A new modelling approach to urban sprawl dynamics is introduced which allows representing qualitative knowledge on relations
between moving actor populations and properties of locations. The results of this Qualitative Attractiveness Migration (QuAM)
Model are scenario-like sets of possible future developments of the urban system, much in contrast to quantitative forecasts
gained by traditional modelling approaches. QuAM models allow for the interaction between internal dynamics and external influences.
The application of the new approach is exemplified by the case of urban sprawl in Leipzig since 1990. It was possible to reproduce
the observed qualitative development and to calculate future scenarios. The scenario runs project a new wave of middle class
driven residential sprawl and suggest implications for sprawl reducing policy interventions. 相似文献
Workers at an electronics recycling plant have previously been shown to have elevated serum levels of polybrominated diphenyl ethers (PBDEs) compared to referents without occupational PBDE exposure. Subsequent structural changes and industrial hygiene measures at the plant were applied to improve the work environment. The present study aims to assess the impact of these work environment changes on the occupational exposure to PBDEs.
Blood were drawn from the workers and analyzed at two different laboratories, and serum concentrations of several PBDE congeners were determined by GC/MS or GC/HRMS. Cross-sectional studies were performed prior to (in 1997; N = 19) and after (in 2000; N = 27) workplace improvements. Longitudinal studies were performed on twelve of the workers that were sampled at both occasions.
Even though the amount of processed goods had doubled in 2000 as compared to 1997, there was a significant decrease in the serum levels of BDE-183 and BDE-209. For BDE-209 the levels observed in year 2000 were even lower than in referents with no occupational exposure. In contrast to the decrease of higher brominated diphenyl ethers, the concentrations of BDE-47 did not significantly change. For BDE-153, the cross-sectional study indicated no change, whereas the longitudinal follow up indicated a significant increase.
This study shows that the industrial hygiene improvements clearly reduced the occupational exposure to BDE-183 and BDE-209 at the plant. Still, the levels of hexa- to nonaBDEs but not BDE-209 were elevated, compared to referents with no occupational exposure. 相似文献
Floral colour patterns are contrasting colour patches on flowers, a part of the signalling apparatus that was considered to display shape and colour signals used by flower-visitors to detect flowers and locate the site of floral reward. Here, we show that flower-naïve bumblebees (Bombus terrestris) spontaneously direct their approach towards the outside margin of artificial flowers, which provides contrast between these dummy flowers and the background. If no floral guides are present, the bumblebees continue to approach the margin and finally touch the marginal area of the dummy flower with the tips of their antennae. Whilst approaching dummy flowers that also have a central floral guide, the bumblebees change their direction of flight: Initially, they approach the margin, later they switch to approaching the colour guide, and finally they precisely touch the floral guide with their antennae. Variation of the shape of equally sized dummy flowers did not alter the bumblebees’ preferential orientation towards the guide. Using reciprocal combinations of guide colour and surrounding colour, we showed that the approach from a distance towards the corolla and the antennal contact with the guide are elicited by the same colour parameter: spectral purity. As a consequence, the dummy flowers eliciting the greatest frequency of antennal reactions at the guide are those that combine a floral guide of high spectral purity with a corolla of less spectral purity. Our results support the hypothesis that floral guides direct bumblebees’ approaches to the site of first contact with the flower, which is achieved by the tips of the antennae.Electronic Supplementary Material Supplementary material is available for this article at 相似文献
District Swat is part of the high mountain Hindu-Kush Himalayan region of Pakistan. Documentation and analysis of land use change in this region is challenging due to very disparate accounts of the state of forest resources and limited accessible data. Such analysis is, however, important due to concerns over the degradation of forest land leading to deterioration of the protection of water catchments and exposure of highly erodible soils. Furthermore, the area is identified as hotspot for biodiversity loss. The aim of this paper is to identify geophysical and geographical factors related to land use change and model how these relationships vary across the district. For three selected zones across the elevation gradient of the district, we analyse land use change by studying land use maps for the years 1968, 1990 and 2007. In the high-altitude zone, the forest area decreased by 30.5 %, a third of which was caused by agricultural expansion. In the mid-elevation zone, agriculture expanded by 70.3 % and forests decreased by 49.7 %. In the lower altitudes, agriculture expansion was 129.9 % consuming 31.7 % of the forest area over the forty-year time period. Annual deforestation rates observed were 0.80, 1.28 and 1.86 % in high, mid and low altitudes, respectively. In the high-altitude ecosystems, accessibility (distance to nearest road and city) had no significant role in agriculture expansion; rather land use change appears significantly related to geophysical factors such as slope, aspect and altitude. In the low-elevation zone, accessibility was the factor showing the closest association with agriculture expansion and abandonment. The analysis illustrates that land use change processes vary quite considerably between different altitudinal and vegetation cover zones of the same district and that environmental constraints and stage of economic development provide important contextual information. 相似文献
Zusammenfassung Ein Eintrag von Arzneimitteln, Diagnostika und Desinfektionsmitteln in die Umweltbereiche Wasser und Boden kann aus Krankenh?usern,
anderen medizinischen Einrichtungen, Haushalten (Verschreibungen durch niedergelassene ?rzte) und der Tierhaltung bzw.-mast
oder-zucht einschlie?lich der Aquakultur (Arzneimittel zur Therapie und Prophylaxe sowie Futtermittelzusatzstoffe) sowie durch
den Gebrauch bei Heimtieren resultieren. Im Folgenden sollen grunds?tzliche Erw?gungen und übergeordnete Gesichtspunkte zum
Eintrag von Pharmaka, Diagnostika und Desinfektionsmitteln ausführlicher er?rtert werden. Im Mittelpunkt stehen dabei neben
den gesetzlichen Regelungen die Eigenschaften der Stoffe, ihr daraus abzuleitendes Umweltverhalten, die damit verbundene Risikoabsch?tzung
sowie notwendige Ma?nahmen zur L?sung des Problemkreises ‘Arzneimittel in der Umwelt’. Neben den eigentlichen Arzneimitteln
werden in der Human- und Tiermedizin eine Vielzahl weiterer Stoffe z.B. für die Diagnostik und aus hygienischen Gründen verwendet.
Sie werden in die Betrachtungen eingeschlossen.
Dieser Beitrag ist Prof. Dr. Fritz Frimmel zum 60. Geburtstag gewidmet.相似文献
An already large and rapidly increasing number of manmade organic contaminants is found to be present in environmental samples from around the world. However, the biological effects of many of these compounds are unknown. Traditional biological testing, albeit important, cannot be done on each chemical due to limitations of the available resources. Therefore, new avenues should be pursued to screen out the hazardous compounds for more intensive research. One of these avenues, quantitative structure-activity correlations, applies the existing knowledge to estimate the effects of other, structurally related compounds. In combination with a fast and cost-effective biological test, this method appears useful in solving both the existing backlog and future needs for information on the safety and environmental effects of new chemicals. 相似文献
ABSTRACT: The resource management problem for the Middle Platte ecosystem is the insufficient water available to meet both instream ecological demands and out‐of‐stream economic needs. This problem of multiple interest groups competing for a limited resource is compounded by sharp disagreement in the scientific community over endangered species' needs for instream flows. In this study, game theory was used to address one dimension of this resource management problem. A sequential auction with repeated bidding was used to determine how much instream flow water each of three states — Colorado, Nebraska, and Wyoming — will provide and at what price. The results suggest that the use of auction mechanisms can improve the prospects for reaching a multi‐state agreement on who will supply instream flow water, if the auction is structured to discourage misrepresentation of costs and if political compensation is allowed. 相似文献