On 28 February 2023, a passenger train and a freight train collided in Thessaly, Greece, resulting in the deaths of at least 36 people and injuries to at least 85 others, making it the deadliest railway accident in Greece since 1968. Background A passenger train departed from Athens at around 7:30 p.m. Eastern European Time (5:30 p.m. UTC) carrying approximately 350 passengers from Athens to Thessaloniki. Meanwhile, a freight train was travelling from Thessaloniki to Larissa. Both trains were hauled by an electric Class 120 locomotive (pictures of the wreck show the remains of locomotives 120-022 and 120-012). The two collided on the Athens-Thessaloniki railway, which is operated by Hellenic Train, a subsidiary of Ferrovie dello Stato Italiane, Italy's state-owned railway company. The accident section was double-tracked and had automatic controls installed but switching and signalling was still being done manually. The president of the Greek train drivers' union said that the accident "would have been avoided if the safety systems were working". Already earlier the same day, at Palaiofarsalos railway...

The electric potential (also called the electric field potential, potential drop, the electrostatic potential) is defined as the amount of work energy needed to move a unit of electric charge from a reference point to the specific point in an electric field. More precisely, it is the energy per unit charge for a test charge that is so small that the disturbance of the field under consideration is negligible. Furthermore, the motion across the field is supposed to proceed with negligible acceleration, so as to avoid the test charge acquiring kinetic energy or producing radiation. By definition, the electric potential at the reference point is zero units. Typically, the reference point is earth or a point at infinity, although any point can be used. In classical electrostatics, the electrostatic field is a vector quantity expressed as the gradient of the electrostatic potential, which is a scalar quantity denoted by V or occasionally φ, equal to the electric potential energy of any charged particle at any location (measured in joules) divided by the charge of that particle (measured in coulombs). By dividing out the...

Boa is a genus of non-venomous boas found in Mexico, the Caribbean, and Central and South America. Five extant species, and one extinct, are currently recognized. Etymology The Online Etymology Dictionary says that the word comes from the "late 14c., "large snake," from Latin boa, type of large serpent mentioned in Pliny's "Natural History;" origin unknown (in medieval folk etymology the name was associated with Greek bous "ox")." Species ) Not including the nominate subspecies.Distribution and habitat Boa species are found in northern Mexico through Central America (Belize, Guatemala, Honduras, El Salvador, Nicaragua, Costa Rica and Panama) to South America north of 35°S (Colombia, Ecuador, Peru, Venezuela, Guyana, Suriname, French Guiana, Brazil, Bolivia, Uruguay and Argentina). One species is present in the Lesser Antilles (Dominica and St. Lucia), on San Andrés, Providencia and many other islands along the Caribbean coasts of Mexico and Central and South America. ...

History (derived from Ancient Greek ἱστορία (historía) 'inquiry; knowledge acquired by investigation') is the systematic study and documentation of human activity. The time period of events before the invention of writing systems is considered prehistory. "History" is an umbrella term comprising past events as well as the memory, discovery, collection, organization, presentation, and interpretation of these events. Historians seek knowledge of the past using historical sources such as written documents, oral accounts, art and material artifacts, and ecological markers. History is not complete and still has debatable mysteries. History is also an academic discipline which uses narrative to describe, examine, question, and analyze past events, and investigate their patterns of cause and effect. Historians often debate which narrative best explains an event, as well as the significance of different causes and effects. Historians also debate the nature of history as an end in itself, as well as its usefulness to give perspective...

The Victoria and Albert Museum (often abbreviated as the V&A) in London is the world's largest museum of applied arts, decorative arts and design, housing a permanent collection of over 2.27 million objects. It was founded in 1852 and named after Queen Victoria and Prince Albert. The V&A is located in the Royal Borough of Kensington and Chelsea, in an area known as "Albertopolis" because of its association with Prince Albert, the Albert Memorial and the major cultural institutions with which he was associated. These include the Natural History Museum, the Science Museum, the Royal Albert Hall and Imperial College London. The museum is a non-departmental public body sponsored by the Department for Digital, Culture, Media and Sport. As with other national British museums, entrance is free. The V&A covers 12.5 acres (5.1 ha) and 145 galleries. Its collection spans 5,000 years of art, from ancient times to the present day, from the cultures of Europe, North America, Asia and North Africa. However, the art of antiquity in most areas is not collected. The holdings of ceramics, glass, textiles, costumes, silver, ironwork...

A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency portion of the electromagnetic spectrum emitted by astronomical objects, just as optical telescopes are the main observing instrument used in traditional optical astronomy which studies the light wave portion of the spectrum coming from astronomical objects. Unlike optical telescopes, radio telescopes can be used in the daytime as well as at night. Since astronomical radio sources such as planets, stars, nebulas and galaxies are very far away, the radio waves coming from them are extremely weak, so radio telescopes require very large antennas to collect enough radio energy to study them, and extremely sensitive receiving equipment. Radio telescopes are typically large parabolic ("dish") antennas similar to those employed in tracking and communicating with satellites and space probes. They may be used singly or linked together electronically in an array. Radio observatories are preferentially located far from major centers of population...

A sarcomere (Greek σάρξ sarx "flesh", μέρος meros "part") is the smallest functional unit of striated muscle tissue. It is the repeating unit between two Z-lines. Skeletal muscles are composed of tubular muscle cells (called muscle fibers or myofibers) which are formed during embryonic myogenesis. Muscle fibers contain numerous tubular myofibrils. Myofibrils are composed of repeating sections of sarcomeres, which appear under the microscope as alternating dark and light bands. Sarcomeres are composed of long, fibrous proteins as filaments that slide past each other when a muscle contracts or relaxes. The costamere is a different component that connects the sarcomere to the sarcolemma. Two of the important proteins are myosin, which forms the thick filament, and actin, which forms the thin filament. Myosin has a long, fibrous tail and a globular head, which binds to actin. The myosin head also binds to ATP, which is the source of energy for muscle movement. Myosin can only bind to actin when the binding sites on actin are exposed by calcium ions. Actin molecules are bound to the Z-line, which forms the borders of the sarcomere. Other bands appear...

A polymer (; Greek poly-, "many" + -mer, "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and natural polymers play essential and ubiquitous roles in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. Their consequently large molecular mass, relative to small molecule compounds, produces unique physical properties including toughness, high elasticity, viscoelasticity, and a tendency to form amorphous and semicrystalline structures rather than crystals. The term "polymer" derives from the Greek word πολύς (polus, meaning "many, much") and μέρος (meros, meaning "part"). The term was coined in 1833 by Jöns Jacob Berzelius, though with a definition distinct from the modern IUPAC definition. The modern concept of polymers...

The Anglo-Saxons were a cultural group who inhabited England in the Early Middle Ages. They traced their origins to settlers who came to Britain from mainland Europe in the 5th century. However, the ethnogenesis of the Anglo-Saxons happened within Britain, and the identity was not merely imported. Anglo-Saxon identity arose from interaction between incoming groups from several Germanic tribes, both amongst themselves, and with indigenous Britons. Many of the natives, over time, adopted Anglo-Saxon culture and language and were assimilated. The Anglo-Saxons established the concept, and the Kingdom, of England, and though the modern English language owes somewhat less than 26% of its words to their language, this includes the vast majority of words used in everyday speech.Historically, the Anglo-Saxon period denotes the period in Britain between about 450 and 1066, after their initial settlement and up until the Norman Conquest. The early Anglo-Saxon period includes the creation of an English nation, with many of the aspects that survive today, including regional government of shires and hundreds. During this period, Christianity was established...