Peer interaction may facilitate acquisition through fostering learner production, feedback, and noticing of form. This study examined learners' awareness of form during peer interaction in role-play and discussion tasks over a three-week period of a tertiary intermediate-level French class. The data for the study comprised transcribed recordings of pair and group work interaction in class and subsequent primed interviews with seven students. The study investigated the incidence, focus, and source of language-related episodes arising during the tasks and explored environmental and social considerations impacting on the students' participation in the episodes. The results suggest that the students' willingness to attend to difficulties with language form during peer task-based interaction is affected both by the task and by social considerations.

This paper reports on the deposition and characterization of piezoelectric AlN and AlXSc1-XN layers. Characterization methods include XRD, SEM, active thermo probe, pulse echo, and piezometer measurements. A special focus is on the characterization of AlN regarding the mechanical stress in the films. The stress in the films changed between -2.2 GPa (compressive) and 0.2 GPa (tensile) and showed a significant dependence on film thickness. The cause of this behavior is presumed to be the different mean grain sizes at different film thicknesses, with bigger mean grain sizes at higher thicknesses. Other influences on film stress such as the sputter pressure or the pulse mode are presented. The deposition of gradient layers using those influences allowed the adjustment of film stress while retaining the piezoelectric properties.

Ultrasonic imaging techniques play an important role in endoscopic pre-operative staging and post operative follow-up of tumour patients as well as for the assessment of cardiac insufficiency. However, cancerous lesions offer only low-contrast targets. Therefore, high sensitivity systems with good contrast as well as flexible and robust handling are required to obtain diagnostic accuracy and confidence. We developed a radial scanning ultrasonic catheter with a total diameter of 2.3 mm, which makes use of a LIGA geared micromotor to turn an ultrasonic transducer directly at the tip of the catheter. Connector rings fitted on a shaft as well as sliding contacts transmit the 20/30 MHz signals from the transmitter/receiver of an ultrasound monitor system (Kretz Technik AG, Austria) to/from the rotating transducer. Due to its excellent performance and easy handling the scanner module will be applied in a number of ultrasonic diagnostic applications.

We investigated the potential of the aluminum nitride films to excite ultrasonic waves at frequencies [50 MHz. The deposition process of the aluminum nitride thin film layers on silicon substrates was investigated and optimized regarding their piezoelectric behavior. Large single element transducers were deposited on silicon substrates with aluminum electrodes, under different parameters for the magnetron sputter process, like pressure and bias voltage. Special test setup and a measuring station were created to characterize the sensors. Acoustical measurements were carried out in pulse echo mode up to 500 MHz and the values of piezoelectric charge constant (d 33 ) were determined. As a result, two parameter sets were found for the sputtering process to obtain an excellent piezoelectric charge constant of about 7.2 pC/N maximum. Then the sputtering process with these parameters was used to deposit sensors on various substrate materials and with different electrode sizes.

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