A barrel vault, also known as a tunnel vault, wagon vault or wagonhead vault, is an architectural element formed by the extrusion of a single curve (or pair of curves, in the case of a pointed barrel vault) along a given distance. The curves are typically circular in shape, lending a semi-cylindrical appearance to the total design. The barrel vault is the simplest form of a vault: effectively a series of arches placed side by side (i.e., one after another). It is a form of barrel roof. As with all arch-based constructions, there is an outward thrust generated against the walls underneath a barrel vault. There are several mechanisms for absorbing this thrust. One is to make the walls exceedingly thick and strong – this is a primitive and sometimes unacceptable method. A more elegant method is to build two or more vaults parallel to each other; the forces of their outward thrusts will thus negate each other. This method was most often used in construction of churches, where several vaulted naves ran parallel down the length of the building. However, the outer walls of the outermost vault would still have to be quite strong or reinforced by buttressing...

Nelson Rolihlahla Mandela (; Xhosa: [xolíɬaɬa mandɛ̂ːla]; 18 July 1918 – 5 December 2013) was a South African anti-apartheid activist and politician who served as the first president of South Africa from 1994 to 1999. He was the country's first black head of state and the first elected in a fully representative democratic election. His government focused on dismantling the legacy of apartheid by fostering racial reconciliation. Ideologically an African nationalist and socialist, he served as the president of the African National Congress (ANC) party from 1991 to 1997. A Xhosa, Mandela was born into the Thembu royal family in Mvezo, South Africa. He studied law at the University of Fort Hare and the University of Witwatersrand before working as a lawyer in Johannesburg. There he became involved in anti-colonial and African nationalist politics, joining the ANC in 1943 and co-founding its Youth League in 1944. After the National Party's white-only government established apartheid, a system of racial segregation...

The Flash is a 2023 American superhero film based on the DC character of the same name. Produced by Warner Bros. Pictures, DC Studios, Double Dream, and the Disco Factory, and distributed by Warner Bros., it is the 13th installment in the DC Extended Universe (DCEU). The film was directed by Andy Muschietti from a screenplay by Christina Hodson, and stars Ezra Miller as Barry Allen / The Flash alongside Sasha Calle, Michael Shannon, Ron Livingston, Maribel Verdú, Kiersey Clemons, Antje Traue, and Michael Keaton. In the film, Barry travels back in time to prevent his mother's death, which brings unintended consequences. Development of a film based on the Flash began in the late 1980s, with multiple writers and directors attached to the project through 2014. The film was then redeveloped as a part of the DCEU, with Miller cast as the title character. Multiple directors were attached to the film over the following years, with Seth Grahame-Smith, Rick Famuyiwa, and the duo of John Francis Daley and Jonathan Goldstein all departing the project over creative differences. Muschietti and Hodson joined the...