Search results for "fault"

CO2 flux measurements in volcanic areas using the dynamic concentration method: the influence of the soil permeability.

2006

In order to evaluate the influence of soil permeability on soil CO2 flux measurements performed with the dynamic concentration method, several tests were carried out using soils characterized by different permeability values and flow rates. A special device was assembled in the laboratory to create a one-dimensional gas flow through a soil of known permeability. Using the advective-diffusion theory, a physical model to predict soil concentration gradients was also developed. The calculated values of CO2 concentrations at different depths were compared with those measured during the tests and a good agreement was found. Four soils with different gas permeability (3.6 x 10(-2) to 1.23 x 10(2)…

A genetic link between synsedimentary tectonics-expelled fluids, microbial sulfate reduction and cone-in-cone structures

2018

14 pages; International audience; The late Jurassic (Tithonian) marlstones of the Boulonnais area (English Channel, France) contains diagenetic carbonate beds and nodules. Some nodules exhibit cone-in-cone structures on their lower face. We studied such nodules using various techniques of imaging and chemical (major and trace-elements) and isotopic analyses (Ccarb, Corg, O and S stable isotopes). We interpret the cone-in-cone to be the end product of carbonate-nodule formation during early diagenesis. The diagenetic carbonate precipitation was induced by microbial activity (bacteria and(?) archeae) fueled by upward-migrating fluids. Fluid expulsion was itself triggered by synsedimentary fau…

Length-scale effects in the nucleation of extended dislocations in nanocrystalline Al by molecular-dynamics simulation

2001

The nucleation of extended dislocations from the grain boundaries in nanocrystalline aluminum is studied by molecular-dynamics simulation. The length of the stacking fault connecting the two Shockley partials that form the extended dislocation, i.e., the dislocation splitting distance, rsplit, depends not only on the stacking-fault energy but also on the resolved nucleation stress. Our simulations for columnar grain microstructures with a grain diameter, d, of up to 70 nm reveal that the magnitude of rsplit relative to d represents a critical length scale controlling the low-temperature mechanical behavior of nanocrystalline materials. For rsplit>d, the first partials nucleated from the bou…

Modelo de cabalgamiento profundo para el Alto Atlas (Marruecos). Implicaciones sísmicas en la zona de colisión entre Eurasia y Africa

2007

Previous crustal models of the High Atlas suppose the existence of a mid-crustal detachment where all the surface thrusts merged and below which the lower crust was continuous. However, both seismic refraction data and gravity modeling detected a jump in crustal thickness between the High Atlas and the northern plains. Here we show that this rapid and vertical jump in the depth of Moho discontinuity suggests that a thrust fault may penetrate the lower crust and offset the Moho (deep-rooted “thick skinned” model). The distribution of Neogene and Quaternary volcanisms along and at the northern part of the High Atlas lineament can be related to the beginning of a partial continental subduction…

Fault detection for discrete-time Markov jump linear systems with partially known transition probabilities

2010

In this article, the fault detection (FD) problem for a class of discrete-time Markov jump linear system (MJLS) with partially known transition probabilities is investigated. The proposed systems are more general, which relax the traditional assumption in Markov jump systems that all the transition probabilities must be completely known. A residual generator is constructed and the corresponding FD is formulated as an H ∞ filtering problem by which the error between residual and fault are minimised in the H ∞ sense. The linear matrix inequality-based sufficient conditions for the existence of FD filter are derived. A numerical example on a multiplier–accelerator model economic system is give…

2014

This paper deals with the fault detection problem for a class of discrete-time wireless networked control systems described by switching topology with uncertainties and disturbances. System states of each individual node are affected not only by its own measurements, but also by other nodes’ measurements according to a certain network topology. As the topology of system can be switched in a stochastic way, we aim to designH∞fault detection observers for nodes in the dynamic time-delay systems. By using the Lyapunov method and stochastic analysis techniques, sufficient conditions are acquired to guarantee the existence of the filters satisfying theH∞performance constraint, and observer gains…

Why banks are not too big to fail - evidence from the CDS market

2013

This paper argues that bank size is not a satisfactory measure of systemic risk because it neglects aspects such as interconnectedness, correlation, and the economic context. In order to differentiate the effect of bank size from that of systemic importance, we control for systemic risk using the CoVaR measure introduced by Adrian and Brunnermeier (2011). We show that a bank's contribution to systemic risk has a significant negative effect on banks’ credit default swap (CDS) spreads, supporting the too‐systemic‐to‐fail hypothesis. Once we control for systemic risk, bank size (relative to gross domestic product (GDP)) has either no or a positive effect on banks’ CDS spreads. The effect of ba…

Comparison of Different Hypotheses Regarding the Spread of Alzheimer’s Disease Using Markov Random Fields and Multimodal Imaging

2018

Alzheimer’s disease (AD) is characterized by a cascade of pathological processes that can be assessed in vivo using different neuroimaging methods. Recent research suggests a systematic sequence of pathogenic events on a global biomarker level, but little is known about the associations and dependencies of distinct lesion patterns on a regional level. Markov random fields are a probabilistic graphical modeling approach that represent the interaction between individual random variables by an undirected graph. We propose the novel application of this approach to study the interregional associations and dependencies between multimodal imaging markers of AD pathology and to compare different hy…

Cognitive reserve impacts on inter-individual variability in resting-state cerebral metabolism in normal aging

2012

There is a great deal of heterogeneity in the impact of aging on cognition and cerebral functioning. One potential factor contributing to individual differences among the elderly is the cognitive reserve, which designates the partial protection from the deleterious effects of aging that lifetime experience provides. Neuroimaging studies examining task-related activation in elderly people suggested that cognitive reserve takes the form of more efficient use of brain networks and/or greater ability to recruit alternative networks to compensate for age-related cerebral changes. In this exploratory multi-center study, we examined the relationships between cognitive reserve, as measured by educa…

The default mode network and the working memory network are not anti-correlated during all phases of a working memory task

2015

INTRODUCTION:\ud \ud The default mode network and the working memory network are known to be anti-correlated during sustained cognitive processing, in a load-dependent manner. We hypothesized that functional connectivity among nodes of the two networks could be dynamically modulated by task phases across time.\ud METHODS:\ud \ud To address the dynamic links between default mode network and the working memory network, we used a delayed visuo-spatial working memory paradigm, which allowed us to separate three different phases of working memory (encoding, maintenance, and retrieval), and analyzed the functional connectivity during each phase within and between the default mode network and the …