Social capital and health: the problematic roles of social networks and social surveys

Social capital, social networks, social support and health have all been linked, both theoretically and empirically. However, the relationships between them are far from clear. Surveys of social capital and health often use measures of social networks and social support in order to measure social capital, and this is problematic for two reasons. First, theoretical assumptions about social networks and social support being part of social capital are contestable. Second, the measures used inadequately reflect the complexity and ambivalence of social relationships, often assuming that all social ties and contacts are of similarly value, are mutually reinforcing, and, in some studies, are based on neighbourhoods. All these assumptions should be questioned. Progress in our understanding requires more qualitative research and improved choice of indicators in surveys; social network analysis may be a useful source of methodological and empirical insight

What influences student participation in asynchronous online discussions

Asynchronous online discussions are widely used in online and blended learning courses. Participation by adult learners can be encouraged by the contributions of teachers, and when online groups are given well-structured tasks that are assessed. The introduction of such discussions to a pre-existing short course in mentorship for qualified health care professionals offered an opportunity to compare participation by different groups studying concurrently. This was done by counting numbers of student contributions to twenty-four different online groups, regardless of length or content. This showed that the contribution of teachers was not an important factor in influencing student participation, though individual students who contributed prolifically tended to encourage their fellow group members to contribute more. These results may not be generalizable: the course was short, the discussions focused on a well-structured and assessed task, and the learners were mature

A simulation evaluation of the engine monitoring and control system display

The Engine Monitoring and Control System (E-MACS) display is a new concept for an engine instrument display, the purpose of which is to provide an enhanced means for a pilot to control and monitor aircraft engine performance. It provides graphically-presented information about performance capabilities, current performance, and engine component or subsystem operational conditions relative to nominal conditions. The concept was evaluated by sixteen pilot-subjects against a traditional, state-of-the-art electronic engine display format. The results of this evaluation showed a substantial pilot preference for the E-MACS display relative to the traditional display. The results of the failure detection portion of the evaluation showed a 100 percent detection rate for the E-MACS display relative to a 57 percent rate for the traditional display. From these results, it is concluded that by providing this type of information in the cockpit, a reduction in pilot workload and an enhanced ability for detecting degraded or off-nominal conditions is probable, thus leading to an increase in operational safety

A compensatory algorithm for the slow-down effect on constant-time-separation approaches

In seeking methods to improve airport capacity, the question arose as to whether an electronic display could provide information which would enable the pilot to be responsible for self-separation under instrument conditions to allow for the practical implementation of reduced separation, multiple glide path approaches. A time based, closed loop algorithm was developed and simulator validated for in-trail (one aircraft behind the other) approach and landing. The algorithm was designed to reduce the effects of approach speed reduction prior to landing for the trailing aircraft as well as the dispersion of the interarrival times. The operational task for the validation was an instrument approach to landing while following a single lead aircraft on the same approach path. The desired landing separation was 60 seconds for these approaches. An open loop algorithm, previously developed, was used as a basis for comparison. The results showed that relative to the open loop algorithm, the closed loop one could theoretically provide for a 6 pct. increase in runway throughput. Also, the use of the closed loop algorithm did not affect the path tracking performance and pilot comments indicated that the guidance from the closed loop algorithm would be acceptable from an operational standpoint. From these results, it is concluded that by using a time based, closed loop spacing algorithm, precise interarrival time intervals may be achievable with operationally acceptable pilot workload

Hot spot abundance, ridge subduction and the evolution of greenstone belts

A number of plate tectonic hypotheses have been proposed to explain the origin of Archaean and Phanerozoic greenstone/ophiolite terranes. In these models, ophiolites or greenstone belts represent the remnants of one or more of the following: island arcs, rifted continental margins, oceanic crustal sections, and hot spot volcanic products. If plate tectonics has been active since the creation of the Earth, it is logical to suppose that the same types of tectonic processes which form present day ophiolites also formed Archaean greenstone belts. However, the relative importance of the various tectonic processes may well have been different and are discussed