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Genki Terauchi Ryo Tsujimoto Joji Ishizaka Hideaki Nakata 《Journal of Oceanography》2014,70(2):175-184
Time series of the chlorophyll-a concentration (Chl-a) observed by ocean color satellites from 1998 to 2009 were used to assess eutrophication in Toyama Bay, the Sea of Japan. An overall mean of Chl-a during the 12-year period was used to divide the study area into “high” or “low” Chl-a areas based on a reference condition of 5 mg m?3. The annual maximum monthly mean Chl-a trend was estimated pixel-wise and its significance examined by the Sen slope test at a 90 % confidence level. By combining the level and trend of remotely sensed Chl-a, Toyama Bay was then classified into six eutrophication states: high-increasing, high-no trend, high-decreasing, low-increasing, low-no trend and low-increasing. Our study indicates that the combined use of both the level and trend of remotely sensed Chl-a can be an efficient method to preliminarily assess eutrophication of coastal waters after a quality screening process with level 2 flags and validation with in situ Chl-a data. 相似文献
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Seto Koji Katsuki Kota Tsujimoto Akira Kitagawa Junko Yamada Kazuyoshi Suzuki Yoshiaki 《Journal of Paleolimnology》2022,68(3):329-343
Journal of Paleolimnology - Sub-annual-scale environmental and ecosystem changes since the mid-18th century were reconstructed in a semi-closed lagoon, Lake Hiruga, located along the Sea of Japan... 相似文献
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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
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Stellar abundance pattern of n-capture elements such as barium is used as a powerful tool to infer how the star formation proceeded in dwarf spheroidal
(dSph) galaxies. It is found that the abundance correlation of barium with iron in stars belonging to dSph galaxies orbiting
the Milky Way, i.e., Draco, Sextans, and Ursa Minor have a feature similar to that in Galactic metal-poor stars. The common
feature of these two correlations can be realized by our in homogeneous chemical evolution model based on the supernova-driven
star formation scenario if dSph stars formed from gas with a velocity dispersion of ∼ 26 km s-1. This velocity dispersion together with the stellar luminosities strongly suggest that dark matter dominated dSph galaxies.
The tidal force of the Milky Way links this velocity dispersion with the currently observed value ≲ 10 km s-1 by stripping the dark matter in dSph galaxies. As a result, the total mass of each dSph galaxy is found to have been originally
∼ 25 times larger than at present. In this model, supernovae immediately after the end of the star formation can expel the
remaining gas over the gravitational potential of the dSph galaxy.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Takuji Tsujimoto Toshikazu Shigeyama Yuzuru Yoshii 《Astrophysics and Space Science》2002,281(1-2):221-222
Following our hypothesis that each supernova (SN) event triggers star formation in the swept-up gas, so that newly formed
stars inherit the elemental abundance pattern of individual SNe, we deduce the production sites and yields for r-process elements. We further show that a strong evidence for the origin of r-process nucleosynthesis products was just there in our backyard - supernova SN1987A -, and conclude that 20 M
⊙ SNe are the predominant production sites for r-process elements.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
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Wayne J. Stephenson Anna J. Taylor Maree A. Hemmingsen Hidekazu Tsujimoto Robert M. Kirk 《地球表面变化过程与地形》2004,29(13):1663-1673
We report a series of short‐term (diurnal) rock surface monitoring studies on inter‐ and supra‐tidal shore platforms using a traversing micro‐erosion meter at two sites, Kaikoura Peninsula, New Zealand, and Apollo Bay, Victoria, Australia. Statistically signi?cant day‐to‐day changes were measured. Surface rise and lowering occurred at rates above instrument error, with a maximum range of 3·378 mm between 1·697 mm (lowering) and ‐1·681 mm (rise). Individual measurements showed rises greater than 2 mm. These daily variations reveal that surface lowering and rise occur at a much shorter time scale than previously reported from other studies. The patterns observed suggest wetting and drying is the most likely process causing surface changes at these temporal scales. We argue that traversing micro‐erosion meter studies operating at a short‐term time scale of day‐to‐day provide meaningful results that open new opportunities for studying rock weathering and erosion in a coastal environment. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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Takaaki Noguchi Makoto Kimura Takahito Hashimoto Mitsuru Konno Tomoki Nakamura Michael E. Zolensky Ryuji Okazaki Masahiko Tanaka Akira Tsuchiyama Aiko Nakato Toshinori Ogami Hatsumi Ishida Ryosuke Sagae Shinichi Tsujimoto Toru Matsumoto Junya Matsuno Akio Fujimura Masanao Abe Toru Yada Toshifumi Mukai Munetaka Ueno Tatsuaki Okada Kei Shirai Yukihiro Ishibashi 《Meteoritics & planetary science》2014,49(2):188-214
On the basis of observations using Cs‐corrected STEM, we identified three types of surface modification probably formed by space weathering on the surfaces of Itokawa particles. They are (1) redeposition rims (2–3 nm), (2) composite rims (30–60 nm), and (3) composite vesicular rims (60–80 nm). These rims are characterized by a combination of three zones. Zone I occupies the outermost part of the surface modification, which contains elements that are not included in the unchanged substrate minerals, suggesting that this zone is composed of sputter deposits and/or impact vapor deposits originating from the surrounding minerals. Redeposition rims are composed only of Zone I and directly attaches to the unchanged minerals (Zone III). Zone I of composite and composite vesicular rims often contains nanophase (Fe,Mg)S. The composite rims and the composite vesicular rims have a two‐layered structure: a combination of Zone I and Zone II, below which Zone III exists. Zone II is the partially amorphized zone. Zone II of ferromagnesian silicates contains abundant nanophase Fe. Radiation‐induced segregation and in situ reduction are the most plausible mechanisms to form nanophase Fe in Zone II. Their lattice fringes indicate that they contain metallic iron, which probably causes the reddening of the reflectance spectra of Itokawa. Zone II of the composite vesicular rims contains vesicles. The vesicles in Zone II were probably formed by segregation of solar wind He implanted in this zone. The textures strongly suggest that solar wind irradiation damage and implantation are the major causes of surface modification and space weathering on Itokawa. 相似文献
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