A non-Gaussian puff model

A model for the dispersion of passive non-Gaussian puffs is presented. The model is based on a general technique for solving the K-equation on the basis of the truncated Gram-Charlier expansion of the concentration field. The model performances are evaluated against experimental ground-level concentrations, using meteorological data collected near the ground

Sensitivity analysis of an operational advanced Gaussian model to different turbulent regimes

A non-reactive air pollution model evaluating ground level concentration is presented. It relies on a new Gaussian formulation (LUPINI R. and TIRABASSI T., J. Appl. Meteor., 20 (1981) 565-570; TIRABASSI T. and RIZZA U., Atmos. Environ., 28 (1994) 611-615) for transport and vertical diffusion in the Atmospheric Boundary Layer (ABL). In this formulation, the source height is replaced by a virtual height expressed by simple functions of meteorological variables. The model accepts a general profile of wind u(z) and eddy diffusivity coefficient Kz . The lateral dispersion coefficient is based on Taylor’s theory (TAYLOR G. I., Proc. London Math. Soc., 20 (1921) 196-204). The turbulence in the ABL is subdivided into various regimes, each characterized by different parameters for length and velocity scales. The model performances under unstable conditions have been tested utilizing two different data sets

Dependence of the irradiation-induced growth kinetics of satellites on the nanoclusters dimension

A paraître dans NIM B, présenté par G. Rizza (LSI)International audienceIrradiation with MeV gold ions of embedded Au nanoclusters in silica matrix results in the formation of a ring of satellites in its surrounding. We show that changing the initial nanoclusters size modifies both the size and the density of the satellites, and therefore alters their kinetic growth. Finally we discuss the limitation of the ion implantation technique to form a model system to study the satellites kinetic growth and we propose a new approach based on the chemical synthesis of metallic nanoparticles to obtain the proper configuration

A surface energy-budget model coupled with a Skewed Puff Model for investigating the dispersion of radionuclides in a sub-tropical area of Brazil

An air pollution model (Skewed Puff Model, SPM) based on the Monin-Obukhov similarity theory was applied to investigate the atmospheric radionuclide dispersion at Iperó in Brazil, the location of a nuclear industrial installation. The SPM numerical simulations were carried out using as input 5-minute averaged wind speed and direction observed at 11.5 m, friction velocity and the Monin-Obukhov length supplied by the surface energy-budget model, along with PBL height, estimated from empirical equilibrium expressions for the nighttime and Mixed-Layer model for the daytime. The agreement between the observed and simulated sensible and latent heat fluxes, friction velocity and Monin-Obukhov length, within a level of confidence of 99.9% indicates that the internal parameters chosen for the surface energy-budget model are representative of the interface soil-vegetation conditions at Iperó. The mean concentration field at the surface was estimated assuming that a hypothetical accident at Iperó produced a continuous emission from a 10 m high point source for 18 hours during the summer of 1993 and for 36 hours during the winter of 1992. The results indicated that, in the case of an accident, the highest concentration values are located near to the source and most of the contaminated area is within a 5 kilometers range, in both seasons. The shape of the contaminated area is defined by the wind speed pattern

A model for the estimation of standard deviation of air pollution concentration in different stability conditions

We propose to estimate the standard deviations of the air pollution concentration in the horizontal and vertical direction, σy and σz, based on Pasquill’s well-known equation, in terms of the wind variance and the Lagrangian integral time scales, on the basis of an atmospheric turbulence spectra model. The main advantage of the spectral model is its treatment of turbulent kinetic energy spectra as the sum of buoyancy and a shear produced part, modelling each one separately. The formulation represents both shear and buoyant turbulent mechanisms characterizing the various regimes of the Planetary Boundary Layer, and gives continuous values at any elevation and all stability conditions from unstable to stable. As a consequence, both the wind variance and the Lagrangian integral time scales in the dispersion parameters are more general than those found in literature, because they are not derived from diffusion experiments as most parameterizations. Furthermore, they provide a formulation continuous for the whole boundary layer resulting more physically consistent. The σy, σz parameters, included in a Gaussian model have been tested and compared with a dispersion scheme reported in the literature, using experimental data in different emission conditions (low and tall stacks) and in several meteorological conditions ranging from stable to convective. Results show that the dispersion model with the sigmas parameterisation included, produces a good fitting of the measured ground-level concentration data in all the experimental conditions considered, performing slightly better than other state-of-art models

Turbulent dispersion from tall stack in the unstable boundary layer: a comparison between Gaussian and K-diffusion modelling for non buoyant emissions

Most air quality dispersionmo dels used for regulatory applications are based onGaussianan d K-diffusionform ulations. The reliability of such models strongly depends on how dispersion parameters and eddy diffusivities are computed on the basis of the update understanding of the Planetary Boundary Layer (PBL) meteorology. In this paper, we compare the performances in simulating pollutants released from continuous point source, by using some Gaussian and K-diffusion models with different assumptions concerning the parameterisation of the dispersionpro cesses. Results show that the Gaussianmo del, inwhic h the dispersion parameters are directly related to spectral peak of turbulence energy, gives the best overall performances. This could be due to a more realistic description of spreading processes occurring into the PBL. This suggests that, in the context of the regulatory applications, this model cangiv e the best combinationb etweengroun d level concentration estimates and computer requirements

Influence of involvement of anterior leaflet versus posterior leaflet on residual regurgitation as assessed by transesophageal echocardiography in patients undergoing valve repair for mitral regurgitation due to mitral valve prolapse

<p>Abstract</p> <p>Background</p> <p>Repair of anterior leaflet prolapse is technically more challenging and this might influence outcomes as compared to the repair of posterior leaflet prolapse in patients undergoing surgical correction of mitral regurgitation. We investigated the association of anterior leaflet prolapse with minor residual mitral regurgitation (MR) in patients with mitral valve prolapse (MVP) who underwent valve repair.</p> <p>Methods</p> <p>Eligible for this study were consecutive patients with severe MR due to MVP, who underwent mitral valve repair with residual MR by postpump transesophageal echocardiography ≤2+ during a 20-month period at Pasquinucci Hospital, Massa. Patients undergoing other cardiovascular surgical interventions were excluded. Two groups were defined according to the involvement of mitral valve leaflets: group 1, consisting of patients with anterior leaflet prolapse (isolated or not); and group 2, consisting of patients with isolated posterior leaflet prolapse.</p> <p>Results</p> <p>A total of 70 patients (18 in group 1 and 52 in group 2) were analyzed. Patients in group 2 were younger than those in group 1, but the difference was not significant (P = 0.052). There were no significant differences between the 2 study groups with respect to other variables. The proportion of patients with residual MR 1+/2+ was higher in group 1 than in group 2 (61.1% vs. 32.7%, respectively; P = 0.034). In a logistic regression model, anterior leaflet prolapse was an independent predictor of residual MR 1+/2+ (odds ratio, 4.0; 95% confidence interval, 1.14 to 14.04; P = 0.03).</p> <p>Conclusion</p> <p>In our study population, patients with anterior leaflet prolapse had a higher proportion of residual MR 1+/2+ as compared to those with posterior leaflet prolapse after repair of mitral valve.</p

Redox proteome analysis of auranofin exposed ovarian cancer cells (A2780)

The effects of Auranofin (AF) on protein expression and protein oxidation in A2780 cancer cells were investigated through a strategy based on simultaneous expression proteomics and redox proteomics determinations. Bioinformatics analysis of the proteomics data supports the view that the most critical cellular changes elicited by AF treatment consist of thioredoxin reductase inhibition, alteration of the cell redox state, impairment of the mitochondrial functions, metabolic changes associated with conversion to a glycolytic phenotype, induction of ER stress. The occurrence of the above cellular changes was extensively validated by performing direct biochemical assays. Our data are consistent with the concept that AF produces its effects through a multitarget mechanism that mainly affects the redox metabolism and the mitochondrial functions and results into severe ER stress. Results are discussed in the context of the current mechanistic knowledge existing on AF

Flux pinning in (1111) iron-pnictide superconducting crystals

Local magnetic measurements are used to quantitatively characterize heterogeneity and flux line pinning in PrFeAsO_1-y and NdFeAs(O,F) superconducting single crystals. In spite of spatial fluctuations of the critical current density on the macroscopic scale, it is shown that the major contribution comes from collective pinning of vortex lines by microscopic defects by the mean-free path fluctuation mechanism. The defect density extracted from experiment corresponds to the dopant atom density, which means that dopant atoms play an important role both in vortex pinning and in quasiparticle scattering. In the studied underdoped PrFeAsO_1-y and NdFeAs(O,F) crystals, there is a background of strong pinning, which we attribute to spatial variations of the dopant atom density on the scale of a few dozen to one hundred nm. These variations do not go beyond 5% - we therefore do not find any evidence for coexistence of the superconducting and the antiferromagnetic phase. The critical current density in sub-T fields is characterized by the presence of a peak effect, the location of which in the (B,T)-plane is consistent with an order-disorder transition of the vortex lattice.Comment: 12 pages, submitted to Phys Rev.