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31.
An array of sediment traps was deployed for the analysis of the pattern of particulate organic carbon (POC) supply to the sea bottom in April, May and July 1988 at the mouth of Otsuchi Bay (about 80 m depth), Northeastern Japan.On the basis of a simple two-component mixing model using stable carbon isotope ratios, the POC flux was separated into marine planktonic and terrestrial components. Both the planktonic and terrestrial POC fluxes had maximum values at 30 m above the sea bottom throughout the three experiments. The planktonic POC flux showed a significant decrease with depth between 30 m and 10 m or 5 m above the bottom. Vertical supply of the planktonic POC and supply of the resuspended planktonic POC were estimated on the basis of regression lines between water depth and the planktonic POC flux in the depth range where the flux decreases with depth.Vertical supply of the planktonic POC and supply of the resuspended planktonic POC to the sea bottom were largest in May (52.1 mgC m–2 d–1 and 19.5 mgC m–2 d–1 at 5 m above the sea bottom), and horizontal supplies of the terrestrial POC were almost constant (31.9±3.5 mgC m–2 d–1 at 5 m above the bottom) throughout the three experiments. 相似文献
32.
Quantitative samples of sediments and macrobenthos were collected with a spade corer to reveal the relationships between macrobenthos communities and bottom environments. Twenty-five stations were established along a transect in the lower sublittoral and bathyal zones between the depths of 120 m and 2,600 m off Sanriku, the northeastern coast of the Japanese mainland, Northwestern Pacific.These stations were clustered into two groups on the basis of the principal component analysis of environmental factors and topographic features of the study area. The clustering of stations corresponded to that based on polychaete species composition.The biomass of macrobenthos followed two different patterns in two oceanographic environments; the first trend is found from the shelf to the seaward margin of the deep-sea terrace where macrobenthos biomass did not depend on depth, and the second trend on the lower continental slope, where biomass decreased exponentially with depth as Rowe's formula predicted. The density of macrobenthos showed a simple exponential decrease with depth over the two ecological zones. The data of stable carbon isotope ratio of organic matter in the sediments and topographic features suggested that the pattern of the biomass of macrobenthos corresponded with two different modes of food supply to the deep-sea bottom communities,i.e., vertical transport of the surface products and horizontal transport of food materials. 相似文献
33.
We have used density functional theory to investigate the stability of MgAl2O4 polymorphs under pressure. Our results can reasonably explain the transition sequence of MgAl2O4 polymorphs observed in previous experiments. The spinel phase (stable at ambient conditions) dissociates into periclase and
corundum at 14 GPa. With increasing pressure, a phase change from the two oxides to a calcium-ferrite phase occurs, and finally
transforms to a calcium-titanate phase at 68 GPa. The calcium-titanate phase is stable up to at least 150 GPa, and we did
not observe a stability field for a hexagonal phase or periclase + Rh2O3(II)-type Al2O3. The bulk moduli of the phases calculated in this study are in good agreement with those measured in high-pressure experiments.
Our results differ from those of a previous study using similar methods. We attribute this inconsistency to an incomplete
optimization of a cell shape and ionic positions at high pressures in the previous calculations. 相似文献
34.
Shigeaki Ono Artem R. Oganov John P. Brodholt Lidunka Vo
adlo Ian G. Wood Andriy Lyakhov Colin W. Glass Alexander S. Ct G. David Price 《Earth and Planetary Science Letters》2008,272(1-2):481-487
Iron sulfide (FeS) was investigated using first-principles calculations up to a pressure of 400 GPa. A number of new phase transitions were found. An antiferromagnetic MnP-type structure, FeS II, was confirmed to be stable at low pressures, whereas at high pressures (40–135 GPa) we find a new stable phase, with a non-magnetic MnP-type structure, FeS VI. The observed first-order change in the cell shape between the two phases can be explained by the difference in magnetic configurations. The calculated cell parameters, atomic coordinates, and bulk modulus of non-magnetic MnP-type phase are consistent with those determined from experiment. The upper pressure limit of the stability of the non-magnetic MnP-type phase was calculated to be 135 GPa. A hitherto unsuspected phase transition from the non-magnetic MnP-type to a phase with Pmmn symmetry, FeS VII, was identified using the evolutionary crystal structure prediction (USPEX) method. The structure of the Pmmn phase has no known analogues, but can be described as a distortion of the NaCl-type structure. The Pmmn phase with the distorted NaCl-type structure is stable from 135 GPa at least up to 400 GPa. According to previous experiments and the present study, the transition sequence of FeS at low temperatures is as follows: troilite ➔ antiferromagnetic MnP-type phase ➔ monoclinic phase ➔ non-magnetic MnP-type phase ➔ Pmmn phase. The calculated volume reduction from the monoclinic to the non-magnetic MnP-type phase is 1.0% at 40 GPa, which is in good agreement with experimental observations. The calculated volume reduction from the non-magnetic MnP-type to the Pmmn phase is 3.7% at 135 GPa. 相似文献
35.
The genetic structure of a population of the Japanese turban shell, Turbo (Batillus) cornutus at Sata-Misaki Point, on the southern coast of Kyushu Island, was determined on the basis of nucleotide sequences of mitochondrial DNA and compared with that of a population of the western coast of Kyushu Island. The significant genetic differentiation between these two populations suggests that the courses of the warm currents along the coast of the Kyushu Island have been relatively stable after the divergence between the two genetically distant groups of the Japanese turban shell, which was estimated to have occurred during some period in Pleistocene. 相似文献
36.
Sakiko Orui Sakaguchi Kiyotaka Takishita Tomoaki Goto Haruka Shibata Shigeaki Kojima Shinji Tsuchida Hiroshi Kitazato Katsunori Fujikura 《Journal of Oceanography》2014,70(5):457-462
Body size, age, and population genetic structure of the broadbanded thornyhead Sebastolobus macrochir inhabiting areas off the Pacific coast of Tohoku and off Abashiri, the Sea of Okhotsk, Japan, were analyzed. On the basis of significant differences in body size (growth) between certain year classes at Tohoku and Abashiri, it appears that S. macrochir does not migrate extensively after settlement and subsists on food within the settled environment. Meanwhile, no genetic isolation was observed between the populations at these two sites. Thus, it is highly likely that its pelagic egg balloons, larvae, and juveniles widely disperse and migrate before settlement. 相似文献
37.
Hydrographic conditions in the Tsushima Strait revisited 总被引:1,自引:1,他引:0
Long-term averaged temperature and salinity distributions in the Tsushima Strait are investigated on the basis of a concurrent
dataset of the eastern and western channels during 1971–2000. Both temperature and salinity show a clear seasonal variation
with weak and strong stratifications in December–April and June–October, respectively. The largest standard deviations occur
in summer around the thermocline for temperature and in the surface layer for salinity. This indicates large interannual variability
in the development of a thermocline and low salinity water advection from the East China Sea. The water masses in both channels
are distinctly different from each other; the water in the western channel is generally colder and fresher than that in the
eastern channel throughout the year. Baroclinic transport based on the density distributions shows a seasonal variation with
a single peak in August for the eastern channel and double peaks in April and August for the western channel. However, this
cannot explain the seasonal variation in the total volume transport estimated from the sea level differences across the channels.
The spatial distribution of baroclinic transport shows a year-round negative transport towards the East China Sea behind the
Iki Island in the eastern part of the eastern channel. This negative transport reflects the baroclinic structure between the
offshore Tsushima Current Water and cold coastal water. The corresponding southwestward currents are found in both Acoustic
Doppler Current Profiler (ADCP) and high frequency (HF) radars observations. 相似文献
38.
Evaporation from the forest floor (EFF) in a deciduous broadleaf forest was measured using microlysimeter and closed‐chamber systems. The microlysimeter was used at six points in the experimental basin, and measurements gave different EFF values at different points. This could be attributed to the local photoenvironment of each sampling point, rather than to litter conditions, if the spatial variation in air temperature (Ta) or vapour pressure deficit (VPD) at the forest floor was small within this basin. A detachable microlysimeter measured condensation in the litter layer during the night, indicating that the litter layer, as well as the mulch layer, played a role in preventing evaporation from the soil layer. The closed‐chamber system made it possible to continuously measure long‐term EFF. EFF was closely related to VPD; even during the night, when solar radiation was zero, EFF amounted to 14·0% of the daily EFF. The daily EFF was 0·20 ± 0·13 mm day?1 during the study period, with two seasonal peaks: in late spring (0·31 mm day?1 in April) and early fall (0·22 mm day?1 in September). The former peak has been reported from two deciduous forests in Japan and is strongly related to the solar radiation reaching the forest floor when the trees are dormant. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
39.
40.
Shigeaki?OnoEmail author Kenichi?Funakoshi Yoichi?Nakajima Yoshinori?Tange Tomoo?Katsura 《Contributions to Mineralogy and Petrology》2004,147(4):505-509
Abstract In situ observations of the zircon-reidite transition in ZrSiO4 were carried out using a multianvil high-pressure apparatus and synchrotron radiation. The phase boundary between zircon and reidite was determined to be P (GPa) = 8.5+0.0017×(T-1200) (K) for temperatures between 1100–1900 K. When subducted slabs, including igneous rocks and sediments, descend into the upper mantle, the zircon in the subducted slab transforms into reidite at pressures of about 9 GPa, corresponding to a depth of 270 km. Reidite found in an upper Eocene impact ejecta layer in marine sediments is thought to have been transformed from zircon by a shock event. The peak pressure generated by the shock event in this occurrence is estimated to be higher than 8 GPa.Editorial responsibility: J. Hoefs 相似文献