Impact of the Costa Concordia shipwreck on a Posidonia oceanica meadow: a multi-scale assessment from a population to a landscape level.

The Costa Concordia shipwreck permitted to assess how multiple disturbances affected marine biota at different spatial and temporal scales, evaluating the effects of mechanical and physical disturbances on Posidonia oceanica (L.) Delile, an endemic seagrass species of the Mediterranean Sea. To assess the impacts of the shipwreck and its salvaging from 2012 to 2017 at a population and a landscape level, a diversified approach was applied based on the application of a geographical information system coupled with seascape metrics and structural descriptors. Benthic habitat maps and seascape metrics highlighted cenotic transitions, as well as fragmentation and erosion phenomena, resulting in 9952 m2 of seagrass area impacted. Regression of the meadow was unveiled by both multivariate and interpolation analysis, revealing a clear spatio-temporal gradient of impacts based on distances from the wreck. Results highlighted the effectiveness of the descriptors involved that permitted to reveal temporal changes at both fine and large scales.

Clausius inequality and optimality of quasistatic transformations for nonequilibrium stationary states.

Nonequilibrium stationary states of thermodynamic systems dissipate a positive amount of energy per unit of time. If we consider transformations of such states that are realized by letting the driving depend on time, the amount of energy dissipated in an unbounded time window then becomes infinite. Following the general proposal by Oono and Paniconi and using results of the macroscopic fluctuation theory, we give a natural definition of a renormalized work performed along any given transformation. We then show that the renormalized work satisfies a Clausius inequality and prove that equality is achieved for very slow transformations, that is, in the quasistatic limit. We finally connect the renormalized work to the quasipotential of the macroscopic fluctuation theory, which gives the probability of fluctuations in the stationary nonequilibrium ensemble.

Current fluctuations in stochastic lattice gases.

We study current fluctuations in lattice gases in the macroscopic limit extending the dynamic approach for density fluctuations developed in previous articles. More precisely, we establish a large deviation theory for the space-time fluctuations of the empirical current which include the previous results. We then estimate the probability of a fluctuation of the average current over a large time interval. It turns out that recent results by Bodineau and Derrida [Phys. Rev. Lett. 92, 180601 (2004)]] in certain cases underestimate this probability due to the occurrence of dynamical phase transitions.

Fluctuations in stationary nonequilibrium states of irreversible processes.

We formulate a dynamical fluctuation theory for stationary nonequilibrium states (SNS) which covers situations in a nonlinear hydrodynamic regime and is verified explicitly in stochastic models of interacting particles. In our theory a crucial role is played by the time reversed dynamics. Our results include the modification of the Onsager-Machlup theory in the SNS, a general Hamilton-Jacobi equation for the macroscopic entropy and a nonequilibrium, nonlinear fluctuation dissipation relation valid for a wide class of systems.