Many cratonic continental fragments dispersed during the rifting and break-up of Gondwana are bound by steep topographic landforms known as 'great escarpments', which rim elevated plateaus in the craton interior. In terms of formation, escarpments and plateaus are traditionally considered distinct owing to their spatial separation, occasionally spanning more than a thousand kilometres. Here we integrate geological observations, statistical analysis, geodynamic simulations and landscape-evolution models to develop a physical model that mechanistically links both phenomena to continental rifting.
View Article and Find Full Text PDFA hydrological and hydrochemical database (produced by the M-TROPICS critical zone observatory) in the upper Nyong Basin from 1998 to 2017 was used to evaluate the river's response to climatic and anthropogenic forcing and examine chemical weathering processes. SiO and HCO constitute about 85 % of the Total dissolved solids (TDS) load, equivalent to 0.12 × 10 kg.
View Article and Find Full Text PDFIt is widely recognized that collisional mountain belt topography is generated by crustal thickening and lowered by river bedrock erosion, linking climate and tectonics. However, whether surface processes or lithospheric strength control mountain belt height, shape and longevity remains uncertain. Additionally, how to reconcile high erosion rates in some active orogens with long-term survival of mountain belts for hundreds of millions of years remains enigmatic.
View Article and Find Full Text PDFJ Geophys Res Earth Surf
June 2018
Glaciers and rivers are the main agents of mountain erosion. While in the fluvial realm empirical relationships and their mathematical description, such as the stream power law, improved the understanding of fundamental controls on landscape evolution, simple constraints on glacial topography and governing scaling relations are widely lacking. We present a steady state solution for longitudinal profiles along eroding glaciers in a coupled system that includes tectonics and climate.
View Article and Find Full Text PDFIEEE Trans Vis Comput Graph
May 2018
Most mountain ranges are formed by the compression and folding of colliding tectonic plates. Subduction of one plate causes large-scale asymmetry while their layered composition (or stratigraphy) explains the multi-scale folded strata observed on real terrains. We introduce a novel interactive modeling technique to generate visually plausible, large scale terrains that capture these phenomena.
View Article and Find Full Text PDFEur J Nucl Med Mol Imaging
August 2008
Purpose: To evaluate the interest of (18)F-fluoro-2-deoxy-D: -glucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) for diagnosis and therapeutic follow-up of patients with sarcoidosis.
Methods: Twenty consecutive patients with biopsy-proven sarcoidosis were retrospectively included, in particular, 13 and seven cases of thoracic and extra-thoracic sarcoidosis, respectively. All patients underwent (18)F-FDG PET/CT, and 12 of them also (67)Ga scintigraphy.
Background: The identification of allergic fungal sinusitis (AFS) is still controversial and much more recent than that of allergic bronchopulmonary aspergillosis (ABPA). Their association has been reported very rarely in the literature.
Methods: The aim of this study was to present a review of 6 cases of AFS associated with ABPA from a series of 12 cases of AFS and to compare AFS associated with ABPA and isolated AFS.
Collision tectonics and the associated transformation of continental crust to high-pressure rocks (eclogites) are generally well-understood processes, but important contradictions remain between tectonothermal models and petrological-isotopic data obtained from such rocks. Here we use 40Ar-39Ar data coupled with a thermal model to constrain the time-integrated duration of an orogenic cycle (the burial and exhumation of a particular segment of the crust) to be less than 13 Myr. We also determine the total duration of associated metamorphic events to be approximately 20 kyr, and of individual heat pulses experienced by the rocks to be as short as 10 years.
View Article and Find Full Text PDFObjectives: Sinonasal sarcoidosis remains a poorly understood and uncommon chronic granulomatous disease of unclear origin. We have attempted to characterize the main clinical and radiologic criteria for diagnosis and to discuss the treatment.
Methods: A retrospective study of 15 cases of chronic, symptomatic, and biopsy-proven sinonasal sarcoidosis and a review of the literature are realized.