1. Joint Institute for High Temperatures, Russian Academy of Sciences, 13/19, Izhorskaia Str., Moscow 125412, Russia
2. National Research University, “Moscow Power Engineering Institute,” Krasnokazarmennaya Str. 14, Moscow 111250, Russia
3. Institut für Physik, Humboldt-Universität zu Berlin, Newtonstraße 15, D-12489 Berlin, Germany