Importance of intracellular Fe pools on growth of marine diatoms by using unialgal cultures and on the Oyashio region phytoplankton community during spring     

Koji Sugie  Kenshi Kuma  Satoshi Fujita  Satomi Ushizaka  Koji Suzuki  Tsutomu Ikeda 《Journal of Oceanography》2011,67(2):183-196

We report on the ability for luxury Fe uptake and the potential for growth utilizing intracellular Fe pools for 4 coastal centric diatom isolates and in situ phytoplankton assemblages, mainly composed of diatoms. Iron uptake of the diatom isolates and natural phytoplankton assemblages in the Oyashio region during spring blooms were prevented by adding hydroxamate siderophore desferrioxamine B (DFB). After the addition of DFB, intracellular Fe in the diatom isolates supported 2.4–4.2 cell divisions with 1.2–2.6 Chl a doublings. The intracellular Fe was primarily used for cell generation rather than Chl a production, leading to a reduction in the Chl a cell quota in the Fe-starved cells with time. The metabolic properties of the Fe-starved cells with their cell morphologies were different among species or genera. An on-deck incubation experiment also exhibited 1.9 cell divisions and 0.81 Chl a doublings of phytoplankton after the addition of DFB, also indicating the preference of cell generation over Chl a production. A decrease in the level of cellular Chl a, a main light-harvesting pigment in Fe-starved diatoms, may become a superior survival strategy to protect the cells from high irradiance that can cause photo-oxidative damages through photosynthesis. Such relatively low-Fe with high-light conditions could often occur in surface waters of the Oyashio region from spring to summer.  相似文献   

Interannual variability of CFC-11 absorption by the ocean: an offline model study     

Vinu Valsala  Hayyan M. Alsibai  Motoyoshi Ikeda  Shamil Maksyutov 《Climate Dynamics》2011,36(7-8):1435-1452

The global ocean Chlorofluorocarbon (CFC-11) was simulated in an offline model driven by re-analysis ocean currents in order to identify the mechanisms of interannual to interdecadal variability of air?Csea CFC fluxes. The model was forced with the observed anthropogenic perturbations of atmospheric CFC-11 from the post industrial period (1938) following the OCMIP-II flux protocols along with the observed winds from 1960 to 1999 in the formulation of surface gas exchanges. The model ocean CFC-11 inventories, at the end of 1990s, accounted approximately 1% of the total atmospheric CFC-11, which is consistent with the corresponding observations. The mid-to-high latitude oceans were venue for strong (weak) oceanic sinks (sources) of CFC-11 during the winter (summer) months. The Southern Ocean (south of 40°S) and the North Atlantic (north of 35°N) provided two largest sinks of CFC-11, through which 31.4 and 14.6% of the global ocean CFC-11 entered, respectively. The eastern tropical Pacific Ocean exhibited large interannual variability of CFC-11 flux with a strong (weak) sink during La Ni?a (El Ni?o) years and represented 36% of the global CFC-11 flux variability. The North Atlantic and Southern Ocean were found as regions of large sink efficiency: a capacity to sink more CFC than outsource, although it reduced by 80 and 70%, respectively, in the last 40?years compared to 1960. The sink to source ratio of global ocean CFC-11 fluxes were reduced from 90 to 50% in the last 40?years. This indicates a saturation of CFC in the above-thermocline subsurface that makes the upper ocean less efficient in absorbing CFC in recent decades. A positive trend in CFC sink is now limited to the Southern Ocean, central tropical Pacific and western boundary current regions which possess active upwelling of old water with long time since last atmospheric contact. However, a globally averaged trend was a reduced CFC-11 sink, by emitting 30% of the total ocean CFC-11 that was absorbed during last 40?years.  相似文献   

Investigating the vibration properties of integrated ceiling systems considering interactions with surrounding equipment     

Liangjie Qi  Keiichiro Kunitomo  Masahiro Kurata  Yoshiki Ikeda 《地震工程与结构动力学》2020,49(8):772-793

Studies on recent earthquakes highlighted that buildings with minimal structural damage still suffer from extensive damage and failure of nonstructural components. The dropping and damage of suspended ceiling systems, which typically consist of acceleration-sensitive nonstructural elements, resulted in lengthy functional disruptions and extended recovery time. This article experimentally and analytically examined the vibration properties of an integrated ceiling system considering the interactions with surrounding electrical equipment. The theoretical stiffness and corresponding frequency of electrical equipment were initially derived and then verified by subsequent vibration tests and numerical analyses. The seismic performance of the air conditioner (AC) was evaluated with different installment configurations based on design spectra and floor response spectra. Vibration tests of the suspended integrated ceiling system considering the interactions with surrounding equipment showed that the inclusion of peripheral constraints increased the first horizontal vibration frequency of the ceiling system by a factor of approximately 6. The natural frequencies of all components in the integrated ceiling system were almost identical, which was attributed to the coupled behavior between the ceiling panels and surrounding equipment, emphasizing the effect of interactions between adjacent components during dynamic analysis. Based on the above experimental investigation, an associated numerical model of the integrated ceiling system was created. Finally, corresponding parametric studies that included the interactions with surrounding equipment, reinforcing braces of ACs and strengthening members at the rise-up location between two elevations were performed.  相似文献   

Managing and bridging communities in temporary housing: case of the Great East Japan Earthquake and Tsunami in Kesennuma City,Japan     

Yasutaka Ueda  Rajib Shaw 《Natural Hazards》2016,80(1):567-587

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Metamorphic condition of a regional metamorphic complex in the Omuta district in northern Kyushu,southwest Japan          下载免费PDF全文

Takeshi Ikeda  Kazuhiro Miyazaki  Hirohisa Matsuura 《Island Arc》2017,26(5)

A high‐temperature (T) metamorphic complex occurs in the Omuta district, northern Kyushu, Japan. Three metamorphic zones are defined based on pelitic mineral assemblage, i.e. chlorite–biotite zone, muscovite–andalusite zone and sillimanite–K‐feldspar zone with ascending metamorphic grade from north to south. Two isograds trend approximately east–west, which is oblique to the boundary between the metamorphic complex and the Tamana Granodiorite located on the southeast. The metamorphic condition of two pelitic rocks that occur in the muscovite–andalusite zone and sillimanite–K‐feldspar zone are estimated as 510 ±30 °C, 300 ±60 MPa and 720 ±30 °C, 620 ±60 MPa, respectively. Thermodynamic consideration reveals that use of the same geothermobarometer enables precise determination of the difference in pressure between the samples as 320 ±10 MPa. This indicates that the pelitic samples were metamorphosed at different depth by 11–12 km that is significantly larger than the geographic distance of 6.8 km between the sample localities. This also suggests that crustal thinning took place after the high‐T metamorphism. The high‐T metamorphic complex is, therefore, not of static contact metamorphism but of dynamic regional metamorphism. The present result combined with petrological and chronological similarities implies that this complex suffered the regional Ryoke metamorphism.  相似文献   

A three-dimensional ocean general circulation model for mesoscale eddies——Ⅱ Diagnostic analysis     

Wang Ji  Moto Ikeda 《海洋学报(英文版)》1997,16(1):29-43

A three-dimensional density field associated with mesoscaie unstable waves generated by the 3-D, primitive-equation model (Wang and Ikeda, 1996) is provided to the quasi-geostrophic pressure tendency and ω-equations, and to the (ageostrophic) Q-vector equation. Diagnostic analyses, analogous to the approaches in meteorology: ω-equation and Q-vector method, are for the first time developed to examine the mesoscaie dynamical processes and mechanisms of the unstable waves propagating in the mid-latitude ocean. The weaknesses and strengths of these two diagnostic approaches are evaluated and compared to the model results. The Q-vector method is then recommended to diagnose the vertical motion associated with the mesoscaie dynamics from a hydrographic CTD (conductivity-temperature-depth) array, while the quasi-geostrophic equations produce some small-scale features (errors) in the diagnosed fields.  相似文献   

Assimilated carbon budget for the hyperiid amphipodThemisto japonica (bovallius) from the Japan sea as influenced by temperature     

Tsutomu Ikeda 《Journal of Oceanography》1991,47(1):7-16

Using a growth model based on moult number, the assimilated carbon budget was constructed forThemisto japonica growing from the specimens just released from the marsupium to mature adults at 1–15°C. As budget parameters, growth (G), metabolism (Me), moult (Mo), and reproduction (Re) were measured and assimilation (A) was estimated as the sum of these four parameters (A=G+Me +Mo +Re). The results of the lifetime budget indicated that among these parameters the greatest allocation ofA was toMe (70–83%). Lifetime expenditure of carbon forMe was the least at 7°C, andMe increased with either increase or decrease of the temperature from 7°C. A female grown to full adult size at 7°C invested 16.6 % forG, 70.2% forMe, 2.1% forMo, and 11.1% forRe of totalA. General features seen in the partition ofA toG, Me, Mo, andRe forT. japonica are similar to those of other planktonic crustaceans being reported. Considering the profound effect of temperature on the assimilated carbon budget, practical problems in defining the representative habitat temperature for diel vertical migrators likeT. japonica in the field are discussed.  相似文献   

The Role of Zooplankton in Global Ecosystem Dynamics: Comparative Studies from the World Oceans     

Valdes  Luis; Harris  Roger; Ikeda  Tsutomu; McKinnell  Skip; Peterson  William T 《ICES Journal of Marine Science》2004,61(4):441-444

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Introduction to Special Section: Kuroshio Observation, State Estimation and Prediction     

Shiro Imawaki  Hiroshi Ichikawa  Motoyoshi Ikeda  Atsuhiko Isobe  Masafumi Kamachi 《Journal of Oceanography》2004,60(2):265-268

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Kuroshio extension variability explored through assimilation of TOPEX/POSEIDON altimeter data into a quasi-geostrophic model     

Yousuke Nishihama  Motoyoshi Ikeda 《Journal of Oceanography》2007,63(6):879-895

Mesoscale features in the eastward extension of the Kuroshio were investigated using assimilation of TOPEX/POSEIDON (T/P) data into a three-layer quasi-geostrophic model. The T/P data exhibited an elongated state of the southern recirculation gyre in 1993–95 and 1997, between whose two periods the gyre had a contracted state in 1995–96. A few stationary eddies were located in the southern gyre during the contracted state. The baroclinic instability, which was indicated by the phase shift from the uppermost-to the lowest-layer anomalies toward the downstream side, was evident near the Kuroshio Extension (KE) path. Since the instability never appeared in the artificial model without bottom topography, the topographic barrier for the eastward flow in the lowest layer was a necessary condition for the instability. The instability synchronized with the transition in the western region of the KE axis from the elongated to the contracted states. This evolution was interpreted as if the baroclinic instability played some part in the KE states and was a trigger for the transition from the elongated to the contracted states.  相似文献