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Estudo das propriedades reológicas de nanocompósitos para a produção de filmes tubulares
(Universidade Federal de São Carlos, 2008-07-08) Beatrice, Cesar Augusto Gonçalves; Bretas, Rosario Elida Suman; https://lattes.cnpq.br/2805349172281345; https://lattes.cnpq.br/6023179925944867
In this work, the use of rheological measurements in substitution or complementation to methods normally employed in the characterization of nanocomposites, such as X-ray diffraction (WAXS) and transmission electron microscopy (TEM), was evaluated. Two polymeric matrices with different chemical structures and polarities and two organophilic nanoclays modified with organic surfactants, which were compatible with the respective polymer matrix, were used. Thus, polyamide 6 (PA6) and high density polyethylene (HDPE) nanocomposites were obtained by melt mixing and blown as films. WAXS measurements showed intercalated structures in the HDPE nanocomposites and exfoliated structures in the PA6 nanocomposites. Shear oscillatory rheological experiments were done to evaluate the clay dispersion and distribution in the polymer matrices, which indicated the presence of a poor dispersion in the HDPE nanocomposites, differently of the PA6 nanocomposites. Shear steady and transient rheological measurements indicated that higher interactions between PA6 and the nanoclay modified with a polar surfactant and inside the EVA masterbatches occurred. From the rheological, morphological, mechanical and transport analysis it was found that the addition of clay modified the interfacial interactions between HDPE and EVA, increasing the system compatibility. In both systems, there was an increase in elastic modulus, yielding and rupture behaviors and barrier properties. In conclusion, the rheological characterization of nanocomposites provides further information about the nanoclay dispersion and distribution in the polymer matrix, in addition to quantify the interactions between the components. However, it can not substitute the usual methods of characterization of the nanocomposites, such as WAXS and TEM.
Desenvolvimento de painel pré-fabricado em alvenaria protendida
(Universidade Federal de São Carlos, 2008-07-08) Souza, Paulo Roberto Amaral; Parsekian, Guilherme Aris; https://lattes.cnpq.br/7798651726059215
This research aims the development of a clay block post-tensioned masonry façade panels, as a new alternative building process. This process provides technical and economic advantages when compared to other process in the market. It presented an analysis of the design of the wall and the process of execution of this type of panels for its use as spandrel panels. Initially the technology of prestressed structural masonry and the systems of precast panels façade are presented to establish the concepts and basic guidelines for the development of this research. The proposed panels building process were tested experimentally with the production of three prototypes, designed for their use as horizontal façade panels. Tests were performed in which the panels were supported at the ends with its self weight and additional mid-span load applied simulating the action of horizontal out-of-plane loading in façades. The experimental tests indicate that the post-tensioned masonry panels have excellent structural behaviour, carrying more load then those estimated in the theoretical analysis, thus proving the full viability of execution and use of this type of panel.
Caracterização genética de populações de jaú (Siluriformes: Pimelodidae) utilizando marcadores moleculares mitocondriais e nucleares
(Universidade Federal de São Carlos, 2008-07-08) Avila, Mauricio Carrillo; Galetti Júnior, Pedro Manoel; https://lattes.cnpq.br/3722377660974573
The genus Zungaro known as jaú, is composed by two species distributed along the rivers of South America: Zungaro jahu is found further south in the basin of the Paraná-Paraguay whereas Zungaro zungaro is found further north in the basin of the rivers Amazon and Orinoco. However, in the literature the classification and distribution of each of those species is still unclear and the basic information on the biology and natural history is scarce. In Brazil the jaú is listed as one of endangered species, over-exploited or threatened by overexploitation; however, the regulations fail to protect the jaú because they have mistakenly identified it as Zungaro zungaro. In Colombia, according to the freshwater species Red Book, the Zungaro zungaro has been declared endangered. Considering the limited information on the population genetics of these fish, the purpose of this study was to obtain the genetic characterization of the jaú population through mitochondrial and nuclear molecular markers. This purpose includes the following research questions: 1- Given the uncertainties encountered in the taxonomic genus Zungaro, is this group composed by two species, or are they two different populations? 2- Considering the jaú´s big size and the fact that they migrate long distances, would than mean that there is a population structure? and 3- The jaú´s endangered condition, its habitat´s changes and overfishing, could be responsible for a reduction of the genetic variation of these catfishes? In order to conduct the characterization we used molecular markers such as the mitochondrial cytochrome b gene, the nuclear gene RAG (Recombination Activation Gene) and the nuclear gene coding for ribosomal protein S7. Additionally, a total of eight polymorphic microsatellite loci capable of producing a considerable genetic variation was prospected. The population analysis of the genus Zungaro with mitochondrial and nuclear markers indicated the existence of a population structure among the individuals sampled. This result is due mainly to the differences between the populations of Pantanal - Paraná and the populations of Meta and Amazon; this finding supports the separation of these species. It was also found that these populations share a central haplotype, indicating a genetic cohesion in the genus, where the populations of Meta-Amazon had a greater number of derived haplotypes suggesting a possible population expansion. The occurrence of a unique and central haplotype to the populations of Pantanal- Parana from which the haplotypes of Meta and the Amazon are derived, when the gene RAG was used, would support the idea that these populations would be the center of dispersion and they would retain the ancestral haplotype. Regarding the prospected microsatellite loci, the results indicated they were efficient in the amplification and verification of polymorphism in Zungaro jahu, and were effective in heterologous amplification of other species of the Pimelodidae family. Statistical analyses on the microsatellites loci showed evidence of a single population of the Z jahu specie inhabiting the north and south Pantanal. In contrast, the two Z zungaro populations studied (the Meta River, basin of the Orinoco and the Amazon River) shown to be significantly different, indicating a population structure. In spite of the jaú being an endangered species, the results of the genetic variation showed values comparable to other species of fish. These results open the possibility of developing clear management programs specifically directed to each of these populations, seeking the protection and recovery of individual fish stocks.