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Kathleen E. Hunt Thomas P. Hahn John C. Wingfield 《Behavioral ecology and sociobiology》1999,45(5):360-369
In males of socially monogamous birds, plasma testosterone (T) typically declines to low levels during the parental phase.
Studies on multiple-brooded species indicate that high T may be incompatible with high-quality paternal care. The length of
the breeding season may affect the costs and benefits of high T and its effect on paternal care. We studied the effect of
experimentally elevated T on paternal care in a single-brooded species with a short breeding season, the Lapland longspur
(Calcarius lapponicus). We monitored T levels and parental behavior in 16 males with subcutaneous T implants, 14 males with empty implants, and
14 unimplanted males. We videotaped nests when nestlings were 2–3 days old and again at 4–5 days. T males with 2- to 3-day-old
young visited nests and fed young less often than control males, and the mates of the T males compensated with elevated visits
and feedings. However, when nestlings were 4–5 days old, T males visited their nests at normal rates – though feeding movements
remained below normal – and T females visited and fed at normal rates. Nestling mass and nest success were similar in both
groups. Overall, high T suppresses paternal care in Lapland longspur males. The partial improvement of paternal care when
nestlings are older, despite high T, may be related to the short 6-week breeding season of this arctic species, and the consequently
reduced benefits of sexual behavior late in the breeding season.
Received: 2 February 1998 / Accepted after revision: 2 November 1998 相似文献
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Johannes Schnöller Philipp Aschenbrenner Manuel Hahn Johann Fellner Helmut Rechberger 《Waste management (New York, N.Y.)》2014,34(11):2171-2175
The biogenic fraction of a simple solid recovered fuel (SRF) mixture (80 wt% printer paper/20 wt% high density polyethylene) is analyzed with the in-house developed adapted balance method (aBM). This fairly new approach is a combination of combustion elemental analysis (CHNS) and a data reconciliation algorithm based on successive linearisation for evaluation of the analysis results. This method shows a great potential as an alternative way to determine the biomass content in SRF. However, the employed analytical technique (CHNS elemental analysis) restricts the probed sample mass to low amounts in the range of a few hundred milligrams. This requires sample comminution to small grain sizes (<200 μm) to generate representative SRF specimen. This is not easily accomplished for certain material mixtures (e.g. SRF with rubber content) by conventional means of sample size reduction.This paper presents a proof of principle investigation of the sample preparation and analysis of an SRF model mixture with the use of cryogenic impact milling (final sample comminution) and the adapted balance method (determination of biomass content). The so derived sample preparation methodology (cutting mills and cryogenic impact milling) shows a better performance in accuracy and precision for the determination of the biomass content than one solely based on cutting mills. The results for the determination of the biogenic fraction are within 1–5% of the data obtained by the reference methods, selective dissolution method (SDM) and 14C-method (14C-M). 相似文献
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F. E. Hahn 《Die Naturwissenschaften》1979,66(4):202-202
The Science of Nature - 相似文献