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He SM, Zhuang JY, Chen CF, Liao RK, Lo ST, Lin YF, Su CY. Plasma-Driven Selenization for Electrical Property Enhancement in Janus 2D Materials. Small Methods 2024:e2400150. [PMID: 38660826 DOI: 10.1002/smtd.202400150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 03/21/2024] [Indexed: 04/26/2024]
Abstract
The recent emergence of Janus 2D materials like SnSSe, derived from SnS2, reveals unique electrical and optical features, such as asymmetrical electronic structure, enhanced carrier mobility, and tunable bandgap. Previous theoretical studies have discuss the electronic properties of Janus SnSSe, but experimental evidence is limited. This study presents a two-step method for synthesizing Janus SnSSe, involving hydrogen plasma treatment and in situ selenization. Optimized conditions (38 W, 1.5 min, 250 °C) are determined using Raman spectroscopy and AFM analysis. XPS confirmed SnSSe's elemental composition, while KPFM reveals a significant reduction in the work function (from 5.26 down to 5.14 eV) for the first time, indicating asymmetrically induced n-type doping. Finally, field-effect transistors (FETs) derived from SnSSe exhibited significantly enhanced mobility and on-current, as well as n-type doping, compared to SnS2-based FETs. These findings lay a crucial foundation for developing high-performance 2D electronic and optoelectronic devices.
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Affiliation(s)
- Shih-Ming He
- Optical Sciences Center, National Central University, Taoyuan, 32001, Taiwan
| | - Jia-Yung Zhuang
- Department of Mechanical Engineering, National Central University, Taoyuan, 32001, Taiwan
| | - Ciao-Fen Chen
- Department of Physics, National Chung Hsing University, Taichung, 40227, Taiwan
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Ren-Kuei Liao
- Department of Mechanical Engineering, National Central University, Taoyuan, 32001, Taiwan
| | - Shun-Tsung Lo
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Yen-Fu Lin
- Department of Physics, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Ching-Yuan Su
- Optical Sciences Center, National Central University, Taoyuan, 32001, Taiwan
- Department of Mechanical Engineering, National Central University, Taoyuan, 32001, Taiwan
- Graduate Institute of Energy Engineering, National Central University, Taoyuan, 32001, Taiwan
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2
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Chen CH, Lai YT, Chen CF, Wu PT, Su KJ, Hsu SY, Dai GJ, Huang ZY, Hsu CL, Lee SY, Shen CH, Chen HY, Lee CC, Hsieh DR, Lin YF, Chao TS, Lo ST. Single-Gate In-Transistor Readout of Current Superposition and Collapse Utilizing Quantum Tunneling and Ferroelectric Switching. Adv Mater 2023; 35:e2301206. [PMID: 37282350 DOI: 10.1002/adma.202301206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 06/01/2023] [Indexed: 06/08/2023]
Abstract
In nanostructure assemblies, the superposition of current paths forms microscopic electric circuits, and different circuit networks produce varying results, particularly when utilized as transistor channels for computing applications. However, the intricate nature of assembly networks and the winding paths of commensurate currents hinder standard circuit modeling. Inspired by the quantum collapse of superposition states for information decoding in quantum circuits, the implementation of analogous current path collapse to facilitate the detection of microscopic circuits by modifying their network topology is explored. Here, the superposition and collapse of current paths in gate-all-around polysilicon nanosheet arrays are demonstrated to enrich the computational resources within transistors by engineering the channel length and quantity. Switching the ferroelectric polarization of Hf0.5 Zr0.5 O2 gate dielectric, which drives these transistors out-of-equilibrium, decodes the output polymorphism through circuit topological modifications. Furthermore, a protocol for the single-electron readout of ferroelectric polarization is presented with tailoring the channel coherence. The introduction of lateral path superposition results into intriguing metal-to-insulator transitions due to transient behavior of ferroelectric switching. This ability to adjust the current networks within transistors and their interaction with ferroelectric polarization in polycrystalline nanostructures lays the groundwork for generating diverse current characteristics as potential physical databases for optimization-based computing.
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Affiliation(s)
- Ching-Hung Chen
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Yu-Ting Lai
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Ciao-Fen Chen
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
- Department of Physics, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Pei-Tzu Wu
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Kuan-Jung Su
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Sheng-Yang Hsu
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Guo-Jin Dai
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Zan-Yi Huang
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Chien-Lung Hsu
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Shen-Yang Lee
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Chuan-Hui Shen
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Hsin-Yu Chen
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Chia-Chin Lee
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Dong-Ru Hsieh
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Yen-Fu Lin
- Department of Physics, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Tien-Sheng Chao
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Shun-Tsung Lo
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
- Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
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3
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Lin CY, Lee MP, Chang YM, Tseng YT, Yang FS, Li M, Chen JY, Chen CF, Tsai MY, Lin YC, Ueno K, Yamamoto M, Lo ST, Lien CH, Chiu PW, Tsukagoshi K, Wu WW, Lin YF. Diffused Beam Energy to Dope van der Waals Electronics and Boost Their Contact Barrier Lowering. ACS Appl Mater Interfaces 2022; 14:41156-41164. [PMID: 36037311 DOI: 10.1021/acsami.2c07679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Contact engineering of two-dimensional semiconductors is a central issue for performance improvement of micro-/nanodevices based on these materials. Unfortunately, the various methods proposed to improve the Schottky barrier height normally require the use of high temperatures, chemical dopants, or complex processes. This work demonstrates that diffused electron beam energy (DEBE) treatment can simultaneously reduce the Schottky barrier height and enable the direct writing of electrical circuitry on van der Waals semiconductors. The electron beam energy projected into the region outside the electrode diffuses into the main channel, producing selective-area n-type doping in a layered MoTe2 (or MoS2) field-effect transistor. As a result, the Schottky barrier height at the interface between the electrode and the DEBE-treated MoTe2 channel is as low as 12 meV. Additionally, because selective-area doping is possible, DEBE can allow the formation of both n- and p-type doped channels within the same atomic plane, which enables the creation of a nonvolatile and homogeneous MoTe2 p-n rectifier with an ideality factor of 1.1 and a rectification ratio of 1.3 × 103. These results indicate that the DEBE method is a simple, efficient, mask-free, and chemical dopant-free approach to selective-area doping for the development of van der Waals electronics with excellent device performances.
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Affiliation(s)
- Che-Yi Lin
- Department of Physics, National Chung Hsing University, Taichung 40227, Taiwan
- Institute of Nanoscience, National Chung Hsing University, Taichung 40227, Taiwan
| | - Mu-Pai Lee
- Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
| | - Yuan-Ming Chang
- Department of Physics, National Chung Hsing University, Taichung 40227, Taiwan
- Institute of Nanoscience, National Chung Hsing University, Taichung 40227, Taiwan
| | - Yi-Tang Tseng
- Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
| | - Feng-Shou Yang
- Institute of Electronic Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Mengjiao Li
- Department of Physics, National Chung Hsing University, Taichung 40227, Taiwan
- Institute of Nanoscience, National Chung Hsing University, Taichung 40227, Taiwan
| | - Jiann-Yeu Chen
- Department of Material Science and Engineering and i-Center for Advanced Science and Technology (i-CAST), National Chung Hsing University, Taichung 40227, Taiwan
- Innovation and Development Center of Sustainable Agriculture, National Chung Hsing University, Taichung 40227, Taiwan
| | - Ciao-Fen Chen
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
| | - Meng-Yu Tsai
- Institute of Electronic Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Yi-Chun Lin
- Instrument Center, National Chung Hsing University, Taichung 40227, Taiwan
| | - Keiji Ueno
- Department of Chemistry, Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan
| | - Mahito Yamamoto
- Department of Pure and Applied Physics, Kansai University, Osaka 564-8680, Japan
| | - Shun-Tsung Lo
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
| | - Chen-Hsin Lien
- Institute of Electronic Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Po-Wen Chiu
- Institute of Electronic Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Kazuhito Tsukagoshi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba 305-0044, Ibaraki, Japan
| | - Wen-Wei Wu
- Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
| | - Yen-Fu Lin
- Department of Physics, National Chung Hsing University, Taichung 40227, Taiwan
- Institute of Nanoscience, National Chung Hsing University, Taichung 40227, Taiwan
- Department of Material Science and Engineering and i-Center for Advanced Science and Technology (i-CAST), National Chung Hsing University, Taichung 40227, Taiwan
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4
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Smith LW, Chen HB, Chang CW, Wu CW, Lo ST, Chao SH, Farrer I, Beere HE, Griffiths JP, Jones GAC, Ritchie DA, Chen YN, Chen TM. Electrically Controllable Kondo Correlation in Spin-Orbit-Coupled Quantum Point Contacts. Phys Rev Lett 2022; 128:027701. [PMID: 35089765 DOI: 10.1103/physrevlett.128.027701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 12/02/2021] [Indexed: 06/14/2023]
Abstract
Integrating the Kondo correlation and spin-orbit interactions, each of which have individually offered unprecedented means to manipulate electron spins, in a controllable way can open up new possibilities for spintronics. We demonstrate electrical control of the Kondo correlation by coupling the bound spin to leads with tunable Rashba spin-orbit interactions, realized in semiconductor quantum point contacts. We observe a transition from single to double peak zero-bias anomalies in nonequilibrium transport-the manifestation of the Kondo effect-indicating a controlled Kondo spin reversal using only spin-orbit interactions. Universal scaling of the Kondo conductance is demonstrated, implying that the spin-orbit interactions could enhance the Kondo temperature. A theoretical model based on quantum master equations is also developed to calculate the nonequilibrium quantum transport.
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Affiliation(s)
- Luke W Smith
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Hong-Bin Chen
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
- Department of Engineering Science, National Cheng Kung University, Tainan 701, Taiwan
- Center for Quantum Frontiers of Research and Technology (QFort), National Cheng Kung University, Tainan 701, Taiwan
| | - Che-Wei Chang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Chien-Wei Wu
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Shun-Tsung Lo
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan
| | - Shih-Hsiang Chao
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - I Farrer
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
- Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom
| | - H E Beere
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - J P Griffiths
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - G A C Jones
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - D A Ritchie
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Yueh-Nan Chen
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
- Center for Quantum Frontiers of Research and Technology (QFort), National Cheng Kung University, Tainan 701, Taiwan
| | - Tse-Ming Chen
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
- Center for Quantum Frontiers of Research and Technology (QFort), National Cheng Kung University, Tainan 701, Taiwan
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5
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Ho SC, Chang HJ, Chang CH, Lo ST, Creeth G, Kumar S, Farrer I, Ritchie D, Griffiths J, Jones G, Pepper M, Chen TM. Imaging the Zigzag Wigner Crystal in Confinement-Tunable Quantum Wires. Phys Rev Lett 2018; 121:106801. [PMID: 30240231 DOI: 10.1103/physrevlett.121.106801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 07/03/2018] [Indexed: 06/08/2023]
Abstract
The existence of Wigner crystallization, one of the most significant hallmarks of strong electron correlations, has to date only been definitively observed in two-dimensional systems. In one-dimensional (1D) quantum wires Wigner crystals correspond to regularly spaced electrons; however, weakening the confinement and allowing the electrons to relax in a second dimension is predicted to lead to the formation of a new ground state constituting a zigzag chain with nontrivial spin phases and properties. Here we report the observation of such zigzag Wigner crystals by use of on-chip charge and spin detectors employing electron focusing to image the charge density distribution and probe their spin properties. This experiment demonstrates both the structural and spin phase diagrams of the 1D Wigner crystallization. The existence of zigzag spin chains and phases which can be electrically controlled in semiconductor systems may open avenues for experimental studies of Wigner crystals and their technological applications in spintronics and quantum information.
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Affiliation(s)
- Sheng-Chin Ho
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Heng-Jian Chang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Chia-Hua Chang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Shun-Tsung Lo
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Graham Creeth
- Department of Electronic and Electrical Engineering, University College London, London WC1E 7JE, United Kingdom
| | - Sanjeev Kumar
- Department of Electronic and Electrical Engineering, University College London, London WC1E 7JE, United Kingdom
| | - Ian Farrer
- Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
- Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, United Kingdom
| | - David Ritchie
- Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Jonathan Griffiths
- Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Geraint Jones
- Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Michael Pepper
- Department of Electronic and Electrical Engineering, University College London, London WC1E 7JE, United Kingdom
| | - Tse-Ming Chen
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
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Huang LI, Yang Y, Liu CW, Elmquist RE, Lo ST, Liu FH, Liang CT. Unusual renormalization group (RG) flow and temperature-dependent phase transition in strongly-insulating monolayer epitaxial graphene. RSC Adv 2017. [DOI: 10.1039/c7ra05463g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
By changing the measurement temperature (T), one can vary the effective sample size so as to study the renormalization group (RG) (or T-driven) flow of a semiconductor, a topological insulator, or a graphene device in the complex conductivity plane.
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Affiliation(s)
- Lung-I. Huang
- National Institute of Standards and Technology (NIST)
- Gaithersburg
- USA
- Department of Physics
- National Taiwan University
| | - Yanfei Yang
- National Institute of Standards and Technology (NIST)
- Gaithersburg
- USA
- Joint Quantum Institute
- University of Maryland
| | - Chieh-Wen Liu
- National Institute of Standards and Technology (NIST)
- Gaithersburg
- USA
- Graduate Institute of Applied Physics
- National Taiwan University
| | | | - Shun-Tsung Lo
- Graduate Institute of Applied Physics
- National Taiwan University
- Taipei 106
- Taiwan
| | - Fan-Hung Liu
- Graduate Institute of Applied Physics
- National Taiwan University
- Taipei 106
- Taiwan
| | - Chi-Te Liang
- Department of Physics
- National Taiwan University
- Taipei 106
- Taiwan
- Graduate Institute of Applied Physics
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Abstract
We report on magneto-transport measurements on low-density, large-area monolayer epitaxial graphene devices grown on SiC. We observe temperature (T)-independent crossing points in the longitudinal resistivity ρxx, which are signatures of the insulator-quantum Hall (I-QH) transition, in all three devices. Upon converting the raw data into longitudinal and Hall conductivities σxx and σxy, in the most disordered device, we observed T-driven flow diagram approximated by the semi-circle law as well as the T-independent point in σxy near e2/h. We discuss our experimental results in the context of the evolution of the zero-energy Landau level at low magnetic fields B. We also compare the observed strongly insulating behaviour with metallic behaviour and the absence of the I-QH transition in graphene on SiO2 prepared by mechanical exfoliation.
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Affiliation(s)
- Lung-I Huang
- National Institute of Standards and Technology (NIST), Gaithersburg,
MD 20899, USA
- Department of Physics, National Taiwan University, Taipei 106,
Taiwan
| | - Yanfei Yang
- National Institute of Standards and Technology (NIST), Gaithersburg,
MD 20899, USA
- Department of Physics, Georgetown University, Washington, DC 20057,
USA
| | - Randolph E. Elmquist
- National Institute of Standards and Technology (NIST), Gaithersburg,
MD 20899, USA
| | - Shun-Tsung Lo
- Graduate Institute of Applied Physics, National Taiwan University,
Taipei 106, Taiwan
| | - Fan-Hung Liu
- Graduate Institute of Applied Physics, National Taiwan University,
Taipei 106, Taiwan
| | - Chi-Te Liang
- Department of Physics, National Taiwan University, Taipei 106,
Taiwan
- Graduate Institute of Applied Physics, National Taiwan University,
Taipei 106, Taiwan
- Geballe Laboratory for Advanced Materials (GLAM), Stanford
University, Stanford, CA 94305, USA
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Lo ST, Collin PJL, Hokken-Koelega ACS. Visual-motor integration in children with Prader-Willi syndrome. J Intellect Disabil Res 2015; 59:827-834. [PMID: 25871504 DOI: 10.1111/jir.12197] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 03/18/2015] [Indexed: 06/04/2023]
Abstract
BACKGROUND Prader-Willi syndrome (PWS) is characterised by hypotonia, hypogonadism, short stature, obesity, behavioural problems, intellectual disability, and delay in language, social and motor development. There is very limited knowledge about visual-motor integration in children with PWS. METHOD Seventy-three children with PWS aged 7-17 years were included. Visual-motor integration was assessed using the Beery Visual-motor Integration test at the start of the study and after 2 years. The association between visual-motor integration and age, gender, genetic subtype and intelligence was assessed. RESULTS Children with PWS scored 'very low' (-3 standard deviations) in visual-motor integration and 'below average' (-1 standard deviation) in visual perception and motor coordination compared with typically developing children. Visual-motor integration was higher in children with a deletion (β = -0.170, P = 0.037), in older children (β = 0.222, P = 0.009) and in those with a higher total IQ (β = 0.784, P < 0.001). Visual perception was higher with a deletion (β = -0.193, P = 0.044) and higher IQ (β = -0.618, P < 0.001), but motor coordination was only higher with a higher total IQ (β = 0.429, P = 0.001). Visual perception and motor coordination were not associated with age or gender. There was a trend for visual-motor integration decline over the 2 year follow-up period (P = 0.099). Visual perception and motor coordination did not change over the follow-up period. CONCLUSIONS Visual-motor integration is very poor in children with PWS. Children scored higher on the time-limited subtests for visual perception and motor coordination than the combined test for visual-motor integration. Separation of visual-motor integration tasks into pure visual or motor tasks and allowing sufficient time to perform the tasks might improve daily activities, both at home and at school.
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Affiliation(s)
- S T Lo
- Department of Pediatric Endocrinology, Dutch Growth Research Foundation, Rotterdam, The Netherlands
| | - P J L Collin
- Department of Child Psychiatry, de Koraalgroep, Sittard, The Netherlands
| | - A C S Hokken-Koelega
- Department of Pediatrics, Subdivision of Endocrinology, Erasmus University Medical Center, Rotterdam, The Netherlands
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Lo ST, Collin PJL, Hokken-Koelega ACS. Psychiatric disorders in children with Prader-Willi syndrome-Results of a 2-year longitudinal study. Am J Med Genet A 2015; 167A:983-91. [PMID: 25712902 DOI: 10.1002/ajmg.a.36998] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 01/15/2015] [Indexed: 01/11/2023]
Abstract
Psychiatric disorders such as psychosis are highly prevalent in adults with Prader-Willi syndrome (PWS). However, knowledge about the presence and progression of psychiatric disorders in children with PWS is very limited. Sixty-one children with PWS aged 7-17 years were tested using the Diagnostic Interview Schedule for Children (DISC) and Compulsive Behaviour Checklist (CBC), and 38/61 were retested after 2 years. Prevalence of psychiatric disorders and the association with age, gender, genetic subtype, and total IQ were assessed. In addition, occurrence and characteristics of compulsions were determined. Prior to the study, two boys were known with psychotic symptoms and treated with antipsychotics. At baseline, none scored positive for psychotic disorder. During the follow-up, only one boy with known psychotic symptoms required a dose adjustment of his antipsychotic medication. After 2 years, none of the children had a psychotic disorder according to the DISC. Oppositional defiant disorder (ODD) was the most common diagnosis and present in 20% of children with PWS, and this was not associated with age (β = -0.081, P = 0.546), gender (β = 0.013, P = 0.923), genetic subtype (β = -0.073, P = 0.584), or total IQ (β = -0.150, P = 0.267). The most common compulsions were hoarding and fixed hygiene sequences. In our large group of 61 children with PWS, the majority had no psychotic disorder and no progression was found during 2-year follow-up. ODD was present in 20% of children. No changes in the prevalence of psychiatric disorders were found during the 2-year follow-up study and genetic subtype was not related to psychosis, depression, or ODD.
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Affiliation(s)
- S T Lo
- Dutch Growth Research Foundation, Rotterdam, The Netherlands; Department of Pediatrics, Erasmus University Medical Center/Sophia Children's Hospital, Subdivision of Endocrinology, Rotterdam, The Netherlands
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Liu FH, Lo ST, Chuang C, Woo TP, Lee HY, Liu CW, Liu CI, Huang LI, Liu CH, Yang Y, Chang CYS, Li LJ, Mende PC, Feenstra RM, Elmquist RE, Liang CT. Hot carriers in epitaxial graphene sheets with and without hydrogen intercalation: role of substrate coupling. Nanoscale 2014; 6:10562-10568. [PMID: 25117572 DOI: 10.1039/c4nr02980a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The development of graphene electronic devices produced by industry relies on efficient control of heat transfer from the graphene sheet to its environment. In nanoscale devices, heat is one of the major obstacles to the operation of such devices at high frequencies. Here we have studied the transport of hot carriers in epitaxial graphene sheets on 6H-SiC (0001) substrates with and without hydrogen intercalation by driving the device into the non-equilibrium regime. Interestingly, we have demonstrated that the energy relaxation time of the device without hydrogen intercalation is two orders of magnitude shorter than that with hydrogen intercalation, suggesting application of epitaxial graphene in high-frequency devices which require outstanding heat exchange with an outside cooling source.
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Affiliation(s)
- Fan-Hung Liu
- Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan.
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Lo ST, Klochan O, Liu CH, Wang WH, Hamilton AR, Liang CT. Transport in disordered monolayer MoS2 nanoflakes--evidence for inhomogeneous charge transport. Nanotechnology 2014; 25:375201. [PMID: 25147958 DOI: 10.1088/0957-4484/25/37/375201] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We study charge transport in a monolayer MoS2 nanoflake over a wide range of carrier density, temperature and electric bias. We find that the transport is best described by a percolating picture in which the disorder breaks translational invariance, breaking the system up into a series of puddles, rather than previous pictures in which the disorder is treated as homogeneous and uniform. Our work provides insight to a unified picture of charge transport in monolayer MoS2 nanoflakes and contributes to the development of next-generation MoS2-based devices.
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Affiliation(s)
- Shun-Tsung Lo
- School of Physics, University of New South Wales, Sydney, NSW 2052, Australia. Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan
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12
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Lo ST, Liu FH, Hsu CS, Chuang C, Huang LI, Fukuyama Y, Yang Y, Elmquist RE, Liang CT. Localization and electron-electron interactions in few-layer epitaxial graphene. Nanotechnology 2014; 25:245201. [PMID: 24872201 DOI: 10.1088/0957-4484/25/24/245201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
This paper presents a study of the quantum corrections caused by electron-electron interactions and localization to the conductivity in few-layer epitaxial graphene, in which the carriers responsible for transport are massive. The results demonstrate that the diffusive model, which can generally provide good insights into the magnetotransport of two-dimensional systems in conventional semiconductor structures, is applicable to few-layer epitaxial graphene when the unique properties of graphene on the substrate, such as intervalley scattering, are taken into account. It is suggested that magnetic-field-dependent electron-electron interactions and Kondo physics are required for obtaining a thorough understanding of magnetotransport in few-layer epitaxial graphene.
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13
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Lu YF, Lo ST, Lin JC, Zhang W, Lu JY, Liu FH, Tseng CM, Lee YH, Liang CT, Li LJ. Nitrogen-doped graphene sheets grown by chemical vapor deposition: synthesis and influence of nitrogen impurities on carrier transport. ACS Nano 2013; 7:6522-32. [PMID: 23879622 DOI: 10.1021/nn402102y] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
A significant advance toward achieving practical applications of graphene as a two-dimensional material in nanoelectronics would be provided by successful synthesis of both n-type and p-type doped graphene. However, reliable doping and a thorough understanding of carrier transport in the presence of charged impurities governed by ionized donors or acceptors in the graphene lattice are still lacking. Here we report experimental realization of few-layer nitrogen-doped (N-doped) graphene sheets by chemical vapor deposition of organic molecule 1,3,5-triazine on Cu metal catalyst. When reducing the growth temperature, the atomic percentage of nitrogen doping is raised from 2.1% to 5.6%. With increasing doping concentration, N-doped graphene sheet exhibits a crossover from p-type to n-type behavior accompanied by a strong enhancement of electron-hole transport asymmetry, manifesting the influence of incorporated nitrogen impurities. In addition, by analyzing the data of X-ray photoelectron spectroscopy, Raman spectroscopy, and electrical measurements, we show that pyridinic and pyrrolic N impurities play an important role in determining the transport behavior of carriers in our N-doped graphene sheets.
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Affiliation(s)
- Yu-Fen Lu
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan
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14
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Liu FH, Hsu CS, Chuang C, Woo TP, Huang LI, Lo ST, Fukuyama Y, Yang Y, Elmquist RE, Liang CT. Dirac fermion heating, current scaling, and direct insulator-quantum Hall transition in multilayer epitaxial graphene. Nanoscale Res Lett 2013; 8:360. [PMID: 23968131 PMCID: PMC3765374 DOI: 10.1186/1556-276x-8-360] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Accepted: 08/12/2013] [Indexed: 06/02/2023]
Abstract
We have performed magnetotransport measurements on multilayer epitaxial graphene. By increasing the driving current I through our graphene devices while keeping the bath temperature fixed, we are able to study Dirac fermion heating and current scaling in such devices. Using zero-field resistivity as a self thermometer, we are able to determine the effective Dirac fermion temperature (TDF) at various driving currents. At zero field, it is found that TDF ∝ I≈1/2. Such results are consistent with electron heating in conventional two-dimensional systems in the plateau-plateau transition regime. With increasing magnetic field B, we observe an I-independent point in the measured longitudinal resistivity ρxx which is equivalent to the direct insulator-quantum Hall (I-QH) transition characterized by a temperature-independent point in ρxx. Together with recent experimental evidence for direct I-QH transition, our new data suggest that such a transition is a universal effect in graphene, albeit further studies are required to obtain a thorough understanding of such an effect.
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Affiliation(s)
- Fan-Hung Liu
- Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan
| | - Chang-Shun Hsu
- Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan
| | - Chiashain Chuang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Tak-Pong Woo
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Lung-I Huang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Shun-Tsung Lo
- Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan
| | - Yasuhiro Fukuyama
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan
| | - Yanfei Yang
- National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, USA
| | - Randolph E Elmquist
- National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, USA
| | - Chi-Te Liang
- Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
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15
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Lo ST, Chen KY, Lin SD, Wu JY, Lin TL, Yeh MR, Chen TM, Liang CT. Controllable disorder in a hybrid nanoelectronic system: realization of a superconducting diode. Sci Rep 2013; 3:2274. [PMID: 23881449 PMCID: PMC3721077 DOI: 10.1038/srep02274] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Accepted: 07/08/2013] [Indexed: 11/09/2022] Open
Abstract
We have studied a hybrid nanoelectronic system which consists of an AlGaAs/GaAs two-dimensional electron gas (2DEG) in close proximity (~70 nm) to an Al superconducting nanofilm. By tuning the current through the Al film, we can change the conductance of the 2DEG and furthermore vary the effective disorder in the Al superconducting film in a controllable way. When a high current is injected into the film, screening which couples the Al film and the 2DEG results in a collapse of anti-symmetric behavior in the current-voltage characteristics, V(I) ~ -V(-I), which holds true in a conventional superconductor. Our results may open a new avenue of experimentally realizing a superconducting diode.
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Affiliation(s)
- Shun-Tsung Lo
- Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan
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16
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Chen WJ, Wu JK, Lin JC, Lo ST, Lin HD, Hang DR, Shih MF, Liang CT, Chang YH. Room-temperature violet luminescence and ultraviolet photodetection of Sb-doped ZnO/Al-doped ZnO homojunction array. Nanoscale Res Lett 2013; 8:313. [PMID: 23826909 PMCID: PMC3711895 DOI: 10.1186/1556-276x-8-313] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 06/27/2013] [Indexed: 05/20/2023]
Abstract
A Sb-doped ZnO microrod array was fabricated on an Al-doped ZnO thin film by electrodeposition. Strong violet luminescence, originated from free electron-to-acceptor level transitions, was identified by temperature-dependent photoluminescence measurements. This acceptor-related transition was attributed to substitution of Sb dopants for Zn sites, instead of O sites, to form a complex with two Zn vacancies (VZn), the SbZn-2VZn complex. This SbZn-2VZn complex has a lower formation energy and acts as a shallow acceptor which can induce the observed strong violet luminescence. The photoresponsivity of our ZnO p-n homojunction device under a negative bias demonstrated a nearly 40-fold current gain, illustrating that our device is potentially an excellent candidate for photodetector applications in the ultraviolet wavelength region.
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Affiliation(s)
- Wei-Jen Chen
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Jen-Kai Wu
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Jheng-Cyuan Lin
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Shun-Tsung Lo
- Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan
| | - Huang-De Lin
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Da-Ren Hang
- Department of Materials and Optoelectronic Science, National Sun Yat-sen University, Kaohsiung 804, Taiwan
- Center for Nanoscience and Nanotechnology, National Sun Yat-sen University, Kaohsiung 804, Taiwan
| | - Ming Feng Shih
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Chi-Te Liang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
- School of Electronic and Electrical Engineering, Sungkyunkwan University, Suwon 440-746, South Korea
| | - Yuan Huei Chang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
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17
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Lo ST, Wang YT, Lin SD, Strasser G, Bird JP, Chen YF, Liang CT. Tunable insulator-quantum Hall transition in a weakly interacting two-dimensional electron system. Nanoscale Res Lett 2013; 8:307. [PMID: 23819745 PMCID: PMC3716820 DOI: 10.1186/1556-276x-8-307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 06/26/2013] [Indexed: 06/02/2023]
Abstract
We have performed low-temperature measurements on a gated two-dimensional electron system in which electron-electron (e-e) interactions are insignificant. At low magnetic fields, disorder-driven movement of the crossing of longitudinal and Hall resistivities (ρxx and ρxy) can be observed. Interestingly, by applying different gate voltages, we demonstrate that such a crossing at ρxx ~ ρxy can occur at a magnetic field higher, lower, or equal to the temperature-independent point in ρxx which corresponds to the direct insulator-quantum Hall transition. We explicitly show that ρxx ~ ρxy occurs at the inverse of the classical Drude mobility 1/μD rather than the crossing field corresponding to the insulator-quantum Hall transition. Moreover, we show that the background magnetoresistance can affect the transport properties of our device significantly. Thus, we suggest that great care must be taken when calculating the renormalized mobility caused by e-e interactions.
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Affiliation(s)
- Shun-Tsung Lo
- Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan
| | - Yi-Ting Wang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Sheng-Di Lin
- Department of Electronics Engineering, National Chiao Tung University, Hsinchu 300, Taiwan
| | - Gottfried Strasser
- Institute for Solid State Electronics and Center for Micro- and Nanostructures, Technische Universität Wien, Floragasse 7, 1040, Vienna, Austria
| | - Jonathan P Bird
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260-1920, USA
| | - Yang-Fang Chen
- Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Chi-Te Liang
- Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
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18
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Chuang C, Lin LH, Aoki N, Ouchi T, Mahjoub AM, Woo TP, Bird JP, Ochiai Y, Lo ST, Liang CT. Experimental evidence for direct insulator-quantum Hall transition in multi-layer graphene. Nanoscale Res Lett 2013; 8:214. [PMID: 23647579 PMCID: PMC3655881 DOI: 10.1186/1556-276x-8-214] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Accepted: 04/24/2013] [Indexed: 06/02/2023]
Abstract
We have performed magnetotransport measurements on a multi-layer graphene flake. At the crossing magnetic field Bc, an approximately temperature-independent point in the measured longitudinal resistivity ρxx, which is ascribed to the direct insulator-quantum Hall (I-QH) transition, is observed. By analyzing the amplitudes of the magnetoresistivity oscillations, we are able to measure the quantum mobility μq of our device. It is found that at the direct I-QH transition, μqBc ≈ 0.37 which is considerably smaller than 1. In contrast, at Bc, ρxx is close to the Hall resistivity ρxy, i.e., the classical mobility μBc is ≈ 1. Therefore, our results suggest that different mobilities need to be introduced for the direct I-QH transition observed in multi-layered graphene. Combined with existing experimental results obtained in various material systems, our data obtained on graphene suggest that the direct I-QH transition is a universal effect in 2D.
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Affiliation(s)
- Chiashain Chuang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
- Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan
| | - Li-Hung Lin
- Department of Electrophysics, National Chiayi University, Chiayi 600, Taiwan
| | - Nobuyuki Aoki
- Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan
| | - Takahiro Ouchi
- Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan
| | - Akram M Mahjoub
- Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan
| | - Tak-Pong Woo
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Jonathan P Bird
- Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, NY 14206-1500, USA
| | - Yuichi Ochiai
- Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan
| | - Shun-Tsung Lo
- Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan
| | - Chi-Te Liang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
- Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan
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19
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Lo ST, Chuang C, Puddy RK, Chen TM, Smith CG, Liang CT. Non-ohmic behavior of carrier transport in highly disordered graphene. Nanotechnology 2013; 24:165201. [PMID: 23538916 DOI: 10.1088/0957-4484/24/16/165201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We report measurements of disordered graphene probed by both a high electric field and a high magnetic field. By applying a high source-drain voltage, Vsd, we are able to study the current-voltage relation I-Vsd of our device. With increasing Vsd, a crossover from the linear I-Vsd regime to the non-linear one, and eventually to activationless-hopping transport occurs. In the activationless-hopping regime, the importance of Coulomb interactions between charged carriers is demonstrated. Moreover, we show that delocalization of carriers which are strongly localized at low T and at small Vsd occurs in the presence of high electric field and perpendicular magnetic field.
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Affiliation(s)
- Shun-Tsung Lo
- Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan
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20
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Lo ST, Lin HE, Wang SW, Lin HD, Chin YC, Lin HH, Lin JC, Liang CT. Electron transport in a GaPSb film. Nanoscale Res Lett 2012; 7:640. [PMID: 23173952 PMCID: PMC3552782 DOI: 10.1186/1556-276x-7-640] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 10/12/2012] [Indexed: 06/01/2023]
Abstract
We have performed transport measurements on a gallium phosphide antimonide (GaPSb) film grown on GaAs. At low temperatures (T), transport is governed by three-dimensional Mott variable range hopping (VRH) due to strong localization. Therefore, electron-electron interactions are not significant in GaPSb. With increasing T, the coexistence of VRH conduction and the activated behavior with a gap of 20 meV is found. The fact that the measured gap is comparable to the thermal broadening at room temperature (approximately 25 meV) demonstrates that electrons can be thermally activated in an intrinsic GaPSb film. Moreover, the observed carrier density dependence on temperature also supports the coexistence of VRH and the activated behavior. It is shown that the carriers are delocalized either with increasing temperature or magnetic field in GaPSb. Our new experimental results provide important information regarding GaPSb which may well lay the foundation for possible GaPSb-based device applications such as in high-electron-mobility transistor and heterojunction bipolar transistors.
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Affiliation(s)
- Shun-Tsung Lo
- Graduate Institute of Applied Physics, National Taiwan University, Taipei, 106, Taiwan
| | - Hung En Lin
- Department of Physics, National Taiwan University, Taipei, 106, Taiwan
| | - Shu-Wei Wang
- Department of Physics, National Taiwan University, Taipei, 106, Taiwan
| | - Huang-De Lin
- Department of Physics, National Taiwan University, Taipei, 106, Taiwan
- Electronics Testing Center, No. 8, Lane 29, Guishan Shiang, Taoyuan County, Taiwan, 333
| | - Yu-Chung Chin
- Graduate Institute of Electronics Engineering, National Taiwan University, Taipei , 106, Taiwan
| | - Hao-Hsiung Lin
- Graduate Institute of Electronics Engineering, National Taiwan University, Taipei , 106, Taiwan
- Department of Electrical Engineering, National Taiwan University, Taipei, 106, Taiwan
| | - Jheng-Cyuan Lin
- Department of Physics, National Taiwan University, Taipei, 106, Taiwan
| | - Chi-Te Liang
- Graduate Institute of Applied Physics, National Taiwan University, Taipei, 106, Taiwan
- Department of Physics, National Taiwan University, Taipei, 106, Taiwan
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21
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Lo ST, Wang YT, Bohra G, Comfort E, Lin TY, Kang MG, Strasser G, Bird JP, Huang CF, Lin LH, Chen JC, Liang CT. Insulator, semiclassical oscillations and quantum Hall liquids at low magnetic fields. J Phys Condens Matter 2012; 24:405601. [PMID: 22968955 DOI: 10.1088/0953-8984/24/40/405601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Magneto-transport measurements are performed on two-dimensional GaAs electron systems to probe the quantum Hall (QH) effect at low magnetic fields. Oscillations following the Shubnikov-de Haas (SdH) formula are observed in the transition from the insulator to QH liquid when the observed almost temperature-independent Hall slope indicates insignificant interaction correction. Our study shows that the existence of SdH oscillations in such a transition can be understood based on the non-interacting model.
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Affiliation(s)
- Shun-Tsung Lo
- Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan
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22
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Wang YT, Kim GH, Huang CF, Lo ST, Chen WJ, Nicholls JT, Lin LH, Ritchie DA, Chang YH, Liang CT, Dolan BP. Probing temperature-driven flow lines in a gated two-dimensional electron gas with tunable spin-splitting. J Phys Condens Matter 2012; 24:405801. [PMID: 22968970 DOI: 10.1088/0953-8984/24/40/405801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We study the temperature flow of conductivities in a gated GaAs two-dimensional electron gas (2DEG) containing self-assembled InAs dots and compare the results with recent theoretical predictions. By changing the gate voltage, we are able to tune the 2DEG density and thus vary disorder and spin-splitting. Data for both the spin-resolved and spin-degenerate phase transitions are presented, the former collapsing to the latter with decreasing gate voltage and/or decreasing spin-splitting. The experimental results support a recent theory, based on modular symmetry, which predicts how the critical Hall conductivity varies with spin-splitting.
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Affiliation(s)
- Yi-Ting Wang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
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23
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Chuang C, Puddy RK, Connolly MR, Lo ST, Lin HD, Chen TM, Smith CG, Liang CT. Evidence for formation of multi-quantum dots in hydrogenated graphene. Nanoscale Res Lett 2012; 7:459. [PMID: 22898058 PMCID: PMC3526389 DOI: 10.1186/1556-276x-7-459] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 08/10/2012] [Indexed: 06/01/2023]
Abstract
We report the experimental evidence for the formation of multi-quantum dots in a hydrogenated single-layer graphene flake. The existence of multi-quantum dots is supported by the low-temperature measurements on a field effect transistor structure device. The resulting Coulomb blockade diamonds shown in the color scale plot together with the number of Coulomb peaks exhibit the characteristics of the so-called 'stochastic Coulomb blockade'. A possible explanation for the formation of the multi-quantum dots, which is not observed in pristine graphene to date, was attributed to the impurities and defects unintentionally decorated on a single-layer graphene flake which was not treated with the thermal annealing process. Graphene multi-quantum dots developed around impurities and defect sites during the hydrogen plasma exposure process.
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Affiliation(s)
- Chiashain Chuang
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK
- Department of Physics, National Taiwan University, Taipei, 106, Taiwan
| | - Reuben K Puddy
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Malcolm R Connolly
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Shun-Tsung Lo
- Graduate Institute of Applied Physics, National Taiwan University, Taipei, 106, Taiwan
| | - Huang-De Lin
- Department of Physics, National Taiwan University, Taipei, 106, Taiwan
| | - Tse-Ming Chen
- Department of Physics, National Cheng Kung University, Tainan, 701, Taiwan
| | - Charles G Smith
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Chi-Te Liang
- Department of Physics, National Taiwan University, Taipei, 106, Taiwan
- Graduate Institute of Applied Physics, National Taiwan University, Taipei, 106, Taiwan
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24
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Luo DS, Lin LH, Su YC, Wang YT, Peng ZF, Lo ST, Chen KY, Chang YH, Wu JY, Lin Y, Lin SD, Chen JC, Huang CF, Liang CT. A delta-doped quantum well system with additional modulation doping. Nanoscale Res Lett 2011; 6:139. [PMID: 21711656 PMCID: PMC3211186 DOI: 10.1186/1556-276x-6-139] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2010] [Accepted: 02/14/2011] [Indexed: 05/31/2023]
Abstract
A delta-doped quantum well with additional modulation doping may have potential applications. Utilizing such a hybrid system, it is possible to experimentally realize an extremely high two-dimensional electron gas (2DEG) density without suffering inter-electronic-subband scattering. In this article, the authors report on transport measurements on a delta-doped quantum well system with extra modulation doping. We have observed a 0-10 direct insulator-quantum Hall (I-QH) transition where the numbers 0 and 10 correspond to the insulator and Landau level filling factor ν = 10 QH state, respectively. In situ titled-magnetic field measurements reveal that the observed direct I-QH transition depends on the magnetic component perpendicular to the quantum well, and the electron system within this structure is 2D in nature. Furthermore, transport measurements on the 2DEG of this study show that carrier density, resistance and mobility are approximately temperature (T)-independent over a wide range of T. Such results could be an advantage for applications in T-insensitive devices.
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Affiliation(s)
| | - Li-Hung Lin
- Department of Electrophysics, National Chiayi University, Chiayi, 600, Taiwan
| | - Yi-Chun Su
- Department of Physics, National Taiwan University, Taipei, 106, Taiwan
| | - Yi-Ting Wang
- Department of Physics, National Taiwan University, Taipei, 106, Taiwan
| | - Zai Fong Peng
- Department of Electrophysics, National Chiayi University, Chiayi, 600, Taiwan
| | - Shun-Tsung Lo
- Department of Physics, National Taiwan University, Taipei, 106, Taiwan
| | - Kuang Yao Chen
- Department of Physics, National Taiwan University, Taipei, 106, Taiwan
| | - Yuan-Huei Chang
- Department of Physics, National Taiwan University, Taipei, 106, Taiwan
| | - Jau-Yang Wu
- Department of Electronics Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan
| | - Yiping Lin
- Department of Physics, National Tsinghwa University, Hsinchu, 300, Taiwan
| | - Sheng-Di Lin
- Department of Electronics Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan
| | - Jeng-Chung Chen
- Department of Physics, National Tsinghwa University, Hsinchu, 300, Taiwan
| | - Chun-Feng Huang
- National Measurement Laboratory, Centre for Measurement Standards, Industrial Technology Research Institute, Hsinchu, 300, Taiwan
| | - Chi-Te Liang
- Department of Physics, National Taiwan University, Taipei, 106, Taiwan
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25
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Liang CT, Lin LH, Kuang Yoa C, Lo ST, Wang YT, Lou DS, Kim GH, Yuan-Huei C, Ochiai Y, Aoki N, Chen JC, Lin Y, Chun-Feng H, Lin SD, Ritchie DA. On the direct insulator-quantum Hall transition in two-dimensional electron systems in the vicinity of nanoscaled scatterers. Nanoscale Res Lett 2011; 6:131. [PMID: 21711637 PMCID: PMC3211178 DOI: 10.1186/1556-276x-6-131] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/14/2010] [Accepted: 02/11/2011] [Indexed: 05/31/2023]
Abstract
A direct insulator-quantum Hall (I-QH) transition corresponds to a crossover/transition from the insulating regime to a high Landau level filling factor ν > 2 QH state. Such a transition has been attracting a great deal of both experimental and theoretical interests. In this study, we present three different two-dimensional electron systems (2DESs) which are in the vicinity of nanoscaled scatterers. All these three devices exhibit a direct I-QH transition, and the transport properties under different nanaoscaled scatterers are discussed.
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Affiliation(s)
- Chi-Te Liang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Li-Hung Lin
- Department of Applied Physics, National Chiayi University, Chiayi 600, Taiwan
| | - Chen Kuang Yoa
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Shun-Tsung Lo
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Yi-Ting Wang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Dong-Sheng Lou
- Department of Physics, National Tsinghwa University, Hsinchu 300, Taiwan
| | - Gil-Ho Kim
- Department of Electronic and Electrical Engineering and SAINT, Sungkyunkwan University, Suwon 440-746, Korea
| | - Chang Yuan-Huei
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Yuichi Ochiai
- Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan
| | - Nobuyuki Aoki
- Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan
| | - Jeng-Chung Chen
- Department of Physics, National Tsinghwa University, Hsinchu 300, Taiwan
| | - Yiping Lin
- Department of Physics, National Tsinghwa University, Hsinchu 300, Taiwan
| | - Huang Chun-Feng
- National Measurement Laboratory, Centre for Measurement Standards, Industrial Technology Research Institute, Hsinchu 300, Taiwan
| | - Sheng-Di Lin
- Department of Electronics Engineering, National Chiao Tung University, Hsinchu 300, Taiwan
| | - David A Ritchie
- Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
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Lo ST, Chuang C, Lin SD, Chen KY, Liang CT, Lin SW, Wu JY, Yeh MR. Magnetotransport in an aluminum thin film on a GaAs substrate grown by molecular beam epitaxy. Nanoscale Res Lett 2011; 6:102. [PMID: 24576326 PMCID: PMC3211146 DOI: 10.1186/1556-276x-6-102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2010] [Accepted: 01/26/2011] [Indexed: 06/03/2023]
Abstract
Magnetotransport measurements are performed on an aluminum thin film grown on a GaAs substrate. A crossover from electron- to hole-dominant transport can be inferred from both longitudinal resistivity and Hall resistivity with increasing the perpendicular magnetic field B. Also, phenomena of localization effects can be seen at low B. By analyzing the zero-field resistivity as a function of temperature T, we show the importance of surface scattering in such a nanoscale film.
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Affiliation(s)
- Shun-Tsung Lo
- Department of Physics, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd. Taipei 106, Taiwan
| | - Chiashain Chuang
- Department of Physics, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd. Taipei 106, Taiwan
| | - Sheng-Di Lin
- Department of Electronics Engineering, National Chiao Tung University, 1001 Ta Hsueh Rd., Hsinchu 300, Taiwan
| | - Kuang Yao Chen
- Department of Physics, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd. Taipei 106, Taiwan
| | - Chi-Te Liang
- Department of Physics, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd. Taipei 106, Taiwan
| | - Shih-Wei Lin
- Department of Electronics Engineering, National Chiao Tung University, 1001 Ta Hsueh Rd., Hsinchu 300, Taiwan
| | - Jau-Yang Wu
- Department of Electronics Engineering, National Chiao Tung University, 1001 Ta Hsueh Rd., Hsinchu 300, Taiwan
| | - Mao-Rong Yeh
- Department of Physics, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd. Taipei 106, Taiwan
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Milburn JA, Lo ST, Szucs ZJ, Humphrey A, Macaulay EM. Transposed brachiobasilic fistula or PTFE arm graft - alternative or complementary? J Vasc Access 2008; 9:117-121. [PMID: 18609527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023] Open
Abstract
PURPOSE Our primary aims were (1) to examine the patency of transposed brachiobasilic (TBB) fistulae compared to arm arteriovenous graft (AVG) without prior transposition, and (2) to examine the patency of AVG with and without prior transposition. METHODS Single institution; analysis of prospectively collected data between January 2001 and January 2007. Dedicated database and medical records were reviewed and results analyzed with SPSS. RESULTS Ninety-one patients underwent 111 procedures (52 TBB: 39 AVG as index); 28 TBB failed with 17 (60%) being replaced with an ipsilateral AVG. TBB compared to AVG (without prior TBB) had significantly (log rank <0.05 ) better primary, primary assisted and secondary patency. Secondary patency at 2 yrs was 47% to 33%, respectively. Ipsilateral AVG after TBB to primary AVG had superior patency rates (secondary patency at 2 yrs 52 vs. 33%) but did not reach significance (log rank =0.073). Combined secondary patency of TBB and AVG after TBB was 81% at 2 yrs. CONCLUSIONS The TBB offers an autogenous fistula in the upper arm which has superior patency rates to an arm AVG. Once a TBB has failed an ipsilateral AVG is technically feasible and may offer better patency than a primary AVG.
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Affiliation(s)
- J A Milburn
- Department of Vascular Surgery, Aberdeen Royal Infirmary, Aberdeen, Scotland.
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Abstract
BACKGROUND The American College of Cardiology and American Heart Association have published guidelines for coronary angiography. We evaluated the compliance rate with these guidelines in clinical practice, its correlation to results of angiography and aimed to identify problem areas of non-compliance. METHODS We prospectively evaluated 802 consecutive referrals for coronary angiography over 5 months in 2002 in a tertiary referral hospital. These referrals were assessed by two independent reviewers blinded to the results of angiography. RESULTS Patient age was 62 +/- 11 years (522 men, 433 inpatients, 369 day-only patients). Referrals were outside published guidelines in 34.3 and 36.2% as evaluated by the two reviewers (concordance rate 88.2%, kappa = 0.74, p < 0.001). Intraobserver agreement was 97.5%. The rate of angiography showing either normal arteries or only minor diseases (<50%) was higher for referrals outside guidelines (68.4 vs 22.6%, P < 0.001). Compliance rate was high with indications of non-ST-elevation myocardial infarction (99.2%) and ST-elevation myocardial infarction (95.8%), valvular disease (80%) and arrhythmia (80%). Compliance rate was lower with assessment of dyspnoea or heart failure (74.3%) and before non-cardiac surgery (72.7%) and was particularly low with assessment of chest pain (53.2%). Younger age (odds ratio (OR) 1.04, P < 0.001), female sex (OR 2.67, P < 0.001), day-only procedure (OR 2.27, P < 0.001) and non-invasive cardiologist referrer (OR 1.41, P = 0.046) were independent predictors of non-compliance. CONCLUSION Referrals for coronary angiography were outside guidelines in a significant proportion of patients. Rate of negative angiography was higher when the referrals were outside guidelines. Problematic areas of non-compliance could be identified. Measures specifically targeting these areas may be more effective in improving the overall guideline compliance in clinical practice.
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Affiliation(s)
- D Y Leung
- Department of Cardiology, Liverpool Hospital, University of New South Wales, Sydney, New South Wales, Australia.
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Kachwalla H, Lo ST, Tie H, Nashed G, Juergens CP, Hopkins AP, Lowe HC. Spontaneous coronary dissection following exertion: support for a hypothesis. Intern Med J 2001; 31:501-3. [PMID: 11720069 DOI: 10.1046/j.1445-5994.2001.00124.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Lee CN, Cavanagh HM, Lo ST, Ng CS. Human papillomavirus infection in non-neoplastic uterine cervical disease in Hong Kong. Br J Biomed Sci 2001; 58:85-91. [PMID: 11440211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
The polymerase chain reaction (PCR) was used to detect and identify human papillomavirus (HPV) in 108 cases of formalin-fixed, paraffin-embedded, non-neoplastic uterine cervical biopsy tissue retrieved from the surgical pathology archives of the Department of Pathology, Caritas Medical Centre, Hong Kong. After DNA extraction, HPV L1 gene primers were used to detect the presence of HPV, and type-specific primers (to HPV types 6, 11, 16, 18, 31 and 33) were used to identify the specific HPV type on HPV L1-positive cases. PCR amplification of the beta-globin gene was used to ensure the quality of amplifiable DNA extracted. Of 94 cases that yielded sufficient good-quality DNA for PCR analysis, three (one endocervical polyp, one chronic inflammation with erosion, and a normal biopsy) had detectable HPV infection. Two of these had high-risk HPV type 16; the other had an uncommon HPV type. In view of the low incidence of HPV found in these patients, large-scale population screening of clinical samples using PCR to detect the presence of HPV and identify high-risk asymptomatic patients would not be cost-effective.
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Affiliation(s)
- C N Lee
- Department of Pathology, United Christian Hospital, Hong Kong, Hong Kong
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Abstract
We found that after audit and physician-guided changes in our protocol, the door-to-inflation times for primary angioplasty/stenting were markedly reduced. Because our preaudit mean time was similar to the national average, this may have wide applicability.
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Affiliation(s)
- M R Ward
- Division of Cardiovascular Medicine, Stanford University Medical Center, California 94305-5218, USA.
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Ward MR, Jeremias A, Hibi K, Herity NA, Lo ST, Filardo SD, Lee DP, Fitzgerald PJ, Yeung AC. The influence of plaque orientation (pericardial or myocardial) on coronary arterial remodeling. Atherosclerosis 2001; 154:179-83. [PMID: 11137098 DOI: 10.1016/s0021-9150(00)00459-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
BACKGROUND Many systemic, regional and lesion factors have been identified which may influence arterial remodeling, but little is known about the importance of extravascular resistance to vessel enlargement. As myocardial systolic splinting may significantly affect vessel expansion the effect of plaque orientation on arterial remodeling in eccentric coronary atherosclerotic lesions was examined. METHODS Using intravascular ultrasound imaging to obtain cross-sectional vessel area (VA), plaque area (PA) and lumen area (LA), remodeling in eccentric left anterior descending coronary artery lesions was compared which predominantly involved the pericardial or free arc (P, n=25) and the myocardial side (M, n=40) of the vessel wall. Normalized vessel area (NVA, VA(lesion)/VA(reference)) was compared as a continuous and categorical variable (positive>1.05, intermediate 0.95-1.05, negative<0.95) as well as remodeling index (RI, VA(lesion)-VA(reference)/PA(lesion)-PA(reference)). RESULTS The two groups were well matched for clinical and lesion characteristics known to affect remodeling. Reference segments areas were similar in the two groups; while lesion LA was also similar, in the pericardial group there was significantly greater lesion PA (P 12.78+/-0.72, M 10.26+/-0.50 mm(2), P<0.05) and VA (P 15.71+/-0.90, M 12.82+/-0.57 mm(2), P<0.05) demonstrating enhanced compensatory remodeling. Outward remodeling was significantly greater in P than in M by both NVA (P 1.03+/-0.03, M 0.86+/-0.03, P<0.01) and RI (P 0.02+/-0.07, M -1.10+/-0.32, P<0.01). Positive, intermediate and negative remodeling occurred in nine, nine and seven lesions in P and in four, ten and 26 lesions in M (P<0.01). CONCLUSIONS Remodeling compensates more for plaque growth in eccentric coronary lesions which are surrounded by the pericardium than those surrounded by the myocardium. Extravascular resistance appears to influence arterial remodeling.
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Affiliation(s)
- M R Ward
- Division of Cardiovascular Medicine, Stanford University Medical Center, 300 Pasteur Drive, Stanford, CA 94305-5218, USA.
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Herity NA, Lo ST, Oei F, Lee DP, Ward MR, Filardo SD, Hassan A, Suzuki T, Rezaee M, Carter AJ, Yock PG, Yeung AC, Fitzgerald PJ. Selective regional myocardial infiltration by the percutaneous coronary venous route: A novel technique for local drug delivery. Catheter Cardiovasc Interv 2000; 51:358-63. [PMID: 11066126 DOI: 10.1002/1522-726x(200011)51:3<358::aid-ccd27>3.0.co;2-f] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Recent advances in the treatment of heart disease, in particular cardiovascular gene therapy and therapeutic angiogenesis, highlight the need for efficient and practical local delivery methods for the heart. We assessed the feasibility of percutaneous selective coronary venous cannulation and injection as a novel approach to local myocardial drug delivery. In anesthetized swine, the coronary sinus was cannulated percutaneously and a balloon-tipped catheter advanced to the anterior interventricular vein (AIV) or middle cardiac vein (MCV). During balloon occlusion, venous injection of radiographic contrast caused regional infiltration of targeted myocardial regions. Complete AIV occlusion had no impact on LAD flow parameters. Videodensitometric analysis following venous injection showed that radiographic contrast persisted for at least 30 min. Selective regional myocardial infiltration is feasible by this approach, targeting selected myocardial beds, including the apex, anterior wall, septum, and inferoposterior wall. This novel technique has potential application for local myocardial drug or growth factor delivery. Cathet. Cardiovasc. Intervent. 51:358-363, 2000.
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Affiliation(s)
- N A Herity
- Center for Research in Cardiovascular Interventions, Stanford University, California 94305, USA
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Tsui WM, Lam PW, Lee KC, Ma KF, Chan YK, Wong MW, Yip SP, Wong CS, Chow AS, Lo ST. The C282Y mutation of the HFE gene is not found in Chinese haemochromatotic patients: multicentre retrospective study. Hong Kong Med J 2000; 6:153-8. [PMID: 10895137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023] Open
Abstract
OBJECTIVE To detect two novel mutations (C282Y and H63D) of the HFE gene in Chinese patients with hepatic iron overload. DESIGN Multicentre retrospective study. SETTING Four public hospitals, Hong Kong. PARTICIPANTS Fifty Chinese patients who presented from January 1987 through December 1999 with hepatic iron overload from various causes. MAIN OUTCOME MEASURES The DNA from liver biopsy samples was tested for HFE mutations by restriction fragment length polymorphism analysis. RESULTS The sample DNA quality was unsatisfactory for analysis of the C282Y mutation in one case and the H63D mutation in nine cases. The C282Y mutation was not detected in any of the 49 satisfactory samples. Three of the 41 samples were heterozygous for the H63D mutation and only one was homozygous, giving an allele frequency of 6.1%. Of the three H63D-heterozygotes, one had beta-thalassaemia major, one had beta-thalassaemia minor, and one had hereditary spherocytosis. None of the 12 patients who were presumed to have primary haemochromatosis were positive for either mutation. CONCLUSIONS The classical form of human leukocyte antigen-linked hereditary haemochromatosis appears to be absent form this locality. The H63D mutation is found in a minority (9.8%) of the patients, in whom it may act synergistically with an erythropoietic factor.
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Affiliation(s)
- W M Tsui
- Department of Pathology, Caritas Medical Centre, Kowloon, Hong Kong
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Li JY, Lo ST, Ng CS. Molecular detection of Mycobacterium tuberculosis in tissues showing granulomatous inflammation without demonstrable acid-fast bacilli. Diagn Mol Pathol 2000; 9:67-74. [PMID: 10850541 DOI: 10.1097/00019606-200006000-00001] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Early diagnosis of tuberculosis (TB) is important for early medical intervention and prevention of spread of the bacteria. It is not uncommon to observe granulomatous inflammation but without demonstrable acid-fast bacilli (AFB) on Ziehl-Neelsen (ZN) staining in tissues sent for histologic examination, and the definitive diagnosis of TB cannot be made because no concurrent tissue is sent for TB culture. In this study, the authors explored the feasibility of using polymerase chain reaction (PCR) for early detection of Mycobacterium tuberculosis (Mtb) in formalin-fixed, paraffin-embedded tissues where a definite diagnosis of TB cannot be made. One hundred fifteen patients (131 paraffin blocks of biopsy specimens) with granulomatous inflammation but ZN-negative for AFB were studied. DNA was extracted from paraffin sections and amplified by PCR with the IS6110 primers (specific for the Mtb complex) and the specific 122-base pairs (bp) PCR product was detected by agarose gel electrophoresis. Sixty-eight of the 115 (59%) patients were TB-PCR positive, thus enabling definite diagnosis of TB in significant numbers of these patients in 3 days. The authors conclude that molecular diagnosis by PCR is useful for early detection of TB in histologic material where morphologic features are suggestive but not confirmatory because of negative staining for AFB.
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Filardo SD, Schwarzacher SP, Lo ST, Herity NA, Lee DP, Huegel H, Mullen WL, Fitzgerald PJ, Ward MR, Yeung AC. Acute myocardial infarction and vascular remodeling. Am J Cardiol 2000; 85:760-2, A8. [PMID: 12000055 DOI: 10.1016/s0002-9149(99)00856-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We used intravascular ultrasound to show that outward remodeling predominates in lesions responsible for acute myocardial infarction, whereas negative remodeling is far more prevalent in lesions responsible for chronic stable angina. The total cholesterol:high-density lipoprotein ratio was also strongly correlated with outward remodeling.
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Affiliation(s)
- S D Filardo
- Division of Cardiovascular Medicine, Stanford University, California, USA
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Abstract
The CD95 (Fas)/CD95 ligand (CD95L) system is an important mechanism triggering apoptosis, and CD95L expression has recently been implicated for immune evasion and aggressive behavior in malignancies. This study aimed to investigate CD95 and CD95L expression in lymphomas and the possible relationship with tumor cell apoptosis, with emphasis on the natural killer (NK) cell lymphomas, which are highly aggressive neoplasms and frequently exhibit tumor cell apoptosis/necrosis. Frozen sections of 82 cases of lymphomas obtained from Queen Elizabeth Hospital and Caritas Medical Center, Hong Kong, were immunostained with polyclonal anti-CD95 and anti-CD95L antibodies. The NK-cell lymphomas were also studied for apoptosis by in situ end labeling (ISEL) method, and zonal tumor cell death was evaluated semiquantitatively. The cases studied included 27 NK-, 22 T-, and 33 B-cell lymphomas. CD95 was expressed in 25 (93%) NK-, 11 (50%) T-, and 14 (42%) B-cell lymphomas. CD95L was expressed in 19 (70%) NK-, 15 (68%) T-, and 3 (9%) B-cell lymphomas. There was significant difference in the frequency of CD95 expression between B- and NK- (P < .001), and between T- and NK-cell lymphomas (P < .05), and in CD95L expression between B- and T- (P < .01) or NK-cell (P < .01) lymphomas. Zonal tumor cell death was present in 21 (78%) NK-cell lymphomas and 1 (4.5%) T-cell lymphoma and showed no correlation with CD95 or CD95L expression. ISEL analysis showed apoptosis predominantly in the viable areas in only 5 (24%) NK-cell lymphomas. In conclusion, CD95L is frequently expressed in NK- and T-cell lymphomas, but rarely in B-cell lymphomas. Zonal tumor cell death is not correlated with CD95 or CD95L expression and thus the CD95/CD95L system probably does not contribute significantly to this phenomenon. We postulate that the frequent expression of CD95L by NK- and T-cell lymphomas may mediate local or systemic tissue damage and immune evasion, and may contribute to the clinical aggressiveness of these tumors.
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Affiliation(s)
- C S Ng
- Department of Pathology, Caritas Medical Center, Kowloon, Hong Kong
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38
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Abstract
Apoptosis is a regulated form of cell death that may be triggered by natural killer (NK) or cytotoxic T cells, which effect target cell lysis by cytolytic effector and related proteins through complex intracellular signals. This study was aimed to investigate whether there is selective expression of these cytolytic markers in the putative NK-cell lymphomas and whether there is correlation with zonal tumor cell death in these tumors. Expression of the cytolytic effectors perforin, granzyme B9, and the granule membrane protein TIA1 were examined in 24 putative NK-cell lymphomas, 18 postthymic T-cell lymphomas (one case CD8+ CD56+ and three anaplastic large cell lymphomas (ALCL), three T-lymphoblastic lymphomas, and 20 B-cell lymphomas. Nineteen (79%) putative NK-cell lymphomas expressed perforin, and all 24 cases expressed granzyme B9 and TIA1. The only CD8+ CD56+ postthymic T-cell lymphoma also expressed all three cytolytic markers, two CD8- ALCL expressed TIA1; other postthymic T-cell, T-lymphoblastic, and B-cell lymphomas were consistently negative. There was strong correlation between percentage perforin-positive cells and zonal tumor cell death. Angioinvasion, in contrast, was present only in a proportion (37%) of these lymphomas despite the frequent presence of zonal tumor cell death (71%). We propose that cytolytic effector and related proteins produced by putative NK and some CD8+ CD56+ postthymic T-cell lymphomas, probably in conjunction with other mechanisms, may effect massive tumor cell apoptosis. The frequent expression of cytolytic effector markers in the CD2+ surface CD3- CD56+ putative NK-cell lymphomas lends further support to their probable NK cell origin.
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Affiliation(s)
- C S Ng
- Department of Pathology, Caritas Medical Center, Shamshuipo, Kowloon, Hong Kong
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Lai KN, Lai FM, Leung NW, Lo ST, Tam JS. Hepatitis with isolated serum antibody to hepatitis B core antigen. A variant of non-A, non-B hepatitis? Am J Clin Pathol 1990; 93:79-83. [PMID: 2104740 DOI: 10.1093/ajcp/93.1.79] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Antibody to hepatitis B core antigen (anti-HBc) has previously been recognized to be a sensitive marker of hepatitis B virus (HBV) infection. In addition, anti-HBc has recently been suggested to be a surrogate marker for non-A, non-B hepatitis agents in donated blood. The authors studied prospectively the HBV antigen and antibody status in four patients with chronic hepatitis and persistent presence of isolated anti-HBc in their sera. The serologic and histopathologic findings of these four patients were compared with those of three groups of patients having chronic hepatitis with or without HBV markers. A low concentration of serum HBV DNA was detected in only one of the four patients with hepatitis with isolated anti-HBc and in another patient with previous HBV infection. HBV antigens and HBV DNA were not detected in the sera and liver biopsies from the remaining patients with hepatitis with isolated anti-HBc and other patients with hepatitis with or without serologic markers of previous hepatitis A or HBV infection. In contrast, all patients with chronic HBV-associated hepatitis had detectable HBV DNA, hepatitis B surface antigen (HBsAg), and hepatitis B e antigen (HBeAg) in their sera and/or liver biopsies. These findings suggest that chronic hepatitis associated with isolated anti-HBc is a heterogenous pathologic entity. The condition of some of these patients may represent a variant of non-A, non-B hepatitis, whereas the remaining patients are chronic hepatitis B carriers with low serum concentrations of HBV.
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Affiliation(s)
- K N Lai
- Department of Medicine, Chinese University of Hong Kong, Shatin
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Lai KN, Lo ST, Lai FM. Immunohistochemical study of the membrane attack complex of complement and S-protein in idiopathic and secondary membranous nephropathy. Am J Pathol 1989; 135:469-76. [PMID: 2675624 PMCID: PMC1879867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Twenty-eight renal biopsies from 12 patients with idiopathic membranous nephropathy (MN), eight patients with lupus MN, and eight patients with hepatitis B virus-(HBV) related MN were investigated by immunofluorescence for the presence of C5b-C9 neoantigens of the terminal sequence of complement and for S-protein, which is a regulatory component of the membrane attack complex (MAC). Glomerular MAC was detected in 50% of patients with idiopathic MN, in 75% of patients with lupus MN, and in only 12.5% of the HBsAg carrier with MN. Glomerular adhesions to Bowman's capsule were associated with a high incidence of glomerular MAC deposition only in patients with idiopathic MN. Lupus patients had a high incidence of MAC deposition and patients with HBV-related MN had a low incidence of MAC deposition, in both cases regardless of the presence of glomerular capsular adhesions. It is unlikely that deposition of S-protein could inhibit the glomerular damage in idiopathic or lupus MN because significant glomerular capsular adhesions and MAC deposition were observed despite the concomitant glomerular deposition of S-protein. It was concluded that activation of terminal components of complement may play a role in glomerular injuries in idiopathic and lupus MN. The rare occurrence of glomerular MAC deposition in HBV-related MN could be related to its distinct immunopathogenetic mechanism and its indolent clinical course.
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Affiliation(s)
- K N Lai
- Department of Medicine, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin
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Abstract
Monoclonal antibodies (AE1/3, CAM 5.2 and PKK-1) and polyclonal antisera against the cytokeratin proteins were reacted with a range of astrocytic tumours, oligodendrogliomas and ependymomas. Seven of 12 cases (58%) of glioblastoma multiforme, five of eight (63%) anaplastic astrocytomas and two of five (40%) well-differentiated astrocytomas were immunoreactive with AE1/3 but not with the other anti-cytokeratin antibodies. In oligodendrogliomas, AE1/3 stained isolated astrocyte-like cells as well as scattered neoplastic oligodendrocytes in four of eight cases (50%) cases. Four ependymomas were negative for all cytokeratin markers examined. The immunostaining of astrocytomas and oligodendrogliomas with AE1/3 might represent co-expression of cytokeratin with glial fibrillary acidic protein by gliomas and calls for caution in the use of these antibodies in the differential diagnosis between gliomas and carcinomas.
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Affiliation(s)
- H K Ng
- Department of Morbid Anatomy, Chinese University of Hong Kong
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Abstract
Nine cases of microcystic meningiomas, a distinct morphological variant of meningiomas, are reported. They are characterized by a vacuolated and myxomatous histological appearance with multiple cystic spaces lined by stellate-shaped tumour cells. Immunohistochemically, they shared a similar pattern of positive staining for epithelial membrane antigen and vimentin with other meningiomas. Their unusual histological features might lead to problems in differential diagnosis from other intracranial tumours, including schwannomas, chordomas, astrocytomas and angioblastic meningiomas.
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Affiliation(s)
- H K Ng
- Department of Morbid Anatomy, Chinese University of Hong Kong
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Abstract
Among 37 consecutive cases of malignant lymphoma in which the skin was either the only site of disease or one of the prominent sites of initial involvement, 19 cases had a distinctive histological appearance. These cases corresponded to what has been termed "angiocentric lymphoma," and all were found to exhibit a T-cell phenotype either by frozen-section immunohistochemistry or by using monoclonal antibodies reactive in paraffin sections. There were nine men and 10 women; the mean age was 48.2 years. The lesions were nodular and were either ulcerated or had intact skin. One case presented with involvement of one anatomical region of skin, five had involvement of multiple regions of skin, and 13 had concurrent extracutaneous disease. The disease pursued an aggressive course and was not uncommonly resistant to treatment. Histologically, the lymphomatous infiltrate occurred predominantly in the mid to deep dermis with involvement of the subcutaneous layer. The pattern was mainly perivascular and peri-adnexal with or without confluence; the overlying epidermis and papillary dermis were often spared. A prominent feature was invasion of small or large blood vessels by lymphoma cells. Eight cases showed extensive coagulative necrosis of the neoplastic and normal tissues, and 12 cases showed intraneural invasion. The neoplastic lymphoid cells consisted of either a monomorphous population or a variable mixture of small, medium-sized, and large cells with stippled chromatin and distinct nucleoli. Although the nuclei were often irregularly folded, few exhibited a cerebriform configuration. The cytoplasm was pale to clear. These cases exhibit a remarkable histological similarity to the T-cell lymphomas of the nasal/nasopharyngeal region; in addition, there are features that overlap with so-called lymphomatoid granulomatosis of the skin.
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Affiliation(s)
- J K Chan
- Institute of Pathology, Queen Elizabeth Hospital, Kowloon, Hong Kong
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46
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Affiliation(s)
- H K Ng
- Department of Morbid Anatomy, Chinese University of Hong Kong
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47
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Ng CS, Chan JK, Hui PK, Chan WC, Lo ST. Application of a T cell receptor antibody beta F1 for immunophenotypic analysis of malignant lymphomas. Am J Pathol 1988; 132:365-71. [PMID: 2456701 PMCID: PMC1880736] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
One hundred sixty-five non-Hodgkin's lymphomas (101 B, 63 T, one histiocytic) were immunostained with an antibody (beta F1) reactive with a common framework determinant on the beta-subunit of the T cell receptor (TCR). beta F1 stained T lymphomas exclusively, including 53% of peripheral T cell lymphomas but only 33% of T lymphoblastic lymphomas. When expression of beta F1 and CD3 were considered together, 4 types of T lymphoma were delineated: 1) beta F1+CD3+; 2) beta F1+CD3-; 3) beta F1-CD3+, and 4) beta F1-CD3-. The first represented lymphomas with classical T immunophenotype. The second might represent T lymphomas with aberrant loss of CD3 expression. The third might represent T lymphomas with a putative second TCR or cases with an immature phenotype expressing cytoplasmic CD3 only. The fourth type included cases that may be derived from natural killer cells instead of T cells, cases of T lymphoma with aberrant loss of both beta F1 and CD3, and some cases of immature T cell (lymphoblastic) lymphoma. beta F1-CD3- lymphomas exhibited a remarkable predilection for the nasal region. beta F1 is useful in studying T cell lymphomas and distinguishing a novel immunophenotype frequently expressed by nasal lymphomas.
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Affiliation(s)
- C S Ng
- Institute of Pathology, Caritas Medical Center, Kowloon, Hong Kong
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48
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Abstract
Antisera to alpha 1-antichymotrypsin, alpha 1-antitrypsin and lysozyme were reacted with 20 cases of glioblastoma multiforme, seven anaplastic astrocytomas, eight astrocytomas, six oligodendrogliomas, four ependymomas and the cerebral cortex from six normal autopsy brains. In addition, two pleomorphic xantho-astrocytomas and two heavily lipidized malignant gliomas were similarly examined. All astrocytic lesions were confirmed with anti-GFAP antisera. Thirty astrocytic tumours (77%), four oligodendrogliomas (67%) and three ependymomas (75%) reacted positively with anti-alpha 1-antichymotrypsin; 25 astrocytic tumours (64%), three oligodendrogliomas (50%) and three ependymomas (75%) showed positive staining for alpha 1-antitrypsin. The pattern of staining with either of these two markers did not correlate with tumour grading. None of the gliomas examined stained positively with anti-lysozyme. Non-neoplastic glial elements did not react with any of the three antisera. The results of this study suggest that staining for alpha 1-antichymotrypsin and alpha 1-antitrypsin is of little value in the differential diagnosis of neuroepithelial or mesenchymal lesions in the brain.
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Affiliation(s)
- H K Ng
- Department of Morbid Anatomy, Chinese University of Hong Kong
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49
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Abstract
The immunochemical nature of the light chains of the mesangial IgA deposits were studied in 13 IgA nephritic patients with only IgA isotype in their renal biopsies. Direct immunofluorescence (IF) using rabbit and goat antihuman monospecific antibodies demonstrated lambda light chain IF in all 13 biopsies (100%). Kappa light chain IF was detected in ten renal biopsies by the rabbit antihuman antisera and in eight renal biopsies by the goat antihuman antisera. Monoclonal antibodies studies showed lambda IF in all 13 biopsies and kappa IF in eight biopsies. Twelve biopsies showed a predominance of lambda light chain IF staining in the mesangial deposits. Identical IF patterns were observed when double IF technique with rhodamine-conjugated antihuman alpha heavy chain antiserum and fluorescein-conjugated antihuman light chain antisera were employed, and these findings confirmed that the light chains IF arose directly from the IgA deposits. These IgA nephritic patients had a significantly higher serum concentration of lambda light chain-IgA and a distinct alteration of kappa/lambda ratio of IgA compared with healthy controls. Our results support our preliminary observation that mesangial IgA deposits in IgA nephropathy consist mostly of IgA with lambda light chain.
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Affiliation(s)
- K N Lai
- Department of Medicine, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin
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50
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Abstract
Without fresh or frozen tissue, it previously has been impossible to confirm the T-cell nature of reactive or neoplastic lymphoid cells. The availability of antibodies reactive with T cells in paraffin sections now allows retrospective analysis of a large number of cases. Two commercially available monoclonal antibodies, MT1 and MT2, were tested for their reactivities with T cells in a wide range of formalin-fixed, paraffin-embedded tissues, including 130 cases of immunologically characterized lymphoma. In reactive lymph nodes, MT1 stained the T-cell areas, whereas MT2 stained both the T-cell areas and mantle-zone B lymphocytes. MT1 stained 38 of 55 T-cell lymphomas (69.1%; 94.7% of cases from one hospital that used a shorter fixation time, and 55.6% of cases from another hospital that used a longer fixation time). MT2 stained only 6 (10.9%) of the T-cell lymphomas. Among the 74 cases of B-cell lymphoma, 3 (4.0%) were stained by MT1 and 30 (40.5%) by MT2.MT1 was also reactive with 3 of 4 cases of granulocytic sarcoma, as expected from its reactivity with normal granulocytes. Neither MT1 nor MT2 stained Reed-Sternberg cells or their variants in HodgKin's disease. We conclude that MT1 is a valuable marker for T cells, particularly when used with a panel of antibodies reactive with B cells in paraffin sections. MT2 is of limited value because of its cross-reactivity with many B-cell lymphomas.
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Affiliation(s)
- C S Ng
- Department of Morbid Anatomy, Prince of Wales Hospital
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