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🔗 Computing 🔗 Mathematics

The Luhn algorithm or Luhn formula, also known as the "modulus 10" or "mod 10" algorithm, named after its creator, IBM scientist Hans Peter Luhn, is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers, National Provider Identifier numbers in the United States, Canadian Social Insurance Numbers, Israel ID Numbers, South African ID Numbers, Greek Social Security Numbers (ΑΜΚΑ), and survey codes appearing on McDonald's, Taco Bell, and Tractor Supply Co. receipts. It is described in U.S. Patent No. 2,950,048, filed on January 6, 1954, and granted on August 23, 1960.

The algorithm is in the public domain and is in wide use today. It is specified in ISO/IEC 7812-1. It is not intended to be a cryptographically secure hash function; it was designed to protect against accidental errors, not malicious attacks. Most credit cards and many government identification numbers use the algorithm as a simple method of distinguishing valid numbers from mistyped or otherwise incorrect numbers.

🔗 Poetry 🔗 Songs

"Desiderata" (Latin: "things desired") is an early 1920s prose poem by the American writer Max Ehrmann. Although he copyrighted it in 1927, he distributed copies of it without a required copyright notice during 1933 and c. 1942, thereby forfeiting his US copyright. Largely unknown in the author's lifetime, its use in devotional and spoken word recordings in 1960 and 1971 called it to the attention of the world.

🔗 France 🔗 Novels 🔗 Philosophy 🔗 Philosophy/Philosophical literature 🔗 Philosophy/Social and political philosophy 🔗 Philosophy/Continental philosophy 🔗 Algeria

The Plague (French: La Peste) is a novel by Albert Camus, published in 1947, that tells the story of a plague sweeping the French Algerian city of Oran. It asks a number of questions relating to the nature of destiny and the human condition. The characters in the book, ranging from doctors to vacationers to fugitives, all help to show the effects the plague has on a populace.

The novel is believed to be based on the cholera epidemic that killed a large percentage of Oran's population in 1849 following French colonization, but the novel is placed in the 1940s. Oran and its surroundings were struck by disease multiple times before Camus published this novel. According to a research report by the Centers for Disease Control and Prevention, Oran was decimated by the plague in 1556 and 1678, but all later outbreaks, in 1921 (185 cases), 1931 (76 cases), and 1944 (95 cases), were very far from the scale of the epidemic described in the novel.

The Plague is considered an existentialist classic despite Camus' objection to the label. The narrative tone is similar to Kafka's, especially in The Trial whose individual sentences potentially have multiple meanings, the material often pointedly resonating as stark allegory of phenomenal consciousness and the human condition.

Camus included a dim-witted character misreading The Trial as a mystery novel as an oblique homage. The novel has been read as an allegorical treatment of the French resistance to Nazi occupation during World War II. Additionally, he further illustrates the human reaction towards the "absurd". The Plague represents how the world deals with the philosophical notion of the Absurd, a theory that Camus himself helped to define.

🔗 Australia 🔗 Birds

Casuarius is a genus of birds in the order Casuariiformes, whose members are the cassowaries (Tok Pisin: muruk, Indonesian: kasuari). It is classified as a ratite (flightless bird without a keel on its sternum bone) and is native to the tropical forests of New Guinea (Papua New Guinea and East Indonesia), Aru Islands (Maluku), and northeastern Australia.

Three species are extant: The most common, the southern cassowary, is the third-tallest and second-heaviest living bird, smaller only than the ostrich and emu. The other two species are represented by the northern cassowary and the dwarf cassowary; the northern cassowary is the most recently discovered and the most threatened. A fourth but extinct species is represented by the pygmy cassowary.

Cassowaries feed mainly on fruit, although all species are truly omnivorous and take a range of other plant foods, including shoots and grass seeds, in addition to fungi, invertebrates, and small vertebrates. Cassowaries are very wary of humans, but if provoked, they are capable of inflicting serious, even fatal, injuries to both dogs and people. The cassowary has often been labeled "the world's most dangerous bird".

🔗 Biography 🔗 California 🔗 California/San Francisco Bay Area 🔗 Medicine 🔗 Physics 🔗 Women scientists 🔗 Biography/science and academia 🔗 Women's History 🔗 Physics/Biographies 🔗 Medicine/Radiology

Elizabeth Fleischman-Aschheim (née Fleischman 5 March 1867 – 3 August 1905) was an American radiographer who is considered an X-ray pioneer. Fleischman was the first woman to die as a result of X-ray radiation exposure.

🔗 Chemistry

A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton (H⁺) to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a hydrogen ion. On the other hand, a conjugate base is what is left over after an acid has donated a proton during a chemical reaction. Hence, a conjugate base is a species formed by the removal of a proton from an acid, as in the reverse reaction it is able to gain a hydrogen ion. Because some acids are capable of releasing multiple protons, the conjugate base of an acid may itself be acidic.

In summary, this can be represented as the following chemical reaction:

Johannes Nicolaus Brønsted and Martin Lowry introduced the Brønsted–Lowry theory, which proposed that any compound that can transfer a proton to any other compound is an acid, and the compound that accepts the proton is a base. A proton is a nuclear particle with a unit positive electrical charge; it is represented by the symbol H⁺ because it constitutes the nucleus of a hydrogen atom, that is, a hydrogen cation.

A cation can be a conjugate acid, and an anion can be a conjugate base, depending on which substance is involved and which acid–base theory is the viewpoint. The simplest anion which can be a conjugate base is the solvated electron whose conjugate acid is the atomic hydrogen.

🔗 Technology 🔗 Software 🔗 Software/Computing 🔗 Apps

Bitchat is a peer-to-peer encrypted messaging app developed by Jack Dorsey, co‑founder of Twitter (now X) and Block, Inc. Announced in July 2025, Bitchat enables users to send messages via Bluetooth Low Energy (BLE) mesh networks without requiring internet connections, cellular service, user accounts, or central servers. Bitchat also uses the internet-based Nostr protocol for global reach.

🔗 Russia 🔗 China

"China's final warning" (Russian: Последнее китайское предупреждение) is a Russian proverb meaning a warning that carries no real consequences.

🔗 Television 🔗 Media

TV-B-Gone is a universal remote control device for turning off a large majority—about 85%—of the available brands of television sets in 2015. It was created to allow people in a public place to turn off nearby television sets. Its inventor has referred to it as "an environmental management device". The device is part of a key-chain, and, like other remote devices, is battery-powered. Although it can require up to 72 seconds for the device to find the proper code for a particular television receiver, the most popular televisions turn off in the first few seconds.