Showing papers by "Universidade Federal de Viçosa published in 2010"

Distributed photovoltaic generation and energy storage systems: A review

Abstract: Currently, in the field of operation and planning of electrical power systems, a new challenge is growing which includes with the increase in the level of distributed generation from new energy sources, especially renewable sources. The question of load redistribution for better energetic usage is of vital importance since these new renewable energy sources are often intermittent. Therefore, new systems must be proposed which ally energy storage with renewable energy generators for reestablishment of grid reliability. This work presents a review of energy storage and redistribution associated with photovoltaic energy, proposing a distributed micro-generation complex connected to the electrical power grid using energy storage systems, with an emphasis placed on the use of NaS batteries. These systems aim to improve the load factor, considering supply side management, and the offer of backup energy, in the case of demand side management.

Effects of Amazon and Central Brazil deforestation scenarios on the duration of the dry season in the arc of deforestation

Abstract: Climate change predictions tied to Amazon deforestation scenarios are increasingly being used by government and non-government organisations for near-future planning applications. Despite incorporating a wide range of biophysical variables, these models neglect future scenarios of land use for adjoining regions, such as the Central Brazil Cerrado, which has been deforested by more than 50%. In this study, we investigate the impact of different Amazon and Central Brazil deforestation scenarios on the rainfall regime of the ‘arc-of-deforestation’ in Amazonia. We demonstrate that both Amazon and Cerrado deforestation contribute to an increase of the duration of the dry season in this region. Combining the effects of both scenarios, the dry season may increase from 5 months to 6 months, which may change the biosphere–atmosphere equilibrium in this region. This study demonstrates that the assessment of future Cerrado land use scenarios is also necessary to understand the future climate and ecosystem health of Amazonia. Copyright © 2009 Royal Meteorological Society

Estresse oxidativo: conceito, implicações e fatores modulatórios

Abstract: O estresse oxidativo decorre de um desequilibrio entre a geracao de compostos oxidantes e a atuacao dos sistemas de defesa antioxidante. A geracao de radicais livres e/ou especies reativas nao radicais e resultante do metabolismo de oxigenio. A mitocondria, por meio da cadeia transportadora de eletrons, e a principal fonte geradora. O sistema de defesa antioxidante tem a funcao de inibir e/ou reduzir os danos causados pela acao deleteria dos radicais livres e/ou especies reativas nao radicais. Esse sistema, usualmente, e dividido em enzimatico (superoxido dismutase, catalase e glutationa peroxidase) e nao-enzimatico. No ultimo caso, e constituido por grande variedade de substâncias antioxidantes, que podem ter origem endogena ou dietetica. Objetivou-se revisar os principais mecanismos de geracao de radicais livres, bem como a acao dos agentes mais relevantes do sistema de defesa antioxidante, ressaltando suas implicacoes sobre os marcadores do estresse oxidativo. Tambem serao abordados os principais fatores exogenos moduladores do estresse oxidativo.

Future change of climate in South America in the late twenty-first century: intercomparison of scenarios from three regional climate models

Abstract: Regional climate change projections for the last half of the twenty-first century have been produced for South America, as part of the CREAS (Cenarios REgio- nalizados de Clima Futuro da America do Sul) regional project. Three regional climate models RCMs (Eta CCS, RegCM3 and HadRM3P) were nested within the Had- AM3P global model. The simulations cover a 30-year period representing present climate (1961-1990) and pro- jections for the IPCC A2 high emission scenario for 2071- 2100. The focus was on the changes in the mean circulation and surface variables, in particular, surface air temperature and precipitation. There is a consistent pattern of changes in circulation, rainfall and temperatures as depicted by the three models. The HadRM3P shows intensification and a more southward position of the subtropical Pacific high, while a pattern of intensification/weakening during sum- mer/winter is projected by the Eta CCS/RegCM3. There is a tendency for a weakening of the subtropical westerly jet from the Eta CCS and HadRM3P, consistent with other studies. There are indications that regions such of North- east Brazil and central-eastern and southern Amazonia may experience rainfall deficiency in the future, while the Northwest coast of Peru-Ecuador and northern Argentina may experience rainfall excesses in a warmer future, and these changes may vary with the seasons. The three models show warming in the A2 scenario stronger in the tropical region, especially in the 5N-15S band, both in summer and especially in winter, reaching up to 6-8C warmer than in the present. In southern South America, the warming in summer varies between 2 and 4C and in winter between 3 and 5C in the same region from the 3 models. These changes are consistent with changes in low level circula- tion from the models, and they are comparable with changes in rainfall and temperature extremes reported elsewhere. In summary, some aspects of projected future climate change are quite robust across this set of model runs for some regions, as the Northwest coast of Peru- Ecuador, northern Argentina, Eastern Amazonia and Northeast Brazil, whereas for other regions they are less robust as in Pantanal region of West Central and south- eastern Brazil.

Remote sensing detection of droughts in Amazonian forest canopies.

Abstract: *Remote sensing data are a key tool to assess large forested areas, where limitations such as accessibility and lack of field measurements are prevalent. Here, we have analysed datasets from moderate resolution imaging spectroradiometer (MODIS) satellite measurements and field data to assess the impacts of the 2005 drought in Amazonia. *We combined vegetation indices (VI) and climatological variables to evaluate the spatiotemporal patterns associated with the 2005 drought, and explore the relationships between remotely-sensed indices and forest inventory data on tree mortality. *There were differences in results based on c4 and c5 MODIS products. C5 VI showed no spatial relationship with rainfall or aerosol optical depth; however, distinct regions responded significantly to the increased radiation in 2005. The increase in the Enhanced VI (EVI) during 2005 showed a significant positive relationship (P < 0.07) with the increase of tree mortality. By contrast, the normalized difference water index (NDWI) exhibited a significant negative relationship (P < 0.09) with tree mortality. *Previous studies have suggested that the increase in EVI during the 2005 drought was associated with a positive response of forest photosynthesis to changes in the radiation income. We discuss the evidence that this increase could be related to structural changes in the canopy.

Thermal state of permafrost and active-layer monitoring in the Antarctic: advances during the International Polar Year 2007-2009

Abstract: Results obtained during the International Polar Year (IPY) on the thermal state of permafrost and the active layer in the Antarctic are presented, forming part of ANTPAS (‘Antarctic Permafrost and ...

Seasonal variation, chemical composition and antioxidant activity of Brazilian propolis samples.

Abstract: Total phenolic contents, antioxidant activity and chemical composition of propolis samples from three localities of Minas Gerais state (southeast Brazil) were determined. Total phenolic contents were determined by the Folin–Ciocalteau method, antioxidant activity was evaluated by DPPH, using BHT as reference, and chemical composition was analyzed by GC/MS. Propolis from Itapecerica and Paula Cândido municipalities were found to have high phenolic contents and pronounced antioxidant activity. From these extracts, 40 substances were identified, among them were simple phenylpropanoids, prenylated phenylpropanoids, sesqui- and diterpenoids. Quantitatively, the main constituent of both samples was allyl-3-prenylcinnamic acid. A sample from Virginopolis municipality had no detectable phenolic substances and contained mainly triterpenoids, the main constituents being α- and β-amyrins. Methanolic extracts from Itapecerica and Paula Cândido exhibited pronounced scavenging activity towards DPPH, indistinguishable from BHT activity. However, extracts from Virginopolis sample exhibited no antioxidant activity. Total phenolic substances, GC/MS analyses and antioxidant activity of samples from Itapecerica collected monthly over a period of 1 year revealed considerable variation. No correlation was observed between antioxidant activity and either total phenolic contents or contents of artepillin C and other phenolic substances, as assayed by CG/MS analysis.

Anticarcinogenic effects of polyphenolics from mango (Mangifera indica) varieties.

Abstract: Many polyphenolics contained in mango have shown anticancer activity. The objective of this study was to compare the anticancer properties of polyphenolic extracts from several mango varieties (Francis, Kent, Ataulfo, Tommy Atkins, and Haden) in cancer cell lines, including Molt-4 leukemia, A-549 lung, MDA-MB-231 breast, LnCap prostate, and SW-480 colon cancer cells and the noncancer colon cell line CCD-18Co. Cell lines were incubated with Ataulfo and Haden extracts, selected on the basis of their superior antioxidant capacity compared to the other varieties, where SW-480 and MOLT-4 were statistically equally most sensitive to both cultivars followed by MDA-MB-231, A-549, and LnCap in order of decreasing efficacy as determined by cell counting. The efficacy of extracts from all mango varieties in the inhibition of cell growth was tested in SW-480 colon carcinoma cells, where Ataulfo and Haden demonstrated superior efficacy, followed by Kent, Francis, and Tommy Atkins. At 5 mg of GAE/L, Ataulfo inhibited t...

In vivo trans-specific gene silencing in fungal cells by in planta expression of a double-stranded RNA

Abstract: Self-complementary RNA transcripts form a double-stranded RNA (dsRNA) that triggers a sequence-specific mRNA degradation, in a process known as RNA interference (RNAi), leading to gene silencing. In vascular plants, RNAi molecules trafficking occur between cells and systemically throughout the plant. RNAi signals can spread systemically throughout a plant, even across graft junctions from transgenic to non-transgenic stocks. There is also a great interest in applying RNAi to pathogenic fungi. Specific inhibition of gene expression by RNAi has been shown to be suitable for a multitude of phytopathogenic filamentous fungi. However, double-stranded (ds)RNA/small interfering (si)RNA silencing effect has not been observed in vivo. This study demonstrates for the first time the in vivo interference phenomenon in the pathogenic fungus Fusarium verticillioides, in which expression of an individual fungal transgene was specifically abolished by inoculating mycelial cells in transgenic tobacco plants engineered to express siRNAs from a dsRNA corresponding to the particular transgene. The results provide a powerful tool for further studies on molecular plant-microbe and symbiotic interactions. From a biotechnological perspective, silencing of fungal genes by generating siRNAs in the host provides a novel strategy for the development of broad fungi-resistance strategies in plants and other organisms.

Atmospheric versus vegetation controls of Amazonian tropical rain forest evapotranspiration: Are the wet and seasonally dry rain forests any different?

Abstract: [1] This study analyzes evapotranspiration data for three wet and two seasonally dry rain forest sites in Amazonia. The main environmental (net radiation, vapor pressure deficit, and aerodynamic conductance) and vegetation (surface conductance) controls of evapotranspiration are also assessed. Our research supports earlier studies that demonstrate that evapotranspiration in the dry season is higher than that in the wet season and that surface net radiation is the main controller of evapotranspiration in wet equatorial sites. However, our analyses also indicate that there are different factors controlling the seasonality of evapotranspiration in wet equatorial rain forest sites and southern seasonally dry rain forests. While the seasonality of evapotranspiration in wet equatorial forests is driven solely by environmental factors, in seasonally dry forests, it is also biotically controlled with the surface conductance varying between seasons by a factor of approximately 2. The identification of these different drivers of evapotranspiration is a major step forward in our understanding of the water dynamics of tropical forests and has significant implications for the future development of vegetation-atmosphere models and land use and conservation planning in the region.

Fatores determinantes da capacidade funcional em idosos longevos

Abstract: CONTEXTUALIZACAO: A faixa etaria que mais cresce no Brasil e no mundo e a de idosos com 80 anos e mais. Entre esses individuos, a prevalencia de incapacidades e morbidades e maior que em outros grupos. OBJETIVOS: Investigar a influencia de fatores socioeconomicos, demograficos, biologicos e de saude, nutricionais, de relacoes sociais, alem da autoavaliacao da saude sobre a capacidade funcional de idosos longevos (80 anos e mais). METODOS: Trata-se de um estudo transversal, de base populacional, em que os dados foram obtidos por meio de questionarios e medidas antropometricas. A capacidade funcional foi avaliada utilizando-se o modelo desenvolvido por Andreotti e Okuma (1999). Foram realizadas analises univariada e multivariada. RESULTADOS: Os fatores independentes associados a pior capacidade funcional foram: ter 85 anos e mais (OR=2,91), ser do genero feminino (OR=6,09), fazer uso continuo de cinco ou mais medicamentos (OR=2,67), nao visitar parentes e/ou amigos pelo menos uma vez por semana (OR=11,91) e considerar a propria saude pior que a de seus pares (OR=4,40). CONCLUSOES: Os resultados sugerem que a capacidade funcional esta associada a uma complexa rede de fatores multidimensionais, sendo importante o desenvolvimento de acoes relacionadas aqueles fatores que sao passiveis de intervencao, visando propiciar melhores condicoes de saude e qualidade de vida a esses individuos.

Intake and digestibility in cattle fed low-quality tropical forage and supplemented with nitrogenous compounds

Abstract: The effects of supplementation with nitrogenous compounds on intake, digestibility, and microbial protein synthesis in cattle fed low-quality tropical forage were assessed. Five rumen fistulated crossbred Holstein × Gir heifers were used, with initial average live weight of 180 ± 21 kg. Signal grass (Brachiaria decumbens) hay (48.6 g kg−1 of crude protein (CP), on a dry matter (DM) basis) was used as roughage. Five treatments were defined according to nitrogen supplementation level (0, 20, 40, 60, and 80 g of CP kg−1 above the CP level of the hay). A mixture of urea, ammonium sulfate, and albumin at the ratios of 4.5:0.5:1.0, respectively, was used as nitrogen source. The experiment consisted of five experimental periods, according to a 5 × 5 Latin square design. The average CP contents in the diets were 51.9, 71.1, 86.0, 116.7, and 130.2 g kg−1, on a DM basis. A quadratic effect was detected (P < 0.10) of the CP levels in the diets on DM and neutral detergent fiber intake (kg/day), with maximum response at the levels of 102.4 and 100.5 g CP kg−1 DM, respectively. The average daily concentration of rumen ammonia nitrogen showed increasing linear pattern (P < 0.01) as function of CP levels in the diet, with estimated value of 9.64 mg dL−1 equivalent to the maximum DM intake. Microbial nitrogen flow in the intestine was linearly and positively related (P < 0.01) with the CP levels in the diet.

Bioactive Compounds in Mango ( Mangifera indica L.)

Abstract: Publisher Summary Mango is an important fruit for human nutrition in several parts of the world. It is a tropical fruit widely accepted by consumers throughout the world for its succulence, sweet taste, and exotic flavor, being called the “king of fruits.” It is a fruit with high nutritional value, supplying the human diet with calories, fiber, vitamins, and minerals. Flesh and agro-industrial residues of mangoes contain several bioactive compounds, comprising nutrient and non-nutrient substances with biological properties that act mainly via redox mechanisms. Compounds contained in mango flesh can act as biological antioxidants, maximizing the human antioxidant defense. Additive and synergistic effects of bioactive compounds from mangoes suggest that the fruit has great potential to improve health and reduce the risk of chronic diseases. Despite the numerous bioactive compounds in mangoes, which may promote benefits to human health, the potential for allergenicity of the fruit has been shown. Conventional technological processing of mango into flesh-containing products does not allow complete elimination of the allergenic potency. All mango varieties can supply the diet with nutrients, but considering that the contents of bioactive compounds are influenced by several factors, it was assumed that population groups with the same mango intake may be ingesting such compounds at different levels, not guaranteeing a comparable modulation potential of risk factors of diseases.

Modelagem matemática e determinação das propriedades termodinâmicas do café (Coffea arabica L.) durante o processo de secagem

Abstract: The aim of the present work was to model the drying process and to obtain the thermodynamic parameters of coffee beans (Coffea arabica L.), cultivar Catuai Amarelo, for three different conditions of temperature and relative humidity (35 oC and 32.1 %; 45 oC and 15.7 %; 55 oC and 10.2 %). Coffee beans were hand picked with an initial moisture content of 1.25 (d.b.) and dried to a mean moisture content of 0.13 (d.b.). Six mathematical models commonly used to represent the drying process of agricultural products were fit to the experimental data. Fick’s second law was used to obtain the diffusion coefficients of coffee beans using the drying kinetics. The activation energy for the drying process of coffee beans, as well as the entropy, enthalpy and Gibbs free energy were determined. The modified Midili model best represented the drying phenomenon of coffee beans. The calculated diffusion coefficients were 2.99 x 10 -11 , 2.39 x 10 11 and 5.98 x 10 -11 m 2 s -1 , to the temperatures of 35, 45 and 55 oC, respectively. Enthalpy decreased with the increase in

Impact and Selectivity of Insecticides to Predators and Parasitoids

Abstract: Problems with the use of insecticides has brought losses, such as, negative impact on natural enemies. When these beneficial insects reduce cause the eruption of pests and resurgence it’s more common. Thus principles of conservation these arthropods are extremely important in the biological natural control of pests, so that these enemies may present a high performance. Because of the negative impacts caused by insecticides on agriculture and their harmful effects on natural enemies, the objective of this article is to approach two important subjects, divided into three parts. Part I relates to the description of the main crop pests and their natural enemies; Part II involves the impact of insecticides on predators and parasitoids and Part III focuses on the selectivity of several groups of insecticides to natural enemies. Before spraying insecticides, it is necessary to choose a product that is efficient to pests and selective to natural enemies. So, it is indispensable to identify correctly the groups and species of natural enemies, since insecticides have an impact on their survival, growth, development, reproduction (sexual ratio, fecundity, longevity and fertility), and behavior (motility, orientation, feeding, oviposition and learning) of insects. The mechanisms of toxicity and selectivity of insecticides are related to the properties of higher or lower solubility and molecular weight. Besides, characteristics of the cuticular composition of the integument of natural enemies are extremely important in the selectivity of a product or the tolerance of a certain predator or parasitoid to this molecules. Impacto e Seletividade de Inseticidas para Predadores e Parasitoides Resumo. Dentre os problemas advindos do uso de inseticidas, a destruicao de inimigos naturais e fator importante. Estes insetos beneficos podem reduzir problemas de erupcao de pragas secundarias, ressurgencia de pragas e manter a praga abaixo do nivel de dano economico. Dessa forma a conservacao de inimigos naturais, para que os mesmos exercam alta performance frente as pragas, e de extrema importância em controle biologico de pragas. Metodo de controle essencial utilizados nos programas de manejo integrado de pragas. Tendo em vista os impactos negativos dos inseticidas na agricultura e os seus efeitos adversos sobre os inimigos naturais, este artigo visa abordar dois assuntos importantes, que para isso e dividido em tres partes. A parte I relacionada com o reconhecimento das principais pragas agricolas e seus inimigos naturais; a parte II envolve o impacto dos inseticidas sobre os predadores e parasitoides e a parte III abordara sobre a seletividade dos diversos grupos de inseticidas aos inimigos naturais. Antes de se pulverizar inseticida e necessario a escolha de um produto que seja seletivo e eficiente, assim torna-se imprescindivel identificar de forma correta os grupos e especies de inimigos naturais. Uma vez que os inseticidas apresentam impacto sobre a sobrevivencia, o crescimento e desenvolvimento, na reproducao (razao sexual, fecundidade, longevidade e fertilidade), no comportamento (mobilidade, orientacao, alimentacao, oviposicao e aprendizado). Os mecanismos de toxicidade e seletividade dos inseticidas estao relacionados as propriedades de maior ou menor solubilidade e peso molecular. Alem disso, caracteristicas da composicao cuticular do integumento dos inimigos naturais sao de extrema importância na seletividade de um produto ou a tolerância de determinado predador ou parasitoide.

Intake, digestibility and rumen dynamics of neutral detergent fibre in cattle fed low-quality tropical forage and supplemented with nitrogen and/or starch.

Abstract: The objective of this work was to evaluate the effects of nitrogenous compounds and/or starch supplementation on the intake, digestibility and rumen dynamics of neutral detergent fibre (NDF) in cattle fed low-quality tropical forage. Four crossbred heifers (Holstein × Zebu) with a body weight 231.9 ± 15.5 kg and fitted with ruminal cannulae were used. The forage fed to the animals consisted of low-quality signal grass (Brachiaria decumbens Stapf.) hay, with an average crude protein (CP) level of 51.6 g/kg, on a dry matter (DM) basis. Four treatments were evaluated: control, without supplementation; supplementation with nitrogenous compounds (CP of the roughage was raised to 100 g/kg), on a DM basis; supplementation with starch at a ratio of 200 g/kg DM of roughage; and supplementation with nitrogenous compounds and starch as described above. A mixture of urea, ammonium sulphate and albumin was used as a source of nitrogenous compounds at a ratio of 4.5:0.5:1.0. The experiment was carried out according to a 4 × 4 Latin square design in a 2 × 2 factorial arrangement. There was a positive effect of the nitrogenous compound supplementation on the DM and NDF intake (P < 0.01). In contrast, starch supplementation decreased forage intake (P < 0.10). Nitrogen supplementation increased the digestibility coefficient of DM and NDF (P < 0.05). Supplementation with nitrogen and starch together increased the microbial assimilation of nitrogenous compounds in the rumen (P < 0.05). We observed that nitrogen supplementation increased the estimated weighted degradation rate of NDF by 14.8%, whilst starch supplementation decreased this rate by 32.5%.

Phylogeography and historical demography of the neotropical stingless bee Melipona quadrifasciata (Hymenoptera, Apidae): incongruence between morphology and mitochondrial DNA*

Abstract: The stingless bees are among the most abundant and ecologically important social invertebrates in tropical communities. The Neotropical stingless bee Melipona quadrifasciata has two subspecies: M. quadrifasciata quadrifasciata and M. quadrifasciata anthidioides. The main difference between subspecies are the yellow metassomal stripes, which are continuous in M. q. quadrifasciata and discontinuous in M. q. anthidioides. Recently, two populations were described with continuous stripes and inhabiting clearly disjunct areas in relation to M. q. quadrifasciata. We sequenced 852 bp of the mtDNA COI gene from 145 colonies from 56 localities, and for the first time performed a detailed phylogeographic study of a neotropical stingless bee. Phylogenetic analyses revealed the existence of two clades exhibiting a south to north distribution: southern populations comprise the subspecies M. q. quadrifasciata, and northern populations are composed of M. q. anthidioides and two disjunct populations with continuous stripes. The divergence time of these two phylogroups was estimated between 0.233 and 0.840 million years ago in the Pleistocene, a period of climatic changes and geomorphological alterations in the Neotropical region. No evidence of genetic structure in relation to the tergal stripes was found, indicating that the morphological trait regarding the pattern of stripes on tergites is not an accurate diagnostic for the subspecies of M. quadrifasciata.

Insecticide-induced hormesis in an insecticide-resistant strain of the maize weevil, Sitophilus zeamais

Abstract: Sublethal responses to insecticides are frequently neglected in studies of insecticide resistance, although stimulatory effects associated with low doses of compounds toxic at higher doses, such as insecticides, have been recognized as a general toxicological phenomenon. Evidence for this biphasic dose-response relationship, or hormesis, was recognized as one of the potential causes underlying pest resurgence and secondary pest outbreaks. Hormesis has also potentially important implications for managing insecticide-resistant populations of insect-pest species, but evidence of its occurrence in such context is lacking and fitness parameters are seldom considered in these studies. Here, we reported the stimulatory effect of sublethal doses of the pyrethroid insecticide deltamethrin sprayed on maize grains infested with a pyrethroid-resistant strain of the maize weevil (Sitophilus zeamais) (Coleoptera: Curculionidae). The parameters estimated from the fertility tables of resistant insects exposed to deltamethrin indicated a peak in the net reproductive rate at 0.05 ppm consequently leading to a peak in the intrinsic rate of population growth at this dose. The phenomenon is consistent with insecticide-induced hormesis and its potential management implications are discussed.