著者

Takashi Kamiyama

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.18, no.1, pp.34-46, 2023-02-28 (Released:2023-03-02)

参考文献数

45

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To evaluate the growth and feeding responses of the polyp stage of the moon jellyfish Aurelia coerulea to natural microzooplankton assemblages, bud production among A. coerulea polyps was monitored in field bottle incubation experiments using fractionated field seawater (<200-µm fraction) in summer. During this incubation period, feeding rates were measured twice by examining changes in the abundance of various microzooplankton taxa over two days. The number of buds increased with incubation period, reaching a mean of 5.8–9.3 buds per polyp after 16 days, at which point the carbon content of the new buds and the mother polyp was estimated to be 1.3–2.5 times higher than the carbon content of the initial polyp. Using these carbon content estimates, I calculated specific growth rates of 0.1–0.2 d−1 during the first 10 days. The results of the present feeding experiments suggest that polyps utilize diverse groups of microzooplankton and achieve relatively high carbon ingestion rates from ciliates, dinoflagellates, molluscs, and copepod nauplii. Total microzooplankton ingestion rates were estimated to be 4.05 and 3.27 µgC polyp−1 d−1 in the two experiments, respectively. These findings show that natural microzooplankton assemblages play a role as prey of polyps and can promote asexual reproduction of polyps under natural summer conditions.

著者

Wataru UNO Kotaro FUJII Eiki NIWA Shuki TORII Ping MIAO Takashi KAMIYAMA Masatomo YASHIMA

出版者

公益社団法人 日本セラミックス協会

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.126, no.5, pp.341-345, 2018-05-01 (Released:2018-05-01)

参考文献数

46

被引用文献数

24

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Crystal structure and neutron scattering length density distribution of a pyrochlore-type ytterbium titanate Yb2Ti2O7 have been investigated by in situ neutron powder diffraction measurements at 293 and 1173 K, Rietveld analysis and maximum-entropy method (MEM). In the MEM neutron scattering length density distributions of Yb2Ti2O7, the oxide ion O48f bonding to Ti cation was relatively localized at lower temperature of 293 K, while it was largely distributed at a higher temperature of 1173 K. At 1173 K, one oxide-ion diffusion path along the 〈110〉 unshared edge of TiO6 octahedron was clearly visualized and the other oxide-ion diffusion path along 〈100〉, strictly 〈2 −8x(O48f) + 3 8x(O48f) − 3〉, shared edge of TiO6 octahedron was also indicated. Here x(O48f) is the atomic coordinate x of O48f anion. The MEM neutron scattering length density distribution and difference bond valence sum map at 1173 K strongly suggested that the energy barrier for oxide-ion migration along 〈110〉 directions was lower than that along the 〈100〉 one. Oxide ions three-dimensionally diffuse through both the 〈110〉 and 〈100〉 paths across the unit cell.