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Quantum spin Hall and quantum valley Hall effects in trilayer graphene and their topological structures

Chinese Physics B 2017年第12期26卷 481-490页

作者： majeed ur rehman A A Abid ICQD Hefei National Laboratory for Physical Sciences at Microscale Department of Physics University of Science and Technology of China Hefei 230026 China Key Laboratory of Geospace Environment(Chinese Academy of Sciences) Department of Geophysics and Planetary Science University of Science and Technology of China Hefei 230026 China

The present study pertains to the trilayer graphene in the presence of spin orbit coupling to probe the quantum spin/valley Hall effect. The spin Chern-number Cs for energy-bands of trilayer graphene having the essence of intrinsic spin-orbit coupling is analytically calculated. We find that for each valley and spin, Cs is three times larger in trilayer graphene as compared to single layer graphene. Since the spin Chern-number corresponds to the number of edge states, consequently the trilayer graphene has edge states, three times more in comparison to single layer graphene. We also study the trilayer graphene in the presence of both electric-field and intrinsic spin-orbit coupling and investigate that the trilayer graphene goes through a phase transition from a quantum spin Hall state to a quantum valley Hall state when the strength of the electric field exceeds the intrinsic spin coupling strength. The robustness of the associated topological bulk-state of the trilayer graphene is evaluated by adding various perturbations such as Rashba spin-orbit （RSO） interaction αR, and exchange-magnetization M. In addition, we consider a theoretical model, where only one of the outer layers in trilayer graphene has the essence of intrinsic spin-orbit coupling, while the other two layers have zero intrinsic spin-orbit coupling. Although the first Chern number is non-zero for individual valleys of trilayer graphene in this model, however, we find that the system cannot be regarded as a topological insulator because the system as a whole is not gaped.

关键词： trilayer graphene quantum spin Hall effect topological insulator quantum phase transition

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Computing Structured Singular Values for Delay and Polynomial Eigenvalue Problems

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Open Journal of Applied Sciences 2017年第7期7卷 348-364页

作者： Mutti-ur rehman Danish majeed Naila Nasreen Shabana Tabassum Department of Mathematics and Statistics The University of Lahore Gujrat Campus Gujrat Pakistan Department of Applied Physics Federal Urdu University of Arts Science and Technology Islamabad Pakistan Department of Mathematics COMSATS Institute of Information Technology Islamabad Campus Islamabad Pakistan

In this article the computation of the Structured Singular Values (SSV) for the delay eigenvalue problems and polynomial eigenvalue problems is presented and investigated. The comparison of bounds of SSV with the well... 详细信息

关键词： μ-Values Block Diagonal Uncertainties Spectral Radius Low-Rank Approximation Delay Eigenvalue Problems Polynomial Eigenvalue Problems

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Application of GIS for the identification and demarcation of selective heavy metal concentrations in the urban groundwater

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Journal of Geographical Sciences 2015年第2期25卷 225-235页

作者： Sobia ASHRAF Farhat ABBAS Muhammad IBRAHIM Umer RASHID Shoaib KHALID Hammad Raza AHMAD Khalid rehman HAKEEM Tahir majeed Department of Environmental Sciences and Engineering Government College University Faisalabad (38000) Pakistan Institute of Advanced Technology Universiti Putra Malaysia UPM Serdang 43400 Selangor Malaysia Department of Geography Government College University Faisalabad 38000 Pakistan institute of Soil & Environmental Sciences University of Agriculture Faisalabad 38040 Pakistan Faculty of Forestry University of Putra Malaysia Serdang 43400 Selangor Malaysia Institute of Soil Chemistry and Environmental Sciences Ayub Agricultural Research Institute (AARI) Jhang Road Faisalabad

Groundwater is the most appropriate and widely used source of drinking water, which is increasingly threatened by pollution from industrial and agricultural activities. To check the severity of the problem, 156 groundwater samples were collected from various depths （60-110 ft） of 52 different localities in Faisalabad city, the third largest metropolis in Pakistan, and analyzed for the metals （Zn, Cu, Cd, Ni, Pb, Mn and Fe） concentration in 2009. Quantification was done by using Flame Atomic Absorption Spectrophotometer technique and the results were compared with WHO standards for drinking water quality. Results showed that the levels of Cu, Mn and Fe were below the WHO standards while the concentrations of Zn, Cd, Ni and Pb were above the recommended levels of safe drinking water. Correlation analysis among the occurrence of these heavy metals revealed a highly significant and positive correlation of Mn with Zn and Fe. A significant and positive correlation of Cd was also found with Cu and groundwater depth showing that there is strong association between Cu-Cd pair and that the Cd concentration varies with depth of groundwater in the study area. Regional patterns of heavy metals occurrence were mapped using Geographical Information System （GIS） for the identification and demarcation of risk areas. The concentration maps may be used by policymakers of the city to mitigate groundwater pollution.

关键词： heavy metals groundwater contamination Faisalabad pollution mitigation

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纳米材料制备及其电化学发光分析应用

纳米材料制备及其电化学发光分析应用

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中国化学会第29届学术年会

作者：祁文静张玲许敏赖建平 Anjum Saima Aziz-ur-rehman majeed Saadat 高文跃 Hanif Saima 徐国宝中国科学院长春应用化学研究所电分析化学国家重点实验室中国科学院研究生院

电致化学发光是一种电化学反应导致的化学发光现象。常见的电化学发光体系有钌配合物、鲁米诺、半导体量子点、纳米簇、光泽精和过氧化草酸酯等。其中钌配合物和鲁米诺电化学发光由于适用范围广、灵敏度高、重现性好、成本低等优点,而... 详细信息

电致化学发光是一种电化学反应导致的化学发光现象。常见的电化学发光体系有钌配合物、鲁米诺、半导体量子点、纳米簇、光泽精和过氧化草酸酯等。其中钌配合物和鲁米诺电化学发光由于适用范围广、灵敏度高、重现性好、成本低等优点,而成为研究最多的体系之一,特别是钌配合物电化学发光在临床分析中的广泛应用更使之成为重点的研究体系。电化学发光中常常用到纳米材料,如将含有发光试剂的纳米材料作为标记物用于免疫分析、核酸分析和基于适配子的分析、将纳米材料用作电化学发光的催化剂或将纳米材料作为电化学发光试剂等[1-3]。而电化学发光分析性能等与其所使用的纳米材料的组成和结构等密切相关。在这里我们介绍近一两年内开展的纳米材料制备及其在吡啶钌和鲁米诺电化学发光分析应用的部分工作,如纳米多面体电化学发光催化研究、基于功能化二氧化硅球的臭氧的检测方法、基于能量转移的TNT分析方法和基于重氮盐功能化纳米材料的电化学发光分析等[4-7]。

关键词：纳米材料电化学发光钌鲁米诺

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