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Poly (lactic acid) was molded under four different kinds of condition to obtain samples with different microstructures. A single crystal was not observed in the specimen molded at 0°C. The size of spherulites became larger with increase of molding temperature. The density of spherulites increased with increase of molding time. Mode I fracture toughness, KIC was measured at a static (1 mm/min) and an impact loading rate (1 m/s). KIC became lower with increase of degree of crystallization at the static loading rate. This is mainly due to suppression of craze formation in the vicinity of crack-tip. On the other hand, at the impact loading rate, KIC increased with increase of degree of crystallization. Thus, the results showed that crystallization has significant influence on KIC, and its effect on the static KIC was different from that on the impact one. Relationship between fracture toughness and fracture micromechanism was discussed on the basis of the results of fracture tests and microscopies.

The non-specific immunostimulation and adjuvant effects of Vibrio anguillarum bacterin (VAB), M-glucan, chitin and Freund's complete adjuvant (FCA) against pasteurellosis were examined in yellowtail, Seriola quinqueradiata. Control fish were injected intraperitoneally with 0.1 ml of sterile phosphate buffered saline (PBS). Experimental fish were injected similarly with either vaccine (lipopolysaccharide-mixed chloroform-killed Pasteurella piscicida, LPS-CKC), an immunostimulant or mixture of the vaccine and an immunostimulant.All fish were subsequently challenged by the same but live P. piscicida strain using an immersion method at 15, 25, 35 and 45 days post-inoculation. Immunostimulants alone were found to slightly increase the protectionagainst Pasteurella infection, but the effects were not statistically significant. The most effective adjuvant wasFCA, however the enhanced protection was not statistically different from that of fish inoculated with LPS-CKCalone. However, the relative percent survival (RPS) of fish vaccinated with M-glucan, chitin or Vibrio bacterinas adjuvant was lower than that of fish vaccinated with only LPS-CKC bacterin alone. Thus, M-glucan, chitin and Vibrio bacterin had no positive adjuvant effects on the P. piscicida vaccine.

Metal molds and machine parts for die-casting need excellent corrosion resistance against molten metals. In this study, we investigated corrosion resistance of various kinds of boride base hard materials ( Mo2FeB2-Fe, Mo2NiB2-Ni, WCoB-Co, W-Mo2NiB2-TiB2 base cermets and TiB2 ceramic ) against a molten Al alloy (JIS ADC10), a Zn alloy (JIS D-2) and soft solders (JIS H5A and H70A). The corrosion resistances of these materials were estimated by measuring the dimensional changes after dipping in the molten metals.The results indicated that the boride base hard materials, especially TiB2 containing materials had higher corrosion resistance than. conventional materials, such as WC-20mass%Co, SKD61 and SK1151. SEM micrographs showed that the binder phases comprising Fe, Co and Ni in the boride base hard materials react with the molten metals, prior to the boride phase. The boride base hard materials are consequently promising candidates for the die-casting machine parts and molds.