Artigos em revistas internacionais_ESAS
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- Lupinus albus L. pathogenesis-related proteins that show similarity to PR-10 proteinsPublication . Pinto, Paula; Ricardo, C. P. P.We describe a group of three acidic proteins, pathogenesis-related (PR)-p16.5a, PR-p16.5b, and PR-p16.5c, that accumulate in the leaves of Lupinus albus L. cv Rio Maior plants when infected with the fungus Colletotrichum gloeosporioides Penz. These proteins co-migrate in sodium dodecyl sulfate-polyacrylamide gels as a single band of 16.5 kD, behaving as charge isomers, and are related to several members of the defense-related PR-10 protein family. Localization of the proteins was investigated by techniques of tissue printing and immunogold electron microscopy; they are predominantly associated with the vascular system and are localized extra-cellularly. The accumulation of PR-p16.5a, PR-p16.5b, and PR-p16.5c also seems to be induced by cucumber mosaic virus and by two forms of abiotic stress, salicylic acid and ultraviolet, suggesting a general defense role for these proteins.
- Active center determination of ethylene polymerisation catalysts using a quenching method with tritiated methanolPublication . Justino, Jorge; Dias, A.R.; Tait, J.P.The subject of this work is ethylene polymerisation using Kaminsky type catalysts: Cp2MR2=methylaluminoxane [M=Zr,W,Nb; R=Cl,CH3]. Active center determination and kinetic studies of the (Cp2WCl2 + methylaluminoxane) and Cp2ZrCl2 + methylaluminoxane) systems are described, using a quenching method with tritiated methanol. The activity of the polymer was determined by liquid scintillation counting. We have found 0.5% and 87% of active centers, respectively for W and Zr system. The catalytic activity of complexes Cp2WCl2 and Cp2NbCl2 was compared with that of Cp2ZrCl2. The W and Nb complexes are found to be less active than the Zr complex.
- Neutron activation analysis of some biological environmental materialsPublication . Freitas, M. C.; Justino, Jorge; Grego, JoséSome biological candidate reference materials were recently or are now being certified for use in quality control of trace element analysis in environmental studies. In this work, the elemental concentration was determined by instrumental neutron activation analysis (INAA) for the materials lichen, poplar leaves, oak tree leaves, eucalyptus leaves and pine needles. As an application of pollution studies, samples of soil and strawberry plants treated with methylbromide as a disinfectant were analysed by INAA. The results evidence contamination with bromide; after several treatments the soil accumulates bromide giving rise to phytoxicity.
- Polymerization of ethylene using metallocene and aluminoxane systemsPublication . Justino, Jorge; Dias, A.R.; Ascenso, J.; Marques, M.M.; Tait, P.J.T.This paper describes ethylene polymerization using a number of metal-locene and aluminoxane catalyst systems, Cp2MR2 and methylaluminoxane [M = Zr, W, Nb; R = Cl, CH3]. Two types of methylaluminoxane, MAO (1) and MAO (2), were used as cocatalysts. The polymerization activities of the complexes Cp2WCl2 and Cp2NbCl2 were compared with that of Cp2ZrCl2. The Nb and W complexes were found to be less active than the Zr complex. Polyethylene characterization was also carried out by the following methods: gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR).
- Homogeneous Ziegler-Natta polymerisation: A kinetic approach .2. Transient-state kineticsPublication . Marques, M.M.; Dias, A.R.; Justino, Jorge; Costa, C.; Lemos, F.; Ribeiro, F.R.An integrated view is presented of several possible mechanisms applicable to the interpretation of homogeneous Ziegler-Natta polymerisation. In this paper, the transient aspects related to the kinetics of Ziegler-Natta polymerisation are investigated. Extensive data are used to construct kinetic profiles (rM vs. t) from a theoretical approach. Special attention is given to the duration of the transient period as a function of the different kinetic parameters. The kinetic models developed are fitted to experimental data, either directly obtained by the authors or published in the literature. These general models have a broad range of application.
- Study of low catalytic activity systems (Biscyclopentadienyl complexes-aluminoxane) on olefin polymerizationPublication . Justino, Jorge; Marques, M.M.; Correia, S.; Dias, A.R.; Lemos, F.; Ribeiro, F.R.Olefin polymerization using low activity catalyst systems: Cp2WCl2-methylaluminoxane, [Cp2Mo(CH3)2][PF6]-methylaluminoxane and Cp2Mo(CH3)2-methylaluminoxane, is described. All these catalyst systems were studied in ethylene and propylene polymerization; however, they only showed catalytic activity for ethylene. Only one type of methylaluminoxane (MAO) was used, prepared in an Al/H2O ratio of 2. The kinetics of polymerization were examined and the experimental data (either presented here or in previous papers) were fitted to the kinetic models developed previously and now extended to account for the methylaluminoxane effect.
- A kinetic approach to homogeneous Ziegler type polymerization. Transient statePublication . Marques, M.M.; Costa, C.; Justino, Jorge; Lemos, F.; Ribeiro, F.R.; Dias, A.R.In this paper we present a kinetic approach to the analysis of transient-state homogeneous Ziegler-Natta polymerization activity data. The main features of the experimental data are discussed and fitted to transient kinetic models.
- Aquatic plants in the rice fields of the Tagus Valley, PortugalPublication . Vasconcelos, T.; Tavares, M.; Gaspar, NatáliaIn 1997, in 50 surveys of irrigated rice fields (Oryza sativa L.), 47 species of vascular plants were recorded in 19 families. Most of the species belonged to the Gramineae and Cyperaceae families. Seven species of algae were found, mostly Hydrodictyon reticulatum (42%) and Chara vulgaris (38%). Echinochloa crus-galli and Paspalum paspalodes showed a relative frequency of 98% and 82%, respectively. An interpretation of the major factors is presented influencing weed distribution. Amongst the weeds recorded, 13 were alien species. For these alien species the probable date of introduction into Portugal and into rice fields was determined. The recently introduced neophytes Heteranthera limosa and Heteranthera reniformis and the increasing presence of red rice (Oryza sativa), represent a potential danger to rice culture.
- Alicyclobacillus acidoterrestris spores in fruit products and design of pasteurization processesPublication . Silva, Filipa V.M.; Gibbs, P.Alicyclobacillus acidoterrestris is a thermoacidophilic, nonpathogenic and sporeforming bacterium which has been found in commercial pasteurized fruit juices in the past. Only few and recent studies were available in the literature, since only in 1984 Cerny et al. [Cerny, G., Hennlich, W., & Poralla, K. (1984). Fruchtsaftverderb durch bacillen: isolierung und charakterisierung des verderbserregers. Z. Lebensmitt. Unters. Forsch. 179, 224-227] reported a spoiled aseptically packaged apple juice with A. acidoterrestris and in 1987 Deinhard et al. [Deinhard, G., Blanz, P., Poralla, K., & Altan, E. (1987). Bacillus acidoterrestris sp. nov., a new thermotolerant acidophile isolated from different soils. Systematic and Applied Microbiology, 10, 47-53] named first this species. Detection and identification methods for A. acidoterrestris were reviewed and data regarding heat resistance of spores and growth in fruits were collected. Finally, a new methodology to design pasteurization processes for high acidic fruit products is presented.
- Corpus Linguistics in the teaching of ESP and literary studiesPublication . Oliveira, Maria José P.