Synthesis and tumor cytotoxicity of novel amide derivatives of β-hederin

Thirteen novel triterpenoid saponins, designed as amide derivatives of the natural cytotoxic saponin β-hederin, were synthesized by a stepwise glycosylation strategy. The in vitro cytotoxic activity of these compounds was evaluated against five different tumor cell lines. Most of the evaluated compounds showed effective inhibitory activity against at least one tumor cell line at micromolar concentrations. The preliminary structure-activity relationships (SAR) indicate that mide derivatization at C-28 resulted in highly cytotoxic derivatives on specific tumor cell lines, and also resulted in an increase in the antitumor selectivity of β-hederin.     

火焰原子吸收光谱法测定羊血中铁、铜和锌3种微量元素

建立了湿法消解-火焰原子吸收光谱法对羊血中Fe、Cu和Zn 3种微量元素测定的方法.方法的校准曲线线性关系良好（r=0.9965-0.9999）,方法加标回收率（n=5）在96.2％-98.5％之间,RSD值（n=5）在1.3％-4.9％之间.为了解动物微量元素含量提供参考,也为进一步研究畜禽疾病与微量元素的相关性提供基础资料.     

四方和正交以及单斜相K0.5Na0.5NbO3的结构稳定性和电子结构的第一性原理研究

采用基于密度泛函理论框架下的第一性原理超原胞方法和虚晶近似方法, 在局域密度近似和广义梯度近似下, 对四方和正交以及单斜相K_0.5Na_0.5NbO₃的能量和原子结 构以及电子结构进行了系统的研究. 计算结果表明三种K_0.5Na_0.5NbO₃相的能量差别较小, 这与实验上它们之间容易发生相转化是一致的. 进一步发现单斜相的能量比四方相和正交相低, 说明单斜相结构更加稳定, 并且理论计算的结构参数与实验值符合得很好. 电子结构结果也表明单斜相的键合作用比四方相和正交相键合作用更强, 进一步说明单斜相结构更加稳定. 关键词： 铌酸钾钠 四方相 单斜相 密度泛函理论     

High-Temperature Dielectric Response and Multiscale Mechanism of SiO2/Si3N4 Nanocomposites

The high-temperature dielectric properties of SiO₂/Si₃N₄ nanocomposites are investigated theoretically and experimentally. Its permittivities and loss tangents at the temperature ranging from room temperature to 1300°C at 9.0GHz are measured by the resonant cavity method. The SiO_2/Si₃N₄ nanocomposites show complex dielectric behaviour at elevated temperature, and a multi-scale model is proposed to describe the dependence of the dielectric properties in the SiO₂/Si₃N₄ on its compositional variations. Such a theory is needed so that the available property measurements could be extrapolated to other operating frequencies and temperatures.     

含有络合功能基的非天然氨基酸的设计、合成及在生物活性肽中的应用

设计合成了一类侧链带有络合基团的非天然氨基酸, 即侧链带有N,N-二羧甲基氨甲基、N,N-二酰胺甲基氨甲基和N,N-二羟乙基氨甲基的苯丙氨酸衍生物, 并将这类非天然氨基酸用于促性腺激素释放激素(LHRH)类似物的固相合成. 高效液相色谱分析结果表明, 粗肽的纯度较好, 易于纯化; 用电喷雾质谱测定了多肽的分子量. 这些非天然氨基酸可作为其它肽类药物合成的构建单元.     

Preparation and Dielectric Properties of Nanostructured ZnO Whiskers

By a novel controlled combustion synthesis method, a large number of nanostructured ZnO whiskers with different morphologies, such as tetra-needles, long-leg tetra-needles and multi-needles, are prepared without any additive in open air at high temperature. The morphologies and crystalline structures of the as-prepared ZnO nanostructured whiskers are investigated by SEM and XRD. The possible growth mechanism on the nanostructured ZnO whiskers is proposed. The experimental results indicate that the dielectric constants and losses of the nanostructured ZnO whiskers are very low, demonstrating that the nanostructured ZnO whiskers are low-loss materials for microwave absorption in X-band. However, obvious microwave absorption in nanostructured ZnO whiskers is observed. The quasi-microantenna model may be attributed to the microwave absorption of the ZnO whiskers.     

Effect of Topological Connectivity on Firing Pattern Transitions in Coupled Neurons

By using the coupled model of Hindmarsh-Rose neuronal systems, we numerically investigate the effect of topology structures on the firing patterns transition （FPT）. A four-cell coupled system with all possible configurations are studied. We select the membrane current Iext as a controllable parameter, and set it to be near the left side for one of the bifurcation points. It is found that to have a response from some external stimuli with the proper amplitude and frequencies, the transition will appear between different firing states only when the cells in the system are coupled with some proper topological structures, which implies the occurrence of FPT induced by the configuration in the coupled system. Similar FPT phenomena could also be observed in a five-cell coupled system. Fbrthermore, we find that such transition behaviors may have some inherent relevance with the synchronization error and the average connective number among cells in the coupled system for different topology structures. These results suggest that the biological neuron systems may achieve an effective response to the external feeble stimulus by selecting the proper configuration and using the corresponding transition mode.     

聚甲基丙烯酸甲酯包覆(CH3NH3)PbBr3纳米晶静电纺丝膜的制备及对氨气的荧光传感

采用原位合成法制备了聚甲基丙烯酸甲酯包覆MAPbBr₃纳米晶(MAPbBr₃@PMMA,MA=甲铵离子)静电纺丝膜。当氨气(NH₃)通入MAPbBr₃@PMMA纤维膜时与MAPbBr₃中的MA发生取代,能显著降低MAPbBr₃@PMMA纤维的荧光强度,以此构建了基于MAPbBr₃@PMMA纤维荧光猝灭的NH₃传感器。通过扫描电镜、透射电镜、粉末X射线衍射和红外对静电纺丝膜的形貌和结构进行表征,通过紫外可见光谱、荧光光谱对其光学特性进行表征。结果表明,传感器的荧光强度与NH₃浓度在8~90 mg·L^-1之间呈现出良好的线性关系(r=0.995 9),NH₃的检出限低(3 mg·L^-1),且具有良好的重现性和选择性。在实际样品气体的测定中,加标回收率为92.2%~102.1%,相对标准偏差(RSD)为1.8%~3.2%。     

非晶Fe40Ni40P14B6合金阳极钝化膜的电子能谱研究

应用表面分析技术XPS和AES（包括深度分布）分析了非晶Fe40Ni40P14B6合金在H3BO3－Na2B4O7（pH＝9．20）缓冲溶液中不同钝化势或不同钝化时间形成的阳极钝化膜的元素化学状态、结构和化学组成，探讨了加入Ⅲ、Ⅴ族B、P对非晶FeNi基合金钝化成膜的影响，并给出了阳极钝性成膜的一种机制．     

Synthesis and photoluminescence study on ZnO nano-particles

A new technique, namely low pressure sputtering, has been developed to fabricate Zn nanoparticles, with a subsequent oxidation to synthesize ZnO nanoparticles in the ambient atmosphere at 500$\,^{\circ}$C. The synthesized ZnO nanoparticle has a size of 6--8~nm with a preferred orientation of $c$-axis. The produced ZnO nanoparticles have a good UV photoluminescence (PL) emission energy of 3.349 eV with a significant enhancement of donor--acceptor pair emission located at 3.305 eV which implies a number of donor and acceptor bounded excitons existing in the synthesized ZnO nano particles. The near band edge PL emission of the fabricated ZnO is dominated by the bounded excitons at 10~K.