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  2. 草部 浩一

草部 浩一

クサカベ コウイチ  (Koichi Kusakabe)

基本情報

所属
兵庫県立大学 理学研究科 物質科学専攻 教授
大阪大学 基礎工学研究科 物質創成専攻 准教授
学位
理学博士(東京大学)
理学修士(東京大学)
J-GLOBAL ID
200901089608768091
researchmap会員ID
1000185126

研究キーワード

 4

研究分野

 3

経歴

 5

受賞

 1

論文

 173
  • Keiki Fukumoto, Seunghee Lee, Shin-ichi Adachi, Yuta Suzuki, Koichi Kusakabe, Rikuto Yamamoto, Motoharu Kitatani, Kunio Ishida, Yoshinori Nakagawa, Michael Merkel, Daisuke Shiga, Hiroshi Kumigashira
    Scientific Reports 14(1) 2024年5月8日  
    Abstract Topological insulators (TI) hold significant potential for various electronic and optoelectronic devices that rely on the Dirac surface state (DSS), including spintronic and thermoelectric devices, as well as terahertz detectors. The behavior of electrons within the DSS plays a pivotal role in the performance of such devices. It is expected that DSS appear on a surface of three dimensional(3D) TI by mechanical exfoliation. However, it is not always the case that the surface terminating atomic configuration and corresponding band structures are homogeneous. In order to investigate the impact of surface terminating atomic configurations on electron dynamics, we meticulously examined the electron dynamics at the exfoliated surface of a crystalline 3D TI (Bi$$_2$$Se$$_3$$) with time, space, and energy resolutions. Based on our comprehensive band structure calculations, we found that on one of the Se-terminated surfaces, DSS is located within the bulk band gap, with no other surface states manifesting within this region. On this particular surface, photoexcited electrons within the conduction band effectively relax towards DSS and tend to linger at the Dirac point for extended periods of time. It is worth emphasizing that these distinct characteristics of DSS are exclusively observed on this particular surface.
  • 草部浩一
    まぐね/Magnetics Jpn. 19(2) 80-88 2024年4月  査読有り筆頭著者
  • Yasuhiro Oishi, Motoharu Kitatani, Koichi Kusakabe
    Beilstein Journal of Organic Chemistry 20 570-577 2024年3月11日  
    We theoretically analyze possible multiple conformations of protein molecules immobilized by 1-pyrenebutanoic acid succinimidyl ester (PASE) linkers on graphene. The activation barrier between two bi-stable conformations exhibited by PASE is confirmed to be based on the steric hindrance effect between a hydrogen on the pyrene group and a hydrogen on the alkyl group of this molecule. Even after the protein is supplemented, this steric hindrance effect remains if the local structure of the linker consisting of an alkyl group and a pyrene group is maintained. Therefore, it is likely that the kinetic behavior of a protein immobilized with a single PASE linker exhibits an activation barrier-type energy surface between the bi-stable conformations on graphene. We discuss the expected protein sensors when this type of energy surface appears and provide a guideline for improving the sensitivity, especially as an oscillator-type biosensor.
  • Halimah Harfah, Yusuf Wicaksono, Gagus Ketut Sunnardianto, Muhammad Aziz Majidi, Koichi Kusakabe
    Physical Chemistry Chemical Physics 26(12) 9733-9740 2024年3月6日  
    Enhanced spin control in graphene/hBN MTJ: boron vacancy tuning yields high TMR ratio of 400%, paving the way for ultra-thin spin valves.
  • 草部浩一
    まぐね/Magnetics Jpn. 18(6) 287-294 2023年12月  査読有り筆頭著者
もっとみる

MISC

 259
  • K. Kusakabe, M. Maruyama, S. Tsuneyuki, K. Akagi, Y. Yoshimoto, J. Yamauchi
    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 E737-E738 2004年5月  
    Based on our theoretical prediction of magnetic nanographite, we examined magnetism in various graphitic structures in nanometer scale using the first-principles calculation. When di-hydrogenated carbon atoms are created at a zigzag edge, high-spin ground states are found in carbon nanorings, which are short zigzag nanotubes, as well as graphene structures. The maximum total spin is proportional to the length of graphene ribbon or the diameter of the nanoring. The magnetism is interpreted as a realization of flat-band ferromagnetism known in the Hubbard model on bipartite lattices. (C) 2003 Elsevier B. V. All rights reserved.
  • K. Kusakabe, M. Maruyama, S. Tsuneyuki, K. Akagi, Y. Yoshimoto, J. Yamauchi
    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 E737-E738 2004年5月  
    Based on our theoretical prediction of magnetic nanographite, we examined magnetism in various graphitic structures in nanometer scale using the first-principles calculation. When di-hydrogenated carbon atoms are created at a zigzag edge, high-spin ground states are found in carbon nanorings, which are short zigzag nanotubes, as well as graphene structures. The maximum total spin is proportional to the length of graphene ribbon or the diameter of the nanoring. The magnetism is interpreted as a realization of flat-band ferromagnetism known in the Hubbard model on bipartite lattices. (C) 2003 Elsevier B. V. All rights reserved.
  • K. Kusakabe, M. Maruyama, S. Tsuneyuki, K. Akagi, Y. Yoshimoto, J. Yamauchi
    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 E737-E738 2004年5月  
    Based on our theoretical prediction of magnetic nanographite, we examined magnetism in various graphitic structures in nanometer scale using the first-principles calculation. When di-hydrogenated carbon atoms are created at a zigzag edge, high-spin ground states are found in carbon nanorings, which are short zigzag nanotubes, as well as graphene structures. The maximum total spin is proportional to the length of graphene ribbon or the diameter of the nanoring. The magnetism is interpreted as a realization of flat-band ferromagnetism known in the Hubbard model on bipartite lattices. (C) 2003 Elsevier B. V. All rights reserved.
  • K. Kusakabe, M. Maruyama, S. Tsuneyuki, K. Akagi, Y. Yoshimoto, J. Yamauchi
    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 E737-E738 2004年5月  
    Based on our theoretical prediction of magnetic nanographite, we examined magnetism in various graphitic structures in nanometer scale using the first-principles calculation. When di-hydrogenated carbon atoms are created at a zigzag edge, high-spin ground states are found in carbon nanorings, which are short zigzag nanotubes, as well as graphene structures. The maximum total spin is proportional to the length of graphene ribbon or the diameter of the nanoring. The magnetism is interpreted as a realization of flat-band ferromagnetism known in the Hubbard model on bipartite lattices. (C) 2003 Elsevier B. V. All rights reserved.
  • 小笠原 章, 草部 浩一
    日本物理学会講演概要集 59(1) 583-583 2004年3月3日  
  • 下司 雅章, 白井 正文, 草部 浩一, 鈴木 直
    日本物理学会講演概要集 59(1) 2004年3月3日  
  • Masanori Maruyama, Koichi Kusakabe
    Journal of the Physical Society of Japan 73(3) 656-663 2004年3月  
    We propose that to modify zigzag edges of nanographite structures by hydrogenation, fluorination or oxidation is a method to create magnetic materials made only from light elements. These reactions and methylene addition are compared with each other in several aspects by considering a graphene ribbon having mono-hydrogenated zigzag edges as a starting material. A local-spin-density approximation was applied to the electronic band-structure calculation of nanographite ribbon structures and stability of each ribbon was tested by the first-principles manner. Among possible reactions for graphene ribbon, hydrogenation produces the largest magnetic moment per a carbon atom. Since the hydrogenation is exothermic, however, fluorination has advantage, where the reaction is endothermic. The possible maximum moment is 1/3 of that for the ideal hydrogenationed graphene ribbon. A graphene ribbon with an oxidized zigzag edge and a monohydrogenated zigzag edge possesses a partially spin-polarized flat band similar to the fluorinated ribbon. A magnetic moment appears at the monohydrogenated zigzag edge but not at the oxidized edge. No evidence of spin polarization, however, has been found for a methylene-substituted graphene ribbon. © 2004 The Physical Society of Japan.
  • M Maruyama, K Kusakabe
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73(3) 656-663 2004年3月  
    We propose that to modify zigzag edges of nanographite structures by hydrogenation, fluorination or oxidation is a method to create magnetic materials made only from light elements. These reactions and methylene addition are compared with each other in several aspects by considering a graphene ribbon having mono-hydrogenated zigzag edges as a starting material. A local-spin-density approximation was applied to the electronic band-structure calculation of nanographite ribbon structures and stability of each ribbon was tested by the first-principles manner. Among possible reactions for graphene ribbon, hydrogenation produces the largest magnetic moment per a carbon atom. Since the hydrogenation is exothermic, however, fluorination has advantage, where the reaction is endothermic. The possible maximum moment is 1/3 of that for the ideal hydrogenationed graphene ribbon. A graphene ribbon with an oxidized zigzag edge and a monohydrogenated zigzag edge possesses a partially spin-polarized flat band similar to the fluorinated ribbon. A magnetic moment appears at the monohydrogenated zigzag edge but not at the oxidized edge. No evidence of spin polarization, however, has been found for a methylene-substituted graphene ribbon.
  • M Maruyama, K Kusakabe
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73(3) 656-663 2004年3月  
    We propose that to modify zigzag edges of nanographite structures by hydrogenation, fluorination or oxidation is a method to create magnetic materials made only from light elements. These reactions and methylene addition are compared with each other in several aspects by considering a graphene ribbon having mono-hydrogenated zigzag edges as a starting material. A local-spin-density approximation was applied to the electronic band-structure calculation of nanographite ribbon structures and stability of each ribbon was tested by the first-principles manner. Among possible reactions for graphene ribbon, hydrogenation produces the largest magnetic moment per a carbon atom. Since the hydrogenation is exothermic, however, fluorination has advantage, where the reaction is endothermic. The possible maximum moment is 1/3 of that for the ideal hydrogenationed graphene ribbon. A graphene ribbon with an oxidized zigzag edge and a monohydrogenated zigzag edge possesses a partially spin-polarized flat band similar to the fluorinated ribbon. A magnetic moment appears at the monohydrogenated zigzag edge but not at the oxidized edge. No evidence of spin polarization, however, has been found for a methylene-substituted graphene ribbon.
  • M Maruyama, K Kusakabe, S Tsuneyuki, K Akagi, Y Yoshimoto, J Yamauchi
    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 65(2-3) 119-122 2004年2月  
    Newly proposed aromatic molecules and graphene fragments are shown to have the high-spin ground state by the first-principles electronic structure calculations. Our strategy to predict magnetic carbon materials is based on our previous conclusion that mono-hydrogenated, di-hydrogenated or mono-fluorinated zigzag edges of honeycomb networks are magnetic. Structural optimization as well as determination of the electronic states was performed for various nanographite ribbons and high-spin molecules, e.g. 1,8,9-di-hydro-anthracene, C19H14 and C14F13. For hydrogenated molecules and ribbons, the total spin S determined by the LSDA calculation coincides with the value expected from a counting rule for the total spin on a bipartite network. However, S depends on structures of fluorinated nanographite. (C) 2003 Elsevier Ltd. All rights reserved.
  • M Maruyama, K Kusakabe, S Tsuneyuki, K Akagi, Y Yoshimoto, J Yamauchi
    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 65(2-3) 119-122 2004年2月  
    Newly proposed aromatic molecules and graphene fragments are shown to have the high-spin ground state by the first-principles electronic structure calculations. Our strategy to predict magnetic carbon materials is based on our previous conclusion that mono-hydrogenated, di-hydrogenated or mono-fluorinated zigzag edges of honeycomb networks are magnetic. Structural optimization as well as determination of the electronic states was performed for various nanographite ribbons and high-spin molecules, e.g. 1,8,9-di-hydro-anthracene, C19H14 and C14F13. For hydrogenated molecules and ribbons, the total spin S determined by the LSDA calculation coincides with the value expected from a counting rule for the total spin on a bipartite network. However, S depends on structures of fluorinated nanographite. (C) 2003 Elsevier Ltd. All rights reserved.
  • M Maruyama, K Kusakabe, S Tsuneyuki, K Akagi, Y Yoshimoto, J Yamauchi
    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 65(2-3) 119-122 2004年2月  
    Newly proposed aromatic molecules and graphene fragments are shown to have the high-spin ground state by the first-principles electronic structure calculations. Our strategy to predict magnetic carbon materials is based on our previous conclusion that mono-hydrogenated, di-hydrogenated or mono-fluorinated zigzag edges of honeycomb networks are magnetic. Structural optimization as well as determination of the electronic states was performed for various nanographite ribbons and high-spin molecules, e.g. 1,8,9-di-hydro-anthracene, C19H14 and C14F13. For hydrogenated molecules and ribbons, the total spin S determined by the LSDA calculation coincides with the value expected from a counting rule for the total spin on a bipartite network. However, S depends on structures of fluorinated nanographite. (C) 2003 Elsevier Ltd. All rights reserved.
  • M Maruyama, K Kusakabe, S Tsuneyuki, K Akagi, Y Yoshimoto, J Yamauchi
    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 65(2-3) 119-122 2004年2月  
    Newly proposed aromatic molecules and graphene fragments are shown to have the high-spin ground state by the first-principles electronic structure calculations. Our strategy to predict magnetic carbon materials is based on our previous conclusion that mono-hydrogenated, di-hydrogenated or mono-fluorinated zigzag edges of honeycomb networks are magnetic. Structural optimization as well as determination of the electronic states was performed for various nanographite ribbons and high-spin molecules, e.g. 1,8,9-di-hydro-anthracene, C19H14 and C14F13. For hydrogenated molecules and ribbons, the total spin S determined by the LSDA calculation coincides with the value expected from a counting rule for the total spin on a bipartite network. However, S depends on structures of fluorinated nanographite. (C) 2003 Elsevier Ltd. All rights reserved.
  • J. Phys. Soc. Jpn. 73, 656-663 (2004). 73, 656-663 2004年  
  • J. Phys. Soc. Jpn. 73, 1426-1429 (2004). 73, 1426-1429 2004年  
  • J. Phys. Soc. Jpn. 73, 1426-1429 (2004). 73, 1426-1429/, 2004年  
  • J. Phys. Soc. Jpn. 73, 1426-1429 (2004). 73, 1426-1429 2004年  
  • 小野 裕己, 草部 浩一, 鈴木 直
    日本物理学会講演概要集 58(2) 745-745 2003年8月15日  
  • 高木 祥光, 草部 浩一
    日本物理学会講演概要集 57(2) 285-285 2002年8月13日  
  • K Kusakabe, Y Tanaka
    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 63(6-8) 1511-1513 2002年6月  
    DC Josephson current in a superconductor/a quantum dot/superconductor junction is studied by a quantum Monte Carlo calculation. Dressed temperature Green's functions are evaluated by using the Hirscb-Fye algorithm and the current is obtained when the bias voltage is zero. Our result reproduces that a pi-junction is realized when the Coulomb blockade occurs at finite temperatures. (C) 2002 Elsevier Science Ltd. All rights reserved.
  • 高木 祥光, 草部 浩一
    日本物理学会講演概要集 57(1) 621-621 2002年3月1日  
  • Shinji Watanabe, Koichi Kusakabe, Yoshio Kuramoto
    Physica B: Condensed Matter 312-313 811-812 2002年3月  
    The ground-state properties of the two-band Hubbard model (TBHM) with semimetallic-band structures are studied by using numerical and analytical methods. Based on the density matrix renormalization group calculation in one dimension (1D), we find that the partially ferromagnetic state is realized by doping the compensated semimetal in the intermediate-coupling regime. We present an exact proof of partial ferromagnetism by using the Perron-Frobenius theorem in a 1D strongly correlated electron model derived from TBHM. © 2002 Elsevier Science B.V. All rights reserved.
  • Y Takagi, K Kusakabe
    PHYSICAL REVIEW B 65(12) 2002年3月  
    We studied phase stability, structural properties, and electronic band structures of graphite fluorides CnF (n=1,2,...,6) using density-functional theory with local density approximation. The calculation shows that CnF with sp(3) bonding has a direct gap, when n=1 or 2. Even though CnF with n>2 has not been identified experimentally, our calculation predicts that they become an indirect gap semiconductor.
  • Koichi Kusakabe, Yukio Tanaka
    Physica C: Superconductivity and its Applications 367(1-4) 123-128 2002年2月15日  
    We have studied theoretically the Josephson effect through a quantum dot array connected with two superconducting electrodes. The dot array has been studied by two models: (1) a Hubbard chain with boundary pair-potentials and (2) an Anderson impurity model coupled to superconducting leads. The first model shows a parity effect. Namely, the system becomes a π-junction for odd Ne or a 0-junction for even Ne, where Ne is the average number of electrons in the array. By shifting the on-site potential at the dot array, Ne increases one by one for finite U. The maximum Josephson current shows peaks of resonant tunneling determined by both the parity effect and the Hubbard gap. In order to consider the Josephson effect at finite temperature, we have generalized the quantum Monte Carlo method by Hirsch and Fye and have applied it to the second model with a quantum dot, which shows occurrence of the Coulomb blockade. © 2002 Elsevier Science B.V. All rights reserved.
  • K. Kusakabe, S. Watanabe, Y. Kuramoto
    J. Phys. Soc. Jpn. Suppl 71 311-313 2002年  
  • K Chihara, K Kusakabe
    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT 145, 225/,(145) 225-228 2002年  
    To consider interaction effects in a directed random system, we have studied a directed random XXZ model numerically. The exact diagonalizaton method is utilized to obtain distribution of complex eigenvalues. Starting from a strong non-Hermiticity limit with J(z) = 0, where the system becomes a non-interacting one-way model, inclusion of antiferromagnetic J(z) makes eigenvalues distributed on many concentric circles grouped by the number of neighboring anti-parallel spin configurations in an Ising limit. In this transition, an Ising gap opens as a result of continual recombination of spectral flows into smaller circles in the complex plane.
  • Koichi Kusakabe, Shinji Watanabe, Yoshio Kuramoto
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 71 311-313 2002年1月  
    Role of the double exchange for appearance of partial ferromagnetism in a semimetal is explored for a semimetallic two-band Hubbard model in one-dimension. In a strong coupling limit, a ferromagnetic exchange interaction between two neighboring triplet excitons becomes dominant compared with anti-ferromagnetic couplings and a partial spin polarization is shown to appear. Exact evaluation of magnetization is possible for the partially ferromagnetic: ground state in this limit. Obtained phase diagram. has a doping dependence similar to our DMRG results for finite interactions. The ferromagnetism is favored in semimetallic systems by the interplay of the intra-orbital Coulomb repulsion and the inter-orbital Hund-rule coupling.
  • TANSO 205 2002年  
  • 367, 123/, 2002年  
  • 145, 225/, 2002年  
  • 312-313, 811/, 2002年  
  • 63, 1511/, 2002年  
  • 71, 31/, 2002年  
  • 炭素 205 2002年  
  • 65, 121103(R)/, 2002年  
  • Koichi Kusakabe
    Journal of the Physical Society of Japan 70(7) 2038-2048 2001年7月  
    By introducing a set of auxiliary equations representing a many-body system, we have derived an extension of the Kohn-Sham scheme for the density functional theory. These equations consist of a Kohn-Sham-type equation determining single-particle orbitals and an eigen-value equation for an effective many-body problem. A variational method similar to the Kohn-Sham technique was utilized to derive effective interactions as well as effective potentials without artificial substitution of a Hubbard-type interaction and a mean-field correction in the energy functional. The second equation is described by an effective many-body Hamiltonian with both 2-body interactions and mean-field terms. Rigorous formulation of the extended Kohn-Sham equation is also given in accordance with the Hadjisavvas-Theophilou formulation. Our formulation can be interpreted as a way to define models of the strongly correlated electron systems, e.g. the Hubbard model.
  • T. Hirai, K. Kusakabe, Y. Tanaka
    Physica C: Superconductivity and its Applications 352(1-4) 169-172 2001年4月  
    Temperature dependence of the Josephson current through a one-dimensional (1D) doped Mott's insulator is investigated by theoretically analyzing a Josephson junction with a 1D electron system (1DES) in the vicinity of the charge gapped phase. Formation of the zero-energy states (ZES) at interfaces between 1DES and anisotropic superconductors affects the Josephson current in the metallic phase. However, approaching the Mott insulating phase, effects of ZES become less prominent. © 2001 Elsevier Science B.V.
  • Solid State Physics (Japan) 36, 639/, 2001年  
  • T Hirai, K Kusakabe, Y Tanaka
    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 62(1-2) 257-260 2001年1月  
    We calculate Josephson current through one-dimensional systems with a spin gap, i.e. Luther-Emery solution, or a charge gap, applying the bosonization method. For the spin-gapped liquid, the gap formation is irrelevant for the Josephson current. On the other hand, formation of the charge gap suppresses the magnitude of the maximum Josephson current at low temperatures. (C) 2000 Elsevier Science Ltd. All rights reserved.
  • 固体物理 36, 639/, 2001年  
  • 352, 169/, 2001年  
  • 62 257-260 2001年  
  • Journal of the Physical Society of Japan 70(7) 2038-2048 2001年  
  • T Deguchi, FHL Essler, F Gohmann, A Klumper, VE Korepin, K Kusakabe
    PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS 331(5) 197-281 2000年7月  
    We review fundamental issues arising in the exact solution of the one-dimensional Hubbard model. We perform a careful analysis of the Lieb-Wu equations, paying particular attention to the so-called 'string solutions'. Two kinds of string solutions occur: Lambda strings, related to spin degrees of freedom and k-Lambda strings, describing spinless bound states of electrons. Whereas Lambda strings were thoroughly studied in the literature, less is known about k-Lambda strings. We carry out a thorough analytical and numerical analysis of k-Lambda strings. We further review two different approaches to the thermodynamics of the Hubbard model, the Yang-Yang approach and the quantum transfer matrix approach, respectively. The Yang-Yang approach is based on strings, the quantum transfer matrix approach is not. We compare the results of both methods and show that they agree. Finally, we obtain the dispersion curves of all elementary excitations at zero magnetic field for the less than half-filled band by considering the zero-temperature limit of the Yang-Yang approach. (C) 2000 Elsevier Science B.V. All rights reserved.
  • Takashi Hirai, Koichi Kusakabe, Yukio Tanaka
    Physica C: Superconductivity and its Applications 336(1) 107-122 2000年7月1日  
    We present a theory for the Josephson effect in an unconventional superconductor/Luttinger liquid/unconventional superconductor (s/LL/s) junction where the Josephson current is carried by components injected perpendicular to the interface. We apply the bosonization method by Haldane and Maslov to the cases with arbitrary barrier height of the insulator formed between the superconductor and the LL. When superconductors on both sides have triplet symmetries, the Josephson current is enhanced at low temperatures due to the zero-energy states formed near the interface independent of the strength of electron-electron interaction and the transparency of the junction.
  • Y Takagi, M Fujita, K Kusakabe
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 340 379-382 2000年  
    We have shown a theoretical method to construct structures called "hyper-graphite which can be regarded as a generalization of the graphite structure. Based on the method, we propose a possible 3-dimensional network, which may be realized as a pi-electron system of hydro-carbon. Naturally, localized edge states emerge at the Fermi level similar to the zigzag-edged graphite sheet.
  • Transaction of Materials Research Society of Japan 25 869-872 2000年  
  • Proceedings of the 12th International Symposium on Superconductivity(ISS' 99) 254 2000年  
  • 340 379-382 2000年  
  • 25 869-872 2000年  

書籍等出版物

 5

所属学協会

 3

Works(作品等)

 8
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共同研究・競争的資金等の研究課題

 37
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