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Biomedical subjects

E J Arthur

Publications and source records attributed to E J Arthur.

7 recordsLinked to original sources
PubMed1997

The perception of spatial layout in real and virtual worlds.

As human-machine interfaces grow more immersive and graphically-oriented, virtual environment systems become more prominent as the medium for human-machine communication. Often, virtual environments (VE) are built to provide exact metrical representations of existing or proposed physical spaces. However, it is not known how individuals develop representational models of these spaces in which they are immersed and how those models may be distorted with respect to both the virtual and real-world equivalents. To evaluate the process of model development, the present experiment examined participant's ability to reproduce a complex spatial layout of objects having experienced them previously under different viewing conditions. The layout consisted of nine common objects arranged on a flat plane. These objects could be viewed in a free binocular virtual condition, a free binocular real-world condition, and in a static monocular view of the real world. The first two allowed active exploration of the environment while the latter condition allowed the participant only a passive opportunity to observe from a single viewpoint. Viewing conditions were a between-subject variable with 10 participants randomly assigned to each condition. Performance was assessed using mapping accuracy and triadic comparisons of relative inter-object distances. Mapping results showed a significant effect of viewing condition where, interestingly, the static monocular condition was superior to both the active virtual and real binocular conditions. Results for the triadic comparisons showed a significant interaction for gender by viewing condition in which males were more accurate than females. These results suggest that the situation model resulting from interaction with a virtual environment was indistinguishable from interaction with real objects at least within the constraints of the present procedure.

Adult↗
PubMed1995

Performance, workload, and fatigue changes associated with automation.

The experiments discussed in this article addressed the influence of part-task automation on operator performance, workload, and fatigue in a multitask environment. The overall task environment included tracking, resource management, and multiple monitoring subtasks. Slower, more accurate monitoring and better resource management were observed when the tracking subtask was automated. Although lower workload was reported when tracking was automated, fatigue increased equally during periods of manual and automatic tracking. When participants could control workload by shifting between manual and automatic tracking, participants with 7 hr of training switched between automatic and manual tracking. Their performance during optional automation periods was superior to their performance in conditions in which only manual control or only automated control was available. The findings argue for the utility of discretionary control of automated systems.

Adult↗
PubMed1994

The effects of sex, target duration, and illumination on the production of time intervals.

An experiment is reported which examined the effects of illumination, sex, and the duration of target intervals on the perception of time. Six male and six female participants made repeated estimates of one, three, seven, and twenty seconds each, using the production technique. There were sixty trials per duration, half of which were performed with the lights on and half with the lights off. Order of administration of lighting condition and duration of target time was randomized. For estimates expressed as ratios of target times, results indicated significant main effects for participant sex and duration of target time on mean time estimates. However, manipulation of lighting condition did not produce a significant main effect. For the variability of response, there was a significant interaction between sex and light condition such that women were less variable in lighted conditions. These findings are discussed in terms of previous equivocal evidence for the influence of participant sex on time perception and the modification of such an influence through change in experimental conditions.

Adult↗
PubMed1979

Endothelial cell morphology and corneal deturgescence.

In a series of 46 patients accepted for cataract removal and intraocular lens implantation, 23 showed visibly obvious variation in endothelial cell size (polymegethism) according to specular microscopic examination. In this group, mean increase in postoperative corneal thickness was 52.7% on the first postoperative day, 35.4% on the third, and 18.0% after 4 weeks. Mean corneal swelling was consistently and significantly less in the 23 patients exhibiting apparently normal endothelial cell patterns (homomegethism). In homomegethous corneas, preoperative cell density was significantly correlated with age (inversely) and postoperative cell loss (directly). Preoperative cell density in polymegethous corneas showed significant, direct correlation with age, suggesting that endothelial cell density may remain relatively constant in this condition. There was no correlation with postoperative cell loss. Significant differences in endothelial functional capability identified within each morphologically-defined group indicate a structure-function continuum. Since 15 homomegethous corneas and only one polymegethous cornea returned to preoperative thickness within 4 weeks, it appears clinically valid to use morphological criteria in predicting functional capability.

Age Factors↗
PubMed1978

The functional reserve of corneal endothelium.

With recent advances in our knowledge of corneal physiology, coupled with the development and increasing availability of the specular microscope as a clinical instrument, valid observations relating the morphologic appearance of the corneal endothelium to its functional capacity are within our reach. Manual methods of data analysis are cumbersome, time consuming, and associated with human error and investigator bias. The Omnicon pattern analysis system lends itself to objective analysis of morphologic features, offers the possibility of quantifying the data obtained and, hopefully, will lead to a better understanding of the many aspects of endothelial cell morphology which, in total, relate to the functional reserve of a given cornea.

Cell Count↗