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.