Algebraic operationIn mathematics, a basic algebraic operation is any one of the common operations of arithmetic, which include addition, subtraction, multiplication, division, raising to a whole number power, and taking roots (fractional power). These operations may be performed on numbers, in which case they are often called arithmetic operations. They may also be performed, in a similar way, on variables, algebraic expressions, and more generally, on elements of algebraic structures, such as groups and fields.
Alexandroff extensionIn the mathematical field of topology, the Alexandroff extension is a way to extend a noncompact topological space by adjoining a single point in such a way that the resulting space is compact. It is named after the Russian mathematician Pavel Alexandroff. More precisely, let X be a topological space. Then the Alexandroff extension of X is a certain compact space X* together with an open embedding c : X → X* such that the complement of X in X* consists of a single point, typically denoted ∞.
Steel-string acoustic guitarThe steel-string acoustic guitar is a modern form of guitar that descends from the gut-strung Romantic guitar, but is strung with steel strings for a brighter, louder sound. Like the modern classical guitar, it is often referred to simply as an acoustic guitar, or sometimes as a folk guitar. The most common type is often called a flat top guitar, to distinguish it from the more specialized archtop guitar and other variations.
Margaret ThatcherMargaret Hilda Thatcher, Baroness Thatcher (; 13 October 1925 - 8 April 2013), was a British stateswoman and Conservative politician who served as Prime Minister of the United Kingdom from 1979 to 1990 and Leader of the Conservative Party from 1975 to 1990. She was the first female British prime minister and the longest-serving of the 20th century. As prime minister, she implemented economic policies that became known as Thatcherism. A Soviet journalist dubbed her the "Iron Lady", a nickname that became associated with her uncompromising politics and leadership style.
