Systematic review of maritime field studies about stress and strain in seafaring.

PURPOSE: The aim of this study was to summarize and evaluate the current scientific literature on stress and strain on seafarers on board as defined by maritime field surveys. METHODS: Using a systematic review, 109 studies on the stress and strain experienced by seafarers were identified for the period January 1990 to January 2012. RESULTS: Only 13 of the identified maritime studies were conducted as field studies, and in 10 of these studies, the focus was on the watch system and/or on fatigue. According to the study results, sleepiness tends to be stronger in the 2-watch system than in the 3-watch system (particularly between 4:00 and 6:00 a.m.). Occasional short sleep episodes appear to provide adequate recovery. Fatigue does not appear to depend on the seafarers' age and is often associated with poor sleep quality; noise and night shifts are also considered to contribute to fatigue. Stress among the seafarers was primarily recorded in sleep diaries (9 times) and with devices for measuring physical activity (4 times). As a rule, a questionnaire was used to assess the strain on the crew on board; 7 studies also additionally recorded biometrical parameters. Only in 6 cases were several groups with different ranks on board investigated. CONCLUSION: The conducted literature review makes it clear that most maritime field studies have focused on fatigue and watch systems in the shipping industry--in each case as univariate parameters. Thus, scientific field studies with comprehensive multivariate stress and strain analyses on board are required.

Burnout syndrome in seafarers in the merchant marine service.

PURPOSE: As seafarers face a wide range of psychosocial stressors on board, they may be endangered to develop burnout syndrome. This study aims to investigate respective indicators. METHODS: In a cross-sectional study, 251 seafarers were asked about demographic data and job-related stressors. Particularly, the subscale emotional exhaustion (EE) of the Maslach Burnout Inventory and the Epworth Sleepiness Scale were used to assess the respective risks of job-related burnout and daytime sleepiness among seafarers. The statistical analysis was carried out using multiple logistic regression. RESULTS: Within the whole study group, the EE score was elevated in 10.8 %. A higher EE score was found in 10.7 % of officers, in 4.5 % of lower crew ranks and in 25.0 % of the galley staff (p = 0.05). Furthermore, long working days were associated with an elevated EE score [OR 3.83 (CI 1.46-10.03)]. Emotional exhaustion was associated with a subjective perception of enough sleep on board [OR 3.33 (CI 1.17-9.46)], lack of care taken by the shipboard superiors and/or the shipping company [OR 1.19 (CI 1.04-1.36)], with high responsibility for work organisation of those involved in leadership [OR 1.46 (CI 1.20-1.78)] and with social problems due to the long periods of separation from their families [OR 1.19 (CI 1.02-1.39)], taking into account relevant demographic parameters. CONCLUSIONS: Compared with the majority of on-shore occupations, the burnout risk in seafaring seems to be moderate. To reduce the EE among seafarers, it is recommended to extend the sleeping time, to avoid long working hours, to improve the superiors' communication and leadership skills, to diminish the superiors' stress load caused by organisational duties and to support low-price telecommunication possibilities at home.

Forest-fire models as a bridge between different paradigms in self-organized criticality

We turn the stochastic critical forest-fire model introduced by Drossel and Schwabl [Phys. Rev. Lett. 69, 1629 (1992)] into a completely deterministic threshold model. This model has many features in common with sandpile and earthquake models of self-organized criticality. Our deterministic forest-fire model exhibits in detail the same macroscopic statistical properties as the original Drossel-Schwabl model. We use the deterministic model to elaborate on the relation between forest-fire, sandpile, and earthquake models.

Universal fluctuations in correlated systems

The probability density function (PDF) of a global measure in a large class of highly correlated systems has been suggested to be of the same functional form. Here, we identify the analytical form of the PDF of one such measure, the order parameter in the low temperature phase of the 2D XY model. We demonstrate that this function describes the fluctuations of global quantities in other correlated equilibrium and nonequilibrium systems. These include a coupled rotor model, Ising and percolation models, models of forest fires, sandpiles, avalanches, and granular media in a self-organized critical state. We discuss the relationship with both Gaussian and extremal statistics.