| Abstract: | The quantum yields of singlet oxygen production and lifetimes at the gas–solid interface in silica gel material are determined. Different photosensitizers (PS) are encapsulated in parallelepipedic xerogel monoliths (PS-SG). PS were chosen according to their known photooxidation properties: 9,10-dicyanoanthracene (DCA), 9,10-anthraquinone (ANT), and a benzophenone derivative, 4-benzoyl benzoic acid (4BB). These experiments are mainly based on time-resolved 1O2 phosphorescence detection, and the obtained FD and tD values are compared with those of a reference sensitizer for production, 1H-phenalen-1- one (PN), included in the same xerogel. The trend between their ability to oxidize organic pollutants in the gas phase and their efficiency for production is investigated through photooxidation experiments of a test pollutant dimethylsulfide (DMS). The FD value is high for DCA-SG relative to the PN reference, whereas it is slightly lower for 4BB-SG and for ANT-SG. FD is related to the production of sulfoxide and sulfone as the main oxidation products for DMS photosensitized oxidation. Additional mechanisms, leading to C!S bond cleaveage, appear to mainly occur for the less efficient singlet oxygen sensitizers 4BB-SG and ANTSG. |
| URI: | http://dyuthi.cusat.ac.in/purl/711 |
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| paper16.pdf | (352.6Kb) |
| Abstract: | Short fiber reinforced thermoplastics have generated much interest these days since fibrous materials tend to increase both mechanical and thermal properties, such as tensile strength, flexural strength, flexural modulus, heat deflection temperature, creep resistance, and some times impact strength of thermoplastics. If the matrix and reinforcement are both based on polymers the composite are recyclable. The rheological behavior of recyclable composites based on nylon fiber reinforced polypropylene (PP) is reported in this paper. The rheological behavior was evaluated both using a capillary rheometer and a torque rheometer. The study showed that the composite became pseudoplastic with fiber content and hence fiber addition did not affect processing adversely at higher shear rates. The torque rheometer data resembled that obtained from the capillary rheometer. The energy of mixing and activation energy of mixing also did not show much variation from that of PP alone. |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/1999 |
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| Short nylon fibre....pdf | (438.5Kb) |
| Abstract: | Optical emission from TiO2 plasma, generated by a nanosecond laser is spectroscopically analysed. The main chemical species are identified and the spatio-temporal distribution of the plasma parameters such as electron temperature and density are characterized based on the study of spectral distribution of the line intensities and their broadening characteristics. The parameters of laser induced plasma vary quickly owing to its expansion at low background pressure and the possible deviations from local thermodynamic equilibrium conditions are tested to show its validity. |
| URI: | http://dyuthi.cusat.ac.in/purl/1820 |
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| Spectral Charac ... from Titanium Dioxide.pdf | (296.3Kb) |
| Abstract: | Complete thermal characterization of liquid crystal mixtures in the smectic phase consisting of various relative volume fractions of cholesterol and 1-hexadecanol have been carried out using the photoacoustic technique. Thermal diffusivity values of these liquid crystal mixtures are evaluated using the open cell photoacoustic technique whereas the thermal effusivity value is measured using the conventional photoacoustic technique. From the measured values of these transient thermophysical parameters, the thermal conductivity and heat capacity of the sample under investigation are calculated. Analyses of the results show that all the thermophysical parameters depend strongly on the volume fraction of the constituents. Results are interpreted in terms of enhanced hydrogen bonding and the consequent enhancement in cohesive thermal energy transport with increasing volume fraction of 1-hexadecanol |
| URI: | http://dyuthi.cusat.ac.in/purl/1804 |
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| Dyuthi-P0264.pdf | (435.4Kb) |
| Abstract: | Optical emission from TiO2 plasma, generated by a nanosecond laser is spectroscopically analysed. The main chemical species are identified and the spatio-temporal distribution of the plasma parameters such as electron temperature and density are characterized based on the study of spectral distribution of the line intensities and their broadening characteristics. The parameters of laser induced plasma vary quickly owing to its expansion at low background pressure and the possible deviations from local thermodynamic equilibrium conditions are tested to show its validity. |
| URI: | http://dyuthi.cusat.ac.in/purl/1823 |
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| Spectral Charac ... from Titanium Dioxide.pdf | (296.3Kb) |
| Abstract: | Complete thermal characterization of liquid crystal mixtures in the smectic phase consisting of various relative volume fractions of cholesterol and 1-hexadecanol have been carried out using the photoacoustic technique. Thermal diffusivity values of these liquid crystal mixtures are evaluated using the open cell photoacoustic technique whereas the thermal effusivity value is measured using the conventional photoacoustic technique. From the measured values of these transient thermophysical parameters, the thermal conductivity and heat capacity of the sample under investigation are calculated. Analyses of the results show that all the thermophysical parameters depend strongly on the volume fraction of the constituents. Results are interpreted in terms of enhanced hydrogen bonding and the consequent enhancement in cohesive thermal energy transport with increasing volume fraction of 1-hexadecanol |
| URI: | http://dyuthi.cusat.ac.in/purl/1805 |
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| Photoacoustic studies on thermal.pdf | (435.4Kb) |
| Abstract: | Optical emission from TiO2 plasma, generated by a nanosecond laser is spectroscopically analysed. The main chemical species are identified and the spatio-temporal distribution of the plasma parameters such as electron temperature and density are characterized based on the study of spectral distribution of the line intensities and their broadening characteristics. The parameters of laser induced plasma vary quickly owing to its expansion at low background pressure and the possible deviations from local thermodynamic equilibrium conditions are tested to show its validity. |
| URI: | http://dyuthi.cusat.ac.in/purl/1821 |
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| Spectral Charac ... from Titanium Dioxide.pdf | (296.3Kb) |
| Abstract: | A novel electrochemical sensor has been developed for the determination of nimesulide. The sensor is based on the NIM- molybdophosphoric acid (MPA) as the electroactive material in PVC matrix in presence of bis(2-ethyl hexyl) phthalate (BEP) as a plasticizer. The sensor showed a fast, stable, near Nernstian response for 1 × 10-2 –1 × 10-6 M NIM over the pH range 5 – 8 with a slope 55.6 ±0.5m V/decade and the response time is < 45 s. Selectivity coefficient data for some common ions show negligible interferences. The sensor was successfully applied for the determination of NIM in tablet and the results obtained are in good agreement with those obtained by the official method. |
| URI: | http://dyuthi.cusat.ac.in/purl/517 |
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| PEA%2025%203%202007%20375-381.pdf | (185.5Kb) |
| Abstract: | The effect of chromium doping on methylene blue sensitized Poly (vinyl alcohol)/Acrylamide was carried out by varying the ratios of Ammonium dichromate and methylene blue. In the case of films without ammonium dichromate, the diffraction efficiency was found to decrease on storage. On chromium doping the storage life was improved. Interestingly, a self-enhancement in efficiency was observed for a particular ratio of methylene blue and ammonium dichromate. |
| URI: | http://dyuthi.cusat.ac.in/purl/712 |
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| Cr doped paper.pdf | (237.8Kb) |
| Abstract: | 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/816 |
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| V C Kishore and ... onductivity...,Jan2007.PDF | (3.706Mb) |
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