Produção de biomassa e padrão de decomposição de adubos verdes cultivados nas entrelinhas de acerola orgânica.

A utilização de adubos verdes constitui uma opção para o adequado aporte de matéria orgânica em solos arenosos sujeitos a um alto grau de degradação. O objetivo deste trabalho foi quantificar a produção e o padrão de decomposição de biomassa de seis espécies de adubos verdes e da vegetação espontânea

Adubação verde com espécies leguminosas nas entrelinhas de coqueiros cultivados na região dos Tabuleiros Costeiros de Alagoas.

O objetivo deste trabalho foi avaliar o potencial de produção de biomassa seca (raízes e parte aérea) e os teores de macronutrientes em três espécies de leguminosas (feijão de porco, Crotalaria juncea e guandu comum) cultivadas nas entrelinhas de um coqueiral em fase produtiva situado nos Tabuleiros Costeiros do Estado de Alagoas. O experimento foi conduzido em área particular no Município de Coruripe/AL, sendo avaliadas três espécies de leguminosas (Canavalia ensiformis, Crotalaria juncea e Cajanus cajan) cultivadas nas entrelinhas de plantio de um coqueiral jovem. A produção de biomassa seca total do feijão de porco foi de 8,55 t/ha, correspondente ao aporte de 112,4 Kg de nitrogênio por hectare. Para a Crotalaria juncea, a produção de biomassa seca foi de 8,04 e o aporte de Nitrogênio foi de 112,8 Kg/ha de N. No caso do Guandu comum, a produção da biomassa seca foi de 8,02 e o aporte de nitrogênio de 149,3 Kg/ha de N. Este alto aporte de N pela parte aérea do guandu comum ocorreu devido à elevada concentração de nitrogênio nos seus talos e folhas (20,24%)

Rapid decomposition of traditionally produced biochar in an Oxisol under savannah in Northeastern Brazil.

Soil amendment with biochar has been claimed as an option for carbon (C) sequestration in agricultural soils. Most studies on biochar/soil organic carbon (SOC) interactions were executed under laboratory conditions. Here we tested the stability of biochar produced in a traditional kiln and its effects on the stocks of native SOC under field conditions

Produtividade do Capim-Marandu sob diferentes doses de nitrogênio.

Objetivou-se com este trabalho avaliar o efeito de diferentes doses de nitrogênio (N) sobre o rendimento de matéria seca (MS) do capim Brachiaria brizantha cv. Marandu. O trabalho foi conduzido, no período de dezembro de 2011 a abril de 2012, no Campo Experimental da Embrapa Meio-Norte, localizado no município de Parnaíba, Piauí

Características agronômicas dos capins Digitaria sp. e Cynodon dactylon cv. Tifton-85 sob diferentes alturas de resíduo.

Com o objetivo de avaliar a produtividade dos capins Digitaria sp. e Cynodon dactylon cv. Tifton-85 em diferentes alturas de resíduo foi conduzido um experimento, no período de abril a junho de 2012, na Embrapa Meio-Norte, localizada no município de Parnaíba, Piauí. O delineamento experimental foi em blocos casualizados em esquema de parcelas divididas, com cinco repetições, tendo nas parcelas as gramíneas (Digitária e Tifton-85) e nas subparcelas as alturas de resíduos (10, 20 e 30 cm)

Space-time Phase Transitions in Driven Kinetically Constrained Lattice Models

Kinetically constrained models (KCMs) have been used to study and understand the origin of glassy dynamics. Despite having trivial thermodynamic properties, their dynamics slows down dramatically at low temperatures while displaying dynamical heterogeneity as seen in glass forming supercooled liquids. This dynamics has its origin in an ergodic-nonergodic first-order phase transition between phases of distinct dynamical "activity". This is a "space-time" transition as it corresponds to a singular change in ensembles of trajectories of the dynamics rather than ensembles of configurations. Here we extend these ideas to driven glassy systems by considering KCMs driven into non-equilibrium steady states through non-conservative forces. By classifying trajectories through their entropy production we prove that driven KCMs also display an analogous first-order space-time transition between dynamical phases of finite and vanishing entropy production. We also discuss how trajectories with rare values of entropy production can be realized as typical trajectories of a mapped system with modified forces

Interatomic potentials for atomistic simulations of the Ti-Al system

Semi-empirical interatomic potentials have been developed for Al, alpha-Ti, and gamma-TiAl within the embedded atomic method (EAM) by fitting to a large database of experimental as well as ab-initio data. The ab-initio calculations were performed by the linear augmented plane wave (LAPW) method within the density functional theory to obtain the equations of state for a number of crystal structures of the Ti-Al system. Some of the calculated LAPW energies were used for fitting the potentials while others for examining their quality. The potentials correctly predict the equilibrium crystal structures of the phases and accurately reproduce their basic lattice properties. The potentials are applied to calculate the energies of point defects, surfaces, planar faults in the equilibrium structures. Unlike earlier EAM potentials for the Ti-Al system, the proposed potentials provide reasonable description of the lattice thermal expansion, demonstrating their usefulness in the molecular dynamics or Monte Carlo studies at high temperatures. The energy along the tetragonal deformation path (Bain transformation) in gamma-TiAl calculated with the EAM potential is in a fairly good agreement with LAPW calculations. Equilibrium point defect concentrations in gamma-TiAl are studied using the EAM potential. It is found that antisite defects strongly dominate over vacancies at all compositions around stoichiometry, indicating that gamm-TiAl is an antisite disorder compound in agreement with experimental data.Comment: 46 pages, 6 figures (Physical Review B, in press

Onset of magnetism in B2 transition metals aluminides

Ab initio calculation results for the electronic structure of disordered bcc Fe(x)Al(1-x) (0.4<x<0.75), Co(x)Al(1-x) and Ni(x)Al(1-x) (x=0.4; 0.5; 0.6) alloys near the 1:1 stoichiometry, as well as of the ordered B2 (FeAl, CoAl, NiAl) phases with point defects are presented. The calculations were performed using the coherent potential approximation within the Korringa-Kohn-Rostoker method (KKR-CPA) for the disordered case and the tight-binding linear muffin-tin orbital (TB-LMTO) method for the intermetallic compounds. We studied in particular the onset of magnetism in Fe-Al and Co-Al systems as a function of the defect structure. We found the appearance of large local magnetic moments associated with the transition metal (TM) antisite defect in FeAl and CoAl compounds, in agreement with the experimental findings. Moreover, we found that any vacancies on both sublattices enhance the magnetic moments via reducing the charge transfer to a TM atom. Disordered Fe-Al alloys are ferromagnetically ordered for the whole range of composition studied, whereas Co-Al becomes magnetic only for Co concentration >0.5.Comment: 11 pages with 9 embedded postscript figures, to be published in Phys.Rev.

Gold nanowires and the effect of impurities

Metal nanowires and in particular gold nanowires have received a great deal of attention in the past few years. Experiments on gold nanowires have prompted theory and simulation to help answer questions posed by these studies. Here we present results of computer simulations for the formation, evolution and breaking of very thin Au nanowires. We also discuss the influence of contaminants, such as atoms and small molecules, and their effect on the structural and mechanical properties of these nanowires

Estabilidade de agregados e DMG determinados por via úmida e via seca, em latossolo vermelho-escuro sob plantio de E. dunnii.

O trabalho determinou o DMG e a estabilidade dos agregados (via úmida e via seca), em Latossolos Vermelho-Escuro, em talhões de Eucalyptus dunnii, numa fase preliminar à adição de resíduos de fabricação de papel e celulose.bitstream/item/105440/1/1295.pd