1. Graduate Research Assistant, E1511 Lafferre Hall, Univ. of Missouri-Columbia, Columbia, MO 65211.
2. Associate Professor, C2640 Lafferre Hall, Univ. of Missouri-Columbia, Columbia, MO 65211 (corresponding author).
3. Associate Professor, E2509 Lafferre Hall, Univ. of Missouri-Columbia, Columbia, MO 65211.