Temporal trend

时间趋势
  • 文章类型: Journal Article
    根据降雪后24小时内的空气样本,获得了16种优先PAHs的气体和颗粒浓度,这为研究大气PAHs的时间趋势提供了良好的契机。观察到与大气浓度有明显的时间趋势,主要受排放源的影响。发现最大浓度(Σ16PAHs)为272.8ng/m3,出现在交通高峰时段。相反,在人为活动最少的时期,最低浓度为82.39ng/m3。颗粒相分数[公式:参见正文])和G/P分配商(logKP)的值随着PAHs的分子量而增加。然而,对于单个PAHs,与[公式:见正文]和logKP的差异在24小时内不明显。此外,不同时期的logKP和logKOA之间存在相似的统计学正相关。根据短抽样程序,化学性质应该是G/P分配时间趋势的主要影响因素。案例研究结果为PAHs的G/P分配研究领域提供了新的见解。
    Based on air samples within 24 h after snowfall, gaseous and particulate concentrations of 16 priority PAHs were obtained, which provided a good opportunity to study the temporal trend of atmospheric PAHs. An obvious temporal trend with atmospheric concentration was observed, which was mainly influenced by emission sources. It was found that the maximum concentration (Σ16PAHs) was 272.8 ng/m3, appeared in the rush hour of traffic. To the contrary, the minimum concentration was 82.39 ng/m3 at the period with the least anthropogenic activities. The values of particle-phase fraction[Formula: see text]) and G/P partitioning quotient (log K P) were increased along with molecular weight of PAHs. However, for individual PAHs, the differences with [Formula: see text] and log K P were not obvious within 24 h. Furthermore, similar statistically significant positive correlations were found between log K P and log K OA among different periods. According to the short sampling program, chemical properties should be the major influencing factor for the temporal trend of G/P partitioning. The results of the case study provided new insights into the research field of G/P partitioning of PAHs.
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  • 文章类型: Journal Article
    2018年,在塔拉戈纳县(加泰罗尼亚,西班牙)。As的水平,Be,Cd,Cr,Hg,Mn,Ni,Pb,Sn,在分析的食品中测定Tl和V,并估计它们的膳食摄入量。锰是浓度最高的元素,而Be,在任何样品中均未检测到Cr和Tl。鱼和贝类是唯一可以检测到所有剩余元素痕迹的食物组。将当前水平与1998年和2013年在同一地区进行的两次调查的结果进行了比较。尽管在2013-2018年期间,食品中分析元素的含量有所增加,但其摄入量平均减少了60%,由于人口消费模式的变化。儿童和青少年超过了EFSA规定的Ni的最大推荐摄入量,而儿童的膳食铅暴露也高于安全值。与2013年发现的浓度相比,Ni是唯一显示出增加的元素,以及人类饮食摄入量的增加。肉,蔬菜和牛奶被确定为镍暴露的主要贡献者。这种趋势也与先前报告的该地区人口的相同元素的生物负担的变化有关,据报道,肺部镍含量增加。基于这些结果,食品安全当局应将Ni作为目标金属包括在内,建议将其纳入未来的总饮食研究。
    In 2018, samples of various food groups were randomly purchased in different establishments of Tarragona County (Catalonia, Spain). The levels of As, Be, Cd, Cr, Hg, Mn, Ni, Pb, Sn, Tl and V were determined in the analyzed foodstuffs and their dietary intakes were estimated. Manganese was the element showing the highest concentration, while Be, Cr and Tl were not detected in any of the samples. Fish and shellfish was the only food group with detectable traces of all the remaining elements. The current levels were compared with the results of two previous surveys conducted in 1998 and 2013 in the same area. Although the levels of the analyzed elements in foodstuffs increased during the period 2013-2018, their intakes decreased by an average of 60%, due to consumption patterns changes by the population. Children and adolescents exceeded the maximum recommended intake of Ni set by the EFSA, while the dietary exposure to Pb for children was also above safety values. Compared with the concentrations found in 2013, Ni was the only element showing an increase, as well as an increase of human dietary intake. Meat, vegetables and milk were identified as the main contributors to Ni exposure. This trend was also correlated with changes in the biological burden of the same elements previously reported for the population of the area, for whom an increase of Ni in lungs was reported. Based on these results, Ni should be included as a target metal by food safety authorities, being suggested its inclusion in future Total Diet Studies.
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  • 文章类型: Journal Article
    Suicide rates in China have declined substantially in the last two decades, however, the correlates of the decreases are still unclear.
    Using hospital-based suicidal acts registry system in Meixian county, we reviewed all episodes of suicidal behaviors presented at hospitals from 2009 to 2014. The data was combined with the suicides reported in the same period by the county\'s Center for Disease Prevention and Control. Stratified by gender and method, age-standardized incidences of suicide death, suicide attempts, suicidal acts, as well as the case-fatalities of suicidal acts, were calculated. Joinpoint regression analysis was applied to test the time trends changes of the annual incidences and case-fatalities. Correlation coefficients between suicide rates and case-fatality were estimated.
    Age-standardized suicide rates among females declined by 20.4% per year, meanwhile, overall suicide rates were characterized by downward trend without statistical significance. The annual proportions of suicide deaths by pesticide self-poisoning ranged from 57.1% to 82.6%. There were positive or marginally positive correlations between suicide rates and case-fatalities of suicidal acts in gender- and method-specific groups (r values range from 0.77 to 0.89).
    Underreporting in the hospital-based registry system and misclassification in the death reporting system. Changes in other related factors are not yet accessible.
    Suicide rates in females declined prominently in Meixian from 2009 to 2014, even though overall suicide rates remained steady. Pesticide ingestion were most common suicide method. Restriction of pesticide and reduction in the case-fatality are critical targets of suicide prevention in rural China.
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  • 文章类型: Journal Article
    背景:先前的研究表明,许多系统综述包含显示时间趋势的荟萃分析,比如第一次研究的结果比后来的研究更极端,或者汇总估计的漂移。我们使用2008-2012年发表的所有Cochrane干预报告评估了时间趋势的程度和特征。
    方法:我们在每个报告中选择了最大的荟萃分析,并使用包括Z检验(第一与后续估计)的方法分析了趋势;广义最小二乘;和累积和图。考虑的预测因素包括荟萃分析大小和评论组。
    结果:在包含至少4项研究的1288项荟萃分析中,第一项研究的点估计更极端,方向与738年的汇总估计相同(57%),在165(13%)中具有统计学上的显着差异(第一次与之后)。广义最小二乘法显示717(56%)的趋势;18%的固定效应分析至少有一次违反累积总和限制。对于某些方法,荟萃分析大小与时间模式和随机效应模型的使用相关,但与审查组没有一致的关联.
    结论:所有结果表明,更多的荟萃分析显示时间模式,而不是偶然的预期。因此,假设没有时间趋势的标准荟萃分析模型有时是不合适的。与趋势相关的因素可能是特定于环境的。
    BACKGROUND: Previous studies suggest that many systematic reviews contain meta-analyses that display temporal trends, such as the first study\'s result being more extreme than later studies\' or a drift in the pooled estimate. We assessed the extent and characteristics of temporal trends using all Cochrane intervention reports published 2008-2012.
    METHODS: We selected the largest meta-analysis within each report and analysed trends using methods including a Z-test (first versus subsequent estimates); generalised least squares; and cumulative sum charts. Predictors considered include meta-analysis size and review group.
    RESULTS: Of 1288 meta-analyses containing at least 4 studies, the point estimate from the first study was more extreme and in the same direction as the pooled estimate in 738 (57%), with a statistically significant difference (first versus subsequent) in 165 (13%). Generalised least squares indicated trends in 717 (56%); 18% of fixed effects analyses had at least one violation of cumulative sum limits. For some methods, meta-analysis size was associated with temporal patterns and use of a random effects model, but there was no consistent association with review group.
    CONCLUSIONS: All results suggest that more meta-analyses demonstrate temporal patterns than would be expected by chance. Hence, assuming the standard meta-analysis model without temporal trend is sometimes inappropriate. Factors associated with trends are likely to be context specific.
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