Orientadores: Roberto Antonio Clemente, Munemasa Machida / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-19T20:53:40Z (GMT). No. of bitstreams: 1 Duarte_ViniciusNjaim_M.pdf: 5509797 bytes, checksum: 163bd7750aa0326f7bf0d0b521dc88f0 (MD5) Previous issue date: 2012 / Resumo: Entre os diferentes métodos alternativos à indução, para sustentação e/ou geração de corrente em plasmas confinados magneticamente, com o objetivo de se obter o funcionamento contínuo de um possível reator de fusão, foi estudado aquele associado a campos magnéticos viajantes produzidos por bobinas helicoidais alimentadas por correntes de radiofrequência defasadas (double helix current drive). O método permite compensar as perdas de caráter resistivo em configurações toroidais de plasma, como os pinches de campo reverso (reversed field pinches - RFP). O problema pode ser reduzido ao estudo dos estados estacionários de uma coluna de plasma sujeita a campos de radiofrequência produzidos por bobinas helicoidais externas. Desprezando efeitos de gradientes de densidade e temperatura, o modelo é regido por um sistema de equações diferenciais ordinárias de segunda ordem não lineares acopladas, reguladas por quatro parâmetros adimensionais de interesse físico, que foram resolvidas numericamente usando o programa Mathematica. Estudou-se a eficiência do método em relação às aplicações em RFP, para os quais o campo magnético longitudinal apresenta uma inversão no interior da coluna de plasma. Isso implicou considerar regiões ainda não bem exploradas para os parâmetros de interesse. Os resultados numéricos são apresentados para configurações de campos magnéticos com simetria dipolar e quadrupolar / Abstract: Among the different methods, alternative to induction, to drive current in magnetically confined plasmas, with aim to obtain a continuous operation of a possible fusion reactor, we have studied the one associated to traveling magnetic field produced by helicoidal coils carrying out of phase radiofrequency currents (double helix current drive). The method allows compensating resistive losses in toroidal plasma configurations, like reversed field pinches. The problem may be reduced to the study of stationary states for a plasma column subjected to radiofrequency fields produced by external helicoidal coils. Neglecting density and temperature gradients, the model is governed by a system of coupled nonlinear second order ordinary differential equations, which depend on four dimensionless parameters of physical interest and can be solved numerically using the software Mathematica. We studied the efficiency of the method with respect to applications in reversed field pinches, for which the longitudinal steady magnetic field shows an inversion inside the plasma column. This implied considering not yet well explored regions of the parameters of interest. Numerical results are presented for magnetic field configurations of dipolar and quadrupolar simmetries / Mestrado / Física / Mestre em Física

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22269号 / 理博第4583号 / 新制||理||1658(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 大須賀 篤弘, 教授 時任 宣博, 教授 依光 英樹 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Single-molecule localisation microscopy (SMLM), has allowed for optical microscopy to probe biological systems beyond the diffraction limit. The intrinsic 3D nature of biology has motivated the development of 3D-SMLM with novel techniques, including the double-helix point spread function (DHPSF). A bespoke microscope platform employing the DHPSF transformation was built, achieving ~10 nm lateral and ~20 nm axial localisation precision over a ~4 μm axial depth. Until recently, the DHPSF has been limited by spherical aberration present when imaging away from coverslip surfaces to the study of small volumes close to the coverslip. By matching the refractive index of the objective lens immersion liquid to that of the imaging media, this aberration can be minimised, facilitating large-volume imaging away from unphysiological flat surfaces. The work presented in this thesis illustrates the capabilities of the DHPSF for 3D-SMLM and single-particle tracking (SPT) in previously inaccessible areas of biological samples (e.g. in the nucleus and on the apical cell surface). Application of the DHPSF for SPT in eukaryotic cells are presented; tracking the motion of T-cell membrane proteins on the apical surface and components of the chromosome remodelling complex in the nucleus of embryonic stem cells. For these applications, meansquared displacement and jump distance diffusion analysis methodologies were extended into 3D and benchmarked against simulated datasets. A variety imaging applications that are facilitated by the extended depth of focus of the DHPSF are presented, focusing on quantification of T-cell membrane protein reorganisation upon immunological activation. Finally, the clustering distribution of the T-cell receptor is investigated by Ripley’s K analysis enabled by duel labelling of its position and the outer membrane in primary T cells.

3-dimensional imaging often requires substantial effort since information along the optical axis is not straight forward gatherable. In many applications it is aimed for depth information along the direction of view. For example fluidic mixing processes and the environmental interaction on a microscopic scale are of particular importance for e.g. pharmaceutical applications and often demand for 3D information. This problem is often solved by stereoscopic approaches, where two cameras are used in order to gather depth information by triangulation technique. Another approach is to scan the object through the focal plane in order to get sharp images of each layer. Since the before mentioned approaches require a lot of video data to be evaluated it would be more convenient to get depth mapping within a single camera recording and without scanning. Here we present a tunable 3D depth-mapping camera technique in combination with dynamic aberration control. By using an incoherent light source, only one camera and a spatial light modulator (LCoS-SLM), it is a simply applicable and highly scalable technique. A double-helix point spread function (DH-PSF) is generated for light emerging from the bserved focal plane. Each object appears as a double-image on the camera. Within the orientation of the double-image, depth information along the optical axis is encoded. By using an additional adaptive element (deformable mirror) the technique is combined with wide-field aberration correction. Here we combine a tunable 3D depth camera with dynamic aberration control in one imaging system.

Cette thèse porte sur l'utilisation du BLASSO, un problème d'optimisation convexe en dimension infinie généralisant le LASSO aux mesures, pour la super-résolution de sources ponctuelles. Nous montrons d'abord que la stabilité du support des solutions, pour N sources se regroupant, est contrôlée par un objet appelé pré-certificat aux 2N-1 dérivées nulles. Quand ce pré-certificat est non dégénéré, dans un régime de petit bruit dont la taille est contrôlée par la distance minimale séparant les sources, le BLASSO reconstruit exactement le support de la mesure initiale. Nous proposons ensuite l'algorithme Sliding Frank-Wolfe, une variante de l'algorithme de Frank-Wolfe avec déplacement continu des amplitudes et des positions, qui résout le BLASSO. Sous de faibles hypothèses, cet algorithme converge en un nombre fini d'itérations. Nous utilisons cet algorithme pour un problème 3D de microscopie par fluorescence en comparant trois modèles construits à partir des techniques PALM/STORM. / This thesis studies the noisy sparse spikes super-resolution problem for positive measures using the BLASSO, an infinite dimensional convex optimization problem generalizing the LASSO to measures. First, we show that the support stability of the BLASSO for N clustered spikes is governed by an object called the (2N-1)-vanishing derivatives pre-certificate. When it is non-degenerate, solving the BLASSO leads to exact support recovery of the initial measure, in a low noise regime whose size is controlled by the minimal separation distance of the spikes. In a second part, we propose the Sliding Frank-Wolfe algorithm, based on the Frank-Wolfe algorithm with an added step moving continuously the amplitudes and positions of the spikes, that solves the BLASSO. We show that, under mild assumptions, it converges in a finite number of iterations. We apply this algorithm to the 3D fluorescent microscopy problem by comparing three models based on the PALM/STORM technics.