The instilled fluid dynamics and surface chemistry of polymers in the preocular tear film.
Using slit lamp fluorophotometry it was demonstrated that the rate of drainage of a vehicle placed in the eye increased with increasing volume and that polymer solutions increased the thickness of the precorneal tear film (PTF). By increasing the viscosity of the delivery vehicle, (e.g., a hydroxypropylmethylcellulose polymer solutions), the PTF retention of fluorescein could be increased. The increased retention was shown to be due to an increase in the tear reservoir volume provided by the more viscous solutions. The PTF retention of fluorescein in a polyvinyl alcohol (PVA) vehicle was not as viscosity dependent, although PVA did seem to produce greater initial PTF fluorescence. This suggested that PVA initially produced a thicker PTF. The PTF retention of fluorescein by five commercial solutions did not have any relation to their wetting properties. The only good correlation with fluorescein retention in the PTF measured, seemed to be the ability of different polymer solutions to stabilize a thick layer of water as measured by the spontaneous spreading of polymer molecules at the air/liquid interface on wet glass surfaces. This model was designed to simulate tear film spreading in vivo. The results suggest that different polymer solutions may produce thicker PTF's than normal by virtue of their ability to drag water with them as they spread over the ocular surface with each blink. Mechanisms by which polymer solutions may increase the thickness of the PTF are discussed. (+info)
Effect of surface tension on alveolar surface area.
At fixed lung volume (VL), alterations in surface tension change alveolar surface area (S) and lung recoil (PL). Wilson (26), using data from fixed lungs (1, 9), quantified the isovolume change in S with PL. We reexamined this question in fresh excised rabbit lungs, with two important differences. First, we measured fractional changes in S by using diffuse light scattering, avoiding the potential upset of the balance of tissue and surface forces during fixation. Second, we altered surface tension by ventilating the lungs with nebulized polydimethylsiloxane, with much less residual fluid compared with lavage. We found that S decreased at low and mid VL (treatment surface tension > control) by about half of Wilson's estimates and was nearly unaffected by treatment at high VL. This suggests that with increased surface tension there is 1) greater septal retraction in lungs fixed by vascular perfusion compared with unfixed lungs and 2) a greater increase in PL and less loss of S than would have been predicted. (+info)
The wetting agent required for swarming in Salmonella enterica serovar typhimurium is not a surfactant.
We compared the abilities of media from agar plates surrounding swarming and nonswarming cells of Salmonella enterica serovar Typhimurium to wet a nonpolar surface by measuring the contact angles of small drops. The swarming cells were wild type for chemotaxis, and the nonswarming cells were nonchemotactic mutants with motor biases that were counterclockwise (cheY) or clockwise (cheZ). The latter strains have been shown to be defective for swarming because the agar remains dry (Q. Wang, A. Suzuki, S. Mariconda, S. Porwollik, and R. M. Harshey, EMBO J. 24:2034-2042, 2005). We found no differences in the abilities of the media surrounding these cells, either wild type or mutant, to wet a low-energy surface (freshly prepared polydimethylsiloxane); although, their contact angles were smaller than that of the medium harvested from the underlying agar. So the agent that promotes wetness produced by wild-type cells is not a surfactant; it is an osmotic agent. (+info)
Relation of aphicidal activity with cuticular degradation by Beauveria bassiana SFB-205 supernatant incorporated with polyoxyethylene-(3)-isotridecyl ether.
The application of Beauveria bassiana SFB-205 supernatant incorporated with polyoxyethylene-(3)-isotridecyl ether (TDE-3) significantly reduced the population of two species of aphids including cotton aphid, Aphis gossypii, and green peach aphid, Myzus persicae, much higher in cotton aphid, compared with supernatant incorporated with Tween 80, which allows the relationship of aphicidal activity with the degradation of aphid cuticles to be determined. Overall, the degradation of the cuticles induced by the supernatant was more remarkable in conjunction with TDE-3 than Tween 80, and this phenomenon was more observable in cotton aphid through SDS-polyacrylamide gel electrophoresis, revealing high correlation with their aphicidal activities. (+info)
Superhydrophilicity and antibacterial property of a Cu-dotted oxide coating surface.
Viscosity and adhesion strength of cream-type denture adhesives and mouth moisturizers.
We evaluated adhesion strength to acrylic resins under various experimental conditions and viscosity of 4 cream-type denture adhesives and 2 mouth moisturizers. The viscosity was determined by a sine-wave vibro viscometer. The adhesion strength tests were performed with 2 resin plates at a universal tester. In Method A, various constant thicknesses of material layer were tested and tensile strength was measured, while in Method B a constant load was applied before measurement. Five tests were carried out for each measurement. With Method A, adhesion strength increased exponentially as the layer got thin. Effect of the material thicknesses (contribution ratio rho=79.0%) was much larger than that of material type (rho=15.3%). Materials with higher viscosity had greater levels of adhesion strength in Method A, whereas those with the higher viscosity had lower levels of adhesion strength in Method B. Adhesion strength was significantly affected by the experimental condition prior to applying tension. (+info)