Zuhong Lu1, Lei Zhu2, Zhongwei Jia3. 1. Department of Biomedical Engineering, Peking University, Beijing 100871, China. 2. National Institute of Drug Dependence, Peking University, Beijing 100191, China. 3. National Institute of Drug Dependence, Peking University, Beijing 100191, China. Email: urchinjj@163.com.