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.

SiO2-saturated potassic alkaline magmatism in the central Amazonian Craton, southernmost Uatumã-Anauá Domain, NE Amazonas, Brazil

Abstract: This paper approaches the record of SiO2 -saturated potassic alkaline magmatism of Castanhal Quartz Monzonite, Mapuera Suite, and Ladeira da Vovo Quartz Syenite. These samples are located near the Northern border of the Amazon Basin. Such rocks show K2 O + 2 > Na2 O and K2 O/Na2 O < 2 values that confirm the potassic or shoshonitic character of these rocks. The Castanhal Quartz Monzonite contains less than 20% volume of quartz, which is also a characteristic of the shoshonitic or SiO2 -satured potassic alkaline A-type magma signature observed on geochemical plots. Listric faults, representing the rifting phase of Amazon Basin formation, emplaced and reworked Ladeira da Vovo Quartz Syenite, which caused its granophyric texture, probably during the Tonian period. A group of 21 zircon crystals was extracted from a hornblende quartz monzonite and yields an average age of 1872 ± 6 Ma (MSWD = 2.4). However, an additional zircon crystal yielded a Trans-Amazonian age of 2062 ± 17 Ma. These potassic alkaline rocks of Orosirian (1872 Ma) age may correspond to a post-collisional setting. Dominantly negative eHft values and Hf TDM ages reveal a large contribution of a mafic crustal component from Mesoarchean to Neoarchean age (2.95 – 2.66 Ga), and a felsic crustal component from Neoarchean to later Siderian ages (2.51 – 2.34 Ga).

Considerações sobre a literatura da região circum-Roraima: originalidade, circulação, transposição e deriva literária

Abstract: Based on the cultural ground of the Circum-Roraima region, located in the extreme north of South America, in the triple border Brazil-Guiana-Venezuela, the essay discusses the theoretical and critical making in the field of literary studies in our days, when the globalizing wave coexists with the claims and inflation of the national, of the local and the ethnic, among other minority manifestations that have gained space in the political and cultural agenda today, from a perspective that privileges reflection on the ways in which literary circulation and the process of literary and cultural exchanges and transfers

Woolliness and leatheriness in late peach cultivars submitted to both delayed storage and to cold storage

Abstract: The study was performed to identify the effect of delayed storage on the control of woolliness and leatheriness during cold storage of the late peach cultivars grown in Brazil. The fruits were harvested at the mature-green stage. All of the cultivars were exposed to temperatures of 20 ± 0.5oC and 75 ± 3% of R.H. in a cold room for 0, 24, or 48 hours. Afterwards, the fruits were kept at 0 ± 0.5oC and 92 ± 3% of R.H. for 28 days. The yellow pulp peaches, regardless of the length of delayed storage, did not present any symptoms of woolliness or leatheriness. The white pulp peaches not submitted to delayed storage developed either one or more of the other physiological disorders. Due to their lower level of pulp firmness, the control fruits of 'Chimarrita' and 'Marli' peaches were classified as woolly fruits. The control fruits of 'Chiripa' peaches, with pulp firmness of more than 30 N, presented leatheriness. High pectinmethylesterase (PE) activity was verified in the woolly fruits. The delayed storage for 48 hours in all the cultivars provided advanced ripening. The delayed storage by 24 hours was effective in the control of physiological disorders in the white pulp cultivars.

Anencephalic babies as donors of organs and tissue for transplants: legal, moral and practical possibilities

Abstract: Os exitos recentes dos transplantes terapeuticos fizeram com que o anencefalo fosse cogitado como possivel fonte de orgaos para o atendimento de neonatos. Os primeiros relatos cientificos de sua execucao bem sucedida estimularam discussoes para averiguar as possibilidades morais de sua concessao. Os resultados dessas discussoes produziram dificuldades praticas quase impeditivas para a conversao do neonato anencefalo de potencial para real doador de orgaos. A doacao de celulas-tronco e medula ossea por portadores de anencefalia, surpreendentemente, nao foi ainda granjeada.

Artificial flooding changes soil chemistry and carbon dynamics in upland forests next to hydropower plant in Amazon basin

Abstract: Upland forest cover in the Amazon basin has been reduced by land use changes, e.g., the establishment of hydropower plants. Such plants cause permanent flooding and may produce periodic flooding in adjacent upland forests. We determined the short- and long-term effects of artificial flooding on the soil chemistry of upland forests adjacent to the Balbina Hydroelectric Reservoir, Amazonas State, Brazil. We randomized 20 sampling units in upland forests located on the banks of streams adjacent to the hydropower plant. Each sampling unit consisted of two paired forests: one artificial “flooded forest” near the stream and an unflooded “control forest.” We performed soil chemical analyses to determine the pH and total organic C, N, Al3+, and nutrient levels (P, Ca, Mg, and K). In the short term, flooding caused soil acidification, C loss, and increased soil nutrient availability, but this effect did not occur in the long term. In the long term, soil acidity decreased, C loss occurred, and available N cumulatively decreased because of annual flooding after the impoundment of the reservoir. These cumulative N losses, associated with high C emissions, may alter the regional climate and contribute to global climate change.