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1.
It is often assumed that nanotechnology (NT) holds the potential to provide a substantial contribution to the solution of various ecological problems, including high consumption of energy and materials and the generation of waste. However, problems surrounding the use and release of hazardous substances remain largely unexplored. For this reason, the Scientific Technical Option Assessment (STOA) Panel of the European Parliament initiated a study on “The Role of Nanotechnology in Chemical Substitution.” The subject and aim of the study was an investigation into preexisting and potential applications of NT that could lead to a reduction in hazardous substances by providing substitutes for them. In terms of method, it was based on electronic searches of the literature, expert interviews, and an expert workshop. This article discusses the results of the project. It focuses on the methodological challenges and the principal problems resulting from a combination of the broad and ill‐defined concept of NT and the specific concept of hazardous substances. The hazardous substances addressed had to be reduced to a manageable number, and the term substitution was understood according to the characteristics of NT and the way in which the latter could reduce the use of hazardous substances. Although several applications of NT were identified that could lead to a considerable reduction in the use of hazardous substances, ambiguities in both the concept of NT and the concept of substitution in relation to NT prevent a comprehensive assessment of the potential of NT in respect to substitution.  相似文献   

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If the sovereignty issue can be shelved, solved, or resolved, the six claimant states of the South China Sea will have to establish a series of international regimes. The following questions need to be answered: Do all the claimants understand the concept of international regimes? Would the regimes be imposed? Would there be hegemon(s) in the South China Sea? If so, which country or multiple entities will be involved? What would be the outcome of having international regimes in the South China Sea? Can the experience elsewhere be applied to the South China Sea?  相似文献   

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A novel approach to improve the accuracy and to reduce the uncertainty associated with the assessment of ecotoxicological risks and the determination of remedial objectives was developed herein for a scenario involving multiple contaminants in soil. This approach used laboratory-derived site-specific toxicological data (i.e., obtained from toxicity testing using species in direct contact with soil such as plants and invertebrates) instead of the more traditional approach using generic toxicological benchmarks for corresponding groups of organisms. Inherent to this approach were the data exploration and reduction; the use of generalized linear models to integrate the data for stressors (site-specific chemical and edaphic characteristics with the potential for influencing toxicity) and effects (biological responses for multiple species and multiple endpoints); and the derivation of tools that could predict the level of impairment associated with any combination of metals’ concentrations measured on site and compare it to a pre-specified acceptable threshold. A case study is presented whereby this method was applied to a large site contaminated with a mixture of metals. Ultimately, the distributions of predicted levels of risk for both soil invertebrates and plants were determined for the entire site and compared to those obtained using the traditional approach using benchmarks.  相似文献   

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大豆叶片CO2补偿点和光呼吸的关系   总被引:2,自引:0,他引:2  
为了探讨CO2 补偿点 (Г)与光呼吸 (Rp)的关系 ,用CI 30 1光合气体分析系统观察了光强等因素对大豆叶片CO2 补偿点的影响。在高于生长光强的强光下 ,Г和Rp随着光强的增高而升高 ,实验表明这可能与强光下发生的无机磷限制有关 ;经 10mmol/L的甘露糖、0 .2 %PEG 6 0 0 0和 10mmol/L的DL 甘油醛处理后 ,Г显著上升 ,前两者使Rp下降 ,而后者使Rp上升 ;给叶片喂 5mmol/L的KH2 PO4 后 ,Г和Rp都降低。并且 ,衰老叶片的Г比刚完全展开的叶片高 ,但前者的Rp却比后者低。这些结果表明 ,光呼吸是影响CO2 补偿点的一个重要因素 ,但不是唯一因素 ,CO2补偿点总是随着光呼吸速率与羧化效率比值的变化而在同一方向上变化  相似文献   

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This article examines China's domestic legal regime for the prevention of vessel source pollution. It pays special attention to the recently adopted Regulation on Prevention and Control of Marine Pollution from Vessels. Potential challenges and emerging issues that China has to confront are addressed, including: application of the legislation to disputed sea areas between China and its neighbors, freedom of navigation in the exclusive economic zone, reduction of emission from ships, and prevention of invasive species from ballast water.  相似文献   

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中国蕨类植物细胞分类学研究概况   总被引:1,自引:0,他引:1  
中国蕨类植物类群十分丰富,由63科230属约2600种组成,其中约有10%的种类为中国特有。迄今为止,中国蕨类植物进行过染色体计数的种类约有395种,仅占中国蕨类植物总数的15%,其中48%为多倍体。本文对中国蕨类植物细胞分类学研究的历史和现状进行了综合评述。文中论述了蕨类植物染色体数目和染色体基数在系统学上的应用以及蕨类植物染色体组型分析、多倍化、无融合生殖、多倍体复合体及网状进化的研究概况。中国20多年的蕨类植物细胞分类学研究表明,蕨类植物的染色体数目、基数、组型分析、多倍化及其繁殖方式对蕨类植物的分类、起源和演化的研究都有重要作用,对种及种复合体的鉴定、科属的划分也有重要的参考价值。并对中国蕨类植物细胞分类学研究提出了一些建议。  相似文献   

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Objectives

The objective of this study was to determine the prevalence of pAmpC beta-lactamases in community-acquired Gram negative bacteria in the Netherlands, and to identify possible risk factors for carriage of these strains.

Methods

Fecal samples were obtained from community-dwelling volunteers. Participants also returned a questionnaire for analysis of risk factors. Screening for pAmpC was performed with selective enrichment broth and a selective screening agar. Confirmation of AmpC-production was performed with two double disc combination tests: cefotaxime and ceftazidime with either boronic acid or cloxacillin as inhibitor. Multiplex PCR was used as gold standard for detection of pAmpC. 16S rRNA PCR and AFLP were performed as required, plasmids were identified by PCR-based replicon typing. Questionnaire results were analyzed with SPSS, version 20.0.

Results

Fecal samples were obtained from 550 volunteers; mean age 51 years (range: 18–91), 61% were females. pAmpC was present in seven E. coli isolates (7/550, 1.3%, 0.6–2.7 95% CI): six CMY-2-like pAmpC and one DHA. ESBL-encoding genes were found in 52/550 (9.5%, 7.3–12.2 95% CI) isolates; these were predominantly blaCTX-M genes. Two isolates had both ESBL and pAmpC. Admission to a hospital in the previous year was the only risk factor we identified.

Conclusions

Our data indicate that the prevalence of pAmpC in the community seems still low. However, since pAmpC-producing isolates were not identified as ESBL producers by routine algorithms, there is consistent risk that further increase of their prevalence might go undetected.  相似文献   

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介绍了国内学者对中国鹿类动物与遗传相关的试验研究的基本情况,涉及血液蛋白等分析、性状相关分析、染色体和线粒体相关分析等方面,对各项内容的总体及各项所采用的技术和方法、部分研究成果进行概述,并对其发展趋势进行展望。  相似文献   

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Gu Yumin 《Human Evolution》1989,4(6):509-514
Two species of fossil gibbon existed in China during the Pleistocene. These wereHylobates concolor andH. hoolock, species still extant in China today. The gibbon's dependence on high canopy forest environments is well known, therefore their presence in the fossil record is reliable environmental indicator. Gibbons were widely distributed throughout southern China during the Pleistocene; however, the southward shift of the northern limit distribution in modern history.  相似文献   

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An incident in the course of the shipment of radioactive material could have serious consequences for affected states, whether or not a release of radiation actually resulted from the incident. In particular, small island states could potentially suffer serious damage to their reputations and to their economies. Pacific Island states are taking an initiative in response to their exposure to this risk. Assurances that they will not be left unsupported in such circumstances are being sought through a process of direct discussions presently taking place with source states and operators involved in the shipment of radioactive material through the Pacific.

This article examines the legal background to these discussions, investigating the legal uncertainties in the situation of states affected by an incident in the course of shipment of radioactive material that arise from limitations in the nuclear civil liability conventions and other aspects of applicable international law.  相似文献   

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对中国转刺蛛属Eriophora进行了修订,共记述8种,其中含3个新组合:宝天曼转刺蛛Eriophora baotianmanensis(Hu,Wang&Wang,1991)和喜马拉稚转刺蛛Ehimalayaensis(Tikader,1975)从园蛛属Araneus移人,杂斑转刺蛛E.poecila(Zhu&Wang,1994)从扇蛛属历肛n移人;3个新异名:王氏转刺蛛E.wangi Zhu et Song,1994和陕西转刺蛛E.shaanxiensis Zhu et Wang,1994均为宝天曼转刺蛛Ebaotianmanensis(Hu.Wang&Wang,1991)的异名,松林园蛛A.pineus Yin et a1.,1990为萨哈林转刺蛛E.sachalinensis(Saito.1934)的异名。  相似文献   

18.
BackgroundTo facilitate the interpretation of meningococcal meningitis epidemiology in the “African meningitis belt”, we aimed at obtaining serogroup-specific pooled estimates of incidence, carriage and case-carrier ratios for meningococcal meningitis in the African meningitis belt and describe their variations across the endemic, hyperendemic and epidemic context.MethodsWe conducted a systematic review and meta-analysis of studies reporting serogroup-specific meningococcal meningitis monthly incidence and carriage in the same population and time period. Epidemiological contexts were defined as endemic (wet season, no epidemic), hyperendemic (dry season, no epidemic), and epidemic (dry season, epidemic).FindingsEight studies reporting a total of eighty pairs of serogroup-specific meningococcal meningitis incidence and carriage estimates were included in this review. For serogroup A, changes associated with the transition from endemic to hyperendemic incidence and from hyperendemic to epidemic incidence were 15-fold and 120-fold respectively. Changes in carriage prevalence associated with both transitions were 1-fold and 30-fold respectively.
For serogroup W and X, the transition from endemic to hyperendemic incidence involved a 4-fold and 1•1-fold increase respectively. Increases in carriage prevalence for the later transition were 7-fold and 1•7-fold respectively. No data were available for the hyperendemic-epidemic transition for these serogroups. Our findings suggested that the regular seasonal variation in serogroup A meningococcal meningitis incidence between the rainy and the dry season could be mainly driven by seasonal change in the ratio of clinical cases to subclinical infections. In contrast appearance of epidemic incidences is related to a substantial increase in transmission and colonisation and to lesser extent with changes in the case-carrier ratio.ConclusionSeasonal change in the rate of progression to disease given carriage together with variations in frequency of carriage transmission should be considered in models attempting to capture the epidemiology of meningococcal meningitis and mainly to predict meningitis epidemics in the African meningitis belt.  相似文献   

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中国栽培稻的起源与演化   总被引:1,自引:0,他引:1  
中国栽培稻起源地主要有4种假说:华南起源说、云南起源说、长江中下游说和长江中游-淮河上游说。对其进行了简要概括,并进行评述:目前没有一种假说能完全符合水稻起源的4个条件,此外有些学者提出水稻的多起源中心;从分子生物学角度综述了栽培稻籼粳分化研究进展,主要有两个起源说:一源论和二次(或多次)起源论,大量研究支持籼稻和粳稻多起源论;从古DNA、水稻落粒性与驯化、植硅石等方面探讨栽培稻起源演化的研究方法。旨在能为水稻的起源演化研究提供有价值的参考。  相似文献   

20.
Extracellular recordings were used to characterize responses to cutaneous mechanical stimulation of 78 neurons in the rat nucleus submedius (SM). Thirty-nine of these units were activated by some type of cutaneous mechanical stimulation. Eighteen cells were activated exclusively by noxious stimuli. In 13 of these cells, responses were of swift onset and relatively rapid termination following stimulus application. In contrast, in three neurons responses were delayed both in onset and termination, and in two the response was immediate, but the markedly increased evoked activity outlasted stimulus application by 13 min. Receptive fields (RFs) of these nociceptive neurons were generally large, although none were bilateral. Four SM neurons were activated by innocuous stimuli, but their maximal response was obtained only after noxious stimulation. Responses of all of these neurons were of immediate onset and recovery, and their RFs were large (two were bilateral). Twelve SM neurons were activated maximally by innocuous stimuli. Responses of seven of these cells were immediate in onset and termination, while that of three were delayed in both onset and termination. Two of the 12 innocuous-only neurons quickly became unresponsive to repeated stimulus applications, and could be reactivated only after a rest period during which no stimuli were applied. RFs of these units were also generally large, and in three cases were bilateral. Five SM neurons responded by decreasing, or completely ceasing, their firing subsequent to noxious-only (n = 2), or innocuous-only (n = 3) stimulation. Four of these units had large RFs (two were bilateral). The remaining 39 SM neurons could not be activated by any type of mechanical cutaneous stimulation we tried.

Electrical stimulation of the ventrolateral orbital cortex (VLO) was employed to examine frontal cortical projections of 21 SM neurons. Ten of these units were activated, although all of them synaptically rather than antidromically, and two were inhibited. There was no clear-cut relationship between neuronal location, physiological type, RF site, or VLO stimulation effects among the 39 SM neurons.

These results provide further support for the involvement of SM neurons in nociceptive information signaling, and suggest additionally that the role of the nucleus is not limited to nociception but encompasses a wider range of cutaneous sensations.  相似文献   

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