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Hwang HY, Baek H, Yi GC, Jho YD. Nanoscale mapping of surface strain in tapered nanorods using confocal photoluminescence spectroscopy. Nanotechnology 2022; 33:485703. [PMID: 35998510 DOI: 10.1088/1361-6528/ac8bd9] [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] [Received: 04/14/2022] [Accepted: 08/22/2022] [Indexed: 06/15/2023]
Abstract
The strain occurs spontaneously at the heterogeneous interfaces of virtually all crystalline materials. Consequently, the analysis across multiple interfaces requires a complementary characterization scheme with a resolution that fits the deformation scale. By implementing two-photon confocal laser scanning nanoscopy with an axial resolution of 10 nm, we extract the surface strain from the photoluminescence (PL) spectra, epitomized by a 2-fold enhancement at the tapered tips in comparison to the substrate of ZnO nanorods. We firstly traced the well-established contribution from quantum confinement (QC) to PL shift in three geometrically classified regions: (I) a strongly tapered region where the diameter increases from 3 to 20 nm; (II) a weakly tapered region with a gradually increasing diameter from 20 to 58 nm; (III) round cylindrical region interfacing the sapphire substrate. The measured PL shift influenced by the deformation is significantly stronger than the attained QC effect. Particularly, surface strain at the strongly tapered region turned out to drastically increase the PL shift which matches well with the analysis based on the surface to volume ratio incorporating mechanical parameters such as the compliance tensor component, strain dislocation constant, and surface stress. The surface strain increased at a lower temperature, further disclosing its inherent dependence on the thermal expansion coefficients in clear contrast to the temperature-invariant characteristics of QC.
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Affiliation(s)
- Hyeong-Yong Hwang
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
| | - Hyeonjun Baek
- Department of Physics, Sogang University, Seoul 04107, Republic of Korea
| | - Gyu-Chul Yi
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul 08826, Republic of Korea
| | - Young-Dahl Jho
- School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea
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Baek H, Brotons-Gisbert M, Campbell A, Vitale V, Lischner J, Watanabe K, Taniguchi T, Gerardot BD. Optical read-out of Coulomb staircases in a moiré superlattice via trapped interlayer trions. Nat Nanotechnol 2021; 16:1237-1243. [PMID: 34556832 PMCID: PMC8592839 DOI: 10.1038/s41565-021-00970-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 07/26/2021] [Indexed: 05/21/2023]
Abstract
Moiré patterns with a superlattice potential can be formed by vertically stacking two layered materials with a relative twist or lattice constant mismatch. In transition metal dichalcogenide-based systems, the moiré potential landscape can trap interlayer excitons (IXs) at specific atomic registries. Here, we report that spatially isolated trapped IXs in a molybdenum diselenide/tungsten diselenide heterobilayer device provide a sensitive optical probe of carrier filling in their immediate environment. By mapping the spatial positions of individual trapped IXs, we are able to spectrally track the emitters as the moiré lattice is filled with excess carriers. Upon initial doping of the heterobilayer, neutral trapped IXs form charged IXs (IX trions) uniformly with a binding energy of ~7 meV. Upon further doping, the empty superlattice sites sequentially fill, creating a Coulomb staircase: stepwise changes in the IX trion emission energy due to Coulomb interactions with carriers at nearest-neighbour moiré sites. This non-invasive, highly local technique can complement transport and non-local optical sensing techniques to characterize Coulomb interaction energies, visualize charge correlated states, or probe local disorder in a moiré superlattice.
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Affiliation(s)
- Hyeonjun Baek
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK.
| | - Mauro Brotons-Gisbert
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK
| | - Aidan Campbell
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK
| | - Valerio Vitale
- Departments of Materials and Physics and the Thomas Young Centre for Theory and Simulation of Materials, Imperial College London, London, UK
| | - Johannes Lischner
- Departments of Materials and Physics and the Thomas Young Centre for Theory and Simulation of Materials, Imperial College London, London, UK
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Brian D Gerardot
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK.
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So JP, Kim HR, Baek H, Jeong KY, Lee HC, Huh W, Kim YS, Watanabe K, Taniguchi T, Kim J, Lee CH, Park HG. Electrically driven strain-induced deterministic single-photon emitters in a van der Waals heterostructure. Sci Adv 2021; 7:eabj3176. [PMID: 34669464 PMCID: PMC8528413 DOI: 10.1126/sciadv.abj3176] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Quantum confinement in transition metal dichalcogenides (TMDCs) enables the realization of deterministic single-photon emitters. The position and polarization control of single photons have been achieved via local strain engineering using nanostructures. However, most existing TMDC-based emitters are operated by optical pumping, while the emission sites in electrically pumped emitters are uncontrolled. Here, we demonstrate electrically driven single-photon emitters located at the positions where strains are induced by atomic force microscope indentation on a van der Waals heterostructure consisting of graphene, hexagonal boron nitride, and tungsten diselenide. The optical, electrical, and mechanical properties induced by the local strain gradient were systematically analyzed. The emission at the indentation sites exhibits photon antibunching behavior with a g(2)(0) value of ~0.3, intensity saturation, and a linearly cross-polarized doublet, at 4 kelvin. This robust spatial control of electrically driven single-photon emitters will pave the way for the practical implementation of integrated quantum light sources.
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Affiliation(s)
- Jae-Pil So
- Department of Physics, Korea University, Seoul 02841, Republic of Korea
| | - Ha-Reem Kim
- Department of Physics, Korea University, Seoul 02841, Republic of Korea
| | - Hyeonjun Baek
- Department of Physics, Korea University, Seoul 02841, Republic of Korea
- Center for Quantum Information, Korea Institute of Science and Technology, Seoul 02841, Republic of Korea
| | - Kwang-Yong Jeong
- Department of Physics, Korea University, Seoul 02841, Republic of Korea
| | - Hoo-Cheol Lee
- Department of Physics, Korea University, Seoul 02841, Republic of Korea
| | - Woong Huh
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Republic of Korea
| | - Yoon Seok Kim
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Republic of Korea
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Jungkil Kim
- Department of Physics, Jeju National University, Jeju 63243, Republic of Korea
| | - Chul-Ho Lee
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Republic of Korea
| | - Hong-Gyu Park
- Department of Physics, Korea University, Seoul 02841, Republic of Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Republic of Korea
- Corresponding author.
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Baek H, Brotons-Gisbert M, Koong ZX, Campbell A, Rambach M, Watanabe K, Taniguchi T, Gerardot BD. Highly energy-tunable quantum light from moiré-trapped excitons. Sci Adv 2020; 6:6/37/eaba8526. [PMID: 32917702 PMCID: PMC7486092 DOI: 10.1126/sciadv.aba8526] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 07/24/2020] [Indexed: 05/20/2023]
Abstract
Photon antibunching, a hallmark of quantum light, has been observed in the correlations of light from isolated atomic and atomic-like solid-state systems. Two-dimensional semiconductor heterostructures offer a unique method to create a quantum light source: Moiré trapping potentials for excitons are predicted to create arrays of quantum emitters. While signatures of moiré-trapped excitons have been observed, their quantum nature has yet to be confirmed. Here, we report photon antibunching from single moiré-trapped interlayer excitons in a heterobilayer. Via magneto-optical spectroscopy, we demonstrate that the discrete anharmonic spectra arise from bound band-edge electron-hole pairs trapped in moiré potentials. Last, we exploit the large permanent dipole of interlayer excitons to achieve large direct current (DC) Stark tuning up to 40 meV. Our results confirm the quantum nature of moiré-confined excitons and open opportunities to investigate their inhomogeneity and interactions between the emitters or energetically tune single emitters into resonance with cavity modes.
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Affiliation(s)
- H Baek
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS, UK.
| | - M Brotons-Gisbert
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS, UK
| | - Z X Koong
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS, UK
| | - A Campbell
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS, UK
| | - M Rambach
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS, UK
| | - K Watanabe
- National Institute for Materials Science, Tsukuba, Japan
| | - T Taniguchi
- National Institute for Materials Science, Tsukuba, Japan
| | - B D Gerardot
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS, UK.
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Brotons-Gisbert M, Baek H, Molina-Sánchez A, Campbell A, Scerri E, White D, Watanabe K, Taniguchi T, Bonato C, Gerardot BD. Spin-layer locking of interlayer excitons trapped in moiré potentials. Nat Mater 2020; 19:630-636. [PMID: 32451512 DOI: 10.1038/s41563-020-0687-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Accepted: 04/17/2020] [Indexed: 05/20/2023]
Abstract
Van der Waals heterostructures offer attractive opportunities to design quantum materials. For instance, transition metal dichalcogenides (TMDs) possess three quantum degrees of freedom: spin, valley index and layer index. Furthermore, twisted TMD heterobilayers can form moiré patterns that modulate the electronic band structure according to the atomic registry, leading to spatial confinement of interlayer excitons (IXs). Here we report the observation of spin-layer locking of IXs trapped in moiré potentials formed in a heterostructure of bilayer 2H-MoSe2 and monolayer WSe2. The phenomenon of locked electron spin and layer index leads to two quantum-confined IX species with distinct spin-layer-valley configurations. Furthermore, we observe that the atomic registries of the moiré trapping sites in the three layers are intrinsically locked together due to the 2H-type stacking characteristic of bilayer TMDs. These results identify the layer index as a useful degree of freedom to engineer tunable few-level quantum systems in two-dimensional heterostructures.
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Affiliation(s)
- Mauro Brotons-Gisbert
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK.
| | - Hyeonjun Baek
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK.
| | - Alejandro Molina-Sánchez
- Institute of Materials Science (ICMUV), University of Valencia, Valencia, Spain
- International Iberian Nanotechnology Laboratory (INL), Braga, Portugal
| | - Aidan Campbell
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK
| | - Eleanor Scerri
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK
| | - Daniel White
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK
| | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Japan
| | | | - Cristian Bonato
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK
| | - Brian D Gerardot
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK.
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Lee E, Park N, Ahn Y, Jung W, Bae I, Yoo J, Baek H, Park W. 951 The wound healing effect of a novel synthetic retinoid, seletinoid G, on cultured keratinocytes and human skin equivalents. J Invest Dermatol 2019. [DOI: 10.1016/j.jid.2019.03.1027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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7
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Baek H, Sariev A, Dong S, Royer S, Kim H. Cerebellar low-intensity focused ultrasound stimulation can normalize asymmetrical hemispheric delta power after mouse ischemic stroke. Brain Stimul 2019. [DOI: 10.1016/j.brs.2018.12.591] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Kim JK, Yoon JO, Baek H. Corticocancellous bone graft vs cancellous bone graft for the management of unstable scaphoid nonunion. Orthop Traumatol Surg Res 2018; 104:115-120. [PMID: 29258960 DOI: 10.1016/j.otsr.2017.11.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 10/31/2017] [Accepted: 11/07/2017] [Indexed: 02/02/2023]
Abstract
INTRODUCTION This study was undertaken to determine whether corticocancellous bone grafting and cancellous bone grafting differ in terms of bone union rate, restoration of scaphoid anatomy, and wrist function when unstable scaphoid nonunions are concomitantly treated by screw fixation. MATERIALS AND METHODS This is retrospective cohort study. In Group A (17 patients), unstable scaphoid nonunion was treated with corticocancellous graft harvested from the iliac crest and headless compression screw using volar approach. In Group B (18 patients), unstable scaphoid nonunion was treated with cancellous graft harvested from the distal radius or iliac crest and headless compression screw using volar approach Mean time to union was measured using CT image. Scaphoid deformity was also measured using lateral intrascaphoid angle and height to length ratio using CT images. Wrist functional status was assessed by measuring grip strength, wrist range of motion, and DASH score at 1 year postoperatively. RESULTS Mean time to union was significantly greater in Group A (15 weeks vs. 11 weeks). No significant intergroup difference was observed for lateral intrascaphoid angle and height to length ratio after treatment of scaphoid nonunion. No significant intergroup difference was observed for grip strength, wrist range of motion, or DASH scores at 1 year postoperatively. CONCLUSIONS Cancellous bone grafting was found to lead to earlier bone union than corticocancellous bone grafting and to similar restorations of scaphoid deformity and wrist function when scaphoid nonunion was treated by headless compression screw fixation and bone grafting. LEVEL OF EVIDENCE Prognostic, III.
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Affiliation(s)
- J K Kim
- Department of Orthopedic Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea.
| | - J O Yoon
- Department of Orthopedic Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea
| | - H Baek
- Department of Orthopedic Surgery, Ewha Womans Universtiy Mokdong Hospital, Seoul, South Korea
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Jung J, Kang E, Gwak JM, Seo AN, Park SY, Lee AS, Baek H, Chae S, Kim EK, Kim SW. Association between basal-like phenotype and BRCA1/2 germline mutations in Korean breast cancer patients. ACTA ACUST UNITED AC 2016; 23:298-303. [PMID: 27803593 DOI: 10.3747/co.23.3054] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
INTRODUCTION BRCA mutation testing allows index patients and their families to be provided with appropriate cancer risk-reduction strategies. Because of the low prevalence of BRCA mutations in unselected breast cancer patients and the high cost of genetic testing, it is important to identify the subset of women who are likely to carry BRCA mutations. In the present study, we examined the association between BRCA1/2 germline mutations and the immunohistochemical features of breast cancer. METHODS In a retrospective review of 498 breast cancer patients who had undergone BRCA testing at Seoul National University Bundang Hospital between July 2003 and September 2012, we gathered immunohistochemical information on estrogen receptor (er), progesterone receptor (pr), her2 (human epidermal growth factor receptor 2), cytokeratin 5/6, egfr (epidermal growth factor receptor), and p53 status. RESULTS Among the 411 patients eligible for the study, 50 (12.2%) had germline mutations in BRCA1 or BRCA2. Of the 93 patients with triple-negative breast cancer (tnbc), 25 with BRCA1/2 mutations were identified (BRCA1, 20.4%; BRCA2, 6.5%). On univariate analysis, er, pr, cytokeratin 5/6, egfr, and tnbc were found to be related to BRCA1 mutations, but on multivariate analysis, only tnbc was significantly associated with BRCA1 mutations. Among patients with early-onset breast cancer or with a family history of breast or ovarian cancer, BRCA1 mutations were significantly more prevalent in the tnbc group than in the non-tnbc group. CONCLUSIONS In the present study, tnbc was the only independent predictor of BRCA1 mutation in patients at high risk of hereditary breast and ovarian cancers. Other histologic features of basal-like breast cancer did not improve the estimate of BRCA1 mutation risk.
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Affiliation(s)
- J Jung
- Department of Surgery, Eulji University Hospital, Daejeon
| | - E Kang
- Department of Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam
| | - J M Gwak
- Department of Pathology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam
| | - A N Seo
- Department of Pathology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam
| | - S Y Park
- Department of Pathology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam
| | - A S Lee
- Department of Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam
| | - H Baek
- Department of Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam
| | - S Chae
- Department of Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam
| | - E K Kim
- Department of Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam
| | - S W Kim
- Department of Surgery, Daerim St. Mary's Hospital, Seoul, Republic of Korea
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Chung K, Yoo H, Hyun JK, Oh H, Tchoe Y, Lee K, Baek H, Kim M, Yi GC. Flexible GaN Light-Emitting Diodes Using GaN Microdisks Epitaxial Laterally Overgrown on Graphene Dots. Adv Mater 2016; 28:7688-7694. [PMID: 27346527 DOI: 10.1002/adma.201601894] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 05/25/2016] [Indexed: 06/06/2023]
Abstract
The epitaxial lateral overgrowth (ELOG) of GaN microdisks on graphene microdots and the fabrication of flexible light-emitting diodes (LEDs) using these microdisks is reported. An ELOG technique with only patterned graphene microdots is used, without any growth mask. The discrete micro-LED arrays are transferred onto Cu foil by a simple lift-off technique, which works reliably under various bending conditions.
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Affiliation(s)
- Kunook Chung
- Department of Physics and Astronomy, Institute of Applied Physics, and Research Institute of Advanced Materials, Seoul National University, Seoul, 151-747, Korea
| | - Hyobin Yoo
- Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul, 151-744, Korea
| | - Jerome K Hyun
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul, 120-750, Korea
| | - Hongseok Oh
- Department of Physics and Astronomy, Institute of Applied Physics, and Research Institute of Advanced Materials, Seoul National University, Seoul, 151-747, Korea
| | - Youngbin Tchoe
- Department of Physics and Astronomy, Institute of Applied Physics, and Research Institute of Advanced Materials, Seoul National University, Seoul, 151-747, Korea
| | - Keundong Lee
- Department of Physics and Astronomy, Institute of Applied Physics, and Research Institute of Advanced Materials, Seoul National University, Seoul, 151-747, Korea
| | - Hyeonjun Baek
- Department of Physics and Astronomy, Institute of Applied Physics, and Research Institute of Advanced Materials, Seoul National University, Seoul, 151-747, Korea
| | - Miyoung Kim
- Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul, 151-744, Korea
| | - Gyu-Chul Yi
- Department of Physics and Astronomy, Institute of Applied Physics, and Research Institute of Advanced Materials, Seoul National University, Seoul, 151-747, Korea.
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Chun Y, Kwon Y, Shin S, Ye D, Baek H. Activation of uPA-uPAR signaling pathway by human CYP1B1 promotes cancer progression and metastasis in human breast cancer cells. Toxicol Lett 2016. [DOI: 10.1016/j.toxlet.2016.06.1412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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12
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Lee K, Tchoe Y, Yoon H, Baek H, Chung K, Lee S, Yoon C, Park BH, Yi GC. Real-time device-scale imaging of conducting filament dynamics in resistive switching materials. Sci Rep 2016; 6:27451. [PMID: 27271792 PMCID: PMC4895219 DOI: 10.1038/srep27451] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [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: 02/15/2016] [Accepted: 05/05/2016] [Indexed: 11/25/2022] Open
Abstract
ReRAM is a compelling candidate for next-generation non-volatile memory owing to its various advantages. However, fluctuation of operation parameters are critical weakness occurring failures in 'reading' and 'writing' operations. To enhance the stability, it is important to understand the mechanism of the devices. Although numerous studies have been conducted using AFM or TEM, the understanding of the device operation is still limited due to the destructive nature and/or limited imaging range of the previous methods. Here, we propose a new hybrid device composed of ReRAM and LED enabling us to monitor the conducting filament (CF) configuration on the device scale during resistive switching. We directly observe the change in CF configuration across the whole device area through light emission from our hybrid device. In contrast to former studies, we found that minor CFs were formed earlier than major CF contributing to the resistive switching. Moreover, we investigated the substitution of a stressed major CF with a fresh minor CF when large fluctuation of operation voltage appeared after more than 50 times of resistive switching in atmospheric condition. Our results present an advancement in the understanding of ReRAM operation mechanism, and a step toward stabilizing the fluctuations in ReRAM switching parameters.
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Affiliation(s)
- Keundong Lee
- Department of Physics and Astronomy, Institute of Applied Physics and Research Institute of Advanced Materials (RIAM), Seoul National University, Seoul 151-747, Korea
| | - Youngbin Tchoe
- Department of Physics and Astronomy, Institute of Applied Physics and Research Institute of Advanced Materials (RIAM), Seoul National University, Seoul 151-747, Korea
| | - Hosang Yoon
- Department of Physics and Astronomy, Institute of Applied Physics and Research Institute of Advanced Materials (RIAM), Seoul National University, Seoul 151-747, Korea
| | - Hyeonjun Baek
- Department of Physics and Astronomy, Institute of Applied Physics and Research Institute of Advanced Materials (RIAM), Seoul National University, Seoul 151-747, Korea
| | - Kunook Chung
- Department of Physics and Astronomy, Institute of Applied Physics and Research Institute of Advanced Materials (RIAM), Seoul National University, Seoul 151-747, Korea
| | - Sangik Lee
- Department of Physics, Konkuk University, Seoul, 143-701, Korea
| | - Chansoo Yoon
- Department of Physics, Konkuk University, Seoul, 143-701, Korea
| | - Bae Ho Park
- Department of Physics, Konkuk University, Seoul, 143-701, Korea
| | - Gyu-Chul Yi
- Department of Physics and Astronomy, Institute of Applied Physics and Research Institute of Advanced Materials (RIAM), Seoul National University, Seoul 151-747, Korea
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Abstract
We report the fabrication and characteristics of vertical microtube light-emitting diode (LED) arrays with a metal core inside the devices. To make the LEDs, gallium nitride (GaN)/indium gallium nitride (In(x)Ga(1-x)N)/zinc oxide (ZnO) coaxial microtube LED arrays were grown on an n-GaN/c-aluminum oxide (Al2O3) substrate. The microtube LED arrays were then lifted-off the substrate by wet chemical etching of the sacrificial ZnO microtubes and the silicon dioxide (SiO2) layer. The chemically lifted-off LED layer was then transferred upside-down on other supporting substrates. To create the metal cores, titanium/gold and indium tin oxide were deposited on the inner shells of the microtubes, forming n-type electrodes inside the metal-cored LEDs. The characteristics of the resulting devices were determined by measuring electroluminescence and current-voltage characteristic curves. To gain insights into the current-spreading characteristics of the devices and understand how to make them more efficient, we modeled them computationally.
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Affiliation(s)
- Youngbin Tchoe
- Department of Physics and Astronomy, Institute of Applied Physics, and Research Institute of Advanced Materials, Seoul National University , Seoul 151-747, Korea
| | - Chul-Ho Lee
- KU-KIST Graduate School of Converging Science and Technology, Korea University , Seoul 136-701, Korea
| | - Jun Beom Park
- Department of Physics and Astronomy, Institute of Applied Physics, and Research Institute of Advanced Materials, Seoul National University , Seoul 151-747, Korea
| | - Hyeonjun Baek
- Department of Physics and Astronomy, Institute of Applied Physics, and Research Institute of Advanced Materials, Seoul National University , Seoul 151-747, Korea
| | - Kunook Chung
- Department of Physics and Astronomy, Institute of Applied Physics, and Research Institute of Advanced Materials, Seoul National University , Seoul 151-747, Korea
| | - Janghyun Jo
- Department of Material Science and Engineering and Research Institute of Advanced Materials, Seoul National University , Seoul 151-744, Korea
| | - Miyoung Kim
- Department of Material Science and Engineering and Research Institute of Advanced Materials, Seoul National University , Seoul 151-744, Korea
| | - Gyu-Chul Yi
- Department of Physics and Astronomy, Institute of Applied Physics, and Research Institute of Advanced Materials, Seoul National University , Seoul 151-747, Korea
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Lee A, Kang E, Baek H, Chae S, Kim EK, Kim S. 54O Evaluation of BRCA1/2 mutation prevalence in Korean women with triple-negative breast cancer. Ann Oncol 2015. [DOI: 10.1093/annonc/mdv519.03] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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15
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Baek H, Kim EK, Lee A, Chae S, Kang E, Kim SW. 91P A survey of margin status evaluation in the Korean Breast Cancer Society member. Ann Oncol 2015. [DOI: 10.1093/annonc/mdv519.40] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Abstract
Visible-light filters constructed from nanostructured materials typically consist of a metallic grating and rely on the excitation of surface plasmon polaritons (SPPs). In order to operate at full efficiency, the number of grating elements needs to be maximized such that light can couple more efficiently to the SPPs through improved diffraction. Such conditions impose a limitation on the compactness of the filter since a larger number of grating elements represents a larger effective size. For emerging applications involving nanoscale transmitters or receivers, a device that can filter localized excitations is highly anticipated but is challenging to realize through grating-type filters. In this work, we present the design of an optical filter operating with a single element, marking a departure from diffractive plasmonic coupling. Our device consists of a ZnO nanorod enclosed by two layers of Ag film. For diffraction-limited light focused on the nanorod, narrow passbands can be realized and tuned via variation of the nanorod diameter across the visible spectrum. The spectral and spatial filtering originates from scattering cancellation localized at the nanorod due to the cavity and nanorod exhibiting opposite effective dipole moments. This ability to realize high-performance optical filtering at the ultimate size introduces intriguing possibilities for nanoscale near-field communication or ultrahigh resolution imaging pixels.
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Affiliation(s)
- Jerome K Hyun
- Department of Chemistry and Nano Science, Ewha Womans University , Seoul 120-750, Korea
| | - Taehee Kang
- Department of Physics and Astronomy, Seoul National University , Seoul 151-742, Korea
| | - Hyeonjun Baek
- Department of Physics and Astronomy, Seoul National University , Seoul 151-742, Korea
| | - Dai-sik Kim
- Department of Physics and Astronomy, Seoul National University , Seoul 151-742, Korea
| | - Gyu-chul Yi
- Department of Physics and Astronomy, Seoul National University , Seoul 151-742, Korea
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17
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Tang Y, Choi J, Kim D, Tudtud-Hans L, Li J, Michel A, Baek H, Hurlow A, Wang C, Nguyen HB. Clinical predictors of adverse outcome in severe sepsis patients with lactate 2-4 mM admitted to the hospital. QJM 2015; 108:279-87. [PMID: 25193540 DOI: 10.1093/qjmed/hcu186] [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] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Severe sepsis patients with initial lactate level 2-4 mM are commonly considered to have lower risk for mortality and adverse outcomes. AIM We aim to determine clinical variables that are associated with adverse outcome in these patients. DESIGN A retrospective cohort study. METHODS Severe sepsis patients with initial lactate ≥ 2 and < 4 mM admitted to our hospital were examined for any of the following primary outcomes: (i) in-hospital death, (ii) vasopressor requirement, (iii) use of mechanical ventilator, (iv) lactate ≥ 4.0 mM or (v) need care in the intensive care unit (ICU) within 48 h. RESULTS Five-hundred and thirty-five patients were enrolled, age 58.7 ± 19.3 years, 53.2% male. The most common sources of infection were urinary tract infection and pneumonia, 38.3 and 35.7%, respectively. One-hundred and twenty-four (23.2%) patients had at least one primary adverse outcome within 48 h, including in-hospital death 1.1%, vasopressor requirement 12.9%, use of mechanical ventilator 13.3%, increase lactate ≥ 4.0 mM in 5.6% patients and 21.5% of patients requiring ICU (including 13.8% of the patients admitted directly to ICU from the emergency department, and 7.7% initially admitted to the general medical ward but later required ICU transfer). Altered mentation, hypotension, tachypnea and elevated blood urea nitrogen at admission were associated with the primary outcome in multivariable logistic regression analysis, odds ratio 2.50 (95% confidence interval: 1.54, 4.06), 3.76 (2.31, 6.10), 1.97 (1.22, 3.17) and 1.78 (1.11, 2.83), respectively. CONCLUSIONS Our study suggests that clinicians should be cautious about the potential adverse outcomes in severe sepsis patients with initial lactate level between 2 and 4 mM and a presentation of altered mentation, hypotension, tachypnea and/or elevated blood urea nitrogen.
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Affiliation(s)
- Y Tang
- From the Department of Medicine, Hospitalist Medicine, School of Medicine, Department of Emergency Medicine and Department of Medicine, Critical Care, Loma Linda University, Loma Linda, CA, USA
| | - J Choi
- From the Department of Medicine, Hospitalist Medicine, School of Medicine, Department of Emergency Medicine and Department of Medicine, Critical Care, Loma Linda University, Loma Linda, CA, USA
| | - D Kim
- From the Department of Medicine, Hospitalist Medicine, School of Medicine, Department of Emergency Medicine and Department of Medicine, Critical Care, Loma Linda University, Loma Linda, CA, USA
| | - L Tudtud-Hans
- From the Department of Medicine, Hospitalist Medicine, School of Medicine, Department of Emergency Medicine and Department of Medicine, Critical Care, Loma Linda University, Loma Linda, CA, USA
| | - J Li
- From the Department of Medicine, Hospitalist Medicine, School of Medicine, Department of Emergency Medicine and Department of Medicine, Critical Care, Loma Linda University, Loma Linda, CA, USA
| | - A Michel
- From the Department of Medicine, Hospitalist Medicine, School of Medicine, Department of Emergency Medicine and Department of Medicine, Critical Care, Loma Linda University, Loma Linda, CA, USA
| | - H Baek
- From the Department of Medicine, Hospitalist Medicine, School of Medicine, Department of Emergency Medicine and Department of Medicine, Critical Care, Loma Linda University, Loma Linda, CA, USA
| | - A Hurlow
- From the Department of Medicine, Hospitalist Medicine, School of Medicine, Department of Emergency Medicine and Department of Medicine, Critical Care, Loma Linda University, Loma Linda, CA, USA
| | - C Wang
- From the Department of Medicine, Hospitalist Medicine, School of Medicine, Department of Emergency Medicine and Department of Medicine, Critical Care, Loma Linda University, Loma Linda, CA, USA
| | - H B Nguyen
- From the Department of Medicine, Hospitalist Medicine, School of Medicine, Department of Emergency Medicine and Department of Medicine, Critical Care, Loma Linda University, Loma Linda, CA, USA From the Department of Medicine, Hospitalist Medicine, School of Medicine, Department of Emergency Medicine and Department of Medicine, Critical Care, Loma Linda University, Loma Linda, CA, USA
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18
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Kim S, Baek H, Lee J, Lee D, Lee S, Choe B. SU-E-J-71: Feasibility Study On MRI-Based BANG3 Gel Dosimetry Using Dual-Source Parallel RF Transmission System. Med Phys 2014. [DOI: 10.1118/1.4888123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Abstract
Direct epitaxial growth of inorganic compound semiconductors on lattice-matched single-crystal substrates has provided an important way to fabricate light sources for various applications including lighting, displays and optical communications. Nevertheless, unconventional substrates such as silicon, amorphous glass, plastics, and metals must be used for emerging optoelectronic applications, such as high-speed photonic circuitry and flexible displays. However, high-quality film growth requires good matching of lattice constants and thermal expansion coefficients between the film and the supporting substrate. This restricts monolithic fabrication of optoelectronic devices on unconventional substrates. Here, we describe methods to grow high-quality gallium nitride (GaN) microdisks on amorphous silicon oxide layers formed on silicon using micropatterned graphene films as a nucleation layer. Highly crystalline GaN microdisks having hexagonal facets were grown on graphene dots with intermediate ZnO nanowalls via epitaxial lateral overgrowth. Furthermore, whispering-gallery-mode lasing from the GaN microdisk with a Q-factor of 1200 was observed at room temperature.
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Affiliation(s)
- Hyeonjun Baek
- National Creative Research Initiative Center for Semiconductor Nanostructures and Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
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20
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Kim YJ, Yoo H, Lee CH, Park JB, Baek H, Kim M, Yi GC. Position- and morphology-controlled ZnO nanostructures grown on graphene layers. Adv Mater 2012; 24:5565-5564. [PMID: 22887784 DOI: 10.1002/adma.201201966] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Indexed: 05/28/2023]
Affiliation(s)
- Yong-Jin Kim
- National Creative Research Initiative, Center for Semiconductor Nanorods, Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
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21
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Baek H, Oh J, Lee H. Relationship Between Leptin, Bronchial Hyperresponsiveness To Mannitol And Urinary Leukotriene E4/exhaled Nitric Oxide Ratio In Asthmatic Children. J Allergy Clin Immunol 2012. [DOI: 10.1016/j.jaci.2011.12.849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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22
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Baek H, Koh J, Kim C, Yang S. 1121 POSTER The Prevalence of Histone Deacetylase (HDAC) Expression in Korean Non-small Cell Carcinoma Patients. Eur J Cancer 2011. [DOI: 10.1016/s0959-8049(11)70764-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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23
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Baek H. The Pathobiologic Effect of Montelukast and Inhaled Budesonide on Exercise-induced Bronchoconstriction in Children. J Allergy Clin Immunol 2011. [DOI: 10.1016/j.jaci.2010.12.339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Baek H, Jayaraman MV, Richardson PD, Karniadakis GE. Flow instability and wall shear stress variation in intracranial aneurysms. J R Soc Interface 2009; 7:967-88. [PMID: 20022896 DOI: 10.1098/rsif.2009.0476] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We investigate the flow dynamics and oscillatory behaviour of wall shear stress (WSS) vectors in intracranial aneurysms using high resolution numerical simulations. We analyse three representative patient-specific internal carotid arteries laden with aneurysms of different characteristics: (i) a wide-necked saccular aneurysm, (ii) a narrower-necked saccular aneurysm, and (iii) a case with two adjacent saccular aneurysms. Our simulations show that the pulsatile flow in aneurysms can be subject to a hydrodynamic instability during the decelerating systolic phase resulting in a high-frequency oscillation in the range of 20-50 Hz, even when the blood flow rate in the parent vessel is as low as 150 and 250 ml min(-1) for cases (iii) and (i), respectively. The flow returns to its original laminar pulsatile state near the end of diastole. When the aneurysmal flow becomes unstable, both the magnitude and the directions of WSS vectors fluctuate at the aforementioned high frequencies. In particular, the WSS vectors around the flow impingement region exhibit significant spatio-temporal changes in direction as well as in magnitude.
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Affiliation(s)
- H Baek
- Division of Applied Mathematics, Brown University, Providence, RI 02912, USA
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25
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Park Y, Kim S, Ok O, Baek H, Lee J, Nam S, Yang J, Cho E, Ahn J, Im Y. Risk stratification by hormonal receptor (ER, PgR) and HER2 status in small (≤1cm) invasive breast cancer: Who might be a possible candidate for adjuvant treatment? J Clin Oncol 2009. [DOI: 10.1200/jco.2009.27.15_suppl.564] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
564 Background: With the increasing use of screening mammography, the proportion of ≤ 1 cm invasive breast cancer is increasing. Identification of breast cancer molecular subtypes has resulted in a better appreciation of the biologic heterogeneity, which is not fully explained by clinicopathologic features including staging system. The aims of this study were: 1) to identify the risk factors of systemic metastases in patients with ≤ 1 cm invasive breast cancer and 2) to investigate the patients group at greatest risk of such failure even in these small tumors. Method: Data were collected retrospectively in the breast cancer registry of our institution for patients with invasive breast cancer from October 1994 to December 2004. Results: Of 4,036 patients who received curative breast cancer surgery, 466 patients who had T1a or T1b breast cancer were identified. 39 patients who received neoadjuvant chemotherapy were excluded in this study. Ipsilateral axillary lymph node involvement was found in 13% (57/427) at the time of surgery. Axillary lymph node involvement was much more common in HER-2 positive group (33% vs 11%, p < 0.0001) and triple negative (TN) group (24% vs 11%, p = 0.002) than in hormone receptor positive group. During median 61 months of follow-up, overall 10 year estimated distant relapse-free survival (DRFS) and overall survival (OS) were 95% and 92%, respectively. Multivariate analysis was conducted in 370 (T1aN0, T1bN0) patients, who had no lymph node involvement. In Cox-regression model, HER-2 positivity and triple negativity were identified as independent prognostic factors to predict DRFS [Hazard ratio (HR) 8.8, p = 0.003 for HER-2 positive group; HR 5.1, p = 0.026 for TN group] and OS (HR 5.0, p = 0.067 for HER-2 positive group; HR 11.1, p = 0.017 for TN group) in T1bN0 tumors. Limiting to T1aN0 tumors, statistical significance was not maintained. Conclusions: Even though T1aN0 and T1bN0 tumors have been known to have a relative low risk of systemic failure, anti-HER-2 directed therapy for HER-2 positive group and new innovative adjuvant systemic treatment for TN group in patients with T1bN0 tumor should be considered. Prospective adjuvant trials should be warranted in these subgroups of patients. No significant financial relationships to disclose.
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Affiliation(s)
- Y. Park
- Samsung Medical Center, Seoul, Republic of Korea
| | - S. Kim
- Samsung Medical Center, Seoul, Republic of Korea
| | - O. Ok
- Samsung Medical Center, Seoul, Republic of Korea
| | - H. Baek
- Samsung Medical Center, Seoul, Republic of Korea
| | - J. Lee
- Samsung Medical Center, Seoul, Republic of Korea
| | - S. Nam
- Samsung Medical Center, Seoul, Republic of Korea
| | - J. Yang
- Samsung Medical Center, Seoul, Republic of Korea
| | - E. Cho
- Samsung Medical Center, Seoul, Republic of Korea
| | - J. Ahn
- Samsung Medical Center, Seoul, Republic of Korea
| | - Y. Im
- Samsung Medical Center, Seoul, Republic of Korea
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26
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Na I, Lee T, Choe D, Kang H, Koh J, Park J, Baek H, Kim C, Ryoo B, Lee J, Yang S. Factors predicting silent brain metastases in patients with non-small-cell lung cancer. J Clin Oncol 2008. [DOI: 10.1200/jco.2008.26.15_suppl.19131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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27
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Choe D, Lee J, Baek H, Park J. P-355 Volume-expanding complications after pneumonectomy:Differential diagnosis with CT. Lung Cancer 2005. [DOI: 10.1016/s0169-5002(05)80849-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Abstract
A new class of water-soluble cyclotriphosphazene-(diamine)platinum(II) conjugate drugs [NP(Am-Li2)(Am.PtA2)]3 (Am: dicarboxylic amino acid; A2: diamine) has been synthesized and characterized by means of elemental analysis, multinuclear (1H, 31P, 13C, 195Pt) NMR and IR spectroscopies. All the title compounds were subjected to both in vitro and in vivo assays against the murine leukemia L1210 cell line and selected human tumor cells. Most of the title compounds have shown higher in vivo antitumor activity than cisplatin and carboplatin, and, in particular, [NP(L-Glu-Li2)(L-Glu.Pt(-dach)]3 (Glu=glutamate, dach=trans(+/-)-1,2-diaminocyclohexane) showed extraordinary high activity (ILS>500%) equally against both parent and cisplatin-resistant leukemia L1210 cell lines. Furthermore, this candidate compound (KI 60606) exhibited a wider spectrum of in vitro activity by showing higher cytotoxicity against all the selected human tumor cells than cisplatin and, therefore, was subjected to preclinical studies which are now near completion.
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Affiliation(s)
- H Baek
- Inorganic Chemistry Laboratory, Korea Institute of Science and Technology, Seoul, South Korea
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29
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Fostier A, Baek H. Inhibition of production of maturation inducing steroid in rainbow trout granulosa cells: effect of oestradiol on gonadotropin stimulated 20 β-hydroxysteroid dehydrogenase activity. ACTA ACUST UNITED AC 1993. [DOI: 10.1051/rnd:19930111] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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