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Instituto de Física
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28
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Departamento de Medicina
22
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    ABSTRACT: Leaf area index (LAI) is a key driver of forest productivity and evapotranspiration; however, it is a difficult and labor-intensive variable to measure, making its measurement impractical for large-scale and long-term studies of tropical forest structure and function. In contrast, satellite estimates of LAI have shown promise for large-scale and long-term studies, but their performance has been equivocal and the biases are not well known. We measured total, overstory, and understory LAI of an Amazon-savanna transitional forest (ASTF) over 3 years and a seasonal flooded forest (SFF) during 4 years using a light extinction method and two remote sensing methods (LAI MODIS product and the Landsat-METRIC method), with the objectives of (1) evaluating the performance of the remote sensing methods, and (2) understanding how total, overstory and understory LAI interact with micrometeorological variables. Total, overstory and understory LAI differed between both sites, with ASTF having higher LAI values than SFF, but neither site exhibited year-to-year variation in LAI despite large differences in meteorological variables. LAI values at the two sites have different patterns of correlation with micrometeorological variables. ASTF exhibited smaller seasonal variations in LAI than SFF. In contrast, SFF exhibited small changes in total LAI; however, dry season declines in overstory LAI were counteracted by understory increases in LAI. MODIS LAI correlated weakly to total LAI for SFF but not for ASTF, while METRIC LAI had no correlation to total LAI. However, MODIS LAI correlated strongly with overstory LAI for both sites, but had no correlation with understory LAI. Furthermore, LAI estimates based on canopy light extinction were correlated positively with seasonal variations in rainfall and soil water content and negatively with vapor pressure deficit and solar radiation; however, in some cases satellite-derived estimates of LAI exhibited no correlation with climate variables (METRIC LAI or MODIS LAI for ASTF). These data indicate that the satellite-derived estimates of LAI are insensitive to the understory variations in LAI that occur in many seasonal tropical forests and the micrometeorological variables that control seasonal variations in leaf phenology. While more ground-based measurements are needed to adequately quantify the performance of these satellite-based LAI products, our data indicate that their output must be interpreted with caution in seasonal tropical forests.
    International Journal of Biometeorology 08/2014; 58:1181-1193.
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    ABSTRACT: The capacities of natural and modified Brazilian bentonite samples as adsorbents to remove hexavalent metal chromium were investigated under several conditions in batch and column methods. The raw material, Ca-bentonite, was modified by anchorament of 3-aminopropyltrietoxisilane (APS) and 3,2-aminoethylaminopropyltrimetoxisilane (AEAPS) in the surface of bentonite sample. This type of new occurrence of bentonite is suitable as a raw material for adsorption process. Adsorption behavior of three bentonite types was strongly depending on pH of adsorbate solution, contact time adsorbent/adsorbate, and initial concentration of Cr(VI). The results were confirmed by column method and reveals that the adsorption process of materials accorded by the Redlich-Peterson, Sips, Dubinin-Radushkevich, and Langmuir isotherm models. The exothermic enthalpic values reflected a favorable energetic process for chromium ions anchored in the material surfaces. The negative Gibbs free energy results supported the spontaneity of three adsorption reactions with Cr(VI) ions.
    International Journal of Mining Science and Technology. 07/2014;
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    ABSTRACT: Disturbances in oxidant/production in favour of oxidizing cause oxidative stress during the cryopreservation process. Vitamin C is an antioxidant non-enzymatic present in seminal plasma that protects sperm from oxidative stress. The aim of this study was to evaluate supplementation with ascorbate in a cryopreservation medium on oxidative stress and quality of cryopreserved sperm membranes. It was used in 24 bulls averaging 31 months and 732kg, kept on pasture for this experiment. One ejaculate was collected from each breeder by electrostimulation. The treatments were CO-Control (no additives) and AS-ascorbate (0.45mgmL(-1)). Ascorbate was added to diluted semen at the time of filling in 0.5-mL straws before the cryopreservation process. Thawing was performed in a water bath at 37°C for 30s. After thawing the samples, aliquots for assessment of plasma and acrosome membrane integrity and evaluation of oxidative stress [TBARS concentration spontaneous (TE) and induced (TI)] were taken. The experiment was conducted in a completely randomised design. Data were analysed by ANOVA and compared by the Tukey average test with a significance level of 5%. No differences were observed (CO- 31.67±2.81 v. AS- 31.08±2.42, P>0.05); the quality of the sperm membrane and oxidative stress (TECO: 5.98±2.13 v. TEAS: 6.62±2.33, P>0.05 and TICO: 62.34±8.22 v. TIAS: 58.52±8.27, P>0.05) in sperm cryopreserved with ascorbate were similar to the control group. Typically, animals under adequate nutritional conditions produce adequate amounts of ascorbate; perhaps because of that the treatment using exogenous ascorbate did not present a significant result. The supplementation of extender with ascorbate did not affect oxidative stress and the quality of the plasma membrane and acrosome sperm cryopreserved. Preliminary studies had shown that the addition of higher concentration (4,5mgmL(-1)) of ascorbate has a beneficial effect on oxidative stress and membrane integrity (P<0.05). Thus, further research should be done to better understand the effects of ascorbate in bovine semen.
    Reproduction Fertility and Development 12/2013; 26(1):226.

Information

  • Address
    Rodovia MT 100 Km 3,5, 78698-000, Cuiabá, Mato Grosso, Brazil
  • Head of Institution
    Alberto Sebastião de Arruda
  • Website
    http://www.ufmt.br
  • Phone
    +556536158734
  • Fax
    +556536158937
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