time = 0.0
        dt = 1.0e-4
        P = []
        T = []
        T_grad = []
        tt = []

        while ((time < 1) and (T_grad > 0.5)) :
            time += dt
            sim.advance(time)
            tt.append(time)
            P.append(r1.thermo.P)
            T.append(r1.thermo.T)
        for n in range(0, len(T)-1):
            T_grad.append(T[n+1] - T[n])

        #print T_grad
        print len(tt)
        print len(T_grad)
        print min(T_grad)