The photoionization and photodissociative ionization processes of p-nitrotoluene(C,H,NO,) have been studied using the photoionization mass spectrometry wlth synchrotronradiation(SR) as the light source- The ionization...The photoionization and photodissociative ionization processes of p-nitrotoluene(C,H,NO,) have been studied using the photoionization mass spectrometry wlth synchrotronradiation(SR) as the light source- The ionization potential (PI) of p-nitrotoluene and eightappearance potentials(P.) of the ionic fragment from the SR photodissociative ionization ofC:H:NO, have been measured. Based on the mass spectra of C,H:NO, obtained with SR pho-tolonization and the relationship of energy in the processes, the most possible channels ofphotodissociative ionization of p-nltrotoluene have been analyzed.展开更多
A temperature-constrained cascade correlation network （TCCCN）, a back-propagation neural network （BP）, and multiple linear regression（MLR） models were applied to quantitative structure-activity relationship（QSA...A temperature-constrained cascade correlation network （TCCCN）, a back-propagation neural network （BP）, and multiple linear regression（MLR） models were applied to quantitative structure-activity relationship（QSAR） modeling, on the basis of a set of 35 nitrobenzene derivatives and their acute toxicities. These structural quantum-chemical descriptors were obtained from the density functional theory（DFT）. Stepwise multiple regression analysis was performed and the model was obtained. The value of the calibration correlation coefficient R is 0. 925, and the value of cross-validation correlation coefficient R is 0. 87. The standard error S = 0. 308 and the cross-validated （ leave-one- out） standard error Scv =0. 381. Principal component analysis（PCA） was carried out for parameter selection. RMS errors for training set via TCCCN and BP are 0. 067 and 0. 095, respectively, and RMS errors for testing set via TCCCN and BP are 0. 090 and 0. 111, respectively. The results show that TCCCN performs better than BP and MLR.展开更多
文摘The photoionization and photodissociative ionization processes of p-nitrotoluene(C,H,NO,) have been studied using the photoionization mass spectrometry wlth synchrotronradiation(SR) as the light source- The ionization potential (PI) of p-nitrotoluene and eightappearance potentials(P.) of the ionic fragment from the SR photodissociative ionization ofC:H:NO, have been measured. Based on the mass spectra of C,H:NO, obtained with SR pho-tolonization and the relationship of energy in the processes, the most possible channels ofphotodissociative ionization of p-nltrotoluene have been analyzed.
基金Supported by the Science and Technology Program, Beijing Municipal Education Commission(No. KM200310028105)
文摘A temperature-constrained cascade correlation network （TCCCN）, a back-propagation neural network （BP）, and multiple linear regression（MLR） models were applied to quantitative structure-activity relationship（QSAR） modeling, on the basis of a set of 35 nitrobenzene derivatives and their acute toxicities. These structural quantum-chemical descriptors were obtained from the density functional theory（DFT）. Stepwise multiple regression analysis was performed and the model was obtained. The value of the calibration correlation coefficient R is 0. 925, and the value of cross-validation correlation coefficient R is 0. 87. The standard error S = 0. 308 and the cross-validated （ leave-one- out） standard error Scv =0. 381. Principal component analysis（PCA） was carried out for parameter selection. RMS errors for training set via TCCCN and BP are 0. 067 and 0. 095, respectively, and RMS errors for testing set via TCCCN and BP are 0. 090 and 0. 111, respectively. The results show that TCCCN performs better than BP and MLR.
