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  • 1
    ISSN: 0309-1651
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2019-08-12
    Description: Mantle convection is a fundamental planetary process. Its plate mode is established and expressed by plate tectonics. Its plume mode also is established and expressed by interregional geological patterns. We developed both an event-based stratigraphic framework to illustrate the surface effects predicted by the plume model of Griffiths et al. (1989) and Griffiths and Campbell (1990) and a methodology to analyze continent-scale geological maps based on unconformities and hiatuses. The surface expression of ascending plumes lasts for tens-of-millions-of-years and rates vary over a few million years. As the plume ascends, its surface expression narrows, but increases in amplitude, leaving distinct geological and stratigraphic patterns in the geologic record, not only above the plume-head center, but also above its margins and in distal regions a few thousands-of-kilometers from the center. To visualize these patterns, we constructed sequential geological maps, chronostratigraphic sections, and hiatus diagrams. Dome-uplift with erosion (Şengör, 2001) and the flood basalts (Duncan and Richards, 1991; Ernst and Buchan, 2001a) are diagnostic starting points for plume-stratigraphic analyses. Mechanical collapse of the dome results in narrow rifting (Burke and Dewey, 1973), drainage-network reorganization (Cox, 1989), and flood-basalt eruption. In the marginal region, patterns of vertical movement, deformation and surface response are transient and complex. At first, the plume margin is uplifted together with the central region, but then it subsides as the plume ascents farther; With plume-head flattening, the plume margin experiences renewed outward-migrating surface uplift, erosion, broad crustal faulting, and drainage reorganization. Knickpoint migration occurs first inward-directed at ½ the rate of plume ascent and later outward-directed at the rate of asthenospheric flow. Interregional-scale unconformity-bounded stratigraphic successions document the two inversions. The distal regions, which did not experience any plume-related uplift, yield complete sedimentary records of the event; Event-related time gaps (hiatuses) in the sedimentary record increase towards the center, but the event horizon is best preserved in the distal region; it may be recognized by tracing its contacts from the center outwards. We extracted system- and series-hiatuses from interregional geological maps and built hiatus maps as proxies for paleo-dynamic topography and as a basis for comparison with results from numerical models. Interregional-scale geological maps are well suited to visualize plume-related geological records of dynamic topography in continental regions. However, geological records and hiatus information at the resolution of stages will be needed at interregional scales. The plume-stratigraphic framework is event-based, interregional, but not global, with time-dependent amplitudes that are significantly larger than those of global eustatic sea-level fluctuations. Global stratigraphic syntheses require integration of plate- and plume-stratigraphic frameworks before eustatic contributions may be assessed.
    Type: Article , PeerReviewed
    Format: text
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  • 3
    Publication Date: 2016-05-18
    Description: Mesenchymal stem cells (MSCs) seeded on specific carrier materials are a promising source for the repair of traumatic cartilage injuries. The best supportive carrier material has not yet been determined. As natural components of cartilage’s extracellular matrix, hyaluronic acid and collagen are the focus of biomaterial research. In order to optimize chondrogenic support, we investigated three different scaffold compositions of a hyaluronic acid (HA)-gelatin based biomaterial. Methods: Human MSCs (hMSCs) were seeded under vacuum on composite scaffolds of three different HA-gelatin ratios and cultured in chondrogenic medium for 21 days. Cell-scaffold constructs were assessed at different time points for cell viability, gene expression patterns, production of cartilage-specific extracellular matrix (ECM) and for (immuno-)histological appearance. The intrinsic transforming growth factor beta (TGF-beta) uptake of empty scaffolds was evaluated by determination of the TGF-beta concentrations in the medium over time. Results: No significant differences were found for cell seeding densities and cell viability. hMSCs seeded on scaffolds with higher ratios of HA showed better cartilage-like differentiation in all evaluated parameters. TGF-beta uptake did not differ between empty scaffolds. Conclusion: Higher ratios of HA support the chondrogenic differentiation of hMSCs seeded on a HA-gelatin composite scaffold.
    Electronic ISSN: 1996-1944
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by MDPI Publishing
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  • 4
    Publication Date: 2016-04-08
    Description: A combination of mesenchymal stem cells (MSCs) and scaffolds seems to be a promising approach for meniscus repair. To facilitate the search for an appropriate scaffold material a reliable and objective in vitro testing system is essential. This paper introduces a new scoring for this purpose and analyzes a hyaluronic acid (HA) gelatin composite scaffold and a polyurethane scaffold in combination with MSCs for tissue engineering of meniscus. The pore quality and interconnectivity of pores of a HA gelatin composite scaffold and a polyurethane scaffold were analyzed by surface photography and Berliner-Blau-BSA-solution vacuum filling. Further the two scaffold materials were vacuum-filled with human MSCs and analyzed by histology and immunohistochemistry after 21 days in chondrogenic media to determine cell distribution and cell survival as well as proteoglycan production, collagen type I and II content. The polyurethane scaffold showed better results than the hyaluronic acid gelatin composite scaffold, with signs of central necrosis in the HA gelatin composite scaffolds. The polyurethane scaffold showed good porosity, excellent pore interconnectivity, good cell distribution and cell survival, as well as an extensive content of proteoglycans and collagen type II. The polyurethane scaffold seems to be a promising biomaterial for a mesenchymal stem cell-based tissue engineering approach for meniscal repair. The new score could be applied as a new standard for in vitro scaffold testing.
    Electronic ISSN: 1996-1944
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by MDPI Publishing
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