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
Neutron cross section of the order of "π r" or roughly 10 cm (thus justifying the definition of the barn). However, if measured experimentally ( "σ" = "R" / ("Φ N") ), the experimental cross sections vary enormously. As an example, for slow neutrons absorbed by the (n, γ) reaction the cross section in some cases (xenon-135) is as much as 2,650,000 barns, while the cross sections for transmutations by gamma-ray absorption are in the neighborhood of 0.001 barn (See here for more example of cross sections). The "nuclear cross section" is consequently a purely conceptual quantity representing how big the nucleus should