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International audience; The present paper focuses on solute segregation occurring in directional solidification processes with sharp solid/liquid interface, like silicon crystal growth. A major difficulty for the simulation of such processes is their inherently multi-scale nature: the impurity segregation problem is controlled at the solute boundary layer scale (micrometers) while the thermal problem is ruled at the crucible scale (meters). The thickness of the solute boundary layer is controlled by the convection regime and requires a specific refinement of the mesh of numerical models. In order to improve numerical simulations, wall functions describing solute boundary layers for convecto-diffusive regimes are derived from a scaling analysis. The aim of these wall functions is to obtain segregation profiles from purely thermo-hydrodynamic simulations , which do not require solute boundary layer refinement at the solid/liquid interface. Regarding industrial applications, various stirring techniques can be used to enhance segregation, leading to fully turbulent flows in the melt. In this context, the scaling analysis is further improved by taking into account the turbulent solute transport. The solute boundary layers predicted by the analytical model are compared to those obtained by transient segregation simulations in a canonical 2D lid driven cavity configuration for validation purposes. Convective regimes ranging from laminar to fully turbulent are considered. Growth rate and molecular diffusivity influences are also investigated. Then, a procedure to predict concentration fields in the solid phase from a hydrodynamic simulation of the solidification process is proposed. This procedure is based on the analytical wall functions and on solute mass conservation. It only uses wall shear-stress profiles at the solidification front as input data. The 2D analytical concentration fields are directly compared to the results of the complete simulation of segregation in the lid driven cavity configuration. Finally, an additional output from the analytical model is also presented. We put in light the correlation between different species convecto-diffusive behaviour; we use it to propose an estimation method for the segregation parameters of various chemical species knowing segregation parameters of one specific species.

International audience; We combine an effective diffusivity model with a numerical approach initially proposed by Meyer (1981) to simulate transient heat and mass transfer phenomena in a directionally solidifying Sn-Bi rod. This particularly efficient 1D numerical model is light enough to be used within the frame of optimization methods at reasonable numerical cost. This approach is tested against reference in situ measurements obtained under microgravity conditions during the Mephisto program. We simulate the final homogenization transient of several experimental runs with different pulling velocities. The solid/liquid interface temperature evolution with time is extracted from the simulations and compared with that obtained by Seebeck in line measurements. After optimization of the model the observed discrepancy between the simulated and measured data is less than 1.5%. This validates both the proposed very efficient 1D numerical approach and the consistency of the set of thermophysical parameters values for dilute Sn-Bi alloys.

International audience; Over the last decade, various nanomaterial systems have been developed as important and powerful strategies to deliver conventional drugs, recombinant proteins, vaccines, aptamers, siRNA, nucleotides and genes. In particular, alongside polymeric, solid–lipid, magnetic and metal based nanoparticles, polymeric micelles and linear polymers, dendrimer nanostructures represent useful nano-carriers in medicine. Today's challenge to find safe and innovative drugs remains as critical as ever.In this review, for the first time, we define the term dendrimer space concept as an approach that affords a new paradigm of thought for medicinal chemists and opens new and promising avenues toward the identification of original dendrimer-based drugs. Thus, the dendrimer space defines a new ‘druggable’ cluster that is included within the vast volume of chemical space. The dendrimer space concept took its inspiration from both the concepts of ‘druglikeness’ and ‘druggability’, which are fully and practically integrated into the drug discovery process, and from different methods of exploration and navigation, such as the ‘chemography’ approach, in chemical space. It was further influenced by the large number of biomedical applications using dendrimers that were developed from only a handful existing in the early 1990s.To define the boundaries of the dendrimer space, this review first focuses on the recent progress in the exploration of specific sub-chemical spaces (clusters within the continuum of chemical space). Chemical space is defined as the entire collection of all meaningful chemical compounds, and its full examination is insuperable. The compounds included in these different clusters can be mapped onto the coordinates of a multidimensional descriptor space, with such variables as physicochemical properties or topological characteristics, and are based on the concepts of ‘druglikeness’ (drug-like space) and ‘leadlikeness’. In addition, the discrete areas occupied by specific biologically active compounds define the boundaries of the ‘target class’ clusters, which can overlap the drug-like space. Second, this review gives an overview of the nanopharmaceutical properties of dendrimers, both as biologically active derivatives per se and as drug delivery systems. Finally, several perspectives using dendrimers as new delivery platforms based on the concept of dendrimer space are presented.

International audience; Most high flux reactors possess for research purposes fuel elements composed of plates. Their relative distance is a crucial parameter, particularly concerning the irradiation history. For the High Flux Reactor (RHF) of the Institute Laue-Langevin (ILL), the measurement of this distance with a microscopic resolution becomes extremely challenging. To address this issue, a specific ultrasonic transducer, presented in a first paper, has been designed and manufactured to be inserted into the 1.8 mm width channel existing between curved fuel plates. It was set on a blade yielding a total device thickness of 1 mm. To achieve the expected resolution, the system is excited with frequencies up to 70 MHz and integrated into a set of high frequency acquisition instruments. Thanks to a specific signal processing, this device allows the distance measurement through the evaluation of the ultrasonic wave time of fight. One of the crucial points is then the evaluation of the local water temperature inside the water channel. To obtain a precise estimation of this parameter, the ultrasonic sensor is used as a thermometer thanks to the analysis of the spectral components of the acoustic signal propagating inside the sensor multilayered structure. The feasibility of distance measurement was proved during the December 2013 experiment in the RHF fuel element of the ILL. Some of the results will be presented as well as some experimental constraints identified to improve the accuracy of the measurement in future works.

International audience; Most high flux reactors for research purposes have fuel elements composed of plates and not pencils. The measure of inter-plate distance of a fuel element is tricky since a resolution of a micron is searched to measure plate swellings of about ten microns while the dimension between the plates is close to the millimeter. This measure should provide information about the fuel and particularly its history of irradiation. That is the reason why a solution has been considered: a robust device based upon high frequency ultrasonic probes adapted to the high radiation environment and thinned to 1 mm to be inserted into a 1.8 mm width water channel between two fuel plates. To achieve the expected resolution, the system is excited with frequencies up to 150 MHz. Thanks to a specific signal processing, this device allows the distance measurement through an ultrasonic wave's time of flight. The feasibility of such challenging distance measurement has already been proved with success on a full size irradiated fuel element of the RHF.