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351.
The effect of increasing cadmium concentration (10, 100 and 1000 μmol dm‐3) on the growth, leaf area, content of assimilation pigments, cadmium content and the regulatory ability of the tissue of maize plants was investigated.

The results obtained document, already after 6 days, a significant decrease of dry weight, reduction of leaf area, chlorophyll a and b as well as carotenoids in plants grown in the nutrient solution containing 1000 μmol dm ‐3 of cadmium. A highly significant inhibition of growth, leaf area and assimilation pigments in plants growing in the nutrient solutions with 100 and 10 μmol dm‐3 of cadmium was registered after 17 days of cultivation. In plants growing in the nutrient solution containing 100 μmol dm‐3 of cadmium a demonstrable reduction of the content of assimilation pigments was registered after 11 days of culture.

With increasing cadmium concentration in the nutrient solution as well as in the plant tissue after 6 and 17 days of culture both the range of the regulatory zone and the extent of optimum pH increased into the acid region. The pH values of the isoelectric point decreased with increasing cadmium content in the solution.  相似文献   
352.
We study the introduction of new technologies when their costs are subject to idiosyncratic uncertainty and can only be fully learned through individual experience. We set up a dynamic model of clean experience goods that replace old polluting consumption options and show how optimal regulation evolves over time. In our base setting where social and private learning incentives coincide, the optimal tax on the polluting consumption is increasing over time. We show, however, that if social and private learning incentives diverge because the private discount rate exceeds the social discount rate, it may be optimal to temporarily increase the tax rate beyond net marginal external damages to induce more learning before reducing the tax rate to the steady state level. Alternatively, one could complement the tax with subsidies for first-time users which can be phased out over time. Similar results apply if consumers have biased expectations. We therefore give a rationale for introductory subsidies on new, clean technologies and non-monotonic tax paths from a perspective of consumer learning.  相似文献   
353.
The US corn ethanol industry has grown from virtually nothing in the early 1980s to over 14 billion gallons in 2011. Subsidies have been an important impetus for the industry, and they have existed in one form or another throughout the life of the industry. This paper provides (1) a brief look at the history of the linkages between energy and agriculture and how they have changed with biofuels; (2) a review of some of the major impacts of the US corn ethanol program; and (3) analysis of prospective impacts of cellulosic biofuels. There is no doubt that biofuels have brought about a new era for global agriculture. Historically, the prices of agricultural and energy products moved in response to supply and demand factors relevant to each market, but moved largely independent of one another. Corn ethanol has changed that, and today there is a link between crude oil and corn that is driven by the demand side. Since agricultural commodity prices are linked both on the demand and supply sides, the corn–crude oil link spills over to other agricultural commodities as well. Development of cellulosic biofuels has been much slower than hoped. The feedstocks are more expensive than initially believed. Conversion technologies remain uncertain and expensive. There are many uncertainties through the cellulosic supply chain, and government policy remains uncertain as well. Thus, the future of the cellulosic biofuels industry is, at this point, an open question.  相似文献   
354.
对美国和加拿大的水利工程生态调度管理框架和管理模式进行了系统分析.就间接(宏观)管理而言,美国和加拿大的生态调度从取水的许可证管理、保留水权的建立、水质标准、濒危物种保护和环境流量设置等方面进行管理;而在直接管理方面,主要包括对联邦水利工程的《濒危物种法》(ESA)符合性审查和非联邦水电站(5MW以上)的联邦能源管理委员会(FERC)的许可管理.通过分析中国水利工程生态调度管理中存在的问题,指出中国水利工程生态调度的体制和机制尚未有效建立,从明确生态需求、确定生态调度实施战略、加强基础研究工作以及建立和完善管理体制等方面,提出了加强中国生态调度管理的建议.在逐步建立流域生态调度管理体制的基础上,指出从生态补偿机制、参与协商机制、信息共享机制和监测反馈机制等方面建立和创新水利工程生态调度运行机制.  相似文献   
355.
The desire to avoid rousing community hostility may encourage firms to behave in an environmentally responsible manner. Firms may engage in corporate social responsibility (CSR) to maintain community support and/or to regain the support of a community where it has been lost. It has been conjectured that such ‘informal regulation’ could effectively replace formal intervention in some settings, and usefully complement it in others. We explore these conjectures with mixed results. Informal regulation is necessarily less efficient than a well-designed formal alternative and the pattern of green behavior induced by the threat of community hostility may increase or decrease welfare. The existence of community pressure may increase or decrease the optimal calibration of a formal intervention (in this case an environmental tax) and may complement or detract from the incentives generated by an optimally calibrated tax.  相似文献   
356.
根据耗散结构论、协同论、突变论等系统学理论和观点,探讨了生态城市系统的演化机理与调控措施。研究结果表明,生态城市系统的演化轨迹,就是生态城市系统从一个较低级的耗散系统,在竞争与协同这两大驱动机制的作用下,通过正/负反馈律、确定/随机律、变异/稳定律、渐变/突变律等一系列的内部自组织/他组织演化机制,推动着其生态流的平稳与涨落、系统功能的冲突与协调、空间结构的自构与被构,沿着螺旋式上升的轨迹发展成为更高等级的耗散系统的过程。要推动生态城市系统的良性发展,应从生产、流通、消费等方面对系统的结构和功能进行合理调控。  相似文献   
357.
We investigate work motivation in the unstudied domain of individuals who pursue very long‐term goals. We highlight the fact that the preponderance of research findings on the psychology of work motivation is based on short‐term studies and discuss the potential relevance to long‐term motivation of literatures including long‐term thinking and time horizons, long‐term goals and goal pursuit, and self‐regulation. We adopt the qualitative research strategy of theory elaboration, with a specific intention of elaborating goal‐setting theory. Analysis of interview data from a unique sample of scientists and others pursuing goals spanning decades or more yielded a structure of psychological factors that can enhance, support, and sustain motivation for the long term. Reconciling our findings with existing goal theories, we develop an integrative model of motivating factors and self‐regulation processes underlying long‐term goal pursuit. We discuss the implications, including an expanded focus for our field on motivating people for the long run. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
358.
为了解当前安全生产规制政策的总体效果与强度,弄清安全生产规制政策的改进方向,完善安全生产监管体制,提高监管的有效性,有必要对安全生产规制效果进行分析和评价。在总结分析安全生产规制效果影响因素的基础上,建立多因素、多层次的安全生产规制总体效果评估指标体系,主要由安全生产规制体制、安全生产规制的内容及方式、规制政策的可靠实施、被规制者特征等4个一级指标及所属14个二级指标构成。借助层次分析法(AHP)和模糊数学方法,构建安全生产规制总体效果模糊定量评估模型。利用该模型试算中国1991—2001年间安全生产规制总体效果,计算结果与实际情况基本相符。但该模型是不完美的,其不能搞清楚各因素变量与规制效果之间存在的具体相关关系。  相似文献   
359.
安全生产监管机制是否健全对于安全监管工作落实具有非常重要的影响,在当前经济转型发展的特殊背景下,建立科学合理的长效监管机制具有重要现实意义。分析伴随经济转型而来的安全生产快速发展现象,进而涌现出的许多生产安全新问题及其相互关系,对此总结得出安全生产各方面监管机制存在的不足。从安全生产监管机制薄弱环节出发并结合经济转型的发展特点,提出建立宏观调控监管机制体系的发展对策,并重点对该机制下的基层监管运行方式进行相应研究。有关研究内容有助于安全监管长效机制的建立,对提高监管水平具有重要的作用。  相似文献   
360.
欧洲的恶臭污染法规及测试技术进展   总被引:1,自引:0,他引:1  
欧洲城市中人口密度的增加导致了严重的恶臭污染,几百年来,各种有关恶臭污染的法规相继出台。在过去的30年中,恶臭测试方法有所发展,人们不再轻信环境健康工作者的主观判断,而是将恶臭测试推向定量化的轨道。根据恶臭排放测试,扩散模式以及恶臭标准(以定量恶臭性质的影响研究为基础,确定恶臭污染的可忍受程度),荷兰率先推动了恶臭量化管理趋势。恶臭标准根据各行业的恶臭污染的具体程度制定。嗅觉计测试臭气浓度是一项可靠的技术,目前已经写入欧洲标准(EN13725:2003),将嗅觉计测试法和日本的三点式比较臭袋法进行比较,发现结果具有显著的一致性。嗅辨员的严格筛选也是促成其一致性的关键因素。  相似文献   
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