347 research outputs found

    Adoption of improved livestock production practices in the Peruvian Amazonia: an econometric analysis

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    Successive Peruvian Administrations have pursued the development of frontier lands in the Amazonia. There are concerns, however, about the socio-economic and technological path of this process. Settlers opt for a variety of farming systems that are in general multioutput in nature and where cattle is an important component;An econometric model is developed to understand the determinants of choice of main activities and technology. The model is based on expected utility theory, taken into consideration concepts of subjective probabilities and perceptions. The analysis considers a system of choice variables related to the demand for inputs, allowing for corner solutions. The model takes into account the degree of fixity in factors of production, and the interrelation between fixity and simultaneity in farm decisions. Technical jointness of beef and milk production, and non-jointness in inputs of livestock and crop production are analyzed;Cross-sectional data were collected from 128 farmers in Peruvian Central Amazonia. Limited dependent variables maximum likelihood (LDVML) and two-stage LDVML are used for estimation of conditional and simultaneous decision systems, respectively;Human capital variables have a special connotation in economic decisions, because migrants come to the Amazonia with diverse background. Schooling has a positive effect on adoption of improved pastures, crossbred cows and supplements; but, it has a negative direct marginal effect on farm production due to a strong relocation of time to off-farm work. Labor is scarce and has a high marginal productivity in all farm activities. Bias towards certain types of technology is explained in part by farmers\u27 previous experience in other regions. Increases in area of improved pastures and in number of crossbred cows increase labor and management productivity on the farm and reduce the probability of off-farm work. Since milk production is more time demanding than beef production, the marginal effect of crop production on milk is larger in absolute value than the corresponding effect on beef. Higher land values and improvement in terms of trade at the farm gate induce intensification per unit of land

    Características físicas de la madera de pino procedente de raleos en el noroeste de España

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    Se estudió la densidad, contracción, higroscopicidad y punto de saturación de la pared celular en la madera de ejemplares jóvenes de tres especies importantes en la producción maderera española: Pinus pinaster, Pinus sylvestris y Pinus radiata. Se muestrearon 29 pinos procedentes de raleos efectuados en diferentes masas forestales de Galicia (noroeste de España). El material de ensayo fueron probetas de pequeñas dimensiones sin defectos. La madera de Pinus pinaster resultó semipesada y más inestable en dimensiones ante los cambios de humedad que las de Pinus radiata y Pinus sylvestris, que resultaron ligeras y relativamente estables, especialmente Pinus radiata. La densidad en Pinus pinaster fue similar a la obtenida en estudios anteriores sobre pies adultos. Pinus radiata y Pinus sylvestris presentaron madera más ligera que la de pies adultos. Las propiedades relativas a la estabilidad dimensional fueron similares en la madera joven analizada y en la madera de pies adultos, a excepción de la madera de Pinus radiata, que resultó más estable en la muestra que en la madera adulta. La variación entre zonas del fuste y entre individuos fue notable para las variables densidad y peso específico, aun en el caso de árboles muestreados en un mismo rodal y estación. AbstractWood density, shrinkage, hygroscopicity and fibre saturation point were studied in young trees corresponding to three important species in the spanish timber production (Pinus pinaster, Pinus sylvestris and Pinus radiata). Twenty-nine thinned pines from different stands of Galicia (northwestern Spain) were sampled. The test material was small size defect-free specimens. The wood of Pinus pinaster exhibited intermediate density and more instability in dimensions, due to environmental moisture changes, than wood of Pinus radiata and Pinus sylvestris. These woods were light and relatively stable, especially Pinus radiata. The density in Pinus pinaster was similar to that obtained in previous studies on adult trees. Pinus radiata and Pinus sylvestris showed lower density than adult trees. The shrinkage properties were similar in the analyzed young wood and in the wood of adult trees, excepting the wood sampled for Pinus radiata, more stable than adult wood. Even with a sample of trees from the same stand in a specific site, there were significant differences in wood density among positions in each tree and among trees

    Translating between Alloy specifications and UML class diagrams annotated with OCL

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    Model-driven engineering (MDE) is a software engineering approach based on model transformations at different abstraction levels. It prescribes the development of software by successively transforming the models from abstract (specifications) to more concrete ones (code). Alloy is an increasingly popular lightweight formal specification language that supports automatic verification. Unfortunately, its widespread industrial adoption is hampered by the lack of an ecosystem of MDE tools, namely code generators. This paper presents a model transformation from Alloy to UML class diagrams annotated with OCL (UML+OCL) and shows how an existing transformation from UML+OCL to Alloy can be improved to handle dynamic issues. The proposed bidirectional transformation enables a smooth integration of Alloy in the current MDE contexts, by allowing UML+OCL specifications to be transformed to Alloy for validation and verification, to correct and possibly refine them inside Alloy, and to translate them back to UML+OCL for sharing with stakeholders or to reuse current model-driven architecture tools to refine them toward code.This work was funded by European Regional Development Fund (ERDF) through the COMPETE Programme (operational program for competitiveness) and by national funds through the FCT (Fundaaco para a Ciencia e a Tecnologia-portuguese Foundation for Science and Technology) within project FCOMP-01-0124-FEDER-020532. Part of the work was done while the first author was visiting the Software Design Group at CSAIL, MIT, USA, funded by FCT sabbatical grant SFRH/BSAB/1187/2011. The second author was also partially supported by QREN (the portuguese National Strategy Reference Chart) project 1621, while visiting the High-Assurance Software Laboratory at Universidade do Minho, Portugal. Finally, we would also like to thank all anonymous reviewers for the valuable comments and suggestions

    Impact of different levels of handling on Solea senegalensis culture: effects on growth and molecular markers of stress

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    [EN] Aquaculture routine practices may cause stress induction on the fish and compromise their welfare affecting the production. This experiment aimed to evaluate the potential links between handling during culture with stress responses and growth on Senegalese sole (Solea senegalensis). We worked with two fish cohorts in terms of initial body weight and culture stage: Trial 1 included specimens in the fattening stage (226 ± 4.96 g) and Trial 2 animals in the pre-fattening stage (27.20 ± 0.44 g). The tested culture protocol, which lasted 6 and 4 months for Trial 1 and 2, respectively, mainly reduced handling-derived stressors in the experimental tanks via lowering routine samplings to a minimum. This decrease of the handling-derived stress was reflected in both trials with lower concentration of circulating cortisol in blood plasma from the experimental fish when compared to controls. Moreover, the proposed protocol promoted higher growth in the fish cultured in the less disturbing protocol in Trial 2. Higher specific growth rates and mean body weight and length were reported. In order to further explore the potential beneficial effects of our protocol, we studied the musculoskeletal from Trial 2 gene expression of key genes regulating glucocorticoid signaling pathway and apoptosis: glucocorticoid receptors 1 and 2 (gr1, gr2), heat shock protein 90 AA (hsp90aa), and caspase 6 (casp6). In line with the cortisol reduced level in this trial, gr1, hsp90aa, and casp6 genes showed lower expression in the samples coming from the experimental group. The findings of this study provide valuable information to the aquaculture industry for the management of Solea senegalensis stress and welfare.SIPublicación en abierto financiada por el Consorcio de Bibliotecas Universitarias de Castilla y León (BUCLE), con cargo al Programa Operativo 2014ES16RFOP009 FEDER 2014-2020 DE CASTILLA Y LEÓN, Actuación:20007-CL - Apoyo Consorcio BUCL

    Escuela de Arquitectura Universidad Católica de Chile

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    The first year of the ST Operation Committee: is there a future ?

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    The main objective of the ST Operation Committee (STOC) was to develop a proactive and homogeneous service of operation that satisfies the needs of the service users. Furthermore, the role of the Technical Control Room (TCR) should have been developed to a unique and competent entry point for ST operation by bringing the operation teams closer together on a daily basis. Have these objectives been achieved and to what extend? Is there a future for this committee and what could it look like? What are the implications of the first year of work on ST operation as a whole? This paper answers these questions and gives recommendations how to make best use of the STOC for the ST partners and ST, respectively
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