This step is slow and irreversible. The thus formed lrO26 is stable under the experimental conditions. The catalytic activity for ethylene combustion on lrO2 is higher than on lr02 and this causes the observed catalytic rate enhancement after electrochemical pretreatment. The assumption for the formation of lrO2 is strongly supported since the catalyst work function after current application is higher than the initial value, since oxygen adsorbates cause increase in work function of clean surfaces.6The 1r02 catalyst can restore its initial activity only after treatment with excess ethylene in absence of oxygen or after cathodic polarization.4
We used both correlation and covariance-principal component analysis (PCA) to classify the same absorption-reflectance data collected from 13 different polymeric fabric materials that was obtained using Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR). The application of the two techniques, though similar, yielded results that represent different chemical properties of the polymeric substances. On one hand, correlation-PCA enabled the classification of the fabric materials according to the organic functional groups of their repeating monomer units. On the other hand, covariance-PCA was used to classify the fabric materials primarily according to their origins; natural (animal or plant) or synthetic. Hence besides major chemical functional groups of the repeat units, it appears covariance-PCA is also sensitive to other characteristic chemical (inorganic and/or organic) or biochemical material inclusions that are found in different samples. We therefore recommend the application of both covariance-PCA and correlation-PCA on datasets, whenever applicable, to enable a broader classification of spectroscopic information through data mining and exploration.
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