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🔗 Computer science 🔗 Mathematics

In computer science and graph theory, the Canadian traveller problem (CTP) is a generalization of the shortest path problem to graphs that are partially observable. In other words, the graph is revealed while it is being explored, and explorative edges are charged even if they do not contribute to the final path.

This optimization problem was introduced by Christos Papadimitriou and Mihalis Yannakakis in 1989 and a number of variants of the problem have been studied since. The name supposedly originates from conversations of the authors who learned of a difficulty Canadian drivers had: traveling a network of cities with snowfall randomly blocking roads. The stochastic version, where each edge is associated with a probability of independently being in the graph, has been given considerable attention in operations research under the name "the Stochastic Shortest Path Problem with Recourse" (SSPPR).

🔗 Biography 🔗 Climate change 🔗 Women 🔗 Guild of Copy Editors 🔗 Biography/politics and government 🔗 Sweden 🔗 Autism

Greta Tintin Eleonora Ernman Thunberg (Swedish: [ˈɡrêːta ˈtʉ̂ːnbærj] (listen); born 3 January 2003) is a Swedish environmental activist who has gained international recognition for promoting the view that humanity is facing an existential crisis arising from climate change. Thunberg is known for her youth and her straightforward speaking manner, both in public and to political leaders and assemblies, in which she criticizes world leaders for their failure to take sufficient action to address the climate crisis.

Thunberg's activism started after convincing her parents to adopt several lifestyle choices to reduce their own carbon footprint. In August 2018, at age 15, she started spending her school days outside the Swedish parliament to call for stronger action on climate change by holding up a sign reading Skolstrejk för klimatet (School strike for climate). Soon, other students engaged in similar protests in their own communities. Together, they organised a school climate strike movement under the name Fridays for Future. After Thunberg addressed the 2018 United Nations Climate Change Conference, student strikes took place every week somewhere in the world. In 2019, there were multiple coordinated multi-city protests involving over a million students each. To avoid flying, Thunberg sailed to North America where she attended the 2019 UN Climate Action Summit. Her speech there, in which she exclaimed "how dare you", was widely taken up by the press and incorporated into music.

Her sudden rise to world fame has made her both a leader and a target for critics. Her influence on the world stage has been described by The Guardian and other newspapers as the "Greta effect". She has received numerous honours and awards including: honorary Fellowship of the Royal Scottish Geographical Society; Time magazine's 100 most influential people and the youngest Time Person of the Year; inclusion in the Forbes list of The World's 100 Most Powerful Women (2019) and two consecutive nominations for the Nobel Peace Prize (2019 and 2020).

🔗 Genetics 🔗 Amphibians and Reptiles

The fertile hybrids of European water frogs (genus Pelophylax) reproduce by hybridogenesis (hemiclonally). This means that during gametogenesis, they discard the genome of one of the parental species and produce gametes of the other parental species (containing a genome not recombined with the genome of the first parental species). The first parental genome is restored by fertilization of these gametes with gametes from the first species (sexual host). In all-hybrid populations of the edible frog Pelophylax kl. esculentus, however, triploid hybrids provide this missing genome.

Because half of the genome is transmitted to the next generation clonally (not excluded unrecombined intact genome), and only the other half sexually (recombined genome of the sexual host), the hybridogenesis is a hemiclonal mode of reproduction.

For example, the edible frog Pelophylax kl. esculentus (mostly RL genome), which is a hybridogenetic hybrid of the marsh frog P. ridibundus (RR) and the pool frog P. lessonae (LL), usually excludes the lessonae genome (L) and generates gametes of the P. ridibundus (R). In other words, edible frogs produce gametes of marsh frogs.

The hybrid populations are propagated, however, not by the above primary hybridisations, but predominantly by backcrosses with one of the parental species they coexist (live in sympatry) with (see below in the middle).

Since the hybridogenetic hybrids require another taxon as sexual host to reproduce, usually one of the parental species, they are called kleptons (with "kl." in scientific names).

There are three known hybridogenetic hybrids of the European water frogs:

• edible frog Pelophylax kl. esculentus (usually genotype RL):
  pool frog P. lessonae (LL) × P. ridibundus (RR)
• Graf's hybrid frog Pelophylax kl. grafi (PR):
  Perez's frog P. perezi (PP) × P. ridibundus (RR) or
  Perez's frog P. perezi (PP) × edible frog P. kl. esculentus (RE)
  (it is unclear which one crossing was the primary hybridisation)
• Italian edible frog Pelophylax kl. hispanicus (RB):
  Italian pool frog P. bergeri (BB) × P. ridibundus (RR)

🔗 Philosophy 🔗 Philosophy/Logic 🔗 Philosophy/Philosophy of mind

Bonini's paradox, named after Stanford business professor Charles Bonini, explains the difficulty in constructing models or simulations that fully capture the workings of complex systems (such as the human brain).

🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Military history/Military science, technology, and theory 🔗 Military history/Weaponry 🔗 Physics 🔗 Chemistry

FOGBANK is a code name given to a material used in nuclear weapons such as the W76, W78 and W80.

FOGBANK's precise nature is classified; in the words of former Oak Ridge general manager Dennis Ruddy, "The material is classified. Its composition is classified. Its use in the weapon is classified, and the process itself is classified." Department of Energy Nuclear Explosive Safety documents simply describe it as a material "used in nuclear weapons and nuclear explosives" along with lithium hydride (LiH) and lithium deuteride (LiD), beryllium (Be), uranium hydride (UH₃), and plutonium hydride.

However National Nuclear Security Administration (NNSA) Administrator Tom D'Agostino disclosed the role of FOGBANK in the weapon: "There's another material in the—it's called interstage material, also known as fog bank", and arms experts believe that FOGBANK is an aerogel material which acts as an interstage material in a nuclear warhead; i.e., a material designed to become a superheated plasma following the detonation of the weapon's fission stage, the plasma then triggering the fusion-stage detonation.

🔗 Archaeology 🔗 Croatia

The Liber Linteus Zagrabiensis (Latin for "Linen Book of Zagreb", also rarely known as Liber Agramensis, "Book of Agram") is the longest Etruscan text and the only extant linen book, dated to the 3rd century BCE. It remains mostly untranslated because of the lack of knowledge about the Etruscan language, though the few words which can be understood indicate that the text is most likely a ritual calendar.

The fabric of the book was preserved when it was used for mummy wrappings in Ptolemaic Egypt. The mummy was bought in Alexandria in 1848 and since 1867 both the mummy and the manuscript have been kept in Zagreb, Croatia, now in a refrigerated room at the Archaeological Museum.

🔗 Germany

Rinderkennzeichnungs- und Rindfleischetikettierungsüberwachungsaufgabenübertragungsgesetz listen  (RkReÜAÜG) (literally, Cattle marking and beef labeling supervision duties delegation law) was a law of the German state of Mecklenburg-Vorpommern of 1999, repealed in 2013. It dealt with the supervision of the labeling of beef.

The name is an example of the virtually unlimited compounding of nouns that is possible in many Germanic languages. German orthography uses "closed" compounds, concatenating nouns to form one long word. This is unlike most English compounds, which are separated using spaces or hyphens.

Strictly speaking, it is made up of two words, because a hyphen at the end of a word is used to show that the word will end in the same way as the following. Consequently, the two words would be Rinderkennzeichnungsüberwachungsaufgabenübertragungsgesetz and Rindfleischetikettierungsüberwachungsaufgabenübertragungsgesetz.

This is the official short title of the law; its full name is Gesetz zur Übertragung der Aufgaben für die Überwachung der Rinderkennzeichnung und Rindfleischetikettierung, corresponding to Law on delegation of duties for supervision of cattle marking and beef labeling. Most German laws have a short title consisting of a composite noun.

Words as long as this are not at all common in German. When the law was proposed in the state parliament, the members reacted with laughter and the responsible minister Till Backhaus apologized for the "possibly excessive length". In 1999, the German Language Society nominated Rindfleischetikettierungsüberwachungsaufgabenübertragungsgesetz for its Word of the Year award, but it lost to das Millennium, a Latin word that gained in usage at that time, complementing the German word for millennium, Jahrtausend.

In 2003, a decree was established that modified some real estate-related regulations; its name was longer than the above law: Grundstücksverkehrsgenehmigungszuständigkeitsübertragungsverordnung (long title: Verordnung zur Übertragung der Zuständigkeiten des Oberfinanzpräsidenten der Oberfinanzdirektion Berlin nach § 8 Satz 2 der Grundstücksverkehrsordnung auf das Bundesamt zur Regelung offener Vermögensfragen, GrundVZÜV), roughly Regulation on the delegation of authority concerning land conveyance permissions. At 67 letters, it surpassed the RkReÜAÜG, but was repealed in 2007.

🔗 Medicine 🔗 Psychology 🔗 Rodents

Rat Park was a series of studies into drug addiction conducted in the late 1970s and published between 1978 and 1981 by Canadian psychologist Bruce K. Alexander and his colleagues at Simon Fraser University in British Columbia, Canada.

Alexander's hypothesis was that drugs do not cause addiction, and that the apparent addiction to opiate drugs commonly observed in laboratory rats exposed to them is attributable to their living conditions, and not to any addictive property of the drug itself.

To test his hypothesis, Alexander built Rat Park, a large housing colony, 200 times the floor area of a standard laboratory cage. There were 16–20 rats of both sexes in residence, food, balls and wheels for play, and enough space for mating. The results of the experiment appeared to support his hypothesis.

The two major science journals, Science and Nature, rejected Alexander, Coambs, and Hadaway's first paper, which appeared instead in Psychopharmacology in 1978. The paper's publication initially attracted no response. Within a few years, Simon Fraser University withdrew Rat Park's funding.

🔗 Biography 🔗 AIDS

Robert Rayford (February 3, 1953 – May 15 or 16, 1969), sometimes identified as Robert R. due to his age, was a teenager from Missouri who has been suggested to represent the earliest case of HIV/AIDS in North America based on evidence published in 1988 in which the authors claimed indicated he was "infected with a virus closely related or identical to human immunodeficiency virus type 1." Rayford died of pneumonia, but his other symptoms baffled the doctors who treated him. A study published in 1988 reported the detection of antibodies against HIV. Results of testing for HIV genetic material were reported once at a scientific conference in Australia in 1999; however, the data have never been published in a peer-reviewed medical or scientific journal.

🔗 Computer science

The Weissman score is an efficiency metric for lossless compression applications, which was developed for fictional use. It compares both required time and compression ratio of measured applications, with those of a de facto standard according to the data type. It was developed by Tsachy Weissman, a professor at Stanford University, and Vinith Mishra, a graduate student, at the request of producers for HBO's television series Silicon Valley, about a fictional tech start-up.

The formula is the following; where r is the compression ratio, T is the time required to compress, the overlined ones are the same metrics for a standard compressor, and alpha is a scaling constant.

Weissman score was used in Dropbox Tech Blog to explain real-world work on lossless compression.