Relatório de gestão da área de P & D ano 2007.

bitstream/CNPF-2009-09/44071/1/Doc170.pd

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 comparison of extremal optimization with flat-histogram dynamics for finding spin-glass ground states

We compare the performance of extremal optimization (EO), flat-histogram and equal-hit algorithms for finding spin-glass ground states. The first-passage-times to a ground state are computed. At optimal parameter of tau=1.15, EO outperforms other methods for small system sizes, but equal-hit algorithm is competitive to EO, particularly for large systems. Flat-histogram and equal-hit algorithms offer additional advantage that they can be used for equilibrium thermodynamic calculations. We also propose a method to turn EO into a useful algorithm for equilibrium calculations. Keywords: extremal optimization. flat-histogram algorithm, equal-hit algorithm, spin-glass model, ground state.Comment: 10 LaTeX pages, 2 figure

Effect of different enrichment media and DNA extraction techniques on Salmonella detection by PCR in SWINE feces

The aim of this study was to evaluate different selective enrichment broths and DNA extraction techniques on the detection of Salmonella Typhimurium in swine feces by PCR. Feces samples (n=10) were inoculated with approximately 102 Salmonella Typhimurium organisms, first enriched in GN-Hajna broth and secondly enriched in Rappaport-Vassiliadis, Muller-Kaufmann tetrathionate and selenite-cystine broths. In order to produce DNA-templates for PCR, aliquots from the broths were subjected to three DNA extraction methods: boiling-centrifugation, salting-out and phenol-chloroform. Detection of Salmonella was significant lower when phenol-chloroform was applied to selenite-cystine and Muller-Kaufmann tetrathionate (P\u3c0.05). The boiling-centrifugation technique had best cost/benefit ratio and can be successfully used as a rapid DNA template preparation from the three enriched broths tested

Broad histogram relation for the bond number and its applications

We discuss Monte Carlo methods based on the cluster (graph) representation for spin models. We derive a rigorous broad histogram relation (BHR) for the bond number; a counterpart for the energy was derived by Oliveira previously. A Monte Carlo dynamics based on the number of potential moves for the bond number is proposed. We show the efficiency of the BHR for the bond number in calculating the density of states and other physical quantities.Comment: 7 pages, 7 figure

Produção de mudas de cupuaçuzeiro em diferentes substratos e tubetes.

Objetivou-se avaliar mudas de cupuaçuzeiro utilizando diferentes substratos e recipientes. O experimento foi conduzido no viveiro de produção de mudas da Embrapa Acre, localizada em Rio Branco - Acre. O substrato utilizado foi composto por uma mistura de terra de subsolo peneirada, esterco de curral peneirado e curtido, numa proporção de 3:1, acrescido de 2 kg de superfosfato simples por metro cúbico da mistura e o segundo o substrato comercial Plantmax©. O delineamento utilizado foi o inteiramente casualizado, no esquema de parcela subdividida, com seis tratamentos e quatro repetições.A parcela constituiu-se de dois tipos de substratos (Substrato 1 e Substrato 2) e, as subparcelas de três tamanhos de tubetes, por que variaram em três níveis de volume (recipiente 1: 288 cm3 ; recipiente 2: 180 cm3 ; e recipiente 3: 120 cm3 ). Com término do período de observação (180 dias após a repicagem), realizou-se a análise destrutiva de três plantas de cada tratamento, em cada repetição. As características avaliadas foram: altura de plantas (cm), diâmetro na altura do colo (mm), número de folhas, massa seca da raiz (g), massa seca do caule (g), massa seca das folhas (g), massa seca total (g) e área foliar (dm2). As mudas de cupuaçuzeiro produzidas nos maiores tubetes apresentaram melhor desempenho. Entre as mudas cultivadas nos dois substratos não houve diferença para: altura das plantas e diâmetro na altura do colo. Houve diferença para massa seca de folhas em todos os recipientes