Elemental and isotope behavior of macromolecular organic matter from CM chondrites during hydrous pyrolysis     

Yasuhiro OBA  Hiroshi NARAOKA 《Meteoritics & planetary science》2009,44(7):943-953

Abstract— A new insight into carbon and hydrogen isotope variations of insoluble organic matter (IOM) is provided from seven CM chondrites, including Murchison and six Antarctic meteorites (Y‐791198, Y‐793321, A‐881280, A‐881334, A‐881458 and B‐7904) as well as Murchison IOM residues after hydrous pyrolysis at 270–330 °C for 72 h. Isotopic compositions of bulk carbon (δ¹³C_bulk) and hydrogen (δD) of the seven IOMs vary widely, ranging from ?15.1 to ?7.6%₀ and +133 to +986%₀, respectively. Intramolecular carboxyl carbon (δ13C_COOH) is more enriched in ¹³C by 7.5. 11%₀ than bulk carbon. After hydrous pyrolysis of Murchison IOM at 330 °C, H/C ratio, δ13C_bulk, δ13C_COOH, and δD values decrease by up to 0.31, 3.5%₀, 5.5%₀, and 961%₀, respectively. The O/C ratio increases from 0.22 to 0.46 at 270 °C and to 0.25 at 300 °C, and decreases to 0.10 at 330 °C. δ13C_bulk‐δD cross plot of Murchison IOM and its pyrolysis residues shows an isotopic sequence. Of the six Antarctic IOMs, A‐881280, A‐881458, Y‐791198 and B‐7904 lie on or near the isotopic sequence depending on the degree of hydrous and/or thermal alteration, while A‐881334 and Y‐793321 consist of another distinct isotope group. A δ13C_bulk‐δ13C_COOH cross‐plot of IOMs, including Murchison pyrolysis residues, has a positive correlation between them, implying that the oxidation process to produce carboxyls is similar among all IOMs. These isotope distributions reflect various degree of alteration on the meteorite parent bodies and/or difference in original isotopic compositions before the parent body processes.  相似文献   

Patchy He ii reionization and the physical state of the intergalactic medium     

Liron Gleser  Adi Nusser  rew J. Benson  Hiroshi Ohno  Naoshi Sugiyama 《Monthly notices of the Royal Astronomical Society》2005,361(4):1399-1414

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The first confirmed Perseid lunar impact flash     

Masahisa Yanagisawa  Kouji Ohnishi  Hiroshi Masuda  Miyoshi Ida  Masayuki Ishida 《Icarus》2006,182(2):489-495

The first confirmed lunar impact flash due to a non-Leonid meteoroid is reported. The observed Perseid meteoroid impact occurred at 18^h28^m27^s on August 11, 2004 (UT). The selenographic coordinates of the lunar impact flash are 48±1° N and 72±2° E, and the flash had a visual magnitude of ca. 9.5 with duration of about 1/30 s. The mass of the impactor is estimated to have been 12 g based on a nominal model with conversion efficiency from kinetic to optical energy of 2×¹⁰⁻³. Extrapolation of a power law size-frequency distribution fitting the sub-centimeter Perseid meteoric particles to large meteoroids suggests that several flashes should have been observed at this optical efficiency. The detection of only one flash may indicate that the optical efficiency for Perseid lunar impact is much lower, or that the slope of the size distribution differs between large meteoroids and typical sub-centimeter meteoric particles.  相似文献   

Deep seismic reflection profiling across the Ou Backbone range, northern Honshu Island, Japan     

Hiroshi Sato  Naoshi Hirata  Takaya Iwasaki  Makoto Matsubara  Takeshi Ikawa   《Tectonophysics》2002,355(1-4)

Knowledge of the crustal structure, especially the geometry of seismogenic faults, is key to understanding active tectonic processes and assessing the size and frequency of future earthquakes. To reveal the relationship between crustal structure and earthquake activity in northern Honshu Island, common midpoint (CMP) deep reflection profiling and earthquake observations by densely deployed seismic stations were carried out across the active reverse faults that bound the Ou Backbone range. The 40-km-long CMP profiles portray a relatively simple fault geometry within the seismogenic layer. The reverse faults merge at a midcrustal detachment just below the base of the seismogenic layer, producing a pop-up structure that forms the Ou Backbone range. The top of the reflective middle to lower crust (4.5 s in travel time (TWT)) nearly coincides with the bottom of seismogenic layer. The P-wave velocity structure and surface geology suggest that the bounding faults are Miocene normal faults that have been reactivated as reverse faults.  相似文献   

Seismological features of island arc crust as inferred from recent seismic expeditions in Japan     

Takaya Iwasaki  Toshikatsu Yoshii  Tanio Ito  Hiroshi Sato  Naoshi Hirata 《Tectonophysics》2002,355(1-4)

Crustal studies within the Japanese islands have provided important constraints on the physical properties and deformation styles of the island arc crust. The upper crust in the Japanese islands has a significant heterogeneity characterized by large velocity variation (5.5–6.1 km/s) and high seismic attenuation (Qp=100–400 for 5–15 Hz). The lateral velocity change sometimes occurs at major tectonic lines. In many cases of recent refraction/wide-angle reflection profiles, a “middle crust” with a velocity of 6.2–6.5 km/s is found in a depth range of 5–15 km. Most shallow microearthquakes are concentrated in the upper/middle crust. The velocity in the lower crust is estimated to be 6.6–7.0 km/s. The lower crust often involves a highly reflective zone with less seismicity, indicating its ductile rheology. The uppermost mantle is characterized by a low Pn velocity of 7.5–7.9 km/s. Several observations on PmP phase indicate that the Moho is not a sharp boundary with a distinct velocity contrast, but forms a transition zone from the upper mantle to the lower crust. Recent seismic reflection experiments revealed ongoing crustal deformations within the Japanese islands. A clear image of crustal delamination obtained for an arc–arc collision zone in central Hokkaido provides an important key for the evolution process from island arc to more felsic continental crust. In northern Honshu, a major fault system with listric geometry, which was formed by Miocene back arc spreading, was successfully mapped down to 12–15 km.  相似文献   

Origin of atmospheric polycyclic aromatic hydrocarbons (PAHs) in Chinese cities solved by compound-specific stable carbon isotopic analyses   总被引：1，自引：0，他引：1  

Tomoaki Okuda  Hidetoshi Kumata  Hiroshi Naraoka  Hideshige Takada 《Organic Geochemistry》2002,33(12)

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1991年江淮特大暴雨的降水性质与对流活动   总被引：11，自引：3，他引：11  

陆尔  丁一汇  M. Murakami  K. Takahashi 《气象学报》1997,55(3):318-333

从计算大尺度热源和分析ＴＢＢ资料两个方面，阐述了１９９１年江淮梅雨期间降水性质与对流活动的季节性演变特征。结果表明：梅雨期间江淮上空３个强上升运动时段分别形成了３场暴雨，由暴雨释放的热量使江淮大气出现了３个时段的强加热；３场暴雨的降水性质呈显著的季节性演变，由第１场暴雨以锋面性降水为主发展到第３场暴雨异常强的对流性降水。文中详细分析了热源和水汽汇的时空分布特征，并从大气运动场和热力结构讨论了盛夏强对流降水期间积云对流以涡动形式对热量和水汽的强铅直输送作用。江淮地区ＴＢＢ值能很好地反映降水状况，雨期一致地对应于ＴＢＢ低于２５０Ｋ的时段。梅雨中后期东亚地区对流活动季节性地增强，带状对流区（特别是ＴＢＢ高负距平区）与雨带位置相符。对流带位置及对流活动强弱与西南暖湿气流活动密切相关，它很好地表征了东亚地区的低空急流（给积云输送热带对流大气）。梅雨期间对流带主要出现在江淮流域，但可在东亚范围内飘移，它落在江淮与否则决定了江淮暴雨的维持与中断  相似文献   

Modeling plot scale dye penetration by a diffusion limited aggregation (DLA) model   总被引：1，自引：0，他引：1  

Magnus Persson  Hiroshi Yasuda  Jean Albergel  Ronny Berndtsson  Patrick Zante  Slah Nasri  Pernilla hrstrm 《Journal of Hydrology》2001,250(1-4):98-105

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Multicomponent observation of crustal activity in the DPRI 800 m borehole close to the Nojima Fault   总被引：1，自引：0，他引：1  

Hiroshi Ishii  Atsushi Mukai  Kunio Fujimori  Shigeru Nakao  Shigeo Matsumoto  Yasuhiro Hirata 《Island Arc》2001,10(3-4):282-287

Abstract An 800 m borehole was drilled near the Nojima Fault, on which a strike–slip larger then 1 m occurred during the 1995 Hyogo-ken Nanbu earthquake ( M = 7.2). Crustal activity near the fault has been observed since May 1996 using a multicomponent instrument installed at the bottom of the borehole. Data of three components of strain, two components of tilt and temperature observed from May 1996 to December 1998 were analyzed. Long-term changes of strain and tilt show a north-east–south-west extension and southwards subsidence. As for the Earth tides and atmospheric effect, orientation of the principal axis of strain was mainly east-west and orientation of the maximum subsidence was mainly north-south. The observational data of strain had variations corresponding to a change in temperature at a depth of 800 m. The thermal expansion coefficient of the crust was calculated to be approximately 2.0 × 10⁻⁶/°K.  相似文献   

The Fourier transform of controlled-source time-domain electromagnetic data by smooth spectrum inversion   总被引：1，自引：0，他引：1  

Yuji Mitsuhata  Toshihiro Uchida  Yutaka Murakami  Hiroshi Amano 《Geophysical Journal International》2001,144(1):123-135

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