Charles University in Prague Faculty of Pharmacy in Hradci Králové Department of Pharmaceutical Botany and Ecology Candidate: Kamila Ambrožová Supervisor: PharmDr. Jana Karlíčková, Ph.D. Title of Thesis: Copper reducing activity of isoflavonoids Copper in our body appears only in trace amounts. Despite this fact is an important component of many enzymes, which are responsible for right function of the whole organism. The most important are antioxidant activity, collagen and conective tissue synthesis, formation of pigmentation and cell respiration. Main target of the organism is control the homeostasis of copper, because excess and deficiency of the element could be pathological. Increase level of copper can cause many of civilization diseases. Isoflavones are the plant metabolites of polyfenolic structure which can positively affect different processes in our body. Research is dedicated to anti-inflammatory and estrogenic effects, antioxidant and anticancer aktivity. The elimination and inactivation of radical elements is performed becase of ability of isoflavones to reduce transition elements or chelate them. The aim of this thesis was to determine the reducing activity of seven isoflavonoids - daidzein, genistein, biochanin A, genistin, glycitein, formononetin and prunetin. The highest reduction...

Les activités anthropiques entraînent une contamination des sédiments de rivière en de nombreux polluants et en particulier en éléments traces métalliques (ETM). Si la majorité des ETM se retrouvent piégés dans les sédiments, ceux-ci peuvent être remobilisés et passer en solution dans certaines conditions physico-chimiques et sous l’action des microorganismes autochtones. Les métaux relargués peuvent alors constituer un danger potentiel pour les organismes vivants dans les sédiments et dans la colonne d'eau. Dans le cas des sols, l’impact de l’activité microbienne autochtone sur la mobilité des ETM a souvent été rapporté. Cependant une telle activité de solubilisation n’a été que rarement étudiée dans le cas des sédiments. Une telle connaissance est pourtant importante pour la prédiction du comportement des métaux contenus dans les sédiments et la gestion de ces derniers, notamment lors de leur stockage suite aux opérations de dragage. Dans ce contexte, l’objectif de cette thèse a été de comprendre et d’évaluer l’importance de certains des processus microbiens et chimiques de mobilité des ETM dans les sédiments en conditions anaérobies. La première phase de notre étude qui a consisté à incuber des sédiments de Seine et de Marne en milieu anaérobie dopé en glucose avait pour objectif d’étudier la corrélation entre le métabolisme microbien et le comportement des métaux en solution et dans les sédiments. Dans ces conditions opératoires, une forte solubilisation du fer et du manganèse (sous forme réduite) associée à une solubilisation de métaux traces (Co, Cu, Ni) a été mise en évidence, ce qui a laissé supposer l’intervention de bactéries ferri-réductrices dans les phénomènes observés. Une activité fermentaire importante a été observée et caractérisée par la production d’acides organiques majoritaires tels que les acides acétique et butyrique. Un tel résultat souligne l’importance des bactéries fermentatrices dans les phénomènes de dissolution observés. La deuxième étape de ce travail a consisté à confirmer l’importance de l’activité ferri-réductrice et à en identifier les acteurs principaux. Les analyses moléculaires menées ont montré que les bactéries ferri-réductrices majoritairement identifiées, appartiennent aux espèces Clostridium butyricum et Paenibacillus polymyxa. L’utilisation d’un modèle géochimique nous a permis de montrer que les voies métaboliques supportant la réduction du fer et la mobilité des métaux étaient les fermentations butyrique et acétique. La troisième étape a consisté à comparer les impacts directs (réduction enzymatique) et indirects (propriétés des acides organiques produits) de Paenibacillus polymyxa et Clostridium butyricum sur la mobilité du fer, du manganèse et des autres métaux. Une telle étude a montré que les acides organiques produits (acétique, lactique, succinique, propionique et butyrique) ont un très faible impact sur la solubilisation aux pH rencontrés dans les sédiments et que la réduction enzymatique microbienne est le principal mécanisme de dissolution des éléments métalliques en milieu anaérobie / Antropic activities lead to the metallic contamination of river sediments. Most of trace metals are sorbed on sediments but a part of them can be released into aquatic environment when environmental conditions are modified. This is often due by the autochthonous microbial activity. Microbial activites and their consequences on the mobility of metals have been widely studied in soils. Metals are released through direct or indirect microbial mechanisms. Such studies in the case of sediments are very seldom. However, it can be usefull to understand the microbial mechanisms of metal release in sediments, and particularly for a good management of dredged sediments. In this environmental framework, the aim of this research work was to understand and to evaluate the role of the microbial and chemical mechanisms in the release of metals from river sediments in anaerobic conditions. Firstly, sediments from the Marne and Seine rivers were incubated in anaerobic conditions. A high solubilisation of iron and manganese occurred associated to the solubilisation of trace metals (Co, Cu, Ni, Pb). Meanwhile, organic acids were produced and the medium was acidified. Thus fermentation was supposed to be the main process of microbial metabolism. Furthermore these observations led us to suppose the presence of iron-reducing bacteria. In a second step, the extent of the iron-reducing activity was studied. The main iron-reducing bacteria identified in the Marne sediments belonged to the species Clostridium butyricum and Paenibacillus polymyxa. The use of a geochemical model revealed that fermentation and reduction of iron(III) were the main metabolic pathways. Finally direct (enzymatic reduction) and indirect (complexation with organic acids, acidification) impacts of iron-reducing bacteria on the release of metals were compared. Acidification and organic acids had a weak impact on metal solubility in the range of studied pH (between 6,5 and 5). Enzymatic reduction is the main mechanisms of metal release in anaerobic conditions. Indeed the metallic concentrations can be 40 times higher in the presence of iron-reducing bacteria

70 Summary The purpose of my thesis is an analysis of the legal limitations a competitive and economic activity of the employee during the duration of employment relationship and after its termination, not only in labor law but also commercial law, criminal and competition law. The thesis is composed of five chapters: The first Chapter addresses the issue of prohibition of competition both according to business law in general and in the related company law. Included was also a part dedicated to the unfair competition. The basic institutions of competition law are also mentioned. The second Chapter of my thesis also includes a view of criminal law, as a law of last instance, used in cases where means of other parts of law have become ineffective. This section also contains the analysis of the two crimes, that covered the issue of prohibition of concurrency. The third Chapter contains a short list of laws related to labor code, but include special treatment of the employment relationship for a specified group of employees. The fourth Chapter is devoted to the area of Labour law. The chapter is subdivided into three parts. First part of chapter describes the historical evolution of the institutions in the Czech law and also evolution of Labour Code. Other part of the chapter is introductory and defines basic...

Charles University Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical Botany and Ecology Candidate: Jakub Mísař Supervisor: PharmDr. Jana Karlíčková, Ph.D. Title of Thesis: Copper reducing effects of quercetin metabolites Copper is an essential trace element in particular due to its ability to easily convert between both redox forms: oxidized (Cu2+ ) and reduced (Cu+ ). Flavonoids are common components of the human diet and they can have positive influence on human health. They are converted into small phenolic acids during digestion by specific bacteria in the colon. Although effects of flavonoids have been extensively studied, the same is not true for their metabolites- phenolic acids. In this in vitro study, eight phenolic acids, which are known metabolites of commonly used flavonoid quercetin, were analyzed for their copper reducing activity at four (patho)physiologically relevant pHs. Simple spectrophotometric method based on an indicator bathocuproinedisulfonic acid disodium salt was used for the assessment reduction of copper ions. The degree of cupric reduction differed among tested compounds. All o- dihydroxycompounds were the most active and achieved 100% of cupric ion reduction in low compound to copper ratio. In conclusion, based on this study, it appears that...

Doctor of Philosophy / Department of Grain Science and Industry / Xiuzhi Susan Sun / Soy protein is one of the most promising bio-degradable adhesives, with great potential as alternatives synthetic petroleum based adhesives for wood composite industries. However, its intrinsic drawbacks such as low water resistance, high viscosity, and short shelf life still limit its broad application. In this research, soy protein was further modified and characterized to improve adhesion properties, flow-ability, water resistance, and long shelf life, which could facilitate the industrialization of soy protein based adhesives. In this study, we exploited the in situ sodium bisulfite (NaHSO3) modification on soy protein in soy flour-water extracts, and then the modified soy protein was obtained through acid precipitation. First, different concentrations of NaHSO3 were used to modify soy flour slurry, then glycinin-rich and β-conglycinin-rich fractions were precipitated at pH 5.4 (SP 5.4) and pH 4.5 (SP 4.5), respectively. Unmodified sample SP 5.4 and SP 4.5 showed clay-like properties and viscoelastic properties, respectively; whereas with addition of NaHSO3 in range of 2-8 g/L, both SP 5.4 and SP 4.5 had the viscous cohesive phase with good handability and flow-ability. The overall adhesion performance of SP 4.5 was better than SP 5.4; the wet strength of these two fractions was in the range of 2.5-3.2 MPa compared to 1.6 MPa of control soy protein isolate. Then soy protein with various β-conglycinin/glycinin (7S/11S) ratios were extracted from soy flour slurry and characterized for adhesion properties based on the different solubility of 7S and 11S globulins. Seven glycinin-rich soy protein fractions and six β- conglycinin-rich soy protein fractions were obtained. According to the morphology, viscosity, and particle size results, we proposed that proper protein-protein interaction, hydration capacity (glycinin-rich fractions), and certain 7S/11S ratios (β-conglycinin-rich fractions) in modified soy protein are crucial to continuous protein phase formation. The viscous cohesive samples were stable for up to several months without phase separation at room temperature, with the wet adhesion strength of 2.0-2.8 MPa. The soy protein modified with NaHSO3 showed good compatibility with commercial glues applied on plywood and paper labeling fields. The modified soy protein made some functional groups, carboxylic (-COOH), hydroxyl (-OH) and amino groups (-NH2) available, which cross-linked with hydroxymethyl groups (-CH2-OH) from urea formaldehyde (UF) wood glue. The modified soy protein (MSP) with pH 4.8 also acted as an acidic catalyst for the self-polymerization of UF based resin. The wet adhesion strength of MSP/UF blends (40/60) was 6.4 MPa with 100% wood cohesive failure, as compared to 4.66 MPa of UF. As to the paper labeling application, peel strength of MSP on glass substrate increased rapidly, with curing time much shorter than commercial polyvinyl acetate based adhesives (PVAc). And the MSP/ PVAc blends showed shorter curing time, higher water resistance and lower viscosity than pure PVAc. Chemical modification could also enhance the adhesion strength of MSP. 2-octen-1- ylsuccinic anhydride (OSA) was proved to be grafted on soy protein through reaction between amine, hydroxyl groups of protein and anhydride groups. The oily nature and hydrophobic long alkyl chains of OSA mainly contributed to the significant water resistance improvement of MSP.

Master of Science / Department of Grain Science and Industry / Rebecca Miller / Sorghum is a vital cereal crop grown in many regions around the world. Tolerance to harsh climates and low moisture conditions are unique traits making sorghum an economical choice in an era of global water scarcity. In recent years, sorghum has gained greater recognition as a gluten-free grain and is a safe alternative for individuals suffering from gluten sensitivities or celiac disease. Still, the lack of gluten proteins does not allow sorghum to form a viscoelastic dough. In this study reducing agents were added to improve functional properties of sorghum kafirins for bread baking. Study objectives were to determine the effect of reducing agents on protein body structure of sorghum kafirins, investigate the influence on the sorghum batter consistency, and evaluate the effects on the physical characteristics of sorghum bread. Protein analysis, accomplished using RP-HPLC, showed reducing agents, L-cysteine and sodium metabisulfite, reduced protein structure; increasing RP-HPLC total peak area up to 747% and 681%, respectively. Batter consistency was obtained using a RVA. Treatments of L-cysteine (2.5% fwb) expressed increased RVA peak viscosity and decreased final viscosity. Samples treated with sodium metabisulfite (500 ppm fwb) had increased peak viscosity, holding strength and final viscosity. Yeast activity of batter treated with ≥3000 ppm (fwb) sodium metabisulfite caused volume loss of 95% yet at 500 ppm (fwb) sodium metabisulfite did not have an effect. Batter with 2.5% (fwb) L-cysteine experienced reduced yeast activity after 20 min. Sorghum bread characteristics were altered. Loaf volume and crumb grain characteristics of bread produced using sodium metabisulfite (500 ppm) were equal to that of the control, while initial texture and staling were improved. The addition of L-cysteine (2.5% fwb) to breads lowered loaf volume but produced softer initial crumb texture and improved in-vitro protein digestibility by 18.8%.

[pt] A produção do ferro primário, intermediário na produção do aço, é realizada majoritariamente pela rota tradicional do alto-forno. No entanto, tecnologias alternativas estão aumentando suas participações no mercado. Dentre elas, a tecnologia emergente brasileira de autorredução Tecnored é bastante promissora e é objeto de estudo desta dissertação. A tecnologia Tecnored utiliza briquetes autorredutores de minério de ferro em fornos de cuba para obter metal líquido como produto final. Os aglomerados autorredutores, curados a frio, são produzidos a partir de uma mistura de fluxantes, ligantes, finos de minério de ferro e/ou resíduos ferrosos, e um agente redutor carbonoso. A caracterização do insumo para a produção de ferro-primário se faz necessária, de modo a conhecer a distribuição de poros para avaliar a integridade estrutural e a mecânica dos fluidos durante a redução, e quantificar e avaliar a distribuição do ferro metálico presente no aglomerado. Esta dissertação objetiva desenvolver uma metodologia para quantificação de ferro metálico nos briquetes autorredutores de minério de ferro, por meio de rotinas automáticas de processamento de imagens capturadas em microscópio ótico de luz refletida (MLR), e mapear os poros e o ferro metálico ao longo das seções retiradas para análise, também de forma automática. Para a pesquisa realizada, foram utilizados dois tipos de redutores – Carvão Mineral (CM) e Coque Verde de Petróleo (CVP), e diferentes condições de tempo e espessura de briquete. O processo experimental apresentou alguns desafios, desde o corte realizado na preparação das seções polidas para observação em MRL, até a identificação e mapeamento das fases presentes no briquete. Para a validação da metodologia, os resultados da quantificação do ferro metálico realizada por análise de imagens foram comparados com a técnica tradicional de análise química. Os mapas de porosidade e ferro metálico permitiram uma avaliação qualitativa das variáveis tempo e espessura do briquete, para cada tipo de redutor. / [en] The production of primary iron, intermediate step in steelmaking chain, is mostly done by the traditional route of blast furnace. However, alternative technologies are increasing their market share. Among the technologies, Tecnored is a very promising Brazilian ironmaking process and the goal of this master dissertation is the study of it iron-bearing burden. The Tecnored technology utilizes self-reduced iron ore briquettes in a modulate shaft furnace to obtain hot metal. The self-reduced agglomerates, cold bonded, are produced from a mixture of flux, binder, fines of iron ore, residues containing iron and carbonaceous material as a reducing agent. The burden characterization in ironmaking process is essential to study the pores distribution and evaluate the structural integrity and mechanics of fluids during the reduction process, and quantify and analyze the metallic iron distribution along the briquette’s volume. This dissertation main goal is to develop a new methodology of quantification of the metallic iron in selfreduced iron ore briquettes, through automatic routines of image processing, captured in bright field of a reflected light optical microscopy (MRL), and mapping pores and metallic iron automatically along the cross-sections analyzed. The tested briquettes utilized two reducing agents – coal fines (CM) and coke of petroleum (CVP), and it was submitted in two different reduction times and two different briquettes’ thickness. The experimental process presented some challenges, from the cross section cut to be polished and observed in MRL, to the identification and mapping of the phases in the briquettes. To validate the methodology, the results of the quantification of metallic iron through image analysis were compared to the results of the traditional technique of chemical analysis. The porosity and metallic iron maps provided a qualitative evaluation of reduction time and the effect of briquettes’ thickness, for each type of cabonaceus reducing agents.

Neste trabalho foram realizadas sínteses do nitrosilo complexo trinuclear de rutênio de fórmula [Ru3O(CH3COO)6(NO)(py)2]PF6 (py = piridina) seguindo duas rotas sintéticas diferentes (convencional (a) e uma nova (b) ) a fim de verificar e comparar a eficiência de ambas. Além disso, foi feito o mapeamento da rota sintética convencional para analisar a melhor forma de conduzi-la em cada etapa para que a síntese fosse bem sucedida. Com isso, foi possível afirmar na rota (a) que é preciso purificar dois precursores: o precursor 1 [Ru3O(CH3COO)6(S)3]+ e 3 [Ru3O(CH3COO)6(CO)(L)2], não sendo necessário a purificação do produto final. As modificações vistas necessárias para a otimização da síntese (a) foram a utilização de uma solução recém preparada de bromo e a substituição do metanol seco no frasco lavador por diclorometano seco. Não se descarta a possibilidade da nova rota sintética (b), somada às modificações apontadas neste trabalho, apresentar bons resultados. As caracterizações foram feitas utilizando técnicas de espectroscopia na região UV-visível, infravermelho e RMN. Os estudos de reatividade mostraram que, para ambos os complexos analisados ([RuIII,III,III3O(CH3COO)6(NO)(py)2]PF6 e [RuIII,III,III3O(CH3COO)6(4-acpy)2(NO)]PF6), sugere-se a formação da espécie [RuIII,III,II3O(CH3COO)6(NO2-)(L)2]- onde L = 4-acpy ou py - sendo esta reação dependente da concentração de íons hidroxila do meio. Estudos da reatividade e redução do [Ru3O(CH3COO)6(NO)(py)2]PF6 com o redutor de interesse biológico ácido ascórbico na presença de íons OH-, permitiram sugerir uma hipótese para o mecanismo de liberação de NO0 com estímulo redox, na ausência de luz. Propõe-se que primeiramente o ligante NO0 coordenado sofra um ataque nucleofílico dos íons hidroxila presentes no meio, concomitante a uma transferência eletrônica intra-molecular que gera a espécie [RuIII,III,II3O(CH3COO)6(NO2-)(py)2]-. Este último é reduzido pelo ácido ascórbico, restaurando o ligante NO0 que, agora coordenado à unidade metálica reduzida [RuIII,III,II3O], finalmente é labilizado, gerando o complexo [Ru3O(CH3COO)6(S)(py)2]0 / In this work, the synthesis of the trinuclear ruthenium complex [Ru3O(CH3COO)6(NO)(py)2]PF6 (py = pyridine) was performed following two different synthetic routes (conventional (a) and a new one (b)) in order to verify and to compare the efficiency of both. In addition, the mapping of the conventional synthetic route was done to analyze the best way to conduct it at each step for the synthesis to be successful. It was possible to state in route (a) that two precursors must be purified: precursor 1 [Ru3O(CH3COO)6(S)3]+ and 3 [Ru3O(CH3COO)6(CO)(L)2], no purification of the final product being necessary. The modifications required for the optimization of synthesis (a) were the use of a freshly prepared solution of bromine and the substitution of the dry methanol in the washing flask by dry dichloromethane. We can not rule out the possibility of the new synthetic route (b), added to the modifications pointed out in this work, to present good results. The characterizations were made using UV-visible, infrared and NMR spectroscopy techniques. Reactivity studies for both complexes analyzed ([RuIII,III,III3O(CH3COO)6(NO)(py)2]PF6 and [RuIII,III,III3O(CH3COO)6(4-acpy)NO)]PF6), suggested the formation of the species [RuIII,III,II3O(CH3COO)6(NO2-)(L)2]- - where L = 4-acpy or py - this reaction being dependent on the concentration of hydroxyl ions in the medium. Studies of the reactivity and reduction of compound [Ru3O(CH3COO)6(NO)(py)2]PF6 with the biological reductant ascorbic acid, in the presence of OH- ions, allowed to suggest a hypothesis for the NO0 release mechanism with redox stimulus, in the absence of light. It is proposed that the coordinated NO0 ligand undergoes a nucleophilic attack of the hydroxyl ions present in the medium, concomitant to an intra-molecular electron transfer that generates the species [RuIII,III,II3O(CH3COO)6(NO2-)(py)2]-. The latter is reduced by ascorbic acid, restoring the ligand NO0 which, now coordinated to the reduced metal unit [RuIII,III,II3O], is finally labilized, generating the complex [Ru3O(CH3COO)6(S)(py)2]0

Os manguezais são ambientes de transição entre os ecossistemas terrestres e marinhos, essenciais para o crescimento e o desenvolvimento de muitas espécies de elevado interesse ecológico e econômico. Apesar de ter sua importância reconhecida, são constantemente impactados por diversos poluentes que influenciam sua estabilidade. Estes ecossistemas caracterizam-se por serem anaeróbicos, ricos em sulfato e em matéria orgânica, sendo os microrganismos fundamentais na ciclagem de nutrientes, em especial os envolvidos no ciclo do enxofre, onde os procariotos redutores de sulfato (sulphate-reducing prokaryotes, SRP) aparecem como um grupo frequente e com um papel preponderante. O presente estudo mostrou que as comunidades de arquéias, bactérias e bactérias redutoras de sulfato (sulphatereducing bacteria SRB) são abundantes, diversas e responsivas aos estados de intervenção dos manguezais. A abundância medida por qPCR mostrou que as quantidades de arquéias e bactérias aumentam com a contaminação. A diversidade estudada por pirosequenciamento do gene ribossomal 16S DNAr indicou que estes grupos são diversos, mostrando filos Euryarcheota e Crenarcheota do domínio Archaea, e os filos Deltaproteobacteria e Gammaproteobacteria, do domínio Bacteria, como grupos frequentes. A estrutura destas comunidades, avaliada por análises de co-ocorrência, revelou que a microbiota responde à contaminação, diminuindo e simplificando as interações, quanto maior for a contaminação. A diversidade dos grupos relacionados ao ciclo do enxofre, estudada por DGGE (aprA e dsrB), pirosequenciamento (dsrB) e GeoChip (aprA, dsrB), mostrou que a classe Deltaproteobacteria, representada pelas ordens Desulfobacterales e Desulfovibrionales, é o grupo prevalente na redução do sulfato, e as classes Gammaproteobacteria e Betaproteobacteria devem atuar na oxidação do enxofre (sulphur-oxidising - SOB). O GeoChip (aprA, dsrB) foi a única metodologia que permitiu detectar arquéias redutoras de sulfato (gêneros Archaeoglobus e Pyrobaculum), sendo esta a primeira descrição de tais organismos em ecossistemas de manguezais. Desse modo, estes resultados evidenciam que a microbiota em áreas de manguezais responde à contaminação, tendo uma alta frequência de SRB e SOB, ressaltando, assim, a importância do ciclo do enxofre em ambientes de manguezais. / Mangroves are transitional environments between terrestrial and marine ecosystems, essential for the growth and development of many species with high ecological and economical interests. Despite its recognized importance, mangroves are constantly impacted by various pollutants, affecting its stability. These ecosystems are characterized as anaerobic, rich in sulfate and organic matter, where the microorganisms are essential to the nutrient cycling, particularly those involved in the sulfur cycle, where sulphate-reducing prokaryotes (SRP) appear as frequent and taking an important role. The present study showed that communities of archaea, bacteria and sulphate reducing bacteria (SRB) are abundant, diverse and responsive to state intervention of the mangrove. The abundance measured by qPCR showed that the quantities of archaea and bacteria increase with the contamination. The diversity studied by pyrosequencing of the 16S rDNA ribosomal gene indicated that these groups are diverse, showing Euryarcheota and Crenarcheota phyla of the domain Archaea, and Deltaproteobacteria and Gammaproteobacteria classes of the domain Bacteria, as the most frequent groups. The structure of these communities, as assessed by analysis of network, revealed that the microbiota responds to contamination, reducing and simplifying interactions in the higher contamination. The diversity of groups related with the sulfur cycle studied by DGGE (aprA and dsrB), pyrosequencing (dsrB) and GeoChip (aprA, dsrB) showed that Deltaproteobacteria, represented by orders Desulfobacterales and Desulfovibrionales, is a prevalent group in the sulfate reduction, while Gammaproteobacteria and Betaproteobacteria are frequent in the sulfur oxidation (sulfur-oxidising bacteria - SOB). The GeoChip (aprA, dsrB) was the only method that allowed to detect sulfate-reducing archaea (genera Archaeoglobus and Pyrobaculum), which is the first description of these organism on mangrove ecosystems. Thus, these results show that the microbiota in mangroves areas responds to contamination, having a high frequency of SRB and SOB, thus highlighting the importance of the sulfur cycle in mangrove environments.

Através de revisão bibliográfica e estudo experimental, o presente trabalho apresenta uma análise da influência de diversos parâmetros sobre a velocidade da reação entre minério de ferro e carbono, aglomerados na forma de pelotas auto-redutoras. Os parâmetros estudados foram: temperatura, tipo e quantidade de redutor, uso de adições, composição e vazão dos gases no recipiente de reação, tamanho da pelota. A técnica experimental consistiu em medi-se a velocidade de reação por análise termogravimétrica, complementada por análise do gás de saída e difração de Raios-X em pelotas parcialmente reduzidas. Verificou-se que o mecanismo controlador da velocidade de reação é determinado por um conjunto de parâmetros inter-relacionados, e que pode mudar o progresso de reação. A etapa química da reação é controlada pela gaseificação do carbono por CO2. Transporte de calor e difusão gasosa através dos poros da pelota exercem forte influência sobre a velocidade; os fatores que favorecem a influência de transporte de calor são: aumento de temperatura; aumento da reatividade do redutor; uso de catalisador; diminuição do diâmetro da pelota; início de reação; redução sob atmosfera CO/CO2 de composição próxima ao equilíbrio wustitaferro. A influência de difusão gasosa se faz sentir quando a reação é efetuada sob atmosfera de gás inerte, que penetra nos poros da pelota, diluindo a atmosfera CO/CO2 reinante no interior da mistura de partículas. Nessas condições, esta influência é maior quanto menor for a temperatura de reação, quanto menos reativo for o redutor, quanto menor for a pelota, e nos estágios finais de reação. Verificou-se ainda que parâmetros relacionados à composição das pelotas, bem como a temperatura do processo, tem grande influência sobre o comportamento dimensional dos aglomerados.Assim, pelotas com ganga básica (com carvão vegetal e adições básicas) tendem a inchar catastroficamente, ao passo que pelotas com ganga ácida (com coque ou carvão mineral como redutores) não apresentam este fenômeno. Microscopia eletrônica de varredura indicou a presença de ferro filamentar em pelotas que apresentaram inchamento catastrófico. Analisou-se ainda como a presença de matéria volátil no redutor afeta a cinética de reação e o comportamento dimensional das pelotas, e também sob que condições o ferro formado na redução catalisa a reação. / The factors that affect the rate of reaction between iron oxides and carbon were analysed by means of literature review and experimental investigation. The iron ore and the carbon were agglomerated in the form of self-reducing pellets. The investigated variables were: temperature, type and amount of redactor, presence of additives, gas composition and flow in the reactor vessel, and pellet\'s size. The experimental technique employed was thermogravimetric analysis, complemented by gas analysis and X-ray diffraction. It was shown that the rate control may change in the course of the reaction, and it depends on a number of interrelated varibles. The slowest reaction of the chemical step is the carbon gaseification by CO2. Heat transfer and gaseous diffusion through pellets pores play an important role in the rate; the factors that favours the heat transfer influence are: temperature increase, reducto\'s reactivity increase, the use of catalyst, pellet\'s size decrease, start up the reaction; reduction under CO/CO2 atmosphere near wustite-iron equilibrium. When the reaction is performed under inert gas atmosphere, gaseous diffusion through pellet\'s pores can dilute the CO/CO2 atmosphere prevailing in the pallet\'s core. Under these conditions, this effect is more pronounced for lower temperature, lower carbon reactivity, smaller pellets and at the end of the reaction. It was also found that variables related to pellet composition as well as process temperature greatly affect the pellet\'s dimensional behavior. In fact, pellets containing basic guangue (e.g.wood charcoal and/or basic additives) show catastrophic swelling; in contrast, pellets containing acid gangue (e.g. coke or coal) have good dimensional stability. Iron whiskers were observed with scanning electron microscope on pellets that swell catastrophically. The influence of reductor\'s volatile matter upon kinetics and dimensional behavior of pellets was also analysed as well as the catalysis of the reaction by the iron formed in the course of the reduction.