Headline News

Bai Chunli Visits Canada and Germany

CAS President Professor Bai Chunli headed a delegation to Canada and Germany in late May. In Canada, Prof. Bai visited National Research Council (NRC), Natural Resources Canada (NRCan) and the Department of Foreign Affairs and Trade (DFAT). Prof. Bai and NRCan Minister discussed future cooperation and signed an arrangement to further implement the MOU for Sustainable Development of Natural Resources signed last year. In Germany, Prof. Bai attended the Second Annual Conference of the International Council for Research (ICR）and its Managing Council Meeting held in Berlin from May 27-29. Representatives of national science foundations, scientific institutions and international organizations from around 50 countries attended the conference. It was decided at the first annual conference that the 2014 ICR conference would be held in Beijing and co-sponsored by the Chinese Academy of Sciences (CAS), the Canadian National Foundation of Science and Engineering, and the National Natural Science Foundation of China. At the Berlin Conference, Prof. Bai briefed about the themes and preparatory work for the 2014 ICR Conference.

New Breakthrough in Angular Correlation Fluctuation X-ray Scattering Technique

Prof. Chen Gang of the Shanghai Synchrotron Radiation Facility at Shanghai Institute of Applied Physics, in collaboration with scientists at Lawrence Berkeley National Laboratory and Pacific Northwest National Laboratory, has theoretically extended the angular correlation fluctuation x-ray scattering technique to determine particle structures from heterogeneous mixed particle systems. Applying this technique, one would be able to follow the structure deformation of protein molecules and the growth and self-assembly process of nano-materials. The result has been published online in Physical Review Letters [PRL 110, 195501 (2013)]. With the development of synchrotron radiation and recent advancement of x-ray free electron laser (XFEL), the single molecule x-ray diffraction technique has brought new hope to structure determination of amorphous materials and gained a lot of attentions, but there are several experimental and theoretical difficulties that hinder the development of this technique, for example, it is technically challenging to select a single particle and align it with a tiny x-ray beam and the following data analyses and structural reconstructions could be complicated due to the lack of information on particle orientations. By taking full advantage of the short pulse and high peak brightness of modern x-ray sources, the angular correlation fluctuation x-ray scattering technique proposed by Zvi Kam promises structure determination without crystallization and attracts intense research activities recently. This spectroscopic technique operates on sampling of many x-ray diffraction patterns from random oriented copies of the same particle to extract angular correlation functions and from them to derive particle structures. Experiments and theoretical works have shown that this technique can overcome many technical difficulties in single molecule diffraction. The theoretical work made at Shanghai Synchrotron Radiation Facility by extending the theorem from homogeneous to heterogeneous systems is a new breakthrough in the angular correlation fluctuation x-ray scattering study.