Martin, you are correct, at this time thermodynamics calls ptracers_integrate and ptracers_impldiff -- Dimitris Menemenlis <menemenlis at jpl.nasa.gov> Jet Propulsion Lab, California Insitute of Technology MS 300-323, 4800 Oak Grove Dr, Pasadena CA 91109-8099 tel: 818-354-1656; fax: 818-393-6720