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256 results on '"Lacorre P."'

51. Neutron-diffraction study of the magnetic ordering in the insulating regime of the perovskites RNiO3 ( R = Pr and Nd)

Author

García-Muñoz, J., Rodriguez-Carvajal, J., Lacorre, P., Institut Laue-Langevin (ILL), ILL, Institut de Ciència de Materials de Barcelona (ICMAB), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay, IBM Almaden Research Center [San Jose], IBM, and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS]Physics [physics], Condensed Matter::Materials Science, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Condensed Matter::Strongly Correlated Electrons, [CHIM.MATE]Chemical Sciences/Material chemistry
Abstract

International audience; Neutron-diffraction experiments and polarization analysis techniques reveal that the metal-insulator transition in the orthorhombic perovskites PrNiO3 and NdNiO3 is accompanied by a sudden three-dimensional magnetic ordering of the Ni sites (mu(Ni) almost-equal-to 0.9mu(B)). The electronic localization is followed by a magnetic ground state consisting of an unusual antiferromagnetic structure, with k = (1/2 , 0, 1/2) relative to the orthorhombic crystal cell. This propagation vector implies the symmetrical coexistence of ferro- and antiferromagnetic couplings along the three pseudocubic axes. This suggests the existence of a nonuniform orbital distribution of the single eg electron. The orbital superlattice may result from the breakdown of the degeneracy of the Ni(III)(t2g6eg1) state due to electronic correlation. This type of spin arrangement has not been observed in other perovskite oxides. These findings are confirmed by the magnetic behavior of the single crystallographic Nd site: half of these ions become ordered and the other half remain disordered as in a simple paramagnet. This can be explained by the combination of polarization effects due to the exchange field from nickel moments and the breaking down of point symmetry at Ni site.

Published
1994

56. RNiO3 perovskites ( R = Pr, Nd): Nickel valence and the metal-insulator transition investigated by x-ray-absorption spectroscopy

Author

Medarde, M., Fontaine, A., García-Muñoz, J., Rodriguez-Carvajal, J., de Santis, M., Sacchi, M., Rossi, G., Lacorre, P., Laboratoire pour l'utilisation du rayonnement électromagnétique (LURE), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-MENRT-Centre National de la Recherche Scientifique (CNRS), Institut Laue-Langevin (ILL), ILL, IBM Almaden Research Center [San Jose], and IBM

Subjects
[PHYS]Physics [physics], [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Condensed Matter::Strongly Correlated Electrons, [CHIM.MATE]Chemical Sciences/Material chemistry
Abstract

International audience; The strongly correlated and nominally trivalent Ni oxides RNiO3 (R = Pr, Nd) show a sharp metal to insulator transition at T(M-I) = 135 and 200 K, respectively. Rare-earth (3d), Ni (1s, 2p), and O(Is) x-ray absorption measurements have been performed above and below the transition temperature in order to investigate (a) the valence of Ni and O atoms and (b) the changes in the electronic structure across the transition. Our results suggest that, in contrast to hole-doped Ni1-xLixO and La2-xSrxNiO4+delta, the electronic structure is characterized by a strongly hybridized ground state of mainly 3d7 character. The differences between the absorption edges at low (insulating) and high (metallic) temperatures are discussed in terms of the possible mechanisms responsible for the metal-insulator transition.

Published
1992

57. Neutron-diffraction study of RNiO3 ( R =La,Pr,Nd,Sm): Electronically induced structural changes across the metal-insulator transition

Author

García-Muñoz, J., Rodriguez-Carvajal, J., Lacorre, P., Torrance, J., Institut Laue-Langevin (ILL), ILL, Laboratoire des oxydes et fluorures (LdOF ), Le Mans Université (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), IBM Almaden Research Center [San Jose], and IBM

Subjects
[PHYS]Physics [physics], [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [CHIM.MATE]Chemical Sciences/Material chemistry
Abstract

International audience; In the RNiO3 series (R = La,Pr,Nd,Sm), the metal-insulator (M-I) transition temperature rises systematically as the size of the rare earth decreases and as the subsequent distortion from the ideal cubic perovskite increases. For R = La the system keeps its metallic character down to 1.5 K, while for R =Pr, Nd, and Sm electronic localization occurs at 135, 200, and 400 K, respectively. High-resolution neutron-powder-diffraction experiments have been performed to investigate the structural anomalies across the first-order M-I transition in the orthorhombic PrNiO3 and NdNiO3 compounds. The cell volume undergoes a subtle increase when the compounds become insulating, due to a slight increase of the Ni-O distances. This effect is accompanied by coupled tilts Of NiO6 octahedra, which imply changes in the Ni-O-Ni angles (DELTA-THETA-O-Ni-O almost-equal-to -0.5-degrees) governing the transfer integral between Ni e(g) and 0 2p orbitals. These changes are sterically driven by the observed increase of the nickel-oxygen distances (DELTA-d Ni-O almost-equal-to +0.004 Angstrom) in the insulating (low-temperature) phase. The results of valence-bond calculations suggest the existence of Ni3+(d7) and R3+ states for nickel and rare earth.

Published
1992

65. Use of uterine manipulator and uterine perforation in minimally invasive endometrial cancer surgery

Author

Sallée, C, Lacorre, A, Despoux, F, Mbou, VB, Margueritte, F, and Gauthier, T

Abstract

Safety of the uterine manipulator (UM) within endometrial cancer (EC) surgery is being questioned. Its use might be one of the issues for potential tumor dissemination during the procedure, especially in the case of uterine perforation (UP). No prospective data on this surgical complication, nor on the oncological consequences exist. The aim of this study was to assess the rate of UP while using UM when performing surgery for EC and the impact of UP on the choice of adjuvant treatment.

Published
2023
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94. Epidermal growth factor receptor expression and KRAS and BRAF mutations: study of 39 sinonasal intestinal-type adenocarcinomas.

Author

Projetti, Fabrice, Durand, Karine, Chaunavel, Alain, Léobon, Sophie, Lacorre, Sylvain, Caire, François, Bessède, Jean-Pierre, Moreau, Jean-Jacques, Coulibaly, Béma, and Labrousse, François

Subjects
COLON cancer, EPIDERMAL growth factor receptors, GENE expression, GENETIC mutation, IN situ hybridization, CELLULAR signal transduction
Abstract

Sinonasal intestinal-type adenocarcinomas (ITACs) are uncommon tumors of poor prognosis defined by their similarities to colorectal adenocarcinomas. The involvement of the epidermal growth factor receptor (EGFR) pathway in colorectal adenocarcinoma oncogenesis is well established, and the same is expected to apply to ITACs. In a series of 39 ITACs, we investigated EGFR amplification and chromosome 7 polysomy by fluorescence in situ hybridization; EGFR, KRAS, and BRAF mutational status by polymerase chain reaction sequencing; EGFR variant messenger RNA expression by quantitative reverse transcriptase polymerase chain reaction; and EGFR protein expression by immunohistochemistry with antibodies targeting the extracellular domain, the intracellular domain, and the phosphorylated isoform. The findings were analyzed with respect to clinical data, histologic typing, and patient outcome. EGFR amplification was observed in 3 cases with a focal distribution. EGFR proteins were overexpressed in all these foci with both extracellular domain and intracellular domain antibodies, suggesting involvement of the whole receptor. Chromosome 7 polysomy was observed in 15 cases and was not associated with EGFR protein expression. EGFR, KRAS, or BRAF mutations were observed in 5 different cases. The EGFRvIII mutant was not detected. In all cases, EGFR variants were expressed. There was no association between these molecular features and patient survival. In conclusion, (1) our study revealed various EGFR expression patterns in ITACs, indicating tumor heterogeneity; (2) EGFR amplification should be distinguished from chromosome 7 polysomy; (3) fluorescence in situ hybridization analysis could be guided by immunohistochemistry; and (4) ITACs share common alterations of the EGFR pathway with colorectal adenocarcinomas, except for a lower frequency of KRAS and BRAF mutations. [ABSTRACT FROM AUTHOR]

Published
2013
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