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São Luís, Brazil

Dias G.,Federal University of Vicosa | Yotoko K.S.C.,Federal University of Vicosa | Gomes L.F.,IFMA | Lino-Neto J.,Federal University of Vicosa
Naturwissenschaften | Year: 2012

Several species of Tenebrionidae are storedgrain pests. Since they belong to a specious family, the systematics of these beetles is still in doubt. In insects, spermatogenesis and the spermatozoa exhibit great diversity, and are therefore commonly used in phylogenetic and taxonomic analyses. During the spermatogenetic process in these organisms, the cells originating from a single spermatogonium develop synchronically in groups referred to as cysts. At the end of this process, there is usually only one sperm bundle per cyst, with all the cells in the same orientation. This paper details the spermiogenesis of the tenebrionid beetles Tenebrio molitor, Zophobas confusa, Tribolium castaneum and Palembus dermestoides using whole mount and histological sections of the cysts. In these species, spermatogenesis is similar to that which occurs in most insects. However, during spermiogenesis, the nuclei of the spermatids migrate to two opposite regions at the periphery of the cyst, leading to the uncommon formation of two bundles of spermatozoa per cyst. This feature is possibly an apomorphy for Tenebrionidae. © Springer-Verlag 2012. Source


De C. Gomes E.,IFMA | De S. Ribeiro L.A.,Federal University of Maranhao | Caracas J.V.M.,Federal University of Maranhao | Catunda S.Y.C.,Federal University of Maranhao | Lorenz R.D.,University of Wisconsin - Madison
2010 IEEE Energy Conversion Congress and Exposition, ECCE 2010 - Proceedings | Year: 2010

This paper derives a new approach for analyzing dc-dc converters for feedback control design. The control-to-output voltage transfer function of the converters, usually predicted by averaging models, and the classical feedback control techniques are replaced by the state space average state block diagram analysis. These state block diagrams are obtained for state space averaging matrixes of the converters combined with their continuous conduction mode differential equations. This decoupling technique yields first order control transfer functions allowing easier synthesis of controllers. The disturbance rejection properties of the controller are analyzed and improved by disturbance input decoupling. The technique is applied to buck converters, and the controllers demonstrate good transient response compared to classical voltage controllers. The structure is easy implement with relevant applications in integrated circuit manufacturing and general industrial environments. © 2010 IEEE. Source


Thuault A.,Crismat | Eve S.,Crismat | Bazin J.,Crismat | Charlet K.,IFMA | And 3 more authors.
Materiaux et Techniques | Year: 2011

In this paper we seeked for correlation among the biocomposition, morphological parameters and mechanical properties of flaw fibre. Seven varieties among the most frequently cultivated in Normandy are examined. Biocomposition analyses have shown no significant differences between the different varieties while noticeable differences have been evidenced between the varieties for mechanical properties, and these are comparable to the dispersion within a given variety. Thus, the differences in mechanical properties among these varieties are not ascribed to morphological or biocomposition parameters. © 2011 EDP Sciences. Source


De Gomes E.C.,IFMA | De Ribeiro L.A.S.,Campus Universitario do Bacanga | Caracas J.V.M.,Campus Universitario do Bacanga | Catunda S.Y.C.,Campus Universitario do Bacanga | Lorenz R.D.,University of Wisconsin - Madison
2010 International Power Electronics Conference - ECCE Asia -, IPEC 2010 | Year: 2010

This paper derives a new approach for analyzing dc-dc converters for feedback control design. The control-to-output voltage transfer function of the converters, usually predicted by averaging models, and the classical feedback control techniques are replaced by the state space average state block diagram analysis. These state block diagrams are obtained for state space averaging matrixes of the converters combined with their continuous conduction mode differential equations. This technique yields first order control transfer functions allowing easier synthesis of controllers. The resulting controllers demonstrate good transient response compared to voltage controllers based on k-factor approach. The structure is easy implement with relevant applications in integrated circuit manufacturing and industrial environment. © 2010 IEEE. Source


Sales F.H.S.,IFMA | Dantas A.L.,UERN | Carrico A.S.,Federal University of Rio Grande do Norte
AIP Advances | Year: 2012

We report a theoretical investigation of new spin slips phases of thin holmium (Ho) films. The new phases originate from the loss of coordination of atoms in the near surface region, which affects the balance between exchange and anisotropy energies, favoring the alignment of near surface spins along the basal plane easy axis directions. Copyright 2012 Author(s). Source

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