An innovative method has been developed to trap silver (Ag) between two layers of silicon carbide (SiC) produced by chemical vapor deposition at 1300°C. The study has shown for the first time that silver diffuses through intact SiC in tristructural isotropic‐coated particles. We also refute some speculations reported in previous studies by showing that silver can diffuse in stoichiometric SiC and that it is the differences in SiC microstructure that play a fundamental role in the diffusion process rather than the formation of nanocracks due to a mechanical process. Our results stress the importance of the microstructure inherent to the SiC produced by fluidized bed chemical vapor deposition on Ag diffusion.

We have studied the effect of microstructure on the diffusion of silver (Ag) in different silicon carbide (SiC) coatings in tristructural isotropic-coated particles. Silicon carbide was deposited at 13001-15001C by fluidized bed chemical vapor deposition. The SiC coatings have been heat treated at 12001-14001C for 240 h. Depending on the microstructure our results confirm that silver can diffuse by grain-boundary diffusion but that a high concentration of nano-and microporosity at the grain boundaries can strongly influence the diffusion process by increasing the diffusion coefficient by at least two orders of magnitude (from B10 À17 for standard coatings to !10 À15 m 2 /s at 12001C). We also show that the presence of excess silicon or the formation of long columnar grains in SiC does not increase the diffusion of silver as previously thought. Our results do not support the idea that silver diffuses through SiC due to the formation of defects produced by mechanical damage (nanocracks). Silver is aiding the recrystallization of SiC when heat treated at 14001C.

Drosophila melanogaster is widely used as a model organism for biological investigations, and food is a major aspect of its ecology and evolutionary biology. Previous studies have shown that this insect can use fruits, yeasts and insect carcasses as its food sources. In this study, we demonstrate that this species is an omnivore, that its larvae can exploit not only fruits and yeast but also foods of animal origin (FAOs), and that larvae consume adult carcasses regularly. FAO-fed larvae develop into adulthood within a normal developmental time frame without the help of microbes. Yeast foods are better for Drosophila development than are foods of plant origin (FPOs) or FAO because in yeast foods, more eggs complete their life cycle, and the body size of emerged flies is much greater. Flies can use a mixture of yeast-FAO, which significantly boosts female fertility. Larvae digest FAOs externally. Larval D. virilis, D. hydei, and D. simulans are also omnivorous and demonstrate the same feeding habits as larval D. melanogaster. These findings prompt us to reconsider previous conclusions about the original adaptations of D. melanogaster and other Drosophila species and have direct implications for diet-related studies using Drosophila as a model organism.

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