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51.
Xuelei Chen Asantha Cooray Naoki Yoshida Naoshi Sugiyama 《Monthly notices of the Royal Astronomical Society》2003,346(3):L31-L35
The first-year Wilkinson Microwave Anisotropy Probe data suggest a high optical depth for Thomson scattering of 0.17 ± 0.04 , implying that the Universe was reionized at an earlier epoch than previously expected. Such early reionization is likely to be caused by ultraviolet (UV) photons from first stars, but it appears that the observed high optical depth can be reconciled within the standard structure formation model only if star formation in the early Universe was extremely efficient. With normal star formation efficiencies, cosmological models with non-Gaussian density fluctuations may circumvent this conflict as high density peaks collapse at an earlier epoch than in models with Gaussian fluctuations. We study cosmic reionization in non-Gaussian models and explore to what extent, within available constraints, non-Gaussianities affect the reionization history. For mild non-Gaussian fluctuations at redshifts of 30 to 50, the increase in optical depth remains at a level of a few per cent and appears unlikely to aid significantly in explaining the measured high optical depth. On the other hand, within available observational constraints, increasing the non-Gaussian nature of density fluctuations can easily reproduce the optical depth and may remain viable in underlying models of non-Gaussianity with a scale-dependence. 相似文献
52.
Naoteru Gouda Takuji Tsujimoto Yukiyasu Kobayashi Tadashi Nakajima Naoki Yasuda Hideo Matsuhara 《Astrophysics and Space Science》2002,280(1-2):89-94
JASMINE is the name of a Japanese infrared (K-band) scanning astrometric satellite. JASMINE (I and/or II-project) is planned to be launched between 2013 and 2017 and will
measure parallaxes and proper motions with the precision of 10μas at K≃ 12 - 15 mag. JASMINE will observe a few hundred million stars belonging to the disk and the bulge components of our Galaxy,
which are hidden by the interstellar dust extinction in optical bands. Furthermore, JASMINE will also obtain photometry of
stars in K, J and H-bands. The main objective of JASMINE is to study the most fundamental structure and evolution of the disk and the bulge components
of the Milky Way Galaxy.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
53.
Takahisa Furuichi Nobutomo Osanai Shin-ichiro Hayashi Norihiro Izumi Tomoko Kyuka Yasuhiro Shiono Tomoyoshi Miyazaki Tomoya Hayakawa Norihiro Nagano Naoki Matsuoka 《Landslides》2018,15(8):1645-1655
In August 2016, Typhoon 1610 (Lionrock) caused heavy rainfall in Hokkaido, which led to the discharge of a large volume of sediment and water from catchments on the eastern slope of the northern Hidaka Range. The eight catchments examined in this study are characterized by granitic lithology and late Pleistocene periglacial landforms with weakly cohesive, low-resistance periglacial debris thickly covering the weathered bedrocks. This characteristic of the landscape presumably provided a transport-limited condition where some debris flows were initiated by shallow landslides. As they moved, the debris flows grew larger through mobilization and erosion of sediment in channel beds and sidewalls. This sediment mobilization and erosion continued for an extensive distance along the course of the river. Morphological changes induced by channel aggradation and bank erosion were considerable and distinctive from upstream to downstream. Granitic periglacial sediments are amply present on the mountain slopes, river channels, and river banks in the area, likely due to the rarity of intensive rainfall events. These distinctive features of fossil periglacial catchments are important for disaster prevention and catchment-scale sediment management in sub-boreal areas, particularly in the context of climate change, which may generate more frequent and intensive rainfall events. 相似文献
54.
55.
David Mimoun Mark A. Wieczorek Leon Alkalai W. Bruce Banerdt David Baratoux Jean-Louis Bougeret Sylvain Bouley Baptiste Cecconi Heino Falcke Joachim Flohrer Raphael F. Garcia Robert Grimm Matthias Grott Leonid Gurvits Ralf Jaumann Catherine L. Johnson Martin Knapmeyer Naoki Kobayashi Alexander Konovalenko David Lawrence Mathieu Le Feuvre Philippe Lognonné Clive Neal Jürgen Oberst Nils Olsen Huub R?ttgering Tilman Spohn Susanne Vennerstrom Graham Woan Philippe Zarka 《Experimental Astronomy》2012,33(2-3):529-585
Farside Explorer is a proposed Cosmic Vision medium-size mission to the farside of the Moon consisting of two landers and an instrumented relay satellite. The farside of the Moon is a unique scientific platform in that it is shielded from terrestrial radio-frequency interference, it recorded the primary differentiation and evolution of the Moon, it can be continuously monitored from the Earth–Moon L2 Lagrange point, and there is a complete lack of reflected solar illumination from the Earth. Farside Explorer will exploit these properties and make the first radio-astronomy measurements from the most radio-quiet region of near-Earth space, determine the internal structure and thermal evolution of the Moon, from crust to core, and quantify impact hazards in near-Earth space by the measurement of flashes generated by impact events. The Farside Explorer flight system includes two identical solar-powered landers and a science/telecommunications relay satellite to be placed in a halo orbit about the Earth–Moon L2 Lagrange point. One lander would explore the largest and oldest recognized impact basin in the Solar System— the South Pole–Aitken basin—and the other would investigate the primordial highlands crust. Radio astronomy, geophysical, and geochemical instruments would be deployed on the surface, and the relay satellite would continuously monitor the surface for impact events. 相似文献
56.
Abstract Sampling of submarine sediments by an improved piston corer and a bucket dredger has been carried out since 1973. The length of the core samples ranged from 0.9 m to 5.4 m. The recovery ratio ranged from 39.1 percent to 98.9 percent. The physical and engineering properties of 16 sediment cores and the physical properties of 125 dredged samples were determined, and variation of these properties was analyzed. Clayey silts and silty clays cover the floor of relatively wide bays and sea areas. Sands and sandy silts blanket the floor of channels that have swift currents, and are also found in the vicinity of estuaries. The piston core samples showed considerable sample disturbance, which should be estimated quantitatively in the future. 相似文献
57.
Naoki Kabeya Nick A. Chappell Wlodek Tych Akira Shimizu Shiho Asano Hiroaki Hagino 《水文科学杂志》2016,61(9):1716-1727
ABSTRACTA new method known as Unobserved Components–Dynamic Harmonic Regression (UC-DHR) was applied to a 39-year record of rainfall and streamflow for three sub-catchments of the Sarukawa Experimental Watershed in southwestern Japan. Some 25% of the timber was harvested from one of the sub-catchments in May–July 1982 and the objective was to quantify the magnitude of this effect relative to the effects of climate cycles (e.g. Southern Oscillation Index). The observed effects of inter-annual climate cycles (i.e. 0.89–1.36 mm/d) were seen to be comparable (i.e. 0.70–1.17 mm/d) to the effects of harvesting 25% of the standing timber. This result underlines the importance of always quantifying the effect of climate on streamflow response when harvesting impacts are studied.
Editor D. Koutsoyiannis; Associate editor T. Okruszko 相似文献
58.
Measurements of Rare Earth Element and Other Element Mass Fractions in Environmental Reference Materials (NIST SRM 1646a,NIST SRM 1400, IAEA‐395 and IAEA‐450) by INAA,ICP‐AES and ICP‐MS 下载免费PDF全文
Vu Dong Cao Raymond Sucgang Thien Quang Tran Doanh Van Ho Naoki Shirai Mitsuru Ebihara 《Geostandards and Geoanalytical Research》2017,41(2):303-315
INAA, ICP‐AES and ICP‐MS were used to elementally characterise four environmental reference materials – NIST SRM 1646a (Estuarine Sediment), NIST SRM 1400 (Bone Ash), IAEA‐395 (Urban Dust) and IAEA‐450 (Algae). An analytical scheme consisting of the three methods was first applied to NIST SRM 1646a to validate the methodology because it has been extensively analysed and has certified values for many elements. With repeated analyses of NIST SRM 1646a, the accuracy and measurement repeatability of the data obtained were evaluated based on two statistical calculations (zeta‐score and Horwitz ratio) and were observed to be good enough for the analytical scheme to be applied to similar sorts of environmental/geochemical samples. Applying the same approach to NIST SRM 1400, IAEA‐395 and IAEA‐450, enabled mass fractions of 29, 38 and 28 elements to be determined, respectively. Among these results, the data for rare earth elements are of particular interest, not only for IAEA‐450 but also for the other three reference samples. The data for Pr, Gd, Dy, Ho, Er and Tm in NIST SRM 1646a are newly reported in this study. By using small test portions (< 100 mg) for NIST SRM 1646a and IAEA‐395, and recommended minimum amounts for NIST SRM 1400 and IAEA‐450, sample homogeneity was evaluated. 相似文献
59.
Reishi Takashima Hiroshi Nishi Toshiro Yamanaka Keiichi Hayashi Amane Waseda Akiko Obuse Takashige Tomosugi Naoki Deguchi Sunao Mochizuki 《Earth and Planetary Science Letters》2010,289(3-4):570-582
Making Upper Cretaceous biostratigraphic correlations between the Northwest Pacific and Tethyan–Atlantic sections have been difficult because of rare frequencies of age-diagnostic macro- and microfossils in the sequences in the Northwest Pacific region. In order to correlate these sections precisely, an integrated planktic foraminiferal and bulk wood carbon-isotope stratigraphy from the upper Cenomanian to the lower Campanian succession (the middle–upper part of the Yezo Group) of Hokkaido, northern Japan is established with an average resolution of 50 k.y. The δ13C curves from bulk wood of the Yezo Group and from bulk carbonate of English Chalk show remarkably similar patterns of isotopic fluctuation, allowing the correlation of 22 carbon isotopic events between these sections. This high-resolution correlation greatly improves the previous micro- and macrofossil biostratigraphic schemes in the Northwest Pacific region, and reveals that global events, such as the oxygen depletion at the OAE 2 horizon, the constant decrease in pCO2 during the Late Cretaceous, and the eustatic sea-level falls in the late middle Turonian, Santonian/Campanian Boundary and early Campanian, are recorded in the Upper Cretaceous sequence of the Northwest Pacific. 相似文献
60.
The Neogene marine sedimentary rock area in the eastern marginal region of the Japan Sea is an area with some of the highest landslide densities in Japan. Some of the landslides in this area have been known to involve saline groundwater, which can be the cause of these landslides. In order to demonstrate the relationships between landslides and saline water, topographic, geological, groundwater, and electromagnetic surveys were performed in the eastern marginal region of the Japan Sea. Many landslides and gravitational slope deformations with linear depressions and small scarps were recognized in the study area. The resistivity profile obtained by an electromagnetic survey suggests that there is a wide zonal distribution of saline water with salt concentrations equivalent to seawater at depths of 50–100 m or more and that the groundwater shallower than 50 m has an electrical conductivity of less than 100 mS/m. The shallow resistive groundwater is inferred to be meteoric water that replaced the saline groundwater, which likely weakened the bedrock, resulting in landslides. A ridge of competent tuff overlying mudstone has many linear depressions from gravitational slope deformation and low‐resistivity water to a depth of 600 m, which suggests that the mudstone was weakened by water replacement and deformed under the tuff caprock. The saline groundwater is inferred to be fossil seawater trapped in pores during sediment deposition, which is brought near the ground surface along with rocks by tectonic movement in the hills. Thus, the saline water and its fresh water replacement are among the important basic causes of the landslides. The oil well data obtained in the eastern marginal region of the Japan Sea suggest that such saline water replacement has occurred widely and that replacement is likely one of the predispositions for the frequent landslides there. 相似文献