La production de nouvelles générations de béton avec des propriétés physiques, structurales et techniques améliorées est très importante, mais elle n'est pas possible sans utiliser divers types d'additifs. Les nanotubes de carbone sont des matériaux prometteurs qui possèdent des propriétés spécifiques permettant leurs utilisations pour une grande variété de matériaux composites, y compris le béton. Certaines études expérimentales ont révélé que les nanotubes de carbone peuvent améliorer les propriétés mécaniques du béton avec une petite quantité d'additifs, en fournissant une structure moins défectueuse de la matrice de ciment. Cependant, les résultats sont encore insuffisants et nécessitent d'être élucidés sur les processus se produisant à l'échelle nanométrique dans la structure en béton modifiée par les nanotubes de carbone. Ainsi, cette thèse, a pour objectif principal l'étude de l'amélioration des propriétés mécaniques du béton modifié par les nanotubes de carbone. Afin de modéliser la structure atomique du gel de la Silicate de Calcium Hydratée, nous avons choisi la tobermorite 11Å avec deux rapports différents de Ca/Si correspondants à 0,83 et 1. Divers types de nanotubes incorporés sont testés pour étudier les propriétés mécaniques du nouveau composite résultant. En outre, l'effet de la concentration de nanotubes de carbone dans le ciment est également détaillé. Enfin, nous étudions l'effet de la pression uniaxial sur la structure du béton incluant des nanotubes de carbone. Nos travaux montrent qu'il possible d'améliorer les caractéristiques mécaniques du béton en insérant des nanomatériaux en général, et des nanotubes de carbone en particulier. / The production of new generations of concrete with improved physical, structural and technical properties is very important, but it is not possible without the use of various types of additives. Carbon nanotubes are promising materials that possess specific properties allowing their uses for a wide variety of composite materials, including concrete. Some experimental studies have revealed that carbon nanotubes can improve the mechanical properties of concrete with a small amount of additives, providing a less defective structure of the cement matrix. However, the results are still insufficient and need to be elucidated on the processes occurring at the nano-scale in the concrete structure modified by carbon nanotubes. Thus, this thesis has as main objective the study of the improvement of the mechanical properties of the concrete modified by the carbon nanotubes. In order to model the atomic structure of the Calcium Silicate Hydrates gel, tobermorite 11Å was selected with two different Ca/Si ratios corresponding to 0.83 and 1. Various types of nanotubes incorporated into the tobermorite 11Å structure were tested to study mechanical properties of the resulting new composite. In addition, the effect of the concentration of carbon nanotubes in the cement was also detailed. Finally, we studied the effect of uniaxial pressure on the concrete structure including carbon nanotubes. The work concludes that it is possible to improve the mechanical characteristics of concrete by inserting nano-materials in general, and carbon nanotubes in particular.

PINTO, Marília Taumaturgo. Estudo comparativo da associação do vírus de epstein-barr com o linfoma de Hodgkin clássico em adulto : estudo imunohistoquimico e por hibridização in situ de casos do Ceará (Brasil) e de diferentes regiões da França. 2003. 80 f. Dissertação (Mestrado em Patologia) - Universidade Federal do Ceará. Faculdade de Medicina, 2003. / Submitted by denise santos (denise.santos@ufc.br) on 2011-12-22T13:48:11Z No. of bitstreams: 1 2003_dis_mtpinto.pdf: 641857 bytes, checksum: b7192fd1d4baa4ab6ad8b6e9c881c513 (MD5) / Approved for entry into archive by Eliene Nascimento(elienegvn@hotmail.com) on 2012-02-02T16:21:46Z (GMT) No. of bitstreams: 1 2003_dis_mtpinto.pdf: 641857 bytes, checksum: b7192fd1d4baa4ab6ad8b6e9c881c513 (MD5) / Made available in DSpace on 2012-02-02T16:21:46Z (GMT). No. of bitstreams: 1 2003_dis_mtpinto.pdf: 641857 bytes, checksum: b7192fd1d4baa4ab6ad8b6e9c881c513 (MD5) Previous issue date: 2003 / A associação do Linfoma de Hodgkin Clássico (LHc) com o vírus de Epstein-Barr (EBV) tem sido observada em vários países de diferentes condições sócio - econômicas. Recentemente usando-se técnica de Imunohistoquímica (IHQ) e Hibridização in situ (HIS) porções virais foi encontrada exclusivamente nas células características do Linfoma de Hodgkin que são as chamadas células de Reed-Sternberg (RS) e suas variantes chamadas células Hodgkin (H). Empregando estas técnicas nosso trabalho foi realizado de modo a fazer uma análise comparativa de uma amostra de 118 casos de origem do Ceará - Nordeste do Brasil e de diferentes regiões da França, sendo todos os pacientes de faixa etária entre 18 e 64 anos de idade. Com o propósito de convencionar parâmetros para análise comparativa e interpretação de resultados buscou-se alguns trabalhos de pesquisadores cujo objetivo maior era de avaliar o percentual dessa associação nos respectivos países onde observou- se uma escassez de trabalhos comparando dois ou mais países. A prevalência do EBV em lesões nodais de 37 pacientes do nordeste brasileiro com Linfoma de Hodgkin clássico foi comparada com 33 pacientes franceses.Houve predominância em pacientes brasileiros do sexo feminino (51,3%) e em pacientes franceses do sexo masculino (65,3%) sendo a média de idade similar em ambos os grupos (34,8 anos).Dos subtipos histológicos a Esclerose Nodular (EN) esteve presente em 23 casos brasileiros e em 29 franceses e Celularidade Mista (CM) em 11 brasileiros e 4 franceses. Depleção Linfocitária (DL) e não classificados foram raros. O LMP1 (Proteína de Membrana Latente) foi expresso nas células RS em 25 (67,5%) dos casos brasileiros e em 10 (30,3%) dos franceses e o Epstein-Barr encoded RNA (EBER) foi evidente em 75,6% de Brasil e 30,3% da França. A relação entre subtipo histológico e detecção viral foi mais freqüente no subtipo Celularidade Mista. Deduz-se com esses resultados que o EBV tenha uma maior participação na patogênese do LH Clássico nos casos do Ceará que em pacientes oriundos da França.

LIMA, Marcos Antonio Pereira de. Estudo do vírus Epstein-Barr (EBV) em adenocarcinoma gástrico : frequência, associação clínico-histopatológica e relação com a expressão das proteínas BCL-2, BAX e c-MYC. 2006. 147 f. Dissertação (Mestrado em Microbiologia Médica) - Universidade Federal do Ceará. Faculdade de Medicina, Fortaleza, 2006. / Submitted by denise santos (denise.santos@ufc.br) on 2012-01-05T13:40:30Z No. of bitstreams: 1 2006_dis_maplima.pdf: 3051748 bytes, checksum: efe5f1c5373b2f71cbc0edfbd4bcb484 (MD5) / Approved for entry into archive by Eliene Nascimento(elienegvn@hotmail.com) on 2012-02-02T14:03:59Z (GMT) No. of bitstreams: 1 2006_dis_maplima.pdf: 3051748 bytes, checksum: efe5f1c5373b2f71cbc0edfbd4bcb484 (MD5) / Made available in DSpace on 2012-02-02T14:03:59Z (GMT). No. of bitstreams: 1 2006_dis_maplima.pdf: 3051748 bytes, checksum: efe5f1c5373b2f71cbc0edfbd4bcb484 (MD5) Previous issue date: 2006 / The Epstein-Barr virus (EBV) has been related to the tumorigenesis of the gastric carcinomas, varying from 1.3-19.3% according to the studied population. Several studies have demonstrated strong evidences of its relation in this process, such as the monoclonality of the viral genome and its the presence in almost all tumor cells. However, most of the mechanisms used by the virus to control this process are still unknown. In this context, the present study aimed to investigate the frequency of the EBV and the association with the BCL-2, BAX and c-MYC proteins. Therefore, 100 cases of gastric carcinoma (67 males and 33 females), obtained from two hospitals in Fortaleza, were assessed to detect the EBV by PCR and in situ hybridization (aimed to the EBER1 transcript) using the standard method and GenPoint®. Immunohistochemistry technique was done to evaluate the expression of the referred cellular proteins, by streptavidin-biotin-peroxidase method. The distribution by sex, age, tumor anatomic site and the histopathologic analysis, in general, reproduced the pattern of the world scientific bibliographies. Regarding virus detection by in situ hybridization, 8 (8%) cases were positive, 6 of these had shown diffuse pattern of staining, and 2 had demonstrated focal pattern. From 100 cases, only 2 presented infected lymphocytes. In general, the EBV demonstrated higher association with: males (87.5%[p=0.265]), tumors situated in the cardia (37.5% [p=0.549]), advanced stage (IIIB and IV), intestinal type (87.5%[p=0.136]), and moderately differentiated (75%).There were no EBV-positive cases which exhibited BCL-2 staining. Although the BAX and the c-MYC (nuclear) proteins have demonstrated significant positivity index and scores averages in the EBV-positive group, these were lower than the values of the EBV-negative group, notably the c-MYC nuclear protein (Mann-Withney test LI p=0.039 and HS p=0.045). The cytoplasmic staining of the c-MYC protein revealed slightly higher staining values in the EBV-positive group. The balance between the BCL-2 and BAX proteins demonstrated that the majority of the evaluated cases had exhibited apoptosis-orientation, however 62.3% of the EBV-positive cases exhibited equilibrium between these proteins. Twenty-nine cases (28 negative and 1 positive) were submitted to the biotinyl tyramide system (in situ hybridization method - GenPoint®), demonstrating the same results obtained by the standard technique. From the 61 cases assessed by PCR, 35 (57.4%) were positive, being verified a low concordance index (kappa = -0.026 [±0.069]) with the standard in situ hybridization technique. The 30bp deletion of LMP1 gene was investigated in 24 out of 35 positive cases, being verified in 37.5% of these. The results obtained in the present study, concerning the EBV frequency and the correlation with clinic-histopathologic data, reproduced findings of researches done in several world regions. The correlation with the proteins suggests that in vivo the virus is not related to the overexpression of BCL-2 and c-MYC (nuclear) that could act in synergism to promote the tumor development. The suppression of the BAX expression might represent a viral mechanism for apoptosis inhibition. The results of the cytoplasmic c-MYC point to a possible involvement of the EBV with transport mechanisms of the nuclear membrane, resulting in its accumulation in the cytoplasm. The low frequency of infected lymphocytes indicates that they are not the main responsible of the high number of positivity in the PCR technique. It could be, at least in part, due to the infected normal and/or pre-neoplastic epithelium, suggesting a new latency pattern which not express the EBER1. / O vírus Epstein-Barr (EBV) tem sido associado com a tumorigênese dos adenocarcinomas gástricos, variando entre 1,3-19,3% de acordo com a população estudada. Diversos estudos têm demonstrado importantes evidências do envolvimento do EBV nesse processo, tais como a monoclonalidade do genoma viral e a presença do vírus em quase todas as células tumorais do sitio primário e em células metastáticas. No entanto, os mecanismos utilizados pelo vírus para orquestrar a transformação tumoral, ainda não foram totalmente elucidados. Neste contexto, o presente estudo objetivou investigar a freqüência do EBV e a associação com as proteínas BCL-2, BAX e c-MYC. Para tanto, 100 casos de adenocarcinomas gástricos (67 homens e 33 mulheres), obtidos de dois hospitais de Fortaleza, foram analisados quanto à presença do EBV, detectado através das técnicas de PCR e de hibridação in situ (direcionada ao transcrito viral EBER1) pelo método usual e GenPoint®. Procedeu-se também, estudo imuno-histoquímico das referidas proteínas celulares, através do método da estreptoavidina-biotina-peroxidase. A distribuição por sexo, idade, sítio anatômico do tumor e as análises histopatológicas, de modo geral, reproduziram as tendências da literatura mundial. Pela técnica de hibridação in situ, 8 (8%) casos foram positivos, 6 destes apresentaram marcação difusa e 2 apresentaram marcação focal. Apenas 2 apresentaram linfócitos infectados. De modo geral, o EBV apresentou maior associação com o sexo masculino (87,5% [p=0,265]), com tumores situados na cárdia (37,5% [p=0,549]), de estadiamento avançado (IIIB e IV), do tipo intestinal (87,5% [p=0,136]) e moderadamente diferenciados (75%). Nenhum dos casos EBV-positivos exibiram marcação para BCL-2. Embora as proteínas BAX e c-MYC (nuclear) apresentaram índices de positividade e médias de escores significativos no grupo EBV-positivo, estes foram inferiores aos valores do grupo EBV-negativo, sobretudo a proteína c-MYC nuclear (Teste de Mann-Withney LI p=0,039 e HS p=0,045). A marcação citoplasmática da proteína c-MYC revelou valores de marcação discretamente superiores no grupo EBV-positivo. O balanço entre as proteínas BCL-2 e BAX demonstrou que a maioria dos casos estudados apresentavam tendência à apoptose, mas 62,5% dos casos EBV-positivos exibiram um equilíbrio. Vinte e nove casos (28 negativos e 1 positivo) foram submetidos a outro método de hibridação in situ que emprega o sistema da biotinil-tiramida (GenPoint®),demonstrando resultados idênticos aos obtidos pela técnica convencional. De 61 casos analisados através da técnica de PCR, 35 (57,4%) foram positivos, sendo constatado um baixíssimo índice de concordância (kappa = -0,026 [±0,069]) com a técnica de hibridação in situ. Em 24/35 casos positivos, a deleção de 30pb do gene LMP1 foi investigada, sendo constatada em 37,5% destes. Os resultados obtidos no presente estudo quanto à freqüência do EBV e a correlação com critérios clínico-histopatológicos, reproduziram os achados de estudos realizados em diversas partes do mundo. A correlação com as proteínas sugere que in vivo, o vírus não esteja relacionado com a expressão de BCL-2 e de c-MYC (nuclear), que poderiam atuar em sinergismo favorecendo o desenvolvimento tumoral. A supressão da expressão de BAX, pode representar um mecanismo viral para inibição da apoptose. Os resultados da c-MYC citoplasmática apontam para um possível envolvimento do EBV com mecanismos de transporte da membrana nuclear, determinando o acúmulo da proteína no citoplasma. A baixa freqüência de linfócitos infectados indica que os mesmos não são os principais responsáveis pela elevada positividade da técnica de PCR, devendo ser ao menos em parte, decorrente de epitélio normal e/ou pré-neoplásico infectado sugerindo um padrão de latência que não expresse EBER1.

No description available.

La synthèse de nouveaux calixarènes fonctionnalisés par des groupes d’imidazolium occupe un grand intérêt qui se justifie par la facilité de fonctionnalisation des atomes d’azote de l’imidazole d’une part et d’autre part, par les propriétés de reconnaissance anionique liée à la charge positive délocalisée.Au cours de la première étape, nous avons effectué la fonctionnalisation des calixarènes au niveau de la partie basse en gardant le t-butyle au niveau de la partie haute. Dans un second temps, nous avons réalisé une substitution des atomes de brome par des dérivés d’imidazoles tel que 1-méthylimidazole, 2,4,6-triméthlimidazole, 2,6-diisopropylimidazole, l’imidazole et le benzimidazole afin de créer des ligands imidazolium, par la suite une réaction des sels d’imidazolium avec le nickelocène a conduit à la formation des complexes du NiCp. Dans une dernière étape, nous avons déterminé les propriétés complexantes des dérivés d’imidazolium vis-à-vis des anions organiques et inorganiques. / The synthesis of new calixarenes functionalized with groups imidazolium occupies a large interest, which is justified by the ease of functionalization of the nitrogen atoms of the imidazole on the one hand and on the other hand, by the anionic recognition properties related the delocalized positive charge.During the first step, we conducted the functionalisation of calixarenes at the lower part bearing the t-butyl at the top. Secondly, we made a substitution of bromine atoms by imidazole derivatives such as 1-methylimidazole, 2,4,6-triméthlimidazole, 2.6-diisopropylimidazole, imidazole and benzimidazole to create imidazolium ligands, subsequently a reaction imidazolium salts with nickelocene led to the formation of complexes NiCp.In a last step, we determined the complexing properties of imidazolium derivatives vis-à-vis organic and inorganic anions.

Abstract Type XII minicollagen chain association was studied using baculovirus-directed insect cell expression. Since insect cells contain low endogenous prolyl 4-hydroxylase activity, the mechanism of the effect of prolyl hydroxylation on trimer formation in this collagen could be studied directly by adding recombinant baculoviruses directing the synthesis of prolyl 4-hydroxylase. Prolyl 4-hydroxylase was shown to be involved in the trimeric assembly process of type XII collagen through its α subunit, and thus through its hydroxylase activity. The transmembrane protein type XIII collagen was also characterized by means of insect cell expression, for which purpose new antibodies against its non-collagenous domains NC2 and NC4 were generated, together with a pan-collagen antibody against collagenous sequences. Type XIII collagen α chains were found to form disulphide-bonded homotrimers, and this was enhanced by prolyl 4-hydroxylation. Analysis of the disulphide-bonding pattern of the eight cysteine residues of the α1(XIII) chains revealed that some of the cysteines in the NC1 domain, and possibly the cysteines at the junction of the COL1 and NC2 domains, are interchain-linked, while the cysteines in the NC4 domain are intrachain-linked. The three collagenous domains of type XIII collagen were shown to be in triple-helical conformation and have different thermal stabilities, i.e. 38±C for the COL1 domain, 49±C for COL2 and 40±C for COL3. Furthermore, it was shown that type XIII collagen is oriented in the plasma membrane of insect cells so that its non-collagenous N-terminus is intracellular and its mostly collagenous C-terminus is extracellular. Type XIII collagen was also found to be cleaved into the insect cell culture medium by a furin-like protease. The expression of various type XIII collagen deletion variants suggested that chain recognition and the association of type XIII collagen α chains into trimers occur in the N-terminal portion of this molecule. An internal in-frame deletion of residues 63-83 immediately adjacent to the transmembrane domain indicated that this short ectodomain sequence is necessary for the formation of disulphide-bonded trimers. Since a sequence homologous with these deleted residues was also found at the same plasmamembrane-adjacent location in other collagenous transmembrane proteins, this points to common features in their chain association.

Abstract Collagen prolyl 4-hydroxylase is the key enzyme in the biosynthesis of collagens, a family of extracellular matrix proteins. Vertebrate collagen prolyl 4-hydroxylases are α2β2 tetramers, the β subunit being identical to the multifunctional protein disulphide isomerase (PDI). Several isoforms of the catalytic α subunit have been identified in various organisms. Prolyl 4-hydroxylases have also been isolated from plants, where they hydroxylate proline-rich structural glycoproteins of the cell walls. The structural and functional properties of the peptide-substrate-binding domain of human collagen prolyl 4-hydroxylase are characterized here. Data obtained from NMR studies indicate that the domain consists of five α helices and one short β strand, this structure being quite different from those of other proline-rich peptide-binding modules. Several residues involved in the binding of a short synthetic peptide were also identified by NMR. Kd values for the binding of several synthetic peptides to the α(I) and α(II) domains were determined by surface plasmon resonance and isothermal calorimetry, and the results indicated that the binding properties of the type I and type II collagen prolyl 4-hydroxylase tetramers can mainly be explained by the binding of peptides to this domain rather than to the catalytic domain. The peptide-substrate-binding domain of human type I collagen prolyl 4-hydroxylase was also crystallized. The crystals were well ordered and diffracted to at least 3 Å, the asymmetric unit most probably containing a domain dimer. The genome of Arabidopsis thaliana was found to encode at least six putative prolyl 4-hydroxylase polypeptides, one of which was cloned and characterized here as a recombinant protein. All the catalytically critical residues identified in animal prolyl 4-hydroxylases were also conserved in this plant prolyl 4-hydroxylase, and their mutagenesis led to inactivation of the enzyme. The recombinant plant enzyme was effective in hydroxylating poly(L-proline) and several synthetic proline-rich peptides. Surprisingly, contrary to previous reports on plant prolyl 4-hydroxylases, the collagen-like peptides were found to be good substrates, the enzyme preferentially hydroxylating prolines in the Y positions of the -X-Y-Gly- triplets, thus resembling the vertebrate collagen prolyl 4-hydroxylases even in this respect. The recombinant plant prolyl 4-hydroxylase also hydroxylated peptides representing the N and C-terminal hydroxylation sites present in the hypoxia-inducible transcription factor α. The fact that these peptides contain only one proline residue indicated that a poly(L-proline) type II conformation was not required for hydroxylation.

Ces travaux de thèse concerne la réalisation et la caractérisation de détecteurs de radiations sub-millimétriques et térahertz par des composants à effets de champs à base d'hétérojonctions de nitrure de Galium (AlGaN/GaN). La première partie de ces travaux présente un état de l'art des différents types de détecteurs de rayonnement térahertz existants que ce soit par une approche électronique, optique ou optoélectronique. Elle permet d'effectuer un comparatif de leurs performances. La seconde partie aborde les aspects de design et de procédés technologiques pour la fabrication de ces composants à base de nitrure de Galium. Elle expose plus particulièrement les difficultés rencontrées et les solutions mises en places lors de la fabrication de composants à réseaux de grilles. La troisième partie concerne la caractérisation en espace libre de ces différentes topologies de détecteurs pour des fréquences allant jusque 550GHz (i.e. NEP, SNR, comparatif avec l’intégration d’antenne cornet…). Cette partie expose les premières mesures d'imagerie en temps réels réalisées à l'aide de détecteur térahertz à base d'hétérojonctions AlGaN/GaN. La dernière partie aborde, quant à elle, l'étude intrinsèque des performances des détecteurs. Celle-ci est basée sur la théorie du mélange résistif. Une modélisation du comportement non linéaire du détecteur est réalisée. Elle s'appuie sur des mesures de mélange faites à l'aide d'un nouveau type de bancs de mesures sous pointes développés au sein du laboratoire. En conclusion, un bilan sur les performances de différentes topologies étudiées essaiera d'offrir des pistes de réponses aux interrogations légitimes sur le sujet abordé. / This thesis relates to the fabrication and the characterization of different types of Gallium nitirde based high electron mobility transistors (GaN/AlGaN heterojunction based HEMT) as millimeter and terahertz radiations detectors. The first part of this work presents a state of the art of different types of THz radiation detectors either by electronics, optics or optoelectronics approaches. This part allows a comparison of their performances. The second part deals with design and process technologies to the fabrication of GaN/AlGaN based devices. This part explains particular difficulties encounterd and solutions omplemented in the process fabrication of gratting-gate transistors. The third part describe the experimental results in free-space, up to 550GHz, of these different types of detectors (i.e. NEP, SNR, integrated horn antenna...). This part outlines the THz real-time imaging performed for the first time with GaN/AlGaN based detectors. The last part deals with the study of the intrinsic performance of these detectors. This study is based on the resistive-mixing theory in HEMTs. Modeling of the nonlinear behavior of transistors is achieved. This part relies on resistive-mixing measurements made using a new type of an on-wafer measurement bench developed in our laboratory. In conclusion, a report on the performances of all detectors studies in this thesis is done. This conclusion attempts to answer in the reasonable questions.

L’objectif de ce travail est la caractérisation expérimentale et la modélisation du comportement mécanique des mélanges de polymères immiscibles à base de PC et de PP. Une microstructure majoritairement sphérique dans la plupart des mélanges PC/PP révèle une faible adhésion. Ceci se traduit par une déviation négative des propriétés mécaniques par rapport au % de PP ajouté. La solution de ce problème consiste à ajouter un troisième composant qui peut favoriser l’adhésion à l’interface. La présence de PP-g-MA, malgré sa faible rigidité et sa fragilité, a permis d’améliorer les propriétés mécaniques du mélange. Une approche multi-échelle est développée pour modéliser le comportement effectif du mélange PC/PP en utilisant deux types de modèles différents. Le premier est basé sur l’homogénéisation analytique et le deuxième est défini dans le cadre de l’homogénéisation numérique. La loi statistique de la répartition spatiale de la phase minoritaire a été déterminée à partir des images MEB. Cette loi a permis de générer un volume élémentaire représentatif (VER). Le comportement des constituants a été défini comme élasto-plastique. L’hypothèse d’une interface parfaite ne permet pas de rendre compte du comportement mécanique des mélanges de manière satisfaisante. Afin d’y remédier, un modèle d’endommagement interfacial a été introduit par des surfaces cohésives avec une loi de traction-séparation. Le modèle est en bon accord avec les résultats expérimentaux. Finalement, une étude paramétrique a été réalisée pour mettre en évidence les effets de la forme, du nombre et de l’orientation des nodules de la phase minoritaire sur les propriétés mécaniques non linéaires du mélange. / The objective of this work is to perform experimental characterization and to model the mechanical behaviour of immiscible PC/PP blends. A predominantly spherical microstructure, in the most PC / PP blends, reveals low adhesion due to high interfacial tension between two phases which was observed under a scanning electron microscope (SEM). This results in a negative deviation of the mechanical tensile properties accordingly to the % of PP. One of the possible solutions is to add a third component that can improve adhesion between two phases. In this work PP-g-MA was chosen. Despite its low rigidity and brittleness, it has partially improved the mechanical properties of the blends. A multi-scale approach was applied to model the homogenised behaviour of the PC / PP blends using two different types of models. The first one is based on analytical homogenization and the second one will be defined in the context of numerical homogenization. The statistical distribution law for the size of the dispersed phase was determined from the SEM images. This law was applied for representative volume element (RVE) generation. The behaviour of the constituents has been defined as elastoplastic. Initially assumed hypothesis of a perfect interface did not describe the mechanical behaviour of the blends in a satisfactory manner. In order to improve this, a model introducing cohesive surfaces to simulate interfacial damage is developed using traction-separation law. The model is in good agreement with the experimental results. Finally, parametric study was carried out to highlight the effect of the shape, the number and the orientation of dispersed phase on the nonlinear response of blends.

L'objectif de ce travail de thèse est d’étudier le comportement au feu de câbles électriques par deux approches, la première consistant à développer des méthodes de caractérisation des propriétés des gaines externes de câbles afin d’en modéliser le comportement au feu. Parallèlement, une approche basée sur le développement d’un banc d'essai original à échelle réduite a été étudiée. La caractérisation des propriétés thermo-physique des matériaux a permis la prédiction de la température et de la perte de masse lors d'expériences thermogravimétriques, de gazéification et de combustion. Il a été montré que tester de mince spécimen de gaine de câbles dans une enceinte à échelle réduite permettait la prédiction des résultats de la norme EN 50399. Ce nouveau test de l'échelle du laboratoire a ensuite utilisé avec succès pour le développement de nouveaux câbles présentant des propriétés feu améliorées. / The aim of this PhD work is to study the behavior of cables following two approaches: numerical modelling and small scale testing. First, methodologies to characterize the properties of the cables jacket materials were developed to further model their fire behavior. Concurrently, an approach was followed by developing a novel bench-scale fire test. Innovative methodologies using simultaneous thermal analyzer, Hot Disc apparatus were developed and so, the thermo-physical properties of the materials were characterized both as a function of temperature and of the decomposition state. Using these parameters as inputs data for a pyrolysis model, the temperature and mass loss rate were well predicted in case of thermo-gravimetric experiments, gasification and mass loss calorimeter. Moreover, it was shown that testing thin specimen of cables jacket materials in a reduced scaled enclosure of the EN 50399 test allowed the prediction of the results obtained on the large scale test carried out on whole cables. This new bench scale test was then successfully to develop new material that can be used as jacket for halogen-free electrical cable.