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OBJETIVO: Determinar a relação entre diferentes índices de atividade física e preditores de adiposidade em adolescentes de ambos os sexos. MÉTODOS: Foram avaliadas 111 crianças (57 meninos e 54 meninas), com idade média de 11,62 ± 0,72. Como preditores de adiposidade foram determinados o IMC, percentagem de gordura corporal e a relação cintura/quadril (RCQ). Quanto aos indicadores de atividade física, calcularam-se o gasto energético total (GET), nível de atividade física habitual (NAFH), nível de atividade física (NAF) e gasto energético com atividade física (GEat) através do questionário de Bouchard e, para a taxa metabólica basal (TMB), a equação de Schofield-HW. RESULTADOS: A amostra apresentou diferenças significativas entre os sexos para idade, % de gordura corporal, RCQ, NAFH, NAF, TMB com p < 0,05. Para os meninos o GET, NAF, TMB e GEat apresentaram correlação significativa com o IMC (r = 0,86; r = 0,70; r = 0,91; r = 0,78) e % de gordura (r = 0,78; r = 0,61; r = 0,90; r = 0,70) com p < 0,01, respectivamente, e o GET, TMB, GEat apresentaram correlação significativa com o RCQ (r = 0,28; r = 0,45 e r = 0,28) com p < 0,05. Para as meninas o GET, NAF, TMB, GEat apresentaram valores significativos com o IMC (r = 0,86; r = 0,82; r = 0,78; r = 0,85); em % de gordura todos os indicadores GET, NAFH, NAF, TMB e GEat foram significativos (r = 0,73; r = -0,29; r = 0,66; r = 0,74; r = 0,70) com p < 0,05. CONCLUSÃO: Os diferentes indicadores de nível de atividade física apresentaram significativa correlação com os preditores de adiposidade com exceção do RCQ para as meninas. O aumento da massa corporal demonstrou relação significância com o aumento do dispêndio energético em função da maior necessidade de energia para movimentar o corpo.

Ceramic matrix composites (CMCs) were developed to overcome the intrinsic brittleness and lack of reliability of monolithic ceramics. Their major advantages include high temperature capability, light weight, corrosion resistance and adequate damage tolerance. All-oxide Ceramic Matrix Composites (OCMCs) offer essential advantages with respect to long time stability in oxidizing atmospheres, when compared to their non-oxide counterparts. Nevertheless, there is at present almost no production concept which meets the requirements in view of cost and performance for these materials. This work aims at producing OCMCs by means of a more flexible production route. This is achieved by integrating well-known powder metallurgy routes with the prepreg technique, used at present for producing commercial high performance polymer matrix composites. The processing consists of the following steps: (a) infiltration of commercial alumina fiber fabrics (3M NextelTM610) with a liquid suspension of the matrix material; (b) lamination of the pre-infiltrated fiber textiles with a paraffin-based suspension for the formation of prepregs; (c) layup of prepregs; (d) warm-pressing for the consolidation of the green body; (e) debinding and (f) reaction bonding and/or sintering for synthesis of the oxide matrix. Pure alumina or Reaction Bonded Aluminum Oxide (RBAO) can be used as matrix materials and damage tolerance is achieved by the porous, weak-matrix approach. Microstructural analysis of a pure alumina composite fabricated by this route show good infiltration of fiber bundles and proves the good adhesion of prepregs during processing. Average strength value of 199 MPa in fiber direction is in good agreement with values presented in the literature for OCMCs produced by other techniques.

For advanced ceramic composites, affordable manufacturing is still the most essential shortcoming with respect to successful commercial use. This holds particularly for components made out of composites with complex hierarchical structures and high demands of mechanical performance and reliability at the same time, e.g. fiber-reinforced ceramic matrix composites (FRCMCs). Therefore, a new processing route is presented here, which is based on the lamination of thermoplastic prepregs. This route allows not only affordable manufacturing, but also advanced mechanical reliability. Powder metallurgy techniques are combined here with concepts from the prepreg technology in a route consisting of the following steps (a) manufacturing of 2 D prepregs using commercial fiber fabrics which are infiltrated with compounds of ceramic particles embedded in an organic matrix, (b) followed by respective stacking and joining, (c) burn out of the organic matrix and (d) sintering to consolidate the matrix. Composites consisting of a porous Al2O3/ZrO2 matrix, reinforced by 8 layers of NextelTM 610 fiber fabric exhibit a bending strength of ~440 MPa, with graceful failure behavior, e.g. a stepwise stress reduction after peak nominal stress. The fracture of these composites is controlled by a series of interfacial delamination events, which enhance energy dissipation during failure.

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