102,017 research outputs found
Geology of the Fontane talc mineralization (Germanasca valley, Italian Western Alps)
No full textThe 1:5000 scale Geological Map of the Fontane talc mineralization (FTM) aims to give new information about the origin and geological structure of an important talc mineralization occurring in the axial sector of the Italian Western Alps. The FTM is hosted within a pre-Carboniferous polymetamorphic complex which was deformed and metamorphosed during both Variscan and Alpine orogenesis, and is part of the Dora-Maira continental crust. Field mapping and underground investigations highlight that the talc bodies (i) never crop out but occur at depth along a well-defined lithostratigraphic association between micaschist, marble and gneiss and (ii) were deformed during different Alpine-related deformation phases (i.e. D1, D2 and D3 syn-metamorphic phases and post-metamorphic extensional faulting). The here defined lithostratigraphic and structural characterization of talc bodies, is an input for further research into the geodynamic context of where talc forms and for new mineral exploration outside the mapped area
The structure of the central Taiwan mountain belt
No full textThe structure of the Taiwan mountain belt is thought to be that of an imbricate thrust and fold belt developed above a shallowly dipping basal detachment. In recent years, however, a growing amount of seismicity data from the internal part of the mountain belt indicates the existence of widespread fault activity in the middle and lower crust. Here, we present new geological mapping from the central part of Taiwan. We suggest that the foreland basin part of the Western Foothills comprises an imbricate thrust system that is structurally and kinematically linked to a basal detachment at between 7 and 10 km depth. To the east of the foreland basin, in the Hsuehshan Range, our data show the presence of major faults that are steeply dipping and which penetrate deep into the crust. A structural and kinematic model in which this part of the mountain belt forms a zone of transpression better fits the available data. Eastward, in the Central Range, deep water sediments appear to form an allochthon that is being overthrust by Mesozoic basement rocks. The involvement of Mesozoic basement in the deformation is suggestive of the reactivation of pre-existing basin-bounding faultsThis research was carried out with the aid of grants by CSIC –Proyectos Intramurales 2006 3 01 010, and MICINN: CGL2009-11843-BTE.Peer Reviewe
Illuminating the Hierarchical Segmentation of Faults Through an Unsupervised Learning Approach Applied to Clouds of Earthquake Hypocenters
No full textAbstract We propose a workflow for the recognition of the hierarchical segmentation of faults through earthquake hypocenter clustering without prior information. Our approach combines density‐based clustering algorithms (DBSCAN and OPTICS), and principal component analysis (PCA). Given a spatial distribution of earthquake hypocenters, DBSCAN identifies first‐order clusters, representing regions with the highest density of connected seismic events. Within each first‐order cluster, OPTICS further identifies nested higher‐order clusters, providing information on their number and size. PCA analysis is applied to first‐ and higher‐order clusters to evaluate eigenvalues, allowing discrimination between seismicity associated with planar features and distributed seismicity that remains uncategorized. The identified planes are then geometrically characterized in terms of their location and orientation in the space, length, and height. This automated procedure operates within two spatial scales: the largest scale corresponds to the longest pattern of approximately equally dense earthquake clouds, while the smallest scale relates to earthquake location errors. By applying PCA analysis, a planar feature outputted from a first‐order cluster can be interpreted as a fault surface while planes outputted after OPTICS can be interpreted as fault segments comprised within the fault surface. The evenness between the orientation of illuminated fault surfaces and fault segments, and that of the nodal planes of earthquake focal mechanisms calculated along the same faults, corroborates this interpretation. Our workflow has been successfully applied to earthquake hypocenter distributions from various seismically active areas (Italy, Taiwan, and California) associated with faults exhibiting diverse kinematics
Safety and efficacy of vaginal hysterectomy in the large uterus with the LigaSure bipolar diathermy system.
No full textOBJECTIVE: This study was undertaken to assess safety and efficacy of vaginal hysterectomy in case of large uterine size (> or = 250 g) using the LigaSure bipolar diathermy (Valleylab, Boulder, CO).
STUDY DESIGN: In a retrospective study, medical records of 102 patients who underwent vaginal hysterectomy and who had uterine weight (evaluated after surgery) 250 g or greater were reviewed. All hysterectomies were performed by using the LigaSure vessel sealing system to secure vascular pedicles (uterosacral-cardinal, uterine and ovarian and round ligaments).
RESULTS: Of the 102 vaginal hysterectomies, 99 were successfully performed (97.1%; 95% confidence interval, 91.6-99.4%), whereas a conversion from the vaginal to the abdominal route was required in 3 cases. The median uterine weight was 455 g (range, 241-1913 g). The weight of the largest uterus successfully removed vaginally was 1600 g, without intraoperative and postoperative complications. The median operative time was 50 minutes (range, 25-50 minutes).
CONCLUSION: The current study confirms that very large uterine volume does not represent a real obstacle to perform vaginal hysterectomy and that results in a safe and effective technique in cases of uterine weight 250 g or greater.Objective: This study was undertaken to assess safety and efficacy of vaginal hysterectomy in case of large uterine size (≥ 250 g) using the LigaSure bipolar diathermy (Valleylab, Boulder, CO). Study Design: In a retrospective study, medical records of 102 patients who underwent vaginal hysterectomy and who had uterine weight (evaluated after surgery) 250 g or greater were reviewed. All hysterectomies were performed by using the LigaSure vessel sealing system to secure vascular pedicles (uterosacral-cardinal, uterine and ovarian and round ligaments). Results: Of the 102 vaginal hysterectomies, 99 were successfully performed (97.1%; 95% confidence interval, 91.6-99.4%), whereas a conversion from the vaginal to the abdominal route was required in 3 cases. The median uterine weight was 455 g (range, 241-1913 g). The weight of the largest uterus successfully removed vaginally was 1600 g, without intraoperative and postoperative complications. The median operative time was 50 minutes (range, 25-50 minutes). Conclusion: The current study confirms that very large uterine volume does not represent a real obstacle to perform vaginal hysterectomy and that results in a safe and effective technique in cases of uterine weight 250 g or greater. © 2008 Mosby, Inc. All rights reserved
The structure and kinematics of the central Taiwan mountain belt derived from geological, GPS, and seismicity data
No full textGeometry reconstruction of the Fontane talc mineralization (Germanasca Valley, Italian Western Alps): integration of geological-structural analysis and geomatics methods
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