Enhancing the dynamic range of Targeted Energy Transfer in acoustics using several nonlinear membrane absorbers

International audienceIn order to enhance the robustness and the energy range of efficiency of targeted energy transfer (TET) phenomena in acoustics, we discuss in this paper about the use of multiple nonlinear membrane absorbers in parallel. We show this way, mainly thanks to an experimental set-up with two membranes, that the different absorbers have additional effects that extend the efficiency and the possibilities of observation of TET. More precisely, we present the different behavior of the system under sinusoidal forcing and free oscillations, characterizing the phenomena for all input energies. The frequency responses are also presented, showing successive clipping of the original resonance peak of the system. A model is finally used to generalize these results to more than two NES and to simulate the case of several very similar membranes in parallel which shows how to extend the existence zone of TET

Assessing the Impact of Financial Aids to Firms: Causal Inference in the presence of Interference

We consider policy evaluations when SUTVA is violated because of the presence of interference among units. We propose to explicitly model interactions as a function of units characteristics. Our approach is applied to the evaluation of a policy implemented in Tuscany (a region in Italy) on small handicraft firms. Results show that the benefits from the policy are reduced when treated firms are subject to high levels of interference. Moreover, the average causal effect is slightly underestimated when interference is ignored. These findings point to the importance of considering possible interference among units when evaluating and planning policy interventions

Assessing the Impact of Financial Aids to Firms: Causal Inference in the presence of Interference

We consider policy evaluations when SUTVA is violated because of the presence of interference among units. We propose to explicitly model interactions as a function of units characteristics. Our approach is applied to the evaluation of a policy implemented in Tuscany (a region in Italy) on small handicraft firms. Results show that the benefits from the policy are reduced when treated firms are subject to high levels of interference. Moreover, the average causal effect is slightly underestimated when interference is ignored. These findings point to the importance of considering possible interference among units when evaluating and planning policy interventions

Toward an adjustable nonlinear low frequency acoustic absorber

International audienceThis paper presents experimental results showing that a loudspeaker used as a suspended piston working outside its range of linearity can also be used as a nonlinear acoustic absorber. The main advantage of this technology of absorber is the perspective to adjust independently the device parameters (mass, nonlinear stiffness and damping) according to the operational conditions. To achieve this purpose, quasi-static and dynamic tests have been performed on three types of commercial devices (one with structural modifications), in order to define the constructive characteristics that it should present. An experimental setup has been developed using a one-dimensional acoustic linear system coupled through a box (acting as a weak spring) to a loudspeaker used as a suspended piston acting as an essentially nonlinear oscillator. The tests carried out on the whole vibro-acoustic system have showed the occurrence of the acoustic TET from the acoustic media to the suspended piston and demonstrated the efficiency of this new kind of absorber at low frequencies over a wide frequency range. Moreover, the experimental analyses conducted with different NES masses have confirmed that it is possible to optimize the noise absorption with respect to the excitation level of the acoustic resonator

Contrôle passif du bruit par pompage énergétique

L'association d'un absorbeur nonlinéaire à un système primaire linéaire permet d'observer le phénomène de transfert énergétique ciblé (également appelé pompage énergétique) et l'application de ce concept à l'acoustique correspond à une nouvelle technique passive de réduction du bruit. Un montage expérimental académique a été développé en utilisant l'air à l'intérieur d'un tube en tant que milieu acoustique primaire, une fine membrane circulaire visco-élastique en tant qu'oscillateur à raideur essentiellement cubique et l'air contenu dans une boîte de grande taille pour assurer un couplage faible entre ces deux éléments. Ce papier s'appuie principalement sur des résultats expérimentaux. Le pompage énergétique est visible sur un des régimes observés sous excitation harmonique, mais également lors des oscillations libres du système. En effet, à partir d'un certain seuil d'énergie initiale, l'extinction sonore dans le tube suit une décroissance quasi-linéaire beaucoup plus rapide que la décroissance classique exponentielle et pendant laquelle l'énergie acoustique du milieu primaire est irréversiblement transférée et dissipée dans la membrane

Multimodal Imaging of Macular Telangiectasia Type 2: Focus on Vascular Changes Using Optical Coherence Tomography Angiography

PURPOSE. To report morphologic features of idiopathic macular telangiectasia (MacTel) type 2 by means of optical coherence tomography angiography (OCTA) and to compare these findings to fundus fluorescein angiography (FFA), fundus autofluorescence (FAF), confocal blue reflectance (CBR), and spectral-domain OCT (SD-OCT). In addition, foveal vessel density and parafoveal vascular density (PFVD), and foveal retinal thickness and parafoveal retinal thickness (PFRT) were compared between MacTel 2 patients and normal aged-matched controls. METHODS. Eight patients (15 eyes) with MacTel 2 and 17 normal controls (17 eyes) underwent retinal multimodal imaging assessment and grading. Results from different imaging techniques were used to compare interimaging modalities. Objective quantification of retinal vessel density and macular thickness was evaluated in MacTel 2 patients (15 eyes). RESULTS. In MacTel 2 eyes a comparison of OCTA to the other imaging techniques showed that the strongest correlations were present with SD-OCT, early FFA, and late FFA. Moderate correlations were found between OCTA and CBR and FAF. Foveal vessel density was significantly lower in MacTel 2 eyes than control eyes both in the superficial plexus (23.74% vs. 33.14%; P = 0.003) and in the deep plexus (24.63% vs. 34.21%; P = 0.005). Superficial PFVD was significantly different in the two groups (47.06% vs. 51.40%; P = 0.005) but not the deep PFVD. Foveal retinal thickness was 214.13 mu m in MacTel 2 eyes and 258.18 mu m in normal controls, and PFRT was 279.60 and 323.29 mu m, respectively (P CONCLUSIONS. Optical coherence tomography angiography is useful for retinal vasculature characterization in MacTel type 2 patients and showed a high correlation with well-established imaging techniques

Une étude expérimentale du pompage énergétique en acoustique

Ce papier présente un dispositif expérimental dont le but est d'étudier le phénomène de pompage énergétique entre un milieu acoustique et un absorbeur non linéaire. Ce montage permet ainsi d'observer un transfert irréversible d'énergie entre le premier mode acoustique d'un tube et une fine membrane visco-élastique. Divers aspects du pompage énergétique sont présentés : différents comportements sous excitation harmonique, seuil de pompage, capture de résonance et réponses impulsionnelles

NRAGE associates with the anti-apoptotic factor Che-1 and regulates its degradation to induce cell death

Neurotrophin receptor-interacting MAGE homolog (NRAGE) has been recently identified as a cell-death inducer, involved in molecular events driving cells through apoptotic networks during neuronal development. Recently, we have focused on the functional role of Che-1, also known as apoptosis-antagonizing transcription factor (AATF), a protein involved in cell cycle control and gene transcription. Increasing evidence suggests that Che-1 is involved in apoptotic signalling in neural tissues. In cortical neurons Che-1 exhibits an anti-apoptotic activity, protecting cells from neuronal damage induced by amyloid β-peptide. Here, we report that Che-1 interacts with NRAGE and that an EGFP-NRAGE fusion protein inhibits nuclear localization of Che-1, by sequestering it within the cytoplasmic compartment. Furthermore, NRAGE overexpression downregulates endogenous Che-1 by targeting it for proteasome-dependent degradation. Finally, we propose that Che-1 is a functional antagonist of NRAGE, because its overexpression completely reverts NRAGE-induced cell-death

Unacylated Ghrelin is associated with the isolated low HDL-cholesterol obese phenotype independently of insulin resistance and CRP level

<p>Abstract</p> <p>Background</p> <p>Low plasma high-density lipoprotein-cholesterol (HDL-c) level is commonly present in obesity and represents an independent cardiovascular risk factor. However, obese patients are a very heterogeneous population and the factors and mechanisms that contribute to low HDL-c remain unclear. The aim of this study was to investigate the association between plasma HDL-c levels and plasma hormonal profiles (insulin, adiponectin, resistin, leptin and ghrelin) in subsets of class II and III obese patients.</p> <p>Methods</p> <p>Fasting plasma levels of glucose, total cholesterol, LDL-c, HDL-c, triglycerides, free fatty acids, apoproteins A-I, B-100, B-48, C-II, C-III, insulin, hs-CRP, adipocytokines (adiponectin, resistin, leptin), unacylated ghrelin, body composition (DXA) and resting energy expenditure were measured in three subsets of obese patients: 17 metabolically abnormal obese (MAO) with metabolic syndrome and the typical metabolic dyslipidaemia, 21 metabolically healthy obese (MHO) without metabolic syndrome and with a normal lipid profile, and 21 isolated low HDL-c obese patients (LHO) without metabolic syndrome, compared to 21 healthy lean control subjects.</p> <p>Results</p> <p>Insulin resistance (HOMA-IR) increased gradually from MHO to LHO and from LHO to MAO patients (<it>p </it>< 0.05 between MHO and MAO and between LHO and MAO). In multiple regression analysis, serum unacylated ghrelin levels were only positively and independently associated with HDL-c levels in the LHO group (<it>p </it>= 0.032).</p> <p>Conclusions</p> <p>These results suggest that, in class II and III obese patients with an isolated low HDL-c phenotype, unacylated ghrelin is positively associated with HDL-c level independently of insulin resistance and CRP levels, and may contribute to the highly prevalent low HDL-c level seen in obesity.</p