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61.
Sheikh Md Rajiuddin Tenna Jensen Tina Beck Hansen Anna Charlotte Schultz 《Food and environmental virology》2020,12(3):226-239
Detection of norovirus (NoV) and hepatitis A virus (HAV) on fruits and vegetables using current standard methodologies can be inefficient. Method optimisat 相似文献
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J. A. Raven D. I. Walker K. R. Jensen L. L. Handley C. M. Scrimgeour S. G. McInroy 《Marine Biology》2001,138(3):537-545
any sacoglossans (opisthobranch gastropods) have the potential for carbon acquisition from photosynthesis by plastids sequestered
from their macroalgal food as well as by ingestion, digestion and assimilation of the organic carbon derived from the alga.
A new method for obtaining a minimum estimate of the fraction of sacoglossan carbon supplied from photosynthesis by kleptoplastids
is suggested, based on the mass balance of stable carbon isotopes at the natural abundance level. The method involves comparison
of 13C/12C ratios in sacoglossans with those of the algae on which they are found. Differences in ratios between alga and sacoglossan
are used to give a minimum estimate of carbon acquisition by kleptoplasty, granted assumptions about the range of 13C/12C fractionation values which can occur for marine photolithotrophs. The new method is applied to several green (ulvophycean)
alga–sacoglossan associations from Rottnest Island, Western Australia, and the values compared with those obtained previously
by other means. The method suggests values of up to 0.6 of the total carbon input to the sacoglossans from photosynthesis
by their kleptoplastids. To improve the estimates of the minimum role of kleptoplastidy in the carbon nutrition of sacoglossans,
further information is needed: (1) on the fidelity of a given sacoglossan to a given algal individual (or species), (2) on
the 13C/12C ratio of the part of the alga ingested by the sacoglossan, and (3) on the allocation of dietary organic carbon and of kleptoplastidic
photosynthate to carbon lost in respiration, mucopolysaccharide production and gametes (and hence not sampled with the animal).
Received: 24 November 1999 / Accepted: 20 October 2000 相似文献
69.
S.G. Sommer H.S. Østergård P. Løfstrøm H.V. Andersen L.S. Jensen 《Atmospheric environment (Oxford, England : 1994)》2009,43(4):915-920
Substantial emission of ammonia (NH3) from animal houses and the related high local deposition of NH3-N are a threat to semi-natural nitrogen-deficient ecosystems situated near the NH3 source. In Denmark, there are regulations limiting the level of NH3 emission from livestock houses near N-deficient ecosystems that are likely to change due to nitrogen (N) enrichment caused by NH3 deposition. The models used for assessing NH3 emission from livestock production, therefore, need to be precise, as the regulation will affect both the nature of the ecosystem and the economy of the farmer. Therefore a study was carried out with the objective of validating the Danish model used to monitor NH3 transport, dispersion and deposition from and in the neighbourhood of a chicken farm. In the study we measured NH3 emission with standard flux measuring methods, NH3 concentrations at increasing distances from the chicken houses using passive diffusion samplers and deposition using 15N-enriched biomonitors and field plot studies. The dispersion and deposition of NH3 were modelled using the Danish OML-DEP model. It was also shown that model calculations clearly reflect the measured NH3 concentration and N deposition. Deposition of N measured by biomonitors clearly reflected the variation in NH3 concentrations and showed that deposition was not significantly different from zero (P < 0.05) at distances greater than 150–200 m from these chicken houses. Calculations confirmed this, as calculated N deposition 320 m away from the chicken farm was only marginally affected by the NH3 emission from the farm. There was agreement between calculated and measured deposition showing that the model gives true estimates of the deposition in the neighbourhood of a livestock house emitting NH3. 相似文献
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Forage fish—small, low trophic level, pelagic fish such as herrings, sardines, and anchovies—are important prey species in marine ecosystems and also support large commercial fisheries. In many parts of the world, forage fish fisheries are managed using precautionary principles that target catch limits below the maximum sustainable yield. However, there are increasing calls to further limit forage fish catch to safeguard their fish, seabird, and marine mammal predators. The effectiveness of these extra-precautionary regulations, which assume that increasing prey abundance increases predator productivity, are under debate. In this study, we used prey-linked population models to measure the influence of forage fish abundance on the population growth rates of 45 marine predator populations representing 32 fish, seabird, and mammal species from 5 regions around the world. We used simulated data to confirm the ability of the statistical model to accurately detect prey influences under varying levels of influence strength and process variability. Our results indicate that predator productivity was rarely influenced by the abundance of their forage fish prey. Only 6 predator populations (13% of the total) were positively influenced by increasing prey abundance and the model exhibited high power to detect prey influences when they existed. These results suggest that additional limitation of forage fish harvest to levels well below sustainable yields would rarely result in detectable increases in marine predator populations. 相似文献