This paper develops a Stackelberg game model for a retailer-led secondary low-carbon supply chain (L-CSC) comprising a manufacturer and a retailer. Then, a two-part pricing contract is designed to investigate the product pricing, carbon reduction, and sales effort decision problems, and relevant management insights are obtained through numerical analysis. The study shows an efficiency loss in decentralized decision making compared to centralized decision making. Considering the sales effort improves the efficiency of the supply chain, retail price, carbon emission reduction (CER), sales effort level, and supply chain profit positively relate to product low carbon preference and sales sensitivity coefficients. The designed two-part pricing contract can increase the profit of the entire L-CSC and optimize the decision level under centralized decision making.

Objective To analyze the diagnostic value of MRI in placenta previa. Methods 100 pregnant women with placenta previa admitted to our hospital from January 2017 to January 2020 were selected as the research objects. They were randomly divided into groups by digital table. Group A (50 cases) carried out magnetic resonance imaging (MRI) examination, and Group B (50 cases) carried out Doppler ultrasound examination. The detection of disease types and diagnostic accuracy were compared, and the imaging manifestations of MRI in the diagnosis of placenta accreta and non placenta accreta were analyzed. Results The detection rate of central type, marginal type and partial type in group A was higher than that in group B (P < 0.05). With surgery and pathology as the gold standard, the diagnostic accuracy and sensitivity of group A were higher than that of group B, and the rate of missed diagnosis was lower than that of group B (P < 0.05). Among the 50 pregnant women in Group A, 9 had placenta implantation and 41 had no placenta implantation. There were differences in the imaging manifestations of the pregnant women, such as the uneven signal in the placenta, the increased/thickened blood vessels in the placenta, and the unclear boundary between the placenta and the uterus (P < 0.05). Conclusion MRI examination is an important way for clinical diagnosis of placenta previa, and it is worth popularizing.