1. Department of Veterinary Pharmacology and Toxicology, National Key Laboratory of Veterinary Public Health Security, College of Veterinary Medicine, China Agricultural University, Beijing 100193, P. R. China
2. Department of Veterinary Theriogenology, College of Veterinary Medicine, China Agricultural University, Beijing 100193, P. R. China
3. Department of Applied Physics, China Agricultural University, Beijing 100083, P. R. China
4. Department of Electrical and Computer Engineering, Waterloo Institute of Nanotechnology (WIN), University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
5. School of Information Science and Technology, North China University of Technology, Beijing 100144, P. R. China