Wide-Field Camera for Gravitational Microlensing Survey: MOA-cam2     

Toshifumi Yanagisawa  Yasushi Muraki  Yutaka Matsubara  Fumio Abe  Kimiaki Masuda  Sachiyo Noda  Takahiro Sumi  Yuji Kato  Mitsuaki Fujimoto  Shuji Sato  Ian Bond  Nicholas Rattenbury  Philip Yock  Pam Kilmartin  John Hearnshaw  Micheal Reid  Denis Sullivan  Brian Carter  Richard Dodd  Garry Nankivell  Noiman Rumsey  Morihiro Honda  Maki Sekiguchi  Masanori Yoshizawa  Takashi Nakamura  Humitaka Sato  Seiji Kabe  Makoto Kobayashi  Yoshiyuki Watase  Jun Jugaku  Toshiharu Saito  Barbel Koribalsky 《Experimental Astronomy》2000,10(4):519-535

We have constructed a large, mosaic CCD camera called MOA-cam2 which has 4096 × 6144-pixelsto search for gravitational microlensing events. MOA-cam2 has three4096 × 2048-pixel SITe CCD chips, which have a very high quantum efficiency (nearly 80% in the wave region 500 to 800 nm),and three buttable sides. We have placed the threechips side by side with 100 m dead space. MOA-cam2 has been installed on the 61 cm Boller and Chivens telescope of the MOA collaboration at the Mt. John University Observatory (MJUO) in NewZealand since July 1998. The field coverage is 0.92° × 1.38° per exposure. The technical details of MOA-cam2 and the first images obtained with the Boller and Chivens telescope are presented. MOA-cam2 introduces a second phase of research on gravitational microlensing by the MOA collaboration.  相似文献   

Thematic Section: Dynamic sedimentation in forearc basins: Results from the Choshi and Sagara drilling projects     

Hiroshi Kitazato  Hideki Wada  Kevin T. Pickering  Asahiko Taira 《Island Arc》2006,15(3):283-284

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Age model, physical properties and paleoceanographic implications of the middle Pleistocene core sediments in the Choshi area, central Japan     

Koji  Kameo  Makoto  Okada  Moamen  El-Masry  Toshio  Hisamitsu  Saneatsu  Saito  Hiroomi  Nakazato  Naohiko  Ohkouchi  Minoru  Ikehara  Hisato  Yasuda  Hiroshi  Kitazato  Asahiko  Taira 《Island Arc》2006,15(3):366-377

Abstract   A continuous, well-preserved core was obtained from the Choshi area, on the Pacific side of Japan, to investigate paleoceanographic and paleoclimatic changes around the northwestern Pacific region during the middle Pleistocene. Siliciclastic sequences in the core are divided into five formations – the Obama, Yokone, Kurahashi and Toyosato Formations in the Inubo Group and the Katori Formation, in ascending order. Examination of calcareous nannofossils and magnetic polarities detected four datums in the core sediments of the Inubo Group: the top of Reticulofenestra asanoi , the base of Helicosphaera inversa , the top of Pseudoemiliania lacunosa and the Brunhes–Matuyama boundary. Fourteen marine isotope stages (MIS24–MIS11) were identified in the δ¹⁸O and δ¹³C records based on detected datums and the graphic correlation with the standard stack oxygen isotope curve. Magnetic susceptibility and gamma-ray attenuation porosity evaluator density were also measured and low values characterize the glacial intervals. Biogenic sedimentation by primary production may be larger during the glacial periods because of invasions of nutrient-rich northern surface-waters related to the southward shift of the Kuroshio front in the Choshi area.  相似文献   

Floral changes in calcareous nannofossils and their paleoceanographic significance in the equatorial Pacific Ocean during the last 500 000 years     

Shun  Chiyonobu  Tokiyuki  Sato  Reika  Narikiyo  Makoto  Yamasaki 《Island Arc》2006,15(4):476-482

Abstract   The late Quaternary calcareous nannofossil assemblages from Ocean Drilling Program Holes 807A and 846B, located in the western and eastern equatorial Pacific Ocean, respectively, were analyzed to clarify changes in surface-water conditions during the last 500 000 years. The uppermost Quaternary sediments in both holes contain abundant nannofossils, and their assemblages are characterized by high species diversity. The absolute abundances of coccoliths (specimens/g) and relative numbers of small reticulofenestrids decreased drastically in both holes between 0.3 and 0.2 Ma, whereas the relative abundance of warm-water species and Florisphaera profunda increased suddenly at this time. These data indicate that upwelling around the western and eastern equatorial Pacific regions weakened after 0.2 Ma, which was caused by a decrease in trade-wind strength.  相似文献   

Lithological and physical properties of core samples from the Sagara oil field: Oil occurrence in Sagara core samples     

Satoshi  Hirano  Yoshiaki  Araki  Koji  Kameo  Hiroshi  Kitazato  Hideki  Wada 《Island Arc》2006,15(3):313-327

Abstract   A drilling and coring investigation of the Sagara oil field, central Honshu, Japan, was conducted to contribute to the understanding of hydrocarbon migration processes in a forearc basin. Core samples were analyzed to determine lithology, physical properties (specifically gas permeability) and the characteristics of oil occurrence. Gas permeability values greater than approximately 10⁻¹¹ m² constitute the basic precondition for any lithology to serve as a potential fluid conduit or reservoir in the Sagara oil field. Cores recovered from the 200.6-m-deep borehole were primarily composed of alternating siltstone, sandstone and conglomerate, all of which are correlated to the late Miocene Sagara Group. Both sandstone and conglomerate can be classified into two types, carbonate-cemented and poorly to non-cemented, based on matrix material characteristics. Oil stains are generally absent in the former lithology and more common in the latter. Variations in physical properties with respect to gas permeability values are directly related to the presence and character of carbonate cement, with higher permeabilities common in poorly to non-cemented rocks. The relationships between lithology, oil-staining, cementation and permeability indicate that cementation preceded oil infiltration and that cementation processes exerted significant control on the evolution of the reservoir.  相似文献   

Performance of a lithium fluoride bolometer for Tokyo dark matter search experiment     

Wataru Ootani  Makoto Minowa  Takayuki Watanabe  Yutaka Ito  Yasuhiro Kishimoto  Kentaro Miuchi  Yoshizumi Inoue  Youiti Ootuka 《Astroparticle Physics》1998,9(4):325-329

The performance of a 21-g lithium fluoride bolometer is presented. The background spectrum was measured in the surface laboratory. We derive an exclusion plot for the spin-dependent coupled Weakly Interacting Massive Particles (WIMPs) cross section.  相似文献   

Ca, Al-rich inclusions in Yamato 791717 (CO3) carbonaceous chondrite: Formation and alteration     

Yangting Lin  Daode Wang  Makoto Kimura 《中国科学D辑(英文版)》1998,41(5):513-521

In three polished thin sections of Yamato 791717 (CO3). fifty-five Ca, Al-rich inclusions were found, which include two hibonite-bearing, eight melilite-rich and forty-five spinel-pyroxene inclusions. Based on the petrography and mineral chemistry of the inclusions, it is proposed that the melilite-rich inclusions and spinel-pyroxene inclusions condensed in the solar nebula, and the hibonite-bearing inclusions crystallized from melts. The heavy alteration of the inclusions in Yamato 791717, which probably took place under a very oxidizing condition in the solar nebular, is also confirmed. Project supported by the National Natural Science Foundation of China (Grant No. 49673200). and by the Japanese Society for Promotion of Sciences (JSPS).  相似文献   

Introduction to the special volume on the Izu–Bonin – Mariana arc system     

Robert J. Stern  & Makoto Arima 《Island Arc》1998,7(3):295-300

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Characteristics of 3-dimensional earthquake ground motions     

Joseph Penzien  Makoto Watabe 《地震工程与结构动力学》1974,3(4):365-373

An orthogonal set of principal axes is defined for earthquake ground motions along which the component variances have maximum, minimum and intermediate values and the covariances equal zero. Corresponding axes are defined which yield maximum values for the covariances. The orthogonal transformations involved are identical in form to those used in the transformation of stress. Examination of real accelerograms reveals that the major principal axis points in the general direction of the epicentre and the minor principal axis is nearly vertical. It is concluded that artificially generated components of ground motion need not be correlated statistically provided they are directed along a set of principal axes.  相似文献   

Thermal-chemical instability in a pre-galactic gas cloud     

Yutaka Sabano  Makoto Tosa 《Astrophysics and Space Science》1986,119(1):167-168

The growth of thermal-chemical instability in a pre-galactic medium is followed by numerical simulation of gas dynamics. Results show that a primordial gas cloud breaks into self-gravitating subcondensations with the mass of normal stars.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献