目的探讨非贫血人群血清铁蛋白(serum ferritin,SF)和转铁蛋白饱和度(transferrin saturation,TSAT)与全因死亡和心血管死亡的相关性。方法选取1999—2000年和2001—2002年国家健康和营养检查调查研究(national health and nutrition ex...目的探讨非贫血人群血清铁蛋白(serum ferritin,SF)和转铁蛋白饱和度(transferrin saturation,TSAT)与全因死亡和心血管死亡的相关性。方法选取1999—2000年和2001—2002年国家健康和营养检查调查研究(national health and nutrition examination survey,NHANES)的非贫血人群7167例,于2006年12月31日前对死亡终点进行随访,采用阈值效应分析和多因素cox回归模型分析SF和TAST与全因死亡和心血管死亡风险的相关性。结果7167例患者中男3533例、女3634例,年龄18~85岁,平均(46.1±20.0)岁,BMI平均(27.9±6.2)kg/m2。平均随访(5.1±1.2)年,共随访11623人/年,其中全因死亡452例、心血管死亡117例。SF与全因死亡和心血管死亡呈非线性相关,SF的截断值为200 ng/ml;当SF<200 ng/ml时,SF每增加100 ng/ml,全因死亡风险增加25%(HR=1.252,95%CI:1.068~1.486,P=0.008),心血管死亡风险增加37%(HR=1.370,95%CI:1.076~1.900,P=0.036)。TSAT与全因死亡率呈L型非线性相关,截断值为30%,当TSAT<30%时,TSAT每增加10%,全因死亡风险降低21%(HR=0.791,95%CI:0.681~0.914,P=0.001);TSAT与心血管死亡风险呈线性负相关(HR=0.803,95%CI:0.660~0.963,P=0.014)。结论非贫血人群的SF与全因死亡和心血管死亡呈非线性相关、截断值为200 ng/ml,TSAT与全因死亡呈L型相关、截断值为30%,且TSAT与心血管死亡呈负相关。建议将非贫血人群的SF与TSAT控制在合适范围,以降低死亡风险,并改善预后。展开更多
To study the mechanical and damage evolution properties of sandstone under triaxial compression, we analyzed the stress strain curve characteristics, deformation and strength properties, and failure process and charac...To study the mechanical and damage evolution properties of sandstone under triaxial compression, we analyzed the stress strain curve characteristics, deformation and strength properties, and failure process and characteristics of sandstone samples under different stress states. The experimental results reveal that peak strength, residual strength, elasticity modulus and deformation modulus increase linearly with confining pressure, and failure models transform from fragile failure under low confining pressure to ductility failure under high confining pressure. Macroscopic failure forms of samples under uniaxial compression were split failure parallel to the axis of samples, while macroscopic failure forms under uniaxial compression were shear failure, the shear failure angle of which decreased linearly with confin- ing pressure. There were significant volume dilatation properties in the loading process of sandstone under different confining pressures, and we analyzed the damage evolution properties of samples based on acoustic emission damage and volumetric dilatation damage, and established damage constitutive model, realizing the real-time Quantitative evaluation of samnles damage state in loading process.展开更多
Based on uniaxial compression experimental results on fractured sandstone with grouting and anchorage, we studied the strength and deformation properties, the failure model, crack formation and evolution laws of fract...Based on uniaxial compression experimental results on fractured sandstone with grouting and anchorage, we studied the strength and deformation properties, the failure model, crack formation and evolution laws of fractured sandstone under different conditions of anchorage. The experimental results show that the strength and elastic modulus of fractured sandstone with different fracture angles are significantly lower than those of intact sandstone. Compared with the fractured samples without anchorage,the peak strength, residual strength, peak and ultimate axial strain of fractured sandstone under different anchorage increase by 64.5–320.0%, 62.8–493.0%, and 31.6–181.4%, respectively. The number of bolts and degree of pre-stress has certain effects on the peak strength and failure model of fractured sandstone. The peak strength of fractured sandstone under different anchorage increases to some extent, and the failure model of fractured sandstone also transforms from tensile failure to tensile–shear mixed failure with the number of bolts. The pre-stress can restrain the formation and evolution process of tensile cracks, delay the failure process of fractured sandstone under anchorage and impel the transformation of failure model from brittle failure to plastic failure.展开更多
基金the National Natural Science Foundation of China (Nos.51323004 and 51574223)the Postdoctoral Science Foundation of China (No.2015M571842)the Open Research Fund of Research Center of Jiangsu Collaborative Innovation Center for Building Energy Saving and Construction Technology (No.SJXTY1502)
文摘To study the mechanical and damage evolution properties of sandstone under triaxial compression, we analyzed the stress strain curve characteristics, deformation and strength properties, and failure process and characteristics of sandstone samples under different stress states. The experimental results reveal that peak strength, residual strength, elasticity modulus and deformation modulus increase linearly with confining pressure, and failure models transform from fragile failure under low confining pressure to ductility failure under high confining pressure. Macroscopic failure forms of samples under uniaxial compression were split failure parallel to the axis of samples, while macroscopic failure forms under uniaxial compression were shear failure, the shear failure angle of which decreased linearly with confin- ing pressure. There were significant volume dilatation properties in the loading process of sandstone under different confining pressures, and we analyzed the damage evolution properties of samples based on acoustic emission damage and volumetric dilatation damage, and established damage constitutive model, realizing the real-time Quantitative evaluation of samnles damage state in loading process.
基金Financial support for this work, provided by the National Natural Science Foundation of China (Nos. 50774082, 50804046 and 51109209)
文摘Based on uniaxial compression experimental results on fractured sandstone with grouting and anchorage, we studied the strength and deformation properties, the failure model, crack formation and evolution laws of fractured sandstone under different conditions of anchorage. The experimental results show that the strength and elastic modulus of fractured sandstone with different fracture angles are significantly lower than those of intact sandstone. Compared with the fractured samples without anchorage,the peak strength, residual strength, peak and ultimate axial strain of fractured sandstone under different anchorage increase by 64.5–320.0%, 62.8–493.0%, and 31.6–181.4%, respectively. The number of bolts and degree of pre-stress has certain effects on the peak strength and failure model of fractured sandstone. The peak strength of fractured sandstone under different anchorage increases to some extent, and the failure model of fractured sandstone also transforms from tensile failure to tensile–shear mixed failure with the number of bolts. The pre-stress can restrain the formation and evolution process of tensile cracks, delay the failure process of fractured sandstone under anchorage and impel the transformation of failure model from brittle failure to plastic failure.
