1. Graduate School of Pharmaceutical Sciences, Ewha Womans University, Seoul 120-750, Korea.
2. Department of Biomedical Sciences, College of Medicine, Inha University, Incheon 402-751, Korea.
3. Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185, Korea.
4. Power Systems Research Division, Electrical Environment Team, Korea Electrotechnology Research Institute, Changwon 642-120, Korea.