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排序方式: 共有238条查询结果,搜索用时 203 毫秒
21.
Ü. Ertan M. A. Alpar M. H. Erkut K. Y. Ekşi Ş. Çalışkan 《Astrophysics and Space Science》2007,308(1-4):73-77
The anomalous X-ray pulsar 4U 0142+61 was recently detected in the mid infrared bands with the SPITZER Observatory (Wang, Chakrabarty and Kaplan: Nature 440, 772 (2006)). This observation is the first instance for a disk around an AXP. From a reanalysis of optical and infrared data, we show that the observations indicate that the disk is likely to be an active disk rather than a passive dust disk beyond the light cylinder, as proposed in the discovering paper. Furthermore, we show that the irradiated accretion disk model can also account for all the optical and infrared observations of the anomalous X-ray pulsars in the persistent state. 相似文献
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Yeşim Çoban-Yildiz Alec F. Gaines Pat E. Keating Gordon D. Love Dennis McLoughlin Colin E. Snape 《Organic Geochemistry》2009,40(2):270-282
The suspended particulate organic matter, SPOM, in the autumnal Black Sea has been characterised using catalytic hydropyrolysis (HyPy) of the total (bound plus free) lipid material. The technique, which generates maximum yields of volatile products from sediments, kerogens and phytoplankton, was followed using gas chromatography and gas chromatography/mass spectrometry. The generated alkanes were dominated by n-C18, hypothesised to arise predominantly from unsaturated C18 fatty acids. Steranes were generated from reductive conversion of free and bound sterols. The generation of branched alkanes and especially of hopanes provided formal evidence for the participation of bacteria in the mineralisation of the SPOM. Whereas similar distributions of n-alkanes were generated from SPOM sampled from different depths of the comparatively well-stirred Rhodes Gyre (eastern Mediterranean), mineralisation of the SPOM at each depth of the central Black Sea produced characteristic changes in the composition and concentration of the HyPy products. Depth profiles of the n-alkanes generated from SPOM in the region of the Rim Current were affected by the local hydrography. Polynuclear aromatic hydrocarbons (PAHs) of anthropogenic origin were present in the surface waters of the central Black Sea. Some methyl benzenes, thiophenes and pyrroles were also generated. 相似文献
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The aim of the study is to investigate the interaction between waters of Lake Girdev and groundwater in the allochthonous
limestone units exposed in the area between Lake Girdev and Kazanpınarı Spring, southwestern Turkey. The features analyzed
include the flow direction and apparent groundwater velocity, their relationship with Lake Girdev, and the effect of lithological
and structural features on the groundwater circulation. The results of a fluorescein tracer test indicate that groundwater
flows east-northeast and the apparent flow velocity ranges from 26.2 to 35.6 m h–1 between the injection site and various observation points. Tritium data suggest that the water of Lake Girdev and groundwater
are probably similar in age, and oxygen-18 isotope data indicate that water derived from Lake Girdev is the main source of
recharge to the aquifer. The aquifer is fed not only by Lake Girdev but also by rainfall percolating through allochthonous
limestones; together, these provide the discharge of springs in Elmalı Polje. The permeability of the allochthonous limestone
aquifer has been enhanced as a result of jointing and faulting.
Received, June 1997 / Revised, June 1998, March 1999 / Accepted, July 1999 相似文献
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S. Türk Çulha M. Çulha İ. Karayücel M. Y. Çelik Y. Işler 《International Journal of Environmental Science and Technology》2017,14(2):385-396
The study was performed between March 2009 and March 2010 at the Sinop Inner Harbor on cultured mussels at the offshore submerged longline system. The samples of mussels, sediment and suspended particulate matter were seasonally taken for the purpose of monitoring differences of metal contents. In addition, burnable organic matter, contamination factors (CF), pollution load index (PLI) in sediment samples, meat yield of mussels were seasonally determined. All metals in suspended particulate matter were found to be above the national limit. Cd concentration in sediment was above the limit according to sediment quality guidelines, and Cd concentration in mussel was above both national and international limit values. According to CF and PLI identified in sediment, it was found that Inner Harbor was under the effect of anthropogenic pollution in terms of Cd accumulation. Provisional tolerable weekly intake calculated in mussel did not exceed the tolerable consumption values. In conclusion, it can be said that this region considered for commercial mussel cultivation is not a suitable area. 相似文献
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Sorption behavior of Lanaset Red (LR) G on lentil straw (LS) was studied as a function of particle size, adsorbent dose, initial pH value, initial dye concentration, and contact time. Sorption kinetics data was well described by logistic model. Modified logistic equation can be used to explain effects of initial dye concentrations and contact time on the sorption of LR G with high R2 value. Freundlich model was found to be excellent in representing the equilibrium data. Thermodynamic parameters like free energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0) were calculated by the use of Langmuir constant. Thermodynamic data showed that the sorption processes were spontaneous and endothermic in nature. Desorption process suggested that strong binding and weak interactions could be formed between adsorbent surface and dye molecules. Results revealed that LS has a remarkable potential for the sorption of LR G. 相似文献
30.
On crustal corrections in surface wave tomography 总被引:1,自引:0,他引:1
Mantle models from surface waves rely on good crustal corrections. We investigated how far ray theoretical and finite frequency approximations can predict crustal corrections for fundamental mode surface waves. Using a spectral element method, we calculated synthetic seismograms in transversely isotropic PREM and in the 3-D crustal model Crust2.0 on top of PREM, and measured the corresponding time-shifts as a function of period. We then applied phase corrections to the PREM seismograms using ray theory and finite frequency theory with exact local phase velocity perturbations from Crust2.0 and looked at the residual time-shifts. After crustal corrections, residuals fall within the uncertainty of measured phase velocities for periods longer than 60 and 80 s for Rayleigh and Love waves, respectively. Rayleigh and Love waves are affected in a highly non-linear way by the crustal type. Oceanic crust affects Love waves stronger, while Rayleigh waves change most in continental crust. As a consequence, we find that the imperfect crustal corrections could have a large impact on our inferences of radial anisotropy. If we want to map anisotropy correctly, we should invert simultaneously for mantle and crust. The latter can only be achieved by using perturbation theory from a good 3-D starting model, or implementing full non-linearity from a 1-D starting model. 相似文献