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๐ Merkle Tree
In cryptography and computer science, a hash tree or Merkle tree is a tree in which every leaf node is labelled with the cryptographic hash of a data block, and every non-leaf node is labelled with the cryptographic hash of the labels of its child nodes. Hash trees allow efficient and secure verification of the contents of large data structures. Hash trees are a generalization of hash lists and hash chains.
Demonstrating that a leaf node is a part of a given binary hash tree requires computing a number of hashes proportional to the logarithm of the number of leaf nodes of the tree; this contrasts with hash lists, where the number is proportional to the number of leaf nodes itself.
The concept of hash trees is named after Ralph Merkle, who patented it in 1979.
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- "Merkle Tree" | 2021-06-06 | 53 Upvotes 10 Comments
๐ Terry Fox
Terrance Stanley Fox (July 28, 1958ย โ June 28, 1981) was a Canadian athlete, humanitarian, and cancer research activist. In 1980, with one leg having been amputated due to cancer, he embarked on an east to west cross-Canada run to raise money and awareness for cancer research. Although the spread of his cancer eventually forced him to end his quest after 143 days and 5,373 kilometres (3,339ย mi), and ultimately cost him his life, his efforts resulted in a lasting, worldwide legacy. The annual Terry Fox Run, first held in 1981, has grown to involve millions of participants in over 60 countries and is now the world's largest one-day fundraiser for cancer research; over C$750ย million has been raised in his name, as of January 2018.
Fox was a distance runner and basketball player for his Port Coquitlam high school, now named after him, and Simon Fraser University. His right leg was amputated in 1977 after he was diagnosed with osteosarcoma, though he continued to run using an artificial leg. He also played wheelchair basketball in Vancouver, winning three national championships.
In 1980, he began the Marathon of Hope, a cross-country run to raise money for cancer research. He hoped to raise one dollar from each of Canada's 24ย million people. He began with little fanfare from St John's, Newfoundland and Labrador, in April and ran the equivalent of a full marathon every day. Fox had become a national star by the time he reached Ontario; he made numerous public appearances with businessmen, athletes, and politicians in his efforts to raise money. He was forced to end his run outside Thunder Bay when the cancer spread to his lungs. His hopes of overcoming the disease and completing his marathon ended when he died nine months later.
In addition to being the youngest person ever named a Companion of the Order of Canada, Fox won the 1980 Lou Marsh Award as the nation's top sportsman and was named Canada's Newsmaker of the Year in both 1980 and 1981. Considered a national hero, he has had many buildings, statues, roads, and parks named in his honour across the country.
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- "Terry Fox" | 2020-09-13 | 47 Upvotes 6 Comments
๐ Trans-African Highway Network
The Trans-African Highway network comprises transcontinental road projects in Africa being developed by the United Nations Economic Commission for Africa (UNECA), the African Development Bank (ADB), and the African Union in conjunction with regional international communities. They aim to promote trade and alleviate poverty in Africa through highway infrastructure development and the management of road-based trade corridors. The total length of the nine highways in the network is 56,683ย km (35,221ย mi).
In some documents the highways are referred to as "Trans-African Corridors" or "Road Corridors" rather than highways. The name Trans-African Highway and its variants are not in wide common usage outside of planning and development circles, and as of 2014 one does not see them signposted as such or labelled on maps, except in Kenya and Uganda where the MombasaโNairobiโKampalaโFort Portal section (or the KampalaโKigali feeder road) of Trans-African Highway 8 is sometimes referred to as the "Trans-Africa Highway".
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- "Trans-African Highway Network" | 2023-09-08 | 13 Upvotes 4 Comments
๐ Royal Mail Rubber Band
A Royal Mail rubber band is a small red elastic loop used by the postal delivery service in the United Kingdom. In the course of its work, the Royal Mail consumes nearly one billion rubber bands per year to tie together bundles of letters at sorting offices. In the 2000s, complaints about Royal Mail rubber bands littering the streets of Britain gave rise to ongoing press interest in this minor cultural phenomenon. The Royal Mail no longer uses red rubber bands.
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- "Royal Mail Rubber Band" | 2021-07-11 | 87 Upvotes 57 Comments
๐ The Man Behind AMD's Zen Microarchitecture: Jim Keller
Jim Keller (born 1958/1959) is a microprocessor engineer best known for his work at AMD and Apple. He was the lead architect of the AMD K8 microarchitecture (including the original Athlon 64) and was involved in designing the Athlon (K7) and Apple A4/A5 processors. He was also the coauthor of the specifications for the x86-64 instruction set and HyperTransport interconnect. From 2012 to 2015, he returned to AMD to work on the AMD K12 and Zen microarchitectures.
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- "The Man Behind AMD's Zen Microarchitecture: Jim Keller" | 2017-08-11 | 99 Upvotes 42 Comments
๐ Bruno Pontecorvo
Bruno Pontecorvo (Italian:ย [ponteหkษrvo]; Russian: ะััฬะฝะพ ะะฐะบัะธฬะผะพะฒะธั ะะพะฝัะตะบะพฬัะฒะพ, Bruno Maksimovich Pontecorvo; 22 August 1913 โ 24 September 1993) was an Italian and Soviet nuclear physicist, an early assistant of Enrico Fermi and the author of numerous studies in high energy physics, especially on neutrinos. A convinced communist, he defected to the Soviet Union in 1950, where he continued his research on the decay of the muon and on neutrinos. The prestigious Pontecorvo Prize was instituted in his memory in 1995.
The fourth of eight children of a wealthy Jewish-Italian family, Pontecorvo studied physics at the University of Rome La Sapienza, under Fermi, becoming the youngest of his Via Panisperna boys. In 1934 he participated in Fermi's famous experiment showing the properties of slow neutrons that led the way to the discovery of nuclear fission. He moved to Paris in 1934, where he conducted research under Irรจne and Frรฉdรฉric Joliot-Curie. Influenced by his cousin, Emilio Sereni, he joined the French Communist Party, as did his sisters Giuliana and Laura and brother Gillo. The Italian Fascist regime's 1938 racial laws against Jews caused his family members to leave Italy for Britain, France and the United States.
When the German Army closed in on Paris during the Second World War, Pontecorvo, his brother Gillo, cousin Emilio Sereni and Salvador Luria fled the city on bicycles. He eventually made his way to Tulsa, Oklahoma, where he applied his knowledge of nuclear physics to prospecting for oil and minerals. In 1943, he joined the British Tube Alloys team at the Montreal Laboratory in Canada. This became part of the Manhattan Project to develop the first atomic bombs. At Chalk River Laboratories, he worked on the design of the nuclear reactor ZEEP, the first reactor outside of the United States that went critical in 1945, followed by the NRX reactor in 1947. He also looked into cosmic rays, the decay of muons, and what would become his obsession, neutrinos. He moved to Britain in 1949, where he worked for the Atomic Energy Research Establishment at Harwell.
After his defection to the Soviet Union in 1950, he worked at the Joint Institute for Nuclear Research (JINR) in Dubna. He had proposed using chlorine to detect neutrinos. In a 1959 paper, he argued that the electron neutrino (
ฮฝ
e) and the muon neutrino (
ฮฝ
ฮผ) were different particles. Solar neutrinos were detected by the Homestake Experiment, but only between one third and one half of the predicted number were found. In response to this solar neutrino problem, he proposed a phenomenon known as neutrino oscillation, whereby electron neutrinos became muon neutrinos. The existence of the oscillations was finally established by the Super-Kamiokande experiment in 1998. He also predicted in 1958 that supernovae would produce intense bursts of neutrinos, which was confirmed in 1987 when Supernova SN1987A was detected by neutrino detectors.
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- "Bruno Pontecorvo" | 2021-10-27 | 13 Upvotes 4 Comments
๐ Telescript programming language
Telescript is an Agent-oriented programming language written by General Magic as part of the overall Magic Cap system. Telescript programs used a modified C-like syntax known as High Telescript and were compiled to a stack-based language called Low Telescript for execution. Low Telescript ran within virtual machine interpreters, or "Telescript engines", on host computers.
The basic model of Telescript is similar to Java, and differs primarily in where the applications would run. Java was modelled to make it possible to download Java applications onto any platform and run them locally. Telescript essentially reversed this, allowing end-user equipment with limited capabilities to upload Telescript programs to servers to allow them to take advantage of the server's capabilities. Telescript could even migrate a running program; the language included features to marshal a program's code and serialized state, transfer it to another Telescript engine (on a device or a server) to continue execution, and finally return to the originating client or server device to deliver its output.
General Magic had originally developed as a team within Apple Inc., and were spun off in 1990. When they began to generate some press buzz in 1992, Apple decided to enter the same market with their Newton tablet computer. General Magic were unable to find a niche within the market, and Telescript services were soon deprecated in favor of new products unrelated to mobile computing.
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- "The Telescript Programming Language" | 2023-09-08 | 48 Upvotes 25 Comments
- "Telescript programming language" | 2018-07-08 | 66 Upvotes 13 Comments
๐ A function that represents all primes
In number theory, a formula for primes is a formula generating the prime numbers, exactly and without exception. No such formula which is efficiently computable is known. A number of constraints are known, showing what such a "formula" can and cannot be.
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- "A function that represents all primes" | 2019-10-05 | 16 Upvotes 8 Comments
๐ 999-Year Lease
A 999-year lease, under historic common law, is an essentially permanent lease of property. The lease locations are mainly in Britain, its former colonies, and the Commonwealth.
A former colony, the Republic of Mauritius (The Raphael Fishing Company Ltd v. The State of Mauritius & Anor (Mauritius) [2008] UKPC 43 (30 July 2008)) established legal precedent on 30 July 2008 in respect of a 'permanent lease' on St. Brandon.
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- "999-Year Lease" | 2019-07-18 | 39 Upvotes 28 Comments
๐ Degrowth
Degrowth (French: dรฉcroissance) is a political, economic, and social movement based on ecological economics, anti-consumerist and anti-capitalist ideas. It is also considered an essential economic strategy responding to the limits-to-growth dilemma (see The Path to Degrowth in Overdeveloped Countries and post-growth). Degrowth thinkers and activists advocate for the downscaling of production and consumption โ the contraction of economies โ arguing that overconsumption lies at the root of long term environmental issues and social inequalities. Key to the concept of degrowth is that reducing consumption does not require individual martyring or a decrease in well-being. Rather, "degrowthers" aim to maximize happiness and well-being through non-consumptive meansโsharing work, consuming less, while devoting more time to art, music, family, nature, culture and community.
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- "Degrowth" | 2012-10-28 | 40 Upvotes 56 Comments