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在前期工作中,我们报道了一个三苯胺基团键接氰基二苯基乙烯单元的分子TPNCF,并认为从局域激发态到电荷转移(CT)激发态的快速内转换,能够有效抑制E/Z异构化反应。为了进一步证明CT态能够诱导E/Z构型的稳定,本文中我们将三苯胺基团替代为给电子能力更强的吩噁嗪基团,设计合成了分子PZNCF,并且成功获得其E/Z异构体。通过对原位核磁及紫外光谱数据的分析,我们发现相比于TPNCF,PZNCF在光辐照下的E/Z异构化反应明显变慢。这说明对于氰基二苯基乙烯单元,一个更强给电子能力基团吩噁嗪的引入能够使其在激发态下具有更稳定的E/Z构型。密度泛函理论计算及光物理测试结果表明PZNCF分子具有较强的电荷转移激发态,这也更加证实了我们先前的结论:通过合理构建给受体结构,能够获得激发态下构型稳定的E/Z异构体。 相似文献
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We study the switching in the magnetic moments of interacting magnetic particles. The dynamics of the magnetic moments is governed by a coupled set of Landau-Lifshitz-Gilbert equations. The magnetic particles are assumed to be spherical in shape, single domain, and have uniaxial anisotropy. Effects of dipolar interaction between the particles, anisotropy energy, an applied switching field with finite spatial extent and a small bias field are considered. When the separation between the particles is small, the dipolar field is significant and it affects the reversal of the magnetic moments. The final configuration attained depends sensitively on the decaying length of the switching field, the inter-particle separation, and the initial configuration. A bias field tends to suppress the effects of a spatially decaying switching field and dipolar interaction between neighbouring particles. 相似文献
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珠状N—亚甲基壳聚糖凝胶的制备及其性质研究 总被引:2,自引:1,他引:2
从虾、蟹壳制得壳聚糖,再将其与甲醛反应,制成珠状N-亚甲基壳聚糖凝胶,探讨了不同反应条件对微珠形成的影响,并测定了这种珠状凝胶的物理化学性质。实验结果表明:反应在40~60℃能顺利进行;壳聚糖的浓度、甲醛与葡胺糖残基的摩尔比等因素对微珠的形成有直接的影响;该微珠对热和有机溶剂有很高的化学稳定性,但在强酸性介质中会发生降解。 相似文献
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提出了一种采用液体透镜(LTL)补偿人眼屈光度变化的新型眼底相机光学系统,应用高斯括号法推导了液体透镜光焦度与人眼屈光度的函数关系式,计算并搭建了包含人眼模型的眼底相机近轴光学系统。在优化过程中控制人眼瞳孔位置与液体透镜共轭并保证位于它们之间的光学系统放大率接近1,使成像光束能够通过液体透镜;光源与角膜共轭,采用环形光源结合偏振光照明,并在探测器前加入检偏器降低系统杂光。设计并研制了视场角为50°、物方工作距为40mm、总长小于220mm的便携式眼底相机光学系统,拍摄了不同屈光度状态下的模型眼在采用液体透镜和不采用液体透镜补偿的眼底图片,结果表明:通过液体透镜的电控变焦能对-10D~+10D(1D=1m-1)的人眼清晰成像。该系统结构紧凑、无机械运动部件,大幅降低了光机系统的复杂程度。 相似文献
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We study the precessional switching of a single domain, uniaxial magnetic disk with shape anisotropy by the micromagnetic simulation. The results show that magnetic switching can be driven by a smaller magnetic field pulse in an elliptic disk with its long semiaxis perpendicular to the easy axis than in a circular disk. The shape anisotropy can change the height of the energy barrier, thus we may obtain an optimal fast magnetization switching by tuning the aspect ratio of the disk under the thermal stability condition. The switching behavior of the elliptic and circular disks is studied in detail It is found that only properly choosing the pulse amplitude and duration can realize the fast precessional switching. 相似文献