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.

Design, syntheses and evaluation of benzoylthioureas as urease inhibitors of agricultural interest

Abstract: Urea is one of the most used nitrogen fertilizers worldwide. However, occurrence of urea hydrolysis to ammonia and carbon dioxide on soil surface, catalyzed by soil ureases, considerably reduces nitrogen availability to crops. In this study, we describe the design, synthesis and screening of sixty five benzoylthioureas (BTUs) for their ability to inhibit purified jack bean and soil ureases. BTUs were readily obtained in one pot, two steps synthesis with no need of cumbersome procedures for product purification. In vitro assays revealed BTUs 11, 12, 14, 19–22 and 37 as the most active jack bean urease inhibitors. Such BTUs were found to be able to bind to both catalytic and allosteric sites of urease, acting therefore as mixed-type inhibitors. Out of 28 compounds that effectively inhibited soil ureases activity, BTUs 3, 6, 10, 12, 16, 19 and 22 were determined to be more potent than the reference inhibitor N-(butyl) thiophosphoric triamide (NBPT; 40%). The other 22 BTUs were as potent as NBPT on soil ureases. The temperature-tolerance of BTUs, along with their ability to inhibit soil ureases, makes of this class of compounds potential additive for urea-based fertilizers.

An ecoregional classification for the state of Roraima, Brazil: the importance of landscape in malaria biology.

Abstract: Understanding the different background landscapes in which malaria transmission occurs is fundamental to understanding malaria epidemiology and to designing effective local malaria control programs. Geology, geomorphology, vegetation, climate, land use, and anopheline distribution were used as a basis for an ecological classification of the state of Roraima, Brazil, in the northern Amazon Basin, focused on the natural history of malaria and transmission. We used unsupervised maximum likelihood classification, principal components analysis, and weighted overlay with equal contribution analyses to fine-scale thematic maps that resulted in clustered regions. We used ecological niche modeling techniques to develop a fine-scale picture of malaria vector distributions in the state. Eight ecoregions were identified and malaria-related aspects are discussed based on this classification, including 5 types of dense tropical rain forest and 3 types of savannah. Ecoregions formed by dense tropical rain forest were named as montane (ecoregion I), submontane (II), plateau (III), lowland (IV), and alluvial (V). Ecoregions formed by savannah were divided into steppe (VI, campos de Roraima), savannah (VII, cerrado), and wetland (VIII, campinarana). Such ecoregional mappings are important tools in integrated malaria control programs that aim to identify specific characteristics of malaria transmission, classify transmission risk, and define priority areas and appropriate interventions. For some areas, extension of these approaches to still-finer resolutions will provide an improved picture of malaria transmission patterns.

Árvores frutíferas nos quintais urbanos de Boa Vista, Roraima, Amazônia brasileira

Abstract: O objetivo do trabalho foi estimar a riqueza e a diversidade das especies de arvores frutiferas cultivadas nos quintais caseiros da cidade de Boa Vista, Roraima, bem como determinar quais sao as especies cultivadas preferencialmente pela populacao urbana local. Os levantamentos foram realizados em dois bairros surgidos com a expansao da cidade em 1982: (1) BEst - Bairro dos Estados (Zona Norte) e (2) BAsa - Bairro Asa Branca (Zona Oeste). Foram observados 722 quintais no BEst (06 a 22.03.2004) e 339 no BAsa (07.04 a 01.07.2004). Trinta e seis especies (19 familias botânicas) foram encontradas no BEst e 37 (20 familias) no BAsa, configurando um total de 43 especies (20 familias) observadas. Deste total, 30 especies (69,8%) de 19 familias (95%) ocorreram em ambos os bairros, sugerindo preferencias frutiferas comuns. Os tres maiores indices de valor de preferencia (IVP) foram coincidentes e registrados para coco (Cocos nucifera L. - BEst: 19,4% e BAsa: 20,5%), manga (Mangifera indica L. - BEst: 14,9% e BAsa: 22,5%) e jambo (Syzygium malaccence (L.) Merr. & L.M. Perry - BEst: 10,5% e BAsa: 10,1%), todos de origem externa a Amazonia, mas que congregaram conjuntamente 44,9% (BEst) e 53,0% (BAsa) de IVP. Estes resultados sugerem que o cultivo de arvores frutiferas em quintais caseiros de Boa Vista segue um padrao que concentra a escolha em poucas especies, nao-originarias da Amazonia, mas tradicionalmente consagradas por seu exito na producao de frutos.

Quality control of commercial tea by x-ray fluorescence

Abstract: Based on the energy-dispersive X-ray fluorescence (EDXRF) technique, the concentrations of elements (22 < Z < 30) were assessed in five kinds of commercial tea from six commercial suppliers: Matricaria chamomilla L. (camomile), Mentha piperita L. (mint), Cymbopogon citratus (DC) Stapf. (herb 'cidreira'), Malus domestica Borkh. (apple tea) and Camellia sinensis (L.) O. Kuntze (black tea). The samples were excited by an X-ray tube with an Mo anode (25 kV and 10 mA), with a Zr filter, and the characteristic X-ray were detected by an Si(Li) detector coupled to a multichannel analyzer. Using standard samples, the relationship between the detection limit and the atomic numbers of Fe, Co, Ni, Cu and Zn was determined. In some tea samples Ti was detected, but it is not an essential microelement for the plant growth. Fe, Ni and Cu were detected in all tea samples analyzed; Ti, Cr, Co and Zn were detected in Matricaria chamomilla and Malus domestica; Ti, Co and Zn in Mentha piperita and Ti, Mn, Co and Zn in Cymbopogon citratus. The inorganic constitution profile of this matrix type and the fingerprints in the production process can be evaluated by employing the EDXRF quality control of the commercial products.

Fixação biológica de nitrogênio em cultivares de feijão-caupi recomendadas para o Estado de Roraima

Abstract: O objetivo deste trabalho foi avaliar a fixacao biologica de nitrogenio (FBN) em cinco cultivares de feijao-caupi: BR 17 Gurgueia, BRS Guariba, BRS Mazagao, UFRR Grao Verde e Pretinho Precoce 1. Em 2007, foram conduzidos um experimento em casa de vegetacao e outro em campo, em esquema fatorial com cinco cultivares de feijao-caupi e quatro fontes de nitrogenio: adubacao com ureia (50 kg ha-1 de N), inoculacao com a estirpe de Bradyrhizobium BR 3262 ou BR 3267 e um controle absoluto. Aos 35 dias apos a emergencia das plantas, foram avaliados numero e massa de nodulos secos, massa de materia seca e N total da parte aerea, eficiencia nodular em casa de vegetacao e rendimento de graos na colheita em campo. Em casa de vegetacao, foi observada alta nodulacao e eficiencia nodular para ambas as estirpes em todas as cultivares. Em campo, a nodulacao e o N total foram menores para todas as cultivares, comparativamente a casa de vegetacao, o que indica interferencia de fatores edafoclimaticos na FBN. Ocorreu aumento no rendimento de graos em todas as cultivares em decorrencia da inoculacao, especialmente com a estirpe BR 3262.