Colour-electric spectral function at next-to-leading order

The spectral function related to the correlator of two colour-electric fields along a Polyakov loop determines the momentum diffusion coefficient of a heavy quark near rest with respect to a heat bath. We compute this spectral function at next-to-leading order, O(alpha_s^2), in the weak-coupling expansion. The high-frequency part of our result (omega >> T), which is shown to be temperature-independent, is accurately determined thanks to asymptotic freedom; the low-frequency part of our result (omega << T), in which Hard Thermal Loop resummation is needed in order to cure infrared divergences, agrees with a previously determined expression. Our result may help to calibrate the overall normalization of a lattice-extracted spectral function in a perturbative frequency domain T << omega << 1/a, paving the way for a non-perturbative estimate of the momentum diffusion coefficient at omega -> 0. We also evaluate the colour-electric Euclidean correlator, which could be directly compared with lattice simulations. As an aside we determine the Euclidean correlator in the lattice strong-coupling expansion, showing that through a limiting procedure it can in principle be defined also in the confined phase of pure Yang-Mills theory, even if a practical measurement could be very noisy there.Comment: 38 page

Genetic heterogeneity of hepatitis E virus in Darfur, Sudan, and neighboring Chad.

The within-outbreak diversity of hepatitis E virus (HEV) was studied during the outbreak of hepatitis E that occurred in Sudan in 2004. Specimens were collected from internally displaced persons living in a Sudanese refugee camp and two camps implanted in Chad. A comparison of the sequences in the ORF2 region of 23 Sudanese isolates and five HEV samples from the two Chadian camps displayed a high similarity (>99.7%) to strains belonging to Genotype 1. But four isolates collected in one of the Chadian camps were close to Genotype 2. Circulation of divergent strains argues for possible multiple sources of infection

How a plantar pressure-based, tongue-placed tactile biofeedback modifies postural control mechanisms during quiet standing

The purpose of the present study was to determine the effects of a plantar pressure-based, tongue-placed tactile biofeedback on postural control mechanisms during quiet standing. To this aim, sixteen young healthy adults were asked to stand as immobile as possible with their eyes closed in two conditions of No-biofeedback and Biofeedback. Centre of foot pressure (CoP) displacements, recorded using a force platform, were used to compute the horizontal displacements of the vertical projection the centre of gravity (CoGh) and those of the difference between the CoP and the vertical projection of the CoG (CoP-CoGv). Altogether, the present findings suggest that the main way the plantar pressure-based, tongue-placed tactile biofeedback improves postural control during quiet standing is via both a reduction of the correction thresholds and an increased efficiency of the corrective mechanism involving the CoGh displacements

Synthesis of Monodisperse Gold Nanoparticles for Plasmonics

International audienceOur research activities concentrate on the synthesis and assembly of gold nanoparticles for plasmonics that is a rapidly growing discipline at the interface of physics, chemistry and biology with promising applications. We use a seed-mediated growth method of colloidal chemistry to synthesize gold nano-and micro-particles of controlled shape and size. This morphology control provides a fine tuning of the plasmon resonance wavelength and of the local field enhancement factor. Compared to top-down materials, these gold particles of high crystalline quality offer better surface-confinement of the electromagnetic field. The figure illustrates some of the monodis-perse gold NPs and gold nanohybrids we have been synthesized. Contrary to spherical and rod-shaped NPs that are commercially-available, other shapes such as nanocubes, na-notriangles and micro-plates with tunable sizes are only produced in our lab and in few laboratories worlwide, mainly in Asia. Triangles are of particular interest for ultrasensitive sensing, and plates (hexagonal or triangular) are very attractive for the construction of original plasmon-based optical devices due to their large atomically flat facets. At the present time, the synthesis of highly uniform triangles and plates still required purification steps that render them difficult to produce. Our research is made in collaboration with various research teams expert in the different field of plasmonics and aims at providing appropriate materials to study enhanced-photochemistry, enhanced-spectroscopy and nanosources of light. In the future, we are eager to widen the application range of these NPs to sensors and metamaterials through new expected collaborations

Towards flavour diffusion coefficient and electrical conductivity without ultraviolet contamination

By subtracting from a recent lattice measurement of the thermal vector-current correlator the known 5-loop vacuum contribution, we demonstrate that the remainder is small and shows no visible short-distance divergence. It can therefore in principle be subjected to model-independent analytic continuation. Testing a particular implementation, we obtain estimates for the flavour-diffusion coefficient (2 pi T D \gsim 0.8) and electrical conductivity which are significantly smaller than previous results. Although systematic errors remain beyond control at present, some aspects of our approach could be of a wider applicability.Comment: 7 pages. v2: clarifications added, published versio

Interest of the Ergo-Kit(®) for the clinical practice of the occupational physician. A study of 149 patients recruited in a rehabilitation program

OBJECTIVE: Functional capacity evaluation is commonly used to assess the abilities of patients to perform some tasks. Ergo-Kit(®) is a validated tool assessing both functional capacities of patients and workplace demands. The objective of this study was to evaluate the relevance of the Ergo-Kit(®) data for occupational physicians during the return-to-work process. METHODS: A retrospective and monocenter study was conducted on all patients included in a rehabilitation program and assessed with the Ergo-Kit(®) tool between 2005 and 2014. Workplace demands and patients\u27 functional capacities were evaluated and confronted. Self-beliefs and perceived disability were also assessed and compared to the functional capacity evaluation. RESULTS: One hundred and forty-nine working-age patients (85 men, 64 women; 39±12 years) suffering from musculoskeletal disorders or other diseases were included. Main causes of mismatch between workplace demands and functional capacities were manual handling of loads, postures with arms away from the body and repetitive motions at work; sitting posture was correlated with a lesser physical workload; and Oswestry score was correlated with functional capacities evaluated by the Ergo-Kit(®). CONCLUSION: Ergo-Kit(®) is a relevant tool to assess the multidimensional aspects of workplace demands and functional capacities. It could be very helpful for occupational physicians to manage return-to-work

Ultraviolet asymptotics of scalar and pseudoscalar correlators in hot Yang-Mills theory

Inspired by recent lattice measurements, we determine the short-distance (a > omega >> pi T) asymptotics of scalar (trace anomaly) and pseudoscalar (topological charge density) correlators at 2-loop order in hot Yang-Mills theory. The results are expressed in the form of an Operator Product Expansion. We confirm and refine the determination of a number of Wilson coefficients; however some discrepancies with recent literature are detected as well, and employing the correct values might help, on the qualitative level, to understand some of the features observed in the lattice measurements. On the other hand, the Wilson coefficients show slow convergence and it appears uncertain whether this approach can lead to quantitative comparisons with lattice data. Nevertheless, as we outline, our general results might serve as theoretical starting points for a number of perhaps phenomenologically more successful lines of investigation.Comment: 27 pages. v2: minor improvements, published versio

Direct observation of the effective bending moduli of a fluid membrane: Free-energy cost due to the reference-plane deformations

Effective bending moduli of a fluid membrane are investigated by means of the transfer-matrix method developed in our preceding paper. This method allows us to survey various statistical measures for the partition sum. The role of the statistical measures is arousing much attention, since Pinnow and Helfrich claimed that under a suitable statistical measure, that is, the local mean curvature, the fluid membranes are stiffened, rather than softened, by thermal undulations. In this paper, we propose an efficient method to observe the effective bending moduli directly: We subjected a fluid membrane to a curved reference plane, and from the free-energy cost due to the reference-plane deformations, we read off the effective bending moduli. Accepting the mean-curvature measure, we found that the effective bending rigidity gains even in the case of very flexible membrane (small bare rigidity); it has been rather controversial that for such non-perturbative regime, the analytical prediction does apply. We also incorporate the Gaussian-curvature modulus, and calculated its effective rigidity. Thereby, we found that the effective Gaussian-curvature modulus stays almost scale-invariant. All these features are contrasted with the results under the normal-displacement measure

CAROTENOID PIGMENTS IN MALE HOUSE FINCH PLUMAGE IN RELATION TO AGE, SUBSPECIES, AND ORNAMENTAL COLORATION

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Inspiral, merger and ring-down of equal-mass black-hole binaries

We investigate the dynamics and gravitational-wave (GW) emission in the binary merger of equal-mass black holes as obtained from numerical relativity simulations. Results from the evolution of three sets of initial data are explored in detail, corresponding to different initial separations of the black holes. We find that to a good approximation the inspiral phase of the evolution is quasi-circular, followed by a "blurred, quasi-circular plunge", then merger and ring down. We present first-order comparisons between analytical models of the various stages of the merger and the numerical results. We provide comparisons between the numerical results and analytical predictions based on the adiabatic Newtonain, post-Newtonian (PN), and non-adiabatic resummed-PN models. From the ring-down portion of the GW we extract the fundamental quasi-normal mode and several of the overtones. Finally, we estimate the optimal signal-to-noise ratio for typical binaries detectable by GW experiments.Comment: 47 pages, 34 figures, full abstract in paper, revtex4, accepted by PRD, miscellaneous revisions throughout pape