xvi, 218 p. : ill. (some col.) / Our theoretical studies involve the control of electronic energy transfer in molecular dimers through the preparation of specific vibrational coherences prior to electronic excitation. Our control strategy is based upon the fact that, following impulsive electronic excitation, nuclear motion acts to change the instantaneous energy difference between site-excited electronic states and thereby influences short-time electronic excitation transfer (EET). By inducing coherent intramolecular vibration in one of the chromophores prior to short-pulse electronic excitation, we exert external control over electronic dynamics. As a means to monitor this coherent control over EET, we propose using multidimensional wave-packet interferometry (md-WPI). Two pairs of polarized phase-related femtosecond pulses following the control pulse would generate superpositions of coherent nuclear wave packets in optically accessible electronic states. Interference contributions to the time- and frequency-integrated fluorescence signal due to overlaps among the superposed wave packets provide amplitude-level information on the nuclear and electronic dynamics. We test both the control strategy and its spectroscopic investigation by calculating pump-probe difference signals for various combinations of pulse polarizations. That signal is the limiting case of the control-influenced md-WPI signal in which the two pulses in the pump pulse-pair coincide, as do the two pulses in the probe pulse-pair. We present calculated pump-probe difference signals for a variety of systems including a simplified model of the covalent dimer dithia-anthracenophane (DTA) in which we treat only the weakly Franck-Condon active ν 12 anthracene vibration at 385 cm -1 . We further present calculated nl-WPI difference signals for an oriented DTA complex, which reveal amplitude-level dynamical information about the interaction of nuclear motion and electronic energy transfer. We also present pump-probe difference signals from a model system in which a CF 3 group, whose torsional angle is strongly Franck-Condon active, has been added to the anthracene monomers which make up DTA. We make use of electronic structure calculations to find the torsional potential of the monomer, from which we calculate the spectroscopic signals of the dimer. We show that a significant measure of control over short-time EET is achievable in this system. This dissertation includes previously published coauthored material. / Commitee in charge: Dr. Michael E. Kellman, Chair; Dr. Jeffrey A. Cina, Advisor; Dr. David R. Herrick; Dr. Andrew H. Marcus; Dr. Daniel A. Steck

xvii, 110 p. : ill. (some col.) / Electron spin states in semiconductors feature long coherence lifetimes, which have stimulated intense interest in the use of these spins for applications in spin based electronics and quantum information processing (QIP). A principal requirement for these spins to be viable candidates in QIP is the ability to coherently control the spins on timescales much faster than the decoherence times. The ability to optically control the spin state can meet this requirement. The spin states of electrons exhibit strong radiative coupling to negatively charged exciton (trion) states, and this radiative coupling makes coherent optical control of spin states possible. This dissertation presents experimental demonstration of coherent control of an electron spin ensemble in a two-dimensional electron gas in a CdTe quantum well. We present two complimentary techniques to optically manipulate these electron spins using a Raman transition. The first demonstration is with a single off-resonant ultrafast optical pulse. This ultrafast pulse acts like an effective magnetic field in the propagation direction of the optical pulse. The second experiment utilizes phase-locked Raman resonant pulse pairs to coherently rotate the quantum state, where the relative phase of the pulse pair sets the axis of rotation. The Raman pulse pair acts like a microwave field driving the spin states. This research demonstrates two significant contributions to the field of coherent optical interactions with semiconductors. First, we have advanced the potential use of electron spin ensembles in semiconductors for optics based quantum information processing hardware through our demonstration of coherent spin flips and complete coherent control. Second, we have experimentally realized full coherent control through the use of phase-locked Raman pulse pairs that overcomes inherent limitations of the single-pulse optical rotation technique, which is the current standard technique used in coherent control. This dissertation includes previously published and unpublished co-authored material. / Committee in charge: Dr. Miriam Deutsch, Chairperson; Dr. Hailin Wang, Advisor; Dr. Steven van Enk, Member; Dr. Raghuveer Parthasarathy, Member; Dr. Catherine Page, Outside Member

Magnetic films have gained great attention for decades because of their broad industrial application. Their modern functionality more and more relies on their domain structure. Magnetic films usually form complex domain patterns with unique structures at different length scales due to the competition between short range attractive and long range repulsive interactions. The ensemble of domains is topologically disordered, although each of them possesses orientational spin order. Since simplifying complexity is the key step to understand and transform nature, finding new orders from the ostensible disordered structures would be a fascinating topic. Scattering techniques are well-known powerful tools to detect orders. Coherent soft xray magnetic resonant scattering becomes accessible with the development of synchrotron radiation facilities. We applied the technique to study the domain structure of CoPd/MnIr multilayer films with perpendicular magnetic anisotropy. By tuning incident photon energy to Co 2p&rarr3d transition edge we collected small angle magnetic scattering patterns by a charged coupled device in transmission geometry. Each pattern is an unique fingerprint of the corresponding illuminated domain structure. The patterns were analyzed by an angular correlation method. A variety of striking rotational orders were discovered. Their evolution with applied fields was investigated. The sustainabilities of the orders under the room temperature, exchange biased (EB) state, and non-EB state were compared, which suggests that certain orders can be well manipulated under the EB condition. By simulating magnetic resonant scattering from domain patterns obtained by a direct imaging method, we probed the range of emerging orders and finite size effect. Our study provides a novel approach to characterizing magnetic films and potentially can be extended to any system with a complex microstructure. / 2015-07-11

[pt] A expansão e a interligação de Sistemas de Energia Elétrica (SEE) tem enfatizado o uso de equivalentes dinâmicos pelas companhias de serviço de eletricidade, nos estudos de planejamento e operação, para representação das porções do sistema não pertinentes à sua área de atuação. Com a redução das dimensões do modelo do sistema obtém-se um aumento de velocidade dos estudos com minimização dos custos e do esforço computacional. Além desses aspectos o uso de equivalentes contorna o problema de capacidade limitada de memória dos sistemas de computação e se enquadra na atual estrutura física e conceitual dos minicomputadores. Em estudos de estabilidade de SEE, o objetivo básico de equivalentes dinâmicos é o de simular as reações do sistema externo quando ocorrem distúrbios no sistema interno. O grande calor deste tipo de simplificação reside em sua capacidade de reconhecer a tendência dinâmica do sistema. Esta pesquisa apresenta um método para cálculo de equivalentes dinâmicos para estudos de estabilidade transitória baseado na agregação de geradores que oscilam conjuntamente após uma dada perturbação. O modelo reduzido obtido por transformações topológicas, e constituído de parâmetros similares aos habitualmente empregados na modelagem de sistemas de energia elétrica sendo numericamente estável. Ao final, alguns resultados são apresentados no intuito de atestar a validade do método proposto. / [en] The spread and the interconection of Electrical Power Systems have been stressed the employment of dynamic equivalents by Electrical Power Companies for representing system áreas that they are not responsible for at planning and operation studies. Due to system model dimension reduction, studies have become faster with reduced costs and computational task requiriments. Besides, dynamic equivalents overcome computational system limited memory capability problems ant fit easily into the up-to-date phisical and coceptual structure of the minicomputers. As an aid to Electrical Power System Stability studies, the objective of the dynamic equivalents is to simulate external system. The great merit of this lind of overcoming is its ability on revealing the system dynamic trend. This research shows a method of computing dynamic equivalents for transitory stability studies based con the agregation of the generators that oscilate together from an initial perturbation on. The reduced model, got from topological transformations, is built of parameters that are similar to usually employed on Electrical Energy System modeling been numerically stable. At the end, some results are shown as an attempt to test the performance of the method.

Questões ambientais estão no centro das discussões nas últimas décadas. A poluição atmosférica, causada pela expansão pós-revolução industrial fez surgir a necessidade de aprender a descrever, usando modelos matemáticos, esse fenômeno. Com esse conhecimento pode-se propor soluções que mitiguem a poluição e os danos colaterais causados ao ambiente. A dispersão de poluentes modelada por soluções analíticas, a partir das equações de advecção-difusão oferecem um conhecimento sobre cada componente que constrói a equação, característica inexistente em outras abordagens, como a numérica. Entretanto ela era incapaz de descrever propriedades que se referem à turbulência, as estruturas coerentes, causadas por componentes não-lineares suprimidas por construção das equações governantes do modelo. Este trabalho estudou uma forma de recuperar características associadas à turbulência através de uma componente fundamental em estruturas coerentes, a fase. Essa é incluída no modelo que passa a descrever manifestações da turbulência em processos de dispersão através de flutuações de pequena escala na concentração da solução do modelo sesquilinear, que é determinístico-estocástico. No decorrer do trabalho há um estudo através de variações de parâmetros para compreender os efeitos da fase no modelo. Ele também foi aplicado ao experimento de Copenhagen e a dois cenários reais com a intenção de compreender o modelo frente à variáveis micrometeorológicas assim como aprimorá-lo para simular a dispersão de poluentes oriundos de fontes de forma realística. / Environmental issues have been at the center of discussions in the last few decades. Atmospheric pollution, caused by post-industrial revolution, has increased the necessity to describe, using mathematical models, this phenomenon. With this knowledge is possible to propose solutions mitigating the pollution and collateral damages caused in the environment. The pollutant dispersion modeled by analytical solutions, from advection-diffusion equations, offers a knowledge about each component that constructs the equation, a characteristic that does not exist in other approaches, such as numerical. However it was unable to describe properties that refer to turbulence, coherent structures, caused by nonlinear components suppressed by constructing the model governing equations. This work studied a way to recover characteristics associated with turbulence through a fundamental component in coherent structures, the phase. This is included in the model which describes manifestations of turbulence in the dispersion process through the presence of small-scale concentration fluctuations in the sesquilinear model, which is deterministicstochastic. In the course of this work there is a study through variations of parameters to understand the phase effects in the model. It was also applied to Copenhagen experiment and to two real scenarios with the intention of understanding the model regarding micrometeorological variables as well as improving it to simulate the pollutant dispersion from sources in a realistic way.

The incidence of gastrointestinal (GI) cancers has been steadily increasing in the UK since the mid 1970’s. These include cancers of the colon and oesophagus. Colon cancers have a high incidence rate, being the fourth most common cancer in the UK for both men and women. Oesophageal cancers in comparison are much rarer, however they have a poor survival rate primarily due to a late diagnosis. The key to improving survival for these cancers and many others is to detect and remove the disease at the early stages, to prevent the cancer from advancing. At present the ‘gold standard’ for diagnosis is a biopsy followed by histopathology. This technique is invasive, time consuming and highly subjective. It is therefore important to look towards non-invasive methods for early and rapid diagnosis. Optical techniques have begun to show such promise. By probing the interactions of tissues with light, diagnostic information is able to be obtained non-invasively. Techniques such as Raman spectroscopy utilise inherent molecular vibrations to extract biochemical information from tissues. Raman spectroscopy, however, is currently fundamentally limited by long acquisition times, due to the inherently weak signals produced. Using coherent Raman techniques such as coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS), the molecular vibrations are coherently driven to provide an enhancement in signal. This thesis explored spectral signatures from snap frozen oesophageal sections in the fingerprint (450 cm-1 to 1850 cm-1) and high wavenumber (2800 cm-1 to 3050 cm-1) regions using spontaneous Raman and compared with spectra from hyperspectral SRS. The diagnostic potential for each technique was assessed for four major pathology groups, normal, Barrett’s oesophagus, dysplasia and adenocarcinoma. Samples were classified using a principal component fed linear discriminant analysis (PCA-LDA) approach with a leave-one-out cross validation. Comparisons were made to haematoxylin and eosin (H&E) stained sections. Raman in the fingerprint region was found to be the most promising for diagnosis. There were minimal changes in the high wavenumber region between pathology groups which was also reflected in the SRS spectra and proved to be insufficient for classification. Further comparisons were made between spontaneous and coherent Raman techniques using frozen colon sections. The morphological and structural information available was explored using a k-means cluster analysis. Both spontaneous and coherent Raman were able to distinguish important structural features in the colon, such as the epithelial cells that form the colonic glands and surrounding connective tissue. Both are important visual markers for cancer diagnosis in the current approach. SRS demonstrated higher spatial resolution and faster acquisition times in comparison to spontaneous Raman. This work has discussed the many advantages of using coherent Raman techniques for tissue applications, but has also highlighted some of the limitations for spectral measurements, arising from the complexity of the system.

abstract: Presented is a study on the chemotaxis reaction process and its relation with flow topology. The effect of coherent structures in turbulent flows is characterized by studying nutrient uptake and the advantage that is received from motile bacteria over other non-motile bacteria. Variability is found to be dependent on the initial location of scalar impurity and can be tied to Lagrangian coherent structures through recent advances in the identification of finite-time transport barriers. Advantage is relatively small for initial nutrient found within high stretching regions of the flow, and nutrient within elliptic structures provide the greatest advantage for motile species. How the flow field and the relevant flow topology lead to such a relation is analyzed. / Dissertation/Thesis / Masters Thesis Mathematics 2015

abstract: The superior brightness and ultra short pulse duration of X-ray free electron laser (XFEL) allows it to outrun radiation damage in coherent diffractive imaging since elastic scattering terminates before photoelectron cascades commences. This “diffract-before-destroy” feature of XFEL opened up new opportunities for biological macromolecule imaging and structure studies by breaking the limit to spatial resolution imposed by the maximum dose that is allowed before radiation damage. However, data collection in serial femto-second crystallography (SFX) using XFEL is affected by a bunch of stochastic factors, which pose great challenges to the data analysis in SFX. These stochastic factors include crystal size, shape, random orientation, X-ray photon flux, position and energy spectrum. Monte-Carlo integration proves effective and successful in extracting the structure factors by merging all diffraction patterns given that the data set is sufficiently large to average out all stochastic factors. However, this approach typically requires hundreds of thousands of patterns collected from experiments. This dissertation explores both experimental and algorithmic methods to eliminate or reduce the effect of stochastic factors in data acquisition and analysis. Coherent convergent X-ray beam diffraction (CCB) is discussed for possibilities of obtaining single-shot angular-integrated rocking curves. It is also shown the interference between Bragg disks helps ab-initio phasing. Two-color diffraction scheme is proposed for time-resolved studies and general data collection strategies are discussed based on error metrics. A new auto-indexing algorithm for sparse patterns is developed and demonstrated for both simulated and experimental data. Statistics show that indexing rate is increased by 3 times for I3C data set collected from beam time LJ69 at Linac coherent light source (LCLS). Finally, dynamical inversion from electron diffraction is explored as an alternative approach for structure determination. / Dissertation/Thesis / Doctoral Dissertation Physics 2016

Les propriétés mécaniques des petits objets diffèrent fortement de celles du matériau massif à partir du moment où leurs dimensions deviennent comparables ou inférieures à celles du libre parcours moyen des dislocations (typiquement quelques microns). Par exemple, leur limite élastique augmente quand leur taille diminue. D'autre part les nanostructures sont exposées à de fortes contraintes, telles que celles imposées par les relations épitaxiales avec le substrat.Il existe donc un besoin clair (supporté par des intérêts industriels) d'une meilleure compréhension des phénomènes physiques qui gouvernent les propriétés des matériaux aux échelles nanométriques.Le laboratoire SIMAP est engagé dans ce domaine de recherche et s'y attelle en combinant croissance d'échantillons, méthodes de caractérisation en laboratoire, méthodes numériques et techniques synchrotron.Une des expériences clés développées par notre équipe est la caractérisation in situ des mécanismes de déformation induits par une pointe d'AFM sur une nanostructure par la diffraction des rayons X cohérents. La diffraction des rayons-X cohérents est une technique émergente de synchrotron; qui permet la mesure détaillée de la structure du cristal, y compris le champ de déformation 3D et les défauts potentiels dans des objets micro ou nano structurés. En principe, une image 3D de la structure de l'échantillon peut-être obtenue à partir des données de diffraction cohérente. En pratique, reconstruire une image de l'échantillon peut s'avérer délicat en présence d'un champ de déformation inhomogène et de nombreux défauts cristallins. Le profil du front d'onde qui est généralement assez éloigné d'une onde plane, peut encore ajouter une complication supplémentaire au problème. Dans ces travaux de thèse, il est démontré qu'une image 3D de l'objet peut être reconstruite dans le cas de systèmes modérément complexes. / The mechanical properties of small objects deviate strongly from the bulk behaviour, as soon as their size becomes comparable or smaller to the dislocation mean free path (typically a few microns). For instance, their elastic limit increase when their size is reduced. On a another hand, nanostructures are exposed to strong constraints, such as that imposed by epitaxial relations with a substrate. Altogether, there is a clear need (supported by industrial interests) for a better understanding of the fundamental phenomena that govern the mechanical properties of materials at the nanometre scale. The lab SIMaP is engaged in this research and tackles the topic by combining sample growth, laboratory characterisation methods, numerical models, and synchrotron techniques.One key experiment developed by our team is the in situ characterisation of the deformation mechanism induced by an AFM tip on a nanostructure using Coherent X-ray Diffraction (CXD). CXD is an emerging synchrotron technique that allows the detailed measurement of the crystal structure,including strain field and defects, of micro/nano-objects. In principle, a 3D image of the structure of the sample can be obtained from the CXD data. However, it remains difficult in realistic cases, when the strain is very inhomogeneous and crystal defects numerous. The problem is further complicated by the wavefront of the beam, which is usually far from a plane wave, particularly when the AFM tip shadows part of the incoming beam. In this PHD work, it is demonstrated that a 3D image of the object can be reconstructed in case of moderately complex systems.

Made available in DSpace on 2015-05-14T12:13:59Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 283471 bytes, checksum: 3c03d229984755f09c77c7e98c3f465e (MD5) Previous issue date: 2011-06-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this work we present a quantum description of a mesoscopic RLC circuit without source. For this purpose, we model this system for that of a damped harmonic oscillator which is described by the Caldirola-Kanai Hamiltonian. Then, with the aid of the quantum invariant method we solve the Schrödinger equation associated with this Hamiltonian and write the corresponding wave functions in terms of a particular solution of the Milne-Pinney equation. We also construct coherent states for the RLC quantized, and evaluate the quantum fluctuations of the charge and the magnetic flux, as well as the corresponding product of uncertainty. / Nesta dissertação, apresentamos uma descrição quântica de um circuito RLC mesoscópico sem fonte. Com esta finalidade, modelamos este sistema para aquele de um oscilador harmônico amortecido, que é descrito pelo Hamiltoniano de Caldirola-Kanai. Então, com a ajuda do método de invariantes quânticos, resolvemos a equação de Schrödinger para este Hamiltoniano e escrevemos as funções de onda correspondentes em termos da solução particular da equação de Milne-Pinney. Também construímos estados coerentes para o circuito RLC quantizado, e calculamos as flutuações quânticas da carga e do fluxo magnético, bem como o produto de incerteza correspondente.