Efficient Exchange of Metadata Information in Geo-Distributed Fog Systems

Metadata information is crucial for efficient geo-distributed fog computing systems. Many existing solutions for metadata exchange overlook geo-awareness or lack adequate failure tolerance, which are vital in such systems. To address this, we propose HFCS, a novel hybrid communication system that combines hierarchical and peer-to-peer elements, along with edge pools. HFCS utilizes a gossip protocol for dynamic metadata exchange. In simulation, we investigate the impact of node density and edge pool size on HFCS performance. We observe a significant performance improvement for clustered node distributions, aligning well with real-world scenarios. Additionally, we compare HFCS with a hierarchical system and a peer-to-peer broadcast approach. HFCS outperforms both in task fulfillment at the cost of an average 16\% detected failures due to its peer-to-peer structures

Electroimanes de estructura variable para resonancia magnética nuclear con ciclado rápido de campo magnético

En este trabajo de tesis se proponen nuevos conceptos y métodos para el diseño de electroimanes FFC, con lo cual se define el estado actual del arte en la materia. Se consideran sistemas basados en bobinados múltiples controlados individualmente y sistemas de electroimanes con geometría variable (siendo ésta la principal innovación que se aporta, definiendo el concepto de electroimán activo). Ambos conceptos fueron a su vez desarrollados para eliminar los complejos procesos de maquinado necesarios en los electroimanes actualmente en uso a nivel global, lográndose otras ventajas que serían expuestas oportunamente. Se implementas un prototipo de sistema de geometría variable, el cual fue probado y verificado utilizando un aparato existente en el laboratorio

Microbial colonization and alteration of basaltic glass

International audienceMicroorganisms have been reported to be associated with the alteration of the glassy margin of seafloor pillow basalts (Thorseth et al., 2001, 2003; Lysnes et al., 2004). The amount of iron and other biological important elements present in basalts and the vast abundance of basaltic glass in the earth's crust, make glass alteration an important process in global element cycling. To gain further insight into microbial communities associated with glass alteration, five microcosm experiments mimicking seafloor conditions were inoculated with seafloor basalt and incubated for one year. Mineral precipitations, microbial attachment to the glass and glass alteration were visualized by scanning electron microscopy (SEM), and the bacterial community composition was fingerprinted by PCR and denaturing gradient gel electrophoresis (DGGE) in combination with sequencing. SEM analysis revealed a microbial community with low morphological diversity of mainly biofilm associated and prosthecate microorganisms. Approximately 30 nm thick alteration rims developed on the glass in all microcosms after one year of incubation; this however was also seen in non inoculated controls. Calcium carbonate precipitates showed parallel, columnar and filamentous crystallization habits in the microcosms as well as in the sterile controls. DGGE analysis showed an alteration in bacterial community profiles in the five different microcosms, as a response to the different energy and redox regimes and time. In all microcosms a reduction in number of DGGE bands, in combination with an increase in cell abundance were recorded during the experiment. Sequence analysis showed that the microcosms were dominated by four groups of organisms with phylogenetic affiliation to four taxa: The Rhodospirillaceae, a family containing phototrophic marine organisms, in which some members are capable of heterotrophic growth in darkness and N2 fixation; the family Hyphomicrobiaceae, a group of prosthecate oligotrophic organisms; the genus Rhizobium, N2 fixating heterotrophs; and the genus Sphingomonas, which are known as bio-film producing oligotrophs. Although no bioalteration of glass could be confirmed from our experiments, oligotrophic surface adhering bacteria such as the Sphingomonas sp. and Hyphomicrobium sp. may nevertheless be important for bioalteration in nature, due to their firm attachment to glass surfaces, and their potential for biofilm production