1. Department of Fibre and Polymer Technology; KTH Royal Institute of Technology; Teknikringen 56 10044 Stockholm Sweden
2. Department of Electrical Engineering; Linköping University; Campus Valla 58183 Linköping Sweden
3. Wallenberg Wood Science Centre; Department of Fibre and Polymer Technology; KTH Royal Institute of Technology; Teknikringen 56 10044 Stockholm Sweden