Received Date: 17 Feb 2010
Revision Received Date: 04 Jun 2010
Electronic Publication Date: 15 Sept 2010
Authors are grateful to Mrs. Sara D’Imporzano for technical assistance and to Marco Salerno, PhD (Italian Institute of Technology, Genova) for useful discussion. Authors declare no conflict of interest directly relevant to this study. This study was presented at the IADR's 87th General Session and Exhibition, Miami, 1-4 April 2009, as a poster.