M. Ravi Kumar

Semi-interpenetrating polymer network beads of crosslinked chitosan–glycine for controlled release of chlorphenramine maleate

Spherical, semi-interpenetrating polymer network beads of chitosan and glycine, crosslinked with different concentrations of glutaraldehyde were prepared for controlled release of drugs. The structural and morphological studies of the beads were carried out with FTIR and SEM techniques. The swelling behavior of the beads at different time intervals was monitored in solutions of different pH. Structural changes of the beads in response to solution pH were put forward using the data obtained from IR/UV spectral analysis. The release experiments were performed in solutions of pH 2.0 and pH 7.4 at 37°C, using chlorphenramine maleate as a model drug. The results indicate that, chitosan might be useful as a vehicle for controlled release of drugs.

Variation of magnetic susceptibility with electronic polarizability in compound semiconductors and alkali halides

Abstract Valence electron plasma energies have been evaluated from the interionic distances for II–VI and III–V group semiconductors and alkali halides based on the assumption that a linear relationship exists between them within a molecular group of compounds. The estimated valence electron plasma energy values are used in the evaluation of electronic polarizability in the above group of solids. Different new relations are proposed between the magnetic susceptibility and electronic polarizability. Good agreement is observed between the computed and literature values of magnetic susceptibility.

Relationships between lattice energy, interionic distance and plasma energy in II–VI group semiconductors

Abstract Lattice energies have been evaluated from the interionic distances for II–VI group semiconducting compounds based on the assumption that a linear relation exists between lattice energies and interionic distances within a molecular group of compounds. A new linear relation has also been proposed for the evaluation of plasma energy directly from the lattice energy values. The calculated plasma energy values are used in the estimation of electronic polarizability in II–VI group semiconducting compounds. Good agreement is observed between computed and literature values of electronic polarizability.

Temperature and concentration dependence af energy gap and refrective index in certain mixed crystals and semiconductors

Abstract Variations of energy gap (Eg) and refractive index (n) with the concentration have been studied through a set of simple empirical equations proposed in the case of certain mixed crystals of technological importance. Similarly, another set of equations has been proposed to explain the temperature dependence of the energy gap in semiconductors such as GaS, GaSe, GaTe, SnS2 and SnSe2. The results obtained in both cases are found to be in excellent agreement with the experimental values. The proposed equations are proved to be simple and advantageous over others in the sense that less computational work is involved in the calculations of Eg and n.

Studies on the opto-electronic properties of alkali halides from optical electronegativities

Abstract A simple method of evaluating refractive indices from Duffys optical electronegativity values is proposed. In the proposed empirical relations the optical electronegativity for the anion as well as the cation are taken into consideration in order to obtain refractive indices in alkali halides. The refractive indices so obtained are used in the evaluation of electronic polarizabilities in these compounds and the results are found to be in good agreement with the standard values.

Studies on the opto-electronic properties of III-V and II-VI group semiconductors from optical electronegativities

Abstract New empirical relations have been proposed to evaluate bond energies ( E s ) in compound semiconductors, first from the knowledge of optical electronegativities of the constituent ions and secondly from the energy gap values. The validity of the two relations has been tested in the case of certain III–V and II–VI group semiconductors by comparing the calculated values of E s , with those in the literature. From the computed values of E s , refractive indices have been calculated. The Penn gap ( E p ), Fermi energy ( E F ) and S o -parameter for these semiconductors have also been determined. The estimated values of these parameters are utilized to evaluate the electronic polarizabilities (α). The computed values of a compare excellently with the standard data.

The correlation between average nuclear effective charge, refractive index, standard heat of atomization and melting point in tetrahedral semiconductors

Abstract Simple correlations between the average nuclear effective charge, standard heat of formation, refractive index and melting point have been given for some tetrahedral semiconductors. Refractive indices and melting points are evaluated. Results are in fair agreement with the experimental values.