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21.
Ohishi Masatoshi Kaifu Norio Suzuki Hiroko Morimoto Masaki 《Astrophysics and Space Science》1986,118(1-2):405-407
A molecular spectral line survey of the title source detected 166 molecular lines from 18 interstellar molecules in the frequency ranges of 34.25–50.00, 83.50–84.50, and 86.00–91.50 GHz. For each molecule, gaussian decomposition of the velocity components in the transition profiles gave consistent radial velocity and linewidth. Rotation diagrams were drawn for each velocity component.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献
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Noriko T. Kita Hiroko Nagahara Shin Tomomura John H. Fournelle 《Geochimica et cosmochimica acta》2010,74(22):6610-6635
We report high precision SIMS oxygen three isotope analyses of 36 chondrules from some of the least equilibrated LL3 chondrites, and find systematic variations in oxygen isotope ratios with chondrule types. FeO-poor (type I) chondrules generally plot along a mass dependent fractionation line (Δ17O ∼ 0.7‰), with δ18O values lower in olivine-rich (IA) than pyroxene-rich (IB) chondrules. Data from FeO-rich (type II) chondrules show a limited range of δ18O and δ17O values at δ18O = 4.5‰, δ17O = 2.9‰, and Δ17O = 0.5‰, which is slightly 16O-enriched relative to bulk LL chondrites (Δ17O ∼ 1.3‰). Data from four chondrules show 16O-rich oxygen isotope ratios that plot near the CCAM (Carbonaceous Chondrite Anhydrous Mineral) line. Glass analyses in selected chondrules are systematically higher than co-existing minerals in both δ18O and Δ17O values, whereas high-Ca pyroxene data in the same chondrule are similar to those in olivine and pyroxene phenocrysts.Our results suggest that the LL chondrite chondrule-forming region contained two kinds of solid precursors, (1) 16O-poor precursors with Δ17O > 1.6‰ and (2) 16O-rich solid precursors derived from the same oxygen isotope reservoir as carbonaceous chondrites. Oxygen isotopes exhibited open system behavior during chondrule formation, and the interaction between the solid and ambient gas might occur as described in the following model. Significant evaporation and recondensation of solid precursors caused a large mass-dependent fractionation due to either kinetic or equilibrium isotope exchange between gas and solid to form type IA chondrules with higher bulk Mg/Si ratios. Type II chondrules formed under elevated dust/gas ratios and with water ice in the precursors, in which the ambient H2O gas homogenized chondrule melts by isotope exchange. Low temperature oxygen isotope exchange may have occurred between chondrule glasses and aqueous fluids with high Δ17O (∼5‰) in LL the parent body. According to our model, oxygen isotope ratios of chondrules were strongly influenced by the local solid precursors in the proto-planetary disk and the ambient gas during chondrule melting events. 相似文献
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Abstract— The role of oxygen isotope exchange during evaporation and condensation of silicate melt is quantitatively evaluated. Silicate dusts instantaneously heated above liquidus temperature are assumed to cool in gas and experience partial evaporation and subsequent recondensation. The results show that isotopic exchange effectively suppresses mass‐dependent O‐isotope fractionation even if the degree of evaporation is large, which is the fundamental difference from the case without isotopic exchange. The final composition of silicate melt strongly depends on the initial abundance of oxygen in the ambient gas relative to that in silicate dust, but not on the cooling rate of the system. The model was applied to O‐isotope evolution of silicate melts in isotopically distinct gas of the protoplanetary disk. It was found that deviation from a straight mixing line toward the δ18O‐rich side on the three‐oxygen isotope diagram is inevitable when mass‐dependent fractionation and isotopic exchange take place simultaneously; the degree of deviation depends on the abundance of oxygen in an ambient gas and isotopic exchange efficiency. The model is applied to explain O‐isotopic compositions of igneous CAIs and chondrules. 相似文献
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Hiroko Okawachi Susumu Ohtsuka Norshida Binti Ismail B. A. Venmathi Maran Kazuo Ogawa 《Ocean Science Journal》2012,47(3):181-187
The seasonal occurrence and microhabitat of the monogenean Udonella fugu that hyperparasitizes exclusively on adults of the caligid copepod Pseudocaligus fugu that infects the skin of the grass puffer Takifugu niphobles were investigated in the Seto Inland Sea, western Japan from November 2004 to December 2006. The udonellids occurred and bred mostly during the occurrence of P. fugu on the fish host. The average prevalence and intensity of U. fugu on P. fugu during the whole investigation were 29% and 3.6, respectively. The main attachment sites of U. fugu were the posterior side of leg 3 and the dorsal marginal side of the cephalothorax for feeding and copulation, while eggs were predominantly located on the ventral side of the urosome to avoid detachment. More attention should be paid to the ecology of U. fugu, due to recent high prevalence of P. fugu on cultured tiger puffer in western Japan. 相似文献
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Aki Ito Hiroko Sugioka Daisuke Suetsugu Hajime Shiobara Toshihiko Kanazawa Yoshio Fukao 《Marine Geophysical Researches》2012,33(3):229-238
A number of seismoacoustic T-wave events were observed between January 2003 and January 2004 by broadband ocean-bottom seismometers installed on the French Polynesia seafloor at depths of 4,000?C5,000?m, well below the conjugate depth of the SOFAR channel. Using T-wave arrival times, we located 89 T-wave events along the Pacific-Antarctic Ridge. Among these, 63 events were not detected by land-based seismic observations of the United States Geological Survey (USGS), which was nearly twice the number of earthquakes reported by the USGS in the area during the observation period. We used a simple method to estimate earthquake magnitude from T-wave energy. The magnitudes of the events unidentified by the USGS ranged from 2.3 to 5.5, whereas magnitudes of the earthquakes reported by the USGS ranged from 4.1 to 6.2. Our study suggests that T-wave observations with abyssal ocean-bottom seismometers can improve the detection of small earthquakes and help our understanding of the seismotectonics of remote oceanic areas. 相似文献
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Monitorings were conducted on DSP toxins in mid-gut gland of scallop (mouse assay), cell numbers of toxic dinoflagellate species of Dinophysis, and diarrhetic shellfish poisoning (DSP) toxins in small-sized (0.7-5 microm) plankton fraction of seawater collected from surface (0 m) and 20 m depth at a station in Mutsu Bay, Aomori Prefecture, Japan, in 2000. A specific enzyme-linked immunosorbent assay (ELISA) was employed for the analysis of DSP toxins in small-sized plankton fraction using a mouse monoclonal anti-okadaic acid antibody which recognizes okadaic acid, dinophysistoxin-1, and dinophysistoxin-3. DSP toxins were detected twice in the mid-gut gland of scallops at 1.1-2.3 MU (mouse units) g(-1) on 26 June and at 0.6-1.2 MU g(-1) on 3 July, respectively. Relatively high cell densities of D. fortii were observed on 26 June and 11 September, and may only contribute to the bivalve toxicity during late June to early July. D. acuminata did not appear to be responsible for the toxicity of scallops in Mutsu Bay in 2000. ELISA monitoring of small-sized plankton fraction in seawater could detect DSP toxins two weeks before the detection of the toxin in scallops, and could do so two weeks after the loss of the bivalve toxicity by mouse assay. On 17 July, toxic D. fortii was detected at only small number, <10 cells l(-1), but DSP toxins were detected by the ELISA assay, suggesting a presence of other toxic small-sized plankton in seawater. For the purpose of reducing negative impacts of DSP occurrences, monitorings have been carried out hitherto on DSP toxins of bivalve tissues by mouse assay and on cell densities of "toxic" species of Dinophysis. Here we propose a usefulness of ELISA monitoring of plankton toxicity, especially in small-sized fraction, which are possible foods of mixotrophic Dinophysis, as a practical tool for detecting and predicting DSPs in coastal areas of fisheries grounds of bivalve aquaculture. 相似文献
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Hiroko Nagahara 《Geochimica et cosmochimica acta》1984,48(12):2581-2595
Petrologic studies were made on the fine-grained matrices of type 3 ordinary chondrites of the lowest petrologic subtype. The matrix minerals, in order of abundance, are olivine (Fo99 to Fo9), enstatite or bronzite, augite or subcalcic augite, albite, Fe-Ni metal, troilite, magnetite, spinel (MgAl2O4), chromite, and calcite. Fe- and Mg-rich fluffy particles and albite-like particles are also major constituents. The chemical compositions of olivine and pyroxenes vary within and among the chondrites and are in gross disequilibrium, showing that the matrix materials were hardly heated after their formation. Textural relationships indicate that magnesian olivine was formed after Ca-pyroxene, followed by intermediate to iron-rich olivine. Intermediate olivine was formed from enstatite and metallic iron under relatively oxidizing conditions. The observations indicate that matrices of chondrites are neither the fragments of chondrules nor the precursors of chondrules. They were mostly the products of condensation and reaction among solids and/or between solids and the ambient gas mostly at low temperatures, and thus they contain records of primitive processes in the nebula. In order to explain the presence of olivines more iron-rich than Fo50, the presence of free SiO2 or a high activity of SiO2 in the gas is necessary, which was not shown in previous thermochemical calculations. Mineral assemblages of matrix minerals of chondrites of different chemical groups differ systematically according to oxidation state of the parental meteorites, indicating that they were formed at different oxygen fugacities. The rims of chondrules, and surrounding matrix materials, must have accreted onto chondrules during turbulent movements of the nebula. 相似文献
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D. Suetsugu H. Shiobara H. Sugioka Y. Fukao T. Kanazawa 《Physics of the Earth and Planetary Interiors》2007,160(3-4):310-318
We analyzed seismic waveforms recorded by the broadband ocean bottom seismographs deployed in the South Pacific superswell to determine the depths of the mantle discontinuities using a receiver function method. We estimated the thickness of the mantle transition zone (MTZ) to be 245 km on average beneath the superswell region, which is close to the global average. The MTZ is found to be thinned locally beneath the Society hot spot by 30 km. Temperature anomalies computed from the thinned transition zone and the Clapeyron slope of the olivine phase transformations are 150–200 K beneath the Society hot spot. Previous studies, using land-based data, suggested the presence of a hot MTZ beneath the Pitcairn hot spot. The locally hot transition zone beneath the hot spots is attributed to narrow mantle plumes probably rising from the lower mantle. The normal average thickness obtained from the present study indicates that there is no broad upwelling across the transition zone beneath the entire superswell region at present. 相似文献