In vitro reconstitution of homologous recombination reactions

The proteins essential to homologous recombination inE. coli have been purified and their individual activities have been identified, permitting biochemical reconstitution of steps that comprise the cellular recombination process. This review focuses on the biochemical events responsible for the initiation and homologous pairing steps of genetic recombination. The properties of an in vitro recombination reaction that requires the concerted action of recA, recBCD, and SSB proteins and that is stimulated by the recombination hotspot, Chi(), are described. The recBCD enzyme serves as the initiator of this reaction; its DNA helicase activity produces single-stranded DNA that is used by the recA protein to promote homologous pairing and DNA strand invasion of supercoiled (recipient) DNA. The SSB protein acts to trap the single-stranded DNA produced by recBCD enzyme and to facilitate pairing by the recA protein. The regulatory sequence acts incis by attenuating the nuclease, but not the helicase, activity of recBCD enzyme. This attenuation assures the preservation of ssDNA produced by the DNA helicase activity and is responsible for the simulation in vitro and, presumably, in vivo. The attenuation of nuclease activity by results in the loss or functional inactivation of the recD subunit.     

锂分子中紫外扩散带受激辐射

本文首次报道了以６２０．０—６６５．０ｕｍ范围内任一波长激光双光子激发模分子或多光子激发锂原子，获得锂分子紫外扩散带受激辐射．文中对有关的辐射特性及激发机制进行了讨论．     

遗传算法中的重组操作

针对传统遗传算法中交换操作的局限性，提出了一种根据适应度对父染色体重组的操作方法，并以Ｎ一皇后问题和求解自然对数为例验证了该方法的有效性．     

杉木树矿井古构造应力场特征及其研究意义

本文通过大量野外观测,对控制杉木树矿井地质构造的古构造应力场作了较全面的分析和研究。首先指出,本区地质构造是由两个不同方向应力场复合作用的产物;其次,利量大量事实阐明,构造应力场的空间分布具有不均匀性的特点,并对两期应力场的应力大小作了估算;最后利用上述结论对矿井地质构造作了总体预测,为其它矿井开展构造研究提供了方法。     

单核细胞增生李斯特菌ncRNA rli60基因缺失株的构建研究

为了构建单核细胞增生李斯特菌(Listeria monocytogenes,LM)ncRNA rli60基因缺失株,采用基因重叠延伸PCR(SOE-PCR)的方法成功构建具有氯霉素抗性的pKSV7-Δrli60穿梭质粒,然后电转化至LM-SB5感受态细胞中,在温度和氯霉素的双重选择压力下进行同源重组,通过PCR进行重组菌鉴定。结果表明:成功筛选得到遗传性稳定的LM ncRNA rli60基因缺失株,为揭示LM ncRNA rli60基因功能提供了研究材料;同时,为进一步研究其在LM致病性及环境应激中的分子机制奠定了基础。     

Self-heating dependent characteristic of GaN-based light-emitting diodes with and without AlGaInN electron blocking layer

In this study, GaN-based light-emitting diodes （LEDs） with and without A1GaInN electron blocking layer （EBL） under self-heating effect are numerically studied. The energy band diagram, carrier transport and distribution characteristics, internal Joule heat and non-radiative recombination heat characteristics, and internal quantum efficiency are investigated. The effect of Auger recombination coefficient on efficiency droop under self-heating effect is also studied. The simulation results show that efficiency droop is markedly improved when an AlGaInN EBL is placed between p-type GaN layer and active region. However, the chip temperature of LED is significantly increased simultaneously. The results also indicate that Auger recombination can be neglected because it is not the major contributor for the internal heat source. The efficiency droop is unrelated to the internal heat source. However, both electron leakage and Auger recombination play important roles in efficiency droop mechanism under self-heating effect.     

砷化镓光导开关中电流丝的自发辐射效应

应用统计物理方法研究了高增益砷化镓光导开关中电流丝的自发辐射效应.导出了高增益砷化镓光导开关中电流丝的自发辐射规律,在砷化镓样品中引入复合辐射强度与辐射的波长分布函数的概念,近似确定了高增益砷化镓光导开关中电流丝的平均辐射复合系数为(883 nm)≈0.1125,导出了各辐射波长的辐射复合系数与平均辐射复合系数之间的关系,验证了峰值波长为890 nm的光输出能量与实验观察结果吻合,在理论上揭示了电流丝顶部的光生载流子密度的分布规律.结果表明:电流丝的体积面积比值和电流丝内平均载流子密度是影响电流丝辐射效应的两个主要因素,波长876 nm的辐射在紧邻电流丝顶部产生的最大载流子密度具有主导作用,最大光生载流子密度比电流丝内平均载流子密度小1–2个数量级.     

特高含水期水驱油藏井网调整效果研究

摘要：通过对试验区水淹解释数据分析和利用数值模拟方法对试验区的历史拟合,研究了目前试验区开发状况,给出了层系重组方案,在层系重组基础上进行了开发井网调整,并对调整后的开发井网进行了不同开发方案的数值模拟预测。预测结果表明：在注采比为1时,生产到含水98%时的最终采收率为47.85%,阶段采出程度7.22%,调整效果最好,比继续应用目前井网开发的阶段采出程度提高了2.69%。     

ZnO纳米棒的湿化学法制备及其表面复合

采用CBD两步生长法和热蒸发法在Si衬底上生长ZnO纳米棒.研究发现,该方法对于ZnO纳米棒阵列的近带边复合发光有效衰减时间有很大影响.采用CBD方法生长的ZnO纳米棒的衰减曲线存在两个衰减指数,而通过热蒸发法生长的ZnO纳米棒只有一个衰减指数,实验结果显示CBD法生长的ZnO纳米棒其中较快的衰减指数与表面复合发光有关,慢的衰减指数对应体材料的衰减.另外,随着热处理温度从500℃到700℃,其表面复合速率急剧减小.