This work provides a fundamental view of the mechanisms which affect the power efficiency of communications processes along with a method for efficiency enhancement. Shannon's work is the definitive source for analyzing information capacity of a communications system but his formulation does not predict an efficiency relationship suitable for calculating the power consumption of a system, particularly for practical signals which may only approach the capacity limit. This work leverages Shannon's while providing additional insight through physical models which enable the calculation and improvement of efficiency for the encoding of signals. The proliferation of Mobile Communications platforms is challenging capacity of networks largely because of the ever increasing data rate at each node. This places significant power management demands on personal computing devices as well as cellular and WLAN terminals. The increased data throughput translates to shorter meantime between battery charging cycles and increased thermal footprint. Solutions are developed herein to counter this trend. Hardware was constructed to measure the efficiency of a prototypical Gaussian signal prior to efficiency enhancement. After an optimization was performed, the efficiency of the encoding apparatus increased from 3.125% to greater than 86% for a manageable investment of resources. Likewise several telecommunications standards based waveforms were also tested on the same hardware. The results reveal that the developed physical theories extrapolate in a very accurate manner to an electronics application, predicting the efficiency of single ended and differential encoding circuits before and after optimization.

No description available.

The main goal of our thesis is to understand qualitative properties of solutions to the Cauchy problem for the semi-linear wave model with time-dependent speed and dissipation. We greatly benefited from very precise estimates for the corresponding linear problem in order to obtain the global existence (in time) of small data solutions. This reason motivated us to introduce very carefully a complete description for classification of our models: scattering, non-effective, effective, over-damping. We have considered those separately.

Les membranes fluorées sont utilisées en particulier dans les dénommées piles à combustible à membrane électrolyte polymère. Grâce à sa grande mobilité en protons, le célèbre ionomer Nafion® (Dupont) est un matériau de référence pour les applications liées aux piles à combustible. En présence d’eau ou d’autres solvants hydrophiles la membrane se sépare en une matrice polymérique hydrophobe et une sous-phase aqueuse contenant des clusters d’eau et ions, dont les tailles et la connectivité augmente quand la quantité d’eau augmente [1]. Quelle est la morphologie du Nafion et la structure du solvant, dans de tels systèmes?Il a été récemment montré [2] sur des simulations de large systèmes que plusieurs modèles morphologiques reproduisent les données expérimentales de diffusion, évoquant l’incapacité des mesures de diffusion seules à élucider la véritable structure du Nafion.Néanmoins, un modèle ’aléatoire’ décrit dans [2], c’est à dire l’unique modèle étudié sans présumer d’une structure initiale particulière, n’a pas pu reproduire les données expérimentales.Générer en simulations moléculaires des configurations du système qui soient vraiment décorrélées de la configuration initiale reste un vrai défi statistique. Les échelles de temps réalisables ne permettent simplement pas d’obtenir des mouvements significatifs du polymère (comme des transitions de conformations, repliements de chaînes, etc.). Nous proposons ainsi dans cette étude un nouveau modèle de Nafion à morphologie aléatoire. Un algorithme récemment développé est utilisée pour générer des chaînes de Nafion avec des chemins et des points de départ aléatoires. Une différence majeure avec le modèle aléatoire dans [2] est que nous ne construisons pas nos systèmes à une densité proche de la densité finale. Pour ne pas démarrer avec des chaînes trop enchevêtrées, les systèmes sont initialement préparés à une densité en dessous de la référence expérimentale. La densité après équilibration est de nouveau proche de l’expérience. Bien qu’il soit facilement envisageable d’améliorer les nouveaux algorithmes, nous démontrons ici qu’avec la présente version plusieurs séries de configurations compatibles avec les données expérimentales de diffusion disponibles peuvent être générées et équilibrées. Douze large systèmes de Nafion à morphologie aléatoire sont construits avec des positions initiales des atomes ainsi que des quantités d’eau et des longueurs de chaînes (Nafion/Hyflon) différentes. Ils sont équilibrés puis simulés sur plusieurs dizaines de nanosecondes. Après équilibration, les structures sont, comme indiqué ci-dessus,compatibles avec les données expérimentales de diffusion. En plus nous étudions un modèle ressemblant à celui de Schmidt-Rohr and Chen [3], c’est à-dire le plus récent modèle morphologique. Avec ce modèle, les données expérimentales sont également reproduites de manière satisfaisante, d’où la prolongation du débat sur la structure du Nafion. La cohésion entre les valeurs calculées et celles mesurées expérimentalement incite à des analyses plus en détails de ces configurations obtenues. Nous caractérisons et analysons les structures locales, intermédiaires et à grande échelle avec divers paramètres structuraux et distributions des tailles de domaines. Nous calculons donc, par exemple, des fonctions de distribution radiale (rdf), des facteurs de structure (S(q)) totaux et partiels tout comme des nombres et des tailles de clusters hydrophiles (selon la définition d’un cluster). La dynamique de diverses espèces dans le système est également examinée,par exemple au travers des déplacements carrés moyens (msd) et des coefficients de diffusion. Ces simulations sont probablement à la limite de ce qui est réalisable aujourd’hui avec des simulations ’full-atom’ du type MD. Nous espérons que ce travail fera avancer le débat sur la structure et la dynamique de ces matériaux importants. / Perfluorinated membranes are used in particular in polymer electrolyte fuel cells(PEFC). The well-known ionomer Nafion® (Dupont) is, due to its high proton mobility,a reference material for fuel cell applications. In water or other hydrophilic solvents themembrane segregates into a hydrophobic backbone matrix and a hydrophilic sub-phasecontaining clusters of both water and ions, where the cluster sizes and connectivity increasewith increasing water content [1].What is the Nafion morphology and the structure of the solvent in such systems? It hasbeen shown recently [2] on large simulated systems that several morphological modelsfit the experimental scattering data, suggesting the inability of scattering experimentsalone to elucidate the true structure of Nafion. However, a ’random’ model describedin [2], i.e. the only explored model that did not assume a particular initial structure,could not reproduce the experimental data.It remains a real computational challenge to generate in molecular simulations systemconfigurations which are really decorrelated from the initial one. The time scales thatcan be achieved simply do not allow to obtain significant motions of the polymer (e.g.conformational changes, folding, etc.). We thus propose in this work a new randommodel of Nafion. A newly developped algorithm is used to generate Nafion chains withrandom growth paths and random starting points. A significant difference with therandom model in [2] is that we do not build our systems at a density close to the finalone. In order not to start with too much entangled chains, the systems are initiallybuilt at a density below the experimental one. The density after equilibration is againclose to the experimental one.Even though further improvements of the new algorithms can easily be envisaged,we demonstrate here that with the present version several sets of configurations thatare compatible with the available scattering data can be generated and equilibrated.Twelve large random Nafion systems are built with different initial positions of theatoms as well as different water contents and side chain lengths (Nafion/Hyflon). Theyare equilibrated and then simulated for several ten nanoseconds. After equilibration,the structures are, as mentioned, compatible with the experimental scattering data. Inaddition we study a model similar to the one by Schmidt-Rohr and Chen [3], i.e. thenewest morphological model of Nafion. The experimental scattering data are also satisfactorilyreproduced with this model, hence, the prolonged debate over the structureof Nafion.This agreement gives confidence that a more detailed analysis of the so-obtained configurationsis scientifically warranted. We characterize and analyze the local, intermediateand large-scale structures by various structural parameters and domain size distributions.We therefore compute, for example, radial distribution functions (rdf), total andpartial structure factors (S(q)) as well as numbers and sizes of hydrophilic clusters (dependingon the definition of a cluster). The dynamics of various species in the systemis also investigated, e.g. via the computation of the mean square displacements (msd)and the self-diffusion coefficients. These simulations are probably at the limit of whatcan today be achieved with all-atom molecular simulations of the MD type. We hopethat this work will advance the ongoing debate on the structure and dynamics of theseimportant materials. / Perfluorierte Membranen werden insbesondere in Polymerelectrolyt-Brennstoffzellen(PEFC) eingesetzt. Das wohlbekannte Ionomer Nafion® (Dupont) ist wegen seinerhohen Protonenbeweglichkeit ein Referenzmaterial für solche Anwendungen in Brennstoffzellen.Die Membran separiert in Wasser oder anderen hydrophilen Lösungsmittelin eine hydrophobe Polymermatrix und eine hydrophile Subphase, die Cluster mitWasser und Ionen enthält. Dabei vergroeßern sich die Ausdehnung der Cluster und ihreKonnektivität mit zunehmendem Wassergehalt [1].Welche ist die Morphologie des Nafions und die Struktur des Lösungsmittels in diesenSystemen? Es ist jüngst anhand großer simulierter Systeme gezeigt worden [2], dassmehrere morphologische Modelle die experimentellen Streudaten wiedergeben können,was nahelegt, dass solche Streudaten alleine nicht geeignet sind, die wahre Strukturdes Nafion aufzudecken. Ein in [2] beschriebenes ’Zufallsmodell’, d.h. das einzigeder untersuchten Modelle, das keine besondere Anfangsstruktur annahm, konnte dieexperimentellen Daten allerdings nicht wiedergeben.In molekularen Computersimulationen Konfigurationen zu erzeugen, die wirklich nichtmehr mit der angenommenen Anfangskonfiguration korreliert sind, bleibt eine echteHerausforderung. Die erreichbaren Zeitskalen sind zu kurz, um eine signifikante Bewegungdes Polymers (z.B Konformationsänderungen, Faltungen, usw.) zuzulassen. Indieser Arbeit wird daher ein neues Zufallsmodell für Nafion vorgestellt. Ein neuentwickelterAlgorithmus erzeugt Nafionketten mit zufälligem Wachstumspfad ausgehendvon zufälligen Anfangspunkten. Ein signifikanter Unterschied zu dem Zufallsmodellvon [2] ist, dass hier nicht versucht wird, die Systeme bei einer Dichte vergleichbarder experimentellen Dichte aufzubauen. Anstattdessen werden die Systeme, um alzustarkes Verknäuelung zu vermeiden, anfangs bei einer deutlich kleineren Dichte erzeugt.Nach äquilibrierung ist die Systemdichte wieder in etwa gleich der experimentellen.Wiewohl weitere Verbesserungen des neu Algorithmuses leicht ins Auge gefaßt werdenkönnen, so kann hier doch gezeigt werden, dass mit der gegenwärtigen VersionKonfigurationen erzeugt und äquilibriert werden können, die mit den verfügbarenStreudaten kompatibel sind. Zwölf große Nafion Zufallssysteme, mit verschiedenenAnfangspositionen der Atome, verschiedenem Wassergehalt und Längen der Seitenketten(Nafion/Hyflon) werden aufgebaut. Diese werden äquilibriert und mehrerezehn Nanosekunden lang simuliert. Nach der äquilibrierung sind die Strukturen, wieerwähnt, kompatibel mit den experimentellen Streudaten. Weiterhin wird ein Modellähnlich dem von Schmidt-Rohr und Chen [3], d.h. dem neuesten morphologischen Modellfür Nafion, studiert. Auch hier werden die experimentellen Streudaten zufriedenstellendwiedergegeben, daher die weiterhin bestehende Debatte über die Struktur desNafion.Die gefundenen übereinstimmungen lassen darauf vertrauen, dass eine detaillierte Analyseder simulierten Konfigurationen wissenschaftlich sinnvoll ist. So wird die Strukturder Systeme auf verschiedenen Längenskalen charakterisiert, zum Beispiel durch radialePaarverteilungsfunktionen (rdf), totale und partielle Strukturfaktoren (S(q)) sowieAnzahl- und Größenverteilungen hydrophiler Cluster (abhängig von der Definition einesClusters). Die Dynamik einzelner Spezies im System wird ebenfalls untersucht, zumBeispiel durch die Berechnung der mittleren quadratischen Verschiebungen (msd) undder Selbstdiffusionskoeffizienten. Diese Simulationen sind wahrscheinlich an der Grenzedessen, was heute mit ’all-atom’ molekularen MD-Simulationen möglich ist. Ich vertrauedarauf, dass diese Arbeit dennoch einen Fortschritt in der aktuellen Debatte überdie Struktur und Dynamik dieser wichtigen Materiale darstellt.

L'optomécanique est la science des interactions entre la lumière et les mouvements mécaniques. Ce rapport de thèse décrit des expériences réalisées avec des microdisques fabriqué dans différents résonateurs semi-conducteurs III-V: l'Arséniure de Gallium (GaAs), l'Arséniure d'Aluminium Gallium (AlGaAs) et l'Arséniure d'Indium Phosphide (InGaP). Ces matériaux sont compatibles avec les fonctionnalités de l’optoélectronique et procurent un couplage optomécanique géant. Pour améliorer les performances des résonateurs en GaAs, nous avons développé des méthodes de traitement de surface permettant de réduire la dissipation optique par un facteur dix et ainsi d'atteindre un facteur de qualité de six millions. En plus de ces études sur le GaAs, nous avons réalisés une étude comparative des interactions optomecaniques dans des microdisques d'InGaP et d'AlGaAs, et nous avons mis en évidences leurs résonances optomécaniques. Finalement, nous avons réalisé des mesures de force avec des résonateurs en GaAs, démontrant un nouveau principe de détection basé sur notre étude de leur la trajectoire dans l'espace de phase et leur bruit de phase / Optomechanics studies the interaction between light and mechanical motion. This PhD thesis reports on optomechanical experiments carried with miniature disk resonators fabricated out of distinct III-V semiconductors: Gallium Arsenide (GaAs), Aluminium Gallium Arsenide (AlGaAs) and Indium Gallium Phosphide (InGaP). These materials are compliant with optoelectronics functionalities and provide giant optomechanical coupling. In order to boost performances of GaAs resonators, we implemented surface control techniques and obtained a ten-fold reduction of optical dissipation, attaining a Q of six million. On top of GaAs, we performed a comparative investigation of optomechanical interactions in InGaP and AlGaAs disk resonators, and demonstrated their operation as optomechanical oscillators. Finally, we carried out optomechanical force sensing experiments with GaAs resonators, analyzing a new sensing principle in light of the phase space trajectory and phase noise of the corresponding oscillators

The asymptotic state of a quantum system, which is in contact with a heat bath, is strongly disturbed by a time-periodic driving in comparison to a time-independent system. In this thesis an extensive picture of the asymptotic state of time-periodic quantum systems is drawn by relating it to the structure of the corresponding classical phase space. To this end the occupation probabilities of the Floquet states are analyzed with respect to their semiclassical property of being either regular or chaotic. The regular Floquet states are occupied with exponential weights e^{-betaeff Ereg} similar to the canonical weights e^{-beta E} of time-independent systems. The regular energies Ereg are defined by the quantization of the time-periodic system, whose classical properties also determine the effective temperature 1/betaeff. In contrast, the chaotic Floquet states acquire almost equal probabilities, irrespective of their time-averaged energy. Beyond these semiclassical properties the existence of avoided crossings in the spectrum is an intrinsic quantum property of time-periodic systems. Avoided crossings can strongly influence the entire occupation distribution. As an impressive application a novel switching mechanism is proposed in a periodically driven double well potential coupled to a heat bath. By a weak variation of the driving amplitude its asymptotic state is switched from the ground state in one well to a state with higher average energy in the other well. / Der asymptotische Zustand eines Quantensystems, das in Kontakt mit einem Wärmebad steht, wird durch einen zeitlich periodischen Antrieb gegenüber einem zeitunabhängigen System nachhaltig verändert. In dieser Arbeit wird ein umfassendes Bild über den asymptotischen Zustand zeitlich periodischer Quantensysteme entworfen, indem es diesen zur Struktur des zugehörigen klassischen Phasenraums in Beziehung setzt. Dazu werden die Besetzungswahrscheinlichkeiten der Floquet-Zustände hinsichtlich ihrer semiklassischen Eigenschaft analysiert, nach welcher sie entweder regulär oder chaotisch sind. Die regulären Floquet-Zustände sind mit exponentiellen Gewichten e^{-betaeff Ereg} ähnlich der kanonischen Verteilung e^{-beta E} zeitunabhängiger Systeme besetzt. Dabei sind die reguläre Energien Ereg durch die Quantisierung des Systems vorgegeben, dessen klassische Eigenschaften auch die effektive Temperatur 1/betaeff bestimmen. Die chaotischen Zustände dagegen haben fast einheitliche Besetzungswahrscheinlichkeiten, welche unabhängig von ihrer mittleren Energie sind. Über diese semiklassischen Eigenschaften hinaus ist das Auftreten von vermiedenen Kreuzungen im Spektrum eine intrinsisch quantenmechanische Eigenschaft zeitlich periodischer Systeme. Diese können die gesamte Besetzungsverteilung nachhaltig beeinflussen und finden eine eindrucksvolle Anwendung in Form eines neuartigen Schaltmechanismus in einem harmonisch modulierten Doppelmuldenpotential in Kontakt mit einem Wärmebad. Der asymptotische Zustand kann unter geringer Variation der Antriebsamplitude vom Grundzustand der einen Mulde in einen Zustand höherer mittlerer Energie in der anderen Mulde geschaltet werden.

The displacement operator is related to the displaced parity operator through a two dimensional Fourier transform. Both operators are important operators in phase space and the trace of both with respect to the density operator gives the Wigner functions (displaced parity operator) and Weyl functions (displacement operator). The generalisation of the parity-displacement operator relationship considered here is called the bi-fractional displacement operator, O(α, β; θα, θβ). Additionally, the bi-fractional displacement operators lead to the novel concept of bi-fractional coherent states. The generalisation from Fourier transform to fractional Fourier transform can be applied to other phase space functions. The case of the Wigner-Weyl function is considered and a generalisation is given, which is called the bi-fractional Wigner functions, H(α, β; θα, θβ). Furthermore, the Q−function and P−function are also generalised to give the bi-fractional Q−functions and bi-fractional P−functions respectively. The generalisation is likewise applied to the Moyal star product and Berezin formalism for products of non-commutating operators. These are called the bi-fractional Moyal star product and bi-fractional Berezin formalism. Finally, analysis, applications and implications of these bi-fractional transforms to the Heisenberg uncertainty principle, photon statistics and future applications are discussed.

Radiotherapy is used in clinics to treat cancer with highly energetic ionizing particles. The radiation dose can be measured indirectly by means of radiation detectors or dosimeters. The dose deposited in a detector can be related to dose deposited in a point within the patient. In theory, however, this is only possible under charged particle equilibrium (CPE). The motivation behind the dissertation was driven by the difficult, yet crucial, dosimetry in non-CPE regions. Inaccurate dose assessment performed with standard dosimetry using ionization chambers may significantly impact the outcomes of radiotherapy treatments. Therefore, advanced dosimetry methods tailored specifically to suit non-CPE conditions must be used. This work aims to improve dosimetry in two types of non-CPE conditions that pose dosimetric challenges: regions near interfaces of tissues with low- and high- density media and in small photon fields. To achieve the main dissertation objectives, an enhanced film dosimetry protocol with a novel film calibration approach was implemented. This calibration method is based on the percent depth dose (PDD) tables and was shown to be efficient and accurate. As a result, the PDD calibration method was used for the film dosimetry process throughout the dissertation work. Monte Carlo (MC) calculations for the small field dosimetry were performed using phase-space files (PSFs) provided by Varian for TrueBeam linac. The MC statistical uncertainty in these types of calculations is limited by the number of particles (due to latent variance) in the used PSFs. This study investigated the behaviour of the latent variances (LV) with beam energy, depth in phantom, and calculation resolution (voxel size). LV was evaluated for standard 10x10 cm2 fields as well as small fields (down to 1.3 mm diameter). The results showed that in order to achieve sub-percent LV in open 10x10 cm2 field MC simulations a single PSF can be used, whereas for small SRS fields (1.3—10 mm) more PSFs (66—8 PSFs) would have to be summed. The first study in this dissertation compared the performance of several dosimetric methods in three multi-layer heterogeneous phantoms with water/air, water/lung, and water/steel interfaces irradiated with 6 and 18 MV photon beams. MC calculations were used, along with Acuros XB, anisotropic analytical algorithm (AAA), GafChromic EBT2 film, and MOSkin dosimeters. PDDs were calculated and measured in these heterogeneous phantoms. The result of this study showed that Acuros XB, AAA, and MC calculations were within 1% in the regions with CPE. At media interfaces and buildup regions, differences between Acuros XB and MC were in the range of +4.4% to -12.8%. MOSkin and EBT2 measurements agreed to MC calculations within ~ 2.5%-4.5%. AAA did not predict the backscatter dose from the high-density heterogeneity. For the third, multilayer lung phantom, 6 MV beam PDDs calculated by all treatment planning system (TPS) algorithms were within 2% of MC. 18 MV PDDs calculated by Acuros XB and AAA differed from MC by up to 3.2 and 6.8%, respectively. MOSkin and EBT2 each differed from MC by up to 3%. All dosimetric techniques, except AAA, agreed within 3% in the regions with particle equilibrium. Differences between the dosimetric techniques were larger for the 18 MV than the 6 MV beam. This study provided a comparative performance evaluation of several advanced dosimeters in heterogeneous phantoms. This combination of experimental and calculation dosimetry techniques was used for the first time to evaluate the dose near these interfaces. The second study in the dissertation aims to improve dose measurement accuracy in small radiotherapy fields. Field output factors of 6 MV beams from TrueBeam linear accelerator (linac) collimated with 1.27-40 mm diameter cones were calculated and measured using MC and EBT3 films. A set of detector specific correction factors for two widely used dosimeters (EFD-3G diode and PTW-60019 microDiamond detectors) were determined based on GafChromic EBT3 film measurements and calculated using MC methods. MC calculations were performed for microDiamond detector in parallel and perpendicular orientations relative to the beam axis. The result of this study showed that the measured OFs agreed within 2.4% for fields ≥10 mm. For the cones of 1.27, 2.46, and 3.77 mm diameter maximum differences were 17.9%, 1.8% and 9.0%, respectively. MC calculated OF in water agreed with those obtained using EBT3 film within 2.2% for all fields. MC calculated output correction factors for microDiamond detector in fields ≥10 mm ranged within 0.975-1.020 for perpendicular and parallel orientations. MicroDiamond detector correction factors calculated for the 1.27, 2.46 and 3.77 mm fields were 1.974, 1.139 and 0.982 with detector in parallel orientation, and these factors were 1.150, 0.925 and 0.914 in perpendicular orientation. EBT3 and MC obtained correction factors agreed within 3.7% for fields of ≥3.77 mm and within 5.9% for smaller cones. This work provided output correction factors for microDiamond and EFD-3G detectors in very small fields of 1.27 – 3.77 mm diameter and demonstrated over and under-response of these detectors in such fields. These correction factors allow improve the accuracy of dose measurements in small photon fields using these detectors. / Graduate / 2019-08-30

Using the method of the star product, the non-relativistic regime of the Dirac equation is evaluated and the NC hamiltonian to the Zeeman e ect is determined. Using the rst-order perturbation theory, the correction to the energy is calculated. We obtain the orbital and spin Land e factors. It is shown that the experimental value for the spin Land e factor put the following upper limit on the magnitude of the momentum NC parameter, p . 0; 34 eV=c. Established also a possible correction of the NC phase space to the presently accepted value of Planck's constant with an uncertainty of 2 part in 1035. By mapping via Boop's shift we obtain the Landau levels and the Hall conductivity for graphene in NC phase space. Using the current experimental precision, respectively, of the Hall conductivity and of the Landau levels in graphene, we obtain the following upper limit to the magnitude of the momentum NC parameter, p . 2; 5eV=c e p . 8; 5eV=c. Finally, by Newton's law in NC space and using the Langevin equations, we describe the Browniano motion, and thus we de ne a new physical parameter that shows the possibility of detecting NC eff ects on the macroscopic scale. / Utilizando-se do m étodo do produto estrela, o regime não relativí stico da equa ção de Dirac é avaliado e o hamiltoniano NC para o efeito Zeeman é determinado. Usando a teoria de perturba ção de primeira ordem, a corre ção para a energia é calculada. Obtemos assim, os fatores de Land é orbital e de spin. É mostrado que o valor experimental para o fator de Land é de spin impõe o seguinte limite superior na magnitude do parâmetro NC de momento,p . 0; 34 eV=c. Estabelecemos tamb ém uma possí vel corre ção do espa ço de fase NC para o valor atualmente aceito da constante de Planck, com uma incerteza de 2 partes em 10 elevado a 35. Atrav és do mapeamento via Boop's shift obtemos os n íveis de Landau e a condutividade Hall para o grafeno no espa ço de fase NC. Utilizando a atual precisão experimental, respectivamente, da condutividade Hall e dos n veis de Landau no grafeno, obtemos os seguintes limites superiores para a magnitude do parâmetro NC de momento,p . 2; 5eV=c ep . 8; 5eV=c. Por fim, atrav és das leis de Newton num espa ço NC e utilizando as equa ções de Langevin, descrevemos o movimento Browniano, e assim defi nimos um novo parâmetro f ísico que mostra a possibilidade de detectar efeitos NC na escala macrosc ópica.

Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2016-12-21T11:30:16Z No. of bitstreams: 0 / Made available in DSpace on 2016-12-21T11:30:16Z (GMT). No. of bitstreams: 0 / O sucesso de uma radioterapia depende do correto planejamento da dose a ser entregue ao volume alvo. Na braquiterapia, modalidade da radioterapia onde um radioisótopo selado é implantado intracavitariamente ou intersticialmente no paciente, há menos avanços em sistemas de planejamento de tratamento computacionais do que na teleterapia, amplamente mais utilizada nos serviços típicos. Porém, a braquiterapia, quando aplicável, é preferível por poupar tecidos sadios vizinhos de uma dose desnecessária. O AMIGOBrachy, um sistema de planejamento para braquiterapia de interface amigável, compatibilidade com outros sistemas comerciais em uso e integrado ao código MCNP6 (Monte Carlo N-Particle Transport Code v. 6) foi desenvolvido no Centro de Engenharia Nuclear do Instituto de Pesquisas Energéticas e Nucleares (CEN-IPEN) e atualmente está em processo de validação. Este trabalho contribuiu para este processo, avaliando três diferentes casos clínicos através do AMIGOBrachy com o formalismo do TG43 da AAPM (Associação Americana de Física Médica), protocolo que rege a dosimetria em braquiterapia, e comparando seus resultados com as distribuições de dose calculadas por outros sistemas comerciais consagrados: Varian BrachyVision TM (Varian Medical Systems; Palo Alto, CA, EUA) e Nucletron Oncentra® (Elekta; Estocolmo, Suécia). Os resultados obtidos estão dentro de uma faixa de concordância de ±10%, estando mais discrepantes em regiões muito próximas do aplicador, onde os sistemas de planejamento comerciais e o AMIGOBrachy divergem devido aos diferentes métodos de cálculo. Em pelo menos dois terços da região de interesse, porém, a dose concordou em uma faixa de ±3% para os três casos. Também foram realizadas simulações utilizando o formalismo do TG186 da AAPM, que considera heterogeneidades no tecido, para avaliar o impacto dos mesmos na dose. Em adição ao processo de validação, também foi realizado um estudo em braquiterapia oftálmica para posterior inserção de um módulo adicional ao AMIGOBrachy; para isso, um modelo de olho humano foi desenvolvido utilizando geometria UM (Unstructured Mesh), para validação com o código MCNP6, que apenas nesta versão demonstra um novo recurso capaz de simular uma geometria híbrida: parcialmente analítica, parcialmente UM. O modelo considera dez diferentes estruturas no olho humano: esclera, coroide, retina, corpo vítreo, córnea, câmara anterior, lente, nervo óptico, parede do nervo óptico, e um tumor definido de forma arbitrária crescendo da superfície externa do globo ocular em direção ao seu centro. Os resultados foram comparados com um modelo de olho puramente analítico modelado com o MCNP6 e tomado como referência. Os resultados foram satisfatórios em todas as simulações desenvolvidas, exceto para as estruturas do nervo óptico e sua parede, que devido ao seu pequeno tamanho e distância da fonte, mostraram erros relativos maiores, mas ainda menores que 10%, e não representam problema de preocupação clínica uma vez que recebem doses muito pequenas. Discutiu-se também a eficácia e problemas encontrados nessa nova capacidade do código MCNP de simular geometrias híbridas, uma vez que é recente e ainda apresenta deficiências, que tiveram que ser contornadas no presente trabalho. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP