Design de nanofils luminescents organiques et hybrides à base de clusters de composés de métaux de transition

Le fort engouement pour les nanostructures luminescentes provient de leurs comportements émissifs originaux et de leur potentiel comme briques élémentaires pour de futurs dispositifs photoniques et optoélectroniques. Dans cette thèse, nous nous sommes intéressés au contrôle de la couleur d émission de nano-systèmes 1D organiques composés de deux types de luminophores. Dans une première partie, une famille peu connue de luminophores nanométriques a été étudiée: les clusters octaédriques de molybdène. Leur comportement photophysique et l ensemble des fréquences des modes de vibration de l entité Mo6Br14 ont été déterminés. Les spécificités de ces clusters ont été exploitées au sein de nanofils.Un premier type de nanofil coaxial synthétisé par méthode template a été conçu afin de séparer les deux types de luminophores. Les clusters (dans une matrice de PMMA) et le PPV ont été sélectionnés comme émetteurs rouge et vert respectivement, pour avoir une séparation spectrale. Le contrôle de la couleur sans transfert de charge ou d énergie entre les deux luminophores a été validé par l étude du comportement de photoluminescence stationnaire et résolue en temps, en accord avec un modèle phénoménologique. A l opposé, des nanofils exploitant deux polymères conjugués fluorescents (PFO bleu, F8T2 vert) comme système donneur-accepteur ont été élaborés. Leur mélange ou leur séparation en géométrie cœur-gaine a permis d explorer une nouvelle voie pour moduler les comportements excitoniques. Ces résultats montrent la versatilité des nanofils à base de polymère pour contrôler à l échelle nanométrique les comportements d émission de systèmes multi-luminophores.Luminescent organic nanostructures are of great importance as building blocks in future miniaturized photonic and optoelectronic devices because these systems rely upon the ability to tune and get new optical characteristics. One-dimensional luminescent nanostructures are new and promising systems with complex morphologies now available. In this work, we particularly investigated the control and the tuning of the emitted color of two-luminophore based nanowires. In a first part, an unfamiliar family of luminophore has been investigated: the octahedral molybdenum clusters. The vibrational modes frequencies of Mo6Br14 cluster were fully determined, as well as their photophysical properties. The unique features of these clusters were exploited into nanowires.Then, using a template method, we designed coaxial nanowires allowing the spatial separation of the two luminophores. The transition metal clusters in a PMMA matrix and PPV were selected as red and green emitters, respectively, to achieve the spectral separation. Remarkably, it was found from time-resolved photoluminescence study and confirmed by a phenomenological model that any charge or energy transfer is involved in this system.Alternatively, coaxial and blend designs were used to investigate and possibly tune energy/charge transfers involved in the donor-acceptor behavior of two conjugated polymers: PFO (blue emitter) and F8T2 (green emitter). These results demonstrate the great versatility of polymer-based nanowires to finely control at the nanoscale the emission features of multi-luminophore materials.LE MANS-BU Sciences (721812109) / SudocSudocFranceF

Improved estimation of the left ventricular ejection fraction using a combination of independent automated segmentation results in cardiovascular magnetic resonance imaging

—This work aimed at combining different segmenta-tion approaches to produce a robust and accurate segmentation result. Three to five segmentation results of the left ventricle were combined using the STAPLE algorithm and the reliability of the resulting segmentation was evaluated in comparison with the result of each individual segmentation method. This comparison was performed using a supervised approach based on a reference method. Then, we used an unsupervised statistical evaluation, the extended Regression Without Truth (eRWT) that ranks different methods according to their accuracy in estimating a specific biomarker in a population. The segmentation accuracy was evaluated by focusing on the left ventricular ejection fraction (LVEF) estimate resulting from the LV contour delineation using a public cardiac cine MRI database. Eight different segmentation methods, including three expert delineations, were studied, and sixteen combinations of the five automated methods were investigated. The supervised and unsupervised evaluations demonstrated that in most cases, STAPLE results provided better estimates of the LVEF than individual automated segmentation methods. In addition, LVEF obtained with STAPLE were within inter-expert variability. Overall, combining different automated segmentation methods improved the reliability of the segmenta-tion result compared to that obtained using an individual metho

Nonsupervised Ranking of Different Segmentation Approaches: Application to the Estimation of the Left Ventricular Ejection Fraction From Cardiac Cine MRI Sequences

International audienceA statistical methodology is proposed to rank several estimation methods of a relevant clinical parameter when no gold standard is available. Based on a regression without truth method, the proposed approach was applied to rank eightmethods without using any a priori information regarding the reliability of each method and its degree of automation. It was only based on a prior concerning the statistical distribution of the parameter of interest in the database. The ranking of the methods relies on figures of merit derived from the regression and computed using a bootstrap process. The methodology was applied to the estimation of the left ventricular ejection fraction derived from cardiac magnetic resonance images segmented using eight approaches with different degrees of automation: three segmentations were entirely manually performed and the others were variously automated. The ranking of methods was consistent with the expected performance of the estimation methods: the most accurate estimates of the ejection fraction were obtained using manual segmentations. The robustness of the ranking was demonstrated when at least three methods were compared. These results suggest that the proposed statistical approach might be helpful to assess the performance of estimation methods on clinical data for which no gold standard is available

Comparison of different segmentation approaches without using gold standard. Application to the estimation of the left ventricle ejection fraction from cardiac cine MRI sequences.

International audienceA statistical method is proposed to compare several estimates of a relevant clinical parameter when no gold standard is available. The method is illustrated by considering the left ventricle ejection fraction derived from cardiac magnetic resonance images and computed using seven approaches with different degrees of automation. The proposed method did not use any a priori regarding with the reliability of each method and its degree of automation. The results showed that the most accurate estimates of the ejection fraction were obtained using manual segmentations, followed by the semiautomatic methods, while the methods with the least user input yielded the least accurate ejection fraction estimates. These results were consistent with the expected performance of the estimation methods, suggesting that the proposed statistical approach might be helpful to assess the performance of estimation methods on clinical data for which no gold standard is available

Opportunities for polymer-based nanowires in optoelectronics and nanophotonics

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Transport et Juste A Temps - 2. Le choix des entreprises

Cahier de Recherche du Groupe HEC Paris, n° 345bi

APIC: A Generic Interface for Sequencing Projects

In this paper, we describe the APIC graphical interface that aims at displaying the results produced by the genomic sequence analysis methods and at helping a comparison of these results. The major feature of APIC lies in its genericity. As a matter of fact, this interface can obviously be used to visualise genetic or physical maps but it also able to display other kinds of information such as curves or pictures. On the one hand, APIC provides the biologist who builds a new sequence analysis method with a standard interface allowing to display his results. Thus, he can avoid implementing a specific visualisation tool. On the other hand, even when the methods already have their own interfaces, using APIC has the advantage of giving a homogeneous way to compare several results coming from different analysis tools. Moreover, it provides some powerful functions for navigating and browsing into the results. 1 Motivations To handle the large amount of data and knowledge pro..

Evaluation of cardiac structure segmentation in cine magnetic resonance imaging

International audienc

Evaluation of cardiac structure segmentation in cine magnetic resonance imaging

International audienc

Definition of a mutual reference shape based on information theory and active contours

In this paper, we propose to consider the estimation of a reference shape from a set of different segmentation results using both active contours and information theory. The reference shape is then defined as the minimum of a criterion that benefits from both the mutual information and the joint entropy of the input segmentations. This energy criterion is here justified using similarities between information theory quantities and area measures, and presented in a continuous variational framework. This framework brings out some interesting evaluation measures such as the specificity and sensitivity. In order to solve this shape optimization problem, shape derivatives are computed for each term of the criterion and interpreted as an evolution equation of an active contour. A mutual shape is then estimated together with the sensitivity and specificity. Some synthetical examples allow us to cast the light on the difference between our mutual shape and an average shape. The applicability and robustness of our framework has also been tested for the evaluation of different segmentation methods of the left ventricular cavity from cardiac MRI