Interstitial order-disorder transformations in tantalum hydrides up to the composition TaH_0.75 have been studied by heat capacity measurements between −100 and +100°C. It is shown that the β₁ phase with an ordered structure Ta₂H_1±x in the range TaH_0.45–TaH_0.75 transforms to the disordered α phase stepwisely through the β₂ phase near Ta₂H and through the α+δ two-phase region in hydrogen-rich compositions, and directly in intermediate compositions. The δ phase has another ordered structure TaH_1−x above TaH_0.75, while the structure of the β₂ phase is unknown as yet. The alloys near TaH_0.75 undergo the transformation around −65°C from γ–Ta₄H₃ to β₁–Ta₂H_1+x.
On the basis of these results, a revised phase diagram is presented. The transformation entropy is well accounted for by the configurational entropy change of the hydrogen atoms evaluated from the structure models proposed here.

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大動脈弁狭窄症（AS）は，有病率の増加，不良な予後，ならびに複雑な病態生理学のために大きな医療問題となっている．心エコーは，ASの包括的な形態学的および血行動態的評価で中心的な役割を果たす．ASの重症度診断は，最大大動脈弁通過血流速度，大動脈弁通過血流平均圧較差（mPG），および大動脈弁口面積（AVA）の3つの血行動態指標に基づいている．しかし，AVAが＜1.0 cm²であるが，mPGが＜40 mmHgの場合など，各指標間で重症度評価が一致しないことも多い．このような病態は低圧較差AS（LGAS）として知られている．特に，一回拍出量や駆出率が低い症候性LGAS患者は，重症度の診断がさらに難しく，予後も不良であるため注意が必要である．このLGASの重症度評価には，負荷心エコーが重要な役割を果たす．外科的大動脈弁置換術（SAVR）の禁忌となる併存疾患を有する高齢患者やハイリスク患者には，経カテーテル大動脈弁置換術（TAVR）が可能となり，ASの治療は大きく変化してきている．TAVRではコンピュータ断層撮影（CT）と共に，心エコーは大動脈弁と周辺の大動脈基部複合体の術前評価に非常に重要である．本総説では，ASの診断と管理に心エコーが果たしてきた役割の進展，大動脈複合体の評価の困難さ，負荷心エコーや3D心エコーといった専門的方法のニーズ拡大について概説する．

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The sputtering yield of Mo honeycomb walls was compared with the yield of flat walls in a d.c. Ar glow discharge. Under the experimental condition where the mean energy is approximately 1 keV and the angle of incidence of primary ions strongly distributed around normal, the yield is reduced by a factor of 20 to 30. Before and after the bombardment, the surface topography of the honeycomb targets was observed by a scanning electron microscope.

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最近,核融合装置の第一壁は,JT-60の例からもわかるように,低Z材料(炭素材料, SiC, Ticなど)を使用することが普通になってきている.しかし低Z材料では,水素と化学反応して損耗していく化学スパッタリングが無視できない場舎が多い.ここでは,これらの材料における化学スパッタリング研究の最近の動きについて,筆者らの研究をまじえながら解説する.また,高融点金属の代表であるタングステンをダイバーター板として綾用する場合の,酸素との反応についても著干ふれる.

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The local vibration spectra of hydrogen atoms dissolved in tantalum have been studied by the energy-loss scattering of pulsed neutrons. The observed time-of-flight spectra show split peaks of the local modes near 120 and 175 meV, which are almost invariant with changing concentration (H/Ta=0.1, 0.5 and 0.7) and configuration of hydrogen at 20° and 85°C. From comparison with previous neutron results on niobium and vanadium hydrides, it is shown that the energies of the split local modes are nearly independent of the metal-hydrogen distance, and the relative intensity and the FWHM of the high energy mode increase in the disordered phase at 85°C in comparison with the ordered phase at 20°C.

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A new technique specially designed to use Auger electron spectroscopy for the measurement of very low sputtering yield has been applied for low energy (0.1-6 keV) proton sputtering of molybdenum and pyrolytic graphite. In molybdenum the sputtering yield above 1 keV is about three times as large as the experimental one obtained by Finfgeld, and below 1 keV it rapidly decreases with decreasing energy. In graphite physical sputtering yield at 500°C is about an order of magnitude larger than that of molybdenum, whereas the energy dependence is very similar to the molybdenum case. But the energy dependence is very different from the theory of Weissmann and Sigmund. The measured temperature dependence of the chemical sputtering yield for pyrolytic graphite at 1 keV shows the maximum value of about 0.08 CH₄ molecules/ion near 750 K.

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