Experimental results of thermally controlled superconducting switches for high frequency operation

As part of a study to develop thermally controlled switches for use in superconducting rectifiers operating at a few hertz and 1 kA, a theoretical model is presented of the thermal behavior of such a switch. The calculations are compared with experimental results of several switches having recovery times between 40 and 200 ms. A discussion is given of the maximum temperature T/sub N/ that occurs in the normal regions when the switch is in the resistive state. Once T/sub N/ is known, it is possible to predict the recovery time, activation energy, stationary dissipation and minimum propagation current. The calculated and measured results, in good agreement, show that T/sub N/ is approximately 12 K and largely independent of the thickness or material of the insulation layer. Mention is made of some problems, related to the room-temperature equipment which drives the rectifier, that so far have prevented the rectifiers from being used at their design specifications

On the size and shape of excluded volume polymers confined between parallel plates

A number of recent experiments have provided detailed observations of the configurations of long DNA strands under nano-to-micrometer sized confinement. We therefore revisit the problem of an excluded volume polymer chain confined between two parallel plates with varying plate separation. We show that the non-monotonic behavior of the overall size of the chain as a function of plate-separation, seen in computer simulations and reproduced by earlier theories, can already be predicted on the basis of scaling arguments. However, the behavior of the size in a plane parallel to the plates, a quantity observed in recent experiments, is predicted to be monotonic, in contrast to the experimental findings. We analyze this problem in depth with a mean-field approach that maps the confined polymer onto an anisotropic Gaussian chain, which allows the size of the polymer to be determined separately in the confined and unconfined directions. The theory allows the analytical construction of a smooth cross-over between the small plate-separation de Gennes regime and the large plate-separation Flory regime. The results show good agreement with Langevin dynamics simulations, and confirm the scaling predictions.Comment: 15 pages, 3 figure

Dual tasking under compromised visual and somatosensory input in elderly fallers and non-fallers

Background: Performance of additional tasks disturbs postural control in elderly. It is unknown, however, how postural control is affected in elderly fallers and non-fallers in a reduced sensory situation. Objective: To compare differences between single and dual tasking in three test conditions; (1) no-vision, (2) under reduced somatosensory information and (3) with a combination of both conditions. Design: An observational cohort study with participants assigned to a 12-month pretest fall assessment and a postural balance assessment. Methods: Fifteen independently living elderly participated (77.5 ± 7.0 [63-87] years). Falls were pre-assessed with a 1- year monthy “fall calendar”. Postural control was analyzed by means of a force platform. Participants were standing quiet (first task) while counting backwards (second task). A 2-factor (group x condition) ANOVA was performed at p<.05. Differences of postural (DTCp) and cognitive dual task costs (DTCc) between test conditions were analyzed (one-way ANOVA). Results: The analysis showed significant group (fallers/non-fallers) and condition effects. Post hoc analyses indicated that the postural control variables were significantly different during the concurrent reduced vision and somatosensory information. Dual task costs showed a significant difference between normal (N) and the combined condition (NV+RP) in non-fallers. Conclusion: The combination of reduced visual and somatosensory information causes a larger disturbance of postural stability compared with the reduction of visual or somatosensory information alone. Non-fallers seem to have no threats to the postural control stability in this combined reduced sensory situation. They reduce their postural control, which leaves them enough resources to compensate for the reduced sensory information

How robust is the language architecture? The case of mood

In neurocognitive research on language, the processing principles of the system at hand are usually assumed to be relatively invariant. However, research on attention, memory, decision-making, and social judgment has shown that mood can substantially modulate how the brain processes information. For example, in a bad mood, people typically have a narrower focus of attention and rely less on heuristics. In the face of such pervasive mood effects elsewhere in the brain, it seems unlikely that language processing would remain untouched. In an EEG experiment, we manipulated the mood of participants just before they read texts that confirmed or disconfirmed verb-based expectations about who would be talked about next (e.g., that “David praised Linda because … ” would continue about Linda, not David), or that respected or violated a syntactic agreement rule (e.g., “The boys turns”). ERPs showed that mood had little effect on syntactic parsing, but did substantially affect referential anticipation: whereas readers anticipated information about a specific person when they were in a good mood, a bad mood completely abolished such anticipation. A behavioral follow-up experiment suggested that a bad mood did not interfere with verb-based expectations per se, but prevented readers from using that information rapidly enough to predict upcoming reference on the fly, as the sentence unfolds. In all, our results reveal that background mood, a rather unobtrusive affective state, selectively changes a crucial aspect of real-time language processing. This observation fits well with other observed interactions between language processing and affect (emotions, preferences, attitudes, mood), and more generally testifies to the importance of studying “cold” cognitive functions in relation to “hot” aspects of the brain

Conversion of the prodrug etoposide phosphate to etoposide in gastric juice and bile.

Etoposide phosphate is a water-soluble prodrug of etoposide. It was expected that this prodrug could be used to overcome the solubility limitations and erratic bioavailability of oral etoposide. To investigate the possibility of prodrug conversion to etoposide within the gastrointestinal lumen, etoposide phosphate was dissolved in water and incubated with human gastric juice or human bile in vitro. Samples were collected during 150 min and analysed for etoposide concentration with high-performance liquid chromatography. Conversion of prodrug to etoposide during incubation with gastric juice was negligible. There was significant conversion during incubation with bile at pH 7-8. The percentage of prodrug converted to etoposide at pH 8 after 60 min was 78 +/- 18% (mean +/- S.D.) for a 0.1 mg ml-1 prodrug solution and 36 +/- 26% for 0.5 mg ml-1. At pH 7, after 60 min 22% of prodrug was converted to etoposide when incubated at 0.1 mg ml-1 and 10% at 0.5 mg ml-1. No conversion was found after inactivation of alkaline phosphate (AP) by overnight heating of bile at 65 degrees C or by the addition of disodium edetate to the bile. In conclusion, because of AP in bile, variable conversion of etoposide phosphate to etoposide can be expected within the intestinal lumen after oral administration. This could have important pharmacokinetic consequences