23 research outputs found
Local influence of boundary conditions on a confined supercooled colloidal liquid
We study confined colloidal suspensions as a model system which approximates
the behavior of confined small molecule glass-formers. Dense colloidal
suspensions become glassier when confined between parallel glass plates. We use
confocal microscopy to study the motion of confined colloidal particles. In
particular, we examine the influence particles stuck to the glass plates have
on nearby free particles. Confinement appears to be the primary influence
slowing free particle motion, and proximity to stuck particles causes a
secondary reduction in the mobility of free particles. Overall, particle
mobility is fairly constant across the width of the sample chamber, but a
strong asymmetry in boundary conditions results in a slight gradient of
particle mobility.Comment: For conference proceedings, "Dynamics in Confinement", Grenoble,
March 201
Predation on artificial nests in open habitats of central Brazil: effects of time and egg size
Methane and carbon dioxide fluxes and their regional scalability for the European Arctic wetlands during the MAMM project in summer 2012
Airborne and ground-based measurements of methane (CH4), carbon dioxide (CO2) and boundary layer thermodynamics were recorded over the Fennoscandian landscape (67â69.5° N, 20â28° E) in July 2012 as part of the MAMM (Methane and other greenhouse gases in the Arctic: Measurements, process studies and Modelling) field campaign. Employing these airborne measurements and a simple boundary layer box model, net regional-scale (~ 100 km) fluxes were calculated to be 1.2 ± 0.5 mg CH4 hâ1 mâ2 and â350 ± 143 mg CO2 hâ1 mâ2. These airborne fluxes were found to be relatively consistent with seasonally averaged surface chamber (1.3 ± 1.0 mg CH4 hâ1 mâ2) and eddy covariance (1.3 ± 0.3 mg CH4 hâ1 mâ2 and â309 ± 306 mg CO2 hâ1 mâ2) flux measurements in the local area. The internal consistency of the aircraft-derived fluxes across a wide swath of Fennoscandia coupled with an excellent statistical comparison with local seasonally averaged ground-based measurements demonstrates the potential scalability of such localised measurements to regional-scale representativeness. Comparisons were also made to longer-term regional CH4 climatologies from the JULES (Joint UK Land Environment Simulator) and HYBRID8 land surface models within the area of the MAMM campaign. The average hourly emission flux output for the summer period (JulyâAugust) for the year 2012 was 0.084 mg CH4 hâ1 mâ2 (minimum 0.0 and maximum 0.21 mg CH4 hâ1 mâ2) for the JULES model and 0.088 mg CH4 hâ1 mâ2 (minimum 0.0008 and maximum 1.53 mg CH4 hâ1 mâ2) for HYBRID8. Based on these observations both models were found to significantly underestimate the CH4 emission flux in this region, which was linked to the under-prediction of the wetland extents generated by the models