Broadband sound propagation in shallow water and geoacoustic inversion.

Part of an experiment to test a measurement package in a shallow water region in the Gulf of Mexico was designed to gather broadband acoustic data suitable for inversion to estimate seabed geoacoustic parameters. Continuous wave tow acoustic signals at multiple frequencies and broadband impulsive source signals were recorded on a horizontal line array in a high-noise environment. Simulated annealing with a normal mode forward propagation model is utilized to invert for a geoacoustic representation of the seabed.

Hematologic changes after daily asymptomatic dives.

Hematologic alterations after daily exposure to compression/decompression in open water are described. A standard dive to 100 fsw for 25 min was employed. Erythrocytes decreased postdive, reaching an apparent minimun 4 to 6 h after exposure and recovering to normal or supranormal value by 20 h postdive.