Effective in situ remediation of groundwater requires the successful delivery of reactive iron particles through soil. In this paper we report the transport characteristics of nanoscale zerovalent iron entrapped in porous silica particles and prepared through an aerosol-assisted process. The entrapment of iron nanoparticles into the silica matrix prevents their aggregation while maintaining the particles' reactivity. Furthermore, the silica particles are functionalized with alkyl groups and are extremely efficient in adsorbing dissolved trichloroethylene (TCE). Because of synthesis through the aerosol route, the particles are of the optimal size range (0.1-1 microm) for mobility through sediments. Column and capillary transport experiments confirm that the particles move far more effectivelythrough model soils than commercially available uncoated nanoscale reactive iron particles. Microcapillary experiments indicate that the particles partition to the interface of TCE droplets, further enhancing their potential for dense non-aqueous-phase liquid source-zone remediation.

PERFORMANCE MEASURES FOR TRAFFIC SIGNAL SYSTEMS:AN OUTCOME-ORIENTED APPROACH This monograph is a synthesis of research carried out on traffic signal performance measures based on highresolution controller event data, assembled into a methodology for performance evaluation of traffic signal systems. High-resolution data consist of a log of discrete events such as changes in detector and signal phase states. A discussion is provided on the collection and management of the signal event data and on the necessary infrastructure to collect these data. A portfolio of performance measures is then presented, focusing on several different topics under the umbrella of traffic signal systems operation. System maintenance and asset management is one focus. Another focus is signal operations, considered from the perspectives of vehicle capacity allocation and vehicle progression. Performance measures are also presented for nonvehicle modes, including pedestrians, and modes that require signal preemption and priority features. Finally, the use of travel time data is demonstrated for evaluating system operations and assessing the impact of signal retiming activities.

The rates of deaths and injuries among pedestrians have fallen in recent years, but still remain public health problems as about 5000 pedestrians die each year. Because pedestrians have been shown to be responsible or partially responsible for many of the crashes in which they are involved, we sought to assess the relationship of distracted walking and performing routine cautionary behaviors of pedestrians crossing a busy street in a southwestern city at an intersection, adjacent a university. The behavior of 866 individuals was recorded by trained observers as pedestrians walked across a 105-foot wide street served by a stop light and zebra painted crosswalk. We defined distracted pedestrians as those wearing headphones, talking on a cell phone, eating, drinking, smoking or talking as they crossed the street. Caution was measured by looking left and right, and entering the crosswalk only when the white proceed light was illuminated. We found that only 13.5% of walkers looked left and right and entered the crosswalk while the white light was flashing. Approximately 20% of walkers were distracted as they crossed the street. Regression analysis indicated that distraction was negatively, but weakly associated with displaying cautious pedestrian behaviors. Because traffic lights were routinely ignored and lack of caution was predicted by distraction, we suggest that inexpensive education efforts target pedestrians near college campuses.

Spherical silica particles containing nanoscale zerovalent iron were synthesized through an aerosol-assisted process. These particles are effective for groundwater remediation, with the environmentally benign silica particles serving as effective carriers for nanoiron transport. Incorporation of iron into porous sub-micrometer silica particles protects ferromagnetic iron nanoparticles from aggregation and may increase their subsurface mobility. Additionally, the presence of surface silanol groups on silica particles allows control of surface properties via silanol modification using organic functional groups. Aerosolized silica particles with functional alkyl moieties, such as ethyl groups on the surface, clearly adsorb solubilized trichloroethylene (TCE) in water. These materials may therefore act as adsorbents which have coupled reactivity characteristics. The nanoscale iron/silica composite particles with controlled surface properties have the potential to be efficiently applied for in situ source depletion and in the design of permeable reactive barriers.

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