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The aim of this study was to evaluate the possibility of the re-use of industrial orange wastes as organic soil fertilizer. The assay was performed with a lettuce variety widely produced and consumed in Portugal and, consequently, with great commercial interest. Lactuca sativa L. (osteolata variety) was cultivated in Mitcherlich pots containing samples of a poor soil of the Algarve region. This soil was prepared with different amounts of either pulp or peel orange-wastes from an orange-juice industry. The wastes were applied according to an increasing amount of nitrogen. The results obtained were submitted to statistical tests, in order to find the relations between the production of fresh and dry matter, and the percentages of nutrients (nitrogen, phosphorous, potassium, calcium, magnesium and iron) that were obtained in the dry matter, with the types and amounts of wastes applied. An increase in the average production of both fresh- and dry-matter with increasing amounts of either pulp or peel wastes applied, and high positive correlation coefficients between the average percentages of nitrogen, phosphorus and potassium obtained in the dry matter with the average production of both fresh- and dry-matter were found. No phytotoxicity was observed.

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In this paper we present results concerning the influence of laser energy and shot density on the electrical resistance, X-ray diffraction pattern, and structure obtained by SEM, on recrystallized a-Si:H thin films produced by using a Nd-YAG laser, working in a wavelength of 532 nm. The base material (undoped and doped a-Si:H) was obtained by Plasma Enhanced Chemical Vapour Deposition (PECVD). The structure and electrical characteristics of the recrystallized thin films are dependent on the laser beam energy density, beam spot size and the number of shots applied to the base a-Si:H thin film used. Overall, the data show recrystallized material with grain sizes larger than 1μm, where the electrical resistance of both, undoped and doped materials, can be varied up to 5 orders of magnitude, by the proper choice of the recrystallization conditions.

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Flavodoxin was isolated and purified from Desulfovibrio desulfuricans ATCC 27774, a sulfatereducing organism that can also utilize nitrate as an alternative electron acceptor. Mid-point oxidation-reduction potentials of this flavodoxin were determined by ultraviolet/visible and EPR methods coupled to potentiometric measurements and their pH dependence studied in detail. The redox potential E(2), for the couple oxidized/semiquinone forms at pH 6.7 and 25 degrees C is -40 mV, while the value for the semiquinone/hydroquinone forms (E(1)), at the same pH, -387 mV. E(2) varies linearly with pH, while E(1) is independent of pH at high values. However, at low pH (<7.0), this value is less negative, compatible with a redox-linked protonation of the flavodoxin hydroquinone. A comparative study is presented for Desulfovibrio salexigens NCIB 8403 flavodoxin {[}Moura, I., Moura, J. J. G., Bruschi, M. and LeGall, J. (1980) Biochim. Biophys. Acta 591, 1-8]. The complete primary amino acid sequence was obtained by automated Edman degradation from peptides obtained by chemical and enzymic procedures. The amino acid sequence was confirmed by FAB/MS. Using the previously determined tridimensional structure of Desulfovibrio vulgaris flavodoxin as a model {[}similarity, 48,6%; Watenpaugh, K. D., Sieker, L. C., Jensen, L. H., LeGall, J. and Dubourdieu M. (1972) Proc. Natl Acad. Sci. USA 69, 3185-3188], the tridimensional structure of D. desulfuricans ATCC 27774 flavodoxin was predicted using AMBER force-field calculations.

A forest cover of a graph is a spanning forest for which each component has at least two nodes. If K is a subset of nodes, a K-forest cover is a forest cover including exactly one node from K in each component. We show that the weighted two matroid intersection algorithm determines the maximum cost K-forest cover.

Desulfoferrodoxin, a non-heme iron protein, was purified previously from extracts of Desulfovibrio desulfuricans (ATCC 27774) (Moura, I., Tavares, P., Moura, J. J. G., Ravi, N., Huynh, B. H., Liu, M.-Y., and LeGall, J. (1990) J. Biol. Chem. 265, 21596-21602). The as-isolated protein displays a pink color (pink form) and contains two mononuclear iron sites in different oxidation states: a ferric site (center I) with a distorted tetrahedral sulfur coordination similar to that found in desulforedoxin from Desulfovibrio gigas and a ferrous site (center II) octahedrally coordinated with predominantly nitrogen/oxygen-containing ligands. A new form of desulfoferrodoxin which displays a gray color (gray form) has now been purified. Optical, electron paramagnetic resonance (EPR), and Mössbauer data of the gray desulfoferrodoxin indicate that both iron centers are in the high-spin ferric states. In addition to the EPR signals originating from center I at g = 7.7, 5.7, 4.1, and 1.8, the gray form of desulfoferrodoxin exhibits a signal at g = 4.3 and a shoulder at g = 9.6, indicating a high-spin ferric state with E/D approximately 1/3 for the oxidized center II. Redox titrations of the gray form of the protein monitored by optical spectroscopy indicate midpoint potentials of +4 +/- 10 and +240 +/- 10 mV for centers I and II, respectively. Mössbauer spectra of the gray form of the protein are consistent with the EPR finding that both centers are high-spin ferric and can be analyzed in terms of the EPR-determined spin Hamiltonian parameters. The Mössbauer parameters for both the ferric and ferrous forms of center II are indicative of a mononuclear high spin iron site with octahedral coordination and predominantly nitrogen/oxygen-containing ligands. Resonance Raman studies confirm the structural similarity of center I and the distorted tetrahedral FeS4 center in desulforedoxin and provide evidence for one or two cysteinyl-S ligands for center II. On the basis of the resonance Raman results, the 635 nm absorption band that is responsible for the gray color of the oxidized protein is assigned to a cysteinyl-S–>Fe(III) charge transfer transition localized on center II. The novel properties and possible function of center II are discussed in relation to those of mononuclear iron centers in other enzymes.

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A evolução do hardware dos computadores para arquitecturas paralelas, incentivou a concepção de novos modelos de programação e o desenvolvimento dos sistemas de suporte à execução correspondentes, de forma a conseguir uma melhor exploração do paralelismo. A linguagem de programação Prolog, pelas suas características declarativas e operacionais, tem vindo a ser objecto de estudo nesta área, através de adaptações da linguagem e/ou da sua máquina de inferência. Este trabalho incide sobre os aspectos de concepção e implementação de um modelo de um sistema de suporte à execução de programas em Prolog, em arquitecturas de múltiplos processadores, com unidades de memória fisicamente distribuídas. O modelo propõe extensões a um executor de Prolog convencional, de forma a disponibilizar funcionalidades que permitam o controlo do paralelismo e da distribuição. Estas funcionalidades podem ser utilizadas para a implementação de modelos de linguagens lógicas concorrentes de mais alto nível, ou então serem utilizadas directamente para a programação de sistemas distribuídos, em que múltiplos executores Prolog cooperam na resolução de um golo, comunicando com base em mensagens. Para avaliar a funcionalidade do modelo proposto, concebeu-se e implementou-se um sistema de distribuição de golos Prolog, que permite recorrer a diversas estratégias para composição sequencial e paralela de golos, escondendo os aspectos de gestão explícita dos recursos efectivos. A dissertação inclui uma discussão dos aspectos mais relevantes da realização do protótipo do modelo proposto sobre uma arquitectura baseada em Transputers.

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A compact cesium ion source with a Wien filter is described. This source has been developed in order to produce a pure beam of cesium ions for positive SIMS analysis. The ions are produced by a surface ionization ion emitter. The initial beam is about 99% pure and the remaining 1% is removed via the Wien filter. An asymmetric einzel lens at the end provides the focusing of the beam on the target. A short description of the source is presented as well as the measured final beam characteristics.

The present work studies the behaviour of bonded steel plates to reinforced concrete elements, which can be used in the strengthening of concrete structural elements. Metallic expansion bolts can be added.The objective of this dissertation is to investigate the behaviour to monotonic actions and particularly to cyclic loading of steel-epoxy-concrete connection with expansion bolts. This cyclic action is of particular interest due to the strong seismicity of the Portuguese territory.The research is mainly based in experimental analysis. The caracterization of the materials was carried out. Six models of the steel-epoxy connection were tested with monotonic loading. Twenty six models of steel-epoxy-concrete bond were submitted either to monotonic or to cyclic actions.Besides the type of action, other parameters were studied in the steel-epoxy-concrete connection models.These were the bond geometry area, the type of concrete, the type of epoxy and connection - with or without metallic expansion bolts.A parametric study with a numerical model of finite elements, as well as a global analysis of the experimental tests of the steel-epoxy-concrete connection was carried out.

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