1. Assistant Research Professor, Univ. of Oklahoma, 660 Parrington Oval, Norman, OK 73072; Univ. of Connecticut, Storrs, CT 06269.
2. Professor, Univ. of Oklahoma, 660 Parrington Oval, Norman, OK 73072 (corresponding author).
3. Research Scientist, Univ. of Oklahoma, 660 Parrington Oval, Norman, OK 73072.
4. Assistant Professor, Beijing Normal Univ., Beijing 100875, China.