排序方式： 共有27条查询结果，搜索用时 321 毫秒
1.
2.
Satoshi?KitajimaEmail author Naoki?Iguchi Naoto?Honda Tatsuro?Watanabe Osamu?Katoh 《Journal of Oceanography》2015,71(3):287-296
We investigated the horizontal distribution of Nemopilema nomurai medusae using a midwater trawl in the southwestern Sea of Japan from September to October of each year from 2006 to 2012. Numerous medusae of this species found in 2006, 2007, and 2009 were mainly distributed far (>40 km) from the mainland of Japan in the western part of the survey area, but were distributed in the stations closest (<25 km) to the mainland in the eastern part, particularly in 2006 and 2009. These distribution patterns were associated with the path of the second branch of the Tsushima Warm Current (TWC) that flows offshore to the west of Oki Islands and usually approaches the mainland of Japan to the east of Oki Islands. Differences in jellyfish distribution across the survey periods were related to the distribution of the second branch being associated with types, position and intensity of eddies in the eastern part of the survey area. Hence, the formations of eddies and consequent variation in the path of the TWC would be responsible for transporting medusae from offshore to near the mainland to the east of Oki Islands. Individuals with large bells accumulated in the northwestern part of the survey area, where a cyclonic eddy was present downstream of the third branch of the TWC. This variation in bell size distribution may be ascribed to differences in the physical and/or biological factors among the three branches of the TWC. 相似文献
3.
In-Jin Choi Takamichi Iguchi Sang-Woo Kim Teruyuki Nakajima Soon-Chang Yoon 《Meteorology and Atmospheric Physics》2014,123(3-4):181-194
This study performed a three-dimensional regional-scale simulation of aerosol and cloud fields using a meso-scale non-hydrostatic model with a bin-based cloud microphysics. The representation of aerosols in the model has been improved to account for more realistic multi-modal size distribution and multiple chemical compositions. Two case studies for shallow stratocumulus over Northeast Asia in March 2005 were conducted with different aerosol conditions to evaluate model performance. Improved condensation nuclei (CN) and cloud condensation nuclei (CCN) are attributable to the newly constructed aerosol size distribution. The simulated results of cloud microphysical properties (cloud droplet effective radius, liquid water path, and optical thickness) with improved CN/CCN number are close to the retrievals from satellite-based observation. The effects of aerosol on the microphysical properties of shallow stratocumulus are investigated by model simulation, in terms of columnar aerosol number concentration. Enhanced aerosol number concentration results in increased liquid water path in humid case, but invariant liquid water path in dry case primarily due to precipitation occurrence. The changes of cloud microphysical properties are more predominant for small aerosol burden than for large aerosol burden with the retarded changes in cloud mass and size due to inactive condensation and collision-coalescence processes. Quantitative evaluation of sensitivity factor between aerosol and cloud microphysical properties indicates a strong aerosol-cloud interaction in Northeast Asian region. 相似文献
4.
Asep Saepuloh Katsuaki Koike Makoto Omura Masato Iguchi Ari Setiawan 《Bulletin of Volcanology》2010,72(2):221-232
Mt. Merapi, Indonesia, is one of the most active and dangerous volcanoes in the Torrid Zone. This volcano has erupted frequently and has produced pyroclastic flows following the collapse of the summit lava dome. We used Synthetic Aperture Radar (SAR) data acquired by JERS-1 and RADARSAT-1 satellites from April 1996 to July 2006 to clarify the distribution patterns of the pyroclastic flow deposits. The extent of the deposits, termed P-zones, was accurately extracted by ratio operation and low-level feature extraction from SAR intensity images. These images highlighted temporal changes of the distribution area, perimeter, flow distance, included angle, and collapse direction. To validate the image-processing results, reflectance spectra of the rock samples collected after the eruption in June 2006 were measured in a laboratory. The reflectance spectra of all samples showed similar characteristics to the reference spectra, which were derived from atmospheric correction of Hyperion sensor image data covering the lava dome at the summit. Therefore, P-zones were confirmed to be the pyroclastic flow deposits originating from destruction of the lava dome at the summit. The image-processing results clarified that the extent of the distribution areas, perimeter, flow distances, and included angle of the P-zones were variable among the eruptions, while the collapse direction had a constant pattern. The collapse pattern followed a clockwise change from the south toward the west. By comparing the ratio maps of Bouguer gravity anomaly data in two periods, the change was interpreted to originate from the inclination of the conduit and the formation of shallow and deep magma reservoirs. 相似文献
5.
Fine particles of various chemical substances—carbon, iron, iron oxide and silica—which are expected to exist in interstellar space are prepared in argon gas. The size, shape, and crystal structure of the powder particles are studied by electron microscopy and electron diffraction, and may have some bearing on models of comets and of the solar nebula.The largest size we have obtained is about 0.1 μm and the smallest about 40Å. Generally the size becomes smaller for lower temperature and also for lower pressure. This tendency is discussed in connection with nucleation theories. Except for iron and iron oxide the powder particles have no crystal structure. 相似文献
6.
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
7.
Takeshi Nishimura Masato Iguchi Ryohei Kawaguchi Surono Muhamad Hendrasto Umar Rosadi 《Bulletin of Volcanology》2012,74(4):903-911
We examine the basic characteristics of inflations at Semeru Volcano, Indonesia, to clarify the pressurization process prior
to two different styles of explosive eruptions: Vulcanian eruptions and gas bursts. Analysis of data obtained from tilt meters
installed close to the active crater allows clarification of the common features and the differences between the two styles
of eruptions. To improve the signal-to-noise ratio and to determine the mean characteristics of the inflations, we stack tilt
signals obtained from eruptions of different magnitudes and evaluate the maximum amplitude of the seismic signal associated
with these eruptions. Vulcanian eruptions, which explosively release large amounts of ash, are preceded by accelerating inflation
about 200–300 s before the eruption, which suggests volume expansion of the gas phase. In contrast, gas bursts, which rapidly
effuse water steam accompanied by explosive sounds, follow non-accelerating changes of inflation starting 20 s before each
emission. Tilt amplitudes increase with the magnitude of eruptions for both eruption styles. This suggests that the volume
and/or pressure of magma or gas stored in the conduit before eruptions controls the magnitude of volcanic eruptions. These
results further suggest that the magnitude of eruptions can be predicted from geodetic measurements of volcano inflation. 相似文献
8.
A. Sakata N. Nakagawa T. Iguchi S. Isobe M. Morimoto F. Hoyle N.C. Wickramasinghe 《Astrophysics and Space Science》1999,268(1-3):133-135
Aromatic material extracted from the Murchison meteorite shows an absorption atλ2200 Å similar to the well-known interstellar absorption feature at this wavelength. This suggests a link between interstellar grain clumps containing organics and the presolar component of carbonaceous chondrites. 相似文献
9.
Koki Aizawa Wataru Kanda Yasuo Ogawa Masato Iguchi Akihiko Yokoo Hiroshi Yakiwara Takayuki Sugano 《Journal of Volcanology and Geothermal Research》2011,199(1-2):165-175
Continuous magnetotelluric (MT) measurements were conducted from May 2008 to July 2009 at Sakurajima, one of the most active volcanoes in Japan. Two observation sites were established at locations 3.3 km east and 3 km west–northwest of the summit crater. At both observation sites, the high-quality component of the impedance tensor (Zyx) showed variations in apparent resistivity of approximately ± 20% and phase change of ± 2°, which continued for 20–180 days in the frequency range between 320 and 4 Hz. The start of the period of changes in apparent resistivity approximately coincided with the start of uplift in the direction of the summit crater, as observed by a tiltmeter, which is one of the most reliable pieces of equipment with which to detect magma intrusion beneath a volcano. A 2D inversion of MT impedance suggests that the resistivity change occurred at a depth around sea level. One of the possible implications of the present finding is that the degassed volatiles migrated not only vertically through the conduit but also laterally through a fracture network, mixing with shallow groundwater beneath sea level and thereby causing the observed resistivity change. 相似文献
10.
Effects of acidified seawater on calcification,photosynthetic efficiencies and the recovery processes from strong light exposure in the coral Stylophora pistillata 
下载免费PDF全文
下载免费PDF全文 Takashi Nakamura Akira Iguchi Atsushi Suzuki Kazuhiko Sakai Yukihiro Nojiri 《Marine Ecology》2017,38(3)
The aim of this study was to investigate whether coral photosynthetic efficiencies and recovery processes are affected by CO2‐driven ocean acidification in symbiont photosynthesis and coral calcification. We investigated the effects of five CO2 partial pressure (pCO2) levels in adjusted seawater ranging from 300 μatm (pre‐industrial) to 800 μatm (near‐future) and strong and weak light intensity on maximum photosynthetic efficiency and calcification of a branching coral, Stylophora pistillata, as this species has often been used in rearing experiments to investigate the effects of acidified seawater on calcification and photosynthetic algae of corals. We found that, the photosynthetic efficiencies and recovery patterns under different light conditions did not differ among pCO2 treatments. Furthermore, calcification of S. pistillata was not affected by acidified seawater under weak or strong light conditions. Our results indicate that the photosynthetic efficiency and calcification of S. pistillata are insensitive to changes in ocean acidity. 相似文献