The work presented details a comprehensive, quantitatively reproducible, and universal assessment method for superhydrophobic materials using the slip-length evaluation.

BackgroundProblems of irrational antibiotic use by prescribers are ongoing and have escalated following reductions in the cost of essential drugs policy. In an attempt to improve prescribing practices for village doctors and rational use of essential drugs, a program designed to audit and monitor drug use was established. However, the effects of the program to control antibiotic resistance and changing the village doctors’ prescribing behaviors remain largely unknown. This study measured the effect of the program on levels of antibiotic use.MethodData was collected covering a 22-month period, before, during and after the program was implemented in rural clinics. Segmented regression analysis with interrupted time series (ITS) data was used to examine whether there had been a significant interaction with the onset of the program in September 2011 and levels of antibiotic use from November 2010 to August 2012. Both serial and 12-month lag autocorrelations were controlled for.ResultsA noticeable drop about 6.15% per month (95% CI: -13.36%; 1.06%, P = 0.089) for the antibiotic use in outpatients, which is lower of effect size assuming that the program has the immediate impact of the program were captured for the immediate effect of the program. Meanwhile, levels of antibiotic use would have continued to decrease by 1.12% per month (P = 0.034) as they did in the absence of the program.ConclusionThe central finding was that the prescription audit and feedback program was associated with significant decreases (P = 0.034) in antibiotic use after its implementation.

So-called "superhydrophobic" surfaces are strongly non-wetting such that fluid droplets very easily roll off when the surface is tilted. Our interest here is in understanding if this is also true, all else held equal, for viscoelastic fluid drops. We study the movement of Newtonian and well-characterised constant-viscosity elastic liquids when various surfaces, including hydrophilic (smooth glass), weakly hydrophobic (embossed polycarbonate) and superhydrophobic surfaces (embossed PTFE), are impulsively tilted. Digital imaging is used to record the motion and extract drop velocity. Optical and SEM imaging is used to probe the surfaces. In comparison with "equivalent" Newtonian fluids (same viscosity, density surface tension and contact angles), profound differences for the elastic fluids are only observed on the superhydrophobic surfaces: the elastic drops slide at a significantly reduced rate and complex branch-like patterns are left on the surface by the drop's wake including, on various scales, beads-on-a-string-like phenomena. The strong viscoelastic effect is caused by stretching filaments of fluid from isolated islands, residing at pinning sites on the surface pillars, of order ∼30 µm in size. On this scale, the local strain rates are sufficient to extend the polymer chains, locally increasing the extensional viscosity of the solution, retarding the drop.

We study the sliding of drops of constant-viscosity dilute elastic liquids (Boger fluids) on various surfaces caused by sudden surface inclination. For smooth or roughened hydrophilic surfaces, such as glass or acrylic, there is essentially no difference between these elastic liquids and a Newtonian comparator fluid (with identical shear viscosity, surface tension, and static contact angle). In contrast for embossed polytetrafluoroethylene superhydrophobic surfaces, profound differences are observed: the elastic drops slide at a significantly reduced rate and complex branch-like patterns are left on the surface by the drop's wake including, on various scales, beads-on-a-string like phenomena. Microscopy images indicate that the strong viscoelastic effect is caused by stretching filaments of fluid from isolated islands, residing at pinning sites on the surface pillars, of the order ∼30 μm in size. On this scale, the local strain rates are sufficient to extend the polymer chains, locally increasing the extensional viscosity of the solution, retarding the drop and leaving behind striking branch-like structures on much larger scales.

No abstract