含噁二唑杂环取代的新型三唑并嘧啶衍生物的合成及其生物活性

2-肼羰基亚甲硫基-5,7-二甲基-1,2,4-三唑并[1,5-a]嘧啶与二硫化碳在乙醇溶液中回流制得化合物2-(5-巯基-1,3,4-噁二唑-2-亚甲硫基)-5,7-二甲基-1,2,4-三唑并[1,5-a]嘧啶, 后者在碱性环境中与卤化苄反应得到17种新型双杂环化合物. 对所得化合物结构均经元素分析, ¹H NMR和MS确认. 初步生物活性测试表明这些化合物具有一定的杀菌活性.     

慎用二次方程根的判别式

在求直线和圆锥曲线的交点时,二次方程根的判别式有着十分重要的作用.根据判别式△的符号,我们可以判定直线和圆锥曲线交点的个数,进而可以判定直线和二次曲线的位置     

SiO_3~(2-)存在下ARS-Cr(Ⅲ)显色体系测定Cr(Ⅲ)

关于铬的光度法测定,文献[1,2]报道了茜素红S(ARS)光度法直接测定铬,ARS-Cr(Ⅲ)配合物显色速度很慢,灵敏度较低(ε=4.2×10~4),且其它离子干扰严重。研究发现,SiO_3~(2-)对茜素红S-Cr(Ⅲ)显色体系具有明显的催化增敏作用,从而提高了灵敏度,选择性亦大大提高。摩尔吸光系数ε=7.4×10~6,线性范围0～4.5μg/25ml,应用于合成含铬水样测定和天然水样分析,结果令人满意。     

新型光标记试剂的合成及其光化学性质研究

光亲和标记(Photoaffinity Labeling)已被生物化学和分子生物学广泛用于研究生物体系的空间邻近组分[1],它为分子空间邻近结构提供了最直接的证据.光标记试剂是一种生物配体,在光照射下它所产生的高活性中间体可共价结合在受体蛋白的结合点上.     

广义变分不等式与极大极小定理

本文讨论映Hausdorff拓扑线性空间到Riesz空间[6]的算子变分问题.给出半序空间上变分不等式的绝对形式和相对形式.     

弛豫过程对能级AC Zeeman(Stark)移动的影响

以衰减的Bloch方程理论为基础计算了二能级原子能级ACZeeman(Stark)移动,结果表明纵向和横向弛豫过程均会对原子能级移动产生影响,随纵向和横向弛豫率的增加,能级移动呈现出不同的变化趋势。两种弛豫相对强弱的不同也会直接影响能级移动的色散性和饱和性。     

Photodetectors based on junctions of two-dimensional transition metal dichalcogenides

Transition metal dichalcogenides(TMDCs) have gained considerable attention because of their novel properties and great potential applications. The flakes of TMDCs not only have great light absorption from visible to near infrared, but also can be stacked together regardless of lattice mismatch like other two-dimensional(2D) materials. Along with the studies on intrinsic properties of TMDCs, the junctions based on TMDCs become more and more important in applications of photodetection. The junctions have shown many exciting possibilities to fully combine the advantages of TMDCs, other2 D materials, conventional and organic semiconductors together. Early studies have greatly enriched the application of TMDCs in photodetection. In this review, we investigate the efforts in photodetectors based on the junctions of TMDCs and analyze the properties of those photodetectors. Homojunctions based on TMDCs can be made by surface chemical doping,elemental doping and electrostatic gating. Heterojunction formed between TMDCs/2D materials, TMDCs/conventional semiconductors and TMDCs/organic semiconductor also deserve more attentions. We also compare the advantages and disadvantages of different junctions, and then give the prospects for the development of junctions based on TMDCs.     

Electron Momentum Distributions of the Highest Occupied Molecular Orbital of CF3Br： Delocalization of Halogen Lone-Pair Orbitals

The highest occupied molecular orbital (HOMO) of trifluorobromomethane (CF3Br) is studied by binary (e,2e)electron momentum spectroscopy. The experimental momentum profile of the HOMO is compared with the Hartree-Fock (HF) and density functional theory (DFT-B3LYP) calculations. The calculated results largely depend on the size of basis sets rather than theoretical methods. Both the HF and DFT calculations using the 6-311 G^** basis set give a good explanation to the experiment. Delocalization of halogen lone-pair orbitals in the series molecules CF3X (X=F, Cl, Br) has been investigated.     

交流电桥采用光隔离放大信号源的设计

交流电桥广泛应用于电子工业、电气工程及非电量的电学测量中,但交流电桥应用时平衡指零仪与交流电桥的电源都要求接地,它们都各具地线而不能直接连通.利用光电池和发光二极管可以有效地解决交流电桥应用过程中的接地问题.本文给出了一种利用光电池解决交流电桥接地问题的设计方案.