Evidence for heavy nuclei in the primary cosmic radiation.
Whereas the event rate from neutrons will be higher for lighter nuclei.
This flight gave evidence for heavy nuclei among the cosmic rays.
Once the universe cooled enough for the electrons and nuclei to form atoms this changed.
For nuclei heavier than iron, one actually releases energy by breaking them up into 2 fragments.
They examined the individual cells, looking for irregular shapes and enlarged nuclei.
Grain boundaries are good sites for nuclei to form.
This emission is actually quite common for active galactic nuclei.
This means that the actual effect for large nuclei will be larger than expected by that model.
For light nuclei, it is usually better to use a model that takes this structure into account.