Estudo da variação do crescimento da cortiça na direcção axial e tangencial

Comunicação apresentada no 4.º Congresso Florestal Nacional que decorreu em Évora em 2001.Neste trabalho efectuou-se o estudo do crescimento da cortiça através da espessuras dos anéis de crescimento de 5 pranchas de cortiça amadia cozida de classe de qualidade 1. Para cada prancha de cortiça efectuaram-se medições das camadas de crescimento segundo a direcção axial e tangencial distanciadas de 3 cm cada num total de 25 medições, 5 para cada direcção. Verificou-se que dentro da mesma prancha, para um determinado ano de crescimento, a variabilidade encontrada para a espessura da camada de crescimento é muito elevada, sendo mais elevada nos primeiros anéis de crescimento com espessuras superiores. Constatou-se que existiam diferenças significativamente entre as várias pranchas, no entanto, é a espessura dos anéis de crescimento que explicam a maior parte da variabilidade encontrada (66%). A variação na direcção axial é praticamente nula, contrariamente ao que se verifica na direcção tangencial devido às tensões de crescimento em diâmetro que vão provocar uma maior variabilidade. A variação do crescimento da cortiça segue uma distribuição da forma E=b0Ab1, em que E – espessura da cortiça, A – anos de crescimento e b0 e b1 são parâmetros ajustados em função do material. Os modelos justificam mais de 97% da variação encontrada

Bee pollen flavonoid/phenolic characterization in different flowering periods

In order to assess the choice made by honey bees all over the time two apiaries in the region of Beira Interior were selected for evaluation of the variance of floral pollen sources used by them in three different flowering periods

Heavy Quark Symmetry Violation in Semileptonic Decays of D Mesons

The decays of $D$ mesons to $K l \nu$ and $K^* l \nu$ final states exhibit significant deviations from the predictions of heavy-quark symmetry, as one might expect since the strange quark's mass is of the same order as the QCD scale. Nonetheless, in order to understand where the most significant effects might lie for heavier systems (such as $B \to D l\nu$ and $B \to D^* l\nu$), the pattern of these deviations is analyzed from the standpoint of perturbative QCD and ${\cal O}(1/m_s)$ corrections. Two main effects are noted. First, the perturbative QCD corrections lead to an overall decrease of predicted rates, which can be understood in terms of production of excited kaonic states. Second, ${\cal O}(1/m_s)$ effects tend to cancel the perturbative QCD corrections in the case of $Kl\nu$ decay, while they have minimal effect in $K^*l\nu$ decay.Comment: 25 pages (LaTeX) + 7 pages of Postscript figures (included at end), EFI-92-3

Resonant and nonresonant D+ -> K- pi+ l+ nu(l) semileptonic decays

We analyse the semileptonic decay D+ -> K- pi+ l+ nu(l) using an effective Lagrangian developed previously to describe the decays D -> P l nu(l) and D -> V l nu(l). Light vector mesons are included in the model which combines the heavy quark effective Lagrangian and chiral perturbation theory approach. The nonresonant and resonant contributions are compared. With no new parameters the model correctly reproduces the measured ratio Gamma(nres)/Gamma(nres + res). We also present useful nonresonant decay distributions. Finally, a similar model, but with a modified current which satisfies the soft pion theorems at the expense of introducing another parameter, is analyzed and the results of the models are compared.Comment: 17 pages, 3 Postscript figures, standard Latex, extended revision, title, abstract and text (especially Sec. IV) changed, results unchange

A importância da verificação das sondas na secagem industrial de madeira

Comunicação apresentada no 4.º Congresso Florestal Nacional que decorreu em Évora em 2001.A grande vantagem da secagem artificial é permitir obter madeira com um teor de água mais adequado para o fim a que se destina, o que nem sempre é possível na secagem natural. No entanto, nunca devemos deixar de ter presente que a madeira é um material higroscópico, anisotrópico e heterogéneo, e portanto, a homogeneidade final pretendida é muito difícil de obter. Como as condições dos secadores são normalmente estabelecidas em função da humidade da madeira em secagem, e os programas prevêem um número relativamente elevado de alterações nas variáveis envolvidas no processo, torna-se necessário estimar frequentemente o teor de humidade da madeira. Portanto essas estimativas devem ser ao mesmo tempo precisas e práticas. Verificou-se, através do teste de Scheffe a 95% de confiança, que a secagem dentro da mesma peça de madeira não é homogénea para valores iguais ou inferiores a 12%, sendo necessário efectuar a leitura em vários pontos da mesma. Para valores de 14% e 15% não existem diferenças significativas do teor em água ao longa da peça. Efectuou-se um estudo preliminar onde se pretende comprovar a importância da posição da colocação das sondas na madeira, e também tentar aplicar as normas europeias às dificuldades existentes em Portugal

Effect of quality, porosity and density on the compression properties of cork

The compression properties of cork were studied on samples obtained from cork planks of two commercial quality classes (good and poor quality), with densities ranging from 0.12–0.20g cm-3 and porosities from 0.5 to 22.0%. The stress-strain curves were characterized by an elastic region up to approximately 5% strain, followed by a large plateau up to 60% strain caused by the progressive buckling of cell walls, and a steep stress increase for higher strains corresponding to cell collapse. The direction of compression was a highly significant factor of variation, with cork showing higher strength for the radial compression. Density influenced compression and cork samples with higher density showed overall larger resistance to compression in the three directions. In the elastic region, an exponential model of Young’s modulus in function of cork density could be adjusted. The effect of porosity on compression was small and the stress-strain curves were similar regardless of the porosity of the samples, although there was a trend toward an overall increase of stress with porosity for higher strains. Porosity was characterised by a high variability in the anatomical features of the lenticular filling material and the presence of collapsed and thick walled lignified cells. The inclusion of a porosity parameter for the modelling of the elastic modulus did not improve the prediction obtained with density-based models. There was no significant difference in the compression properties of cork samples obtained from cork planks of good and poor quality classes.info:eu-repo/semantics/publishedVersio

Populational fluctuation and spatial distribution of Alphitobius diaperinus (Panzer) (Coleoptera; Tenebrionidae) in a poultry house, Cascavel, Parana state, Brazil.

Abstract Knowledge of the population fluctuation and spatial distribution of pests is fundamental for establishing an appropriate control method. The population fluctuation and spatial distribution of the Alphitobius diaperinus in a poultry house in Cascavel, in the state of Parana, Brazil, was studied between October, 2001 and October 2002. Larvae and adults of the lesser mealworm were sampled weekly using Arends tube traps (n = 22) for six consecutive flock grow-outs. The temperature of the litter and of the poultry house was measured at the same locations of the tube traps. Beetle numbers increased continuously throughout all the sampling dates (average 5,137 in the first week and 18,494 insects on the sixth week). Significantly greater numbers of larvae were collected than adults (1 to 20 times in 95% of the sampling points). There was no correlation between temperature and the number of larvae and adults collected, therefore no fluctuation was observed during the sampling period. The population growth was correlated to litter re-use. The highest temperatures were observed in deep litter. The spatial distribution of larvae and adults in the poultry house was heterogeneous during the whole period of evaluation. Results suggest that monitoring in poultry houses is necessary prior to adopting and evaluating control measures due to the great variability of the insect distribution in the poultry house. Keywords: lesser mealworm, poultry house, temperature, population dynamicbitstream/item/78871/1/ID-27879.pd