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🔗 Mathematics 🔗 Physics 🔗 Systems 🔗 Systems/Dynamical systems

The Abelian sandpile model, also known as the Bak–Tang–Wiesenfeld model, was the first discovered example of a dynamical system displaying self-organized criticality. It was introduced by Per Bak, Chao Tang and Kurt Wiesenfeld in a 1987 paper.

The model is a cellular automaton. In its original formulation, each site on a finite grid has an associated value that corresponds to the slope of the pile. This slope builds up as "grains of sand" (or "chips") are randomly placed onto the pile, until the slope exceeds a specific threshold value at which time that site collapses transferring sand into the adjacent sites, increasing their slope. Bak, Tang, and Wiesenfeld considered process of successive random placement of sand grains on the grid; each such placement of sand at a particular site may have no effect, or it may cause a cascading reaction that will affect many sites.

The model has since been studied on the infinite lattice, on other (non-square) lattices, and on arbitrary graphs (including directed multigraphs). It is closely related to the dollar game, a variant of the chip-firing game introduced by Biggs.

🔗 Africa 🔗 Geology 🔗 Archaeology 🔗 Africa/Mauritania

The Richat Structure, also called Guelb er Richât (Arabic: قلب الريشات, romanized: Qalb ar-Rīšāt), is a prominent circular geological feature in the Sahara's Adrar Plateau, near Ouadane, west–central Mauritania, Northwest Africa. In the local dialect, Richat means feather and it also is known locally in Arabic as tagense. Tagense refers to the circular opening of the leather pouch used to draw water from local wells.

It is an eroded geological dome, 40 kilometres (25 mi) in diameter, exposing sedimentary rock in layers which appear as concentric rings. Igneous rock is exposed inside and there are spectacular rhyolites and gabbros which have undergone hydrothermal alteration, and a central megabreccia. The structure is also the location of exceptional accumulations of Acheulean archaeological artifacts.

🔗 Biography 🔗 France

Pierre Picaud (French: [piko]) was a 19th-century shoemaker in Nîmes, France who may have been the basis for the character of Edmond Dantès in Alexandre Dumas, père's 1844 novel The Count of Monte Cristo.

In 1807, Picaud was engaged to marry a rich woman, but three jealous friends — Loupian, Solari, and Chaubart — falsely accused him of being a spy for England (a fourth friend, Allut, knew of their conspiracy, but did not report it). He was imprisoned in the Fenestrelle fortress for seven years, not even learning why until his second year there. During his imprisonment he ground a small passageway into a neighboring cell and befriended a wealthy Italian priest named Father Torri who was also held in the fortress. A year later, a dying Torri bequeathed to Picaud a treasure he had hidden in Milan. When Picaud was released after the fall of the French Imperial government in 1814, he took possession of the treasure, returned under another name to Paris and spent 10 years plotting revenge against his former friends.

Picaud first murdered Chaubart or had him murdered. Picaud's former fiancée had, two years after his disappearance, married his former friend Loupian, who became the subject of his most brutal revenge. Picaud tricked Loupian's daughter into marrying a criminal, whom he then had arrested. Loupian's daughter promptly died of shock. Picaud then burned down Loupian's restaurant, or arranged to have it burned down, leaving Loupian impoverished. Next, he fatally poisoned Solari and either manipulated Loupian's son into stealing some gold jewelry or framed him for committing the crime. The boy was sent to jail, and Picaud stabbed Loupian to death. He was himself then abducted by a vengeful Allut, who seriously injured Picaud while holding him captive. Picaud was eventually found by the French police, who recorded his confession before dying of his injuries. . Allut's deathbed confession forms the bulk of the French police records of the case. The detailed description of Picaud's experiences in prison, which could not have been known to Allut, were supposedly dictated to him by the ghost of Father Torri.

🔗 Medicine 🔗 Viruses

Variolation or inoculation was the method first used to immunize an individual against smallpox (Variola) with material taken from a patient or a recently variolated individual, in the hope that a mild, but protective, infection would result. The procedure was most commonly carried out by inserting/rubbing powdered smallpox scabs or fluid from pustules into superficial scratches made in the skin. The patient would develop pustules identical to those caused by naturally occurring smallpox, usually producing a less severe disease than naturally acquired smallpox. Eventually, after about two to four weeks, these symptoms would subside, indicating successful recovery and immunity. The method was first used in China and the Middle East before it was introduced into England and North America in the 1720s in the face of some opposition. The method is no longer used today. It was replaced by smallpox vaccine, a safer alternative. This in turn led to the development of the many vaccines now available against other diseases.

🔗 Video games 🔗 Video games/Nintendo

Link: The Faces of Evil, Zelda: The Wand of Gamelon and Zelda's Adventure are action-adventure games produced by Philips for their CD-i format as part of Nintendo's The Legend of Zelda video game series. Not designed for Nintendo platforms, the games owe their existence to negotiations related to Nintendo's decision not to have Philips create a CD add-on to the Super NES. During these negotiations, Philips secured the rights to use Nintendo characters in CD-i third-party developer games. The Faces of Evil and The Wand of Gamelon were developed by Animation Magic and were both released in North America on October 10, 1993, and Zelda's Adventure was developed by Viridis and was released in North America on June 5, 1994. The games were given little funding or development time, and Nintendo provided only cursory input. None of the games are canonical to the Zelda franchise.

CD-i players did not sell well and the games saw relatively small sales figures. Though the games initially received largely positive reviews, they have been universally criticized since the mid-2000s. This is attributed to the reaction of many gamers to the obscure games' full motion video cutscenes when they first became widely available through video-sharing websites such as YouTube. The cutscenes are perceived to be of poor quality. Because the aging early 1990s visual effects of the titles failed to live up to the graphic effects of the 2000s, and because for many fans this was their first experience of the games, the CD-i Zelda titles have developed a critical reputation as particularly poor based largely on animation quality and to an extent awkward controls. In the eyes of "devout" hardcore gamers, according to Edge, the games are now considered "tantamount to blasphemy".

Faces of Evil and Wand of Gamelon are played using the side-scrolling view introduced in Zelda II: The Adventure of Link, while Zelda's Adventure has a top-down view reminiscent of the original The Legend of Zelda. All the CD-i Zelda games begin with animated FMVs to illustrate the capabilities of the CD-ROM format, save Zelda's Adventure, which begins with a live-action video.

🔗 Books 🔗 Transhumanism 🔗 Alternative Views

Engines of Creation: The Coming Era of Nanotechnology is a 1986 molecular nanotechnology book written by K. Eric Drexler with a foreword by Marvin Minsky. An updated version was released in 2007. The book has been translated into Japanese, French, Spanish, Italian, Russian, and Chinese.

🔗 Law 🔗 England 🔗 Middle Ages 🔗 Middle Ages/History

The Charter of the Forest of 1217 (Latin: Carta Foresta) is a charter that re-established for free men rights of access to the royal forest that had been eroded by William the Conqueror and his heirs. Many of its provisions were in force for centuries afterwards. It was originally sealed in England by the young King Henry III, acting under the regency of William Marshall, 1st Earl of Pembroke. It was in many ways a companion document to Magna Carta, and redressed some applications of the Anglo-Norman Forest Law that had been extended and abused by William Rufus.

🔗 Aviation 🔗 Aviation/aircraft 🔗 Aviation/gliding

The yaw string, also known as a slip string, is a simple device for indicating a slip or skid in an aircraft in flight. It performs the same function as the slip-skid indicator ball, but is more sensitive, and does not require the pilot to look down at the instrument panel. Technically, it measures sideslip angle, not yaw angle, but this indicates how the aircraft must be yawed to return the sideslip angle to zero.

It is typically constructed from a short piece or tuft of yarn placed in the free air stream where it is visible to the pilot. In closed-cockpit aircraft, it is usually taped to the aircraft canopy. It may also be mounted on the aircraft's nose, either directly on the skin, or elevated on a mast, in which case it may also be fitted with a small paper cone at the trailing end. They are commonly used on gliders, but may also be found on jet aircraft (especially fighters), ultralight aircraft, light-sport aircraft, autogyros, airplanes and helicopters. Its usefulness on airplanes with a tractor configuration (single propeller at the nose) is limited because the propeller creates turbulence and the spiral slipstream displaces the string to one side.

The yaw string is considered a primary flight reference instrument on gliders, which must be flown with near zero sideslip angle to reduce drag as much as possible. It is valued for its high sensitivity, and the fact that it is presented in a head-up display. Even the most sophisticated modern racing sailplanes are fitted with yaw strings by their pilots, who reference them constantly throughout the flight.

🔗 Physics 🔗 Chemistry 🔗 Geology 🔗 Rocks and minerals

A quasiperiodic crystal, or quasicrystal, is a structure that is ordered but not periodic. A quasicrystalline pattern can continuously fill all available space, but it lacks translational symmetry. While crystals, according to the classical crystallographic restriction theorem, can possess only two-, three-, four-, and six-fold rotational symmetries, the Bragg diffraction pattern of quasicrystals shows sharp peaks with other symmetry orders—for instance, five-fold.

Aperiodic tilings were discovered by mathematicians in the early 1960s, and, some twenty years later, they were found to apply to the study of natural quasicrystals. The discovery of these aperiodic forms in nature has produced a paradigm shift in the fields of crystallography. Quasicrystals had been investigated and observed earlier, but, until the 1980s, they were disregarded in favor of the prevailing views about the atomic structure of matter. In 2009, after a dedicated search, a mineralogical finding, icosahedrite, offered evidence for the existence of natural quasicrystals.

Roughly, an ordering is non-periodic if it lacks translational symmetry, which means that a shifted copy will never match exactly with its original. The more precise mathematical definition is that there is never translational symmetry in more than n – 1 linearly independent directions, where n is the dimension of the space filled, e.g., the three-dimensional tiling displayed in a quasicrystal may have translational symmetry in two directions. Symmetrical diffraction patterns result from the existence of an indefinitely large number of elements with a regular spacing, a property loosely described as long-range order. Experimentally, the aperiodicity is revealed in the unusual symmetry of the diffraction pattern, that is, symmetry of orders other than two, three, four, or six. In 1982 materials scientist Dan Shechtman observed that certain aluminium-manganese alloys produced the unusual diffractograms which today are seen as revelatory of quasicrystal structures. Due to fear of the scientific community's reaction, it took him two years to publish the results for which he was awarded the Nobel Prize in Chemistry in 2011. On 25 October 2018, Luca Bindi and Paul Steinhardt were awarded the Aspen Institute 2018 Prize for collaboration and scientific research between Italy and the United States.

🔗 Computer science

Cuckoo hashing is a scheme in computer programming for resolving hash collisions of values of hash functions in a table, with worst-case constant lookup time. The name derives from the behavior of some species of cuckoo, where the cuckoo chick pushes the other eggs or young out of the nest when it hatches; analogously, inserting a new key into a cuckoo hashing table may push an older key to a different location in the table.