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🔗 Mathematics 🔗 Systems 🔗 Systems/Chaos theory

Fractal compression is a lossy compression method for digital images, based on fractals. The method is best suited for textures and natural images, relying on the fact that parts of an image often resemble other parts of the same image. Fractal algorithms convert these parts into mathematical data called "fractal codes" which are used to recreate the encoded image.

🔗 Germany 🔗 Military history 🔗 Military history/Military aviation 🔗 Military history/Maritime warfare 🔗 Military history/World War II 🔗 Military history/German military history 🔗 Military history/European military history 🔗 Military history/British military history

Operation Sea Lion, also written as Operation Sealion (German: Unternehmen Seelöwe), was Nazi Germany's code name for the plan for an invasion of the United Kingdom during the Battle of Britain in the Second World War. Following the Battle of France, Adolf Hitler, the German Führer and Supreme Commander of the Armed Forces, hoped the British government would accept his offer to end the war, and he reluctantly considered invasion only as a last resort if all other options failed.

As a precondition, Hitler specified the achievement of both air and naval superiority over the English Channel and the proposed landing sites, but the German forces did not achieve either at any point during the war, and both the German High Command and Hitler himself had serious doubts about the prospects for success. Nevertheless, both the German Army and Navy undertook a major programme of preparations for an invasion: training troops, developing specialised weapons and equipment, and modifying transport vessels. A large number of river barges and transport ships were gathered together on the Channel coast, but with Luftwaffe aircraft losses increasing in the Battle of Britain and no sign that the Royal Air Force had been defeated, Hitler postponed Sea Lion indefinitely on 17 September 1940 and it was never put into action.

🔗 Books 🔗 Food and drink

This Is the Boke of Cokery, or The Boke of Cokery, is believed to be the first cookery book printed in English. The name of the author is unknown. It was printed and published by Richard Pynson in 1500. The book remained in print for many years in the 16th century, but was superseded and forgotten by the 18th. The only known surviving copy of the book is in the possession of the Marquess of Bath at Longleat House, Wiltshire.

🔗 Russia 🔗 Disaster management 🔗 Terrorism 🔗 Russia/politics and law of Russia 🔗 Russia/history of Russia

The Russian apartment bombings were a series of explosions that hit four apartment blocks in the Russian cities of Buynaksk, Moscow and Volgodonsk in September 1999, killing more than 300, injuring more than 1000, and spreading a wave of fear across the country. The bombings, together with the Invasion of Dagestan, triggered the Second Chechen War. Then-prime minister Vladimir Putin's handling of the crisis boosted his popularity greatly and helped him attain the presidency within a few months. Russian courts ruled that the attacks were orchestrated by Chechen-linked militants, while some scholars, journalists, and politicians have argued that Russian security services likely organized the bombings.

The blasts hit Buynaksk on 4 September and in Moscow on 9 and 13 September. On 13 September, Russian Duma speaker Gennadiy Seleznyov made an announcement in the Duma about receiving a report that another bombing had just happened in the city of Volgodonsk. A bombing did indeed happen in Volgodonsk, but only three days later, on 16 September. Chechen militants were blamed for the bombings, but denied responsibility, along with Chechen president Aslan Maskhadov.

A suspicious device resembling those used in the bombings was found and defused in an apartment block in the Russian city of Ryazan on 22 September. On 23 September, Vladimir Putin praised the vigilance of the inhabitants of Ryazan and ordered the air bombing of Grozny, which marked the beginning of the Second Chechen War. Three FSB agents who had planted the devices at Ryazan were arrested by the local police. On 24 September 1999, head of FSB Nikolay Patrushev announced that the incident in Ryazan had been an anti-terror drill and the device found there contained only sugar.

The official Russian investigation of the Buynaksk bombing was completed in 2000, while the investigation of Moscow and Volgodonsk bombings was completed in 2002. In 2000, seven people were convicted of perpetrating the Buinaksk attack. According to the court ruling on the Moscow and Volgodonsk bombings, which was announced in 2004, the attacks were organised and led by Achemez Gochiyaev, who remains at large. All bombings, the court ruled, were ordered by Islamist warlords Ibn Al-Khattab and Abu Omar al-Saif, who have been killed. Five other suspects have been killed and six have been convicted by Russian courts on terrorism-related charges.

Parliament member Yuri Shchekochikhin filed two motions for a parliamentary investigation of the events, but the motions were rejected by the Russian Duma in March 2000. An independent public commission to investigate the bombings was chaired by Duma deputy Sergei Kovalev. The commission was rendered ineffective because of government refusal to respond to its inquiries. Two key members of the Kovalev Commission, Sergei Yushenkov and Yuri Shchekochikhin, have since died in apparent assassinations. The Commission’s lawyer and investigator Mikhail Trepashkin was arrested and served four years in prison for revealing state secrets. Former FSB agent Alexander Litvinenko, who defected and blamed the FSB for the bombings, was poisoned and killed in London in 2006. A British inquiry later determined that Litvinenko's murder was "probably" carried out with the approval of Putin and Patrushev.

The 1999 attacks were officially attributed to Chechen terrorists. According to some historians and journalists, the bombings were coordinated by the Russian state security services to bring Putin into the presidency. Others disagree with such theories. Independent investigations have faced obstruction from Russian security services, raising further suspicions about their involvement in the attacks.

🔗 Russia 🔗 Crime 🔗 Death 🔗 Russia/politics and law of Russia

The assassination of Boris Nemtsov, a Russian politician opposed to the government of Vladimir Putin, occurred in central Moscow on Bolshoy Moskvoretsky Bridge at 23:31 local time on 27 February 2015. An unknown assailant fired seven or eight shots from a Makarov pistol; four of them hit Boris Nemtsov in the head, heart, liver and stomach, killing him almost instantly. He died hours after appealing to the public to support a march against Russia's war in Ukraine. Nemtsov's Ukrainian partner Anna Duritskaya survived the attack as its sole eyewitness.

The assassination was met with worldwide condemnation and concern for the situation of the Russian opposition. Russian authorities also condemned the murder and vowed to conduct a thorough investigation.

On 8 March 2015, Russian authorities charged Anzor Gubashev and Zaur Dadaev, both originating from the Northern Caucasus, with involvement in the crime. According to Russian authorities, Dadaev confessed to involvement in the murder. However, he later retracted his statement, as extracted by torture. Three more suspects were arrested around the same time and, according to Russian media, another suspect blew himself up in Grozny when Russian police forces surrounded his apartment block.

🔗 United States 🔗 Biography 🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Military history/Military biography 🔗 Biography/military biography

Harold L. Hering (born 1936) is a former officer of the United States Air Force, who was discharged in 1975 for requesting basic information about checks and balances to prevent an unauthorized order to launch nuclear missiles. Major Hering was subsequently presented the 2017 Courage of Conscience Award at the Peace Abbey, Boston, Massachusetts.

🔗 Science Fiction 🔗 Robotics 🔗 Theatre 🔗 Czech Republic

R.U.R. is a 1920 science-fiction play by the Czech writer Karel Čapek. "R.U.R." stands for Rossumovi Univerzální Roboti (Rossum's Universal Robots, a phrase that has been used as a subtitle in English versions). The play had its world premiere on 2 January 1921 in Hradec Králové; it introduced the word "robot" to the English language and to science fiction as a whole. R.U.R. soon became influential after its publication. By 1923 it had been translated into thirty languages. R.U.R. was successful in its time in Europe and North America. Čapek later took a different approach to the same theme in his 1936 novel War with the Newts, in which non-humans become a servant-class in human society.

🔗 Aviation 🔗 Aviation/rotorcraft

Jesus nut is a slang term for the main rotor retaining nut or mast nut, which holds the main rotor to the mast of some helicopters. The related slang term Jesus pin refers to the lock pin used to secure the retaining nut. More generally, Jesus nut (or Jesus pin) has been used to refer to any component that is a single point of failure which results in catastrophic consequences.

🔗 Michigan 🔗 Popular Culture 🔗 Finland

Sisu is a Finnish concept described as stoic determination, tenacity of purpose, grit, bravery, resilience, and hardiness and is held by Finns themselves to express their national character. It is generally considered not to have a literal equivalent in English.

🔗 Physics 🔗 Weather 🔗 Weather/Meteorological instruments and data

The wet-bulb temperature (WBT) is the temperature read by a thermometer covered in water-soaked cloth (a wet-bulb thermometer) over which air is passed. At 100% relative humidity, the wet-bulb temperature is equal to the air temperature (dry-bulb temperature); at lower humidity the wet-bulb temperature is lower than dry-bulb temperature because of evaporative cooling.

The wet-bulb temperature is defined as the temperature of a parcel of air cooled to saturation (100% relative humidity) by the evaporation of water into it, with the latent heat supplied by the parcel. A wet-bulb thermometer indicates a temperature close to the true (thermodynamic) wet-bulb temperature. The wet-bulb temperature is the lowest temperature that can be reached under current ambient conditions by the evaporation of water only.

Even heat-adapted people cannot carry out normal outdoor activities past a wet-bulb temperature of 32 °C (90 °F), equivalent to a heat index of 55 °C (130 °F). The theoretical limit to human survival for more than a few hours in the shade, even with unlimited water, is a wet-bulb temperature of 35 °C (95 °F) – theoretically equivalent to a heat index of 70 °C (160 °F), though the heat index does not go that high.