SYNTHESIS OF PbS NANOCRYSTAL/FUNCTIONALIZED CONDUCTING POLYMERS FOR PLASTIC SOLAR CELLS

Lead-based nanocrystals (NCs) are promising materials for high-efficiency solar cells since they are able to generate multiexcitons with high efficiency. One complication of utilizing these NCs is the insulating ligands capping their surfaces. In this paper, we have successfully developed and characterized a phosphonate-functionalized poly-3-hexylthiophene (POP3HT-50) and used it in the direct synthesis of PbS NCs within the polymeric host matrix without extraneous ligands. Devices made of POP3HT-50/PbS nanocomposites show an order of magnitude improvement in η when compared to that reported for a P3HT/ PbS device (η = 0.011% versus 0.001%). The improved performance is consistent with better electronic contact between PbS NCs and POP3HT-50.

Computer Simulation Modeling for Recreation Management: A Study on Carriage Road Use in Acadia National Park, Maine, USA

/ The number of visits to outdoor recreation areas has increased dramatically in the last three decades, leading managers and researchers to wonder if there is a limit to the amount of use a resource such as a park can accommodate. One of the difficulties in addressing this carrying capacity-related question has been the complex nature of visitor travel patterns on often extensive networks of roads and trails. Systematic direct observation is often impractical and anecdotal information is usually inadequate. This study explores the utility of computer simulation as a tool for describing visitor travel by building a dynamic model of visitor travel on the carriage roads of Acadia National Park, Maine, USA. The simulation model uses empirical inputs such as travel routes and travel speeds to generate simulated recreation days on the carriage roads. Data on persons-per-viewscape (PPV) conditions were then gathered from multiple model runs and incorporated into the National Park Service's visitor experience and resource protection (VERP) planning process. Results show that PPV conditions under present-day use levels do not violate proposed standards of quality. Results also show likely PPV conditions under scenarios of increasing use and in different areas within the carriage road system. Goodness-of-fit validity tests indicate the model is an accurate representation of the actual system. The findings of this study suggest that computer simulation is useful for estimating current carrying capacity conditions, predicting future conditions, and guiding related research. KEY WORDS: Computer simulation modeling; Carrying capacity; Recreation management; Acadia National Park