Browsing by Issue Date, starting with "1993"
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- An efficient parallel implementation of a least squares problemPublication . Ruano, Antonio; Fleming, P. J.; Jones, D. I.Least squares solutions are a very important problem, which appear in a broad range of disciplines (for instance, control systems, statistics, signal processing). Our interest in this kind of problems lies in their use of training neural network controllers.
- A música, a dança e o traje tradicionais: práticas significantes no concelho de LouléPublication . Raimundo, Helder Faustino; Vieira, DanielA recolha e investigação etnográfica que desenvolvemos há cerca de 11 anos, no Algarve e nomeadamente no concelho de Loulé, prova-nos a existência de um conjunto de práticas significantes, ligadas a ciclos de vida rurais e arcaizantes.
- Fish ultrasonography characterization of cardiac morphology and blood flowPublication . Coucelo, Josefina; Joaquim, N.; Aníbal, J.; Coucelo, JosefinaNon invasive identification and characterization of cardiac morphology and flow of Lophius s.p. and Halobactrachius s.p. was performed using color echo doppler. We used an ALOKA echo camera SSD 830 with a 5 MHZ transducer. Fishes were kept alive with water circulation device. The transducer was applied in the ventral middle line over heart chambers. Bidimensional images were obtained from long and short axis incidences at various levels of cardiac chambers. During each cardiac cycle and for every specimen it was possible to identify the relationship between each structure, measure longitudinal and transversal diameters, identify blood ?uxes and quantify their velocities. Conclusion: In live specimens it is possible, applying non invasive techniques, to observe the cardiac structures and to study the kinetic of the ventricle and bulbus, to identify blood ?ow and to measure his velocity. This can be used as an experimental model for cardiac function.
- Utilización de reservas en fructificación en el mandarino "Fortune". Influencia de las técnicas de cuajadoPublication . Duarte, Amílcar; Guardiola, J. L.The utilization of reserves in fruiting in the "Fortune" mandarin. The influence of fruit set techniques.The effects on fruit set of GA3, BA, and NAA applications, and that of girdling, has been determined in relation to the mobilization of the reserves during flowring and June drop.Under the conditions of this experiment, performed with high flowering trees, carbohydrate and nitrogen contents in the leaves during flowering and fruitlet abscision were lower than the content found in other cultivars. We could not establish a relationship between metabolite availability and fruit set. Girdling was the only effective fruit set treatment. It had no effect on the carbohydrate and the total nitrogen contents in the leaves, and reduced the amino nitrogen content.
- Osmostress response of the yeast SaccharomycesPublication . Mager, Peter; Varela, J.Exposure of yeast cells to high osmolarities leads to dehydration, collapse of ion gradients over the plasma membrane and decrease in cell viability. The response of yeast cells to high external osmolarities is designated osmostress response. It is likely that both osmoregulatory and general stress reactions are involved in this so far poorly understood process. Part of the response aims at raising the internal osmotic potential, i.e. the production of osmolytes such as glycerol, and exclusion of toxic solutes. In addition, heat-shock proteins and trehalose are synthesized, probably to protect cellular components and to facilitate repair and recovery. Recent analyses of osmosensitive yeast mutants strongly suggest the involvement of protein kinase-mediated signal-transduction pathways in the maintenance of the osmotic integrity of the cell. This has stimulated interesting hypotheses as to the actual osmosensing mechanism.
- Charge transport in poly(3-methylthiophene) schottky barrier diodesPublication . Gomes, Henrique L.; Taylor, D. M.; Underhill, A. E.Schottky-barrier devices were formed from electropolymerised films of poly (3-methylthiophene) (PMeT). Thermal annealing of a partially undoped film led to diodes with rectification ratios as high as 5900 at 1 V and 50,000 at 2.5 V and ideality factors slightly above 2. The temperature dependence of ac loss tangent and forward currents are identical suggesting that bulk effects dominate device behaviour event at very low forward voltages. Below 250 K forward currents are essentially independent of temperature. Preliminary TSC measurements show the presence of at least two trapping levels in the devices. © 1993.
- Deep-water macroalgae from the Canary Islands: new records and biogeographical relationshipsPublication . Haroun, R. J.; Prud'homme van Reine, W. F.; Müller, D. G.; Serrão, Ester; Herrera, R.Due to the geographical location and paleobiogeography of the Canary Islands, the seaweed flora contains macroalgae with different distributional patterns. In this contribution, the biogeographical relations of several new records of deep-water macroalgae recently collected around the Canarian archipelago are discussed. These are Bryopsidella neglecta (Berthotd) Rietema,Discosporangium mesarthrocarpum (Meneghini) Hauck, Hincksia onslowensis (Amsler et Kapraun)P.C. Silva, Syringoderma floridana Henry, Peyssonnelia harveyana J. Agardh, Cryptonemia seminervis(C. Agardh) J. Agardh, Botryodadia wynnei Ballantine, Gloiocladia blomquistii (Searles) R. E.Norris, PIahchrysis peltata (W. R. Taylor) P. Huv4 et H. Huv4, Leptofauchea brasiliensis Joly, and Sarcodiotheca divaricata W. R. Taylor. These new records, especially those in the Florideophyceae,support the strong affinity of the Canary Islands seaweed flora with the warm-temperate Mediterranean-Atlantic region. Some species are recorded for the first time from the east coast of the Atlantic Ocean, enhancing the biogeographic relations of the Canarian marine flora with that of the western Atlantic regions.
- Turnover rate of metallothionein and cadmium in Mytilus edulisPublication . Bebianno, Maria João; Langston, W. J.The results demonstrate the first attempt to determine metallothionein turnover in the whole soft tissues of mussels Mytilus edulis exposed to cadmium. Half-lives for metallothionein and cadmium are 25 and 300 days, respectively. As metallothionein degrades the released cadmium induces further synthesis of the protein, to which the metal becomes resequestered. The slow metallothionein turnover rates (compared with mammals) and the lack of significant cadmium excretion testify to the relatively stable nature of the cadmium-metallothionein complex in these invertebrates and supports the view of a detoxifying role for metallothionein in the mussels.
- Quantitative study of the effects of the European Community enlargement on the processed tomatoes market: particular reference to the case of the Portuguese sectorPublication . de Noronha, Maria Teresa; Alvensleben, R. von; Soares, F. BritoIt is well known that the enlargemenl of European Community by the integration of Portugal and Spain raised concerns not only with respect to the impact that an extended Common Agricultural Policy (CAP) had on international markets of different commodities but also on the fact that the European Market achieves surpluses in certain commodities whose production has a strong financial support from the CAP.
- Reaction of pyrroles with ethyl 2-nitroso- and 2-azo-propenoates, and with ethyl cyanoformate N-oxide: a comparison of the reaction pathwaysPublication . Gilchrist, Thomas L.; Lemos, A.The reaction of ethyl 2-nitrosopropenoate 2a with 1 -methylpyrrole, 2.5-dimethylpyrrole and 2.5- diphenylpyrrole has been investigated. In every case the products result from highly regioselective attack at C-2 of the pyrrole by the electrophile. The azopropenoate esters 2b and 2c react similarly with pyrroles, to the extent that even 1 -(triisopropylsilyl)pyrrole is attacked exclusively at the 2-position by the azo ester 2b. In contrast, the nitrile oxide ethyl cyanoformate N-oxide 12 reacts at the 3-position of 2.5- dimethyl- and of 2,5-diphenyl-pyrrole. The reactions of the nitroso and azo esters with pyrroles are interpreted as Diels-Alder cycloadditions with inverse electron demand.
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