1. Department of Materials, University of Oxford, Oxford OX1 3PH, U.K.
2. Pharmaceutical Development, AstraZeneca, Macclesfield SK10 2NA, U.K.
3. Department of Physics, University of Warwick, Coventry CV4 7AL, U.K.
4. Department of Chemistry, Durham University, Durham DH1 3LE, U.K.
5. Early Product Development, Pharmaceutical Sciences, IMED Biotech Unit, AstraZeneca Gothenburg, Mölndal SE-431 83, Sweden