Using a variational method, we have developed an approximate model of the dynamics of soliton coupling described by coupled nonlinear Schrodinger equations. The results are analytical and can be recast into a suggestive particlelike description providing a physical insight into the problem.The particular case of the nonlinear coherent coupler is emphasized, and an estimate of the soliton switching peak power is obtained. A symmetry-breaking instability is also described, in a simple way, with the potential-well picture.

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.Access and use of this website and the material on it are subject to the Terms and Conditions set forth at Modulation of the polymorphism of the palmitic acid/cholesterol system by the pH Ouimet, Jaclin; Croft, Stéphanie; Pare, Chantal; Katsaras, John; Lafleur, Michel http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/droits L'accès à ce site Web et l'utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D'UTILISER CE SITE WEB. NRC Publications Record / Notice d'Archives des publications de CNRC:http://nparc.cisti-icist.nrc-cnrc.gc.ca/eng/view/object/?id=f1ca22fa-07cd-4c05-89e1-6819f0f1503f http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/voir/objet/?id=f1ca22fa-07cd-4c05-89e1-6819f0f1503f Differential scanning calorimetry, infrared spectroscopy, solid-state 13 C and 2 H NMR spectroscopy, and X-ray diffraction were used to characterize hydrated mixtures of palmitic acid (PA) and cholesterol (chol), at low (5.4) and high (8.5-9.0) pH. The pH affects the ionization state of the fatty acid, and it was found to modulate its interaction with cholesterol, and the architecture of the resulting complexes. At low pH, this system undergoes a transition from a phase-separated crystalline state to a lamellar liquid-ordered (lo) phase, in agreement with previous results (Langmuir 2001, 17, 5587-5594). The apparent pKa of PA in these conditions is found to be about 8.2. At high pH, when the fatty acid is deprotonated and consequently negatively charged, both components participate in the formation of an lo lamellar structure that was found to be stable over a large temperature range (20-70°C). For 50/50 PA/chol mixtures, only this phase, with a d spacing of approximately 49 Å, is detected. These fluid bilayers can be characterized as having solubilized cholesterol and highly ordered PA hydrocarbon chains. It is thus proposed that the electrostatic repulsion between carboxylate headgroups allows cholesterol molecules to integrate into the palmitate matrix. T...

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It is well established that cholesterol induces the formation of a liquid-ordered phase in phosphatidylcholine (PC) bilayers. The goal of this work is to examine the influence of cholesterol on phosphatidylethanolamine polymorphism. The behavior of 1-palmitoyl-2-oleoyl-phosphatidylethanolamine (POPE)/cholesterol mixtures was characterized using infrared and 2H nuclear magnetic resonance (NMR) spectroscopy (using POPE bearing a perdeuterated palmitoyl chain in the latter case). Our results reveal that cholesterol induces the formation of a liquid-ordered phase in POPE membranes, similar to those observed for various PC/cholesterol systems. However, the coexistence region of the gel and the liquid-ordered phases is different from that proposed for PC/cholesterol systems. The results indicate a progressive broadening of the gel-to-fluid phase transition, suggesting the absence of an eutectic. In addition, there is a progressive downshift of the end of the transition for cholesterol content higher than 10 mol %. Cholesterol has an ordering effect on the acyl chains of POPE, but it is less pronounced than for the PC equivalent. This study also shows that the cholesterol effect on the lamellar-to-hexagonal (L(alpha)-H(II)) phase transition is not monotonous. It shifts the transition toward the low temperatures between 0 and 30 mol % cholesterol but shifts it toward the high temperatures when cholesterol content is higher than 30 mol %. The change in conformational order of the lipid acyl chains, as probed by the shift of the symmetric methylene C-H stretching, shows concerted variations. Finally, we show that cholesterol maintains its chain ordering effect in the hexagonal phase.