Quantification of the morphology of gold grains in 3D using X-ray microscopy and SEM photogrammetry

The shape of gold is widely used in mineral exploration and in sedimentology to estimate the distance of transport from the source to the site of deposition. However, estimation of the morphology is based on qualitative observations or on the quantification of shape in 2D. The 3D analysis of grain shape is useful for accurate morphometric quantification and to evaluate its volume, which is related to particle size. This study compares X-ray 3D microscope and 3D SEM photogrammetry to reconstruct the shape of gold particles. These new methods are exploited to quantify the shape of gold grains 85 to 300 μm in size. The shape parameters, such as axial lengths, surface area, volume, diameter of curvature of all corners, and diameter of the largest inscribed sphere and smallest circumscribed sphere are measured on a particle in order to estimate shape factors such as flatness ratios, shape indices, sphericity, and roundness. Most shape parameters and shape factors estimated on the same gold grain with simple geometry are similar between the two approaches. This result validates these methods for the 3D description of gold particles with simple morphology, while providing a methodology for describing grains with more complex geometry

Multi-method 2D and 3D reconstruction of gold grains morphology in alluvial deposits : a review and application to the Rivière du Moulin (Québec, Canada)

The aim of this paper is to document and compare the 2D qualitative and semi-quantitative methods currently used to describe the shape of gold grains in fluvial environments with the 3D quantitative methods using X-ray microtomography and SEM photogrammetry. These 3D methods are used to compute flatness, roundness, convexity, sphericity and ellipticity shape descriptors of 13 gold grains from the Rivière du Moulin (Québec, Canada) in order to quantify the morphological change along 9 km of fluvial transport. Gold grains have moderate to high values of flatness, compactness, sphericity and ellipticity indices that do not change significantly with distance of transport, whereas the roundness increases during transport. Gold grains are used to compare 2D and 3D methods, and the results show small differences (<8%) when shape descriptors are computed using image analysis software, whereas the difference (up to 70%) is more important for 2D measurements performed by a human operator. For application and characterization on a large set of gold grains, the 2D methods offer the advantage of speed, whereas, for a more detailed study on a limited number of gold grains, 3D methods enable estimation of the volume and yield more detailed shape descriptor changes during fluvial transport

CO or no CO? Narrowing the CO abundance constraint and recovering the H2O detection in the atmosphere of WASP-127 b using SPIRou

Precise measurements of chemical abundances in planetary atmospheres are necessary to constrain the formation histories of exoplanets. A recent study of WASP-127b, a close-in puffy sub-Saturn orbiting its solar-type host star in 4.2 d, using HST and Spitzer revealed a feature-rich transmission spectrum with strong excess absorption at 4.5 um. However, the limited spectral resolution and coverage of these instruments could not distinguish between CO and/or CO2 absorption causing this signal, with both low and high C/O ratio scenarios being possible. Here we present near-infrared (0.9--2.5 um) transit observations of WASP-127 b using the high-resolution SPIRou spectrograph, with the goal to disentangle CO from CO2 through the 2.3 um CO band. With SPIRou, we detect H2O at a t-test significance of 5.3 sigma and observe a tentative (3 sigma) signal consistent with OH absorption. From a joint SPIRou + HST + Spitzer retrieval analysis, we rule out a CO-rich scenario by placing an upper limit on the CO abundance of log10[CO]<-4.0, and estimate a log10[CO2] of -3.7^(+0.8)_(-0.6), which is the level needed to match the excess absorption seen at 4.5um. We also set abundance constraints on other major C-, O-, and N-bearing molecules, with our results favoring low C/O (0.10^(+0.10)_(-0.06)), disequilibrium chemistry scenarios. We further discuss the implications of our results in the context of planet formation. Additional observations at high and low-resolution will be needed to confirm these results and better our understanding of this unusual world.Comment: 23 pages, 13 figures, Submitted for publication in the Monthly Notice of the Royal Astronomical Societ

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]

L'érosion des terres agricoles de la région Nord-Pas-de-Calais

Erosion by water of farming lands in North-Pas-de-Calais region (France) Runoff and soil erosion by water in North-Pas-de-Calais region result from superficial impermeability of loamy soils infered by crop management practices. Climatic factor appears insignificant. A study, with purpose of soil-erosion hazard cartography, has been based on an inventory of rill-marks, soil analysis, measures of penetrometry and infiltration capacity. It led to proposals for a campaign against soil-erosion, the applying of which has considerably reduced the risk.L'apparition du ruissellement et de l'érosion des sols dans la région Nord-Pas-de-Calais est due à la battance des sols limoneux que favorisent les successions culturales et la mécanisation. Le facteur climatique paraît en revanche négligeable. Une étude menée en vue de cartographier les risques d'érosion s'est appuyée sur un inventaire des traces d'érosion, des analyses de sols, des mesures de pénétrométrie et d'infiltration. Elle a conduit à des propositions pour une lutte anti-érosive qui a considérablement réduit le risque là où elle a été mise en application.Masson François-Xavier. L'érosion des terres agricoles de la région Nord-Pas-de-Calais. In: Hommes et Terres du Nord, 1987/3. Risques naturels dans le Nord – Pas-de-Calais. pp. 139-145

Contribution à la gestion intégrée de l'eau pluviale en milieu urbain (un système d'information pour l'aide à la planification urbaine et pour l'aide à l'élaboration et au suivi de projet d'aménagement)

BETHUNE-BU Sci. appli. et éco. (621192101) / SudocSudocFranceF

Les causes de l'érosion et les modes de prévention sur l'amont des bassins versants Exemple de la région Nord de la France

La lutte contre le ruissellement et l'érosion constitue un enjeu économique important pour la gestion des écoulements, la prévention des inondations et des risques d'envasement des ouvrages situés à l'aval des bassins versants. Le transfert des matières en suspension par les eaux de ruissellement provenant des bassins versants ruraux amont participe à la turbidité des eaux. Les mécanismes qui contrôlent les apports de sédiments peuvent être estimés ou quantifiés. La connaissance de ces mécanismes permet d'envisager des méthodes de prévention limitant partiellement les transferts solides vers l'aval

Sediment Transfer Variation Approach at Large Rural Watersheds Scale of Northern France

International audienc

Aide au suivi du phénomène de dénitrification naturelle pour une gestion durable de la ressource en eau du Béthunois

Cities face a substantial increase in population and in industrial activities which entails an increasing demand for water. Our aim is to develop a management and decision-making framework for a better knowledge of the resource and to support the planning and decisions in the water boards of medium-size local communities. The framework will allow the reasoned exploitation of the aquifer system and in particular the preservation of the natural denitrification process which occurs in the chalk aquifer in the Béthunois area in northern France. In this article, we propose the setting-up of a control panel thanks to a GIS platform coupled with a hydrological model. Our research work is applied to the SIVOM of the Béthunois