University of Grenoble

About: University of Grenoble is a education organization based out in Saint-Martin-d'Hères, France. It is known for research contribution in the topics: Population & Context (language use). The organization has 25658 authors who have published 45143 publications receiving 909760 citations.

An Indication of Anisotropy in Arrival Directions of Ultra-high-energy Cosmic Rays through Comparison to the Flux Pattern of Extragalactic Gamma-Ray Sources

Abstract: A new analysis of the data set from the Pierre Auger Observatory provides evidence for anisotropy in the arrival directions of ultra-high-energy cosmic rays on an intermediate angular scale, which is indicative of excess arrivals from strong, nearby sources. The data consist of 5514 events above 20 EeV with zenith angles up to 80 recorded before 2017 April 30. Sky models have been created for two distinct populations of extragalactic gamma-ray emitters: active galactic nuclei from the second catalog of hard Fermi-LAT sources (2FHL) and starburst galaxies from a sample that was examined with Fermi-LAT. Flux-limited samples, which include all types of galaxies from the Swift-BAT and 2MASS surveys, have been investigated for comparison. The sky model of cosmic-ray density constructed using each catalog has two free parameters, the fraction of events correlating with astrophysical objects, and an angular scale characterizing the clustering of cosmic rays around extragalactic sources. A maximum-likelihood ratio test is used to evaluate the best values of these parameters and to quantify the strength of each model by contrast with isotropy. It is found that the starburst model fits the data better than the hypothesis of isotropy with a statistical significance of 4.0σ, the highest value of the test statistic being for energies above 39 EeV. The three alternative models are favored against isotropy with 2.7σ-3.2σ significance. The origin of the indicated deviation from isotropy is examined and prospects for more sensitive future studies are discussed.

European contribution to the study of ROS : a summary of the findings and prospects for the future from the COST action BM1203 (EU-ROS)

Abstract: The European Cooperation in Science and Technology (COST) provides an ideal framework to establish multi-disciplinary research networks COST Action BM1203 (EU-ROS) represents a consortium of researchers from different disciplines who are dedicated to providing new insights and tools for better understanding redox biology and medicine and, in the long run, to finding new therapeutic strategies to target dysregulated redox processes in various diseases This report highlights the major achievements of EU-ROS as well as research updates and new perspectives arising from its members The EU-ROS consortium comprised more than 140 active members who worked together for four years on the topics briefly described below The formation of reactive oxygen and nitrogen species (RONS) is an established hallmark of our aerobic environment and metabolism but RONS also act as messengers via redox regulation of essential cellular processes The fact that many diseases have been found to be associated with oxidative stress established the theory of oxidative stress as a trigger of diseases that can be corrected by antioxidant therapy However, while experimental studies support this thesis, clinical studies still generate controversial results, due to complex pathophysiology of oxidative stress in humans For future improvement of antioxidant therapy and better understanding of redox-associated disease progression detailed knowledge on the sources and targets of RONS formation and discrimination of their detrimental or beneficial roles is required In order to advance this important area of biology and medicine, highly synergistic approaches combining a variety of diverse and contrasting disciplines are needed

Decomposition of experimental X-ray diffraction patterns (profile fitting); a convenient way to study clay minerals

Abstract: This paper thoroughly describes the decomposition procedure, using the example of DE-COMPXR (Lanson 1990). The steps of the decomposition procedure are: 1) preliminary data processing; 2) decomposition; 3) validation of results; and 4) use of the results. The use of decomposition is restricted to the separation of contributions from various phases. The effect of preliminary data processing steps (data smoothing, background stripping) on profile shape is shown to be limited and their implementation is detailed. Potential experimental limitations such as peak symmetry, experimental reproducibility or discrimination are equally minor. A logical decomposition process starts from the definition of the angular range to be fitted, proceeds with the determination of the number of elementary peaks to be fitted and ends with the check for results consistency. Numerical data processing is a powerful tool for the accurate identification of monophases, because of the additional parameters available to constrain XRD profile simulation. Ultimately, however, the match over the whole angular range of both the experimental and the simulated patterns remains the only valid way to characterize the phases present in the sample. Additionally, the decomposition procedure permits both the identification of complex clay mineral assemblages and the characterization of their evolution. This step constrains, and may help to determine, the reaction mechanisms of a transformation; and, as a consequence, to characterize and to model the kinetics of this transformation.

Improved water electrolysis using magnetic heating of FeC–Ni core–shell nanoparticles

Abstract: Water electrolysis enables the storage of renewable electricity via the chemical bonds of hydrogen. However, proton-exchange-membrane electrolysers are impeded by the high cost and low availability of their noble-metal electrocatalysts, whereas alkaline electrolysers operate at a low power density. Here, we demonstrate that electrocatalytic reactions relevant for water splitting can be improved by employing magnetic heating of noble-metal-free catalysts. Using nickel-coated iron carbide nanoparticles, which are prone to magnetic heating under high-frequency alternating magnetic fields, the overpotential (at 20 mA cm−2) required for oxygen evolution in an alkaline water-electrolysis flow-cell was decreased by 200 mV and that for hydrogen evolution was decreased by 100 mV. This enhancement of oxygen-evolution kinetics is equivalent to a rise of the cell temperature to ~200 °C, but in practice it increased by 5 °C only. This work suggests that, in the future, water splitting near the equilibrium voltage could be possible at room temperature, which is currently beyond reach in the classic approach to water electrolysis. Electrocatalytic water splitting to produce H2 is impeded by slow reaction kinetics over noble-metal-free catalysts at the electrodes. Here, the authors use high-frequency alternating magnetic fields to locally heat FeC–Ni core–shell catalysts, enhancing the kinetics of the oxygen and hydrogen evolution reactions.