Resposta da laranjeira-pêra aos nutrientes N, P, K em Latossolo Amarelo no nordeste paraense.

Publicado também: FRAZÃO, D. A. C.; HOMMA, A. K. O; VIÉGAS, I. de J. M. (Ed.). Contribuição ao desenvolvimento da fruticultura na Amazônia. Belém, PA: Embrapa Amazônia Oriental, 2006. p. 279-284

Comportamento de plantas de açaizeiro em relação a diferentes doses de NPK na fase de formação e produção.

O presente trabalho tem como objetivo determinar os níveis de nitrogênio, fósforo e potássio adequados para a fase de formação e produção do açaizeiro no Nordeste Paraense. O estudo foi desenvolvido no município de Inhangapi, em Latossolo Amarelo textura média, com delineamento em blocos ao acaso no esquema fatorial fracionado (4 x 4 x 4)½, em blocos incompletos. Os dados obtidos foram avaliados estatisticamente, através de análise de variância (teste F), para todas as variáveis. Curvas de regressão foram ajustadas para avaliação das respostas a aplicação de N, P, K em função das variáveis. Os resultados indicaram que as doses mais adequadas para o primeiro ano, foram: 50g por planta de N, 55g por planta de P2O5 e 124g por planta de K2O e para o segundo ano foram: 117 g de N, 158 g de P2O5 e 170 g por planta de K2O

A dynamic method for charging-up calculations: the case of GEM

The simulation of Micro Pattern Gaseous Detectors (MPGDs) signal response is an important and powerful tool for the design and optimization of such detectors. However, several attempts to simulate exactly the effective charge gain have not been completely successful. Namely, the gain stability over time has not been fully understood. Charging-up of the insulator surfaces have been pointed as one of the responsible for the difference between experimental and Monte Carlo results. This work describes two iterative methods to simulate the charging-up in one MPGD device, the Gas Electron Multiplier (GEM). The first method uses a constant step for avalanches time evolution, very detailed, but slower to compute. The second method uses a dynamic step that improves the computing time. Good agreement between both methods was reached. Despite of comparison with experimental results shows that charging-up plays an important role in detectors operation, should not be the only responsible for the difference between simulated and measured effective gain, but explains the time evolution in the effective gain.Comment: Minor changes in grammatical statements and inclusion of some important information about experimental setup at section "Comparison with experimental results

Influência da adubação NPK sobre a qualidade dos frutos da laranjeira em latossolo amarelo do nordeste paraense.

Publicado também: FRAZÃO, D. A. C.; HOMMA, A. K. O; VIÉGAS, I. de J. M. (Ed.). Contribuição ao desenvolvimento da fruticultura na Amazônia. Belém, PA: Embrapa Amazônia Oriental, 2006. p. 285-290

Further progress in ion back-flow reduction with patterned gaseous hole-multipliers

A new idea on electrostatic deviation and capture of back-drifting avalanche-ions in cascaded gaseous hole-multipliers is presented. It involves a flipped reversed-bias Micro-Hole & Strip Plate (F-R-MHSP) element, the strips of which are facing the drift region of the multiplier. The ions, originating from successive multiplication stages, are efficiently deviated and captured by such electrode. Experimental results are provided comparing the ion-blocking capability of the F-R-MHSP to that of the reversed-bias Micro-Hole & Strip Plate (R-MHSP) and the Gas Electron Multiplier (GEM). Best ion-blocking results in cascaded hole-multipliers were reached with a detector having the F-R-MHSP as the first multiplication element. A three-element F-R-MHSP/GEM/MHSP cascaded multiplier operated in atmospheric-pressure Ar/CH4 (95/5), at total gain of ~10^{5}, yielded ion back-flow fractions of 3*10^{-4} and 1.5*10^{-4}, at drift fields of 0.5 and 0.2 kV/cm, respectively. We describe the F-R-MHSP concept and the relevance of the obtained ion back-flow fractions to various applications; further ideas are also discussed.Comment: 17 pages, 11 figures, published in JINS

Simulation of gain stability of THGEM gas-avalanche particle detectors

Charging-up processes affecting gain stability in Thick Gas Electron Multipliers (THGEM) were studied with a dedicated simulation toolkit. Integrated with Garfield++, it provides an effective platform for systematic phenomenological studies of charging-up processes in MPGD detectors. We describe the simulation tool and the fine-tuning of the step-size required for the algorithm convergence, in relation to physical parameters. Simulation results of gain stability over time in THGEM detectors are presented, exploring the role of electrode-thickness and applied voltage on its evolution. The results show that the total amount of irradiated charge through electrode's hole needed for reaching gain stabilization is in the range of tens to hundreds of pC, depending on the detector geometry and operational voltage. These results are in agreement with experimental observations presented previously

Efeitos de fontes e doses de nitrogênio em mudas de aceroleira (Malpighia glabra, L.).

Foram estudados os efeitos de doses e fontes de adubos nitrogenados na produção de matéria seca e composição mineral de mudas de aceroleira, num experimento conduzido em vasos de plastico em casa de vegetação. O delineamento experimental utilizado foi o inteiramente casualizado, em esquema fatorial 3 x 4, com quatro repetições. Os tratamentos constituíram de três doses de nitrogênio (0; 75 e 150 mg.kg-1) e quatro fontes de nitrogênio (sulfato de amônio, ureia, salitre do Chile e nitrato de cálcio). Determinaram-se as produções de matéria seca e os teores de N, P, K, Ca, Mg e S nas folhas, caules e raízes das plantas. os resultados mostraram que, apesar de os adubos nitrogenados amoniacais reagirem diferentemente no solo, tendo reduzido o pH e aumentado o teor de Al3+, as fontes de nitrogênio nitricas reagiram inversamente. As maiores produções de matéria seca foram obtidas através das doses de 75 e 150 mg.kg-1 de sulfato de amônio, seguido pela fonte de nitrato de cálcio, revelando uma forte influencia dos íons secundários desses fertilizantes, contribuindo com as maiores concentrações de S e Ca nas plantas. De uma maneira geral, todas as fontes e doses de N promoveram aumento das concentrações desse nutriente na planta

Simulation of VUV electroluminescence in micropattern gaseous detectors: the case of GEM and MHSP

Electroluminescence produced during avalanche development in gaseous avalanche detectors is an useful information for triggering, calorimetry and tracking in gaseous detectors. Noble gases present high electroluminescence yields, emitting mainly in the VUV region. The photons can provide signal readout if appropriate photosensors are used. Micropattern gaseous detectors are good candidates for signal amplification in high background and/or low rate experiments due to their high electroluminescence yields and radiopurity. In this work, the VUV light responses of the Gas Electron Multiplier and of the Micro-Hole Strip Plate, working with pure xenon, are simulated and studied in detail using a new and versatile C++ toolkit. It is shown that the solid angle subtended by a photosensor placed below the microstructures depends on the operating conditions. The obtained absolute EL yields, determined for different gas pressures and as functions of the applied voltage, are compared with those determined experimentally.Comment: Accepted for publication in Journal of Instrumentatio

Caracterização físico-hídrica de um podzólico vermelho-amarelo textura arenosa/média sob diferentes usos, em Igarapé-Açu, Pará.

bitstream/item/57484/1/CPATU-BP174.pd