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Behrnd NR Couderc G Wübbenhorst M Hulliger J 《Physical chemistry chemical physics : PCCP》2006,8(35):4132-4137
Scanning pyroelectric microscopy (SPEM) was applied to investigate grown-in polarity in trans-4-chloro-4'-nitrostilbene (CNS) single crystals. Sectors {011} and {011} were scanned for cross sections perpendicular to the a-direction. A rotational analysis for {011}, {011} faces was performed for a needle like crystal turned around the a-axis. All pyroelectric experiments confirm a bipolar grown-in state of polarity for sector involving the twofold axis b. These measurements agree with theoretical force field and stochastic calculations, predicting a bipolar state and a nearly identical extent of polarity for two different sectors. 相似文献
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Raúl Mariaca Norwid-Rasmus Behrnd Fabien Helbling Gaëtan Couderc Helen Stoeckli-Evans 《Journal of fluorine chemistry》2009,130(2):175-20379
The syntheses and crystal structures of a series of fluoro-substituted halogeno (Cl, Br, I)-cyano-stilbenes containing donor and acceptor groups (D-π-A) are reported. These molecules show a tendency to form antiparallel chain-like structures and herringbone packing, crystallising predominantly in a centric space group. However, second harmonic generation measurements bear evidence for orientational disorder leading to partial polar order below the ordinary X-ray structure determination limit. Some co-crystals are isostructural with their components. The non-fluoro as well as the halogeno-fluoro substituted components of co-crystals seem to impose their crystal structure on the complementary fluoro- or cyano-fluoro substituted components. Co-crystallization enhanced the deviation from centrosymmetry. 相似文献
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Johnson ER; McDonald NR 《The Quarterly Journal of Mechanics and Applied Mathematics》2007,60(1):65-72
An explicit solution for a layer of fluid with constant vorticitysurrounding a thin plate of finite length is obtained usingelementary conformal mapping methods. In the limit of largeplate length the behaviour of the solution near the ends ofthe plate tends to that of the previously known solution fora semi-infinite plate. Contour dynamics is used to investigatethe stability of the steady solutions. 相似文献
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