S. Mullainathan

Ultrasonic Investigation of Molecular Interactions in Binary Mixtures at 303 K

The ultrasonic velocity, density and viscosity at 303 K have been measured in the binary systems of toluene with benzene and o-xylone with benzene. The acoustical parameters such as adiabatic compressibility, free length, free volume and acoustical impedance are calculated. The results are interpreted in terms of molecular interaction between the components of the mixtures

Reassessment and comparison of natural radioactivity levels in relation to granulometric contents of recently excavated major river sediments

River sediment depositions on the bottom of rivers most frequently consist of sand and gravel particles, which make them particularly valuable for the building construction. Knowledge of radioactivity present in building material enables one to assess any possible radiological hazard to mankind by the use of such materials. The natural radionuclide (238U, 232Th and 40K) contents have been analyzed for the recently excavated sediment samples of Cauvery, Vellar, Ponnaiyar and Palaru rivers with an aim of evaluating the radiation hazard nature. To know the radiological characteristics of the sediment, the different radiological parameters are calculated. Natural radioactivity level is higher in Palaru river and it is lower in Vellar river sediments. In all the rivers, concentration of 238U is decreased, and concentrations of 232Th and 40K are increased towards the river mouth. Granulometric analysis shows that the sand is the main constituent in all the river sediment samples. Content of sand is gradually decreased, and contents of silt and clay are gradually increased towards the river mouth. Cluster analysis was carried out to find the similarity level between the radioactivity and granulometric measurements. The radioactivity level of all the four river sediments mainly depends upon the contents of silt and clay. Averages of the all calculated radiation hazard indices are lower than recommended level in Cauvery, Vellar and Ponnaiyar river sediments. Therefore, the sediment of the above rivers does not pose any significant radiological threat to the population when it is used as a building construction material.

Evaluation of natural radioactivity and its associated health hazard indices of a south Indian river

The activity concentration of the natural radionuclides (226)Ra, (232)Th and (40)K was measured for sediment samples collected from thirty-three different locations along the Bharathapuzha river basin by using high-resolution gamma-ray spectrometry. The concentrations of the natural radionuclides were found to vary from location to location, and their mean values are 19.6, 82.87 and 19.44% higher than the worldwide mean values of (226)Ra, (232)Th and (40)K, respectively. The value of (232)Th was found to be higher than that of (226)Ra in 82% of the samples collected for this study. The calculated values of indoor gamma dose rate (DIN) ranged between 89.55 and 194.24 nGy h(-1), and the overall mean value is 63.2% higher than the recommended safe and criterion limit by UNSCEAR. The internal and external hazard indices (H(in) and H(ex)), the representative gamma index and alpha index (I(gamma) and I(alpha)), the annual gonad dose equivalent (AGDE) and the excess lifetime cancer risk (ELCR) were also calculated and compared with the international recommended values. Multivariate statistical analyses were also carried out to determine the relation between the natural radionuclides and various radiological parameters.

Ultrasonic Study of Molecular Interactions in Binary Mixtures at 303 K

The ultrasonic velocity, density and viscosity at 303 K have been measured in the binary systems of 1,4-dioxane and acetone with water. From the experimental data, various acoustical parameters such as adiabatic compressibility (β), intermolecular free length (Lf), free volume (Vf), internal pressure (πi), Rao’s constant (R), Wada’s constant (W) and specific acoustical impedance (Z) were calculated. The results are interpreted in terms of molecular interaction between the components of the mixtures.

Evaluation of natural radioactivity in rocks of Nilgiri hills and their radiation hazard to mankind

Twenty three rock samples were collected from various altitudes of Nilgiri hills, Tamil Nadu, India. A survey was carried out to determine the activity concentration of selected radionuclides ( 238 U, 232 Th, 40 K) by means of gamma-ray spectroscopy using NaI (Tl) detector. From the measured spectra, the mean activity of 238 U, 232 Th, 40 K are 7.13 Bq kg -1 , 30.47 Bq kg -1 and 346.06 Bq kg -1 , respectively. To evaluate the radiological effects, the absorbed dose rate, effective absorbed dose rate, radium equivalent activity, external and internal hazard indices, and radioactivity level index are also calculated. The mean absorbed dose rate of gamma radiation ranged from 11.90 nGy h -1 to 108.22 nGy h -1 . The activity concentration of 238 U, 232 Th, 40 K and the various radiological effects are below the internationally recommended maximum values.

Acoustical Studies on the Ternary Mixture of 1, 4- Dioxane

Ultrasonic velocity, density and viscosity of the ternary mixture of 1, 4dioxane + chloroform + cyclohexane, were measured at 303.15, 308.15 and 313.15 K. The thermodynamical parameters such as adiabatic compressibility (β), intermolecular free length (Lf), free volume (Vf), internal pressure (πi), acoustic impedance (Z), molar sound velocity (R) and molar compressibility (W) have been obtained from the experimental data for all the mixtures, with a view to investigate the exact nature of molecular interaction. Adiabatic compressibility and intermolecular free length decrease with increase in concentration and temperature. The other parameters show almost increasing concentration of solutes. These parameters have been further used to interpret the molecular interaction part of the solute and solvent in the mixtures.