Reverted changes of the variable 'nucleus' to 'heteronucleus'.
The command used was:
svn merge -r5308:5302 ./physical_constants.py
This error was noticed by Edward d'Auvergne in a post at:
https://mail.gna.org/public/relax-devel/2008-04/msg00033.html (# Message-id:
<7f080ed10804040741x3e26f862r808982451ab522c8@...>)
