The design operating conditions of rubber dams were analyzed,and it is found that the operating conditions are similar to the actual operating conditions of changes in the internal pressure ratio of a specific rubber ...The design operating conditions of rubber dams were analyzed,and it is found that the operating conditions are similar to the actual operating conditions of changes in the internal pressure ratio of a specific rubber dam bag in the process of filling and draining. Based on this,the linear relationship curve between the internal pressure head H0 and the real-time dam height H and its approximate analytical formula can be obtained,which can be used as a supplement and correction method for the measurement method of real-time dam height during rubber dam operation,and provides reference for rubber dam project managers.展开更多
The catalytic activity and selectivity of CO_(2)reduction reaction(CO_(2)RR)towards C1 and C2 products are fundamentally restricted by the inherent linear scaling relationship among the adsorption-free energies of int...The catalytic activity and selectivity of CO_(2)reduction reaction(CO_(2)RR)towards C1 and C2 products are fundamentally restricted by the inherent linear scaling relationship among the adsorption-free energies of intermediates.To face this challenge,we have proposed a novel multifunctional M1M2@BN electrocatalysts to break the linear scaling relationships in CO_(2)RR and efficiently obtain C1 and C2 products.Our results reveal that the optimal limiting potential is increased from−0.58 V for M@BN to−0.39 V for M1M2@BN,which achieves ultrahigh activity of CO_(2)RR.Further mechanism analysis illuminates that M1M2@BN can selectivity modulate the adsorption strength of OCHO*and OCH_(2)O*/OCHOH*,breaking the linear scaling relationship of adsorption-free energies of key intermediates to achieve the enhanced catalytic activity.Notably,the sufficient active sites on M_(1)M_(2)@BN electrocatalysts can promote the sluggish C–C coupling by capturing two CO intermediates simultaneously,further generating high-value multi-carbon(CH_(2)CH_(2)OH)products.Meanwhile,the thermodynamic stability of M1M2@BN has been demonstrated by ab initio molecular dynamics(AIMD)simulations,which shows the feasibility of commercial application in CO_(2)RR.Our findings provide a novel strategy to modulate the binding strength of intermediates and develop the design of efficient multi-active-site CO_(2)RR electrocatalysts.展开更多
Background and aims:Although some studies have identified a possible link between the De Ritis ratio and the mortality of patients with COVID-19),the predictive value and the optimal cut-value remain unclear.This stud...Background and aims:Although some studies have identified a possible link between the De Ritis ratio and the mortality of patients with COVID-19),the predictive value and the optimal cut-value remain unclear.This study aimed to explore the correlation between the De Ritis ratio and mortality in hospitalized COVID-19.Methods:The data for this cohort study came from a retrospective cohort study that was carried out in a medical system in New York City.The primary outcome was the in-hospital mortality of included patients.The researchers ran multivariate Cox regression analyses,curve fitting,and subgroup analysis to support our findings.Overall survival in different De Ritis ratio groups was plotted as Kaplan-Meier survival curves.Results:The study enrolled 4371 participants with COVID-19 from March 1,2020 to April 16,2020.The overall mortality was 24.8%(1082/4371).The curve fitting analyses indicated that the De Ritis ratio has a positive linear connection with mortality in patients with COVID-19.After adjusting for all covariates,participants with a De Ritis ratio≥2 exhibited 1.29 times the risk of in-hospital mortality compared with those with a De Ritis ratio<1(hazard ratio 1.29,95%confidence interval 1.02-1.62,p=0.031).The p for trend was<0.05 for all models.Patients in the group with a De Ritis ratio≥2 experienced the shortest survival time in the Kaplan-Meier survival analysis.Conclusions:A higher baseline De Ritis ratio is correlated with a corresponding higher mortality among hospitalized people with COVID-19.展开更多
Interdecadal and interannual timescales are dominant in the North China rainfall in rainy season (July and August). On the interdecadal timescale, the North China rainfall exhibited an abrupt decrease at the end of 19...Interdecadal and interannual timescales are dominant in the North China rainfall in rainy season (July and August). On the interdecadal timescale, the North China rainfall exhibited an abrupt decrease at the end of 1970s. In this study, we examined the effect of this abrupt rainfall decrease on the association between rainfall and circulation on the interannual timescale, and found that the interdecadal variation does not change the physical mechanism responsible for the interannual variation of North China rainfall. There is a linear relationship between the interdecadal and interannual variabilities of North China rainfall in rainy season.展开更多
In this paper, a multivariate linear functional relationship model, where the covariance matrix of the observational errors is not restricted, is considered. The parameter estimation of this model is discussed. The es...In this paper, a multivariate linear functional relationship model, where the covariance matrix of the observational errors is not restricted, is considered. The parameter estimation of this model is discussed. The estimators are shown to be a strongly consistent estimation under some mild conditions on the incidental parameters.展开更多
Several chromatography systems with ionic liquids and a mixture of water with the modifier as mobile phase were characterized via the linear solvation energy relationships（LSER） model. The effects of the ionic liqui...Several chromatography systems with ionic liquids and a mixture of water with the modifier as mobile phase were characterized via the linear solvation energy relationships（LSER） model. The effects of the ionic liquids and modifier（methanol） concentrations on the retention of 10 solutes（caffeine, pyridine, aniline, phenol, methylparaben, acetopenone, m-cresol, p-cresol, o-cresol, and benzene） were discussed. The LSER model demonstrated high potential to predict retention factors with high squared correlation coefficients（r^2〉 0.97）. A comparison of predictable and experimental retention factors revealed that LSER can adequately reproduce the experimental retention factors of the solutes under different investigated experimental conditions. This model is a helpful tool to evaluate the retention characteristics of ionic liquid systems and to understand the interactions of solutes and ionic liquids.展开更多
The correlation relationships of apparent extraction equilibrium constant (1gK(ex)) with the electronic effect parameter( Sigma sigma(Phi)) and the steric effect parameter ( Sigma upsilon ) of the substituents in extr...The correlation relationships of apparent extraction equilibrium constant (1gK(ex)) with the electronic effect parameter( Sigma sigma(Phi)) and the steric effect parameter ( Sigma upsilon ) of the substituents in extractant molecules are investigated by linear regression analysis in the extraction of rare earths by various classes and structures of monoacidic organophosphorus extractants. The results indicate that in Linear free energy relationship formula 1gK(ex) = rho Sigma sigma(Phi) + psi Sigma upsilon + h generally follows for this kind of extraction systems. Accordingly, the quantitative structure-behaviour relationships of extractants are discussed. These relationships can be preliminarily applied to predict the 1gK(ex) values of rare earth extraction with definite structures of this class of extractants, and thus can provide some directions for the design of new RE extractants.展开更多
here are limitations in using the seasonal rainfall total in studies of Monsoon rainfall climatology. A correlation analysis of the individual station seasonal rainfall with all India seasonal mean rainfall has been m...here are limitations in using the seasonal rainfall total in studies of Monsoon rainfall climatology. A correlation analysis of the individual station seasonal rainfall with all India seasonal mean rainfall has been made. After taking the significance test (strictly up to 5% level) the stations which are significantly correlated have been considered in this study in normal, flood and drought years respectively. Analysis of seasonal rainfall data of 50 stations spread over a period of 41 years suggests that a linear relationship fits better than the logarithmic relationship when seasonal rainfall versus number of rainy days is studied. The linear relationship is also found to be better in the case of seasonal rainfall versus mean daily intensity.展开更多
10 quantum chemical descriptors of 21 aromatic compounds have been calculated by the semi-empirical quantum chemical method AM1. The Quantitative Structure-Biodegradability Relationships （QSBR） studies were performe...10 quantum chemical descriptors of 21 aromatic compounds have been calculated by the semi-empirical quantum chemical method AM1. The Quantitative Structure-Biodegradability Relationships （QSBR） studies were performed by the multiple linear regression （MLR）, principal component regression （PCR） and back propagation artificial neural network （BP-ANN）, respectively. The root mean square error （RMSE） of the training and validation sets of the BP-ANN model are 0.1363 and 0.0244, the mean absolute percentage errors （MAPE） are 0.1638 and 0.0326, the squared correlation coefficients （R^2） are 0.9853 and 0.9996, respectively. The results show that the BP-ANN model achieved a better prediction result than those of MLR and PCR. In addition, some insights into the structural factors affecting the aerobic biodegradation mechanism were discussed in detail.展开更多
The molecular electronegativity-distance vector （MEDV） was used to describe the molecular structure of volatile components of Rosa banksiae Ait, and QSRR model was built up by use of multiple linear regression （MLR...The molecular electronegativity-distance vector （MEDV） was used to describe the molecular structure of volatile components of Rosa banksiae Ait, and QSRR model was built up by use of multiple linear regression （MLR）. Furthermore, in virtue of variable screening by the stepwise multiple regression technique, the QSRR models of 10 and 6 variables and linear retention index （LRI） 10, 7 and 6 varieables were built up by combinating MEDV with the Ultra2 column GC retention time （tR） of 53 volatile components of Rosa Banksiae Air. The multiple correlation coefficients （R） of modeling calculation values of QSRR model were 0.906, 0.906, 0.949, 0.943 and 0.949, respectively. The cross-verification multiple correlation coefficients （RCV） were 0.903, 0.904, 0.867, 0.901 and 0.904, respectively. The results show that the models constructed could provide estimation stability and favorable predictive ability.展开更多
Studying the depth-diameter relationship of impact craters around the Oceanus Procellarum area together with values for simple crater,complex crater and basin confirms two inflections in the depth/diameter （d/D） cur...Studying the depth-diameter relationship of impact craters around the Oceanus Procellarum area together with values for simple crater,complex crater and basin confirms two inflections in the depth/diameter （d/D） curve.We classify impact craters to three types,which are simple crater,complex crater and basin.Using the most ＇pristine＇ or deepest craters in the data,three kinds of depth-diameter relationships are determined：the linear fit for simple crater is d=0.126D＋0.490 2;the best empirical power fit for complex crater is d=0.327 3D0.625 2;the best empirical power fit for basin is d=0.300 4D0.463 3,where d is the depth of the crater and D is the diameter of the crater,both in kilometers.The depth-diameter relationship for basin is characterized by a lower slope than that for complex craters,demonstrating that this morphologic transition corresponds to a further decrease in the depth of an impact structure relative to its diameter with increasing size.These relationships can then be used to estimate the theoretical depth of any impact radius,and therefore can be used to estimate the pristine shape of the crater around the Oceanus Procellarum area.The study of Oceanus Procellarum will help humankind to learn more about the origin and evolution of the moon.展开更多
With the artificial neural network（ANN） method combined with the multiple linear regression（MLR）,based on a series of quantum chemical descriptors and molecular connectivity indexes,quantitative structure-activity...With the artificial neural network（ANN） method combined with the multiple linear regression（MLR）,based on a series of quantum chemical descriptors and molecular connectivity indexes,quantitative structure-activity relationship（QSAR） models to predict the acute toxicity（-lgEC50） of substituted aromatic compounds to Photobacterium phosphoreum were established.Four molecular descriptors that appear in the MLR model,namely,the second order valence molecular connectivity index（2XV）,the energy of the highest occupied molecular orbital（EHOMO）,the logarithm of n-octyl alcohol/water partition coefficient（logKow） and the Connolly molecular area（MA）,were inputs of the ANN model.The root-mean-square error（RMSE） of the training and validation sets of the ANN model are 0.1359 and 0.2523,and the correlation coefficient（R） is 0.9810 and 0.8681,respectively.The leave-one-out（LOO） cross validated correlation coefficient（Q L2OO） of the MLR and ANN models is 0.6954 and 0.6708,respectively.The result showed that the two methods are complementary in the calculations.The regression method gave support to the neural network with physical explanation,and the neural network method gave a more accurate model for QSAR.In addition,some insights into the structural factors affecting the acute toxicity and toxicity mechanism of substituted aromatic compounds were discussed.展开更多
In current paper, a quantitative structure-activity relationship （QSAR） study was performed for the prediction of acute toxicity of aromatic amines. A set of 56 compounds was randomly divided into a training set of ...In current paper, a quantitative structure-activity relationship （QSAR） study was performed for the prediction of acute toxicity of aromatic amines. A set of 56 compounds was randomly divided into a training set of 46 compounds and a test set of 10 compounds. The electronic and topological descriptors computed by the Scigress package and Dragon software were used as predictor variables. Multiple linear regression （MLR） and support vector machine （SVM） were utilized to build the linear and nonlinear QSAR models, respectively. The obtained models with five descriptors show strong predictive ability. The linear model fits the training set with R2 = 0.71, with higher SVM values of R2 = 0.77. The validation results obtained from the test set indicate that the SVM model is comparable or superior to that obtained by MLR, both in terms of prediction ability and robustness.展开更多
In the present study,（QSRR） study had been carried out for volatile components from Rosa banksiae Ait.based on various quantum-chemical and physicochemical descriptors derived by B3LYP method.To build QSRR models,a ...In the present study,（QSRR） study had been carried out for volatile components from Rosa banksiae Ait.based on various quantum-chemical and physicochemical descriptors derived by B3LYP method.To build QSRR models,a multiple linear regression （MLR） stepwise method was used.The generated models have good predictive ability and are of high statistical significance with good correlation coefficients （R2≥0.734） and p values far less than 0.05.Preliminary results indicated that the application of the models,especially the prediction of GC retention time and linear retention index of volatile components from Rosa banksiae Ait.,will be helpful.The models contribute also to the identification of important quantum-chemical and physicochemical descriptors responsible for the retention time and linear retention index.It was found that the shape attribute （ShpA） and logP value play a vital role in determining component’s GC retention time and linear retention index which increase with the lipophilicity of volatile components.The larger the shape attribute of analyte is,the larger the deformability is,the stronger the interaction between analyte and stationary phase is,and the longer the GC retention time is,the larger the linear retention index is.The importance of E HOMO,q＋,and SEV is also embodied in models,but they are not dominant.展开更多
文摘The design operating conditions of rubber dams were analyzed,and it is found that the operating conditions are similar to the actual operating conditions of changes in the internal pressure ratio of a specific rubber dam bag in the process of filling and draining. Based on this,the linear relationship curve between the internal pressure head H0 and the real-time dam height H and its approximate analytical formula can be obtained,which can be used as a supplement and correction method for the measurement method of real-time dam height during rubber dam operation,and provides reference for rubber dam project managers.
基金financially supported by the National Natural Science Foundation of China(Nos.52403306 and 51902084)the Natural Science Foundation of Hebei Province(Nos.B2024202047 and B2020202089)+1 种基金the Hebei Province Higher Education Science and Technology Research Foundation(No.QN2019030)the Program for Changjiang Scholars and Innovative Research Team in University(No.PCSIRT:IRT17R33).
文摘The catalytic activity and selectivity of CO_(2)reduction reaction(CO_(2)RR)towards C1 and C2 products are fundamentally restricted by the inherent linear scaling relationship among the adsorption-free energies of intermediates.To face this challenge,we have proposed a novel multifunctional M1M2@BN electrocatalysts to break the linear scaling relationships in CO_(2)RR and efficiently obtain C1 and C2 products.Our results reveal that the optimal limiting potential is increased from−0.58 V for M@BN to−0.39 V for M1M2@BN,which achieves ultrahigh activity of CO_(2)RR.Further mechanism analysis illuminates that M1M2@BN can selectivity modulate the adsorption strength of OCHO*and OCH_(2)O*/OCHOH*,breaking the linear scaling relationship of adsorption-free energies of key intermediates to achieve the enhanced catalytic activity.Notably,the sufficient active sites on M_(1)M_(2)@BN electrocatalysts can promote the sluggish C–C coupling by capturing two CO intermediates simultaneously,further generating high-value multi-carbon(CH_(2)CH_(2)OH)products.Meanwhile,the thermodynamic stability of M1M2@BN has been demonstrated by ab initio molecular dynamics(AIMD)simulations,which shows the feasibility of commercial application in CO_(2)RR.Our findings provide a novel strategy to modulate the binding strength of intermediates and develop the design of efficient multi-active-site CO_(2)RR electrocatalysts.
基金supported by the National Natural Science Foundation of China(No.31972719)the Shenzhen Municipal Health Commission project(No.SZXJ2018018).
文摘Background and aims:Although some studies have identified a possible link between the De Ritis ratio and the mortality of patients with COVID-19),the predictive value and the optimal cut-value remain unclear.This study aimed to explore the correlation between the De Ritis ratio and mortality in hospitalized COVID-19.Methods:The data for this cohort study came from a retrospective cohort study that was carried out in a medical system in New York City.The primary outcome was the in-hospital mortality of included patients.The researchers ran multivariate Cox regression analyses,curve fitting,and subgroup analysis to support our findings.Overall survival in different De Ritis ratio groups was plotted as Kaplan-Meier survival curves.Results:The study enrolled 4371 participants with COVID-19 from March 1,2020 to April 16,2020.The overall mortality was 24.8%(1082/4371).The curve fitting analyses indicated that the De Ritis ratio has a positive linear connection with mortality in patients with COVID-19.After adjusting for all covariates,participants with a De Ritis ratio≥2 exhibited 1.29 times the risk of in-hospital mortality compared with those with a De Ritis ratio<1(hazard ratio 1.29,95%confidence interval 1.02-1.62,p=0.031).The p for trend was<0.05 for all models.Patients in the group with a De Ritis ratio≥2 experienced the shortest survival time in the Kaplan-Meier survival analysis.Conclusions:A higher baseline De Ritis ratio is correlated with a corresponding higher mortality among hospitalized people with COVID-19.
基金supported by the Key Project of the Chinese Academy of Sciences(Grant No.KZCX2-203)the National Natural Science Foundation of China(Grant Nos.40075016 and 40023001).
文摘Interdecadal and interannual timescales are dominant in the North China rainfall in rainy season (July and August). On the interdecadal timescale, the North China rainfall exhibited an abrupt decrease at the end of 1970s. In this study, we examined the effect of this abrupt rainfall decrease on the association between rainfall and circulation on the interannual timescale, and found that the interdecadal variation does not change the physical mechanism responsible for the interannual variation of North China rainfall. There is a linear relationship between the interdecadal and interannual variabilities of North China rainfall in rainy season.
基金Supported by National Natural Science Foundation of China(No.19771065).
文摘In this paper, a multivariate linear functional relationship model, where the covariance matrix of the observational errors is not restricted, is considered. The parameter estimation of this model is discussed. The estimators are shown to be a strongly consistent estimation under some mild conditions on the incidental parameters.
基金Supported by the Center for Advanced Bioseparation Technology, Inha University, Korea
文摘Several chromatography systems with ionic liquids and a mixture of water with the modifier as mobile phase were characterized via the linear solvation energy relationships（LSER） model. The effects of the ionic liquids and modifier（methanol） concentrations on the retention of 10 solutes（caffeine, pyridine, aniline, phenol, methylparaben, acetopenone, m-cresol, p-cresol, o-cresol, and benzene） were discussed. The LSER model demonstrated high potential to predict retention factors with high squared correlation coefficients（r^2〉 0.97）. A comparison of predictable and experimental retention factors revealed that LSER can adequately reproduce the experimental retention factors of the solutes under different investigated experimental conditions. This model is a helpful tool to evaluate the retention characteristics of ionic liquid systems and to understand the interactions of solutes and ionic liquids.
文摘The correlation relationships of apparent extraction equilibrium constant (1gK(ex)) with the electronic effect parameter( Sigma sigma(Phi)) and the steric effect parameter ( Sigma upsilon ) of the substituents in extractant molecules are investigated by linear regression analysis in the extraction of rare earths by various classes and structures of monoacidic organophosphorus extractants. The results indicate that in Linear free energy relationship formula 1gK(ex) = rho Sigma sigma(Phi) + psi Sigma upsilon + h generally follows for this kind of extraction systems. Accordingly, the quantitative structure-behaviour relationships of extractants are discussed. These relationships can be preliminarily applied to predict the 1gK(ex) values of rare earth extraction with definite structures of this class of extractants, and thus can provide some directions for the design of new RE extractants.
文摘here are limitations in using the seasonal rainfall total in studies of Monsoon rainfall climatology. A correlation analysis of the individual station seasonal rainfall with all India seasonal mean rainfall has been made. After taking the significance test (strictly up to 5% level) the stations which are significantly correlated have been considered in this study in normal, flood and drought years respectively. Analysis of seasonal rainfall data of 50 stations spread over a period of 41 years suggests that a linear relationship fits better than the logarithmic relationship when seasonal rainfall versus number of rainy days is studied. The linear relationship is also found to be better in the case of seasonal rainfall versus mean daily intensity.
基金supported by the Natural Science Foundation of Fujian Province (D0710019)the Natural Science Foundation of Overseas Chinese Affairs Office of the State Council (09QZR07)
文摘10 quantum chemical descriptors of 21 aromatic compounds have been calculated by the semi-empirical quantum chemical method AM1. The Quantitative Structure-Biodegradability Relationships （QSBR） studies were performed by the multiple linear regression （MLR）, principal component regression （PCR） and back propagation artificial neural network （BP-ANN）, respectively. The root mean square error （RMSE） of the training and validation sets of the BP-ANN model are 0.1363 and 0.0244, the mean absolute percentage errors （MAPE） are 0.1638 and 0.0326, the squared correlation coefficients （R^2） are 0.9853 and 0.9996, respectively. The results show that the BP-ANN model achieved a better prediction result than those of MLR and PCR. In addition, some insights into the structural factors affecting the aerobic biodegradation mechanism were discussed in detail.
文摘The molecular electronegativity-distance vector （MEDV） was used to describe the molecular structure of volatile components of Rosa banksiae Ait, and QSRR model was built up by use of multiple linear regression （MLR）. Furthermore, in virtue of variable screening by the stepwise multiple regression technique, the QSRR models of 10 and 6 variables and linear retention index （LRI） 10, 7 and 6 varieables were built up by combinating MEDV with the Ultra2 column GC retention time （tR） of 53 volatile components of Rosa Banksiae Air. The multiple correlation coefficients （R） of modeling calculation values of QSRR model were 0.906, 0.906, 0.949, 0.943 and 0.949, respectively. The cross-verification multiple correlation coefficients （RCV） were 0.903, 0.904, 0.867, 0.901 and 0.904, respectively. The results show that the models constructed could provide estimation stability and favorable predictive ability.
基金supported by the 863 Key Project (No. 2004AA735020)the Chang’e Data Special Funding
文摘Studying the depth-diameter relationship of impact craters around the Oceanus Procellarum area together with values for simple crater,complex crater and basin confirms two inflections in the depth/diameter （d/D） curve.We classify impact craters to three types,which are simple crater,complex crater and basin.Using the most ＇pristine＇ or deepest craters in the data,three kinds of depth-diameter relationships are determined：the linear fit for simple crater is d=0.126D＋0.490 2;the best empirical power fit for complex crater is d=0.327 3D0.625 2;the best empirical power fit for basin is d=0.300 4D0.463 3,where d is the depth of the crater and D is the diameter of the crater,both in kilometers.The depth-diameter relationship for basin is characterized by a lower slope than that for complex craters,demonstrating that this morphologic transition corresponds to a further decrease in the depth of an impact structure relative to its diameter with increasing size.These relationships can then be used to estimate the theoretical depth of any impact radius,and therefore can be used to estimate the pristine shape of the crater around the Oceanus Procellarum area.The study of Oceanus Procellarum will help humankind to learn more about the origin and evolution of the moon.
基金supported by the Natural Science Foundation of Fujian Province (D0710019)the Natural Science Foundation of Overseas Chinese Affairs Office of the State Council (06QZR09)
文摘With the artificial neural network（ANN） method combined with the multiple linear regression（MLR）,based on a series of quantum chemical descriptors and molecular connectivity indexes,quantitative structure-activity relationship（QSAR） models to predict the acute toxicity（-lgEC50） of substituted aromatic compounds to Photobacterium phosphoreum were established.Four molecular descriptors that appear in the MLR model,namely,the second order valence molecular connectivity index（2XV）,the energy of the highest occupied molecular orbital（EHOMO）,the logarithm of n-octyl alcohol/water partition coefficient（logKow） and the Connolly molecular area（MA）,were inputs of the ANN model.The root-mean-square error（RMSE） of the training and validation sets of the ANN model are 0.1359 and 0.2523,and the correlation coefficient（R） is 0.9810 and 0.8681,respectively.The leave-one-out（LOO） cross validated correlation coefficient（Q L2OO） of the MLR and ANN models is 0.6954 and 0.6708,respectively.The result showed that the two methods are complementary in the calculations.The regression method gave support to the neural network with physical explanation,and the neural network method gave a more accurate model for QSAR.In addition,some insights into the structural factors affecting the acute toxicity and toxicity mechanism of substituted aromatic compounds were discussed.
基金Supported by the Ministry of Environmental Protection of China(No.2011467037)
文摘In current paper, a quantitative structure-activity relationship （QSAR） study was performed for the prediction of acute toxicity of aromatic amines. A set of 56 compounds was randomly divided into a training set of 46 compounds and a test set of 10 compounds. The electronic and topological descriptors computed by the Scigress package and Dragon software were used as predictor variables. Multiple linear regression （MLR） and support vector machine （SVM） were utilized to build the linear and nonlinear QSAR models, respectively. The obtained models with five descriptors show strong predictive ability. The linear model fits the training set with R2 = 0.71, with higher SVM values of R2 = 0.77. The validation results obtained from the test set indicate that the SVM model is comparable or superior to that obtained by MLR, both in terms of prediction ability and robustness.
基金Supported by Shanghai Education Committee Project (No. 11YZ224)Shanghai Leading Academic Discipline Project (No. J51503)
文摘In the present study,（QSRR） study had been carried out for volatile components from Rosa banksiae Ait.based on various quantum-chemical and physicochemical descriptors derived by B3LYP method.To build QSRR models,a multiple linear regression （MLR） stepwise method was used.The generated models have good predictive ability and are of high statistical significance with good correlation coefficients （R2≥0.734） and p values far less than 0.05.Preliminary results indicated that the application of the models,especially the prediction of GC retention time and linear retention index of volatile components from Rosa banksiae Ait.,will be helpful.The models contribute also to the identification of important quantum-chemical and physicochemical descriptors responsible for the retention time and linear retention index.It was found that the shape attribute （ShpA） and logP value play a vital role in determining component’s GC retention time and linear retention index which increase with the lipophilicity of volatile components.The larger the shape attribute of analyte is,the larger the deformability is,the stronger the interaction between analyte and stationary phase is,and the longer the GC retention time is,the larger the linear retention index is.The importance of E HOMO,q＋,and SEV is also embodied in models,but they are not dominant.
