From fluid and structure dynamical behaviors to vascular pathologies

International audienceIntroduction: The aim of my work is to develop biomechanical models to broaden the current knowledge of fluid and structure dynamics which are associated with the function and dysfunction of some vascular systems. This research enables to identify the potential correlations between fluid and structure behaviors and dysfunctions to bring insights on some pathologies. Over the last ten years three complementary approaches have been considered at the macroscopic level: the fluid, the structure and the tissue, allowing to describe their couplings. The works carried out at this scale have highlighted the necessity of assessing the microscopic scale to better understand some mechanisms involved in the genesis and development of pathologies. Numerous works on fluid dynamics have not only been achieved in pathological geometrical models such as arterial or valvular stenoses, arterial grafts, abdominal aortic aneurysms, aortic dissections but also in stents, endovascular and mechanical valvular prostheses. Besides, studies at the microscopic scale related to the behavior of red blood cell concentrated suspensions under flow as well as those linked with the influence of mechanical solicitations on the cellular response that acts on tissue remodeling have also been conducted. Others works on the mechanical behavior of the aortic wall have been carried out at different scales. They investigated the arterial wall microstructure at the fibers level to better understand the mechanisms that drive the macroscopic mechanical response and also to design biomimetic analog materials

Prediction of intervertebral disc mechanical response to axial load using isotropic and fiber reinforced FE models

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Etude des écoulements intra anévrismaux par PIV stéréoscopique.

Cette étude a pour objectif de décrire l'hydrodynamique instationnaire d'un fluide rhéofluidifiant dans un élargissement de section asymétrique représentant un anévrisme de l'aorte abdominale. La métrologie utilisée, PIV stéréoscopique, permet une analyse précise de l'anneau tourbillonnaire qui se développe et se propage dans le sac anévrismal au cours du cycle cardiaque

Azimuthal anisotropy of charged jet production in root s(NN)=2.76 TeV Pb-Pb collisions

We present measurements of the azimuthal dependence of charged jet production in central and semi-central root s(NN) = 2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as nu(ch)(2) (jet). Jet finding is performed employing the anti-k(T) algorithm with a resolution parameter R = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero nu(ch)(2) (jet) is observed in semi-central collisions (30-50% centrality) for 20 <p(T)(ch) (jet) <90 GeV/c. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the nu(2) of single charged particles at high p(T). Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe

Pseudorapidity and transverse-momentum distributions of charged particles in proton-proton collisions at root s=13 TeV

The pseudorapidity (eta) and transverse-momentum (p(T)) distributions of charged particles produced in proton-proton collisions are measured at the centre-of-mass energy root s = 13 TeV. The pseudorapidity distribution in vertical bar eta vertical bar <1.8 is reported for inelastic events and for events with at least one charged particle in vertical bar eta vertical bar <1. The pseudorapidity density of charged particles produced in the pseudorapidity region vertical bar eta vertical bar <0.5 is 5.31 +/- 0.18 and 6.46 +/- 0.19 for the two event classes, respectively. The transverse-momentum distribution of charged particles is measured in the range 0.15 <p(T) <20 GeV/c and vertical bar eta vertical bar <0.8 for events with at least one charged particle in vertical bar eta vertical bar <1. The evolution of the transverse momentum spectra of charged particles is also investigated as a function of event multiplicity. The results are compared with calculations from PYTHIA and EPOS Monte Carlo generators. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Centrality evolution of the charged-particle pseudorapidity density over a broad pseudorapidity range in Pb-Pb collisions at root s(NN)=2.76TeV

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From fluid and structure dynamical behaviors to vascular pathologies

International audienceIntroduction: The aim of my work is to develop biomechanical models to broaden the current knowledge of fluid and structure dynamics which are associated with the function and dysfunction of some vascular systems. This research enables to identify the potential correlations between fluid and structure behaviors and dysfunctions to bring insights on some pathologies. Over the last ten years three complementary approaches have been considered at the macroscopic level: the fluid, the structure and the tissue, allowing to describe their couplings. The works carried out at this scale have highlighted the necessity of assessing the microscopic scale to better understand some mechanisms involved in the genesis and development of pathologies. Numerous works on fluid dynamics have not only been achieved in pathological geometrical models such as arterial or valvular stenoses, arterial grafts, abdominal aortic aneurysms, aortic dissections but also in stents, endovascular and mechanical valvular prostheses. Besides, studies at the microscopic scale related to the behavior of red blood cell concentrated suspensions under flow as well as those linked with the influence of mechanical solicitations on the cellular response that acts on tissue remodeling have also been conducted. Others works on the mechanical behavior of the aortic wall have been carried out at different scales. They investigated the arterial wall microstructure at the fibers level to better understand the mechanisms that drive the macroscopic mechanical response and also to design biomimetic analog materials

Fluid Structure Interaction in aortic dissections

International audienceAortic dissections (AD) result in two lumens of circulation separated by the neointimal membrane (NIF). Type A ADs requires replacement of the pathological segment but can still evolve in a residual dissection. There are currently no clinical criteria that are sufficiently discriminating to predict this evolution to optimize the patient management. The clinical relevance of numerical modeling to tackle these issues is obvious. However, the choice of the parameters of the elasto-hemodynamic models is decisive. Models including fluid-structure interaction (FSI) are developed. The results highlight that (i) rigid structure modeling overestimates velocities and high wall shear stresses (WSS) values, underestimates low WSS values compared to FSI modeling (ii) a deformable NIF with rigid aortic wall does not bring any significant difference on the flow behavior compared to full rigid modeling (iii) the relevance of FSI analysis is linked to the mechanical behavior of the NIF and dissected descending aorta

Geometric vascular singularities, hemodynamic markers and pathologies

International audienceVascular pathologies are numerous and varied, and their genesis and development are multifactorial. Nevertheless, it is now known that thecharacterization and analysis of the dynamics of fluids and structures involved in the functioning of certain segments of the vascular system allowtheir dysfunction to be better understood, and correlations to be established between these dynamics and the genesis and development of vascularpathologies. The purpose of this chapter is to describe flow behaviors in certain geometric singularities of the cardiovascular system, whether native or pathological, and to correlate their dynamics with the evolution of cardiovascular pathologies. These correlations can be made usingassociations between the spatiotemporal distributions of certain hemodynamic markers/indexes and in vivo observation of deleteriousclinical events. Certain in silico and in vitro works conducted within the IRPHE Biomechanics team, mostly over the period of the “Biomechanics offluids and transfers, biological structure-fluid interaction” and “MEChAnics of BIOlogical materials and fluids” research groups, will notably serve toillustrate the remarks, which will not necessarily be exhaustive