Optimisation of material properties for the modelling of large deformation manufacturing processes using a finite element model of the Gleeble compression test

The finite element modelling of manufacturing processes often requires a large amount of large plastic strain flow stress data in order to represent the material of interest over a wide range of temperatures and strain rates. Compression data generated using a Gleeble thermo-mechanical simulator is difficult to interpret due to the complex temperature and strain fields, which exist within the specimen during the test. In this study, a non-linear optimisation process is presented, which includes a finite element model of the compression process to accurately determine the constants of a five-parameter Norton–Hoff material model. The optimisation process is first verified using a reduced three-parameter model and then the full five-parameter model using a known set of constants to produce the target data, from which the errors are assessed. Following this, the optimisation is performed using experimental target data starting from a set of constants derived from the test data using an initial least-squares fit and also an arbitrary starting point within the parameter space. The results of these tests yield coefficients differing by a maximum of less than 10% and significantly improve the representation of the flow stress of the material

Frequency shifts of photoassociative spectra of ultracold metastable Helium atoms : a new measurement of the s-wave scattering length

We observe light-induced frequency shifts in one-color photoassociative spectra of magnetically trapped $^4$He$^*$ atoms in the metastable $2^3S_1$ state. A pair of ultracold spin-polarized $2^3S_1$ helium atoms is excited into a molecular bound state in the purely long range $0_u^+$ potential connected to the $2^3S_1 - 2^3P_0$ asymptote. The shift arises from the optical coupling of the molecular excited bound state with the scattering states and the bound states of two colliding $2^3S_1$ atoms. We measure the frequency-shifts for several ro-vibrational levels in the $0^+_u$ potential and find a linear dependence on the photoassociation laser intensity. Comparison with a theoretical analysis provides a good indication for the s-wave scattering length $a$ of the quintet ($^5\Sigma_g^+$) potential, $a=7.2\pm 0.6$ nm, which is significantly lower than most previous results obtained by non-spectroscopic methods.Comment: 7 pages, 4 figure

Evolution entre 2007 et 2009 de la résistance des Entérobactéries et de Pseudomonas aeruginosa à la ciprofloxacine, en fonction de la consommation de fluoroquinolones au CHU d'Angers

National audienc

Estimation du DFG en oncopédiatrie : clairance au 51CR-EDTA vs clairance à la créatinine par méthode Jaffé et enzymatique

National audienceObjectifs.– Étudier la possibilité de suivre la fonction rénale chez des patients depédiatrie sous chimiothérapie uniquement par l’estimation du DFG au moyende la clairance à la créatinine (eDFG), méthode plus simple et déjà utilisée enclinique pour le suivi de l’insuffisance rénale chronique chez l’adulte. Le mDFG(un desgold standard) a été comparé séparément aux eDFG obtenus avec uneméthode de Jaffé (MJ) et au eDFG obtenu avec une méthode enzymatique (ME).Matériels et méthodes.– L’étude a été réalisée par recueil rétrospectif sur93 patients (cinq mois–21 ans) de janvier 2007 à septembre 2012. La clai-rance au51Cr-EDTA (n= 181) a été calculée à partir d’une méthode à quatrepoints (correction de Brochner–Mortensen 2009) et les clairances à la créati-nine ont été estimées par la formule de Schwartz (127 en MJ et 54 en ME).Le mDFG a été comparé aux eDFG obtenus par MJ et ME par un test sta-tistique de Student pour séries appariées. La concordance entre les méthodesa été évaluée graphiquement par la méthode de Bland et Altman, le biais(erreur systématique), les précisions à 30 % et 10 % ont aussi été calcu-lés. Enfin, les méthodes ont été comparées lors d’un suivi longitudinal sur26 patients.Résultats.– Le test de Student met en évidence une différence significative deseDFG avec le mDFG (p< 0,001 avec MJ et ME ;= 0,05). L’étude de Blandet Altman révèle d’une part des biais moyen (moyenne des différences entresles deux méthodes) important de 81 mL/min/1,73 m2pour MJ et modéré de16 mL/min/1,73 m2pour ME, soit respectivement une surestimation moyennede 80 % et 17 % en faveur du eDFG, et d’autre part des écart-types importantégal à 50 mL/min/1,73m2pour MJ et 33 mL/min/1,73m2pour ME. Les préci-sions à 30 % et 10 % sont respectivement très faibles (11 % et 2 %) pour MJ etmodérée (75 % et 33 %) pour ME. Le suivi longitudinal met en évidence desdivergences critiques de résultats (stabilité, élévation, diminution du DFG) entremDFG et eDFG.Conclusions.– L’ensemble des résultats obtenus permet de conclure à la non-transposabilité des méthodes et d’exclure l’utilisation du eDFG pour suivre lafonction rénale des patients d’oncologie pédiatrique en routine clinique

Two-photon fluorescence isotropic-single-objective microscopy

International audienceTwo-photon excitation provides efficient optical sectioning in three-dimensional fluorescence microscopy, independently of a confocal detection. In two-photon laser-scanning microscopy, the image resolution is governed by the volume of the excitation light spot, which is obtained by focusing the incident laser beam through the objective lens of the microscope. The light spot being strongly elongated along the optical axis, the axial resolution is much lower than the transverse one. In this Letter we show that it is possible to strongly reduce the axial size of the excitation spot by shaping the incident beam and using a mirror in place of a standard glass slide to support the sample. Provided that the contribution of sidelobes can be removed through deconvolution procedures, this approach should allow us to achieve similar axial and lateral resolution

Isotropic Single Objective (ISO) microscopy : Theory and Experiment

International audienceIsotropic single-objective (ISO) microscopy is a recently proposed imaging technique that can theoretically exhibit the same axial and transverse resolutions as 4Pi microscopy while using a classical single-objective confocal microscope. This achievement is obtained by placing the sample on a mirror and shaping the illumination beam so that the interference of the incident and mirror-reflected fields yields a quasi-spherical spot. In this work, we model the image formation in the ISO fluorescence microscope and simulate its point spread function. Then, we describe the experimental implementation and discuss its practical difficulties

Construindo a identidade agroecológica através de trocas de experiências entre assentamentos da reforma agrária no estado de São Paulo.

Resumo: Este trabalho faz parte do projeto ?Capacitação sócio-ambiental para construção de projetos de desenvolvimento sustentável em assentamentos rurais no estado de São Paulo?, uma parceria da Embrapa Meio Ambiente com o INCRA, MST e outras organizações de agricultores assentados. Assim, propomos apresentar uma etapa dos trabalhos que vem sendo desenvolvido nos assentamentos Itapeva e Sepé Tiaraju, nos respectivos municípios de Itapeva/SP e Ribeirão Preto/SP. Iniciado em 2009, este trabalho visa a assessorar e potencializar os trabalhos de transição agroecológica através da aproximação de agricultores assentados com processos diferentes de ocupação da terra, porém com mesmos objetivos de diversificação do sistema produtivo de forma sustentável. Abstract: This work is part of the project "Capacity building for social and environmental projects for sustainable development in rural settlements in the state of São Paulo, a partnership withEmbrapa Environment INCRA, MST and other organizations offarmers settled.Therefore, we propose to present a step in the work being donein the settlements and Itapeva Sepe Tiaraju, in their municipality of Itapeva / SP, Ribeirao Preto / SP. Started in 2009, this work aims to assist and enhance the work through the transitionalagro- ecological approach to resettled farmers with different processes acupaçao of the earth, but with the same objectivesof diversification of the productive system in a sustainable manner

The STAR Silicon Strip Detector (SSD)

The STAR Silicon Strip Detector (SSD) completes the three layers of the Silicon Vertex Tracker (SVT) to make an inner tracking system located inside the Time Projection Chamber (TPC). This additional fourth layer provides two dimensional hit position and energy loss measurements for charged particles, improving the extrapolation of TPC tracks through SVT hits. To match the high multiplicity of central Au+Au collisions at RHIC the double sided silicon strip technology was chosen which makes the SSD a half million channels detector. Dedicated electronics have been designed for both readout and control. Also a novel technique of bonding, the Tape Automated Bonding (TAB), was used to fullfill the large number of bounds to be done. All aspects of the SSD are shortly described here and test performances of produced detection modules as well as simulated results on hit reconstruction are given.Comment: 11 pages, 8 figures, 1 tabl