Observations intensives de la température et de la salinité de surface dans le Pacifique tropical ouest entre 20°S et 20°N (1991 - 1993)

L'importance du rôle de la salinité et de la température, sur les échanges entre l'océan et l'atmosphère a rendu nécessaire une amélioration de la qualité des mesures traditionnelles. Pour les mesures de surface, l'échantillonnage au seau météorologique s'est révélé être insuffisante. L'installation d'un thermosalinographe sur des navires de commerce parcourant des lignes de navigation régulières a permis de mesurer correctement la salinité et la température de surface. Le système d'acquisition est basé sur l'utilisation d'un thermosalinographe installé sur le circuit d'eau de mer de refroidissement de la machine. Ses mesures sont enregistrées toutes les 5 minutes sur un microordinateur de type PC installé à la passerelle. La position, fournie par un récepteur de navigation GPS autonome est également enregistrée. Une comparaison des mesures obtenues avec cette méthode et celles obtenues avec la technique du seau météorologique montre une amélioration très nette de la qualité des mesures de salinité. (D'après résumé d'auteur

Proceedings of US - PRC international TOGA symposium

A series of 12 meridional transect along longitude 165°E in the Western Equatorial Pacific ocean were made between mid-1986 and mi-1988 : a time interval spanning an El Nino/Southern Oscillation (ENSO) event. Data collected on these cruises provide a detailed (albeit temporally sparse) view of the oceanic changes which occur in the Western Pacific during an ENSO event. The present work focuses on the evolution of the upper ocean thermohaline and zona velocity fields as revealed by high resolution hydrographic casts and direct near surface velocity measurements. (D'après résumé d'auteur

Impact of relative humidity variations on Carrara marble mechanical properties investigated by nonlinear resonant ultrasound spectroscopy

International audienceLike many other stones, marble mechanical properties can be significantly changed in presence of water. Water most often induces a weakening which can lead to marble degradation when coupled to temperature variations. Yet, marble artefacts are more frequently subjected to relative humidity (RH) variations than episodes of water imbibition and/or drastic temperature variations. Thus, one could wonder how do variations of RH alone impact marble mechanical state. In this study, Carrara Gioia marble samples are subjected to adsorption-desorption cycles. They were previously thermally-damaged between 40 and 105 °C, and their microstructure was characterized for each heating temperature. The evolution of their mechanical properties is monitored non-destructively with two parameters measured by Nonlinear Resonant Ultrasound Spectroscopy. The resonant frequency decreases weakly with increasing RH, indicating a diminution in sample stiffness due to low moisture-induced softening. The nonlinear parameter increases strongly, probably due to higher capillary pressure associated to a capillary condensation increase with RH. However, these phenomena are reversible: during adsorption-desorption cycling both parameters remain quite constant for a given RH. Therefore, while a RH increase impacts the mechanical properties of Carrara marble, adsorption-desorption cycling shows a reversible behavior which does not induce any permanent change in mechanical properties

Progressive thermal decohesion in Carrara marble monitored with nonlinear resonant ultrasound spectroscopy

This version of the article has been accepted for publication, after peer review and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: http://dx.doi.org/10.1007/s10064-024-03875-8.International audienceMarble has been used in sculpture and architecture since Antiquity. When exposed outdoors, it is subjected to physical, chemical, or biological weathering. Studies have shown that some deterioration (bowing, microcrack generation, thermal damage) can result from the exposure to cyclical thermal variations, but the actual temperature range triggering these phenomena remains unknown. Specifically, it is not yet understood if these phenomena are activated at a certain threshold temperature or by prolongated cyclic temperature exposure . In this work, the evolution of the mechanical state of Carrara Gioia marble samples under thermal stress is followed by means of Nonlinear Resonant Ultrasound Spectroscopy (NRUS). The results show, on the one hand, a progressive decrease of the linear parameter (resonant frequency) with heating temperature. This evolution agrees with results from previous works and with the consequent evolution of the microstructure. The (nonclassical) nonlinear parameter, on the other hand, exhibits an increase in the mild temperature range (40 -85°C), followed by a decrease for the highest temperatures (85 -250°C). This evolution of the NRUS parameters, as well as microstructural observations, depicts mild temperature induced degradation in Carrara marble. Carrara marble decohesion starts at the mesoscopic scale as evidenced by the initial increase in the nonlinear parameter, and then progressively expands to the macroscopic scale as highlighted by the resonant frequency evolution

A consistent picture of phosphate–divalent cation binding from models with implicit and explicit electronic polarization

The binding of divalent cations to the ubiquitous phosphate group is essential for a number of key biological processes, such as DNA compaction, RNA folding or interaction of some proteins with membranes. Yet, probing their binding sites, modes and associated binding free energy is a challenge for both experiments and simulations. In simulations, standard force fields strongly overestimate the interaction between phosphate groups and divalent cations. Here, we examine how different strategies to include electronic polarization effects in force fields—implicitly through the use of scaled charges or pair-specific Lennard-Jones parameters, or explicitly with the polarizable force fields Drude and AMOEBA—capture the interaction of a model phosphate compound, dimethylphosphate, with calcium and magnesium divalent cations. We show that both implicit and explicit approaches, when carefully parametrized, are successful in capturing the overall binding free energy, and that common trends emerge from the comparison of different simulation approaches. Overall, the binding is very moderate, slightly weaker for Ca2+ than Mg2+, and the solvent-shared ion pair is the most stable. Our results thus suggest practical ways to capture the divalent cations with biomolecular phosphate groups in complex biochemical systems. In particular, the computational efficiency of implicit models makes them ideally suited for large-scale simulations of biological assemblies, with improved accuracy compared to state-of-the-art fixed-charge force fields

A consistent picture of phosphate-divalent cation binding from models with implicit and explicit electronic polarization

International audienceThe binding of divalent cations to the ubiquitous phosphate group is essential for a number of key biological processes, such as DNA compaction, RNA folding or interactions of some proteins with membranes. Yet, probing their binding sites, modes and associated binding free energy is a challenge for both experiments and simulations. In simulations, standard force fields strongly overestimate the interaction between phosphate groups and divalent cations. Here, we examine how different strategies to include electronic polarization effects in force fields-implicitly through the use of scaled charges or pair-specific Lennard-Jones parameters, or explicitly with the polarizable force fields Drude and AMOEBA-capture the interactions of a model phosphate compound, dimethylphosphate, with calcium and magnesium divalent cations. We show that both implicit and explicit approaches, when carefully parametrized, are successful in capturing the overall binding free energy, and that common trends emerge from the comparison of different simulation approaches. Overall, the binding is very moderate, slightly weaker for Ca 2+ than Mg 2+ , and the solvent-shared ion pair is slightly more stable than the contact monodentate ion pair. The bidentate ion pair is higher in energy (or even fully unstable for Mg 2+). Our results thus suggest practical ways to capture the divalent cations with biomolecular phosphate groups in complex biochemical systems. In particular, the computational efficiency of implicit models makes them ideally suited for large-scale simulations of biological assemblies, with improved accuracy compared to state-ofthe-art fixed-charge force fields

Spatial distribution and quantitative analysis of extracellular matrix remodelling in lung fibrosis using multiphoton microscopy

International audienceThe micro- and macro- organization of collagen during fibrotic processes is usually characterized by 2D assessment using histochemical stains on selected slides such as Masson's Trichrome or Sirius Red. However, these staining methods are limited to semi quantitative evaluation on restricted surfaces. Quantitative evaluation of collagen contents, such as Hydroxyproline or Sircol assays, performed on lung homogenates requires large amounts of tissue, are time consuming and do not give the spatial distribution of collagen. Non linear multimodal, multiphoton microscopy provides novel insights into collagen deposition in tissues. In this study, the micrometerscale three-dimensional spatial distribution of fi brosis was characterized in normal mouse lung (n=5) and in the murine model of bleomycininduced lung fi brosis (n=5) by second harmonic generation (SHG) of fi brillar collagen, using C56Bl/6 mice at day 14 post intra-tracheal instillation of bleomycin, 80 µg in 50 µl of 0.9 % sterile saline

Rapport de la campagne COARE-POI à bord du N.O. le Noroit, 1er décembre 1992-2 mars 1993, de 5°N à 5°S le long du méridien 156°E

Dans le cadre du programme international TOGA-COARE (Tropical Ocean and Global Atmosphere - Coupled Ocean Atmosphere Response Experiment), la campagne COARE-POI a eu lieu à bord du navire océanographique LE NOROIT du 1er décembre 1992 au 2 mars 1993. Cette campagne a été mise en oeuvre et réalisée par le Groupe SURTROPAC du Centre ORSTOM de Nouméa, Nouvelle Calédonie, avec la participation effective de plusieurs équipes internationales. Elle comprend 18 sections courantologiques et hydrologiques effectuées le long du méridien 156°E de 5°S à 5°N, ainsi que 2 sections en Mer du Corail entre 20°S-163°E et 6°S-156°E. Au cours de la campagne COARE-POI, les travaux suivants ont été effectués : 165 stations à la sonde CTD (0-1000/1700 m) avec prélèvements à la rosette tous les 0.5/1° de latitude, des mesures en continu du courant absolu (0-400 m) à l'aide d'un profileur acoustique à effet Dopler, des mesures en continu de la température et de la salinité de surface par thermosalinographe, des observations météorologiques au moins toutes les 3 heures, le déploiement de 54 bouées dérivantes, des mesures fines à l'interface air-mer, des XBT, ainsi que des relevages et poses de mouillages. Ce rapport décrit le déroulement de la campagne ainsi que le matériel et les méthodes utilisés. Il présente également les figures correspondant aux premiers résultats. (Résumé d'auteur

Angiographic Anatomy of External Iliac Arteries in the Sheep.

External iliac artery atherosclerotic disease and aneurism occur in man. For treatment, imaging is required to facilitate minimally invasive introduction and advancement of stents within the intended vessels. Sheep are commonly used to test and improve stents. However, little information is published regarding the angiographic anatomy of the iliac arteries in the ovine species. The objective of this study was to describe the angiographic anatomy of the iliac arteries in the sheep. Computed tomography (CT) angiography and gross anatomical dissection were performed in, respectively, 10 and 43 adult ewes. Diameters and lengths of the arteries were measured. In comparison with man, salient anatomical differences were identified in the sheep: (1) the absence of common iliac arteries, (2) the common trunk at the origin of internal iliac arteries and (3) the location of the bifurcation of the external iliac arteries into femoral arteries in the pelvis (not in the limb). External iliac arteries in this series of sheep were 86 mm long in average and had a mean diameter of 7.5 mm. Lengths of arteries are only slightly different between man and sheep, while diameters are rather similar. Therefore, the sheep model appears to be sufficiently similar to man to test stent properties. This study provides useful reference images and measures of lengths and diameters of relevant arteries that could be applied to research with ovine models