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In computer science and mathematics, a full employment theorem is a term used, often humorously, to refer to a theorem which states that no algorithm can optimally perform a particular task done by some class of professionals. The name arises because such a theorem ensures that there is endless scope to keep discovering new techniques to improve the way at least some specific task is done.

For example, the full employment theorem for compiler writers states that there is no such thing as a provably perfect size-optimizing compiler, as such a proof for the compiler would have to detect non-terminating computations and reduce them to a one-instruction infinite loop. Thus, the existence of a provably perfect size-optimizing compiler would imply a solution to the halting problem, which cannot exist. This also implies that there may always be a better compiler since the proof that one has the best compiler cannot exist. Therefore, compiler writers will always be able to speculate that they have something to improve. A similar example in practical computer science is the idea of no free lunch in search and optimization, which states that no efficient general-purpose solver can exist, and hence there will always be some particular problem whose best known solution might be improved.

Similarly, Gödel's incompleteness theorems have been called full employment theorems for mathematicians. In theoretical computer science this field of study is known as Kolmogorov complexity, or the smallest program which outputs a given string.

Tasks such as virus writing and detection, and spam filtering and filter-breaking are also subject to Rice's theorem.

🔗 Cryptography 🔗 Cryptography/Computer science

In cryptography and steganography, plausibly deniable encryption describes encryption techniques where the existence of an encrypted file or message is deniable in the sense that an adversary cannot prove that the plaintext data exists.

The users may convincingly deny that a given piece of data is encrypted, or that they are able to decrypt a given piece of encrypted data, or that some specific encrypted data exists. Such denials may or may not be genuine. For example, it may be impossible to prove that the data is encrypted without the cooperation of the users. If the data is encrypted, the users genuinely may not be able to decrypt it. Deniable encryption serves to undermine an attacker's confidence either that data is encrypted, or that the person in possession of it can decrypt it and provide the associated plaintext.

In their pivotal 1996 paper, Ran Canetti, Cynthia Dwork, Moni Naor, and Rafail Ostrovsky introduced the concept of deniable encryption, a cryptographic breakthrough that ensures privacy even under coercion. This concept allows encrypted communication participants to plausibly deny the true content of their messages. Their work lays the foundational principles of deniable encryption, illustrating its critical role in protecting privacy against forced disclosures. This research has become a cornerstone for future advancements in cryptography, emphasizing the importance of deniable encryption in maintaining communication security. The notion of deniable encryption was used by Julian Assange and Ralf Weinmann in the Rubberhose filesystem.

🔗 Food and drink 🔗 Brands 🔗 Food and drink/Beverages

OK Soda was a soft drink created by The Coca-Cola Company in 1993 that courted the American Generation X demographic with unusual advertising tactics, including neo-noir design, chain letters and deliberately negative publicity. After the soda did not sell well in select test markets, it was officially declared out of production in 1995 before reaching nationwide distribution. The drink's slogan was "Things are going to be OK."

🔗 United States 🔗 Africa 🔗 African diaspora 🔗 United States/Kentucky 🔗 Africa/Liberia

Kentucky in Africa was a colony in present-day Montserrado County, Liberia, founded in 1828 and settled by American free people of color, many of them former slaves. A state affiliate of the American Colonization Society, the Kentucky State Colonization Society raised money to transport people of color from Kentucky—freeborn volunteers as well as enslaved individuals set free on the condition that they leave the United States for Liberia. The Kentucky society bought a 40-square-mile (100 km²) site along the Saint Paul River (quite near the site of the present-day capital city of Monrovia) and named it Kentucky in Africa. Clay-Ashland. named after Henry Clay's Ashland Plantation, was the colony's primary settlement.

Notable residents of Kentucky in Africa include Alfred Francis Russell, the 10th President of Liberia, and William D. Coleman, the 13th President of Liberia, whose family settled in Clay-Ashland after emigrating from Fayette County, Kentucky.

Kentucky in Africa was annexed by Liberia in about 1847.

🔗 Physics 🔗 Astronomy

In astrophysics and physical cosmology, Olbers' paradox, named after the German astronomer Heinrich Wilhelm Olbers (1758–1840), also known as the "dark night sky paradox", is the argument that the darkness of the night sky conflicts with the assumption of an infinite and eternal static universe. In the hypothetical case that the universe is static, homogeneous at a large scale, and populated by an infinite number of stars, any line of sight from Earth must end at the surface of a star and hence the night sky should be completely illuminated and very bright. This contradicts the observed darkness and non-uniformity of the night.

The darkness of the night sky is one of the pieces of evidence for a dynamic universe, such as the Big Bang model. That model explains the observed non-uniformity of brightness by invoking spacetime's expansion, which lengthens the light originating from the Big Bang to microwave levels via a process known as redshift; this microwave radiation background has wavelengths much longer than those of visible light, and so appears dark to the naked eye. Other explanations for the paradox have been offered, but none have wide acceptance in cosmology.

🔗 Literature

Some writers have had prolific careers with hundreds of their works being published. While some best-selling authors have written a small number of books that have sold millions of copies, others have had lengthy careers and maintained a high level of output year after year. Dame Agatha Christie, the most-published novelist in history, is estimated to have sold 4 billion books, having written 69 novels and 19 plays. Her works were published between 1920 and 1976, equating to around three publications every two years. Dame Barbara Cartland has also sold millions of copies of her books but wrote many more than Christie. She spent 80 years as a novelist with 722 books published, averaging one book released every 40 days of her career. While Cartland wrote a significant number of full-length novels, other authors have been published many more times but have specialised in short stories. Spanish author Corín Tellado wrote over 4,000 novellas, selling 400 million copies of her books.

Not all authors work alone. Groups of writers, sometimes led by one central figure, have published under shared pseudonyms. The Stratemeyer Syndicate, started by Edward Stratemeyer in 1905, created numerous book series including 190 volumes of The Hardy Boys and 175 volumes of Nancy Drew. More than 1,300 books were published by the group, and although Edward L. Stratemeyer wrote several hundred, he also employed ghostwriters to keep up with the demand. These writers were given storylines and strict guidelines to follow to ensure a level of consistency within each series. Amongst the writing team was Howard R. Garis, who contributed several hundred books to the collection, one of the most active authors. Sales were estimated at over two hundred million copies before the syndicate was sold to Simon & Schuster in 1984.

Most authors carefully craft their work, writing and rewriting several times before publication. Some authors simply use pen and paper, while others such as Isaac Asimov spent hours at a stretch working at a typewriter. Philip M. Parker, by one measure the world's most prolific author, has an entirely different approach. Parker has over 200,000 titles listed on Amazon.com, having developed an algorithm to gather publicly available data and compile it into book form. The computer-generated nature of the books is not detailed on the sales page and the books are printed only when ordered.

🔗 Finance & Investment 🔗 Economics

A perpetual bond, also known colloquially as a perpetual or perp, is a bond with no maturity date, therefore allowing it to be treated as equity, not as debt. Issuers pay coupons on perpetual bonds forever, and they do not have to redeem the principal. Perpetual bond cash flows are, therefore, those of a perpetuity.

🔗 Animal anatomy 🔗 Neuroscience 🔗 Anatomy 🔗 Anatomy/Neuroanatomy

The enteric nervous system (ENS) or intrinsic nervous system is one of the main divisions of the autonomic nervous system (ANS) and consists of a mesh-like system of neurons that governs the function of the gastrointestinal tract. It is capable of acting independently of the sympathetic and parasympathetic nervous systems, although it may be influenced by them. The ENS is also called the second brain.It is derived from neural crest cells.

The enteric nervous system is capable of operating independently of the brain and spinal cord, but does rely on innervation from the autonomic nervous system via the vagus nerve and prevertebral ganglia in healthy subjects. However, studies have shown that the system is operable with a severed vagus nerve. The neurons of the enteric nervous system control the motor functions of the system, in addition to the secretion of gastrointestinal enzymes. These neurons communicate through many neurotransmitters similar to the CNS, including acetylcholine, dopamine, and serotonin. The large presence of serotonin and dopamine in the gut are key areas of research for neurogastroenterologists.

🔗 Psychology 🔗 Education

Bloom's 2 sigma problem refers to an educational phenomenon observed by educational psychologist Benjamin Bloom and initially reported in 1984 in the journal Educational Researcher. Bloom found that the average student tutored one-to-one using mastery learning techniques performed two standard deviations better than students who learn via conventional instructional methods — that is, "the average tutored student was above 98% of the students in the control class". Additionally, the variation of the students' achievement changed: "about 90% of the tutored students ... attained the level of summative achievement reached by only the highest 20%" of the control class. Bloom's graduate students J. Anania and A. J. Burke conducted studies of this effect at different grade levels and in different schools, observing students with "great differences in cognitive achievement, attitudes, and academic self-concept".