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Figure 3
The `Cluster Analysis' story board was used to examine iron K-edge XANES X-ray spectromicroscopy data of a Roman ceramics sample (§3.1[link]) into four clusters. We show the iron concentration map obtained (§2.2[link]) from comparison of the 7100–7160 eV pre-edge and 7155–7175 eV post-edge spectral regions (a), the color-coded cluster index map of which cluster spectrum is predominant at which pixel (b), and the color-coded cluster spectra (c). The cluster spectra were then used to calculate composition maps which give thickness or weighting maps (d) for each of the cluster spectra; red regions represent negative weightings which can occur with cluster analysis, and which are addressed by using non-negative matrix approximation methods that will soon be integrated into MANTiS. The cluster thickness maps (e) show a combination of differing iron concentrations (ratios of post-edge to pre-edge absorption), and different iron phases as described in §3.1[link].

Journal logoJOURNAL OF
SYNCHROTRON
RADIATION
ISSN: 1600-5775
Volume 21| Part 5| July 2014| Pages 1206-1212
doi:10.1107/S1600577514013964
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