Dosímetros Luminescentes Opticamente Estimulados (OSL) vêm sendo testados como alternativa dosimétrica no controle da qualidade e verificação de tratamentos por possuir características adequadas para esse fim, como elevada sensibilidade à radiação ionizante, alta resolução espacial e facilidade de leitura. Neste trabalho, o óxido de alumínio, dopado com diferentes concentrações de carbono (Al2O3:C), foi estudado como material dosimétrico OSL. Nanotubos de carbono de paredes simples também foi avaliado como dopante, associados ao mesmo material, Al2O3:NTC, em alguns testes preliminares de resposta em função da dose em feixes de fótons de 50 kVp. O presente trabalho apresenta o processo de fabricação do dosímetro OSL, além de testes dosimétricos envolvendo metodologia experimental e por simulação Monte Carlo com o código PENELOPE para avaliação da resposta dosimétrica do Al2O3:C em função da concentração do carbono dopante. Neste trabalho foi investigada a resposta do dosímetro OSL para doses entre 50 cGy e 1000 cGy, em um amplo intervalo de energia de feixes de fótons. Foi analisada também, a interferência do uso do dosímetro OSL de Al2O3:C nas doses superficial e profunda em tratamentos radioterápicos. O dosímetro Al2O3:C(1%) apresentou diferença percentual máxima de 12% na homogeneidade de resposta em um grupo de 100 dosímetros e linearidade de resposta entre as doses de 50 cGy e 800 cGy para feixes de fótons de alta energia de 1,25 MV, 6 MV e 15 MV. Já para feixes de fótons de baixas energias, de 50 kVp, 120 kVp e 200 kVp, o dosímetro apresentou diferença significativa entre as respostas, evidenciando dependência com a energia. Além disso, foi investigada a estabilidade do sinal OSL em função do tempo e estipulado um tempo mínimo de armazenamento do dosímetro, entre a exposição e a leitura. O dosímetro Al2O3:NTC apresentou um aumento de sensibilidade de até 30% em relação ao dosímetro Al2O3:C(1%). Os resultados encontrados neste trabalho sugerem o uso do material dosimétrico OSL estudado como ferramenta em controle da qualidade em procedimentos clínicos de rotina na Radioterapia. / Optically Stimulated Luminescent dosimeters (OSL) have been tested as a dosimetric alternative in quality control and treatment verification since they have suitable characteristics for this purpose, such as high sensitivity to ionizing radiation, high spatial resolution and readability. In this work the aluminum oxide, doped with different concentrations of carbon (Al2O3:C), was studied as OSL dosimetric material. Single-walled carbon nanotubes were also evaluated as a dopant associated with the same material, Al2O3:NTC, and preliminary tests of response to dose in photon beams of 50 kVp were performed. This work presents the fabrication process of the OSL dosimeter, and dosimetric tests involving experimental methodology and Monte Carlo simulation with PENELOPE code to evaluate the response of the dosimetric Al2O3:C as a function of the concentration of carbon dopant. In this study we investigated the response of the OSL dosimeter for doses ranging from 50 cGy to 1000 cGy in a wide range of energy of photon beams. The interference of the OSL dosimeter Al2O3:C in superficial and deep doses in Radiotherapy treatments was also analyzed. The dosimeter Al2O3:C (1%) had a maximum percentage difference of 12% in the homogeneity of a group of 100 dosimeters and presented linearity of response in a dose range of 50 cGy and 800 cGy for photon beams of high energy of 1.25 MV, 6 MV and 15 MV. As for photon beams of low energies of 50 kVp, 120 kVp and 200 kVp, the dosimeter showed a significant difference between responses, indicationg dependence on energy. In addition, we investigated the stability of the OSL signal as a function of time and set a minimum time of storage of the dosimeter, between exposure and reading. The dosimeter Al2O3:NTC showed an increased sensitivity of up to 30% over the dosimeter Al2O3:C (1%). The findings on this study suggest the use of the material studied as OSL dosimeter as a tool in quality control in routine clinical procedures in Radiotherapy.

Desde o desenvolvimento do primeiro equipamento de Tomografia Computadorizada (TC) no começo dos anos 1970, essa modalidade de diagnóstico por imagem passou por diversas melhorias. Produção de imagens de alta qualidade e exclusivamente digitais sem a superposição de estruturas anatômicas, exames com a duração de até cinco segundos e a capacidade de detectar patologias importantes sem a necessidade de cirurgias exploratórias são algumas das grandes vantagens obtidas quando essa técnica é utilizada. Como consequência, o papel dessa modalidade diagnóstica tem crescido amplamente ao redor do mundo. Nos Estados Unidos, por exemplo, 2,2 milhões de exames de TC foram realizados em 1980, apenas 10 anos após sua implementação. Esse número cresceu para 78,7 milhões no ano de 2015. Como resultado, a dose de radiação absorvida por pacientes devido ao uso dessa técnica tem se tornado uma preocupação entre radiologistas, pesquisadores e fabricantes, levando ao desenvolvimento de diferentes metodologias para estima-la. Câmaras de ionização, dosimetria termoluminescente (TL) e, mais recentemente, dosimetria luminescente opticamente estimulada (OSL), por exemplo, têm sido amplamente aplicados para se estimar dose em órgãos in vivo, em cadáveres e em objetos simuladores (phantoms). Outra abordagem extensivamente utilizada é a computacional, baseada em simulações Monte Carlo, que pode ser utilizada na comparação com resultados experimentais. Nesse trabalho, uma abordagem experimental utilizando TLDs e OSLDs em objetos simuladores adulto e pediátrico foi utilizada. Diversas análises foram realizadas com o objetivo de estabelecer o melhor caminho para conseguir os principais resultados alcançados e a metodologia desenvolvida foi eficiente para a finalidade proposta. As características dos OSLDs foram analisadas para verificar sua aplicabilidade no estudo de doses provenientes de procedimentos de TC. As respostas dos dosímetros demonstraram homogeneidade, linearidade com o kerma no ar incidente, reprodutibilidade, possibilidade de reutilização e dependência energética. Esses dosímetros foram utilizados em objetos simuladores adulto e pediátrico para o estudo de doses provenientes de protocolos clínicos de TC selecionados após uma análise de banco de dados de pacientes coletados do Instituto de Radiologia da Faculdade de Medicina da Universidade de São Paulo. As doses em órgãos medidas com os dosímetros foram comparadas com simulações Monte Carlo. Para órgãos contidos na região de exame, as diferenças entre doses medidas e simuladas estão no intervalo de ±20%. Esses resultados demonstraram, ainda, que o alinhamento e posicionamento incorretos do paciente antes do exame podem ocasionar um aumento maior do que 100% na dose de um órgão. / Since the development of the first Computed Tomography (CT) equipment in the early 1970s, this diagnostic imaging modality has gone through several improvements. Exclusively digital and high quality images production without superposition of anatomical structures, examinations as fast as five seconds, and the capability of diagnosing important pathologies with no need of exploratory surgeries are some of the great advantages when using this technique. As a consequence, the role of this diagnostic procedure has been widely increasing worldwide. In the US, for instance, 2.2 million CT exams were performed in 1980, only 10 years after its implementation. This number increased to 78.7 million in 2015. As a result, absorbed dose by patients due to this technique has become a concern among radiologists, researchers and manufacturers, leading to the development of different methodologies to evaluate it. Ionization chambers, thermoluminescence (TL) and, more recently, optically stimulated luminescence (OSL) dosimetry, for instance, have been widely applied in order to estimate in vivo organ doses, in post-mortem subjects and in phantoms. Another approach that has been extensively used are the Monte Carlo simulations, which can be applied in comparison with experimental results. An experimental approach to evaluate organ doses in pediatric and adult anthropomorphic phantoms by using TLDs and OSLDs was employed in the present study. Several analyses were performed in order to stablish the best way to achieve the main results in this investigation and the methodology proved to be efficient. The characteristics of the OSLDs were analyzed to verify their applicability for evaluating doses from CT procedures. The characterization included homogeneity, linearity with the incident air kerma, reproducibility, reusability and an energy-dependent response to distinct effective energies evaluation. These dosimeters were applied along with TLDs in an adult and a pediatric anthropomorphic phantoms to evaluate organ doses due to clinical CT protocols. These protocols were selected after an analysis of patient data collected from the Institute of Radiology of the School of Medicine of the University of São Paulo (Instituto de Radiologia da Faculdade de Medicina da Universidade de São Paulo). Organ doses measured with dosimeters were compared with Monte Carlo simulations. Differences between measured and simulated absorbed organ doses were within ±20%. Moreover, these results showed that a misalignment and incorrect positioning of the patient in the couch can increase an organ dose by more than 100%.

Im Zuge dieser Arbeit wurden die für die Dosimetrie mit BeO-OSL-Detektoren wichtigen Größen Energieansprechvermögen und Nachweiseffizienz experimentell ermittelt. Anschließend konnten die Ergebnisse genutzt werden, um ein Modell der lokalen Sättigung zur Berechnung der Effizienz für unterschiedlichste Bestrahlungsbedingungen zu generieren. Mit Hilfe des Modells lassen sich Vorhersagen zur Nachweiseffizienz für Photonen und Elektronen in dem in der Personen- und Ortsdosimetrie gängigen Energiebereich von 10 keV bis zu mehreren MeV treffen. Dabei nimmt die Effizienz für Elektronen mit sinkenden Energien kontinuierlich ab. Photonen zeigen einen ähnlichen Effekt, jedoch kommt es bei Energien im Bereich von 40-80 keV zu einem kurzen Anstieg der Effizienz mit fallender Energie, welcher sich durch die Wechselwirkungseigenschaften der Photonen erklären lässt. Die experimentellen und modellierten Nachweiseffizienzen können genutzt werden, um die Anzeige eines BeO-OSL-Detektor aus mit Strahlungstransportprogrammen ermittelten Dosiswerten zu berechnen. Auf experimentell gestützte Optimierungen von Bestrahlungsgeometrien kann so größtenteils verzichtet werden. Als Beispiel für die Anwendung der Nachweiseffizienz werden das Energieansprechvermögen für Beta-Strahler, des iBeOx-Personendosimeters sowie die Konzeption eines OSL-Ortsdosimeters aufgeführt.:1 Einleitung 2 Theoretische Grundlagen 2.1 Grundlagen zur Dosimetrie ionisierender Strahlung 2.2 Optisch Stimulierte Lumineszenz 2.3 Dosimetrie mit Hilfe der Optisch Stimulierten Lumineszenz 3 Material und Methoden 3.1 Berylliumoxiddetektoren und Dosimeter 3.2 Auswerteverfahren 3.3 Bestrahlungsmöglichkeiten 3.4 Strahlungstransportberechnungen 4 Experimentelle Ergebnisse 4.1 Rechnerisches Ansprechvermögen für BeO-OSL-Detektoren 4.2 Experimentelles Ansprechvermögen für BeO-OSL-Detektoren 4.3 Vergleich von rechnerischem und experimentellem ASV für BeO- Detektoren 4.4 Effizienz für BeO-OSL-Detektoren 5 Modellierung der Effizienz von BeO-OSL-Detektoren 5.1 Target-Modell 5.2 Berechnung der Effizienz auf Grundlage des Modells der lokalen Sättigung 5.3 Ergebnisse der Modellierung 6 Anwendungen 6.1 Ansprechvermögen für Beta-Strahler 6.2 Energieansprechvermögen des iBeOx-Personendosimeters 6.3 Konzeption eines Ortsdosimeters auf Basis des iBeOx-Dosimetriesystems 7 Zusammenfassung 8 Literaturverzeichnis A Anhang A.1 Theorie A.2 Messdaten und Ergebnisse A.3 Effizienzen für unterschiedliche Bestrahlungsgeometrien / In the course of this work, the experimental detection efficiency for BeO-OSL-detectors was determined for different radiation qualities. Subsequently the results were used to generate a model of local saturation for calculating the efficiency for different irradiation conditions. With the help of the model predictions for the detection efficiency for photons and electrons in the common energy range for personal and environmental dosimetry, reaching from 10 keV up to some MeV, are possible. The efficiency for electrons decreases with falling energy continuously. Photons show a similar effect, but for energies ranging from 40-80 keV the efficiency increases with decreasing energy. This can be explained by the interaction effects of the photons with the detector material. The experimental and modelled detection efficiencies can be used to calculate the display of a BeO-OSL detector from dose values determined with radiation transport programs. Three examples, the energy dependence for beta emitters, for the iBeOx personal dosimeters and the development of an environmental OSL-dosimeter are listed.:1 Einleitung 2 Theoretische Grundlagen 2.1 Grundlagen zur Dosimetrie ionisierender Strahlung 2.2 Optisch Stimulierte Lumineszenz 2.3 Dosimetrie mit Hilfe der Optisch Stimulierten Lumineszenz 3 Material und Methoden 3.1 Berylliumoxiddetektoren und Dosimeter 3.2 Auswerteverfahren 3.3 Bestrahlungsmöglichkeiten 3.4 Strahlungstransportberechnungen 4 Experimentelle Ergebnisse 4.1 Rechnerisches Ansprechvermögen für BeO-OSL-Detektoren 4.2 Experimentelles Ansprechvermögen für BeO-OSL-Detektoren 4.3 Vergleich von rechnerischem und experimentellem ASV für BeO- Detektoren 4.4 Effizienz für BeO-OSL-Detektoren 5 Modellierung der Effizienz von BeO-OSL-Detektoren 5.1 Target-Modell 5.2 Berechnung der Effizienz auf Grundlage des Modells der lokalen Sättigung 5.3 Ergebnisse der Modellierung 6 Anwendungen 6.1 Ansprechvermögen für Beta-Strahler 6.2 Energieansprechvermögen des iBeOx-Personendosimeters 6.3 Konzeption eines Ortsdosimeters auf Basis des iBeOx-Dosimetriesystems 7 Zusammenfassung 8 Literaturverzeichnis A Anhang A.1 Theorie A.2 Messdaten und Ergebnisse A.3 Effizienzen für unterschiedliche Bestrahlungsgeometrien

A Serra do Mar pertence ao complexo litorâneo brasileiro, preenchendo todo o litoral desde Santa Catarina até o Rio de Janeiro. As feições de seu relevo são peculiares, resultantes de um tectonismo recente com acelerado processo de intemperismo, que acarreta em feições distintas ao longo de todo o complexo da Serra do Mar. A evolução deste relevo tem como fator resultante a adequação da drenagem às falhas e rupturas presentes nas rochas. Desta forma a evolução da Serra do Mar e compreensão das anomalias de drenagem, tal como a Captura Fluvial do alto rio Guaratuba, passa a ser ponto de investigação desta pesquisa, utilizando datação por Luminescência Opticamente Estimulada (LOE). Para o desenvolvimento da pesquisa foi proposta uma divisão do relevo em três compartimentos geomorfológicos (Planalto, Planície do alto rio Guaratuba, Bordas e escarpa da Serra). A compartimentação foi elaborada respeitando as morfologias e a drenagem local, baseada na teoria de AbSaber (1969) sobre a forma de se estudar o Quaternário. Foram elaboradas cartas temáticas (declividade, hipsometria, orientação das vertentes, etc.) para um embasamento visual da teoria discutida no trabalho, vinculando a elas os pontos de coleta das amostras. A partir da compartimentação do relevo desenvolveu-se atividade de campo para coleta de material sedimentar de possíveis trechos do antigo leito fluvial. As amostras coletadas foram trabalhadas em laboratório por datação através da técnica de LOE, utilizando-se o protocolo de alíquota única (SAR). As amostras foram trabalhadas quimicamente para que se obtivesse o grão de quartzo na sua forma mais pura. A partir dos dados adquiridos através da IX datação, as informações foram trabalhadas em planilhas e softwares voltados para a interpretação dos dados. Os valores alcançados foram discutidos ao longo da pesquisa, justificando-se os apontamentos positivos e negativos das amostras. Os dados obtidos concordam com a literatura abordada sobre a evolução geomorfológica da Serra do Mar. / The Serra do Mar mountain range belongs to the Brazilian coastal complex which runs from the state of Santa Catarina to Rio de Janeiro. Its relief has peculiar features, derived from a recent tectonism with accelerated weathering process, which leads to distinct features throughout the complex of the Serra do Mar. The evolution of this relief results in the drainage adequacy to the failures and disruptions found in the rocks. Therefore, the evolution of the Serra do Mar and understanding of drainage anomalies, such as the Guaratuba upper river fluvial capture, becomes the point of investigation in this research, using Optically Stimulated Luminescence (OSL) for dating. For the development of the research, the relief was divided into three geomorphologic compartments (Plateau, Guaratuba upper river plain, Borders and Scarp of the Serra do Mar). The compartmentation was developed in compliance with the morphologies and local drainage, based on the Ab\'Saber Theory (1969) on how to study the Quaternary. Thematic maps were drawn (slope, hypsometry, orientation of the strands, etc.) for a visual basis of the theory discussed in the thesis, linking them to the points of sample collection. From the relief compartmentation a field activity was carried out for the collection of sedimentary material of possible sections of the old riverbed. The samples were processed in the laboratory through the technique of dating OSL, using the single-aliquot regenerative-dose (SAR). Samples were chemically worked out to obtain the quartz grain in its pure form. From the data acquired through dating, the information was analyzed on spreadsheets and software focused on the interpretation of data. The values achieved were discussed throughout the thesis research to explain any positive XI and negative results of the samples. The data obtained agree with the literature on the geomorphological evolution of the Serra do Mar that is presented in the thesis.

Depuis deux décennies, les nombreux développements des techniques de radiothérapie par modulation d’intensité (RCMI) ont permis de mieux conformer la dose au volume cible et ainsi, d’augmenter les taux de réussite des traitements des cancers. Ces techniques ont souvent l’avantage de réduire la dose aux organes à risque proches de la zone traitée, mais elles ont l’inconvénient d’apporter un niveau de dose périphérique plus important que les techniques basiques sans modulation d’intensité. Dans ce contexte, l’augmentation du taux de survie des patients qui en résulte, accroît également la probabilité de manifestation d’effets iatrogènes dus aux doses périphériques (tels que les cancers secondaires). Aujourd’hui, la dose périphérique n’est pas considérée lors de la planification du traitement et il n’existe aucun outil numérique fiable pour sa prédiction. Il devient cependant indispensable de prendre en compte le dépôt de dose périphérique lors de la planification du traitement, notamment dans les cas pédiatriques. Cette étude doctorale a permis la réalisation de plusieurs étapes du développement d’un outil numérique, précis et rapide, de prédiction de la dose hors-champ fondé sur le code Monte Carlo PENELOPE. Dans cet objectif, nous avons démontré la capacité du code PENELOPE à estimer la dose périphérique en comparant ses résultats avec des mesures de référence réalisées à partir de deux configurations expérimentales (métrologique et pré-clinique). Ces travaux expérimentaux ont notamment permis la mise en place d’un protocole d’utilisation des dosimètres OSL pour la mesure des faibles doses. En parallèle, nous avons pu mettre en évidence la convergence lente et rédhibitoire du calcul en vue d’une utilisation clinique. Par conséquent nous avons réalisé un travail d’accélération du code en implémentant une nouvelle technique de réduction de variance appelée transport pseudo-déterministe spécifiquement dédiée à l’amélioration de la convergence dans des zones lointaines du faisceau principal. Ces travaux ont permis d’améliorer l’efficacité des estimations dans les deux configurations de validation définies (gain d’un facteur 20) pour atteindre des temps de calcul raisonnables pour une application clinique. Des travaux d’optimisation du code restent à entreprendre de façon à améliorer encore la convergence de l’outil pour ensuite en envisager une utilisation clinique. / Over the last two decades, many technical developments have been achieved on intensity modulated radiotherapy (IMRT) and allow a better conformation of the dose to the tumor and consequently increase the success of cancer treatments. These techniques often reduce the dose to organs at risk close to the target volume; nevertheless they increase peripheral dose levels. In this situation, the rising of the survival rate also increases the probability of secondary effects expression caused by peripheral dose deposition (second cancers for instance). Nowadays, the peripheral dose is not taken into account during the treatment planification and no reliable prediction tool exists. However it becomes crucial to consider the peripheral dose during the planification, especially for pediatric cases. Many steps of the development of an accurate and fast Monte Carlo out-of-field dose prediction tool based on the PENELOPE code have been achieved during this PhD work. To this end, we demonstrated the ability of the PENELOPE code to estimate the peripheral dose by comparing its results with reference measurements performed on two experimental configurations (metrological and pre-clinical). During this experimental work, we defined a protocol for low doses measurement with OSL dosimeters. In parallel, we highlighted the slow convergence of the code for clinical use. Consequently, we accelerated the code by implementing a new variance reduction technique called pseudo-deterministic transport which is specifically with the objective of improving calculations in areas far away from the beam. This step improved the efficiency of the peripheral doses estimation in both validation configurations (by a factor of 20) in order to reach reasonable computing times for clinical application. Optimization works must be realized in order improve the convergence of our tool and consider a final clinical use.

A Serra do Mar pertence ao complexo litorâneo brasileiro, preenchendo todo o litoral desde Santa Catarina até o Rio de Janeiro. As feições de seu relevo são peculiares, resultantes de um tectonismo recente com acelerado processo de intemperismo, que acarreta em feições distintas ao longo de todo o complexo da Serra do Mar. A evolução deste relevo tem como fator resultante a adequação da drenagem às falhas e rupturas presentes nas rochas. Desta forma a evolução da Serra do Mar e compreensão das anomalias de drenagem, tal como a Captura Fluvial do alto rio Guaratuba, passa a ser ponto de investigação desta pesquisa, utilizando datação por Luminescência Opticamente Estimulada (LOE). Para o desenvolvimento da pesquisa foi proposta uma divisão do relevo em três compartimentos geomorfológicos (Planalto, Planície do alto rio Guaratuba, Bordas e escarpa da Serra). A compartimentação foi elaborada respeitando as morfologias e a drenagem local, baseada na teoria de AbSaber (1969) sobre a forma de se estudar o Quaternário. Foram elaboradas cartas temáticas (declividade, hipsometria, orientação das vertentes, etc.) para um embasamento visual da teoria discutida no trabalho, vinculando a elas os pontos de coleta das amostras. A partir da compartimentação do relevo desenvolveu-se atividade de campo para coleta de material sedimentar de possíveis trechos do antigo leito fluvial. As amostras coletadas foram trabalhadas em laboratório por datação através da técnica de LOE, utilizando-se o protocolo de alíquota única (SAR). As amostras foram trabalhadas quimicamente para que se obtivesse o grão de quartzo na sua forma mais pura. A partir dos dados adquiridos através da IX datação, as informações foram trabalhadas em planilhas e softwares voltados para a interpretação dos dados. Os valores alcançados foram discutidos ao longo da pesquisa, justificando-se os apontamentos positivos e negativos das amostras. Os dados obtidos concordam com a literatura abordada sobre a evolução geomorfológica da Serra do Mar. / The Serra do Mar mountain range belongs to the Brazilian coastal complex which runs from the state of Santa Catarina to Rio de Janeiro. Its relief has peculiar features, derived from a recent tectonism with accelerated weathering process, which leads to distinct features throughout the complex of the Serra do Mar. The evolution of this relief results in the drainage adequacy to the failures and disruptions found in the rocks. Therefore, the evolution of the Serra do Mar and understanding of drainage anomalies, such as the Guaratuba upper river fluvial capture, becomes the point of investigation in this research, using Optically Stimulated Luminescence (OSL) for dating. For the development of the research, the relief was divided into three geomorphologic compartments (Plateau, Guaratuba upper river plain, Borders and Scarp of the Serra do Mar). The compartmentation was developed in compliance with the morphologies and local drainage, based on the Ab\'Saber Theory (1969) on how to study the Quaternary. Thematic maps were drawn (slope, hypsometry, orientation of the strands, etc.) for a visual basis of the theory discussed in the thesis, linking them to the points of sample collection. From the relief compartmentation a field activity was carried out for the collection of sedimentary material of possible sections of the old riverbed. The samples were processed in the laboratory through the technique of dating OSL, using the single-aliquot regenerative-dose (SAR). Samples were chemically worked out to obtain the quartz grain in its pure form. From the data acquired through dating, the information was analyzed on spreadsheets and software focused on the interpretation of data. The values achieved were discussed throughout the thesis research to explain any positive XI and negative results of the samples. The data obtained agree with the literature on the geomorphological evolution of the Serra do Mar that is presented in the thesis.

A partir d’une approche pluridisciplinaire (géo-historique, cartographique et pédologique), cette étude nous a permis d’établir un bilan complet sur l’état (origines, formes et évolutions) des systèmes de haies en Alsace depuis le Moyen Age. L’étude pédologique de topo séquences de sols dans des zones de loess très sensibles à l’érosion (Habsheim, Uffheim) a également permis de procéder à un bilan de l’érosion depuis le Néolithique et montré comment le stockage de colluvions à l’amont de haies modifiait le relief par la formation de rideaux de culture, dont les plus anciens remontent à la fin de l’Age du bronze. Nous avons quantifié le potentiel des systèmes de haies en tant que frein à l’érosion et en tant que puits de carbone, dans l’optique d’une lutte contre le réchauffement climatique (initiative 4‰). En termes de potentiel de stockage de colluvions, le site d’Habsheim révèle une capacité de stockage énorme avec par exemple des stockages de 17,8 t/m linéaire de haie. D’autre part, à partir de nos sites de référence, on a pu démontrer aussi la grande activité érosive de ces espaces et cela depuis la préhistoire : entre 5700 et 2700 BP le taux d’érosion moyen mesuré a été de 4,5 t/ha/an, équivalant à celui de l’agriculture intensive dans les mêmes zones, ce qui relativise en partie le rôle de l’agriculture moderne. Le potentiel réel des colluvions loessiques est plus nuancé en termes de stockage de carbone. De nombreux processus comme la minéralisation du carbone et la faible efficacité du complexe argilohumique rendent les interprétations délicates sans pour autant que le potentiel des sols agricoles limoneux comme puit de carbone doive être écarté. / This study is a pluridisciplinary approach combining geohistory, spatial study and soil science that proposes an exhaustive analysis of origins, shapes and evolution of hedges systems in Alsace since Middle Ages. An erosion budget since Neolithic was obtained from the study of soil topographical sequences in an erosion sensitive loess area (Habsheim, Uffheim, 68, France). The colluvium stored in the upperside of the hedge modifies the topography by creating lynchets (the oldest were from the Bronze Age). We quantified the potential of hedges systems to reduce erosion and to store carbon in order to struggle against climate change (4‰ project). In Habsheim the storage of carbon potential is huge with some stocks reaching 17,8 t per meter of linear hedge. Moreover, based on the reference sites, we demonstrated the great erosion processes that has occured in these landscapes since Prehistory: between 5700 and 2700 BP the average erosion rate measured (4,5 t/ha/yr) is equivalent to the present day rates under intensive agriculture. The potential of loess colluvium, from the stock of carbon point of view, is more questionable. Interpretations are more difficult because of processes like mineralization of carbon and low efficiency of argilo-humic complex but so far the storage function of loamy soils cannot be neglected.

The application of optically stimulated luminescence (OSL) dating to desert sand dunes has allowed accumulation histories to be used as tools to infer past environmental change. In response to issues facing the interpretation of these records, two research questions are addressed in this thesis. (i) Are dune chronologies representative of dune stratigraphies? And (ii) how can we most appropriately interpret dune chronologies as records of Quaternary environmental conditions? Five dune profiles were sampled for OSL dating at two sites in the northeastern Rub’ al Khali in the southern Arabian Peninsula. The visible stratigraphy was used to guide sampling for three of the profiles and the effectiveness of this approach is assessed. A key finding is that bounding surfaces are not always identifiable as chronological hiatuses by OSL dating, given the level of precision that can be achieved. Using hierarchical relationships visible in two-dimensional exposures is therefore not guaranteed to identify the depositional units necessary to reconstruct dune histories. Comparison of the depositional records from three sampled profiles shows that there is significant variability in chronologies at both the dune and dunefield scales. In light of these findings, the use of ‘range-finder’ OSL dating was investigated as a method of increasing sample throughput in the laboratory. It is concluded that the use of partially prepared samples and shortened measurement techniques can be used to rapidly assess the chronological context of samples and target those units most useful in constructing dune profiles. A new method of presenting dunefield OSL datasets as net accumulation rates, incorporating accumulation thickness rather than relying on the frequency of ages, is presented. Within the last 30 ka, regional accumulation and preservation occurred at ~30-26, 22.5-18, 16-9, 6-2.7, 2.1-1.6, 1.1 and 0.7 ka. In conjunction with numerical model results and a review of other palaeoenvironmental archives, the regional aeolian record is interpreted as a response to changing forcing factors. High rates of net accumulation between ~16-9 ka are attributed to coeval increases in sediment supply and transport capacity. A hiatus in accumulation between ~9-6 ka is interpreted as a result of reduced sediment availability due to high moisture levels. The importance of both external forcing factors and local controls on dune accumulation processes is recognised, and therefore the importance of sampling at multiple locations to distinguish these factors is emphasised.

O presente trabalho tem como objetivo principal o estudo da Termoluminescência (TL) e a Luminescência Opticamente Estimulada (LOE) de cristais de quartzo retirados de sedimentos localizados no litoral do Estado do Maranhão. Foi efetuada uma análise do comportamento da TL e da LOE do quartzo em relação à irradiação com radiação gama e beta, pré-aquecimentos e exposição à luz solar. Esta análise foi feita visando comparar os resultados obtidos por TL e LOE para aplicação na datação de cristais de quartzo. Os centros paramagnéticos da amostra foram analisados e identificados através de medidas de Ressonância Paramagnética Eletrônica (RPE), uma correlação dos centros de TL e LOE foi encontrada. Na datação por grão único observamos um comportamento inesperado, sendo um indício de que os centros responsáveis pela TL e a LOE não são os mesmos. As idades obtidas por LOE dependem apenas dos grãos que têm maior intensidade, por outro lado idades obtidas por TL resultam da contribuição de todos os grãos. As medidas de Difração de Raios-X (DRX), feitas no Laboratório Nacional de Luz Sincroton (LNLS), confirmaram que os grãos eram de quartzo apesar de apresentarem propriedades de emissão LOE diferentes, sugerindo que essas propriedades estão relacionadas às impurezas e defeitos pontuais intrínsecos de cada grão. Foram observados os sinais de RPE correspondentes ao quartzo e usando microondas com uma potência de 0,161 mW conseguiu-se isolar o sinal do centro E1 do quartzo. Observou-se que este centro cresce quando aquecido de 120 até 300 oC e para tratamentos acima de 300 oC até 450 oC ele decresce, podendo ser relacionado com os picos TL de altas temperaturas. As medidas de RPE, em baixa temperatura, mostraram a presença dos centros de Al. Foram encontradas Doses Anuais (DA) de 0,7 até 3,0 mGy/ano, e para alguns perfis os valores de DA foram mais constantes (Local B: 1,77-1,95 mGy/ano). As idades obtidas por LOE e TL (Protocolo Multiple Aliquot Regeneration: MAR) são bem próximas. Embora as obtidas por LOE, em geral, são um pouco menores do que as idades obtidas por TL. As profundidades estratigráficas dos sedimentos são diretamente proporcionais às idades obtidas. As três idades do segundo perfil estão dentro do Pleistoceno, já os outros perfis apresentam idades começando no Pleistoceno até o Holoceno. / The principal aim of the present work is to study the Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) of quartz crystals obtained from sediments located at coast of the state of Maranhão. The analysis using OSL and TL properties was carried out after gamma and beta irradiation, pre-heating, and exposure of samples to solar radiation, having in mind the dating of these sediments. EPR measurements were performed to investigate the possible paramagnetic centers in the sample, as well as establishing some correlation with the OSL and TL centers. Measurements of single grain dating showed an unexpected behavior. This result could be an evidence that the centers responsible for TL and OSL are not the same. Ages obtained by OSL depend only on the grain having greater intensity, on the other hand, ages obtained by TL depend on the contribution of multiple grains. The XRD measurements carried out at LNLS confirmed that all the separated grains were quartz grains, although different grains produced different OSL emission, suggesting that these properties are related to different intrinsic point defects and impurities in the grains. EPR signals were measured for quartz grains, using microwave power of 0.161 mW. It was able to isolate the signal of the E\'1-center. This signal is known to increase from 120 to 300 ºC and decreases by treatment beyond 300 ºC up to 450 ºC and may be related to the TL peaks at high temperatures. ESR measurements at 77 K showed the presence of Al centers. Annual Dose values were found to be between 0.7 to 3.0 mGy/year, and for some profiles the values were more constant (Location B: 1.77 to 1.95 mGy/year). The ages obtained by OSL and TL by MAR protocol are quite similar, although those obtained by OSL usually are somewhat smaller than the ages obtained by TL. The stratigraphic depths of sediments are directly proportional to the ages obtained. The three ages of the second profile are within the Pleistocene, since the other profiles show ages starting in the Late Pleistocene to Holocene.

A forma isomórfica predominante nos biominerais (casca de ostra, coral, madrepérola e concha) estudados foi a aragonita. Contudo, o surgimento da fase calcita deu-se à temperatura de 500°C a uma taxa de aquecimento de 10°C/s para todas as amostras; e para a amostra de coral, à temperatura de 400°C, independente da taxa de aquecimento. O elemento mais abundante nas amostras de biominerais foi o Ca na forma de CaO e para os silicatos (tremolita, diopsídio e rodonita), o Si na forma de SiO. O elemento traço mais presente nas amostras de biominerais foi o Fe. A análise de ressonância paramagnética eletrônica mostrou as linhas de Mn2+ nas amostras de coral e madrepérola, antes da irradiação. Para amostras irradiadas, os defeitos encontrados foram os radicais CO2-, CO33-, CO3-, SO2-, SO3-, e num intervalo de g entre 2,0010 e 2,0062. Na análise por absorção óptica dos biominerais foram encontradas transições devido à presença de Mn nas amostras. Foi observado um pico termoluminescente (TL) em aproximadamente 140°C para os biominerais e em 180°C para os silicatos, cuja intensidade depende diretamente da dose. Para amostras expostas a diferentes tipos de radiações, o pico TL ocorre em temperaturas mais baixas. Para as curvas dose-resposta obtidas para esses materiais, foi possível determinar um intervalo de linearidade para o qual a sua aplicação em dosimetria de doses altas se torna possível. Levando-se em consideração o tipo de radiação, dentre os biominerais e os silicatos, obteve-se a menor dose detectável (40mGy), para a radiação gama em amostra de casca de ostra utilizando-se a técnica de medição de luminescência opticamente estimulada (LOE). Para radiação beta, as amostras de tremolita e diopsídio obtiveram a menor dose detectável (60mGy). No geral, obteve-se uma boa reprodutibilidade para as amostras, utilizando-se as técnicas TL, LOE e emissão exoeletrônica termicamente estimulada (TSEE) para as radiações alfa, beta e gama. Portanto, pode-se concluir que as amostras caracterizadas neste trabalho podem ser utilizadas como detectores/dosímetros de doses altas. / The predominant isomorphous form in the biominerals studied in this work (oyster shell, coral, mother of pearl and shell) was aragonite. The appearence of the calcite phase occurred at 500°C at a heating rate of 10°C/s for all samples except for the coral sample, which was 400°C, independent of the heating rate. The most abundant element in the biominerals samples was Ca in the CaO form, and in the silicates (tremolite, diopside and rhodonite) Si in the SiO form. The most common trace element observed in the biominerals samples was Fe. The analyses of electron paramagnetic resonance showed lines of Mn2+ in the coral and mother-of-pearl samples before irradiation. In the case of the irradiated samples, the defects found were CO2-, CO33-, CO3- and SO2-, in the g range between 2.0010 and 2.0062. In the analyses by optical absorption of biominerals, transitions due to the presence of Mn in the samples were found. A thermoluminescent (TL) peak at approximately 140°C was found for the biominerals and at 180°C for silicates, which intensity depends directly on the dose. For samples exposed to different types of radiation, the TL peak occurred at lower temperatures. From the dose-response curves obtained for these materials, it was possible to determine a linear range for which their application in high dose dosimetry becomes possible. Taking into account the radiation type, among biominerals and silicates, the lowest detectable dose (40mGy) to gamma radiation was achieved for oyster shell samples using the measuring technique of optically stimulated luminescence (OSL). Using beta radiation, for diopside and tremolite samples the lowest detectable dose of 60mGy was obtained. For all samples, using the TL, OSL and thermally stimulated exoelectron emission (TSEE) techniques in alpha, beta and gamma radiation beans a good response reproducibility was obtained. Therefore, the samples characterized in this work are suitable to be used as high dose detectors/dosimeters.