Biological effects of selenium and relationships with carcinogenesis†

Selenium is an element that is both essential, at low levels of dietary intake, and toxic, at high levels, to man and a wide range of animals. The purpose of the communication is to review the evidence for the involvement of hyper‐ and hypo‐selenosis in the aetiology of cancer. High levels of selenium intake have been blamed for an increase in cancer, dental caries and an array of other conditions. Critical evaluation of the evidence, however, leads to the conclusion that such claims have little substance. On the other hand, low levels of selenium intake may be associated with an increased incidence of certain forms of cancer and there appears to be an inverse relationship between blood selenium levels and cancer death rate in the United States. Keshan Disease, in the People's Republic of China has only been shown to occur in populations severely depleted of selenium. In well nourished populations there is no evidence to indicate that selenium supplements have any prophylactic or therapeutic benefit against human diseases such as cancer, cardiovascular disease or cystic fibrosis.     

Enhancement of UV and chromate mutagenesis by nickel ions in the Chinese hamster HGPRT Assay †

1. The HGPRT (Hypoxanthine‐Guanine‐Phospho‐Ribosyl‐Transferase) assay with Chinese Hamster V79 cells was used to measure the mutagenic effects of UV irradiation, potassium dichromate and nickel chloride. The agents were tested separately and in the combinations of UV plus nickel and dichromate plus nickel.

2. UV, Cr(VI) and Ni(II) were confirmed to be mutagenic in the V79 cell assay. The combination of UV(5J/m²) and Ni(II) (0.5 mM) caused a mutation rate 11.2 times above that corresponding to the sum of the individual mutation rates of these agents. The combined action of Cr(VI) (0.1 mM) and Ni(II) (0.5 mM) produced a mutation rate 2.8 fold above that corresponding to the sum of the individual rates of the separate agents.

3. The enhancing effect of nickel chloride on the mutagenicity of UV or Cr(VI) is interpreted by an interference of Ni(II) with the repair of DNA lesions.     

城市化对北京霾日数影响统计分析

近年来,随着超大城市/城市群大气灰霾等复合污染加剧,引起人们对区域生态环境与及公共健康问题越来越多的关注。应用北京地区1980—2012年气候资料及同期城市发展统计指标,统计分析了城、郊区间霾日数的变化特征,并在此基础上探讨了北京城市化及局地气候差异对霾日数的影响。分析表明：北京城区霾日数要明显多于郊区,在2007年以前城、郊区站点均有相似的波动增长趋势,但城区站霾日数增加速率（约21 d/10 a）要远大于郊区站（约7.2 d/10 a）;北京各地霾日数与主要城市发展指数之间的相关系数均超过0.001显著性水平,随着城市化而迅速增加的能源消耗和机动车尾气排放是导致北京地区灰霾天气逐渐增多的主要污染源,污染源的不均匀分布是导致城、郊霾日数差异的主要因素。分析还发现,城市化导致的区域气候差异对局地灰霾亦有较明显的影响。伴随着城市化的快速发展,城、郊区气候差异逐渐变大,城市下垫面粗糙度增加导致近地面层风速减小。大城市热岛效应背景下,更容易出现较厚的逆温层,这将阻碍空气垂直方向的对流输送。此外,城区气温持续上升,相对湿度下降,平均风速减小,小风频率增加,也会阻碍空气的水平流通,使得城市排放颗粒污染物的扩散难以扩散,有利于霾日增加。这表明北京地区城市气候效应对区域生态环境具有不可忽视的影响。     

Maternal investment in eggs is affected by male feet colour and breeding conditions in the blue-footed booby, <Emphasis Type="Italic">Sula nebouxii</Emphasis>

Females are expected to vary investment in offspring according to variables that may influence the offspring fitness in a way that optimises her inclusive fitness for a particular context. Thus, when sexual ornaments signal the quality of the male, females might invest in reproduction as a function of the attractiveness of their mate. We tested whether breeding conditions and male feet colour influence reproductive decisions of blue-footed booby females. In the blue-footed booby, male feet colour is a dynamic condition-dependent sexually selected trait that is related to paternal effort. During two consecutive years, an El Niño year (poor breeding conditions) and a year with good breeding conditions, we experimentally reduced male attractiveness by modifying their feet colour after the first egg was laid and recorded female investment in the second egg. We found that, relative to the first egg in the clutch, females laid heavier second eggs during the poor year than during the good year. Females paired with males with duller feet colour reduced second-egg mass and volume and delayed the laying of the second egg, independently of the year. Absolute yolk androstenedione (A4) concentration (but not testosterone, T) in second eggs was higher during a poor year than during a good year. Only during a year with poor breeding conditions, females paired with experimental males decreased the relative A4 concentration (but not T) in the second egg compared to control females. Thus, blue-footed booby females probably favour brood reduction by decreasing egg quality and increasing size asymmetry between chicks when the breeding and the mate conditions are poor.     

纳米材料对藻细胞毒性效应及致毒机理

纳米材料因其独特的性质被广泛应用于生物医疗、光学工程、催化等领域。随着纳米材料的生产量逐年增大,越来越多的纳米粒子被释放到水生生态环境中,其生态毒性效应影响也备受人们的关注。本文根据纳米材料的分类总结了不同种类纳米材料对水生生态系统的初级生产者藻类的毒性效应,归纳了纳米材料影响藻类毒性大小的主要因素,如纳米材料的物理化学性质、水体性质和藻种等,并探讨了纳米材料对藻类的致毒机理,如金属离子溶出、氧化损伤和遮光效应等,最后总结展望了纳米毒理学研究的发展方向,以期为纳米材料对藻类的毒性研究提供一定的理论依据。     

基坑开挖与邻近高层建筑施工耦合模拟研究

以一邻近在建观光楼的基坑工程为背景,采用有限元软件MIDAS GTS-NX对其进行基坑开挖及邻近观光楼全过程数值模拟分析,结合模拟计算分析了邻近在建高层建筑的基坑开挖的耦合作用.模拟结果表明:在邻近在建建筑物的基坑开挖情况下,两者间的耦合作用明显;在邻近在建高层建筑物影响下,基坑支护结构水平位移差为10.1 mm;土体...     

The effect of contextual information on professional judgment: Reliability and biasability of expert workplace safety inspectors

Introduction: A critical aspect of occupational safety is workplace inspections by experts, in which hazards are identified. Scientific research demonstrates that expectation generated by context (i.e., prior knowledge and experience) can bias the judgments of professionals and that individuals are largely unaware when their judgments are affected by bias. Method: The current research tested the reliability and biasability of expert safety inspectors’ judgments. We used a two-study design (Study 1, N = 83; Study 2, N = 70) to explore the potential of contextual, task-irrelevant, information to bias professionals’ judgments. We examined three main issues: (1) the effect that biasing background information (safe and unsafe company history) had on professional regulatory safety inspectors’ judgments of a worksite; (2) the reliability of those judgments amongst safety inspectors and (3) inspectors’ awareness of bias in their judgments and confidence in their performance. Results: Our findings establish that: (i) inspectors’ judgments were biased by historical contextual information, (ii) they were not only biased, but the impact was implicit: they reported being unaware that it affected their judgments, and (iii) independent of our manipulations, inspectors were inconsistent with one another and the variations were not a product of experience. Conclusion: Our results are a replication of findings from a host of other professional domains, where honest, hardworking professionals underappreciate the biasing effect of context on their decision making. The current paper situates these findings within the relevant research on safety inspection, cognitive bias and decision making, as well as provides suggestions for bias mitigation in workplace safety inspection. Practical Application: Our results have implications for occupational health and safety given that inspection is an integral aspect of an effective safety system. In addition to our findings, this study contributes to the literature by providing recommendations regarding how to mitigate the effect of bias in inspection.     

Behavioral pathways in bicycle-motor vehicle crashes: From contributing factors,pre-crash actions,to injury severities

Introduction: This study performed a path analysis to uncover the behavioral pathways (from contributing factors, pre-crash actions to injury severities) in bicycle-motor vehicle crashes. Method: The analysis investigated more than 7,000 bicycle-motor vehicle crashes in North Carolina between 2007 and 2014. Pre-crash actions discussed in this study are actions of cyclists and motorists prior to the event of a crash, including “bicyclist failed to yield,” “motorist failed to yield,” “bicyclist overtaking motorist,” and “motorist overtaking bicyclist.” Results: Model results show significant correlates of pre-crash actions and bicyclist injury severity. For example, young bicyclists (18 years old or younger) are 23.5% more likely to fail to yield to motor traffic prior to the event of a crash than elder bicyclists. The “bicyclist failed to yield” action is associated with increased bicyclist injury severity than other actions, as this behavior is associated with an increase of 5.88 percentage points in probability of a bicyclist being at least evidently injured. The path analysis can highlight contributing factors related to risky pre-crash actions that lead to severe injuries. For example, bicyclists traveling on regular vehicle travel lanes are found to be more likely to involve the “bicyclist failed to yield” action, which resulted in a total 44.38% (7.04% direct effect + 37.34% indirect effect) higher likelihood of evident or severe injuries. The path analysis can also identify factors (e.g., intersection) that are not directly but indirectly correlated with injury severity through pre-crash actions. Practical Applications: This study offers a methodological framework to quantify the behavioral pathways in bicycle-motor vehicle crashes. The findings are useful for cycling safety improvements from the perspective of bicyclist behavior, such as the educational program for cyclists.     

南京市湿地水质对城市化影响强度的响应研究

选取28个受城市化影响程度不同的典型湿地,对其水质进行连续监测.另一方面利用GIS技术及景观生态学原理对城市湿地所在集水区不透水类型及林地类型进行景观分析,并构建城市化影响指数(UEI),进一步对区域城市化水平与湿地水质进行相关分析.结果表明:①南京仙林新市区湿地水质季节性变化表现为夏季水质较差,冬季水质相对较好,春、秋季节差别不大.②湿地水质与城市化水平有着明显的相关关系,城市化水平等级越高,湿地水质越差,其中高等城市化水平(HU)湿地TP、TN、NH4+-N、Chla等富营养化指标质量浓度分别达到0.27、1.07、0.15、17.94 mg.L-1,而低等城市化水平(LW)湿地其质量浓度则分别为0.12、0.56、0.12、4.85 mg.L-1.③城市化影响指数与湿地水质存在着阈值关系,整体来看,当UEI值超过2.2时,湿地水质恶化速度加快.     

Bioaccumulation and biological effects in the earthworm Eisenia fetida exposed to natural and depleted uranium

The accumulations of both natural (U) and depleted (DU) uranium in the earthworms (Eisenia fetida) were studied to evaluate corresponding biological effects. Concentrations of metals in the experimental soil ranged from 1.86 to 600 mg kg⁻¹. Five biological endpoints: mortality, animals’ weight increasing, lysosomal membrane stability by measuring the neutral red retention time (the NRRT), histological changes and genetic effects (Comet assay) were used to evaluate biological effects in the earthworms after 7 and 28 days of exposure. No effects have been observed in terms of mortality or weight reduction. Cytotoxic and genetic effects were identified at quite low U concentrations. For some of these endpoints, in particular for genetic effects, the dose (U concentration)-effect relationships have been found to be non-linear. The results have also shown a statistically significant higher level of impact on the earthworms exposed to natural U compared to depleted U.