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Takeshi Ohba Takeshi Sawa Noriyasu Taira Tsanyao Frank Yang Hsiao Fen Lee Tefang Faith Lan Michiko Ohwada Noritoshi Morikawa Kohei Kazahaya 《Applied Geochemistry》2010
Two distinctive magmatic fluids were recognized in the Tatun volcanic group (TVG), Taiwan. One is a relatively reduced fluid represented by the fumarolic gases at Hsiao-you-ken (HYK) geothermal field. Another is an oxidized fluid containing high concentrations of HCl represented by the fumarolic gases at Da-you-ken (DYK). An intermediate gas was recognized at Gung-tze-ping (GTP) and She-hung-ping (SHP). The fumarolic gases at HYK and GTP possess the features of so-called primary steam generated on mixing of magmatic gas and meteoric groundwater. The fumarolic gases at DYK are a simple mixture between magmatic gas and water vapor of meteoric origin. The CO2/H2O molar ratio of the magmatic component in the fumarolic gases at DYK was estimated to be 0.018, meanwhile it was estimated to be 0.027 for the fumarolic gases at HYK and GTP, suggesting the magma beneath DYK is depleted in volatiles relative to the magma beneath HYK and GTP. The estimated CO2/H2O ratio for the magmatic component is comparable to that of some active volcanoes in Japan, suggesting the enrichment of volatiles in the magmas beneath TVG. 相似文献
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Study of the effect of water-soluble fractions of heavy-oil on coastal marine organisms using enclosed ecosystems,mesocosms 总被引：1，自引：0，他引：1
Ohwada K Nishimura M Wada M Nomura H Shibata A Okamoto K Toyoda K Yoshida A Takada H Yamada M 《Marine pollution bulletin》2003,47(1-6):78-84
Mesocosm facilities composed of 4 experimental and 2 reservoir tanks (1.5 m in diameter, 3.0 m in depth and 5 tons in capacity) made of FRP plastics, were constructed in the concrete fish rearing pond in the Fisheries Laboratory, The University of Tokyo. The water-soluble fraction of Rank A heavy residual oil was formed by mixing 500 g of the oil with 10 l of seawater, which was introduced to the 5000 l-capacity tanks. Experimental Run 4 was conducted from May 31 to June 7, 2000. Oil concentrations in the tanks were 4.5 microg/l called LOW, and 13.5 microg/l, called HIGH tank. Bacterial growth rates very quickly accelerated in the HIGH tank just after the loading of oil which corresponded with a high increase of bacterial cells in the same tank after 2 days. Later, bacterial numbers in HIGH tank rapidly decreased, corresponding with the rapid increase of heterotrophic nano-flagellates and virus numbers on the same day. Sediment traps were deployed at the bottom of the experimental tanks, and were periodically retrieved. These samples were observed both under light microscope and epi-fluorescent microscope with UV-excitation. It was observed that the main components of the vertical flux were amorphous suspended matter, mostly originating from dead phytoplankton and living diatoms. It was further observed from the pictures that vertical transport of oil emulsions were probably conducted after adsorption to amorphous suspended matter and living diatoms, and were settling in the sediment traps at the bottom of the tanks. This means that the main force which drives the soluble fraction of oil into bottom sediment would be vertical flux of such amorphous suspended particles and phytoplankton. Further incubation of the samples revealed that the oil emulsions were degraded by the activity of autochtonous bacteria in the sediment in aerobic condition. 相似文献
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Assessment of nitrogen loading from the Kiso-Sansen Rivers into Ise Bay using stable isotopes 总被引：1，自引：0，他引：1
Ryo Sugimoto Akihide Kasai Kouichi Fujita Kenichi Sakaguchi Tomomi Mizuno 《Journal of Oceanography》2011,67(2):231-240
Concentrations of particulate organic nitrogen (PN), dissolved inorganic nitrogen (DIN), and their nitrogen isotope ratios
(δ
15N) in the Kiso-Sansen Rivers were determined from monthly observations over the course of a year to assess variations in the
form and sources of riverine nitrogen discharged into Ise Bay. The δ
15N values of NO3
− observed in the Kiso-Sansen Rivers showed a logarithmic decreasing trend from 8 to 0‰, which varied with the river discharge,
indicating mixing between point sources with high δ
15N and non-point sources with low δ
15N. The influence of isotope fractionation of in situ biogeochemical processes (mainly DIN assimilation by phytoplankton) on
δ
15N of NO3
− was negligible, because sufficient concentrations of NH4
+ for phytoplankton demand would inhibit the assimilation of NO3
−. A simple relationship between river discharge and δ
15N of NO3
− showed that the fraction of total NO3
− flux arising from point sources increased from 4.0–6.3% (1.1–1.8 tN day−1) during higher discharge (>600 m3 s−1) to 30.2–48.3% (2.6–4.1 tN day−1) during lower discharge (<300 m3 s−1). Riverine NO3
− discharge from the Kiso-Sansen Rivers can explain 75% of the variations in surface NO3
− at the head of Ise Bay over the year. 相似文献
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Imaging Atmospheric Cherenkov Telescopes have revealed more than 100 TeV sources along the galactic plane, around 45% of them remain unidentified. However, radio observations revealed that dense molecular clumps are associated with 67% of 18 unidentified TeV sources. In this paper, we propose that an electron–positron magnetospheric accelerator emits detectable TeV gamma-rays when a rapidly rotating black hole enters a gaseous cloud. Since the general-relativistic effect plays an essential role in this magnetospheric lepton accelerator scenario, the emissions take place in the direct vicinity of the event horizon, resulting in a point-like gamma-ray image. We demonstrate that their gamma-ray spectra have two peaks around 0.1 GeV and 0.1 TeV and that the accelerators become most luminous when the mass accretion rate becomes about 0.01% of the Eddington accretion rate. We compare the results with alternative scenarios such as the cosmic-ray hadron scenario, which predicts an extended morphology of the gamma-ray image with a single power-law photon spectrum from GeV to 100 TeV. 相似文献
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Tomonori Watai Koh Harada Kouichi Gotoh Shohei Murayama Takakiyo Nakazawa 《Journal of Oceanography》1999,55(6):655-665
In order to examine latitudinal distribution and seasonal change of the surface oceanic fCO2, we analyzed the data obtained in the North Pacific along 175°E during the NOPACCS cruises in spring and summer of 1992–1996. Except for around the equator where the fCO2 was significantly affected by the upwelling of deep water, the latitudinal distribution of fCO2 showed distinctive seasonal variation. In the spring, the fCO2 decreased and then increased going southward with the minimum value of about 300 µatm around 35°N, while in the summer, the fCO2 displayed high variability, showing minimum and maximum values at latitudes of around 44° and 35°N, respectively. It was also found that the fCO2 was well correlated with the SST, but the relationship between the two was different for different hydrographic regions. In the subpolar gyre, the frontal regions between the Water-Mass Front and the Kuroshio bifurcation front, and between the Kuroshio bifurcation front and the Kuroshio Extension current, SST, DIC and TA influenced the seasonal fCO2 change through seasonally-dependent biological activities and vertical mixing and stratification of seawater. In the central subtropical gyre and the North Equatorial current, the seasonal fCO2 change was found to be produced basically by changes in SST and DIC. The summertime oceanic fCO2 generally increased with time over the period covered by this study, but the increased rate was clearly higher than those expected from other measurements in the western North Pacific. 相似文献
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Kouichi Hirotani 《Astrophysics and Space Science》2005,297(1-4):81-91
We investigate a stationary pair production cascade in the outer magnetosphere of an isolated, spinning neutron star. The
charge depletion due to global flows of charged particles, causes a large electric field along the magnetic field lines. Migratory
electrons and/or positrons are accelerated by this field to radiate gamma-rays via curvature and inverse-Compton processes.
Some of such gamma-rays collide with the X-rays to materialize as pairs in the gap. The replenished charges partially screen
the electric field, which is self-consistently solved together with the energy distribution of particles and gamma-rays at
each point along the field lines. By solving the set of Maxwell and Boltzmann equations, we demonstrate that an external injection
of charged particles at nearly Goldreich-Julian rate does not quench the gap but shifts its position and that the particle
energy distribution cannot be described by a power-law. The injected particles are accelerated in the gap and escape from
it with large Lorentz factors. We show that such escaping particles migrating outside of the gap contribute significantly
to the gamma-ray luminosity for young pulsars and that the soft gamma-ray spectrum between 100 MeV and 3 GeV observed for
the Vela pulsar can be explained by this component. We also discuss that the luminosity of the gamma-rays emitted by the escaping
particles is naturally proportional to the square root of the spin-down luminosity. 相似文献
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Chiyuki Sassa Kouichi Kawaguchi Yuichi Hirota Minoru Ishida 《Deep Sea Research Part I: Oceanographic Research Papers》2007,54(12):2181-2193
We describe the day–night vertical distribution patterns of 18 species or types of myctophid fish larvae at the transforming stage based on discrete depth sampling from the surface down to 1000-m depth in the subtropical–tropical western North Pacific. A total of 551 transforming stage larvae were collected at the 19 sampling stations. Except for the Diaphus species and Notolychnus valdiviae, all of the transforming stage larvae (including genera Benthosema, Bolinichthys, Centrobranchus, Ceratoscopelus, Diogenichthys, Hygophum, Lampanyctus, Lobianchia, Myctophum, Symbolophorus, and Triphoturus) were collected in the lower mesopelagic zone from 600- to 900-m depth during both day and night, showing no diel vertical migration (DVM). On the contrary, the Diaphus species and N. valdiviae larvae undergo DVM during the transforming stage, occurring below 200-m layer during the daytime and migrating up to the upper 150-m layer at night, i.e., they show earlier adaptation to juvenile–adult behaviors. Most myctophid fish larvae are known to undertake substantial ontogenetic vertical migration (OVM) from the epipelagic to mesopelagic zones during their early life stage. Although considerable sampling effort was carried out in this study, transforming larvae, except for the above two migratory ones, were not collected in the epipelagic and upper mesopelagic zones, strongly suggesting that their sinking speed would be high. It would be advantageous for survival to spend their highly vulnerable transforming stage in the lower mesopelagic zone, where predation pressures are lower and physical conditions are more stable than in the upper layers. 相似文献