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11.
Hitoshi Chiba Minoru Kusakabe Shin-Ichi Hirano Sadao Matsuo Shigeyuki Somiya 《Earth and Planetary Science Letters》1981,53(1):55-62
Oxygen isotope exchange between anhydrite and water was studied from 100 to 550°C, using the partial equilibrium method. The exchange rate was extremely low in NaCl solution. In the lower-temperature range, acid solutions were used to produce sufficient reaction to determine the oxygen isotope fractionation factors. The fractionation factors obtained in the present study are definitely different from those given by Lloyd [8]. They are similar to those for the HSO4?-water system studied by Mizutani and Rafter [19], and are consistently 2‰ higher than those of the barite-water system by Kusakabe and Robinson [5]. The temperature dependence of the oxygen isotope fractionation factors was calculated by the least squares method in which the weight was taken to be inversely proportional to the experimental error. The fractionation is given by:103lnαanhydrite-water=3.21×(103/T)2?4.72Available δ18O values of natural anhydrite were used to test the validity of this expression. It is shown that this newly revised geothermometer can be successfully applied to natural hydrothermal anhydrite. 相似文献
12.
The gravitational instability in the dust layer of a protoplanetary disk with nonuniform dust density distributions in the direction vertical to the midplane is investigated. The linear analysis of the gravitational instability is performed. The following assumptions are used: (1) One fluid model is adopted, that is, difference of velocities between dust and gas are neglected. (2) The gas is incompressible. (3) Models are axisymmetric with respect to the rotation axis of the disk. Numerical results show that the critical density at the midplane is higher than the one for the uniform dust density distribution by Sekiya (1983, Prog. Theor. Phys. 69, 1116-1130). For the Gaussian dust density distribution, the critical density is 1.3 times higher, although we do not consider this dust density distribution to be realistic because of the shear instability in the dust layer. For the dust density distribution with a constant Richardson number, which is considered to be realized due to the shear instability, the critical density is 2.85 times higher and is independent of the value of the Richardson number. Further, if a constant Richardson number could decrease to the order of 0.001, the gravitational instability would be realized even for the dust to gas surface density ratio with the solar abundance. Our results give a new restriction on planetesimal formation by the gravitational instability. 相似文献
13.
Minoru Tomizawa 《地震工程与结构动力学》1980,8(3):251-265
The propriety of adopting a multi-degree-of-freedom lumped mass–spring–dampers system driven by white noise support excitation as a one-dimensional model for a soil-layer–bedrock system during an earthquake is investigated by means of statistical system identification of the model with noisy measurement of the earthquake ground velocity. The present discussion also suggests that this model may not be applicable to all observed earthquake records, since the model itself depends on the statistical nature of the earthquake motion. For appropriate earthquake records, the system identification procedure may be accomplished; then dynamical properties of the soil-layer and the power spectral density for white noise excitation acting upon the bedrock can be estimated as shown in a numerical example. 相似文献
14.
Yoshida A Nomura H Toyoda K Nishino T Seo Y Yamada M Nishimura M Wada M Okamoto K Shibata A Takada H Kogure K Ohwada K 《Marine pollution bulletin》2006,52(1):89-95
Microbial responses to the addition of oil with or without a chemical dispersant were examined in mesocosm and microcosm experiments by using denaturing gradient gel electrophoresis of bacterial ribosomal DNA and direct cell counting. When a water-soluble fraction of oil was added to seawater, increases in cell density were observed in the first 24h, followed by a decrease in abundance and a change in bacterial species composition. After addition of an oil-dispersant mixture, increases in cell density and changes in community structure coincided, and the amount of bacteria remained high. These phenomena also occurred in response to addition of only dispersant. Our results suggest that the chemical dispersant may be used as a nutrient source by some bacterial groups and may directly or indirectly prevent the growth of other bacterial groups. 相似文献
15.
The tetrad field equations of general relativity discussed in previous articles are applied to Robertson-Walker cosmological models. A generalized Friedmann equation is derived and some of its consequences are discussed. 相似文献
16.
Stability of Remanent Magnetization of Igneous Rocks 总被引:1,自引:0,他引:1
E. Larson Mituko Ozima Minoru Ozima T. Nagata D. Strangway 《Geophysical Journal International》1969,17(3):263-292
17.
Elucidating the scale of gene flow among populations is an important challenge for understanding the ecological dynamics and local adaptation of marine organisms. We assessed whether gene flow is restricted even at a small spatial scale in the Japanese common intertidal goby Chaenogobius annularis, using highly polymorphic DNA markers, involving the mitochondrial DNA (mtDNA) control region and 15 microsatellite DNA (msDNA), because past ecological studies have suggested low dispersal ability for rocky intertidal fishes. We found significant heterogeneities between four neighboring local populations by both mtDNA and msDNA analyses. In addition, no genetic heterogeneity was detected by either method across generations within a population; it was considered that such genetic differentiation is retained across generations and that the gene flow of this species is restricted to within a radius of a few kilometers. This is the first report showing a clear genetic subdivision in rocky intertidal fish. 相似文献
18.
Although earthquakes are thought to be one of the factors responsible for the occurrence of landslides in Hokkaido, there
exist no enough records which can allow correlating many of the old slope failures in the island with earthquakes. In the
absence of these records, an attempt was done in this study to use the abundance, frequency, magnitude, depth, and distribution
of historical earthquakes to deduce that many of the slope failures in the region were triggered by strong and continuous
seismicity. The determination of the zones of influences of selected earthquakes using an existing empirical function has
also supported this conclusion. Moreover, the use of a 10% probability of exceedance of earthquake intensity in 50 years,
and the geological and slope maps has allowed preparing a landslide hazard map which explains the role of future earthquakes
in the formation of slope failures. The result indicates a high probability of occurrences of landslides in the hilly regions
of the southeastern part of Hokkaido due to expected strong seismicity and earthquake intensities in these areas. On the other
hand, the low level of intensity in the north has given rise to low probability of landslide hazard. There are also places
in the center of the island and high intensity regions in the east where the probability of landslide hazard was influenced
by the contribution of the geological and slope maps. 相似文献
19.
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
20.
Yoshihisa?MinoEmail author Chiho?Sukigara Makio?C.?Honda Hajime?Kawakami Kazuhiko?Matsumoto Masahide?Wakita Minoru?Kitamura Tetsuichi?Fujiki Kosei?Sasaoka Osamu?Abe Jan?Kaiser Toshiro?Saino 《Journal of Oceanography》2016,72(6):819-836
Intensive observations using hydrographical cruises and moored sediment trap deployments during 2010 and 2012 at station K2 in the North Pacific Western Subarctic Gyre (WSG) revealed seasonal changes in δ 15N of both suspended and settling particles. Suspended particles (SUS) were collected from depths between the surface and 200 m; settling particles by drifting sediment traps (DST; 100–200 m) and moored sediment traps (MST; 200 and 500 m). All particles showed higher δ 15N values in winter and lower in summer, contrary to the expected by isotopic fractionation during phytoplankton nitrate consumption. We suggest that these observed isotopic patterns are due to ammonium consumption via light-controlled nitrification, which could induce variations in δ 15N(SUS) of 0.4–3.1 ‰ in the euphotic zone (EZ). The δ 15N(SUS) signature was reflected by δ 15N(DST) despite modifications during biogenic transformation from suspended particles in the EZ. δ 15N enrichment (average: 3.6 ‰) and the increase in C:N ratio (by 1.6) in settling particles suggests year-round contributions of metabolites from herbivorous zooplankton as well as TEPs produced by diatoms. Accordingly, seasonal δ 15N(DST) variations of 2.4–7.0 ‰ showed a significant correlation with primary productivity (PP) at K2. By applying the observed δ 15N(DST) vs. PP regression to δ 15N(MST) of 1.9–8.0 ‰, we constructed the first annual time-series of PP changes in the WSG. This new approach to estimate productivity can be a powerful tool for further understanding of the biological pump in the WSG, even though its validity needs to be examined carefully. 相似文献