Elemental and compound semiconductors, including widebandgap semiconductors, are critically examined for high-power electronic applications in terms of on-state resistance, power loss caused by junction leakage, heat conduction, radiation hardness, high-frequency performance, and high-temperature operation. Based on a new analysis applicable to a wide range of semiconducting materials and by using the available measured physical parameters, it is shown that widebandgap semiconductors such as SIC and diamond could offer significant advantages compared to either silicon or group 111-V compound semiconductors for these applications. The new analysis uses peak electric field strength at avalanche breakdown as a critical material parameter for evaluating the quality of a semiconducting material for highpower electronics. Theoretical calculations show improvement by orders of magnitude in the on-resistance, twentyfold improvement in the maximum frequency of operation, and potential for successful operation at temperatures beyond 600°C for diamond high-power devices. New figures of merit for power-handling capability that emphasize electrical and thermal conductivities of the material are derived and are applied to various semiconducting materials. It is shown that improvement in power-handling capabilities of semiconductor devices by three orders of magnitude is feasible by replacing silicon with silicon carbide; improvement in power-handling capability by six orders of magnitude is projected for diamond-based devices.

Decubitus ulcers are a worldwide health care concern affecting tens of thousands of patients and costing over a billion dollars a year. Susceptibility to pressure ulcers comes from a combination of external factors (pressure, friction, shear force, and moisture), and internal factors (e.g. fever, malnutrition, anaemia, and endothelial dysfunction). Often, enough damage is done to create the basis for a decubitus ulcer after as little as 2 h of immobility, a situation which may be difficult to avoid if the patient must undergo prolonged surgery or remain bedridden. Damage owing to pressure may also occur hours before the patient receives medical attention, especially if the patient falls or becomes immobilized owing to a vascular event. Several classification systems for decubitus ulcers have been described, based on where injury first occurs. The histologic progression of decubitus ulcers is a dynamic process involving several stages, each having characteristic histologic features. A team-focused approach integrating all aspects of care, including pressure relief, infection control, nutrition, and surgery, may improve healing rates. With accurate risk assessment and preventative care, we can hope to minimize complications and mortality owing to decubitus ulcers.

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