Associativité et liberté dans La Philosophie de l’algèbre de Jules Vuillemin

Qu’est-ce qui conduit Vuillemin, dans sa Philosophie de l’algèbre, à considérer la propriété formelle d’associativité comme caractéristique des actes de la conscience morale ? Quelles traces cette thèse a-t-elle laissées dans son œuvre ? L’article suggère quelques pistes d’interprétations possibles.Why does Vuillemin consider in his Philosophie de l’algèbre the formal property of associativity as characteristic of acts of moral consciousness? What traces of this thesis remain in his work? The paper outlines some possible interpretations

La similitude des figures chez Leibniz : entre géométrie et rhétorique

info:eu-repo/semantics/publishe

Systematic effects in the determination of the piNN Coupling from pbar p -> nbar n differential cross section

We show that the $\pi NN$ coupling constant extracted model-independently from $\bar pp$ charge exchange is subject to a systematic correction, and, more importantly, that the strong absorption in the critical region prevents a determination of the coupling constant to high precision using this process. This attenuates the possible conflict with the value determined from the np charge exchange cross sections.Comment: 14 pages, LaTeX, 4 encapsulated Postscript figures (uses epsf.tex), to be published in Phys. lett.

Role of AMP-activated protein kinase in regulating hypoxic survival and proliferation of mesenchymal stem cells

Aims Mesenchymal stem cells (MSCs) are widely used for cell therapy, particularly for the treatment of ischaemic heart disease. Mechanisms underlying control of their metabolism and proliferation capacity, critical elements for their survival and differentiation, have not been fully characterized. AMP-activated protein kinase (AMPK) is a key regulator known to metabolically protect cardiomyocytes against ischaemic injuries and, more generally, to inhibit cell proliferation. We hypothesized that AMPK plays a role in control of MSC metabolism and proliferation. Methods and results MSCs isolated from murine bone marrow exclusively expressed the AMPKα1 catalytic subunit. In contrast to cardiomyocytes, a chronic exposure of MSCs to hypoxia failed to induce cell death despite the absence of AMPK activation. This hypoxic tolerance was the consequence of a preference of MSC towards glycolytic metabolism independently of oxygen availability and AMPK signalling. On the other hand, A-769662, a well-characterized AMPK activator, was able to induce a robust and sustained AMPK activation. We showed that A-769662-induced AMPK activation inhibited MSC proliferation. Proliferation was not arrested in MSCs derived from AMPKα1-knockout mice, providing genetic evidence that AMPK is essential for this process. Among AMPK downstream targets proposed to regulate cell proliferation, we showed that neither the p70 ribosomal S6 protein kinase/eukaryotic elongation factor 2-dependent protein synthesis pathway nor p21 was involved, whereas p27 expression was increased by A-769662. Silencing p27 expression partially prevented the A-769662-dependent inhibition of MSC proliferation. Conclusion MSCs resist hypoxia independently of AMPK whereas chronic AMPK activation inhibits MSC proliferation, p27 being involved in this regulatio

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

Highlights from the Pierre Auger Observatory

The Pierre Auger Observatory is the world's largest cosmic ray observatory. Our current exposure reaches nearly 40,000 km$^2$ str and provides us with an unprecedented quality data set. The performance and stability of the detectors and their enhancements are described. Data analyses have led to a number of major breakthroughs. Among these we discuss the energy spectrum and the searches for large-scale anisotropies. We present analyses of our X$_{max}$ data and show how it can be interpreted in terms of mass composition. We also describe some new analyses that extract mass sensitive parameters from the 100% duty cycle SD data. A coherent interpretation of all these recent results opens new directions. The consequences regarding the cosmic ray composition and the properties of UHECR sources are briefly discussed.Comment: 9 pages, 12 figures, talk given at the 33rd International Cosmic Ray Conference, Rio de Janeiro 201

Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory

The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO

Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principle calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI. Supplemental material in the ancillary file