ABSTRACT
Two novel algorithms that employed the idea of ensemble models(stacked generalization or stacked regression), stacked multivariate calibration(PCR and PLS) and stacked moving-window multivariate calibration(PCR and PLS), were reported. The proposed algorithms established parallel, conventional PCR or PLS models based on all intervals of a set of spectra to take advantage of the information from the whole spectrum. Unlike traditional methods, they stack or incorporate these parallel models in a way to emphasize intervals(regions) highly related to the target property. These two stacking algorithms generate more parsimonious regression models with better predictive power than that of conventional PCR and PLS, and perform best when the spectral information is neither isolated to a single, small region, nor spread uniformly over the spectral data. The predictive performance of these two new algorithms is similar. Thus, two real NIR spectra were used here to show the improvement in predictive performance from these two new algorithms.
ABSTRACT
<p><b>OBJECTIVE</b>The study was to explore extracting and purifying technology of taxol from the branches of Taxus media.</p><p><b>METHOD</b>In extracting phase, the solvent extraction, ultrasonic extraction and the supercritical CO2 fluid extraction were studied respectively; In purifying phase, the extracts were disposed by silica gel column chromatography and preparation lamella chromatography, then crystaled by N-Hexane. The content of taxol was detected by HPLC.</p><p><b>RESULT</b>The results showed that the recovery of extracting toxal with the method of ultrasonic was the highest and the selectivity of supercritical CO2 fluid extraction was the best; The sample after being extracted should be purified two stages by silica gel column chromatography with dichloromethane-chloroform-methane (53:44:3) as elution and the lamella chromatography was chloroform-ethyl acetate-methane (88:7:5) as elution, finally we reached the fawn crystal.</p><p><b>CONCLUSION</b>In that production, the content of taxol reached 87. 3% and the recovery 89.7%, which indicat that the taxol is well enrichment.</p>