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Oral Presentation at AGU 2020 Fall meeting 2020 https://agu.confex.com/agu/fm20/meetingapp.cgi/Paper/744547 Arctic environments are a prime example for ecosystems facing manifold vast and rapid changes in the wake of climate change, outpacing the global rate of temperature increases. The risk of thawing permafrost soils raises concerns about a positive feedback process being mediated by increased microbial activity that does not acclimate over time freeing greenhouse gases. However, the mechanistic understanding of the controls on microbial carbon cycling upon warming is still vague. In the following study we investigate microbial growth and soil organic matter decomposition in different soil horizons of the active layer and upper permafrost, covering different polygonal landscape units in two small catchments at the Canadian Yukon Coast. 81 soil samples were subjected to a short-term warming experiment under controlled temperature (4 °C and 14 °C) and moisture conditions. Microbial respiration was measured weekly whereas microbial biomass and physiological parameters were determined at the end of the incubation period and used to assess temperature responses. Microbial growth was estimated by measuring the incorporation of 18O from labelled water into DNA and used to calculate CUE. Microbial biomass was determined via chloroform fumigation. Potential activities of extracellular enzymes were measured using microplate fluorometric assays. Microbial biomass carbon was not affected by warming except for permafrost layers where it either increased or decreased depending on the examined catchment. Microbial respiration strongly responded to warming following the pattern organic layers > upper frozen permafrost > cryoturbated material > mineral layers. Mass specific growth and extracellular enzymatic activities were also enhanced with short-term warming in all soil horizons. This led to rather variable CUE being unaffected in mineral and cryoturbated layers whereas we could observe a minor reduction in organic and permafrost layers where the response of respiration outpaced the one of microbial growth. Our results are not indicative for any physiological acclimatization of permafrost microbes when subjected to 8 weeks of experimental warming and hence support the current concern for potential prolonged carbon losses from warming tundra soils. This work is part of the EU H2020 project “Nunataryuk”.

Resumen Dentro de las principales razones para que la TV Móvil basada en el estándar DVB-H no haya tenido una acogida similar a la TV convencional por parte de los televidentes, están la ausencia de soporte para interactividad bidireccional en el consumo de servicios, el tiempo empleado en el salto de un canal a otro, el bajo tiempo de uso promedio del servicio de la TV móvil, los pocos dispositivos que soportan el estándar, y la ausencia de un middleware abierto para el desarrollo de aplicaciones interactivas de TV Móvil. Este artículo plantea un sistema de recomendaciones de contenidos multimedia basados en filtros colaborativos que hace uso del clasificador de Naive Bayes como una alternativa a los problemas de salto de canal y acceso al contenido multimedia, en el entorno de televisión mencionado. El sistema de recomendaciones desarrollado está enmarcado dentro de un sistema para el consumo de servicios de TV Móvil y ha sido evaluado en el escenario de las comunidades académicas virtuales de televisión construidas por el proyecto ST-CAV de la Universidad del Cauca. Abstract Some of the reasons why Mobile TV based on the DVB-H standard is not widely used by viewers as conventional TV are the lack of support for bi-directional interaction when using TV services, the time required to switch from one channel to other, the relatively low average usage time of the mobile TV service, and the absence of an open middleware for the development of interactive mobile TV applications. This paper presents a recommendation system of multimedia content, based on collaborative filtering and using Naive Bayes classifier as an alternative to the problems of channel hopping and access to multimedia content on the television environment mentioned above. The recommendation system is part of a system of mobile TV services usage and has been evaluated by TV virtual academic communities, built in the ST-CAV project of Universidad del Cauca.