Pressure-induced structural evolution of pyrite-type SiO<Subscript>2</Subscript>     

Yasuhiro Kuwayama  Kei Hirose  Nagayoshi Sata  Yasuo Ohishi 《Physics and Chemistry of Minerals》2011,38(8):591-597

The equation of state and pressure-induced structural evolution of pyrite-type SiO₂ have been investigated based on synchrotron X-ray diffraction measurements in a diamond-anvil cell. The Rietveld refinement revealed that the oxygen coordinate x of pyrite-type SiO₂ increases with increasing pressure. The SiO₆ coordination polyhedra of pyrite-type SiO₂ is less compressible than the unit cell, and the increase in x induces a rotation of the SiO₆ coordination polyhedra to fill the blank space in the unit cell. Thus, the volume reduction in pyrite-type SiO₂ is achieved mainly by the rotation of the SiO₆ polyhedra, rather than by the compression of the SiO₆ polyhedra. In addition, the increase in x with increasing pressure enhances a distortion of the coordination polyhedra of pyrite-type SiO₂, implying that pyrite-type SiO₂ is not likely to transform into a fluorite-type structure at higher pressures.  相似文献   

Sound velocities of Na0.4Mg0.6Al1.6Si0.4O4 NAL and CF phases to 73 GPa determined by Brillouin scattering method     

Lidong Dai  Yuki Kudo  Kei Hirose  Motohiko Murakami  Yuki Asahara  Haruka Ozawa  Yasuo Ohishi  Naohisa Hirao 《Physics and Chemistry of Minerals》2013,40(3):195-201

The sound velocities of two aluminum-rich phases in the lower mantle, hexagonal new Al-rich phase (NAL) and its corresponding high-pressure polymorph orthorhombic Ca-ferrite-type phase (CF), were determined with the Brillouin scattering method in a pressure range from 9 to 73 GPa at room temperature. Both NAL and CF samples have identical chemical composition of Na_0.4Mg_0.6Al_1.6Si_0.4O₄ (40 % NaAlSiO₄–60 % MgAl₂O₄). Infrared laser annealing in the diamond anvil cell was performed to minimize the stress state of the sample and obtain the high-quality Brillouin spectra. The results show shear modulus at zero pressure G ₀ = 121.960 ± 0.087 GPa and its pressure derivative G’ = 1.961 ± 0.009 for the NAL phase, and G ₀ = 129.653 ± 0.059 GPa and G’ = 2.340 ± 0.004 for the CF phase. The zero-pressure shear velocities of the NAL and CF phases are obtained to be 5.601 ± 0.005 km/sec and 5.741 ± 0.001 km/sec, respectively. We also found that shear velocity increases by 2.5 % upon phase transition from NAL to CF at around 40 GPa.  相似文献   

Characterizing atmospheric circulation signals in Greenland ice cores: insights from a weather regime approach     

Pablo Ortega  Didier Swingedouw  Valérie Masson-Delmotte  Camille Risi  Bo Vinther  Pascal Yiou  Robert Vautard  Kei Yoshimura 《Climate Dynamics》2014,43(9-10):2585-2605

Greenland ice cores offer seasonal to annual records of δ¹⁸O, a proxy for precipitation-weighted temperature, over the last few centuries to millennia. Here, we investigate the regional footprints of the North Atlantic weather regimes on Greenland isotope and climate variability, using a compilation of 22 different shallow ice-cores and the atmospheric pressure conditions from the twentieth century reanalysis (20CR). As a first step we have verified that the leading modes of winter and annual δ¹⁸O are well correlated with oceanic (Atlantic multidecadal oscillation) and atmospheric [North Atlantic oscillation (NAO)] indices respectively, and also marginally with external forcings, thus confirming earlier studies. The link between weather regimes and Greenland precipitation, precipitation-weighted temperature and δ¹⁸O is further explored by using an isotope simulation from the LMDZ-iso model, where the 3-dimensional wind fields are nudged to those of 20CR. In winter, the NAO+ and NAO? regimes in LMDZ-iso produce the largest isotopic changes over the entire Greenland region, with maximum anomalies in the South. Likewise, the Scandinavian blocking and the Atlantic ridge also show remarkable imprints on isotopic composition over the region. To assess the robustness and model dependency of our findings, a second isotope simulation from the isotopic model is also explored. The percentage of Greenland δ¹⁸O variance explained by the ensemble of weather regimes is increased by a factor near two in both LMDZ-iso and IsoGSM when compared to the contribution of the NAO index only. Similarly, weather regimes provide a net gain in the δ¹⁸O variance explained of similar magnitude for the whole set of ice core records. Greenland δ¹⁸O also appears to be locally affected by the low-frequency variations in the centres of action of the weather regimes, with clearer imprints in the LMDZ-iso simulation. This study opens the possibility for reconstructing past changes in the frequencies of occurrence of the weather regimes, which would rely on the sensitive regions identified here, and the use of additional proxies over the North Atlantic region.  相似文献   

Equilibrium configurations of strongly magnetized neutron stars with realistic equations of state     

Kenta Kiuchi  Kei Kotake 《Monthly notices of the Royal Astronomical Society》2008,385(3):1327-1347

We investigate equilibrium sequences of magnetized rotating stars with four kinds of realistic equations of state (EOSs) of SLy, FPS, Shen and LS, employing the Tomimura–Eriguchi scheme to construct the equilibrium configurations. We study the basic physical properties of the sequences in the framework of Newtonian gravity. In addition, we take a new step by taking into account a general relativistic effect to the magnetized rotating configurations. With these computations, we find that the properties of the Newtonian magnetized stars, e.g. structure of magnetic field, highly depends on the EOSs. The toroidal magnetic fields concentrate rather near the surface for Shen and LS EOSs than those for SLy and FPS EOSs. The poloidal fields are also affected by the toroidal configurations. Paying attention to the stiffness of the EOSs, we analyse this tendency in detail. In the general relativistic stars, we find that the difference due to the EOSs becomes small because all the employed EOSs become sufficiently stiff for the large maximum density, typically greater than  10¹⁵ g cm⁻³  . The maximum baryon mass of the magnetized stars with axis ratio   q ∼ 0.7  increases about up to 20 per cent for that of spherical stars. We furthermore compute equilibrium sequences at finite temperature, which should serve as an initial condition for the hydrodynamic study of newly born magnetars. Our results suggest that we may obtain information about the EOSs from the observation of the masses of magnetars.  相似文献   

Water vapor δD dynamics over China derived from SCIAMACHY satellite measurements     

LIU ZhongFang  Kei YOSHIMURA  Casey D. KENNEDY  WANG XinHui & PANG ShuoGuang 《中国科学:地球科学(英文版)》2014,57(4):813-823

This study investigates water vapor isotopic patterns and controls over China using high-quality water vapor δD data retrieved from the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography(SCIAMACHY) observations.The results show that water vapor δD values on both annual and seasonal time-scales broadly exhibit a continental effect,with values largely decreasing northwestward from coastal lowlands to high-elevation mountainous regions.However,region-specific analysis reveals spatially distinct patterns of water vapor δD between seasons.In the monsoon domain(e.g.,China south of 35°N),depletion in D in the summer and fall seasons is closely tied to monsoon moisture sources(the Indian and Pacific oceans) and subsequent amount effect,but higher δD values in winter and spring are a result of isotopically-enriched continental-sourced moisture proceeded by less rainout.In contrast,farther inland in China(non-monsoon domain),moisture is derived overwhelmingly from the dry continental air masses and local evaporation,and δD values are largely controlled by the temperature effect,exhibiting a seasonality with isotopically enriched summer and depleted winter/spring.The observation that the spatial pattern of water vapor δD is the opposite to that of precipitation δD in the summer season also suggests that partial evaporation of falling raindrops is a key driver of water vapor isotope in the non-monsoon domain.This study highlights the importance of non-Rayleigh factors in governing water vapor isotope,and provides constraints on precipitation isotope interpretation and modern isotope hydrological processes over China.  相似文献   

Uptake and biological effects of synthetic glucocorticoids in common carp (Cyprinus carpio)     

Kei Nakayama  Yoshiyuki Inoue  Naomi Ikeda  Naoki Hashizume  Hidekazu Murakami  Takeshi Ishibashi  Hirofumi Ikeda  Tomohiko Isobe  Shin-Ichi Kitamura  Go Suzuki 《Marine pollution bulletin》2014

Uptake and biological effects of synthetic glucocorticoids (GCs) were analyzed using common carp (Cyprinus carpio). Fish were exposed to clobetasol propionate (CP) or clobetasone butyrate (CB) individually or in mixture at 1 μg L⁻¹ for 21 days. Bioconcentration factor (BCF) of CB was calculated as 100, and BCF of CP was less than 16. No effects were found in fish erythrocyte and leukocyte numbers and serum glucose levels after exposure to the selected GCs. On the other hand, serum concentrations of free amino acids significantly increased in GC-exposed groups. Thus, exposures to synthetic GCs at relatively low concentrations seemed to cause enhancement of protein degradation and subsequent increase of serum free amino acids without a corresponding increase in serum glucose levels, an effect which might be related to partial induction of gluconeogenesis by GC.  相似文献   

Preliminary results of the Japan-Taiwan joint survey on combining ocean radar data in the Kuroshio upstream region     

Kaoru Ichikawa  Wen Chang Yang  Akihiko Morimoto  Yutaka Yoshikawa  Shigeo Sugitani  Wen-Shan Chiang  Jian-Wu Lai  En Yu Liang  Cho-Teng Liu  Chang-Wei Lee  Kei Yufu  Moeto Kyushima  Satoshi Fujii  Tomoharu Senju  Yoshihiko Ide 《Ocean Science Journal》2013,48(1):141-148

  相似文献   

Oxygen Isotopic Study on the Date‐Nagai Skarn‐Type Tungsten Deposit,Northeastern Japan     

Luvsannyam Oyunjargal  Kei Matsukura  Ken‐ichiro Hayashi 《Resource Geology》2019,69(4):448-459

The skarn‐type tungsten deposit of the Date‐Nagai mine is genetically related to the granodiorite batholith of the Iidateyama body. Skarn is developed along the contact between pelitic hornfels and marble that remains as a small roof pendant body directly above the granodiorite batholith. Zonal arrangement of minerals is observed in skarn. The zonation consists of wollastonite, garnet, garnet‐epidote, and vesuvianite‐garnet zones, from marble to hornfels. Sheelite is included in garnet, garnet‐epidote, and vesuvianite‐garnet zones. The oxygen isotope values of skarn minerals were obtained as δ¹⁸O = 4.2–7.7‰ for garnet, 5.9–6.9‰ for vesuvianite, ?0.3–3.4‰ for scheelite, 6.0–10.9‰ for quartz, and 8.2‰ for muscovite. The temperature of skarn‐formation was calculated from oxygen isotopic values of scheelite‐quartz pairs to be 288°C. Calculated oxygen isotope values of fluid responsible for skarn minerals were 6.1–9.5‰ for garnet, 1.2–4.8‰ for scheelite, ?1.3‐3.6‰ for quartz, and 4.5‰ for muscovite. Garnet precipitated from the fluids of different δ¹⁸O values from scheelite, quartz, and muscovite. These δ¹⁸O values suggest that the origin of fluid responsible for garnet was magmatic water, while evidence for the presence of a meteoric component in the fluids responsible for middle to later stages minerals was confirmed.  相似文献   

Subsolidus and melting phase relations of basaltic composition in the uppermostlower mantle     

Kei Hirose  Yingwei Fei 《Geochimica et cosmochimica acta》2002,66(12):2099-2108

The phase relations and the element partitioning in a mid-oceanic ridge basalt composition were determined for both above-solidus and subsolidus conditions at 22 to 27.5 GPa by means of a multianvil apparatus. The mineral assemblage at the solidus changes remarkably with pressure; majorite and stishovite at 22 GPa, joined by Ca-perovskite at 23 GPa, further joined by CaAl₄Si₂O₁₁-rich CAS phase at 25.5 GPa, and Mg-perovskite, stishovite, Ca-perovskite, CF phase (approximately on the join NaAlSiO₄-MgAl₂O₄), and NAL phase ([Na,K,Ca]₁[Mg,Fe²⁺]₂[Al,Fe³⁺,Si]_5.5-6.0O₁₂) above 27 GPa. The liquidus phase is Ca-perovskite, and stishovite, a CAS phase, a NAL phase, Mg-perovskite, and a CF phase appear with decreasing temperature at 27.5 GPa. Partial melt at 27 to 27.5 GPa is significantly depleted in SiO₂ and CaO and enriched in FeO and MgO compared with those formed at lower pressures, reflecting the narrow stability of (Fe,Mg)-rich phases (majorite or Mg-perovskite) above solidus temperature. The basaltic composition has a lower melting temperature than the peridotitic composition at high pressures except at 13 to 18 GPa (Yasuda et al., 1994) and therefore can preferentially melt in the Earth’s interior. Recycled basaltic crusts were possibly included in hot Archean plumes, and they might have melted in the uppermost lower mantle. In this case, Ca-perovskite plays a dominant role in the trace element partitioning between melt and solid. This contrasts remarkably with the case of partial melting of a peridotitic composition in which magnesiowüstite is the liquidus phase at this depth.  相似文献   

滇01井水位动态与地震关系的分析研究     

万登堡  夏菲  张爱玲 《地震研究》1988,(6)

滇01井近年来多次住滇东断裂系上地震前有较好的反映,为了揭示该井水位映震关系,作者对观测以来6年的资料开展了单井区域地质、水文地质条件、水位正常动态、异常动态特征的分忻研究,并利用多种数学方法判定异常,总结了11次震例,提出了该井异常、预报指标,还对映震能力作了分析。  相似文献