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101.
Shinya Kouketsu Hitoshi Kaneko Takeshi Okunishi Kosei Sasaoka Sachihiko Itoh Ryuichiro Inoue Hiromichi Ueno 《Journal of Oceanography》2016,72(3):439-451
We investigated the relationship between chlorophyll a (Chl-a) concentrations estimated from satellite observations and the activity of eddies in the Kuroshio Extension region. High (low) area-averaged Chl-a concentrations were frequently observed in the core of cyclonic (anticyclonic) eddies. Such relationships between Chl-a concentrations and eddy cores were not frequently observed in the southern part of the recirculation gyre, and advection of background meridional gradient of Chl-a by eddy-edge currents accounted for Chl-a spatial variability. Decadal-scale changes of Chl-a concentrations around the Kuroshio Extension were strongly affected by eddy activity and transport but not by large-scale near-surface isopycnal heaving. We also found that decadal changes of nutrient concentrations near the main stream could affect Chl-a concentrations in the southern part of the recirculation gyre via southward transport of eddies and mean flow. 相似文献
102.
103.
104.
Arnold Gucsik Taro Endo Hirotsugu Nishido Kiyotaka Ninagawa Masahiro Kayama Szaniszló Bérczi Szabolcs Nagy Péter Ábrahám Yuki Kimura Hitoshi Miura Ildikó Gyollai Irakli Simonia Péter Rózsa József Posta Dániel Apai Krisztián Mihályi Mihály Nagy Ulrich Ott 《Meteoritics & planetary science》2013,48(12):2577-2596
Highly forsteritic olivine (Fo: 99.2–99.7) in the Kaba meteorite emits bright cathodoluminescence (CL). CL spectra of red luminescent forsterite grains have two broad emission bands at approximately 630 nm (impurity center of divalent Mn ions) in the red region and above 700 nm (trivalent Cr ions) in the red–IR region. The cores of the grains show CL blue luminescence giving a characteristic broad band emission at 400 nm, also associated with minor red emissions related to Mn and Cr ions. CL color variation of Kaba forsterite is attributed to structural defects. Electron probe microanalyzer (EPMA) analysis shows concentrations of Ca, Al, and Ti in the center of the forsterite grain. The migration of diffusible ions of Mn, Cr, and Fe to the rim of the Kaba meteoritic forsterite was controlled by the hydrothermal alteration at relatively low temperature (estimated at about 250 °C), while Ca and Al ions might still lie in the core. A very unusual phase of FeO (wüstite) was also observed, which may be a terrestrial alteration product of FeNi‐metal. 相似文献
105.
T. Takakura K. Ohki N. Shibuya M. Fujii M. Matsuoka S. Miyamoto J. Nishimura M. Oda Y. Ogawara S. Ota 《Solar physics》1971,16(2):454-464
The location and size of a solar impulsive hard X-ray burst have been determined in one dimension to a considerable precision with a balloon-borne X-ray modulation collimator. The center of the X-ray source is on the line passing through the center of a big H flare region of 3 arc min. The size of the X-ray source is remarkably smaller and may be one arc min or less. 相似文献
106.
Hitoshi Hasegawa Takashi Ichikawa Shinsuke Abe Shiomo Hamamura Koji Ohnishi Jun-Ich Watanabe 《Earth, Moon, and Planets》1997,78(1-3):353-358
Near-infrared photometric and polarimetric observations of comet Hale-Bopp (1995 O1) using KONIC (Kiso Observatory Near-Infrared
Camera) are reported. Observations were carried out on March 18 UT and April 26 UT 1997, when the heliocentric distances of
the comet were 0.94 and 1.02 AU, and the phase angles were 48.5 deg and 32.9 deg, respectively. In the J, H, and K′ bands,
we obtained linear polarization of the near-nucleus region of 16.4 ± 1.2, 18.8 ± 1.3, and 15.1 ± 0.9 percent on March 18UT
and 7.1 ± 1.1, 8.9 ± 1.0, and 6.9 ± 0.6 percent on April 26, respectively. These values were higher than those observed for
1P/Halley. The maximum polarization was found at H band on both dates. Polarization maps showed higher polarization regions
toward the anti-solar direction in the J and H bands. No distinct correlation was found between high polarization regions
and bright regions. The projected expansion velocity of the arc structure of the dust jet was 375 ± 35.7 m/s on 17–19 March.
The periodicity was found to be 11.1 ± 2.8 hours.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
107.
Mean transit times were estimated for a small headwater catchment in Japan (the Fukuroyamasawa Experimental Watershed) using the step shift in input chloride (Cl?) concentrations that occurred immediately after an episode of forest clear‐cutting. Measured Cl? concentrations in stream water began to decrease immediately after clear‐cutting, and this trend continued for 6 years. Before clear‐cutting, the input Cl? concentrations were controlled by wet and dry deposition processes, and most of the dry Cl? deposition was collected by the forest canopy and reached the ground as throughfall and stemflow. After clear‐cutting, dry deposition was no longer collected by the canopy in this way, thus causing a sharp decrease in input Cl? concentrations. By comparing measured Cl? concentrations in stream water with estimates based on the input and evaporative Cl? concentrations, it was shown that the decrease in stream water Cl? concentrations was caused mainly by this step shift in the Cl? input. It was proposed that the change in Cl? concentrations after forest cutting could be used to represent the replacement of ‘old’ water that existed before cutting by ‘new’ water that was supplied after cutting. The breakthrough curve for the new water fraction gave an approximately exponential distribution of transit times in flow‐corrected time. The mean flow‐corrected transit time was estimated as 1068 days (runoff: 3497 mm). It was therefore concluded that the step change in input Cl? concentrations immediately following forest clear‐cutting could be successfully used to estimate transit times for the entire catchment. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
108.
Yasuhiro Yamasaki Yanan Zou Jyoji Go Tomoyuki Shikata Yukihiko Matsuyama Kiyohito Nagai Yohei Shimasaki Kenichi Yamaguchi Yuji Oshima Tatsuya Oda Tsuneo Honjo 《Journal of Sea Research》2011,65(1):76-83
We used bi-algal culture experiments to investigate and verify the roles of growth interaction between Heterocapsa circularisquama and Prorocentrum dentatum in monospecific bloom formation. Growth of H. circularisquama was slightly inhibited when inoculated at 102 cells mL–1 along with P. dentatum at 104 cells mL–1. In other combinations of inoculation densities, P. dentatum density rapidly decreased to extremely low levels in the presence of H. circularisquama. We used a mathematical model to simulate growth and interactions of H. circularisquama and P. dentatum in bi-algal cultures. The model indicates that one species will always inhibit the growth of the other and that the relative initial cell densities of the species are critical in determining the outcome. When cultured together under conditions without cell contact, growth of H. circularisquama and P. dentatum was not inhibited. As with P. dentatum, the growth of Heterosigma akashiwo and Skeletonema costatum was inhibited in intact cell suspensions with H. circularisquama, but a nontoxic species, Heterocapsa triquetra, did not affect the growth of P. dentatum or the other species. Similarly, cell suspensions of H. circularisquama showed hemolytic activity toward rabbit erythrocytes, but those of H. triquetra did not. In addition, the cell-free supernatant of H. circularisquama cultures showed no significant hemolytic activity. These results suggest that H. circularisquama causes lethality in P. dentatum by direct cell contact in which live-cell-mediated hemolytic activity might be a contributing factor. 相似文献
109.
Based on the geological tectonics, aftershock activity, earthquake surface rupture and peak ground motion, the geometric and
dynamic characteristics of seismogenic tectonics about the 1995 Hanshin earthquake are analysed. Nojima fault and Rokko fault
have the same trending direction, but opposite dips. Their rising and falling plates are in symmetrically diagonal distribution.
The two faults can be defined as thrust-strike slip faults and constitute a pivotal strike-slip fault. The earthquake just
occurred at the pivot, which is the seismotectonics for the earthquake to develop and occur. The pivotal movement along a
strike-slip fault often leads to the occurrence of large earthquakes, whose dynamic process can be demonstrated by the stress
analysis on the torsion of a beam with rectangle section. The displacement of earthquake surface rupture, aftershock density
and peak acceleration change in a certain range of epicentral distance just similar as the shear stress changes from the center
to the sides in the rectangle section.
The distribution characteristics of the heaviest damage areas are also discussed in the article from the aspects of special
geological tectonics and seismotectonic condition. The result obtained from the article can be applied not only to realizing
the potencial earthquake sources in middle-long time, but also to build reasonably the prediction model about earthquake hazard. 相似文献
110.
Detection and Evaluation of Gas Hydrates in the Eastern Nankai Trough by Geochemical and Geophysical Methods 总被引:2,自引:0,他引:2
Abstract: Interstitial waters extracted from the sediment cores from the exploration wells, “BH‐1” and “MITI Nankai Trough”, drilled ~60 km off Omaezaki Peninsula in the eastern Nankai Trough, were analyzed for the chloride and sulfate concentrations to examine the depth profiles and occurrence of subsurface gas hydrates. Cored intervals from the seafloor to 310 mbsf were divided into Unit 1 (~70 mbsf, predominated by mud), Unit 2 (70–150 mbsf, mud with thin ash beds), Unit 3 (150–250+ mbsf, mud with thin ash and sand), and Unit 4 (275–310 mbsf, predominated by mud). The baseline level for Cl “concentrations was 540 mM, whereas low chloride anomalies (103 to 223 mM) were identified at around 207 mbsf (zone A), 234–240 mbsf (zone B), and 258–265 mbsf (zone C) in Unit 3. Gas hydrate saturation (Sh %) of sediment pores was calculated to be 60 % (zone A) to 80 % (zones B and C) in sands whereas only a few percent in clay and silt. The total amount of gas hydrates in hydrate‐bearing sands was estimated to be 8 to 10 m3 of solid gas hydrate per m2, or 1.48 km3 CH4 per 1 km2. High saturation zones (A, B and C) were consistent with anomaly zones recognized in sonic and resistivity logs. 2D and high‐resolution seismic studies revealed two BSRs in the study area. Strong BSRs (BSR‐1) at ~263 mbsf were correlated to the boundary between gas hydrate‐bearing sands (zone C) and the shallower low velocity zone, while the lower BSRs (BSR‐2) at~289 mbsf corresponded to the top of the deeper low velocity zone of the sonic log. Tectonic uplift of the study area is thought to have caused the upward migration of BGHS. That is, BSR‐1 corresponds to the new BGHS and BSR‐2 to the old BGHS. Relic gas hydrates and free gas may survive in the interval between BSR‐1 and BSR‐2, and below BSR‐2, respectively. Direct measurements of the formation temperature for the top 170 m interval yield a geothermal gradient of ~4.3d?C/ 100 m. Extrapolation of this gradient down to the base of gas hydrate stability yields a theoretical BGHS at~230 mbsf, surprisingly ~35 m shallower than the base of gas hydrate‐bearing sands (zone C) and BSR‐1. As with the double BSRs, another tectonic uplift may explain the BGHS at unreasonably shallow depths. Alternatively, linear extrapolation of the geothermal gradient down to the hydrate‐bearing zones may not be appropriate if the gradient changes below the depths that were measured. Recognition of double BSRs (263 and 289 mbsf) and probable new BGHS (~230 mbsf) in the exploration wells implies that the BGHS has gradually migrated upward. Tectonically induced processes are thought to have enhanced dense and massive accumulation of gas hydrate deposits through effective methane recycling and condensation. To test the hypothetical models for the accumulation of gas hydrates in Nankai accretionary prism, we strongly propose to measure the equilibrium temperatures for the entire depth range down to the free gas zone below predicted BGHS and to reconstruct the water depths and uplift history of hydrate‐bearing area. 相似文献