Accelerated closure of biopsy-type wounds by mechanical stimulation.

OBJECTIVE: To determine whether a device designed to provide low-intensity, low-frequency mechanical stimulation improves healing time of acute wounds. DESIGN: Repeated measures using mechanical stimulation on one side of a rat and sham stimulation on the contralateral side. SETTING: Academic animal facility. PARTICIPANTS: Six male Sprague-Dawley rats, approximately 400 g. INTERVENTION: Mechanical stimulation of 4-mm biopsy wounds in rats was produced through the use of permanent magnets cyclically attracted and repelled by activation of an electromagnet by a square wave generator at a frequency of 1 Hz and a force equivalent to 64 mm Hg pressure. MAIN OUTCOME MEASURE: Days to complete closure of 4-mm biopsy punch wounds. MAIN RESULTS: This form of stimulation reduced time to close the biopsy wounds by nearly 50%. Mechanically stimulated wounds closed in 3.8 +/- 1.6 days (mean +/- SD) compared with 6.8 +/- 1.9 days for sham-stimulated wounds (P = .0002). CONCLUSION: Production of a mechanical stimulation device with a miniaturized controller and power source and trials on humans are needed to determine the efficacy and potential cost savings of such a device in the management of wounds.

At-sea measurements of sound penetration into sediments using a buried vertical synthetic array.

Acoustic bottom penetration experiments were carried out in a medium-grain sandy bottom at a site in St. Andrews Bay, Florida. These investigations used a new buried, vertical, one-dimensional synthetic array system where a small hydrophone was water-jetted into the sediment to a depth of approximately 2 m. Once buried, this hydrophone was mounted to a vertical robotics stage that translated the hydrophone upward in 1-cm increments. A broadband (3 to 80 kHz) spherical source, positioned 50 cm above the sediment-water interface, was used to insonify the sediment. Measurements were made with insonification angles above and below the critical angle by changing the horizontal distance of the source relative to the insertion point. This new measurement system is detailed, and results are presented that include temporal, frequency, and wavenumber analysis for natural and roughened interfaces. The measured compressional sound speed and attenuation are shown to be self-consistent using the Kramers-Kronig relation. Furthermore, only a single fast compressional wave was observed. There was no observation of a second slower compressional wave as predicted by some applications of the Biot model to unconsolidated water-saturated porous media.