Numerical Analysis of Drag Reduction Characteristics of Biomimetic Puffer Skin: Effect of Spinal Height and Tilt Angle.

Based on the migratory phenomenon of the puffer and the cone-shaped structures on its skin, the effects of spinal height and tilt angle on the drag reduction characteristics is presented by numerical simulation in this paper. The results show that the trend of total drag reduction efficiency changes from slow growth to a remarkable decline, while the viscous drag reduction efficiency changes from an obvious increase to steady growth. The total and viscous drag reduction efficiencies are 19.5% and 31.8%, respectively. In addition, with the increase in tilt angle, the total drag reduction efficiency decreases gradually; the viscous drag reduction efficiency first increases and then decreases, finally tending to be stable; and the total and viscous drag reduction efficiency reaches 20.7% and 26.7%, respectively. The flow field results indicate that the pressure drag mainly originates at the front row of the spines and that the total pressure drag can be effectively controlled by reducing the former pressure drag. With the increase in low-speed fluid and the reduction in the near-wall fluid velocity gradient, the viscous drag can be weakened. Nevertheless, the drag reduction effect is achieved only when the decrement of viscous drag is greater than the increment of pressure drag. This work can serve as a theoretical basis for optimizing the structure and distribution parameters of spines on bionic non-smooth surfaces.

Oxymatrine inhibits collagen synthesis in keloid fibroblasts via inhibition of transforming growth factor-ß1/Smad signaling pathway.

BACKGROUND: Keloids are benign dermal tumors characterized by fibroblastic proliferation and excessive accumulation of collagen. Oxymatrine (OMT) is an alkaloid extracted from the Chinese herb Sophora japonica with capacities of anti-fibrosis. OBJECTIVE: To evaluate the effects of OMT on collagen production and to explore its mechanisms. METHODS: OMT was applied to human keloid fibroblasts in vitro. Collagen, transforming growth factor (TGF)-ß1, TGF-ß receptor, and Smads were analyzed by Western Blot, reverse transcription polymerase chain reaction, and immunofluorescence. RESULTS: We found that both collagen synthesis and Smad3 production were significantly suppressed in a dose-dependent administration of OMT. However, expression of TGF-ß1, TGF-ß receptor1, TGF-ß receptor2, Smad4, and Smad7 was unchanged. We also found that OMT reversed phosphorylation and nuclear translocation of Smad3 induced by TGF-ß1. CONCLUSIONS: OMT inhibited collagen synthesis, which might be associated with TGF-ß/Smad signaling pathway. These findings suggest that OMT may be a promising candidate to prevent keloid and other fibrotic diseases.