Processing techniques for producing microcellular silicon carbide, mullite, and cordierite ceramics have been developed by a reaction method that incorporates a polysiloxane and reactive fillers. The techniques developed in this study offer substantial flexibility for producing microcellular ceramics whereby cell size, cell density, degree of interconnectivity, composition, and porosity can all be effectively controlled. It is demonstrated that the adjustment of filler composition enables the possibility of tailoring the composition and properties of the microcellular ceramics. The present results suggest that the proposed novel processing techniques are suitable for the manufacture of microcellular ceramics with high morphological uniformity.

New population synthesis models, with the effects of metallicity spread and the horizontal-branch (HB) morphology, provide a way to break the well-known age-metallicity degeneracy in the analysis of the integrated light of elliptical galaxies. Our models suggest that the far- UV radiation of these systems is dominated by a minority population of metal-poor, hot HB stars and their post-HB progeny, while the optical radiation is dominated by a metal-rich population. The systematic variation of UV upturn depends on the contribution from metal-poor, hot HB stars and their post-HB progeny, which in turn depends on the ages of old stellar populations in galaxies. Our result implies a prolonged epoch of galaxy formation, in the sense that more massive galaxies (in denser environments) formed first. Our models also suggest that the strenghth of Hβ index is strongly affected by HB stars, and hence previous age estimation without detailed modeling of the HB would underestimate the ages of ellipticals by ~7 Gyr.