Graphite particles induce ROS formation in cell free systems and human cells.

It is commonly accepted that the toxicity of carbonaceous particulate matter (PM) is due to the production of reactive oxygen species (ROS) which induce biological damage in the exposed cells. It is also known that PM produced during the combustion processes consists of a carbonaceous core "dressed" with other organic and/or inorganic materials. In spite of this knowledge, the role of these materials in the production of ROS has not yet been clear. This work aims at understanding whether "naked" carbonaceous particles are capable of forming ROS either in cell-free or in-cell systems. The problem has been treated based on the data collected from pure graphite samples of different sizes obtained by ball-milling pure graphite for various lengths of time. The experimental approach considered Raman, ESR (spin trapping), cell viability and fluorescence spectroscopy measurements. These techniques allowed us to carry out measurements both in cell and cell-free systems and the results consistently indicate that also pure naked carbonaceous particles can catalyze the electron transfer that produces superoxide ions. The process depends on the particle size and enlightens the role of the edges of the graphitic platelets. Evidence has been collected that even "naked" graphitic nanoparticles are capable of producing ROS and decreasing the cell viability thus representing a potential danger to human health.

Influence of Eulerian and Lagrangian scales on the relative dispersion properties in Lagrangian stochastic models of turbulence.

The influence of Eulerian and Lagrangian scales on the turbulent relative dispersion is investigated through a three-dimensional Eulerian consistent Lagrangian stochastic model. As a general property of this class of models, it is found to depend solely on a parameter beta based on the Kolmogorov constants C(K) and C0. This parameter represents the ratio between the Lagrangian and Eulerian scales and is related to the intrinsic inhomogeneity of the relative dispersion process. In particular, the quantity g*=g/C(0) (where g is the Richardson constant) and the temporal extension of the t(3) regime are found to be strongly dependent on the value adopted for beta.

Venice: sea-lagoon exchange in a modified tide regime.

Salinity and tide heights recorded for a month at P(0), a point in the northern section of the Venetian lagoon, are the basic experimental data used to construct a numerical model which describes the salinity variations at P(0) as a function of the tides measured at the Lido entrance. The time variation of the salinity pattern iss interpreted in terms of a lagoon system in which a freshwater source of constant intensity is in a quasi-steady equilibrium with a tide-modulated sink. The mean residence time of a contaminant in this simulated lagoon is predicted from the change in the salinity pattern due to a reduction in the entrance size.

Infrared radiation extinction sensitivity to the modified gamma distribution parameters for haze and fog droplet polydispersions.

The volume extinction coefficients at 1.03 microm, 3.70 microm, and 10.38 microm, normalized to that at 0.50-microm wavelength, are calculated as a function of the shape parameters of the modified gamma size distribution using parameter ranges appropriate for haze and fog droplet polydispersions. Based on the sensitivity of the normalized volume extinction coefficients on the shape parameters, different procedures are proposed for utilizing the extinction features in giving form to the size distribution corresponding to the various evolutionary stages of the water droplet population. Such a methodology presents applicability in the field of fog forecast.