Bloch, J. E. Marsden and G. Sanchez. 43 Oscillatory Descent for Function Minimization R. Brockett. 65 On the Well-Posedness of the Rational Covariance Extension Problem C. l. Byrnes, H. J. Landau and A. Lindquist. 83 Singular Limits in Fluid Mechanics P. Constantin. 109 Singularities and Defects in Patterns Far from Threshold N. M. Ercolani. 137 Mathematical Modeling and Simulation for Applications of Fluid Flow in Porous Media R. E. Ewing. 161 On Loeb Measure Spaces and their Significance for N on­ Cooperative Game Theory M. A. Khan and Y. Sun. 183 Mechanical Systems with Symmetry, Variational Principles, and Integration Algorithms J. E. Marsden and J. M. Wendlandt. 219 Preface The applied sciences are faced with increasingly complex problems which call for sophisticated mathematical models.