The first observations of dislocations by TEM were published in 1956. Since then the technique has been developed into an indispensable tool for the materials scientist, not only for the characterization of the extended defect structure of materials, but also for the elucidation of the mechanisms controlling their properties. To mark the 50th anniversary of the original work, this Special Issue consists of reprints of the three original papers and some 22 current state-of-the-art articles, which provide a snapshot of the (...) tremendous power and versatility of the technique at the present time. It is also hoped that this collection of papers from different areas of application and including different techniques might stimulate some cross-fertilization. In this introduction, we comment briefly on the context in which the original work was performed, trace some of the important developments that have taken place in the intervening period and identify some of the outstanding problems. (shrink)

In this paper I explore the relationship between the production and the value of Big Data. In particular I examine the concept of social media ‘prosumption’—which has predominantly been theorized from a Marxist, political economic perspective—to consider what other forms of value Big Data have, imbricated with their often speculative economic value. I take the example of social media firms in their early stages of operation to suggest that, since these firms do not necessarily generate revenue, data collected through user (...) contributions do not always realize economic value, at least in a Marxist sense, and that, in addition to their speculative value, these data have value beyond an economic valence. Instead I argue that in addition to their function as systems for accumulation, social media and their associated data have an affective value, related closely to their economic value, and demonstrate the efficacy of social media as systems designed for the appropriation and circulation of user attention. (shrink)