PubMed · 10291435
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J Haskin, L Marx. Nursing QA: Step V--The problem focused study.. https://doi.org/10.1111/j.1945-1474.1988.tb00358.x
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A two-stage model of sustained neural activity in the prefrontal cortex is proposed in order to simulate feature binding and capacity limits in visual working memory. In the first stage, object features are stored in parallel network layers without explicit conjunctions. A second stage binds features into integrated objects consistent with the recent proposal of Wheeler and Treisman (J. Exp. Psychol. Gen. 131 (2002) 48). Model neurons have extended dendrites which are capable of active non-linear integration. Computer simulation illustrates model ability to segregate feature values of the different objects into cells with different activity amplitude and to maintain segregated feature representations for a limited number of objects. Depending on the task demands, features are retrieved in a second stage and form a unified object representation.
Optical tomography of turbid media has so far been limited by systems that require fixed geometries or measurements employing fibers. We present a system that records noncontact optical measurements from diffuse media of arbitrary shapes and retrieves the three-dimensional surface information of the diffuse medium. We further present a novel method of combining this composite data set and obtain accurate fluorescence reconstructions. This approach offers significant experimental simplicity and yields high-information-content datasets. The performance of this novel tomographic approach is demonstrated with experimental reconstructions of phantoms.
We describe a technique that uses Doppler optical coherence tomography to estimate accurately the scattering fluid-flow velocity without a priori knowledge of the Doppler angle. Our technique is based on the combined use of the Doppler shift on the interference signal and the Doppler spectrum broadening caused by the particles moving across the probe beam. It is shown that the estimated values of the Doppler angle and average fluid velocity from the experiments agree well with the preset values.