High resolution gas chromatographic relative retention time (HRGC-RRT) models were developed to p... more High resolution gas chromatographic relative retention time (HRGC-RRT) models were developed to predict relative retention times of the 209 individual polychlorinated biphenyls (PCBs) congeners. To estimate and predict the HRGC-RRT values of all PCBs on 18 different stationary phases, a multiple linear regression equation of the form RRT = a o + a 1 (no. o-Cl) + a 2 (no. m-Cl) + a 3 (no. p-Cl) + a 4 (V M or S M) was used. Molecular descriptors in the models included the number of ortho-, meta-, and para-chlorine substituents (no. o-Cl, m-Cl and p-Cl, respectively), the semi-empirically calculated molecular volume (V M), and the molecular surface area (S M). By means of the final variable selection method, four optimal semi-empirical descriptors were selected to develop a QSRR model for the prediction of RRT in PCBs with a correlation coefficient between 0.9272 and 0.9928 and a leave-one-out cross-validation correlation coefficient between 0.9230 and 0.9924 on each stationary phase. The root mean squares errors over different 18 stationary phases are within the range of 0.0108-0.0335. The accuracy of all the developed models were investigated using crossvalidation leave-one-out (LOO), Y-randomization, external validation through an odd-even number and division of the entire data set into training and test sets.
ción en el escenario de los intelectuales disidentes cubanos dentro y fuera de la Isla. La revist... more ción en el escenario de los intelectuales disidentes cubanos dentro y fuera de la Isla. La revista configuró un espacio abierto a los disidentes cubanos que se denominan pós castristas y presenta discusiones que envuelven las más variadas temáticas sobre historia y cultura cubanas, tales como la historia, la economia. sociologia, arquitectura,ecologia, artes, cine, música y otros. La importancia de Jesús Díaz en el escenario intelectual es destacada para la comprensión del campo literário cubano de la diáspora e inserir Encuentro en el rol de las revistas culturales cubanas que desde las primeras décadas del siglo XX vienen colaborando para la profusión de la cultura y del debate sobre la identidad cubana, caribeña y latinoamericana.
High resolution gas chromatographic relative retention time (HRGC-RRT) models were developed to p... more High resolution gas chromatographic relative retention time (HRGC-RRT) models were developed to predict relative retention times of the 209 individual polychlorinated biphenyls (PCBs) congeners. To estimate and predict the HRGC-RRT values of all PCBs on 18 different stationary phases, a multiple linear regression equation of the form RRT = a o + a 1 (no. o-Cl) + a 2 (no. m-Cl) + a 3 (no. p-Cl) + a 4 (V M or S M) was used. Molecular descriptors in the models included the number of ortho-, meta-, and para-chlorine substituents (no. o-Cl, m-Cl and p-Cl, respectively), the semi-empirically calculated molecular volume (V M), and the molecular surface area (S M). By means of the final variable selection method, four optimal semi-empirical descriptors were selected to develop a QSRR model for the prediction of RRT in PCBs with a correlation coefficient between 0.9272 and 0.9928 and a leave-one-out cross-validation correlation coefficient between 0.9230 and 0.9924 on each stationary phase. The root mean squares errors over different 18 stationary phases are within the range of 0.0108-0.0335. The accuracy of all the developed models were investigated using crossvalidation leave-one-out (LOO), Y-randomization, external validation through an odd-even number and division of the entire data set into training and test sets.
ción en el escenario de los intelectuales disidentes cubanos dentro y fuera de la Isla. La revist... more ción en el escenario de los intelectuales disidentes cubanos dentro y fuera de la Isla. La revista configuró un espacio abierto a los disidentes cubanos que se denominan pós castristas y presenta discusiones que envuelven las más variadas temáticas sobre historia y cultura cubanas, tales como la historia, la economia. sociologia, arquitectura,ecologia, artes, cine, música y otros. La importancia de Jesús Díaz en el escenario intelectual es destacada para la comprensión del campo literário cubano de la diáspora e inserir Encuentro en el rol de las revistas culturales cubanas que desde las primeras décadas del siglo XX vienen colaborando para la profusión de la cultura y del debate sobre la identidad cubana, caribeña y latinoamericana.
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