ABSTRACT
Using replica integral equations in the reference hypernetted-chain (RHNC) approximation we calculate vapor-liquid spinodals, chemical potentials, and compressibilities of fluids with angle-averaged dipolar interactions adsorbed to various disordered porous media. Comparison with previous RHNC results for systems with true angle-dependent Stockmayer (dipolar plus Lennard-Jones) interactions indicate that, for a dilute hard sphere matrix, the angle-averaged fluid-fluid (ff) potential is a reasonable alternative for reduced fluid dipole moments m( *2)=mu(2)/(epsilon(0)sigma(3))< or =2.0. This range is comparable to that estimated in bulk fluids, for which RHNC results are presented as well. Finally, results for weakly polar matrices suggest that angle-averaged fluid-matrix (fm) interactions can reproduce main features observed for true dipolar (fm) interactions such as the shift of the vapor-liquid spinodals towards lower temperatures and higher densities. However, the effective attraction induced by dipolar (fm) interaction is underestimated rather than overestimated as in the case of angle-averaged ff interactions.
ABSTRACT
Based on replica integral equations in the (reference) hypernetted chain approximation we investigate the structural features and phase properties of a dipolar Stockmayer fluid confined to a disordered dipolar matrix. The integral equations are applied to the homogeneous high-temperature phase where the system is globally isotropic. At low densities we find the influence of dipolar interactions between fluid (f) and matrix (m) particles to be surprisingly similar to the previously investigated effect of attractive isotropic (fm) interactions: the critical temperature of the vapor-liquid transition decreases with increasing (fm) coupling, while the critical density increases. The anisotropic nature of the dipolar (fm) interactions turns out to play a more dominant role at high fluid densities where we observe a pronounced sensitivity in the dielectric constant and a strong degree of local orientational ordering of the fluid particles along the local fields generated by the matrix. Moreover, an instability of the dielectric constant, which is a precursor of ferroelectric ordering occurring both in bulk Stockmayer fluids and in fluids in nonpolar matrices, is observed only for very small dipolar (fm) couplings.
ABSTRACT
The study sought to determine the effectiveness of a model program of psychiatric care for human immunodeficiency virus (HIV)-infected patients. This was a cohort study of 126 HIV-positive outpatients referred for psychiatric evaluation and treatment (average follow up of 14 months) in a HIV-dedicated primary-care outpatient clinic in the inner city. A global outcome measure (encompassing symptom relief, functioning, and HIV-risk behaviors), and a measure of abstinence from alcohol and illicit substances were used. Fifty percent of patients improved, with 19% "nearly well" at follow-up. Abstinence was achieved 48% of the time. Good compliance with treatment and the absence of injection drug use were the primary predictors of good outcomes. Of the compliant patients, 94% improved, with 45.7% being nearly well. Psychiatric treatment of HIV-infected patients is effective when located in the HIV primary-care setting and administered by a multidisciplinary team under the direction of a psychiatrist, using evidence-based interventions.
