Papers by Author: Takaaki Shishido

Abstract: In simulator studies, the Biolox-forte hip prosthesis were run for 5 million cycles (Mc) using 50% new born calf serum for both the standard test (STD) mode and the micro-separation test (MSX) mode. Wear measurements were carried out every 0.5 Mc. The wear patterns were mapped and observed by SEM. In a clinical study, the OstealTM hip prostheses which were implanted for 15 to 19 years and 17 year BioloxTM hip prostheses were analyzed. According to the same technique as the simulator study, the wear patterns were analyzed using SEM. The steady-state wear rates for alumina THR ranged from 0.16 to 0.65 mm3/Mc in the MSX mode and 0.011 mm3/Mc in the STD mode. The MSX simulator mode produced two narrow wear scars (stripes) of dull appearance on the ball. In the SEM analysis, the stripe scars showed mild wear after 5 Mc duration. In the Biolox and the Osteal retrieval alumina ball, the stripe scars showed severe wear. The Osteal retrievals had one grade lower wear in the main worn area than the Biolox retrievals on SEM analysis. The stripe wear and its location in the retrieval balls were seen in the simulator study. The area and wear severity of the stripe wear were influenced by the quality of alumina, design of THA and various actual motions in patients.

Abstract: Single crystals of AlMgB ₁₄ and AlMgB ₂₂ were grown from a high-temperature aluminum metal flux in an Ar atmosphere. The optimum conditions for growing AlMgB ₂₂ and AlMgB ₁₄ were established using the starting mixtures of B/Mg=0.5-1.0 and B/Mg=2.0-6.0. The AlMgB ₁₄ and AlMgB ₂₂ crystals obtained have well-developed {001} and {100} faces, and were black with a metallic luster. The maximum dimensions of these crystals were about 5.2 mm and 4.6 mm, respectively. The values of micro-Vickers hardness of the AlMgB ₁₄ and AlMgB ₂₂ crystals are in the ranges of 23.9±0.6-27.6±0.6 GPa. The oxidation process of AlMgB ₁₄ and AlMgB ₂₂ crystals were studied up to 1473 K by TG-DTA method. The susceptibility of AlMgB14 with an increase at low temperatures does not show any particular features, being indicative of a paramagnetic contribution, which is likely due to impurities. The susceptibility of the AlMgB ₂₂ sample shows no apparent contribution from impurities and also does not have any anomalous behavior.