Wear of rotary plows operating in a tropical clay loam soil

The wear resistance of rotary plows operating in a clay loam soil was studied. The degree of damage caused to the soil and the amount of mass lost by the tools were determined in order to establish correlations between the physical properties of the soil and the wear mechanisms acting on the tribosystem. Field tests were carried out in 12 plots and a randomized experimental design with 4 levels, 3 replicas per level and 2 passes per plot was applied. The levels relate to the tillage implements employed: rotary tiller, rotary power harrow, small motorized rotary tiller and control (unaltered soil). The highest mass losses were measured in rotary tiller and rotary power harrow's tools, while the small motorized rotary tiller's tools showed generally lower levels of damage. It was determined that the effective contact time between tool and soil, the rotating speed and the sudden impact forces are the most significant factors affecting the wear resistance in field operations. Thirty days after tillage operation the soil samples were taken from each plot at a mean depth of 100 mm in order to determine bulk density, gravimetric moisture content and percentage of aggregates smaller than 5 mm. No significant differences among the values of these properties were found in the experiments. The wear mechanisms acting on the tools' surface are complex and include 2-body and 3-body abrasion as well as the presence of sudden impact forces.

Application of Sulfentrazone in Stages of Germination of IAC 90 Cassava Cuttings in Clay Soils and Sandy

Weeds interfere dramatically in the productive potential of cassava; however, information regarding herbicides that are selective to crops is still scarce. Thus, the aim in this study was to assess the initial growth of IAC 90 cassava plants after the application of sulfentrazone at different stages of germination of cassava in clayey and sandy soils. Three experiments were simultaneously deployed: the first experiment consisted in the application of sulfentrazone in the non-germinated stage of cassava cuttings; the second one in the stage of germinated cassavas cuttings (0.9 cm shoots); and the third one in applications in the stage of cassava cuttings with buds emerging (6.5 cm shoots and emerging from the soil). For each experiment the experimental design in randomized blocks was used in the 2 x 5 factorial arrangement with four replications. The factors were composed of two soils (sandy and clayey) and five doses of sulfentrazone (0, 250, 500, 750 and 1,000 g ha-1). It was found that depending on the herbicide dose, development stage of the buds of cassava cuttings and the type of soil, damage can occur in the initial development of the IAC 90 cassava plants. The greatest potential of sulfentrazone selectivity has occurred in applications in the non-germinated cassava cuttings stage and in doses lower than 500 g ha-1 in the clayey soil.

Reflexos da utilização de farelo de coco sobre o valor nutricional do filé de tilápia-do-nilo (Oreochromis niloticus Linnaeus, 1857)

O uso do farelo de coco pode representar uma fonte alternativa na alimentação de peixe. Por esse motivo avaliaram-se os reflexos de sua utilização sobre o valor nutricional do filé de tilápia-do-nilo. O experimento foi realizado em um delineamento inteiramente ao acaso com 4 tratamentos (T1 - 0%, T2 - 10%, T3 - 20% e T4 - 30% de inclusão de farelo de coco) e cinco repetições. Foram determinados a composição centesimal, o teor de colesterol e os teores de ácidos graxos. Observou-se diferença (p < 0,05) entre T1 e T3, T2 e T3 para os teores de umidade; entre T2 e T3 para os lipídios; T1 apresentou diferença com relação aos demais tratamentos referentes aos carboidratos; e quanto aos teores de cinzas foi observada diferença de T1 e T2 entre T3 e T4. Os teores de colesterol apresentaram um aumento gradual significativo. Com relação aos ácidos graxos, observou-se diferença (p < 0,05) entre os tratamentos referentes aos C10:0; C12:0; C14:0; C18:1; C18:3 (gama); C20:3; e C22:6 numa proporção tal que não determinou diferença na qualidade nutricional do produto.

Os pilares institucionais da política cambial e a industrialização nos anos 1930

The Institutional pillars of the foreign exchange policy and industrialization in Brazil in the 1930s. The 1930s constitute one milestone in the Brazilian economic development, as the accelerated industrialization process has started and became the dominant domestic policy. This paper reviews this period focusing on the institutional changes restructuring exchange transactions, to curb financial flows and balance external payments

A Reforma Pedreira na Academia de Belas Artes (1854-1857) e a constituição do espaço social do artista

Manuel Araújo Porto Alegre (1808-1879) teve atuação fundamental nas instituições culturais do Segundo Reinado, tendo sido pintor, crítico de arte, jornalista e poeta, entre outras atividades. Como diretor da Academia Imperial de Belas Artes, o pintor promoveu a maior reforma que a instituição sofreu durante o Império. Parte da chamada Reforma Pedreira (1854-1857), as introduzidas por Porto Alegre buscavam adaptar a instituição aos progressos técnicos de meados do século XIX, e fazer da corte imperial, o Rio de Janeiro, uma cidade sintonizada com a "civilização". É com este objetivo que o pintor faz da técnica um dos temas centrais de sua administração. Neste artigo, tendo como objeto a intervenção de Araújo Porto Alegre na Aiba, pretendemos refletir como as inovações introduzidas na Academia contribuíram para a constituição de um novo espaço social para o artista do Império.