It is generally accepted that visual perception results from the activation of a feed-forward hierarchy of areas, leading to increasingly complex representations. Here we present evidence for a fundamental role of backward projections to the occipito-temporal region for understanding conceptual object properties. The evidence is based on two studies. In the first study, using high-density EEG, we showed that during the observation of how objects are used there is an early activation of occipital and temporal areas, subsequently reaching the pole of the temporal lobe, and a late reactivation of the visual areas. In the second study, using transcranial magnetic stimulation over the occipital lobe, we showed a clear impairment in the accuracy of recognition of how objects are used during both early activation and, most importantly, late occipital reactivation. These findings represent strong neurophysiological evidence that a top-down mechanism is fundamental for understanding conceptual object properties, and suggest that a similar mechanism might be also present for other higher-order cognitive functions.

The convergence quality of the cross-entropy (CE) optimizer relies critically on the mechanism meant for randomly generating data samples, in agreement with the inference drawn in the earlier works--the fast simulated annealing (FSA) and fast evolutionary programming (FEP). Since tracing a near-global-optimum embedded on a nonconvex search space can be viewed as a rare event problem, a CE algorithm constructed using a longtailed distribution is intuitively attractive for effectively exploring the optimization landscape. Based on this supposition, a set of CE algorithms employing the Cauchy, logistic and Laplace distributions are experimentally validated in a wide range of optimization functions, which are shifted, rotated, expanded and/or composed, characterized by convex, unimodal, discontinuous, noisy and multimodal fitness landscapes. The Laplace distribution has been demonstrated to be more suitable for the CE optimization, since the samples drawn have jump-lengths long enough to elude local optima and short enough to preserve sufficient candidates in the global optimum neighborhood. Besides, a theoretical analysis has been carried out to understand the following: (i) benefits offered by the long-tailed distributions towards evasion of local optima; (ii) link between the variation in scale parameter estimate and the probability of producing candidate solutions arbitrarily close to the global optimum.

We consider a simplified 1-dimensional PDE-model describing the effect of contact inhibition in growth processes of normal and abnormal cells. Varying the value of a significant parameter, numerical tests suggest two different types of contact inhibition between the cell populations: the two populations move with constant velocity and exhibit spatial segregation, or they stop to move and regions of coexistence are formed. In order to understand the different mechanisms, we prove that there exists a segregated traveling wave solution for a unique wave speed, and we present numerical results on the ``stability" of the segregated waves. We conjecture the existence of a non-segregated standing wave for certain parameter values.

An algorithm for coupling SPH with an externalsolution is presented. The external solution can be either anotherSPH solution (possibly with different discretization) or a differentnumerical solver or an analytical solution.The interaction between the SPH solver and the externalsolution is achieved through an interface region. The interfaceregion is defined as a fixed portion of the computational domainthat provides a boundary condition for the SPH solver. A ghostfluid, composed by fully lagrangian particles (i.e. ghost particles)covering the interface region, is used to impose the boundarycondition. The ghost particle evolution, including its position, isintegrated in time according to the field of the external solution.The physical quantities of the ghost particles needed in theintegration scheme are obtained through an MLS interpolationon the field of the external solution. When a ghost particle crossesthe boundary of the interface region, entering in the SPH domain, it evolves according to the SPH governing equation. The spatial distribution of the ghost particles can become largely non-uniform due to the forcing by the external solution. Thus, a packing algorithm is applied on the ghost particles in the interface region, to guarantee a particle distribution suitable for SPH operators. Since the ghost particles can exit from the interface region, a seeding algorithm is needed to introduce new ghost-particles. The algorithm is tested on several benchmarks and with the external solutions given by other SPH solvers with different discretizations and by analytical solutions. The technique is deeply investigated in terms of accuracy, efficiency and possible applications. Finally a coupled simulation involving a finite volume solver is presented.

The turbulent flow behind a rotating marine propeller is analysed by integration of the Reynolds-Averaged Navier-Stokes Equations with both the Spalart & Allmaras (1994) eddy viscosity model and by a Detached Eddy Simulation approach (Spalart et al 1997) in order to assess advantages and limits of the two different turbulence models. As far as global quantities (like thrust and torque) are concerned, it is shown that the two methods perform equally well. On the contrary, local flow features (like the evolution of the wake or the onset of tip vortices instability) are capured by DES, whereas the eddy viscosity modelling proves to be overly dissipative.

The present work is aimed to assess the capability of a numerical code based on the solution of the Reynolds averaged Navier--Stokes Equations for the study of propeller functioning in off design conditions; this aspect is becoming of central interest in naval hydrodynamics research because of its crucial implications on design aspects and performance analysis of the vessel during its operational life. A marine propeller working in oblique flow conditions is numerically simulated by the unsteady Reynolds averaged Navier-Stokes equations (uRaNSe) and a dynamically overlapping grid approach. The test case considered is the CNR-INSEAN E779A propeller model. Two different loading conditions have been considered at different incidence angles (10° to 30°) in order to analyze the propeller performance during idealized off-design conditions, similar to those experienced during a tight manoeuvre. The main focus is on hydrodynamic loads (forces and moments) that act on a single blade, on the hub and on the complete propeller; peculiar characteristics of pressure distribution on the blade will be presented as well. Verification of the numerical computations have been asses sed by grid convergence analysis.

The flow past a rotating marine propeller is analyzed with the aim of establishing limits and capabilities and, hence, the field of applicability of different turbulence modeling approaches for this class of prob- lems. To this purpose the eddy viscosity model of Spalart and Allmaras (1994) [1] and the DES approach [2] have been used. It is shown that the RANSE method can give a very good prediction of global quan- tities such as thrust and torque, with a relatively small number of grid points. However, when the unsteady fluctuation of the flow or instability processes in the wake are of interest (for noise assessment, for instance), RANSE modeling proves to be too dissipative, as it smoothes out most of the finest flow fea- tures. On the contrary, DES modeling can track the vorticity field for a longer distance and successfully predicts the onset of instabilities in the wake, with excellent agreement with experiments.

The present work is aimed to assess the capability of a numerical code based on the solution of the Rey- nolds averaged Navier-Stokes equations for the study of propeller functioning in off design conditions; this aspect is becoming of central interest in naval hydrodynamics research because of its crucial impli- cations on design aspects and performance analysis of the vessel during its operational life. A marine pro- peller working in oblique flow conditions is numerically simulated by the unsteady Reynolds averaged Navier-Stokes equations (uRaNSe) and a dynamically overlapping grid approach. The test case consid- ered is the CNR-INSEAN E779A propeller model. Two different loading conditions have been analyzed at different incidence angles (10-30°) in order to characterize the propeller performance during idealized off-design conditions, similar to those experienced during a tight manoeuvre. The main focus is on hydro- dynamic loads (forces and moments) that act on a single blade, on the hub and on the complete propeller; peculiar characteristics of pressure distribution on the blade and downstream wake will be presented as well. Verification of the numerical computations have been assessed by grid convergence analysis

The dynamics of extended bodies endowed with multipolar structure up to the mass quadrupole moment is investigated in the Schwarzschild background according to Dixon's model, extending previous works. The whole set of evolution equations is numerically integrated under the simplifying assumptions of constant frame components of the quadrupole tensor and that the motion of the center of mass be confined on the equatorial plane, the spin vector being orthogonal to it. The equations of motion are also solved analytically in the limit of small values of the characteristic length scales associated with the spin and quadrupole with respect to the background curvature characteristic length. The results are qualitatively and quantitatively different from previous analyses involving only spin structures. In particular, the presence of the quadrupole turns out to be responsible for the onset of a nonzero spin angular momentum, even if initially absent.

The gravitational field of a static body with the quadrupole moment is described by an exact solution found by Erez and Rosen. Here, we investigate the role of the quadrupole in the motion, deflection and lensing of a light ray in the above metric. The standard lensing observables such as image positions and magnification have been explicitly obtained in the weak-field and small quadrupole limit. In this limit, the spacetime metric appears as the natural generalization to quadrupole corrections of the metric form adopted also in current astrometric models. Hence, the corresponding analytical solution of the inverse ray tracing problem and the consistency with other approaches are also discussed.

The optical medium analogy of a radiation field generated by either an exact gravitational plane wave or an exact electromagnetic wave in the framework of general relativity is developed. The equivalent medium of the associated background field is inhomogeneous and anisotropic in the former case, whereas it is inhomogeneous but isotropic in the latter. The features of light scattering are investigated by assuming the interaction region to be sandwiched between two flat spacetime regions, where light rays propagate along straight lines. Standard tools of ordinary wave optics are used to study the deflection of photon paths due to the interaction with the radiation fields, allowing for a comparison between the optical properties of the equivalent media associated with the different background fields.

We evaluate the modifications to the cosmic microwave background anisotropy spectrum that result from a semiclassical expansion of the Wheeler-DeWitt equation. Recently, such an investigation in the case of a real scalar field coupled to gravity has led to the prediction that the power at large scales is suppressed. We make here a more general analysis and show that there is an ambiguity in the choice of solution to the equations describing the quantum gravitational effects. Whereas one of the two solutions describes a suppression of power, the other one describes an enhancement. We investigate possible criteria for an appropriate choice of solution. The absolute value of the correction term is in both cases of the same order and currently not observable. We also obtain detailed formulas for arbitrary values of a complex parameter occurring in the general solution of the nonlinear equations of the model. We finally discuss the modification of the spectral index connected with the power spectrum and comment on the possibility of a quantum-gravity induced unitarity violation.

We complete the analytical determination, at the 4th post-Newtonian approximation, of the main radial potential describing (within the effective one-body formalism) the gravitational interaction of two bodies. The (non logarithmic) coefficient $a_5(\nu)$ measuring this 4th post-Newtonian interaction potential is found to be linear in the symmetric mass ratio $\nu$. Its $\nu$-independent part $a_5(0)$ is obtained by an analytical gravitational self-force calculation that unambiguously resolves the formal infrared divergencies which currently impede its direct post-Newtonian calculation. Its $\nu$-linear part $a_5(\nu)-a_5(0)$ is deduced from recent results of Jaranowski and Schaefer, and is found to be significantly negative.

Protected areas are continuously subjected to ecological change due to anthropic pressures. Analyses of changes in the extent and intensity of pressures over time are essential for adaptive management, yet such analyses are rarely conceptualized or performed in a well-defined, standardized way, with a frequent lack of clarity in development, definition and measurement. Over-time remote sensing data has great potential for mapping spatial pattern of pressures and their impacts. Some pressures can be mapped directly (e.g. land use dynamics, some invasive species), whereas for others the nature, intensity and spatial pattern of impacts can be used to infer on pressures. This paper develops a framework within which remote sensing datasets in combination with GIS and ecological modeling may be used to identify potential pressure growth through either direct detection or indirect monitoring of impacts on landscapes, land cover/habitat types, communities and species through multi-temporal remote sensing image series. The use of this framework is illustrated through categorization of pressure-derived impacts on protected areas in six countries - Greece, Italy, Portugal, Wales, The Netherlands, and India - located in diverse biogeographic, environmental and social-ecological contexts, and facing a different range of pressures. The framework is conceptually robust, geographically invariant, scalable and spatially-explicit, connecting to the growing data sets from remote sources, and we urge it to be tested over a wide range of pressures and social-ecological settings.