Variations in the redox state of As and Fe measured by X-ray absorption spectroscopy in aquifers of Bangladesh and their effect on As adsorption     

Takaaki Itai  Yoshio Takahashi  Ashraf Ali Seddique  Teruyuki Maruoka  Muneki Mitamura 《Applied Geochemistry》2010

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Latitudinal and downcore (0–750 ka) changes in n-alkane chain lengths in the eastern equatorial Pacific     

Keiji Horikawa  Masafumi Murayama  Masao Minagawa  Yoshihisa Kato  Takuya Sagawa 《Quaternary Research》2010,73(3):573-582

The n-alkane C₃₁/(C₂₉ + C₃₁) ratios from surface sediments in the eastern equatorial Pacific (EEP) exhibit higher values to the north and lower values to the south across the southern edge (2–4°N) of the Intertropical Convergence Zone (ITCZ). Since plants tend to synthesize longer chain length n-alkanes in response to elevated temperature and/or aridity, the higher C₃₁/(C₂₉ + C₃₁) ratios at northern sites suggest a higher contribution of vegetation under hot and/or dry conditions. This is consistent with the observation that northern sites receive higher levels of plant waxes transported by northeasterly trade winds from northern South America, where hot and dry conditions prevail. Furthermore, from a sediment core covering the past 750 ka (core HY04; 4°N, 95°W) we found that C₃₁/(C₂₉ + C₃₁) ratios exhibit a long-term decrease from MIS (marine oxygen isotope stage) 17 to 13. During this period, the zonal SST (sea-surface temperature) gradient in the equatorial Pacific increased, suggesting an increase in Walker circulation. Such intensified Walker circulation may have enhanced moisture advection from the equatorial Atlantic warm pool to the adjacent northern South America, causing arid regions in northern South America to contract, which may explain long-term decrease in n-alkane chain lengths.  相似文献   

Accreting white dwarfs as supersoft X‐ray sources     

M. Kato 《Astronomische Nachrichten》2010,331(2):140-145

I review various phenomena associated with mass‐accreting white dwarfs (WDs) in the view of supersoft X‐ray sources. When the mass‐accretion rate is low (Ṁ_acc < a few × 10^–7 M⊙yr^–1), hydrogen nuclear burning is unstable and nova outbursts occur. A nova is a transient supersoft X‐ray source (SSS) in its later phase which timescale depends strongly on the WD mass. The X‐ray turn on/off time is a good indicator of the WD mass. At an intermediate mass‐accretion rate an accreting WD becomes a persistent SSS with steady hydrogen burning. For a higher mass‐accretion rate, the WD undergoes “accretion wind evolution” in which the WD accretes matter from the equatorial plane and loses mass by optically thick winds from the other directions. Two SSS, namely RX J0513‐6951 and V Sge, are corresponding objects to this accretion wind evolution. We can specify mass increasing WDs from light‐curve analysis based on the optically thick wind theory using multiwavelength observational data including optical, IR, and supersoft X‐rays. Mass estimates of individual objects give important information for the binary evolution scenario of type Ia supernovae (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Kalman filter finite element method applied to dynamic ground motion     

Yusuke Kato  Mutsuto Kawahara  Naoto Koizumi 《国际地质力学数值与分析法杂志》2009,33(9):1135-1151

The purpose of this paper is to investigate the estimation of dynamic elastic behavior of the ground using the Kalman filter finite element method. In the present paper, as the state equation, the balance of stress equation, the strain–displacement equation and the stress–strain equation are used. For temporal discretization, the Newmark ¼ method is employed, and for the spatial discretization the Galerkin method is applied. The Kalman filter finite element method is a combination of the Kalman filter and the finite element method. The present method is adaptable to estimations not only in time but also in space, as we have confirmed by its application to the Futatsuishi quarry site. The input data are the measured velocity, acceleration, etc., which may include mechanical noise. It has been shown in numerical studies that the estimated velocity, acceleration, etc., at any other spatial and temporal point can be obtained by removing the noise included in the observation. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

The　Early　Summer　Seasonal　Change　of　Large－scale　Circulation　over　East　Asia　and　Its　Relation　to　Change　of　The　Frontal　Features　and　Frontal　Rainfall　Environment　During　1991　Summer   总被引：5，自引：0，他引：5  

Gong-Wang Si  Kuranoshin Kato  Takao Takeda 《大气科学进展》1995,12(2):151-176

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Crustal movements in the tohoku district, Japan, during the period 1900–1975, and their tectonic implications     

Teruyuki Kato 《Tectonophysics》1979,60(3-4):141-167

Vertical crustal movements in the Tohoku district in the past 75 years are discussed with reference to their tectonic implications.

For this purpose, the author first compiled a map of accumulated vertical movement in the past 75 years, by making proper correction for closure. In addition, a new presentation technique utilizing a time-space domain representation of elevation changes is applied to the data. These contour maps provide an informative summary of the vertical crustal movement history in this district. From them, we see that the northeastern part of the district has subsided continuously and aseismically, with an area of significant subsidence inland at a distance about 300 km or more from the trench axis.

In order to explain the mechanism of the remarkable extension of the subsiding area, the finite element method is applied to model the elastic strain field in the district. It is shown that a simple model of uniform dragging at the interface of a sinking slab does not provide a good interpretation of the inland distribution of subsidence. A modification of the conventional model is proposed which hypothesizes vertical movement of the subducting lithospheric slab under the Tohoku district.  相似文献   

The Dependence of Constitutive Properties on Temperature and Effective Normal Stress in Seismogenic Environments     

Aitaro Kato  Shingo Yoshida  Mitiyasu Ohnaka  Hiromine Mochizuki 《Pure and Applied Geophysics》2004,161(9-10):1895-1913

— We have evaluated how the parameters prescribing the slip-dependent constitutive law are affected by temperature and effective normal stress, by conducting the triaxial fracture experiments on Tsukuba-granite samples in seismogenic environments, which correspond to a depth range to 15 km. The normalized critical slip displacement D _c almost remains constant below 300^oC (insensitive to both temperature and effective normal stress σ _n ^eff); D _c increases with increasing temperature above 300 °C, and the rate of D _c increase with temperature tends to be largest at higher σ _n ^eff. The breakdown stress drop Δτ _b for the granite at constant σ _n ^eff is roughly 80 MPa below 300 °C, and does not depend on σ _n ^eff. Above 300 °C, Δτ _b decreases gradually with increasing temperature, and the rate of Δτ _b reduction with temperature increases at higher σ _n ^eff. The peak shear strength τ _p increases nearly linearly with increasing σ _n ^eff below 300 °C. However, τ _p becomes lower above 300 °C, deviating from the linear relation extrapolated from below 300 °C. This is consistent with the onset of crystal plastic deformation mechanisms of Tsukuba granite.  相似文献   

Examining the aerosol indirect effect over China using an SO₂ emission inventory     

Kazuaki Kawamoto  Tadahiro Hayasaka  Teruyuki Nakajima  David Streets  Jung-Hun Woo 《Atmospheric Research》2004,72(1-4):353

The relationship between SO₂ emissions and the effective particle radius of low-level water clouds (r_e) over China was investigated to determine anthropogenic effects on clouds. Sulfur dioxide emission values were obtained from a statistical inventory, and r_e origins were retrieved by satellite remote sensing on a 0.5° grid. Comparisons between annual mean SO₂ emissions and r_e showed generally decreasing r_e values, explained by the Twomey effect. The existence of the Twomey effect is supported by comparisons with simulated aerosol optical depths. Results further suggest that clouds over land show sensitivity to the Twomey effect as well as clouds over the ocean.  相似文献   

Isotopic composition of carbon in diamonds of diamondites: record of mass fractionation in the upper mantle     

Teruyuki Maruoka  Gero Kurat  Christian Koeberl 《Geochimica et cosmochimica acta》2004,68(7):1635-1644

Carbon isotope data have been obtained for diamonds in diamondites (framesites, polycrystalline diamond) of unknown origin (presumably from southern Africa), which contain minor amounts of garnet (plus rare clinopyroxene). The carbon isotope abundance ratios show wide inter- and intra-sample ranges. The δ¹³C variations of diamonds from diamondites with “peridotitic” or “eclogitic” garnets are indistinguishable from each other, with a range from −3.2 to −27.9‰, and a peak around −18‰, indicating a depletion in ¹³C relative to most silicate-bearing single crystal diamonds. This ¹³C depletion could have been produced by mass fractionation of C from an isotopically homogeneous mantle source in a C-O-H fluid system. Fluids traveling between regions of varying redox conditions in the mantle could have provided the necessary vehicle. The variations of δ¹³C can be explained by different degrees of oxidation during the fluid/melt ascent.  相似文献   

Fault system of the 2004 Mid Niigata Prefecture Earthquake and its aftershocks     

Naoshi Hirata  Hiroshi Sato  Shin’ichi Sakai  Aitaro Kato  Eiji Kurashimo 《Landslides》2005,2(2):153-157

Data recorded by a seismic network deployed the day after the 2004 Mid Niigata Prefecture Earthquake (M6.8) in central Japan are used to determine the major source faults responsible for the mainshock and major aftershocks. Using this high-resolution seismic data, three major source faults are identified: two parallel faults dipping steeply to the west located 5 km apart, and the other dipping eastward and oriented perpendicular to the west-dipping faults. The analysis also reveals that the lateral variation in seismic velocity observed at the surface extends to a depth of 15 km, encompassing the source area of the mainshock. This strong heterogeneity of the crust, related to the complex geological and tectonic evolution of the area, is considered to be responsible for the prominent aftershock activity following the 2004 Niigata event.  相似文献