6-氯-8-烃基-9-芳基嘌呤类衍生物的合成

以4,6-二氯-5-氨基嘧啶为原料,经N-烃基化反应、缩合反应和氯化反应,合成了一系列未见文献报道的6-氯-8-烃基-9-芳基嘌呤衍生物,所有化合物均通过1H NMR、MS和元素分析确定其结构。 研究结果表明,N-烃基化反应时,芳胺使用盐酸作催化剂,芳基脂肪胺用有机碱三乙胺作催化剂,缩合反应时,多聚磷酸(PPA)用量过多会影响传质效果,影响反应的收率。 讨论了微波反应方式对氯化反应的影响。     

移动窗口二维相关光谱技术

移动窗口二维相关光谱是一种新的二维相关分析方法,它将移动窗口的概念和二维相关分析方法有效地结合在了一起,利用移动窗口将庞大的光谱数据按矩阵分割成若干个便于操作的子矩阵,用二维相关光谱分别处理,将得到的结果综合分析,用以光谱变量和扰动变量为坐标的等高图表现出来,从中可以非常直观地观察出光谱强度在扰动变量方向上的变化,进而找出引起光谱强度突变的特征扰动点。本文主要介绍了移动窗口二维相关光谱的计算方法、基本特征、影响因素和实际应用,同时还详细介绍了以它为基础改进得到的扰动相关移动窗口二维相关光谱。扰动相关移动窗口二维相关光谱包括同步图和异步图,它不仅能很好地反映出引起光谱强度突变的特征扰动,还能详尽地描述出光谱强度在扰动过程中的变化情况。     

溶胶-凝胶法制备Ca0.4Sr0.6Bi4Ti4O15细晶陶瓷

采用凝胶预碳化处理工艺制备了颗粒粒径较小,无硬团聚的Ca0.4Sr0.6Bi4Ti4O15纳米粉体,以Ca0.4Sr0.6Bi4Ti4O15非晶团簇粉体为陶瓷素坯的原料,同组分高浓度的Ca0.4Sr0.6Bi4Ti4O15溶胶为粘结剂,制备了Ca0.4Sr0.6Bi4Ti4O15细晶陶瓷,研究了Ca0.4Sr0.6Bi4Ti4O15粉体的相结构和微观形貌以及陶瓷的显微结构和铁电性能.实验结果表明:700 ℃焙烧粉体呈现为非晶团簇,800 ℃焙烧粉体形成了纯层状钙钛矿结构,粒径在100～150 nm之间,无硬团聚;950 ℃烧结的Ca0.4Sr0.6Bi4Ti4O15细晶陶瓷结构致密,晶粒尺寸在0.2～0.5 μm之间,其铁电性能优良,剩余极化Pr=12.5 μC/cm2,矫顽场强Ec=50 kV/cm.     

~6Li原子跃迁频率和超精细分裂的精密测量

本文实现了可用于锂原子频率精密测量的冷原子系统,获得了大数目的原子样品;利用西西弗斯冷却和速度选择相干布居俘获实现了~6Li的冷原子的灰色黏胶冷却,原子的温度被冷却到多普勒冷却极限以下,达到50μK;利用光学频率梳,实验上测量了D1线的跃迁频率和超精细分裂,测量结果和理论计算相接近,可以和目前最精确的测量相比较.这些测量为进一步的轻质量原子频率的精密测量、α常数以及核半径的精确标定打下了基础.     

Experimental study of the dependences of retrieval efficiencies on time delay between magneto-optical-trap being turned off and optical storage

We report an experimental study of electromagnetically induced transparency(EIT)-based light storage in a cloud of cold atoms loaded into a magneto-optical-trap(MOT). After the MOT is turned off, the retrieval efficiencies of rightand left-circularly polarized signal light fields each as a function of storage time are measured for different time delays between MOT off and the storage event, respectively. The results show that in the delay ranging from 0.015 ms to 3.5 ms,the retrieval efficiency for a zero-storage time(0.2 μs) and the storage lifetime can exceed 15% and 1.4 ms, respectively.The measured results will provide important help for optimizing the storage of the polarized entanglement photons in cold atomic ensembles.     

First-principles study of the elastic and thermodynamic properties of thorium hydrides at high pressure

The high pressure behaviors of Th_4H_(15) and ThH_2 are investigated by using the first-principles calculations based on the density functional theory(DFT). From the energy–volume relations, the bct phase of ThH_2 is more stable than the fcc phase at ambient conditions. At high pressure, the bct ThH_2 and bcc Th_4H(15) phases are more brittle than they are at ambient pressure from the calculated elastic constants and the Poisson ratio. The thermodynamic stability of the bct phase ThH_2 is determined from the calculated phonon dispersion. In the pressure domain of interest, the phonon dispersions of bcc Th_4H(15) and bct ThH_2 are positive, indicating the dynamical stability of these two phases, while the fcc ThH_2 is unstable. The thermodynamic properties including the lattice vibration energy, entropy, and specific heat are predicted for these stable phases. The vibrational free energy decreases with the increase of the temperature, and the entropy and the heat capacity are proportional to the temperature and inversely proportional to the pressure. As the pressure increases, the resistance to the external pressure is strengthened for Th_4H_(15) and ThH_2.     

High temperature characteristics of bilayer epitaxial graphene field-effect transistors on SiC Substrate

In this paper,high temperature direct current(DC) performance of bilayer epitaxial graphene device on SiC substrate is studied in a temperature range from 25℃ to 200℃.At a gate voltage of-8 V(far from Dirac point),the drainsource current decreases obviously with increasing temperature,but it has little change at a gate bias of +8 V(near Dirac point).The competing interactions between scattering and thermal activation are responsible for the different reduction tendencies.Four different kinds of scatterings are taken into account to qualitatively analyze the carrier mobility under different temperatures.The devices exhibit almost unchanged DC performances after high temperature measurements at 200℃ for 5 hours in air ambience,demonstrating the high thermal stabilities of the bilayer epitaxial graphene devices.     

毛秔子梢中天然高活性的神经氨酸酶抑制成分的研究

从天然产物中筛选高效低毒的神经氨酸酶抑制剂(NAI), 以期发现可抗流感病毒(H1N1)的化合物. 方法: 采用经典的NA活性检测实验(FL-MH-NANA method), 对从豆科植物毛秔子梢中分离得到10个化合物进行筛选, 检测这些化合物对NA的抑制活性. 结论: 化合物1, 2, 3, 5对流感病毒株的神经氨酸酶(NA)均具有抑制作用, 其中化合物1的抑制活性最强, 其IC₅₀值为16.76 μmol/L. 化合物1～4为新化合物, 化合物5～10为该植物中首次分得.     

2,5-二氯苯甲酸与5,5′-二甲基-2,2′-联吡啶稀土钬配合物的晶体结构、热分解反应动力学及热力学

本文通过常规溶剂挥发法,合成了钬的三元配合物:[Ho(2,5-DClBA)_3(5,5′-DM-2,2′-bipy)]2(2,5-DClBA=2,5-二氯苯甲酸根; 5,5′-DM-2,2′-bipy=5,5′-二甲基-2,2′-联吡啶).通过EDTA络合滴定分析、元素分析、红外光谱以及X射线粉末衍射等手段对配合物进行了表征,利用X射线单晶衍射仪测定了钬配合物的单晶结构.晶体结构分析表明,该晶体是一个双核分子,属于三斜晶系, Pī空间群.每个双核分子包含两个Ho(Ⅲ)离子、6个2,5-二氯苯甲酸根配体和两个5,5′-二甲基-2,2′-联吡啶配体.相邻的双核单元通过C–H···Cl氢键以及Cl-π作用组装成一维和二维超分子结构.利用TG-DTG/FTIR技术研究了钬配合物的热分解机理.用非线性等转化率法得到钬配合物第二步分解反应的活化能E随转化率a的变化关系,结果表明该步是一个简单反应,因此,进一步采用改进的双等双步法来确定钬配合物第二步分解反应的机理函数.通过计算得到了钬配合物的动力学参数(活化能E和指前因子A)和热力学参数(ΔH~≠、ΔG~≠和ΔS~≠).利用差示扫描量热(DSC)技术对钬配合物的摩尔热容值进行了测定.将所得的平均摩尔热容值与折合温度利用最小二乘法进行拟合得到了多项式方程.将多项式方程结合热力学方程进行计算得到了配合物的舒平摩尔热容值以及焓变、熵变等热力学函数值.     

Fibre Optical Parametric Amplification in Defect Bragg Fibres with Zero Dispersion Slow Light Effect

Nonlinearity enhancement by slow light effect and strong light confinement in defect Bragg fibres is demonstrated and anMysed in applications of fibre optical parametric amplifiers. Broadband low group velocity and zero dispersion as well as the strong light confinement by band gap enhances the nonlinear coefficient up to more than one order than the conventional high nonlinear fibres. Moreover, the zero dispersion wavelength of coupled core mode can be designed arbitrarily, under which the phase-matching bandwidth of the nonlinear process can be extended.