+
Distant changes alter curvature cancellation
¥damage: remove bending energy from core region

central force F decreases
curvature cancellation is incomplete
\cancellation uniform elasticity
Thus: curvature cancellation results from global constraints. 
deform: circular rim¨elliptical rim
   Mean curvature varies along the rim
   Becomes negative at minor axis
r
0
Jin Wang, TW 2009