O trabalho foi conduzido na EEA-UFRGS, em Eldorado do Sul/RS, entre dez/2011 e nov/2013 com o objetivo de estudar o efeito da estrutura do pasto no consumo de matéria seca e na emissão de metano e relacionar essa emissão com o desempenho animal em pastagem nativa submetida a níveis de oferta diária de forragem de 4, 8, 8.12, 12 e 16 kg de MS/100 kg de PV, ou %PV. Esses tratamentos foram distribuídos num delineamento experimental de blocos com duas repetições. Em pastoreio contínuo foram utilizadas novilhas mestiças com 24 meses de idade e 223 ± 24 kg em 2012 e 12 meses e 274 ± 17 kg em 2013 quando da entrada dos animais no protocolo experimental. As variáveis para descrever a estrutura do pasto foram: massa de forragem, taxa de acúmulo de forragem, altura do pasto e frequência de touceiras. Na avaliação de consumo de matéria seca utilizou-se a técnica dos n-alcanos a partir da teoria do duplo n-alcano. As emissões de metano foram estimadas pela técnica do marcador hexafluoreto de enxofre. Foi utilizado o delineamento experimental de blocos com duas repetições. As ofertas 4 e 8% emitiram menores quantidades de CH4/animal que as ofertas de forragem 16, 12 e 8.12% do PV. Os modelos estudados demonstraram que a variabilidade das emissões é explicada, em maior proporção, pelo conjunto de estrutura do pasto (R2=0.53), e que a relação entre emissão de CH4 e consumo de matéria seca foi altamente significativa (P<0.001), porém o consumo explicou a variância dos dados em proporção limitada (R2= 0.20). Anualmente a emissão de CH4 foi determinada por mudanças no consumo e na estrutura do pasto, principalmente, na taxa de acúmulo de forragem. Com baixa taxa de acúmulo, principalmente no inverno, há maior gasto de energia para realização da metanogênese. A relação observada entre a quantidade de CH4 emitido por kg de MS consumida em função do consumo diário de MS apresentou comportamento inversamente proporcional. O aumento da OF até níveis moderados de intensidade de pastejo proporcionam maiores GPV e maiores emissões de CH4 por animal que oferta de forragem baixa. Porém as ofertas de forragens alta e moderadas (16,12 e 8.12 ) emitiram menor quantidade de metano por área e por kg de peso vivo produzido. Portanto a busca por estruturas de pasto ideal através de manejos com intensidades de pastejo moderadas aliada a altas taxas de acúmulo do pasto, formam ambientes de pastejos na qual os bovinos mitigam metano por kg de MS consumida, por ha e por kg de PV produzido. / The study was conducted at the EEA-UFRGS, in Eldorado do Sul/ RS, from Dec/2011 to Nov/2013 in order to study the effect of the structure and dry matter intake in methane emissions and relate that to animal performance in native grassland. The treatments consisted of the following forage allowance levels: 4, 8, 8:12, 12 and16 kg DM / 100 kg live weight (LW), or % LW. The animal testers were crossbred heifers with 24 months of age and 223 ± 24 kg in 2012 and 12 months and 274 ± 17 kg in 2013 when the entry of animals in the experimental protocol. The variables to describe the pasture structure were: herbage mass, herbage accumulation rate, pasture height and frequency of tussocks. For the dry matter intake evaluation, it was used the technique of nalkanes technique based on the double alkane teory. Methane emissions were measured by the sulfur hexafluoride tracer technique. The experimental design was a randomized block design with two replications (paddocks) was used. The 4 and 8% LW herbage allowance treatments emited less CH4/animal than 16, 12 and 12.8% LW. The models showed that the variability of the emission is explained in a greater proportion, the set of pasture structure (R2 = 0,53), and that the relationship between emission of methane emission and dry matter intake was highly significant (P <0.001). On the other hand, consumption explained a smaller amount of the data variance (R2 = 0.20). Annuall methane emission was determined by changes in herbage consumption and sward structure, mainly herbage accumulation rate. With low herbage accumulation rate, especially in winter, there was a greater, waste of energy for methanogenesis. There was an inverse relationship between the amount of methane emitted per kg dry matter intake as a function of daily dry matter consumption. Increasing herbage allowance to moderate grazing intensity levels resulted in a greater LW gain and also higher CH4 emission per animal. However, high to moderate herbage allowance tratments (16, 12 and 8-12) emited less methane per area and per kg of LW produced. Managing native grasslands under moderate levels of herbage allowance can creat canopy strutures that favor both consumption and herbage accumulation rate, and also mitigate beff cattle methane emissions per kg of DM, per area and per kg LW produced.

O trabalho foi conduzido na EEA-UFRGS, em Eldorado do Sul/RS, entre dez/2011 e nov/2013 com o objetivo de estudar o efeito da estrutura do pasto no consumo de matéria seca e na emissão de metano e relacionar essa emissão com o desempenho animal em pastagem nativa submetida a níveis de oferta diária de forragem de 4, 8, 8.12, 12 e 16 kg de MS/100 kg de PV, ou %PV. Esses tratamentos foram distribuídos num delineamento experimental de blocos com duas repetições. Em pastoreio contínuo foram utilizadas novilhas mestiças com 24 meses de idade e 223 ± 24 kg em 2012 e 12 meses e 274 ± 17 kg em 2013 quando da entrada dos animais no protocolo experimental. As variáveis para descrever a estrutura do pasto foram: massa de forragem, taxa de acúmulo de forragem, altura do pasto e frequência de touceiras. Na avaliação de consumo de matéria seca utilizou-se a técnica dos n-alcanos a partir da teoria do duplo n-alcano. As emissões de metano foram estimadas pela técnica do marcador hexafluoreto de enxofre. Foi utilizado o delineamento experimental de blocos com duas repetições. As ofertas 4 e 8% emitiram menores quantidades de CH4/animal que as ofertas de forragem 16, 12 e 8.12% do PV. Os modelos estudados demonstraram que a variabilidade das emissões é explicada, em maior proporção, pelo conjunto de estrutura do pasto (R2=0.53), e que a relação entre emissão de CH4 e consumo de matéria seca foi altamente significativa (P<0.001), porém o consumo explicou a variância dos dados em proporção limitada (R2= 0.20). Anualmente a emissão de CH4 foi determinada por mudanças no consumo e na estrutura do pasto, principalmente, na taxa de acúmulo de forragem. Com baixa taxa de acúmulo, principalmente no inverno, há maior gasto de energia para realização da metanogênese. A relação observada entre a quantidade de CH4 emitido por kg de MS consumida em função do consumo diário de MS apresentou comportamento inversamente proporcional. O aumento da OF até níveis moderados de intensidade de pastejo proporcionam maiores GPV e maiores emissões de CH4 por animal que oferta de forragem baixa. Porém as ofertas de forragens alta e moderadas (16,12 e 8.12 ) emitiram menor quantidade de metano por área e por kg de peso vivo produzido. Portanto a busca por estruturas de pasto ideal através de manejos com intensidades de pastejo moderadas aliada a altas taxas de acúmulo do pasto, formam ambientes de pastejos na qual os bovinos mitigam metano por kg de MS consumida, por ha e por kg de PV produzido. / The study was conducted at the EEA-UFRGS, in Eldorado do Sul/ RS, from Dec/2011 to Nov/2013 in order to study the effect of the structure and dry matter intake in methane emissions and relate that to animal performance in native grassland. The treatments consisted of the following forage allowance levels: 4, 8, 8:12, 12 and16 kg DM / 100 kg live weight (LW), or % LW. The animal testers were crossbred heifers with 24 months of age and 223 ± 24 kg in 2012 and 12 months and 274 ± 17 kg in 2013 when the entry of animals in the experimental protocol. The variables to describe the pasture structure were: herbage mass, herbage accumulation rate, pasture height and frequency of tussocks. For the dry matter intake evaluation, it was used the technique of nalkanes technique based on the double alkane teory. Methane emissions were measured by the sulfur hexafluoride tracer technique. The experimental design was a randomized block design with two replications (paddocks) was used. The 4 and 8% LW herbage allowance treatments emited less CH4/animal than 16, 12 and 12.8% LW. The models showed that the variability of the emission is explained in a greater proportion, the set of pasture structure (R2 = 0,53), and that the relationship between emission of methane emission and dry matter intake was highly significant (P <0.001). On the other hand, consumption explained a smaller amount of the data variance (R2 = 0.20). Annuall methane emission was determined by changes in herbage consumption and sward structure, mainly herbage accumulation rate. With low herbage accumulation rate, especially in winter, there was a greater, waste of energy for methanogenesis. There was an inverse relationship between the amount of methane emitted per kg dry matter intake as a function of daily dry matter consumption. Increasing herbage allowance to moderate grazing intensity levels resulted in a greater LW gain and also higher CH4 emission per animal. However, high to moderate herbage allowance tratments (16, 12 and 8-12) emited less methane per area and per kg of LW produced. Managing native grasslands under moderate levels of herbage allowance can creat canopy strutures that favor both consumption and herbage accumulation rate, and also mitigate beff cattle methane emissions per kg of DM, per area and per kg LW produced.

Palladium-catalyzed reactions for carbon-carbon bond formation have had a significant impact on the field of organic chemistry in recent decades. Illustrative is the 2010 Nobel Prize, awarded for “palladium-catalyzed cross couplings in organic synthesis”, and the numerous applications of these transformations in industrial settings. This thesis describes recent developments in C(sp2)-C(sp3) bond formation, focusing on alkane arylation reactions and arylative dearomatization transformations. In the first part, our contributions to the development of intramolecular C(sp3)-H arylation reactions from aryl chlorides are described (Chapter 2). The use of catalytic quantities of pivalic acid was found to be crucial to observe the desired reactivity. The reactions are highly chemoselective for arylation at primary aliphatic C-H bonds. Theoretical calculations revealed that C-H bond cleavage is facilitated by the formation of an agostic interaction between the palladium centre and a geminal C-H bond. In the following section, the development of an alkane arylation reaction adjacent to amides and sulfonamides is presented (Chapter 3). The mechanism of C(sp3)-H bond cleavage in alkane arylation reactions is also addressed through an in-depth experimental and theoretical mechanistic study. The isolation and characterization of an intermediate in the catalytic cycle, the evaluation of the roles of both carbonate and pivalate bases in reaction mechanism as well as kinetic studies are reported. Our serendipitous discovery of an arylation reaction at cyclopropane methylene C-H bonds is discussed in Chapter 4. Reaction conditions for the conversion of cyclopropylanilines to quinolines/tetrahydroquinolines via one-pot palladium(0)-catalyzed C(sp3)-H arylation with subsequent oxidation/reduction are described. Initial studies are also presented, which suggest that this transformation is mechanistically unique from other Pd catalyzed cyclopropane ring-opening reactions. Preliminary investigations towards the development of an asymmetric alkane arylation reaction are highlighted in Chapter 5. Both chiral carboxylic acid additives and phosphine ligands have been examined in this context. While high yields and enantiomeric excesses were never observed, encouraging results have been obtained and are supported by recent reports from other research groups. Finally, in part two, the use of Pd(0)-catalysis for the intramolecular arylative dearomatization of phenols is presented (Chapter 7). These reactions generate spirocyclohexadienones bearing all-carbon quaternary centres in good to excellent yields. The nature of the base, although not well understood, appears to be crucial for this transformation. Preliminary results in the development of an enantioselective variant of this transformation demonstrate the influence of catalyst activation on levels of enantiomeric excess.

The general objective of this thesis is the analysis of selective reactions for group VI grafted metal complexes via methods and principles of SOMC. For this objective, three approaches have been chosen. The first chapter is an introduction to the topic of selectivity in catalysis, emphasizing heterogeneous catalysis and more specifically the different approaches to support catalysts on surfaces. The concept of catalysis by design is introduced as a new way to use the surface as a ligand. Chapter 2 presents the results of a library of well-defined catalysts of group VI with identical catalytic functionality, but different ligand environment. The results reveal, that metal-carbynes are able to switch their catalytic reactivity based on the substrate that they are contacted with. The difference in reaction mechanisms and the differing reactivities towards the substrates are presented. It can be concluded that the classical ROMP is selectively achieved with cyclic alkene substrates leading to polymers whereas cyclic alkanes yield exclusively higher and lower homologues of the substrate without polymeric products. Chapter 3 presents the study of olefin metathesis of cis-2-pentene with metal-carbynes of group VI, where the selectivity of the catalyst library towards yield of cis-/trans products is analyzed. It is presented, that the ligand environment of the catalysts is showing an influence in the selectivity. Rates of cis/trans isomerization of the products are high and are approaching thermodynamic equilibrium at high conversion. Product isomerization, thermodynamic equilibrium and reactivity differences between liquid phase and gas phase products are analyzed. Chapter 4 presents the full characterization of tungsten-hydrides by selective transformation into tungsten-hydroxides. These newly discovered well-defined tungstenhydroxides are fully characterized by ICP, TEM, DRIFT, double quantum and triple quantum solid-state NMR. The presented results allow to predict that tungsten-hydrides on KCC-1700 are present as two distinct species. Catalysis results with cyclooctane show, that due to burial of the complexes in the KCC-1700 surface the tungsten-hydrides are less active towards cyclic alkane metathesis reactions with bulky cyclooctane than the metalcarbyne complexes. Chapter 5 is giving a conclusion of results and an outlook for catalytic applications of the generated tungsten-hydroxides of chapter 4.

The fact that hydrogen is a clean and versatile fuel offers an attractive carbon-free source of energy and leverages the U.S. economy toward long-term sustainable economic growth. At an industrial scale, hydrogen production is mostly relying on methane steam reforming producing stoichiometric amounts of carbon oxides (CO and CO2), which imposes economic and environmental concerns. To mitigate the issue, we propose NH3 assisted anaerobic reforming of natural gas liquids (ethane and propane) as an alternative approach to produce COx free hydrogen. Here, in the first chapter, through comprehensive performance evaluation, characterization, and transient kinetic studies, it is shown that the atomically dispersed Re-oxo grafted into framework Al of the HZSM-5 zeolite are highly active and stable for the ammonia reforming of ethane and propane at temperatures comparable to steam reforming ≤ 650 °C. In the second chapter, an alternative non- noble Ni/Ga intermetallic compound (IMC) with various Ni to Ga ratios is synthesized through the solvothermal synthesis by forming the oxalate MOF precursor. The result indicates that while Ni-rich samples form pure Ni3Ga IMC with promising catalytic performance, the Ga rich catalyst consists of segregated phases of Ni/Ga IMC and Ga2O3 with ill-defined structure showing lower stability despite the high activity. In chapter 3, a bifunctional Ni/Ga supported ZSM-5 is successfully developed in ethane aromatization. Influence of metal function in early-stage and steady-state activity and stability as well as structure reactivity relation was investigated applying comprehensive characterization, performance test, deactivation modeling, and transient studies. The results suggest that a tandem reaction mechanism between Ni3Ga intermetallic compound, Ga cation, and Bronsted acid sites of zeolite is responsible for the superior performance of bimetallic catalysts compared to their monometallic counterpart. In the last chapter, applying transient kinetic technique, the mechanism of ethane aromatization over Pt and Zn supported ZSM-5 model catalysts was precisely explored. The results reveal that despite mechanistic differences between these catalysts, ethane amortization on both catalysts follows a hydrocarbon pool mechanism.

京都大学 / 新制・課程博士 / 博士(農学) / 甲第24671号 / 農博第2554号 / 新制||農||1099(附属図書館) / 学位論文||R5||N5452(農学部図書室) / 京都大学大学院農学研究科応用生命科学専攻 / (主査)教授 小川 順, 教授 阪井 康能, 教授 白井 理 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

En milieu marin le carbone organique particulaire (POC) représente 25 % du carbone organique total. Sa dégradation est réalisée par des microorganismes hétérotrophes ayant mis en place diverses stratégies pour parvenir à le dissoudre et l’assimiler. Peu d’études se sont intéressées à la dégradation des composés polymériques et/ou hydrophobes, quasiment insolubles dans l’eau constituant le POC. Parmi ces composés, on retrouve les lipides et les hydrocarbures regroupés sous le terme de COH (composés organiques hydrophobes). La dégradation des COH est réalisée par des bactéries dîtes oléolytiques ayant entre autre pour stratégie la formation de biofilms également qualifiés d’oléolytique. Nos connaissances sur la diversité et la fonctionnalité des biofilms oléolytiques se limitent actuellement aux bactéries spécifiquement étudiées pour leur capacité à dégrader les HC. Ainsi la dégradation des lipides est souvent négligée alors que cette famille de molécules représente une part significative du POC.La diversité taxonomique des bactéries formant des biofilms oléolytiques a été déterminée par un criblage de 199 souches marines sur 4 substrats : un alcane (paraffine), un triglycéride (tristéarine), un acide gras (acide palmitique) et une cire (l’hexadécyl palmitate). Cette étude a révélé que les bactéries oléolytiques (formant un biofilm sur au moins 1 des substrats) sont relativement répandues parmi les bactéries marines puisque qu’elles représentent 18.7 % des souches testée. Cette étude montre également que les bactéries capables d’assimiler les alcanes sont également capables d’assimiler au moins un lipide. Les bactéries hydrocarbonoclastes, jusqu’alors décrites comme spécialisées, voir restreintes à l’assimilation des hydrocarbures, présentent donc une gamme de substrats s’étendant aux lipides. La corrélation positive entre la capacité d’assimilation des alcanes et l’assimilation des lipides suggère un lien physiologique entre l’assimilation de ces deux familles de COH. L’activité lipase qui est essentielle à l’assimilation des triglycérides mais pas à l’assimilation des alcanes, a été mesurée dans des cultures de souches oléolytiques poussant sur acétate, triglycéride ou hexadécane. Comme attendu, les cultures sur triglycérides montrent toutes une surexpression de l’activité lipases par rapport aux cultures sur acétate. Les cultures sur hexadécane montraient aussi une surexpression de l’activité lipase renforçant l’idée d’un lien physiologique entre dégradation des alcanes et dégradation des lipides. De plus les souches oléolytiques n’ont pas montré de capacité à former un biofilm sur une surface inerte hydrophobe telle que le polystyrène ou sur une surface hydrophile telle que le verre à la hauteur de celles constaté sur COH. Une étude quantitative de l’adhésion sur COH et substrats inertes réalisée par microscopie montre que l’adhésion (dans les conditions testées) n’est pas un facteur déterminant de la formation de biofilm sur ces mêmes substrats. Cela suggère que la spécificité de formation de biofilm sur les substrats COH, ne réside pas dans l’adhésion mais vraisemblablement dans les étapes de développement du biofilm plus tardives.Enfin, les biofilms oléolytiques mettant en jeux des produits extracellulaires (enzymes et facteurs de solubilisation) qui constituent des biens communs, sont propices à l’établissement de comportements sociaux. Nous avons mis en évidence des comportements synergiques (5/8 des comportements observés) ou compétitifs au sein de biofilm oléolytiques (3/8 des comportements observés). / Particulate organic carbon (POC), in marine environment, accounts for 25% of total organic carbon. POC degradation is carried out by heterotrophic microorganisms which have developed strategies to dissolve and assimilate it. Few studies have investigated the degradation of the polymeric and / or hydrophobic components of POC, which are almost insoluble in the water. Among these compounds, there are lipids and hydrocarbons (HC) grouped under the term of HOCs (hydrophobic organic compounds). The degradation of the HOCs is carried out by oleolytic bacteria which form biofilms at the HOC– water interface. Our knowledge of the diversity and functionality of oleolytic biofilms is mostly limited to HC degrading bacteria, while the degradation of lipids is often neglected although this family of molecules represents a significant part of the POC. A screening of 199 marine strains on 4 substrates: an alkane (paraffin), a triglyceride (tristearin), a fatty acid (palmitic acid) and a wax ester (hexadecyl palmitate) was performed to determine the taxonomic diversity of bacteria able to form oleolytic biofilms. This study revealed that oleolytic bacteria (forming a biofilm on at least 1 substrate) were relatively widespread among marine bacteria since they represented 18.7% of tested strains. This study also showed that bacteria able to assimilate alkanes were also able to assimilate at least one lipid. Hydrocarbonoclastic bacteria, previously described as specialized, or restricted to the assimilation of hydrocarbons, have actually a substrate range spanning from HC to lipids. The positive correlation between the ability to form a biofilm on alkanes and on lipids suggested a physiological link between the assimilation of these two HOC families. The lipase activity, which is essential for triglycerdides assimilation but not for the alkanes assimilation, was measured in oleolytic strains cultures growing on acetate, triglyceride or hexadecane. As expected, overexpression of lipase activity was observed in cultures on triglycerides compared to cultures on acetate. Moreover, overexpression of lipase activity was also observed in cultures on hexadecane reinforcing the idea of a physiological link between alkanes and lipids degradation.Oleolytic strains exhibited a very weak ability to form a biofilm on the inert surfaces (non-nutritive) polystyrene or glass compared to the HOC nutritive surface indicating that oleolytic strains have a specificity for HOC to form a biofilm. A quantitative study of adhesion on HOC and inert substratums carried out by microscopy shows that adhesion (in the tested conditions) is not a determining factor of the biofilm formation on these same substrates. This suggests that the specificity of biofilm formation on HOC substrates does not reside in adhesion but presumably in later biofilm development stages.Lastly, oleolytic biofilms, involving extracellular products (enzymes and solubilization factors) that constitute public goods, are favorable to the establishment of social behaviors. We have demonstrated synergistic behaviors (5/8 of observed behaviors) or competitive behaviors (3/8 of observed behaviors) in oleolytic biofilms.

Cette thèse concerne l’auto-assemblage d'alcanes semi-fluorés (FnHm) et de fluorocarbures (FCs) aux interfaces et leurs interactions avec des phospholipides (PLs) en 2D et 3D. Nous avons étudié les sphérulites formées dans des films de diblocs FnHm. La morphologie de ces sphérulites, concentrique ou radiale, est contrôlée par la longueur des blocs Fn et Hm et la vitesse de refroidissement. Les nanodomaines de diblocs FnHm dans les monocouches de Langmuir sont incompressibles et forment des gels physiques 2D, même à pression nulle. Les blocs Hm sont cristallisés et inclinés d’ ~30°C par rapport à la normale à la surface. La réflectivité de neutrons a montré que l’albumine adsorbée sur des monocouches de PL est désorbée par un FC gazeux. Ce résultat pourrait permettre de lutter contre l’inactivation du surfactant pulmonaire par les protéines sériques. L’ajout de diblocs à des films de PLs accroit l'élasticité des monocouches. Nous avons préparé des microbulles stables à parois de PLs/FnHm, les diblocs agissant en co-surfactants. / This thesis focuses on the self-assembly of semi-fluorinated alkanes (FnHm) and fluorocarbons (FCs) at interfaces and their interactions with phospholipids (PLs) in 2D and 3D. 2D Spherulites were identified in FnHm films for the first time. Their morphology, ring-banded or radial, was controlled by varying block lengths and cooling rate. Nanodomains of FnHm in monolayers formed incompressible 2D physical gels, even at zero surface pressure. The Hm segments are crystalline and titled by 30°C to the normal to the surface. Neutron reflectivity showed that albumin adsorbed on PLs monolayers is desorbed by exposure to FC gas, which opens the potential use of FCs to treat the inactivation of the lung surfactant by serum proteins. Incorporating FnHm into PL monolayers increases their elasticity. Small, stable microbubbles of PLs/FnHm were obtained. FnHm diblocks function as co-surfactants for stabilizing microbubbles.

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2016-09-05T17:15:32Z No. of bitstreams: 1 MARTINS G.S. 2016.pdf: 11805657 bytes, checksum: 112f32d3100030fafec5c3f6222a4b72 (MD5) / Made available in DSpace on 2016-09-05T17:15:32Z (GMT). No. of bitstreams: 1 MARTINS G.S. 2016.pdf: 11805657 bytes, checksum: 112f32d3100030fafec5c3f6222a4b72 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geociências - Geoquímica. Niterói, RJ / Este trabalho consiste na reconstrução paleoambiental de dois lagos amazônicos através de dados sedimentares e geoquímicos com especial ênfase a geoquímica orgânica e isotópica. Os lagos estudados apresentam-se em duas área climáticas distintas da Amazônia, sendo o Lago do Saci localizado ao sul do estado do Pará, em área de clima tropical com estação seca definida; e a Lagoa da Pata, localizada no extremo norte do Amazonas em regime de clima sempre úmido. O registro do Lago Saci abrange o intervalo entre 35.000 cal AP até o último milênio e o registro da Lagoa da Pata abrange os últimos 7500 cal AP. Na lagoa da Pata observou-se a existência de condições secas durante o Holoceno Inferior (7.500 – 6.500 anos cal AP) e o Holoceno Médio (6.500 – 3.600 anos cal AP) com baixos valores de COT (Carbono orgânico Total) e altos valores de 13C, sugerindo baixo nível do lago e aumento na contribuição de plantas C4. Durante o Holoceno Superior (3.600 anos cal AP até o presente) a estabilização de um clima mais úmido é observado na Lagoa da Pata, suportado pelo aumento significativo nos valores de COT e redução nos valores de 13C, sugerindo um aumento no nível do lago e contribuição de plantas C3. O registro molecular da Lagoa da Pata sugere a existência de uma vegetação adaptada a condições de alto estresse hídrico em função do tipo de solo presente na região do Morro dos Seis Lagos. A composição isotópica de carbono do n-alcano apresentou um range de valores característicos de vegetação C3 (-33,6‰ e -36,9‰) durante os últimos 7.500 anos cal AP. No Pleistoceno Superior, o Lago do Saci é caracterizado pelos menores valores de COT e valores mais enriquecidos de 13C sedimentar, sugerindo um baixo nível lacustre e grandes contribuições de plantas C4. O ápice do clima seco acontece entre 22.000 – 21.000 anos cal AP, com ocorrências significativas de incêndios, indicado pelos valores de BC (Carbono Grafítico). A transição para o Holoceno é marcado pela ausência de sedimentação entre 18.200-9.200 anos cal AP, sugerindo a ocorrência de uma fase seca severa ou evento erosivo atuante no fim do período glacial. O Holoceno no Lago do Saci marca um aumento no nível do lago, refletido pelo aumento na produtividade e acumulação da matéria orgânica. Esse período tem como característica a ocorrência de eventos de transporte de material da bacia de drenagem, representado pelos pulsos de areia.Os dados de biomarcadores moleculares sugerem condições de estresse hídrico durante o Pleistoceno e o Holoceno Médio na Lago do Saci, em função dos altos valores de ACL (Comprimento médio da Cadeia), sendo esses períodos os com maiores contribuições de plantas C4 como indicado pela razão C33:(C27+C29). Os valores de 13C dos n-alcanos (- 33.2‰ e -35.7‰) sugerem que a região foi coberta por vegetação C3 durante todo o período e mostram uma variação significativa entre o Pleistoceno Superior e o Holoceno, associada a alterações fisiológicas da vegetação. O registro de D sugere um período de precipitação reduzida no Pleistoceno e um período de chuvas mais abundantes no Holoceno. Ambos os registros (Lago do Saci e na Lagoa da Pata) sugerem condições ligeiramente mais úmidas durante o Holoceno, com a existência de uma fase seca no Holoceno Médio, caracterizados por uma redução significativa no nível lacustre e maior contribuição de plantas C4. As chuvas se tornam mais abundantes na Lagoa da Pata e o Lago do Saci a partir de 4.000 anos cal AP onde ocorre a expansão da floresta. Em Ambos os sítios, o sinal isotópico de biomarcadores, apesar de indicar alterações na precipitação, apresentou um enriquecimento do sinal isotópico em função da evapotranspiração ou alteração na vegetação fonte (C3 ou C4), alterando o processo de fracionamento do deutério. / In this work we present the paleoenvironmental reconstruction of two Amazonian lakes based in sedimentary and geochemical data with focus on organic and isotopic geochemistry.The lakes are presented in two distinct climatic area of the Amazon, the Saci Lake are located in south of Para state, in tropical area with dry season; and Pata Lake, located on the northern of the Amazon in a humid climate regime. The Saci lake core covers the range between 35,000 cal BP until the last millennium and Pata Lake covers the last 7,500 cal BP. Pata lake record dry conditions during the Early Holocene (7,500-6,500 cal years BP) and the Middle Holocene (6,500-3,600 cal years BP) with low TOC values (Total Organic Carbon) and high 13C values, suggesting low lake level and an increase of C4 plants contribution. During the Late Holocene (3,600 years cal BP to the present) is observed a stabilization of humid conditions, supported by the increase in TOC values and reduction in 13C values, suggesting an increase in lake level and C3 plants. The molecular record of Pata Lake suggests the existence of a vegetation adapted to high water stress conditions due the soil characteristic in the Six Lakes Morro region. The isotopic composition of n-alkane carbon presented a range of C3 vegetation (-33.6 ‰ and -36.9 ‰) over the last 7,500 years AP. In the Late Pleistocene, Saci lake is characterized by lower TOC values and more enriched 13C values, suggesting a low lake level and more C4 plants contributions. The dry climate occurs between 22,000 to 21,000 cal years BP, with significant occurrences of fires, indicated by the BC (Black Carbon) values. The transition to the Holocene is marked by the absence of sedimentation between 18,200-9,200 cal years BP, suggesting the occurrence of a severe drought phase or active erosive event at the end of the glacial period. The Holocene in Saci Lake is marked by an increase in lake level, reflected by the increase of productivity and organic matter accumulation. This period is characterized by the occurrence of runoff events, represented by sand pulses. The molecular biomarker data suggest water stress during the Pleistocene and the Middle Holocene in Lake Saci, with high ACL values (Average Chain Length), and more C4 plants contributions as indicated by the reason C33: (C27 + C29). The 13C values of nalkanes (-33.2 and -35.7 ‰ ‰) suggest that the area was covered by C3 vegetation during the whole period and show a significant variation between the Pleistocene and Holoceno associated with physiological changes in the C3 vegetation. The D record suggests a reduced precipitation in the Pleistocene and a period of more abundant rainfall in the Holocene. Both records (Saci lake and Pata Lake) suggest wetter conditions during the Holocene, with the existence of a dry phase in the Middle Holocene, characterized by a significant reduction in lake levels and greater contribution of C4 plants. The rains become more abundant in Pata Lake and Saci Lake after 4,000 cal years BP, where the forest expansion occurs. In both sites, the isotopic biomarkers indicate changes in precipitation, however the D enrichment could be explained by the evapotranspiration processes or change in vegetation source (C3 or C4), which interfers the deuterium fractionation process.

Les cristaux apériodiques possèdent la propriété d’avoir un ordre à grande distance mais sans la symétrie de translation. Ces cristaux se décrivent dans des superespaces cristallographiques de dimension supérieure à trois. Dans ce mémoire, nous nous intéressons plus particulièrement aux brisures de symétrie présentes dans de tels espaces cristallographiques en considérant la famille prototype de n-alcane/urée. Des études par diffraction de rayons X sur sources synchrotron révèlent de multiples solutions structurales impliquant des changements ou non de la dimension du groupe de superespace. Une fois la caractérisation du paramètre d’ordre et de la brisure de symétrie faite nous présentons les phénomènes prétransitionnels critiques associés à ces transitions de phase de type groupe/sous-groupe. La diffusion cohérente de neutrons et la diffusion de rayons X inélastiques permettent une analyse dynamique des différentes excitations dans ces matériaux (phonons, phasons). Les composés d’inclusion avec des molécules invitées courtes (alcane CnH2n+2 avec n variant de 7 à 13) révèlent à température ambiante des phases « quasi-liquides » uni-dimensionnelles. Ce désordre dynamique le long de la direction d'incommensurabilité de ces matériaux génère à basse température des solutions structurales nouvelles (composite monoclinique intermodulé, ancrages commensurables). / Aperiodic crystals have the property to possess long range order without translational symmetry. These crystals are described within the formalism of superspace crystallography. In this manuscript, we will focus on symmetry breakings which take place in such crystallographic superspace groups, considering the prototype family of n-alkane/urea. Studies performed by X-ray diffraction using synchrotron sources reveal multiple structural solutions implying or not changes of the dimension of the superspace. Once the characterization of the order parameter and of the symmetry breaking is done, we present the critical pretransitionnal phenomena associated to phase transitions of group/subgroup types. Coherent neutron scattering and X-ray scattering allow a dynamical analysis of different kind of excitations in these materials (phonons, phasons). The inclusion compounds with short guest molecules (alkane CnH2n+2, n varying from 7 to 13) show at room temperature unidimensional “liquid-like” phases. The dynamical disorder along the incommensurate direction of these materials generates new structural solutions at low temperature (intermodulated monoclinic composite, commensurate lock-in).