FRANCISCAN COMPLEX STRUCTURAL ARCHITECTURE, DEPOSITIONAL AGE, AND PROVENANCE FOR WEST MT. TAMALPAIS, CA

Author(s):  
Owen A. Anfinson ◽  
◽  
David A. Bero ◽  
Loren A. Raymond ◽  
Victoria Simoneau

Author(s):  
Christopher D. Newton ◽  
Jonathan P. Jones ◽  
Adam L. Chamberlain ◽  
Martin R. Bache

The complex structural architecture and inherent processing artefacts within ceramic matrix composites combine to induce inhomogeneous deformation and damage prior to ultimate failure. Bulk measurements of strain via extensometry or even localised strain gauging will fail to characterise such inhomogeneity when performing conventional mechanical testing on laboratory scaled coupons. The current research project has, therefore, applied digital image correlation (DIC) techniques to the room temperature axial assessment of a SiCf/SiC composite under static and ratchetted loading. As processed SiCf/SiC panels were subjected to detailed X-ray computed tomography (XCT) inspection prior to specimen extraction and subsequent mechanical testing. In situ DIC strain measurements were taken throughout the period of room temperature monotonic and ratchet style tensile tests. Contemporary acoustic emission (AE) signals were also recorded to indicate significant damage events and the onset of ultimate failure. Data from these separate monitoring techniques were correlated to indicate the sensitivity or otherwise to pre-existing artefacts within the as received CMC panels.



Author(s):  
Christopher D. Newton ◽  
J. Paul Jones ◽  
Louise Gale ◽  
Martin R. Bache

The complex structural architecture and inherent processing artefacts within ceramic matrix composites combine to induce inhomogeneous deformation and damage prior to ultimate failure. Sophisticated mechanical characterisation is vital in support of a fundamental understanding of deformation in ceramic matrix composites. On the component scale, “damage tolerant” design and lifing philosophies depend upon laboratory assessments of macro-scale specimens, incorporating typical fibre architectures and matrix under representative stress-strain states. Bulk measurements of strain via extensometry or even localised strain gauging will fail to characterise such inhomogeneity when performing conventional mechanical testing on laboratory scaled coupons. The current research project has, therefore, applied digital image correlation (DIC), electrical resistance monitoring and acoustic emission techniques to the room and high temperature assessment of a SiCf/SiC composite under axial fatigue loading. Data from these separate monitoring techniques plus ancillary use of X-Ray computed tomography and optical inspection were correlated to monitor the onset and progression of damage during cyclic loading.



2018 ◽  
Author(s):  
Koen Torremans ◽  
Philippe Muchez ◽  
Manuel Sintubin

Abstract. A structural analysis has been carried out along the southeast margin of the Chambishi-Nkana Basin in the Central African Copperbelt, hosting the world-class Cu-Co Nkana orebody. The geometrically complex structural architecture is interpreted to have been generated during a single NE-SW oriented compressional event, clearly linked to the Pan-African Lufilian orogeny. This progressive deformation resulted primarily in asymmetric multiscale parasitic fold assemblages, characterized by non-cylindrical NW-SE elongated, periclinal folds that strongly interfere laterally, leading to fold linkage and bifurcation. The vergence and amplitude of these folds consistently reflect their position along an inclined limb of a NW plunging megascale first-order fold. A clear relation is observed between development of parasitic folds and certain lithofacies assemblages in the Copperbelt Orebody Member, which hosts most of the ore. Differences in fold amplitude, wavelength and shape are explained by changes in mechanical stratigraphy caused by lateral lithofacies variation in ore-bearing horizons. In addition, strong differences in strain partitioning occur within the deforming basin, which is interpreted to be in part controlled by changes in mechanical anisotropy in the layered rock package. This work provides an essential backdrop to understand the influence of the Lufilian orogeny on metal mineralization and (re-)mobilization in the Copperbelt.



2018 ◽  
Author(s):  
Victoria Simoneau ◽  
◽  
Owen A. Anfinson ◽  
David A. Bero ◽  
Joseph Adams ◽  
...  


Solid Earth ◽  
2018 ◽  
Vol 9 (4) ◽  
pp. 1011-1033
Author(s):  
Koen Torremans ◽  
Philippe Muchez ◽  
Manuel Sintubin

Abstract. A structural analysis has been carried out along the south-east margin of the Chambishi–Nkana Basin in the Central African Copperbelt, hosting the world-class copper and cobalt (Cu–Co) Nkana orebody. The geometrically complex structural architecture is interpreted to have been generated during a single NE–SW-oriented compressional event, clearly linked to the Pan-African Lufilian orogeny. This progressive deformation resulted primarily in asymmetric multiscale parasitic fold assemblages, characterised by non-cylindrical NW–SE-oriented periclinal folds that strongly interfere laterally, leading to fold linkage and bifurcation. The vergence and amplitude of these folds consistently reflect their position along an inclined limb of a NW-plunging megascale first-order fold. A clear relation is observed between the intensity of parasitic folding and the degree of shale content in the Copperbelt Orebody Member (COM), which hosts most of the ore. Differences in fold amplitude, wavelength and shape are explained by changes in mechanical stratigraphy caused by lateral lithofacies variation in ore-bearing horizons. In addition, strong differences in strain partitioning occur within the deforming basin, which is interpreted to be in part controlled by changes in mechanical anisotropy in the layered rock package. This work provides an essential backdrop to understand the influence of the Lufilian orogeny on metal mineralisation and (re-)mobilisation in the Copperbelt.



2019 ◽  
Author(s):  
Christopher John ◽  
Greg M. Swain ◽  
Robert P. Hausinger ◽  
Denis A. Proshlyakov

2-Oxoglutarate (2OG)-dependent dioxygenases catalyze C-H activation while performing a wide range of chemical transformations. In contrast to their heme analogues, non-heme iron centers afford greater structural flexibility with important implications for their diverse catalytic mechanisms. We characterize an <i>in situ</i> structural model of the putative transient ferric intermediate of 2OG:taurine dioxygenase (TauD) by using a combination of spectroelectrochemical and semi-empirical computational methods, demonstrating that the Fe (III/II) transition involves a substantial, fully reversible, redox-linked conformational change at the active site. This rearrangement alters the apparent redox potential of the active site between -127 mV for reduction of the ferric state and 171 mV for oxidation of the ferrous state of the 2OG-Fe-TauD complex. Structural perturbations exhibit limited sensitivity to mediator concentrations and potential pulse duration. Similar changes were observed in the Fe-TauD and taurine-2OG-Fe-TauD complexes, thus attributing the reorganization to the protein moiety rather than the cosubstrates. Redox difference infrared spectra indicate a reorganization of the protein backbone in addition to the involvement of carboxylate and histidine ligands. Quantitative modeling of the transient redox response using two alternative reaction schemes across a variety of experimental conditions strongly supports the proposal for intrinsic protein reorganization as the origin of the experimental observations.





Sign in / Sign up

Export Citation Format

Share Document