[1] Microsoft, 725 Granville St, Vancouver, BC V7Y 1L1, Canada
[2] ING Tech Romania, Tipografilor 11-15,Sect 1, RO-013714 Bucharest, Romania
[3] Univ Politehn Bucuresti, Dept Phys, 313 Splaiul Independentei, RO-060042 Bucharest, Romania
[4] Yerevan State Univ, Dept Solid State Phys, Yerevan 0025, Armenia
[5] Univ Antioquia UdeA, Fac Ciencias Exactas & Nat, Inst Fis, Grp Mat Condensada UdeA, Calle 70 52-21, Medellin, Colombia