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๐ Sangaku
Sangaku or San Gaku (็ฎ้ก; lit. translation: calculation tablet) are Japanese geometrical problems or theorems on wooden tablets which were placed as offerings at Shinto shrines or Buddhist temples during the Edo period by members of all social classes.
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- "Sangaku" | 2017-03-01 | 55 Upvotes 2 Comments
๐ Prawo Jazdy (Alleged Criminal)
"Prawo Jazdy" was a supposed Polish national who was listed by the Garda Sรญochรกna in a police criminal database as having committed more than 50 traffic violations in Ireland. A 2007 memorandum stated that an investigation revealed prawo jazdy [หpra.vษ หjaz.dษจ] to be Polish for 'driving licence', with the error arising due to officers mistaking the phrase, printed on Polish driving licenses, to be a personal name while issuing traffic tickets.
๐ Diatoms make 20% of Earth's oxygen and can double in population every 24 hours
Diatoms (diรก-tom-os 'cut in half', from diรก, 'through' or 'apart'; and the root of tรฉm-n-ล, 'I cut'.) are a major group of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of the Earth's biomass: they generate about 20 to 50 percent of the oxygen produced on the planet each year, take in over 6.7 billion metric tons of silicon each year from the waters in which they live, and contribute nearly half of the organic material found in the oceans. The shells of dead diatoms can reach as much as a half-mile (800m) deep on the ocean floor, and the entire Amazon basin is fertilized annually by 27 million tons of diatom shell dust transported by transatlantic winds from the African Sahara, much of it from the Bodรฉlรฉ Depression, which was once made up a system of fresh-water lakes.
Diatoms are unicellular: they occur either as solitary cells or in colonies, which can take the shape of ribbons, fans, zigzags, or stars. Individual cells range in size from 2 to 200 micrometers. In the presence of adequate nutrients and sunlight, an assemblage of living diatoms doubles approximately every 24 hours by asexual multiple fission; the maximum life span of individual cells is about six days. Diatoms have two distinct shapes: a few (centric diatoms) are radially symmetric, while most (pennate diatoms) are broadly bilaterally symmetric. A unique feature of diatom anatomy is that they are surrounded by a cell wall made of silica (hydrated silicon dioxide), called a frustule. These frustules have structural coloration due to their photonic nanostructure, prompting them to be described as "jewels of the sea" and "living opals". Movement in diatoms primarily occurs passively as a result of both water currents and wind-induced water turbulence; however, male gametes of centric diatoms have flagella, permitting active movement for seeking female gametes. Similar to plants, diatoms convert light energy to chemical energy by photosynthesis, although this shared autotrophy evolved independently in both lineages. Unusually for autotrophic organisms, diatoms possess a urea cycle, a feature that they share with animals, although this cycle is used to different metabolic ends in diatoms. The family Rhopalodiaceae also possess a cyanobacterial endosymbiont called a spheroid body. This endosymbiont has lost its photosynthetic properties, but has kept its ability to perform nitrogen fixation, allowing the diatom to fix atmospheric nitrogen.
The study of diatoms is a branch of phycology. Diatoms are classified as eukaryotes, organisms with a membrane-bound cell nucleus, that separates them from the prokaryotes archaea and bacteria. Diatoms are a type of plankton called phytoplankton, the most common of the plankton types. Diatoms also grow attached to benthic substrates, floating debris, and on macrophytes. They comprise an integral component of the periphyton community. Another classification divides plankton into eight types based on size: in this scheme, diatoms are classed as microalgae. Several systems for classifying the individual diatom species exist. Fossil evidence suggests that diatoms originated during or before the early Jurassic period, which was about 150 to 200 million years ago.
Diatoms are used to monitor past and present environmental conditions, and are commonly used in studies of water quality. Diatomaceous earth (diatomite) is a collection of diatom shells found in the earth's crust. They are soft, silica-containing sedimentary rocks which are easily crumbled into a fine powder and typically have a particle size of 10 to 200 ฮผm. Diatomaceous earth is used for a variety of purposes including for water filtration, as a mild abrasive, in cat litter, and as a dynamite stabilizer.
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- "Diatoms make 20% of Earth's oxygen and can double in population every 24 hours" | 2019-07-07 | 11 Upvotes 2 Comments
๐ SHA-3 NIST announcement controversy
SHA-3 (Secure Hash Algorithm 3) is the latest member of the Secure Hash Algorithm family of standards, released by NIST on August 5, 2015. Although part of the same series of standards, SHA-3 is internally different from the MD5-like structure of SHA-1 and SHA-2.
SHA-3 is a subset of the broader cryptographic primitive family Keccak (), designed by Guido Bertoni, Joan Daemen, Michaรซl Peeters, and Gilles Van Assche, building upon RadioGatรบn. Keccak's authors have proposed additional uses for the function, not (yet) standardized by NIST, including a stream cipher, an authenticated encryption system, a "tree" hashing scheme for faster hashing on certain architectures, and AEAD ciphers Keyak and Ketje.
Keccak is based on a novel approach called sponge construction. Sponge construction is based on a wide random function or random permutation, and allows inputting ("absorbing" in sponge terminology) any amount of data, and outputting ("squeezing") any amount of data, while acting as a pseudorandom function with regard to all previous inputs. This leads to great flexibility.
NIST does not currently plan to withdraw SHA-2 or remove it from the revised Secure Hash Standard. The purpose of SHA-3 is that it can be directly substituted for SHA-2 in current applications if necessary, and to significantly improve the robustness of NIST's overall hash algorithm toolkit.
The creators of the Keccak algorithms and the SHA-3 functions suggest using the faster function KangarooTwelve with adjusted parameters and a new tree hashing mode without extra overhead for small message sizes.
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- "SHA-3 NIST announcement controversy" | 2014-07-20 | 77 Upvotes 33 Comments
๐ Stochastic Resonance
Stochastic resonance (SR) is a phenomenon where a signal that is normally too weak to be detected by a sensor, can be boosted by adding white noise to the signal, which contains a wide spectrum of frequencies. The frequencies in the white noise corresponding to the original signal's frequencies will resonate with each other, amplifying the original signal while not amplifying the rest of the white noise (thereby increasing the signal-to-noise ratio which makes the original signal more prominent). Further, the added white noise can be enough to be detectable by the sensor, which can then filter it out to effectively detect the original, previously undetectable signal.
This phenomenon of boosting undetectable signals by resonating with added white noise extends to many other systems, whether electromagnetic, physical or biological, and is an area of research.
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- "Stochastic Resonance" | 2018-03-10 | 125 Upvotes 26 Comments
๐ Romanesco broccoli has a form naturally approximating a fractal
Romanesco broccoli (also known as Roman cauliflower, Broccolo Romanesco, Romanesque cauliflower, or simply Romanesco) is an edible flower bud of the species Brassica oleracea. First documented in Italy in the 16th century, it is chartreuse in color, and has a form naturally approximating a fractal. When compared to a traditional cauliflower, it has a firmer texture and delicate, nutty flavor.
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- "Romanesco broccoli has a form naturally approximating a fractal" | 2020-12-28 | 10 Upvotes 1 Comments
๐ The Theory of Interstellar Trade, Paul Krugman (1978)
The Theory of Interstellar Trade is a paper written in 1978 by the economist Paul Krugman. The paper was first published in March 2010 in the journal Economic Inquiry. He described the paper as something he wrote to cheer himself up when he was an "oppressed assistant professor" caught up in the academic rat race.
Krugman analyzed the question of
How should interest rates on goods in transit be computed when the goods travel at close to the speed of light? This is a problem because the time taken in transit will appear less to an observer traveling with the goods than to a stationary observer.
Krugman emphasized that in spite of its farcical subject matter, the economic analysis in the paper is correctly done. In his own words,
while the subject of this paper is silly, the analysis actually does make sense. This paper, then, is a serious analysis of a ridiculous subject, which is of course the opposite of what is usual in economics.
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- "The Theory of Interstellar Trade, Paul Krugman (1978)" | 2009-09-12 | 21 Upvotes 6 Comments
๐ Chesapeake Bay Impact Crater
The Chesapeake Bay impact crater was formed by a bolide that impacted the eastern shore of North America about 35.5 ยฑ 0.3 million years ago, in the late Eocene epoch. It is one of the best-preserved "wet-target" impact craters in the world.
Continued slumping of sediments over the rubble of the crater has helped shape the Chesapeake Bay.
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- "Chesapeake Bay Impact Crater" | 2019-12-17 | 113 Upvotes 23 Comments
๐ Council of Trent
The Council of Trent (Latin: Concilium Tridentinum), held between 1545 and 1563 in Trent (or Trento), now in northern Italy, was the 19th ecumenical council of the Catholic Church. Prompted by the Protestant Reformation at the time, it has been described as the embodiment of the Counter-Reformation.
The Council issued condemnations of what it defined to be heresies committed by proponents of Protestantism, and also issued key statements and clarifications of the Church's doctrine and teachings, including scripture, the biblical canon, sacred tradition, original sin, justification, salvation, the sacraments, the Mass, and the veneration of saints. The Council met for twenty-five sessions between 13 December 1545 and 4 December 1563. Pope Paul III, who convoked the Council, oversaw the first eight sessions (1545โ47), while the twelfth to sixteenth sessions (1551โ52) were overseen by Pope Julius III and the seventeenth to twenty-fifth sessions (1562โ63) by Pope Pius IV.
The consequences of the Council were also significant with regard to the Church's liturgy and practices. In its decrees, the Council made the Latin Vulgate the official biblical text of the Roman Church (without prejudice to the original texts in Hebrew and Greek, nor to other traditional translations of the Church, but favoring the Latin language over vernacular translations, such as the controversial English-language Tyndale Bible). In doing so, they commissioned the creation of a revised and standardized Vulgate in light of textual criticism, although this was not achieved until the 1590s. The Council also officially affirmed (for the second time at an ecumenical council) the traditional Catholic Canon of biblical books in response to the increasing Protestant exclusion of the deuterocanonical books. The former dogmatic affirmation of the Canonical books was at the Council of Florence in the 1441 bull Cantate Domino, as affirmed by Pope Leo XIII in his 1893 encyclical Providentissimus Deus (#20). In 1565, a year after the Council finished its work, Pius IV issued the Tridentine Creed (after Tridentum, Trent's Latin name) and his successor Pius V then issued the Roman Catechism and revisions of the Breviary and Missal in, respectively, 1566, 1568 and 1570. These, in turn, led to the codification of the Tridentine Mass, which remained the Church's primary form of the Mass for the next four hundred years.
More than three hundred years passed until the next ecumenical council, the First Vatican Council, was convened in 1869.
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- "Council of Trent" | 2023-06-02 | 24 Upvotes 12 Comments
๐ Paternoster
Pater Noster, or the Lord's Prayer, is a prayer in Christianity.
Pater Noster or Paternoster may also refer to:
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- "Paternoster" | 2015-03-29 | 127 Upvotes 72 Comments