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Arthur J Freeman - One of the best experts on this subject based on the ideXlab platform.
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co2mnx x si ge sn heusler Compounds an ab initio study of their structural electronic and magnetic properties at zero and elevated pressure
Physical Review B, 2002Co-Authors: Silvia Picozzi, A Continenza, Arthur J FreemanAbstract:The structural, electronic, and magnetic properties of Co 2 MnX (X = Si, Ge, Sn) Heusler Compounds have been determined by means of all-electron full-potential linearized augmented plane wave (FLAPW) calculations. We focuson the effects on the electronic and magnetic properties induced by: (i) substitution of the X atom, (ii) applied pressure, and (iii) the use of the local spin density approximation (LSDA) vs the generalized gradient approximation (GGA) in density functional theory. A comparison between LSDA and GGA for the exchange-correlation functional shows that GGA is essential for an accurate description of the equilibrium volumes and of the electronic and magnetic properties of these systems. We find that both the energy gap and the spin gap increase as the X atomic number decreases. As a result of the semiconducting (Metallic) character found in the minority (majority) spin band structure, the Si and Ge based alloys are predicted to be half-Metallic. In contrast, Co 2 MnSn is found to be a "nearly half-Metallic" Compound, since the minority valence band maximum crosses the Fermi level. The calculated total magnetization of 5 μ B is in excellent agreement with recent experiments. By including a fully self-consistent treatment of spin-orbit coupling, the GGA calculated orbital moments are shown to be very small (about 0.008 μ B for Mn and about 0.02 μ B for Co), showing that the quenching of the orbital magnetic moment is nearly complete. The calculated hyperfine fields, both at zero and elevated pressure, are compared with available experimental data, and show general agreement, except for Mn. Finally, the calculated Mn 2p exchange splittings, found to be in good agreement with experiment, are proportional to the Mn magnetic moments, suggesting a localized nature of ferromagnetism in these Heusler Compounds.
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co2mnx x si ge sn heusler Compounds an ab initio study of their structural electronic and magnetic properties at zero and elevated pressure
Physical Review B, 2002Co-Authors: Silvia Picozzi, A Continenza, Arthur J FreemanAbstract:The structural, electronic, and magnetic properties of ${\mathrm{Co}}_{2}\mathrm{Mn}X$ $(X=\mathrm{Si},$ Ge, Sn) Heusler Compounds have been determined by means of all-electron full-potential linearized augmented plane wave (FLAPW) calculations. We focus on the effects on the electronic and magnetic properties induced by: (i) substitution of the X atom, (ii) applied pressure, and (iii) the use of the local spin density approximation (LSDA) vs the generalized gradient approximation (GGA) in density functional theory. A comparison between LSDA and GGA for the exchange-correlation functional shows that GGA is essential for an accurate description of the equilibrium volumes and of the electronic and magnetic properties of these systems. We find that both the energy gap and the spin gap increase as the X atomic number decreases. As a result of the semiconducting (Metallic) character found in the minority (majority) spin band structure, the Si and Ge based alloys are predicted to be half-Metallic. In contrast, ${\mathrm{Co}}_{2}\mathrm{MnSn}$ is found to be a ``nearly half-Metallic'' Compound, since the minority valence band maximum crosses the Fermi level. The calculated total magnetization of $5{\ensuremath{\mu}}_{B}$ is in excellent agreement with recent experiments. By including a fully self-consistent treatment of spin-orbit coupling, the GGA calculated orbital moments are shown to be very small (about $0.008{\ensuremath{\mu}}_{B}$ for Mn and about $0.02{\ensuremath{\mu}}_{B}$ for Co), showing that the quenching of the orbital magnetic moment is nearly complete. The calculated hyperfine fields, both at zero and elevated pressure, are compared with available experimental data, and show general agreement, except for Mn. Finally, the calculated Mn $2p$ exchange splittings, found to be in good agreement with experiment, are proportional to the Mn magnetic moments, suggesting a localized nature of ferromagnetism in these Heusler Compounds.
D Bourgeois - One of the best experts on this subject based on the ideXlab platform.
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structure of superoxide reductase bound to ferrocyanide and active site expansion upon x ray induced photo reduction
Structure, 2004Co-Authors: Virgile Adam, Vincent Nivière, Antoine Royant, Fernando P Molinaheredia, D BourgeoisAbstract:Abstract Some sulfate-reducing and microaerophilic bacteria rely on the enzyme superoxide reductase (SOR) to eliminate the toxic superoxide anion radical (O 2 · − ). SOR catalyses the one-electron reduction of O 2 · − to hydrogen peroxide at a nonheme ferrous iron center. The structures of Desulfoarculus baarsii SOR (mutant E47A) alone and in complex with ferrocyanide were solved to 1.15 and 1.7 A resolution, respectively. The latter structure, the first ever reported of a complex between ferrocyanide and a protein, reveals that this organo-Metallic Compound entirely plugs the SOR active site, coordinating the active iron through a bent cyano bridge. The subtle structural differences between the mixed-valence and the fully reduced SOR-ferrocyanide adducts were investigated by taking advantage of the photoelectrons induced by X-rays. The results reveal that photo-reduction from Fe(III) to Fe(II) of the iron center, a very rapid process under a powerful synchrotron beam, induces an expansion of the SOR active site.
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Structure of superoxide reductase bound to ferrocyanide and active site expansion upon X-ray-induced photo-reduction.
Structure, 2004Co-Authors: Virgile Adam, Vincent Nivière, Antoine Royant, Fernando P Molina-heredia, D BourgeoisAbstract:Some sulfate-reducing and microaerophilic bacteria rely on the enzyme superoxide reductase (SOR) to eliminate the toxic superoxide anion radical (O2*-). SOR catalyses the one-electron reduction of O2*- to hydrogen peroxide at a nonheme ferrous iron center. The structures of Desulfoarculus baarsii SOR (mutant E47A) alone and in complex with ferrocyanide were solved to 1.15 and 1.7 A resolution, respectively. The latter structure, the first ever reported of a complex between ferrocyanide and a protein, reveals that this organo-Metallic Compound entirely plugs the SOR active site, coordinating the active iron through a bent cyano bridge. The subtle structural differences between the mixed-valence and the fully reduced SOR-ferrocyanide adducts were investigated by taking advantage of the photoelectrons induced by X-rays. The results reveal that photo-reduction from Fe(III) to Fe(II) of the iron center, a very rapid process under a powerful synchrotron beam, induces an expansion of the SOR active site.
Silvia Picozzi - One of the best experts on this subject based on the ideXlab platform.
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co2mnx x si ge sn heusler Compounds an ab initio study of their structural electronic and magnetic properties at zero and elevated pressure
Physical Review B, 2002Co-Authors: Silvia Picozzi, A Continenza, Arthur J FreemanAbstract:The structural, electronic, and magnetic properties of Co 2 MnX (X = Si, Ge, Sn) Heusler Compounds have been determined by means of all-electron full-potential linearized augmented plane wave (FLAPW) calculations. We focuson the effects on the electronic and magnetic properties induced by: (i) substitution of the X atom, (ii) applied pressure, and (iii) the use of the local spin density approximation (LSDA) vs the generalized gradient approximation (GGA) in density functional theory. A comparison between LSDA and GGA for the exchange-correlation functional shows that GGA is essential for an accurate description of the equilibrium volumes and of the electronic and magnetic properties of these systems. We find that both the energy gap and the spin gap increase as the X atomic number decreases. As a result of the semiconducting (Metallic) character found in the minority (majority) spin band structure, the Si and Ge based alloys are predicted to be half-Metallic. In contrast, Co 2 MnSn is found to be a "nearly half-Metallic" Compound, since the minority valence band maximum crosses the Fermi level. The calculated total magnetization of 5 μ B is in excellent agreement with recent experiments. By including a fully self-consistent treatment of spin-orbit coupling, the GGA calculated orbital moments are shown to be very small (about 0.008 μ B for Mn and about 0.02 μ B for Co), showing that the quenching of the orbital magnetic moment is nearly complete. The calculated hyperfine fields, both at zero and elevated pressure, are compared with available experimental data, and show general agreement, except for Mn. Finally, the calculated Mn 2p exchange splittings, found to be in good agreement with experiment, are proportional to the Mn magnetic moments, suggesting a localized nature of ferromagnetism in these Heusler Compounds.
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co2mnx x si ge sn heusler Compounds an ab initio study of their structural electronic and magnetic properties at zero and elevated pressure
Physical Review B, 2002Co-Authors: Silvia Picozzi, A Continenza, Arthur J FreemanAbstract:The structural, electronic, and magnetic properties of ${\mathrm{Co}}_{2}\mathrm{Mn}X$ $(X=\mathrm{Si},$ Ge, Sn) Heusler Compounds have been determined by means of all-electron full-potential linearized augmented plane wave (FLAPW) calculations. We focus on the effects on the electronic and magnetic properties induced by: (i) substitution of the X atom, (ii) applied pressure, and (iii) the use of the local spin density approximation (LSDA) vs the generalized gradient approximation (GGA) in density functional theory. A comparison between LSDA and GGA for the exchange-correlation functional shows that GGA is essential for an accurate description of the equilibrium volumes and of the electronic and magnetic properties of these systems. We find that both the energy gap and the spin gap increase as the X atomic number decreases. As a result of the semiconducting (Metallic) character found in the minority (majority) spin band structure, the Si and Ge based alloys are predicted to be half-Metallic. In contrast, ${\mathrm{Co}}_{2}\mathrm{MnSn}$ is found to be a ``nearly half-Metallic'' Compound, since the minority valence band maximum crosses the Fermi level. The calculated total magnetization of $5{\ensuremath{\mu}}_{B}$ is in excellent agreement with recent experiments. By including a fully self-consistent treatment of spin-orbit coupling, the GGA calculated orbital moments are shown to be very small (about $0.008{\ensuremath{\mu}}_{B}$ for Mn and about $0.02{\ensuremath{\mu}}_{B}$ for Co), showing that the quenching of the orbital magnetic moment is nearly complete. The calculated hyperfine fields, both at zero and elevated pressure, are compared with available experimental data, and show general agreement, except for Mn. Finally, the calculated Mn $2p$ exchange splittings, found to be in good agreement with experiment, are proportional to the Mn magnetic moments, suggesting a localized nature of ferromagnetism in these Heusler Compounds.
Antoine Royant - One of the best experts on this subject based on the ideXlab platform.
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structure of superoxide reductase bound to ferrocyanide and active site expansion upon x ray induced photo reduction
Structure, 2004Co-Authors: Virgile Adam, Vincent Nivière, Antoine Royant, Fernando P Molinaheredia, D BourgeoisAbstract:Abstract Some sulfate-reducing and microaerophilic bacteria rely on the enzyme superoxide reductase (SOR) to eliminate the toxic superoxide anion radical (O 2 · − ). SOR catalyses the one-electron reduction of O 2 · − to hydrogen peroxide at a nonheme ferrous iron center. The structures of Desulfoarculus baarsii SOR (mutant E47A) alone and in complex with ferrocyanide were solved to 1.15 and 1.7 A resolution, respectively. The latter structure, the first ever reported of a complex between ferrocyanide and a protein, reveals that this organo-Metallic Compound entirely plugs the SOR active site, coordinating the active iron through a bent cyano bridge. The subtle structural differences between the mixed-valence and the fully reduced SOR-ferrocyanide adducts were investigated by taking advantage of the photoelectrons induced by X-rays. The results reveal that photo-reduction from Fe(III) to Fe(II) of the iron center, a very rapid process under a powerful synchrotron beam, induces an expansion of the SOR active site.
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Structure of superoxide reductase bound to ferrocyanide and active site expansion upon X-ray-induced photo-reduction.
Structure, 2004Co-Authors: Virgile Adam, Vincent Nivière, Antoine Royant, Fernando P Molina-heredia, D BourgeoisAbstract:Some sulfate-reducing and microaerophilic bacteria rely on the enzyme superoxide reductase (SOR) to eliminate the toxic superoxide anion radical (O2*-). SOR catalyses the one-electron reduction of O2*- to hydrogen peroxide at a nonheme ferrous iron center. The structures of Desulfoarculus baarsii SOR (mutant E47A) alone and in complex with ferrocyanide were solved to 1.15 and 1.7 A resolution, respectively. The latter structure, the first ever reported of a complex between ferrocyanide and a protein, reveals that this organo-Metallic Compound entirely plugs the SOR active site, coordinating the active iron through a bent cyano bridge. The subtle structural differences between the mixed-valence and the fully reduced SOR-ferrocyanide adducts were investigated by taking advantage of the photoelectrons induced by X-rays. The results reveal that photo-reduction from Fe(III) to Fe(II) of the iron center, a very rapid process under a powerful synchrotron beam, induces an expansion of the SOR active site.
Takehiko Nohmi - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of the in vivo Mutagenicity of Nickel Subsulfide in the Lung of F344 gpt delta Transgenic Rats Exposed by Intratracheal Instillation: A Collaborative Study for the gpt delta Transgenic Rat Mutation Assay
Genes and Environment, 2012Co-Authors: Tomoyuki Kamigaito, Tadashi Noguchi, Kazunori Narumi, Rie Takashima, Shuichi Hamada, Hisakazu Sanada, Masayuki Hasuko, Hiroyuki Hayashi, Ken-ichi Masumura, Takehiko NohmiAbstract:This study was conducted to evaluate the effectiveness of a transgenic rat mutation assay using F344 gpt delta rats. We investigated the mutagenic potential in the lung of nickel subsulfide (Ni3S2), an insoluble fine-crystalline-Metallic Compound and a carcinogen in the rodent and human lung. Ni3S2 carcinogenicity has been proposed to act via both genotoxic and non-genotoxic mechanisms. Ni3S2 was intratracheally instilled into male gpt delta rats at doses of 0.5 and 1 mg/animal once a week for four weeks; these doses of Ni3S2 are high enough to induce inflammation in the lung. Following a period of 28 and 90 days after the first administration, the gpt mutant frequencies (MFs) in lung were determined in four independent laboratories, and Spi− selection for larger deletion mutations was done in one laboratory. The gpt MFs of the rats treated with Ni3S2 were not increased: all four laboratories obtained similar results with no statistical differences. The Spi− MFs were also not increased by exposure to Ni3S2. These results indicate that intratracheally instilled Ni3S2 is non-mutagenic in the lung of gpt delta transgenic rats; however, whether Ni3S2 is non-mutagenic in the lung or it induces mutations which are not detectable by transgenic rodent mutation assays requires further investigation.