La structuration des réseaux neuronaux est un processus fondamental qui assure le bon fonctionnement du cerveau. Afin de comprendre la formation et l’activité de ces réseaux, nous souhaitons développer une méthode qui permette de contrôler in vivo sous l’action de la lumière l'expression de gènes ciblés impliqués dans ce phénomène,à l’échelle d’une cellule neuronale individuelle. Pour ce faire, nous utilisons une réaction de photo-clivage permettant de libérer de façon contrôlée un inducteur d’expression de gène sous l’action de la lumière, à l’aide de groupements photo-labiles sensibles aux excitations bi-photoniques développés au laboratoire et favorables aux applications in vivo. Afin de photo-réguler l'expression des gènes in vivo et avec un contrôle spatiotemporel élevé, nous combinons le système d’expression de gène inductible par la tétracycline « Tet-on » à une variété de précurseurs photo-activables d’analogues de tétracycline que nous avons synthétisés. Ceci devrait nous permettre de disposer d’un système efficace pour l’expression in vivo d’un gène d’intérêt par excitation lumineuse,et plus précisément dans le but de photo-réguler le gène Kir2.1 impliqué dans la régulation de l’activité électrique des neurones. / The structural neural network’s is a fundamental process that ensures the proper functioning of the brain. To understand the formation and activity of these networks, we are developing a method which spatio-temporally controlled in vivo, the expression of targeted genes involved in this process at individual neuron cells scale by light. To achieve this in vivo tests, it is necessary to work with methods which are orthogonal to their cellular environment. Photochemical activation by photo-cleavage of an inert biological precursor offers a unique orthogonal way to attain this spatio-temporal control. Therefore, we have recently developed a new family of photoremovable group which are sensitive to two-photon (TP) excitation sensitive, in order to irradiate at favorable wave-lengths for in vivo applications. Moreover, to photo-regulate the expression of genes with high spatial and temporal resolution, we are combining the inducible gene expression system by tetracycline called « Tet-on » system to different photo-activable precursors of tetracycline analogs obtained by hemi-synthesis. All this, should allow us to get an effective system for the in vivo expression of a gene of interest by light excitation in order to photoactivate Kir2.1, a gene that cell autonomously silences the electrical activity of neurons in a subset of cells.

Orientador: Carlos Henrique de Brito Cruz / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-09-27T13:12:22Z (GMT). No. of bitstreams: 1 PadilhaJunior_LazaroAurelio_D.pdf: 3832856 bytes, checksum: ee1e342cd7bc49e51127fe13ee9ed626 (MD5) Previous issue date: 2006 / Resumo: Nesta tese as propriedades ópticas lineares e não-lineares em pontos quânticos de semicondutores de band-gap diretos, CdTe e CdSe, são estudados em escala temporal de femtossegundos, especialmente aquelas propriedades importantes para aplicações em chaveamento totalmente óptico, como o tempo de resposta e a susceptibilidade de terceira ordem. Os processos de recombinação de elétrons fotoexcitados são investigados assim como seus tempos de resposta, usando um modelo teórico que considera a influência dos estados de armadilhas de superfície e da recombinação Auger. As propriedades ópticas não lineares de terceita ordem, absorção de dois fótons e efeito Kerr óptico, são estudados através de diferente técnicas experimentais: Z-scan, bombeio e prova e foto-luminescência excitada por dois fótons. Forte influência do tamanho dos nanocristais é observada, especialmente nos espectros de absorção de dois-fótons. Modelos teóricos baseados na aproximação de massa efetiva e no modelo p k de Kane são usados para descrever a influência do confinamento quântico nos processos de absorção de dois-fótons degenerados e não-degenerados. A importância da mistura das bandas de buracos é observada no ajuste teórico dos espectros de absorção de dois fótons. Finalmente, chaves totalmente ópticas operando por saturação de absorção e por controle de polarização são demonstradas para pontos quânticos de CdTe em matriz vítrea / Abstract: In this thesis the linear and non-linear optical properties of direct band-gap semiconductors, CdTe and CdSe, quantum dots are studied at femtosecond time scale, mainly those properties important for applications in all-optical switching such as response time and third order susceptibility. The photo-excited electron recombination processes are investigated as well their response time using a theoretical model considering the influence of the surface trapping states and the Auger recombination. The third order nonlinear optical properties, two-photon absorption and optical Kerr effect, are studied by different experimental techniques: Z-scan, pump and probe and two-photon induced photo-luminescence. Strong influence from the nanocrystals size is observed, especially on the two-photon absorption spectra. Theoretical models based on the effective mass approximation and Kane¿s p k model are used to describe the influence of the quantum confinement on the degenerate and non-degenerate two-photon absorption processes. The importance of the hole band mixing is easily seen from the two-photon absorption fitting. Finally, all-optical switching by absorption saturation and polarization control are demonstrated for CdTe quantum dots in doped glass / Doutorado / Propriedades Óticas e Espectroscopia da Matéria Condensada ; Outras Inter. da Matéria Com. Rad. e Part / Doutor em Ciências

Ce travail intitulé " Libération du monoxyde d'azote induite par deux photons à partir de complexes ruthénium-nitrosyle contenant des ligands de capacités push-pull différentes " a été consacré à l'étude des principaux facteurs qui déterminent l'efficacité des complexes ruthénium- nitrosyles (Ru(NO)) dans l'absorption à deux photons (ADP) et à l'amélioration de leur section efficace ADP par modification de la nature et de la structure de leurs ligands. A partir de complexes précédemment obtenus dans le groupe de recherche du Prof. I. Malfant, nous avons effectué diverses modifications structurales. Il a été montré que la substitution des ligands monodentes par la 2,2'-bipyridine dans les complexes de Ru(NO) conduit à une légère augmentation de la section efficace, mais cette modification diminue le rendement quantique du relargage du monoxyde d'azote NO. La partie synthétique du travail a principalement porté sur la modification du ligand. / The work "Two-photon induced photorelease of nitric oxide from ruthenium-nitrosyl complexes containing ligands of various push-pull capabilities" was devoted to the revealing of main factors that determine the efficiency of ruthenium-nitrosyl complexes in two-photon absorption (TPA) and the improvement of TPA cross-section through modification of the ligands nature and their structure. Starting from complexes previously obtained by the research group of Prof. I. Malfant, we have modified their structure in several directions. It was shown that substitution of monodentate ligands by 2,2'-bipyridine in ruthenium complexes with nitrosyl ligands leads to a slight increase of their TPA cross- section, however this modification decreases the quantum yield of the nitric oxide photo release. Synthetic part of the work was mainly aimed at the modification of the ligand.

<p> </p><p>The interaction between light and organometallic chromophores has been investigated theoretically in a strive for fast optical filters. The main emphasis is on two-photon absorption and excited state absorption as illustrated in the Jablonski diagram. We stress the need for relativistic calculations and have developed methods to address this issue. Furthermore, we present how quantum chemical calculations can be combined with Maxwell's equations in order to simulate propagation of laser pulses through a materials doped with chromophores with high two-photon absorption cross sections. Finally, we also discuss how fast agile filters using spin-transition materials can be modeled in order to accomplish theoretical material design.</p> / Report code: LIU-TEK-LIC-2006:55. On the day of the defence date the status on article III was Manuscript, article IV was Accepted and article V was Submitted.

The present thesis concerns aspects of the interaction ofmatter in gas, liquid and solid phases, with electromagneticradiation, ranging from the optical to the X-ray region. Overthe last decade the availability of ultrashort strong laserpulses as well as of high power synchrotron sources of tunableX-ray radiation has stimulated a rapid development of newexperimental techniques which makes it possible to analysedifferent physical, chemical and biological processes inunprecedented detail. All of this urges a concomitantdevelopment of adequate theoretical language and methodscombined with simulation techniques. The first part of the thesis addresses nonlinear propagationof strong optical pulses. This study is motivated by thebreakthrough in synthesis of novel organic materials possessingprespecified nonlinear optical properties and which has led toa multitude of potential applications such as, for example, 3Dimaging and data storage, optical limiting and photodynamiccancer therapy. In order to clarify the underlying physics, astrict solution has been derived of the density matrixequations of a material aiming at an explicit treatment of itsnonlinear polarization without addressing a conventional Taylorexpansion over field amplitudes. Such a formalism is developedfor many-level molecules, allowing to solve the coupledMaxwell's and density matrix equations for the propagation of afew interacting laser pulses through a nonlinear molecularmedium. The theory presented is capable to account formulti-photon processes of an arbitrary order and for differentsaturation effects. The theory is applied to simulations oftwo- and three-photon absorption as well as to upconvertedstimulated emission of organic molecules in solvents. The second part of the thesis is devoted to resonant X-rayRaman scattering from free molecules, solutions and polymerfilms. The temporal analysis of the spectral profiles isperformed using the technique of scattering duration whichallows to select physical processes with different time scales.The slowing-down/speeding-up of the scattering by frequencydetuning provides insight in the formation of the differentparts of the scattering profile like atomic and molecularbands, resonant and vertical scattering channels, anomalousenhancement of the Stokes doubling effect. The lifetimevibrational interference (LVI), playing a crucial role inresonant scattering, is found to strongly influence thedispersion of the Auger resonances of polymers in agreementwith experiment. An almost complete quenching of the scatteringcross section by LVI is observed for the N2molecule. It is found that the interferenceelimination of the scattering amplitude gives valuableinformation on molecular geometry. The electron Doppler effectis minutely studied making use of a wave packet technique. Thesimulations show an "interference burning" of a narrow hole onthe top of the Doppler broadened profile of the Auger spectraof molecular oxygen. For the SF6molecule the Auger Doppler effect is found to besensitive to the detuning due to the scattering anisotropy. Inall of these studies the temporal language was foundconstructive and enormously helpful for understanding theunderlying physical processes. Most theoretical predictionsmade have been verified by experiments.

This thesis provides an extensive study of the first molecular hyperpolarizability b of charge-transfer chromophores using hyper-Rayleigh scattering (HRS). The charge-transfer chromophores used in present work involve the tricyanohydrofuran¡]TCF¡^group as an electron acceptor, and/or thiophene in the pi-electron bridge. TCF is a very strong electron acceptor and thiophene greatly lowers the resonance energy. Their presence significantly increases the beta value of the chromophore, therefore enhancing potentials in applications. In hyper-Rayleigh scattering experiments, the laser radiation with tunable wavelengths is used as an excitation source for measuring the frequency dependence of beta. The experiment shows beta exhibiting a significant dispersion in the two-photon resonance region. Using the linear absorption spectrum in coordination with theory, we show that it is possible to use Kramers-Kronig (K-K) transform to reproduce the experimental beta value in the two-photon resonance region. The K-K approach provides an extension to the conventional Oudar-Chemla equation, which is invalid in the spectral region in which two-photon resonance occurs. Using the new approach, it is shown that reliable values of intrinsic hyperpolarizabilities beta_zero of charge-transfer chromophores can be extracted. The coordination of beta_zero with molecular structure provides one with an insight for the origin of the enhancement of the first molecular hyperpolarizability of charge-transfer chromophores. This thesis examines the variation of beta_zero with molecular structure. The same technique is also applied to a dendrimer that has charge-transfer nonlinear optical chromophores incorporated in the dendritic structure. The measured frequency dependent hyperpolarizability of the dendrimer is compared with that calculated from the linear absorption spectrum by the KK transform technique. The intrinsic hyperpolarizability beta_zero of the dendrimer obtained is compared with that of the single chromophore having a structure similar to that incorporated in the dendrimer. The comparison shows that the 3D dendritic structure is effective in reducing the interaction between chromophores by providing sufficient space between them, hence avoiding the possibility of aggregation formation due to attractive interactions between chromophores. The topic of two-photon fluorescence (TPF), which is related to HRS, is also investigated. The intensity of TPF is generally proportional to the square of the incident excitation intensity. Careful measurements of the TPF intensity of a nonlinear optical chromophore in conjunction with required auxiliary parameters have been used as a technique for determining the two-photon absorption cross-section. The TPF intensity measurement carried out in this thesis uses a variety of intensities. At low intensity excitation, the TPF intensity follows the usual quadratic intensity law (QIL), whereas deviations from the QIL are observed at higher incident intensities. The observation of similar lineshape associated with one- and two-photon fluorescence spectra suggests a 3-level model for the description of TPF excited by the incident intensity at various strengths. It is shown that by fitting the observed TPF intensity to an equation developed from the three-level model, it is possible to deduce the two-photon absorption cross section of the nonlinear optical chromophore in solution. The new technique developed using the three-level model is tested on a Rhodamine B/Chloroform solution. The two-photon absorption cross-section obtained by using the new technique is found in agreement with that reported in the literature. Having demonstrated the suitability of the new technique, it is used to determine the two-photon absorption cross-section of a novel nonlinear optical chromophore. The two-photon absorption cross-section using the new technique is then compared with that obtained by the nonlinear transmittance method. The two results are in good agreement, indicating the applicability of the new technique. The new technique is more convenient than the conventional low excitation TPF method as it does not require various auxiliary parameters, some of them are difficult to obtain. The second harmonic generation (SHG) of a chromophore/polymer film which is optically poled by using a coherent superposition of a fundamental and its second harmonic beams. The growth rate of the SHG intensity is found to be proportional to the fourth power of the incident intensity of the fundamental beam, and the plateau intensity SHG is proportional to the square of the incident intensity. These observations are not in agreement with the published theory. While the reason for disagreement is yet to be clarified, the information obtained is useful for the development of nonlinear optical devices.

This dissertation describes the investigation of the synthesis and characterization of new squaraine-based photonic and electronic materials. In the first part of this thesis, squaraine dyes with large conjugation systems, including extended squaraines consisting of bis(donor)substituted vinylene-heterocycles and bis(indolinylenemethyl)squaraine-based oligomers linking through different π-bridges were designed, synthesized and characterized to exhibit strong two-photon absorption (2PA) for femotosecond and nanosecond optical-power limiting applications in the near-infrared (NIR). One of the dendronized squaraine forms smooth and high optical quality films with large NIR transparency window. In the second part, a series of squaraine- and phthalocyanine-based metal complexes were studied. Those dyes did not show large triplet quantum yield but significantly improved photovoltaic performance compared to the metal-free compounds. In the last part, an effective approach on optimizing bis(indolinylenemethyl)-based squaraine sensitizers with various surface anchor groups and π-linkers, achieved high power conversion efficiencies (PCEs) of 6.7% in liquid dye-sensitized solar cells (DSSCs) and 2.7% in solid-state DSSCs, which stand out all the previous reported squaraine-based sensitizers.

<p>The present thesis concerns aspects of the interaction ofmatter in gas, liquid and solid phases, with electromagneticradiation, ranging from the optical to the X-ray region. Overthe last decade the availability of ultrashort strong laserpulses as well as of high power synchrotron sources of tunableX-ray radiation has stimulated a rapid development of newexperimental techniques which makes it possible to analysedifferent physical, chemical and biological processes inunprecedented detail. All of this urges a concomitantdevelopment of adequate theoretical language and methodscombined with simulation techniques.</p><p>The first part of the thesis addresses nonlinear propagationof strong optical pulses. This study is motivated by thebreakthrough in synthesis of novel organic materials possessingprespecified nonlinear optical properties and which has led toa multitude of potential applications such as, for example, 3Dimaging and data storage, optical limiting and photodynamiccancer therapy. In order to clarify the underlying physics, astrict solution has been derived of the density matrixequations of a material aiming at an explicit treatment of itsnonlinear polarization without addressing a conventional Taylorexpansion over field amplitudes. Such a formalism is developedfor many-level molecules, allowing to solve the coupledMaxwell's and density matrix equations for the propagation of afew interacting laser pulses through a nonlinear molecularmedium. The theory presented is capable to account formulti-photon processes of an arbitrary order and for differentsaturation effects. The theory is applied to simulations oftwo- and three-photon absorption as well as to upconvertedstimulated emission of organic molecules in solvents.</p><p>The second part of the thesis is devoted to resonant X-rayRaman scattering from free molecules, solutions and polymerfilms. The temporal analysis of the spectral profiles isperformed using the technique of scattering duration whichallows to select physical processes with different time scales.The slowing-down/speeding-up of the scattering by frequencydetuning provides insight in the formation of the differentparts of the scattering profile like atomic and molecularbands, resonant and vertical scattering channels, anomalousenhancement of the Stokes doubling effect. The lifetimevibrational interference (LVI), playing a crucial role inresonant scattering, is found to strongly influence thedispersion of the Auger resonances of polymers in agreementwith experiment. An almost complete quenching of the scatteringcross section by LVI is observed for the N₂molecule. It is found that the interferenceelimination of the scattering amplitude gives valuableinformation on molecular geometry. The electron Doppler effectis minutely studied making use of a wave packet technique. Thesimulations show an "interference burning" of a narrow hole onthe top of the Doppler broadened profile of the Auger spectraof molecular oxygen. For the SF₆molecule the Auger Doppler effect is found to besensitive to the detuning due to the scattering anisotropy. Inall of these studies the temporal language was foundconstructive and enormously helpful for understanding theunderlying physical processes. Most theoretical predictionsmade have been verified by experiments.</p>

The interaction between light and organometallic chromophores has been investigated theoretically in a strive for fast optical filters. The main emphasis is on two-photon absorption and excited state absorption as illustrated in the Jablonski diagram. We stress the need for relativistic calculations and have developed methods to address this issue. Furthermore, we present how quantum chemical calculations can be combined with Maxwell's equations in order to simulate propagation of laser pulses through a materials doped with chromophores with high two-photon absorption cross sections. Finally, we also discuss how fast agile filters using spin-transition materials can be modeled in order to accomplish theoretical material design. / <p>Report code: LIU-TEK-LIC-2006:55. On the day of the defence date the status on article III was Manuscript, article IV was Accepted and article V was Submitted.</p>

Un tiers des urgences dentaires et un pourcentage élevé de maux de dents sont endodontie liés. Instruments rotatifs utilisés dans le traitement endodontique peuvent se briser à l'intérieur du canal radiculaire en raison de la fatigue des matériaux. Une fois cassé, l'extraction de la partie fracturée du canal est un travail difficile et ennuyeux de le patient et le dentiste. Par conséquent, l'alerte d'une fracture imminente lors de l'utilisation clinique ou développer de bonnes stratégies pour augmenter ses propriétés mécaniques sera d'une grande aide pour éviter les complications médicales / juridique. La recherche est étudié à partir de deux parties. La première partie a établi une plate-forme de test standard, simulant plusieurs paramètres de canal, propose une série de stratégies visant à améliorer la vie de la fatigue et des propriétés mécaniques de matériaux. Aussi, un système de surveillance utilisant de réseaux de Bragg (FBG) capteurs a été tentée. la raison de l'utilisation de la glycémie à jeun est sa petite taille qui est très prometteur dans l'intégration avec la pièce à main de l'équipement endodontique. dans le travail actuel, en ramassant et en analysant l'onde de contrainte par transformée de Fourier rapide (FFT), nous peut révéler la variation d'énergie et la fréquence phénomène déplaçant dans certaines fréquences caractéristiques. on espère que, avec ces informations, nous pouvons éviter / atténuer la survenue de fracture inattendue. Comme pour l'essai de fatigue, les données ont montré que la résistance à la fatigue peut être améliorée certain traitement thermique ou à mouvement alternatif méthode de rotation appliqué. tel phénomène peut être étroitement liée à la composition de la phase en ni-Ti en alliage et la contrainte de traction maximale est réduite lorsque le mouvement alternatif appliqué. études ont montré que plus la teneur de la phase martensite dans l'aiguille, l'plus de vie à la fatigue peut être atteint. Cependant, il peut être nécessaire de prendre des compromis avec l'efficacité de coupe de l'aiguille. pour cette question, nous pouvons combiner le traitement cryogénique et traitement thermique pour obtenir une meilleure résistance à la fatigue sans compromettre son efficacité de coupe. La deuxième partie est de fabriquer haute résolution, grande taille de la nouvelle Type aiguilles d'endodontie en utilisant la polymérisation à deux photons (TTP) technique. Le travail se fait à l'université de Joseph-Fourier LiPhy laboratoire, France. Contrairement à la fabrication traditionnelle du PPT, qui avait une limitation de sa taille de produits en raison du faible pouvoir lase, taux de redoublement et piézo entraîné stade, nous utilisons résine Ormocer, 130 kHz, 1W puissant laser de 532 nm à l'étape motorisé étage XY pour fabriquer une grande 800 échafaud um cellulaire bio-compatible et 1.2 cm aiguille de hauteur. aussi, pour améliorer la qualité du produit de TPP, l'approche de correction de la puissance du laser avait été tentée. Pendant TPP fabrication, la forme de focalisation laser changé lorsque la surface de la fabrication a été déplacé dans la direction z. Cela se traduit par le fait que nous avons besoin de plus afin d'assurer la taille de voxel est identique à z différent. pour corriger ce défaut, un procédé pour la correction de la puissance du laser et de la formule pour la puissance de correction sont proposées. la formule est dérivé du concept de maintien de conditions d'exposition identiques.