Fungos associados a sementes de araucária coletadas em três municípios do Estado do Paraná.

Resumo

Influence of surface conductivity on the apparent zeta potential of amorphous silica nanoparticles

Zeta potential is a physico-chemical parameter of particular importance in describing ion adsorption and double layer interactions between charged particles [1]. However, for metal oxide nanoparticles, the conversion of electrophoretic mobility measurements into zeta potentials is a complex problem. This complexity arises because of their high surface electrical conductivity, which is inversely proportional to the size of the particle [2]. To describe the electrochemical properties of amorphous silica nanoparticles, we use a basic Stern model whose parameters are independently adjusted by potentiometric titration and electrophoretic mobility measurements at high salinity (10-1 M NaCl) [3]. At low ionic strengths, because of the strong retardation and relaxation effect due to charged counter-ions at the silica/water interface, amplitude of the predicted zeta potential is significantly higher than that of the apparent zeta potential estimated with electrophoretic mobility measurements and Smoluchowski equation. Electrophoretic mobilities are calculated using Henry's electrokinetic model [4] with the predicted specific surface conductivities and zeta potentials. The very good agreement between calculated and measured electrophoretic mobilities confirms that the magnitude of the true zeta potential corresponds to the magnitude of the electrical potential located at the outer Helmholtz plane. Therefore, the assumption of the presence of a stagnant diffuse layer at the amorphous silica/water interface is not required. This study was done within the framework of the NANOMORPH Project (ANR-2011-NANO-008) coordinated by BRG

Investigation of livestock for presence of Trypanosoma brucei gambiense in Tafa Local Government Area of Niger State, Nigeria

The study investigated the presence of Trypanosoma brucei gambiense in livestock to ascertain their reservoir role and also screened for other pathogenic trypanosomes of animals in Tafa Local Government Area of Niger state, Nigeria. A total of 460 livestock comprising (cattle, sheep, goats, and dogs) selected at random were bled, examined using the buffy coat and Giemsa stained thin film and packed cell volume estimated. Questionnaire was filled for each animal on demography, awareness and management practices. An overall prevalence of 2.17% with Trypanosoma brucei, T. congolense, T. vivax and a mixed infection of T. brucei and T. congolense observed microscopically awaiting characterization. Interviews revealed high awareness (82.8%) of tsetse and trypanosomiasis described as bush disease and abortion in four cows. The PCV values were within the normal range, however, a significant decrease (P<0.05) was observed in sheep aged 7months to 4years in two communities. Therefore, the study indicated the presence of T. brucei and other trypanosomes suggesting that animal trypanosomiasis is still a problem to animal health and wellbeing in the study area. The study recommends effective integrated chemotherapy and vector control including livestock rearing under intensive management system to boost livestock production and productivity

A review on development and application of plant-based bioflocculants and grafted bioflocculants

Flocculation is extensively employed for clarification through sedimentation. Application of eco-friendly plant-based bioflocculants in wastewater treatment has attracted significant attention lately with high removal capability in terms of solids, turbidity, color, and dye. However, moderate flocculating property and short shelf life restrict their development. To enhance the flocculating ability, natural polysaccharides derived from plants are chemically modified by inclusion of synthetic, nonbiodegradable monomers (e.g., acrylamide) onto their backbone to produce grafted bioflocculants. This review is aimed to provide an overview of the development and flocculating efficiencies of plant-based bioflocculants and grafted bioflocculants for the first time. Furthermore, the processing methods, flocculation mechanism, and the current challenges are discussed. All the reported studies about plant-derived bioflocculants are conducted under lab-scale conditions in wastewater treatment. Hence, the possibility to apply natural bioflocculants in food and beverage, mineral, paper and pulp, and oleo-chemical and biodiesel industries is discussed and evaluated