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🔗 Linguistics 🔗 Linguistics/Etymology

OK (spelling variations include okay, O.K., and ok) is an English word (originally American English) denoting approval, acceptance, agreement, assent, acknowledgment, or a sign of indifference. OK is frequently used as a loanword in other languages. It has been described as the most frequently spoken or written word on the planet. The origins of the word are disputed.

As an adjective, OK principally means "adequate" or "acceptable" as a contrast to "bad" ("The boss approved this, so it is OK to send out"); it can also mean "mediocre" when used in contrast with "good" ("The french fries were great, but the burger was just OK"). It fulfills a similar role as an adverb ("Wow, you did OK for your first time skiing!"). As an interjection, it can denote compliance ("OK, I will do that"), or agreement ("OK, that is fine"). It can mean "assent" when it is used as a noun ("the boss gave her the OK to the purchase") or, more colloquially, as a verb ("the boss OKed the purchase"). OK, as an adjective, can express acknowledgement without approval. As a versatile discourse marker or back-channeling item, it can also be used with appropriate intonation to show doubt or to seek confirmation ("OK?", "Is that OK?").

🔗 Biology 🔗 Astronomy 🔗 Color 🔗 Evolutionary biology 🔗 Project-independent assessment

The Purple Earth Hypothesis (PEH) is an astrobiological hypothesis, first proposed by molecular biologist Shiladitya DasSarma in 2007, that the earliest photosynthetic life forms of Early Earth were based on the simpler molecule retinal rather than the more complex porphyrin-based chlorophyll, making the surface biosphere appear purplish rather than its current greenish color. It is estimated to have occurred between 3.5 and 2.4 billion years ago during the Archean eon, prior to the Great Oxygenation Event and Huronian glaciation.

Retinal-containing cell membranes exhibit a single light absorption peak centered in the energy-rich green-yellow region of the visible spectrum, but transmit and reflect red and blue light, resulting in a magenta color. Chlorophyll pigments, in contrast, absorb red and blue light, but little or no green light, which results in the characteristic green reflection of plants, green algae, cyanobacteria and other organisms with chlorophyllic organelles. The simplicity of retinal pigments in comparison to the more complex chlorophyll, their association with isoprenoid lipids in the cell membrane, as well as the discovery of archaeal membrane components in ancient sediments on the Early Earth are consistent with an early appearance of life forms with purple membranes prior to the turquoise of the Canfield ocean and later green photosynthetic organisms.

The basic principles of war propaganda (Principes élémentaires de propagande de guerre) is a monograph by Anne Morelli published in 2001. It has not been translated into English. The subtitle recommends its "usability in case of cold war, hot war and lukewarm war" (Utilisables en cas de guerre froide, chaude ou tiède).

The ten "commandments" of propaganda which Anne Morelli elaborates in this work are, above all, an analytical framework for pedagogical purposes and for media analysis. Morelli does not want to take sides or defend "dictators", but show the regularity of use of the ten principles in the media and in society:

"I will not put to test the purity of one or the other's intentions. I am not going to find out who is lying and who is telling the truth, who is believing what he says, and who does not. My only intention is to illustrate the principles of propaganda that are used and to describe their functioning." (P. 6)

Nonetheless, it seems undeniable to the author that after the wars that characterize our epoch (Kosovo, Second Gulf War, Afghanistan War, Iraq War), Western democracies and their media  must be discussed.

As Rudolph Walter in his review in Die Zeit shows, Morelli in this work adapts the typical forms of various contents of propaganda to news of her time. She takes up Arthur Ponsonby's Falsehood in War-Time and George Demartial's La mobilisation des consciences. La guerre de 1914 about propaganda in the First World War, systematizes them in the form of ten principles, and applies them to both world wars, the war in the Balkan, and the war in Afghanistan. Four of the following principles, according to Walter just emanate directly from the principle of friend or foe, "we and them" mindset and simplistic thinking in terms of black and white.

🔗 Mathematics

The Trachtenberg system is a system of rapid mental calculation. The system consists of a number of readily memorized operations that allow one to perform arithmetic computations very quickly. It was developed by the Russian Jewish engineer Jakow Trachtenberg in order to keep his mind occupied while being in a Nazi concentration camp.

The rest of this article presents some methods devised by Trachtenberg. Some of the algorithms Trachtenberg developed are ones for general multiplication, division and addition. Also, the Trachtenberg system includes some specialised methods for multiplying small numbers between 5 and 13.

The section on addition demonstrates an effective method of checking calculations that can also be applied to multiplication.

🔗 Biography 🔗 London 🔗 Trains 🔗 Civil engineering 🔗 Ships 🔗 River Thames 🔗 Wiltshire 🔗 Hampshire 🔗 Bristol 🔗 Trains/UK Railways

Isambard Kingdom Brunel (; 9 April 1806 – 15 September 1859) was a British civil engineer who is considered "one of the most ingenious and prolific figures in engineering history", "one of the 19th-century engineering giants", and "one of the greatest figures of the Industrial Revolution, [who] changed the face of the English landscape with his groundbreaking designs and ingenious constructions". Brunel built dockyards, the Great Western Railway (GWR), a series of steamships including the first propeller-driven transatlantic steamship, and numerous important bridges and tunnels. His designs revolutionised public transport and modern engineering.

Though Brunel's projects were not always successful, they often contained innovative solutions to long-standing engineering problems. During his career, Brunel achieved many engineering firsts, including assisting in the building of the first tunnel under a navigable river and the development of SS Great Britain, the first propeller-driven, ocean-going, iron ship, which, when launched in 1843, was the largest ship ever built.

On the GWR, Brunel set standards for a well-built railway, using careful surveys to minimise gradients and curves. This necessitated expensive construction techniques, new bridges, new viaducts, and the two-mile (3.2 km) long Box Tunnel. One controversial feature was the wide gauge, a "broad gauge" of 7 ft ¹⁄₄ in (2,140 mm), instead of what was later to be known as "standard gauge" of 4 ft 8 ¹⁄₂ in (1,435 mm). He astonished Britain by proposing to extend the GWR westward to North America by building steam-powered, iron-hulled ships. He designed and built three ships that revolutionised naval engineering: the SS Great Western (1838), the SS Great Britain (1843), and the SS Great Eastern (1859).

In 2002, Brunel was placed second in a BBC public poll to determine the "100 Greatest Britons". In 2006, the bicentenary of his birth, a major programme of events celebrated his life and work under the name Brunel 200.

🔗 Antarctica 🔗 Transport

The Antarctic Snow Cruiser was a vehicle designed from 1937 to 1939 under the direction of Thomas Poulter, intended to facilitate transport in Antarctica during the United States Antarctic Service Expedition (1939–41). The Snow Cruiser was also known as "The Penguin," "Penguin 1" or "Turtle" in some published material.

Poulter had been second in command of Byrd's Second Antarctic Expedition, launched in 1934. From his time in the Antarctic, Poulter had devised several innovative features. However, the massive Snow Cruiser generally failed to operate as hoped under the difficult conditions, and was eventually abandoned in Antarctica. Rediscovered under a deep layer of snow in 1958, it later disappeared again due to shifting ice conditions.

🔗 Telecommunications

A payphone (alternative spelling: pay phone) is typically a coin-operated public telephone, often located in a telephone booth or in high-traffic outdoor areas, with pre-payment by inserting money (usually coins) or by billing a credit or debit card, or a telephone card. Prepaid calling cards also facilitate establishing a call by first calling the provided toll-free telephone number, entering the card account number and PIN, then the desired telephone number. An equipment usage fee may be charged as additional units, minutes or tariff fee to the collect/third-party, debit, credit, telephone or prepaid calling card when used at payphones. By agreement with the landlord, either the phone company pays rent for the location and keeps the revenue, or the landlord pays rent for the phone and shares the revenue.

Payphones are often found in public places to contribute to the notion of universal access to basic communication services. One thesis, written as early as 2003, recognised this as a digital divide problem.

In the 20th century, payphones in some countries, such as Spain, used token coins, available for sale at a local retailer, to activate pay phones, instead of legal tender coins. In some cases, these were upgraded to use magnetic cards or credit card readers over the years.

In the past, payphones were ubiquitous worldwide, but their prevalence has decreased significantly over the years due to the increasing availability of mobile phones, even though cell phone service is not always available in emergencies.

🔗 China 🔗 Novels 🔗 Novels/Science fiction 🔗 Science Fiction

The Dark Forest (Chinese: 黑暗森林) is a 2008 science fiction novel by the Chinese writer Liu Cixin. It is the sequel to the Hugo Award-winning novel The Three-Body Problem in the trilogy titled Remembrance of Earth's Past, but Chinese readers generally refer to the series by the title of the first novel. The English version, translated by Joel Martinsen, was published in 2015. The novel is about the dark forest hypothesis (which was named after the novel), a possible solution to the Fermi paradox, though similar theories have been described as early as 1983.

🔗 Spaceflight 🔗 Physics 🔗 Systems 🔗 Systems/Dynamical systems

The Interplanetary Transport Network (ITN) is a collection of gravitationally determined pathways through the Solar System that require very little energy for an object to follow. The ITN makes particular use of Lagrange points as locations where trajectories through space are redirected using little or no energy. These points have the peculiar property of allowing objects to orbit around them, despite lacking an object to orbit. While it would use little energy, transport along the network would take a long time.

🔗 Computing 🔗 Computing/Software 🔗 Computing/Free and open-source software 🔗 C/C++ 🔗 C/C++/C

The GLib Object System, or GObject, is a free software library providing a portable object system and transparent cross-language interoperability. GObject is designed for use both directly in C programs to provide object-oriented C-based APIs and through bindings to other languages to provide transparent cross-language interoperability, e.g. PyGObject.