Implementing atomic actions in Ada 95

Atomic actions are an important dynamic structuring technique that aid the construction of fault-tolerant concurrent systems. Although they were developed some years ago, none of the well-known commercially-available programming languages directly support their use. This paper summarizes software fault tolerance techniques for concurrent systems, evaluates the Ada 95 programming language from the perspective of its support for software fault tolerance, and shows how Ada 95 can be used to implement software fault tolerance techniques. In particular, it shows how packages, protected objects, requeue, exceptions, asynchronous transfer of control, tagged types, and controlled types can be used as building blocks from which to construct atomic actions with forward and backward error recovery, which are resilient to deserter tasks and task abortion

Sexual behaviour and its medicalisation: in sickness and in health

No abstract available

Trends in teenage pregnancy in England and Wales: how can we explain them?

Teenage pregnancy is associated with adverse social and physical outcomes for both mother and child. We drew on various sources-birth and abortion statistics from the Office for National Statistics, data from the National Survey of Sexual Attitudes and Lifestyles, and routinely collected data from family planning clinics-to identify trends in England and Wales and their possible determinants. The rate of teenage sexual activity has increased steadily and consistently over the past four decades, whilst the rate of teenage fertility has shown greater variation. When the teenage fertility rate is calculated against the denominator of sexually active women, rather than the total sample of teenage women, the underlying trend in teenage fertility over the past four decades has been downwards, though not consistently so. Fluctuations in the teenage fertility rate seem to track intervention-related factors such as access to, and use of, contraceptive services and the general climate surrounding the sexual health of young people

Staff training in integrated sexual health services

Coordination of family planning and GUM services has the potential to boost the effectiveness of bot

Can virtual seminars be used cost‐effectively to enhance student learning?

This paper describes a virtual seminar initiative designed to investigate the extent to which computer‐mediated communication (CMC) can cost‐effectively strengthen staff‐student interaction and enhance student group discussion, and thereby improve collaborative learning. After setting the scene by means of a brief review of the discursive potential of CMC, the establishment of an asynchronous bulletin board system on three modules in the Department of Sociology at the University of Manchester using industry standard software is described. Detailed time diaries kept by all staff involved revealed that organizing and running the virtual seminars were very much less time‐consuming than running face‐to‐face seminars. However, analysis of the students’ access to and mage of the virtual seminars indicates that some of them were disadvantaged by CMC and that they favoured face‐to‐face contact with lecturers over virtual seminars. The latter should therefore be part of a portfolio of teaching techniques rather than the sole form of collaborative learning. The conclusion is that a significant obstacle to benefiting from CMC is the further demand on staff time that results from adding virtual seminars as a supplement to existing teaching practices. Even though these extra demands may be modest, effectively deploying the discursive potential of CMC to enhance student learning increases staff effort rather than reducing it, as many have hoped or promised it would

The role of fathers in breastfeeding: Decision-making and support

Background In recent years closer attention has been paid to the role of fathers in both the decision about whether to breastfeed and in supporting a breastfeeding mother. This qualitative study explores couples' decision-making regarding infant feeding, parents' views on the father's role in relation to breastfeeding, and examines some dilemmas fathers face when supporting a breastfeeding partner. Methods Eighteen men and women using maternity services at the Royal Sussex County Hospital were interviewed by telephone. Results Fathers acknowledged that the decision to breastfeed should be made by the mother and a father's role was to endorse his partner's decision and provide practical and emotional support. Those who faced breastfeeding difficulties described the processes involved in deciding whether to continue. Conclusions This small study draws upon the views of men and women living in the south-east of England in a city with high rates of breastfeeding initiation. Findings may not be generalizable to the wider population. However, in this setting new parents need information about breastfeeding and support to make informed decisions about duration and further input from health professionals when facing difficulties. </jats:sec

Replica determinism and flexible scheduling in hard real-time dependable systems

Fault-tolerant real-time systems are typically based on active replication where replicated entities are required to deliver their outputs in an identical order within a given time interval. Distributed scheduling of replicated tasks, however, violates this requirement if on-line scheduling, preemptive scheduling, or scheduling of dissimilar replicated task sets is employed. This problem of inconsistent task outputs has been solved previously by coordinating the decisions of the local schedulers such that replicated tasks are executed in an identical order. Global coordination results either in an extremely high communication effort to agree on each schedule decision or in an overly restrictive execution model where on-line scheduling, arbitrary preemptions, and nonidentically replicated task sets are not allowed. To overcome these restrictions, a new method, called timed messages, is introduced. Timed messages guarantee deterministic operation by presenting consistent message versions to the replicated tasks. This approach is based on simulated common knowledge and a sparse time base. Timed messages are very effective since they neither require communication between the local scheduler nor do they restrict usage of on-line flexible scheduling, preemptions and nonidentically replicated task sets