Combining IR and X‐ray microtomography data sets: Application to Itokawa particles and to Paris meteorite     

Zelia Dionnet  Rosario Brunetto  Alice Alon‐Toppani  Stefano Rubino  Donia Baklouti  Ferenc Borondics  Anne‐Ccile Buellet  Zahia Djouadi  Andrew King  Tomoki Nakamura  Alessandra Rotundi  Christophe Sandt  David Troadec  Akira Tsuchiyama 《Meteoritics & planetary science》2020,55(7):1645-1664

In the near future, a new generation of sample return missions (Hayabusa2, OSIRIS‐REx, MMX, etc.) will collect samples from small solar system bodies. To maximize the scientific outcome of laboratory studies and minimize the loss of precious extraterrestrial samples, an analytical sequence from less destructive to more destructive techniques needs to be established. In this work, we present a combined X‐ray and IR microtomography applied to five Itokawa particles and one fragment of the primitive carbonaceous chondrite Paris. We show that this analytical approach is able to provide a 3‐D physical and chemical characterization of individual extraterrestrial particles, using the measurement of their 3‐D structure and porosity, and the detection of mineral and organic phases, and their spatial co‐localization in 3‐D. We propose these techniques as an efficient first step in a multitechnique analytical sequence on microscopic samples collected by space missions.  相似文献   

Wind and buoyancy driven intermediate-layer overturning in the Sea of Okhotsk     

Junji Matsuda  Humio Mitsudera  Tomohiro Nakamura  Keisuke Uchimoto  Takuya Nakanowatari  Naoto Ebuchi 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(9):1401-1418

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Observation of Sea-Ice Thickness Using ENVISAT Data From LÜtzow-Holm Bay, East Antarctica     

Nakamura  K. Wakabayashi  H. Uto  S. Ushio  S. Nishio  F. 《Geoscience and Remote Sensing Letters, IEEE》2009,6(2):277-281

To investigate the suitability of synthetic aperture radar (SAR) polarization data to estimate the sea-ice thickness in early summer in Lutzow-Holm Bay, Antarctica, we compared in situ ice thicknesses with the corresponding backscattering co-efficient for each polarization and the VV-to-HH backscattering ratio. The VV-to-HH backscattering ratio was derived from data acquired by ENVISAT Advanced SAR (ASAR). This ratio is related to the near-surface dielectric constant of the sea ice, which is, in turn, related to the developing process of ice and, thus, its thickness via changes in the near-surface sea-ice salinity. The sea ice encountered in the study area is close first-year pack ice and fast ice. For these old and relatively rough sea-ice types, the VV-to-HH backscattering ratio can be expected to depend on salinity-driven changes in the near-surface dielectric constant rather than changes of the surface roughness. We applied the empirical relationships between the ice thickness and the VV-to-HH backscattering ratio with the linear and logarithm fits to ASAR data. The linear fit gave the reliable result, with an rms error being 0.08 m and a correlation coefficient being 0.91, when compared to in situ fast-ice thickness.  相似文献   

Sedimentary Steryl Chlorin Esters (SCEs) and Other Photosynthetic Pigments as Indicators of Paleolimnological Change Over the Last 28,000 Years from the Buguldeika Saddle of Lake Baikal     

Yuko Soma  Yukinori Tani  Mitsuyuki Soma  Hideo Mitake  Ryo Kurihara  Shinya Hashomoto  Takahiro Watanabe  Toshio Nakamura 《Journal of Paleolimnology》2007,37(2):163-175

Detailed depth profiles of photosynthetic pigments in a sediment core (G-12) collected at the BDP93 site, the Buguldeika saddle, of south Lake Baikal, along with depth profiles of total organic carbon (TOC) and biogenic silica, were studied to elucidate the temporal changes of phytoplankton assemblages in the lake during the past 28 kyr. In addition to the quantification of carotenoids by high-performance liquid chromatography with photodiode-array detection (HPLC-PDA), steryl chlorin esters (SCEs) were analyzed by HPLC-PDA, HPLC-mass spectrometry (LC-MS) and sterols in SCEs by gas chromatography–mass spectrometry (GC–MS) to enrich the taxonomical information on the phytoplankton composition. Allochthonous input of organic matter from the Selenga River resulted in the higher TOC contents in core G-12 than in a previously reported core (G-6) collected at another site from the southern basin. The poorer correlation in core G-12 than in G-6 between TOC and chlorophyll-a-originating pigments, which are indicative of autochthonous production, also indicated a significant allochthonous input at the site. The abundance of lutein among the carotenoids detected, and the good correlation of total chlorophyll a and b shows that green algae represented a significant portion of the phytoplankton, accompanying the diatoms at the G-12 site, after the last glacial period. The presence of cryptomonads and cyanobacteria were confirmed from marker carotenoids in the sediment core. GC–MS analysis of sterols in SCEs detected marker sterols of diatoms, green algae, chrysophytes and dinoflagellates. The depth profiles of the measured indicators gave consistent features for temporal changes in phytoplankton assemblage at the G-12 site of Lake Baikal after the last glacial maximum. Notably, the profile of a chrysophyte-specific sterol in SCEs was consistent with the reported distribution of chrysophyte cysts during the Holocene. The presence of phytoplankton, such as green algae, diatoms and chrysophytes, in Lake Baikal during the late last glacial period was indicated by the analysis of sterols in SCEs. Sedimentary carotenoids and sterols in SCEs were found to give complementary information about phytoplankton composition. These molecular indicators allow us to reconstruct past lake phytoplankton assemblages responding to environmental changes with a time resolution as high as age–depth relationship in sediments attainable at present.  相似文献   

Oceanic crust and Moho of the Pacific Plate in the eastern Ogasawara Plateau region     

Takeshi  Tsuji  Yasuyuki  Nakamura  Hidekazu  Tokuyama  Millard F.  Coffin  Keita  Koda 《Island Arc》2007,16(3):361-373

Abstract   To show the structure of oceanic crust and Moho around the eastern Ogasawara Plateau, we have analyzed industry-standard two-dimensional multichannel seismic reflection data. To obtain improved velocity models, phase information of seismic signals was used for velocity analysis and velocity models for oceanic crust above Moho were determined. We apply this velocity analysis technique to seismic reflection data around the eastern Ogasawara Plateau, with the result of clear images of structures within oceanic crust and Moho. South of the Ogasawara Plateau, Moho deepens proximal to the Plateau. Moho distal to the Plateau is ca 7 km below sea floor (bsf), whereas it is ca 10 km bsf near the Plateau. The characters of oceanic crust and Moho differ significantly north and south of the Plateau. To the north, the structure of oceanic crust is ambiguous, the sea floor is shallower and less smooth, and Moho is discontinuous. To the south, structures within oceanic crust and Moho are imaged clearly, and the sea floor is deeper. A strong Moho reflection south of the Plateau might represent a sharp boundary between layered gabbro and peridotite. However, discontinuous Moho reflections north of the Plateau might represent rough topography because of intensive magmatism or a gradual downward increase in velocity within a thick Moho transition zone. A fracture zone north of the Plateau also appears to separate oceanic crust and Moho of different characters, suggesting vigorous magmatism between the Plateau and the fracture zone, and that the Ogasawara Plateau and the fracture zone influenced the genesis of oceanic crust and upper mantle. Differences in acoustic characteristics to the north and south of the Plateau are apparent in profiles illuminated by seismic attributes.  相似文献   

Semidiurnal tides from the extended Canadian Middle Atmosphere Model (CMAM) and comparisons with TIMED Doppler interferometer (TIDI) and meteor radar observations     

J. Du  W.E. Ward  J. Oberheide  T. Nakamura  T. Tsuda 《Journal of Atmospheric and Solar》2007,69(17-18):2159

The extended Canadian Middle Atmosphere Model (extended CMAM) is a general circulation model, which extends from the surface to about 210 km. Spatial complex spectral analysis is applied to horizontal winds simulated by the extended CMAM to obtain semidiurnal tidal amplitudes and phases (from e5 to w5) in the mesosphere and lower thermosphere (MLT) region. The dominant w2 migrating component and the presence of eight nonmigrating tides (w3, w4, w5, e1, e2, e3, e4 and e5) in the mid-latitudes are identified. Components w1 and s0, which tend to maximize at high latitudes, will be discussed separately in a later paper. The migrating semidiurnal tide (w2) has amplitudes reaching over 20 m s⁻¹ for both zonal and meridional winds in the mid-latitude region. Its form compares well to the published results. The amplitudes of nonmigrating semidiurnal tides are non-negligible compared with the migrating semidiurnal tides. The amplitudes for w3 and e2 exceed 12 and 8 m s⁻¹, respectively.Comparisons are made with four nonmigrating semidiurnal components (w3, w4, e1 and e2) derived from the TIMED Doppler interferometer (TIDI) wind measurements between 85 and 105 km altitude and between 45°S and 45°N latitude. Overall, the basic CMAM and TIDI latitudinal structures of the amplitudes agree well and the agreement between the annual mean amplitudes varies with component. Relative to the TIDI results, the CMAM seasonal variations of w4 are in good agreement, of e2 are in reasonable agreement, of w3 are in partial agreement and of e1 are in poor agreement.The 11 semidiurnal components from the model are superimposed to generate the total semidiurnal winds at Jakarta (6°S, 106°E) and Kototabang (0°, 100°E) and are compared with measurements from two equatorial meteor radar stations at these sites. The relative contributions of components to the reconstructed amplitude vary from month to month. The CMAM reconstructions are generally larger than the radar results by a factor varying between one and two. The phases in the radar data are typically stationary with respect to height, whereas they generally decrease with height in the CMAM reconstruction.  相似文献   

Remote effects of tropical storm Cristobal upon a cut-off cyclone over Europe in August 2002     

T. Enomoto  W. Ohfuchi  H. Nakamura  M. A. Shapiro 《Meteorology and Atmospheric Physics》2007,96(1-2):29-42

Summary In August 2002, many parts of central Europe were affected by heavy precipitation and flooding caused by a cut-off cyclone. This study shows that this cyclone developed as a result of the propagation of a Rossby wave packet. The wave-packet propagation along the relatively weak subtropical jet was accompanied by wave-breaking and re-emission in the subtropics. In particular, there was an interaction between the Rossby wave packet and a precipitation band along the east coast of North America associated with tropical storm Cristobal. This interaction had a significant influence upon the formation of the European cut-off low. Results from numerical simulations from two different initial conditions are investigated to study this interaction. Downstream influences from tropical storm Cristobal upon the development of this cyclone and associated flooding precipitation are confirmed by sensitivity analysis using ensemble forecasts. It is concluded from analysis and simulations that poor forecast skills of tropical storm Cristobal affected the predictability of the European cut-off low.  相似文献   

Volcanoes as possible indicators of tectonic stress orientation — principle and proposal     

Kazuaki Nakamura 《Journal of Volcanology and Geothermal Research》1977,2(1):1-16

A method is proposed for determining the orientation of average tectonic stress, using surface features indicating radial dike patterns of volcanoes. The approximate pattern of radial dikes is revealed by the distribution of sites of flank eruptions on the slope of polygenetic volcanoes. This conclusion is deduced from the understanding that flank eruptions are caused by the magma that laterally offshoots from the main polygenetic pipe conduit and that conduits of flank volcanoes are most probably fissure-shaped because most of them are monogenetic volcanoes. Radial dikes are more likely to develop in a direction normal to the minimum horizontal compression of the regional stress. Thus, the distribution of flank craters will be elongate in the direction of the maximum horizontal compression of the regional stress.The regional stress can sometimes be ascribed solely to the effect of the gravity rather than tectonic stress. When a number of independent polygenetic volcanoes dotted with more than several flank volcanoes, are distributed in a belt or over a broad area, it is possible to distinguish the tectonic stress from the direct gravitational effect by the regional uniformity in orientation of the zones of flank volcanoes. When the maximum compression of tectonic stress is horizontal, the trends of the zones of flank eruptions on polygenetic volcanoes are more or less linear and parallel, and at a high angle to the trend of the main volcanic belt.  相似文献   

Elevated serum vitellogenin levels and gonadal abnormalities in wild male flounder (Pleuronectes yokohamae) from Tokyo Bay, Japan.   总被引：8，自引：0，他引：8  

S Hashimoto  H Bessho  A Hara  M Nakamura  T Iguchi  K Fujita 《Marine environmental research》2000,49(1):37-53

Concentrations of vitellogenin (VTG) in serum of wild male flounder (Pleuronectes yokohamae) were investigated, as a biomarker for environmental estrogens in marine waters, from January 1997 to May 1998 in Tokyo Bay, Japan (n = 130) and from a reference site in Hokkaido, Japan, far from urban areas (about 40 km from Hakodate city) from March 1997 to June 1998 (n = 62). Statistically higher concentrations of serum VTG were detected in wild male flounder collected in Tokyo Bay (range: 25-2200 ng ml-1) compared to fish from Hokkaido (range: 31-91 ng ml-1) throughout the entire sampling period. Three out of 20 males collected off Haneda, in the inner part of Tokyo Bay, showed testes containing small numbers of oocytes. This intersex condition was not found among males collected from the reference site. This study suggests that the abnormally high levels of VTG and the presence of oocytes in the testis of male flounder collected from Tokyo Bay could be the effect of environmental estrogens.  相似文献   

Geochemical record of the Holocene Jomon transgression and human activity in coastal lagoon sediments of the San'in district, SW Japan   总被引：1，自引：0，他引：1  

H. Ishiga  T. Nakamura  Y. Sampei  T. Tokuoka  K. Takayasu   《Global and Planetary Change》2000,25(3-4)

Coastal lagoon muds were analyzed to evaluate changes in sedimentary environments by the Jomon transgression from the lower to middle Holocene age and human activities. Core samples from Lake Shinji, Southwest Japan were utilized, which cover the entire Holocene Nakaumi Formation (ca. 23-m thick), and comprise the Lower, Middle, Upper and Uppermost members. Total sulfur (TS) contents and Fe₂O₃/Al₂O₃ ratios increase from the boundary of Middle and Upper members, which is 1 m below the Kikai-Akahoya (K-Ah) volcanic ash of 6300 years BP. This change coincides to the pollen flora zone boundary of the Pinus–Abies and the Cyclobalanopsis–Castanopsis, suggesting transition to a warming climate. Chemical index of alteration (CIA) values [(ratio of Al to Al+Ca+Na+K)×100] and Rb/K ratios also show gradual increase from the middle part of the Upper member, due to its derivation from highly weathered source material probably formed under warming and rainy condition. Al₂O₃/TiO₂ and SiO₂/TiO₂ show little variation from the Lower to the Upper members, probably related to consistent feldspar composition in the source rocks, and homogeneously mixed clays. In the Uppermost member (from 1500 years), sharp increases in Ti/Zr and decreases in both Nb/Y and Zr/Y occurred, suggesting heavy mineral fractionation. This change was caused by iron sand processing called Kannanagashi and charcoal-making in the most mountainous regions. Soil erosion by these processes brought changes in mud composition, shown by the enrichment in Al₂O₃, and depletion in Zr and Cr. Human activities thus had severe impacts on sedimentary environments compared with the natural changes since the Jomon transgression.  相似文献