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Comparison of the barrier to fusion of asymmetric bilayers containing an average volume fraction of hexagonal formers of φ2 = 0.35 as calculated along the standard pathway (squares) and the second stalk-hole pathway (triangles) for three different volume fractions of hexagonal formers in the cis layer; 
0.395, 0.431. Also shown is the free energy of a stalk (circles) in the same systems.
