Excitonic effects in the optical properties of CdSe nanowires

Using a first-principle approach beyond density functional theory we calculate the electronic and optical properties of small diameter CdSe nanowires.Our results demonstrate how some approximations commonly used in bulk systems fail at this nano-scale level and how indispensable it is to include crystal local fields and excitonic effects to predict the unique optical properties of nanowires. From our results, we then construct a simple model that describes the optical gap as a function of the diameter of the wire, that turns out to be in excellent agreement with experiments for intermediate and large diameters.Comment: submitte

Effects of thickness on the spin susceptibility of the 2D electron gas

Using available quantum Monte Carlo predictions for a strictly 2D electron gas, we have estimated the spin susceptibility of electrons in actual devices taking into account the effect of the finite transverse thickness and finding a very good agreement with experiments. A weak disorder, as found in very clean devices and/or at densities not too low, just brings about a minor enhancement of the susceptibility.Comment: 4 pages, 3 figure

Participative ergonomics for the improvement of occupational health and safety in industry: a focus group-based approach

This paper introduces a participative approach to the investigation and promotion of health and safety in industry. The proposed methodology promotes the active participation of the workers in the analysis of consequences and causes of unsafe behaviours that may result in work-related musculoskeletal disorders, accidents, injuries or near-misses. The developed participative technique is the Focus Group with Workers, based on the Fault Tree Analysis method (FGW-FTA). Focus groups are conventionally used by social and behavioural researchers to understand opinions, motivations, attitudes, and mental processes that underlie people behaviours. The innovative procedure in this paper addresses researchers and safety professionals during the focus groups with the workers for the identification of critical risk factors in the workplace. The result is a structured analysis, operated by and with the workers, for the identification of consequences and causes of unsafe behaviours. Finally, the developed methodology addresses the definition of a set of preventive and protective measures, and corrective actions for the improvement of health and safety in the workplace. An experimental study in an Italian boiler manufacturer describes the proposed methodology and the results of the focus groups with the workers. An evaluation questionnaire was elaborated to investigate the workers’ knowledge on occupational health and safety. A second questionnaire was developed to understand the workers’ perception on occupational risks. Each participant was invited to fill in both the questionnaires before and after the focus groups with the workers. The results of the study proved the effectiveness of the developed methodology in improving workers knowledge and perceptions on occupational health and safety

Knowledge Acquisition by Networks of Interacting Agents in the Presence of Observation Errors

In this work we investigate knowledge acquisition as performed by multiple agents interacting as they infer, under the presence of observation errors, respective models of a complex system. We focus the specific case in which, at each time step, each agent takes into account its current observation as well as the average of the models of its neighbors. The agents are connected by a network of interaction of Erd\H{o}s-Renyi or Barabasi-Albert type. First we investigate situations in which one of the agents has a different probability of observation error (higher or lower). It is shown that the influence of this special agent over the quality of the models inferred by the rest of the network can be substantial, varying linearly with the respective degree of the agent with different estimation error. In case the degree of this agent is taken as a respective fitness parameter, the effect of the different estimation error is even more pronounced, becoming superlinear. To complement our analysis, we provide the analytical solution of the overall behavior of the system. We also investigate the knowledge acquisition dynamic when the agents are grouped into communities. We verify that the inclusion of edges between agents (within a community) having higher probability of observation error promotes the loss of quality in the estimation of the agents in the other communities.Comment: 10 pages, 7 figures. A working manuscrip

Grapevine yellows diseases in Spain: eight years survey of disease spread and molecular characterization of phytoplasmas involved.

Among grapevine yellows phytoplasma diseases in Europe, flavescence dor\ue9e (FD) is the most devastating and in the last decade has reached Spanish vineyards, mainly in Catalonia. An eight-year survey was carried out in the areas where the disease has spread (Alt Empord\ue0, Catalonia, Northern Spain) and in the remaining vine-growing areas of Catalonia. Sequence analyses of a portion of the 16S-23S ribosomal DNA cistron, from selected grapevine samples from Catalonia, showed that the phytoplasmas involved in grapevine yellows belong to 16S ribosomal subgroups V-D (flavescence dor\ue9e, FD) and XII-A (bois noir, BN). A set of Spanish FD isolates collected during these years were further studied by RFLP analyses of the 16S-23S ribosomal DNA fragment, as well as the rpS3 and SecY genes. All the FD phytoplasma strains studied were related to phytoplasmas belonging to ribosomal protein subgroup rp-E

SPARC is a new myeloid-derived suppressor cell marker licensing suppressive activities

Myeloid-derived suppressor cells (MDSC) are well-known key negative regulators of the immune response during tumor growth, however scattered is the knowledge of their capacity to influence and adapt to the different tumor microenvironments and of the markers that identify those capacities. Here we show that the secreted protein acidic and rich in cysteine (SPARC) identifies in both human and mouse MDSC with immune suppressive capacity and pro-tumoral activities including the induction of epithelial-to-mesenchymal transition (EMT) and angiogenesis. In mice the genetic deletion of SPARC reduced MDSC immune suppression and reverted EMT. Sparc−/− MDSC were less suppressive overall and the granulocytic fraction was more prone to extrude neutrophil extracellular traps (NET). Surprisingly, arginase-I and NOS2, whose expression can be controlled by STAT3, were not down-regulated in Sparc−/− MDSC, although less suppressive than wild type (WT) counterpart. Flow cytometry analysis showed equal phosphorylation of STAT3 but reduced ROS production that was associated with reduced nuclear translocation of the NF-kB p50 subunit in Sparc−/− than WT MDSC. The limited p50 in nuclei reduce the formation of the immunosuppressive p50:p50 homodimers in favor of the p65:p50 inflammatory heterodimers. Supporting this hypothesis, the production of TNF by Sparc−/− MDSC was significantly higher than by WT MDSC. Although associated with tumor-induced chronic inflammation, TNF, if produced at high doses, becomes a key factor in mediating tumor rejection. Therefore, it is foreseeable that an unbalance in TNF production could skew MDSC toward an inflammatory, anti-tumor phenotype. Notably, TNF is also required for inflammation-driven NETosis. The high level of TNF in Sparc−/− MDSC might explain their increased spontaneous NET formation as that we detected both in vitro and in vivo, in association with signs of endothelial damage. We propose SPARC as a new potential marker of MDSC, in both human and mouse, with the additional feature of controlling MDSC suppressive activity while preventing an excessive inflammatory state through the control of NF-kB signaling pathway

Hydrogeochemistry of Magra Valley (Italy) Aquifers: Geochemical Background of an Area Investigated for Seismic Precursors

AbstractWe present the results of a hydrogeochemical survey of 111 springs and wells from Magra Valley, a seismic area located in northern Tuscany, Italy. This survey was aimed at defining the geochemical background and the underground fluid circulation scheme of an area currently investigated for earthquake precursory phenomena, with the final goal of identifying a suitable location for installation of a continuous automatic monitoring station for the remote control of hydrogeochemical parameters. Six springs of the project were identified suitable for the purpose, and the Equi Na-Cl-type spring emerged as the best candidate for the installation of a monitoring station