Professor Ciprian Foias, at that time distinghuised Professor of Mathematics at Indiana University in Bloomington U.S.A., has been the Stieltjes Visiting Professor for the year 2000. From May 15 till July 15 he developed and participated in a number of activities of the Stieltjes Institute. At the Vrije Universiteit he gave a series of five two hour lectures on *Rigorous mathematical approaches to turbulence theory*, an area in which he has a great research record, cf. [4]. The first lecture concerned deterministic solutions on the Navier-Stokes equations. This included a survey of classical results on the initial value problem for these equations, as well as more recent results on the global behavior of the solutions. The other lectures concentrated on various aspects of statistical solutions and normal forms of the Navier-Stokes equations, and covered topics like invariant measures, the global attractors and the universality problem in fully developed turbulence, the existence problem for self-similar decaying homogeneous turbulence, asymptotic integration and the associated normal form. The lectures presented a beautiful and effective mix of concrete problems from mathematical physics and fundamental methods from functional analysis. Open problems were discussed too. His ``inaugural address" as Stieltjes Professor, which he presented on June 8 at a meeting of the Stieltjes Institute at Leiden, was devoted to another topic in which he excels: the problem of commutant lifting from operator theory. The text of this lecture is published in the *Nieuw Archief voor Wiskunde* [1]. Equally important were the many informal discussions he had with colleagues from different institutions in the Netherlands. During his visit, not his first to the Stieltjes Institute, old friendships were renewed and new ones were made. His visit was a stimulant for further research and a starting point for new joint research projects (cf. [2], [3]).

**References**

[1] C. FOIAS, The general commutant extension problem, *NAW,* Serie 5, 2 (2) (2001),109-113.

[2] C. FOIAS, A.E. FRAZHO, M.A. KAASHOEK, Relaxation of metric constrained interpolation and a new lifting theorem, *Integral Equations and Operator Theory*, 42 (2002), 253-310.

[3] C. FOIAS, A.E. FRAZHO, M.A. KAASHOEK, Contractive liftings and the commutator, submitted.

[4] C. FOIAS, O. MANLEY, R. ROSA, R. TEMAM, *Navier-Stokes equations and turbulence,* Encyclopedia of Mathematics and its Applications, 83. Cambridge University Press, Cambridge, 2001.