Multi-Photon Quantum Interference covers the phenomena of quantum interference through the multi-photon effects of photon correlation. The author’s focus is on the temporal correlation among photons and how it influences the interference effect.

The goal of this monograph is to summarize the different quantum­ mechanical methods developed in the last 20 years to treat the electronic structure of polymers. Owing to the nature of the problem, these methods consist of a mixture of quantum-chemical and solid-state physical tech­ niques. The theory described in Part I treats, besides the Hartree-Fock problem, the· electron correlation, and it has also been developed for disordered polymeric systems. Though for obvious reasons the book could not include all the existing calculations, each new method des­ cribed is illustrated by a few applications, with a discussion of the numerical results obtained. Far more details see the Introduction to Part I. The second part contains the theoretical calculation of different properties of polymers based on the methods systematically introduced in the first part. The properties calculated include the electronic and vibrational spectra of polymers, and the computation of their transport, magnetic, and mechanical properties. In cases where reliable ex­ perimental data are available, the theoretical results are compared with them.

leagues and, in many cases, students, of Professor Onsager. Professor Onsager, himself, has contributed a paper on Illife in early times" to the volume. Among the topics discussed are some interesting applications of low temperature experimental techniques to cardiology and astrophysics. We would like to express our particular appreciation to Mrs. Helga Billings and Miss Sara Lesser for their excellent typing of these Proceedings and to Mrs. Jacquelyn Zagursky, as well as to Mrs. Billings and Miss Lesser for their invaluable assistance with the details of the conference and the publication of these Proceedings. The Editors CONTENTS Section One BIOLOGY Life in the Early Days Lars Onsager.

"Optimal Control" reports on new theoretical and practical advances essential for analysing and synthesizing optimal controls of dynamical systems governed by partial and ordinary differential equations. New necessary and sufficient conditions for optimality are given. Recent advances in numerical methods are discussed. These have been achieved through new techniques for solving large-sized nonlinear programs with sparse Hessians, and through a combination of direct and indirect methods for solving the multipoint boundary value problem. The book also focuses on the construction of feedback controls for nonlinear systems and highlights advances in the theory of problems with uncertainty. Decomposition methods of nonlinear systems and new techniques for constructing feedback controls for state- and control constrained linear quadratic systems are presented. The book offers solutions to many complex practical optimal control problems.