Terahertz Faraday and Kerr rotation spectroscopy of Bi1−x_{1-x}Sbx_x films in high magnetic fields up to 30 Tesla

We report results of terahertz Faraday and Kerr rotation spectroscopy measurements on thin films of $\text{Bi}_{1-x}\text{Sb}_{x}$, an alloy system that exhibits a semimetal-to-topological-insulator transition as the Sb composition $x$ increases. By using a single-shot time-domain terahertz spectroscopy setup combined with a table-top pulsed mini-coil magnet, we conducted measurements in magnetic fields up to 30~T, observing distinctly different behaviors between semimetallic ($x < 0.07$) and topological insulator ($x > 0.07$) samples. Faraday and Kerr rotation spectra for the semimetallic films showed a pronounced dip that blue-shifted with the magnetic field, whereas spectra for the topological insulator films were positive and featureless, increasing in amplitude with increasing magnetic field and eventually saturating at high fields ($>$20~T). Ellipticity spectra for the semimetallic films showed resonances, whereas the topological insulator films showed no detectable ellipticity. To explain these observations, we developed a theoretical model based on realistic band parameters and the Kubo formula for calculating the optical conductivity of Landau-quantized charge carriers. Our calculations quantitatively reproduced all experimental features, establishing that the Faraday and Kerr signals in the semimetallic films predominantly arise from bulk hole cyclotron resonances while the signals in the topological insulator films represent combined effects of surface carriers originating from multiple electron and hole pockets. These results demonstrate that the use of high magnetic fields in terahertz magnetopolarimetry, combined with detailed electronic structure and conductivity calculations, allows us to unambiguously identify and quantitatively determine unique contributions from different species of carriers of topological and nontopological nature in Bi$_{1-x}$Sb$_x$.Comment: 17 pages, 22 figure

Change in brain plasmalogen composition by exposure to prenatal undernutrition leads to behavioral impairment of rats.

Epidemiological studies suggest that poor nutrition during pregnancy influences offspring predisposition to experience developmental and psychiatric disorders. Animal studies have shown that maternal undernutrition leads to behavioral impairment, which is linked to alterations in monoaminergic systems and inflammation in the brain. In this study, we focused on the ethanolamine plasmalogen of the brain as a possible contributor to behavioral disturbances observed in offspring exposed to maternal undernutrition. Maternal food or protein restriction between gestational day (GD) 5.5 and GD 10.5 resulted in hyperactivity of rat male adult offspring. Genes related to the phospholipid biosynthesis were found to be activated in the prefrontal cortex (PFC), but not in the nucleus accumbens or striatum, in the offspring exposed to prenatal undernutrition. Corresponding to these gene activations, increased ethanolamine plasmalogen (18:0p-22:6) was observed in the PFC using mass spectrometry imaging. A high number of crossings and the long time spent in the center area was observed in the offspring exposed to prenatal undernutrition and was mimicked in adult rats via the intravenous injection of ethanolamine plasmalogen (18:0p-22:6) incorporated into the liposome. Additionally, plasmalogen (18:0p-22:6) increased only in the PFC, and not in the nucleus accumbens or striatum. These results suggest that brain plasmalogen is one of the key molecules to control behavior and its injection using liposome is a potential therapeutic approach for cognitive impairment.Significance Statement:Maternal undernutrition correlates to developmental and psychiatric disorders. Here, we found that maternal undernutrition in early pregnancy led to hyperactivity in rat male offspring and induced gene activation of phospholipid-synthesizing enzyme and elevation of ethanolamine plasmalogen (18:0p-22:6) level in the prefrontal cortex (PFC). Intravenous injection of ethanolamine plasmalogen (18:0p-22:6) incorporated into the liposome maintained crossing activity and was circumscribed to the center area for a long time period, in prenatally undernourished offspring with aberrant behavior. Furthermore, the amount of ethanolamine plasmalogen (18:0p-22:6) increased in the PFC of the rat after injection. Our result suggests that brain plasmalogen is one of the key molecules to control behavior and that its injection using liposome is a potential therapeutic approach for cognitive impairment

An Enforcement of 'Distinct Teaching Practice' at Hiroshima University (III)

本稿の目的は, 一昨年度より本格的に実施された「特色ある教育実習プログラム」の実施に関して, 「教育実習指導A」及び「教育実習指導B」の効果に焦点化して報告することである。検討の結果以下の点が明らかとなった。①「教育実習指導A」は「小学校教育実習Ⅰ」に向け, 実習に対する意欲の喚起, さらに課題意識の明確化に有効であったといえる。しかし, 授業観察の観点, 時間割作成等に関する改善点・要望の記述が多くみられた。今後はこれらに対する支援の充実が課題である。②「教育実習指導B」は, 「教育実習の理解度」「教育実習に参加した印象」「本実習までの課題」に関して概ね目的の達成が見られたといえる。課題としては, やはり3日間という短期間であるためか, 教科指導の観察が中心となり, 学級経営などの理解が十分でないことを挙げることができる。③「特色ある教育実習プログラム」全体の中での「教育実習指導A」及び「教育実習指導B」の目的の明確化と, 1年次生から3年次生まで配置されている各種教育実習との整合性が課題として指摘された。広島大学教育学部・各附属学校で育成すべき教師像を明確化し, 再度教育実習システム全体を再構築することが必要とされた

An Enforcement of 'Distinct Teaching Practice' at Hiroshima University (II)

本研究の目的は, 2008年度に実施された「特色ある教育実習プログラム」に関して, 「教育実習観察」の効果に焦点化して報告することである。検討の結果以下の点が明らかとなった。①「小学校教育実習観察」は, 目標とした小学校教育実習のイメージの形成, 教職に関する意識向上, 次年度の教育実習に向けた課題意識の形成の点で有効であった。しかし, 参加学生の当日の態度, 事前指導等に関して改善を要する課題も明らかになった。次年度に向けて, 参加学生の目的意識の涵養や社会人としてのマナーの向上のために事前指導の内容を改善すること, とりわけ2年次生と3年次生との事前の連絡を充実することが課題とされた。②「中・高等学校教育実習観察」は, 目標とした中・高等学校教育実習のイメージの形成, 教職に関する意識向上, 次年度の教育実習に向けた課題意識の形成の点で有効であった。しかし, 参加学生の目標の理解, 次年度実習に向けた学生の課題の解決, 成績評価の方法等に関して今後取り組むべき課題も明らかになった。今後は, 次年度の授業化に向けて観察する内容の情報伝達について事前指導を充実すると共に, 成績評価の方法を整備することが課題とされた