This trial was conducted to investigate the effects of supplementary quercetin on growth performance, serum lipids levels and whole fish body composition in tilapia (Oreochromis niloticus). Four hundred fish were randomly divided into five treatment groups with four replicates in each group and 20 fish in each replicate. The dietary quercetin levels of the five treatment groups were: 0 (control group), 200, 400, 800, and 1600 mg/kg, respectively; the trial period was 7 weeks. Compared with the control group, specific growth rate and condition factor of quercetin groups were improved significantly (P<0.05). No significant differences in feed conversion rate and survival rate were found between the control group and all quercetin groups (P>0.05). The triglyceride concentration in serum was decreased significantly with the increasing levels of quercetin supplementation (P<0.05), while the highdensity lipoprotein cholesterol concentration was increased significantly by the supplementation of quercetin (P<0.05). The significant difference of low-density lipoprotein cholesterol concentration was found only between control group and highest dietary quercetin level group (P<0.05). The levels of moisture, crude protein and crude lipid of whole fish body were significantly affected by the supplementation of quercetin (P<0.05), the ash levels of all groups were similar (P>0.05). In conclusion, we demonstrated a promotion of growth performance and the reduction of lipid levels in serum and whole fish body with the supplementation of quercetin.

The influence of the alloying elements Re, Co and W on the propagation of the (010) [101] Ni/Ni 3 Al interface crack has been investigated by molecular dynamics simulations and the discrete-variational method. The simulation results show that the interface crack propagates in a brittle manner at low temperature (5 K), but in ductile manner at high temperature (1273 K), both with and without the addition of alloying elements. Owing to the scientific and technological importance of superalloys, the effects of the chemical bonding behavior between the alloying element X (X = Re, Co, or W) and Ni atoms on the crack shape, crack propagation velocity, and dislocation emission were investigated. At low temperature, the alloying elements Re and W inhibit the propagation of the Ni/Ni 3 Al interface crack, while at high temperature Re, Co and W can improve the ductility of Ni-based single-crystal superalloys. Furthermore, the adhesion work of the interface, surface energy, and unstable stacking energy were calculated to understand the propagation mechanism of the Ni/Ni 3 Al interface crack because of alloying element addition. The results of this study may provide useful information for the design of Ni-based superalloys.

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