Dynamics of attached bacteria at the water-sediment interface in a mesotrophic swampy bog of Japan     

Motoo Utsumi  Yukihiro Nojiri  Nozomi Ytow  Humitake Seki 《Journal of Oceanography》1998,54(2):179-184

The population dynamics of attached bacteria at the water-sediment interface were studied in a mesotrophic swampy bog, Matsumi-ike, near Tsukuba, Japan. The density of attached bacteria was higher at the sediment boundary layer than in the water column, and low inside the sediment (deeper, than 10 mm below the sediment surface) throughout the year. The density of bacteria attached on the glass slide was highest during spring when the source of organic matter in the water column was mainly withered cattail, and gradually decreased toward summer, while the phytoplankton became the dominant source of organic matter in the water column. The epibacterial populations in the water column and at the boundary showed almost the same seasonal fluctuation in attachment and detachment rates. However, bacterial growth rates did not show the same seasonal fluctuation, and annual average growth rates on the glass slides were all lower than that of bacterioplankton (free-living bacteria in water) in the water column.  相似文献   

Narrower grid structure of artificial reef enhances initial survival of in situ settled coral     

Suzuki G  Kai S  Yamashita H  Suzuki K  Iehisa Y  Hayashibara T 《Marine pollution bulletin》2011,62(12):2803-2812

The initial factors that cause a decline in the survival of in situ settled corals remain poorly understood. In this study, we demonstrated through field experiments that the design of artificial grid plates may influence the initial survival of Acropora corals, with narrower grids being the most effective. In fact, grid plates with a 2.5-cm mesh presented the highest recorded survival rate (14%) at 6 months after settlement (representing approximately 50 corals per 0.25 m² of plate). This is the first study where such high survival rates, matching those of cultures under aquarium conditions, were obtained in the field without using additional protective measures, such as guard nets against fish grazing after seeding. Therefore, our results provide a foundation for establishing new and effective coral restoration techniques for larval seeding, in parallel to clarifying the details of the early life stages of reef-building corals.  相似文献   

In situ flash X-ray observation of projectile penetration processes and crater cavity growth in porous gypsum target analogous to low-density asteroids     

Minami Yasui  Masahiko Arakawa  Sunao Hasegawa  Yukihiro Fujita  Toshihiko Kadono 《Icarus》2012,221(2):646-657

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Comparison of stable isotopes,ratios of Cl/Cl and I/I in brine and deep groundwater from the Pacific coastal region and the eastern margin of the Japan Sea     

Yasunori Mahara  Tomoko Ohta  Tomochika Tokunaga  Hiroyuki Matsuzaki  Eiji Nakata  Yuki Miyamoto  Yukihiro Mizuochi  Toshiharu Tashiro  Masahiro Ono  Toshifumi Igarashi  Keisuke Nagao 《Applied Geochemistry》2012

Fifty-three samples, including brines associated with oil and natural gas reservoirs and groundwater samples from deep boreholes, were collected from the Pacific and Japan Sea coastal regions in Japan. The ¹²⁹I/¹²⁷I and ³⁶Cl/Cl ratios, and stable isotopes (δD and δ¹⁸O) are compared to investigate differences related to the geotectonic settings of the two regions. The δD and δ¹⁸O data indicate that brine and groundwater from the Pacific coastal region reflect mixing of meteoric water with connate seawater in the pores of sedimentary rocks. On the other hand, brine and groundwater from the Japan Sea coastal region have been hydrothermally altered. In particular, brines associated with petroleum accumulations at Niigata and Akita showed the same isotopic characteristics as fluids found in the Kuroko deposits of the Green Tuff region in northeastern Japan. There is little difference in the ³⁶Cl/Cl ratios in brine and groundwater from the Pacific and Japan Sea coasts. Most brine and some deep groundwater, except those from the Pleistocene Kazusa Group, have already reached the average secular equilibrium ratio of 9.9 ± 2.7 × 10⁻¹⁵ for their mudstone and sandstone reservoirs. There was no correlation between the ³⁶Cl/Cl ratios and differences in geotectonic setting between the Pacific and the Japan Sea coast. The molar I/Br ratio suggests that the I in all of water samples was of biogenic origin. The average ¹²⁹I/¹²⁷I ratio was 290 ± 130 × 10⁻¹⁵ to 294 ± 105 × 10⁻¹⁵ in both regions, showing no relationship to the different geotectonic settings. The uncontaminated brine and groundwater samples are likely to have retained the original ¹²⁹I/¹²⁷I ratios of marine I released from the old organic matter stored in sedimentary rock.  相似文献   

The stability and equation of state for the cotunnite phase of TiO2 up to 70 GPa     

Daisuke Nishio-Hamane  Asa Shimizu  Ritsuko Nakahira  Ken Niwa  Asami Sano-Furukawa  Taku Okada  Takehiko Yagi  Takumi Kikegawa 《Physics and Chemistry of Minerals》2010,37(3):129-136

The stability and equation of state for the cotunnite phase in TiO₂ were investigated up to a pressure of about 70 GPa by high-pressure in situ X-ray diffraction measurements using a laser-heated diamond anvil cell. The transition sequence under high pressure was rutile → α-PbO₂ phase → baddeleyite phase → OI phase → cotunnite phase with increasing pressure. The cotunnite phase was the most stable phase at pressures from 40 GPa to at least 70 GPa. The equation of state parameters for the cotunnite phase were established on the platinum scale using the volume data at pressures of 37–68 GPa after laser annealing, in which the St value, an indicator of the magnitude of the uniaxial stress component in the samples, indicates that these measurements were performed under quasi-hydrostatic conditions. The third-order Birch-Murnaghan equation of state at K ₀′ = 4.25 yields V ₀ = 15.14(5) cm³/mol and K ₀ = 294(9), and the second-order Birch-Murnaghan equation of state yields V ₀ = 15.11(5) cm³/mol and K ₀ = 306(9). Therefore, we conclude that the bulk modulus for the cotunnite phase is not comparable to that of diamond.  相似文献   

Effects of low pCO2 conditions on sea urchin larval size     

Ryota Suwa  Yukihiro Nojiri  Tsuneo Ono  Yoshihisa Shirayama 《Marine Ecology》2013,34(4):443-450

Ocean acidification results from an increase in the concentrations of atmospheric carbon dioxide (CO₂) impacts on marine calcifying species, which is predicted to become more pronounced in the future. By the end of this century, atmospheric pCO₂ levels will have doubled relative to the pre‐industrial levels of 280 ppm. However, the effects of pre‐industrial pCO₂ levels on marine organisms remain largely unknown. In this study, we investigated the effects of pre‐industrial pCO₂ conditions on the size of the pluteus larvae of sea urchins, which are known to be vulnerable to ocean acidification. The larval size of Hemicentrotus pulcherrimus significantly increased when reared at pre‐industrial pCO₂ level relative to the present one, and the size of Anthocidaris crassispina larvae decreased as the pCO₂ levels increased from the pre‐industrial level to the near future ones after 3 days' exposure. In this study, it is suggested that echinoid larvae responded to pre‐industrial pCO₂ levels. Ocean acidification may be affecting some sensitive marine calcifiers even at the present pCO₂ level.  相似文献   

Distribution of fluoride in waters of Tokyo Bay     

Yasushi Kitano  Yukihiro Furukawa 《Journal of Oceanography》1972,28(3):121-125

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Geoengineering techniques used in the construction of underground openings in jointed rocks     

Kenji Aoki  Yukihiro Shiogama 《Engineering Geology》1993,35(3-4):167-173

Aoki, K. and Shiogama, Y., 1993. Geoengineering techniques used in the construction of underground openings in jointed rocks. In: M. Langer, K. Hoshino and K. Aoki (Editors), Engineering Geology in the Utilization of Underground Space.Eng. Geol., 35: 167–173.

Examples of underground openings used for pumped storage hydroelectric power stations and storage facilities for crude oil in Japan are described. In these examples the observational construction technique is important to compensate for missing data in the preliminary surveys. Some new drilling and assessment techniques that have been developed are also introduced.  相似文献   

Development of density measurement for metals at high pressures and high temperatures using X-ray absorption imaging combined with externally heated diamond anvil cell     

Yusaku Takubo  Hidenori Terasaki  Tadashi Kondo  Shingo Mitai  Seiji Kamada  Takumi Kikegawa  Akihiko Machida 《Comptes Rendus Geoscience》2019,351(2-3):182-189

A technique for density measurement under high pressure and high temperature was developed using the X-ray absorption imaging method combined with an externally heated diamond anvil cell. The densities of solid and liquid In were measured in the pressure and temperature ranges of 3.2–18.6 GPa and 294–719 K. The densities obtained through the X-ray absorption imaging method were in good agreement (less than 2.0% difference) with those obtained through X-ray diffraction. Based on the measured density, the isothermal bulk modulus of solid In is determined as 48.0 ± 1.1?40.9 ± 0.8 GPa at 500 K, assuming K′ = 4 to 6. The compression curve of liquid In approaches that of solid In at higher pressures and does not cross over the solid compression curve in the measurement range. The present technique enables us to determine the densities of both solids and liquids precisely in a wide pressure and temperature range.  相似文献   

Iron-water reaction at high pressure and temperature, and hydrogen transport into the core     

Eiji Ohtani  Naohisa Hirao  Tadashi Kondo  Masayoshi Ito  Takumi Kikegawa 《Physics and Chemistry of Minerals》2005,32(1):77-82

We observed a direct reaction of metallic iron with water to form iron hydride and iron oxide, 3Fe + H₂O–>2FeH_x + FeO, at pressures from 6 GPa to 84 GPa and temperatures above 1,000 K in diamond anvil cell (DAC). Iron hydride is dhcpFeH_x or -FeH_x, and iron oxide has the rhombohedral or B1 structure at pressures at least up to 37 GPa. The formation of an assembly composed of dhcpFeH_x and FeO with the B8 structure was observed at 84 GPa. In primordial Earth, water formed by dehydration of the low temperature primitive materials reacts with metallic iron in the high temperature component to form iron hydride FeH_x and iron oxide FeO. The former would be incorporated in the iron forming the core. Thus hydrogen could be an important element of the Earths core. This reaction would be essential for transport of hydrogen into the core in the accretion stage of the Earth.  相似文献