Assessing the response of nematode communities to climate change-driven warming : a microcosm experiment

Biodiversity has diminished over the past decades with climate change being among the main responsible factors. One consequence of climate change is the increase in sea surface temperature, which, together with long exposure periods in intertidal areas, may exceed the tolerance level of benthic organisms. Benthic communities may suffer structural changes due to the loss of species or functional groups, putting ecological services at risk. In sandy beaches, free-living marine nematodes usually are the most abundant and diverse group of intertidal meiofauna, playing an important role in the benthic food web. While apparently many functionally similar nematode species co-exist temporally and spatially, experimental results on selected bacterivore species suggest no functional overlap, but rather an idiosyncratic contribution to ecosystem functioning. However, we hypothesize that functional redundancy is more likely to occur and observe when taking into account the entire diversity of natural assemblages. Therefore, we conducted a microcosm experiment with two natural communities drawn directly from their environment to assess their stress response to elevated temperature. The two communities differed in diversity (high [HD] vs. low [LD]) and environmental origin (harsh vs. moderate conditions). We assessed their stress resistance to the experimental treatment in terms of species and diversity changes, and their function in terms of abundance, individual and community biomass, and trophic diversity. According to the Insurance Hypothesis (IH), we hypothesized that the HD community would cope better with the stressful treatment due to the species functional overlap, whereas the LD community functioning would benefit from species better adapted to harsh conditions. Our results indicate no evidence of functional redundancy in the studied nematofaunal communities. The species loss was more prominent and size specific in the HD; large predators and omnivores were lost, which may have important consequences for the benthic food web.Yet, we found some evidence for alternative diversity–ecosystem functioning relationships such as the Rivets and the Idiosyncrasy Model

A necessary condition for a power series to be a formal solution of a singular linear differential equation of order k

AbstractWe obtain a necessary condition on the coefficients of a formal power series, which is a formal solution of a nontrivial singular linear differential equation of order k, with analytic coefficients and prove a “uniqueness” theorem for the differential equation

Independent and joint effects of parental attitudes and special health care needs on physical activity and screen time among chlldren and adolescents in the United States

Sedentary lifestyles pose a threat to the health of children, especially those with special health care needs (SHCN). Using data from the 2007 National Survey of Children's Health, this study examined relationships between parental attitudes and low physical activity and high screen time among 6- to 17-year-olds with and without SHCN. Perceived limitation was associated with increased likelihood of low physical activity (AOR, 1.339; 95%CI, 1.079-1.662). Parenting stress (AOR, 1.189; 95%CI, 1.052-1.344) and lack of trust (AOR, 1.243; 95%CI, 1.104-1.399) were associated with increased likelihood of high screen time. Perceived limitation modified the effect of special health care needs status on high screen time. The likelihood of combined low physical activity and high screen time was greatest among children with SHCN whose parents reported both functional limitations in the child and parenting stress (AOR, 2.659; 95%CI, 1.741-4.060). Parental attitudes and SHCN should be addressed in interventions to promote active lifestyles

Smooth-Particle Phase Stability with density and density-gradient potentials

Stable fluid and solid particle phases are essential to the simulation of continuum fluids and solids using Smooth Particle Applied Mechanics. We show that density-dependent potentials, such as Phi=(1/2)Sum (rho-rho_0)^2, along with their corresponding constitutive relations, provide a simple means for characterizing fluids and that a special stabilization potential, Phi=(1/2)Sum (delrho)^2, not only stabilizes crystalline solid phases (or meshes) but also provides a surface tension which is missing in the usual density-dependent-potential approach. We illustrate these ideas for two-dimensional square, triangular, and hexagonal lattices.Comment: 10 pages, 5 figure