Search

Neutrino evolution, of great importance in environments such as neutron star mergers (NSMs) because of their impact on explosive nucleosynthesis, is still poorly understood due to the high complexity and variety of possible flavor conversion mechanisms. In this study, we focus on so-called "fast flavor oscillations", which can occur on timescales of nanoseconds and are connected to the existence of a crossing between the angular distributions of electron (anti)neutrinos. Based on the neutrino radiation field drawn from a three dimensional neutron star merger simulation, we use an extension of the two-moment formalism of neutrino quantum kinetics, and perform a linear stability analysis to determine the characteristics of fast flavor instabilities across the simulation. We compare the results to local (centimeter-scale) three-dimensional two-flavor simulations using either a moment method or a particle-in-cell architecture. We get generally good agreement in the instability growth rate and typical instability lengthscale, although the imperfections of the closure used in moment methods remain to be better understood.

On 2019 August 14, the Advanced LIGO and Virgo interferometers detected the high-significance gravitational wave (GW) signal S190814bv. The GW data indicated that the event resulted from a neutron star-black hole (NSBH) merger, or potentially a low-mass binary BH merger. Due to the low false-alarm rate and the precise localization (23 deg2 at 90%), S190814bv presented the community with the best opportunity yet to directly observe an optical/near-infrared counterpart to an NSBH merger. To search for potential counterparts, the GROWTH Collaboration performed real-time image subtraction on six nights of public Dark Energy Camera images acquired in the 3 weeks following the merger, covering >98% of the localization probability. Using a worldwide network of follow-up facilities, we systematically undertook spectroscopy and imaging of optical counterpart candidates. Combining these data with a photometric redshift catalog, we ruled out each candidate as the counterpart to S190814bv and placed deep, uniform limits on the optical emission associated with S190814bv. For the nearest consistent GW distance, radiative transfer simulations of NSBH mergers constrain the ejecta mass of S190814bv to be M ej < 0.04 M o˙ at polar viewing angles, or M ej < 0.03 M o˙ if the opacity is κ < 2 cm2g-1. Assuming a tidal deformability for the NS at the high end of the range compatible with GW170817 results, our limits would constrain the BH spin component aligned with the orbital momentum to be χ < 0.7 for mass ratios Q < 6, with weaker constraints for more compact NSs.

In this paper, the acoustic behavior of Helmholtz's resonator type liner used in aeronautics applications is presented. The aim of this work is to study how the liner properties can be modified by the mounting conditions on the wall of a cylindrical duct element. To achieve this objective the measured multi-port scattering matrix, power acoustic dissipations are compared with results performed by FEM assuming axi-symmetry and a uniform and locally reacting material which impedance is measured or resulting from a model. Results show that in plane wave conditions the agreement between experiment and theory is satisfying but that a large discrepancy occurs when higher order mode is incident on the liner element pointing out a modification of the acoustic properties of the lined wall. [ABSTRACT FROM AUTHOR]

Objective: Chronic musculoskeletal pain (CMSP) is frequent in chronic diseases, decreasing the quality of life of these patients. In a survey conducted in Belgium in 2019, chronic pain was named by patients as the main factor of complexity in their lives. The objective of our research was to provide elements to understand why and how CMSP contributes to the complexity of these people's lives., Design: Qualitative study through semi-structured interviews., Setting: The study was conducted in Belgium with French-speaking individuals. The interviews took place at the university, in a teaching hospital, in private clinics or in individuals' homes., Participants: We included 24 individuals with CMSP and living complex situations. The recruitment was made in two phases in agreement with the grounded theory methodology and to reach the saturation of ideas., Results: The complexity experienced by people with CMSP turns around the notion of recognition, which can be broken down into 3 spheres: intimate, social and legal. The poor quality of listening and the fragmented vision of aid and care professionals generate a feeling of loneliness and incomprehension in the face of illness. The unsuitability of the world of work, the opacity of protocols and the attitude of medical experts reveal inequalities in access to recognition for immigrants and people of low socio-professional status., Conclusion: The complexity of the situations experienced could be reduced by implementing health policies that facilitate: legal recognition of this illness; adaptability in the workplace; raising awareness about pain mechanisms; the risks of stigmatization and the need of interprofessional collaboration., Patient or Public Contribution: Patients and the public participated in the dissemination of our research and were able to help us with recruitment through social networks (call for participation published on Facebook by the association 'Aidants proches') or word of mouth. The presentation of preliminary results at conferences as well as the publication of a public article in Belgian journals (http://www.lejournaldumedecin.com/magazine/douleurs-chroniques-un-veritable-parcours-du-combattant/article-normal-63055.html?cookie&#95;check=1671467500%22) facilitated the contact with the public., (© 2024 The Author(s). Health Expectations published by John Wiley & Sons Ltd.)

Digital image correlation, deflectometry and digital holography are some of the full-field optical measurement techniques that have matured in recent years. Their use in vibroacoustic applications is gaining attention and there is a need for cataloging their performance in order to provide, to a broad community of users and potential future users, quantitative and qualitative evaluations of these three approaches. This paper presents an experimental comparison of the three optical methods in the context of vibration measurements, along with classical reference measurements provided by an accelerometer and a laser Doppler vibrometer. The study is carried out on two mechanical structures exhibiting various vibration responses when submitted to an impact., (© 2023. The Author(s).)

Objectives: This study investigated the effect of positive preconditioning on the specific modality of verbal and touch interventions, in pain management., Methods: We compared pain ratings in 51 participants who underwent a cold pressor test twice (T1, T2). The results from the first test were used as a reference. For the second test, the participants were divided into 5 groups. Four groups received verbal or touch intervention during the test, with or without preconditioning. The fifth group was a control group. We compared dVAS (pain ratings at T1 minus T2) between groups to assess the effect of the interventions and the preconditioning. We also explored the within-group association between dVAS and pain-related traits., Results: We found a significant effect of preconditioning on dVAS. The post hoc test showed that the preconditioned verbal group reported higher dVAS than the non-preconditioned one. Participants' emotional awareness scores were negatively correlated with dVAS in the preconditioned touch group., Conclusion: These data suggested that preconditioning enhances pain management, regardless of intervention modalities. However, the preconditioning effect for the touch modality was negatively associated with the participants' emotional awareness., Practice Implications: Communication must be adapted with caution, depending on the treatment and the patients' emotional status., Competing Interests: Declaration of Competing Interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Numerical simulations of neutron star-neutron star and neutron star-black hole binaries play an important role in our ability to model gravitational-wave and electromagnetic signals powered by these systems. These simulations have to take into account a wide range of physical processes including general relativity, magnetohydrodynamics, and neutrino radiation transport. The latter is particularly important in order to understand the properties of the matter ejected by many mergers, the optical/infrared signals powered by nuclear reactions in the ejecta, and the contribution of that ejecta to astrophysical nucleosynthesis. However, accurate evolutions of the neutrino transport equations that include all relevant physical processes remain beyond our current reach. In this review, I will discuss the current state of neutrino modeling in general relativistic simulations of neutron star mergers and of their post-merger remnants. I will focus on the three main types of algorithms used in simulations so far: leakage, moments, and Monte-Carlo scheme. I will review the advantages and limitations of each scheme, as well as the various neutrino-matter interactions that should be included in simulations. We will see that the quality of the treatment of neutrinos in merger simulations has greatly increased over the last decade, but also that many potentially important interactions remain difficult to take into account in simulations (pair annihilation, oscillations, inelastic scattering)., Competing Interests: Conflict of interestThe author declares no conflict of interest., (© The Author(s) 2023.)

This paper presents analytical modeling of the speckle decorrelation noise in digital Fresnel holographic interferometry. The theoretical analysis is carried out by considering the complex coherence factor between two speckled images from two digitally reconstructed holograms at two different instants. The expression giving the modulus of the coherence factor is established and depends on the local surface deformation and parameters from the holographic setup. The analysis is supported by realistic simulations and experiments. Both simulations and experimental results exhibit a very good agreement with the theoretical prediction.

The use of high-speed cameras permits to visualize, analyze or study physical phenomena at both their time and spatial scales. Mixing high-speed imaging with coherent imaging allows recording and retrieving the optical path difference and this opens the way for investigating a broad variety of scientific challenges in biology, medicine, material science, physics and mechanics. At high frame rate, simultaneously obtaining suitable performance and level of accuracy is not straightforward. In the field of mechanics, this prevents high-speed imaging to be applied to full-field vibrometry. In this paper, we demonstrate a coherent imaging approach that can yield full-field structural vibration measurements with state-of-the-art performances in case of high spatial and temporal density measurements points of holographic measurement. The method is based on high-speed on-line digital holography and recording a short time sequence. Validation of the proposed approach is carried out by comparison with a scanning laser Doppler vibrometer and by realistic simulations. Several error criteria demonstrate measurement capability of yielding amplitude and phase of structural deformations.

Due to the manufacturing process, some fibrous materials like glasswool may be transversely isotropic (TI): fibers are mostly parallel to a plane of isotropy within which material properties are identical in all directions whereas properties are different along the transverse direction. The behavior of TI fibrous material is well described by the TI Biot's model, but it requires one to measure several mechanical parameters and to solve the TI Biot's equations. This paper presents an equivalent fluid model that can be suitable for TI materials under certain assumptions. It takes the form of a classical wave equation for the pressure involving an effective density tensor combining both limp and rigid frame behaviors of the material. This scalar wave equation is easily amenable to analytical and numerical treatments with a finite element method. Numerical results, based on the proposed model, are compared with experimental results obtained for two configurations with a fibrous material. The first concerns the absorption of an incident plane wave impinging on a fibrous slab and the second corresponds to the transmission loss of a splitter-type silencer in a duct. Both configurations highlight the effect of the sample orientation and give an illustration of the unusual TI behavior for fluids.

Extracting the unique information on ultradense nuclear matter from the gravitational waves emitted by merging neutron-star binaries requires robust theoretical models of the signal. We develop a novel effective-one-body waveform model that includes, for the first time, dynamic (instead of only adiabatic) tides of the neutron star as well as the merger signal for neutron-star-black-hole binaries. We demonstrate the importance of the dynamic tides by comparing our model against new numerical-relativity simulations of nonspinning neutron-star-black-hole binaries spanning more than 24 gravitational-wave cycles, and to other existing numerical simulations for double neutron-star systems. Furthermore, we derive an effective description that makes explicit the dependence of matter effects on two key parameters: tidal deformability and fundamental oscillation frequency.

The purpose of this study was to create a polymer phantom mimicking the mechanical properties of soft tissues using experimental tests and rheological models. Multifrequency Magnetic Resonance Elastography (MMRE) tests were performed on the present phantom with a pneumatic driver to characterize the viscoelastic (μ, η) properties using Voigt, Maxwell, Zener and Springpot models. To optimize the MMRE protocol, the driver behavior was analyzed with a vibrometer. Moreover, the hyperelastic properties of the phantom were determined using compressive tests and Mooney-Rivlin model. The range of frequency to be used with the round driver was found between 60 Hz and 100 Hz as it exhibits one type of vibration mode for the membrane. MRE analysis revealed an increase in the shear modulus with frequency reflecting the viscoelastic properties of the phantom showing similar characteristic of soft tissues. Rheological results demonstrated that Springpot model better revealed the viscoelastic properties (μ=3.45 kPa, η=6.17 Pas) of the phantom and the Mooney-Rivlin coefficients were C(10)=1.09.10(-2) MPa and C(01)=-8.96.10(-3) MPa corresponding to μ=3.95 kPa. These studies suggest that the phantom, mimicking soft tissue, could be used for preliminary MRE tests to identify the optimal parameters necessary for in vivo investigations. Further developments of the phantom may allow clinicians to more accurately mimic healthy and pathological soft tissues using MRE., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

An indirect technique for educing the homogenized acoustic impedance of a liner mounted on the wall of a barrel is presented. It is based on measurements and computational simulations of the multimodal scattering matrix of this lined duct. Measurements are performed with a multisource method and the use of an anechoic duct termination. The numerical computation of the scattering matrix relies on a finite element model, and assume that the duct is axisymmetric and uniformly covered by a locally reacting material. The impedance is educed by minimizing the difference between the theoretical and experimental acoustic power dissipations, which are deduced from the scattering matrix. The source is an incoming pressure field generated at one end of the duct only and composed of all cut-on modes. This technique was tested on a cylindrical barrel whose wall was partially lined with a realistic, locally reacting material made of honeycomb cells and a perforated facing sheet. Results for the acoustic impedance are compared with those deduced from semiempirical models and the experimental two microphone method. The best agreement with the indirect method is found with the semiempirical impedance results when the difference between the acoustic power dissipated by the actual lined barrel and the reference barrel is chosen as the cost function of the minimizing procedure.

A flow duct acoustic facility was developed to measure liner efficiency in attenuating higher order acoustic duct modes propagation conditions with mean air flow. The method is based on measurement, upstream and downstream of a liner, of the acoustic power produced by a periodic source. Directly measured total or modal acoustic powers are deduced from the local measurement, in both cross sections, of acoustic pressure, axial acoustic particle velocity, and axial mean flow velocity which are supplied by a probe made of a microphone and a single hot film. In this paper, the equipment, signal processing, and the data treatment process of this facility are first described. Then, information on the accuracy of the methodology is provided by a validation test performed with a rigid wall duct section. Finally, the results of an experiment carried out with a locally reacting liner and a mean flow velocity of 20 m/s will be presented. Measurements of the main attenuation frequency and of the main total acoustic power dissipated agree with the values for which the liner was designed. These results point out the limitations of the method presented to sources with high-level periodic sounds to provide a sufficient signal-to-noise ratio, the noise being produced by fluctuations of the turbulent flow.