c=2;l=30; modell={u'[z]==v[z], v'[z]== - c v[z] - u[z] (1 - u[z]), u[0]==0.999, v[0]==-0.001}; loesung=NDSolve[modell,{u,v},{z,0,l}]; abb=Plot[Evaluate[u[z]/.loesung],{z,0,l}, PlotPoints->50,PlotRange->All, ImageSize->{400,300},AxesLabel->{"z","u"}];