Geophysical modeling of Valle de Banderas graben and its structural relation to Bahia de Banderas, Mexico

A gravimetric survey consisting of five lines and 483 stations, as well as a magnetotelluric (MT) survey consisting of 17 observation sites, were made in the Valle de Banderas region for the determination of the structural characteristics of the valley. Additionally, data from a previous aeromagnetic survey were analyzed to correlate them with our geophysical measurements. The gravimetric and MT models confirm that the valley corresponds to a graben structure with slumped blocks that vary from similar to 2000 m deep close to Bahia de Banderas to shallow burial depths (similar to 100 m) toward the NE end of the valley. Faults flanking the valley, inferred from the gravity and magnetic models, trend toward offshore faults in Bahia de Banderas, indicating a structural connection between land and sea. From the MT measurements we conclude that a 2-D resistivity behavior is observed within the graben whereas outside of the graben the behavior is 1-D, in spite of the rough topography of this region. Our gravimetric models also indicate the occurrence of basin-like structures within the graben, coinciding with similar structures reported offshore in the Bahia de Banderas, suggesting that such structures may be typical erosional features of the graben. The aeromagnetic analysis correlates with the gravimetric and W models, and suggests that the graben structure is an extensional zone on granitic crus

Delimitation of ground failure zones due to land subsidence using gravity data and finite element modeling in the Queretaro valley, Mexico

Sedimentary basins of and and semiarid zones are often subject to regimes of intense ground-water withdrawal as it is normally the only source of water for development of communities. An associated phenomenon is land subsidence, which can develop to ground failures, and consequently, damage to infrastructure. Aquifer deformation can be analyzed using a stress-strain or a flux-force approach depending on the aquifer material (compact or loose) and on whether the water withdrawal forms a predominant flow direction toward a cone of depression. Geometry of the aquifer system also plays an important role as uneven thickness induces differential compaction and hence, tensional and shear stresses on the ground mass. In this work we present a stress-strain approach to analyze subsidence for an unconfined aquifer of varying thicknes

Production of Osteopontin by Cultured Porcine Epithelial Cell Rests of Malassez

Background:  The epithelial cell rests of Malassez (ERM) are derived from Hertwig's epithelial root sheath (HERS). During development the cells of HERS deposit a variety of molecules on the newly forming root surface. The possibility that ERM retain this potential after root development is completed and secrete bone or cementum-related proteins needs to be investigated. The purpose of this study was to determine the expression of the non-collagenous proteins osteopontin (OPN) and bone sialoprotein (BSP) by cells derived from the epithelial cell rests of porcine periodontium. Methods:  ERM and fibroblasts were cultured from porcine periodontal ligament. The cells were identified and characterized using transmission electron microscopy, immunohistochemistry, western blot analysis of proteins, reverse transcription–polymerase chain reaction and ability to form mineralized nodules in culture. In particular the expression of the mineralized tissue-related proteins, BSP and OPN, was studied. Results:  Cells from porcine periodontal ligaments were successfully cultured; separated and characterized as being of either an epithelial or fibroblastic phenotype. Although the ERM did not form mineralized nodules in culture, they did express a significant amount of mRNA for OPN. Conclusion:  The results from this study provide evidence that ERM express mRNA for at least one bone/cementum-related protein. Whether this function would be consistent with a role for ERM in tissue formation, inflammation and regeneration remains to be established