The authors describe ACT-R/perceptual-motor (ACT-R/PM), an integrated theory of cognition, perception, and action that consists of the ACT-R production system and a set of perceptual-motor modules. Each module (including cognition) is essentially serial, but modules run in parallel with one another. ACT-R/PM can model simple dual tasks such as the psychological refractory period (PRP), includin...

We give new examples of discrete Schrδdinger operators with potentials taking finitely many values that have purely singular continuous spectrum. If the hull X of the potential is strictly ergodic, then the existence of just one potential x in X for which the operator has no eigenvalues implies that there is a generic set in X for which the operator has purely singular continuous spectrum. A su...

Most studies using the psychological refractory period (PRP) design suggest that dual-task performance is limited by a central bottleneck. Because subjects are usually told to emphasize Task 1, however, the bottleneck might reflect a strategic choice rather than a structural limitation. To evaluate the possibility that central operations can proceed in parallel, albeit with capacity limitations...

This study sought to characterise the swabbing pattern in the Spanish Influenza Sentinel Surveillance System (SISSS) and ascertain to what extent the system meets the guidelines currently being drafted by The European Influenza Surveillance Scheme (EISS). Data on seasons 2002/2003 to 2005/2006 were drawn from SISSS. The study analysed collection and dispatch of swab specimens for virological an...

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background: umbilical cord tissue is a very rich source of mesenchymal stem cells. instead of discarding this source we are banking the tissue along with cord blood for possible future cell based applications. the cord tissue needs to be transported and stored properly in order for it to be good enough for cell isolation at a later date. in this paper we have carried out a validation study to d...