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1.
There is a general consensus that most of today’s nonvenomous snakes are descendants of venomous snakes that lost their venomous capabilities secondarily. This implies that the evolutionary history of venomous snakes and their venom apparatus should be older than the current evidence from the fossil record. We compared some of the oldest-known fossil snake fangs from the Lower Miocene of Germany with those of modern viperids and elapids and found their morphology to be indistinguishable from the modern forms. The primary function of recent elapid and viperid snake fangs is to facilitate the extremely rapid, stab-like application of highly toxic venoms. Our findings therefore indicate that the other components of the venom-delivery system of Early Miocene vipers and elapids were also highly developed, and that these snakes used their venom in the same way as their modern relatives. Thus, the fossil record supports the view that snakes used their venoms to rapidly subdue prey long before the mid-Tertiary onset of the global environmental changes that seem to have supported the successful radiation of venomous snakes.  相似文献   

2.
船舶油污侵权是民事侵权行为的一种,针对该种侵权的民事赔偿责任,国际上制订了专门的国际公约,一些国家也制定了自己的有关船舶油污损害的赔偿体系。在船舶油污损害责任制度下,一个核心问题就是责任主体问题,只有明确了责任主体,才能使油污损害赔偿得以顺利进行。但是调整国际油污损害赔偿的冲突规则比较匮乏,各国国内法的规定也不尽相同,如何适用法律,各国司法实践多有不同。立足于中国现行的法律体系,首先明确了各种船舶油污损害应当适用的法律,然后依据所适用的法律具体分析责任主体的确定问题。  相似文献   

3.
藻毒素与健康效应的研究进展   总被引:18,自引:0,他引:18  
淡水水体的富营养化导致蓝藻水的普遍发生,蓝藻产生的多种毒素,如微囊藻毒素,节球藻毒素等,不仅常常引起动物中毒,而且也会影响人类的健康,该文从毒理学的角度阐述了多种藻毒素的毒性,及其所引起的健康效应和发生的可能机制。  相似文献   

4.
云南热海热田中的碱金属元素   总被引:2,自引:0,他引:2  
1982至1983年在云南腾冲一已知水热区及其毗邻约 60km2 范围内采集了131个土壤样品。样品分析结果表明锂和铷的异常能圈定两个已知水热区,且与若干已知热田地球化学指示元素的异常相当一致,从而进一步肯定了这一地区的开发前景。与此同时,对区内水样中的钠钾含量也进行了测定并做出解译。锂铷和已知地球化学指标之间的相关分析表明它们之间确存有某种内在联系,同时可看出盐湖与古地热系统之间的一些联系。最后得出结论:土壤中的锂铷可作为圈定热田的地球化学指标;地热系统不仅能作为能源资源而且也应视作矿产资源。  相似文献   

5.
垃圾填埋场空气中微量挥发性有机物的组成和分布   总被引:7,自引:0,他引:7       下载免费PDF全文
通过对广州一垃圾填埋场大气中微量挥发性有机污染物(VolatileOrganic Compounds,VOCs)的定性和定量分析,研究了其中部分VOCs的浓度分布规律并探讨了其对周围居民区环境的影响.结果表明,在检测到的 60种VOCs中,有 17种USEPA优先控制污染物,苯及烷基苯化合物浓度最高,在2.54~1508.48μg/m3之间;通过对比填埋场内外空气中 VOCs的浓度水平发现,填埋场内空气中各VOCs的浓度比场外的高,在地势较低的地方空气中各VOCs的浓度比地势较高的地方浓度高,这些VOCs对周围居民区的环境没有明显影响。  相似文献   

6.
分别用常规法和离子色谱法对近岸海域大气NOX 进行同步监测,并对两方法间的相关性和测定结果的换算进行了研究。结果表明: 两者呈极显著的正相关,相关系数达0-835(n= 9) ,其测定结果是可换算的。为此,建立了采用离子色谱法测定气溶胶NO-3 浓度预测近岸大气NOX 浓度的方法。  相似文献   

7.
本文对华北地区下古生界海相烃源岩生物标志化合物地球化学进行了系统的研究工作,并在烃源岩抽提物中检测到种类丰富的生物标志物,在此基础上讨论了生物标志化合物的分布特征及其地球化学意义,这一工作不仅为华北地区下古生界油气勘探提供了理论依据,而且丰富了碳酸盐岩有机地球化学理论。  相似文献   

8.
Methanogens, the members of domain Archaea are potent contributors in global warming. Being confined to the strict anaerobic environment, their direct cultivation as pure culture is quite difficult. Therefore, a range of culture-independent methods have been developed to investigate their numbers, substrate uptake patterns, and identification in complex microbial communities. Unlike other approaches, fluorescence in situ hybridization (FISH) is not only used for faster quantification and accurate identification but also to reveal the physiological properties and spatiotemporal dynamics of methanogens in their natural environment. Aside from the methodological aspects and application of FISH, this review also focuses on culture-dependent and -independent techniques employed in enumerating methanogens along with associated problems. In addition, the combination of FISH with micro-autoradiography that could also be an important tool in investigating the activities of methanogens is also discussed.  相似文献   

9.
Neanderthals disappeared sometime between 30,000 and 24,000?years ago. Until recently, Neanderthals were understood to have been predominantly meat-eaters; however, a growing body of evidence suggests their diet also included plants. We present the results of a study, in which sequential thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) were combined with morphological analysis of plant microfossils, to identify material entrapped in dental calculus from five Neanderthal individuals from the north Spanish site of El Sidrón. Our results provide the first molecular evidence for inhalation of wood-fire smoke and bitumen or oil shale and ingestion of a range of cooked plant foods. We also offer the first evidence for the use of medicinal plants by a Neanderthal individual. The varied use of plants that we have identified suggests that the Neanderthal occupants of El Sidrón had a sophisticated knowledge of their natural surroundings which included the ability to select and use certain plants.  相似文献   

10.
Over the last decade, there has been a major shift in the study of adaptive patterns and processes towards including the role of host-parasite interactions, informed by concepts from evolutionary ecology. As a consequence, a number of major questions have emerged. For example, how genetics affects host-parasite interactions, whether parasitism selects for offspring diversification, whether parasite virulence is an adaptive trait, and what constrains the use of the host's immune defences. Using bumblebees, Bombus spp, and their parasites as a model system, answers to some of these questions have been found, while at the same time the complexity of the interaction has led expectations away from simple theoretical models. In addition, the results have also led to the unexpected discovery of novel phenomena concerning, for instance, female mating strategies.  相似文献   

11.
本文根据我国现代火山所处的地质构造环境,将其划分为四种构造类型,即环太平洋火山、陆缘火山、碰撞带火山和大陆板内火山。分析了我国现代火山在时间上的活动特点.喷发频率、火山喷发类型及其现代活动表现。提出了我同现代火山活动监测研究方向。  相似文献   

12.
Investigators have long been interested in the natural phenomenon of fetal and placental cell trafficking into the maternal circulation. The scarcity of these circulating cells makes their detection and isolation technically challenging. However, as a DNA source of fetal origin not mixed with maternal DNA, they have the potential of considerable benefit over circulating cell-free DNA-based noninvasive prenatal genetic testing (NIPT). Endocervical trophoblasts, which are less rare but more challenging to recover are also being investigated as an approach for cell-based NIPT. We review published studies from around the world describing both forms of cell-based NIPT and highlight the different approaches’ advantages and drawbacks. We also offer guidance for developing a sound cell-based NIPT protocol.  相似文献   

13.
剩余污泥预处理技术概览   总被引:23,自引:5,他引:18  
全球气候大会以及中国政府在CO2减排方面的承诺使剩余污泥厌氧消化产生能源这一老生常谈的问题再次受到关注.污泥生物细胞裂解/水解是限制厌氧消化效率的重要瓶颈,而污泥预处理技术可有效提高细胞破裂、水解效果,最大限度地发掘出剩余污泥中的有机能源.目前全球研发的污泥预处理技术多种多样,其中既有具备工程应用经验的超声波、聚焦脉冲...  相似文献   

14.
Following an article on the charm model (Naturwissenschaften 64, 229 (1977)) and its predictions, the present paper reviews the current status of its experimental verification. Four out of six predicted mesons with charm have been detected by their nonleptonic decay. The semileptonic decay of charmed mesons has also been established proving the predicted weak nature of the decay. In addition, there are strong indications as to the existence of charmed baryons from a photoproduction experiment corroborating clues given earlier by neutrino experiments.  相似文献   

15.
The genus Orthoreovirus contains nonenveloped viruses with double-stranded gene segments encased in a double-layered icosahedral capsid shell. These features constitute major determinants of virion stability in the environment and virion resistance against physical and chemical agents. Reovirus (ReoV) is the general term most commonly used for all virus strains that infect humans and nonhuman animals. Several studies have demonstrated the frequent occurrence of ReoV in wastewaters and natural waters, including surface and ground waters from different geographical areas. Most of these studies have reported higher concentrations of ReoV than any other enteric virus analyzed. They are more commonly isolated in chlorine-disinfected wastewaters than other enteric viruses, and appear to survive longer in water. The ability of ReoV to form large aggregates, even with different types of enteric viruses (e.g., poliovirus) and their ability to undergo mechanisms of gene segment reassortment among different serotypes may also explain their greater stability. Different approaches have been applied for concentration of ReoV from water; however, the recovery efficiency of the filtration methods has not been fully evaluated. Recently, molecular methods for identification of ReoV strains and quantification of virus genome have been developed. Studies have shown that the overall detection sensitivity of ReoV RNA is enhanced through initial replication of infectious virions in cell culture. More studies are needed to specifically address unresolved issues about the fate and distribution of ReoV in the environment since this virus is not commonly included in virological investigations.  相似文献   

16.
The purpose of this study was to characterize the situation of Portuguese Small and Medium Enterprises (SMEs) concerning the certification of their Quality Management Systems (QMS), Environmental Management Systems (EMS) and Occupational Health and Safety Management Systems (OHSMS), in their individually form, to identify benefits, drawbacks and difficulties associated with the certification process and to characterize the level of integration that has been achieved. This research was based on a survey carried out by the research team; it was administered to 46 Portuguese SMEs. Our sample comprised 20 firms (43%) from the Trade/Services activity sector, 17 (37%) from the Industrial sector, 5 (11%) from the Electricity/Telecommunications sector and 4 (9%) from the Construction area. All SMEs surveyed were certified according to the ISO 9001 (100%), a quarter of firms were certified according to the ISO 14001 (26.1%) and a few certified by OHSAS 18001 (15.2%). We undertook a multivariate cluster analysis, which enabled grouping variables into homogeneous groups or one or more common characteristics of the SMEs participating in the study. Results show that the main benefits that Portuguese SMEs have gained from the referred certifications have been, among others, an improvement of both their internal organization and external image. We also present the main difficulties in achieving certification. Overall, 7 of the Portuguese SMEs examined indicated that the main benefits of the IMS implementation management included costs reduction, increased employee training and easier compliance of legislation. The respective drawbacks and difficulties are also presented. Finally, we presented the main integrated items in the certified Portuguese SMEs we examined.  相似文献   

17.
针对云南农村环境现状展开了调查研究,对农村环境存在的主要问题和产生原因进行了分析,提出了相应的整治措施和对策。  相似文献   

18.
船舶大功率柴油机NOx排放控制技术的比较研究   总被引:3,自引:0,他引:3  
江彦桥 《交通环保》1999,20(1):8-14
在扼要地讨论了柴油机NOx生成特性及其对环境的危害后,着重就燃油乳化、废气再循环、燃油-水分层喷射以及选择性催化还原法等船舶柴油机NOx净化效果、对油耗率等因素进行了分析,并对其中主要净化技术的净化效果,投资费用和运行费用等进行了比较分析。  相似文献   

19.
在总结目前关于氨基酸溶金作用研究成果的基础上,对桂西北明山卡林型金矿床表生带的矿石样品进行了氨基酸的分离、定性和定量研究,结果表明,各种氨基酸的稳定性与所处的成岩成矿环境有关,因此不同环境中对成岩成矿发挥作用的氨基酸种类是不同的,所起的作用也有所差异;进行氨基酸溶金作用模拟实验时应该首先考虑氨基酸在不同成岩成矿环境中的稳定性。结合已有的氨基酸溶金作用模拟实验所得到的认识,对桂西北卡林型金矿成矿过程中氨基酸的作用进行了探讨。  相似文献   

20.
陈晖  温婧  庞军  陈政  韦雨杉 《中国环境科学》2021,40(12):5540-5550
基于MRIO模型方法自主编制了2012年中国区域间投入产出表,测算了中国31省在生产者责任和消费者责任视角下的碳排放量,以及省际贸易隐含碳转移量.在此基础上,分别从各省在省际贸易隐含碳净转移与隐含GDP净转移之间的关系、污染贸易条件值以及碳基尼系数三个方面分析了我国省际碳公平性问题.由于经济发展水平、资源禀赋、产业结构和能源结构的差异,各省在生产者和消费者视角下的碳排放量存在明显差异;隐含碳净转入省份多位于西部或属于欠发达省份,隐含碳净转出省份多为经济发达省份.中国31省在省际贸易中存在着明显的碳不公平现象,部分发达省份不仅让外省承担了自身的部分碳排放,而且获得了来自外省的GDP净输入,污染贸易条件值也小于1,在碳排放空间分配及经济效益上均处于绝对优势地位;而部分西部省份不仅为外省承接了部分碳排放还对外省净输出了GDP,污染贸易条件值也大于1,在碳排放空间分配和经济效益上均处于绝对劣势地位.2012年我国31省碳基尼系数在消费者责任视角下为0.24,在生产者责任视角下则达到了0.31,表明生产者责任视角下我国省际碳排放空间分配不公平性有所增强.  相似文献   

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