Gerenciamento de resíduos sólidos em comunidades rurais do Estado do Amazonas: estudo de caso na comunidade de Manairão.

Este trabalho busca sensibilizar as famílias de agricultores sobre as forma corretas do descarte dos resíduos sem afetar o meio ambiente e sobre as normas da reciclagem e elucidar os problemas sofridos nas comunidades com relação ao lixo; nas comunidades examinadas não havia coletor de lixo, levando o proprietário a uma única solução, jogá-lo na sua propriedade

A semiquantitative approach to the impurity-band-related transport properties of GaMnAs nanolayers

We investigate the spin-polarized transport of GaMnAs nanolayers in which a ferromagnetic order exists below a certain transition temperature. Our calculation for the self-averaged resistivity takes into account the existence of an impurity band determining the extended ("metallic" transport) or localized (hopping by thermal excitation) nature of the states at and near the Fermi level. Magnetic order and resistivity are inter-related due to the influence of the spin polarization of the impurity band and the effect of the Zeeman splitting on the mobility edge. We obtain, for a given range of Mn concentration and carrier density, a "metallic" behavior in which the transport by extended carriers dominates at low temperature, and is dominated by the thermally excited localized carriers near and above the transition temperature. This gives rise to a conspicuous hump of the resistivity which has been experimentally observed and brings light onto the relationship between transport and magnetic properties of this material

Disorder and the effective Mn-Mn exchange interaction in Ga1−x_{1-x}Mnx_xAs diluted magnetic semiconductors

We perform a theoretical study, using {\it ab initio} total energy density-functional calculations, of the effects of disorder on the $Mn-Mn$ exchange interactions for $Ga_{1-x}Mn_xAs$ diluted semiconductors. For a 128 atoms supercell, we consider a variety of configurations with 2, 3 and 4 Mn atoms, which correspond to concentrations of 3.1%, 4.7%, and 6.3%, respectively. In this way, the disorder is intrinsically considered in the calculations. Using a Heisenberg Hamiltonian to map the magnetic excitations, and {\it ab initio} total energy calculations, we obtain the effective \JMn, from first ($n=1$) all the way up to sixth ($n=6$) neighbors. Calculated results show a clear dependence in the magnitudes of the \JMn with the Mn concentration $x$. Also, configurational disorder and/or clustering effects lead to large dispersions in the Mn-Mn exchange interactions, in the case of fixed Mn concentration. Moreover, theoretical results for the ground-state total energies for several configurations indicate the importance of a proper consideration of disorder in treating temperature and annealing effects

Games and play: paths towards childhood humanization

This paper aims at discussing games and plays and the way children perceive their realities throughout these dynamical processes. In other words, playing subsidizes childhood humanization. Here we assume the importance of pedagogical work with children within school and we problematize how education can contribute to the relationship between children and play, and how it can help the process of childhood humanizatio

Caracterização de germoplasma de mandioca quanto ao teor de compostos cianogênicos

A cultura da mandioca apresenta grande importância sócio-econômica para o Brasil e para o mundo. É a terceira fonte mais importante de calorias nos países tropicais, sendo para mais de 600 milhões de pessoas paradigma de segurança alimentar. Pode ser classificada como mansa e brava, diferindo estas pelo teor de compostos cianogênicos de suas raízes. Contudo, ela é uma das plantas cujo conteúdo potencial de cianeto pode causar problemas de toxicidade, tanto para o homem como para animais, pois interfere na condução do oxigênio às células do organismo.1 CD-ROM