Plasma and UV piloton bombardment of an icy object in tile outer solar system can lead to ejection of atoms and molecules from the surface which can, in turn, produce an extended neutral atmosphere. We present new laboratory studies of the sputtering of water ice by keV ions 0C through Ne +) made •using a sensitive microbalance technique that allows measurements at very low ion fluences. These results for the sputtering yield of ice by keV O + ions, the dominant sputtering agents in the Saturnian magnetosphere, are much larger than those used previously to model the neutral cloud associated with the icy satellites. The data presented are used to recalculate previously published sputtering rates for the icy. satellites of Jupiter and Saturn, and for the E-ring grains at Saturn. The new results can account, in part, for the discrepancy between the predicted and observed OH cloud near Tethys in Saturn's inner magnetosphere. We compare the yields induced by the incident ions to the recently measured UV photosputtering yield, and discuss possible synergism between UV photon and plasma ion induced erosion. He, and is also presented. We then compare these yields to recently measured UV photosputtering yield [Westley et al., 1995] and discuss briefly the nature of the ejection process. The new data combined xvith data from previous experiments are then used to recalculate the sputtering rates in the Jovian and Saturnian magnetospheres.

Over the past half-century, ultrasound imaging has become a key technology for assessing an ever-widening range of medical conditions at all stages of life. Despite ultrasound’s proven value, expensive systems that require domain expertise in image acquisition and interpretation have limited its broad adoption. The proliferation of portable and low-cost ultrasound imaging can improve global health and also enable broad clinical and academic studies with great impact on the fields of medicine. Here, we describe the design of a complete ultrasound-on-chip, the first to be cleared by the Food and Drug Administration for 13 indications, comprising a two-dimensional array of silicon-based microelectromechanical systems (MEMS) ultrasonic sensors directly integrated into complementary metal–oxide–semiconductor-based control and processing electronics to enable an inexpensive whole-body imaging probe. The fabrication and design of the transducer array with on-chip analog and digital circuits, having an operating power consumption of 3 W or less, are described, in which approximately 9,000 seven-level feedback-based pulsers are individually addressable to each MEMS element and more than 11,000 amplifiers, more than 1,100 analog-to-digital converters, and more than 1 trillion operations per second are implemented. We quantify the measured performance and the ability to image areas of the body that traditionally takes three separate probes. Additionally, two applications of this platform are described—augmented reality assistance that guides the user in the acquisition of diagnostic-quality images of the heart and algorithms that automate the measurement of cardiac ejection fraction, an indicator of heart health.

We have directly measured the absolute efficiency of the 9.8-eV M-band luminescence from the decay of Ar 2 * excimers in solid Ar bombarded by 1.5-MeV He ϩ and 10-50-keV H ϩ ions. About 54% of the electronic energy deposited by the projectiles is converted to 9.8-eV luminescence energy, or about 5.5 photons per 100-eV deposited. The efficiency is also found to be independent of ion and ion energy for those tested over a range of stopping cross sections from 6.5 to 400 eV/(10 15 atoms/cm 2). This work clearly establishes the M band as the major relaxation pathway for electronically deposited energy in solid Ar, a pathway that is an important source of radiation damage and sputtering and which can be affected by electron emission. ͓S0163-1829͑97͒00535-3͔

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