António R. Tavares

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There is a growing interest in wireless local area networks [1] that is a consequence of the large-scale utilization of personal computers and mobile communications. The portable personal computer integrates computational power and mobility in a single platform and introduces the need for accessing communication networks without the restrictions imposed by(More)
The performance of optical wireless transmission systems is mainly impaired by the shot noise induced by ambient light, interference produced by artificial light sources, transmitted optical power limitations due to high path losses and channel bandwidth limitations due to inter-symbol interference (ISI) produced by the multipath dispersion of the optical(More)
We propose and study the use of angle diversity to combat the ambient noise in indoor optical wireless communication systems. Models for the radiation pattern of spot lamps and for the spatial distribution of the ambient light based on an isotropic and a directional noise component are derived. Performance evaluation of receivers using angle diversity is(More)
Scorpion stings are a public health problem in the Brazilian Amazon. However, detailed clinical characterization with the proper animal identification is scarce. Here we report a confirmed case of envenoming by Tityus cf. silvestris in the Brazilian Amazon. The case evolved with generalized muscle spasms and was treated with antivenom and supportive(More)
A cross-sectional study was carried out on the residents of one in every four dwellings in the town of Barcelos (in the northern part of the State of Amazonas, on the right bank of the Rio Negro, 490 kilometers from Manaus by river), in order to evaluate social and sanitary conditions and specific indicators for intestinal parasites and Chagas' infection.(More)
The main degrading factor of infrared communication systems is the shot noise due to ambient light. Due to the directional nature of both signal and noise, the signal-to-noise ratio (SNR) at the receiver can vary significantly. In order to minimise these SNR fluctuation effects, this paper discusses some advanced techniques for the design of non-directed(More)
INTRODUCTION Snake bite, a problem in public health, generally occurs where there is no electric power. METHODS A comparative clinical study was conducted with 102 victims of Bothrops snake bite, from the state of Amazonas, Brazil; 58 victims were treated with liofilizated trivalent antivenom serum (SATL) and 44 victims treated with liquid bivalent and(More)