Objective To explore the impact of different moving patterns during the dip-coating process on thickness distributions of polymer heart valves.Methods Based on the volume of fluid(VOF)multiphase flow model,the Eulerian wall-film(EWF)model,and dynamic mesh technology,the dip-coating manufacturing process of polymer heart valves were numerically simulated.The effects of vertical,horizontal,and circular moving patterns on flow characteristics of the surface impregnation liquid and liquid film distributions under self-rotation conditions of the models were mainly studied.Subsequently,seven identical test points were set on each valve leaflet to collect thickness data,and the coefficient of variation(CV)was calculated to evaluate the uniformity of the liquid film thickness.Given that the vertical and horizontal patterns had fewer moving planes,limiting the optimization space,the circular pattern(45°)with richer moving planes was selected as the basis for optimization,and comparative analysis of numerical simulation was conducted.Results In the vertical pattern,the peak CV was 0.461 3;in the horizontal pattern,the CV was 0.060 8;and in the circular pattern,the CV at 30°,45° and 60° were 0.457 5,0.272 8,and 0.255 6,respectively.After optimization,the CV for the circular pattern(45°)decreased to 0.052 5,representing an 80.7％reduction compared to the pre-optimization value.Conclusions The moving patterns significantly affect the uniformity of dip-coating thickness distributions.The horizontal pattern demonstrates the best uniformity,while the vertical pattern shows the poorest uniformity.The CV for the circular pattern decreases as the angle increases,with its uniformity between that of the vertical and horizontal patterns.Optimization of moving pattern parameters based on simulation results has improved the uniformity of thickness distributions.

Objective To investigate the impact of eccentric placement for various types of artificial aortic valves on downstream flow dynamics.Methods A physiological pulsatile circulation simulation system was employed and particle image velocimetry(PIV)was utilized to analyze the downstream flow field variations for bioprosthetic and mechanical valves under two placement conditions:centralized placement(0 mm)and eccentric placement(1 mm).Hemodynamic parameters such as velocity,vorticity,and viscous shear stress were assessed to evaluate the flow field characteristics.Results By analyzing the flow field variations at four characteristic time points,namely,early systole,acceleration phase,peak systole,and deceleration phase,a significant difference in flow field distribution between bioprosthetic and mechanical valves was observed.The bioprosthetic valve exhibited a centrally symmetric jet with a higher flow velocity,whereas the mechanical valve displayed a three-jet structure with a lower central flow velocity.Under eccentric placement,the blood flow in the aortic sinus region was sluggish,with a reduction in average velocity,hindering the formation and maintenance of vortices.During the peak systolic phase,the maximum viscous shear stresses in the sinus region for the bioprosthetic and mechanical valves were 0.45 and 0.67 Pa,respectively,approaching the threshold for endothelial cell damage.Conclusions Eccentric placement of both mechanical and bioprosthetic valves resulted in reduced sinus blood flow velocity and diminished viscous shear stress,creating favorable conditions for thrombus formation.In clinical practice,careful attention should be given to the placement of valve replacement to prevent eccentric placement.

Objective To explore the impact of different moving patterns during the dip-coating process on thickness distributions of polymer heart valves.Methods Based on the volume of fluid(VOF)multiphase flow model,the Eulerian wall-film(EWF)model,and dynamic mesh technology,the dip-coating manufacturing process of polymer heart valves were numerically simulated.The effects of vertical,horizontal,and circular moving patterns on flow characteristics of the surface impregnation liquid and liquid film distributions under self-rotation conditions of the models were mainly studied.Subsequently,seven identical test points were set on each valve leaflet to collect thickness data,and the coefficient of variation(CV)was calculated to evaluate the uniformity of the liquid film thickness.Given that the vertical and horizontal patterns had fewer moving planes,limiting the optimization space,the circular pattern(45°)with richer moving planes was selected as the basis for optimization,and comparative analysis of numerical simulation was conducted.Results In the vertical pattern,the peak CV was 0.461 3;in the horizontal pattern,the CV was 0.060 8;and in the circular pattern,the CV at 30°,45° and 60° were 0.457 5,0.272 8,and 0.255 6,respectively.After optimization,the CV for the circular pattern(45°)decreased to 0.052 5,representing an 80.7％reduction compared to the pre-optimization value.Conclusions The moving patterns significantly affect the uniformity of dip-coating thickness distributions.The horizontal pattern demonstrates the best uniformity,while the vertical pattern shows the poorest uniformity.The CV for the circular pattern decreases as the angle increases,with its uniformity between that of the vertical and horizontal patterns.Optimization of moving pattern parameters based on simulation results has improved the uniformity of thickness distributions.

Objective To investigate the impact of eccentric placement for various types of artificial aortic valves on downstream flow dynamics.Methods A physiological pulsatile circulation simulation system was employed and particle image velocimetry(PIV)was utilized to analyze the downstream flow field variations for bioprosthetic and mechanical valves under two placement conditions:centralized placement(0 mm)and eccentric placement(1 mm).Hemodynamic parameters such as velocity,vorticity,and viscous shear stress were assessed to evaluate the flow field characteristics.Results By analyzing the flow field variations at four characteristic time points,namely,early systole,acceleration phase,peak systole,and deceleration phase,a significant difference in flow field distribution between bioprosthetic and mechanical valves was observed.The bioprosthetic valve exhibited a centrally symmetric jet with a higher flow velocity,whereas the mechanical valve displayed a three-jet structure with a lower central flow velocity.Under eccentric placement,the blood flow in the aortic sinus region was sluggish,with a reduction in average velocity,hindering the formation and maintenance of vortices.During the peak systolic phase,the maximum viscous shear stresses in the sinus region for the bioprosthetic and mechanical valves were 0.45 and 0.67 Pa,respectively,approaching the threshold for endothelial cell damage.Conclusions Eccentric placement of both mechanical and bioprosthetic valves resulted in reduced sinus blood flow velocity and diminished viscous shear stress,creating favorable conditions for thrombus formation.In clinical practice,careful attention should be given to the placement of valve replacement to prevent eccentric placement.

Inflammatory bowel disease,a type of intestinal chronic inflammatory disease caused by multi-factors,which include ulcerative colitis,Crohn's disease and inflammatory bowel disease unclassified.The morbidity of inflammatory bowel disease has been increasing by years with a younger age trend.Nowadays the pediatric inflammatory bowel disease is prevalent.Pediatric inflammatory bowel disease is different from adult at many aspects such as clinical manifestation,disease type,treatment,complications etc.It is because children are in a special condition with fast growth and development.This article will elaborate the current status of treatment and progresses of inflammatory bowel disease especially pediatric inflammatory bowel disease.

The blocking action and selectivity of 1 - (? -naphthylmethyl)-2 - methyl - 6,7 - dimethoxy -1,2,3,4 -tetrahydroisoquinoline (86040) on a - a-drenoceptor have been investigated in isolated tissues. 86040 suppressed the inhibition of clonidine for the electrically stimulated twitch response of rat vas deferens ( - adre - noceptor), with pA2 value of 5. 85. 86040 could competitively inhibit anococcygeus muscle contraction (?1 -a-drenoceptor ) induced by phenylephrine with pA2 value of 7. 62. 86040 was found that the selectivity radio to block ?2 - and ?2 adrenoceptor(?1/?2)was 60. these results indicate that 86040 is a potentant relatively selective ?1 - adrenoceptor blocker.