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Surface morphology and electronic structure in stoichiometric superconductor CaKFe_(4)As_(4) robed by scanning tunneling microscopy/spectroscopy

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Science China(Physics,Mechanics & Astronomy) 2021年第12期64卷 144-150页

作者： Xiaodong Yu Zhongxu Wei Zhanyi Zhao Tao Xie Chang Liu Ge He Qihong Chen Lei Shan Huiqian Luo Qing Huan Jie Yuan Kui Jin Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China walther meissner institute Bayerische Akademie der WissenschaftenGarching 85748Germany Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of Education Institutes of Physical Science and Information TechnologyAnhui UniversityHefei 230601China Songshan Lake Materials Laboratory Dongguan 523808China

CaKFe_(4)As_(4) is a new-type superconductor with a relatively high transition temperature of 35 K among stoichiometric iron-based superconductors. Based on scanning tunneling microscopy/spectroscopy, the surface morphology and electronic structure of CaKFe_(4)As_(4) single crystal were systematically investigated. The cleaved CaKFe_(4)As_(4) showed various morphologies, such as atomically resolved 1×1, 1×2, and √2×√2 lattices. By analyzing the geometrical correlations of these morphologies, the 1×1 and 1×2 lattices were identified as the original and reconstructed As layers, respectively, whereas the √2×√2 lattice was distinguished as the reconstructed alkaline-earth-metal or alkali-metal layer. The superconducting energy gap of 7.3 me V and bosonic mode of 12.7 me V were resolved in the scanning tunneling spectra. In addition, the superconducting energy gaps measured on different terminations were identical and consistent with the values obtained by bulk-sensitive techniques, indicating that the electronic structures of CaKFe_(4)As_(4) were insensitive to the surface reconstructions. Our study clarifies the relationships between complex surface reconstructions and surface terminations and preliminarily presents that there is no obvious effect of surface reconstructions on electronic states.

关键词： CaKFe_(4)As_(4) scanning tunneling microscopy surface reconstructions superconductivity

Behavior of wood basic density according to environmental variables

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Journal of Forestry Research 2022年第2期33卷 497-505页

作者： Gabriel Marcos Vieira Oliveira JoséMárcio de Mello Carlos Rogério de Mello JoséRoberto Soares Scolforo Eder Pereira Miguel Thiago Campos Monteiro Brazil institute of Agricultural and Forestry Defense of Espírito Santo(IDAF) Av.Lourival Lugon Moulinnº300CentroJerônimo MonteiroES CEP:29.550-000Brazil Department of Forestry Sciences Universidade Federal de Lavras-UFLACaixa Postal 3037LavrasMG CEP:37.200-000Brazil Engineering Department Universidade Federal de Lavras-UFLACaixa Postal 3037LavrasMG CEP:37.200-000Brazil Forestry Engineering Department Faculdade de TecnologiaUniversity of Brasilia-UnBCampus Universitário Darcy RibeiroCaixa Postal 4357Asa Norte-BrasíliaDF CEP:70910-900Brazil Department of Forestry Engineering and Technology Universidade Federal do Paraná-UFPRAv.Pref.Lothário Meissner632Jardim BotânicoCuritibaPR CEP:80.210-170Brazil

The relationships between climate conditions and wood density in tropical forests are still poorly understood.To quantify spatial dependence of wood density in the state of Minas Gerais(MG,Brazil),map spatial distribution of density,and correlate density with climate variables,we extracted data from the Forest Inventory of Minas Gerais for 1988 trees scaled throughout the territory and measured wood density of discs removed from the trees.Environmental variables were extracted from the database of the Ecological-Economic Zoning of Minas Gerais.For spatial analysis,tree densities were measured at 44 georeferenced sampling points.The data were subjected to exploratory analysis,variography,cross-validation,model selection,and ordinary kriging.The relationships between wood density and environmental variables were calculated using dispersion matrices,linear correlation,and regression.Wood density proved to be highly spatially dependent,reaching a correlation of 96%,and was highly continuous over a distance of 228 km.The distribution of wood density followed a continuous gradient of 514-659 kg m^(−3),enabling corre-lation with environment variables.Density was correlated with mean annual precipitation(−0.57),temperature(0.63),and evapotranspiration(0.83).Geostatistical methods proved useful in predicting wood density in native tropical forests with different climate conditions.Our results confirmed the sensitivity of wood density to climate change,which could affect future carbon stock in forests.

关键词： Biomass Climate variables Geostatistics Hardwood Forest inventory Minas Gerais

Experimental evidence for type-1.5 superconductivity in ZrB_(12)single crystal

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Science China(Physics,Mechanics & Astronomy) 2022年第9期65卷 119-127页

作者： An-Lei Zhang Li-Xin Gao Jing-Yu He Volodimir B.Filipov Shixun Cao Qi-Ling Xiao Jun-Yi Ge Materials Genome institute Shanghai UniversityShanghai 200444China Frantsevich institute for Problems of Materials Science NASUKiev 03680Ukraine Department of Physics Shanghai Key Laboratory for High Temperature SuperconductorsShanghai UniversityShanghai 200444China Zhejiang Laboratory Hangzhou 311100China

Recent studies proposed the two-band effect and the related type-1.5 superconductivity in Zr B12single crystal.Here,by combining both macroscopic and microscopic measurements,the superconducting properties and the intricate vortex matter of Zr B12are studied in detail.The vortex phase diagram is constructed,where the temperature dependence of the upper critical field can be well reproduced using a two-band Werthamer-Helfand-Hohenberg(WHH)model.A pronounced surface superconductivity is also found in the same temperature range,where the semi-meissner state is observed.Both phenomena are attributed to the weakly coupled two-band effect.The direct visualization of the semi-meissner state exhibits an inhomogeneous distribution of vortex clusters,vortex chains and large meissner areas.With the increase of magnetic field,a transition from the semi-meissner state to the mixed state is revealed and further supported by statistical analysis of the vortex pattern.Our results provide direct experimental evidence for the type-1.5 superconductivity in ZrB_(12).

关键词： type-1.5 superconductivity vortex semi-meissner state MFM

Cooper instability and superconductivity of the Penrose lattice

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Science China(Physics,Mechanics & Astronomy) 2022年第8期65卷 110-120页

作者： Yu-Bo Liu Juan-Juan Hao Yongyou Zhang Ye Cao Wei-Qiang Chen Fan Yang School of Physics Beijing Institute of TechnologyBeijing100081China Department of Physics Southern University of Science and TechnologyShenzhen518055China Shenzhen institute for Quantum Science and Engineering Southern University of Science and TechnologyShenzhen518055China Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices Southern University of Science and TechnologyShenzhen518055China

Bulk superconductivity(SC) has recently been observed in the Al-Zn-Mg quasicrystal(QC). To settle several fundamental issues of the SC on the QC, we use an attractive Hubbard model to perform a systematic study on the Penrose lattice. The first issue is the Cooper instability of the QC, i.e., no Fermi surface under an infinitesimal attractive interaction. Starting from the two-electron problem outside a filled Fermi sea, we analytically prove that an infinitesimal Hubbard attraction can lead to the Cooper instability as long as the density of the state is nonzero at the Fermi level. The findings provide a basis for the SC on the QC. Our numerical results show that the Cooper pairing always takes place between two time-reversal states, satisfying Anderson’s theorem. On this theorem, we perform a mean-field(MF) study at zero and finite temperatures. The MF study shows that an arbitrarily weak attraction can lead to a pairing order, with the resulting pairing state being well described by the Bardeen-Cooper-Schrieffer theory and the thermal dynamic behaviors being well consistent with the experimental results. The second issue is about the superfluid density on the QC without translational symmetry. Our findings clarify that although the normal state of the system locates at the critical point of the metal-insulator transition, the pairing state exhibits a real SC, carrying finite superfluid density that can be verified by the meissner effect. This finding is consistent with the experiment results. This study also reveals that the properties of the SC on the Penrose lattice are universal for all QCs.

关键词： superconductivity quasicrystal cooper instability

PI 3-kinase pathway is responsible for antiapoptotic effects of atrial natriuretic peptide in rat liver transplantation

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World Journal of Gastroenterology 2006年第7期12卷 1049-1055页

作者： Uwe Grutzner Melanie Keller Michael Bach Alexandra K Kiemer Herbert meissner Manfred Bilzer Stefan Zahler Alexander L Gerbes Angelika M Vollmar institute for Surgical Research Klinikum GroBhadernUniversity of MunichD-81377 MunichGermany Department of Pharmacy University of MunichD-81377 MunichGermany Department institute of Pathology University of MunichD-81377 MunichGermany

AIM:To investigate the in vivo effect of atrial natriureticpeptide(ANP)and its signaling pathway during ortho-topic rat liver transplantation.METHODS:Rats were infused with NaCl,ANP(5 μg/kg),wortmannin(WM,16 μg/kg),or a combination ofboth for 20 min.Livers were stored in UW solution(4°C)for 24 h,transplanted and reperfused.Apoptosis wasexamined by caspase-3 activity and TUNEL staining.Phosphorylation of Akt and Bad was visualized by West-ern blotting and phospho-Akt-localization by confocalmicroscopy.RESULTS:ANP-pretreatment decreased caspase-3activity and TUNEL-positive cells after cold ischemia,indicating antiapoptotic effects of ANP in vivo.The an-tiapoptotic signaling of ANP was most likely caused byphosphorylation of Akt and Bad,since pretreatment withPI 3-kinase inhibitor WM abrogated the ANP-inducedreduction of caspase-3 activity.Interestingly,analysis ofliver tissue by confocal microscopy showed translocationof phosphorylated Akt to the plasma membrane of hepa-tocytes evoked by ANP.CONCLUSION:ANP activates the PI-3-kinase pathwayin the liver in vivo leading to phosphorylation of Bad, an event triggering antiapoptotic signaling cascade inischemic liver.

关键词： 3-激酶尿钠排泄肝移植细胞凋亡缺血损伤

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悬链线旋转壳体的对称小变形和应力分析

Acta Mechanica Sinica 2022年第2期38卷 119-129,I0004页

作者：孙博华 School of Civil Engineering&institute of Mechanics and Technology Xi'an University of Architecture and TechnologyXi'an 710055China

链线旋转壳体由于其优良的力学特性被广泛应用于教堂结构中.为了更好地理解悬链线旋转壳体的变形和应力,我们推导了两种悬链线旋转壳体的主曲率半径,以及悬链线旋转壳体位移型控制方程.对于悬链线旋转壳体的这个位移型方程和Reissner-Me... 详细信息

链线旋转壳体由于其优良的力学特性被广泛应用于教堂结构中.为了更好地理解悬链线旋转壳体的变形和应力,我们推导了两种悬链线旋转壳体的主曲率半径,以及悬链线旋转壳体位移型控制方程.对于悬链线旋转壳体的这个位移型方程和Reissner-meissner混合型方程进行了数值计算和对比.计算结果显示悬链线旋转壳体的力学性能对于悬链线几何参量c非常敏感.揭示了对于一些荷载情况悬链线旋转壳体的力学性能优于相应的球壳.论文还提供了两个完整的Maple程序.

关键词：旋转壳体 Maple程序悬链线主曲率半径混合型方程荷载情况几何参量

Age-Dependent Alpha-Synuclein Accumulation and Phosphorylation in the Enteric Nervous System in a Transgenic Mouse Model of Parkinson＇s Disease

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Neuroscience Bulletin 2017年第5期33卷 483-492页

作者： Chong-Bin Zhong Qian-Qian Chen Caroline Haikal Wen Li Alexander Svanbergssona Meike Diepenbroek Jia-Yi Li institute of Bioengineering Northeastern UniversityShenyang 110819China institute of Neuroscience College of Life and HealthSciencesNortheastern UniversityShenyang 110819China Neural Plasticity and Repair Unit Wallenberg Neuroscience CenterDepartment of Experimental Medical ScienceLund UniversityBMC A1022184 LundSweden

The enteric nervous system （ENS） controls the function of the gastrointestinal tract and has been impli- cated in various diseases, including Parkinson＇s disease （PD）. PD is a neurodegenerative disease with Lewy bodies （LBs） and Lewy neurites （LNs） as the main pathological features. In addition to the typical motor symptoms in PD, attention has been drawn to non-motor symptoms, such as constipation, implying dysfunction of the ENS. In the present study, we characterized the age-dependent mor- phological alterations and aggregation of α-synuclein （α- syn）, the primary protein component in LBs and LNs, in the ENS in an α-syn transgenic mouse model. We found that the expression and accumulation of α-syn increased gradually in neurons of meissner＇s and Auerbach＇s plexuses of the gastrointestinal tract with age （from 1 week to 2 years）. In addition, α-syn was increasingly phosphorylated at the serine 129 residue, reflecting patho- logical alterations of the protein over time. Furthermore,α- syn was present in different subtypes of neurons expressing vasoactive intestinal polypeptide, neuronal nitric oxide synthase, or calretinin. The results indicated that BAC-α- Syn-GFP transgenic mice provide a unique model in which to study the relationship between ENS and PD pathogenesis.

关键词： Enteric system · Parkinson＇s disease · αt-synuclein · Phosphorylation · Protein aggregation

Design of a superconducting magnet for CADS

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Chinese Physics C 2012年第9期36卷 886-890页

作者：杨晓亮马力祯吴巍郑石钧杜俊杰韩少斐关明智何源 institute of Modern Physics Chinese Academy of Sciences Graduate University of Chinese Academy of Sciences

This paper describes a superconducting magnet system for the China Accelerator Driven System （CADS）. The magnetic field is provided by one main, two bucking and four racetrack coils. The main coil produces a central field of up to 7 T and the effective length is more than 140 mm, the two bucking coils can shield most of the fringe field, and the four racetrack superconducting coils produce the steering magnetic field. Its leakage field in the cavity zone is about 5 × 10^-5 T when the shielding material Niobium and cryogenic permalloy are used as the meissner shielding and passive shielding respectively. The quench calculations and protection system are also discussed.

关键词： ADS SC solenoid design leakage field magnetic shielding quench calculation

SUPERCONDUCTIVITY AT 89K OF Ba-Y-Cu-O THIN FILMS

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Chinese Physics Letters 1987年第6期4卷 280-282页

作者：赵柏儒王会生陆勇史引焕黄锡成赵玉英李林 The institute of Physics Academia SinicaBeijing

High Tc Ba-Y-Cu-O thin films have been successfully prepared by the RF magnetron sputtering method.The highest Tc onset is determined to be 89.5K and the Tc midpoint is about 55K.Inductive measurement showed that the ... 详细信息

关键词： method highest