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PEGylation of therapeutic oligonucletides： From linear to highly branched PEG architectures

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Nano Research 2018年第10期11卷 5519-5534页

作者： Xueguang Lu ke zhang Department of Chemistry and Chemical Biology Northeastern University Boston Massachusetts 02115 USA

PEGylation, the attachment of poly（ethylene glycol）（PEG）, has been adopted to improve the pharmacokinetic properties of oligonucleotide therapeutics for nearly 30 years. Prior efforts mainly focused on the investigation of linear or slightly branched PEG having different molecular weights, terminal functional groups, and possible oligonucleotide sites for functionalization. Recent studies on highly branched PEG （including brush, star, and micellar structures） indicate superior properties in several areas including cellular uptake, gene regulation efficac~ reduction of side effects, and biodistribution. This review focuses on comparing the effects of PEG architecture on the physiochemical and biological properties of the PEGylated oligonucleotide.

关键词： PEGylation oligonucleotide brush polymer antisense small interfering RNA aptamer phosphorothioate

Comprehensive multivariate grey incidence degree based on principal component analysis

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Journal of Systems Engineering and Electronics 2014年第5期25卷 840-847页

作者： ke zhang Yintao zhang Pinpin Qu Business School Hohai University

To overcome the too fine-grained granularity problem of multivariate grey incidence analysis and to explore the comprehensive incidence analysis model, three multivariate grey incidences degree models based on principal component analysis （PCA） are proposed. Firstly, the PCA method is introduced to extract the feature sequences of a behavioral matrix. Then, the grey incidence analysis between two behavioral matrices is transformed into the similarity and nearness measure between their feature sequences. Based on the classic grey incidence analysis theory, absolute and relative incidence degree models for feature sequences are constructed, and a comprehensive grey incidence model is proposed. Furthermore, the properties of models are researched. It proves that the proposed models satisfy the properties of translation invariance, multiple transformation invariance, and axioms of the grey incidence analysis, respectively. Finally, a case is studied. The results illustrate that the model is effective than other multivariate grey incidence analysis models.

关键词： grey system multivariate grey incidence analysis behavioral matrix principal component analysis (PCA).

Polymer Synthesis Based on Self-Accelerating 1,3-Dipolar Cycloaddition Click Reactions

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Chinese Journal of Chemistry 2021年第11期39卷 3093-3100页

作者： Qingquan Tang ke zhang College of Materials Science and Engineering State Key Laboratory of New Textile Materials&Advanced Processing TechnologyWuhan Textile UniversityWuhanHubei430200 China Laboratory of Polymer Physics and Chemistry Beijing National Laboratory for Molecular SciencesInstitute of ChemistryThe Chinese Academy of SciencesBeijing100190 China University of Chinese Academy of Sciences Beijing100049 China

This review reports our recent work on developing polymer synthesis methods based on a self-accelerating double-strain-promoted 1,3-dipole-alkyne cycloaddition(DSPDAC)click *** DSPDAC,the cycloaddition of 1,3-dipole with the first alkyne of sym-dibenzo-1,5-cyclooctadiene-3,7-diyne(DIBOD)activates the second unreacted alkyne,which reacts with 1,3-dipole much faster than the original alkyne of *** using DIBOD and bis-dipole compounds as monomer pairs,the self-accelerating property of DSPDAC allows us to develop a stoichiometric imbalance-promoted step-growth polymerization *** could produce polymers with ultrahigh molecular weight in the presence of excess DIBOD *** using DIBOD to ring-close linear polymers with 1,3-dipole end groups,the self-accelerating property of DSPDAC facilitates us to develop a unique bimolecular ring-closure *** could efficiently prepare pure cyclic polymers in the presence of excess DIBOD small linkers to linear polymer precursors.

关键词： Polymerization Self-accelerating reaction Click chemistry Cyclic polymer Reactive intermediates

A multivariate grey incidence model for different scale data based on spatial pyramid pooling

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Journal of Systems Engineering and Electronics 2020年第4期31卷 770-779页

作者： zhang ke CUI Le YIN Yao Business School Hohai UniversityNanjing 211100China

In order to solve the problem that existing multivariate grey incidence models cannot be applied to time series on different scales, a new model is proposed based on spatial pyramid ***, local features of multivariate time series on different scales are pooled and aggregated by spatial pyramid pooling to construct n levels feature pooling matrices on the same scale. Secondly,Deng's multivariate grey incidence model is introduced to measure the degree of incidence between feature pooling matrices at each level. Thirdly, grey incidence degrees at each level are integrated into a global incidence degree. Finally, the performance of the proposed model is verified on two data sets compared with a variety of algorithms. The results illustrate that the proposed model is more effective and efficient than other similarity measure algorithms.

关键词： grey system spatial pyramid pooling grey incidence multivariate time series

The infrared spectral features of circumstellar envelope of evolved low- and intermediate-mass stars

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Science China(Physics,Mechanics & Astronomy) 2008年第9期51卷 1187-1199页

作者： zhang ke JIANG BiWei Department of Astronomy Beijing Normal UniversityBeijing 100875China

The circumstellar envelope of evolved stars of low- and intermediate-mass is an important site for dust formation. In comparison with the interstellar medium, they have more types of organics and different types of inorganics. Various infrared features in the circumstellar envelope can reveal the composition and abundance of dust, as well as the chemical and physical conditions of the circumstellar shell. Infrared features and their carriers are different in the C-rich or O-rich environment, and the mixed-environment where the C-rich and O-rich circumstellar materials co-exist. The C-rich sources exhibit a series of spectral features which are attrib- uted to organic molecules. They also show two prominent features at 21 μm and 30 μm which emit a large portion of infrared radiation. The O-rich sources exhibit the strong 9.7 μm and 18 μm features attributed to the Si-O bending and O-Si-O stretching modes of amorphous silicate dust. With the ISO/SWS spectrometer, about 50 narrow bands are identified with the crystalline silicate grains, mainly forsterite and enstatite. In addition, a series of features, at 13 μm, 16.8 μm, 19.5 μm and 31.8 μm, appearing to be correlated with each other, are attributed to oxides. Some objects simultaneously show the C-rich and O-rich features, e.g. some C-rich sources have silicate features. There is no well-accepted interpretation for such mixed appearance, though a binary model is suggested.

关键词： star: AGB post-AGB PN star: circumstellar matter infrared: star

A novel method of periodic orbit computation in circular restricted three-body problem

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Science China(Technological Sciences) 2011年第8期54卷 2197-2203页

作者： zhang HanQing LI YanJun zhang ke The College of Astronautics Northwestern Polytechnical University Xi'an 710072 China

Periodic orbits are fundamental keys to understand the dynamical system of circular restricted three-body problem, and they play important roles in practical deep-space exploration. Current methods of periodic orbit computation need a high-order analytical approximate solution to start the iteration process, thus making the computation complicated and limiting the types of periodic orbits that can be obtained. By utilizing the symmetry of the restricted three-body problem, a special kind of flow function is constructed, so as to map a state on the plane of symmetry to another state that also lies in this plane. Based on this flow function, a new method of periodic orbit computation is derived. This method needs neither a starting analytic approximation nor the state transition matrix to be computed, so it can be conveniently implemented on a computer. Besides, this method is unaffected by the nonlinearity of the dynamical system, allowing a large set of periodic orbits which have x-z plane symmetry to be computed numerically. As examples, some planar periodic orbits (e.g. Lyapunov orbit) and spatial periodic orbits (e.g. Halo orbit) are computed. By further combining with a differential correction process, the method introduced here can be used to design resonant orbits that can jump between different resonant frequencies. One such resonant orbit is given in this paper, verifying the efficiency of this method.

关键词： circular restricted three-body problem libration point periodic orbit numerical method resonant orbit

Electrochemical codeposition of typical α+β phases Mg-Li alloys from the molten LiCl-KCl-MgCl_2 system

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Rare Metals 2010年第2期29卷 198-203页

作者： YE ke CHEN Ye zhang Milin key Laboratory of the Ministry of Education for Superlight Materials ＆ Surface Technology College of Materials Science and Chemical Engineering Harbin Engineering University Harbin 150001 China

Electrochemical codeposition of Mg-Li alloys on molybdenum electrodes was investigated in LiCl-KCl（50 wt.%：50 wt.%） melts containing different concentrations of MgCl2 at 973 *** voltammograms show that the underpotential deposition of lithium on pre-deposited magnesium leads to the formation of liquid Mg-Li *** deposition potentials of Mg（II） and Li（I） ions gradually near each other with MgCl2 concentration ***-Li alloys with typical α ＋ β phases could be obtained by potentiostatic electrolysis from LiCl-KCl melts containing 5 wt.% MgCl2 at -2.25 V ***/AgCl（cathodic current density 1.70 A·cm-2） for 2.5 h.α phase, α ＋ β phases, and β phase Mg-Li alloys with different lithium contents were obtained by potentiostatic electrolysis from LiCl-KCl melts with the different concentrations of *** samples were characterized by X-ray diffraction and scanning electron microscopy.

关键词： physical chemistry Mg-Li alloys electrochemical codeposition molten salt electrolysis

Friction and Wear Behaviors of Nanostructured Metals

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Journal of Materials Science & Technology 2008年第4期24卷 483-494页

作者： Zhong HAN Yusheng zhang ke LU Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang110016 China

Nanostructured （ns） materials, i.e., polycrystalline materials with grain sizes in the nanometer regime （typically below 100 nm）, have drawn considerable attention in the past decades due to their unique properties such as high strength and hardness. Wear resistance of ns materials, one of the most important properties for engineering materials, has been extensively investigated in the past decades. Obvious differences have been identified in friction and wear behaviors Between the ns materials and their corresponding coarse-grained （cg） counterparts, consistently correlating with their unique structure characteristics and mechanical properties. On the other hand, the superior tribological properties of ns materials illustrate their potential applications under contact loads. The present overview will summarize the important progresses achieved on friction and wear behaviors of ns metallic materials, including ultrafine-grained （ufg） materials in recent years. Tribological properties and effects on friction and wear behaviors of ns materials will be discussed under different wear conditions including abrasive wear, sliding wear, and fretting wear. Their correlations with mechanical properties will be analyzed. Perspectives on development of this field will be highlighted as well.

关键词： Nanostructured metals Friction Wear Mechanical properties Tribological properties

Application of subfossil cladocerans(water fleas) in assessing ecological resilience of shallow Yangtze River floodplain lake systems(China)

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Science China Earth Sciences 2018年第9期61卷 1157-1168页

作者： Giri KATTEL ke zhang Xiangdong YANG State key Laboratory of Lake Science and Environment Nanjing Institute of Geography and LimnologyChinese Academy of Sciences Environmental Hydrology and Water Resources Group Department of Infrastructure EngineeringThe University of Melbourne

Majority of shallow floodplain lake ecosystems of the middle and lower reaches of the Yangtze River(China) have gone through serious eutrophication problems over the recent past. The severe environmental deterioration accompanied by cyanobacterial blooms have become major water resource management challenges in the region. An advanced research method is urgently needed to tackle these challenges. The concept of ecological resilience address pressing questions of non-linear dynamics, threshold effects and regime shifts in shallow floodplain lakes, and help manage the ecosystem effectively. Palaeolimnological techniques are important for assessing long term resilience and associated thresholds effects of shallow lake ecosystems. However, the lack of reliable proxy methods available, the assessment of long term ecological resilience of shallow Yangtze River lake systems has become increasingly difficult. Cladocerans(water fleas) play a central role in lacustrine food webs by responding to external drivers and internal ecosystem processes in lakes. Their subfossils are well preserved and becoming one of potential proxy indicators of lake ecosystems change for a longer time scale. This study explores the potential application of subfossil cladocerans and their ephippia in assessing a long term ecological resilience and help better management strategies of lake ecosystems and water resources of the middle and lower reaches of the Yangtze River in China.

关键词： Subfossil cladoceran Yangtze River lake system Food web Ecological resilience Regime shift Threshold