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1.
People take addictive drugs to elevate mood, but with repeated use these drugs produce serious unwanted effects, which can include tolerance to some drug effects, sensitization to others, and an adapted state - dependence - which sets the stage for withdrawal symptoms when drug use stops. The most serious consequence of repetitive drug taking, however, is addiction: a persistent state in which compulsive drug use escapes control, even when serious negative consequences ensue. Addiction is characterized by a long-lasting risk of relapse, which is often initiated by exposure to drug-related cues. Substantial progress has been made in understanding the molecular and cellular mechanisms of tolerance, dependence and withdrawal, but as yet we understand little of the neural substrates of compulsive drug use and its remarkable persistence. Here we review evidence for the possibility that compulsion and its persistence are based on a pathological usurpation of molecular mechanisms that are normally involved in memory.  相似文献   

2.
The question of the use of the placebo is one of the most controversial in the field of the ethics of research today. The use of the placebo remains the standard practice of biomedical research in spite of the fact that various revisions of the Helsinki Declaration have sought to limit its use. In Canada, the Tri-council policy statement: Ethical conduct for research involving humans adopted a very restrictive position with respect to the use of placebos, precisely defining the situations in which its use would meet the demands of ethical research. The positions taken by the various ethical decision-making bodies are, however, hardly shared by regulatory bodies such as the Food and drug administration (FDA), the Council for international organization of medical sciences (CIOMS) or the European agency for the evaluation of medicinal products (EMEA). This divergence of opinions reveals two quite different conceptions of what constitutes the ethical. In the case of decision-making bodies in the ethical field, it is clearly medicine's Hippocratic Oath which explains their reluctance to use placebos. The first responsibility of the doctor is to "do no harm" to his or her patient. This duty is inherent to the medical profession and as such is not grounded in the view of medicine as a contract for care. In the case of regulatory bodies, it is the vision of "medicine as contract" which is in view; and it is this notion that justifies the use of placebos once free and informed consent has been obtained. It is also worth noting that these regulatory bodies make frequent use of arguments based on utilitarian ends. In an unprecedented move, the World medical association published in October 2001 a clarification note about the use of placebos. An analysis of this text raises the question about its real meaning: clarification or concession?  相似文献   

3.
中国土地利用空间格局动态变化模拟——以规划情景为例   总被引:5,自引:0,他引:5  
孙晓芳  岳天祥  范泽孟 《生态学报》2012,32(20):6440-6451
土地利用变化研究在环境可持续发展研究领域中具有重要的地位,其空间分布格局的变化影响到生物地球化学循环、气候变化、生物多样性等。采用土地利用动态变化模型Dyna-CLUE模拟了在规划情景下中国土地利用变化未来空间分布格局。将土地利用类型分为六大类,即耕地、草地、林地、建设用地、水域和其它用地。驱动因子包括地形地貌、气候、社会交通等方面,对动态驱动因子如气温、降水、人口交通等,考虑了其在未来情景下的发展趋势。基于土地利用类型与驱动因子之间的定量关系和土地利用类型之间的转换规则等,模拟出至2020年中国土地利用分布格局。结果表明,至2020年,中国东南部、黄淮海平原、四川盆地等地区耕地面积将增加,东北、西北等农牧交错区、农林交错区和沙漠边缘耕地面积将会呈轻度减少趋势;林地面积将增加1417.91万hm2,主要发生在中国东北部以及西南部水热条件好的地区;中国草地在面积上保持稳定,空间上中东部、东南地区草地面积减少,内蒙古中部,青海东部,四川盆地北缘区和青藏高原等地面积增加;建设用地增加531.76万hm2,主要发生在中国的东部地区。  相似文献   

4.
It was shown in experiments with CBA/Lac J mice that both a single use of doxorubicin (MID) and its use during a treatment course (1/10 LD50.10) induced impairment of the morphological composition of the central and peripheral lymphoid organs along with changes in the functional activity of separate cell populations of the immune system which persisted over a prolonged period up to 3 months. The course use of the drug resulted in a significant decrease in the proliferative response of the splenocytes to the polyclonal T- and B-cell mitogens in 1 month, which was followed by inhibition of interleukin-2 production. On the contrary, 1 month later, the single administration of the cytostatic induced activation of the LPS-responding cell populations and an increase in production of the growth factor in the culture of T-lymphocytes.  相似文献   

5.
洪惠坤  廖和平  魏朝富  李涛  谢德体 《生态学报》2015,35(24):8016-8027
土地利用系统健康评价研究能够有效引导土地合理利用,协调城市发展与自然生态保护之间的矛盾。构建基于PSR模型的土地利用系统健康评价指标体系,并采用改进TOPSIS方法对三峡库区生态敏感区的典型区域—重庆市进行实证分析。结果表明:1)研究区土地利用系统健康综合分值整体呈现T型带状分布格局,可分为四个健康等级,即健康、临界健康、不健康、病态。2)渝东北、渝东南和重庆市西南片区部分地区因其土地生态系统脆弱敏感,土地利用风险性大和生态系统稳定性差,土地生态系统呈现病态和不健康状态,属于高风险-高压力区域;重庆市主城区环线区域因其属于城市核心拓展区和人类活动频繁区域,人口压力指数和土地利用压力指数较大,土地利用风险性较小,健康度较为良好,是低风险-中度压力区域。3)PSR模型能够较好地改变现有研究主要关注自然资源环境的状况,更准确地反映土地利用系统健康的各要素之间的关系和影响土地生态系统健康的关键因素,为三峡库区生态敏感区土地利用系统健康状态起到一定的预警作用。4)以改进TOPsis方法计算土地利用系统健康指数,消除了不同指标量纲的影响,并能充分利用原始数据的信息,能充分反映各方案之间的差距,客观真实的反映实际情况。5)为保障三峡库区生态敏感区土地利用系统的健康发展,应加强土地利用规划与调整,控制人类过度开发,维持生态系统正常功能。  相似文献   

6.
The original definition of the guild is reiterated and the concept discussed and placed in the context of related concepts such as resources and competition. From this conceptual framework the current use of guilds in studies of plant community ecology is evaluated. We discuss the criteria with which species are assigned to guilds, the association of guilds with specific communities, the resource classes on which guilds are based, and the competitive relationships between species of a guild. We conclude that the guild is presently applied in a much more loose way as compared to its original definition. In particular, the a priori assignment of species to guilds on the basis of the use of well-defined resource classes is often relaxed. This obscures the insight that the guild structure may provide in the role of resource partitioning and competition in structuring the community. A more strict use of the concept is advocated.  相似文献   

7.
Life cycle assessments of circular economy measures (CE LCA) of consumer products have been criticized for oversimplifying important aspects of the use phase such as user behavior and rebound effects, limiting our understanding of the environmental performance of circular economy measures. This study tests the usefulness of a framework designed to facilitate accounting for such aspects, by applying the framework to a case study of reuse of shell jackets enabled by “premium secondhand” outdoor stores. Methods for collecting use phase data were user surveys and interviews with store managers. Using the framework on this case study generated several novel insights which are interesting in themselves and as inputs to CE LCA. For instance, secondhand shell jackets have a significantly lower frequency of use during their first use span compared to the second and to shell jackets in the linear reference scenario. This implies that reuse in this case does not function as a mere use extension of otherwise similar use phases as is commonly assumed. The generation of such insights, which hitherto have been lacking in CE LCAs, points to the usefulness of the framework as a tool for opening the “black box” of the use phase in CE LCAs to improve understanding of the environmental performance of circular economy measures.  相似文献   

8.
The choice of which language strategies to use in schools in Africa is the subject of much debate. In the Life Sciences, cultural issues associated with the use of biological terminology add to this debate. In our study, we examined the language choices made by Grade 7 Natural Sciences teachers in South Africa during their teaching of human reproduction. A mixed method approach was employed, involving firstly a survey questionnaire amongst 40 teachers in urban schools followed by a multiple case study of 10 of these teachers. Data were collected during classroom observations by means of field notes and audio-recordings followed by interviews which were transcribed and coded. We found that teachers used a variety of language strategies including use of home languages, English or code switching. The teacher’s and/or learners’ fluency in English and the teacher’s perception of the need for learners to feel at ease when discussing human reproduction influenced their choices. In addition, teachers’ belief in the importance of using biological terminology rather than traditional metaphors in order to create a more formal and thus respectful discourse, led them to use the English version of the biological terms. We argue that different language choices are appropriate for different urban contexts, and that teachers should use the language/s in which learners are most comfortable in order to enable deep and rich discussions on the sensitive subject of human reproduction.  相似文献   

9.
土地利用模型时间尺度预测能力分析——以CLUE\|S模型为例   总被引:11,自引:0,他引:11  
刘淼  胡远满  常禹  贺红士  布仁仓 《生态学报》2009,29(11):6110-6119
模型模拟是生态学中的重要方法,特别是当实验不可进行时.在不同预案下基于模型的土地利用预测对于土地利用规划和政策制定具有十分重要意义.然而,很多研究没有对模型在研究区的时间尺度预测能力加以分析,从而可能导致模拟结果的不可靠.以岷江上游地区为例,采用Kappa指数系列对CLUE-S模型在研究区的时间尺度预测能力进行研究.结果表明CLUE-S模型在岷江上游地区时间尺度上的最大预测能力为22a,超过时间预测能力的预测结果不可靠.研究为土地利用模型模拟时间尺度确定提供了一种有效的方法.  相似文献   

10.
Summary The present paper describes a method which makes it possible to use the paraldehyde technique for the photometric determination of the neurosecretion in the posterior lobe of the hypophysis.  相似文献   

11.
The choice facing anthropologists wishing to use the concept of corporateness has been to use either a model unique to the law of property in Western societies or a looser definition which does not justify replacement of traditional terms. This paper suggests that alternative models may be more appropriate where it is necessary to depict arrangements involving group tenure .  相似文献   

12.
王玥  周旺明  王绍先  牛丽君  代力民 《生态学报》2014,34(19):5635-5641
受自然保护区旅游业快速发展影响,长白山自然保护区外围土地利用变化加剧。因此,对区域土地利用布局进行科学规划具有十分重要的意义。以长白山自然保护区外围30 km区域为研究对象,探讨了CLUE-S模型在小尺度土地利用规划中的应用。在分析研究区1991—2007年土地利用变化的驱动力基础上,根据区域规划预案,模拟2020土地利用布局。利用模拟结果划定空间管制区和乡镇布局,并与现有规划进行了对比。结果表明,基于CLUE-S模型的土地规划明显抑制了区域景观破碎化进程,减弱了人为活动对景观的影响,该方法可以为长白山区域土地利用规划提供有力的技术手段和科学支撑。  相似文献   

13.
Chimpanzees of Kasoge use tools in the trees for collecting arboreal ants (Camponotus spp.) mostly in woodland vegetation. Ant-gathering by the use of tools is routine behaviour, at least during the first half of the rainy season. Three kinds of tools were recognized: wiping handkerchief, expelling stick and poking rod. Although the first two types were observed only once, this is the first time that these methods of using plants to obtain insects have been recorded. The poking rods can be divided into five categories which differentiate between the materials used and the way and the degree to which these materials are modified. The use of a mid-rib of the leaf as a rod is a modification peculiar to a chimpanzee of Kasoge. The apparent selectivity of the plant species as the material for a tool was made clear, with special reference to the ethnobotany of the sympatric Batongwe tribe. The tool-using activity of “chimpanzee level” does not require the exclusive specialization of one hand. Ant-gathering was seen during the time when chimpanzees usually take a rest between the two intensive feeding periods of a day. This implies that ant-gathering by use of tools is a kind of luxury.  相似文献   

14.
Reports of cercopithecine cheek pouch use and functional significance are largely anecdotal, and to date there have been no investigations into its use by species living in closed forest habitats. Here, I report on cheek pouch use in Cercopithecus ascanius and Lophocebus albigena in the Kibale National Park, Uganda, between July-October 1997. Two hypotheses were evaluated: this feature was selected for because of its role in 1) increasing feeding efficiency via a reduction in potential feeding competition, and/or 2) reducing vulnerability to predation. Results indicate that both species were more likely to use their cheek pouches when feeding on contestable foods and, after filling cheek pouches, retreated to more densely vegetated ("safer") positions for processing food. There was no influence of age and sex on L. albigena cheek pouch use. Subadult C. ascanius cheek-pouched less frequently than adults, although there were no differences between adult males and females. There was no relationship between feeding-patch size and number of plant food items cheek-pouched in either species. However, the diameter of breast height (dbh; a measure of patch size) of trees in which C. ascanius used their cheek pouches was significantly larger than the dbh of trees in which they did not. Both species were more likely to use their cheek pouches in the presence of greater numbers of conspecifics. These data provide insight into the relationship(s) among oral anatomy and feeding efficiency, and facilitate understanding into the selection for this important oral feature in stem cercopithecines.  相似文献   

15.
Rat peritoneal mast cells and mast cell granules were evaluated by radioimmunoassay for the presence of beta-thromboglobulin and platelet factor 4. The initial assays indicated that a beta-thromboglobulin cross reacting material was released from mast cells by compound 48/80 in a similar dose-dependent manner as histamine release. The material was also found to be associated with purified granules. However, the use of protease inhibitors in the buffers completely abolished the positive assays. Further evaluation of the effects of various proteases on the beta-thromboglobulin assay indicated that elastase would also generate a false positive assay which could then be neutralized by the use of alpha 1-antitrypsin as a protease inhibitor. There was no protease effect on the platelet factor 4 radioimmunoassay which always showed no detectable amounts with mast cells, granules or proteases. These results clearly indicate the artifactual positive assays which can arise when using certain radioimmunoassay tests in the presence of cell proteases. The use of protease inhibitors is a necessary control when applying a radioimmunoassay to a system with potentially active proteases.  相似文献   

16.
《Anthrozo?s》2013,26(4):491-502
ABSTRACT

Nonhuman animals are abused in many ways in farming but this arouses little disquiet in society where most people actively support the industry. A corpus of writing in a popular South African farming magazine was analyzed and found to contain, along with other discourses, one which may be described as a discourse of production. Within this discourse are “use terms” which portray nonhumans as having anthropocentric purposes or uses for their lives. This ideology of purpose or implicit use has significant implications for facilitating moral disengagement both in those working in the industry and those supporting it. These implied purposes may derive in part from an old but persistent ideology that the world is composed of greater and lesser beings with the “lesser beings” existing for the purposes and use of the “greater beings.” A scheme is proposed to show how these use terms may play a part in the facilitation of mass nonhuman abuse. Further investigation reveals that use terms are not confined to farming but are widespread and common in everyday speech. It is suggested that an awareness of such constructions and their ideological implications, combined with challenges in such areas as education and science, may contribute towards a re-examination by some people of their ideology concerning nonhumans, their supposed life purposes, and their condoned exploitation.  相似文献   

17.
The literature on monitoring rivers using benthic algal communities is reviewed, especially that for Europe during the past 20 years. In particular, papers in a series of symposia at approximately 3-year intervals are considered to assess the extent to which aims and methods have shifted. A variety of methods were being tested in the early 1990s, and some put to practical use. However, the requirements of the EU Urban Waste Water Directive in 1991 have gradually narrowed procedures in most countries outside Scandinavia to the use of indices based on benthic diatoms to monitoring nutrients, especially phosphate. Most countries in Europe now adopt one of a few indices. The same indices are being used to deal with the requirements of the EU Water Framework Directive introduced in 2000 to achieve good ecological status by 2015. It is argued, however, that features of upland river sites require the development of revised indices for this purpose. Features of many sites include highly variable nutrient concentrations and ratios, and the greater importance of organic phosphate. Two possible approaches are suggested to developing a revised index. One is a diatom index which incorporates information about the environmental features important here. The other is to use an index which incorporates data on genera from all algal phyla, with emphasis on those which are long-lived.  相似文献   

18.
While archeologists have the capacity to track changing food use in the archeological record, they have not tended to use food systems in the study of social and political change. To do so, an awareness must be gained of the meanings of foods, which then can illuminate the strategic use of a particular food in the creation of relationships of dependence and prestige. Archeological evidence from the central Andes of Peru indicates that the role of maize changed between A.D. 500 and 1500, shifting from a culinary item, simply prepared by boiling, to a more complex symbolic food, transformed through grinding and brewing into beer, with elaborated political meanings. This change in maize processing and consumption occurred at a time of heightened political and social tensions. We propose that the shift in maize use reflected and participated in new political dynamics, demonstrating how foodways can inform archeologists about past social and political systems.  相似文献   

19.
Life Cycle Impact assessment of land use based on the hemeroby concept   总被引:1,自引:0,他引:1  
The impact category ‘land use’ describes in the Life Cycle Assessment (LCA) methodology the environmental impacts of occupying, reshaping and managing land for human purposes. Land use can either be the long-term use of land (e.g. for arable farming) or changing the type of land use (e.g. from natural to urban area). The impact category ‘land use’ comprises those environmental consequences, which impact the environment due to the land use itself, for instance through the reduction of landscape elements, the planting of monocultures or artificial vegetation, or the sealing of surfaces. Important environmental consequences of land use are the decreasing availability of habitats and the decreasing diversity of wildlife species. The assessment of the environmental impacts of land use within LCA studies is the objective of this paper. Land use leads to a degradation of the naturalness of the area utilised. In this respect the naturalness of any area can be defined as the sum of land actually not influenced by humans and the remaining naturalness of land under use. To determine the remaining naturalness of land under use, this study suggests applying the Hemeroby concept. “Hemeroby is a measure for the human influence on ecosystems” (Kowarik 1999). The Hemeroby level of an area describes the intensity of land use and can therefore be used to characterise different types of land use. Characterization factors are proposed, which allow calculating the degradation of the naturalness of an area due to a specific type of land use. Since the resource ‘nature/naturalness’ is on a larger geographical scale by far not homogeneous, the assessment of land use needs to be regionalised. Therefore, the impact category ‘land use’ has been subdivided into the impact sub-categories ‘land use in European biogeographic regions’. Following the general LCA framework, normalization values for the impact sub-categories are calculated in order to facilitate the evaluation of the characterization results with regard to their share in a reference value. Weighting factors, which enable an aggregation of the results of the different land use sub-categories and make them comparable to other impact categories (e.g. climate change or acidification) are suggested based on the assumption that the current land use pattern in the European biogeographic regions is acceptable.  相似文献   

20.
Understanding the factors that contribute to a population’s habitat use is important for conservation planners and managers to identify reasons behind a population’s distribution. Habitat use often differs between sexes, however few studies on sexually monomorphic species document this difference, resulting in misleading ecological interpretations and non-targeted management actions. The aim of this study was to test for sex-specific differences in the seasonal habitat use of Indo-Pacific bottlenose dolphins (Tursiops aduncus) off Bunbury, Australia. Systematic, boat-based, photographic identification dolphin surveys (n?=?587) were conducted across seasons over 6 years during 2007–2013. Generalised additive models explored relationships between the presence-absence of dolphins and sex, water depth and benthic habitat type. Results highlighted that: (i) habitat use differed seasonally for males and females, (ii) depth had a strong influence on habitat use, which differed between sexes for summer, winter and spring, and (iii) there were no sex differences in habitat use in autumn, which coincides with the peak breeding season. In summer and autumn dolphins were concentrated in shallow, near-shore waters predominantly over reef and sand, and in winter and spring dolphins had a broader distribution over reef and mud/silt with the use of deeper, offshore waters. This pattern is consistent with the seasonally-dependent dolphin abundance that has been documented for this population. Identification of sex differences in habitat use provides management agencies with insights to implement informed actions for the conservation of this coastal dolphin population which is forecast to decline by 50% in the next two decades.  相似文献   

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