I was surprised to find promotional copy for a problem solver of a
kind that may be of interest to the list. It is Open Source,
and available at no charge. Here is an extract from the blurb:
"You can find examples of the use of xmds for solving complex (and
simple) problems in the examples page of the xmds web site:
<http://www.xmds.org/examples/>
"So, if you're trying to model a bunch of atoms bouncing around
together, the diffusion of an electrolyte solution, the reaction of
enzymes with a substrate, or the volatility of stock prices, then xmds
is the simulation tool for you.