Experimental demonstration of rainbow trapping of elastic waves in two-dimensional axisymmetric phononic crystal platesa)

Structures with specific graded geometries or properties can cause spatial separation and local field enhancement of wave energy. This phenomenon is called rainbow trapping, which manifests itself as stopping the propagation of waves at different locations according to their frequencies. In acoustics, most research on rainbow trapping has focused on wave propagation in one dimension. This research examined the elastic wave trapping performance of a two-dimensional (2D) axisymmetric grooved phononic crystal plate structure. The performance of the proposed structure is validated using numerical simulations based on finite element analysis and experimental measurements using a laser Doppler vibrometer. It is found that rainbow trapping within the frequency range of 165-205 kHz is achieved, where elastic waves are trapped at different radial distances in the plate. The results demonstrate that the proposed design is capable of effectively capturing elastic waves across a broad frequency range of interest. This concept could be useful in applications such as filtering and energy harvesting by concentrating wave energy at different locations in the structure.

The impact of behavioural skills training on the knowledge, skills and well-being of front line staff in the intellectual disability sector: a clustered randomised control trial

BACKGROUND

Staff with varying backgrounds and educational qualifications can be effectively trained to implement procedures in line with evidence-based practice. Behavioural skills training (BST) is a competency-based training model used to effectively educate a broad selection of professionals, including front line staff, in a range of work-related skills. However, BST has yet to be evaluated in a large group-based experiment.

METHODS

This study involved a parallel cluster randomised control trial. Six service sites, with a total of 54 participants, were randomised to the intervention condition using the 'coin toss' method. The intervention condition used BST to coach intellectual disability staff in reinforcement, systematic prompting, functional communication training and task analysis. Six service sites, with a total of 50 participants, were also randomised to a control condition in which generalised training in behavioural interventions was restricted. Recruited service sites were randomly assigned to the intervention condition (N = 6, n = 54) or the control condition (N = 6, n = 50) at one point in time, immediately after recruitment and before baseline testing took place. Allocations were stratified by service type (residential or day) and geographical region. One member of the research team allocated service sites using the 'coin toss' method, and another member, blind to the allocations, decided which experimental arm would receive the intervention and which would be designated as control. It was not possible to mask the intervention from participants, but they were recruited prior to randomisation.

RESULTS

Participants in the intervention condition demonstrated statistically significant improvements in their knowledge scores over the study period. Participants in the control condition showed no change or a statistically significant decrease in their knowledge scores. No statistically significant changes to well-being were observed for either group. There was clear evidence of knowledge maintenance, as well as skill acquisition and subsequent generalisation to the workplace environment, among participants in the intervention condition. Participants also evaluated the BST intervention positively.

CONCLUSIONS

Results support BST as a method for disseminating evidence-based practice to front line staff working with adults with intellectual and developmental disabilities.

Diagnosis of breast calcifications: comparison of contact, magnified, and television-enhanced images

Matched contact and microfocal-spot-magnified images of 31 breasts, each containing a cluster of microcalcifications within a biopsy-proved benign (n = 21) or malignant (n = 10) lesion, were evaluated. Each matched set consisted of one image magnified 1.5 or 2.0 times by a microfocal spot; one contact film-screen mammogram; and one television-digitized, enhanced, and optically magnified contact film-screen mammogram. Three experienced mammographers and three senior diagnostic radiology residents with 2 weeks of training in mammography interpreted the calcifications. The average area under the receiver-operating-characteristic curve for the experienced mammographers was 0.60 for contact radiographs, 0.61 for the television-digitized images, and 0.69 for the microfocal-spot-magnified radiographs. The less experienced senior residents scored below a random choice, 0.44, for the television-digitized images; 0.51 for contact radiographs; and 0.69 for the microfocal-spot-magnified radiographs. We conclude that when evaluating microcalcifications, radiologists without extensive experience in mammography should not substitute television-digitized and enhanced contact mammograms for microfocal-spot-magnified mammograms; rigorous clinical evaluation is needed before this system is accepted for clinical use.

Digital mammography. A comparison of two digitization methods

A preliminary study of 40 different radiodense breasts digitized with a Fuji high resolution BAFBr:EU2+ imaging plate enabled us to establish acceptable enhancement procedures with a Fuji Computer Radiology 201 system. Screen-film images of 36 of these breasts were also digitized and enhanced on a Damon DETECT TV system. Three radiologists specializing in mammography reviewed each pair of images. For the 20 normal examinations, both digital methods were considered equivalent in image quality, while for the 16 cases containing pathology (masses and/or calcifications) the TV system was considered to provide the best image quality twice as often as the laser scanned system. The radiologists rejected both methods of enhancement for 8% of the images. Despite cost differences between the two systems, both have equal capability in penetrating dense breasts. However, both systems have several significant deficiencies which preclude their clinical use. At the present time, there is no objective justification for using either system for breast imaging other than in an experimental capacity.