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651.
652.
The resilience of any system, human or natural, centres on its capacity to adapt its structure, but not necessarily its function, to a new configuration in response to long‐term socio‐ecological change. In the long term, therefore, enhancing resilience involves more than simply improving a system's ability to resist an immediate threat or to recover to a stable past state. However, despite the prevalence of adaptive notions of resilience in academic discourse, it is apparent that infrastructure planners and policies largely continue to struggle to comprehend longer‐term system adaptation in their understanding of resilience. Instead, a short‐term, stable system (STSS) perspective on resilience is prevalent. This paper seeks to identify and problematise this perspective, presenting research based on the development of a heuristic ‘scenario–episode’ tool to address, and challenge, it in the context of United Kingdom infrastructure resilience. The aim is to help resilience practitioners to understand better the capacities of future infrastructure systems to respond to natural, malicious threats. 相似文献
653.
Andrew J. Higgins 《Journal of the American Water Resources Association》1984,20(3):425-434
The project was designed to demonstrate the potential benefits of utilizing sewage sludge as a soil conditioner and fertilizer on Sassafras sandy loam soil. Aerobically digested, liquid sewage sludge was applied to the soil at rates of 0, 22.4, and 44.8 Mg of dry solids/ha for three consecutive years between 1978 and 1981. Groundwater, soil, and crop contamination levels were monitored to establish the maximum sewage solids loading rate that could be applied without causing environmental deterioration. The results indicate that application of 22.4 Mg of dry solids/ha of sludge is the upper limit to ensure protection of the groundwater quality on the site studied. Application rates at or slightly below 22.4 Mg of dry solids/ha are sufficient for providing plant nutrients for the dent corn and rye cropping system utilized in the study. 相似文献
654.
Leonard J. Greenfield Curtis R. Hare 《Journal of the American Water Resources Association》1973,9(5):923-931
ABSTRACT: Analyses of soil and water were made in a stretch of shallow ground north of a cypress head in South Florida. The area is covered with water for part of the year, and it flows slowly southward. The soil is primarily peat formed from the local graminid vegetation during its decay. The top layer consists of a blue-green algal mat whose decay products contribute to the peat also. Collections of soil (including the top layer) were made layer by layer and anlyzed for cations and anions and for ion exchange capacity. The latter appears to be high enough in all layers to account for the ion content within the soil and surrounding waters. It probably is a very important buffer system that retards limestone erosion. CEC values ranged from 20 to 190 meg/100 gm dry soil from bedrock to surface. 相似文献
655.
The heart is often perceived as a difficult organ to understand by ultrasound during fetal life. This is undoubtedly reflected in the low detection rate of cardiac abnormalities as compared to those of most other organ systems in the fetus. In this article we start by updating classical concepts of cardiac embryology, many of which were previously difficult to understand since they were overly simplistic or purely observational. We then lead on to the structure and growth of the fully formed fetal heart where we review the anatomy and ultrasound appearances in detail and provide comparisons with major abnormalities. We emphasise the fact that a solid understanding of cardiac anatomy can enable those involved in fetal medicine to make full use of the views of the heart that are obtained by ultrasound and which are often only transient. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
656.
657.
658.
Repeated cutting of vegetation at or near ground level in power-line corridors is a common practice for inhibiting tree growth
and regeneration. However, few data exist on long-term community responses. In this study, we sampled 20 northern Kentucky
power-line corridors and compared their seedling and sapling communities to the edges and interiors of adjacent undisturbed
forests. Mean seedling and sapling density in corridors was roughly twice that of adjacent undisturbed forest interiors, suggesting
that repeated cutting is not a viable method of inhibiting tree regeneration. Corridor communities were dominated byRobinia pseudoacacia (black locust) andFraxinus americana (white ash), but ordinations indicated strong similaritties among communities in corridors and adjacent forests. Many of
the tree species found in adjacent forests, with the exception of a few shade-tolerant species, had highest seedling and sapling
densities in corridors. Stump or root sprouting by many species appears to regenerate forests quickly after cutting. However,
disturbed soil and detritus accumulations caused by management crews and their equipment may also create a large variety of
microsites for seedling establishment. Because repeated cutting selects for dominance by species with highest sprout growth
rates, it should not be used as the sole management technique. It may instead be used to alter the vigor, stature, and stored
reserves of trees so that herbicides or other methods of tree control can be used more efficiently. 相似文献
659.
660.
Andrew S. Laughland Lynn M. Musser Wesley N. Musser James S. Shortle 《Journal of the American Water Resources Association》1993,29(2):291-299
ABSTRACT: A survey of individuals during a Giardia contamination incident provided data to calculate the cost of boiling, hauling, or purchasing water to avoid infection. Three different approaches to the valuation of time were used to assess the implications of the opportunity cost of time for the measurement of averting costs. Mean monthly household averting costs were $33.47 using family income to value time, $13.07 using the minimum wage to value time, and $5.60 using zero opportunity cost of time. Comparisons of the mean costs for different sources and household characteristics indicated the value of time from family income was too high and that the other methods of valuing time were superior. 相似文献