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1.
基金经理在选择投资组合风险时,不仅会考虑基金的业绩排名,同时会考虑基金业绩之间的差距,由此提出了业绩差距排名,并提出了新的实证方法,即线性回归的方法来研究业绩差距排名对基金经理风险承担的影响,同时验证了BHS结论在中国基金市场中的适用性。结果表明BHS结论在中国基金市场中是不成立的,同时表明在中国基金市场中基金经理具有相对业绩排名目标,但此相对业绩排名是本文中所提出的业绩差距排名,此结论可以为监管部门规范基金投资行为以及为投资者选择基金提供参考。  相似文献   

2.
自然保护区的森林健康评价有别于普通的森林健康评价,在评价中要考虑森林对自然保护区的影响。从森林对生态系统、森林社会价值、森林对珍稀保护物种影响等方面构建了自然保护区森林健康评价指标体系,得出自然保护区森林健康综合指数,从而判别自然保护区森林的健康程度,并对北京百花山国家级自然保护区的森林进行健康评价。评价结果表明,15块样地中,有8块样地处于健康以上状态,比例达到了53.3%,亚健康状态样地占到了46.7%,表明百花山保护区森林健康状况良好,与实际调查情况一致,表明指标体系有较好的适用性。图1表3参21  相似文献   

3.
Originally created by the international peasant movement La Vía Campesina, the concept of ??food sovereignty?? is being used with increasing frequency by agrifood activists and others in the Global North. Using the analytical lens of framing, I explore the effects of this diffusion on the transformative potential of food sovereignty. US agrifood initiatives have recently been the subject of criticism for their lack of transformative potential, whether because they offer market-based solutions rather than demanding political ones or because they fail to adequately address existing social injustice. In this paper, I consider how food sovereignty measures up to this critique both as it was originally framed by Vía Campesina and as it is being reframed for the US context. First I briefly compare food sovereignty to community food security (CFS), which was developed more explicitly for the North American context and has been criticized for its lack of transformative potential. I then explore how the potential of food sovereignty has been affected as it is reframed to resonate with US audiences through an examination of its use on the web sites of US-based organizations. I find that, while some reframing of the concept to highlight consumer choice does seem to be occurring, it remains a primarily political concept. It may not, however, be fulfilling its potential for addressing social injustice in the US agrifood system because it tends to be used either in reference to international issues or, when applied to the US context, treated as a rough synonym for local control. I conclude that, if advocates can successfully guide the reframing process, food sovereignty could serve as a valuable counter-hegemonic vision to complement the more pragmatic and locally-grounded work of CFS advocates.  相似文献   

4.
为探讨不同品种断奶仔猪混群后社会等级重建过程中行为差异及其对仔猪生长发育的影响,通过行为评定划分断奶仔猪社会等级,比较保育期民猪仔猪和大白猪仔猪行为差异,分析社会等级与断奶仔猪生产性能关系。采用全事件记录法观测和记录仔猪争斗行为,利用二元交互水平社会关系测量方法确定个体优势等级。研究表明,大白猪仔猪争斗行为次数随所处等级位置升高而增加,民猪仔猪争斗行为次数与其所处等级位置无明显关系;与大白猪相比,民猪仔猪混群后争斗行为次数远低于大白猪仔猪,群居秩序较早达稳定状态;民猪仔猪皮肤损伤程度与所处等级位置呈显著负相关(P<0.05),大白猪仔猪皮肤损伤程度与所处等级位置呈显著正相关(P<0.05)。民猪仔猪等级指数与断奶重存在显著正相关(P<0.05),大白猪仔猪等级指数与断奶重、相对生长速率、日增重均存在显著正相关(P<0.05)。可见,群体结构发生改变时,民猪仔猪争斗行为较少,对新环境适应性较强,群体内社会等级重建对其生产性能影响较小,民猪仔猪更适合混群饲养。  相似文献   

5.
6.
Circadian clocks are influenced by social interactions in a variety of species, but little is known about the sensory mechanisms underlying these effects. We investigated whether social cues could reset circadian rhythms in Drosophila melanogaster by addressing two questions: Is there a social influence on circadian timing? If so, then how is that influence communicated? The experiments show that in a social context Drosophila transmit and receive cues that influence circadian time and that these cues are likely olfactory.  相似文献   

7.
Wang F  Zhu J  Zhu H  Zhang Q  Lin Z  Hu H 《Science (New York, N.Y.)》2011,334(6056):693-697
Dominance hierarchy has a profound impact on animals' survival, health, and reproductive success, but its neural circuit mechanism is virtually unknown. We found that dominance ranking in mice is transitive, relatively stable, and highly correlates among multiple behavior measures. Recording from layer V pyramidal neurons of the medial prefrontal cortex (mPFC) showed higher strength of excitatory synaptic inputs in mice with higher ranking, as compared with their subordinate cage mates. Furthermore, molecular manipulations that resulted in an increase and decrease in the synaptic efficacy in dorsal mPFC neurons caused an upward and downward movement in the social rank, respectively. These results provide direct evidence for mPFC's involvement in social hierarchy and suggest that social rank is plastic and can be tuned by altering synaptic strength in mPFC pyramidal cells.  相似文献   

8.
An outline of a theory ofvalues-based labeling as a social movementargues that it is motivated by the need tore-embed the agro-food economy in the largersocial economy. A review of some basic premisesof embeddedness theories derived from the workof Karl Polanyi reveals their connection toparticular values-based labeling efforts. Fromthis perspective, values-based labelingpresents itself as primarily an ethical andmoral effort to counter unsustainable trendswithin presently existing capitalism. Theselabels distinguish themselves from ordinarycommercial labels by a focus on processand on quality. Evaluating thetransformative potential and progressive natureof values-based labeling poses a key challenge.One avenue for gauging this potential isconventions theory. This approach can beadapted to consider the decision makingprocesses that go on within values-basedlabeling groups, as well as consumer decisionmaking based on such labels, as instances ofwhat is termed a politics of ethical judgment.The conclusion emphasizes the need for moreresearch in this area and suggests how it couldbe furthered.  相似文献   

9.
At maturity, female baboons in the Amboseli National Park of Kenya generally attain a rank position among adults near to that of their mothers. However, the age of a female's mother and the difference in ages between sisters also influence the rank acquisition process. These latter demographic variables, which are sensitive to changes in resource availability, may account for the close association both within and among primate species of specific patterns of rank organization and specific environmental conditions.  相似文献   

10.
Insecticide use: Contexts and ecological consequences   总被引:2,自引:0,他引:2  
Constraints to the sustainability of insecticide use include effects on human health, agroecosystems (e.g., beneficial insects), the wider environment (e.g., non-target species, landscapes and communities) and the selection of insecticide-resistant traits. It is possible to find examples where insecticides have impacted disastrously on all these variables and others where the hazards posed have been (through accident or design) ameliorated. In this review, we examine what can currently be surmised about the direct and indirect long-term, field impacts of insecticides upon the environment. We detail specific examples, describe current insecticide use patterns, consider the contexts within which insecticide use occurs and discuss the role of regulation and legislation in reducing risk. We consider how insecticide use is changing in response to increasing environmental awareness and inevitably, as we discuss the main constraints to insecticide use, we suggest why they cannot easily be discarded. Gregor Devine has an MSc in pest management and a PhD in applied entomology from Imperial College, London. He is a Senior Research Scientist employed by Rothamsted Research, UK. He is currently investigating novel disease vector control methods in Peru in association with the US Naval Medical Research Center Detachment, the Peruvian Ministry of Health, the University of California-Davis, and the US Centers for Disease Control. Michael Furlong has an MSc in pest management and a PhD in applied entomology from Imperial College, London. He is a Lecturer and Researcher in the School of Integrative Biology at the University of Queensland, Australia. His research interests include biological control, and the design and implementation of sustainable Integrated Pest Management strategies for international development. He works in Australia, China, North Korea and the Pacific Islands.  相似文献   

11.
In this paper I examine how knowledge claims operating through two types of governance techniques can guide product innovations in the agri-food sector. The notion that knowledge claims have strong social and material components informs the analysis undertaken, developed through a discussion of social science approaches to the role of human groups and biophysical properties in social change. I apply this socio-technical perspective to two case studies: defining dietary fiber and reducing saturated fat. The first involves attempts to produce an international definition of dietary fiber standards in the Codex Alimentarius Commission. The second involves efforts by food manufacturers to reduce the saturated fat content of food products in line with UK government guidelines. The case studies draw upon observations, document analysis, and over forty interviews. I suggest that although knowledge claims are active constituents of both governance processes, important differences are evident and arise from the history of scientific and technical controversies, and from the scope for articulating broader questions. In particular, the different criteria for judging “success” guide how knowledge claims are implicated in the governance of product innovation. I suggest that further work is required to understand the wider implications of efforts to change the composition of foods, not only for public heath, but also in relation to food security, quality, safety, and availability in a rapidly changing context. In order to do this successfully, knowledge claims made about the material properties of food should be made objects of social science analysis.  相似文献   

12.
Briefly noted is Rep. Albert Gore's introduction of legislation to create a commission to review developments in genetic engineering with potential human application. The proposed commission would consider medical, legal, ethical, and social implications of this research. It would be a purely advisory commission composed of six scientists; six experts in law, theology, ethics, or the social sciences; and three laymen.  相似文献   

13.
本文运用ELECTRE—Ⅰ法划分黄土丘陵地区草场的类型,为草地建设和利用提供科学依据。ELECTRE—Ⅰ法的基本思想:对于一多目标决策问题,构造级别高于关系S,再运用级别高于关系S,从方案集中筛选出级别较高的方案来。该方法不仅具有计算简捷,容易掌握的优点,而且综合性强,精度高。  相似文献   

14.
农田生态系统内,鼠害的形成是土地农业利用和开发的“副产品”,农业生产格局、作物布局和各种农业措施等都会对鼠类的生存与发展产生影响。不科学的灭鼠不仅不能控制害鼠,而且还会刺激鼠类数量的增长。制定农田鼠类管理措施,除了需要掌握鼠类本身的发生规律、种群动态等生物生态学特性外,应关注农业生产格局对鼠类群落产生的重大影响,充分发挥农业措施对鼠类群落种群发生发展的作用。同时,还应注意人类的经济建设活动对鼠类群落的影响,必须认识到鼠害治理是一项社会性的工程。  相似文献   

15.
Humans routinely classify others according to both their individual attributes, such as social status or wealth, and membership in higher order groups, such as families or castes. They also recognize that people's individual attributes may be influenced and regulated by their group affiliations. It is not known whether such rule-governed, hierarchical classifications are specific to humans or might also occur in nonlinguistic species. Here we show that baboons recognize that a dominance hierarchy can be subdivided into family groups. In playback experiments, baboons respond more strongly to call sequences mimicking dominance rank reversals between families than within families, indicating that they classify others simultaneously according to both individual rank and kinship. The selective pressures imposed by complex societies may therefore have favored cognitive skills that constitute an evolutionary precursor to some components of human cognition.  相似文献   

16.
甘肃省县域社会发展水平的综合评价与分析   总被引:1,自引:8,他引:1  
县域社会是县域社会经济系统的重要组成部分,它的快速发展对于社会经济的健康、协调发展,全面小康社会的早日实现都具有重要意义。本文在构建出甘肃县域社会发展评价指标体系的基础上,运用主成分分析法,对甘肃 67 个县的社会经济发展水平进行了定量测度和排序。比较甘肃县域社会和经济发展综合评价得分,可以看出,县域经济发展水平的高低在相当大的程度上决定着社会发展水平;甘肃县域之间社会经济发展水平存在较大差距,而且这种差距很可能由于经济等基础条件的差异不断拉大;县域社会发展是经济、人口、教育科学、文化卫生等因素全面联动发展的系统工程。通过对评价结果的分析得出:甘肃县域社会发展水平的提高有赖于经济快速发展的强有力支撑、人口数量的有效控制和人口素质的大力提高以及科学教育、文化卫生、交通运输等事业的全面改善。同时,应密切注意并防范县域之间发展差距的继续拉大。  相似文献   

17.
Centola D 《Science (New York, N.Y.)》2011,334(6060):1269-1272
How does the composition of a population affect the adoption of health behaviors and innovations? Homophily--similarity of social contacts--can increase dyadic-level influence, but it can also force less healthy individuals to interact primarily with one another, thereby excluding them from interactions with healthier, more influential, early adopters. As a result, an important network-level effect of homophily is that the people who are most in need of a health innovation may be among the least likely to adopt it. Despite the importance of this thesis, confounding factors in observational data have made it difficult to test empirically. We report results from a controlled experimental study on the spread of a health innovation through fixed social networks in which the level of homophily was independently varied. We found that homophily significantly increased overall adoption of a new health behavior, especially among those most in need of it.  相似文献   

18.
性打搅行为是指非人灵长类社群内非交配个体对正在发生性行为个体的干扰行为,该行为在非人灵长类中普遍存在,通过综述目前已知的36种非灵长类的性打搅行为的报道,探讨性打搅行为的功能和意义。性打搅行为具有更高度的种间和种内差异,种间的性打搅的方式不同、同时受到社会结构和婚配制度的影响;在种内受到性别、年龄、等级等因素的影响。结合川金丝猴性打搅的研究结果,从性打搅的类型、被打搅的反应、性打搅的功能以及相关假说等方面入手,对非人灵长类性打搅行为进行系统总结,旨在为我国相关领域的研究提供参考,为生殖行为学研究者启发思路,推动本领域的发展。  相似文献   

19.
蚯蚓粪作为土壤重金属污染修复剂的潜力分析   总被引:4,自引:0,他引:4  
随着工农业的发展,重金属对土壤和农作物的污染问题越来越突出,对土壤重金属的修复研究也越来越重要。蚯蚓作为土壤环境中最常见的无脊椎动物在生活过程中的摄食、做穴、移动、排便等行为都会对土壤重金属产生影响。通过对蚯蚓粪作为土壤重金属污染修复剂的潜力进行总结、分析,对蚯蚓粪修复土壤重金属污染的研究方向提出了建议与展望。  相似文献   

20.
While I have wandered from the main subject of the sun, to consider the source of stellar energy, the two topics are so intimately related that their solutions are identical. I consider that I have demonstrated the reasonableness of Jeans's theory by the manner in which it seems to fit the observed facts. There is, as I can see, no important objection to the hypothesis. It is too much to hope that the foregoing analysis is rigidly complete, but I confidently believe that the main points are established and that further modification will consist in the clearing up of details. The application of astrophysics and atomic theory to a new field appears to have met with considerable success. In spite of this success, however, caution is necessary. The present position of the theory advocated in this paper is somewhat analogous to the place once held by the theory of Helmholtz-i.e., it is the only one sufficiently elastic to stretch over the region of known facts. Our knowledge is yet limited and, with our vision thus impaired, we can not predict the future. Some unforeseen event may upset our present hypothesis as completely as that of Helmholtz; we have built as securely as possible upon observation, and it remains for the future to test the accuracy of this or any other theory so established. In an attempt to discover a reasonable explanation of the origin and duration of the solar radiation, all possible sources of energy are examined. The following hypotheses are reviewed and discarded, the arguments against their validity being too well known to necessitate a review at this place; (1) Original Heat; (2) Chemical; (3) Gravitational, (a) Meteoric, (b) Contraction; (4) Radioactive.  相似文献   

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