Magnetic and thermal properties of 4f-3d ladder-type molecular compounds

We report on the low-temperature magnetic susceptibilities and specific heats of the isostructural spin-ladder molecular complexes L$_{2}$[M(opba)]_{3\cdot xDMSO$\cdot y$H$_{2}$O, hereafter abbreviated with L$_{2}$M$_{3}$ (where L = La, Gd, Tb, Dy, Ho and M = Cu, Zn). The results show that the Cu containing complexes (with the exception of La$_{2}$Cu$_{3}$) undergo long range magnetic order at temperatures below 2 K, and that for Gd$_{2}$Cu$_{3}$ this ordering is ferromagnetic, whereas for Tb$_{2}$Cu$_{3}$ and Dy$_{2}$Cu$_{3}$ it is probably antiferromagnetic. The susceptibilities and specific heats of Tb$_{2}$Cu$_{3}$ and Dy$_{2}$Cu$_{3}$ above $T_{C}$ have been explained by means of a model taking into account nearest as well as next-nearest neighbor magnetic interactions. We show that the intraladder L--Cu interaction is the predominant one and that it is ferromagnetic for L = Gd, Tb and Dy. For the cases of Tb, Dy and Ho containing complexes, strong crystal field effects on the magnetic and thermal properties have to be taken into account. The magnetic coupling between the (ferromagnetic) ladders is found to be very weak and is probably of dipolar origin.Comment: 13 pages, 15 figures, submitted to Phys. Rev.

Oil pollution on coral reefs: a review of the state of knowledge and management needs

This paper reviews the current state of knowledge of the effects that oil pollution has on scleractinian corals. Areview of results obtained in laboratory as well as in field conditions are given and suitable management tools are discussed. Studies made in the 1970s and 1980s presented conflicting results regarding the impacts of oil on coral physiology, but later results confirmed the detrimental effect of oil on corals. The world's coral reefs are severely threatened by an array of factors, one of which is oil pollution. More laboratory and field work with current oils and dispersants is urgently needed in order to update our knowledge in this field and reduce impacts in case of a major oil spill on coral reefs

In situ reduction of core-shell Ag@In2O3 nanoparticles observed through environmental electronic microscopy

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In situ environmental HRTEM study of the restructuration under reducing atmosphere of small oxidized silver-indium nanoparticles

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Comparaison de la tenue en oxydation cyclique de superalliages revêtus d'aluminiure

Cette étude porte sur la résistance à l'oxydation cyclique à 1100°C de deux revêtements d'aluminiure, l'un obtenu par le procédé Codep, l'autre obtenu par le procédé APVS, sur trois superalliages (DSR142, N4 et N5) ainsi que d'un revêtement d'aluminiure modifié par le palladium sur le DSR142. La caractérisation de l'état initial des revêtements d'aluminiure étudiés montre que le procédé APVS garantit un revêtement d'épaisseur et de composition plus régulières que le procédé Codep. Après 400 et 800 cycles d'oxydation, les revêtements APVS développent un oxyde moins épais que les revêtements Codep, les échanges diffusionnels au sein des revêtements APVS semblant concentrés dans la zone externe alors que la zone de diffusion des revêtements Codep évolue notablement. Ceci semble associé à la répartition différente du chrome et des autres éléments d'alliage dans ces deux types de revêtement. Nous constatons que le palladium favorise la formation d'un oxyde plus mince et plus continu ainsi qu'il ralentit les modifications au sein du revêtement

In situ reduction of core-shell Ag@In2O3 nanoparticles observed through environmental electronic microscopy

International audienc

In situ environmental HRTEM study of the restructuration under reducing atmosphere of small oxidized silver-indium nanoparticles

International audienc

In situ environmental HRTEM study of the restructuration under reducing atmosphere of small oxidized silver-indium nanoparticles

International audienc