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Medhat M.E.,Nuclear Research Center - Negev | Medhat M.E.,CAS Institute of High Energy Physics | Pires L.F.,State University of Ponta Grossa | Arthur R.C.J.,Center for Nuclear Energy in Agriculture
Journal of Radioanalytical and Nuclear Chemistry | Year: 2014

In the present work the total mass attenuation coefficients (μ/ρ) for some soils collected from the Southeast and South of Brazil were measured at 59.5 (241Am) and 661.6 keV (137Cs) photon energies. The experimental values of the soils μ/ρ were compared with XCOM program calculations and GEANT4 Monte Carlo simulations. Total atomic and electronic cross-sections, effective atomic and electron numbers of all soil samples were calculated in a wide energy range (1 keV-100 GeV). The values of these parameters have been found to vary with photon energy and chemical composition of the soil. The variations of these parameters with energy are shown graphically for total photon interactions. The results showed that loamy soils have low photon attenuation parameters than clayey ones for the region of 59.5 keV. © 2014 Akadémiai Kiadó. Source

De Oliveira E.C.A.,Federal Rural University of Pernambuco | de Castro Gava G.J.,Sao Paulo State Agribusiness Technology Agency APTA | Trivelin P.C.O.,Center for Nuclear Energy in Agriculture | Franco H.C.J.,CTBE - Brazilian Bioethanol Science and Technology Laboratory
Journal of Plant Nutrition and Soil Science | Year: 2013

Adequate measurements of the nitrogen (N) concentration in the aboveground biomass of sugarcane throughout the growth cycle can be obtained using the critical N dilution curve (CNDC) concept, which provides an N-nutrition index (NNI). The aim of this work was to determine the CNDC value for Brazilian sugarcane variety SP81-3250, establish the critical concentration of N, and determine the NNI in the aboveground biomass throughout the cane plant and first ratoon crop cycles. The study was performed in three experimental areas located in São Paulo, Brazil, during the crop cycles of 2005/2006 (18-month cane plant) and 2006/2007 (first ratoon). The plant cane crop was fertilized with treatments of 40, 80, or 120kg N ha-1 and a control treatment without N. After the plant cane harvest, rates of 0, 50, 100, or 150kg N ha-1 were applied to the control plot and the 120kg N ha-1-treatment plot in a split-plot experimental design with four repetitions. Throughout both sugarcane cycles, measurements of aboveground biomass were used to determine the dry-mass (DM) production and N concentration for each treatment. CNDC varied between the growth cycles, with a higher N concentration observed in the initial stages of the first ratoon and a lower N dilution observed throughout the plant cane cycle. The NNI value indicated excessive N storage in the initial stages and limiting concentrations at the end of the growth cycle. CNDC and NNI allow for the identification of the N-nutrition variation rate and the period in which the nutrient concentration limits the production of aboveground biomass. The equations for the critical N (Ncr) level obtained in this study for plant cane (Ncr = 19.0 DM-0.369) and ratoons (Ncr = 20.3 DM-0.469) can potentially be used as N-nutritional diagnostic parameters for sugarcane N nutrition. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Cohen M.C.L.,Federal University of Para | Alves I.C.C.,Federal University of Para | Franca M.C.,Federal University of Para | Pessenda L.C.R.,Center for Nuclear Energy in Agriculture | de Fatima Rossetti D.,National Institute for Space Research
Catena | Year: 2015

An integrated approach focused on sedimentology, geochemistry, palynology, C and N isotopes and radiocarbon dating of a sediment core from an herbaceous plain not flooded by tides of the Amapá littoral, near the Amazon River mouth, allowed identification of two phases with marine and terrestrial influences. Mangroves occurred over tidal mud flats with marine influence between >5610-5470 and 470-310calyr BP. The absence of mangrove vegetation since 470-310calyr was followed by the transition of brackish water organic matter to terrestrial C3 plants. Also, the geochemical data indicate a decrease in sea water influence during this last time interval. Likely, the displacement of mangrove forest to lower surfaces was caused by a relative sea-level fall that may be associated with drier conditions with less rainfall during the second part of the last millennium. As suggested by this work, slight relative sea-level fluctuations caused by regional or global climatic change may affect significantly the current mangrove area. © 2015 Elsevier B.V. Source

Cohen M.C.L.,Federal University of Para | Franca M.C.,Federal University of Para | de Fatima Rossetti D.,National Institute for Space Research | Pessenda L.C.R.,Center for Nuclear Energy in Agriculture | And 5 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2014

The sedimentary deposits of the deltaic plain of the Doce and Barra Seca rivers, Southeastern Brazil, were studied by facies analysis, pollen records, δ13C, C/N analysis and AMS 14C-dating. Today, this deltaic plain is dominated by beach ridges and sandy terraces occupied by arboreal and herbaceous vegetation. Between ~47,500 and ~29,400calyrB.P., a deltaic system was developed in response mainly to eustatic sea-level fall. Although the studied stratigraphic succession is compatible with the trend of global sea-level fall, the earlier sea-level suggested by the topographic position of these deltaic deposits was above the one expected during the MIS3 stage. A tectonic uplift likely occurred during the late Quaternary and raised these deposits. The post-glacial sea-level rise caused a marine incursion with invasion of embayments and broad valleys, and it favored the evolution of an estuary with wide tidal mud flats occupied by mangroves between ~7400 and ~5100calyrB.P. The high river sand supply and/or the relative sea-level fall in the late Holocene led to seaward and downward translation of the shoreline during normal/forced regression, producing progradational deposits with shrinkage of mangrove stands and expansion of marshes colonized by herbaceous vegetation. Therefore, the stratigraphic architecture and evolution of the Doce River deltaic plain suggest that fluvial sediment supply and relative sea-level fluctuations related to Quaternary global climatic changes and local tectonism exerted major controls on sedimentation through the variation of accommodation space and base-level changes. © 2013 Elsevier B.V. All rights reserved. Source

Longo C.,Center for Nuclear Energy in Agriculture | Longo C.,University of Bonn | Longo C.,Julich Research Center | Hummel J.,University of Bonn | And 7 more authors.
Czech Journal of Animal Science | Year: 2012

Leucaena leucocephala (LEU) and three under-utilized tanniferous legumes, Styzolobium aterrimum L. (STA), Styzolobium deeringianum (STD), and Mimosa caesalpiniaefolia Benth (MIC) were chemically characterized and the biological activity of tannins was evaluated using in vitro simulated ruminal fermentation through tannin-binding polyethylene glycol (PEG) and compared with a non-tanniferous tropical grass hay, Cynodon spp. (CYN). The Hohenheim gas test was used and gas production (GP) was recorded at 4, 8, 12, 24, 32, 48, 56, 72, 80, and 96 h incubation with and without PEG. Kinetic parameters were estimated by an exponential model. STA, STD, and LEU contained higher (P < 0.05) crude protein than MIC, which had greater neutral detergent fibre and acid detergent fibre. Total phenols, total tannins, and condensed tannins (CT) were consistently the highest in MIC. Gas production was the lowest from MIC (P < 0.05) and the highest in LEU and STA. MIC + PEG largely reduced (P < 0.05) the lag phase and the fractional rate of fermentation and increased potential GP. Kinetic parameters of STA + PEG and LEU + PEG were not affected. LEU + PEG produced greater gas increment (P < 0.05) than STD + PEG, although both legumes had the same CT. All legumes except MIC were more extensively degraded than CYN. However, fermentation of the legumes was differently affected by the presence and proportions of CT, indigestible fibre or both. Source

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