著者
Kinoshita Chiken Nakai Kiyomichi Fukumoto Ken-ichi Kutsuwada Masanori Nogita Kazuhiro
出版者
Tohoku University
雑誌
Science reports of the Research Institutes, Tohoku University. Ser. A, Physics, chemistry and metallurgy (ISSN:00408808)
巻号頁・発行日
vol.35, no.2, pp.417-425, 1991-03-05

The cascade damage and its kinetic behavior in various kinds of ceramics irradiated with fission- and fusion-neutrons have been examined through transmission electron microscopy. Fission- and fusion-neutrons introduce relatively dilute concentration of point defects around primary knock-on atoms through the displacement cascade process in low-Z ceramics. Higher concentration of point defects, which induces the contrast corresponding to the cascade damage though TEM, is induced only in covalent crystals consisting of relatively high-Z elements. The nucleation and growth process of interstitialloops is strongly affected by the crystal structure and structural vacancy.
著者
中島 淑恵
出版者
Tohoku University
巻号頁・発行日
2014-03-26

課程
著者
熊谷 隆次
出版者
Tohoku University
巻号頁・発行日
2021-09-24

要約のみ
著者
佐藤 真海
出版者
Tohoku University
巻号頁・発行日
2021-07-15

要約のみ
著者
泉田 邦彦
出版者
Tohoku University
巻号頁・発行日
2021-03-25

要約のみ
著者
Niitsuma Nobuaki
出版者
Tohoku University
雑誌
The science reports of the Tohoku University. Second series, Geology = 東北大学理科報告. 地質学 (ISSN:0082464X)
巻号頁・発行日
vol.43, no.1, pp.1-39, 1971-10-20

The purpose of the present study is to find the relationship of a geomagnetic field reversal to the changes in a foraminiferal fauna and the sedimentary environments. A fossiliferous marine sedimentary section of the middle part of the Kokumoto Formation continuously exposed at Kamiyanagawa in the Boso Peninsula, Chiba Prefecture, Central Japan, was chosen for the investigation of the behaviour of the geomagnetic field during its reversal between the Matuyama and Brunhes Polarity epochs which took place around 0.69 m.y. ago. The behaviour of the geomagnetic field was established as to the inclination, declination and intensity of the Jn/J_R recorded in the sedimentary rocks. Along the same section, analyses were made on the grain-size of the sediments, oxygen isotope ratio in the planktonic and benthonic foraminiferal tests, and the faunal assemblages of the planktonic and benthonic foraminifers. The intensity of the magnetic field fluctuated with a period of approximately 6700 years and did not disappear during the reversal. The migration of the virtual magnetic north pole at the magnetic field reversal between the Matuyama and Brunhes Polarity epochs occurred roughly along the meridian of 120°E long. in the period of 4700 years. In the same duration the depth of the sea water, under which the sediments accumulated, fluctuated within the range of 200-300 m with a period of approximately 7000 years. No particular relation between the magnetic field reversal and fluctuation of the water depth was recognized. The result of paleotemperature and faunal analyses of the foraminifers showed that the magnetic field reversal at the Matuyama Brunhes Polarity Epoch boundary may have been related to the changes in the circulation pattern of the upper watermasses which caused more influx of cold water into this area in the northwestern Pacific as compared with the period before the geomagnetic polarity change.