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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.

🔗 Economics

The Penn effect is the economic finding that real income ratios between high and low income countries are systematically exaggerated by gross domestic product (GDP) conversion at market exchange rates. It is associated with what became the Penn World Table, and it has been a consistent econometric result since at least the 1950s.

The "Balassa–Samuelson effect" is a model cited as the principal cause of the Penn effect by neo-classical economics, as well as being a synonym of "Penn effect".

🔗 Time

The Pax calendar was invented by James A. Colligan, SJ in 1930 as a perennializing reform of the annualized Gregorian calendar.

🔗 Computing 🔗 Computing/Computer hardware 🔗 Computing/Software

Compute Express Link (CXL) is an open standard for high-speed central processing unit (CPU)-to-device and CPU-to-memory connections, designed for high performance data center computers. CXL is built on the PCI Express (PCIe) physical and electrical interface and includes PCIe-based block input/output protocol (CXL.io) and new cache-coherent protocols for accessing system memory (CXL.cache) and device memory (CXL.mem).

🔗 Games

The Hardest Logic Puzzle Ever is a logic puzzle so called by American philosopher and logician George Boolos and published in The Harvard Review of Philosophy in 1996. Boolos' article includes multiple ways of solving the problem. A translation in Italian was published earlier in the newspaper La Repubblica, under the title L'indovinello più difficile del mondo.

It is stated as follows:

Three gods A, B, and C are called, in no particular order, True, False, and Random. True always speaks truly, False always speaks falsely, but whether Random speaks truly or falsely is a completely random matter. Your task is to determine the identities of A, B, and C by asking three yes-no questions; each question must be put to exactly one god. The gods understand English, but will answer all questions in their own language, in which the words for yes and no are da and ja, in some order. You do not know which word means which.

Boolos provides the following clarifications: a single god may be asked more than one question, questions are permitted to depend on the answers to earlier questions, and the nature of Random's response should be thought of as depending on the flip of a fair coin hidden in his brain: if the coin comes down heads, he speaks truly; if tails, falsely.

🔗 Plants

A floral formula is a notation for representing the structure of particular types of flowers. Such notations use numbers, letters and various symbols to convey significant information in a compact form. They may represent the floral form of a particular species, or may be generalized to characterize higher taxa, usually giving ranges of numbers of organs. Floral formulae are one of the two ways of describing flower structure developed during the 19th century, the other being floral diagrams. The format of floral formulae differs according to the tastes of particular authors and periods, yet they tend to convey the same information.

A floral formula is often used along with a floral diagram.

🔗 United States 🔗 Religion 🔗 United States/Massachusetts 🔗 Christianity 🔗 Occult

The Salem witchcraft trial of 1878, also known as the Ipswich witchcraft trial and the second Salem witch trial, was an American civil case held in May 1878 in Salem, Massachusetts, in which Lucretia L. S. Brown, an adherent of the Christian Science religion, accused fellow Christian Scientist Daniel H. Spofford of attempting to harm her through his "mesmeric" mental powers. By 1918, it was considered the last witchcraft trial held in the United States. The case garnered significant attention for its startling claims and the fact that it took place in Salem, the scene of the 1692 Salem witch trials. The judge dismissed the case.

🔗 United States 🔗 Biography 🔗 Criminal Biography 🔗 United States/Colorado

Marvin John Heemeyer (October 28, 1951 – June 4, 2004) was an automobile muffler repair shop owner who demolished numerous buildings with a modified bulldozer in Granby, Colorado, on June 4, 2004.

Heemeyer had feuded with Granby town officials, particularly over fines for violating city health ordinances after local officials disconnected Heemeyer's business from the city sewage system to make way for a concrete plant on an adjacent parcel. He was subsequently fined for improperly dumping sewage from his business instead of connecting to the city sewer system. Over about eighteen months Heemeyer had secretly modified a Komatsu D355A bulldozer by adding layers of steel and concrete, intended to serve as armor. On June 4, 2004, Heemeyer's feud with Granby culminated in a spree in which he used the armored bulldozer to demolish the Granby town hall, the former mayor's house, and several other buildings. Heemeyer's rampage concluded with his suicide, after his bulldozer became trapped in the basement of a hardware store he had been in the process of destroying.

🔗 Greece 🔗 Songs

"Misirlou" (Greek: Μισιρλού < Turkish: Mısırlı 'Egyptian' < Arabic: مصر Miṣr 'Egypt') is a folk song from the Eastern Mediterranean region. The original author of the song is not known, but Arabic, Greek, and Jewish musicians were playing it by the 1920s. The earliest known recording of the song is a 1927 Greek rebetiko/tsifteteli composition. There are also Arabic belly dancing, Albanian, Armenian, Serbian, Persian, Indian and Turkish versions of the song. This song was popular from the 1920s onwards in the Arab American, Armenian American and Greek American communities who settled in the United States.

The song was a hit in 1946 for Jan August, an American pianist and xylophonist nicknamed "the one-man piano duet". It gained worldwide popularity through Dick Dale's 1962 American surf rock version, originally titled "Miserlou", which popularized the song in Western popular culture; Dale's version was influenced by an earlier Arabic folk version played with an oud. Various versions have since been recorded, mostly based on Dale's version, including other surf and rock versions by bands such as the Beach Boys, the Ventures, and the Trashmen, as well as international orchestral easy listening (exotica) versions by musicians such as Martin Denny and Arthur Lyman. Dale's surf rock version was heard in the 1994 film Pulp Fiction.

🔗 Environment 🔗 Disaster management 🔗 London 🔗 Ecology 🔗 River Thames

The Great Stink was an event in central London in July and August 1858 during which the hot weather exacerbated the smell of untreated human waste and industrial effluent that was present on the banks of the River Thames. The problem had been mounting for some years, with an ageing and inadequate sewer system that emptied directly into the Thames. The miasma from the effluent was thought to transmit contagious diseases, and three outbreaks of cholera before the Great Stink were blamed on the ongoing problems with the river.

The smell, and fears of its possible effects, prompted action from the local and national administrators who had been considering possible solutions for the problem. The authorities accepted a proposal from the civil engineer Joseph Bazalgette to move the effluent eastwards along a series of interconnecting sewers that sloped towards outfalls beyond the metropolitan area. Work on high-, mid- and low-level systems for the new Northern and Southern Outfall Sewers started at the beginning of 1859 and lasted until 1875. To aid the drainage, pumping stations were placed to lift the sewage from lower levels into higher pipes. Two of the more ornate stations, Abbey Mills in Stratford and Crossness on the Erith Marshes, are listed for protection by English Heritage. Bazalgette's plan introduced the three embankments to London in which the sewers ran—the Victoria, Chelsea and Albert Embankments.

Bazalgette's work ensured that sewage was no longer dumped onto the shores of the Thames and brought an end to the cholera outbreaks; his actions are thought to have saved more lives than the efforts of any other Victorian official. His sewer system operates into the 21st century, servicing a city that has grown to a population of over eight million. The historian Peter Ackroyd argues that Bazalgette should be considered a hero of London.