From ULB, in September 1969, Manuel moved to the Department of
Physics at University of Texas at Austin where Ilya Prigogine was the Director of a Research Center at that time. There, continuing under his
guidance, he started research in Fluid Physics with Robert S. Schechter.
In a two-year postdoc period he dealt with the role of the crosstransport
of matter, mass diffusion, under the action of a temperature
gradient (the Soret effect) in triggering hydrodynamic instability. This
instability leading to convection masked the genuine molecular transport.
He elucidated the role that indeed convection played in quite
many experimental studies and publications. This research led to
three papers, one in Advances in Chemical Physics, which until now
are used by researchers. Worth mentioning is that his predictions
about the onset of instability and his estimate of the convected fluxes
were beautifully verified in new experiments, motivated by his papers,
were carried out by H. J. Val Tyrrell.