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Feeding habits of harp and hooded seals in drift ice waters along the east coast of Greenland in summer and winter 总被引：2，自引：0，他引：2
Results of analyses of stomach and intestinal contents from hooded ( Cystophora cristata ) and harp ( Phoca groenlandica ) seals captured in the pack ice belt of the Greenland Sea in summer (July-August) in 2000 and winter (February-March) in 2001 revealed that the diet of both species were comprised of relatively few prey taxa. Pelagic amphipods of the genus Parathemisto , the squid Gonatus fabricii , polar cod ( Boreogadus saida ) and capelin ( Mallotus villosus ) constituted 63-99% of the observed diet biomass in both seal species, irrespective of sampling period, but their relative contribution to the diet varied both with species and sampling period/area. For hooded seals, G. fabricii and capelin were the dominant food items in winter 2001, but the summer 2000 diet comprised a mixture of this squid and polar cod. Parathemisto was most important for the harp seals during summer 2000; in winter 2001 the contribution from krill and capelin were comparable to that of Parathemisto . Multivariate analyses revealed differences in the intestinal contents of hooded and harp seals in areas where the two species' occurrence spatially overlapped. Different foraging depths of the two species may have contributed to the observed differences in diets. 相似文献
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Equilibrium models of differentially rotating nascent neutron stars are constructed, which represent the result of the accretion-induced collapse of rapidly rotating white dwarfs. The models are built in a two-step procedure: (1) a rapidly rotating pre-collapse white dwarf model is constructed; (2) a stationary axisymmetric neutron star having the same total mass and angular momentum distribution as the white dwarf is constructed. The resulting collapsed objects consist of a high-density central core of size roughly 20 km, surrounded by a massive accretion torus extending over 1000 km from the rotation axis. The ratio of the rotational kinetic energy to the gravitational potential energy of these neutron stars ranges from 0.13 to 0.26, suggesting that some of these objects may have a non-axisymmetric dynamical instability that could emit a significant amount of gravitational radiation. 相似文献
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Eduardo Zorita Anders Moberg Lotta Leijonhufvud Rob Wilson Rudolf Brázdil Petr Dobrovolný Jürg Luterbacher Reinhard Böhm Christian Pfister Dirk Riemann Rüdiger Glaser Johan Söderberg Fidel González-Rouco 《Climatic change》2010,101(1-2):143-168
Two European temperature reconstructions for the past half-millennium, January-to-April air temperature for Stockholm (Sweden) and seasonal temperature for a Central European region, both derived from the analysis of documentary sources and long instrumental records, are compared with the output of climate simulations with the model ECHO-G. The analysis is complemented by comparisons with the long (early)-instrumental record of Central England Temperature (CET). Both approaches to study past climates (simulations and reconstructions) are burdened with uncertainties. The main objective of this comparative analysis is to identify robust features and weaknesses in each method which may help to improve models and reconstruction methods. The results indicate a general agreement between simulations obtained with temporally changing external forcings and the reconstructed Stockholm and CET records for the multi-centennial temperature trend over the recent centuries, which is not reproduced in a control simulation. This trend is likely due to the long-term change in external forcing. Additionally, the Stockholm reconstruction and the CET record also show a clear multi-decadal warm episode peaking around AD 1730, which is absent in the simulations. Neither the reconstruction uncertainties nor the model internal climate variability can easily explain this difference. Regarding the interannual variability, the Stockholm series displays, in some periods, higher amplitudes than the simulations but these differences are within the statistical uncertainty and further decrease if output from a regional model driven by the global model is used. The long-term trend of the CET series agrees less well with the simulations. The reconstructed temperature displays, for all seasons, a smaller difference between the present climate and past centuries than is seen in the simulations. Possible reasons for these differences may be related to a limitation of the traditional ‘indexing’ technique for converting documentary evidence to temperature values to capture long-term climate changes, because the documents often reflect temperatures relative to the contemporary authors’ own perception of what constituted ‘normal’ conditions. By contrast, the amplitude of the simulated and reconstructed inter-annual variability agrees rather well. 相似文献
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Summary Groundwater control is a means of ensuring that no gas leakage occurs from unlined rock storage caverns. To achieve a better understanding of the principles of gas containment under groundwater and how to obtain maximum gas storage capacity, analyses of groundwater conditions surrounding storage caverns and the effects of different factors on gas storage capacity have been performed and are reported in this paper. The analysis results indicate that the critical gas pressure of a storage facility is considerably less than the natural hydrostatic pressure around the caverns and somewhat less than the water curtain pressure. High gas storage capacity can be obtained by optimizing the design of cavern configuration, water curtain layout, cavern depth, etc. The principles of such optimization are outlined in this paper. 相似文献
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The combination of fluid inclusion analyses and microfossil analyses is an excellent method to study the preservation process of deep sub-seafloor microorganisms. By studying fluid inclusions in the same mineral phases as microfossils, it is possible to reconstruct the conditions that prevailed when the microorganisms where entombed and to put them in a geological and environmental context.This study has been performed on carbonate and gypsum veins in drilled basalt samples from three seamounts belonging to the Emperor Seamounts in the Pacific Ocean: Detroit, Nintoku and Koko Seamounts. The study show that variations in salt composition (MgCl2, NaCl, KCl and CaCl2) and salinity (2.1 and 10.5 eq. wt% NaCl) of the hydrothermal fluids do not have an influence on the occurrence of microfossils throughout the samples. The microorganisms were trapped and entombed at minimum temperatures of ∼130 °C which implies that the microorganisms could have existed at temperatures of ∼130 °C for shorter periods of time. The microorganisms were entrapped at shallow-marine to submarine conditions and the entrapment of the microorganisms occurred relatively late compared to the volcanic activity. 相似文献
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Five centuries of Stockholm winter/spring temperatures reconstructed from documentary evidence and instrumental observations 总被引：1，自引：0，他引：1
Lotta Leijonhufvud Rob Wilson Anders Moberg Johan Söderberg Dag Retsö Ulrica Söderlind 《Climatic change》2010,101(1-2):109-141
Historical documentary sources, reflecting different port activities in Stockholm, are utilised to derive a 500-year winter/spring temperature reconstruction for the region. These documentary sources reflect sea ice conditions in the harbour inlet and those series that overlap with the instrumental data correlate well with winter/spring temperatures. By refining dendroclimatological methods, the time-series were composited to a mean series and calibrated (1756–1841; r 2?=?66%) against Stockholm January–April temperatures. Strong verification was confirmed (1842–1892; r 2?=?60%; RE/CE?=?0.55). By including the instrumental data, the quantified (QUAN) reconstruction indicates that recent two decades have been the warmest period for the last 500 years. Coldest conditions occurred during the 16th/17th and early 19th centuries. An independent qualitative (QUAL) historical index was also derived for the Stockholm region. Comparison between QUAN and QUAL shows good coherence at inter-annual time-scales, but QUAL distinctly appears to lack low frequency information. Comparison is also made to other winter temperature based annually resolved records for the Baltic region. Between proxy coherence is generally good although it decreases going back in time with the 1500–1550 period being the weakest period—possibly reflecting data quality issues in the different reconstructions. 相似文献
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The Proterozoic Pahtohavare Cu-Au deposit is located in the greenstone belt near Kiruna, northern Sweden. The greenstone consists of mafic volcanic rocks with pillow lavas, mafic sills and albitized rocks, including tuffites, black schists and mafic sills, together with carbonates and mineralized zones. Mineralization occurs as impregnations, epigenetic quartz-rich breccias and fracture fillings with pyrite, chalcopyrite, pyrrhotite and gold in a complex tectonic environment. Fluid inclusions indicate an early formation of quartz and pyrite at temperatures initially near 500°C and a pressure of 2–2.4 kbar from a supersaturated aqueous solution of magmatic origin. In addition to halite cubes, daughter minerals of sylvite, calcite, hematite, graphite and two unknown phases are found. The main stage of chalcopyrite and gold deposition is characterized by aqueous fluids of variable salinity (up to 30 eq. wt.% NaCl including CaCl2), at temperatures below 350°C and pressures between 1 and 2 kbar. A minor CO2 phase with some N, accompanies this stage. Gold was transported as a chloride complex which destabilized due to an increase in pH (as a consequence of the CO2 loss) as well as cooling and dilution of the solution. The ore deposition occurred as a result of mixing with a low salinity aqueous solution during tectonic fracturing with pressure fluctuations and CO2 unmixing. Late oxidation of ores was caused by low to moderately saline (3 to 13 eq. wt.% NaCl) low temperature aqueous solutions. 相似文献
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In an effort to further characterize the Middle and Late Helladic pottery industry on Aegina, we have analyzed amphibole in 23 sherds imported to the coastal settlement of Asine. The sherds derive from vessels of different classes and shapes and range in age from MH I‐II to LH IIIB‐IIIC Early. All sherds come from vessels that carry manufacturing marks, and their amphiboles have compositions that are incompatible with those of Methana, Poros, and Melos. Twenty of the sherds have amphiboles that are identical in composition and overlap a narrow range of amphibole compositions found in specific lava flows on the northern portion of Aegina. Given that the dacites across Aegina contain amphiboles with a wide range in compositions, we suggest that the narrow range of amphibole compositions in the sherds indicates that they were derived from either a specific clay source on the island, located in a stream system southeast of the prehistoric settlement at Kolonna, or that the potters used a specific temper source along the same stream system. Multiple clay or temper sources would have produced sherds with a broader range of amphibole compositions reflecting the diversity of amphibole compositions found on Aegina. One sherd has amphibole compositions indicative of an additional Aeginetan component that is not found in the other sherds. Two sherds have amphiboles with compositions that do not match any known reference amphiboles for Aegina, Methana, Poros, or Melos. These may have been derived from still unsampled dacites on Aegina or have been manufactured from materials located outside the Saronic Gulf. © 2004 Wiley Periodicals, Inc. 相似文献