1. Department of Physical Chemistry, University of Pannonia, P.O. Box 158, H-8201 Veszprém, Hungary
2. Department of Mathematics, University of Warwick, CV4 7AL Coventry, United Kingdom
3. Department of Material- and Geo-Sciences, Technische Universität Darmstadt, Petersenstr. 23, D-64287 Darmstadt, Germany
4. Department of Physiology and Biophysics, Rush University Medical Center, Chicago, Illinois 60612, USA