The first demonstration of laser action in ruby was made in 1960 by T. H. Maiman of Hughes Research Laboratories, USA. Many laboratories worldwide began the search for lasers using different materials, operating at different wavelengths. In the UK, academia, industry and the central laboratories took up the challenge from the earliest days to develop these systems for a broad range of applications. This historical review looks at the contribution the UK has made to the advancement of the technology, the development of systems and components and their exploitation over the last 60 years.

If selection is interpreted as involving repeated cycles of replication, variation, and environmental interaction so structured that environmental interaction causes replication to be differential, then selection in gene-based biological evolution and the reaction of the immune system to antigens are relatively unproblematic examples of selection processes. Operant learning and cultural evolution pose more serious problems. In this response we deal with operant learning as a selection process.

Background. There are no prospective cohort studies of prognostic factors on the outcome of Gulf War veterans. We aimed to test the hypotheses that Gulf War veterans who were older; had more severe symptoms; had more exposures during deployment; had increased psychological distress and believed they had ‘Gulf War syndrome’ would experience greater fatigue and poorer physical functioning at follow-up.

Method. Gulf War veterans who responded to an earlier retrospective cohort study were followed with a postal survey. More symptomatic individuals were oversampled. Outcome was measured on the Chalder fatigue questionnaire, the General Health Questionnaire and the Medical Outcome Study Short-Form 36.

Results. Of those surveyed, 73·8% responded. We found some evidence for four of the five hypotheses. More self-reported exposures at baseline were not associated with poorer outcome, but older people, those with more severe symptoms at baseline, those with psychological distress and who believed they were suffering from ‘Gulf War syndrome’ had more fatigue at follow-up. Officer status was associated with a better outcome. A similar lack of association was found for exposures and physical functioning and GHQ-12 score. ‘Gulf War syndrome’ attribution was associated with a worse outcome for GHQ-12 and physical functioning even after controlling for severity of symptoms at baseline.

Conclusions. This study suggests that while multiple vaccination and military exposures are important risk factors for the onset of symptoms in Gulf War veterans, these are not important risk factors for persistence of such symptoms. Instead the severity of the initial symptoms; psychological distress and attributions may be more important determinants of outcome.

Background. Peace-keeping duties are associated with unique stresses for military personnel. There have been few reports on the effects of peace-keeping on psychological health.

Method. We used data from a cross-sectional study originally established to examine health effects of service in the Gulf War, which included a control group who had been deployed in Bosnia (N=2049). This group was examined to establish which demographic, occupational, and deployment-related risk factors were associated with psychological distress measured on the General Health Questionnaire (GHQ-12) and stress symptoms akin to a post-traumatic stress reactions.

Results. The main risk factors for stress symptoms in the Bosnia group were – lower rank, being deployed early in the campaign, having more deployment-related exposures, and serving on staff duties. There was no protective effect of previous deployments to the Falklands or Northern Ireland, and time off following deployment was not protective. For GHQ-12 cases, the main risk factors were: female gender, lower rank, increased deployment-related exposures and serving on staff duties.

Conclusions. This study suggests that stress symptoms and GHQ-12 cases, are strongly predicted both by experiences during deployment and demographic factors.