Showing papers by "Manchester Metropolitan University published in 1993"
TL;DR: The polymorphism in intron 2 of the interleukin-1 receptor antagonist gene is investigated and two new alleles of the system are identified and the variable copy number of an 86-bp sequence may have functional significance.
Abstract: We have investigated the polymorphism in intron 2 of the interleukin-1 receptor antagonist gene and identified two new alleles of the system. We have shown that the polymorphism is caused by the variable copy number of an 86-bp sequence, by using the polymerase chain reaction and primers immediately flanking the repeat region, and by direct sequencing. The repeat region contains three potential protein-binding sites and therefore the variable copy number may have functional significance.
676 citations
TL;DR: The authors found that experienced players' cognitive knowledge permitted more meaningful associations between players' positions resulting in more efficient retrieval, and experienced soccer players seem to have a more complex and discriminating organisation of long-term memory which facilitates the encoding of task-specific information.
Abstract: This study tested the proposition that experienced soccer players exhibit greater task-specific cognitive knowledge than novice players. 12 experienced and 12 inexperienced subjects viewed structured and unstructured soccer action sequences on a 3.65-m2 video projection screen. In recalling specific player positions following brief 10-sec. film clips, inexperienced players had larger recall of errors than the experienced players on structured trials only. This indicated that experienced players' cognitive knowledge permitted more meaningful associations between players' positions resulting in more efficient retrieval. When recognition of previously viewed film clips was examined, experienced subjects were more accurate in recognising structured trials only. Experienced soccer players seem to have a more complex and discriminating organisation of long-term memory which facilitates the encoding of task-specific information.
143 citations
TL;DR: Action learning is becoming widely accepted methodology for the development of managers and managerial competence in both public and private sector organizations and within the context of certificated and organisationally based programmes as discussed by the authors. But although this approach promises to answer some of the problems of traditional management education, it is not without its own critics.
Abstract: SUMMARY
This paper examines the proposition that action learning is a new paradigm in management education. Action learning is becoming widely accepted methodology for the development of managers and managerial competence. This is in both public and private sector organizations and within the context of certificated and organisationally based programmes. The paper seeks to use Kuhn's work on the nature of paradigms and change as a way of explaining the increase of interest in his approach. Importantly, although this approach promises to answer some of the problems of traditional management education, it is not without its own critics. Kuhn's criteria for a paradigm change are explained with reference to action learning literature and knowledge of practice. From this a framework is developed that compares a traditional approach to management education with an action learning approach on three levels. Our conclusion is that action learning is a new paradigm, but for the maximum benefit to be gained from the approach its application needs to be more carefully considered, particularly in relation to the provision of some wider external frameworks for the manager to use as‘tools for thinking’
127 citations
TL;DR: One occupation which has undergone enormous legislative and occupational change during the last five years or more is the teaching profession, and more research to identify occupational stress has been undertaken, particularly on front line teachers themselves.
Abstract: Over the years, research into occupational health and stress has concentrated on jobs suspected of being ‘stress risks’, such as air traffic controllers (Crump, Cooper & Maxwell, 1981). the police (Cooper et al., 1982), executives (van der Ploeg, Vis, Cooper & Spielberger, 1986), nurses working with the critically ill and dying (Cooper & Mitchell, 1990) and so on. Until recently, little systematic empirical work had been conducted to explore occupations or groups of workers undergoing transformation and change, although normally not thought to be under particular stress. One occupation which has undergone enormous legislative and occupational change during the last five years or more is the teaching profession (Cole & Walker. 1989). As the pressure has grown for those in teaching, more research to identify occupational stress has been undertaken, particularly on front line teachers themselves (Kyriacou & Pratt, 1985: Kyriacou, 1989).
126 citations
TL;DR: The calculated potential ATP production suggests that, overall, glutamine is the major contributor of cellular energy.
Abstract: The energy metabolism of a mammalian cell line grown in vitro was analyzed by substrate consumption rates and metabolic flux measurements. The data allowed the determination of the relative importance of the pathways of glucose and glutamine metabolism to the energy requirements of the cell. Changes in the substrate concentrations during culture contributed to the changing catalytic activities of key enzymes, which were determined.
1.
A murine B-lymphocyte hybridoma (PQXB1/2) was grown in batch culture to a maximum cell density of 1–2×106 cells/mL in 3–4 d. The intracellular protein content showed a maximum value during the exponential growth phase of 0.55 mg/106 cells. Glutamine was completely depleted, but glucose only partially depleted to 50% of its original concentration when the cells reached a stationary phase following exponential growth.
2.
The specific rates of glutamine and glucose utilization varied during culture and showed maximal values at the midexponential phase of 2.4-nmol/min/106 cells and 4.3 nmol/min/106 cells, respectively.
3.
A high proportion of glucose (96%) was metabolized by glycolysis, but only limited amounts by the pentose phosphate pathway (3.3%) and TCA cycle (0.21%).
4.
The maximum catalytic activity of hexolinase approximates to the measured flux of glycolysis and is suggested as a rate-limiting step. In the stationary phase, the hexokinase activity reduced to 11% of its original value and may explain the reduced glucose utilization at this stage.
5.
The maximal activities of two TCA cycle enzymes were well above the measured metabolic flux and are unlikely to pose regulatory barriers. However, the activity of pyruvate dehydrogenase was undetectable by spectrophotometric assay and explains the low level of flux of glycolytic metabolites into the TCA cycle.
6.
A significant proportion of the glutamine (36%) utilized by the cells was completely oxidized to CO2.
7.
The measured rate of glutamine transport into the cells approximated to the metabolic flux and is suggested as a rate-limiting step.
8.
Glutamine metabolism is likely to occur via glutaminase and amino transaminase, which have significantly higher activities than glutamate dehydrogenase.
9.
The calculated potential ATP production suggests that, overall, glutamine is the major contributor of cellular energy. However, at the midexponential phase, the energy contribution from the catabolism of the two substrates was finely balanced—glutamine (55%) and glucose (45%).
110 citations
TL;DR: In this article, a Walsh operational matrix of PWM waveforms is introduced as a means of obtaining the Walsh spectral equations of waveforms, and a noniterative algorithm that produces piecewise-linear, global solutions between angles and for the angles is proposed.
Abstract: A method for selective harmonic elimination in pulse-width-modulated (PWM) inverter waveforms by the use of Walsh functions is presented. The Walsh operational matrix of PWM is introduced as a means of obtaining the Walsh spectral equations of PWM waveforms. The slope and intercept Fourier operational matrices of PWM are also introduced as a means of obtaining Fourier spectral equations of PWM waveforms. A noniterative algorithm that produces piecewise-linear, global solutions between angles and for the angles is proposed. The algorithm also produces the full range of variation of fundamental voltage for given harmonic elimination constraints. The set of systems of linear equations obtained replaces the system of nonlinear transcendental equations used in the Fourier series harmonic elimination approach. In general, the algorithm makes possible the synthesis of two-state PWM inverter waveforms with specified old harmonic content. >
100 citations
TL;DR: Three-dimensional video techniques were used to obtain images of basketball jump shots from one of three distances, finding that the increased impulse necessary for the ball to reach the basket at increased shooting distances was derived from both an increase in angular velocity of the elbow joint of the shooting arm and an increased Velocity of the centre of mass in the direction of the baskets at release.
Abstract: Three‐dimensional video techniques (50 Hz) were used to obtain images of basketball jump shots from one of three distances ‐ short range (group 1, n = 5); medium range (group 2, n = 5); long range (group 3, n = 5) ‐ from the basket, as performed by members of the men's quarter‐finalist teams at the games of the XVI Universiade in Sheffield in 1991. Fifteen sequences were digitized, beginning 20 frames prior to take‐off to 10 frames after release. To facilitate analysis, the sequences were rotated about the ball position in the final frame so that the shot direction was parallel to one of the pre‐defined orthogonal axes. Mean (+1 s.d.) ball release speed was found to increase with distance from the basket (group 1 = 3.04±0.65 m s‐1, group 2 = 4.71+0.74 m s‐1, group 3 = 6.24 + 0.80 m s‘1), while mean release angles were similar for all groups (group 1=48.8 + 10.1°, group 2 = 47.8 + 5.8°, group 3 = 51.9 + 5.5°). The increased impulse necessary for the ball to reach the basket at increased shooting distances ...
94 citations
86 citations
TL;DR: Three-dimensional analysis of the best throws from the women's and men's javelin competitions at the 1991 World Student Games in Sheffield indicated the possibility of two different throwing techniques, within and between individuals, relating both to the timing of hip joint actions within the kinematic chain and the trade-off between the impulse applied to the Javelin and run-up speed.
Abstract: This paper reports a three‐dimensional kinematic analysis of the best throws from the women's and men's javelin competitions at the 1991 World Student Games in Sheffield. This was undertaken to obtain accurate three‐dimensional release parameter values for elite javelin throwers in a top competition, to relate the release parameters to important temporal and kinematic features of the javelin throwing technique and to carry out an assessment of the adequacy of two‐dimensional estimates of release parameter values in comparison with those from the three‐dimensional analysis. Cine‐film was taken using two phase‐locked Panasonic 1PL cameras running at a frame rate of 100 Hz, and every other frame was digitized. All methodologies were in accord with the guidelines of the British Association of Sports Sciences. The results indicated the possibility of two different throwing techniques, within and between individuals, relating both to the timing of hip joint actions within the kinematic chain and the trade‐off b...
83 citations
TL;DR: The sexual behaviour and sharing of two groups of female injectors were compared, one whose primary use was heroin, the other amphetamine, and marked differences were observed in sexual behaviour, amphetamine injectors reporting greater interest in sex and greater frequency of intercourse.
Abstract: The incidence of HIV infection among women in Europe and the US is growing rapidly. Women who inject drugs are paricularly vulnerable-they may acquire the infection through sharing injecting equipment and through sexual contact with an infected male. Opioids and stimulants are reputed to have different effects upon sexual activity and a sex life enhanced by drugs may increase the risk further. In the context of two larger studies of HIV-related risk behaviours among opioid and amphetamine users in the North West of England, the sexual behaviour and sharing of two groups of female injectors were compared, one whose primary use was heroin, the other amphetamine. Reported incidence of sharing was similar and high
64 citations
TL;DR: The resistances to charge transfer, measured using complex ac impedance, are affected dramatically by film composition as discussed by the authors, and diffusion coefficients of intercalating ions do not vary greatly with film composition.
TL;DR: In this paper, a specific careers guidance action plan, used in conjunction with one of the original training credits pilot schemes, is investigated, and it revealed tensions between the pragmatically rational way in which young people reported making career decisions and the technically rational system of guidance built into the design of the scheme.
Abstract: A specific careers guidance action plan, used in conjunction with one of the original training credits pilot schemes, is investigated. Analysis revealed tensions between the pragmatically rational way in which young people reported making career decisions and the technically rational system of guidance built into the design of the scheme. These tensions created operational difficulties for careers officers, and raise important issues for further debate about the nature of careers education and guidance
TL;DR: The debates with the Church of England about whether or not the churches should develop policies and provide moral guidelines about the use of atomic bombs have been studied in this paper, where the authors argue that the Church should provide policies and moral guidelines.
Abstract: The debates with the Church of England about whether or not the churches should develop policies and provide moral guidelines about the use of atomic bombs
TL;DR: In this article, the attitudes of employers with regard to age discrimination and the use of media advertising to infer age preference without actually stating an age 'bar' are examined. But, they do not consider that the older end of the age spectrum can still offer commitment, attitudinal maturity, and mentoring roles.
Abstract: Examines the attitudes of employers with regard to age discrimination and the use of media advertising to infer age preference without actually stating an age‐bar. Analyses how, through discrete advertising in selected newspapers and journals, some employers are still youth‐oriented and not taking into consideration that the older end of the age spectrum can still offer commitment, attitudinal maturity, and mentoring roles. Also discloses how the use of recruitment agencies as a means for age discrimination/selection is the choice of many organizations, so avoiding the business of selection until the short‐list stage.
TL;DR: Key relatives of 30 psychotic patients were interviewed (for a second time) 18 months after participating in an initial assessment of expressed emotion (EE) and a significant association between EE rating at 18 months and psychiatric status of the patient during the follow-up period emerged.
Abstract: Key relatives of 30 first or early admission psychotic patients (mainly with a diagnosis of schizophrenia) were interviewed (for a second time) 18 months after participating in an initial assessment of expressed emotion (EE). The patients were followed up throughout the interim period, during which time 17 experienced a psychotic relapse. Although there continued to be a negligible association between initial EE rating (established during the index admission) and relapse, a significant association between EE rating at 18 months and psychiatric status of the patient during the follow-up period emerged. Results are discussed in the context of recent interactional theories of the relationship between household EE and psychiatric morbidity.
TL;DR: The impact of first names on ratings of physical attractiveness as judged by British undergraduate subjects using male and female full-face pictures presented on photographic slides with attractive names, unattractive names, or without any name indicated was examined.
Abstract: I examined the impact of first names on ratings of physical attractiveness as judged by British undergraduate subjects using male and female full-face pictures presented on photographic slides. The photographs were identified with attractive names, unattractive names, or without any name indicated. Subjects rated the stimulus figures for physical attractiveness. Names accounted for approximately 6% of the variance in subjects' ratings of physical attractiveness. This effect was highly significant for pictures of women (p .05).
TL;DR: These experiments were designed to study the effect of resistance exercise on parameters pertinent to the hemostatic and fibrinolytic systems and found no significant changes in the parameters measured in the resting condition over the three testing occasions.
Abstract: These experiments were designed to study the effect of resistance exercise on parameters pertinent to the hemostatic and fibrinolytic systems. Seven normal healthy subjects (6 male, 1 female, 25 +/- 3 yr mean SD) were studied under three conditions: control (C) [no exercise], high volume resistance exercise (HVRE), and low volume resistance exercise (LVRE), which were randomized for each subject, with 7 d separating tests. Both HVRE and LVRE trials encompassed the performance of five sets of nine exercises. After establishing one repetition maximum (1 RM), the HVRE involved the performance of moderate resistance, higher repetition, and shorter resting periods, whereas LVRE involved the use of high resistance, lower repetition, and longer resting intervals. Heart rate (HR) was monitored at rest and continuously during trials and venous blood was removed with minimum stasis, before and immediately after HVRE, LVRE, and before and after 38 min of supine rest (C). The blood was enzymatically analyzed for lactic acid (LA) and assayed using chromogenic substrates for the determination of tissue plasminogen activator (t-PA), plasminogen activator inhibitor (PAI), and Factor VIII (FVIII) activities. Global fibrinolysis (GF) was also screened in the fibrin plate and hematocrit ratios were employed to calculate percent plasma volume changes. Values were corrected for changes in plasma volume then data were analyzed using repeated measures ANOVA. There were no significant (P > 0.05) changes in the parameters measured in the resting condition over the three testing occasions and no significant differences (P > 0.05) were observed during the control experiment.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: In this paper, a nonlinear optical loop mirror composed of two fibres with different dispersion and/or nonlinearity is simulated and optical switching is possible with a symmetric coupler along with the possibility of the pulse compression.
Abstract: Simulation of a nonlinear optical loop mirror composed of two fibres with different dispersion and/or nonlinearity is reported. Results show that optical switching is possible with a symmetric coupler along with the possibility of the pulse compression
TL;DR: In this article, the life and work of one teacher over the past decade or so is celebrated, and the relationship between his manifest and latent identities is explored, which, it is argued, presents a powerful immunological response to the state's attempted policy 'grafts'.
Abstract: This paper celebrates the life and work of one teacher over the past decade or so. As such, it reasserts a degree of indeterminacy, contestation and contradiction into analyses of schooling. It presents data obtained from ethnographic conversations with a headteacher of a working‐class, urban primary school. His intellectual and moral vision, his theories and his practices, are set in the context of recent state policy. The relationship between his manifest and latent identities is explored, which, it is argued, presents a powerful immunological response to the state's attempted policy ‘grafts’. In conclusion, the paper moves from the particular to an exploration of the usefulness of the head's responses as a model for the understanding of teachers’ experiences of the New Right project generally.
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01 Jul 1993TL;DR: In this paper, the authors argue that there are two different traditions in research and that they can be labelled the physics approach and the biological approach, and that case studies are in the latter domain and are therefore not understood by people whose world view belongs to the physics domain.
Abstract: There are two major sources of confusion about the term ‘case study’. The first arises from two different objectives, training and research, the second from a confusion about what is meant by research. This paper argues that there are two different traditions in research and that they can be labelled the physics approach and the biological approach. Case studies are in the latter domain and are therefore not understood by people whose world view belongs to the physics domain. The paper includes advice on using cases as a research method.
01 Jan 1993
TL;DR: In this article, the authors identified ten basic manual disassembly processes for use in planning disassembly and showed that disassembly of product samples can yield useful data for estimating the feasibility of large-scale plants.
Abstract: Both market pressures and the threat of legislation are causing a rapid growth in interest in disassembly and recycling. In the UK, as elsewhere, the recycling industry is fragmented and undeveloped; demand for recycled materials will need to increase before recycling operations can be greatly expanded. Complex products of mixed materials are the feedstock of disassembly plants; these products can be classified by their structure, complexity and the degree to which the recycling value is concentrated within them. We have identified ten basic manual disassembly processes for use in planning disassembly. Tests carried out on computer monitors show that the disassembly times for individual processes are variable but that disassembly of product samples can yield useful data for estimating the feasibility of large-scale plants. Such plants can handle single products or mixed streams: the plant layout needs to be planned bearing in mind buffer storage, sorting of the parts removed and work on specific subassemblies.
TL;DR: The effects of physiological integration on clone behaviour are examined at various structural scales, using data from the stoloniferous herb Glechoma hederacea to refute the commonly-quoted view that physiological integration between the ramets of clonal herbs evens out the effects of variation in environmental quality, and promotes equitable ramet performance.
Abstract: The effects of physiological integration on clone behaviour are examined at various structural scales, using data from the stoloniferous herb Glechoma hederacea. The consequences for clone expansion of traumatic fragmentation of the connections between clonal ramets are also illustrated. These results, together with information from other species, are used to refute the commonly-quoted view that physiological integration between the ramets of clonal herbs evens out the effects of variation in environmental quality, and promotes equitable ramet performance. Instead, clonal species are responsive, at a variety of structural scales, to environmental quality. Therefore, in a heterogeneous habitat, within-clone variation in the performance of ramets and clonal sub-structures is to be expected. The seminal study which purports to demonstrate environmental averaging in clonal herbs is shown to be both inadequately designed and inappropriately analysed to accomplish its aim.
Physiological and architectural reasons for the local responses to environmental quality seen in the majority of clonal herbs are discussed.
06 Oct 1993
TL;DR: This paper describes first steps towards the formal specification and verification of Distributed Artificial Intelligence systems, through the use of temporal belief logics, and develops a logic that may be used to reason about Concurrent MetateM systems.
Abstract: This paper describes first steps towards the formal specification and verification of Distributed Artificial Intelligence (DAI) systems, through the use of temporal belief logics. The paper first describes Concurrent MetateM, a programming language for DAI, and then develops a logic that may be used to reason about Concurrent MetateM systems. The utility of this logic for specifying and verifying Concurrent MetateM systems is demonstrated through a number of examples. The paper concludes with a brief discussion of the wider implications of the work, and in particular on the use of similar logics for reasoning about DAI systems in general.
TL;DR: In this paper, the preconditioning of amorphous poly(ethylene terephthalate) sheet and biaxially oriented bottle material by heating for 48 h in a nitrogen atmosphere at 60 and 90°C improves both thermal hydrolytic and UV stabilities.
TL;DR: In the context of a gradually ageing labour force and skills shortages, discrimination against older workers has recently become an issue of public policy concern as mentioned in this paper, and ageism is arguably more pervasive in the hospitality industry than elsewhere; a recent followup study confirms that hospitality organizations continue to rely heavily on younger workers and show little disposition to capitalize on the acknowledged benefits which older workers can offer.
Abstract: In the context of a gradually ageing labour force and skills shortages, discrimination against older workers has recently become an issue of public policy concern. Ageism is arguably more pervasive in the hospitality industry than elsewhere; a recent follow‐up study confirms that hospitality organizations continue to rely heavily on younger workers and show little disposition to capitalize on the acknowledged benefits which older workers can offer. Consequently, these organizations do not appear to be well placed to manage future developments in the labour market, particularly in relation to obtaining managers.
TL;DR: Common referencing techniques used to provide immunity against the undesirable variable optical losses in analogue intensity modulated optical fibre sensors are described.
Abstract: Common referencing techniques used to provide immunity against the undesirable variable optical losses in analogue intensity modulated optical fibre sensors are described. Major strategies are investigated using a simple analytical approach to assist in the evaluation of each scheme for its referencing effectiveness. The techniques are assessed for their operational efficiency in the areas where predominant common-mode variations are experienced; namely those areas associated with optical source variations and those variations caused by optical propagation factors.
01 Dec 1993
TL;DR: Original receiver sensitivity calculations show that the optimum digital PPM system offers an 8.6 dB improvement over a typical PCM system, and clearly illustrates that receiver complexity can be simplified without large reductions in sensitivity.
Abstract: The discrete time modulation format, known as digital PPM, has been used to exchange channel bandwidth for improved signal-to-noise ratio in optical communication systems. However, the filter that optimises signal detection is complex in that it comprises a prewhitened matched filter in cascade with a proportional-derivative-delay network. In this form, the receiver would be unrealistic for a commercial system. This paper examines the use of both optimum and suboptimum detection. Three suboptimum predetection filters are considered: a matched filter, an optimised three-pole filter and a third-order Butterworth filter. Original receiver sensitivity calculations, carried out at a bit rate of 140 Mbit/s and a wavelength of 1.3 μm, show that the optimum digital PPM system offers an 8.6 dB improvement over a typical PCM system. The suboptimum predetection filters result in sensitivity degradations of 0.4, 0.9 and 1.1 dB, respectively. This clearly illustrates that receiver complexity can be simplified without large reductions in sensitivity. In particular, the well known and simple Butterworth filter can be employed with only 1.1 dB degradation in sensitivity.
TL;DR: It is concluded that the lactate concentration value during incremental and submaximal exercise (at 4 mmol·l−1 OBLA) is dependent on the blood sampling site, and should be considered in studies concerned with the determination of OBL a.
Abstract: This study examined lactate concentration during incremental and submaximal treadmill exercise at work rates corresponding to 4 mmol· 1−1 lactate concentration, determined by fingertip (OBLAI) and venous blood (OBLA2). Initially, eight subjects performed a 4-min incremental exercise test until exhaustion. On two other occasions, seven of the subjects undertook submaximal exercise tests (30 min) at work rates corresponding to OBLA1 and OBLA2. Blood was simultaneously obtained from both sites at rest and at the end of each exercise stage during the incremental exercise, and at 5, 10, 20 and 30 min during the submaximal exercise and 5 min into recovery. Fingertip blood lactate concentrations were significantly higher (P<0.05) than venous blood at rest, throughout the incremental exercise, consistently during exercise at OBLA1 and OBLA2, and into recovery. Data also revealed an exercise intensity-dependent lactate difference between the two sampling sites during both exercise protocols. Exercise at OBLA1 did not result in a progressive increase in lactate level nor exhaustion, and the lactate value at the end of 30 min corresponded to the predetermined value. However, exercise at OBLA2 resulted in a significantly higher (P<0.05) lactate level than OBLA1, the lactate concentration at the end of 30 min was substantially higher than the predetermined value (P<0.05) and exhaustion was evident. It is concluded that the lactate concentration value during incremental and submaximal exercise (at 4 mmol·l−1 OBLA) is dependent on the blood sampling site. This finding should be considered in studies concerned with the determination of OBLA.
TL;DR: In this paper, a conceptual framework is developed to analyse the process of managing product development while taking into account the environmental attributes of products. But the authors do not address the implications of evolving environmental concern over the management of product development.
Abstract: Concern about the nature and consequences of industrial progress has had an increasing impact on industry. Some commentators have suggested that environmental pressures will advance to the point where they cease to be one of the many strategic issues facing industry and become the very framework within which all other business issues are considered.
This paper aims to address the implications of evolving environmental concern over the management of product development. It develops a conceptual framework to analyse the process of managing product development while taking into account the environmental attributes of products. The paper moves on to consider the implications of such a conceptual framework against the empirical evidence emerging about product development in the white goods industry. Finally, conclusions are drawn about the nature of organisational change in business as it adjusts to the environmental agenda and suggestions are made about the significance of the findings of this research to product development in other industries.
TL;DR: It is concluded that irregular sleep patterns strongly affect sleep and that circadian and homeostatic influences are clearly discernible despite the irregularity.
Abstract: For many occupational groups there is an implicit requirement that sleep be taken according to very irregular schedules. The purpose of this study was to investigate the effects of an irregular sleep schedule on sleep and to determine if such effects could be attributed to the timing of sleep. Eight subjects slept in an isolation unit according to an irregular schedule comprising four 8-hour sleep periods, 12 6-hour sleep periods and 12 1-hour naps. The schedule was designed to give normal amounts of time (1/3 of total) in bed. Large variations in mean sleep efficiency (100-46%) were observed, which in individual cases frequently involved a complete absence of sleep. In 6-hour sleep periods the loss was due to an inability to maintain sleep, whereas in naps the loss was due to an inability to initiate sleep. The major causes of reduced sleep were short prior time awake and bedtime close to the circadian acrophase of rectal temperature (i.e. late afternoon). These two components accounted for 46% of the intraindividual variance of total sleep time (TST). TST increased by 9.2 minutes for each hour of prior time awake and by 10 minutes for each hour of deviation from the circadian acrophase of rectal temperature. Prior time awake also exerted a strong influence on slow-wave sleep (SWS), and circadian phase exerted a similar influence on rapid eye movement sleep. We concluded that irregular sleep patterns strongly affect sleep and that circadian and homeostatic influences are clearly discernible despite the irregularity.(ABSTRACT TRUNCATED AT 250 WORDS)