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Using a water-confined carbon nanotube to probe the electricity of sequential charged segments of macromolecules

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Chinese Physics B 2012年第7期21卷 403-409页

作者：王禹赵艳皎黄吉平 Department of Physics and State Key Laboratory of Surface Physics Fudan University Advanced Materials Laboratory Fudan University

The detection of macromolecular conformation is particularly important in many physical and biological applications. Here we theoretically explore a method for achieving this detection by probing the electricity of sequential charged segments of macromolecules. Our analysis is based on molecular dynamics simulations, and we investigate a single file of water molecules confined in a half-capped single-walled carbon nanotube （SWCNT） with an external electric charge of ＋e or -e （e is the elementary charge）. The charge is located in the vicinity of the cap of the SWCNT and along the centerline of the SWCNT. We reveal the picosecond timescale for the re-orientation （namely, from one unidirectional direction to the other） of the water molecules in response to a switch in the charge signal, -e -＋＋e or ＋e -＋ --e. Our results are well understood by taking into account the electrical interactions between the water molecules and between the water molecules and the external charge. Because such signals of re-orientation can be magnified and transported according to Tu et al. [2009 Proc. Natl. Aead. Sci. USA 106 18120], it becomes possible to record fingerprints of electric signals arising from sequential charged segments of a macromolecule, which are expected to be useful for recognizing the conformations of some particular macromolecules.

关键词： molecular dynamics simulation macromolecular conformation single-walled carbon nan-otube water molecule

Stabilizing Mechanism and Running Behavior of Couplers on Heavy Haul Trains

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Chinese Journal of Mechanical Engineering 2014年第6期27卷 1211-1218页

作者： XU Ziqiang WU Qing LUO Shihui MA Weihua DONG Xiaoqing Traction Power State Key Laboratory Southwest Jiaotong University Locomotive and Car Research Institute China Academy of Railway Sciences Centre for Railway Engineering Central Queensland UniversityRockhamptonQueensland QLD4701Australia Locomotive and Car Research Institute China Academy of Railway Sciences

Published studies in regard to coupler systems have been mainly focused on the manufacturing process or coupler strength issues. With the ever increasing of tonnage and length of heavy haul trains, lateral in-train forces generated by longitudinal in-train forces and coupler rotations have become a more and more significant safety issue for heavy haul train operations. Derailments caused by excessive lateral in-train forces are frequently reported. This article studies two typical coupler systems used on heavy haul locomotives. Their structures and stabilizing mechanism are analyzed before the corresponding models are developed. Coupler systems models are featured by two distinct stabilizing mechanism models and draft gear models with hysteresis considered. A model set which consists of four locomotives and three coupler systems is developed to study the rotational behavior of different coupler systems and their implications for locomotive dynamics. Simulated results indicate that when the locomotives are equipped with the type B coupler system, locomotives can meet the dynamics standard on tangent tracks; while the dynamics performance on curved tracks is very poor. The maximum longitudinal in-train force for locomotives equipped with the type B coupler system is 2000 kN. Simulations revealed a distinct trend for the type A coupler system. Locomotive dynamics are poorer for the type A case when locomotives are running on tangent tracks, while the dynamics are better for the type A case when locomotives are running on curved tracks. Theoretical studies and simulations carried out in this article suggest that a combination of the two types of stabilizing mechanism can result in a good design which can significantly decrease the relevant derailments.

关键词： dynamic heavy haul train coupler systems stable mechanism coupler angle safety

Changes of 5＇ Terminal Nucleotides of PCR Primers Causing Variable T-A Cloning Efficiency

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Journal of Integrative Plant Biology 2007年第3期49卷 382-385页

作者： Mei-Qin Liu Xin Shen Wei-Lun Yin Cun-Fu Lu College of Biological Sciences and Biotechnology Beijing Forestry University Beijing 100083 China

T-A cloning takes advantage of the unpaired adenosyl residue added to the 3＇ terminus of amplified DNAs by Taq and other thermostable DNA polymerase and uses a Ilnearlzed plasmld vector with a protruding 3＇ thymldylate residue at each of Its 3＇ termini to clone polymerase chain reaction （PCR）-derived DNA fragments. It Is a simple, reliable, and efficient Ilgatlon-dependent cloning method for PCR products, but the drawback of variable cloning efficiency occurs during application. In the present work, the relationship between variable T-A cloning efficiency and the different 5＇ end nucleotlde base of primers used In PCR amplification was studied. The results showed that different cloning efficiency was obtained with different primer pairs containing A, T, C and G at the 5＇ terminus respectively. The data shows that when the 5＇ end base of primer pair was adenosyl, more white colonies could be obtained In cloning the corresponding PCR product In comparison with other bases. And the least white colonies were formed when using the primer pair with 5＇ cytldylate end. The gluanylate end primers resulted In almost the same cloning efficiency In the white colonies amount as the thymldylate end primer did, and this efficiency was much lower than that of adenosyl end primers. This presumably is a consequence of variability In 3＇dA addition to PCR products mediated by Taq polymerase. Our results offer instructions for primer design for researchers who choose T-A cloning to clone PCR products.

关键词： efficiency polymerase chain reaction primer T-A cloning terminal nucleotide

Image Region Selection and Ensemble for Face Recognition

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Journal of Computer Science & Technology 2006年第1期21卷 116-125页

作者：耿新周志华 National Laboratory for Novel Software Technology Nanjing University Nanjing 210093 P.R. China

In this paper, a novel framework for face recognition, namely Selective Ensemble of Image Regions （SEIR）, is proposed. In this framework, all possible regions in the face image are regarded as a certain kind of features. There are two main steps in SEIR： the first step is to automatically select several regions from all possible candidates; the second step is to construct classifier ensemble from the selected regions. An implementation of SEIR based on multiple eigenspaces, namely SEME, is also proposed in this paper. SEME is analyzed and compared with eigenface, PCA ＋ LDA, eigenfeature, and eigenface ＋ eigenfeature through experiments. The experimental results show that SEME achieves the best performance.

关键词： face recognition region selection multiple eigenspaces ensemble learning selective ensemble.

Efficient Scheme for Dense Coding in Cavity QED and Ion Trap Systems

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Communications in Theoretical Physics 2006年第6期45卷 1011-1012页

作者： ZHENG Shi-Biao Department of Electronic Science and Applied Physics Fuzhou University Fuzhou 350002 China

We propose a scheme for realizing dense coding in cavity QED. The scheme is based on the resonant interaction of two atoms with a cavity mode. The scheme may be realizable with presently available techniques in the mi... 详细信息

关键词： dense coding cavity QED ion trap

Influence of Solvent Size on Structural Properties of Bottle-brush Polymers

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Chemical Research in Chinese Universities 2010年第5期26卷 838-841页

作者： LIU ying-tao LIU Hong LIU Yu-hua LU Zhong-yuan State Key Laboratory of Theoretical and Computational Chemistry Institute of Theoretical Chemistry Jilin University Changchun 130021 P. R. China

We proposed a modified dissipative particle dynamics simulation model by which one can effectively avoid the bond-crossing problem, and investigated the effect of solvent size on the structural properties of bottle-brush polymers in dilute solution on the basis of this model. It was found that with the increase of solvent size, the radius of the gyration of the bottle-brush polymer decreases considerably in the athermal solvent but increases in the selective solvent favoring the backbone, respectively.

关键词： Dissipative particle dynamics Bottle-brush polymer Solvent size Bond-crossing

Visible-light-driven external-photocatalyst-free alkylative carboxylation of alkenes with CO_(2)

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Science china Chemistry 2021年第7期64卷 1164-1169页

作者： Ya-Nan Niu Xing-Hao Jin Li-Li Liao He Huang Bo Yu Yu-Ming Yu Da-Gang Yu Urumqi Key Laboratory of Green Catalysis and Synthesis Technology Key Laboratory of Energy Materials ChemistryMinistry of EducationKey Laboratory of Advanced Functional MaterialsAutonomous RegionCollege of ChemistryXinjiang UniversityUrumqi 830046China Key Laboratory of Green Chemistry&Technology of Ministry of education College of ChemistrySichuan UniversityChengdu 610064China

Herein,we report a novel protocol for visible-light-driven alkylative carboxylation of alkenes with CO_(2) in the absence of external *** the irradiation of visible light,a variety of 4-alkyl-1,4-dihydropyridines(alkyl-DHPs)serve as not only alkyl radical precursors but also photoexcited reductants probably with the potential to reduce benzyl *** styrenes and acrylates are applicable in this reaction to give structurally diverse carboxylic acids in good to excellent *** reactions feature mild reaction conditions(1 atm of CO_(2),room temperature,visible light,photocatalyst-and transition metalfree),good functional group tolerance,easy scalability,as well as high regio-,and *** investigations provide evidence that alkyl radical,benzyl radical and carbanion might be involved in this reaction,providing a novel strategy for CO_(2) utilization.

关键词： carbon dioxide external-photocatalyst-free visible light alkylative carboxylation alkene

High-power linearly-polarized tunable Raman fiber laser

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Chinese Physics B 2018年第9期27卷 316-321页

作者： Jiaxin Song Hanshuo Wu Jiangming Xu Hanwei Zhang Jun Ye Jian Wu and Pu Zhou College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangsha 410073China

In this study, we demonstrate an all-fiber high-power linearly-polarized tunable Raman fiber laser system. An in- house high-power tunable fiber laser was employed as the pump source. A fiber loop mirror （FLM） serving as a high reflectivity mirror and a flat-cut endface serving as an output coupler were adopted to provide broadband feedback. A piece of 59-m commercial passive fiber was used as the Raman gain medium. The Raman laser had a 27.6 nm tuning range from 1112 nm to 1139.6 nm and a maximum output power of 125.3 W, which corresponds to a conversion efficiency of 79.4%. The polarization extinction ratio （PER） at all operational wavelengths was measured to be over 21 dB. To the best of our knowledge, this is the first report on a hundred-watt level linearly-polarized tunable Raman fiber laser.

关键词： Raman laser linearly polarized tunable fiber laser

Novel Method for Selection of Regularization Parameter in the Near-field Acoustic Holography

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Chinese Journal of Mechanical Engineering 2011年第2期24卷 285-292页

作者： ZHANG Yongbin BI Chuanxing XU Liang CHEN Xinzhao Institute of Sound and Vibration Research Hefei University qf Technology Hefei 230009 China

Because of the ill-posedness of the near-field acoustic holography（NAH）,the regularization method is required to stabilize the computational process of *** regularization effect is related to how to select the parameter correctly and *** the L-curve method commonly used for the selection of regularization parameters has the disadvantages of wrong selection and incorrect selection,which influences the application of *** the purpose of solving the problems existed in the L-curve method,the （？）-curve method is introduced into the field of NAH,and the performance applied to NAH directly is analyzed on the basis of equivalent source method-based ***,it is found out via investigations that the（？）-curve method in NAH also has the problem of wrong selection and is unable to choose the regularization parameter *** order to select the parameter correctly and effectively,a novel method for selecting regularization parameters is proposed based on the original（？）-curve method,which can be called improved （？）-curve *** the proposed method the regularization parameters are discretized linearly between the largest singular value and the smallest singular value,and the solution norm and the residual norm corresponding to these regularization parameters are also described in a linear coordinate instead of in a lg-lg coordinate,which are the two main differences compared with the L-curve and with the original（？）-curve *** linear coordinate and using the linearly discretized regularization parameters,the solution norm is a monotonically decreasing function of the residual norm as the increase of the regularization parameter,moreover the curve is convex *** the regularization parameters can be selected correctly and effectively based on the improved（？）-curve *** a numerical simulation is done with a simply supported plate to verify the validity of the proposed *** with two actual sources,a clamped plat

关键词： near-field acoustic holography(NAH) regularization parameter selection