No abstract

The pyrolysis of ethylene has been studied in the temperature range 50G600 "C and the pressure range 15-60 cm. The main products were ethane, propylene, butene, butadiene, and a polymer of molecular weight corresponding to C, or higher. Small amounts of methane, butane, unsaturated C5, unsaturated C6, and benzene were also measured. Of the main products, propylene, butene, and butadiene showed an induction period, as long as several minutes at the lowest temperature. The order with respect to ethylene of ethane, propylene, and butene was close to two and the activation energy of the rates was approxin~ately 40 kcal/~nole. The results have been interpreted in terms of a free radical chain polymerization. It is suggested that the polymer formed is unstable and decomposes to yield the products for which an induction period was observed.

Over the past decade, fixed recorders have come into increasing use for long-term sampling of whale calls in remote ocean regions. Concurrently, the development of several types of autonomous underwater vehicles has demonstrated measurement capabilities that promise to revolutionize ocean science. These two lines of technical development were merged with the addition of broadband (5 Hz to 30 kHz) omni-directional hydrophones to seagliders. In August 2006, the capability of three Acoustic Seagliders (ASGs) to detect whale calls was tested in an experiment offshore Monterey, California. In total, 401 dives were completed and over 107 hours of acoustic data recorded. Blue whale calls were detected on all but two of the 76 dives where acoustic data were analyzed in detail, while humpback and sperm whale calls were detected on roughly 20% of those dives. Various whistles, clicks and burst calls, similar to those produced by dolphins and small whales, were also detected, suggesting that the capability of ASGs can be expanded to sample a broad range of marine mammal species. The potential to include whale call detection in the suite of standard oceanographic measures is unprecedented and provides a foundation for mobile sampling strategies at scales that better match the vertical and horizontal movements of the whales themselves. This capability opens new doors for investigation of cetacean habitats and their role in marine ecosystems, as envisioned in future ocean observing systems.

No abstract

A heuristic rough-surface scattering model is given and compared with experimental results obtained from model rough surfaces. The theoretical model is developed from separate calculations of the coherent and incoherent parts of the scattered field. This allows a direct comparison between theoretical and experimental coherent and incoherent scattering coefficients to be made. The model is consistent in that the correct limiting forms for zero roughness and for large-scale roughness are obtained. Non-Gaussian surface statistics are incorporated in the model and the resulting theoretical predictions agree closely with specular- and forward-scattering experimental data.