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🔗 Mathematics

In mathematics, the Bernoulli numbers B_n are a sequence of rational numbers which occur frequently in number theory. The Bernoulli numbers appear in (and can be defined by) the Taylor series expansions of the tangent and hyperbolic tangent functions, in Faulhaber's formula for the sum of m-th powers of the first n positive integers, in the Euler–Maclaurin formula, and in expressions for certain values of the Riemann zeta function.

The values of the first 20 Bernoulli numbers are given in the adjacent table. Two conventions are used in the literature, denoted here by ${\displaystyle B_{n}^{-{}}}$ and ${\displaystyle B_{n}^{+{}}}$; they differ only for n = 1, where ${\displaystyle B_{1}^{-{}}=-1/2}$ and ${\displaystyle B_{1}^{+{}}=+1/2}$. For every odd n > 1, B_n = 0. For every even n > 0, B_n is negative if n is divisible by 4 and positive otherwise. The Bernoulli numbers are special values of the Bernoulli polynomials ${\displaystyle B_{n}(x)}$, with ${\displaystyle B_{n}^{-{}}=B_{n}(0)}$ and ${\displaystyle B_{n}^{+}=B_{n}(1)}$ (Weisstein 2016).

The Bernoulli numbers were discovered around the same time by the Swiss mathematician Jacob Bernoulli, after whom they are named, and independently by Japanese mathematician Seki Kōwa. Seki's discovery was posthumously published in 1712 (Selin 1997, p. 891; Smith & Mikami 1914, p. 108) in his work Katsuyo Sampo; Bernoulli's, also posthumously, in his Ars Conjectandi of 1713. Ada Lovelace's note G on the Analytical Engine from 1842 describes an algorithm for generating Bernoulli numbers with Babbage's machine (Menabrea 1842, Note G). As a result, the Bernoulli numbers have the distinction of being the subject of the first published complex computer program.

🔗 Technology 🔗 Physics 🔗 Physics/Fluid Dynamics

Fluidics, or fluidic logic, is the use of a fluid to perform analog or digital operations similar to those performed with electronics.

The physical basis of fluidics is pneumatics and hydraulics, based on the theoretical foundation of fluid dynamics. The term fluidics is normally used when devices have no moving parts, so ordinary hydraulic components such as hydraulic cylinders and spool valves are not considered or referred to as fluidic devices.

A jet of fluid can be deflected by a weaker jet striking it at the side. This provides nonlinear amplification, similar to the transistor used in electronic digital logic. It is used mostly in environments where electronic digital logic would be unreliable, as in systems exposed to high levels of electromagnetic interference or ionizing radiation.

Nanotechnology considers fluidics as one of its instruments. In this domain, effects such as fluid-solid and fluid-fluid interface forces are often highly significant. Fluidics have also been used for military applications.

🔗 Internet 🔗 Internet culture 🔗 Philosophy 🔗 Futures studies

Roko's basilisk is a thought experiment which states that an otherwise benevolent artificial superintelligence (AI) in the future would be incentivized to create a virtual reality simulation to torture anyone who knew of its potential existence but did not directly contribute to its advancement or development. It originated in a 2010 post at discussion board LessWrong, a technical forum focused on analytical rational enquiry. The thought experiment's name derives from the poster of the article (Roko) and the basilisk, a mythical creature capable of destroying enemies with its stare.

While the theory was initially dismissed as nothing but conjecture or speculation by many LessWrong users, LessWrong co-founder Eliezer Yudkowsky reported users who described symptoms such as nightmares and mental breakdowns upon reading the theory, due to its stipulation that knowing about the theory and its basilisk made one vulnerable to the basilisk itself. This led to discussion of the basilisk on the site to be banned for five years. However, these reports were later dismissed as being exaggerations or inconsequential, and the theory itself was dismissed as nonsense, including by Yudkowsky himself. Even after the post's discreditation, it is still used as an example of principles such as Bayesian probability and implicit religion. It is also regarded as a modern version of Pascal's wager. In the field of artificial intelligence, Roko's basilisk has become notable as an example that raises the question of how to create an AI which is simultaneously moral and intelligent.

🔗 Technology 🔗 Sweden 🔗 Metalworking

Gauge blocks (also known as gage blocks, Johansson gauges, slip gauges, or Jo blocks) are a system for producing precision lengths. The individual gauge block is a metal or ceramic block that has been precision ground and lapped to a specific thickness. Gauge blocks come in sets of blocks with a range of standard lengths. In use, the blocks are stacked to make up a desired length.

An important feature of gauge blocks is that they can be joined together with very little dimensional uncertainty. The blocks are joined by a sliding process called wringing, which causes their ultra-flat surfaces to cling together. A small number of gauge blocks can be used to create accurate lengths within a wide range. By using 3 blocks at a time taken from a set of 30 blocks, one may create any of the 1000 lengths from 3.000 to 3.999 mm in 0.001 mm steps (or .3000 to .3999 inches in 0.0001 inch steps). Gauge blocks were invented in 1896 by Swedish machinist Carl Edvard Johansson. They are used as a reference for the calibration of measuring equipment used in machine shops, such as micrometers, sine bars, calipers, and dial indicators (when used in an inspection role). Gauge blocks are the main means of length standardization used by industry.

🔗 Europe 🔗 England 🔗 Linguistics 🔗 Geography 🔗 Languages 🔗 Culture 🔗 English Language 🔗 European Union

Euro English or European English, less commonly known as EU English and EU Speak, is a pidgin dialect of English based on the technical jargon of the European Union and the native languages of its non-native English speaking population. It is mostly used among EU staff, expatriates from EU countries, young international travellers (such as exchange students in the EU’s Erasmus programme), European diplomats, and sometimes by other Europeans that use English as a second or foreign language (especially Continental Europeans).

🔗 Medicine 🔗 Viruses

Original antigenic sin, also known as antigenic imprinting or the Hoskins effect, refers to the propensity of the body's immune system to preferentially utilize immunological memory based on a previous infection when a second slightly different version of that foreign pathogen (e.g. a virus or bacterium) is encountered. This leaves the immune system "trapped" by the first response it has made to each antigen, and unable to mount potentially more effective responses during subsequent infections. Antibodies or T-cells induced during infections with the first variant of the pathogen are subject to a form of original antigenic sin, termed repertoire freeze.

The phenomenon of original antigenic sin has been described in relation to influenza virus, dengue fever, human immunodeficiency virus (HIV) and to several other viruses.

This phenomenon was first described in 1960 by Thomas Francis Jr. in the article "On the Doctrine of Original Antigenic Sin". It is named by analogy to the theological concept of original sin. According to Francis as cited by Richard Krause:

"The antibody of childhood is largely a response to dominant antigen of the virus causing the first type A influenza infection of the lifetime. [...] The imprint established by the original virus infection governs the antibody response thereafter. This we have called the Doctrine of the Original Antigenic Sin."

🔗 Psychology

The narcissism of small differences (German: der Narzissmus der kleinen Differenzen) is the thesis that communities with adjoining territories and close relationships are especially likely to engage in feuds and mutual ridicule because of hypersensitivity to details of differentiation. The term was coined by Sigmund Freud in 1917, based on the earlier work of British anthropologist Ernest Crawley. In language differing only slightly from current psychoanalytic terminology, Crawley declared that each individual is separated from others by a taboo of personal isolation, a narcissism of minor differences.

🔗 Mathematics

In geometry, a 65537-gon is a polygon with 65,537 (2¹⁶ + 1) sides. The sum of the interior angles of any non–self-intersecting 65537-gon is 11796300°.

🔗 Biography 🔗 Computing 🔗 Business 🔗 Biography/science and academia 🔗 New York (state) 🔗 Criminal Biography 🔗 Computing/Computer Security 🔗 New Jersey 🔗 New York (state)/Cornell University 🔗 Computing/Networking

Robert Tappan Morris (born November 8, 1965) is an American computer scientist and entrepreneur. He is best known for creating the Morris worm in 1988, considered the first computer worm on the Internet.

Morris was prosecuted for releasing the worm, and became the first person convicted under the then-new Computer Fraud and Abuse Act. He went on to co-found the online store Viaweb, one of the first web-based applications, and later the funding firm Y Combinator—both with Paul Graham.

He later joined the faculty in the department of Electrical Engineering and Computer Science at the Massachusetts Institute of Technology, where he received tenure in 2006. He was elected to the National Academy of Engineering in 2019.

🔗 Computing 🔗 Microsoft Windows 🔗 Microsoft Windows/Computing 🔗 Software 🔗 Software/Computing 🔗 Microsoft

Universal Disk Format (UDF) is a profile of the specification known as ISO/IEC 13346 and ECMA-167 and is an open vendor-neutral file system for computer data storage for a broad range of media. In practice, it has been most widely used for DVDs and newer optical disc formats, supplanting ISO 9660. Due to its design, it is very well suited to incremental updates on both recordable and (re)writable optical media. UDF is developed and maintained by the Optical Storage Technology Association (OSTA).

Normally, authoring software will master a UDF file system in a batch process and write it to optical media in a single pass. But when packet writing to rewritable media, such as CD-RW, UDF allows files to be created, deleted and changed on-disc just as a general-purpose filesystem would on removable media like floppy disks and flash drives. This is also possible on write-once media, such as CD-R, but in that case the space occupied by the deleted files cannot be reclaimed (and instead becomes inaccessible).

Multi-session mastering is also possible in UDF, though some implementations may be unable to read disks with multiple sessions.