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Ribas M.O.,Faculdades Integradas Espirita | Kremer G.M.,Federal University of Parana
Gravitation and Cosmology | Year: 2010

The accelerated-decelerated transition in a primordial Universe is investigated by using the dynamics of fermion fields within the context of the Einstein-Cartan theory, where, apart from the curvature, the space-time is also described by a torsion field. The model analyzed here has only a fermion field as a source of the gravitational field. The term associated with the spin of the fermion field plays the role of an inflaton which contributes to an accelerated regime whereas the one related to the fermion mass behaves as a matter field and is responsible for a decelerated regime. Hence, by taking into account the spin of a massive fermion field, it is possible to characterize the transition from an accelerated to a decelerated period of the primordial Universe. © 2010 Pleiades Publishing, Ltd. Source


Chimento L.P.,University of Buenos Aires | Forte M.,University of Buenos Aires | Kremer G.M.,Federal University of Parana | Ribas M.O.,Faculdades Integradas Espirita
General Relativity and Gravitation | Year: 2010

In this work a tachyonization of the ΛCDM model for a spatially flat Friedmann-Robertson-Walker space-time is proposed. A tachyon field and a cosmological constant are considered as the sources of the gravitational field. Starting from a stability analysis and from the exact solutions for a standard tachyon field driven by a given potential, the search for a large set of cosmological models which contain the ΛCDM model is investigated. By the use of internal transformations two new kinds of tachyon fields are derived from the standard tachyon field, namely, a complementary and a phantom tachyon fields. Numerical solutions for the three kinds of tachyon fields are determined and it is shown that the standard and complementary tachyon fields reproduces the ΛCDM model as a limiting case. The standard tachyon field can also describe a transition from an accelerated to a decelerated regime, behaving as an inflationary field at early times and as a matter field at late times. The complementary tachyon field always behaves as a matter field. The phantom tachyon field is characterized by a rapid expansion where its energy density increases with time. © 2010 Springer Science+Business Media, LLC. Source


Seneme A.M.,Faculdades Integradas Espirita | Possamai E.,Federal University of Parana | Vanzolini S.,Sao Paulo State University | Martins C.C.,Sao Paulo State University
Revista Arvore | Year: 2012

The objective of this work was to evaluate the effect of dormancy overcoming treatments andstorage environment on physiological and phitopathologic quality of canafístula seeds (Peltophorum dubium).Seeds were submitted to the following treatments of dormnancy superação: scarification with sandpaper (200);immersion in water at room temperature for 24 and 72 hours; (c) immersion in sulfuric acid for 2, 6, 10,15, 20 and 30 minutes); immersion in hot water (70, 80 and 90°C); (e) moistening of the substratum with KNO 3 solution of (0.2%). Seeds were stored at room temperature and at 10°C for 210 days. Effects of treatmentsand storage were evaluated by water content, germination test (five replicates of 30 seeds), seedlings lengthand sanity test (400 seeds), with eight-day incubation. It was used a complete random experimental designfor data statistics analysis with a 2 x 14 factorial design (storage conditions x treatments for dormancy overcoming).Means were compared by the Tukey test (P>0.5). Regarding non-stored seeds, the best treatments to overcomedormancy and to promote germination were scarification with sandpaper or sulfuric acid for 15 and 30 minutes;regarding stored seeds, there was immersion in hot water (70 and 80°C). Fungi detected in the samples werePestalotia sp., Alternaria sp., Rhizopus sp., Nigrospora sp., Curvularia sp., Fusarium sp., Rhizoctonia sp.,Aspergillus sp., Cladosporium sp. and Fusarium semitectum. Source


do Amaral W.,Faculdades Integradas Espirita | Deschamps C.,Federal University of Parana | Machado M.P.,Federal University of Parana | Koehler H.S.,Federal University of Parana | And 3 more authors.
Horticultura Brasileira | Year: 2012

The cultivar Mandirituba is the only genetic material for chamomile cultivation in southern Brazil. Besides the limitations regarding floral buds and the yield of essential oil presented by this cultivar, phytosanitary problems have also been observed. The objectives of this work were to compare the genetic materials from the Netherlands, Denmark and Mandirituba and to evaluate the effect of seeding rate on floral heads development and essential oil production, yield and quality. The experiments were carried out at field conditions in Piraquara, Paraná state, Brazil. The essential oil extraction was obtained by hydrodistillation using a Clevenger apparatus and the oil composition was analyzed by gas chromatography coupled to mass spectrometry (GC/MS). The genetic materials from the Netherlands and Mandirituba presented statistically higher dry mass accumulation than the ones from Denmark. However the material from Mandirituba showed a great essential oil yield (4.7 μL g-1 ms) and productivity (2.40 L ha-1). The genetic material from Denmark and Mandirituba showed similar essential oil composition. The density of 1.0 kg ha-1 for cultivar Mandirituba resulted on great plant development and essential oil production. The use of 3.0 kg ha-1 of seeds did not increase plant density due to the high plant competition. Source


Martins C.C.,Sao Paulo State University | MacHado C.G.,State University of Goias | Martinelli-Seneme A.,Faculdades Integradas Espirita | Zucareli C.,State University Londrina
Semina:Ciencias Agrarias | Year: 2012

The harvesting method of fruits of tree species should be adequate to obtain seeds of maximum physiological quality. When present, the dormancy of Cassia ferruginea seeds is due to seed coat impermeability to water. This research work viewed to find the best methods both for the harvesting and for the breaking of dormancy of seeds of that species. The experiment was conducted during two years. In the first, fruits shed from the mother plant and laying on the ground were picked and their seeds submitted to the following treatments: 1. control, 2. mechanical scarification of the seeds with sandpaper no. 220, 3. hot water for 5 minutes (initial and final temperatures of 82 and 69 °C, respectively), 4. hot water for 15 minutes (initial and final temperatures of 82 and 51 °C, respectively), 5. chemical scarification with H 2SO 4 (95%) for 20, 30, 40, 50. 60, 70, and 80 minutes. In the second year, seeds were submitted to treatments 2, 3, and 4 whereas acid scarification was applied for 30, 45, and 60 minutes. The results showed that seeds picked from the ground and those taken directly from the mother plant differ in their response to the dormancy breaking procedure. The results also showed that the seeds picked from the ground are better than those harvested directly from the plant and that, when dormant, the best results are attained when seeds are either submitted to mechanical scarification or chemical scarification with sulfuric acid for periods between 30 and 60 minutes. Source

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