Agricultural systems are situated within social and political environments that have tremendous influence on how they operate. If agricultural systems are to be sustainable, it is critical to understand how they are influenced by social and political factors. An expert panel approach was used to identify and rank the importance of social and political factors on agricultural systems in the US and to provide some insights into their impacts, interactions and mechanisms of influence. The panel identified a wide range of social and political factors that affect agricultural systems. The factors were divided into three categories: internal social factors, external social factors and political factors. Factors from each of the three categories were highly ranked, indicating that no single category dominated the others. Although there were contrasting views about the importance of some factors, there was strong consensus about many of them. Globalization and low margins that require increased scale and efficiency were identified as the two most important factors affecting agricultural systems. Several newly emerging factors were identified as well as factors needing further research. A comprehensive understanding of these factors is imperative to help guide scientific research so that beneficial discoveries are accepted and used, and to ensure that policy decisions enhance the future sustainability of agricultural production.

The sensitivity of Porous Silicon (PSi) to the presence of charged molecules and its large internal surface area represent two important properties that make this material and ideal candidate for electrical biosensor development. We have demonstrated the use of a macroporous silicon electrical sensor for label-free detection of DNA hybridization in real time as well as identification of organic solvents in liquid phase. Binding of DNA inside the PSi matrix induces a change in capacitance and conductance. Having demonstrated the suitability of macroporous silicon layers for real time detection of DNA hybridization on single devices, we have extended our findings to the fabrication of a microarray with individual device electrical addressing capabilities. On a crystalline p-type silicon wafer, process steps such as KOH etching and electrochemical dissolution are employed in selected regions to create a free-standing porous membrane for sensing applications. Individual electrical contacts are made on the front side of the wafer while the infiltration of the probe and target molecules is done from the back avoiding any direct interaction of the molecules with the contact sites. We will report on the design considerations of the electrical porous silicon array and the preliminary results obtained using synthetic DNA as a model molecule.

The highly sensitive surface of porous silicon (PSi) and the possibility to measure changes in its electrical properties can be used for electrical biosensor applications. The sensing scenario can be extended from the well-characterized organic solvents and pH sensors to detection of biological processes involving the presence of charged molecules. We have investigated the change in electrical properties (capacitance and conductance) of macroporous silicon layers upon exposure to organic solvents and water. Evaluation of our sensor to detect a biological event was done by addressing DNA hybridization. As opposed to the previous work published in this field, in our devices the electrical contact is made on the crystalline silicon (c-Si) substrate. This allows a complete exposure of the surface to the sensing species and reduces the generation of ionic currents through the porous silicon matrix. We will report results of a complete characterization of our device including response speed, selectivity and sensitivity.