The human populations of the Brazilian Amazon were formed by interethnic crosses between Europeans, Africans, and Amerindians. The relative contribution of men and women of different ethnic groups was not homogeneous, since the social policies of the first three centuries of Brazilian colonization encouraged mating between European men and indigenous women and, later on, African women. In order to test this model based on historical data, we compared the relative contribution of the Y-DNA and mtDNA of Amerindian and non-Amerindian populations to the formation of the urban population of the town of Belém, in the Amazon region, on the basis of a C-->T mutation at locus DYS199 present in 90% of the Amerindian Y-DNA and of five markers that define 99% of the mitochondrial sequences of Amerindians. The contribution of indigenous men to the formation of this population was less than 5%, whereas the contribution of indigenous women was estimated at more than 50% of the mitochondrial sequences of the same population. Thus, the present results demonstrate that the contribution of indigenous women to the formation of the Belém population was 10 times higher than the contribution of indigenous men, a genetic consequence of social behavior and attitudes of the past; our results also help clarify the process of integration of indigenous communities into the urban societies in Brazil and possibly in other countries.

RESUMOO desenvolvimento de compósitos reforçados com fibras naturais se alia à nova lógica do desenvolvimento sustentável e potencializa a produção de materiais ambientalmente corretos. A chave para tornar economicamente viável e ambientalmente favoráveis estes novos materiais passa pela adaptação de técnicas consagradas de fabricação de compósitos às propriedades peculiares e intrínsecas das fibras naturais, como o processo de infusão, que por se tratar de um processamento em molde fechado contribui para a redução das emissões de voláteis ao meio ambiente na etapa de fabricação. Neste trabalho estudaram-se como as principais variá-veis do processo de infusão afetam as propriedades do compósito quando são utilizadas fibras naturais como reforço de uma matriz de poliéster insaturado. Produziram-se placas reforçadas com fibras de curauá, juta e palha da costa arranjadas na forma de fios alinhados ou tecido em estilo plano sob diferentes níveis de vácuo no processamento. A elevação do nível de vácuo altera a condição de compactação das fibras modificando sua porosidade, interface fibra/matriz e consequentemente as propriedades do compósito. Os compósitos foram caracterizados quanto à sua resistência à tração, módulo de elasticidade, impacto Charpy e porosidade. Os resultados mostraram que o processo de infusão possibilitou a fabricação de compósitos com até 45% de fração volumétrica de fibra, com porosidade em torno de 2% e excelente estabilidade dimensional. Verificouse ainda que, no geral, a elevação do nível de vácuo alterou significativamente as condições de compactação dos reforços, alterando, a depender da estrutura da fibra utilizada, a eficiência da interface matriz/reforço. Palavras-chave: infusão, curauá, juta, palha da costa. ABSTRACTThe development of composites reinforced with natural fibers is allied to the new logic of sustainable development and enhances the production of environmentally friendly materials. The key to making economically viable and environmentally friendly these new materials involves the adaptation of standard techniques of composites manufacturing to the peculiar and intrinsic properties of natural fibers, such as the infusion process which in function to be a closed mold processing helps reduce of volatile emission to the environment at the fabrication stage. In this work we have been studied as the primary variables of the infusion process affect the properties of the composite when natural fibers are used as reinforcing an unsaturated polyester matrix. They were produced plates reinforced with curaua fibers, jute and raffia arranged in form of aligned fibers or fabric in plain style under different vacuum levels in processing. The increase in the vacuum level changes the fiber compaction condition modifying its porosity, fiber / matrix interface and consequently composite properties. The composites were characterized for its tensile strength, elastic modulus, Charpy impact and porosity. The results showed that the infusion process enabled the manufacture of composites with up t...

Mechanical properties of composites reinforced with lignocellulosic fibers have been researched in recent decades. Jute and mallow fibers are reinforcement alternatives, as they can contribute to increase the mechanical strength of composite materials. The present work aims to predict the Young’s modulus with application of continuous and aligned lignocellulosic fibers to be applied as reinforcement in polyester matrix. Fibers were manually separated and then arranged and aligned in the polyester matrix. Composites with addition 5, 15, and 25 vol% jute and mallow fibers were produced by vacuum-assisted hand lay-up/vaccum-bagging procedure. Samples were tested in tensile and the tensile strength, elasticity modulus, and deformation were determined. Results showed that the intrinsic Young’s modulus of the fibers was set at values around 17.95 and 11.72 GPa for jute and mallow fibers, respectively. Statistical analysis showed that composites reinforced with 15 and 25 vol% jute and mallow presented the highest values of tensile strength and Young’s modulus. The incorporation of 25 vol% of jute and mallow fibers increased the matrix Young’s modulus by 534% and 353%, respectively, effectively stiffening the composite material. Prediction models presented similar values for the Young’s modulus, showing that jute and mallow fibers might be used as potential reinforcement of polymeric matrices

Composite materials made from organic matrices are generally combustible. It is necessary to determine in each case their behaviour under fire and determine whether they fulfil the requirements of the applicable standards in order to match each material to each specific application.Polyester polymer mortar is a material that provides much better mechanical characteristics than traditional mortars but one of its weak points is fire reaction, in this paper, fire reaction of a particular polyester polymer mortar is determined based on Spanish standards, in order to establish its suitability as a coating and cladding material for building construction.PMs contain an easily flammable and combustible component, the resin.They usually produce a great quantity of smoke and hazardous gases when burning.One of the first groups of researchers to deal with this problem (Suzuki et al., 1975) carried out tests according to J IS (Japanese Industrial Standards).After the very first tests, the material disintegrated and hence they recommend the use of a fire retardant agent to inhibit combustion. For the use of PMs in structural elements a fire-protection coating is proposed.Further tests were made using Dawsonite (pirolysis-modified mineral, NaAl(0H) 2 C0 3 ) as fire retardant agent. According to the manufacturer's specifications its addition also reduces the heat generation. The ignition-Brought to you by | Western University

Composite materials stand out for enabling the development of new materials that are environmentally friendly, whose manufacturing processes and waste are increasingly less harmful, associated with good mechanical properties. In this context, this work sought to investigate the mechanical behavior in flexural and impact of polyester matrix composites with the inclusion of short fibers of sisal, piassava, raffia, mallow and jute arranged randomly. The mechanical properties of flexural were evaluated according to ASTM D 790 and the impact toughness Charpy with the ASTM D 6110 standard. The results showed that when subjected to flexural stresses, the composites presented resistance of 112 .12 MPa for the neat matrix and 35.21; 34.45; 27.29; 25.89 and 20.56 MPa with the inclusion of sisal, piassava, raffia, mallow and jute fibers, respectively. As for the impact test, they showed values of 31.50 kJ/m² for the neat matrix and 57.06; 52.52; 48.03; 38.02; 37.65 kJ/m² with the inclusion of sisal, piassava, raffia, mallow and jute fibers, respectively. Then, the fracture surface of the composites was analyzed with a microscope in order to correlate the fracture aspects with the mechanical properties.