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    Tribological properties of room temperature fluorinated graphite heat-treated under fluorine atmosphere

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    This work is concerned with the study of the tribologic properties of room temperature fluorinated graphite heat-treated under fluorine atmosphere. The fluorinated compounds all present good intrinsic friction properties (friction coefficient in the range 0.05–0.09). The tribologic performances are optimized if the materials present remaining graphitic domains (influenced by the presence of intercalated fluorinated species) whereas the perfluorinated compounds, where the fluorocarbon layers are corrugated (armchair configuration of the saturated carbon rings) present higher friction coefficients. Raman analyses reveal that the friction process induces severe changes in the materials structure especially the partial re-building of graphitic domains in the case of perfluorinated compounds which explains the improvement of μ during the friction tests for these last materials

    Search for dinucleon decay into pions at Super-Kamiokande

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    A search for dinucleon decay into pions with the Super-Kamiokande detector has been performed with an exposure of 282.1 kiloton-years. Dinucleon decay is a process that violates baryon number by two units. We present the first search for dinucleon decay to pions in a large water Cherenkov detector. The modes 16^{16}O(pp)(pp) \rightarrow 14^{14}Cπ+π+\pi^{+}\pi^{+}, 16^{16}O(pn)(pn) \rightarrow 14^{14}Nπ+π0\pi^{+}\pi^{0}, and 16^{16}O(nn)(nn) \rightarrow 14^{14}Oπ0π0\pi^{0}\pi^{0} are investigated. No significant excess in the Super-Kamiokande data has been found, so a lower limit on the lifetime of the process per oxygen nucleus is determined. These limits are: τppπ+π+>7.22×1031\tau_{pp\rightarrow\pi^{+}\pi^{+}} > 7.22 \times 10^{31} years, τpnπ+π0>1.70×1032\tau_{pn\rightarrow\pi^{+}\pi^{0}} > 1.70 \times 10^{32} years, and τnnπ0π0>4.04×1032\tau_{nn\rightarrow\pi^{0}\pi^{0}} > 4.04 \times 10^{32} years. The lower limits on each mode are about two orders of magnitude better than previous limits from searches for dinucleon decay in iron.Comment: 20 pages, 17 figures. Accepted for publication in Physical Review D on March 30, 201
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