1. Department of Materials Chemistry, National Center for HREM, Lund University, P.O. Box 124, S-22100 Lund, Sweden, Institute of Scientific and Industrial Research (ISIR), Osaka University, Osaka, Japan, Centre for Materials Research, School of Physical Sciences, University of Kent, Canterbury CT2 7NR, United Kingdom, and Department of Materials Science, The Ångström Laboratory, Uppsala University, Uppsala, Sweden