High-pressure phase behavior of MnTiO<Subscript>3</Subscript>: decomposition of perovskite into MnO and MnTi<Subscript>2</Subscript>O<Subscript>5</Subscript>     

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   

Altered feeding habits and strategies of a benthic forage fish (Fundulus heteroclitus) in chronically polluted tidal salt marshes     

Goto D  Wallace WG 《Marine environmental research》2011,72(1-2):75-88

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   

Foraminiferal evidence of submarine sediment transport and deposition by backwash during the 2004 Indian Ocean tsunami     

Daisuke  Sugawara  Koji  Minoura  Naoki  Nemoto  Shinji  Tsukawaki  Kazuhisa  Goto  Fumihiko  Imamura 《Island Arc》2009,18(3):513-525

Micropaleontological analysis of nearshore to offshore sediments recovered from the southwestern coast of Thailand was performed to clarify the submarine processes of sediment transport and deposition during the 2004 Indian Ocean tsunami. The distribution pattern of benthic foraminifers showed seaward migration after the tsunami event. Agglutinated foraminifers, which are characteristic of an intertidal brackish environment, were identified in the post-tsunami samples from foreshore to offshore zones. These suggest that sediments originally distributed in foreshore to nearshore zones were transported offshore due to the tsunami backwash. On the other hand, the distribution pattern of planktonic and benthic species living in offshore zones showed slight evidence of landward migration by the tsunami. This suggests that landward redistribution of sediments by the tsunami run-up did not occur in the offshore seafloor of the study area. Our results and a review of previous studies provide an interpretation of submarine sedimentation by tsunamis. It is possible that tsunami backwashes induce sediment flows that transport a large amount of coastal materials seaward. Thus, traces of paleotsunami backwashes can be identified in offshore sedimentary environments as the accumulation of allochthonous materials. This can be recognized as changes in benthic foraminiferal assemblages.  相似文献   

真鲷饵料生物褶皱臂尾轮虫和眼点拟微绿藻的大量培养     

刘新富  雷霁霖  刘忠强  柳学周 《海洋科学》2000,24(5):47-51

于1992～1994年 ,在中国水科院黄海水产研究所小麦岛试验基地(青岛)进行的“中日合作真鲷增殖放流项目”执行期间 ,对真鲷饵料生物———眼点拟微绿藻 (Nannochloropsisoculata)和L型褶皱臂尾轮虫 (Branchionus plicatilis)进行了大量培养。眼点拟微绿藻的平均接种密度为1211.3×104个/ml,经5～6d的室内或室外露天培养即可达到平均为2341.0×104 个/ml的收获密度 ;采用眼点拟微绿藻和新鲜面包酵母作为混合饵料 ;褶皱臂尾轮虫 (L型 )培养3～4d即可由接种时平均密度148.0个/ml,增长至平均216.8个/ml的采收密度。眼点拟微绿藻和轮虫的日间增殖密度分别是12.8 %和26.6 %。每生产108个褶皱臂尾轮虫需要消耗0.73m3眼点拟微绿藻 (密度为2000×104/ml)和790.8g 鲜面包酵母。采用此法 ,作者连续3a成功地为每年百万尾以上真鲷苗种提供了足够的生物饵料。总结3a苗种培育和生物饵料培养之间的关系 ,作者认为 ,大规模稳定生产海水鱼类苗种时,育苗与饵料生物培养 (褶皱臂尾轮虫和眼点拟微绿藻 )水体的合理比例应为1∶1～1.5∶3。  相似文献   

Relevance of intracellular partitioning of metals in prey to differential metal bioaccumulation among populations of mummichogs (Fundulus heteroclitus)     

Daisuke Goto  William G. Wallace   《Marine environmental research》2009,68(5):257-267

Intracellular partitioning of trace metals is critical to metal tolerance in aquatic organisms and may also influence metal trophic transfer in ecosystems. In this study, we tested the relevance of metal (Cd, Cu, Pb, and Zn) intracellular partitioning in prey as an indicator of metal trophic availability to benthic forage fish, mummichogs (Fundulus heteroclitus), in chronically metal-polluted salt marshes in New York, USA. Two common prey of mummichogs in the study area, Palaemonetes pugio and Nereis acuminata, generally stored increasingly higher proportions of non-essential metals (particularly Pb) in insoluble (less trophically available) cellular components, as the whole body burdens increased. In contrast, intracellular partitioning of essential metals (Cu and Zn) in invertebrate prey varied relatively little among sites. Differential Cd and Pb intracellular partitioning patterns within P. pugio among sites were significantly associated with Cd and Pb whole body burdens in mummichogs, respectively (i.e., prey-driven bioreduction of metals), while bioaccumulation of Cu and Zn in mummichogs was similar among populations. The findings in this study suggest that metal intracellular partitioning within prey may be partially responsible for metal trophic availability to a predator in metal-polluted habitats, while there was also evidence that some predator-dependent processes may offset differential trophic availabilities from prey.  相似文献   

Development of a GPGPU-parallelized hybrid finite-discrete element method for modeling rock fracture     

Daisuke Fukuda  Mojtaba Mohammadnejad  Hongyuan Liu  Sevda Dehkhoda  Andrew Chan  Sang-Ho Cho  Gyeong-Jo Min  Haoyu Han  Jun-ichi Kodama  Yoshiaki Fujii 《国际地质力学数值与分析法杂志》2019,43(10):1797-1824

The hybrid finite-discrete element method (FDEM) is widely used for engineering applications, which, however, is computationally expensive and needs further development, especially when rock fracture process is modeled. This study aims to further develop a sequential hybrid FDEM code formerly proposed by the authors and parallelize it using compute unified device architecture (CUDA) C/C++ on the basis of a general-purpose graphics processing unit (GPGPU) for rock engineering applications. Because the contact detection algorithm in the sequential code is not suitable for GPGPU parallelization, a different contact detection algorithm is implemented in the GPGPU-parallelized hybrid FDEM. Moreover, a number of new features are implemented in the hybrid FDEM code, including the local damping technique for efficient geostatic stress analysis, contact damping, contact friction, and the absorbing boundary. Then, a number of simulations with both quasi-static and dynamic loading conditions are conducted using the GPGPU-parallelized hybrid FDEM, and the obtained results are compared both quantitatively and qualitatively with those from either theoretical analysis or the literature to calibrate the implementations. Finally, the speed-up performance of the hybrid FDEM is discussed in terms of its performance on various GPGPU accelerators and a comparison with the sequential code, which reveals that the GPGPU-parallelized hybrid FDEM can run more than 128 times faster than the sequential code if it is run on appropriate GPGPU accelerators, such as the Quadro GP100. It is concluded that the GPGPU-parallelized hybrid FDEM developed in this study is a valuable and powerful numerical tool for rock engineering applications.  相似文献   

Possible observational evidence for the θ⁻² angular distribution of the opening half-angle of gamma-ray burst jets     

Daisuke Yonetoku  Ryo Yamazaki  Takashi Nakamura  Toshio Murakami 《Monthly notices of the Royal Astronomical Society》2005,362(3):1114-1118

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The Effect of Bioturbation Activity of the Ark Clam Scapharca subcrenata on the Fluxes of Nutrient Exchange at the Sediment–Water Interface     

ZHANG Shuo  FANG Xin  ZHANG Junbo  YIN Fang  ZHANG Hu  WU Lizhen  KITAZAWA Daisuke 《中国海洋大学学报(英文版)》2020,19(1):232-240

Filter-feeding shellfish are common benthos and significantly affect the biogeochemical cycle in the shallow coastal ecosystems.Ark clam Scapharca subcrenata is one of the widely cultured bivalve species in many coastal areas owing to its tremendous economic value.However,there is little information regarding the effects of the bioturbation of S.subcrenata on the fluxes of nutrient exchange in the sediment-water interface(SWI).In this regard,S.subcrenata was sampled during October 2016 to determine the effects of its bioturbation activity on the nutrient exchange flux of the SWI.The results showed that the biological activity of S.subcrenata could increase the diffusion depth and the rate of the nutrients exchange in the sediments.The bioturbation of S.subcrenata could allow the nutrients to permeate into the surface sediments at 6-10cm and increase the release rate of nutrients at the SWI.The releasing fluxes of DIN and PO43−-P in the culture area were found to be around three times higher than that in the non-cultured region.The culture of S.subcrenata has been proved to be an important contributor to nutrient exchange across the SWI in the farming area of Haizhou Bay.Nutrients exchange in the SWI contributes a part of 86%DIN,71%PO43−-P and 18%SiO32−-Si for the aquaculture farm.  相似文献   

Oxygen isotope evolution of the Lake Owyhee volcanic field,Oregon, and implications for the low-δ18O magmatism of the Snake River Plain–Yellowstone hotspot and other low-δ18O large igneous provinces     

Tyler B. Blum  Kouki Kitajima  Daisuke Nakashima  Ariel Strickland  Michael J. Spicuzza  John W. Valley 《Contributions to Mineralogy and Petrology》2016,171(11):92

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134Cs and 137Cs in the North Pacific Ocean derived from the March 2011 TEPCO Fukushima Dai-ichi Nuclear Power Plant accident,Japan. Part one: surface pathway and vertical distributions     

Michio Aoyama  Yasunori Hamajima  Mikael Hult  Mitsuo Uematsu  Eitarou Oka  Daisuke Tsumune  Yuichiro Kumamoto 《Journal of Oceanography》2016,72(1):53-65

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