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381.
382.
Environmental and Ecological Statistics - 相似文献
383.
384.
Anthony Uzodinma Egbu 《The Environmentalist》2000,20(1):13-17
The issue of environmental protection and the need to establish the practice of environmental friendly programmes in national development consciousness are matters of paramount importance. While environmental consciousness in the developed world has witnessed over the past two decades generally effective mechanisms for pollution abatement, the situation in many third world nations is at best tepid.In Nigeria, the problem of environmental pollution has been of crisis proportions with the problem in some sectors possibly the worst in the world. In response, the government has put in place legislation and established agencies for environmental protection. A number of positive results have been achieved by the nation's main environmental watchdog, the Federal Environmental Protection Agency (FEPA). However, a lot still needs to be done, in terms of improving institutional capacity and adopting economic measures for the management of pollution problems.This paper, therefore, examines the major sources of Nigeria's environmental problems, discusses the weaknesses of existing legal and institutional arrangements and suggests strategies for a more effective pollution control management in Nigeria. 相似文献
385.
Peter Hopkinson Peter James Anthony Sammut 《Journal of Environmental Planning and Management》2000,43(6):873-895
The appropriate means of benchmarking environmental performance within and between companies is a matter of considerable debate and raises issues such as what information to compare and the reliability and consistency of data. Comparing environmental performance through company environment reports is an approach which has been widely used but, as this paper shows, is difficult and has severe limitations. This paper presents a unique analysis, based on the UK water industry, which compares data reported in company environmental reports and data on the same companies reported through the industry regulators. In turn, this is compared with the environmental performance indicators proposed by two other systems, one advanced by the UK water industry itself. The results demonstrate the difficulty of specifying environmental indicators that enable meaningful comparison. The difficulty of comparing environmental performance in a sector with a comprehensive approach to, and long history of, environmental performance reporting presents some hard lessons for other sectors. 相似文献
386.
Preeclampsia and intrauterine growth restriction (IUGR) are major contributors to perinatal mortality and morbidity worldwide. Both are characterized by impaired trophoblastic invasion of the maternal spiral arteries and their conversion from narrow muscular vessels to wide non-muscular channels. Despite improvement in the understanding of the pathophysiology of these conditions, ability to accurately identify pregnant woman who will develop them is limited. This greatly impairs the development and testing of preventive interventions. While different measures of placental dysfunction have been associated with increased risk for adverse pregnancy outcomes, the ability of any single one to accurately predict these outcomes is poor. Developing predictive tests is further challenged by difficulty in the timing of the measurements, as both the structural and biochemical characteristics of the placenta change with increasing gestational age. The ideal screening test would accurately predict the development of adverse pregnancy outcomes early enough to provide a window for preventive interventions. Improvement in ultrasound technology provides potentially useful novel tools for evaluating placental structure, but measuresments need to be standardized in order to be useful. Maternal serum analyte screening is a noninvasive test of placental biochemical function, but present serum marker alone is not sufficiently accurate to suggest its routine use in clinical practice. The use of first trimester biochemical markers in combination with uterine artery Doppler screening is promising as a potential screening tool. Prospective longitudinal studies using standardized methodology are necessary to further evaluate the choice of parameters and strategies of combination to achieve the best predictive models. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
387.
Brady A. Porter Anthony C. Fiumera John C. Avise 《Behavioral ecology and sociobiology》2002,51(4):350-359
In a variety of fish species with paternal care of offspring, females prefer to spawn in nests that already contain eggs.
This female preference has been hypothesized to explain egg thievery in male sticklebacks, allopaternal care of eggs in minnows,
and the evolution of egg-mimicking body features in male cichlids and darters. Here we employ microsatellite-based parentage
analyses to evaluate the reproductive success of striped darter (Etheostoma virgatum) males that appear to utilize two of these functionally related tactics to entice females to spawn in their nests. In an
isolated population (Clear Creek, Ky.), we observed that breeding males develop conspicuous white spots on their pectoral
fins. If these spots are egg mimics, as we suspect, then this represents the fourth independent evolutionary origin of egg
mimicry documented to date in darters, the first based on pigmentation (as opposed to physical structures), and the first
in which the egg mimics vary greatly in number among males. From direct counts of microsatellite genotypes in clutches of
embryos, at least 3.8 females contributed to the progeny within a typical nest, and females tended to spawn preferentially
with males that were larger and displayed more egg-mimic spots. In another population (Hurricane Creek, Tenn.) without egg
mimics, the multi-locus genetic data document that allopaternal care is common, especially among the smallest males who sometimes
tend nests containing their own as well as an earlier sire's offspring. Thus, these foster males had adopted egg-containing
nests and then successfully spawned with subsequent females. Overall, the genetic data on paternity and maternity, in conjunction
with field observations, suggest that egg mimicry and allopaternal care are two mate-attracting reproductive tactics employed
by striped darter males to exploit female preferences for spawning in nests with 'eggs'.
Electronic Publication 相似文献
388.
Which comes first,organizational culture or performance? A longitudinal study of causal priority with automobile dealerships 下载免费PDF全文
Anthony S. Boyce Levi R. G. Nieminen Michael A. Gillespie Ann Marie Ryan Daniel R. Denison 《组织行为杂志》2015,36(3):339-359
Prior research supports a link between organizational culture and performance but generally falls short of establishing causality or determining the direction of a culture–performance (C‐P) relationship. Using data collected from 95 franchise automobile dealerships over 6 years, we studied longitudinal culture–performance relationships to determine whether culture or performance has causal priority, or alternatively, whether a reciprocal relationship exists. Results from cross‐lagged panel analyses indicate that culture “comes first,” consistently predicting subsequent ratings of customer satisfaction and vehicle sales. Furthermore, the positive effect of culture on vehicle sales is fully mediated by customer satisfaction ratings. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
389.
Salinity as a Limiting Factor for Biological Condition in Mining‐Influenced Central Appalachian Headwater Streams 下载免费PDF全文
Anthony J. Timpano Stephen H. Schoenholtz David J. Soucek Carl E. Zipper 《Journal of the American Water Resources Association》2015,51(1):240-250
Recent studies have found that Appalachian coal mining causes increased surface water salinity, and that benthic macroinvertebrate communities in salinized mining‐influenced streams differ from communities in streams draining unmined areas. Understanding the role of salinity in shaping these communities is challenging because such streams are often influenced by a variety of stressors in addition to salinity. We characterized associations of salinity with biotic condition while isolating salinity from other stressors through rigorous site selection. We used a multimetric index of biotic condition to characterize benthic macroinvertebrate communities in headwater streams in the Central Appalachian Ecoregion of Virginia across a gradient of sulfate‐dominated salinity. We found strong negative seasonal correlations between biotic condition and three salinity measures (specific conductance, total dissolved solids, and SO42? concentration). We found no evidence to suggest stressors other than salinity as significant influences on biotic condition in these streams. Our results confirm negative associations of salinity with benthic macroinvertebrate community condition, as observed in other studies. Thus, our findings demonstrate that elevated salinity is an important limiting factor for biological condition in Central Appalachian headwater streams. 相似文献
390.
Gary P. Griffith Elizabeth A. Fulton Rebecca Gorton Anthony J. Richardson 《Conservation biology》2012,26(6):1145-1152
An important challenge for conservation is a quantitative understanding of how multiple human stressors will interact to mitigate or exacerbate global environmental change at a community or ecosystem level. We explored the interaction effects of fishing, ocean warming, and ocean acidification over time on 60 functional groups of species in the southeastern Australian marine ecosystem. We tracked changes in relative biomass within a coupled dynamic whole‐ecosystem modeling framework that included the biophysical system, human effects, socioeconomics, and management evaluation. We estimated the individual, additive, and interactive effects on the ecosystem and for five community groups (top predators, fishes, benthic invertebrates, plankton, and primary producers). We calculated the size and direction of interaction effects with an additive null model and interpreted results as synergistic (amplified stress), additive (no additional stress), or antagonistic (reduced stress). Individually, only ocean acidification had a negative effect on total biomass. Fishing and ocean warming and ocean warming with ocean acidification had an additive effect on biomass. Adding fishing to ocean warming and ocean acidification significantly changed the direction and magnitude of the interaction effect to a synergistic response on biomass. The interaction effect depended on the response level examined (ecosystem vs. community). For communities, the size, direction, and type of interaction effect varied depending on the combination of stressors. Top predator and fish biomass had a synergistic response to the interaction of all three stressors, whereas biomass of benthic invertebrates responded antagonistically. With our approach, we were able to identify the regional effects of fishing on the size and direction of the interacting effects of ocean warming and ocean acidification. Predicción de Interacciones entre Pesca, Calentamiento de Océanos y Acidificación de Océanos en un Sistema Marino con Modelos de Ecosistemas Completos 相似文献