(Table 1) Nesting characteristics of greater snow geese (Chen caerulescens atlanticus) on Bylot Island between 1995-2005

1. Habitat heterogeneity and predator behaviour can strongly affect predator-prey interactions but these factors are rarely considered simultaneously, especially when systems encompass multiple predators and prey. 2. In the Arctic, greater snow geese Anser caerulescens atlanticus L. nest in two structurally different habitats: wetlands that form intricate networks of water channels, and mesic tundra where such obstacles are absent. In this heterogeneous environment, goose eggs are exposed to two types of predators: the arctic fox Vulpes lagopus L. and a diversity of avian predators. We hypothesized that, contrary to birds, the hunting ability of foxes would be impaired by the structurally complex wetland habitat, resulting in a lower predation risk for goose eggs. 3. In addition, lemmings, the main prey of foxes, show strong population cycles. We thus further examined how their fluctuations influenced the interaction between habitat heterogeneity and fox predation on goose eggs. 4. An experimental approach with artificial nests suggested that foxes were faster than avian predators to find unattended goose nests in mesic tundra whereas the reverse was true in wetlands. Foxes spent 3-5 times more time between consecutive attacks on real goose nests in wetlands than in mesic tundra. Their attacks on goose nests were also half as successful in wetlands than in mesic tundra whereas no difference was found for avian predators. 5. Nesting success in wetlands (65%) was higher than in mesic tundra (56%) but the difference between habitats increased during lemming crashes (15%) compared to other phases of the cycle (5%). Nests located at the edge of wetland patches were also less successful than central ones, suggesting a gradient in accessibility of goose nests in wetlands for foxes. 6. Our study shows that the structural complexity of wetlands decreases predation risk from foxes but not avian predators in arctic-nesting birds. Our results also demonstrate that cyclic lemming populations indirectly alter the spatial distribution of productive nests due to a complex interaction between habitat structure, prey-switching and foraging success of foxes.

(Table 1) Water storage changes of the 33 world's largest river basins between 2002-2009

Global change in land water storage and its effect on sea level is estimated over a 7-year time span (August 2002 to July 2009) using space gravimetry data from GRACE. The 33 World largest river basins are considered. We focus on the year-to-year variability and construct a total land water storage time series that we further express in equivalent sea level time series. The short-term trend in total water storage adjusted over this 7-year time span is positive and amounts to 80.6 ± 15.7 km**3/yr (net water storage excess). Most of the positive contribution arises from the Amazon and Siberian basins (Lena and Yenisei), followed by the Zambezi, Orinoco and Ob basins. The largest negative contributions (water deficit) come from the Mississippi, Ganges, Brahmaputra, Aral, Euphrates, Indus and Parana. Expressed in terms of equivalent sea level, total water volume change over 2002-2009 leads to a small negative contribution to sea level of -0.22 ± 0.05 mm/yr. The time series for each basin clearly show that year-to-year variability dominates so that the value estimated in this study cannot be considered as representative of a long-term trend. We also compare the interannual variability of total land water storage (removing the mean trend over the studied time span) with interannual variability in sea level (corrected for thermal expansion). A correlation of ~0.6 is found. Phasing, in particular, is correct. Thus, at least part of the interannual variability of the global mean sea level can be attributed to land water storage fluctuations.

Proyecto de construcción del alumno de 3º año: curso de 1877-78

Proyecto de un viaducto de 408 metros de longitud y 20 metros de ancho formado con largueros reticulados del sistema Warren, que sirva para dar paso a una carretera por donde circula un tranvía.Contiene además: Proyecto de preparación mecánica de las menas

El concepto de límite en el B-mu de François Roche

Algunos proyectos, como el Dusty relief/B-mu (2002) de François Roche demuestran como edificios complejos, que toman distancia desde los modelos mecanicistas para referirse a nuevos paradigmas, se pueden interpretar y comprenderse mejor gracias a un análisis perceptivo que acerca el proyecto de arquitectura a cuestiones como la relación psicológica del hombre con la arquitectura, el miedo al espacio, y las patologías vinculadas a la percepción y a las neurosis modernas. En este caso, aparte de las repercusiones que la fachada de polvo podría tener en el ámbito de la ecología urbana, es interesante analizar algunos aspectos ligados a la dicotomía entre forma externa y volúmenes internos para la que François Roche cita como referencia el raumplan de Adolf Loos, pero que presenta motivos para una reflexión vinculada a los aspectos perceptivos. El artículo trata de analizar como François Roche proyecta sus edificios extremando la dicotomía entre interior/visual y exterior/táctil, desarrollando así una nueva relación con el lugar. Roche diseña la fachada exterior del B-mu autoimponiéndose una limitación del sentido de la vista, a favor de una dimensión háptica del proyecto y lo hace envolviendo los ámbitos arquitectónicos más familiares de una interfaz abstracta y táctil.

Oeuures de M. François de Salignac de la Mothe Fenelon : [Texto impreso] precepteur des enfants de France, Archevêque-Duc de Cambrai : tome huitieme

Marca tip. en port.: "Jombert inv., Milliere sculp. 1782"