Introduction.- Theory in Singularly Perturbed Geometrical Domains.- Steklov-Poincare´ Operator for Helmholtz Equation.- Topological Derivatives for Optimal Control Problems.- Optimality Conditions with Topological Derivatives.- A Gradient-Type Method and Applications.- Synthesis of Compliant Thermomechanical Actuators.- Synthesis of Compliant Piezomechanical Actuators.- Asymptotic Analysis of Variational Inequalities.- A Newton-Type Method and Applications.- The Electrical Impedance Tomography Problem.