Universidade Federal de Viçosa

About: Universidade Federal de Viçosa is a education organization based out in Viçosa, Brazil. It is known for research contribution in the topics: Population & Biology. The organization has 16012 authors who have published 26711 publications receiving 353416 citations.

Variação espacial e temporal da precipitação no estado do Pará.

Abstract: Estudos sobre a climatologia das precipitacoes no Estado do Para sao essenciais para o planejamento das atividades agricolas. A variacao da precipitacao anual e sazonal no Estado do Para foi analisada com base em series historicas de 23 anos (1976-1998) de dados diarios de chuva. A analise foi realizada para 31 localidades do Estado do Para, sendo os resultados representados em mapas com a utilizacao de tecnicas de sistemas de informacoes geograficas (SIG). A variabilidade da precipitacao anual e sazonal foi caracterizada com base no coeficiente de variacao e no indice de variabilidade interanual relativo. A variacao desses coeficientes para a precipitacao anual no Estado do Para foi de 15 a 30%. As caracteristicas mensais da estacao chuvosa, em termos de inicio, fim e duracao, foram determinadas utilizando-se o criterio proposto por KASSAM (1979). A variacao entre as datas de plantio precoces e tardias corresponderam aos decendios identificados pelos dias julianos 309319 e 353363, respectivamente.

Insecticide resistance in populations of Tuta absoluta (Lepidoptera: Gelechiidae)

Abstract: 1 Control failures of insecticides used against the tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) in Brazil led to the investigation of the possible occurrence of resistance of this insect pest to abamectin, cartap, methamidophos and permethrin. 2 The insect populations were collected from seven sites in the states of Minas Gerais, Rio de Janeiro, and Sao Paulo. These populations were subjected to concentration–mortality bioassays using insecticide-impregnated filter papers. 3 We were unable to obtain a single population which provided a susceptibility standard for all insecticides tested. Therefore, the resistance levels were estimated in relation to the most susceptible population to each insecticide. Resistance to abamectin and cartap were observed in all populations when compared with the susceptible standard population, with resistance ratios ranging from 5.2- to 9.4-fold and from 2.2- to 21.9-fold for abamectin and cartap, respectively. Resistance to permethrin was observed in five populations with resistance ratios ranging from 1.9- to 6.6-fold, whereas resistance to methamidophos was observed in four populations with resistance ratios ranging from 2.6- to 4.2-fold. 4 The long period and high frequency of use of these insecticides against this insect pest suggest that the evolution of insecticide resistance on them has been relatively slow. Alternatively, the phenomenon might be widespread among Brazilian populations of T. absoluta making the finding of suitable standard susceptible populations difficult and leading to an underestimation of the insecticide resistance levels in this pest. 5 Higher levels of resistance to abamectin, cartap and permethrin are correlated with greater use of these compounds by growers. This finding suggests that local variation in insecticide use was an important cause of variation in susceptibility.

Sustainable energy: A review of gasification technologies

Abstract: Biomass has been widely recognized as a clean and renewable energy source, with increasing potential to replace conventional fossil fuels in the energy market. The abundance of biomass ranks it as the third energy resource after oil and coal. The reduction of imported forms of energy, and the conservation of the limited supply of fossil fuels, depends upon the utilization of all other available fuel energy sources. Energy conversion systems based on the use of biomass are of particular interest to scientists because of their potential to reduce global CO2 emissions. With these considerations, gasification methods come to the forefront of biomass-to-energy conversions for a number of reasons. Primarily, gasification is more advantageous because of the conversion of biomass into a combustible gas, making it a more efficient process than other thermochemical processes. Biomass gasification has been studied widely as an efficient and sustainable technology for the generation of heat, production of hydrogen and ethanol, and power generation. Renewable energy can have a significant positive impact for developing countries. In rural areas, particularly in remote locations, transmission and distribution of energy generated from fossil fuels can be difficult and expensive, a challenge that renewable energy can attempt to correct by facilitating economic and social development in communities. This paper aims to take stock of the latest technologies for gasification.