http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/488 Fri, 24 May 2013 13:33:05 GMT 2013-05-24T13:33:05Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/873 Reusable Recording Medium based on MBPVA and Vinyl Acetate Sudha Kartha,C A new photopolymerizable recording media is introduced based on poly (vinyl alcohol) and vinyl acetate sensitized with methylene blue. It is observed that this MBPVA/VAc system can be reused a number of times without significant decrease in diffraction efficiency. The PVA-VAc ratio was optimized at 2:1. Diffraction efcienc4y of 6.3% was obtained without any fixing at a dye concentration of 9.3 x 10- mol/l at an exposure of 750mJ/cm2. The material is attractive on account of its reusability. Sun, 13 Mar 2005 00:00:00 GMT http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/873 2005-03-13T00:00:00Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/817 Photoconductivity in Molecularly Doped Poly (methylmethacrylate)Sandwich Cells Sudha Kartha,C Poly(methyl)methacrylate was made photoconducting by molecular doping and the photoconductivity was investigated using modulated photocurrent technique . Low-temperature current-voltage measurements showed that the transport mechanism was thermally activated hopping. An experimental investigation of the photoconductivity action spectrum along with theoretical calculation enabled an estimation of the diffusion coefficient of the material. The presence of states with a distribution of lifetimes could be understood from the frequency response of the photocurrent . The photocurrent was due to the field-assisted dissociation of these states. Sat, 13 Jan 2007 00:00:00 GMT http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/817 2007-01-13T00:00:00Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/612 Reusable Recording Medium Based on MBPVA and Vinyl Acetate Sudha Kartha,C A new photopolymerizable recording media is introduced based on poly (vinyl alcohol) and vinyl acetate sensitized with methylene blue. It is observed that this MBPVA/VAc system can be reused a number of times without significant decrease in diffraction efficiency. The PVA-VAc ratio was optimized at 2:1. Diffraction efficiency of 6.3% was obtained without any fixing at a dye concentration of 9.3 10 4 mol/l at an exposure of 750 mJ/cm2. The material is attractive on account of its reusability. Sun, 13 Mar 2005 00:00:00 GMT http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/612 2005-03-13T00:00:00Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/611 Optimization of pH and Direct Imaging Conditions of Complexed Methylene Blue Sensitized Poly(vinyl chloride) Films Sudha Kartha,C Significant results of our experimental investigations on the dependence of pH on real time transmission characteristics on recording media fabricated by doping PVC with complexed methylene blue are presented. The optimum pH value for faster bleaching was found to be 4×5. In typical applications, the illumination from one side, normal to the surface of this material, initiates a chemical sequence that records the incident light pattern in the polymer. Thus direct imaging can be successfully done on this sample. The recorded letters were very legible with good contrast and no scattering centres. Diffraction efficiency measurements were also carried out on this material. Mon, 24 Feb 2003 00:00:00 GMT http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/611 2003-02-24T00:00:00Z