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.

Ácido cianídrico em tecidos de mandioca em função da idade da planta e adubação nitrogenada

Abstract: O objetivo deste trabalho foi avaliar o teor de acido cianidrico em tecidos de mandioca, em funcao da idade da planta e niveis de adubacao nitrogenada. Utilizou-se o delineamento experimental de blocos ao acaso, em arranjo de parcelas subdivididas, com quatro repeticoes. As doses de nitrogenio em cobertura (0, 30, 60, 150 e 330 kg ha -1 ) foram alocadas nas parcelas, e as epocas de avaliacao (90, 120, 150, 180, 240, 300 e 360 dias apos o plantio), nas subparcelas. Os teores de acido cianidrico foram avaliados em tecidos da folha, caule, polpa e cortex da raiz da cultivar Aciolina. Os efeitos das doses de N e das epocas de avaliacao foram independentes. Doses entre 219 e 241 kg ha -1 de N em cobertura proporcionam os maiores teores de acido cianidrico, que variaram de 332 a 401 mg kg -1 de materia fresca nos tecidos avaliados. O teor de acido cianidrico nos tecidos reduz-se linearmente com a idade da planta. O cortex da raiz acumula o maior teor de acido cianidrico, e a polpa da raiz o menor. Por ocasiao da colheita, aos 360 dias apos o plantio, essa cultivare classificada como mandioca mansa.

Synthesis, characterization and thermogravimetric study of zinc group halides adducts with imidazole

Abstract: The synthesis, characterization and thermogravimetric study of the adducts ZnCl 2 ·2Imi, ZnBr 2 ·2Imi, CdCl 2 ·Imi, CdCl 2 ·2Imi, CdBr 2 ·2Imi, CdBr 2 ·3Imi, CdI 2 ·2.5Imi, HgCl 2 ·2Imi, HgBr 2 ·1.5Imi and HgI 2 ·1.5Imi (Imi = imidazole) is reported. The following sequence of thermal stability is observed for the synthesized adducts: Zn>Hg>Cd. It is also verified that larger cations, as well as larger anions, result in a smaller number of imidazole molecules in the coordination sphere of the considered cation and that hard acids exhibit stronger bonds to imidazole than soft acids, and this fact is reflected in the thermal stability sequence. ZnCl 2 ·2Imi behaves as a non-electrolyte in acetonitrile and ethanol, whereas ZnBr 2 ·2Imi is a non-electrolyte in acetonitrile and a 1:1 electrolyte in ethanol. CdI 2 ·2.5Imi is a non-electrolyte in acetonitrile and a 1:2 electrolyte in ethanol.

Tannin-Rich Plants as Natural Manipulators of Rumen Fermentation in the Livestock Industry.

Abstract: Condensed tannins (CTs) are plant anti-herbivore compounds with antimicrobial activity that can be used in ruminant diets as ruminal microbiome manipulators However, not all CTs from fodder legumes are bioactive due to their wide structural diversity The aim of our study was to investigate the effect of 10 CT-containing plants (Flemingia macrophylla, Leucaena leucocephala, Stylosanthes guianensis, Gliricidia sepium, Cratylia argentea, Cajanus cajan, Desmodium ovalifolium, Macrotiloma axilare, D paniculatum, and Lespedeza procumbens) on in vitro fermentation kinetics of Nelore beef cattle Polyethylene glycol (PEG), a specific CT-binding agent, was added to neutralize condensed tannin Tifton and alfalfa hay were used as controls lacking CT The experimental layout included a randomized complete block with factorial design and four blocks The data were subjected to analysis of variance followed by Duncan's test to determine differences (p < 005) among treatment means The addition of PEG in browse incubations resulted in increased gas production, fermentation rate, short-chain fatty acid (SCFA) and N-NH3 release Within our study, Lespedeza procumbens, Desmodium paniculatum, Leucaena leucocephala, Desmodium ovalifolium, and Flemingia macrophylla showed superior bioactivity compared to other species evaluated, suggesting a natural alternative for replacing ionophores to modify ruminal fermentation Condensed tannins from L pocumbens, D paniculatum, L leucocephala, D ovalifolium, and F macrophylla have the potential to modify rumen fermentation in beef cattle

K'Mudku A-type magmatism in the southernmost Guyana Shield, central-north Amazon Craton (Brazil): the case of Pedra do Gavião syenogranite

Abstract: The Mesoproterozoic K'Mudku event (1490 - 1147 Ma) is represented by a britlle-ductile shear belt that cuts across the Paleoproterozoic units in the southernmost Guyana shield, central-north Amazon craton. This event produced mylonitization and cataclasites at low/medium- to high-grade metamorphic, and local within-plate magmatism. In the Amazonas State, Brazil, A-type magmatism chronologically associated to K'Mudku has been reported for the Pedra do Gaviao and Samauma syenogranites. However, the spatial relationship between K´Mudku event and A-type magma generation are not yet adequately clarified in the region. The Pedra do Gaviao syenogranite is a high-K alkaline, metaluminous, reduced A-type granite with a post-collisional to within-plate geochemical signature. It has U-Pb zircons crystallization age of 1218 Ma and inherited zircons with ages between 1820 and 1720 Ma, which, together with the Sm-Nd data, suggest melting of Paleoproterozoic basement rocks of the Cauaburi Complex (1810 - 1780 Ma) regional unit. These data demonstrate that the effects of the A-type magmatism associated to the end of the Grenvillian-Sunsas orogeny, reported primarily in the southwestern margin of the Amazon craton, may also be extended for the central-northern part of the Amazon craton. Probably the generation or emplacement mechanisms of A-type magma occurred with some degree of involvement in the final stages of the K´Mudku event. However, this tectonic framework conception still needs more geological and geophysical investigations. Therefore, these news data should instigate to the return of geological research in the region, as well as to debate on the tectonic evolution and A-type granites production during the Ectasian-Stenian period in the central-north Amazon craton.

Chromosomal mapping of repetitive sequences (Rex3, Rex6, and rDNA genes) in hybrids between Colossoma macropomum (Cuvier, 1818) and Piaractus mesopotamicus (Holmberg, 1887).

Abstract: Some species of Characiformes are known for their high economic value, such as Colossoma macropomum and Piaractus mesopotamicus, and are used in aquaculture programs to generate hybrid tambacu (interbreeding of C. macropomum females and P. mesopotamicus males). The present work aimed to investigate the location of the Rex3 and Rex6 transposable elements in the hybrid and in the species, in addition to checking the genomic organization of the 18S and 5S rDNA in tambacu. The diploid number found for the hybrid was equal to 54 chromosomes, with heterochromatic blocks distributed mainly in the centromeric portions. The chromosomal location of the mobile elements Rex3 and Rex6 in C. macropomum, P. mesopotamicus, and in the hybrid between these species enabled knowledge expansion and the generation of data on such mobile elements. In addition, the location of such elements is not related to the distribution of ribosomal DNA sites. The mapping of the 18S rDNA was shown to be effective in cytogenetic identification of the hybrid tambacu, allowing for differentiation from the parent species and from the hybrid between C. macropomum and the other species from Piaractus (P. brachypomus).