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Carbon-supported La 1−x Ca x Mn 1−y Fe y O 3 nanoparticles were synthesized, and their oxygen reduction activities and electronic states were investigated. A reverse micelle method using KMnO 4 as a source of high valence state Mn successfully yielded carbon-supported La 1−x Ca x Mn 1−y Fe y O 3 nanoparticles even when calcined under a reducing atmosphere. The oxygen reduction activity of carbonsupported La 1−x Ca x Mn 1−y Fe y O 3 exceeded that of carbon-supported Pt nanoparticles when the Ca composition was limited to the range of 0.4 to 0.8. X-ray photoelectron spectroscopy (XPS) measurements of La 1−x Ca x Mn 1−y Fe y O 3 particle surfaces revealed the existence of Mn 4+ , which is important in the oxygen reduction activity. Depth analysis of La 1−x Ca x Mn 1−y Fe y O 3 nanoparticles by XPS revealed the formation of a CaCO 3 impurity and an A-site deficient perovskite-type oxide containing a high surface concentration of Mn 4+ .

Summary: A chitin‐xylan hybrid polysaccharide having β(1 → 4)‐linked alternating structure of N‐acetyl‐D‐glucosamine and D‐xylose was synthesized via chitinase‐catalyzed polymerization. An oxazoline derivative of D‐xylosyl‐β(1 → 4)‐N‐acetyl‐D‐glucosamine (1) was effectively polymerized by the catalysis of chitinase from Bacillus sp., giving rise to a water‐soluble chitin‐xylan hybrid polysaccharide (2) in good yields. Molecular weights ($\overline M _{\rm n}$) of 2 reached 1 500, which corresponds to 8–10 saccharide units.A chitin‐xylan hybrid polysaccharide (2) synthesized via chitinase‐catalyzed polymerization.magnified imageA chitin‐xylan hybrid polysaccharide (2) synthesized via chitinase‐catalyzed polymerization.

A catalytic combustion-type gas sensor using a positive temperature coefficient (PTC) thermistor, which shows a sharp resistance change around Curie temperature, was developed for the detection of hydrogen. La-doped BaTiO 3 (Ba 0.998 La 0.002 TiO 3 ) was prepared through a solid-state method and an oxalic acid method. La-doped BaTiO 3 obtained by the oxalic acid method showed improved PTC properties, due to the formation of fine particles, as compared to that prepared with the solid-state method. The resulting sensor device showed a fairly high H 2 sensitivity in the range of 100-1000 ppm. In addition, the H 2 sensitivity and response speed were improved by coating a Pt/SiO 2 catalyst on the sensor device because the catalytic combustion efficiency of H 2 was improved by the catalyst coating.D. Damjanovic-contributing editor Manuscript No. 32105. J ournalMoreover, we also investigated the effect of a Pt-based combustion catalyst on the sensor response.