PubMed Health⌕ Search

Biomedical subjects

BV Tata

Publications and source records attributed to BV Tata.

9 recordsLinked to original sources
PubMed2000

Gas-liquid transition in a two-dimensional system of millimeter-sized like-charged metal balls

Metal balls with a diameter of 1.59 mm, gently rubbed against a dielectric surface using a shaker, are seen to spontaneously exhibit a two-dimensional liquidlike order with macroscopic dimensions, viz., interball distances of several millimeters. This liquidlike order transforms to a gaslike order through coexistence upon decreasing the area fraction of the balls. The measured pair interaction of like-charged balls surprisingly exhibits a long-range attractive term analogous to that in charged colloids.

Journal Article↗
PubMed2000

Reply to "Comment on 'Monte carlo study of structural ordering in charged colloids using a long-range attractive interaction' "

In the Comment by Grier and Crocker (preceding paper) the authors tried to refute our criticism [Phys. Rev. E 58, 2237 (1998)] on their work [J. C. Crocker and D. G. Grier, Phys. Rev. Lett. 77, 1897 (1996)] by simply fitting once again their old experimental data. Grier and Crocker claim that their pair-potential measurements on aqueous dilute suspension of charged colloidal particles confined between charged glass walls at gap of about 8 &mgr;m provide evidence for the failure of Sogami-Ise (SI) theory and demonstrate the applicability of the Dejaguin, Landau, Vervey, and Overbeek (DLVO) theory. Grier and Crocker do not provide additional experimental proof to counter our criticism. We continue to claim here based on our conductivity and conductometric titration measurements, which allow estimating the effective charge and determining the number and nature of the dissociable sites respectively, that their measurements using not well-characterized samples cannot provide clear evidence for the failure of SI theory. With the evidences available in literature, we refute all of the Grier and Crocker comments, including the effect of charged wall confinement on the measured colloidal interactions.

Journal Article↗
PubMed2000

Structure of charged colloids under a wedge confinement

Monte Carlo simulations have been performed to study the influence of a wedge confinement by hard walls on the ordering of charged colloidal particles interacting through screened Coulomb repulsive potential in an aqueous medium. The density distribution of particles for a fixed wedge angle straight theta(0) is studied for different suspension parameters, viz., bulk volume fraction straight phi, salt concentration C(s), and charge Ze on the particles. The density distribution rho(straight theta) along the angular direction and that along the radial direction, rho(r), have been analyzed in different regions of the wedge. Simulations show the formation of layered structure along the angular direction and a large gathering of particles along the wall. The number of layers as well as the density of particles within the layer are found to change as the strength and range of the interaction are varied, whereas the density profiles calculated close to the vertex region showed no significant variation in the density. The radial density profiles rho(r) corresponding to the vertex region show one-dimensional (1D) ordering of particles parallel to the vertex at a distance that is close to a wedge height, h equal to diameter of the particle. This 1D ordering is found to be destroyed upon the addition of salt or lowering the straight phi. The reported experimental observations on the "vacuum phase" are discussed in the light of the present results.

Journal Article↗