1,454 research outputs found

    Modeling and forecasting extreme hot events in the central Ebro Valley, a continental-mediterranean area

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    This work has three objectives, first, to analyze the observed change in the summer maximum daily temperature during the period 1951–2004, in the centre of the Ebro river basin, a region situated in the NE of the Iberian Peninsula. Secondly, to characterize the extreme hot event behaviour by means of a statistical model consisting of a non-homogeneous Poisson process, to represent the occurrence, and three regression models, each with an adequate non-Normal error distribution, to model its severity. The model parameters are allowed to depend on temperature covariates, to take into account the influence of global warming in hot event generating process. Finally, using the fitted model and different outputs from a GCM, we obtain a medium term projection, up to 2050, of the expected behaviour of these extreme events

    Firm size and productivity from occupational choices

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    We model the distributions of firm sizes and of firms’ total factor productivity (TFP) as outcomes of a market equilibrium from the occupational decisions of individuals with different entrepreneurial skills, of working as employees, employers, or solo entrepreneurs. The model explains empirical regularities such as (i) the positive cross-section correlation between average size of firms and average labor productivity of countries, (ii) the positive association between size and TFP of firms in an economy, and (iii) the power law distribution of firm sizes. Two parameters of the model, one that measures the organizational size diseconomies and other related to the dispersion of the distribution of entrepreneurial skills in the population, appear as main determinants of the differences in firm sizes and in productivity, across economies and among firms within an economy. The results of the paper should be of interest for the design and evaluation of firm-size-dependent policies

    Enhancing Interferon Regulatory Factor 7 Mediated Antiviral Responses and Decreasing Nuclear Factor Kappa B Expression Limit HIV-1 Replication in Cervical Tissues

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    Establishment of a productive HIV-1 infection in the female reproductive tract likely depends on the balance between anti-viral and pro-inflammatory responses leading to activation and proliferation of HIV target cells. Immune modulators that boost anti-viral and depress pro-inflammatory immune responses may decrease HIV-1 infection or replication. Polyinosinic: polycytidylic [Poly (I:C)] has been reported to down-regulate HIV-1 replication in immune cell subsets and lymphoid tissues, yet the scope and mechanisms of poly (I:C) regulation of HIV-1 replication in the cervicovaginal mucosa, the main portal of viral entry in women remain unknown. Using a relevant, underexplored ex vivo cervical tissue model, we demonstrated that poly (I:C) enhanced Interferon Regulatory Factor (IRF)7 mediated antiviral responses and decreased tissue Nuclear Factor Kappa B (NF Îș B) RNA expression. This pattern of cellular transcription factor expression correlated with decreased HIV-1 transcription and viral release. Reducing IRF7 expression up-regulated HIV-1 and NFÎșB transcription, providing proof of concept for the critical involvement of IRF7 in cervical tissues. By combining poly (I:C) with a suboptimal concentration of tenofovir, the leading anti-HIV pro-phylactic microbicide candidate, we demonstrated an earlier and greater decrease in HIV replication in poly (I:C)/tenofovir treated tissues compared with tissues treated with tenofovir alone, indicating overall improved efficacy. Poly (I:C) decreases HIV-1 replication by stimulating IRF7 mediated antiviral responses while reducing NFÎșB expression. Early during the infection, poly (I:C) improved the anti-HIV-1 activity of suboptimal concentrations of tenofovir likely to be present during periods of poor adherence i.e. inconsistent or inadequate drug use. Understanding interactions between anti-viral and pro-inflammatory immune responses in the genital mucosa will provide crucial insights for the identification of targets that can be harnessed to develop preventative combination strategies to improve the efficacy of topical or systemic antiviral prophylactic agents and protect women from HIV-1 and other sexually transmitted infections

    Evaluating anemometer drift: A statistical approach to correct biases in wind speed measurement

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    Recent studies on observed wind variability have revealed a decline (termed “stilling”) of near-surface wind speed during the last 30–50 years over many mid-latitude terrestrial regions, particularly in the Northern Hemisphere. The well-known impact of cup anemometer drift (i.e., wear on the bearings) on the observed weakening of wind speed has been mentioned as a potential contributor to the declining trend. However, to date, no research has quantified its contribution to stilling based on measurements, which is most likely due to lack of quantification of the ageing effect. In this study, a 3-year field experiment (2014–2016) with 10-minute paired wind speed measurements from one new and one malfunctioned (i.e., old bearings) SEAC SV5 cup anemometer which has been used by the Spanish Meteorological Agency in automatic weather stations since mid-1980s, was developed for assessing for the first time the role of anemometer drift on wind speed measurement. The results showed a statistical significant impact of anemometer drift on wind speed measurements, with the old anemometer measuring lower wind speeds than the new one. Biases show a marked temporal pattern and clear dependency on wind speed, with both weak and strong winds causing significant biases. This pioneering quantification of biases has allowed us to define two regression models that correct up to 37% of the artificial bias in wind speed due to measurement with an old anemometer

    Multipath Adaptive A∗: Factors That Influence Performance in Goal-Directed Navigation in Unknown Terrain

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    Indexación: Scopus.Incremental heuristic search algorithms are a class of heuristic search algorithms applicable to the problem of goal-directed navigation. D∗ and D∗Lite are among the most well-known algorithms for this problem. Recently, two new algorithms have been shown to outperform D∗Lite in relevant benchmarks: Multi-Path Adaptive A∗ (MPAA∗) and D∗ExtraLite. Existing empirical evaluations, unfortunately, do not allow to obtain meaningful conclusions regarding the strengths and weaknesses of these algorithms. Indeed, in the paper introducing D∗ExtraLite, it is shown that D∗Lite outperforms MPAA∗ in benchmarks in which the authors of MPAA∗ claim superiority over D∗Lite. The existence of published contradictory data unfortunately does not allow practitioners to make decisions over which algorithm to use given a specific application. In this paper, we analyze two factors that significantly influence the performance of MPAA∗, explaining why it is possible to obtain very different results depending on such factors. We identify a configuration of MPAA∗ which, in the majority of the benchmark problems we use, exhibits superior performance when compared to both D∗Lite and D∗ExtraLite. We conclude that MPAA∗ should be the algorithm of choice in goal-directed navigation scenarios in which the heuristic is accurate, whereas D∗ExtraLite should be preferred when the heuristic is inaccurate.https://ieeexplore.ieee.org/document/912000

    Effect of different application rates of metamitron as fruitlet chemical thinner on thinning efficacy and fluorescence inhibition in Gala and Fuji apple

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    Crop thinning is an important and difficult agricultural practice. Knowing the effect of the application dose of a product is a crucial element of any thinning program. The aims of this study were to investigate the effect of different metamitron doses on Gala and Fuji apples applied at fruit king diameters of between 8 and 10 mm and to determine fluorescence inhibition at the different application rates. Trials were conducted over two seasons from 2015 to 2016 in apple orchards in Lleida (Spain). Photosynthesis inhibition caused by metamitron was also analysed and measured, using chlorophyll fluorescence and biexponential pharmacokinetic models. Under the trial conditions, the application of metamitron reduced final fruit set, number of fruits per tree and crop load depending on the application rate. A dose effect was observed in all yield parameters. Moreover, when metamitron showed high efficacy, there was an improvement in fruit weight, coloration and diameter. The estimated parameters A, α and B using a biexponential equation were related with final fruit set, however the period of inhibition has to be finished before prediction can be made of metamitron efficacy in the year. The fluorescence analysis showed a dose effect, with metamitron dose increasing inhibition. Additionally, the same result was also observed in the area under curve analysis, with metamitron dose reducing the area and inhibition increasing. In all yield parameters, the fluorescence and area under curve analyses showed differences between cultivars, with the inhibition caused by metamitron higher in Gala than in Fuji. Moreover, differences between years were observed. 2015 was warmer than 2016, and the higher temperatures increased the thinning efficacy of metamitron.This study was supported financially by project INIA (RTA2012-00116-00-00) in collaboration with ADAMA-Spain

    Evaluation of chemical fruit thinning efficiency using Brevis¼ (Metamitron) on apple trees (‘Gala’) under Spanish conditions

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    Thinning is an important technique in apple growing which is used to reduce the number of fruits per plant and achieve commercial fruit size and quality. The objective of this work was to evaluate the efficacy of one and two applications of the chemical thinner Brevis¼ in Gala apple applied at different fruit sizes and at different intervals between the first and second spray. The trials were conducted over two seasons from 2015 to 2016 in apple orchards of the IRTA experimental agricultural stations of Mas Badia and Lleida (Spain). One or two applications with Brevis¼ were applied at different fruit sizes (king fruit diameter ranging between 7.5 and 13.5 mm) and at a rate of 1.65 kg/ha for all treatments. Under the trial conditions, a Brevis¼ thinning effect was observed in all trials with a reduction in crop load, fruit set and number of fruits per tree which varied according to the number of applications. In addition, average fruit weight, color and diameter increased significantly with treatments in which Brevis¼ reduced the number of fruits per tree. The degree of abscission of Brevis¼ was highly dependent on night temperature and, for this reason, there was a high degree of variability between trials in terms of efficacy. Our results show that the number of days between applications was not as important a factor for Brevis¼ efficacy as the difference in night temperature in the days immediately after its application.This study was supported financially by project INIA (Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (Spain)) (RTA2012-00116-00-00) in collaboration with ADAMA-Spain

    Green Roofs in Arid Cities. Efficiency as Energy Saving Strategy in Summer and Winter

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    Los techos vegetados constituyen estrategias de enverdecimiento que a escala edilicia controlan las altas temperaturas estivales en espacios interiores y a escala urbana contribuyen a mitigar el fenĂłmeno isla de calor. Este trabajo evalĂșa, el efecto de cubiertas vegetadas con especies adaptadas -Aptenia cordifolia, Sedum spectabile- a climas cĂĄlido-secos sobre el comportamiento tĂ©rmico de espacios interiores y su consecuente ahorro energĂ©tico. MetodolĂłgicamente se ha monitoreado el desempeño tĂ©rmico durante verano e invierno en tres box experimentales -uno con cubierta tradicional y dos vegetados-. Los resultados indican que las cubiertas vegetadas en verano disminuyen la temperatura interior 1,6 °C generando ahorros medios de energĂ­a para refrigeraciĂłn del 30-35 %. En invierno si bien no hay variaciones notables, se observan ahorros energĂ©ticos diurnos del 2-4 %. El diseño de esta tecnologĂ­a requiere evaluarse a nivel local para maximizar su eficiencia energĂ©tica y garantizar la sustentabilidad urbano-edilicio segĂșn los recursos y tecnologĂ­as disponibles.Green roofs are greening strategies that controls the high summer temperatures in the indoor spaces at building scale and help mitigate the heat island phenomenon in urban scale. This work evaluates the effect of vegetated roofs with adapted species -Aptenia cordifolia, Sedum spectabile- in warm-dry climate in relation to the thermal behavior of indoors spaces and the consequent energy savings. Methodologically the thermal performance during summer and winter has monitored, in three experimental boxes- one with a traditional roof and two with vegetated roofs-. The results indicate that in the green roofs, indoor summer temperature decreases of 1,6 °C generate energy savings for refrigeration of 30 to 35%. In winter, although there are not notable variations, diurnal energy savings of 2-4% is observed. The design of these new technologies should be assessed at local level to maximize energy efficiency and ensure urban-building sustainability according to resources and technologies available.Eje: Eficiencia energĂ©tica edilicia (Actas).Facultad de Arquitectura y Urbanism
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