Polyimine represents a rapidly emerging class of readily accessible and affordable covalent adaptable networks(CANs)that have been extensively studied in the past few years.While being highly malleable and recyclable,...Polyimine represents a rapidly emerging class of readily accessible and affordable covalent adaptable networks(CANs)that have been extensively studied in the past few years.While being highly malleable and recyclable,the pioneering polyimine materials are relatively soft and not suitable for certain applications that require high mechanical performance.Recent studies have demonstrated the possibility of significantly improving polyimine properties by varying its monomer building blocks,but such component variations are usually not straightforward and can be potentially challenging and costly.Herein,we report an in situ oxidation polymerization strategy for preparation of mechanically strong poly(imine-amide)(PIA)hybrid CANs from simple amine and aldehyde monomers.By converting a portion of reversible imine bonds into high-strength amide linkages in situ,the obtained hybrid materials exhibit gradually improved Young’s modulus and ultimate tensile strength as the oxidation level increased.Meanwhile,the PIAs remain reprocessable and can be depolymerized into small molecules and oligomers similar as polyimine.This work demonstrates the great potential of the in situ transformation strategy as a new approach for development of various mechanically tunable CANs from the same starting building blocks.展开更多
Sequential activation of cyclin-dependent kinases(Cdks)controls mammalian cell cycle.Here we demonstrate that the upregulation of cyclin-dependent kinase 2(Cdk2)activity coincides with the loss of mitochondrial membra...Sequential activation of cyclin-dependent kinases(Cdks)controls mammalian cell cycle.Here we demonstrate that the upregulation of cyclin-dependent kinase 2(Cdk2)activity coincides with the loss of mitochondrial membrane potential(MMP)in paclitaxel-induced apoptosis.Ectopic expression of the dominant negative Cdk2(Cdk2-dn)and a specific Cdk2 inhibitor,p21WAF1/CIP1,effectively suppresses the loss of MMP,the release of cytochrome c,and subsequent activation of caspase-3 in paclitaxel-treated cells.Whereas forced activation of Cdk2 by overexpression of cyclin A dramatically promotes these events.We further show that Cdk2 activation status does not interfere with a procedure that lies downstream of cytochrome c release induced by Bax protein.These findings suggest that Cdk2 kinase can regulate apoptosis at earlier stages than mitochondrial permeability transition and cytochrome c release.展开更多
The loglinear model under product-multinomial sampling with constraints is considered. The asymptotic expansion and normality of the restricted minimum φ-divergence estimator (RMφDE) which is a generalization of the...The loglinear model under product-multinomial sampling with constraints is considered. The asymptotic expansion and normality of the restricted minimum φ-divergence estimator (RMφDE) which is a generalization of the maximum likelihood estimator is presented. Then various statistics based on φ-divergence and RMφDE are used to test various hypothesis test problems under the model considered. These statistics contain the classical loglikelihood ratio test statistics and Pearson chi-squared test statistics. In the last section, a simulation study is implemented.展开更多
Based on the empirical likelihood method, the subset selection and hypothesis test for parameters in a partially linear autoregressive model are investigated. We show that the empirical log-likelihood ratio at the tru...Based on the empirical likelihood method, the subset selection and hypothesis test for parameters in a partially linear autoregressive model are investigated. We show that the empirical log-likelihood ratio at the true parameters converges to the standard chi-square distribution. We then present the definitions of the empirical likelihood-based Bayes information criteria(EBIC) and Akaike information criteria(EAIC).The results show that EBIC is consistent at selecting subset variables while EAIC is not. Simulation studies demonstrate that the proposed empirical likelihood confidence regions have better coverage probabilities than the least square method, while EBIC has a higher chance to select the true model than EAIC.展开更多
基金the University of Colorado Boulder and the National Science Foundation (No. 49100423C0008, Y.J.) for financial support
文摘Polyimine represents a rapidly emerging class of readily accessible and affordable covalent adaptable networks(CANs)that have been extensively studied in the past few years.While being highly malleable and recyclable,the pioneering polyimine materials are relatively soft and not suitable for certain applications that require high mechanical performance.Recent studies have demonstrated the possibility of significantly improving polyimine properties by varying its monomer building blocks,but such component variations are usually not straightforward and can be potentially challenging and costly.Herein,we report an in situ oxidation polymerization strategy for preparation of mechanically strong poly(imine-amide)(PIA)hybrid CANs from simple amine and aldehyde monomers.By converting a portion of reversible imine bonds into high-strength amide linkages in situ,the obtained hybrid materials exhibit gradually improved Young’s modulus and ultimate tensile strength as the oxidation level increased.Meanwhile,the PIAs remain reprocessable and can be depolymerized into small molecules and oligomers similar as polyimine.This work demonstrates the great potential of the in situ transformation strategy as a new approach for development of various mechanically tunable CANs from the same starting building blocks.
基金supported by the National Natural Science Foundation of China(Grant Nos.90813003 and 31070670)by a grant from the National Research Laboratory Fund(M10104000129-02J0000-05910)from the Ministry of Science and Technology,Korea,to S.K.Lee.
文摘Sequential activation of cyclin-dependent kinases(Cdks)controls mammalian cell cycle.Here we demonstrate that the upregulation of cyclin-dependent kinase 2(Cdk2)activity coincides with the loss of mitochondrial membrane potential(MMP)in paclitaxel-induced apoptosis.Ectopic expression of the dominant negative Cdk2(Cdk2-dn)and a specific Cdk2 inhibitor,p21WAF1/CIP1,effectively suppresses the loss of MMP,the release of cytochrome c,and subsequent activation of caspase-3 in paclitaxel-treated cells.Whereas forced activation of Cdk2 by overexpression of cyclin A dramatically promotes these events.We further show that Cdk2 activation status does not interfere with a procedure that lies downstream of cytochrome c release induced by Bax protein.These findings suggest that Cdk2 kinase can regulate apoptosis at earlier stages than mitochondrial permeability transition and cytochrome c release.
基金Supported by the National Natural Science Foundation of China (No. 10871188, 10801123, 11231010)Guang-dong Province Natural Science Fund (No.S2012040007622)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KJCX3-SYW-S02)
文摘The loglinear model under product-multinomial sampling with constraints is considered. The asymptotic expansion and normality of the restricted minimum φ-divergence estimator (RMφDE) which is a generalization of the maximum likelihood estimator is presented. Then various statistics based on φ-divergence and RMφDE are used to test various hypothesis test problems under the model considered. These statistics contain the classical loglikelihood ratio test statistics and Pearson chi-squared test statistics. In the last section, a simulation study is implemented.
基金Supported by the National Natural Science Foundation of China(No.10871188,10801123)
文摘Based on the empirical likelihood method, the subset selection and hypothesis test for parameters in a partially linear autoregressive model are investigated. We show that the empirical log-likelihood ratio at the true parameters converges to the standard chi-square distribution. We then present the definitions of the empirical likelihood-based Bayes information criteria(EBIC) and Akaike information criteria(EAIC).The results show that EBIC is consistent at selecting subset variables while EAIC is not. Simulation studies demonstrate that the proposed empirical likelihood confidence regions have better coverage probabilities than the least square method, while EBIC has a higher chance to select the true model than EAIC.
