Browsing by Issue Date, starting with "2001-09"
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- Isolation, characterization and quantification of microcystins (heptapeptides hepatotoxins) in Microcystis aeruginosa dominated bloom of Lalla Takerkoust lake–reservoir (Morocco)Publication . Martins, RosarioThis paper presents the first data on the identification, characterization and quantification of microcystins isolated from both an extract of a cyanobacteria natural bloom, collected from a eutrophic Moroccan reservoir (Lalla Takerkoust, Marrakesh) and an isolated strain cultivated under laboratory conditions. The isolation and purification of toxins was performed by reverse phase HPLC and then characterized by amino acid analysis and fast atom bombardment mass spectrometry (FAB-MS). Chemical characterization of the toxins from the bloom revealed variants of microcystins such as Mcyst-LR, Mcyst-RR, Mcyst-YR and [D-Asp3]Mcyst-LR. However, the Microcystis aeruginosa strain produced only Mcyst-RR. Using an ELISA assay the total microcystin contents of eight bloom samples collected from 1994 to 1997 ranged from 0.7 to 8.8 μg/mg of lyophilized material. The two isolated Microcystis strains contained higher amounts of microcystins (0.65 μg/ mg of dry weight) than the Pseudanabaena strains (0.021 μg/mg of dry weight). Our results show that the presence of cyanobacteria toxins in water used for drinking in a North African country may be regarded as an health hazard. These results are a contribution to the knowledge of the biogeography of toxic cyanobacteria and their toxins, namely in north African countries.
- Fourier analysis of multi-legged periodic gaitsPublication . Rodrigues, Carlos M. B.; Tenreiro Machado, J. A.This paper analyses periodic gaits of multi-legged locomotion systems. The joint signals are studied in the Fourier domian, namely from the point of view of its reproducibility through low-pass actuators. The influence of several parameters is also considered and their critical values are investigated.
- Research issues in intelligent transportation systemsPublication . Figueiredo, Lino; Jesus, Isabel S.; Tenreiro Machado, J. A.; Ferreira, José Rui; Carvalho, J. L. Martins deThis paper presents a review of the state of the art on intelligent transportation systems. ITS involves a large number od research areas and, therefore, this paper focus on those we belive to be the most relevant. The main purpose is to study the achievements attained in the last years and to give an overview of possible directions towards future research.
- Towards emerging intelligent transportation systems technologiesPublication . Figueiredo, Lino; Jesus, Isabel S.; Tenreiro Machado, J. A.; Ferreira, José Rui; Carvalho, J. L. Martins deThis paper presents a review of the state of the art on Intelligent Transportation Sytems. ITS involves a large number of research areas and, therefore, this paper focus on those we believe to be the most relevant. The main purpose is to study the achievements attained in the last years and to give an overview of possible directions towards future research.
- Fractional-order dynamics in the trajectory control of redundant manipulatorsPublication . Duarte, Fernando B. M.; Tenreiro Machado, J. A.Redundant manipulators have som advantages when compared with classical arms because they allow the trajectory optimization, both on the free space and the presence of obstacles, and the resolution of singularities. For this type of arms the proposed kinematic control algorithms adopt generalized inverse matrices but, in general, the corresponding trajectory planning schemes show important limitations. Motivated by these problems this paper studies the chaos revelead by the pseudoinverse-based trajectroy planning algorithms, using the theory of fractional claculus.