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https://en.wikipedia.org/wiki/Microcin | Microcins are very small bacteriocins, composed of relatively few amino acids. For this reason, they are distinct from their larger protein cousins. The classic example is microcin V, of Escherichia coli. Subtilosin A is another bacteriocin from Bacillus subtilis. The peptide has a cyclized backbone and forms three cross-links between the sulphurs of Cys13, Cys7 and Cys4 and the alpha-positions of Phe22, Thr28 and Phe31.
Microcins produced by commensal E. coli strains target and eliminate enteric pathogens such as Salmonella enterica by mimicking the siderophores the pathogens use for iron scavenging. Microcins also help commensal strains of E. coli outcompete pathogenic strains.
BACTIBASE database is an open-access database for bacteriocins including microcins. |
https://en.wikipedia.org/wiki/Hybrid%20automaton | In automata theory, a hybrid automaton (plural: hybrid automata or hybrid automatons) is a mathematical model for precisely describing hybrid systems, for instance systems in which digital computational processes interact with analog physical processes. A hybrid automaton is a finite state machine with a finite set of continuous variables whose values are described by a set of ordinary differential equations. This combined specification of discrete and continuous behaviors enables dynamic systems that comprise both digital and analog components to be modeled and analyzed.
Examples
A simple example is a room-thermostat-heater system where the temperature of the room evolves according to laws of thermodynamics and the state of the heater (on/off); the thermostat senses the temperature, performs certain computations and turns the heater on and off. In general, hybrid automata have been used to model and analyze a variety of embedded systems including vehicle control systems, air traffic control systems, mobile robots, and processes from systems biology.
Formal definition
An Alur–Henzinger hybrid automaton comprises the following components:
A finite set of real-numbered variables. The number is called the dimension of . Let be the set of dotted variables that represent first derivatives during continuous change, and let be the set of primed variables that represent values at the conclusion of discrete change.
A finite multidigraph . The vertices in are called control modes. The edges in are called control switches.
Three vertex labeling functions init, inv, and flow that assign to each control mode three predicates. Each initial condition init is a predicate whose free variables are from . Each invariant condition inv is a predicate whose free variables are from . Each flow condition flow is a predicate whose free variables are from .
So this is a labeled multidigraph.
An edge labeling function jump that assigns to each control switch a predicate. Ea |
https://en.wikipedia.org/wiki/Heliodisplay | The Heliodisplay is an air-based display using principally air that is already present in the operating environment (room or space). The system developed by IO2 Technology in 2001 uses a projection unit focused onto multiple layers of air and dry micron-size atomized particles in mid-air, resulting in a two-dimensional display that appears to float (3d when using 3d content). This is similar in principle to the cinematic technique of rear projection and can appear three-dimensional when using appropriate content. As dark areas of the image may appear invisible, the image may be more realistic than on a projection screen, although it is still not volumetric. However the system does allow for multiple viewing and dual viewing (back and front) when combined with two light sources. The necessity of an oblique viewing angle +/- 30 degrees may be required for various configurations due to the rear-projection requirement.
Heliodisplay can operate as a free-space touchscreen when the equipment is ordered as an interactive unit with embedded sensors in the equipment. The original prototype of 2001 used a PC that sees the Heliodisplay as a pointing device, like a mouse. With the supplied software installed, one can use a finger, pen, or another object as cursor control and navigate or interact with simple content. As of 2010, no computer or drivers are required. The interactive version ("i") of the heliodisplay contains an embedded processor that controls these functions internally for single touch, or multiple touch interactivity using an equipment mounted arrangement but without the IR laser field found on the earlier versions. The smaller Heliodisplay version is transportable at and is as big as a lunchbox (30 cm x 30 cm x 12 cm) similar to the 2002 version. The larger equipment such as the systems that project life-size people capable of image diagonals up to 2.3 m also have the same footprint, about the same size as a sheet of paper.
The air-based system is formed b |
https://en.wikipedia.org/wiki/Hollow-cathode%20lamp | A hollow-cathode lamp (HCL) is type of cold cathode lamp used in physics and chemistry as a spectral line source (e.g. for atomic absorption spectrometers) and as a frequency tuner for light sources such as lasers. An HCL takes advantage of the hollow cathode effect, which causes conduction at a lower voltage and with more current than a cold cathode lamp that does not have a hollow cathode.
An HCL usually consists of a glass tube containing a cathode, an anode, and a buffer gas (usually a noble gas). A large voltage across the anode and cathode will cause the buffer gas to ionize, creating a plasma. The buffer gas ions will then be accelerated into the cathode, sputtering off atoms from the cathode. Both the buffer gas and the sputtered cathode atoms will in turn be excited by collisions with other atoms/particles in the plasma. As these excited atoms decay to lower states, they will emit photons. These photons will then excite the atoms in the sample, which will release their own photons and be used to generate data.
An HCL can also be used to tune light sources to a specific atomic transition by making use of the optogalvanic effect, which is a result of direct or indirect photoionization. By shining the light source into the HCL, one can excite or even eject electrons (directly photoionize) from the atoms inside the lamp, so long as the light source includes frequencies corresponding to the right atomic transitions. Indirect photoionization can then occur when electron collisions with the excited atom eject an atomic electron.
= atom, = photon, = atom in excited state, and = electron
The newly created ions cause an increase in the current across the cathode/anode and a resulting change in the voltage, which can then be measured.
To tune the light source to a specific transition frequency, a tuning parameter (often the driving current) of the light source is varied. By looking for a resonance on a data plot of the voltage signal versus source |
https://en.wikipedia.org/wiki/Polar%20ecology | Polar ecology is the relationship between plants and animals in a polar environment. Polar environments are in the Arctic and Antarctic regions. Arctic regions are in the Northern Hemisphere, and it contains land and the islands that surrounds it. Antarctica is in the Southern Hemisphere and it also contains the land mass, surrounding islands and the ocean. Polar regions also contain the subantarctic and subarctic zone which separate the polar regions from the temperate regions. Antarctica and the Arctic lie in the polar circles. The polar circles are imaginary lines shown on maps to be the areas that receives less sunlight due to less radiation. These areas either receive sunlight (midnight sun) or shade (polar night) 24 hours a day because of the earth's tilt. Plants and animals in the polar regions are able to withstand living in harsh weather conditions but are facing environmental threats that limit their survival.
Climate
Polar climates are cold, windy and dry. Because of the lack of precipitation and low temperatures the Arctic and Antarctic are considered the world's largest deserts or Polar deserts. Much of the radiation from the sun that is received is reflected off the snow making the polar regions cold. When the radiation is reflected, the heat is also reflected. The polar regions reflect 89-90% of the sun radiation that the earth receives. And because Antarctica is closer to the sun at perihelion, it receives 7% more radiation than the Arctic. Also in the polar region, the atmosphere is thin. Because of this the UV radiation that gets to the atmosphere can cause fast sun tanning and snow blindness.
Polar regions are dry areas; there is very little precipitation due to the cold air. There are some times when the humidity may be high but the water vapor present in the air may be low. Wind is also strong in the polar region. Wind carries snow creating blizzard like conditions. Winds may also move small organisms or vegetation if it is present. The wind |
https://en.wikipedia.org/wiki/Colloblast | Colloblasts are unique, multicellular structures found in ctenophores. They are widespread in the tentacles of these animals and are used to capture prey. Colloblasts consist of a collocyte containing a coiled spiral filament, internal granules and other organelles.
Like the cnidocytes of cnidarians, colloblasts are discharged from the animals’ tentacles, and are used to capture prey. However, unlike cnidocytes, which are venomous cells, colloblasts contain adhesives which stick to, rather than sting the prey.
Form, function, and occurrence
Colloblasts were first described in 1844.
The apical surface of colloblasts consist of numerous cap cells that secrete eosinophilic granules that are thought to be the source of adhesion. On contact, these granules rupture, and release an adhesive substance onto the prey. The spiral filament absorbs the impact of the rupture, preventing the ensnared prey from escaping. Colloblasts are found in all ctenophores except those of the order Beroida, which lack tentacles, and the species Haeckelia rubra, which use cnidocytes from cnidarian prey. |
https://en.wikipedia.org/wiki/List%20of%20contributors%20to%20general%20relativity | This is a dynamic list of persons who have made major contributions to the (mainstream) development of general relativity, as acknowledged by standard texts on the subject. Some related lists are mentioned at the bottom of the page.
A
Peter C. Aichelburg (Aichelburg–Sexl ultraboost, generalized symmetries),
Miguel Alcubierre (numerical relativity, Alcubierre drives),
Richard L. Arnowitt (ADM formalism),
Abhay Ashtekar (Ashtekar variables, dynamical horizons)
B
Robert M L Baker, Jr. (high-frequency gravitational waves),
James M. Bardeen (Bardeen vacuum, black hole mechanics, gauge-invariant linear perturbations of Friedmann-Lemaître cosmologies),
Barry Barish (LIGO builder, gravitational-waves observation),
Robert Bartnik (existence of ADM mass for asymptotically flat vacuums, quasilocal mass),
Jacob Bekenstein (black hole entropy),
Vladimir A. Belinsky (BKL conjecture, inverse scattering transform solution generating methods),
Peter G. Bergmann (constrained Hamiltonian dynamics),
Bruno Bertotti (Bertotti–Robinson electrovacuum),
Jiří Bičák (exact solutions of Einstein field equations),
Heinz Billing (prototype of laser interferometric gravitational-wave detector),
George David Birkhoff (Birkhoff's theorem),
Hermann Bondi (gravitational radiation, Bondi radiation chart, Bondi mass–energy–momentum, LTB dust, maverick models),
William B. Bonnor (Bonnor beam solution),
Robert H. Boyer (Boyer–Lindquist coordinates),
Vladimir Braginsky (gravitational-wave detector, quantum nondemolition (QND) measurement)
Carl H. Brans (Brans–Dicke theory),
Hubert Bray (Riemannian Penrose inequality),
Hans Adolph Buchdahl (Buchdahl fluid, Buchdahl theorem),
Claudio Bunster (BTZ black hole, Surface terms in Hamiltonian formulation),
William L. Burke (Burke potential, textbook)
C
Bernard Carr (self-similarity hypothesis, primordial black holes),
Brandon Carter (no-hair theorem, Carter constant, black-hole mechanics, variational principle for Ernst vacuums),
|
https://en.wikipedia.org/wiki/Timing | Timing is the tracking or planning of the spacing of events in time. It may refer to:
Timekeeping, the process of measuring the passage of time
Synchronization, controlling the timing of a process relative to another process
Time metrology, the measurement of time
Timing in different fields
Timing (comedy), use of rhythm, tempo and pausing to enhance comedy and humour
Timing (linguistics), rhythmic division of time into equal portions by a language
Timing (music), ability to "keep time" accurately and to synchronise to an ensemble
Color timing, photochemical process of altering and enhancing the color of an image
Ignition timing, timing of piston and crankshaft so that a spark will occur near the end of the compression stroke
Market timing, by attempting to predict future market price movements
Memory timings (or RAM timings), measure of the performance of DRAM memory
Valve timing, the precise timing of the opening and closing of the valves in a piston engine
Time |
https://en.wikipedia.org/wiki/Ronald%20Rivlin | Ronald Samuel Rivlin (6 May 1915 in London – 4 October 2005) was a British-American physicist, mathematician, rheologist and a noted expert on rubber.
Life
Rivlin was born in London in 1915. He studied physics and mathematics at St John's College, Cambridge, being awarded a BA in 1937 and a ScD in 1952. He worked for the General Electric Company, then the UK Ministry of Aircraft Production, then the British Rubber Producers Research Association, to which he was recruited to at the suggestion of L. R. G. Treloar by John Wilson, over a “lavish meal” and game of pool. This included one sabbatical year at the National Bureau of Standards, USA. His post at the BRPRA was the start of his interest in rubber.
In 1953 he took up the post of Professor of Applied Mathematics at Brown University, moving to Lehigh University in 1967 to become director of the Center for the Application of Mathematics until his retirement in 1980. He married Violet LoRusso in 1948 (they had a son, John) and became an American citizen in 1955.
Work
His work began with his 1944 observation that "although very little force is required to detach Scotch tape from an adherend, the work expended in doing so is very large". This is from the elastic effects of the adhesive, on which he commented even if "one idealized the adhesive as a perfectly elastic material there appeared to be no body of mathematical theory which would provide a basis for calculations". Existing theories were only on very small deformations, so from 1945 to 1951, Rivlin was one of the creators of the modern theory of large elastic deformations, including theory of Neo-Hookean solids and Mooney-Rivlin solids. He also made major contributions to the theory of non-Newtonian fluid flow, including in the Rivlin-Ericksen expansion.
Honours and awards
Bingham Medal of the Society of Rheology in 1958.
Timoshenko Medal of the ASME in 1987
Charles Goodyear Medal of the American Chemical Society's Rubber Division in 1992.
von Karma |
https://en.wikipedia.org/wiki/Long%20branch%20attraction | In phylogenetics, long branch attraction (LBA) is a form of systematic error whereby distantly related lineages are incorrectly inferred to be closely related. LBA arises when the amount of molecular or morphological change accumulated within a lineage is sufficient to cause that lineage to appear similar (thus closely related) to another long-branched lineage, solely because they have both undergone a large amount of change, rather than because they are related by descent. Such bias is more common when the overall divergence of some taxa results in long branches within a phylogeny. Long branches are often attracted to the base of a phylogenetic tree, because the lineage included to represent an outgroup is often also long-branched. The frequency of true LBA is unclear and often debated, and some authors view it as untestable and therefore irrelevant to empirical phylogenetic inference. Although often viewed as a failing of parsimony-based methodology, LBA could in principle result from a variety of scenarios and be inferred under multiple analytical paradigms.
Causes
LBA was first recognized as problematic when analyzing discrete morphological character sets under parsimony criteria, however Maximum Likelihood analyses of DNA or protein sequences are also susceptible. A simple hypothetical example can be found in Felsenstein 1978 where it is demonstrated that for certain unknown "true" trees, some methods can show bias for grouping long branches, ultimately resulting in the inference of a false sister relationship. Often this is because convergent evolution of one or more characters included in the analysis has occurred in multiple taxa. Although they were derived independently, these shared traits can be misinterpreted in the analysis as being shared due to common ancestry.
In phylogenetic and clustering analyses, LBA is a result of the way clustering algorithms work: terminals or taxa with many autapomorphies (character states unique to a single branch) may by |
https://en.wikipedia.org/wiki/Bolster%20heath | Bolster heath or cushion moorland is a type of vegetation community that features a patchwork of very low growing, tightly packed plants found at the limits of some alpine environments. The cushion plants form a smooth surfaced 'cushions' from several different plants, hence the common name of cushion heath. The cushion growth habit provides protection against the desiccating wind and help keep the cluster warm.
Bolster heath is very slow growing and thus very fragile. Most propagation is by slow expansion, although two species, Abrotanella forsteroides and Pterygopappus lawrencei produce enough viable seed to survive fire. The other species are generally permanently destroyed by fire.
The soil in bolster heath is generally quite poor, often gravel with a thin layer of peat.
Tasmanian bolster heaths
Asteraceae
Abrotanella forsteroides (Abrotanella)
Ewartia meredithiae (Ewartia)
Pterygopappus lawrencei (Pterygopappus)
Caryophyllaceae
Colobanthus pulvinatus (Colobanthus)
Scleranthus biflorus (Scleranthus)
Donatiaceae
Donatia novae-zelandiae (Donatia)
Epacridaceae
Dracophyllum minimum (Dracophyllum)
Loganiaceae
Mitrasacme archeri (Mitrasacme)
Scrophulariaceae
Chionohebe ciliolata (Chionohebe)
Stylidiaceae
Phyllachne colensoi (Phyllachne)
Thymelaeaceae
Pimelea pygmaea (Pimelea)
Centrolepidaceae
Centrolepis monogyna (Centrolepis)
Centrolepis muscoides (Centrolepis)
Gaimardia fitzgeraldii (Gaimardia)
Gaimardia setacea (Gaimardia)
Cyperaceae
Carpha rodwayi (Carpha)
Oreobolus acutifolius (Oreobolus)
Oreobolus oligocephalus (Oreobolus)
Oreobolus oxycarpus (Oreobolus)
Oreobolus pumilio (Oreobolus) |
https://en.wikipedia.org/wiki/L%C3%A1szl%C3%B3%20Fejes%20T%C3%B3th | László Fejes Tóth (, 12 March 1915 – 17 March 2005) was a Hungarian mathematician who specialized in geometry. He proved that a lattice pattern is the most efficient way to pack centrally symmetric convex sets on the Euclidean plane (a generalization of Thue's theorem, a 2-dimensional analog of the Kepler conjecture). He also investigated the sphere packing problem. He was the first to show, in 1953, that proof of the Kepler conjecture can be reduced to a finite case analysis and, later, that the problem might be solved using a computer.
He was a member of the Hungarian Academy of Sciences (from 1962) and a director of the Alfréd Rényi Institute of Mathematics (1970-1983). He received both the Kossuth Prize (1957) and State Award (1973).
Together with H.S.M. Coxeter and Paul Erdős, he laid the foundations of discrete geometry.
Early life and career
As described in a 1999 interview with István Hargittai, Fejes Tóth's father was a railway worker, who advanced in his career within the railway organization ultimately to earn a doctorate in law. Fejes Tóth's mother taught Hungarian and German literature in a high school. The family moved to Budapest, when Fejes Tóth was five; there he attended elementary school and high school—the Széchenyi István Reálgimnázium—where his interest in mathematics began.
Fejes Tóth attended Pázmány Péter University, now the Eötvös Loránd University. As a freshman, he developed a generalized solution regarding Cauchy exponential series, which he published in the proceedings of the French Academy of Sciences—1935. He then received his doctorate at Pázmány Péter University, under the direction of Lipót Fejér.
After university, he served as a soldier for two years, but received a medical exemption. In 1941 he joined the University of Kolozsvár (Cluj). It was here that he became interested in packing problems. In 1944, he returned to Budapest to teach mathematics at Árpád High School. Between 1946 and 1949 he lectured at Pázmány Péter Un |
https://en.wikipedia.org/wiki/Anemophily | Anemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Almost all gymnosperms are anemophilous, as are many plants in the order Poales, including grasses, sedges, and rushes. Other common anemophilous plants are oaks, pecans, pistachios, sweet chestnuts, alders and members of the family Juglandaceae (hickory or walnut family). Approximately 12% of plants across the globe are pollinated by anemophily, including cereal crops like rice and corn and other prominent crop plants like wheat, rye, barley, and oats. In addition, many pines, spruces, and firs are wind-pollinated.
Syndrome
Features of the wind-pollination syndrome include a lack of scent production, a lack of showy floral parts (resulting in small, inconspicuous flowers), reduced production of nectar, and the production of enormous numbers of pollen grains. This distinguishes them from entomophilous and zoophilous species (whose pollen is spread by insects and vertebrates respectively).
Anemophilous pollen grains are smooth, light, and non-sticky, so that they can be transported by air currents. Wind-pollinating plants have no predisposition to attract pollinating organisms. They freely expel a myriad of these pollen grains, and only a small percentage of them ends up captured by the female floral structures on wind-pollinated plants. They are typically in diameter, although the pollen grains of Pinus species can be much larger and much less dense. Anemophilous plants possess lengthy, well-exposed stamens to catch and distribute pollen. These stamens are exposed to wind currents and also have large, feathery stigma to easily trap airborne pollen grains. Pollen from anemophilous plants tends to be smaller and lighter than pollen from entomophilous ones, with very low nutritional value to insects due to their low protein content. However, insects sometimes gather pollen from staminate anemophilous flowers at times when higher-protein pollens from entomophilous flowers |
https://en.wikipedia.org/wiki/Riders%20on%20the%20Storm | "Riders on the Storm" is a song by American rock band the Doors, released in June 1971 by Elektra Records as the second single from the band's sixth studio album, L.A. Woman. It is famous for being the last song that Jim Morrison recorded prior to his sudden death in Paris on July 3, 1971.
The song reached number 14 on the U.S Billboard Hot 100, number 22 on the UK Singles Chart, and number seven in the Netherlands.
Background and composition
"Riders on the Storm" has been classified as a psychedelic rock, jazz rock, art rock song, and a precursor of gothic music. According to guitarist Robby Krieger and keyboardist Ray Manzarek, it was inspired by the country song "(Ghost) Riders in the Sky: A Cowboy Legend", written by Stan Jones and popularized by Vaughn Monroe. The lyrics were written and brought to rehearsal by Morrison, of which a portion of it refers to hitchhiking killer Billy "Cockeyed" Cook, who was the subject of the 1953 film, The Hitch-Hiker. Manzarek noted that some lines express Morrison's love to his companion Pamela Courson. The track is notated in the key of E Minor; the main keyboard riff descends throughout the pitches of Dorian Mode scale, and features a progression of i–IV–i7–IV.
It is popularly believed that "Riders on the Storm" is the song that longtime Doors producer Paul A. Rothchild disparaged as "cocktail music", precipitating his departure from the L.A. Woman sessions, which was corroborated by guitarist Robby Krieger. Rothchild himself denied that claim, stating that he actually applied the epithet to "Love Her Madly". Following Rothchild's departure, longtime engineer Bruce Botnick was selected to take over production duties, alongside the Doors themselves.
"Riders on the Storm" was recorded at the Doors Workshop in December 1970 with the assistance of Botnick. Later in January 1971, after Morrison had recorded his main vocals, the group gathered at Poppi Studios to complete the mixing of L.A. Woman, at which Morrison then whisper |
https://en.wikipedia.org/wiki/Gunnar%20Nordstr%C3%B6m | Gunnar Nordström (12 March 1881 – 24 December 1923) was a Finnish theoretical physicist best remembered for his theory of gravitation, which was an early competitor of general relativity. Nordström is often designated by modern writers as The Einstein of Finland due to his novel work in similar fields with similar methods to Einstein.
Education and career
Nordström graduated high-school from Brobergska skolan in central Helsinki 1899. At first he went on to study mechanical engineering, graduating in 1903 from the Polytechnic institute in Helsinki, later renamed Helsinki University of Technology and today a part of the Aalto University. During his studies he developed an interest for more theoretical subjects, proceeding after graduation to further study for a master's degree in natural science, mathematics and economy at the University of Helsinki (1903–1907).
Nordström then moved to Göttingen, Germany, where he had been recommended to go to study physical chemistry. However, he soon lost interest in the intended field and moved to study electrodynamics, a field the University of Göttingen was renowned for at the time. He returned to Finland to complete his doctoral dissertation at the University of Helsinki in 1910, and become a docent at the university. Subsequently, he became fascinated with the very novel and soon burgeoning field of gravitation and wanted to move to the Netherlands where scientists with contributions to that fields such as Hendrik Lorentz, Paul Ehrenfest and Willem de Sitter were active. Nordström was able to move to Leiden in 1916 to work under Ehrenfest, in the midst of the First World War, due to his Russian passport. Nordström spent considerable time in Leiden where he met a Dutch physics student, Cornelia van Leeuwen, with whom he went on to have several children. After the war he declined a professorship at the University of Berlin, a post awarded instead to Max Born, in order to return to Finland in 1918 and hold at first the profess |
https://en.wikipedia.org/wiki/Luther%20P.%20Eisenhart | Luther Pfahler Eisenhart (13 January 1876 – 28 October 1965) was an American mathematician, best known today for his contributions to semi-Riemannian geometry.
Life
Eisenhart was born in York, Pennsylvania, and graduated from Gettysburg College in 1896. He earned his doctorate in 1900 at Johns Hopkins University, where he was influenced (at long range) by the work of Gaston Darboux and at shorter range by that of Thomas Craig. During the next two decades, Eisenhart's research focused on moving frames after the French school, but around 1921 took a different turn when he became enamored of the mathematical challenges and entrancing beauty of a new theory of gravitation, Albert Einstein's general theory of relativity.
Eisenhart played a central role in American mathematics in the early twentieth century. He served as chairman of the mathematics department at Princeton University and later as Dean of the Graduate School there from 1933 to 1945. He is widely credited with guiding the development in America of the mathematical background needed for the further development of general relativity, through his influential textbooks and his personal interaction with Albert Einstein, Oswald Veblen, and John von Neumann at the nearby Institute for Advanced Study, as well as with gifted students such as Abraham Haskel Taub.
In the early 40s he chaired the "Reference Committee", formed in June 1940 for editors of scientific journals to send the papers submitted to them, in order to check that the papers did not contain results (especially regarding nuclear physics) whose public knowledge could be detrimental to the US war efforts.
Publications
Notes
External links
National Academy of Sciences Biographical Memoir
1876 births
1965 deaths
People from York, Pennsylvania
Differential geometers
20th-century American mathematicians
Gettysburg College alumni
Princeton University faculty
Presidents of the American Mathematical Society
Johns Hopkins University alumni
Mathemati |
https://en.wikipedia.org/wiki/Andr%C3%A9%20Lichnerowicz | André Lichnerowicz (January 21, 1915, Bourbon-l'Archambault – December 11, 1998, Paris) was a French differential geometer and mathematical physicist. He is considered the founder of modern Poisson geometry.
Biography
His grandfather Jan fought in the Polish resistance against the Prussians. Forced to flee Poland in 1860, he finally settled in France, where he married a woman from Auvergne, Justine Faure. Lichnerowicz's father, Jean, held agrégation in classics and was secretary of the Alliance française, while his mother, a descendant of paper makers, was one of the first women to earn the agrégation in mathematics. Lichnerowicz's paternal aunt, Jeanne, was a novelist and translator known under the pseudonym .
André attended the Lycée Louis-le-Grand and then the École Normale Supérieure in Paris, gaining agrégation in 1936. After two years, he entered the Centre national de la recherche scientifique (CNRS) as one of the first researchers recruited by this institution.
Lichnerowicz studied differential geometry under Élie Cartan. His doctoral dissertation, completed in 1939 under the supervision of Georges Darmois, was entitled "Problemes Globaux en Mécanique Relativiste" (Global problems in relativistic mechanics).
His academic career began under the cloud of Nazi occupation, during World War II. In 1941 he started teaching at the University of Strasbourg, which was moved to Clermont Ferrand and only returned to Strasbourg in 1945, after the end of the war. In November 1943 he was arrested during a raid but managed to escape. During 1944 he was invited to give a Cours Peccot at the Collège de France.
From 1949 to 1952 he held a position at the University of Paris, and in 1952 he was appointed professor at the Collège de France, where he worked until his retirement in 1986.
Lichnerowicz served as president of the Société mathématique de France during 1959. He was elected member of several national and international academies: the Accademia dei Lincei in 1962, |
https://en.wikipedia.org/wiki/Mooney%E2%80%93Rivlin%20solid | In continuum mechanics, a Mooney–Rivlin solid is a hyperelastic material model where the strain energy density function is a linear combination of two invariants of the left Cauchy–Green deformation tensor . The model was proposed by Melvin Mooney in 1940 and expressed in terms of invariants by Ronald Rivlin in 1948.
The strain energy density function for an incompressible Mooney–Rivlin material is
where and are empirically determined material constants, and and are the first and the second invariant of (the unimodular component of ):
where is the deformation gradient and . For an incompressible material, .
Derivation
The Mooney–Rivlin model is a special case of the generalized Rivlin model (also called polynomial hyperelastic model) which has the form
with where are material constants related to the distortional response and are material constants related to the volumetric response. For a compressible Mooney–Rivlin material and we have
If we obtain a neo-Hookean solid, a special case of a Mooney–Rivlin solid.
For consistency with linear elasticity in the limit of small strains, it is necessary that
where is the bulk modulus and is the shear modulus.
Cauchy stress in terms of strain invariants and deformation tensors
The Cauchy stress in a compressible hyperelastic material with a stress free reference configuration is given by
For a compressible Mooney–Rivlin material,
Therefore, the Cauchy stress in a compressible Mooney–Rivlin material is given by
It can be shown, after some algebra, that the pressure is given by
The stress can then be expressed in the form
The above equation is often written using the unimodular tensor :
For an incompressible Mooney–Rivlin material with there holds and . Thus
Since the Cayley–Hamilton theorem implies
Hence, the Cauchy stress can be expressed as
where
Cauchy stress in terms of principal stretches
In terms of the principal stretches, the Cauchy stress differences for an incompressible hypere |
https://en.wikipedia.org/wiki/Scott%20Swedorski | Scott Swedorski is the founder of Tucows (The Ultimate Collection of Winsock Software), a large Internet domain name reseller, and Internet service provider.
History
Scott served in the military and then received an associate degree from Mott Community College in Flint.
In 1993 he worked for the Flint Area Library Online Network (FALCON) Swedorski felt there was a need for public access to Internet-related software. Working from home, he created a site to provide the public with free and easily downloaded software.
In 2002, Swedorski received the lifetime achievement award from the Shareware Industry Awards Foundation (SIAF) for his work with shareware software authors.
Swedorski retired from Tucows in 2003 and launched a new software promotions company. He is also the Vice President of distribution and marketing at CoffeeCup Software, where he helped co-found the Organization of Independent Software Vendors. Scott also runs FileLight.com, a large shareware download site. |
https://en.wikipedia.org/wiki/DOS%20XL | DOS XL is a discontinued Disk Operating System (DOS) written by Paul Laughton, Mark Rose, Bill Wilkinson, and Mike Peters and published by Optimized Systems Software (OSS) for the Atari 8-bit family of home computers. It was designed to be compatible with Atari DOS which came shipped with Atari, Inc.'s disk drives, which had also been written by the same team.
Description
Features
A direct descendant of OS/A+, DOS XL provided additional features to Atari's equipped with floppy disk drives. These included single and double density support, a command-line mode (called the command processor or CP), a menu mode (an executable loaded in memory), batch file support, and support for XL extended memory and OSS SuperCartridge banked memory. Later versions included Axlon RamDisk support, Mosaic RamDisk support, BIT-3 support and BUG/65.
In addition to supporting auto-booting AUTORUN.SYS files, DOS XL's batch features provided an auto-booting batch feature. Naming a batch file to STARTUP.EXC would have it execute batch commands on startup (same as OS/A+). Unfortunately, this feature wasn't compatible with some programs (e.g. AtariWriter).
Distribution
DOS XL was distributed on a flippy disk. One side had the single-density version, the other had the double-density version. As more features and add-ons were included, these were placed on the double-density side only due to lack of disk space.
The manual for DOS XL was a subset of OS/A+. OSS considered the manual an "addendum" to OS/A+. Over 150+ pages, it was bound at the spine, not in loose-leaf form like the OS/A+ manual.
DOS XL came in two versions, 2.20 and 2.30 (2.20 users had to pay $20 to upgrade to 2.30). The last version was 2.30P. DOS XL originally sold for $30, but the price later increased to $39.
File writing verify was turned off in DOS XL. This was due to OSS's own experience that resulted in faster writes with virtually no risk of errors. The command file VERIFY.COM was included to reenable writes with ve |
https://en.wikipedia.org/wiki/Pedotransfer%20function | In soil science, pedotransfer functions (PTF) are predictive functions of certain soil properties using data from soil surveys.
The term pedotransfer function was coined by Johan Bouma as translating data we have into what we need. The most readily available data comes from a soil survey, such as the field morphology, soil texture, structure and pH. Pedotransfer functions add value to this basic information by translating them into estimates of other more laborious and expensively determined soil properties. These functions fill the gap between the available soil data and the properties which are more useful or required for a particular model or quality assessment. Pedotransfer functions utilize various regression analysis and data mining techniques to extract rules associating basic soil properties with more difficult to measure properties.
Although not formally recognized and named until 1989, the concept of the pedotransfer function has long been applied to estimate soil properties that are difficult to determine. Many soil science agencies have their own (unofficial) rule of thumb for estimating difficult-to-measure soil properties. Probably because of the particular difficulty, cost of measurement, and availability of large databases, the most comprehensive research in developing PTFs has been for the estimation of water retention curve and hydraulic conductivity.
History
The first PTF came from the study of Lyman Briggs and McLane (1907). They determined the wilting coefficient, which is defined as percentage water content of a soil when the plants growing in that soil are first reduced to a wilted condition from which they cannot recover in an approximately saturated atmosphere without the addition of water to the soil, as a function of particle-size:
Wilting coefficient = 0.01 sand + 0.12 silt + 0.57 clay
With the introduction of the field capacity (FC) and permanent wilting point (PWP) concepts by Frank Veihmeyer and Arthur Hendricksen (1927), resea |
https://en.wikipedia.org/wiki/Horton%20overland%20flow | In soil science, Horton overland flow describes the tendency of water to flow horizontally across land surfaces when rainfall has exceeded infiltration capacity and depression storage capacity. It is named after Robert E. Horton, the engineer who made the first detailed studies of the phenomenon.
Paved surfaces such as asphalt, which are designed to be flat and impermeable, rapidly achieve Horton overland flow. It is shallow, sheetlike, and fast-moving, and hence capable of extensively eroding soil and bedrock.
Horton overland flow is most commonly encountered in urban construction sites and unpaved rural roads, where vegetation has been stripped away, exposing bare dirt. The process also poses a significant problem in areas with steep terrain, where water can build up great speed and where soil is less stable, and in farmlands, where soil is flat and loose.
See also
Horton's equation
Urban runoff |
https://en.wikipedia.org/wiki/Glossary%20of%20category%20theory | This is a glossary of properties and concepts in category theory in mathematics. (see also Outline of category theory.)
Notes on foundations: In many expositions (e.g., Vistoli), the set-theoretic issues are ignored; this means, for instance, that one does not distinguish between small and large categories and that one can arbitrarily form a localization of a category. Like those expositions, this glossary also generally ignores the set-theoretic issues, except when they are relevant (e.g., the discussion on accessibility.)
Especially for higher categories, the concepts from algebraic topology are also used in the category theory. For that see also glossary of algebraic topology.
The notations and the conventions used throughout the article are:
[n] = {0, 1, 2, …, n}, which is viewed as a category (by writing .)
Cat, the category of (small) categories, where the objects are categories (which are small with respect to some universe) and the morphisms functors.
Fct(C, D), the functor category: the category of functors from a category C to a category D.
Set, the category of (small) sets.
sSet, the category of simplicial sets.
"weak" instead of "strict" is given the default status; e.g., "n-category" means "weak n-category", not the strict one, by default.
By an ∞-category, we mean a quasi-category, the most popular model, unless other models are being discussed.
The number zero 0 is a natural number.
A
B
C
D
E
F
G
H
I
K
L
M
N
O
P
Q
R
S
T
U
W
Y
Z
Notes |
https://en.wikipedia.org/wiki/AdBrite | AdBrite, Inc. was an online ad exchange, based in San Francisco, California, which was founded by Philip J. Kaplan and Gidon Wise in 2002. Founded as Marketbanker.com, the site was relaunched as AdBrite in 2004 as an advertising network and then in 2008 as an ad exchange.
AdBrite remained an independent ad exchange, reaching more than 160 million U.S. unique visitors each month and providing site-level transparency, display and video capabilities, and an open platform for data providers and real-time bidders. AdBrite was led by Hardeep Bindra, CEO, and Joaquin Delgado, CTO, who had worked at Yahoo! Right Media, another ad exchange. It was backed by Sequoia Capital, and DAG Ventures.
Closing
In 2012, Hardeep Bindra joined AdBrite as its CEO and was tasked to sell the company or its assets. On January 28, 2013, AdBrite sent an email to all of its publishers and advertisers stating that it would cease operations as of February 1, 2013, after a deal to sell the company fell through. In addition, it laid off all 26 employees.
Acquisition of IP Assets
On June 20, 2013 SiteScout announced via press release the acquisition of certain intellectual property assets developed by AdBrite in a deal whose details remain confidential.
See also
Ad serving
Advertising network
Pay-per-click
Website monetization |
https://en.wikipedia.org/wiki/Dogic | The Dogic () is an icosahedron-shaped puzzle like the Rubik's Cube. The 5 triangles meeting at its tips may be rotated, or 5 entire faces (including the triangles) around the tip may be rotated. It has a total of 80 movable pieces to rearrange, compared to the 20 pieces in the Rubik's Cube.
History
The Dogic was patented by Zsolt and Robert Vecsei in Hungary on 20 October 1993. The patent was granted 28 July 1998 (HU214709). It was originally sold by VECSO in two variants under the names "Dogic" and "Dogic 2", but was only produced in quantities far short of the demand.
In 2004, Uwe Mèffert acquired the plastic molds from its original manufacturer at the request of puzzle fans and collectors worldwide, and made another production run of the Dogics. These Dogics were first shipped in January 2005, and are now being sold by Meffert in his puzzle shop, Meffert's until September 2010 when the lack of interest for Meffert's Dogics made Uwe Meffert stop his Dogic production run.
According to Uwe Mèffert, 2000 units have been produced by him.
Description
The basic design of the Dogic is an icosahedron cut into 60 triangular pieces around its 12 tips and 20 face centers. All 80 pieces can move relative to each other. There are also a good number of internal moving pieces inside the puzzle, which are necessary to keep it in one piece as its surface pieces are rearranged. There are two types of twists that it can undergo: a shallow twist which rotates the 5 triangles around a single tip, and a deep twist which rotates 5 entire faces (including the triangles around the tip) around the tip. The shallow twist moves the triangles between faces but keeps them around the same tip; the deeper twist moves the triangles between the 5 tips lying at the base of the rotated faces but keeps them on the same faces. Each triangle has a single color, while the face centers may have up to 3 colors, depending on the particular coloring scheme employed.
Solutions
The solutions for t |
https://en.wikipedia.org/wiki/Entomophily | Entomophily or insect pollination is a form of pollination whereby pollen of plants, especially but not only of flowering plants, is distributed by insects. Flowers pollinated by insects typically advertise themselves with bright colours, sometimes with conspicuous patterns (honey guides) leading to rewards of pollen and nectar; they may also have an attractive scent which in some cases mimics insect pheromones. Insect pollinators such as bees have adaptations for their role, such as lapping or sucking mouthparts to take in nectar, and in some species also pollen baskets on their hind legs. This required the coevolution of insects and flowering plants in the development of pollination behaviour by the insects and pollination mechanisms by the flowers, benefiting both groups. Both the size and the density of a population are known to affect pollination and subsequent reproductive performance.
Coevolution
History
The early spermatophytes (seed plants) were largely dependent on the wind to carry their pollen from one plant to another. Prior to the appearance of flowering plants some gymnosperms, such as Bennettitales, developed flower-like structures that were likely insect pollinated. Insects pollination for gymnosperms likely originated in the Permian period. Candidates for pollinators include extinct long proboscis insect groups, including Aneuretopsychid, Mesopsychid and Pseudopolycentropodid scorpionflies, Kalligrammatid and Paradoxosisyrine lacewings and Zhangsolvid flies, as well as some extant families that specialised on gymnosperms before switching to angiosperms, including Nemestrinid, Tabanid and Acrocerid flies. Living cycads have mutualistic relationships with specific insect species (typically beetles) which pollinate them. Such relationships extend back to at least the late Mesozoic, with both oedemerid beetles (which today are exclusively found on flowering plants) and boganiid beetles (which still pollinate cycads today) from the Cretaceous being |
https://en.wikipedia.org/wiki/Seabird%20Colony%20Register | The Seabird Colony Register (SCR) is a database, managed by the British Joint Nature Conservation Committee, which contains counts of breeding seabirds at British seabird colonies made between 1969 and 1998, which is used for analysing past changes in breeding seabird numbers and changes in their colony size in Britain and Ireland.
Data included in the SCR include results of two complete seabird censuses of Britain and Ireland: Operation Seafarer (1969/70) and the Seabird Colony Register Census (1985–1987), as well as ad hoc counts and counts from other surveys. Data are held for all 25 species of seabird breeding throughout Britain and Ireland.
The SCR has been partially superseded by the Seabird 2000 database. |
https://en.wikipedia.org/wiki/IOPS | Input/output operations per second (IOPS, pronounced eye-ops) is an input/output performance measurement used to characterize computer storage devices like hard disk drives (HDD), solid state drives (SSD), and storage area networks (SAN). Like benchmarks, IOPS numbers published by storage device manufacturers do not directly relate to real-world application performance.
Background
To meaningfully describe the performance characteristics of any storage device, it is necessary to specify a minimum of three metrics simultaneously: IOPS, response time, and (application) workload. Absent simultaneous specifications of response-time and workload, IOPS are essentially meaningless. In isolation, IOPS can be considered analogous to "revolutions per minute" of an automobile engine i.e. an engine capable of spinning at 10,000 RPMs with its transmission in neutral does not convey anything of value, however an engine capable of developing specified torque and horsepower at a given number of RPMs fully describes the capabilities of the engine.
The specific number of IOPS possible in any system configuration will vary greatly, depending upon the variables the tester enters into the program, including the balance of read and write operations, the mix of sequential and random access patterns, the number of worker threads and queue depth, as well as the data block sizes. There are other factors which can also affect the IOPS results including the system setup, storage drivers, OS background operations etc. Also, when testing SSDs in particular, there are preconditioning considerations that must be taken into account.
Performance characteristics
The most common performance characteristics measured are sequential and random operations. Sequential operations access locations on the storage device in a contiguous manner and are generally associated with large data transfer sizes, e.g. ≥ 128 kB. Random operations access locations on the storage device in a non-contiguous manner and a |
https://en.wikipedia.org/wiki/XML%20Interface%20for%20Network%20Services | XML Interface for Network Services (XINS) is an open-source technology for definition and implementation of internet applications, which enforces a specification-oriented approach.
Specification-oriented approach
The specification-oriented approach is at the heart of XINS:
first specifications need to be written;
then documentation and code is generated from these specifications;
then both testing and implementation can start.
From specifications, XINS is able to generate:
HTML documentation
test forms
SOAP-compliant WSDL
a basic Java web application
unit test code (in Java)
stubs (in Java)
client-side code (in Java)
Components of the XINS technology
Technically, XINS is composed of the following:
An XML-based specification format for projects, APIs, functions, types and error codes
A POX-style RPC protocol (called the XINS Standard Calling Convention), compatible with web browsers (HTTP parameters in, XML out).
A tool for generating human-readable documentation, from the specifications.
A tool for generating WSDL, from the specifications.
A Log4J-based technology for logging (called Logdoc), offering a specification format, internationalization of log messages, generation of HTML documentation and generation of code.
A Java library for calling XINS functions, the XINS/Java Client Framework; in xins-client.jar.
A server-side container for Java-based XINS API implementations, the XINS/Java Server Framework; in xins-server.jar. This is like a servlet container for XINS APIs.
A Java library with some common functionality, used by both the XINS/Java Client Framework and the XINS/Java Server Framework: the XINS/Java Common Library, in xins-common.jar.
An introductory tutorial called the XINS Primer takes the reader by the hand with easy-to-follow steps to perform, with screenshots.
Since version 1.3.0, the XINS/Java Server Framework supports not only POX-style calls, but also SOAP and XML-RPC. And it supports conversion using XSLT. As of version 2. |
https://en.wikipedia.org/wiki/Revolving%20stage | A revolving stage is a mechanically controlled platform within a theatre that can be rotated in order to speed up the changing of a scene within a show. A fully revolving set was an innovation constructed by the hydraulics engineer Tommaso Francini for an elaborately produced pageant, Le ballet de la délivrance de Renaud, which was presented for Marie de Medici in January 1617 at the Palais du Louvre and noted with admiration by contemporaries. Such a stage is also commonly referred to as a turntable.
Kabuki theatre development
Background
Kabuki theatre began in Japan around 1603 when Okuni, a Shinto priestess of the Izumi shrine, traveled with a group of priestesses to Kyoto to become performers. Okuni and her nuns danced sensualized versions of Buddhist and Shinto ritual dances, using the shows as a shop window for their services at night. They originally performed in the dry river bed of the River Kamo on a makeshift wooden stage, but as Okuni’s shows gained popularity they began to tour, performing at the imperial court at least once. Eventually, they were able to build a permanent theatre in 1604, modeled after Japan's aristocratic Nōh theatre which had dominated the previous era. Kabuki, with its origins in popular entertainment, drew crowds of common folk, along with high-class samurai looking to win their favorite performer for the night. This mixing of social classes troubled the Tokugawa Shogunate, who stressed the strict separation of different classes. When rivalries between Okuni’s samurai clients grew too intense, the shogunate took advantage of the conflict and banned women from performing onstage in 1629. The women were replaced by beautiful teenage boys who took part in the same after-dark activities, leading Kabuki to be banned from the stage completely in 1652. An actor-manager in Kyoto, Murayama Matabei, went to the authorities responsible and staged a hunger strike outside their offices. In 1654 Kabuki was allowed to return with restrictions. |
https://en.wikipedia.org/wiki/Pig | The pig (Sus domesticus), often called swine (: swine), hog, or domestic pig when distinguishing from other members of the genus Sus, is an omnivorous, domesticated, even-toed, hoofed mammal. It is variously considered a subspecies of Sus scrofa (the wild boar or Eurasian boar) or a distinct species. The pig's head-plus-body length ranges from , and adult pigs typically weigh between , with well-fed individuals even exceeding this range. The size and weight of hogs largely depends on their breed. Compared to other artiodactyls, a pig's head is relatively long and pointed. Most even-toed ungulates are herbivorous, but pigs are omnivores, like their wild relative. Pigs grunt and make snorting sounds.
When used as livestock, pigs are farmed primarily for the production of meat, called pork. A group of pigs is called a passel, a team, or a sounder. The animal's bones, hide, and bristles are also used in products. Pigs, especially miniature breeds, are kept as pets.
Biology
The pig typically has a large head, with a long snout which is strengthened by a special prenasal bone and a disk of cartilage at the tip. The snout is used to dig into the soil to find food and is a very acute sense organ. The dental formula of adult pigs is , giving a total of 44 teeth. The rear teeth are adapted for crushing. In the male, the canine teeth can form tusks, which grow continuously and are sharpened by constantly being ground against each other.
Four hoofed toes are on each foot, with the two larger central toes bearing most of the weight, but the outer two also being used in soft ground.
Most pigs have rather a bristled sparse hair covering on their skin, although woolly-coated breeds such as the Mangalitsa exist.
Pigs possess both apocrine and eccrine sweat glands, although the latter appear limited to the snout and dorsonasal areas. Pigs, however, like other "hairless" mammals (e.g. elephants, rhinos, and mole-rats), do not use thermal sweat glands in cooling. Pigs are also le |
https://en.wikipedia.org/wiki/Blum%20axioms | In computational complexity theory the Blum axioms or Blum complexity axioms are axioms that specify desirable properties of complexity measures on the set of computable functions. The axioms were first defined by Manuel Blum in 1967.
Importantly, Blum's speedup theorem and the Gap theorem hold for any complexity measure satisfying these axioms. The most well-known measures satisfying these axioms are those of time (i.e., running time) and space (i.e., memory usage).
Definitions
A Blum complexity measure is a pair with a numbering of the partial computable functions and a computable function
which satisfies the following Blum axioms. We write for the i-th partial computable function under the Gödel numbering , and for the partial computable function .
the domains of and are identical.
the set is recursive.
Examples
is a complexity measure, if is either the time or the memory (or some suitable combination thereof) required for the computation coded by i.
is not a complexity measure, since it fails the second axiom.
Complexity classes
For a total computable function complexity classes of computable functions can be defined as
is the set of all computable functions with a complexity less than . is the set of all boolean-valued functions with a complexity less than . If we consider those functions as indicator functions on sets, can be thought of as a complexity class of sets. |
https://en.wikipedia.org/wiki/Stretched%20tuning | Stretched tuning is a detail of musical tuning, applied to wire-stringed musical instruments, older, non-digital electric pianos (such as the Fender Rhodes piano and Wurlitzer electric piano), and some sample-based synthesizers based on these instruments, to accommodate the natural inharmonicity of their vibrating elements. In stretched tuning, two notes an octave apart, whose fundamental frequencies theoretically have an exact 2:1 ratio, are tuned slightly farther apart (a stretched octave). "For a stretched tuning the octave is greater than a factor of 2; for a compressed tuning the octave is smaller than a factor of 2."
Melodic stretch refers to tunings with fundamentals stretched relative to each other, while harmonic stretch refers to tunings with harmonics stretched relative to fundamentals which are not stretched. For example, the piano features both stretched harmonics and, to accommodate those, stretched fundamentals.
Fundamentals and harmonics
In most musical instruments, the tone-generating component (a string or resonant column of air) vibrates at many frequencies simultaneously: a fundamental frequency that is usually perceived as the pitch of the note, and harmonics or overtones that are multiples of the fundamental frequency and whose wavelengths therefore divide the tone-generating region into simple fractional segments (1/2, 1/3, 1/4, etc.). (See harmonic series.) The fundamental note and its harmonics sound together, and the amplitude relationships among them strongly affect the perceived tone or timbre of the instrument.
In the acoustic piano, harpsichord, and clavichord, the vibrating element is a metal wire or string; in many non-digital electric pianos, it is a tapered metal tine (Rhodes piano) or reed (Wurlitzer electric piano) with one end clamped and the other free to vibrate. Each note on the keyboard has its own separate vibrating element whose tension and/or length and weight determines its fundamental frequency or pitch. In electric |
https://en.wikipedia.org/wiki/Peek%27s%20law | In physics, Peek's law defines the electric potential gap necessary for triggering a corona discharge between two wires:
ev is the "visual critical corona voltage" or "corona inception voltage" (CIV), the voltage required to initiate a visible corona discharge between the wires. It is named after Frank William Peek (1881–1933).
mv is an irregularity factor to account for the condition of the wires. For smooth, polished wires, mv = 1. For roughened, dirty or weathered wires, 0.98 to 0.93, and for cables, 0.87 to 0.83, namely the surface irregularities result in diminishing the corona threshold voltage.
r is the radius of the wires in cm.
S is the distance between the center of the wires.
gv is the "visual critical" electric field, and is given by:
δ is the air density factor with respect to SATP (25°C and 76 cmHg):
g0 is the "disruptive electric field."
c is an empirical dimensional constant.
The values for the last two parameters are usually considered to be about 30-32 kV/cm (in air) and 0.301 cm½ respectively. This latter law can be considered to hold also in different setups, where the corresponding voltage is different due to geometric reasons. |
https://en.wikipedia.org/wiki/Indian%20Institute%20of%20Astrophysics | The Indian Institute of Astrophysics (IIA), with its headquarters in Bengaluru, is an autonomous research institute wholly funded by the Department of Science and Technology, Government of India. IIA conducts research primarily in the areas of astronomy, astrophysics and related fields.
The institute has a network of laboratories and observatories in India, including Kodaikanal (the Kodaikanal Solar Observatory), Kavalur (the Vainu Bappu Observatory), Gauribidanur (the Gauribidanur Radio Observatory), Hanle (the Indian Astronomical Observatory) and Hosakote.
IIA contributed to Astrosat, India's first dedicated multi-wavelength space observatory. The Astrosat project is a collaborative effort of many different research institutions from India. The institute led the development of Ultra-Violet Imaging Telescope (UVIT).
Areas of research
Researchers at IIA work on a diverse set of topics related to Astronomy and Astrophysics. However, the research can be broadly classified under the following areas:
Sun & Solar System
Stellar Astronomy
Galactic Astronomy
Extragalactic Astronomy & Cosmology
Theoretical Astrophysics & Physics
Techniques & Instrumentation
Space Astronomy
History
William Petrie (died: 1816), an officer of the East India Company set up private observatory in his residence located in Egmore, Chennai (formerly Madras), India. The main aim of the observatory, according to Petrie, was
"to provide navigational assistance to the company ships and help determine the longitudes by observing the eclipses of Moon and satellites of Jupiter".
In 1790, this private observatory was taken over by the East India Company, with Michael Topping (1747–96) as an astronomer. In 1792, the observatory was expanded and shifted to a complex in Nungambakkam area of Chennai. This was the first modern observatory outside Europe.
As early as 1881, Mr. Blanford, then Meteorological Reporter to the government of India, recommended "the improvement of the work of solar observatio |
https://en.wikipedia.org/wiki/Location | In geography, location or place are used to denote a region (point, line, or area) on Earth's surface. The term location generally implies a higher degree of certainty than place, the latter often indicating an entity with an ambiguous boundary, relying more on human or social attributes of place identity and sense of place than on geometry. A populated place is called a settlement.
Types
Locality
A locality, settlement, or populated place is likely to have a well-defined name but a boundary that is not well defined varies by context. London, for instance, has a legal boundary, but this is unlikely to completely match with general usage. An area within a town, such as Covent Garden in London, also almost always has some ambiguity as to its extent. In geography, location is considered to be more precise than "place".
Relative location
A relative location, or situation, is described as a displacement from another site. An example is "3 miles northwest of Seattle".
Absolute location
An absolute location can be designated using a specific pairing of latitude and longitude in a Cartesian coordinate grid (for example, a spherical coordinate system or an ellipsoid-based system such as the World Geodetic System) or similar methods. For example, the position of New York City in the United States can be expressed using the coordinate system as the location 40.7128°N (latitude), 74.0060°W (longitude).
Absolute locations are also relative locations, since even absolute locations are expressed relative to something else. For example, longitude is the number of degrees east or west of the Prime Meridian, a line arbitrarily chosen to pass through Greenwich, England. Similarly, latitude is the number of degrees north or south of the equator. Because latitude and longitude are expressed relative to these lines, a position expressed in latitude and longitude is also a relative location.
See also
Locale (geography)
Location,Location
Location Location Location Austra |
https://en.wikipedia.org/wiki/Skewb%20Diamond | The Skewb Diamond is an octahedron-shaped combination puzzle similar to the Rubik's Cube. It has 14 movable pieces which can be rearranged in a total of 138,240 possible combinations. This puzzle is the dual polyhedron of the Skewb. It was invented by Uwe Mèffert, a German puzzle inventor and designer.
Description
The Skewb Diamond has 6 octahedral corner pieces and 8 triangular face centers. All pieces can move relative to each other. It is a deep-cut puzzle; its planes of rotation bisect it.
It is very closely related to the Skewb, and shares the same piece count and mechanism. However, the triangular "corners" present on the Skewb have no visible orientation on the Skewb Diamond, and the square "centers" gain a visible orientation on the Skewb Diamond. In other words, the corners on the Skewb are equivalent to the centers on the Skewb diamond. Combining pieces from the two can either give you an unscrambleable cuboctahedron or a compound of cube and octahedron with visible orientation on all pieces.
Number of combinations
The purpose of the puzzle is to scramble its colors, and then restore it to its original solved state.
The puzzle has 6 corner pieces and 8 face centers. The positions of four of the face centers is completely determined by the positions of the other 4 face centers, and only even permutations of such positions are possible, so the number of arrangements of face centers is only 4!/2. Each face center has only a single orientation.
Only even permutations of the corner pieces are possible, so the number of possible arrangements of corner pieces is 6!/2. Each corner has two possible orientations (it is not possible to change their orientation by 90° without disassembling the puzzle), but the orientation of the last corner is determined by the other 5. Hence, the number of possible corner orientations is 25.
Hence, the number of possible combinations is:
See also
Skewb Ultimate
External links
Jaap's Skewb Diamond page
Combination puzzles |
https://en.wikipedia.org/wiki/Marquee%20%28structure%29 | A marquee is most commonly a structure placed over the entrance to a hotel, theatre, casino, train station, or similar building. It often has signage stating either the name of the establishment or, in the case of theatres, the play or movie and the artist(s) appearing at that venue. The marquee is sometimes identifiable by a surrounding cache of light bulbs, usually yellow or white, that flash intermittently or as chasing lights.
Etymology
The current usage of the modern English word marquee, that in US English refers specifically to a canopy projecting over the main entrance of a theater, which displays details of the entertainment or performers, was documented in the academic journal American Speech in 1926: "Marquee, the front door or main entrance of the big top." In British English "marquee" refers more generally to a large tent, usually for social uses. The English word marquee is derived from the Middle French word marquise (the final /z/ probably being mistaken as -s plural), the feminine form corresponding to marquis ('nobleman'). The word marquise was also used to refer to various objects and fashions regarded as elegant or pleasing, hence: a kind of pear (1690), a canopy placed over a tent (1718), a type of settee (1770), a canopy in front of a building (1835), a ring with an elongated stone or setting, a diamond cut as a navette (late 19th century), and a style of woman's hat (1889). The oldest form of the word's root *merg- meant "boundary, border." Other words that descended from this Proto-Indo-European root include margin, margrave, and mark.
Early examples of the modern use of marquee include
1931, The American Mercury: "Marquee, the canopy at the main entrance [of a circus]."
1933, Billboard, The marquee of the Rivoli, where Samarang is playing, reads: 'One of the most exciting films ever shown.'
1967, The Boston Globe: "British actors mean little on an American movie marquee and Sherlock Holmes always seems old-fashioned."
History
Movie m |
https://en.wikipedia.org/wiki/Cem%20Y%C4%B1ld%C4%B1r%C4%B1m | Cem Yalçın Yıldırım (born 8 July 1961) is a Turkish mathematician who specializes in number theory.
Education
Yıldırım obtained his B.Sc from Middle East Technical University in Ankara, Turkey and his PhD from the University of Toronto in 1990. His advisor was John Friedlander. He is currently a faculty member at Boğaziçi University in Istanbul, Turkey.
Research
In 2009, Dan Goldston, János Pintz, and Yıldırım proved that for any positive number ε there exist primes p and p′ such that the difference between p and p′ is smaller than ε log p. This result was originally reported in 2003 by Goldston and Yıldırım but was later retracted. Then Janos Pintz joined the team and they completed the proof in 2005 and developed the so called GPY sieve.
See also
Landau's problems |
https://en.wikipedia.org/wiki/Yang%E2%80%93Mills%20existence%20and%20mass%20gap | The Yang–Mills existence and mass gap problem is an unsolved problem in mathematical physics and mathematics, and one of the seven Millennium Prize Problems defined by the Clay Mathematics Institute, which has offered a prize of US$1,000,000 for its solution.
The problem is phrased as follows:
Yang–Mills Existence and Mass Gap. Prove that for any compact simple gauge group G, a non-trivial quantum Yang–Mills theory exists on and has a mass gap Δ > 0. Existence includes establishing axiomatic properties at least as strong as those cited in , and .
In this statement, a quantum Yang–Mills theory is a non-abelian quantum field theory similar to that underlying the Standard Model of particle physics; is Euclidean 4-space; the mass gap Δ is the mass of the least massive particle predicted by the theory.
Therefore, the winner must prove that:
Yang–Mills theory exists and satisfies the standard of rigor that characterizes contemporary mathematical physics, in particular constructive quantum field theory, and
The mass of all particles of the force field predicted by the theory are strictly positive.
For example, in the case of G=SU(3)—the strong nuclear interaction—the winner must prove that glueballs have a lower mass bound, and thus cannot be arbitrarily light.
The general problem of determining the presence of a spectral gap in a system is known to be undecidable.
Background
The problem requires the construction of a QFT satisfying the Wightman axioms and showing the existence of a mass gap. Both of these topics are described in sections below.
The Wightman axioms
The Millennium problem requires the proposed Yang–Mills theory to satisfy the Wightman axioms or similarly stringent axioms. There are four axioms:
W0 (assumptions of relativistic quantum mechanics)
Quantum mechanics is described according to von Neumann; in particular, the pure states are given by the rays, i.e. the one-dimensional subspaces, of some separable complex Hilbert space.
The Wight |
https://en.wikipedia.org/wiki/Liquid%E2%80%93liquid%20extraction | Liquid–liquid extraction (LLE), also known as solvent extraction and partitioning, is a method to separate compounds or metal complexes, based on their relative solubilities in two different immiscible liquids, usually water (polar) and an organic solvent (non-polar). There is a net transfer of one or more species from one liquid into another liquid phase, generally from aqueous to organic. The transfer is driven by chemical potential, i.e. once the transfer is complete, the overall system of chemical components that make up the solutes and the solvents are in a more stable configuration (lower free energy). The solvent that is enriched in solute(s) is called extract. The feed solution that is depleted in solute(s) is called the raffinate. LLE is a basic technique in chemical laboratories, where it is performed using a variety of apparatus, from separatory funnels to countercurrent distribution equipment called as mixer settlers. This type of process is commonly performed after a chemical reaction as part of the work-up, often including an acidic work-up.
The term partitioning is commonly used to refer to the underlying chemical and physical processes involved in liquid–liquid extraction, but on another reading may be fully synonymous with it. The term solvent extraction can also refer to the separation of a substance from a mixture by preferentially dissolving that substance in a suitable solvent. In that case, a soluble compound is separated from an insoluble compound or a complex matrix.
From a hydrometallurgical perspective, solvent extraction is exclusively used in separation and purification of uranium and plutonium, zirconium and hafnium, separation of cobalt and nickel, separation and purification of rare earth elements etc., its greatest advantage being its ability to selectively separate out even very similar metals. One obtains high-purity single metal streams on 'stripping' out the metal value from the 'loaded' organic wherein one can precipitate or de |
https://en.wikipedia.org/wiki/Algebraic%20space | In mathematics, algebraic spaces form a generalization of the schemes of algebraic geometry, introduced by Michael Artin for use in deformation theory. Intuitively,
schemes are given by gluing together affine schemes using the Zariski topology, while algebraic spaces are given by gluing together affine schemes using the finer étale topology. Alternatively one can think of schemes as being locally isomorphic to affine schemes in the Zariski topology, while algebraic spaces are locally isomorphic to affine schemes in the étale topology.
The resulting category of algebraic spaces extends the category of schemes and allows one to carry out several natural constructions that are used in the construction of moduli spaces but are not always possible in the smaller category of schemes, such as taking the quotient of a free action by a finite group (cf. the Keel–Mori theorem).
Definition
There are two common ways to define algebraic spaces: they can be defined as either quotients of schemes by etale equivalence relations, or as sheaves on a big etale site that are locally isomorphic to schemes. These two definitions are essentially equivalent.
Algebraic spaces as quotients of schemes
An algebraic space X comprises a scheme U and a closed subscheme R ⊂ U × U satisfying the following two conditions:
1. R is an equivalence relation as a subset of U × U
2. The projections pi: R → U onto each factor are étale maps.
Some authors, such as Knutson, add an extra condition that an algebraic space has to be quasi-separated, meaning that the diagonal map is quasi-compact.
One can always assume that R and U are affine schemes. Doing so means that the theory of algebraic spaces is not dependent on the full theory of schemes, and can indeed be used as a (more general) replacement of that theory.
If R is the trivial equivalence relation over each connected component of U (i.e. for all x, y belonging to the same connected component of U, we have xRy if and only if x=y), then the al |
https://en.wikipedia.org/wiki/Gynoecium | Gynoecium (; ; : gynoecia) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more) pistils and is typically surrounded by the pollen-producing reproductive organs, the stamens, collectively called the androecium. The gynoecium is often referred to as the "female" portion of the flower, although rather than directly producing female gametes (i.e. egg cells), the gynoecium produces megaspores, each of which develops into a female gametophyte which then produces egg cells.
The term gynoecium is also used by botanists to refer to a cluster of archegonia and any associated modified leaves or stems present on a gametophyte shoot in mosses, liverworts, and hornworts. The corresponding terms for the male parts of those plants are clusters of antheridia within the androecium. Flowers that bear a gynoecium but no stamens are called pistillate or carpellate. Flowers lacking a gynoecium are called staminate.
The gynoecium is often referred to as female because it gives rise to female (egg-producing) gametophytes; however, strictly speaking sporophytes do not have a sex, only gametophytes do. Gynoecium development and arrangement is important in systematic research and identification of angiosperms, but can be the most challenging of the floral parts to interpret.
Introduction
Unlike most animals, plants grow new organs after embryogenesis, including new roots, leaves, and flowers. In the flowering plants, the gynoecium develops in the central region of the flower as a carpel or in groups of fused carpels. After fertilization, the gynoecium develops into a fruit that provides protection and nutrition for the developing seeds, and often aids in their dispersal. The gynoecium has several specialized tissues. The tissues of the gynoecium develop from genetic and hormonal interactions along three-major axes. These tissue |
https://en.wikipedia.org/wiki/Zoophily | Zoophily, or zoogamy, is a form of pollination whereby pollen is transferred by animals, usually by invertebrates but in some cases vertebrates, particularly birds and bats, but also by other animals. Zoophilous species frequently have evolved mechanisms to make themselves more appealing to the particular type of pollinator, e.g. brightly colored or scented flowers, nectar, and appealing shapes and patterns. These plant-animal relationships are often mutually beneficial because of the food source provided in exchange for pollination.
Pollination is defined as the transfer of pollen from the anther to the stigma. There are many vectors for pollination, including abiotic (wind and water) and biotic (animal). There are benefits and costs associated with any vector. For instance, using animal pollination is beneficial because the process is more directed and often results in pollination. At the same time it is costly for the plant to produce rewards, such as nectar, to attract animal pollinators. Not producing such rewards is one benefit of using abiotic pollinators, but a cost associated with this approach is that the pollen may be distributed more randomly. In general, pollination by animals occurs after they reach inside the flowers for nectar. While feeding on the nectar, the animal rubs or touches the stamens and is covered in pollen. Some of this pollen will be deposited on the stigma of the next flower it visits, pollinating the flower.
Insect pollination
This is known as entomophily. There are many different subtypes.
Bee pollination (melittophily)
There are diverse types of bees (such as honeybees, bumblebees, and orchid bees), forming large groups that are quite distinctive in size, tongue length and behaviour (some solitary, some colonial); thus generalization about bee pollination is difficult. Some plants can only be pollinated by bees because their anthers release pollen internally, and it must be shaken out by buzz pollination (also known as "sonicati |
https://en.wikipedia.org/wiki/Hydrophily | Hydrophily is a fairly uncommon form of pollination whereby pollen is distributed by the flow of waters, particularly in rivers and streams. Hydrophilous species fall into two categories:
(i) Those that distribute their pollen to the surface of water. e.g. Vallisneria'''s male flower or pollen grain are released on the surface of water, which are passively carried away by water currents; some of them eventually reach the female flower
(ii) Those that distribute it beneath the surface. e.g. seagrasses in which female flower remain submerged in water and pollen grains are released inside the water.
Surface pollination
Surface pollination is more frequent, and appears to be a transitional phase between wind pollination and true hydrophily. In these the pollen floats on the surface and reaches the stigmas of the female flowers as in Hydrilla, Callitriche, Ruppia, Zostera, Elodea. In Vallisneria the male flowers become detached and float on the surface of the water; the anthers are thus brought in contact with the stigmas of the female flowers. Surface hydrophily has been observed in several species of Potamogeton as well as some marine species.
Submerged pollination
Species exhibiting true submerged hydrophily include Najas, where the pollen grains are heavier than water, and sinking down are caught by the stigmas of the extremely simple female flowers, Posidonia australis or Zostera marina and Hydrilla''.
Evolution
Hydrophily is unique to obligate submersed aquatic angiosperms with sexually reproductive parts completely submerged below the water surface. Hydrophily is the adaptive evolution of completely submersed angiosperms to aquatic habitats. True hydrophily occurs in 18 submersed angiosperm genera, which is associated with an unusually high incidence of unisexual flowers. |
https://en.wikipedia.org/wiki/Pine%20barrens | Pine barrens, pine plains, sand plains, or pineland areas occur throughout the U.S. from Florida to Maine (see Atlantic coastal pine barrens) as well as the Midwest, West, and Canada and parts of Eurasia. Perhaps the most well known pine-barrens area to North Americans is the New Jersey Pine Barrens. Pine barrens are generally pine forests in otherwise "barren" and agriculturally challenging areas. Such pine forests often occur on dry, acidic, infertile soils, and also include grasses, forbs, and low shrubs. The most extensive pine barrens occur in large areas of sandy glacial deposits (including outwash plains), lakebeds, and outwash terraces along rivers.
Description
Botany
The most common trees are the jack pine, red pine, pitch pine, blackjack oak, and scrub oak; a scattering of larger oaks is not unusual. The understory includes grasses, sedges, and forbs, many of them common in dry prairies, and rare plants such as the sand-plain gerardia (Agalinis acuta). Plants of the heath family, such as blueberries and bearberry, and shrubs, such as prairie willow and hazel, are common. These species have adaptations that permit them to survive or regenerate well after fire.
Fauna
Pine barrens support a number of rare species, including Lepidoptera such as the Karner blue butterfly (Plebejus melissa samuelis) and the barrens buck moth (Hemileuca maia).
Fire ecology
The American Indians used fire to maintain such areas as rangeland. Suppression of wildfires has allowed larger climax forest vegetation to take over in most one-time barrens. Barrens are dependent on fire to prevent invasion by less fire-tolerant species. In the absence of fire, barrens will proceed through successional stages from pine forest to a larger climax forest, such as oak-hickory forest. However, temperatures in a white pine forest on Long Island were high enough to destroy the pine cones which led to a slow recovery of the pine forest that varied depending on the availability of seedlings and |
https://en.wikipedia.org/wiki/Mex%20%28mathematics%29 | In mathematics, the mex ("minimum excluded value") of a subset of a well-ordered set is the smallest value from the whole set that does not belong to the subset. That is, it is the minimum value of the complement set.
Beyond sets, subclasses of well-ordered classes have minimum excluded values. Minimum excluded values of subclasses of the ordinal numbers are used in combinatorial game theory to assign nim-values to impartial games.
According to the Sprague–Grundy theorem, the nim-value of a game position is the minimum excluded value of the class of values of the positions that can be reached in a single move from the given position.
Minimum excluded values are also used in graph theory, in greedy coloring algorithms. These algorithms typically choose an ordering of the vertices of a graph and choose a numbering of the available vertex colors. They then consider the vertices in order, for each vertex choosing its color to be the minimum excluded value of the set of colors already assigned to its neighbors.
Examples
The following examples all assume that the given set is a subset of the class of ordinal numbers:
where is the limit ordinal for the natural numbers.
Game theory
In the Sprague–Grundy theory the minimum excluded ordinal is used to determine the nimber of a normal-play impartial game. In such a game, either player has the same moves in each position and the last player to move wins. The nimber is equal to 0 for a game that is lost immediately by the first player, and is equal to the mex of the nimbers of all possible next positions for any other game.
For example, in a one-pile version of Nim, the game starts with a pile of stones, and the player to move may take any positive number of stones. If is zero stones, the nimber is 0 because the mex of the empty set of legal moves is the nimber 0. If is 1 stone, the player to move will leave 0 stones, and , gives the nimber for this case. If is 2 stones, the player to move can leave 0 or 1 sto |
https://en.wikipedia.org/wiki/Synovial%20osteochondromatosis | Synovial osteochondromatosis (SOC) (synonyms include synovial chondromatosis, primary synovial chondromatosis, synovial chondrometaplasia) is a rare disease that creates a benign change or proliferation in the synovium or joint-lining tissue, which changes to form bone-forming cartilage. In most occurrences, there is only one joint affected, either the knee, the hip, or the elbow. Rarely involves the TMJ.
The cause is unknown.
In this condition, cartilaginous metaplasia takes place within the synovial membrane of the joint. Metaplastic synovium organizes into nodules. With minor trauma, nodules are shed as small bodies into the joint space. In some patients, the disease process may involve tendon sheaths and bursal sacs.
Cartilaginous intra-articular bodies float freely within the synovial fluid, which they require for nutrition and growth. Progressive enlargement and ossification occur with time. If they remain free, they continue to grow larger and more calcified. In severe cases, they may occupy the entire joint space or penetrate to adjacent tissues. Also, they can deposit in the synovial lining, reestablish a blood supply, and become replaced by bone. On occasion, synovial reattachment can lead to complete reabsorption of the cartilage fragment.
Signs and symptoms
Chronic, progressive pain and swelling of the affected joint are exacerbated by physical activity. Joint effusion and limited range of motion are common associated features. It affects primarily large joints, including knee (>50% of cases), elbow, hip, and shoulder. SOC is twice as common in men as women. Some patients have intra-articular bodies resting in stable positions within joint recesses or bursae. These patients may be asymptomatic, with SOC merely as an incidental finding at imaging.
Complications
Malignant transformation to synovial chondrosarcoma. This is a very rare complication occurring in chronic cases. Treatment entails synovial excision and total joint replacemen |
https://en.wikipedia.org/wiki/Shared%20Whois%20Project | The Shared Whois Project (SWIP) is the process used to submit, maintain and update information to ensure up-to-date and efficient maintenance of WHOIS records, as structured in RFC 1491. The process updates WHOIS to contain information regarding what organization is using a specific IP address, or a specific block of addresses. Additionally, it provides means to track the use of an organization's current allocations of IP addresses, so that additional allocation of IP addresses may be justified and usage reports or case studies may be done.
SWIP must be used within seven days of any reassignment of an IP address space to a downstream customer to:
Provide new reassignments of blocks of eight or more IP addresses
Delete existing reassignments, or
Modify data connected to existing reassignments.
In contrast, an organization is not required to submit a SWIP template for fewer than eight IP addresses.
Allocations, assignments or reassignments of blocks of 8,192 addresses and more (greater than a /19 block) must be approved by ARIN beforehand. Companies assigned a block of 65,536 addresses or more will be responsible for maintaining all IN-ADDR.ARPA domain records for their customers.
There are two types of registration. The first is an allocation, for blocks of IP addresses which will later be reallocated or reassigned to third parties. The second is an assignment, for blocks that will not be reassigned, or the recipient is an end-user. |
https://en.wikipedia.org/wiki/List%20of%20pine%20barrens | The following is a list of pine barrens.
Canada
Kaladar Jack Pine Barrens in Ontario
United States
Kentucky
Hi Lewis Pine Barrens State Nature Preserve
Maine
Waterboro Barrens Preserve
Hollis Plains
Massachusetts
Plymouth Pinelands
Michigan
Huron National Forest
New Hampshire
Ossipee Pine Barrens
Concord Pine Barrens
New Jersey
Pine Barrens
New York
Albany Pine Bush
Altona Flat Rock Jack Pine Barrens
Long Island Central Pine Barrens
Rome Sand Plains
Shawangunk Ridge
Pennsylvania
Long Pond Barrens
Scotia Barrens
Rhode Island
Kingston Pine Barrens
West Virginia
North Fork Mountain
Wisconsin
Great Lakes Barrens
Moquah Barrens Research Natural Area
Northwest Wisconsin Pine Barrens
Gotham Jack Pine Barrens
Spread Eagle Barrens
Virginia
Zuni Pine Barrens
Nature-related lists
Ecoregions |
https://en.wikipedia.org/wiki/Sustentacular%20cell | A sustentacular cell is a type of cell primarily associated with structural support, they can be found in various tissues.
Sustentacular cells of the olfactory epithelium (also called supporting cells or Sertoli cells) have been shown to be involved in the phagocytosis of dead neurons, odorant transformation and xenobiotic metabolism.
One type of sustentacular cell is the Sertoli cell, in the testicle. It is located in the walls of the seminiferous tubules and supplies nutrients to sperm. They are responsible for the differentiation of spermatids, the maintenance of the blood-testis barrier, and the secretion of inhibin, androgen-binding protein and Mullerian-inhibiting factor.
The organ of Corti in the inner ear and taste buds also contain sustentacular cells.
Another type of sustentacular cell is found with glomus cells of the carotid and aortic bodies.
About 40% of carcinoids have a scattering of sustentacular cells, which stain positive for S-100. |
https://en.wikipedia.org/wiki/Opportunism | Opportunism is the practice of taking advantage of circumstances – with little regard for principles or with what the consequences are for others. Opportunist actions are expedient actions guided primarily by self-interested motives. The term can be applied to individual humans and living organisms, groups, organizations, styles, behaviors, and trends.
Opportunism or "opportunistic behaviour" is an important concept in such fields of study as biology, transaction cost economics, game theory, ethics, psychology, sociology and politics.
Definitions
Opportunism is the conscious policy and practice of taking advantage of circumstances.
Although in many societies opportunism often has a strong negative moral connotation, it may also be defined more neutrally as putting self-interest before other interests when there is an opportunity to do so, or flexibly adapting to changing circumstances to maximize self-interest (though usually in a way that negates some principle previously followed).
Opportunism is sometimes defined as the ability to capitalize on the mistakes of others: to exploit opportunities created by the errors, weaknesses or distractions of opponents to one's own advantage.
Taking a realistic or practical approach to a problem can involve "weak" forms of opportunism. For the sake of doing something that will work, or that successfully solves the problem, a previously agreed principle is knowingly compromised or disregardedwith the justification that alternative actions would, overall, have a worse effect.
In choosing or seizing opportunities, human opportunism is most likely to occur where:
People can make maximum gains at the least cost to themselves.
Relevant internal or external controls on their behavior are absent.
People are pressured to choose and act.
Criticism of opportunism usually refers to a situation where beliefs and principles are tested or challenged.
Human opportunism should not be confused with "seeking opportunities", or "makin |
https://en.wikipedia.org/wiki/Blood%E2%80%93testis%20barrier | The blood–testis barrier is a physical barrier between the blood vessels and the seminiferous tubules of the animal testes. The name "blood-testis barrier" is misleading as it is not a blood-organ barrier in a strict sense, but is formed between Sertoli cells of the seminiferous tubule and isolates the further developed stages of germ cells from the blood. A more correct term is the Sertoli cell barrier (SCB).
Structure
The walls of seminiferous tubules are lined with primitive germ layer cells and by Sertoli cells. The barrier is formed by tight junctions, adherens junctions and gap junctions between the Sertoli cells, which are sustentacular cells (supporting cells) of the seminiferous tubules, and divides the seminiferous tubule into a basal compartment (outer side of the tubule, in contact with blood and lymph) and an endoluminal compartment (inner side of the tubule, isolated from blood and lymph). The tight junctions are formed by intercellular adhesion molecules in between cells that are anchored to actin fibers within the cells. For the visualization of the actin fibers within the seminiferous tubules see Sharma et al.'s immunofluorescence studies.
Function
The presence of the SCB allows Sertoli cells to control the adluminal environment in which germ cells (spermatocytes, spermatids and sperm) develop by influencing the chemical composition of the luminal fluid.
The barrier also prevents passage of cytotoxic agents (bodies or substances that are toxic to cells) into the seminiferous tubules.
The fluid in the lumen of seminiferous tubules is quite different from plasma; it contains very little protein and glucose but is rich in androgens, estrogens, potassium, inositol and glutamic and aspartic acid. This composition is maintained by blood–testis barrier.
The barrier also protects the germ cells from blood-borne noxious agents,
prevents antigenic products of germ cell maturation from entering the circulation and generating an autoimmune response, and ma |
https://en.wikipedia.org/wiki/Solarroller | Solarroller is a BEAM dragster photovore robot run by solar panel that utilizes sunlight. In competitions between solarrollers, each one must run one meter in the shortest time possible. Components include pager motors,
capacitors, resistors, transistors, and solar panels.
There are several different kinds of configurations of solarrollers, with bigger or smaller wheels, one or two motors. Configurations differences include:
motor (number and output),
wheels (number and size), and
frame designs
This robot type always moves forwards. The motor drives one or more wheels. A "Solar Engine" circuit is used to feed the robot.
Solarroller's speed is directly related to the amount of light robot registers on its optical sensor. Most are driven by an electronic "relaxation oscillator", in which a charge is accumulated in a capacitor while at rest and then suddenly released in the drive mechanism.
See also
Mark Tilden
Further reading
"Simple Solaroller". Electronics Now, June, 1997.
Solarroller circuits. Mark Tilden's hand-written notes (c. 1990), solarbotics.net.
Solarroller mechanics. Mark Tilden's hand-written notes (c. 1990), solarbotics.net.
External articles
Solarbotics.net gallery of Solarrollers
BEAM robotics Yahoo! group
Beam-Online sollarrolers gallery with several different configurations
2003 BEAM SolarRoller Race, robotgames.net
Solarrollers on the BEAM Wiki
Solar car racing
Solar energy
BEAM robotics |
https://en.wikipedia.org/wiki/Relativistic%20aberration | Relativistic aberration is the relativistic version of aberration of light, including relativistic corrections that become significant for observers who move with velocities close to the speed of light. It is described by Einstein's special theory of relativity.
Suppose, in the reference frame of the observer, the source is moving with speed at an angle relative to the vector from the observer to the source at the time when the light is emitted. Then the following formula, which was derived by Einstein in 1905 from the Lorentz transformation, describes the aberration of the light source, , measured by the observer:
In this circumstance, the rays of light from the source which reach the observer are tilted towards the direction of the source's motion (relative to the observer). It is as if light emitted by a moving object is concentrated conically, towards its direction of motion; an effect called relativistic beaming. Also, light received by a moving object (e.g. the view from a very fast spacecraft) also appears concentrated towards its direction of motion.
Searchlight Effect
A consequence is that a forward observer should normally be expected to intercept a greater proportion of the object's light than a rearward one; this concentration of light in the object's forward direction is referred to as the "searchlight" or "headlight" effect. Light from a relativistic source becomes more forward directed and Doppler shifted with increasing velocity (). |
https://en.wikipedia.org/wiki/STONITH | STONITH ("Shoot The Other Node In The Head" or "Shoot The Offending Node In The Head"), sometimes called STOMITH ("Shoot The Other Member/Machine In The Head"), is a technique for fencing in computer clusters.
Fencing is the isolation of a failed node so that it does not cause disruption to a computer cluster. As its name suggests, STONITH fences failed nodes by resetting or powering down the failed node.
Multi-node error-prone contention in a cluster can have catastrophic results, such as if both nodes try writing to a shared storage resource. STONITH provides effective, if rather drastic, protection against these problems.
Single node systems use a comparable mechanism called a watchdog timer. A watchdog timer will reset the node if the node does not tell the watchdog circuit that it is operating well. A STONITH decision can be based on various decisions which can be customer specific plugins.
Google's inclusive language developer documentation discourages usage of this term. |
https://en.wikipedia.org/wiki/OpenBSM | OpenBSM is an open source implementation of Sun's Basic Security Module (BSM) Audit API and file format. BSM, which is a system used for auditing, describes a set of system call and library interfaces for managing audit records as well as a token stream file format that permits extensible and generalized audit trail processing.
OpenBSM includes system include files appropriate for inclusion in an operating system implementation of Audit, libbsm, an implementation of the BSM library interfaces for generating, parsing, and managing audit records, auditreduce and praudit, audit reduction and printing tools, API documentation, and sample configuration files. Works in progress include extensions to the libbsm API to support easier audit trail analysis, including a pattern matching library.
OpenBSM is derived from the BSM audit implementation found in Apple's open source Darwin operating system, which upon request, Apple relicensed under a BSD licence to allow for integration into FreeBSD and other systems. The Darwin BSM implementation was created by McAfee Research under contract to Apple, and has since been extensively extended by the volunteer TrustedBSD team. OpenBSM is included in FreeBSD as of version 6.2 and later, and has been announced as a Mac OS X Snow Leopard feature.
External links
TrustedBSD: OpenBSM
FreeBSD Handbook: Security Event Auditing
Apple Computer: Common Criteria
BSD software
Operating system security
Software using the BSD license |
https://en.wikipedia.org/wiki/List%20of%20experimental%20errors%20and%20frauds%20in%20physics | Experimental science demands repeatability of results but many experiments are not due to fraud or error. The list of papers whose results were later retracted or discredited, thus leading to invalid science is growing. Some errors are introduced when the experimenter's desire for a certain result unconsciously influences selection of data (a problem which is possible to avoid in some cases with double-blind protocols). There have also been cases of deliberate scientific misconduct.
Famous experimental errors
N-rays (1903)
A reported faint visual effect that experimenters could still "see" even when the supposed causative element in their apparatus had been secretly disconnected.
Claimed experimental disproof of special relativity (1906)
Published in Annalen der Physik and said to be the first journal paper to cite Einstein's 1905 electrodynamics paper. Walter Kaufmann – stated that his results were not compatible with special relativity. According to Gerald Holton, it took a decade for the shortcomings of Kaufmann's test to be realised: during this time, critics of special relativity were able to claim that the theory was invalidated by the available experimental evidence.
Premature verification of the gravitational redshift effect (1924)
A number of earlier experimenters claimed to have found the presence or lack of gravitational redshift, but Walter Sydney Adams's result was supposed to have settled the issue. Unfortunately the measurement and the prediction were both in error such that it initially appeared to be valid. It is no longer considered credible and there has been much debate about whether the results were fraud or that his data may have been contaminated by stray light from Sirius A. The first "reliable" confirmations of the effect appeared in the 1960s.
First reproducible synthetic diamond (1955)
Originally reported in Nature in 1955 and later. Diamond synthesis was later determined to be impossible with the apparatus. Subsequent analysis indica |
https://en.wikipedia.org/wiki/R2d2%20%28mouse%20gene%29 | R2d2 is a mouse gene that is sometimes a selfish gene.
R2d2 is short for "Responder to meiotic drive 2", It was discovered by UNC School of Medicine researchers to display transmission bias.
R2d2 is a stretch of DNA on mouse chromosome 2 that contains multiple copies of the Cwc22 gene. When seven or more copies of that latter gene are present, R2d2 becomes selfish.
In one lab breeding population, in a selective sweep, R2d2 increased from being in 50 percent of the lab mice's chromosomes to 85 percent in 10 generations. By 15 generations, it reached fixation.
In female mice, R2d2 somehow displaces the chromosome that doesn’t contain it and it is preferentially incorporated into eggs. It has spread in the wild to several parts of the world.
See also
gene drive
Homing endonuclease gene |
https://en.wikipedia.org/wiki/Puzz%203D | Puzz 3D is the brand name of three-dimensional jigsaw puzzles, manufactured by Hasbro and formerly by Wrebbit, Inc. Unlike traditional puzzles which are composed of series of flat pieces that when put together, create a single unified image, the Puzz 3D series of puzzles are composed on plastic foam, with part of an image graphed on a stiff paper facade glued to the underlying foam piece and cut to match the piece's dimensions. When the pieces are put together, they create a standing structure.
History
Puzz 3D puzzles, invented by Paul Gallant, were first made in 1991 under the Quebec-based company Wrebbit. Throughout the 1990s, three-dimensional puzzles were made, leading to a rapid growth in the company.
In 1993, Hasbro's Milton Bradley Company bought Wrebbit's Puzz 3D Line, and in 2005 Hasbro themselves completely bought Wrebbit, in 2006, moved the manufacture of Wrebbit's puzzles to its East Longmeadow, Massachusetts facility.
The last series made under Hasbro was Towers Made to Scale. The series consisted of 13 skyscrapers from around the world. All of the structures were made to be at 1:585 scale, and all of the towers glowed in the dark.
By 2006, all of the Puzz 3D puzzles had been discontinued, but in 2011, the Puzz 3D line was revitalized by Winning Solutions, Inc. Winning Solutions first released the Eiffel Tower and Empire State Building, and released a model of Anif Palace in 2012. As of 2014, Hasbro has brought some of the old Puzz 3D line back into production (made in China) in the same boxes. A separate company Wrebbit3D, making new products along with some of the old line, has been created by some of the old Wrebbit staff.
Puzzles
Typically, the structures released were famous landmarks, including the White House, Big Ben, CN Tower, and the Neuschwanstein castle. In addition to this, Puzz 3D has also released science-fiction themed puzzles, such as the Millennium Falcon spacecraft from the Star Wars franchise, and structures from legends suc |
https://en.wikipedia.org/wiki/Gramine | Gramine (also called donaxine) is a naturally occurring indole alkaloid present in several plant species. Gramine may play a defensive role in these plants, since it is toxic to many organisms.
Occurrence
Gramine has been found in the giant reed, Arundo donax, Acer saccharinum (Silver Maple), Hordeum, (a grass genus that includes barley) and Phalaris (another grass genus).
Effects and toxicity
Gramine has been found to act as an agonist of the adiponectin receptor 1 (AdipoR1).
The LD50 of gramine is 44.6 mg/ kg iv in mice and 62.9 mg/ kg iv in rats.
Numerous studies have been done on the toxicity in insects harmful to crops for use as a possible insecticide. |
https://en.wikipedia.org/wiki/Noddy%20%28camera%29 | Noddy was a camera system used for generating idents for the BBC One and BBC Two television channels from late 1963 to February 1985.
The Noddy video camera was controlled by a servomotor to pan and tilt (or 'nod', hence the name Noddy) across a set of pre-arranged physical objects; captions and mechanical models. The camera was black-and-white, with colour electronically added to its output. This system eliminated the delay associated with swapping graphics upon a conventional copy stand. It also allowed for the depth required by mechanical objects such as clocks and a rotating globe.
History
The BBC first employed the system in the 1960s, before the advent of colour. The system's remote operation allowed the operator to control it with ease, and allowed the idents to be of no fixed length as the clock symbols could continue for many minutes at a time. A smaller black and white camera was introduced as camera technology progressed and, from 1969, a process was introduced to add colour signals to the camera output. This electronic addition of colour was convenient and made the networks' rebrands easy to perform.
BBC One mirrored globes
The most famous idents of the Noddy system were the BBC One mirrored globes used between 1969 and 1985, albeit with minor colour changes. The system consisted of an internally lit, rotating globe in front of a concave mirror. The oceans were painted onto the globe in metallic black paint, leaving the land masses as unpainted patches. The original globe ident introduced on 15 November 1969 featured blue continents and logo against a black background. The logo included the word 'COLOUR' after the BBC One (then BBC 1) corporate logo, to identify the new programme format and act as an advertisement to the vast majority of viewers who were still watching in black and white (as the colour version of the television licence, which financed the BBC, was much more expensive). Full colour broadcasts across the UK did not become available unti |
https://en.wikipedia.org/wiki/Pallawa | In the Buginese language, pallawa is a punctuation symbol. It is composed of three cascading diagonal dots. A pallawa is used to separate rhythmico-intonational groups, thus functionally corresponding to the full stop and comma of the Latin script.
See also
Lontara script |
https://en.wikipedia.org/wiki/Linux%20adoption | Linux adoption is the adoption of Linux computer operating systems (OS) by households, nonprofit organizations, businesses, and governments.
Many factors have resulted in the expanded use of Linux systems by traditional desktop users as well as operators of server systems, including the desire to minimize software costs, increase network security and support for open-source philosophical principles. In recent years several governments, at various levels, have enacted policies shifting state-owned computers to Linux from proprietary software regimes.
In August 2010, Jeffrey Hammond, principal analyst at Forrester Research, declared, "Linux has crossed the chasm to mainstream adoption," a statement attested by the large number of enterprises that had transitioned to Linux during the late-2000s recession. In a company survey completed in the third quarter of 2009, 48% of surveyed companies reported using an open-source operating system.
The Linux Foundation regularly releases publications regarding the Linux kernel, Linux OS distributions, and related themes. One such publication, "Linux Adoption Trends: A Survey of Enterprise End Users," is freely available upon registration.
Traditionally, the term Linux adoption refers to adoption of a Linux OS made for "desktop" computers, the original intended use (or adoption on servers, that is essentially the same form of OS). Adoption of that form on personal computers is still low relatively, while adoption of the Android operating system is very high. The term Linux adoption, often overlooks that operating system or other uses such as in ChromeOS that also use the Linux kernel (but have almost nothing else in common, not even the name – Linux – usually applied; while Android is the most popular variant – in fact the most popular operating system in the world).
Linux adopters
Outside of traditional web services, Linux powers many of the biggest Internet properties (e.g., Google, Amazon, Facebook, eBay, Twitter or Yahoo! |
https://en.wikipedia.org/wiki/Karush%E2%80%93Kuhn%E2%80%93Tucker%20conditions | In mathematical optimization, the Karush–Kuhn–Tucker (KKT) conditions, also known as the Kuhn–Tucker conditions, are first derivative tests (sometimes called first-order necessary conditions) for a solution in nonlinear programming to be optimal, provided that some regularity conditions are satisfied.
Allowing inequality constraints, the KKT approach to nonlinear programming generalizes the method of Lagrange multipliers, which allows only equality constraints. Similar to the Lagrange approach, the constrained maximization (minimization) problem is rewritten as a Lagrange function whose optimal point is a (global) saddle point, i.e. a global maximum (minimum) over the domain of the choice variables and a global minimum (maximum) over the multipliers, which is why the Karush–Kuhn–Tucker theorem is sometimes referred to as the saddle-point theorem.
The KKT conditions were originally named after Harold W. Kuhn and Albert W. Tucker, who first published the conditions in 1951. Later scholars discovered that the necessary conditions for this problem had been stated by William Karush in his master's thesis in 1939.
Nonlinear optimization problem
Consider the following nonlinear optimization problem in standard form:
minimize
subject to
where is the optimization variable chosen from a convex subset of , is the objective or utility function, are the inequality constraint functions and are the equality constraint functions. The numbers of inequalities and equalities are denoted by and respectively. Corresponding to the constrained optimization problem one can form the Lagrangian function
where
The Karush–Kuhn–Tucker theorem then states the following.
Since the idea of this approach is to find a supporting hyperplane on the feasible set , the proof of the Karush–Kuhn–Tucker theorem makes use of the hyperplane separation theorem.
The system of equations and inequalities corresponding to the KKT conditions is usually not solved directly, except in the few sp |
https://en.wikipedia.org/wiki/Tiling%20puzzle | Tiling puzzles are puzzles involving two-dimensional packing problems in which a number of flat shapes have to be assembled into a larger given shape without overlaps (and often without gaps). Some tiling puzzles ask you to dissect a given shape first and then rearrange the pieces into another shape. Other tiling puzzles ask you to dissect a given shape while fulfilling certain conditions. The two latter types of tiling puzzles are also called dissection puzzles.
Tiling puzzles may be made from wood, metal, cardboard, plastic or any other sheet-material. Many tiling puzzles are now available as computer games.
Tiling puzzles have a long history. Some of the oldest and most famous are jigsaw puzzles and the tangram puzzle.
Other examples of tiling puzzles include:
Conway puzzle
Domino tiling, of which the mutilated chessboard problem is one example
Eternity puzzle
Geometric magic square
Puzz-3D
Squaring the square
Tantrix
T puzzle
Many three-dimensional mechanical puzzles can be regarded as three-dimensional tiling puzzles.
See also
Dissection puzzle
Polyforms
Sliding puzzle
Tessellation
Wang tile
Tessellation |
https://en.wikipedia.org/wiki/Beal%20conjecture | The Beal conjecture is the following conjecture in number theory:
If
where A, B, C, x, y, and z are positive integers with x, y, z ≥ 3, then A, B, and C have a common prime factor.
Equivalently,
The equation has no solutions in positive integers and pairwise coprime integers A, B, C if x, y, z ≥ 3.
The conjecture was formulated in 1993 by Andrew Beal, a banker and amateur mathematician, while investigating generalizations of Fermat's Last Theorem. Since 1997, Beal has offered a monetary prize for a peer-reviewed proof of this conjecture or a counterexample. The value of the prize has increased several times and is currently $1 million.
In some publications, this conjecture has occasionally been referred to as a generalized Fermat equation, the Mauldin conjecture, and the Tijdeman-Zagier conjecture.
Related examples
To illustrate, the solution has bases with a common factor of 3, the solution has bases with a common factor of 7, and has bases with a common factor of 2. Indeed the equation has infinitely many solutions where the bases share a common factor, including generalizations of the above three examples, respectively
and
Furthermore, for each solution (with or without coprime bases), there are infinitely many solutions with the same set of exponents and an increasing set of non-coprime bases. That is, for solution
we additionally have
where
Any solutions to the Beal conjecture will necessarily involve three terms all of which are 3-powerful numbers, i.e. numbers where the exponent of every prime factor is at least three. It is known that there are an infinite number of such sums involving coprime 3-powerful numbers; however, such sums are rare. The smallest two examples are:
What distinguishes Beal's conjecture is that it requires each of the three terms to be expressible as a single power.
Relation to other conjectures
Fermat's Last Theorem established that has no solutions for n > 2 for positive integers A, B, and C. If any solutions |
https://en.wikipedia.org/wiki/Sliding%20puzzle | A sliding puzzle, sliding block puzzle, or sliding tile puzzle is a combination puzzle that challenges a player to slide (frequently flat) pieces along certain routes (usually on a board) to establish a certain end-configuration. The pieces to be moved may consist of simple shapes, or they may be imprinted with colours, patterns, sections of a larger picture (like a jigsaw puzzle), numbers, or letters.
Sliding puzzles are essentially two-dimensional in nature, even if the sliding is facilitated by mechanically interlinked pieces (like partially encaged marbles) or three-dimensional tokens. In manufactured wood and plastic products, the linking and encaging is often achieved in combination, through mortise-and-tenon key channels along the edges of the pieces. In at least one vintage case of the popular Chinese cognate game Huarong Road, a wire screen prevents lifting of the pieces, which remain loose. As the illustration shows, some sliding puzzles are mechanical puzzles. However, the mechanical fixtures are usually not essential to these puzzles; the parts could as well be tokens on a flat board that are moved according to certain rules.
Unlike tour puzzles, a sliding block puzzle prohibits lifting any piece off the board. This property separates sliding puzzles from rearrangement puzzles. Hence, finding moves and the paths opened up by each move within the two-dimensional confines of the board are important parts of solving sliding block puzzles.
The oldest type of sliding puzzle is the fifteen puzzle, invented by Noyes Chapman in 1880; Sam Loyd is often wrongly credited with making sliding puzzles popular based on his false claim that he invented the fifteen puzzle. Chapman's invention initiated a puzzle craze in the early 1880s.
From the 1950s through the 1980s sliding puzzles employing letters to form words were very popular. These sorts of puzzles have several possible solutions, as may be seen from examples such as Ro-Let (a letter-based fifteen puzzle), |
https://en.wikipedia.org/wiki/Puzzle%20lock | A puzzle lock or puzzle padlock is a type of mechanical puzzle. It consists of a lock with unusual or hidden mechanics. Puzzle locks are reconfigurable mechanisms where the topological structure changes during the operation. Such locks are sometimes called trick locks, because there is a trick to opening them which needs to be found. Puzzle locks exist both with keys and without keys.
China
Puzzle locks with exposed keyholes were widely used in ancient China and can be very tricky to open.
There are three main types in China:
Locks with extra obstacle
Locks with indirect insertion
Multi-stage locks.
Europe
In Europe, many small puzzle padlocks had front plate with a face or mask. The padlocks were designed to secure small bags or pouches and could be found across Europe with the most around the Danubian provinces and Aquileia. They were often shaped like rings and may have been fitted around the mouth of a bag as a sort of tamper-proof seal. The earliest Roman puzzle locks date back to the 2nd century BCE.
In the 1850s in the UK, "puzzle lock" was synonymous with "letter lock" and used to denote a lettered combination lock.
See also
Puzzle box |
https://en.wikipedia.org/wiki/Digital%20cassettes | Digital audio cassette formats introduced to the professional audio and consumer markets:
Digital Audio Tape (or DAT) is the most well-known, and had some success as an audio storage format among professionals and "prosumers" before the prices of hard drive and solid-state flash memory-based digital recording devices dropped in the late 1990s. Hard-drive recording has mostly made DAT obsolete, as hard disk recorders offer more editing versatility than tape, and easier importation into digital audio workstations (DAWs) and non-linear video editing (NLE) systems.
Digital Compact Cassette was intended as a digital replacement for the mass-market analog cassette tape, but received very little attention or adaptation. Its failure is generally attributed to higher production costs than audio CDs, durability and lukewarm reception by consumers.
Digital videocassettes include:
Betacam IMX (Sony)
D-VHS (JVC)
D1 (Sony)
D2 (Sony)
D3
D5 HD
Digital-S D9 (JVC)
Digital Betacam (Sony)
Digital8 (Sony)
DV
HDV
ProHD (JVC)
MiniDV
MicroMV
Analog cassettes used as digital data storage:
Historically, the compact audio cassette which was originally designed for analog storage of music was used as an alternative to disk drives in the late 1970s and early 1980s to provide data storage for home computers.
The ADAT system uses Super VHS tapes to record 8 synchronized digital audiotracks at once.
There have also been several audio recording systems which used VHS video recorders as storage devices and video tape transports, generally by encoding the digital data to be recorded into an analog composite video signal (which resembles static) and then recording this to magnetic tape. These systems were generally used as "mixdown" recorders, to record the finished mix from a multi-track recorder in preparation for the manufacture of a vinyl record, cassette tape, or CD. An example was the Dbx Model 700.
Several companies sold VHS backup solutions in the 80s and 90s where data was c |
https://en.wikipedia.org/wiki/Quinupristin | Quinupristin is a streptogramin B antibiotic, used in combination with dalfopristin under the trade name Synercid. It has activity against Gram-positive and atypical bacteria but not Gram-negative bacteria. It inhibits bacterial protein synthesis. The combination of quinupristin and dalfopristin is not active against Enterococcus faecalis and needs to be given in combination with other antibacterials for mixed infections that involve Gram-negative organisms.
Antibiotics |
https://en.wikipedia.org/wiki/Univariate | In mathematics, a univariate object is an expression, equation, function or polynomial involving only one variable. Objects involving more than one variable are multivariate. In some cases the distinction between the univariate and multivariate cases is fundamental; for example, the fundamental theorem of algebra and Euclid's algorithm for polynomials are fundamental properties of univariate polynomials that cannot be generalized to multivariate polynomials.
In statistics, a univariate distribution characterizes one variable, although it can be applied in other ways as well. For example, univariate data are composed of a single scalar component. In time series analysis, the whole time series is the "variable": a univariate time series is the series of values over time of a single quantity. Correspondingly, a "multivariate time series" characterizes the changing values over time of several quantities. In some cases, the terminology is ambiguous, since the values within a univariate time series may be treated using certain types of multivariate statistical analyses and may be represented using multivariate distributions.
In addition to the question of scaling, a criterion (variable) in univariate statistics can be described by two important measures (also key figures or parameters): Location & Variation.
Measures of Location Scales (e.g. mode, median, arithmetic mean) describe in which area the data is arranged centrally.
Measures of Variation (e.g. span, interquartile distance, standard deviation) describe how similar or different the data are scattered.
See also
Arity
Bivariate (disambiguation)
Multivariate (disambiguation)
Univariate analysis
Univariate binary model
Univariate distribution |
https://en.wikipedia.org/wiki/Numbering%20%28computability%20theory%29 | In computability theory a numbering is the assignment of natural numbers to a set of objects such as functions, rational numbers, graphs, or words in some formal language. A numbering can be used to transfer the idea of computability and related concepts, which are originally defined on the natural numbers using computable functions, to these different types of objects.
Common examples of numberings include Gödel numberings in first-order logic, the description numbers that arise from universal Turing machines and admissible numberings of the set of partial computable functions.
Definition and examples
A numbering of a set is a surjective partial function from to S (Ershov 1999:477). The value of a numbering ν at a number i (if defined) is often written νi instead of the usual .
Examples of numberings include:
The set of all finite subsets of has a numbering , defined so that and so that, for each finite nonempty set , where (Ershov 1999:477). This numbering is a (partial) bijection.
A fixed Gödel numbering of the computable partial functions can be used to define a numbering W of the recursively enumerable sets, by letting by W(i) be the domain of φi. This numbering will be surjective (like all numberings) but not injective: there will be distinct numbers that map to the same recursively enumerable set under W.
Types of numberings
A numbering is total if it is a total function. If the domain of a partial numbering is recursively enumerable then there always exists an equivalent total numbering (equivalence of numberings is defined below).
A numbering η is decidable if the set is a decidable set.
A numbering η is single-valued if η(x) = η(y) if and only if x=y; in other words if η is an injective function. A single-valued numbering of the set of partial computable functions is called a Friedberg numbering.
Comparison of numberings
There is a preorder on the set of all numberings. Let and be two numberings. Then is reducible to , written |
https://en.wikipedia.org/wiki/Second-order%20cellular%20automaton | A second-order cellular automaton is a type of reversible cellular automaton (CA) invented by Edward Fredkin where the state of a cell at time depends not only on its neighborhood at time , but also on its state at time .
General technique
In general, the evolution rule for a second-order automaton may be described as a function that maps the neighborhood of a cell to a permutation on the states of the automaton. In each time step , for each cell of the automaton, this function is applied to the neighborhood of to give a permutation . Then, this permutation is applied to the state of cell at time , and the result is the state of the cell at time
. In this way, the configuration of the automaton at each time step is computed from two previous time steps: the immediately previous step determines the permutations that are applied to the cells, and the time step before that one gives the states on which these permutations operate.
The reversed time dynamics of a second-order automaton may be described by another second-order automaton with the same neighborhood, in which the function mapping neighborhoods to permutations gives the inverse permutation to . That is, on each possible neighborhood , and should be inverse permutations. With this reverse rule, the automaton described by function correctly computes the configuration at time from the configurations at time and . Because every second-order automaton can be reversed in this way, it follows that they are all reversible cellular automata, regardless of which function is chosen to determine the automaton rule.
For two-state automata
If a cellular automaton has only two states, then there are also only two possible permutations of states: the identity permutation that maps each state to itself, and the permutation that maps each state to the other state. We may identify these two permutations with the two states of the automaton.
In this way, every second-order cellular automaton (defined by a functi |
https://en.wikipedia.org/wiki/Block%20cellular%20automaton | A block cellular automaton or partitioning cellular automaton is a special kind of cellular automaton in which the lattice of cells is divided into non-overlapping blocks (with different partitions at different time steps) and the transition rule is applied to a whole block at a time rather than a single cell. Block cellular automata are useful for simulations of physical quantities, because it is straightforward to choose transition rules that obey physical constraints such as reversibility and conservation laws.
Definition
A block cellular automaton consists of the following components:
A regular lattice of cells
A finite set of the states that each cell may be in
A partition of the cells into a uniform tessellation in which each tile of the partition has the same size and shape
A rule for shifting the partition after each time step
A transition rule, a function that takes as input an assignment of states for the cells in a single tile and produces as output another assignment of states for the same cells.
In each time step, the transition rule is applied simultaneously and synchronously to all of the tiles in the partition. Then, the partition is shifted and the same operation is repeated in the next time step, and so forth. In this way, as with any cellular automaton, the pattern of cell states changes over time to perform some nontrivial computation or simulation.
Neighborhoods
The simplest partitioning scheme is probably the Margolus neighborhood, named after Norman Margolus, who first studied block cellular automata using this neighborhood structure. In the Margolus neighborhood, the lattice is divided into -cell blocks (or squares in two dimensions, or cubes in three dimensions, etc.) which are shifted by one cell (along each dimension) on alternate timesteps.
A closely related technique due to K. Morita and M. Harao consists in partitioning each cell into a finite number of parts, each part being devoted to some neighbor. The evolution proceeds by exch |
https://en.wikipedia.org/wiki/Comparison%20of%20time-tracking%20software | This is a comparison of notable time-tracking software packages and web hosted services.
See also
Deployment management
Flextime plan
Project management software
Timesheet
Working time |
https://en.wikipedia.org/wiki/Lonicera%20fly | The Lonicera fly, a hybrid in the genus Rhagoletis, is a North American fruit fly of the family Tephritidae. Its larvae feed on the berries of species of introduced honeysuckle (Lonicera) that were brought to America within the last 250 years as ornamental plants. A research team led by Dietmar Schwarz has argued that it most likely developed within that time by hybridization of two other species: R. mendax, the blueberry maggot, and R. zephyria, the snowberry maggot. Few cases of animal species arising from hybridization are known, although with DNA analysis more are being found. |
https://en.wikipedia.org/wiki/Gunfright | Gunfright is an action-adventure game developed by Ultimate Play the Game and published by U.S. Gold. It was first released for the ZX Spectrum in December 1985, then released for Amstrad CPC and the MSX the following year. The player takes the role of a sheriff in the town of Black Rock and is tasked with eliminating outlaws who are scattered throughout the settlement.
The game was developed directly after Nightshade, and re-uses the latter game's Filmation II game engine that allows images to be rendered without overlapping each other. The game received mostly positive reviews upon release; praise was directed at the graphics and presentation, but criticism was directed at the game's similarity to Nightshade. It was later included in Rare Replay, Rare's 2015 Xbox One retrospective compilation.
Gameplay
The game is presented in an isometric format and set in the fictional town of Black Rock. The player takes on the role of Sheriff Quickdraw, whose main objective is to track down and kill a gang of outlaws who are hiding in the town. The game begins with a first-person perspective targeting minigame in which vertically scrolling bags of money can be shot at using crosshairs. Shooting the bags give the player initial sums of money which can be used to purchase ammunition.
Sheriff Quickdraw must locate the wanted outlaws one by one. Once an outlaw has been found and shot to initiate a duel, the game shifts to the first-person targeting minigame. This time, the player must shoot the rapidly moving outlaw as quickly as possible. The player can either wait for the outlaw to draw, or take the initiative and shoot first, which will make the bandit draw his weapon as well. If the player successfully shoots an outlaw, a bounty is paid (increasing with every round), and a new outlaw enters the town.
Players encounter helpful residents who will point the way to outlaws. The residents need to be protected during gameplay, as the player has to pay a fine if any are shot by |
https://en.wikipedia.org/wiki/Core%20Data | Core Data is an object graph and persistence framework provided by Apple in the macOS and iOS operating systems. It was introduced in Mac OS X 10.4 Tiger and iOS with iPhone SDK 3.0. It allows data organized by the relational entity–attribute model to be serialized into XML, binary, or SQLite stores. The data can be manipulated using higher level objects representing entities and their relationships. Core Data manages the serialized version, providing object lifecycle and object graph management, including persistence. Core Data interfaces directly with SQLite, insulating the developer from the underlying SQL.
Just as Cocoa Bindings handle many of the duties of the controller in a model–view–controller design, Core Data handles many of the duties of the data model. Among other tasks, it handles change management, serializing to disk, memory footprint minimization and queries against the data.
Usage
Core Data describes data with a high level data model expressed in terms of entities and their relationships plus fetch requests that retrieve entities meeting specific criteria. Code can retrieve and manipulate this data on a purely object level without having to worry about the details of storage and retrieval. The controller objects available in Interface Builder can retrieve and manipulate these entities directly. When combined with Cocoa bindings the UI can display many components of the data model without needing background code.
For example: a developer might be writing a program to handle vCards. In order to manage these, the author intends to read the vCards into objects, and then store them in a single larger XML file. Using Core Data the developer would drag their schema from the data designer in Xcode into an interface builder window to create a GUI for their schema. They could then write standard Objective-C or Swift code to read vCard files and put the data into Core Data managed entities. From that point on the author's code manipulates these Core Data o |
https://en.wikipedia.org/wiki/Minibar | A minibar is a small refrigerator, typically an absorption refrigerator, in a hotel room or cruise ship stateroom. The hotel staff fill it with drinks and snacks for the guest to purchase during their stay. It is stocked with a precise inventory of goods, with a price list. The guest is charged for goods consumed when checking out of the hotel. Some newer minibars use infrared or other automated methods of recording purchases. These detect the removal of an item, and charge the guest's credit card right away, even if the item is not consumed. This is done to prevent loss of product, theft and lost revenue.
The minibar is commonly stocked with small bottles of alcoholic beverages, juice, bottled water, and soft drinks. There may also be candy, cookies, crackers, and other small snacks. Prices are generally very high compared to similar items purchased from a store, because the guest is paying for the convenience of immediate access and also the upkeep of the bar. Prices vary, but it is common for one can of non-alcoholic beverage to cost $6–10 USD. Due to the convenience of room service and the minibar, prices charged to the patron are much higher than the hotel's restaurant or tuck shop. As premium bottled water has become popular with guests since the 2000s, there is "ambient placement" of such chargeable products outside the minibar and in the guests' line of vision; for example "by placing [bottled] water on bedside tables, during the night, people are more likely to grab it than get up to get a glass of water".
The world's first minibar was introduced at the Hong Kong Hilton Hotel by manager Robert Arnold in 1974. In the months following its introduction in-room drink sales increased 500%, and the Hong Kong Hilton's overall annual revenue was boosted by 5%. The following year the Hilton group rolled out the minibar concept across all its hotels.
In recent years, as minibars become less and less popular with guests, hotels have been eliminating this feature f |
https://en.wikipedia.org/wiki/Artificial%20kidney | Artificial kidney is often a synonym for hemodialysis, but may also refer to the other renal replacement therapies (with exclusion of kidney transplantation) that are in use and/or in development. This article deals mainly with bioengineered kidneys/bioartificial kidneys that are grown from renal cell lines/renal tissue.
The first successful artificial kidney was developed by Willem Kolff in the Netherlands during the early 1940s: Kolff was the first to construct a working dialyzer in 1943.
Medical uses
Kidney failure
Kidneys are paired vital organs located behind the abdominal cavity at the bottom of the ribcage corresponding to the levels T12-L3 of the spine vertebrae. They perform about a dozen physiologic functions and are fairly easily damaged. Some of these functions include filtration and excretion of metabolic waste products, regulation of necessary electrolytes and fluids and stimulation of red blood cell-production. These organs routinely filter about 100 to 140 liters of blood a day to produce 1 to 2 liters of urine, composed of wastes and excess fluid.
Kidney failure results in the slow accumulation of nitrogenous wastes, salts, water, and disruption of the body's normal pH balance. This failure typically occurs over a long period of time, and when the patient's renal function declines enough over the course of the disease, is commonly known as end stage renal disease (ESRD; which is also known as Level 5 or 6 kidney disease, depending on whether dialysis or renal replacement therapy is used). Detecting kidney disease before the kidneys start to shut down is uncommon, with high blood pressure and decreased appetite being symptoms that indicate a problem. Diabetes and high blood pressure are seen as the 2 most common causes of kidney failure. Experts predict that the demand for dialysis will increase as the prevalence of diabetes increases. Until the Second World War, kidney failure generally meant death for the patient. Several insights into kidney f |
https://en.wikipedia.org/wiki/Cassini%27s%20laws | Cassini's laws provide a compact description of the motion of the Moon. They were established in 1693 by Giovanni Domenico Cassini, a prominent scientist of his time.
Refinements of these laws to include physical librations have been made, and they have been generalized to treat other satellites and planets.
Cassini's laws
The Moon has a 1:1 spin–orbit resonance. This means that the rotation–orbit ratio of the Moon is such that the same side of it always faces the Earth.
The Moon's rotational axis maintains a constant angle of inclination from the ecliptic plane. The Moon's rotational axis precesses so as to trace out a cone that intersects the ecliptic plane as a circle.
A plane formed from a normal to the ecliptic plane and a normal to the Moon's orbital plane will contain the Moon's rotational axis.
In the case of the Moon, its rotational axis always points some 1.5 degrees away from the North ecliptic pole. The normal to the Moon's orbital plane and its rotational axis are always on opposite sides of the normal to the ecliptic.
Therefore, both the normal to the orbital plane and the Moon's rotational axis precess around the ecliptic pole with the same period. The period is about 18.6 years and the motion is retrograde.
Cassini state
A system obeying these laws is said to be in a Cassini state, that is: an evolved rotational state where the spin axis, orbit normal, and normal to the Laplace plane are coplanar while the obliquity remains constant. The Laplace plane is defined as the plane about which a planet or satellite orbit precesses with constant inclination. The normal to the Laplace plane for a moon is between the planet's spin axis and the planet's orbit normal, being closer to the latter if the moon is distant from the planet. If a planet itself is in a Cassini state, the Laplace plane is the invariable plane of the stellar system.
Cassini state 1 is defined as the situation in which both the spin axis and the orbit normal axis are on the same |
https://en.wikipedia.org/wiki/Food%20and%20drink%20prohibitions | Some people do not eat various specific foods and beverages in conformity with various religious, cultural, legal or other societal prohibitions. Many of these prohibitions constitute taboos. Many food taboos and other prohibitions forbid the meat of a particular animal, including mammals, rodents, reptiles, amphibians, fish, molluscs, crustaceans and insects, which may relate to a disgust response being more often associated with meats than plant-based foods. Some prohibitions are specific to a particular part or excretion of an animal, while others forgo the consumption of plants or fungi.
Some food prohibitions can be defined as rules, codified by religion or otherwise, about which foods, or combinations of foods, may not be eaten and how animals are to be slaughtered or prepared. The origins of these prohibitions are varied. In some cases, they are thought to be a result of health considerations or other practical reasons; in others, they relate to human symbolic systems.
Some foods may be prohibited during certain religious periods (e.g., Lent), at certain stages of life (e.g., pregnancy), or to certain classes of people (e.g., priests), even if the food is otherwise permitted. On a comparative basis, what may be declared unfit for one group may be perfectly acceptable to another within the same culture or across different cultures. Food taboos usually seem to be intended to protect the human individual from harm, spiritually or physically, but there are numerous other reasons given within cultures for their existence. An ecological or medical background is apparent in many, including some that are seen as religious or spiritual in origin. Food taboos can help utilizing a resource more efficiently, but when applied to only a subsection of the community, a food taboo can also lead to the monopolization of a food item by those exempted. A food taboo acknowledged by a particular group or tribe as part of their ways, aids in the cohesion of the group, helps that |
https://en.wikipedia.org/wiki/Kibu.com | Kibu.com was an American website for teenage girls that was created in 1999 and launched in 2000. The website was founded as an online community for girls to discuss and exchange advice.
Kibu.com secured a US$22 million investment from high-profile figures in the tech industry, including Jim Clark. However, following the dot-com bubble burst, Kibu.com shut down on October 2, 2000, in only 46 days after launch. The company's leaders disclosed that the decision to shut down Kibu.com was made because of concerns in securing revenue in the future.
History
Kibu.com was created in April 1999 as an online community for teenage girls. The name "Kibu" was derived from the Japanese word for "foundation" (). Judy Macdonald, the founder of the art CD-ROM PrintPak, was brought into staff as its CEO in September 1999. Molly Lynch, a former employee of @Home Network was also added as a staff member. In February 2000, Kibu.com received an investment of US$22 million from high-profile figures in Silicon Valley, such as Netscape co-founder Jim Clark, former @Home Network chairman Tom Jermoluk, the venture capital firm Kleiner Perkins Caufield & Byers, and CNET chairman Shelby Bonnie. Unlike other websites struggling from the dot-com bubble burst, the investors believed Kibu.com had the advantage in its demographic, as there had been a growth in teenage users online. Kibu.com predicted the investment would sustain the website up to Q2 2001 and hoped to make a profit by late 2001, with plans to have their own branded retail products and its own center in Ghirardelli Square located in San Francisco, California. In addition, ChickClick founder Heidi Swanson and her sister, Heather, were hired to work on the website.
Kibu.com went online on May 1, 2000. The website ran on revenue from sponsorship deals with Skechers, Barnes & Noble, and The Princeton Review, as well as attracting advertisements from Kmart. Unlike other websites, which used banner ads, Kibu.com offered product samples |
https://en.wikipedia.org/wiki/Angle%20bisector%20theorem | In geometry, the angle bisector theorem is concerned with the relative lengths of the two segments that a triangle's side is divided into by a line that bisects the opposite angle. It equates their relative lengths to the relative lengths of the other two sides of the triangle.
Theorem
Consider a triangle . Let the angle bisector of angle intersect side at a point between and . The angle bisector theorem states that the ratio of the length of the line segment to the length of segment is equal to the ratio of the length of side to the length of side :
and conversely, if a point on the side of divides in the same ratio as the sides and , then is the angle bisector of angle .
The generalized angle bisector theorem states that if lies on the line , then
This reduces to the previous version if is the bisector of . When is external to the segment , directed line segments and directed angles must be used in the calculation.
The angle bisector theorem is commonly used when the angle bisectors and side lengths are known. It can be used in a calculation or in a proof.
An immediate consequence of the theorem is that the angle bisector of the vertex angle of an isosceles triangle will also bisect the opposite side.
Proofs
There exist many different ways of proving the angle bisector theorem. A few of them are shown below.
Proof using similar triangles
As shown in the accompanying animation, the theorem can be proved using similar triangles. In the version illustrated here, the triangle gets reflected across a line that is perpendicular to the angle bisector , resulting in the triangle with bisector . The fact that the bisection-produced angles and are equal means that and are straight lines. This allows the construction of triangle that is similar to . Because the ratios between corresponding sides of similar triangles are all equal, it follows that . However, was constructed as a reflection of the line , and so those two lines are of equal le |
https://en.wikipedia.org/wiki/Static%20build | A static build is a compiled version of a program which has been statically linked against libraries.
Linking
In computer science, linking means taking one or more objects generated by compilers and assembling them into a single executable program. The objects are program modules containing machine code and symbol definitions, which come in two varieties:
Defined or exported symbols are functions or variables that are present in the module represented by the object, and which should be available for use by other modules.
Undefined or imported symbols are functions or variables that are called or referenced by this object, but not internally defined.
A linker program then resolves references to undefined symbols by finding out which other object defines a symbol in question, and replacing placeholders with the symbol's address. Linkers can take objects from a collection called a library. The final program does not include the whole library, only those objects from it that are needed. Libraries for diverse purposes exist, and one or more system libraries are usually linked in by default.
Dynamic linking
Modern operating system environments allow dynamic linking, or the postponing of the resolving of some undefined symbols until a program is run. That means that the executable still contains undefined symbols, plus a list of objects or libraries that will provide definitions for these. Loading the program will load these objects/libraries as well, and perform a final linking.
Dynamic linking offers three advantages:
Often-used libraries (for example the standard system libraries) need to be stored in only one location, not duplicated in every single binary.
If a library is upgraded or replaced, all programs using it dynamically will immediately benefit from the corrections. Static builds would have to be re-linked first.
The binary executable file size is smaller than its statically linked counterpart.
Static building
In a statically built program, no dynamic link |
https://en.wikipedia.org/wiki/Danda | In Indic scripts, the daṇḍa (Sanskrit: दण्ड "stick") is a punctuation mark. The glyph consists of a single vertical stroke.
Use
The daṇḍa marks the end of a sentence or line, comparable to a full stop (period) as commonly used in the Latin alphabet, and is used together with Western punctuation in Hindi and Nepali.
The daṇḍa and double daṇḍa are the only punctuation used in Sanskrit texts. No distinct punctuation is used to mark questions or exclamations, which must be inferred from other aspects of the sentence.
In metrical texts, a double daṇḍa is used to delimit verses, and a single daṇḍa to delimit a pada, line, or semi-verse. In prose, the double daṇḍa is used to mark the end of a paragraph, a story, or section.
Computer encoding
The Devanagari character can be found at code point U+0964 () in Unicode. The "double daṇḍa" is at U+0965 (). The Unicode standard recommends using this character also in other Indic scripts, like Bengali, Telugu, Oriya, and others. Encoding it separately for every Indic script was proposed, but as of 2020, this proposal has not been implemented.
Danda and similar characters are encoded separately for some scripts in which its appearance or use is significantly different from the Devanagari one. These include forms with adornments, such as the Rgya Gram Shad.
ISCII encodes daṇḍa at 0xEA.
See also
Vertical bar
Footnotes |
https://en.wikipedia.org/wiki/Richard%20Schoen | Richard Melvin Schoen (born October 23, 1950) is an American mathematician known for his work in differential geometry and geometric analysis. He is best known for the resolution of the Yamabe problem in 1984.
Career
Born in Celina, Ohio, and a 1968 graduate of Fort Recovery High School, he received his B.S. from the University of Dayton in mathematics. He then received his PhD in 1977 from Stanford University. After faculty positions at the Courant Institute, NYU, University of California, Berkeley, and University of California, San Diego, he was Professor at Stanford University from 1987–2014, as Bass Professor of Humanities and Sciences since 1992. He is currently Distinguished Professor and Excellence in Teaching Chair at the University of California, Irvine. His surname is pronounced "Shane."
Schoen received an NSF Graduate Research Fellowship in 1972 and a Sloan Research Fellowship in 1979. Schoen is a 1983 MacArthur Fellow. He has been invited to speak at the International Congress of Mathematicians (ICM) three times, including twice as a Plenary Speaker. In 1983 he was an Invited Speaker at the ICM in Warsaw, in 1986 he was a Plenary Speaker at the ICM in Berkeley, and in 2010 he was a Plenary Speaker at the ICM in Hyderabad. For his work on the Yamabe problem, Schoen was awarded the Bôcher Memorial Prize in 1989. He was elected to the American Academy of Arts and Sciences in 1988 and to the National Academy of Sciences in 1991, became Fellow of the American Association for the Advancement of Science in 1995, and won a Guggenheim Fellowship in 1996. In 2012 he became a Fellow of the American Mathematical Society. He received the 2014–15 Dean’s Award for Lifetime Achievements in Teaching from Stanford University. In 2015, he was elected Vice President of the American Mathematical Society. He was awarded an Honorary Doctor of Science from the University of Warwick in 2015. He received the Wolf Prize in Mathematics for 2017, shared with Charles Fefferman. I |
https://en.wikipedia.org/wiki/Algal%20mat | Algal mats are one of many types of microbial mat that forms on the surface of water or rocks. They are typically composed of blue-green cyanobacteria and sediments. Formation occurs when alternating layers of blue-green bacteria and sediments are deposited or grow in place, creating dark-laminated layers. Stromatolites are prime examples of algal mats. Algal mats played an important role in the Great Oxidation Event on Earth some 2.3 billion years ago. Algal mats can become a significant ecological problem, if the mats grow so expansive or thick as to disrupt the other underwater marine life by blocking the sunlight or producing toxic chemicals.
Cyanobacteria forming algal mats
Cyanobacteria found in sedimentary rocks indicate that bacterial life began on Earth during the Precambrian age. Fossilized cyanobacteria are commonly found in rocks that date back to Mesoproterozoic. Cyanobacteria are photoautotrophs in nature; they convert carbon dioxide and sunlight into food and energy via photosynthesis. Some species are also able to fix atmospheric nitrogen and convert it into the biologically-usable form of nitrate or nitrite. This gives them competitive advantage over other organisms that may be limited by the shortage of biologically available nitrogen. The cyanobacteria colonies contain two types of cells, the regular cells with chlorophyll carrying out the photosynthesis, and heterocysts which fix the nitrogen. These heterocysts have thick walls and lack chlorophyll, both of which limits their exposure to oxygen, the presence of which inhibits nitrogen fixation. For the same reason, fixation may also be limited to nighttime when the light-dependent reactions of photosynthesis are shut down, minimizing oxygen production.
Stromatolites
Stromatolites are alternating layers of cyanobacteria and sediments. The grain size of sediment portion of stromatolites is affected by the depositional environment. During the Proterozoic, stromatolites' compositions were dominated |
https://en.wikipedia.org/wiki/Abraham%20H.%20Taub | Abraham Haskel Taub (; February 1, 1911 – August 9, 1999) was a distinguished American mathematician and physicist who made important contributions to the early development of general relativity, as well as differential geometry and differential equations.
Work
In a 1948 paper dealing with relativistic shock waves, Taub introduced a relativistic generalization of the Rankine-Hugoniot jump conditions across a shock, which is now known as the Taub Adiabat. He also introduced the Taub–NUT space in general relativity.
Taub graduated in 1931 with a bachelor's degree in mathematics and physics from the University of Chicago. He earned his doctorate at Princeton University in 1935, under the direction of the prominent relativist Howard P. Robertson. At Princeton, Taub was also influenced by Oswald Veblen. After a postdoctoral year at the Institute for Advanced Study, Taub became an assistant professor at the University of Washington in Seattle.
In 1948, Abe Taub went to the University of Illinois as the chief mathematician associated with a project to build a computer based on von Neumann's plans. The computer, called ORDVAC, was completed in 1952 and delivered to the Aberdeen Proving Ground. A second copy of the computer, ILLIAC I, remained at Illinois and was the prototype for several other computers. Taub was head of the Digital Computer Laboratory at Illinois from 1961 until 1964, when he moved to the University of California, Berkeley, as director of the Computer Center (1964–68) with a joint appointment in the department of mathematics. He was a full time professor of mathematics from 1967 to 1978, when he retired as professor emeritus.
Upon his death he was survived by his widow, three children, and a grandchild. |
https://en.wikipedia.org/wiki/Lanczos%20tensor | The Lanczos tensor or Lanczos potential is a rank 3 tensor in general relativity that generates the Weyl tensor. It was first introduced by Cornelius Lanczos in 1949. The theoretical importance of the Lanczos tensor is that it serves as the gauge field for the gravitational field in the same way that, by analogy, the electromagnetic four-potential generates the electromagnetic field.
Definition
The Lanczos tensor can be defined in a few different ways. The most common modern definition is through the Weyl–Lanczos equations, which demonstrate the generation of the Weyl tensor from the Lanczos tensor. These equations, presented below, were given by Takeno in 1964. The way that Lanczos introduced the tensor originally was as a Lagrange multiplier on constraint terms studied in the variational approach to general relativity. Under any definition, the Lanczos tensor H exhibits the following symmetries:
The Lanczos tensor always exists in four dimensions but does not generalize to higher dimensions. This highlights the specialness of four dimensions. Note further that the full Riemann tensor cannot in general be derived from derivatives of the Lanczos potential alone. The Einstein field equations must provide the Ricci tensor to complete the components of the Ricci decomposition.
The Curtright field has a gauge-transformation dynamics similar to that of Lanczos tensor. But Curtright field exists in arbitrary dimensions > 4D.
Weyl–Lanczos equations
The Weyl–Lanczos equations express the Weyl tensor entirely as derivatives of the Lanczos tensor:
where is the Weyl tensor, the semicolon denotes the covariant derivative, and the subscripted parentheses indicate symmetrization. Although the above equations can be used to define the Lanczos tensor, they also show that it is not unique but rather has gauge freedom under an affine group. If is an arbitrary vector field, then the Weyl–Lanczos equations are invariant under the gauge transformation
where the subsc |
https://en.wikipedia.org/wiki/Rainbow%20table | A rainbow table is a precomputed table for caching the outputs of a cryptographic hash function, usually for cracking password hashes. Passwords are typically stored not in plain text form, but as hash values. If such a database of hashed passwords falls into the hands of an attacker, they can use a precomputed rainbow table to recover the plaintext passwords. A common defense against this attack is to compute the hashes using a key derivation function that adds a "salt" to each password before hashing it, with different passwords receiving different salts, which are stored in plain text along with the hash.
Rainbow tables are a practical example of a space–time tradeoff: they use less computer processing time and more storage than a brute-force attack which calculates a hash on every attempt, but more processing time and less storage than a simple table that stores the hash of every possible password.
Rainbow tables were invented by Philippe Oechslin as an application of an earlier, simpler algorithm by Martin Hellman.
Background
For user authentication, passwords are stored either as plaintext or hashes. Since passwords stored as plaintext are easily stolen if database access is compromised, databases typically store hashes instead. Thus, no one – including the authentication system – can learn a password merely by looking at the value stored in the database.
When a user enters a password for authentication, a hash is computed for it and then compared to the stored hash for that user. Authentication fails if the two hashes do not match; moreover, authentication would equally fail if a hashed value were entered as a password, since the authentication system would hash it a second time.
To learn a password from a hash is to find a string which, when input into the hash function, creates that same hash. This is the same as inverting the hash function.
Though brute-force attacks (e.g. dictionary attacks) may be used to try to invert a hash function, they can bec |
https://en.wikipedia.org/wiki/Strained%20silicon%20directly%20on%20insulator | Strained silicon directly on insulator (SSDOI) is a procedure developed by IBM which removes the silicon germanium layer in the strained silicon process leaving the strained silicon directly on the insulator. In contrast, strained silicon on SGOI provides a strained silicon layer on a relaxed silicon germanium layer on an insulator, as developed by MIT. |
https://en.wikipedia.org/wiki/Intense%20Pulsed%20Neutron%20Source | Intense Pulsed Neutron Source (IPNS) was a scientific user facility at Argonne National Laboratory for neutron scattering research. The IPNS was the world's first pulsed neutron source open to external users and started operations in 1981. The facility ceased operation in January, 2008 after the omnibus spending bill forced Basic Energy Sciences (BES) to cease IPNS operations. |
https://en.wikipedia.org/wiki/Virtual%20assistant%20%28occupation%29 | A virtual assistant (typically abbreviated to VA, also called a virtual office assistant) is generally self-employed and provides professional administrative, technical, or creative (social) assistance to clients remotely from a home office. Because virtual assistants are independent contractors rather than employees, clients are not responsible for any employee-related taxes, insurance, or benefits, except in the context that those indirect expenses are included in the VA's fees. Clients also avoid the logistical problem of providing extra office space, equipment, or supplies. Clients pay for 100% productive work and can work with virtual assistants, individually, or in multi-VA firms to meet their exact needs. Virtual assistants usually work for other small businesses but can also support busy executives. It is estimated that there are as few as 5,000 to 10,000 or as many as 25,000 virtual assistants worldwide. The profession is growing in centralized economies with "fly-in fly-out" staffing practices.
Pay and salary
In terms of pay, according to Glassdoor, the annual salary for virtual assistants in the US is $35,922. However, worldwide, many virtual assistants work as freelancers on an hourly wage. One recent survey involving 400 virtual assistants on the popular freelancer site Upwork shows a huge discrepancy in hourly pay commanded by virtual assistants in different countries.
Modes of communication
Common modes of communication and data delivery include the internet, e-mail and phone-call conferences, online work spaces, and fax machine. Increasingly, virtual assistants are utilizing technology such as Skype and Zoom, Slack, as well as Google Voice. Professionals in this business work on a contractual basis, and a long-lasting cooperation is standard. Typically, administrative experience in an office is expected at such positions as executive assistant, office manager/supervisor, secretary, legal assistant, paralegal, legal secretary, real estate assistant, |
https://en.wikipedia.org/wiki/Dropped%20ceiling | A dropped ceiling is a secondary ceiling, hung below the main (structural) ceiling. It may also be referred to as a drop ceiling, T-bar ceiling, false ceiling, suspended ceiling, grid ceiling, drop in ceiling, drop out ceiling, or ceiling tiles and is a staple of modern construction and architecture in both residential and commercial applications.
History
Dropped ceilings and ceiling tiles were used in Japan for aesthetic reasons as early as the Muromachi Period (1337 to 1573). These could be made with simple planks, or coffered. Blackfriars Theatre in London, England, built in 1596, had dropped ceilings to aid acoustics.
U. S. Patent No. 1,470,728 for modern dropped ceilings was applied for by E. E. Hall on May 28, 1919, and granted on October 16, 1923. Initially modern dropped ceilings were built using interlocking tiles and the only way to provide access for repair or inspection of the area above the tiles was by starting at the edge of the ceiling, or at a designated "key tile", and then removing contiguous tiles one at a time until the desired place of access was reached. Once the repair or inspection was completed, the tiles had to be reinstalled. This process could be time-consuming and expensive. On September 8, 1958, Donald A. Brown of Westlake, Ohio, filed for a patent for Accessible Suspended Ceiling Construction. This invention provided suspended ceiling construction in which access may readily be obtained at any desired location. Patent Number US 2,984,946 A was granted on May 23, 1961. Brown has sometimes been credited as being the inventor of the dropped ceiling even though other patents preceded his as shown in the table below.
Design objectives
Effective building design requires balancing multiple objectives: aesthetics, acoustics, environmental factors, and integration with the building's infrastructure—not to mention cost of construction as well as long-term operation costs.
Aesthetics
Modern dropped ceilings were initially created to hide |
https://en.wikipedia.org/wiki/Neurosteroid | Neurosteroids, also known as neuroactive steroids, are endogenous or exogenous steroids that rapidly alter neuronal excitability through interaction with ligand-gated ion channels and other cell surface receptors. The term neurosteroid was coined by the French physiologist Étienne-Émile Baulieu and refers to steroids synthesized in the brain. The term, neuroactive steroid refers to steroids that can be synthesized in the brain, or are synthesized by an endocrine gland, that then reach the brain through the bloodstream and have effects on brain function. The term neuroactive steroids was first coined in 1992 by Steven Paul and Robert Purdy. In addition to their actions on neuronal membrane receptors, some of these steroids may also exert effects on gene expression via nuclear steroid hormone receptors. Neurosteroids have a wide range of potential clinical applications from sedation to treatment of epilepsy and traumatic brain injury. Ganaxolone, a synthetic analog of the endogenous neurosteroid allopregnanolone, is under investigation for the treatment of epilepsy.
Classification
Based on differences in activity and structure, neurosteroids can be broadly categorized into several different major groupings.
Inhibitory neurosteroids
These neurosteroids exert inhibitory actions on neurotransmission. They act as positive allosteric modulators of the GABAA receptor (especially δ subunit-containing isoforms), and possess, in no particular order, antidepressant, anxiolytic, stress-reducing, rewarding, prosocial, antiaggressive, prosexual, sedative, pro-sleep, cognitive and memory-impairing, analgesic, anesthetic, anticonvulsant, neuroprotective, and neurogenic effects.
Major examples include tetrahydrodeoxycorticosterone (THDOC), the androstane 3α-androstanediol, the cholestane cholesterol and the pregnanes pregnanolone (eltanolone), allopregnanolone (3α,5α-THP).
Excitatory neurosteroids
These neurosteroids have excitatory effects on neurotransmission. They act as pote |
https://en.wikipedia.org/wiki/Magnetization | In classical electromagnetism, magnetization is the vector field that expresses the density of permanent or induced magnetic dipole moments in a magnetic material. Accordingly, physicists and engineers usually define magnetization as the quantity of magnetic moment per unit volume.
It is represented by a pseudovector M. Magnetization can be compared to electric polarization, which is the measure of the corresponding response of a material to an electric field in electrostatics.
Magnetization also describes how a material responds to an applied magnetic field as well as the way the material changes the magnetic field, and can be used to calculate the forces that result from those interactions.
The origin of the magnetic moments responsible for magnetization can be either microscopic electric currents resulting from the motion of electrons in atoms, or the spin of the electrons or the nuclei. Net magnetization results from the response of a material to an external magnetic field.
Paramagnetic materials have a weak induced magnetization in a magnetic field, which disappears when the magnetic field is removed. Ferromagnetic and ferrimagnetic materials have strong magnetization in a magnetic field, and can be magnetized to have magnetization in the absence of an external field, becoming a permanent magnet. Magnetization is not necessarily uniform within a material, but may vary between different points.
Definition
The magnetization field or M-field can be defined according to the following equation:
Where is the elementary magnetic moment and is the volume element; in other words, the M-field is the distribution of magnetic moments in the region or manifold concerned. This is better illustrated through the following relation:
where m is an ordinary magnetic moment and the triple integral denotes integration over a volume. This makes the M-field completely analogous to the electric polarisation field, or P-field, used to determine the electric dipole moment |
https://en.wikipedia.org/wiki/Friis%20transmission%20equation | The Friis transmission formula is used in telecommunications engineering, equating the power at the terminals of a receive antenna as the product of power density of the incident wave and the effective aperture of the receiving antenna under idealized conditions given another antenna some distance away transmitting a known amount of power. The formula was presented first by Danish-American radio engineer Harald T. Friis in 1946. The formula is sometimes referenced as the Friis transmission equation.
Friis' original formula
Friis' original idea behind his transmission formula was to dispense with the usage of directivity or gain when describing antenna performance. In their place is the descriptor of antenna capture area as one of two important parts of the transmission formula that characterizes the behavior of a free-space radio circuit.
This leads to his published form of his transmission formula:
where:
is the power fed into the transmitting antenna input terminals;
is the power available at receiving antenna output terminals;
is the effective aperture area of the receiving antenna;
is the effective aperture area of the transmitting antenna;
is the distance between antennas;
is the wavelength of the radio frequency;
and are in the same units of power;
, , , and are in the same units.
Distance large enough to ensure a plane wave front at the receive antenna sufficiently approximated by where is the largest linear dimension of either of the antennas.
Friis stated the advantage of this formula over other formulations is the lack of numerical coefficients to remember, but does require the expression of transmitting antenna performance in terms of power flow per unit area instead of field strength and the expression of receiving antenna performance by its effective area rather than by its power gain or radiation resistance.
Contemporary formula
Few follow Friis' advice on using antenna effective area to characterize antenna performance over the contem |
https://en.wikipedia.org/wiki/Poincar%C3%A9%20recurrence%20theorem | In mathematics and physics, the Poincaré recurrence theorem states that certain dynamical systems will, after a sufficiently long but finite time, return to a state arbitrarily close to (for continuous state systems), or exactly the same as (for discrete state systems), their initial state.
The Poincaré recurrence time is the length of time elapsed until the recurrence. This time may vary greatly depending on the exact initial state and required degree of closeness. The result applies to isolated mechanical systems subject to some constraints, e.g., all particles must be bound to a finite volume. The theorem is commonly discussed in the context of ergodic theory, dynamical systems and statistical mechanics. Systems to which the Poincaré recurrence theorem applies are called conservative systems.
The theorem is named after Henri Poincaré, who discussed it in 1890 and proved by Constantin Carathéodory using measure theory in 1919.
Precise formulation
Any dynamical system defined by an ordinary differential equation determines a flow map f t mapping phase space on itself. The system is said to be volume-preserving if the volume of a set in phase space is invariant under the flow. For instance, all Hamiltonian systems are volume-preserving because of Liouville's theorem. The theorem is then: If a flow preserves volume and has only bounded orbits, then, for each open set, any orbit that intersects this open set intersects it infinitely often.
Discussion of proof
The proof, speaking qualitatively, hinges on two premises:
A finite upper bound can be set on the total potentially accessible phase space volume. For a mechanical system, this bound can be provided by requiring that the system is contained in a bounded physical region of space (so that it cannot, for example, eject particles that never return) – combined with the conservation of energy, this locks the system into a finite region in phase space.
The phase volume of a finite element under dynamics is conse |
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