Orientador: Luiz Antonio de Oliveira Nunes / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-07-23T03:24:35Z (GMT). No. of bitstreams: 1 ValenzuelaBell_MariaJose_D.pdf: 2482925 bytes, checksum: c7c2ac2e9f1c918193c474c99a560bdc (MD5) Previous issue date: 1997 / Resumo: Neste trabalho foi realizada a caracterização óptica de super-redes de GaAs com dopagem delta de Si, por técnicas de espectroscopia óptica tais como fotoluminescência (PL), fotoluminescência de excitação (PLE), fotoluminescêcnia resolvida no tempo, espectroscopia Raman, fotorefletância (PR) e fotorefletância resolvida no tempo. Neste tipo de super-redes, a estrutura eletrônica é tal que os elétrons ficam confinados na direção de crescimento em minibandas na banda de condução e apresentam características quase bi e tridimensionais. Foram determinadas as transições interbanda diretas e indiretas no espaço real, e seus respectivos tempos de recombinação, através da técnica de fotoluminescência resolvida no tempo. Comparações dos resultados experimentais com o cálculo das respectivas estruturas eletrônicas das amostras mostraram bom acordo. Também foi estudado um processo de interferência entre excitações eletrônicas de partícula independente e fônons LO, que resulta em formas de linha assimétricas do tipo Fano. Mostra-se que a contribuição vibracional para o processo é fortemente dependente da orientação relativa do GaAs em relação a direção das polarizações da luz incidente e espalhada. Na orientação particular em que a contribuição do fônon LO é nula observou-se uma anti-ressonância, característica da ressonância de Fano. O estudo da ressonância de Fano à temperatura ambiente mostrou que há uma contribuição indesejada para o espalhamento Raman vindo da região da superfície, na qual ocorre transferência de carga entre o primeiro poço de potencial delta e os estados de superfície. Assim, forma-se um campo elétrico (responsável pela formação de uma camada de depleção de cargas na região próxima aà superfície) que foi estudado via fotorefletância e fotorefletância resolvida no tempo. Esta última mostrou que o tempo de resposta da fotorefletância é extremamente sensível ao efeito fotovoltáico. Com isso, foi possível estudar a redução do campo elétrico com a injeção de pares elétron-buraco fotoinduzidos. Porém, há um aparente comportamento de saturação do efeito fotovoltáico, o que resulta em reduções pequenas do campo elétrico / Abstract: We performed the GaAs Si delta doped superlattices optical characterization, using spectroscopic techniques as photoluminescence, photoluminescence sxcitation, time resolved photoluminescence, Raman scattering and time resolved photorefletance. Their electronic structure is such that the electron gas is confined in minibands along the growth direction and present 2D and 3D properties depending on the superlattice period. Interband transitions and their respective recombination times were experimentally determined, by time resolved photoluminescence. Results obtained are in good agreement with the calculated electronic structure. In addition, it was studied the coupling between single particle electronic excitations and LO phonons, which results in asymmetric Fano-like lineshapes. It is shown that vibracional contribution depends strongly on the crystaline axis orientation relative to the incident and scattered light polarization directions. The Fano-like resonance was performed in the backscattering Raman geometry, at room temperature. The spectra showed another contribution from the depletion region at the surface, due to the charge transfer from the first delta doped layer and the surface states. As a consequence, there is a surface electric field, which was studied via photoreflectance and time resolved photoreflectance. Our intention was studied via photoreflectance and time resolved photoreflectance. Our intention was to eliminate the electric field by light injection of electron-hole pairs (photovoltaic effect). It is shown that photoreflectance response time is very to the photovoltaic effect. However, the surface electric field suppression was frustrated due to the observed saturation behavior of the photovoltaic effect as light intensity is increased. / Doutorado / Física / Doutor em Ciências

As society becomes increasingly reliant on information technology for data exchange and long-term data storage the need for a system of data management to document and provide access to the 'societal memory' is becoming imperative. An examination of both the literature and current 'best practice' underlines the absence to date of a proven universal conceptual basis to digital data preservation. The examination of differences in nature and sources of origin, between traditional 'print-based' and digital objects leads to a re-appraisal of current practices of data selection and preservation. The need to embrace past, present and future metadata developments in a rapidly changing environment is considered. Various hypotheses were formulated and supported regarding: the similarities and differences required in selection criteria for different types of Digital Data Objects (DDOs), the ability to define universal threshold standards for a framework of metadata for digital data preservation, and the role of selection criteria in such a framework. The research uses Soft Systems Methodology to investigate the potential of the metadata concept as the key to universal data management. Semi-structured interviews were conducted to explore the attitudes of information professionals in the United Kingdom towards the challenges facing information-dependent organisations attempting to preserve digital data over the long-term. In particular, the nature of DDOs being encountered by stakeholders, the reasons, policies, and procedures for preserving them, together with a range of specific issues such as: the role of metadata, access to, and rights management of DDOs. The societal need for selection to ensure efficient long-term access is considered. Drawing on - SSM modelling, this research develops a flexible, long-term management framework for digital data at a level higher than metadata, with selection as an essential component. The framework's conceptual feasibility has been examined from both financial and societal benefit perspectives, together with the recognition of constraints. The super-metadata framework provides a possible systematic approach to managing a wide range of digital data in a variety of formats, created/owned by a spectrum of information-dependent organisations.

La première partie du travail de thèse a été l’étude de nanoparticules organiques (NPFs) de BODIPY de forte brillance (plus de 5000 molécules encapsulées). Des expériences par fluorescence résolue en temps ont permis de déterminer la présence d’agrégats non fluorescents et d’excimères (temps de vie de 1,8 ns). D’autre part, des expériences d’anisotropie de fluorescence résolue en temps et de spectroscopie d’absorption transitoire femtoseconde ont révélé l’existence de transferts d’énergie ultrarapides et efficaces, migration intermoléculaire (< 25 ps) et annihilation singulet-singulet (< 2 ps). Enfin, le suivi de l’émission des NPFs par spectroscopie de particules uniques a permis d’observer leur clignotement à l’échelle de la centaine de millisecondes. Cependant, due à une trop forte densité de molécules émissives, aucune extinction totale de fluorescence (état OFF) n’a été observée. L’absence d’état OFF ne permettant pas l’utilisation d’une méthode de localisation de molécules uniques, la deuxième partie du travail a concerné le développement d’une méthode de traitement des données d’imagerie de fluorescence de molécules uniques possédant une forte densité de molécules émissives. Cette méthode (MAPPIX, MAPping Pixel dissimilarity) utilise la fluctuation d’intensité de l’émission de fluorescence des sondes au cours du temps et est basée sur un calcul de dissimilarité. Les résultats obtenus sur des données simulées et des images réelles se sont avérés très concluant. Bien que n’ayant pas pu être rationalisé en termes de gain de résolution, une amélioration de contraste permettant de dépasser la limite de diffraction a été observée. / The first part of the thesis was the study of bright BODIPY nanoparticles (NPFs) (more than 5000 encapsulated molecules). Non-fluorescent aggregates and excimers (lifetime of 1.8 ns) were characterized by time resolved fluorescence experiments. In addition time-resolved fluorescence anisotropy and femtosecond transient absorption spectroscopy experiments revealed efficient ultrafast energy transfer, intermolecular migration (< 25 ps) and singlet-singlet annihilation (< 2 ps). Single particle spectroscopy on NPFs, function of the number of excited molecules within a NPF, revealed some blinking at the scale of about a hundred of milliseconds. However, due to too high density of emissive molecules, complete extinction of fluorescence (OFF state) could not be observed. The absence of OFF state forbid the use of a single molecule localization methods, the second part of this work was thus focused on the development of a data treatment method for single molecule fluorescence images containing high density of emitters. This method (MAPPIX, MAPping Pixel dissimilarity) uses the intensity fluctuations of the probes fluorescence emission over time and is based on a dissimilarity calculation. The results obtained on simulated data and real images were very conclusive. Although it was not possible to be rationalized it in terms of resolution, a contrast improvement bypassing the diffraction limit was observed.

Image super-resolution technique mainly aims at restoring high-resolution image with satisfactory novel details. In recent years, leaning-based single-image super-resolution has been developed and proved to produce satisfactory results. With one or some dictionaries trained from a training set, learning-based super-resolution is able to establish a mapping relationship between low-resolution images and their corresponding high-resolution ones. Among all these algorithms, sparsity-based super-resolution has been proved with outstanding performance from extensive experiments. By utilizing compact dictionaries, this class of super-resolution algorithms can be efficient with lower computation complexity and has shown great potential for the practical applications. Our proposed model, which is known as Joint Dictionary-based Super-Resolution (JDSR) algorithm, is a new sparsity-based super-resolution approach. Based on the observation that the initial values of Non-locally Centralized Sparse Representation (NCSR) model will affect the final reconstruction, we change its initial values by using results of Zeyde's model. Besides, with the purpose of further improvement, we also add a gradient histogram preservation term in the sparse model of NCSR, and modify the reference histogram estimation by a simple edge detection based enhancement so that the estimated histogram will be closer to the ground truth. The experimental results illustrate that our method outperforms the state-of-the-art methods in terms of sharper edges, clearer textures and better novel details.

In this thesis, we discuss several phenomena exhibiting `limiting behaviour' in physics. This includes the duality principle, delegated quantum computation, and super-resolution. The duality principle places a limit on the coexistence of wave and particle behaviours. We develop a framework that explains apparent violations of this principle while staying within the scope of quantum mechanics. In addition, we relate the duality principle to the sub-fidelity and weak-values. We also show that the maximum recoverable coherence of a qubit has a sharp transition from 0 to 1 when we have access to half of the environment to which the qubit is correlated. Delegated quantum computation consists of a computational weak client who wishes to delegate a complex quantum computation to a powerful quantum server. We develop a new protocol for delegated quantum computation requiring less quantum power than its predecessor. Finally, we develop and test a new theory for eigenmode super-resolution.

The diffraction limit restricts conventional light microscopes to approximately 250 nm laterally and 500 nm axially, these limits being first proposed by Abbe in 1873. Despite this, optical microscopes have found many applications in biological research and single cells that are 10 - 100 um in size. Furthermore by coupling the non-invasive nature of a light microscope with highly sensitive fluorescent probes, fluorescence microscopy has also become a standard imaging technique. Recent advances in fluorescence microscopy now provide a number of methods to circumvent the Abbe diffraction limit, with many techniques becoming prevalent over the last 10 years including direct Stochastic Optical Reconstruction Microscopy (dSTORM). A dSTORM system has been constructed and calibrated using a commercially available inverted florescence microscope and total internal reflection florescence (TIRF) imaging. dSTORM relies on the ability to switch sparse subsets of fluorophores and temporally separate them. Provided the spatial separation is sufficient between any member of a subset, the average error with which the emission can be localized is much less than size of the emission profile itself. The underlying mechanism for this switching is detailed based on the principle of photoinduced electron transfer (PET). The switching characteristics of the common florescent dye Alexa Fluor 568 are investigated and shown to be controlled by a number of factors including the excitation intensity and concentration of the primary thiol cysteamine beta-MEA. A number of parameters are defined, including the dye switching rate, for a given set of physical parameters. U2OS cells are labelled for the microtubule protein Tubulin using immunofluorescent labelling strategies. A direct comparison is made between diffraction limited TIRF images and dSTORM reconstructed images, with an average width for microtubules determined to (58.2 ± 8.1) nm. Further measurements are made by labelling the Rab5 effector Early Endosome Antigen 1 (EEA1). From this the aspect ratio for early endosomes is determined to be 1.68 ± 0.7 with an average radius of (45.8 ± 18.8) nm. The point spatial distribution of EEA1 is investigated by using the linearised form of Ripley's K-function H(r) and the null hypothesis of complete spatial randomness tested. EEA1 is shown to cluster at radius of 58.7 nm on individual endosomes, thought to be due to the well defined binding domains present on early endosomes for EEA1. Further evidence suggests that clustering is also exhibited at another maximum of approximately 500 nm when looking at an ensemble of EEA1 and early endosomes.

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京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22242号 / 理博第4556号 / 新制||理||1654(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 中家 剛, 准教授 WENDELL Roger, 教授 鶴 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Advanced combustion concepts are required to meet the increasing global energy demand and stringent emission regulations imposed by the governments on automobile manufacturers. Improvement in efficiency and reduction in emissions can be achieved by downsizing the Spark Ignition (SI) engines. The operating range of SI engine is limited by occurrence of knock, pre-ignition and the following super-knock due to boosting of intake pressure, to account for the reduction of power, as a result of downsizing the engine. Super-knock, which represents high momentary pressure accompanied with pressure oscillations, is known to permanently damage the moving component of the engines. Therefore fundamental comprehensive understanding of the mechanism involved in pre-ignition and super-knock are required to design highly efficient spark ignition engines with lower emissions that can meet the increasing government regulations. \nThe thesis focuses on auto-ignition characteristics of endgas and the bulk mixture properties that favor transition of pre-ignition to super-knock. Direct numerical studies indicate that super-knock occurs to due to initiation of premature flame front that transition into detonation. In literature, many sources are reported to trigger pre-ignition. Due to the uncertainty of the information on the sources that trigger pre-ignition, it is extremely difficult to predict and control pre-ignition event in SI engines. Since the information on the source of pre-ignition is not available, the main focus of this work is to understand the physical and chemical mechanisms involved in super-knock, factors that influence super-knock and methods to predict super-knock. \n
Pre-ignition was initiated at known locations and crank angle using a hotspot of known size and strength. Different parametric cases were studied and the location and timing of pre-ignition initiation is found to be extremely important in determining the transition of pre-ignition event to super-knock. Pre-ignition increases the temperature of the endgas and the overall bulk mixture, that transitions the pre-ignition flame front to a detonation. The transition of the flame propagation mode from deflagration to detonation was investigated with different type of analysis methods and all results confirmed the transition of pre-ignition flame front to detonation that results in super- knock.

In recent years super-hydrophobic micro-patterned substrates (SHS) have been successfully used for the suspension of a few biological molecules, allowing the further characterization in a background-free environment by label-free techniques such as Raman spectroscopy, SEM and TEM in one device. This result is due to the combined action of laminar flow and shear stress exerted on the molecules contained in a drop that is spotted on top of the SHS and slowly evaporates. This new method is here proposed for the label-free formation and background-free characterization of amyloid fibers. Amyloids are insoluble aggregates formed by proteins that convert from a misfolded form into highly-organized β-sheet structures that could accumulate in different organs and compromise their normal physiological functions. Known amyloid-related diseases, named amyloidosis, are for instance Alzheimer, Parkinson, and type 2 diabetes. In classical crystallography, the study of the amyloid aggregates structure is often hampered by the laborious and time consuming sample preparation techniques. Therefore the need of a quick reproducible technique, has emerged. The amyloid fibers investigated in this work are derived from a lysozyme protein and a Tau-derived short peptide, both known to be related to two forms of amyloidosis. With this technique we demonstrate that threads of protein fibers are deposited on the substrate helped by the patterning of the SHS and its properties, and by characterizing them with Raman spectroscopy technique we revealed that they are anisotropic structures of amyloid nature. This type of sample preparation technique arises from the effect of the evaporation on the SHS, and opens up new possibilities for the formation of oriented fibers of amyloids and more in general, of proteins, ready for a substrate-free characterization, while classic crystallographic methods could have a limitation.