Made available in DSpace on 2015-03-26T13:39:44Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1531901 bytes, checksum: 69697e96df2b1bbf173ae091acbd58e6 (MD5) Previous issue date: 2011-07-26 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Understanding the factors that regulate populations of insect pests is of fundamental importance in the development of programs for integrated pest management. Scale insects, especially Pseudococcidae family, have reached the "status" in many pests in crops such as coffee plant. In one group of pests is the most important species Planococcus citri (Risso) (Hemiptera: Pseudococcidae). However, there are few studies on the mechanisms that regulate their populations. Thus, this study aimed to determine the factors that regulate P. citri populations in coffee using ecological life tables. For this purpose, were made during 50 generations ecological life tables for P. citri. The population of P. citri was kept in balance mainly due to predators. The predators of eggs and nymphs of 1st and 2nd instars were: Neuroptera: Chrysopidae, Diptera: Syrphidae and Diptera: Dolichopodidae and adults and larvae of Coleoptera: Coccinelidae. Predators of 3rd instar nymphs and adults were: Harmonia axyridis (Pallas), Chrysoperla Steinmann (Steinmann) and Chrysoperla externa (Hagen). The critical stage of mortality of P. citri was the third instar nymphs and the key factors of mortality were the predators H. axyridis, C. Steinmann and C. externa. Therefore, the population of P. citri in coffee plant was regulated by predation on third instar nymphs by these natural enemies. / O entendimento dos fatores que regulam as populações dos insetos praga é de fundamental importância na elaboração de programas de manejo integrado de pragas. As cochonilhas, sobretudo às da família Pseudococcidae, vêm alcançando o “status” de praga em muitos cultivos como no cafeeiro. Neste grupo de pragas uma das espécies mais importantes é Planococcus citri (Risso) (Hemiptera: Pseudococcidae). Entretanto, poucos são os estudos sobre os mecanismos que regulam suas populações. Assim, neste trabalho objetivamos determinar os fatores que regulam as populações P. citri no cafeeiro usando tabelas de vida ecológicas. Para tanto, foram confeccionadas durante 50 gerações tabelas de vida ecológicas para P. citri. A população de P. citri foi mantida em equilíbrio devido a principalmente aos predadores. Os predadores de ovos e ninfas de 1º e 2º ínstares foram: Neuroptera: Chrysopidae, Diptera: Syrphidae e Diptera: Dolichopodidae e adultos e larvas de Coleoptera: Coccinelidae. Os predadores de ninfas de 3º ínstar e de adultos foram: Harmonia axyridis (Pallas), Chrysoperla steinmann (Steinmann) e Chrysoperla externa (Hagen). O estádio crítico de mortalidade de P. citri foi o de ninfas de 3º ínstar e o fator-chave de mortalidade foram os predadores H. axyridis, C. steinmann e C. externa. Portanto a população de P. citri no cafeeiro foi regulada pela predação de ninfas de 3º ínstar por estes inimigos naturais.

Effects of Nb2O5 addition on the formation and properties of the Bi-based superconductors were studied. The superconducting samples were synthesized by two different methods, the solid state reaction (SSR) and ammonium nitrate melt route (ANM) to obtain information about the growth techniques. Ten samples (five with each method) with the chemical compositions of Bi1.6Pb0.4Sr2Ca2Cu3NbxOy, with x= 0.00, 0.05, 0.10, 0.20, and 0.30 were prepared. Phase identification, structural and microstructural analysis were carried out using powder X-ray diffraction method, scanning electron microscopy and energy dispersive X-ray (EDX) analysis. The transition temperature and the critical current measurements were carried out using the electromagnetic measurement system. The critical parameters of the samples were also determined by AC susceptibility and magnetization measurements. Improvements in the formation of the Bi-2223 phase with Nb addition have been observed by both methods. The ANM method leads mixtures of Bi-2223 and Bi-2212 phases, but with the SSR method pure Bi-2223 phase was obtained. With small amounts of Nb addition the critical temperature, Tc, remains the same for ANM samples and it increases for the SSR samples. For both series of samples Tc decreases with further increase of Nb content. With Nb addition the critical currents of the ANM sample almost remain the same and those of the SSR samples increases. Observations based on AC susceptibility measurements showed that Nb addition improve inter-grain coupling. Inductive critical current densities obtained from magnetization measurements agree with the critical currents stated above and show that Jc increase with increase Nb content.