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🔗 History of Science 🔗 Sweden

Ytterby (Swedish pronunciation: [ˈʏ̂tːɛrˌbyː]) is a village on the Swedish island of Resarö, in Vaxholm Municipality in the Stockholm archipelago. Today the residential area is dominated by suburban homes.

The Swedish name of the village translates literally into "outer village". Ytterby is the single richest source of elemental discoveries in the world; the chemical elements yttrium (Y), terbium (Tb), erbium (Er), and ytterbium (Yb) are all named after Ytterby, and the elements holmium (Ho), scandium (Sc), thulium (Tm), tantalum (Ta), and gadolinium (Gd) were also first discovered there.

Local roads connect Ytterby to county road 274 and hence the mainland. Except for the winter months, passenger ships of the Waxholmsbolaget call at a pier in Ytterby, providing a connection to Vaxholm town and Stockholm. Ytterby is as well served by several local bus lines of the north east SL district, connecting the area directly to Stockholms Östra station.

🔗 Human rights 🔗 Mass surveillance 🔗 Espionage 🔗 Technology 🔗 Lists 🔗 Politics

This is a list of government surveillance projects and related databases throughout the world.

🔗 Germany 🔗 Measurement

The obsolete units of measurement of German-speaking countries consist of a variety of units, with varying local standard definitions. Some of these units are still used in everyday speech and even in stores and on street markets as shorthand for similar amounts in the metric system. For example, some customers ask for one pound (ein Pfund) of something when they want 500 grams.

The metric system became compulsory on 1 January 1872, in Germany and on 1 January 1876, in Austria.

Some obsolete German units have names similar to units that were traditionally used in other countries, and that are still used in the United Kingdom (imperial units) and the United States (United States customary units).

🔗 Aviation

In aviation, the sterile flight deck rule or sterile cockpit rule is a procedural requirement that during critical phases of flight (normally below 10,000 feet (3,050 m)), only activities required for the safe operation of the aircraft may be carried out by the flight crew, and all non-essential activities in the cockpit are forbidden. In the United States, the Federal Aviation Administration (FAA) imposed the rule in 1981, after reviewing a series of accidents that were caused by flight crews who were distracted from their flying duties by engaging in non-essential conversations and activities during critical parts of the flight.

One such accident was Eastern Air Lines Flight 212, which crashed just short of the runway at Charlotte/Douglas International Airport in 1974 while conducting an instrument approach in dense fog. The National Transportation Safety Board (NTSB) concluded that a probable cause of the accident was lack of altitude awareness due to distraction from idle chatter among the flight crew during the approach phase of the flight.

🔗 China 🔗 Politics

Document Number Nine (or Document No. 9), more properly the Communiqué on the Current State of the Ideological Sphere (also translated as the Briefing on the Current Situation in the Ideological Realm), is a confidential internal document widely circulated within the Communist Party of China in 2013 by the General Office of the Communist Party of China. The document was first circulated in July 2012. The document warns of seven dangerous Western values, allegedly including media freedom and judicial independence. Teaching on any of the seven topics is forbidden. There is an emphasis on controlling and preventing communication using the internet of ideas subversive to one party rule. The document was issued in the context of planned economic reforms and increased calls for political reform. It has been described as a critique of the "liberal ways of thinking".

The document was not made available to public by the Communist Party or any branches of the Chinese government, but in July 2013 was allegedly leaked by Chinese dissident journalist Gao Yu, who was in turn sentenced to a seven-year imprisonment for "leaking state secrets".

It is unclear whether this document is official Chinese policy or just a faction within the party. However, The New York Times suggests that it "bears the unmistakable imprimatur of Xi Jinping". It is thought that Document No. 9 was issued by the Central Committee General Office, and would have required the approval of Mr. Xi and other top leaders. A severe crackdown against human rights lawyers, media outlets, academics, and other such independent thinkers has followed the document's publication.

🔗 Mathematics 🔗 Statistics

In statistics, the 68–95–99.7 rule, also known as the empirical rule, is a shorthand used to remember the percentage of values that lie within an interval estimate in a normal distribution: 68%, 95%, and 99.7% of the values lie within one, two, and three standard deviations of the mean, respectively.

In mathematical notation, these facts can be expressed as follows, where Pr() is the probability function, Χ is an observation from a normally distributed random variable, μ (mu) is the mean of the distribution, and σ (sigma) is its standard deviation:

${\displaystyle {\begin{aligned}\Pr(\mu -1\sigma \leq X\leq \mu +1\sigma )&\approx 68.27\%\\\Pr(\mu -2\sigma \leq X\leq \mu +2\sigma )&\approx 95.45\%\\\Pr(\mu -3\sigma \leq X\leq \mu +3\sigma )&\approx 99.73\%\end{aligned}}}$

The usefulness of this heuristic especially depends on the question under consideration.

In the empirical sciences, the so-called three-sigma rule of thumb (or 3σ rule) expresses a conventional heuristic that nearly all values are taken to lie within three standard deviations of the mean, and thus it is empirically useful to treat 99.7% probability as near certainty.

In the social sciences, a result may be considered "significant" if its confidence level is of the order of a two-sigma effect (95%), while in particle physics, there is a convention of a five-sigma effect (99.99994% confidence) being required to qualify as a discovery.

A weaker three-sigma rule can be derived from Chebyshev's inequality, stating that even for non-normally distributed variables, at least 88.8% of cases should fall within properly calculated three-sigma intervals. For unimodal distributions, the probability of being within the interval is at least 95% by the Vysochanskij–Petunin inequality. There may be certain assumptions for a distribution that force this probability to be at least 98%.

"Fart Proudly" (also called "A Letter to a Royal Academy about farting", and "To the Royal Academy of Farting") is the popular name of an essay about flatulence written by Benjamin Franklin c. 1781 while he was living abroad as United States Ambassador to France. It is an example of flatulence humor.

🔗 Aviation 🔗 Aviation/aircraft

The Giffard dirigible or Giffard airship was an airship built in France in 1852 by Henri Giffard, the first powered and steerable (French: dirigeable – "directable") airship to fly. The craft featured an elongated hydrogen-filled envelope that tapered to a point at each end. From this was suspended a long beam with a triangular, sail-like rudder at its aft end, and beneath the beam a platform for the pilot and steam engine. Due to the highly flammable nature of the lift gas, special precautions were taken to minimise the potential for the envelope to be ignited by the engine beneath it. The engine's exhaust was diverted downwards to a long pipe projecting below the platform, and the area surrounding the boiler's stoke hole was surrounded by wire gauze. On 24 September 1852, Giffard flew the airship from the hippodrome at Place de l'Etoile to Élancourt, covering the 27 km (17 mi) in around 3 hours, demonstrating maneuvering along the way. The engine, however, was not sufficiently powerful to allow Giffard to fly against the wind to make a return journey.

🔗 Computing 🔗 Computing/Computer hardware

The RTX2010 manufactured by Intersil is a radiation hardened stack machine microprocessor which has been used in numerous spacecraft.

🔗 Mathematics

A squircle is a shape intermediate between a square and a circle. There are at least two definitions of "squircle" in use, the most common of which is based on the superellipse. The word "squircle" is a portmanteau of the words "square" and "circle". Squircles have been applied in design and optics.