Designing for the home: a comparative study of support aids for central heating systems.

The study examined the influence of different types of enhanced system support on user performance during the management of a central heating system. A computer-based simulation of a central heating system, called CHESS V2.0, was used to model different interface options, providing different support facilities to the user (e.g., historical, predictive, and instructional displays). Seventy-five participants took part in the study and completed a series of operational scenarios under different support conditions. The simulation environment allowed the collection of performance measures (e.g., energy consumption), information sampling, and system control behaviour. Subjective user evaluations of various aspects of the system were also measured. The results showed performance gains for predictive displays whereas no such benefits were observed for the other display types. The data also revealed that status and predictive displays were valued most highly by users. The implications of the findings for designers of central heating systems are discussed.

Feedback quality and environmentally friendly use of domestic central heating systems.

The study examined the influence of system-embedded feedback on user behaviour during the environmentally friendly operation of a central heating system. A PC-based simulation, called CHESS, was developed to model the critical features of a central heating system. After having received 30 min of training on the simulation task, 60 participants worked on a series of operational scenarios under different levels of system feedback. In addition to the collection of various performance measures (e.g. energy consumption, energy wastage), a range of user variables was collected (e.g. environmental concern). As hypothesized, the results showed that increased feedback resulted in improved environmentally friendly performance and, more importantly, the specific feedback indicator influenced the type of strategy used to improve human - machine system performance. A major implication is that system designers need to develop feedback indicators that are chiefly influenced by user behaviour and are largely immune to factors that are beyond the user's control (e.g. weather conditions).

Effects of training on short- and long-term skill retention in a complex multiple-task environment.

The paper reports the results of an experiment on the performance and retention of a complex task. This was a computer-based simulation of the essential elements of a spacecraft's life support system. It allowed the authors to take a range of measures, including primary and secondary task performance, system intervention and information sampling strategies, mental model structure, and subjective operator state. The study compared the effectiveness of two methods of training, based on low level (procedure-based) and high level (system-based) understanding. Twenty-five participants were trained extensively on the task, then given a 1-h testing session. A second testing session was carried out 8 months after the first (with no intervening practice) with 17 of the original participants. While training had little effect on control performance, there were considerable effects on system management strategies, as well as in structure of operator's mental model. In the second testing session, the anticipated general performance decrement did not occur, though for complex faults there was an increase in selectivity towards the primary control task. The relevance of the findings for training and skill retention in real work environments is discussed in the context of a model of compensatory control.

A conceptual framework for designing micro-worlds for complex work domains: a case study of the Cabin Air Management System.

A conceptual framework for the design of micro-worlds is presented in this paper. This is illustrated by a micro-world, called Cabin Air Management System (CAMS), that has been used in a research program to investigate human behavior during work with complex systems. Although CAMS is based on the operational context of spaceflight, its underlying principles correspond to a process control task. The authors propose a theoretical framework for micro-world design, which was used to guide the development of the CAMS micro-world. This may provide a helpful guideline for researchers wishing to develop a micro-world by using a more structured approach. A detailed technical description of CAMS is given to demonstrate the kind of real-world scenarios that may be simulated with this task environment. Finally, general aspects of the utility of micro-world research are discussed.

Performance evaluation in analogue space environments: adaptation during an 8-month Antarctic wintering-over expedition.

BACKGROUND: This paper reports a study which examined the impact of long-term isolation and confinement on multiple-task performance. METHODS: A group of 10 scientists and 6 technicians from a French wintering-over expedition in the Antarctic participated in the 8-mo study. The group was tested 8 times on a computerized simulation of a complex life support system. The task environment allowed the measurement of primary and secondary task performance, system control activities and subjective operator state. RESULTS: No signs of serious performance decrements were observed but a number of subtle indications of hidden decrements emerged. The data also revealed strong differences in performance between the professional groups. Finally, the paper discusses the implications of the work for extended spaceflight.

Maintenance of complex performance during a 135-day spaceflight simulation.

BACKGROUND: The maintenance of crew performance during extended space missions has been a major concern because of the problems associated with prolonged isolation and confinement. Previous research has failed to address this problem by not using appropriate performance tests. METHOD: Three Russian cosmonauts were tested on a PC-based simulation of a spacecraft's life support system during a 135-d simulation of a MIR spaceflight. A complex multiple-task environment was used to examine a comprehensive range of task management variables, including both primary and secondary task performance, control activity and information sampling behavior. Subjective state variables were also measured. RESULTS: The data suggested an overall successful adjustment to isolation and confinement, though some indications of temporary disruptions of some performance indicators were observed. Information sources were sampled less frequently with increasing mission length while system control activities showed a tendency to increase. CONCLUSION: Suggestions are made to address the problem of continuous learning during repeated testing sessions. Using well-designed computer simulations of complex task environments appears to be a promising approach for the evaluation of crew member performance.

Multiple-task performance on a computer-simulated life support system during a space mission simulation.

This paper presents an experiment which examined the effects of isolation and confinement during a simulation of a short-term space mission. During the 7-day spaceflight simulation, four Canadian astronauts were tested daily on a 30-min performance task. The task, CAMS (Cabin Air Management System), represents a computer-based simulation of a generic life support system. As a multiple-task environment, it allows the measurement of a wide range of task management variables such as primary and secondary task performance, and system control activities. Measures of subjective state variables were also taken. The results did not show any evidence of serious performance decrements for any crew member. The analysis revealed different adjustment patterns with which crew members responded as a function of mission duration and variations in workload. Among the secondary tasks employed, prospective memory was found to be more sensitive than reaction time to increases in workload. The paper concludes with a discussion of the utility of spaceflight simulations and computer-based simulations of space work.

Effective multidisciplinary communication in healthcare: cooperative documentation systems.

To support multidisciplinary communication and cooperation in healthcare, cooperative documentation systems (CDSs) have been developed. However, in the current generation of systems, communication problems that can pose a serious threat to smooth and effective cooperation have occurred and remain to be addressed. This paper presents a set of features that need to be considered in the design of a new generation of CDSs to avoid breakdowns in communication and cooperation. Our approach is solidly grounded in linguistic and social theories and based on empirical investigations of communication patterns in multidisciplinary healthcare. It is argued that this work provides a theoretically rigorous approach to the design of CDSs that will enable effective multidisciplinary communication and cooperation in healthcare.

Effects of sleep deprivation and user interface on complex performance: a multilevel analysis of compensatory control.

This study was carried out to test the compensatory control model, which predicts performance maintenance under stress at the expense of effort and increased selectivity. It examined the effects of sleep deprivation on performance in an automated process control task based on a simplified life support system with two types of operator control panel interface: machine centered (M-C), in which access to the system was scheduled by the computer, and human-centered (H-C), in which access was ad-lib. The task environment also permitted the analysis of changes in strategy and in subsidiary activities (alarm reaction time, prospective memory). In a 2 x 2 repeated-measures design, 16 participants carried out the task with each interface after both normal sleep and one night of sleep deprivation (SD). No effects of SD were observed on primary task performance. As predicted, SD effects were confined to strategy changes and subsidiary task impairment and occurred only under the (low control) M-C interface. Subjective effort was increased under SD, with greater increases of effort associated with high levels of performance protection. The findings provide strong evidence in favor of the compensatory control model and argue for the use of complex, multilevel tasks in the analysis of performance under stress. Actual or potential applications include the development of more sensitive performance-testing systems based on multilevel analysis of decrement, and the design of interfaces for shift work and other suboptimal work conditions.

Skill maintenance in extended spaceflight: a human factors analysis of space and analogue work environments.

This paper discusses the implications of increasing mission lengths of manned spaceflight for the design of future space systems from a human factors point of view. It is argued that the increase in mission duration has brought about a number of new problems, which have not been sufficiently addressed in space research. Therefore, a review of analogue work environments is carried out to make up for the paucity of space research found in the area of human performance in long-duration spaceflight. This resulted in an evaluation of seven analogue environments concerning their similarity to space with industrial process control and nuclear submarines coming out as the closest match on the technical dimension. Finally, some recommendations are given from the lessons learned in spaceflight, simulation studies and appropriate analogue environments.

Five-year performance of high-copper content amalgam restorations in a multiclinical trial of a posterior composite.

PURPOSE: This paper reports the 5-year performance of the restorations of the high-copper content dental amalgam alloys included in the worldwide programme of clinical trials of Occlusin, including unique data on wear. METHODS: The methods employed are common to those previously reported for the multiclinical evaluation of Occlusin. Analysis of the data is limited to simple statistical procedures. RESULTS: The findings lend support to existing knowledge concerning the favourable performance of restorations of high-copper content dental amalgam alloys, notably in relation to restorations in moderate- to large-sized Class II preparations in permanent molar teeth. Analysis of the data sheds new light on the influences of variables, including type of tooth restored, size and class of restoration and the presence or absence of occlusal contact(s) on performance. CONCLUSION: Conclusions are drawn regarding ways in which protocols for future evaluations of the type reported should be expanded, and, together with suggestions for further work, it is concluded that this paper is a timely reminder of the value of existing dental amalgam alloys.

Dentists' attitudes to cross-infection control.

The wearing of gloves by dentists undertaking clinical procedures has been recommended by many authorities as an essential element of dental surgery cross-infection control. This paper reports an investigation into patterns of glove-wearing by practising dentists, and considers the effect of practice location and practising arrangements on this issue and other aspects of cross-infection control. The results show that these factors, including the type of patient treated, may influence the pattern of glove-wearing by dentists in England and Wales. These findings suggest that groups least likely to follow the recommended infection control procedures should be targeted when assessing dental education requirements.

Glove use in clinical practice: a survey of 2000 dentists in England and Wales.

Attitudes to glove wearing by dentists practising within the NHS Regulations were tested by means of a questionnaire distributed to 2000 dentists in England and Wales. The response was 76.5%. The results indicate that 68% of the respondents wore gloves routinely for all patients and procedures, 3% never wore gloves, while the remainder (29%) wore gloves for only selected patients or selected procedures. Reasons given for not wearing gloves routinely included problems of comfort, loss of tactile sensation and the risk of cross-infection, which was perceived to be small. Of the routine glove wearers, only 12% changed gloves between patients, cost being considered to be a factor by 57% of respondents who used gloves for more than one patient. The results indicate that the respondents practising and personal details had an influence on the pattern of glove wearing, with single-handed practitioners and those who graduated before 1979 being less likely to wear gloves routinely. Comparison with the findings of earlier studies of similar type suggest that there is increased awareness in the dental profession of the necessity for glove wearing, but that there is still a need to encourage routine glove use, especially amongst certain groups of GDPs.

A comparison of two splints in the treatment of TMJ pain dysfunction syndrome. Can occlusal analysis be used to predict success of splint therapy?

Controversy surrounds the diagnosis and treatment of TMJ pain dysfunction syndrome (TMJPDS). This is also reflected in the widely divergent recommendations in splint design. A study was undertaken to examine the comparative success rates of treatment by two occlusal splints with apparently diametrically opposed modes of action and to determine whether there were any factors which could be utilised to predict the success of splint therapy. Sixty-eight TMJPDS patients were randomly distributed into one of two comparable groups and were treated solely with an occlusal splint for night time wear. One group was treated with a stabilisation splint (SS) and the other with a localised occlusal interference splint (LOIS). The success rate at review with the SS was 67.6% and with the LOIS was 80.9%. This difference was not statistically significant. Pretreatment occlusal analysis demonstrated three indicators of successful splint therapy which appeared to be independent of design. These were the absence of centric relation occlusion, the existence of non-working side interferences and an absence of ideal anterior guidance.

Soft occlusal splint therapy in the treatment of migraine and other headaches.

Fifty-seven patients suffering from migraine, tension headache or tension vascular headache were prescribed a soft occlusal splint for night-time wear. Dental, psychosocial/psychiatric and neurological data were recorded prior to commencement of therapy and at the conclusion of a 3 month treatment period. A statistically significant number of patients presenting with migraine or tension vascular headache experienced marked improvement or complete relief of headache symptoms, but most patients suffering from tension headache failed to benefit from splint therapy. A majority of patients displaying intercurrent features of craniomandibular dysfunction experienced reduction in these symptoms also. There was a statistically significant association between TMJ improvement and headache type. Prior to treatment, patients who subsequently benefited from splint therapy in terms of headache improvement had experienced significantly fewer headaches than patients who failed to respond, although headache intensity and duration were similar in both groups. It is suggested that headache type and frequency may be prognostic indicators of the likely success of dental splint therapy in treatment of headache. Nevertheless, the use of occlusal splints in the treatment of patients complaining of headache in the absence of evidence of craniomandibular dysfunction should not be embarked upon until medical examination has excluded the possibility of organic neurological disorder.

Trigeminal somatosensory evoked potentials: technical parameters, reliability and potential in clinical dentistry.

Various parameters of the short-latency trigeminal somatosensory evoked potential (TSEP) waveform were investigated in 12 healthy volunteers. The waveform was found to comprise two principal components at 23 (N1) and 39 (P1) ms and to show a significant contralateral dominance. Varying the stimulus strength significantly affected the amplitudes but not the peak latencies. The waveform pattern was maintained irrespective of whether the reference site was Fpz or Cv7. The peak latencies of N1 and P1 were found to be very reproducible. To a lesser extent, N1-P1 amplitude was also reproducible. The results show that clear and reliable TSEPs can be conveniently generated at the pain threshold intensity, and that they could be suitable for clinical investigations of lesions involving the trigeminal pathway. The clinical application of TSEPs has helped in treatment planning for patients with lesions of branches of the trigeminal nerve. Three cases are presented in which the TSEP confirmed the presence of the lesion, and was used to forecast its prognosis.

Spectral analysis of the masseter and anterior temporalis: an assessment of reliability for use in the clinical situation.

The electromyogram (EMG) of contracting muscles can be analysed in the frequency domain by spectral analysis. However, there is a need to establish the reproducibility of spectral parameters such as mean power frequency (MPF). This study examined the variation of MPF (masseter and anterior temporalis) between and within recording sessions. The MPF was found to be significantly reliable for both muscles, but considerable within-subject variation was found despite comprehensive measures to standardize recording methods and conditions. It is concluded that MPF may have clinical application in the diagnosis and treatment of patients with facial pain arising from muscle dysfunctions, but caution should be exercised in interpreting small changes in frequency, given the inherent variability of MPF.

Image analysis of radiolucencies in approximal enamel: a comparison of xeroradiographic and conventional film images.

Xeroradiographic and conventional film bitewing images of radiolucencies in approximal enamel were compared using a computer-aided image analysis system. Densitometric analysis of the conventional film types used in the study showed that the "lead foil free" film exhibited lower overall density when compared with conventional D-speed film. Computer-aided image analysis of radiolucencies in approximal enamel found that xeroradiographs depicted a higher degree of demineralization and a larger area than conventional radiography with the "lead foil free" film.

A double-blind cross-over trial of a mucin-containing artificial saliva.

A double-blind, five phase, cross-over clinical trial was used to compare a mucin-based artificial saliva (Saliva Orthana) with its non-mucin base and water. Thirty patients, acting as their own controls, took part. Saliva Orthana offered significantly greater relief from xerostomia compared with its base or water, and was significantly better at relieving soreness than water. In terms of overall preference, it was ranked significantly higher than either alternative.