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51.
Yoko KEBUKAWA Satoru NAKASHIMA Takahiro OTSUKA Keiko NAKAMURA‐MESSENGER Michael E. ZOLENSKY 《Meteoritics & planetary science》2009,44(4):545-557
Abstract— Organic contamination (?2965 and ?1260 cm?1peaks) was found on Tagish Lake (C2) and Murchison (CM2) carbonaceous chondrites containing abundant hydrous minerals by Fourier transform infrared (FTIR) microspectroscopy on the samples pressed on Al plates. On the other hand, anhydrous chondrite (Moss, CO3) was not contaminated. This contamination occurred within one day of storage, when the samples pressed on Al were stored within containers including silicone rubber mats. Volatile molecules having similar peaks to the contaminants were detected by long‐path gas cell FTIR measurements for the silicone rubber mat. Rapid adsorption of the volatile contaminants also occurred when silica gel and hydrous minerals such as serpentine were stored in containers including silicone rubber, silicone grease, or adhesive tape. However, they did not show any contamination when stored in glass and polystyrene containers without these compounds. Therefore, precious astronomical samples such as meteorites, interplanetary dust particles (IDPs), and mission‐returned samples from comets, asteroids, and Mars, should be measured by micro FTIR within one day of storage in glass containers without silicone rubber, silicone grease, or adhesive tape. 相似文献
52.
Takahiro Nagata 《Geochimica et cosmochimica acta》2010,74(21):6000-6013
Aqueous iodine species occur mainly as iodide (I−) and iodate (IO3−), depending on redox conditions. The adsorption of IO3− on naturally occurring oxides under oxic conditions is of environmental concern. The adsorption behaviors of IO3− by hydrous ferric oxide (HFO), α-FeOOH, and γ-Al2O3 were examined in this study as functions of pH, ionic strength, and solid concentration. Adsorption data were analyzed using an extended triple-layer model (ETLM) for surface complexation modeling to infer IO3− adsorption reactions and equilibrium constants. Results of ETLM analysis suggest that adsorption of IO3− is both an outer-sphere and an inner-sphere process, as expressed by the following complexation reactions, which are consistent with the independent pressure jump kinetic results and adsorption enthalpy measurements
53.
Takahiro Kudoh Shantanu Basu Youichi Ogata Takashi Yabe 《Monthly notices of the Royal Astronomical Society》2007,380(2):499-505
We employ the first fully three-dimensional simulation to study the role of magnetic fields and ion–neutral friction in regulating gravitationally driven fragmentation of molecular clouds. The cores in an initially subcritical cloud develop gradually over an ambipolar diffusion time while the cores in an initially supercritical cloud develop in a dynamical time. The infalling speeds on to cores are subsonic in the case of an initially subcritical cloud, while an extended (≳0.1 pc) region of supersonic infall exists in the case of an initially supercritical cloud. These results are consistent with previous two-dimensional simulations. We also found that a snapshot of the relation between density (ρ) and the strength of the magnetic field ( B ) at different spatial points of the cloud coincides with the evolutionary track of an individual core. When the density becomes large, both the relations tend to B ∝ρ0.5 . 相似文献
54.
A trial for monitoring temporal variation of seismic velocity using an ACROSS system 总被引:4,自引:0,他引:4
Koshun Yamaoka Takahiro Kunitomo Koji Miyakawa Kazunori Kobayashi Mineo Kumazawa 《Island Arc》2001,10(3-4):336-347
Abstract The temporal variation of seismic velocity near the Nojima Fault, which ruptured during the 1995 Kobe earthquake (Hyogo-ken Nanbu earthquake), was detected using an accurately controlled routine-operated seismic source (ACROSS). The source generates elastic waves by a centrifugal force of an eccentric mass rotating around an axis. The mass is driven with an AC servomotor whose angular position is accurately controlled with reference to a very accurate global positioning system (GPS) clock. The error of the mass' position is less than 0.002 radian and does not accumulate. As a result, the source generates sinusoidal waves of very narrow spectral peaks enabling their detection with an excellent signal-to-noise ratio. Although the stability of the rotation is quite excellent, a large daily variation was found, which seems to be caused by changes in atmospheric temperature. The daily variation was 10% in amplitude and 0.1 radian in phase of the signal observed at the 800 m borehole seismometer. A significant variation was found to be due to that of coupling between the rotational source and the foundation made of reinforced concrete in which the source was situated. In order to make a correction on the signal of the 800 m borehole seismometer, the vibration of the foundation was measured and modeled assuming a rigid body movement. The correction successfully reduced the daily variation by approximately 90%, resulting in a variation of 1% in amplitude and 0.01 radian in phase. The phase variation of 0.01 radian corresponds to 100 μs and less than 0.1% in velocity over 1000 m between the source and the receiver. 相似文献
55.
Abstract Apatite and zircon fission-track (FT) analyses of the Shimanto accretionary complex and its vicinities, southwest Japan, unraveled the episodic material migration of the deep interiors of the accretionary complex. Apatite data with 100°C closure temperature (Te) generally indicate ~10 Ma cooling throughout the Shimanto complex. In contrast, zircon data with 260°C Te exhibit a wide range of apparent ages as a consequence of paleotemperature increase to the zircon partial annealing zone. In the Muroto and Kyushu regions, maximum temperatures tend to have been higher in the northern, older part of the complex, with indistinguishable temperature differences between coherent and melange units adjacent to each other. It thus suggests, along with vitrinite reflectance data, that older accretionary units occurring to the north sustain greater maximum burial during the accretion-burial-exhumation process. Zircon data suggest two cooling episodes: ~70 Ma cooling at widespread localities in the Cretaceous Shimanto Belt and Sambagawa Belt, and ~15 Ma cooling in the central Kii Peninsula. The former is consistent with 40Ar/39Ar cooling ages from the Sambagawa Belt, whereas the latter slightly predates the widespread 10 Ma apatite cooling ages. These data imply that the extensive material migration and exhumation took place in and around the Shimanto complex in Late Cretaceous as well as in Middle Miocene. Considering tectonic factors to control evolution of accretionary complexes, the episodic migration is best explained by accelerated accretion of sediments due to increased sediment influx at the ancient Shimanto trench, probably derived from massive volcano-plutonic complexes contemporaneously placed inland. Available geo- and thermochronologic data suggest that extensive magmatism triggered regional exhumation twice in the past 100 Ma, shedding new light on the cordilleran orogeny and paired metamorphism concepts. 相似文献
56.
Rasoul B Sorkhabi Arvind K Jain Susumu Nishimura Tetsumaru Itaya Nand Lal R M Manickavasagam Takahiro Tagami 《Journal of Earth System Science》1994,103(1):83-97
Thermotectonic history of the Trans-Himalayan Ladakh Batholith in the Kargil area, N. W. India, is inferred from new age data
obtained here in conjunction with previously published ages. Fission-track (FT) ages on apatite fall around 20±2 Ma recording
cooling through temperatures of ∼100°C and indicating an unroofing of 4 km of the Ladakh Range since the Early Miocene. Coexisting
apatite and zircon FT ages from two samples in Kargil show the rocks to have cooled at an average rate of 5–6°C/Ma in the
past 40 Ma. Zircon FT ages together with mica K−Ar cooling ages from the Ladakh Batholith cluster around 40–50 Ma, probably
indicating an Eocene phase of uplift and erosion that affected the bulk of the batholith after the continental collision of
India with the Ladakh arc at 55 Ma. Components of the granitoids in Upper Eocene-Lower Oligocene sediments of the Indus Molasse
in Ladakh supports this idea. Three hornblende K−Ar ages of 90 Ma, 55 Ma, and 35 Ma are also reported; these distinctly different
ages probably reflect cooling through 500–550°C of three phases of I-type plutonism in Ladakh also evidenced by other available
radiometric data: 102 Ma (mid-Cretaceous), 60 Ma (Palaeocene), and 40 Ma (Late Eocene); the last phase being localised sheet
injections. The geodynamic implications of the age data for the India-Asia collision are discussed. 相似文献
57.
Kazuaki Iishi Mitiko Miura Yuji Shiro Hiromu Murata 《Physics and Chemistry of Minerals》1983,9(2):61-66
On the basis of the polarizable-ion model (PIM) the effect of the width of the atomic electron distribution on the lattice dynamics of α-quartz was taken into account using the Birman method. The frequencies of optical mode, elastic constants and piezoelectric constants were reproduced using the parameters of this model (an effective charge z, a width parameter w, an electronic polarizability α, and force constants). The width parameter of oxygen atom was found to be about 0.59 Å, and the effective charge of the silicon atom 1.42 electron charges. 相似文献
58.
Toshihiko Ohnuki Takahiro Yoshida Takuo Ozaki Mohamad Samadfam Naofumi Kozai Kunio Yubuta Toshiaki Mitsugashira Takeshi Kasama Arokiasamy J. Francis 《Chemical Geology》2005,220(3-4):237-243
We assessed the accumulation of uranium (VI) by a bacterium, Bacillus subtilis, suspended in a slurry of kaolinite clay, to elucidate the role of microbes on the mobility of U(VI). Various mixtures of bacteria and the koalinite were exposed to solutions of 8 × 10− 6 M- and 4 × 10− 4 M-U(VI) in 0.01 M NaCl at pH 4.7. After 48 h, the mixtures were separated from the solutions by centrifugation, and treated with a 1 M CH3COOK for 24 h to determine the associations of U within the mixture. The mixture exposed to 4 × 10− 4 M U was analyzed by transmission electron microscope (TEM) equipped with EDS. The accumulation of U by the mixture increased with an increase in the amount of B. subtilis cells present at both U concentrations. Treatment of kaolinite with CH3COOK, removed approximately 80% of the associated uranium. However, in the presence of B. subtilis the amount of U removed was much less. TEM–EDS analysis confirmed that most of the U removed from solution was associated with B. subtilis. XANES analysis of the oxidation state of uranium associated with B. subtilis, kaolinite, and with the mixture containing both revealed that it was present as U(VI). These results suggest that the bacteria have a higher affinity for U than the kaolinite clay mineral under the experimental conditions tested, and that they can immobilize significant amount of uranium. 相似文献
59.
Exsolution textures in orthopyroxene in aluminous granulites as indicators of UHT metamorphism: New evidence from the Eastern Ghats Belt, India 总被引:1,自引:0,他引:1
Highly aluminous orthopyroxene, coexisting with sapphirine, cordierite, sillimanite, quartz and garnet in various combinations, constitute granoblastic mosaic peak metamorphic assemblages in aluminous granulites from three localities in the Eastern Ghats Belt, India. Orthopyroxene contains four types of intergrowths: (a) involving sapphirine with or without cordierite, (b) involving spinel, but without sapphirine, (c) involving cordierite, but without sapphirine and spinel, and (d) involving garnet, without sapphirine, spinel or cordierite. On the basis of textural and compositional data, origin of the intergrowths is ascribed to breakdown of Mg-Tschermak component, locally also involving Fe- and Ti-Tschermak. An attempt is made to compute the “pre-breakdown” compositions of orthopyroxene by image analysis, which shows maximum Al2O3 content of 13.4 wt.% in the pristine orthopyroxene. Geothermometry, phase equilibria consideration and application of existing experimental data on alumina solubility in orthopyroxene coexisting with sapphirine and quartz, collectively indicate extreme thermal conditions of metamorphism (> 1000 °C) for the studied assemblages. This re-affirms the notion that Al2O3 solubility in orthopyroxene is the most powerful indicator of UHT metamorphism (Harley, S.L., 2004. Extending our understanding of ultrahigh temperature crustal metamorphism. J. Mineral. Petrol. Sci. 99, 140–158). The intergrowths are considered to have formed due to cooling from the thermal peak spanning a temperature range of approximately 150 °C. Appearance of diverse types of intergrowths is probably related to subtle differences in bulk composition, particularly Fe:Mg ratios. 相似文献
60.
Chemical Assessment of Oceanic and Terrestrial Sulfur in the Marine Boundary Layer over the Northern North Pacific during Summer 总被引:2,自引:0,他引:2
K. Aranami S. Watanabe S. Tsunogai A. Ohki K. Miura H. Kojima 《Journal of Atmospheric Chemistry》2002,41(1):49-66
Dimethylsulfide (DMS) in surface seawater and the air, methanesulfonic acid (MSA) and non-sea-salt sulfate (nss-SO4
2–) in aerosol, and radon-222 (Rn-222) were measured in the northern North Pacific, including the Bering Sea, during summer (13 July – 6 September 1997). The mean atmospheric DMS concentrations in the eastern region (21.0 ± 5.8 nmole/m3 (mean ± S.D.), n=30) and Bering Sea (19.9 ± 9.8 nmole/m3, n=10) were higher than that in the western region (11.1 ± 6.4 nmole/m3, n=31) (p<0.05), although these regions did not significantly differ in the mean DMS concentration in surface seawater. Mean sea-to-air DMS flux in the eastern region (21.0 ± 10.4 mole/m2/day, n=19) was larger than those in the western region (11.3 ± 16.9 mole /m2/day, n=22) and Bering Sea (11.2 ± 7.8 mole/m2/day, n=7) (p<0.05). This suggests that the longitudinal difference in atmospheric DMS was produced by that in DMS flux owing to wind speed, while the possible causes of the higher DMS concentrations in the Bering Sea include (1) later DMS oxidation rates, (2) lower heights of the marine boundary layer, and (3) more inactive convection. The mean MSA concentrations in the eastern region (1.18 ± 0.84 nmole/m3, n=35) and Bering Sea (1.17 ± 0.87 nmole/m3, n=13) were higher than that in the western region (0.49 ± 0.25 nmole/m3, n=28) (p < 0.05). Thus the distribution of MSA was similar to that of DMS, while the nss-SO4
2– concentrations were higher near the continent. This suggests that nss-SO4
2– concentrations were regionally influenced by anthropogenic sulfur input, because the distribution of nss-SO4
2– was similar to that of Rn-222 used as a tracer of continental air masses. 相似文献