Nanostructured semiconductor materials for dye-sensitized solar cells

Since O'Regan and Grätzel's first report in 1991, dye-sensitized solar cells (DSSCs) appeared immediately as a promising low-cost photovoltaic technology. In fact, though being far less efficient than conventional silicon-based photovoltaics (being the maximum, lab scale prototype reported efficiency around 13%), the simple design of the device and the absence of the strict and expensive manufacturing processes needed for conventional photovoltaics make them attractive in small-power applications especially in low-light conditions, where they outperform their silicon counterparts. Nanomaterials are at the very heart of DSSC, as the success of its design is due to the use of nanostructures at both the anode and the cathode. In this review, we present the state of the art for both n-type and p-type semiconductors used in the photoelectrodes of DSSCs, showing the evolution of the materials during the 25 years of history of this kind of devices. In the case of p-type semiconductors, also some other energy conversion applications are touched upon. © 2017 Carmen Cavallo et al

Biofilm is a major virulence determinant in bacterial colonization of chronic skin ulcers independently from the multidrug resistant phenotype

Bacterial biofilm is a major factor in delayed wound healing and high levels of biofilm production have been repeatedly described in multidrug resistant organisms (MDROs). Nevertheless, a quantitative correlation between biofilm production and the profile of antimicrobial drug resistance in delayed wound healing remains to be determined. Microbial identification, antibiotic susceptibility and biofilm production were assessed in 135 clinical isolates from 87 patients. Gram-negative bacteria were the most represented microorganisms (60.8%) with MDROs accounting for 31.8% of the total isolates. Assessment of biofilm production revealed that 80% of the strains were able to form biofilm. A comparable level of biofilm production was found with both MDRO and not-MDRO with no significant differences between groups. All the methicillin-resistant Staphylococcus aureus (MRSA) and 80% of Pseudomonas aeruginosa MDR strains were found as moderate/high biofilm producers. Conversely, less than 17% of Klebsiella pneumoniae extended-spectrum beta-lactamase (ESBL), Escherichia coli-ESBL and Acinetobacter baumannii were moderate/high biofilm producers. Notably, those strains classified as non-biofilm producers, were always associated with biofilm producer bacteria in polymicrobial colonization. This study shows that biofilm producers were present in all chronic skin ulcers, suggesting that biofilm represents a key virulence determinant in promoting bacterial persistence and chronicity of ulcerative lesions independently from the MDRO phenotype

Analysis of Composite Space Structures Subjected to Loading Factor

Reinforced structures are mandatory in the space structures on which the lightweight is the main project parameter. The coupling between simple thin-walled plate and different systems of ribs or beams along one or more directions make it possible to meet the requirements of lightness and strength. During the project phase a structure is usually analysed via Finite Element Method (FEM), where different approaches can be used but the pointed out one common essential characteristic, a mesh discretization of a continuous domain into a set of discrete subdomains, usually called elements. Three main finite elements (FEs) are widely used in the commercial code, but only the Solid (3D) FE represents more faithfully the behaviour of a real structure. The solid FE models require a large number of degrees of freedoms (DOFs) and therefore the analyses are computational expensive [1]. For these reason that usually the reduced models are used as substitute of solid models. The reduced models are made using shell (2D) and beam (1D) FEs, and they are suitable to build a reinforced structure, in fact the shell are used for the skin and the beam for the stringers. The present work uses a refined 1D model based on the Carrera Unified Formulation (CUF) [2] to analyse space structures made coupling skin and stringers. Thanks to its refined cinematic the present model can be used to represent both skin and stringers. The whole structure is obtained connecting simple one-dimensional structures using a new approach called Component-Wise (CW) [3]. This is possible because the unknowns are only displacements. Free-vibration analysis of isotropic and composite space structures with non-structural masses and loading factor are considered. A space vehicle is inspired to Arian 5 with a central body, on which the cryogenic fuel and the payload are accommodated, and two lateral boosters, on which solid fuel is stored. The results show the quasi-3D capabilities of the present 1D CUF model and the coupling with the CW approach provide accurate results nearest to solid FE results than the classical refined FEs models. In conclusion the present 1D refined model appears suitable for the analysis of reinforced thin-walled structures, it provides accurate results with the benefit to reduce the computational costs with respect to the classical refined FE approaches. References [1] E. Carrera, E. Zappino and T. Cavallo. Accurate free vibration analysis of launcher structures using refined 1D models. International Journal of Aeronautical and Space Sciences,vol. 16(2) 206-222, 2015. [2] E. Carrera, G. Giunta and M. Petrolo. Beam Structures: Classical and Advanced Theories. Jhon Wiley & Sons Ltd, 2011. [3] E. Carrera, A. Pagani and M. Petrolo. Component-wise Method Applied to Vibration of Wing Structures. J Appl Mech, vol. 80(4), 041012-1-041012-15, 2013

Association between leukocyte telomere shortening and exposure to traffic pollution: a cross-sectional study on traffic officers and indoor office workers

Background: Telomere shortening in blood leukocytes has been associated with increased morbidity and death from cardiovascular disease and cancer, but determinants of shortened telomeres, a molecular feature of biological aging, are still largely unidentified. Traffic pollution has been linked with both cardiovascular and cancer risks, particularly in older subjects. Whether exposure to traffic pollution is associated with telomere shortening has never been evaluated. Methods: We measured leukocyte telomere length (LTL) by real-time PCR in blood DNA from 77 traffic officers exposed to high levels of traffic pollutants and 57 office workers (referents). Airborne benzene and toluene, as tracers for traffic exposure, were measured using personal passive samplers and gas-chromatography/flame-ionization detector analysis. We used covariate-adjusted multivariable models to test the effects of the exposure on LTL and obtain adjusted LTL means and 95% Confidence Intervals (CIs). Results: Adjusted mean LTL was 1.10 (95%CI 1.04-1.16) in traffic officers and 1.27 in referents (95%CI 1.20-1.35) [p < 0.001]. LTL decreased in association with age in both traffic officers (p = 0.01) and referents (p = 0.001), but traffic officers had shorter LTL within each age category. Among traffic officers, adjusted mean relative LTL was shorter in individuals working in high (n = 45, LTL = 1.02, 95%CI 0.96-1.09) compared to low traffic intensity (n = 32, LTL = 1.22, 95%CI 1.13-1.31) [p < 0.001]. In the entire study population, LTL decreased with increasing levels of personal exposure to benzene (p = 0.004) and toluene (p = 0.008). Conclusion: Our results indicate that leukocyte telomere length is shortened in subjects exposed to traffic pollution, suggesting evidence of early biological aging and disease risk