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🔗 Mathematics

The Ulam spiral or prime spiral is a graphical depiction of the set of prime numbers, devised by mathematician Stanisław Ulam in 1963 and popularized in Martin Gardner's Mathematical Games column in Scientific American a short time later. It is constructed by writing the positive integers in a square spiral and specially marking the prime numbers.

Ulam and Gardner emphasized the striking appearance in the spiral of prominent diagonal, horizontal, and vertical lines containing large numbers of primes. Both Ulam and Gardner noted that the existence of such prominent lines is not unexpected, as lines in the spiral correspond to quadratic polynomials, and certain such polynomials, such as Euler's prime-generating polynomial x² − x + 41, are believed to produce a high density of prime numbers. Nevertheless, the Ulam spiral is connected with major unsolved problems in number theory such as Landau's problems. In particular, no quadratic polynomial has ever been proved to generate infinitely many primes, much less to have a high asymptotic density of them, although there is a well-supported conjecture as to what that asymptotic density should be.

In 1932, more than thirty years prior to Ulam's discovery, the herpetologist Laurence Klauber constructed a triangular, non-spiral array containing vertical and diagonal lines exhibiting a similar concentration of prime numbers. Like Ulam, Klauber noted the connection with prime-generating polynomials, such as Euler's.

🔗 Birds

The term Pfeilstorch (German for "arrow stork") is given to storks injured by an arrow while wintering in Africa, before returning to Europe with the arrow stuck in their bodies. To date, around 25 Pfeilstörche have been documented.

The first and most famous Pfeilstorch was a white stork found in 1822 near the German village of Klütz, in the state of Mecklenburg-Vorpommern. It was carrying a 30-inch (76 cm) spear from central Africa in its neck. The specimen was stuffed and can be seen today in the zoological collection of the University of Rostock. It is therefore referred to as the Rostocker Pfeilstorch.

This Pfeilstorch was crucial in understanding the migration of European birds. Before migration was understood, people struggled to explain the sudden annual disappearance of birds like the white stork and barn swallow. Besides migration, some theories of the time held that they turned into other kinds of birds, mice, or hibernated underwater during the winter, and such theories were even propagated by zoologists of the time. The Rostocker Pfeilstorch in particular proved that birds migrate long distances to wintering grounds.

🔗 Business 🔗 Automobiles

The Toyota Way is a set of principles and behaviors that underlie the Toyota Motor Corporation's managerial approach and production system. Toyota first summed up its philosophy, values and manufacturing ideals in 2001, calling it "The Toyota Way 2001". It consists of principles in two key areas: continuous improvement, and respect for people.

🔗 Disability 🔗 Writing systems 🔗 Constructed languages

Blissymbols or Blissymbolics is a constructed language conceived as an ideographic writing system called Semantography consisting of several hundred basic symbols, each representing a concept, which can be composed together to generate new symbols that represent new concepts. Blissymbols differ from most of the world's major writing systems in that the characters do not correspond at all to the sounds of any spoken language.

Blissymbols was published by Charles K. Bliss in 1949 and found use in the education of people with communication difficulties.

🔗 Computer science

TLA⁺ is a formal specification language developed by Leslie Lamport. It is used to design, model, document, and verify programs, especially concurrent systems and distributed systems. TLA⁺ has been described as exhaustively-testable pseudocode, and its use likened to drawing blueprints for software systems; TLA is an acronym for Temporal Logic of Actions.

For design and documentation, TLA⁺ fulfills the same purpose as informal technical specifications. However, TLA⁺ specifications are written in a formal language of logic and mathematics, and the precision of specifications written in this language is intended to uncover design flaws before system implementation is underway.

Since TLA⁺ specifications are written in a formal language, they are amenable to finite model checking. The model checker finds all possible system behaviours up to some number of execution steps, and examines them for violations of desired invariance properties such as safety and liveness. TLA⁺ specifications use basic set theory to define safety (bad things won't happen) and temporal logic to define liveness (good things eventually happen).

TLA⁺ is also used to write machine-checked proofs of correctness both for algorithms and mathematical theorems. The proofs are written in a declarative, hierarchical style independent of any single theorem prover backend. Both formal and informal structured mathematical proofs can be written in TLA⁺; the language is similar to LaTeX, and tools exist to translate TLA⁺ specifications to LaTeX documents.

TLA⁺ was introduced in 1999, following several decades of research into a verification method for concurrent systems. A toolchain has since developed, including an IDE and distributed model checker. The pseudocode-like language PlusCal was created in 2009; it transpiles to TLA⁺ and is useful for specifying sequential algorithms. TLA⁺² was announced in 2014, expanding language support for proof constructs. The current TLA⁺ reference is The TLA⁺ Hyperbook by Leslie Lamport.

🔗 Books 🔗 Socialism 🔗 Anarchism

Bullshit Jobs: A Theory is a 2018 book by anthropologist David Graeber that argues the existence and societal harm of meaningless jobs. He contends that over half of societal work is pointless, which becomes psychologically destructive when paired with a work ethic that associates work with self-worth. Graeber describes five types of meaningless jobs, in which workers pretend their role is not as pointless or harmful as they know it to be: flunkies, goons, duct tapers, box tickers, and taskmasters. He argues that the association of labor with virtuous suffering is recent in human history, and proposes universal basic income as a potential solution.

The book is an extension of a popular essay Graeber published in 2013, which was later translated into 12 languages and whose underlying premise became the subject of a YouGov poll. Graeber subsequently solicited hundreds of testimonials of meaningless jobs and revised his case into a book that was published by Simon & Schuster in May 2018.

🔗 Mathematics

In mathematics, 0.999... (also written as 0.9, among other ways) denotes the repeating decimal consisting of infinitely many 9s after the decimal point (and one 0 before it). This repeating decimal represents the smallest number no less than every decimal number in the sequence (0.9, 0.99, 0.999, ...). This number is equal to 1. In other words, "0.999..." and "1" represent the same number. There are many ways of showing this equality, from intuitive arguments to mathematically rigorous proofs. The technique used depends on the target audience, background assumptions, historical context, and preferred development of the real numbers, the system within which 0.999... is commonly defined. (In other systems, 0.999... can have the same meaning, a different definition, or be undefined.)

More generally, every nonzero terminating decimal has two equal representations (for example, 8.32 and 8.31999...), which is a property of all base representations. The utilitarian preference for the terminating decimal representation contributes to the misconception that it is the only representation. For this and other reasons—such as rigorous proofs relying on non-elementary techniques, properties, or disciplines—some people can find the equality sufficiently counterintuitive that they question or reject it. This has been the subject of several studies in mathematics education.

🔗 Internet 🔗 Soviet Union 🔗 Russia 🔗 History 🔗 Computing 🔗 Russia/technology and engineering in Russia 🔗 Russia/mass media in Russia

.su was assigned as the country code top-level domain (ccTLD) for the Soviet Union (USSR) on 19 September 1990. Even though the Soviet Union itself was dissolved a mere 15 months later, the .su top-level domain remains in use today. It is administered by the Russian Institute for Public Networks (RIPN, or RosNIIROS in Russian transcription).

🔗 Biography 🔗 India 🔗 India/Bihar

Dashrath Manjhi (1934 – 17 August 2007), also known as Mountain Man, was a laborer in Gehlaur village, near Gaya in Bihar, India, who carved a path 110 m long (360 ft), 9.1 m (30 ft) wide and 7.7 m (25 ft) deep through a ridge of hills using only a hammer and chisel. After 22 years of work, Dashrath shortened travel between the Atri and Wazirganj blocks of Gaya town from 55 km to 15 km.

🔗 United States/U.S. Government 🔗 United States

"Stellar Wind" (or "Stellarwind") was the code name of a warrantless surveillance program begun under the George W. Bush administration's President's Surveillance Program (PSP). The National Security Agency (NSA) program was approved by President Bush shortly after the September 11, 2001 attacks and was revealed by Thomas Tamm to The New York Times in 2004. Stellar Wind was a prelude to new legal structures that allowed President Bush and President Barack Obama to reproduce each of those programs and expand their reach.