Quinones as electron acceptors. X-ray structures, spectral (EPR, UV-vis) characteristics and electron-transfer reactivities of their reduced anion radicals as separated vs contact ion pairs

Successful isolation of a series of pure (crystalline) salts of labile quinone anion radicals suitable for X-ray crystallographic analysis allows for the first time their rigorous structural distinction as "separated" ion pairs (SIPs) vs "contact" ion pairs (CIPs). The quantitative evaluation of the precise changes in the geometries of these quinones (Q) upon one-electron reduction to afford the anion radical (Q-*) is viewed relative to the corresponding (two-electron) reduction to the hydroquinone (H2Q) via the Pauling bond-length/bond-order paradigm. Structural consequences between such separated and contact ion pairs as defined in the solid state with those extant in solution are explored in the context of their spectral (EPR, UV-vis) properties and isomerization of tightly bound CIPs. Moreover, the SIP/CIP dichotomy is also examined in intermolecular interactions for rapid (self-exchange) electron transfer between Q-* and Q with second-order rate constants of kET approximately equal to 10(8) M-1 s-1, together with the spectral observation of the paramagnetic intermediates [Q,Q-*]leading to 1:1 adducts, as established by X-ray crystallography.     

The essential oil constituents and antimicrobial activity of Anthemis aciphylla BOISS. var. discoidea BOISS

The essential oil of aerial parts, leaves and flowers of the endemic Anthemis aciphylla BOISS. var. discoidea BOISS. (Asteraceae) were obtained by hydrodistillation. The oils were analyzed both by GC and GC-MS on a polar column. The monoterpenes alpha-pinene (9-49%) and terpinen-4-ol (22-32%) were characterized as the main constituents. An unknown component isolated from the essential oil was characterized by means of MS, HR-MS, FT-IR, 1D- and 2D-NMR techniques as isofaurinone (1). Furthermore, the biological activity of the essential oils was evaluated in various human pathogenic microorganisms using the broth microdilution method. Weak to moderate inhibitions (0.06-1.0 mg/ml) was observed.     

Micromechanical modelling and two-scale simulation of epoxy/glass composites with interphases and interfaces

Composite systems consisting of glass fibres and epoxy matrix with interphases and interfaces will be considered in the modelling approach. The interphase forms the transition zone between the epoxy matrix and the glass fibre. The interface is the layer between the glass fibre and the surrounding interphase. The macroscopic strength of the composite material is intrinsically related to the bond strength of the polymeric/solid interface and the micromechanical characteristics of the three phases (epoxy, glass and interphase). Homogenization is an appropriate methodology to link these two scales to predict the overall physical behaviour of the composite. The nonlinear behaviour of amorphous polymers, cohesive interface elements and the elastic behaviour of glass fibres as part of the considered composite material are presented, as well as a representative example to show the necessity of taking interface influences into account. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

128× 128 InSb探测器结构模型研究

热冲击下红外焦平面探测器的高碎裂概率制约着其成品率.为明晰碎裂机理, 基于等效设想, 利用小面阵等效大面阵解决了128×128面阵探测器三维结构建模所需单元数过多的问题, 同时综合考虑材料线膨胀系数的温度依赖性、材料强度的各向异性、表面加工损伤效应, 合理选取InSb材料性能参数, 建立起128×128面阵探测器结构有限元分析模型.模拟结果表明:热冲击下最大Von Mises 应力值出现在N电极区域, 其极值呈非连续分布, 这意味着热冲击下128×128面阵探测器的裂纹起源于N电极区域, 且不止一条.上述结论与碎裂统计分析报告中典型裂纹起源地及裂纹分布这两方面相符合, 这为后续面阵探测器碎裂诱因的研究及结构可靠性设计提供了切实可行的研究思路．     

微通道板的饱和效应对条纹相机动态范围的影响分析

条纹相机通常采用微通道板的内增强或外增强这两种方式来提高信号探测阈值, 也由此引入了微通道板饱和效应对系统动态范围的限定. 通过一个非连续电阻电容打拿极链的通道模型, 对微通道板的饱和效应进行了描述,说明了在条纹相机中, 微通道板输入输出的线性范围限定于通道的贮存电荷, 即使是在外增强方式中采用低阻抗微通道板,传导电流的补偿作用也极其有限, 微通道板内增强和外增强条纹相机应具有相近的动态范围, 低阻抗微通道板仅在高重复率的连续拍摄时方可发挥功效, 同时还说明了微通道板增益的正确设置对条纹相机动态范围的重要影响.     

熔石英表面损伤修复点的损伤概率

针对3个光斑尺寸的CO2激光辐照尺寸小于400 m损伤点后得到的修复点,从4个方面对损伤修复点经355 nm激光辐照后的损伤概率分别进行研究。结果表明,根据修复光斑尺寸或损伤点尺寸分别讨论修复点的损伤概率,更能反映修复点的抗激光损伤能力。通过分别讨论可以看出,采用小光斑CO2激光辐照损伤点或者修复尺寸小于200 m的损伤点,修复成功率超过90%。同时,可以通过损伤修复点的激光损伤阈值都服从正态分布的规律来预测修复点的损伤概率。     

环境中纳米材料的分离与分析方法

随着纳米科技的发展和纳米材料的广泛应用,进入环境中的纳米材料必将随之增加。由于纳米材料可能对生态环境和人体健康带来潜在的危害,了解环境中纳米材料的浓度水平和行为有助于正确认识和评价纳米材料的环境风险,并做出相应的防治对策。然而,纳米材料所具有的诸多特殊性质直接影响它们的环境行为和生态毒性,因此,环境中纳米材料的分析不仅包括浓度的定量测定,还包括对其组成、粒径和表面电荷等性质的表征,是一项具有挑战性的工作。本文综述了近年来关于环境纳米材料分离、表征及检测的相关手段和方法,重点包括场流分离、色谱分离和电泳分离在纳米材料分离以及显微和谱学技术在纳米材料分析中的应用;提出了一些思考和展望,希望能够增进对环境中纳米材料分离和分析方法的了解,有助于纳米材料环境分析方法的建立和推动纳米材料环境行为和生态毒理研究的进一步规范。     

无膜微通道板第三代像增强器的可行性及技术途径探究

砷化镓光阴极的量子效率大大优于超二代多碱光阴极,但由于微通道板(MCP)输入面上的离子阻挡膜的存在,第三代像增强器,即使是薄膜第三代像增强器,相比于同时期技术水平的超二代像增强器,在标准测试条件下的信噪比和分辨力等参数上并无明显优势。通过引入MCP噪声因子的概念,对像增强器光阴极量子效率的有效利用率进行了评价。强调了实现无膜MCP第三代像增强器的必要性,并指明了目前的无膜MCP第三代像增强器开发中所存在的问题,对改善MCP耐电子清刷除气能力及进一步地减少MCP中的有害物种含量的有效方法进行了研究,进而明确了实现高可靠性高性能无膜MCP第三代像增强器的可行性和有效技术途径。     

一种用于减少相位突变点的衍射光学元件改进设计方法

提出了一种基于数字图像处理技术的用于降低相位突变点的改进型Gerchbery-Saxton(G-S)衍射光学元件设计方法。与普通的G-S衍射光学元件设计算法相比,这种改进型的G-S算法能够使得衍射光学元件的相位分布曲线更加光滑,并且在迭代计算过程中具有更强的收敛能力。利用该种算法获得了由高斯光束变换成空心光束时所需要的衍射光学元件的相位分布,在同样参数条件下,均方根误差为8.31%,优于普通G-S算法的9.46%;并且约有33.2%的像素的相位值得到了改进,从而平滑了衍射光学元件的相位分布曲线,便于实际的微加工。     

纠缠光子法绝对定标光电探测器量子效率的研究

为了应对国际上“坎德拉”新定义的动向,开展了利用纠缠光子法测量光电探测器量子效率的研究,并建立了测量装置。装置采用351.1 nm连续激光抽运BBO晶体产生纠缠光子场,然后通过双通道门控计数器组成的符合测量系统在702.2 nm和788.7 nm两个波长点对光电倍增管的量子效率进行了测量。同时对单光子脉冲信号获取、噪声抑制及提取、符合时间特性、偶然符合、暗背景计数和器件透过率等影响测量结果的关键因素进行了实验分析并给出了修正分量,最终在两个波长点量子效率测量不确定度小于0.7%。