Perfect Resonant Absorption of Guided Water Waves by Autler-Townes Splitting.

The control of guided water wave propagation based on the Autler-Townes splitting resonance concept is demonstrated experimentally, numerically, and theoretically. Complete wave absorption is achieved using an asymmetric pointlike scatterer made of two closely spaced resonant side channels connected to a guide and designed so that its energy leakage is in perfect balance with the inherent viscous losses in the system. We demonstrate that the nature of the resonators and guide junction completely controls the positions of the wave numbers at the reflection and transmission zeros on the real axis; the asymmetry of the resonators completely controls their positions on the imaginary axis. Thus, by adjusting these two independent parameters, we obtain a zero reflection and transmission.

A stable, unified model for resonant Faraday cages.

We study some effective transmission conditions able to reproduce the effect of a periodic array of Dirichlet wires on wave propagation, in particular when the array delimits an acoustic Faraday cage able to resonate. In the study of Hewett & Hewitt (2016 Proc. R. Soc. A 472, 20160062 (doi:10.1098/rspa.2016.0062)) different transmission conditions emerge from the asymptotic analysis whose validity depends on the frequency, specifically the distance to a resonance frequency of the cage. In practice, dealing with such conditions is difficult, especially if the problem is set in the time domain. In the present study, we demonstrate the validity of a simpler unified model derived in Marigo & Maurel (2016 Proc. R. Soc. A 472, 20160068 (doi:10.1098/rspa.2016.0068)), where unified means valid whatever the distance to the resonance frequencies. The effectiveness of the model is discussed in the harmonic regime owing to explicit solutions. It is also exemplified in the time domain, where a formulation guaranteeing the stability of the numerical scheme has been implemented.

[Impact on quality of life and autonomy of patients aged over 75 years treated with anti-PD-1 for metastatic melanoma: A single-centre prospective study]. / Impact sur la qualité de vie et l'autonomie des patients de plus de 75 ans traités par anti-PD-1 pour un mélanome métastatique : étude prospective monocentrique.

INTRODUCTION: We previously studied anti-PD-1 safety in elderly (≥80 years) patients and reported a retrospective two-centre cohort with a similar safety profile in elderly and in younger patients. Quality-of-life evaluation data is still lacking in this specific population. MATERIALS AND METHODS: A prospective, single-centre study in patients aged over 75 years presenting metastatic melanoma treated with anti-PD-1. The endpoint was monitoring of quality of life (by a specific survey) and onco-geriatric assessment at the beginning of therapy, then at 3 and 6 months (nutritional status, comorbidities, autonomy, thymic and cognitive disorders). RESULTS: Fourteen patients were included of median age 86.5 years [range: 78-94] from March to September 2018. General status was good, with a median Charlson score of 0 [extremes 0-4]. Nine patients were evaluated at 3 months and six patients at 6 months. There was no significant difference in quality-of-life scores obtained at baseline, 3 months and 6 months. DISCUSSION: This study shows that neither quality of life nor autonomy appears to be affected by anti-PD-1 treatment in patients aged over 75 years. However, these results should be interpreted with caution due to the small number of patients included, the short follow-up period and the single-centre data. Nevertheless, the prospective analysis and the complete onco-geriatric evaluation and monitoring yielded unique and original data.

Enhanced resonance of sparse arrays of Helmholtz resonators-Application to perfect absorption.

The influence of the spacing on the resonance of a periodic arrangement of Helmholtz resonators is inspected. An effective problem is used which accurately captures the properties of the resonant array within a large range of frequencies, and whose simplified version leaves an impedance condition. It is shown that the strength of the resonance is enhanced when the array becomes sparser. This degree of freedom on the radiative damping is of particular interest since it does not affect the resonance frequency nor the damping due to losses within each resonator; in addition, it does not affect the total thickness of the array. It is shown that it can be used for the design of a perfect absorbing wall.

Generalized method for retrieving effective parameters of anisotropic metamaterials.

Electromagnetic or acoustic metamaterials can be described in terms of equivalent effective, in general anisotropic, media and several techniques exist to determine the effective permeability and permittivity (or effective mass density and bulk modulus in the context of acoustics). Among these techniques, retrieval methods use the measured reflection and transmission coefficients (or scattering coefficients) for waves incident on a metamaterial slab containing few unit cells. Until now, anisotropic effective slabs have been considered in the literature but they are limited to the case where one of the axes of anisotropy is aligned with the slab interface. We propose an extension to arbitrary orientations of the principal axes of anisotropy and oblique incidence. The retrieval method is illustrated in the electromagnetic case for layered media, and in the acoustic case for array of tilted elliptical particles.

Experimental realization of a water-wave metamaterial shifter.

We demonstrate by quantitative experimental measurements that metamaterials with anisotropic properties can be used in the context of water waves to produce a reflectionless bent waveguide. The anisotropic medium consists in a bathymetry with subwavelength layered structure that shifts the wave in the direction of the waveguide bending (10°, 20°, and 30°). The waveguide filled with such metamaterial is tested experimentally and compared to a reference empty bent waveguide. The experimental method used to characterize the wave field allows for space-time resolved measurements of water elevation. Results show the efficiency of the shifter. Modal treatment of the experimental data confirms that the metamaterial prevents higher modes from being excited in the waveguide.

Time reversal of water waves.

We present time reversal experiments demonstrating refocusing of gravity-capillary waves in a water tank cavity. Owing to the reverberating effect of the cavity, only a few channels are sufficient to reconstruct the surface wave at the point source, even if the absorption is not negligible. Space-time-resolved measurements of the waves during the refocusing allow us to quantitatively demonstrate that the quality of the refocusing increases linearly with the number of reemitting channels. Numerical simulations corresponding to water waves at larger scales, with negligible damping, indicate the possibility of very high quality refocusing.

Different regimes for water wave turbulence.

We present an experimental study on gravity capillary wave turbulence in water. By using space-time resolved Fourier transform profilometry, the behavior of the wave energy density |η(k,ω)|(2) in the 3D (k,ω) space is inspected for various forcing frequency bandwidths and forcing amplitudes. Depending on the bandwidth, the gravity spectral slope is found to be either forcing dependent, as classically observed in laboratory experiments, or forcing independent. In the latter case, the wave spectrum is consistent with the Zakharov-Filonenko cascade predicted within wave turbulence theory.

Estimating the dynamic effective mass density of random composites.

The effective mass density of an inhomogeneous medium is discussed. Random configurations of circular cylindrical scatterers are considered, in various physical contexts: fluid cylinders in another fluid, elastic cylinders in a fluid or in another solid, and movable rigid cylinders in a fluid. In each case, time-harmonic waves are scattered, and an expression for the effective wavenumber due to Linton and Martin [J. Acoust. Soc. Am. 117, 3413-3423 (2005)] is used to derive the effective density in the low frequency limit, correct to second order in the area fraction occupied by the scatterers. Expressions are recovered that agree with either the Ament formula or the effective static mass density, depending upon the physical context.

One-step management of apple-peel atresia.

PURPOSE: Apple-peel atresia is a rare form of bowel atresia associating proximal jejunal atresia with a typical coil-shaped distal small bowel. Many of the children suffering from this condition are still managed with initial enterostomy followed by delayed anastomosis. PATIENTS AND METHOD: Between 2000 and 2007, we managed four patients with apple-peel atresia. Three by primary anastomosis and one by initial enterostomy with delayed anastomosis. RESULTS: Total duration of total parenteral nutrition (TPN) was an average 109 days. Survival rate was 100% with an average follow-up of 4.3 years. CONCLUSION: Nowadays, the prognosis of apple-peel atresia depends mainly on prolonged TPN-related morbidity rather than immediate postoperative complications. We therefore recommend that those infants affected be managed by primary anastomosis in order to reduce the duration of parenteral nutrition, followed by careful nutrition by teams experienced in neonatal TPN and short bowel syndrome.

[An excessive diagnosis of constipation in children complaining of abdominal pain in a pediatric emergency department: an example of practice patterns]. / Une prévalence excessive du diagnostic de constipation chez les enfants consultant pour douleurs abdominales aux urgences: un exemple d'évaluation des pratiques.

UNLABELLED: Prescriptions of abdominal x-ray and diagnosis of constipation seemed too frequent in children evaluated for abdominal pain (AP) in a paediatric emergency unit. OBJECTIVE: To evaluate the prevalence of constipation in children with AP, to determine clinical and radiological signs related to this diagnosis, and to compare frequencies of clinical criteria of functional chronic constipation (FCC) in children with AP with those of controls (children with mild traumatisms without AP). METHODS: This prospective observational study included children older than 4 years of age consulting for AP. RESULTS: Among 196 patients with AP, 53% had a diagnosis of constipation on discharge (28% isolated and 25% associated with an other diagnosis), and 88% had a plain abdominal x-ray. A faecal retention was considered by emergency practitioners in 92% of children with the diagnosis of constipation vs 22% with other diagnosis (OR=38; CI 95%: 15-101). Clinical criteria of FCC were associated with the diagnosis of constipation (OR=2.7; CI 95%: 1.4-5.2). A FCC was as prevalent in the control population as in AP population (32 vs 34%). CONCLUSION: An excessive prevalence of diagnosis of constipation was mainly associated with contestable x-ray diagnosis of faecal retention secondary to inappropriate indications of abdominal x-ray.

A nonuniformly stretched vortex.

A stretched vortex model is proposed which includes a nonuniform stretching in the radial direction that is clearly present in real flows, as well as a slow variation of velocity profiles along the vortex axis. Both features of this boundary layer approximation depart from the classical Burgers solution. This model is shown to be in very good agreement with experimental velocity measurements.

Determination of Lamb mode eigenvalues.

An original method is presented to determine the complex Lamb wave spectrum by using a numerical spectral method applied to the elasticity equations. This method presents the advantage to directly determine complex wave numbers for a given frequency via a classical matricial eigenvalue problem, and allows the wave numbers to be determined at relatively high frequencies (i.e., corresponding to many propagating modes). It does not need initial guess values for the wave numbers, contrary to the usual method of root finding of the Rayleigh-Lamb frequency equations (dispersion relation) in the complex plane. Results are presented and the method is discussed.

[Preoperative prognostic factors for squamous cell carcinomas of the thoracic esophagus]. / Facteurs pronostiques préopératoires des cancers épidermoïdes de l'oesophage thoracique.

AIM OF THE STUDY: To identify preoperative survival prognostic factors in patients with resectable squamous cell carcinoma of the thoracic esophagus. POPULATION: From January 1982 to September 1999, 868 patients underwent surgery for esophageal carcinoma in our department, including 493 for squamous cell carcinoma of the thoracic esophagus. The following parameters were retrospectively included in univariate and multivariate analysis: age, sex, undernutrition, dysphagia, tumor diameter and nodal involvement on the CT-scan, preoperative treatment, surgical technique, curative resection, pTNM classification, histologic type and postoperative complications. The actuarial survival was determined. RESULTS: Survival prognostic factors were dysphagia, nodal involvement on CT-scan and depth of tumor invasion at pathological examination. Three groups of patients were identified on the two preoperative variables: group 1: patients without dysphagia (n=102), group 2: patients with dysphagia but without nodal involvement on the CT- scan (n=244), group 3: patients with dysphagia and with nodal involvement on the CT- scan (n=147). The median survivals were 62.4, 19.1 and 14.4 months in groups 1, 2 and 3, respectively, and 5-year actuarial survivals were 50%, 21% and 11% (P<0.009). CONCLUSION: Our study confirms that dysphagia and nodal involvement on the CT-scan are simple preoperative prognostic factors in patients with resectable squamous cell carcinoma of the thoracic esophagus.

Scattering of sound by a vorticity filament: an experimental and numerical investigation.

A vorticity filament is investigated experimentally using the transmission of an ultrasonic wave through the flow. The analysis of the wave-front distortion provides noninvasive measurements of the vortex circulation and size. The latter is estimated by analytical calculations of the scattering of a plane wave by a vorticity filament. The case of a cylindrical wave incident on a vortex leads to similar experimental results which are successfully compared to a parabolic equation simulation. Finally, a finite-difference code based on linear acoustics is presented, in order to investigate the structure of the scattered wave numerically.

Irregular scattering of acoustic rays by vortices.

The scattering of high-frequency sound wave, under geometrical acoustic approximation, by three stationary vortices in two dimensions is investigated. For a sufficiently high Mach number of the vortex flow, the scattering of sound rays becomes irregular, displaying a new example of chaotic scattering for a time-reversal breaking system. The fractal dimension, as well as the unstable and stable manifolds of the scattering dynamics, is presented.