140 resultados para Sollid, Hilde


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Sapropels -organic-matter rich layers- are common in Neogene sediments of the eastern Mediterranean Sea. The formation of these layers has been attributed to climate-related increases in organic-matter production (Calvert et al., 1992, doi:10.1038/359223a0; Rossignol-Strick et al., 1982, doi:10.1038/295105a0; Rohling, 1994, doi:10.1016/0025-3227(94)90202-X) and increased organic-matter preservation due to oxygen depletion in more stagnant bottom waters (Rossignol-Strick et al., 1982, doi:10.1038/295105a0; Rohling, 1994, doi:10.1016/0025-3227(94)90202-X). Here we report that eastern Mediterranean Pliocene sapropels (Emeis et al., 1996, doi:10.2973/odp.proc.ir.160.102.1996) contain molecular fossils of a compound (isorenieratene) known to be synthesized by photosynthetic green sulphur bacteria, suggesting that sulphidic (euxinic) -and therefore anoxic- conditions prevailed in the photic zone of the water column. These sapropels also have a high trace-metal content, which is probably due to the efficient scavenging of these metals by precipitating sulphides in a euxinic water column. The abundance and sulphur-isotope composition of pyrite are consistent with iron sulphide formation in the water column. We conclude that basin-wide water-column euxinia occurred over substantial periods during Pliocene sapropel formation in the eastern Mediterranean Sea, and that the ultimate degradation of the increased organic-matter production was strongly influential in generating and sustaining the euxinic conditions.

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Recent revisions of the geological time scale by Kent and Gradstein (in press) suggest that, on the average, Cretaceous magnetic anomalies are approximately 10 m.y. older than in Larson and Hilde's (1975) previous time scale. These revised basement ages change estimates for the duration of alteration in the ocean crust, based on the difference between secondary-mineral isochron ages and magnetic isochron-crustal ages, from 3 to approximately 13 m.y. In addition to the revised time scale, Burke et al.'s (1982) new data on the temporal variation of 87Sr/86Sr in seawater allow a better understanding of the timing of alteration and more realistic determinations of water/rock ratios during seawater-basalt interaction. Carbonates from all DSDP sites which reached Layer 2 of Atlantic crust (Sites 105, 332, 417, and 418) are deposited within 10-15 m.y. of crustal formation from solutions with 87Sr/86Sr ratios identical to unaltered or contemporaneous seawater. Comparisons of the revised seawater curve with the 87Sr/86Sr of basement carbonates is consistent with a duration of approximately 10-15 m.y. for alteration in the ocean crust. Our preliminary Sr and 87Sr/86Sr data for carbonates from Hole 504B, on 5.9-m.y.-old crust south of the Costa Rica Rift, suggest that hydrous solutions from which carbonates precipitated contained substantial amounts of basaltic Sr. For this reason, carbonate 87Sr/86Sr cannot be used to estimate the duration of alteration at this site. A basalt-dominated alteration environment at Hole 504B is consistent with heat-flow evidence which indicates rapid sediment burial of crust at the Costa Rica Rift, sealing it from access by seawater and resulting in unusually low water/rock ratios during alteration.

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Populist radical right parties have become major political actors in Europe. This paper analyses the path and the different phases that have led them from the fringes of public debate to their present signifi cance, which is based on their capacity to attract electoral support and infl uence the political agendas in their respective countries. Besides, an analysis of the core ideological beliefs of these parties, and of the topics on which their mobilization capacity rests, is provided, as well as of the type of voters that are attracted by them. Finally, the authors discuss the meaning and impact of the growing popularity of the ideas and proposals put forward by the populist radical right parties.

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In pursuit of its mandate to raise the safety standards in the country’s fishing fleet, the Norwegian Maritime Authority will rely on dialogue with the industry.

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Decades of costly failures in translating drug candidates from preclinical disease models to human therapeutic use warrant reconsideration of the priority placed on animal models in biomedical research. Following an international workshop attended by experts from academia, government institutions, research funding bodies, and the corporate and nongovernmental organisation (NGO) sectors, in this consensus report, we analyse, as case studies, five disease areas with major unmet needs for new treatments. In view of the scientifically driven transition towards a human pathway-based paradigm in toxicology, a similar paradigm shift appears to be justified in biomedical research. There is a pressing need for an approach that strategically implements advanced, human biology-based models and tools to understand disease pathways at multiple biological scales. We present recommendations to help achieve this.