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372 results on '"Payen, C."'

104. Observatoire régional du pneumocoque. Bilan 1995 de la région provençale

Author

May, C., primary, Bellon, O., additional, Lagier, E., additional, Lefrand, H., additional, Brisou, P., additional, Michel Nguyen, A., additional, Bietrix, M., additional, Duluc, F., additional, Durand, F., additional, Rousselier, P., additional, Bertrand, J.J., additional, Lacombe, M.F., additional, Payen, C., additional, Carrere, J., additional, Cordoleani, B., additional, Merabet, A., additional, Collet, L., additional, Geslin, P., additional, and Chardon, H., additional

Published
1997
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112. High-dose therapy in multiple myeloma: A prospective randomized study of the “intergroupe français du myelome”

Author

Attal, M., primary, Harousseau, J. L., additional, Stoppa, A. M., additional, Sotto, J. J., additional, Fuzibet, G., additional, Rossi, J. F., additional, Casassus, P., additional, Thyss, A., additional, Maisonneuve, H., additional, Façon, T., additional, Ifrah, N., additional, Payen, C., additional, and Bataille, R., additional

Published
1996
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113. Consolidation treatment of adult acute lymphoblastic leukemia: a prospective, randomized trial comparing allogeneic versus autologous bone marrow transplantation and testing the impact of recombinant interleukin-2 after autologous bone marrow transplantation. BGMT Group

Author

Attal, M, primary, Blaise, D, additional, Marit, G, additional, Payen, C, additional, Michallet, M, additional, Vernant, JP, additional, Sauvage, C, additional, Troussard, X, additional, Nedellec, G, additional, and Pico, J, additional

Published
1995
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136. Mössbauer effect at 119Sn4+ nuclei in fine crystalline MnO.

Author

Fabrichnyi, P., Korolenko, M., Tkachenko, V., Danot, M., and Payen, C.

Abstract

The hyperfine structure of the low-temperature Mössbauer spectra of dopant 119Sn4+ ions (0.4 at. %) in a fine crystalline MnO sample, characterized by X-ray diffraction and magnetic measurements, has been studied. The 119Sn spectra show that tin is distributed over positions with an inhomogeneous cationic environment. The appearance of such positions is explained by the local compensation for the excess charge of Sn4+ by manganese vacancies V Mn and segregation of defects resulting in precipitation of MnSnO3 clusters. The non-uniform distribution of Sn4+ and the related dependence of the number of broken magnetic bonds on the local tin concentration are responsible for the fluctuation of the T N values, which is “perceived” by 119Sn in different MnO crystallites. The 119Sn spectra exclude the possibility that tin enters into the composition of superpara-magnetic particles. [ABSTRACT FROM AUTHOR]

Published
2007
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140. Unconventional antiferromagnetic correlations of the doped Haldane gapsystem Y 2BaNi 1 - xZn xO 5.

Author

Villar, V., Mélin, R., Paulsen, C., Souletie, J., Janod, E., and Payen, C.

Abstract

We make a new proposal to describe the very low temperature susceptibility of the doped Haldane gap compound Y2BaNi1-xZnxO5. We propose a new mean field model relevant for this compound. The ground state of this mean field model is unconventional because antiferromagnetism coexists with random dimers. We present new susceptibility experiments at very low temperature. We obtain a Curie-Weiss susceptibility χ( T ) ∼ C /(Θ + T ) as expected for antiferromagnetic correlations but we do not obtain a direct signature of antiferromagnetic long range order. We explain how to obtain the “impurity” susceptibility ( T ) by subtracting the Haldane gap contribution to the total susceptibility. In the temperature range [1 K, 300 K] the experimental data are well fitted by T ( T ) = C imp 1 + T imp / T . In the temperature range [100 mK, 1 K] the experimental data are well fitted by T ( T ) = A ln( T / T c ), where T c increases with x. This fit suggests the existence of a finite Néel temperature which is however too small to be probed directly in our experiments. We also obtain a maximum in the temperature dependence of the ac-susceptibility ( T ) which suggests the existence of antiferromagnetic correlations at very low temperature. [ABSTRACT FROM AUTHOR]

Published
2002
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143. Unconventional antiferromagnetic correlations of the doped Haldane gapsystem Y 2 BaNi 1 - x Zn x O 5

Author

Villar, V., Mélin, R., Paulsen, C., Souletie, J., Janod, E., and Payen, C.

Abstract

Abstract:: We make a new proposal to describe the very low temperature susceptibility of the doped Haldane gap compound Y2BaNi1-xZnxO5. We propose a new mean field model relevant for this compound. The ground state of this mean field model is unconventional because antiferromagnetism coexists with random dimers. We present new susceptibility experiments at very low temperature. We obtain a Curie-Weiss susceptibility χ( T ) ∼ C /(Θ + T ) as expected for antiferromagnetic correlations but we do not obtain a direct signature of antiferromagnetic long range order. We explain how to obtain the “impurity” susceptibility ( T ) by subtracting the Haldane gap contribution to the total susceptibility. In the temperature range [1 K, 300 K] the experimental data are well fitted by T ( T ) = C imp 1 + T imp / T . In the temperature range [100 mK, 1 K] the experimental data are well fitted by T ( T ) = A ln( T / T c ), where T c increases with x. This fit suggests the existence of a finite Néel temperature which is however too small to be probed directly in our experiments. We also obtain a maximum in the temperature dependence of the ac-susceptibility ( T ) which suggests the existence of antiferromagnetic correlations at very low temperature.

Published
2002
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144. Na3Cr2P3S12and K3Cr2P3S12: Two New One-Dimensional Thiophosphate Compounds with a Novel Structure

Author

Coste, S., Kopnin, E., Evain, M., Jobic, S., Payen, C., and Brec, R.

Abstract

Two new alkali metal chromium thiophosphates, Na3Cr2P3S12and K3Cr2P3S12, have been synthesized and their structure determined from single-crystal or powder X-ray diffraction analyses. These isostructural compounds, which exhibit a novel structural arrangement, crystallize in the monoclinic system (space group P21/c) with the cell parameters a=17.4076(10) Å, b=11.1723(10) Å, c=19.2502(11) Å, β=149.731(3)° (V=1887.1(2) Å3, Z=4) and a=17.9690(14) Å, b=12.0607(5) Å, c=19.3109(16) Å, β=150.008(3)° (V=2091.98(16) Å3, Z=4) for Na3Cr2P3S12(I) and K3Cr2P3S12(II), respectively. For (I), the single-crystal refinement led to R/Rw(F2)=0.0417/0.0650 (for 4125 independent reflections and 182 refined parameters). For (II), the Rietveld refinement led to Rp/Rwp=0.0181/0.0233 (for 90 refined parameters). In both materials, the structures consist of 1∞[Cr2P3S12]3−chains built upon two edge-sharing [CrS6] octahedra capped by two [PS4] tetrahedra defining isolated [Cr2P2S12]−8entities. These entities are linked to each other through an extra [PS4] tetrahedral group. Magnetic measurements evidence antiferromagnetic coupling between Cr3+cations. The charge balance of the phase is MI3CrIII2PV3S−II12.

Published
2001
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147. Copper sublattice ordering in layered CuMP2Se6(M=In, Cr)

Author

Bourdon, X, Maisonneuve, V, Cajipe, V.B, Payen, C, and Fischer, J.E

Abstract

The structures of the lamellar selenodiphosphates CuMP2Se6(M=Cr, In) are reexamined using powder diffraction and auxiliary techniques. Antiferromagnetic behavior observed in CuCrP2Se6below 40 K is shown to be consistent with the existence of separate, triangular Cu and Cr sublattices rather than a random cation distribution. Analyses of neutron powder diffraction patterns recorded at various temperatures for CuCrP2Se6confirm this as well as reveal partial occupation by copper of equivalent sites shifted away from the layer midplane. Diffraction evidence is also given for site disorder involving off-center positions in the copper sublattice of CuInP2Se6at room temperature. The deduced off-center shift for copper in CuCrP2Se6is less than in CuInP2Se6; moreover, these displacements are significantly smaller than in the thiophosphates CuMP2S6(M=Cr, In). No indication of dipole ordering within the copper sublattice of CuCrP2Se6was found down to T=10 K, in contrast with the appearance of antipolar copper order in CuCrP2S6below 150 K. On the other hand, calorimetry detected a transition in CuInP2Se6between T=200 and 240 K, a range much lower and broader than for the ferro-paraelectric transition in CuInP2S6(Tc=315 K). The possible nature of the low T-phase of CuInP2Se6is discussed based on preliminary diffraction data and the known thermal behavior of CuInP2S6.

Published
1999
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148. Electrochemical Synthesis for the Control of γ-Fe<INF>2</INF>O<INF>3</INF> Nanoparticle Size. Morphology, Microstructure, and Magnetic Behavior

Author

Pascal, C., Pascal, J. L., Favier, F., Moubtassim, Elidrissi, L., M., and Payen, C.

Abstract

The electrochemical synthesis of nanoparticles of γ-Fe2O3 was performed in an organic medium. The size was directly controlled by the imposed current density, and the resulting particles were stabilized as a colloidal suspension by the use of cationic surfactants. The size distributions of the particles were narrow, with the average sizes varying from 3 to 8 nm. The amorphous character of the nanoparticles was clearly established by X-ray powder diffraction and TEM analysis. The microstructure of this phase could nevertheless be spectroscopically related to maghemite, γ-Fe2O3. 57Fe Mossbauer spectroscopy and magnetization measurements indicated that the dry powders exhibit superparamagnetic behavior at room temperature.

Published
1999

149. Ionic conductivity in ferroic CuInP2S6 and CuCrP2S6

Author

Maisonneuve, V., Reau, J. M., Dong, Ming, Cajipe, V. B., Payen, C., and Ravez, J.

Abstract

ac electrical measurements are reported for the paraelectric phases of the ferroelectric CuInP2S6 and antiferroelectric CuCrP2S6. A complex permittivity analysis confirms previous dielectric results for CuInP2S6. Arrhenius behaviors with nearly identical activation energies were observed for the dc conductivities and modulus relaxation frequencies. A hopping mechanism for Cu(I) transport in these materials is thus suggested.

Published
1997
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