纳米Ag/TiO_(2)纳米管阵列基底构建及表面增强拉曼散射光谱检测与降解盐酸四环素北大核心CSCD

将阳极氧化与光还原法结合,在TiO_(2)纳米管阵列(TiO_(2)NTAs)表面修饰Ag纳米粒子,获得一种均匀有序、稳定性高且可循环的TiO_(2)NTAs/Ag活性基底。采用X射线粉末衍射(XRD)、X射线光电子能谱(XPS)、紫外可见漫反射光谱(UV-Vis DRS)、表面增强拉曼散射光谱(SERS)和扫描电子显微镜(SEM)等手段对TiO_(2)NTAs/Ag的组成和结构进行了表征。进一步研究了该TiO_(2)-NTAs/Ag阵列对盐酸四环素(TC-HCl)的SERS响应,结果表明,该复合基底对TC-HCl具有较高的检测灵敏度,在水中检测限可达1×10^(−14) mol/L,而TiO_(2)-NTAs与Ag之间的协同效应对其检测性能的提高起着关键作用。此外,TiO_(2)NTAs/Ag基底在光照下对TC-HCl展示了优异的降解活性,且至少可循环使用8次。表明该TiO_(2)NTAs/Ag基底在环境中有机污染物的SERS检测和降解领域具有潜在的应用前景。     

Thermoelastic stress analysis of multilayered films in a micro-thermoelectric cooling device

This paper presents an analytical solution for the thermoelastic stress in a typical in-plane’s thin-film micro-thermoelectric cooling device under different operating conditions. The distributions of the permissible temperature fields in multilayered thin-films are analytically obtained, and the characteristics, including maximum temperature difference and maximum refrigerating output of the thermoelectric device, are discussed for two operating conditions. Analytical expressions of the thermoelastic stresses in the layered thermoelectric thin-films induced by the temperature difference are formulated based on the theory of multilayer system. The results demonstrate that, the geometric dimension is a significant factor which remarkably affects the thermoelastic stresses. The stress distributions in layers of semiconductor thermoelements, insulating and supporting membrane show distinctly different features. The present work may profitably guide the optimization design of high-efficiency micro-thermoelectric cooling devices.     

三种基于2，4，6-三(3-吡啶基)-1，3，5-苯配体的Ni(Ⅱ)基配位聚合物的合成、结构及催化性能

通过调变溶剂热的反应条件,我们合成了3种Ni (Ⅱ)基的配位聚合物(CPs)[Ni (CH₃-BDC)(3-TBT)(H₂O)₂]·EtOH·2H₂O (CP1)、[Ni₃(CH₃-BDC)₃(3-TBT)₂(H₂O)₅]·2DMF·2H₂O (CP2)和[Ni₃(CH₃-BDC)₃(3-TBT)₂(H₂O)₆]·2DMF·4H₂O (CP3),其中CH₃-H₂BDC=5-methylisophthalic acid,3-TBT=2,4,6-tris (3-pyridyl)-1,3,5-benzene。X射线单晶衍射分析表明,3个CPs都是由相似的Ni₂(CH₃-BDC)₂的双核单元构建的,并分别呈现出从零维(0D)、2D到3D结构的网络骨架。反应条件的微小调变,导致了不同结构的配位聚合物。同时,催化实验表明,3在无溶剂的温和反应条件下,CP3对苄醇及其衍生物与苯胺的氧化-偶联反应表现出极好的催化活性和循环稳定性。     

语音信号序列的Volterra预测模型

对给定的英语音素、单词和语句进行了采集并完成预处理. 分别应用互信息法和Cao 氏法确定了实际采集的语音信号序列的延迟时间和嵌入维数, 以完成语音序列的相空间重构. 通过计算实际采集的语音信号序列的最大Lyapunov指数, 完成了语音信号的混沌特性识别, 判定其具有混沌特性. 引入Volterra级数, 提出了一种具有显式结构的语音信号非线性预测模型. 为克服最小均方误差算法在Volterra模型系数更新时固有的缺点, 在最小二乘法基础上, 应用基于后验误差假设的可变收敛因子技术, 构建了一种基于Davidon-Fletcher-Powell算法的二阶Volterra 模型(DFPSOVF), 并将其应用于具有混沌特性的语音信号序列预测. 仿真结果表明: DFPSOVF非线性预测模型对于单帧和多帧语音信号均具有更好的预测精度, 优于线性预测模型, 并且能够很好地反映语音序列变化的趋势和规律, 完全可以满足语音预测的要求; 可以根据语音信号序列的嵌入维数选取预测模型的记忆长度. 所提出模型可以为语音信号重构和压缩编码开辟一条新途径, 以改善语音信号处理方法的复杂度和处理效果.     

Genotyping of two single nucleotide polymorphisms in 5,10-methylenetetrahydrofolate reductase by multiplex polymerase chain reaction and capillary electrophoresis

Two single nucleotide polymorphisms (SNPs) of 5,10-methylenetetrahydrofolate reductase (MTHFR) gene, A1298C and C677T, were widely considered to be related with various neoplasia disorders. We established a simple and effective capillary electrophoresis (CE) method for detection of two SNPs in MTHFR gene simultaneously. DNA samples were amplified by multiplex PCR with universal fluorescence-labeled primer and analyzed by single-strand conformation polymorphism (SSCP)-CE method. The CE method was performed using 1.5% hydroxyethyl cellulose in 1× TBE buffer containing 1 M urea. The PCR products after SSCP procedure were electrokinetically injected at −10 kV, 30 s. Separation voltage was −6 kV and the temperature was set at 20 °C. The optimal SSCP-CE method was applied to detect two polymorphisms in MTHFR gene of acute lymphoblastic leukemia (ALL) and attention-deficit/hyperactivity disorder (ADHD) patients. Genotyping results were evaluated in terms of relationships between outcomes for ADHD patients after ALL chemotherapy and ALL disease. The SSCP-CE method and multiplex PCR with universal fluorescence primer were used as the fast technique for screening two SNPs in MTHFR gene, A1298C and C677T. The genotyping data were coincident with DNA sequencing. This SSCP-CE method was found feasible for detecting mutation of MTHFR gene in populations.     

Multicomponent Reaction for Synthesis of 2-(Indol-3-yl)pyridine Derivatives Under Microwave Irradiation

A short, practical, and efficient preparation of 2-(indol-3-yl)pyridine derivatives via a one-pot procedure of 3-cyanoacetylindole, chalcones, and ammonium acetate under microwave irradiation was described. All these compounds were obtained in good yield, and their structures were confirmed by ¹H NMR, infrared, and elementary analysis.      

Maximum entropy approach to the coupled quadrupole system

The spectral functions of the spin pair correlation functions in a coupled quadrupole system are evaluated using the maximum entropy formalism starting from the exact derivation of the frequency moments to fourth order at the high temperature limit. The numerical computations are carried out for different wave vectors and ratios of the anisotropic field to the quadrupolar interaction. The effects of these parameters on the spectral function are discussed.     

炔丙型硫Ylide环丙烷化反应及其立体选择性

炔丙型硫Ylide与丙烯酸酯的反应是一个多反应竞争的复杂反应, 通常环丙烷化产物收率很低. 本文通过对反应底物的优化, 成功获得了高收率、高选择性的反式环丙烷化产物. 同时利用Gaussian 03程序, 选择密度泛函BHHLYP方法, 6-31G**基组对反应路径及过渡态模型进行了计算, 进而采用密度泛函理论中的B3LYP方法, 选择6-31G**基组, 对顺、反式产物的热稳定性进行了分析, 明确了该反应的高非对映选择性是由过渡态的能量差异和产物的热稳定性两个因素共同决定的, 而过渡态的能量差异可以归于分子内弱的立体电子效应的不同.     

Synthesis and characterization of organometallic rhenium(І) and technetium(І) bile acid complexes

Eight bile acid derivatives have been synthesized with alkyl chains of various length based tridentate ligand chelating system. These derivatives have been reacted with the precursor [Et₄N]₂[Re(CO)₃Br₃] and fac-[M(CO)₃(H₂O)₃]⁺ (M = ^99mTc, Re) in ethanol or ethanol–aqueous media to form water-soluble and stable organometallic complexes in good yields. ¹H NMR, ¹³C NMR, IR and elemental analysis or HRMS spectroscopic analyses confirmed the tridentate complexation of the metal–tricarbonyl fragment exclusively via the tridentate chelates. In addition, the corresponding radioactive technetium-99m complexes were prepared successfully and challenged for stability in physiological phosphate buffer at 37 °C for 24 h. No decomposition of the complexes could be detected under the condition proving the stability of these complexes.