This diploma thesis deals with application of evolutionary engineering on PHA producing bacterial strains. Two bacterial strains, Cupriavidus necator H16 and Halomonas halophila, were chosen for the evolutionary experiments. Copper cations (Cu2+) and sodium chloride (NaCl) were chosen as the selective pressure for C. necator H16; acetic acid (AA) and levulinic acid (LA) for Halomonas halophila. The adapted strains were during long-time evolutionary experiments characterized by GC-FID and SEC-MALS. The growth of the adapted strains was studied by the mean of optical density measurement. The amount of viable cells was determined by spectral FC after their expositon to selected stress factors. Specific enzyme activities of enzymes involved in citrate and glyoxalate cycle, enzymes generating NADPH, LA metabolism enzyme and PHA biosynthesis enzymes were determined. The adapted strains were compared with the wild-type of strains. The successfull adaptation of C. necator H16 adapted to Cu2+ was detected. Biomass and PHA production of both wild and adapted H. halophila strains cultivated in lignocellulosis waste were determined. It was found out that H. halophila adapted to the LA is capable of producing more PHA than the wild strain of this bacteria.

La résistance aux antibiotiques est une menace sérieuse pour la santé publique. En effet, si on ne change pas rapidement notre consommation excessive d'antibiotiques, la situation actuelle va se dégrader jusqu'à basculer dans une ère dite "post-antibiotique", dans laquelle plus aucun antibiotique ne sera efficace contre les infections microbiennes. Bien que ce phénomène de résistance apparaît naturellement, l'utilisation abusive d'antibiotiques accélère le processus. De plus, la présence de pathogènes multi-résistants neutralise l'effet des traitements existants et dans le cas de chirurgies courantes (césariennes, transplantations d'organe...), la situation peut rapidement s'aggraver voire devenir mortelle. C'est pourquoi des directives, émanant des autorités sanitaires, doivent être mises en place afin de contrôler l'utilisation des médicaments, et ce, à tous les niveaux de la société, des individus au secteur agricole en passant par les professionnels de santé et les industries pharmaceutiques. Le monde de la recherche scientifique, quant à elle, doit trouver des nouvelles stratégies pour enrayer la propagation de la résistance. Dans ce contexte, cette thèse a pour objectif le développement d'une méthode de prédiction, par calculs d'énergie libre, des mutations de β-lactamases favorables à l'hydrolyse des β-lactames. Ces travaux méthodologiques ont donc conduit au développement : (1) de nouveaux paramètres pour les enzymes à zinc, implémentés dans le champ de force OPLS-AA et validés par des simulations de dynamique moléculaire sur un panel de métalloenzymes représentatives, (2) d'un protocole de paramétrisation de ligands covalents pour étudier le comportement de certains β-lactames dans CMY-136, une nouvelle β-lactamase caractérisée au laboratoire, et (3) d'un protocole de calcul d'énergie libre évalué au moyen de compétitions internationales de prédiction. Ce dernier a ensuite été utilisé pour tenter d'expliquer pourquoi la carbamylation de la sérine catalytique n'a pas lieu dans certaines oxacillinases. Au travers de ces travaux, nous avons pu améliorer significativement notre approche computationnelle et désormais tout est en place pour une exploration exhaustive des mutations possibles dans les β-lactamases. / Antibiotic resistance is a global concern threatening worldwide health. Indeed, if we don't change our overconsumption of antibiotics, the current situation could worsen until a "post-antibiotic" era in which existing treatment would be ineffective against microbial infections. Despite the natural occurrence of antibiotic resistance, the misuse of antibiotics is speeding up the process. Furthermore, presence of multi-resistant pathogens negates the effect of modern treatments and usual surgeries (caesarean sections, organ transplantations...) might be riskier in the future, or even lethal. That's why, common guidelines have to be edicted by health authorities in order to control antibiotic use at every level of society, from individuals to healthcare industry including health professionals and agriculture sector. As for scientific research, new strategies have to be considered in order to limit the spread of antibiotic resistance. In that context, the presented thesis aimed at developing a protocol to predict, by free energy calculations, β-lactamase mutations which could promote the hydolysis of β-lactams antibiotics. In order to achieve that, we developed several methodological approaches including: (1) new parameters for zinc enzymes implemented in OPLS-AA force field and thereafter validated using molecular dynamics simulations of representative zinc-containing metalloenzymes, (2) a protocol to parameterize covalent ligands in order to analyze the dynamical behavior of some β-lactams in CMY-136, a novel β-lactamase recently characterized in our laboratory, and (3) a pmx-based free energy protocol. The latter was also assessed through several international blinded prediction challenges, and finally used to find out why carbamylation of the catalytic serine is not observed in certain OXA enzymes. Throughout this work, we made significant improvements in our protocol, and now everything is in place for an exhaustive prediction of possible mutations in β-lactamases.

In hierdie studie word betoog dat korporatiewe sosialeverantwoordelikheid (KSV) minstens twee funksies het: om tot volhoubare ontwikkeling by te dra; en om strategiese voordeel vir die maatskappy te skep. Doeltreffende kommunikasie word as noodsaaklik beskou om beide bogenoemde funksies te vervul. Gevolglik word betoog dat maatskappye oor (om strategiese voordeel te trek) en in (om tot volhoubare ontwikkeling by te dra) KSV behoort te kommunikeer. Daaruit volg dat ʼn model vir KSV-kommunikasie beide soorte KSV-kommunikasie moet insluit. Die teoretiese veld van KSV-kommunikasie is tans ontoereikend en daarom word teorieë uit ander velde geraadpleeg om ʼn teoretiese begronding voor te stel. Daar word geredeneer dat kommunikasie oor KSV aan die uitgangspunte van drie kommunikasiebestuursbenaderings behoort te voldoen, aangesien hierdie benaderings dieselfde doelwitte as kommunikasie oor KSV nastreef. Die benaderings sluit in: simmetriese tweerigtingkommunikasie, die reflektiewe benadering asook strategiese kommunikasiebestuur. Betreffende kommunikasie in KSV word betoog dat hierdie vorm van kommunikasie aan die uitgangspunte van die deelnemende benadering tot ontwikkelingskommunikasie behoort te voldoen, aangesien dit volhoubare ontwikkeling as doelwit nastreef. Op grond van ʼn literatuurstudie oor bogenoemde kommunikasiebenaderings, word ʼn teoretiese model vir KSV-kommunikasie in die huidige studie voorgestel. Die empiriese deel van die studie fokus op die landbousektor en die teoretiese KSV-kommunikasiemodel word in die landbousektor toegepas om vas te stel hoe nuttig dit is. Hierdie studie stel voor dat ondersteuning aan opkomende boere die hooffokus van landboumaatskappye se KSV behoort te wees. Daar word gevolglik aanvaar dat landboumaatskappye met opkomende boere (as bevoordeeldes) in KSV behoort te kommunikeer, terwyl hulle met kommersiële boere (as kliënte, verskaffers en soms aandeelhouers) oor KSV behoort te kommunikeer. Die huidige studie het twee landboumaatskappye – Senwes en NWK – se KSV-kommunikasie ondersoek. Die empiriese deel van die studie is kwalitatief benader en die navorsingsmetodes is semigestruktureerde onderhoude, fokusgroepe en kwalitatiewe inhoudsanalise. Kwalitatiewe inhoudsanalise is ook ingespan om die resultate te ontleed wat deur die ander navorsingsmetodes bekom is. Daar is bevind dat kommunikasie tussen die betrokke werknemers van die landboumaatskappye en opkomende boere in KSV grootliks aan die uitgangspunte van die deelnemende benadering tot ontwikkelingskommunikasie voldoen. Die opkomende boere was oor die algemeen heel tevrede met kommunikasie soos dit tans geskied. Daarteenoor wil dit voorkom asof die landboumaatskappye so ver moontlik vermy om oor hulle KSV-inisiatiewe met kommersiële boere te kommunikeer. Geen van die kommersiële boere wat aan die studie deelgeneem het, was bewus van die maatskappye se betrokkenheid by ontwikkelende landbou nie, en was uiters negatief oor hierdie gebrek aan kommunikasie. Uit die voorgestelde model vir KSV-kommunikasie blyk dat die kommunikasiekanale, aard van kommunikasie en kommunikasiebeginsels grootliks dieselfde is vir kommunikasie in en oor KSV. Die doelwitte van hierdie twee soorte KSV-kommunikasie stem gedeeltelik ooreen, maar dit kan ook uiteenlopend wees. Die integrasie van kommunikasie in en oor KSV in een model word egter bemoeilik deurdat die metateoretiese raamwerke wat die relevante basisteorieë vir die ondersoek onderlê, oënskynlik uiteenlopende beskouings oor die doel van kommunikasie huldig. / PhD (Communication Studies), North-West University, Potchefstroom Campus, 2015

In hierdie studie word betoog dat korporatiewe sosialeverantwoordelikheid (KSV) minstens twee funksies het: om tot volhoubare ontwikkeling by te dra; en om strategiese voordeel vir die maatskappy te skep. Doeltreffende kommunikasie word as noodsaaklik beskou om beide bogenoemde funksies te vervul. Gevolglik word betoog dat maatskappye oor (om strategiese voordeel te trek) en in (om tot volhoubare ontwikkeling by te dra) KSV behoort te kommunikeer. Daaruit volg dat ʼn model vir KSV-kommunikasie beide soorte KSV-kommunikasie moet insluit. Die teoretiese veld van KSV-kommunikasie is tans ontoereikend en daarom word teorieë uit ander velde geraadpleeg om ʼn teoretiese begronding voor te stel. Daar word geredeneer dat kommunikasie oor KSV aan die uitgangspunte van drie kommunikasiebestuursbenaderings behoort te voldoen, aangesien hierdie benaderings dieselfde doelwitte as kommunikasie oor KSV nastreef. Die benaderings sluit in: simmetriese tweerigtingkommunikasie, die reflektiewe benadering asook strategiese kommunikasiebestuur. Betreffende kommunikasie in KSV word betoog dat hierdie vorm van kommunikasie aan die uitgangspunte van die deelnemende benadering tot ontwikkelingskommunikasie behoort te voldoen, aangesien dit volhoubare ontwikkeling as doelwit nastreef. Op grond van ʼn literatuurstudie oor bogenoemde kommunikasiebenaderings, word ʼn teoretiese model vir KSV-kommunikasie in die huidige studie voorgestel. Die empiriese deel van die studie fokus op die landbousektor en die teoretiese KSV-kommunikasiemodel word in die landbousektor toegepas om vas te stel hoe nuttig dit is. Hierdie studie stel voor dat ondersteuning aan opkomende boere die hooffokus van landboumaatskappye se KSV behoort te wees. Daar word gevolglik aanvaar dat landboumaatskappye met opkomende boere (as bevoordeeldes) in KSV behoort te kommunikeer, terwyl hulle met kommersiële boere (as kliënte, verskaffers en soms aandeelhouers) oor KSV behoort te kommunikeer. Die huidige studie het twee landboumaatskappye – Senwes en NWK – se KSV-kommunikasie ondersoek. Die empiriese deel van die studie is kwalitatief benader en die navorsingsmetodes is semigestruktureerde onderhoude, fokusgroepe en kwalitatiewe inhoudsanalise. Kwalitatiewe inhoudsanalise is ook ingespan om die resultate te ontleed wat deur die ander navorsingsmetodes bekom is. Daar is bevind dat kommunikasie tussen die betrokke werknemers van die landboumaatskappye en opkomende boere in KSV grootliks aan die uitgangspunte van die deelnemende benadering tot ontwikkelingskommunikasie voldoen. Die opkomende boere was oor die algemeen heel tevrede met kommunikasie soos dit tans geskied. Daarteenoor wil dit voorkom asof die landboumaatskappye so ver moontlik vermy om oor hulle KSV-inisiatiewe met kommersiële boere te kommunikeer. Geen van die kommersiële boere wat aan die studie deelgeneem het, was bewus van die maatskappye se betrokkenheid by ontwikkelende landbou nie, en was uiters negatief oor hierdie gebrek aan kommunikasie. Uit die voorgestelde model vir KSV-kommunikasie blyk dat die kommunikasiekanale, aard van kommunikasie en kommunikasiebeginsels grootliks dieselfde is vir kommunikasie in en oor KSV. Die doelwitte van hierdie twee soorte KSV-kommunikasie stem gedeeltelik ooreen, maar dit kan ook uiteenlopend wees. Die integrasie van kommunikasie in en oor KSV in een model word egter bemoeilik deurdat die metateoretiese raamwerke wat die relevante basisteorieë vir die ondersoek onderlê, oënskynlik uiteenlopende beskouings oor die doel van kommunikasie huldig. / PhD (Communication Studies), North-West University, Potchefstroom Campus, 2015

Introdução: A anemia aplástica (AA) adquirida é uma doença grave, caracterizada por pancitopenia e medula óssea hipocelular sem que haja associação com aumento de reticulina ou infiltração anormal na medula. Embora o mecanismo fisiopatológico não esteja totalmente elucidado, atribui-se a uma resposta imunomediada dos linfócitos T no ambiente medular. A trombopoetina (codificada pelo gene THPO) é um hormônio glicoproteico produzido pelo fígado e responsável pelo estímulo de crescimento de megacariócitos, desenvolvimento plaquetário e de demais linhagens e, quando disfuncional, contribui para o desenvolvimento da AA adquirida. Objetivos: Investigar a presença de variantes genéticas no THPO em amostras de sangue periférico e medula óssea de pacientes com AA adquirida (grupo caso) e de indivíduos saudáveis (grupo controle) e verificar a presença de alterações no número de plaquetas durante o seguimento dos pacientes com AA adquirida. Métodos: O gene THPO foi sequenciado em amostras de DNA de medula óssea de 92 pacientes com AA adquirida e no DNA de sangue periférico de 92 controles, cujas amostras haviam sido previamente armazenado no Laboratório de Hematologia da Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo (FMRP-USP). O sequenciamento foi realizado pelo método de Sanger. Realizou-se também a associação entre a presença (ou ausência) de variantes em THPO e o número de plaquetas em 83 pacientes utilizando o teste ANOVA Para outras análises estatísticas, foram utilizados os testes t e qui-quadrado com nível de significância de 5%. Resultados: Foram encontrados três polimorfismos de nucleotídeo único (SNPs) nos pacientes com AA adquirida (rs956732, rs6141 e rs3804618). Os mesmos três SNPs foram observados nos indivíduos do grupo controle (p>0,05). Não houve associação entre o número de plaquetas e a presença de SNPs nos pacientes (p>0,05). Conclusões: Três SNPs foram encontrados em frequências alélicas semelhantes tanto no grupo de pacientes quanto nos controles, sugerindo que a trombopoetina não apresenta alterações genéticas que possam ser associadas à fisiopatologia da AA adquirida nessa coorte. / Introduction: Acquired aplastic anemia (AA) is a severe illness, characterized by pancytopenia and hypocellular bone marrow without increased reticulin or abnormal infiltration of the bone marrow. Although the physiopathological mechanism has not been completely understood, an immune-mediated T-lymphocyte response has been attributed to the bone marrow environment. Thrombopoietin (encoded by THPO), a glycoprotein hormone produced by the liver and responsible for stimulating the growth of megakaryocytes, development of platelets and other lineages that when dysfunctional, contributes to the progress of acquired AA. Objectives: To screen the THPO gene for genetic variants in bone marrow of acquired AA patients and in the peripheral blood of controls, and to verify the correlation between the THPO status and platelet counts in the patients during the treatment. Method: Sanger sequencing of the THPO gene was carried out in 92 acquired AA patients (case group) and 92 controls, in DNA samples previously stored in the Hematology Laboratory of the Ribeirão Preto School of Medicine at the University of São Paulo. The association between the THPO status and the platelet counts was performed in 83 patients through the ANOVA test. The Chi-squared test and t-test were also applied for statistical analysis with a 5% significance level. Results: Three single nucleotide polymorphisms (SNPs) were found in the AA patients (rs956732, rs6141, and rs3804618), as well as in the healthy subjects (p>0,05). No association was verified between the platelet counts and the presence of SNPs in the AA patients (p>0,05). Conclusion: Three SNPs were found in both groups, suggesting that thrombopoietin does not harbor genetic variants that could be etiological for the acquired AA in our cohort.

Componentes extrudados da liga de alumínio AA 7108 pertencente ao sistema Al-Zn-Mg são frequentemente utilizados na área de transporte. No presente trabalho, a microestrutura da liga 7108 foi estudada nas seguintes condições: bruta de solidificação, após homogeneização e após extrusão. Foram utilizadas as seguintes técnicas complementares de caracterização microestrutural: microscopia óptica, microscopia eletrônica de varredura (MEV), microanálise por dispersão de energia acoplada ao MEV, difração de raios X, medidas de dureza Vickers e de condutividade elétrica. Após solidificação, a liga apresentou estrutura dendrítica, microssegregação e compostos intermetálicos. Após tratamento de homogeneização por cerca de 10 horas a 486ºC, ocorreu dissolução quase completa das partículas de intermetálicos e diminuição da microssegregação. Foi detectada também a presença da fase Al3(Zr,Ti), que não se dissolveu durante tratamento térmico de homogeneização de até 20 horas de duração. Durante a extrusão ocorreu recristalização com significativo refino de grão, além de formação de zona periférica de grãos grosseiros. A técnica de difração de raios X utilizando o método proposto por Williamsonn e Hall mostrou eficaz e promissora para acompanhar a homogeneização. / Extruded components of the aluminum alloy AA 7108 belonging to the Al-Zn-Mg system are often used in the transport area. In the present work, the microstructure of alloy 7108 was studied in the following conditions: after solidification, after homogenization heat treatment and after extrusion. The following complementary techniques of microstructural characterization were used: optical microscopy, scanning electron microscopy (SEM), energy dispersive microanalysis coupled to SEM, X-ray diffraction, Vickers hardness measurements and electrical conductivity. After solidification, the alloy presented dendritic structure, microssegregation and intermetallic compounds. After homogenization heat treatment for about 10 hours at 486 °C, almost complete dissolution of the intermetallic particles occurred and decreased microssegregation. The presence of Al3(Zr, Ti) phase was also detected, which did not dissolve during the homogenization heat treatment of up to 20 hours. During extrusion, recrystallization occurred with significant grain refining, in addition to formation of peripheral coarse grains zone. The technique of X-ray diffraction using the method proposed by Williamsonn and Hall showed effective and promising to accompany the homogenization.

Introdução: A anemia aplástica (AA) adquirida é uma doença grave, caracterizada por pancitopenia e medula óssea hipocelular sem que haja associação com aumento de reticulina ou infiltração anormal na medula. Embora o mecanismo fisiopatológico não esteja totalmente elucidado, atribui-se a uma resposta imunomediada dos linfócitos T no ambiente medular. A trombopoetina (codificada pelo gene THPO) é um hormônio glicoproteico produzido pelo fígado e responsável pelo estímulo de crescimento de megacariócitos, desenvolvimento plaquetário e de demais linhagens e, quando disfuncional, contribui para o desenvolvimento da AA adquirida. Objetivos: Investigar a presença de variantes genéticas no THPO em amostras de sangue periférico e medula óssea de pacientes com AA adquirida (grupo caso) e de indivíduos saudáveis (grupo controle) e verificar a presença de alterações no número de plaquetas durante o seguimento dos pacientes com AA adquirida. Métodos: O gene THPO foi sequenciado em amostras de DNA de medula óssea de 92 pacientes com AA adquirida e no DNA de sangue periférico de 92 controles, cujas amostras haviam sido previamente armazenado no Laboratório de Hematologia da Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo (FMRP-USP). O sequenciamento foi realizado pelo método de Sanger. Realizou-se também a associação entre a presença (ou ausência) de variantes em THPO e o número de plaquetas em 83 pacientes utilizando o teste ANOVA Para outras análises estatísticas, foram utilizados os testes t e qui-quadrado com nível de significância de 5%. Resultados: Foram encontrados três polimorfismos de nucleotídeo único (SNPs) nos pacientes com AA adquirida (rs956732, rs6141 e rs3804618). Os mesmos três SNPs foram observados nos indivíduos do grupo controle (p>0,05). Não houve associação entre o número de plaquetas e a presença de SNPs nos pacientes (p>0,05). Conclusões: Três SNPs foram encontrados em frequências alélicas semelhantes tanto no grupo de pacientes quanto nos controles, sugerindo que a trombopoetina não apresenta alterações genéticas que possam ser associadas à fisiopatologia da AA adquirida nessa coorte. / Introduction: Acquired aplastic anemia (AA) is a severe illness, characterized by pancytopenia and hypocellular bone marrow without increased reticulin or abnormal infiltration of the bone marrow. Although the physiopathological mechanism has not been completely understood, an immune-mediated T-lymphocyte response has been attributed to the bone marrow environment. Thrombopoietin (encoded by THPO), a glycoprotein hormone produced by the liver and responsible for stimulating the growth of megakaryocytes, development of platelets and other lineages that when dysfunctional, contributes to the progress of acquired AA. Objectives: To screen the THPO gene for genetic variants in bone marrow of acquired AA patients and in the peripheral blood of controls, and to verify the correlation between the THPO status and platelet counts in the patients during the treatment. Method: Sanger sequencing of the THPO gene was carried out in 92 acquired AA patients (case group) and 92 controls, in DNA samples previously stored in the Hematology Laboratory of the Ribeirão Preto School of Medicine at the University of São Paulo. The association between the THPO status and the platelet counts was performed in 83 patients through the ANOVA test. The Chi-squared test and t-test were also applied for statistical analysis with a 5% significance level. Results: Three single nucleotide polymorphisms (SNPs) were found in the AA patients (rs956732, rs6141, and rs3804618), as well as in the healthy subjects (p>0,05). No association was verified between the platelet counts and the presence of SNPs in the AA patients (p>0,05). Conclusion: Three SNPs were found in both groups, suggesting that thrombopoietin does not harbor genetic variants that could be etiological for the acquired AA in our cohort.

Submitted by Cleide Dantas (cleidedantas@ufpa.br) on 2014-04-07T16:32:48Z No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_AvaliacaoPropriedadesMecanicas.pdf: 2280831 bytes, checksum: 8cbbc4418fd7b34f38d5e833857a0c11 (MD5) / Approved for entry into archive by Ana Rosa Silva (arosa@ufpa.br) on 2014-06-18T12:35:15Z (GMT) No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_AvaliacaoPropriedadesMecanicas.pdf: 2280831 bytes, checksum: 8cbbc4418fd7b34f38d5e833857a0c11 (MD5) / Made available in DSpace on 2014-06-18T12:35:15Z (GMT). No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_AvaliacaoPropriedadesMecanicas.pdf: 2280831 bytes, checksum: 8cbbc4418fd7b34f38d5e833857a0c11 (MD5) Previous issue date: 2009 / No presente trabalho, foram feitos experimentos com a liga de Al – 0,6%Mg - 0,8%Si não refinada, com variações no teor de cobre (0,05% e 0,3%), que objetivaram avaliar dois aspectos do comportamento da liga. O primeiro aspecto diz respeito a afinidade entre esta e o molde, no qual busca se observar o efeito das variáveis térmicas de solidificação sobre a estrutura do fundido e sua correlação com propriedades mecânicas e elétricas, o segundo aspecto está relacionado com o comportamento intrínseco da variação da composição química quando submetida a baixas velocidades e taxas de resfriamento. Para a avaliação das variáveis térmicas de solidificação (velocidades das isotermas liquidus, taxas de resfriamento) utilizouse um dispositivo de solidificação unidirecional horizontal. Os lingotes produzidos a partir da solidificação da liga passaram pelos processos mecânicos de usinagem, laminação e trefilação, examinados em diferentes posições e diâmetros, através do ensaio de tração e condutividade elétrica. Foram analisadas as fraturas em função das microcavidades e diferentes concentrações de teores de cobre constatando-se que em relação ao material deformado a frio, o LRT tem uma tendência de crescimento para a liga de maior concentração de cobre. Os valores avaliados também possibilitaram concluir que a condutividade elétrica cresce quanto maior for o diâmetro das microcavidades e menor o teor de cobre. Com o objetivo de se avaliar somente o comportamento intrínseco da variação da composição química da liga, foi utilizado um segundo dispositivo de solidificação, molde em “U”, pintado internamente com solução de caulim que atribui ao molde baixas velocidades de resfriamento. Os resultados mostram que para os dois teores de cobre há uma tendência de crescimento do LRT com o aumento da redução sofrida pelas amostras, sendo o LRT maior para a liga com maior teor de cobre. Atribuímos este comportamento ao maior teor de soluto que por sua vez apresentou melhor resposta a deformação plástica, encruando mais o material. Entretanto, a caracterização elétrica ocorre de modo inverso, a exemplo do constatado na solidificação unidirecional, onde o menor teor de cobre foi mais eficiente. / At the present work, experiments were made with the unrefined alloy Al – 0,6%Mg - 0,8%Si, with variations in copper content (0,05% e 0,3%), that aimed to evaluate two aspects of the alloy behavior. The first aspect concerns the affinity between it and the mold, which seeks to observe the effect of the solidification thermal variables of the structure of molten and the correlation with mechanical and electrical properties, the second aspect is related with the intrinsic behavior of the variation on the chemical composition subject at low speed and cooling rates. For evaluating the solidification thermal variables (liquidus isotherms velocities, cooling rates) was used a device for horizontal unidirectional solidification. The ingots produced from the solidification of the alloy rose by mechanical machining, laminating and steel drawing, examined in different positions and diameters, by testing the traction and electric conductivity. Fractures were analyzed in terms of micro cavities and different levels of copper and it was found that in the cold deformed material, the limit of tensile strength has a trend of growth for the alloys of higher concentration of copper. The measured values have also concluded that the electrical conductivity increases the greater the diameter of the micro cavities and lower the copper content. In order to evaluate only the intrinsic variation behavior of the alloy chemical composition, a second device was used for solidification, mold in "U", painted internally in solution of kaolin that attaches to such low rates of cooling. The results show that for both copper content there is a tendency of increase in the limit of tensile strength with increasing reduction suffered by the samples, the limit of tensile strength greater for the alloy with higher copper content. We attach this behavior to the higher content of solute which in turn showed better response to plastic deformation, compressing the material. However, the electrical characterization occurs in an opposite way, as seen in unidirectional solidification, where the lowest copper content was more efficient.

Made available in DSpace on 2016-12-08T17:19:17Z (GMT). No. of bitstreams: 1 Andre Hekermann Buss .pdf: 72415 bytes, checksum: 43e0cc48f7c70cb7ee759bf4ed7d78b9 (MD5) Previous issue date: 2002-05-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O alumínio vem a cada momento sendo mais solicitado pelas empresas, pois possui propriedades que atendem as suas principais expectativas, quando fala - se nas propriedades do alumínio tem se que citar a relação densidade / resistência mecânica e a boa resistência à corrosão. Algumas propriedades podem ser aprimoradas como, por exemplo, dispersando partículas duras, como é o caso da adição de partículas de silício, resultando num acréscimo da resistência ao desgaste. O silício agirá como um reforço ao material, e características como esta são bem vistas pelo mercado consumidor. Com um mercado crescente e receptivo em diferentes áreas, como o setor automobilístico, setor aeronáutico ou ainda em áreas militares, há a necessidade de se incrementar ainda os estudos com as ligas de alumínio. Neste contexto desenvolveu-se uma pesquisa voltada para da liga AA 2124, com adições de 13% e 17% em partículas de silício, obtidas via moagem em moinho de bolas por um tempo de 10h, numa relação de pó / bolas de 1:10. Os pós de silício foram peneirados e agrupados conforme distribuição granulométrica considerando tamanhos grandes (partículas entre 100 e 120 mesch), tamanho médio (partículas entre 200 e 270 mesch) e tamanhos pequenos (partículas menores do que 325 mesch). A obtenção do produto final foi através da mistura manual, e posterior compactação para a obtenção das pré formas e extrusão e quente numa temperatura de 500 oC. Com as barras de extrusão se destinaram algumas para o tratamento térmico de solubilização a 505 oC e envelhecimento a 190 oC por 12 hs. A caracterização mecânica das amostras foi feita através de dureza, resistência ao desgaste, tração, e caracterizadas estruturalmente via microscopia ótica e MEV, possibilitando a comparação entre os resultados e sem o tratamento térmico. Buscou - se identificar a influência da morfologia das partículas sobre as propriedades mecânicas do material. Com isto é possível obter um comparativo entre as propriedades e as condições morfológicas do material e prever algumas aplicações práticas.

Excess fluoride (F-) in drinking water poses a health threat to millions of people around the world. In the present work, activated alumina (AA) has been used as an adsorbent. Data obtained from batch experiments were fitted to the (i) pseudo-first order, (ii) pseudo-second order, and (iii) Langmuir kinetic model. Model (ii) performed better than model (i), and fitted the data well. However, the rate constant for adsorption ka had to be varied as a function of the initial concentration of F- in the liquid phase c0. A more satisfactory approach is provided by Langmuir model, which fitted the data reasonably even though ka was independent of c0. Shreyas (2008) developed a model for the batch adsorption of F- onto porous pellets of AA. Some errors were detected in his computer program were corrected. The parameters of the model were estimated by fitting predictions to data. The parameter values suggest that the adsorption process is likely to be diffusion limited. Column experiments were conducted as follows. The pellets were soaked in deionized water for a time ts before they were loaded into columns. A feed solution having a fluoride concentration cf = 3 mg/L was fed to column and the concentration of F- in the exit stream ce was measured at regular intervals. Breakthrough was deemed to have occurred when ce exceeded the permissible limit (= 1 mg/L). Constant values of the bed height H, and the empty bed contact time tc were used in the experiments. The volume of treated water V, scaled by the volume of the bed Vb, varied strongly with the soaking time ts, with a maximum at ts = 24 h. To understand the possible reasons for this behaviour, XRD, FESEM, and FTIR were used to characterize the surface of AA. Though the concentrations of the surface hydroxyl groups may influence the adsorption of F-, FTIR studies show there is no direct correlation between V/Vb and the concentrations of these groups. The FESEM and XRD studies indicate that fresh AA consists mainly of boehmite, which gradually converted to gibbsite during soaking. For fixed values of H and tc, the dimensionless volume of treated water V/Vb was a maximum at D = 45 mm. This behaviour may be caused by wall effects for small values of D and by occurrence of quasi-static regions near the wall for large values of D. The cost of treated of water was Rs. 0.42/L. It decreased slightly to Rs. 0.37/L after one regeneration cycle, but increased to Rs. 0.41/L after two cycles. The volume of treated water after two regeneration cycles was 595 L/kg. The concentration of Al3+ ions ca in the treated water increased and exceeded the permissible limit of 0.2 mg/L as the number of regeneration cycles increased. The concentration of F- in regeneration effluent cre was in the range 32-70 mg/L. The effluent was subjected to solar distillation, leading to a distillate whose fluoride concentration F- was in the range 9-12 mg/L. The distillate can be discharged into the public sewers, as the permissible limit is 15 mg/L.