Browsing by Author "Pillai, VPM"

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    Effect of thermal annealing on the structural and optical properties of nanostructured zinc oxide thin films prepared by pulsed laser ablation
    (SOLAR ENERGY MATERIALS AND SOLAR CELLS, 2009) Vinodkumar, R; Lethy, KJ; Beena, D; Satyanarayana, M; Jayasree, RS; Ganesan, V; Nayar, VU; Pillai, VPM
    Zinc oxide (ZnO) films are prepared by pulsed laser ablation, on an optically flat quartz substrate for different deposition time. The influence of annealing temperature, on the structural and optical properties of ZnO films is investigated systematically using X-ray diffraction (XRD), energy dispersive Xray analysis (EDX), scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectra, UV-vis spectroscopy and photoluminescence spectroscopy (PL). The XRD pattern shows that the as-deposited films are amorphous and the annealed films are polycrystalline. The average size of the crystalline grains varies from 9 to 26 nm in the films. The SEM and AFM images reveal uniform distribution of grains in the films and the grains are in the nanoscale dimension. Raman spectra suggest the hexagonal wurtzite phase for the ZnO films. The UV-visible spectra show an increase in transmittance with annealing temperature. The observation of very intense PL emission from the films annealed at 773 K, suggest the suitability of these films for applications as light emitters in the visible region. The ability to produce the stochiometric ZnO thin films with reproducible structural, morphological and optical characteristics should be useful as a suitable window material for practical industrial solar cell and display devices. (C) 2008 Elsevier B.V. All rights reserved.
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    Raman and infrared spectral analysis of corrosion products on zinc NaZn4Cl(OH)(6)SO4-6H(2)O and Zn4Cl2(OH)(4)SO4 center dot 5H(2)O
    (MATERIALS CHEMISTRY AND PHYSICS, 2006) Jayasree, RS; Pillai, VPM; Nayar, VU; Odnevall, I; Keresztury, G
    Two corrosion products of zinc namely NaZn4Cl(OH)(6)SO4 center dot 6H(2)O which occurs mainly in marine and traffic environments and Zn4Cl2(OH)(4)SO4 center dot 5H(2)O which occurs in industrial, rural and urban environments were analysed using infrared and Raman spectroscopic methods and the vibrational modes of SO42- ion, OH radical and H2O molecules have been identified and discussed. The symmetric stretching vibrations of the SO42- ion of the compounds give an indication of the distorted structure for the SO4 anion in the compounds, the distortion being more in Zn4Cl2(OH)(4)SO4 center dot 5H(2)O. Due to the presence of strong hydrogen bond network, an unusual lowering of the symmetric stretching mode of SO4 is observed in both the compounds. In NaZn4Cl(OH)(6)SO4 center dot 6H(2)O, medium to weak hydrogen bonding network is present while strong to weak hydrogen bonding is present in Zn4Cl2(OH)(4)SO4 center dot 5H(2)O. (c) 2005 Elsevier B.V. All rights reserved.
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    Segmentation and volumetric analysis of the caudate nucleus in Alzheimer's disease
    (EUROPEAN JOURNAL OF RADIOLOGY, 2013) Jiji, S; Smitha, KA; Gupta, AK; Pillai, VPM; Jayasree, RS
    Objectives: A quantitative volumetric analysis of caudate nucleus can provide valuable information in early diagnosis and prognosis of patients with Alzheimer's diseases (AD). Purpose of the study is to estimate the volume of segmented caudate nucleus from MR images and to correlate the variation in the segmented volume with respect to the total brain volume. We have also tried to evaluate the caudate nucleus atrophy with the age related atrophy of white matter (WM), gray matter (GM) and cerebrospinal fluid (CSF) in a group of Alzheimer's disease patients. Methods: 3D fast low angle shot (3D FLASH) brain MR images of 15 AD patients, 15 normal volunteers and 15 patients who had normally diagnosed MR images were included in the study. Brain tissue and caudate nuclei were segmented using the statistical parametric mapping package and a semi-automatic tool, respectively and the volumes were estimated. Volume of segmented caudate nucleus is correlated with respect to the total brain volume. Further, the caudate nucleus atrophy is estimated with the age related atrophy of WM, GM and CSF in a group of AD patients. Results: Significant reduction in the caudate volume of AD patients was observed compared to that of the normal volunteers. Statistical analysis also showed significant variation in the volume of GM and CSF of AD patients. Among the patients who had normal appearing brain, 33% showed significant changes in the caudate volume. We hypothesize that these changes can be considered as an indication of early AD. Conclusion: The method of volumetric analysis of brain structures is simple and effective way of early diagnosis of neurological disorders like Alzheimer's disease. We have illustrated this with the observed changes in the volume of caudate nucleus in a group of patients. A detailed study with more subjects will be useful in correlating these results for early diagnosis of AD. (C) 2013 Elsevier Ireland Ltd. All rights reserved.
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    Segmentation and volumetric analysis of the caudate nucleus inAlzheimer’s disease
    (European J Radiol., 2013-08) Jiji, S; Smitha, KA; Gupta, AK; Pillai, VPM; Jayasree, RS