http://nopr.niscpr.res.in/handle/123456789/39421 Sat, 10 Oct 2026 15:20:47 GMT 2026-10-10T15:20:47Z http://nopr.niscpr.res.in/handle/123456789/39701 Title: Method for Plotting Sound Ray Paths in the Potential Layer from Bathythermograms Authors: Rao, T. C. S. Abstract: Vertical distribution of temperature in the oceans influences greatly the sound propagation, particularly in bending the rays from their straight line paths. The changes in temperature structure are more common in the surface layers due to heating, cooling, mixing, etc., and contribute for the formation of several layers with different temperature gradients and thicknesses. Plotting of sound ray paths for such bathythermograms becomes difficult and also time-consuming if all these layers are to be considered separately. A method has been evolved which reduces the layers in the potential layer to a maximum of 3 layers irrespective of the number of layers present in the potential layer. The method is applied to several bathythermograph records and the ray paths plotted by this method are found almost similar to those plotted for the original structure of the record. Page(s): 103-109 Mon, 01 Dec 1975 00:00:00 GMT http://nopr.niscpr.res.in/handle/123456789/39701 1975-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/39700 Title: Seismic Profiler and Magnetic Studies off Quilon, South-west India Authors: Rao, T. C. S.; Bhattacharya, G. C. Abstract: Continuous seismic profiling and total magnetic field data were recorded on board R/V Chain in May 1971 along a profile nearly 500 km long, covering the continental shelf, slope and the deep sea off Quilon, the south-west coast of India. Bathymetric features recognized from the seismic reflection records included a Terrace adjacent to the continental shelf edge and the basement Highs in the deep sea. Total magnetic field data showed long wavelengths and high amplitude anomalies over these features. Seismic and magnetic characteristics of these features suggest that the Indian shelf extends further west into the Arabian Sea and has undergone major faulting and subsidence. Page(s): 110-114 Mon, 01 Dec 1975 00:00:00 GMT http://nopr.niscpr.res.in/handle/123456789/39700 1975-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/39699 Title: Sea Levels and Waves Along the Madras Coast Authors: Varadarajulu, R.; Dhanalakshmi, S. Abstract: Annual and seasonal characteristics of tides and waves have been studied with a view to understanding the coastal processes along the Madras Coast in relation to sea levels and waves. Monthly mean sea level has a range of variation of 34 cm with lowest and highest during April and November respectively. Fluctuations in monthly and annual sea levels are attributed to the physical properties of sea water and climate in the neighbourhood of Madras. Most frequent waves from south-west during south-west monsoon and waves from north-east and east during north-east monsoon are correlated with the wind field over the Bay of Bengal during different months. Sediment transport in the nearshore water has been explained in relation to wave characteristics. Geomorphological changes of the neighbouring shore lines have been explained as resulting change in the circulation pattern in the coastal zone after the erection of artificial marine structures. Page(s): 115-123 Mon, 01 Dec 1975 00:00:00 GMT http://nopr.niscpr.res.in/handle/123456789/39699 1975-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/39698 Title: Geochemical behaviour of Natural Thorium and Its Daughter Products in the Sediments of the West Coast of India Authors: Joshi, L. U.; Ganguly, A. K. Abstract: Samples of marine sediments of the west coast of India are leached with 5% ethylenediaminetetraacetic acid for the extraction of thorium from the sediment particle surfaces without attacking the mineral core of the particles. Large variations in 228Th/232Th and 230Th/232Th activity ratios have been observed in the samples collected from different regions of the coastline. Concentrations of 228Ra in sediments and sea water are also determined. Variations in the 228Th/232Th activity ratios are attributed to the preferential leaching of 228Ra by ambient sea water. 230Th/232 activity ratio is mainly dependent on the precipitation of 230Th in adjacent sediments. The dynamic chemical processes in the marine environment of the sediment-water interface are the most important, and equilibria at any given time are established only amongst labile chemical species occurring at the surface of the sediment and the ambient medium. Page(s): 124-127 Mon, 01 Dec 1975 00:00:00 GMT http://nopr.niscpr.res.in/handle/123456789/39698 1975-12-01T00:00:00Z