Magellan started mapping the planet Venus on September 15, 1990, and after one cycle (one Venus day or 243 Earth days) had mapped 84% of the planet's surface. This returned an image data volume greater than all past planetary missions combined. Spacecraft problems were experienced in flight. Changes in operational procedures and reprogramming of onboard computers minimized the amount of mapping data lost. Magellan data processing is the largest planetary image‐processing challenge to date. Compilation of global maps of tectonic and volcanic features, as well as impact craters and related phenomena and surface processes related to wind, weathering, and mass wasting, has begun. The Magellan project is now in an extended mission phase, with plans for additional cycles out to 1995. The Magellan project will fill in mapping gaps, obtain a global gravity data set between mid‐September 1992 and May 1993, acquire images at different view angles, and look for changes on the surface from one cycle to another caused by surface activity such as volcanism, faulting, or wind activity.

Wikis represent flexible tools functioning as open-ended environments for collaboration while also offering process and group writing support. Here we focus on a project to innovate the use of wikis for collaborative writing within student groups in a final-year undergraduate political science course. The primary questions guiding our research were in what ways could wikis assist collaborative learning in an undergraduate course in political science and how we could support educators' in the effective use of wikis? Curiously, wikis may serve as a mediating artifact for collaborative writing even among students who are reluctant to post online drafts. The paper raises questions concerning the nature and limits of lecturer and tutor power to deliver transformative educational innovations in relation to the capacity of students to embrace, comply with, or resist such innovation. In analysing the negotiation of the use of wikis in the course by and among the lecturer, tutors, and students, we draw on two principles in activity theory, which Yrjo Engestrom argued are central to his model of expansive learning: multi-voicedness and contradictions [Engestrom, Yrjo . (1987). Learning by expanding: An activity-theoretical approach to developmental research. Helsinki: Orienta-Konsultit; Engestrom, Yrjo . (2001). Expansive learning at work: Toward an activity theoretical reconceptualization. Journal of Education and Work 14(1), 133-156.]. We add a third principle, transparency, to more fully capture what we observed.

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This paper examines Letters to the Editor (LEs) in two Zimbabwean magazines in 1990. Zimbabwe celebrated 10 years of independence in 1990 and the marking of a decade stimulated evaluation of the achievements of independence. The LEs in independently owned magazines provided a site for non-elite writers to engage in an alternative discourse to the `celebratory' discourse of the state-controlled daily press. We examine the corpus of LEs in terms of discourse structure and lexico-grammatical features, using critical discourse analysis and computer concordancing to identify features of this alternative discourse. We conclude that there is an emergent `discourse of disillusionment' which suggests the gradual erosion of the post-independence national consensus. We discuss briefly the relevance of this discourse to the role of media and civil society in Zimbabwe.

Summary.We conducted a review of published literature reporting relationships between the size of plant modules and the abundance or performance of gall insects. Insects in the family Tenthredinidae were recently reviewed and thus omitted from this review. The abundance or performance of approximately half of 53 species examined was positively related to plant module size. However, negative and parabolic relationships were found for all major insect families with sample sizes > 5 (i.e., Adelgidae/Aphididae, Cynipidae and Cecidomyiidae for abundance and Adelgidae/Aphididae for performance). This suggests that relationships between plant module size and the abundance or performance of non-tenthredinid gallers, although often positive, are best characterized as variable.

Abstract-Our review highlights research during the past century focussed on the population ecology of outbreak-prone insect defoliators in Canadian forests. Based on reports from national and provincial surveys that began in the 1930s, there have been at least 106 insect defoliators reported to outbreak, most of which are native Lepidoptera, Hymenoptera (sawflies), or Coleoptera (in order of frequency from most to least). Studies comparing life-history traits of outbreak versus non-outbreak species to better understand why certain species are more outbreak-prone indicate several traits especially common among outbreak species, including egg clustering and aggregative larval feeding. There have been at least 50 time-series studies examining the spatiotemporal population behaviour of 12 major defoliator species. These studies provide evidence for both regular periodicity and spatial synchrony of outbreaks for most major species. Life-table studies seeking to understand the agents causing populations to fluctuate have been carried out for at least seven outbreak species, with the majority identifying natural enemies (usually parasitoids) as the major driver of outbreak collapse. Our review concludes with several case studies highlighting the impact and historical underpinnings of population studies for major defoliator species and a discussion of potential avenues for future research.

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