Etude de la structuration spontanée de films polymères en nano-impression thermique

La lithographie de nano-impression par déstabilisation spontanée de polymère est unevariante de la technique de nano-impression thermique, et permet de limiter le contact directentre moule et polymère. Le but de cette thèse est d étudier cette déstabilisation spontanée etde déterminer si elle peut conduire à la formation de nanostructures en dupliquant de façonpositive un moule nano-structuré. Ce procédé est influencé, en particulier, par la température,le champ électrique externe ou interne au niveau des interfaces moule air polymère, ainsique par la distance d séparant les structures du moule et la surface du polymère.Les études réalisées au cours de cette thèse se sont concentrées sur l influence de cesdifférents paramètres. Nous avons montré que la formation de motifs dépend plus de l effetde charges que de la température, dans la mesure où le polymère peut néanmoins fluer. Nousavons surtout mis en évidence le scénario de structuration suivant : une duplication positiveapparaît dans un premier temps, et est suivie, dans certains cas, d un remplissage des cavitésdu moule conduisant à une duplication négative. Un modèle théorique a été utilisé pourcalculer la longueur d onde de déstabilisation la plus favorable, et une comparaison avec nosrésultats expérimentaux a permis d expliquer pourquoi et dans quels cas la structurationfinale est positive ou négative. Une investigation a été accomplie sur la déstabilisationspontanée de substrats souples, mais la grande épaisseur des films conduit à unedéstabilisation de grande longueur d onde, et donc à un remplissage complet du moule.NanoImprint lithography by spontaneous polymer destabilization is an alternative toThermal NanoImprint, which limits physical contact between polymer and mold surfaces.The purpose of this thesis is to investigate this spontaneous destabilization and to work out ifit can lead to the formation of nanostructures by duplicating positively a structured mold.This process is in particular affected by temperature or electric field present at mold - air -polymer interfaces and by the distance d between the structures of the mold and the polymersurface.The studies of this thesis were focused on the influence of these process parameters. Itwas shown that the structuration depends more of charges effect than temperature, since thepolymer can creep. We highlighted the following scenario of structuration: a positiveduplication appears first and is followed, in some cases, by the filling of the mold cavitiesleading to a negative duplication. A theoretical model was used to calculate the mostfavorable destabilization wavelength, and a comparison with experimental results helped toexplain why and under which circumstances the final structuration is positive or negative. Aninvestigation was performed on the spontaneous destabilization of flexible substrate but thebigger thickness of flexible films led to a destabilisation with a wide wavelength and so tothe filling of molds cavities.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Cardiac metaiodobenzylguanidine uptake in patients with moderate chronic heart failure: relationship with peak oxygen uptake and prognosis

AbstractOBJECTIVESThis prospective study was undertaken to correlate early and late metaiodobenzylguanidine (MIBG) cardiac uptake with cardiac hemodynamics and exercise capacity in patients with heart failure and to compare their prognostic values with that of peak oxygen uptake (VO2).BACKGROUNDThe cardiac fixation of MIBG reflects presynaptic uptake and is reduced in heart failure. Whether it is related to exercise capacity and has better prognostic value than peak VO2is unknown.METHODSNinety-three patients with heart failure (ejection fraction <45%) were studied with planar MIBG imaging, cardiopulmonary exercise tests and hemodynamics (n = 44). Early (20 min) and late (4 h) MIBG acquisition, as well as their ratio (washout, WO) were determined. Prognostic value was assessed by survival curves (Kaplan–Meier method) and uni- and multivariate Cox analyses.RESULTSLate cardiac MIBG uptake was reduced (131 ± 20%, normal values 192 ± 42%) and correlated with ejection fraction (r = 0.49), cardiac index (r = 0.40) and pulmonary wedge pressure (r = −0.35). There was a significant correlation between peak VO2and MIBG uptake (r = 0.41, p < 0.0001). With a mean follow-up of 10 ± 8 months, both late MIBG uptake (p = 0.04) and peak VO2(p < 0.0001) were predictive of death or heart transplantation, but only peak VO2emerged by multivariate analysis. Neither early MIBG uptake nor WO yielded significant insights beyond those provided by late MIBG uptake.CONCLUSIONSMetaiodobenzylguanidine uptake has prognostic value in patients with wide ranges of heart failure, but peak VO2remains the most powerful prognostic index

Photoluminescence and photoluminescence excitation studies of lateral size effects in Zn_{1-x}Mn_xSe/ZnSe quantum disc samples of different radii

Quantum disc structures (with diameters of 200 nm and 100 nm) were prepared from a Zn_{0.72}Mn_{0.28}Se/ZnSe single quantum well structure by electron beam lithography followed by an etching procedure which combined dry and wet etching techniques. The quantum disc structures and the parent structure were studied by photoluminescence and photoluminescence excitation spectroscopy. For the light-hole excitons in the quantum well region, shifts of the energy positions are observed following fabrication of the discs, confirming that strain relaxation occurs in the pillars. The light-hole exciton lines also sharpen following disc fabrication: this is due to an interplay between strain effects (related to dislocations) and the lateral size of the discs. A further consequence of the small lateral sizes of the discs is that the intensity of the donor-bound exciton emission from the disc is found to decrease with the disc radius. These size-related effects occur before the disc radius is reduced to dimensions necessary for lateral quantum confinement to occur but will remain important when the discs are made small enough to be considered as quantum dots.Comment: LaTeX2e, 13 pages, 6 figures (epsfig

Controlled angular redirection of light via nanoimprinted disordered gratings

International audienceEnhanced control of diffraction through transparent substrates is achieved via disordered gratings in a silica sol-gel film. Tailoring the degree of disorder allows tuning of the diffractive behavior from discrete orders into broad distributions over large angular range. Gratings of optical quality are formed by silica sol-gel nanoimprint lithography and an optical setup for the measurement of continuous diffraction patterns is presented. Sound agreement is found between measurements and simulation, validating both the approach for redirection of light and the fabrication process. The disordered gratings are presented in the context of improved interior daylighting and may furthermore be suited to a wide variety of applications where controlled angular redirection of light is desired

Electron microscopy of quantum dots

This brief review describes the different types of semiconductor quantum dost systems, their main applications and which types of microscopy methods are used to characterize them. Emphasis is put on the need for a comprehensive investigation of their size distribution, microstructure, chemical composition, strain state and electronic properties, all of which influence the optical properties and can be measured by different types of imaging, diffraction and spectroscopy methods in an electron microscope

Electrical modalities beyond pacing for the treatment of heart failure

In this review, we report on electrical modalities, which do not fit the definition of pacemaker, but increase cardiac performance either by direct application to the heart (e.g., post-extrasystolic potentiation or non-excitatory stimulation) or indirectly through activation of the nervous system (e.g., vagal or sympathetic activation). The physiological background of the possible mechanisms of these electrical modalities and their potential application to treat heart failure are discussed

Le débat sur la gestion scolaire et sa dimension religieuse en Ontario français : une communauté divisée (1980-1998)

Cet article fait l’étude du débat sur les enjeux religieux de la gestion scolaire au sein du milieu associatif franco-ontarien. Ce débat montre la persistance, du moins dans certains milieux, du rôle structurant du référent religieux dans l’institutionnalisation de la francophonie ontarienne après le désengagement public de l’Église et les bouleversements idéologiques de la Révolution tranquille. Ce phénomène a été largement négligé par l’historiographie. Dans les années 1980, l’espace public de la collectivité franco-ontarienne est de plus en plus caractérisé par un pluralisme idéologique, culturel et religieux qui ne conduit pas, néanmoins, à évacuer le catholicisme de la conscience identitaire d’une partie substantielle de la population francophone de la province. Dans ses revendications pour obtenir le contrôle de ses institutions scolaires, le réseau associatif réclame ainsi un double réseau de conseils scolaires de langue française, catholiques et publics, à la grandeur de la province, qu’il obtient finalement en 1998.This article studies the debate on the religious stakes of school management within the Franco-Ontarian community. This debate shows the persistence, at least in certain circles, of the structuring role of the religious referent in the institutionalization of the Franco-Ontarian community after the public disengagement of the Church and the ideological upheaval of the Quiet Revolution. This phenomenon has been largely neglected by historiography. In the 1980s, the public space of the Franco-Ontarian community was increasingly characterized by an ideological, cultural and religious pluralism that did not, however, lead to the elimination of Catholicism from the identity consciousness of a substantial part of the province’s francophone population. In its demands to gain control of its educational institutions, the network of civil society organizations thus called for a dual network of French-language school boards, both Catholic and public, throughout the province, which it finally obtained in 1998