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  • 1995-1999  (1)
  • 1985-1989  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Coral reefs 18 (1999), S. 213-218 
    ISSN: 1432-0975
    Keywords: Key words Sedimentation ; Porites ; Skeletal density banding ; Growth characteristics ; Tissue thickness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract  The construction in 1988 of an open-cut gold mine and ore-processing facility at Misima Island, Papua New Guinea, resulted in disturbance of the adjacent fringing coral reef, mostly because of large increases in sedimentation. This provided an opportunity to examine whether growth characteristics of the major reef-building coral, Porites, changed in response to this sudden and sustained increase in sedimentation. Annual variation in skeletal density was measured in 93 colonies variously affected by sedimentation. The colonies provided data for average annual density, annual extension and annual calcification covering the periods 5 y before and 5 y after mining operations began. The average depth of skeleton occupied by tissue (tissue layer thickness) was also measured for most colonies. There was high mortality of Porites in regions strongly affected by increased sedimentation. In colonies that survived, density, extension and calcification tended to be less (in some cases significantly) in the period after mining operations began compared with pre-construction levels. However, these decreases were not linked with proximity to the mine site and probably reflect a regional-scale response of Porites growth to some other environmental change. This suggests that periods of high sedimentation may not be recorded by the growth characteristics of massive Porites. Average growth characteristics of surviving Porites from Misima Island were similar to those from inshore reefs of the northern Great Barrier Reef (GBR). Tissue layer thickness in Porites from the control areas at Misima Island were also similar to colonies from the northern inshore GBR reefs. However, tissue layer thickness significantly decreased with increased proximity to the mine site at Misima Island.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 64 (1986), S. 45-61 
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The paper is concerned with the mechanics of granular material under quasi-equilibrium conditions. The characterisation of the microstructure of granular material is discussed and the relationship between the microstructure and the stress tensor is examined. Results from computer simulated experiments on a large, initially random, dense assembly of different sized discs are used to investigate the evolution of both stress and structure. Two tests are reported: one a constant mean stress test and the other a constant volume test. It is shown that, although the two tests were subjected to different strain histories the degree of induced structural anisotropy evolved in an identical manner. The computer simulated tests show that there also exists a statical anisotropy due to the biased distribution of contact forces within an assembly. This also evolves in the same way for both tests reported. Consequently, the evolution of the angle of internal shearing resistance with strain is found to be unique.
    Type of Medium: Electronic Resource
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