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Significantly Enhanced Melt Memory Effect of Metallocene-made Isotactic Polypropylene Containing Talc

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Chinese Journal of Polymer Science 2024年第2期42卷 213-222,I0008页

作者： Hong-Wen Sun fu-Shan Wang Yan Gao fu-Qing Wei Jia-chun Feng State Key Laboratory of Molecular Engineering of Polymers Department of Macromolecular ScienceFudan UniversityShanghai200433China Lanzhou Petrochemical Corporation of PetroChina Lanzhou730060China Lanzhou Petrochemical Research Center Petrochemical Research Institute of PetroChinaLanzhou730060China

The melt memory effect is a widely observed phenomenon in semi-crystalline polymers. In practical applications, various additives are usually introduced into polymers, which may affect their melt memory behavior. In this work, the effect of talc on the melt memory effect of metallocene-made isotactic polypropylene(M-PP) was investigated in detail by using the differential scanning calorimetry. The results indicated that the introduction of talc significantly strengthened the melt memory effect of M-PP. Specifically, the upper limit temperature of Domain II increased from 161 ℃ to 174 ℃, resulting in a substantial widening of the temperature range of Domain IIa from 1 ℃ to 14 ℃. Analysis of the crystal orientation of the M-PP containing talc cooled from various Ts suggested that the remarkably enhanced melt memory effect could be ascribed to the stabilization of oriented nuclei facilitated by talc. This stabilizing effect was likely attributable to the prefreezing effect or the sorption interaction between talc and the M-PP chains.

关键词： Metallocene-made isotactic polypropylene Talc Melt memory effect Crystal orientation

Elastic three-dimensional phononic topological insulators with Dirac hierarchy

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Science China(Physics,Mechanics & Astronomy) 2024年第5期67卷 54-62页

作者： Shao-Yong Huo Qiu-Shuang Yang Jiu-Jiu Chen Hong-Kang Li Long-Chao Yao fu-chun He chun-Ming fu College of Mechanical Engineering University of South ChinaHengyang 421001China State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle EngineeringHunan UniversityChangsha 410082China

Three-dimensional(3D)phononic topological insulators(TIs)featuring two-dimensional(2D)surface states and one-dimensional(1D)hinge states have opened up a new route for multi-dimensional robust wave transport,providing unprecedented methods for integrated acoustic sensors and energy harvesting ***,aiming at the elastic 3D phononic TI with gapless surface states and hinge states,the realization of elastic 3D phononic TIs with gapless surface states and hinge states is a significant challenge due to the complicated multi-mode polarization of elastic waves in 3D *** this study,we demonstrate an elastic 3D phononic TI with a Dirac hierarchy by elaborately operating the corresponding spatial symmetries of the chiral honeycomb ***,a 3D double Dirac cone of elastic wave can be achieved by doubling the lattice along the outof-plane direction to fold two iso-frequency Weyl *** topological phase transitions and 2D gapless two-fold Dirac surface states of elastic wave are realized by breaking the half-lattice spatial translation ***,based on the Brillouin zone folding along the in-plane direction,the 2D gapless two-fold surface Dirac cones are folded into four-fold surface Dirac ***,by inducing the relative radius of adjacent holes to break the in-plane spatial inversion symmetry,the fourfold surface Dirac cones are gapped and associated with a surface state inversion,in which the gapless 1D hinge Dirac dispersion is *** research offers a route for engineering the hierarchies of TIs in 3D elastic wave systems and provides new possibilities for designing 3D ultrasonic devices with unconventional functions.

关键词： Dirac topological hierarchy

Soil bacterial and fungal communities resilience to long-term nitrogen addition in subtropical forests in China

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Journal of Forestry Research 2024年第2期35卷 95-108页

作者： Xinlei fu Yunze dai Jun Cui Pengfei Deng Wei Fan Xiaoniu Xu School of Forestry and Landscape Architecture Anhui Agricultural UniversityHefei 230036AnhuiPeople’s Republic of China Suzhou Polytechnic Institute of Agriculture Suzhou 215008JiangsuPeople’s Republic of China College of Life and Environment Sciences Huangshan UniversityHuangshan 245041AnhuiPeople’s Republic of China

Atmospheric nitrogen(N)deposition is predicted to increase,especially in the ***,the responses of soil microorganisms to long-term N addition at the molecular level in N-rich subtropical forests have not been clarified.A long-term nutrient addition experiment was conducted in a subtropical evergreen old-growth forest in *** four treatments were:control,low N(50 kg N ha^(-1)a^(-1)),high N(100 kg N ha^(-1)a^(-1)),and combined N and phosphorus(P)(100 kg N ha^(-1)a^(-1)+50 kg P ha^(-1)a^(-1)).Metagenomic sequencing characterized diversity and composition of soil microbial communities and used to construct bacterial/fungal co-occurrence ***-treated soils were more acidic and had higher levels of dissolved organic carbon than *** were no significant differences in microbial diversity and community composition across *** addition of nutrients increased the abundance of copiotrophic bacteria and potentially beneficial microorganisms(e.g.,Gemmatimonadetes,Chaetomium,and Aureobasidium).Low N addition increased microbiome network *** rare fungi were identified as module hubs under nutrient addition,indicating that low abundance fungi were more sensitive to increased *** results indicate that the overall composition of microbial communities was stable but not static to long-term N *** findings provide new insights that can aid predictions of the response of soil microbial communities to long-term N addition.

关键词： Long-term nitrogen addition Old-growth subtropical forest Metagenomics Beneficial microorganisms Co-occurrence network

Study on the Performance of the GRANDProto300 Particle Detector Array by Simulation

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Research in Astronomy and Astrophysics 2024年第1期24卷 173-177页

作者： fu-Lin dai Quan-Bu Gou Xiaoyuan Huang Yi-Qing Guo Key Laboratory of Dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210023China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China Key Laboratory of Particle Astrophysics Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China University of Chinese Academy of Sciences Beijing 100049China

The Giant Radio Array for Neutrino Detection(GRAND)is a proposed large-scale observatory designed to detect cosmic rays,gamma-rays,and neutrinos with energies exceeding 100 Pe *** GRANDProto300 experiment is proposed as the early stage of the GRAND project,consisting of a hybrid array of radio antennas and scintillator *** latter,as a mature and traditional detector,is used to cross-check the nature of the candidate events selected from radio *** this study,we developed a simulation software called G4GRANDProto300,based on the Geant4 software package,to optimize the spacing of the scintillator detector array and to investigate its effective *** analysis was conducted at various zenith angles under different detector spacings,including 300,500,600,700,and 900 *** results indicate that,for large zenith angles used to search for cosmic-ray in the GRAND project,the optimized effective area is with a detector spacing of 500 *** G4GRANDProto300 software that we developed could be used to further optimize the layout of the particle detector array in future work.

关键词： astroparticle physics instrumentation:detectors (ISM:)cosmic rays

Insight into the Role of Isolated Gold Atoms-Ceria Conjunction in Catalyzing the Water-Gas Shift Reaction

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Chinese Journal of Chemistry 2024年第6期42卷 636-644页

作者： Xin-Pu fu Hui-Zhao Wei-Wei Wang chun-Jiang Jia Key Laboratory for Colloid and Interface Chemistry Key Laboratory of Special Aggregated MaterialsSchool of Chemistry and Chemical EngineeringShandong UniversityJinanShandong250100 China

As the promising catalysts for the water-gas shift(WGS)reaction,the activity of Au-CeO_(2) composites is susceptible to the aggregation size and electronic state of Au *** reports were extensively focused on the discrepancy between nonmetallic Au and metallic Au nanoparticles,whereas the understanding of the authentic role of the isolated Au atoms was ***,we investigated the catalytic behavior and structural information over two types of Au/CeO_(2) catalysts,in which the predominant conjunctions were isolated Au1-CeO_(2) and Aun-CeO_(2),*** on comprehensive characterizations,particularly by in-situ Raman and in-situ DRIFTS,we found that the isolated Au atoms were responsible for enhancing the reducibility of the CeO_(2) *** CO adsorption ability on the isolated Au sites was significantly inferior to clustered Au atoms,especially at relatively high temperatures(>200°C).As a result,the boosted O vacancy on the isolated Au1-CeO_(2) conjunctions could improve the H2O activation ability for the Au-CeO_(2) catalysts and demonstrate a comparable activity to the clustered Aun-CeO_(2) *** work might deepen understanding of the catalytic function for the isolated Au1 site within Au/CeO_(2) systems while catalyzing the WGS reaction.

关键词： Isolated Au atoms Ceria-based catalysts Water-gas shift reaction Defect Adsorption

The effects of various factors on spontaneous imbibition in tight oil reservoirs

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Petroleum Science 2024年第1期21卷 315-326页

作者： Cheng Liu Tian-Ru Wang Qing You Yue-chun Du Guang Zhao Cai-Li dai School of Energy Resources China University of GeosciencesBeijing100083PR China School of Petroleum Engineering China University of PetroleumQingdao266580ShandongPR China

Slickwater fracturing fluids have gained widespread application in the development of tight oil reservoirs. After the fracturing process, the active components present in slickwater can directly induce spontaneous imbibition within the reservoir. Several variables influence the eventual recovery rate within this procedure, including slickwater composition, formation temperature, degree of reservoir fracture development, and the reservoir characteristics. Nonetheless, the underlying mechanisms governing these influences remain relatively understudied. In this investigation, using the Chang-7 block of the Changqing Oilfield as the study site, we employ EM-30 slickwater fracturing fluid to explore the effects of the drag-reducing agent concentration, imbibition temperature, core permeability, and core fracture development on spontaneous imbibition. An elevated drag-reducing agent concentration is observed to diminish the degree of medium and small pore utilization. furthermore, higher temperatures and an augmented permeability enhance the fluid flow properties, thereby contributing to an increased utilization rate across all pore sizes. Reduced fracture development results in a lower fluid utilization across diverse pore types. This study deepens our understanding of the pivotal factors affecting spontaneous imbibition in tight reservoirs following fracturing. The findings act as theoretical, technical, and scientific foundations for optimizing fracturing strategies in tight oil reservoir transformations.

关键词： Tight oil reservoir Spontaneous imbibition Nuclear magnetic resonance Slickwater fracturing fluid Fluid utilization degree

The preface: Interplay of topological and magnetic orders in the Mn-Bi-Te family

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National Science Review 2024年第2期11卷 6-7页

作者： fu-chun Zhang Hai-Zhou Lu X.C.Xie Kavli Institute for Theoretical Sciences University of Chinese Academy of Sciences Department of Physics Southern University of Science and Technology (SUSTech) International Center for Quantum Materials School of Physics Peking University

The discovery and synthesis of MnBi2Te4in 2013 initially garnered little attention [1]. Yet, the revelation of its topological properties in 2019 [2–6] sparked a surge of research into the MnBiTe family. These extensive studies are primarily driven by two objectives:the realization of a high-temperature quantum anomalous Hall effect （QAHE） and the exploration of exotic phases born from the interplay of topological and magnetic orders,

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Precise immobilization of metal single atoms into a porphyrinic metal-organic framework for an efficient alkene hydrosilylation

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Nano Research 2024年第7期17卷 5914-5921页

作者： chun-Ying Chen Qi-Jie Mo fu-Zhen Li Hai-Li Song Li Zhang MOE Laboratory of Bioinorganic and Synthetic Chemistry Lehn Institute of Functional MaterialsSchool of ChemistrySun Yat-Sen UniversityGuangzhou 510006China

Alkene hydrosilylation is one of the most concise and atom-economical methods to synthesize organosilicon ***,we reported the precise immobilization of metal single atoms(M-SAs;M=Ru,Rh,Ir,Pd,Pt,and Au)into a porphyrinic metalorganic framework(MOF)of PCN-222(PCN=porous coordination network),and then applied the resultant MOF composites of M-SAs@PCN-222 to alkene *** solvent-free conditions,Pt-SAs@PCN-222 displayed an especially high catalytic efficiency with the turnover frequency up to 119 s−1 and the maximum turnover number of 906,250 at room *** and theoretical studies revealed that there existed strong interactions between Pt-SAs@PCN-222 and the substrates,which helped to condense the substrates in the cavities of the porous *** density functional theory calculations and molecular dynamics simulations disclosed that PCN-222 could transfer electrons to Pt-SAs to enhance the silane oxidative addition and drive the reaction to proceed smoothly via Chalk–Harrod pathway.

关键词： alkene hydrosilylation single atom catalysts metal-organic frameworks precision chemistry synergistic catalysis

Intrinsically asymmetric atomic character regulates piezoelectricity in two-dimensional materials

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Frontiers of physics 2024年第3期19卷 153-162页

作者： Yun-Qin Li Qi-Wen He dai-Song Tang Xiao Shang Xiao-chun Wang School of Physics Science and Information Technology Liaocheng UniversityLiaocheng 252000China Key Laboratory of Polar Materials and Devices Ministry of EducationDepartment of ElectronicsEast China Normal UniversityShanghai 200241China Institute of Atomic and Molecular Physics Jilin UniversityChangchun 130012China

Decreasing of layer thickness causes the decrease of polarization until it disappears due to the existence of depolarization ***,the search for strong piezoelectric materials is highly desirable for multifunctional ultra-thin piezoelectric ***,we propose a common strategy for achieving strong piezoelectric materials through the electronic asymmetry induced by the intrinsically asymmetric atomic character of different chalcogen ***,in the tetrahedral lattice structures,for example,M4X3Y3(M=Pd/Ni,X/Y=S,Se or Te,X≠Y)monolayers are proved to display excellent out-of-plane ***4Se3Te3 possesses the largest piezoelectric coefficient d33 of 61.57 pm/V,which is much larger than that of most 2D *** the electronic asymmetry further increases the out-of-plane piezoelectricity of Janus M4X3Y3 ***,the out-of-plane piezoelectricity is positively correlated with the ratio of electronegativity difference(Red)and the electric dipole moment(P).This work provides alternative materials for energy harvesting nano-devices or self-energized wearable devices,and supplies a valuable guideline for predicting 2D materials with strong out-of-plane piezoelectricity.

关键词： piezoelectricity intrinsically asymmetric atomic character ratio of electronegativity difference electric dipole moment first-principles calculations