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Taku Okada Takehiko Yagi Daisuke Nishio-Hamane 《Physics and Chemistry of Minerals》2011,38(4):251-258
The phase relations and compression behavior of MnTiO3 perovskite were examined using a laser-heated diamond-anvil cell, X-ray diffraction, and analytical transmission electron
microscopy. The results show that MnTiO3 perovskite becomes unstable and decomposes into MnO and orthorhombic MnTi2O5 phases at above 38 GPa and high temperature. This is the first example of ABO3 perovskite decomposing into AO + AB2O5 phases at high pressure. The compression behavior of volume, axes, and the tilting angle of TiO6 octahedron of MnTiO3 perovskite are consistent with those of other A2+B4+O3 perovskites, although no such decomposition was observed in other perovskites. FeTiO3 is also known to decompose into two phases, instead of transforming into the CaIrO3-type post-perovskite phase and we argue that one of the reasons for the peculiar behavior of titanate is the weak covalency
of the Ti–O chemical bonds. 相似文献
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Dayana Castilho de Souza Marcos Daisuke Oyama 《Theoretical and Applied Climatology》2011,103(3-4):345-357
The climatic impacts of gradual desertification in the semi-arid area of Northeast Brazil (SANEB) were evaluated using the MM5 regional model. Simulations for the rainy season of SANEB (March, April, and May) were performed. Desertification simulations were grouped into three numerical runs: total (all SANEB covered by desert), partial (desert areas placement based on future environmental degradation scenarios for SANEB), and random desertification (desert areas placed randomly within SANEB). Total desertification led to a pronounced and significant precipitation reduction in large parts of SANEB. Climatic impacts of partial desertification were guided by the southward expansion of desert areas. For intermediate desertification extensions, a dipole pattern with precipitation reduction (increase) in the northern (southern) areas of SANEB was found. Random desertification led to climatic impacts spread over the whole SANEB. In both partial and random desertification, a quasi-linear precipitation reduction was found as desertification extension increases. 相似文献
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Sex‐related differences in size,function and regeneration of the major cheliped in the hermit crab Pagurus filholi 下载免费PDF全文
Pagurus hermit crabs have a well‐developed right cheliped (major cheliped) and in some species the major cheliped of males is longer than that of females. This paper describes sex‐related differences in major cheliped length and regeneration pattern of the major cheliped in the hermit crab Pagurus filholi. We also examined the function of the major cheliped in male–male competition. Major cheliped length of males was longer than that of females in P. filholi. Males regenerated larger chelipeds than females at the first molt after experimentally induced autotomy. Body size growth in males of the regeneration group was less than that in intact males of the control group while there was no significant difference in body size growth of females between regeneration and control groups. Major cheliped length was included in the best model to explain the outcome of male–male competition and thus sexual selection appears to be a causative factor in the sex‐related difference of the major cheliped length. Sex‐related differences in the regeneration pattern may reflect differences in evolutionary pressures on males for large major chelipeds and females for large body size. 相似文献
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Submarine slope–fan sedimentation in an ancient forearc related to contemporaneous magmatism: The Upper Cretaceous Izumi Group,southwestern Japan 下载免费PDF全文
The Izumi Group in southwestern Japan is considered to represent deposits in a forearc basin along an active volcanic arc during the late Late Cretaceous. The group consists mainly of felsic volcanic and plutonic detritus, and overlies a Lower to Upper Cretaceous plutono‐metamorphic complex (the Ryoke complex). In order to reconstruct the depositional environments and constrain the age of deposition, sedimentary facies and U–Pb dating of zircon grains in tuff were studied for a drilled core obtained from the basal part of the Izumi Group. On the basis of the lithofacies associations, the core was subdivided into six units from base to top, as follows: mudstone‐dominated unit nonconformably deposited on the Ryoke granodiorite; tuffaceous mudstone‐dominated unit; tuff unit; tuffaceous sandstone–mudstone unit; sandstone–mudstone unit; and sandstone‐dominated unit. This succession suggests that the depositional system changed from non‐volcanic muddy slope or basin floor, to volcaniclastic sandy submarine fan. Based on a review of published radiometric age data of the surrounding region of the Ryoke complex and the Sanyo Belt which was an active volcanic front during deposition of the Izumi Group, the U–Pb age (82.7 ±0.5 Ma) of zircon grains in the tuff unit corresponds to those of felsic volcanic and pyroclastic rocks in the Sanyo Belt. 相似文献
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A model for the stress‐dependent elastic wave velocity response of fractured rock mass is proposed based on experimental evidence of stress‐dependent fracture normal and shear stiffness. Previously proposed models and previous experimental studies on stress‐dependent fracture stiffness have been reviewed to provide a basis for the new model. Most of the existing stress‐dependent elastic wave velocity models are empirical, with model parameters that do not have clear physical meanings. To propose the new model, the rock mass is assumed to have randomly oriented microscopic fractures. In addition, the characteristic length of microfractures is assumed to be sufficiently short compared to the rock mass dimensions. The macroscopic stress‐dependent elastic wave velocity response is assumed to be attributed to the stress dependency of fracture stiffness. The stress‐dependent fracture normal stiffness is defined as a generalized power law function of effective normal stress, which is a modification of the Goodman's model. On the other hand, the stress dependency of fracture shear stiffness is modeled as a linear function of normal stress based on experimental data. Ultrasonic wave velocity responses of a dry core sample of Berea sandstone were tested at effective stresses ranging from 2 to 55 MPa. Visual observation of thin sections obtained from the Berea sandstone confirms that the assumptions made for microstructure of rock mass model are appropriate. It is shown that the model can describe the stress‐dependent ultrasonic wave velocity responses of dry Berea sandstone with a set of reasonable material parameter values. Published 2013. This article is a U.S. Government work and is in the public domain in the USA. 相似文献
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Responses in feeding ecology of a benthic forage fish, mummichogs (Fundulus heteroclitus), to altered prey resources were investigated in chronically polluted salt marshes (the Arthur Kill-AK, New York, USA). The diet niche breadth of the AK populations of mummichogs was significantly lower than that of the reference population, reflecting reduced benthic macroinfaunal species diversity. Most of the AK populations also had 2-3 times less food in their gut than the reference population. This disparity in gut fullness among the populations appeared to be partly due to ingested prey size shifts; some of the AK populations ingested fewer large prey than the reference population. Furthermore, benthic assemblages were strongly associated with sediment-associated mercury; gut fullness of the AK populations also significantly decreased with increasing mercury body burdens. These results indicate that chronic pollution may have directly (chemical bioaccumulation) and indirectly (reduced prey availability) altered the feeding ecology of mummichogs. 相似文献
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Previous studies have shown that metal partitioned to a subcellular compartment containing trophically available metal (TAM) is readily available to predators and may be enhanced by increased binding of metal to heat-stable proteins (HSP - e.g., metallothioneins). The aim of the current investigation was to determine the influence of TAM on the trophic transfer of Cd along an experimental, three-level food chain: Artemia franciscana (brine shrimp)-->Palaemonetes pugio (grass shrimp)-->Fundulus heteroclitus (mummichog). P. pugio were fed for 7 days on A. franciscana exposed to Cd in solution (including (109)Cd as radiotracer) and subjected to subcellular fractionation or fed to F. heteroclitus. An HSP-driven increase in the percentage of Cd associated with TAM (TAM-Cd%) in A. franciscana exposed to 1 muM Cd resulted in a bioenhancement (i.e., a greater than linear increase with respect to A. franciscana exposure) of Cd trophic transfer to P. pugio. Increased dietary Cd exposure did not affect TAM-Cd% in P. pugio nor trophic transfer to F. heteroclitus. 相似文献