Before revision:  The corresponding maximum likelihoodestimator for the global diffusion coefficient of multiple trajectories can be efficiently evaluated in \mathcal{O extend the model to mixtures of subpopulations differing in their diffusion coefficients, which we estimate by using the expectation-maximization algorithm.
After revision:  The corresponding maximum likelihoodestimator for the global diffusion coefficient of multiple trajectories can be efficiently evaluated in \mathcal{O extend the model to mixtures of subpopulations differing in their diffusion coefficients, which we estimate with the help of the expectation-maximization algorithm.