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🔗 Classical Greece and Rome 🔗 Greece

The Delphic Hymns are two musical compositions from Ancient Greece, which survive in substantial fragments. They were long regarded as being dated c. 138 BC and 128 BC, respectively, but recent scholarship has shown it likely they were both written for performance at the Athenian Pythaides in 128 BC. If indeed it dates from ten years before the second, the First Delphic Hymn is the earliest unambiguous surviving example of notated music from anywhere in the western world whose composer is known by name. Inscriptions indicate that the First Delphic Hymn was written by Athenaeus, son of Athenaeus, while Limenius is credited the Second Delphic Hymn's composer.

🔗 Australia 🔗 Military history 🔗 Australia/Western Australia 🔗 Military history/Australia, New Zealand and South Pacific military history 🔗 Australia/Australian history

The Emu War, also known as the Great Emu War, was a nuisance wildlife management military operation undertaken in Australia over the latter part of 1932 to address public concern over the number of emus said to be running amok in the Campion district of Western Australia. The unsuccessful attempts to curb the population of emus, a large flightless bird indigenous to Australia, employed soldiers armed with Lewis guns—leading the media to adopt the name "Emu War" when referring to the incident. While a number of the birds were killed, the emu population persisted and continued to cause crop destruction.

🔗 Germany 🔗 Astronomy 🔗 Archaeology 🔗 Visual arts

The Nebra sky disk is a bronze disk of around 30 centimeters (11 ³⁄₄ in) diameter and a weight of 2.2 kilograms (4.9 lb), having a blue-green patina and inlaid with gold symbols. These symbols are interpreted generally as the Sun or full moon, a lunar crescent, and stars (including a cluster of seven interpreted as the Pleiades). Two golden arcs along the sides, interpreted to mark the angle between the solstices, were added later. A final addition was another arc at the bottom surrounded with multiple strokes (of uncertain meaning, variously interpreted as a Solar Barge with numerous oars, the Milky Way, or a rainbow).

The disk is attributed to a site in present-day Germany near Nebra, Saxony-Anhalt, and dated by Archaeological association to c. 1600 BC. Researchers suggest the disk is an artifact of the Bronze Age Unetice culture.

The style in which the disk is executed was unlike any artistic style then known from the period, with the result that the object was initially suspected of being a forgery, but is now widely accepted as authentic.

The Nebra sky disk features the oldest concrete depiction of the cosmos yet known from anywhere in the world. In June 2013 it was included in the UNESCO Memory of the World Register and termed "one of the most important archaeological finds of the twentieth century."

🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Military history/Military science, technology, and theory 🔗 Military history/Weaponry

The M65 atomic cannon, often called "Atomic Annie", was an artillery piece built by the United States and capable of firing a nuclear device. It was developed in the early 1950s, at the beginning of the Cold War, and fielded, between April 1955 and December 1962, in West Germany, South Korea and on Okinawa.

🔗 United States 🔗 Soviet Union 🔗 Russia 🔗 Russia/technology and engineering in Russia 🔗 Spaceflight 🔗 China

Docking and berthing of spacecraft is the joining of two space vehicles. This connection can be temporary, or partially permanent such as for space station modules.

Docking specifically refers to joining of two separate free-flying space vehicles. Berthing refers to mating operations where an inactive module/vehicle is placed into the mating interface of another space vehicle by using a robotic arm. Because the modern process of un-berthing needs more labor and is time-consuming, berthing operations are unsuited for rapid crew evacuations in the event of an emergency.

🔗 India 🔗 India/Indian literature workgroup

The Shishupala Vadha (Sanskrit: शिशुपालवध, IAST: Śiśupāla-vadha, lit. "the slaying of Shishupala") is a work of classical Sanskrit poetry (kāvya) composed by Māgha in the 7th or 8th century. It is an epic poem in 20 sargas (cantos) of about 1800 highly ornate stanzas, and is considered one of the six Sanskrit mahakavyas, or "great epics". It is also known as the Māgha-kāvya after its author. Like other kavyas, it is admired more for its exquisite descriptions and lyrical quality than for any dramatic development of plot. Its 19th canto is noted for verbal gymnastics and wordplay; see the section on linguistic ingenuity below.

🔗 Film 🔗 Germany 🔗 Film/German cinema

Gold is a 1934 German science fiction film directed by Karl Hartl. The film involves a British scientist who is attempting to create a device that turns base materials into gold. He later forces the German scientist's assistant Werner Holk (Hans Albers), who was working on a similar experiment, to come to his underwater nuclear reactor to help him. Gold was made in both German-language and French-language versions with Brigitte Helm reprising her role in both.

🔗 Chemistry

The vanadium redox battery (VRB), also known as the vanadium flow battery (VFB) or vanadium redox flow battery (VRFB), is a type of rechargeable flow battery that employs vanadium ions in different oxidation states to store chemical potential energy. The vanadium redox battery exploits the ability of vanadium to exist in solution in four different oxidation states, and uses this property to make a battery that has just one electroactive element instead of two. For several reasons, including their relative bulkiness, most vanadium batteries are currently used for grid energy storage, i.e., attached to power plants or electrical grids.

The possibility of creating a vanadium flow battery was explored by Pissoort in the 1930s, NASA researchers in the 1970s, and Pellegri and Spaziante in the 1970s, but none of them were successful in demonstrating the technology. The first successful demonstration of the all-vanadium redox flow battery which employed vanadium in a solution of sulfuric acid in each half was by Maria Skyllas-Kazacos at the University of New South Wales in the 1980s. Her design used sulfuric acid electrolytes, and was patented by the University of New South Wales in Australia in 1986.

The main advantages of the vanadium redox battery are that it can offer almost unlimited energy capacity simply by using larger electrolyte storage tanks; it can be left completely discharged for long periods with no ill effects; if the electrolytes are accidentally mixed, the battery suffers no permanent damage; a single state of charge between the two electrolytes avoids the capacity degradation due to a single cell in non-flow batteries; the electrolyte is aqueous and inherently safe and non-flammable; and the generation 3 formulation using a mixed acid solution developed by the Pacific Northwest National Laboratory operates over a wider temperature range allowing for passive cooling. VRFBs can be used at depth of discharge (DOD) around 90% and more, i.e. deeper DODs than solid-state batteries (e.g. lithium-based and sodium-based batteries, which are usually specified with DOD=80%). In addition, VRFBs exhibit very long cycle lives: most producers specify cycle durability in excess of 15,000-20,000 charge/discharge cycles. These values are far beyond the cycle lives of solid-state batteries, which is usually in the order of 4,000-5,000 charge/discharge cycles. Consequently, the levelized cost of energy (LCOE, i.e. the system cost divided by the usable energy, the cycle life, and round-trip efficiency) of present VRFB systems is typically in the order of a few tens of $ cents or € cents, namely much lower than the LCOEs of equivalent solid-state batteries and close to the targets of $0.05 and €0.05, stated by the US Department of Energy and the European Commission Strategic Energy Technology (SET) Plan, respectively.

The main disadvantages with vanadium redox technology are a relatively poor energy-to-volume ratio in comparison with standard storage batteries, and the relatively poor round trip efficiency. Furthermore, the aqueous electrolyte makes the battery heavy and therefore only useful for stationary applications. Another disadvantage is the relatively high toxicity of oxides of vanadium (see vanadium § Safety).

Numerous companies and organizations involved in funding and developing vanadium redox batteries include Avalon Battery, Vionx (formerly Premium Power), UniEnergy Technologies and Ashlawn Energy in the United States; Renewable Energy Dynamics Technology in Ireland; Enerox GmbH (formerly Gildemeister energy storage) in Austria; Cellennium in Thailand; Rongke Power in China; Prudent Energy in China; Sumitomo in Japan; H2, Inc. in South Korea; redT in Britain., Australian Vanadium in Australia, and the now defunct Imergy (formerly Deeya). Lately, also several smaller size vanadium redox flow batteries were brought to market (for residential applications) mainly from StorEn Technologies (USA), Schmid Group, VoltStorage and Volterion (all three from Germany), VisBlue (Denmark) or Pinflow energy storage (Czechia).

🔗 Internet 🔗 Computing 🔗 Computing/Computer hardware 🔗 Finance & Investment 🔗 Economics 🔗 Law 🔗 Computing/Software 🔗 Computing/Free and open-source software 🔗 Computing/Computer science 🔗 Cryptography 🔗 Cryptography/Computer science 🔗 Numismatics 🔗 Guild of Copy Editors 🔗 Numismatics/Cryptocurrency 🔗 Cryptocurrency 🔗 Open 🔗 Computing/Computer Security

Bitcoin (₿) is a cryptocurrency. It is a decentralized digital currency without a central bank or single administrator that can be sent from user to user on the peer-to-peer bitcoin network without the need for intermediaries.

Transactions are verified by network nodes through cryptography and recorded in a public distributed ledger called a blockchain. Bitcoin was invented in 2008 by an unknown person or group of people using the name Satoshi Nakamoto and started in 2009 when its source code was released as open-source software. Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies, products, and services. Research produced by University of Cambridge estimates that in 2017, there were 2.9 to 5.8 million unique users using a cryptocurrency wallet, most of them using bitcoin.

Bitcoin has been criticized for its use in illegal transactions, its high electricity consumption, price volatility, and thefts from exchanges. Some economists, including several Nobel laureates, have characterized it as a speculative bubble. Bitcoin has also been used as an investment, although several regulatory agencies have issued investor alerts about bitcoin.

🔗 Mathematics 🔗 Statistics

The Akaike information criterion (AIC) is an estimator of out-of-sample prediction error and thereby relative quality of statistical models for a given set of data. Given a collection of models for the data, AIC estimates the quality of each model, relative to each of the other models. Thus, AIC provides a means for model selection.

AIC is founded on information theory. When a statistical model is used to represent the process that generated the data, the representation will almost never be exact; so some information will be lost by using the model to represent the process. AIC estimates the relative amount of information lost by a given model: the less information a model loses, the higher the quality of that model.

In estimating the amount of information lost by a model, AIC deals with the trade-off between the goodness of fit of the model and the simplicity of the model. In other words, AIC deals with both the risk of overfitting and the risk of underfitting.

The Akaike information criterion is named after the Japanese statistician Hirotugu Akaike, who formulated it. It now forms the basis of a paradigm for the foundations of statistics; as well, it is widely used for statistical inference.