Association of serum levels of perfluoroalkyl substances with gestational diabetes mellitus and postpartum blood glucose

This study was conducted to examine the association of perfluoroalkyl substance(PFAS)exposure with gestational diabetes mellitus(GDM) risk and postpartum fasting blood glucose.We used a 1:2 matched case–control study with 84 GDM subjects and 168 healthy pregnant women from Beijing, China. The maternal blood was collected at 1–2 days before delivery, and eight linear isomers and fourteen branched isomers were determined in maternal serum.Logistic regression analyses were performed to evaluate the associations after adjusting for potential confounders. The median of the sum of levels of total PFASs was 4.24 ng/m L with a interquartile range(IQR) of 2.82–6.54 ng/m L. Although maternal PFAS exposure was not associated with risk of GDM, significant positive associations were observed between evaluated exposure to specific PFAS congeners and increasing blood glucose. The odds ratio(ORs) of the highest category of postpartum fasting blood glucose for perfluoro-1-metylheptylsulfonat(1 m-PFOS), perfluoro-3/4-metylheptylsulfonat(3 m+4 m-PFOS), perfluoro-5-metylheptylsulfonat(5 m-PFOS), and perfluorohexane sulfonate(PFHx S) were 2.03(95% CI: 1.09–3.77), 1.93(95% CI:1.04–3.58), 2.48(95% CI: 1.33–4.65), and 2.26(95% CI: 1.21–4.21), respectively, suggesting negative effects of maternal exposure to specific PFAS compounds on glucose metabolism.     

APEC期间北京市PM_(2.5)时空分布与过程分析

运用Models-3/CMAQ模式系统,模拟分析了2014年11月3~11日APEC会议期间北京市PM_(2.5)污染的时空分布特征,并利用过程分析工具IPR研究了会期两次短时间污染过程(4日13:00~5日12:00和10日13:00~11日12:00)中各种大气物理化学过程对城区官园和郊区定陵两个代表性站点近地面PM_(2.5)生成的贡献.结果表明,CMAQ模型合理地再现了北京市PM_(2.5)的浓度水平和时间变化.北京地区4日和10日发生不利于污染物扩散的气象条件,导致PM_(2.5)小时浓度出现高值(分别为188,124μg/m~3),但受减排措施和冷高压的作用,PM_(2.5)高值维持时间较短.4日13:00~5日12:00,水平传输是官园和定陵站点PM_(2.5)的主要贡献者,贡献率分别为49.6%和90.9%.此次污染过程北京地区受南部污染传输影响较强.10日13:00~11日12:00,官园站点PM_(2.5)主要来自源排放在本地的积累(78.8%),定陵站点PM_(2.5)主要来自较弱的水平传输(93.9%).此次过程体现出更加明显的局地性污染特征.两次过程中,PM_(2.5)的主要去除途径均为垂直传输.     

聚氨酯固化剂清洁生产技术分析

研究以一个利用分子蒸馏技术生产聚氨酯固化剂的大型新建项目为例,对其原料、产品、工艺和设备进行类比分析,提出了在聚氨酯固化剂生产中推行清洁生产的建议和措施,以期为制造单位在今后的工艺、工程设计、清洁生产和环境管理等方面提供一些科学依据。     

海军某型飞机典型电连接器失效分析

目的分析得出电连接器失效的主要原因。方法以海军某型飞机三个型号典型电连接器插孔端为主要研究对象,对电连接器宏观形貌进行目视检查分析,并采用扫描电子显微镜进行微观形貌观察,采用能谱分析仪进行微观成分分析,研究壳体表面和插孔接触面的化学成分组成。结果腐蚀和磨损是外场电连接器失效的主要诱因,电连接器有一定程度的局部腐蚀,表面积聚的灰尘和海盐颗粒对腐蚀有较明显的促进作用。插拔不当造成的插针与插孔间同心度的偏差,与微动磨损共同作用加速了局部腐蚀。结论插拔不当、微振磨损与局部腐蚀是导致电连接器性能下降乃至失效的三大主要因素。     

汲取液对正渗透微生物燃料电池处理垃圾渗滤液的影响

以垃圾渗滤液为阳极液,系统研究了汲取液种类和浓度对正渗透微生物燃料电池(OsMFC)工艺处理垃圾渗滤液性能的影响.结果表明,在汲取液为氯化钠的情况下,OsMFC工艺的最大功率密度可达0.44 W·m~(-2),表观内阻为236.75Ω,水通量为0.98 L·m~(-2)·h~(-1),TOC、NH_4~+-N、TN和TP的去除率分别达到89.51%、93.27%、94.01%和96.95%,均好于碳酸氢钠和碳酸氢铵作为汲取液时的处理效果.此外,氯化钠汲取液浓度越大,产电性能越好,表观内阻越小,水通量越大.产电性能随汲取液浓度的增大变化不大,在汲取液浓度为1 mol·L~(-1)的情况下,水通量和盐返混量的比值最大,处理效果最好.     

A model of fishing vessel accident probability

Problem: Commercial fishing is one of the least safe occupations. Method: The researchers develop a fishing vessel accident probability model for fishing areas off the northeastern United States using logit regression and daily data from 1981 to 1993. Results: The results indicate that fishing vessel accident probability declined over the study period. Higher wind speed is associated with greater accident probability. Medium-size vessels have the highest accident probability, while small vessels have the lowest. Within the study region, accident probability is lower in the southwestern section than in the northeastern section. Accidents are likely to occur closer to shore than offshore. Accident probability is lowest in spring. Impact on Industry: The probability model is an important building block in development and quantitative assessment of management mechanisms related to safety in the commercial fishing industry.     

阳(阴)离子复配修饰两性磁性膨润土的表面特征差异及对苯酚吸附的影响

以膨润土(BT)为基质,采用共沉淀法制备负载Fe3O4的磁性膨润土(MBT),在两性表面活性剂十二烷基二甲基甜菜碱(BS-12)修饰(BS-MBT)的基础上,以阳离子表面活性剂十六烷基三甲基溴化铵(CTMAB)/阴离子表面活性剂十二烷基磺酸钠(SDS)为复配修饰剂,通过湿法分别制备2种两性复配修饰磁性膨润土(BS-CT-MBT/BS-SDS-MBT),采用扫描电镜、X-射线衍射、热重、红外光谱对样品进行表征,测定磁性、比表面积和孔容等性质,通过批处理实验法对比两性复配修饰磁性膨润土对苯酚的吸附.结果表明,两性复配修饰膨润土具有良好的磁分离性能.与BS-MBT相比,BS-CT-MBT的C、N质量分数增大,复配修饰剂质量分数增加,孔容和比表面积减小,BS-SDS-MBT的C、N质量分数减小,复配修饰剂质量分数减少,孔容减小,比表面积增大.在pH 6.0的0.1 mol·L~(-1)Na Cl溶液中各修饰剂的解吸率低于9%.各土样对苯酚的等温吸附数据符合Henry模型,以分配吸附为主,吸附量顺序为BS-CT-MBTBS-MBTBS-SDS-MBTBTMBT,修饰剂质量分数是影响苯酚吸附的决定性因素,CTMAB提升土样吸附苯酚能力的效果高于SDS.     

The enigma of progress in denitrification research.

Humans have dramatically increased the amount of reactive nitrogen (primarily ammonium, nitrogen oxides, and organically bound N) circulating in the biosphere and atmosphere, creating a wide array of desirable products (e.g., food production) and undesirable consequences (e.g., eutrophication of aquatic ecosystems and air pollution). Only when this reactive N is converted back to the chemically unreactive dinitrogen (N2) form, do these cascading effects of elevated reactive N cease to be of concern. Among the quantitatively most important processes for converting reactive N to N2 gas is the biological process of classical denitrification, in which oxides of nitrogen are used as terminal electron acceptors in anaerobic respiration. This Invited Feature on denitrification includes a series of papers that integrate our current state of knowledge across terrestrial, freshwater, and marine systems on denitrification rates, controlling factors, and methodologies for measuring and modeling denitrification. In this paper, we present an overview of the role of denitrification within the broader N cycle, the environmental and health concerns that have resulted from human alteration of the N cycle, and a brief historical perspective on why denitrification has been so difficult to study. Despite over a century of research on denitrification and numerous recent technological advances, we still lack a comprehensive, quantitative understanding of denitrification rates and controlling factors across ecosystems. Inherent problems of measuring spatially and temporally heterogeneous N2 production under an N2-rich atmosphere account for much of this slow progress, but lack of interdisciplinary communication of research results and methodological developments has also impeded denitrification research. An integrated multidisciplinary approach to denitrification research, from upland terrestrial ecosystems, to small streams, river systems, estuaries, and continental shelf ecosystems, and to the open ocean, may yield new insights into denitrification across landscapes and waterscapes.     

富氡地热水中δ34SSO42-、δ13CDIC同位素特征及其意义—以息烽温泉为例

贵州息烽温泉被誉为"亚洲第一氡泉",富含多种有益元素.选取息烽地热水和与其有关的地表径流水及岩溶泉水为研究对象,利用水文地球化学、δ34SSO2-、δ13CHco3-同位素等方法对区内富氡地热水中硫、碳元素来源及水-岩作用过程进行研究.结果 显示,地热水水化学类型为HCO3·SO4-Ca·Mg型,pH呈弱碱性,其阴离子...     

混凝土锈胀开裂的抑制措施

钢筋锈蚀是影响混凝土结构耐久性最重要的因素。钢筋锈胀体积膨胀,对周围混凝土产生压力,继而导致保护层的受拉开裂,出现锈胀裂缝,这对结构整体的安全性和耐久性十分有害。研究混凝土锈胀裂缝的抑制措施,对提高结构的耐久性具有重要意义。从结构构造入手,以快速通电加速纵向钢筋锈蚀的方法,研究了混凝土保护层厚度和箍筋间距对混凝土构件锈胀开裂的影响;同时通过计算机仿真,对试验构件进行了数值试验。在此基础上,建立了构件表面应力与混凝土保护层厚度及箍筋间距的相关关系,得到了不同保护层厚和箍筋间距对试件表面锈胀裂缝的影响规律。