Nanotribology: Nonlinear mechanisms of friction

Friction with its related nonlinear dynamics is a vast interdisciplinary field, involving complex physical processes over a wide range of length and time scales. The accelerated progress in experimental and computational techniques, often leading to complex detailed dynamical patterns, has vigorously stimulated the search and implementation of idealized experimental frameworks and simplermathematical models, capable of describing and interpreting, in amore immediateway, the essential physics involved in nonlinear sliding phenomena

Microimaging of transient guest profiles to monitor mass transfer in nanoporous materials

The intense interactions of guest molecules with the pore walls of nanoporous materials is the subject of continued fundamental research. Stimulated by their thermal energy, the guest molecules in these materials are subject to a continuous, irregular motion, referred to as diffusion. Diffusion, which is omnipresent in nature, influences the efficacy of nanoporous materials in reaction and separation processes. The recently introduced techniques of microimaging by interference and infrared microscopy provide us with a wealth of information on diffusion, hitherto inaccessible from commonly used techniques. Examples include the determination of surface barriers and the sticking coefficient's analogue, namely the probability that, on colliding with the particle surface, a molecule may continue its diffusion path into the interior. Microimaging is further seen to open new vistas in multicomponent guest diffusion ( including the detection of a reversal in the preferred diffusion pathways), in guest-induced phase transitions in nanoporous materials and in matching the results of diffusion studies under equilibrium and nonequilibrium conditions

Observation of the J/ψψ →\to μ+μ−μ+μ−μ^+μ^-μ^+μ^- decay in proton-proton collisions at s\sqrt{s} = 13 TeV

A preprint version of the article is available at arXiv:2403.11352v2 [hep-ex], https://arxiv.org/abs/2403.11352. Comments: Replaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at https://cms-results.web.cern.ch/cms-results/public-results/publications/BPH-22-006 (CMS Public Pages). Report number: CMS-BPH-22-006, CERN-EP-2024-058.The /→+⁢−⁢+⁢− decay has been observed with a statistical significance in excess of five standard deviations. The analysis is based on an event sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS experiment in 2018 and corresponding to an integrated luminosity of 33.6  fb−1. Normalizing to the /→+⁢− decay mode leads to a branching fraction of [10.1+3.3 −2.7⁢(stat)±0.4⁢(syst)]×10−7, a value that is consistent with the standard model prediction.SCOAP3