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Braga WS Kimura NM Luders DD Sampaio AR Santoro PA Palangana AJ 《The European physical journal. E, Soft matter》2007,24(3):247-250
The phase diagram is an interesting field of research, particularly in lyotropic liquid crystals (LLC). In this way, one of the most important phase diagrams of this LLC system was reported by Yu and Saupe. Two uniaxial (calamitic--N(C) and discotic--N(D)) and one biaxial nematic (N(B)) phases were determined by these authors. Furthermore, in this phase diagram the classical isotropic phase (I was observed at high temperature as well as a reentrant isotropic phase (I(RE)) which takes place at lower temperature. Later, this phase diagram was also studied by several authors and in all cases the I(RE)-N(C)-I phase transitions were not observed. In this work, we present a study of this phase diagram through digital image processing and refractometry optical techniques. The occurrence of these phase transitions is investigated and characterized. In addition, the order parameter is obtained based on the Vuks hypothesis from a particular point, in the range of the N(C) phase, where the absolute value of the optical birefringence (Deltan is maximum. 相似文献
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The present work is focused on thermal diffusivity (D) measurements, via Z -scan experiment, in a discotic nematic phase of the lyotropic mixture comprised of potassium laurate, decanol and D2O. In this experiment, the nematic sample is translated through the focal region of a focused Gaussian laser beam. The experimental data are analyzed according to the thermal lens model and the ratio between the thermal diffusivities parallel (D∥) and perpendicular (D⊥) to the director of the nematic sample has been found to be smaller than one. The results are compared to others obtained with different liquid crystals and explained by using a simple model where this ratio is correlated to the shape anisotropy of the micelles. 相似文献
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CM Silva MF Duarte ML Mira MH Florêncio K Versluis AJ Heck 《Rapid communications in mass spectrometry : RCM》1999,13(12):1098-1103
Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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D. A. Oliveira D. D. Luders G. P. Souza N. M. Kimura A. J. Palangana 《Crystal Research and Technology》2009,44(11):1255-1258
Lyotropic nematic textures are investigated, using optical microscopy, near the reentrant isotropic (IRE) ‐ discotic nematic (ND‐) ‐ biaxial nematic (NB) ‐ calamitic nematic (NC+) ‐ isotropic (I) phase transitions in a lyotropic mixture of potassium laurate, decanol and D2O. The NB, intermediate phase between the two uniaxial nematic ones, is characterized by optical birefringence measurements. In this way, using a polarizing microscope and a colour CCD digital camera, the NB – NC+ phase transition is identified as well as the domain of the NB phase and ND‐ – NB transition point in accordance with optical birefringence data (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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In this work the temperature dependence of the extraordinary/ordinary refractive indices and the optical birefringence are determined near the reentrant isotropic-discotic nematic-isotropic phase transitions for a lyotropic mixture of potassium laurate, decanol and D2O. These parameters are related to the extraordinary/ordinary molar refractivity through Vuks's equation and discussed in terms of structural changes in the micellar configuration at the transitions. 相似文献
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