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Federal University of Roraima

Education
About: Federal University of Roraima is a based out in . It is known for research contribution in the topics: Population & Thermogravimetry. The organization has 981 authors who have published 1218 publications receiving 7849 citations. The organization is also known as: Federal University of Roraima.


Papers
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Journal ArticleDOI
TL;DR: The results show that stable (or at least metastable) structures are possible with metallic properties and that these structures can be obtained by a direct interconversion from SWNT(2,2).
Abstract: Recently, Lagos et al. [Nat. Nanotechnol. 4, 149 (2009)] reported the discovery of the smallest possible silver square cross-section nanotube. A natural question is whether similar carbon nanotubes can exist. In this work we report ab initio results for the structural, stability, and electronic properties for such hypothetical structures. Our results show that stable (or at least metastable) structures are possible with metallic properties. They also show that these structures can be obtained by a direct interconversion from SWNT(2,2). Large finite cubanelike oligomers, topologically related to these new tubes, were also investigated.

18 citations

Journal ArticleDOI
TL;DR: In this paper, the first intercalation into VOPO 4 ·2H 2 O performed through a solid-state reaction at room temperature was reported, and the profile of the absorption bands due to the lattice vibration around 1000 cm −1 was retained after reaction.

18 citations

Journal ArticleDOI
TL;DR: In this paper, the authors apply ecological niche modeling to analyze and predict the distributions of malaria vectors based on entomological collection points in the State of Roraima in the northern Brazilian Amazon Basin.
Abstract: Knowledge of vector distribution is important for the design of effective local malaria control programs. Here we apply ecological niche modeling to analyze and predict the distributions of malaria vectors based on entomological collection points in the State of Roraima in the northern Brazilian Amazon Basin. Anopheline collections were conducted from 1999 to 2003 at 76 localities, all with active malaria transmission. A total of 13 anopheline species was identified from 17, 074 adult females collected: Anopheles darlingi, An. albitarsis s.l., An. nuneztovari, An. triannulatus s.l., An. braziliensis, An. peryassui, An. oswaldoi s.l., An. mattogrossensis, An. strodei, An. evansae, An. squamifemur, An. mediopunctatus s.l., An. intermedius. Anopheles darlingi, and An. albitarsis were the most frequently found species. An. squamifemur was found for the first time in Roraima. A distributional prediction model (genetic algorithm for rule-set prediction-GARP) and environmental variables were used to pre...

18 citations

Journal ArticleDOI
TL;DR: The Wapichana and Macuxi informants felt that the invasion by A. mangium had caused negative effects on the natural environment and on community subsistence in the indigenous lands due to its rapid and unwanted propagation.
Abstract: Invasive plants can impact biodiversity as well as the lives of native human populations. Natural ecosystems represent sources of natural resources essential for the subsistence and socio-cultural continuity of these social groups. Approximately 30,000 ha of Acacia mangium were planted for commercial purposes in savanna areas surrounding indigenous lands in Roraima State, Brazil, at the end of the 1990s. We examined the local ecological knowledge of indigenous Wapichana and Macuxi Amerindians, members of the Arawak and Carib linguistic families, respectively, concerning A. mangium Willdenow (Fabaceae) in a savanna ecosystem (“Lavrado”) to attempt to understand its propagation beyond the limits of the commercial plantations and contribute to mitigating its impacts on socio-ecological systems. The present study was undertaken in the Moskow, Sao Domingos, and Malacacheta communities in the Moskow and Malacacheta Indigenous Lands (ILs) in the Serra da Lua region of Roraima State, in the northern Brazilian Amazon region. Interviews were conducted with a total of 94 indigenous individuals of both sexes, with ages between 18 and 76, and low levels of formal schooling, with an average time of permanence in the area of 21 years; some still spoke only their native languages. The interviews focused on their ecological knowledge of the invasive, non-native A. mangium and their uses of it. The informants affirmed that A. mangium negatively impacted the local fauna and flora, making their subsistence more difficult and altering their daily routines. Among the problems cited were alterations of water quality (71.3%), negative impacts on crops (60.6%), negative impacts on the equilibrium of the local fauna (52.1%), increased farm labor requirements (41.5%), and restriction of access to indigenous lands (23.4%). There were no significant differences between the opinions of men and women, nor between community leaders and nonleaders. Most of the interviewees (89%) felt that A. mangium had no positive importance for the local economy and saw no future prospects of beneficial use. The Wapichana and Macuxi informants felt that the invasion by A. mangium had caused negative effects on the natural environment and on community subsistence in the indigenous lands due to its rapid and unwanted propagation. The similarity between the opinions of men and women and between community leaders and nonleaders demonstrates the existence of knowledge that is well distributed among these communities and transmitted within their communities through social–cultural interactions.

18 citations

Journal ArticleDOI
TL;DR: In this article, the delta-resonance formation in a relativistic mean field theory was investigated for very asymmetric and quasi-symmetric nuclear matter, as an extension of works restricted to the symmetric nuclear subject matter treatment.
Abstract: In the context of a relativistic mean field theory the delta-resonance matter formation in a highly compressed nuclear medium is investigated. For a given set of nucleon–meson coupling constants, the delta-resonance formation is studied by changing the delta-meson coupling constants. The effect on the equation of state and on the delta-resonance population with respect to changes in the delta-resonance coupling constants values is discussed for very asymmetric and quasi-symmetric nuclear matter, as an extension of works restricted to the symmetric nuclear matter treatment.5,6

18 citations


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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
20232
20222
2021125
2020183
201992
201899