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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Magnetic Resonance Gradient Echo Phase Imaging as a Means of Detecting Alterations in the Tissue Microarchitecture of the Human Corpus Callosum

Schreiber, Sharon Kristen 26 June 2012 (has links)
No description available.
12

In situ Nanoscale Quantification of Corrosion Kinetics by Quantitative Phase  Microscopy

Fanijo, Ebenezer Oladayo 23 November 2022 (has links)
Corrosion-related degradation incurs a significant cost to infrastructure and society. In 2016, the direct corrosion cost was estimated at $276 billion, which is 3.1% of the U.S. gross domestic product. Despite the known consequences of corrosion damage, many unknowns still exist, such as the mechanisms and rates of chloride-induced corrosion initiation and propagation. There is also a lack of high-quality quantitative kinetic data and analysis that can obtain the fundamental micro- and nanostructural mechanisms and initiation of metal corrosion. The corrosion initiation in metals is considered to be governed by dynamic processes that take place at the nanoscale. Thus, the measurement of nanoscale surface structures correlated with electrochemical properties in metals is critical in the understanding of corrosion initiation, and microstructure-corrosion relationship, as well as efforts toward materials design for corrosion mitigation. As a fundamental approach to this study, a systematic review of different surface characterization techniques was initially discussed. This entailed their principles, applications, and perspectives for surface corrosion monitoring, enabling the development of next-generation inhibition technologies, and improving corrosion predictive models. Unprecedented, this research study presented a novel application of a quantitative phase microscopy technique, spectral modulation interferometry (SMI), for in situ nanoscale characterization of corrosion of different alloys in real-time. SMI offers high sensitivity, rapid image acquisition, and speckle-free images; thus, real-time quantification of surface topography evolution during corrosion can be obtained accurately to evaluate the temporally- and spatially-dependent corrosion rates. With an innovative additive-manufactured fluid cell, experiments were performed under flowing solution conditions. Electrochemical tests via stepwise polarization and solution chemistry through collected aliquots of outflow solution were also performed alongside the nanoscale SMI experiment to simultaneously provide corroborating corrosion rate measurements. This innovative approach to measuring dissolution rates of metal at three levels can provide highly quantitative kinetic data of reacting surfaces that are rarely explored in the literature. First, the in situ SMI combined with the stepwise potentiostatic tests and the solution chemistry analysis was used to investigate the nanoscale characterization of corrosion of an AA6111-T4 aluminum alloy in real-time. The corrosion experiment was conducted in a 0.5 wt.% NaCl flowing solution acidified to pH ⁓2.9 by acetic acid. Based on the quantitative 3D height profiles across the corroded surface, pit formation resulting from rapid local corrosion was predominant, which is heterogeneously distributed and was appearing at different times. The computed time-dependent dissolution rates of aluminum also varied as the experiment proceeded, with the combination of linear and nonlinear surface normal distributions. An initial mean linear dissolution rate of (0.40 ± 0.007) μmol m−2 s−1 transitioned to a more rapid mean rate of (1.95 ± 0.035) μmol m−2 s−1, driven by the anodic polarization. Dissolution rates from the three performed methods follow similar trends and there is the visibility of linking the nanoscale in situ SMI data to the electrochemical corrosion measurements and ex situ chemical solution analysis. At the end of the corrosion period, rates of 118, 71, and 2.45 μmol m−2 s−1 were obtained from electrochemical measurements, ex situ solution analyses, and in situ SMI corrosion measurements, respectively. In addition, SMI–electrochemical experiments were performed to evaluate the effect of thermal history on corrosion modes and rates of AA6111. Quantitative estimates of the corrosion initiation and propagation in the alloy were also assessed. A single coil of AA6111 alloy that was solution heat treated at a temperature above 500°C and quenched with 2 different water quench rates (i.e., slow-quenched at 131ºC/s and fast-quenched at 506ºC/s) with each in T4 and T82 temper condition was investigated in this study. Irrespective of the quenched and/or temper conditions, the electrochemical potential-current (E-i) results showed a similar pattern in the polarization curve and similar current response over the immersed time, and a small difference in their corrosion behavior will be difficult to detect due to the dissolution kinetics that takes place on the nanoscale. As revealed from the SMI topography map, the corrosion modes at the nanoscale were very distinct despite having similar electrochemical responses and chemical compositions. Primarily, heterogeneous dissolution of intergranular corrosion (IGC) and crystallographic pitting was observed in the tested alloy substrates, with the slow-quenched samples susceptible to IGC and the fast-quenched samples susceptible to crystallographic pitting. The nucleation of IGC sites is triggered by the increased coarsening and formation of precipitates in the grain boundary, while the pitting corrosion is attributed to the coarsening of the precipitates in the grain bodies. The quantitative analysis of topography evolution from the SMI data revealed a non-uniform (i.e., heterogenous) surface dissolution, as is typical for aluminum alloys. Notably, the fast-quenched material resisted corrosion initiation for a longer time and showed great resistance even at higher anodic polarization. However, an instant breakdown then occurred after 60mV of polarization and corrosion accelerated faster, relative to the slow-quenched material which initiated sooner (i.e. with less overpotential). In this setup, it is now possible to detect and evaluate these differences quantitatively through a quick corrosion test with the combined electrochemical-SMI technique. Therefore, this work showed that the corrosion susceptibility of AA6111 alloy is influenced by the thermal history, which can be controlled with a proper quench rate and further tempering. Additionally, this research also utilized the novel SMI techniques to investigate in situ chloride-induced corrosion of A615 low-carbon steel at the nanoscale. Along with surface topography monitoring, a potentiostat was connected to simultaneously monitor the bulk electrochemical activity of the carbon steel. Experiments were conducted in chloride-free and chloride-enriched solutions at pH 5 to investigate the role of chloride on topography evolution, dissolution mode, and corrosion kinetics. The 3D topography map acquired from the SMI showed an early formation of localized shallow pits on the surface subjected to the chloride free-solution. A more detrimental form of corrosion was obtained on the samples in chloride-enriched solution, which revealed early-age microcracks or intergranular defective sites associated with the heterogeneous roughening of the sample surface. The presence of chloride ions also influenced the initiation period of corrosion. Indeed, higher grain defects were obtained in samples immersed in 5.0 wt.% NaCl solution than the sample in 1.0 wt.% NaCl solution. The quantitative analysis of the height profile data (acquired from SMI) verified the heterogeneity of the corrosion process of both samples either susceptible to pitting corrosion and/or intergranular corrosion behavior. A faster dissolution rate was acquired on the sample immersed in 5.0 wt.% NaCl solution, with the rate of (3.53 ± 0.103) μmol m−2 s−1 and (5.64 ± 0.0225) μmol m−2 s−1 computed at the initiation and propagation stages, respectively. Likewise, the estimated volume loss followed a similar trend to the 3D surface topography data, but a distinct behavior in the volume loss was observed when compared to the void volume obtained from the electrochemical monitoring. This confirmed that the electrochemical measurement overestimates metal loss and does not present a good representation of material dissolution on the nanoscale. Finally, a different perspective of corrosion mitigation in the metallic alloy was presented. The extensive application of deicing salts has led to significant deterioration in many transportation infrastructures and automobiles due to corrosion. In this regard, the work investigated the corrosion inhibition performance of 2 corn-derived polyols, namely: sorbitol, and mannitol, on reinforced steel rebar. The results demonstrated that the incorporation of polyols in the deicing solution reduced the corrosion initiation while the inhibition rate increased as the polyol content increased from 0% to 5wt.%. The outcome of this study contributed to the search for mitigation strategies to minimize the impact of deicing chemicals on steel infrastructures. Overall, it is evident that corrosion is a huge durability problem and requires significant consideration when designing metals or alloys that are usually exposed to hostile environments. Understanding the nanostructural and kinetics of corrosion at both the initiation and propagation periods, as well as its thermodynamics, is important for designing a suitable protection strategy. This dissertation is expected to present the application of the surface technique to directly quantify the dynamic evolution of site-specific local corrosion of metals during early initiation stages at the nanoscale. / Doctor of Philosophy / Corrosion-related degradation incurs a significant cost to infrastructure and society. In 2016, the direct corrosion cost was estimated at $276 billion, which is 3.1% of the U.S. gross domestic product. Despite the known consequences of corrosion damage, many unknowns still exist, such as the mechanisms and rates of chloride-induced corrosion initiation and propagation. There is also a lack of high-quality quantitative kinetic data and analysis that can obtain the fundamental micro- and nanostructural mechanisms and initiation of metal corrosion. The corrosion initiation in metals is considered to be governed by dynamic processes that take place at the nanoscale. Thus, the measurement of nanoscale surface structures correlated with electrochemical properties in metals is critical in the understanding of corrosion initiation, and microstructure-corrosion relationship, as well as efforts toward materials design for corrosion mitigation. As a fundamental approach to this study, a systematic review of different surface characterization techniques was initially discussed. This entailed their principles, applications, and perspectives for surface corrosion monitoring, enabling the development of next-generation inhibition technologies, and improving corrosion predictive models. Unprecedented, this research study presented a novel application of a quantitative phase microscopy technique, spectral modulation interferometry (SMI), for in situ nanoscale characterization of corrosion of different alloys in real-time. SMI offers high sensitivity, rapid image acquisition, and speckle-free images; thus, real-time quantification of surface topography evolution during corrosion can be obtained accurately to evaluate the temporally- and spatially-dependent corrosion rates. With an innovative additive-manufactured fluid cell, experiments were performed under flowing solution conditions. Electrochemical tests via stepwise polarization and solution chemistry through collected aliquots of outflow solution were also performed simultaneously with the nanoscale SMI experiment to provide corroborating corrosion rate measurements. This innovative approach to measuring dissolution rates of metal at three levels simultaneously can now provide highly quantitative kinetic data of reacting surfaces that are not explored in the literature.
13

Quantitative Anisotropy Imaging based on Spectral Interferometry

Li, Chengshuai 01 February 2019 (has links)
Spectral interferometry, also known as spectral-domain white light or low coherence interferometry, has seen numerous applications in sensing and metrology of physical parameters. It can provide phase or optical path information of interest in single shot measurements with exquisite sensitivity and large dynamic range. As fast spectrometer became more available in 21st century, spectral interferometric techniques start to dominate over time-domain interferometry, thanks to its speed and sensitivity advantage. In this work, a dual-modality phase/birefringence imaging system is proposed to offer a quantitative approach to characterize phase, polarization and spectroscopy properties on a variety of samples. An interferometric spectral multiplexing method is firstly introduced by generating polarization mixing with specially aligned polarizer and birefringence crystal. The retardation and orientation of sample birefringence can then be measured simultaneously from a single interference spectrum. Furthermore, with the addition of a Nomarski prism, the same setup can be used for quantitative differential interference contrast (DIC) imaging. The highly integrated system demonstrates its capability for noninvasive, label-free, highly sensitive birefringence, DIC and phase imaging on anisotropic materials and biological specimens, where multiple intrinsic contrasts are desired. Besides using different intrinsic contrast regime to quantitatively measure different biological samples, spectral multiplexing interferometry technique also finds an exquisite match in imaging single anisotropic nanoparticles, even its size is well below diffraction limit. Quantitative birefringence spectroscopy measurement over gold nanorod particles on glass substrate demonstrates that the proposed system can simultaneously determine the polarizability-induced birefringence orientation, as well as the scattering intensity and the phase differences between major/minor axes of single nanoparticles. With the anisotropic nanoparticles' spectroscopic polarizability defined prior to the measurement with calculation or simulation, the system can be further used to reveal size, aspect ratio and orientation information of the detected anisotropic nanoparticle. Alongside developing optical anisotropy imaging systems, the other part of this research describes our effort of investigating the sensitivity limit for general spectral interferometry based systems. A complete, realistic multi-parameter interference model is thus proposed, while corrupted by a combination of shot noise, dark noise and readout noise. With these multiple noise sources in the detected spectrum following different statistical behaviors, Cramer-Rao Bounds is derived for multiple unknown parameters, including optical pathlength, system-specific initial phase, spectrum intensity as well as fringe visibility. The significance of the work is to establish criteria to evaluate whether an interferometry-based optical measurement system has been optimized to its hardware best potential. An algorithm based on maximum likelihood estimation is also developed to achieve absolute optical pathlength demodulation with high sensitivity. In particular, it achieves Cramer-Rao bound and offers noise resistance that can potentially suppress the demodulation jump occurrence. By simulations and experimental validations, the proposed algorithm demonstrates its capability of achieving the Cramer-Rao bound over a large dynamic range of optical pathlengths, initial phases and signal-to-noise ratios. / PHD / Optical imaging is unique for its ability to use light to provide both structural and functional information from microscopic to macroscopic scales. As for microscopy, how to create contrast for better visualization of detected objects is one of the most important topic. In this work, we are aiming at developing a noninvasive, label-free and quantitative imaging technique based on multiple intrinsic contrast regimes, such as intensity, phase and birefringence. Spectral multiplexing interferometry method is firstly introduced by generating spectral interference with polarization mixing. Multiple parameters can thus be demodulated from single-shot interference spectrum. With Jones Matrix analysis, the retardation and orientation of sample birefringence can be measured simultaneously. A dual-modality phase/birefringence imaging system is proposed to offer a quantitative approach to characterize phase, polarization and spectroscopy properties on a variety of samples. The high integrated system can not only deliver label-free, highly sensitive birefringence, DIC and phase imaging of anisotropic materials and biological specimens, but also reveal size, aspect ratio and orientation information of anisotropic nanoparticles of which the size is well below diffraction limit. Alongside developing optical imaging systems based on spectral interferometry, the other part of this research describes our effort of investigating the sensitivity limit for general spectral interferometry based systems. The significance of the work is using Cramer-Rao Bounds to establish criteria to evaluate whether an optical measurement system has been optimized to its hardware best potential. An algorithm based on maximum likelihood estimation is also developed to achieve absolute optical pathlength demodulation with high sensitivity. In particular, it achieves Cramer-Rao bound and offers noise resistance that can potentially suppress the demodulation jump occurrence.
14

Development of confocal optical holographic microscopy

McLeod, Robert A. 06 September 2006 (has links)
Optical Confocal Holography is a combination of two well known concepts: confocal microscopy and optical (laser) holography. Confocal microscopy places an aperture at a conjugate focus to the specimen focus. This filters any rays that are not on the focus plane, allowing a 3-dimensional image of the specimen to be built up over a set of planes. Holography is the measurement of both the amplitude and phase characteristics of light. Typically most methods only measure the amplitude of the image. The phenomenon of interference allows the determination of the phase shift for a coherent source as well. The phase information is directly related to the index of refraction of a material, which in turn is a function of the temperature and composition. As a technique, confocal holography holds promise to better characterize many physical processes in materials science, such as combustion and convection. It also may contribute to the biological sciences by imaging low-contrast, weak-phase objects. Thanks to the ongoing, continued improvement in computer processing speed, it has recently become practical to interpret data from confocal holography microscopy with a computer. The objective of the microscope is to non-invasively measure the three-dimensional, internal temperatures and compositions (e.g. solute/solvent gradient) of a specimen. My contributions over the course of two years to the project were: generation and optimization of an optical design with a software package known as Zemax; sourcing and purchasing all components; formation of a CAD model of the microscope; experiments to characterize building vibrations and air currents; and the development of software in Visual Basic to simulate holograms and execute reconstruction algorithms for the specific application of confocal holography.
15

Technical Improvements in Quantitative Susceptibility Mapping

Liu, Saifeng 04 1900 (has links)
<p>Quantitative susceptibility mapping (QSM) is a promising technique to study tissue properties and function <em>in vivo</em>. The presence of a susceptibility source will lead to a non-local field variation which manifests as a non-local behavior in magnetic resonance phase images. QSM is an ill-posed inverse problem that maps the phase back to the susceptibility source. In practice, the phase images are usually contaminated by background field inhomogeneities. In this thesis, several technical advances in QSM have been made which accelerate the data processing and improve the accuracy of this ill-posed problem. For background field removal, the local spherical mean value filtering (LSMV) is proposed, in which the global phase unwrapping is bypassed. This algorithm improves the time-efficiency and robustness of background field removal. For solving the inverse problem, an improved version of the k-space/image domain iterative algorithm is demonstrated using multi-level thresholding to account for the variation in the susceptibilities of different structures in the brain. The susceptibility maps could be used to generate orientation independent weighting masks, to form a new type of susceptibility weighted image (SWI), referred to here as true-SWI (tSWI). The tSWI data show improved contrast-to-noise ratio (CNR) of the veins and reduced blooming artefacts of the microbleeds. Finally, it is shown that the effective magnetic moment, being the product of the apparent volume and the measured susceptibility of the small object, is constant. This can be used to improve the susceptibility quantification, if <em>a priori</em> information of the volume is available.</p> / Doctor of Philosophy (PhD)
16

La recherche d’exoplanètes autour de naines blanches : analyses et performances de la méthode d’imagerie de noyaux de phase avec JWST/MIRI

Thibault, Katherine 12 1900 (has links)
Le nombre de systèmes planétaires connus ne cesse de croître depuis la découverte de la première exoplanète il y a déjà quelques décennies. Cependant, ces systèmes connaîtront éventuellement la mort de leur étoile, s’ils ne l’ont pas déjà connue. Ces étoiles deviendront des naines blanches. Pourtant, peu de planètes ont été découvertes autour de naines blanches. Une théorie populaire propose la survie des planètes géantes autour de celles-ci. Il est toutefois difficile de rechercher des planètes autour de naines blanches, entre autres, à cause de leurs petits rayons et de leurs raies spectrales peu nombreuses. L’imagerie de noyaux de phase est une méthode prometteuse pour la recherche d’exoplanètes autour de naines blanches puisqu’elle permet l’exploration à des séparations angulaires très petites allant jusqu’à la moitié de la limite de diffraction. Il s’agit de détecter un signal astrophysique par l’entremise de l’annulation des erreurs de phase instrumentales produites par le télescope. Ce projet vise à évaluer les performances de l’instrument MIRI du JWST pour détecter des exoplanètes autour de naines blanches avec cette technique. Pour ce faire, les observations de quatre naines blanches ont été analysées. Ce projet a permis de découvrir deux exoplanètes candidates, soient WD 1202−232 b et WD 2105−820 b sur un échantillon de quatre naines blanches. Elles ont été détectées par imagerie directe standard, mais aussi par imagerie de noyaux de phase. Les candidates se trouvent respectivement à une séparation de 1230 ± 20 mas et 2210 ± 20 mas de leur étoile et leurs rapports de flux sont de 63 ± 2 pour le système WD 1202−232 et de 29 ± 3 pour le système WD 2105−820. Si les candidates sont confirmées, la masse de WD 1202−232 b se situerait entre 1 et 7 \(M_J\), alors que la masse de WD 2105−820 b se situerait entre 1 et 2 \(M_J\). Des analyses et des simulations ont aussi été faites dans le but de tester les performances de l’imagerie par noyaux de phase avec les observations du JWST/MIRI à différents régimes de signal sur bruit. / The number of known planetary systems has been continuously increasing since the discovery of the first exoplanet several decades ago. However, these systems will eventually experience the death of their star, if they have not already. These stars will become white dwarfs. Yet, few planets have been discovered around white dwarfs. A favored theory suggests the survival of giant planets around them. However, it is challenging to search for planets around white dwarfs, among other reasons, due to their small radii and limited number of spectral lines. Kernel phase imaging is a promising method for the search for exoplanets around white dwarfs as it allows exploration at very small angular separations down to half the diffraction limit. This involves detecting an astrophysical signal through the cancellation of instrumental phase errors produced by the telescope. This project aims to evaluate the performance of JWST’s MIRI instrument in detecting exoplanets around white dwarfs using this technique. To achieve this, the observations of four white dwarfs were analyzed. This project has led to the discovery of two candidate exoplanets, namely WD 1202−232 b and WD 2105−820 b, in a sample of four white dwarfs. They were detected through standard direct imaging but also through kernel phase imaging. The candidates are located at a separation of 1230 ± 20 mas and 2210 ± 20 mas from their star, with flux ratios of 63 ± 2 for the WD 1202−232 system and 29 ± 3 for the WD 2105−820 system. If confirmed, the mass of WD 1202−232 b would be between 1 and 7 \(M_J\), while the mass of WD 2105−820 b would be between 1 and 2 \(M_J\). Analyses and simulations were also conducted to test the performance of kernel phase imaging with JWST/MIRI observations under various signal-to-noise regimes.
17

Diffraction et imagerie aux rayons X en utilisant un faisceau cohérent : applications aux optiques rayons X et au cristaux comportant des hétérogénéités de phase / X-ray diffraction and imaging with a coherent beam : application to X-Ray optical elements and crystal exhibiting phase inhomogeneities

Masiello, Fabio 13 May 2011 (has links)
Les propriétés exceptionnelles des sources de rayonnement synchrotron ont été et sont de plus en plus exploités dans des disciplines très différentes, allant de l'archéologie à la chimie, de la science des matièraux a la biologie, de la médecine à la physique. Parmi ces propriétés, il est important de mentionner la haute brillance, le spectre continu, le haut degré de polarisation, la structure temporelle, la petite taille de la source et la petite divergence du faisceau. Ces dernières propriètèes entraînant une forte cohérence transversale du rayonnement produit. La cohérence du faisceau a permis le développement des nouvelles techniques comme par exemple, l'imagerie à contraste de phase, la spectroscopie à corrélation des photons et l'imagerie par diffraction des photons cohérents. Par conséquent, il est de première importance que les éléments optiques puissent préserver cette propriété, perturbant le moins possible la front d'onde. Ce travail de thèse se constitue de trois parties. Dans la premiere partie, je vais présenter le travail effectué au sein du groupe optique de l'ESRF dans la caractérisation des cristaux de diamant synthétique de haute qualité prévus pour des applications aux optiques pour les rayons X. Cet caractérisation a été effectué en utilisant différentes techniques rayons X complémentaires, telles que la diffractométrie à haute résolution, la topographie, la diffraction en incidence rasante, la réflectométrie et des mesures de préservation de cohérence en utilisant l'effet Talbot. Dans la deuxième partie, je expose les résultats obtenu dans l'étude du comportement à haute température des domaines ferroélectriques dans un cristal périodiquement polarisé. Dans cet type d'étude, basé sur la diffraction de Bragg-Fresnel, est nécessaire un haute cohérence du faisceau. Dans la troisième partie, je présents des résultats obtenu dans la caractérisation des diamants prévus pour des applications autres que les optique rayons X. / The exceptional properties of synchrotron light sources have been and increasingly are exploited in very different disciplines, from archaeology to chemistry, from material science to biology, from medicine to physics. Among these properties it is important to mention the high brilliance, continuum spectrum, high degree of polarization, time structure, small source size and divergence of the beam, the last resulting in a high transversal coherence of the produced radiation. This high transversal coherence of the synchrotron sources has permitted the development of new techniques, e.g. phase contrast imaging, X-ray photon correlation spectroscopy and coherent X-ray diffraction imaging (CXDI). The thesis work will consist essentially of three parts. In the first part it will be presented the work done as a member of the X-ray Optics Group of ESRF in the characterization of high quality diamond crystals foreseen as X-ray optical elements. The characterization has been done using different complementary X-ray techniques, such as high resolution diffraction, topography, grazing incidence diffraction, reflectivity and measurements of the coherence preservation using the Talbot effect. In the second part, I will show the result obtained in the study of the temperature behaviours of the domain in periodically poled ferroelectrics crystals. This type of measurements, based on Bragg-Fresnel diffraction, are possible only thanks to the high degree of coherence of the beam In the third part, I will present the results obtained in the characterization of diamonds foreseen for applications other than X-ray optical elements.
18

Holografický modul pro světelnou mikroskopii / Holographic module for a light microscopy

Škrabalová, Denisa January 2019 (has links)
The new arrangement of the off-axis holographic module, which is using polarizationactive diffraction grating divides signal into reference and subject wave of an interferometer based on their polarization. However, current design of the module does not have a possibility to tune a length of the optical paths. Thus the inability to tune optical paths leads to a reduced quality of interference structure during observation of biological samples. The current module is only suitable for technical applicating due to this limitation. Possibility of tuning branches is key step in biological applications. Therefore a new computer-controlled module is created in order to enable use for biological samples.
19

Optical heating of gold nanoparticles and thermal microscopy : applications in hydrothermal chemistry and single cell biology / Chauffage optique de nanoparticules d'or et microscopie thermique : application en chimie hydrothermale et en biologie cellulaire

Robert, Hadrien 09 May 2018 (has links)
L’étude de phénomènes thermiques à l’échelle microscopique peut s’avérer compliquée à mettre en place, principalement à cause de l’absence de technique de mesure de température fiable. Dans ce contexte, une technique de mesure de température appelée TIQSI a été développée au sein de l’Institut Fresnel. Dans l’objectif d’étudier des phénomènes thermo-induit à l’échelle microscopique, j’ai monté un microscope capable de contrôler et de quantifier une élévation de température à l'aide de TIQSI et de nanoparticules d’or. Différents phénomènes ont ainsi pu être étudiés.La synthèse hydrothermale regroupe les réactions chimiques utilisant de l’eau liquide à des températures plus élevées que la température d’ébullition. L’utilisation de nanoparticules permet d’avoir de l’eau liquide à des températures supérieures à 100°C (état métastable). J’ai pu ainsi effectuer des réactions de synthèse hydrothermale sans autoclave ce qui constitue un nouveau concept en chimie de synthèse.Une cellule vivante peut-être endommagée par un stress de chaleur ce qui peut détériorer ses protéines. En réponse à ce stress, la synthèse de HSP permet la réparation des protéines endommagées. J’ai pu étudier la dynamique de réponse des HSP ce qui a permis d’illustrer l’intérêt d’une chauffe locale et de TIQSI pour ce genre d’expérience.Une autre application mêlant le surchauffage de l’eau liquide et la biologie a été abordée. Les organismes hyperthermophiles vivent à de très hautes températures (80-110◦C). J’ai pu durant mes expériences observer le déplacement d’hyperthermophiles. Cette avancée constitue les prémices d’expériences plus ambitieuses comme l’étude de l’interaction entre hyperthermophiles. / Nowadays, thermal experiments at the microscopic scale remain challenging to conduct due to the lack of reliable temperature measurment techniques. To solve these problems, a label-free temperature measurement technique called TIQSI has been developed in the Institut Fresnel.With the objective to study new thermal-induced effects on the microscale using TIQSI, I built a microscope aimed to control heat diffusion on the microscale using nanoparticle. Thus, I could study different phenomena in chemistry and biology.Hydrothermal methods in chemical synthesis rely on the use of superheated liquid water as a solvent. It has been shown that gold nanoparticles can be used superheated water in a metastable state. I managed to conduct hydrothermal chemistry experiments using thermoplasmonics without autoclave which represents a new paradigm in chemistry.A living cell can be damaged by a heat stress which can misfold its proteins. To response to this stress, the HSP synthesis enables the reparation of misfolded proteins. I could study the heat stress response of HSP at short time scale which allowed me to illustrate the interest of using TIQSI and a local heat.As an application mixing superheating water and biology, I studied organisms that are able to live at high temperature (80-110°C) namely hyperthermophiles. Motion of these organisms has been studied without autoclave which paves the way to more sophisticated experiments such as the interaction between hyperthermophiles.
20

Koherencí řízený holografický mikroskop nové generace / New Generation of a Coherence-Controlled Holographic Microscope

Slabý, Tomáš January 2015 (has links)
This doctoral thesis deals with design of a new generation of coherence-controlled holographic microscope (CCHM). The microscope is based on off-axis holographic configuration using diffraction grating and allows the use of temporally and spatially incoherent illumination. In the theoretical section a new optical configuration of the microscope is proposed and conditions for different parameters of the microscope and its optical components are derived. The influence of different sources of noise on phase detection sensitivity is studied. In the next section design of experimental setup is described and automatable adjustment procedure is proposed. Last section describes experimental verification of the most important optical parameters of the experimental setup. When compared to previous generation of CCHM, the newly proposed configuration uses infinity-corrected objectives and common microscope condensers, allows more space for the specimens, eliminates the limitation of spectral transmittance and significantly simplifies the adjustment procedure so that automation of this procedure is possible.

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