Federal University of Roraima

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.

Dengue virus in Aedes aegypti larvae and infestation dynamics in Roraima, Brazil

Abstract: OBJECTIVE: To detect the presence of dengue virus in larval forms of Aedes aegypti and to associate vector presence with rainfall and incidence of disease. METHODS: Eighteen households were randomly selected for egg collection in a neighborhood of the city of Boa Vista, Roraima, in Northern Brazil. Two oviposition traps were installed per home, and removed after one week. This was repeated on a monthly basis between November 2006 and May 2007. Trap positivity rate and egg density were calculated. Following the eclosion of 1,422 eggs, 44 pools of at least 30 larvae each were formed, which were evaluated for presence of dengue virus using RT-PCR and hemi-nested PCR. Dengue incidence rates in the period were correlated with rainfall rates. The association between these two variables and the number of eggs collected was determined using Pearson correlation. RESULTS: None of the pools tested positive for presence of dengue virus, despite the high incidence of dengue in the neighborhood during the studied period. The density of Ae. aegypti increased with rainfall, but was not correlated with incidence of dengue. CONCLUSIONS: The results suggest that transovarial transmission of dengue virus in mosquitoes occurs at a very low frequency, and therefore virus persistence in urban settings may not depend on such transmission. The mosquito population increased during the rainy season due to increased formation of breeding sites; the lack of correlation with incidence of dengue may be due to underestimation of incidence data during epidemics.

Antibacterial and antifungal activity of extracts and exudates of the Amazonian medicinal tree Himatanthus articulatus (Vahl) Woodson (common name: sucuba)

Abstract: Himatanthus articulatus (Vahl) Woodson is a tree found in the northern Amazon savannahs (common name: sucuba) that is used in local Amerindian medicine. Leaf, bark and branch wood methanol extracts, sequentially obtained hexane, ethyl acetate and methanol extracts and latex were evaluated for antifungal and antibacterial activities against American Type Culture Collection (ATCC) and local clinical strains using the disc diffusion method. Methanol extracts and latex inhibited Candida albicans, leaf methanol extracts inhibited Staphylococcus aureus and Bacillus subtilis and bark methanol extracts inhibited B. subtilis. Active extracts inhibited the ATCC and clinical strains. Polar antifungal and antibacterial principles in latex and extracts are thought to be responsible for the inhibition.

Diversidade de Leguminosae em uma área de savana do estado de Roraima, Brasil

Abstract: Leguminosae is the most diverse family in the savannas of Roraima, which are the largest savanna areas in the Brazilian Amazon. This paper presents a floristic survey and an analysis of the geographic distribution patterns of Leguminosae taxa in a savanna area at Boa Vista, Roraima (02o52´07´´N; 60o43´03´´W). The survey identified 80 taxa belonging to 38 genera. Six taxa are new records for the flora of Roraima. The best-represented genera were Aeschynomene and Chamaecrista, both with seven species each. Leguminosae-Papilionoideae was the most diverse subfamily based on the number of genera (24) and infrageneric taxa (53). The phytogeographical analysis revealed predominance of taxa with a Neotropical distribution. The savanna site analyzed represents a legume diverse area, because it concentrates 87% of legume diversity referred for the savannas of Roraima.

Circular cosmic string loop in Brans-Dicke theory

Abstract: The gravitational field of a stationary circular cosmic string loop, externally supported against collapse, is investigated in the context of Brans-Dicke theory in the weak field approximation of the field equations. The solution is quasi-conformally related to the corresponding solution in Einstein's General Relativity(GR) and goes over to the corresponding solution in GR when the Brans-Dicke parameter w becomes infinitely large.