排序方式: 共有16条查询结果,搜索用时 15 毫秒
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Aurelian Andrei Radu Tatiana Angelescu Valentin Curtef Florin Delia Daniel Felea Ioana Goia Dumitru Ha?egan Bogdan Lucaschi Ancuta Manea Vlad Popa Ioan Rali?? Radu V?c?reanu 《Experimental Astronomy》2012,34(1):31-42
Around the world, several scientific projects share the interest of a global network of small Cherenkov telescopes for monitoring observations of the brightest blazars??the DWARF network. A small, ground based, imaging atmospheric Cherenkov telescope of last generation is intended to be installed and operated in Romania as a component of the DWARF network. To prepare the construction of the observatory, two support projects have been initiated. Within the framework of these projects, we have assessed a number of possible sites where to settle the observatory. In this paper we submit a brief report on the general characteristics of the best four sites selected after the local infrastructure, the nearby facilities and the social impact criteria have been applied. 相似文献
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Luciano N. Padovani María Delia Viñas Felisa SánchezHermes Mianzan 《Journal of Sea Research》2012,67(1):85-90
The trophic role of the hyperiid amphipod Themisto gaudichaudii in the southern Patagonian shelf food web was assessed from the analysis of stomach contents of the local fish assemblage. A total of 461 trawl samples were collected during seven seasonal cruises. A total of 17 out of 38 fish species were found to ingest T. gaudichaudii. This amphipod was a main prey item in five of these species, showing high values of alimentary index: Seriolella porosa (99.9%), Macruronus magellanicus (68.8%), Micromesistius australis (59.1%), Patagonotothen ramsayi (48.6%), and Merluccius hubbsi (10.9%). The contribution of T. gaudichaudii, in weight, to their summer diet was 60%, on average. This contribution was minimal in winter and maximal in summer. Fisheries studies have indicated that these five species, mainly M. magellanicus, account for almost 85% of the fish biomass in the area. Although the remaining 15% did not feed heavily on T. gaudichaudii, they are known to prey on the main hyperiid predators. Our study shows that T. gaudichaudii contributes greatly, both directly and indirectly, to supporting the fish community. We thus proposed that T. gaudichaudii plays a key role as a “wasp-waist” species in the sub-Antarctic region, similar to that of krill in Antarctic waters, channeling the energy flow and enabling a short and efficient food chain. 相似文献
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Continuous temperature logs to depths between 750 and 1400 m in the Transylvanian Basin, Romania, in many cases show temperature gradient variations with depth which cannot be explained by depth variations in thermal conductivity, topography and ground water flow. The only possible responsible agent seems to be past surface temperature variations. The temperature logs from nine boreholes have been interpreted individually and jointly by least squares inverse modelling with the surface temperature history and background heat flux as unknown parameters. All the temperature profiles are consistent with a temperature rise at the end of the last glaciation. The effects of borehole depth, of a wrong choice of thermal conductivity, and the level of uncorrelated random noise were examined using synthetic examples. 相似文献
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Karla Petry Dougal A. Jerram Delia del Pilar M. de Almeida Henrique Zerfass 《Journal of Volcanology and Geothermal Research》2007
The formation of volcanic–sedimentary interaction features in extreme arid environments is not a commonly described process. Specifically the occurrence of dynamically mixed sediments and juvenile igneous clasts as peperites, for water has been considered one major important factor in the processes of magma dismantling and mingling with unconsolidated sediment to form such deposits. The study area, located in south Brazil, shows a sequence of lava flows and intertrapic sandstone layers from the Paraná Basin, associated with the formation of clastic dykes, flow striations, peperite and ‘peperite-like’ breccias. Four processes are suggested for the genesis of the peperites: (a) fragmentation of the flow front and base; (b) sand injection; (c) dune collapse; (d) magma cascade downhill. The continued flow of a lava, while its outer crust is already cooling, causes it to break, especially in the front and base, fragments falling in the sand and getting mixed with it, generating the flow front ‘peperite-like’ breccia. The weight of the lava flow associated to shear stress at the base cause sand to be injected inwards the flow, forming injection clastic dykes in the cooled parts and injection peperite in the more plastic portions. The lava flow may partially erode the dune, causing the dune to collapse and forming the collapse ‘peperite-like’ breccia. The shear stress at the base of a flowing lava striates the unconsolidated sand, forming the flow striations. The sand that migrates over a cooled, jointed lava flow may get caught in the cavities and joints, forming the filling clastic dykes. These deposits are analogous to those found in the Etendeka, NW Namibia, and show that sediment–lava interactions in arid settings are widespread throughout the Paraná-Etendeka province during the onset of flood volcanism. 相似文献
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Stephen J. Livingstone David H. Roberts Bethan J. Davies David J. A. Evans Colm
Cofaigh Delia M. Gheorghiu 《第四纪科学杂志》2015,30(8):790-804
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Detailed faunal, isotopic, and lithic marine records provide new insight into the stability and climate progression of the last interglacial period, Marine Isotope Stage (MIS) 5, which peaked approximately 125,000 years ago. In the eastern subpolar North Atlantic, at the latitude of Ireland, interglacial warmth of the ice volume minimum of substage 5e (MIS 5e) lasted 10,000 years (10 ka) and its demise occurred in two cooling steps. The first cooling step marked the end of the climatic optimum, which was 2–3 ka long. Minor ice rafting accompanied each cooling step; the second, larger, step encompassing cold events C26 and C25 was previously identified in the northwestern Atlantic. Approximately 4 °C of cooling occurred between peak interglacial warmth and C25, and the region experienced an additional temporary cooling of at least 1–2 °C during C24, a cooling event associated with widespread ice rafting in the North Atlantic. Beginning with C24, MIS 5 was characterized by oscillations of at least 1–2 °C superimposed on a generally cool baseline. The results of this study imply that the marine climatic optimum of the last interglacial was shorter than previously thought. The finding that the eastern subpolar North Atlantic cooled significantly before C24 reconciles terrestrial evidence for progressive climate deterioration at similar and lower latitudes with marine conditions. Our results also demonstrate a close association between modest ice rafting, cooling, and deep ocean circulation even during the peak of MIS 5e and in the earliest stages of ice growth. 相似文献
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Delia Rösel Steven David Boger Andreas Möller Birgit Gaitzsch Matthias Barth Jeffrey Oalmann Thomas Zack 《地学学报》2014,26(1):64-71
Provenance studies from Cambro‐Ordovician sediments of the North Gondwana passive margin typically ascribe a North African source, a conclusion that cannot be reconciled with all observations. We present new U‐Pb ages from detrital rutile and zircon from Late Ordovician sediments from Saxo‐Thuringia, Germany. Detrital zircons yield age populations of 500–800 Ma, 900–1050 Ma and 1800–2600 Ma. The detrital rutile age spectra are unimodal with ages between 500 and 650 Ma and likely represent, together with the 500–800 Ma and 1800–2600 Ma zircon populations, detritus sourced predominantly from North Africa. In contrast, the c. 950 Ma zircons, which are persistently found in Cambro‐Ordovician sediments of North Gondwana, have no obvious African source. We propose that these zircons are sourced from the Rayner Complex–Eastern Ghats regions of Antarctica and India. An Indo‐Antarctic source indicates either continental‐scale sedimentary transport from central Gondwana to its peripheries or multiple cycles of sediment reworking and redeposition. 相似文献
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Protist communities were studied monthly at Santoña beach (Cantabrian Sea, Spain) throughout one year. Twelve abiotic parameters were analyzed. The following functional groups (defined according to the preferential source of food) were considered: photoautotrophs (P), saprotrophs (S), bacterivores (B), algivores (A), non-selectives (N), and predators or raptors (R). A total of 269 species was found. The percentage of species in each functional group was: 11.66% A, 33.66% B, 26.45% N, 28.02% P, and 0.21% R. No species belonging to functional group S were found. Functional groups B and N had the highest percentage of biomass (up to 100% in certain months). The percentage of biomass for each functional group was calculated. There was a remarkable negative correlation between groups B and N at the four sampling sites. The biomass percentage of group A was important at several sampling points in March, June, and July, coinciding with an increase in their source of food. The percentage of group P rose in April and May, the months the period of irradiance was longer. The canonical population analysis showed that there were no significant differences with respect to the composition in terms of functional groups at the four sampling sites. These data were compared with those found in the literature on both marine and freshwater areas, by means of a hierarchical conglomerate analysis. The statistical analysis showed that there are generally noticeable differences between these two types of media. It is suggested that each area may have a characteristic species composition respect to functional groups, which is influenced by the environmental parameters. 相似文献