Sciencia Acta Xaveriana

1 - 8

Authors: T. R. Rajasekaran, R. Mary Jenila, J. Benet Charles

Single crystals of pure and MgF2 added Di-Ammonium Penta Fluoro Antimonates , an electro optic crystal has been grown by slow evaporation technique. The grown crystals are subjected to single crystal X-ray diffraction, UV-Vis studies, Fourier Transform Infrared (FTIR) and Microhardness studies. Single crystal X-ray diffraction confirms the crystals belongs to Orthorhombic system.The FTIR spectrum analysis has confirmed the functional groups in the grown crystals. The optical behavior was examined by UV-Vis studies and found that the crystal is transparent in the entire visible region. Microhardness studies reveal the mechanical strength of the grown crystals. The addition of MgF2 makes the surface of the crystal more softer than that of the pure (NH4)2SbF5 crystal.

21 - 38

Authors: T. Mathivanan, A. Lourdusamy, C. Muthulakshmi Sasikala

In graph pebbling games, one considers a distribution of pebbles on the vertices of a graph, and a pebbling move consists of taking two pebbles off one vertex and placing one on adjacent vertex. The pebbling number, f(G), of a graph G is the smallest m such that for every initial distribution of m pebbles on V(G) and every target vertex x, there exists a sequence of pebbling moves leading to a distribution with at least one pebble at x. In this paper, we determine the pebbling number of the square of an odd cycle.

51 - 64

Authors: Ize iyamu O.K., Okojie V.U., Osuide M.O., Ebu S.

A study was carried out to investigate the concentrations, distribution and speciation of some heavy metals such as Cd, Cu, Pb, and Cr in the bottom sediments of Ijana River which has been contaminated by effluent from petroleum exploitation activities. The total concentration levels of Cd, Pb, Cu, and Cr were determined specifically at upstream, effluent zone, downstream and recipient of storm water of the river. Pb, Cu, and Cr were found to be the most abundant metals in the river. The distribution pattern of the river indicates the source of pollution to be land-based. Sequential extraction showed that 30 -60% of Cd, were exchangeable fraction, indicating that Cd in the sediments posed a high risk to local environments while Cu, Pb and Cr were at moderate risk levels. From the relationship between percentage fraction of metal speciation and total metal concentration, it was found that the distribution of Cd, Cu, and Pb in some fractions were dynamic in the process of pollutants migration and the stability of metals in sediment of the Ijana River decreased in the order Cr > Pb > Cd > Cu. The correlation analysis suggest that some of the metals are strongly associated, indicating a common source or chemical similarity. The pollution load index (PLI) of the studied area ranged from 0.10 to 50.78 which indicated the sediments were polluted while the index of geoaccumulation showed that all the sampling points may face a severe metal pollution/contamination problem in the future.