JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. Knowing how an increase in the resource base of a food web produces effects that propagate through the web is central to developing a clearer understanding of foodweb structure and dynamics. In a detritus-based terrestrial food web, we measured the responses of predaceous arthropods to increases in prey arthropods that occurred in response to experimentally enhancing the web's resource base. Open 2 X 5 m plots on the floor of a deciduous forest were randomly assigned to either a Food Enhancement or Control treatment. We supplemented the resource base of the arthropod community of the leaf litter layer for 3.5 mo by periodically adding chopped mushrooms, potatoes, and instant fruit fly medium to the Food Enhancement plots. Major taxa of detritivores and fungivores increased in response to added food. Densities of springtails (Collembola) were on average 3 X higher in the Food Enhancement than Control plots. Numbers of adult fungus gnats (Diptera: Sciaridae and Mycetophilidae) did not differ significantly between treatments after 6 wk but were >2X higher in Food Enhancement plots at the end of the experiment. Total Diptera were twice as abundant in Food Enhancement plots on both census dates.Arthropod groups that include a range of feeding strategies also increased. Mites (Acarina), which include detritivores, fungivores, and predators, were twice as abundant in the experimental treatment. Staphylinid and carabid beetles (Coleoptera), which are primarily predaceous but include omnivorous species, were several times more numerous in the Food Enhancement plots.Effects of increasing the resource base propagated through the food web, leading to higher densities of the major strictly predaceous arthropod taxa. Centipedes (Chilopoda), pseudoscorpions (Pseudoscorpionida), and spiders (Araneae) were -2X as abundant in the Food Enhancement treatment. Thus, our experiment uncovered substantial bottom-up limitation in this detritus-based food web, expressed as responses by predaceous arthropods at least two trophic links removed from the experimentally elevated resource. order consumers; physical structure of the habitat; abiotic factors; the prevalence of intraguild predation (IGP) and trophic-level omnivory; and whether or not the system is a grazing or detrital food web, or encompasses both (Abrams 1996, Persson et al. 1996).A major reason for the continuing controversy is not fundamental disagreement over possible mechanisms, but the absence of adequate numbers of experimental studies with a diversity of food webs. Experimentation has been most extensive with grazing webs...

Knowing how an increase in the resource base of a food web produces effects that propagate through the web is central to developing a clearer understanding of foodweb structure and dynamics. In a detritus-based terrestrial food web, we measured the responses of predaceous arthropods to increases in prey arthropods that occurred in response to experimentally enhancing the web's resource base. Open 2 ϫ 5 m plots on the floor of a deciduous forest were randomly assigned to either a Food Enhancement or Control treatment. We supplemented the resource base of the arthropod community of the leaf litter layer for 3.5 mo by periodically adding chopped mushrooms, potatoes, and instant fruit fly medium to the Food Enhancement plots. Major taxa of detritivores and fungivores increased in response to added food. Densities of springtails (Collembola) were on average 3ϫ higher in the Food Enhancement than Control plots. Numbers of adult fungus gnats (Diptera: Sciaridae and Mycetophilidae) did not differ significantly between treatments after 6 wk but were Ͼ2ϫ higher in Food Enhancement plots at the end of the experiment. Total Diptera were twice as abundant in Food Enhancement plots on both census dates.Arthropod groups that include a range of feeding strategies also increased. Mites (Acarina), which include detritivores, fungivores, and predators, were twice as abundant in the experimental treatment. Staphylinid and carabid beetles (Coleoptera), which are primarily predaceous but include omnivorous species, were several times more numerous in the Food Enhancement plots.Effects of increasing the resource base propagated through the food web, leading to higher densities of the major strictly predaceous arthropod taxa. Centipedes (Chilopoda), pseudoscorpions (Pseudoscorpionida), and spiders (Araneae) were ϳ2ϫ as abundant in the Food Enhancement treatment. Thus, our experiment uncovered substantial bottom-up limitation in this detritus-based food web, expressed as responses by predaceous arthropods at least two trophic links removed from the experimentally elevated resource.

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Embedding AMI guidelines into practice was associated with improved 30-day and one-year mortality. This benefit is most marked when patients are cared for using standardized, evidence-based clinical care tools.

OBJECTIVE Peripherally inserted central catheter (PICC) tip malposition is potentially associated with complications, and postplacement adjustment of PICCs is widely performed. We sought to characterize the association between central line–associated bloodstream infection (CLABSI) or venous thrombus (VT) and PICC adjustment. DESIGN Retrospective cohort study. SETTING University of Michigan Health System, a large referral hospital. PATIENTS Patients who had PICCs placed between February 2007 and August 2007. METHODS The primary outcomes were development of CLABSI within 14 days or VT within 60 days of postplacement PICC adjustment, identified by review of patient electronic medical records. RESULTS There were 57 CLABSIs (2.69/1,000 PICC-days) and 47 VTs (1.23/1,000 PICC-days); 609 individuals had 1, 134 had 2, and 33 had 3 or more adjustments. One adjustment was protective against CLABSI (P = .04), whereas 2 or 3 or more adjustments had no association with CLABSI (P = .58 and .47, respectively). One, 2, and 3 or more adjustments had no association with VT formation (P = .59, .85, and .78, respectively). Immunosuppression (P < .01), power-injectable PICCs (P = .05), and 3 PICC lumens compared with 1 lumen (P = .02) were associated with CLABSI. Power-injectable PICCs were also associated with increased VT formation (P = .03). CONCLUSIONS Immunosuppression and 3 PICC lumens were associated with increased risk of CLABSI. Power-injectable PICCs were associated with increased risk of CLABSI and VT formation. Postplacement adjustment of PICCs was not associated with increased risk of CLABSI or VT.