  We illustrate the equivalence between the non-unitary evolution of an open
quantum system governed by a Markovian master equation and a process of
continuous measurements involving this system. We investigate a system of two
coupled modes, only one of them interacting with external degrees of freedom,
represented, in the first case, by a finite number of harmonic oscillators,
and, in the second, by a sequence of atoms where each one interacts with a
single mode during a limited time. Two distinct regimes appear, one of them
corresponding to a Zeno-like behavior in the limit of large dissipation.
