Investigation of Hidden Periodic Structures on SEM Images of Opal-like Materials Using FFT and IFFT

We have developed a method to use fast Fourier transformation (FFT) and inverse fast Fourier transformation (IFFT) to investigate hidden periodic structures on SEM images. We focused on samples of natural, play-of-color opals that diffract visible light and hence are periodically structured. Conventional sample preparation by hydrofluoric acid etch was not used; untreated, freshly broken surfaces were examined at low magnification relative to the expected period of the structural features, and, the SEM was adjusted to get a very high number of pixels in the images. These SEM images were treated by software to calculate autocorrelation, FFT, and IFFT. We present how we adjusted SEM acquisition parameters for best results. We first applied our procedure on an SEM image on which the structure was obvious. Then, we applied the same procedure on a sample that must contain a periodic structure because it diffracts visible light, but on which no structure was visible on the SEM image. In both cases, we obtained clearly periodic patterns that allowed measurements of structural parameters. We also investigated how the irregularly broken surface interfered with the periodic structure to produce additional periodicity. We tested the limits of our methodology with the help of simulated image

Star formation triggered by non-head-on cloud-cloud collisions, and clouds with pre-collision sub-structure

In an earlier paper, we used smoothed particle hydrodynamics (SPH) simulations to explore star formation triggered by head-on collisions between uniform-density 500 M clouds, and showed that there is a critical collision velocity, vCRIT. At collision velocities below vCRIT, a hub-and-spoke mode operates and delivers a monolithic cluster with a broad mass function, including massive stars (M 10 M) formed by competitive accretion. At collision velocities above vCRIT, a spider’s-web mode operates and delivers a loose distribution of small sub-clusters with a relatively narrow mass function and no massive stars. Here we show that,if the head-on assumption is relaxed, vCRIT is reduced. However, if the uniform-density assumption is also relaxed, the collision velocity becomes somewhat less critical: a low collision velocity is still needed to produce a global hub-and-spoke system and a monolithic cluster, but, even at high velocities, large cores – capable of supporting competitive accretion and thereby producing massive stars – can be produced. We conclude that cloud–cloud collisions may be a viable mechanism for forming massive stars – and we show that this might even be the major channel for forming massive stars in the Galaxy

Applications de la métrologie submicrométrique à la caractérisation exoscopique des processus de l'érosion des quartz et des quartzites

L'exoscopie désigne l'analyse de la surface des objets minéraux par microscopie électronique à balayage. Elle s'applique aux marques d'érosion enregistrées par les grains de sable ou les fragments rocheux, en particulier par ceux qui sont formés de quartz, et procure ainsi un niveau d'observation supplémentaire en géomorphologie. Les logiciels de métrologie submicrométrique représentent dans ce domaine un outil innovant en raison de leur capacité à construire des images des microreliefs en trois dimensions, tels que des cartes, profils topographiques et blocs-diagrammes, mais aussi de leur aptitude à compléter la caractérisation des états de surface par le calcul d'indices de rugosité. Cet outil est appliqué ici, à titre d'exemple, aux marques de la corrasion éolienne, de l'abrasion glaciaire, de l'usure littorale et de l'altération chimique, à partir de quatre séries d'échantillons de fragments rocheux et de graviers constitués de quartz ou de quartzites. Il se présente comme un moyen d'analyse, d'illustration et de mesure des formes d'érosion, comme un procédé de caractérisation et de comparaison des états de surface, mais aussi comme une source supplémentaire d'informations sur les processus.Exoscopy is the analysis of the surface of mineral objects by scanning electron microscopy. It is applied to the erosion marks recorded by grains of sand or rock fragments, particularly those formed from quartz, and thus provides an additional level of observation in geomorphology. In this field, submicrometric metrology software represents an innovative tool due to its abilities to construct three-dimensional images of microreliefs, such as maps, topographic profiles and block diagrams, and to enhance the characterization of surfaces by the calculation of roughness indices. As an example, this tool is applied here to marks resulting from wind corrasion, glacial abrasion, coastal erosion and chemical change, on four series of samples of rock fragments and gravels constituted of quartz or quartzite. It is presented as a mean of analyzing, illustrating and measuring forms of erosion, as a procedure for characterizing and comparing surfaces, and as an additional source of information about the processes involved

Direct nanopatterning of polymer/silver nanoblocks under low energy electron beam irradiation

International audienc

Aggregation‐Induced Emission Properties of Copper Iodide Clusters

International audienc

New airtight transfer box for SEM experiments: Application to lithium and sodium metals observation and analyses

International audienc

New KRb 2 Sb 4 BO 13 and Rb 3 Sb 4 BO 13 compounds prepared by Rb + /K + ion exchange from the K 3 Sb 4 BO 13 ion conductor

International audienceThe crystal structures of new K3−xRbxSb4BO13 compounds (x = 2, 3), prepared via ion exchange from K3Sb4BO13, are reported. They adopt the triclinic crystal system and exhibit a localized Rb/K disorder at room temperature. The crystal structures were determined from single-crystal X-ray diffraction at T = 25 °C for both end-members of the family, leading to a reinvestigation of the K3Sb4BO13 crystal structure, and one intermediate composition KRb2Sb4BO13. The structure consists of hexagonal Sb3O9 bronze-like layers alternately separated by edge-sharing Sb2O10 dimers and BO3 triangles, forming interconnected tunnels filled by Rb+/K+ ions. The differences between the structures are based on the Rb/K disorder inside the tunnels conferring an advanced view of the cation diffusion paths. Additional information about conduction pathways was provided by the bond valence energy landscape (BVEL) method

Persistent viremia and presence of hepatitis e virus rna in pig muscle meat after experimental co-infection with porcine reproductive and respiratory syndrome virus

International audienceAlthough hepatitis E virus (HEV) transmission has been demonstrated after consumption of products containing infected pig liver, human cases can be also associated with other pig meat products, such as sausages. Data on HEV viremia and dissemination in muscle meat of infected animals are still sparse, especially during long-term infection. Previously, we have shown that experimental co-infection of pigs with HEV and porcine reproductive and respiratory syndrome virus (PRRSV) lengthens HEV infection up to 49 days and increases the likelihood of the presence of HEV RNA in the liver of the pig at a later stage of infection. In the present study, we show that during experimental HEV-PRRSV co-infection, prolonged HEV viremia, up to 49 days post-inoculation (dpi), is detected. The long-term viremia observed was statistically associated with the absence of HEV seroconversion. HEV RNA was also frequently detected, at a late stage of infection (49 dpi), in the three different types of muscle tested: femoral biceps, psoas major or diaphragm pillar. The HEV RNA load could reach up to 1.10(6) genome copies per gram of muscle. Detection of HEV in muscle meat was statistically associated with high HEV loads in corresponding liver and fecal samples. The presence of HEV in pig blood, femoral biceps and major psoas, corresponding to ham and tenderloin muscles respectively, is of concern for the food industry. Hence, these results indicate new potential risks for consumers and public health regarding pork products

Photoactive CuI-Cross-Linked Polyurethane Materials

International audienceUsing multinuclear copper iodide complexes as cross-linking agents in a polyurethane matrix, original photo-luminescent stimuli-responsive materials were synthesized. The intrinsic photoluminescence properties of the covalently incorpo-rated copper iodide complexes are thus transferred to the materials while retaining the beneficial characteristics of the polymer host. The transparent materials exhibit room-temperature phosphor-escence with emission switching properties by displaying luminescence thermochromism and solvatochromism. The lumi-nescence thermochromism is characterized by a change in the wavelength and intensity of the emission with temperature, and the vapochromic effect presents a contrasted response of extinction or exaltation according to the nature of the solvent of exposure. By combining the luminescence characteristics of photoactive copper iodide complexes with the ease of polymer processing, the application of these luminescent materials as phosphors in LED (light-emitting diode) devices was also demonstrated. The present study shows that the use of copper iodide complexes as cross-linkers in polymeric materials is a relevant strategy to design materials with enhanced functionalities in addition to their low cost and sustainable characteristics