RESUMO
Near-infrared spectroscopy (NIRS) combined with indocyanine green (ICG) dilution is applied externally on the head to determine the cerebral hemodynamics of neurointensive care patients. We applied Monte Carlo simulation for the analysis of a number of problems associated with this method. First, the contamination of the optical density (OD) signal due to the extracerebral tissue was assessed. Second, the measured OD signal depends essentially on the relative blood content (with respect to its absorption) in the various transilluminated tissues. To take this into account, we weighted the calculated densities of the photon distribution under baseline conditions within the different tissues with the changes and aberration of the relative blood volumes that are typically observed under healthy and pathologic conditions. Third, in case of NIRS ICG dye dilution, an ICG bolus replaces part of the blood such that a transient change of absorption in the brain tissues occurs that can be recorded in the OD signal. Our results indicate that for an exchange fraction of Delta=30% of the relative blood volume within the intracerebral tissue, the OD signal is determined from 64 to 74% by the gray matter and between 8 to 16% by the white matter maximally for a distance of d=4.5 cm.
Assuntos
Encéfalo/irrigação sanguínea , Encéfalo/fisiologia , Circulação Cerebrovascular/fisiologia , Diagnóstico por Computador/métodos , Verde de Indocianina , Modelos Neurológicos , Espectrofotometria Infravermelho/métodos , Adulto , Algoritmos , Simulação por Computador , Humanos , Luz , Masculino , Método de Monte Carlo , Reprodutibilidade dos Testes , Espalhamento de Radiação , Sensibilidade e EspecificidadeRESUMO
We use neural networks with pointer map architectures to provide simple attentional processing in a robotic task. A pointer map comprises a map of neurons that encode a stimulus. Besides global feedback inhibition, the map receives feedback excitation via a small group of pointer neurons that encode the location of a salient stimulus on the map as a vectorial representation. The pointer neurons are able to apply selective processing to a particular region of the network. The robot uses these properties to manoeuver in relation to an attended object. We implemented a controller composed of two pointer maps, and a motor map. The first pointer map reports the direction of a salient obstacle in a one-dimensional map of distance derived from infrared sensors. The second pointer map reports the direction to potential obstacles in a two-dimensional edge-enhanced image derived from a forward looking CCD-camera. These outputs are applied to a motor map, where they bias the motor control signals issued to the robots wheels, according to navigational intentions.
Assuntos
Redes Neurais de Computação , Robótica/métodos , Comportamento Espacial , Percepção Visual , Aprendizagem da Esquiva , Retroalimentação , Locomoção , Neurônios Motores/fisiologia , Vias Neurais , Neurônios Aferentes/fisiologia , Orientação , Robótica/instrumentaçãoRESUMO
From February 1990 until late October 1991, M. xenopi was isolated from the sputa of 30 persons in one of the 4 boroughs of Ostrava. This species could also be identified in water samples and smears taken in 7 out of 14 tested households of both colonized persons and patients with mycobacteriosis xenopi. As established, the optimum conditions for multiplication of M. xenopi exist in exchanger units; control measures for this agent in the exchanger facilities are proposed.
