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排序方式: 共有1048条查询结果,搜索用时 187 毫秒
91.
Paoletti E Contran N Manning WJ Castagna A Ranieri A Tagliaferro F 《Environmental pollution (Barking, Essex : 1987)》2008,155(3):464-472
Treatments with ethylenediurea (EDU) protect plants from ozone foliar injury, but the processes underlying this protection are poorly understood. Adult ash trees (Fraxinus excelsior), with or without foliar ozone symptoms in previous years, were treated with EDU at 450ppm by gravitational trunk infusion in May-September 2005 (32.5ppmh AOT40). At 30-day intervals, shoot growth, gas exchange, chlorophyll a fluorescence, and water potential were determined. In September, several biochemical parameters were measured. The protective influence of EDU was supported by enhancement in the number of leaflets. EDU did not contribute its nitrogen to leaf tissue as a fertiliser, as determined from lack of difference in foliar N between treatments. Both biochemical (increase in ascorbate-peroxidase and ascorbic acid, and decrease in apoplastic hydrogen peroxide) and biophysical (decrease in stomatal conductance) processes regulated EDU action. As total ascorbic acid increased only in the asymptomatic trees, its role in alleviating O(3) effects on leaf growth and visible injury is controversial. 相似文献
92.
The dyadic level of conceptualization and analysis: A missing link in multilevel OB research? 下载免费PDF全文
Despite burgeoning multilevel research in organizational behavior over the past two decades, our understanding of dyadic relationships at work remains underdeveloped. Focusing on leader–member exchange, we discuss conceptual and methodological challenges that have hampered research at this level and illustrate how and why such analysis might provide new insights. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
93.
The properties of electro-activated (EA) aqueous solutions as well as the dynamics of their changes were considered in the current study using aqueous solutions of NaCl and NaHCO3. The concentrations of the salt solutions were 0.5, 0.25, 0.125 and 0.05 M. The tests were performed at the DC current densities of 25, 37.5, and 50 Å/m2. The electro-activation reactor consisted of three individual cells assembled together and separated by anion-exchange (AEM) and cation-exchange (CEM) membranes. During the experiments, four configurations of the membrane placements and solutions concentrations were studied. The obtained results showed the dynamics of the electro-activation process that allows obtaining electro-activated solutions with targeted properties such as pH and oxydo-reduction potential (ORP). It was possible to obtain electro-activated solutions at the anodic side (acid anolyte) with pH of 3.0, 3.5, and 4.0 and ORP of +1100 ± 15 mV when NaCl solution was used as electrolyte. Furthermore, several types of electro-activated solutions with high redox potential (ORP = +921 ± 12 mV) and neutral pH (6.48 ± 0.05) were obtained on the anode side when sodium carbonate was used. At the same time, two types of solutions, one with acid pH (2.14 ± 0.14) and the other one with alkaline pH (10.46 ± 0.03) with ORP = +689 ± 10 and 110 ± 21 mV, respectively, were obtained in the central compartment which considered as electro-activated solutions obtained by means of noncontact electro-activation. 相似文献
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95.
《环境工程》2015,33(1)
针对注烟道气稠油热采中管道输送烟道气酸凝结问题,以连续性方程、能量方程和动量方程为基础建立了烟道气沿管道流动与传热计算模型,计算了烟道气沿管道的压力分布、温度分布和酸凝结点距离,分析了不同入口参数和烟道气成分对管道中烟道气的压力、温度、酸凝结点的影响。结果表明:SO3或水蒸汽含量增加时,烟道气酸凝结点温度提高,凝结点距离减小;入口烟道气压力提高,烟道气压降变小,温降不变,酸凝结点距离减小;入口烟温升高,压降和温降都增大,酸凝结点距离增大;保温层厚度增加,温降减小,酸凝结点距离增大。计算和分析结果表明:减少烟道气中SO3或水蒸汽含量可以有效地增大酸凝结点距离,减轻管道腐蚀问题。 相似文献
96.
Simona Caprarescu Mihai Cosmin Corobe Violeta Purcar Catalin Ilie Spataru Raluca Ianchis Gabriel Vasilievici Zina Vuluga 《环境科学学报(英文版)》2015,35(9):27-37
Heterogeneous membranes were obtained by using styrene-acrylonitrile copolymer (SAN) blends with low content of ion-exchanger particles (5 wt.%). The membranes obtained by phase inversion were used for the removal of copper ions from synthetic wastewater solutions by electrodialytic separation. The electrodialysis was conducted in a three cell unit, without electrolyte recirculation. The process, under potentiostatic or galvanostatic control, was followed by pH and conductivity measurements in the solution. The electrodialytic performance, evaluated in terms of extraction removal degree (rd) of copper ions, was better under potentiostatic control then by the galvanostatic one and the highest (over 70%) was attained at 8 V. The membrane efficiency at small ion-exchanger load was explained by the migration of resin particles toward the pores surface during the phase inversion. The prepared membranes were characterized by various techniques i.e. optical microscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis and differential thermal analysis and contact angle measurements. 相似文献
97.
利用灰色预测法对上海市入境旅游11个国家和地区的赴沪旅游者人数和旅游外汇收入进行了预测,推断出上海市入境旅游市场中不同国家和地区的市场潜力;运用灰色关联分析法,探索不同市场潜力等级的入境旅游国家和地区与上海市旅游外汇收入间的关系.针对亚洲和欧美各国家或地区的实际情况,提出了针对性的对策和建议. 相似文献
98.
Joseph N.T. Darbah Mark E. Kubiske Katre Kets Anu Sober David F. Karnosky 《Environmental pollution (Barking, Essex : 1987)》2010,158(4):983-19373
Photosynthetic acclimation under elevated carbon dioxide (CO2) and/or ozone (O3) has been the topic of discussion in many papers recently. We examined whether or not aspen plants grown under elevated CO2 and/or O3 will acclimate after 11 years of exposure at the Aspen Face site in Rhinelander, WI, USA. We studied diurnal patterns of instantaneous photosynthetic measurements as well as A/Ci measurements monthly during the 2004-2008 growing seasons. Our results suggest that the responses of two aspen clones differing in O3 sensitivity showed no evidence of photosynthetic and stomatal acclimation under either elevated CO2, O3 or CO2 + O3. Both clones 42E and 271 did not show photosynthetic nor stomatal acclimation under elevated CO2 and O3 after a decade of exposure. We found that the degree of increase or decrease in the photosynthesis and stomatal conductance varied significantly from day to day and from one season to another. 相似文献
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100.
工业废水中测定六价铬的预处理技术 总被引:3,自引:0,他引:3
根据复合絮凝剂与阳离子交换树脂两者在分离与处理技术上所起的不同作用 ,提出了将两法联合用作工业废水中测定Cr6 的预处理技术 ,通过一系列条件试验 ,确定最佳预处理条件。结果表明 ,该法具有去色、去浊率高 ,分离效果佳 ,排除干扰离子能力强 ,分析样品重现性好 ,准确度高 ,操作简便、快捷的优点。 相似文献