  We prove that a crossing change along a double point circle on a 2-knot is
realized by ribbon-moves for a knotted torus obtained from the 2-knot by
attaching a 1-handle. It follows that any 2-knots for which the crossing change
is an unknotting operation, such as ribbon 2-knots and twist-spun knots, have
trivial Khovanov-Jacobsson number.

Geometric Topology;Quantum Algebra