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排序方式: 共有322条查询结果,搜索用时 31 毫秒
51.
Robert A Becker 《Journal of Environmental Economics and Management》1982,9(2):165-185
This paper examines the trade-off between capital accumulation and environmental quality that determines an intergenerationally equitable program according to the Rawls maximin criterion. This trade-off is explored by an analysis of regular maximin programs in the framework developed by Brock. This results in a constant utility path supported by competitive prices with government imposed effluent charges and environmental rentals. Sufficient conditions for a regular maximin path to satisfy a Hartwick rule in deciding on the combination of capital and environmental quality left to future generations are given. 相似文献
52.
Body mass is a consistent individual trait that characterises the state of adult birds and mammals and is positively related
with long-term reproductive success. However, whether and to what extent body mass changes over lifetime in long-lived birds
is poorly studied. In this paper, we investigate how individual body mass varies with age. Furthermore, we try to separate
possible effects of age and experience on body mass. This study was conducted in a Common Tern colony on the German Wadden
Sea coast. Transponders allowed registration of individuals throughout the breeding season and consecutive years with an antenna
system combined with electronic balances for recording individual body-mass changes within and between years. Individual body
masses of males and females were measured during three stages of the breeding season: at arrival, during incubation and chick
rearing when mass was lowest in both sexes. Individual-based longitudinal analyses clearly showed that body mass during arrival,
incubation and chick rearing increased up to an age of 5 or 6 years. First-time breeders had lower body mass than experienced
breeders. Experience had stronger effects on incubation mass than age. Recruiting age also affected body-mass development
of breeders: Three-year-old recruits showed a stronger increase in mass with experience than 4-year-old recruits. We assume
that increasing experience enables birds to cope better with the physiological challenge of reproduction. To explain the general
phenomenon of higher body mass in older birds, our results support the constraint hypothesis rather than either the selection
or restraint hypothesis. 相似文献
53.
成百上千的活性物质正被用于人药和兽药处方中.由于药物的广泛应用,它们的残留物可通过多种途径进入环境.虽然主要通过尿和粪便的排泄,但是药品生产中的排放也应被考虑.当抗生素用于水产业,就会产生更直接的影响.污水处理设备不能完全除去药物,因此药物会出现在地表和地下水样品中.近年来,人们对环境中药物的兴趣正在增加,需要建立一种快速、灵敏、有选择性的方法来分析水样. 相似文献
54.
M Zachariah Peery Benjamin H Becker Steven R Beissinger 《Ecological applications》2006,16(4):1516-1528
Identifying source-sink dynamics is of fundamental importance for conservation but is often limited by an inability to determine how immigration and emigration influence population processes. We demonstrate two ways to assess the role of immigration on population processes without directly observing individuals dispersing from one population to another and apply these methods to a population of Marbled Murrelets (Brachyramphus marmoratus) in California (USA). In the first method, the rate of immigration (i) is estimated by subtracting local recruitment (recruitment from within the population due to reproduction) estimated with demographic data from total recruitment (f; recruitment from within the population plus recruitment from other populations) estimated using temporal symmetry mark-recapture models developed by R. Pradel. The second method compares population growth rates estimated with temporal symmetry models (lambdaTS) and/or population growth rates estimated from counts of individuals over multiple sampling periods (lambdaC) with growth estimates from a stage-structured projection matrix model (lambdaM). Both lambdaTS and lambdaC incorporate all demographic processes affecting population change (birth, death, immigration, and emigration), whereas matrix models are usually constructed without incorporating immigration. Thus, if lambdaTS and lambdaC are > or = 1 and lambdaM < 1, the population is sustained by immigration and is considered to be a sink. Using the first method, recruitment estimated with temporal symmetry models was high (f= 0.182, SE = 0.058), the mean adult birth rate, as estimated using the ratio of juveniles to > or = 1 year old individuals (observed during ship-based surveys) was low (bA = 0.039, SE = 0.014), and immigration was 0.160 (SE = 0.057). Using the second method, murrelet numbers in central California were stable (lambdaC = 1.058, SE = 0.047; lambdaTS = 1.064, SE = 0.033), but were projected to decline 9.5% annually in the absence of immigration (lambdaM = 0.905, SE = 0.053). Our results suggest that Marbled Murrelets in central California represent a sink population that is stable but would decline in the absence of immigration from larger populations to the north. However, the extent to which modeled immigration is due to permanent recruitment or temporarily dispersing individuals that simply mask population declines is uncertain. 相似文献
55.
Mayer J Linnemann H Becker E Rentschler W Jockel W Wilbring P Gerchel B 《Chemosphere》2000,40(9-11):1025-1027
AMESA (adsorption method for sampling of dioxins) is a fully automatic system for long term monitoring of dioxin emissions from industrial processes based on the adsorption method. The system has been tested and undergoing a certification procedure according to the German guidelines for certification of systems for continuous monitoring of special substances. The certification covered parameters such as disposability of the system, reproducibility of the results and comparability of the sampling method with German and European standard methods. Furthermore break through, blanks and sample storability were investigated. The results prove that AMESA is a state of the art sampling system for continuous monitoring of dioxin/furan emissions. 相似文献
56.
Testing biodegradability with standardized methods 总被引:11,自引:0,他引:11
Udo Pagga 《Chemosphere》1997,35(12):2953-2972
Laboratory test methods are used by industry laboratories to determine biodegradability, an important parameter for the evaluation of the ecological behaviour of substances. Biodegradability has a key role due to the simple fact that a degradable substance will cause no long term risk in the environment. The great variety of biodegradation processes in the natural environment and in technical plants for treating waste water and solid wastes gave rise to a rather large number of test methods based on different test principles. To guarantee the acceptance of the test results by authorities and customers internationally standardized methods (ISO, OECD) and established quality criteria (GLP, EN 45000, ISO 9000) are used. 相似文献
57.
Magnetfeld-Einfluß auf die Galeriebau-Richtung bei Termiten 总被引:1,自引:0,他引:1
Günther Becker 《Die Naturwissenschaften》1971,58(1):60-60
58.
W. Bader G. Becker M. Kiese Hans Ulrich Wilhelm Simon M. Czerny F. Stöckmann 《Die Naturwissenschaften》1952,39(15):356-360
59.
The Science of Nature - 相似文献
60.