Two-phase flows are encountered in a wide range of applications both on-ground and in space. The dynamics of such flows in the absence of gravity is completely different from that in normal gravity due to the absence of buoyancy forces. A deeper understanding of the behavior of multiphase flows is essential in order to improve the operation of devices which require the use of two-phase systems. Analytical and experimental work is still needed for enhancing the control of two-phase flows, due to the theoretical complexity and the lack of experimental data for certain configurations. In this work, the behavior of two-phase flows has been studied experimentally in normal gravity and in microgravity conditions. In particular, the single-jet configuration has been investigated for bubbly jets and droplet jets. Dynamics of individual bubbles and droplets as well as the global structure of the jets has been considered. The opposed-jet configuration has been investigated for bubbly flows. Different separation between jets and orientation angles have been studied in normal gravity, and the obtained results have been compared to the microgravity case. A numerical model has been implemented to study single-phase jet impingement and opposed bubbly jets at different gravity levels. Good qualitative agreement between the simulations and the experiments has been obtained. The bubble bouncing process, prior to coalescence, after collision with a flat free surface has been also studied experimentally in normal gravity conditions. The results presented in this work will help to improve the general understanding of two-phase flows in normal gravity and in microgravity conditions, with general applications on mixing devices, environmental and propulsion systems.

In the past century, experimental discoveries have witnessed phenomena in Nature which challenge our everyday classical intuition. In order to explain these facts, quantum theory was developed, which so far has been able to reproduce the observed results. However, I believe that our understanding of quantum mechanics can be significantly improved by the search for an operational meaning behind its mathematical formulation, which would help to identify the limitations and possibilities of the theory for information processing. An intriguing property of quantum theory is its intrinsic randomness. Indeed, Einstein, Podolsky and Rosen in 1935 questioned the completeness of quantum theory. They argued the possibility of the existence of a complete theory where variables to which we have not access determine the behaviour of physical systems, and the randomness observed in quantum mechanics is then due to our ignorance of these variables. These hidden variables theories, however, were proved not to be enough for explaining the predictions of quantum theory, as shown in the no-go theorems by Bell on quantum-nonlocality and by Kochen and Specker on quantum-contextuality. In the past decades, many experiments have corroborated the nonlocal and contextual character of Nature. However, no intuition behind these phenomena has been found, in particular about what limits their strength. In fact, special relativity alone would allow for phenomena which are more nonlocal than what quantum theory allows. Hence, much effort has been devoted to find the physical properties of quantum theory that restricts these phenomena. In this thesis, we study the constraints that arise on nonlocal and contextual phenomena when a certain exclusiveness structure compatible with quantum theory is imposed in the space of events. Here, an event denotes the situation where an outcome is obtained given that a measurement is performed on the physical system. Regarding nonlocality, we introduce a notion of orthogonality that states that events involving different outcomes of the same local measurement are exclusive, and construct constraints that the correlations among observers should satisfy. We denote this by Local Orthogonality principle (LO), which is the first intrinsically multipartite principle for bounding quantum correlations. We prove that LO identifies the supra-quantum character of some bipartite and multipartite correlations, and gets close to the quantum boundary. When studying contextuality, the same abstract event may correspond to outcomes of different measurements, which introduces a non-trivial structure in the space of events. For its study, we develop a general formalism for contextuality scenarios in the spirit of the recent approach by Cabello, Severini and Winter. In our framework, nonlocality arises as a particular case of contextuality, which allows us to study a generalization of LO. Both in nonlocality and contextuality, we find close connections to problems in combinatorics and hence use graph-theoretical tools for studying correlations. Finally, this thesis also studies the detection of nonlocal correlations. Most results on quantum nonlocality focus on few particles' experiments, while less is known about the detection of quantum nonlocality in many-body systems. Standard many-body observables involve correlations among few particles, while there is still no multipartite Bell inequality to test nonlocality merely from these data. In this thesis, we provide the first proposal for nonlocality detection in many-body systems using two-body correlations. We construct families of Bell inequalities from two-body correlators, which can detect nonlocality for systems with large number of constituents. In addition, we prove violations by systems which are relevant in nuclear and atomic physics, and show how to test these inequalities by measuring global spin components, hence opening the problem to experimental realizations.

Granular materials are multi-particle systems involved in many industrial process and everyday life. The mechanical behavior of granular media such as sand, coffee beans, planetary rings and powders are current challenging tasks. In the last years, these systems have been widely examined experimentally, analytically and numerically, and they continue producing relevant and unexpected results. Despite the fact that granular media are often composed of grains with anisotropic shapes like rice, lentils or pills, most experimental and theoretical studies have concerned spherical particles. The aim of this thesis has been to examine numerically the behavior of granular media composted by spherical and non-spherical particles. Our numerical implementations have permitted the description of the macroscopic properties of mechanically stable granular assemblies, which have been experimentally examined in a framework of the projects "Estabilidad y dinámica de medios granulares anisótropos" (FIS2008- 06034-C02-02) University of Girona and "Interacciones entre partículas y emergencia de propiedades macroscópicas en medios granulares" (FIS2008-06034-C02-01) University of Navarra / Els materials granulars són sistemes de moltes partícules implicats en diversos processos industrials i en la nostra vida quotidiana. El comportament mecànic de conjunts granulars, com la sorra, grans de cafè, anells o pols planetàries, representa actualment un repte per a la ciència. En els últims anys aquests sistemes s’han estudiat àmpliament de forma experimental, analítica i numèrica. De totes maneres, avui dia es continuen obtenint resultats rellevants, i en moltes ocasions, inesperats. Malgrat el fet que els materials granulars sovint estan compostos per grans amb forma anisotròpica, com l’arròs, les llenties o les píndoles, la majoria dels estudis experimentals i teòrics se centren en partícules esfèriques. L’objectiu d’aquesta tesi ha estat analitzar numèricament el comportament dels mitjans granulars compostos per partícules esfèriques i no esfèriques. Els mètodes numèrics implementats han permès la descripció de les propietats macroscòpiques de piles i columnes granulars, que s’han estudiat experimentalment en el marc dels projectes "Estabilidad y dinámica de medios granulares anisótropos" (FIS2008-06034-C02- 02) de la Universitat de Girona i "Interacciones entre partículas y emergencia de propiedades macroscópicas en medios granulares" (FIS2008-06034-C02- 01) de la Universitat de Navarra

Neste trabalho apresenta-se um estudo sobre os mecanismos de transporte atmosférico de gases traços e de partículas de aerossóis na bacia Amazônica. As influências da meteorologia regional e de larga escala na composição da atmosfera Amazônica e investigada. Estudos de casos durante as estações úmida e seca são abordados, evidenciando as características peculariares a cada período. Resultados do experimento LBA-CLAIRE \"Cooperative LBA Airborne Re-gional Experiment\", na regiao Amazônica durante a estação chuvosa de 1998, são apresenta-dos. A analise da composição elementar de aerossóis da região Amazônica identificou a ocor-rência de um episódio no qual as concentrações de aerossóis minerais, contendo majoritaria-mente Na, AI, Si, Ca, Ti, Mn, Fe, entre outros, foram, por fatores entre 6 e 20 vezes maiores que os valores de \"background\". Análises estatísticas e de retro-trajetórias de parcelas de ar possibilitaram a identificação e caracterização deste episódio como sendo um evento de transporte e deposição de aerossóis minerais do Saara na bacia Amazônica. Índice de aeros-sóis, derivados a partir de medidas de radiação ultra-violeta pelo sensor Nimbus-7/TOMS \"To-tal Owne Mapping Spectrometer\" , sobre o oceano Atlântico, fornecem um suporte adicional as interpretações dadas as observações locais. Este trabalho, evidencia-se também as proprie-dades dos aerossóis biogênicos e a importância do transporte de aerossóis do Saara nos ciclos biogeoquímicos. São também apresentados e discutidos resultados de medidas de gases reali-zados no Suriname, quando foram detectados sinais de transporte de emissões de queimadas da baixa para a alta troposfera via convecção profunda. Apresenta-se um estudo dos meca-nismos de transporte atmosférico de aerossóis e gases emitidos em queimadas, durante a estação seca. Resultados do experimento SCAR-B \"Smoke, Clouds, and Radiation-Brazil\", reali-zado durante os meses de agosto e setembro de 1995, sao discutidos. Uma analise de tra-jet6rias baseadas em uma simulação numérica do período de estudo foi realizada. Evidenciou-se que as características fisiográficas e da circulação de grande escala produzem dois corredo-res de exportação de poluentes emitidos por queimadas: em direção ao oceano Pacifico, entre as latitudes 10°N e 10°S ; e em direção ao oceano Atlântico, na altura da latitude 30°S. Sonda-gens de ozônio lançadas a partir de Cuiabá, entre os dias 16 de agosto e 10 de setembro, mos-traram um enriquecimento do \'O IND.3\' troposférico (entre 40 e 90 ppbv), em relação ao valores observados durante a estação úmida ( ~ 15 ppbv). O \'O IND.3\' troposférico e traçadores de aerossóis de queimadas, tais como medidas da espessura óptica de aerossóis na coluna atmosférica e medidas de \"black-carbon\" ao nível da superfície, apresentaram uma correlação mutua porém, sensível ao padrão de circulação. A analise de trajetórias e medidas do \"Cloud LIDAR System\" a bordo da aeronave ER-2 indicaram que o enriquecimento do ozônio troposférico observado deve-se, não apenas a emissões diretas de queimadas locais, mas também a contribuições de áreas urbano/industriais e a recirculação de fumaça envelhecida. / This a study on the mechanisms of atmospheric transport of trace gases and aerosols in the Amazon basin. The influences of the regional and large scale meteorology in the Amazon atmospheric composition is investigated. Cases studies during the wet and dry season are performed, evidencing the characteristics of each period. The first case study are results of the LBA-CLAIRE \"Cooperative LBA Regional Airborne Experiment\" , in the Amazon basin during the wet season of 1998. Analysis of the elementary composition of aerosols of the Amazon region, identified the occurrence of an episode in which the concentrations of mineral aerosols, major contents are Na, Al, Si,Ca, You, Mn, Fe, among others, they were, for factors among 6 to 20 larger than the background values. Statistical analyses and backward trajectories of air parcels possibilited the identification and characterization of this episode as being a transport and deposition of Saharan aerosols event in the Amazon basin. Aerosol index, derived from measurements of ultra-violet radiation of the Nimbus-7/TOMS \" Total Orone Mapping Spectrometer \" on the ocean Atlantic, supplied an additional support to the interpretations given to the local observations. In this work, it is also evidenced some properties of the biogenic aerosols and the importance of the Saharan aerosols transported to the Amazon basin in the biogeochemi-cal cycles. Results of airborne trace gases measurements at Suniname, where signs of biomass burning emission were detected on high levels, transported from the low to the high tropos-phere through deep convection, are also presented and discussed. A study on the mechanisms of atmospheric transport of aerosols and gases emitted by biomass burning, during the dry season, is the second part of this work. Results of the SCAR-B\" Smoke, Clouds, and Radiation-Brazil\" experiment, during the months of August and September of 1995, are discussed. Tra-jectory analyses based on a numerical simulation of the atmospheric period was performed. It was evidenced that the fisiographics and the large scale circulation characteristics, during the winter in Southern Hemisphere, produce two corridors of pollutants export: to the Pacific oce-an, between the latitudes 100S and lOoN; and to the Atlantic ocean, around 300S latitude. Ozonesondes launched from Cuiaba, between August 16 and September 10, have showed an enrichment of troposferic orone (values between 40 and 90 ppbv), compared to the values observed during the wet season (\"\'15 ppbv). Tropospheric orone and tracers of biomass bur-ning aerosols, such as aerosol optical thickness in the atmosphericcolumn and black-carbon at the surface level, presented a mutual correlation sensitive to the circulation pattern. Trajec-tory analyses and measures of the Cloud to Lidar System on board of the ER-2 airborne indica-ted that the tropospheric ozone enrichment observed is not just due local biomass burning direct emissions, but also contributions ofurbano/industriais areas and recirculão of aged smoke plume

We explore the possibility that CPT symmetry is broken in the neutrino sector at a high enough energy, using for this the high-energy neutrino flux that is expected to come from distant astrophysical sources such as active galaxies and gamma-ray bursts. CPT violation (CPTV) can affect neutrino oscillations either by modifying the oscillation length or its amplitude. We show that when only the oscillation length is affected, such as when CPTV is introduced through a modified dispersion relation, the effects on the astrophysical neutrino flavour fluxes are not visible. Hence, in order to modify also the oscillation amplitude, CPT is instead violated by adding a nondiagonal energy-independent contribution to the standard, mass-driven, neutrino oscillation Hamiltonian, within the context of the Standard Model Extension, and allowing it to become comparable in magnitude to the latter at a scale of 1 PeV. The CPTV term introduces three new mixing angles, two new eigenvalues and three new phases, all of which have currently unknown values. We have allowed these new parameters to vary, together with the ones associated to pure standard oscillations, and explored the consequences on the flavour fluxes. Detection prospects at the IceCube neutrino telescope, and in a fictional larger detector, have been studied, assuming different models for the neutrino flux. Our results suggest that, when the flavour fluxes at production are in the ratios φ0e : φ0μ : φ0τ = 1 : 2 : 0 or 0 : 1 : 0, the modifications to the flavour fluxes at Earth are larger and more clearly separable from the standard-oscillations predictions. When the ratios are 1 : 0 : 0, the separation is less clear. We conclude that, for certain values of the CPTV parameters, IceCube might be able to detect potentially large deviations from the standard flavour fluxes, even for flux models as low as the Waxman-Bahcall bound. Precision measurements of these parameters, however, are unlikely to be made unless a much larger ˘ Cerenkov detector or a one of a different kind are used. / En esta tesis exploramos la posible ruptura de la simetría CPT en el sector de neutrinos, a una energía suficientemente alta, usando para esto el flujo de neutrinos de alta energía que se espera que provenga de fuentes astrofísicas lejanas como galaxias activas y explosiones de rayos gamma. La violación de CPT (CPTV) puede afectar las oscilaciones de neutrinos en dos formas: modificando la longitud de oscilación o la amplitud de la misma. Demostramos que cuando sólo la longitud de oscilación es afectada, tal y como sucede cuando la CPTV es introducida a través de una relación de dispersión modificada, los efectos sobre los flujos de neutrinos de distintos sabores no son visibles. Por lo tanto, con la intención de modificar también la amplitud de oscilación, violamos CPT a través de la adición de una contribución, no diagonal e independiente de la energía, al Hamiltoniano de oscilaciones estándar, dentro del contexto de la Extensión del Modelo Estándar, y permitimos que esta contribución se vuelva comparable en magnitud al término estándar, a una escala de 1 PeV. El término de CPTV introduce tres nuevos ángulos de mezcla, dos nuevos autovalores y tres nuevas fases, todos los cuales tienen valores actualmente desconocidos. Hemos variado estos parámetros, junto con los parámetros asociados a las oscilaciones estándar, y explorado las consecuencias para los flujos de sabor. Hemos explorado también la posible detección en IceCube, y en un detector ficcional más grande, asumiendo diferentes modelos para el flujo de neutrinos. Nuestros resultados sugieren que, cuando las razones de sabor en la producción son Ө0e: Ө0μ : Ө0τ= 1 : 2 : 0 ´o 0 : 1 : 0, las modificaciones a los flujos en Tierra son más pronunciadas y más claramente separables de las predicciones de las oscilaciones estándar. Cuando las razones son 1 : 0 : 0, la separación es menos clara. Concluimos que, para ciertos valores de los parámetros de CPTV, IceCube podría ser capaz de detectar desviaciones potencialmente grandes respecto de los valores estándar, incluso para modelos de flujo tan bajos como el límite Waxman-Bahcall. Una medición precisa de los parámetros, sin embargo, será difícil a menos que se utilice un detector Čerenkov mucho más voluminoso, o uno de diferente tipo. / Tesis

Orientador: Vicente Pleitez / Doutor

Descreve-se um estudo feito, durante um ano e meio, no Instituto de Educação General Flores da Cunha - Escola Estadual de 12. e 22. graus (e formadora de professores para as séries iniciais) -de Porto Alegre, com o objetivo de analisar o papel da Física na formação de professores para as séries iniciais do 12. grau. Após situar a disciplina de Física no currículo do 22. grau Magistério, do ponto de vista da legislação, faz-se a caracterização da escola-caso e um breve histórico de como essa disciplina foi abordada ao longo dos anos nessa Escola. A experiência pessoal da pesquisadora durante um ano (22. sem. de 1989 e 12. sem. de 1990) com o ti-po de ensino de Física praticado pela Escola, aliada aos resultados de entrevistas realizadas com as professoras das séries iniciais em serviço na Escola ( 12. sem. de1990) subsidiaram uma mudança de enfoque para a Física no 22. grau Magistério: uma nova estratégia de ensino, de natureza construtivista, enfatizando apenas a aprendizagem significativa de conceitos relevantes para o ensino de Ciências nas séries iniciais, foi implementada no 22. semestre de 1990. Os efeitos do uso dessa estratégia, avaliados através de testes de conhecimento, escala de atitudes e entrevistas, foram amplamente satisfatórios e conduziram a uma proposta para o ensino da Física no 22. grau Magistério que lhe dá especificidade e, provavelmente, contribui também para a formação pedagógica dos futuros docentes. / A one-and-a-half-year study carried out at Instituto de Educação General Flores da Cunha is described. Instituto de Educação is a public schoollocated in Porto Alegre, which offers primary and secondary education and prepares elementary school teachers. The aim of the study was to analyse the role of physics in the curriculum of the elemantary school teacher preparation course in this school. Initially, the role of physics in the curriculum of this kind of course was examined from a legal point of view. Then, the study focused on the role of physics in the curriculum implemented in this particular school and on how physics has been taught over the years. The researcher's one-year personal experience (second semester of 1989 and first semester of 1990) with this kind of teaching and the results of interviews carried out (first semester of 1990) with in-service elementary school teachers provided ba.ckground for a change in the teaching of physics at the prepatation course: a new instructional strategy was implemented in the second semester of 1990 . This strategy is constructivist and emphasizes the meaningfullearning of physical concepts specifically relevant for science teaching at elementary school levei. The effects of this strategy, evaluated through quizzes, attitude scales and interviews, were fully satisfactory and lead to a proposal for the teaching of physics in the preparation of elementary school teachers. This pr()posal assigns specificity to the teaching of physics in such a way that it is likely to contribute to the pedagogical training of the prospective teachers as well.

Orientador: Diogenes Galetti / Mestre

Dissertação apresentada para obtenção do grau de Mestre em Física, no Instituto Superior Técnico da Universidade Técnica de Lisboa, sob a orientação do Prof. Doutor Jorge Manuel Amaro Henriques Loureiro

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