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21.
We study the duopolistic interaction between two monopolists located in two different countries who sell an imperfect substitute good in two markets. The traded good is transported between the two nations on ships using solid wood packing materials (SWPMs) and hence the presence of one or more invasive species is a problem. We use a game model to analyze this interaction in three steps. First, we study the benchmark case of autarky or no trade between the two nations. Second, we introduce transport costs and then study the effect of free trade on the profits of the two monopolists. Finally, we suppose that invasive species are present in the SWPMs. This fact requires compliance with an environmental protocol. We model this compliance by increasing the transport costs associated with trade and then demonstrate that a version of the so called Porter hypothesis holds. In other words, we show that compliance with a cost increasing environmental protocol can give rise to higher profits for the two monopolists under consideration.  相似文献   
22.
根据张集铁路绿色通道建设的需要,在张集铁路集宁地区路基边坡实施树种选择试验。在试验中,对应试树种的发芽率、生长量及越冬率等方面进行调查,根据调查数据分析,筛选出适合该项目路基边坡防护的树种,旨在为全线路基边坡植物防护的实施提供依据。  相似文献   
23.
生物污损造成的环境生态破坏问题是近些年来海洋环境保护工作者研究的一个热点问题。船舶的生物污损带来的外来物种入侵问题也引起了IMO的高度关注,该问题在2008年召开的散装液体和气体分委会(BLG)第12次会议上成为正式议题。文中简要介绍了船舶生物污损的危害,结合国外一些国家对生物污损问题的管理经验,与压栽水公约的立法过程进行对比,针对IMO可能采取的立法措施进行了分析,对我国航运业应采取的应对措施提出了意见和建议。  相似文献   
24.
The warm oceanic current Kuroshio and the continental shelf water of the East China Sea meet in the western North Pacific, north of Taiwan and form an upwelling when they converge. The intrusion of the Kuroshio westward over the East China Sea shelf thus results in complicated exchanges of waters between these two water masses. We studied the copepods in the plankton collection taken from an east–west transect crossing these waters in April 1995 when the intrusion of the Kuroshio over the East China Sea shelf was beginning to retreat. The taxonomy of copepods was carefully treated and erroneous species records reported in the literature were guarded against. We evaluated the copepod diversity, the association of copepod species, and the association of stations in these water masses.  相似文献   
25.
Zooplankton communities were studied in southeastern Beaufort Sea (Arctic Ocean) in September–October 2002. Cluster analysis and non-metric multidimensional scaling revealed three distinct mesozooplankton assemblages. A neritic assemblage occurred on the Mackenzie Shelf and in Franklin Bay, while distinct off-shelf assemblages prevailed in the Cape Bathurst Polynya and on the Beaufort Slope respectively. Over 95% of the mesozooplankton was comprised of eight copepod taxa. Pseudocalanus spp. contributed predominantly to the discrimination of the three assemblages and was the only significant indicator of the Shelf assemblage. Oithona similis, Oncaea borealis, Metridia longa and Calanus hyperboreus were indicators of the Polynya assemblage. Cyclopina sp. and Microcalanus pygmaeus were indicative of the overall off-shelf community (Polynya and Slope assemblages). The importance of omnivores and carnivores increased from the shelf to the polynya and the slope. Station depth and duration of reduced ice conditions during summer (< 50% ice concentration) underpinned the distribution of the assemblages (r2 = 0.71 and 0.45 respectively). The abundance of Pseudocalanus spp. was independent of depth and increased with the duration of reduced ice conditions (rs = 0.438). The abundance of Cyclopina sp., M. pygmaeus and other indicators of the offshore assemblages followed the opposite trend (rs = − 0.467 and − 0.5 respectively). Under continued climate warming, a reduction of the ice cover will affect the biogeography of mesozooplankton on and around the Mackenzie Shelf, to the potential advantage of Pseudocalanus spp. and other calanoid herbivores.  相似文献   
26.
目的 探讨Peroxiredoxin (Prx)1基因的小分子干扰RNA(siRNA)对人肝癌细胞系HepG2和SMMC-7721的放射增敏作用及机制.方法 通过逆转录PCR方法研究Prx家族(Prx1~6)在人肝癌细胞HepG2和SMMC-7721中的mRNA表达谱;使用siRNA敲低HepG2和SMMC-7721细...  相似文献   
27.
目的通过评价线粒体功能研究线粒体介导的caspase-9激活通路参与成人大骨节病关节软骨细胞凋亡的机制。方法关节软骨细胞培养,Hoechst 33258染色检测软骨细胞核形态,流式细胞仪检测软骨细胞凋亡率和细胞内活性氧含量,Western bloting检测细胞色素c的表达,荧光法检测caspase-9和caspase-3活性。结果大骨节病患者关节软骨细胞较正常软骨细胞凋亡百分率增加,线粒体细胞色素c释放,caspase-9和caspase-3活性增高,且活性氧含量增加。结论线粒体氧化应激参与了大骨节病软骨细胞的病理生理变化,线粒体功能障碍可能在大骨节病关节软骨细胞凋亡过程发挥了重要作用。  相似文献   
28.
长白山区公路生态恢复的植物选择   总被引:1,自引:0,他引:1  
长白山区森林面积较大,植被覆盖率高,是整个欧亚东大陆北半球上物种最丰富的地区及中国生物多样性保护的关键区域[1]。目前,长白山区新建或改建公路较多,如何选择植物种类进行公路生态恢复成为长白山区公路建设亟需解决的问题。  相似文献   
29.
海洋生物入侵已成为世界海洋生态环境面临的四大问题之一。我国目前针对海洋外来生物入侵的数据资料缺乏,且未形成时空分布的数据系统。本文通过文献查找、资料收集与历史数据整理,现场调研等多种手段,拟掌握我国近海外来生物入侵时空演变历史及现状,提出基于GIS软件的数据库系统的建设方案。本系统的建设可实现海洋入侵物种查询,外来入侵物种判定、不同时期下,外来生物入侵我国近海海域的发生地点、入侵种类、灾害发生时间、灾害影响的对比分析等功能。  相似文献   
30.
膨胀土地区公路边坡绿化植物种类组合研究按文献研究、实地考察、室内分析三个方面的研究进行,通过对草本、木本植物固坡及水土保持功能以及草本、木本植物群落特点的比较,结合依托工程,得出了三个膨胀土路域最佳人工植物群落组合,这对于膨胀土地区公路边坡绿化防护具有重要的指导价值。  相似文献   
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