Géraldine Castets

Laboratory implementation of X-ray diffraction/scattering computed tomography

This article demonstrates the possibility to perform X-ray diffraction/scattering computed tomography experiments with a laboratory diffraction setup. This technique is useful to characterize samples with inhomogeneities on a length scale of a couple of hundred micrometres. Furthermore, the method can be applied to preliminary phase-selective imaging prior to higher-resolution characterization using synchrotron radiation. This article presents the results of test experiments carried out on a rhombohedral C60 sample previously studied at the ESRF.

Postcards from the outside: European-contact rock art imagery and occupation on the southern Arnhem Land plateau, Jawoyn lands

The archaeomorphological study of Nawarla Gabarnmang in Australias Northern Territory challenges us to think in new ways about how Aboriginal people interacted with their surroundings; here a site of everyday engagement was a place of construction that retains material traces of past engagements. At Nawarla Garbarnmang, we show through archaeomorphological research how the changing physical layout of a site can be cross-examined against the impacts of human engagements through time. While the scope and scale of activities involved the anthropogenic removal over tens of thousands of years of rock pillars below the caves roof, other practices came and went over time, the complex sequence of rock art conventions being an apt example. These artistic transformations, much like the era of pillar clearances, are a clear example of changing cultural practices in a part of Australia where some 50,000 years of human occupation can be shown.The Arnhem Land plateau in northern Australia contains a particularly rich rock art assemblage. The area has a small number of large rockshelters with numerous and extensive suites of superimposed motifs (c. 2 per cent of 630 recorded shelters have >200 images). Studies of the rock art of Arnhem Land have primarily been concerned with attempting to understand the age of the art, with particular interest on the Pleistocene to mid-Holocene periods (Chaloupka 1977, 1984, 1985, 1993; Chippindale and Taçon 1993; Haskovec 1992; Lewis 1998; Taçon and Chippindale 1994). Most of these efforts have largely relied on interpretations of styles and their respective patterns of superimposition. Taçon (e.g. 1987, 1989a, 1989b, 1992) has written extensively on X-ray rock art from the northern perimeter of the plateau, and his work on ‘recent’ period art remains the most important study on this subject. The production of X-ray art has also been shown to have been popular during the European-contact period of the past 200 years or so (Chaloupka 1993; May et al. 2010; Wesley 2013). The most detailed study of rock art in the late Holocene period is the extensive radiocarbon dating of beeswax figures by Nelson et al. (2000), most of which fall within the past 500 years (but see Bednarik 2001).This chapter explores [the] incongruity in the distribution of Western-contact motifs contrasting northwestern and southwestern Arnhem Land in relation to the rich corpus of other kinds of rock art on the plateau. We stress from the onset that while images of ‘Western-contact art’ derive from a wide variety of responses to outsider influences, and include imagery that employs conventions akin and often indistinguishable to those of the pre–Western contact period, in this chapter we restrict our discussion to images of introduced objects and demonstrably foreign peoples.