Nuclear magnetic resonance is a non-invasive way to observe material properties on a molecular level. Magnetic resonance imaging is an important diagnostic tool in medicine. Molecules of several metabolites in muscle tissue show similar interactions as molecules partially oriented in orienting media. These interactions could provide new information about processes in vivo, this can serve for diagnostics of metabolism. New insight into the function is gained by observation of metabolites in orienting media. Observable anisotropic interactions in muscle tissue in vivo could be used for diagnostic purposes. Anisotropic NMR interaction of solvent as a new method for observation of phase transition of hydrogel with temperature change or change of solvent composition. Use of magnetic resonance imaging in slices to observe the collapse of polyacrylamide in water-acetone mixtures. Use of diffusion-weighted magnetic resonance imaging to observe phase transition of PNIPAM-based semi-interpenetrating polymer.

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NMR experiments performed under the effect of electric fields, either continuous or pulsed, can provide quantitative parameters related to ion association and ion transport in solution.  Electrophoretic NMR (eNMR) is based on a diffusion pulse-sequence with electric fields applied in the form of pulses. Magnetic field gradients enable the measurement of the electrophoretic mobility of charged species, a parameter that can be related to ionic association. The effective charge of the tetramethylammonium cation ion in water, dimethylsulphoxide (DMSO), acetonitrile, methanol and ethanol was estimated by eNMR and diffusion measurements and compared to the value predicted by the Debye-Hückel-Onsager limiting law. The difference between the predicted and measured effective charge was attributed to ion pairing which was found to be especially significant in ethanol. The association of a large set of cations to polyethylene oxide (PEO) in methanol, through the ion-dipole interaction, was quantified by eNMR. The trends found were in good agreement with the scarce data from other methods. Significant association was found for cations that have a surface charge density below a critical value. For short PEO chains, the charge per monomer was found to be significantly higher than for longer PEO chains when binding to the same cations. This was attributed to the high entropy cost required to rearrange a long chain in order to optimize the ion-dipole interactions with the cations. Moreover, it was suggested that short PEO chains may exhibit distinct binding modes in the presence of different cations, as supported by diffusion measurements, relaxation measurements and chemical shift data. The protonation state of a uranium (VI)-adenosine monophosphate (AMP) complex in aqueous solution was measured by eNMR in the alkaline pH range. The question whether or not specific oxygens in the ligand were protonated was resolved by considering the possible association of other species present in the solution to the complex. The methodology of eNMR was developed through the introduction of a new pulse-sequence which suppresses artifactual flow effects in highly conductive samples. In another experimental setup, using NMR imaging, a constant current was applied to a lithium ion (Li ion) battery model. Here, 7Li spin-echo imaging was used to probe the spin density in the electrolyte and thus visualize the development of Li+ concentration gradients. The Li+ transport number and salt diffusivity were obtained within an electrochemical transport model. The parameters obtained were in good agreement with data for similar electrolytes. The use of an alternative imaging method based on CTI (Constant Time Imaging) was explored and implemented. / <p>QC 20140825</p>

Les études non destructives des processus physiologiques dans les produits agronomiques exigent des résolutions spatiales et temporelles de plus en plus élevées. L'imagerie par résonance magnétique nucléaire (RMN) est une technique totalement non-invasive qui permet d'accéder à plusieurs types de variables (architecture des tissus, variabilités spatiales de la composition, flux entrants et internes au cours de la croissance du fruit) plus difficilement quantifiables avec des méthodes destructives classiques. Un des enjeux majeur également réside dans la faculté de localiser spatialement ces transformations physiologiques et morphologiques dans les produits agronomiques. Les travaux de recherches réalisés dans le cadre de cette thèse ont pour objectif principal, la mise en œuvre d'une méthodologie de calcul et d'analyse quantitative en imagerie RMN appliquée à l'agronomie. L'implémentation, l'optimisation et la validation de la séquence FLASH combinée avec des agents de contraste efficaces en terme de relaxivité et bio-compatibles a permis d'une part, la cartographie des paramètres de relaxation et d'autre part, la quantification du transport de l'eau in vivo d'un système agronomique modèle au cours de sa croissance. Les nanoparticules de l'agent de contraste Gd3+[Fe(CN)6]3-/Mannitol ont été utilisées comme des marqueurs afin de localiser les flux hydriques dans le fruit. Le choix de la séquence d'imagerie FLASH a été motivé par la nécessite d'atteindre des résolutions temporelles suffisante pour suivre la dynamique des changements physiologiques liés au transport de l'eau dans ce type de matériau. La validation de la méthode de calcul du T1 menée sur le fantôme a révélé un bon accord par rapport aux T1 mesurés par relaxométrie. Nous avons également mis au point une procédure d'évaluation du rapport signal sur bruit et des incertitudes commises dans chaque voxel des images paramétriques M0 et T1. L'évaluation de ces incertitudes est un élément fondamental de cette analyse quantitative, afin d'assurer des interprétations fiables des images RMN. La segmentation des images nous a permis de localiser précisément les tissus où règne une forte activité cellulaire. Enfin, la modélisation compartimentale mis en oeuvre nous a permis de quantifier les paramètres cinétiques liés au transport de l'eau dans le fruit.Mots-clés: Imagerie RMN quantitative, paramètres intrinsèques, segmentation, modélisation compartimentale, agents de contraste, tissus végétaux / Non destructive studies of physiological processes in agronomic products require increasingly higher spatial and temporal resolutions. Nuclear Magnetic Resonance (NMR) imaging is a completely non-invasive technique providing access to several types of variables (tissue architecture, spatial variability of the composition, external and internal flow during fruit growth) more difficult to quantify with conventional destructive methods. One of major challenge lies in the ability to spatially localize the physiological and morphological changes in the agricultural products. The main objective of the research work in this thesis is to carry out a methodology in order to calculate and analyze quantitative NMR imaging applied to agronomy. The implementation, optimization and validation of the FLASH imaging sequence is performed in combination with innovative biocompatible contrast agents efficient in terms of relativity which allow to map in vivo relaxation parameters and then to explore water transportation in an agronomic model : the tomato during its growth. Nanoparticles of Gd3+[Fe(CN)6]3-/Mannitol contrast agents have been used as markers to localize the water flow in the fruit. The choice of the FLASH imaging sequence is motivated by the necessity to achieve sufficient high temporal resolution for monitoring the dynamics of physiological changes related to the water transport. The validation of the T1 calculation method performed on a phantom shows a good agreement compared to T1 measured by relaxometry. A systematic procedure for the estimation of the signal to noise ratio on the parametric images is also proposed which ensures a carefull determination of the intrinsic parameters of living tissues (M0 and T1) and their uncertainties. This step in the analysis ensures reliable interpretation of NMR images and permits image segmentation in order to precisely localize the tissues where there is a high cellular activity. Finally, the time dependance and the compartmental modeling allow to quantify the kinetic parameters associated with the water transport in the fruit.Keywords: Quantitative NMR imaging, intrinsic parameters, segmentation, compartmental modeling, contrast agents, plant tissues

A metodologia GMAX, (Gradient-Modulated Adiabatic Excitation), caracteriza-se pelo uso de pulsos adiabáticos para localização de volumes em espectroscopia e seleção de fatias em MRI. A sua utilidade surge do interessante perfil de inversão da magnetização transversal induzido ao longo da amostra. Entretanto, a interpretação desse comportamento tem sido dada apenas de forma qualitativa, através da utilização da condição de adiabaticidade como ponto de partida. Neste trabalho é apresentada uma descrição analítica partindo da solução em termos da função hipergeométrica para os pulsos sech e tanh. A partir desse procedimento encontramos um conjunto de resultados com os quais é possível inferir analiticamente o comportamento característico da magnetização, tendo como objetivo obter um maior controle da magnetização a partir dos parâmetros da metodologia que proporcionam interpretação física. / The Gradient-Modulated Adiabatic Excitation (GMAX) methodology is characterized by the use of adiabatic pulses for volume localization in spectroscopy and slice selection in MRI. Its use derives from the interesting nodal point transverse magnetization profile induced throughout the sample. Nevertheless, the interpretation of such behavior for the magnetization has been of qualitative purpose only, using the adiabatic condition as a starting point. Here, we present an analytical description, starting from the solution in terms of the hypergeometric functions for sech and tanh pulses. From this procedure we found a set of results with which is possible to infer analytically the characteristic behavior of the magnetization. This is on the purpose of obtaining greater control of the magnetization from parameters of the methodology that carry physical interpretation.

A metodologia GMAX, (Gradient-Modulated Adiabatic Excitation), caracteriza-se pelo uso de pulsos adiabáticos para localização de volumes em espectroscopia e seleção de fatias em MRI. A sua utilidade surge do interessante perfil de inversão da magnetização transversal induzido ao longo da amostra. Entretanto, a interpretação desse comportamento tem sido dada apenas de forma qualitativa, através da utilização da condição de adiabaticidade como ponto de partida. Neste trabalho é apresentada uma descrição analítica partindo da solução em termos da função hipergeométrica para os pulsos sech e tanh. A partir desse procedimento encontramos um conjunto de resultados com os quais é possível inferir analiticamente o comportamento característico da magnetização, tendo como objetivo obter um maior controle da magnetização a partir dos parâmetros da metodologia que proporcionam interpretação física. / The Gradient-Modulated Adiabatic Excitation (GMAX) methodology is characterized by the use of adiabatic pulses for volume localization in spectroscopy and slice selection in MRI. Its use derives from the interesting nodal point transverse magnetization profile induced throughout the sample. Nevertheless, the interpretation of such behavior for the magnetization has been of qualitative purpose only, using the adiabatic condition as a starting point. Here, we present an analytical description, starting from the solution in terms of the hypergeometric functions for sech and tanh pulses. From this procedure we found a set of results with which is possible to infer analytically the characteristic behavior of the magnetization. This is on the purpose of obtaining greater control of the magnetization from parameters of the methodology that carry physical interpretation.

Afin d'étudier la diffusion et la libération de molécules de tailles inférieures dans un gel polymère, les coefficients d'auto-diffusion d'une série de polymères en étoile avec un noyau d'acide cholique et quatre branches de poly(éthylène glycol) (PEG) ont été déterminés par spectroscopie RMN à gradient de champ pulsé dans des solutions aqueuses et des gels de poly(alcool vinylique). Les coefficients de diffusion obtenus ont été comparés avec ceux des PEGs linéaires et dendritiques pour étudier l'effet de l'architecture des polymères. Les polymères en étoile amphiphiles ont des profils de diffusion en fonction de la concentration similaires à leurs homologues linéaires dans le régime dilué. Ils diffusent plus lentement dans le régime semi-dilué en raison de leur noyau hydrophobe. Leurs conformations en solution ont été étudiées par des mesures de temps de relaxation spin-réseau T1 du noyau et des branches. L'imagerie RMN a été utilisée pour étudier le gonflement des comprimés polymères et la diffusion dans la matrice polymère. Les comprimés étaient constitués d'amidon à haute teneur en amylose et chargés avec de l'acétaminophène (de 10 à 40% en poids). Le gonflement des comprimés, ainsi que l'absorption et la diffusion de l'eau, augmentent avec la teneur en médicament, tandis que le pourcentage de libération du médicament est similaire pour tous les comprimés. Le gonflement in vitro des comprimés d'un complexe polyélectrolyte à base d'amidon carboxyméthylé et de chitosane a également été étudié par imagerie RMN. Ces comprimés sont sensibles au pH : ils gonflent beaucoup plus dans les milieux acides que dans les milieux neutres en raison de la dissociation des deux composants et de la protonation des chaînes du chitosane. La comparaison des résultats avec ceux d'amidon à haute teneur en amylose indique que les deux matrices ont des gonflements et des profils de libération du médicament semblables dans les milieux neutres, alors que les comprimés complexes gonflent plus dans les milieux acides en raison de la dissociation du chitosane et de l'amidon. / In an effort to study the diffusion and release of small molecules in a polymeric system, the self-diffusion coefficients of a series of star polymers with a cholic acid core bearing four poly(ethylene glycol) (PEG) arms in aqueous solutions and gels of poly(vinyl alcohol) were determined by pulsed gradient spin-echo NMR techniques. The results have been compared with those of linear and dendritic PEGs to elucidate the effect of the architecture of the polymers. The amphiphilic star polymers show similar concentration-dependent diffusion behaviors in the dilute regime to their linear homologues. They diffuse more slowly in the semi-dilute regime than the linear PEGs due to the presence of the hydrophobic core. The conformation of the star polymers in the solutions was studied by measuring the T1 values of the core and the arms of the diffusants. NMR imaging was used to study the swelling of polymeric tablets and diffusion in the polymer matrix. The tablets investigated were made of cross-linked high amylose starch (CHAS) and loaded with acetaminophen (10, 20 and 40 wt%). The swelling, water uptake and diffusion in the CHAS network are faster at higher drug loading levels, while the drug release rates are similar among all the tablets. The in vitro swelling of the tablets made of a polyelectrolyte complex based on chitosan and carboxymethylated starch has also been studied by NMR imaging. These tablets showed pH-sensitive behavior. They swelled much more in acidic media than in neutral media due to dissociation of the two components and the protonation of the amino groups in the chitosan residues. The comparison of the results with those obtained with the CHAS tablets indicates that the two matrices have similar swelling and drug release profile in neutral media, while the complex tablets showed a greater extent of swelling in acidic media due the dissociation of the chitosan from the complex.

Afin d'étudier la diffusion et la libération de molécules de tailles inférieures dans un gel polymère, les coefficients d'auto-diffusion d'une série de polymères en étoile avec un noyau d'acide cholique et quatre branches de poly(éthylène glycol) (PEG) ont été déterminés par spectroscopie RMN à gradient de champ pulsé dans des solutions aqueuses et des gels de poly(alcool vinylique). Les coefficients de diffusion obtenus ont été comparés avec ceux des PEGs linéaires et dendritiques pour étudier l'effet de l'architecture des polymères. Les polymères en étoile amphiphiles ont des profils de diffusion en fonction de la concentration similaires à leurs homologues linéaires dans le régime dilué. Ils diffusent plus lentement dans le régime semi-dilué en raison de leur noyau hydrophobe. Leurs conformations en solution ont été étudiées par des mesures de temps de relaxation spin-réseau T1 du noyau et des branches. L'imagerie RMN a été utilisée pour étudier le gonflement des comprimés polymères et la diffusion dans la matrice polymère. Les comprimés étaient constitués d'amidon à haute teneur en amylose et chargés avec de l'acétaminophène (de 10 à 40% en poids). Le gonflement des comprimés, ainsi que l'absorption et la diffusion de l'eau, augmentent avec la teneur en médicament, tandis que le pourcentage de libération du médicament est similaire pour tous les comprimés. Le gonflement in vitro des comprimés d'un complexe polyélectrolyte à base d'amidon carboxyméthylé et de chitosane a également été étudié par imagerie RMN. Ces comprimés sont sensibles au pH : ils gonflent beaucoup plus dans les milieux acides que dans les milieux neutres en raison de la dissociation des deux composants et de la protonation des chaînes du chitosane. La comparaison des résultats avec ceux d'amidon à haute teneur en amylose indique que les deux matrices ont des gonflements et des profils de libération du médicament semblables dans les milieux neutres, alors que les comprimés complexes gonflent plus dans les milieux acides en raison de la dissociation du chitosane et de l'amidon. / In an effort to study the diffusion and release of small molecules in a polymeric system, the self-diffusion coefficients of a series of star polymers with a cholic acid core bearing four poly(ethylene glycol) (PEG) arms in aqueous solutions and gels of poly(vinyl alcohol) were determined by pulsed gradient spin-echo NMR techniques. The results have been compared with those of linear and dendritic PEGs to elucidate the effect of the architecture of the polymers. The amphiphilic star polymers show similar concentration-dependent diffusion behaviors in the dilute regime to their linear homologues. They diffuse more slowly in the semi-dilute regime than the linear PEGs due to the presence of the hydrophobic core. The conformation of the star polymers in the solutions was studied by measuring the T1 values of the core and the arms of the diffusants. NMR imaging was used to study the swelling of polymeric tablets and diffusion in the polymer matrix. The tablets investigated were made of cross-linked high amylose starch (CHAS) and loaded with acetaminophen (10, 20 and 40 wt%). The swelling, water uptake and diffusion in the CHAS network are faster at higher drug loading levels, while the drug release rates are similar among all the tablets. The in vitro swelling of the tablets made of a polyelectrolyte complex based on chitosan and carboxymethylated starch has also been studied by NMR imaging. These tablets showed pH-sensitive behavior. They swelled much more in acidic media than in neutral media due to dissociation of the two components and the protonation of the amino groups in the chitosan residues. The comparison of the results with those obtained with the CHAS tablets indicates that the two matrices have similar swelling and drug release profile in neutral media, while the complex tablets showed a greater extent of swelling in acidic media due the dissociation of the chitosan from the complex.