Design and Simulation of a Passive Micromixer with Gourd-Shaped Channel.

A gourd-shaped contraction-expansion design is proposed for a passive planar micromixer in this study. The mixing performance of the micromixer is analyzed numerically and compared with a T-shaped planar micromixer. The gourd-shaped contraction-expansion structure can enhance the vortex-formation and mixing abilities of the micromixer. The numerical simulation reveals that the gourd-shaped structure can improved vortex generation and mixing efficiency within a high Reynolds number range. The micromixer with an optimized waist width of 50 µm reaches a mixing efficiency of approximately 83.25% and maintains a moderate pressure drop of 4860 Pa at Re = 100. This study can shed light on the design of new 2D micromixers from the point view of bionics.

[Effect of laparoscopic proctectomy and open proctectomy on plasma levels of vascular endothelial growth factor].

OBJECTIVE: To investigate the effect of laparoscopic and open proctectomy on plasma levels of vascular endothelial growth factor (VEGF). METHODS: From January 2011 to December 2012, 100 rectal cancer patients in Shantou Central Hospital were enrolled in the study. Patients were divided into laparoscopic (LR) group and open (OR) group based on the decision of the patients. There were 63 patients in the LR group (44 cases undergoing low anterior resection and 19 abdominoperineal resection) and 37 patients in the OR group(26 cases undergoing low anterior resection and 11 abdominoperineal resection). Double antibody sandwich enzyme-linked immunohistochemistry was used to detect the level of VEGF on 1-day before and 1-day, 3-day, 7-day after operation. RESULTS: In the LR group, the postoperative levels of VEGF increased slowly, and the level of VEGF was significantly higher than that before operation until the 7-day after operation(P<0.05) regardless of the procedure. In the OR group, all the postoperative levels of VEGF were significantly increased(P<0.05). There was no significant difference of the VEGF level on 1-day before and 1-day after operation between the two groups(all P>0.05). The VEGF level in the OR group was significantly higher than that in the LR group on the day 3 and day 7 after operation(P<0.05). CONCLUSION: Compared with open approach, laparoscopic proctectomy has smaller short-term impact on the plasma level of VEGF in rectal cancer patients.