mast cell that lead to its activation. Although this reaction is most well understood in terms of allergy, it appears to have evolved as a defense system against parasites and bacteria. [ 14 ]
Mast cells (MCs) have been shown to release their nuclear DNA and subsequently form mast cell extracellular traps (MCETs) comparable to neutrophil extracellular traps, which are able to entrap and kill various microbes. [ 15 ]
A unique, stimulus-specific set of mast cell mediators is released through degranulation following the activation of cell surface receptors on mast cells. [ 12 ] Examples of mediators that are released into the extracellular environment during mast cell degranulation include: [ 7 ] [ 12 ] [ 16 ]
Histamine dilates post-capillary venules, activates the endothelium , and increases blood vessel permeability. This leads to local edema (swelling), warmth, redness, and the attraction of other inflammatory cells to the site of release. It also depolarizes nerve endings (leading to itching or pain ). Cutaneous signs of histamine release are the "flare and wheal "-reaction. The bump and redness immediately following a mosquito bite are a good example of this reaction, which occurs seconds after challenge of the mast cell by an allergen. [ 7 ]
The other physiologic activities of mast cells are much less-understood. Several lines of evidence suggest that mast cells may have a fairly fundamental role in innate immunity : They are capable of elaborating a vast array of important cytokines and other inflammatory mediators such as TNF-α; they express multiple "pattern recognition receptors" thought to be involved in recognizing broad classes of pathogens; and mice without mast cells seem to be much more susceptible to a variety of infections. [ citation needed ]
Mast cell granules carry a variety of bioactive chemicals. These granules have been found to be transferred to adjacent cells of the immune system and neurons in a process of transgranulation via mast cell pseudopodia . [ 17 ]
Unlike other hematopoietic cells of the immune system , mast cells naturally occur in the human brain where they interact with the neuroimmune system . [ 4 ] In the brain, mast cells are located in a number of structures that mediate visceral sensory (e.g. pain) or neuroendocrine functions or that are located along the blood–cerebrospinal fluid barrier , including the pituitary stalk , pineal gland , thalamus , and hypothalamus , area postrema , choroid plexus , and in the dural layer of the meninges near meningeal nociceptors . [ 4 ] Mast cells serve the same general functions in the body and central nervous system, such as effecting or regulating allergic responses, innate and adaptive immunity, autoimmunity , and inflammation. [ 4 ] [ 18 ] Across systems, mast cells serve as the main effector cell through which pathogens can affect the gut–brain axis . [ 19 ] [ 20 ]
In the gastrointestinal tract, mucosal mast cells are located in close proximity to sensory nerve fibres, which communicate bidirectionally. [ 21 ] [ 19 ] [ 20 ] When these mast cells initially degranulate, they release mediators (e.g., histamine, tryptase, and serotonin) which activate, sensitize, and upregulate membrane expression of nociceptors (i.e., TRPV1 ) on visceral afferent neurons via their receptors (respectively, HRH1 , HRH2 , HRH3 , PAR2 , 5-HT3 ); [ 21 ] in turn, neurogenic inflammation, visceral hypersensitivity , and intestinal dysmotility (i.e., impaired peristalsis ) result. [ 21 ] Neuronal activation induces neuropeptide ( substance P and calcitonin gene-related peptide ) signaling to mast cells where they bind to their associated receptors and trigger degranulation of a distinct set of mediators ( β-Hexosaminidase , cytokines , chemokines , PGD2 , leukotrienes , and eoxins ). [ 21 ] [ 12 ]
FcεR1 is a high affinity IgE-receptor that is expressed on the surface of the mast cell. FcεR1 is a tetramer made of one alpha (α) chain, one beta (β) chain, and two identical, disulfide-linked gamma (γ) chains. The binding site for IgE is formed by the extracellular portion of the α chain that contains two domains that are similar to Ig. One transmembrane domain contains an aspartic acid residue, and one contains a short cytoplasmic tail. [ 22 ] The β chain contains, a single immunoreceptor tyrosine-based activation motif ITAM , in the cytoplasmic region. Each γ chain has one ITAM on the cytoplasmic region. The signaling cascade from the receptor is initiated when the ITAMs of the β and γ chains are phosphorylated by a tyrosine kinase. This signal is required for the activation of mast cells. [ 23 ] Type 2 helper T cells,( Th2 ) and many other cell types lack the β chain, so signaling is mediated only by the γ chain. This is due to the α chain containing endoplasmic reticulum retention signals that causes the α-chains to remain degraded in the ER. The assembly of the α chain with the co-transfected β and γ chains mask the ER retention and allows the α β γ complex to be exported to the golgi apparatus to the plasma membrane in rats. In humans, only the γ complex is needed to counterbalance the α chain ER retention. [ 22 ]
Allergen-mediated FcεR1 cross-linking signals are very similar to the signaling event resulting in antigen binding to lymphocytes . The Lyn tyrosine kinase is associated with the cytoplasmic end of the FcεR1 β chain. The antigen cross-links the FcεR1 molecules, and Lyn tyrosine kinase phosphorylates the ITAMs in the FcεR1 β and γ chain in the cytoplasm. Upon the phosphorylation , the Syk tyrosine kinase gets recruited to the ITAMs located on the γ chains. This causes activation of the Syk tyrosine kinase, causing it to phosphorylate. [ 23 ] Syk functions as a signal amplifying kinase activity due to the fact that it targets multiple proteins and causes their activation. [ 24 ] This antigen stimulated phosphorylation causes the activation of other proteins in the FcεR1-mediated signaling cascade. [ 25 ]
An important adaptor protein activated by the Syk phosphorylation step is the linker for activation of T cells (LAT). LAT can be modified by phosphorylation to create novel binding sites. [ 24 ] Phospholipase C gamma (PLCγ) becomes phosphorylated once bound to LAT, and is then used to catalyze phosphatidylinositol bisphosphate breakdown to yield inositol trisphosphate (IP3) and diacyglycerol (DAG). IP3 elevates calcium levels, and DAG activates protein kinase C (PKC). This is not the only way that PKC is made. The tyrosine kinase FYN phosphorylates Grb2-associated-binding protein 2 (Gab2), which binds to phosphoinositide 3-kinase , which activates PKC. PKC leads to the activation of myosin light-chain phosphorylation granule movements, which disassembles the actin–myosin complexes to allow granules to come into contact with the plasma membrane. [ 23 ] The mast cell granule can now fuse with the plasma membrane. Soluble N-ethylmaleimide sensitive fusion attachment protein receptor SNARE complex mediates this process. Different SNARE proteins interact to form different complexes that catalyze fusion. Rab3 guanosine triphosphatases and Rab-associated kinases and phosphatases regulate granule membrane fusion in resting mast cells.
Human mast-cell-specific G-protein-coupled receptor MRGPRX2 plays a key role in the recognition of pathogen associated molecular patterns (PAMPs) and initiating an antibacterial response. MRGPRX2 is able to bind to competence stimulating peptide (CSP) 1 - a quorum sensing molecule (QSM) produced by Gram-positive bacteria. [ 26 ] This leads to signal transduction to a G protein and activation of the mast cell. Mast cell activation induces the release of antibacterial mediators including ROS, TNF-α and PRGD2 which institute the recruitment of other immune cells to inhibit bacterial growth and biofilm formation.
The MRGPRX2 receptor is a possible therapeutic target and can be pharmacologically activated using the agonist compound 48/80 to control bacterial infection. [ 27 ] It is also hypothesised that other QSMs and even Gram-negative bacterial signals can activate this receptor. This might particularly be the case during Bartonella chronic infections where it appears clearly in human symptomatology that these patients all have a mast cell activation syndrome due to the presence of a not yet defined quorum sensing molecule (basal histamine itself?). Those patients are prone to food intolerance driven by another less specific path than the IgE receptor path: certainly the MRGPRX2 route. These patients also show cyclical skin pathergy and dermographism, every time the bacteria exits its hidden intracellular location.
Mast cells are activated in response to infection by pathogenic parasites, such as certain helminths and protozoa , through IgE signaling. [ 28 ] Various species known to be affected include T.spiralis , S.ratti , and S.venezuelensis . [ 28 ] This is accomplished via Type 2 cell-mediated effector immunity, which is characterized by signaling from IL-4 , IL-5 , and IL-13 . [ 28 ] [ 29 ] It is the same immune response that is responsible for allergic inflammation more generally, and includes effectors beyond mast cells. [ 28 ] [ 29 ] In this response, mast cells are known to release significant quantities of IL-4 and IL-13 along with mast cell chymase 1 ( CMA1 ), which is considered to help expel some worms by increasing vascular permeability. [ 28 ]
Mast cell activation disorders ( MCAD ) are a spectrum of immune disorders that are unrelated to pathogenic infection and involve similar symptoms that arise from secreted mast cell intermediates, but differ slightly in their pathophysiology , treatment approach, and distinguishing symptoms. [ 30 ] [ 31 ] The classification of mast cell activation disorders was laid out in 2010. [ 30 ] [ 31 ]
Allergies are mediated through IgE signaling which triggers mast cell degranulation. [ 30 ] Recently, IgE-independent " pseudo-allergic " reactions are thought to also be mediated via the MRGPRX2 receptor activation of mast cells (e.g. drugs such as muscle relaxants , opioids , Icatibant and fluoroquinolones ). [ 32 ]
Many forms of cutaneous and mucosal allergy are mediated in large part by mast cells; they play a central role in asthma , eczema , itch (from various causes), allergic rhinitis and allergic conjunctivitis . Antihistamine drugs act by blocking histamine action on nerve endings. Cromoglicate -based drugs (sodium cromoglicate, nedocromil) block a calcium channel essential for mast cell degranulation, stabilizing the cell and preventing release of histamine and related mediators. Leukotriene antagonists (such as montelukast and zafirlukast ) block the action of leukotriene mediators and are being used increasingly in allergic diseases. [ 7 ]
Calcium triggers the secretion of histamine from mast cells after previous exposure to sodium fluoride. The secretory process can be divided into a fluoride-activation step and a calcium-induced secretory step. It was observed that the fluoride-activation step is accompanied by an elevation of cyclic adenosine monophosphate (cAMP) levels within the cells. The attained high levels of cAMP persist during histamine release. It was further found that catecholamines do not markedly alter the fluoride-induced histamine release. It was also confirmed that the second, but not the first, step in sodium fluoride-induced histamine secretion is inhibited by theophylline. [ 33 ] Vasodilation and increased permeability of capillaries are a result of both H1 and H2 receptor types. [ 34 ]
Stimulation of histamine activates a histamine (H2)-sensitive adenylate cyclase of oxyntic cells, and there is a rapid increase in cellular [cAMP] that is involved in activation of H+ transport and other associated changes of oxyntic cells. [ 35 ]
In anaphylaxis (a severe systemic reaction to allergens , such as nuts, bee stings, or drugs), the body-wide degranulation of mast cells leads to vasodilation and, if severe, symptoms of life-threatening shock . [ 36 ] [ 37 ] Products released from these granules include histamine , serotonin , heparin , chondroitin sulphate , tryptase , chymase , carboxypeptidase , and TNF-α . [ 36 ] These can vary in their quantities and proportions between individuals, which may explain some of the differences in symptoms seen across patients. [ 36 ]
Histamine is a vasodilatory substance released during anaphylaxis. [ 34 ]
Mast cells may be implicated in the pathology associated with autoimmune, inflammatory disorders of the joints. They have been shown to be involved in the recruitment of inflammatory cells to the joints (e.g., rheumatoid arthritis ) and skin (e.g., bullous pemphigoid ), and this activity is dependent on antibodies and complement components. [ 38 ]
Mastocytosis is a rare clonal mast cell disorder involving the presence of too many mast cells ( mastocytes ) and CD34 + mast cell precursors. [ 39 ] Mutations in c-Kit are associated with mastocytosis. [ 30 ] More specifically, the majority (>80%) of patients with mastocytosis have a mutation at codon 816 in the kinase domain of KIT, known as the KIT D816V mutation. [ 40 ] [ 41 ] This mutation, as well as expression of either CD2 or CD25 (confirmed by immunostaining or flow cytometry ), are characteristic of primary clonal/monoclonal mast cell activation syndrome (CMCAS/MMAS). [ 41 ] The most commonly affected organs in mastocytosis are the skin and bone marrow. [ 42 ]
Mastocytomas , or mast cell tumors, can secrete excessive quantities of degranulation products. [ 30 ] [ 31 ] They are often seen in dogs and cats. [ 43 ] Other neoplastic disorders associated with mast cells include mast cell sarcoma and mast cell leukemia .
Mast cell activation syndrome (MCAS) is an idiopathic immune disorder that involves recurrent and excessive mast cell degranulation and which produces symptoms that are similar to other mast cell activation disorders. [ 30 ] [ 31 ] The syndrome is diagnosed based upon four sets of criteria involving treatment response, symptoms, a differential diagnosis , and biomarkers of mast cell degranulation. [ 30 ] [ 31 ]
Mast cells were first described by Paul Ehrlich in his 1878 doctoral thesis on the basis of their unique staining characteristics and large granules. These granules also led him to the incorrect belief that they existed to nourish the surrounding tissue, so he named them Mastzellen (from German Mast ' fattening ' , as of animals). [ 44 ] [ 45 ] They are now considered to be part of the immune system .
Research into an immunological contribution to autism suggests that autism spectrum disorder (ASD) children may present with "allergic-like" problems in the absence of elevated serum IgE and chronic urticaria , suggesting non-allergic mast cell activation in response to environmental and stress triggers. This mast cell activation could contribute to brain inflammation and neurodevelopmental problems. [ 46 ]
Toluidine blue : one of the most common stains for acid mucopolysaccharides and glycoaminoglycans , components of mast cells granules. [ 47 ]
Bismarck brown: stains mast cell granules brown. [ 48 ]
Surface markers: cell surface markers of mast cells were discussed in detail by Heneberg, [ 49 ] claiming that mast cells may be inadvertently included in the stem or progenitor cell isolates, since part of them is positive for the CD34 antigen. The classical mast cell markers include the high-affinity IgE receptor, CD117 (c-Kit), and CD203c (for most of the mast cell populations). Expression of some molecules may change in course of the mast cell activation. [ 50 ]
Mast cell heterogeneity significantly impacts the efficacy of mast cell stabilizing drugs disodium cromoglycate and ketotifen in preventing mediator release. In experiments, ketotifen inhibits mast cells from lung and tonsillar tissues when stimulated via an IgE-dependent histamine release mechanism, while disodium cromoglycate is less effective but still inhibited these mast cells. However, both agents fail to inhibit mediator release from skin mast cells, indicating that these cells are unresponsive to these stabilizers. Such differences in mast cell activation suggests the existence of different mast cell types across various tissues—a topic of ongoing research. [ 51 ] [ 52 ]
Mast cells and enterochromaffin cells are the source of most serotonin in the stomach in rodents . [ 53 ] | https://en.wikipedia.org/wiki/Mast_cell |
Master distiller is a title often used for a distilling expert or a key leader or owner at modern distilleries. The title doesn't have a fixed definition and can mean different things at different companies. [ 1 ] Although the craft of distilling has existed for centuries throughout history, the term "master distiller" only dates back as far as the 1800s when it was first used to acknowledge the distilling expertise and knowledge a person gained after practicing and perfecting the craft of distilling for many years. [ 2 ] In more recent usage, the term can have a much broader meaning and is sometimes used for owners and company leaders who run their companies but do not actively create the distilling recipes and processes used at their distilleries. [ 3 ]
The craft of fermenting and distilling beverages dates back centuries, but the actual term "master distiller" has not been around for nearly as long. The 1867 edition of The English Cyclopaedia (Arts and Sciences section) offers a clear definition of the original meaning of the term: [ 4 ]
"He tests the specific gravity of all the liquids as often as he pleases; he requires that the numerous pipes shall be painted, some black, some red, some blue, and some white, in order that he may know which is for the conveyance of wort, which for wash, which for the first spirit, and which for the finished spirit; he demands the aid of ladders and passages to give him access to every part of every piece of apparatus. In short, the master distiller is so thoroughly controlled in all the operations, that nothing but the prospect of large profits, arising out of a large business, would induce a manufacturer to wear such shackles."
Originally, master distiller was a term most commonly used in relation to bourbon whiskey , both before and after Prohibition in the U.S. , and its historical usage was typically limited to only those who had truly mastered the craft of distilling. In particular, Kentucky bourbon makers often had a hierarchy that consisted of distiller, head distiller, and master distiller. [ 2 ]
Although the level of scientific involvement may vary, master distillers usually supervise the production of the spirits made at their distilleries and are responsible for the final products and their quality. It was once common for master distillers to simply learn through years of hands-on experience, often as apprentices , but now many distillers – even those not labeled as master distillers – have related academic backgrounds with degrees in chemistry , biology , microbiology , food science , or actual distilling. [ 5 ]
At the very least, those with master distiller titles typically have some type of related experience and the skills necessary to manage staff and supervise food safety throughout the distilling process. They also frequently possess the public relations skills needed to communicate with the public and the press. [ 5 ]
A master distiller's exact responsibilities will vary, depending on the company, but common job duties include:
A modern master distiller who fits the traditional definition and actively participates in the production of existing spirits and the creation of new ones often has a background in chemistry and yeast physiology combined with years of distilling experience. However, some learn to master their craft without a formal education or training, instead learning from mentors who train them on the job. Regardless of the method, they learn how to take raw base ingredients, such as various grains for different types of whiskey or sugar cane for rum , and create fermented washes designed to produce spirits with very specific desired characteristics. [ 6 ]
The spirit produced at different points in the distillation process varies in quality and has different characteristics. Making "cuts" to the distilled spirit to separate the heads (foreshots), hearts, and tails (feints) is an important part of the process that is often supervised by master distillers. They also choose the type of container for aging, such as wooden casks , and make decisions about blending, filtration , coloring , and bottling . [ 6 ]
Even when master distillers entrust recipe-based decisions on malting , fermentation, maturation, and blending to other experts on their teams, they are generally responsible for the quality of the final product. They usually source the raw materials themselves and work with tasters on quality control to ensure consistent quality and flavor across all batches. They also have to ensure the distillery maintains the proper facilities and equipment for long-term storage for products that require aging. [ 5 ]
Master distillers often participate in the development of marketing campaigns and financing initiatives for new and existing products. With a goal of maximizing the value of the spirits produced by the distillery, they often incorporate the opinions of marketing teams and tasters into the product development phases. [ 5 ]
Additionally, master distillers often serve as the "face" of the distillery, meaning they are usually the recognizable person who interacts with the public and the press at tastings, product launch events, trade shows , and other key events. They work with everyone from customers to wholesalers and sometimes even other distilleries to promote products and gain a loyal following of satisfied customers. [ 5 ]
In addition to managing staff, master distillers are often responsible for managing the day-to-day operations of the distillery, including handling finances and organizing distribution systems . They may have varying levels of involvement in the distilling process but usually at least manage the distilling team and plan staff training and development for a range of duties, including distillery functions like mashing and fermenting and administrative functions like accounting . Ensuring the team meets food safety standards at all times is also a key responsibility. [ 5 ]
On an administrative level, master distillers are sometimes in charge of regulatory paperwork to ensure all spirits remain in compliance with government rules and standards. The information that is monitored includes details about raw ingredients, equipment, and final product specifications. [ 6 ] Master distillers either record each phase of the distillation process themselves or assign this duty to someone else. Detailed records are necessary to ensure the right procedures are followed to create products that meet all the quality and food safety guidelines. [ 5 ]
In 2019 Discovery Channel (owned by Warner Brothers ) debuted a reality based competition show called Moonshiners: Master Distillers [ 7 ] [ 8 ] . The show is currently in its 5th season in 2023.
Various schools and institutes offer programs to teach distilling. Additionally, some distilleries offer educational programs, often combined with on-the-job training . [ 9 ] [ 10 ]
Jeff Arnett is the seventh Master Distiller in the history of the Jack Daniel Distillery , [ 11 ] having served in the position since 2008. He was honored by Whisky Magazine as "Master Distiller of the Year" in 2017. [ 12 ]
Don Facundo Bacardi Masso – Spanish by birth, the namesake of Bacardi rum emigrated to Cuba and opened a general store with his brothers in the early 1800s. In 1862, Bacardi purchased a small distillery and worked with Jose Leon Boutellier to create the charcoal mellowing distilling technique used to make the world's first white rum . [ 13 ]
James B. Beam – The Beam family has been distilling bourbon in Kentucky for more than two centuries. James Beauregard Beam, the namesake of the Jim Beam brand, revived the company after Prohibition. [ 14 ]
Joseph L. Beam – Another member of the Kentucky Beam family, Joseph was the original master distiller at Heaven Hill Distillery, the company he founded with Ed Shapira after Prohibition ended. Many of the company's brands are named after notable local distillers, including Evan Williams, Elijah Craig, and J.W. Dant. [ 15 ]
John Brannick – The co-founder and master distiller of Dublin Whiskey Distillery Company for many years beginning in 1872, Brannick produced D.W.D. Whisky for the company before leaving in 1887 to reopen Banagher Distillery. [ 16 ]
Vanessa Braxton – Declared the first female African-American master distiller and blender of a nationally distributed vodka within the United States by the New York Legislature. Today, Braxton owns and operates Black Momma Vodka, which she founded in 2013. [ 17 ] [ 18 ]
Elijah Craig – Craig was a Baptist minister in an eastern Kentucky county that was originally part of Virginia. Also a whiskey distiller, he is labeled the "Father of Bourbon" by maker Heaven Hill Distillery, who adds that note to most of its Elijah Craig labels . [ 19 ]
Don Jose Antonio de Cuervo – The namesake of Jose Cuervo tequila received the land grant for growing blue agave plants from the king of Spain in 1758. Jose Cuervo celebrated its 250th birthday in 2009. [ 20 ] [ 21 ]
Jack Daniel – After learning the craft of distilling from Nearest Green, Daniel went on to establish his own distillery with Green by his side. Today, the top-selling Jack Daniel's Old No. 7 whiskey is one of several whiskeys bearing the Jack Daniel name. [ 22 ]
J.W. Dant – 1830s bourbon distiller J.W. Dant used hollowed out logs instead of copper pot stills to distill bourbon. Today, J.W. Dant is a rye-based bourbon with an inexpensive price point. [ 23 ]
Marianne Barnes Eaves – Formerly the master distiller at Castle & Key Distillery in Frankfort, Kentucky , in 2016, Eaves became the first female bourbon master distiller in the state since before Prohibition. [ 24 ]
William Grant – The Scottish founder of William Grant & Sons – the parent company of Glenfiddich Scotch whisky – built the original distillery by hand in 1886 with the help of five of his nine children. [ 25 ] [ 26 ]
Nathan "Nearest" Green – The actual first master distiller of Jack Daniel's whiskey went unacknowledged for more than a century, but Brown-Forman – the owner of Jack Daniel's – officially recognized Green, an African American former slave, as the mentor of a young Jack Daniel in May 2017. Two new whiskeys named after Green – Uncle Nearest 1856 aged whiskey and Uncle Nearest 1856 silver whiskey – were released the same year. [ 22 ]
John Jameson – Scottish by birth, Jameson took over management of the Bow Street Distillery in Dublin after marrying Margaret Haig, a cousin of the owners. Jameson Irish Whiskey was created at the distillery under his tutelage. [ 27 ]
Elmer T. Lee was a master distiller at Buffalo Trace Distillery famous for launching Blanton's , the first modern bourbon brand marketed as a single barrel bourbon. [ 28 ]
Colonel James E. Pepper – Pepper was known for his flamboyance and bold claims about his family's whiskey, Old Pepper. He also claimed his family's distillery was the largest in the world and the oldest in the United States [ 29 ]
Benjamin Prichard – Prichard originally distilled whiskey in the early 1800s in Davidson County, Tennessee . In 1997, his descendant, Phil Prichard, rejuvenated the family's distilling business in Kelso, Tennessee . Today, Prichard's distills rums and liqueurs in addition to Tennessee whiskeys . [ 30 ] [ 31 ]
Jimmy Russell – As master distiller at Wild Turkey , Russel has decades of hands-on distilling experience. His son, Eddie Russell, also became a master distiller for the company in 2015. [ 32 ] [ 3 ]
Jim Rutledge — Master distiller for over 20 years at Four Roses .
Don Cenobio Sauza – Often referred to as the "Father of Tequila", Sauza experimented with different varieties of plants before settling on mezcal azul as the one that produced the best flavor. This ultimately led to the exclusive use of this type of agave plant to make tequila . [ 33 ]
Charles Tanqueray – Tanqueray established his London gin distillery in the Bloomsberg area in 1830. As of 2016, the United States was the largest market for Tanqueray gin . [ 34 ]
Evan Williams – A Welsh immigrant and the first wharf master of Louisville, Kentucky , Williams started distilling in the late 1700s in Kentucky. The black label Evan Williams bottle claims he was Kentucky's first distiller in 1783. [ 35 ] | https://en.wikipedia.org/wiki/Master_distiller |
A master mix is a mixture containing precursors and enzymes used as an ingredient in polymerase chain reaction techniques in molecular biology. Such mixtures contain a mixture dNTPs (required as a substrate for the building of new DNA strands), MgCl 2 , Taq polymerase (an enzyme required to building new DNA strands), a pH buffer and come mixed in nuclease -free water. [ 1 ] [ 2 ] [ 3 ] [ 4 ]
Master mixes for real-time PCR include a fluorescent compound (frequently SYBR green ), and the choice of mix also influence test sensitivity and consistency. [ 5 ]
Differences in the choice of master mixes can sometimes explain difference in experimental results, a particular case being the measurement of telomere length. [ 6 ] [ 7 ]
This molecular biology article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Master_mix_(PCR) |
A Master of Bioscience Enterprise (abbreviated MBE or MBioEnt ) is a specialised degree taught at The University of Auckland , New Zealand, Karolinska Institute , Sweden and The University of Cambridge , United Kingdom. The MBE is an interdisciplinary programme incorporating multiple faculties and includes significant industry involvement.
The degree is primarily focused on the commercialisation of biotechnology. Both universities have developed the MBE programme to provide specialist business and legal skills relevant to employment in the bio-economy. The context in which both programmes were developed are significantly different. These differences are reflected in internship placements, thesis topics and postgraduate employment opportunities. [ 1 ]
Inaugurated in 2006, the MBE programme was developed in partnership between the School of Biological Sciences (SBS), the Business School and the Law School. [ 1 ] [ 2 ]
The prerequisite for the first year (the Postgraduate Diploma ) is a Bachelor of Science with a major or specialisation in Biological Sciences, Bioinformatics, Biomedical Science, Food Science, Medicinal Chemistry, Pharmacology or Physiology; a Bachelor of Engineering in Biomedical Engineering; a Bachelor of Pharmacy; or a Bachelor of Technology in Biotechnology. The Postgraduate Diploma of Bioscience Enterprise is required for entry into the Masters year. Associate degrees are also available.
There is an academic component in both the Post Graduate Diploma and Masters year.
The Postgraduate Diploma year has five core papers required for the Postgraduate Diploma in Bioscience Enterprise. Students are also required to take three electives, which are generally science-based papers.
SCIENT 701 (15 points)
Accounting and Finance for Scientists SCIENT 702 (15 points)
Marketing for Scientific and Technical Personnel SCIENT 703 (15 points)
Frontiers in Biotechnology SCIENT 704 (15 points)
Law and Intellectual Property SCIENT 705 (15 points)
Research Commercialisation SCIENT 706 (15 Points)
Commercialisation Project
SCIENT 720 (15 Points)
Science Enterprise Research Methods SCIENT 721 (15 points)
Product Development and Regulatory Environments SCIENT 722 (15 points)
Current Issues in Bioscience Enterprise
SCIENT 794 A & B(90 points) The thesis component requires students to undertake a research project within an industry organisation. Topics vary and have included a wide variety of areas.
In the Masters year (year two), students undertake an internship within the biotechnology industry either in New Zealand or internationally for six months. During the internships, students complete a project for the company which generally relates to and influences the thesis topic, which is written during the internship period.
Two awards are given annually. The Baldwins award is given to the top achiever in Law and Intellectual Property. The award is designed to reward excellence in IP and encourage the graduates to consider future employment in this area. [ 3 ] The second award is given to the student with the best Masters thesis.
Founded in 2002, the MBE course is delivered by faculty of the Institute of Biotechnology and Judge Business School. [ 4 ]
Students’ progress is continuously assessed, and feedback and marks from each module are provided to the students throughout the programme. There are no formal written examinations.
Students undertake an internship placement with a company or organisation, conducting research on a project of real commercial interest . The internship provides experience of working in a business environment as well as an opportunity to collect data as the basis for a dissertation. Students may opt, circumstances permitting, to work within multinational companies, start-ups, small to medium-sized enterprises or service providers to the biotech sector, such as accounting, legal or IP practices. Normally students spend 4 – 6 weeks with a company and are encouraged to put into practise the lessons learnt from the academic aspects of the programme as well as to demonstrate original research and analysis. The dissertation is an important component of programme assessment and contributes 30% of the total marks. | https://en.wikipedia.org/wiki/Master_of_Bioscience_Enterprise |
Master of Business Informatics ( MBI ) is a postgraduate degree in Business Informatics (BI). BI programs combine information technology (IT) and management courses and are common in central Europe. [ 1 ] The first master programs in Business Informatics were offered by the University of Rostock , as a face-to-face program, and by the Virtual Global University (VGU) together with the European University Viadrina Frankfurt (Oder) as an online program (see virtual education ).
An MBI programme, which includes inter-cultural studies affecting business operations in European markets, was first offered by Dublin City University . Within the Bologna process , many Central European universities have been, or are in the process of, setting up master programmes in Business Informatics. Due to legal frameworks and restrictions, however, most of these programs are forced to award an M.Sc. degree instead of an MBI degree.
A typical MBI program is the VGU 's "International Master of Business Informatics" program in Germany. Since this program was set up and accredited in accordance with nationwide guidelines for content and structure, it reflects well the state-of-the-art of Business Informatics master programs. If studied full-time, the MBI program is a four-semester program and can be composed of courses from the following areas of study. [ 2 ] Another typical MBI program is the MIAGE [ 3 ] (Méthodes Informatiques Appliquées à la Gestion des Entreprises) program in France, present in more than 20 universities ( MIAGE Toulouse , MIAGE Nancy , MIAGE Paris Ouest Nanterre La Défense , MIAGE Dauphine , MIAGE Aix-Marseille , MIAGE Grenoble Alpes , MIAGE Sorbonne , MIAGE Lille , MIAGE Rennes , MIAGE Bordeaux ).
Some MBI programs are organized in tracks or profiles, guiding the students in the design of their master study plan. This is the case of the "Master in Business Informatics" [ 4 ] in Utrecht University , which allows students to specialize in one of the following four career areas: [ 5 ] business consultant (provides business advice from an ICT perspective), IT consultant (provides ICT advice from a business perspective), entrepreneur (independent entrepreneur who develops ICT products), and IT researcher (continuing with a PhD or targeting a research and development department in a software company).
Courses may include topics like applied computer science, computer networks and Internet technology , website engineering, programming, or information security.
Courses may focus on information systems development, database management, information systems architectures, business intelligence, or business process modelling.
Management oriented topics may be studied in courses on management information systems, information management, project management, management control, knowledge management, management and organization of IT departments, or software engineering management.
Important application domains of Business Informatics may be investigated in courses like enterprise resource planning, e-commerce and e-business networking, industrial information systems, or electronic finance/electronic banking.
Graduates in Business Informatics can fill positions like information manager, systems analyst, systems designer, project manager, business solutions developer, IT entrepreneur, IS specialist, consultant in areas like enterprise resource planning, supply chain management, customer relationship management, or knowledge management. | https://en.wikipedia.org/wiki/Master_of_Business_Informatics |
Master of Business Systems ( MBS ) is a Postgraduate / Master's degree in Business Systems.
Business Systems programs combine Information Technology (IT) and Business / Management courses and are common in Australia .
This article relating to education is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Master_of_Business_Systems |
In genetics , a master regulator gene is a regulator gene at the top of a gene regulation hierarchy, particularly in regulatory pathways related to cell fate and differentiation .
Most genes considered master regulators code for transcription factor proteins, which in turn alter the expression of downstream genes in the pathway. [ 1 ] Canonical examples of master regulators include Oct-4 (also called POU5F1), SOX2 , and NANOG , all transcription factors involved in maintaining pluripotency in stem cells . [ 1 ] Master regulators involved in development and morphogenesis can also appear as oncogenes relevant to tumorigenesis and metastasis , as with the Twist transcription factor . [ 2 ]
Other genes reported as master regulators code for SR proteins , which function as splicing factors , [ 3 ] and some noncoding RNAs . [ 4 ]
The master regulator concept has been criticized for being a "simplified paradigm" that fails to account for the multifactorial influences on some cell fates. [ 5 ] | https://en.wikipedia.org/wiki/Master_regulator_gene |
In mathematics, the master stability function is a tool used to analyze the stability of the synchronous state in a dynamical system consisting of many identical systems which are coupled together, such as the Kuramoto model .
The setting is as follows. Consider a system with N {\displaystyle N} identical oscillators. Without the coupling, they evolve according to the same differential equation , say x ˙ i = f ( x i ) {\displaystyle {\dot {x}}_{i}=f(x_{i})} where x i {\displaystyle x_{i}} denotes the state of oscillator i {\displaystyle i} . A synchronous state of the system of oscillators is where all the oscillators are in the same state.
The coupling is defined by a coupling strength σ {\displaystyle \sigma } , a matrix A i j {\displaystyle A_{ij}} which describes how the oscillators are coupled together, and a function g {\displaystyle g} of the state of a single oscillator. Including the coupling leads to the following equation:
It is assumed that the row sums ∑ j A i j {\displaystyle \sum _{j}A_{ij}} vanish so that the manifold of synchronous states is neutrally stable.
The master stability function is now defined as the function which maps the complex number γ {\displaystyle \gamma } to the greatest Lyapunov exponent of the equation
The synchronous state of the system of coupled oscillators is stable if the master stability function is negative at σ λ k {\displaystyle \sigma \lambda _{k}} where λ k {\displaystyle \lambda _{k}} ranges over the eigenvalues of the coupling matrix A {\displaystyle A} . | https://en.wikipedia.org/wiki/Master_stability_function |
In telecommunications , a master station is a station that controls or coordinates the activities of other stations in the system.
Examples:
In data transmission, a master station can be set to not wait for a reply from a slave station after transmitting each message or transmission block . In this case the station is said to be in "continuous operation". [ 2 ]
This article incorporates public domain material from Federal Standard 1037C . General Services Administration . Archived from the original on 22 January 2022. | https://en.wikipedia.org/wiki/Master_station |
Mastering , a form of audio post production , is the process of preparing and transferring recorded audio from a source containing the final mix to a data storage device (the master ), the source from which all copies will be produced (via methods such as pressing, duplication or replication ). In recent years, digital masters have become usual, although analog masters—such as audio tapes—are still being used by the manufacturing industry, particularly by a few engineers who specialize in analog mastering. [ 1 ]
Mastering requires critical listening; however, software tools exist to facilitate the process. Results depend upon the intent of the engineer, their skills, the accuracy of the speaker monitors, and the listening environment. Mastering engineers often apply equalization and dynamic range compression in order to optimize sound translation on all playback systems. [ 2 ] It is standard practice to make a copy of a master recording—known as a safety copy—in case the master is lost, damaged or stolen.
In the earliest days of the recording industry, all phases of the recording and mastering were entirely mechanical processes. Performers sang or played into a large acoustic horn and the master recording was created by the transfer of acoustic energy from the diaphragm of the recording horn to the mastering lathe , typically located in an adjoining room. The cutting head, driven by the energy from the horn, inscribed a modulated groove into the surface of a rotating cylinder or disc. [ 3 ] These masters were usually made from either a soft metal alloy or from wax ; this gave rise to the colloquial term waxing , referring to the cutting of a record. [ 4 ]
After the introduction of the microphone and electronic amplifier in the mid-1920s, the mastering process became electro-mechanical, and electrically driven mastering lathes came into use for cutting master discs (the cylinder format by then having been superseded). Until the introduction of tape recording, master recordings were almost always cut direct-to-disc . [ 3 ] Only a small minority of recordings were mastered using previously recorded material sourced from other discs.
In the late 1940s, the recording industry was revolutionized by the introduction of magnetic tape . Magnetic tape was invented for recording sound by Fritz Pfleumer in 1928 in Germany, based on the invention of magnetic wire recording by Valdemar Poulsen in 1898. Not until the end of World War II could the technology be found outside Europe. The introduction of magnetic tape recording enabled master discs to be cut separately in time and space from the actual recording process. [ 3 ]
Although tape and other technical advances dramatically improved the audio quality of commercial recordings in the post-war years, the basic constraints of the electro-mechanical mastering process remained, and the inherent physical limitations of the main commercial recording media—the 78 rpm disc and later the 7-inch 45 rpm single and 33-1/3 rpm LP record —meant that the audio quality, dynamic range , [ a ] and running time [ b ] of master discs were still limited compared to later media such as the compact disc .
From the 1950s until the advent of digital recording in the late 1970s, the mastering process typically went through several stages. Once the studio recording on multi-track tape was complete, a final mix was prepared and dubbed down to the master tape, usually either a single-track mono or two-track stereo tape. Prior to the cutting of the master disc, the master tape was often subjected to further electronic treatment by a specialist mastering engineer.
After the advent of tape it was found that, especially for pop recordings, master recordings could be made so that the resulting record would sound better. This was done by making fine adjustments to the amplitude of sound at different frequency bands ( equalization ) prior to the cutting of the master disc.
In large recording companies such as EMI , the mastering process was usually controlled by specialist staff technicians who were conservative in their work practices. These big companies were often reluctant to make changes to their recording and production processes. For example, EMI was very slow in taking up innovations in multi-track recording [ c ] and did not install 8-track recorders in their Abbey Road Studios until the late 1960s, more than a decade after the first commercial 8-track recorders were installed by American independent studios. [ 5 ]
In the 1990s, electro-mechanical processes were largely superseded by digital technology, with digital recordings stored on hard disk drives or digital tape and mastered to CD . The digital audio workstation (DAW) became common in many mastering facilities, allowing the off-line manipulation of recorded audio via a graphical user interface (GUI). Although many digital processing tools are common during mastering, it is also very common to use analog media and processing equipment for the mastering stage. Just as in other areas of audio, the benefits and drawbacks of digital technology compared to analog technology are still a matter for debate. However, in the field of audio mastering, the debate is usually over the use of digital versus analog signal processing rather than the use of digital technology for storage of audio. [ 2 ]
Digital systems have higher performance and allow mixing to be performed at lower maximum levels. When mixing to 24-bits with peaks between −3 and −10 dBFS on a mix, the mastering engineer has enough headroom to process and produce a final master. [ 6 ] Mastering engineers recommend leaving enough headroom on the mix to avoid distortion. [ 7 ] The reduction of dynamics by the mix or mastering engineer has resulted in a loudness war in commercial recordings. [ 8 ]
The source material, ideally at the original resolution , is processed using equalization, compression , limiting and other processes. Additional operations, such as editing , specifying the gaps between tracks, adjusting level, fading in and out, noise reduction and other signal restoration and enhancement processes can also be applied as part of the mastering stage. [ 8 ] The source material is put in the proper order, commonly referred to as assembly (or 'track') sequencing. These operations prepare the music for either digital or analog, e.g. vinyl, replication.
If the material is destined for vinyl release, additional processing, such as dynamic range reduction or frequency-dependent stereo–to–mono fold-down and equalization may be applied to compensate for the limitations of that medium. For compact disc release, start of track , end of track , and indexes are defined for playback navigation along with International Standard Recording Code (ISRC) and other information necessary to replicate a CD . Vinyl LP and cassettes have their own pre-duplication requirements for a finished master. Subsequently, it is rendered either to a physical medium, such as a CD-R or DVD-R, or to computer files, such as a Disc Description Protocol (DDP) file set or an ISO image . Regardless of what delivery method is chosen, the replicator factory will transfer the audio to a glass master that will generate metal stampers for replication.
The process of audio mastering varies depending on the specific needs of the audio to be processed. Mastering engineers need to examine the types of input media, the expectations of the source producer or recipient, the limitations of the end medium and process the subject accordingly. General rules of thumb can rarely be applied.
Steps of the process typically include the following:
Examples of possible actions taken during mastering: [ 8 ]
A mastering engineer is a person skilled in the practice of taking audio (typically musical content) that has been previously mixed in either the analogue or digital domain as mono, stereo, or multichannel formats and preparing it for use in distribution , whether by physical media such as a CD, vinyl record, or as some method of streaming audio.
The mastering engineer is responsible for a final edit of a product and preparation for manufacturing copies. Although there are no official requirements to work as an audio mastering engineer, practitioners often have comprehensive domain knowledge of audio engineering, and in many cases, may hold an audio or acoustic engineering degree . Most audio engineers master music or speech audio material. The best mastering engineers might possess arrangement and production skills, allowing them to troubleshoot mix issues and improve the final sound. Generally, good mastering skills are based on experience, resulting from many years of practice.
Generally, mastering engineers use a combination of specialized audio-signal processors, low-distortion-high-bandwidth loudspeakers (and corresponding amplifiers with which to drive them), within a dedicated, acoustically-optimized playback environment. The equipment and processors used within the field of mastering are almost entirely dedicated to the purpose; engineered to a high standard, often possessing low signal-to-noise ratios [at nominal operating levels] and in many cases, the incorporation of parameter-recall, such as indented potentiometers, or in some more-sophisticated designs, via a digital-controller. Some advocates for digital software claim that plug-ins are capable of processing audio in a mastering context, though without the same degree of signal degradation as those introduced from processors within the analog domain. The quality of the results varies according to the algorithms used within these processors, which in some cases, can introduce distortions entirely exclusive to the digital domain.
Real-time analyzers , phase oscilloscopes , and also peak, RMS, VU and K meters are frequently used within the audio analysis stage of the process as a means of rendering a visual representation of the audio, or signal, being analyzed.
Most mastering engineer accolades are given for their ability to make a mix consistent with respect to subjective factors based on the perception of listeners, regardless of their playback systems and the environment. This is a difficult task due to the varieties of systems now available and the effect it has on the apparent qualitative attributes of the recording . For instance, a recording that sounds great on one speaker / amplifier combination playing CD audio, may sound drastically different on a computer-based system playing back a low- bitrate MP3 . Some engineers maintain that the main mastering engineer's task is to improve upon playback systems translations while the position of others is to make a sonic impact. [ 9 ]
Prolonged periods of listening to improperly mastered recordings usually leads to hearing fatigue that ultimately takes the pleasure out of the listening experience. [ 10 ] | https://en.wikipedia.org/wiki/Mastering_(audio) |
The Harold Masursky Award for Meritorious Service to Planetary Science , usually called the Masursky Award, is awarded annually by the Division for Planetary Sciences (DPS) of the American Astronomical Society . The award for Meritorious Service to Planetary Science was established by the DPS to recognize and honor individuals who have rendered outstanding service to planetary science and exploration through engineering, managerial, programmatic, or public service activities. [ 1 ] For purposes of this award, planetary science and exploration refers to the multidisciplinary study of the Solar System and its members, excluding work dealing primarily with the Sun or the Earth . It was named in honor of Harold Masursky . The award has been given annually since 1991, except 2001, 2002, and 2009.
Source: American Astronomical Society | https://en.wikipedia.org/wiki/Masursky_Award |
The Matalon–Matkowsky–Clavin–Joulin theory refers to a theoretical hydrodynamic model of a premixed flame with a large-amplitude flame wrinkling, developed independently by Moshe Matalon & Bernard J. Matkowsky and Paul Clavin & Guy Joulin , [ 1 ] [ 2 ] following the pioneering study by Paul Clavin and Forman A. Williams [ 3 ] and by Pierre Pelcé and Paul Clavin . [ 4 ] The theory, for the first time, calculated the burning rate of the curved flame that differs from the burning rate of the planar flame due to flame stretch , associated with the flame curvature and the strain imposed on the flame by the flow field. [ 5 ]
According to Matalon–Matkowsky–Clavin–Joulin theory, if S L {\displaystyle S_{L}} and δ L {\displaystyle \delta _{L}} are the laminar burning speed and thickness of a planar flame (and τ L = D T , u / S L 2 {\displaystyle \tau _{L}=D_{T,u}/S_{L}^{2}} be the corresponding flame residence time with D T , u {\displaystyle D_{T,u}} being the thermal diffusivity in the unburnt gas), then the burning speed S T {\displaystyle S_{T}} for the curved flame with respect to the unburnt gas is given by [ 6 ] [ page needed ]
where n {\displaystyle \mathbf {n} } is the unit normal to the flame surface (pointing towards the burnt gas side), v {\displaystyle \mathbf {v} } is the flow velocity field evalauted at the flame surface and M c {\displaystyle {\mathcal {M}}_{c}} and M s {\displaystyle {\mathcal {M}}_{s}} are the two Markstein numbers , associated with the curvature term ∇ ⋅ n {\displaystyle \nabla \cdot \mathbf {n} } and the term n n : ∇ v {\displaystyle \mathbf {n} \mathbf {n} :\nabla \mathbf {v} } corresponding to flow strain imposed on the flame. [ 7 ] | https://en.wikipedia.org/wiki/Matalon–Matkowsky–Clavin–Joulin_theory |
In metadata , a match report is a report that compares two distinct data dictionaries and creates a list of the data elements that have been identified as semantically equivalent .
Match reports are critical for systems that wish to automatically exchange data, such as intelligent software agents. [ 1 ] If one computer system is requesting a report from a remote system that uses a distinct data dictionary and all of the data elements on the report manifest are included in the match report the report request can be executed.
Match reports are useful if data dictionaries use a metadata tagging system such as the UDEF . [ 2 ]
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Match_report |
Matched molecular pair analysis ( MMPA ) is a method in cheminformatics that compares the properties of two molecules that differ only by a single chemical transformation, such as the substitution of a hydrogen atom by a chlorine one. Such pairs of compounds are known as matched molecular pairs (MMP). Because the structural difference between the two molecules is small, any experimentally observed change in a physical or biological property between the matched molecular pair can more easily be interpreted. The term was first coined by Kenny and Sadowski in the book Chemoinformatics in Drug Discovery . [ 1 ]
MMP can be defined as a pair of molecules that differ in only a minor single point change (See Fig 1). Matched molecular pairs (MMPs) are widely used in medicinal chemistry to study changes in compound properties which includes biological activity , toxicity, environmental hazards and much more, which are associated with well-defined structural modifications. Single point changes in the molecule pairs are termed a chemical transformation or Molecular transformation. Each molecular pair is associated with a particular transformation. An example of transformation is the replacement of one functional group by another. More specifically, molecular transformation can be defined as the replacement of a molecular fragment having one, two or three attachment points with another fragment. Useful Molecular transformation in a specified context is termed as "Significant" transformations. For example, a transformation may systematically decrease or increase a desired property of chemical compounds. Transformations that affect a particular property/activity in a statistically significant sense are called as significant transformations. The transformation is considered significant, if it increases the property value "more often" than it decreases it or vice versa. Thus, the distribution of increasing and decreasing pairs should be significantly different from the binomial ("no effect") distribution with a particular p-value (usually 0.05).
MMP based analysis is an attractive method for computational analysis because they can be algorithmically generated and they make it possible to associate defined structural modifications at the level of compound pairs with chemical property changes, including biological activity. [ 2 ] [ 3 ] [ 4 ]
MMPA is quite useful in the field of quantitative structure–activity relationship (QSAR) modelling studies. One of the issues of QSAR models is they are difficult to interpret in a chemically meaningful manner. While it can be pretty easy to interpret simple linear regression models, the most powerful algorithms like neural networks , support vector machine are similar to "black boxes", which provide predictions that can't be easily interpreted. [ 5 ] This problem undermines the applicability of QSAR model in helping the medicinal chemist to make the decision. If the compound is predicted to be active against some microorganism, what are the driving factors of its activity? Or if it is predicted to be inactive, how its activity can be modulated? The black box nature of the QSAR model prevents it from addressing these crucial issues. The use of predicted MMPs allows to interpret models and identify which MMPs were learned by the model. [ 6 ] The MMPs, which were not reproduced by the model, could correspond to experimental errors or deficiency of the model (inappropriate descriptors, too few data, etc.). [ citation needed ]
Analysis of MMPs (matched molecular pair) can be very useful for understanding the mechanism of action. A medicinal chemist might be interested particularly in "activity cliff". Activity cliff is a minor structural modification, which changes the target activity significantly. [ citation needed ]
Activity cliffs are pairs or groups of compounds that are highly similar in the structures but have large different in potency towards the same target. [ 7 ] Activity cliffs received great attention in computational chemistry and drug discovery as they represent a discontinuity in structure-activity relationship (SAR). [ 7 ] This discontinuity also indicates high SAR information content, because small chemical changes in the set of similar compounds lead to large changes in activity. The assessment of activity cliffs requires careful consideration of similarity and potency difference criteria. [ 8 ] [ 9 ] [ 10 ]
Matched molecular pair (MMPA) analyses can be classified into two types: supervised and unsupervised MMPA.
In supervised MMPA, the chemical transformations are predefined, then the corresponding matched pair compounds are found within the data set and the change in end point computed for each transformation. [ citation needed ]
Also known as automated MMPAs. A machine learning algorithm is used to finds all possible matched pairs in a data set according to a set of predefined rules. This results in much larger numbers of matched pairs and unique transformations, which are typically filtered during the process to identify those transformations that correspond to statistically significant changes in the targeted property with a reasonable number of matched pairs. [ citation needed ]
Here instead of looking at the pair of molecules which differ only at one point, a series of more than 2 molecules different at a single point is considered. The concept of matching molecular series was introduced by Wawer and Bajorath. [ 11 ] It is argued that longer matched series is more likely to exhibit preferred molecular transformation while, matched pairs exhibit only a small preference. [ 12 ]
The application of the MMPA across large chemical databases for the optimization of ligand potency is problematic because same structural transformation may increase or decrease or doesn't affect the potency of different compounds in the dataset. Selection of practical significant transformation from a dataset of molecules is a challenging issue in the MMPA. Moreover, the effect of a particular molecular transformation can significantly depend on the Chemical context of transformations. [ 13 ] [ 14 ]
Beside these, MMPA might pose some limitations in terms of computational resources, especially when dealing with databases of compounds with a large number of breakable bonds. Further, more atoms in the variable part of the molecule also leads to combinatorial explosion problems. To deal with this, the number of breakable bonds and number of atoms in the variable part can be used to pre-filter the database. | https://en.wikipedia.org/wiki/Matched_molecular_pair_analysis |
In mathematics , the matching distance [ 1 ] [ 2 ] is a metric on the space of size functions .
The core of the definition of matching distance is the observation that the
information contained in a size function can be combinatorially stored in a formal series of lines and points of the plane, called respectively cornerlines and cornerpoints .
Given two size functions ℓ 1 {\displaystyle \ell _{1}} and ℓ 2 {\displaystyle \ell _{2}} , let C 1 {\displaystyle C_{1}} (resp. C 2 {\displaystyle C_{2}} ) be the multiset of
all cornerpoints and cornerlines for ℓ 1 {\displaystyle \ell _{1}} (resp. ℓ 2 {\displaystyle \ell _{2}} ) counted with their
multiplicities, augmented by adding a countable infinity of points of the
diagonal { ( x , y ) ∈ R 2 : x = y } {\displaystyle \{(x,y)\in \mathbb {R} ^{2}:x=y\}} .
The matching distance between ℓ 1 {\displaystyle \ell _{1}} and ℓ 2 {\displaystyle \ell _{2}} is given by d match ( ℓ 1 , ℓ 2 ) = min σ max p ∈ C 1 δ ( p , σ ( p ) ) {\displaystyle d_{\text{match}}(\ell _{1},\ell _{2})=\min _{\sigma }\max _{p\in C_{1}}\delta (p,\sigma (p))} where σ {\displaystyle \sigma } varies among all the bijections between C 1 {\displaystyle C_{1}} and C 2 {\displaystyle C_{2}} and
Roughly speaking, the matching distance d match {\displaystyle d_{\text{match}}} between two size functions is the minimum, over all the matchings
between the cornerpoints of the two size functions, of the maximum
of the L ∞ {\displaystyle L_{\infty }} -distances between two matched cornerpoints. Since
two size functions can have a different number of cornerpoints,
these can be also matched to points of the diagonal Δ {\displaystyle \Delta } . Moreover, the definition of δ {\displaystyle \delta } implies that matching two points of the diagonal has no cost. | https://en.wikipedia.org/wiki/Matching_distance |
In the mathematical fields of graph theory and combinatorics , a matching polynomial (sometimes called an acyclic polynomial ) is a generating function of the numbers of matchings of various sizes in a graph. It is one of several graph polynomials studied in algebraic graph theory .
Several different types of matching polynomials have been defined. Let G be a graph with n vertices and let m k be the number of k -edge matchings.
One matching polynomial of G is
Another definition gives the matching polynomial as
A third definition is the polynomial
Each type has its uses, and all are equivalent by simple transformations. For instance,
and
The first type of matching polynomial is a direct generalization of the rook polynomial .
The second type of matching polynomial has remarkable connections with orthogonal polynomials . For instance, if G = K m , n , the complete bipartite graph , then the second type of matching polynomial is related to the generalized Laguerre polynomial L n α ( x ) by the identity:
If G is the complete graph K n , then M G ( x ) is an Hermite polynomial:
where H n ( x ) is the "probabilist's Hermite polynomial" (1) in the definition of Hermite polynomials . These facts were observed by Godsil (1981) .
If G is a forest , then its matching polynomial is equal to the characteristic polynomial of its adjacency matrix .
If G is a path or a cycle , then M G ( x ) is a Chebyshev polynomial . In this case
μ G (1, x ) is a Fibonacci polynomial or Lucas polynomial respectively.
The matching polynomial of a graph G with n vertices is related to that of its complement by a pair of (equivalent) formulas. One of them is a simple combinatorial identity due to Zaslavsky (1981) . The other is an integral identity due to Godsil (1981) .
There is a similar relation for a subgraph G of K m , n and its complement in K m , n . This relation, due to Riordan (1958), was known in the context of non-attacking rook placements and rook polynomials.
The Hosoya index of a graph G , its number of matchings, is used in chemoinformatics as a structural descriptor of a molecular graph. It may be evaluated as m G (1) ( Gutman 1991 ).
The third type of matching polynomial was introduced by Farrell (1980) as a version of the "acyclic polynomial" used in chemistry .
On arbitrary graphs, or even planar graphs , computing the matching polynomial is #P-complete ( Jerrum 1987 ). However, it can be computed more efficiently when additional structure about the graph is known. In particular,
computing the matching polynomial on n -vertex graphs of treewidth k is fixed-parameter tractable : there exists an algorithm whose running time, for any fixed constant k , is a polynomial in n with an exponent that does not depend on k ( Courcelle, Makowsky & Rotics 2001 ).
The matching polynomial of a graph with n vertices and clique-width k may be computed in time n O( k ) ( Makowsky et al. 2006 ). | https://en.wikipedia.org/wiki/Matching_polynomial |
Matchstick models are scale models made from matches as a hobby . Regular matches are not used, however, but a special modeling type which do not have the combustible heads, and can be bought from art and craft shops. Though before the serial production of these, actual matches were used with heads trimmed off, or kept on to add coloured detail.
Originally, matchstick models were a pastime of prisoners (especially naval prisoners of war ) during the 18th century. At the time, better funded modelers preferred to use more replicated parts for their models, like professionals today, and the poor couldn't afford to use up so many matches.
An early pioneer in matchstick models as an art form was Australian artist Len Hughes, whose first large-scale piece was a recreation of the Battle of the Spanish Armada that included 331 replica ships. Hughes went on to open the World of Matchcraft Museum in Caloundra, Queensland , which later closed. [ 1 ]
The matches are cut by means of a sharp knife and fixed together using glue , often being held in place by paperboard "formers" until the glue is dry. While the smallest gaps can be filled with glue, larger ones can be filled with specially carved matches. A number of hobbyists prefer to build their models from scratch. Many kits are available, consisting of instructions, pre-cut card formers and sufficient modeling matches for the project.
An exceptionally large and impressive matchstick model was a scratch-built replica of Notre Dame Cathedral which included electric lights and measured over six feet in length.
Gladbrook, Iowa is home to the Matchstick Marvels Museum that includes numerous models by matchstick model artist Patrick Acton. His work includes a 13-foot scale model of the USS Iowa . [ 2 ]
Religious art from natches is a unique form of folk art practiced by several artists who specialize in crafting intricate models from matchsticks, often with a focus on Jewish religious themes.
One of the notable pioneers of this art form was Hanan Weissman, [ 3 ] a Holocaust survivor born near the border of Russia and Poland. [ 4 ] Weissman immigrated to Israel at the age of 49 and, upon his retirement, began methodically constructing models of synagogues that were destroyed during the Holocaust—entirely out of matchsticks. Until his passing at the age of 89, Weissman built over 50 detailed models of synagogues that had been lost during the Holocaust in Europe. These include the synagogue of the town of Wadowice near Kraków; a model of the synagogue in Vileyka, near Kaunas (burned down in 1942); the synagogue in Gąbin, west of Warsaw (burned down in 1939); and the synagogue of Kopychyntsi, his birthplace near the Poland–Ukraine border, among others. Some of his works are on display at the Testimony House (Beit HaEdut) in Nir Galim, Israel. [ 5 ]
Another prominent matchstick artist is Shachar Puni, [ 6 ] born in Israel in 1971. Puni began building matchstick models during his military service in the early 1990s. Much of his work consists of replicas of ritual Judaica objects, such as an etrog (citron) used during the festival of Sukkot, representations of the Seven Species, a Havdalah set for the conclusion of Shabbat, a scribe’s inkwell used for writing Torah scrolls. [ 7 ] and more. [ 8 ]
This art -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Matchstick_model |
Mate choice is one of the primary mechanisms under which evolution can occur. It is characterized by a "selective response by animals to particular stimuli" which can be observed as behavior. [ 1 ] In other words, before an animal engages with a potential mate, they first evaluate various aspects of that mate which are indicative of quality—such as the resources or phenotypes they have—and evaluate whether or not those particular trait(s) are somehow beneficial to them. The evaluation will then incur a response of some sort. [ 1 ]
These mechanisms are a part of evolutionary change because they operate in a way that causes the qualities that are desired in a mate to be more frequently passed on to each generation over time. For example, if female peacocks desire mates who have a colourful plumage , then this trait will increase in frequency over time as male peacocks with a colourful plumage will have more reproductive success . [ 2 ] Further investigation of this concept, has found that it is in fact the specific trait of blue and green colour near the eyespot that seems to increase the females likelihood of mating with a specific peacock. [ 3 ]
Mate choice is a major component of sexual selection , another being intrasexual selection . Ideas on sexual selection were first introduced in 1871, by Charles Darwin , then expanded on by Ronald Fisher in 1915. At present, there are five sub mechanisms that explain how mate choice has evolved over time. These are direct phenotypic benefits, sensory bias, the Fisherian runaway hypothesis, indicator traits and genetic compatibility.
In the majority of systems where mate choice exists, one sex tends to be competitive with their same-sex members [ 4 ] and the other sex is choosy (meaning they are selective when it comes to picking individuals to mate with). There are direct and indirect benefits of being the selective individual. [ 5 ] [ 6 ] [ 7 ] In most species, females are the choosy sex which discriminates among competitive males, [ 4 ] but there are several examples of reversed roles (see below). It is preferable for an individual to choose a compatible mate of the same species, in order to maintain reproductive success. [ 8 ] Other factors that can influence mate choice include pathogen stress and the major histocompatibility complex (MHC).
Charles Darwin first expressed his ideas on sexual selection and mate choice in his book The Descent of Man, and Selection in Relation to Sex in 1871. He was perplexed by the elaborate ornamentation that males of some species have, because such features appeared to be detrimental to survival and to have negative consequences for reproductive success. Darwin proposed two explanations for the existence of such traits: these traits are useful in male-male combat or they are preferred by females. [ 9 ] This article focuses on the latter. Darwin treated natural selection and sexual selection as two different topics, although in the 1930s biologists defined sexual selection as being a part of natural selection. [ 10 ]
In 1915, Ronald Fisher wrote a paper on the evolution of female preference and secondary sexual characteristics . [ 11 ] Fifteen years later, he expanded this theory in a book called The Genetical Theory of Natural Selection . There he described a scenario, Fisherian runaway , where feedback between mate preference and a trait results in elaborate characters such as the long tail of the male peacock.
In 1948, using Drosophila as a model, Angus John Bateman presented experimental evidence that male reproductive success is limited by the number of mates obtained, while female reproductive success is limited by the number of pregnancies that she can have in her lifetime. [ 12 ] Thus a female must be selective when choosing a mate because the quality of her offspring depends on it. Males must fight, in the form of intra-sexual competition, for the opportunity to mate because not all males will be chosen by females. This became known as Bateman's principle , and although this was a major finding that added to the work of Darwin and Fisher, it was overlooked until George C. Williams emphasised its importance in the 1960s and 1970s. [ 13 ] [ 14 ]
In 1972, soon after Williams' revival of the subject, Robert L. Trivers presented his parental investment theory. Trivers defined parental investment as any investment made by the parent that benefits his or her current offspring at the cost of investment in future offspring. These investments include the costs of producing gametes as well as any other care or efforts that parents provide after birth or hatching. Reformulating Bateman's ideas, Trivers argued that the sex which exhibits less parental investment (not necessarily the male) will have to compete for mating opportunities with the sex that invests more. The differences in levels of parental investment create the condition that favours mating biases. [ 15 ]
The act of being choosy was likely selected for as a way to assess whether or not a potential partner's contribution(s) would be capable of producing and/or maintaining the viability of an offspring. Utilizing these behaviors usually results in two types of benefits to the individual who is being choosy:
Usually, animal biologists assume that mate choice is biased against relatives because of the negative consequences of inbreeding . [ 16 ] However certain natural constraints act to limit the evolution of inbreeding avoidance , particularly when there is a risk of mating with a partner of a different species ( heterospecific mating ) and losing fitness through hybridization. [ 16 ] Inclusive fitness appears to be maximized in matings of intermediately related individuals. [ 17 ]
As of 2018 [update] , five proposed mechanisms address the evolution of mate choice:
Direct and/or indirect benefits drive the mating biases described in each mechanism. It is possible that these mechanisms co-occur, although the relative roles of each have not been evaluated adequately. [ 4 ]
A choosy mate tends to have preferences for certain types of traits—also known as phenotypes —which would benefit them to have in a potential partner. These traits must be reliable, and commutative of something that directly benefits the choosy partner in some way. [ 18 ] Having a mating preference is advantageous in this situation because it directly affects reproductive fitness. Direct benefits are widespread and empirical studies provide evidence for this mechanism of evolution. [ 19 ] [ 20 ]
One example of a sexually selected trait with direct benefits is the bright plumage of the northern cardinal , a common backyard bird in the eastern United States. Male northern cardinals have conspicuous red feathers, while the females have a more cryptic coloration. In this example, the females are the choosy sex and will use male plumage brightness as a signal when picking a mate — research suggests that males with brighter plumage feed their young more frequently than males with duller plumage. [ 21 ] This increased help in caring for the young lifts some of the burden from the mother so that she can raise more offspring than she could without help.
Though this particular mechanism operates on the premise that all phenotypes must communicate something that benefits the choosy mate directly, such selected phenotypes can also have additional indirect benefits for the mother by benefiting the offspring. For example, with the increased help in feeding their young seen in Northern Cardinals with more plumage-brightness, comes an increase in the overall amount of food that is likely to be given to the offspring - even if the mother has more children. [ 22 ] Though females may choose this trait with the presumed directly advantageous aim of allowing them more time and energy to allocate to producing more offspring, it also benefits the offspring in that two parents provide food instead of one, thereby increasing the likelihood of the overall amount of food available to the offspring despite a possible increase in the amount of offspring siblings. [ 22 ]
The sensory-bias hypothesis states that the preference for a trait evolves in a non-mating context and is then exploited by the less choosy sex in order to obtain more mating opportunities. The competitive sex evolves traits that exploit a pre-existing bias that the choosy sex already possesses. Following this hypothesis, increased selectivity for one of these specific traits can explain remarkable trait differences in closely related species because it produces a divergence in signaling systems which leads to reproductive isolation . [ 23 ]
Sensory bias has been demonstrated in guppies , freshwater fish from Trinidad and Tobago . In this mating system, female guppies prefer to mate with males with more orange body-coloration. However, outside of a mating context, both sexes prefer animate orange objects, which suggests that preference originally evolved in another context, like foraging. [ 24 ] Orange fruits are a rare treat that fall into streams where the guppies live. The ability to find these fruits quickly is an adaptive quality that has evolved outside of a mating context. Sometime after the affinity for orange objects arose, male guppies exploited this preference by incorporating large orange spots to attract females.
Another example of sensory exploitation is the case of the water mite Neumania papillator , an ambush predator which hunts copepods (small crustaceans) passing by in the water column. [ 25 ] When hunting, N. papillator adopts a characteristic stance termed the "net stance": it holds its first four legs out into the water column, with its four hind legs resting on aquatic vegetation; this allows it to detect vibrational stimuli produced by swimming prey and to use this to orient towards and clutch at prey. [ 26 ] During courtship, males actively search for females; [ 27 ] if a male finds a female, he slowly circles around the female whilst trembling his first and second leg near her. [ 25 ] [ 26 ] Male leg-trembling causes females (who were in the "net stance") to orient towards and often to clutch the male. [ 25 ] This does not damage the male or deter further courtship; the male then deposits spermatophores and begins to vigorously fan and jerk his fourth pair of legs over the spermatophore, generating a current of water that passes over the spermatophores and towards the female. [ 25 ] Sperm-packet uptake by the female would sometimes follow. [ 25 ] Heather Proctor hypothesised that the vibrations made by trembling male legs mimic the vibrations that females detect from swimming prey. This would trigger the female prey-detection responses, causing females to orient and then clutch at males, mediating courtship. [ 25 ] [ 28 ] If this was true and males were exploiting female predation responses, then hungry females should be more receptive to male trembling. Proctor found that unfed captive females did orient and clutch at males significantly more than fed captive females did, consistent with the sensory exploitation hypothesis. [ 25 ]
Other examples of the sensory-bias mechanism include traits in auklets , [ 29 ] wolf spiders , [ 30 ] and manakins . [ 31 ] Further experimental work is required to reach a fuller understanding of the prevalence and mechanisms of sensory bias. [ 32 ]
This creates a positive feedback loop in which a particular trait is desired by a female and present in a male, and that desire for and presence of that particular trait are then reflected in their offspring. [ 22 ] If this mechanism is strong enough, it can lead to a type of self-reinforcing coevolution. [ 22 ] If runaway selection is strong enough, it may incur significant costs, such as increased visibility to predators and energetic costs to maintain the trait's full expression; hence peacocks' extravagant feathers, or any number of lek mating displays. This model does not predict a genetic benefit; rather, the reward is more mates.
In a study done on great reed warblers , models based on the polygyny threshold and sexy-son hypotheses predict that females should gain evolutionary advantage in either short-term or long-term in this mating system. Although the importance of female choice was demonstrated, the study did not support the hypotheses. [ 33 ] Other studies, such as those conducted on long-tailed widowbirds , have demonstrated the existence of female choice. [ 34 ] Here, females chose males with long tails, and even preferred those males with experimentally lengthened tails over shortened tails and those of naturally occurring length. Such a process shows how female choice could give rise to exaggerated sexual traits through Fisherian runaway selection.
Indicator traits signal good overall quality of the individual. Traits perceived as attractive must reliably indicate broad genetic quality in order for selection to favor them and for preference to evolve. This is an example of indirect genetic benefits received by the choosy sex, because mating with such individuals will result in high-quality offspring. The indicator traits hypothesis is split into three highly related subtopics: the handicap theory of sexual selection, the good genes hypothesis, and the Hamilton–Zuk hypothesis.
People rate the importance of certain traits differently when referring to their own or to others' ideal long-term partners. Research suggests that women consider traits indicating genetic fitness as more important for their own partner, while prioritising traits that provide benefits to others for their sister's ideal partner. [ 35 ]
Indicator traits are condition-dependent and have associated costs. Therefore, individuals which can handle these costs well ( cf. "I can do X [here, survive] with one hand tied behind my back") should be desired by the choosy sex for their superior genetic quality. This is known as the handicap theory of sexual selection. [ 36 ]
The good genes hypothesis states that the choosy sex will mate with individuals who possess traits that signify overall genetic quality. In doing so, they gain an evolutionary advantage for their offspring through indirect benefit.
The Hamilton–Zuk hypothesis posits that sexual ornaments are indicators of parasite- and disease-resistance. [ 37 ] To test this hypothesis, red jungle-fowl males were infected with a parasitic roundworm and monitored for growth and developmental changes. Female preference was also evaluated. The researchers found that parasites affected the development and final appearance of ornamental traits and that females preferred males who were not infected. This supports the idea that parasites are an important factor in sexual selection and mate choice. [ 38 ]
One of many examples of indicator traits is the condition-dependent patch of red feathers around the face and shoulders of the male house finch. This patch varies in brightness among individuals because the pigments that produce the red color (carotenoids) are limited in the environment. Thus, males who have a high-quality diet will have brighter red plumage. In a much-cited manipulation experiment, female house finches were shown to prefer males with brighter red patches. Also, males with naturally brighter patches proved better fathers and exhibited higher offspring-feeding rates than duller males. [ 20 ]
Genetic compatibility refers to how well the genes of two parents function together in their offspring. Choosing genetically compatible mates could result in optimally fit offspring and notably affect reproductive fitness. However, the genetic compatibility model is limited to specific traits due to complex genetic interactions (e.g. major histocompatibility complex in humans and mice). The choosy sex must know their own genotype as well as the genotypes of potential mates in order to select the appropriate partner. [ 39 ] This makes testing components of genetic compatibility difficult and controversial .
A controversial but well-known experiment suggests that human females use body odor as an indicator of genetic compatibility. In this study, males were given a plain T-shirt to sleep in for two nights in order to provide a scent sample. College women were then asked to rate odors from several men, some with similar MHC (major histocompatibility complex) genes to their own and others with dissimilar genes. MHC genes code for receptors that identify foreign pathogens in the body so that the immune system may respond and destroy them. Since each different gene in the MHC codes for a different type of receptor, it is expected that females will benefit from mating with males who have more dissimilar MHC genes. This will ensure better resistance to parasites and disease in offspring. Researchers found that women tended to rate the odors higher if the male's genes were more dissimilar to their own. They concluded that the odors are influenced by the MHC and that they have consequences for mate choice in human populations today. [ 40 ]
Similar to the humans of the odor-rating experiment, animals also choose mates based upon genetic compatibility as determined by evaluating the body odor of their potential mate(s). Some animals, such as mice, assess a mate's genetic compatibility based on their urine odor. [ 41 ]
In an experiment studying three-spined sticklebacks , researchers found that females prefer to mate with males that share a greater diversity of major histocompatibility complex (MHC) and in addition possess a MHC haplotype specific to fighting the common parasite Gyrodactylus salaris . [ 42 ] Mates that have MHC genes different from one another will be superior when reproducing with regard to parasite resistance, body condition and reproductive success and survival. [ 43 ]
The genetic diversity of animals and life reproductive success (LRS) at the MHC level is optimal at intermediate levels rather than at its maximum, [ 44 ] [ 45 ] despite MHC being one of the most polymorphic genes. [ 46 ] In a study, researchers discovered that mice heterozygous at all MHC loci were less resistant than mice homozygous at all loci to salmonella, so it appears disadvantageous to display many different MHC alleles due to the increased loss of T-cells, [ 47 ] which aid an organism's immune system and trigger its appropriate response. [ 48 ]
MHC diversity may also correlate with MHC gene expression . As long as a heritable component exists in expression patterns, natural selection is able to act upon the trait. Therefore, gene expression for MHC genes might contribute to the natural selection processes of certain species and be in fact evolutionarily relevant. For example, in another study of three-spined sticklebacks, exposure to parasite species increased MHC class IIB expression by over 25%, proving that parasitic infection increases gene expression. [ 49 ]
MHC diversity in vertebrates may also be generated by the recombination of alleles on the MHC gene. [ 50 ]
In species where mating biases exist, females are typically the choosy sex because they provide a greater parental investment than males. [ 51 ] [ 52 ] However, there are some examples of sex role reversals where females must compete with each other for mating opportunities with males. Species that exhibit parental care after the birth of their offspring have the potential to overcome the sex differences in parental investment (the amount of energy that each parent contributes per offspring) and lead to a reversal in sex roles. [ 4 ] The following are examples of male mate choice (sex role reversal) across several taxa.
For many years it has been suggested that sexual isolation caused by differences in mating behaviours is a precursor for reproductive isolation (lack of gene flow ), and consequently speciation , in nature. [ 59 ] Mate choice behaviours are thought to be important forces that can result in speciation events because the strength of selection for attractive traits is often very strong. Speciation by this method occurs when a preference for some sexual trait shifts and produces a pre-zygotic barrier (preventing fertilisation). These processes have been difficult to test until recently with advances in genetic modelling. [ 60 ] Speciation by sexual selection is gaining popularity in the literature with increasing theoretical and empirical studies.
There is evidence of early speciation through mate preference in guppies . Guppies are located across several isolated streams in Trinidad and male colour patterns differ geographically. Female guppies have no coloration but their preference for these colour patterns also vary across locations. In a mate choice study, female guppies were shown to prefer males with colour patterns that are typical of their home stream. [ 61 ] This preference could result in reproductive isolation if two populations came into contact again. There is a similar trend shown in two species of the wood white butterfly, L. reali and L. sinapis . Female L. sinapis controls mate choice by engaging only in conspecific mating, while males attempt to mate with either species. This female mate choice has encouraged speciation of the two wood whites. [ 62 ]
The black-throated blue warbler , a North American bird, is another example. Asymmetric recognition of local and non-local songs has been found between two populations of black-throated blue warblers in the United States, one in the northern United States (New Hampshire) and the other in the southern United States (North Carolina). [ 63 ] Males in the northern population respond strongly to the local male songs but relatively weakly to the non-local songs of southern males. In contrast, southern males respond equally to both local and non-local songs. The fact that northern males exhibit differential recognition indicates that northern females tend not to mate with "heterospecific" males from the south; thus it is not necessary for the northern males to respond strongly to the song from a southern challenger. A barrier to gene flow exists from South to North as a result of the female choice, which can eventually lead to speciation.
In humans, males and females differ in their strategies to acquire mates. Females exhibit more mate choice selectivity than males. According to Bateman's principle , human females display less variance in their Lifespan Reproductive Success , due to their high obligatory parental investment . [ 64 ] Human female sexual selection is indicated by sexually dimorphism, especially in traits that serve little other evolutionary purpose, such as the presence in men of beards, overall lower voice pitch, and average greater height. Women have reported a preference for men with beards and lower voices. [ 65 ] [ 66 ] The traits most salient to female human mate choice are parental investment, resource provision and the provision of good genes to offspring. [ 67 ] Women as well as men may seek short-term mating partners. [ 68 ] This could gain them resources; provide genetic benefit, as through the sexy son hypothesis ; facilitate a desired break-up; and allow them to assess a mate's suitability as a long-term partner. [ 67 ] Women prefer long-term partners over short-term mates, as they have a larger investment in a child through pregnancy and lactation. [ 67 ] Factors in female mate choice include the woman's own perceived attractiveness, the woman's personal resources, mate copying and parasite stress . [ 67 ] Romantic love is the mechanism through which long-term mate choice occurs in human females. [ 69 ]
In humans, females have to endure a nine-month pregnancy and childbirth. [ 67 ] Females thus provide a greater biologically obligatory parental investment to offspring than males. [ 67 ] [ 70 ] This provides males with a greater window of opportunity to mate and reproduce than females, hence females are usually more choosy, but males still make mate choices. [ 70 ] When finding a short-term mate, males highly value women with sexual experience and physical attractiveness. Men seeking short-term sexual relationships are likely to avoid women who are interested in commitment or require investment. [ 71 ] For a long-term relationship, males may look for commitment, facial symmetry , femininity , physical beauty, waist–hip ratio , large breasts , [ 72 ] and youth. [ 73 ] [ 69 ] [ 74 ] [ 75 ] [ 76 ] Due to the higher obligatory biological investment, women are choosier in short-term mating, as the perceived paternal investment is low to non existent, whereas men and women are equally choosy when deciding for long-term mates, as men and women then have an equal parental investment, as men then invest heavily in the offspring by resource provisioning. [ 77 ]
The parasite-stress theory suggests that parasites or diseases stress an organism, making them look less sexually attractive. [ 78 ] Choosing a mate for attractiveness could thus help to find a healthy mate resistant to parasites. [ 79 ] [ 80 ]
Scarification could be viewed by prospective mates as evidence that a person has overcome parasites and is thus more attractive. [ 81 ] [ 82 ] Masculinity , especially in the face, could equally indicate robust parasite-free health. [ 83 ] [ 84 ] [ 85 ] [ 86 ] Polygamy is predicted by pathogen stress in the tropics. [ 87 ] [ 88 ]
Human leukocyte antigen (HLA) proteins are essential for immune system functioning and are highly variable, assumed to be a result of frequency-dependent parasite-driven selection and mate choice. There is some evidence that women detect and select HLA type by odour, though this is disputed. [ 89 ] [ 90 ] [ 91 ] [ 92 ] [ 93 ] Human facial preferences correlate with both MHC-similarity and MHC-heterozygosity. [ 94 ]
In the late 19th century, Charles Darwin proposed that cognition, or " intelligence ," was the product of two combined evolutionary forces: natural selection and sexual selection . [ 95 ] Research on human mate choice showed that intelligence is sexually selected for, and is highly esteemed by both sexes. [ 96 ] [ 97 ] Some evolutionary psychologists have suggested that humans evolved large brains because the cognitive abilities associated with this size increase were successful in attracting mates, consequently increasing reproductive success : brains are metabolically costly to produce and are an honest signal of mate quality. [ 98 ] Cognition may be functioning to attract mates in other taxa . [ 99 ] If the possession of higher cognitive skills enhances a male's ability to gather resources, then females may benefit directly from choosing more intelligent males, through courtship feeding or allofeeding . [ 100 ] Assuming cognitive skills are heritable to some degree, females may also benefit indirectly through their offspring . [ 99 ] Additionally, cognitive ability has been shown to vary significantly, both within and between species, and could be under sexual selection as a result. [ 101 ] Recently, researchers have started to ask to what extent individuals assess the cognitive abilities of the opposite sex when choosing a mate. [ 99 ] In fruit flies , the absence of sexual selection was accompanied by a decline in male cognitive performance. [ 102 ]
Female preference for males with enhanced cognitive ability "may be reflected in successful males' courtship displays , foraging performance, courtship feeding or diet-dependent morphological traits." [ 99 ] However, few are the studies that assess whether females can discriminate between males through direct observation of cognitively demanding tasks. Instead, researchers generally investigate female choice by reason of morphological traits correlated with cognitive ability. [ 99 ]
Although there is some evidence that females assess male cognitive ability when choosing a mate, the effect that cognitive ability has on survival and mating preference remain unclear. [ 99 ] Many questions need to be answered to be able to better appreciate the implications that cognitive traits may have in mate choice. Some discrepancies also need to be resolved. For example, in 1996, Catchpole suggested that in songbirds , females preferred males with larger song repertoires. Learned song repertoire was correlated with the size of the High Vocal Center (HVC) in the brain; females may then use song repertoire as an indicator of general cognitive ability. [ 116 ] However, a more recent study found learned song repertoire to be an unreliable signal of cognitive ability. Rather than a general cognitive ability, male songbirds were found to have specific cognitive abilities that did not positively associate. [ 117 ] [ 118 ]
As of 2011, more research was needed on what extent cognitive abilities determine foraging success or courtship displays, what extent behavioural courtship displays rely on learning through practice and experience, what extent cognitive abilities affect survival and mating success, and what indicator traits could be used as a signal of cognitive ability. [ 99 ] Researchers have started to explore links between cognition and personality; some personality traits such as boldness or neophobia may be used as indicators of cognitive ability, although more evidence is required to characterize personality-cognition relationships. [ 119 ] As of 2011, empirical evidence for the benefits, both direct and indirect, of choosing mates with enhanced cognition is weak. One possible research direction would be on the indirect benefits of mating with males with enhanced spatial cognition in mountain chickadees. [ 99 ] [ 111 ] Additional focus in research is needed on developmental and environmental effects on cognitive ability, as such factors have been shown to influence song learning and could therefore influence other cognitive traits. [ 99 ] | https://en.wikipedia.org/wiki/Mate_choice |
In humans, males and females differ in their strategies to acquire mates and focus on certain qualities. There are two main categories of strategies that both sexes utilize: short-term and long-term. Human mate choice , an aspect of sexual selection in humans , depends on a variety of factors, such as ecology, demography, access to resources, rank/social standing, genes , and parasite stress .
While there are a few common mating systems seen among humans, the amount of variation in mating strategies is relatively large. This is due to how humans evolved in diverse niches that were geographically and ecologically expansive. This diversity, as well as cultural practices and human consciousness, have all led to a large amount of variation in mating systems. Below are some of the overarching trends of mate choice.
Although human males and females are both selective in deciding with whom to mate, females exhibit more mate choice selectivity than males, as is seen in nature. Relative to most other animals however, female and male mating strategies are found to be more similar to each other. According to Bateman's principle of Lifespan Reproductive Success (LRS) , human females display the least variance of the two sexes in their LRS due to their high obligatory parental investment , that is a nine-month gestational period, as well as lactation following birth in order to feed offspring so that their brain can grow to the required size. [ 1 ]
Human female sexual selection can be examined by looking at ways in which males and females are sexually dimorphic, especially in traits that serve little other evolutionary purpose. For example, male traits such as the presence of beards, overall lower voice pitch, and average greater height are thought to be sexually selected traits as they confer benefits to either the women selecting for them, or to their offspring. Experimentally, women have reported a preference for men with beards and lower voices. [ 2 ] [ 3 ] [ 4 ]
Female mate choice hinges on many different coinciding male traits, and the trade-off between many of these traits must be assessed. The ultimate traits most salient to female human mate choice, however, are parental investment, resource provision and the provision of good genes to offspring. Many phenotypic traits are thought to be selected for as they act as an indication of one of these three major traits. The relative importance of these traits when considering mate selection differ depending on the type of mating arrangement females engage in. Human women typically employ long-term mating strategies when choosing a mate, however they also engage in short-term mating arrangements, so their mate choice preferences change depending on the function of the type of arrangement. [ 5 ]
David Buss outlines several hypotheses as to the function of women's short-term mate choices:
The provision of economic resources, or the potential to acquire many economic resources, is the most obvious cue towards the ability of a man to provide resources, and women in the United States have been shown experimentally to rate the importance of their partner's financial status more highly than men. [ 5 ] However, many other traits exist that may act as cues towards a man's ability to provide resources that have been sexually selected for in women's evolutionary history. These include older age—older males have had more time to accrue resources—industriousness, dependability and stability—if a woman's long-term partner is not emotionally stable or is not dependable then their provision of resources to her and her offspring are likely to be inconsistent. Additionally, the costs associated with an emotionally unstable partner such as jealousy and manipulation may outweigh the benefits associated with the resources they are able to provide. [ 5 ]
Women's mate choices will also be constrained by the context in which they are making them, resulting in conditional mate choices. [ 1 ] Some of the conditions that may influence female mate choice include the woman's own perceived attractiveness, the woman's personal resources, mate copying and parasite stress . [ 5 ] Romantic love is the mechanism through which long-term mate choice occurs in human females. [ 6 ]
When finding a short-term mate, males highly value women with sexual experience and physical attractiveness. [ 7 ] Men seeking short-term sexual relationships are likely to avoid women who are interested in commitment or require investment. In short-term sexual relationships, men are less choosy because of low parental investment.
Examples of short-term mating strategies in males:
Humans have the ability to rely on biological signals of reproductive success and non-biological signals, such as the female's willingness to marry. [ 8 ] Unlike many animals, humans are not able to consciously display physical changes to their body when they are ready to mate, so they have to rely on other forms of communication before engaging in a consensual relationship. Romantic love is the mechanism through which long-term mate choice occurs in human males. [ 6 ] For long-term sexual relationships, men are usually equally choosy because they have a similar parental investment like the women, as they heavily invest in the offspring in form of resource provisioning.
Males may look for:
The parasite-stress theory , otherwise known as pathogen stress, states that parasites or diseases put stress on the life development of an organism, leading to a change in the appearance of their sexually attractive traits. The initial research on the Hamilton–Zuk hypothesis [ 14 ] (see indicator traits ) showed that, within one species (brightly colored birds), there was greater sexual selection for males that had brighter plumage (feathers). In addition, Hamilton and Zuk showed that, comparing across multiple species, there is greater selection for physical attributes in species under greater parasitic stress. This has influenced research regarding human mate choice.
In societies with a high prevalence of parasites or pathogens , members would derive greater evolutionary advantage from selecting for physical attractiveness/good looks in mate choice compared to that derived by members of societies with lower prevalence. Humans could use physical attractiveness to determine resistance to parasites and diseases, which are believed to lower their sufferers' ability to portray attractive traits from then on and limit the number of high-quality pathogen-resistant mates. [ 15 ] In cultures where parasitic infection is especially high, members could use cues available to them to determine the physical health status of the potential mate. [ 16 ] Regardless of the wealth or ideology, the females in areas that are more at risk or have higher rates of parasites and diseases would weigh masculinity more highly when rating potential mates.
Gangested and Buss (2009) say that research indicates that parasite stress may have only influenced mate choice through females searching for "good genes" which show parasite resistance, in areas which have high prevalence of parasites. [ 25 ] John Cartwright also points out that females may be simply avoiding the transmission of parasites to themselves rather than it being them choosing males with good genes and that females look for more than just parasite-resistant genes. [ 16 ]
Major histocompatibility complex (MHC) or, in humans, human leukocyte antigen (HLA) produces proteins that are essential for immune system functioning. The genes of the MHC complex have extremely high variability, assumed to be a result of frequency-dependent parasite-driven selection and mate choice. This is believed to be so it promotes heterozygosity improving the chances of survival for the offspring.
In humans, there is evidence that women will rate men's odor as more pleasant if the odor has MHC-dissimilar antigens, which is proposed as a way of avoiding inbreeding and increasing heterozygosity. [ 26 ] [ 27 ] However, women on contraceptive pills rate the odor of MHC-similar men as being more pleasant, it is unknown why women on contraceptive pills rate smell in this way. It was found that when processing MHC-similar smells were processed faster. [ 28 ] Contrary to these findings, other studies have found that there is no correlation between attraction and odor by testing males' odor preferences on women's odors. The study concludes that there is no correlation in attraction between men and women of dissimilar HLA proteins. [ 29 ] Research completed on a Southern Brazilian student population resulted in similar findings that found significant differences in the attraction ratings of giving to male sweat and MHC-difference. [ 30 ]
Human facial preferences have been shown to correlate with both MHC-similarity and MHC-heterozygosity. [ 31 ] Research into MHC-similarity with regards to facial attractiveness is limited. One study found that women may prefer mates with MHC-similar faces, despite evidence that they prefer men with dissimilar body odors. [ 26 ] While facial asymmetry hasn't been correlated with MHC-heterozygosity, the perceived healthiness of skin appears to be. [ 32 ] It appears to be that only MHC-heterozygosity and no other genetic markers are correlated with facial attractiveness in males [ 33 ] and it has been shown that so far that there is no correlation that has been found in females. [ 34 ] [ 35 ] Slightly different from facial attractiveness, facial masculinity is not shown to correlate with MHC heterogeneity (a common measure of immunocompetence). [ 36 ]
A review article published in June 2018 concluded that there is no correlation between HLA and mate choice. [ 37 ] In addition to assessing previous studies on HLA-Mate choice analysis to identify errors in their research methods (such as small population sizes), the study collects a larger set of data and re-runs the analysis of the previous studies. By using the larger data set to conduct analysis on 30 couples of European descent, they generate findings contrary to previous studies that identified significant divergence in the mate choice with accordance to HLA genotyping. Additional studies have been conducted simultaneously on African and European populations that only show correlation of MHC divergence in European but not African populations. [ 38 ] | https://en.wikipedia.org/wiki/Mate_choice_in_humans |
Mate guarding is a reproductive behaviour , primarily of males, in an attempt to increase the likelihood of success of their own sperm fertilizing the eggs of females when competition is involved. Mate guarding behaviour can be pre- or post-copulatory. [ 1 ] Studies on the behaviour both based on theory and through experiments have been conducted on a wide range of species. [ 2 ] Mate guarding also occurs in humans .
In organisms where polygamy is dominant such as in most mammals, birds, and insects, there is significant male-male competition even prior to copulation. When organisms mate with multiple males and store sperm, maintaining their viability within storage structures, there is sperm competition and males evolve mechanisms to increase their odds of successful parenting. In some species such as the Apollo butterflies the males produce mating plugs that prevent the female from mating again. In some dragonflies, males will physically hold females after copulation to increase the chances that their own sperm fertilize the eggs laid. [ 3 ] [ 4 ] [ 5 ] In some moths where males prefer virgin females to mate, males may mark females with chemical compounds after copulation that make them less attractive to males. [ 6 ] Mate guarding by males comes with costs for them in terms of reduced time available for feeding and other activities. [ 7 ] Males may also have to choose between strategies of mating with multiple females or in choosing fewer females and guarding them during the critical phases. [ 8 ] Female strategies can include multiple mating to ensure that they obtain fitter sperm to pass on benefits to their offspring and so mate guarding can sometimes appear as a hindrance to them, however females may also receive other benefits such as protection from predation through the actions of the guarding males. [ 9 ] [ 10 ] | https://en.wikipedia.org/wiki/Mate_guarding |
A material is a substance or mixture of substances that constitutes an object . Materials can be pure or impure, living or non-living matter. Materials can be classified on the basis of their physical and chemical properties , or on their geological origin or biological function. Materials science is the study of materials, their properties and their applications.
Raw materials can be processed in different ways to influence their properties, by purification, shaping or the introduction of other materials. New materials can be produced from raw materials by synthesis .
In industry , materials are inputs to manufacturing processes to produce products or more complex materials, [ 1 ] and the nature and quantity of materials used may form part of the calculation for the cost of a product or delivery under contract, such as where contract costs are calculated on a " time and materials " basis. [ 2 ]
Materials chart the history of humanity. The system of the three prehistoric ages ( Stone Age , Bronze Age , Iron Age ) were succeeded by historical ages: steel age in the 19th century, polymer age in the middle of the following century (plastic age) and silicon age in the second half of the 20th century. [ 3 ]
Materials can be broadly categorized in terms of their use, for example:
Material selection is a process to determine which material should be used for a given application.
The relevant structure of materials has a different length scale depending on the material. The structure and composition of a material can be determined by microscopy or spectroscopy .
In engineering , materials can be categorised according to their microscopic structure: [ 4 ] : 15–17
A metamaterial is any material engineered to have a property that is not found in naturally occurring materials, usually by combining several materials to form a composite and / or tuning the shape , geometry , size , orientation and arrangement to achieve the desired property. [ 5 ]
In foams and textiles , the chemical structure is less relevant to immediately observable properties than larger-scale material features: the holes in foams, and the weave in textiles.
Materials can be compared and classified by their large-scale physical properties.
Mechanical properties determine how a material responds to applied forces .
Examples include:
Materials may degrade or undergo changes of properties at different temperatures. Thermal properties also include the material's thermal conductivity and heat capacity , relating to the transfer and storage of thermal energy by the material.
Materials can be compared and categorized by any quantitative measure of their behavior under various conditions. Notable additional properties include the optical, electrical, and magnetic behavior of materials. [ 4 ] : 5–7 | https://en.wikipedia.org/wiki/Material |
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