About the influence of friction and polydispersity on the jamming behavior of bead assemblies L. Pournin, M. Ramaioli, P. Folly and Th. M. Liebling Eur. Phys. J. E, 23 2 (2007) 229-235 Published online: 14 June 2007 DOI: 10.1140/epje/i2007-10176-5