• 2000-pres, Centennial Professor of Mathematics, Vanderbilt University, Nashville, TN;
• 2003-pres, Professor Molecular Physiology and Biophysics
• 2000-2005, Director of the Biomathematics Study Group, Vanderbilt University, Nashville, TN;
• 1986-2000 Professor, Department of Mathematics, Northwestern University, Evanston, IL;
• 1987-1999, Professor, Univ. of Rome, Tor Vergata, Italy;
• 1984-1987, Associate Professor, Department of Mathematics, Northwestern University, Evanston, IL;
• 1983-1984, Assistant Professor, Department of Mathematics, Indiana University, Bloomington IN;
• 1982-1983, Assistant Professor, Department of Mathematics, Northwestern University, Evanston, IL;
• 1979-1982, Vaclav Hlavaty Research Assistant Professor, Department of Mathematics, Indiana University, Bloomington, IN;
• 1979-1980, Research Associate, Mathematics Research Center, University of Wisconsin, Madison, WI;
• 1976-1979, Teaching Assistant, Department of Mathematics, University of Texas at Austin, Austin, TX;
• 1975-1976, Assistant Professor of Rational Mechanics, Department of Mathematics, University of Florence, Italy,