Federal University of Viosa
Federal University of Viosa
Alves E.F.,SUNY College of Environmental Science and Forestry |
Bose S.K.,SUNY College of Environmental Science and Forestry |
Francis R.C.,SUNY College of Environmental Science and Forestry |
Colodette J.L.,Federal University of Viosa |
And 3 more authors.
Carbohydrate Polymers | Year: 2010
The carbohydrate composition of lignocellulosic biomass is normally obtained by the quantification of monomers after two stages of hydrolysis in H2SO4. A new two-stage hydrolysis protocol has recently been developed but so far only results for temperate hardwoods have been reported. In this investigation the new protocol was used in the analysis of depithed sugarcane bagasse, Eucalyptus grandis and bamboo. The results were compared to those from the traditional hydrolysis protocol. Sugar monomers were quantified by 1H NMR and high performance liquid chromatography (HPLC) and there were no significant differences between the two techniques. The new and traditional hydrolysis protocols gave nearly identical results for the bagasse and bamboo samples both of which contain <0.10 uronic acids per xylose unit. However, the new protocol gave a higher xylan yield (13.2% vs. 12.1%) for the E. grandis that contained >0.20 uronic acids per xylose units. For both hydrolysis protocols, summative analyses in the range of 97.5-101.0% were obtained for the three biomass samples. However, the range was narrower (98.6-99.5%) for the new hydrolysis protocol coupled with 1H NMR analysis. © 2010 Elsevier Ltd.
Zauza E.A.V.,Federal University of Viosa |
Couto M.M.F.,Federal University of Viosa |
Lana V.M.,Federal University of Viosa |
Maffia L.A.,Federal University of Viosa |
Alfenas A.C.,Federal University of Viosa
Australasian Plant Pathology | Year: 2010
Rust, caused by Puccinia psidii, is an important disease in eucalyptus nurseries and plantations in Brazil. In the field, eucalyptus plants taller than 34 m are not infected by the pathogen. We hypothesised that microclimatic conditions above 3 m do not favour either pathogen establishment or disease development. Therefore, we evaluated the effect of the height gradient on rust incidence, related to leaf wetness duration and the number of airborne urediniospores. Young eucalyptus plants were maintained at heights from 0.5 to 4.0 m, and disease was assessed weekly at all heights in five plant sets. Rust incidence reduced as height increased. The values of area under rust progress and rust incidence were negatively correlated (P ≤ 0.05) with height and positively correlated (P ≤ 0.05) with the number of both hours with leaf wetness and airborne urediniospores. Thus establishment and progress of eucalyptus rust were affected by leaf wetness duration and concentration of airborne urediniospores, which decreased as the height increased. © 2010 Australasian Plant Pathology Society.
Guerra M.B.B.,Hampshire College |
Guerra M.B.B.,Federal University of São Carlos |
Amarasiriwardena D.,Hampshire College |
Schaefer C.E.G.R.,Federal University of Viosa |
And 4 more authors.
Journal of Analytical Atomic Spectrometry | Year: 2011
A method for direct determination of Pb by LA-ICP-MS in lichen samples collected in a heavily anthropogenically impacted area of Maritime Antarctica was developed. The lichen samples were cryogenically ground and digested with nitric acid and hydrogen peroxide. Lead determination by solution-based ICP-MS was validated by the use of 2 certified reference materials. Once the Pb concentrations were measured with adequate accuracy and precision, a method for its direct determination by LA-ICP-MS was developed. The laser ablation parameters were optimized by the use of a Doehlert design matrix. The final optimized conditions were: laser energy (60%), spot size (150 μm) and repetition rate (10 Hz). Lead concentration of the analyzed lichen samples were plotted against the intensity of the lead isotopes (208Pb, 207Pb and 206Pb) determined by LA-ICP-MS. Satisfactory linear correlation factors were obtained when 13C was used as internal standard. Lead distribution profiles in lichen thalli cross-sections were also obtained. By these results, LA-ICP-MS emerges as a potential analytical tool for Pb concentration estimation in lichen samples. Minimum amount of sample required, bioimaging capability, high analytical throughput, and minimization of waste generation are the major analytical features of this approach. The significant differences between the Pb concentration in the lichen samples from the control site (1.12 ± 0.05 mg kg-1) and from the impacted points (mean = 5.03 ± 0.57 mg kg-1) permitted qualify these organisms as good biomonitors. Elemental bioimaging of lichens demonstrated that the medulla region of lichen thalli is consistently the main atmospheric lead bioaccumulating lichen tissue. © 2011 The Royal Society of Chemistry.
Szinwelski N.,Federal University of Viosa |
Rosa C.S.,Federal University of Viosa |
Rosa C.S.,Minas Gerais State University |
Schoereder J.H.,Federal University of Viosa |
And 2 more authors.
International Journal of Zoology | Year: 2012
We evaluated the relation of cricket species richness and composition with forest regeneration time, evaluating canopy and litter depth as environmental drivers. Effects of forest patch area, nearest distance to the 300-year patch, cricket abundance, sampling sufficiency, and nestedness were also evaluated. We collected 1174 individuals (five families, 19 species). Species richness increased asymptotically with regeneration time and linearly with canopy cover and litter depth. Canopy cover increased linearly, while litter depth increased asymptotically. Richness was not affected by patch area and nearest distance to the 300-year patch. Richness increased with cricket abundance, and this explanation could not be distinguished from regeneration time, evidencing collinearity of these two explanatory variables. Rarefaction curve slopes increased with regeneration time. Species composition differed among patches, with no nested pattern. We suggest that regeneration and consequent increases in canopy and litter promote recovery of cricket biodiversity, abundance, and changes in species composition. We conclude that the recovery of cricket diversity involves an increase along the spatial scale of complementarity, together with a change in species composition. © 2012 Neucir Szinwelski et al.
Mamani Moreno C.,CONICET |
Stadler T.,CONICET |
Da Silva A.A.,Federal University of Viosa |
Barbosa L.C.A.,Federal University of Viosa |
De Queiroz M.E.L.R.,Federal University of Viosa
Talanta | Year: 2012
In recent years, the release of information about the preventative and curative properties of garlic on different diseases and their benefits to human health has led to an increase in the consumption of garlic. To meet the requirements of international markets and reach competitiveness and profitability, farmers seek to extend the offer period of fresh garlic by increasing post-harvest life. As a result, the use of maleic hydrazide (1,2-dihydropyridazine-3,6-dione) [MH], a plant growth regulator, has been widespread in various garlic growing regions of the world. The present work was undertaken to develop and validate a new analytical procedure based on MH extraction from garlic previously frozen by liquid nitrogen and submitted to low temperature clean-up. The applicability of the method by analysis of garlic samples from a commercial plantation was also demonstrated. The influence of certain factors on the performance of the analytical methodology were studied and optimized. The approach is an efficient extraction, clean-up and determination alternative for MH residue-quantification due to its specificity and sensitivity. The use of liquid nitrogen during the sample preparation prevents the degradation of the analyte due to oxidation reactions, a major limiting factor. Moreover, the method provides good linearity (r 2: 0.999), good intermediate precision (coefficient of variation (CV): 8.39%), and extracts were not affected by the matrix effect. Under optimized conditions, the limit of detection (LOD) (0.33 mg kg -1) was well below the maximum residue level (MRL) set internationally for garlic (15 mg kg -1), with excellent rates of recovery (over 95%), good repeatability and acceptable accuracy (CV averaged 5.74%), since garlic is a complex matrix. The analytical performance of the methodology presented was compared with other techniques already reported, with highly satisfactory results, lower LOD and higher recoveries rates. In addition, the extraction process is simple, not expensive, easily executable and requires lower volumes of organic solvent. The proposed methodology removes the need of extensive typical laboratory extraction procedures, reducing the amount of time needed for pesticide analysis and increasing sample throughput. Adopting this method gives food safety laboratories the potential to increase cost savings by a suitable technique in routine testing to determine MH residues in garlic. © 2011 Elsevier B.V. All rights reserved.
Goodenough A.E.,University of Gloucestershire |
Elliot S.L.,University of Gloucestershire |
Elliot S.L.,Federal University of Viosa |
Hart A.G.,University of Gloucestershire
International Journal of Zoology | Year: 2011
Nest ectoparasites have been linked previously to patterns of nest-site choice and breeding success in birds. Recent research has shown nestboxes facing south-southwest are occupied less frequently by great tits (Parus major) than identical boxes facing other directions, and are associated with reduced offspring condition. Here, we investigate the hypothesis that these findings are due to ectoparasite load being directionally nonuniform, possibly because of nonuniformity in nestbox internal temperature. Nests contained, in order of prevalence, hen fleas (Ceratophyllus gallinae), haematophagous blowflies (Protocalliphora spp.), biting lice (Ischnocera), and ticks/mites (Acari). Although southwest-facing nestboxes were significantly warmer than other boxes, there was no directional difference in total ectoparasite load or abundance of particular species. Similarly, there was no relationship between abundance of any ectoparasite species (either per-nest or per-chick) and avian offspring condition determined using wing length or relative mass. We discuss several possible, nonmutually exclusive, explanations for this, including compensatory responses, costs of parasitism being transferred to parents, and condition-dependent effects. © 2011 Anne E. Goodenough et al.
Tsukada J.,University of Campinas |
Zanin H.,University of Campinas |
Barbosa L.C.A.,Federal University of Viosa |
Da Silva G.A.,Federal University of Ouro Preto |
And 4 more authors.
Journal of the Electrochemical Society | Year: 2012
Direct syntheses of carbon structures including nanodiamond, microdiamond and diamond-like carbon (DLC) on silicon wafers by liquid phase electro-deposition are presented. The solution (ethanolwater) was employed as electrolyte at different concentration levels. Assays were carried out maintaining constant the electric potential between the silicon electrodes in the range of (80-300V) at current density of approximately 2.0mAcm 2. Scanning electron microscopy showed that non-uniform, smooth and heterogeneous structures were produced. The structural composition was evaluated by micro-Raman spectroscopy. A mechanism for the formation of sp 3+ and sp 2 hybridizations is proposed. © 2012 The Electrochemical Society.
Pereira M.P.S.,National Institute of Amazonian Research |
Pereira M.P.S.,University of Amazon |
Malhado A.C.M.,Federal University of Alagoas |
Costa M.H.,Federal University of Viosa
Geophysical Research Letters | Year: 2012
Accurate studies of the impacts of climate change on the distribution of major vegetation types are essential for developing effective conservation and land use policy. Such studies require the development of models that accurately represent the complex and interacting biophysical factors that influence regional patterns of vegetation. Here we investigate the impacts of Sea Surface Temperature (SST) on the vegetation of the Amazon, testing the hypothesis that changes in Amazonian vegetation structure are a consequence of an ocean-atmosphere-biosphere interaction. We design a numerical experiment in which we force a coupled climate-biosphere model by 10 SST patterns produced by different IPCC AR4 models, for the A2 scenario for the period 2000-2050. Simulations for 2011-2050 show that certain patterns of SST are likely to decrease the ensemble for tropical evergreen rainforest and savanna, and that these areas will be occupied mainly by tropical deciduous rainforest, emitting an average of 0.53 Pg-C.yr -1 during the transition. © Copyright 2012 by the American Geophysical Union.
Santos M.C.,Federal University of Viosa |
Santos M.C.,Federal University of Ouro Preto |
Munford M.L.,Federal University of Viosa |
Bianchi R.F.,Federal University of Ouro Preto
Materials Science and Engineering B: Solid-State Materials for Advanced Technology | Year: 2012
In the present work, we concentrate on the study of effects of metallic electrodes, multilayer thickness and temperature in ac and dc electrical conductivity of polyaniline/poly(vinyl sulfonic acid) (PANI/PVS) ultrathin films. The polymer system was obtained from layer-by-layer (Lbl) self-assembly technique on a glass substrate with an electrode array of adhesion layer of NiCr (20 nm) covered with Au (180 nm). We observed a significant and abrupt increase in the value of dc conductivity and a change of ac conductivity behavior of NiCr/Au-PANI/PVS-NiCr/Au structure when the thickness of PANI/PVS system reaches the Au layer. These effects were ascribed to the ideal contact of Au-PANI/PVS and the relative high interfacial contact resistance between PANI/PVS and NiCr, thus reducing the parallel resistance of NiCr/Au-PANI/PVS interfacial layer in an ideal parallel plate capacitor structure. Atomic Force Microscopy images confirm this assumption. Furthermore, the ac conductivity of Au-PANI/PVS-Au structure was typical of solid disordered materials. A model based on carrier hopping in a medium with randomly varying energy barriers was presented for the ac conductivity of the polymer system, which also encompasses the high dielectric constant of PANI/PVS blended films, the neutral contact Au-PANI/PVS, and the electrical resistance of NiCr-PANI/PVS interfacial layer. The model allowed separating the interface and the bulk effects in the electrical response of NiCr/Au-PANI/PVS-NiCr/Au structure and in addition the highest activation energy (35 MeV) correlated with an optimization of hopping distance (30 nm) for carriers jumps in PANI/PVS system. © 2012 Elsevier B.V. All rights reserved.