1. State Key Laboratory of High Performance Ceramics and Superfine MicrostructureShanghai Institute of CeramicsChinese Academy of Sciences Shanghai 200050 P. R. China
2. Department of UltrasoundSir Run Run Shaw HospitalSchool of MedicineZhejiang University Hangzhou 310000 P. R. China
3. Department of ChemistryUniversity 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 China