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71.
Children are considered particularly important in debates about the possibilities and dangers of information and communication technologies (ICT). Discourses on ICT contain paradoxical representations of childhood. On the one hand, unlike most other understandings of child/adult relations, these discourses assume children to be equally, if not more, technologically competent than adults. On the other hand, children's very competence at using ICT is alleged to be putting them “at risk” of abuse or corruption. This paper addresses these moral panics about children and ICT by exploring to what extent and why parents are concerned about their children's safety in on‐line space. In doing so the paper reflects on the extent to which anxieties about children in cyberspace replicate concerns about public outdoor space and the way networked computers emerge as different tools in different households. 相似文献
72.
Murphy Sarah J. Washington Richard Downing Thomas E. Martin Randall V. Ziervogel Gina Preston Anthony Todd Martin Butterfield Ruth Briden Jim 《Natural Hazards》2001,23(2-3):171-196
One of the most promising developments for early warning of climate hazards is seasonal climate forecasting. Already forecasts are operational in many parts of the tropics and sub-tropics, particularly for droughts and floods associated with ENSO events. Prospects for further development of seasonal forecasting for a range of climatichazards are reviewed, illustrated with case studies in Africa, Australia, the U.S.A. and Europe. A critical evaluation of the utility of seasonal forecasts centres on vulnerability, communicationchannels, and effective responses. In contrast to short-term prediction, seasonal forecasts raise new issues of preparedness and the use of information. 相似文献
73.
Lawrence S. Hamilton Dr. 《GeoJournal》1992,27(1):13-22
While additional research in needed on the hydrological and erosional effects of changes in mountain forests, sufficient knowledge is available, or may be inferred from existing research, to question, refute or reaffirm some of the conventional wisdom about the protective role of these forests. A major difficulty is sorting out the consequences of natural processes from those caused by anthropogenic actions. The effects of alteration or removal/conversion of mountain forests on rainfall, surface erosion, mass erosion, sediment, floods and low flows is reviewed. It is suggested that a key factor in the cause/effect scenario is the size of the catchment unit being appraised. 相似文献
74.
ABSTRACTEnvironmental flow standards are a management tool that can help to protect the ecosystem services sustained by rivers. Although environmental flow requirements can be assessed using a variety of methods, most of these methods require establishing relationships between flow and habitat of species of concern. Here, we conducted a synthesis of past flow–ecology studies in the southeast USA. For each state or interstate river basin, we used the published data to determine the flow metrics that resulted in the greatest changes in ecological metrics, and the ecological metrics that were most sensitive to hydrologic alteration. The flow metrics that were most important in preserving ecological metrics were high-flow duration and frequency, 3-day maximum and minimum, and number of reversals. The ecological metrics most sensitive to hydrologic alteration were mostly related to presence or absence of key indicator species. 相似文献
75.
76.
The San Francisco Estuary Regional Monitoring Program initiated surveillance monitoring to identify previously unmonitored synthetic organic contaminants in the San Francisco Estuary. Organic extracts of water samples were analyzed using gas chromatography-mass spectrometry in full scan mode. The major contaminant classes identified in the samples were fire retardants, pesticides, personal care product ingredients, and plasticizers. Evidence from the literature suggests that some of these contaminants can persist in the environment, induce toxicity, and accumulate in marine biota and in higher food chain consumers. The major sources of these contaminants into the marine environment are the discharge of municipal and industrial wastewater effluents, urban stormwater, and agricultural runoff. As a proactive effort, it is suggested that surveillance studies be used routinely in monitoring programs to identify and prevent potential problem contaminants from harming the marine environment. 相似文献
77.
Sarah L. Holloway 《Geoforum》2007,38(1):7-20
In the past decade geographers have critiqued the exclusivity of idyllic representations of rurality and sought to explore the diverse experiences of Other social groups in the countryside. This paper builds upon that small but significant strand of research which has highlighted the whiteness of representations of rurality and the consequences of this for racialised minorities. These debates have been crucially important in forwarding our understanding of racially-exclusive constructions of idyllic country living; however, it is important that academics neither assume that such ideas are forever fixed, nor that they affect all minority ethnic groups in the same ways. This paper takes both the potential power and frailty of these ideas seriously, as it examines how the concepts of race, racism and rurality are deployed by different commentators as they debate the place of one specific minority ethnic group in the English countryside. The route taken into this is a consideration of print-media reporting of events in Firle, Sussex, where, in 2003, some white rural residents symbolically purged their village of Gypsy-Travellers by burning a mock caravan complete with effigies at their annual bonfire celebrations. In conclusion, the paper challenges the relative lack of attention to these issues within the white-dominated discipline of geography, and argues that it is imperative to trace the dynamic ways in which the whiteness of idyllic understandings of the rural are reinforced and challenged through contemporary social practice. 相似文献
78.
In spite of raising Asian per capita food production by 27% and making India food self-sufficient, the Green Revolution has received much criticism for its environmental and socio-economic impacts. Taking on board post-development critiques of ‘speaking for’ Third World ‘others’, this paper seeks to examine the Green Revolution from the points of view of people directly affected by it. Comparative, historically-informed research in three villages for which 1972 baseline data exist reveal that the Green Revolution has ensured, in the words of one marginal farmer that ‘nobody sleeps with an empty stomach nowadays’. Most villagers associate the Green Revolution with increases in living standards and weakening community-based wealth hierarchies. Nevertheless, socio-economic inequalities between certain Scheduled Castes and other villagers are still very apparent. 相似文献
79.
Henry P. Huntington Michelle Boyle Gwenn E. Flowers John W. Weatherly Lawrence C. Hamilton Larry Hinzman Craig Gerlach Rommel Zulueta Craig Nicolson Jonathan Overpeck 《Climatic change》2007,82(1-2):77-92
Human activities in the Arctic are often mentioned as recipients of climate-change impacts. In this paper we consider the
more complicated but more likely possibility that human activities themselves can interact with climate or environmental change
in ways that either mitigate or exacerbate the human impacts. Although human activities in the Arctic are generally assumed
to be modest, our analysis suggests that those activities may have larger influences on the arctic system than previously
thought. Moreover, human influences could increase substantially in the near future. First, we illustrate how past human activities
in the Arctic have combined with climatic variations to alter biophysical systems upon which fisheries and livestock depend.
Second, we describe how current and future human activities could precipitate or affect the timing of major transitions in
the arctic system. Past and future analyses both point to ways in which human activities in the Arctic can substantially influence
the trajectory of arctic system change. 相似文献
80.
Rare-earth abundances in chondritic meteorites 总被引:1,自引:0,他引:1
Fifteen chondrites, including eight carbonaceous chondrites, have been analyzed for rare earth element (REE) abundances by isotope dilution. These analyses complement and extend earlier isotope dilution REE determinations in chondrites, performed in other laboratories, so that coverage of major chondrite classes is now complete. An examination of this body of precise and comparable REE data from individual chondrites reveals that only a small proportion of the analyses have flat, unfractionated REE patterns within experimental error. A statistical procedure is used to derive revised chondritic abundances of REE by selection of unfractionated patterns. A number of the remaining analyses show Eu anomalies and fractionated patterns consistent with magmatic fractionation as encountered in the products of planetary differentiation. However, many patterns exhibit features not readily explicable by known magmatic processes; in particular, positive Ce anomalies are often encountered. Abundance anomalies can be quantitatively determined by the use of a least-squares curve fitting procedure. The wide variety of anomalous patterns and the uncertainties in model parameters preclude detailed modeling of the origin of anomalies, but it is probable that at least some arise from fractional condensation in the solar nebula, as has been demonstrated for Allende inclusions. Elemental abundance anomalies are found in all major chondrite classes. If these anomalies are ignored, the range and nature of variation within chondrite classes are consistent with a parent body model, in which solid-liquid or solid-solid equilibria induce variations from an unfractionated bulk composition. Absolute abundances in the H, L and LL parent bodies are almost twice those of the E parent body.The persistence of anomalies in chondritic materials relatively removed from direct condensational processes implies that anomalous components are resistant to equilibration or were introduced at a late stage of chondrite formation. Large scale segregation of gas and condensate is also implied, and raises the possibility of bulk variations in REE abundances between planetary bodies. 相似文献