Publications (14)8.83 Total impact
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Article: Antiferromagnetic ground state of a C(60)-covered Si(001) surface.
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ABSTRACT: Modeling magnetism: The antiferromagnetic ground state of the C(60)/Si(001)-c(4x4) surface is predicted by means of density functional theory calculations. Two adjacent dangling bonds (DBs) generated by the adsorption of C(60) are antiferromagnetically coupled with each other. This study demonstrates that magnetic Si surfaces can be prepared by engineering single Si DBs with unpaired electrons.ChemPhysChem 01/2009; 10(2):334-6. · 3.41 Impact Factor -
Article: Nox 2 stimulates muscle differentiation via NF-kappaB/iNOS pathway.
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ABSTRACT: The NF-kappaB/iNOS pathway stimulates muscle differentiation downstream of the PI 3-kinase/p38 MAPK pathway and diverse antioxidants block muscle differentiation. Therefore, we here investigated whether Nox 2 links those two myogenic pathways in H9c2 and C2C12 myoblasts. Compared with the proliferation stage, ROS generation was enhanced from the early stage of differentiation and gradually increased as differentiation progressed. Antioxidants suppressed the activated NF-kappaB/iNOS pathway during muscle differentiation. Nox 2 activity was also increased during muscle differentiation. Treatment with DPI and apocynin, two inhibitors of NADPH oxidase, and suppression of Nox 2 expression using siRNA, but not Nox 1, inhibited NADPH oxidase activity, muscle differentiation, and the NF-kappaB/iNOS pathway. Inhibition of PI 3-kinase and p38 MAPK suppressed the Nox 2/NF-kappaB/iNOS pathway. Nitric oxide restored muscle differentiation blocked by treatment with antioxidants or suppression of the Nox 2/NF-kappaB/iNOS pathway. In conclusion, Nox 2 stimulates muscle differentiation downstream of the PI 3-kinase/p38 MAPK pathway by activating the NF-kappaB/iNOS pathway via ROS generation.Free Radical Biology and Medicine 05/2005; 38(8):989-1001. · 5.42 Impact Factor -
Article: Atomic structure of alkali metal (Li, Na, K) adsorbed Ge(111)-(3×1) surfaces
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ABSTRACT: We have studied the atomic structure of alkali metal (AM) adsorbed Ge(111)-(3×1) surfaces using the pseudopotential and density-functional theory. Our total-energy calculations for Li, Na, and K demonstrate that the AM/Ge(111)-(3×1) surfaces have the same ground-state structure as the AM/Si(111)-(3×1) surfaces, which is referred to as the honeycomb-chain-channel model, and show systematic variations in surface bonding geometry over the AM adsorbates. Details of the structural changes are reported and discussed in connection to the questions raised by recent scanning tunneling microscopy and x-ray photoelectron spectroscopy studies.Phys. Rev. B. 12/2002; 66(23). -
Article: Ge-Si intermixing at the Ge/Si(001) surface
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ABSTRACT: Ge-Si intermixing at the Ge/Si(001) surface is studied for 0.5-ML and 1-ML Ge coverages by using pseudopotential density-functional theory. We calculate the total energies of various Ge-Si intermixing configurations and estimate the possibility of Ge interdiffusion in the thermodynamic regime. We find that, while most of Ge atoms stay in the surface layer at room temperature, Ge interdiffusion tends to increase with temperature. Our results not only provide a quantitative understanding of recent experimental observations of high-temperature Ge interdiffusion at the Ge/Si(001) surface, but also demonstrate that there is a strong “site selectivity” of Ge arising from the dimerized surface reconstruction.Phys. Rev. B. 01/2000; 61(3). -
Article: Geometry and core-level shifts of As on GaAs(110)
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ABSTRACT: The atomic structure of the As-covered GaAs(110) surface in one-monolayer coverage is studied using the pseudopotential density-functional theory. We compare the adsorption geometry of As/GaAs(110) with that of the well-studied isoelectronic Sb/GaAs(110) system and discuss the large difference in the desorption temperature found in both systems, based on the calculated adsorption energies. In addition, we calculate the As 3d and Ga 3d core-level shifts at As/GaAs(110) using initial-state theory. Our calculations not only produce well the surface components resolved in a recent photoemission experiment, but predict an additional surface core level for the substrate As atom bonded to the adsorbed As atom.Phys. Rev. B. 05/1999; 59(19). -
Conference Proceeding: Multiple target tracking in clutter backgrounds using self-organizing feature map
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ABSTRACT: Target tracking in a real world situation is a difficult problem because of continuous variations in images, huge amount of data, and high processing speed demands. The problem becomes even harder in the case of sea background. This paper presents an initial study of neural network based method for target detection and tracking in cluttering environment. The approach uses a combination of the differential motion analysis, Kohonen self-organizing network and region growing method. The network is capable of detecting the mass-centers of moving objects within one frame. The history of neuron positions in the sequential frames approximates the traces of the targets. The experiments done with the network in simulated environment showed promising resultsNeural Networks Proceedings, 1998. IEEE World Congress on Computational Intelligence. The 1998 IEEE International Joint Conference on; 06/1998 -
Article: Geometry and core-level shifts of an adsorbed Sb monolayer on GaAs(110)
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ABSTRACT: The atomic geometry and the core-level shifts of an Sb monolayer adsorbed on the GaAs(110) surface have been determined using the pseudopotential density-functional theory. The results clearly favor the epitaxial continued layer structure (ECLS) model, and demonstrate the need to include the Ga partial-core correction for both the GaAs bulk lattice constant and the Sb-Ga bond length. Furthermore, within the ECLS geometry, both the initial- and the final-state model calculations lead to the same conclusion that the 4d core-level binding energy of an Sb atom bonded to Ga shifts downwards by about 0.4 eV relative to that of an Sb bonded to As. These findings provide the theoretical basis for the interpretation of recent photoelectron diffraction experiments.Phys. Rev. B. 01/1998; 57(3). -
Conference Proceeding: A fuzzy self-organized backpropagation using nervous system
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ABSTRACT: We consider a fuzzy multilayer neural network with a single hidden layer. A conventional backpropagation learning algorithm used widely in multilayer neural network has a possibility of local minima due to the inadequate initial weights and the insufficient number of hidden nodes. So we propose a fuzzy self-organized backpropagation algorithm that self-generates hidden nodes by a compound method of supervised learning and unsupervised learning. From the input layer to the hidden layer, a modified fuzzy ART is used to produce nodes. A winner-take-all method is adopted to the connection weight adaption, so that stored pattern for some pattern becomes updated. In simulation results, our method reduces the possibility of local minima and improves learning speed and paralysis than conventional error backpropagationSystems, Man, and Cybernetics, 1997. Computational Cybernetics and Simulation., 1997 IEEE International Conference on; 11/1997 -
Article: Adsorption structure of a single C60 molecule on Si(111)-(7×7): Density-functional calculations
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ABSTRACT: We have studied the structure and bonding nature of a single C60 molecule adsorbed on the Si(1 1 1)-(7 × 7) surface using density-functional theory calculations. Based on total-energy calculations and scanning-tunneling-microscopy (STM) simulations, we propose a structural model for the most representative adsorption configuration reported by STM experiments. In this model, C60 adsorbs at a position about 1 Å apart from the middle of the half unit cell with a C–C bond shared by pentagon and hexagon rings facing down toward the surface. We find in the calculated surface density of states that the highest occupied molecular orbital (HOMO) peak of C60 is resolved by the interaction with the surface into two levels, in good agreement with photoelectron spectroscopy data. It is shown in the charge characters of the affected electronic states that the nature of the molecule-surface interaction is basically the C–Si covalent bondings.Surface Science. 602(7):1408-1412. -
Article: Theoretical investigation of the Au/Si(111)-(5×2) surface structure
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ABSTRACT: The atomic structure of the Au/Si(1 1 1)-(5 × 2) surface has been studied by density-functional theory calculations. Two structure models, proposed experimentally by Marks et al. and Hasegawa et al., have been examined on an equal ground. In our total-energy calculations, both models are found to be locally stable and energetically comparable. In our electronic-structure analyses, however, both models fail to reproduce the key features of angle-resolved photoemission spectra and scanning-tunneling-microscopy images, indicating that the considered models need to be modified. Suggestions for the modification are given based on the present calculations.Surface Science. -
Article: Si 2p core-level shifts at the As/Si(001) and Sb/Si(001) surfaces
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ABSTRACT: We calculate the Si 2p core-level shifts at the As/Si(001)-(2×1) and Sb/Si(001)-(2×1) surfaces using final-state pseudopotential theory. We find a large difference in the surface core-level shifts originating from the first-layer Si atoms between the two systems, in good agreement with photoemission experiments. We also find the surface components of Si 2p core levels for second- and third-layer Si atoms. Our results for the As/Si(001) system provide an interpretation of several surface components observed in a recent high-resolution core-level spectra.Phys. Rev. B. 55(23). -
Article: Structure and bonding nature of C_ {60}∕ Si (100)-c (4× 4): Density-functional theory calculations
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ABSTRACT: We have studied the adsorption structure and bonding nature of the C60∕Si(100)-c(4×4) surface using density-functional theory calculations. Based on energetics and scanning-tunneling-microscopy simulations, we propose a structural model where C60 adsorbs in between Si dimer rows with a C–C bond shared by two hexagon faces headed down and aligned perpendicular to Si dimer rows. This structure shows a semiconducting band structure, and the modified occupied and unoccupied molecular-orbital levels are resolved. Our charge character analysis figures out the bonding nature as covalent by the evidence of C–Si σ bond formations. The calculated surface density of states, well reflecting the modified molecular levels, explains well the position and origin of the peaks measured by photoelectron spectroscopy study.Phys. Rev. B. 75(12). -
Article: First-principles study of the Cl and Br adsorbed Si(100) surfaces
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ABSTRACT: We have studied the atomic and electronic structure of the Cl and Br adsorbed Si(100) surfaces using density-functional theory calculations. We find that the Cl- and Br-terminated Si(100)-(2×1) surfaces show many adsorbate-induced surface electronic features, the energy levels and charge characters of which explain well the electronic origin of the Cl and Br hoppings observed in recent scanning-tunneling-microscopy (STM) experiments. The atomic structures and simulated STM images of Cl and Br vacancies are also examined. The vacancy structures underlying experimental STM images are identified, and the experimental bias-voltage dependence of Cl and Br vacancy images is reproduced in our simulations.Phys. Rev. B. 69(11). -
Article: Nox 2 stimulates muscle differentiation via NF-κB/iNOS pathway
[show abstract] [hide abstract]
ABSTRACT: The NF-κB/iNOS pathway stimulates muscle differentiation downstream of the PI 3-kinase/p38 MAPK pathway and diverse antioxidants block muscle differentiation. Therefore, we here investigated whether Nox 2 links those two myogenic pathways in H9c2 and C2C12 myoblasts. Compared with the proliferation stage, ROS generation was enhanced from the early stage of differentiation and gradually increased as differentiation progressed. Antioxidants suppressed the activated NF-κB/iNOS pathway during muscle differentiation. Nox 2 activity was also increased during muscle differentiation. Treatment with DPI and apocynin, two inhibitors of NADPH oxidase, and suppression of Nox 2 expression using siRNA, but not Nox 1, inhibited NADPH oxidase activity, muscle differentiation, and the NF-κB/iNOS pathway. Inhibition of PI 3-kinase and p38 MAPK suppressed the Nox 2/NF-κB/iNOS pathway. Nitric oxide restored muscle differentiation blocked by treatment with antioxidants or suppression of the Nox 2/NF-κB/iNOS pathway. In conclusion, Nox 2 stimulates muscle differentiation downstream of the PI 3-kinase/p38 MAPK pathway by activating the NF-κB/iNOS pathway via ROS generation.Free Radical Biology and Medicine.
Top co-authors
Top Journals
Institutions
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2009
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Hanyang University
Ansan, Gyeonggi, South Korea
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1998–2002
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Pohang University of Science and Technology
- Department of Physics
Andong, North Gyeongsang, South Korea -
Pusan National University
- Department of Computer Science
Pusan, Busan, South Korea
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