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- Gylland, Anders S., et al.
(author)
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Soil property sensitivity in progressive failure of slopes
- 2012
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In: International Review of Civil Engineering (IRECE). - 2036-9913. ; 3:4
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Journal article (peer-reviewed)abstract
- The presence of sensitive clay pose a challenge when performing slope stability assessments. Because of the strain softening behavior, the validity of conventional calculation methods based on the principle of limit equilibrium (LE) are not fully valid. This paper studies downward progressive failure in long natural slopes with an aim of identifying the governing parameters and the validity range of LE methods. A FEM approach which accounts for the non-linear stress-strain curve of the material, including the post peak softening behavior, is used. Sensitivity of the analyses to variations of key parameters like in-situ shear stress at the failure plane, brittleness, stiffness of the soil mass, and geometry are investigated in terms of critical load for initiating the slide and the corresponding critical length. The results show that the capacity of the slope in terms of external actions is reduced the steeper the slope is, the more strain softening behavior the material display and the lower stiffness the overlying soil has. The initial shear stress level is identified as a highly sensitive parameter. Further, by studying variations in the critical length it is indicated that the validity of classical LE methods is limited for steep slopes in soft and very sensitive clay.
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- Bernander, R., et al.
(author)
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Genome ploidy in different stages of the Giardia lamblia life cycle
- 2001
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In: CELLULAR MICROBIOLOGY. - : BLACKWELL SCIENCE LTD. - 1462-5814. ; 3:1, s. 55-62
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Journal article (peer-reviewed)abstract
- The early diverging eukaryotic parasite Giardia lamblia is unusual in that it contains two apparently identical nuclei in the vegetative trophozoite stage. We have determined the nuclear and cellular genome ploidy of G. lamblia cells during all stages of
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- Bernander, Stig, et al.
(author)
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Downhill progressive landslides in long natural slopes: triggering agents and landslide phases modeled with a finite difference method
- 2016
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In: Canadian geotechnical journal (Print). - : Canadian Science Publishing. - 0008-3674 .- 1208-6010. ; 53:10, s. 1565-1582
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Journal article (peer-reviewed)abstract
- A large landslide in Tuve (Gothenburg, Sweden 1977) initiated the development of a model for slope stability analysis taking the deformation-softening of soft sensitive clays into consideration. The model studies triggering agents and five phases in progressive slope failure are identified: (1) in-situ, (2) disturbance, (3) unstable ‘dynamic’, (4) transitory (or permanent) equilibrium, and (5) ‘global’ failure. The clay resistance in these phases may differ widely; mostly due to different rates of loading. Two time dependent failure criteria are defined: (i) the triggering load condition in the disturbance Phase (2), and (ii) the transitory equilibrium in Phase (4), indicating whether minor downhill displacements or a veritable landslide catastrophe will occur. The analysis explains why downhill landslides tend to spread over vast areas of almost horizontal ground further down-slope. The model has been applied to landslides in Scandinavia and Canada. Three case studies are briefly discussed. The model is a finite difference approach, where local downhill deformations caused by normal forces is maintained compatible with deviatory shear deformations above the potential (or the established) failure surface. Software and an easy-to-use spreadsheet are introduced as well as recent developments. See also Video Abstract.
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- Darelid, Johan, et al.
(author)
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A single genotype of Legionella pneumophila serogroup 1 found in 96% of isolates from a hospital and minucipal water distribution system over a 12-year period
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Other publication (other academic/artistic)abstract
- The genotypic distribution of Legionella pneumophila serogroup 1 was investigated in the water distribution system of a 450 bed Swedish hospital and the surrounding community. A single genotype identified by amplified fragment length polymorphism (AFLP) analysis, was found in all 34 hospital isolates and in 18/20 (90%) community isolates over a 12-year surveillance period. All enviromnental isolates were either monoclonal antibody subtypes Benidorm or Bellingham. In a geographic comparison, the hospital genotype was also identified in two out of six Swedish hospitals; both located within 100 km of the studied community. In all, 70 isolates from seven Swedish communities clustered in four groups, each also containing one AFLP type as defined by the European Working Group on Legionella Infections (EWGLI). It was concluded that a single Legionella pneumophila serogroup 1 genotype may colonise a large water distribution system over a long period of time, and that certain clones seem to be widely spread in the environment. Results frorn molecular typing of isolates originating from a limited geographical area must, therefore, be interpreted cautiously in epidemiological investigations of Legionnaires' disease.
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- Locat, Ariane, et al.
(author)
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Study of a lateral spread failure in an eastern Canada clay deposit in relation with progressive failure : the Saint Barnabé-Nord slide
- 2008
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In: Proceedings of the 4th Canadian Conference on Geohazards. - : Presse de l'Université Laval. - 9782978763781 ; , s. 89-95
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Conference paper (peer-reviewed)abstract
- A review of the concept of progressive failure in the context of slope stability and an application of this concept to a spread failure in an eastern Canada clay deposit have been made in the search of a better understanding of the role of progressive failure in this type of mass movement. The study led to the identification of two failure modes for lateral spread failures. In the first one, the disturbing agent is located up slope (e.g. presence of a fill on top of the slope) resulting in an increase of earth pressure and possibly entailing a passive failure. In the second one, the disturbing agent is located down slope (e.g. river erosion at the toe of a slope) causing a decrease of earth pressure and possibly an acctive failure. The application of progressive failure to a lateral spread failure in clay has therefore enabled the development of new ideas regarding the failure mechanism in large landslides where limit equilibrium stability analysis is not applicable.
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- Reiner, David S., et al.
(author)
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Synchronisation of Giardia lamblia : identification of cell cycle stage-specific genes and a differentiation restriction point
- 2008
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In: International Journal of Parasitology. - : Elsevier BV. - 0020-7519 .- 1879-0135. ; 38:8-9, s. 935-944
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Journal article (peer-reviewed)abstract
- The intestinal parasite Giardia lamblia undergoes cell differentiations that entail entry into and departure from the replicative cell cycle. The pathophysiology of giardiasis depends directly upon the ability of the trophozoite form to replicate in the host upper small intestine. Thus, cell proliferation is tightly linked to disease. However, studies of cell cycle regulation in Giardia have been hampered by the inability to synchronise cultures. Here we report that Giardia isolates of the major human genotypes A and B can be synchronised using aphidicolin, a mycotoxin that reversibly inhibits replicative DNA polymerases in eukaryotic cells. Aphidicolin arrests Giardia trophozoites in the early DNA synthesis (S) phase of the cell cycle. We identified a set of cell cycle orthologues in the Giardia genome using bioinformatic analyses and showed that synchronised parasites express these genes in a cell cycle stage-specific manner. The synchronisation method also showed that during encystation, exit from the ordinary cell cycle occurs preferentially in GZ and defines a restriction point for differentiation. Synchronisation opens up possibilities for further molecular and cell biological studies of chromosome replication, mitosis and segregation of the complex cytoskeleton in Giardia.
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