Institute of Socio-Environmental Studies,Federal University of Goiás,74001-970,Goiania,Goiás,Brazil
Department of Physics,State University of Ponta Grossa,84030-900,Ponta Grossa,Paraná,Brazil
Department of Physics,Institute of Natural Sciences,Federal University of Lavras,37200-900,Lavras,Minas Gerais,Brazil