1. Department of Civil
and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, United States
2. Department of Physics, Low Energy Neutron Source, Indiana University, Bloomington, Indiana 47405, United States
3. Biology and Soft Matter Division, Neutron
Scattering Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393, United States, and Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States