1. Professor, Bioengineering Dept., Oregon State Univ., Corvallis, OR 97330.
2. Professor and Head, Bioresource and Agricultural Engineering Dept., California Polytechnic Univ., 1 Grand Ave., San Luis Obispo, CA 93407.
3. Professor and Head, Biological Systems Engineering Dept., Univ. of Nebraska-Lincoln, 223 LW Chase Hall, Lincoln, NE 68583-0726.