An inverse method for determining source characteristics for emergency response applications

Following a malicious or accidental atmospheric release in an outdoor environment it is essential for first responders to ensure safety by identifying areas where human life may be in danger. For this to happen quickly, reliable information is needed on the source strength and location, and the type of chemical agent released. We present here an inverse modelling technique that estimates the source strength and location of such a release, together with the uncertainty in those estimates, using a limited number of measurements of concentration from a network of chemical sensors considering a single, steady, ground-level source. The technique is evaluated using data from a set of dispersion experiments conducted in a meteorological wind tunnel, where simultaneous measurements of concentration time series were obtained in the plume from a ground-level point-source emission of a passive tracer. In particular, we analyze the response to the number of sensors deployed and their arrangement, and to sampling and model errors. We find that the inverse algorithm can generate acceptable estimates of the source characteristics with as few as four sensors, providing these are well-placed and that the sampling error is controlled. Configurations with at least three sensors in a profile across the plume were found to be superior to other arrangements examined. Analysis of the influence of sampling error due to the use of short averaging times showed that the uncertainty in the source estimates grew as the sampling time decreased. This demonstrated that averaging times greater than about 5min (full scale time) lead to acceptable accuracy.

A police state? The Nyasaland emergency and colonial intelligence.

The Nyasaland Emergency in 1959 proved a decisive turning point in the history of the Federation of Rhodesia and Nyasaland, which from 1953 to 1963 brought together the territories of Northern Rhodesia (Zambia), Southern Rhodesia (Zambia) and Nyasaland (Malawi) under a settler-dominated federal government. The British and Nyasaland governments defended the emergency by claiming to have gathered intelligence which showed that the Nyasaland African Congress was preparing a campaign of sabotage and murder. The Devlin Commission, appointed to investigate the emergency, dismissed the evidence of a ‘murder plot’, criticised the Nyasaland government's handling of the Emergency and, notoriously, described Nyasaland as a ‘police state’. This article has two principal aims. First, using the recently declassified papers of the Intelligence and Security Department (ISD) of the Colonial Office, it seeks to provide the first detailed account of what the British government knew of the intelligence relating to the ‘murder plot’ and how they assessed it, prior to the outbreak of the emergency. It demonstrates that officials in the ISD and members of the Security Service adopted a far more cautious attitude towards the intelligence than did Conservative ministers, and had greater qualms about allowing it into the public domain to justify government policy. Second, the article examines the implications of Devlin's use of the phrase ‘police state’ for Nyasaland and for the late colonial state in general. It contrasts Devlin's use of the term with that of security experts in the ISD, who routinely applied it to policing systems that diverged from their own preferred model. Hence, whereas Devlin compared policing in Nyasaland unfavourably with that in Southern Rhodesia, implying, ironically, that Nyasaland was ‘under-policed’ (because there were fewer police per head of population in Nyasaland than in Southern Rhodesia), the ISD regarded the intensive system of policing operated by the British South Africa Police in Southern Rhodesia as characteristic of a ‘police state’. The article suggests that the frequent use of the term ‘police state’ was indicative of broader anxieties about what Britain's legacy would be for the post-independence African state.

Enhancing fieldwork learning with technology: practitioner's perspectives

This research paper reports the findings from an international survey of fieldwork practitioners on their use of technology to enhance fieldwork teaching and learning. It was found that there was high information technology usage before and after time in the field, but some were also using portable devices such as smartphones and global positioning system whilst out in the field. The main pedagogic reasons cited for the use of technology were the need for efficient data processing and to develop students' technological skills. The influencing factors and barriers to the use of technology as well as the importance of emerging technologies are discussed.