Systemic praxis in the education of the agricultural systems practitioner

This paper describes the context and the systemic experiential theories that have informed the praxis of educating agricultural systems practitioners. The praxis has involved a process of action research with students and with clients in farming and other rural community organizations. The praxis encourages learners to bring a range of methodologies of inquiry to bear upon problematic issues, contingent upon the nature of such issues. Informed by a number of different theories, and by reflecting on our own work, an earlier model of a nested hierarchy of systems of inquiry has been reconstructed to become a more useful guide to educational strategies: Each contingent methodology can now be seen to have its own learning, meta-learning, and epistemic learning dimensions. A key to enriched learning for responsible changes in agriculture and rural development lies in the facilitation of the consciousness of, and competency at, such a systemic pluralism of methodologies.     

Mid-infrared images of beta Pictoris and the possible role of planetesimal collisions in the central disk

When viewed in optical starlight scattered by dust, the nearly edge-on debris disk surrounding the A5V star beta Pictoris (distance 19.3 pc; ref. 1) extends farther than 1,450 au from the star. Its large-scale complexity has been well characterized, but the detailed structure of the disk's central approximately 200-au region has remained elusive. This region is of special interest, because planets may have formed there during the star's 10-20-million-year lifetime, perhaps resulting in both the observed tilt of 4.6 degrees relative to the large-scale main disk and the partial clearing of the innermost dust. A peculiarity of the central disk (also possibly related to the presence of planets) is the asymmetry in the brightness of the 'wings', in which the southwestern wing is brighter and more extended at 12 microm than the northeastern wing. Here we present thermal infrared images of the central disk that imply that the brightness asymmetry results from the presence of a bright clump composed of particles that may differ in size from dust elsewhere in the disk. We suggest that this clump results from the collisional grinding of resonantly trapped planetesimals or the cataclysmic break-up of a planetesimal.