History of the metric system levels of the krypton 86 atom as the new standard for the metre. The standard metre artefact was retired. In 1960, Giorgi's proposals were adopted as the basis of the "Système International d'Unités" (International System of Units), the SI. This initial definition of the SI included six base units, the metre, kilogram, second, ampere, degree Kelvin and candela, and sixteen coherent derived units. The evolution of the SI after its publication in 1960 has seen the addition of a seventh base unit, the "mole", and six more derived units, the "pascal" for pressure, the "gray", "sievert" and "becquerel" for radiation,
Induced radioactivity Induced radioactivity Induced radioactivity, also called artificial radioactivity or man-made radioactivity, is the process of using radiation to cause a previously stable material to become radioactive. The husband and wife team of Irène Joliot-Curie and Frédéric Joliot-Curie (they both began using the surname Joliot-Curie when they married in 1926) discovered induced radioactivity in 1934, and they shared the 1935 Nobel Prize in Chemistry for this discovery. Irène Curie began her research with her parents, Marie Curie and Pierre Curie, studying the natural radioactivity found in radioactive isotopes. Irène and Pierre Joliot-Curie Irene branched off from the Curies to study turning