Artigos Científicos - ICEN
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Item Acesso aberto (Open Access) Phytosterols isolated from endophytic fungus Colletotrichum gloeosporioides (Melanconiaceae)(Instituto Nacional de Pesquisas da Amazônia, 2016-03) CARVALHO, Josiwander Miranda; PAIXÃO, Luanna Karyna Olimpio da; DOLABELA, Maria Fâni; MARINHO, Patrícia Santana Barbosa; MARINHO, Andrey Moacir do RosárioEndophytic fungi are fungi that colonize internal tissues of plants. There are few studies of compounds isolated from endophytic fungi of Amazon plants. Thus, the aim this study was the isolation and structural identification of sitosterol (1), stigmasterol (2), sitostenone (3), squalene (4), ergosterol (5) and ergosterol peroxide (6) from fungus Colletotrichum gloeosporioides isolated as endophytic from Virola michelli, a typical Amazon plant, used in folk medicine against skin infection. Compounds were isolated by chromatography column on silica and identified by 1 H and 13C NMR and MS. The presence of phytosterols in fungi is rare and this is the first report of the isolation of the phytosterols sitosterol, stigmasterol and sitostenone from the genus Colletotrichum.Item Acesso aberto (Open Access) Sedimentary transport influences on diagenetic processes at the Amazon continental shelf, Brazil(SCIENCEDOMAIN International, 2019) APRILE, Fábio Marques; SIQUEIRA, Gilmar Wanzeller; DARWICH, Assad José; IRION, Georg FriedrichThis research aimed to correlate the sedimentary transport with the diagenetic processes in the coastal zone and Amazon Continental Shelf (ACS). Physical and physical-chemical parameters, trace element contents (Cr, Pb, Ni, Zn and Hg), and O2, CO2 and iron flux were determined in sediment and pore water. Sedimentary incubation (96 hours) and algorithms were applied to determine the variation of the activity coefficient (ΔI) and ionic strength (Fi) of the predominant chemical species, and to estimate the net production and mineralization of the organic matter (ΔCO2T) in the system. There are not many studies applying incubation tests to identify the diagenetic processes, especially in fluvial-marines sediments. The results showed a strong zonation associated to the transport and deposition processes, influenced mainly by the grain-size and texture of sediment and fluvial streams. The distribution of trace elements followed the trend of the sedimentary pattern, with higher levels of metals in the deposits of clay minerals and organic matter. A factor of weight (Fw), calculated to establish the degree of importance of each parameter under the distribution and mobility of trace elements, suggests that the mobility of Cr, Ni and Zn is controlled by depth, clay and organic compounds contents, and concentration of dissolved oxygen.The vertical flow of O2 and CO2 and the Fe2+/Fe3+ ratio in the pore water suggest a predominance of organic matter oxidation in the sedimentary layer between 0.0 and 0.2 m, with partially anaerobic mineralization of the sediments below 0.4 m. Increases in trace element concentrations were observed in iron reduction zones, indicating processes of desorption of oxides and hydroxides of Fe and mineralization of organic matter. The extrapolation of the results of the incubation test to the studied system allowed to establish three hypotheses related to the diagenetic processes: 1) the flow of marine currents may be allowing the aerobic oxidation in the sandy sediments, with the nitrification route more accentuated than the ammonification route; 2) in the region of the coastal zone and inner continental shelf the routes of oxidation and reduction may be alternating according to the physical-chemical factors and seasonality; 3) in the coastal zone and inner shelf the net mineralization rate exceeded the net production rate of the organic matter (ΔCO2T >0).Item Acesso aberto (Open Access) Theoretical study of plasmonically induced transparency effect in arrays of graphene-based double disk resonators(Sociedade Brasileira de Micro-ondas e Optoeletrônica, 2019-03) PORTELA, Gianni Masaki Tanaka; DMITRIEV, Victor Alexandrovich; OLIVEIRA, Cristiano Braga de; CASTRO, Wagner Ormanes PalhetaIn this paper, we consider coupled disk-shaped resonators separated by a thin dielectric substrate that can be used as frequency-tunable filters or as electromagnetic switches in the terahertz frequency band. The two disks are electromagnetically coupled and resonate with dipole plasmonic modes. By using a Temporal Coupled-Mode Theory based approach, we show how to analytically calculate the frequency response of such structures.The analytical results are in good agreement with those obtained from computational simulations based on the finite element method.