1. Material Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899, United States
2. Formulation Sciences Department, MedImmune Inc., Gaithersburg, Maryland 20878, United States
3. NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
4. Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States