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🔗 Russia 🔗 Mathematics 🔗 Statistics 🔗 Russia/science and education in Russia

In statistics, the Gauss–Markov theorem states that the ordinary least squares (OLS) estimator has the lowest sampling variance within the class of linear unbiased estimators, if the errors in the linear regression model are uncorrelated, have equal variances and expectation value of zero. The errors do not need to be normal, nor do they need to be independent and identically distributed (only uncorrelated with mean zero and homoscedastic with finite variance). The requirement that the estimator be unbiased cannot be dropped, since biased estimators exist with lower variance. See, for example, the James–Stein estimator (which also drops linearity) or ridge regression.

The theorem was named after Carl Friedrich Gauss and Andrey Markov, although Gauss' work significantly predates Markov's. But while Gauss derived the result under the assumption of independence and normality, Markov reduced the assumptions to the form stated above. A further generalization to non-spherical errors was given by Alexander Aitken.

🔗 Russia 🔗 Russia/technology and engineering in Russia 🔗 Physics 🔗 Physics/relativity 🔗 Russia/science and education in Russia

Cherenkov radiation (; Russian: Эффект Вавилова — Черенкова, Vavilov-Cherenkov effect) is electromagnetic radiation emitted when a charged particle (such as an electron) passes through a dielectric medium at a speed greater than the phase velocity (speed of propagation of a wavefront in a medium) of light in that medium. A classic example of Cherenkov radiation is the characteristic blue glow of an underwater nuclear reactor. Its cause is similar to the cause of a sonic boom, the sharp sound heard when faster-than-sound movement occurs. The phenomenon is named after Soviet physicist Pavel Cherenkov.

🔗 Meteorology 🔗 Tropical cyclones

A hypercane is a hypothetical class of extreme tropical cyclone that could form if ocean temperatures reached approximately 50 °C (122 °F), which is 15 °C (27 °F) warmer than the warmest ocean temperature ever recorded. Such an increase could be caused by a large asteroid or comet impact, a large supervolcanic eruption, a large submarine flood basalt, or extensive global warming. There is some speculation that a series of hypercanes resulting from an impact by a large asteroid or comet contributed to the demise of the non-avian dinosaurs. The hypothesis was created by Kerry Emanuel of MIT, who also coined the term.

🔗 Software 🔗 Software/Computing 🔗 Norway

Razor 1911 (RZR) is a warez and demogroup founded in Norway, 1986. It was the first ever such group to be initially founded exclusively as a demogroup, before moving into warez in 1987. According to the US Justice Department, Razor 1911 is the oldest software cracking group that is still active on the internet. Razor 1911 ran the diskmag 'Propaganda' until 1995.

🔗 United States

The Leary–Lettvin debate was a May 3, 1967 debate between Dr. Jerome Lettvin, a medical doctor and professor at MIT, and Dr. Timothy Leary, a licensed psychologist, about the merits and dangers of the hallucinogenic drug LSD. It took place in the Kresge Auditorium at the Massachusetts Institute of Technology.

🔗 Computer science

In computer science, the sleeping barber problem is a classic inter-process communication and synchronization problem between multiple operating system processes. The problem is analogous to that of keeping a barber working when there are customers, resting when there are none, and doing so in an orderly manner.

The Sleeping Barber Problem is often attributed to Edsger Dijkstra (1965), one of the pioneers in computer science.

🔗 Germany 🔗 Trains 🔗 Trains/Rail transport in Germany

The Breitspurbahn (German pronunciation: [ˈbʁaɪtʃpuːɐ̯baːn], transl. broad-gauge railway) was a railway system planned and partly surveyed by Nazi Germany. Its track gauge – the distance between the two running rails – was to be 3000 mm (9 ft 10+1⁄8 in), more than twice that of the 1435 mm (4 ft 8+1⁄2 in) standard gauge used in western Europe. The railway was intended initially to run between major cities of the Greater Germanic Reich (the regime's expanded Germany) and neighbouring states.

🔗 Business 🔗 Parliamentary Procedure

Robert's Rules of Order, often simply referred to as Robert's Rules, is a manual of parliamentary procedure by U.S. Army officer Henry Martyn Robert. "The object of Rules of Order is to assist an assembly to accomplish the work for which it was designed [...] Where there is no law [...] there is the least of real liberty". The term "Robert's Rules of Order" is also used more generically to refer to any of the more recent editions, by various editors and authors, based on any of Robert's original editions, and the term is used more generically in the United States to refer to parliamentary procedure.

Robert's manual was first published in 1876 as an adaptation of the rules and practice of the United States Congress to the needs of non-legislative societies. Robert's Rules is the most widely used manual of parliamentary procedure in the United States. It governs the meetings of a diverse range of organizations—including church groups, county commissions, homeowners associations, nonprofit associations, professional societies, school boards, and trade unions—that have adopted it as their parliamentary authority. Robert published four editions of the manual before his death in 1923, the last being the thoroughly revised and expanded Fourth Edition published as Robert's Rules of Order Revised in May 1915.

🔗 Military history 🔗 Military history/Military science, technology, and theory 🔗 Architecture 🔗 Urban studies and planning 🔗 Military history/Fortifications 🔗 Civil engineering 🔗 Engineering

A bastion fort or trace italienne (a phrase improperly derived from French, literally meaning Italian outline), is a fortification in a style that evolved during the early modern period of gunpowder when the cannon came to dominate the battlefield. It was first seen in the mid-15th century in Italy. Some types, especially when combined with ravelins and other outworks, resembled the related star fort of the same era.

The design of the fort is normally a polygon with bastions at the corners of the walls. These outcroppings eliminated protected blind spots, called "dead zones", and allowed fire along the curtain from positions protected from direct fire. Many bastion forts also feature cavaliers, which are raised secondary structures based entirely inside the primary structure.

🔗 Biology 🔗 Science Fiction 🔗 Chemistry

Hypothetical types of biochemistry are forms of biochemistry speculated to be scientifically viable but not proven to exist at this time. The kinds of living organisms currently known on Earth all use carbon compounds for basic structural and metabolic functions, water as a solvent, and DNA or RNA to define and control their form. If life exists on other planets or moons, it may be chemically similar; it is also possible that there are organisms with quite different chemistries—for instance, involving other classes of carbon compounds, compounds of another element, or another solvent in place of water.

The possibility of life-forms being based on "alternative" biochemistries is the topic of an ongoing scientific discussion, informed by what is known about extraterrestrial environments and about the chemical behaviour of various elements and compounds. It is of interest in synthetic biology and is also a common subject in science fiction.

The element silicon has been much discussed as a hypothetical alternative to carbon. Silicon is in the same group as carbon on the periodic table and, like carbon, it is tetravalent. Hypothetical alternatives to water include ammonia, which, like water, is a polar molecule, and cosmically abundant; and non-polar hydrocarbon solvents such as methane and ethane, which are known to exist in liquid form on the surface of Titan.