Ref HAL: hal-01562695_v1
DOI: 10.1016/j.jnoncrysol.2017.03.012
WoS: WOS:000404205100002
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8 Citations
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In this work we have carried out variable-load indentation testing on three sodium borosilicate glassesand characterized the indentation imprints using Raman spectroscopy. The resulting analysis of thespectra helps describe the relative amount of densification and shear ow appearing in each glass, as wellas the different microstructural mechanisms that take place during deformation. Additionally, we showthat the two glasses that are relatively poor in sodium exhibit enhanced mixing of the silicate and borateunits after indentation. For the indentations performed using the highest load, we also acquired spectraby focusing at various depths below the imprint, in order to characterize the deformed region of theglasses and estimate its size. Similar experiments have been also carried out for one of the three glassesafter neutron irradiation, in order to study the effects of mechanical deformation on its depolymerizedand swollen structure.

Ref HAL: hal-01555273_v1
DOI: 10.1126/science.aam9353
WoS: 000404351500034
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37 Citations
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Two-boson interference, a fundamentally quantum effect, has been extensively studied with photons through the Hong-Ou-Mandel effect and observed with guided plasmons. Using two freely propagating surface plasmon polaritons (SPPs) interfering on a lossy beam splitter, we show that the presence of loss enables us to modify the reflection and transmission factors of the beam splitter, thus revealing quantum interference paths that do not exist in a lossless configuration.We investigate the two-plasmon interference on beam splitters with different sets of reflection and transmission factors. Through coincidence-detection measurements, we observe either coalescence or anti-coalescence of SPPs.The results show that losses can be viewed as a degree of freedom to control quantum processes.

Ref HAL: hal-01548255_v1
DOI: 10.1038/s41598-017-04271-x
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Nowadays powerful X-ray sources like synchrotrons and free-electron lasers are considered as ultimate tools for probing microscopic properties in materials. However, the correct interpretation of such experiments requires a good understanding on how the beam affects the properties of the sample, knowledge that is currently lacking for intense X-rays. Here we use X-ray photon correlation spectroscopy to probe static and dynamic properties of oxide and metallic glasses. We find that although the structure does not depend on the flux, strong fluxes do induce a non-trivial microscopic motion in oxide glasses, whereas no such dependence is found for metallic glasses. These results show that high fluxes can alter dynamical properties in hard materials, an effect that needs to be considered in the analysis of X-ray data but which also gives novel possibilities to study materials properties since the beam can not only be used to probe the dynamics but also to pump it.

Ref HAL: hal-01541319_v1
Ref Arxiv: 1701.00936
DOI: 10.1103/PhysRevE.95.052125
WoS: 000401455100001
Ref. & Cit.: NASA ADS
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12 Citations
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We numerically analyse the density field of three-dimensional randomly jammed packings of monodisperse soft frictionles spherical particles, paying special attention to fluctuations occurring at large lengthscales. We study in detail the two-point static structure factor at low wavevectors in Fourier space. We also analyse the nature of the density field in real space by studying the large-distance behavior of the two-point pair correlation function, of density fluctuations in subsystems of increasing sizes, and of the direct correlation function. We show that such real space analysis can be greatly improved by introducing a coarse-grained density field to disentangle genuine large-scale correlations from purely local effects. Our results confirm that both Fourier and real space signatures of vanishing density fluctuations at large scale are absent, indicating that randomly jammed packings are not hyperuniform. In addition, we establish that the pair correlation function displays a surprisingly complex structure at large distances, which is however not compatible with the long-range negative correlation of hyperuniform systems but fully compatible with an analytic form for the structure factor. This implies that the direct correlation function is short-ranged, as we also demonstrate directly. Our results reveal that density fluctuations in jammed packings do not follow the behavior expected for random hyperuniform materials, but display instead a more complex behavior.

Commentaires: 11 pages, 9 figs. Réf Journal: Phys. Rev. E 95, 052125 (2017)

Ref HAL: hal-01539636_v1
Ref Arxiv: 1704.08864
DOI: 10.1103/PhysRevX.7.021039
WoS: 000402816600002
Ref. & Cit.: NASA ADS
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102 Citations
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Successful computer studies of glass-forming materials need to overcome both the natural tendency to structural ordering and the dramatic increase of relaxation times at low temperatures. We present a comprehensive analysis of eleven glass-forming models to demonstrate that both challenges can be efficiently tackled using carefully designed models of size polydisperse supercooled liquids together with an efficient Monte Carlo algorithm where translational particle displacements are complemented by swaps of particle pairs. We study a broad range of size polydispersities, using both discrete and continuous mixtures, and we systematically investigate the role of particle softness, attractivity and non-additivity of the interactions. Each system is characterized by its robustness against structural ordering and by the efficiency of the swap Monte Carlo algorithm. We show that the combined optimisation of the potential's softness, polydispersity and non-additivity leads to novel computer models with excellent glass-forming ability. For such models, we achieve over ten orders of magnitude gain in the equilibration timescale using the swap Monte Carlo algorithm, thus paving the way to computational studies of static and thermodynamic properties under experimental conditions. In addition, we provide microscopic insights into the performance of the swap algorithm which should help optimizing models and algorithms even further.

Ref HAL: hal-01536101_v1
DOI: 10.1103/PhysRevLett.118.238002
WoS: 000402979400019
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6 Citations
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Recent diffraction experiments on metallic glasses have unveiled an unexpected non-cubic scaling 14 law between density and average interatomic distance, which lead to the speculations on the presence of 15 fractal glass order. Using X-ray tomography we identify here a similar non-cubic scaling law in 16 disordered granular packing of spherical particles. We find that the scaling law is directly related to the 17 contact neighbors within first nearest neighbor shell, and therefore is closely connected to the 18 phenomenon of jamming. The seemingly universal scaling exponent around 2.5 arises due to the isostatic 19 condition with contact number around 6, and we argue that the exponent should not be universal. .

Ref HAL: hal-01531104_v1
PMID 28558053
DOI: 10.1371/journal.pcbi.1005555
WoS: 000402889500040
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10 Citations
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The well established phenomenon of ribosome drop-off plays crucial roles in translational accuracy and nutrient starvation responses during protein translation. When cells are under stress conditions, such as amino acid starvation or aminoacyl-tRNA depletion due to a high level of recombinant protein expression, ribosome drop-off can substantially affect the efficiency of protein expression. Here we introduce a mathematical model that describes the effects of ribosome drop-off on the ribosome density along the mRNA and on the concomitant protein synthesis rate. Our results show that ribosome premature termination may lead to non-intuitive ribosome density profiles, such as a ribosome density which increases from the 5' to the 3' end. Importantly, the model predicts that the effects of ribosome drop-off on the translation rate are mRNA-specific, and we quantify their resilience to drop-off, showing that the mRNAs which present ribosome queues are much less affected by ribosome drop-off than those which do not. Moreover, among those mRNAs that do not present ribosome queues, resilience to drop-off correlates positively with the elongation rate, so that sequences using fast codons are expected to be less affected by ribosome drop-off. This result is consistent with a genome-wide analysis of S. cerevisiae, which reveals that under favourable growth conditions mRNAs coding for proteins involved in the translation machinery, known to be highly codon biased and using preferentially fast codons, are highly resilient to ribosome drop-off. Moreover, in physiological conditions, the translation rate of mRNAs coding for regulatory, stress-related proteins, is less resilient to ribosome drop-off. This model therefore allows analysis of variations in the translational efficiency of individual mRNAs by accounting for the full range of known ribosome behaviours, as well as explaining mRNA-specific variations in ribosome density emerging from ribosome profiling studies.