Fig. 3: Normalized Osmium concentrations (OsCT) in some reference materials in arbitrary units.

Some materials are solid and cannot be penetrated by Os vapor. The divergence from zero Os intensity for solid materials can therefore only be explained by polychromatic X-ray artifacts. Other materials are porous, i.e. powders with grain size smaller than the image resolution or biological material within inherent porosity. The boxplots show the 0%, 25%, 50%, 75, and 100% percentiles of varying sample numbers (n) after outlier detection. The two images show representative slices through X-ray tomograms of char and plant samples.