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101.
In order to understand the role of aqueous fluid on the differentiation of the mantle, the compositions of aqueous fluids coexisting with mantle minerals were investigated in the system MgO-SiO2-H2O at pressures of 3 to 10 GPa and temperatures of 1000 to 1500°C with an MA8-type multianvil apparatus. Phase boundaries between the stability fields of forsterite + aqueous fluid, forsterite + enstatite + aqueous fluid, and enstatite + aqueous fluid were determined by varying the bulk composition at constant temperature and pressure. The composition of aqueous fluid coexisting with forsterite and enstatite can be defined by the intersection of these two phase boundaries. The solubility of silicate components in aqueous fluid coexisting with forsterite and enstatite increases with increasing pressure up to 8 GPa, from about 30 wt% at 3 GPa to about 70 wt% at 8 GPa. It becomes almost constant above 8 GPa. The Mg/Si weight ratio of these aqueous fluids is much higher than at low pressure (0.2 at 1.5 GPa) and almost constant (1.2) at pressures between 3 and 8 GPa. At 10 GPa, it becomes about 1.4. Aqueous fluid migrating upward through the mantle can therefore dissolve large amounts of silicates, leaving modified Mg/Si ratios of residual materials. It is suggested that the chemical stratification of Mg/Si in the Earth may have been formed as a result of aqueous fluid migration. 相似文献
102.
Kazuya Tanaka Yoshio Takahashi Kenji Horie Hiroshi Shimizu Takashi Murakami 《Physics and Chemistry of Minerals》2010,37(4):249-254
We examined the LIII-edge Pb X-ray absorption near-edge structure (XANES) of three natural zircon samples with different amounts of radiation
doses (1.9 × 1015 to 6.8 × 1015 α-decay events/mg). The results suggest that the oxidation state of radiogenic Pb in the zircon sample with the highest radiation
dose is divalent. The XANES spectra of the two other samples with lower radiation doses suggest that radiogenic Pb(II) is
present, and further that some Pb may be tetravalent. This is the first work on the determination of the oxidation state of
radiogenic Pb in natural zircon using XANES. 相似文献
103.
Chris Blake Michael B. Pracy Warrick J. Couch Kenji Bekki Ian Lewis Karl Glazebrook Ivan K. Baldry Carlton M. Baugh Joss Bland-Hawthorn Terry Bridges Russell Cannon Shaun Cole Matthew Colless Chris Collins Gavin Dalton Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Carlos S. Frenk Carole Jackson Ofer Lahav Stuart Lumsden Steve Maddox Darren Madgwick Peder Norberg John A. Peacock Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2004,355(3):713-727
104.
We propose a new automatic orbital tuning algorithm to adjust climatic signals to insolation. This can tune two signals with periodicity only without shape similarity. A Genetic Algorithm (GA) is used as an optimizing method. The new age model for the Brunhes epoch in Lake Baikal core BDP98 defined climatic shifts at about 250 kyr B.P., 350 kyr B.P. and 700 kyr B.P. The sedimentation rate for the interval from 350 kyr B.P. to 700 kyr B.P. was comparatively low and stable. This new model also indicates that there was a stadial during the super interglacial period (MIS 11), and that the terrestrial response to climate change was complex in this period. 相似文献
105.
Makoto Makita † Kenji Miyawaki Takuya Matsuda 《Monthly notices of the Royal Astronomical Society》2000,316(4):906-916
We perform 2D and 3D numerical simulations of an accretion disc in a close binary system using the simplified flux vector splitting (SFS) finite volume method. In our calculations, the gas is assumed to be ideal with γ =1.01, 1.05, 1.1 and 1.2 . The mass ratio of the mass-losing star to the mass-accreting star is unity. Our results show that spiral shocks are formed on the accretion disc in all cases. In 2D calculations we find that the smaller γ is, the more tightly the spiral winds. We observe this trend in 3D calculations as well in a somewhat weaker sense. Mach numbers in our discs are less than 10. These values are lower than the values in observed accretion discs in close binary systems.
Recently, Steeghs, Harlaftis & Horne found the first convincing evidence for spiral structure in the accretion disc of the eclipsing dwarf nova binary IP Pegasi, using the technique known as Doppler tomography. Although the Mach numbers in present calculations are rather low, we may claim that the spiral structure that we discovered in earlier numerical simulations is now found observationally. 相似文献
Recently, Steeghs, Harlaftis & Horne found the first convincing evidence for spiral structure in the accretion disc of the eclipsing dwarf nova binary IP Pegasi, using the technique known as Doppler tomography. Although the Mach numbers in present calculations are rather low, we may claim that the spiral structure that we discovered in earlier numerical simulations is now found observationally. 相似文献
106.
107.
Kenji Bekki 《Astrophysics and Space Science》2001,276(2-4):1033-1036
A significant fraction of clusters of galaxies are observed to have substructure, which implies that merging between clusters
and subclusters is a rather common physical process in cluster formation. It still remains unclear how cluster merging affects
the evolution of cluster member galaxies. We report the results of numerical simulations that show the dynamical evolution
of a gas-rich, late-type spiral in a merger between a small group of galaxies and a cluster. The simulations demonstrate that
the time-dependent tidal gravitational field during merging excites non-axisymmetric structure of the galaxy, subsequently
drives efficient transfer of gas to the central region and finally triggers a secondary starburst. This result provides a
close physical relationship between the emergence of starburst galaxies and the formation of substructure in clusters. We
accordingly interpret post-starburst galaxies located near substructure of the Coma Cluster as one observational example indicating
the global tidal effects of group–cluster merging. Our numerical results further suggest a causal link between the observed
excess of blue galaxies in distant clusters and the cluster virialization process through hierarchical merging of subclusters.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
108.
109.
Yuji Ito Toshiya Katano Naoki Fujii Masumi Koriyama Kenji Yoshino Yuichi Hayami 《Journal of Oceanography》2013,69(4):467-479
Eucampia zodiacus Ehrenberg is harmful, as it causes reduction in the quality of the aquacultured Porphyra thalli owing to nutrient depletions during dense blooms in the late winter in the macrotidal Ariake Sea, Japan. To understand the mechanism of bloom development, changes in the abundance of E. zodiacus during a bloom were investigated along vessel transects from February to April 2012. In addition, marine environmental variables were continuously monitored by the Ariake Sea Monitoring Tower, which revealed that turbidity periodically decreased during neap tides. During the 16 February neap tide, a high Secchi depth (4.3 m) was recorded at offshore stations and the Z 1% depth, at which the light intensity attenuates to 1 % of that at the sea surface, exceeded the water depth. On 16 February, the abundance of E. zodiacus was 52–732 cells mL?1, peaking at 7.0 m depth offshore. Subsequently, abundance increased at all stations. During the 22 February spring tide, abundance became vertically uniform. On 19 March, abundance at the tower reached 3758 cells mL?1 at the surface. We conclude that an improvement in light conditions in the deeper layer triggered the bloom, although the size and the duration of the bloom were determined by nutrient availability. Thus, decreases in turbidity during neap tides and subsequent strong vertical mixing during spring tides may be instrumental in the population dynamics of the large diatom E. zodiacus in macrotidal environments. 相似文献
110.
Ernst Kerkhoven Thian Yew Gan Michiharu Shiiba Gerhard Reuter Kenji Tanaka 《水文研究》2006,20(9):1961-1978
In order to evaluate cumulus parameterization (CP) schemes for hydrological applications, the Pennsylvania State University–National Center for Atmospheric Research's fifth‐generation mesoscale model (MM5) was used to simulate a summer monsoon in east China. The performances of five CP schemes (Anthes–Kuo, Betts–Miller, Fritsch–Chappell, Kain–Fritsch, and Grell) were evaluated in terms of their ability to simulate amount of rainfall during the heavy, moderate, and light phases of the event. The Grell scheme was found to be the most robust, performing well at all rainfall intensity and spatial scales. The Betts–Miller scheme also performed well, particularly at larger scales, but its assumptions may make it inapplicable to non‐tropical environments and at smaller scales. The Kain–Fritsch scheme was the best at simulating moderate rainfall rates, and was found to be superior to the Fritsch–Chappell scheme on which it was based. The Anthes–Kuo scheme was found to underpredict precipitation consistently at the mesoscale. Simulation performance was found to improve when schemes that included downdrafts were used in conjunction with schemes that did not include downdrafts. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献