Papal cross Papal cross The papal cross is a Christian cross, which serves as an emblem for the office of the Pope in ecclesiastical heraldry. It is depicted as a staff with three horizontal bars near the top, in diminishing order of length as the top is approached. The cross is thus analogous to the two-barred archiepiscopal cross used in heraldry to indicate an archbishop, and seems to have been used precisely to indicate an ecclesiastical rank still higher than that of archbishop. In the past, this design of the cross was often used in ecclesiastical heraldry as a distinctive mark of
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