Use of an in situ artificial substrate for biological accumulation and monitoring of aqueous trace metals a preliminary field investigation

A preliminary field study was undertaken to investigate the use of attached periphyton on an artificial substrate as a water column composite sampler for trace metals. Spatial and temporal trends are presented of trace metal biological accumulation terms of the substrate placement in the vicinity of a synthetic fiber chemical manufacturing plant. Seasonal distribution and biological accumulation of antimony, chromium, copper, mercury and zinc is discussed. Statistical analysis of metal accumulated as a function of substrate placement, showed significantly higher levels of chromium for the discharge station compared to the reference stations. In contrast sediment analysis of the discharge station showed only slightly higher levels of zinc and no significant chromium accumulation when compared to a upriver reference station.     

Model-Based Verification of a Security Protocol for Conditional Access to Services

We use the formal language LOTOS to specify and verify the robustness of the Equicrypt protocol under design in the European OKAPI project for conditional access to multimedia services. We state some desired security properties and formalize them. We describe a generic intruder process and its modelling, and show that some properties are falsified in the presence of this intruder. The diagnostic sequences can be used almost directly to exhibit the scenarios of possible attacks on the protocol. Finally, we propose an improvement of the protocol which satisfies our properties.     

Enhanced power from chambered benthic microbial fuel cells

We describe a new chamber-based benthic microbial fuel cell (BMFC) that incorporates a suspended, high surface area and semi-enclosed anode to improve performance. In Yaquina Bay, OR, two chambered BMFC prototypes generated current continuously for over 200 days. One BMFC was pumped intermittently, which produced power densities more than an order of magnitude greater than those achieved by previous BMFCs with single buried graphite-plate anodes. On average, the continuous power densities with pumping were 233 mW/m2 (2.3 W/m3); peak values were 380 mW/m2 (3.8 W/m3), and performance improved over the time of the deployments. Without pumping, high power densities could similarly be achieved after either BMFC was allowed to rest at open circuit. A third chambered BMFC with a 0.4 m2 footprint was deployed at a cold seep in Monterey Canyon, CA to test the new design in an environment with natural advection. The power density increased 5-fold (140 mW/m2 vs 28 mW/m2) when low-pressure check valves allowed unidirectional flow through the chamber.