Hairpin Probe for Sequence-specific Recognition of Double-stranded DNA on Simian Virus 40

Simian virus 40(SV40) is a polyomavirus and can induce a series of different tumors. The recognition of SV40 genome is crucial to tumor diagnosis and gene therapy. Herein, a sensitive and selective colorimetric method for sequence-specific recognition of homopyrimidine·homopurine duplex DNA(dsDNA) of SV40(4424—4440, gp6) was established with a hairpin probe based upon the formation of triplex DNA. Hairpin probe 5'-CCC TAC CCA TTT TTT CTT CTC TTT CCT GGG TAG GGC GGG TTG GG-3'(HP) containing G-rich sequence and 17-bp triplex-forming sequence was used as the signal probe, which was stem-loop structure alone and exhibited low catalytic activity. Upon its binding to the target duplex of SV40, hairpin probe transferred from stem-loop structure to parallel triplex DNA, accompanied by the recovery of catalytic activity of DNAzyme and a sharp increase of absorbance. Under optimum conditions, the absorbance was increased proportionally to the concentration of dsDNA over the range from 500 pmol/L to 40.0 nmol/L with a detection limit of 433 pmol/L. Moreover, satisfied results were obtained when the assay was used to recognize the mismatched sequences.     

熔体变质对超高重力场燃烧合成TiC-TiB2组织均匀性的影响

通过在(Ti+ B4C)反应体系中相应增加(CrO3+ Al)高能铝热剂添加量,使燃烧体系绝热温度依次达到3000℃、3200℃、3400℃、3600℃与3800℃,进行加速度2000 g的超高重力场燃烧合成实验,制备出系列TiC-TiB2复合陶瓷,探讨高能铝热剂的引入对陶瓷显微组织、凝固行为与力学性能的影响.经XRD、FESEM与EDS测试,发现陶瓷显微组织均由TiB2基体相、不规则TiC第二相、少量的Cr基合金相及Al2O3夹杂物构成,增加高能铝热剂的引入量,通过提高反应熔体温度并增加金属液相,对陶瓷合成过程进行耦合控制,不仅急剧降低Al2O3夹杂含量与尺寸,而且明显细化陶瓷组织、改善其均质性,进而当绝热温度超过3600℃,出现TiB2片晶平均尺寸1μm的超细晶组织,使陶瓷致密性、抗弯强度与断裂韧性均显著提升.     

TiO2/SiO2双层减反射膜的制备及其性能研究

采用真空电子束蒸发法制备TiO2/SiO2双层减反射膜,实现宽波段范围内的低反射率,以满足砷化镓三结太阳电池对入射光的需求.主要研究了基片温度、电子束流和充氧量对TiO2、SiO2单层膜性能(膜层厚度、折射率)的影响.研究过程中,按照三因素两水平的正交实验进行,用分光光度计对TiO2、SiO2薄膜样品的折射率进行测试.实验结果显示,两种氧化物介质膜的折射率均随基片温度和束流的升高而增加,随氧压的升高而降低,工艺参数对TiO2膜性能影响较大.     

航空遥感三轴惯性稳定平台双速度环控制

航空遥感三轴惯性稳定平台用于稳定成像载荷,获取高分辨率的遥感数据。针对惯性稳定平台视轴稳定控制中单速度环对干扰力矩抑制的不足,提出采用以编码器进行数字测速构成速度内环、利用速率陀螺构成速度外环的双速度环复合控制方案,将稳定回路抗内部干扰功能和隔离外界干扰功能分开设计实现,以提高系统稳定精度。分别对单速度环和双速度环对扰动的抑制能力进行了理论分析和对比,并在理论分析基础上,对单速度环和双速度环的扰动抑制能力进行了Matlab仿真分析和实验验证。结果表明：与单速度环相比,双速度环可明显减小质量偏心、摩擦等主要内部干扰以及外部基座低频扰动造成的稳态误差,静基座摇摆伺服稳定角速度RMS值减小了52.3%,静基座调平姿态精度RMS值减小了22.1%,动基座调平姿态精度RMS值减小了37.4%。     

基于自反应淬熄法制备空心复相陶瓷微珠吸波剂的凝固组织分析

本文以Al-TiO2-Fe-MnO2-Fe2O3-蔗糖和O2为反应体系与送粉气,利用自反应淬熄法合成了空心复相陶瓷微珠.借助SEM、EDS与XRD等现代分析测试方法,对微珠的凝固过程进行了表征与分析.结果表明,高热的空心陶瓷熔滴进入冷却介质(蒸馏水)后,发生快速淬熄转变,发生表面枝晶长大及纳米条状晶形成,内部柱状晶形成,内部纳米等轴晶粒形成等现象形成空心复相陶瓷微珠,同时共晶组织的形成伴随凝固全过程.微珠由Al2O3与呈尖晶石结构的Fe3O4、Mn3O4、(Fe2.5Ti0.5)O4、Mn2AlO4组成,其中呈尖晶石结构的后四种成分形成固溶体,并与Al2O3形成共晶组织.超大过冷度条件可能是产生以上组织的主要原因.     

温度对Al2O3-C材料中β-Sialon晶须形成的影响研究

本文研究了温度对Al3O3-C耐火材料中β-Si3Al3O3N5晶须形成的影响规律.研究发现:在弱还原性气氛下,Al2O3-Si-Al-C稳定存在的非氧化物物相为Al4C3 、AlN、SiC和p-Sialon相.其中,催化作用下,Al2O3-C耐火材料中的金属Al在1000℃时转化为AlN,金属Si在1200℃时转化成SiC,在1400℃时有β-Sialon相生成;而无催化剂存在时,生成的物相仅为SiC和AlN相.催化作用下,AlN形貌呈短柱状;SiC呈晶须状,直径为亚微米级,且晶须有液点存在;β-Sialon相呈纳米晶须状.SiC和β-Sialon晶须的生长都符合气-液-固机理.     

高岭土成型体水热转化无粘结剂4A分子筛研究

以煤系高岭土与碳质造孔剂、凹凸棒石增强剂加水混匀成型,经高温焙烧活化,水热反应转化4A分子筛,重点探讨了成型体的活化制度及造孔剂的作用机制.结果表明,造孔剂过量会使成型体的强度降低,欠量则不能形成丰富的前驱孔通道,无法保证晶化液进入体内充分反应;成型体的煅烧温度过低和/或时间过短,高岭石及造孔剂得不到充分分解,而温度过高和/或时间过长,会使偏高岭土的活性降低,且使前驱孔通道塌陷,皆影响分子筛的转化.高岭土与11;造孔剂和3;增强剂加水混匀并滚制成φ3mm的小球,在750℃锻烧3h,形成多孔活化体,再经水热转化可形成结晶良好、晶体互联交织生长的4A分子筛聚集体,宏观上保持原有的球形未变,其抗压碎力达115 N/颗,静态水吸附率达23.75;.     

离子液体辅助超声法合成Zn1-xCdxS纳米粒子及光催化性能研究

以硝酸锌,氯化镉和硫代乙酰胺为原料,以离子液体的水溶液为溶剂,用超声法成功合成了Zn1-xCdxS(x=0～1)纳米粒子.用XRD,SEM,以及UV-Vis等手段对所制备样品的晶型、形貌和光学特性进行了表征;以紫外光为光源、罗丹明B为目标降解物质评价了Zn1-xCdxS纳米粒子的光催化活性.结果表明,通过调整Zn和Cd的配比可获得不同粒径的Zn1-xCdxS纳米粒子,随着x值的增大纳米粒子的吸收带边发生红移,光催化降解罗丹明B的能力变强,Zn0.25Cd0.75S拥有最高的光催化性能.对比实验表明,离子液体和超声的协同作用可获得较小粒径的纳米粒子和较强的光催化活性,这可能源于离子液体在初生纳米粒子上的吸附和超声作用下的快速成核作用.     

Molecular Dynamic Studies on Langmuir Monolayers of Stearic Acid

Compression isotherm for stearic acid was obtained by means of molecular dynamic simulation and compared to experimentally measured values for the Langmuir monolayers. Compared to the previous simulation, the present simulation has provided a method to reproduce the compression of the monolayer. The result is consistent with other experimental results. By analyzing the alkyl tails, the configuration of stearic acid molecules during the compression process was studied and a uniform monolayer was obtained after compression. Stearic acid molecules were observed to form fine organized monolayer from completely random structure. Hexatic order of the arrangement has been identified for the distribution of stearic acid molecules in the monolayer. At the end of the compression, the stearic acid molecules were tightly packed in the gap of two other molecules. At last, the hydrogen bonds in the system were analyzed. The main hydrogen bonds were from stearic acid-water interaction and their intensities constantly decreased with the decreased of surface area per molecule. The weak hydrogen bond interaction between stearic acid molecules may be the reason of easy collapse.     

Effects of Combinatorial Expression of selA,selB and selC Genes on the Efficiency of Selenocysteine Incorporation in Escherichia coli

In Escherichia coli, four gene products(selA, selB, selC and selD) and a selenocysteine(Sec) insertion sequence(SECIS) are required for the correct translation of UGA codons encoding Sec. Previous studies have shown that the stoichiometry of selenoproteine mRNA and elongation factor SelB affect the efficiency of Sec incorporation. Herein lies a detailed analysis of the effects of co-expressing selA, selB and selC genes under inducible promoters on the incorporation efficiency of Sec. Over-expression of either selA or selB reduced the efficiency of Sec incorporation by 61.1% or 11.6%, respectively, compared to the over-expression of the reporter vector alone did. Concomitant over-expression of selC with selA or selB completely reversed the reduce of the efficiency of Sec but still reduced the efficiency of the incorporation relative to that observed for expression of selC alone. Over-expression of selC gene alone under L-arabinose induction reduced the efficiency of the incorporation relative to that observed for co-expressing selC with selA and selB under the control of its endogenous promoter in the absence of L-arabinose. Co-expression of selA, selB and selC with selA or selB under the control of inducible promoters increased the efficiency of Sec incorporation by 69.7%. Moreover, inducing selenoprotein-related gene expression during the late exponential phase increased the efficiency of Sec incorporation by a factor of 5.4 relative to that observed for the reporter vector alone. These results suggest that the co-expression of selA, selB and selC in Escherichia coli under the control of inducible promoters is a viable and promising strategy for increasing the yields of selenoproteins.