Allt fler människor använder sig av Youtube och andra öppna internetmiljöer för att lära sig matematik. Enligt tidigare studier finns det en stor spridning när det gäller bostadsort och ålder bland deltagarna i dessa miljöer. Min undersökning visar att ett urval om 10 Youtubevideor om ekvationslösning och deras kommentarsfält också kännetecknas av en stor spridning av matematikdiskurser bland deltagarna. En studie av 85 dialoger i kommentarsfälten visar att i omkring hälften av dialogerna uttrycker sig olika deltagare på sätt som kännetecknar olika matematikdiskurser, medan i den andra hälften alla deltagare uttrycker sig på sätt som kännetecknar samma matematikdiskurs. De förra dialogerna slutar mer sällan med att deltagarna upplever förståelse, medan lärandet i de senare dialogerna begränsas av vad som går att uttrycka inom ramen för den rådande diskursen. Genom att utveckla begrepp och kategorier för att beskriva matematikdiskurserna lägger studien grunden för fortsatt forskning, både kvalitativa med intervjuer av deltagare och kvantitativa med större material. / The use of Youtube and other open internet environments for learning mathematics is becoming increasingly common. According to earlier studies there is a great diversity of ages and nationalities among participants in these environments. My investigation shows that a selection of 10 Youtube videos about equation solving and their comments sections also are characterized by a diversity of mathematics discourses. A study of 85 dialogues in the comments sections shows that in approximately half of the dialogues different participants express themselves in manners characteristic of different mathematics discourses, while in the other half all the participants express themselves in manners characteristic of the same mathematics discourse. The former dialogues more seldom end with experiences of understanding, while learning in the latter group of dialogues is limited by what is possible to express within the dominant discourse. By developing terms and categories for describing the mathematics discourses this study lays the foundation for further research, both qualitative research comprising interviews with participants and quantitative research on greater amounts of data.

Made available in DSpace on 2014-10-09T12:35:04Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:00:44Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:43:06Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:05:36Z (GMT). No. of bitstreams: 1 06125.pdf: 6631284 bytes, checksum: 0d7cb7ea79949cb8c3121b13b630793a (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2015-05-15T11:46:16Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 578974 bytes, checksum: e512f47deae8cd03667ae8e7c2143b34 (MD5) Previous issue date: 2013-05-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The notions of connection and covariant derivative has its origin in the field of Riemannian geometry , where there is no distinction between them. In fact, in this study we found that these notions are equivalent if we consider modules over K-algebras of finite type. We also show that the existence of connections implies the existence of covariant derivative. The main goal of this study is to determine which modules admit connections. We easily verified that the projective modules admit connections. In fact, they form an affine space. But we also display a module that is not projective and has connection. Later, inspired by Swan's theorem, we explore in a straightforward way modules formed by sections of the tangent bundle of some surfaces in 3-dimensional real space. Finally, we study the notion of connection introduced by Alain Connes in modules over K-algebras not necessarily commutative. And we find in that context that the modules that have connection are exactly the projectives modules. / As noções de conexão e derivada covariante tem sua origem na área de geometria riemanniana, onde não existe distinção entre elas. De fato, nós verificamos neste trabalho, que estas noções são equivalentes se considerarmos módulos sobre K-álgebras comutativas de tipo finito. Também mostramos que a existência de conexões implica na existência de derivada covariante. O objetivo central deste trabalho é determinar que módulos admitem conexão. Verificamos facilmente que os módulos projetivos admitem conexões. De fato, elas formam um espaço afim. Mas também exibimos um módulo não projetivo que possui conexão. Posteriormente, inspirados pelo teorema de Swan, exploramos de maneira direta os módulos formados pelas seções do fibrado tangente de algumas superfícies no espaço 3- dimensional real. Por fim, estudamos a noção de conexão introduzida por Alain Connes em módulos sobre K-álgebras não necessariamente comutativas. E verificamos nesse contexto que os módulo que admitem conexão são exatamente os módulos projetivos.

Foram realizadas medidas do alinhamento atômico do Ta, W e Au depois da ionização da subcamada L3 desses elementos por impacto de elétrons, via distribuição angular das linhas de raios x L, empregando alvos finos. As medições foram realizadas na linha de feixe de 10100 keV do Microtron de São Paulo. Os alvos foram confeccionados no Laboratório de Filmes Finos, pela técnica de deposição física de vapor (alvo de Au), e no Laboratório de Materiais Magnéticos, pela técnica de sputtering (alvos de Ta e W), enquanto que a caracterização deles foi realizada no Laboratório de Materiais e Feixes Iônicos, pela técnica de espectrometria de retroespalhamento Rutherford. O Microtron de São Paulo, bem como os laboratórios onde os alvos foram confeccionados e caracterizados, estão no Instituto de Física da Universidade de São Paulo. Os raios x decorrentes da ionização dos alvos foram detetados simultaneamente por três Silicon Drift Detectors localizados a 31°, 90° e 125° com relação à direção do feixe incidente. A determinação da eficiência de pico dos detetores foi realizada com um modelo analítico testado separadamente. As intensidades das linhas do multipleto de raios x L foram ajustadas em um único procedimento empregando funções Voigt para descrevê-las. O parâmetro de alinhamento A20 foi estimado a partir do conjunto de intensidades das linhas Ll, L1 e L2. A fim de comparar os resultados experimentais com as previsões teóricas foi calculado o parâmetro de alinhamento com a aproximação de Born de ondas planas não relativística, empregando as aproximações de HartreeSlater e DiracHartreeSlater para descrever os potenciais atômicos. Os resultados experimentais confirmaram a emissão não isotrópica dos raios x decorrentes de vacâncias preenchidas na subcamada L3, sendo que a magnitude desta anisotropia varia com a energia do feixe de elétrons incidente. Além disso, foram observadas anisotropias de sinais opostos para as linhas L1 e L2. A dependência em energia do parâmetro de alinhamento A20 mostra uma queda rápida de A20, com duas inversões de sinal, uma em torno de 2 E/E(L3) e outra em torno de 8 E/E(L3), e um valor não nulo de alinhamento em torno de 10 E/E(L3), para os três elementos estudados. A comparação dos resultados experimentais com os cálculos realizados mostra um bom acordo ate cerca de 5 E/E(L3) para o feixe de elétrons incidente, a partir deste ponto o experimento evidencia uma segunda inversão no sinal de A20, que não é prevista por essa teoria. Este é, a nosso saber, o primeiro trabalho a quantificar o alinhamento atômico na ionização de átomos pesados por impacto de elétrons, via distribuição angular de raios x na faixa de 1 a 10 E/E(L3). / Measurements of the atomic alignment of Ta, W and Au after the ionization of the L3 subshell of these elements were performed by electron impact via the angular distribution of x-ray lines employing thin targets. The targets were made in the Laboratório de Filmes Finos, by the technique of physical vapor deposition (Au target), and in the Laboratório de Materiais Magnéticos, by the sputtering technique (Ta and W targets), while their characterization was performed in the Laboratório de Materiais e Feixes Iônicos, by Rutherford Backscattering Spectrometry. The Microtron of São Paulo, as well as the laboratories where the targets were made and characterized, are placed at Instituto de Física of the Universidade de São Paulo. The x-rays from the ionization of the targets were detected simultaneously by three Silicon Drift Detectors placed at 31°, 90° and 125° with respect to the direction of the incident beam. The determination of the full energy peak efficiency of the detectors was performed with an analytical model previously tested. In the data analysis the L x-ray multiplet lines were fitted in a single procedure employing Voigt functions to describe them, and the Ll, L1 and L2 lines were employed simultaneously in the estimation of the alignment parameter A20. In order to compare the experimental results with the theoretical predictions, the alignment parameter was calculated with the non-relativistic plane-wave Born approximation using HartreeSlater and DiracHartreeSlater atomic potentials. The experimental results confirmed the nonisotropic emission of x-rays from filled vacancies in the L3 subshell, with the magnitude of this anisotropy varying with the energy of the incident electron beam. In addition, anisotropies of opposite signs were observed for the L1 and L2 lines. The energy dependence of the alignment parameter A20 shows a sharp fall of A20, with two sign inversions, one around 2 E/E(L3) and another around 8 E/E(L3), and a non-zero alignment value around 10 E/E(L3), for the three studied elements. Comparison of the experimental results with the performed calculations shows a good agreement up to about 5 E/E(L3) for the incident electron beam, from which the experiment evidences a second inversion in the sign of A20, which is not predicted by this theory. This is, to our knowledge, the first work to quantify the atomic alignment in the ionization of heavy atoms by electron impact, via an angular distribution of x-rays in the interval from 1 to 10 E/E(L3).

Alvos naturais de Mg, Al, Si, Cr, Ti, Ni e Zr foram irradiados com prótons e as seções de choque para várias reações nucleares foram determinadas a energias inferiores a 30 MeV. As irradiações foram efetuadas nos ciclotrons CV-28 e CYCLONE 30 do IPEN, que possuem energia nominal de 24 e 30 MeV, respectivamente. O feixe de prótons foi monitorado por meio de lâminas de Cu ou a partir da formação de nuclídeos na própria amostra com seção de choque conhecida para as energias utilizadas. Especial interesse foi dedicado às reações raras di tipo (p, 2alfa) e (p, ANTPOT.3 H) das quais existem, em geral, poucos dados publicados, principalmente para energias próximas do limiar. A determinação da seção de choque foi realizada a partir da medida da atividade residual dos produtos pelo método de espectroscopia gama simples. Um detector HPG com resolução menor que 2 keV foi utilizado. Devido ao valor reduzido da seção de choque das reações de interesse no intervalo de energia considerado, uma análise estatística cuidadosa dos dado foi necessária. Em áreas reduzidas dos picos detectados precisaram da quantificação, em alguns casos, da contribuição de nuclídeos formados na própria amostra por outras reações, a partir de impurezas ou provenientes do fundo radioativo. Entre os produtos obtidos encontram-se os nuclídeos ANTPOT.22 Na, ANTPOT.26 Al, ANTPOT.44 Ti, e ANTPOT.54 Mn. A detecção de ANTPOT.26 Al nas amostras de Al e Si, permitiu estimar os limites do método proposto para o estudo de reações raras de interesse astrofísico. No total, são apresentados neste trabalho 72 valores de seção de choque. Desse total, 21 dados são apresentados pela primeira vez ou foram obtidos pela primeira vez pelo método proposto ou às energias estudadas. Os resultados mais importantes referem-se às reações ANTPOT.29 Si(p, 2alfa)ANTPOT.22 Na,ANTPOT.53 Cr(p, 2alfa)ANTPOT.46 Sc, ANTPOT.46 Ti(p, ANTPOT.3 H)ANTPOT.44 Ti, )ANTPOT.58 Ni(p, ANTPOT.3 H)ANTPOT.56 Ni e ANTPOT.90 Zr(p, ANTPOT.3 H)ANTPOT.88 Zr. Os resultados foram comparados com valores publicados na literatura e com o resultado do cálculo realizado a partir de modelos teóricos conhecidos, permitindo a obtenção de conclusões relativas ao método experimental, assim como aos mecanismos da reação envolvidos. / Natural targets of Mg, Al, Si, Cr, Ti, Ni and Zr were irradiated with protons and the cross section for several reactions were determined for incident energies up to 30 MeV. The irradiations were performed at the CV-28 and CYCLONE 30 cyclotrons from the IPEN, which have nominal energies of 24 and 30 MeV, respectively. The protons beams were monitored by copper foils or by the nuclide formation in the irradiated targets with known cross sections for the used energy. Special interest was dedicated to rare reactions of the (p, 2alfa) and (p, ANTPOT.3 H) kind, from which we have a few published data, mainly for energies near the threshold. The cross section determination was accomplished by the residual actives measurement of the reaction products by the simple gamma spectroscopy method using an HPGe detector with resolution better than 2 keV. Due to the low value of the cross section for the considered reaction, a careful statistical analysis of the obtained data was needed. The small areas of the detected peaks required the quantification of the contributions of nuclides produced by others reactions, from contaminants or from the radioactive background. Among others, the ANTPOT.22 Na, ANTPOT.26 Al, ANTPOT.44 Ti and ANTPOT.54 Mn products have been detected. The detection of ANTPOT.26 Al in the Al and Si targets allow the estimation of the limits of the proposed method for the study of astrophysical interest reaction. In total, 72 cross section values are being presented. Out of this amount, 21 are being presented for the first time or have been obtained for the first time by the method or for the studied energies. The most important results refer to the ANTPOT.29 Si(p, 2gamma)²²Na, ANTPOT.53 Cr(p, 2gamma)ANTPOT.46 Sc, ANTPOT.46 Ti(p, ANTPOT.3 H)ANTPOT.44 Ti, ANTPOT.58 Ni(p, ANTPOT.3 H)ANTPOT.56 Ni and ANTPOT.90 Zr(p, ANTPOT.3 H)ANTPOT.88 Zr reactions. The results have been compared to published vales and calculations using known theoretical models, allowing the achievement of conclusions related to the experimental method, as well as the reaction mechanism involved.

Made available in DSpace on 2014-10-09T12:35:04Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:00:44Z (GMT). No. of bitstreams: 0 / Este trabalho apresenta a realização de experimentos no reator nuclear IPEN/MB-01 submetido à presença de um refletor com água pesada instalado na sua face oeste. Após a instalação do refletor no reator foram conduzidos três tipos de experimentos: A calibração das barras de controle, a verificação da influência do aumento da temperatura do moderador na reatividade e a medição das taxas de reações por meio da irradiação de fios e folhas de ativação. Devido às propriedades nucleares de interação de nêutrons com água pesada, notadamente sua elevada capacidade de espalhamento e sua baixa capacidade de absorção, é possível notar alterações no funcionamento do reator observadas pelas mudanças dos padrões de retiradas e inserções de barras de controle no núcleo. Essas alterações são apresentadas no decorrer do trabalho. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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The 14Be nucleus is a good candidate for having a halo structure. When a three- body model is used to calculate the properties of this nucleus, it relies on a knowledge of the potentials involved and hence on the structure of the underlying two-body subsystem 13Be. Previuosly published calculations showed that, in order to describe 13Be and 14Be simultaneously, 13Be had to be either bound, or have a p-shell ground state, which is not consistent with the experimental data. In this thesis 13Be and 14Be are described as one or two neutrons outside a deformed 12Be core. The idea of the method is that deformation of the core couples the neutron motion with core excitations. The core is treated as a rigid rotor here, and for the neutron-core interaction we used a deformed Woods-Saxon potential. We explore the potential parameters compatible with the known properties of 12Be, 13Be and 14Be. The three-body model for 14Be used a hyperspherical expansion including core degrees of freedom. Compared to the previous works, we find that both 14Be and 13Be are described simultaneously if the 12Be core has large positive quadrupole deformation. The resulting three-body model wave function was used in calculations of reaction observables. The reaction cross section of 14Be on a carbon target at 850 MeV/A was calculated in a four-body Glauber model, after the formalism was extended to include core degrees of freedom. The calculated reaction cross section agrees with the experiment. One-neutron knockout reactions of the Borromean nuclei 6He, 11Li and 14Be are discussed. The integrated cross sections for stripping and diffraction processes are calculated in the four-body Glauber model including core excited components in the wave function for 14Be. The neutron-core relative energy distributions within 5He, 10Li and 13Be following one-neutron removal, are calculated by a spectator model in the eikonal limit. The integrated cross sections and energy distributions for 6He are in agreement with the experiment. The results for 11Li and 14Be breakup demonstrated that the further investigation of the reaction model is needed.

ToF-SIMS imaging has been drawing attention due to the wide range of applications in the biological and biomedical fields. These applications include the acquisition of quantitative and qualitative data that ranges in scale from single cells to organs, image visualisation and interpretation of biomarkers for diagnosis and development of pharmaceutics. This study focused on molecular imaging of mouse brain tissue sections using cluster primary ion beams. First, cluster ion beams were applied to comparative background studies of biomolecules and brain total lipid extract. Enhancement of the secondary ion signal was observed using water-containing cluster primary ion beams, especially for [M+H]+ type secondary ions. Water-containing clusters were then used to acquire ToF-SIMS images from the cerebellar area of serial mouse brain tissue sections. Again, water-containing cluster beams produced the highest secondary ion yields in both grey and white matter, gaining a new level of insight into the lipid compositions of both types of tissue in the brain. A clinical case was also evaluated with ToF-SIMS imaging, using cluster beams for the analysis of 3xTg-AD mouse brain tissue. SIMS images were registered with fluorescence microscopy images for the in situ identification and co-localisation of the Amyloid-β plaques on the SIMS images. Spectra from regions of interest were analysed to identify possible ion fragments derived from the Aβ protein. The co-localisation of cholesterol was also studied from images obtained with different primary ion beams. The results presented show that cluster ToF-SIMS can be successfully applied to brain tissue imaging. New primary ion beam technologies allow us to acquire data with more useful secondary ion yield for clinical applications and biological research. Nevertheless, future technological improvements are required for specialised applications e.g. cellular imaging. Moreover, processing the data obtained is still challenging and more data processing tools are also needed for interpretation.