Ultrasonic microfluidic technology is a technique that couples high-frequency ultrasonic excitation to microfluidic chips. To improve the issues of poor disturbance effects with flexible tip structures and the susceptibility of bubbles to thermal deformation, we propose an enhanced ultrasonic microchannel structure that couples flexible tips with bubbles aiming to improve the disturbance effects and the stability duration. Firstly, we used finite element analysis to simulate the flow field distribution characteristics of the flexible tip, the bubble, and the coupling structure and obtained the steady-state distribution characteristics of the velocity field. Next, we fabricated ultrasonic microfluidic chips based on these three structures, employing 2.8 μm polystyrene microspheres as tracers to analyze the disturbance characteristics of the flow field. Additionally, we analyzed the bubble size and growth rate within the adhering bubbles and coupling structures. Finally, we verified the applicability of the coupling structure for biological samples using human red blood cells (RBCs). Experimental results indicated that, compared to the flexible tip and adhering bubble structures, the flow field disturbance range of the coupling structure increased by 439.53% and 133.48%, respectively; the bubble growth rate reduced from 14.4% to 3.3%. The enhanced ultrasonic microfluidic structure proposed in this study shows great potential for widespread applications in micro-scale flow field disturbance and particle manipulation.
Objective To systematically review the relationship between periodontal disease and gastric cancer risk. Methods We retrieved PubMed, EMbase, CNKI, WanFang Data, VIP, and CBM databases to collect studies about the correlation between periodontal disease and gastric cancer from inception to January 31st, 2017. Two reviewers independently screened literature, extracted data and assessed the risk of bias of included studies. Then, meta-analysis was performed using RevMan 5.3 software. Results Five studies were included. The results of meta-analysis showed that there was no significant correlation between periodontal disease and gastric cancer (RR=0.99, 95%CI 0.83 to 1.19, P=0.93). Sensitivity analysis showed good stability. Subgroup analysis showed that the type of study, race and type of effect size have no statistically impact on the outcome, there was no significant correlation between periodontal disease and gastric cancer. Conclusion According to the current evidence, periodontal disease probably is not a risk factor of gastric cancer. Due to limited quality and quantity of the included studies, more high quality studies are needed to verify above conclusion.
ObjectiveTo systematically review the association between periodontal disease and the incidence risk of colorectal cancer (CRC).MethodsPubMed, EMbase, WanFang Data and CNKI databases were searched to collect cohort studies and case-control studies for the association between periodontal disease and the incidence risk of CRC from inception to February 28th, 2017. Two reviewers independently screened literature, extracted data and assessed the risk of bias of included studies, then, meta-analysis was performed by using RevMan 5.3 software.ResultsA total of 5 prospective cohort studies were included. The results from adjusted data based meta-analysis showed that the periodontal disease was not associated with the incidence risk of CRC (RR=1.14, 95%CI 0.88 to 1.49, P=0.32).ConclusionsThe current evidence suggests that periodontal disease is not associated with the risk of CRC.