血管内皮生长因子基因修饰人羊膜间充质干细胞利于超长随意皮瓣的成活

背景:研究证实血管内皮生长因子能够诱导新生血管形成,人羊膜间充质干细胞也可通过多种机制改善皮瓣移植的缺血再灌注损伤。因此,用血管内皮生长因子基因修饰人羊膜间充质干细胞为促进皮瓣成活提供了可能。目的:探索局部应用血管内皮生长因子基因修饰人羊膜间充质干细胞对超长比例随意皮瓣成活的影响。方法:将30只成年SD大鼠随机分为Ⅰ、Ⅱ、Ⅲ组,每组10只,在其背部左右分别构建2 cm×8 cm超长缺血随意皮瓣模型,皮瓣蒂部位于髂棘水平,分别为Ⅰ-left,Ⅰ-right,Ⅱ-left,Ⅱ-right,Ⅲ-left,Ⅲ-right。皮瓣掀起后即刻,Ⅰ-left、Ⅱ-left注射0.5m LLG-DMEM培养基划分为对照组,Ⅰ-right、Ⅲ-left注射0.5m L细胞浓度为1×10~9 L^(-1)的人羊膜间充质干细胞悬液划分为实验组1,Ⅱ-right、Ⅲ-right注射0.5 mL细胞浓度为1×109L-1转染血管内皮生长因子基因的人羊膜间充质干细胞悬液划分为实验组2,每个皮瓣共注射5点,每点注射0.1m L。移植后即刻、24,48h以及4,7d,激光多普勒血流监测仪监测皮瓣中部和蒂部的血流灌注值,移植后7d观察各组皮瓣的成活率,取成活皮瓣组织通过组织学观察各组皮瓣毛细血管密度,荧光显微镜观察人羊膜间充质干细胞在皮瓣内的分布及存活状况,Westernblot检测皮瓣组织中血管内皮生长因子蛋白水平。结果与结论:①实验组2皮瓣成活率、血流灌注值、皮瓣毛细血管密度明显高于实验组1及对照组,实验组1皮瓣成活率、血流灌注值、皮瓣毛细血管密度明显高于对照组,差异有显著性意义(P <0.05);②在荧光显微镜下观察发现,实验组1、实验组2皮瓣组织内有CM-Dil标记的人羊膜间充质干细胞;③各组皮瓣组织血管内皮生长因子蛋白表达均呈阳性,实验组2皮瓣组织血管内皮生长因子蛋白表达明显高于实验组1及对照组,实验组1皮瓣组织血管内皮生长因子蛋白表达明显高于对照组,差异有显著性意义(P <0.05);④结果证实,在超长随意皮瓣中、远部位应用人羊膜间充质干细胞可明显改善皮瓣成活率;人羊膜间充质干细胞经血管内皮生长因子基因转染后能够分泌更多的血管内皮生长因子蛋白,进而促进超长随意皮瓣血管新生,提高皮瓣成活率。

聚合物及聚合物/表面活性剂二元复合驱油体系在超长岩心中运移规律

为了获得聚合物及聚合物/表面活性剂二元复合驱油体系在油层中真实的运移规律,采用J油田油砂建立15 m超长岩心物理驱油实验模型,利用现场在用聚合物3640(丙烯酰胺、丙烯酸共聚物,相对分子质量2000万,水解度20%,浓度1200 mg/L)和表面活性剂HDS(由α-烯烃磺酸盐与APG等表面活性剂按比例复配而成,浓度2000 mg/L)配制二元复合驱体系和聚合物体系,在油藏温度57℃条件下研究了二元复合体系和聚合物驱油体系的运移情况。研究结果表明:两种体系中聚合物浓度和黏度均随着运移距离的增大而降低,聚合物溶液的黏度损失程度比浓度更严重。二元复合驱与聚合物驱相比注入压力低,采收率提高4.94%,较低的界面张力(10^(-2)m N/m数量级)仅可维持约1/2井距的距离,最终界面张力值与聚合物溶液相近。二元复合体系与原油在岩心内可形成稳定的乳状液,随着运移距离增大,表面活性剂的吸附损失会导致乳状液发生破乳、聚并。

Secondary settlement estimation in surcharge preload subject to time effect of secondary consolidation coefficient

In order to eliminate the settlement underestimation in surcharge preload engineering, a study based on Bjerrum's creep diagram and the tangent slope definition of secondary consolidation coefficient was carried out to analyze the time effect of secondary consolidation coefficient of over consolidated soil, and a time–growth model for it was formulated. As Bjerrum's creep diagram is an idealized model, oedometer tests were performed to improve the above time–growth model of secondary consolidation coefficient for the purpose of achieving a better agreement with the actual ground situations. It is found that secondary consolidation coefficient of over consolidated soil not only decreases with the ratio of historical maximum to current effective stress of soil(OCR), but also increases with the development time of secondary consolidation. No matter how large OCR is, the long-term time effect of secondary consolidation coefficient of over consolidated soil is all significant. Based on the above results, a model for settlement estimation was formulated and a case study to estimate it indicates that the settlement estimated by our method is 2–5 times larger than that estimated by the previous method. Moreover, the larger the OCR is as well as the longer the service life is, the larger the difference between our method and the previous method is. Thus, the post-construction secondary settlement in surcharge preload engineering will be underestimated when neglecting the time effect of secondary consolidation coefficient in over consolidated state.

超长(n,n)型碳纳米管的密度泛函理论研究

用密度泛函B3LYP/3-21G(d)方法,并利用周期边界条件,研究了n=2—20不同管径的超长(n,n)型单壁碳纳米管的结构、能量、能带结构和能隙.结果表明,管径和能量(或生成焓)都随n有很好的变化规律,并可拟合成很好的解析函数.当n为2和3时,碳纳米管的能隙分别为1.836eV和0.228eV,呈半导体特征,且具有间接带隙;当n=4—20时,能隙介于0.027eV和0.079eV之间,呈较强的金属性,且具有直接带隙.