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This report reviews the literature of sequential or within-event precipitation sampler construction and includes a limited survey of their applications. Collection apparatus have been classified as manually segmenting samplers, linked collection vessels, automatically segmenting samplers and continuous monitors (Robertson et. al., U.S. EPA Report, 1980). Design criteria for an ideal collector are discussed.  相似文献   

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<正>近年来,随着我国的社会转型和技术发展,各种"环境风险议题"密集出现,成为媒体的焦点,有时甚至引发民众恐慌与一定程度的社会对抗。比如各地民众反对PX项目、垃圾焚烧项目、以及反核项目就是如此。诸多环境事件以邻避运动形态出现,在一定程度上影响了公共利益的最大化,造成了政府和民众的"双输"困局。这种双输局面的根源则在于政府和民众之间缺乏更为制度化的有效沟通方  相似文献   

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粮食与营养安全研究评述及展望   总被引:1,自引:0,他引:1  
当前国际粮食安全局势堪忧,大多数发展中国家饥饿、营养素缺乏与营养过剩三重困境并存,实现全球粮食安全与营养安全的双重目标任重道远。本文梳理了95篇文献,旨在理清粮食与营养安全的发展脉络及演变规律,提出中国未来粮食与营养安全的研究重点。首先对全球粮食与营养安全的概念演变进行回顾,指出粮食安全概念由谷物供给总量安全到所有食物数量安全、再到食物质量与营养安全与可持续内涵的动态演化,由单一可供应维度向可供应、可获得性、可利用性、稳定性、可持续性多维度不断拓展。随后,从宏观国家层面梳理中国粮食与营养需求分析及预测、粮食生产能力和进口能力的相关研究,从微观家庭及个人层面评述收入、市场、城镇化、农户农业生产对食物消费及营养的影响。最后,基于未来城乡居民营养均衡发展目标,对中国粮食与营养安全研究的主要趋势和未来研究重点作出展望,指出未来展开对农业生产多样性、作物种植结构调整及作物营养强化,城镇化与市场建设的影响,城市中低收入人群和农村贫困人口营养问题的研究具有重大意义。  相似文献   

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文章基于文献综述梳理和探究长江经济带绿色发展的研究现状、状态水平、空间格局及制约因素等,结果表明:长江经济带绿色发展水平呈稳步上升趋势,在全国处于中上游水平;整体而言,长江经济带经济增长质量略滞后于生态环境治理,生态系统健康与生态服务是新时期长江经济带绿色发展的重点工作;长江经济带绿色发展水平空间差异明显,下游更易受资源环境的约束,中游面临产业结构固化的困境,上游发展绿色经济动能乏力;长江经济带既有的增长方式和发展模式形成了较难转型的路径依赖,在创新驱动发展、优化资源配置、改善协调关系等方面还需进一步加强。本文结合相关研究和热点进行述评,以期为长江经济带在多重目标下寻找平衡,创新绿色发展模式提供借鉴和参考。  相似文献   

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作为新发展理念之一,绿色发展是当前研究的重点议题。本文从绿色发展的内涵实质、评估工具和方法以及绿色发展路径三个层面对已有文献进行了梳理,力图呈现国内关于绿色发展研究的进展脉络,明晰进一步研究的重点和方向。文献梳理发现,现有研究主要从概念构成、内涵维度、理论辨析和演化脉络四个方面阐释绿色发展的理论内涵,理论深度和广度都存在一定的不足,与主流经济发展理论的衔接存在较大距离。关于绿色发展评估,主要从投入产出效率、综合绩效、环境与经济协调三个视角进行,但是目前仍然缺少一个兼顾地域差别的公允性工具和方法。针对绿色发展路径的研究呈现出理论机制较少、实践路径较多的特点,但实践路径的研究仍较为宏观和宽泛,中微观尺度的研究较为欠缺。这些都有待在进一步的研究中深化和拓展。  相似文献   

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Mercury is an important pollutant, released into aquatic ecosystems both naturally and by anthropogenic action. This element is transferred to aquatic organisms in different ways, causing potential health risks. In addition, mercury can be accumulated by humans, especially through the consumption of contaminated food. This systematic review aims to present mercury pathways, the major routes through which this element reaches the aquatic environment and its transformations until becoming available to living animals, leading to bioaccumulation and biomagnification phenomena. The key biotic and abiotic factors affecting such processes, the impact of mercury on animal and human health and the issue of seafood consumption as a source of chronic mercury contamination are also addressed. A total of 101 articles were retrieved from a standardized search on three databases (PubMed, Emabse, and Web of Science), in addition to 28 other studies not found on these databases but considered fundamental to this review (totaling 129 articles). Both biotic and abiotic factors display fundamental importance in mediating mercurial dynamics, i.e., muscle tropism, and salinity, respectively. Consequently, mercurial contamination in aquatic environments affects animal health, especially the risk of extinction species and also on human health, with methylmercury the main mercury species responsible for acute and chronic symptomatology.  相似文献   

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In this overview the current knowledge of the relationship between an increased nuchal translucency (NT) measurement and fetal heart structure and function in chromosomally normal fetuses is reviewed. Relevant pathophysiological theories behind the increased NT are discussed. Fetuses with an increased NT have an increased risk for congenital heart disease (CHD) with no particular bias for one form of CHD over another. This risk increases with increasing NT measurement. Although the NT measurement is only a modestly effective screening tool for all CHD when used alone, it may indeed be effective in identifying specific CHD “likely to benefit” from prenatal diagnosis. The combination of an increased NT, tricuspid regurgitation and an abnormal ductus venosus (DV) Doppler flow profile, is a strong marker for CHD. A fetal echocardiogram should be performed at 20 weeks' gestation in fetuses with an NT ≥ 95th percentile but < 99th percentile. When the NT measurement is ≥ 99th percentile, or when tricuspid regurgitation and/or an abnormal DV flow pattern is found along with the increased NT, an earlier echocardiogram is indicated, followed by a repeat scan at around 20 weeks' gestation. The resultant increased demand for early fetal echocardiography and sonographers with this special expertise needs to be planned and provided for. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

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Many problems in drinking water distribution systems (DWDSs) are caused by microbe, such as biofilm formation, biocorrosion and opportunistic pathogens growth. More iron release from corrosion scales may induce red water. Biofilm played great roles on the corrosion. The iron-oxidizing bacteria (IOB) promoted corrosion. However, when iron-reducing bacteria (IRB) and nitrate-reducing bacteria (NRB) became the main bacteria in biofilm, they could induce iron redox cycling in corrosion process. This process enhanced the precipitation of iron oxides and formation of more Fe3O4 in corrosion scales, which inhibited corrosion effectively. Therefore, the IRB and NRB in the biofilm can reduce iron release and red water occurrence. Moreover, there are many opportunistic pathogens in biofilm of DWDSs. The opportunistic pathogens growth in DWDSs related to the bacterial community changes due to the effects of micropollutants. Micropollutants increased the number of bacteria with antibiotic resistance genes (ARGs). Furthermore, extracellular polymeric substances (EPS) production was increased by the antibiotic resistant bacteria, leading to greater bacterial aggregation and adsorption, increasing the chlorine-resistance capability, which was responsible for the enhancement of the particle-associated opportunistic pathogens in DWDSs. Moreover, O3-biological activated carbon filtration-UV-Cl2 treatment could be used to control the iron release, red water occurrence and opportunistic pathogens growth in DWDSs.  相似文献   

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Cystic hygromas have historically been associated with a grim prognosis when discovered during prenatal sonographic study of the fetus. This same grim prognosis is not observed by the paediatric surgeon who evaluates the neonate or paediatric patient. We present a fetal patient with a massive anterior cystic hygroma discovered in the third trimester prior to 30 weeks. This case and a review of the literature suggest tailoring the prognosis by category when counselling patients: (1) first trimester, normal karyotype-good; (2) first trimester, abnormal karyotype-poor; (3) second trimester and early third-poor to guarded; and (4) mid to late third trimester-good.  相似文献   

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1 IntroductionDuringthepastfewyears,membraneseparationshavebecomemorewidelyused,andreplacedsomeoftheconventionalconcentrationt?..  相似文献   

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While the concepts of remanufacturing and reverse logistics are gaining popularity in practice, the available literature and theory on strategic decision making in these areas are limited. This paper is designed to address this gap, in particular, for the automotive industry aftermarket. In doing so, the authors reviewed literature pertaining to: customer demand(s), product design and development, cost-benefit analysis of reman, core (i.e., used product) supply management, reman competencies and skills, product life cycle strategies, reman and reverse logistics network design, relationships among key stakeholders, environmental considerations, regulations, and impact of emerging economies. The literature findings along with our experience in working with automotive reman products were used as inputs to guide the formulation of seven major propositions for the strategic factors in decision making within reman. The propositions were then tested through a case study. The case study reconfirmed many of the factors like product life cycle, regulations, etc. from the literature review and also identified new factors like OE customer requirements. Our results provide a foundation for further research for companies that deal with Original Equipment (OE) Sales, Original Equipment Service (OES), as well as Independent Aftermarket (IAM) business in the automotive industry.  相似文献   

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