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Search Results: 1 - 10 of 134527 matches for " WANG Gui-Bin "
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Intervalley coupling by quantum dot confinement potentials in monolayer transition metal dichalcogenides
Gui-Bin Liu,Hongliang Pang,Yugui Yao,Wang Yao
Physics , 2014, DOI: 10.1088/1367-2630/16/10/105011
Abstract: Monolayer transition metal dichalcogenides (TMDs) offer new opportunities for realizing quantum dots (QDs) in the ultimate two-dimensional (2D) limit. Given the rich control possibilities of electron valley pseudospin discovered in the monolayers, this quantum degree of freedom can be a promising carrier of information for potential quantum spintronics exploiting single electrons in TMD QDs. An outstanding issue is to identify the degree of valley hybridization, due to the QD confinement, which may significantly change the valley physics in QDs from its form in the 2D bulk. Here we perform a systematic study of the intervalley coupling by QD confinement potentials on extended TMD monolayers. We find that the intervalley coupling in such geometry is generically weak due to the vanishing amplitude of the electron wavefunction at the QD boundary, and hence valley hybridization shall be well quenched by the much stronger spin-valley coupling in monolayer TMDs and the QDs can well inherit the valley physics of the 2D bulk. We also discover sensitive dependence of intervalley coupling strength on the central position and the lateral length scales of the confinement potentials, which may possibly allow tuning of intervalley coupling by external controls
Construction and characterization of calreticulin-HBsAg fusion gene recombinant adenovirus expression vector
Chun-Ling Ma, Gui-Bin Wang, Run-Guo Gu, Fang Wang
World Journal of Gastroenterology , 2010,
Abstract: AIM: To generate recombinant adenoviral vector containing calreticulin (CRT)-hepatitis B surface antigen (HBsAg) fusion gene for developing a safe, effective and HBsAg-specific therapeutic vaccine.METHODS: CRT and HBsAg gene were fused using polymerase chain reaction (PCR), endonuclease digestion and ligation methods. The fusion gene was cloned into pENTR/D-TOPO transfer vector after the base pairs of DNA (CACC) sequence was added to the 5′ end. Adenoviral expression vector containing CRT-HBsAg fusion gene was constructed by homologous recombinantion. The human embryo kidney (HEK) 293A cells were transfected with linearized DNA plasmid of the recombinant adenoviral vector to package and amplify recombinant adenovirus. The recombinant adenovirus titer was characterized using the end-dilution assay. The expression of the CRT/HBsAg fusion protein in Ad-CRT/HBsAg infected 293A cells was detected by Western blotting.RESULTS: The CRT-HBsAg fusion gene was characterized by PCR and sequencing and its length and sequence were confirmed to be accurate. The CRT-HBsAg fusion gene recombinant pENTR/D-TOPO transfer vector was constructed. The recombinant adenoviral vector, Ad-CRT/HBsAg, was generated successfully. The titer of Ad-CRT/HBsAg was characterized as 3.9 × 1011 pfu/mL. The CRT-HBsAg fusion protein was expressed by HEK 293A cells correctly.CONCLUSION: CRT/HBsAg fusion gene recombinant replication-defective adenovirus expression vector is constructed successfully and this study has provided an experimental basis for further studies of Hepatitis B virus gene therapy.
Three-band tight-binding model for monolayers of group-VIB transition metal dichalcogenides
Gui-Bin Liu,Wen-Yu Shan,Yugui Yao,Wang Yao,Di Xiao
Physics , 2013, DOI: 10.1103/PhysRevB.88.085433
Abstract: We present a three-band tight-binding (TB) model for describing the low-energy physics in monolayers of group-VIB transition metal dichalcogenides $MX_2$ ($M$=Mo, W; $X$=S, Se, Te). As the conduction and valence band edges are predominantly contributed by the $d_{z^{2}}$, $d_{xy}$, and $d_{x^{2}-y^{2}}$ orbitals of $M$ atoms, the TB model is constructed using these three orbitals based on the symmetries of the monolayers. Parameters of the TB model are fitted from the first-principles energy bands for all $MX_2$ monolayers. The TB model involving only the nearest-neighbor $M$-$M$ hoppings is sufficient to capture the band-edge properties in the $\pm K$ valleys, including the energy dispersions as well as the Berry curvatures. The TB model involving up to the third-nearest-neighbor $M$-$M$ hoppings can well reproduce the energy bands in the entire Brillouin zone. Spin-orbit coupling in valence bands is well accounted for by including the on-site spin-orbit interactions of $M$ atoms. The conduction band also exhibits a small valley-dependent spin splitting which has an overall sign difference between Mo$X_{2}$ and W$X_{2}$. We discuss the origins of these corrections to the three-band model. The three-band TB model developed here is efficient to account for low-energy physics in $MX_2$ monolayers, and its simplicity can be particularly useful in the study of many-body physics and physics of edge states.
Electronic structures and theoretical modelling of two-dimensional group-VIB transition metal dichalcogenides
Gui-Bin Liu,Di Xiao,Yugui Yao,Xiaodong Xu,Wang Yao
Physics , 2015, DOI: 10.1039/C4CS00301B
Abstract: Atomically thin group-VIB transition metal dichalcogenides (TMDs) have recently emerged as a new class of two-dimensional (2D) semiconductors with extraordinary properties including the direct band gap in the visible frequency range, the pronounced spin-orbit coupling, the ultra-strong Coulomb interaction, and the rich physics associated with the valley degree of freedom. These 2D TMDs exhibit great potentials for device applications and have attracted vast interest for the exploration of new physics. 2D TMDs have complex electronic structures which underlie their physical properties. Here we review the bulk electronic structures in these new 2D materials as well as the theoretical models developed at different levels, along which we sort out the understandings on the origins of a variety of properties observed or predicted.
Magnetoelectric effects and valley controlled spin quantum gates in transition metal dichalcogenide bilayers
Zhirui Gong,Gui-Bin Liu,Hongyi Yu,Di Xiao,Xiaodong Cui,Xiaodong Xu,Wang Yao
Physics , 2013, DOI: 10.1038/ncomms3053
Abstract: In monolayer group-VI transition metal dichalcogenides (TMDC), charge carriers have spin and valley degrees of freedom, both associated with magnetic moments. On the other hand, the layer degree of freedom in multilayers is associated with electrical polarization. Here, we show that TMDC bilayers offer an unprecedented platform to realize a strong coupling between the spin, layer pseudospin, and valley degrees of freedom of holes. Such coupling not only gives rise to the spin Hall effect and spin circular dichroism in inversion symmetric bilayer, but also leads to a variety of magnetoelectric effects permitting quantum manipulation of these electronic degrees of freedom. Oscillating electric and magnetic fields can both drive the hole spin resonance where the two fields have valley-dependent interference, making possible a prototype interplay between the spin and valley as information carriers for potential valley-spintronic applications. We show how to realize quantum gates on the spin qubit controlled by the valley bit.
Nonlinear valley and spin currents from Fermi pocket anisotropy in 2D crystals
Hongyi Yu,Yue Wu,Gui-Bin Liu,Xiaodong Xu,Wang Yao
Physics , 2014, DOI: 10.1103/PhysRevLett.113.156603
Abstract: Controlled flow of spin and valley pseudospin is key to future electronics exploiting these internal degrees of freedom of carriers. Here we discover a universal possibility for generating spin and valley currents by electric bias or temperature gradient only, which arises from the anisotropy of Fermi pockets in crystalline solids. We find spin and valley currents to the second order in the electric field, as well as their thermoelectric counterparts, i.e. the nonlinear spin and valley Seebeck effects. These second-order nonlinear responses allow two unprecedented possibilities to generate pure spin and valley flows without net charge current: (i) by an AC bias; or (ii) by an arbitrary inhomogeneous temperature distribution. As examples, we predict appreciable nonlinear spin and valley currents in two-dimensional (2D) crystals including graphene, monolayer and trilayer transition metal dichalcogenides, and monolayer gallium selenide. Our finding points to a new route towards electrical and thermal generations of spin and valley currents for spintronic and valleytronic applications based on 2D quantum materials.
Coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides
Di Xiao,Gui-Bin Liu,Wanxiang Feng,Xiaodong Xu,Wang Yao
Physics , 2011, DOI: 10.1103/PhysRevLett.108.196802
Abstract: We show that inversion symmetry breaking together with spin-orbit coupling leads to coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides, making possible controls of spin and valley in these 2D materials. The spin-valley coupling at the valence band edges suppresses spin and valley relaxation, as flip of each index alone is forbidden by the valley contrasting spin splitting. Valley Hall and spin Hall effects coexist in both electron-doped and hole-doped systems. Optical interband transitions have frequency-dependent polarization selection rules which allow selective photoexcitation of carriers with various combination of valley and spin indices. Photo-induced spin Hall and valley Hall effects can generate long lived spin and valley accumulations on sample boundaries. The physics discussed here provides a route towards the integration of valleytronics and spintronics in multi-valley materials with strong spin-orbit coupling and inversion symmetry breaking.
Majorana Fermions on Zigzag Edge of Monolayer Transition Metal Dichalcogenides
Rui-Lin Chu,Gui-Bin Liu,Wang Yao,Xiaodong Xu,Di Xiao,Chuanwei Zhang
Physics , 2013, DOI: 10.1103/PhysRevB.89.155317
Abstract: Majorana fermions, quantum particles with non-Abelian exchange statistics, are not only of fundamental importance, but also building blocks for fault-tolerant quantum computation. Although certain experimental breakthroughs for observing Majorana fermions have been made recently, their conclusive dection is still challenging due to the lack of proper material properties of the underlined experimental systems. Here we propose a new platform for Majorana fermions based on edge states of certain non-topological two-dimensional semiconductors with strong spin-orbit coupling, such as monolayer group-VI transition metal dichalcogenides (TMD). Using first-principles calculations and tight-binding modeling, we show that zigzag edges of monolayer TMD can host well isolated single edge band with strong spin-orbit coupling energy. Combining with proximity induced s-wave superconductivity and in-plane magnetic fields, the zigzag edge supports robust topological Majorana bound states at the edge ends, although the two-dimensional bulk itself is non-topological. Our findings points to a controllable and integrable platform for searching and manipulating Majorana fermions.
Effects of waterlogging on growth, porosity and radial oxygen loss of three tree species
涝渍对3个树种生长、组织孔隙度和渗漏氧的影响

WANG Gui-Bin,CAO Fu-Liang,WANG Yuan,
汪贵斌
,曹福亮,王媛

植物生态学报 , 2012,
Abstract: Aims Flooding reduces soil oxygen content, and leads to oxygen deprivation in the root system of plants. Since oxygen is essential for mitochondrial respiration, this process cannot be maintained under anoxic conditions and must be replaced by other pathways. Our objective was to understand flooding adaptation mechanisms of baldcypress (Taxodium distichum), Chinese tallow tree (Sapium sebiferum) and pecan (Carya illinoensis) under waterlogged conditions. Methods One-year seedlings of baldcypress, Chinese tallow tree and pecan were grown in pots, and three treatments were implemented: CK (control, common soil water content), WA (waterlogging, water level equal with soil surface) and FL (flooding, water level 8 cm above soil surface). Treatments lasted 65 days, and indexes of growth, porosity and root oxygen consumption were determined at different times after treatment. Important findings We found that WA and FL treatments inhibited growth of both Chinese tallow tree and pecan, but biomass and biomass increment of baldcypress increased under WA condition, indicating that baldcypress was more tolerant to flooding. Root/shoot ratio of the three tree species increased significantly under WA and FL treatments, which was primarily due to the decrease of stem and leaf biomass. WA and FL treatments also stimulated aerenchyma formation in the roots, stems and leaves of the three tree species, thereby the porosity in the roots, stems and leaves of the three tree species increased significantly under WA and FL conditions. The aerenchyma formation and increased porosity enhanced O2 diffusion to roots and rhizosphere. Our results indicate that baldcypress, Chinese tallow tree and pecan exhibit several adaptive mechanisms in response to waterlogging, including formation of new roots, aerenchyma formation, increased porosity of the roots, stems and leaves, and increased O2 release into the rhizosphere.
Application of chemometrics methods for the estimation of heavy metals contamination in river sediments
WANG Ya-wei,YUAN Chun-gang,JIN Xing-long,JIANG Gui-bin,
WANG Ya-wei
,YUAN Chun-gang,JIN Xing-long,JIANG Gui-bin

环境科学学报(英文版) , 2005,
Abstract: The concentration and speciation of six heavy metals in sediments of eight sampling sites of Haihe River were investigated. The metals, namely Cd, Cu, Co, Ni, Mn and Pb were considered. By using sequential extraction(SE), the total metals were divided into five fractions: exchangeable, carbonate bound, iron/manganese oxide bound, sulfides and organic matter fraction and residual fraction. A multivariate statistical approach(principal component analysis, PCA) was used to evaluate the contamination of heavy metals by the total levels and chemical forms, respectively. The results showed that the total metals concentration(TMC) could not provide sufficient and accurate information because the mobility, bioavailability and toxicity of metals depend not only on their total concentration but also on the physicochemical form in which they occur.
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