Efeito da adubação nitrogenada, em diferentes densidades de plantios, na produção de biomassa de pimenta longa (Piper hispidinervum C.DC.).

Os objetivos deste trabalho foram avaliar os efeitos da densidade de plantio e diferentes níveis de adubação nitrogenada na produção de biomassa seca de pimenta longa, em um Argissolo Vermelho Escuro, textura argilosa, do município de Rio Branco, AC. As densidades de plantio foram 6.666; 10.000, 13.333 e 16.666 plantas ha-1, arranjadas nos espaçamentos de, respectivamente, 1,5 x 1,0, 1,0 x 1,0, 1,5 x 0,5 e 1,0 x 0,5 m, os quais constituíram as parcelas principais, em delineamento experimental de parcelas subdivididas com três repetições. Nas subparcelas foram aplicadas às doses de nitrogênio (0, 25, 50, 75 e 100 kg ha-1), tendo como fonte o sulfato de amônio. Foram avaliadas a altura de plantas, e a produção de matéria seca total, matéria seca do caule, matéria seca das folhas e porcentagem de matéria seca das folhas em relação ao peso seco total da parte aérea das plantas. A análise de variância para o efeito principal da densidade de plantio mostrou-se significativa (p < 0,05) para todas as características avaliadas, exceto a porcentagem de matéria seca nas folhas em relação ao peso seco total da planta. Não houve efeito significativo, para as variáveis avaliadas, para a interação densidade de plantio x dose de nitrogênio e para o subtratamento dose de nitrogênio. Os resultados indicaram que a densidade de plantio de 13.333 plantas ha-1 proporcionou a maior produção de biomassa das folhas de pimenta longa e a adubação nitrogenada não foi eficiente no aumento da produção de biomassa

O uso de poleiros para a atração de aves frugívoras em áreas degradadas da Floresta Estacional Semidecidual.

Organizado por Patricia Póvoa de Mattos, Celso Garcia Auer, Rejane Stumpf Sberze, Katia Regina Pichelli e Paulo César Botosso

Transport properties of graphene quantum dots

In this work we present a theoretical study of transport properties of a double crossbar junction composed by segments of graphene ribbons with different widths forming a graphene quantum dot structure. The systems are described by a single-band tight binding Hamiltonian and the Green's function formalism using real space renormalization techniques. We show calculations of the local density of states, linear conductance and I-V characteristics. Our results depict a resonant behavior of the conductance in the quantum dot structures which can be controlled by changing geometrical parameters such as the nanoribbon segments widths and relative distance between them. By applying a gate voltage on determined regions of the structure, it is possible to modulate the transport response of the systems. We show that negative differential resistance can be obtained for low values of gate and bias voltages applied.Comment: 9 pages, 9 figures, accepted to Phys. Rev.

Treating some solid state problems with the Dirac equation

The ambiguity involved in the definition of effective-mass Hamiltonians for nonrelativistic models is resolved using the Dirac equation. The multistep approximation is extended for relativistic cases allowing the treatment of arbitrary potential and effective-mass profiles without ordering problems. On the other hand, if the Schrodinger equation is supposed to be used, our relativistic approach demonstrate that both results are coincidents if the BenDaniel and Duke prescription for the kinetic-energy operator is implemented. Applications for semiconductor heterostructures are discussed.Comment: 06 pages, 5 figure

Período de atividade externa, carregamento de isca granulada e controle de Acromyrmex crassispinus em floresta de Pinus taeda.

Resumo 34

Stacking Gravitational Wave Signals from Soft Gamma Repeater Bursts

Soft gamma repeaters (SGRs) have unique properties that make them intriguing targets for gravitational wave (GW) searches. They are nearby, their burst emission mechanism may involve neutron star crust fractures and excitation of quasi-normal modes, and they burst repeatedly and sometimes spectacularly. A recent LIGO search for transient GW from these sources placed upper limits on a set of almost 200 individual SGR bursts. These limits were within the theoretically predicted range of some models. We present a new search strategy which builds upon the method used there by "stacking" potential GW signals from multiple SGR bursts. We assume that variation in the time difference between burst electromagnetic emission and burst GW emission is small relative to the GW signal duration, and we time-align GW excess power time-frequency tilings containing individual burst triggers to their corresponding electromagnetic emissions. Using Monte Carlo simulations, we confirm that gains in GW energy sensitivity of N^{1/2} are possible, where N is the number of stacked SGR bursts. Estimated sensitivities for a mock search for gravitational waves from the 2006 March 29 storm from SGR 1900+14 are also presented, for two GW emission models, "fluence-weighted" and "flat" (unweighted).Comment: 17 pages, 16 figures, submitted to PR

Influência do parcelamento de diferentes fontes de nitrogênio no teor de proteína em milho QPM e normal.

bitstream/item/58850/1/Pesq.And.-36-1.pd

Expected Coalescence Rate of Double Neutron Stars for Ground Based Interferometers

In this paper we present new estimates of the coalescence rate of neutron star binaries in the local universe and we discuss its consequences for the first generations of ground based interferometers. Our approach based on both evolutionary and statistical methods gives a galactic merging rate of 1.7 10$^{-5}$ yr$^{-1}$, in the range of previous estimates 10$^{-6}$ - 10$^{-4}$ yr$^{-1}$. The local rate which includes the contribution of elliptical galaxies is two times higher, in the order of 3.4 10$^{-5}$ yr$^{-1}$. We predict one detection every 148 and 125 years with initial VIRGO and LIGO, and up to 6 events per year with their advanced configuration. Our recent detection rate estimates from investigations on VIRGO future improvements are quoted.Comment: talk given at the GWDAW9 (Annecy, 2004) to be published in CQ