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Mechanisms of chemical-reaction-induced tensile deformation of an Fe/Ni/Cr alloy revealed by reactive atomistic simulations. RSC Adv 2023; 13:6630-6636. [PMID: 36860537 PMCID: PMC9969177 DOI: 10.1039/d2ra07039a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Accepted: 02/03/2023] [Indexed: 03/02/2023] Open
Abstract
High entropy alloys (HEAs) have demonstrated excellent potential in various applications owing to the unique properties. One of the most critical issues of HEAs is the stress corrosion cracking (SCC) which limits its reliability in practical applications. However, the SCC mechanisms have not been fully understood yet because of the difficulty of experimental measuring of atomic-scale deformation mechanisms and surface reactions. In this work, we conduct atomistic uniaxial tensile simulations using an FCC-type Fe40Ni40Cr20 alloy as a typical simplification of normal HEAs, in order to reveal how a corrosive environment such as high-temperature/pressure water affects the tensile behaviors and deformation mechanisms. In a vacuum, we observe the generation of layered HCP phases in an FCC matrix during tensile simulation induced by the formation of Shockley partial dislocations from surface and grain boundaries. While, in the corrosive environment of high-temperature/pressure water, the alloy surface is oxidized by chemical reactions with water and this oxide surface layer can suppress the formation of Shockley partial dislocation as well as the resulting FCC-to-HCP phase transition; instead, a BCC phase is preferred to generate in the FCC matrix for releasing the tensile stress and stored elastic energy, leading to a reduced ductility as the BCC phase is typically more brittle than the FCC and HCP. Overall, the deformation mechanism of the FeNiCr alloy is changed by the presence of a high-temperature/pressure water environment-from FCC-to-HCP phase transition in vacuum to FCC-to-BCC phase transition in water. This theoretical fundamental study may contribute to the further improvement of HEAs with high resistance to SCC in experiments.
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Molecular-Level Elucidation of a Fracture Process in Slide-Ring Gels via Coarse-Grained Molecular Dynamics Simulations. Macromolecules 2022. [DOI: 10.1021/acs.macromol.1c01981] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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3
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Atom-by-Atom and Sheet-by-Sheet Chemical Mechanical Polishing of Diamond Assisted by OH Radicals: A Tight-Binding Quantum Chemical Molecular Dynamics Simulation Study. ACS APPLIED MATERIALS & INTERFACES 2021; 13:41231-41237. [PMID: 34403585 DOI: 10.1021/acsami.1c09468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Ultraflat and damage-free single-crystal diamond is a promising material for use in electronic devices such as field-effect transistors. Diamond surfaces are conventionally prepared by the chemical mechanical polishing (CMP) method, although the CMP efficiency remains a critical issue owing to the extremely high hardness of diamond. Recently, OH radicals have been demonstrated to be potentially useful for improving the CMP efficiency for diamond; however, the underlying mechanisms are still elusive. In this work, we applied our previously developed CMP-specialized tight-binding quantum chemical molecular dynamics simulator to comprehensively elucidate the CMP mechanisms of diamond assisted by OH radicals. Our simulation results indicate that the diamond surface is oxidized by reactions with OH radicals and then a concomitant surface reconstruction takes place due to the distorted and unstable nature of the oxidized diamond surface structure. Furthermore, we interestingly reveal that the reconstruction of the diamond surface ultimately leads to two distinct removal mechanisms: (i) gradual atom-by-atom removal through the desorption of gaseous molecules (e.g., CO2 and H2CO3) and (ii) drastic sheet-by-sheet removal through the exfoliation of graphitic ring structures. Hence, we propose that promoting the oxidation-induced graphitization of the diamond surface may provide a route to further improving the CMP efficiency.
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Role of OH Termination in Mitigating Friction of Diamond-like Carbon under High Load: A Joint Simulation and Experimental Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:6292-6300. [PMID: 33956461 DOI: 10.1021/acs.langmuir.1c00727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Diamond-like carbon (DLC) has recently attracted much attention as a promising solid-state lubricant because it exhibits low friction, low abrasion, and high wear resistance. Although we previously reported the reason why H-terminated DLC exhibits low friction based on a tight-binding quantum chemical molecular dynamics (TB-QCMD) simulation, experimentally, the low-friction state of H-terminated DLC is not stable, limiting its application. In the present work, our TB-QCMD simulations suggest that H/OH-terminated DLC could give low friction even under high loads, whereas H-terminated DLC could not. By using gas-phase friction experiments, we confirm that OH termination can indeed provide much more stable lubricity than H termination, validating the predictions from simulations. We conclude that H/OH-terminated DLC is a new low-friction material with high load capacity and high stable lubricity that may be suitable for practical use in industrial applications.
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Cooperative roles of chemical reactions and mechanical friction in chemical mechanical polishing of gallium nitride assisted by OH radicals: tight-binding quantum chemical molecular dynamics simulations. Phys Chem Chem Phys 2021; 23:4075-4084. [DOI: 10.1039/d0cp05826b] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Chemical mechanical polishing (CMP) of Ga-face GaN is accelerated by the chemical reactions with OH radicals.
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Non-Empirical Law for Nanoscale Atom-by-Atom Wear. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:2002827. [PMID: 33511015 PMCID: PMC7816698 DOI: 10.1002/advs.202002827] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/26/2020] [Revised: 09/11/2020] [Indexed: 06/12/2023]
Abstract
Wear of contact materials results in energy loss and device failure. Conventionally, wear is described by empirical laws such as the Archard's law; however, the fundamental physical and chemical origins of the empirical law have long been elusive, and moreover empirical wear laws do not always hold for nanoscale contact, collaboratively hindering the development of high-durable tribosystems. Here, a non-empirical and robustly applicable wear law for nanoscale contact situations is proposed. The proposed wear law successfully unveils why the nanoscale wear behaviors do not obey the description by Archard's law in all cases although still obey it in certain experiments. The robustness and applicability of the proposed wear law is validated by atomistic simulations. This work affords a way to calculate wear at nanoscale contact robustly and theoretically, and will contribute to developing design principles for wear reduction.
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Coarse-grained Molecular Dynamics Simulation of the Wear Mechanism of Cyclic Polymer Brushes. CHEM LETT 2020. [DOI: 10.1246/cl.200323] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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8
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Trajectory on-the-fly molecular dynamics approach to tunneling splitting in the electronic excited state: A case of tropolone. J Comput Chem 2020; 41:1549-1556. [PMID: 32239685 DOI: 10.1002/jcc.26199] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 03/10/2020] [Accepted: 03/16/2020] [Indexed: 11/10/2022]
Abstract
The semiclassical tunneling method is applied to evaluate the tunneling splitting of tropolone due to the intramolecular proton transfer in the electronic excited state, first time, in a framework of the trajectory on-the-fly molecular dynamics (TOF-MD) approach. To prevent unphysical zero-point vibrational energy transfer among the normal modes of vibration, quantum zero-point vibrational energies are assigned only to the vibrational modes related to intramolecular proton transfer, whereas the remaining modes are treated as bath modes. Practical ways to determine the tunnel-initiating points and tunneling path are introduced. It is shown that the tunneling splitting decreases as the bath-mode energy increases. The experimental tunneling splitting value is well reproduced by the present TOF-MD approach based on the Wentzel-Kramers-Brillouin (WKB) approximation.
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Triboemission of hydrocarbon molecules from diamond-like carbon friction interface induces atomic-scale wear. SCIENCE ADVANCES 2019; 5:eaax9301. [PMID: 31763455 PMCID: PMC6858253 DOI: 10.1126/sciadv.aax9301] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 09/17/2019] [Indexed: 06/10/2023]
Abstract
Understanding atomic-scale wear is crucial to avoid device failure. Atomic-scale wear differs from macroscale wear because chemical reactions and interactions at the friction interface are dominant in atomic-scale tribological behaviors, instead of macroscale properties, such as material strength and hardness. It is particularly challenging to reveal interfacial reactions and atomic-scale wear mechanisms. Here, our operando friction experiments with hydrogenated diamond-like carbon (DLC) in vacuum demonstrate the triboemission of various hydrocarbon molecules from the DLC friction interface, indicating its atomic-scale chemical wear. Furthermore, our reactive molecular dynamics simulations reveal that this triboemission of hydrocarbon molecules induces the atomic-scale mechanical wear of DLC. As the hydrogen concentration in hydrogenated DLC increases, the chemical wear increases while mechanical wear decreases, indicating an opposite effect of hydrogen concentration on chemical and mechanical wear. Consequently, the total wear shows a concave hydrogen concentration dependence, with an optimal hydrogen concentration for wear reduction of around 20%.
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Molecular Interactions between Pentacene and Imidazolium Ionic Liquids: A Molecular Dynamics Study. CHEM LETT 2018. [DOI: 10.1246/cl.180450] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Effect of Fluorination on Friction Forces between Concentrated Polymer Brushes in the Dry State: All-atom Molecular Dynamics Simulation Study. CHEM LETT 2018. [DOI: 10.1246/cl.180183] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Tight-Binding Quantum Chemical Molecular Dynamics Study on the Friction and Wear Processes of Diamond-Like Carbon Coatings: Effect of Tensile Stress. ACS APPLIED MATERIALS & INTERFACES 2017; 9:34396-34404. [PMID: 28914057 DOI: 10.1021/acsami.7b07551] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Diamond-like carbon (DLC) coatings have attracted much attention as an excellent solid lubricant due to their low-friction properties. However, wear is still a problem for the durability of DLC coatings. Tensile stress on the surface of DLC coatings has an important effect on the wear behavior during friction. To improve the tribological properties of DLC coatings, we investigate the friction process and wear mechanism under various tensile stresses by using our tight-binding quantum chemical molecular dynamics method. We observe the formation of C-C bonds between two DLC substrates under high tensile stress during friction, leading to a high friction coefficient. Furthermore, under high tensile stress, C-C bond dissociation in the DLC substrates is observed during friction, indicating the atomic-level wear. These dissociations of C-C bonds are caused by the transfer of surface hydrogen atoms during friction. This work provides atomic-scale insights into the friction process and the wear mechanism of DLC coatings during friction under tensile stress.
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A Study on Electrolytic Corrosion of Boron-Doped Diamond Electrodes when Decomposing Organic Compounds. ACS APPLIED MATERIALS & INTERFACES 2016; 8:28299-28305. [PMID: 26934500 DOI: 10.1021/acsami.5b11638] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Electrolytic corrosion of boron-doped diamond (BDD) electrodes after applying a high positive potential to decompose organic compounds in aqueous solution was studied. Scanning electron microscopy images, Raman spectra, and glow discharge optical emission spectroscopy revealed that relatively highly boron-doped domains were primarily corroded and relatively low boron-doped domains remained after electrolysis. The corrosion due to electrolysis was observed especially in aqueous solutions of acetic acid or propionic acid, while it was not observed in other organic compounds such as formic acid, glucose, and methanol. Electron spin resonance measurements after electrolysis in the acetic acid solution revealed the generation of methyl radicals on the BDD electrodes. Here, the possible mechanisms for the corrosion are discussed. Dangling bonds may be formed due to abstraction of OH groups from C-OH functional groups by methyl radicals generated on the surface of the BDD electrodes. As a result, the sp3 diamond structure would be converted to the sp2 carbon structure, which can be easily etched. Furthermore, to prevent electrolytic corrosion during electrolysis, both the current density and the pH condition in the aqueous solution were optimized. At low current densities or high pH, the BDD electrodes were stable without electrolytic corrosion even in the acetic acid aqueous solution.
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Theoretical investigation of enantioselectivity of cage-like supramolecular assembly: The insights into the shape complementarity and host-guest interaction. J Comput Chem 2015; 36:459-66. [DOI: 10.1002/jcc.23821] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 11/25/2014] [Accepted: 12/08/2014] [Indexed: 12/25/2022]
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Ab initio molecular dynamics approach to tunneling splitting in polyatomic molecules. J Comput Chem 2011; 33:60-5. [DOI: 10.1002/jcc.21943] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 08/15/2011] [Accepted: 08/17/2011] [Indexed: 11/08/2022]
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Ab initio molecular dynamics simulation of photoisomerization in azobenzene in the nπ[sup ∗] state. J Chem Phys 2009; 131:194306. [DOI: 10.1063/1.3263918] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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Erratum: “Relativistic calculation of nuclear magnetic shielding tensor using the regular approximation to the normalized elimination of the small component. II. Consideration of perturbations in the metric operator” [J. Chem. Phys. 126, 174102 (2007)]. J Chem Phys 2008. [DOI: 10.1063/1.2836431] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Decoupling of the Dirac equation correct to the third order for the magnetic perturbation. J Chem Phys 2007; 127:084117. [PMID: 17764239 DOI: 10.1063/1.2759199] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
A two-component relativistic theory accurately decoupling the positive and negative states of the Dirac Hamiltonian that includes magnetic perturbations is derived. The derived theory eliminates all of the odd terms originating from the nuclear attraction potential V and the first-order odd terms originating from the magnetic vector potential A, which connect the positive states to the negative states. The electronic energy obtained by the decoupling is correct to the third order with respect to A due to the (2n+1) rule. The decoupling is exact for the magnetic shielding calculation. However, the calculation of the diamagnetic property requires both the positive and negative states of the unperturbed (A=0) Hamiltonian. The derived theory is applied to the relativistic calculation of nuclear magnetic shielding tensors of HX (X=F,Cl,Br,I) systems at the Hartree-Fock level. The results indicate that such a substantially exact decoupling calculation well reproduces the four-component Dirac-Hartree-Fock results.
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Relativistic calculation of nuclear magnetic shielding tensor using the regular approximation to the normalized elimination of the small component. II. Consideration of perturbations in the metric operator. J Chem Phys 2007; 126:174102. [PMID: 17492852 DOI: 10.1063/1.2733650] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
A previous relativistic shielding calculation theory based on the regular approximation to the normalized elimination of the small component approach is improved by the inclusion of the magnetic interaction term contained in the metric operator. In order to consider effects of the metric perturbation, the self-consistent perturbation theory is used for the case of perturbation-dependent overlap integrals. The calculation results show that the second-order regular approximation results obtained for the isotropic shielding constants of halogen nuclei are well improved by the inclusion of the metric perturbation to reproduce the fully relativistic four-component Dirac-Hartree-Fock results. However, it is shown that the metric perturbation hardly or does not affect the anisotropy of the halogen shielding tensors and the proton magnetic shieldings.
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Relativistic calculation of nuclear magnetic shielding tensor including two-electron spin-orbit interactions. J Chem Phys 2006; 125:164106. [PMID: 17092062 DOI: 10.1063/1.2361292] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
A relativistic calculation of nuclear magnetic shielding tensor including two-electron spin-orbit interactions is performed. In order to reduce the computational load in evaluating the two-electron relativistic integrals, the charge density is approximated by a linear combination of the squares of s-type spatial basis functions. Including the two-electron spin-orbit interaction effect is found to improve the calculation results.
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Relativistic calculation of nuclear magnetic shielding using normalized elimination of the small component. J Chem Phys 2006; 124:224106. [PMID: 16784262 DOI: 10.1063/1.2204606] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The normalized elimination of the small component (NESC) theory, recently proposed by Filatov and Cremer, is extended to include magnetic interactions and applied to the calculation of the nuclear magnetic shielding in HX (X=F, Cl, Br, I) systems. The NESC calculations are performed at the levels of the zeroth-order regular approximation (ZORA) and the second-order regular approximation (SORA). The calculations show that the NESC-ZORA results are very close to the NESC-SORA results, except for the shielding of the I nucleus. Both the NESC-ZORA and NESC-SORA calculations yield very similar results to the previously reported values obtained using the relativistic infinite-order two-component coupled Hartree-Fock method. The difference between NESC-ZORA and NESC-SORA results is significant for the shieldings of iodine.
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Relativistic calculation of nuclear magnetic shieldings of xenon difluoride. J Chem Phys 2006; 124:116101. [PMID: 16555919 DOI: 10.1063/1.2173999] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
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Emergency Laparoscopic Surgery for Massive Hemorrhage in a Patient with Pyogenic Granuloma of The Jejunum. ACTA ACUST UNITED AC 2004. [DOI: 10.3862/jcoloproctology.57.39] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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[Concomitant operation of CABG and splenectomy following high-dose transvenous gamma-globulin therapy in a patient with idiopathic thrombocytopenic purpura--a case report]. [ZASSHI] [JOURNAL]. NIHON KYOBU GEKA GAKKAI 1994; 42:1222-5. [PMID: 7525793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A 60-year-old man with effort angina and idiopathic thrombocytopenic purpura (ITP) underwent concomitant operation of coronary artery bypass grafting (CABG) and splenectomy. High-dose transvenous gamma-globulin therapy (400 mg/kg/day) was performed for five days before surgery. The platelet count increased from 1.4 X 10(4)/mm3 to 8.7 X 10(4)/mm3. CABG was performed immediately followed by splenectomy. This is the first case with concomitant operation of cardiac surgery and splenectomy which was safely performed after high-dose transvenous gamma-globulin therapy.
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