Resource partitioning in the silphid fauna of southern Ontario is examined in detail, using baited pitfall traps placed in four different habitats. During 1979 and 1980, a total of 9549 specimens of Silphidae were collected, representing 12 species, of which 5 were in the subfamily Silphinae and 7 in the subfamily Nicrophorinae. The roles of different seasonal patterns, habitat specificity, and food type and size in resource partitioning are discussed for all species. At the subfamilial level, resource partitioning is accomplished through selection of different sizes of carcasses, while at the specific level, seasonal patterns and habitat specificity appear to be the primary means permitting coexistence.In the Silphidae, competition for food resources appears to be the primary factor inducing ecological character displacement. The possible origins of patterns of resource use in this assemblage are discussed in an ecological and geological time framework.
The catalytic enantioselective conjugate addition reaction of α-nitroacetate to α,β-unsaturated enones promoted by chiral bifunctional organocatalysts is described. The treatment of α-nitroacetate to α,β-unsaturated enones afforded the corresponding Michael adducts with high enantioselectivity. The conjugate addition adducts are easily converted to chiral γ-nitro ketones and δ-keto esters.
This paper describes the sampling procedure and the results of large diameter (150 mm) CID triaxial tests made on samples recovered from the weathered clay crust of the Champlain sea deposits.A visual inspection of the fissures at the depth of sampling (3 m) revealed two types of discontinuities: (a) sub-vertical joints containing black organic matter, spaced approximately every 10 cm, and (b) closed microfissures, randomly distributed in spacing and direction. In order to recover unremoulded samples of this material and avoid a difficult retrimming in the laboratory, a double core barrel 150 mm in diameter (the same as that of the triaxial cell base) was used. Eight compression tests under low confining stresses were made; they showed that the post-peak strength parameters were substantially higher than those back-calculated from a landslide involving the same weathered crust. Examination of the shape of the failure planes and of the stress–strain curves led to the conclusion that, in spite of the large sample size, the propagation of the fractures was controlled by the intact clay matrix rather than by the fissures. Since this was not believed to reproduce the actual field behaviour, a complementary test programme was undertaken, which indicated that the strength parameters were better evaluated from CID tests performed in the normally consolidated range. Keywords: fissured clays, weathering, landslides, triaxial test, shear strength parameters, sampling, back-analysis.
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