http://reply.papertrans.cn/1/11/1086/1086-31.png
http://reply.papertrans.cn/1/11/1086/1086-32.png
Submitted on: 24 August 2010.
Revised on: 25 October 2010.
Accepted on: 09 November 2010.
___________________AIMS Molecular Science---AMER INST MATHEMATICAL SCIENCES-AIMS
http://reply.papertrans.cn/1/11/1086/1086-34.png
http://reply.papertrans.cn/1/11/1086/1086-35.png
Submitted on: 23 June 2004.
Revised on: 15 October 2004.
Accepted on: 11 December 2004.
___________________AIMS Molecular Science---AMER INST MATHEMATICAL SCIENCES-AIMS