This study uses structural equation modeling to test a model hypothesizing the impacts of overload and non-participation on job strain, turnover and commitment of urban transit drivers. The study sample comprises 331 responses from transit drivers from bus companies in Australia. The results show that non-participation has a direct and negative impact on organizational commitment while role overload has a direct and positive influence on intent to leave. An unexpected finding is that while overload and non-participation have significant positive impacts on job strain, there is no significant relationship between strain and organizational commitment. The implications are that work-related stressors appear to influence the organizational commitment and intent to leave of transit drivers directly rather than indirectly through job strain. Role overload and non-participation have not often been considered in the context of the commitment and intent to leave in stressful occupations such as urban transit driving.

In the present paper, we study the evolution of an overloaded cyclic polling model that starts empty. Exploiting a connection with multitype branching processes, we derive fluid asymptotics for the joint queue length process. Under passage to the fluid dynamics, the server switches between the queues infinitely many times in any finite time interval causing frequent oscillatory behavior of the fluid limit in the neighborhood of zero. Moreover, the fluid limit is random. In addition, we suggest a method that establishes finiteness of moments of the busy period in an M/G/1 queue.

Dietary reference values for essential trace elements are designed to meet requirements with minimal risk of deficiency and toxicity. Risk–benefit analysis requires data on habitual dietary intakes, an estimate of variation and effects of deficiency and excess on health. For some nutrients, the range between the upper and lower limits may be extremely narrow and even overlap, which creates difficulties when setting safety margins. A new approach for estimating optimal intakes, taking into account several health biomarkers, has been developed and applied to selenium, but at present there are insufficient data to extend this technique to other micronutrients. The existing methods for deriving reference values for Cu and Fe are described. For Cu, there are no sensitive biomarkers of status or health relating to marginal deficiency or toxicity, despite the well-characterised genetic disorders of Menkes and Wilson's disease which, if untreated, lead to lethal deficiency and overload, respectively. For Fe, the wide variation in bioavailability confounds the relationship between intake and status and complicates risk–benefit analysis. As with Cu, health effects associated with deficiency or toxicity are not easy to quantify, therefore status is the most accessible variable for risk–benefit analysis. Serum ferritin reflects Fe stores but is affected by infection/inflammation, and therefore additional biomarkers are generally employed to measure and assess Fe status. Characterising the relationship between health and dietary intake is problematic for both these trace elements due to the confounding effects of bioavailability, inadequate biomarkers of status and a lack of sensitive and specific biomarkers for health outcomes.

The terminology used for describing intervention groups in randomised controlled trials (RCT) on the effect of intravenous fluid on outcome in abdominal surgery has been imprecise, and the lack of standardised definitions of the terms ‘standard’, ‘restricted’ and ‘liberal’ has led to some confusion and difficulty in interpreting the literature. The aims of this paper were to clarify these definitions and to use them to perform a meta-analysis of nine RCT on primarily crystalloid-based peri-operative intravenous fluid therapy in 801 patients undergoing elective open abdominal surgery. Patients who received more or less fluids than those who received a ‘balanced’ amount were considered to be in a state of ‘fluid imbalance’. When ‘restricted’ fluid regimens were compared with ‘standard or liberal’ fluid regimens, there was no difference in post-operative complication rates (risk ratio 0·96 (95% CI 0·56, 1·65), P=0·89) or length of hospital stay (weighted mean difference (WMD) −1·77 (95% CI −4·36, 0·81) d, P=0·18). However, when the fluid regimens were reclassified and patients were grouped into those who were managed in a state of fluid ‘balance’ or ‘imbalance’, the former group had significantly fewer complications (risk ratio 0·59 (95% CI 0·44, 0·81), P=0·0008) and a shorter length of stay (WMD −3·44 (95% CI −6·33, −0·54) d, P=0·02) than the latter. Using imprecise terminology, there was no apparent difference between the effects of fluid-restricted and standard or liberal fluid regimens on outcome in patients undergoing elective open abdominal surgery. However, patients managed in a state of fluid balance fared better than those managed in a state of fluid imbalance.

En dépit des progrès enregistrés en Arthroplastie Totale de Hanche (ATH), sous certainesconditions, les contraintes prothétiques peuvent être amplifiées et transmises auxancrages osseux avec un risque accru de descellement (B. The et al., J. Biomech. 41 (2008)100–105). Les pics de chargement sont identifiés parmi les facteurs qui conduisent auxéchecs des ATH (A. Boulila, Optimisation et aide à la conception d’implants orthopédiques– Étude de l’usure d’implants articulaires de hanche, Travaux non publiés et Rapportd’avancement, INO MT Kassab, décembre 2006, Tunis, 82 p.). Cette étude porte sur unesimulation numérique des prothèses de hanche hybrides, de géométrie et de couple dematériaux différents. On montre que certaines géométries (∅28 × 56 mm) et certains couplesde matériaux (alumine/polyéthylène), peuvent atténuer les contraintes induites après chocet protéger la prothèse contre l’usure ou les ruptures prématurées. Devant une panoplied’une cinquantaine de modèles de prothèses de hanche existant sur le marché (M.R. Urist,Curr. Prob. Surge. 12 (1975) 1–54), certaines PTH de diamètre (interne et externe)incompatible avec un niveau de contraintes admissible doivent être éliminées. Unecombinaison judicieuse des matériaux de contact pour favoriser l’amortissement (cas ducouple polyéthylène/céramique) peut être une solution pour absorber les chocs et remédierau problème de descellement.

Admission control can be employed to avoid congestion in queueing networks subject to overload. In distributed networks, the admission decisions are often based on imperfect measurements on the network state. In this paper, we study how the lack of complete state information affects the system performance, by considering a simple network model for distributed admission control. The stability region of the network is characterized and it is shown how feedback signaling makes the system very sensitive to its parameters.

As part of a wider study of family caregiving, a sample of 297 women caring for an ageing parent were identified through a random statewide telephone survey involving over 26,000 households in Victoria, Australia. In addition to elder care, half these women were in paid employment and a third had dependent children. Overload was highest for carers with multiple roles, particularly those of parent or worker. Resentment in the caring role was highest for those who had fewer roles apart from elder care, particularly those who had quit work, and those without a partner. Life satisfaction was higher for partnered and working carers. These findings highlight the need for structures to support carers to maintain multiple roles, including greater flexibility in the workplace and encouragement of greater reliance on informal networks and formal services, both of which require increased societal acknowledgment of the elder care role.