6,709 research outputs found

    Comparison between the results of a new version of the AVACTA II atmospheric diffusion model and tracer experiments

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    A new version of the AVACTA II code (a code recommended by EPA) has been implemented and evaluated. AVACTA II is a code based on a mixed segmentpuff approach, which allows numerical simulations of both non-stationary and nonhomogeneous conditions. In our version, the wind field is calculated through the 3D mass-consistent code WINDS developed at the Department of Physics of the University of Genoa, Italy. The model evaluation of this new version of the AVACTA II code has been performed using field experiment data on flat, but rough, terrain (Karlsruhe Nuclear Research Center (KNRC) tracer experiments) and wind tunnel measurements(EPA Rushil experiments) both in flat and complex terrain. A comparison is made between simulated and measured concentration distributions. The results of these evaluations are very encouraging

    Leakage flow noise and related flow pattern in a low-speed axial fan with rotating shroud

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    The effect of rotational speed and pressure rise on the leakage flow noise radiated by a low-speed axial fan, provided with rotating shroud, has been systematically investigated. The leakage flow noise generally increases with the blade loading, with a trend which is qualitatively independent from the rotational speed but non-monotonic, as its growth is interrupted by local minima. As the loading increases, the SPL spectrum shows important modifications, since the characteristic frequency of the subharmonic narrowband humps related to the leakage noise decreases. The flow in the gap region has been studied by means of PIV measurements taken in the meridional plane. At low blade loading, the leakage flow is restrained close to the rotor ring and, at higher loading, it forms a wide recirculation zone. In the latter conditions, an unsteady flow separation likely takes place in the blade tip region which may be observed in the instantaneous flow field only. Possibly, it is responsible for the observed frequency shift of the humps

    A Two-Step Approach to Tune the Micro and Nanoscale Morphology of Porous Niobium Oxide to Promote Osteointegration

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    We present a two-step surface modification process to tailor the micro and nano morphology of niobium oxide layers. Niobium was firstly anodized in spark regime in a Ca-and P-containing solution and subsequently treated by acid etching. The effects of anodizing time and applied potential on the surface morphology is investigated with SEM and AFM, complemented by XPS compositional analysis. Anodizing with a limiting potential of 250 V results in the fast growth of oxide layers with a homogeneous distribution of micro-sized pores. Cracks are, however, observed on 250 V grown layers. Limiting the anodizing potential to 200 V slows down the oxide growth, increasing the anodizing time needed to achieve a uniform pore coverage but produces fracture-free oxide layers. The surface nano morphology is further tuned by a subsequent acid etching process that leads to the formation of nano-sized pits on the anodically grown oxide surface. In vitro tests show that the etching-induced nanostructure effectively promotes cell adhesion and spreading onto the niobium oxide surface

    Trends of influenza B during the 2010–2016 seasons in 2 regions of north and south Italy: The impact of the vaccine mismatch on influenza immunisation strategy

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    Influenza A and B viruses are responsible for respiratory infections, representing globally seasonal threats to human health. The 2 viral types often co-circulate and influenza B plays an important role in the spread of infection. A 6-year retrospective surveillance study was conducted between 2010 and 2016 in 2 large administrative regions of Italy, located in the north (Liguria) and in the south (Sicily) of the country, to describe the burden and epidemiology of both B/Victoria and B/Yamagata lineages in different healthcare settings. Influenza B viruses were detected in 5 of 6 seasonal outbreaks, exceeding influenza A during the season 2012–2013. Most of influenza B infections were found in children aged ≤ 14 y and significant differences were observed in the age-groups infected by the different lineages. B/Victoria strains prevailed in younger population than B/Yamagata, but also were more frequently found in the community setting. Conversely, B/Yamagata viruses were prevalent among hospitalized cases suggesting their potential role in the development of more severe disease. The relative proportions of viral lineages varied from year to year, resulting in different lineage-level mismatch for the B component of trivalent influenza vaccine. Our findings confirmed the need for continuous virological surveillance of seasonal epidemics and bring attention to the adoption of universal influenza immunization program in the childhood. The use of tetravalent vaccine formulations may be useful to improve the prevention and control of the influenza burden in general population

    Instantaneous PIV data related to the leakage flow of a low-speed axial-flow fan with rotating shroud

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    The present paper is companion to Large-scale unsteady flow structures in the leakage flow of a low-speed axial fan with rotating shroud, Canepa et al., 2019. Two-dimensional PIV has been used in order to investigate the leakage flow in a low-speed fan with rotating shroud at three operating conditions. The reported data are constituted by about 3000 instantaneous meridional velocity fields, which are statistically independent. Each velocity field contains 41 7 55 velocity values deployed on a rectangular grid. In order to allow taking ensemble averages of the data, each velocity field has been assigned to a 4-deg bin in the rotor reference. The data are particularly valuable, since no data of this kind and detail have been made available to the scientific community yet

    On the curvature in logarithmic plots of rate coefficients for chemical reactions

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    In terms of the reduced potential energy barrier ζ = ΔuTS/kT, the rate coefficients for chemical reactions are usually expressed as proportional to e-ζ. The coupling between vibrational modes of the medium to the reaction coordinate leads to a proportionality of the regularized gamma function of Euler Q(a,ζ) = Γ(a,ζ)/Γ(a), with a being the number of modes coupled to the reaction coordinate. In this work, the experimental rate coefficients at various temperatures for several chemical reactions were fitted to the theoretical expression in terms of Q(a,ζ) to determine the extent of its validity and generality. The new expression affords lower deviations from the experimental points in 29 cases out of 38 and it accounts for the curvature in the logarithmic plots of rate coefficients versus inverse temperature. In the absence of tunneling, conventional theories predict the curvature of these plots to be identically zero

    Doping of nanocrystalline SnO2 for high sensitivity resistivity sensors to detect H2S (g) in air

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    In this work, several factors to increase the sensitivity of a high precision resistive type sensor able todetect from (10 to 15) ppm de H2S (g) in air, are considered. It is accepted that the doping of the material sensor (SnO2) increases the dispositive sensibility. Several dopants were proved, concluding that the CuO was the most convenient. Several papers are found in the bibliography presenting different techniques to dope the material sensor but, in this work, an own developed at DEINSO technique was employed, in which the dopant is homogeneously distributed in the SnO2 crystalline lattice. At first, it was proposed to dope the nanocrystalline SnO2 with different CuO concentrations (1 %wt. 5 %wt. and 6 %wt.) to choose the most convenient one, which resulted 5 % wt. CuO. Under these conditions, a more sensible sensor was built and other factors were studied to increase even more the sensitivity. The 5 %wt CuO-SnO2 was deposited on thin films (or layers) forming a multilayers system (which employed from three to six layers or superimposed thin films). The sensor material was characterized with different techniques, such as: DRX, SEM-EDS and GISAXS, which enabled to determinethe mean crystallite size, the multilayer system thickness, the crystallinity, the chemical composition and the layers porosity. With the built sensor, (10 to 15) ppm of H2S (g) in air concentration was measured at an operation temperature (To) of 140 ºC. This finding enabled to solve the request of an ambiance security sensor for the oil cracking plant of an important Argentine oil company.The following subject is not included in this paper but, it is interesting to inform that higher sensitivity of the same described sensor it was possible to detect concentrations from (4 - 5) ppm of H2S (g) in air at To=~ 30 ºC, which makes possible to build a medical use sensor to detect H2S (g) very low concentrations (minor than 5ppm) which are found in halitosis of hepatic maladies.Fil: Poiasina, Mariana Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Universidad Nacional de San Martín. Instituto Sabato; ArgentinaFil: Bianchetti, Mario Fidel. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; ArgentinaFil: Heredia, Eduardo Armando. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; ArgentinaFil: Canepa, Horacio Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; ArgentinaFil: Walsöe de Reca, Noemi E.. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentin

    Deterministic Factors Overwhelm Stochastic Environmental Fluctuations as Drivers of Jellyfish Outbreaks

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    16 pages, 4 figures, 1 table, supporting Information http://dx.doi.org/10.1371/journal.pone.0141060Jellyfish outbreaks are increasingly viewed as a deterministic response to escalating levels of environmental degradation and climate extremes. However, a comprehensive understanding of the influence of deterministic drivers and stochastic environmental variations favouring population renewal processes has remained elusive. This study quantifies the deterministic and stochastic components of environmental change that lead to outbreaks of the jellyfish Pelagia noctiluca in the Mediterranen Sea. Using data of jellyfish abundance collected at 241 sites along the Catalan coast from 2007 to 2010 we: (1) tested hypotheses about the influence of time-varying and spatial predictors of jellyfish outbreaks; (2) evaluated the relative importance of stochastic vs. deterministic forcing of outbreaks through the environmental bootstrap method; and (3) quantified return times of extreme events. Outbreaks were common in May and June and less likely in other summer months, which resulted in a negative relationship between outbreaks and SST. Cross- and along-shore advection by geostrophic flow were important concentrating forces of jellyfish, but most outbreaks occurred in the proximity of two canyons in the northern part of the study area. This result supported the recent hypothesis that canyons can funnel P. noctiluca blooms towards shore during upwelling. This can be a general, yet unappreciated mechanism leading to outbreaks of holoplanktonic jellyfish species. The environmental bootstrap indicated that stochastic environmental fluctuations have negligible effects on return times of outbreaks. Our analysis emphasized the importance of deterministic processes leading to jellyfish outbreaks compared to the stochastic component of environmental variation. A better understanding of how environmental drivers affect demographic and population processes in jellyfish species will increase the ability to anticipate jellyfish outbreaks in the futureThe authors gratefully acknowledge financial support by the European Community Seventh Framework Programme (FP7/2007–2013) for the project VECTORS (grant agreement no. 266445) (URL: http://cordis.europa.eu/fp7/home_en.html). AC was supported by a doctoral fellowship from the Chilean National Commission for Scientific and Technological Research (CONICYT – PFCHA/Doctorado al Extranjero 4a Convocatoria, 72120016).Peer Reviewe
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