Papal tiara Papal tiara The papal tiara is a crown that was worn by popes of the Catholic Church from as early as the 8th century to the mid-20th. It was last used by Pope Paul VI in 1963 and only at the beginning of his reign. The name "tiara" refers to the entire headpiece, no matter how many crowns, circlets or diadems have adorned it through the ages, while the three-tiered form that it took in the 14th century is also called the triregnum, triple tiara, or triple crown. From 1143 to 1963, the papal tiara was solemnly placed on the
Nuclear cross section inelastic scattering; of the latter, amongst neutron cross sections the absorption cross sections are of particular interest. In nuclear physics it is conventional to consider the impinging particles as point particles having negligible diameter. Cross sections can be computed for any sort of process, such as capture scattering, production of neutrons, etc. In many cases, the number of particles emitted or scattered in nuclear processes is not measured directly; one merely measures the attenuation produced in a parallel beam of incident particles by the interposition of a known thickness of a particular material. The cross section obtained in this way