category c1 Refereed Journal Article, Huu Dung Tran signedVUIR pt.20/5/11. Not checked in Sherpa, 24/06/11 RD. White in Sherpa, Author's Pre-print: archiving status unclear, author can archive post-print (ie final draft post-refereeing) with Restrictions: 90 days after publication.  Published June 2010. email sent to Huu Dung Tran 14.11.11-MMM. recd 28.11.11-MMM. Changed name from: Ng, W. M. Anne to Ng, A. W. M as requested by author (Anne) see email in LibShare, May 2014--MMM. Supporting documentation added to dark upload - HD 5/6/18