The incremental stress-strain relation of dense packings of polygons is investigated by using moleculardynamics simulations. The comparison of the simulation results to the continuous theories is performed using explicit expressions for the averaged stress and strain over a representative volume element. The discussion of the incremental response raises two important questions of soil deformati...

In this study we report the bacterial diversity of biological soil crusts (biocrusts) inhabiting polar desert soils at the northern land limit of the Arctic polar region (83° 05 N). Employing pyrosequencing of bacterial 16S rRNA genes this study demonstrated that these biocrusts harbor diverse bacterial communities, often as diverse as temperate latitude communities. The effect of wetting pulse...

Soil organic matter contains fractions that range from very active to passive, relative to microbiological activity Soil organic matter (SOM) contains fractions that range from very (Schimel et al., 1985), suggesting that classification of active to passive, relative to microbial-driven ecosystem processes and functions. A classification system is needed that can test the hypothesis SOM forms m...

The specific bio-species and their spatial patterns play crucial roles in regulating eco-hydrologic process, which is significant for large-scale habitat promotion and vegetation restoration in many dry-land ecosystems. Such effects, however, are not yet fully studied. In this study, 12 micro-plots, each with size of 0.5 m in depth and 1 m in length, were constructed on a gentle grassy hill-slo...

Savannas cover at least 13% of the global terrestrial surface and are often nutrient limited, especially by nitrogen. To gain a better understanding of their microbial diversity and the microbial nitrogen cycling in savanna soils, soil samples were collected along a granitic and a basaltic catena in Kruger National Park (South Africa) to characterize their bacterial and archaeal composition and...

In this paper, we generalize the models used by MacKay [1] in his analysis of evolutionary strategies that are based on sexual, rather than asexual, reproduction methods. This analysis can contribute to the understanding of the relative power of genetic algorithms over search methods based upon stochastic hill-climbing, e.g. [2], [3].

conclusions glenohumeral joint reduction with reconstruction of the humeral head seems to be possible even in a neglected locked posterior shoulder fracture-dislocation. if the depressed osteochondral fragment is still spheric, signs of the avascular necrosis are absent on ct, and mal:union: of the fragment has occurred, it is quite possible to reconstruct the head. although results of the case...

Our ability to identify and manage riparian sites for groundwater nitrate (NOAh) removal is limited by uncertainty surrounding the relative importance of plant uptake vs. microbially mediated removal processes. Microcosm studies often demonstrate negligible transformation rates in the subsoil of riparian forests, even in situations where groundwater well networks showed substantial groundwater ...