In-line spectroscopy is a useful tool for monitoring processing conditions and polymer quality in the melt state in processes such as extrusion and injection moulding. This study extends the scope of this technique to the quantitative detection of poly(lactic acid) (PLA), which is a contaminant of concern in recycled poly(ethylene terephthalate) (PET). The near-infrared spectra of thermally treated PLA were studied for evidence of spectral changes which could be used as markers for PLA in PET, and these are discussed in detail. Several chemometric models for quantifying PLA in PET were developed and the influence of chemical or physical changes on the performance of the models is discussed. The selection of the final model was based on criteria aimed at eliminating interference due to spectral changes resulting from physical processes to give a robust model based specifically on the chemistry of the polymers studied. Finally, the models were tested against a new test mixture of known composition and the outputs are discussed.
interventional trials. Participants in this CF study had a field-based estimate of exercise capacity and objective measurement of physical activity at each study visit. Methods Participants wore a pedometer for 7 days prior to each visit. At each visit, London patients performed a standard incremental shuttle-walk test and Edinburgh patients a modified shuttle test (in which running was allowed). Data are expressed as mean (SD). Results Data were analysed from 192 patients over 648 visits. Age at enrolment was 24 (11.9) years (London) and 20.8 (9.9) (Edinburgh) (p¼0.052); FEV 1 was 67 (17.7)% and 79 (19.5)% for each site respectively (p<0.001). Daily step count at visit 1 was 7491 (2887) in London and 8872 (4089) in Edinburgh (p¼0.04) and this difference persisted across subsequent visits. The coefficient of variation (CV) in step counts between visits was 21.3%. Number of shuttles completed in London was 61 (15), and Edinburgh 90 (33) with no trend over the four visits (CV¼10 and 16% respectively). In Edinburgh there was a correlation between mean step count and the number of completed shuttles (r¼0.46, p<0.001).Step count from both sites, and the number of shuttles completed in Edinburgh, correlated with FEV 1 % predicted (r¼0.24, p<0.001 and r¼0.27, p<0.001 respectively) and with age (r¼À0.28, p<0.001 and r¼À0.30, p<0.001 respectively). Such correlations were either weaker or not observed in London, however, in this group, number of shuttles correlated with height (r¼0.51, p<0.001).Conclusions No changes were detected in exercise capacity or daily activity levels over time. Between site differences were observed in both measures; however, these populations also differ in age and FEV 1 . The modified shuttle test performed in Edinburgh appeared to better correlate with clinical markers than the standard incremental shuttle test performed in London, and is independent of height. We believe that testing exercise capacity is important in CF and we plan to investigate the other testing methods in the run up to our Multi
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.