Earlier models on the evolution of dispersal have suggested that evolutionarily stable dispersal rates should increase with the frequency of local extinctions. Most metapopulation models assume site saturation (i.e., no local population dynamics), yet the majority of species distributed as metapopulations rarely attain carrying capacity in all occupied patches. In this article, we relax this assumption and examine the evolutionarily stable dispersal rate under nonsaturated but still competitive demographic conditions. Contrary to previous predictions, we show that increasing local extinction rates may allow decreasing dispersal rates to evolve.

One of the essential requirements of the Tagged Neutron Inspection System, which is the principle of the EURITRACK project, is an efficient and inexpensive gamma ray detector. For this purpose properties of cylindrical 3"×3" and 5"×5" BGO, and 3"×3", two different 5"×5", and a rectangular 5"x5"x10" NaI(Tl) scintillators were explored. In this communication we report on light yield, energy and time resolution of the investigated crystals at high energies of γ γ γ γ-rays. Additionally, results of Monte Carlo simulations of the crystals' efficiencies are compared to peak-to-total ratios obtained experimentally for various combinations of PMTs and the scintillators.

Electron energy-loss spectroscopy (EELS) and elemental imaging under the energy-filtered transmission electron microscope are powerful tools for the characterization of iron-rich particles present in natural waters. Features present in EEL spectra (Fe-M 2,3 Fe-L 2,3 and O-K ionization edges) of goethite (a-FeOOH) have been studied with an energy filter operated at 80 keV to determine optimal quantification and elemental imaging of Fe-rich natural aquatic particles in the 30-200 nm range of thickness. For quantitative aims, the Fe-M 2,3 ionization edge cannot be used easily, but the Fe-L 2,3 edge provides more accurate results owing to a better background extrapolation. The partial cross-section of the Fe(III) M shell has been determined for iron oxide. The use of two-windows (jumpratio) and three-windows (background stripping) imaging methods is discussed in relation to the specimen thickness.

No abstract