Mathematical Modeling of Epicardial RF Ablation of Atrial Tissue with Overlying Epicardial Fat

The efficacy of treating atrial fibrillation by RF ablation on the epicardial surface is currently under question due to the presence of epicardial adipose tissue interposed between the ablation electrode and target site (atrial wall). The problem is probably caused by the electrical conductivity of the fat (0.02 S/m) being lower than that of the atrial tissue (0.4-0.6 S/m). Since our objective is to improve epicardial RF ablation techniques, we planned a study based on a two-dimensional mathematical model including an active electrode, a fragment of epicardial fat over a fragment of atrial tissue, and a section of atrium with circulating blood. Different procedures for applying RF power were studied, such as varying the frequency, using a cooled instead of a dry electrode, and different modes of controlling RF power (constant current, temperature and voltage) for different values of epicardial fat thickness. In general, the results showed that the epicardial fat layer seriously impedes the passage of RF current, thus reducing the effectiveness of atrial wall RF ablation

Cultural Readjustment After Crisis: Regulation and Learning from Crisis Within the UK Soccer Industry

Challenging Turner's (1976, 1978) implicit assumption that cultural readjustment typically follows a crisis, this paper examines the evolution of the regulation of safety management within the UK soccer industry since 1946. Employing a longitudinal case study approach, the industry's response to four crises is examined. This study explores the industry's response to changes in the regulatory framework, through the lens of Gouldner's (1954) patterns of industrial bureaucracy and institutional theory. The persistence of indulgent and mock patterns of behaviour, following a series of disasters, challenges Turner's implicit assumption. Although a move towards a punitive approach to regulatory behaviour effected some changes, there was limited evidence of cultural readjustment due in part to a 'mindset of invulnerability' (Wicks, 2001). This included the fixed belief that hooligan behaviour was the primary problem facing the industry. Our findings suggest that more participative forms of regulation encourage more effective learning from crisis because they challenge core organizational and individual assumptions. Copyright Blackwell Publishing Ltd 2006.