カガクユソウハンノウニヨルV[n]O[2n-1]3≦n≦8ノケッショウセイチョウトソノデンキテキセイシツ

京都大学0048新制・課程博士理学博士甲第1147号理博第226号新制||理||147(附属図書館)3154UT51-46-G307京都大学大学院理学研究科化学専攻(主査)教授 高田 利夫, 教授 可知 祐次, 教授 辻川 郁二学位規則第5条第1項該当Kyoto UniversityDA

Measurement of nonlinear frequency shift coefficient in spin-torque oscillators based on MgO tunnel junctions

The nonlinear frequency shift coefficient, which represents the strength of the transformation of amplitude fluctuations into phase fluctuations of an oscillator, is measured for MgO-based spin-torque oscillators by analyzing the current dependence of the power spectrum. We have observed that linewidth against inverse normalized power plots show linear behavior below and above the oscillation threshold as predicted by the analytical theories for spin-torque oscillators. The magnitude of the coefficient is determined from the ratio of the linear slopes. Small magnitude of the coefficient has been obtained for the device exhibiting narrow linewidth at high bias current.Comment: 4 pages, 5 figures; accepted for publication in Applied Physics Letter

Amplitude-Phase Coupling in a Spin-Torque Nano-Oscillator

The spin-torque nano-oscillator in the presence of thermal fluctuation is described by the normal form of the Hopf bifurcation with an additive white noise. By the application of the reduction method, the amplitude-phase coupling factor, which has a significant effect on the power spectrum of the spin-torque nano-oscillator, is calculated from the Landau-Lifshitz-Gilbert-Slonczewski equation with the nonlinear Gilbert damping. The amplitude-phase coupling factor exhibits a large variation depending on in-plane anisotropy under the practical external fields.Comment: 4 pages, 4 figures, submitted to Journal of Applied Physics via MMM 200

A rediscovery of Limnotrachelobdella okae (Hirudinida: Piscicolidae) from flathead grey mullet Mugil cephalus in Japan

2007年7月に三重県の鍋田川河口部に近い汽水域で採集したボラMugil cephalus幼魚の鰓腔壁，2013年3月に岡山県沿岸の瀬戸内海に続く汽水路で採集したボラ未成魚の体表にヒダビルLimnotrachelobdella okae（Moore, 1924）の寄生を認めた。ヒダビルのボラへの寄生は1914年に記録されていたが，それはこれまで見落とされてきた。本報告は，ボラからのヒダビルの100年ぶりの記録である。One and seven specimens of the fish leech Limnotrachelobdella okae (Moore, 1924) were collected, respectively, from the branchial cavity of a young flathead grey mullet (Mugil cephalus) (Mugiliformes: Mugilidae) in the brackish-water estuary near the mouth of the Nabeta River, Mie Prefecture, central Japan, in June 2007, and from the body surface of five immature flathead grey mullet in a brackish waterway connected to the Seto Inland Sea on the coast of Okayama Prefecture, western Japan, in March 2013. Although the leech was reported from M. cephalus as early as in 1914 in Japan, its record has been overlooked for 100 years. The present collections represent a rediscovery of L. okae from M. cephalus

Effects of specific cultivar usage and preparation methods in Japanese potato starches.

Potato starch is one of the important agricultural products in Hokkaido, the northernmost and second largest island of Japan. The aim of this study was to evaluate the effects of cultivars and starch preparation methods on the quality parameters of Japanese potato starch. Potato starches from four cultivars, Hokkaikogane, Eniwa, Benimaru and Norin No. 1, grown over a period of several years in Hokkaido were used. The starches produced with tap water in a local starch factory and with distilled water in a laboratory were investigated for phosphorus content, median granule size and peak viscosity and breakdown as determined with a Rapid Visco Analyzer (RVA). Among the starch samples used in this study, significant differences were observed across starch quality parameters. We investigated the differences in quality parameters as an effect of individual cultivars. The starch median granule size among potato cultivars varied in the following order: Benimaru (43.1 μm) > Hokkaikogane (39.1 μm) ≈Eniwa (38.2 μm) > Norin No. 1 (33.9 μm). We found that starches of Hokkaikogane and Eniwa, both with a measurably higher phosphorus content, displayed significantly higher peak viscosity and breakdown than those of Benimaru and Norin No. 1. We also examined the effect that the preparation method has on starch quality parameters within the same potato cultivar. We found that the starch preparation method had a little or no influence on phosphorus content. Median granule size was also completely independent on the preparation method. The RVA evaluation revealed that, even within the same cultivar, starches produced in a factory showed lower peak viscosity and breakdown than those produced in a laboratory

Mesenchymal stromal cells in bone marrow express adiponectin and are efficiently targeted by an adiponectin promoter-driven Cre transgene

Stromal cells in bone marrow (BM) constitute a specific microenvironment supporting the development and maintenance of hematopoietic cells. Adiponectin is a cytokine secreted by adipocytes. Besides its anti-diabetic and anti-atherogenic roles, adiponectin reportedly regulates the development and function of hematopoietic cells in BM. However, it remains unclear whether mesenchymal stromal cells in BM express adiponectin. Here, we show that PDGFRβ+VCAM-1+ stromal cells express adiponectin. Lineage tracing revealed that a majority of PDGFRβ+VCAM-1+ cells were targeted by an adiponectin promoter-driven Cre (Adipoq-Cre) transgene. Additionally, the Adipoq-Cre transgene targets a minority of osteoblasts at a younger age but larger populations are targeted at an older age. Furthermore, the Adipoq-Cre transgene targets almost all CXCL12-abundant reticular (CAR) cells and most of the stromal cells targeted by the Adipoq-Cre transgene are CAR cells. Finally, deletion of interleukin-7 (IL-7) by the Adipoq-Cre transgene resulted in severe impairment of B lymphopoiesis in BM. These results demonstrate that PDGFRβ+VCAM-1+ stromal cells in BM express adiponectin and are targeted by the Adipoq-Cre transgene, suggesting a broader specificity of the Adipoq-Cre transgene

Hematopoietic cell-derived IL-15 supports NK cell development in scattered and clustered localization within the bone marrow

骨髄のNK細胞の分化に造血細胞が産生するIL-15が必須である --2種類の局在を示すNK細胞の新規分化モデル--. 京都大学プレスリリース. 2023-09-20.Natural killer (NK) cells are innate immune cells critical for protective immune responses against infection and cancer. Although NK cells differentiate in the bone marrow (BM) in an interleukin-15 (IL-15)-dependent manner, the cellular source of IL-15 remains elusive. Using NK cell reporter mice, we show that NK cells are localized in the BM in scattered and clustered manners. NK cell clusters overlap with monocyte and dendritic cell accumulations, whereas scattered NK cells require CXCR4 signaling. Using cell-specific IL-15-deficient mice, we show that hematopoietic cells, but not stromal cells, support NK cell development in the BM through IL-15. In particular, IL-15 produced by monocytes and dendritic cells appears to contribute to NK cell development. These results demonstrate that hematopoietic cells are the IL-15 niche for NK cell development in the BM and that BM NK cells are present in scattered and clustered compartments by different mechanisms, suggesting their distinct functions in the immune response