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281.
Robert S. Wright Emery J. Kong Mark A. Bahner C. Andrew Clayton Carlos M. Nuñez Geddes H. Ramsey 《Journal of the Air & Waste Management Association (1995)》2013,63(9):1110-1115
ABSTRACT Research Triangle Institute and the U.S. Environmental Protection Agency conducted several projects to measure hydrocarbon emissions associated with the manufacture of fiberglass-reinforced plastics. The purpose of these projects was to evaluate pollution prevention techniques to reduce emissions by altering raw materials, application equipment, and operator technique. Analytical techniques were developed to reduce the cost of these emission measurements. Emissions from a small test mold in a temporary total enclosure (TTE) correlated with emissions from full-size production molds in a separate TTE. Gravimetric mass balance measurements inside the TTE generally agreed to within ± 30 % with total hydrocarbon (THC) measurements in the TTE exhaust duct. Pure styrene evaporation tests served as quality control checks for THC measurements and generally agreed to within ± 5 %. 相似文献
282.
Decades of acid deposition have caused acidification of lakes in Sweden. Here we use data for 3000 lakes to run the acidification model MAGIC and estimate historical and future acidification. The results indicate that beginning in about 1920 a progressively larger number of lakes in Sweden fell into the category of “not naturally acidified” (∆pH > 0.4). The peak in acidification was reached about 1985; since then many lakes have recovered in response to lower levels of acid deposition. Further recovery from acidification will occur by the year 2030 given implementation of agreed legislation for emissions of sulphur (S) and nitrogen (N) in Europe. But the number of catchments with soils being depleted in base cations will increase slightly. MAGIC-reconstructed history of acidification of lakes in Sweden agrees well with information on fish populations. Future acidification of Swedish lakes can be influenced by climate change as well as changes in forest harvest practices. 相似文献
283.
284.
Jonathan Wright 《Behavioral ecology and sociobiology》1998,42(6):423-429
Despite the success of kin selection in explaining helping-at-the-nest among communally breeding birds, we know almost nothing
about how helpers regulate their chick-feeding effort. This is especially interesting given how much we now know about parental
provisioning `rules-of-thumb' and the evolution of chick begging as an honest signal of `need'. This study explores the provisioning
rules of helpers and parents in Arabian babblers (Turdoides squamiceps), using tape play-backs to supplement chick-begging signals and increase apparent brood demand. In all eight groups tested,
both helpers and parents fed older, noisier broods at higher rates. Total provisioning rates to nests increased during begging
play-back days compared to control days. Absolute provisioning rates by helpers and the scale of their responses to play-backs
were statistically indistinguishable from those of parents. In both helpers and parents, increases in nest visits during play-backs
were associated with reductions in foraging distance from the nest and increases in size of prey delivered. Older birds of
both sexes delivered slightly larger prey items, possibly reflecting differences in foraging ability due to experience. These
results are consistent with the idea that, like the parents, helpers-at-the-nest in Arabian babblers provision nestlings as
part of a strategy of investment, irrespective of helper age, dominance status or sex. In this species, high relatedness within
groups may provide parents and helpers with similar kin-selected fitness benefits, although the mutualistic advantages to
helpers from simply augmenting group sizes cannot be ruled out.
Received: 17 June 1997 / Accepted after revision: 28 February 1998 相似文献