Papers by Author: Akira Saito

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Authors: Makito Nakano, Akira Saito, Nobuyuki Wada
Abstract: The electrical degradation mechanisms of BaTiO3-based ceramics were investigated by measuring the dependence of leakage current on high electric fields. Before the degradation, the leakage current predominately obeyed Ohm’s law and Poole-Frenkel relation. As the degradation progressed, the Poole-Frenkel emission current increased. Moreover, the total current at the high electric fields also comprised Schottky emissions between cathodes and dielectric layers.
Authors: Makito Nakano, Akira Saito, Nobuyuki Wada
Abstract: The factors causing a decrease in the resistivity of multilayer ceramic capacitors (MLCCs) with a decrease in the thickness of dielectric layers were examined by carrying out measurements and finite element method (FEM) simulations. The obtained electric field vs. current density plots (E–J characteristics) indicated that the local concentration of electric field increased with the decrease in the thickness of the dielectric layers. The investigation of the local concentration of electric field at the grain boundaries using an FEM showed that the decrease in resistivity was caused by the roughness of the interface between dielectric layers and inner electrodes and the presence of large grains in the dielectric layers.
Authors: Yoshiyuki Yokogawa, Akira Saito, Naoki Ogawa, Atsutomo Nakamura, Ippei Kishida
Abstract: The encapsulation and immobilization of biomolecules on/in mesoporous silica materials (MPS) have been studied by using transmission electron microscopy (TEM). The mixture of tetraethyl orthosilicate (TEOS) and the triblock copolymer as a template was stirred, hydrothermally treated to form the mesoporous SBA-15 structure, and heat-treated at 550 °C. SEM observation indicated that long and narrow particles were linked together in the long axis direction to form secondary particles of SBA-15. UV-spectrometry was performed to determine the amount of bovine serum albumin (BSA), cytochrome C, myoglobin or -lactoglobulin encapsulated on/in SBA-15. The time profiles for adsorption of proteins can be well described by intraparticle diffusion model. The TEM observations of proteins on/in mesoporous SBA-15 revealed that proteins were embedded on/in mesoporous SBA-15 and the protein behaviors given by TEM observations may correspond to the intraparticle diffusion model.
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