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Factors affecting the geographical distribution of invasive species in China

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Journal of Integrative Agriculture 2022年第4期21卷 1116-1125页

作者： CHEN xiao-ling NING Dong-dong xiao qian JIANG Qiu-ying LU Yong-yue XU Yi-juan Department of Entomology South China Agricultural UniversityGuangzhou 510642P.R.China

Frequent international trade has accelerated alien species invasion. However, data on the distribution of invasive species after their introduction and research on the factors that determine their geographical distribution are lacking. This study analyzed the distributional trends of invasive species in China and the drivers for such trends, by identifying the effect of international trade from a dynamic analysis of 13 main invasive insect pests in three time periods - before China’s reform and opening up in 1978, from 1979 to 2001, and after China’s accession to the World Trade Organization in 2001. The results showed that the abundance of invasive species gradually decreased from south to north and from southeast coast to inland. Guangdong(442 species) and Yunnan(404 species) provinces have the highest abundance of invasive species. Among the 13 key invasive insects investigated, 3, 10 and 13 occurred chronologically in the three periods, and invaded 7, 28 and 34 provinces, respectively. Alien pests are found to invade China through Xinjiang, the Bohai Rim and the southeast. Value of imports was a strong predictor of the number of invasive species in China, and followed by temperature heterogeneity, in explaining the richness pattern of invasive animal, plants and insects, but not that of microorganisms. This study provides a scientific basis for furthering international quarantine and effective invasive species control.

关键词： international trade biological invasion population dispersal international quarantine

Particle interaction during magnetization reversal process of anisotropic Sm_2Fe_(17)N_x powders

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Rare Metals 2018年第10期37卷 875-880页

作者： Ci-Fu Lu Xiu-Feng Hong xiao-qian Bao Xue-Xu Gao Jie Zhu State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing

The particle interaction during magnetization reversal process is important for the applications and magnetic properties improvement of Sm2Fe17Nx powders. In this paper, an anisotropic Sm2Fe17Nx powder free of α- Fe was prepared by ball milling. The magnetically soft Sm2Fe17 powders with different particle sizes were added into the α-Fe-free SmaFe17Nx powder as easy nucleation sites, and the effects of these magnetically soft phases on the magnetization reversal process were investigated quantitatively. It is found that the squareness of Sm2Fe17Nx powder decreases obviously with the increasing number of Sm2Fe17 particle and the demagnetization curves can be divided into two stages. The magnetization reversal process suggests that the addition of magnetically soft powder should only reduce the coercivity of a specific part of Sm2Fe17Nx particles and the reversed domain walls cannot move easily across neighboring Sm2Fe17Nx particles. Based on the observed magnetization reversal process, the mechanical properties of magnetically soft phase should be considered in the preparation of anisotropic Sm2Fe17Nx powders.

关键词： Rare earth permanent magnets Sm2Fe17Nx Magnetic domain behavior

Texture-based magnetostriction calculation of oriented polycrystalline cobalt ferrites

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Rare Metals 2018年第5期37卷 421-426页

作者： Ji-Quan Wang Ji-Heng Li Chao Yuan xiao-qian Bao Xue-Xu Gao State Key Laboratory of Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083China

Oriented polycrystalline cobalt ferrites with different alignments were prepared via a ceramic method. The maximum magnetostriction λs up to -270×10^-6 was achieved for oriented samples, when the oriented magnetic field was above 1.0 T. Textures of all samples were determined by electron back-scattered diffraction （EBSD） technique and were used to calculate magnetostriction values of oriented polycrystalline cobalt ferrite samples. Results show that a preferred 〈001〉 orientation has been obtained within oriented sample. Calculation was done by considering the magnetostriction value as the sum of the content in volume fraction-weighted single-crystal behavior along [100], [110], [210], [310], [311], [211] and [111] directions. The calculated magnetostriction values when compared with experimentally obtained values show identical behavior as a function of applied magnetization orientation field. Good consistency of change rules between calculated values and measured ones illustrates the successful application of this method in predicting magnetostriction values of polycrystalline materials.

关键词： Magnetostriction calculation Oriented polycrystalline Cobalt ferrites Texture

Inhibition force of precipitates for promoting abnormal grain growth in magnetostrictive Fe83Ga17-(B,NbC) alloy sheets

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Rare Metals 2017年第11期36卷 886-893页

作者： Ji-Heng Li Wen-Lan Zhang Chao Yuan xiao-qian Bao Xue-Xu Gao State Key Laboratory of Advanced Metals and Materials University of Science and Technology Beijing 100083 China

Inhibition force of precipitate particles for pro- moting abnormal grain growth in magnetostrictive Feg3Ga17-（B,NbC） alloy sheets was investigated in this study. After a continuous heating and a high-temperature annealing, the Fe83Gat7 ＋ 0.5 at% B alloy sheets do not occur significant abnormal grain growth. Correspondingly, textures of { 111 }〈112〉 and { 100}〈00l〉 in addition to the Goss texture are obtained in the final annealed alloy sheets. By contrast, after the same annealing processes, the size of {110} textured grains is very large in the final annealed Fe83Gaj7 ＋ 0.5 at% NbC alloy sheets due to the abnormal grain growth, which results in a sharp Goss texture. BN precipitates were introduced into Fes3Ga17 ＋ 0.2 at% B alloy sheets by nitriding annealing at 800℃ for 2 min under NH3 atmosphere. The abnormal grain growth of Goss grains is achieved in 0.2 at% B-doped Fe83Ga17 alloy sheets after a high-temperature annealing, which is attributed to the enhanced inhibition force by introducing BN precipitates. During the recrystallization annealing process, Fe2B precipitates is easy to coarsen and decom- pose at high temperature due to the low thermal stability, resulting in a decrease or even disappearance of the inhi- bition force. For NbC and BN precipitates, the thermal stability and hardness of particles are both better than those of Fe2B precipitates, leading to strong inhibition force. Because of the preferred Goss texture, the magnetostriction of 2.05 × 10-4 and 1.81 × 10 4 is obtained in the sec- ondary recrystallized Fe83Gal7 ＋ 0.5 at% NbC and Fes3Gaw ＋ 0.2 at% B alloy sheets, respectively.

关键词： Fe-Ga alloy Magnetostriction Grain growth Inhibition force Precipitates

Comparative Analysis of Eubacterial DNA Polymerase III Alpha Subunits

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Genomics, Proteomics & Bioinformatics 2006年第4期4卷 203-211页

作者： xiao-qian Zhao Jian-Fei Hu and Jun Yu Beijing Institute of Genomics Chinese Academy of SciencesBeijing 101300China Graduate School ofChinese Academy of Sciences Beijing 100049China College of Life Sciences Peking UniversityBeijing100871China James D.Watson Institute of Genome Sciences Zhejiang UniversityHangzhou 310008China.

DNA polymerase Ⅲ is one of the five eubacterial DNA polymerases that is responsible for the replication of DNA duplex. Among the ten subunits of the DNA polymerase Ⅲ core enzyme, the alpha subunit catalyzes the reaction for polymerizing both DNA strands. In this study, we extracted genomic sequences of the alpha subunit from 159 sequenced eubacterial genomes, and carried out sequence- based phylogenetic and structural analyses. We found that all eubacterial genomes have one or more alpha subunits, which form either homodimers or heterodimers. Phylogenetic and domain structural analyses as well as copy number variations of the alpha subunit in each bacterium indicate the classification of alpha subunit into four basic groups: polC, dnaE1, dnaE2, and dnaE3. This classification is of essence in genome composition analysis. We also consolidated the naming convention to avoid further confusion in gene annotations.

关键词： DNA polymerase III alpha subunit dnaE polC

Enhancement of magnetic properties and thermal stability of nanocrystalline (NdDyTb)_(12.3)(FeZrNbCu)_(81.7)B_(6.0) alloy with Co substitution

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International Journal of Minerals,Metallurgy and Materials 2009年第6期16卷 696-700页

作者： xiao-qian Bao Wei Li Jie Zhu Xue-xu Gao Shou-zeng Zhou State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China College of Materials Science and Engineering Yanshan University Qirdauangdao 066004 China

The major drawbacks of Nd-Fe-B magnets are relatively low Curie temperature and poor thermal stability. Ribbons with the near stoichiometric 2：14：1 composition of Nd10.8Dy0.75Tb0.75Fe79.7-xCoxZr0.8Nb0.8Cu0.4B6.0 （x=0, 3, 6, 9, 12, 15） were prepared by rapid quenching and subsequent heat treatment. The effect of Co element on the magnetic properties, thermal stability, and microstructure of the ribbons was systematically studied by vibrating sample magnetometer （VSM）, thermal magnetic analysis, atomic force microscopy （AFM）, and transmission electron microscopy （TEM）. It was found that Co substitution was significantly effective in improving the magnetic properties and the thermal stability of nanocrystalline ribbons. Although the intrinsic coercivity decreased from 1308.7 kA/m for x=0 to 817.4 kA/m for x=15, the remanence polarization and maximum energy product increased from 0.839 T and 116.5 kJ/m^3 for the Co-free samples to 1.041 T and 155.1 kJ/m^3 for the 12at% Co-substituted samples, respectively. About 10 K increase in Curie temperature was observed for the 2：14：1 phase with 1at% Co substitution. The absolute values of temperature coefficients of induction and coercivity were significantly decreased with Co substitution, which may be attractive for high operational temperature applications. The microstructure of nanocrystalline ribbons was slightly refined with Co substitution.

关键词： nanocrystalline magnets Nd-Fe-B magnets Co substitution magnetic properties thermal stability microstructure

Microstructure and magnetostrictive performance of NbC-doped <100>oriented Fe-Ga alloys

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International Journal of Minerals,Metallurgy and Materials 2015年第1期22卷 52-58页

作者： Chao Yuan Ji-heng Li Wen-lan Zhang xiao-qian Bao Xue-xu Gao State Key Laboratory of Advanced Metals and Materials University of Science and Technology Beijing

The〈100〉oriented Fe83Ga17 alloy rods with various NbC contents less than 1at%were prepared by the directional solidification method at a growth rate of 720 mm·h^-1. Low NbC-content was found to affect the oriented grain growth and slightly improve the〈100〉ori-entation. Flat grain boundaries in the alloys with low NbC contents less than 0.2at%became greatly curved at higher NbC contents, and a large amount of Nb-rich precipitates were observed in the alloys with high NbC contents. Small amounts of NbC, less than 0.2at%, resulted in an increase in magnetostrictive strain due to the improvement of the〈100〉orientation, and a high magnetostrictive strain value of 335 ×10^-6 under a pre-stress of 15 MPa was obtained in the 0.1at%NbC-doped alloys. The magnetostrictive performance obviously decreased with the NbC addition higher than 0.5at%, and the strain sensitivity under no pre-stress was lower than that in the binary Fe？Ga alloy.

关键词： iron gallium alloys magnetostriction texture niobium carbide directional solidification

Estimation of OCDD degradation rate in soil

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Journal of Environmental Sciences 2005年第6期17卷 981-983页

作者： ZHAO Xing-ru ZHENG Ming-hui ZHANG Bing qian Yong XU xiao-bai State Key Laboratory of Environmental Chemistry and Ecotoxicology Research Center for Eco-Environmental Sciences Chinese Academy of ScienceBeijing 100085 China

The current concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans （PCDD/Fs） were determined in soils contaminated with Chinese technical product sodium pentachlorophenate （ Na- PCP）. The estimated half-life of octachlorodioxin （OCDD） was about 14 years in contaminated soils based on the local historical record and mass balance calculation during the past 43 years（ 1960-2003）. The isomer profiles remained the same regardless of paddy field soil or riverbank soil. The results indicated that the congenerspecific information was efficient in estimating the PCDD/Fs fate in contaminated soils.

关键词： OCDD degradation rate Na-PCP

Synthesis of(S) and(R)-tilisolol hydrochloride

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Chinese Chemical Letters 2009年第6期20卷 648-650页

作者： Shan qian xiao Juan Ye Fan Zheng Li Yang Yong Wu Key Laboratory of Drug Targeting West China School of Pharmacy Sichuan University Chengdu Sichuan 610041 China

Tilisolol hydrochloride 1, a non-selective β-adrenoceptor blocker, was developed as a drug for the treatment of hypertension and angina pectoris. The optical active forms of 1, la and lb were synthesized from inexpen... 详细信息

关键词： Tilisolol hydrochloride Optical Synthesis