. Author manuscript; available in PMC: 2015 May 21.
Published in final edited form as: AIMS Biophys. 2015 Mar 23;2(1):21–35. doi: 10.3934/biophy.2015.1.21
© 2015, J Bernard Heymann, licensee AIMS Press.
This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0)