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Nery J.R.C.,Federal University of Amapa | Bonotto D.M.,Claro
Journal of Environmental Radioactivity

Activity profiles of excess 210Pb determined in three sediment cores from Amazon River mouth, Macapá city, Brazil, provided the evaluation of sedimentation rates, contributing to a better knowledge of the hydrological conditions in the site that is the capital of Amapá State and is drained by the waters of the huge Amazon River. Chemical data were also determined in the sediments, allowing identify signatures coupled to anthropogenic inputs held in the past in Amapá State. Significant direct relationships between LOI (loss on ignition) and organic matter were found for all sediments profiles. Silica was found to be inversely related to organic matter in the three profiles; its decrease accompanied an increase on the specific surface of the sediments. This relationship was confirmed by a great number of inverse significant correlations among silica and oxides Na2O, K2O, CaO, MgO, Al2O3, P2O5, Fe2O3 and MnO. It was possible to identify the role of organic matter on adsorption of several oxides in the core sediments profiles. Apparent sediment mass accumulation rates corresponding to values between 450 and 2510 mg cm-2yr-1 were obtained, and are compatible with the results of others studies. The 210Pb activities in one sampling point suggested the occurrence of anthropogenic inputs related to the initial period of the mining activities conducted in Serra do Navio, Amapá State, for the commercialization of Mn ores. This was reinforced by the abrupt fluctuations in chemical data obtained for the sediments and composition of the interstitial waters occurring there. The Atlantic hurricane activity also appeared to affect the sedimentation rates in the area, as two different values were recorded in each profile. © 2011 Elsevier Ltd. Source

Da Silva C.P.,Federal University of Amapa
International Conference on Intelligent Systems Design and Applications, ISDA

With the first version of this work, Text2MARK, it was possible to obtain representations of database models with over 90% of accuracy. In this continuing work, some grammatical rules of the Portuguese language, called lexical predicates, were constructed, alongside other text mining metrics. With the incorporation of these new elements, Text2MARK was then applied to text sections taken from five scientific articles from different areas of knowledge. 84.2% of valid tuples were extracted and then applied in the construction of concept maps. Subsequently, these maps underwent a subjective evaluation by three different groups of users, who then attributed grades to the maps, ranging from 0 to 10, with means of 8.1, 8.1 and 8.3 per group. These results indicate that it is possible to extract and use tuples in the NAME-VERB-NAME format to represent knowledge by means of concept maps. © 2014 IEEE. Source

Prist P.R.,University of Sao Paulo | Michalski F.,Federal University of Amapa | Michalski F.,Pro Carnivoros Institute | Metzger J.P.,University of Sao Paulo
Landscape Ecology

The effects of habitat configuration on species persistence are predicted to be most apparent when remaining habitat cover is below 30%. We tested this prediction by comparing vertebrate communities in 21 landscapes located in the southern Amazonia, including 7 control landscapes (~100% of forest cover) and 14 fragmented landscapes (4 × 4 km). The fragmented landscapes retained similar proportions of forest (~25%), but had contrasting configurations, resulting from two different deforestation patterns: the "fish-bone pattern" common in small properties, and the large-property pattern generally used by large ranchers. Vertebrates were surveyed in all landscapes in February-July 2009 with interviews (n = 150). We found a significant difference in reported species richness among the fish-bone, large-property, and control areas (mean = 29. 3, 38. 8 and 43. 5 respectively). Control areas and large-properties tended to have a higher number of specialist species (mean = 13. 7, and 11. 7, respectively), when compared with the fish-bone pattern (5. 1). Vertebrate community composition in the control and large-properties was more similar to one another than to those of the fish-bone landscapes. The number of fragments was the main factor affecting the persistence of species, being negatively associated with specialist species richness. Species richness was also positively related with the size of the largest fragment structurally connected to the studied landscapes (i. e., a regional scale effect). Our results demonstrated that the large-property pattern, which results in less fragmented landscapes, can maintain a more diverse community of large vertebrates, including top predators, which are considered fundamental for maintaining ecosystem integrity. These results support the hypothesis that landscape configuration contributes to the persistence and/or extirpation of species. © 2012 Springer Science+Business Media B.V. Source

Weibel D.E.,Federal University of Rio Grande do Sul | Kessler F.,Federal University of Rio Grande do Sul | Da Silva Mota G.V.,Federal University of Amapa
Polymer Chemistry

The surfaces of polystyrene (PS) thin films were selectively functionalized by a combination of monochromatic synchrotron radiation with oxygen exposure. By selecting specific K-shell excitation energies, it was shown that highly efficient surface functionalization can be obtained. After the treatments, several oxygen functionalities were detected by XPS and NEXAFS spectroscopy. The functionalization strongly depended on the excitation energy. C 1s → σ * C-C transitions produced an extremely efficient oxidation of the uppermost monolayer of the PS films. The COO and CO elemental contributions in the C 1s envelope at the PS surface was higher than 70%. On the contrary, other excitation energies did not introduce COO functionalities efficiently. The obtained results were explained by taking into account the known Auger stimulated desorption mechanism. The present research will open new ways to functionalize a polymer surface by a combination of monochromatic inner-shell excitation together with exposure to a reactive gas atmosphere. © 2010 The Royal Society of Chemistry. Source

Mota G.V.S.,Federal University of Amapa | Neto A.M.J.C.,Federal University of Para
Journal of Computational and Theoretical Nanoscience

We study the theoretical UV absorption spectra to understand the absorption bands and the density of state (DOS) to the methylxanthines derived such the caffeine (CAF), theobromine (TB) and theophylline (TP), providing information about the variation of the bands more intense in the absorption spectra to theses molecules. The absorption spectrum are analyzed by ZINDO/S-CI/TD-DFT/ 6-31G+(d,p) method, where they are compared with regard to experimental data. The semi- empirical results presented a shift forward higher wavelength in the UV spectra, differently to the ab initio method. Unfortunately, spectrometric methods have been poorly developed what impede a better comparison with respect to experimental data on literature. Copyright © 2010 American Scientific Publishers. All rights reserved. Source

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