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Carbon fiber based composite material is of considerable interest for the replacement of steel in large concrete structures, such as bridges, where corrosion is a serious problem. A new two-span concrete highway bridge built in the city of Calgary in 1993 is the first in the world to use carbon fiber composite prestressing tendons in several of its precast concrete deck support girders. We have instrumented a number of these girders with an array of fiber optic intracore Bragg grating sensors in order to monitor the changes in the internal strain that take place over an extended period of time. Afour-channel fiber laser demodulation system was developed for interrogating the set of Bragg grating sensors embedded within the bridge girders. This demodulation system was demonstrated to be rugged, compact and transportable to the bridge construction site where it allowed changes in the internal strain on all three types of prestressing tendon (steel and two types of carbon fiber composite) to be tracked over several months. The same set of structurally integrated Bragg grating sensors has also been used to measure the change in the internal strain within the deck girders arising from both static and dynamic loading of the bridge with a 21 ton truck. This first permanent testbed for structurally integrated Bragg grating sensors demonstrates the feasibility of building into new bridges fiber optic long-term structural monitoring sensing technology that will allow the use of these advanced composite materials to be monitored in a manner not previously practical. The strain information available from this type of monitoring system will assist engineers in their assessment of new materials and innovative design features, and has a potential role in maintenance and repair activities.

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By simultaneously subjecting microbial cells to high amplitude pulsed electric fields and flash heating of the cell suspension fluid, effective release of intracellular contents was achieved. The synergistic effect of the applied electric field and elevated temperature on cell lysis in a flow-through device was demonstrated for Gram-negative and Gram-positive bacteria, and Mycobacterium species. The resulting lysate is suitable for downstream nucleic acid amplification and detection without requiring further preparation. The lysis chamber employs surface enhanced blocking electrodes which possess an etched micro-structured surface and a thin layer of dielectric metal oxide which provides a large effective area and blocks transmission of electrical current. The surface enhanced blocking electrodes enable simultaneous suppression of the rapid onset of electric field screening in the bulk of the cell suspension medium and avoidance of undesired electrochemical processes at the electrode-electrolyte interface. In addition the blocking layer ensures the robustness of the cell lysis device in applications involving prolonged flow-through processing of the microbial cells.