Survivability of presolar oxygen isotopic signature of amorphous silicate dust in the protosolar disk     

Daiki Yamamoto  Shogo Tachibana  Noriyuki Kawasaki  Hisayoshi Yurimoto 《Meteoritics & planetary science》2020,55(6):1281-1292

Oxygen isotope exchange experiments between tens of nanometer‐sized amorphous enstatite grains and water vapor were carried out under a condition of protoplanetary disk‐like low water vapor pressure in order to investigate the survivability of distinct oxygen isotope signatures of presolar silicate grains in the protosolar disk. Oxygen isotope exchange between amorphous enstatite and water vapor proceeded at 923–1003 K and 0.3 Pa of water vapor through diffusive isotope exchange in the amorphous structure. The rate of diffusive isotope exchange is given by D (m² s^–1) = (5.0 ± 0.2) × 10^–21 exp[–161.3 ± 1.7 (kJ mol^–1) R^–1 (1/T–1/1200)]. The activation energy for the diffusive isotope exchange for amorphous enstatite is the same as that for amorphous forsterite within the analytical uncertainties, but the isotope exchange rate is ~30 times slower in amorphous enstatite because of the difference in frequency factor of the reaction. The reaction kinetics indicates that 0.1–1 μm‐sized presolar amorphous silicate dust with enstatite and forsterite compositions would avoid oxygen isotope exchange with protosolar disk water vapor only if they were kept at temperatures below ~500–650 K within the lifetime of the disk gas.  相似文献   

Solute transfer during consolidation based on a solid‐fluid‐solute coupling model          下载免费PDF全文

Shun Nomura  Katsuyuki Kawai  Shinya Tachibana  Atsushi Iizuka 《国际地质力学数值与分析法杂志》2018,42(10):1172-1196

The migration of contaminant through soil is usually modeled using the advection‐dispersion equation and assumes that the porous media is stationary without introducing a constitutive equation to represent soil structure. Consequently, time‐dependent deformation induced by soil consolidation or physical remediation is not considered, despite the need to consider these variables during planning for the remediation of contaminated ground, the prediction of contaminated groundwater movement, and the design of engineered landfills. This study focuses on the numerical modeling of solute transfer during consolidation as a first step to resolve some of these issues. We combine a coupling theory‐based mass conservation law for soil‐fluid‐solute phases with finite element modeling to simulate solute transfer during deformation and groundwater convection. We also assessed the sensitivity of solute transfer to the initial boundary conditions. The modeling shows the migration of solute toward the ground surface as a result of ground settlement and the dissipation of excess pore water pressure. The form of solute transport is dependent on the ground conditions, including factors such as the loading schedule, contamination depth, and water content. The results indicate that an understanding of the interaction between coupling phases is essential in predicting solute transfer in ground deformation and could provide an appropriate approach to ground management for soil remediation.  相似文献   

Accumulation of trace elements in harp seals (Phoca groenlandica) from Pangnirtung in the Baffin Island, Canada     

Agusa T  Nomura K  Kunito T  Anan Y  Iwata H  Tanabe S 《Marine pollution bulletin》2011,63(5-12):489-499

Nineteen trace elements were determined in liver, muscle, kidney, gonads, and hair of 18 harp seals (Phoca groenlandica) from Pangnirtung in the Baffin Island, Canada. Concentrations of V, Mn, Fe, Cu, Mo, Ag, and Hg in the liver, Co, Cd, and Tl in the kidney, and Ba and Pb in the hair were significantly higher than those in other tissues. Significant positive correlations between Hg concentrations in the hair, and liver, kidney and testis imply usefulness of the hair sample for non-destructive monitoring of Hg in the harp seals. It is suggested that whereas Hg preferentially accumulates in the liver, the accumulation in other tissues is induced at higher hepatic Hg levels. In contrast, Se may not be accumulated in other tissues compared with the liver even at higher hepatic Hg levels because of the presence of excess Se for Hg detoxification in other tissues.  相似文献   

Spatio-temporal deposition profile of an experimentally produced turbidity current with a continuous suspension supply     

Shun Nomura  Giovanni De Cesare  Mikito Furuichi  Yasushi Takeda  Hide Sakaguchi 《国际泥沙研究》2022,37(3):299-306

A turbidity current is a turbulent, particle-laden gravity current that is driven by density differences resulting from the presence of suspended sediment particles. The current travels downslope, bearing a large amount of sediment over a great distance, and forms fluvial and submarine bedforms. Knowledge of the spatio-temporal deposition profile of turbidity-deposited sediment is important for a better understanding of sediment transport by turbidity currents. In the current study, the depositi...  相似文献   

Long-period waves in the vicinity of Onagawa Bay (III)     

Isamu Aida  Morio Koyama  Daiki Date  Shiko Sakashita 《Journal of Oceanography》1975,31(2):61-70

Characteristics of seiches in Onagawa Bay are investigated on the basis of observations at the bay head, Konorihama, from May 1972 to May 1973 and at the outside of the bay, Enoshima during the same period. At Konorihama seiches with the double amplitude of 7 to 11 cm occurred most frequently (63 percent of the total samples) and the maximum reached 31 cm. Short-time spectral analyses indicate that the periods of the spectral peaks shift considerably with the lapse of time, and that the location of the nodal line near the bay mouth moves offshore and inshore of Enoshima. The cause of these phenomena seems to be attributed to the change of incident angle of waves coming from the open sea to excite seiches. Amplitudes of the fundamental and of the lateral modes of seiches increase or decrease alternately with time, suggesting the energy transfer between these modes. Bay oscillations induced by remarkable atmospheric pressure-waves were observed. However, the amplitudes of the oscillations were within a few centimeters and dissipated in a few hours.  相似文献   

Boron isotopic composition of fumarolic condensates from some volcanoes in Japanese island arcs     

Masao Nomura  Tadao Kanzaki  Takejiro Ozawa  Makoto Okamoto  Hidetake Kakihana 《Geochimica et cosmochimica acta》1982,46(11):2403-2406

Boron samples from 40 fumarolic condensates from volcanoes in the Ryukyu arc (Satsuma Iwo-jima and Shiratori Iwo-yama) and the North-east Japan arc (Usu-shinzan, Showa-shinzan, Esan and Issaikyo-yama) all have ${}^{11}\text{B}{}^{10}\text{B}$ ratios close to 4.07. Higher values, from 4.09 to 4.13, were only observed in condensates from volcanoes in the southernmost end of the North-east Japan arc (Nasu-dake), the northern part of the Izu-Bonin arc (Hakone), and the North Mariana arc (Ogasawara Iwo-jima). These higher values suggest geological interaction of the magmas with sea-water enriched in ¹¹B.  相似文献   

Iron sulfides in the sediment cores from the Sea of Japan and their geophysical implications     

Kazuo KobayashiMasafumi Nomura 《Earth and Planetary Science Letters》1972

Ferromagnetic iron sulfides have been identified by thermomagnetic, X-ray crystallographic and reflection-microscopic analyses of deep-sea sediment cores taken from the Sea of Japan. Occurrence of iron sulfides at certain depths of the cores seems to indicate that the paleoenvironment of the deep basin in the Sea of Japan was very stagnant, probably due to the enclosure by lands caused by the lowering of the sea level during the glacial periods. Oxidation of sulfides as well as sulfuration of oxides in the sedimentary layer may account for the abnormally high heat flow in the deep basin.  相似文献   

Gender differences in agricultural productivity: evidence from maize farm households in southern Ethiopia     

Gebre  Girma Gezimu  Isoda  Hiroshi  Rahut  Dil Bahadur  Amekawa  Yuichiro  Nomura  Hisako 《GeoJournal》2021,86(2):843-864

GeoJournal - This study examines the impact of gender differences on maize productivity in Dawuro Zone, southern Ethiopia. Our study addressed the limitations of the previous studies in two ways....  相似文献   

Relation Between Coronal Hole Areas and Solar Wind Speeds Derived from Interplanetary Scintillation Measurements     

Munetoshi Tokumaru  Daiki Satonaka  Ken’ichi Fujiki  Keiji Hayashi  Kazuyuki Hakamada 《Solar physics》2017,292(3):41

We investigate the relation between coronal hole (CH) areas and solar wind speeds during 1995?–?2011 using the potential field (PF) model analysis of magnetograph observations and interplanetary scintillation (IPS) observations by the Institute for Space-Earth Environmental Research (formerly Solar-Terrestrial Environment Laboratory) of Nagoya University. We obtained a significant positive correlation between the CH areas (\(A\)) derived from the PF model calculations and solar wind speeds (\(V\)) derived from the IPS observations. The correlation coefficients between them are usually high, but they drop significantly in solar maxima. The slopes of the \(A\)?–?\(V\) relation are roughly constant except for the period around solar maximum, when flatter or steeper slopes are observed. The excursion of the correlation coefficients and slopes at solar maxima is ascribed partly to the effect of rapid structural changes in the coronal magnetic field and solar wind, and partly to the predominance of small CHs. It is also demonstrated that \(V\) is inversely related to the flux expansion factor (\(f\)) and that \(f\) is closely related to \(A^{-1/2}\); hence, \(V \propto A^{1/2}\). A better correlation coefficient is obtained from the \(A^{1/2}\)?–?\(V\) relation, and this fact is useful for improving space weather predictions. We compare the CH areas derived from the PF model calculations with He i 1083 nm observations and show that the PF model calculations provide reliable estimates of the CH area, particularly for large \(A\).  相似文献   

Effect of human activity on Lake Saroma (Japan) during the past 150 years: Evidence by variation of diatom assemblages     

Kota Katsuki  Koji Seto  Ritsuo Nomura  Kimihiko Maekawa  Boo-Keun Khim 《Estuarine, Coastal and Shelf Science》2009

Diatom assemblages of the surface and in core sediment samples from Lake Saroma (Japan) were examined for the purpose of evaluating anthropogenic effect on the coastal environmental changes. Before the first inlet excavation, the lake's water quality and ecology were controlled by water exchange with the Okhotsk Sea as well as lake-level variation. However, large-scale ecological modification occurred, mainly due to artificial excavation and shellfish industrial farms. A distinct record of the succession of the dominant diatom taxa was preserved in core sediments. Low-oxygen water was prevalent in the lake in 1929, before the first inlet excavation. Immediately after the first inlet excavation, the low-oxygen water in the western basin of the lake began to disappear, in a trend that became increasing transparent, which has been attributed to an increasing rate of water exchange. However, the lacustrine environment of bottom sediments resumes deterioration 20 years after since the first artificial excavation: the resultant deposition of river-mouth materials into the deep basin caused eutrophication and environmental disturbance of the lake bottom. At the same time, the eutrophication of surface water became intensified with the onset of intense scallop culturing beginning in 1966. Increasing organic loads deposited onto the bottom layer in the form of excreta from the scallop nursery led to more oxygen deficiency and the elution of nitrogen and phosphorus from the sediment, which again brought about eutrophication of the surface layer. Such environmental change was reflected in a decrease of benthic diatom taxa and an increase of planktonic taxa, trends which have continued until today. Particularly, the numbers of diatom assemblage have been decreasing all over the lake during the last 10 years, which suggests that Lake Saroma's present-day deterioration and eutrophication will continue or become even worse.  相似文献