1. Institute
of Macromolecular Compounds, Russian Academy of Sciences, av. Bol’shoi
31, St. Petersburg 199004, Russia
2. Department
of Physics, St. Petersburg State University, Ulianovskaya str. 1, St. Petersburg 198504, Russia
3. Department
of Medical Physics and Bioengineering, St. Petersburg State Polytechnical University, Polytechnicheskaya str. 29, St. Petersburg 195251, Russia