Early complex societies developed in the Central Andes as a result of in situ processes of culture change. However, the developments commonly associated with complex societiespermanent village settlement, monumental architecture, intensive agriculture, and institutionalized stratificationwere neither uniformly nor simultaneously adopted. Rather, they appear to have been the result of different trajectories that initially were tied to changes among populations in certain circumscribed areasoften within individual valley systems. This dissertation explores the cultural and historical contexts of emerging complexity in one such areathe lower Jequetepeque Valley in northern Peru. This area encompasses several quebrada drainages and associated landforms along the lower, western flanks of the Andes, which were the focus of intensive Preceramic occupation (~11,000-4000 14C BP). The Preceramic Period correlates with the transition from the Terminal Pleistocene to the mid-Holocene, which involved changes in the local environment from cooler, wetter conditions to warmer, drier conditions that approximate the modern arid setting. Despite these deteriorating conditions, transitional late Early through Middle Preceramic (LE/M) populations (~9000-4500 14C BP) continued to occupy the project areawith some adjustments compared to their Paijanense predecessors (~11,000-9000 14C BP)based on survey and excavation data from 138 sites. These data consist of faunal remains, lithic tools and debris, hearth features, land snail middens, limited paleobotanical remains, and remnants of simple domestic structures and two possible rudimentary canals. Analyses of these data indicate that LE/M populations had intensified the localization of their settlement and subsistence patterns, and transformed their use and materialization of certain spaces to which they had become tethered. Taken collectively with evidence of Early through Middle Preceramic occupation in the nearby Zana and Chicama Valleys, the regional patterns observed among these three drainages indicate that a broad-spectrum diet, territoriality, ritualistic activities, and the separation of public and private spheres of activity preceded the adoption of intensive agriculture, socio-economic stratification, and the construction of large-scale monumental architecture, among other, more recognizable markers of cultural complexity. Further, these patterns indicate that Preceramic populations in this region actively negotiated changes in their local environment and social landscape by employing strategies of adaptational flexibility.

A maritime, rather than agricultural, foundation for civilization has been postulated for the central coast of Perú; the model has been subsequently modified in light of new evidence to include exchange with farming communities in middle valleys. A key question is what caused the sudden appearance of sites with monumental architecture before the introduction of ceramics on the central Andean coast? Recent reports call for further refinement of this hypothesis, and here we present new evidence —the finding of very ancient calendaric temples, ushnus that were observatories in the Chillón Valley. We argue that the stimulus for intensification of production of storable foods required for continued population expansion was the climate shock of the end of the Optimum Climaticum in the third millennium BC. These observatories marked dates of great practical importance for both agriculture and marine production. Astronomer priests came to manage the architecture and representational art in the Late Preceramic Chillón Valley. These powerful priests, with their own special dwellings at the site, acquired power that would have superseded the family/ayllu dimension. The complexity of the observatories at Buena Vista is without precedent in the Americas. The power guarded by those first astronomer priests may have been precariously held; an unpredicted flood could have destroyed their credibility. In any case, the ushnus at Buena Vista show that a wide variety of astronomical instruments were developed: a sighting device, the gaze of a personified figure, and the photon capturing device of a special light chamber, as well as entryway and stairwell alignments. This astronomical tradition is exhibited in a very complex stage of development by 2000 BC, at the site of Buena Vista. / Desde hace mucho tiempo, diversos investigadores han postulado un carácter marítimo, en vez de agrícola, para los orígenes de la civilización en la costa central del Perú. Este modelo ha sido subsecuentemente modificado a la luz del hallazgo de nuevas evidencias para incluir el intercambio con comunidades agrícolas establecidas en los valles medios. Una pregunta clave en relación con este tema concierne a la causa de la súbita aparición de sitios con arquitectura monumental antes de la introducción de la cerámica en la costa central andina. Los trabajos recientes reclaman mayores refinamientos para esta hipótesis, por lo que los autores presentan aquí nuevas pruebas: el hallazgo de templos calendáricos muy antiguos, un tipo de "ushnus" que sirvieron de observatorios en el valle del Chillón. Se postula aquí que el estímulo para la intensificación de la producción de alimentos factibles de almacenaje requeridos por una población en continua expansión fue la convulsión climática ocurrida a fines del Optimum Climaticum en el tercer milenio a.C. Estos observatorios marcaron fechas de gran importancia práctica tanto para la producción agrícola como marítima. De esta manera, los sacerdotes-astrónomos pasaron a administrar la arquitectura y el arte figurativo en el valle del Chillón del Periodo Precerámico Tardío. Estos poderosos individuos, que poseían viviendas especiales en el sitio, adquirieron un poder que pudo haber reemplazado la dimensión de la familia/ayllu. La complejidad de los observatorios en Buena Vista no tiene precedentes en las Américas, pero el poder ejercido por estos primeros sacerdotes-astrónomos pudo haber sido precariamente sostenido; en ese sentido, una inundación no prevista podría haber destruido su credibilidad. En todo caso, los ushnus de este complejo muestran que se desarrolló una amplia variedad de instrumentos astronómicos: un dispositivo de observación, la mirada fija de una escultura de barro con rasgos antropomorfos, un mecanismo de captura de fotones en una cámara especial, así como el alineamiento de entradas y escaleras. El despliegue de esta tradición astronómica se da en una etapa muy compleja de desarrollo hacia 2000 a.C. en el sitio de Buena Vista.

Purpose: To evaluate the tensile strength properties of Rx Naturelle Plus and Option (high-palladium) alloys on soldered connectors under simulated preceramic and postceramic soldering conditions. Materials and methods: Eighty cylindrical castings were fabricated (40 using Rx Naturelle Plus alloy and 40 using Option alloy). The 40 castings for each alloy were subdivided into 2 groups of 20 each. In the first group, castings for each alloy were randomly paired and soldered with SMG2 solder to produce 10 preceramic test connector specimens for each alloy. In the second group, castings were similarly paired and soldered with 490 fine solder to produce 10 postceramic test connector specimens for each alloy. Each solder connector was subjected to tensile force until failure using an Instron testing machine. Statistical analysis using a Wilcoxon Rank Sums Test was performed.Results: No significant difference was found between the mean connector strength for Rx Naturelle Plus preceramic solder (mean tensile failure stress, 50,000 Psi; STD, 11,250) compared to Option preceramic solder (mean tensile failure stress, 59,700.4 Psi; STD, 16,350) (p= 0.1202). However, the connector strength for Rx Naturelle Plus postceramic solder (mean tensile failure stress, 37,800 Psi; STD, 32,450) was significantly lower than the Option postceramic solder (mean tensile failure stress, 45,300 Psi; STD, 17,550) (p= 0.0407). Not only did Rx Naturelle Plus postceramic solder connectors show evidence of lower strength, but also an increased variation among specimens.Conclusions: Rx Naturelle Plus solder connectors provided better strength with the preceramic are opposed with the postceramic connectors. For postsolder connectors, Rx Naturelle Plus alloy had less acceptable strength and a wider variation, suggesting it is more technique sensitive than Option alloy connectors.

O carbeto de silício (SiC) é um material que apresenta baixa expansão térmica, altas resistências mecânica e ao choque térmico e alta condutividade térmica. Em razão disto é empregado na confecção de mobília de fornos de sinterização. O SiC no entanto sofre degradação a altas temperaturas quando submetido a atmosferas agressivas. A utilização de recobrimentos protetores evita a exposição direta da superfície do material à atmosfera dos fornos; a mulita pode ser um recobrimento protetor apropriado em razão de sua alta estabilidade em temperaturas elevadas e seu coeficiente de expansão térmica compatível com o do SiC (4x10-6/°C e 5,3x10-6/°C, respectivamente). No presente trabalho foi estudada a obtenção de recobrimento de mulita, para refratário de SiC, a partir da utilização de polímero precursor cerâmico e alumínio particulado. Foram preparadas composições com 10, 20, 30 e 50% (vol.) de alumínio adicionado ao polímero, sendo utilizados pós de alumínio de diferentes distribuições de tamanhos de partículas. As composições foram submetidas a diversos ciclos térmicos para determinação da condição mais adequada à obtenção de alto teor de mulita. A composição que apresentou melhor resultado foi a contendo 20% do pó de Al de menor tamanho de partículas. A partir desta, foi preparada e aplicada suspensão para ser aplicada sobre o refratário de SiC. A suspensão aplicada, após seca, reticulada e tratada termicamente a 1580°C, originou um recobrimento de mulita. Foram realizados ciclos de choque térmico em amostras com e sem recobrimento para comparação, num total de 26 ciclos. As condições foram 600°C/30 min. seguida de resfriamento ao ar até a temperatura ambiente. Após cada choque térmico, as amostras foram caracterizadas por microscopia óptica e eletrônica e determinado o módulo de elasticidade. Os recobrimentos apresentaram boa adesão e não foram detectados danos significativos após os choques térmicos. / Silicon carbide (SiC) presents low thermal expansion, high strength and thermal conductivity. For this reason it is used as kiln furniture for materials sintering. On the other hand, SiC degrades at high temperature under aggressive atmosphere. The use of protective coatings can avoid the right exposition of SiC surface to the furnace atmosphere. Mullite can be a suitable material as protective coating because of its high corrosion resistance and thermal expansion coefficient matching that of SiC (4,7 x10-6/°C e 5,3 x10-6/°C, respectively). In the present work a mullite coating obtained from ceramic precursor polymer and aluminium powder was studied to be applied over SiC refractories. Compositions were prepared with 10, 20, 30 and 50% (vol.) of aluminium powder added to the polymer. They were used aluminium powders with different distributions sizes These compositions were heat treated at different thermal cycles to determine a suitable condition to obtain a high mullite content. The composition with 20% of the smaller particle size Al powder was selected and used to be applied as a suspension over SiC refractory. The applied suspension, after dried, crosslinked and heat treated, formed a mullite coating over SiC refractory. Cycles of thermal shock were performed in coated and uncoated SiC samples to compare each other. They were carried out 26 cycles of thermal shock, in the following conditions: 600°C/30 min. and air cooling to room temperature. After each thermal shock, samples were analised by mean of optical and electron microscopy, elastic modulus was also determined. After thermal shock cycles the coating presented good adhesion and no significant damage were observed.

O carbeto de silício (SiC) é um material que apresenta baixa expansão térmica, altas resistências mecânica e ao choque térmico e alta condutividade térmica. Em razão disto é empregado na confecção de mobília de fornos de sinterização. O SiC no entanto sofre degradação a altas temperaturas quando submetido a atmosferas agressivas. A utilização de recobrimentos protetores evita a exposição direta da superfície do material à atmosfera dos fornos; a mulita pode ser um recobrimento protetor apropriado em razão de sua alta estabilidade em temperaturas elevadas e seu coeficiente de expansão térmica compatível com o do SiC (4x10-6/°C e 5,3x10-6/°C, respectivamente). No presente trabalho foi estudada a obtenção de recobrimento de mulita, para refratário de SiC, a partir da utilização de polímero precursor cerâmico e alumínio particulado. Foram preparadas composições com 10, 20, 30 e 50% (vol.) de alumínio adicionado ao polímero, sendo utilizados pós de alumínio de diferentes distribuições de tamanhos de partículas. As composições foram submetidas a diversos ciclos térmicos para determinação da condição mais adequada à obtenção de alto teor de mulita. A composição que apresentou melhor resultado foi a contendo 20% do pó de Al de menor tamanho de partículas. A partir desta, foi preparada e aplicada suspensão para ser aplicada sobre o refratário de SiC. A suspensão aplicada, após seca, reticulada e tratada termicamente a 1580°C, originou um recobrimento de mulita. Foram realizados ciclos de choque térmico em amostras com e sem recobrimento para comparação, num total de 26 ciclos. As condições foram 600°C/30 min. seguida de resfriamento ao ar até a temperatura ambiente. Após cada choque térmico, as amostras foram caracterizadas por microscopia óptica e eletrônica e determinado o módulo de elasticidade. Os recobrimentos apresentaram boa adesão e não foram detectados danos significativos após os choques térmicos. / Silicon carbide (SiC) presents low thermal expansion, high strength and thermal conductivity. For this reason it is used as kiln furniture for materials sintering. On the other hand, SiC degrades at high temperature under aggressive atmosphere. The use of protective coatings can avoid the right exposition of SiC surface to the furnace atmosphere. Mullite can be a suitable material as protective coating because of its high corrosion resistance and thermal expansion coefficient matching that of SiC (4,7 x10-6/°C e 5,3 x10-6/°C, respectively). In the present work a mullite coating obtained from ceramic precursor polymer and aluminium powder was studied to be applied over SiC refractories. Compositions were prepared with 10, 20, 30 and 50% (vol.) of aluminium powder added to the polymer. They were used aluminium powders with different distributions sizes These compositions were heat treated at different thermal cycles to determine a suitable condition to obtain a high mullite content. The composition with 20% of the smaller particle size Al powder was selected and used to be applied as a suspension over SiC refractory. The applied suspension, after dried, crosslinked and heat treated, formed a mullite coating over SiC refractory. Cycles of thermal shock were performed in coated and uncoated SiC samples to compare each other. They were carried out 26 cycles of thermal shock, in the following conditions: 600°C/30 min. and air cooling to room temperature. After each thermal shock, samples were analised by mean of optical and electron microscopy, elastic modulus was also determined. After thermal shock cycles the coating presented good adhesion and no significant damage were observed.

In the first part of this dissertation, poly(methylsilyne) was produced both in small and large-scales. In the small-scale, the aim was to synthesize the polymer by electrochemical polymerization of methyltrichlorosilane at a constant potential of -6 V supplied by batteries, using sodium dodecyl sulfate (SDS) as the supporting electrolyte. The polymer was characterized by 1H-NMR, FTIR, UV-Visible Spectroscopy and GPC in addition to its distinctive yellow color. The yellow color and the 1H-NMR, FTIR, UV-Visible and GPC results proved that poly(methylsilyne) was produced successfully in small-scale. In the second part of the synthesis, the objective was to scale-up the electrochemical synthesis of poly(methylsilyne) while investigating the effects of the parameters like the electrode, solvent and supporting electrolyte types, monomer/solvent ratio and reaction time on the synthesis. Although successful results were obtained in large-scale synthesis with acetonitrile and SDS, the problems with the reproducibility of the synthesis were solved using a system containing 1.2-dimethoxyethane (DME) and tetrabutylammonium perchlorate (TBAP). In the second part of the dissertation, the aim was to prepare polypropylene/silicon-based preceramic polymer blends and to characterize them in terms of flammability, thermal and mechanical properties and morphologies. In order to investigate the effect of the silicon-based preceramic polymers, two different polymers were used: poly(methylsilyne) (PMSy) and allylhydridopolycarbosilane (SMP-10) where the latter was a commercially available silicon carbide precursor. Triphenylphosphate (TPP) and a metal complex were also used in polypropylene based composites to gain a synergy with the silicon containing polymers. The polymer composites were prepared using a twin-screw extruder and molded in an injection molding machine. As a result of the flammability tests, it was seen that in order to achieve a significant decrease in the flammability of polypropylene, at least 20 wt% additive was needed. Furthermore, it was observed that the most significant improvement in flame retardancy was obtained in PP/10SMP/5TPP/5M sample containing 10 wt% SMP-10, 5 wt% TPP and 5 wt% metal complex with a limiting oxygen index (LOI) value of 23.5%. This was explained by the synergy obtained by SMP-10, TPP and the metal complex. With the addition of these silicon containing polymers, thermal properties of the composites increased to a great extent. For the mechanical properties, it was seen that impact strength of the composites significantly increased with the addition of SMP-10, PMSy and TPP.

Three archaeological cases from different areas of the Andes are employed to study the rise of social and cultural complexity in varying social and economic contexts, with the intention of distinguishing certain environmental and cultural factors in each case. The purpose also is to search not only for differences but for commonalities to be used for cross-cultural comparisons and to learn more about the developmental cultural history of the societies representing these cases. / En el presente trabajo se analizan tres casos de diferentes áreas de los Andes para estudiar el incremento de la complejidad cultural en contextos sociales y económicos variados con el fin de distinguir factores definidos de carácter ambiental y cultural en cada caso. El propósito final es el de la búsqueda de diferencias, así como de las características en común que se utilizan para hacer comparaciones culturales y para aprender más acerca de la historia del desarrollo cultural de las sociedades que representan estos ejemplos.

Les céramiques de type non-oxyde à base de silicium (SiC, Si3N4, Si-C-N) ont été très largement étudiées comme matrice dans le domaine des Composites à Matrices Céramiques (CMCs) en raison de leurs propriétés thermostructurales généralement très supérieures à celles des matériaux plus conventionnels comme les métaux et les céramiques de type oxyde. Ces matériaux proposent par ailleurs des propriétés mécaniques (dureté, résistance au fluage et à la rupture) et une résistance à l’oxydation de premier plan. Comme matrices, ils sont généralement produits en voie gazeuse par la méthode CVI (Chemical Vapor Infiltration). Dans le cadre de la présente thèse, nous nous intéressons à leur élaboration en voie liquide à travers la méthode PDCs (Polymer Derived Ceramics), qui pourra être éventuellement couplée à terme à la méthode CVI, dont la mise en œuvre est plus aisée et les coûts de production des CMCs plus faibles. L’objectif principal est de travailler la chimie de polymères précéramiques commerciaux afin, d’une part, d’optimiser les étapes d’imprégnation des préformes fibreuses et de pyrolyse des composites ‘crus’ obtenus (Polymer Infiltration and Pyrolysis (PIP)) et d’autre part d’améliorer les propriétés thermostructurales des composites SiC et Si-C-N pour un fonctionnement à des températures de l’ordre de 1500°C. Après une étude bibliographique sur la thématique abordée (chapitre 1) et un chapitre 2 dédié à la partie expérimentale et à la description des outils de caractérisation, les travaux de thèse se sont orientés dans les chapitres 3 et 4 vers la modification de polymères précéramiques commerciaux comme l’allyhydridopolycarbosilane (AHPCS, précurseur SiC) et le poly(vinylméthyl)-co-(hydridométhyl)silazane (HTT1800, précurseur Si-C-N) par l’élément bore. L’idée générale est de diminuer les températures de gélification de ces polymères tout en augmentant leur rendement céramique et d’obtenir, après pyrolyse, des céramiques amorphes de type Si-B-C-(N) avec une meilleure stabilité thermique à haute température. Dans le chapitre 5, les travaux se sont dirigés vers la préparation de mélange HTT1800-perhydridopolysilazane (PHPS, précurseur Si3N4) pour s’affranchir de la présence de carbone libre dans les matériaux finaux. Une caractérisation complète, allant de la structure chimique des polymères jusqu’à l’évolution de la microstructure des matériaux finaux traités à haute température, a été conduite dans chacun des chapitres. La fabrication de pièces denses, par la méthode dite de casting, à partir des polymères sélectionnés a permis d’accéder aux propriétés mécaniques des matériaux. Des essais préliminaires de fabrication de composites sont présentés en fin de chaque chapitre. / Non-oxide Si-based ceramics (SiC, Si3N4, Si-C-N) have been extensively studied as matrices in Fiber-Reinforced Ceramics Matrix Composites (CMCs) because of their thermostructural properties which are generally significantly higher than those displaying by more conventional materials such as metals and oxide ceramics. These materials also offer superior mechanical properties (hardness, resistance to creep and rupture) and excellent resistance toward oxidation. As a matrix, they are produced in gas phase by the well-known Chemical Vapor Infiltration (CVI) process. Within the framework of the thesis, we focus on their synthesis in liquid phase through the PDCs (Polymer Derived Ceramics) route because of its easier access and lower production cost. The main objective is to focus on the chemistry of preceramic polymers to 1) optimize each step of the PIP (Infiltration and Pyrolysis Polymer) process and 2) improve the thermostructural properties of SiC, Si-C-N matrix composites prepared from commercially-available preceramic polymers. After a state-of-the art part (Chapter 1) on the targeted topic and an experimental part completed by the description of the characterization tools (Chapter 2), the manuscript focused on the modification of commercial preceramic polymers such as allylhydridopolycarbosilane (AHPCS, SiC precursor) and poly(vinylmethyl)-co-(hydridomethyl)silazane (HTT1800, Si-C-N precursor) with boron elements. The idea behind this work was to reduce the gelification temperature of these polymers while to increase their ceramic yield. Thus, after pyrolysis, we obtain amorphous Si-B-C-(N) ceramics with better thermal stability at high temperature. This work is described in the chapters 3 and 4 of the manuscript. In chapter 5, the work concerned the preparation of polymer blends based on HTT1800 and perhydridopolysilazane (PHPS, precursor Si3N4). The idea behind the chapter 5 was to avoid the presence of free carbon in the final materials. A complete characterization, ranging from the chemical structure of the polymers to the evolution of the microstructure of the final materials, is done in each chapter. Dense pieces were prepared by the casting method from the selected polymers and their mechanical properties have been investigated. Composite materials have been also prepared to evaluate the quality of interface between the matrix and the surface of the fibers which is presented at the end of each chapter.

Les vestiges archéologiques découverts dans les Vallées centrales de Oaxaca ont permis de documenter une séquence d'occupation continue au moins depuis le début de l'Holocène. Il s'agit de l'une des régions les mieux documentées sur les périodes archaïque et préclassique du centre sud du Mexique; les connaissances sur ces périodes restent, malgré tout, encore lacunaires. D'importants processus développés au cours de l'Archaïque et du Préclassique (cf. domestication de plantes et sédentarité) ont contribué à modifier les modes de vie des individus. Dans cette thèse, nous étudions la transition entre ces deux périodes chronologiques. Ce travail s'attache à analyser le matériel lithique taillé de la fin de la période archaïque et du début du Préclassique afin de mieux caractériser les industries. À travers une approche technologique et une étude détaillée des matières premières, nous avons tenté de rapprocher les ensembles lithiques de chaque période. Les résultats nous ont permis de proposer des modalités d'exploitation et de production particulières. la mise en parallèle des données issues d'un abri rocheux précéramique avec des informations provenant de deux hameaux agricoles préclassiques nous a aidé à éclaircir certains aspects sur le contexte de production de l'outillage et sur l'emploi des matières premières minérales disponibles dans la Vallée. / Archaeological evidence from the Valley of Oaxaca has documented a continual sequence of occupation from at least the early Holocene (ca. 8000 BC). While the Valley of Oaxaca is one of the better-documented regions for the Archaic and Preclassic in southern Mexico, knowledge of these periods remains significantly incomplete. The development of plant domestication and sedentism during this time contributed to major changes in human life ways. The present research studies the transition from the Archaic to the Preclassic by characterizing chipped stone industries from both periods. I compare lithic collections from a preceramic rock shelter and from two preclassic hamlets using a technological approach and through a detailed study of the raw materials used during each period. The results allow definition of specifie modalities of exploitation of raw materials available in the valley and of contexts of stone tool production.

The objectives of this study are to synthesize poly(dimethylsilane) (PDMS) preceramic polymer and to investigate its effect on morphology, flame retardant and mechanical properties of polypropylene (PP) based composites. There are mainly two parts in this thesis. In the first part, PDMS was synthesized by electrochemical polymerization of dichlorodimethylsilane, which was dissolved in 1,2 dimethoxyethane (DME) solvent consisting of tetrabutyl ammonium perchlorate (TBAP), as supporting electrolyte. PDMS was obtained in powder form and characterized with Fourier transform infrared, ultraviolet-visible and proton nuclear magnetic resonance spectroscopic analyses, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Since PDMS has some impurities coming from TBAP and DME, alternatively, the PDMS synthesis was done by electrochemical reduction of dichlorodimethylsilane without using solvent and/or supporting electrolyte for seven days. PDMS was produced as pure and characterized with the same methods used for previous synthesis. In the second part of this thesis, PP based composites with additives were prepared by using a twin-screw extruder and injection molding machine and were characterized with limiting oxygen index (LOI), horizontal burning, TGA, differential scanning calorimetry (DSC), tensile and impact tests and SEM analysis. Triphenyl phosphate, boron phosphate, magnesium hydroxide, intumescent flame retardants (IFR) (melamine phosphate (MP) and pentaerythritol (PER)), antimony trioxide and poly(methylsilsesquioxane) were additives used in this study other than PDMS. According to LOI test results, the highest LOI value among the PDMS composites was obtained in 1% PDMS, 14.25% MP and 4.75% PER (w/w) containing composite as 24%, whereas the LOI value of neat PP was measured as 17.5%. It was determined that elastic moduli of all the composites studied were higher than neat PP.