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11.
Takahiro Kuribayashi Asami Sano-Furukawa Toshiro Nagase 《Physics and Chemistry of Minerals》2014,41(4):303-312
Pressure-induced phase transition of δ-AlOOH was confirmed between 6.1 and 8.2 GPa by using a single-crystal synchrotron X-ray diffraction method. The phase transition is reversible and unquenchable. Results from analysis of the distribution of X-ray diffraction intensities at 8.2 GPa reveal an additional systematic, absence of k + l odd for 0kl in comparison with h + l odd for h0l observed prior to the phase transition (space group, P21 nm). The space group of the post-transition phase should be Pnnm or Pnn2 to satisfy the systematic absence rule. Crystal structure refinements of the post-transition phase conducted for the three models (Pnnm, Pnn2, and P21 nm) indicate that the space group of the post-transition phase is Pnnm. The O–O distance of hydrogen bond in the post-transition phase at 8.2 GPa is 2.439(6) Å and is significantly longer than the predicted distance (2.366 Å) of the hydrogen bond symmetrization in δ-AlOOH. The H distribution in the post-transition phase would display a fully disordered hydrogen bond pattern. 相似文献
12.
The waveform inversion method described in Woodhouse & Dziewonski (1984) was modified to retrieve regional scale 3-D heterogeneities by using the minor arc part of seismograms. The lateral heterogeneities are expanded horizontally into blocks (10°× 10°) and radially into Legendre polynomials up to order 3 (0–670 km), and thus the results show much fine details of lateral variation than previous global scale studies. We assumed that the heterogeneities produce the perturbation of eigenfrequencies which are the minor arc average of local eigenfrequency shift. We applied the method to the upper mantle beneath the Atlantic Ocean and its environments. Care was taken about the weighting of the data set. We found that the fit of each seismogram became better when the weighting of each seismogram is proportional to the inverse of initial data residuals. Resolution is good in the triangular region surrounded by South America, Europe, and North America. Resolution is not good in the South Atlantic because of the poor path coverage. Depth resolution is not clear, because of the use of Legendre polynomials, though the results suggest a broad half-width of the order of 200 km or more. We found some similarities between previous global studies and our results. For example, low velocities beneath the East Pacific Rise, Chile Rise and Azores triple junction and a high velocity Canadian shield are obtained. However, there are also differences; the high-velocity zone beneath the Brazilian shield at shallow depth is not a prominent feature in this study. Instead, we found a somewhat unexpected feature near the Romanche and Vema fracture zones where shallow positive anomalies exist. Smoothed results calculated by the spherical harmonic expansion are also shown for the purpose of comparison with global studies. 相似文献
13.
Sei-Ichi Saitoh Denzo Inagake Kousei Sasaoka Joji Ishizaka Yukihiro Nakame Toshiro Saino 《Journal of Oceanography》1998,54(5):495-508
Synoptic ship and satellite observations were performed of the Kuroshio warm-core ring (KWCR) 93A and its adjacent waters,
off Sanriku, northwestern North Pacific, between early April and late June 1997. The temporal and spatial distribution of
chlorophylla (Chl-a) and sea surface temperature in the study area were analyzed using data from ADEOS Ocean Color and Temperature Scanner (OCTS)
and NOAA Advanced Very High Resolution Radiometer (AVHRR). The objective of this study was to describe the temporal and spatial
variability of the spring bloom and understand its relationship with the changes in the hydrographic structure of these waters
in and around KWCR 93A. The maximum value of Chl-a concentration in the ring was less than 1 mg/m3 during April. The spring bloom in the ring occurred early in May and the relatively high maximum (>1.0 mg/m3) continued from early in May to mid-June. In late June, a ship-observed surface Chl-a concentration of less than 0.4 mg/m3 suggests that the spring bloom had already declined in and around KWCR 93A. Double spiral structures of warm and cold streamers
appeared from late April to mid-May, which may have an influence on the occurrence of the spring bloom in and around the ring.
In this episodic event, the warm streamer can maintain the available potential energy of the ring and the strength of upwelling
around the ring. The cold streamer provided water with a high Chl-a concentration to the surface layer of the ring. In order to understand the temporal and spatial variability of Chl-a distribution in the ring, the behavior of the warm and cold streamers needs to be taken into consideration. 相似文献
14.
Toshiro Saino Shaoling Shang Yoshihisa Mino Koji Suzuki Hideaki Nomura Sei-ichi Saitoh Hideo Miyake Toshiyuki Masuzawa Koh Harada 《Journal of Oceanography》1998,54(5):583-592
A sediment trap experiment was carried out in conjunction with an over flight of Ocean Color Temperature Scanner (OCTS) on
board Advanced Earth Observing Satellite (ADEOS) at 40°N, 143°E off Sanriku in April to May 1997. Short term variability of
particle fluxes was examined at depths of 450 m and 600 m from April 6 to May 1 with a sampling interval of two days, and
at 450 m with one day interval from 2nd to 10th May. Daily averaged mass flux at 450 m and 600 m was 815 mg m−2d−1 and 862 mg m−2d−1, respectively. A sharp increase in mass flux was observed during the period from April 26 to April 29 with the highest mass
flux of 8 g m−2d−1. About 85% of the total mass flux for the entire duration (26 days) was collected within these 4 days. Trapped material during
the peak flux period was mainly composed of diatoms dominated byThalassiosira spp. and resting spores ofChaetoceros spp. This suggested that the peak flux was the result of (a) diatom bloom(s) in the euphotic column. Current meter records
at 420 m showed that on April 26 and 27, the period when the peak flux was observed, the southwestward current had diminished
in strength and changed its direction northwestward. Low current speeds appeared to have enhanced trap efficiency to help
form the peak flux. A time series of OCTS Intensive-LAC (Local Area Coverage: Region B) images from mid-March to early May
was examined todetect phytoplankton bloom(s). In the March 26th Chl image, high concentration region was restricted to the
southwest off Cape Erimo, but spread around the warm core ring (WCR) 93A by April 10. East of the WCR93A, high Chl concentration
remained steady until May, but to the west of the WCR93A, Chl decreased rapidly before the 19th of April. From this observation
we suspect that the peak flux observed at the end of April originated from a bloom, which ceased on the 17th or 18th of April,
in the region north of 40°N and west of 143°E. Taking the current meter records into account, the source region for the trapped
material is most likely around southwest of the Cape Erimo. 相似文献
15.
Taxonomic composition, size composition, standing stock, and chemical composition of mesozooplankton were determined to examine
the contribution of their fecal pellets to the vertical flux of organic carbon at the outside, the edge, and the center of
the warm core ring. The warm core ring significantly affects not only their taxonomic composition and size composition but
also their standing stock and chemical composition. The zooplankton at the center of the warm core ring was characterized
by the absence of carnivores at the top of the size-trophic relation and filter feeding planktonic tunicates at the bottom.
Zooplankton carbon biomass at the outside of the ring was one-third less than that at the center of the ring. The vertical
flux of fecal pellets obtained from the pellet volume (12.3 mgC m−2d−1) contributed 19 to 96% of the flux (13 to 64 mgC m−2 d−1) estimated from the body carbon and the fecal pellet production rate. The estimated flux of fecal pellets was 6 to 27% of
vertical carbon flux (236 mgC m−2d−1) determined by the sediment traps. Microscopic determination of fecal pellets and plankton in the sediment trap samples indicated
high grazing activity during the sinking process. Those observations might suggest that particles other than fecal pellets
contributed significantly to the vertical carbon flux and fecal pellets were settled directly without loss or being recycled
within the surface mixed layer. 相似文献
16.
Chlorophyll-specific absorption coefficients and pigments of phytoplankton off Sanriku, northwestern North Pacific 总被引:4,自引:0,他引:4
Koji Suzuki Motoaki Kishino Kousei Sasaoka Sei-Ichi Saitoh Toshiro Saino 《Journal of Oceanography》1998,54(5):517-526
The variety in shape and magnitude of thein vivo chlorophyll-specific absorption spectra of phytoplankton was investigated in relation to differences in pigment composition
off Sanriku, northwestern North Pacific. Site-to-site variations of the absorption coefficients,a
ph
* (λ), and pigment composition were clearly observed. At warm-streamer stations, higher values ofa
ph
* (440) anda
ph
* (650) were found with relatively high concentrations of chlorophyllb (a green algae marker). At stations located in the Oyashio water (cold streamer),a
ph
* (440) values were lower and fucoxanthin (a diatom marker) concentrations were higher, compared to the other stations. The
peak in the absorption spectra at the Oyashio stations was shifted toward shorter wavelengths, which was probably due to the
presence of phaeopigments. In a Kuroshio warm-core ring, the magnitude ofa
ph
* (440) was in between those at the warm-streamer and Oyashio stations, and the diagnostic pigment was peridinin (a dinoflagellate
marker). These findings indicated that major differences in phytoplankton absorption spectra of each water mass were a result
of differences in the phytoplankton pigment composition of each water mass, which was probably related to the phytoplankton
community. 相似文献
17.
Effects of bottom bracings on torsional dynamic characteristics of horizontally curved twin I-girder bridges with different curvatures 总被引:1,自引:0,他引:1
Curved twin I-girder bridges (CTIGBs) have low torsional stiffness that makes them vulnerable to dynamic loads.This study investigates the effects of bottom bracings on the torsional dynamic characteri... 相似文献
18.
This study is intended to evaluate the influence of dynamic bridge-train interaction (BTI) on the seismic response of the
Shinkansen system in Japan under moderate earthquakes. An analytical approach to simulate the seismic response of the BTI
system is developed. In this approach, the behavior of the bridge structure is assumed to be within the elastic range under
moderate ground motions. A bullet train car model idealized as a sprung-mass system is established. The viaduct is modeled
with 3D finite elements. The BTI analysis algorithm is verified by comparing the analytical and experimental results. The
seismic analysis is validated through comparison with a general program. Then, the seismic responses of the BTI system are
simulated and evaluated. Some useful conclusions are drawn, indicating the importance of a proper consideration of the dynamic
BTI in seismic design. 相似文献
19.
Tetsuichi Fujiki Kazuhiko Matsumoto Shuichi Watanabe Takuji Hosaka Toshiro Saino 《Journal of Oceanography》2011,67(3):295-303
We deployed a profiling buoy system incorporating a fast repetition rate fluorometer in the western subarctic Pacific and
carried out time-series observations of phytoplankton productivity from 9 June to 15 July 2006. The chlorophyll a (Chl a) biomass integrated over the euphotic layer was as high as 45–50 mg Chl a m−2 in the middle of June and remained in the 30–40 mg Chl a m−2 range during the rest of observation period; day-to-day variation in Chl a biomass was relatively small. The daily net primary productivity integrated over the euphotic layer ranged from 144 to 919 mg C m−2 day−1 and varied greatly, depending more on insolation rather than Chl a biomass. In addition, we found that part of primary production was exported to a 150-m depth within 2 days, indicating that
the variations in primary productivity quickly influenced the organic carbon flux from the upper ocean. Our results suggest
that the short-term variability in primary productivity is one of the key factors controlling the carbon cycle in the surface
ocean in the western subarctic Pacific. 相似文献
20.
The sediment parameters and nematode assemblages in the intertidal zone of the Hichirippu shallow lagoon, Hokkaido, Japan, were investigated. The objectives of this study were to observe the seasonal variation in the nematodes in the sediment, and to investigate the relationships between the nematodes and environmental factors. Samples were collected bi-monthly from five stations on the tidal flat from April 2003 to February 2004. It was found that the sediment parameters (Chl a concentration, AVS, TOC and TN contents) varied throughout the 10-month study. Fifty-four species of nematodes were found in the study area. The density and biomass of the nematodes varied in accordance with the sediment temperature during the sampling period. In this study, there was a seasonal variation in the nematode assemblage found in the intertidal zone of this shallow lagoon. The important factors affecting this variation were sediment temperature, and food competition among the nematodes themselves. The seasonal variation of the nematode also showed a relationship with the Chl a concentration in the sediment during the sampling period. 相似文献