Rill erosion on an oxisol influenced by a thin compacted layer

The presence of compacted layers in soils can induce subprocesses (e.g., discontinuity of water flow) and induces soil erosion and rill development. This study assesses how rill erosion in Oxisols is affected by a plow pan. The study shows that changes in hydraulic properties occur when the topsoil is eroded because the compacted layer lies close below the surface. The hydraulic properties that induce sediment transport and rill formation (i.e., hydraulic thresholds at which these processes occur) are not the same. Because of the resistance of the compacted layer, the hydraulic conditions leading to rill incision on the soil surface differed from the conditions inducing rill deepening. The Reynolds number was the best hydraulic predictor for both processes. The formed rills were shallow and could easily be removed by tillage between crops. However, during rill development, large amounts of soil and contaminants could also be transferred.

Plasma polymerized acetaldehyde thin films for retention of volatile organic compounds

The aim of this work is the production and characterization of plasma polymerized acetaldehyde thin films. These films show highly polar species, are hydrophilic, organophilic and easily adsorb organic reactants with CO radicals but only allow permeation of reactants with OH radicals. The good step coverage of films deposited on aluminum trenches is useful for sensor development. Films deposited on hydrophobic substrates may result in a discontinued layer, which allows the use of preconcentration in sample pretreatment. Deposition on microchannels showed the possibility of chromatographic columns and/or retention system production to selectively detect or remove organic compounds from gas flows.

Five generations of peace operations: from the "thin blue line" to "painting a country blue"

This article combines both international practice and analytical contributions into a systematic and synthetic presentation of the evolution of peace operations from their modern inception in 1948 to the present. It seeks to serve a didactic purpose in proposing a basic structure for Brazilian scholars' burgeoning debate on peace operations and intervention, rather than a definitive characterization of blue helmet practice. Peace operations' progression is traced through five analytical "generations," each adding a crucial factor distinguishing it from its predecessors. Each generation is placed in relation to changes in the nature of conflict and in the interpretation of the foundational principles of peace operations, and links to broader theoretical issues in International Relations are made explicit at each stage.