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Although southern sea otters (Enhydra lutris nereis) are not considered prey for white sharks (Carcharodon carcharias), sharks do nonetheless bite sea otters. We analyzed spatial and temporal trends in shark bites on sea otters in California, assessing the frequency of shark bite wounds in 1,870 carcasses collected since 1985. The proportion of stranded sea otters having shark bites has increased sharply since 2003, and white shark bites now account for >50% of recovered carcasses. The trend was most pronounced in the southern part of the range, from Estero Bay to Point Conception, where shark bite frequency has increased eightfold. Seasonal trends were also evident: most shark‐bitten carcasses are recovered in late summer and fall; however, the period of elevated shark bite frequency has lengthened. The causes of these trends are unclear, but possible contributing factors include increased white shark abundance and/or changes in white shark behavior and distribution. In particular, the spatiotemporal patterns of shark‐bitten sea otters match increases in pinniped populations, and the increased availability of marine mammal prey for white sharks may have led to more sharks spending more time in nearshore waters utilized by both sea otters and pinnipeds.  相似文献   

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Asthma prevalence has increased over the last fifty years, but the more recent changes have not been conclusively determined. Studies in children indicate that a plateau in the prevalence of asthma may have been reached, but this has not yet been confirmed in adults. Epidemiological studies have suggested that the prevalence of asthma in adults is approximately 7-10% in different parts of the western world.We have now performed a large-scale epidemiological evaluation of the prevalence of asthma and respiratory symptoms in adults between the ages of 16-75 in West Sweden. Thirty thousand randomly chosen individuals were sent a detailed questionnaire focusing on asthma and respiratory symptoms, as well possible risk factors. Sixty-two percent of the contacted individuals responded to the questionnaire. Asthma prevalence, defined as asthma diagnosed by a physician, was 8.3%. Moreover, the prevalence of respiratory symptoms was lower compared to previous studies. The most common respiratory symptom was any wheeze (16.6%) followed by sputum production (13.3%). In comparison with studies performed 18 years ago, the prevalence of asthma has not increased, and the prevalence of most respiratory symptoms has decreased. Therefore, our data argues that the continued increase in asthma prevalence that has been observed over the last half century is over.  相似文献   

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The paper touches the problem which of the results of historical anthropology having aroused much attention over the past years require more scepticism than has usually been assumed, i.e. the function of the nurses during the Middle Ages and the different way of life of children and adolescents between birth and the age of fifteen. Subsequently, some examples are adduced to show during which centuries of the Middle Ages a fear of future diseases of the children was wide-spread and during which centuries contacts among men and children in the course of their early years were especially close.  相似文献   

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Tree mortality is an important process in forest ecosystems, frequently hypothesized to be highly climate sensitive. Yet, tree death remains one of the least understood processes of forest dynamics. Recently, changes in tree mortality have been observed in forests around the globe, which could profoundly affect ecosystem functioning and services provisioning to society. We describe continental‐scale patterns of recent tree mortality from the only consistent pan‐European forest monitoring network, identifying recent mortality hotspots in southern and northern Europe. Analyzing 925,462 annual observations of 235,895 trees between 2000 and 2012, we determine the influence of climate variability and tree age on interannual variation in tree mortality using Cox proportional hazard models. Warm summers as well as high seasonal variability in precipitation increased the likelihood of tree death. However, our data also suggest that reduced cold‐induced mortality could compensate increased mortality related to peak temperatures in a warming climate. Besides climate variability, age was an important driver of tree mortality, with individual mortality probability decreasing with age over the first century of a trees life. A considerable portion of the observed variation in tree mortality could be explained by satellite‐derived net primary productivity, suggesting that widely available remote sensing products can be used as an early warning indicator of widespread tree mortality. Our findings advance the understanding of patterns of large‐scale tree mortality by demonstrating the influence of seasonal and diurnal climate variation, and highlight the potential of state‐of‐the‐art remote sensing to anticipate an increased likelihood of tree mortality in space and time.  相似文献   

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The factors associated with the deaths of 31 asthma patients were examined. The subjects, whose deaths occurred in the period 1967 through 1979, had all received some care at the Hospital for Sick Children in Toronto, but only nine died there. The greatest single cause of death was the inappropriate use of beta-agonists, with or without the concurrent use of epinephrine. In seven patients an asthma attack that occurred outside hospital progressed so rapidly that there was insufficient time for them to obtain adequate therapy. In five cases the assessment of the patient''s condition or the therapy recommended by the attending physician appeared to have been inadequate. Two patients suffered an acute attack in hopital and did not respond to treatment that appeared to have been adequate. In six cases the available information was insufficient to indicate the cause of death. Over half (18) of the deaths occurred in teenagers. Various ways of preventing death from asthma are discussed, including better education of physicians and patients, adequate management of factors that provoke bronchospasm, sufficient follow-up -- especially in teenagers -- and the use of approaches with teenagers that encourage better compliance.  相似文献   

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《Journal of bryology》2013,35(4):709-714
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The occurrence of microphyllous branches, variable disposition of inflorescences, structural range in female bract-lobule, perianth keels, seta anatomy and sporophyte details of Archilejeunea apiculifolia St., which were previously not known, are described.  相似文献   

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Gametocytes of Plasmodium falciparum were produced in continuous cultures but eventually declined in numbers after 3--4 months in vitro. Their development progressed in a consistent pattern, from small rounded, through triangular, to ellipsoidal, and finally after 8 days to crescentic forms. Morphologic maturity occurred at 8--9 days, but the gametocytes would not exflagellate in vitro, even after 14--18 days of development. Thus, current culture methods cannot produce a continuous supply of functional gametes for further studies.  相似文献   

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OBJECTIVES: To test whether recent declines in mortality from coronary heart disease were associated with increased mortality from other cardiovascular diseases. DESIGN: Poisson regression analysis of national data on causes of death and hospital discharges. SETTING AND SUBJECTS: Population of the Netherlands, 1969-93. MAIN OUTCOME MEASURES: Annual changes in mortality from coronary heart disease, stroke, and other cardiovascular diseases and annual changes in hospital discharge rates for acute coronary events, stroke, and congestive heart failures. RESULTS: Patterns of cardiovascular mortality changed abruptly in 1987-93. Annual decline in mortality from coronary heart disease increased sharply for women and men: from -1.9% (95% confidence interval -2.2% to -1.6%) and -1.7% (-1.9% to -1.4%) respectively in 1979-86 to -3.1% (-3.5% to -2.6%) and -4.2% (-4.6% to -3.9%) in 1987-93. The longstanding decline in mortality from stroke levelled off: from annual change of -3.3% (-3.7% to -2.8%) and -3.2% (-3.7% to -2.8%) in 1979-86 to -0.1% (-0.7% to 0.4%) and -1.1% (-1.7% to -0.5%) in 1987-93. Mortality from other cardiovascular diseases, however, started to increase: from -2.0% (-2.4% to -1.6%) and -0.2% (-0.5% to 0.2%) in 1979-86 to 1.5% (1.0% to 2.0%) and 1.9% (1.5% to 2.3%) in 1987-93. Hospital discharge rates for acute coronary heart disease, congestive heart failure, and stroke increased during 1980-6. During 1987-93 discharge rates for stroke and coronary heart disease stabilised but rates for congestive heart failure increased. CONCLUSION: Improved management of coronary heart disease seems to have reduced mortality, but some of the gains are lost to deaths from stroke and other cardiovascular diseases. The increasing numbers of patients with coronary heart disease who survive will increase demands on health services for long term care.  相似文献   

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A. Little 《CMAJ》1969,100(10):485-487
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