Phase Diagram for Unzipping DNA Using a Bond-Force Criterion
  Using the criterion that the mechanical unzipping transition in a bound homopolymer is triggered when the average force exerted by the single unbound strands on the first base pair in the bound section exceeds the force binding the pair together, the temperature dependence of the critical unzipping force is obtained. In the resulting phase diagram, the critical force decreases monotonically with increasing temperature, from a finite value at zero Kelvin to zero at the critical temperature. 
Richard M. Neumann