1. Mechanical and Manufacturing Department, MGEP Mondragon Goi Eskola Politeknikoa, Loramendi 4 Apdo. 23, 20500 Mondragon, Spain
2. Physikalisches Institut, Universität Bayreuth, D-95440 Bayreuth, Germany
3. MRC, CP165/62, Université Libre de Bruxelles, Ave. F.D. Roosevelt, 50, B-1050 Brussels, Belgium