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321.
A number of industries monitor levels of chemicals in their effluent, but few have undertaken prolonged biological monitoring of this wastewater. The focus of the present study was to determine whether past chemical data for effluent from a lead smelter could be used to estimate its past toxicity. Since the interactive effects of metals in effluents are often assumed to be additive, it was hypothesized that an additive model, 100/[sigma(metal concentration in effluent/EC50 for individual metal)], could be used to generate an EC50 from chemical data (where EC50 is the concentration of test material that affects 50% of the test organisms). To test the approach, a larval development toxicity test with the marine polychaete, Galeolaria caespitosa, was used to test 26 separate samples of effluent from a lead smelter, generating empirical EC50 values. EC50 values for each individual metal in the effluent were also generated using the larval development toxicity test. The concentrations of trace metals in each effluent sample were determined and, using the additive model, EC50 values were calculated. For the majority of effluent samples tested, the additive model underestimated toxicity, suggesting the presence of additional unidentified contaminants in the effluent samples. Additionally, a nonlinear rather than linear regression curve was found to best describe the relationship between the model and empirically derived EC50 values. This relationship was then used to estimate past trends in toxicity of the smelter effluent. Forty-eight percent of the variability in measured toxicity was explained by the model, with the model underestimating toxicity in the majority of samples. 相似文献
322.
Despite the widespread use of incentive systems in manufacturing organizations, few studies have used a standard, quasi-experimental research design to directly compare the effects of different plans on employee perceptions and work outcomes. In this study, multiple methods were used to assess changes at a company which ended an individually-oriented piecework plan and subsequently began a high-involvement gainsharing plan. This piecework-to-gainsharing transition involved (a) terminating individual incentives, (b) paying plant-wide bonuses for performance improvements, and (c) developing a highly structured ‘idea’ system which allowed employees limited participation in work decisions. Survey responses obtained two months before the transition and again 15 months later revealed improvements in perceptions of teamwork and concern for performance. Interrupted time series analysis of over four years of objective data showed a significant decrease in grievances and a significant increase in product quality occurring at the time of the intervention. Concerning the latter, defective products per 1000 shipped decreased from 20.93 under piecework to 2.31 under gainsharing. The results are discussed within the framework of Deutsch's (1949a) theory of cooperation and competition. 相似文献
323.
Summary We investigated the process of sexual maturation in winged queens of the fire ant Solenopsis invicta, a species with two distinct forms of social organization. We found that queens of the monogynous social form (single reproductive queen per colony) differ little or not at all from queens of the polygynous form (multiple reproductive queens per colony) in weight and fat content when these are pupae or newly-eclosed adults. Furthermore, the size of a sclerotized region of the adult thorax, which is set during larval growth, does not differ between queens of the two forms. In contrast, winged queens of the two social forms differ dramatically in their physiological phenotypes once they have matured, with monogynous queens weighing more and having greater fat reserves than polygynous queens. A crossfostering experiment revealed that the different maturation processes of queens of the two forms are induced largely by the type of colony in which a queen matures (monogynous or polygynous) rather than being due to intrinsic genetic differences between the forms. However, genetic variation at a single locus does appear to play some role in determining physiological phenotype in queens of the polygynous form, providing an example of genotype-environment interaction in the expression of these physiological traits. Differences between the social forms in the mature phenotypes that are produced constrain the reproductive options of queens, so that the characteristic social organization of a colony is perpetuated by virtue of the social environment in which new queens are reared.
Correspondence to: L. Keller 相似文献
324.
Modeling obsolete computer stock under regional data constraints: An Atlanta case study 总被引:1,自引:0,他引:1
Nancey Green Leigh Matthew J. Realff Ning Ai Steven P. French Catherine L. Ross Bert Bras 《Resources, Conservation and Recycling》2007,51(4):847-869
In this paper, we report on our efforts to develop a research framework that can be used to quantify waste flows for different geographical areas in the face of limited waste data availability. We demonstrate this framework in our case study of obsolete computers in the Atlanta metropolitan area. We develop computer obsolescence rates at the national metropolitan level, and couple this data with economic information at the census tract level to generate product inventory estimates (PIE) of the stock of obsolete computers from both business and household sectors in the Atlanta metropolitan area. We seek to improve the accuracy of waste flow estimates for specific geographic areas over those of previous studies, provide an easily replicable and cost effective methodology, highlight the ensuing spatial implications for collection and recycling systems using GIS, and demonstrate the potential economic benefits from diverting electronic wastes within a region. The modeling framework we have developed is intended to be applicable to other regions and to other medium range durable goods discarded by households, businesses, or obtained from buildings. 相似文献
325.
Auristela Mueses Ahmed Said Mark Ross 《Journal of the American Water Resources Association》2007,43(2):473-481
Abstract: A discharge rating is a relationship between stage and discharge at a specific point in a river stream or lake outlet structure. Rating curves are useful for interpolating and perhaps extrapolating flow measurements and for use directly in storage routing models. However, rating data and stations are limited. A generalized nondimensional mathematical expression that describes the rating relation of depth and discharge has been developed and tested against observations from 46 stations in West‐Central Florida. Three approaches were tested in sequence to select the best fit. The proposed model is a log‐linear equation with zero intercept and a slope that fits more than 50% of the stations were analyzed. The model is normalized by the depth and discharge values at 10% exceedance from data published by the U.S. Geological Survey. For ungauged applications, Q10 and d10 were derived from a relationship shown to be reasonably well correlated to the watershed drainage area. The average relative error for this parameter set shows that for the flow range up to the Q10 discharge, better than 30% agreement with the USGS rating data can be expected for about 50% of the stations. Further analysis is required to determine why so many stations exhibit such similar behavior and to identify the criteria or parameters governing the differences. 相似文献
326.
327.
We studied the lipid dynamics (lipid contents, classes and fatty acids) during oogenesis and early embryogenesis of 7 viviparous
and 3 oviparous deepwater chondrichthyans. Mature pre-ovulated ovarian follicles of all species were high in lipid content,
indicative of large energetic expenditure and high maternal investment. Larger lipid reserves were found in viviparous dogshark
(28–36% wet weight, ww) compared to oviparous chimaeras (19–24% ww) and catshark, F. boardmani (18% ww). Neutral lipids and monounsaturated fatty acids were the main source of lipidic energy during vitellogenesis and
gestation. For most species, there was a peak in total lipid content, levels of storage lipids and essential fatty acids at
time of ovulation. Interspecific variation of total lipid yolk reserves and lipid class profiles was largely explained by
differences in parity mode, reproductive (continuous vs. non-continuous oocytes development) strategy and depth-related physiological adaptations. Fatty acid profiles were less variable
among species with the most important fatty acids including: 16:0, 18:1ω9, 20:1ω9, 20:4ω6 and 22:6ω3. These findings provide
a greater biochemical understanding of different maternal-embryonic relationships among chondrichthyans, which can be used
as a baseline for subsequent comparative studies. 相似文献
328.
Chapple RS Ramp D Bradstock RA Kingsford RT Merson JA Auld TD Fleming PJ Mulley RC 《Environmental management》2011,48(4):659-674
Effective management of large protected conservation areas is challenged by political, institutional and environmental complexity
and inconsistency. Knowledge generation and its uptake into management are crucial to address these challenges. We reflect
on practice at the interface between science and management of the Greater Blue Mountains World Heritage Area (GBMWHA), which
covers approximately 1 million hectares west of Sydney, Australia. Multiple government agencies and other stakeholders are
involved in its management, and decision-making is confounded by numerous plans of management and competing values and goals,
reflecting the different objectives and responsibilities of stakeholders. To highlight the complexities of the decision-making
process for this large area, we draw on the outcomes of a recent collaborative research project and focus on fire regimes
and wild-dog control as examples of how existing knowledge is integrated into management. The collaborative research project
achieved the objectives of collating and synthesizing biological data for the region; however, transfer of the project’s outcomes
to management has proved problematic. Reasons attributed to this include lack of clearly defined management objectives to
guide research directions and uptake, and scientific information not being made more understandable and accessible. A key
role of a local bridging organisation (e.g., the Blue Mountains World Heritage Institute) in linking science and management
is ensuring that research results with management significance can be effectively transmitted to agencies and that outcomes
are explained for nonspecialists as well as more widely distributed. We conclude that improved links between science, policy,
and management within an adaptive learning-by-doing framework for the GBMWHA would assist the usefulness and uptake of future
research. 相似文献
329.
Abstract Media and academic debates about the environment have increasingly made reference to the so-called ‘eco-preneur’ (‘green entrepreneur’ or ‘environmental entrepreneur’). These discussions encourage us to see the potential of such figures to act as drivers of environmental innovation. Their combination of entrepreneurial zeal and green motivations is seen as providing them with the ability to transcend the usual tensions between business and the environment. In academic circles a new literature is beginning to emerge around this perspective, ‘eco-preneurship’. In this paper we investigate the usefulness of eco-preneurship for understanding environmental innovation. In particular we ask where this literature, supported by popular images in the media, fixes our gaze when we think about environmental innovation in society. And, crucially, what might we be missing by concentrating our attention on these eco-preneurs? The paper concludes by suggesting that environmental innovation is better understood as an inherently messy and complex institutional process, which cannot be reduced to the psychology of entrepreneurial personalities. 相似文献
330.
Hungate BA Johnson DW Dijkstra P Hymus G Stiling P Megonigal JP Pagel AL Moan JL Day F Li J Hinkle CR Drake BG 《Ecology》2006,87(1):26-40
Experimentally increasing atmospheric CO2 often stimulates plant growth and ecosystem carbon (C) uptake. Biogeochemical theory predicts that these initial responses will immobilize nitrogen (N) in plant biomass and soil organic matter, causing N availability to plants to decline, and reducing the long-term CO2-stimulation of C storage in N limited ecosystems. While many experiments have examined changes in N cycling in response to elevated CO2, empirical tests of this theoretical prediction are scarce. During seven years of postfire recovery in a scrub oak ecosystem, elevated CO2 initially increased plant N accumulation and plant uptake of tracer 15N, peaking after four years of CO2 enrichment. Between years four and seven, these responses to CO2 declined. Elevated CO2 also increased N and tracer 15N accumulation in the O horizon, and reduced 15N recovery in underlying mineral soil. These responses are consistent with progressive N limitation: the initial CO2 stimulation of plant growth immobilized N in plant biomass and in the O horizon, progressively reducing N availability to plants. Litterfall production (one measure of aboveground primary productivity) increased initially in response to elevated CO2, but the CO2 stimulation declined during years five through seven, concurrent with the accumulation of N in the O horizon and the apparent restriction of plant N availability. Yet, at the level of aboveground plant biomass (estimated by allometry), progressive N limitation was less apparent, initially because of increased N acquisition from soil and later because of reduced N concentration in biomass as N availability declined. Over this seven-year period, elevated CO2 caused a redistribution of N within the ecosystem, from mineral soils, to plants, to surface organic matter. In N limited ecosystems, such changes in N cycling are likely to reduce the response of plant production to elevated CO2. 相似文献