On the effects of compression of a gaseous disc by thermal and dynamical pressures of intergalactic gas     

Yasuki Kumai  Makoto Tosa 《Astrophysics and Space Science》1986,119(1):211-212

We consider a galaxy moving in a cluster of galaxies and study the effects of compression of the gas disc by both thermal and dynamical pressures of intergalactic gas. As the result of compression, massive gas clouds are formed. They are not stripped by dynamical pressure of the intergalactic gas but stay in the galaxy until they are disrupted by formation of massive stars.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   

Large-scale active coronal phenomena in Yohkoh SXT images     

František Fárník  Zdeněk Švestka  Hugh S. Hudson  Yutaka Uchida 《Solar physics》1996,168(2):331-343

We discuss Yohkoh SXT observations of stationary giant post-flare arches which occurred on 3–6 May, 1992 and study in detail the last arch, associated with the flare at 19:02 UT on 5 May, which extended above the west limb. The arch was similar to the first giant arch discovered on board the SMM, on 21–22 May, 1980. We demonstrate that the long lifetimes of these structures necessarily imply additional energy input from the underlying active region: otherwise, conduction would cool these arches in less than one hour and even with the unlikely assumption of conduction inhibited, pure radiative cooling would not produce the temperature decrease observed. All arch tops, although varying in brightness, stayed for several days at a fairly constant altitude of 100 000 km, and the arch studied, on 5–6 May, was just a new brightening of the pre-existing decaying structure. The brightening was apparently due to inflow of hot plasma from the flare region. Yohkoh data confirm that these stationary arches are rare phenomena when compared with the rising arches studied in Paper I and with Uchida et al.'s expanding active regions.  相似文献   

Asteroids approaching the Earth from directions around the Sun     

Syuzo Isobe  Makoto Yoshikawa 《Earth, Moon, and Planets》1995,71(3):263-266

We have estimated close asteroid encounters with the Earth by numerical integrations of a system with the Sun, 9 planets, and 188 near-earth-asteroids during the period 1994–4600. Asteroids approach the Earth from directions within 30 around the Sun in more than 20% of encounters with the closest distance less than 0.01 AU. Since ground-based observations cannot detect these objects, we should develop space-borne and/or lunar observatories in a short time to allow enough warning time before a catastrophic collision.  相似文献   

Log N — log S of radio sources at 10 GHz with flat spectra     

Ko Aizu  Hiroto Tabara  Tatsuji Kato  Makoto Inoue 《Astrophysics and Space Science》1986,119(1):257-261

A logN — logS relation at 10 GHz is constructed for sources with the flat spectra 0.5 (flux densitySv ^–) from observations at NRO, MPIfR and others. Based on the source distribution on log (Luminosity) volume plane we obtain an epoch-depending luminosity function which explains the above relation.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.Nobeyama Radio Observatory, a branch of the Tokyo Astronomical Observatory, University of Tokyo, is a facility open for general use by researchers in the field of astronomy and astrophysics.  相似文献   

Study on the managanese nodule     

Akihiko Okada  Makoto Shima 《Journal of Oceanography》1970,26(3):151-158

Chemical and X-ray analyses were performed on the fifteen manganese nodules collected from the Pacific Ocean floor. The results were discussed compared with the previous data on the manganese nodules. Minerals were found to be todorokite, δ-MnO₂ and other silicates, montmorillonite, illite, phillipsite and α-SiO₂. Average composition shows that copper is concentrated on the deep sea nodules more than the shallow ones, and that the todorokite rich nodules contain more copper and nickel than the δ-MnO₂ rich ones. The analyses of fresh water iron-manganese precipitates by bacterial activity suggest that biological process is one of the important factors on the genesis of the sedimentary iron-manganese deposits, including the manganese nodule. The Institute of Physical and Chemical Research  相似文献   

Growth characteristics ofChattonella antiqua (Raphidophyceae)     

Yasuo Nakamura  Makoto M. Watanabe 《Journal of Oceanography》1983,39(3):110-114

Chattonella antiqua (Raphidophyceae), which causes heavy red tides in the Seto Inland Sea, Japan, was placed in axenic clonal culture by micropipette washing. The effects of temperature, salinity, light intensity and pH on growth were monitored. Maximum growth occurred at 25°C, at salinities between 25 and 41‰, under light intensities above 0.04 ly min^?1. The pH effect was not significant in the pH range from 7.6 to 8.3. Comparisons of our results with those from field observations suggest that the development of theC. antiqua red tide is strongly temperature dependent.  相似文献   

Estimating the Kuroshio Axis South of Japan Using Combination of Satellite Altimetry and Drifting Buoys   总被引：3，自引：4，他引：3  

Daisuke Ambe  Shiro Imawaki  Hiroshi Uchida  Kaoru Ichikawa 《Journal of Oceanography》2004,60(2):375-382

By tracking the locally strongest part of the sea-surface velocity field, which was obtained by integrating data of satellite altimeters and surface drifting buoys, we extracted the Kuroshio axis south of Japan every 10 days from October 1992 to December 2000. The obtained axes clearly express the effect of the bottom topography; three modes were observed when the Kuroshio ran over the Izu Ridge. The axis was very stable to the south of ‘Tosa-bae,’ off the Kii Channel. Mean current speed at the Kuroshio axis gradually increased from 0.65 m/s south of Kyushu to 1.45 m/s off Enshu-nada. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Seasonal Variation in Host Utilization of Epiphytic Lacuna Species in Mixed Algal and Surfgrass Stands in Japan     

Makoto Kanamori  Seiji Goshima  & Hiroshi Mukai 《Marine Ecology》2004,25(1):51-69

Abstract.  On the subtidal rocky shore of Akkeshi Bay, Hokkaido, Japan, the congeneric phytal gastropods, Lacuna uchidai and L. decorata , inhabit the multispecific vegetation consisting of the surfgrass, Phyllospadix iwatensis and the brown alga, Cystoseira hakodatensis . We studied the phenologies of Phyllospadix and Cystoseira , host utilization patterns and life histories of Lacuna spp. to examine how these gastropods accommodate the seasonal fluctuations of the habitat. The preferences for macrophyte by Lacuna spp. were examined by laboratory experiments. The phenologies of macrophytes, the seasonal and between-substrata variations of Lacuna spp. were examined by monthly sampling from Phyllospadix and Cystoseira beds between May 1999 and May 2000. Lacuna uchidai showed significant preference for Phyllospadix , whereas L. decorata had no preference for a particular substratum. Most L. uchidai were collected from the Phyllospadix bed, however L. decorata appeared in both Phyllospadix and Cystoseira beds. The peak of new recruit of L. uchidai coincided with that of Phyllospadix biomass. The synchronization of life cycle with the phenology of the host may be adaptive for using the limited habitat. Seasonal variation in density of L. decorata coincided with neither patterns for Phyllospadix nor Cystoseira . Seasonal variation in density and size frequency distribution suggested L. decorata migrated among adjacent macrophytes. Although it was a little vague, this hypothesis was probably the best explanation of our results. Our study shows that two co-occurring Lacuna species utilize the macrophytes as habitats by the different life histories and utilization patterns and, may be alternatively accommodated to the seasonal fluctuations of their habitats.  相似文献   

Interannual variability of the Kuroshio transport passing through the 137°E meridian in an OGCM related to the North Pacific windstress     

Yoshinobu Wakata  Takashi Setou  Ikuo Kaneko  Hiroshi Uchida  Shiro Imawaki 《Journal of Oceanography》2006,62(1):25-35

The interannual variability of the Kuroshio volume transport passing through the 137°E meridian south of Japan was simulated with an ocean general circulation model (OGCM). The time series of the Kuroshio volume transport over the 1000 m depth in the OGCM is well reproduced by the one-dimensional quasi-geostrophic (QG) vorticity equation with a windstress forcing. In our analysis of the OGCM and QG results, we found that peaks and troughs of the time series of the Kuroshio volume transport with 2–3 yr time-scale were induced by windstress curl, both local and immediately eastward, whereas longer time-scale variability was also induced by windstress curl near the dateline.  相似文献   

Observation of behavior of a sergestid shrimpSergestes lucens Hansen by underwater photography     

Suguru Ohta  Makoto Omori 《Journal of Oceanography》1974,30(2):86-89

Some behavior ofSergestes lucens by day was observed by underwater camera with an electronic flash. A number of species was snapped at about 2–60 m above the steep continental slope where the bottom ranged between 341 and 437 m depths. They were often abundant from 3–4 to 10 m above the bottom. It suggests that the shrimps scatter widely along the continental slope by day. The maximum concentration of the shrimp was 1.2 individuals/m³. None of the shrimps was found on the bottom, and the majority were swimming in horizontal position.  相似文献