[1] Tech Univ Darmstadt, Dept Phys, Emmy Noether Res Grp, D-64289 Darmstadt, Germany
[2] Univ Paris 06, Inst Jean Le Rond Alembert, F-75252 Paris 05, France
[3] Aristotle Univ Thessaloniki, Polytech Sch, Lab Mech & Mat, Thessaloniki 54124, Greece
[4] Michigan Technol Univ, Ctr Mech Mat Instabil & Mfg Proc, Houghton, MI 49931 USA