External support stent is a potential means for restricting the deformation and reducing wall stress of the vein graft, thereby improving the long-term patency of the graft in coronary artery bypass surgery. However, there still lacks a theoretical reference for choosing the size of stent based on the diameter of graft. Taking the VEST (venous external support) stent currently used in the clinical practice as the object of study, we constructed three models of VEST stents with different diameters and coupled them respectively to a model of the great saphenous vein graft, and numerically simulated the expansion-contraction process of the vein graft under the constraint of the stents to quantitatively evaluate the influence of stent size on the radial deformation and wall stress of the vein graft. The results showed that while the stent with a small diameter had a high restrictive effect in comparison with larger stents, it led to more severe concentration of wall stress and sharper changes in radial deformation along the axis of the graft, which may have adverse influence on the graft. In order to solve the aforementioned problems, we ameliorated the design of the stent by means of changing the cross-sectional shape of the thick and thin alloy wires from circle into rectangle and square, respectively, while keeping the cross-sectional areas of alloy wires and stent topology unchanged. Further numerical simulations demonstrated that the ameliorated stent evidently reduced the degrees of wall stress concentration and abrupt changes in radial deformation, which may help improve the biomechanical environment of the graft while maintaining the restrictive role of the stent.
Objective To explore the teaching ability of the neurology refresher doctors by case teaching method combined with flipped classroom teaching mode. Methods The refresher doctors who were studying in the infection group of Department of Neurology, Xuanwu Hospital Capital Medical University between March 2019 and September 2020 were selected. According to the time of admission, the enrolled refresher doctors were divided into control group (grade 2019) and observation group (grade 2020). The control group adopted the traditional teaching mode, and the observation group adopted the case teaching method combined with the flipped classroom teaching mode. A self-designed questionnaire was used to compare the teaching ability of the two groups of refresher doctors. Results A total of 44 refresher doctors were included. Among them, there were 24 refresher doctors in the control group and 20 refresher doctors in the observation group. The self-evaluation of the teaching ability of the two groups of refresher doctors and the evaluation of their teaching ability by the teachers showed that, except for the item “enthusiasm for teaching and willingness to spend enough time to participate in the evaluation of teaching work” of humanistic quality (P>0.05), the observation group was better than the control group in professional knowledge, teaching ability, teaching methods and humanistic quality (P<0.05). Conclusions Through the case teaching method combined with flipped classroom teaching mode, the teaching ability of refresher doctors can be cultivated, which is helpful for training more high-quality doctors for the country and promoting the sustainable and coordinated development of medical education. However, the awareness and enthusiasm of the refresher doctors to teaching work need to be improved.