http://hdl.handle.net/2289/150 Search the Channel search http://dspace.rri.res.in:8080/jspui/simple-search http://hdl.handle.net/2289/5336 Title: Modulated phases of phospholipid bilayers induced by tocopherols<br/><br/>Authors: Kamal, M.D. Arif; Raghunathan, V. A.<br/><br/>Abstract: The influence of α-, γ‐ and δ-tocopherols on the structure and phase behavior of dipalmitoyl phosphatidylcholine (DPPC) bilayers has been determined from X-ray diffraction studies on oriented multilayers. In all the three cases the main-transition temperature (Tm) of DPPC was found to decrease with increasing tocopherol concentration up to around 25 mol%. Beyond this the main transition is suppressed in the case of γ‐tocopherol, whereas Tm becomes insensitive to composition in the other two cases. The pre-transition is found to be suppressed over a narrow tocopherol concentration range between 7.5 and 10 mol% in DPPC‐γ-tocopherol and DPPC-δ‐tocopherol bilayers, and the ripple phase occurs down to the lowest temperature studied. In all the three cases a modulated phase is observed above a tocopherol concentration of about 10 mol%, which is similar to the Pβ phase reported in DPPC–cholesterol bilayers. This phase is found to occur even in excess water conditions at lower tocopherol concentrations, and consists of bilayers with periodic height modulation. These results indicate the ability of tocopherols to induce local curvature in membranes, which could be important for some of their biological functions<br/><br/>Description: Restricted Access. Mon, 29 Oct 2012 22:58:59 GMT http://hdl.handle.net/2289/5333 Title: Ethanol electrocatalysis on gold and conducting polymer nanocomposites: A study of the kinetic parameters<br/><br/>Authors: Pandey, Rakesh K.; Lakshminarayanan, V.<br/><br/>Abstract: The study attempts to compare the electrocatalytic effect of gold nanoparticles dispersed conjugated polymers using activation energy, Tafel slopes and reaction orders for the evaluation of their performance. A simple and rapid in situ chemical and electrochemical method was adopted for the synthesis of gold and different conducting polymers nanocomposites on electrode surfaces. The method involves the polymerization of the monomer to yield the polymer nanocomposite film with dispersed gold nanoparticles. Polyaniline, polypyrrole, polythiophene and poly(3,4-ethylenedioxythiophene) are the four polymers studied in this work. A systematic comparison among the nanocomposites reveals that although all the conducting polymers have good catalytic activity in alkaline medium however polyaniline dispersed with gold nanoparticles has the best catalytic properties among them as evidenced by its very low activation energy, low onset potential and reproducible currents.<br/><br/>Description: Restricted Access. Sun, 29 Jul 2012 22:58:59 GMT http://hdl.handle.net/2289/5291 Title: Defect-mediated lamellar-isotropic transition of amphiphile bilayers<br/><br/>Authors: Pal, Antara; Pabst, Georg; Raghunathan, V.A.<br/><br/>Abstract: We report the observation of an isotropic phase of amphiphile bilayers, characterized by small average inter-bilayer spacing and short-range positional correlations. These bilayers form a weakly swollen lamellar (Lα) phase over a wide range of water content, which transforms into an isotropic (Li) phase on heating. This transition is not observed in samples without excess water, where the Lα phase is stable at higher temperatures. Small-angle X-ray scattering and ionic conductivity studies indicate that the Lα–Li transition is driven by the unbinding of edge dislocation loops, which has been shown to destroy the quasi-long-range positional order of the lamellar phase. Observation of similar behavior in other bilayer forming systems dominated by attractive inter-bilayer interactions suggests that this isotropic phase is generic to such systems.<br/><br/>Description: Restricted Access. Thu, 20 Sep 2012 22:58:59 GMT http://hdl.handle.net/2289/5283 Title: Two distinct modulated layer structures of an asymmetric bent-shape smectic liquid crystal<br/><br/>Authors: Zhang, Cuiyu; Diorio, Nicholas; Radhika, S.; Sadashiva, B.K.; Sprunt, Samuel N; Jakli, Antal<br/><br/>Abstract: We present chemical synthesis, polarising optical microscopy, electric current, and small-angle X-ray scattering measurements on a strongly anisotropic bent-shape liquid crystal material. We find that it has two layer-undulated ferroelectric phases, M1 and M2. In the higher temperature M2 phase the undulation amplitude and period increases on cooling, similar to other published materials. It can be identified with a tilted modulated phase. In the M1 phase the molecular plane is not tilted, and – in sharp contrast with all prior observations – the modulation amplitude and period decrease on cooling. These observations can be explained with a ‘leaning’ director structure, where the leaning angle is decreasing on cooling.<br/><br/>Description: Restricted Access. Sat, 08 Sep 2012 22:58:59 GMT