• 1990-     Principal Researcher, Institute of Mathematics of the Romanian Academy.
• 1991-     Associate Lecturer, Polytechnical University  of Bucharest.
• 1979-1990:  Research Scientist, Department of Mathematics of the National Institute for Scientifical and Technical Creation (INCREST), Bucharest.
• 1976-1979: Computer Analyst, Computing Center of the Geological and Geophysical Prospecting Enterprise (IPGGH), Bucharest.

Visiting positions
 

• 2001: Invited researcher at Georgia State University (two months), supported by a COBASE grant of NRC.
• 2000-2002:  Visiting Associate Professor at the University of Lyon (three semesters).
• 1999:  Visiting Associate Professor at Georgia Institute of Technology, Atlanta (two quarters).
• 1998:  Visiting Associate Professor at Georgia Institute of Technology, Atlanta (one quarter).
• 1996:  Invited Professor at the University of Lille, France (one month).
• 1994-1995: Visiting Associate Professor at Georgia Institute of Technology, Atlanta.
• 1992: Invited Professor at the University of Bordeaux, France (one semester).
• 1991: Participant at the Mittag-Leffler year on function spaces (one month).
• 1990-1991: Invited Scholar at Indiana University, Bloomington (three months), UCLA (one month), Texas A&M University (one month).
• 1983, 1985: Invited researcher at Steklov Institute, St.Petersburg (one month and two weeks respectively).
• 1984: Invited researcher at the Institute of Mathematics of the Czechoslovac Academy (one month).

Participation in scientific meetings

            Invited lectures and contributed presentations at different professional meetings:  International Meetings on Operator Theory (Timisoara and Bucharest, Romania, 1978-1996),  International Seminars on Functional Analysis (Czechoslovakia, 1981, 1982, 1983, 1984, 1988; Czeckia 1993), Mittag-Leffler semester on invariant subspaces (Stockholm, 1980), International Conference on Operator Theory and Numerical Analysis(Warsaw, 1981), Operator Theory days (Luminy, 1993 and 1995, Lille 1997), Analysis Conference dedicated to B.Sz-Nagy (Szeged, 1993), Banach Semester on operator theory (Warsaw, 1994 and 1996), Southeastern Analysis Meeting (Atlanta, 1995; Tuscaloosa, 1998, Nashville, 1999), Great Plains Operator Theory Symposion (Cincinnati, 1995), East Carolina Analysis Days (Greenville, 1998).

            Colloquium talks at various universities and research institutes including: Institute of Mathematics of the Czechoslovac Academy of Sciences (1979, 1984), Steklov Institute at St.Petersburg (1983, 1985), College of William and Mary, Williamsburg (1990), University of California at Berkeley (1991), University of California at San Diego (1991), University of Montpellier (1992), Texas A&M University (1995, 1998), University of Bordeaux (1996, 2000), University of Kansas (1998), University of Texas at San Antonio (1998), Universidad Central de Venezuela (1998), University of Lille (1998, 2000), University of Lyon (1998), University of Krakow (1999), Georgia State University (2001), Virginia Tech (2001), Kansas State University (2001).

Teaching
 
Operator Theory, Functional Analysis (upper-undergraduate level), Mathematical Analysis, Calculus, Measure theory (undergraduate level) at the University of Bucharest, Linear Algebra (undergraduate level) at the Polytechnical Institute of Bucharest, Mathematical Analysis and Linear Algebra (undergraduate level) at the University of Bordeaux, various undergraduate and graduate courses at Georgia Institute of Technology and at the University of Lyon.