Made available in DSpace on 2017-07-24T19:22:03Z (GMT). No. of bitstreams: 1 John Alexis Domingues.pdf: 1971333 bytes, checksum: 6d76db539da045af70dd08f004b5c7c8 (MD5) Previous issue date: 2015-08-13 / The objectives of this study were: 1) to evaluate the degree of conversion, shrinkage stress, flexural and compressive strength of an experimental resin with a lactic polyacid and castor oil; 2) to evaluate the cytotoxicity of an experimental resin with a lactic polyacid, and castor oil; 3) evaluate, degree of conversion, shrinkage stress, flexural and compressive strength an experimental resin with addition of a high molecular weight polyethylene; 4) to assess the cytotoxicity of an experimental resin with addition of a high molecular weight polyethylene. Initially, it was synthesized a poly (lactic acid) (PLA) via a polycondensation process. After 24 hours, the castor oil (OR) was incorporated by an esterification process with N, N-Dicyclonecylcarbodimide and 99% 4-Dimethylamino-Pyridine in 40 mL of tetrahydrofuran. After this, the blend was characterized by X-ray diffraction (XRPD), Raman spectroscopy, scanning electron microscopy (SEM) and shrinkage stress, where was proven the incorporation of PLA + OR in the experimental composite resin. In the third chapter, PLA + OR were manipulated in two concentrations (1.5% and 3%) in an experimental composite: (2,2 bis [4- (2-hydroxy-3-metacrilatoxypropoxy) phenol] (BisGMA) Triethylene glycol dimethacrylate (TEGDMA), camphorquinone (CQ), N, N-dimethylaminoethyl methacrylate (DEMA-EMA), butylated hydroxytoluene (BHT), silanated barium borosilicate glass, and the tests of degree of conversion, compressive and flexural strength and shrinkage stress were made. The cytotoxicity assay was done; a suspension of 3 x 103 cells/mL of culture medium was prepared. For this, the cells were detached from the bottom of the bottle by the addition of trypsin with EDTA, after incubation in 5% CO2 with 3 mL Eagle's medium supplemented culture. After 24 h incubation period, the culture medium was removed and 200 uL of a solution of culture medium and methylltetrazolium salt (MTT). Subsequently, the analysis of mitochondrial activity was performed in a spectrophotometer (Biotek EL 800, Biotek, Winooski, VT, USA) with a 10 wavelength of 570 nm. The data from each test were analyzed by one-way ANOVA. No significant differences were found (p <0.005) in compressive and degree of conversion tests, and significant differences in shrinkage stress where obtained, up to 69% decrease. and flexion, statistically significant . In the fourth chapter, it was incorporated a high molecular weight polyethylene and polypropiylene, in the experimental resin proposed in chapter two, at two concentrations (1.5% and 3%), and tested by degree of conversion, compressive and flexural strength and shrinkage stress. The data from each test were analyzed by one way ANOVA, finding no significant difference (p> 0.005) in degree of conversion, compressive and flexural strength, and the contraction stress showed a significant reduction of up to 40%. Conclusion: PLA + castor oil and the high molecular weight polyethylene decreases the shrinkage stress and properties like flexural and compressive strength and degree of conversion were not influenced. / Os objetivos deste estudo foram: 1) avaliar o grau de conversão, tensão de contração, resistência à flexão e compressão de uma resina experimental com um poliácido lático e óleo de rícino; 2) avaliar a citotoxicidade de uma resina experimental com um poliácido lático e óleo de rícino; 3) avaliar o grau de conversão, tensão de contração, resistência à flexão e compressão de uma resina experimental com adição de um polietileno de alto peso molecular e 4) avaliar a citotoxicidade de uma resina experimental com adição de um polietileno de alto peso molecular. Previamente realizou-se a síntese de um Poli-ácido lático (PLA) por meio de um processo de policondensação. Após 24 horas, foi incorporado o óleo de rícino (OR) por meio de um processo de esterificação junto a N,N-Diciclonecilcarbodimida e 4-Dimetilamino-Piridina a 99% em 40 mL de tetrahidrofeurano. Em seguida, o conjunto foi caracterizado por difração de espectroscopia Raman, microscopia eletrônica de varredura (MEV) e estresse de contração, onde foi comprovada a incorporação do PLA+OR numa resina composta experimental. No terceiro capítulo foi feita a incorporação do PLA+OR em duas concentrações (1,5% e 3%) numa resina composta experimental: (2,2 bis[4-(2-hidroxi-3-metacrilatoxipropoxi)fenol](BisGMA), Trietilglicoldimetacrilato (TEGDMA), canforoquinona (CQ), N,N– dimetilaminoetil metacrilato (DMAEMA), hidroxitolueno butilado (BHT), vidro de borossilicato de bário silanizado e foram realizados os testes de flexão, compressão, grau de conversão e estresse de contração. Foi feito o teste de citotoxicidade, uma suspensão de 3 x 103 células/mL de meio de cultura foi preparada. Para isso, as células foram descoladas do fundo da garrafa por meio da adição de tripsina com EDTA, após incubação em estufa com 5% de CO2 e 3 mL de meio de cultura Eagle suplementado. Após o período de incubação de 24 h, o meio de cultura foi removido e 200 μL de uma solução de meio de cultura e sal metiltetrazólio (MTT).Posteriormente, a análise da atividade mitocondrial foi realizada em espectrofotômetro (Biotek EL 800, Biotek, Winooski, VT, EUA) com comprimento de onda de 570 nm. Os dados obtidos de cada teste foram analisados com ANOVA um fator. Não encontrou-se diferença significativa (p> 0.005) nos testes de compressão e grau de conversão; já para o teste de estresse de contração, houve diminuição estatisticamente significativa de até 69% e no teste de resistência à flexão . No quarto capítulo foi feita a incorporação de um polipropileno (PP) e o polietileno de ultra-alto peso molecular (UTEC) a uma resina experimental com os mesmos materiais manipulados no capítulo dois, em duas concentrações (1,5% e 3%), e realizados os testes de compressão, flexão, grau de conversão e estresse de contração. Os dados de cada teste foram analisados com ANOVA um fator. Não houve diferença significativa (p> 0.005) nos testes de compressão, flexão e grau de conversão; já para o teste de estresse de contração houve diminuição estatisticamente significativa de até 40%. Conclusão: OPLA+óleo de rícino e o polietileno de ultra alto peso molecular em 1,5%, diminuíram o estresse de contração e propriedades como resistência à flexão, compressão e grau de conversão não foram influenciadas.

O presente estudo foi realizado em duas etapas com os seguintes objetivos: (i) avaliar os efeitos da suplementação com leguminosa tropical em comparação ao concentrado em gramínea tropical na ingestão de nutrientes por cordeiros; (ii) avaliar a inclusão de leguminosa tropical em pastagem de gramínea sobre o consumo de nutrientes por cordeiros recebendo polietileno glicol 4000. O delineamento experimental foi em blocos ao acaso e no segundo experimento em parcela subdividida. No primeiro estudo (capítulo III), 72 cordeiros foram alocados em 12 piquetes (0,1 ha cada) de capim Aruana (Panicum maximum cv. IZ-5) e submetidos aos tratamentos por 90 dias: 1) S0,0 – sem suplementação; 2) S1,5 - suplementação com concentrado a 1,5% de PV; 3) S2,5 -suplementação com concentrado a 2,5% PV, 4) SFG - suplementação com pastejo controlado em 0,1 ha de feijão Guandu (Cajanus cajan cv. Anão) por três horas/dia. No segundo experimento (capítulo IV), 54 cordeiros foram alocados em nove piquetes (0,2 ha cada) submetidos aos tratamentos por 84 dias: 1) Aruana – somente capim Aruana; 2) AFG - consórcio de feijão Guandu e capim Aruana, em faixa, 3) Guandu - somente feijão Guandu, cada tratamento foi subdividido em parcelas com e sem PEG (polietileno glicol 4000). No experimento 1, as variáveis de comportamento ingestivo, consumo e digestibilidade de nutrientes foram influenciadas pelos tratamentos (P < 0,05), tendo os cordeiros do grupo S2,5 apresentado melhor ingestão de nutrientes e o grupo SFG consumo intermediário. Em geral, o grupo SFG apresentou resultados semelhantes ao S1,5. No segundo experimento, as variáveis de comportamento ingestivo não foram influenciadas pelos tratamentos e pelo uso do PEG (P > 0,05). Houve interação entre os sistemas de alimentação e uso de PEG para a ingestão de nutrientes e digestibilidade (P > 0,05), com os melhores resultados para os grupos sem PEG (P < 0,05). Em geral, os animais que não receberam PEG e que foi incluído Guandu na dieta, apresentaram aumento no consumo de nutrientes. Assim, o feijão Guandu pode substituir o concentrado em nível de até 1,5% do PV como suplemento para o capim Aruana. A inclusão da leguminosa tropical com presença de taninos condensados favorece o consumo de nutrientes por cordeiros criados em pastagem tropical. / This study was performed in two stages with the following objectives: (i) to evaluate the effects of topical legume supplementation compared with the concentrate in tropical grass in the intake of nutrients by lambs; (ii) to evaluate the inclusion of tropical legume in grass pasture on intake of nutrients for lambs receiving polyethylene glycol 4000 (PEG). A randomized block design was use in the first experiment and split plot design was use in the second experiment. In the first study (Chapter III), 72 lambs were divided into 12 paddocks (0.1 ha each) of Aruana grass de (Panicum maximum cv. IZ-5) and subjected to treatments for 90 days: 1) S0,0 - only Aruana grass; 2) S1.5 - supplementation with concentrated to 1.5% of lamb BW; 3) S2.5 - supplementation with concentrated to 2.5% of lamb BW; 4) SFG – supplementation with controlled grazing on 0.1 ha of pigeon pea (Cajanus cajan cv. Anão) for three h / d. In the second study (Chapter IV), 54 lambs were divided into nine paddocks (0.2 ha each) and subjected to treatments for 84 days: 1) Aruana – only Aruana grass; 2) AFG - consortium with Aruana grass and pigeon pea; 3) Guandu – only pigeon pea, where each treatment was divided into plots with or without PEG (polyethylene glycol 4000). In the experiment 1, the ingestive behavior variables, intake and digestibility of nutrients were affect by treatments (P < 0.05) with the lambs of the group S2.5 presented better intake of nutrients and the group SFG intake intermediate. In general, the SFG group showed similar results to S1.5. In the second experiment, the ingestive behavior variables were not affected by the treatments and the use of PEG (P>0.05). There was interaction between the feeding systems and use of PEG for intake of nutrients and digestibility (P < 0.05), with the best result for the treatments without PEG (P < 0.05). In general, animals that did not receive PEG and that included pigeon pea in the diet, showed an increase in the intake of nutirents. Thus, pigeon pea can substitute the concentrate at a level of 1,5% PV as a supplement for the Aruana grass. The inclusion of the tropical legume with presence of condensed tannin favors the intake of nutrients by lambs raised in tropical pasture.

Une des propriétés fondamentales des diélectriques est d'accumuler des charges sous l'effet d'un champ électrique. Si cet effet est exploité dans certaines applications telles que les mémoires il est la plupart du temps la cause de défaillance dans de nombreux systèmes tels que les câbles haute tension ou les microsystèmes. De nombreuses études ont démontré que l'interface entre le diélectrique et l'électrode jouait un rôle prédominant dans le fonctionnement du système complet et en particulier influençait le phénomène d'injection de charge à l'origine des défaillances. Au cours des dernières années le phénomène d'injection de charges à l'interface électrode/diélectrique a largement été étudié. Pour expliquer la différence entre les résultats expérimentaux et les modèles, l'hypothèse la plus plausible est la présence d'états d'interfaces entre l'électrode (métal ou semiconducteur) et le diélectrique. Cette hypothèse permet en particulier d'expliquer l'indépendance de la quantité de charge injectée vis-à-vis du métal servant d'électrode. Toutefois, les propriétés des interfaces restent mal connues en particulier car ces phénomènes nanométriques sont caractérisés à partir de mesures microscopique. L'objectif de cette thèse est de caractériser les propriétés chimiques et électriques de l'interface grâce à un contrôle rigoureux de son procédé de fabrication. L'apport majeur de ces travaux est lié à l'utilisation de la microscopie à force atomique pour déterminer les propriétés de l'interface à l'échelle nanométrique. Nous avons en particulier caractérisé morphologiquement (mesure de propriétés mécaniques par PFQNM - Peak Force Quantitative NanoMechanical) et électriquement (mesure de potentiel de surface par KPFM - Kelvin Probe Force Microscopy). Nous avons ainsi pu montrer que le procédé de fabrication influençait les propriétés chimiques (oxydation de surface...) de l'interface sans que cela ait de conséquences notables sur les propriétés électriques. En effet, la quantité de charges injectées reste du même ordre de grandeur quel que soit le procédé de fabrication. Les mesures AFM ont montré que l'interface morphologique était abrupte alors que l'interface électrique était progressive (plusieurs microns). Grâce à un modèle nous avons pu extraire des mesures de potentiel de surface KPFM la densité de charge d'interface. / One of the fundamental properties of dielectrics is to accumulate charges under an electric field. Even if this phenomena is exploited in some applications such as memories, it is the main cause of failure in a large amount of applications such as high voltage cables or microsystems. Numerous studies have demonstrated that dielectric/electrode interface has strong impact on complete system and particularly on charge injection phenomenon which induce failures. During the past decades, charge injection phenomena electrode / dielectric interface has been extensively studied. To explain the difference between experimental and modelling, the most plausible hypothesis is the presence of interface states between the electrode (metal or semiconductor) and the dielectric. This hypothesis explain the independence of injected charge density respect to the electrode meta (work function). However, interfaces properties remain poorly understood mainly because all nanometric phenomena accuring at its localization are characterized thanks to microscopic measurements. The aim of this PhD thesis is to characterize chemical and electrical properties of the interface through a rigorous control of its manufacturing process. The major contribution of this work is related to the use of Atomic Force Microscopy (AFM) to determine interface properties at nanoscale. In particular, interfaces are characterized morphologically (mechanical properties measurements by PFQNM - Peak Quantitative Quantum NanoMechanical) and electrically (surface potential measurements by KPFM - Kelvin Probe Force Microscopy). Thus, results demonstrate that the manufacturing process influenced the chemical properties (surface oxidation ...) of the interface without having any significant influence on the electrical properties. Indeed, the amount of injected charges remains quite the same regardless of the manufacturing process. AFM measurements showed that the morphological interface was abrupt whereas the electrical interface was progressive (several microns). A Matlab model permits us to extract interface charge density to KPFM surface potential measurements.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Yolanda Leigh Hinton. / M.S.

Butt fusion welding process is an extensively used method of joining for high density polyethylene (HDPE) pipe. With the increasing number of HDPE resin and pipe manufacturers and the diversity of industries utilising HDPE pipes, a wide range of different standards have evolved to specify the butt fusion welding parameters with inspection and testing methods, to maintain quality and structural integrity of welds. There is a lack of understanding and cohesion in these standards for the selection of welding parameters; effectiveness, accuracy, and selection of the test methods and; correlation of the mechanical properties to the micro and macro joint structure. The common standards (WIS 4-32-08, DVS 2207-1, ASTM F2620, and ISO 21307) for butt fusion welding were used to derive the six welding procedures. A total of 48 welds were produced using 180 mm outer diameter SDR 11 HDPE pipe manufactured from BorSafe™ HE3490-LS black bimodal PE100 resin. Three short term coupon mechanical tests were conducted. The waisted tensile test was able to differentiate the quality of welds using the energy to break parameter. The tensile impact test due to specimen geometry caused the failure to occur in the parent material. The guided side bend specimen geometry proved to be too ductile to be able to cause failures. A statistical t-test was used to analyse the results of the short term mechanical tests. The circumferential positon of the test specimen had no impact on their performance. Finite element analysis (FEA) study was conducted for the long term whole pipe tensile creep rupture (WPTCR) test to find the minimum length of pipe required for testing based on pipe geometry parameters of outer diameter and SDR. Macrographs of the weld beads supplemented with heat treatment were used to derive several weld bead parameters. The FEA modelling of the weld bead parameters identified the length to be a key parameter and provided insight into the relationship between the geometry of the weld beads and the stresses in the weld region. The realistic bead geometry digitised using the macrographs contributed a 30% increase in pipe wall stress due to the stress concentration effect of the notches formed between the weld beads and the pipe wall. The circumferential position of the weld bead had no impact on the pipe wall stresses in a similar manner to the results of the different mechanical tests. IV Nanoindentation (NI) and differential scanning calorimetry (DSC) techniques were used to study the weld microstructure and variation of mechanical properties across the weld at the resolutions of 100 and 50 microns, respectively. NI revealed signature 'twin-peaks and a valley' distribution of hardness and elastic modulus across the weld. The degrees of crystallinity obtained from DSC followed the NI pattern as crystallinity positively correlates with the material properties. Both techniques confirm annealing of the heat affected zone (HAZ) material towards the MZ from the parent material. The transmission light microscopy (TLM) was used to provide dimensions of the melt zone (MZ) which displays an hour glass figure widening to the size of the weld bead root length towards the pipe surfaces. Thermal FEA modelling was validated using both NI and TLM data to predict the HAZ size. The HAZ-parent boundary temperature was calculated to be 105 ⁰C. The 1st contribution of the study is to prove the existence of a positive correlation between the heat input calculated from FEA and the energy to break values obtained from the waisted tensile test. The 2nd contribution providing the minimum length of pipe for WPTCR based on the pipe dimensions. The 3rd contribution is the recommendation for the waisted tensile test with the test using the geometry designed to minimise deformation of the loading pin holes. The 4th contribution related the weld bead parameters to pipe wall stresses and the effect of notches as stress concentrators. The 5th contribution is a new method of visualising a welding procedure that can be used to not only compare the welding procedures but also predict the size of the MZ and the HAZ. The 6th contribution of the study is the proposal of new weld bead geometry that consist of the MZ bounded by the HAZ, for butt fusion welded joints of HDPE pipes.

Made available in DSpace on 2014-06-11T19:30:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-08-16Bitstream added on 2014-06-13T20:01:02Z : No. of bitstreams: 1 gaspar_rt_dr_sjrp.pdf: 649983 bytes, checksum: 1fcf82fd9f75312b80b50e055388690d (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O Poli(etileno glicol) (PEG) é um polímero sintético cujas características tem despertado grande interesse em diversas áreas. Suas aplicações podem ser vistas nas mais variadas áreas, desde biotecnologia e medicina até aplicações industriais e cosméticos. Alguns aspectos físicos como a estrutura adotada por esse polímero em diferentes solventes e detalhes sobre a interação entre essas moléculas ainda necessitam de maiores esclarecimentos, o que o torna objeto de intensa investigação. Essa tese visa desenvolver um modelo para moléculas de PEG, que possa ser utilizado em experimentos de dinâmica molecular. Resultados de simulações com esse modelo foram comparados a dados experimentais presentes na literatura, de forma a verificar o comportamento do modelo em diferentes condições, avaliando assim sua adequação. Os valores de densidade, obtidos dos sistemas simulados, apresentaram erro máximo de 1,14% para concentrações de até 50% de PEG400. A densidade do sistema em função da temperatura concorda com os dados da literatura, mantendo um erro fixo de 0,35%, que está relacionado com a concentração de 50% utilizada nessa simulação. A estrutura helicoidal, apresentada pelas moléculas de PEG ao final do processo de preparação dos modelos, é perdida rapidamente em todas as diferentes condições em que o sistema foi simulado, indicando que tal estrutura é energeticamente desfavorável em água. Com o aumento da concentração de PEG, as seguintes estruturas foram encontradas: moléculas de PEG livres em solução em concentrações inferiores a 5%, aglomerados de PEG entre 5 e 50%, com uma transição gradual entre uma estrutura e outra. Os resultados obtidos para concentrações acima de 50% não são conclusivos. Seguindo o procedimento aplicado ao modelo inicial, de PEG400, foi desenvolvido... / Poly(ethylene glycol) (PEG) is a synthetic polymer whose characteristics have attracted great interest in different fields. It has been applied in very different areas, from biotechnology and medicine to industry and cosmetics. Physical aspects like the structure PEG assumes in different solvent and details on the interaction between these polymers still lack clarity, make PEG an object of intense investigation. This Thesis aims do develop a model for PEG molecules that can be used in molecular dynamic simulations. Results of simulations using this model were compared to published experimental data, in order to investigate the behavior of the model under different conditions to evaluate its validity. The density values obtained from the simulations exhibit a maximum error of 1.14% for PEG400 concentrations up to 50%. The system density as a function of temperature agrees with experimental data from the literature within an error of 0.35% for the 50% PEG in the simulation. The helicoidal structure assumed by the PEG molecules at the end of the procedure of the model preparation is quickly lost under every simulation condition, thus indicating that the helicoidal structure is not energetically favorable for PEG in water. As PEG concentration is increased, the following structures were found: free PEG molecules below ca 5%, PEG clusters from ca 5-50%, with a gradual transition from one structure to another. The results for concentrations higher than 50% are not conclusive. Following the procedure applied to the initial PEG400 model, a second model was developed, almost four times larger, and used to investigate possible molecular effects capable to induce phase thermoseparation. The transition from different system states took place on average temperatures between 423.3 K and 424.1 K at the average pressure of 8.98 Bar.

Orientador: Cláudia Helena Pellizon / Banca: Silvana Artioli Schellini / Banca: Cláudia Valeria Seullner Brandão / Resumo: Alterações oculares, em especial a perda de volume nas cavidades evisceradas, promovem uma série de modificações ao paciente tanto funcional do órgão quanto psicológica e estética. Uma grande preocupação ao longo do tempo é a procura de um material que possa preencher o volume perdido de forma a dar um maior conforto no ponto de visto psicológico e estético ao paciente. Para contribuir nessa direção, esse trabalho teve como objetivo testar experimentalmente prótese de polietileno granulado de ultra-alto peso molecular, material de baixo custo, em órbitas de coelhos submetidos à evisceração cirúrgica em vários tempos experimentais, onde foram avaliados aspectos macroscópicos e microscópicos e de toxicidade sistêmica do material. Os resultados desse trabalho mostram que o material utilizado no implante de cavidade não apresenta alteração significativa nos parâmetros analisados quando comparados ao grupo controle. Sendo resultados bastante promissores indicando que o implante de polietileno poroso desenvolvido por uma indústria nacional tem alto potencial para se realizar testes em humanos / Abstract: Ocular changes especially the loss of volume in eviscerated cavities promotes several modifications to patients - organ functioning and psychological and esthetical changes. A material that could replace the lost volume in order to guarantee to patients more psychological and esthetical comfort has long been worryingly searched. Contributing in this direction this work aimed at testing experimentally a prosthesis polyethylene granulate of ultra-high molecular weight made of a low cost material to be implanted in orbit of rabbits through surgical evisceration during several experimental times to assess macroscopic and microscopic aspects of systemic toxicity of the respective material. The results show that the material used for the implant of the prosthesis in the cavity does not present significant alteration in the analysed parameters when compared to the control group. Thus, we point with this study promising results indicating that the porous polyethylene implant developed by a national enterprise presents high potential to be tested in humans / Mestre

Le principal objectif des travaux présentés dans ce manuscrit était d’étudier certains paramètres régissant l’efficacité et la durabilité de moustiquaires avec des molécules insecticides incorporées dans les fils de polyéthylène. Pour cela deux axes de travail ont été identifiés : l’étude des phénomènes de migration des molécules insecticide dans les fils de polyéthylène et l’étude des mécanismes de photo-dégradation de l’insecticide étudié : la deltaméthrine.L’étude de l’influence du procédé de fabrication des moustiquaires sur la morphologie du polyéthylène a permis de montrer que l’étape d’étirage à froid était critique dans la définition des propriétés morphologiques (cristallinité et orientation de la structure cristalline) et mécaniques des fils. L’effet du recuit observé est plus modéré (légère augmentation de l’épaisseur des lamelles cristallines). Néanmoins, il a été montré que les modifications induites par le recuit sur la morphologie du polyéthylène ont une influence sur les phénomènes de migration des molécules insecticides dans les fils. En effet, alors qu’un retard est observé dans les courbes de désorption des fils non recuits, ce retard disparaît pour les fils recuits. Il a été également montré que la faible vitesse d’évaporation de la deltaméthrine permet de limiter la migration de la deltaméthrine hors des fils.L’étude de la photo-dégradation de la deltaméthrine a permis de mettre en évidence les principaux mécanismes de dégradation (isomérisation, scission de la fonction ester et de la fonction cyclopropane). L’ajout d’additifs de type antioxydants ou filtres UV permet de limiter la vitesse de dégradation de la deltaméthrine / The main objective of the works presented in this manuscript was to study some of the parameters ruling the efficacy and the durability of the mosquito nets with incorporated insecticide in the polyethylene yarns. To achieve this goal, two lines of research were identified: the study of the insecticide migration phenomena in the yarns and the study of the photodegradation mechanisms of the molecule of interest: the deltamethrin.The study of the influence of the nets fabrication process on the polyethylene morphology showed that the cold-drawing step was critical to define the morphological (crystallinity and orientation of the crystalline structure) and mechanical properties. The observed influence of the heat-setting appeared less important (slight increase of the crystalline lamellae thickness). However, the heat-setting induced modifications which affected the migration of the insecticide molecules in the yarns. Indeed, while a delay is observed in the desorption curves of the non-heat-set yarns, this time-lag disappeared in the heat-set yarns. It was also shown that the low evaporation rate of deltamethrin permits to impede the migration of deltamethrin out of the yarns.The study of the photodegradation of deltamethrin permitted to highlight the main degradation mechanisms (isomerization, ester cleavage and cyclopropane cleavage). Antioxidant and UV absorber additives can be used to reduce the deltamethrin degradation rate

Os nervos periféricos são extensões do sistema nervoso central e responsáveis pela interação das atividades das extremidades, em suas funções sensitiva e motora. São vulneráveis aos mesmos tipos de traumas que afetam outros tecidos: contusão, compressão, esmagamento, estiramento, avulsão e laceração. Desta forma, a interrupção de continuidade da estrutura do nervo, por algum tipo de trauma, resulta na interrupção de transmissão dos impulsos nervosos e na desorganização de suas atividades funcionais. Para tanto, em vista da evolução tecnológica e o desenvolvimento de equipamentos mais sofisticados, a microcirurgia vem ganhando cada vez mais espaço no campo da investigação experimental referente a recuperação de nervos periféricos lesionados. Em uma secção simples, sem perda tecidual, a neurorrafia denominada término-terminal apresenta bons resultados, contudo, quando ocorre perda de tecido nervoso ou, não se têm mais os cotos distais do nervo, outras técnicas devem ser empregadas, até porque, não se pode de modo algum tencionar o nervo numa tentativa de coaptá-lo novamente. Várias técnicas de tubulização utilizando-se materiais biológicos e não biológicos, para criar um meio por onde ocorrerá a regeneração nervosa já foram ou ainda estão sendo testados com resultados insatisfatórios sob o aspecto funcional.É sabido que em um trauma sem perda tecidual, numa neuropraxia, por exemplo, o nervo recupera espontaneamente de forma satisfatória. É sabido também que em um feixe vásculo-nervoso, o nervo periférico encontra-se em íntimo contato com a adventícia de artérias e veias. A adventícia dos vasos é constituída por tecido conjuntivo frouxo, rico em adipócitos. Assim, em um trauma, os neuritos oriundos do coto proximal do nervo lesado, ficam diretamente em contato com esses adipócitos. Seguindo este raciocínio, e com base em trabalhos anteriores onde foi usada veia preenchida com músculo esquelético a fresco como enxerto, decidimos testar a possibilidade de crescimento axonal por meio de enxerto com tubo de polietileno preenchido por tecido adiposo autólogo. Para tanto será utilizado um tubo com 12 mm de comprimento por 0,25 mm de diâmetro, com poros de 80 µm de diâmetro, preenchido com tecido adiposo in natura retirado das adjacências do referido nervo, na tentativa de se recuperar o nervo isquiático. A certificação do sucesso da recuperação do nervo será feita por meio de técnicas de microcirurgia, microscopia e morfometria. O enxerto de polietileno mostrou ter resistência a pressões, uma vez que não foi observado colapso estrutural. A gordura mostrou ser bom material trófico já que no grupo onde a utilizou apresentou resultados mais próximos do controle final. / Peripheral nerves are extensions of the central nervous system and are responsible for the interaction of the activities of the extremities in their sensory and motor function. They are vulnerable to these types of injuries that affect other tissues: contusion, compression, crush, stretch, tear and avulsion. Thus, the interruption of continuity of the nerve structure, due to some sort of trauma, results in the interruption of transmission of nerve impulses and disruption of their functional activities. Therefore, in view of technological evolution and development of more sophisticated equipment, microsurgery is gaining more space in the field of experimental research concerning the recovery of injured peripheral nerves. In a single section, without loss of tissue, called the end-terminal neurorrhaphy was also good, however, when there is loss of nervous tissue or, if not longer have the distal nerve stumps, other techniques must be employed, because, in any circumstance the nerve should be tensioned as an attempt to coaptation again. Several techniques of tubing, using biological materials and non-biological means to create a place where nerve regeneration have been or are still being tested with unsatisfactory results in the functional aspect. It is known that in a trauma without loss of tissue, a neuropraxia, for example, the nerve recovers spontaneously and satisfactorily. It is also known that in a neurovascular bundle, the peripheral nerve is in close contact with the adventitia of arteries and veins. The adventitia of the vessels is composed of loose connective tissue rich in adipocytes. Thus, in trauma, the neurites from the proximal stump of injured nerve, are directly in contact with these adipocytes. Following this reasoning, and based on previous work where it was used vein filled with fresh skeletal muscle as a graft, decided to test the possibility of axonal growth by grafting polyethylene tube filled with autologous adipose tissue. For that will be used with a tube 12 mm long and 0.25 mm in diameter, with pores of 80 microns in diameter, filled with fresh adipose tissue removed from the vicinity of that nerve, in an attempt to recover the sciatic nerve. Certification of successful nerve recovery will be done through microsurgical techniques, microscopy and morphometry. The graft polyethylene proved to have pressure resistance, since no structural collapse was observed. The fat was found to be good material as trophic group which had used the results closer to the ultimate control.

Metilaluminoxano, trietilalumínio e trimetilalumínio foram encapsulados em uma rede de sílica usando sol-gel não hidrolítico. Óxidos mistos foram produzidos através da combinação dos precursores da sílica com Mg(OEt)2, MgCl2 e MgCl2 .6H2O. Os xerogéis resultantes foram caracterizados por uma série de técnicas para determinar os elementos, estrutura, textura e características morfológicas dos cocatalisadores encapsulados. A natureza do cocatalisador afeta o tempo de geleificação. A quantidade de cocatalisador encapsulado não parece ser afetada pelo volume do alquilalumínio, mas a rede de sílica e a organização do xerogel foram, de acordo com os resultados do infravermelho e XRD. Uma forte redução da área específica ocorre comparando os sistemas encapsulados com as sílicas sintetizadas em condições semelhantes. Os alquilalumínios encapsulados foram avaliados na polimerização de eteno usando Cp2ZrCl2 como catalisador na presença e ausência de MAO externo. Os cocatalisadores encapsulados não foram ativos em uma relação Al/Zr de 250 a 500. Para os sistemas mistos combinando MAO homogêneo (externo) com MAO encapsulado, a adição do cocatalisador encapsulado parece não afetar a atividade catalítica. O peso molecular dos polímeros obtido usando catalisador encapsulado é inferior ao obtido a partir das reações homogêneas. No entanto, a polidispersão obtida nos polímeros usando cocatalisador encapsulado foi maior que a obtida a partir de sistemas homogêneos e impregnado. / Methylaluminoxane, tetraethylaluminum and trimethylaluminum were encapsulated within a silica-based material using a non-hydrolytic sol-gel process. Mixed oxides were also produced by combining silica precursors with Mg(OEt)2, MgCl2 and MgCl2 .6H2O. The resulting xerogels were characterized by a series of complementary techniques to determine the elemental, the structural, the textural and the morphological characteristics of the encapsulated cocatalysts. The nature of the alkyl aluminum strongly affects the gelification time. The amount of encapsulated cocatalyst did not appear to be affected by the alkylaluminum volume, but the silica network and the xerogel organization were, according to infrared and X-ray diffraction measurements. There was a large surface reduction for the encapsulated systems compared with the silica that was synthesized under the same conditions. The resulting supported alkylaluminum was evaluated in the polymerization of ethylene using Cp2ZrCl2 as the catalyst in the presence and the absence of external MAO. The encapsulated cocatalysts were not shown to be active in the Al/Zr range of 250-500. For the mixed systems that combined homogeneous MAO with encapsulated MAO, the addition of the encapsulated cocatalyst did not appear to affect the catalyst activity. The molecular weight of the polymers that were obtained by using the encapsulated cocatalyst was lower than the molecular weight of the polymers that were obtained by using the homogeneous catalyst. Nevertheless, the polydispersity of the polymers that were obtained in the presence of the encapsulated cocatalyst was greater than polydispersity of the polymers that were produced with the homogeneous catalyst or the impregnated MAO.