Effect of time to sentinel-node biopsy on the prognosis of cutaneous melanoma

Introduction: In patients with primary cutaneous melanoma, there is generally a delay between excisional biopsy of the primary tumour and sentinel-node biopsy. The objective of this study is to analyse the prognostic implications of this delay. Patients and method: This was an observational, retrospective, cohort study in four tertiary referral hospitals. A total of 1963 patients were included. The factor of interest was the interval between the date of the excisional biopsy of the primary melanoma and the date of the sentinel-node biopsy (delay time) in the prognosis. The primary outcome was melanoma-specific survival and disease-free survival. Results: A delay time of 40 days or less (hazard ratio (HR), 1.7; confidence interval (CI), 1.2-2.5) increased Breslow thickness (Breslow ⩾2 mm, HR, >3.7; CI, 1.4-10.7), ulceration (HR, 1.6; CI, 1.1-2.3), sentinel-node metastasis (HR, 2.9; CI, 1.9-4.2), and primary melanoma localised in the head or neck were independently associated with worse melanoma-specific survival (all P < 0.03). The stratified analysis showed that the effect of delay time was at the expense of the patients with a negative sentinel-node biopsy and without regression. Conclusion: Early sentinel-node biopsy is associated with worse survival in patients with cutaneous melanoma

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L‟objectif de ce travail de thèse est de reprendre les travaux précédents sur le couplage diffusion / plasticité sous Abaqus et d‟implémenter dans le code éléments finis un processus de piégeage transitoire dans une procédure utilisateur UMATHT, l‟équation de la chaleur dans une procédure UEL, et de modifier le comportement mécanique dans la procédure UMAT, afin de résoudre de manière couplée et simultanée les problèmes de diffusion/piégeage de l‟hydrogène soumis à des chargements thermomécaniques.Le modèle ainsi développé avec un couplage diffusion/piégeage transitoire a été confronté dans un premier temps, et validé sur plusieurs matériaux (tungstène et fer) par des comparaisons sur des cas tests avec d‟autres codes de la littérature (notamment le code MRE HIIPC). Puis, en considérant les variations des champs thermiques, l‟outil et l‟implémentation ont été validées sur des résultats expérimentaux de TDS sur du tungstène ainsi que sur d‟autres codes de la littérature sur le fer.Enfin, le modèle entièrement couplé a ainsi été utilisé sur des applications de chargements thermiques complexes sur une composante du futur tokamak d‟ITER (DFW). Les simulations 3D sur cette structure ont mis en évidence les effets de géométrie qui ne peuvent être pris en compte dans des simulations 1D. Elles ont permis de mettre également en exergue le rôle de la pression hydrostatique, la prise en compte de la dilatation thermique pouvant induire des écarts importants sur les résultats.The aim of this thesis work is to take up the previous work on diffusion / plasticity coupling under Abaqus and to implement in the finite element code a transient trapping process in a UMATHT user procedure, the equation of heat in a UEL procedure, and modify the mechanical behavior in the UMAT procedure, in order to solve in a coupled and simultaneous way the diffusion / trapping problems of hydrogen subjected to thermomechanical loadings.The model thus developed with transient diffusion / trapping coupling was first confronted, and validated on several materials (tungsten and iron) by comparisons on test cases with other codes of the literature (in particular the MRE HIIPC code). Then, considering the variations of the thermal fields, the tool and the implementation were validated on experimental results of TDS on tungsten as well as on other codes of the literature on the iron.Finally, the fully coupled model has been used on complex thermal load applications on a component of the future ITER Tokomak (DFW). 3D simulations on this structure have highlighted geometric effects that cannot be taken into account in 1D simulation. They have also highlighted the role of hydrostatic pressure, taking into account thermal expansion that can lead to significant differences in results

Simulations EF du couplage entre diffusion et piégeage de l’hydrogène sous sollicitations thermomécaniques : Applications relatives au fer et au tungstène

The aim of this thesis work is to take up the previous work on diffusion / plasticity coupling under Abaqus and to implement in the finite element code a transient trapping process in a UMATHT user procedure, the equation of heat in a UEL procedure, and modify the mechanical behavior in the UMAT procedure, in order to solve in a coupled and simultaneous way the diffusion / trapping problems of hydrogen subjected to thermomechanical loadings.The model thus developed with transient diffusion / trapping coupling was first confronted, and validated on several materials (tungsten and iron) by comparisons on test cases with other codes of the literature (in particular the MRE HIIPC code). Then, considering the variations of the thermal fields, the tool and the implementation were validated on experimental results of TDS on tungsten as well as on other codes of the literature on the iron.Finally, the fully coupled model has been used on complex thermal load applications on a component of the future ITER Tokomak (DFW). 3D simulations on this structure have highlighted geometric effects that cannot be taken into account in 1D simulation. They have also highlighted the role of hydrostatic pressure, taking into account thermal expansion that can lead to significant differences in results.L‟objectif de ce travail de thèse est de reprendre les travaux précédents sur le couplage diffusion / plasticité sous Abaqus et d‟implémenter dans le code éléments finis un processus de piégeage transitoire dans une procédure utilisateur UMATHT, l‟équation de la chaleur dans une procédure UEL, et de modifier le comportement mécanique dans la procédure UMAT, afin de résoudre de manière couplée et simultanée les problèmes de diffusion/piégeage de l‟hydrogène soumis à des chargements thermomécaniques.Le modèle ainsi développé avec un couplage diffusion/piégeage transitoire a été confronté dans un premier temps, et validé sur plusieurs matériaux (tungstène et fer) par des comparaisons sur des cas tests avec d‟autres codes de la littérature (notamment le code MRE HIIPC). Puis, en considérant les variations des champs thermiques, l‟outil et l‟implémentation ont été validées sur des résultats expérimentaux de TDS sur du tungstène ainsi que sur d‟autres codes de la littérature sur le fer.Enfin, le modèle entièrement couplé a ainsi été utilisé sur des applications de chargements thermiques complexes sur une composante du futur tokamak d‟ITER (DFW). Les simulations 3D sur cette structure ont mis en évidence les effets de géométrie qui ne peuvent être pris en compte dans des simulations 1D. Elles ont permis de mettre également en exergue le rôle de la pression hydrostatique, la prise en compte de la dilatation thermique pouvant induire des écarts importants sur les résultats

Numerical simulation of the transient hydrogen trapping process using an analytical approximation of the McNabb and Foster equation

International audienc

Numerical simulation of the transient hydrogen trapping process using an analytical approximation of the McNabb and Foster equation. Part 2: domain of validity

International audienceIn a previous study [1], a resolution scheme called Generalized Oriani's Approximation (GOA) was proposed to solve a transient transport and trapping problem in the Abaqus Finite Element software. This proposition was motivated by the convergence of the Finite Element problem linked to the estimation of several functions during the computation (and especially the dudt one). In this study, the GOA is shown to be able to provide an accurate estimation of the trapped concentration in transient trapping processes as soon as the time increment is small enough for two configurations: hydrogen in metals and water in polymers. An estimation of the induced error is given. The GOA approach is illustrated on a simple configuration with various trapping parameters. Last, the ability of Abaqus to converge while modeling a transient trapping and transport problem is analyzed considering several dudt: it is shown especially that its estimation based on the GOA allows the solver to efficiently converge toward the solution

Piégeage transitoire de l'hydrogène dans les matériaux métalliques

National audienc

Multidimensional Finite Element Simulations of the diffusion and trapping of hydrogen in plasma-facing components including thermal expansion

International audienceUnderstanding the diffusion and trapping of hydrogen isotopes (HI) in plasma facing components (PFC) is an important issue for future fusion device operations. For such a purpose, specific macroscopic rate equations (MRE) codes were developed to solve both diffusion and full kinetic trapping of HI in metals, using the McNabb and Foster equation. Numerical simulations based on these codes have shown the important role played by temperature on HI inventory, so that a particular attention must be paid to the determination of the thermal field, especially for 2D geometry. Furthermore, the modification of the mechanical properties due to spatio-temporal temperature variation could impact the HI inventory.In order to understand the thermo-mechanical coupling, a special focus has to be made to develop numerical models which, beside HI transport and trapping, include the coupled resolution of the thermal and mechanical problem, for 2D and 3D complex geometries. In this work, we propose a fully coupled 3D MRE code, based on the generalized transport and trapping temporal equations, the heat equation, and the mechanical behaviour. The model is based on the 3DS Abaqus finite element software. This code basically solve the mechanical and the diffusion problem; using User Subroutines, a kinetic trapping, a transient multi-diffusion process and a thermal expansion effect have been added.Several simulations are then performed, dedicated to model the tritium diffusion and trapping through a port plug first wall of the ITER tokamak during Deuterium-Tritium (D-T) operations, made of a 316L stainless steel. Tritium retention predicted with the Abaqus code based on the 2D transient thermal field and trapping resolutions will be compared with the 1D equivalent case, and with less comprehensive thermal field (asteady state time-dependant temperature assumption) and trapping process (Oriani’s equilibrium assumption) resolution cases. Last, the role of thermal expansion will be discussed

Effet des chargements thermiques sur le transport et le piégeage de l'hydrogène dans les matériaux métalliques

National audienc

Numerical simulation by finite element modelling of diffusion and transient hydrogen trapping processes in plasma facing components

International audienceIn order to simulate hydrogen charging and discharging cycles of mechanically loaded structures full 3D Macroscopic Rate Equation (MRE) modelling is proposed based on a finite element method (FEM). The model, implemented in the 3DS Abaqus software, uses a generalized transport equation, which accounts for mechanical fields, hydrogen transport and trapping, and their evolution with time. The influence of a-priori known thermal field has also been included. To ensure the solution convergence and the numerical stability, the trapping kinetic is introduced by using an approximation of the analytical solution the McNabb and Foster equation. Comparisons with a relevant 1D MRE code and with thermal programmed desorption (TPD) experimental results are performed on a 1D configuration to validate the model. Next, the model is used to simulate the tritium diffusion and trapping in a 2D geometry of interest in the upper plug of ITER tokamak, and results of tritium inventory are compared with an equivalent 1D calculation