RESUMEN
McKay et al. [(1996) Science 273, 924-930] suggested that carbonate globules in the meteorite ALH84001 contained the fossil remains of Martian microbes. We have characterized a subpopulation of magnetite (Fe(3)O(4)) crystals present in abundance within the Fe-rich rims of these carbonate globules. We find these Martian magnetites to be both chemically and physically identical to terrestrial, biogenically precipitated, intracellular magnetites produced by magnetotactic bacteria strain MV-1. Specifically, both magnetite populations are single-domain and chemically pure, and exhibit a unique crystal habit we describe as truncated hexa-octahedral. There are no known reports of inorganic processes to explain the observation of truncated hexa-octahedral magnetites in a terrestrial sample. In bacteria strain MV-1 their presence is therefore likely a product of Natural Selection. Unless there is an unknown and unexplained inorganic process on Mars that is conspicuously absent on the Earth and forms truncated hexa-octahedral magnetites, we suggest that these magnetite crystals in the Martian meteorite ALH84001 were likely produced by a biogenic process. As such, these crystals are interpreted as Martian magnetofossils and constitute evidence of the oldest life yet found.
Asunto(s)
Hierro/química , Óxidos/química , Fenómenos Fisiológicos Bacterianos , Carbono , Cristalización , Óxido Ferrosoférrico , Magnetismo , Marte , AguaRESUMEN
Nursing stress: the effects of coping strategies and job satisfaction in a sample of Australian nurses The study reported in this paper examined relationships between nursing work-related stressors and coping strategies, and their impact upon nurses' levels of job satisfaction and mood disturbance. It was proposed that higher levels of perceived work stress and use of avoidance coping would increase mood disturbance, while problem-focused coping would be associated with less mood disturbance. The study also aimed to explore the possible 'buffering effects' of using humour in coping with stress, and the effect of job satisfaction on the stress-mood relationship. The sample consisted of 129 qualified Australian nurses who volunteered to complete standardized questionnaires, including the Nursing Stress Scale, Ways of Coping Questionnaire, the Coping Humour Scale, Job Satisfaction Scale of the Nurse Stress Index, and the shortened version of the Profile of Mood States. Results revealed a significant positive relationship between nursing stress and mood disturbance, and a significant negative relationship between nursing stress and job satisfaction. The use of avoidance coping and the perception of work overload were found to be significant predictors of mood disturbance. No evidence was found to indicate that the use of humour had a moderating effect on the stress-mood relationship but there was support for the influence of job satisfaction upon this relationship. These results provided some support for a transactional model of stress since situational factors were found to influence the nurses' coping and perceptions of stress.