Publications

2018

Experimental investigation of elastomer mode I fracture: an attempt to estimate the critical strain energy release rate using SENT tests
- Roucou David
- Diani Julie
- Brieu Mathias
- Witz Jean-Francois
- Mbiakop-Ngassa Armel
International Journal of Fracture, Springer Verlag, 2018, 209 (1-2), pp.163 - 170. The resistance to mode I failure of rubbers is studied by submitting single edge notch samples to uniaxial tension. Reproducing the seminal work of Rivlin and Thomas (J Polym Sci 10:291–318, 1953), single edge notch tension specimens, presenting notches of various lengths, are stretched until break. A styrene butadiene rubber, unfilled and filled with carbon-black, and an unfilled rubber from the latter mentioned work, were considered. When the notch is smaller than one fifth of the sample width, mode I crack opening is observed, leading to catastrophic failure that creates smooth mirror-like crack surfaces. Nonetheless, the experimental force-elongation responses show that the mode I critical energy release rate cannot be calculated by a classical Griffith elastic failure analysis. When notches are longer, the SENT samples are not submitted to pure uniaxial tension only. Structural bending leads to uncontrolled mixed mode crack propagation. The surfaces created when the long notches propagate are rough and bifurcations are witnessed for the filled rubbers. (10.1007/s10704-017-0251-x)
DOI : 10.1007/s10704-017-0251-x
The importance of the pericardium for cardiac biomechanics: From physiology to computational modeling
- Pfaller Martin
- Hoermann Julia
- Weigl Martina
- Nagler Andreas
- Chabiniok Radomir
- Bertoglio Cristóbal
- Wall Wolfgang A.
Biomechanics and Modeling in Mechanobiology, Springer Verlag, 2018. The human heart is enclosed in the pericardial cavity. The pericardium consists of a layered thin sac and is separated from the myocardium by a thin film of fluid. It provides a fixture in space and friction-less sliding of the myocardium. The influence of the pericardium is essential for predictive mechanical simulations of the heart. However, there is no consensus on physiologically correct and computationally tractable pericardial boundary conditions. Here we propose to model the pericardial influence as a parallel spring and dashpot acting in normal direction to the epicardium. Using a four-chamber geometry, we compare a model with pericardial boundary conditions to a model with fixated apex. The influence of pericardial stiffness is demonstrated in a parametric study. Comparing simu-lation results to measurements from cine magnetic resonance imaging reveals that adding pericardial boundary conditions yields a better approximation with respectto atrioventricular plane displacement, atrial filling, and overall spatial approximation error. We demonstrate that this simple model of pericardial-myocardial interaction can correctly predict the pumping mechanisms ofthe heart as previously assessed in clinical studies. Utilizing a pericardial model can not only provide much more realistic cardiac mechanics simulations but also allows new insights into pericardial-myocardial interaction which cannot be assessed in clinical measurement.
Airborne ultrasound surface motion camera: application to seismocardiography
- Shirkovskiy Pavel
- Laurin Alexandre
- Jeger-Madiot Nathan
- Chapelle Dominique
- Fink Mathias
- Ing Ros Kiri
Applied Physics Letters, American Institute of Physics, 2018, 112. The recent achievements in the accelerometer-based seismocardiography field indicate a strong potential for this technique to address wide variety of clinical needs. Recordings from different locations on the chest can give a more comprehensive observation and interpretation of wave propagation phenomena than a single-point recording, can validate existing modeling assumptions (such as the representation of the sternum as a single solid body), and provide better identifiability for models using richer recordings. Ultimately, the goal is to advance our physiological understanding of the processes to provide useful data to promote cardiovascular health. Accelerometer-based multichannel system is a contact method and laborious for use in practice, also even ultralight accelerometers can cause non-negligible loading effects. We propose a new contactless ultrasound imaging method to measure thoracic and abdominal surface motions, demonstrating that it is adequate for typical seismocardiogram use. The developed method extends non-contact surface-vibrometry to fast 2D mapping by originally combining multi-element airborne ultrasound arrays, a synthetic aperture implementation and pulsed-waves. Experimental results show the ability of the developed method to obtain 2D seismocardiographic maps of the body surface 30×40 cm 2 in dimension, with a temporal sampling rate of several hundred Hz, using ultrasound waves with the central frequency of 40 kHz. Our implementation was validated in-vivo on eight healthy human participants. The shape and position of the zone of maximal absolute acceleration and velocity during the cardiac cycle were also observed. This technology could potentially be used to obtain more complete cardio-vascular information than single-source SCG in and out of clinical environments, due to enhanced identifiability provided by distributed measurements, and observation of propagation phenomena. (10.1063/1.5028348)
DOI : 10.1063/1.5028348
A conservative penalisation strategy for the semi-implicit time discretisation of incompressible elastodynamics equation
- Caforio Federica
- Imperiale Sébastien
Advanced Modeling and Simulation in Engineering Sciences, Springer, 2018, 5 (1), pp.1-27. The principal aim of this work is to provide an adapted numerical scheme for the approximation of elastic wave propagation in incompressible solids. We rely on high-order conforming finite element with mass lumping for space discretisation and implicit/explicit, second-order, energy-preserving time discretisation. The time step restriction only depends on the shear wave velocity and at each time step a Poisson problem must be solved to account for the incompressibility constraint that is imposed by penalisation techniques.
Crack nucleation in variational phase-field models of brittle fracture
- Tanné E.
- Li T.
- Bourdin B.
- Marigo J.-J.
- Maurini C.
Journal of the Mechanics and Physics of Solids, Elsevier, 2018, 110, pp.80 - 99. Phase-field models, sometimes refered to as gradient damage or smeared crack models, are widely used methods for the numerical simulation of crack propagation in brittle materials. Theoretical results and numerical evidences show that they can predict the propagation of a pre-existing crack according to Grith' criterion. For a one-dimensional problem, it has been shown that they can predict nucleation upon a critical stress, provided that regularization parameter be identified with the material's internal or characteristic length. In this article, we draw on numerical simulations to study crack nucleation in commonly encountered geometries for which closed-form solutions are not available. We use U-and V-notches to show that the nucleation load varies smoothly from that predicted by a strength criterion to that of a toughness criterion, when the strength of the stress concentration or singularity varies. We present validation and verifications numerical simulations for both types of geometries. We consider the problem of an elliptic cavity in an infinite or elongated domain to show that variational phase field models properly account for structural and material size e↵ects. We conclude that variational phase-field models can accurately predict crack nucleation through energy minimization in a nonlinear damage model instead of introducing ad-hoc criteria. (10.1016/j.jmps.2017.09.006)
DOI : 10.1016/j.jmps.2017.09.006
High-Resolution Wavenumber Analysis (HRWA) for the mechanical characterization of viscoelastic beams
- Margerit Pierre
- Lebée Arthur
- Caron Jean-François
- Boutillon Xavier
Journal of Sound and Vibration, Elsevier, 2018, 443, pp.198-211. The High-Resolution Wavenumber Analysis (HRWA) is presented. It identifies complex wavenumbers and amplitudes of waves composing the harmonic response of a beam. Based on the frequency dependence of these wavenumbers, experimental dispersion equations of various beam mechanisms (e.g bending, torsion) can be retrieved. The HRWA method is compared to the Mc Daniel and the Inverse Wave Correlation (IWC) methods. It overcomes some drawbacks of these methods: the wavenumber resolution is enhanced. Also, the wavenumber search problem is expressed as a linear problem, making the method computationally efficient. A number of wavenumbers can be identified automatically, thanks to a statistical criterion. First, the noise sensitivity of each method is investigated in the basis of synthesised measurements. For this criterion, the HRWA and Mc Daniel method performances are close and much better than IWC. Moreover, the HRWA is five to twenty times faster to compute than other methods, depending on the mesh size. Second, an experimental case is presented where bending and torsion waves are identified, yielding an apparent viscoelastic Young and shear moduli on a wide-frequency range. (10.1016/j.jsv.2018.06.062)
DOI : 10.1016/j.jsv.2018.06.062
Strain-gradient vs damage-gradient regularizations of softening damage models
- Le Duc Trung
- Marigo Jean-Jacques
- Maurini Corrado
- Vidoli Stefano
Computer Methods in Applied Mechanics and Engineering, Elsevier, 2018, 340, pp.424-450. Local damage models with softening needs localization limiters to preserve the mathematical and physical consistency. In this paper we compare the properties of strain-gradient and damage-gradient regularizations. Gradient-damage models introduce a quadratic dependency of the dissipated energy on the gradient of the damage field and are nowadays extensively used as phase-field approximation of brittle fracture. Their key feature is to provide a smeared approximation of a crack as a band of localised damage with a finite energy dissipation per unit of surface, that can be identified with the fracture toughness of the Griffith model. Strain gradient models introduce a quadratic dependence of the elastic energy on the gradient of the strain field. A similar term can be physically interpreted as the presence in the material of linear, but nonlocal, stiffnesses, that can be eventually be affected by damage. Despite this attractive interpretation, we have found that strain-gradient regularized models can hardly be used to approximate brittle fracture, because smeared cracks with non-vanishing and finite dissipated energies are hardly obtained. Our analysis is based on variational models and focuses on the one-dimensional traction problem. (10.1016/j.cma.2018.06.013)
DOI : 10.1016/j.cma.2018.06.013
An interface model for homogenization of acoustic materials
- Marigo Jean-Jacques
- Maurel Agnes
, 2018, 2, pp.Chapter 14, pp. 599-645. Acoustic metamaterials consisting in massive materials perforated by periodic subwavelength holes or more sparse structures involving periodic arrangement of wires have been shown to be able to control the wave propagation with high flexibility. In comparison, phononic crystals have a priori higher dimensions because of their wavelength-scale period. However, if the metamaterial has subwavelength period, many of the observed phenomena are attributable to Fabry-Perot type resonances, resonances in the hole or resonances of the wires. Therefore, these structures have a limitation in their thickness, which has to be at wavelength scale to produce such resonances (and thickness refers to the size in the direction perpendicular to the plane containing the periodic cells). In order to reduce the size of the devices, structures with subwavelength thickness have been developed. They are known as metasurfaces and metafilms. Despite the vanishing thickness in comparison to the incident wavelength, the capability of these ultrathin devices to control the wave propagation has been evidenced. This is because they are based on a resonance which is not related to their thickness. It can be a thin elastic membrane within the unit cell, or resonances of labyrinthine or curled elements squeezed in the unit cell. (10.1142/9789813228702_0014)
DOI : 10.1142/9789813228702_0014
Nusinersen versus Sham Control in Later-Onset Spinal Muscular Atrophy
- Vogt Sibylle
- Krueger Marcus
- Pechmann Astrid
- Rippberger Bianca
- Eckenweiler Matthias
- Schara Ulrike
- Koelbel Heike
- Andres Barbara
- Rupprich Katrin
- Gangfuss Andrea
- Jachertz Philipp
- Della Marina Adela
- Sponemann Nina
- Pane Markia
- Palermo Concetta
- Piastra Marco
- Fanelli Lavinia
- de Sanctis Roberto
- Genovese Orazio
- Antonaci Laura
- Pera Maria Carmela
- Lamendola Priscilla
- Messina Sonia
- Vita Gianluca
- Di Bella Vincenzo
- Sframeli Maria
- Rosa Matteo La
- Barcellona Costanza
- Distefano Maria Grazia
- Cavallaro Filippo
- Versaci Antonio
- de Luca Francesco
- Vita Giuseppe
- Nacimento Osorio Andres
- Tizzano Eduardo
- Ortez Gonzalez Carlos Ignacio
- Ortigoza Escobar Juan Dario
- Colomer Oferil Juame
- Medina Cantillo Julita
- Febrer Rotger Anna
- Vigo Morancho Meritxell
- Eldblom Johanneh
- Darin Niklas
- Kroksmark Anna Karin
- Lindstedt Asa
- Michael Eva
- Kimber Eva
- Wahlgren Lisa
- Chan Sophelia Hoi-Shan
- Chim Stella
- Chiu Joseph
- Ho Alvin Chi Chung
- Ip Jing Kun Janice
- Lam Wendy Wai Man
- Ng Maggie Chui-San
- Wan Connie
- Wong Virginia Chun Nei
- Yue Yvonne
- Arakawa Reiko
- Yamauchi Akemi
- Nagata Satoru
- Ito Yasushi
- Nakatsukasa Hidetsugu
- Takeshita Akiko
- Hirasawa Kyoko
- Ikai Tetsuo
- Eto Kaoru
- Otamni Yui
- Takeshima Yasuhiro
- Fukuda Noroki
- Tanaka Yasuhiro
- Shimomura Hideki
- Lee Tomoko
- Shibano Takayuki
- Mercuri Eugenio
- Tachikawa Tomohiro
- Darras Basile T
- Chae Jong-Hee
- Chiriboga Claudia A
- Lim Byung Chan
- Day John W
- Shin Hyung-Ik
- Campbell Craig
- Kim Soo Yeon
- Connolly Anne M
- Choi Sun Ah
- Iannaccone Susan T
- Son Woo Sung
- Kirschner Janbernd
- Jo Hyemi
- Chun Seong Min
- Saito K.
- Kim Hyuna
- Shieh Perry B
- Tulinius Már
- Mazzone Elena Stacy
- Bishop Kathie M
- Yang Qingqing
- Foster Richard
- Gheuens Sarah
- Bennett C. Franck
- Farwell Wildon
- Schneider Eugene
- Finkel Richard S
- Bradley Walter G.
- Kaufmann Petra
- Dickson Patricia I.
- Reingold Stephen C.
- Davis Charles S.
- Arredondo Kristen
- Castro Diana
- Cowie Margaret
- Farrow-Gillespie Alan
- Hebert Andrew
- Kauk Melissa
- Miller Nancy
- Nelson Leslie
- Spain Thomas
- Cappell Joshua
- Constantinescu Andrei
- Cruz Rosangel
- Dastgir Jahannaz
- de Vivo Darryl
- Dunaway Sally
- Engelstad Kristin
- Khandji Alexander G.
- Kramer Samantha
- Marra Jonathan
- Popolizio Molly
- Salazar Rachel
- Weimer Louis H.
- Aziz-Zaman Sonya
- Lamarca Nicole
- Ghosh Partha
- Al-Ghamdi Fouad
- Liew Wendy
- Graham Robert
- Berde Charles
- Sethna Navil
- Koka Anjali
- Wang Luke
- Laine Regina
- Souris Michelle
- Ordonez Grace
- Harrington Timothy
- Szelag Heather
- Pasternak Amy
- Mirek Elizabeth
- Quigley Janet
- Berry Debbie
- Civitello Matthew
- Endsley Julie Duke
- Eden Candace
- Leon Wendy
- O'Reardon Kathleen
- Sigurdardottir Laufey
- Johnson Craig
- Turner Jenna
- Vega Melisa
- Weber-Guzman Fabiola
- Zinn Matthias
- Rocha Ana Carolina Tesi
- Watson Karolina
- d'Souza Genevieve
- Ramamurthi R. J.
- Gee Richard
- Kitsuwa-Lowe Janis
- Hagerman Katharine
- Crasta Sheela
- Welsh Lesly
- Paulose Shirley
- Mcfall Danielle
- Perez Jennifer
- Patnaik Swetapadma
- Sanjanwala Bharati
- Sakamuri Sarada
- Proud Crystal
- Purse Bona Park
- Duong Trinh Tina
- Sampson Jacinda
- Tennekoon Gihan
- Brandsema John
- Glanzman Allan
- Flickinger Jean
- Toms Michele
- Adang Laura
- Stanford Delores
- Mayer Oscar
- Zigmont Joshua
- Chadehumbe Madeline
- Kichula Elizabeth
- Finanger Erika
- Russman Barry
- Roberts Colin
- Frank Andrea
- Benjamin Danielle
- Zilke Kirsten
- Golumbek Paul T
- Zaidman Craig M.
- Anand Pallavi
- Gadeken Rebecca
- Siener Catherine
- Kuntz Nancy
- Epstein Leon
- Krueger Jena
- Goldman Stewart
- Krosschell Kristin
- Blomgren Colleen
- Choi Hyoung Won
- Kurz Jonathan
- Parsons Julie
- Janas Joanne
- Yang Michele
- Ballard Alison
- Carry Terri
- Shea Stephanie
- Bielsky Alan
- Booker Kaylee
- Camuto Alicia
- Lord-Halvorson Sierra
- Gibbons Melissa
- Zimmerman Carl
- Allen Victoria
- Fuhr Peter
- Johnson Hannah
- Tran Vi
- Vanderveen Gina
- Shieh Perry
- Fowler Eileen
- Parziale Nicholas
- Rao Lekha
- Skura Christy
- Kelley Carolyn
- Shu Francy
- Oskoui Maryam
- Zielinski David
- Poulin Chantal
- Ingelmo Pablo Mauricio
- Desilets Sarah Turgeon
- Dinunzio Pamela
- Rivera Gonzalo
- Srour Myriam
- Arpin Stephanie
- Goobie Sharan
- Gibson Paul
- Scholtes Cheryl
- Mcdonald Wendy
- Zapata Eugenio
- Nguyen Cam-Tu Emilie
- Servais Laurent
- Gargaun Elena
- Le Moing Anne-Gaelle
- Gidaro Teresa
- Vialle Raphael
- Guye Marie-Laurence
- Lilien Charlotte
- Olliver Gwenn
- Gilabert Stephanie
- Borell Sabine
- Wider Sabine
- Stein Sabine
- Montes Jacqueline
New England Journal of Medicine, Massachusetts Medical Society, 2018, 378 (7), pp.625-635. BACKGROUND Nusinersen is an antisense oligonucleotide drug that modulates pre-messenger RNA splicing of the survival motor neuron 2 (SMN2) gene. It has been developed for the treatment of spinal muscular atrophy (SMA). METHODS We conducted a multicenter, double-blind, sham-controlled, phase 3 trial of nusinersen in 126 children with SMA who had symptom onset after 6 months of age. The children were randomly assigned, in a 2: 1 ratio, to undergo intrathecal administration of nusinersen at a dose of 12 mg (nusinersen group) or a sham procedure (control group) on days 1, 29, 85, and 274. The primary end point was the least-squares mean change from baseline in the Hammersmith Functional Motor Scale-Expanded (HFMSE) score at 15 months of treatment; HFMSE scores range from 0 to 66, with higher scores indicating better motor function. Secondary end points included the percentage of children with a clinically meaningful increase from baseline in the HFMSE score (>= 3 points), an outcome that indicates improvement in at least two motor skills. RESULTS In the prespecified interim analysis, there was a least-squares mean increase from baseline to month 15 in the HFMSE score in the nusinersen group (by 4.0 points) and a least-squares mean decrease in the control group (by -1.9 points), with a significant between-group difference favoring nusinersen (least-squares mean difference in change, 5.9 points; 95% confidence interval, 3.7 to 8.1; P< 0.001). This result prompted early termination of the trial. Results of the final analysis were consistent with results of the interim analysis. In the final analysis, 57% of the children in the nusinersen group as compared with 26% in the control group had an increase from baseline to month 15 in the HFMSE score of at least 3 points (P< 0.001), and the overall incidence of adverse events was similar in the nusinersen group and the control group (93% and 100%, respectively). CONCLUSIONS Among children with later-onset SMA, those who received nusinersen had significant and clinically meaningful improvement in motor function as compared with those in the control group. (Funded by Biogen and Ionis Pharmaceuticals; CHERISH ClinicalTrials. gov number, NCT02292537.) (10.1056/NEJMoa1710504)
DOI : 10.1056/NEJMoa1710504

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