Fingering instability down the outside of a vertical cylinder

We present an experimental and numerical study examining the dynamics of a gravity-driven contact line of a thin viscous film traveling down the outside of a vertical cylinder of radius R. Experiments on cylinders with radii ranging between 0.159 and 3.81 cm show that the contact line is unstable to a fingering pattern for two fluids with differing viscosities, surface tensions, and wetting properties. The dynamics of the contact line is studied and results are compared to previous studies of inclined plane experiments in order to understand the influence substrate curvature plays on the fingering pattern. A lubrication model is derived for the film height in the limit that ε = H/R≪1, where H is the upstream film thickness, and in terms of a Bond number ρgR3/(γH), and the linear stability of the contact line is analyzed using traveling wave solutions. Curvature controls the capillary ridge height of the traveling wave and the range of unstable wavelength when ε = O(10-1), whereas the shape and stability of the contact line converge to the behavior one observes on a vertical plane when ε ≤ O(10-2). The most unstable wave mode, cutoff wave mode for neutral stability, and maximum growth rate scale as 0.45 where = ρgR2/γ ≥ 1.3, and the contact line is unstable to fingering when ≥ 0.56. Using the experimental data to extrapolate outside the range of validity of the thin film model, we estimate the contact line is stable when <0.56. Agreement is excellent between the model and the experimental data for the wave number (i.e., number of fingers) and wavelength of the fingering pattern that forms along the contact line.

Training in Mental Health: Evaluation of the Telephone Conference Network

The Telephone Conference Network, sponsored by The Pennsylvania State University's Coordinating Council for Health Care, is designed as a cost-effective format for providing inservice training in geriatric mental health for individuals who serve the elderly. Institutions which subscribe to the Telephone Conference Network are equipped with a conference speaker and telephone hook-up providing a two-way line of communication, and may choose from a variety of inservice programs. Mailed evaluations were completed by participants (N=73) in the "Skills to Manage Moods" program, a series of four 1-hour sessions designed to teach participants the skills needed to help patients cope with depression and to deliver the program to others. The majority of respondents reported high levels of satisfaction with the Telephone Conference Network system and the specific program in which they participated. Although 85 percent reported that they would be able to use the skills learned in the program on the job, 50 percent reported that they would not be interested in teaching these skills to others. The convenience and efficiency of the Telephone Conference Network were the most frequently mentioned strengths of the system, while the physical facilities and the program delivery format adopted by the individual institutions were the most frequently mentioned weaknesses. These data suggested several recommendations for Network subscribers and for professionals offering telephone conference programs, including ensuring optimal class enrollment and adequate physical facilities, and participant involvement in program implementation.