In this work,ethylene glycol monomethylether(EE) was chosen as an entrainer for the azeotropic distillation of 1,3,5-trimethylbenzene+1-methyl-2-ethylbenzene system to investigate the influence of the entrainer on vap...In this work,ethylene glycol monomethylether(EE) was chosen as an entrainer for the azeotropic distillation of 1,3,5-trimethylbenzene+1-methyl-2-ethylbenzene system to investigate the influence of the entrainer on vapor liquid equilibrium(VLE) of this system.Three sets of binary VLE data in the system consisting of EE + 1,3,5-trimethylbenzene +1-methyl-2-ethylbenzene were measured using the Dvorak-Boublik still.The binary parameters of NRTL model were correlated by using the likelihood method.The ternary VLE data of the system were measured as well and were predicted by using the binary parameters of NRTL model.The test results indicated that the binary data passed the thermodynamic consistency tests,and the difference between the predicted values of ternary VLE and the experimental data reached the research standard for VLE data.Addition of EE had a great influence on the relative volatility between 1,3,5-trimethylbenzene and 1-methl-2-ethyl-benzene:when the ratio of solvent was 4,and the relative volatility between 1,3,5-trimethylbenzene and 1-methyl-2-ethylbenzene increased from 1.0125(without solvent addition) to 1.283.展开更多
Two triterpenoid saponins （compound Ⅰ and Ⅱ） have been isolated from Gymnocladus chinensis Baill., and compound Ⅰ was determined as a new compound. The structure of compound Ⅰ was assigned as 2β,23-dihydroxy-ac...Two triterpenoid saponins （compound Ⅰ and Ⅱ） have been isolated from Gymnocladus chinensis Baill., and compound Ⅰ was determined as a new compound. The structure of compound Ⅰ was assigned as 2β,23-dihydroxy-acacic acid-3-O-α-L-arabinopyranosyl-21-O-{（6S）-2-E-2,6-dimethyl-6-O-[4-O-（6S）-2-E- 2,6 -dimethyl-6-O-β-D-glucopyranosyl-α-L-arabinopyranosyl-2,7-octadienoyl} -28-O-β-D-xylopyranosyl（ 1 →3 ）-β-D-xylopymnosyl （ 1→4）- α-L-rhamnopyranosyl（1→2）-[α-L-rhamnopyranosyl-（1→6）]-β-D-glucopyranoside by extensive MS and NMR studies.展开更多
The system energy of H atom occupying different positions in Cr2O3 crystal lattice is calculated by adopting the first-principles calculation method based on density functional theory in this paper. The results indica...The system energy of H atom occupying different positions in Cr2O3 crystal lattice is calculated by adopting the first-principles calculation method based on density functional theory in this paper. The results indicate that the most stable position of H atom in Cr2O3 crystal lattice locates at the bilateral positions of the center of the unoccupied O octahedral interstice. The reason resulting in this situation is analyzed by comparing the change of Cr2O3 lattice distortion and density of states in Cr2O3_H system when H atom locates at different positions in octahedral interstice. The diffusion activation energy of H atom is 0.73 eV,which is determined by seeking the diffusion path and transition state of H atom in Cr2O3 crystal lattice. The effective attempt frequency of H atom in Cr2O3 crystal lattice is also calculated by using molecular dynamics. Combining with diffusion activation energy data,the diffusion coefficient of H atom in Cr2O3 crystal is determined.展开更多
Chloroplasts are organelles found in plant cells that conduct photosynthesis. The subchloroplast locations of proteins are correlated with their functions. With the availability of a great number of protein data, it i...Chloroplasts are organelles found in plant cells that conduct photosynthesis. The subchloroplast locations of proteins are correlated with their functions. With the availability of a great number of protein data, it is highly desired to develop a com- putational method to predict the subchloroplast locations of chloroplast proteins. In this study, we proposed a novel method to predict subchloroplast locations of proteins using tripeptide compositions. It first used the binomial distribution to optimize the feature sets. Then the support vector machine was selected to perform the prediction of subchloroplast locations of proteins. The proposed method was tested on a reliable and rigorous dataset including 259 chloroplast proteins with sequence identity ≤ 25%. In the jack-knife cross-validation, 92.21% envelope proteins, 93.20% thylakoid mem- brane, 52.63% thylakoid lumen and 85.00% stroma can be correctly identified. The overall accuracy achieves 88.03% which is higher than that of other models. Based on this method, a predictor called ChloPred has been built and can be freely available from http：//cobi.uestc.edu.cn/people/hlin/tools/ChloPred/. The predictor will provide important information for theoretical and experimental research of chloroplast proteins.展开更多
Desorption of zinc （Zn） from soil is an important factor governing Zn concentration in the soil solution and Zn availability to plants. Batch experiments were performed to study the kinetics of Zn desorption by diet...Desorption of zinc （Zn） from soil is an important factor governing Zn concentration in the soil solution and Zn availability to plants. Batch experiments were performed to study the kinetics of Zn desorption by diethylenetriaminepentaacetic acid （DTPA） from 15 calcareous soil samples taken from Golestan Province in northern Iran. Soils were equilibrated with 0.005 mol L-1 DTPA solutions for 0.25 to 192 h. The results showed that the extraction process consisted of rapid extraction in the first 2 h followed by much slower extraction for the remainder of the experiment. Desorption kinetic data was fitted to pseudo-first-order kinetic model. The experimental data were found to deviate from the straight line of the pseudo-first-order plots after 2 h. The model of two first-order reactions was fitted to the kinetic data and allowed to distinguish two pools for Zn： a labile fraction （Q1）, quickly extracted with a rate constant kl, and a slowly labile fraction （Q2）, more slowly extracted with a rate constant k2. The applicability of pseudo-second-order model in describing the kinetic data of Zn desorntion was also evaluated.展开更多
基金supported by the SINOPEC Corporation (Contact No. 408069)
文摘In this work,ethylene glycol monomethylether(EE) was chosen as an entrainer for the azeotropic distillation of 1,3,5-trimethylbenzene+1-methyl-2-ethylbenzene system to investigate the influence of the entrainer on vapor liquid equilibrium(VLE) of this system.Three sets of binary VLE data in the system consisting of EE + 1,3,5-trimethylbenzene +1-methyl-2-ethylbenzene were measured using the Dvorak-Boublik still.The binary parameters of NRTL model were correlated by using the likelihood method.The ternary VLE data of the system were measured as well and were predicted by using the binary parameters of NRTL model.The test results indicated that the binary data passed the thermodynamic consistency tests,and the difference between the predicted values of ternary VLE and the experimental data reached the research standard for VLE data.Addition of EE had a great influence on the relative volatility between 1,3,5-trimethylbenzene and 1-methl-2-ethyl-benzene:when the ratio of solvent was 4,and the relative volatility between 1,3,5-trimethylbenzene and 1-methyl-2-ethylbenzene increased from 1.0125(without solvent addition) to 1.283.
基金National Natural Science Foundation of China (GrantNo. 30772639)
文摘Two triterpenoid saponins （compound Ⅰ and Ⅱ） have been isolated from Gymnocladus chinensis Baill., and compound Ⅰ was determined as a new compound. The structure of compound Ⅰ was assigned as 2β,23-dihydroxy-acacic acid-3-O-α-L-arabinopyranosyl-21-O-{（6S）-2-E-2,6-dimethyl-6-O-[4-O-（6S）-2-E- 2,6 -dimethyl-6-O-β-D-glucopyranosyl-α-L-arabinopyranosyl-2,7-octadienoyl} -28-O-β-D-xylopyranosyl（ 1 →3 ）-β-D-xylopymnosyl （ 1→4）- α-L-rhamnopyranosyl（1→2）-[α-L-rhamnopyranosyl-（1→6）]-β-D-glucopyranoside by extensive MS and NMR studies.
基金supported by the National Natural Science Foundation of China (Grant Nos.50771104,50871122)
文摘The system energy of H atom occupying different positions in Cr2O3 crystal lattice is calculated by adopting the first-principles calculation method based on density functional theory in this paper. The results indicate that the most stable position of H atom in Cr2O3 crystal lattice locates at the bilateral positions of the center of the unoccupied O octahedral interstice. The reason resulting in this situation is analyzed by comparing the change of Cr2O3 lattice distortion and density of states in Cr2O3_H system when H atom locates at different positions in octahedral interstice. The diffusion activation energy of H atom is 0.73 eV,which is determined by seeking the diffusion path and transition state of H atom in Cr2O3 crystal lattice. The effective attempt frequency of H atom in Cr2O3 crystal lattice is also calculated by using molecular dynamics. Combining with diffusion activation energy data,the diffusion coefficient of H atom in Cr2O3 crystal is determined.
文摘Chloroplasts are organelles found in plant cells that conduct photosynthesis. The subchloroplast locations of proteins are correlated with their functions. With the availability of a great number of protein data, it is highly desired to develop a com- putational method to predict the subchloroplast locations of chloroplast proteins. In this study, we proposed a novel method to predict subchloroplast locations of proteins using tripeptide compositions. It first used the binomial distribution to optimize the feature sets. Then the support vector machine was selected to perform the prediction of subchloroplast locations of proteins. The proposed method was tested on a reliable and rigorous dataset including 259 chloroplast proteins with sequence identity ≤ 25%. In the jack-knife cross-validation, 92.21% envelope proteins, 93.20% thylakoid mem- brane, 52.63% thylakoid lumen and 85.00% stroma can be correctly identified. The overall accuracy achieves 88.03% which is higher than that of other models. Based on this method, a predictor called ChloPred has been built and can be freely available from http：//cobi.uestc.edu.cn/people/hlin/tools/ChloPred/. The predictor will provide important information for theoretical and experimental research of chloroplast proteins.
基金Supported by the Gorgan University of Agricultural Sciences and Natural Resources,Iran
文摘Desorption of zinc （Zn） from soil is an important factor governing Zn concentration in the soil solution and Zn availability to plants. Batch experiments were performed to study the kinetics of Zn desorption by diethylenetriaminepentaacetic acid （DTPA） from 15 calcareous soil samples taken from Golestan Province in northern Iran. Soils were equilibrated with 0.005 mol L-1 DTPA solutions for 0.25 to 192 h. The results showed that the extraction process consisted of rapid extraction in the first 2 h followed by much slower extraction for the remainder of the experiment. Desorption kinetic data was fitted to pseudo-first-order kinetic model. The experimental data were found to deviate from the straight line of the pseudo-first-order plots after 2 h. The model of two first-order reactions was fitted to the kinetic data and allowed to distinguish two pools for Zn： a labile fraction （Q1）, quickly extracted with a rate constant kl, and a slowly labile fraction （Q2）, more slowly extracted with a rate constant k2. The applicability of pseudo-second-order model in describing the kinetic data of Zn desorntion was also evaluated.
