Determination of post-perovskite phase transition boundary up to 4400 K and implications for thermal structure in D″ layer     

Shigehiko Tateno  Kei Hirose  Nagayoshi Sata  Yasuo Ohishi 《Earth and Planetary Science Letters》2009,277(1-2):130-136

We have determined the post-perovskite phase transition boundary in MgSiO₃ in a wide temperature range from 1640 to 4380 K at 119–171 GPa on the basis of synchrotron X-ray diffraction measurements in-situ at high-pressure and -temperature in a laser-heated diamond-anvil cell (LHDAC). The results show a considerably high positive Clapeyron slope of + 13.3 ± 1.0 MPa/K and a transition temperature of about 3520 ± 70 K at the core–mantle boundary (CMB) pressure. The thermal structure in D″ layer can be tightly constrained from precisely determined post-perovskite phase transition boundary and the depths of paired seismic discontinuities. These suggest that temperature at the CMB may be around 3700 K, somewhat lower than previously thought. A minimum bound on the global heat flow from the core is estimated to be 6.6 ± 0.5 TW.  相似文献   

Editors’ Message Hydrogeological activities in Japan     

Yasuo Sakura  Chanyuan Tang 《Hydrogeology Journal》2000,8(4):355-355

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Heating experiments of the Tagish Lake meteorite: Investigation of the effects of short‐term heating on chondritic organics     

Queenie H. S. Chan  Aiko Nakato  Yoko Kebukawa  Michael E. Zolensky  Tomoki Nakamura  Jessica A. Maisano  Matthew W. Colbert  James E. Martinez  A. L. David Kilcoyne  Hiroki Suga  Yoshio Takahashi  Yasuo Takeichi  Kazuhiko Mase  Ian P. Wright 《Meteoritics & planetary science》2019,54(1):104-125

We present in this study the effects of short‐term heating on organics in the Tagish Lake meteorite and how the difference in the heating conditions can modify the organic matter (OM) in a way that complicates the interpretation of a parent body's heating extent with common cosmothermometers. The kinetics of short‐term heating and its influence on the organic structure are not well understood, and any study of OM is further complicated by the complex alteration processes of the thermally metamorphosed carbonaceous chondrites—potential analogues of the target asteroid Ryugu of the Hayabusa2 mission—which had experienced posthydration, short‐duration local heating. In an attempt to understand the effects of short‐term heating on chondritic OM, we investigated the change in the OM contents of the experimentally heated Tagish Lake meteorite samples using Raman spectroscopy, scanning transmission X‐ray microscopy utilizing X‐ray absorption near edge structure spectroscopy, and ultraperformance liquid chromatography fluorescence detection and quadrupole time of flight hybrid mass spectrometry. Our experiment suggests that graphitization of OM did not take place despite the samples being heated to 900 °C for 96 h, as the OM maturity trend was influenced by the heating conditions, kinetics, and the nature of the OM precursor, such as the presence of abundant oxygenated moieties. Although both the intensity of the 1s?σ* exciton cannot be used to accurately interpret the peak metamorphic temperature of the experimentally heated Tagish Lake sample, the Raman graphite band widths of the heated products significantly differ from that of chondritic OM modified by long‐term internal heating.  相似文献   

Subsurface thermal environment and groundwater flow around Tokyo Bay,Japan     

Vuthy Monyrath  Yasuo Sakura  Akinobu Miyakoshi  Takeshi Hayashi 《Environmental Earth Sciences》2010,60(5):923-932

Previous studies and borehole temperature measurements suggest that subsurface temperature distribution on the west side of Tokyo Bay (from Tokyo to Yokohama) is higher than that of the east side (Chiba side). To understand the groundwater flow and other factors which may contribute to the subsurface temperature discrepancy such as geological setting in the study area, groundwater temperature profiles were measured in 119 boreholes around the Tokyo Bay from 2002 to 2007. The data were analyzed and compared with previous studies. Horizontal distribution of subsurface temperature at the depths of −50 and −100 m was made to show the distribution of thermal regime. A cross-section across the bay of Tokyo was made to see the isothermal lines and distribution of hydraulic heads in a vertical perspective. These results show that the highest subsurface temperature zone is in the Tokyo area, along the river valley. Subsurface temperature at the depth of 50- and 100-m below sea level in the western part of the bay is comparatively higher than its eastern side at the same elevation and distance from the bay. This fact suggests that there is a regional groundwater flow system in the area and it is strongly affected by the geological structure, particularly buried valley systems of the bay during the Paleo-Tokyo River and the topographical driving force which is the result of the different elevation of recharge areas. Groundwater discharge is concentrated along the buried valley of Paleo-Tokyo River.  相似文献   

The changing iconography of Japanese political geography     

Yasuo Miyakawa 《GeoJournal》2000,52(2):345-352

Our world is very fluid, very complex, constantly moving, made up of a great number of interdependent components. Therefore, the locus and the orbit of a particular area play an important role in geography and in politics. The purpose of this study is to examine the iconography of orbit and freedom of movement through an analysis of the transformation of the international politico-economic structure and its impact on Japan and to make clear the footsteps of Jean Gottmann on political geography. Due to its locus being on the crossroad of international power struggles, Japan had accepted different iconographies of orbits every time she faced great mutation in her history. This, in turn, accelerated the synchronism, synergism and synthesis of different iconographies that came to converge at the crossroad. The integration of imported cultures with the Japanese traditional culture promoted the transformation of Japanese society and community to emphasize the freedom of movements. The flexibility of Japanese society and the unifying iconography of Japanese community have enabled Japan to adapt and readapt to changing politico-economic phases. Interested in the relationship between freedom of movement and iconography, Jean Gottmann spent a considerable portion of his academic life inquiring into the changing dynamics of Japanese iconography on the global scene. After a quarter-century pursuit, he contributed to the establishment of political geography in Japan.  相似文献   

Radiant point,trajectory and velocity from single photographic or TV observation     

Yasuo Shiba 《Earth, Moon, and Planets》1995,68(1-3):503-508

The radiant point can be decided by using assumption that a meteor's velocity is constant by only one photograph with rotation shutter or one TV camera. Trajectory and initial velocity can be decided by using additional assumption beginning with the height of a meteor. In this method, the radiant point can be computed accurately when trajectory length is long enough which can be regarded constant velocity and measurement's error is small.  相似文献   

A Perovskitic Lower Mantle Inferred from High-pressure, High-temperature Sound Velocity Data     

Motohiko Murakami  Yasuo Ohishi  Naohisa Hirao  Kei Hirose 《Journal of the Geological Society of India》2012,80(1):147

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Evaluation of slope stability by finite element method using observed displacement of landslide   总被引：1，自引：0，他引：1  

Yasuo Ishii  Keiichi Ota  Senro Kuraoka  Ryosuke Tsunaki 《Landslides》2012,9(3):335-348

To monitor land deformation in detail, we ran a large-scale field test in which an artificial landslide was induced by the application of a load to a natural slope. The measured landslide displacement was reproduced numerically through the use of finite element model analysis with a two-dimensional elasto-viscoplastic model. The analysis suggested that the strength of the sliding surface decreased as the landslide mass moved. We propose a simple method for estimating safety factors. The method involves back-calculation of shear strength parameters through reproduction of observed landslide displacements and calculating the ratio of driving force to resisting force acting on the sliding surface as modeled by joint elements. This ratio, the “stability index”, shows the same trend as safety factors calculated by a two-dimensional limit equilibrium method and a shear strength reduction method that use back-calculated shear strength parameters estimated from the limit equilibrium state. The results indicate that the stability index may be applicable to the assessment of slope stability.  相似文献   

Generalized Shifted-Factor Analysis Method for Multivariate Geo-Referenced Data     

William F. Christensen  Yasuo Amemiya 《Mathematical Geology》2001,33(7):801-824

Multivariate data with spatial dependencies arise in many areas of application, including geology, precision agriculture, and ecology. For analysis of such data, a methodology based on a generalized shifted-factor model is developed. The model incorporates potential lagged dependencies between factors and observed variables, representing asymmetric spatial dependencies observed in practice. Identification and estimation issues are discussed. A prediction procedure that exploits both the multivariate and spatial dependence in the data is proposed and illustrated.  相似文献   

Kinetics of nitrogen- or phosphorus-limited growth and effects of growth conditions on nutrient uptake inChattonella antiqua     

Yasuo Nakamura 《Journal of Oceanography》1985,41(6):381-387

Chattonella antiqua was grown in a nitrogen- or phosphorus-limited semicontinuous culture system. Using the cells in steady growth state, the relationship between growth rate and cell quota and effects of growth conditions on nitrate, ammonium and phosphate uptake were examined. Under nitrogen-limited conditions, growth rate as a function of nitrogen cell quota followed the empirical Droop equation and the uptake of nitrate and ammonium was not significantly affected by growth rate. Similarly, under phosphorus-limited conditions, the growth rate as a function of phosphorus cell quota also followed the Droop equation and phosphate uptake was not significantly affected by growth rate.Combining the results obtained in the present study with those from previous studies on nutrient uptake, half saturation constants for growth (K _g ) were calculated for nitrate, ammonium and phosphate. Comparisons ofK _g with nutrient concentrations in the Seto Inland Sea in summer, where red tides ofC. antiqua often occur, suggest that phosphate is one of the controlling factors for the population ofC. antiqua.  相似文献