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A shaft passer is a hypothetical device that allows a spoked wheel to rotate despite having a shaft (such as the axle of another wheel) passing between its spokes. The device is usually mentioned as a joke between nerds, in the manner of a fool's errand, since there is no evidence of one ever having been constructed until very recently.

One of the earliest printed references to these devices was made by Richard Feynman, who was told by a colleague at Frankford Arsenal in Philadelphia that the cable-passing version of the device had been used during both world wars on German naval mine mooring cables, to prevent the mines from being caught by British cables swept along the sea bottom.

The device was supposed to work using a spoked, rimless wheel that allows cables to pass through as it rotates. The ends of the spokes are widened, and the cable is held together by a short curved sleeve through which these spoke ends slide.

🔗 Environment 🔗 Biology 🔗 Physics 🔗 Guild of Copy Editors 🔗 Energy 🔗 Chemical and Bio Engineering

Artificial photosynthesis is a chemical process that biomimics the natural process of photosynthesis to convert sunlight, water, and carbon dioxide into carbohydrates and oxygen. The term artificial photosynthesis is commonly used to refer to any scheme for capturing and storing the energy from sunlight in the chemical bonds of a fuel (a solar fuel). Photocatalytic water splitting converts water into hydrogen and oxygen and is a major research topic of artificial photosynthesis. Light-driven carbon dioxide reduction is another process studied that replicates natural carbon fixation.

Research of this topic includes the design and assembly of devices for the direct production of solar fuels, photoelectrochemistry and its application in fuel cells, and the engineering of enzymes and photoautotrophic microorganisms for microbial biofuel and biohydrogen production from sunlight.

Vital articles are lists of subjects for which the English Wikipedia should have corresponding featured-class articles. They serve as centralized watchlists to track the status of Wikipedia's most important articles. The very most important articles are in Level 1.

This page constitutes Level 3 of the vital articles list and includes approximately 1,000 articles. All articles from higher levels are also included in lower levels. For example, all 100 subjects on the Level 2 list (shown on this page in bold font) are included here in Level 3. And the Level 2 list also includes the 10 subjects on Level 1 (shown on this page in bold italics). A larger Level 4 list of 10,000 articles also exists, and a Level 5 list of 50,000 articles is in the process of being created.

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Articles should not be added or removed from this list without a consensus on the talk page. For more information on this list and the process for adding or removing articles, please see the Frequently Asked Questions (FAQ) page.

🔗 Philosophy

The teletransportation paradox or teletransport paradox (also known in alternative forms as the duplicates paradox) is a thought experiment on the philosophy of identity that challenges common intuitions on the nature of self and consciousness. It first appeared under this name in full published form presumably in Derek Parfit's 1984 book Reasons and Persons.

The Polish science-fiction writer Stanisław Lem described the same problem in the mid-twentieth century. He put it in writing in his philosophical text "Dialogs", 1957. Similarly, in Lem's Star Diaries ("Fourteenth Voyage") of 1957 the hero visits a planet and he finds himself recreated from a backup record, after his death from a meteorite strike, which on this planet is a very commonplace procedure.

Similar questions of identity have been raised as early as 1775.

I would be glad to know your Lordship's opinion whether when my brain has lost its original structure, and when some hundred years after the same materials are fabricated so curiously as to become an intelligent being, whether, I say that being will be me; or, if, two or three such beings should be formed out of my brain; whether they will all be me, and consequently one and the same intelligent being.

🔗 Shipwrecks

In maritime law, flotsam, jetsam, lagan, and derelict are specific kinds of shipwreck. The words have specific nautical meanings, with legal consequences in the law of admiralty and marine salvage. A shipwreck is defined as the remains of a ship that has been wrecked—a destroyed ship at sea, whether it has sunk or is floating on the surface of the water.

🔗 Medicine 🔗 Smithsonian Institution

During the 1940s–1960s, nude photographs were routinely taken of incoming freshmen at elite colleges in the United States, such as the Ivy Leagues and Seven Sisters schools. Purportedly taken to assess the posture and health of the students, the bulk of the photographs were produced by W. H. Sheldon, a psychologist and eugenicist who believed non-white races were intellectually stunted. Sheldon developed a theory that measuring a human body could predict the subject's intelligence, temperament, and moral worth. The inspiration to take mass photos for his research came from the founder of eugenics, Francis Galton, who proposed such a photo archive for the British population.

The institutions that had "posture photo" programs included Harvard, Yale, Princeton, Brown, Vassar, Wellesley, Mount Holyoke, Swarthmore, University of Pennsylvania, Hotchkiss, Syracuse, University of California, University of Wisconsin, Purdue, Brooklyn College, the Oregon Hospital for the Criminally Insane, and others. The years that each institution participated vary. Some schools, such as Harvard and Wellesley, had their own practice of taking posture photos well before Sheldon's involvement, as early as the 1880s.

Most of the photo archives were destroyed voluntarily by the schools in the 1960s and '70s, after ending their posture photo practices. After Sheldon's death in 1977, his personal archive of over 20,000 photos and negatives was acquired by the Smithsonian Institution's National Anthropological Archives. These were never displayed, and could only be viewed by researchers who petitioned the chief archivist. After a write-up in the New York Times Magazine in 1995, the Smithsonian sealed the documents completely, and destroyed the Yale archives upon request.

Some celebrities have mentioned their experiences getting their posture photo taken, including Sylvia Plath, Nora Ephron, Dick Cavett and Judith Martin (the etiquette expert known as Miss Manners). In the 2020s posture photos of the actors James Franciscus and Bill Hinnant resurfaced and were sold on eBay.

🔗 Religion 🔗 Bible 🔗 Linguistics

In corpus linguistics, a hapax legomenon ( also or ; pl. hapax legomena; sometimes abbreviated to hapax) is a word that occurs only once within a context, either in the written record of an entire language, in the works of an author, or in a single text. The term is sometimes incorrectly used to describe a word that occurs in just one of an author's works, but more than once in that particular work. Hapax legomenon is a transliteration of Greek ἅπαξ λεγόμενον, meaning "(something) being said (only) once".

The related terms dis legomenon, tris legomenon, and tetrakis legomenon respectively (, , ) refer to double, triple, or quadruple occurrences, but are far less commonly used.

Hapax legomena are quite common, as predicted by Zipf's law, which states that the frequency of any word in a corpus is inversely proportional to its rank in the frequency table. For large corpora, about 40% to 60% of the words are hapax legomena, and another 10% to 15% are dis legomena. Thus, in the Brown Corpus of American English, about half of the 50,000 distinct words are hapax legomena within that corpus.

Hapax legomenon refers to a word's appearance in a body of text, not to either its origin or its prevalence in speech. It thus differs from a nonce word, which may never be recorded, may find currency and may be widely recorded, or may appear several times in the work which coins it, and so on.

🔗 Telecommunications

Digital mobile radio (DMR) is a limited open digital mobile radio standard defined in the European Telecommunications Standards Institute (ETSI) Standard TS 102 361 parts 1–4 and used in commercial products around the world. DMR, along with P25 phase II and NXDN are the main competitor technologies in achieving 6.25 kHz equivalent bandwidth using the proprietary AMBE+2 vocoder. DMR and P25 II both use two-slot TDMA in a 12.5 kHz channel, while NXDN uses discrete 6.25 kHz channels using frequency division and TETRA uses a four-slot TDMA in a 25 kHz channel.

DMR was designed with three tiers. DMR tiers I and II (conventional) were first published in 2005, and DMR III (Trunked version) was published in 2012, with manufacturers producing products within a few years of each publication.

The primary goal of the standard is to specify a digital system with low complexity, low cost and interoperability across brands, so radio communications purchasers are not locked into a proprietary solution. In practice, given the current limited scope of the DMR standard, many vendors have introduced proprietary features that make their product offerings non-interoperable with other brands.