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Biomedical subjects

A V Lopes

Publications and source records attributed to A V Lopes.

2 recordsLinked to original sources

The ecological and taxonomic importance of flower volatiles of Clusia species (Guttiferae).

The chemical composition of floral volatiles of sixteen species of Clusia (Guttiferae) belonging to four different taxonomic sections of the genus was investigated. The volatiles were extracted from fresh petals by microhydrodistillation and analysed by GC/MS. The composition of the volatiles was in part, but not always, related to the taxonomic position of the species, and to a minor extent to the type of pollinator observed on the flowers as revealed by clustering analysis. The composition of the volatile components of female and male flowers belonging to the same species (C. grandiflora, C. lanceolata, C. paralicola, C. parviflora and C. spiritu-sanctensis) was found to be almost identical. Field bioassays showed the petal extracts to be attractive to pollinating bees.

Chromatography, Gas↗

Electrotactile stimulator for artificial proprioception.

With the goal of investigating artificial proprioception elicited by electrical stimulation, we have developed a tactile phi phenomenon-based stimulator. This two-channel microprocessed pulse amplitude modulation system generates two different envelope waveforms (triangular and elliptical) and allows programming and visualizing of its main parameters: pulse with (0.1-10 ms), pulse frequency (0.1-10 kHz), modulation frequency (0.3-10 Hz), current intensity (up to 20 mA), and the amplitude modulation index (0-100%). In vivo experiments with 5 normal persons have shown that it is possible to elicit a moving fused phantom image with good resolution. A triangular envelope is good for straight line sensations while the elliptical one is more comfortable and has better resolution for all kinds of moving images.

Biofeedback, Psychology↗