Neutron cross section according to its neutron cross section and how it reacts to an incident neutron. Nuclides that tend to absorb a neutron and either decay or keep the neutron in its nucleus are neutron absorbers and will have a "capture cross section" for that reaction. Isotopes that fission, are fissionable fuels and have a corresponding "fission cross section". The remaining isotopes will simply scatter the neutron, and have a "scatter cross section". Some isotopes, like uranium-238, have nonzero cross sections of all three. Isotopes which have a large scatter cross section and a low mass are good neutron moderators (see chart
How Long Has This Been Going On? this been going on?" Many recordings omit the first verse; Louis Armstrong's instead omits the second, which more strongly presupposes a female singer. How Long Has This Been Going On? "How Long Has This Been Going On?" is a song composed by George Gershwin, with lyrics by Ira Gershwin for the musical "Funny Face" in 1928. Replaced by "He Loves and She Loves" in "Funny Face", it was eventually introduced in the musical "Rosalie" (1928) by Bobbe Arnst as Mary O'Brien. The lyrics used as first released by Gershwin started with the refrain: "As a tot, when I trotted in