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Basing on the theoretical model and empirical analysis, this paper provides a discussion of the hedging effectiveness between the stock market and index future market under the imperfect market conditions. In theoretical analysis, the relation of market imperfection with market microstructure noise and hedging effectiveness is established. In empirical analysis, one approach based on nonparametric estimation is established and applied to real data. The reasonableness of model assumptions and the correction of model conclusions are verified by using 5-minute frequency intra data. Both theoretical and empirical analyses show that the higher the degree of market imperfection, the more necessary to consider the impact of market microstructure noise when using stock index futures to hedge the stock market risk. The empirical results also show that there exists a high degree of imperfection between stock market and stock index future market, but the degree of imperfection has a decreasing trend. [ABSTRACT FROM AUTHOR]

Objective To evaluate and compare the value of quantitative parameters of preoperative dual-energy CT and MRI on KRAS mutation in rectal cancer,and to explore the correlations between postoperative pathological indicators and KRAS mutation. Methods This study retrospectively analyzed 50 patients with rectal cancer confirmed by surgery and pathology and receiving KRAS genetic testing in Lanzhou University Second Hospital from August 2017 to April 2021.According to the results of genetic testing,the patients were assigned into a wild-type group (29 patients) and a mutant type group (21 patients).The preoperative baseline data included sex,age,and serum tumor markers,and the postoperative pathological data included pathological stage,lymphovascular invasion,perineural invasion,and lymph node metastasis.The quantitative parameters of three-phase energy spectral CT included iodine (water) concentration,water (iodine) concentration,effective atomic number,and normalized iodine concentration.The quantitative parameters of apparent diffusion coefficient (ADC) included minimum ADC,average ADC,and relative ADC.In addition,the width of the superior rectal vein was obtained from the CT images of the venous phase,and the tumor segmentation,the maximum axial length of tumor,and the maximum longitudinal length of tumor were obtained from the MRI images.The qualitative and quantitative data were compared by χ 2 test, t -test,and Mann-Whitney U test.The diagnostic efficacy of the two detection methods for KRAS mutations in rectal cancer was compared,and the receiver operating characteristic curve was employed to evaluate the diagnostic efficacy. Results The KRAS mutation rate was higher in the carbohydrate antigen 199 abnormal group than the normal group ( P =0.036) and higher in the positive group of lymphovascular invasion ( P =0.034).The KRAS mutant type group had higher normalized iodine concentration in the venous phase ( P =0.016) and lower average ADC and relative ADC ( P =0.008, P =0.002,respectively) than the wild-type group.Among them,relative ADC had the highest diagnostic efficiency (AUC=0.755). Conclusion The quantitative parameters of dual-energy CT and ADC have similar diagnostic efficiency for KRAS mutation in rectal cancer,and relative ADC is superior to other parameters.