New age constraints on counter-clockwise rotation of NE Japan     

Ayumi K. Baba  Takaaki Matsuda  Tetsumaru Itaya  Yutaka Wada  Noriyuki Hori  Masahiko Yokoyama  Nobuaki Eto  Rieko Kamei  Haider Zaman  Tesfaye Kidane  Yo-Ichiro Otofuji 《Geophysical Journal International》2007,171(3):1325-1341

  相似文献   

Preservation of near-solar neon isotopic ratios in Icelandic basalts     

Eleanor T. Dixon  Masahiko Honda  Ian McDougall  Ian H. Campbell  Ingvar Sigurdsson 《Earth and Planetary Science Letters》2000,180(3-4):309-324

Neon isotopic ratios measured in olivine and basaltic glass from Iceland are the most primitive observed so far in terrestrial mantle-derived samples. Ratios were measured in gas released from olivine and basaltic glass from a total of 10 samples from the Reykjanes Peninsula, Iceland, and one sample from central Iceland. The neon isotopic ratios include solar-like, mid-ocean ridge basalt (MORB)-like and atmospheric compositions. Neon isotopic ratios near the air–solar mixing line were obtained from the total gas released from glass separates from five samples. MORB-like neon isotopic compositions were measured in the total gas released from olivine and glass separates from four samples. Although there is clear evidence for a solar neon component in some of the Icelandic samples, there is no corresponding evidence for a solar helium ratio (320R_a>³He/⁴He>100R_a). Instead, ³He/⁴He ratios are mainly between 12±2(R_a) and 29±3(R_a), similar to the range observed in ocean island basalts, indicating that the He–Ne isotopic systematics are decoupled. The mantle source of Icelandic basalts is interpreted to be highly heterogeneous on a local scale to explain the range in observed helium and neon isotopic ratios. The identification of solar-like neon isotopic ratios in some Icelandic samples implies that solar neon trapped within the Earth has remained virtually unchanged over the past 4.5 Ga. Such preservation requires a source with a high [Ne_solar]/[U+Th] ratio so that the concentration of solar neon overwhelms the nucleogenic ²¹Ne* produced from the decay of U and Th in the mantle over time. High [Ne_solar]/[U+Th] ratios are unlikely to be preserved in the mantle if it has experienced substantial melting. An essentially undegassed primitive mantle component is postulated to be the host of the solar neon in the Icelandic plume source. Relatively small amounts of this primitive mantle component are likely to mix with more depleted and degassed mantle such that the primitive mantle composition is not evident in other isotopic systems (e.g. strontium and neodymium). The lower mantle plume source is inferred to be relatively heterogeneous owing to being more viscous and less well stirred than the upper mantle. This discovery of near-solar neon isotopic ratios suggests that relatively primitive mantle may be preserved in the Icelandic plume source.  相似文献   

Crystallization temperature determination of Itokawa particles by plagioclase thermometry with X‐ray diffraction data obtained by a high‐resolution synchrotron Gandolfi camera     

Masahiko Tanaka  Tomoki Nakamura  Takaaki Noguchi  Aiko Nakato  Hatsumi Ishida  Toru Yada  Kei Shirai  Akio Fujimura  Yukihiro Ishibashi  Masanao Abe  Tatsuaki Okada  Munetaka Ueno  Toshifumi Mukai 《Meteoritics & planetary science》2014,49(2):237-244

The crystallization temperatures of Itokawa surface particles recovered by the space probe Hayabusa were estimated by a plagioclase geothermometer using sodic plagioclase triclinicity. The Δ131‐index required for the thermometer, which is the difference in X‐ray diffraction peak positions between the 131 and 11 reflections of plagioclase, was obtained by a high‐resolution synchrotron Gandolfi camera developed for the third generation synchrotron radiation beamline, BL15XU at SPring‐8. Crystallization temperatures were successfully determined from the Δ131‐indices for four particles. The observed plagioclase crystallization temperatures were in a range from 655 to 660 °C. The temperatures indicate crystallization temperatures of plagioclases in the process of prograde metamorphism before the peak metamorphic stage.  相似文献   

The Structure of Young Stellar Jets and Winds Revealed by High Resolution [Fe II] λ1.644μm Line Observations     

Tae-Soo Pyo  Masahiko Hayashi  Naoto Kobayashi  Alan T. Tokunaga  Hiroshi Terada  Miwa Goto  Takuya Yamashita  Yoichi Itoh  Hideki Takami  Naruhisa Takato  Yutaka Hayano  Wolfgang Gaessler  Yukiko Kamata  Yosuke Minowa  Masanori Iye 《Astrophysics and Space Science》2003,287(1-4):21-24

We present high angular resolution spectra taken along the jets from L1551 IRS 5 and DG Tau obtained with the Subaru Telescope. The position-velocity diagrams of the [Fe II] λ 1.644 μmemission line revealed remarkably similar characteristics for the two sources, showing two distinct velocity components separated from each other in both velocity and space with the entire emission range blueshifted with respect to the stellar velocity. The high velocity component (HVC) has a velocity of –200 ––300 km s^-1 with a narrow line width, while the low velocity component (LVC) is around –100 km s^-1 exhibitinig a broad line width. The HVC is located farther away from the origin and is more extended than the LVC. Our results suggest that the HVC is a well-collimated jet originating from the region close to the star, while the LVC is a widely-opened wind accelerated in the region near the inner edge of the accretion disk.  相似文献   

Recovery of entire shocked samples in a range of pressure from ~100 GPa to Hugoniot elastic limit          下载免费PDF全文

Keita Nagaki  Toshihiko Kadono  Tatsuhiro Sakaiya  Tadashi Kondo  Kosuke Kurosawa  Yoichiro Hironaka  Keisuke Shigemori  Masahiko Arakawa 《Meteoritics & planetary science》2016,51(6):1153-1162

We carried out laser shock experiments and wholly recovered shocked olivine and quartz samples. We investigated the petrographic features based on optical micrographs of sliced samples and found that each recovered sample comprises three regions, I (optically dark), II (opaque), and III (transparent). Scanning electron microscopy combined with electron backscattered diffraction shows that there are no crystal features in the region I; the materials in the region I have once melted. Moreover, numerical calculations performed with the iSALE shock physics code suggest that the boundary between regions II and III corresponds to Hugoniot elastic limit (HEL). Thus, we succeeded in the recovery of the entire shocked samples experienced over a wide range of pressures from HEL (~10 GPa) to melting pressure (~100 GPa) in a hierarchical order.  相似文献   

Halogens and noble gases in Mathematician Ridge meta-gabbros,NE Pacific: implications for oceanic hydrothermal root zones and global volatile cycles     

Mark A. Kendrick  Masahiko Honda  David A. Vanko 《Contributions to Mineralogy and Petrology》2015,170(5-6):1-20

  相似文献   

The effect of ENSO on rainfall characteristics in the tropical peatland areas of Central Kalimantan,Indonesia     

Gatot E. Susilo  Koichi Yamamoto  Tsuyoshi Imai  Yoshiyuki Ishii  Hiroshi Fukami  Masahiko Sekine 《水文科学杂志》2013,58(3):539-548

Abstract

The effect of the El Niño Southern Oscillation (ENSO) on rainfall characteristics in the tropical peatland areas of Central Kalimantan, Indonesia, is demonstrated. This research used rainfall data collected between 1978 and 2008. The results suggest a relationship between ENSO events and the trend in rainfall observed in the study area. Further analyses show that El Niño events have a stronger effect on the rainfall compared to La Niña events. El Niño events were also correlated to the increase in the number of days with less than 1 mm of rainfall in the dry season. The analysis reveals that the impact of El Niño events on rainfall in dry seasons is intensifying annually. Furthermore, ENSO events are not the only factors affecting rainfall trends in the observed area. Other factors, such as deforestation, may also affect the trend.

Editor Z.W. Kundzewicz

Citation Susilo, G.E., Yamamoto, K., Imai, T., Ishii, Y., Fukami, H., and Sekine, M., 2013. The effect of ENSO on rainfall characteristics in the tropical peatland areas of Central Kalimantan, Indonesia. Hydrological Sciences Journal, 58 (3), 539–548.  相似文献   

Longitudinal asymmetry of craters' density distributions on the icy satellites     

Jacek Leliwa-Kopystynski  Marcin Banaszek  Ireneusz Wlodarczyk 《Planetary and Space Science》2012,60(1):181-192

Crater's density distribution versus satellitographical longitude was searched for seven icy satellites: two of Jupiter (Ganymede and Callisto) and five of Saturn (Mimas, Tethys, Dione, Rhea and Iapetus). Craters were classified according to their size. Four bins of the craters' diameter were used. Density distributions were found in the longitudinal sectors of the near-equatorial stripes that circumscribe the satellites. The size distributions (R-plots) were done independently for each of the eight longitudinal sectors of the satellites. Searching for the leading/trailing (apex/antapex) and the near-side/far-side asymmetry was done. It was found that the crater density is longitudinally asymmetric for all seven satellites being studied. However, the apex–antapex asymmetry is much less pronounced than predicted by theory of Zahnle et al. (2003), for impacts on the satellites by ecliptic comets. We conclude that the impact craters observed on the considered satellites are mostly originated from planetocentric swarm of debris. In that case longitudinal asymmetry is not expected, as stated by Horedt and Neukum, 1984a, Horedt and Neukum, 1984b. However, cratering longitudinal asymmetry that we observe for Mimas perfectly agrees with calculations of Alvarellos et al. (2005). It is very likely that important part of craters on Mimas were formed due to impacts of ejecta originated from crater Herschel.  相似文献   

Criteria for the occurrence of wind-driven coastal upwelling associated with “Aoshio” on the southeast shore of Tokyo Bay     

Zhongfan Zhu  Masahiko Isobe 《Journal of Oceanography》2012,68(4):561-574

At the head of Tokyo Bay, coastal upwelling of oxygen-depleted bottom water, induced by northeasterly wind-driven circulation, sometimes leads to the deaths of many shellfish and other aquatic animals across large areas, resulting in substantial economic losses to coastal fisheries. One of the chemical actions associated with this dynamic process is the oxidation of hydrogen sulfide in the bottom water into a colloidal sulfur substance. When sunshine reflects off surface water containing these sulfur particles, the seawater appears milky blue. This phenomenon has been termed “Aoshio.” One of the most important issues to address concerning upwelling in relation to Aoshio is to accurately predict when it will occur as well as its area and scale. In the preliminary study described here, we propose criteria for the occurrence of wind-driven upwelling associated with Aoshio on the southeast shore of Tokyo Bay using two analytical solutions. These two solutions were derived based on some specific assumptions in the context of a two-layered fluid. Comparison with observation data suggested that the criteria were valid. The results of analyses of the sensitivity of the solutions to all of the parameters incorporated into them were also found to be in accord with our qualitative understanding of this phenomenon.  相似文献   

Availability of an equation to evaluate error by optical path discretization in radiative transfer computation based on the successive order of scattering method   总被引：1，自引：0，他引：1  

Akihiko Tanaka  Masahiko Fujii  Tomohiko Oishi 《Journal of Oceanography》2012,68(1):215-218

The availability of an equation to evaluate the influence of multiple scattering in the single scattering process corresponding to a layer of arbitrary optical thickness was established. In order to confirm the validity of this equation, the radiance distribution in this layer was computed using a plane–parallel layer model based on the successive order of scattering method. The relative errors in a radiance distribution computed were evaluated as a function of optical thickness by the derived equation. It was shown that this equation provides a theoretical background for determining layer thickness using the plane–parallel layer model.  相似文献