Toward continuous quantification of lava extrusion rate: Results from the multidisciplinary analysis of the 2 January 2010 eruption of Piton de la Fournaise volcano, La Reunion

International audienceThe dynamics of the 2–12 January 2010 effusive eruption at Piton de la Fournaise volcano were examined through seismic and infrasound records, time-lapse photography, SO2 flux measurements, deformation data, and direct observations. Digital elevation models were constructed for four periods of the eruption, thus providing an assessment of the temporal evolution of the morphology, the volume and the extrusion rate of the lava flow. These data were compared to the continuous recording of the seismic and infrasonic waves, and a linear relationship was found between the seismic energy of the tremor and the lava extrusion rate. This relationship is supported by data from three other summit eruptions of Piton de la Fournaise and gives total volume and average lava extrusion rate in good agreement with previous studies. We can therefore provide an estimate of the lava extrusion rate for the January 2010 eruption with a very high temporal resolution. We found an average lava extrusion rate of 2.4 m3s−1 with a peak of 106.6 m3s−1 during the initial lava fountaining phase. We use the inferred average lava extrusion rate during the lava fountaining phase (30.23 m3s−1) to estimate the value of the initial overpressure in the magma reservoir, which we found to range from 3.7×106 Pa to 5.9×106 Pa. Finally, based on the estimated initial overpressure, the volume of magma expelled during the lava fountaining phase and geodetic data, we inferred the volume of the magma reservoir using a simple Mogi model, between 0.25 km3 and 0.54 km3, which is in good agreement with previous studies

Global quieting of high-frequency seismic noise due to COVID-19 pandemic lockdown measures

Human activity causes vibrations that propagate into the ground as high-frequency seismic waves. Measures to mitigate the COVID-19 pandemic caused widespread changes in human activity, leading to a months-long reduction in seismic noise of up to 50%. The 2020 seismic noise quiet period is the longest and most prominent global anthropogenic seismic noise reduction on record. While the reduction is strongest at surface seismometers in populated areas, this seismic quiescence extends for many kilometers radially and hundreds of meters in depth. This provides an opportunity to detect subtle signals from subsurface seismic sources that would have been concealed in noisier times and to benchmark sources of anthropogenic noise. A strong correlation between seismic noise and independent measurements of human mobility suggests that seismology provides an absolute, real-time estimate of population dynamics

Not only training but also exposure to chlorinated compounds generates a response to oxidative stimuli in swimmers.: training, exposure to chlorinated compounds in swimmers

International audienceRelations between exposure to chlorinated compounds and biological markers of response to oxidative stimuli were investigated in swimmers, taking into account the effect of training. Twenty-two male swimmers aged 15-25 years were surveyed twice. Prevalence of irritant symptoms and asthma and number of hours of training were reported. Exposure to nitrogen trichloride (NCl3) and blood response to oxidative stimuli [catalase, superoxide dismutase (Cu2+/Zn2+ SOD), glutathione peroxidase (GSH-Px) activities and ceruloplasmin, ferritin and total antioxidant concentrations] were measured. Univariate analyses were completed by multivariate analyses. High prevalences of irritant symptoms and asthma were found. Multivariate analysis confirmed the results of the univariate analyses and showed that Cu2+/Zn2+ SOD activity was increased by exposure and by training (P = 0.01, P = 0.0001, respectively). Erythrocyte GSH-Px was decreased, whereas plasma GSH-Px was increased by exposure (P = 0.002, P = 0.002). No other association was found. Higher irritant symptoms and increases in the activities of erythrocyte Cu2+/Zn2+ SOD and of plasma GSH-Px with exposure support the hypothesis that the production of reactive oxygen species is not only related to training but also to exposure to chlorinated compounds. Other athletes tend to have respiratory problems such as asthma, but the exposure to chlorinated compounds may increase the respiratory disease among swimmers

083: Medical hypothesis: heart rate on admission and CRP are correlated, in acute pericarditis: a link between heart rate and pericardial inflammation?

IntroductionRest is usually recommended in acute pericarditis, as it could help to lower heart rate (HR) and contribute to limit “mechanical inflammation”. Whether HR on admission could be correlated and perhaps participate to inflammation has not been reported.MethodsBetween March 2007 and February 2010, we conducted a retrospective study on all patients admitted in our center for acute pericarditis. Diagnosis criteria included 2 among the following: typical chest pain, friction rub, pericardial effusion on cardiac echography, or typical ECG findings. Primary endpoint was biology: CRP on admission, on days 1, 2, 3, and especially peak. We evaluated also recurrences and clinical events during hospitalization and at one month.ResultsWe included 73 patients. Median age was 38.0 y (CI 25-75% 28.0-51.0) and median hospitalization duration was 2.0 d (1.5-3.0). 27% of the patients presented pericardial effusion. Heart rate on admission was 88.0 bpm (CI 25-75%: 76.0-100.0) and on discharge 72.0 (65.0-80.0)). Heart rate on admission was significantly correlated with CRP on admission (r=0.34, n=69; p=0.004), CRP peak (r=0.54; n=61; p<0.0001), CRP on discharge (r=0.32; p=0.021) and temperature on admission (r=0.40; n=39; p=0.01). Multivariate analysis showed that HR on admission is associated with an elevated CRP peak, independently of temperature on admission. Fever was scarcely observed (19.5%), and was neither correlated to HR nor CRP, after multivariate analysis.ConclusionIn acute pericarditis, HR on admission is independently correlated with CRP levels. These observations could suggest a link between HR and pericardial inflammation