Viscosity measurements under Newtonian flow conditions have been performed at 40 °C to study the effect of aromatic hydrocarbons (benzene, toluene, or o-xylene) on aqueous micellar solutions of 0.1 M cetylpyridinium bromide (CPB) containing different salts. Two series of salts, viz. (i) inorganic (KX; X ) Cl, Br, or NO3) and (ii) symmetrical quaternary ammonium (R4NBr; R ) H, CH3, C2H5, n-C3H7, or n-C4H9), were used to explore the effect of their nature and concentration. The hydrocarbons had marginal effect on viscosity when added to CPB solutions having no salt. However, in the presence of salts, the viscosity behavior was quite different (synergistic effect). Relative viscosity (ηr) versus concentration of hydrocarbon plots were constructed for various fixed salt concentrations. Most of the time, after reaching a maximum value, ηr decreased on further addition of hydrocarbons, showing a peaked behavior. The peak position (maximum) as well as the viscosity at the maximum, ηr max , was found to be dependent on the nature/ concentration of salts, hydrocarbons, and counterions. However, the viscosity behavior was different with the R4N salts having a longer alkyl (R) part (the synergism progressively diminished). The effect of concentration of salt was reversed and peaked behavior was also lost. This reversal and change in behavior have been explained in terms of the salting-in nature of these salts as compared to the salting-out nature of the salts of series i.

The selective transmission of CCR5-tropic viral variants is unlikely to result simply from differential coreceptor abundance at the genital epithelia.

We sought to characterize how adherent leukocytes at the vessel wall, and the presence of erythrocytes, alter the streamlines (paths) of blood flow in the postcapillary venules. We directly visualized blood flow and leukocyte-endothelial cell interactions in postcapillary venules located in the cremaster muscle of anesthetized mice. Fluid streamlines were visualized by perfusing the cremaster muscle tissue with 0.5-micron fluorescent beads suspended in either buffer or whole blood, to examine the effect that erythrocytes have on the directionality of flow. Acute inflammation was induced in some animals by pretreatment of the vessels with tumor necrosis factor-alpha. To quantify the flow direction, the average deflection angle was defined as a scalar metric. Tracer bead trajectories were measurably altered by the presence of systemic levels of hematocrit, determined in each animal to be about 45%. Deviation from undirectional flow was also found to: (i) decrease with increasing vessel diameter, and (ii) increase with the number of adherent leukocytes. Fluid streamlines in the presence or absence of leukocyte adhesion or red cells agreed qualitatively with those obtained from theoretical calculations of blood flow using multiparticle adhesive dynamics. The microscale characteristics of venular flow are significantly altered during inflammation or changes in local hematocrit.