Yosuke Shiratori

Carbon nanotube (CNT) emitters were formed on line-patterned cathodes in microtrenches through a thermal CVD process. Single-walled carbon nanotubes (SWCNTs) self-organized along the trench lines with a submicron inter-CNT spacing. Excellent field emission (FE) properties were obtained: current densities at the anode (J(a)) of 1 microA cm(-2), 10 mA cm(-2) and 100 mA cm(-2) were recorded at gate voltages (V(g)) of 16, 25 and 36 V, respectively. The required voltage difference to gain a 1:10 000 contrast of the anode current was as low as 9 V, indicating that a very low operating voltage is possible for these devices. Not only a large number of emission sites but also the optimal combination of trench structure and emitter morphology are crucial to achieve the full FE potential of thin CNTs with a practical lifetime. The FE properties of 1D arrays of CNT emitters and their optimal design are discussed. Self-organization of thin CNTs is an attractive prospect to tailor preferable emitter designs in FE devices.

BaTiO₃ powders with various crystallite sizes, which were prepared through microemulsion‐mediated synthesis, were thoroughly studied by Raman spectroscopy. Clear evidence for the presence of the tetragonal phase was found for ultrafine powders with an average crystallite size above 30 nm. The lifetime of phonons that are specifically assigned to the tetragonal phase decreased with decreasing crystallite size below a critical size of 100 nm. In particles as fine as 100 nm, the short mean free path of phonons, mainly due to internal pressure, causes decoupling of the coupled A₁ (TO) phonons and a diffuse phase transition behaviour (T_C = 115 °C). Coupled A₁(TO) phonons, which give a spectral dip at around 180 cm⁻¹ and a lesser extent of diffuseness, were revealed for powders consisting of particles as large as 0.17 µm (T_C = 123 °C). Further coarsening upon annealing induced the formation of aggregates, resulting in the shift of phase transition points to higher temperatures for the rhombohedral to orthorhombic and the orthorhombic to tetragonal transitions and to lower temperatures for the tetragonal to cubic transition, respectively. Phase stability in powders is discussed by considering possible factors such as internal pressure in isolated particles and internal stress in aggregates. Copyright © 2007 John Wiley & Sons, Ltd.

BaTiO₃ dense ceramics with different grain sizes from 5.6 µm down to 35 nm were thoroughly studied by Raman spectroscopy. The temperature characteristics of optical phonons were compared with those obtained for powders. The micrograined ceramic revealed the well‐known spectrum profiles and transitions, typical for bulk BaTiO₃. On the other hand, the Raman spectra obtained for a nanograined ceramic with an average grain size of 35 nm revealed a tetragonally distorted pure BaTiO₃ phase showing a diffused phase transition behaviour with respect to temperature. Abnormality of phonon damping characteristics for the nanograined ceramic was demonstrated through comparison with powders with various crystallite sizes and the micrograined ceramic. The Curie temperature of the nanograined ceramic was estimated to be 105 °C from the temperature characteristic of a sharp peak at 307 cm⁻¹, which is one of the most specific tetragonal features for bulk BaTiO₃. In the present study, local stabilization of the tetragonal phase in ultra‐fine grains was experimentally demonstrated from comparison between the Raman spectroscopic results for powders and ceramics prepared through microemulsion‐mediated synthesis. Rather long phonon mean free paths can exist even in such ultra‐fine grains, but the phonon characteristics originating from various grains are diffused mainly because of the effect of internal stress. Copyright © 2007 John Wiley & Sons, Ltd.

Many patients with liver cirrhosis are in a state of protein and energy malnutrition and require careful nutritional support. Our research has revealed that approximately 30% of the patients have protein-energy malnutrition, 40% protein malnutrition, and 10% energy malnutrition; 20% are in a normal nutritional state. Supplementation with branched-chain amino acids alleviates chronic liver failure, improves the protein nutritional state, and subsequently prolongs survival. In contrast, therapeutic modalities for energy malnutrition have not yet been fully elucidated and await further studies. Improved survival of the cirrhotic patients essentially brings a higher incidence of hepatocellular carcinoma (HCC). A synthetic analogue of vitamin A (acyclic retinoid or 4,5-dehydrogeranyl geranoic acid) prevents at least the development of second primary tumors after curative treatment of preceding HCC. The mechanism of this cancer chemo-prevention is clonal deletion of premalignant and latent malignant cells by the retinoid. We describe our clinical experiences with these two nutritional pharmacotherapies of chronic liver diseases and review their basic mechanisms.