A complex sinusoids estimation method based on the deconvolution of the periodogram : "expulse"

EXPULSEmethod lifts the main drawback of the classical high resolution spectral analysis methods (MUSIC, MINORM, . . .) which have a poor robustness with respect to an unreliable knowledge of the number of sources . Its novelty stems from the modeling of the periodogram of complex sinusoids embedded in an additive noise, as the convolution of a perfectly known kernel (depending upon the window) and a compound Bernoulli-Gaussian process, plus a noise . The discrete frequencies where the Bernoulli process takes 1 values locate the sinusoids ; the gaussian process describes the amplitudes .La méthode EXPULSE pallie l'une des principales limitations des techniques traditionnelles d'Analyse Spectrale à Haute Résolution ASHR (MUSIC, Norme minimale, etc.) à savoir la faible robustesse vis-à-vis d'une méconnaissance de leur nombre. Son originalité repose sur l'interprétation d'un périodogramme mis en oeuvre sur un processus de raies pures noyées dans un bruit additif, comme la convolution, à un bruit près, d'un processus composite Bernoulli-Gaussien avec une fonction spectrale parfaitement connue qui dépend de la calibration retenue du périodogramme (type de fenêtre d' apodisation, lissage temporel ou fréquentiel, etc.). Les fréquences discrètes où le processus de Bemoulli prend la valeur 1 sont des raies potentielles de l'espace signal ; le processus gaussien caractérise quant à lui l'amplitude des raies

Towards third generation matrix metalloproteinase inhibitors for cancer therapy

The failure of matrix metalloproteinase (MMP) inhibitor drug clinical trials in cancer was partly due to the inadvertent inhibition of MMP antitargets that counterbalanced the benefits of MMP target inhibition. We explore how MMP inhibitor drugs might be developed to achieve potent selectivity for validated MMP targets yet therapeutically spare MMP antitargets that are critical in host protection

The Corinth Rift Laboratory, Greece (CRL): A Multidisciplinary Near Fault Observatory (NFO) on a Fast Rifting System

The western rift of Corinth (Greece) is one of the most active tectonic structures of the euro-mediterranean area. Its NS opening rate is 1.5 cm/yr ( strain rate of 10-6/yr) results into a high microseismicity level and a few destructive, M>6 earthquakes per century, activating a system of mostly north dipping normal faults. Since 2001, monitoring arrays of the European Corinth Rift Laboratory (CRL, www.crlab.eu) allowed to better track the mechanical processes at work, with short period and broad band seismometers, cGPS, borehole strainmeters, EM stations, …). The recent (300 kyr) tectonic history has been revealed by onland (uplifted fan deltas and terraces) and offshore geological studies (mapping, shallow seismic, coring), showing a fast evolution of the normal fault system. The microseismicity, dominated by swarms lasting from days to months, mostly clusters in a layer 1 to 3 km thick, between 6 and 9 km in depth, dipping towards north, on which most faults are rooting. The diffusion of the microseismicity suggests its triggering by pore pressure transients, with no or barely detected strain. Despite a large proportion of multiplets, true repeaters seem seldom, suggesting a minor contribution of creep in their triggering, although transient or steady creep is clearly detected on the shallow part of some majors faults. The microseismic layer may thus be an immature, downward growing detachment, and the dominant rifting mechanism might be a mode I, anelastic strain beneath the rift axis , for which a mechanical model is under development. Paleoseismological (trenching, paleoshorelines, turbidites), archeological and historical studies completed the catalogues of instrumental seismicity, motivating attempts of time dependent hazard assessment. The Near Fault Observatory of CRL is thus a multidisciplinary research infrastructure aiming at a better understanding and modeling of multiscale, coupled seismic/aseismic processes on fault systems.Grant for Researchers (CC) ID 188753

Evaluation of bacteriophage as an adjunct therapy for treatment of peri-prosthetic joint infection caused by Staphylococcus aureus

Phage therapy offers a potential alternate strategy for the treatment of peri-prosthetic joint infection (PJI), particularly where limited effective antibiotics are available. We undertook preclinical trials to investigate the therapeutic efficacy of a phage cocktail, alone and in combination with vancomycin, to reduce bacterial numbers within the infected joint using a clinically-relevant model of Staphylococcus aureus-induced PJI. Infected animals were randomised to 4 treatment groups, with treatment commencing 21-days post-surgery: bacteriophage alone, vancomycin alone, bacteriophage and vancomycin, and sham. At day 28 post-surgery, animals were euthanised for microbiological and immunological assessment of implanted joints. Treatment with phage alone or vancomycin alone, led to 5-fold and 6.2-fold reductions, respectively in bacterial load within peri-implant tissue compared to shamtreated animals. Compared to sham-treated animals, a 22.5-fold reduction in S. aureus burden was observed within joint tissue of animals that were administered phage in combination with vancomycin, corresponding with decreased swelling in the implanted knee. Microbiological data were supported by evidence of decreased inflammation within the joints of animals administered phage in combination with vancomycin, compared to sham-treated animals. Our findings provide further support for phage therapy as a tolerable and effective adjunct treatment for PJI

Stress‐Dependent b Value Variations in a Heterogeneous Rate‐and‐State Fault Model

International audienceThe magnitudes of earthquakes are known to follow a power law distribution referred to as the Gutenberg‐Richter empirical law. Seismological observations and laboratory experiments suggest a decrease of the decay exponent (b value) with differential stress. The physical mechanism controlling this decrease, however, remains unclear. The present study is dedicated to the origin of relative b value variations with stress obtained in a 2‐D rate‐and‐state planar fault model considering a population of asperities with size‐dependent fracture energy. The simulations show that both b value in the intermediate magnitude range and mainshock magnitude increase with normal stress. Analytical relationships are derived, showing that the increase of b value is related to the decrease of critical nucleation length with normal stress, enhancing the productivity of small‐magnitude events and partial ruptures. The theoretical formulas also show how the increase of mainshock magnitude is a consequence of normal stress dependence of stress drop

Interactions and triggering in a 3-D rate-and-state asperity model

International audienceWe present a 3-D continuous quasi-dynamic rate-and-state model of multipleseismic asperities forced by surrounding aseismic creep and motivated by observations ofcoplanar multiplets. Our model allows to study the physics of interactions among a set ofasperities. First, we show that the amount of interactions and clustering, characterized bythe Omori law and interevent time distribution, depends on how far the system is from acritical density of asperities, which is related to the friction properties of the barriersseparating the sources. This threshold controls the ability of a population of asperities todestabilize the creeping barriers between them and therefore determines whether dynamicsequences including several asperities in the same event might occur, in agreement withwhat is expected from observed magnitude-frequency distributions. Therefore, theconcept of critical density of asperity provides a mechanical interpretation of statisticalproperties of seismicity. As an illustration, we used our numerical results in the specificcase of Parkfield in the period preceding the Mw 6, 2004 earthquake, in order to infer thesteady state friction parameter (a–b) characterizing the creep of this part of the SanAndreas Fault. We estimate a value of (a-b) that locally exceeds 0.001, which is in theupper range of what has already been proposed for the postseimic period of theMw 6,2004 Parkfield earthquake

Creep modulation of Omori law generated by a Coulomb stress perturbation in a 3-D rate-and-state asperity model

International audienceWe present numerical simulations conducted with a quasi-dynamic, 3-Drate-and-state asperity model and an analytical approach in order to study the behavior ofa seismic asperity surrounded by aseismic creep in response to external Coulomb stressperturbations. This work is inspired by the observation of Omori decay characterizing therecurrence time of isolated repeating earthquakes, such as at the Parkfield segment of theSan Andreas Fault during the postseismic phase of the 2004 Mw 6 event. Based on thenumerical results and on an analysis of phase diagrams, we identify two possible regimesthat characterize the response of an asperity surrounded by aseismic creep to a stress step,depending on an effective steady state friction parameter A. For the specific perturbationused in this study, we observe that when A is positive, the relaxation of the system isgoverned by the response of the creeping segments of the fault, and the asperity rupturesin an Omori sequence. In this regime, we demonstrate that the duration of the relaxationprocess depends on A. Furthermore, we show that this effective strengthening behavior isequivalent to a subcritical density of asperities meaning that the shape of the Omori decayis controlled by the relative proportion of seismic and aseismic material within the fault.On the other hand, a fault characterized by effective steady state weakening (A<0)behaves like a spring and slider system that loses the memory of the stress perturbationonce the first aftershock occurred, at least in the simulations presented here

Effects of asperities distribution on induced seismicity and permeability during deep underground exploitation

International audienc