Near-wall nanovelocimetry based on Total Internal Reflection Fluorescence with continuous tracking

The goal of this work is to make progress in the domain of near-wall velocimetry. The technique we use is based on the tracking of nanoparticles in an evanescent field, close to a wall, a technique called TIRF (Total Internal Reflection Fluorescence)-based velocimetry. At variance with the methods developed in the literature, we permanently keep track of the light emitted by each particle during the time the measurements of their positions ('altitudes') and speeds are performed. By performing the Langevin simulation, we quantified effect of biases such as Brownian motion, heterogeneities induced by the walls, statistical biases, photo bleaching, polydispersivity and limited depth of field. Using this method, we obtained slip length on hydrophilic surfaces of 1$\pm$5 nm for sucrose solution, and 9$\pm$10 nm for water; On hydrophobic surface, 32$\pm$5 nm for sucrose solution, and 55$\pm$9 nm for water. The errors (based on 95% confidence intervals) are significantly smaller than the state-of-the-art, but more importantly, the method demonstrates for the first time a capacity to measure slippage with a satisfactory accuracy, while providing a local information on the flow structure with a nanometric resolution. Our study confirms the discrepancy already pointed out in the literature between numerical and experimental slip length estimates. With the progress conveyed by the present work, TIRF based technique with continuous tracking can be considered as a quantitative method for investigating flow properties close to walls, providing both global and local information on the flow.Comment: 24 pages, 13 figure

Anisotropic super-attenuation of capillary waves on driven glass interfaces

Metrological AFM measurements are performed on the silica glass interfaces of photonic band-gap fibres and hollow capillaries. The freezing of attenuated out-of-equilibrium capillary waves during the drawing process is shown to result in a reduced surface roughness. The roughness attenuation with respect to the expected thermodynamical limit is determined to vary with the drawing stress following a power law. A striking anisotropic character of the height correlation is observed: glass surfaces thus retain a structural record of the direction of the flow to which the liquid was submitted

Gene expression profile of androgen modulated genes in the murine fetal developing lung

<p>Abstract</p> <p>Background</p> <p>Accumulating evidences suggest that sex affects lung development. Indeed, a higher incidence of respiratory distress syndrome is observed in male compared to female preterm neonates at comparable developmental stage and experimental studies demonstrated an androgen-related delay in male lung maturation. However, the precise mechanisms underlying these deleterious effects of androgens in lung maturation are only partially understood.</p> <p>Methods</p> <p>To build up a better understanding of the effect of androgens on lung development, we analyzed by microarrays the expression of genes showing a sexual difference and those modulated by androgens. Lungs of murine fetuses resulting from a timely mating window of 1 hour were studied at gestational day 17 (GD17) and GD18, corresponding to the period of surge of surfactant production. Using injections of the antiandrogen flutamide to pregnant mice, we hunted for genes in fetal lungs which are transcriptionally modulated by androgens.</p> <p>Results</p> <p>Results revealed that 1844 genes were expressed with a sexual difference at GD17 and 833 at GD18. Many genes were significantly modulated by flutamide: 1597 at GD17 and 1775 at GD18. Datasets were analyzed by using in silico tools for reconstruction of cellular pathways. Between GD17 and GD18, male lungs showed an intensive transcriptional activity of proliferative pathways along with the onset of lung differentiation. Among the genes showing a sex difference or an antiandrogen modulation of their expression, we specifically identified androgen receptor interacting genes, surfactant related genes in particularly those involved in the pathway leading to phospholipid synthesis, and several genes of lung development regulator pathways. Among these latter, some genes related to Shh, FGF, TGF-beta, BMP, and Wnt signaling are modulated by sex and/or antiandrogen treatment.</p> <p>Conclusion</p> <p>Our results show clearly that there is a real delay in lung maturation between male and female in this period, the latter pursuing already lung maturation while the proper is not yet fully engaged in the differentiation processes at GD17. In addition, this study provides a list of genes which are under the control of androgens within the lung at the moment of surge of surfactant production in murine fetal lung.</p

Micromechanisms of fracture propagation in glassy polymers

While most glassy polymers are nominally brittle at macroscopic scales, they are known to exhibit plastic deformation in indentation, scratching, and microcutting when the loaded region is sufficiently small. The same applies to the micrometer size process zone at the tip of a propagating crack. While the presence and approximate size of this microscale plastic zone is well described by the Dugdale model, the prediction of the toughness of these materials is not possible without accounting for the details of the local large strain field and the work hardening behaviour of these polymers, which can be inferred from their response to compressive tests. Strain localization mechanisms such as crazing or shear banding should also be taken into account to properly model toughness. Finally, viscoplastic creep plays a major role in determining the dependence of the toughness on crack propagation velocity, as well as the important difference between the initiation and propagation toughness, which is responsible for the occurrence of a characteristic stick-slip propagation under some loading conditions. Please click Additional Files below to see the full abstract

Fresnel diffraction in an interferometer: application to MATISSE

While doing optical study in an instrument similar to the interferometers dedicated to the Very Large Telescope (VLT), we have to take care of the pupil and focus conjugations. Modules with artificial sources are designed to simulate the stellar beams, in terms of collimation and pupil location. They constitute alignment and calibration tools. In this paper, we present such a module in which the pupil mask is not located in a collimated beam thus introducing Fresnel diffraction. We study the instrumental contrast taking into account the spatial coherence of the source, and the pupil diffraction. The considered example is MATISSE, but this study can apply to any other instrument concerned with Fresnel diffraction.Comment: 8 pages- to appear in Proceedings of SPIE Astronomical Telescopes and Instrumentation 201

Large and non-linear permeability amplification with polymeric additives in hydrogel membranes

Hydrogels which are hydrophilic and porous materials have recently emerged as promising systems for filtration applications. In our study, we prepare hydrogel membranes by the photopolymerization of a mixture of poly (ethylene glycol) diacrylate (PEGDA) and large poly(ethylene glycol) (PEG) chains of 300 000 g.mol-1 in the presence of a photoinitiator. We find that this addition of free PEG chains induces a large and non-linear increase of the water permeability. Indeed, by changing the content of PEG chains added, we obtain variations of the hydrogel water permeability over two orders of magnitude. The highest water permeability values are obtained for the membranes when the PEG concentration is equal to its critical overlap concentration C*. Moreover, we find that the flow rate of water through the membranes varies non-linearly with the pressure. We relate this result to the deformability of the membranes as the applied pressure leads to a compression of the pores. This study provides new perspectives for the design of flexible hydrogel membranes with controlled permeability and their application in water treatment and bioseparation

Fracture propagation in glassy polymers: From nanometer to centimeter

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Indications and results of liver transplantation for Echinococcus alveolar infection: an overview

Background: Alveolar echinococcosis (AE) of the liver, caused by the larval stage of the fox tapeworm Echinococcus multilocularis, has the characteristics of a slow-growing liver cancer. It is one of the rare parasitic diseases for which a parasitolytic drug is not yet available, and AE is lethal in the absence of appropriate therapeutic management. Complete surgical resection of the parasite at an early stage of infection provides favourable prospects for cure, but, due to a long clinical latency, many cases are diagnosed at an advanced stage, so that partial liver resection can be performed in only 35% of patients. Benzimidazole (BZM) treatment is given in inoperable cases but these compounds are only parasitostatic, and lifelong therapy is required. During the past 20 years some centres have considered liver transplantation (LT) for the treatment of incurable AE. Methods: Our review summarizes the results of this experience based on a series of 47 European patients who received transplants between 1985 and 2002, tries to specify the real place of LT for AE, and underlines the measures that could be undertaken in the future to improve the results. Results: Five-year survival was 71%. Five-year survival without recurrence was 58%. Major technical difficulties related either to previous laparotomies or to the loco-regional involvement were observed. The nine early deaths concerned AE patients with a long past-history of symptomatic AE (iterative cholangitis, secondary biliary cirrhosis). Five late deaths were directly related to ongoing AE, located in the brain in three cases, a very rare AE location that was not investigated before LT in these patients. Conclusions: In general, the pre-LT screening for distant AE metastases appeared insufficient in this series. Heavy immunosuppressive schemes, absence or delayed re-introduction of BZM after LT have clearly played a role in this unfavourable course. This unique experience indicates that, despite major technical difficulties, LT for incurable AE is feasible and could be discussed in very symptomatic cases. Before LT, interventional radiology should be preferred to repeated laparotomies. Pre-LT and post-LT BZM treatment is mandatory. A careful evaluation of possible distant metastases should be done before the decision for LT is made. After LT, the possibility of an ongoing AE must be permanently kept in mind. This could be reduced by lightening the immunosuppressants, carefully following the specific circulating antibodies, and applying a systematic radiological evaluation, not only to the graft but also to the lungs and the brai

Sieving and clogging in PEG-PEGDA hydrogel membranes

Hydrogels are promising systems for separation applications due to their structural characteristics (i.e. hydrophilicity and porosity). In our study, we investigate the permeation of suspensions of rigid latex particles of different sizes through free-standing hydrogel membranes prepared by photopolymerization of a mixture of poly (ethylene glycol) diacrylate (PEGDA) and large poly (ethylene glycol) (PEG) chains of 300 000 g.mol-1 in the presence of a photoinitiator. Atomic force microscopy (AFM) and cryoscanning electron microscopy (cryoSEM) were employed to characterize the structure of the hydrogel membranes. We find that the 20 nm particle permeation depends on both the PEGDA/PEG composition and the pressure applied during filtration. In contrast, we do not measure a significant permeation of the 100 nm and 1 $\mu$m particles, despite the presence of large cavities of 1 $\mu$m evidenced by cryoSEM images. We suggest that the PEG chains induce local nanoscale defects in the cross-linking of PEGDA-rich walls separating the micron size cavities, that control the permeation of particles and water. Moreover, we discuss the decline of the permeation flux observed in the presence of latex particles, compared to that of pure water. We suggest that a thin layer of particles forms on the surface of the hydrogels

Approche méthodologique pour intégrer des scénarios de végétation forestière tenant compte des changements climatiques dans la prédiction des méthodes de restauration minière sous climat humide au Québec

La restauration des parcs à résidus générateurs de drainage minier acide (DMA) constitue un défi environnemental important pour l’industrie minière. Au Québec, différentes techniques de contrôle du DMA provenant de parcs à résidus sont utilisées pour empêcher la contamination de l’environnement, parmi lesquelles on retrouve les recouvrements d’ingénierie appelés barrières à l’oxygène (Bussière et al., 2003; Aubertin et al., 2016; Bussière et Guittonny, 2020). Dans le contexte de restauration de sites miniers, l’objectif est de mettre en place un recouvrement permettant de contrôler la contamination et pouvant supporter une végétation pérenne qui s’intègre bien à l’environnement du site (MEND, 2014). Cependant, la végétation peut affecter le bilan hydrique, les propriétés des matériaux des barrières à l’oxygène et, par le fait même, leur performance (MEND, 2014; Guittonny et al., 2018). À ce jour, les caractéristiques à long terme de la végétation forestière qui s’installera sur les parcs à résidus restaurés sont encore mal connues et nécessitent de prendre en compte l’influence des changements climatiques (CC) sur l’évolution des écosystèmes. En effet, les CC conduisent à une redistribution généralisée des espèces à l’échelle planétaire (IPCC, 2014; Bonebrake et al., 2018). Un changement des conditions climatiques pourrait entraîner un changement dans la distribution des espèces d’arbres et dans la composition des forêts. Les conditions climatiques ont déjà changé et affectent déjà la distribution de certaines espèces d’arbres au Canada (Williamson et al., 2009; Price et al., 2013; Berteaux et al., 2014; Ressources naturelles Canada, 2017). Le climat existant dans une région où une espèce vit et se reproduit se trouvera vraisemblablement ailleurs dans l’avenir (McKenney et al., 2007; Berteaux et al., 2014; Sittaro et al., 2017). Le présent rapport vise à proposer une approche méthodologique pour la prise en compte de l’influence de la végétation forestière sur la performance à long terme des barrières à l’oxygène sur base des scénarios de végétation sous CC au Québec. En amont de ce rapport, une revue de littérature sur les changements d’aire de répartition des essences clés de la forêt feuillue et boréale, en réponse aux CC, a été réalisée (Botula et al., 2019). Celle-ci a permis d’identifier la composition de la végétation qui sera présente de manière plausible d’ici 2100 pour deux sites miniers : l’un en activité, la mine Westwood en Abitibi, et l’autre abandonné, le site Lorraine au Témiscamingue. En se basant sur ces travaux, des scénarios de végétation d’ici 2100 seront proposés dans ce rapport pour les deux sites, ainsi que des gammes de valeurs correspondantes pour les paramètres de végétation à intégrer aux modèles numériques hydrogéologiques utilisés pour la prédiction de la performance des barrières à l’oxygène. Les résultats présentés ici pourront aider les partenaires miniers à déterminer si l’évolution de la végétation sur leurs sites suite aux CC affectera la performance à long terme des méthodes de restauration utilisées, et si des mesures de gestion de cette végétation devront être mises en place. Ce rapport est divisé en trois chapitres et se termine par une conclusion et des suggestions : le premier chapitre est une synthèse des connaissances en lien avec les effets des CC sur la distribution des essences clés de la forêt feuillue et boréale au Québec; le deuxième chapitre est une synthèse des connaissances en lien avec l’influence de la végétation forestière sur la performance des barrières à l’oxygène au Québec; le troisième chapitre est une analyse qualitative de l’influence des CC sur les paramètres de la végétation utilisés pour évaluer la performance des barrières à l’oxygène avec application à deux sites miniers : Westwood et Lorraine