Crystal and Magnetic Structures of Double Hexagonal Close-Packed Iron Deuteride

鉄重水素化物(FeDx)の4-6 GPa, 1023-300Kの中性子回折実験を行った。二重六方最密構造(dhcp)FeDxの重水素組成の温度圧力関係を決定した。さらに、FeDxの磁気構造を磁気構造解析により決定した

Neutron diffraction study on the site occupancy of hydrogen in Fe0.95Si0.05 at 14.7 GPa and 800 K

地球の核の主要成分であるFeには軽金属が固溶していると考えられている。本研究ではそのモデル物質としてFe0.95Si0.05合金の水素化物について、水素吸蔵サイトと水素誘起格子体積膨張量を中性子その場観察により評価した。14.7 GPaでの測定とリートベルト解析の結果、水素は八面体サイトのみを占有し、水素誘起体積膨張量は2.33Å^3と算出された。SiがFeに加わることによって水素誘起体積膨張量はほとんど変化しないことが明らかになった。密度一定の条件では水素とSiの量は反相関の関係にあると結論づけた

Abdominal expiratory activity in the rat brainstem–spinal cord in situ: patterns, origins and implications for respiratory rhythm generation

We studied respiratory neural activity generated during expiration. Motoneuronal activity was recorded simultaneously from abdominal (AbN), phrenic (PN), hypoglossal (HN) and central vagus nerves from neonatal and juvenile rats in situ. During eupnoeic activity, low-amplitude post-inspiratory (post-I) discharge was only present in AbN motor outflow. Expression of AbN late-expiratory (late-E) activity, preceding PN bursts, occurred during hypercapnia. Biphasic expiratory (biphasic-E) activity with pre-inspiratory (pre-I) and post-I discharges occurred only during eucapnic anoxia or hypercapnic anoxia. Late-E activity generated during hypercapnia (7–10% CO2) was abolished with pontine transections or chemical suppression of retrotrapezoid nucleus/ventrolateral parafacial (RTN/vlPF). AbN late-E activity during hypercapnia is coupled with augmented pre-I discharge in HN, truncated PN burst, and was quiescent during inspiration. Our data suggest that the pons provides a necessary excitatory drive to an additional neural oscillatory mechanism that is only activated under conditions of high respiratory drive to generate late-E activity destined for AbN motoneurones. This mechanism may arise from neurons located in the RTN/vlPF or the latter may relay late-E activity generated elsewhere. We hypothesize that this oscillatory mechanism is not a necessary component of the respiratory central pattern generator but constitutes a defensive mechanism activated under critical metabolic conditions to provide forced expiration and reduced upper airway resistance simultaneously. Possible interactions of this oscillator with components of the brainstem respiratory network are discussed