Generalized analytic model for rotational and anisotropic metasolids

An analytical approach is presented to model a metasolid accounting for anisotropic effects and rotational mode. The metasolid is made of either cylindrical or spherical hard inclusions embedded in a stiff matrix via soft claddings, and the analytical approach to study the composite material is a generalization of the method introduced by Liu \textit{et al.} [Phys. Rev. B, 71, 014103 (2005)]. It is shown that such a metasolid exhibits negative mass densities near the translational-mode resonances, and negative density of moment of inertia near the rotational resonances. The results obtained by this analytical and continuum approach are compared with those from discrete mass-spring model, and the validity of the later is discussed. Based on derived analytical expressions, we study how different resonance frequencies associated with different modes vary and are placed with respect to each other, in function of the mechanical properties of the coating layer. We demonstrate that the resonances associated with additional modes taken into account, that is, axial translation for cylinders, and rotations for both cylindrical and spherical systems, can occur at lower frequencies compared to the previously studied plane-translational modes.Comment: 30 pages, 10 figure

In Vivo Detection of Succinate by Magnetic Resonance Spectroscopy as a Hallmark of SDHx Mutations in Paraganglioma

International audiencePurpose: Germline mutations in genes encoding mitochon-drial succinate dehydrogenase (SDH) are found in patients with paragangliomas, pheochromocytomas, gastrointestinal stromal tumors, and renal cancers. SDH inactivation leads to a massive accumulation of succinate, acting as an oncometabolite and which levels, assessed on surgically resected tissue are a highly specific biomarker of SDHx-mutated tumors. The aim of this study was to address the feasibility of detecting succinate in vivo by magnetic resonance spectroscopy. Experimental Design: A pulsed proton magnetic resonance spectroscopy (1 H-MRS) sequence was developed, optimized, and applied to image nude mice grafted with Sdhb À/À or wild-type chromaffin cells. The method was then applied to patients with paraganglioma carrying (n ¼ 5) or not (n ¼ 4) an SDHx gene mutation. Following surgery, succinate was measured using gas chromatography/mass spectrometry, and SDH protein expression was assessed by immunohistochemistry in resected tumors. Results: A succinate peak was observed at 2.44 ppm by 1 H-MRS in all Sdhb À/À-derived tumors in mice and in all paragangliomas of patients carrying an SDHx gene mutation, but neither in wild-type mouse tumors nor in patients exempt of SDHx mutation. In one patient, 1 H-MRS results led to the identification of an unsus-pected SDHA gene mutation. In another case, it helped define the pathogenicity of a variant of unknown significance in the SDHB gene. Conclusions: Detection of succinate by 1 H-MRS is a highly specific and sensitive hallmark of SDHx mutations. This non-invasive approach is a simple and robust method allowing in vivo detection of the major biomarker of SDHx-mutated tumors. Clin Cancer Res; 22(5); 1120–9. Ó2015 AACR

Two-component versus three-component metasolids

International audienceAnalytic analysis and parametric investigation are employed to study and compare metamaterial properties of two types of composite metasolids. Metasolids are composed of either an elastic inclusion or a rigid core coated by an elastic material, embedded in a stiff matrix. For these types of materials, results related to cylindrical as well as spherical inclusions are presented. Such mono-inclusion two-component and bi-inclusion three-component metasolids have been previously known to exhibit negative mass density near local-resonance frequencies. Through a unified formulation, it is analytically shown how and why adding a rigid mass inside the elastic inclusion to make a bi-inclusion three-component material can dramatically change the homogenized property of the resultant inclusion and increase the tunability of the composite, particularly in terms of local-resonance frequencies and the associated metamaterial-effect frequency bandwidth. In this way, concerning distinctly sound and vibration insulation, a lowfrequency metamaterial effect with larger bandwidth can be designed via an inverse problem using a simplified mass-spring model.

Coplanar propagation paths of 3D cracks in infinite bodies loaded in shear

AbstractBower and Ortiz, recently followed by Lazarus, developed a powerful method, based on a theoretical work of Rice, for numerical simulation of planar propagation paths of mode 1 cracks in infinite isotropic elastic bodies. The efficiency of this method arose from the need for the sole 1D meshing of the crack front. This paper presents an extension of Rice’s theoretical work and the associated numerical scheme to mixed-mode (2+3) shear loadings. Propagation is supposed to be channeled along some weak planar layer and to remain therefore coplanar, as in the case of a geological fault for instance. The capabilities of the method are illustrated by computing the propagation paths of cracks with various initial contours (circular, elliptic, rectangular, heart-shaped) in both fatigue and brittle fracture. The crack quickly reaches a stable, almost elliptic shape in all cases. An approximate but accurate analytic formula for the ratio of the axes of this stable shape is derived

Vibration of microphone membrane: Effects of thermal stress

International audienceThe aim of this work is to improve theoretical and experimental tools for modelling and characterising the global behaviour of measurement microphones in a large range of environmental conditions. In most of measurement microphones, the sensitive part is a vibrating membrane stretched and clamped on the body of the microphone. If the sensor is operated at ambient temperatures that significantly differ from atmospheric one, thermal expansion of the microphone membrane and body causes strain and stress variations in the membrane, which lead to altered vibrational behaviour when it is submitted to an acoustic wave. An analytical approach is developed here to express the thermal stress related to the fact that thermal expansions of the microphone membrane and body are different. These effects are then taken into account in a classical modelling procedure for describing the vibration of a microphone membrane in vacuo. An experiment, that relies on the electrostatic actuator technique, has been performed in a fine vacuum to characterise the first resonance mode of a commercial microphone membrane in low temperatures range, from atmospheric to cryogenic. The experimental results highlight the significant effects of the thermal stress induced by the differences between thermal expansion properties of the materials constituting the microphone. These results are consistent with the membrane vibration predicted by the analytical modelling proposed. Thus, even small differences between the thermal expansion properties of the microphone membrane and body have to be taken into account in a modelling procedure to get reliable predictions of the membrane vibration at various ambient temperatures

Rotational and anisotropic metasolids: A generalized analytical model

International audienceIn this talk, an analytical approach will be presented to model a metasolid accounting for anisotropic effects and rotational motions. Based on the initial experiences reported in [1], the aim of this study is to give a generalization of the method introduced by the same group [2] to describe the physics of this metasolid. This structure, made of either cylindrical or spherical hard inclusions embedded in a stiff matrix via soft claddings, exhibits negative mass densities near the translational-mode resonances (local resonance for translational motions). Within the large wavelength limit, in micro level hypothesis of rigid solid behavior has been made for both the inclusion and the matrix in this three-component medium. This assumption simplifies the analytical study of the problem, while yielding the physical dynamics of the medium. In this work, firstly we give the frequency-dependent components of the effective mass density that appears to be anisotropic considering the cylindrical inclusions. Figure 1 (left) shows this result for cylindrical or spherical inclusions, obtained by continuum model, as well as those from the discrete model based on an analogy with mass-spring system. The latter, which can be easily derived from quasi-static homogenization of the soft cladding [3], may be useful to tune effective metasolids with desired acoustic properties. We systematically investigate the limit of the validity of this discrete model, which gives a very accurate estimation of the first local-resonance frequencies of the structure. The second extension concerns the rotational modes, which exhibit similar properties at different frequencies: a negative density of moment of inertia near the rotational resonances is observed and well-estimated by a simple discrete model based on inerti

Rotational and anisotropic metasolids: A generalized analytical model

International audienceIn this talk, an analytical approach will be presented to model a metasolid accounting for anisotropic effects and rotational motions. Based on the initial experiences reported in [1], the aim of this study is to give a generalization of the method introduced by the same group [2] to describe the physics of this metasolid. This structure, made of either cylindrical or spherical hard inclusions embedded in a stiff matrix via soft claddings, exhibits negative mass densities near the translational-mode resonances (local resonance for translational motions). Within the large wavelength limit, in micro level hypothesis of rigid solid behavior has been made for both the inclusion and the matrix in this three-component medium. This assumption simplifies the analytical study of the problem, while yielding the physical dynamics of the medium. In this work, firstly we give the frequency-dependent components of the effective mass density that appears to be anisotropic considering the cylindrical inclusions. Figure 1 (left) shows this result for cylindrical or spherical inclusions, obtained by continuum model, as well as those from the discrete model based on an analogy with mass-spring system. The latter, which can be easily derived from quasi-static homogenization of the soft cladding [3], may be useful to tune effective metasolids with desired acoustic properties. We systematically investigate the limit of the validity of this discrete model, which gives a very accurate estimation of the first local-resonance frequencies of the structure. The second extension concerns the rotational modes, which exhibit similar properties at different frequencies: a negative density of moment of inertia near the rotational resonances is observed and well-estimated by a simple discrete model based on inerti

Value of Non-Coding RNA Expression in Biofluids to Identify Patients at Low Risk of Pathologies Associated with Pregnancy

Pregnancy-related complications (PRC) impact maternal and fetal morbidity and mortality and place a huge burden on healthcare systems. Thus, effective diagnostic screening strategies are crucial. Currently, national and international guidelines define patients at low risk of PRC exclusively based on their history, thus excluding the possibility of identifying patients with de novo risk (patients without a history of disease), which represents most women. In this setting, previous studies have underlined the potential contribution of non-coding RNAs (ncRNAs) to detect patients at risk of PRC. However, placenta biopsies or cord blood samples are required, which are not simple procedures. Our review explores the potential of ncRNAs in biofluids (fluids that are excreted, secreted, or developed because of a physiological or pathological process) as biomarkers for identifying patients with low-risk pregnancies. Beyond the regulatory roles of ncRNAs in placental development and vascular remodeling, we investigated their specific expressions in biofluids to determine favorable pregnancy outcomes as well as the most frequent pathologies of pregnant women. We report distinct ncRNA panels associated with PRC based on omics technologies and subsequently define patients at low risk. We present a comprehensive analysis of ncRNA expression in biofluids, including those using next-generation sequencing, shedding light on their predictive value in clinical practice. In conclusion, this paper underscores the emerging significance of ncRNAs in biofluids as promising biomarkers for risk stratification in PRC. The investigation of ncRNA expression patterns and their potential clinical applications is of diagnostic, prognostic, and theragnostic value and paves the way for innovative approaches to improve prenatal care and maternal and fetal outcomes