Problem with Differential Eq

*To*: mathgroup at smc.vnet.net*Subject*: [mg82544] Problem with Differential Eq*From*: "Dave" <david.fourie at ncl.ac.uk>*Date*: Wed, 24 Oct 2007 04:27:48 -0400 (EDT)*Organization*: Newcastle University

The following .nb file just won't run!!! I can't see what is wrong as it is a relativly simple series of self evaluating differential equations. [code] lpmk10[u_] := 1/(1 + Exp[(u + 12.3)/-11.8]); lptaumk1[u_] := 14.4 - 12.8/(1 + Exp[(u + 28.3)/-19.2]); solution = NDSolve[{lpmk1'[t] == (lpmk10[lpv[t]] - lpmk1[t])*(1/lptaumk1[lpv[t]]), lpmk1[0] == lpmk10[-80]*(1/lptaumk1[-80]) lpv'[t] == -1*(+1*125*(lpmk1[t]^4)*(lpv[t] + 80)), lpv[0] == -80}, {lpv, lpmk1}, {t, 0, 1500}, Method -> Automatic]; ParametricPlot[Evaluate[{t, lpv[t]} /. solution], {t, 0, 1500}, PlotPoints -> 1500, PlotRange -> All]; [/code] if any one can shed some light on this it would be great