Autonomous underwater vehicles (AUV) are untethered submarine robots that can be used to carry out deepwater mapping and seabed-characterization surveys (seafloor to 150-m depth). AUV surveys are used in the marine petroleum industry for various exploration, environmental, geohazard, and engineering applications. Typically, AUVs are launched from a mother ship. They execute a preprogrammed survey pattern and are recovered, and the survey data are downloaded for analysis. Data on water depth, geomorphology, stratigraphy, and structure ranging downward to 150 m below the seafloor routinely are collected using a variety of sensing technology. Principal survey tools include a multibeam echo sounder to provide water column, bathymetric, and seafloor-reflectivity data; a side-scan sonar to provide high-resolution seafloor imagery; and a subbottom profiler (1-to 24-kHz seismic-reflection tool) to show subseafloor stratigraphy and structural features. Other AUV survey tools can include still cameras, lidar scanners, magnetometers, geochemical sensors (CO 2 , CH 4 , PAH, dissolved oxygen), and temperature and salinity sensors. AUV surveys help deepwater exploration and development to proceed efficiently and safely and thus have become an indispensable tool for deepwater operations.

No abstract

Tetanus is a life-threatening disease that continues to have a high prevalence in developing countries. Severe muscle spasms often require patients to receive tracheostomy, high-dose sedatives, and sometimes prolonged neuromuscular blockade. Magnesium sulfate (MgSO4) infusion has great promise as an adjunct treatment for severe tetanus, as it may allow clinicians to decrease the dose of other sedative medications. Although the mechanism of action of MgSO4 is not well understood, it appears to attenuate both the muscle spasms and autonomic instability associated with severe tetanus infections. However, MgSO4 infusions are often managed based on serial measurements of serum magnesium levels and other laboratory tests such as arterial blood gases, which can be difficult to obtain in resource-poor settings. We describe a case of severe tetanus in Bhutan managed through the use of magnesium infusion titrated solely to physical examination findings.