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11.
Bacterial degradation of the hydrocarbons of lubricating oils was investigated by mass spectrometric analysis which gives both total amount and the composition of hydrocarbon types of residual oil. An unused lubricating oil, which mainly consisted of hydrocarbon types with only a small percentage ofn-alkanes, was degraded by marineBacillus sp. andPseudomonas sp. with 55 % and 25 % decreases in 10 days, respectively. Susceptibility of respective hydrocarbon types to biodegradation was in the following order: alkanes > non-condensed cycloalkanes, mono-aromatics > condensed cycloalkanes. A used lubricating oil of different brand showed a larger decrease than the unused oil. Both species of bacteria degraded large portions of alkane fraction of Arabian light crude oil.  相似文献   
12.
Ablation processes of snow under a thin dust cover are complicated compared with those under a thick cover, mainly owing to the effects of aggregation (redistribution) of dust particles on the conditions of surface melting. Aggregation of dust particles causes the snow surface to brighten after the initial dust configuration, thus affecting the relationship between initial dust concentration and surface albedo. In order to estimate snow ablation rate under a thin dust cover, we used a composite energy balance model in which the surface albedo is taken as a measured input variable. The estimated results of snow ablation agreed reasonably well with the observation, considering the measurement errors inherited in the snow depressions. Comparison of the two cases, that is, one considering the aggregation of dust particles (observation: albedo variable) and the other without aggregation (assumption: albedo constant), showed that the ablation rates were noticeably lower on the former case. This suggests that the aggregation of dust particles induces a reduction of snow ablation. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
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— Accurate simulation of seismic ground motion for three-dimensionally complex topography and structures is one of the most important goals of strong motion seismology. The finite-element method (FEM) is well suited for this kind of simulation, since traction-free conditions are already included in the formulation, and the Courant condition is less strict than for the finite-difference method (FDM). However, the FEM usually requires both large memory and computation time. These limitations can be overcome by using a mesh consisting of voxels (rectangular prisms) with isotropy built into the explicit formulation of the dynamic matrix equation. Since operators in the voxel FEM are the combinations of ordinary FDM operators and additional terms, the method keeps accuracy of the same order as FDM and the terms relax the Courant condition. The voxel FEM requires a similar amount of memory and only takes 1.2~1.4 times longer computation time. The voxel mesh can be generated considerably faster than the popular tetrahedral mesh. Both ground motions and static displacements due to a point or line source can be calculated using the voxel FEM approach. Comparisons with the reflectivity method and theoretical solutions demonstrate the successful implementation of the method, which is then applied to more complex problems.  相似文献   
15.
Vertical profiles of total sulfur and organic carbon have been measured in two deep-sea piston cores from the southwestern Japan Sea where sulfate reduction is proceeding within the sediments. The content of total sulfur, most of which is present as pyrite, increases gradually with increasing depth, showing several peaks. The amount of diagenetically deposited sulfide-sulfur is estimated using a steady-state model that considers vertical change in the diffusion coefficient. It is suggested that two-thirds to three-fourths of the observed total sulfur content has been deposited diagenetically.  相似文献   
16.
Spinifex-like textured metaperidotites from the Higo Metamorphic Rocks (HMR), west-central Kyushu, Japan, may be formed by high-pressure dehydration of antigorite, and may indicate deep subduction of serpentinite reaching a pressure–temperature condition of 1.6 GPa and 740–750 °C. Three rock types have been identified based on mineral assemblage and rock texture: Type I (L) consisting of medium-grained (1–5 cm long) olivine + enstatite + chromite ±tremolite with secondary talc and anthophyllite that occurs in low-grade metamorphic rocks of the biotite zone, Type I (H) of coarse-grained (up to 10 cm long) olivine + enstatite (with clinoenstatite lamella) + chromite ±tremolite with secondary talc that occurs in high-grade metamorphic rocks of the garnet-cordierite zone, and Type II composed of Al-spinel + chlorite + olivine + apatite + ilmenite with minor sodic gedrite in the garnet-cordierite zone together with Type I (H). Olivines in all rock types are mostly serpentinized during exhumation. The chromite-olivine thermometer gives 560–690 °C for Type I (L) rocks, and the spinel-olivine thermometer gives 610–740 °C for Type II rocks. The peak metamorphic pressure will be higher than 1.6 GPa based on the location of the experimentally determined invariant point (P = 1.6 GPa and T = 670 °C) of antigorite + forsterite + enstatite + talc + H2O. This estimate is consistent with the occurrence of chlorite in Type II rocks, which is stable up to 890 °C at 2.0 GPa. The spinifex-like textured metaperidotites occur as small bodies in the low P/T type gneisses, implying tectonic juxtaposition of them probably during exhumation of the HMR. Recent findings of medium pressure (0.9–1.2 GPa) granulites and gneisses from the HMR may indicate that the HMR has a deep root into the wedge mantle from which the spinifex-like textured metaperidotites have derived.  相似文献   
17.
We have elucidated the seasonal and spatial variation in the potential denitrifying activity in estuarine and coastal lagoonal sediments in Lakes Shinji and Nakaumi, Japan. The denitrifying activity increased from summer through autumn and was positively correlated with the temperature of the overlying water at all sites except one, where the bottom was always more reductive than at the other sites and there was no NO3 as a substrate for denitrification from spring to autumn. Moreover, the relationship between the denitrifying activity and the distance from the sea showed different trends in estuarine and lagoonal sediments. These spatial differences indicate that different factors regulate the denitrification in estuarine and lagoonal sediments. Denitrifying activity in estuarine sediment was regulated by the discharge of freshwater containing NO3 or organic matter, while in the lagoonal sediments the occurrence of nitrification via the intrusion of oxic seawater into the reductive sediment appears to be a key requirement for the process of denitrification. Therefore, the denitrifying activity in the lagoonal sediment appears to be greater near the sea. Water intrusion is one of the key factors controlling denitrification in coastal marine ecosystems by affecting the supply of substrate available for denitrification.  相似文献   
18.
With full-depth LADCP velocity data collected in a wide area southeast of Kyushu, Japan, large velocity currents, occasionally exceeding 15 cm s?1, were observed in a thick, 500–1,500 m, near-homogeneous density layer below approximately 3,000 m depth around the steep topographies. The currents were found not to flow along the topographic contours, and to be strongly ageostrophic. The directions of the bottom-layer currents are rather related with phase of the semi-diurnal tides, suggesting deeply intruded internal tides generated at the steep topographies.  相似文献   
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In recent earthquakes in developing countries, severe damage was observed on reinforced concrete buildings. This study focuses on exterior beam-column joints with substandard beam rebar anchorage and seismic strengthening by installing wing walls. First, a series of experiments was conducted to investigate the seismic behavior of exterior joints with substandard beam rebar anchorage representing typical Bangladeshi buildings. Two 0.7-scaled exterior joint specimens were tested, and these specimens showed beam rebar anchorage failure and/or joint shear failure. Prior to strengthening of the joint, a series of pullout tests was conducted on postinstalled bonded anchors in low-strength concrete for strengthening design. Then, an experiment was performed to apply the strengthening method by wing walls to one of the exterior joint specimens to improve the integrity, and this method was intended to prevent the failure of beam rebar anchorage. The strengthening method is proposed to extend the development length of beam longitudinal bars by considering the embedment length along the wing walls. The test results verified the effectiveness and applicability of the proposed strengthening method to upgrade exterior RC beam-column joints with deficient beam rebar anchorage.  相似文献   
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