A number of recent studies have attempted to trace diet at different stages of an individual's life by comparing isotope ratios of bone from different gross anatomical sites within the skeleton. In this study we develop this approach further by separating bone of differing mineral densities within one skeletal element, where each density fraction represents a different period of time. Isotope ratios are measured for these fractions. Each density fraction represents a period of bone formation and maturation, where younger (more recently formed) bone is less well-mineralized and therefore less dense than relatively older packets of bone. In an adult, bone is therefore able to partition approximately the last 15 years of life. Bone fractions were recovered by stepped ultracentrifugation in a series of organic solvents of increasing density, and then collagen was recovered by decalcification in dilute acid, and stable carbon isotope ratios ((13)C/(12)C) were measured. Bone density microstructure was checked for bacterial remodelling using backscattered electron imaging in a scanning electron microscope. Our results indicate that the bone density fractionation method is applicable to archaeological material, here extending to a maximum of 5,000 years BP, and that collagen can successfully be extracted from such fractions. The carbon isotope values for bone fractions of different densities patterned out as expected in one modern control bone and in specimens from five archaeological human skeletons, including three precolonial hunter-gatherers and two 18th/19th century individuals. The latter two are known (from previous assessments) to have undergone marked changes in diet during their lifetimes. Postmortem alteration was evident in some of the specimens examined. The bone density fractionation approach has allowed greater resolution of diet than has hitherto been possible and has provided access to the elusive last years and months of an individual's life.
Residential universities are increasingly integrating online interaction within courses in the form of synchronous online chats, asynchronous online discussions and access to interactive resources. This article evaluates the educational effectiveness of online chats within a Humanities postgraduate course and a final year Commerce course. We consider the roles of course design, group dynamics, and facilitation style in the successful use of online collaboration within primarily face-to-face courses, as well as the potential for online collaboration within a blended course design to facilitate more inclusive learning conversations than are possible with exclusively face-to-face interaction.
Several scholars and organizations suggest that institutional policy is a key enabling factor for academics to contribute their teaching materials as open educational resources (OER). But given the diversity of institutions comprising the higher education sector-and the administrative and financial challenges facing many institutions in the Global South-it is not always clear which type of policy would work best in a given context. Some policies might act simply as a "hygienic" factor (a necessary but not sufficient variable in promoting OER activity) while others might act as a "motivating" factor (incentivizing OER activity either among individual academics or the institution as a whole).In this paper, we argue that the key determination in whether a policy acts as a hygienic or motivating factor depends on the type of institutional culture into which it is embedded. This means that the success of a proposed OER-related policy intervention is mediated by an institution's existing policy structure, its prevailing social culture and academics' own agency (the three components of what we're calling "institutional culture"). Thus, understanding how structure, culture, and agency interact at an institution offers insights into how OER policy development could proceed there, if at all. Based on our research at three South African universities, each with their distinct institutional cultures, we explore which type of interventions might actually work best for motivating OER activity in these differing institutional contexts.
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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