Seismicity induced during the development of the Rittershoffen geothermal field, France

The development of the Rittershoffen deep geothermal field (Alsace, Upper Rhine Graben) between 2012 and 2014 induced unfelt seismicity with a local magnitude of less than 1.6. This seismicity occurred during two types of operations: (1) mud losses in the Muschelkalk formation during the drilling of both wells of the doublet and (2) thermal and hydraulic stimulations of the GRT-1 well. Seismicity was also observed 4 days after the main hydraulic stimulation, although no specific operation was performed. During chemical stimulation, however, no induced seismicity was detected. In the context of all field development operations and their injection parameters (flow rates, overpressures, volumes), we detail the occurrence or lack of seismicity, its magnitude distribution and its spatial distribution. The observations suggest the presence of the rock stress memory effect (Kaiser effect) of the geothermal reservoir as well as uncritically stressed zones connected to the GRT-1 well and/or rock cohesion. A reduction of the seismic rate concurrent with an increase of injectivity was noticed as well as the reactivation of a couple of faults, including the Rittershoffen fault, which was targeted by the wells. These results are derived from the homogeneous and consistent catalogue of more than 1300 local earthquakes that is provided. This reference catalogue is based on a standard detection method, whose output was manually verified and improved. The given absolute locations have been computed in a calibrated, geologically realistic 3D velocity model. Our work builds on previous analyses addressing the seismicity induced by the GRT-1 hydraulic stimulation and places the results into a historical context, thus considering the full dynamics of the observed phenomena. This paper also complements existing descriptions of the hydrothermal characteristics of the deep reservoir by providing insights separate from the wells

Les détergents et les désinfectants : les risques liés à l'usage médical des biocides (2e partie)

International audienceObjectives: Biocides are used intensively in a large variety of applications, usually with inanimate objects or on the skin. The general consumer markets led to increase their use by the general public and the risk assessment should be affected by the wide frequency of contact with these products for humans or environment. Risks: Increasingly accurate legislation takes into account physical and chemical risks and the best prevention is the respect of security rules. The evaluation of biological risks is not so easy because antibacterial products activity is linked either to major agents (disinfectant) or to additional agents used as preservatives. Mode of action and biological risk: Some similarities between these antibacterial compounds and antibiotic action have been described maintaining some fears on development or induction of a coping mechanism that should result in a new or increased antibiotic resistance. In fact, these resistances are described as increase in minimal inhibitory concentration (MIC) of antibiotics and not as loss of efficacy at usual concentrations. Resistance and survival: Mainly, there is an over way for microorganisms to survive like very well organized communities manned "biofilms" which preserve organisms of adverse effects including biocide action and present real health and environmental risks

Staphylococcus Aureus Carriage in French Athletes at Risk of CA-MRSA Infection: a Prospective, Cross-sectional Study.

International audienceStaphylococcus aureus (SA) is a leading cause of infectious diseases in sports teams. In recent decades, community-associated SA (CA-SA) strains have emerged worldwide and have been responsible for outbreaks in sports teams. There are very few data on the prevalence of these strains in France, and none on the carriage among athletes.We conducted a cross-sectional study to determine the SA carriage proportion among athletes practicing sports at risk for CA-SA infection in a French county, and determined the methicillin-resistant and/or CA-SA proportion. We also analyzed SA carriage according to risks factors and studied the SA clonality in a sample of our population.We included 300 athletes; SA carriage proportion was 61% (n = 183) and one was MRSA carrier (0.33%). The MRSA strain belonged to the clonal complex ST5. None of the strain produced Panton Valentine Leucocidin, and we did not find clonal distribution within the teams. Interestingly, we found a high throat-only carriage (n = 57), 31.1% of the SA carriers.We found a high SA carriage with a local epidemiology quite different than that reported in a similar population in the USA. Further studies on SA carriage should include throat sampling.The approved protocol was registered on ClinicalTrial.gov , NCT01148485

Les détergents et les désinfectants : rôle en médecine (1re partie)

International audienceRésumé Objectifs: Faire le point sur le rôle des détergents et désinfectants en médecine. Les produits: Les détergents, désinfectants (y compris les antiseptiques) sont des produits chimiques. Ils sont soumis à l'évolution constante des réglementations qui veillent à privilégier des produits présentant le meilleur rapport bénéfice/risques tant pour l'homme que pour l'environnement. Mode d'action: Les détergents agissent sur les salissures alors que les désinfectants agissent sur les micro-organismes. Les modes d'action sont complexes et varient en fonction de nombreux paramètres. La plupart des désinfectants ou des antiseptiques sont inhibés par les matières organiques, ce qui rend le préalable de la détergence indispensable à leur utilisation. Utilisation en médecine: Les détergents et les désinfectants sont des produits largement utilisés dans de nombreuses applications concernant les objets inertes ou la peau. Ils sont utilisés en médecine que ce soit en curatif ou en préventif pour l'homme ou son environnement

Benefits of a 14-year surgical site infections active surveillance programme in a French teaching hospital

International audienc

Across and along-strike crustal structure variations of the western Afar margin and adjacent plateau: insights from receiver functions analysis

We used teleseismic receiver function analysis to image the crustal structure beneath 24 broadband seismic stations densely deployed along two profiles traversing different structural units across the western Afar margin. Our high-resolution receiver function results image pronounced spatial variations in the crustal structure along the profiles and provide improved insights to understand how strain is partitioned in the crust during rifting. Beneath the western plateau next to northern Afar, the crust is likely felsic-to-intermediate in composition (average Vp/Vs 1.74), with a step like thinning of the crust from an average of 38 km beneath the western plateau to an average of 22 km beneath the marginal graben. Consistently thicker crust is observed beneath the southern profile (central Afar), showing four distinct regions of uniform crustal thickness: 1) an average crustal thickness of 42 km beneath the western plateau; 2) 34 km beneath the foothills area; 3) 28 km beneath the marginal graben and the wide extensional basin and 4) 21 km beneath the central rift axis. We use crustal thickness results to estimate a stretching factor β of 2.2 and 2.7 for central Afar and northern Afar respectively. Our estimated values are lower than β > 3.0 predicted from plate reconstructions, and we interpret that the variations are best explained by 2–5 km magmatic addition into the crust. The crustal composition beneath the southern profile is more complex with elevated Vp/Vs ratios ranging between 1.79 and 1.85 beneath the western plateau and marginal graben. This is consistent with a greater mafic component and best explained by crust altered by intrusions due to significant pre and syn-rift magmatic activity. Abnormally high Vp/Vs ratios of more than 1.90 are observed beneath the axial rift zone of central Afar, which most likely suggests the localization of partial melt within the crust