The TGF-β/Smad Repressor TG-Interacting Factor 1 (TGIF1) Plays a Role in Radiation-Induced Intestinal Injury Independently of a Smad Signaling Pathway

Despite advances in radiation delivery protocols, exposure of normal tissues during the course of radiation therapy remains a limiting factor of cancer treatment. If the canonical TGF-β/Smad pathway has been extensively studied and implicated in the development of radiation damage in various organs, the precise modalities of its activation following radiation exposure remain elusive. In the present study, we hypothesized that TGF-β1 signaling and target genes expression may depend on radiation-induced modifications in Smad transcriptional co-repressors/inhibitors expressions (TGIF1, SnoN, Ski and Smad7). In endothelial cells (HUVECs) and in a model of experimental radiation enteropathy in mice, radiation exposure increases expression of TGF-β/Smad pathway and of its target gene PAI-1, together with the overexpression of Smad co-repressor TGIF1. In mice, TGIF1 deficiency is not associated with changes in the expression of radiation-induced TGF-β pathway-related transcripts following localized small intestinal irradiation. In HUVECs, TGIF1 overexpression or silencing has no influence either on the radiation-induced Smad activation or the Smad3-dependent PAI-1 overexpression. However, TGIF1 genetic deficiency sensitizes mice to radiation-induced intestinal damage after total body or localized small intestinal radiation exposure, demonstrating that TGIF1 plays a role in radiation-induced intestinal injury. In conclusion, the TGF-β/Smad co-repressor TGIF1 plays a role in radiation-induced normal tissue damage by a Smad-independent mechanism

Comparison between numerical and experimental water-in-oil dispersion in a microchannel

International audienceThe dispersion of water inside a flow of oil is investigated in a microfluidic device, producing a water-in-oilemulsion. The liquid–liquid flow mainly differs from those presented in existing literature through its high capillarynumber (between 3 and 14), and in the head-on collision between water and oil streams. By comparing withexperimental data, numerical simulations can provide more information about the topology of the flow. A coupledVolume of Fluid and Level Set method (CLSVOF) is used to treat the interface between both phases andincompressible Navier-Stokes equations are solved. Three set of parameters, close to those in the experimentalsetup, are investigated to compare experimental and numerical results. The comparison between experimentsand simulation provides a precise knowledge of the liquid-liquid dispersion process and the overall flow patternwithin the microfluidic device

Comparison of different tracers for PIV measurements in EHD airflow

International audienceIn this study, a proposed method for selecting a tracer for PIV measurement in EHD flows was developed. To begin with, several published studies were identified that exploit different tracers; such as oil smoke, cigarette smoke, and TiO 2. An assortment of tracers was then selected based on comparisons with conventional dimensionless numbers; Stokes number (St), Archimedes number (Ar) and electrical mobility ratio (M). Subsequently, an experimental study for testing tracers was developed, which enabled the velocity profile of an ionic wind generated by a needle/ring configuration to be measured. Air velocity measurements carried out with a Pitot tube, considered as the reference measurements, were compared to PIV measurements for each tracer. In addition, the current-voltage curves and the evolution of the current during seeding were measured. All the experimental results show that TiO 2 , SiO 2 microballoons and incense smoke are the ideal tracers in the series of tracers investigated

Distribution of thermal energy of child-droplets issued from an optimal micro-explosion

The micro-explosion phenomenon is involved in emulsified fuel droplets placed in a hot atmosphere, such as spray combustion. Droplets of water-in-sunflower oil emulsion are used, since they are representative of a class of emulsions used in practical applications of biofuels. Once the micro-explosion is triggered after a short delay, the rapid (<= 1 ms) vaporization of the inside water droplets and the subsequent disintegration of the emulsion droplet blow the fragmented droplets away. These fragmented droplets are called "child-droplets", and they are too small and fast for an on-the-fly infra-red imaging thermal characterization. The present study focuses on the thermal reaction of a thin plate when impacted by them. Thorough and detailed tests are carried out, to make sure that the plate and the acquisition system are collecting a data that is actually representative of the child-droplets thermal energy. A quantitative post-processing is applied to the transient temperature field on the plate. It leads to the thermal energy of the whole plate, and of representative samples of individual child-droplets. The results show that their thermal energy is governed by a log-normal distribution

Distribution of thermal energy of child-droplets issued from an optimal micro-explosion

The micro-explosion phenomenon is involved in emulsified fuel droplets placed in a hot atmosphere, such as spray combustion. Droplets of water-in-sunflower oil emulsion are used, since they are representative of a class of emulsions used in practical applications of biofuels. Once the micro-explosion is triggered after a short delay, the rapid (<= 1 ms) vaporization of the inside water droplets and the subsequent disintegration of the emulsion droplet blow the fragmented droplets away. These fragmented droplets are called "child-droplets", and they are too small and fast for an on-the-fly infra-red imaging thermal characterization. The present study focuses on the thermal reaction of a thin plate when impacted by them. Thorough and detailed tests are carried out, to make sure that the plate and the acquisition system are collecting a data that is actually representative of the child-droplets thermal energy. A quantitative post-processing is applied to the transient temperature field on the plate. It leads to the thermal energy of the whole plate, and of representative samples of individual child-droplets. The results show that their thermal energy is governed by a log-normal distribution

Gas flow measurements by 3D Particle Tracking Velocimetry using coloured tracer particles

This work describes an original approach for 3D Particle Tracking Velocimetry (3D PTV), applicable also for gaseous flows and based on tracer particles of different colours. On the images acquired by several cameras, tracer particles are handled by colour recognition and 3D localisation. Then, the PTV tracking algorithm rebuilds the trajectories of the tracer particles using a criterion of Minimum Acceleration. Theoretical and numerical calculations are first presented to demonstrate that the employed coloured tracer particles follow in a suitable manner the considered gas flows. The test cases analysed comprise low Reynolds number flows involving a variety of interesting features, in particular boundary layer separation, continuous acceleration and recirculations. The experimental setup and the 3D PTV procedure are then described. All results are analysed in a quantitative manner and demonstrate the performance of the developed measurement strategy in gas flows

Improved 3-D Particle Tracking Velocimetry with colored particles

This work describes an original approach for 3D Particle Tracking Velocimetry (3D PTV), applicable also for gaseous flows and based on tracer particles of different colours. On the images acquired by several cameras, tracer particles are handled by colour recognition and 3D localisation. Then, the PTV tracking algorithm rebuilds the trajectories of the tracer particles using a criterion of Minimum Acceleration. Theoretical and numerical calculations are first presented to demonstrate that the employed coloured tracer particles follow in a suitable manner the considered gas flows. The test cases analysed comprise low Reynolds number flows involving a variety of interesting features, in particular boundary layer separation, continuous acceleration and recirculations. The experimental setup and the 3D PTV procedure are then described. All results are analysed in a quantitative manner and demonstrate the performance of the developed measurement strategy in gas flows