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Spatial variation in soil inorganic nitrogen across an arid urban ecosystem   总被引:4,自引:1,他引:3  
We explored variations in inorganic soil nitrogen (N) concentrations across metropolitan Phoenix, Arizona, and the surrounding desert using a probability-based synoptic survey. Data were examined using spatial statistics on the entire region, as well as for the desert and urban sites separately. Concentrations of both NO3-N and NH4-N were markedly higher and more heterogeneous amongst urban compared to desert soils. Regional variation in soil NO3-N concentration was best explained by latitude, land use history, population density, along with percent cover of impervious surfaces and lawn, whereas soil NH4-N concentrations were related to only latitude and population density. Within the urban area, patterns in both soil NO3-N and NH4-N were best predicted by elevation, population density and type of irrigation in the surrounding neighborhood. Spatial autocorrelation of soil NO3-N concentrations explained 49% of variation among desert sites but was absent between urban sites. We suggest that inorganic soil N concentrations are controlled by a number of ‘local’ or ‘neighborhood’ human-related drivers in the city, rather than factors related to an urban-rural gradient.  相似文献   
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For the past two decades there has been much debate about the future of family farming. The basic question on which this debate has turned is whether current pressures on family farm systems should be understood as symptomatic of a terminal condition, in which farmers are replaced progressively by corporate ownership; or whether family farms will persist as a social formation, albeit increasingly subsumed by off-farm interests. Using evidence from the Australian processing tomato sector, this article documents the changing social and economic formation of ‘family farming’. We argue that in this industry, the appropriate way to describe farmers is through the deployment of that a new category of farming; farm family entrepreneurs. This phrase is coined to describe the situation where family units remain at the social and economic heart of farm ownership and operation, but in the context where they relate to their land-based assets through legal and financial structures characteristic of the wider economy. As this article explores, this formation seems to represent an accommodating modus operandi for farm units within neo-liberal agricultural governance. Nevertheless, however, this duality of family-based structures and capitalist entrepreneurialism inevitably provokes a series of tensions, whose resolution requires a variety of organizational strategies to be put in place.  相似文献   
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This paper describes and analyses the author's attempts to engage in a user-led design/research process. This was undertaken during an MA in Design Research for Disability. The first section of the study delineates the background and context of the process of inquiry. This involves examination of the common features within design participation and emancipatory research. The second section of the study uses six principles of emancipatory research, defined by Emma Stone and Mark Priestley (1996), as a framework for analysis of the author's own process of inquiry.  相似文献   
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Many observers doubt the capacity of digital media to change the political game. The rise of a transnational activism that is aimed beyond states and directly at corporations, trade and development regimes offers a fruitful area for understanding how communication practices can help create a new politics. The Internet is implicated in the new global activism far beyond merely reducing the costs of communication, or transcending the geographical and temporal barriers associated with other communication media. Various uses of the Internet and digital media facilitate the loosely structured networks, the weak identity ties, and the patterns of issue and demonstration organizing that define a new global protest politics. Analysis of various cases shows how digital network configurations can facilitate: permanent campaigns; the growth of broad networks despite relatively weak social identity and ideology ties; transformation of individual member organizations and whole networks; and the capacity to communicate messages from desktops to television screens. The same qualities that make these communication-based politics durable also make them vulnerable to problems of control, decision-making and collective identity.  相似文献   
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Previous research concerned with children's belief-desire psychology has examined the capacity to predict or interpret action on the basis of the implicit proposition that ‘when an actor desires a particular end and believes that a particular action will achieve that end, he or she will undertake that action’. The limitations of this formulation for understanding acts of omission are outlined and an elaborated version of belief-desire psychology introduced. This version holds that ‘when an actor desires a particular end and believes that a particular action will achieve that end, and when it is believed that there are no co-occurring outcomes of that action whose avoidance is desired more highly than is the originally conceived end, then the actor will undertake the action which will satisfy the original desire’. An experiment is reported which examines 4-, 5, and 7-year-olds' ability to predict story characters' actions on the basis of either their true or false beliefs concerning undesirable outcomes associated with the pursuit of a desired end. Children of all age-groups provided evidence of understanding the elaborated version of belief-desire psychology. However, a significant improvement was noted between the ages of 4 and 7 years in the ability to understand circumstances involving false beliefs.  相似文献   
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Are the decisions of American policymakers informed by generaltrends in the public’s ideology or by the public’spolicy-specific preferences? In this article we discuss twoexplanations for the types of public opinion information thatpoliticians collect and use. Using a unique data set of privatepolls from the White House of Richard Nixon, we find that whenopinion data on specific policies were available, the presidentrelied on them and not on general ideology data. On less importantissues, however, we find that the president often chose notto collect policy-specific data and instead relied on generalideology data. The differential collection and use of informationby policymakers reflect varying strategic calculations. Theyalso have profound implications for representative democracyand the demands placed on citizens and governors.  相似文献   
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