Biomedical subjects

P S Tsang

Publications and source records attributed to P S Tsang.

11 recordsLinked to original sources

PubMed1998

Age, attention, expertise, and time-sharing performance.

Time-sharing efficiency and resource allocation from a group of pilots with expertise in time-sharing and a group of nonpilots (ages 20-79 years) were examined. Participants performed 5 dual tasks that represented different degrees of structural similarity as characterized by the structure-specific resource model. Age, expertise, and structural similarity were found to interactively affect time-sharing performance through attentional resources. Age-related deficits in time-sharing were evident under conditions of intense attentional demands and when precise control was required. Modest expertise modulation of the age effects is likely to increase with more domain-specific time-sharing. The structure-specific resource model provided a useful framework for interpreting the relationship between aging and time-sharing performance.

Adult↗

PubMed1996

Viability of resource theories in explaining time-sharing performance.

The primary objective of the present research was to test for performance tradeoff induced by priority instructions with the purportedly unbiased optimum-maximum method. In experiment 1, performance tradeoff was observed when the tracking task was optimized but not when the Sternberg memory task was optimized. It was hypothesized that the tracking task was protected by peripheral vision when subjects focused on the optimized memory task. The second experiment tested the generality of the results with additional variations of the task pairs selected to represent different degrees of shared resources. The extent of performance tradeoff and time-sharing efficiency varied systematically with the extent of predicted resource overlap between the time-shared tasks. The observed performance tradeoff was strongly indicative of subjects' voluntary allocation control. Further, subjective ratings suggested that such control was effortful. These results were supportive of multiple resource theories and the viability of resource explanation of task interference.

Adolescent↗

PubMed1996

Diagnosticity and multidimensional subjective workload ratings.

A new multidimensional subjective workload assessment instrument -- Workload Profile -- was introduced and evaluated against two unidimensional instruments -- Bedford and Psychophysical scaling. Subjects performed two laboratory tasks separately (single task) and simultaneously (dual task). The multidimensional procedure compared well with the unidimensional procedures in terms of sensitivity to task demands, concurrent validity with performance, and test-retest reliability. The results suggested that the subjective workload profiles would only have limited predictive value on performance. However, results of the canonical analysis demonstrated that the multidimensional ratings provided diagnostic information on the nature of task demands. Further, the diagnostic information was consistent with the a priori task characterization. This strongly supports the notion that mental workload is multidimensional and that subjects are capable of reporting the demands on separate workload dimensions. Theoretical implications on mental workload models and practical implications on the assessment approaches are discussed.

Adult↗

PubMed1996

Boundaries of cognitive performance as a function of age and flight experience.

Age and expertise effects on time-sharing performance were examined. Pilots were considered to have an expertise in time-sharing because of their cockpit experience. Ninety pilots and nonpilots performed a battery of cognitive tasks that represented different aspects of piloting. The results revealed that time-sharing performance was age sensitive. However, expertise appeared to have some moderating influence on the age effects. Further, analysis of the overlap of the response distributions from different age groups suggested that age alone was not a definitive discriminator of an individual's time-sharing skill.

Adult↗

PubMed1995

Resource scarcity and outcome conflict in time-sharing performance.

The efficacy of the resource-scarcity and outcome-conflict views in explaining dual-task interference was examined. A discrete-continuous task pair was purposely chosen to allow fine-grained analysis of time-shared performance. The relative priority of the dual task was manipulated by a secondary task technique to test for performance tradeoff that would be indicative of resource allocation. The temporal predictability of the discrete stimuli was manipulated to examine possible strategic avoidance of interference. The moment-by-moment data did not reveal any evidence for a switching strategy. It was concluded that the intricate interference patterns could be more easily interpreted within the resource framework than within the outcome-conflict framework.

Adolescent↗

PubMed1989

Cognitive demands in automation.

As the nature of a task changes with increasing automation, so do the cognitive demands on the human operator. The present study examines the implications of such changes on subjective workload and automation design issues. A variety of tasks (continuous flight control, discrete target acquisition, and decision making) was used to tax the different cognitive systems. Each task could be performed alone or in combination with other tasks. Performance and subjective workload ratings, obtained by three workload scales, were examined as a function of the level of automation. Results demonstrated the usefulness of the multiple resource approach to task analysis. All three workload scales were found to be sensitive to the task demands. The Bedford scale was particularly impressive in distinguishing the different types of resources in demand. Both the multiple resource model's performance predictions and the subjective workload ratings were shown to be invaluable for decisions on how and what to automate.

Adolescent↗

PubMed1989

The visually guided control of simulated altitude.

Simulated "flights" over three different ground textures were used to examine people's ability to extract optical information useful for active regulation of altitude. The textures were regularly spaced lines as follows: 1) orthogonal to the direction of flight (latitude texture); 2) parallel to the direction of flight (meridian texture); and 3) both parallel and orthogonal (square texture). Visual constant velocity forward flight simulations were displayed on a CRT screen, and subjects asked to maintain one of three initial altitudes using a rate control stick. This task was made difficult by the presence of lateral (irrelevant) and vertical (relevant) "wind gusts." The attitude never varied as winds, forward speed, and vertical rate control resulted in only translational movements. Adjusted root mean square errors (ARMSE) showed altitude regulation was more difficult at higher altitudes and when flying over meridian textures. Refined analysis of a single subject's data showed that this was due both to poorer regulation of the vertical wind disturbance and to a tendency to confuse the lateral wind disturbance for a vertical disturbance.

Adolescent↗

PubMed1987

A monoclonal antibody directed against a serotype-specific, outer-membrane protein of Haemophilus influenzae type b.

Monoclonal antibodies (Mabs) were produced against outer-membrane proteins (OMPs) of Haemophilus influenzae type b. The clones were screened by ELISA with outer-membrane preparations of H. influenzae type b and untypable strains as coating antigens. Antibodies directed against the proteins of mol. wt (10(3)) 43, 37 and 13 were identified by immunoblotting of SDS-PAGE patterns of OMPs. Proteolytic enzyme treatments of the OMPs resulted in reduction of Mab reactivity as measured by ELISA. Furthermore, the absence of reactivity of Mab Hb-2 with a preparation of lipopolysaccharide confirmed the protein nature of its corresponding epitope. Binding assays with live bacteria showed that Hb-2 reacted with a cell surface-exposed antigenic determinant. Mab Hb-2 was bactericidal in vitro in the presence of complement. The characterisation of Hb-2 (IgG2a) by Western immunoblotting analysis revealed that it was directed against the 37 X 10(3)-mol. wt OMP. In a dot-enzyme immunoassay, Hb-2 reacted specifically with 326 strains of H. influenzae type b. It did not cross-react with the other serotypes or untypable strains of H. influenzae or with other bacterial species. This is the first report of a monoclonal antibody identifying a serotype-specific surface-exposed OMP of H. influenzae type b.

Antibodies, Monoclonal↗

PubMed1986

High yield monoclonal antibody production in ascites.

BALB/c males were mated with Swiss Webster/HPB females to produce a first generation cross. Hybridoma cells derived from fusing SP2/0 myeloma cells and histocompatible spleen cells were injected intraperitoneally into these mice to induce formation of ascites tumors and production of ascitic fluid containing large quantities of monoclonal antibody. Mice, 80 days old weighing between 28 g to 35 g, were treated with 0.5 ml of pristane 18 days before inoculation of 3.2 X 10(6) hybridoma cells. The first generation crosses, (BALB/c male X SW/HPB female)F1, produced up to 4 times more ascitic fluid of equally high antibody level over a longer period compared to the BALB/c parent. This first generation cross is a cost effective means for monoclonal antibody production.

Animals↗

PubMed1986

Can pilots time-share better than non-pilots?

Time-sharing performance of a group of pilots was compared with that of a group of college students. In a secondary task paradigm, both groups were required to perform five dual tasks with various degrees of structural similarity. A higher degree of task interference was observed for the structurally more similar task pairs. The data were consistent with the results from previous research and support the concept of multiple resources. Although the pilots appeared to be more efficient in one of the dual task conditions, evidence for a general difference in time-sharing ability between the students and the pilots was not compelling. It was concluded that the degree to which time-sharing performance is structure dependent is not easily alterable by training. The results suggested that laboratory findings on the structural determinants of time-sharing efficiency are generalisable to operational environments.

Journal Article↗

PubMed1986

Mouse models of infection for Neisseria meningitidis B,2b and Haemophilus influenzae type b diseases.

A disseminated and fatal infection was established in C57BL mice, injected intraperitoneally with either Neisseria meningitidis B,2b or Haemophilus influenzae type b bacteria plus enhancement factors. The effects of mucin, hemoglobin, and iron dextran as enhancement of bacterial infectivity in mice were evaluated individually and in combination. A mixture of mucin and hemoglobin was most effective in enhancing the virulence of the pathogens. Inbred mouse lines were more susceptible than outbred ones. Relative virulence of a number of bacterial strains was also compared in one selected mouse line. Neisseria meningitidis B,2b and Haemophilus influenzae type b strains were more virulent than non-B,2b and nontypable strains. Finally, the course of bacteremia for the two infections in mice was followed by quantitative blood cultures. The animals succumbed to the generalized condition within 72 h. In the case of Neisseria meningitidis B,2b, 10 organisms with 4% mucin and 1.6% hemoglobin were sufficient to kill 50% of the animals. For Haemophilus influenzae type b, 300 bacteria with 5% mucin and 2% hemoglobin were necessary to obtain similar effects.

Animals↗