87 research outputs found
Higher establishment success in specialized parasitoids: support for the existence of trade-offs in the evolution of specialization
Most animals do not feed on all the resources available to them, but the mechanisms behind the evolution of dietary specialization are still debated. A central but unanswered question is whether specialists generally gain fitness advantages on their resource compared to generalists, experiencing a trade-off between the ability to use a broad range of resources and the fitness reached on each single one.Empirical tests so far suffered from difficulties in measuring fitness; they were restricted to few species, and results were equivocal. This lack of support for the importance of trade-offs gave rise to theories explaining the evolution of specialization without such trade-offs.Using a large dataset of intentional biological control introductions of 254 species of parasitoids from 15 families to locations outside their native range, we show that establishment success, a measure of total fitness, is higher in specialized species. This result holds when controlling for possible confounding factors such as the number of introduced individuals (propagule pressure).The outcome of this study provides robust evidence that dietary specialization implies fitness advantages in an entire species-rich taxon, indicating that trade-offs might be widely involved in the evolution of specialization
Predicting risk among non-respondents in prospective studies
Potential non-response bias was investigated in a follow-up study of 2,011 chronically disabled patients. 82.5% and 73.3% of the study subjects responded to self-administered mail questionnaires respectively at 6-month and 1-year follow-up. Information on employment status, the outcome of interest, of approximately 90% of the non-respondents was obtained from indirect sources. Employment rate was lower among the non-respondents than the respondents. Non-response was associated with age, social class, previous employment record, and the type of disability; but none of these characteristics were associated with the outcome. Out of the five known independent risk factors for unemployment, only one (incompletion of rehabilitation course) was associated with non-response. The employment rate among the respondents was also assessed according to the delay in response, that is the number of reminders sent to achieve response. The outcome among- the late respondents was similar to that among the nonrespondents. These data suggest that (a) risk estimates may be biased even when the response rate is greater than 80%, (b) the prevalence of risk factors among non-respondents may not indicate the presence or the degree of non-response bias, but (c) reliable estimates can be obtained from extrapolations of the rates among the respondents according to the delay in response.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42663/1/10654_2004_Article_BF00152716.pd
Exploring the feasibility of a stand alone muon facility for muSR research
The current paper discusses possible designs for a high
intensity stand alone muon source formuSR studies of condensed
matter. In particular we shall focus upon the potential
implementation of a new generation of high power but
relatively compact and cost effective proton drivers based
on non-scaling fixed field alternating gradient (ns-FFAG)
accelerator technology. The technical issues which must
be addressed are also considered
Neutron reflectometry from solid-solid and solid-liquid interfaces at the TAS8 spectrometer at Risø
Using MIKE basin, ecological suitability curves and economic valuation to safeguard environmental flows and support integrated water resoures management
Using economic valuation of environmental flows to integrate ecological aspects into water management
F2-P4 the DR3 Risø reactor as a user facility for applied neutron scattering experiments: Texture, internal strain and applied small angle scattering
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