生产、使用O型通用型红细胞(universal red blood cells)是未来输血医学发展的方向,本文综述了近年制备通用型红细胞的技术。第1种是红细胞血型抗原修饰技术,又分为2种方法:①糖苷酶酶解法,利用特异的外切糖苷水解酶将红细胞表面的A、B...生产、使用O型通用型红细胞(universal red blood cells)是未来输血医学发展的方向,本文综述了近年制备通用型红细胞的技术。第1种是红细胞血型抗原修饰技术,又分为2种方法:①糖苷酶酶解法,利用特异的外切糖苷水解酶将红细胞表面的A、B抗原的糖基去除,制备酶解转变的O型红细胞(ECO-RBC);B型红细胞制备的ECO-RBC已经成功地进行了临床输血试验,可安全地输给A型和O型患者;由于A抗原结构的复杂性,A型红细胞的酶解转变研究存在很大困难,目前应用细菌来源的新型糖苷酶同时实现了A1→O、A2→O的转变;②PEG化技术,利用化学材料甲氧基聚乙二醇(mPEG)非特异地遮蔽红细胞表面抗原,制备O型及表面稀有血型抗原阴性的通用型红细胞。第2种是诱导多能干细胞或成体细胞分化为成熟的红细胞的技术,不仅可制备ORh-型红细胞,还可作为新的血液来源以解决目前的血源短缺问题。目前,可用来诱导产生红细胞体系的启动细胞有造血干细胞(HSC),诱导性多能干细胞(iPSC)和人胚胎干细胞(hESC)或真皮成纤维细胞(Fib);利用多能干细胞制备通用型红细胞尚处于实验研究阶段,其生产工艺、生产成本及生产的红细胞的安全性、有效性距离临床应用还有许多问题有待解决。尽管如此,这些研究结果对防止血荒或血液传染性疾病的发生,保障应急用血,提高临床输血安全具有重要意义。展开更多
An analytical solution is derived from the generalized governing equations of equal-strain consolidation with vertical drains under multi-ramp surcharge preloading. The hydraulic boundary conditions at both top and bo...An analytical solution is derived from the generalized governing equations of equal-strain consolidation with vertical drains under multi-ramp surcharge preloading. The hydraulic boundary conditions at both top and bottom of the consolidating soil are modelled as impeded drainage. The impeded drainage is described by using the third type boundary condition with a characteristic factor of drainage efficiency. Fully drained and undrained boundary conditions can also be modelled by applying an infinite and a zero characteristic factor, respectively. Simultaneous radial and vertical flow conditions are considered, together with the effects of drain resistance and smear. An increase in total stress due to multi-ramp loading is reasonably modelled as a function of both time and depth. A solution to calculate excess pore-water pressure at any arbitrary point in soil is derived, and the overall average degree of consolidation is obtained. It shows that the proposed solution can be used to analyze not only vertical-drain consolidation but also one-dimensional consolidation under either one-way or two-way vertical drainage conditions. The characteristic factors of drainage efficiency of top and bottom boundaries have a potentially important influence on consolidation. The boundary may be considered fully drained when the characteristic factor is greater than 100 and fully undrained when the characteristic factor is less than 0.1. The stress distribution along depth induced by the surcharge loading has a limited effect on the overall average degree of consolidation.展开更多
文摘生产、使用O型通用型红细胞(universal red blood cells)是未来输血医学发展的方向,本文综述了近年制备通用型红细胞的技术。第1种是红细胞血型抗原修饰技术,又分为2种方法:①糖苷酶酶解法,利用特异的外切糖苷水解酶将红细胞表面的A、B抗原的糖基去除,制备酶解转变的O型红细胞(ECO-RBC);B型红细胞制备的ECO-RBC已经成功地进行了临床输血试验,可安全地输给A型和O型患者;由于A抗原结构的复杂性,A型红细胞的酶解转变研究存在很大困难,目前应用细菌来源的新型糖苷酶同时实现了A1→O、A2→O的转变;②PEG化技术,利用化学材料甲氧基聚乙二醇(mPEG)非特异地遮蔽红细胞表面抗原,制备O型及表面稀有血型抗原阴性的通用型红细胞。第2种是诱导多能干细胞或成体细胞分化为成熟的红细胞的技术,不仅可制备ORh-型红细胞,还可作为新的血液来源以解决目前的血源短缺问题。目前,可用来诱导产生红细胞体系的启动细胞有造血干细胞(HSC),诱导性多能干细胞(iPSC)和人胚胎干细胞(hESC)或真皮成纤维细胞(Fib);利用多能干细胞制备通用型红细胞尚处于实验研究阶段,其生产工艺、生产成本及生产的红细胞的安全性、有效性距离临床应用还有许多问题有待解决。尽管如此,这些研究结果对防止血荒或血液传染性疾病的发生,保障应急用血,提高临床输血安全具有重要意义。
基金Project(51278171)supported by the National Natural Science Foundation of ChinaProject(B13024)supported by Program of Introducing Talents of Discipline to Universities("111" Project),ChinaProject(2014B04914)supported by the Fundamental Research Funds for the Central Universities of China
文摘An analytical solution is derived from the generalized governing equations of equal-strain consolidation with vertical drains under multi-ramp surcharge preloading. The hydraulic boundary conditions at both top and bottom of the consolidating soil are modelled as impeded drainage. The impeded drainage is described by using the third type boundary condition with a characteristic factor of drainage efficiency. Fully drained and undrained boundary conditions can also be modelled by applying an infinite and a zero characteristic factor, respectively. Simultaneous radial and vertical flow conditions are considered, together with the effects of drain resistance and smear. An increase in total stress due to multi-ramp loading is reasonably modelled as a function of both time and depth. A solution to calculate excess pore-water pressure at any arbitrary point in soil is derived, and the overall average degree of consolidation is obtained. It shows that the proposed solution can be used to analyze not only vertical-drain consolidation but also one-dimensional consolidation under either one-way or two-way vertical drainage conditions. The characteristic factors of drainage efficiency of top and bottom boundaries have a potentially important influence on consolidation. The boundary may be considered fully drained when the characteristic factor is greater than 100 and fully undrained when the characteristic factor is less than 0.1. The stress distribution along depth induced by the surcharge loading has a limited effect on the overall average degree of consolidation.
