Nonlinear mappings preserving product XY+YX∗ on factor von Neumann algebras

Let A and B be two factor von Neumann algebras. For A,B∈A, define by A
• B=AB+BA∗ the new product of A and B. In this article, it is proved that a not necessarily linear bijective mapping Φ:A→B satisfies Φ(A
• B)=Φ(A)
• Φ(B) for all A,B∈A if and only if Φ is a ∗-ring isomorphism. In particular, if the von Neumann algebras A and B are type I factors, then Φ is a unitary isomorphism or a conjugate unitary isomorphism.