Action of low frequency vibration on liquid droplets and particles.

Liquids handling is an important issue in biomedical analysis. Two different devices for acoustic manipulation of droplets have already been tested. The first one, more classical, uses a high frequency travelling wave and acoustic streaming. The second one uses low frequency flexural standing waves in a plate. This means of liquid handling is original and easy to implement but the physical principle is not obvious. In order to understand more precisely the phenomena involved we present new observations on droplet displacement between two planes and on the behaviour of a droplet on an inclined vibrating plane with this method. The physical principle involved is discussed. The common acoustic radiation pressure formulation is expressed via the non-linear theory of sound propagation, but in our case the acoustic wavelength is much smaller than the height of a water droplet. To get a better understanding of the phenomenon, further experiments on the internal liquid flow and behaviour of particles in the droplet have been performed. These will be compared with results obtained with particles in a thin water-filled vibrating glass tube. The general conclusion is that the phenomenon is practical to use for droplet displacement even if its complex mechanism is not completely understood.

Evaluation of two concurrent drug-delivery systems in a skilled-nursing facility.

Traditional and modified traditional drug-delivery systems were compared in a 91-bed, two-floor, skilled-nursing facility. Both floors used a traditional system during the first study period. One of the floors then initiated a modified traditional (30-day card) system. Both floors were remeasured two months later for nursing time, pharmacist time, pharmacy-technician time, and error rates. Concordance data were obtained to determine in data-collection methods were reproducible. Savings expected from returnable 30-day cards were extrapolated from wasted medications collected. A significant decrease in nursing administration-time errors was observed on the modified floor, which may have been due to the modified traditional system. Pharmacist and pharmacy technician time were significantly increased by the modified-traditional system. Nursing time was not significantly altered. Potential savings from decreased waste was +677 per year. Nonetheless, the modified traditional system imposed an overall added cost of +942 annually, or approximately +0.24 per prescription. A cost-effective advantage was not demonstrated by the modified traditional system as compared with the traditional system.