Ranjini Bandyopadhyay

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Multispeckle x-ray photon correlation spectroscopy was employed to characterize the slow dynamics of a suspension of highly charged, nanometer-sized disks. At wave vectors q corresponding to interparticle length scales, the dynamic structure factor follows a form f(q,t) approximately exp([-(t/tau)(beta)], where beta approximately 1.5. The relaxation time(More)
The nonlinear flow behavior of a viscoelastic gel formed due to entangled, cylindrical micelles in aqueous solutions of the surfactant cetyl trimethylammonium tosilate (CTAT) has been studied. On subjecting the system to a step shear rate lying above a certain value, the shear and normal stresses show interesting time dependent behavior. The analysis of the(More)
The dispersion processes of aqueous samples of clay are studied using ultrasound attenuation spectroscopy. The attenuation spectra that are acquired in the frequency range 10-100 MHz are used to determine the particle size distributions (PSDs) for different concentrations and ages of the clay suspensions. Our analysis, using equivalent spherical diameter(More)
The primary and secondary relaxation timescales of aging colloidal suspensions of Laponite are estimated from intensity autocorrelation functions obtained in dynamic light scattering (DLS) experiments. The dynamical slowing down of these relaxation processes are compared with observations in fragile supercooled liquids by establishing a one-to-one mapping(More)
We explore the origins of slow dynamics, aging and glassy rheology in soft and living matter. Non-diffusive slow dynamics and aging in materials characterised by crowding of the constituents can be explained in terms of structural rearrangement or remodelling events that occur within the jammed state. In this context, we introduce the jamming phase diagram(More)
We report x-ray photon correlation spectroscopy and diffusing wave spectroscopy studies of depletion gels formed from nanoscale silica colloids in solutions of nonabsorbing polymer following the cessation of shear. The two techniques provide a quantitatively coherent picture of the dynamics as ballistic or convective motion of colloidal clusters whose(More)
Three drugs, ibuprofen, aspirin, and erythromycin, are encapsulated in spherical Pluronic F127 micelles. The shapes and the size distributions of the micelles in dilute, aqueous solutions, with and without drugs, are ascertained using cryo-scanning electron microscopy and dynamic light scattering (DLS) experiments, respectively. Uptake of drugs above a(More)
Optical limiting behaviour of suspensions of single-walled carbon nanotubes in water, ethanol and ethylene glycol is reported. Experiments with 532 nm, 15 nsec duration laser pulses show that optical limiting occurs mainly due to nonlinear scattering. The observed host liquid dependence of optical limiting in different suspensions suggests that the(More)