Ultrasonic velocimetry studies on different salts of chitosan: Effect of ion size.

In the present investigation, the effect of ion size on the thermodynamical properties such as ultrasonic velocity (U), adiabatic compressibility (ß), acoustic impedance (Z), adiabatic bulk modulus (Ks), relaxation strength (rs) have been obtained for the different salts of chitosan viz., formate (3.5Å), acetate (4.5Å), Succinate (5Å) and Adipate (6Å). To find the effect of ion size, the effect due to water has been removed by calculating the change in ultrasonic velocity (dU), change in adiabatic compressibility (dß), in acoustic impedance (dZ), in adiabatic bulk modulus (dKs), and in relaxation strength (drs). Space filling factor and polarizability has been obtained from the refractive index data through Lorentz-Lorentz relation. FTIR studies confirm the formation of different quaternary salts of chitosan and their size (mass) effects which has been verified with Hooke's law. All the said properties vary both with ion size and concentration of different salts of chitosan. This investigation may throw some light on better usage of chitosan in biomedical applications. The detailed results are presented and discussed.

Laser induced semiconductor-metal transition in a Quantum Well.

The possibility of Semiconductor-Metal Transition under the influence of intense Laser field in a quasi-two dimensional semiconducting system like Al(x)Ga(1-x)As/GaAs Quantum Well in the finite barrier model has been investigated by showing an abrupt change in diamagnetic susceptibility of donor at critical concentration, which can be controlled by the amplitude of Laser field, using variational principle.