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A distributed micromachined ultrasound source is presented. Electrostatic actuators operating at frequencies exceeding 100 kHz are coupled to a Helmholtz resonator in order to achieve high output velocities. They consist of a 1200 /spl mu/m/spl times/1200 /spl mu/m/spl times/1.36 /spl mu/m composite diaphragm, a perforated P++ backplate and a 3 /spl mu/m air gap. The actuators cover the entire surface of a 4" wafer and are grouped in four individually addressable quadrants. A robust micromachining technology with >80% yield, employing anodic glass-silicon bonding, dissolved wafer process and advanced deep silicon etching has been developed for fabrication of the actuator array. The dynamic behavior of the diaphragm was studied using laser interferometry, and operation was verified at 96 kHz by acoustic measurement.

Inflammatory pseudotumors of the lung are uncommon and etiologically diverse lesions that often present as solitary masses in the lung. It may be difficult to distinguish these lesions from more commonly encountered lung neoplasms. Inflammatory pseudotumors can also occur in other organs, but the lung is most commonly involved. We describe a 63-year-old male coal miner with a 40-year history of dust exposure, who had a large right middle lobe mass on chest roentgenograms, with slow growth over the 7 years prior to admission. Repeated transthoracic echo-guided biopsies of the mass were indicative of an inflammatory and reactive process. The radiographic, histologic, and clinical findings indicated a diagnosis of inflammatory pseudotumor. The patient refused surgical intervention and was regularly followed at our outpatient clinic. Follow-up chest roentgenograms for 1 year revealed that the tumor size was stable. This case suggested that inflammatory pseudotumor, although uncommon, should be included in the differential diagnosis in a patient with pneumoconiosis and a solitary mass in the lung.

The performance of synthetic jets produced by an electrostatically driven acoustic resonator is discussed. A reduced order model of the coupled membrane motion and acoustic field in the resonator is used to determine thrust and power consumption. The coupled system presents unique features depending on the pressure coupling parameter defined as the ratio of the pressure force on the membrane to its inertia. Thrust output increases as the pressure coupling parameter decreases and for stiffer membranes. Theoretical thrust performance of the order of 50 mN per resonator, andpower to thrust ratio in th e range 20-60 m/s could be achieved. We report also progress in the development of a micro propulsion system based on synthetic jets. Measurements of the membrane deformation and flow at the exit of the synthetic jets are reported. the ejector exit area, and U INTRODUCTION resulting in higher Reynolds number. Also, at The development of high impulse momentum sources for application to micro propulsion and flow control remains a very difficult challenge. Recently zero-mass-flux synthetic jets have been proposed as an actuator for flow control