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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 143 (1994), S. 117-149 
    ISSN: 1420-9136
    Keywords: Rock fracture in compression ; 3-D cracks ; laser technique of crack initiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Fracture of rocks containing a multitude of pre-existing cracks is considered from both theoretical and experimental points of view, paying attention mainly to the underlying mechanisms. The competition between a number of mechanisms in producing tear or shear type fractures is discussed in relation to the properties of the rock and the system of pre-existing cracks on the one hand and the type of loading on the other hand. First, 2-D theoretical models and experimental results aimed at the explanation and description of brittle fracture under compression are considered. Their insufficiency and the necessity to address the 3-D peculiarities of crack growth in rock are shown on the basis of new experimental results on 3-D crack propagation in transparent rock-like brittle materials under uniaxial compression. The results show that in contrast to the 2-D case, a single 3-D crack cannot propagate any appreciable distance and the loading results in dynamic, burst-like failure of the sample. Possible mechanisms of the routinely observed extensive fracture propagation in rock samples (splitting), as well as the possibility of shear (oblique) fracture in uniaxial compression, are discussed in connection with these experiments.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 186 (1992), S. 67-74 
    ISSN: 1432-0568
    Keywords: Rat embryos ; Limb bud ; Regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The regulative potential of the fore-limb region following the removal of the limb bud was investigated in 11.5-day rat embryos. Fore-limb buds were amputated from a total of 54 embryos. Five embryos were immediately examined via scanning electron microscopy (SEM) to assess the quality of the operation and the reproducibility of the technique. In all cases, the forelimb bud and adjacent tissues extending down to the celomic cavity at the same level were completely removed. The remaining 49 operated embryos were cultured in vitro and examined at different time intervals. Gross inspection of embryos which had been cultured for 24 h, revealed that 24 out of 37 had developed a pair of limb bud-like protrusions at the operation site. Twelve formed only a single protrusion, while nothing was found in the remaining embryo. These protrusions were examined in greater detail under SEM and light microscopy. SEM observations showed that these protrusions were covered with an intact layer of ectoderm. In embryos with a pair of protrusions, these outgrowths developed opposite somites 7 to 13. The failure of either one of these two outgrowths to form, produced our second type of experimental embryo, those which had just a single protrusion. Histological examination revealed that an apical ectodermal ridge (AER) was discernible on the protrusions of 36% of the embryos. Finally, we have established how these protrusions were constructed from SEM observations of operated embryos cultured for 6 h and 10 h.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 184 (1991), S. 583-590 
    ISSN: 1432-0568
    Keywords: Avian embryos ; Latex beads ; Fibronectin ; Limb bud
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Latex beads were implanted into the chick wing bud to determine whether parameters other than active movement, for example matrix-driven translocation and growth of the limb bud, were responsible for the extensive re-allocation of myogenic cells that occurs during limb development. Latex beads were implanted into nine stage 20–24 Hamburger and Hamilton (H.H.) wing buds, and were allowed to develop for 3 days before examination. In all cases, it was found that most of the latex beads (86.57%±11.4%) were confined to the implantation site. A small percentage of beads was observed in the connective and myogenic regions proximal and distal to the graft side. In general the displacement of these beads was relatively short, although in one specimen a few beads were translocated to regions as far as the autopod. The surface of the latex beads was also coated with fibronectin prior to transplantation, to ascertain whether the extracellular matrix can influence the translocation of beads within the limb bud. Ten specimens were examined, and as for uncoated latex beads, most of the fibronectin-coated beads (87.14%±11.67%) were contained within the transplantation site. Again a mall percentage of beads was found in the connective and myogenic but not in the chondrogenic tissues proximal and distal to the graft side. In one specimen fibronectin-coated beads were translocated to regions in the autopod, but in general, bead displacement was relatively short. In sum, latex beads can not move to any great extent within the limb bud, and the coating of these beads with fibronectin did not influence bead translocation.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 184 (1991), S. 153-157 
    ISSN: 1432-0568
    Keywords: Mouse embryos ; Limb bud ; Regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ability of day E10 mouse fore-limb bud to regulate following the removal of a portion of limb tissue was investigated. A longitudinal strip of tissue, two to three somites in width and extending from the base of the limb bud to its distal tip, was excised. The embryos were then maintained in a roller culture system for periods of 6 h, 12 h or 24 h post-operatively prior to fixation and subsequent examination. The embryos were examined with scanning electron microscopy (SEM) and light microscopy. SEM revealed that about two thirds of the operated limbs grossly restored their overall morphology. The sequence of morphological changes involved in the restoration process is described. The ability of the restored limb bud to develop an apical ectodermal ridge (AER) is shown in histological sections.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 182 (1990), S. 547-551 
    ISSN: 1432-0568
    Keywords: Avian limb bud ; Myogenic cell movement ; Autoradiography ; Homospecific and heterospecific transplantations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Species specificity and the use of quail cells as a marker in the study of myogenic cell movement in the developing avian limb was investigated. In order to establish whether or not observed myogenic cell movement in quail/chick limb transplantation experiments might be an artefact produced by cellular interaction between these cell types a series of homospecific and heterospecific transplantations was performed. Chick wing fragments (staged 20–25 H.H.) were labelled with tritiated thymidine and inserted into unlabelled chick wing bud (homospecific) in ovo. In addition, quail wing fragments were also labelled with tritiated thymidine and transplanted in the same manner into chick (heterospecific), so that the effectiveness of tritium as a marker could be assessed. After 4 days post-incubation, myogenic cell movement was detected in eight out of the ten homospecific transplantions performed. Myogenic cell movement in avian limbs is therefore not produced by interaction between chick and quail cells, as migration was also detected in the chick/chick transplants. Nonetheless, heterospecific transplantation results revealed that autoradiographic methods failed to reveal completely the true extent to which myogenic cell movement occurred, because tritiated thymidine was subject to dilution.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 179 (1989), S. 395-402 
    ISSN: 1432-0568
    Keywords: Fowl mutant ; Limb development ; Myogenic cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Talpid 3 is a recessive lethal mutant of the fowl. It has been shown previously that, in vitro, talpid 3 limb mesenchyme cells are more adhesive and less mobile than normal cells. It is therefore of interest to investigate the effect of the gene on cell movement in vivo, in the limb bud itself, in cells in which it is known to occur in normal embryos. Myogenic cells, which normally migrate into the limb bud from the somites, continue to move distalwards when grafted into the limb bud at a later stage. Blocks of normal or talpid 3 limb mesenchyme containing myogenic cells were transplanted into quail limb buds in ovo. Since quail cells are histologically distinguishable from chick cells the progress of myogenic cell movement 5 days after transplantation could be observed. In 10 out of 14 cases normal myogenic cells migrated extensively in a proximo-distal direction within the limb bud for the quail host. In contrast, only 2 out of 11 talpid 3 transplants showed a moderate degree of distalwards movement.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 180 (1989), S. 293-300 
    ISSN: 1432-0568
    Keywords: Myogenic cell ; Limb bud ; Cell movement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Quail limb mesenchyme containing myogenic cells of somitic origin were transplanted into chick limb buds to determine whether cell movement might play a role in avian limb myogenesis. In general, cell displacement was not detected 1-day after implantation: all quail cells were found at the graft site. Migration was evident 2-days after implantation but not all cell types were capable of movement; myogenic cells were very invasive while chondrocytes were relatively immobile. The spreading of myogenic cells was discernible up to 4-days after implantation and specifically in a proximodistal direction towards the apex of the limb.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-0568
    Keywords: Cranial neural crest ; Microinjection ; Mouse embryo ; Neurulation ; Migration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ability of cells and latex beads to become incorporated into the cranial region of embryos after microinjection into the amniotic cavity was studied. Premigratory neural crest cells isolated from the lateral margins of the neuroepithelium, 3T3 fibroblast cells or H35 hepatoma cells were labelled with WGA-gold conjugates, and were then microinjected into the amniotic cavity of embryos with two to three somites in vitro. Latex beads were similarly microinjected into different groups of embryos. Incorporation of injected cells or latex beads was found in the neural crest of the midbrain and the hindbrain of 5–20% of the recipients 4 h after microinjection. At 6 and 12 h, increasingly more embryos (20–77%) were observed with labelled cells or latex beads in the crest region. While hepatoma cells and latex beads were restricted to the crest region, injected neural crest cells and fibroblasts were also found in the lateral mesenchyme, bounded laterally by the surface ectoderm and medially by the closing neural tube. By 24 h after microinjection, the injected cells or latex beads were found in 50–80% of the recipients. Neural crest cells and fibroblasts, which showed similar patterns of distribution in the embryos, were located on the dorsal aspect of the neural tube, the lateral mesenchyme, the pharyngeal arches and the regions for ganglia. Hepatoma cells and latex beads were limited to the dorsal regions of the neural tube. When microinjection was carried out in embryos with seven to eight somites, incorporation of cells or latex beads was found in 44–75% of embryos, but no dispersion of the incorporated cells or latex beads into the mesenchyme was found 24 h after microinjection. Incorporation and dispersion of cells and latex beads were not observed when embryos with 18–20 somites were used as recipients. The present study showed that neural crest or fibroblast cells when injected into the amniotic cavity could be incorporated into the neural crest, and then undergo migration along the neural crest pathways, whereas hepatoma cells and latex beads could only be incorporated. The incorporation and migration of the exogenous tissues are related to the formation and the accessibility of the neural crest in the recipients.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Environmental geology 35 (1998), S. 278-286 
    ISSN: 1432-0495
    Keywords: Key words Natural environment ; Glass fiber ; Environmental assessment ; Groundwater contamination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The natural environment of an environmental conflict site in Incheon, Korea was assessed with a focus on the hydrogeological environment. Residents had made claims against a company because of health problems, including skin tumors. More specifically, the residents suspected that their drinking groundwater had been contaminated by glass fibers which had caused the health problems. Air, soil, and groundwater samples were analyzed to estimate whether environmental pollution could have caused the problems claimed by the residents. No specific evidence was found from this study to support the groundwater contamination by glass fibers, but groundwater contamination by leaked fuel oils was confirmed in the course of evaluating the glass fiber problem.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-0495
    Keywords: Key words Nanjido Landfill ; Landfill leachate ; Landfill gas ; Environmental impact
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The Nanjido Landfill is the largest uncontrolled landfill in Korea and it causes various kinds of environmental problems. Landfill gases and leachate are recognized as the most serious environmental problems associated with the landfill. This study employs a series of numerical models and uses test data to interpret the distribution and flow of landfill gases and leachate. Leachate seepage appears about 40–60 m higher than the estimated basal groundwater table. Thus, seepage data indicate that perched or floating leachate layers are formed in the unsaturated zone of the landfill. The leachate production rate is estimated using infiltration test data and a model for unsaturated groundwater flow. Geochemical data indicate that the landfill leachate degrades the basal groundwater quality along the downgradient zone. The environmental impact of the leachate on river water is estimated.
    Type of Medium: Electronic Resource
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