  We study the survival probability of an immobile target in presence of N
independent diffusing walkers. We address the problem of the Mean Target
Lifetime and its dependence on the number and initial distribution of the
walkers when the trapping is perfect or imperfect. We consider the diffusion on
lattices and in the continuous space and we address the bulk limit
corresponding to a density of diffusing particles and only one isolated trap.
Also, we use intermittent motion for optimization of search strategies.
