Laser Ablating Biomimetic Periodic Array Fish Scale Surface for Drag Reduction.

Reducing resistance to surface friction is challenging in the field of engineering. Natural biological systems have evolved unique functional surfaces or special physiological functions to adapt to their complex environments over centuries. Among these biological wonders, fish, one of the oldest in the vertebrate group, have garnered attention due to their exceptional fluid dynamics capabilities. Fish skin has inspired innovation in reducing surface friction due to its unique structures and material properties. Herein, drawing inspiration from the unique properties of fish scales, a periodic array of fish scales was fabricated by laser ablation on a polished aluminum template. The morphology of the biomimetic fish scale surface was characterized using scanning electron microscopy and a white-light interfering profilometer. Drag reduction performance was measured in a closed circulating water tunnel. The maximum drag reduction was 10.26% at a Reynolds number of 39,532, and the drag reduction performance gradually decreased with an increase in the distance between fish scales. The mechanism of the biomimetic drag reduction surface was analyzed using computational fluid dynamics. Streamwise vortices were generated at the valley of the biomimetic fish scale, replacing sliding friction with rolling friction. These results are expected to provide a foundation for in-depth analysis of the hydrodynamic performance of fish and serve as new inspiration for drag reduction and antifouling.

Effect of Different Salt Concentrations on Dimethyl Sulfoxide (DMSO) Nanocluster Structures by Molecular Dynamics Simulations.

We performed MD simulations to examine dimethyl sulfoxide (DMSO) nanocluster structures in NaCl aqueous solution with different concentrations (0.45 g/100 mL, 0.9 g/100 mL, 1.8 g/100 mL, 2.7 g/100 mL, and 3.6 g/100 mL). Results showed that interaction between Na+ and DMSO at the first solvation shells was weakened due to acceleration rotational influence of ion driven by NaCl concentration. We investigated the tetrahedral order parameter and average H-B number of water molecules. These results indicated that NaCl influenced the solvation structure of water cluster, but that of DMSO was not affected by NaCl. We also found that Na+ was prior solvated by water solution in these mixture systems, and Cl- only existed in the water cluster in our simulation systems. Consequently, we herein proposed a decentralized model that depicts microphysical structure images of DMSO in NaCl aqueous solution systems.

Biliary tract and pancreatic surgery complicated by acute pancreatitis: a clinical analysis.

OBJECTIVE: To study the clinical treatment features of biliary tract and pancreatic surgery complicated by acute pancreatitis. METHODS: A retrospective analysis of 21 cases of biliary tract and pancreatic surgery complicated by acute pancreatitis in the Department of General Surgery in our hospital during May 2005 to July 2011 was performed; the clinical treatment features were analyzed in terms of surgical option, onset interval of acute pancreatitis after last surgery, length of stay in hospital and Ranson score. RESULTS: There was no statistic difference between the two groups (A: The onset interval of acute pancreatitis after last surgery < 0.5 year. B: The onset interval of acute pancreatitis after last surgery > 0.5 year) in pathogenetic condition and length of stay in hospital. All patients were discharged after treatment, a follow-up of 6-18 months found no recurrence of pancreatitis. CONCLUSION: There is no relevance between the treatment feature and onset interval of biliary and pancreatic surgery complicated by acute pancreatitis. The disease is still treated meanly with symptomatic and supportive treatment, while the etiological treatment is also particularly important.