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Structural analysis does not consider weld seam. Research on welding seldom pays attention to structural strength analysis. The working conditions of super large structure are complex, and the design requirements are very high. The coupled relationship between the structure of weld toe and frame stiffness in actual working conditions is analyzed to improve the accuracy of finite element model. Using the finite element method as basis, this study establishes the finite element model for the frame. The fillet joint models for the different forms of weld toe are established on the basis of thermo-elastic/plastic theory. Weld toe optimization scheme is applied to analyze frame strength. The accuracy of the model is verified by experiments. Results show that high stress appears at the connection position of the left-right longitudinal beam and rear torsion tube and the middle of rear torsion tube due to the interaction of torsion and braking. Stress between the frontal longitudinal beam and portal-type girder assembly does not significantly vary. The weld height and toe of the fillet joint are 20 mm, and the stress peak value is small. The stress distribution of the frame is analyzed by optimizing the weld toe. The stress peak value is reduced from 453.8 MPa to 340.6 MPa. Through the repair welding of the weld toe position for the optimization scheme, the welding seam surface forms a concave arc and reduces the stress concentration effectively. Failure time of the frame increases by no more than 5000 hours and does not exhibit fatigue failure. Research results are crucial for establishing coupled relationship with weld toe and frame strength and optimizing welding. [ABSTRACT FROM AUTHOR]

MicroRNA-mediated post-transcriptional regulation plays key roles in stem cell self-renewal and tumorigenesis. However, the in vivo functions of specific microRNAs in controlling mammary stem cell (MaSC) activity and breast cancer formation remain poorly understood. Here we show that miR-31 is highly expressed in MaSC-enriched mammary basal cell population and in mammary tumors, and is regulated by NF-κB signaling. We demonstrate that miR-31 promotes mammary epithelial proliferation and MaSC expansion at the expense of differentiation in vivo. Loss of miR-31 compromises mammary tumor growth, reduces the number of cancer stem cells, as well as decreases tumor-initiating ability and metastasis to the lung, supporting its pro-oncogenic function. MiR-31 modulates multiple signaling pathways, including Prlr/Stat5, TGFβ and Wnt/β-catenin. Particularly, it activates Wnt/β-catenin signaling by directly targeting Wnt antagonists, including Dkk1. Importantly, Dkk1 overexpression partially rescues miR31-induced mammary defects. Together, these findings identify miR-31 as the key regulator of MaSC activity and breast tumorigenesis. [ABSTRACT FROM AUTHOR]

Genetic variation of insulin-like growth factor binding protein-3 was analyzed in 17 pig breeds (14 native Chinese and 3 European). Using PCR-single strand conformation polymorphism, we found a polymorphism in intron 2, and this SNP was the combined mutation of G897T-G903A-C911T. The Chinese breeds carried a higher TAT/TAT genotype frequency (over 50%), except for Bamei (22%), Yujiang Black (0.0%), and Erhualian (10.0%); the European breeds had a higher GGC/GGC genotype frequency (Large White 1.67%, Landrace 13.89%, Duroc 0.0%). The allelic frequency of TAT in Chinese breeds was over 50%, except for Yujiang Black (12.5%); the allelic frequency of GGC was over 50% in all European breeds. The effect of genotype on 43 performance traits was investigated in one population (Lantang × Landrace). Pigs with the TAT/TAT genotype had higher B-point and C-point back-fat thickness than pigs with the GGC/GGC genotype. The TAT/TAT pigs also scored higher in meat color than the GGC/GGC pigs. These results implied that IGFBP-3 may affect meat quality and carcass traits. [ABSTRACT FROM AUTHOR]