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When undertaking any study of the isotope abundance values of a bulk material, consideration should be given to the source materials and how they are combined to reach the final product being measured. While it is demonstrative to measure and record the values of clean papers, such as the results published as part one of this series, the majority of forensic casework samples would have undergone some form of writing or printing process prior to examination. Understanding the effects of these processes on the δ13C values of paper is essential for interpretation and comparison with clean samples, for example in cases where printed documents need to be compared to paper from an unprinted suspect ream. This study was undertaken so that the source materials, the effects of the production process and the effects of printing and forensic testing could be observed with respect to 80 gsm white office papers. Samples were taken sequentially from the paper production facility at the Australian Paper Mill (Maryvale, VIC). These samples ranged from raw wood chips through the pulping, whitening and refinement steps to the final formed and packed paper. Cellulose was extracted from each sample to observe both fractionation and mixing steps and their effect on the δ13C values. Overall, the mixing steps were observed to have a larger effect on the isotopic values of the bulk materials than any potential fractionation. Printing of papers using toner and inkjet printing processes and forensic testing were observed to have little effect on δ13C. These experiments highlighted considerations for sampling and confirmed the need for a holistic understanding of sample history to inform the interpretation of results. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the notion of loss of sustainability of a mechanical state in a granular assembly is investigated. The vanishing of the second-order work, defined on the macroscopic scale from tensorial variables, is shown to play a fundamental role in detecting the occurrence of this type of bifurcation. Then a link is established between the macroscopic second-order work on the specimen scale and a discrete local expression that introduces microscopic variables defined on each contact scale. This relation opens up a micro-mechanical interpretation allowing one to examine which micro-structural features are responsible for the vanishing of the macroscopic second-order work. Finally, it is established that both geometrical and material micro-structural origins may combine to induce the occurrence of bifurcation on a specimen scale. [Copyright &y& Elsevier]