Is sledding safe? Beyond acute,traumatic injuries: Estimating the spine loads sustained by children while sledding

ObjectiveCompare acceleration level between two sleds used for downhill winter sliding. The hypotheses include (a) acceleration levels will differ significantly between sled types, (b) acceleration levels will be unsafe, (c) acceleration levels will not differ significantly between genders.DesignCross sectional study, within subject design. A cross correlation was used to verify similar terrain and path of travel between the two sleds. The trials with the highest correlation, between sleds, were then used in a t-test to analyze the differences in the mean, maximum, minimum, peak accelerations, average and maximum peak levels between the two sleds and genders. A one-way ANOVA evaluated the relationship among gender and all variables.SettingIn a randomized order, participants slid down the hill three times with one sled, followed by three times with the other. Acceleration was captured with a PBC piezoelectric accelerometer connected to a Larson Davis Human Vibration Meter 100.ParticipantsFive males and seven females, age 7–14 years, were recruited for this study. Participants were a sample of convenience.ResultsThe measured accelerations exceeded safe levels with values ranging from 1.07 m/s² to 1330 m/s² (mean = 241.97 m/s²). Two-tailed t-test showed no significant difference in acceleration between sleds. A one-way ANOVA determined that there is no significant difference between gender or sled for any measured variables.ConclusionAcceleration magnitudes did not differ significantly between sled types or between genders. Peak acceleration levels were determined to be unsafe, in particular with regard to the forces transmitted to the spine.     

三苯基锡对热带爪蟾胚胎的致畸效应

用于船舶防污漆和农作物杀菌剂的三苯基锡(TPT)对淡水生态环境具有潜在的危害.用1 ～6 μgSn/L的TPT对热带爪蟾(Xenopus tropicalis)胚胎从NF11/12阶段开始进行72h暴露.结果表明,6μgSn/L暴露组胚胎的存活率比对照组降低了83％,3.5 μgSn/L及以上质量浓度的TPT暴露使胚胎的体长减少16％～35％,2.25μgSn/L及以上质量浓度暴露组胚胎的总畸形率均达100％.畸形现象主要包括眼睛异常,躯干拉长,泄殖腔突出,鳍变窄或消失,尾巴弯曲和皮肤色素减少等.在所有畸形表型中,TPT对鳍的影响最突出.暴露组胚胎的尾鳍宽度比对照组减少了17％ ～ 100％,并呈现明显的剂量效应关系.因此,TPT能抑制热带爪蟾胚胎的生长,并具有极强的致畸性,能特异性地阻碍爪蟾鳍的形成.     

Design and laboratory testing of a new flow-through directional passive air sampler for ambient particulate matter

A new type of directional passive air sampler (DPAS) is described for collecting particulate matter (PM) in ambient air. The prototype sampler has a non-rotating circular sampling tray that is divided into covered angular channels, whose ends are open to winds from sectors covering the surrounding 360°. Wind-blown PM from different directions enters relevant wind-facing channels, and is retained there in collecting pools containing various sampling media. Information on source direction and type can be obtained by examining the distribution of PM between channels. Wind tunnel tests show that external wind velocities are at least halved over an extended area of the collecting pools, encouraging PM to settle from the air stream. Internal and external wind velocities are well-correlated over an external velocity range of 2.0-10.0 m s?1, which suggests it may be possible to relate collected amounts of PM simply to ambient concentrations and wind velocities. Measurements of internal wind velocities in different channels show that velocities decrease from the upwind channel round to the downwind channel, so that the sampler effectively resolves wind directions. Computational fluid dynamics (CFD) analyses were performed on a computer-generated model of the sampler for a range of external wind velocities; the results of these analyses were consistent with those from the wind tunnel. Further wind tunnel tests were undertaken using different artificial particulates in order to assess the collection performance of the sampler in practice. These tests confirmed that the sampler can resolve the directions of sources, by collecting particulates preferentially in source-facing channels.     

防波堤:未来海岸线不可缺少的卫士

笔者航海多年,见证了世界各国不同的防波堤。 翻翻国内各种字典、词典,给防波堤的定义都是与海港有关．如《现代汉语词典》给的定义是：海港、大湖泊或水库中为了防止波浪冲击停泊的船只等而修建的建筑物,多用沙、石等材料筑成。随便在网上搜索一下,防波堤定义都没有跳出港湾这个圈子。     

Continuity,social change and Katrina

For some time, disaster researchers have looked for social change and mostly found continuity. This paper argues that shifting the focus from investigating social change to documenting continuity may enhance the understanding and planning of post‐disaster situations especially in industrialised societies like the United States. Drawing from qualitative data from post‐Katrina New Orleans, it proposes using the concept of continuity as an analytical device both to identify the axes of continuity and evaluate the likelihood and possible dimensions of social change. The analysis of long‐term recovery plans, along with field observations and interviews with evacuees, suggest that despite the well‐documented emergence of conflict in post‐Katrina New Orleans, the likelihood of social change appears limited.     

航电电源板层间CAF短路失效机理及退化时间分析

目的 掌握CAF失效机理MTTF分析方法,以便于在实际案例中实施工程优化决策,从而降低故障危害风险和寿命周期总费用。方法 以某航电电源母板CAF失效为例,基于CAF失效机理的物理化学变化时间特性模型算法,建立电压、介质间距和MTTF变化关系,以辅助工程优化决策。结果 基于仿真计算数据,形成对特定范围产品的改进和处置决策,从而限制失效危害风险的进一步扩散,降低了产品生命周期维护费用,并提升了客户满意度。结论 掌握装备常见失效机理和采取适宜的应对措施,是持续改进装备可用性、可靠性和环境适应性的必要条件。     

不同沉水植物净水能力与植株体细菌群落组成相关性

选取苦草(Vallisneria natans)、密刺苦草(Vallisneria denseserrulata)、黑藻(Hydrilla verticillata)、伊乐藻(Elodea canadensis)、金鱼藻(Ceratophyllum demersum)、竹叶眼子菜(Potamogeton malaianus)、篦齿眼子菜(Potamogeton pectinatus)和微齿眼子菜(Potamogeton maackianus)这8种亚热带地区常见的沉水植物为研究对象,在室内静水条件下对其氮、磷吸收和水质净化能力进行对比试验,并结合16S rRNA基因测序对沉水植物关联细菌群落组成进行测定,研究沉水植物对水体的净化能力与植株体菌群之间的相关性.结果表明,8种沉水植物对水体中的氮磷的去除主要通过植物增效作用,植物吸收富集作用去除率较低.其中密刺苦草对水体中TN、TP的去除率最高,达到了91. 58%和96. 81%.伊乐藻、金鱼藻对水中氮磷自身吸收能力高于其他组,密刺苦草和苦草的植物增效的净化能力最强.经分析,8种沉水植物对水体中氮磷的净化能力较强可能是因为植物关联的细菌大多具有降解作用.根瘤菌目(Rhizobiales)、伯克霍尔德氏菌目(Burkholderiales)、黄杆菌目(Flavobacteriales)、产碱杆菌科(Alcaligenaceae)、贪铜菌属(Cupriavidus)和芽孢杆菌属(Bacillales)的细菌可能是引起密刺苦草增效的净化能力较强的优势菌群,异常球菌纲(Deinococci)、丛毛单胞菌科(Comamonadaceae)、腐螺旋菌科(Saprospiraceae)和生丝微菌属(Hyphomicrobium)的细菌可能是引起苦草增效的净化能力较强的优势菌群.     

太原市城区夏季VOCs来源及其对O3生成的贡献

采集太原市城区夏季VOCs样品并分析其浓度特征,使用参数修正法得到VOCs初始浓度,分析其来源及对O₃生成的贡献.结果显示：太原市城区总VOCs平均浓度为48.13 μg/m³,烷烃（25.52 μg/m³）为主要组分.VOCs浓度呈明显日变化特征,在日间（10：00~14：00）光化学产生O₃的关键时段浓度最低.油品挥发、机动车排放、燃煤、植物排放与液化石油气/天燃气（LPG/NG）使用源对修正后环境VOCs的贡献分别为26.89%、25.55%、21.14%、14.99%、11.44%,对O₃生成的贡献分别为21.44%、33.10%、24.07%、13.77%、7.62%.机动车为新鲜排放气团VOCs的重要来源,而油品挥发、燃煤的输送与本地积累是其他（混合、夜间与反应）气团VOCs的重要来源.机动车排放、油品挥发与燃煤为VOCs与O₃生成的重要贡献源,控制此类源排放可减少太原市城区环境VOCs浓度并有效降低O₃生成.     

低剂量双酚A影响哺乳动物神经发育研究现状及争议

为全面认识低剂量BPA（双酚A）对哺乳动物神经发育的影响,本文从中国知网、PubMed和Web of Science 3个数据库中获取了国内外关于低剂量BPA影响哺乳动物神经发育的研究报道,并使用toxR工具对其可信度进行评估,最终筛选获得26项相关研究;从美国食品药品监督管理局（FDA）工作网站上获取最新BPA毒性报告1篇.通过比较分析这些研究,发现大部分研究报道低剂量BPA暴露导致哺乳动物神经行为、特定脑区内组织学结构和细胞特征、神经递质和激素稳态、脑中关键基因表达以及表观遗传特征发生改变.但是,就导致的神经行为的改变而言,一些研究的结果并不一致甚至有诸多矛盾之处.这些不一致的结果可能与动物实验设计的差异有关,其中神经行为测试的质量控制和统计方法中统计单元的选择对于研究结果的影响尤其值得关注.总之,从目前的文献来看,低剂量BPA对哺乳动物神经发育的影响尚待进一步的确认.     

Comparing dark- and photo-Fenton-like degradation of emerging pollutant over photo-switchable Bi2WO6/CuFe2O4: Investigation on dominant reactive oxidation species

The extensive use of tetracycline hydrochloride (TCH) poses a threat to human health and the aquatic environment. Here, magnetic p-n Bi₂WO₆/CuFe₂O₄ catalyst was fabricated to efficiently remove TCH. The obtained Bi₂WO₆/CuFe₂O₄ exhibited 92.1% TCH degradation efficiency and 50.7% and 35.1% mineralization performance for TCH and raw secondary effluent from a wastewater treatment plant in a photo-Fenton-like system, respectively. The remarkable performance was attributed to the fact that photogenerated electrons accelerated the Fe(III)/Fe(II) and Cu(II)/Cu(I) conversion for the Fenton-like reaction between Fe(II)/Cu(I) and H₂O₂, thereby generating abundant ?OH for pollutant oxidation. Various environmental factors including H₂O₂ concentration, initial pH, catalyst dosage, TCH concentration and inorganic ions were explored. The reactive oxidation species (ROS) quenching results and electron spin resonance (ESR) spectra confirmed that ?O₂^? and ?OH were responsible for the dark and photo-Fenton-like systems, respectively. The degradation mechanisms and pathways of TCH were proposed, and the toxicity of products was evaluated. This work contributes a highly efficient and environmentally friendly catalyst and provides a clear mechanistic explanation for the removal of antibiotic pollutants in environmental remediation.