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Objective: The fatigue strength of a new type of vertical retort under the cyclic load of heat engine was studied, especially the residual fatigue life of the pot body after the crack appeared and the factors affecting the fatigue crack propagation of the germicidal pot. Methods: The mechanical characteristics of retort under sterilization and three kinds of cyclic loads were analyzed by Workbench, the design fatigue life of the retort under three alternating stresses was studied based on the S-N curve. The effect of the initial crack size, pressure and temperature on the stress strength factor and residual fatigue life of the crack retort were studied based on fracture mechanics. Results: The design fatigue life of this type of vertical retort was calculated to be 5×105 times, which meet the design requirements, and has a certain safety margin. Based on the fracture mechanics analysis, the crack size life curve of the sterilization retort was obtained, and the residual life of the sterilization retort with defects was predicted, which had certain innovation. Conclusion: Attention should be paid to the occurrence and propagation of cracks in the pot during use. The strength analysis and life prediction analysis of crack defects in the sterilization retort can be carried out according to the method proposed in this paper and experiment.

Objective: The flow channel distribution of polylactic acid in four screw extruder with different screw arrangement was studied. Methods: The three-dimensional modeling software Solidworks was used to establish the screw model and the corresponding fluid region model under the arrangement of one-word screw, four-square screw and encircle screw. Numerical simulation was carried out by the simulation software Polyflow. Results: The screw arrangement of monotype and surround type had better pressure building ability and distribution mixing ability than the square arrangement, and the square arrangement had weaker transport ability of polylactic acid. Conclusion: The four-screw extruder with one-line screw arrangement has a good effect on the processing of PLA.

Objective: To investigate the effect of the screw configuration on the polylactic acid flow field on the structural parameters of the screw on the end face of the screw in the meshing counter rotating twin screw extruder. Methods: The theoretical model of the heterodirectional double-ended threaded element was established by Solidworks software and the geometry of the threaded element after adjusting the structural parameters in two different ways. The established three-dimensional model was imported into Gambit software for meshing, and then Polyflow software was applied to the flow field simulation calculation. Finally, the flow field distribution results were extracted by Fieldview software, and the effects of the adjustment of the structural parameters on the end surface of the threaded element during correction were compared and analyzed on the shear rate field, viscosity field and speed field. Results: The structural parameters of the threaded element during correction will affect the polylactic acid flow field after being adjusted in two ways. The two adjustment methods of structural parameters have reduced the shear rate gradient in the runner to varying degrees, and the first method has also caused the viscosity of the polymer lactic acid in the runner to be reduced. Conclusion: From the perspective of the influence on the shear rate field, viscosity field and speed field, the threaded element adjusted by mode one is more conducive to extrusion, while the solid configuration of the threaded element adjusted by mode two is closer to the theoretical configuration of the threaded component.

Objective: Explore the effects of different combinations of forward screw elements in the melt conveying section on the melt conveying characteristics of reverse screw elements. Methods: Two different models were constructed by changing the lead, using SolidWorks software to establish a three-dimensional model, and using Polyflow software to numerically simulate the extrusion process of the two models in the melt conveying section. The effects of the screw groove width and screw edge thickness of the screw elements on the flow field under different lead lengths and the changes in the flow field at different rotational speeds were analyzed, and the effects of rotational speed on the material mixing were verified through experiments. Results: The constructed model can allow the melt to pass through the reverse threaded element. At the same screw speed, the pressure building capacity and conveying capacity of model one constructed from large lead screw elements were stronger than that of model two constructed from small lead screw elements. Model one was superior to Model two in terms of decentralized mixing ability, and weaker than Model two in terms of distributed mixing ability. Under the same pressure difference at both ends, increasing the rotational speed could improve the dispersion and mixing effects of materials. Conclusion: Using model one in the improved processing of polylactic acid and increasing the rotational speed of the screw can further crush the material and improve the quality of the extrusion.

Objective: In order to explore the distribution law of the flow channel of polylactic acid in different screw contact states of the counter-rotating twin-screw extruder. Methods: Partially meshing screw and non-meshing screw were established by Solidworks software. Numerical sim-ulation was carried out using POLYFLOW fluid simulation software. The pressure field, shear rate field and viscosity field of polylactic acid fluid under different contact states of three screws were compared. Results: The counter-rotating twin-screw extruder in the partially meshed state has better pressure-building ability and dispersing and mixing ability for polylactic acid. Conclusion: The extrusion effect of polylactic acid in the partially meshed state is better than the other two screw contact states.

Objective: To explore the influence of different screw configurations of intermeshing co-rotating twin -screw extruder on the flow field and improve the material properties of PLA. Methods: The geometric model of double threaded element was established by using Solidworks software, and the numerical simulation was carried out in Polyflow. The post-processing analysis of the simulation results was carried out with the help of Fieldview software. The shear rate field, pressure field, velocity field, viscosity field and the residence time distribution RTD were compared to obtain the influence of screw groove depth on the flow field. Results: When the center distance was the same, the depth of the screw groove was changed by changing the ratio of the outer diameter to the inner diameter of the threaded element, physical fields and mixing performance had great differences in the flow field of intermeshing co-rotating twin-screw extruder under the same process conditions. Compared with configuration 2, configuration 1 had stronger shear effect, but configuration 2 had better pressure building ability. In the extrusion process, configuration 2 had good axial mixing ability but poor self-cleaning ability, while configuration 1 had poor axial mixing ability and good self-cleaning ability. Conclusion: The change in screw groove depth has certain effects and rules on the mixing performance of the flow field, which can effectively guide the design of threaded element for twin-screw extruder.

Abstract Prolyl hydroxylase domain 3 (PHD3) is a hypoxia inducible factor-α (HIFα) regulator; it degrades HIFα in the presence of oxygen. Recently, there have been an increasing number of studies about the role of PHD3 in proliferation and apoptosis of cancer cells. However, most of the evidence for the role of PHD3 is observational, and little is known of the molecular mechanism. In our current study, we constructed a recombinant eukaryotic expression vector containing the PHD3 gene and detected its biological activity in human hepatoma cell line (HepG2 cells). We successfully constructed a recombinant pcDNA 3.1(+)-PHD3 plasmid; the results showed that PHD3 overexpression could inhibit the proliferation of HepG2 cells and induce apoptosis by activating caspase-3 activity. Our study has provided preliminary materials and data for further investigation of the effect of PHD3 on HepG2 cells.