1. State Key Laboratory of High Performance Ceramics and Superfine MicrostructureShanghai Institute of CeramicsChinese Academy of Sciences Shanghai 200050 P. R. China
2. Shanghai Key Laboratory of Orthopedic ImplantsDepartment of Orthopedic Surgery Shanghai Ninth People's HospitalShanghai Jiao Tong University School of Medicine Shanghai 200011 P. R. China
3. Department of ChemistryThe University of Chicago Chicago IL 60637 USA
4. Department of Medical UltrasoundTenth People's Hospital of Tongji UniversityUltrasound Research and Education InstituteTongji University School of Medicine Shanghai 200072 P. R. China