Biomechanics of corneal wound healing

The re-establishment of tissue continuity, function, and mechanical proper ties after a through-and-through incision is an important issue in corneal surgery and trauma. Variations in healing can affect vision and patient activity during the recovery period, which may last up to five years. Growth factors introduced into the open wound have the potential to speed up the wound-healing process. The current investigation is concerned with quantitatively characterizing the mechanical properties of corneal tissue and evaluating the effects of epidermal growth factor (EGF), insulin-like growth factor (IGF), and platelet-derived growth factor (PDGF) on accelerating the wound-healing process as compared to a control group treated with phosphate-buffered saline (PBS). A 30 day topical application period was employed to assess the influence of EGF, IGF, and PDGF versus PBS treated corneas following through-and-through incisions. Corneal test specimens were harvested at 3, 10, and 30 days postoperatively and subjected to uniaxial tension loading (perpendicular to the wound) with load and displacement values recorded. Gross strength properties of fracture toughness, peak tangent modulus, and peak stress were calculated and the stiffness characteristics of the test specimens were obtained through curve fitting of the stress - stretch ratio profile. Comparison of strength properties indicated that IGF application enhanced peak stress, tangent modulus, and fracture toughness at 3 and 10 days while EGF application produced dominant responses at 30 days. Stiffness characterization revealed enhanced stiffness with EGF at 3 and 30 days, while PDGF treatment showed dominant stiffness characteristics at 10 days. The results suggest that select growth factors may preferentially augment the time course of corneal wound healing

Intégration de guides d'onde et microrésonateurs à modes de galerie par assemblage à puce retournée

Les microrésonateurs à modes de galerie ont suscité l’intérêt de la communauté scientifique au cours des dernières années en raison de leur potentiel en optique non linéaire à faible puissance et pour la réalisation de biocapteurs intégrés ultrasensibles. La difficulté de coupler les résonateurs à facteur de qualité ultra-élevé avec des guides d’onde intégrés sur puce a été établie comme l’un des principaux défis technologiques à surmonter avant d’envisager leur déploiement commercial à grande échelle. Ce mémoire de maîtrise fait l’étude d’une solution permettant de coupler des guides d’onde intégrés et des microrésonateurs à facteur de qualité ultra-élevés. La solution proposée consiste à fabriquer les résonateurs et les guides d’onde séparément et à les assembler par un procédé de soudure à puce retournée (flip-chip) avec une précision d’alignement sousmicrométrique. Un procédé de soudure par thermocompression permettant de lier des couches d’or de quelques centaines de nanomètres d’épaisseur a été développé. Les guides d’onde proposés sont des canaux suspendus en SiO2, de section transverse rectangulaire. Ils sont définis à même la couche d’oxyde thermique d’une gaufre de silicium par photolithographie et gravure ionique réactive (RIE). Leur design et leur fabrication sont optimisés afin de minimiser les pertes et d’obtenir un couplage critique avec le microrésonateur. La nécessité d’ancrer les guides d’onde suspendus au substrat a motivé l’élaboration d’un formalisme mathématique permettant de prédire les pertes causées par ces ancrages et d’étudier leur impact sur la répartition de l’énergie dans les modes des guides d’onde. L’effet de la propagation dans l’ancrage est décomposé sur la base des modes guidés afin de définir une matrice de propagation. L’effet combiné d’une série d’ancrages et de guides peut alors être obtenu en enchaînant les produits matriciels. Ce formalisme permet également de déduire une série de règles de design simples permettant d’optimiser la transmission des guides d’onde. La caractérisation des différentes sources de pertes a permis de déterminer que l’effet combiné de la rugosité et des ancrages limite la performance des guides d’onde et empêche de mesurer le signal transmis. La réduction des pertes optiques et l’augmentation de la précision d’alignement ont été identifiées comme des améliorations nécessaires pour les dispositifs futurs.----------Abstract Ultra-high quality-factor whispering gallery microresonators attracted considerable interest in the scientific community thanks to their potential applications in low-power nonlinear optics and ultra-sensitive label-free biosensing. Integrating resonators with on-chip waveguides is one of the main technological challenges to overcome before large scale commercial applications can emerge from research. This Master’s thesis presents a new solution for integrating SiO2 waveguides and microresonators. Resonators and waveguides are fabricated on separated wafers, and are then assembled using thermocompression flip-chip bonding with sub-micron placement accuracy. The proposed waveguide design consists of suspended channel waveguides that are etched out of a thermal oxide film and released by underetching the silicon substrate. Design and fabrication of the devices are optimized to reduce optical losses and obtain critical coupling. Achieving this coupling regime poses stringent requirements on alignment and coupling distance, and therefore a thermocompression process for bonding thin (hundreds of nanometers) gold layers has been developed and characterized. The necessity to use anchor structures to link the suspended waveguides to the substrate motivated the development of a mathematical model for predicting losses in those anchors and to model how they affect the modal distribution in the waveguide. Characterization propagation loss sources allowed to assess that the combined effect of sidewall roughness and anchor mode scambling is preventing adequate signal transmission through the waveguide. Together with flip-chip alignment imprecision, this factor was identified as a necessary improvement for future devices

Monitoring infiltration under a real on-site treatment system of domestic wastewater and evaluation of soil transfer function (Paris Basin, France)

The problematic of evacuation of treated domestic wastewater has been investigated through a field study on a real undrained on-site treatment system (UOSTS). This system imposes a special mode of infiltration into the soil which is irregular. In order to characterize the hydraulic properties of this type of flow, soil texture, organic matter content and in situ saturated hydraulic conductivity (Ks) were measured for each of 15 m² of soil under the bottom of the UOSTS. In addition, the variation of water table and rainfall and the evolution of soil moisture and matrix potential were monitored by using the sensors implanted under the system. The mean of the measured Ks is 100 times higher than values deduced from empirical pedotransfer functions based on the soil matrix properties. The measured Ks vary greatly on the 15 m² area. Moreover, large and variable quantities of stone fragments (> 2 mm) were found in the soil samples. These results suggest that a heterogeneous flow may occur in the stony soil via the macropores which shortcut the soil matrix. Indeed, according to their position, a non-uniform reaction of the sensors to the infiltration of treated wastewater was observed. In addition, two daily periodic peaks of water consumption in the house have been detected by the water content and tensiometer probes, confirming that the saturation rate is controlled by infiltration and not the water table

Improved Dual Network Model for Aging of Rubber Composites under Set Strains

A new model is presented to predict rubber behavior during chemical aging at fixed strains. The model is validated using a carbon black-filled nitrile butadiene rubber aged in air at 125 °C. The model improves upon Tobolsky’s dual network theory, designed for unfilled elastomers undergoing conventional aging but which has also often been used in rubber composites undergoing more complex aging scenarios. This work explores the shortcomings of the original model and demonstrates how the new model overcomes them. The model was validated using uniaxial tensile samples aged at 125 °C for 24–72 h at strains from 0–30%. The permanent set was measured, and the samples were tested on an Instron uniaxial test machine after aging. The cross-link density was estimated by equilibrium swelling. Results show that the new model more accurately models the stress–strain behavior to higher strains and provides more reliable estimates of chain scission and cross-linking after aging

Evapotranspiration evaluation using three different protocols on a large green roof in the greater Paris area

Nature-based solutions have appeared as relevant solutions to mitigate urban heat islands. To improve our knowledge of the assessment of this ecosystem service and the related physical processes (evapotranspiration), monitoring campaigns are required. This was the objective of several experiments carried out on the Blue Green Wave, a large green roof located in Champs-sur-Marne (France). Three different protocols were implemented and tested to assess the evapotranspiration flux at different scales: the first one was based on the surface energy balance (large scale); the second one was carried out using an evapotranspiration chamber (small scale); and the third one was based on the water balance evaluated during dry periods (point scale). In addition to these evapotranspiration estimates, several hydrometeorological variables (especially temperature) were measured. Related data and Python programs providing preliminary elements of the analysis and graphical representation have been made available. They illustrate the space–time variability in the studied processes regarding their observation scale. The dataset is available at https://doi.org/10.5281/zenodo.8064053 (Versini et al., 2023).</p

Characterising the friction coefficient between rubber O-rings and a rigid surface under extreme pressures

Previous research into the friction behaviour of elastomers has typically focused on the effects of velocity, contact pressure, counter surface and lubrication on the coefficient of friction. O-ring type elastomer seals are common in many different industries. Friction plays a critical role during the setting and in service of these components. An experimental O-ring friction testing rig has been developed that can measure the effects of sliding speed and hydrostatic pressure on elastomer friction. Finite element analysis (FEA) packages can adopt fixed friction coefficients or ones that are pressure dependent. For the latter case, the dependence of the frictional behaviour is typically obtained from the instantaneous stress response at any given pressure and then related to the normal force response. The friction rig described in this paper uses industry standard dimensions for the O-ring gland, the pre-compression levels, extrusion gap size and pressure rating. The coefficient of friction is derived by dividing the measured friction force by the normal force, which was determined using an FEA modelling approach, as it could not be measured directly. Finally, a relationship between the frictional velocity and surface roughness is obtained in order to provide a frequency dependent Coefficient of Friction (CoF) that is easily translatable between surfaces

Use of green roofs to solve storm water issues at the basin scale – Study in the Hauts-de-Seine County (France)

International audienceAt the building scale, green roof has demonstrated a positive impact on urban runoff (decrease in the peak discharge and runoff volume). This work aims to study if similar impacts can be observed at basin scale. It is particularly focused on the possibility to solve some operational issues caused by storm water.For this purpose, a methodology has been proposed. It combines: a method to estimate the maximum roof area that can be covered by green roof, called green roofing potential, and an urban rainfall-runoff model able to simulate the hydrological behaviour of green roof.This methodology was applied to two urban catchments affected one by flooding and the other one by combined sewage overflow. The results show that green roof can reduce the frequency and the magnitude of such problems depending on the covered roof surface. Combined with other infrastructures, they represent an interesting solution for urban water management

L’art contemporain pour penser la mémoire antillaise post-esclavagiste et coloniale

Comment penser la mémoire antillaise post-esclavagiste et coloniale aujourd’hui ? Le travail de Jay Ramier, ancré dans une réflexion politique de la représentation du corps noir, prend sa source dans la pratique du graffiti et s’inspire de la culture populaire visuelle et musicale africaine-américaine. Les poses et les figures créées et célébrées par le hip-hop auxquelles Jay Ramier se réfère s’inscrivent dans une généalogie longue qui remonte aux temps de l’esclavage. Les vêtements, les bijoux, les rituels qu’il observe dans la Guadeloupe où il est né font écho aux corps contemporains étatsuniens habillés de couleurs et de matières brillantes qu’il représente. Les archives photographiques qu’il collectionne, les souvenirs d’enfance qu’il convoque sont des jalons qu’il adosse à sa pratique picturale. Dans cet entretien, il interroge l’histoire coloniale post-esclavagiste et s’y confronte de façon consciente, nous indiquant qu’il ne faut jamais perdre sa vigilance politique tout en laissant ouvertes les possibilités poétiques offertes par la création.How do we think about the post-slavery and colonial Caribbean memory today? Jay Ramier's work is inspired by popular African-American visual and musical culture; it is rooted in the practice of graffiti and is deeply anchored in a political reflection on the representation of the black body. The poses and figures created and celebrated by the hip-hop culture to which Ramier refers are part of a long genealogy that goes back to the times of slavery. The contemporary bodies dressed in colors and shiny materials that he represents in his work echo the clothes, jewelry and rituals he observes in Guadeloupe where he was born. The photographic archives that he collects, the childhood memories that he convokes are milestones that he leans his pictorial practice on. In this interview, he questions the post-slavery colonial history and confronts it in a conscious way. In doing so, he emphasizes the importance of not losing one's political consciousness while leaving open the poetic possibilities offered by creation. ¿Cómo pensar hoy la memoria antillana posesclavista y colonial? El trabajo de Jay Ramier, basado en una reflexión política acerca de la representación del cuerpo negro, se origina en la práctica del grafiti y se inspira en la cultura popular visual y musical afronorteamericana. Las poses y las figuras creadas y celebradas por el hip-hop a las que se refiere Jay Ramier se inscriben en una larga genealogía que se remonta a la época de la esclavitud. La vestimenta, la joyería, los rituales que observa en Guadalupe, donde nació, resuenan en los cuerpos contemporáneos estadounidenses vestidos de colores y de materiales brillantes que representa. Los archivos fotográficos que colecciona, los recuerdos de infancia a los que alude son jalones que respaldan su práctica pictórica. En esta entrevista interroga la historia colonial posesclavista, confrontándose con ella de manera consciente, indicándonos que nunca debe perderse la vigilancia política, al tiempo que deja abiertas las posibilidades poéticas que ofrece la creación.Como pensar a memória das Antilhas pós-escravista e colonial hoje? O trabalho de Jay Ramier, baseado numa reflexão política da representação do corpo negro, origina-se na prática do graffiti e inspira-se da cultura popular visual e musical africana e americana. As poses e as figuras criadas e celebradas pelo hip-hop referidas por Jay Ramier inscrevem-se numa genealogia longa que volta no tempo da escravidão. Os vestidos, as joias, os rituais que ele observa na Guadalupe onde nasceu lembram os corpos contemporâneos nos Estados Unidos vestidos de cores e de materiais cintilantes que ele representa. Os documentos fotográficos que Ramier colecciona, as lembranças da infância que ele convoca são como marcos de sua prática pictural. Nesta entrevista, ele questiona a história colonial pós-escravista que ele enfrenta de maneira consciente, indicando que é necessário mantermos a nossa vigilância política, deixando abertas as possibilidades poéticas oferecidas pela criação

Characterization of the Evapotranspiration flux on a Blue Green Solution (Blue Green Wave)

International audienceThe rapid growth of urban areas, jointly with the effects of climate change, is the major challenge to face the transition towards sustainable cities. Climate change leads to substantial modifications of the water cycle in cities, increasing the frequency of intense precipitation, drought and heat wave events. The replacement of natural surfaces by dark and impervious ones is the main cause of Urban Heat Islands (UHI) phenomenon. UHIs are microclimates characterized by significant temperature differences between inner cities and the surrounding rural areas. Part of a solution to tackle this issue is the re-naturalization of cities through the installation of Blue Green Solutions (BGS), such as green roofs, favoring the evapotranspiration (ET) process and thus reducing the air temperature. To benefit BGS implementation, it is crucial to understand the thermo-hydric processes that govern them. For this purpose, the ET process of a 1 ha green roof implemented in front of the Ecole de Ponts ParisTech (France) called Blue Green Wave (BGW) was studied to determine its possible cooling effect to mitigate UHIs. Therefore, three methods were tested and compared to estimate ET: (i) the water balance during dry periods through the difference on the soil moisture content measured via a wireless sensors network, (ii) the absolute humidity measured by a dynamic transpiration chamber, and (iii) a scintillometer to assess the sensible heat flux, which allows to deduce the latent heat flux by computing the energy balance. The wireless sensors demonstrated to assess correctly ET trends over long time periods, while the dynamic chamber allows to identify more precisely the ET behavior during shorter periods of measurement due to a better resolution. Indeed, ET computed via the water budget appeared significantly high compared to the values estimated by the dynamic chamber, and without showing an obvious daily pattern. In addition, ET trends estimated by both scintillometer and transpiration chamber methods were very close, but the corresponding values suffered from a significant difference. The divergence in ET flux computed by the three methods can be caused by: (1) errors in the sensible heat flux estimated by the scintillometer, leading overestimations of the latent heat flux; (2) noisy data of soil water content, induced by the rainfall events and the local soil characteristics where the sensors are implemented, and (3) modifications of the atmospheric conditions within the transpiration chamber. More generally, ET appeared higher in spring season and during the first days of summer, when high temperatures were reached and soil water content was enough to support ET without inducing a deficit for plants. Conversely, despite significant temperatures at the end of summer, ET rate was lower due to the lack of water content in the soil. This suggests that during summer, when the UHI intensity is stronger and the cooling effects of the green roofs are needed, the ET potential could not be sufficient. To go further in the space-time characterization of ET flux, additional experiments and multi-fractal analysis will be carried out soon

Structures poreuses tridimensionnelles de biopolymères pour l'ingénierie tissulaire

Les structures poreuses tridimensionnelles fonctionnelles possèdent un fort potentiel dans de nombreuses applications biomédicales. Nous avons ainsi orienté nos travaux vers l'élaboration de nouveaux matériaux capables de répondre à plusieurs critères pour l'ingénierie tissulaire osseuse. Du fait de leur biodisponibilité, leur biocompatibilité et leur biodégradabilité, les poly(3-hydroxyalcanoate)s (PHAs) présentent des propriétés particulièrement adaptées pour ce type d'application. Dans un premier temps, nous avons développé de nouvelles stratégies contrôlées, rapides et aisées, de synthèse de copolymères à blocs à base de PHAs ainsi que de production d'oligoesters par activation sous micro-ondes. Par ailleurs, l'absence d'effet non-thermique des micro-ondes sur la polymérisation par ouverture de cycles du D,L-lactide a également été démontrée grâce à une investigation systématique. Dans un second temps, l'élaboration de divers matériaux tridimensionnels nanofibreux par électrofilage ( electrospinning ) a été réalisée afin de fabriquer des structures à base de PHAs de différentes morphologies avec la formation de fibres dans une large gamme de diamètres ou encore avec des topographies de surface contrôlées (nanopores ou rainures). Plusieurs stratégies de fonctionnalisation superficielle ont été également mises au point telles que le dépôt de nanoparticules d'hydroxyapatite selon un procédé original couplant les techniques de l' electrospinning et de l' electrospraying , ou encore le co-electrospinning de la gélatine. De nouvelles approches de couplage covalent de molécules en surface des fibres de PHAs par chimie click ou par ouverture de fonctions époxyde préalablement introduites ont également été développées. Enfin, des investigations biologiques in vitro ont permis de mettre en lumière les potentialités de ces nouveaux matériaux nanofibreux comme supports de culture cellulaire à travers l'évaluation de l'adhérence, la prolifération et la différentiation de cellules souches mésenchymateuses humaines (hMSCs) pluripotentes vers un phénotype ostéoblastiqueFunctional three-dimensional porous scaffolds possess a high potential in many biomedical applications. We have thus oriented our work toward the elaboration of new materials able to meet several criteria for bone tissue engineering. Due to their renewability, their biocompatibility, and their biodegradability, poly(3-hydroxyalkanoate)s (PHAs) exhibit properties particularly suitable for this type of application. First, we have developed novel controlled strategies that are rapid and straightforward for the synthesis of PHA-based block copolymers as well as for the production of oligoesters upon microwave activation. Moreover, the absence of non-thermal microwave effect in the ring-opening polymerization of D,L-lactide was also demonstrated through a systematic investigation. Second, the elaboration of miscellaneous three-dimensional nanofibrous materials by electrospinning has been performed to produce PHA-based frameworks with different morphologies through the formation of fibers in a wide range of diameters or with controlled surface topography (nanopores or channels). Several strategies for surface functionalization have also been implemented, such as the deposition of hydroxyapatite nanoparticles by an original combination of the electrospinning and electrospraying techniques or by the co-electrospinning of gelatin. New approaches toward covalent coupling of molecules on the PHA fiber surface by click chemistry or by ring-opening of previously introduced epoxide groups have also been developed. Lastly, in-vitro biological investigations have highlighted the potential of these new nanofibrous materials as cell culture supports through the evaluation of the adhesion, proliferation, and differentiation of pluripotent human mesenchymal stem cells (hMSCs) toward an osteoblastic phenotypePARIS-EST-Université (770839901) / SudocSudocFranceF