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

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

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

Palaeomagnetism, rock magnetism and AMS of the Cabo Magmatic Province, NE Brazil, and the opening of South Atlantic

P>Reconstruction of the South Atlantic opening has long been a matter of debate and several models have been proposed. One problem in tracing properly the Atlantic history arises from the existence of a long interval without geomagnetic reversals, the Cretaceous Normal Superchron, for which ages are difficult to assign. Palaeomagnetism may help in addressing this issue if high-quality palaeomagnetic poles are available for the two drifting continental blocks, and if precise absolute ages are available. In this work we have investigated the Cabo Magmatic Province, northeastern Brazil, recently dated at 102 +/- 1 Ma (zircon fission tracks, Ar39/Ar40). All volcanic and plutonic rocks showed stable thermal and AF demagnetization patterns, and exhibit primary magnetic signatures. AMS data also support a primary origin for the magnetic fabric and is interpreted to be contemporaneous of the rock formation. The obtained pole is located at 335.9 degrees E/87.9 degrees S (N = 24; A(95) = 2.5; K = 138) and satisfies modern quality criteria, resulting in a reference pole for South America at similar to 100 Ma. This new pole also gives an insight to test and discuss the kinematic models currently proposed for the South Atlantic opening during mid-Cretaceous

Rare cardiac tumor simulating ST elevated acute myocardial infarction

info:eu-repo/semantics/publishedVersio

Monitoramento da fauna de solo sob diferentes coberturas vegetais em um sistema integrado de produção agroecológica, Seropédica (R.J.).

Metodologia; Descrição da área; Amostragem.bitstream/CNPAB-2010/27118/1/cit003.pd

Trocas de energia e fluxo de carbono entre a vegetação de caatinga e atmosfera no Nordeste brasileiro.

Neste estudo foram avaliadas as variações sazonais dos fluxos de dióxido de carbono, de vapor de água e de energia em área de caatinga nativa, no nordeste do Brasil. A taxa de evapotranspiração (LE) do sistema é muito baixa tanto na estação seca quanto na estação chuvosa devido à baixa disponibilidade de água na região, com valores próximos de zero no final da estação seca. Durante a estação seca, cerca de 60 % da energia disponível (Rn) foi utilizada para aquecer o ar (H) e LE correspondeu a 10% de Rn, em média. Durante a estação chuvosa essas taxas foram, respectivamente, 46 e 17%. Quanto ao fluxo de CO2, o ecossistema atua como sumidouro de CcO2 no início da estação seca, quando o solo ainda contém umidade decorrente da estação chuvosa anterior, bem como na estação chuvosa. Já no final da estação seca, quando os estômatos se fecham e há uma redução significativa no folhedo em função do déficit hídrico, a taxa de fotossíntese torna-se nula e o sistema passa a atuar como fonte de CcO2

Viabilidade econômica de um sistema de produção de cabras leiteiras no Submédio do São Francisco.

O objetivo desse trabalho foi fazer um levantamento dos custos de produção visando determinar a receita mínima para garantir a viabilidade de um sistema de produção de leite de cabra na região do submédio do rio São Francisco. Os dados foram coletados durante o período de julho de 2007 a junho de 2008. Foram determinados os índices produtivos do rebanho, os custos operacionais efetivos, custos indiretos e o custo total e a relação benefício/custo. A produção média de leite foi de 1,2 L/cabra/dia, com 90 cabras em lactação, por um período de seis meses. Os custos com mão-de-obra e ração concentrada corresponderam a 60,8% dos custos operacionais. A pesquisa registrou resultados economicamente insatisfatórios em diversos índices econômicos. A relação benefício/custo foi de 0,68% e o ponto de nivelamento foi de 33372 L/ano. A situação mínima desejada seria a produtividade média de 1,8 L/ cabra/dia e o preço de R$ 1,00/ L de leite. Na situação desejada, a relação benefício/custo seria 1,11% e o ponto de nivelamento de 25576 L/ano. No período avaliado, o sistema de produção do sistema de cabras leiteiras mostrou-se ineficiente

Healing activity induced by glucose/mannose lectins in mice

This work aimed the use of glucose/mannose lectins (Cramoll, EmaL and Con A) in the treatment of cutaneous wounds in mice.Surgical wounds were treated daily with the lectins and parameters such as edema, hyperemia, scab, granulation and scar tissues as well as contraction of wounds were analyzed. The lectin wounds showed higher edema and arrival of more polimorphonuclear cells at the site of lesions when compared with control group (0.15 M NaCl). Granulation tissue and collagen fiber deposition were observed with higher intensity in all lectin treated wounds promoting excellent closing and repair of lesions in less time than other groups. Results showed that Cramoll was more effective in the repair of experimental lesions in mice;however, the glucose/mannose lectins can be used as future cicatricial compounds