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31.
The spinel solid solution was found to exist in the whole range between Fe3O4 and γ-Fe2SiO4 at over 10 GPa. The resistivity of Fe3−
x
Si
x
O4 (0.0<x<0.288) was measured in the temperature range of 80∼300 K by the AC impedance method. Electron hopping between Fe3+ and Fe2+ in the octahedral site of iron-rich phases gives a large electric conductivity at room temperature. The activation energy
of the electron hopping becomes larger with increasing γ-Fe2SiO4 component. A nonlinear change in electric conductivity is not simply caused by the statistical probability of Fe3+–Fe2+ electron hopping with increasing the total Si content. This is probably because a large number of Si4+ ions occupies the octahedral site and the adjacent Fe2+ keeping the local electric neutrality around Si4+ makes a cluster, which generates a local deformation by Si substitution.
The temperature dependence of the conductivity of solid solutions indicates the Verwey transition temperature, which decreases
from 124(±2) K at x=0 (Fe3O4) to 102(±5) K at x=0.288, and the electric conductivity gap at the transition temperature decreases with Si4+ substitution.
Received: 15 March 2000 / Accepted: 4 September 2000 相似文献
32.
Taku Tada Yoshinobu Tsuji Masahito Tsukamoto Yoshikazu Ueno Masayuki Kawashima Takashi Egawa Yasuhiro Yamazaki 《Pure and Applied Geophysics》1992,138(2):309-322
We carried out observations of sea-level fluctuations simultaneously at three stations on the coast of Heda Bay, Honshu, Japan, using supersonic-type water level gauges controlled by a personal computer. Analyses of the obtained data showed predominant spectral peaks at periods of 7.6, 2.0 and 1.3 minutes for all three stations. Comparison of the observed data with numerically calculated normal oscillation modes of the bay indicates that these three spectral peaks correspond to the theoretical first, third and seventh normal modes of the basin respectively, judging from the results of cross-spectral analyses. The reason for the absence of the remaining normal modes, especially of the second or the lateral first mode of the basin, is briefly considered. 相似文献
33.
Spatial distribution of deuterium in atmospheric water vapor: Diagnosing sources and the mixing of atmospheric moisture 总被引:1,自引:0,他引:1
We measured the stable isotopic composition of hydrogen (δD) within atmospheric water vapor collected simultaneously at six sites in the vicinity of a lake (Lake Kasumigaura, Eastern Japan) to determine its spatial distribution characteristics and thereby diagnose sources and mixing of atmospheric moisture. The measured spatial distribution of δD showed no relation to distance from the lake, although it showed a correlation with the distribution of the water-vapor mixing ratio Q. For two of the three sampling days, we found a simple two-component (i.e., water vapor transpiring from local land surfaces and pre-existing vapor in the background atmosphere) mixing line in a Keeling plot (i.e., δ − 1/Q diagram). On a third day, however, contributions from lake evaporation were detected in addition to the above components. On this day, lake-derived vapor accounted for approximately 10-20% of atmospheric water vapor at the sites located leeward of the lake. The observed differences in mixing patterns among sampling days can be explained by a simple atmospheric moisture budget. Thus, it is likely that simultaneous isotopic measurements of atmospheric water vapor at multiple locations with aid of Keeling plot are capable of giving us useful information in diagnosing the sources and mixing pattern of the vapor. 相似文献
34.
Wataru Ootani Makoto Minowa Takayuki Watanabe Yutaka Ito Yasuhiro Kishimoto Kentaro Miuchi Yoshizumi Inoue Youiti Ootuka 《Astroparticle Physics》1998,9(4):325-329
The performance of a 21-g lithium fluoride bolometer is presented. The background spectrum was measured in the surface laboratory. We derive an exclusion plot for the spin-dependent coupled Weakly Interacting Massive Particles (WIMPs) cross section. 相似文献
35.
Yasuhiro Hashimoto J. Patrick Henry Hans Böhringer 《Monthly notices of the Royal Astronomical Society》2007,380(2):835-838
We investigated the influence of environment on cluster morphology by examining the alignment of the cluster position angle with respect to the nearest neighbour cluster. The cluster position angle and ellipticity were measured using high spatial resolution X-ray data taken from the Chandra archive, while the nearest neighbour sample was extracted from the Abell cluster catalogue. We found high confidence for an alignment when neighbour distance (Dn) was less than 70 h −1 Mpc, while we found no significant variations of the confidence level at various values of Dn less than 70 h −1 Mpc. 相似文献
36.
Besshi-type Cu deposits are strata-bound volcanogenic massive sulfide deposits usually associated with mafic volcanic rocks or their metamorphic equivalents. Although there are numerous Besshi-type deposits in the Sanbagawa metamorphic belt, Japan, their tectonic settings and depositional environments remain controversial because of a lack of depositional age constraints. We report Re-Os data for the Iimori deposit, one of the largest Besshi-type deposits in western Kii Peninsula, in order to examine the robustness of the Re-Os isotope system for dating sulfide minerals in the high-P/T metamorphic belt and to elucidate the primary depositional environment of the Iimori sulfide ores. An 11-point Re-Os isochron plot yields an age of 156.8 ± 3.6 Ma. As this Re-Os isochron age is significantly older than the timing of the Sanbagawa peak metamorphism (110-120 or ∼90 Ma) and a well-defined isochron was obtained, the Re-Os age determined here is most likely the primary depositional age. Despite high-grade metamorphism at up to 520 ± 25 °C and 8-9.5 kbar, the Re-Os isotope system of the Iimori sulfides was not disturbed. Hence, we consider that the whole-rock Re-Os closure temperature for the Iimori sulfide ores was probably higher than 500 °C. As the accretion age of the Sanbagawa metamorphic belt is considered to be 120-130 or 65-90 Ma on the basis of radiolarian and radiometric ages, we estimated the time from the Iimori sulfide deposition on the paleo-seafloor to its accretion at the convergent plate boundary to be greater than 25 Myr. Consequently, the depositional environment of the Iimori sulfide ores was not in the marginal sea, but was truly pelagic. 相似文献
37.
38.
Sachiko Oguma Tsuneo Ono Akira Kusaka Hiromi Kasai Yasuhiro Kawasaki Tomonori Azumaya 《Journal of Oceanography》2008,64(4):525-539
In this study we used two stable isotopes, δ13C and δ18O, for water mass classification in the coastal region off eastern Hokkaido. δ13C* values, which were corrected for the biological effect, and δ
18O values up to 300 m depth suggested that the isotopic character of the onshore and offshore water in the southern Okhotsk
Sea, the Nemuro Strait and the western North Pacific could be explained by the mixing of three source waters: the Oyashio
water (OYW), Soya Warm Current water (SWCW) and East Sakhalin Current water (ESCW). In summer, δ
13C*-δ
18O plots indicated mixing between SWCW from the southern Okhotsk Sea and OYW in the Pacific coast of southeastern Hokkaido,
while temperature-salinity plots of the onshore water showed minimal difference from the offshore OYW. In winter, on the other
hand, the mixed water of ESCW and OYW (or SWCW) appeared in the Pacific coastal region, distributed as cold, low salinity
onshore water. Finally, we estimated mixing ratios of OYW, SWCW and ESCW in the coastal region of western North Pacific using
their mean values of δ
13C* and δ
18O as endmembers. These results suggest seasonal and yearly changes of water mass combination en route from the southern Okhotsk
Sea to the western North Pacific. 相似文献
39.
40.
Comparative analysis of contributing parameters for rainfall-triggered landslides in the Lesser Himalaya of Nepal 总被引:6,自引:0,他引:6
Ranjan Kumar Dahal Shuichi Hasegawa Minoru Yamanaka Santosh Dhakal Netra Prakash Bhandary Ryuichi Yatabe 《Environmental Geology》2009,58(3):567-586
In the Himalaya, people live in widely spread settlements and suffer more from landslides than from any other type of natural
disaster. The intense summer monsoons are the main factor in triggering landslides. However, the relations between landslides
and slope hydrology have not been a focal topic in Himalayan landslide research. This paper deals with the contributing parameters
for the rainfall-triggered landslides which occurred during an extreme monsoon rainfall event on 23 July 2002, in the south-western
hills of Kathmandu valley, in the Lesser Himalaya, Nepal. Parameters such as bedrock geology, geomorphology, geotechnical
properties of soil, and clay mineralogy are described in this paper. Landslide modeling was performed in SEEP/W and SLOPE/W
to understand the relationship of pore water pressure variations in soil layers and to determine the spatial variation of
landslide occurrence. Soil characteristics, low angle of internal friction of fines in soil, medium range of soil permeability,
presence of clay minerals in soil, bedrock hydrogeology, and human intervention were found to be the main contributing parameters
for slope failures in the region. 相似文献