This book contains four contributions dealing with topics in dynamical systems: Transversal homoclinic orbits of area-preserving diffeomorphisms of the plane, asymptotic periodicity of Markov operators, classical particle channeling in perfect crystals, and adiabatic invariants in classical mechanics. All the authors give a careful and readable presentation of recent research results, which are of interest to mathematicians and physicists alike. The book is written for graduate students and researchers in mathematics and physics and it is also suitable as a text for graduate level seminars in dynamical systems.