A combined evolutionary search and multilevel optimisation approach to graph-partitioning

The graph-partitioning problem is to divide a graph into several pieces so that the number of vertices in each piece is the same within some defined tolerance and the number of cut edges is minimised. Important applications of the problem arise, for example, in parallel processing where data sets need to be distributed across the memory of a parallel machine. Very effective heuristic algorithms have been developed for this problem which run in real-time, but it is not known how good the partitions are since the problem is, in general, NP-complete. This paper reports an evolutionary search algorithm for finding benchmark partitions. A distinctive feature is the use of a multilevel heuristic algorithm to provide an effective crossover. The technique is tested on several example graphs and it is demonstrated that our method can achieve extremely high quality partitions significantly better than those found by the state-of-the-art graph-partitioning packages.

Psychology and interventions for pupils at risk of underachievement and school exclusion: the year 10 effect

Findings are presented from a longitudinal study of over 1,500 adolescents. Some were engaged in interventions aimed at reducing social disaffection. Participants completed measures of social-identification, academic self-concept and motivation, and social, emotional and behavioural difficulties. Consistent with our previous research, developmental trends in identity and self-concept were found - adolescents became more negative about some school-based factors and more positive about aspects of identity. Trends were less clear in the 120 adolescents receiving interventions. Findings demonstrate the importance of psychology in work with young people. [Source: (2008) 'Invited Address, IUPsyS Invited Symposium, Invited Symposium, Symposium, Paper Session, Poster Session', International Journal of Psychology, 43:3, 348 - 527]

Chaetopterid tubes from vent and seep sites: Implications for fossil record and evolutionary history of vent and seep annelids

Vestimentiferan tube worms living at deep-sea hydrothermal vents and cold seeps have been considered as a clade with a long and continuing evolutionary history in these ecosystems. Whereas the fossil record appears to support this view, molecular age estimates do not. The two main features that are used to identify vestimentiferan tubes in the fossil record are longitudinal ridges on the tube's surface and a tube wall constructed of multiple layers. It is shown here that chaetopterid tubes from modern vents and seeps—as well as a number of fossil tubes from shallow-water environments—also show these two features. This calls for a more cautious interpretation of tubular fossils from ancient vent and seep deposits. We suggest that: current estimates for a relatively young evolutionary age based on molecular clock methods may be more reliable than the inferences of ancient “vestimentiferans” based on putative fossils of these worms; not all of these putative fossils actually belong to this group; and that tubes from fossil seeps should be investigated for chitinous remains to substantiate claims of their potential siboglinid affinities.