Ba1-xSrxTiO3（BST）powders were fabricated by sol-gel process by using strontium carbonate for the substitution of strontium acetate.Barium acetate,strontium carbonate and titanium-tetrabutoxide were used as raw mater...Ba1-xSrxTiO3（BST）powders were fabricated by sol-gel process by using strontium carbonate for the substitution of strontium acetate.Barium acetate,strontium carbonate and titanium-tetrabutoxide were used as raw materials.The BST gel was studied by thermal analysis techniques,the physical structure of the BST powders was measured by XRD and the grain size was measured.The results showed that the powders possess a single perovskite phase after 700℃ and the ideal powder size even after 800℃ calcining.This indicated that the powder can be used for BST ceramics and the fabrication of the sol-gel derived BST can be carried out well by using carbonate as the starting materials.展开更多
文摘Bst DNA聚合酶具有热稳定性、链置换活性及聚合酶活性,在体外DNA等温扩增反应中起重要作用.本文利用Bst DNA聚合酶的5'→3'聚合酶、核苷酸(末端)转移酶及链置换酶活性发展了一种新的体外环式DNA扩增技术跨越式滚环等温扩增(saltatory rolling circle amplification,SRCA).在SRCA反应中,Bst DNA聚合酶以上游引物P1为模板合成其互补链RcP1,并和P1形成双链DNA;之后,Bst DNA聚合酶用其核苷酸转移酶活性在其P1的3'末端沿5'→3'方向随机掺入脱氧核糖核苷酸聚合形成寡聚核苷酸(dNMP)m序列,即DNA的合成反应跨越了RcP1与下游引物P2之间的缺口;然后,以下游引物P2为模板形成互补序列(RcP2);接着,Bst DNA聚合酶继续将脱氧核糖核苷酸随机添加到RcP2的3'末端,形成(dNMP)n序列.继而,Bst DNA聚合酶以RcP1为模板,继续催化聚合反应合成互补新链,并通过其链置换酶活性替换P1;如此往复,形成[P1-(dNMP)m-RcP2-(dNMP)n-…]序列.本文通过电泳、酶切、测序等方法对扩增产物进行分析,演绎出上述扩增过程,并就工作原理进行了讨论.该反应可能对开发等温扩增技术检测微生物有一定助益,也为解释环介导等温扩增技术中假阳性反应和滚环等温扩增反应中的背景信号提供了线索.
文摘Ba1-xSrxTiO3（BST）powders were fabricated by sol-gel process by using strontium carbonate for the substitution of strontium acetate.Barium acetate,strontium carbonate and titanium-tetrabutoxide were used as raw materials.The BST gel was studied by thermal analysis techniques,the physical structure of the BST powders was measured by XRD and the grain size was measured.The results showed that the powders possess a single perovskite phase after 700℃ and the ideal powder size even after 800℃ calcining.This indicated that the powder can be used for BST ceramics and the fabrication of the sol-gel derived BST can be carried out well by using carbonate as the starting materials.
