No abstract

SYNOPSISA prediction equation for thermal conductivity of polymer composites reported in our previous papers has been revised in terms of two view points: ( 1) estimation of thermal conductivity of a composite using an idea of reduced thermal conductivity; and ( 2 ) the effect of ease in forming conductive filler chains on thermal conductivity is related to the CVF value in electric conductivity of the composite. The new equation was confirmed to be adaptable to thermal conductivities of varieties of polymer composite systems filled with spherical or irregular fillers. The equation was also considered to explain thermal conductivity of polymer composites filled with fibers. Further, it was found that thermal conductivities of fiber composites can be estimated by introducing a factor of the CVF value or aspect ratio ( L I D ) into the new equation.

Selection of good quality oocytes is important for improvement of assisted reproductive technology. Here, we studied the relationship of the mitochondrial distribution in metaphase II stage (MII) oocytes with fertility, since mitochondria in ooplasm are essential for energy production required for fertilization and embryo development. To observe mitochondria non-invasively, we used oocytes from a transgenic mouse, in which enhanced green fluorescent protein is targeted to the mitochondrial matrix and thus fluorescence is observed exclusively in the mitochondria. Control oocytes with mitochondria distributed around the nucleus showed normal embryo developmental competence, whereas oocytes with abnormal diffuse and fragmented mitochondria showed a significantly lower rate of embryo development after activation by intracytoplasmic sperm injection or strontium, which is a very effective agent for activation of mouse oocytes. Also, we showed that the reduced developmental competence of oocytes with diffuse and fragmented mitochondria caused by vitrification and thawing is similar to that of oocytes with abnormal mitochondrial foci obtained naturally. These findings suggest that abnormal mitochondrial distribution in oocytes at MII is a cause of developmental retardation and therefore normal mitochondrial distribution could be used as a criterion for selection of good oocytes.

SYNOPSISThermal conductivity of polyethylene composites, filled with randolr.ly dispersed and disoriented (oriented at random) carbon fibers with various aspect ratios, were investigated. Orientation of fibers was quantitatively evaluated by Hermans' parameter. In specimens of isotropic composites, i.e., filled with randomly dispersed and disoriented fibers, thermal conductivity increased with an increase in the fiber length. The resub; is discussed in comparison with electric conductivity of the composites and explained by the contact probability of filled fibers. Further, it was confirmed that our model previously proposed could be adopted to predict thermal conductivity of the isotropic composite fillod with carbon fibers. Also, the effect of fiber length of the C2 parameter included in the m3del is discussed and C2 was found to have a linear relation with the aspect ratio of fibers #it a sufficiently large value. In this study, a shape factor of a filler (aspect ratio) could be directly introduced into the equation, which was shown in our previous paper.

SYNOPSISWe measured thermal conductivities as well as electric conductivities of some composites in several types of dispersion systems. The dispersion state, that is, the ease in forming conductive chains in these composites, was estimated by the characteristic electric conductivities and compared with the thermal conductivities. Thus, it became clear that thermal conductivity of a composite was significantly affected by the dispersion state in the composite. Further, it was confirmed that the predictive model proposed in the previous report was adaptable to the thermal conductivity of the composites in several types of dispersion systems. It was made clear that the dispersion state of a composite affected the values C1 and C2 in the previous model.