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| Abstract: | The double sulfate family (ABSO4), where A and B are alkali metal cations, is the object of great interest owing to the complexity and richness of its sequence of phase transition induced by temperature variation. A new sulfate salt characterized by the presence of water molecule in the unit cell with the chemical formula, Li2Na3(SO4)2⋅6H2O (LSSW), was obtained. The ultrasonic velocity measurement was done with pulse echo overlap technique [PEO]. All the six second order elastic stiffness constants, C11 = C22, C33, C44 = C55, C12, C14 and C13 = C23 are reported for the first time. The anisotropy in the elastic properties of the crystal are well explained by the pictorial representation of the polar plots of phase velocity, slowness, Young’s modulus and linear compressibility in a–b and a–c planes. |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/1977 |
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| Anisotropy in elastic properties of lithium....pdf | (467.9Kb) |
| Abstract: | A detailed ultrasonic study of the elastic properties of lithium ammonium sulfate ~LiNH4SO4! or LAS has been carried out below room temperature. The elastic constants of LAS at room temperature are reported. The discrepancy present in earlier elastic constant data associated with the different choice of axes for this orthorhombic system are clarified. The results of the temperature variation study down to 220 K confirm the ferroelastic phase transition at 285 K and establish a thermal hysteresis of about 2.5 K between the cooling and heating cycles. Results of the investigation on the suspected weak phase transition at 256 K suggest that this transition occurs at 242 K on cooling and at 256 K on heating, thus having a thermal hysteresis of about 14 K. However, since the observed elastic anomaly for this transition is very small, the nature of this transition still remains unclear |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/1974 |
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| Godfry, L,.pdf | (116.4Kb) |
| Abstract: | A red rain phenomenon occurred in Kerala, India starting from 25th July 2001, in which the rainwater appeared coloured in various localized places that are spread over a few hundred kilometers in Kerala. Maximum cases were reported during the first 10 days and isolated cases were found to occur for about 2 months. The striking red colouration of the rainwater was found to be due to the suspension of microscopic red particles having the appearance of biological cells. These particles have no similarity with usual desert dust. An estimated minimum quantity of 50,000 kg of red particles has fallen from the sky through red rain. An analysis of this strange phenomenon further shows that the conventional atmospheric transport processes like dust storms etc. cannot explain this phenomenon. The electron microscopic study of the red particles shows fine cell structure indicat- ing their biological cell like nature. EDAX analysis shows that the major elements present in these cell like particles are carbon and oxygen. Strangely, a test for DNA using Ethidium Bromide dye fluorescence technique indicates absence of DNA in these cells. In the context of a suspected link between a meteor airburst event and the red rain, the possibility for the extraterrestrial origin of these particles from cometary fragments is discussed. |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/1976 |
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| Red rain phenomenon of Kerala.pdf | (412.3Kb) |
| Abstract: | The red cells found in the red rain in Kerala, India are now considered as a possible case of extraterrestrial life form. These cells can undergo rapid replication even at an extreme high temperature of 300 deg C. They can also be cultured in diverse unconventional chemical substrates. The molecular composition of these cells is yet to be identified. This paper reports the unusual autofluorescence characteristic of the cultured red rain cells. A spectrofluorimetric study has been performed to investigate this, which shows a systematic shift of the fluorescence emission peak wavelength as the excitation wavelength is increased. Conventional biomolecules are not known to have this property. Details of this investigation and the results are discussed. |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/1973 |
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| Godfry, Louis.pdf | (553.2Kb) |
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