1. D. A. Edwards, A. Ben-Jebria, J. Mintzes, Department of Chemical Engineering, Pennsylvania State University, 204 Fenske Laboratory, University Park, PA 16802, USA.
2. J. Hanes, J. Hrkach, R. Langer, Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
3. G. Caponetti, Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA, and Department of Pharmacy, Universite di Parma, 43100 Parma, Italy.
4. M. L. Eskew, Environmental Resources Research Institute, Pennsylvania State University, Fenske Laboratory, University Park, PA 16802, USA.
5. D. Deaver, Department of Animal Science, Pennsylvania State University, 324 Henning Building, University Park, PA 16802, USA.