Tesi sul tema "Microscopie électronique à balayage et à transmission"
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Haas, Benedikt. "Développement de techniques quantitatives en microscopie électronique à balayage en transmission". Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY018/document.
Testo completoIn this work, different scanning transmission electron microscopy (STEM) techniques have been developed and applied to several material systems. The creation of novel materials and devices has been a backbone of society’s development and characterization methods are needed to investigate these materials in order to understand and improve them. With the advent of nanotechnology, electron microscopy has become an invaluable tool, as it is able to visualize the atomic structure of thin samples and produces a plethora of quantifiable signals.In a first part, the numerous developments realized in this thesis are presented. Several STEM based techniques have been improved: scanning moiré fringes (SMF), nano-beam precession diffraction (NPED) and high-resolution STEM (HR-STEM). These developments allow for more accurate strain measurements, the quantitative mapping of electric fields and to realize accurate chemical profiles.In a second part, the developed methods are applied to different material systems and compared to more classical techniques, like holography and differential phase contrast (DPC). In a II/VI solar cell structure the interface chemistry is determined from strain with atomic resolution. Very faint strain gradients that are vital for the topological insulator properties of HgTe are measured. Accurate two-dimensional strain maps are obtained of a SiGe transistor. Simultaneous strain and electric field maps of m-plane AlN/GaN reveal the influence of dislocations in the material. Core-shell type inversion domains are described for the first time in GaN nanowires. They were found in many samples grown by molecular beam epitaxy. Thanks to quantitative analysis the exact atomic structure of inversion domains in GaN is described and compared to simulations
Bogner, Agnès. "Le Mode d'imagerie wet-STEM : développement, optimisation et compréhension : application aux mini-émulsions et latex". Lyon, INSA, 2006. http://theses.insa-lyon.fr/publication/2006ISAL0066/these.pdf.
Testo completoContrary to conventional electron microscopy, ESEM (Environmental Scanning Electron Microscopy) does not require high vacuum conditions in the microscope chamber. One of the most unique features of ESEM is that it become possible to use electron microscopy for the observation of entirely liquid specimens in their native state with no prior treatment. The present PhD study concerns the development of a new imaging mode: the wet-STEM, which extends the potentialities of ESEM for the characterization of liquid samples to nanometric resolution and very important contrast. The principle is to image a thin liquid film containing nanometric objects in transmission using annular dark-field detection conditions. This technique seems especially suitable for imaging mini-emulsions and lattices, as well as non aqueous liquids and micro-organisms
Acevedo, Reyes Daniel. "Evolution de l'état de précipitation au cours de l'austénitisation d'aciers microalliés au vanadium et au niobium". Lyon, INSA, 2007. http://theses.insa-lyon.fr/publication/2007ISAL0008/these.pdf.
Testo completoGrain size control during heat treatments in austenite can be ensured by vanadium and niobium carbonitrides. However, the evolution of the precipitation state must be known to optimise the austenisation treatment, and no quantitative characterisation of this kind is available nowadays. This study deals with the dissolution kinetics of vanadium and niobium carbonitrides in austenite, for two high purity model alloys FeCV and FeCVNb, and a commercial alloy designed for springs fabrication. The characterisation combines several experimental techniques : structure and chemical composition of precipitates are established by transmission electronic microscopy and related techniques (EDS analysis, HAADF), particle size distribution is measured by means of scanning electronic microscopy (using a STEM detector), and volume fraction of precipitates is estimated by dosing the precipitated phases after an electrolytic dissolution of the matrix. In order to predict the evolution of the precipitation state during an austenitisation treatment, a precipitation-dissolution model has been developed. The modelling approach used in this work allows the description of (i) a non stoichiometric binary precipitate, the coexistence of two independent binary precipitates, (iii) the evolution of a single family of homogeneous ternary precipitates with varying chemical composition (VxNb1-xC). These different approaches were calibrated and validated on model alloys, then applied to the industrial alloy
Mory, Claudine. "Étude théorique et expérimentale de la formation de l'image en microscopie électronique à balayage par transmission". Paris 11, 1985. http://www.theses.fr/1985PA112134.
Testo completoThis thesis contains a theoretical and experimental study of image formation in a dedicated scanning transmission electron microscope (STEM). Using a detailed description of the different optical elements between the field emission source and the specimen, one calculates the shape and size of the primary probe of electrons impinging on the sample. This modelization enables to estimate the spatial resolution in the different imaging or micro analytical modes. The influence of the specimen and the role of the various detectors are taken into account to calculate the point speed function of the instrument in STEM imaging modes. An experimental study of the characteristic properties of phase contrast bright field micrographs and incoherent dark field ones is performed by comparison of digitally recorded images in similar conditions. Spatial resolution, contrast and signal/noise ratio are assessed by correlation methods, Fourier analysis and statistical considerations; one can deduce the optimum focusing conditions. Limits such as the point resolution on quasi-atomic metallic clusters are determined and an analysis of the capabilities of signal mixing concludes this work. Applications are offered in various domains such as the visualization of small metallic particles, biomolecules and unstained biological sections
Courtois, Eglantine. "Etude de la Précipitation des Carbures et des Carbonitrures de Niobium dans la Ferrite par Microscopie Electronique en Transmission et Techniques Associées". Lyon, INSA, 2005. http://theses.insa-lyon.fr/publication/2005ISAL0103/these.pdf.
Testo completoTEM study aims to further the understanding of the mechanisms of precipitation of carbides and carbonitrides in niobium microalloyed steels. In this work, two model ferritic alloys have been used. From a general point of view, TEM techniques have been consistently used for studying the crystallography, size, shape and volume fraction of the precipitates. Both thin foils and extraction replicasz in AlOx have been studied. Analysis performed with Tomographic Atom Probe (TAP) confirmed TEM results. At the early stages of precipitation, in Fe-Nb-C-N system, niobium nitride monoatomic platelets, such as Guinier Preston zones, have been simultaneously with already formed precipitates Nb(C, N), with a F. C. C. Structure and in Baker-Nutting relationship with the matrix. For more advanced stages of precipitation, the chemical composition of nanoparticles as small as 6 nm in diameter, is determined by EELS. Experiments indicate the coexistence of two types of precipitates : (i) pure niobium nitrides and (ii) mixed niobium carbonitrides with increasing carbon fraction and decreasing nitrogen during the precipitation kinetic. In order to understand the chemical composition evolution of these precipitates, a thermodynamical formalism has been developed to evaluate (i) the nucleation and growth rates (classical nucleation theory) and (ii) the chemical composition of nuclei and existing precipitates. The results of this model are in excellent qualitative agreement with the experiments, that is both populations evolve simultaneously in equilibrium, and nitrides are found in a lower number but with a larger size than carbonitrides
Autillo-Touati, Amapola. "Etude in vitro de la morphogenèse et de la polarité neuronale : analyse en miscroscopie électronique à transmission et à balayage". Aix-Marseille 2, 1992. http://www.theses.fr/1992AIX21901.
Testo completoEl, Hajraoui Khalil. "Études in-situ dans un microscope électronique en transmission des réactions à l’état solide entre métal et nanofil de Ge". Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY012/document.
Testo completoSemiconductor nanowires (NWs) are promising candidates for many device applications ranging from electronics and optoelectronics to energy conversion and spintronics. However, typical NW devices are fabricated using electron beam lithography and therefore source, drain and channel length still depend on the spatial resolution of the lithography. In this work we show fabrication of NW devices in a transmission electron microscope (TEM) where we can obtain atomic resolution on the channel length using in-situ propagation of a metallic phase in the semiconducting NW independent of the lithography resolution. We show results on semiconducting NW devices fabricated on two different electron transparent Si3N4 membranes: a planar membrane and a membrane where devices are suspended over holes. First we show the process of making lithographically defined reliable electrical contacts on individual NWs. Second we show first results on in-situ propagation of a metal-semiconductor phase in Ge NWs by joule heating, while measuring the current through the device. Two different devices are studied: one with platinum metal contacts and one with copper contacts. Different phenomena can occur in CuGe NWs during phase propagation
Gourmala, Ouassila. "Optimisation de la croissance de GaN de bonne qualité par HVPE et ELO-HVPE". Clermont-Ferrand 2, 2010. http://www.theses.fr/2010CLF22032.
Testo completoCrouzier, Loïc. "Développement d'une nouvelle approche hybride combinant AFM et MEB pour la métrologie dimensionnelle des nanoparticules". Thesis, Poitiers, 2020. http://www.theses.fr/2020POIT2260.
Testo completoIn order to take advantages of remarkable properties of the nanomaterials related to their size but also assess their potential risks, industrial actors need to rely on robust measurement methods that provide all the required dimensional information. However, there is no instrument capable of measuring a nanoparticle in all three dimensions of space with controlled uncertainty. The aim of this work is to combine diameter measurements by scanning electron microscopy (SEM) with height measurements by atomic force microscopy (AFM). The use of silica particles, supposedly spherical, allows to validate this hybrid approach combining AFM and SEM. First, the uncertainty budget associated with the measurement of nanoparticles by SEM was established. We have demonstrated that the main contribution to the uncertainty budget is the size of the electron beam, which is difficult to measure. Two methods, based on Monte Carlo modelling, have been developed to evaluate the influence of this parameter on the SEM measurement. The first is based on the comparison between experimental and simulated signals. The second is based on the segmentation of the SEM images using a remarkable point, not influenced by the dimensions of the electron beam. These two methods have shown that the error related to the beam size is largely overestimated using conventional image segmentation tools. From these results, a direct comparison of AFM and SEM measurements was performed on the same particles. A systematic discrepancy was observed between the two techniques for the smallest particles related to their non-sphericity. The use of a third technique, transmission electron microscopy (TEM), confirms these observations. Finally, the hybrid approach has been implemented for measuring the three characteristic dimensions of the complex-shaped nano-objects with very non-spherical morphology
Perrot, Philippe. "Modifications morphologiques et microstructurales du matériau actif des cathodes de batteries à l'ion lithium induites par broyage et traitement thermique". Poitiers, 1998. http://www.theses.fr/1998POIT2264.
Testo completoVizzini, Sébastien. "Elaboration et caractérisation d'oxydes d'aluminium ultra-minces pour une application aux jonctions tunnels magnétiques". Aix-Marseille 2, 2008. http://theses.univ-amu.fr.lama.univ-amu.fr/2008AIX22036.pdf.
Testo completoUsing different techniques of investigation (AES, LEED, STM, HR-TEM, EELS and PES) we have developed an original process, which consists to grow the aluminuim oxide layer by layer. This procedure so-called Atomic Layer Deposition and Oxidation (ALDO procedure) allows to get an artificial oxide film perfectly homogeneous in depth and chemical composition as well. Several properties like gap measurement, stoichiometry, surface morphology and electrons transport allows to mind that oxid could be in good agreement with microelectronics applications (Magnetic Tunnel Junction and Magnetic memories)
Bitar, Rajaa. "Auto-organisation de nanoparticules d'or dans un cristal liquide cholestérique : élaboration, structure et propriétés optiques". Toulouse 3, 2012. http://thesesups.ups-tlse.fr/1565/.
Testo completoDuring my thesis, I worked on self-organization of gold nanoparticles (nps) in a cholesteric liquid crystal (CLC). This work consists of two parts. The first part is devoted to the study of the cholesteric matrix before the introduction of nps. For this, we realized many studies starting from preparing the open film to the characterization of complementary imaging methods, and a study of the optical response. During this study, we discovered a new scenario to change the color of a cholesteric without modifying the extrinsic and intrinsic parameters of the material. This color change is controlled only by the annealing time which induces a change in the distribution of the helical axis at the interface with air and which propagates in the volume when the annealing time increases. This detailed study has allowed us to propose a 3D representation of our system. The second part of my thesis deals with the introduction of gold nps in the cholesteric matrix using in the first part. We defined a simple protocol to mix the two bodies, and make a film of CLC-nps. The fact that our compounds can fix the structure below 50 °C, helped us to show self-organization of nps by electron micrograph (SEM) and transmission electron microscopy (TEM). In addition, we presented a multi-scale structural study going from the nanoscale to the macroscale, by additional imaging. These data do not exist in the literature even for neighboring systems, especially since most organizations studied were short scale and using microparticles. Finally, we defined the couple concentration of nps-film thickness CLC-nps as the parameters that control the self-organization of nps and decide of gold nanostructures obtained (fingerprints, double spirals, and targets)
Meuret, Sophie. "Intensity interferometry experiments in a scanning transmission electron microscope : physics and applications". Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS112/document.
Testo completoQuantum optics performed at the nanometer scale is an important challenge, especially for quantum emitters characterization. They can be point defects in material (few ang- ströms) or confined structures of a few nanometers. A way to reach this scale is by using cathodoluminescence (CL) performed in a scanning transmission electron microscope (CL- STEM), which has only recently been done [1]. However, when aiming at studying the statistical properties of the light coming out of a CL experiment, which is necessary to e. g. study the quantum nature of Single Photon Emitters (SPE) emission, dedicated expe- riments on top of regular CL ones have to be designed. Few months before my arrival in the STEM-group of the LPS, an intensity interferometry experiment (HBT) that measures the autocorrelation function g(2) of the CL signal intensity was built [2]. It is well known that the clear signature of SPE as measured in photoluminescence (PL) is antibunching in the g(2)(τ), namely that the autocorrelation function is always less than one. It was re- cently demonstrated on a famous SPE, the Nitrogen vacancy (NV) defect in diamond, that CL-STEM is similar to PL when only one SPE is involved. In this thesis we will see how CL-STEM allowed to characterize a new point defect in h-BN, showing the relevance of HBT experiments in a CL-STEM for discovering and characterizing new SPE. However, by studying the excitation of multiple SPE in CL, we discovered a new emission phenomenon, characterized by a huge bunching effect of the g(2)(τ) function (g(2)(0) > 35), in complete contradiction to PL measurements and expectations (g(2)(0)<1). In my thesis manuscript, this surprising effect will be experimentally investigated, theoretically explained and applied to lifetime measurement at the nanometer scale. Because quantum optics is often linked to quantum plasmonics, I will present, to conclude, a theoretical proposal, in collaboration with J. Garcia de Abajo, about quantum plasmonics measurement in a STEM
Lantiat-Baillargue, David. "Morphologie et auto-organisation de nanoparticules d'argent dispersées dans les matrices diélectriques : influence sur les propriétés optiques". Poitiers, 2008. http://theses.edel.univ-poitiers.fr/theses/2008/Lantiat-Baillargue-David/2008-Lantiat-Baillargue-David-These.pdf.
Testo completoThe aim of this work is to adjust the spectral position of the surface plasmon resonance of noble-metal nanoparticles embedded in a dielectric matrix by tailoring their morphology and their spatial organization. We show that when the growth is performed on plane substrates, it is possible to modify the aspect ratio of the particles H/D, and thus their optical response by changing the nature of the matrix. Quantitative structural analyzes carried out by using high angle annular dark field scanning transmission electronic microscopy (HAADF-STEM) imaging reveal that H/D is a decreasing function of the diameter D, independently of the deposited metal amount. In order to understand these effects of the matrix on the structural and optical properties of the particles, various studies (influence of the metal and deposited amount, presence of a buffer layer, influence of the elaboration conditions, covering rate of the particles,. . . ) are presented and numerical simulations of the optical spectra are proposed by integrating the structural parameters from the HAADF analysis in a model of Yamaguchi. A second step consists in using nanostructured sapphire surfaces in order to induce a surface organization of the particles, and thus to involve an anisotropy of their optical properties. We show that according to the geometry used during the deposition (normal incidence, grazing incidence, orientation and angle of incidence of atomic flux), it is possible to select the type of facets on which the growth takes place (shadowing effect), and consequently to elaborate self-organized systems of metal nanoislands constituted of stripes or linear chains of particles, whose optical properties display a light-polarization dependence
Hernandez, Avila Marcelo. "Etude de mélanges ternaires epoxyde/PMMA/montmorillonite : élaboration, contrôle de la morphologie et des propriétés". Lyon, INSA, 2007. http://theses.insa-lyon.fr/publication/2007ISAL0065/these.pdf.
Testo completoPMMA-epoxy-clay ternary composites have been prepared combining the polymerization induced phase separation phenomenon with two dispersion processing methods: a melt-blending and an ultrasonic-blending with solvent. Transmission electron microscopy (TEM) analysis shows that phase separation between PMMA and epoxy network was obtained as spherical nodules in both processing methods. Organoclay particles were finely dispersed into thermosetting network and predominantly delaminated in ultrasonic-blending, whereas organoclays formed micrometer-sized aggregates in melt-blending. Exfoliation state has been investigated using Small Angle X-Ray scattering (SAXS) in cured systems and during reaction. For reacted systems, an exfoliation of platelets can occur through the de-aggregation of large agglomerates into smaller particles composed of a few platelets. For in-situ SAXS studies, the distribution of the thicknesses of diffusing entities and the evolution of this distribution with reaction time were followed. This technique has showed also that movements at a nanometer scale of clay tactoids are possible even after the gel point. The effect of thermoplastic PMMA and clay Cloisite 30B addition on the cure kinetics of an epoxy/amine thermosetting system was investigated using differential scanning calorimetry (DSC). It appeared that the addition of PMMA slow down the reaction up to the phase separation due to a dilution effect of the reactive species. In opposition, the presence of clay accelerates the reaction (probably due to a catalytic effect of some metal ions introduced with the clay) but it has no sensitive effect on the cloud point conversion in the presence of PMMA. The reactivity of different systems has been studied and one kinetic model has been developed for the ternary system with help of previous studies with binary systems. The mechanics properties of different composites have been evaluated and discussed with help of fracture surfaces obtained by scanning electron microscopy. It was showed that the best dispersion of surfaces of clay did not give the best resistance to fracture critical initiation
Renauld, Elisabeth. "Etude de la fissuration par corrosion sous contrainte de l'alliage d'aluminium 7010 (Al-Zn-Mg-Cu) : Influence du traitement thermique". Bordeaux 1, 1994. http://www.theses.fr/1994BOR10574.
Testo completoVerguet, Amandine. "Développements méthodologiques et informatiques pour la microscopie électronique en transmission appliqués à des échantillons biologiques Alignment of Tilt Series (Chapter 7 of the Book: Cellular Imaging: Electron Tomography and Related Techniques, Hanssen Eric) An ImageJ tool for simplified post-treatment of TEM phase contrast images (SPCI) Comparison of methods based on feature tracking for fiducial-less image alignment in electron tomography". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS487.
Testo completoTransmission Electron Microscopy is a major tool for performing structural studies in biology. Some methods used for image sampling and analysis need to be improved in order to observe electron dose sensitive samples with good contrast and good signal to noise ratio. During this thesis, various methodological and computational approaches have been studied which aim to improve image quality. First, I evaluated the relevance of combining energy filtered imaging with the STEM mode. I show that this allows an improvement of the signal to noise ratio of images. Then, I devised an algorithm that generates an image from phase data. This approach allows improving the image contrast over direct imaging. The use of a phase plate and focal tilt series are both efficient tools to achieve this goal. While working on the software approach for processing of tilt series, we found that a qualitative result can be obtained from a single image. I developped the SPCI plugin for the ImageJ software. It allows processing between one and three focal images. My work involves optimization of the tomographic reconstruction process, including working with both alignment algorithms and reconstruction algorithms. I expose my studies on image alignment methods used on tilt series. These methods do rely on the use of key points and associated local descriptors. They have proved to be efficient to process images lacking fiducial markers. Finally, I propose a new unified algorithmic approach for 3D reconstruction of tomographic tilt series acquired with sparse sampling. I then derived another novel method that integrates the image alignment step in the process. Studies and developments will continue on both methods in futur work
Bousta, Faisl. "Amélioration de la rétention par le bois des sels d'ammonium quaternaire et conséquences sur la résistance à l'attaque des champignons : Etude du comportement, face aux basidiomycètes, du bois greffé par des motifs acyles à longue chaîne carbonée". Nancy I, 1998. http://www.theses.fr/1998NAN10235.
Testo completoTillous, Kessein Éric. "Contribution à l'étude de l'aluminium et ses alliages 2214-T6 et 7050-T74 transformés par oxydation micro-arcs (OMA)". Vandoeuvre-les-Nancy, INPL, 2006. http://docnum.univ-lorraine.fr/public/INPL/2006_TILLOUS_K_E.pdf.
Testo completoThe process of micro-arcs oxidation (OMA), whose principle is based on that of traditional anodization, applies to a group of metals and their alloys (Al, Mg, Ti, Zn, Nb, Ta, Hf, W, Sb, Mo, Bi). The specificity of this process lies in the participation of discharges or micro-arcs (followed by a gaseous emission) in the formation of the coating by conversion of the substrate. The discharges cause the formation of a coating made up of alumina whose properties are considerably different from those of layers obtained by traditional anodization. After a review about traditional anodization and micro-arcs oxidation, this work tackles the characterization of OMA coatings by several techniques: optical microscopy (OM), scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS) and electron probe microscopy analysis (EPMA) with wave-length dispersive spectrometry (WDS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and microtomography. Each technique of analysis produces complementary results making it possible to look deeper into the understanding of the growth mechanism of the three layers of the coating: porous outer layer, dense inner layer and the so called “barrier layer” at the coating / substrate interface. An assessment of the coating morphology can be suggested from the appearance of the surface treated in silicate bath. The defects of OMA coating are revealed. Correlations are established between the parameters of treatment (density and frequency of the current, ratio of negative to positive charge quantity applied to the electrode (qn / qp) and duration of the treatment), the nature of the substrate and the coating features (proportions of defects, various types of alumina, thickness of the layers) From these results of characterization, a model of the discharges formation and coating growth is proposed in the case of an aluminium alloy
Servanton, Germain. "Analyse quantitative de la distribution de l’arsenic dans les composants silicium nanométriques par spectroscopie de perte d’énergie des électrons, et contribution à l’étude de son incorporation par différentes techniques résolues à l’échelle atomique". Grenoble, 2010. http://www.theses.fr/2010GRENY048.
Testo completoNowadays, the developments of new technological nodes (CMOS 40-45 nm) require to improve physical characterization techniques in order to quantitatively map silicon dopant distribution, such as arsenic. Moreover, the dopant electrical deactivation process needs to be understood to optimize semiconductor component performances. We used Scanning Transmission Electron Microscopy (STEM) in Electron Energy Loss Spectroscopy (EELS) and Energy Dispersive X-ray (EDX) modes in order to quantitatively map at the nanometric scale the arsenic dopant distribution. We showed the necessity the lowered the primary beam energy down to 120 keV in order to significantly reduce the silicon radiation damages. The comparison between the two spectroscopic modes demonstrates that the EDX detector shows a fast saturation, while it is possible using EELS technique to map the As distribution in semiconductor components. Several applications from STMicroelectronics devices (CMOS, BiCMOS) are shown. Results demonstrate sensitivity down to 1. 10! cm° (0. 02%) with a spatial resolution close to 2 nm. In a second part of the thesis, we focused on the arsenic dopant deactivation process from epitaxially grown samples (As:Si and Ge:Si). It is known that As,;V, (V, vacancy) clusters tend to inactivate arsenic. Using Extended X-ray Absorption Fine Structure (EXAFS), we show the progressive arsenic clustering tendancy when the As concentrations increase. Atom Probe Tomography (APT) experiments performed at the Groupe de Physique des Matériaux (GPM) from the University of Rouen evidenced on the same layers a difference between the As-As and the Ge-Ge inter atomic distances. To conclude, on the contrary to the germanium, the arsenic atoms incorporates frequently in complex sites (not substitutional), which explains the low electrical activity from the studied layers
Delhaye, David. "Détermination expérimentale des caractéristiques physiques et chimiques de particules de suie émises par des turboréacteurs d'avion". Phd thesis, Université de la Méditerranée - Aix-Marseille II, 2007. http://tel.archives-ouvertes.fr/tel-00261972.
Testo completotraînées de condensation qui peuvent évoluer en nuage de type cirrus. Par ailleurs, ces particules de taille submicrométrique, dont l'impact sur la qualité de l'air est avéré, sont également source de questionnement quant à leur(s) effet(s) sur la santé publique.
La présente étude a pour objet la détermination expérimentale des caractéristiques physiques et chimiques des particules de suie émises par des turboréacteurs d'avions commerciaux. Les prélèvements sont effectués sur un banc d'essai de la société SNECMA
(groupe SAFRAN) par un dispositif mis au point au cours de ce travail et localisé derrière des turboréacteurs CFM56-5C et CFM56-5B qui équipent respectivement des avions long-courriers et moyen-courriers.
Diverses techniques expérimentales telles que la microscopie électronique en transmission (MET), la microscopie électronique à balayage (MEB), la spectrométrie dispersive d'énergie de rayons X (XREDS), et la spectroscopie infrarouge à transformée de Fourier (IRTF) sont mises en oeuvre pour étudier la morphologie, la structure, la distribution en taille, la composition chimique élémentaire des particules primaires de suie, et la nature des groupes fonctionnels présents à leur surface. La dimension fractale ( Df ) des agrégats de suie et leur diamètre de giration ( d g ) sont également établis.
Les résultats expérimentaux montrent que les suies émises par les deux turboréacteurs
étudiés présentent :
- des valeurs similaires de la dimension fractale des agrégats
- des distributions en taille log-normales pour les particules primaires et les agrégats
- des compositions chimiques élémentaires et des groupes fonctionnels très similaires
- des diamètres de giration des agrégats qui diffèrent
Par ailleurs, nous montrons que la phase de préparation des échantillons, préalable aux observations en MEB, a une influence importante sur la valeur déterminée de la moyenne géométrique de la distribution en taille des particules primaires. Par conséquent, nous préconisons de réaliser l'étude des caractéristiques physiques des particules primaires de suie aéronautique par MET plutôt que par MEB.
Leclerc, Gérald. "Etude et caractérisations de films minces de PLZT orientés : influence de la composition sur les propriétés ferroélectriques". Caen, 2006. http://www.theses.fr/2006CAEN2010.
Testo completoThis thesis deals with the elaboration of <111>-oriented PLZT thin films and with the characterizations of their structural and electrical properties. Materials such as (Pb,La) (Zr,Ti)O3 (PLZT) are also attractive because the modulation of the ferroelectric properties may be achieved by changing the amount of La dopant or by varying the Zr/Ti ratio. Thin films were deposited on Si-based substrate covered with <111> Pt. An ultra thin TiO2 layer is deposited prior to PLZT in order to obtain predominant <111> orientation. In a first step, experimental process was optimized by studying the influence of key deposition parameters, film thickness and orientation on the electrical and microstructural properties of these films. A RF multi-target sputtering technique was used and allowed the study of the whole PLZT phase diagram. The main objective is to reach high dielectric permittivity. Dielectric constant of 2100 and capacitance density of 72nF/mm² were obtained with the composition PLZT 22/28/72. To investigate the role of the substrate, PLZT films were also deposited on monocristalline-based substrates (LaAlO3/Pt and MgO/Pt). Strong modifications of thin film properties were obtained, polarisation of 47µC/cm² and permittivity of 3300 were measured depending of the chosen composition. Compared to Si/Pt substrate, such behaviour may be explained by a different configuration of the ferroelectric domain related to the epitaxial strain
Lourenço-Martins, Hugo. "Experiment and theory of plasmon coupling physics, wave effects and their study by electron spectroscopies". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS284/document.
Testo completoSurface plasmons (SP) are electromagnetic waves propagating at the interface between two media typically a metal and a dielectric. SPs can confine electromagnetic fields in very short volumes (typically one to few nanometers), well below the light diffraction limit. This property has a tremendous number of applications ranging from fundamental physics (e.g. quantum optics) to applications (e.g. cancer therapy). However, the price to pay is that SPs suffer from huge ohmic losses in the metal which leads to very short lifetimes (typically few femtoseconds). Theoretically, this presence of dissipation dramatically hardens the theoretical description of SPs. Another consequence of the sub-wavelength confinement of light associated with SPs is that their observation requires a nanometric resolution - which excludes the use of standard optical techniques. Yet, the scanning transmission electron microscope (STEM) is a particularly suitable tool to study SPs as it employs fast electrons with typical wavelength from 1 to 10 picometers. Thus, the last decade has seen the tremendous development of electron-based spectroscopies applied to nano-optics such as electron energy loss spectroscopy (EELS), cathodoluminescence spectroscopy (CL) or STEM- Hanbury Brown and Twiss interferometry (HBT). In this thesis, I explored different open problems of plasmonics and nano-optics under the scope of electron microscopy and spectroscopies. In chapter 3, I develop a formalism taking into account both the quantum and relativistic nature of EELS experiments using elements of quantum field theory. In chapter 4, I apply the latter formalism to the case of EELS measurements of SPs using electrons with shaped phase. In chapter 5, I give several theoretical and experimental results on coupling experiments involving SPs. Particularly, I demonstrate a counterintuitive type of coupling, the so-called self- hybridization which is a consequence of the non-Hermitian nature of the LSP eigenproblem and draw analogy with open quantum system. Finally, in chapter 6, I discuss the recent result on vibrational EELS in monochromated STEM
Letrouit, Angélique. "Nouveaux oxydes de métaux de post-transition : synthèses, structures cristallines et caractérisations". Caen, 2010. http://www.theses.fr/2010CAEN2031.
Testo completoMany post transition metal oxides exibit original electrochemical and conducting properties. For example, the tin doped In2O3 oxides or the antimony doped SnO2 oxides are transparent conductors, the Sb2O5. NH2O hydrated oxide is a proton conductor, the SnO2 oxide is anode material for lithium battery and the bismuth oxides Bi2-xLnxO3 (Ln = Lanthanides ions) or Bi2-xAxO3-x/2 (A = Sr, Ba) are anionic conductors. In order to generate new materials with such properties, the synthesis of new post transition metal oxides has been undertaken. Eleven new phases have been isolated and their crystal structures have been characterized. Structural characterizations have been achieved using powder or single crystal X-Ray diffraction coupled with Scanning (Imagery) or Transmission Electron Microscopy (Electron Diffraction, High Resolution). Five new phases (A1,5+xSbM5O11,5 (A/x= Sr/0,18 ; Ba/0) (M=Al, Ga), Sr1,5+xSb2-xAl5+xO14 (x= 0,21) and Na3Sb2Al5O14) constitute a new layered family of aluminum and antimony oxides named (AxSb2-yAl5+yO14)n(A1+UAl5O9)m. Three new phases BaSb2Al4O12, Sr33Sb24,25Al48O141,4 et K0,84Sb1,38Al0,78O4 are antimony and aluminum oxides isotypic or isostructural of already known post transition metal oxides. Electrochemical measurements of Li+ ions insertion have been performed on BaSb2Al4O12 phase which presents a hollandite structure. Three new phases AxSn2+2Si2O with (A/x=Na/2; K/2; Ba/1) are isotypic of antimony and aluminum oxides. Electrochemical measurements of supercapacity on those compounds have been reported
Rima, Wael. "Apport de la microscopie electronique dans la compréhension des mécanismes d’interactions entre nanoparticules et cellules biologiques". Thesis, Lyon, INSA, 2012. http://www.theses.fr/2012ISAL0131/document.
Testo completoOver the last few decades, nanoparticles have been studied in theranostic field with the objective of exhibiting a long circulation time through the body coupled to major accumulation in tumor tissues, rapid elimination, therapeutic potential and contrast properties. In this context, we developed sub-5 nm gadolinium-based nanoparticles that possess in vitro efficient radiosensitizing effects at moderate concentration when incubated with head and neck squamous cell carcinoma cells (SQ20B). Two main cellular internalization mechanisms were evidenced and quantified: passive diffusion and macro- pinocytosis. Whereas the amount of particles internalized by passive diffusion is not sufficient to induce in vitro a significant radiosensitizing effect, the cellular uptake by macropinocytosis leads to a successful radiotherapy in a limited range of particles incubation concentration. Macropinocytosis processes in two steps: formation of agglomerates at vicinity of the cell followed by their collect via the lamellipodia (i.e. the “arms”) of the cell. The first step is strongly dependent on the physicochemical characteristics of the particles, especially their zeta potential that determines the size of the agglomerates and their distance from the cell. These results should permit to control the quantity of particles internalized in the cell cytoplasm, promising ambitious opportunities towards a particle-assisted radiotherapy using lower radiation doses
Mikosch, Cuka Andi. "Développement d'expérimentations mécanique in situ dans un microscope électronique à balayage et en transmission environnemental pour étudier à l'échelle nanométrique les propriétés et le comportement de nanoparticules sous contraintes mécanique et environnementale". Thesis, Antilles, 2019. http://www.theses.fr/2019ANTI0329/document.
Testo completoThe need to be able to visualize and manipulate nano-samples of mineral or biological materials, while conducting quantitative tensile, compression, bending and shearing experiments, led to the development of a nano-manipulation device that can evolve in an electron microscope. scanning in environmental transmission.Such a device will therefore make it possible to measure the various forces involved and to visualize the interface of interest during the various manipulations performed under controlled environmental conditions (gas partial pressure of 10-8 to 2500 Pa, liquid medium).For each of these experiments a precise and meticulous analysis of the images realized with the SEM allowed us to extract data making it possible to quantify the phenomena studied
Poupard-Potin, Annick. "Etude par microscopie électronique STEM des joints de grains dans les céramiques électroniques : application aux cas des varistances à base de ZnO et des diélectriques BaTiO3-LiF". Phd thesis, Université Sciences et Technologies - Bordeaux I, 1986. http://tel.archives-ouvertes.fr/tel-00182709.
Testo completoNelayah, Jaysen. "Propriétés optiques de nanoparticules metalliques aux échelles sous-longueur d’onde". Paris 11, 2007. http://www.theses.fr/2007PA112331.
Testo completoFrom a fundamental point of view as well as for potential applications, understanding the srinking optical properties of metallic nanoparticles is crucial. In this manuscript, we showed on different metallic nanosystems, the possibility of mapping at the sub-wavelength scale the spatial variations of the electromagnetic fields associated to surface Plasmon resonances in the visible domain. This has been made possible by combining energy resolution improvements brought about during this thesis to low-loss electron energy loss spectroscopy (EELS) and the nanometer resolution accessible in a scanning transmission electron microscope. Experiments undertaken on triangular silver nanoprisms, gold nanodecahedra and dimers of triangular silver nanoprisms have enabled us to study, in particular, the correlation existing between the surface plasmons maps and the direction of the excitation its symmetry and the shapes of the nanoparticles. Moreover, using the recent link established between low-loss EELS signals and the local density of photonic states (this is a universal quantity analogous to the local density of electronis states measured in tunneling microscope), we have been able to analytically calculate and simulate the EELS response of a molecule in the presence of planar metallic surface and thus, verify the feasibility of single molecule EELS spectroscopy
Matei, Constantin Ionut. "Recherche des assemblages moléculaires actifs en biolubrification en vue du diagnostic et de la thérapeutique précoce de pathologies articulaires". Phd thesis, Université Claude Bernard - Lyon I, 2012. http://tel.archives-ouvertes.fr/tel-00932693.
Testo completoRima, Wael. "Apport de la microscopie electronique dans la compréhension des mécanismes d'interactions entre nanoparticules et cellules biologiques". Phd thesis, INSA de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00876351.
Testo completoBelin, Monique. "Les hydathodes et les nectaires foliaires de plantes tropicales : aspects morphologiques, ontogeniques et ultrastructuraux". Paris 6, 1986. http://www.theses.fr/1986PA066056.
Testo completoDesmarest, Cyrille. "Propriétés électromagnétiques de matériaux superparamagnètiques : préparation, et caractérisation magnétique et optique". Versailles-St Quentin en Yvelines, 2000. http://www.theses.fr/2000VERSA011.
Testo completoBoudarham, Guillaume. "Nanooptique avec des électrons rapides : métamatériaux, formulation modale de la EMLDOS pour des systèmes plasmoniques". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2011. http://tel.archives-ouvertes.fr/tel-00624471.
Testo completoShinde, Deodatta. "Utilisation de la sonde atomique tomographique laser pour les études spectroscopiques des matériaux pour l'énergie". Rouen, 2016. http://www.theses.fr/2016ROUES042.
Testo completoLaser assisted atom probe tomography (LaAPT) is a powerful technique for the structural and chemical analysis of materials at near atomic resolution and in 3-dimensions. Considering the nanoscale specimen and the use of ultra-fast laser pulses in the technique, this instrument can also be used to study light-matter interaction at the nanoscale. Hence the technique will not only give structural and chemical characterization at atomic scale of materials but also new insight on the optical and electrical properties at nano-scale. In this regard, the prime objective of this thesis is to study the feasibility of LaAPT as a versatile tool to investigate structural and optical properties of the nanoscale material with particular emphasis on materials for solar-energy plant, like METallic CERamics (CERMET), and for light emission, like InGaN/GaN quantum wells. The optical absorption properties of nanotips of Au-nanoparticles embedded in MgO and Fe2O3 matrix, have been studied coupling LaAPT analysis with optical and electron microscopy. Moreover, the heating process induced by the laser-energy absorption was also discussed. In the case of InGaN/GaN quantum wells, a novel correlative approach was introduced to study the direct correlation between structural and optical emission properties using LaAPT, Scanning Transmission Electron Microscopy (STEM) and micro-photoluminescence (µ-PL) spectroscopy
Khong, Benjamin. "Fiabilité prédictive de composants de puissance soumis à des tests de fatigue accélérée". Toulouse, INSA, 2007. http://eprint.insa-toulouse.fr/archive/00000177/.
Testo completoUnder regular operating conditions, power devices designed for automotive applications have to undergo cyclic stresses, generally electro-thermally driven. To perform accelerated aging tests of these MOS-based devices, a dedicated test bench has been set up. The aim of this work is twofold : firstly determining the influence of the input parameters (temperature, cycle period, injected current) on the power device failure. Then analyzing the microstructure of aged components at different scales to establish the physical causes of failure. In a first part, this study briefly describes the different types of power components, their main application and how they have technologically evolved in the past years. The SPSS (Single Power Side Switch) herein investigated is a switch whose fabrication is based on the "SmartMos" technology, recently developed by Freescale Semiconductor. The inner and outer structure of the device (connexions, source-grid active region, heat sink and solders) as well as the tools used for the analysis (TEM, SEM, FIB, SAM and SAT) are then described. A new procedure, based on the controlled aging of the devices led to the establishment of the power die/heat sink delamination as the main electric failure mode. It also allowed the monitoring of the propagation of the delamination. This power die/heat sink delamination is probably the cause of more abrupt failures leading to the complete ruin of the devices. In parallel, we have shown that the grain structure of the source metal, made of aluminum, evolves according to both the number of cycles and the condition of the tested device
Bahri, Mounib. "Caractérisation structurale des hétérostructures à base de GaSb et de GaP épitaxiées sur silicium (001)". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS045/document.
Testo completoMonolithique integration of III-V compound semiconductors on silicon makes possible the large scale integration of compound semiconductors for optical and electronic devices. However, the growth of III-V semiconductors on silicon generate several defects (threading dislocations, twins and antiphase boundaries). In this PhD thesis, we studied structural properties of GaSb-based and GaP-based hetero-structures grown on silicon using X-Ray diffraction and Transmission Electon Microscopy. Threading dislocations are the major defects in the growth of GaSb on Si because of the high lattice mismatch between the two materials(12.2%). Other defects like twins are presents on the growth of GaSb on Si. Twins are related to the crystalline quality of surface substrate (contaminants and roughness). We developed a cleaning process of surfaces which shows a high efficiency on twins density reduction. We reduced the high defects density using super-lattices . The super-lattices act not only as a dislocations filter but also help antiphase domains closure. The efficiency of super-lattices depends on its nature (thickness and strain) and its position on the structure. With our dislocations geometrical recombination model, we bring out the global interaction between dislocations and we define essential interaction parameters between dislocations. For the growth of GaP on Si, We have shown that the initial coverage of gallium on the substrate in the early stages of growth has a major effect on the presence of micro-twins, but also on the size and density of the antiphase domains. Due to the small lattice mismatch between GaP and Si (0.37%), antiphase boundaries and domains are the major defects on the GaP-based heterostructures. Antiphase domains can be blocked near the interface using specific growth conditions (substrate miscut, growth temperature, strained thin films). We showed with the two heterostructures (GaP-based and GaSb-based) that the suppression of antiphase boundaries decreases semiconductors roughness. We studied the influence of Nitride incorporation on the STEM-HAADF contrast of GaPN films. This inversed contrast (GaPN layers are more brilliant than GaP ) depend on two parameters: the deformation state of GaPN lattice compared to GaP one and the punctual defects related to the Nitride incorporation. Those defects can be Interstitial or anti-site Ga atoms
Losquin, Arthur. "Surface Plasmon modes revealed by fast electron based spectroscopies : from simple model to complex". Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00919765.
Testo completoFarizy, Gaëlle. "Mécanisme de fluage sous air de composites SiCf-SiBC à matrice auto-cicatrisante". Caen, 2002. http://www.theses.fr/2002CAEN2035.
Testo completoFlageolet, Benjamin. "Effet du vieillissement du superalliage base nickel N18 pour disques de turbines sur sa durabilité en fatigue et en fatigue-fluage à 700°C". Poitiers, 2005. http://www.theses.fr/2005POIT2274.
Testo completoThe engines that will equip second generation civil supersonic aircrafts will be supposed to have a longer lifetime and a better efficiency than existing ones. As a consequence, turbine disks will be exposed to a high temperature, close to 700 °C for long periods of time. The purpose of this work is to analyse, in these conditions, the microstructural evolution of the disk alloy N18 induced by a prolonged high temperature exposition, and to assess its effect on the material fatigue and creep-fatigue durability at 700 °C. Our experimental approach is based on the characterization of the modifications of the gamma' precipitation, that essentially concerns the finest population (tertiary), but also on different types of high temperature mechanical tests. We propose different approaches to describe the coarsening process undergone by tertiary precipitates during short term ageing, and to illustrate the strong kinetics slow down evidenced for long term ageing experiments. No microstructural effect has been observed on the material's durability when it is tested in fatigue conditions. However, we note a reduced creep-fatigue life after prior high temperature exposure. This lifetime reduction has been analysed through the damaging process and the strong coupled effects existing between creep, fatigue and oxidation
Mahfoud, Zackaria. "Nanometric spectroscopies of plasmonic structures and semi-conductors nanocrystals". Thesis, Troyes, 2014. http://www.theses.fr/2014TROY0003/document.
Testo completoFor this thesis, I have realised some experimental works using electron microscopy and electron spectroscopies for the study of plasmonic nanostructures and semiconductor nanocrystals . The aim being to study their optical properties with spatial resolutions of the order of a few nm. At this level it is possible to observe the electric near-field associated to the localised surface plasmon resonances supported by metallic nanostructures . So I was able to study the effect due to the presence of roughness on single gold nanorods and I have found that their presence locally alterate the structure of the electric near-field . Combined measurement of electron energy loss spectroscopy (EELS ) and cathodoluminescence spectroscopy were used to compare the near-field and far-field responses respectively. A study by EELS on the coupling between two metal nanorods positioned end to end and separated by a disance of tens of nanometers was used to map the localisation of hybridised modes separately on each branch of the dimers. Finally, comparative studies of cathodoluminescence and photoluminescence on single quantum dots have shown the equivalence of the information collected by these two techniques for such light emitters
Bélier, Benoît. "Développement de micro-leviers à fonctions optiques intégrées pour la microscopie à effet tunnel photonique et la microconnexion optique". Montpellier 2, 1999. http://www.theses.fr/1999MON20145.
Testo completoTerryn, Christine. "Mesure locale de la concentration en eau à l'échelle subcellulaire dans le matériel biologique par imagerie champ sombre et spectroscopie de pertes d'énergie des électrons dans la région des faibles pertes. Caractérisation d'effets cytotoxiques". Reims, 2001. http://www.theses.fr/2001REIMS022.
Testo completoHabib, Lamice. "Étude des propriétés membranaires des vésicules lipidiques incorporant des triterpènes oxygénés bioactifs d'origine végétale : application à la cucurbitacine E et à l'érythrodiol". Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10022/document.
Testo completoCucurbitacin E and erythrodiol are natural oxygenated triterpenes having respectively, a tetra and pentacyclic skeleton. They are known for their numerous biological properties. In this thesis, we studied their interaction with the membranes of lipid vesicles to better understand their pharmacodynamics. We have prepared liposomes in the absence and presence of cucurbitacin E and erythrodiol using the reverse phase evaporation technique followed by extrusion, the hydration of lipid film and the ethanol injection techniques. The physicochemical characteristics of lipid vesicles incorporating or not the triterpenic molecules were investigated by appropriate techniques. The determination of cucurbitacin E and erythrodiol in the vesicles by high performance liquid chromatography showed high incorporation efficiencies of both triterpenes. Size measurements obtained by dynamic light scattering showed that liposomes incorporating triterpenes were smaller than empty liposomes. The images obtained by transmission electron microscopy confirmed the formation of spherical vesicles. Measurements of vesicles dimensions by atomic force microscopy (AFM) demonstrated that liposomes incorporating cucurbitacin E were higher and more resistant to the force exerted by the AFM tip than the blank liposomes. Liposomes incorporating erythrodiol were more fragile and tend to break up into lipid bilayers on the mica surface. Results obtained by differential scanning calorimetry suggested that cucurbitacin E is localized at the polar-apolar interface of the liposomal membrane while erythrodiol is inserted between the acyl chains of the phospholipids leading to the formation of heterogeneous lipid domains. The release kinetics of the sulforhodamin B encapsulated into the aqueous phase and measured by fluorescence spectroscopy revealed that the liposomal membrane becomes in the presence of cucurbitacin E, more permeable to this probe. The overall results suggest that cucurbitacin E and erythrodiol affect differently
Salhi, Billel. "Synthèse et caractérisation de nanofils et des nanostructures 3 D à base de silicium". Lille 1, 2007. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2007/50376-2007-5.pdf.
Testo completoTorres, Nogueira Luisa Maria. "Les lésions osseuses tranchantes (par scies) et tranchantes contondantes : analyse des mécanismes lésionnels et des instruments à l'origine de ces lésions". Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0272/document.
Testo completoIn this experimental work bone lesions produced by saws and a hatchet on human and animal samples were analyzed. With regard to the saws, 170 experimental false starts lesions were studied under stereomicroscope produced by five different saws. Universal saws behave like crosscut saws, because each tooth displays a tilt backwards. The minimum width of the kerf makes it possible to classify bone lesions according to Symes’ categories. Convex profiles indicate the use of a universal or crosscut saw. Concave profiles vary a great deal and indicate the use of a rip saw. The shape of the walls allows for determining the type of set except when they are straight or difficult to analyze. Among the secondary criteria, the appearance of the striae on the kerf floor is able to point the type of set. For the study of bone lesions by a hatchet a standardized device was used to produce small bone lesions. The stereomicroscope was able to observe the vertical striae explained by the vertical movement of the instrument at the time of impact. The scanning electron microscope allowed for a detailed analysis of bone lesions and made it possible to understand the uprising and the lateral pushing back. The presence of a lateral pushing back and of vertical striae is sufficient to determine that the bone lesions were achieved by a sharp blunt instrument. These characters are visible even after carbonization
Bergeau, Dorian. "Contribution à l'études des systèmes de sécrétion chez la bactérie Pseudomonas fluorescens". Rouen, 2015. http://www.theses.fr/2015ROUES026.
Testo completoType III secretion systems (T3SS) are used by some pathogenic bacteria to inject effectors through the eukaryotic cell membranes. These structures allow the colonization of the host cell and the paralysis of its defenses. Recently, T3SS genes were detected in Pseudomonas fluorescens saprophytic rhizobacterium surprisingly found in clinical environment. The T3SS genes diversity, phylogeny and virulence were investigated in P. Fluorescens found in hospital or plant environments. A cluster integrates isolates of blood infections, close to P. Putida and P. Mosselii species. These bacteria harbor T3SS genes belonging to Ysc family and share 99% of homology with T3SS of the opportunistic pathogen P. Aeruginosa. The second cluster includes other hospital isolates (respiratory tract or abscess) close to environmental P. Fluorescens. These bacteria are psychrotrophs and have a broader phylogenetic diversity. Their T3SS genes belong to the Hrp1 family, usually found in the plant pathogen P. Syringae. A study of external components of some P. Fluorescens models was performed by transmission electron microscopy. It reveals the first images of a P. Fluorescens T3SS. This T3SS is a Hrp1 pilus of around 1. 5 μm long whose production is induced by plant and fungal sugars. It could be involved in the induction of plant defense systems. Our study also reveals the presence of dendritic fibril bundles and vesicles, possibly involved in adhesion, nutrition and /or communication at the scale of the microbial colony
Zhao, Zhao. "Identification d'une nouvelle phase d'hydrure de zirconium et modélisation à l'échelle mésoscopique de sa précipitation". Thesis, Lille 1, 2008. http://www.theses.fr/2008LIL10166/document.
Testo completoLn pile, zirconium alloys in contact with the primary medium are submitted to hydrogen absorption that has significant consequences on their thermodynamic, mechanical and corrosion behaviors. Therefore, hydrogen in solid solution or hydrides precipitation can affect Zirconium alloys behaviors during service but also in long term storage and in accidental conditions. For both fundamentals aspects and safety reasons it is important te understand the precipitation process and to predict the influence various parameters like temperature, stresses, cooling rates and microstructure may have. Numerical modeling at the mesoscopic scale is an appealing approach to describe the precipitation and the "phase field" method appears to be particularly weil suited. The achievement of a realistic mesoscopic modeling should take into account an accurate kinetic, thermodynamic and structural data base in order to properly describe hydride nucleation, growth and coalescence as weil as hydride interaction with externat stresses. Such a data base relies on experimental data that are not always available; this is the reason why an accu rate structural characterization was performed. Therefore transmission electron microscopy observations were carried out on Zircaloy 4 specimens with various H contents. From this study, a new hydride phase called <, coherent with the matrix, was identified
Duval, Jean-Luc. "Étude de l'influence de divers paramètres biologiques et physico-chimiques sur l'affinité cellulaire de différents biomatériaux en culture in vitro, en vue de leur utilisation comme revêtement prothétique". Compiègne, 1993. http://www.theses.fr/1993COMPDU07.
Testo completoMonier, Etienne. "Reconstruction rapide d'images multi-bandes partiellement échantillonnées en spectromicroscopie EELS". Thesis, Toulouse, INPT, 2020. http://www.theses.fr/2020INPT0090.
Testo completoIn electron energy loss spectroscopy (EELS), the sample to be analyzed is exposed to an electron beam, and the measure of the energy loss after passing through the material informs about the chemical composition. For samples particularly sensitive to electronic irradiation damages, such as organic materials, the experimenter is constrained to reduce the total electron dose received by the sample while obtaining a satisfying signal-to-noise ratio. With the recent development of sampling modules adapted to scanning transmission electron microscopes (STEM), the initial raster acquisition (i.e., line-by-line) has become highly configurable. Henceforth, it is now possible to visit any set of spatial positions during the acquisition. Based on these technical advances, a lot of works proposed optimized acquisition schemes for preserving sensitive samples. For a global electron dose equivalent to standard sampling, these strategies consist in visiting less spatial positions, i.e., to perform partial sampling. As a consequence, a higher electron dose per spatial position is allowed, which permits to increase the signal-to-noise ratio for each sampled spectrum. Yet, a post-processing step is required to infer the missing spectra. Among the reconstruction techniques used in the literature, the interpolation methods are fast but rather inaccurate ; they are particularly efficient for displaying the full image along the acquisition process. On the contrary, the dictionary learning-based methods are very performant, but are memory and computation demanding. They are chosen in priority to refine the reconstructed image after experimenting. Finally, only a few works attempt to fill this gap. The main objective of this Ph.D. thesis is to propose fast and accurate reconstruction algorithms for STEM-EELS imaging. Similarly to the interpolation methods, they should be fast enough to visualize the reconstructed image along the acquisition. Meanwhile, they should also achieve better reconstruction performances than those reached by interpolation, close to those of dictionary learning-based methods. To that end, regularized least square methods are proposed in the context of spatially smooth samples or of periodic crystalline samples. The proposed algorithms are then tested based on synthetic as well as real data experiments. The interest of partial-sampling based methods and the performances with respect to other reconstruction methods are evaluated
Du, Fang. "Optimisation de l'architecture de mélanges de polymères polaires contenant des nanocharges hydrophiles : étude morphologique et rhéologique". Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10204.
Testo completoImmiscible ternary blends constituted of PA11 and PEO or PA6 and PA11 containing either modified or native clay were prepared by melt extrusion or by water-assisted extrusion. The effect of the type of clay and water injection during extrusion on thermal, rheological and mechanical properties has been evaluated for all ternary blends. Transmission electron microscopy highlighted a selective localization of clay in the less viscous phase in both blends, independently of the type of clay. With the injection of water during extrusion, the migration of a part of clay particles from the less viscous phase to the more viscous phase was observed for certain PA11/PEO blends. The theoretical prediction, based on the wetting coefficient according to Sumita’s model, does not correspond to the observed localization. Several explanations have been proposed, particularly the influence of viscosity ratio between the two phases. Morphological observations by scanning electron microscopy showed the influence of clay and water on the size of the dispersed phase. Rheological study revealed the impact of modified or native clay on the degradation of polymers which can be limited by water-assisted extrusion