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๐Ÿ”— Taarof

๐Ÿ”— Iran

Taarof or Tarof (also transliterated as Taสฟรขrof; Persian: ุชุนุงุฑูโ€Ž) is a Persian word which refers to an Iranian form of civility or art of etiquette that emphasizes both deference and social rank.

Etymologically the origins of the word trace back to an Arabic word meaning "acquaintance" or "knowledge", but Iranians have transformed taarof into something "uniquely Iranian" and tend to understand it as a ritual politeness that levels the playing field and promotes equality in a hierarchical culture. Taarof between friends, or a host and guest, emphasizes the value of friendship as a priority to everything else in the world. Another understanding is that taarof is a way of managing social relations with decorous manners. It could be used as a basis for mutual goodwill (positively) or as "a social or political weapon that confuses the recipient and puts him at a disadvantage" (negatively). Those who are intimately familiar with Iranian culture seem to agree that taarof is one of the most fundamental things to understand about Iranian culture.

According to Middle East scholar William O. Beeman, "Taarof is an extraordinarily difficult concept encompassing a broad complex of behaviors which mark and underscore differences in social status." For example, in Iranian culture, whoever walks through a doorway first gets a form of status, but the person who makes the other go through the door first also gains status by having made the other person do it through their show of grace and deference. When it comes to matters of rank, "one defers to superiors (tribute), and confers on inferiors (favor), presses honor on equals (neither tribute nor favor) or accepts the honor from a proper source, and thereby "wins". Status is relative for individuals in different interactions, according to Beeman, and rights and obligations shift constantly with changes in social environments.

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๐Ÿ”— Gary Kildall

๐Ÿ”— United States ๐Ÿ”— Biography ๐Ÿ”— California ๐Ÿ”— Computing ๐Ÿ”— Computing/Software ๐Ÿ”— United States/Washington - Seattle ๐Ÿ”— United States/Washington

Gary Arlen Kildall (; May 19, 1942ย โ€“ July 11, 1994) was an American computer scientist and microcomputer entrepreneur who created the CP/M operating system and founded Digital Research, Inc. (DRI). Kildall was one of the first people to see microprocessors as fully capable computers, rather than equipment controllers, and to organize a company around this concept. He also co-hosted the PBS TV show The Computer Chronicles. Although his career in computing spanned more than two decades, he is mainly remembered in connection with IBM's unsuccessful attempt in 1980 to license CP/M for the IBM Personal Computer.

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๐Ÿ”— Arrow's impossibility theorem

๐Ÿ”— Mathematics ๐Ÿ”— Economics ๐Ÿ”— Politics ๐Ÿ”— Elections and Referendums

In social choice theory, Arrow's impossibility theorem, the general possibility theorem or Arrow's paradox is an impossibility theorem stating that when voters have three or more distinct alternatives (options), no ranked voting electoral system can convert the ranked preferences of individuals into a community-wide (complete and transitive) ranking while also meeting a specified set of criteria: unrestricted domain, non-dictatorship, Pareto efficiency, and independence of irrelevant alternatives. The theorem is often cited in discussions of voting theory as it is further interpreted by the Gibbardโ€“Satterthwaite theorem. The theorem is named after economist and Nobel laureate Kenneth Arrow, who demonstrated the theorem in his doctoral thesis and popularized it in his 1951 book Social Choice and Individual Values. The original paper was titled "A Difficulty in the Concept of Social Welfare".

In short, the theorem states that no rank-order electoral system can be designed that always satisfies these three "fairness" criteria:

  • If every voter prefers alternative X over alternative Y, then the group prefers X over Y.
  • If every voter's preference between X and Y remains unchanged, then the group's preference between X and Y will also remain unchanged (even if voters' preferences between other pairs like X and Z, Y and Z, or Z and W change).
  • There is no "dictator": no single voter possesses the power to always determine the group's preference.

Cardinal voting electoral systems are not covered by the theorem, as they convey more information than rank orders. However, Gibbard's theorem extends Arrow's theorem for that case. The theorem can also be sidestepped by weakening the notion of independence.

The axiomatic approach Arrow adopted can treat all conceivable rules (that are based on preferences) within one unified framework. In that sense, the approach is qualitatively different from the earlier one in voting theory, in which rules were investigated one by one. One can therefore say that the contemporary paradigm of social choice theory started from this theorem.

The practical consequences of the theorem are debatable: Arrow has said "Most systems are not going to work badly all of the time. All I proved is that all can work badly at times."

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๐Ÿ”— Psychohistory

๐Ÿ”— Psychology

Psychohistory is an amalgam of psychology, history, and related social sciences and the humanities. It examines the "why" of history, especially the difference between stated intention and actual behavior. Psychobiography, childhood, group dynamics, mechanisms of psychic defense, dreams, and creativity are primary areas of research. It works to combine the insights of psychology, especially psychoanalysis, with the research methodology of the social sciences and humanities to understand the emotional origin of the behavior of individuals, groups and nations, past and present. Work in the field has been done in the areas of childhood, creativity, dreams, family dynamics, overcoming adversity, personality, political and presidential psychobiography. There are major psychohistorical studies of studies of anthropology, art, ethnology, history, politics and political science, and much else.

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๐Ÿ”— London Bridge (Lake Havasu)

๐Ÿ”— United States ๐Ÿ”— United States/Arizona ๐Ÿ”— London Transport

London Bridge is a bridge in Lake Havasu City, Arizona. It was built in the 1830s and formerly spanned the River Thames in London, England. It was dismantled in 1967 and relocated to Arizona. The Arizona bridge is a reinforced concrete structure clad in the original masonry of the 1830s bridge, which was purchased by Robert P. McCulloch from the City of London. McCulloch had exterior granite blocks from the original bridge numbered and transported to America to construct the present bridge in Lake Havasu City, a planned community he established in 1964 on the shore of Lake Havasu. The bridge was completed in 1971 (along with a canal), and links an island in the Colorado River with the main part of Lake Havasu City.

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๐Ÿ”— TLA+

๐Ÿ”— 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.

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  • "TLA+" | 2021-03-08 | 230 Upvotes 69 Comments
  • "TLA+" | 2015-05-25 | 105 Upvotes 21 Comments

๐Ÿ”— Counting rods

๐Ÿ”— China

Counting rods (traditional Chinese: ็ฑŒ; simplified Chinese: ็ญน; pinyin: chรณu; Japanese: ็ฎ—ๆœจ; rลmaji: sangi; Korean: sangaji) are small bars, typically 3โ€“14ย cm long, that were used by mathematicians for calculation in ancient East Asia. They are placed either horizontally or vertically to represent any integer or rational number.

The written forms based on them are called rod numerals. They are a true positional numeral system with digits for 1โ€“9 and a blank for 0, from the Warring states period (circa 475 BCE) to the 16th century.

๐Ÿ”— Atomic gardening

๐Ÿ”— Agriculture ๐Ÿ”— Food and drink ๐Ÿ”— Plants ๐Ÿ”— Horticulture and Gardening ๐Ÿ”— Genetics

Atomic gardening is a form of mutation breeding where plants are exposed to radioactive sources, typically cobalt-60, in order to generate mutations, some of which have turned out to be useful.

The practice of plant irradiation has resulted in the development of over 2000 new varieties of plants, most of which are now used in agricultural production. One example is the resistance to verticillium wilt of the "Todd's Mitcham" cultivar of peppermint which was produced from a breeding and test program at Brookhaven National Laboratory from the mid-1950s. Additionally, the Rio Star Grapefruit, developed at the Texas A&M Citrus Center in the 1970s, now accounts for over three quarters of the grapefruit produced in Texas.

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๐Ÿ”— The Cathedral and the Bazaar

๐Ÿ”— Computing ๐Ÿ”— Books ๐Ÿ”— Computing/Software

The Cathedral and the Bazaar: Musings on Linux and Open Source by an Accidental Revolutionary (abbreviated CatB) is an essay, and later a book, by Eric S. Raymond on software engineering methods, based on his observations of the Linux kernel development process and his experiences managing an open source project, fetchmail. It examines the struggle between top-down and bottom-up design. The essay was first presented by the author at the Linux Kongress on May 27, 1997 in Wรผrzburg (Germany) and was published as part of the book in 1999.

The illustration on the cover of the book is a 1913 painting by Liubov Popova titled Composition with Figures and belongs to the collection of the State Tretyakov Gallery. The book was released under the Open Publication License v2.0 around 1999.

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๐Ÿ”— The Machine Stops

๐Ÿ”— Novels ๐Ÿ”— Radio ๐Ÿ”— Novels/Science fiction ๐Ÿ”— Novels/Short story

"The Machine Stops" is a science fiction short story (12,300 words) by E. M. Forster. After initial publication in The Oxford and Cambridge Review (November 1909), the story was republished in Forster's The Eternal Moment and Other Stories in 1928. After being voted one of the best novellas up to 1965, it was included that same year in the populist anthology Modern Short Stories. In 1973 it was also included in The Science Fiction Hall of Fame, Volume Two.

The story, set in a world where humanity lives underground and relies on a giant machine to provide its needs, predicted technologies similar to instant messaging and the Internet.

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