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Departamento de Agronomia
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Departamento de Farmácia
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    ABSTRACT: Fire has been recognized as an important environmental process that affects soil systems. Here, we have reported the effects of temperature on soil aggregate properties of aggregate stability, mean weight diameter, water repellency, water retention, and soil carbon depletion due to soil heating. The study was performed under laboratory conditions by using a muffle furnace. However, realistic temperature gradients from 25 to 650 °C were obtained previously through measurements in the field. The soil tested here is a subtropical Humic Cambisol with 500 g kg− 1 clay content. Most of our results were different from those reported in the literature. Following the temperature gradient, we found a sharp threshold at ~ 550 °C. The threshold indicated two different mechanisms that affect soil aggregate properties. The first mechanism, which affects the physical characteristics of the aggregates, was associated with organic matter and water repellency reduction (≤ 550 °C). The second mechanism was due to the thermal fusion of particles and recrystallization of mineral clays at 650 °C. The reduction in soil organic carbon had a linear effect on aggregate stability, mean weight diameter, and water retention following a temperature gradient. We noted that the longer exposure time at moderate to high temperatures could not compensate for the effect of a very high peak temperature lasting for a short time on soil aggregates. For the tested soil, we found a mixed response pattern explaining the effect of soil heating on aggregate stability.
    Geoderma 10/2014; s 230–231:243–249. DOI:10.1016/j.geoderma.2014.04.025
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    ABSTRACT: Slurry sampling electrothermal atomic absorption spectrometry was used for direct determination of Cr, Pb and Cd in honey without sample pretreatment. The honey slurries were prepared in aqueous solution containing hydrogen peroxide and nitric acid. The slurries were directly introduced in the pyrolytic graphite tubes. Pd-Mg was used as a chemical modifier only for Cd determination. Analytical curves were performed with aqueous standards for Pb and Cr and with addition of fructose for Cd. The quantification limits for Cd, Pb and Cr were 2.0, 5.4 and 9.4ngg(-1), respectively. Acceptable precision of the methodology was obtained through repeatability and intermediate precision. In the accuracy study, recoveries were satisfactory (94-101%) for the three elements. The methodology was applied in honey from Paraná (Brazil). The concentrations of Pb, Cd and Cr ranged from 141 to 228ngg(-1), <2.0 to 8ngg(-1) and 83 to 94ngg(-1), respectively.
    Food Chemistry 03/2014; 146:166-73. DOI:10.1016/j.foodchem.2013.09.065
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    ABSTRACT: Poly(lactic acid) (PLA) and PLA-poly(ethylene glycol) (PLA-PEG) nanoparticles containing resveratrol (RVT) were developed, and their antioxidant activity was evaluated. An analytical method using high performance liquid chromatography (HPLC)/photodiode array (PDA) detection was also developed and validated for RVT determination in nanoparticles. The mobile phase consisted of methanol : water (51 : 49, v/v) flowed at 0.9 mL/min, and the PDA detector was set at wavelength of 306 nm. The mean diameter of the nanoparticles varied between 180 and 220 nm, and the encapsulation efficiency of RVT ranged from 60% to 88%. The nanoparticles containing RVT were evaluated for their ability to scavenge the radical (2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt) (ABTS(•+)). The profile obtained from the PLA nanoparticles containing RVT demonstrated that after 24 h, there was almost no increase in antioxidant activity, which was lower than that of the free RVT and RVT-loaded PLA-PEG nanoparticles. For PLA-PEG nanoparticles, the radical-scavenging activity of RVT was shown to increase with time, and after 48 h, it was similar to that observed with free RVT.
    The Scientific World Journal 10/2013; 2013:506083. DOI:10.1155/2013/506083


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    Rua Camargo Varela de Sá, 03 - Vila Carli, 85040-080, Guarapuava, Paraná, Brazil
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09/2010; 6. DOI:10.5380/raega.v6i0.18518
Colloids and surfaces B: Biointerfaces 06/2012; 101C:353-360. DOI:10.1016/j.colsurfb.2012.06.024

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