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Recent experiments on transient disturbances generated by three-dimensional roughness have used spanwiseperiodic arrays of geometrically simple cylindrical roughness elements. Connecting these laboratory experiments to more realistic situations requires the study of surfaces with distributed roughness. This is accomplished in this work by numerically generating quasi-random rough surfaces and manufacturing these surfaces using rapid-prototyping technology. Measurements of the disturbances that the rough surface creates in a Blasius boundary layer are obtained for three test configurations corresponding to roughness-based Reynolds numbers of [Re.sub.k] = 164, 227 and 301. The two lower values give laminar flow; the highest value results in localized transition approximately 140 mm downstream of the leading edge of the roughness. All three configurations exhibit transient growth of steady disturbances. Unsteady fluctuations indicate that transition in the [Re.sub.k] = 301 configuration is likely an example of a bypass transition mechanism in which the unsteady-disturbance growth outpaces the stabilizing relaxation of the steady flow. Measurements above the roughness surface in the [Re.sub.k] = 227 configuration provide a phenomenological model for distributed receptivity.

The role of surface roughness in boundary layers continues to be a topic of significant interest, especially with regard to how controlled roughness might be used to delay laminar-to-turbulent transition. Although it may be useful for control, large-amplitude roughness may itself lead to transition. In an effort to understand the breakdown mechanics associated with large-amplitude surface roughness, experiments are conducted to investigate the steady and unsteady disturbances generated by three-dimensional roughness elements whose amplitudes are close to the critical roughness-based Reynolds number [Re.sub.k] for roughness-induced transition. Measurements are obtained in a flat-plate boundary layer downstream of a spanwise array of cylindrical roughness elements at both subcritical and supercritical values of [Re.sub.k]. The steady disturbance field has strong shear in the wall-normal and spanwise directions, and the unsteady streamwise velocities in the roughness elements' wake show evidence of hairpin vortices. The locations of maximum fluctuation intensity correspond to the locations of inflection points in the steady flow streamwise velocity, and this suggests that the fluctuations may result from a Kelvin-Helmholtz-type instability. Temporal power spectra indicate an unstable band of frequencies from 300 to 800 Hz. The Strouhal number associated with the 650-Hz fluctuations that are often observed to be the strongest give Sr = 0.15, a value that is in good agreement with previous findings. At supercritical [Re.sub.k], rapid transition takes place when the unsteady disturbances reach nonlinear amplitudes. The disturbance growth rates indicate that in this situation transition can be understood as a competition between the unsteady disturbance growth and the rapid relaxation of the steady flow that tends to stabilize these disturbances.

This study examined radiography students' perceptions regarding mistreatment during the clinical portion of their education. Results suggest that a majority of students perceived mistreatment and that second-year students were 4 times more likely to perceive mistreatment than first-year students. Most students who perceived mistreatment indicated that the abuse was verbal and came primarily from staff technologists. Most perceived the mistreatment to be slightly important and slightly upsetting. However, approximately one third perceived the mistreatment to be very important and very upsetting. As part of the study, students were asked to suggest preventive measures that could help eradicate abusive behavior in the clinical setting. This study was supported in part by a grant from the Texas Society of Radiologic Technologists., Most health science curricula include a clinical component. Clinical education provides the cornerstone of a student's practical experience and should take place in a warm, supportive and challenging environment.[1] As [...]