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πŸ”— M-DISC: The storage medium that lasts 1000 years

πŸ”— Computing πŸ”— Computing/Computer hardware πŸ”— Collections Care

M-DISC (Millennial Disc) is a write-once optical disc technology introduced in 2009 by Millenniata, Inc. and available as DVD and Blu-ray discs.

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πŸ”— Mach kernel

πŸ”— Apple Inc./Macintosh πŸ”— Apple Inc. πŸ”— Computing πŸ”— Apple Inc./iOS

Mach () is a kernel developed at Carnegie Mellon University to support operating system research, primarily distributed and parallel computing. Mach is often mentioned as one of the earliest examples of a microkernel. However, not all versions of Mach are microkernels. Mach's derivatives are the basis of the operating system kernel in GNU Hurd and of Apple's XNU kernel used in macOS, iOS, iPadOS, tvOS, and watchOS.

The project at Carnegie Mellon ran from 1985 to 1994, ending with Mach 3.0, which is a true microkernel. Mach was developed as a replacement for the kernel in the BSD version of Unix, so no new operating system would have to be designed around it. Mach and its derivatives exist within a number of commercial operating systems. These include all using the XNU operating system kernel which incorporates an earlier non-microkernel Mach as a major component. The Mach virtual memory management system was also adopted in 4.4BSD by the BSD developers at CSRG, and appears in modern BSD-derived Unix systems, such as FreeBSD.

Mach is the logical successor to Carnegie Mellon's Accent kernel. The lead developer on the Mach project, Richard Rashid, has been working at Microsoft since 1991 in various top-level positions revolving around the Microsoft Research division. Another of the original Mach developers, Avie Tevanian, was formerly head of software at NeXT, then Chief Software Technology Officer at Apple Inc. until March 2006.

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πŸ”— Never Event

πŸ”— Medicine

A never event is the "kind of mistake (medical error) that should never happen" in the field of medical treatment. According to the Leapfrog Group never events are defined as "adverse events that are serious, largely preventable, and of concern to both the public and health care providers for the purpose of public accountability."

A 2012 study reported there may be as many as 1,500 instances of one never event, a retained foreign object, per year in the United States. The same study suggests an estimated total of surgical mistakes at just over 4,000 per year in the United States, but these statistics are extrapolations from small samples rather than actual event counts.

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πŸ”— Edgelord

πŸ”— Internet culture πŸ”— Sociology

An edgelord is someone on the Internet who tries to impress or shock by posting edgy opinions such as nihilism or extremist views.

The term is a portmanteau derived from "edgy" and "shitlord" – a person who "basks in the bitterness and misery of others".

Merriam-Webster gave the following example:

We decided to watch It's A Wonderful Life and my dad said, β€œEvery year I wait for Jimmy Stewart to jump off that bridge but he never does it” - merry Xmas from the original edgelord.

Edgelords were characterised by author Rachel Monroe in her account of criminal behaviour, Savage Appetites:

...internet cynics lumped the online Nazis together with the serial killer fetishists and the dumbest goths and dismissed them all as edgelords: kids who tried to be scary online. I thought of most of these edgelords as basement-dwellers, pale faces lit by the glow of their computer screen, puffing themselves up with nihilism. An edgelord was a scrawny guy with a LARP-y vibe, possibly wearing a cloak, dreaming of omnipotence. Or a girl with excessive eyeliner and lots of Tumblr posts about self-harm. The disturbing content posted by edgelords was undermined by its predictability...

It is frequently associated with the forum site 4chan.

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πŸ”— Karnaugh map

πŸ”— Mathematics

The Karnaugh map (KM or K-map) is a method of simplifying Boolean algebra expressions. Maurice Karnaugh introduced it in 1953 as a refinement of Edward Veitch's 1952 Veitch chart, which actually was a rediscovery of Allan Marquand's 1881 logical diagram aka Marquand diagram but with a focus now set on its utility for switching circuits. Veitch charts are therefore also known as Marquand–Veitch diagrams, and Karnaugh maps as Karnaugh–Veitch maps (KV maps).

The Karnaugh map reduces the need for extensive calculations by taking advantage of humans' pattern-recognition capability. It also permits the rapid identification and elimination of potential race conditions.

The required Boolean results are transferred from a truth table onto a two-dimensional grid where, in Karnaugh maps, the cells are ordered in Gray code, and each cell position represents one combination of input conditions, while each cell value represents the corresponding output value. Optimal groups of 1s or 0s are identified, which represent the terms of a canonical form of the logic in the original truth table. These terms can be used to write a minimal Boolean expression representing the required logic.

Karnaugh maps are used to simplify real-world logic requirements so that they can be implemented using a minimum number of physical logic gates. A sum-of-products expression can always be implemented using AND gates feeding into an OR gate, and a product-of-sums expression leads to OR gates feeding an AND gate. Karnaugh maps can also be used to simplify logic expressions in software design. Boolean conditions, as used for example in conditional statements, can get very complicated, which makes the code difficult to read and to maintain. Once minimised, canonical sum-of-products and product-of-sums expressions can be implemented directly using AND and OR logic operators. Diagrammatic and mechanical methods for minimizing simple logic expressions have existed since at least the medieval times. More systematic methods for minimizing complex expressions began to be developed in the early 1950s, but until the mid to late 1980s the Karnaugh map was the most common used in practice.

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πŸ”— Hawthorne Effect

πŸ”— Mass surveillance πŸ”— Business πŸ”— Psychology πŸ”— Sociology

The Hawthorne effect is a type of human behavior reactivity in which individuals modify an aspect of their behavior in response to their awareness of being observed. The effect was discovered in the context of research conducted at the Hawthorne Western Electric plant; however, some scholars feel the descriptions are apocryphal.

The original research involved workers who made electrical relays at the Hawthorne Works, a Western Electric plant in Cicero, Illinois. Between 1924 and 1927, the lighting study was conducted. Workers experienced a series of lighting changes in which productivity was said to increase with almost any change in the lighting. This turned out not to be true. In the study that was associated with Elton Mayo, which ran from 1928 to 1932, a series of changes in work structure were implemented (e.g., changes in rest periods) in a group of five women. However, this was a methodologically poor, uncontrolled study that did not permit any firm conclusions to be drawn.

One of the later interpretations by Landsberger suggested that the novelty of being research subjects and the increased attention from such could lead to temporary increases in workers' productivity. This interpretation was dubbed "the Hawthorne effect".

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πŸ”— Cyclomatic Complexity

πŸ”— Computing πŸ”— Computer science πŸ”— Computing/Software

Cyclomatic complexity is a software metric used to indicate the complexity of a program. It is a quantitative measure of the number of linearly independent paths through a program's source code. It was developed by Thomas J. McCabe, Sr. in 1976.

Cyclomatic complexity is computed using the control-flow graph of the program: the nodes of the graph correspond to indivisible groups of commands of a program, and a directed edge connects two nodes if the second command might be executed immediately after the first command. Cyclomatic complexity may also be applied to individual functions, modules, methods or classes within a program.

One testing strategy, called basis path testing by McCabe who first proposed it, is to test each linearly independent path through the program; in this case, the number of test cases will equal the cyclomatic complexity of the program.

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πŸ”— Exotic Atom

πŸ”— Physics

An exotic atom is an otherwise normal atom in which one or more sub-atomic particles have been replaced by other particles of the same charge. For example, electrons may be replaced by other negatively charged particles such as muons (muonic atoms) or pions (pionic atoms). Because these substitute particles are usually unstable, exotic atoms typically have very short lifetimes and all currently observed atoms cannot persist under normal conditions.

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πŸ”— Carrosses Γ  Cinq Sols

The carrosses Γ  cinq sols (English: five-sol coaches) were the first modern form of public transport in the world, developed by mathematician and philosopher Blaise Pascal.

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πŸ”— Stenotype

πŸ”— Technology πŸ”— Law πŸ”— Business πŸ”— Occupational Safety and Health

A stenotype, stenotype machine, shorthand machine or steno writer is a specialized chorded keyboard or typewriter used by stenographers for shorthand use. In order to pass the United States Registered Professional Reporter test, a trained court reporter or closed captioner must write speeds of approximately 180, 200, and 225 words per minute (wpm) at very high accuracy in the categories of literary, jury charge, and testimony, respectively. Some stenographers can reach 300 words per minute. The website of the California Official Court Reporters Association (COCRA) gives the official record for American English as 375 wpm.

The stenotype keyboard has far fewer keys than a conventional alphanumeric keyboard. Multiple keys are pressed simultaneously (known as "chording" or "stroking") to spell out whole syllables, words, and phrases with a single hand motion. This system makes real-time transcription practical for court reporting and live closed captioning. Because the keyboard does not contain all the letters of the English alphabet, letter combinations are substituted for the missing letters. There are several schools of thought on how to record various sounds, such as the StenEd, Phoenix, and Magnum Steno theories.

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