Neotectonic modeling of the Ibero-Maghrebian region

15 páginas, 12 figuras.Thin-shell finite element techniques have been applied to model the neotectonics of the Ibero-Maghrebian region, in the westernmost Mediterranean. This region is characterized by a complex seismotectonic pattern and moderate seismic activity associated with the convergence between Africa and Eurasia. We compare two end-member models using different fault networks. Model predictions, including anelastic strain rates, vertically integrated stresses and velocity fields, are compared to the seismicity map and to data on directions of maximum horizontal compression. Best results are obtained assuming a low fault friction coefficient (0.05) and when the Betics and Rif are modeled as parts of the same arc-shaped chain. The highest predicted fault slip rates are in the Tell mountains. Farther to the west, fault slip is more homogeneously distributed over the Betic-Rif chain, Gulf of Cadiz, and Alboran Sea, indicating a diffuse geometry of the plate boundary in this area. The areas of highest predicted strain rates coincide with the most seismically active regions, located in northern Algeria and northeastern Morocco. Our best model also reproduces a major change of the stress regime, from thrusting in the east (Tell mountains) to predominantly strike-slip and normal faulting in the west (Betic-Rif chain and Alboran Sea). The Alboran basin is shown to be undergoing significant internal transpression and therefore cannot be considered as a rigid microplate. The western part of the Alboran Sea and surrounding areas are being extruded to the WNW with respect to Iberia.Spanish research programs Ramón y Cajal, BTE2002-02462, REN2000-0777-C02-01/RIES, DGESIC PB97-1267-C03-01, and a grant from the Foundation Jaime del Amo (University Complutense of Madrid) have partially supported this work.Peer reviewe

Overriding Plate Thickness as a Controlling Factor for Trench Retreat Rates in Narrow Subduction Zones

Slab width is a significant factor in controlling subduction zone dynamics, particularly the retreat velocities, which tend to decrease with wider slabs. However, observations of natural narrow subduction zones reveal no correlation between slab width and trench velocities. This suggests that other factors may exert a greater influence. In this study, we employ 3D numerical subduction models to systematically assess the impact of slab width, strength of slab coupling to the lateral plate (LP), and overriding plate (OP) thickness on trench kinematics and geometry. Our models focus on narrow slabs (400–1,200 km), and the results demonstrate that, in the case of narrow subduction zones, the slab width has little effect on trench migration rates and the viscous coupling at the lateral slab edge is only important for very narrow subduction zones (≤800 km). Conversely, the OP thickness emerges as a crucial factor, with increasing plate thickness leading to a strong decrease in trench velocities. These findings provide an explanation for the observed trench velocities in natural narrow subduction zones, where an inverse relationship with OP thickness is evident. Furthermore, our study reveals that not only slab width, but also the OP thickness and the slab coupling to the LP, significantly influence trench geometry. Strong lateral coupling promotes the formation of concave trench geometries, while thick overriding plates favor the development of “w”‐shaped geometries. Overall, a comprehensive understanding of subduction processes necessitates considering the interplay between slab width, OP thickness, and slab coupling to the LP

Chikungunya virus infections among travellers returning to Spain, 2008 to 2014

Since the first documented autochthonous transmission of chikungunya virus in the Caribbean island of Saint Martin in 2013, the infection has been reported within the Caribbean region as well as North, Central and South America. The risk of autochthonous transmission of chikungunya virus becoming established in Spain may be elevated due to the large numbers of travellers returning to Spain from countries affected by the 2013 epidemic in the Caribbean and South America, as well as the existence of the Aedes albopictus vector in certain parts of Spain. We retrospectively analysed the laboratory diagnostic database of the National Centre for Microbiology, Institute of Health Carlos III (CNM-ISCIII) from 2008 to 2014. During the study period, 264 confirmed cases, of 1,371 suspected cases, were diagnosed at the CNM-ISCIII. In 2014 alone, there were 234 confirmed cases. The highest number of confirmed cases were reported from the Dominican Republic (n = 136), Venezuela (n = 30) and Haiti (n = 11). Six cases were viraemic in areas of Spain where the vector is present. This report highlights the need for integrated active case and vector surveillance in Spain and other parts of Europe where chikungunya virus may be introduced by returning travellers

Differential body composition effects of protease inhibitors recommended for initial treatment of HIV infection: A randomized clinical trial

This article has been accepted for publication in Clinical Infectious Diseases ©2014 The Authors .Published by Oxford University Press on Clinical Infectious Disease 60.5. DOI: 10.1093/cid/ciu898Background. It is unclear whether metabolic or body composition effects may differ between protease inhibitor-based regimens recommended for initial treatment of HIV infection. Methods. ATADAR is a phase IV, open-label, multicenter randomized clinical trial. Stable antiretroviral-naive HIV-infected adults were randomly assigned to atazanavir/ritonavir 300/100 mg or darunavir/ritonavir 800/100 mg in combination with tenofovir/emtricitabine daily. Pre-defined end-points were treatment or virological failure, drug discontinuation due to adverse effects, and laboratory and body composition changes at 96 weeks. Results. At 96 weeks, 56 (62%) atazanavir/ritonavir and 62 (71%) darunavir/ritonavir patients remained free of treatment failure (estimated difference 8.2%; 95%CI -0.6 to 21.6); and 71 (79%) atazanavir/ritonavir and 75 (85%) darunavir/ritonavir patients remained free of virological failure (estimated difference 6.3%; 95%CI -0.5 to 17.6). Seven vs. five patients discontinued atazanavir/ritonavir or darunavir/ritonavir due to adverse effects. Total and HDL cholesterol similarly increased in both arms, but triglycerides increased more in atazanavir/ritonavir arm. At 96 weeks, body fat (estimated difference 2862.2 gr; 95%CI 726.7 to 4997.7; P=0.0090), limb fat (estimated difference 1403.3 gr; 95%CI 388.4 to 2418.2; P=0.0071), and subcutaneous abdominal adipose tissue (estimated difference 28.4 cm2; 95%CI 1.9 to 55.0; P=0.0362) increased more in atazanavir/ritonavir than in darunavir/ritonavir arm. Body fat changes in atazanavir/ritonavir arm were associated with higher insulin resistance. Conclusions. We found no major differences between atazanavir/ritonavir and darunavir/ritonavir in efficacy, clinically-relevant side effects, or plasma cholesterol fractions. However, atazanavir/ritonavir led to higher triglycerides and total and subcutaneous fat than darunavir/ritonavir and fat gains with atazanavir/ritonavir were associated with insulin resistanceThis is an Investigator Sponsored Research study. It was supported in part by research grants from Bristol‐Myers Squibb and Janssen‐Cilag; Instituto de Salud Carlos III (PI12/01217) and Red Temática Cooperativa de Investigación en SIDA G03/173 (RIS‐EST11), Ministerio de Ciencia e Innovación, Spain. (Registration number: NCT01274780; registry name: ATADAR; EUDRACT; 2010‐021002‐38)

Influence of cratonic lithosphere on the formation and evolution of flat slabs : insights from 3-D time-dependent modeling.

Several mechanisms have been suggested for the formation of flat slabs including buoyant features on the subducting plate, trenchward motion and thermal or cratonic structure of the overriding plate. Analysis of episodes of flat subduction indicate that not all flat slabs can be attributed to only one of these mechanisms and it is likely that multiple mechanisms work together to create the necessary conditions for flat slab subduction. In this study we examine the role of localized regions of cratonic lithosphere in the overriding plate in the formation and evolution of flat slabs. We explicitly build on previous models, by using time-dependent simulations with three-dimensional variation in overriding plate structure. We find that there are two modes of flat subduction: permanent underplating occurs when the slab is more buoyant (shorter or younger), while transient flattening occurs when there is more negative buoyancy (longer or older slabs). Our models show how regions of the slab adjacent to the subcratonic flat portion continue to pull the slab into the mantle leading to highly contorted slab shapes with apparent slab gaps beneath the craton. These results show how the interpretation of seismic images of subduction zones can be complicated by the occurrence of either permanent or transient flattening of the slab, and how the signature of a recent flat slab episode may persist as the slab resumes normal subduction. Our models suggest that permanent underplating of slabs may preferentially occur below thick and cold lithosphere providing a built-in mechanism for regeneration of cratons

Induction of Eosinophil Apoptosis by the Cyclin-Dependent Kinase Inhibitor AT7519 Promotes the Resolution of Eosinophil-Dominant Allergic Inflammation

Eosinophils not only defend the body against parasitic infection but are also involved in pathological inflammatory allergic diseases such as asthma, allergic rhinitis and contact dermatitis. Clearance of apoptotic eosinophils by macrophages is a key process responsible for driving the resolution of eosinophilic inflammation and can be defective in allergic diseases. However, enhanced resolution of eosinophilic inflammation by deliberate induction of eosinophil apoptosis using pharmacological agents has not been previously demonstrated. Here we investigated the effect of a novel cyclin-dependent kinase inhibitor drug, AT7519, on human and mouse eosinophil apoptosis and examined whether it could enhance the resolution of a murine model of eosinophil-dominant inflammation in vivo.Eosinophils from blood of healthy donors were treated with AT7519 and apoptosis assessed morphologically and by flow-cytometric detection of annexin-V/propidium iodide staining. AT7519 induced eosinophil apoptosis in a concentration dependent manner. Therapeutic administration of AT7519 in eosinophil-dominant allergic inflammation was investigated using an established ovalbumin-sensitised mouse model of allergic pleurisy. Following ovalbumin challenge AT7519 was administered systemically at the peak of pleural inflammation and inflammatory cell infiltrate, apoptosis and evidence of macrophage phagocytosis of apoptotic eosinophils assessed at appropriate time points. Administration of AT7519 dramatically enhanced the resolution of allergic pleurisy via direct induction of eosinophil apoptosis without detriment to macrophage clearance of these cells. This enhanced resolution of inflammation was shown to be caspase-dependent as the effects of AT7519 were reduced by treatment with a broad spectrum caspase inhibitor (z-vad-fmk).Our data show that AT7519 induces human eosinophil apoptosis and enhances the resolution of a murine model of allergic pleurisy by inducing caspase-dependent eosinophil apoptosis and enhancing macrophage ingestion of apoptotic eosinophils. These findings demonstrate the utility of cyclin-dependent kinase inhibitors such as AT7519 as potential therapeutic agents for the treatment of eosinophil dominant allergic disorders

Contribution of Genetic Background, Traditional Risk Factors, and HIV-Related Factors to Coronary Artery Disease Events in HIV-Positive Persons

We show in human immunodeficiency virus-positive persons that the coronary artery disease effect of an unfavorable genetic background is comparable to previous studies in the general population, and comparable in size to traditional risk factors and antiretroviral regimens known to increase cardiovascular ris

Different styles of continental delamination: the influence of the viscosity structure and radiogenic heat production

[ES] En este estudio se aplican algoritmos termomecánicos para modelizar la evolución asimétrica de una litosfera orogénica engrosada, con un conducto adyacente de baja viscosidad, que atraviesa la litosfera. Analizamos la influencia en la evolución de la delaminación de la estratificación de viscosidad, de la producción radiogénica de calor y de la naturaleza del material presente en el conducto de baja viscosidad. Esta evolución es muy sensible a la viscosidad del manto litosférico y, en menor grado, a la viscosidad de la astenosfera y de la corteza inferior. Un aumento de tan sólo un orden de magnitud de la viscosidad máxima permitida para la litosfera (de 1022 a 1023 Pa s) produce un cambio de una delaminación bien desarrollada, con una fuerte migración del punto de delaminación, a una completa inhibición del proceso. Los resultados muestran que la producción radiogénica de calor tiene una fuerte influencia en la geometría del manto litosférico en hundimiento. Los modelos con una elevada producción de calor en la corteza inferior predicen el ascenso astenosférico, sin que se forme una estructura de tipo slab en el manto superior. Obtenemos que la naturaleza del material que constituye el conducto de baja viscosidad, bien sea material astenosférico o bien manto litosférico de baja viscosidad, no afecta significativamente al proceso de delaminación. Sugerimos que tanto el debilitamiento litosférico por procesos de deshidratación como el adelgazamiento térmico son mecanismos plausibles para la formación de conductos de baja viscosidad capaces de desencadenar la delaminación.[EN] Thermo-mechanical algorithms are applied in this study to model the asymmetric evolution of a thickened orogenic lithosphere with an adjacent ‘low viscosity conduit’ across the lithosphere. We investigate the influence of viscosity stratification, crustal radiogenic heat production, and nature of the material filling the ‘low viscosity conduit’ on the evolution of delamination. This evolution is shown here to be very sensitive to the lithospheric mantle viscosity and, to a lesser degree, to asthenosphere and lower crust viscosities. An increase of only one order of magnitude in the maximum viscosity of the lithospheric mantle (from 1022 to 1023 Pa s) causes a change from a well-developed delamination with large displacement of delamination point to a complete inhibition of this process. Radiogenic heat production is shown to have a strong influence on the resulting geometry of the sinking lithospheric mantle. Models with high radiogenic heat production in lower crust reproduce asthenospheric upwelling but without creating a slab-like structure in the upper mantle. We obtain that the nature of the material filling the low viscosity conduit, either asthenospheric material or low viscosity lithospheric mantle, does not significantly affect the development of delamination. We suggest that both lithospheric weakening by dehydration processes and thermal thinning processes are plausible mechanisms for the formation of ‘low viscosity conduits’ able to sustain delamination.Peer reviewe

Evidence for eastward mantle flow beneath the Caribbean plate from neotectonic modeling

We have applied a thin-shell modeling technique to study the neotectonics of the Caribbean plate. Kinematic conditions computed assuming rotation poles and velocities from NUVEL-1A and from recent geodetic studies have been applied at the lateral boundaries of the model to represent the motion of the adjacent plates with respect to the Caribbean. We have generated a large number of models varying the values of the fault friction coefficient and shear traction on the base of the plate exerted by mantle flow. The quality of the models has been evaluated by comparing their predictions with data on seismic strain rate, stress direction, geodetic baseline changes, and slip rates. Our results indicate that the only successful models are those with low values of fault friction coefficient and significant basal shear traction exerted by eastward mantle flow beneath the Caribbean.AN was supported by the Spanish Ministerio de Ciencia y Tecnología research projects BTE2002-02462 and ‘Ramón y Cajal’Peer reviewe