Biometrics Research, Merck Research Laboratories, West Point, PA 19486, USA. xiaohua_zhang@merck.com|Biometrics Research, Merck Research Laboratories, West Point, PA 19486, USA. xiaohua_zhang@merck.com|Biometrics Research, Merck Research Laboratories, West Point, PA 19486, USA. xiaohua_zhang@merck.com|Biometrics Research, Merck Research Laboratories, West Point, PA 19486, USA. xiaohua_zhang@merck.com|Biometrics Research, Merck Research Laboratories, West Point, PA 19486, USA. xiaohua_zhang@merck.com|Biometrics Research, Merck Research Laboratories, West Point, PA 19486, USA. xiaohua_zhang@merck.com|Biometrics Research, Merck Research Laboratories, West Point, PA 19486, USA. xiaohua_zhang@merck.com|Biometrics Research, Merck Research Laboratories, West Point, PA 19486, USA. xiaohua_zhang@merck.com|Biometrics Research, Merck Research Laboratories, West Point, PA 19486, USA. xiaohua_zhang@merck.com|Biometrics Research, Merck Research Laboratories, West Point, PA 19486, USA. xiaohua_zhang@merck.com|Biometrics Research, Merck Research Laboratories, West Point, PA 19486, USA. xiaohua_zhang@merck.com|Biometrics Research, Merck Research Laboratories, West Point, PA 19486, USA. xiaohua_zhang@merck.com|Biometrics Research, Merck Research Laboratories, West Point, PA 19486, USA. xiaohua_zhang@merck.com|Biometrics Research, Merck Research Laboratories, West Point, PA 19486, USA. xiaohua_zhang@merck.com|Biometrics Research, Merck Research Laboratories, West Point, PA 19486, USA. xiaohua_zhang@merck.com