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Elliptic shear applied to a homeotropically oriented nematic above the electric bend Freedericks transition (FT) generates slow precession of the director. The character of the accompanying nonlinear waves changes from diffusive phase waves to dispersive ones exhibiting spirals and spatiotemporal chaos as the FT is approached from above. An exact solution of the flow alignment equations captures the observed precession and predicts its reversal for non-flow-aligning materials. The FT transforms into a Hopf bifurcation opening the way to understand the wave phenomena. 相似文献
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Aitala EM Amato S Anjos JC Appel JA Ashery D Banerjee S Bediaga I Blaylock G Bracker SB Burchat PR Burnstein RA Carter T Carvalho HS Copty NK Costa I Cremaldi LM Darling C Denisenko K Fernandez A Gagnon P Gerzon S Gobel C Gounder K Halling AM Herrera G Hurvits G James C Kasper PA Kwan S Langs DC Leslie J Lundberg B MayTal-Beck S Meadows B de Mello Neto JR Milburn RH de Miranda JM Napier A Nguyen A d'Oliveira AB O'Shaughnessy K Peng KC Perera LP Purohit MV Quinn B Radeztsky S Rafatian A 《Physical review letters》1996,77(12):2384-2387
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Stibrany RT Fikar R Brader M Potenza MN Potenza JA Schugar HJ 《Inorganic chemistry》2002,41(20):5203-5215
A series of Cu(II) and Cu(I)/Cu(II) complexes containing the cis-N(amine)(2)S(thiolate)(2) copper complex rac-2 has been synthesized to provide a basis for understanding the charge-transfer spectra of mixed-valence thiolate-bridged Cu(I)/Cu(II) complexes. In combination with Cu(Me(2)-13-N(4)ane), rac-2 yields a monobridged dinuclear homovalent adduct, rac-5, while reaction with CuCl yields the mixed-valance pentanuclear complex rac-6. In the presence of Cu(II)(acac)(2), chiral R,R-1 reacts to form a mixed-valence pentanuclear cation R,R-7. rac-6 exhibits a relatively short Cu(I). Cu(II) contact [2.8231(9) A] and associated structural features that suggest the presence of a weak Cu(I).Cu(II) interaction in a valence-trapped system. Additional structural features in rac-6 and R,R-7 include singly and doubly bridging thiolates, three- and four-coordinated Cu(I) ions, and varying Cu(I) ligand sets. These features extend the types and complexities of electronic absorptions significantly. Spectra of rac-6 and R,R-7 exhibit multiple overlapping absorptions over the entire visible and ultraviolet spectral regions studied, consonant with these observations. Trends resulting from variations in structure type and oxidation state permit a first approach toward developing a detailed assignment of the individual ligand Rydberg, LF, LMCT, MLCT, and possible MMCT absorptions in these complexes. 相似文献
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We investigate bulk and interfacial properties of a recently proposed hard-body model for a ternary mixture of amphiphilic particles, spheres and needles using density functional theory. The simple model amphiphiles are formed by bonding a vanishingly thin needle tail radially to a hard-sphere head group. Such particles provide a natural amphiphile when added to a binary mixture of spheres and needles. As all interactions are hard, we seek to find whether amphiphilic effects can be driven by entropy without the need to invoke attractive interactions. In order to assess the amphiphilic character of the model we first examine the spatial and orientational distribution of the amphiphiles at the free interface between demixed needle-rich and amphiphile-rich fluid phases of the binary amphiphile-needle subsystem. We then consider the free interface between sphere-rich and needle-rich phases upon adding amphiphiles with low concentration to the demixed system. In both cases the orientational distribution of the particles in the interface provides strong evidence that amphiphilic properties can arise purely from geometrical packing effects. 相似文献