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🔗 Physics

Flux pinning is the phenomenon where a superconductor is pinned in space above a magnet. The superconductor must be a type-II superconductor because type-I superconductors cannot be penetrated by magnetic fields. The act of magnetic penetration is what makes flux pinning possible. At higher magnetic fields (above Hc1 and below Hc2) the superconductor allows magnetic flux to enter in quantized packets surrounded by a superconducting current vortex (see Quantum vortex). These sites of penetration are known as flux tubes. The number of flux tubes per unit area is proportional to the magnetic field with a constant of proportionality equal to the magnetic flux quantum. On a simple 76 millimeter diameter, 1-micrometer thick disk, next to a magnetic field of 28 kA/m, there are approximately 100 billion flux tubes that hold 70,000 times the superconductor's weight. At lower temperatures the flux tubes are pinned in place and cannot move. This pinning is what holds the superconductor in place thereby allowing it to levitate. This phenomenon is closely related to the Meissner effect, though with one crucial difference — the Meissner effect shields the superconductor from all magnetic fields causing repulsion, unlike the pinned state of the superconductor disk which pins flux, and the superconductor in place.

🔗 Russia 🔗 Crime 🔗 Death

The 2022 Russian businessmen mystery deaths are a series of unusual deaths of Russian-connected businessmen in 2022. Most of the deaths were officially declared to be suicides, but a number of commentators have suggested that the circumstances of the suicides appear to be suspicious and may have been staged.

🔗 Visual arts

Iron gall ink (also known as common ink, standard ink, oak gall ink or iron gall nut ink) is a purple-black or brown-black ink made from iron salts and tannic acids from vegetable sources. It was the standard ink formulation used in Europe for the 1400-year period between the 5th and 19th centuries, remained in widespread use well into the 20th century, and is still sold today.

🔗 Philosophy 🔗 Philosophy/Logic

The Texas sharpshooter fallacy is an informal fallacy which is committed when differences in data are ignored, but similarities are overemphasized. From this reasoning, a false conclusion is inferred. This fallacy is the philosophical or rhetorical application of the multiple comparisons problem (in statistics) and apophenia (in cognitive psychology). It is related to the clustering illusion, which is the tendency in human cognition to interpret patterns where none actually exist.

The name comes from a joke about a Texan who fires some gunshots at the side of a barn, then paints a shooting target centered on the tightest cluster of hits and claims to be a sharpshooter.

🔗 Russia 🔗 Military history 🔗 Geography 🔗 Poland 🔗 Lithuania 🔗 Military history/Russian, Soviet and CIS military history 🔗 Military history/Polish military history 🔗 Military history/European military history 🔗 Belarus 🔗 NATO

The Suwałki Gap, also known as the Suwałki corridor ([suˈvawkʲi] (listen)), is a sparsely populated area immediately southwest of the border between Lithuania and Poland, between Belarus and the Russian exclave of Kaliningrad Oblast. Named after the Polish town of Suwałki, this choke point has become of great strategic and military importance since Poland and the Baltic states joined the North Atlantic Treaty Organization (NATO).

The border between Poland and Lithuania was formed after the Suwałki Agreement of 1920; but it carried little importance in the interwar period as at the time, the Polish lands stretched farther northeast, while during the Cold War, Lithuania was part of the Soviet Union and communist Poland belonged to the Soviet-led Warsaw Pact alliance. The dissolution of the Soviet Union and the Warsaw Pact created borders that cut through the shortest land route between Kaliningrad (Russian territory isolated from the mainland) and Belarus (Russia's ally). As the Baltic states and Poland eventually joined NATO, this narrow border stretch between Poland and Lithuania became a vulnerability for the military bloc because, if a hypothetical military conflict were to erupt between Russia and Belarus on one side and NATO on the other, the capture of the 65 km (40 mi)-long strip of land between Russia's Kaliningrad Oblast and Belarus would likely jeopardise NATO's attempts to defend the Baltic states. NATO's fears about the Suwałki Gap intensified after 2014, when Russia annexed Crimea and launched the war in Donbas, and further increased after Russia invaded Ukraine in February 2022. These worries prompted the alliance to increase its military presence in the area, and an arms race was triggered by these events.

Both Russia and the European Union countries also saw great interest in civilian uses of the gap. In the 1990s and early 2000s, Russia attempted to negotiate an extraterritorial corridor to connect its exclave of Kaliningrad Oblast with Grodno in Belarus, but Poland, Lithuania and the EU did not consent. Movement of goods through the gap was disrupted in summer 2022, during the Russian invasion of Ukraine, as Lithuania and the European Union introduced transit restrictions on Russian vehicles as part of their sanctions. The Via Baltica road, a vital link connecting Finland and the Baltic states with the rest of the European Union, goes through the area and, as of November 2022, is under construction in Poland as expressway S61.

🔗 Mathematics 🔗 Physics

The Fresnel integrals S(x) and C(x) are two transcendental functions named after Augustin-Jean Fresnel that are used in optics and are closely related to the error function (erf). They arise in the description of near-field Fresnel diffraction phenomena and are defined through the following integral representations:

The simultaneous parametric plot of S(x) and C(x) is the Euler spiral (also known as the Cornu spiral or clothoid).

🔗 Astronomy 🔗 Astronomy/Astronomical objects

Wolf 359 is a red dwarf star located in the constellation Leo, near the ecliptic. At a distance of approximately 7.9 light years from Earth, it has an apparent magnitude of 13.54 and can only be seen with a large telescope. Wolf 359 is one of the nearest stars to the Sun; only the Alpha Centauri system (including Proxima Centauri), Barnard's Star and the brown dwarfs Luhman 16 and WISE 0855−0714 are known to be closer. Its proximity to Earth has led to its mention in several works of fiction.

Wolf 359 is one of the faintest and lowest-mass stars known. At the light-emitting layer called the photosphere, it has a temperature of about 2,800 K, which is low enough for chemical compounds to form and survive. The absorption lines of compounds such as water and titanium(II) oxide have been observed in the spectrum. The surface has a magnetic field that is stronger than the average magnetic field on the Sun. As a result of magnetic activity caused by convection, Wolf 359 is a flare star that can undergo sudden increases in luminosity for several minutes. These flares emit strong bursts of X-ray and gamma ray radiation that have been observed by space telescopes. Wolf 359 is a relatively young star with an age of less than a billion years. Two planetary companions are suspected but as yet no debris disks have been unmasked.

🔗 North America

The Alcoa 50,000 ton forging press is a heavy press operated at Howmet Aerospace's Cleveland Operations. It was built as part of the Heavy Press Program by the United States Air Force. It was manufactured by Mesta Machinery of West Homestead, Pennsylvania, and began operation on May 5, 1955.

Alcoa ran the plant from the time of its construction, and purchased it outright in 1982. In 2008, cracks were discovered in the press, which had to be shut down for safety reasons. Repairs, originally estimated at a cost of $68 million (equivalent to $81.04 million in 2019), cost a total of $100 million, and were completed in early 2012.

🔗 Biography 🔗 Germany 🔗 Mexico 🔗 Biography/arts and entertainment 🔗 Anarchism

B. Traven (German: [ˈbeː ˈtʁaːvn̩]; Bruno Traven in some accounts) was the pen name of a presumably German novelist, whose real name, nationality, date and place of birth and details of biography are all subject to dispute. One of the few certainties about Traven's life is that he lived for years in Mexico, where the majority of his fiction is also set—including The Treasure of the Sierra Madre (1927). The film adaptation of the same name won three Academy Awards in 1948.

Virtually every detail of Traven's life has been disputed and hotly debated. There were many hypotheses on the true identity of B. Traven, some of them wildly fantastic. The person most commonly identified as Traven is Ret Marut, a German stage actor and anarchist who supposedly left Europe for Mexico around 1924 and who had edited an anarchist newspaper in Germany called Der Ziegelbrenner (The Brick Burner). Marut is thought to have operated under the "B. Traven" pseudonym, although no details are known about Marut's life before 1912, and many hold that "Ret Marut" was in fact also a pseudonym.

Some researchers further argue that Marut/Traven's original name was Otto Feige and that he was born in Schwiebus in Brandenburg, modern-day Świebodzin in Poland. This theory is not universally accepted. B. Traven in Mexico is also connected with the names of Berick Traven Torsvan and Hal Croves, both of whom appeared and acted in different periods of the writer's life. Both, however, denied being Traven and claimed that they were his literary agents only, representing him in contacts with his publishers.

B. Traven is the author of twelve novels, one book of reportage and several short stories, in which the sensational and adventure subjects combine with a critical attitude towards capitalism. B. Traven's best known works include the novels The Death Ship from 1926, The Treasure of the Sierra Madre from 1927 (filmed in 1948 by John Huston), and the so-called "Jungle Novels", also known as the Caoba cyclus (from the Spanish word caoba, meaning mahogany). The Jungle Novels are a group of six novels (including The Carreta and Government), published in the years 1930–1939 and set among Mexican Indians just before and during the Mexican Revolution in the early 20th century. B. Traven's novels and short stories became very popular as early as the interwar period and retained this popularity after the Second World War; they were also translated into many languages. Most of B. Traven's books were published in German first, with their English editions appearing later; nevertheless, the author always claimed that the English versions were the original ones and that the German versions were only their translations. This claim is mostly treated by Traven scholars as a diversion or a joke, although there are those who accept it.

🔗 Computing 🔗 Computing/Computer hardware

The Pentium FDIV bug is a hardware bug affecting the floating-point unit (FPU) of the early Intel Pentium processors. Because of the bug, the processor would return incorrect binary floating point results when dividing certain pairs of high-precision numbers. The bug was discovered in 1994 by Thomas R. Nicely, a professor of mathematics at Lynchburg College. Missing values in a lookup table used by the FPU's floating-point division algorithm led to calculations acquiring small errors. While these errors would in most use-cases only occur rarely and result in small deviations from the correct output values, in certain circumstances the errors can occur frequently and lead to more significant deviations.

The severity of the FDIV bug is debated. Though rarely encountered by most users (Byte magazine estimated that 1 in 9 billion floating point divides with random parameters would produce inaccurate results), both the flaw and Intel's initial handling of the matter were heavily criticized by the tech community.

In December 1994, Intel recalled the defective processors in what was the first full recall of a computer chip. In its 1994 annual report, Intel said it incurred "a $475 million pre-tax charge ... to recover replacement and write-off of these microprocessors."