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Quantum Transport Properties of Chemically Functionalized Long Semiconducting Carbon Nanotubes

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Nano Research 2010年第4期3卷 288-295页

作者： Alejandro Lopez-Bezanilla Xavier Blase stephan roche Commissariat a l’Energie Atomique 38054 Grenoble CedexFrance Institut Néel CNRS and UniversitéJoseph FourierB.P.16638042 Grenoble Cedex 09France CIN2(CSIC-ICN)Barcelona Campus UABE-08193 BellaterraSpain

We present a first-principles study of the electronic transport properties of micrometer long semiconducting carbon nanotubes randomly covered with carbene functional groups. Whereas prior studies suggested that metallic tubes are hardly affected by such addends, we show here that the conductance of semiconducting tubes with standard diameter is, on the contrary, severely damaged. The configurational-averaged conductance as a function of tube diameter, with a coverage of up to one hundred molecules, is extracted. Our results indicate that the search for a conductance-preserving covalent functionalization route remains a challenging issue.

关键词： Nanotubes functionalization carbene electronic transport

Highly defective graphene： A key prototype of two- dimensional Anderson insulators

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Nano Research 2013年第5期6卷 326-334页

作者： Aurelien Lherbier stephan roche Oscar A. Restrepo Yann-Michel Niquet Arnaud Delcorte Jean-Christophe Charlier Universite catholique de Louvain (UCL) Institute of Condensed Matter and Nanoscience (IMCN) NAPS-ETSF Chemin des ~toiles 8 1348 Louvain-la-Neuve Belgium CIN2 (ICN-CSIC) and Universitat Autonoma de Barcelona Catalan Institute of Nanotechnology Campus UAB 08193 Bellaterra (Barcelona) Spain ICREA Institucio Catalana de Recerca i Estudis Avancats 08070 Barcelona Spain Universite catholique de Louvain (UCL) Institute of Condensed Matter and Nanoscience (IMCN) BSMA Place Croix du Sud 1 (Boltzmann) 1348 Louvain-la-Neuve Belgium L_Sim SP2M UMR-E CEA/UJF-Grenoble 1 INAC 17 rue des Martyrs 38054 Grenoble Cedex 9 France

Electronic structure and transport properties of highly defective two-dimensional （2D） sp2 graphene are investigated theoretically. Classical molecular dynamics are used to generate large graphene planes containing a considerable amount of defects. Then, a tight-binding Hamiltonian validated by ab initio calculations is constructed in order to compute quantum transport within a real-space order-N Kubo-Greenwood approach. In contrast to pristine graphene, the highly defective sp2 carbon sheets exhibit a high density of states at the charge neutrality point raising challenging questions concerning the electronic transport of associated charge carriers. The analysis of the electronic wavepacket dynamics actually reveals extremely strong multiple scattering effects giving rise to mean free paths as low as 1 nm and localization phenomena. Consequently, highly defective graphene is envisioned as a remarkable prototype of 2D Anderson insulating materials.

关键词： graphene electronic transport Anderson insulators localization

Charge Transport in Disordered Graphene-Based Low Dimensional Materials

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Nano Research 2008年第5期1卷 361-394页

作者： Alessandro Cresti Norbert Nemec Blanca Biel Gabriel Niebler François Triozon Gianaurelio Cuniberti stephan roche CEA LETIMINATECF38054 GrenobleFrance CEA Institute for Nanoscience and CryogenicsINAC/SPSMS/GT17 rue des Martyrs38054 Grenoble Cedex 9France Theory of Condensed Matter Group Cavendish LaboratoryUniversity of CambridgeTrinity LaneCambridge CB217NUK Institute for Materials Science TU DresdenD-01062 DresdenGermany Department of Condensed Matter Physics Faculty of Mathematics and PhysicsCharles UniversityKe Karlovu 512116 Prague 2Czech Republic

Two-dimensional graphene,carbon nanotubes,and graphene nanoribbons represent a novel class of low dimensional materials that could serve as building blocks for future carbon-based *** these systems share a similar underlying electronic structure,whose exact details depend on confi nement effects,crucial differences emerge when disorder comes into *** this review,we consider the transport properties of these materials,with particular emphasis on the case of graphene *** summarizing the electronic and transport properties of defect-free systems,we focus on the effects of a model disorder potential(Anderson-type),and illustrate how transport properties are sensitive to the underlying *** provide analytical expressions for the elastic mean free path of carbon nanotubes and graphene nanoribbons,and discuss the onset of weak and strong localization regimes,which are genuinely dependent on the transport *** also consider the effects of edge disorder and roughness for graphene nanoribbons in relation to their armchair or zigzag orientation.

关键词： Graphene charge transport carbon nanotubes

Large edge magnetism in oxidized few-layer black phosphorus nanomeshes

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Nano Research 2017年第2期10卷 718-728页

作者： Yudai Nakanishi Ayumi Ishi Chika Ohata David Soriano Ryo Iwaki Kyoko Nomura~ Miki Hasegawa Taketomo Nakamura Shingo Katsumoto stephan roche Junji Haruyama Faculty of Science and Engineering Aoyama Gakuin University 5- I0-1 Fuchinobe Sagamihara Kanagawa 252-5258 Japan Chemistry and Biological Science Aoyama Gakuin University 5-10-1 Fuchinobe Sagamihara Kanagawa 252-5258 Japan Catalan Institute of Nanoscience and Nanotechnology (ICN2) CSIC and The Barcelona Institute of Science and Technology Campus UAB Bellaterra 08193 Barcelona Spain Institucio Catalana de Recercai Estudis Avancats (ICREA) 08010 Barcelona Spain Institute for solid state physics The University of Tokyo 5- I-5 Kashiwanoha Kashiwa Chiba 277-8581 Japan

The formation and control of a room-temperature magnetic order in two- dimensional （2D） materials is a challenging quest for the advent of innovative magnetic- and spintronic-based technologies. To date, edge magnetism in 2D materials has been experimentally observed in hydrogen （H）-terminated graphene nanoribbons （GNRs） and graphene nanomeshes （GNMs）, but the measured magnetization remains far too small to allow envisioning practical applications. Herein, we report experimental evidences of large room-temperature edge ferromagnetism （FM） obtained from oxygen （O）-terminated zigzag pore edges of few-layer black phosphorus （P） nanomeshes （BPNMs）. The magnetization values per unit area are -100 times larger than those reported for H-terminated GNMs, while the magnetism is absent for H-terminated BPNMs. The magnetization measurements and the first-principles simulations suggest that the origin of such a magnetic order could stem from ferromagnetic spin coupling between edge P with O atoms, resulting in a strong spin localization at the edge valence band, and from uniform oxidation of full pore edges over a large area and interlayer spin interaction. Our findings pave the way for realizing high-efficiency 2D flexible magnetic and spintronic devices without the use of rare magnetic elements.

关键词： black phosphorus nanomesh edge magnetism spintronics zigzag edge oxygen termination rare-metal free

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用CPLD实现步进电机驱动器

电子设计技术 EDN CHINA 2007年第5期14卷 116-116页

作者： stephan roche Santa Rosa CA

本设计实例基于摩托罗拉（现为飞思卡尔）广为使用但已淘汰的SAA1042步进电机驱动器JC，用一片CPLD（复杂可编程逻辑器件）实现了步进电机驱动器．它也可以代替基于SAA1027或UCN5804B设计中的驱动器。本设计只使用了Xilinx XC9536CPLD中... 详细信息

本设计实例基于摩托罗拉（现为飞思卡尔）广为使用但已淘汰的SAA1042步进电机驱动器JC，用一片CPLD（复杂可编程逻辑器件）实现了步进电机驱动器．它也可以代替基于SAA1027或UCN5804B设计中的驱动器。本设计只使用了Xilinx XC9536CPLD中的6个宏单元，因此可以在一个小容量CPLD中实现多个步进电机驱动器。CPLD步进电机驱动器需要时钟、方向、步长和复位输入。时钟输入接受逻辑电平脉冲．并在脉冲正沿上有效。

关键词：步进电机驱动器 CPLD 复杂可编程逻辑器件 SAA1042 设计实例 Xilinx 时钟输入摩托罗拉

装入CPLD/FPGA的步进电机运动控制器与驱动器

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电子设计技术 EDN CHINA 2007年第9期14卷 120-120页

作者： stephan roche Santa Rosa CA

本设计实例进一步拓展了以前将步进电机驱动器集成到CPLD中的设计（参考文献1）。本实例不仅集成了驱动器．而且还集成了一个简单的单轴步进电机运动控制器。根据CPLD大小，可以将多个运动控制器设计到单一设备中。例如，单轴运动控制... 详细信息

本设计实例进一步拓展了以前将步进电机驱动器集成到CPLD中的设计（参考文献1）。本实例不仅集成了驱动器．而且还集成了一个简单的单轴步进电机运动控制器。根据CPLD大小，可以将多个运动控制器设计到单一设备中。例如，单轴运动控制器采用68％或63％的可用宏单元设计到Xilinx XC95108中。运动控制器以确定的速度与时间曲线顺时针或逆时针旋转步进电机指定的步数。运动开始时，控制器对电机加速，直到其达到巡航速度，然后减速直到停止（图1）。

关键词： CPLD/FPGA 单轴运动控制器步进电机驱动器设计实例 Xilinx 巡航速度控制器设计逆时针旋转

(Not) an elementary question:How to mobilize the iron in the wall?

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Molecular Plant 2021年第10期14卷 1610-1611页

作者： stephan Clemens Department of Plant Physiology and Faculty of Life Sciences:Food Nutrition and HealthUniversity of BayreuthUniversitätsstrasse 3095440 BayreuthGermany

Photosynthesis,respiration,and countless other processes are dependent on proteins that carry iron(Fe)as an essential *** Fe was recruited for biological functions early in evolution,it was an available *** Earth's at... 详细信息

关键词： element. elementary sulfide

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Roots dOdge streSs

Molecular Plant 2023年第12期16卷 1885-1886页

作者： stephan Clemens Department of Plant Physiology University of BayreuthUniversitatsstrasse 3095440BayreuthGermany

A hallmark of plant development is *** system architecture modulation in response to fluctuations of nutrient and water supply is a case in point(Giehl et al.,2014).The formation and length of lateral roots or the density of root hairs are strongly influenced by the availability of macro-and *** actively forage for mineral-rich patches in the typically heterogeneous soil environment and adjust their development systemically to increase the surface for nutrient ***,the opposite can happen as well.A recent study by Wang et al.(2023)convincingly demonstrated an active avoidance of unfavorable conditions by rice *** the seminal root of rice seedlings was placed between two agar blocks,one of them containing cations at toxic concentrations,adventitious roots developed only on the non-stress side,while development on the stress side was arrested(Figure 1).Besides,far more lateral roots were formed than in the absence of asymmetrically applied *** a while,this resulted in a total root biomass equivalent to that of control *** roots,in other words,had successfully shifted away from the stressful environment.

关键词： soil roots Figure

On combinatorial Gauss-Bonnet Theorem for general Euclidean simplicial complexes

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Frontiers of Mathematics in China 2016年第5期11卷 1345-1362页

作者： stephan KLAUS Scientific Administrator of the MFO and Adjunct Professor at Mainz University Mathematisches Forschungsinstitut Oberwolfach gGmbH (MFO) Schwarzwaldstrasse 9-11 D-77709 Oberwolfach-Walke Germany

For a finitely triangulated closed surface M2, let αx be the sum of angles at a vertex x. By the well-known combinatorial version of the 2- dimensional Gauss-Bonnet Theorem, it holds ∑x（2π- αx） =2αχ（M^2）, where X denotes the Euler characteristic of M^2, αx denotes the sum of angles at the vertex x, and the sum is over all vertices of the triangulation. We give here an elementary proof of a straightforward higher-dimensional generalization to Euclidean simplicial complexes K without assuming any combinatorial manifold condition. First, we recall some facts on simplicial complexes, the Euler characteristics and its local version at a vertex. Then we define δ（τ） as the normed dihedral angle defect around a simplex τ. Our main result is ∑τ（-1）^dim（τ）δ（τ） = χ（K）, where the sum is over all simplices τ of the triangulation. Then we give a definition of curvature k（x） at a vertex and we prove the vertex-version ∑x∈K0 k（x） = χ（K） of this result. It also possible to prove Morse-type inequalities. Moreover, we can apply this result to combinatorial （n ＋ 1）-manifolds W with boundary B, where we prove that the difference of Euler characteristics is given by the sum of curvatures over the interior of W plus a contribution from the normal curvature along the boundary B： χ（W）- 1/2 χ（B） = ∑τ∈W-B（-1）^dim（τ）δ（τ）＋ ∑τB（-1）^dim（τ）ρ（τ）.

关键词： Curvature dihedral angle Euclidean simplex triangulation Euler characteristic Euler manifold combinatorial manifold pseudo manifold