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11.
Felipe García-Rodríguez Laura Del Puerto Carola Castieira Hugo Inda Roberto Bracco Peter Spechmann Burkhard Wilhelm Scharf 《Limnologica》2001,31(3)
Physical, chemical and biological data from a sedimentary profile of Rocha lagoon (Uruguay) are presented. Analyses of silica remains showed that opal phytoliths, diatoms, sponge spicules and chrysophyte cysts were the most important contributors to biogenic silica. Organic matter, total nitrogen and total phosphorus were used to infer past trophic development. Physical analysis of sediments allowed us to identify five lithological units related to sea level variation and climatic events. 相似文献
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B. W. Fairley L. R. Jones C. Scharf H. Ebeling E. Perlman D. Horner G. Wegner M. Malkan 《Monthly notices of the Royal Astronomical Society》2000,315(4):669-678
We present a measurement of the cluster X-ray luminosity–temperature ( L – T ) relation out to high redshift ( z ∼0.8). Combined ROSAT PSPC spectra of 91 galaxy clusters detected in the Wide Angle ROSAT Pointed Survey (WARPS) are simultaneously fitted in redshift and luminosity bins. The resulting temperature and luminosity measurements of these bins, which occupy a region of the high-redshift L – T relation not previously sampled, are compared with existing measurements at low redshift in order to constrain the evolution of the L – T relation. We find the best fit to low-redshift ( z <0.2) cluster data, at T >1 keV, to be L ∝ T 3.15±0.06 . Our data are consistent with no evolution in the normalization of the L – T relation up to z ∼0.8. Combining our results with ASCA measurements taken from the literature, we find η =0.19±0.38 (for Ω0 =1, with 1 σ errors) where L Bol ∝(1+ z ) η T 3.15 , or η =0.60±0.38 for Ω0 =0.3. This lack of evolution is considered in terms of the entropy-driven evolution of clusters. Further implications for cosmological constraints are also discussed. 相似文献
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Mirko Dreßler Anja Schwarz Thomas Hübener Sven Adler Burkhard W. Scharf 《Journal of Paleolimnology》2011,45(2):223-241
Fossil diatoms from lake sediments have been used to infer both past trophic state and climate conditions. In Europe, climate
reconstructions focused on northern and alpine regions because these areas are climatically sensitive and anthropogenic impact
was low. In contrast, anthropogenic impact was often high in the central European lowlands, such as northern Germany, beginning
in the Neolithic Age, ~3700 BC. Since that time, trophic state change was the main factor that affected diatom assemblages
in central European lowland lakes. Therefore, it was considered difficult or impossible to identify climate changes in the
region using sedimented diatoms. We used diatom assemblage changes, diatom-inferred total phosphorus concentrations and the
relative abundance of planktonic diatoms from sediments of three lakes that differ in their location, size, morphology, catchment
area and current trophic state to test whether we could distinguish between trophic state and climate signals over the past
5,000 years in northern Germany. In this study, changes in trophic state and climate were well differentiated. In the study
lakes, relative abundance of planktonic diatoms seems to be linked to the length of lake mixing phases. Planktonic diatom
abundance decreased during years with shorter mixing duration, and these shorter mixing times probably reflect colder winters.
The diatom-inferred periods of short mixing phases from 1000 BC to AD 500 and from AD 1300 to 1800 coincide well with two
known cooling phases in Europe and the North Atlantic region. 相似文献
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B. J. Maughan † L. R. Jones H. Ebeling C. Scharf 《Monthly notices of the Royal Astronomical Society》2006,365(2):509-529
The X-ray properties of a sample of 11 high-redshift (0.6 < z < 1.0) clusters observed with Chandra and/or XMM–Newton are used to investigate the evolution of the cluster scaling relations. The observed evolution in the normalization of the L – T , M – T , M g – T and M – L relations is consistent with simple self-similar predictions, in which the properties of clusters reflect the properties of the Universe at their redshift of observation. Under the assumption that the model of self-similar evolution is correct and that the local systems formed via a single spherical collapse, the high-redshift L – T relation is consistent with the high- z clusters having virialized at a significantly higher redshift than the local systems. The data are also consistent with the more realistic scenario of clusters forming via the continuous accretion of material.
The slope of the L – T relation at high redshift ( B = 3.32 ± 0.37) is consistent with the local relation, and significantly steeper than the self-similar prediction of B = 2 . This suggests that the same non-gravitational processes are responsible for steepening the local and high- z relations, possibly occurring universally at z ≳ 1 or in the early stages of the cluster formation, prior to their observation.
The properties of the intracluster medium at high redshift are found to be similar to those in the local Universe. The mean surface-brightness profile slope for the sample is β= 0.66 ± 0.05 , the mean gas mass fractions within R2500( z ) and R 200( z ) are 0.069 ± 0.012 and 0.11 ± 0.02 , respectively, and the mean metallicity of the sample is 0.28 ± 0.11 Z⊙ . 相似文献
The slope of the L – T relation at high redshift ( B = 3.32 ± 0.37) is consistent with the local relation, and significantly steeper than the self-similar prediction of B = 2 . This suggests that the same non-gravitational processes are responsible for steepening the local and high- z relations, possibly occurring universally at z ≳ 1 or in the early stages of the cluster formation, prior to their observation.
The properties of the intracluster medium at high redshift are found to be similar to those in the local Universe. The mean surface-brightness profile slope for the sample is β= 0.66 ± 0.05 , the mean gas mass fractions within R
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Lorenz Wüthrich Ezequiel Garcia Morabito Jana Zech Mareike Trauerstein Heinz Veit Christian Gnägi Silke Merchel Andreas Scharf Georg Rugel Marcus Christl Roland Zech 《Swiss Journal of Geoscience》2018,111(1-2):295-303
The combined Rhone and Aare Glaciers presumably reached their last glacial maximum (LGM) extent on the Swiss Plateau prior to 24 ka. Two well-preserved, less extensive moraine stades, the Gurten and Bern Stade, document the last deglaciation of the Aare Valley, yet age constraints are very scarce. In order to establish a more robust chronology for the glacial/deglacial history of the Aare Valley, we applied 10Be surface exposure dating on eleven boulders from the Gurten and Bern Stade. Several exposure ages are of Holocene age and likely document post-depositional processes, including boulder toppling and quarrying. The remaining exposure ages, however yield oldest ages of 20.7 ± 2.2 ka for the Gurten Stade and 19.0 ± 2.0 ka for the Bern Stade. Our results are in good agreement with published chronologies from other sites in the Alps. 相似文献
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Lake Breiter Luzin, located in north-eastern Germany, is known for the rare occurrence of sympatric populations of European cisco, Coregonus albula and C. lucinensis. Moreover, the lake is inhabited by the glacial relict crustacean Mysis relicta, currently found in only three other lakes in Germany. In the present study, the role of M. relicta in the diet of ciscoes was investigated. Between 2001 and 2002 ciscoes, mysids and zooplankton were caught in Lake Breiter Luzin and stomach contents of ciscoes were analysed. There were seasonal changes in the food items in the stomachs, largely reflecting changes in prey availability. The main food items were copepods (45–81%) and mysids (5–26%). Cladocerans had high amounts in the diet only in summer. Seasonal changes in selectivity were also noted for most prey groups. There were also some consistent patterns of prey preference, with an overall preference for mysids. In general, the prey composition in cisco stomachs did not show significant diet changes, but there were some significant differences between day and night feeding in single prey groups, such as cladocerans. Diet composition of ciscoes varied with the different depth strata in which the fish were caught. With increasing depth, the proportion of mysids in the diet significantly increased, whereas that of copepods significantly decreased. Between C. albula and C. lucinensis, no distinct differences in feeding were evident. Mysids provided an additional and important food resource to ciscoes, and were mainly consumed when the availability of other prey organisms decreased, as in autumn and in the deeper strata of the water column. However, mysids preyed on the same food organisms as ciscoes, indicating a strong competition for food between fish and mysids. 相似文献
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MR Lipiński JSF van der Vyver P Shaw WHH Sauer 《African Journal of Marine Science》2016,38(4):589-593
This short note summarises past and current knowledge of the life cycle of chokka-squid Loligo reynaudii d’Orbigny, 1845, in South African waters. Prior to approximately 2010, the chokka-squid stock was considered simple and uniform, with one paralarval pool, the drift of paralarvae westwards, one main nursery area and one main, long spawning migration of adult squid eastwards, back to the main spawning grounds. Based on new information, this life-history scheme has been revised. Genetically, the stock is uniform; however, morphologically, it comprises three main geographic groups. It is proposed that the differences between the groups originate from many different paralarval events and that short (not long) migrations dominate the life cycle. 相似文献
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