Magnetite and its transformation to hematite in a soil derived from steatite.

O presente trabalho objetivou caracterizar o mineral magnetico e identificar suas rotas pedogeneticas de transformacao em um solo formado sobre esteatito, de Minas Gerais, Brasil. O oxido de ferro isoestrutural ao espinelio foi identificado e caracterizado por analises quimicas, difracao de raios X, espectroscopia Mossbauer e medidas de magnetizacao de saturacao. Na rocha fresca, foi encontrada magnetita estequiometrica e bem cristalizada, com parametro da rede cubica, ao = 0.8407(5) nm. Nas fracoes areia e silte, foram detectadas magnetita parcialmente alterada e hematita estequiometrica e bem cristalizada, com parametros de rede hexagonal, a = 0.5036(3) nm e c = 1.375(4)nm. A ocorrencia dessas hematitas deveu-se principalmente a oxidacao do Fe2+ a Fe3+, no sitio octaedrico de magnetita, durante a pedogenese. Esse processo foi caracterizado pelo aparecimento de pequena quantidade de Fe3+ eletronicamente desacoplada, encontrada nas magnetitas parcialmente oxidadas, cujas formulas para as diferentes estequiometrias foram propostas. Verificou-se tambem pequena quantidade de ilmenita nas amostras de rocha e de solo

Psilídeo-dos-ponteiros-do eucalipto - Ctenarytaina spatulata (Hemiptera: Psyllidae).

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Psilídeos em eucaliptos no Brasil.

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Facebook As A Campaign Tool During The 2012 Elections: A New Dimension To Agenda Setting Discourse

The social networking site Facebook has risen to become an important campaign tool for politicians while also raising new questions about how its use is reshaping the agenda setting paradigm. This research examines the extent to which the Facebook messages of presidential nominees during the 2012 U.S. presidential campaign were transferred to the online public on Facebook and, via a two-step flow, to the greater citizen’s agenda. Findings demonstrate that in their political campaigns on Facebook, politicians are successfully transferring their first- and, to a lesser extent, second-level agendas to the Facebook public agenda, which largely mirrors the greater public agenda.

Voidage distribution around bubbles in a fluidized bed: influence on throughflow

In this work, a new method for measuring void fraction distribution around endogenous bubbles in a 2D fluidized bed is presented. The technique is based on illuminating a transparent-wall 2-dimensional bed with diffuse light from the rear and recording the distribution of light that penetrates the bed. The recording is made with a high speed video-camera, which gives frames with grey level corresponding to the light penetration and from which the voidage distribution around the bubbles can be determined. In this way, voidage distribution in the region very close to the bubble contour (r/Rb≲1.2) is obtained, which was not possible in previous studies due to limitations in spatial resolution. A correlation is proposed for the voidage at the contour of the bubble, with the voidage depending on the radial position and the polar angle ε(r, θ). In addition, the effect of the voidage distribution on the throughflow crossing the bubbles was studied and an increase of 20% was determined for the average bubble geometry of the more than 100 bubbles analysedPublicad