295 research outputs found

    Current ozone levels threaten gross primary production and yield of Mediterranean annual pastures and nitrogen modulates the response

    Full text link
    Pastures are among the most important ecosystems in Europe considering their biodiversity and dis- tribution area. However, their response to increasing tropospheric ozone (O 3 ) and nitrogen (N) deposi- tion, two of the main drivers of global change, is still uncertain. A new Open-Top Chamber (OTC) experiment was performed in central Spain, aiming to study annual pasture response to O 3 and N in close to natural growing conditions. A mixture of six species of three representative families was sowed in the fi eld. Plants were exposed for 40 days to four O 3 treatments: fi ltered air, non- fi ltered air (NFA) repro- ducing ambient levels and NFA supplemented with 20 and 40 nl l � 1 O 3 . Three N treatments were considered to reach the N integrated doses of “ background ” , þ 20 or þ 40 kg N ha � 1 . Ozone signi fi cantly reduced green and total aboveground biomass (maximum reduction 25%) and increased the senescent biomass (maximum increase 40%). Accordingly, O 3 decreased community Gross Primary Production due to both a global reduction of ecosystem CO 2 exchange and an increase of ecosystem respiration. Nitrogen could partially counterbalance O 3 effects on aboveground biomass when the levels of O 3 were moderate, but at the same time O 3 exposure reduced the fertilization effect of higher N availability. Therefore, O 3 must be considered as a stress factor for annual pastures in the Mediterranean areas

    ¿Existe una personalidad jaquecosa?.

    Get PDF
    Se revisa brevemente el concepto actual de jaqueca y se analiza detalladamente la literatura existente sobre la personalidad jaquecosa. El concepto de personalidad jaquecosa fue mantenido por clínicos y autores de orientación psicoanalítica en las décadas de 1930-1950. los estudios recientes efectuados con criterios epidemiológicos (no basados en estudios hospitalarios) y realizados, empleando tests psicológicos estandarizados no son concordantes con la existencia de una personalidad jaquecosa

    ¿Existe una personalidad jaquecosa?.

    Get PDF
    Se revisa brevemente el concepto actual de jaqueca y se analiza detalladamente la literatura existente sobre la personalidad jaquecosa. El concepto de personalidad jaquecosa fue mantenido por clínicos y autores de orientación psicoanalítica en las décadas de 1930-1950. los estudios recientes efectuados con criterios epidemiológicos (no basados en estudios hospitalarios) y realizados, empleando tests psicológicos estandarizados no son concordantes con la existencia de una personalidad jaquecosa

    Crystalline silicon solar cells beyond 20% efficiency

    Get PDF
    —This paper describes a fabrication process to obtain high efficiency c-Si cells (> 20%) based on the Laser Fired Contact Passivated Emitter Rear Cell (LFC-PERC) concept. Photovoltaic efficiencies beyond 20% have been achieved using thermal SiO2 as a rear passivation layer on 2 cm x 2 cm solar cells with 0.45 cm Fz c-Si substrates. Efficiencies up to 22% are expected for material resistivities in the 0.4–5 cm using an optimized rear contact gridPostprint (published version

    Dependence of Induced Biological Damage on the Energy Distribution and Intensity of Clinical Intra-Operative Radiotherapy Electron Beams

    Get PDF
    The survival fraction of epithelial HaCaT cells was analysed to assess the biological damage caused by intraoperative radiotherapy electron beams with varying energy spectra and intensities. These conditions were achieved by irradiating the cells at different depths in water using nominal 6 MeV electron beams while consistently delivering a dose of 5 Gy to the cell layer. Furthermore, a Monte Carlo simulation of the entire irradiation procedure was performed to evaluate the molecular damage in terms of molecular dissociations induced by the radiation. A significant agreement was found between the molecular damage predicted by the simulation and the damage derived from the analysis of the survival fraction. In both cases, a linear relationship was evident, indicating a clear tendency for increased damage as the averaged incident electron energy and intensity decreased for a constant absorbed dose, lowering the dose rate. This trend suggests that the radiation may have a more pronounced impact on surrounding healthy tissues than initially anticipated. However, it is crucial to conduct additional experiments with different target geometries to confirm this tendency and quantify the extent of this effect
    corecore