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排序方式: 共有159条查询结果,搜索用时 31 毫秒
61.
Journal of Material Cycles and Waste Management - Carbon-fiber-reinforced plastics (CFRPs) are used as structural materials in the aircraft and automotive industries owing to their lightweight and...  相似文献   
62.
To evaluate the quantities of 137Cs from past nuclear tests being transported to and deposited in Japan by naturally-occurring phenomena, the authors developed long-range transport models for 137Cs considering Asian dust. The simulation using these models backed the observed recent increase of 137Cs deposition along the coast of the Sea of Japan in early spring. For the sake of public safety, it is vital to ascertain whether an increase of radioactive deposition is caused by natural phenomena or a nuclear accident. The observations in recent years have suggested that dust and soil containing 137Cs is transported from the regions around Inner Mongolia to Japan by the wind. In this paper, using observation data from the early spring of 2002 and 2006, the authors have found good agreement between the simulations and the measurements. The simulations reproduced the entrainment of 137Cs and subsequent transport to Japan caused by strong winds associated with low pressure areas around the Inner Mongolian grasslands. The most likely cause of high-level 137Cs deposition over northern Japan during March 2002 was 137Cs associated with particles transported at low-altitude (1 km) and subjected to precipitation on the 22nd to 24th.  相似文献   
63.
To analyze the effect of polychlorinated biphenyl (PCB) 118 on fish bone metabolism, we examined osteoclastic and osteoblastic activities, as well as plasma calcium levels, in the scales of PCB (118)-injected goldfish. In addition, effect of PCB (118) on osteoclasts and osteoblasts was investigated in vitro. Immature goldfish, in which the endogenous effects of sex steroids are negligible, were used. PCB (118) was solubilized in dimethyl sulfoxide at a concentration of 10 ppm. At 1 and 2 days after PCB (118) injection (100 ng/g body weight), both osteoclastic and osteoblastic activities, and plasma calcium levels were measured. In an in vitro study, then, both osteoclastic and osteoblastic activities as well as each marker mRNA expression were examined. At 2 days, scale osteoclastic activity in PCB (118)-injected goldfish increased significantly, while osteoblastic activity did not change significantly. Corresponding to osteoclastic activity, plasma calcium levels increased significantly at 2 days after PCB (118) administration. Osteoclastic activation also occurred in the marker enzyme activities and mRNA expressions in vitro. Thus, we conclude that PCB (118) disrupts bone metabolism in goldfish both in vivo and in vitro experiments.  相似文献   
64.
The diffusion pathways of porous sandstone were examined by a three-dimensional (3-D) imaging technique based on X-ray computed tomography (CT) using the SPring-8 (Super Photon ring-8 GeV, Hyogo, Japan) synchrotron radiation facility. The analysis was undertaken to develop better understanding of the diffusion pathways in natural rock as a key factor in clarifying the detailed mechanism of the diffusion of radionuclides and water molecules through the pore spaces of natural barriers in underground nuclear waste disposal facilities. A cylindrical sample (diameter 4 mm, length 6 mm) of sandstone (porosity 0.14) was imaged to obtain a 3-D image set of 450(3) voxels=2.62(3) mm(3). Through cluster-labeling analysis of the 3-D image set, it was revealed that 89% of the pore space forms a single large pore-cluster responsible for macroscopic diffusive transport, while only 11% of the pore space is made up of isolated pores that are not involved in long-range diffusive transport. Computer simulations of the 3-D diffusion of non-sorbing random walkers in the largest pore cluster were performed to calculate the surface-to-volume ratio of the pore, tortuosity (diffusion coefficient in free space divided by that in porous rock). The results showed that (i) the simulated surface-to-volume ratio is about 60% of the results obtained by conventional pulsed-field-gradient proton nuclear magnetic resonance (NMR) laboratory experiments and (ii) the simulated tortuosity is five to seven times larger than the results of laboratory diffusion experiments using non-sorbing I(-) and Br(-). These discrepancies are probably attributed to the intrinsic sample heterogeneity and limited spatial resolution of the CT system. The permeability was also estimated based on the NMR diffusometry theory using the results of the random walk simulations via the Kozeny-Carman equation. The estimated permeability involved an error of about 20% compared with the permeability measured by the conventional method, suggesting that the diffusometry-based NMR well logging with gradient coils is applicable to the in-situ permeability measurement of strata. The present study demonstrated that X-ray CT using synchrotron radiation is a powerful tool for obtaining 3-D pore structure images without the beam-hardening artifacts inevitable in conventional CT using X-ray tubes.  相似文献   
65.
For a better understanding of the soil-to-plant transfer of radionuclides, their behavior in the soil solution should be elucidated, especially at the interface between plant roots and soil particles, where conditions differ greatly from the bulk soil because of plant activity. This study determined the concentration of stable Cs and Sr, and U in the soil solution, under plant growing conditions. The leafy vegetable komatsuna (Brassica rapa L.) was cultivated for 26 days in pots, where the rhizosphere soil was separated from the non-rhizosphere soil by a nylon net screen. The concentrations of Cs and Sr in the rhizosphere soil solution decreased with time, and were controlled by K+NH(4)(+) and Ca, respectively. On the other hand, the concentration of U in the rhizosphere soil solution increased with time, and was related to the changes of DOC; however, this relationship was different between the rhizosphere and non-rhizosphere soil.  相似文献   
66.
The abundance and species composition of diatoms were investigated along the PN line from the Okinawa Islands to the inner continental shelf in the East China Sea in the early spring of 1996. Viable diatom resting stages in sediments on the shelf were also enumerated by the extinction dilution method (most probable number method). Clear differentiation in the water masses was observed, with less saline, cold water (shelf water) on the shelf region, and warm, saline water (Kuroshio water) prevalent off the shelf and on the shelf edge. In the Kuroshio water, the abundance of diatoms was generally low but species diversity of diatoms was relatively high. In contrast, the spring bloom of diatoms was clearly observed in the shelf water where the water column was weakly stratified. The bloom was dominated by Chaetoceros debilis, contributing occasionally >80% of the diatom community. Resting stages of this species were also the most abundant taxon in the sediments on the shelf. Resuspension of the sediment during winter mixing of the water column should have enabled the resting stages to germinate at the surface. Subsequent vegetative growth after germination led to the formation of an early spring bloom of C. debilis when the water column was stratified and light availability had increased. Intermittent resuspension of sediment on the shelf, driven by strong winds and tidal currents, probably provides opportunities for diatoms with a resting stage to exploit favorable conditions for their germination and subsequent vegetative growth. It is further suggested that complex hydrographic conditions in the East China Sea result in a dynamic bloom with contributions by both autochthonous and allochthonous species.Communicated by T. Ikeda, Hakodate  相似文献   
67.
In the actual work environment, a specific objective noise, like machine and industrial noises, shows impulsive fluctuation form. Furthermore, it often occurs that a specific noise is partially or completely contaminated by background noise. In that case, the fluctuation wave form of the specific noise has to be estimated moment by moment in order to evaluate and/or improve the work environment. In this study, a digital filter for estimating an impulsively fluctuating specific noise is proposed. More specifically, after introducing a generalized time series regressive model of the specific noise, a method for estimating the impulsive noise based on an observation contaminated by the background noise is theoretically derived. Furthermore, the proposed method is applied to the actual task of estimating an industrial impact noise.  相似文献   
68.
69.
Fujise H  Annoura T  Sasawatari S  Ikeda T  Ueda K 《Chemosphere》2002,46(9-10):1505-1511
Endocrine disrupters such as sex hormone-like chemicals and the non-physiological ligands for aryl hydrocarbon receptor (AhR) exert many adverse biological effects. The ligands for AhR disturb gene expression downstream of the gene induced by estrogen receptor at a very low concentration. Thus, transepithelial transport and cellular accumulation of cortisol (COR) and estrogen as congeners of sex hormone-like chemicals, and 3,3,4,4-tetrachlorobiphenyl (TeCB) as one of the ligands for AhR were examined in a monolayer of porcine kidney cells transfected with human P-glycoprotein (LLC-COL). The net basal-to-apical transport of COR increased in LLC-COL compared to that in the wild type cells (LLC-PK1) the same as in vinblastine, whereas the net transport of estradiol (EST) was not detected in either cell group. Though the diffusion transports of EST for both directions, basal-to-apical and apical-to-basal, were higher than that of COR, cellular accumulation of EST was higher than that of COR. Transepithelial transport of TeCB was very low and the net basal-to-apical transport was not detected, while it was highly accumulated in the epithelial cells. The accumulation was slightly higher in LLC-COL than in LLC-PK1 at high dose.  相似文献   
70.
Pinonaldehyde and some other organics in rain and snow in central Japan.   总被引:1,自引:0,他引:1  
Solvent-extractable organic compounds in the rain and snow collected at local cities in the mountainous region in central Japan, were analyzed by GC/MS and GC. Pinonaldehyde (2,2-dimethyl-3-acetyl-cyclobutyl-ethanal), an atmospheric reaction product of alpha-pinene, was detected in the rain and snow for the first time, and n-alkanes (C17-C33), fatty acids (C8-C23), and benzoic acid were also detected as major organic components. Concentrations of pinonaldehyde, C17-C33 n-alkanes, C8-C11 fatty acids, C12-C23 fatty acids and benzoic acid ranged between <0.02-13, 0.10-35, 0.55-5.7, 4.2-19 and <0.02-6.0 microg/l, respectively. Their composition showed some difference in summer and winter. In summer, fatty acids and benzoic acid were more abundant, while pinonaldehyde and n-alkanes were much less. Higher photochemical reactivity and higher bioactivity in summer could explain these seasonal changes except for pinonaldehyde, which would suffer from further oxidation in the atmosphere after its photochemical production from alpha-pinene. Predominance of pinonaldehyde and C12-C23 fatty acids in the rain and snow showed a remarkable contrast to n-alkanes in aerosol phase, which were the most abundant components. It indicated that oxygenated products from biogenic compounds might be important as cloud condensation nuclei in forest areas.  相似文献   
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