Evidence from the Rb‐Sr system for 4.4 Ga alteration of chondrules in the Allende (CV3) parent body     

Gen SHIMODA  Noboru NAKAMURA  Makoto KIMURA  Tomomi KANI  Susumu NOHDA  Koshi YAMAMOTO 《Meteoritics & planetary science》2005,40(7):1059-1072

Abstract— The timing and processes of alteration in the CV parent body are investigated by the analysis of Sr isotopes, major and trace elements, and petrographic type and distribution of the secondary minerals (nepheline and sodalite) in 22 chondrules from the Allende (CV3) chondrite. The Sr isotopic compositions of the chondrules are scattered around the 4.0 Ga reference line on the ⁸⁷Sr/⁸⁶Sr evolution diagram, indicating that the chondrules have been affected by late thermal alteration event(s) in the parent body. The degree of alteration, determined for individual chondrules based on the distribution of nepheline and sodalite, is unrelated to the disturbance of the Rb‐Sr system, suggesting that the alteration process that produced nepheline and sodalite is different from the thermal process that disturbed the Rb‐Sr system of the chondrules. Considering the geochemical behavior of Rb and Sr, the main host phase of Sr in chondrules is likely to be mesostasis, which could be most susceptible to late thermal alteration. As there is a poor connection between the alteration degree determined from abundances of nepheline and sodalite and the disturbance of Rb‐Sr isotopic system, we consider the mesostasis to provide a constraint on the late parent body alteration process. From this point of view, 23 mesostasis‐rich chondrules, including those from literature data, were selected. The selected chondrules are closely correlated on the ⁸⁷Sr/⁸⁶Sr evolution diagram, with an inferred age of 4.36 ± 0.08 Ga. This correlation would represent an age of the final major Sr isotopic redistribution of the chondrules in the parent body.  相似文献   

Reliability analysis of shallow foundations in reference to design codes development     

Yusuke Honjo  Makoto Suzuki  Minoru Matsuo 《Computers and Geotechnics》2000,26(3-4):331-346

In this study, FORM analysis is carried out for shallow foundation of a typical building in order to evaluate relative magnitude of uncertainties involved in the force and the resistance sides. The distinguished feature of this study is to take into account the uncertainty of the earthquake force as much as possible. Tthis is because, the seismic design dominates major part of structural design in Japan, and without referring to this problem, no useful information of practical value is gained. The results of the FORM analysis exhibited the reliability index values between 2.0 to 3.5, which is considered to be in a reasonable range. Since the 50 year maximum earthquake force is considered in the reliability calculation, calculated reliability index values are for the period of 50 years. The sensitivity factor obtained in a case more realistic ground variability is taken into account exhibited values not very different from those obtained in the upper structures.  相似文献   

The buried Balmer-edge signatures from quasars     

Makoto Kishimoto  Robert Antonucci  Catherine Boisson  Omer Blaes 《Monthly notices of the Royal Astronomical Society》2004,354(4):1065-1092

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Bathymetric patterns of meiofaunal abundance and biomass associated with the Kuril and Ryukyu trenches, western North Pacific Ocean   总被引：2，自引：0，他引：2  

Makoto Itoh  Kiichiro KawamuraTomo Kitahashi  Shigeaki KojimaHideki Katagiri  Motohiro Shimanaga 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(1):86-97

The abundance and biomass of metazoan meiofauna and their relationships with environmental factors [chloroplastic pigment equivalents (CPE) and sediment characteristics] were studied quantitatively around and within the Kuril Trench (560-7090 m) and the Ryukyu Trench (1290-7150 m), which are located in eutrophic and oligotrophic regions, respectively, of the western North Pacific. Faunal abundance and biomass, as well as the CPE content of sediments, were considerably higher in the Kuril region than in the Ryukyu region. In both cases, CPE tended to decrease with water depth, but relatively high values were found in the deepest areas, suggesting that organic matter has accumulated in both trenches. Meiofaunal abundance and biomass were lower than expected from sediment CPE values at hadal stations below 6000 m. Differences in the density and biomass of meiofauna between these two trenches appeared to reflect differences in overall ocean productivity above them. When the analysis was restricted to each region, however, no association was found between the abundance and biomass of meiofauna and food availability. Furthermore, the factors regulating the bathymetric patterns in these meiofaunal parameters appeared to differ between the two trenches.  相似文献   

Construction of Wide Field Cryogenic Telescope     

Minoru Ando  Tetsuya Nagata  Shuji Sato  Makoto Watanabe  Kunio Itoh  Toshihide Kawai  Hidehiko Nakaya  Yoshiharu Namba  Takeshi Takezawa 《Experimental Astronomy》2002,13(3):119-134

We constructed a wide field cryogenic telescope (WFCT) containing a whole Ritchey-Chrétien system and a focal plane array in a cryostat for near infrared observations to cover the field of view of 0.4°. The telescope has a primary mirror of 220 mm and an engineering grade 256 × 256 InSb array. The optical components such as two mirrors, filters, spiders, and radiation shield tube are cooled down to 180 K as well as the InSb array to 35 K by a mechanical refrigerator. We show the results of the background surface brightnesses and the limiting magnitudes at 3.3 and 3.67 μm measured at Sutherland, South Africa. We describe the on-going upgrade of this instrument, equipped with a 1024 × 1024 ALADDIN InSb science grade array. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Petrology of green polished stone axes of the Jomon period from the Sannai-Maruyama site,Japan, investigating the origin of source rock     

Hirokazu Maekawa  Kazuyoshi Ohtsuka  Koshi Yamamoto  Nobuo Gouchi  Keiko Hattori 《Island Arc》2021,30(1):e12384

Numerous green polished stone axes have been excavated from the Sannai-Maruyama site, one of Japan's largest archeological sites in the Jomon period (5.9–4.2 cal kyr BP). The axes are composed of weakly metamorphosed fine-grained volcaniclastic rock having a peculiar texture that includes numerous acicular actinolites growing in random directions within a quartz and albite matrix. Cobbles of Aotora stone found along the Nukabira River, Biratori town, southern Hokkaido, are the most likely raw material for these stone axes. Aotora stones have alternate bands of a soft dark-green picritic layer and a hard SiO₂-rich pale-green layer. The pale-green layer has a texture similar to the stone axes. Basaltic and picritic volcanic rocks of the Sorachi-Yezo Belt occupy the area along the Shidoni River, a tributary of the Nukabira River. Volcaniclastic rocks similar in texture, mineralogy, and bulk rock compositions to the Aotora stone are exposed in the area. These rocks underwent metamorphism under the actinolite-pumpellyite facies conditions. Their protolith is submarine hyaloclastic rocks that are intercalated with laminated picrite detritus. The stone axes, pale-green layers of Aotora stone, and those of the volcaniclastic rocks of the Shidoni River area all have high SiO₂ (~ 55 wt%), Cr (~ 840 μg/g), and Ni (~ 370 μg/g). The rare earth element patterns with abundant light rare earth elements and depleted heavy rare earth elements of stone axes were also consistent with the pale-green layers of the outcrop. These pale-green layers, interleaved with dark-green layers of picritic detritus, were the likely source rock of the stone axes. The high SiO₂ content in the pale-green layer caused the crystallization of quartz and albite in the matrix, which resulted in high-quality raw material for making stone axes.  相似文献   

Formation of stars by implosion of a gas cloud     

Toshiya Kimura  Makoto Tosa 《Astrophysics and Space Science》1987,135(2):261-269

In the standard Friedmann cosmology the black-body radiation spectrum is usually taken (without explicit proof as far as we know) to have the same familiarT ⁴-form that it has in a flat space. With explicit use of the equation of motion of a quantized massless field propagating in a curved background Robertson-Walker metric we show (for the readily tractable scalar field case) that the assumption is in fact true for an open Universe. For a closed Universe, we find that there is an in principle modification to theT ⁴-law. Unfortunately, the correction turns out to be too small to be experimentally detectable. In passing, we also obtain a simple derivation for the cosmological red shift of frequencies.  相似文献   

Dehydration kinetics of antigorite using in situ high-temperature infrared microspectroscopy     

Michiyo Sawai  Ikuo Katayama  Arisa Hamada  Makoto Maeda  Satoru Nakashima 《Physics and Chemistry of Minerals》2013,40(4):319-330

The dehydration kinetics of serpentine was investigated using in situ high-temperature infrared microspectroscopy. The analyzed antigorite samples at room temperature show relatively sharp bands at around 3,655–3,660 cm^?1 (band 1), 3,570–3,595 cm^?1 (band 2), and 3,450–3,510 cm^?1 (band 3). Band 1 corresponds to the Mg–OH bond, and bands 2 and 3 correspond to OH associated with the substitution of Al for Si. Isothermal kinetic heating experiments at temperatures ranging from 625 to 700 °C showed a systematic decrease of the OH band absorbance with heating duration. The one-dimensional diffusion was found to provide the best fit to the experimental data, and diffusion coefficients were determined with activation energies of 219 ± 37 kJ mol^?1 for the total water band area, 245 ± 46 kJ mol^?1 for band 1, 243 ± 57 kJ mol^?1 for band 2, and 256 ± 53 kJ mol^?1 for band 3. The results indicate that the dehydration process is controlled by one-dimensional diffusion through the tetrahedral geometry of serpentine. Fluid production rates during antigorite dehydration were calculated from kinetic data and range from 3 × 10^?4 to 3 × 10^?5  $ {\text{m}}_{\text{fluid}}^{ 3} \,{\text{m}}_{\text{rock}}^{ - 3} \,{\text{s}}^{ - 1} $ . The rates are high enough to provoke hydraulic rupture, since the relaxation rates of rocks are much lower than these values. The results suggest that the rapid dehydration of antigorite can trigger an intermediate-depth earthquake associated with a subducting slab.  相似文献   

http://www.sciencedirect.com/science/article/pii/S167498711200062X     

Tetsuya Tokiwa  Kimikazu Tsusaka  Makoto Matsubara  Taiki Ishikawa  Daisuke Ogawa 《地学前缘(英文版)》2013,4(1):105-111

This paper focuses on the formation mechanism of fractures induced by excavation of a gallery in soft sedimentary rocks in the Horonobe area of Japan.Detailed fracture mapping of the gallery indicates that the fractures consist of both pre-existing shear fractures and excavation damaged zone(EDZ) fractures. EDZ fractures correspond to weak planes associated with bedding planes or transgranular cracks.The EDZ fractures terminate against pre-existing shear fractures.Therefore,even for excavations in soft sedimentary rocks,formation of the EDZ fractures are controlled by pre-existing fractures and earlier weak planes.  相似文献   

The potential of intra-regional supply and demand of agricultural products in an urban fringe area: A case study of the Kanto Plain,Japan     

Hideharu Kurita  Makoto Yokohari  Jay Bolthouse 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):147-159

Geografisk Tidsskrift—Danish Journal of Geography 109(2):147–159, 2009

The increasingly global reach of industrial agricultural production has progressively distanced consumers and producers. Not surprisingly, opposition to the global food system commonly seeks to re-localize agriculture by cutting the distance between agricultural production and consumption. Analysis of potential foodsheds can provide an important basis upon which to recover local systems of production and consumption. Here, we examine the potential for municipal and micro-level foodsheds in the greater Tokyo mega-region. Similar to other large cities in Asia, the urban fringe of Tokyo has extensive areas of mixed urban and agricultural land-uses which are often seen as problematic, but which may have many merits from the standpoint of sustainable foodsheds. Indeed, our results indicate that many areas on the urban fringe of the Tokyo mega-region bear potential to meet demand for both rice and vegetables within their borders. Moreover, many people could meet their food needs within a short distance of their residence. These results demonstrate the need to examine the potential for micro-level foodsheds on the urban fringe.  相似文献