Thermal ion measurements on board Interball Auroral Probe by the Hyperboloid experiment

Hyperboloid is a multi-directional mass spectrometer measuring ion distribution functions in the auroral and polar magnetosphere of the Earth in the thermal and suprathermal energy range. The instrument encompasses two analyzers containing a total of 26 entrance windows, and viewing in two almost mutually perpendicular half-planes. The nominal angular resolution is defined by the field of view of individual windows ≈13° × 12.5°. Energy analysis is performed using spherical electrostatic analyzers providing differential measurements between 1 and 80 eV. An ion beam emitter (RON experiment) and/or a potential bias applied to Hyperboloid entrance surface are used to counteract adverse effects of spacecraft potential and thus enable ion measurements down to very low energies. A magnetic analyzer focuses ions on one of four micro-channel plate (MCP) detectors, depending on their mass/charge ratio. Normal modes of operation enable to measure H+, He+, O++, and O+ simultaneously. An automatic MCP gain control software is used to adapt the instrument to the great flux dynamics encountered between spacecraft perigee (700 km) and apogee (20 000 km). Distribution functions in the main analyzer half-plane are obtained after a complete scan of windows and energies with temporal resolution between one and a few seconds. Three-dimensional (3D) distributions are measured in one spacecraft spin period (120 s). The secondary analyzer has a much smaller geometrical factor, but offers partial access to the 3D dependence of the distributions with a few seconds temporal resolution. Preliminary results are presented. Simultaneous, local heating of both H+ and O+ ions resulting in conical distributions below 80 eV is observed up to 3 Earth's radii altitudes. The thermal ion signatures associated with large-scale nightside magnetospheric boundaries are investigated and a new ion outflow feature is identified associated to the polar edge of the auroral oval. Detailed distribution functions of injected magnetosheath ions and ouflowing cleft fountain ions are measured down to a few eVs in the dayside.Key words. Ionosphere (auroral ionosphere; particle acceleration; ionosphere-magnetosphere interactions) &nbsp

Cardioprotective effects of a synthetic peptide targeting the extrinsic apoptotic pathway in a mouse model of ischemia-reperfusion

International audienceIntroduction: Apoptosis is a main contributor of myocardial reperfusion injury during acute infarction. In a previous study, we showed that reperfusion injury was mediated by the FAS-dependent apoptotic signal mobilizing the DAXX (death-associated protein) adaptor protein. Objective: to evaluate the cardioprotective effects of a synthetic peptide that uncouples FAS to the DAXX downstream pathway.Methods: The SPOT technology was used to design an synthetic peptide interfering with FAS:DAXX interaction. This peptide was couple to the Tat cell penetrating peptide (Tat-DAXXp). Infarct size and apoptosis were evaluated in the left ventricle of mice subjected to a surgical protocol of reversible coronary artery ligation and treated by the peptide at the onset of reperfusion. Cellular internalization of the peptide was measured using a fluorescent peptide by immunofluorescence both in primary cultures of cardiomyocytes or in left ventricles after surgery. Results Anti-apoptotic properties of the synthetic peptide were demonstrated in primary cardiomyocytes. In vivo, one bolus of Tat-DAXXp (1 mg/kg), injected intravenously 5 min before reperfusion in a murine myocardial ischemia-reperfusion model decreased infarct size by 48% after 24 hours of reperfusion. After a 30-min delayed administration, Tat-DAXXp was still able to protect against reperfusion-induced apoptosis and was completely degraded and eliminated within 24 hours thereby reducing risks of potential side effects. Importantly, post-infarction mortality was reduced by 67% by Tat-DAXXp treatment. Mechanistically, cardioprotection was supported by both antiapoptotic and prosurvival effects, and an improvement of myocardial functional recovery as evidenced in ex vivo experiments.Conclusion:Our study demonstrates that a single dose of Tat-DAXXp injected intravenously at the onset of reperfusion leads to a strong cardioprotection in vivo by inhibiting ischemia-reperfusion injury

The mass spectrum analyzer (MSA) onboard BEPI COLOMBO MMO: Scientific objectives and prototype results

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Thermal ion measurements on board Interball Auroral Probe by the Hyperboloid experiment

International audienceHyperboloid is a multi-directional mass spectrometer measuring ion distribution functions in the auroral and polar magnetosphere of the Earth in the thermal and suprathermal energy range. The instrument encompasses two analyzers containing a total of 26 entrance windows, and viewing in two almost mutually perpendicular half-planes. The nominal angular resolution is defined by the field of view of individual windows ˜13° × 12.5°. Energy analysis is performed using spherical electrostatic analyzers providing differential measurements between 1 and 80 eV. An ion beam emitter (RON experiment) and/or a potential bias applied to Hyperboloid entrance surface are used to counteract adverse effects of spacecraft potential and thus enable ion measurements down to very low energies. A magnetic analyzer focuses ions on one of four micro-channel plate (MCP) detectors, depending on their mass/charge ratio. Normal modes of operation enable to measure H+, He+, O++, and O+ simultaneously. An automatic MCP gain control software is used to adapt the instrument to the great flux dynamics encountered between spacecraft perigee (700 km) and apogee (20 000 km). Distribution functions in the main analyzer half-plane are obtained after a complete scan of windows and energies with temporal resolution between one and a few seconds. Three-dimensional (3D) distributions are measured in one spacecraft spin period (120 s). The secondary analyzer has a much smaller geometrical factor, but offers partial access to the 3D dependence of the distributions with a few seconds temporal resolution. Preliminary results are presented. Simultaneous, local heating of both H+ and O+ ions resulting in conical distributions below 80 eV is observed up to 3 Earth's radii altitudes. The thermal ion signatures associated with large-scale nightside magnetospheric boundaries are investigated and a new ion outflow feature is identified associated to the polar edge of the auroral oval. Detailed distribution functions of injected magnetosheath ions and ouflowing cleft fountain ions are measured down to a few eVs in the dayside