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https://en.wikipedia.org/wiki/Costa
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Costa may refer to:
Biology
Rib (Latin: costa), in vertebrate anatomy
Costa (botany), the central strand of a plant leaf or thallus
Costa (coral), a stony rib, part of the skeleton of a coral
Costa (entomology), the leading edge of the forewing of winged insects, as well as a part of the male clasper
Arts and entertainment
Costa!, a 2001 Dutch film
Costa!!, a 2022 Dutch film
Costa Book Awards, formerly the Whitbread Book Award, a literary award in the UK
Organisations
Costa Caribe, a Nicaraguan basketball team
Costa Coffee, a British coffee shop chain, sponsor of the book award
Costa Cruises, a leading cruise company in Europe
Costa Del Mar, an American manufacturer of polarized sunglasses
Costa Group, Australian food supplier
Places
Costa, Haute-Corse, France, a commune on the island of Corsica
Costa, Lajas, Puerto Rico, a barrio
Costa, West Virginia, US, or Brushton, a community
Costa Head, a headland on the Orkney Islands
People
Costa (surname), including origin of the name and people sharing the surname
Costa (footballer) (born 1973), Portuguese football manager and former player
Costa-Gavras (born 1933), Greek-French filmmaker
See also
Costal (disambiguation)
Costas, a name of Greek origin
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https://en.wikipedia.org/wiki/Annihilator
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Annihilator(s) may refer to:
Mathematics
Annihilator (ring theory)
Annihilator (linear algebra), the annihilator of a subset of a vector subspace
Annihilator method, a type of differential operator, used in a particular method for solving differential equations
Annihilator matrix, in regression analysis
Music
Annihilator (band), a Canadian heavy metal band
Annihilator (album), a 2010 album by the aforementioned band
Other media
Annihilator (Justice League), an automaton in the fictional series Justice League Unlimited
Annihilators (Marvel Comics), a team of superheroes
Annihilator, a 2015 science fiction comic by Grant Morrison and Frazer Irving
Annihilator (film), a 1986 television film starring Mark Lindsay Chapman
The Annihilators (film), a 1985 action film by Charles E. Sellier Jr.
The Annihilators (novel), a 1983 novel by Donald Hamilton
See also
Annihilation (disambiguation)
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https://en.wikipedia.org/wiki/Alan%20Fersht
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Sir Alan Roy Fersht (born 21 April 1943) is a British chemist at the MRC Laboratory of Molecular Biology, Cambridge, and an Emeritus Professor in the Department of Chemistry at the University of Cambridge. He was Master of Gonville and Caius College, Cambridge from 2012 to 2018. He works on protein folding, and is sometimes described as a founder of protein engineering.
Early life and education
Fersht was born on 21 April 1943 in Hackney, London. His father, Philip, was a ladies' tailor and his mother, Betty, a dressmaker. His grandparents were Jewish immigrants from Poland, Romania, Lithuania and Belarus. He was educated at Sir George Monoux Grammar School, an all-boys grammar school in Walthamstow, London. He was a keen chess player and was the Essex County Junior champion in 1961. He was awarded a State Scholarship to read Natural Sciences at Gonville and Caius College, Cambridge, where he obtained First Class in Pt I of the Natural Sciences Tripos in 1964, First Class in Pt II (Chemistry) in 1965 and was awarded his PhD degree in 1968. He was President of the University of Cambridge Chess Club in 1964–65 and awarded a half blue in 1965.
Career and research
Fersht spent a post-doctoral year (1968–1969) at Brandeis University working under William Jencks. He returned to Cambridge in 1969 as a group leader at the Laboratory of Molecular Biology until 1977 and a junior research fellow at Jesus College, Cambridge until 1972. Fersht was Wolfson Research Professor of the Roya
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https://en.wikipedia.org/wiki/Bengt%20N%C3%B6lting
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Bengt Nölting (1 May 1962 – 16 September 2009) was a German physicist and biophysicist who pioneered various methods in biophysics and engineering. Achievements include studying biological macromolecules, the development of self-evolving computer programs, and the development new energy technologies. From 1994–1997 Nölting was scientist at Cambridge University and the Cambridge Centre for Protein Engineering (UK) where he developed, together with Sir Alan R. Fersht, methods for the high resolution of protein folding.
Works
References
1962 births
2009 deaths
21st-century German physicists
20th-century German physicists
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https://en.wikipedia.org/wiki/Linear%20approximation
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In mathematics, a linear approximation is an approximation of a general function using a linear function (more precisely, an affine function). They are widely used in the method of finite differences to produce first order methods for solving or approximating solutions to equations.
Definition
Given a twice continuously differentiable function of one real variable, Taylor's theorem for the case states that
where is the remainder term. The linear approximation is obtained by dropping the remainder:
This is a good approximation when is close enough to since a curve, when closely observed, will begin to resemble a straight line. Therefore, the expression on the right-hand side is just the equation for the tangent line to the graph of at . For this reason, this process is also called the tangent line approximation. Linear approximations in this case are further improved when the second derivative of a, , is sufficiently small (close to zero) (i.e., at or near an inflection point).
If is concave down in the interval between and , the approximation will be an overestimate (since the derivative is decreasing in that interval). If is concave up, the approximation will be an underestimate.
Linear approximations for vector functions of a vector variable are obtained in the same way, with the derivative at a point replaced by the Jacobian matrix. For example, given a differentiable function with real values, one can approximate for close to by the formula
The right-h
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https://en.wikipedia.org/wiki/Alexander%20polynomial
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In mathematics, the Alexander polynomial is a knot invariant which assigns a polynomial with integer coefficients to each knot type. James Waddell Alexander II discovered this, the first knot polynomial, in 1923. In 1969, John Conway showed a version of this polynomial, now called the Alexander–Conway polynomial, could be computed using a skein relation, although its significance was not realized until the discovery of the Jones polynomial in 1984. Soon after Conway's reworking of the Alexander polynomial, it was realized that a similar skein relation was exhibited in Alexander's paper on his polynomial.
Definition
Let K be a knot in the 3-sphere. Let X be the infinite cyclic cover of the knot complement of K. This covering can be obtained by cutting the knot complement along a Seifert surface of K and gluing together infinitely many copies of the resulting manifold with boundary in a cyclic manner. There is a covering transformation t acting on X. Consider the first homology (with integer coefficients) of X, denoted . The transformation t acts on the homology and so we can consider a module over the ring of Laurent polynomials . This is called the Alexander invariant or Alexander module.
The module is finitely presentable; a presentation matrix for this module is called the Alexander matrix. If the number of generators, , is less than or equal to the number of relations, , then we consider the ideal generated by all minors of the matrix; this is the zeroth Fit
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https://en.wikipedia.org/wiki/Felix%20Iversen
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Felix Christian Herbert Iversen (22 October 1887 – 31 July 1973) was a Finnish mathematician and a pacifist. He was a student of Ernst Lindelöf, and later an associate professor of mathematics at the University of Helsinki. Although he stopped performing serious research in mathematics around 1922, he continued working as a professor until his retirement in 1954 and published a textbook on mathematics in 1950. The Soviet Union awarded Felix Iversen the Stalin Peace Prize in 1954.
References
1887 births
1973 deaths
Finnish mathematicians
Academic staff of the University of Helsinki
Stalin Peace Prize recipients
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https://en.wikipedia.org/wiki/Szczecin%20University%20of%20Technology
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Szczecin University of Technology () was one of the biggest universities in Szczecin, Poland.
History
Szczecin University of Technology was established on 1 December 1946 as School of Engineering in Szczecin (Polish: Szkoła Inżynierska w Szczecinie). Initially it included three faculties - Faculty of Electrical Engineering (Polish: Wydział Elektryczny), Faculty of Civil Engineering (Polish: Wydział Inżynierii Lądowej) and Faculty of Mechanical Engineering (Polish: Wydział Mechaniczny). In the following academic year, it was expanded with opening of Faculty of Chemical Engineering (Polish: Wydział Chemiczny).
On 1 September 1955 it took over departments of liquidated School of Economics in Szczecin (Polish: Szkoła Ekonomiczna w Szczecinie) and established Faculty of Engineering and Economics of Transport (Polish: Wydział Inżynieryjno-Ekonomiczny Transportu). On 3 September 1955 it was transformed into Technical University of Szczecin.
In 1985 University of Szczecin took over Faculty of Engineering and Economics of Transport.
The university has been existing to 1 January 2009, when in result of fusion with University of Agriculture in Szczecin, was created West Pomeranian University of Technology.
Organization of former University
Faculties
Faculty of Chemical Engineering (Polish: Wydział Technologii i Inżynierii Chemicznej)
Faculty of Civil Engineering and Architecture (Polish: Wydział Budownictwa i Architektury)
Faculty of Computer Science and Information Technology
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https://en.wikipedia.org/wiki/Spectrum%20%28disambiguation%29
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A spectrum is a condition or value that is not limited to a specific set of values but can vary infinitely within a continuum.
Spectrum may also refer to:
Science and technology
Physics
Electromagnetic spectrum
Visible spectrum or optical spectrum, a subset of the electromagnetic spectrum
Emission spectrum, observed in light
Absorption spectrum, observed in light
Radio spectrum, radio frequency subset of the electromagnetic spectrum
Stellar spectrum, the combination of continuum, absorption, and emission lines produced by a star
Energy spectrum, of a collection of particles (particle physics)
Frequency spectrum, of a signal
Power spectrum, of a signal
Medicine
Spectrum disorder, a group of mental disorders of similar appearance or thought to share an underlying mechanism
Autism spectrum, encompassing autism, Asperger's, etc.
Antimicrobial spectrum, the range of microorganisms an antibiotic can kill or inhibit
Mathematics
In mathematics, spectrum frequently denotes a set of numbers associated to an object:
Spectrum of a matrix, its set of eigenvalues, in linear algebra
Spectrum (functional analysis), a generalization of the concept of matrix eigenvalues to operators
Spectrum of a graph, studied in spectral graph theory
Pseudospectrum
Spectrum of a polygon, the set of numbers of possible equidissections
Spectrum of a sentence, in mathematical logic
Spectrum of a theory, in mathematical logic
There are also several other, unrelated meanings:
Spectrum (
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https://en.wikipedia.org/wiki/Brian%20D.%20Farrell
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Brian Dorsey Farrell is a professor of biology and curator in entomology at Harvard University's Museum of Comparative Zoology. , Farrell is also Director of the David Rockefeller Center for Latin American Studies at Harvard University.
Early life and education
Farrell was one of eight children born to a United States born mother and Lebanese-descendent father. He earned his BA in zoology and botany from the University of Vermont and his M.S. and Ph.D. from the University of Maryland.
Career
Farrell accepted a position at the University of Colorado Boulder, where he had his first child. In 1995, he returned to the East Coast to accept a position at Harvard University as a Professor in the Department of Organismic and Evolutionary Biology.
In 2014, Farrell was named Director of the David Rockefeller Center for Latin American Studies at Harvard University. He also received a grant to study insect fossils in the Museum of Comparative Zoology at Harvard. In 2018, he was named Faculty Dean of Leverett House.
Personal life
Farrell and his wife Irina Ferreras have two children, who also enrolled in Harvard.
References
External links
Lab homepage at the Harvard Museum of Comparative Zoology
Google Scholar
CV
Living people
21st-century American zoologists
Harvard University staff
Year of birth missing (living people)
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https://en.wikipedia.org/wiki/Hasse%27s%20theorem
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In mathematics, there are several theorems of Helmut Hasse that are sometimes called Hasse's theorem:
Hasse norm theorem
Hasse's theorem on elliptic curves
Hasse–Arf theorem
Hasse–Minkowski theorem
See also
Hasse principle, the principle that an integer equation can be solved by piecing together modular solutions
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https://en.wikipedia.org/wiki/Calculus%20%28disambiguation%29
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Calculus (from Latin calculus meaning ‘pebble’, plural calculī) in its most general sense is any method or system of calculation.
Calculus may refer to:
Biology
Calculus (spider), a genus of the family Oonopidae
Caseolus calculus, a genus and species of small land snails
Mathematics
Infinitesimal calculus (or simply Calculus), which investigate motion and rates of change
Differential calculus
Integral calculus
Non-standard calculus, an approach to infinitesimal calculus using Robinson's infinitesimals
Calculus of sums and differences (difference operator), also called the finite-difference calculus, a discrete analogue of "calculus"
Functional calculus, a way to apply various types of functions to operators
Schubert calculus, a branch of algebraic geometry
Tensor calculus (also called tensor analysis), a generalization of vector calculus that encompasses tensor fields
Vector calculus (also called vector analysis), comprising specialized notations for multivariable analysis of vectors in an inner-product space
Matrix calculus, a specialized notation for multivariable calculus over spaces of matrices
Numerical calculus (also called numerical analysis), the study of numerical approximations
Umbral calculus, the combinatorics of certain operations on polynomials
The calculus of variations, a field of study that deals with extremizing functionals
Itô calculus An extension of calculus to stochastic processes.
Logic
Logical calculus, a formal system that d
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https://en.wikipedia.org/wiki/Jacob%20A.%20Marinsky
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Jacob Akiba Marinsky (April 11, 1918, Buffalo, New York – September 1, 2005) was a chemist who was the co-discoverer of the element promethium.
Biography
Marinsky was born in Buffalo, New York on April 11, 1918. He attended the State University of New York at Buffalo, beginning at age 16 and receiving a bachelor's degree in chemistry in 1939.
During World War II he was employed as a chemist for the Manhattan Project, working for Clinton Laboratories (now Oak Ridge National Laboratory) from 1944 to 1946. In 1945, together with Lawrence E. Glendenin and Charles D. Coryell, he isolated the previously undocumented rare earth element 61 (promethium). Marinsky and Glendenin produced it both by extraction from fission products and by bombarding neodymium with neutrons. They isolated it using ion-exchange chromatography. Publication of the finding was delayed until later due to the war. Marinsky and Glendenin announced the discovery at a meeting of the American Chemical Society in September 1947. Upon the suggestion of Charles D. Coryell's wife Grace Coryell, the team named the new element for the mythical god Prometheus, who stole fire from the gods and was punished for the act by Zeus. They had also considered naming it "clintonium" for the facility where it was isolated.
Marinsky was among the Manhattan Project scientists who in 1945 signed a petition against using an atomic bomb on Japan.
He resumed his education after the war, obtaining a PhD in Nuclear and Inorganic Chemist
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https://en.wikipedia.org/wiki/Raymond%20Lemieux
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Raymond Urgel Lemieux, CC, AOE, FRS (June 16, 1920 – July 22, 2000) was a Canadian organic chemist, who pioneered many discoveries in the field of chemistry, his first and most famous being the synthesis of sucrose. His contributions include the discovery of the anomeric effect and the development of general methodologies for the synthesis of saccharides still employed in the area of carbohydrate chemistry. He was a fellow of the Royal Society of Canada and the Royal Society (England), and a recipient of the prestigious Albert Einstein World Award of Science and Wolf Prize in Chemistry.
Life and career
Dr. Raymond U. Lemieux was born in Lac La Biche, Alberta, Canada. His family moved to Edmonton, Alberta in 1926. He studied chemistry at the University of Alberta and received a BSc with Honours in Chemistry in 1943. He went on to study at McGill University, where he received his PhD in Organic Chemistry in 1946. He won a post-doctoral scholarship at Ohio State University, where Bristol Laboratories Inc. sponsored his research on the structure of streptomycin. He met his future wife, a doctoral student, at Ohio State and they were married in 1948.
In following years, he returned to Canada where he spent two years as an assistant professor at the University of Saskatchewan. Next he served as Senior Research Officer at the National Research Council's Prairie Regional Laboratory in Saskatoon. In 1953 he and a fellow researcher, George Huber, were the first scientists to s
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https://en.wikipedia.org/wiki/Math%20League
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Math League is a math competition for elementary, middle, and high school students in the United States, Canada, and other countries. The Math League was founded in 1977 by two high school mathematics teachers, Steven R. Conrad and Daniel Flegler. Math Leagues, Inc. publishes old contests through a series of books entitled Math League Press. The purpose of the Math League Contests is to provide students "an enriching opportunity to participate in an academically-oriented activity" and to let students "gain recognition for mathematical achievement".
Math League runs three contest formats:
Grades 4-5: 30 multiple-choice questions to solve in 30 minutes, covering arithmetic and basic principles
Grades 6-8: 35 multiple-choice questions to solve in 30 minutes, covering advanced arithmetic and basic topics in geometry and algebra
Grades 9-12: Series of 6 contests. Each contest contains 6 short-answer questions to solve in 30 minutes, covering geometry, algebra, trigonometry, and other advanced pre-calculus topics.
Only plain paper, pencil or pen, and a calculator without QWERTY keyboard are allowed.
Students who score above 12 points in grades 4 and 5, and above 15 points in grades 6-8 are awarded a 'Certificate of Merit." Which means they win
References
External links
Math League Homepage
Mathematics competitions
Recurring events established in 1977
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https://en.wikipedia.org/wiki/Dyon
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In physics, a dyon is a hypothetical particle in 4-dimensional theories with both electric and magnetic charges. A dyon with a zero electric charge is usually referred to as a magnetic monopole. Many grand unified theories predict the existence of both magnetic monopoles and dyons.
Dyons were first proposed by Julian Schwinger in 1969 as a phenomenological alternative to
quarks. He extended the Dirac quantization condition to the dyon and used the model to predict the existence of a particle with the properties of the J/ψ meson prior to its discovery in 1974.
The allowed charges of dyons are restricted by the Dirac quantization condition. This states in particular that their magnetic charge must be integral, and that their electric charges must all be equal modulo 1. The Witten effect, demonstrated by Edward Witten in his 1979 paper, states that the electric charges of dyons must all be equal, modulo one, to the product of their magnetic charge and the theta angle of the theory. In particular, if a theory preserves CP symmetry then the electric charges of all dyons are integers.
References
External links
Electromagnetic duality for children, lecture notes by José Figueroa-O'Farrill
Gauge theories
Magnetic monopoles
Physics beyond the Standard Model
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https://en.wikipedia.org/wiki/Loop-erased%20random%20walk
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In mathematics, loop-erased random walk is a model for a random simple path with important applications in combinatorics, physics and quantum field theory. It is intimately connected to the uniform spanning tree, a model for a random tree. See also random walk for more general treatment of this topic.
Definition
Assume G is some graph and is some path of length n on G. In other words, are vertices of G such that and are connected by an edge. Then the loop erasure of is a new simple path created by erasing all the loops of in chronological order. Formally, we define indices inductively using
where "max" here means up to the length of the path . The induction stops when for some we have . Assume this happens at J i.e. is the last . Then the loop erasure of , denoted by is a simple path of length J defined by
Now let G be some graph, let v be a vertex of G, and let R be a random walk on G starting from v. Let T be some stopping time for R. Then the loop-erased random walk until time T is LE(R([1,T])). In other words, take R from its beginning until T — that's a (random) path — erase all the loops in chronological order as above — you get a random simple path.
The stopping time T may be fixed, i.e. one may perform n steps and then loop-erase. However, it is usually more natural to take T to be the hitting time in some set. For example, let G be the graph Z2 and let R be a random walk starting from the point (0,0). Let T be the time when R first hits the circle of ra
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https://en.wikipedia.org/wiki/U-87%20MG
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In cell biology, U-87 MG is a human glioblastoma cell line that is commonly used in brain cancer research.
History and Characteristics
Formally known as U-87 MG (abbreviation for Uppsala 87 Malignant Glioma), the U87 cell line has an epithelial morphology and was obtained from a 44-year-old female patient in 1966 at Uppsala University. The cell line was thought to be deposited at the Memorial Sloan Kettering Cancer Center in 1973, after which the ATCC obtained it in 1982. However, in 2016 the commonly used version of U87MG (from the ATCC) was found to be non-identical to its patient of origin. Analysis of DNA profile and mtDNA position suggest that the Uppsala U-87 MG line is authentic to the original tumor tissue while the ATCC U-87 MG line is not; The ATCC line is likely a bona fide human glioblastoma cell line of unknown origin. The entire sequence of the genome of U-87 MG has been published in PLoS Genetics.
U-87 MG can be obtained from the American Type Culture Collection (ATCC) where it is known by the accession number HTB-14 and it is reported that the cell line comes from a male patient of unknown age.
Growth conditions
U87 growth media is generally made with Eagle's minimum essential medium + 10% FBS + 100 U/mL penicillin + 100 µg/mL streptomycin. It is propagated at 37 °C in a 5% carbon dioxide atmosphere.
References
External links
ATCC record for HTB-14
Cellosaurus entry for U87
Human cell lines
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https://en.wikipedia.org/wiki/Twitch
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Twitch may refer to:
Biology
Muscle contraction
Convulsion, rapid and repeated muscle contraction and relaxation
Fasciculation, a small, local, involuntary muscle contraction
Myoclonic twitch, a jerk usually caused by sudden muscle contractions
Myokymia, a continuous, involuntary muscle twitch that affects the muscles of the face
Spasm, a sudden, involuntary contraction
Tic, an involuntary, repetitive, nonrhythmic action
Tremor, an involuntary, repetitive, somewhat rhythmic action
Twitching motility, a form of crawling some bacteria use to move over surfaces
Entertainment
Twitch (service), an Amazon subsidiary live streaming video website
Twitch (film), a 2005 short directed by Leah Meyerhoff
Screen Anarchy, formerly Twitch Film or Twitch, a film news and review website
Maximilian "Twitch" Williams, a character in the comic series Sam and Twitch
"Twitch", a fictional character from the book How to Eat Fried Worms and its 2006 film adaptation
Twitch gameplay, a computer or video game that challenges the player's reaction time
Music
Twitch (Ministry album), 1986
Twitch (Aldo Nova album), 1985, or the title track
Twitch (EP), by Jebediah, 1996
"Twitch", a 2001 song by Christina Milian from her self-titled album
People
Stephen "tWitch" Boss (1982–2022), American freestyle hip-hop dancer, entertainer and actor
Jeremy Stenberg (born 1981), American motocross rider
Other uses
Twitch (device), used to restrain horses
Twitch grass
Twitch, in birdwatching, t
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https://en.wikipedia.org/wiki/Modular%20representation%20theory
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Modular representation theory is a branch of mathematics, and is the part of representation theory that studies linear representations of finite groups over a field K of positive characteristic p, necessarily a prime number. As well as having applications to group theory, modular representations arise naturally in other branches of mathematics, such as algebraic geometry, coding theory, combinatorics and number theory.
Within finite group theory, character-theoretic results proved by Richard Brauer using modular representation theory played an important role in early progress towards the classification of finite simple groups, especially for simple groups whose characterization was not amenable to purely group-theoretic methods because their Sylow 2-subgroups were too small in an appropriate sense. Also, a general result on embedding of elements of order 2 in finite groups called the Z* theorem, proved by George Glauberman using the theory developed by Brauer, was particularly useful in the classification program.
If the characteristic p of K does not divide the order |G|, then modular representations are completely reducible, as with ordinary (characteristic 0) representations, by virtue of Maschke's theorem. In the other case, when |G| ≡ 0 mod p, the process of averaging over the group needed to prove Maschke's theorem breaks down, and representations need not be completely reducible. Much of the discussion below implicitly assumes that the field K is sufficiently large
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https://en.wikipedia.org/wiki/Multiplicative%20group
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In mathematics and group theory, the term multiplicative group refers to one of the following concepts:
the group under multiplication of the invertible elements of a field, ring, or other structure for which one of its operations is referred to as multiplication. In the case of a field F, the group is , where 0 refers to the zero element of F and the binary operation • is the field multiplication,
the algebraic torus GL(1)..
Examples
The multiplicative group of integers modulo n is the group under multiplication of the invertible elements of . When n is not prime, there are elements other than zero that are not invertible.
The multiplicative group of positive real numbers is an abelian group with 1 its identity element. The logarithm is a group isomorphism of this group to the additive group of real numbers, .
The multiplicative group of a field is the set of all nonzero elements: , under the multiplication operation. If is finite of order q (for example q = p a prime, and ), then the multiplicative group is cyclic: .
Group scheme of roots of unity
The group scheme of n-th roots of unity is by definition the kernel of the n-power map on the multiplicative group GL(1), considered as a group scheme. That is, for any integer n > 1 we can consider the morphism on the multiplicative group that takes n-th powers, and take an appropriate fiber product of schemes, with the morphism e that serves as the identity.
The resulting group scheme is written μn (or ). It gives ris
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https://en.wikipedia.org/wiki/Tail%20call
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In computer science, a tail call is a subroutine call performed as the final action of a procedure. If the target of a tail is the same subroutine, the subroutine is said to be tail recursive, which is a special case of direct recursion. Tail recursion (or tail-end recursion) is particularly useful, and is often easy to optimize in implementations.
Tail calls can be implemented without adding a new stack frame to the call stack. Most of the frame of the current procedure is no longer needed, and can be replaced by the frame of the tail call, modified as appropriate (similar to overlay for processes, but for function calls). The program can then jump to the called subroutine. Producing such code instead of a standard call sequence is called tail-call elimination or tail-call optimization. Tail-call elimination allows procedure calls in tail position to be implemented as efficiently as goto statements, thus allowing efficient structured programming. In the words of Guy L. Steele, "in general, procedure calls may be usefully thought of as GOTO statements which also pass parameters, and can be uniformly coded as [machine code] JUMP instructions."
Not all programming languages require tail-call elimination. However, in functional programming languages, tail-call elimination is often guaranteed by the language standard, allowing tail recursion to use a similar amount of memory as an equivalent loop. The special case of tail-recursive calls, when a function calls itself, may be m
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https://en.wikipedia.org/wiki/Pulickel%20Ajayan
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Pulickel Madhavapanicker Ajayan, known as P. M. Ajayan, is the Benjamin M. and Mary Greenwood Anderson Professor in Engineering at Rice University. He is the founding chair of Rice University's Materials Science and NanoEngineering department and also holds joint appointments with the Department of Chemistry and Department of Chemical and Biomolecular Engineering. Prior to joining Rice, he was the Henry Burlage Professor of Material Sciences and Engineering and the director of the NYSTAR interconnect focus center at Rensselaer Polytechnic Institute until 2007. Known for his pioneering work of designing and carrying out the first experiments to make nanotubes intentionally.
Early life and education
Ajayan was born on 15 July 1962 at Kodungallur, a coastal town in Thrissur District, in the Indian state of Kerala, to Pulickal Madhava Panickar, a telephone mechanic, and Radha, a teacher at the local school. He studied in a government school in Kodungallur where the medium of instruction was Malayalam until 6th standard, after which he moved to Loyola School, Thiruvananthapuram, a high school he has credited for making a strong impact on him, and for making him "realize that learning is the most exciting thing one can ever befriend". He graduated from Loyola in 1977. In 1985, Ajayan graduated at the top of his class with a BTech degree in Metallurgical Engineering from Indian Institute of Technology (BHU) Varanasi. In 1989, he earned a PhD in Materials Science and Engineering fro
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https://en.wikipedia.org/wiki/Galois%20cohomology
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In mathematics, Galois cohomology is the study of the group cohomology of Galois modules, that is, the application of homological algebra to modules for Galois groups. A Galois group G associated to a field extension L/K acts in a natural way on some abelian groups, for example those constructed directly from L, but also through other Galois representations that may be derived by more abstract means. Galois cohomology accounts for the way in which taking Galois-invariant elements fails to be an exact functor.
History
The current theory of Galois cohomology came together around 1950, when it was realised that the Galois cohomology of ideal class groups in algebraic number theory was one way to formulate class field theory, at the time it was in the process of ridding itself of connections to L-functions. Galois cohomology makes no assumption that Galois groups are abelian groups, so this was a non-abelian theory. It was formulated abstractly as a theory of class formations. Two developments of the 1960s turned the position around. Firstly, Galois cohomology appeared as the foundational layer of étale cohomology theory (roughly speaking, the theory as it applies to zero-dimensional schemes). Secondly, non-abelian class field theory was launched as part of the Langlands philosophy.
The earliest results identifiable as Galois cohomology had been known long before, in algebraic number theory and the arithmetic of elliptic curves. The normal basis theorem implies that the first
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https://en.wikipedia.org/wiki/Reaction%20%28physics%29
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As described by the third of Newton's laws of motion of classical mechanics, all forces occur in pairs such that if one object exerts a force on another object, then the second object exerts an equal and opposite reaction force on the first. The third law is also more generally stated as: "To every action there is always opposed an equal reaction: or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts." The attribution of which of the two forces is the action and which is the reaction is arbitrary. Either of the two can be considered the action, while the other is its associated reaction.
Examples
Interaction with ground
When something is exerting force on the ground, the ground will push back with equal force in the opposite direction. In certain fields of applied physics, such as biomechanics, this force by the ground is called 'ground reaction force'; the force by the object on the ground is viewed as the 'action'.
When someone wants to jump, he or she exerts additional downward force on the ground ('action'). Simultaneously, the ground exerts upward force on the person ('reaction'). If this upward force is greater than the person's weight, this will result in upward acceleration. When these forces are perpendicular to the ground, they are also called a normal force.
Likewise, the spinning wheels of a vehicle attempt to slide backward across the ground. If the ground is not too slippery, this results in a pair of friction
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https://en.wikipedia.org/wiki/Chloroacetic%20acids
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In organic chemistry, the chloroacetic acids (systematic name chloroethanoic acids) are three related chlorocarbon carboxylic acids:
Chloroacetic acid (chloroethanoic acid), CH2ClCOOH
Dichloroacetic acid (dichloroethanoic acid; bichloroacetic acid, BCA), CHCl2COOH
Trichloroacetic acid (trichloroethanoic acid), CCl3COOH
Properties
As the number of chlorine atoms increases, the electronegativity of that end of the molecule increases, and the molecule adopts a progressively more ionic character: its density, boiling point and acidity all increase.
{| class="wikitable sortable"
! Acid || Melting point (°C) || Boiling point (°C) || Density (g/cm3) || pKa
|-
| Acetic acid || 16.5 || 118.1 || 1.05 || 4.76
|-
| Chloroacetic acid || 61–63 || 189 || 1.58 || 2.87
|-
| Dichloroacetic acid || 9.5 || 194 || 1.57 || 1.25
|-
| Trichloroacetic acid || 57 || 196 || 1.63 || 0.77
|}
Production
Chloroacetic acid is mainly made by hydrolysing trichloroethylene in the presence of sulfuric acid:
CCl2=CHCl + 2 H2O → CH2ClCOOH + 2 HCl
Dichloroacetic acid is manufactured in small quantities by reducing trichloroacetic acid.
Trichloroacetic acid is made by directly reacting chlorine with acetic acid using a suitable catalyst.
Uses
Chloroacetic acid is chemical intermediate for production of various pharmaceuticals and insecticides.
Trichloroacetic acid is used for various analytic tests in biochemistry. In sufficient concentration it will cause protein, DNA and RNA to precipitate out
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https://en.wikipedia.org/wiki/Genetics%20and%20the%20Origin%20of%20Species
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Genetics and the Origin of Species is a 1937 book by the Ukrainian-American evolutionary biologist Theodosius Dobzhansky. It is regarded as one of the most important works of modern synthesis and was one of the earliest. The book popularized the work of population genetics to other biologists and influenced their appreciation for the genetic basis of evolution. In his book, Dobzhansky applied the theoretical work of Sewall Wright (1889–1988) to the study of natural populations, allowing him to address evolutionary problems in a novel way during his time. Dobzhansky implements theories of mutation, natural selection, and speciation throughout his book to explain the habits of populations and the resulting effects on their genetic behavior. The book explains evolution in depth as a process over time that accounts for the diversity of all life on Earth. The study of evolution was present, but greatly neglected at the time. Dobzhansky illustrates that evolution regarding the origin and nature of species during this time in history was deemed mysterious, but had expanding potential for progress to be made in its field.
Background
In Darwin's theory of natural selection, more organisms are produced than can survive. Some have variations that give them a competitive advantage, and they have the best chance of surviving and procreating. The main element lacking in the theory was any mechanism that would allow organisms to pass on these favorable variations. Lacking such a mechanism,
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https://en.wikipedia.org/wiki/Unordered%20pair
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In mathematics, an unordered pair or pair set is a set of the form {a, b}, i.e. a set having two elements a and b with no particular relation between them, where {a, b} = {b, a}. In contrast, an ordered pair (a, b) has a as its first element and b as its second element, which means (a, b) ≠ (b, a).
While the two elements of an ordered pair (a, b) need not be distinct, modern authors only call {a, b} an unordered pair if a ≠ b.
But for a few authors a singleton is also considered an unordered pair, although today, most would say that {a, a} is a multiset. It is typical to use the term unordered pair even in the situation where the elements a and b could be equal, as long as this equality has not yet been established.
A set with precisely two elements is also called a 2-set or (rarely) a binary set.
An unordered pair is a finite set; its cardinality (number of elements) is 2 or (if the two elements are not distinct) 1.
In axiomatic set theory, the existence of unordered pairs is required by an axiom, the axiom of pairing.
More generally, an unordered n-tuple is a set of the form {a1, a2,... an}.
Notes
References
.
Basic concepts in set theory
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https://en.wikipedia.org/wiki/African%20philosophy
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African philosophy is the philosophical discourse produced in Africa or by indigenous Africans. African philosophers are found in the various academic fields of present philosophy, such as metaphysics, epistemology, moral philosophy, and political philosophy. One particular subject that several modern African philosophers have written about is that on the subject of freedom and what it means to be free or to experience wholeness. Philosophy in Africa has a rich and varied history, some of which has been lost over time. Some of the world's oldest philosophical texts have been produced in Ancient Egypt (Kemet), written in Hieratic and on papyrus, from ca. 2200 to 1000 BCE, one of the earliest known African philosophers was Ptahhotep, an ancient Egyptian philosopher. In general, the ancient Greeks acknowledged the Egyptian forebearers, and in the fifth century BCE, the philosopher Isocrates declared that earliest Greek thinkers traveled to Egypt to seek knowledge; one of them Pythagoras of Samos who “was first to bring to the Greeks all philosophy.” In the 21st century, new research by Egyptologists has indicated that the word "philosopher" itself seems to stem from Egypt: "the founding Greek word philosophos, lover of wisdom, is itself a borrowing from and translation of the Egyptian concept mer-rekh (mr-rḫ) which literally means “lover of wisdom,” or knowledge." In the early and mid-twentieth century, anti-colonial movements had a tremendous effect on the development of a dist
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https://en.wikipedia.org/wiki/Monte%20Carlo%20integration
|
In mathematics, Monte Carlo integration is a technique for numerical integration using random numbers. It is a particular Monte Carlo method that numerically computes a definite integral. While other algorithms usually evaluate the integrand at a regular grid, Monte Carlo randomly chooses points at which the integrand is evaluated. This method is particularly useful for higher-dimensional integrals.
There are different methods to perform a Monte Carlo integration, such as uniform sampling, stratified sampling, importance sampling, sequential Monte Carlo (also known as a particle filter), and mean-field particle methods.
Overview
In numerical integration, methods such as the trapezoidal rule use a deterministic approach. Monte Carlo integration, on the other hand, employs a non-deterministic approach: each realization provides a different outcome. In Monte Carlo, the final outcome is an approximation of the correct value with respective error bars, and the correct value is likely to be within those error bars.
The problem Monte Carlo integration addresses is the computation of a multidimensional definite integral
where Ω, a subset of Rm, has volume
The naive Monte Carlo approach is to sample points uniformly on Ω: given N uniform samples,
I can be approximated by
.
This is because the law of large numbers ensures that
.
Given the estimation of I from QN, the error bars of QN can be estimated by the sample variance using the unbiased estimate of the variance.
which
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https://en.wikipedia.org/wiki/Paraconsistent%20mathematics
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Paraconsistent mathematics, sometimes called inconsistent mathematics, represents an attempt to develop the classical infrastructure of mathematics (e.g. analysis) based on a foundation of paraconsistent logic instead of classical logic. A number of reformulations of analysis can be developed, for example functions which both do and do not have a given value simultaneously.
Chris Mortensen claims (see references):
One could hardly ignore the examples of analysis and its special case, the calculus. There prove to be many places where there are distinctive inconsistent insights; see Mortensen (1995) for example. (1) Robinson's non-standard analysis was based on infinitesimals, quantities smaller than any real number, as well as their reciprocals, the infinite numbers. This has an inconsistent version, which has some advantages for calculation in being able to discard higher-order infinitesimals. The theory of differentiation turned out to have these advantages, while the theory of integration did not. (2)
References
McKubre-Jordens, M. and Weber, Z. (2012). "Real analysis in paraconsistent logic". Journal of Philosophical Logic 41 (5):901–922. doi: 10.1017/S1755020309990281
Mortensen, C. (1995). Inconsistent Mathematics. Dordrecht: Kluwer.
Weber, Z. (2010). "Transfinite numbers in paraconsistent set theory". Review of Symbolic Logic 3 (1):71–92. doi:10.1017/S1755020309990281
External links
Entry in the Internet Encyclopedia of Philosophy
Entry in the Stanford Encyclo
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https://en.wikipedia.org/wiki/GNU%20Scientific%20Library
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The GNU Scientific Library (or GSL) is a software library for numerical computations in applied mathematics and science. The GSL is written in C; wrappers are available for other programming languages. The GSL is part of the GNU Project and is distributed under the GNU General Public License.
Project history
The GSL project was initiated in 1996 by physicists Mark Galassi and James Theiler of Los Alamos National Laboratory. They aimed at writing a modern replacement for widely used but somewhat outdated Fortran libraries such as Netlib. They carried out the overall design and wrote early modules; with that ready they recruited other scientists to contribute.
The "overall development of the library and the design and implementation of the major modules" was carried out by Brian Gough and Gerard Jungman. Other major contributors were Jim Davies, Reid Priedhorsky, M. Booth, and F. Rossi.
Version 1.0 was released in 2001. In the following years, the library expanded only slowly; as the documentation stated, the maintainers were more interested in stability than in additional functionality. Major version 1 ended with release 1.16 of July 2013; this was the only public activity in the three years 2012–2014.
Vigorous development resumed with publication of version 2.0 in October 2015. The latest version 2.7 was released in June 2021.
Example
The following example program calculates the value of the Bessel function of the first kind and order zero for 5:
#include <stdio.h>
#i
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https://en.wikipedia.org/wiki/Combinatorial%20number%20system
|
In mathematics, and in particular in combinatorics, the combinatorial number system of degree k (for some positive integer k), also referred to as combinadics, or the Macaulay representation of an integer, is a correspondence between natural numbers (taken to include 0) N and k-combinations. The combinations are represented as strictly decreasing sequences ck > ... > c2 > c1 ≥ 0 where each ci corresponds to the index of a chosen element in a given k-combination. Distinct numbers correspond to distinct k-combinations, and produce them in lexicographic order. The numbers less than correspond to all of }. The correspondence does not depend on the size n of the set that the k-combinations are taken from, so it can be interpreted as a map from N to the k-combinations taken from N; in this view the correspondence is a bijection.
The number N corresponding to (ck, ..., c2, c1) is given by
.
The fact that a unique sequence corresponds to any non-negative number N was first observed by D. H. Lehmer. Indeed, a greedy algorithm finds the k-combination corresponding to N: take ck maximal with , then take ck−1 maximal with , and so forth. Finding the number N, using the formula above, from the k-combination (ck, ..., c2, c1) is also known as "ranking", and the opposite operation (given by the greedy algorithm) as "unranking"; the operations are known by these names in most computer algebra systems, and in computational mathematics.
The originally used term "combinatorial representat
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https://en.wikipedia.org/wiki/Wolstenholme%27s%20theorem
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In mathematics, Wolstenholme's theorem states that for a prime number , the congruence
holds, where the parentheses denote a binomial coefficient. For example, with p = 7, this says that 1716 is one more than a multiple of 343. The theorem was first proved by Joseph Wolstenholme in 1862. In 1819, Charles Babbage showed the same congruence modulo p2, which holds for . An equivalent formulation is the congruence
for , which is due to Wilhelm Ljunggren (and, in the special case , to J. W. L. Glaisher) and is inspired by Lucas' theorem.
No known composite numbers satisfy Wolstenholme's theorem and it is conjectured that there are none (see below). A prime that satisfies the congruence modulo p4 is called a Wolstenholme prime (see below).
As Wolstenholme himself established, his theorem can also be expressed as a pair of congruences for (generalized) harmonic numbers:
(Congruences with fractions make sense, provided that the denominators are coprime to the modulus.)
For example, with p=7, the first of these says that the numerator of 49/20 is a multiple of 49, while the second says the numerator of 5369/3600 is a multiple of 7.
Wolstenholme primes
A prime p is called a Wolstenholme prime iff the following condition holds:
If p is a Wolstenholme prime, then Glaisher's theorem holds modulo p4. The only known Wolstenholme primes so far are 16843 and 2124679 ; any other Wolstenholme prime must be greater than 109. This result is consistent with the heuristic argument that
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https://en.wikipedia.org/wiki/Instruction%20scheduling
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In computer science, instruction scheduling is a compiler optimization used to improve instruction-level parallelism, which improves performance on machines with instruction pipelines. Put more simply, it tries to do the following without changing the meaning of the code:
Avoid pipeline stalls by rearranging the order of instructions.
Avoid illegal or semantically ambiguous operations (typically involving subtle instruction pipeline timing issues or non-interlocked resources).
The pipeline stalls can be caused by structural hazards (processor resource limit), data hazards (output of one instruction needed by another instruction) and control hazards (branching).
Data hazards
Instruction scheduling is typically done on a single basic block. In order to determine whether rearranging the block's instructions in a certain way preserves the behavior of that block, we need the concept of a data dependency. There are three types of dependencies, which also happen to be the three data hazards:
Read after Write (RAW or "True"): Instruction 1 writes a value used later by Instruction 2. Instruction 1 must come first, or Instruction 2 will read the old value instead of the new.
Write after Read (WAR or "Anti"): Instruction 1 reads a location that is later overwritten by Instruction 2. Instruction 1 must come first, or it will read the new value instead of the old.
Write after Write (WAW or "Output"): Two instructions both write the same location. They must occur in their original
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https://en.wikipedia.org/wiki/Geoff%20Crammond
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Geoff Crammond is a computer game designer and programmer who specialises in motor racing games. A former defence industry systems engineer, he claims to have had little interest in motor racing before programming his first racing game (Revs) back in 1984, but he holds a physics degree, which may explain the realism of some of his programming. As a consequence of that project he became a big fan of Formula One motor racing. At the end of the 80s, this interest, plus the ever improving capabilities of home computers, inspired him to specialise in programming Formula One racing simulations.
Games
One of his early releases was Aviator, a Spitfire simulator released by Acornsoft for the BBC Micro in March 1984. Having been motivated to make his own flight simulator from the hardware level upwards, Crammond identified the possibility of using one of the increasingly sophisticated home computers, if only "to cannibalise it". Recognising the potential of the BBC Micro, he ordered one in 1981 and, upon receiving it six months later, then set about familiarising himself with the system, taking a detour to produce a Space Invaders clone, Super Invaders, which was accepted for publication and sold by Acornsoft. Discussion with Acornsoft about his plans for making a flight simulator led to the Aviator concept, and the program itself was written in a period of nine months.
Although displayed in only four colours and has few of the features of modern simulators for more powerful compute
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https://en.wikipedia.org/wiki/Hurwitz%27s%20automorphisms%20theorem
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In mathematics, Hurwitz's automorphisms theorem bounds the order of the group of automorphisms, via orientation-preserving conformal mappings, of a compact Riemann surface of genus g > 1, stating that the number of such automorphisms cannot exceed 84(g − 1). A group for which the maximum is achieved is called a Hurwitz group, and the corresponding Riemann surface a Hurwitz surface. Because compact Riemann surfaces are synonymous with non-singular complex projective algebraic curves, a Hurwitz surface can also be called a Hurwitz curve. The theorem is named after Adolf Hurwitz, who proved it in .
Hurwitz's bound also holds for algebraic curves over a field of characteristic 0, and over fields of positive characteristic p>0 for groups whose order is coprime to p, but can fail over fields of positive characteristic p>0 when p divides the group order. For example, the double cover of the projective line y2 = xp −x branched at all points defined over the prime field has genus g=(p−1)/2 but is acted on by the group SL2(p) of order p3−p.
Interpretation in terms of hyperbolicity
One of the fundamental themes in differential geometry is a trichotomy between the Riemannian manifolds of positive, zero, and negative curvature K. It manifests itself in many diverse situations and on several levels. In the context of compact Riemann surfaces X, via the Riemann uniformization theorem, this can be seen as a distinction between the surfaces of different topologies:
X a sphere, a compac
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https://en.wikipedia.org/wiki/Mutator%20method
|
In computer science, a mutator method is a method used to control changes to a variable. They are also widely known as setter methods. Often a setter is accompanied by a getter, which returns the value of the private member variable. They are also known collectively as accessors.
The mutator method is most often used in object-oriented programming, in keeping with the principle of encapsulation. According to this principle, member variables of a class are made private to hide and protect them from other code, and can only be modified by a public member function (the mutator method), which takes the desired new value as a parameter, optionally validates it, and modifies the private member variable. Mutator methods can be compared to assignment operator overloading but they typically appear at different levels of the object hierarchy.
Mutator methods may also be used in non-object-oriented environments. In this case, a reference to the variable to be modified is passed to the mutator, along with the new value. In this scenario, the compiler cannot restrict code from bypassing the mutator method and changing the variable directly. The responsibility falls to the developers to ensure the variable is only modified through the mutator method and not modified directly.
In programming languages that support them, properties offer a convenient alternative without giving up the utility of encapsulation.
In the examples below, a fully implemented mutator method can also validate the
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https://en.wikipedia.org/wiki/Order%20%28ring%20theory%29
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In mathematics, an order in the sense of ring theory is a subring of a ring , such that
is a finite-dimensional algebra over the field of rational numbers
spans over , and
is a -lattice in .
The last two conditions can be stated in less formal terms: Additively, is a free abelian group generated by a basis for over .
More generally for an integral domain contained in a field , we define to be an -order in a -algebra if it is a subring of which is a full -lattice.
When is not a commutative ring, the idea of order is still important, but the phenomena are different. For example, the Hurwitz quaternions form a maximal order in the quaternions with rational co-ordinates; they are not the quaternions with integer coordinates in the most obvious sense. Maximal orders exist in general, but need not be unique: there is in general no largest order, but a number of maximal orders. An important class of examples is that of integral group rings.
Examples
Some examples of orders are:
If is the matrix ring over , then the matrix ring over is an -order in
If is an integral domain and a finite separable extension of , then the integral closure of in is an -order in .
If in is an integral element over , then the polynomial ring is an -order in the algebra
If is the group ring of a finite group , then is an -order on
A fundamental property of -orders is that every element of an -order is integral over .
If the integral closure of in is an -order th
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https://en.wikipedia.org/wiki/Helen%20Rodd
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Helen Rodd is a Canadian zoologist who is a professor of Ecology and Evolutionary Biology at the University of Toronto.
Rodd's work focuses on reproductive strategies among live-bearing fish as a system to understand mate selection among animals. Her work on mate preference in guppy fish (Poecilia reticulata) attracted media attention in numerous nature magazines and the United States public broadcasting service, as well as academic notice, based upon her research finding that female guppies in Trinidad may choose males for orange coloration similar to a favored food, the fruit of a local tree. In 2001, Rodd was awarded a Premier's Research Excellence Award by the Ontario government for her work in guppy mate selection.
Rodd received her Ph.D. in Biology from York University in Toronto with a thesis titled: Phenotypic plasticity in the life history traits and sexual behaviour of Trinidadian guppies (Poecilia reticulata) in response to their social environment.
References
Year of birth missing (living people)
Living people
University of Toronto alumni
Academic staff of the University of Toronto
York University alumni
Canadian zoologists
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https://en.wikipedia.org/wiki/Lw%C3%B3w-Warsaw%20School
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Lwow–Warsaw School may refer to:
Lwów–Warsaw school of logic
Lwów School of Mathematics
Warsaw School of Mathematics
Lwów–Warsaw School of History
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https://en.wikipedia.org/wiki/NEMA%20%28machine%29
|
In the history of cryptography, the NEMA (NEue MAschine) ("new machine"), also designated the T-D (Tasten-Druecker-Maschine) ("key-stroke machine"), was a 10-wheel rotor machine designed by the Swiss Army during the World War II as a replacement for their Enigma machines.
History
The Swiss became aware that their current machine, a commercial Enigma (the Swiss K), had been broken by both Allied and German cryptanalysts.
A new design was begun between 1941 and 1943 by Captain Arthur Alder, a professor of mathematics at the University of Bern. The team which designed the machine also included Professors Hugo Hadwiger and Heinrich Emil Weber.
In the spring of 1944, the first prototype had become available. After some modifications, the design was accepted in March 1945, and production of 640 machines began the following month by Zellweger AG. The first machine entered service in 1947.
NEMA was declassified on 9 July 1992, and machines were offered for sale to the public on 4 May 1994.
The machine
NEMA uses 10 wheels, of which four are normal electrical rotors with 26 contacts at each end that are scramble wired in a way unique to each rotor type; one is an electrical reflector (like the Enigma's Umkehrwalze) with one set of 26 pairwise cross connected contacts; and the remaining five are "drive wheels", with mechanical cams that control the stepping of the rotors and the reflector. The wheels are assembled on an axle in pairs consisting of a drive wheel and an electrical ro
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https://en.wikipedia.org/wiki/Exotic%20sphere
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In an area of mathematics called differential topology, an exotic sphere is a differentiable manifold M that is homeomorphic but not diffeomorphic to the standard Euclidean n-sphere. That is, M is a sphere from the point of view of all its topological properties, but carrying a smooth structure that is not the familiar one (hence the name "exotic").
The first exotic spheres were constructed by in dimension as -bundles over . He showed that there are at least 7 differentiable structures on the 7-sphere. In any dimension showed that the diffeomorphism classes of oriented exotic spheres form the non-trivial elements of an abelian monoid under connected sum, which is a finite abelian group if the dimension is not 4. The classification of exotic spheres by showed that the oriented exotic 7-spheres are the non-trivial elements of a cyclic group of order 28 under the operation of connected sum.
Specifically, this means that the elements of this group (n ≠ 4) are the equivalence classes of smooth structures on Sn, where two structures are considered equivalent if there is an orientation preserving diffeomorphism carrying one structure onto the other. The group operation is defined by [x] + [y] = [x + y],
where x and y are arbitrary representatives of their equivalence classes, and "x + y" denotes the smooth structure on the smooth Sn that is the connected sum of x and y. It is necessary to show that such a definition does not depend on the choices made; indeed this can be sh
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https://en.wikipedia.org/wiki/Infinite%20Energy%20%28magazine%29
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Infinite Energy is a bi-monthly magazine published in New Hampshire that details theories and experiments concerning alternative energy, new science and new physics. The magazine was founded by the late Eugene Mallove, and is owned by the non-profit New Energy Foundation. It was established in 1994 as Cold Fusion magazine and changed its name in March 1995.
Topics of interest include "new hydrogen physics," also called cold fusion; vacuum energy, or zero point energy; and so-called "environmental energy" which they define as the attempt to violate the Second Law of Thermodynamics, for example with a perpetual motion machine. This is done in pursuit of the founder's commitment to "unearthing new sources of energy and new paradigms in science." The magazine has also published articles and book reviews that are critical of the Big Bang theory that describes the origin of the universe.
The magazine has a print run of 3,000, and is available on U.S. newsstands. The issues range in size from 48 to 100 pages.
References
External links
Sustainable energy
Bimonthly magazines published in the United States
Science and technology magazines published in the United States
Cold fusion
Criticism of science
Free energy conspiracy theories
Magazines established in 1994
Perpetual motion
Magazines published in New Hampshire
Energy magazines
Pseudoscience literature
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https://en.wikipedia.org/wiki/Discrepancy%20theory
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In mathematics, discrepancy theory describes the deviation of a situation from the state one would like it to be in. It is also called the theory of irregularities of distribution. This refers to the theme of classical discrepancy theory, namely distributing points in some space such that they are evenly distributed with respect to some (mostly geometrically defined) subsets. The discrepancy (irregularity) measures how far a given distribution deviates from an ideal one.
Discrepancy theory can be described as the study of inevitable irregularities of distributions, in measure-theoretic and combinatorial settings. Just as Ramsey theory elucidates the impossibility of total disorder, discrepancy theory studies the deviations from total uniformity.
A significant event in the history of discrepancy theory was the 1916 paper of Weyl on the uniform distribution of sequences in the unit interval.
Theorems
Discrepancy theory is based on the following classic theorems:
The theorem of van Aardenne–Ehrenfest
Axis-parallel rectangles in the plane (Roth, Schmidt)
Discrepancy of half-planes (Alexander, Matoušek)
Arithmetic progressions (Roth, Sarkozy, Beck, Matousek & Spencer)
Beck–Fiala theorem
Six Standard Deviations Suffice (Spencer)
Major open problems
The unsolved problems relating to discrepancy theory include:
Axis-parallel rectangles in dimensions three and higher (folklore)
Komlós conjecture
Heilbronn triangle problem on the minimum area of a triangle determined by
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https://en.wikipedia.org/wiki/Atomic%20commit
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In the field of computer science, an atomic commit is an operation that applies a set of distinct changes as a single operation. If the changes are applied, then the atomic commit is said to have succeeded. If there is a failure before the atomic commit can be completed, then all of the changes completed in the atomic commit are reversed. This ensures that the system is always left in a consistent state. The other key property of isolation comes from their nature as atomic operations. Isolation ensures that only one atomic commit is processed at a time. The most common uses of atomic commits are in database systems and version control systems.
The problem with atomic commits is that they require coordination between multiple systems. As computer networks are unreliable services, this means no algorithm can coordinate with all systems as proven in the Two Generals Problem. As databases become more and more distributed, this coordination will increase the difficulty of making truly atomic commits.
Usage
Atomic commits are essential for multi-step updates to data. This can be clearly shown in a simple example of a money transfer between two checking accounts.
This example is complicated by a transaction to check the balance of account Y during a transaction for transferring 100 dollars from account X to Y. To start, first 100 dollars is removed from account X. Second, 100 dollars is added to account Y. If the entire operation is not completed as one atomic commit, then severa
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https://en.wikipedia.org/wiki/Imidazole
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Imidazole (ImH) is an organic compound with the formula C3N2H4. It is a white or colourless solid that is soluble in water, producing a mildly alkaline solution. In chemistry, it is an aromatic heterocycle, classified as a diazole, and has non-adjacent nitrogen atoms in meta-substitution.
Many natural products, especially alkaloids, contain the imidazole ring. These imidazoles share the 1,3-C3N2 ring but feature varied substituents. This ring system is present in important biological building blocks, such as histidine and the related hormone histamine. Many drugs contain an imidazole ring, such as certain antifungal drugs, the nitroimidazole series of antibiotics, and the sedative midazolam.
When fused to a pyrimidine ring, it forms a purine, which is the most widely occurring nitrogen-containing heterocycle in nature.
The name "imidazole" was coined in 1887 by the German chemist Arthur Rudolf Hantzsch (1857–1935).
Structure and properties
Imidazole is a planar 5-membered ring, that exists in two equivalent tautomeric forms because hydrogen can be bound to one or another nitrogen atom. Imidazole is a highly polar compound, as evidenced by its electric dipole moment of 3.67 D, and is highly soluble in water. The compound is classified as aromatic due to the presence of a planar ring containing 6 π-electrons (a pair of electrons from the protonated nitrogen atom and one from each of the remaining four atoms of the ring). Some resonance structures of imidazole are shown belo
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https://en.wikipedia.org/wiki/Lyapunov%20time
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In mathematics, the Lyapunov time is the characteristic timescale on which a dynamical system is chaotic. It is named after the Russian mathematician Aleksandr Lyapunov. It is defined as the inverse of a system's largest Lyapunov exponent.
Use
The Lyapunov time mirrors the limits of the predictability of the system. By convention, it is defined as the time for the distance between nearby trajectories of the system to increase by a factor of e. However, measures in terms of 2-foldings and 10-foldings are sometimes found, since they correspond to the loss of one bit of information or one digit of precision respectively.
While it is used in many applications of dynamical systems theory, it has been particularly used in celestial mechanics where it is important for the problem of the stability of the Solar System. However, empirical estimation of the Lyapunov time is often associated with computational or inherent uncertainties.
Examples
Typical values are:
See also
Belousov–Zhabotinsky reaction
Molecular chaos
Three-body problem
References
Dynamical systems
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https://en.wikipedia.org/wiki/Language%20Of%20Temporal%20Ordering%20Specification
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In computer science Language Of Temporal Ordering Specification (LOTOS) is a formal specification language based on temporal ordering of events. LOTOS is used for communications protocol specification in International Organization for Standardization (ISO) Open Systems Interconnection model (OSI) standards.
LOTOS is an algebraic language that consists of two parts: a part for the description of data and operations, based on abstract data types, and a part for the description of concurrent processes, based on process calculus.
Work on the standard was completed in 1988, and it was published as ISO 8807 in 1989. Between 1993 and 2001, an ISO committee worked to define a revised version of the LOTOS standard, which was published in 2001 as E-LOTOS.
See also
Formal methods
List of ISO standards
CADP
E-LOTOS
Process calculus
References
ISO/IEC international standard 8807:1989. Information Processing Systems - Open Systems Interconnection - LOTOS: A Formal Description Technique based on the Temporal Ordering of Observational Behaviour. Geneva, September 1989.
The Formal Description Technique LOTOS, P.H.J. van Eijk et al., editors, North-Holland, 1989.
LOTOSphere: Software Development with LOTOS, Tommaso Bolognesi, Jeroen van de Lagemaat, and Chris Vissers, editors, Kluwer Academic Publishers, 1995.
Hubert Garavel, Frédéric Lang, and Wendelin Serwe, From LOTOS to LNT. In Joost-Pieter Katoen, Rom Langerak, and Arend Rensink, editors, ModelEd, TestEd, TrustEd - Essays De
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https://en.wikipedia.org/wiki/VSEPR%20theory
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Valence shell electron pair repulsion (VSEPR) theory ( , ), is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms. It is also named the Gillespie-Nyholm theory after its two main developers, Ronald Gillespie and Ronald Nyholm.
The premise of VSEPR is that the valence electron pairs surrounding an atom tend to repel each other. The greater the repulsion, the higher in energy (less stable) the molecule is. Therefore, the VSEPR-predicted molecular geometry of a molecule is the one that has as little of this repulsion as possible. Gillespie has emphasized that the electron-electron repulsion due to the Pauli exclusion principle is more important in determining molecular geometry than the electrostatic repulsion.
The insights of VSEPR theory are derived from topological analysis of the electron density of molecules. Such quantum chemical topology (QCT) methods include the electron localization function (ELF) and the quantum theory of atoms in molecules (AIM or QTAIM).
History
The idea of a correlation between molecular geometry and number of valence electron pairs (both shared and unshared pairs) was originally proposed in 1939 by Ryutaro Tsuchida in Japan, and was independently presented in a Bakerian Lecture in 1940 by Nevil Sidgwick and Herbert Powell of the University of Oxford. In 1957, Ronald Gillespie and Ronald Sydney Nyholm of University College London refined this concept into a
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https://en.wikipedia.org/wiki/Automatic%20programming
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In computer science, automatic programming is a type of computer programming in which some mechanism generates a computer program to allow human programmers to write the code at a higher abstraction level.
There has been little agreement on the precise definition of automatic programming, mostly because its meaning has changed over time. David Parnas, tracing the history of "automatic programming" in published research, noted that in the 1940s it described automation of the manual process of punching paper tape. Later it referred to translation of high-level programming languages like Fortran and ALGOL. In fact, one of the earliest programs identifiable as a compiler was called Autocode. Parnas concluded that "automatic programming has always been a euphemism for programming in a higher-level language than was then available to the programmer."
Program synthesis is one type of automatic programming where a procedure is created from scratch, based on mathematical requirements.
Origin
Mildred Koss, an early UNIVAC programmer, explains: "Writing machine code involved several tedious steps—breaking down a process into discrete instructions, assigning specific memory locations to all the commands, and managing the I/O buffers. After following these steps to implement mathematical routines, a sub-routine library, and sorting programs, our task was to look at the larger programming process. We needed to understand how we might reuse tested code and have the machine help in progra
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https://en.wikipedia.org/wiki/John%20R.%20Hendricks
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John Robert Hendricks (September 4, 1929 – July 7, 2007) was a Canadian amateur mathematician notable for his work in magic squares and hypercubes. He published many articles in the Journal of Recreational Mathematics as well as other mathematics-related journals.
Early life, education and career
Hendricks was born in Regina, Saskatchewan, in 1929, moving with his family to Vancouver, British Columbia at an early age.
He attended the University of British Columbia and graduated with a B.A. in mathematics.
He began his career as a meteorology instructor in the NATO flight training program, and was subsequently employed for 33 years by the Canadian Meteorological Service, until his retirement in Winnipeg, Manitoba in 1984.
Hendricks volunteered for groups including the Monarchist League of Canada and the Manitoba Provincial Council, Duke of Edinburgh's Award in Canada. He received the Canada 125 medal for his volunteer work.
Amateur mathematician
When he was 13, Hendricks started collecting magic squares. As his interest in mathematics grew, so did his love of magic squares, and cubes.
His interest in magic squares led to higher dimensions: magic cubes, tesseracts, etc. He developed a new diagram for the four-dimensional tesseract. This was published in 1962 when he showed constructions of four-, five-, and six-dimensional magic hypercubes of order three. He later was the first to publish diagrams of all 58 magic tesseracts of order 3.
Hendricks was also an authority on
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https://en.wikipedia.org/wiki/Journal%20of%20Recreational%20Mathematics
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The Journal of Recreational Mathematics was an American journal dedicated to recreational mathematics, started in 1968. It had generally been published quarterly by the Baywood Publishing Company, until it ceased publication with the last issue (volume 38, number 2) published in 2014. The initial publisher (of volumes 1–5) was Greenwood Periodicals.
Harry L. Nelson was primary editor for five years (volumes 9 through 13, excepting volume 13, number 4, when the initial editor returned as lead) and Joseph Madachy, the initial lead editor and editor of a predecessor called Recreational Mathematics Magazine which ran during the years 1961 to 1964, was the editor for many years. Charles Ashbacher and Colin Singleton took over as editors when Madachy retired (volume 30 number 1). The final editors were Ashbacher and Lamarr Widmer. The journal has from its inception also listed associate editors, one of whom was Leo Moser.
The journal contains:
Original articles
Book reviews
Alphametics And Solutions To Alphametics
Problems And Conjectures
Solutions To Problems And Conjectures
Proposer's And Solver's List For Problems And Conjectures
Indexing
The journal is indexed in:
Academic Search Premier
Book Review Index
International Bibliography of Periodical Literature
International Bibliography of Book Reviews
Readers' Guide to Periodical Literature
The Gale Group
References
Recreational mathematics
Mathematics journals
Academic journals established in 1968
Publication
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https://en.wikipedia.org/wiki/Terence%20Tao
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Terence Chi-Shen Tao (; born 17 July 1975) is an Australian mathematician. He is a professor of mathematics at the University of California, Los Angeles (UCLA), where he holds the James and Carol Collins chair. His research includes topics in harmonic analysis, partial differential equations, algebraic combinatorics, arithmetic combinatorics, geometric combinatorics, probability theory, compressed sensing and analytic number theory.
Tao was born to ethnic Chinese immigrant parents and raised in Adelaide. Tao won the Fields Medal in 2006 and won the Royal Medal and Breakthrough Prize in Mathematics in 2014. He is also a 2006 MacArthur Fellow. Tao has been the author or co-author of over three hundred research papers. He is widely regarded as one of the greatest living mathematicians and has been referred to as the "Mozart of mathematics."
Life and career
Family
Tao's parents are first-generation immigrants from Hong Kong to Australia. Tao's father, Billy Tao, was a Chinese paediatrician who was born in Shanghai and earned his medical degree (MBBS) from the University of Hong Kong in 1969. Tao's mother, Grace Leong, was born in Hong Kong; she received a first-class honours degree in mathematics and physics at the University of Hong Kong. She was a secondary school teacher of mathematics and physics in Hong Kong. Billy and Grace met as students at the University of Hong Kong. They then emigrated from Hong Kong to Australia in 1972.
Tao also has two brothers, Trevor and Nige
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https://en.wikipedia.org/wiki/Fixation
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Fixation may refer to:
Carbon fixation, a biochemical process, usually driven by photosynthesis, whereby carbon dioxide is converted into organic compounds
Fixation (alchemy), a process in the alchemical magnum opus
Fixation (histology) in biochemistry, histology, cell biology and pathology, the technique of preserving a specimen for microscopic study
Fixation (population genetics), the state when every individual in a population has the same allele at a particular locus
Fixation (psychology), the state in which an individual becomes obsessed with an attachment to another human, an animal, or an inanimate object
Fixation (surgical), an operative technique in orthopedics
Fixation (visual) maintaining the gaze in a constant direction
Fixation agent, a process chemical
Fixation in Canadian copyright law, a concept in Canadian copyright law
Nitrogen fixation, a process by which nitrogen is converted from its inert molecular form to a compound more readily available and useful to living organisms
Session fixation, computer security attack
Target fixation, attentional phenomenon
“Fixation”, an episode of The Good Doctor
See also
Fix (disambiguation)
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https://en.wikipedia.org/wiki/Linearization
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In mathematics, linearization is finding the linear approximation to a function at a given point. The linear approximation of a function is the first order Taylor expansion around the point of interest. In the study of dynamical systems, linearization is a method for assessing the local stability of an equilibrium point of a system of nonlinear differential equations or discrete dynamical systems. This method is used in fields such as engineering, physics, economics, and ecology.
Linearization of a function
Linearizations of a function are lines—usually lines that can be used for purposes of calculation. Linearization is an effective method for approximating the output of a function at any based on the value and slope of the function at , given that is differentiable on (or ) and that is close to . In short, linearization approximates the output of a function near .
For example, . However, what would be a good approximation of ?
For any given function , can be approximated if it is near a known differentiable point. The most basic requisite is that , where is the linearization of at . The point-slope form of an equation forms an equation of a line, given a point and slope . The general form of this equation is: .
Using the point , becomes . Because differentiable functions are locally linear, the best slope to substitute in would be the slope of the line tangent to at .
While the concept of local linearity applies the most to points arbitrarily close to , tho
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https://en.wikipedia.org/wiki/Arbitrarily%20large
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In mathematics, the phrases arbitrarily large, arbitrarily small and arbitrarily long are used in statements to make clear of the fact that an object is large, small and long with little limitation or restraint, respectively. The use of "arbitrarily" often occurs in the context of real numbers (and its subsets thereof), though its meaning can differ from that of "sufficiently" and "infinitely".
Examples
The statement
" is non-negative for arbitrarily large ."
is a shorthand for:
"For every real number , is non-negative for some value of greater than ."
In the common parlance, the term "arbitrarily long" is often used in the context of sequence of numbers. For example, to say that there are "arbitrarily long arithmetic progressions of prime numbers" does not mean that there exists any infinitely long arithmetic progression of prime numbers (there is not), nor that there exists any particular arithmetic progression of prime numbers that is in some sense "arbitrarily long". Rather, the phrase is used to refer to the fact that no matter how large a number is, there exists some arithmetic progression of prime numbers of length at least .
Similar to arbitrarily large, one can also define the phrase " holds for arbitrarily small real numbers", as follows:
In other words:
However small a number, there will be a number smaller than it such that holds.
Arbitrarily large vs. sufficiently large vs. infinitely large
While similar, "arbitrarily large" is not equivalent t
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https://en.wikipedia.org/wiki/Carbene
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In organic chemistry, a carbene is a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons. The general formula is or where the R represents substituents or hydrogen atoms.
The term "carbene" may also refer to the specific compound , also called methylene, the parent hydride from which all other carbene compounds are formally derived. Carbenes are classified as either singlets or triplets, depending upon their electronic structure. Most carbenes are very short lived, although persistent carbenes are known. One well-studied carbene is dichlorocarbene , which can be generated in situ from chloroform and a strong base.
Structures and bonding
The two classes of carbenes are singlet and triplet carbenes. Singlet carbenes are spin-paired. In the language of valence bond theory, the molecule adopts an sp2 hybrid structure. Triplet carbenes have two unpaired electrons. Most carbenes have a nonlinear triplet ground state, except for those with nitrogen, oxygen, or sulphur, and halides substituents bonded to the divalent carbon. Substituents that can donate electron pairs may stabilize the singlet state by delocalizing the pair into an empty p orbital. If the energy of the singlet state is sufficiently reduced it will actually become the ground state.
Bond angles are 125–140° for triplet methylene and 102° for singlet methylene (as determined by EPR).
For simple hydrocarbons, triplet carbenes usually are 8 kcal/mol (33 kJ/mol) more
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https://en.wikipedia.org/wiki/Death%20and%20What%20Comes%20Next
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"Death and What Comes Next" is a fantasy short story by British writer Terry Pratchett, part of his Discworld series. It tells the story of a discussion between Death and a philosopher, in which the philosopher attempts to use the many-worlds interpretation of quantum mechanics to argue that death is not a certainty.
The story was written in 2002 for the now-defunct online puzzle game TimeHunt and the text contains a hidden word puzzle, also devised by Pratchett, which provided a codeword for the game.
Like "Theatre of Cruelty", another of his short stories, Pratchett allowed it to be put on the L-Space Web.
See also
Parallel universe (fiction)
External links
The "Death and What Comes Next" L-Space page including various translations
Discworld short stories
Fantasy short stories
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https://en.wikipedia.org/wiki/DCP
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DCP may refer to:
Medicine
Des-gamma carboxyprothrombin, a liver cancer marker
Dicycloplatin, a chemotherapy medication
Diphenylcyclopropenone, a medication for alopecia areata
Dynamic compression plate, a metallic plate used in orthopedics
Police
Deputy Commissioner of Police, a post in the police commissionerate in india.
Chemistry
Dichlorophenol, several chemical compounds which are derivatives of phenol
1,3-Dichloropropene, an organochlorine pesticide
Angiotensin-converting enzyme, an enzyme
Dicalcium phosphate, a misnomer for dibasic calcium phosphate (CaHPO4)
Computing
Digital Cinema Package, a distribution package
Discovery and Configuration Protocol, a protocol within the PROFINET standard
Dedicated charging port, a USB port type for charging which does not have data signals
Disk Control Program, an MS-DOS derivative by East-German VEB Robotron
Other uses
David Carrier Porcheron, a Canadian snowboarder
Detroit Collegiate Preparatory Academy at Northwestern, now Northwestern High School, Michigan, US
Dick Clark Productions, American television production company
Disney College Program, a US national internship program
Disney Consumer Products, a subsidiary of Disney Parks, Experiences and Products segment of the Walt Disney Company
Dodge City Productions, a British music group
Deputy Commissioner of Police (disambiguation), a senior rank in many police forces
Data Collection Platform, an installation of meteorological instruments used in wea
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https://en.wikipedia.org/wiki/Axiom%20of%20real%20determinacy
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In mathematics, the axiom of real determinacy (abbreviated as ADR) is an axiom in set theory. It states the following:
The axiom of real determinacy is a stronger version of the axiom of determinacy (AD), which makes the same statement about games where both players choose integers; ADR is inconsistent with the axiom of choice. It also implies the existence of inner models with certain large cardinals.
ADR is equivalent to AD plus the axiom of uniformization.
See also
AD+
Axiom of projective determinacy
Topological game
Axioms of set theory
Determinacy
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https://en.wikipedia.org/wiki/Dedekind%20sum
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In mathematics, Dedekind sums are certain sums of products of a sawtooth function, and are given by a function D of three integer variables. Dedekind introduced them to express the functional equation of the Dedekind eta function. They have subsequently been much studied in number theory, and have occurred in some problems of topology. Dedekind sums have a large number of functional equations; this article lists only a small fraction of these.
Dedekind sums were introduced by Richard Dedekind in a commentary on fragment XXVIII of Bernhard Riemann's collected papers.
Definition
Define the sawtooth function as
We then let
be defined by
the terms on the right being the Dedekind sums. For the case a = 1, one often writes
s(b, c) = D(1, b; c).
Simple formulae
Note that D is symmetric in a and b, and hence
and that, by the oddness of (( )),
D(−a, b; c) = −D(a, b; c),
D(a, b; −c) = D(a, b; c).
By the periodicity of D in its first two arguments, the third argument being the length of the period for both,
D(a, b; c) = D(a+kc, b+lc; c), for all integers k,l.
If d is a positive integer, then
D(ad, bd; cd) = dD(a, b; c),
D(ad, bd; c) = D(a, b; c), if (d, c) = 1,
D(ad, b; cd) = D(a, b; c), if (d, b) = 1.
There is a proof for the last equality making use of
Furthermore, az = 1 (mod c) implies D(a, b; c) = D(1, bz; c).
Alternative forms
If b and c are coprime, we may write s(b, c) as
where the sum extends over the c-th roots of unity other than 1, i.e. over all su
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https://en.wikipedia.org/wiki/Tubule
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In biology, a tubule is a general term referring to small tube or similar type of structure. Specifically, tubule can refer to:
a small tube or fistular structure
a minute tube lined with glandular epithelium
any hollow cylindrical body structure
a minute canal found in various structures or organs of the body
a slender elongated anatomical channel
a minute tube, especially as an anatomical structure.
Examples of tubules
Collecting tubules: terminal channels of the nephrons
Cuvierian tubules: clusters of sticky tubules located at the base of the respiratory tree, which may be discharged by some sea cucumbers (holothurians) when mechanically stimulated (i.e. being threatened by a predator)
Dentinal tubules or dental canaliculi: minute channels in the dentine of a tooth that extend from the pulp cavity to the cementum or the enamel
Distal convoluted tubule: the convoluted portion of the vertebrate nephron that lies between the loop of Henle and the nonsecretory part of the nephron and that is concerned especially with the concentration of urine
Galactophorous tubule or lactiferous ducts: small channels for the passage of milk from the secreting cells in the mammary gland to the nipple
Loop of Henle: the long U-shaped part of the renal tubule, extending through the medulla from the end of the proximal convoluted tubule. It begins with a descending limb (comprising the proximal straight tubule and the thin tubule ), followed by the ascending limb (the distal straigh
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https://en.wikipedia.org/wiki/Biosynthesis
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In molecular biology, biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined to form macromolecules. This process often consists of metabolic pathways. Some of these biosynthetic pathways are located within a single cellular organelle, while others involve enzymes that are located within multiple cellular organelles. Examples of these biosynthetic pathways include the production of lipid membrane components and nucleotides. Biosynthesis is usually synonymous with anabolism.
The prerequisite elements for biosynthesis include: precursor compounds, chemical energy (e.g. ATP), and catalytic enzymes which may need coenzymes (e.g. NADH, NADPH). These elements create monomers, the building blocks for macromolecules. Some important biological macromolecules include: proteins, which are composed of amino acid monomers joined via peptide bonds, and DNA molecules, which are composed of nucleotides joined via phosphodiester bonds.
Properties of chemical reactions
Biosynthesis occurs due to a series of chemical reactions. For these reactions to take place, the following elements are necessary:
Precursor compounds: these compounds are the starting molecules or substrates in a reaction. These may also be viewed as the reactants in a given chemical process.
Chemical energy: chemical energy can be found in the form of hig
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https://en.wikipedia.org/wiki/Accounting%20method%20%28computer%20science%29
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In the field of analysis of algorithms in computer science, the accounting method is a method of amortized analysis based on accounting. The accounting method often gives a more intuitive account of the amortized cost of an operation than either aggregate analysis or the potential method. Note, however, that this does not guarantee such analysis will be immediately obvious; often, choosing the correct parameters for the accounting method requires as much knowledge of the problem and the complexity bounds one is attempting to prove as the other two methods.
The accounting method is most naturally suited for proving an O(1) bound on time. The method as explained here is for proving such a bound.
The method
A set of elementary operations which will be used in the algorithm is chosen and their costs are arbitrarily set to 1. The fact that the costs of these operations may differ in reality presents no difficulty in principle. What is important is that each elementary operation has a constant cost.
Each aggregate operation is assigned a "payment". The payment is intended to cover the cost of elementary operations needed to complete this particular operation, with some of the payment left over, placed in a pool to be used later.
The difficulty with problems that require amortized analysis is that, in general, some of the operations will require greater than constant cost. This means that no constant payment will be enough to cover the worst case cost of an operation, in
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https://en.wikipedia.org/wiki/Limit%20load%20%28physics%29
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Limit load is the maximum load that a structure can safely carry. It's the load at which the structure is in a state of incipient plastic collapse. As the load on the structure increases, the displacements increases linearly in the elastic range until the load attains the yield value. Beyond this, the load-displacement response becomes non-linear and the plastic or irreversible part of the displacement increases steadily with the applied load. Plasticity spreads throughout the solid and at the limit load, the plastic zone becomes very large and the displacements become unbounded and the component is said to have collapsed.
Any load above the limit load will lead to the formation of plastic hinge in the structure. Engineers use limit states to define and check a structure's performance.
Bounding Theorems of Plastic-Limit Load Analysis:
Plastic limit theorems provide a way to calculate limit loads without having to solve the boundary value problem in continuum mechanics. Finite element analysis provides an alternative way to estimate limit loads. They are:
The Upper Bound Plastic Collapse Theorem
The Lower Bound Plastic Collapse Theorem
The Lower Bound Shakedown Theorem
The Upper Bound Shakedown Theorem
The Upper Bound Plastic Collapse Theorem states that an upper bound to the collapse loads can be obtained by postulating a collapse mechanism and computing the ratio of its plastic dissipation to the work done by the applied loads.
References
Notes
Sources
Brown Unive
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https://en.wikipedia.org/wiki/Ferranti
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Ferranti or Ferranti International PLC was a UK electrical engineering and equipment firm that operated for over a century from 1885 until it went bankrupt in 1993. The company was once a constituent of the FTSE 100 Index.
The firm was known for work in the area of power grid systems and defence electronics. In addition, in 1951 Ferranti began selling an early computer, the Ferranti Mark 1. The Belgian subsidiary lives on as Ferranti Computer Systems and as of 1994 is part of the Nijkerk Holding.
History
Beginnings
Sebastian Ziani de Ferranti established his first business Ferranti, Thompson and Ince in 1882. The company developed the Ferranti-Thompson Alternator. Ferranti focused on alternating current power distribution early on, and was one of the few UK experts. In 1885 Dr. Ferranti established a new business, with Francis Ince and Charles Sparks as partners, known as S.Z. de Ferranti. According to J.F. Wilson, Dr. Ferranti's association with the electricity meter persuaded Ince to partner him in this new venture, and meter development was fundamental to the survival and growth of his business for several decades to come.
Despite being a prime exponent of alternating current, Ferranti became an important supplier to many electric utility firms and power-distribution companies for both AC and DC meters.
In 1887, the London Electric Supply Corporation (LESCo) hired Dr. Ferranti for the design of their power station at Deptford. He designed the building, the genera
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https://en.wikipedia.org/wiki/Foster%27s%20rule
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Foster's rule, also known as the island rule or the island effect, is an ecogeographical rule in evolutionary biology stating that members of a species get smaller or bigger depending on the resources available in the environment. For example, it is known that pygmy mammoths evolved from normal mammoths on small islands. Similar evolutionary paths have been observed in elephants, hippopotamuses, boas, sloths, deer (such as Key deer) and humans. It is part of the more general phenomenon of island syndrome which describes the differences in morphology, ecology, physiology and behaviour of insular species compared to their continental counterparts.
The rule was first formulated by van Valen in 1973 based on the study by mammalogist J. Bristol Foster in 1964. In it, Foster compared 116 island species to their mainland varieties. Foster proposed that certain island creatures evolved larger body size (insular gigantism) while others became smaller (insular dwarfism). Foster proposed the simple explanation that smaller creatures get larger when predation pressure is relaxed because of the absence of some of the predators of the mainland, and larger creatures become smaller when food resources are limited because of land area constraints.
The idea was expanded upon in The Theory of Island Biogeography, by Robert MacArthur and Edward O. Wilson. In 1978, Ted J. Case published a longer paper on the topic in the journal Ecology.
Recent literature has also applied the island rule to pl
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https://en.wikipedia.org/wiki/Truly%20neutral%20particle
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In particle physics, a truly neutral particle is a subatomic particle that is its own antiparticle. In other words, it remains itself under the charge conjugation, which replaces particles with their corresponding antiparticles. All charges of a truly neutral particle must be equal to zero. This requires particles to not only be electrically neutral, but also requires that all of their other charges (such as the colour charge) be neutral.
Examples
Known examples of such elementary particles include photons, Z bosons, and Higgs bosons, along with the hypothetical neutralinos, sterile neutrinos, and gravitons. For a spin-½ particle such as the neutralino, being truly neutral implies being a Majorana fermion.
Composite particles can also be truly neutral. A system composed of a particle forming a bound state with its antiparticle, such as the neutral pion (), is truly neutral. Such a state is called an "onium", another example of which is positronium, the bound state of an electron and a positron ( ).
By way of contrast, neutrinos are not truly neutral since they have a weak isospin of , or equivalently, a non-zero weak hypercharge, both of which are charge-like quantum numbers. (The example presumes on evidence to date, which gives no indication that neutrinos are Majorana particles.)
References
Further reading
Particle physics
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https://en.wikipedia.org/wiki/Pericyclic%20reaction
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In organic chemistry, a pericyclic reaction is the type of organic reaction wherein the transition state of the molecule has a cyclic geometry, the reaction progresses in a concerted fashion, and the bond orbitals involved in the reaction overlap in a continuous cycle at the transition state. Pericyclic reactions stand in contrast to linear reactions, encompassing most organic transformations and proceeding through an acyclic transition state, on the one hand and coarctate reactions, which proceed through a doubly cyclic, concerted transition state on the other hand. Pericyclic reactions are usually rearrangement or addition reactions. The major classes of pericyclic reactions are given in the table below (the three most important classes are shown in bold). Ene reactions and cheletropic reactions are often classed as group transfer reactions and cycloadditions/cycloeliminations, respectively, while dyotropic reactions and group transfer reactions (if ene reactions are excluded) are rarely encountered.
In general, these are considered to be equilibrium processes, although it is possible to push the reaction in one direction by designing a reaction by which the product is at a significantly lower energy level; this is due to a unimolecular interpretation of Le Chatelier's principle. There is thus a set of "retro" pericyclic reactions.
Mechanism of pericyclic reaction
By definition, pericyclic reactions proceed through a concerted mechanism involving a single, cyclic trans
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https://en.wikipedia.org/wiki/Markov%20decision%20process
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In mathematics, a Markov decision process (MDP) is a discrete-time stochastic control process. It provides a mathematical framework for modeling decision making in situations where outcomes are partly random and partly under the control of a decision maker. MDPs are useful for studying optimization problems solved via dynamic programming. MDPs were known at least as early as the 1950s; a core body of research on Markov decision processes resulted from Ronald Howard's 1960 book, Dynamic Programming and Markov Processes. They are used in many disciplines, including robotics, automatic control, economics and manufacturing. The name of MDPs comes from the Russian mathematician Andrey Markov as they are an extension of Markov chains.
At each time step, the process is in some state , and the decision maker may choose any action that is available in state . The process responds at the next time step by randomly moving into a new state , and giving the decision maker a corresponding reward .
The probability that the process moves into its new state is influenced by the chosen action. Specifically, it is given by the state transition function . Thus, the next state depends on the current state and the decision maker's action . But given and , it is conditionally independent of all previous states and actions; in other words, the state transitions of an MDP satisfy the Markov property.
Markov decision processes are an extension of Markov chains; the difference is the addition o
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https://en.wikipedia.org/wiki/Photosystem
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Photosystems are functional and structural units of protein complexes involved in photosynthesis. Together they carry out the primary photochemistry of photosynthesis: the absorption of light and the transfer of energy and electrons. Photosystems are found in the thylakoid membranes of plants, algae, and cyanobacteria. These membranes are located inside the chloroplasts of plants and algae, and in the cytoplasmic membrane of photosynthetic bacteria. There are two kinds of photosystems: PSI and PSII.
PSII will absorb red light, and PSI will absorb far-red light. Although photosynthetic activity will be detected when the photosystems are exposed to either red or far-red light, the photosynthetic activity will be the greatest when plants are exposed to both wavelengths of light. Studies have actually demonstrated that the two wavelengths together have a synergistic effect on the photosynthetic activity, rather than an additive one.
Each photosystem has two parts: a reaction center, where the photochemistry occurs, and an antenna complex, which surrounds the reaction center. The antenna complex contains hundreds of chlorophyll molecules which funnel the excitation energy to the center of the photosystem. At the reaction center, the energy will be trapped and transferred to produce a high energy molecule.
The main function of PSII is to efficiently split water into oxygen molecules and protons. PSII will provide a steady stream of electrons to PSI, which will boost these in ene
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https://en.wikipedia.org/wiki/Hadlock%20Field
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Hadlock Field is a minor league baseball stadium in Portland, Maine. It is primarily home to the Portland Sea Dogs of the Eastern League but also the Portland High School Bulldogs and Deering High School Rams baseball teams. The stadium is named for Edson B. Hadlock Jr., a long-time Portland High School baseball coach and physics teacher and member of the Maine Baseball Hall of Fame.
History and development
The park opened on April 18, 1994, with a capacity of 6,000. A year later, 500 seats were added, boosting capacity to 6,500. Expansion in 1998 increased capacity to 6,860 and in 2002 to 6,975. About 400 seats were added in right field before the start of the 2006 season, and the park currently seats 7,368. Hadlock Field is located between Interstate 295, the historic Fitzpatrick Stadium, and the Portland Exposition Building, the second-oldest arena in continuous operation in the United States. In 2003, when the Sea Dogs affiliated with the Boston Red Sox, a replica Green monster, called the Maine Monster, was added to left field to match the original at the Red Sox' Fenway Park. A replica Citgo sign and Coke bottle were added as well to make the field look even more like Fenway Park.
In 2006, the tenant Sea Dogs were Eastern League champions. The left-field fence is from home plate, the center field-fence is , and the right-field fence is away. New video boards were added prior to the 2014 season.
Field of Dreams Day at Hadlock Field is always a special date on the Po
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https://en.wikipedia.org/wiki/Anticipation%20%28genetics%29
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In genetics, anticipation is a phenomenon whereby as a genetic disorder is passed on to the next generation, the symptoms of the genetic disorder become apparent at an earlier age with each generation. In most cases, an increase in the severity of symptoms is also noted. Anticipation is common in trinucleotide repeat disorders, such as Huntington's disease and myotonic dystrophy, where a dynamic mutation in DNA occurs. All of these diseases have neurological symptoms. Prior to the understanding of the genetic mechanism for anticipation, it was debated whether anticipation was a true biological phenomenon or whether the earlier age of diagnosis was related to heightened awareness of disease symptoms within a family.
Trinucleotide repeats and expansion
Trinucleotide repeats are apparent in a number of loci in the human genome. They have been found in introns, exons and 5' or 3' UTR's. They consist of a pattern of three nucleotides (e.g. CGG) which is repeated a number of times. During meiosis, unstable repeats can undergo triplet expansion (see later section); in this case, the germ cells produced have a greater number of repeats than are found in the somatic tissues.
The mechanism behind the expansion of the triplet repeats is not well understood. One hypothesis is that the increasing number of repeats influences the overall shape of the DNA, which can have an effect on its interaction with DNA polymerase and thus the expression of the gene.
Disease mechanisms
For m
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https://en.wikipedia.org/wiki/Ziehl%E2%80%93Neelsen%20stain
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The Ziehl-Neelsen stain, also known as the acid-fast stain, is a bacteriological staining technique used in cytopathology and microbiology to identify acid-fast bacteria under microscopy, particularly members of the Mycobacterium genus. This staining method was initially introduced by Paul Ehrlich (1854–1915) and subsequently modified by the German bacteriologists Franz Ziehl (1859–1926) and Friedrich Neelsen (1854–1898) during the late 19th century.
The acid-fast staining method, in conjunction with auramine phenol staining, serves as the standard diagnostic tool and is widely accessible for rapidly diagnosing tuberculosis (caused by Mycobacterium tuberculosis) and other diseases caused by atypical mycobacteria, such as leprosy (caused by Mycobacterium leprae) and Mycobacterium avium-intracellulare infection (caused by Mycobacterium avium complex) in samples like sputum, gastric washing fluid, and bronchoalveolar lavage fluid. These acid-fast bacteria possess a waxy lipid-rich outer layer that contains high concentrations of mycolic acid, rendering them resistant to conventional staining techniques like the Gram stain.
After the Ziehl-Neelsen staining procedure using carbol fuchsin, acid-fast bacteria are observable as vivid red or pink rods set against a blue or green background, depending on the specific counterstain used, such as methylene blue or malachite green, respectively. Non-acid-fast bacteria and other cellular structures will be colored by the counterstain, all
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https://en.wikipedia.org/wiki/Nature%20Neuroscience
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Nature Neuroscience is a monthly scientific journal published by Nature Publishing Group. Its focus is original research papers relating specifically to neuroscience and was established in May 1998. The chief editor is Shari Wiseman. According to the Journal Citation Reports, Nature Neuroscience had a 2022 impact factor of 25.0.
References
External links
Neuroscience journals
Nature Research academic journals
Academic journals established in 1998
Monthly journals
English-language journals
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https://en.wikipedia.org/wiki/Optimization%20problem
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In mathematics, engineering, computer science and economics, an optimization problem is the problem of finding the best solution from all feasible solutions.
Optimization problems can be divided into two categories, depending on whether the variables are continuous or discrete:
An optimization problem with discrete variables is known as a discrete optimization, in which an object such as an integer, permutation or graph must be found from a countable set.
A problem with continuous variables is known as a continuous optimization, in which an optimal value from a continuous function must be found. They can include constrained problems and multimodal problems.
Continuous optimization problem
The standard form of a continuous optimization problem is
where
is the objective function to be minimized over the -variable vector ,
are called inequality constraints
are called equality constraints, and
and .
If , the problem is an unconstrained optimization problem. By convention, the standard form defines a minimization problem. A maximization problem can be treated by negating the objective function.
Combinatorial optimization problem
Formally, a combinatorial optimization problem is a quadruple , where
is a set of instances;
given an instance , is the set of feasible solutions;
given an instance and a feasible solution of , denotes the measure of , which is usually a positive real.
is the goal function, and is either or .
The goal is then to find for som
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https://en.wikipedia.org/wiki/Invariant%20%28mathematics%29
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In mathematics, an invariant is a property of a mathematical object (or a class of mathematical objects) which remains unchanged after operations or transformations of a certain type are applied to the objects. The particular class of objects and type of transformations are usually indicated by the context in which the term is used. For example, the area of a triangle is an invariant with respect to isometries of the Euclidean plane. The phrases "invariant under" and "invariant to" a transformation are both used. More generally, an invariant with respect to an equivalence relation is a property that is constant on each equivalence class.
Invariants are used in diverse areas of mathematics such as geometry, topology, algebra and discrete mathematics. Some important classes of transformations are defined by an invariant they leave unchanged. For example, conformal maps are defined as transformations of the plane that preserve angles. The discovery of invariants is an important step in the process of classifying mathematical objects.
Examples
A simple example of invariance is expressed in our ability to count. For a finite set of objects of any kind, there is a number to which we always arrive, regardless of the order in which we count the objects in the set. The quantity—a cardinal number—is associated with the set, and is invariant under the process of counting.
An identity is an equation that remains true for all values of its variables. There are also inequalities that r
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https://en.wikipedia.org/wiki/Invariant%20%28physics%29
|
In theoretical physics, an invariant is an observable of a physical system which remains unchanged under some transformation. Invariance, as a broader term, also applies to the no change of form of physical laws under a transformation, and is closer in scope to the mathematical definition. Invariants of a system are deeply tied to the symmetries imposed by its environment.
Invariance is an important concept in modern theoretical physics, and many theories are expressed in terms of their symmetries and invariants.
Examples
In classical and quantum mechanics, invariance of space under translation results in momentum being an invariant and the conservation of momentum, whereas invariance of the origin of time, i.e. translation in time, results in energy being an invariant and the conservation of energy. In general, by Noether's theorem, any invariance of a physical system under a continuous symmetry leads to a fundamental conservation law.
In crystals, the electron density is periodic and invariant with respect to discrete translations by unit cell vectors. In very few materials, this symmetry can be broken due to enhanced electron correlations.
Another examples of physical invariants are the speed of light, and charge and mass of a particle observed from two reference frames moving with respect to one another (invariance under a spacetime Lorentz transformation), and invariance of time and acceleration under a Galilean transformation between two such frames moving at low
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https://en.wikipedia.org/wiki/Fajans%27%20rules
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In inorganic chemistry, Fajans' rules, formulated by Kazimierz Fajans in 1923, are used to predict whether a chemical bond will be covalent or ionic, and depend on the charge on the cation and the relative sizes of the cation and anion. They can be summarized in the following table:
{| class="wikitable"
!Ionic Character
!Covalent Character
|-
|Low positive charge
|High positive charge
|-
|Large cation
|Small cation
|-
|Small anion
|Large anion
|}
Thus sodium chloride (with a low positive charge (+1), a fairly large cation (~1 Å) and relatively small anion (0.2 Å) is ionic; but aluminium iodide (AlI3) (with a high positive charge (+3) and a large anion) is covalent.
Polarization will be increased by:
high charge and small size of the cation
Ionic potential Å Z+/r+ (= polarizing power)
High charge and large size of the anion
The polarizability of an anion is related to the deformability of its electron cloud (i.e. its "softness")
An incomplete valence shell electron configuration
Noble gas configuration of the cation produces better shielding and less polarizing power
e.g. Hg2+ (r+ = 102 pm) is more polarizing than Ca2+ (r+ = 100 pm)
The "size" of the charge in an ionic bond depends on the number of electrons transferred. An aluminum atom, for example, with a +3 charge has a relatively large positive charge. That positive charge then exerts an attractive force on the electron cloud of the other ion, which has accepted the electrons from the aluminum (or other) positive io
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https://en.wikipedia.org/wiki/Ivar%20Jacobson
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Ivar Hjalmar Jacobson (born 1939) is a Swedish computer scientist and software engineer, known as major contributor to UML, Objectory, Rational Unified Process (RUP), aspect-oriented software development and Essence.
Biography
Ivar Jacobson was born in Ystad, Sweden, on September 2, 1939. He received his Master of Electrical Engineering degree at Chalmers Institute of Technology in Gothenburg in 1962. After his work at Ericsson, he formalized the language and method he had been working on in his PhD at the Royal Institute of Technology in Stockholm in 1985 on the thesis Language Constructs for Large Real Time Systems.
After his master's degree, Jacobson joined Ericsson and worked in R&D on computerized switching systems AKE and AXE including PLEX. After his PhD thesis in April 1987, he started Objective Systems with Ericsson as a major customer. A majority stake of the company was acquired by Ericsson in 1991, and the company was renamed Objectory AB. Jacobson developed the software method Object-Oriented Software Engineering (OOSE) published 1992, which was a simplified version of the commercial software process Objectory (short for Object Factory).
In October, 1995, Ericsson divested Objectory to Rational Software and Jacobson started working with Grady Booch and James Rumbaugh, known collectively as the Three Amigos.
When IBM bought Rational in 2003, Jacobson decided to leave, after he stayed on until May 2004 as an executive technical consultant.
In mid-2003 Jacob
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https://en.wikipedia.org/wiki/Gemma%20Frisius
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Gemma Frisius (; born JemReinerszoon; December 9, 1508 – May 25, 1555) was a Dutch physician, mathematician, cartographer, philosopher, and instrument maker. He created important globes, improved the mathematical instruments of his day and applied mathematics in new ways to surveying and navigation. Gemma's rings, an astronomical instrument, are named after him. Along with Gerardus Mercator and Abraham Ortelius, Frisius is often considered one of the founders of the Netherlandish school of cartography, and significantly helped lay the foundations for the school's golden age (approximately 1570s–1670s).
Biography
Frisius was born in Dokkum, Friesland (present-day Netherlands), of poor parents who died when he was young. He moved to Groningen and later studied at the University of Leuven (Louvain), Belgium, beginning in 1525. He received the degree of MD in 1536 and remained on the faculty of medicine of Leuven for the rest of his life where, in addition to teaching medicine, he also taught mathematics, astronomy and geography. His oldest son, Cornelius Gemma, edited a posthumous volume of his work and continued to work with Ptolemaic astronomical models.
One of his most influential teachers at Leuven was Franciscus Monachus who, circa 1527, had constructed a famous globe in collaboration with the Leuven goldsmith Gaspar van der Heyden Under the guidance of Monachus and the technical assistance of Van der Heyden, Frisius set up a workshop to produce globes and mathematical i
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https://en.wikipedia.org/wiki/Jos%C3%A9%20Giral
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José Giral y Pereira (22 October 1879 – 23 December 1962) was a Spanish politician, who served as the 75th Prime Minister of Spain during the Second Spanish Republic.
Life
Giral was born in Santiago de Cuba. He had degrees in Chemistry and Pharmacy from the University of Madrid. In 1905 he became professor of chemistry in the University of Salamanca. He founded Acción Republicana with Manuel Azaña. During the dictatorship of Miguel Primo de Rivera he conspired against the regime, and was imprisoned three times. When the Second Republic was declared, he was named director of the Universidad Complutense de Madrid and advisor of State. Between 1931 and 1933 he served as Minister of the Navy.
After the failure of Diego Martínez Barrio to form a government to restrain the military revolt of 17 July 1936, Azaña ordered Giral to form a new government constituted exclusively by republicans. This 133rd Prime Minister government lasted from 19 July to 4 September 1936. Then, with the fall of Talavera de la Reina and the Army of Morocco within reach of Madrid, Giral was forced to cede power to Francisco Largo Caballero.
After the end of the Spanish Civil War he went to France, then to Mexico. In 1945 he succeeded Juan Negrín as prime minister of the Spanish Republican government in Exile until 1947.
He died in Mexico.
He married María Luisa González y de la Calle.
Cabinet
Members of Giral's cabinet of 19 July 1936 – 4 September 1936 were:
References
Sources
1879 births
1962 deat
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https://en.wikipedia.org/wiki/Chromosome%20jumping
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Chromosome jumping is a tool of molecular biology that is used in the physical mapping of genomes. It is related to several other tools used for the same purpose, including chromosome walking.
Chromosome jumping is used to bypass regions difficult to clone, such as those containing repetitive DNA, that cannot be easily mapped by chromosome walking, and is useful in moving along a chromosome rapidly in search of a particular gene. Unlike chromosome walking, chromosome jumping is able to start on one point of the chromosome in order to traverse potential distant point of the same chromosome without cloning the intervening sequences. The ends of a large DNA fragment is the target cloning section of the chromosome jumping while the middle section gets removed by sequences of chemical manipulations prior to the cloning step.
Process
Chromosome jumping enables two ends of a DNA sequence to be cloned without the middle section. Genomic DNA may be partially digested using restriction endonuclease and with the aid of DNA ligase, the fragments are circularized at low concentration. From a known sequence, a primer is designed to sequence across the circularized junction. This primer is used to jump 100 kb-300 kb intervals: a sequence 100 kb away would have come near the known sequence on circularization, it permits jumping and sequencing in an alternative manner. Thus, sequences not reachable by chromosome walking can be sequenced. Chromosome walking can also be used from the new ju
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https://en.wikipedia.org/wiki/Sirsoe%20methanicola
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Sirsoe methanicola is a species of polychaete worm that inhabits methane clathrate deposits in the ocean floor. The worms colonize the methane ice and appear to survive by gleaning bacteria, which in turn metabolize the clathrate.
In 1997, Charles Fisher, professor of biology at Pennsylvania State University, discovered the worm living on mounds of methane ice at a depth of half a mile (~800 m) on the ocean floor in the Gulf of Mexico. Fisher reported that experiments with live specimens showed that mature worms could survive in an anoxic environment for up to 96 hours. The experiments also showed that the larvae were dispersed by currents, and died after 20 days if they did not find a place to feed.
The worm has been found to be able to utilize a range of nitrogen, sulfur, and organic carbon compounds through microbial taxa. These taxa allow the worm to take advantage of the harsh environment by allowing it to feed and gain nutrition through organic compounds that are found in the methane clathrate deposits.
References
External links
Phyllodocida
Animals described in 1998
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https://en.wikipedia.org/wiki/Hyperon
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In particle physics, a hyperon is any baryon containing one or more strange quarks, but no charm, bottom, or top quark. This form of matter may exist in a stable form within the core of some neutron stars. Hyperons are sometimes generically represented by the symbol Y.
History and research
The first research into hyperons happened in the 1950s and spurred physicists on to the creation of an organized classification of particles.
The term was coined by French physicist Louis Leprince-Ringuet in 1953, and announced for the first time at the cosmic ray conference at Bagnères de Bigorre in July of that year, agreed upon by Leprince-Ringuet, Bruno Rossi, C.F. Powell, William B. Fretter and Bernard Peters.
Today, research in this area is carried out on data taken at many facilities around the world, including CERN, Fermilab, SLAC, JLAB, Brookhaven National Laboratory, KEK, GSI and others. Physics topics include searches for CP violation, measurements of spin, studies of excited states (commonly referred to as spectroscopy), and hunts for exotic forms such as pentaquarks and dibaryons.
Properties and behavior
Being baryons, all hyperons are fermions. That is, they have half-integer spin and obey Fermi–Dirac statistics. Hyperons all interact via the strong nuclear force, making them types of hadron. They are composed of three light quarks, at least one of which is a strange quark, which makes them strange baryons.
Excited hyperon resonances and ground-state hyperons with a '*
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https://en.wikipedia.org/wiki/Ferdinand%20Cohn
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Ferdinand Julius Cohn (24 January 1828 – 25 June 1898) was a German-Polish biologist. He is one of the founders of modern bacteriology and microbiology.
Ferdinand J. Cohn was born in the Jewish quarter of Breslau in the Prussian Province of Silesia (which is now Wroclaw, Poland). His father, Issak Cohn, was a successful merchant and manufacturer. At the age of 10 Ferdinand suffered hearing impairment (for an unknown reason). Starting at age 16 he studied botany under Heinrich Goppert at the University of Breslau. Due to Cohn's Jewish background he was prevented from taking the final degree examinations at Breslau. He then moved to the University of Berlin. At age 19 in 1847 he received a degree in botany at Berlin. He remained studying botany for another couple of years in Berlin, where he came in contact with many of the top scientists of his time.
In 1849 he returned to the University of Breslau and he remained at that university for the rest of his career as a teacher and researcher. On his initial return to Breslau in his early twenties, his father had bought for him a large and expensive microscope made by Simon Plössl. This microscope, which the University of Breslau and most universities did not have, was Ferdinand Cohn's main research tool in the 1850s. In the 1850s he studied the growth and division of plant cells. In 1855 he produced papers on the sexuality of Sphaeroplea annulina and later Volvox globator. In the 1860s he studied plant physiology in several diffe
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https://en.wikipedia.org/wiki/Ugelstad%20Laboratory
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The Ugelstad Laboratory was founded at the Norwegian University of Science and Technology (NTNU), Trondheim, Norway, in January 2002 to commemorate the late Professor John Ugelstad.
The laboratory specialises in surfactant chemistry and its technical applications, emulsions and emulsion technology, preparation of polymers and polymer particles - such as the monosized microbeads - and their technical applications, plasma chemical modification of surfaces and silica-based chemistry.
Applications include crude oil production and processing, wood pulp and paper, biomedicine, catalysis and material science.
The main purpose is to raise the national level of colloidal science.
External links
Official website
Norwegian University of Science and Technology
Research institutes in Norway
2002 establishments in Norway
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https://en.wikipedia.org/wiki/Maximum%20parsimony%20%28phylogenetics%29
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In phylogenetics and computational phylogenetics, maximum parsimony is an optimality criterion under which the phylogenetic tree that minimizes the total number of character-state changes (or minimizes the cost of differentially weighted character-state changes). Under the maximum-parsimony criterion, the optimal tree will minimize the amount of homoplasy (i.e., convergent evolution, parallel evolution, and evolutionary reversals). In other words, under this criterion, the shortest possible tree that explains the data is considered best. Some of the basic ideas behind maximum parsimony were presented by James S. Farris in 1970 and Walter M. Fitch in 1971.
Maximum parsimony is an intuitive and simple criterion, and it is popular for this reason. However, although it is easy to score a phylogenetic tree (by counting the number of character-state changes), there is no algorithm to quickly generate the most-parsimonious tree. Instead, the most-parsimonious tree must be sought in "tree space" (i.e., amongst all possible trees). For a small number of taxa (i.e., fewer than nine) it is possible to do an exhaustive search, in which every possible tree is scored, and the best one is selected. For nine to twenty taxa, it will generally be preferable to use branch-and-bound, which is also guaranteed to return the best tree. For greater numbers of taxa, a heuristic search must be performed.
Because the most-parsimonious tree is always the shortest possible tree, this means that—in
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https://en.wikipedia.org/wiki/Diethyltryptamine
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DET, also known under its chemical name N,N-diethyltryptamine and as T-9, is a psychedelic drug closely related to DMT and 4-HO-DET. However, despite its structural similarity to DMT, its activity is induced by an oral dose of around 50–100 mg, without the aid of MAO inhibitors, and the effects last for about 2–4 hours.
Chemistry
DET is an analogue of the common tryptamine hallucinogen N,N-Dimethyltryptamine or DMT.
Pharmacology
The mechanism of action is thought to be serotonin receptor agonism, much like other classic psychedelics.
DET is sometimes preferred over DMT because it can be taken orally, whereas DMT cannot. This is because the enzyme monoamine oxidase degrades DMT into an inactive compound before it is absorbed. To overcome this, it must be administered in a different manner, i.e. intravenously, intramuscularly, by inhalation, by insufflation, rectally, or by ingestion along with an inhibitor of monoamine oxidase. Because DET has ethyl groups attached to its nitrogen atom, monoamine oxidase is unable to degrade it. This is also true for many other tryptamines with larger nitrogen substituents.
Biochemistry
Although DET is a synthetic compound with no known natural sources, it has been used in conjunction with the mycelium of Psilocybe cubensis to produce the synthetic chemicals 4-PO-DET (Ethocybin) and 4-HO-DET (Ethocin), as opposed to the naturally occurring 4-PO-DMT (Psilocybin) and 4-HO-DMT (Psilocin). Isolation of the alkaloids resulted in 3.3% 4-HO-DET
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https://en.wikipedia.org/wiki/Bioinorganic%20chemistry
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Bioinorganic chemistry is a field that examines the role of metals in biology. Bioinorganic chemistry includes the study of both natural phenomena such as the behavior of metalloproteins as well as artificially introduced metals, including those that are non-essential, in medicine and toxicology. Many biological processes such as respiration depend upon molecules that fall within the realm of inorganic chemistry. The discipline also includes the study of inorganic models or mimics that imitate the behaviour of metalloproteins.
As a mix of biochemistry and inorganic chemistry, bioinorganic chemistry is important in elucidating the implications of electron-transfer proteins, substrate bindings and activation, atom and group transfer chemistry as well as metal properties in biological chemistry. The successful development of truly interdisciplinary work is necessary to advance bioinorganic chemistry.
Composition of living organisms
About 99% of mammals' mass are the elements carbon, nitrogen, calcium, sodium, chlorine, potassium, hydrogen, phosphorus, oxygen and sulfur. The organic compounds (proteins, lipids and carbohydrates) contain the majority of the carbon and nitrogen and most of the oxygen and hydrogen is present as water. The entire collection of metal-containing biomolecules in a cell is called the metallome.
History
Paul Ehrlich used organoarsenic (“arsenicals”) for the treatment of syphilis, demonstrating the relevance of metals, or at least metalloids, to med
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https://en.wikipedia.org/wiki/REDOC
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In cryptography, REDOC II and REDOC III are block ciphers designed by Michael Wood (cryptographer) for Cryptech Inc and are optimised for use in software. Both REDOC ciphers are patented.
REDOC II (Cusick and Wood, 1990) operates on 80-bit blocks with a 160-bit key. The cipher has 10 rounds, and uses key-dependent S-boxes and masks used to select the tables for use in different rounds of the cipher. Cusick found an attack on one round, and Biham and Shamir (1991) used differential cryptanalysis to attack one round with 2300 encryptions. Biham and Shamir also found a way of recovering three masks for up to four rounds faster than exhaustive search. A prize of US$5,000 was offered for the best attack on one round of REDOC-II, and $20,000 for the best practical known-plaintext attack.
REDOC III is a more efficient cipher. It operates on an 80-bit block and accepts a variable-length key of up to 20,480 bits. The algorithm consists only of XORing key bytes with message bytes, and uses no permutations or substitutions. Ken Shirriff describes a differential attack on REDOC-III requiring 220 chosen plaintexts and 230 memory.
References
Thomas W. Cusick and Michael C. Wood: The REDOC II Cryptosystem, CRYPTO 1990, pp545–563.
Eli Biham and Adi Shamir, Differential Cryptanalysis of Snefru, Khafre, REDOC-II, LOKI and Lucifer. Advances in Cryptology – CRYPTO '91, Springer-Verlag, pp156–171 (gzipped PostScript).
Ken Shirriff, Differential Cryptanalysis of REDOC-III, (PS)
Block ciphe
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https://en.wikipedia.org/wiki/Heliosphere
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The heliosphere is the magnetosphere, astrosphere, and outermost atmospheric layer of the Sun. It takes the shape of a vast, bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding interstellar medium. The "bubble" of the heliosphere is continuously "inflated" by plasma originating from the Sun, known as the solar wind. Outside the heliosphere, this solar plasma gives way to the interstellar plasma permeating the Milky Way. As part of the interplanetary magnetic field, the heliosphere shields the Solar System from significant amounts of cosmic ionizing radiation; uncharged gamma rays are, however, not affected. Its name was likely coined by Alexander J. Dessler, who is credited with the first use of the word in the scientific literature in 1967. The scientific study of the heliosphere is heliophysics, which includes space weather and space climate.
Flowing unimpeded through the Solar System for billions of kilometers, the solar wind extends far beyond even the region of Pluto, until it encounters the "termination shock", where its motion slows abruptly due to the outside pressure of the interstellar medium. The "heliosheath" is a broad transitional region between the termination shock and the heliosphere's outmost edge, the "heliopause". The overall shape of the heliosphere resembles that of a comet; being roughly spherical on one side, with a long trailing tail opposite, known as "heliotail".
Two Voyager program spacecraf
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https://en.wikipedia.org/wiki/Dedekind%20zeta%20function
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In mathematics, the Dedekind zeta function of an algebraic number field K, generally denoted ζK(s), is a generalization of the Riemann zeta function (which is obtained in the case where K is the field of rational numbers Q). It can be defined as a Dirichlet series, it has an Euler product expansion, it satisfies a functional equation, it has an analytic continuation to a meromorphic function on the complex plane C with only a simple pole at s = 1, and its values encode arithmetic data of K. The extended Riemann hypothesis states that if ζK(s) = 0 and 0 < Re(s) < 1, then Re(s) = 1/2.
The Dedekind zeta function is named for Richard Dedekind who introduced it in his supplement to Peter Gustav Lejeune Dirichlet's Vorlesungen über Zahlentheorie.
Definition and basic properties
Let K be an algebraic number field. Its Dedekind zeta function is first defined for complex numbers s with real part Re(s) > 1 by the Dirichlet series
where I ranges through the non-zero ideals of the ring of integers OK of K and NK/Q(I) denotes the absolute norm of I (which is equal to both the index [OK : I] of I in OK or equivalently the cardinality of quotient ring OK / I). This sum converges absolutely for all complex numbers s with real part Re(s) > 1. In the case K = Q, this definition reduces to that of the Riemann zeta function.
Euler product
The Dedekind zeta function of has an Euler product which is a product over all the non-zero prime ideals of
This is the expression in analytic terms of
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https://en.wikipedia.org/wiki/Weil%20pairing
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In mathematics, the Weil pairing is a pairing (bilinear form, though with multiplicative notation) on the points of order dividing n of an elliptic curve E, taking values in nth roots of unity. More generally there is a similar Weil pairing between points of order n of an abelian variety and its dual. It was introduced by André Weil (1940) for Jacobians of curves, who gave an abstract algebraic definition; the corresponding results for elliptic functions were known, and can be expressed simply by use of the Weierstrass sigma function.
Formulation
Choose an elliptic curve E defined over a field K, and an integer n > 0 (we require n to be coprime to char(K) if char(K) > 0) such that K contains a primitive nth root of unity. Then the n-torsion on is known to be a Cartesian product of two cyclic groups of order n. The Weil pairing produces an n-th root of unity
by means of Kummer theory, for any two points , where and .
A down-to-earth construction of the Weil pairing is as follows. Choose a function F in the function field of E over the algebraic closure of K with divisor
So F has a simple zero at each point P + kQ, and a simple pole at each point kQ if these points are all distinct. Then F is well-defined up to multiplication by a constant. If G is the translation of F by Q, then by construction G has the same divisor, so the function G/F is constant.
Therefore if we define
we shall have an n-th root of unity (as translating n times must give 1) other than 1. With thi
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https://en.wikipedia.org/wiki/Neutron%20flux
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The neutron flux, φ, is a scalar quantity used in nuclear physics and nuclear reactor physics. It is the total distance travelled by all free neutrons per unit time and volume. Equivalently, it can be defined as the number of neutrons travelling through a small sphere of radius in a time interval, divided by a maximal cross section of the sphere (the great disk area, ) and by the duration of the time interval. The dimension of neutron flux is and the usual unit is cm−2s−1 (reciprocal square centimetre times reciprocal second).
The neutron fluence is defined as the neutron flux integrated over a certain time period. So its dimension is and its usual unit is cm−2 (reciprocal square centimetre). An older term used instead of cm−2 was "n.v.t." (neutrons, velocity, time).
Natural neutron flux
Neutron flux in asymptotic giant branch stars and in supernovae is responsible for most of the natural nucleosynthesis producing elements heavier than iron. In stars there is a relatively low neutron flux on the order of 105 to 1011 cm−2 s−1, resulting in nucleosynthesis by the s-process (slow neutron-capture process). By contrast, after a core-collapse supernova, there is an extremely high neutron flux, on the order of 1032 cm−2 s−1, resulting in nucleosynthesis by the r-process (rapid neutron-capture process).
Earth atmospheric neutron flux, apparently from thunderstorms, can reach levels of 3·10−2 to 9·10+1 cm−2 s−1. However, recent results (considered invalid by the original investi
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https://en.wikipedia.org/wiki/The%20Origins%20of%20Virtue
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The Origins of Virtue is a 1996 popular science book by Matt Ridley, which has been recognised as a classic in its field. In the book, Ridley explores the issues surrounding the development of human morality. The book, written from a sociobiological viewpoint, explores how genetics can be used to explain certain traits of human behaviour, in particular morality and altruism.
Starting from the premise that society can on a simplistic level be represented as a variant of the prisoner's dilemma, Ridley examines how it has been possible for a society to arise in which people choose to co-operate rather than defect.
Ridley examines the history of different attempts which have been made to explain the fact that humans in society do not defect, looking at various computer generated models which have been used to explain how such behaviour could arise. In particular he looks at systems based on the idea of tit for tat, where members of the group only cooperate with those who also cooperate and exclude those who do not. This allows altruistic behaviour to develop, and causes the optimum solution to the dilemma, to no longer be to defect but instead to cooperate. He applies this to humans and suggests that genes which generated altruistic-tit for tat behaviour would be likely to be passed on and therefore give rise to the kind of behaviour we see today.
From this argument Ridley argues that society operates best in groups of around 150 individuals, which he suggests is the level at
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https://en.wikipedia.org/wiki/Stephen%20Tall
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Stephen Tall was the most common pseudonym of American science fiction writer Compton Newby Crook (June 14, 1908 – January 15, 1981).
Biography
Born in Rossville, Tennessee, Crook studied biology at Peabody College, and did graduate work at Arizona State University and Johns Hopkins University. He began teaching biology at Towson University in 1939, where he remained until his retirement in 1973. He was married to writer Beverly Crook and had three children with her. He died in Phoenix, Maryland.
Crook's first published story was a winner in the Boy Scouts of America's first short story writing contest. He began publishing science fiction in 1955 with the appearance of "The Lights on Precipice Peak" in Galaxy. His short story "The Bear with the Knot on His Tail" (1971) was nominated for the 1972 Hugo Award for short fiction. His activity in the field grew in the mid-1970s before his death.
In 1983, the Compton Crook/Stephen Tall Memorial Award was established by the Baltimore Science Fiction Society in his name for best first science fiction novel in a given year.
Bibliography
Stardust series
The Stardust Voyages (collection, 1975)
The Ramsgate Paradox (novel, 1976)
Novels
The People Beyond the Wall (1980)
Short stories
"The Lights on Precipice Peak" (1955)
"A Star Called Cyrene" (aka "Seventy Light-Years from Sol") (1966)
"The Angry Mountain" (1970)
"Talk with the Animals" (1970)
"Allison, Carmichael and Tattersall" (1970)
"The Mad Scientist and The FBI" (1970)
"B
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https://en.wikipedia.org/wiki/Proliferation
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Proliferation may refer to:
Weapons
Nuclear proliferation, the spread of nuclear weapons, material, and technology
Chemical weapon proliferation, the spread of chemical weapons, material, and technology
Small arms proliferation, the spread of small weapons
Counter-proliferation, efforts to stop weapon proliferation
Computer science
License proliferation, a problem caused by incompatible software licenses
Data proliferation, the challenge of dealing with large amounts of data
Medicine and biology
Cell proliferation, cell growth and division
Proliferation, a phase of wound healing
Atypical small acinar proliferation, a concept in urologic pathology
Intravenous atypical vascular proliferation, a skin condition
Massive periretinal proliferation, a disease of the eye
Music
Proliferation (album), a 2008 album by Mike Reed's People, Places & Things
Other uses
Conceptual proliferation, a concept in Buddhism
Product proliferation, an organization's marketing of many variations of the same product
See also
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https://en.wikipedia.org/wiki/Claudio%20Stampi
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Claudio Stampi (born 19 June 1953, in São Paulo, Brazil) is the founder (in 1997), director and sole proprietor of the Chronobiology Research Institute which he runs from his home in Newton, Massachusetts, US. He is an academic sleep-researcher with a particular interest in the use of short naps in extreme conditions.
Life
Born to Italian parents in Bresil, he moved to Italy as a teenager and earned a doctorate in medicine in 1977, followed by a Ph.D. in biomedical engineering in 1983, and a degree in neurology the following year from the University of Bologna in Italy.
An avid sailor since his early youth, his MD-thesis was based on data he had collected during the 1975 Clipper Race, the first race he participated in, on the performance in relation to their sleep habits of the six team members on board.
That marked the start of his particular research interest in chronobiology, leading him to follow a number of his fellow long distance sail boat racing comrades, who had adopted a systematic polyphasic sleep pattern with minimal impairment. Stampi participated in two global sail races, including the 1981-2 Whitbread Race, where he served as Chief Scientist and Skipper of the research yacht La Barca Laboratorio; a boat that did not finish the race.
Building on his experience, he continued in the following years to work as a consultant for many single-hand competitive sailors to help them adapt their on-board sleeping habits for maximum performance. Among his most notable
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