In a nuclear reactor, in case of a severe accident occurs, backup circuits are usedlike SIS and CSS, flooding the reactor with water. This might lead to many liquidleakages outside the reactor containment building. These leakages contain a lot offission products and especially iodine that is dangerous in terms of radiotoxicity oncereleased into the environment. Therefore, it is necessary to model correctly the liquidleakage in a reactor to size their impact properly. Their re-injection with a newpump implemented as part of the safety review for the extension lifetime of reactorsbeyond 40 years constitutes also a safety improvement to reduce the source term inthe environment.Modelling the transfer of fission products through liquid leakage and the re-injectionof said leakages is performed at IRSN with the ASTEC code. This thesis focuses onthe optimization of this model, and the consequences of modification in the code forfission products. Indeed, the model of pump used for leakages and re-injection hadsome issues that had to be circumvented.Also, the efficiency of re-injection will be tested with the new model, knowing thatthis implementation has already been proven to be effective in reducing releases tothe environment. Besides, this thesis studies the failure of the reinjection of liquidleaks that can lead to an accumulation of fission products in the auxiliary safeguardingbuilding. Other pH sensitivities in different areas are also studied. / Om en allvarlig olycka inträffar i en kärnreaktor används reservkretsar som SISoch CSS för att översvämma reaktorn med vatten. Detta kan leda till mångavätskeläckage utanför reaktorns inneslutningsbyggnad. Dessa läckage innehållermycket fissionsprodukter och särskilt jod som är farligt i form av radiotoxicitet när detsläpps ut i miljön. Det är därför nödvändigt att modellera vätskeläckage i en reaktorpå ett korrekt sätt för att kunna bedöma konsekvenserna. Återinsprutning med en nypump som genomförs som en del av säkerhetsöversynen för att förlänga reaktorernaslivslängd till mer än 40 år utgör också en säkerhetsförbättring för att minska källan imiljön.Modellering av överföringen av fissionsprodukter genomvätskeutsläpp och återinjektion av dessa läckage utförs vid IRSN med ASTEC-koden.Denna avhandling är inriktad på optimering av denna modell och konsekvenserna avändringar i koden för fissionsprodukter. Den pumpmodell som används för läckageoch återinjektion hade nämligen vissa problem som måste kringgås.Effektiviteten av återinsprutningen kommer också att testas med den nya modellen,eftersom det redan har visat sig att denna implementering är effektiv när detgäller att minska utsläppen till miljön. Dessutom studeras i denna avhandlingmisslyckandet med återinjektion av vätskeläckage som kan leda till en ackumuleringav fissionsprodukter i den extra säkerhetsbyggnaden. Andra pH-känsligheter i olikaområden studeras också.

The author discusses the difficulties that arise with the determination of the concentration of the iodinated contrast agents in the blood stream via the traditional gray-scale computer tomography and searches for the new imaging modalities that would provide for better sensitivity. The topic of the energy-discriminative color CT is discussed as a potential solution and its suitability is evaluated by performing the experiments on the contrast materials phantom and the phantom containing the iohexol solutions of varying concentrations on the original CT system assembled by the author. A method of the effective atomic number mapping is discussed as a viable alternative to the traditional attenuation-based tomography. The dependency of the effective atomic number of the compound on the energy of the x-ray beam is a phenomenon well recorded in the literature, yet no formal study exists to correctly predict the effective atomic number for a given compound. An extensive physical model is developed based on the previously presented models and adaptations unique to the task in order to determine the effective atomic numbers for exact energies experimentally. The method is tested on different materials. The resultant effective atomic numbers for the water, oil, and iohexol-water solutions of varying concentrations are presented in the study. The effects of the k-edge on both the linear attenuation curve and the effective atomic number curve are discussed. The possible future venues of the research are presented in the final part of the thesis. / Master of Science

When a pressurized water reactor is operated for a sufficiently long period of time, a small number of fuel rods will develop ruptures in their claddings. These defects will leak volatile fission products into the primary coolant, including radioactive iodine. During steady-state operation of the reactor a low level iodine activity is thus present in the coolant. Initiation of a down-power or up-power transient will result in a rapid climb in the activity of the iodine which peaks at a level much higher than the initial activity. After this time the activity levels out and then slowly begins to decay back to a new steady-state level. This phenomenon is termed "iodine spiking.” A physical model of this process is sought for explanatory and predictive purposes. A FORTRAN code is developed that solves a system of differential equations which describe the production and removal of iodine in the fuel, gap region, and primary coolant. As much physics as possible is employed but some complicated diffusion processes have led to the utilization of certain parametric results obtained from empirical data. Actual PWR spiking data is also employed for comparison and adjustment of the model. It is the goal of this project to be able to utilize the model for predictive analysis· during actual PWR operation so that a better understanding of iodine spiking behavior can be obtained. / Master of Science

Abordaram-se diversos aspectos da reação de contração de álcoois homoalílicos promovida por trinitrato de tálio (TTN). A configuração relativa do indano obtido como produto foi estabelecida graças a uma difratometria de raio-x de seu derivado sólido, possibilitando a elaboração de um mecanismo detalhado desta transformação. As reações de contração de anel de alquenóis secundários e terciários com TTN produzem indanos em 33-65%. Por outro lado, os 3-alquenóis terciários que possuem uma metila a mais em posição alílica conduzem a produtos oriundos de uma reação de fragmentação em 51-69%, com a perda de uma molécula de acetona. Álcoois homoalílicos primários, ao reagirem com iodo ou iodo hipervalente, sofrem uma reação de fragmentação, formando formaldeído, que sofre uma ciclização de Prins com o substrato, produzindo hexahidro- benzo-isocromenos em 26-48%. No caso da reação com iodo, parte do substrato sofre também uma ciclização 5-endo-trig seguida de aromatização, levando a um di-hidro-naftofurano em até 30% de rendimento. A ciclização de Prins de 3-alquenóis primário, secundário ou terciário com quantidades equimolares de aldeídos - aromáticos ou alifáticos - ou cetonas alifáticas catalisada por 5 mol% de iodo pode ser alcançada em rendimentos de 54-82%. Estas reações foram efetuadas em condições brandas e não anidras. Esta metodologia foi expandida para a preparação de uma hexa-hidro-benzo-isoquinolina à partir de uma tosilamida homoalílica, em 60% de rendimento. Um método simples e eficiente para a 2,2-dicloração de 1-tetralonas, da indanona e da benzosuberona foi desenvolvido utilizando-se água de cloro e metanol (5:1), à temperatura ambiente, em 61-90% de rendimento. A caramboxina é uma neurotoxina extraída da carambola. Sua síntese seria desejável para a confirmar sua estrutura e realizar novos ensaios biológicos. A rota sintética estudada possui, como etapa-chave, uma reação de Diels-Alder seguida de uma retro-Diels-Alder entre um éster clorotetrólico e um ciclo-hexadieno derivado da dimedona. No entanto, a síntese não pode ser concluída e um análogo ciclizado da caramboxina, uma isoquinolona, foi obtido em um rendimento global de 7%, em 10 etapas, à partir da dimedona. / Several aspects concerning the reaction of homoallylic alcohols and thallium trinitrate were addressed. The relative configuration of the indan obtained as product was established based on an x-ray diffration analysis of its solid derivative. With this information a more detailed mechanism was proposed. The ring contraction reactions of secondary and tertiary alkenols with TTN produced indans in 33-65% yield. Nevertheless, 3-alkenols bearing a methyl group on the allylic position lead to fragmentation products in 51- 69% yield, with the loss of a molecule of acetone. Treatment of primary homoallylic alcohols with iodine or hypervalent iodine leads to hexahydrobenzoisochromenes in 26-48% yield via a fragmentation reaction where formaldehyde is produced and reacts with the substrate on a Prins cyclization reaction. When iodine is used, dihydronaphtofuranes are also produced in up to 30% yield through a 5-endo-trig cyclization followed by an aromatization reaction. The Prins cyclization of 3-alkenols primary, secondary or tertiary with equimolar amounts of aldehydes - aromatic or aliphatic or aliphatic ketones catalysed by 5 mol% of iodine was accomplished in 54- 82% yield. These reactions were performed in mild and non-anhydrous conditions.This methodology was also used for the preparation of a hexahydrobenzoisoquinoline from a homoallylic tosylamide, in 60% yield. An easy and efficient method to the 2,2-dichlorination of 1-tetralones, indanone and benzosuberone was developed using household bleach and methanol (5:1), at room temperature in 61-90% Caramboxin is a neurotoxin isolated from star fruit. Its synthesis was desired to confirm its structure and perform new biological tests. The key step of the synthetic path is a Diels Alder followed by a retro-Diels Alder between a chlorotetrolic ester and a cyclohexene derived from dimedone. Unfortunately the synthesis was not concluded and a cyclized analogous of caramboxin, an isoquinoline, was obtained in 7% global yield, in 10 steps, from dimedone.

O tratamento do câncer de próstata com o implante permanente das sementes de iodo-125 cresceu expressivamente nos Estados Unidos da América nos últimos anos. A técnica também vem sendo utilizada por hospitais e clínicas particulares no Brasil. As sementes utilizadas são importadas a custos elevados, o que as tornam proibitivas para uso em hospitais públicos, pois um implante requer, pelos menos, 80 sementes. Para minimizar custos financeiros e possibilitar a distribuição para entidades de saúde pública, iniciou-se o desenvolvimento da técnica de produção das sementes no País. A soldagem a laser é uma das técnicas de selagem da semente de iodo-125, que é feita nas duas extremidades do tubo de titânio, de modo a permitir a classificação da semente como fonte selada, atendendo aos rigorosos testes estabelecidos nas normas ISO 2919 e ISO 9978. O objetivo deste trabalho foi estudar e desenvolver um sistema alternativo de soldagem a laser Nd:YAG para sementes de iodo-125, com o propósito de fornecer dados de projeto e parâmetros operacionais para implantação de uma produção rotineira automatizada no IPEN-CNEN/SP. O desenvolvimento do trabalho apresentou as seguintes fases: corte e limpeza do material (tubo de titânio), projeto, fabricação e montagem de um sistema completo automatizado para a soldagem dos tubos de titânio, determinação dos parâmetros de soldagem (feixe de laser, gás de assistência e focalização), ensaios dos corpos de prova soldados e avaliação da repetitibilidade e eficiência do sistema. O sistema de soldagem a laser desenvolvido mostrou-se eficaz em virtude do eficiente processo de automação utilizado, capaz de produzir sementes de iodo-125 com soldas de qualidade que atendem aos critérios dos severos ensaios determinados nas normas ISO 2919 e ISO 9978. / The treatment for prostate cancer by permanent implant of iodine-125 seeds has increased significantly in the United States of America in recent years. This technique has also been used by hospitals and private clinics in Brazil. The seeds used are imported at a high cost, which makes them prohibitive for use in public hospitals, since an implant requires, at least, 80 seeds. In order to reduce the financial costs and enable the distribution to public health institutions, the technique for the seeds production in the country has been developed. The laser welding is one of the possible procedures to seal the iodine-125 seeds and it will be performed in both ends of the titanium tube: this will allow the seed classification as a sealed source, meeting the rigorous assays established by the ISO 2919 and the ISO 9978 standards. The objective of this research was to study and develop an alternative Nd:YAG laser welding system for iodine-125 seeds, with the purpose of providing project data and operational parameters for the implementation of an automated routine production at IPEN-CNEN/SP. The development of this work presented the following phases: the material (titanium tube) cutting and cleaning, the project, manufacture and assembly of a complete automated system to weld the titanium tubes. The determination of the welding parameters (laser beam, shield gas and focus), the assays of the welded specimens and the evaluation of repeatability and system efficiency have, also, been carried out. The laser welding system developed showed to be efficient for the automation process used and capable of producing seeds of iodine-125 with high quality weldings, meeting the criteria for the severe assays determined by the ISO 2919 and the ISO 9978.

Abordaram-se diversos aspectos da reação de contração de álcoois homoalílicos promovida por trinitrato de tálio (TTN). A configuração relativa do indano obtido como produto foi estabelecida graças a uma difratometria de raio-x de seu derivado sólido, possibilitando a elaboração de um mecanismo detalhado desta transformação. As reações de contração de anel de alquenóis secundários e terciários com TTN produzem indanos em 33-65%. Por outro lado, os 3-alquenóis terciários que possuem uma metila a mais em posição alílica conduzem a produtos oriundos de uma reação de fragmentação em 51-69%, com a perda de uma molécula de acetona. Álcoois homoalílicos primários, ao reagirem com iodo ou iodo hipervalente, sofrem uma reação de fragmentação, formando formaldeído, que sofre uma ciclização de Prins com o substrato, produzindo hexahidro- benzo-isocromenos em 26-48%. No caso da reação com iodo, parte do substrato sofre também uma ciclização 5-endo-trig seguida de aromatização, levando a um di-hidro-naftofurano em até 30% de rendimento. A ciclização de Prins de 3-alquenóis primário, secundário ou terciário com quantidades equimolares de aldeídos - aromáticos ou alifáticos - ou cetonas alifáticas catalisada por 5 mol% de iodo pode ser alcançada em rendimentos de 54-82%. Estas reações foram efetuadas em condições brandas e não anidras. Esta metodologia foi expandida para a preparação de uma hexa-hidro-benzo-isoquinolina à partir de uma tosilamida homoalílica, em 60% de rendimento. Um método simples e eficiente para a 2,2-dicloração de 1-tetralonas, da indanona e da benzosuberona foi desenvolvido utilizando-se água de cloro e metanol (5:1), à temperatura ambiente, em 61-90% de rendimento. A caramboxina é uma neurotoxina extraída da carambola. Sua síntese seria desejável para a confirmar sua estrutura e realizar novos ensaios biológicos. A rota sintética estudada possui, como etapa-chave, uma reação de Diels-Alder seguida de uma retro-Diels-Alder entre um éster clorotetrólico e um ciclo-hexadieno derivado da dimedona. No entanto, a síntese não pode ser concluída e um análogo ciclizado da caramboxina, uma isoquinolona, foi obtido em um rendimento global de 7%, em 10 etapas, à partir da dimedona. / Several aspects concerning the reaction of homoallylic alcohols and thallium trinitrate were addressed. The relative configuration of the indan obtained as product was established based on an x-ray diffration analysis of its solid derivative. With this information a more detailed mechanism was proposed. The ring contraction reactions of secondary and tertiary alkenols with TTN produced indans in 33-65% yield. Nevertheless, 3-alkenols bearing a methyl group on the allylic position lead to fragmentation products in 51- 69% yield, with the loss of a molecule of acetone. Treatment of primary homoallylic alcohols with iodine or hypervalent iodine leads to hexahydrobenzoisochromenes in 26-48% yield via a fragmentation reaction where formaldehyde is produced and reacts with the substrate on a Prins cyclization reaction. When iodine is used, dihydronaphtofuranes are also produced in up to 30% yield through a 5-endo-trig cyclization followed by an aromatization reaction. The Prins cyclization of 3-alkenols primary, secondary or tertiary with equimolar amounts of aldehydes - aromatic or aliphatic or aliphatic ketones catalysed by 5 mol% of iodine was accomplished in 54- 82% yield. These reactions were performed in mild and non-anhydrous conditions.This methodology was also used for the preparation of a hexahydrobenzoisoquinoline from a homoallylic tosylamide, in 60% yield. An easy and efficient method to the 2,2-dichlorination of 1-tetralones, indanone and benzosuberone was developed using household bleach and methanol (5:1), at room temperature in 61-90% Caramboxin is a neurotoxin isolated from star fruit. Its synthesis was desired to confirm its structure and perform new biological tests. The key step of the synthetic path is a Diels Alder followed by a retro-Diels Alder between a chlorotetrolic ester and a cyclohexene derived from dimedone. Unfortunately the synthesis was not concluded and a cyclized analogous of caramboxin, an isoquinoline, was obtained in 7% global yield, in 10 steps, from dimedone.

<p align="justify"><i>Note des Bibliothèques :la thèse du Dr Vanderpas a été défendue en 1991 mais il n'est techniquement pas possible d'indiquer cette date dans le logiciel Bictel/e.</i></p><p><p><p align="justify"><u>Première partie</u> :Fonction thyroïdienne de la naissance à 7 ans chez les enfants d’un essai clinique de supplémentation d’huile iodée versus placebo à la femme enceinte.</p><p><p><p align="justify">L’endémie goitreuse du Nord-Congo (République démocratique, ex-Zaïre) a fait l’objet d’un programme de santé publique de prévention du goitre et du crétinisme dans le cadre du Centre d’Etudes Médicales de l’Université Libre de Bruxelles pour les actions de coopération de 1974 à 1995. Le partenaire congolais était l’Institut de Recherche Scientifique et le Bureau National des Troubles dus à la Carence Iodée.</p><p><p><p align="justify">Le présente travail s’inscrit dans ce contexte et analyse plus particulièrement la fonction thyroïdienne chez l’enfant de zéro à sept ans, dans la continuité d’un suivi d’un essai clinique pharmacologique randomisé et contrôlé (RCT, Randomised Clinical Trial) de phase 2 consistant à administrer une huile iodée (Lipiodol®) à des femmes enceintes se présentant à la maternité de Karawa. Cette cohorte de femmes enceintes a été précédemment étudiée par le Professeur Claude-Hector Thilly*.</p><p><p><p align="justify">Chez les enfants nés de mères non supplémentées en iode, l’histoire fonction thyroïdienne se caractérise comme suit :<p><li>Une fonction thyroïdienne relativement stable au ours de la première année de vie par rapport aux valeurs de TSH et de T4 sériques du sang de cordon ;les moyennes de ces marqueurs biologiques sont clairement indicateurs d’un niveau de carence iodée par rapport aux normes d’une population d’enfants belges d’âge comparable (T4 sérique abaissée et TSH sérique élevée) ;</li><p><li>Une aggravation des altérations de la TSH et de la T4 sériques au cours de la deuxième année de vie, aggravation qui se poursuit jusqu’à la quatrième année ;</li><p><li>Un maintien de marqueurs biologiques de TSH et T4 sérique fortement altérés au moins jusqu’à l’âge de 7 ans (étendue d’âge étudiée).</li></p><p><p><p align="justify">Dans cette région, le manioc est connu pour son rôle goitrogène, au travers de son contenu en glucosides cyanogènes, et il avait été précédemment démontré que le thiocyanate élevé des mères passait librement la barrière placentaire. Au cours de la première année de vie, lorsque les nourrissons sont essentiellement alimentés au sein, le thiocyanate sérique diminue fortement et se rapproche de valeurs observées chez des enfants d’autres régions non exposés au manioc. La dégradation de la fonction thyroïdienne au cours de la deuxième année de vie coïncide avec l’introduction du manioc dans l’alimentation. Pour une valeur de concentration urinaire en iode stable au cours des 7 premières années de vie, la prévalence de goitre et les variations de T4 et TSH sériques suivent celles du thiocyanate sérique. Cela est confirmé au travers d’une analyse multi-variée qui met en évidence l’association entre les valeurs moyennes de TSH et T4 et les concentrations urinaires en iode et en thiocyanate.</p> <p><p><p align="justify">L’administration intra-musculaire d’huile iodée prévient les altérations de la fonction thyroïdienne chez la mère (Thilly 1978), et cette protection s’étend chez l’enfant jusqu’à 24 mois, c’est-à-dire jusqu’à ce que l’allaitement maternel reste le principal apport nutritionnel. Au-delà de 24 mois, des altérations de la fonction thyroïdienne apparaissent chez certains de ces enfants (Elévation de la TSH et abaissement de la T4), et au-delà de 4 ans, la fréquence des altérations de la fonction thyroïdienne est aussi fréquente chez les enfants de mères traitées que chez les enfants de mères non traitées.</p><p><p><p align="justify">Au vu de la fréquence fort élevée d’altérations de la fonction thyroïdienne entre 4 et 7 ans (2/3 ont une TSH anormalement élevée > 10 mU/L), seuls certains enfants présentent les stigmates d’une hypothyroïdie prolongée depuis le début de l’existence. Il apparaît qu’il y a lieu de distinguer des hypothyroïdies juvéniles de durée, de sévérité, et de timing différents. Si l’hypothyroïdie juvénile est aussi fréquente au-delà de 4 ans dans les deux groupes de l’étude, les stigmates cliniques d’hypothyroïdie persistante sont plus fréquemment observés chez les enfants nés de mères non supplémentées en iode que chez les autres. De plus, la sévérité des stigmates cliniques (degré d’arriération mentale ;importance du retard de développement statural) démontre que l’hypothyroïdie persistante s’est installée plus précocement chez ertains enfants nés de mères non supplémentées en iode que chez les autres. Dans les formes les plus sévères, l’évolution staturale et le niveau d’intelligence de ces enfants avec hypothyroïdie persistante sont compatibles avec le tableau clinique de crétinisme myxédémateux endémique décrits chez le sujet adulte par les Professeurs François Delange et Jacques Dumont.</p><p><p><p><p align="justify"><u>Deuxième partie</u>: étude du métabolisme iodé chez les enfants hypothyroïdiens et mise en évidence de la carence combinée en iode et en sélénium.</p> <p><p><p align="justify">Certains enfants hypothyroïdiens le sont depuis longtemps (depuis la naissance, éventuellement), d’autres le sont transitoirement, sans que leur hypothyroïdie passagère ne laisse de séquelles évidentes en termes de retard statural ou d’arriération mentale.</p><p><p><p align="justify">Ceux qui sont en hypothyroïdie persistante au-delà de 4 ans ont une fonction thyroïdienne altérée :lorsqu’on leur administre de l’iode, leur glande ne répond pas à cette correction de carence iodée, et ils demeurent profondément hypothyroïdiens. Ce phénomène de non réponse à la correction de la carence iodée n’estpas observé chez les enfants hypothyroïdiens plus jeunes :cela démontre qu’il y a, chez certains enfants, une perte progressive de la capacité fonctionnelle de la thyroïde à répondre à la supplémentation iodée. Ces sujets développent le tableau clinique de crétin myxédémateux endémique.</p><p><p><p align="justify">On constate que l’hypothyroïdie juvénile recouvre un vaste spectre depuis les cas d’hypothyroïdie transitoire jusqu’aux cas d’hypothyroïdie irréversible, même après correction de la carence iodée.</p><p><p><p align="justify">Sur base d’hypothèse physiopathologique de cette perte de capacité fonctionnelle de la thyroïde chez certains jeunes enfants, il a été proposé qu’une carence combinée en iode et en sélénium pourrait expliquer ce processus. Une telle carence combinée a été décrite dans notre travail dans la région goitreuse du Nord-Congo, et pas dans d’autres régions non goitreuses du même pays ou dans d’autres endémies goitreuses avec peu de crétinisme myxédémateux endémique (Soudan, Sénégal).</p> <p><p><p align="justify"><FONT size=1>*Thilly Claude-Hector, Delange François, Lagasse Raphael, Bourdoux Pierre, Ramioul L, Berquist Helen, Ermans André-Marie. Fetal hypothyroidism and maternal thyroid status in severe endemic goiter. Journal of Clinical Endocrinology and Metabolism.</FONT></P><p><p> / Agrégation de l'enseignement supérieur, Orientation médecine / info:eu-repo/semantics/nonPublished

Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Fully exfoliated polystyrene-clay nanocomposites were prepared via free radical polymerization in dispersion polymerization, in a mixture of ethanol and water. Sodium montomorillonite clay (MMT) was pre-modified using 3-(trimethoxysilyl) propyl methacrylate (MPTMS) before being used in a dispersion polymerization process. The particles obtained were not completely stable and TEM images showed that most of the clay platelets were distributed in the dispersing phase. A second objective included, the preparation of low molecular weight of polystyrene (PS) and amphiphilic block copolymers of poly(styrene-b-2-hydroxyethyl acrylate) (PS-b-PHEA)using reverse iodine transfer polymerization (RITP) living/controlled free radical polymerization.The reaction kinetic profile of the RITP process for styrene and 2-Hydroxyethyl acrylate (HEA) was also studied. The formation of the block copolymer PS-b-PHEA was confirmed by GPC and gradient HPLC. The resulting PS-I and (PS-b-PHEA)-I were chemically modified by dimethylethylamine and triethylamine respectively, ended with PS and PS-b-PHEA has quaternary ammonium end-chain functionality (PS-cationic and (PS-b-PHEA)-cationic). The obtained functional polymers (PS-cationic) and (PS-b-PHEA)-cationic) were then grafted onto MMT via a simple ion-exchange process to offer MMT with polymer chains on the surface (PS-MMT) and (PS-b-PHEA)-MMT). Furthermore, the ability of the interaction ofPS-b-PHEA with MMT by adsorption via several functional groups was also investigated. The third objectiveincluded the use of this new class of pre-modified clay PS-MMT in the preparation of PCNs as stabilizers, the clay particles were encapsulated into PS latexes with a partially exfoliated structure at 100% CEC, upon stoppage of the polymerization process, and the final dispersion found to be stable for up to 5 wt% of clay filler loading. The thermal and thermo-mechanical properties of PS-nanocomposites were found to be dependent on both nanocomposites morphology, and clay loading. (PS-b-PHEA)-MMT was also used as stabilizers in the preparation of PS via dispersion polymerization. PS colloidal particles obtained were found to be armoured by (PS-b-PHEA)-MMT layers, with particles sizes in the micro-size range, with fair stability were obtained for clay loadings up to 5%. Analysis of the structure and thermo-mechanical properties of the resulting PCNs revealed the efficiency of the clay surface pre-modification in stabilizing the system throughout the heterophasic polymerization process.The melt flow properties of final PCNs were found to be strongly dependent on the clay loading, with shift observed from liquid-like viscoelastic to solid-like viscoelastic behaviour as the clay content increased due to percolation of the clay network within the PS matrix taking place upon film formation above Tg. / AFRIKAANSE OPSOMMING: Die eerste doelwit was die voorbereiding van ten volle geëksfolieerde polistireen-klei nanosamestellings deur vrye radikaal polimerisasie in dispersie-polimerisasie, in 'n mengsel van etanol en water. Natrium montmorilloniet klei (MMT) is gemodifiseer deur gebruik te maak van 3-(trimetoksiesiliel) propiel metakrilaat (MPTMS), voordat dit gebruik is in die dispersie-polimerisasie. Die bekomde partikels was nie heeltemal stabiel nie. Transmissie elektronmikroskopie (TEM) resultate het getoon dat die meeste van die klei plaatjies in die dispersie-fase versprei is. Die tweede doelwit was die voorbereiding van polistireen (PS) met 'n lae molekulêre massa, gevolg deur die vorming van amfifiliese blok kopolimere van poli(stireen-b-2-hidroksie-etiel akrilaat) (PS-b-PHEA) met behulp van omgekeerde jodium oordrag polimerisasie (RITP) lewendige/gekontroleerde vrye radikaal polimerisasie. Die reaksie kinetiese profiel van die RITP proses was bestudeer met betrekking tot stireen en 2-hidroksie-etiel akrilaat (HEA). Die vorming van die blok kopolimeer PS-b-PHEA is bevestig deur GPC en gradiënt HPLC. Die gevolglike PS-I en (PS-b-PHEA)-I was chemies gewysig deur onderskeidelik dimetieletielamien en trietielamien, waardeur PS en PS-b-PHEA een kwaternêre ammonium ketting-endfunksionaliteit bekom het (PS-kationies en (PS-b- PHEA)-kationies). Laasgenoemde twee funksionele polimere was toe gekoppel aan MMT deur 'n eenvoudige ioon-ruilingsproses wat MMT met polimeerkettings op die oppervlak (PS-MMT) en (PS-b-PHEA)-MMT) tot gevolg het. Die interaksie van PS-b-PHEA met MMT deur middel van adsorpsie van verskeie funksionele groepe is ook ondersoek. Die derde doel was gerig op die gebruik van hierdie nuwe klas gemodifiseerde klei PS-MMT as stabiliseerders vir die voorbereiding van polimeer-klei-nanosamestellings (PCNs). Die 100% CEC gemodifiseerde klei deeltjies is ge-inkapsuleer in die PS emulsies met 'n gedeeltelik geëksfolieërde struktuur, na afloop van die polimerisasie proses. Die finale dispersie was stabiel tot en met 'n klei inhoud van 5 wt%. Daar is gevind dat die termiese en termo-meganiese eienskappevan die PS-nanosamestellings afhanklik is van beide die morfologie en die klei inhoud. (PS-b-PHEA)-MMT was ook gebruik as stabiliseerder in die voorbereiding van PS deur dispersie polimerisasie. Daar is gevind dat die PS kolloïdale partikels wat verkry is, versterk was deur (PS-b-PHEA)-MMT lae. Partikel groottes was in die mikro-grootte gebied, en voldoende stabiliteit is verkry vir 'n klei inhoud van tot 5%. Analise van die struktuur en die termo-meganiese eienskappe van die bekomde PCNs het getoon dat die vooraf modifisering van die klei oppervlak doeltreffend was in die stabilisering van die sisteem gedurende die heterofase polimerisasie proses. Daar is ook gevind dat die smelt vloei eienskappe van die finale PCNs sterk afhang van die klei inhoud; 'n verskuiwing vanaf vloeistof-agtige viskoelastiese tot vaste-agtige viskoelastiese gedrag is waargeneem soos die klei-inhoud verhoog. Hierdie verskynsel was te danke aan perkolasie van die klei netwerk binne die PS matriks wat plaasvind tydens film vorming by 'n hoër temperatuur as die glasoorgangstemperatuur (Tg).

Thermochemical water splitting cycles have been conceptualized and researched for over half a century, yet to this day none are commercially viable. The heavily studied Sulfur-Iodine cycle has been stalled in the early development stage due to a difficult HI-H₂O separation step and material compatibility issues. In an effort to avoid the azeotropic HI-H₂O mixture, an imidazolium-based ionic liquid was used as a reaction medium instead of water. Ionic liquids were selected based on their high solubility for SO₂, I₂, and tunable miscibility with water. The initial low temperature step of the Sulfur-Iodine cycle was successfully carried out in ionic liquid reaction medium. Kinetics of the reaction were investigated by I₂ colorimetry. The reaction also evolved H₂S gas, which led to the conceptual idea of a new Sulfur-Sulfur thermochemical cycle, shown below: / 4I₂(l)+4SO₂(l)+8H₂O(l)↔4H₂SO₄(l)+ 8HI(l) / 8HI(l)+H₂SO₄(l)↔ H₂S(g)+4H₂O(l)+4I₂(l) / 3H₂SO₄(g)↔ 3H₂O(g)+3SO₂(g)+1½O₂(g) / H₂S(g)+2H₂O(g)↔ SO₂(g)+3H₂(g) / The critical step in the Sulfur-Sulfur cycle is the steam reformation of H₂S. This highly endothermic step is shown to successfully occur at temperatures in excess of 800˚C in the presence of a molybdenum catalyst. A parametric study varying the H₂O:H₂S ratio, temperature, and residence time in a simple tubular quartz reactor was carried out and Arrhenius parameters were estimated. All reactive steps of the Sulfur-Sulfur cycle have been either demonstrated previously or demonstrated in this work. A theoretical heat-to-hydrogen thermal efficiency is estimated to be 55% at a hot temperature of 1100 K and 59% at 2000 K. As a highly efficient, all-fluid based thermochemical cycle, the Sulfur-Sulfur cycle has great potential for feasible process implementation for the transformation of high quality heat to chemical energy. / Graduation date: 2012

Nosso grupo de pesquisa vem se dedicado, há vários anos, ao estudo das reações de ciclização eletrofílica de substratos insaturados que contêm um nucleófilo interno (oxigênio ou nitrogênio). Este trabalho teve como objetivo obter derivados de éteres cíclicos de cinco e seis membros diferentemente funcionalizados. Compostos 1,3-dicarbonílicos e ß-hidróxi carbonílicos, contendo dupla ligação em posição apropriada, foram submetidos à reação de ciclização mediada tanto por iodo quanto por dimetildioxirana. De maneira semelhante, ß-enamino ésteres alquenilados foram submetidos à reação de iodociclização visando à síntese de diidropirróis, pirrolidínas e tetraidroindóis. Os heterociclos funcionalizados com iodo foram submetidos à reação de desidroiodação, promovida por base, fornecendo os correspondentes produtos de eliminação. / Our research group has been studying, for several years, eletrophilic cyclization reactions of unsaturated substrates bearing internal nucleophiles such as oxygen or nitrogen. This work aimed to obtain five and six membered cyclic ether derivatives differently functionalized. 1,3-Dicarbonyl and ß-hydroxy carbonyl compounds bearing double bonds suitably positioned were submitted to cyclization reaction mediated by either iodine or dimethyldioxirane. Similarly, alkenyl substituted ß-enamino esters were also prepared and submitted to iodo-cyclization reaction leading to dihydropyrrols, to pyrrolidines or to tetrahydroindols. The heterocyclic compounds bearing iodine were submitted to the corresponding dehydroiodination reaction mediated by base, furnishing elimination products